Metals Handbook Desk Edition 2nd Edition

Citation preview

ASM INTERNATIONAL

Publication Information and Contributors

Metals Handbook Desk Edition, Second Edition was published in 1998. It was prepared under the direction of the ASM International Handbook Committee. The Desk Edition was edited by Joseph R. Davis.

Editorial Advisory Board • • • • • • • • • • • •

Peter J. Blau, Oak Ridge National Laboratory Rodney R. Boyer, Boeing Commercial Airplane Group Kenneth H. Eckelmeyer, Sandia National Laboratories Dennis D. Huffman, The Timken Company Lawrence J. Korb, Rockwell International David V. Neff, Metaullics Systems Company LP David LeRoy Olson, Colorado School of Mines Dennis B. O'Neil, Caterpillar Inc. Thomas S. Piwonka, University of Alabama S. Lee Semiatin, Wright Laboratory George F. Vander Voort, Buehler Ltd. Harry W. Walton, The Torrington Company

Foreword to the Print Edition ASM International is proud to mark the 75th anniversary of ASM Handbooks. In 1923, the American Society for Steel Treating (later the American Society for Metals, now ASM International) published a small loose-leaf collection of data sheets--the first edition of what became known as Metals Handbook. The series has developed over the years into a multivolume collection of reference books--each volume a thorough, comprehensive, and authoritative treatise on the subject to which it is devoted. The series--now titled ASM Handbook--continues to evolve and expand to serve the changing needs of metallurgy professionals throughout the world. One example of this evolution is the release this year of the ASM Handbook on CD-ROM. This year also marks the 50th anniversary of the classic 1948 edition of Metals Handbook--the last "regular" edition to be contained in one volume. The 1948 edition was the inspiration for the first Metals Handbook Desk Edition, published almost 15 years ago. This Second Edition is intended to serve the same function as its two predecessors: to provide an accessible, convenient, and practical single-volume first reference to all of metals technology. It was with some trepidation that ASM International entered into the project to revise and update the Desk Edition. The task seemed overwhelming. The ASM Handbook series had grown to 20 current volumes--almost twice as many as were in existence when the first Desk Edition was compiled. Would it be possible to create a work that included all of the vital information from the first edition, plus the most significant knowledge and data compiled in the years since its release, and still remain within the physical limits of a single volume? We believe that the new Metals Handbook Desk Editionmore than meets that objective. The credit for this monumental achievement belongs to Joseph R. Davis. Joe was Handbook Editor for many years at ASM, and his extraordinary knowledge of the handbooks along with his considerable editorial skills made him uniquely qualified to oversee this project. We are grateful to Joe for his hard work and for his commitment to creating the best Desk Edition possible. To assist in this effort, Joe assembled an outstanding Editorial Advisory Board, made up of many longtime handbook contributors and friends of ASM, and we extend our thanks to them as well. We also wish to recognize the ASM editorial and production staff members for their dedicated efforts on this Volume. Of course, we are especially grateful to the thousands of metallurgy professionals who have contributed to ASM Handbooks over the past 75 years. Their willingness to share their knowledge and expertise--as authors, reviewers, volume organizers, and Handbook Committee members--has made this book possible. With their ongoing support, ASM Handbooks will continue to thrive for at least another 75 years.

Alton D. Romig, Jr. President, ASM International Michael J. DeHaemer Managing Director, ASM International

Preface The Metals Handbook Desk Edition is intended to serve as a comprehensive single-volume reference source on the properties, selection, processing, testing, and characterization of metals and their alloys. Although the information presented in this Volume is drawn principally from the 20 volumes of the ASM Handbook series, it should not be considered simply an abridged version of the larger work. Instead, the Metals Handbook Desk Edition draws upon the complete arsenal of ASM products--both print and electronic--as well as other key sources of information originating from other publications, company literature, technical societies, and government agencies. Volume Content Because of the familiarity, success, and ease-of-use of the original Desk Edition published in 1984, it was determined from the outset of the project that the editorial approach and outline for the new edition should follow in a similar manner. The challenge in successfully revising the first edition was to determine what strategic additions (or reductions)and improvements should be made. Complicating this task was the fact that a complete edition cycle of the ASM Handbook (including completely new volumes on corrosion, tribology, materials characterization, and other topics) had been published since the earlier edition was produced. To ensure that the best product possible resulted from the revision/updating process, a 12-member Editorial Advisory Board representing industry, academia, and research laboratories was formed. All board members have been key contributors to the Handbook series or have been involved with other important ASM activities over the past decade. Under their guidance, an outline was established for the second edition that divided the book into five major parts: General Information; Irons, Steels, and High-Performance Alloys; Nonferrous Alloys and Special-Purpose Materials; Processing; and Testing, Inspection, and Materials Characterization. General Information contains a glossary of more than 3000 terms, a collection of common engineering tables, and graphs

comparing properties of metals and nonmetals. It also includes contributions on crystal structure, practical uses of phase diagrams, engineering design, and factors to be considered in the materials selection process. Irons, Steels, and High-Performance Alloys. Emphasis is placed on properties and selection of ferrous alloys and heat-

resistant superalloys. Important relationships between structure and properties in irons and steels are described. The effects of modern steelmaking practices on properties are examined, as is the influence of improved melting/refining methods on superalloy performance. New or expanded information is presented on austempered ductile irons, highstrength low-alloy steels, stainless steels(including duplex stainless steels), and powder metallurgy steels. Nonferrous Alloys and Special-Purpose Materials comprises 14 major sections that describe the properties and selection of

conventional (structural) nonferrous alloys and materials used for such special-purpose applications as magnetic or electrical devices, biomedical devices, and advanced aircraft/aerospace components. Metal-matrix composites and structural intermetallics--more recently developed materials not covered in the previous Desk Edition--are also described. Processing. Processes extending through the entire life-cycle of a component are described, including extractive

metallurgy, casting, forming, heat treatment, joining, surface cleaning, finishing and coating, and recycling. An entirely new section on powder metallurgy has also been added. The increased coverage of recycling technology reflects the response of the metals industry to environmental concerns. Testing, Inspection, and Materials Characterization. In addition to offering information on failure analysis, fractography, nondestructive testing, mechanical testing, and metallography, a new section describes in practical terms the selection of characterization methods for bulk elemental analysis, bulk microstructural analysis, and surface analysis. New information on wear testing and tests for evaluating stress-corrosion cracking and hydrogen embrittlement is also presented.

Acknowledgments

Before acknowledging contributors to the present volume, it is important to recognize the outstanding work of the first edition's editors: Timothy L. Gall and Howard E. Boyer (sadly, Howard passed away in 1990). Tim was truly the driving force behind the original Desk Edition. His vision, combined with Howard's superlative technical craftsmanship, resulted in what most consider the "flagship" publication of ASM. In order to build upon the foundation of the first edition, the present editor had to call on many old friends and colleagues. In addition to serving on the Editorial Advisory Board, the following individuals were major contributors to the second edition: Kenneth H. Eckelmeyer (Sandia National Laboratories)authored the Section "Materials Characterization" and coauthored the article "Very High Density Metals." Ken, who has contributed numerous handbook articles over the years, was also a key member of the Organizing Committee for Materials Characterization, Volume 10 of the ASM Handbook, published in 1986. George F. Vander Voort (Buehler Ltd.) revised the Section "Metallography" and contributed to the Section "Fractography." George, who is the most prolific author in the 75 year history of the Metals/ASM Handbook, has contributed definitive reviews on embrittlement mechanisms in irons and steel, the use of light microscopy for metallographic and fractographic analysis, and image analysis for quantitative determination of microstructural constituents. Rodney R. Boyer (Boeing Commercial Airplane Group) revised the Section "Titanium and Titanium Alloys" and helped revise other articles throughout the Handbook that deal with titanium alloys. Rod also served as the principal editor of the Materials Properties Handbook: Titanium Alloys,published by ASM in 1994. Thomas S. Piwonka (University of Alabama) authored the Section "Casting." Tom also served as a section chairman and contributing author for Casting, Volume 15 of the ASM Handbook, published in 1988. Peter J. Blau (Oak Ridge National Laboratory) authored the article "Wear Testing." Peter also served as volume chairman of Friction, Lubrication, and Wear Technology, Volume 18 of the ASM Handbook, published in 1992. Other notable contributors include Hugh Baker (Consulting Editor, ASM International), who authored the Section "Structure and Properties of Metals" and reviewed the Section "Magnesium and Magnesium Alloys."Hugh, who served on the Handbook staff from 1970 to 1979, was also the editor of Alloy Phase Diagrams, Volume 3 of ASM Handbook, published in 1992. Matthew J. Donachie (Rensselaer at Hartford)and Stephen J. Donachie (Special Metals Corporation) revised the Section "Superalloys."Matt, who edited the Superalloys Source Book published by ASM in 1984, also authored the article "Biomaterials." Erhard Klar (OMG Americas, retired) authored the Section "Powder Metallurgy"and reviewed several other P/M-related articles. Erhard also served as volume coordinator of Powder Metallurgy, Volume 7 of the ASM Handbook, published in 1984. Brajendra Mishra (Colorado School of Mines) authored the Sections "Steelmaking Practices and Their Influence on Properties" and "Extractive Metallurgy." John C. Bittence(Welshfield Studios) revised the Section "Recycling and Life-Cycle Analysis"and assisted in editing the Sections "Forming" and "Forging." The efforts of the ASM staff must also be acknowledged. In particular, I would like to thank veteran technical editors Steven R. Lampman and Edward J. Kubel, Jr. for their help in completing the Sections "Failure Analysis,""Nondestructive Testing," and "Mechanical, Wear, and Corrosion Testing," and Scott D. Henry, Assistant Director of Technical Publications, for his unflagging support and patience throughout the project. The kind assistance of the ASM Library is also duly noted. As a result of the collective experience and talent of all those listed above, the rich tradition of the Metals Handbook continues. Whether in print form, CD-ROM format, via the Internet, or some other remarkable vehicle made possible by the computer age, it will undoubtedly continue to serve the metallurgical community well into the next millennium. The best is yet to come! Joseph R. Davis Davis & Associates, Chagrin Falls, Ohio

Source Acknowledgments Major sources for the Sections in this Handbook are listed below. Additional source information is provided in the reference lists that appear in many of the articles. Structure and Properties of Metals Much of this Section was adapted from Alloy Phase Diagrams, Volume 3, ASM Handbook, 1992, pages 1-1 to 1-29. Design Considerations and Materials Selection

Much of this Section was adapted from various articles appearing in Materials Selection and Design, Volume 20, ASM Handbook, 1997. Structure/Property Relationships in Irons and Steels Much of this Section was adapted from various articles appearing in Materials Selection and Design, Volume 20, ASM Handbook, 1997, pages 357-382. Carbon and Alloy Steels This Section was condensed from Properties and Selection: Irons, Steels, and High-Performance Alloys, Vol 1, ASM Handbook, 1990, pages 105 to 822. Supplemental information was also adapted from the ASM Specialty Handbook: Carbon and Alloy Steels,1996, and Fatigue and Fracture, Vol 20, ASM Handbook, 1996. Cast Irons This Section was condensed from the ASM Specialty Handbook:Cast Irons, 1996, p 3 to 130. Ferrous Powder Metallurgy Materials This Section was condensed from Properties and Selection: Irons, Steels, and High-Performance Alloys, Volume 1, ASM Handbook, 1990, pages 800 to 821 and from Powder Metallurgy,Volume 7, ASM Handbook, 1984, pages 79 to 99. Tool Steels This Section was condensed from the ASM Specialty Handbook:Tool Materials, 1995, pages 10 to 20, 21 to 31, 119 to 153, and 383 to 395. Stainless Steels Much of this Section was condensed from the ASM Specialty Handbook:Stainless Steels, 1994. Supplemental information was also adapted from the ASM Specialty Handbook: Heat-Resistant Materials,1997, pages 123 to 178. Superalloys For more detailed information on superalloys, the reader is referred to the ASM Specialty Handbook: Heat-Resistant Materials (see, in particular, pages 219 to 344). Aluminum and Aluminum Alloys This Section was assembled from a variety of sources, including Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 3 to 215; the ASM Specialty Handbook: Aluminum and Aluminum Alloys, 1993, pages 3 to 159; and Corrosion, Volume 13, ASM Handbook, 1987, pages 583 to 609. Updated statistical information and property data were obtained from the Aluminum Association Inc. Copper and Copper Alloys This Section was assembled from a variety of sources, including Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 216 to 427, Corrosion, Volume 13, ASM Handbook, 1987, pages 610 to 640, and Materials Selection and Design, Volume 20, ASM Handbook, 1997, pages 389 to 393. Updated statistical information and composition/property data were obtained from the Copper Development Association Inc. Magnesium and Magnesium Alloys This Section was condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 455 to 479, and from Corrosion, Volume 13, ASM Handbook, 1987, pages 740 to 754.

Titanium and Titanium Alloys For more detailed information on titanium and titanium alloys, the reader is referred to the Materials Properties Handbook: Titanium Alloys published by ASM International in 1994 and to Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2 of ASM Handbook, 1990 (see pages 586 to 660). Zinc and Zinc Alloys This Section was condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 527 to 542, and from Corrosion, Volume 13, ASM Handbook, 1987, pages 432 to 445 and 755 to 769. Tin and Tin Alloys This Section was condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 517 to 526. Lead and Lead Alloys This Section was condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 543 to 556, and from Corrosion, Volume 13, ASM Handbook, 1987, pages 784 to 792. Nickel and Nickel Alloys This Section was condensed from Corrosion, Volume 13, ASM Handbook, 1987, pages 641 to 657, and Materials Selection and Design, Volume 20, ASM Handbook, 1997, pages 393 to 396. Cobalt and Cobalt Alloys This Section was condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 446 to 454. Zirconium and Hafnium This Section was condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 661 to 669, and from Corrosion, Volume 13, ASM Handbook, 1987, p 707 to 721. Precious Metals and Alloys This Section was condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 688 to 719. Refractory Metals and Alloys This Section was condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 557 to 585, and from the ASM Specialty Handbook:Heat-Resistant Materials, 1997, pages 361 to 382. Cemented Carbides and Cermets This Section was condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 950 to 977, and from Friction, Lubrication, and Wear Technology, Volume 18, ASM Handbook, 1992, pages 795 to 800. Special-Purpose Materials

Portions of this Section were condensed from Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 761 to 1089. Supplemental information was also adapted from the ASM Specialty Handbook: Aluminum and Aluminum Alloys, 1993, pages 160 to 179 (aluminum-matrix composites), ASM Specialty Handbook: Heat-Resistant Materials, 1997, p 389 to 414 (structural intermetallics), and Friction, Lubrication, and Wear Technology, Volume 18, ASM Handbook, 1992, pages 741 to 765 (sliding bearings and hardfacing alloys). Forming This Section was condensed from Forming and Forging,Volume 14, ASM Handbook, 1988. Forging This Section was condensed from Forming and Forging,Volume 14, ASM Handbook, 1988. Powder Metallurgy More detailed information on powder metallurgy can be found in Powder Metal Technologies and Applications, Volume 7, ASM Handbook, 1998. Machining This Section was condensed from Machining, Volume 16, ASM Handbook, 1989, and the Machining Data Handbook,3rd ed., published by Metcut Research Associates, Inc., Cincinnati, OH. Supplemental information was also taken from Surface Engineering, Volume 5, ASM Handbook, 1994, and the ASM Specialty Handbook:Tool Materials, 1995. Heat Treating This Section was condensed from Heat Treating, Volume 4, ASM Handbook, 1991. Joining This Section was condensed from Welding, Brazing, and Soldering, Volume 6, ASM Handbook, 1993. Surface Engineering This Section was condensed from Surface Engineering,Volume 5, ASM Handbook, 1994. Supplemental information was also taken from Materials Selection and Design, Volume 20, ASM Handbook, 1997, pages 470 to 490. Recycling and Life-Cycle Analysis This Section was condensed from Properties and Selection: Irons, Steels, and High-Performance Alloys, Volume 1, ASM Handbook, 1990, pages 1023 to 1033; from Properties and Selection:Nonferrous Alloys and Special-Purpose Materials, Volume 2, ASM Handbook, 1990, pages 1205 to 1232; and from Materials Selection and Design, Volume 20, ASM Handbook, 1997, pages 96 to 103 and 131 to 138. Failure Analysis This Section was condensed from Failure Analysis and Prevention, Volume 11, ASM Handbook, 1986, and Fatigue and Fracture, Volume 19, ASM Handbook, 1996, pages 371 to 380. Fractography Parts of this Section were condensed from Fractography,Volume 12, ASM Handbook, 1987. Updated material from the previous Metals Handbook Desk Edition, 1984, is also included. Nondestructive Testing

This Section was condensed from Nondestructive Evaluation and Quality Control, Volume 17, ASM Handbook, 1989. Mechanical, Wear, and Corrosion Testing This Section was condensed from Mechanical Testing,Volume 8, ASM Handbook, 1985, and from Fatigue and Fracture, Volume 19, ASM Handbook, 1996.

General Information Officers and Trustees of ASM International(1997-1998) Officers

• • • • •

Alton D. Romig, Jr., President and Trustee , Sandia National Laboratories Hans H. Portisch, Vice President and Trustee , Krupp VDM Austria GmbH Michael J. DeHaemer, Secretary and Managing Director , ASM International W. Raymond Cribb, Treasurer , Brush Wellman Inc. George Krauss, Immediate Past President , Colorado School of Mines

Trustees

• • • • • • • • •

Nicholas F. Fiore, Carpenter Technology Corporation Gerald G. Hoeft, Caterpillar Inc. Jennie S. Hwang, H-Technologies Group Inc. Thomas F. McCardle, Kolene Corporation Bhakta B. Rath, U.S. Naval Research Laboratory C. (Ravi) Ravindran, Ryerson Polytechnic University Darrell W. Smith, Michigan Technological University Leo G. Thompson, Lindberg Corporation James C. Williams, GE Aircraft Engines

Members of the ASM Handbook Committee (1997-1998) • • • • • • • • • • • • • • • • • • • •

Michelle M. Gauthier, (Chair 1997-;Member 1990-) , Raytheon Electronic Systems Craig V. Darragh, (Vice Chair 1997-;Member 1989-) , The Timken Company Bruce P. Bardes (1993-) , Materials Technology Solutions Company Rodney R. Boyer (1982-1985; 1995-) , Boeing Commercial Airplane Group Toni M. Brugger (1993-) , Carpenter Technology Corporation R. Chattopadhyay (1996-) , Consultant Rosalind P. Cheslock (1994-) Aicha Elshabini-Riad (1990-) , Virginia Polytechnic Institute & State University Henry E. Fairman (1993-) , MQS Inspection Inc. Michael T. Hahn (1995-) , Northrop Grumman Corporation Larry D. Hanke (1994-) , Materials Evaluation and Engineering Inc. Jeffrey A. Hawk (1997-) , U.S. Department of Energy Dennis D. Huffman (1982-) , The Timken Company S. Jim Ibarra, Jr. (1991-) , Amoco Corporation Dwight Janoff (1995-) , FMC Corporation Paul J. Kovach (1995-) , Stress Engineering Services Inc. Peter W. Lee (1990-) , The Timken Company William L. Mankins (1989-) Mahi Sahoo (1993-) , CANMET Wilbur C. Simmons (1993-) , Army Research Office

• • • • • •

Karl P. Staudhammer (1997-) , Los Alamos National Laboratory Kenneth B. Tator (1991-) , KTA-Tator Inc. Malcolm C. Thomas (1993-) , Allison Engine Company George F. Vander Voort (1997-) , Buehler Ltd. Jeffrey Waldman (1995-) , Drexel University Dan Zhao (1996-) , Essex Group Inc.

Previous Chairs of the ASM Handbook Committee • • • • • • • • • • • • • • • • • • • • • • • • •

R.J. Austin, (1992-1994) (Member 1984-) L.B. Case, (1931-1933) (Member 1927-1933) T.D. Cooper, (1984-1986) (Member 1981-1986) E.O. Dixon, (1952-1954) (Member 1947-1955) R.L. Dowdell, (1938-1939)(Member 1935-1939) J.P. Gill, (1937) (Member 1934-1937) J.D. Graham, (1966-1968) (Member 1961-1970) J.F. Harper, (1923-1926) (Member 1923-1926) C.H. Herty, Jr., (1934-1936)(Member 1930-1936) D.D. Huffman, (1986-1990)(Member 1982-) J.B. Johnson, (1948-1951)(Member 1944-1951) L.J. Korb, (1983) (Member 1978-1983) R.W.E. Leiter, (1962-1963)(Member 1955-1958, 1960-1964) G.V. Luerssen, (1943-1947)(Member 1942-1947) G.N. Maniar, (1979-1980) (Member 1974-1980) W.L. Mankins, (1994-1997)(Member 1989-) J.L. McCall, (1982) (Member 1977-1982) W.J. Merten, (1927-1930) (Member 1923-1933) D.L. Olson, (1990-1992) (Member 1982-1988, 1989-1992) N.E. Promisel, (1955-1961)(Member 1954-1963) G.J. Shubat, (1973-1975) (Member 1966-1975) W.A. Stadtler, (1969-1972)(Member 1962-1972) R. Ward, (1976-1978) (Member 1972-1978) M.G.H. Wells, (1981) (Member 1976-1981) D.J. Wright, (1964-1965) (Member 1959-1967)

Staff ASM International staff who contributed to the development of the Volume included Scott D. Henry, Assistant Director of Reference Publications; Grace M. Davidson, Manager of Handbook Production; Bonnie R. Sanders, Manager of Copy Editing; Kathleen S. Dragolich, Production Coordinator; Erika K. Baxter and Alexandra B. Hoskins, Copy Editors; Alexandru Popaz-Pauna, Candace K. Mullet, and Jill A. Kinson, Production Assistants. Editorial assistance was provided by Denise Kelly, Heather Lampman, and Mary Jane Riddlebaugh. The Volume was prepared under the direction of William W. Scott, Jr., Director of Technical Publications. Conversion to Electronic Files Metals Handbook Desk Edition was converted to electronic files in 2000. The conversion was based on the first printing (1998). No substantive changes were made to the content of the Volume, but some minor corrections and clarifications were made as needed. ASM International staff who contributed to the conversion of the Volume included Sally Fahrenholz-Mann, Bonnie Sanders, Marlene Seuffert, Gayle Kalman, Scott Henry, and Robert Braddock. The electronic version was prepared under the direction of William W. Scott, Jr., Technical Director, and Michael J. DeHaemer, Managing Director. Copyright Information (for Print Volume)

Copyright © 1998 by ASM International® All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the written permission of the copyright owner. First printing, December 1998 This book is a collective effort involving hundreds of technical specialists. It brings together a wealth of information from world-wide sources to help scientists, engineers, and technicians solve current and long-range problems. Great care is taken in the compilation and production of this Volume, but it should be made clear that NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE GIVEN IN CONNECTION WITH THIS PUBLICATION. Although this information is believed to be accurate by ASM, ASM cannot guarantee that favorable results will be obtained from the use of this publication alone. This publication is intended for use by persons having technical skill, at their sole discretion and risk. Since the conditions of product or material use are outside of ASM's control, ASM assumes no liability or obligation in connection with any use of this information. No claim of any kind, whether as to products of information in this publication, and whether or not based on negligence, shall be greater in amount than the purchase price of this product or publication in respect of which damages are claimed. THE REMEDY HEREBY PROVIDED SHALL BE THE EXCLUSIVE AND SOLE REMEDY OF BUYER, AND IN NO EVENT SHALL EITHER PARTY BE LIABLE FOR SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHETHER OR NOT CAUSED BY OR RESULTING FROM THE NEGLIGENCE OF SUCH PARTY. As with any material, evaluation of the material under enduse conditions prior to specification is essential. Therefore, specific testing under actual conditions is recommended. Nothing contained in this book shall be construed as a grant of any right of manufacture, sale, use, or reproduction, in connection with any method, process, apparatus, product, composition, or system, whether or not covered by letters patent, copyright, or trademark, and nothing contained in this book shall be construed as a defense against any alleged infringement of letters patent, copyright, or trademark, or as a defense against liability for such infringement. Comments, criticisms, and suggestions are invited, and should be forwarded to ASM International. Library of Congress Cataloging-in-Publication Data (for Print Volume) Metals handbook/edited by J.R. Davis; prepared under the direction of the ASM International Handbook Committee.-Desk ed.; 2nd ed. Includes bibliographical references and index. 1. Metals--Handbooks, manuals, etc. I. Davis, J.R. II. ASM International. Handbook Committee. TA459.M288 1998 620.1'6 dc21 98-45866 SAN 204-7586 ISBN 0-87170-654-7

Engineering Data for Metals and Alloys

Table 1 Density of metals and alloys Metal or alloy

Density

g/cm3

lb/in.3

2.6989

0.0975

EC, 1060 alloys

2.70

0.098

1100

2.71

0.098

2011

2.82

0.102

2014

2.80

0.101

2024

2.77

0.100

2218

2.81

0.101

3003

2.73

0.099

4032

2.69

0.097

5005

2.70

0.098

5050

2.69

0.097

5052

2.68

0.097

5056

2.64

0.095

5083

2.66

0.096

5086

2.65

0.096

Aluminum and aluminum alloys

Aluminum (99.996%)

Wrought alloys

5154

2.66

0.096

5357

2.70

0.098

5456

2.66

0.096

6061, 6063

2.70

0.098

6101, 6151

2.70

0.098

7075

2.80

0.101

7079

2.74

0.099

7178

2.82

0.102

242.0

2.81

0.102

295.0

2.81

0.102

356.0

2.68

0.097

380.0

2.76

0.099

413.0

2.66

0.096

443.0

2.69

0.097

514.0

2.65

0.096

520.0

2.57

0.093

Pure copper

8.96

0.324

Electrolytic tough pitch copper (ETP)

8.89

0.321

Casting alloys

Copper and copper alloys

Wrought coppers

Deoxidized copper, high residual phosphorus (DHP)

8.94

0.323

0.5% Te

8.94

0.323

1.0% Pb

8.94

0.323

Gilding, 95%

8.86

0.320

Commercial bronze, 90%

8.80

0.318

Jewelry bronze, 87.5%

8.78

0.317

Red brass, 85%

8.75

0.316

Low brass, 80%

8.67

0.313

Cartridge brass, 70%

8.53

0.308

Yellow brass

8.47

0.306

Muntz metal

8.39

0.303

Leaded commercial bronze

8.83

0.319

Low-leaded brass (tube)

8.50

0.307

Medium-leaded brass

8.47

0.306

High-leaded brass (tube)

8.53

0.308

High-leaded brass

8.50

0.307

Extra-high-leaded brass

8.50

0.307

Free-cutting brass

8.50

0.307

Leaded Muntz metal

8.41

0.304

Free-machining copper

Wrought alloys

Forging brass

8.44

0.305

Architectural bronze

8.47

0.306

Inhibited admiralty

8.53

0.308

Naval brass

8.41

0.304

Leaded naval brass

8.44

0.305

Manganese bronze (A)

8.36

0.302

5% (A)

8.86

0.320

8% (C)

8.80

0.318

10% (D)

8.78

0.317

1.25%

8.89

0.321

Free-cutting phosphor bronze

8.89

0.321

30%

8.94

0.323

10%

8.94

0.323

65-18

8.73

0.315

55-18

8.70

0.314

High-silicon bronze (A)

8.53

0.308

Low-silicon bronze (B)

8.75

0.316

Aluminum bronze, 5% Al

8.17

0.294

Phosphor bronze

Cupronickel

Nickel silver

Aluminum bronze (3)

7.78

0.281

Aluminum-silicon bronze

7.69

0.278

Aluminum bronze (1)

7.58

0.274

Aluminum bronze (2)

7.58

0.274

Beryllium copper

8.23

0.297

Chromium copper (1% Cr)

8.7

0.31

88Cu-10Sn-2Zn

8.7

0.31

88Cu-8Sn-4Zn

8.8

0.32

89Cu-11Sn

8.78

0.317

88Cu-6Sn-1.5Pb-4.5Zn

8.7

0.31

87Cu-8Sn-1Pb-4Zn

8.8

0.32

87Cu-10Sn-1Pb-2Zn

8.8

0.32

80Cu-10Sn-10Pb

8.95

0.323

83Cu-7Sn-7Pb-3Zn

8.93

0.322

85Cu-5Sn-9Pb-1Zn

8.87

0.320

78Cu-7Sn-15Pb

9.25

0.334

70Cu-5Sn-25Pb

9.30

0.336

85Cu-5Sn-5Pb-5Zn

8.80

0.318

83Cu-4Sn-6Pb-7Zn

8.6

0.31

81Cu-3Sn-7Pb-9Zn

8.7

0.31

Casting alloys

76Cu-2.5Sn-6.5Pb-15Zn

8.77

0.317

72Cu-1Sn-3Pb-24Zn

8.50

0.307

67Cu-1Sn-3Pb-29Zn

8.45

0.305

61Cu-1Sn-1Pb-37Zn

8.40

0.304

60 ksi

8.2

0.30

65 ksi

8.3

0.30

90 ksi

7.9

0.29

110 ksi

7.7

0.28

Alloy 9A

7.8

0.28

Alloy 9B

7.55

0.272

Alloy 9C

7.5

0.27

Alloy 9D

7.7

0.28

12% Ni

8.95

0.323

16% Ni

8.95

0.323

20% Ni

8.85

0.319

25% Ni

8.8

0.32

Silicon bronze

8.30

0.300

Silicon brass

8.30

0.300

Manganese bronze

Aluminum bronze

Nickel silver

Iron and iron alloys

Pure iron

7.874

0.2845

Ingot iron

7.866

0.2842

Wrought iron

7.7

0.2

Gray cast iron

7.15(a)

0.258(a)

Malleable iron

7.27(b)

0.262(b)

Ductile iron

7.15

0.258

High-nickel iron (Ni-Resist)

7.5

0.271

High-chromium white iron

7.4

0.267

0.06% C steel

7.871

0.2844

0.23% C steel

7.859

0.2839

0.435% C steel

7.844

0.2834

1.22% C steel

7.830

0.2829

0.5% Mo steel

7.86

0.283

1Cr-0.5Mo steel

7.86

0.283

1.25Cr-0.5Mo steel

7.86

0.283

2.25Cr-1.0Mo steel

7.86

0.283

5Cr-0.5Mo steel

7.78

0.278

7Cr-0.5Mo steel

7.78

0.278

9Cr-1Mo steel

7.67

0.276

Low-carbon chromium-molybdenum steels

Medium-carbon alloy steels

1Cr-0.35Mo-0.25V steel

7.86

0.283

H11 die steel (5Cr-1.5Mo-0.4V)

7.75

0.280

A-286

7.91

0.286

16-25-6 alloy

8.08

0.292

RA-330

8.03

0.290

Incoloy 800

7.95

0.287

Incoloy 901

8.23

0.297

T1 tool steel

8.67

0.313

M2 tool steel

8.16

0.295

W1 tool steel

7.84

0.282

O6 tool steel

7.70

0.277

A2 tool steel

7.86

0.284

H22 tool steel

8.36

0.302

L6 tool steel

7.86

0.284

P20 tool steel

7.85

0.284

20Cb3

8.08

0.292

20W-4Cr-2V-12Co steel

8.89

0.321

Invar (36% Ni)

8.00

0.289

Hipernik (50% Ni)

8.25

0.298

Other iron-base alloys

4% Si

7.6

0.27

10.27% Si

6.97

0.252

CA-15

7.612

0.2750

CA-40

7.612

0.2750

CB-30

7.53

0.272

CC-50

7.53

0.272

CE-30

7.67

0.277

CF-8

7.75

0.280

CF-20

7.75

0.280

CF-8M, CF-12M

7.75

0.280

CF-8C

7.75

0.280

CF-16F

7.75

0.280

CH-20

7.72

0.279

CK-20

7.75

0.280

CN-7M

8.00

0.289

HA

7.72

0.279

HC

7.53

0.272

HD

7.58

0.274

Stainless steels and heat-resistant alloys

Corrosion-resistant steel castings

Heat-resistant alloy castings

HE

7.67

0.277

HF

7.75

0.280

HH

7.72

0.279

HI

7.72

0.279

HK

7.75

0.280

HL

7.72

0.279

HN

7.83

0.283

HT

7.92

0.286

HU

8.04

0.290

HW

8.14

0.294

HX

8.14

0.294

Type 301

7.9

0.29

Type 302

7.9

0.29

Type 302B

8.0

0.29

Type 303

7.9

0.29

Type 304

7.9

0.29

Type 305

8.0

0.29

Type 308

8.0

0.29

Type 309

7.9

0.29

Type 310

7.9

0.29

Wrought stainless and heat-resistant steels

Type 314

7.72

0.279

Type 316

8.0

0.29

Type 317

8.0

0.29

Type 321

7.9

0.29

Type 347

8.0

0.29

Type 403

7.7

0.28

Type 405

7.7

0.28

Type 410

7.7

0.28

Type 416

7.7

0.28

Type 420

7.7

0.28

Type 430

7.7

0.28

Type 430F

7.7

0.28

Type 431

7.7

0.28

Types 440A, 440B, 440C

7.7

0.28

Type 446

7.6

0.27

Type 501

7.7

0.28

Type 502

7.8

0.28

19-9DL

7.97

0.29

PH15-7Mo

7.804

0.2819

17-4 PH

7.8

0.28

Precipitation-hardening stainless steels

17-7 PH

7.81

0.282

D-979

8.27

0.299

Nimonic 80A

8.25

0.298

Nimonic 90

8.27

0.299

M-252

8.27

0.298

Inconel 600

8.41

0.304

Inconel "X" 550

8.30

0.300

Inconel 718

8.22

0.297

Inconel "713C"

7.913

0.2859

Waspaloy

8.23

0.296

René 41

8.27

0.298

Hastelloy alloy B

9.24

0.334

Hastelloy alloy C

8.94

0.323

Hastelloy alloy X

8.23

0.297

Udimet 500

8.07

0.291

GMR-235

8.03

0.290

CMSX-2

8.56

0.309

PWA 1484

8.95

0.323

8.23

0.296

Nickel-base alloys

Cobalt-chromium-nickel-base alloys

N-155 (HS-95)

S-590

8.36

0.301

S-816

8.68

0.314

V-36

8.60

0.311

HS-25

9.13

0.330

HS-36

9.04

0.327

HS-31

8.61

0.311

HS-21

8.30

0.300

10.2

0.368

Chemical lead (99.90+% Pb)

11.34

0.4097

Corroding lead (99.73+% Pb)

11.36

0.4104

Arsenical lead

11.34

0.4097

Calcium lead

11.34

0.4097

5-95 solder

11.0

0.397

20-80 solder

10.2

0.368

50-50 solder

8.89

0.321

11.27

0.407

Cobalt-base alloys

Molybdenum-base alloy

Mo-0.5Ti

Lead and lead alloys

Antimonial lead alloys

1% antimonial lead

Hard lead

96Pb-4Sb

11.04

0.399

94Pb-6Sb

10.88

0.393

8% antimonial lead

10.74

0.388

9% antimonial lead

10.66

0.385

SAE 13

10.24

0.370

SAE 14

9.73

0.352

Alloy 8

10.04

0.363

Babbitt (SAE 15)

10.1

0.365

"G" Babbitt

10.1

0.365

1.738

0.06279

AM100A

1.81

0.065

AZ63A

1.84

0.066

AZ81A

1.80

0.065

AZ91A, B, C

1.81

0.065

AZ92A

1.82

0.066

HK31A

1.79

0.065

Lead-base babbitt alloys

Lead-base babbitt

Arsenical lead

Magnesium and magnesium alloys

Magnesium (99.8%)

Casting alloys

HZ32A

1.83

0.066

ZH42, ZH62A

1.86

0.067

ZK51A

1.81

0.065

ZE41A

1.82

0.066

EZ33A

1.83

0.066

EK30A

1.79

0.065

EK41A

1.81

0.065

M1A

1.76

0.064

A3A

1.77

0.064

AZ31B

1.77

0.064

PE

1.76

0.064

AZ61A

1.80

0.065

AZ80A

1.80

0.065

ZK60A, B

1.83

0.066

ZE10A

1.76

0.064

HM21A

1.78

0.064

HM31A

1.81

0.065

Nickel (99.95% Ni + Co)

8.902

0.322

Nickel 200

8.89

0.321

Wrought alloys

Nickel and nickel alloys

Nickel 270

8.89

0.321

Duranickel 301

8.26

0.298

Cast nickel

8.34

0.301

Monel 400

8.80

0.318

"K" Monel

8.47

0.306

"H" Monel (cast)

8.5

0.31

"S" Monel (cast)

8.36

0.302

Inconel 625

8.44

0.305

Hastelloy B

9.24

0.334

Hastelloy C

8.94

0.323

Hastelloy D

7.8

0.282

Hastelloy F

8.17

0.295

Hastelloy N

8.79

0.317

Hastelloy W

9.03

0.326

Hastelloy X

8.23

0.297

Illium G

8.58

0.310

Illium R

8.58

0.310

8.4

0.30

Nickel-molybdenum-chromium-iron alloys

Nickel-chromium-molybdenum-copper alloys

Electrical resistance alloys

80Ni-20Cr

60Ni-24Fe-16Cr

8.247

0.298

35Ni-45Fe-20Cr

7.95

0.287

Constantan

8.9

0.32

7.3

0.264

30% Pb

8.32

0.301

37% Pb

8.42

0.304

Alloy 1

7.34

0.265

Alloy 2

7.39

0.267

Alloy 3

7.46

0.269

Alloy 4

7.53

0.272

Alloy 5

7.75

0.280

White metal

7.28

0.263

Pewter

7.28

0.263

99.9% Ti

4.507

0.1628

99.2% Ti

4.507

0.1628

99.0% Ti

4.52

0.163

Ti-6Al-4V

4.43

0.160

Tin and tin alloys

Pure tin

Soft solder

Tin babbitt

Titanium and titanium alloys

Ti-5Al-2.5Sn

4.46

0.161

Ti-2Fe-2Cr-2Mo

4.65

0.168

Ti-8Mn

4.71

0.171

Ti-7Al-4Mo

4.48

0.162

Ti-4Al-4Mn

4.52

0.163

Ti-4Al-3Mo-1V

4.507

0.1628

Ti-2.5Al-16V

4.65

0.168

Pure zinc

7.133

0.2577

AG40A alloy

6.6

0.24

AC41A alloy

6.7

0.24

0.08% Pb

7.14

0.258

0.06 Pb, 0.06 Cd

7.14

0.258

03 Pb, 0.3 Cd

7.14

0.258

Copper-hardened, rolled zinc, 1% Cu

7.18

0.259

Rolled zinc alloy, 1 Cu, 0.010 Mg

7.18

0.259

Zn-Cu-Ti alloy, 0.8 Cu, 0.15 Ti

7.18

0.259

Silver

10.49

0.379

Gold

19.32

0.698

Zinc and zinc alloys

Commercial rolled zinc

Precious metals

70Au-30Pt

19.92

...

Platinum

21.45

0.775

Pt-3.5Rh

20.9

...

Pt-5Rh

20.65

...

Pt-10Rh

19.97

...

Pt-20Rh

18.74

...

Pt-30Rh

17.62

...

Pt-40Rh

16.63

...

Pt-5Ir

21.49

...

Pt-10Ir

21.53

...

Pt-15Ir

21.57

...

Pt-20Ir

21.61

...

Pt-25Ir

21.66

...

Pt-30Ir

21.70

...

Pt-35Ir

21.79

...

Pt-5Ru

20.67

...

Pt-10Ru

19.94

...

Palladium

12.02

0.4343

60Pd-40Cu

10.6

0.383

95.5Pd-4.5Ru

12.07(a)

...

95.5Pd-4.5Ru

11.62(b)

...

Permanent magnet materials

Cunico

8.30

0.300

Cunife

8.61

0.311

Comol

8.16

0.295

Alnico I

6.89

0.249

Alnico II

7.09

0.256

Alnico III

6.89

0.249

Alnico IV

7.00

0.253

Alnico V

7.31

0.264

Alnico VI

7.42

0.268

Barium ferrite

4.7

0.17

Vectolite

3.13

0.113

Antimony

6.62

0.239

Beryllium

1.848

0.067

Bismuth

9.80

0.354

Cadmium

8.65

0.313

Calcium

1.55

0.056

Cesium

1.903

0.069

Chromium

7.19

0.260

Cobalt

8.85

0.322

Pure metals

Gallium

5.907

0.213

Germanium

5.323

0.192

Hafnium

13.1

0.473

Indium

7.31

0.264

Iridium

22.5

0.813

Lithium

0.534

0.019

Manganese

7.43

0.270

Mercury

13.546

0.489

Molybdenum

10.22

0.369

Niobium

8.57

0.310

Osmium

22.583

0.816

Plutonium

19.84

0.717

Potassium

0.86

0.031

Rhenium

21.04

0.756

Rhodium

12.44

0.447

Ruthenium

12.2

0.441

Selenium

4.79

0.174

Silicon

2.33

0.084

Silver

10.49

0.379

Sodium

0.97

0.035

Tantalum

16.6

0.600

Thallium

11.85

0.428

Thorium

11.72

0.423

Tungsten

19.3

0.697

Vanadium

6.1

0.22

Zirconium

6.5

0.23

8.23(c)

...

6.66(d)

...

6.77(e)

...

Dysprosium

8.55(f)

...

Erbium

9.15(f)

...

Europium

5.245(e)

...

Gadolinium

7.86(f)

...

Holmium

6.79(f)

...

Lanthanum

6.19(d)

...

6.18(c)

...

5.97(e)

...

Lutetium

9.85(f)

...

Neodymium

7.00(d)

...

6.80(e)

...

6.77(d)

...

Rare earth metals

Cerium

Praseodymium

6.64(e)

...

Samarium

7.49(g)

...

Scandium

2.99(f)

...

Terbium

8.25(f)

...

Thulium

9.31(f)

...

Ytterbium

6.96(c)

...

Yttrium

4.47(f)

...

Actinium

10.1

0.3648

Berkelium

14.78

0.5339

Californium

15.10

0.5455

Curium

7

0.3

Einsteinium

8.84

0.3194

Actinide metals

(a) 6.95 to 7.35 g/cm3 (0.251 to 0.265 lb/in.3).

(b) 7.20 to 7.34 g/cm3 (0.260 to 0.265 lb/in.3).

(c) Face-centered cubic.

(d) Hexagonal.

(e) Body-centered cubic.

(f) Close-packed hexagonal.

(g) Rhombohedral

Table 2 Linear thermal expansion of metals and alloys Temperature, °C

Coefficient of expansion, μin./in. · °C

20-100

23.6

EC, 1060, 1100

20-100

23.6

2011, 2014

20-100

23.0

2024

20-100

22.8

2218

20-100

22.3

3003

20-100

23.2

4032

20-100

19.4

5005, 5050, 5052

20-100

23.8

5056

20-100

24.1

5083

20-100

23.4

5086

60-300

23.9

5154

20-100

23.9

5357

20-100

23.7

5456

20-100

23.9

6061, 6063

20-100

23.4

6101, 6151

20-100

23.0

7075

20-100

23.2

Metal or alloy

Aluminum and aluminum alloys

Aluminum (99.996%)

Wrought alloys

7079, 7178

20-100

23.4

242.0

20-100

22.5

295.0

20-100

22.9

356.0

20-100

21.4

380.0

20-100

21.2

413.0

20-100

20.5

443.0

20-100

22.1

514.0

20-100

23.9

520.0

20-100

25.2

Pure copper

20

16.5

Electrolytic tough pitch copper (ETP)

20-100

16.8

Deoxidized copper, high residual phosphorus (DHP)

20-300

17.7

Oxygen-free copper

20-300

17.7

Free-machining copper, 0.5% Te or 1% Pb

20-300

17.7

Gilding, 95%

20-300

18.1

Commercial bronze, 90%

20-300

18.4

Jewelry bronze, 87.5%

20-300

18.6

Casting alloys

Copper and copper alloys

Wrought coppers

Wrought alloys

Red brass, 85%

20-300

18.7

Low brass, 80%

20-300

19.1

Cartridge brass, 70%

20-300

19.9

Yellow brass

20-300

20.3

Muntz metal

20-300

20.8

Leaded commercial bronze

20-300

18.4

Low-leaded brass

20-300

20.2

Medium-leaded brass

20-300

20.3

High-leaded brass

20-300

20.3

Extra-high-leaded brass

20-300

20.5

Free-cutting brass

20-300

20.5

Leaded Muntz metal

20-300

20.8

Forging brass

20-300

20.7

Architectural bronze

20-300

20.9

Inhibited admiralty

20-300

20.2

Naval brass

20-300

21.2

Leaded naval brass

20-300

21.2

Manganese bronze (A)

20-300

21.2

5% (A)

20-300

17.8

8% (C)

20-300

18.2

Phosphor bronze

10% (D)

20-300

18.4

1.25%

20-300

17.8

Free-cutting phosphor bronze

20-300

17.3

30%

20-300

16.2

10%

20-300

17.1

65-18

20-300

16.2

55-18

20-300

16.7

65-12

20-300

16.2

High-silicon bronze(a)

20-300

18.0

Low-silicon bronze(b)

20-300

17.9

Aluminum bronze (3)

20-300

16.4

Aluminum-silicon bronze

20-300

18.0

Aluminum bronze (1)

20-300

16.8

Beryllium copper

20-300

17.8

88Cu-8Sn-4Zn

21-177

18.0

89Cu-11Sn

20-300

18.4

88Cu-6Sn-1.5Pb-4.5Zn

21-260

18.5

87Cu-8Sn-1Pb-4Zn

21-177

18.0

Cupronickel

Nickel silver

Casting alloys

87Cu-10Sn-1Pb-2Zn

21-177

18.0

80Cu-10Sn-10Pb

21-204

18.5

78Cu-7Sn-15Pb

21-204

18.5

85Cu-5Sn-5Pb-5Zn

21-204

18.1

72Cu-1Sn-3Pb-24Zn

21-93

20.7

67Cu-1Sn-3Pb-29Zn

21-93

20.2

61Cu-1Sn-1Pb-37Zn

21-260

21.6

60 ksi

21-204

20.5

65 ksi

21-93

21.6

110 ksi

21-260

19.8

Alloy 9A

...

17

Alloy 9B

20-250

17

Alloys 9C, 9D

...

16.2

20

11.7

0.06% C

20-100

11.7

0.22% C

20-100

11.7

0.40% C

20-100

11.3

Manganese bronze

Aluminum bronze

Iron and iron alloys

Pure iron

Fe-C alloys

0.56% C

20-100

11.0

1.08% C

20-100

10.8

1.45% C

20-100

10.1

Invar (36% Ni)

20

2.0

13Mn-1.2C

20

18.0

13Cr-0.35C

20-100

10.0

12.3Cr-0.4Ni-0.09C

20-100

9.8

17.7Cr-9.6Ni-0.06C

20-100

16.5

18W-4Cr-1V

0-100

11.2

Gray cast iron

0-100

10.5

Malleable iron (pearlitic)

20-400

12

Corroding lead (99.73 + % Pb)

17-100

29.3

5-95 solder

15-110

28.7

20-80 solder

15-110

26.5

50-50 solder

15-110

23.4

1% antimonial lead

20-100

28.8

96Pb-6Sb

20-100

28.8

94Pb-6Sb

20-100

27.2

8% antimonial lead

20-100

26.7

Lead and lead alloys

Hard lead

9% antimonial lead

20-100

26.4

SAE 14

20-100

19.6

Alloy 8

20-100

24.0

20

25.2

AM100A

18-100

25.2

AZ63A

20-100

26.1

AZ91A, B, C

20-100

26

AZ92A

18-100

25.2

HZ32A

20-200

26.7

ZH42

20-200

27

ZH62A

20-200

27.1

ZK51A

20

26.1

EZ33A

20-100

26.1

EK30A, EK41A

20-100

26.1

M1A, A3A

20-100

26

AZ31B, PE

20-100

26

AZ61A, AZ80A

20-100

26

Lead-base babbitt

Magnesium and magnesium alloys

Magnesium (99.8%)

Casting alloys

Wrought alloys

ZK60A, B

20-100

26

HM31A

20-93

26.1

Nickel (99.95% Ni + Co)

0-100

13.3

Duranickel

0-100

13.0

Monel

0-100

14.0

Monel (cast)

25-100

12.9

Inconel

20-100

11.5

Ni-o-nel

27-93

12.9

Hastelloy B

0-100

10.0

Hastelloy C

0-100

11.3

Hastelloy D

0-100

11.0

Hastelloy F

20-100

14.2

Hastelloy N

21-204

10.4

Hastelloy W

23-100

11.3

Hastelloy X

26-100

13.8

Illium G

0-100

12.19

Illium R

0-100

12.02

80Ni-20Cr

20-1000

17.3

60Ni-24Fe-16Cr

20-1000

17.0

35Ni-45Fe-20Cr

20-500

15.8

Nickel and nickel alloys

Constantan

20-1000

18.8

0-100

23

70Sn-30Pb

15-110

21.6

63Sn-37Pb

15-110

24.7

99.9% Ti

20

8.41

99.0% Ti

93

8.55

Ti-5Al-2.5Sn

93

9.36

Ti-8Mn

93

8.64

Pure zinc

20-250

39.7

AG40A alloy

20-100

27.4

AC41A alloy

20-100

27.4

0.08 Pb

20-40

32.5

0.3 Pb, 0.3 Cd

20-98

33.9(a)

Rolled zinc alloy, 1 Cu, 0.010 Mg

20-100

34.8(b)

Zn-Cu-Ti alloy, 0.8 Cu, 0.15 Ti

20-100

24.9(c)

Tin and tin alloys

Pure tin

Solder

Titanium and titanium alloys

Zinc and zinc alloys

Commercial rolled zinc

Pure metals

Beryllium

25-100

11.6

Cadmium

20

29.8

Calcium

0-400

22.3

Chromium

20

6.2

Cobalt

20

13.8

Gold

20

14.2

Iridium

20

6.8

Lithium

20

56

Manganese

0-100

22

Palladium

20

11.76

Platinum

20

8.9

Rhenium

20-50

6.7

Rhodium

20-100

8.3

Ruthenium

20

9.1

Silicon

0-1400

5

Silver

0-100

19.68

Tungsten

27

4.6

Vanadium

23-100

8.3

Zirconium

...

5.85

(a) Longitudinal; 23.4 transverse.

(b) Longitudinal; 21.1 transverse.

(c) Longitudinal; 19.4 transverse

Table 3 Thermal conductivity of metals and alloys Metal or alloy

Thermal conductivity near room temperature, cal/cm2 · cm · s · °C

Aluminum and aluminum alloys

Wrought alloys

EC (O)

0.57

1060 (O)

0.56

1100

0.53

2011 (T3)

0.34

2014 (O)

0.46

2024 (L)

0.45

2218 (T72)

0.37

3003 (O)

0.46

4032 (O)

0.37

5005

0.48

5050 (O)

0.46

5052 (O)

0.33

5056 (O)

0.28

5083

0.28

5086

0.30

5154

0.30

5357

0.40

5456

0.28

6061 (O)

0.41

6063 (O)

0.52

6101 (T6)

0.52

6151 (O)

0.49

7075 (T6)

0.29

7079 (T6)

0.29

7178

0.29

Casting alloys

242.0 (T77, sand)

0.36

295.0 (T4, sand)

0.33

356.0 (T51, sand)

0.40

380.0 (F, die)

0.26

413.0 (F, die)

0.37

443.0 (F, sand)

0.35

514.0 (F, sand)

0.33

520.0 (T4, sand)

0.21

Copper and copper alloys

Wrought coppers

Pure copper

0.941

Electrolytic tough pitch copper (ETP)

0.934

Deoxidized copper, high residual phosphorus (DHP)

0.81

Free-machining copper

0.5% Te

0.88

1% Pb

0.92

Wrought alloys

Gilding, 95%

0.56

Commercial bronze, 90%

0.45

Jewelry bronze, 87.5%

0.41

Red brass, 85%

0.38

Low brass, 80%

0.33

Cartridge brass, 70%

0.29

Yellow brass

0.28

Muntz metal

0.29

Leaded-commercial bronze

0.43

Low-leaded brass (tube)

0.28

Medium-leaded brass

0.28

High-leaded brass (tube)

0.28

High-leaded brass

0.28

Extra-high-leaded brass

0.28

Leaded Muntz metal

0.29

Forging brass

0.28

Architectural bronze

0.29

Inhibited admiralty

0.26

Naval brass

0.28

Leaded naval brass

0.28

Manganese bronze (A)

0.26

Phosphor bronze

5% (A)

0.17

8% (C)

0.15

10% (D)

0.12

1.25%

0.49

Free-cutting phosphor bronze

0.18

Cupronickel

30%

0.07

10%

0.095

Nickel silver

65-18

0.08

55-18

0.07

65-12

0.10

High-silicon bronze (A)

0.09

Low-silicon bronze (B)

0.14

Aluminum bronze, 5% Al

0.198

Aluminum bronze (3)

0.18

Aluminum-silicon bronze

0.108

Aluminum bronze (1)

0.144

Aluminum bronze (2)

0.091

Beryllium copper

0.20(a)

Casting alloys

Chromium copper (1% Cr)

0.4(a)

89Cu-11Sn

0.121

88Cu-6Sn-1.5Pb-4.5Zn

(b)

87Cu-8Sn-1Pb-4Zn

(c)

87Cu-10Sn-1Pb-2Zn

(c)

80Cu-10Sn-10Pb

(c)

Manganese bronze, 110 ksi

(d)

Aluminum bronze

Alloy 9A

(e)

Alloy 9B

(f)

Alloy 9C

(b)

Alloy 9D

(c)

Propeller bronze

(g)

Nickel silver

12% Ni

(h)

16% Ni

(h)

20% Ni

(i)

25% Ni

(j)

Silicon bronze

(h)

Iron and iron alloys

Pure iron

0.178

Cast iron (3.16 C, 1.54 Si, 0.57 Mn)

0.112

Carbon steel

0.23 C, 0.64 Mn

0.124

1.22 C, 0.35 Mn

0.108

Alloy steel (0.34 C, 0.55 Mn, 0.78 Cr, 3.53 Ni, 0.39 Mo, 0.05 Cu)

0.079

Type 410

0.057

Type 304

0.036

T1 tool steel

0.058

Lead and lead alloys

Corroding lead (99.73 + % Pb)

0.083

5-95 solder

0.085

20-80 solder

0.089

50-50 solder

0.111

1% antimonial lead

0.080

Hard lead

96Pb-4Sb

0.073

94Pb-6Sb

0.069

8% antimonial lead

0.065

9% antimonial lead

0.064

Lead-base babbitt

SAE 14

0.057

Alloy 8

0.058

Magnesium and magnesium alloys

Magnesium (99.8%)

0.367

Casting alloys

AM100A

0.17

AZ63A

0.18

AZ81A (T4)

0.12

AZ91A, B, C

0.17

AZ92A

0.17

HK31A (T6, sand cast)

0.22

HZ32A

0.26

ZH42

0.27

ZH62A

0.26

ZK51A

0.26

ZE41A (T5)

0.27

EZ33A

0.24

EK30A

0.26

EK41A (T5)

0.24

Wrought alloys

M1A

0.33

AZ31B

0.23

AZ61A

0.19

AZ80A

0.18

ZK60A, B (F)

0.28

ZE10A (O)

0.33

HM21A (O)

0.33

HM31A

0.25

Nickel and nickel alloys

Nickel (99.95% Ni + Co)

0.22

"A" nickel

0.145

"D" nickel

0.115

Monel

0.062

"K" Monel

0.045

Inconel

0.036

Hastelloy B

0.027

Hastelloy C

0.03

Hastelloy D

0.05

Illium G

0.029

Illium R

0.031

60Ni-24Fe-16Cr

0.032

35Ni-45Fe-20Cr

0.031

Constantan

0.051

Tin and tin alloys

Pure tin

0.15

Soft solder (63Sn-37Pb)

0.12

Tin foil (92Sn-8Zn)

0.14

Titanium and titanium alloys

Titanium (99.0%)

0.043

Ti-5Al-2.5Sn

0.019

Ti-2Fe-2Cr-2Mo

0.028

Ti-8Mn

0.026

Zinc and zinc alloys

Pure zinc

0.27

AG40A alloy

0.27

AC41A alloy

0.26

Commercial rolled zinc

0.08 Pb

0.257

0.06 Pb, 0.06 Cd

0.257

Rolled zinc alloy (1 Cu, 0.010 Mg)

0.25

Zn-Cu-Ti alloy (0.8 Cu, 0.15 Ti)

0.25

Pure metals

Beryllium

0.35

Cadmium

0.22

Chromium

0.16

Cobalt

0.165

Germanium

0.14

Gold

0.71

Indium

0.057

Iridium

0.14

Lithium

0.17

Molybdenum

0.34

Niobium

0.13

Palladium

0.168

Platinum

0.165

Plutonium

0.020

Rhenium

0.17

Rhodium

0.21

Silicon

0.20

Silver

1.0

Sodium

0.32

Tantalum

0.130

Thallium

0.093

Thorium

0.090

Tungsten

0.397

Uranium

0.071

Vanadium

0.074

Yttrium

0.035

(a) Depends on processing.

(b) 18% of Cu.

(c) 12% of Cu.

(d) 9.05% of Cu.

(e) 15% of Cu.

(f) 16% of Cu.

(g) 11% of Cu.

(h) 7% of Cu.

(i) 6% of Cu.

(j) 6.5% of Cu

Table 4 Electrical conductivity and resistivity of metals and alloys Metal or alloy

Conductivity, % IACS

Resistivity, μΩ· cm

1100 (O)

59

2.9

2024 (O)

50

3.4

3003 (O)

50

3.4

4032 (O)

40

4.3

5052 (all)

35

4.9

5056 (O)

29

5.9

6061 (T6)

43

4.0

6101 (T6)

57

3.0

7075 (O)

45

3.8

7075 (T6)

33

5.2

Pure copper

103.06

1.67

Electrolytic tough pitch copper (ETP)

101

1.71

Oxygen-free copper (OF)

101

1.71

Aluminum and aluminum alloys

Copper and copper alloys

Wrought copper

Free-machining copper

0.5% Te

95

1.82

1.0% Pb

98

1.76

Cartridge brass, 70%

28

6.2

Yellow brass

27

6.4

Leaded commercial bronze

42

4.1

Phosphor bronze, 1.25%

48

3.6

Nickel silver, 55-18

5.5

31

Low-silicon bronze (B)

12

14.3

Beryllium copper

22-30(a)

5.7-7.8(a)

Chromium copper (1% Cr)

80-90(a)

2.10

88Cu-8Sn-4Zn

11

15

87Cu-10Sn-1Pb-2Zn

11

15

0.04 oxide

100

1.72

1.25 Sn + P

48

3.6

5 Sn + P

18

11

8 Sn + P

13

13

15 Zn

37

4.7

Wrought alloys

Casting alloys

Electrical contact materials

Copper alloys

20 Zn

32

5.4

35 Zn

27

6.4

2 Be + Ni or Co(b)

17-21

9.6-11.5

Fine silver

104

1.59

92.5Ag-7.5Cu

88

2

90Ag-10Cu

85

2

72Ag-28Cu

87

2

72Ag-26Cu-2Ni

60

2.9

85Ag-15Cd

35

4.93

97Ag-3Pt

45

3.5

97Ag-3Pd

58

2.9

90Ag-10Pd

27

5.3

90Ag-10Au

40

4.2

60Ag-40Pd

8

23

70Ag-30Pd

12

14.3

Platinum

16

10.6

95Pt-5Ir

9

19

90Pt-10Ir

7

25

85Pt-15Ir

6

28.5

Silver and silver alloys

Platinum and platinum alloys

80Pt-20Ir

5.6

31

75Pt-25Ir

5.5

33

70Pt-30Ir

5

35

65Pt-35Ir

5

36

95Pt-5Ru

5.5

31.5

90Pt-10Ru

4

43

89Pt-11Ru

4

43

86Pt-14Ru

3.5

46

96Pt-4W

5

36

Palladium

16

10.8

95.5Pd-4.5Ru

7

24.2

90Pd-10Ru

6.5

27

70Pd-30Ag

4.3

40

60Pd-40Ag

4.0

43

50Pd-50Ag

5.5

31.5

72Pd-26Ag-1.71-2Ni

4

43

60Pd-40Cu

5

35(c)

45Pd-30Ag-20Au-5Pt

4.5

39

35Pd-30Ag-14Cu-10Pt-10Au-1Zn

5

35

Palladium and palladium alloys

Gold and gold alloys

Gold

75

2.35

90Au-10Cu

16

10.8

75Au-25Ag

16

10.8

72.5Au-14Cu-8.5Pt-4Ag-1Zn

10

17

69Au-25Ag-6Pt

11

15

41.7Au-32.5Cu-18.8Ni-7Zn

4.5

39

78.5Ni-20Cr-1.5Si (80-20)

1.6

108.05

73.5Ni-20Cr-5Al-1.5Si

1.2

137.97

68Ni-20Cr-8.5Fe-2Si

1.5

116.36

60Ni-16Cr-22.5Fe-1.5Si

1.5

112.20

35Ni-20Cr-43.5Fe-1.5Si

1.7

101.4

72Fe-23Cr-5Al

1.3

138.8

55Fe-37.5Cr-7.5Al

1.2

166.23

Molybdenum

34

5.2

Platinum

16

10.64

Tantalum

13.9

12.45

Tungsten

30

5.65

Electrical heating alloys

Ni-Cr and Ni-Cr-Fe alloys

Fe-Cr-Al alloys

Pure metals

Nonmetallic heating element materials

Silicon carbide (SiC)

1-1.7

100-200

Molybdenum disilicide (MoSi2)

4.5

37.24

Graphite

...

910.1

98Cu-2Ni

35

4.99

94Cu-6Ni

17

9.93

89Cu-11Ni

11

14.96

78Cu-22Ni

5.7

29.92

55Cu-45Ni (constantan)

3.5

49.87

87Cu-13Mn (manganin)

3.5

48.21

83Cu-13Mn-4Ni (manganin)

3.5

48.21

85Cu-10Mn-4Ni (shunt manganin)

4.5

38.23

70Cu-20Ni-10Mn

3.6

48.88

67Cu-5Ni-27Mn

1.8

99.74

99.8 Ni

23

7.98

71Ni-29Fe

9

19.95

80Ni-20Cr

1.5

112.2

Instrument and control alloys

Cu-Ni alloys

Cu-Mn-Ni alloys

Nickel-base alloys

75Ni-20Cr-3Al + Cu or Fe

1.3

132.98

76Ni-17Cr-4Si-3Mn

1.3

132.98

60Ni-16Cr-24Fe

1.5

112.2

35Ni-20Cr-45Fe

1.7

101.4

1.3

135.48

17.75

9.71

75Fe-22Ni-3Cr

3

78.13

72Mn-18Cu-10Ni

1.5

112.2

67Ni-30Cu-1.4Fe-1Mn

3.5

56.52

75Fe-22Ni-3Cr

12

15.79

66.5Fe-22Ni-8.5Cr

3.3

58.18

0.65% C

9.5

18

1% C

8

20

Chromium steel, 3.5% Cr

6.1

29

Tungsten steel, 6% W

6

30

Fe-Cr-Al alloy

72Fe-23Cr-5Al-0.5Co

Pure metals

Iron (99.99%)

Thermostat metals

Permanent magnet materials

Carbon steel

Cobalt steel

17% Co

6.3

28

36% Co

6.5

27

Cunico

7.5

24

Cunife

9.5

18

Comol

3.6

45

Alnico I

3.3

75

Alnico II

3.3

65

Alnico III

3.3

60

Alnico IV

3.3

75

Alnico V

3.5

47

Alnico VI

3.5

50

M-50

9.5

18

M-43

6-9

20-28

M-36

5.5-7.5

24-33

M-27

3.5-5.5

32-47

M-22

3.5-5

41-52

M-19

3.5-5

41-56

Intermediate alloys

Alnico alloys

Magnetically soft materials

Electrical steel sheet

M-17

3-3.5

45-58

M-15

3-3.5

45-69

M-14

3-3.5

58-69

M-7

3-3.5

45-52

M-6

3-3.5

45-52

M-5

3-3.5

45-52

Moderately high-permeability materials(d)

Thermenol

0.5

162

16 Alfenol

0.7

153

Sinimax

2

90

Monimax

2.5

80

Supermalloy

3

65

4-79 Moly Permalloy, Hymu 80

3

58

Mumetal

3

60

1040 alloy

3

56

High Permalloy 49, A-L 4750, Armco 48

3.6

48

45 Permalloy

3.6

45

Supermendur

4.5

40

2V Permendur

4.5

40

35% Co, 1% Cr

9

20

High-permeability materials(e)

Ingot iron

17.5

10

0.5% Si steel

6

28

1.75% Si steel

4.6

37

3.0% Si steel

3.6

47

Grain-oriented 3.0% Si steel

3.5

50

Grain-oriented 50% Ni iron

3.6

45

50% Ni iron

3.5

50

Low-carbon iron

17.5

10

1010 steel

14.5

12

1% Si

7.5

23

2.5% Si

4

41

3% Si

3.5

48

3% Si, grain-oriented

3.5

48

4% Si

3

59

Type 410

3

57

Type 416

3

57

Type 430

3

60

Relay steels and alloys after annealing

Low-carbon iron and steel

Silicon steels

Stainless steels

Type 443

3

68

Type 446

3

61

50% Ni

3.5

48

78% Ni

11

16

77% Ni (Cu, Cr)

3

60

79% Ni (Mo)

3

58

Type 302

3

72

Type 309

2.5

78

Type 316

2.5

74

Type 317

2.5

74

Type 347

2.5

73

Type 403

3

57

Type 405

3

60

Type 501

4.5

40

HH

2.5

80

HK

2

90

HT

1.7

100

Nickel irons

Stainless and heat-resistant alloys

(a) Precipitation hardened; depends on processing.

(b) A heat treatable alloy.

(c) Annealed and quenched.

(d) At low field strength and high electrical resistance.

(e) At higher field strength; annealed for optimal magnetic properties

Table 5 Approximate melting temperatures of metals and alloys Metal or alloy

Temperature

°C

°F

1100

655

1215

2017

640

1185

Alclad 2024

635

1180

3003

655

1210

5052

650

1200

6061

650

1205

7075

635

1175

242.0

635

1175

295.0

645

1190

336.0

565

1050

A380.0

595

1100

Aluminum and aluminum alloys

Wrought alloys

Casting alloys

413.0

580

1080

B443.0

630

1170

514.0

640

1185

520.0

605

1120

1080

1980

1.7% Be, 0.25% Co

870-980

1600-1800

1.9% Be, 0.25% Co

870-980

1600-1800

Red brass, 15% Zn

1025

1880

Cartridge brass, 30% Zn

955

1750

Yellow brass

930

1710

Muntz metal

905

1660

Admiralty brass

940

1720

Naval brass

900

1650

5% Sn

1050

1920

10% Sn

1000

1830

Aluminum bronze, 7% Al, 2.5% Fe

1045

1915

High-silicon bronze, 3.3% Si

1025

1880

Copper and copper alloys

Wrought copper and copper alloys

Pure copper

Beryllium copper

Phosphor bronze

Copper-nickel

10% Ni

1150

2100

21% Ni

1150-1200

2100-2190

30% Ni

1240

2260

72-18

1150

2100

65-18

1110

2030

55-18

1055

1930

85Cu-5Zn-5Sn-5Pb

1005

1840

G bronze, 10% Sn, 2% Zn

980

1800

M bronze, 8.5% Sn, 4% Zn

1000

1832

83Cu-7Sn-7Pb-3Zn

980

1800

Nickel-tin bronze (A)

1025

1880

Nickel-tin bronze (B)

1025

1880

Nickel-aluminum bronze

1045-1060

1910-1940

10% Ni

1150

2100

30% Ni

1240

2260

1000

1830

Nickel-silver

Casting alloys

Copper nickel

Nickel-silver

12% Ni

20% Ni

1145

2090

25% Ni

1045

1910

55.5Bi-44.5Pb

125

255

58Bi-42Sn

138

281

50Bi-26.7Pb-13.3Sn-10Cd

70

158

44.7Bi-22.6Pb-19.1In-5.3Cd-8.3Sn

47

117

Lead, 99.9% min Pb

327

621

Antimonial lead, 10% Sb

285

545

Tellurium lead, 0.04% Te, 0.06% Cu

327

621

50-50 lead-tin solder

216

421

60-40 tin-lead solder

190

374

Tin, 99.8% min Sn

232

449

0.08% Pb

419

786

1% Cu, 0.01% Mg

422

792

AG40A

387

728

AC41A

386

727

Low-melting-point metals and alloys

Zinc and zinc alloys

Rolled zinc

Magnesium and magnesium alloys

Casting alloys

AZ91B

595

1105

AZ91C

595

1105

AZ92A

593

1100

EZ33A

643

1189

HZ32A

648

1198

AZ31B

630

1170

AZ80A

610

1130

HK31A

651

1204

ZK60A

635

1175

ASTM grade 1

1683

3063

ASTM grade 2

1704

3100

ASTM grade 4

1670

3038

Ti-0.2Pd

1704

3100

Ti-5Al-2.5Sn

1650

3002

Ti-6Al-2Sn-4Zr-2Mo

1650

3000

Ti-6Al-6V-2Sn

1705

3100

Ti-6Al-4V

1650

3000

Ti-6Al-2Sn-4Zr-6Mo

1675

3050

Wrought alloys

Titanium and titanium alloys

Unalloyed titanium

Nickel and nickel alloys

Low-alloy nickels and nickel-coppers

Nickel 200, 201, and 205, 99.5% min Ni

1445

2635

Nickel 211, 95% Ni, 4.9% Mn, 0.1% C

1425

2600

Nickel 270, 99.98% min Ni

1455

2650

Duranickel 301

1440

2620

Nickel-beryllium, 2.7% Be

1265

2310

Monel alloy 400

1350

2460

Monel alloy R-405

1350

2460

Monel alloy K-500

1350

2460

"S" Monel (cast)

1290

2350

Inconel alloy 600

1415

2575

Inconel alloy 601

1370

2494

Inconel alloy 617

1375

2510

Inconel alloy 625

1350

2460

Inconel alloy 690

1375

2510

Inconel alloy 718

1335

2437

Inconel alloy X-750

1425

2600

Inconel alloy 751

1425

2600

Nickel-chromium-iron alloys

Nickel-chromium alloys

Nimonic alloy 75

1380

2515

Nimonic alloy 80A

1370

2500

Nimonic alloy 90

1370

2500

Nimonic alloy 115

1315

2400

Hastelloy alloy C-276

1370

2500

Hastelloy alloy G

1345

2450

Hastelloy alloy N

1400

2550

Hastelloy alloy S

1380

2516

Hastelloy alloy W

1315

2400

Hastelloy alloy X

1355

2470

Chlorimet 2 and 3

1315

2400

Incoloy alloy 800

1385

2525

Incoloy alloy 801

1385

2525

Incoloy alloy 802

1370

2500

Incoloy alloy 825

1400

2550

Alloy 713C (casting)

1290

2350

Alloy 713LC

1320

2410

A-286

1400

2550

IN-100

1335

2435

Nickel-chromium-molybdenum alloys

High-temperature high-strength alloys

IN-102

1290

2350

IN-738

1230-1315

2250-2400

IN-939

1230-1340

2255-2444

Alloy 25 (L-605)

1410

2570

Alloy 188

1330

2425

MAR-M 246

1355

2475

M-252

1370

2500

René 41

1370

2500

TD nickel

1455

2650

Udimet alloy 500

1395

2540

Udimet alloy 700

1400

2550

Waspaloy

1355

2475

B-1900

1300

2375

Multimet alloy N-155

1355

2470

Discaloy

1465

2665

Ingot iron

1535

2795

Wrought iron

1510

2750

Gray cast iron

1175

2150

Malleable iron

1230

2250

Irons and steels

Irons

Ductile iron

1175

2150

Ni-Resists (15.5-35% Ni)

1230

2250

Duriron (14.5% Si)

1260

2300

Carbon steel (SAE 1020)

1515

2760

4340 steel

1505

2740

9% Ni steel

1500

2730

Maraging steels (18Ni-200)

1455

2650

Type 201

1400-1450

2550-2650

Type 304

1400-1450

2550-2650

Type 316

1375-1400

2500-2550

Type 405

1480-1530

2700-2790

Type 409

1480-1530

2700-2790

Type 420

1450-1510

2650-2750

Type 430

1425-1510

2600-2750

Type 440C

1370-1480

2500-2700

Type 446

1425-1510

2600-2750

17-4 PH

1400-1440

2560-2625

AM 350

1400

2550

Steels

Wrought stainless steels

Cast stainless steels

Corrosion-resistant alloys

CA-15

1510

2750

CA-40

1495

2725

CB-7Cu-1

1510

2750

CF-8

1425

2600

CF-3M

1400

2550

CF-20

1415

2575

CH-20

1425

2600

CN-7M

1455

2650

HA

1510

2750

HC

1495

2725

HD

1480

2700

HE

1455

2650

HF

1400

2550

HH

1370

2500

HK

1400

2550

HL

1425

2600

HN

1370

2500

HP, HT, and HU

1345

2450

HW AND HX

1290

2350

Heat-resistant alloys

Refractory metals and alloys

Niobium

2470

4475

Nb-1Zr

2400

4350

Molybdenum

2610

4730

Mo-0.5Ti

2610

4730

Tantalum

2995

5425

Tungsten

3410

6170

W-25Re

3100

5612

W-50Re

2550

4622

Gold (99.995% min Au)

1063

1945

Silver (99.9% min Ag)

961

1761

BAg-1 (brazing alloy)

635

1175

Platinum

1791

3256

Palladium

1552

2826

Iridium

2443

4429

Rhodium

1960

3560

90Pt-10Ir

1782

3240

60Pd-40Ag

1338

2440

Precious metals and alloys

Table 6 Physical properties of common gases and liquids Name

Formula

Molecular weight

Density, g/L(a)

Melting point, °C

Boiling point, °C

Autoignition point, °C

Explosive limits, percent by volume air

point, °C Lower

Upper

Acetylene

C2H2

26.04

1.173

-81

-83.6 subl.(c)

335

2.5

80.0

Air

...

28.97(b)

1.2929

...

...

...

...

...

Ammonia

NH3

17.03

0.7710

-77.7

-33.4

780

16.0

27.0

Argon

Ar

39.94

1.784

-189.2

-185.7

...

...

...

Butane-n

C4H10

58.12

2.703

-138

-0.6

430

1.6

8.5

Butane-i

C4H10

58.12

2.637

-159

-11.7

...

...

...

Butylene-n

C4H8

56.10

2.591

-185

-6.3

...

1.7

9.0

Carbon dioxide

CO2

44.01

1.977

-57 (at 5 atm)

-78.5 subl.(c)

...

...

...

Carbon monoxide

CO

28.01

1.250

-207

-191

650

12.5

74.2

Chlorine

Cl2

70.91

3.214

-101

-34

...

...

...

Ethane

C2H6

30.07

1.356

-172

-88.6

510

3.1

15.0

Ethylene

C2H4

28.05

1.261

-169

-103.7

543

3.0

34.0

Helium

He

4.003

0.1785

-272

-268.9

...

...

...

Heptane-n

C7H16

100.20

0.684 g/cm3

-90.6

98.4

233

1.0

6.0

Hexane-n

C6H14

86.17

0.6594 g/cm3

-95.3

68.7

248

1.2

6.9

Hydrogen

H2

2.016

0.0899

-259.2

-252.8

580

4.1

74.2

Hydrogen chloride

HCl

36.47

1.639

-112

-84

...

...

...

Hydrogen

HF

20.01

0.921

-92.3

19.5

...

...

...

fluoride

Hydrogen sulfide

H2S

34.08

1.539

-84

-62

...

4.3

45.5

Methane

CH4

16.04

0.7168

-182.5

-161.5

538

5.3

13.9

Nitrogen

N2

28.016

1.2506

-209.9

-195.8

...

...

...

Octane-n

C8H18

114.23

0.7025 g/cm3

-56.8

125.7

232

0.8

3.2

Oxygen

O2

32.00

1.4290

-218.4

-183.0

...

...

...

Pentane-n

C5H12

72.15

0.016 g/cm3

-131

36.2

310

1.4

8.0

Propane

C3H8

44.09

2.020

-189

-44.5

465

2.4

9.5

Propylene

C3H6

42.05

1.915

-184

-48

458

2.0

11.1

Sulfur dioxide

SO2

64.06

2.926

-75.7

-10.0

...

...

...

Source: Corrosion Tests and Standards: Application and Interpretation, ASTM, 1995, p 27 (a) Density of gases is given in g/L at 0 °C and 760 mm Hg (1 atm). Density of liquids is given in g/cm3 at 20 °C.

(b) Because air is a mixture, it does not have a true molecular weight. This is the average molecular weight of its constituents.

(c) Subl. indicates that the substance sublimes at the temperature listed.

Table 7 Approximate equivalent hardness numbers for nonaustenitic steels (Rockwell C hardness range) For carbon and alloy steels in the annealed, normalized, and quenched-and-tempered conditions. Rockwell C hardness No., 150 kgf, HRC

Vickers hardness No., HV

68

Brinell No.

hardness

Knoop hardness No., 500 gf and over, HK

Rockwell hardness No.

Rockwell superficial hardness No.

A scale, 60 kgf, HRA

D scale, 100 kgf, HRD

15-N scale, 15 kgf, HR15-N

30-N scale, 30 kgf, HR 30-N

45-N scale, 45 kgf, HR 45-N

Sclerscope hardness No.

Rockwell C Tensile strength (approximate) ksi

10 mm standard ball, 3000 kgf, HBS

10 mm carbide ball, 3000 kgf, HBW

940

...

...

920

85.6

76.9

93.2

894.4

75.4

97.3

...

67

900

...

...

895

85.0

76.1

92.9

83.6

74.2

95.0

...

66

865

...

...

870

84.5

75.4

92.5

82.8

73.3

92.7

...

65

832

...

(739)

846

83.9

74.5

92.2

81.9

72.0

90.6

...

64

800

...

(722)

822

83.4

73.8

91.8

81.1

71.0

88.5

...

63

772

...

(705)

799

82.8

73.0

91.4

80.1

69.9

86.5

...

62

746

...

(688)

776

82.3

72.2

91.1

79.3

68.8

84.5

...

61

720

...

(670)

754

81.8

71.5

90.7

78.4

67.7

82.6

...

60

697

...

(654)

732

81.2

70.7

90.2

77.5

66.6

80.8

...

59

674

...

(634)

710

80.7

69.9

89.8

76.6

65.5

79.0

351

58

653

...

615

690

80.1

69.2

89.3

75.7

64.3

77.3

338

57

633

...

595

670

79.6

68.5

88.9

74.8

63.2

75.6

325

56

613

...

577

650

79.0

67.7

88.3

73.9

62.0

74.0

313

55

595

...

560

630

68.5

66.9

87.9

73.0

60.9

72.4

301

54

577

...

543

612

78.0

66.1

87.4

72.0

59.8

70.9

292

53

560

...

525

594

77.4

65.4

86.9

71.2

58.6

69.4

283

52

544

(500)

512

576

76.8

64.6

86.4

70.2

57.4

67.9

273

51

528

(487)

496

558

76.3

63.8

85.9

69.4

56.1

66.5

264

50

513

(475)

481

542

75.9

63.1

85.5

68.5

55.0

65.1

255

49

498

(464)

469

526

75.2

62.1

85.0

67.6

53.8

63.7

246

48

484

451

455

510

74.7

61.4

84.5

66.7

52.5

62.4

238

47

471

442

443

495

74.1

60.8

83.9

65.8

51.4

61.1

229

46

458

432

432

480

73.6

60.0

83.5

64.8

50.3

59.8

221

45

446

421

421

466

73.1

59.2

83.0

64.0

49.0

58.5

215

44

434

409

409

452

72.5

58.5

82.5

63.1

47.8

57.3

208

43

423

400

400

438

72.0

57.7

82.0

62.2

46.7

56.1

201

42

412

390

390

426

71.5

56.9

81.5

61.3

45.5

54.9

194

41

402

381

381

414

70.9

56.2

80.9

60.4

44.3

53.7

188

40

392

371

371

402

70.4

55.4

80.4

59.5

43.1

52.6

182

39

382

362

362

391

69.9

54.6

79.9

58.6

41.9

51.5

177

38

372

353

353

380

69.4

53.8

79.4

57.7

40.8

50.4

171

37

363

344

344

370

68.9

53.1

78.8

56.8

39.6

49.3

166

36

354

336

336

360

68.4

52.3

78.3

55.9

38.4

48.2

161

35

345

327

327

351

67.9

51.5

77.7

55.0

37.2

47.1

156

34

336

319

319

342

67.4

50.8

77.2

54.2

36.1

46.1

152

33

327

311

311

334

66.8

50.0

76.6

53.3

34.9

45.1

149

32

318

301

301

326

66.3

49.2

76.1

52.1

33.7

44.1

146

31

310

294

294

318

65.8

48.4

75.6

51.3

32.5

43.1

141

30

302

286

286

311

65.3

47.7

75.0

50.4

31.3

42.2

138

29

294

279

279

304

64.8

47.0

74.5

49.5

30.1

41.3

135

28

286

271

271

297

64.3

46.1

73.9

48.6

28.9

40.4

131

27

279

264

264

290

63.8

45.2

73.3

47.7

27.8

39.5

128

26

272

258

258

284

63.3

44.6

72.8

46.8

26.7

38.7

125

25

266

253

253

278

62.3

43.8

72.2

45.9

25.5

37.8

123

24

260

247

247

272

62.4

43.1

71.6

45.0

24.3

37.0

119

23

254

243

243

266

62.0

42.1

71.0

44.0

23.1

36.3

117

22

248

237

237

261

61.5

41.6

70.5

43.2

22.0

35.5

115

21

243

231

231

256

61.0

40.9

69.9

42.3

20.7

34.8

112

20

238

226

226

251

60.5

40.1

69.4

41.5

19.6

34.2

110

Note: Values in parenthesis are beyond the normal range and are presented for information only. Source: ASTM E 140

Table 8 Approximate equivalent hardness numbers for nonaustenitic steels (rockwell B hardness range) For carbon and alloy steels in the annealed, normalized, and quenched-and-tempered conditions Rockwell B hardness No., 100 kgf, HRB

Vickers hardness No., HV

100

Tensile strength (approximate), ksi

Rockwell B hardness No., 100 kgf, HRB

72.9

116

100

82.5

71.9

114

99

81.8

70.9

109

98

Brinell hardness No., 3000 kgf, HBS

Knoop hardness No., 500 gf and over, HK

Rockwell A hardness No., 60 kgf, HRA

Rockwell F hardness No., 60 kgf, HRF

Rockwell superficial hardness No.

15-T scale, 15 kgf, HR 15-T

30-T scale, 30 kgf, HR 30-T

45-T scale, 45 kgf, HR 45-T

240

240

251

61.5

...

93.1

83.1

99

234

234

246

60.9

...

92.8

98

228

228

241

60.2

...

92.5

97

222

222

236

59.5

...

92.1

81.1

69.9

104

97

96

216

216

231

58.9

...

91.8

80.4

68.9

102

96

95

210

210

226

58.3

...

91.5

79.8

67.9

100

95

49

205

205

221

57.6

...

91.2

79.1

66.9

98

94

93

200

200

216

57.0

...

90.8

78.4

65.9

94

93

92

195

195

211

56.4

...

90.5

77.8

64.8

92

92

91

190

190

206

55.8

...

90.2

77.1

63.8

90

91

90

185

185

201

55.2

...

89.9

76.4

62.8

89

90

89

180

180

196

54.6

...

89.5

75.8

61.8

88

89

88

176

176

192

54.0

...

89.2

75.1

60.8

86

88

87

172

172

188

53.4

...

88.9

74.4

59.8

84

87

86

169

169

184

52.8

...

88.6

73.8

58.8

83

86

85

165

165

180

52.3

...

88.2

73.1

57.8

82

85

84

162

162

176

51.7

...

87.9

72.4

56.8

81

84

83

159

159

173

51.1

...

87.6

71.8

55.8

80

83

82

156

156

170

50.6

...

87.3

71.1

54.8

77

82

81

153

153

167

50.0

...

86.9

70.4

53.8

73

81

80

150

150

164

49.5

...

86.6

69.7

52.8

72

80

79

147

147

161

48.9

...

86.3

69.1

51.8

70

79

78

144

144

158

48.4

...

86.0

68.4

50.8

69

78

77

141

141

155

47.9

...

85.6

67.7

49.8

68

77

76

139

139

152

47.3

...

85.3

67.1

48.8

67

76

75

137

137

150

46.8

99.6

85.0

66.4

47.8

66

75

74

135

135

147

46.3

99.1

84.7

65.7

46.8

65

74

73

132

132

145

45.8

98.5

84.3

65.1

45.8

64

73

72

130

130

143

45.3

98.0

84.0

64.4

44.8

63

72

71

127

127

141

44.8

97.4

83.7

63.7

43.8

62

71

70

125

125

139

44.3

96.8

83.4

63.1

42.8

61

70

69

123

123

137

43.8

96.2

83.0

62.4

41.8

60

69

68

121

121

135

43.3

95.6

82.7

61.7

40.8

59

68

67

119

119

133

42.8

95.1

82.4

61.0

39.8

58

67

66

117

117

131

42.3

94.5

82.1

60.4

38.7

57

66

65

116

116

129

41.8

93.9

81.8

59.7

37.7

56

65

64

114

114

127

41.4

93.4

81.4

59.0

36.7

...

64

63

112

112

125

40.9

92.8

81.1

58.4

35.7

...

63

62

110

110

124

40.4

92.2

80.8

57.7

34.7

...

62

61

108

108

122

40.0

91.7

80.5

57.0

33.7

...

61

60

107

107

120

39.5

91.1

80.1

56.4

32.7

...

60

59

106

106

118

39.0

90.5

79.8

55.7

31.7

...

59

58

104

104

117

38.6

90.0

79.5

55.0

30.7

...

58

57

103

103

115

38.1

89.4

79.2

54.4

29.7

...

57

56

101

101

114

37.7

88.8

78.8

53.7

28.7

...

56

55

100

100

112

37.2

88.2

78.5

50.0

27.7

...

55

54

...

...

111

36.8

87.7

78.2

52.4

26.7

...

54

53

...

...

110

36.3

87.1

77.9

51.7

25.7

...

53

52

...

...

109

35.9

86.5

77.5

51.0

24.7

...

52

51

...

...

108

35.5

86.0

77.2

50.3

23.7

...

51

50

...

...

107

35.0

85.4

76.9

49.7

22.7

...

50

49

...

...

106

34.6

84.8

76.6

49.0

21.7

...

49

48

...

...

105

34.1

84.3

76.2

48.3

20.7

...

48

47

...

...

104

33.7

83.7

75.9

47.7

19.7

...

47

46

...

...

103

33.3

83.1

75.6

47.0

18.7

...

46

45

...

...

102

32.9

82.6

75.3

46.3

17.7

...

45

44

...

...

101

32.4

82.0

74.9

45.7

16.7

...

44

43

...

...

100

32.0

81.4

74.6

45.0

15.7

...

43

42

...

...

99

31.6

80.8

74.3

44.3

14.7

...

42

41

...

...

98

31.2

80.3

74.0

43.7

13.6

...

41

40

...

...

97

30.7

79.7

73.6

43.0

12.6

...

40

39

...

...

96

30.3

79.1

73.3

42.3

11.6

...

39

38

...

...

95

29.9

78.6

73.0

41.0

10.6

...

38

37

...

...

94

29.5

78.0

72.7

41.0

9.6

...

37

36

...

...

93

29.1

77.4

72.3

40.3

8.6

...

36

35

...

...

92

28.7

76.9

72.0

39.6

7.6

...

35

34

...

...

91

28.2

76.3

71.7

39.0

6.6

...

34

33

...

...

90

27.8

75.7

71.4

38.3

5.6

...

33

32

...

...

89

27.4

75.2

71.0

37.6

4.6

...

32

31

...

...

88

27.0

74.6

70.7

37.0

3.6

...

31

30

...

...

87

26.6

74.0

70.4

36.3

2.6

...

30

Source: ASTM E 140

Table 9 Approximate equivalent hardness numbers for austenitic stainless steel sheet (Rockwell C hardness range) For types 201, 202, 301, 302, 304, 304L, 305, 316, 316L, 321 and 347. Tempers range from annealed to extra hard for type 301, with a smaller range for the other types. Test coupon thickness; 0.1 to 0.050 in. (2.5 to 1.27 mm) Rockwell hardness No.

Rockwell superficial hardness No.

C scale, 150 kgf, diamond penetrator, HRC

A scale, 60 kgf, diamond penetrator, HRA

15-N scale, 15 kgf, superficial diamond penetrator, HR 15-N

30-N scale, 30 kgf, superficial diamond penetrator, HR 30-N

45-N scale, 45 kgf, superficial diamond penetrator, HR 45-N

48

74.4

84.1

66.2

52.1

47

73.9

83.6

65.3

50.9

46

73.4

83.1

64.5

49.8

45

72.9

82.6

63.6

48.7

44

72.4

82.1

62.7

47.5

43

71.9

81.6

61.8

46.4

42

71.4

81.0

61.0

45.2

41

70.9

80.5

60.1

44.1

40

70.4

80.0

59.2

43.0

39

69.9

79.5

58.4

41.8

38

69.3

79.0

57.5

40.7

37

68.8

78.5

56.6

39.6

36

68.3

78.0

55.7

38.4

35

67.8

77.5

54.9

37.3

34

67.3

77.0

54.0

36.1

33

66.8

76.5

53.1

35.0

32

66.3

75.9

52.3

33.9

31

65.8

75.4

51.4

32.7

30

65.3

74.9

50.5

31.6

29

64.8

74.4

49.6

30.4

28

64.3

73.9

48.8

29.3

27

63.8

73.4

47.9

28.2

26

63.3

72.9

47.0

27.0

25

62.8

72.4

40.2

25.9

24

62.3

71.9

45.3

24.8

23

61.8

71.3

44.4

23.6

22

61.3

70.8

43.5

22.5

21

60.8

70.3

42.7

21.3

Source: ASTM E 140

Table 10 Approximate equivalent hardness numbers for austenitic stainless steel sheet (Rockwell B hardness range) For types 201, 202, 301, 302, 304, 304L, 305, 316, 316L, 321 and 347. Tempers range from annealed to extra hard for type 301, with a smaller range for the other types. Test coupon thickness; 0.1 to 0.050 in. (2.5 to 1.27 mm) Rockwell hardness No.

B 100

scale, kgf,

Rockwell superficial hardness No.

A scale, 60 kgf, diamond penetrator, HRA

F 60

scale, kgf,

15-T scale, 15 kgf,

30-T scale, 30 kgf,

45-T scale, 45 kgf,

in. (1.588 mm) ball, HRF

in. (1.588 mm) ball, HR 15-T

in. (1.588 mm) ball, HR 30-T

in. (1.588 mm) ball, HR 45-T

100

61.5

(113.9)

91.5

80.4

70.2

99

60.9

(113.2)

91.2

79.7

69.2

98

60.3

(112.5)

90.8

79.0

68.2

97

59.7

(111.8)

90.4

78.3

67.2

96

59.1

(111.1)

90.1

77.7

66.1

95

58.5

(110.5)

89.7

77.0

65.1

94

58.0

(109.8)

89.3

76.3

64.1

93

57.4

(109.1)

88.9

75.6

63.1

92

56.8

(108.4)

88.6

74.9

62.1

91

56.2

(107.8)

88.2

74.2

61.1

90

55.6

(107.1)

87.8

73.5

60.1

89

55.0

(106.4)

87.5

72.8

59.0

88

54.5

(105.7)

87.1

72.1

58.0

87

53.9

(105.0)

86.7

71.4

57.0

86

53.3

(104.4)

86.4

70.7

56.0

85

52.7

(103.7)

86.0

70.0

55.0

in. (1.588 mm) ball, HRB

84

52.1

(103.0)

85.6

69.3

54.0

83

51.5

(102.3)

85.2

68.6

52.9

82

50.9

(101.7)

84.9

67.9

51.9

81

50.4

(101.0)

84.5

67.2

50.9

80

49.8

(100.3)

84.1

66.5

49.9

79

49.2

99.6

83.8

65.8

48.9

78

48.6

99.0

83.4

65.1

47.9

77

48.0

98.3

83.0

64.4

46.8

76

47.4

97.6

82.6

63.7

45.8

75

46.9

96.9

82.3

63.0

44.8

74

46.3

96.2

81.9

62.4

43.8

73

45.7

95.6

81.5

61.7

42.8

72

45.1

94.9

81.2

61.0

41.8

71

44.5

94.2

80.8

60.3

40.7

70

43.9

93.5

80.4

59.6

39.7

69

43.3

92.8

80.1

58.9

38.7

68

42.8

92.2

79.7

58.2

37.7

67

42.2

91.5

79.3

57.5

36.7

66

41.6

90.8

78.9

56.8

35.7

65

41.0

90.1

78.6

56.1

34.7

64

40.4

89.5

78.2

55.4

33.6

63

39.8

88.8

77.8

54.7

32.6

62

39.3

88.1

77.5

54.0

31.6

61

38.7

87.4

77.1

53.3

30.6

60

38.1

86.8

76.7

52.6

29.6

Note: Rockwell F numbers in parenthesis are beyond the normal range and are presented for information only. Source: ASTM E 140

Fig. 1 Hardness of some alloy microconstituents and minerals

Table 11 Approximate Brinell-Rockwell B hardness numbers for equivalent austenitic stainless steel plate in the annealed condition Rockwell hardness No., B scale (100 kgf, 1.588 mm ball) HRB

Brinell hardness No. (3000 kgf, 10 mm steel ball), HBS

100

256

99

248

98

240

97

233

96

226

95

219

94

213

93

207

92

202

91

197

90

192

89

187

88

183

87

178

86

174

85

170

84

167

83

163

82

160

81

156

80

153

79

150

78

147

77

144

76

142

75

139

74

137

73

135

72

132

71

130

70

128

69

126

68

124

67

122

66

120

65

118

64

116

63

114

62

113

61

111

60

110

Table 12 Approximate equivalent hardness numbers for wrought aluminum products Brinell hardness No., 500 kgf, 10 mm ball, HBS

Vickers hardness No., 15 kgf, HV

Rockwell hardness No.

Rockwell superficial hardness No.

B scale, 100 kgf,

E scale, 100 kgf,

H scale, 60 kgf,

15-T scale, 15 kgf,

30-T scale, 30 kgf,

15-W scale, 15 kgf,

in. ball, HRB

in. HRE

in. ball, HRH

in. ball, HR 15-T

in. ball, HR 30-T

in. ball, HR 15-W

ball,

160

189

91

...

...

89

77

95

155

183

90

...

...

89

76

95

150

177

89

...

...

89

75

94

145

171

87

...

...

88

74

94

140

165

86

...

...

88

73

94

135

159

84

...

...

87

71

93

130

153

81

...

...

87

70

93

125

147

79

...

...

86

68

92

120

141

76

101

...

86

67

92

115

135

72

100

...

86

65

91

110

129

69

99

...

85

63

91

105

123

65

98

...

84

61

91

100

117

60

...

...

83

59

90

95

111

56

96

...

82

57

90

90

105

51

94

108

81

54

89

85

98

46

91

107

80

52

89

80

92

40

88

106

78

50

88

75

86

34

84

104

76

47

87

70

80

28

80

102

74

44

86

65

74

...

75

100

72

...

85

60

68

...

70

97

70

...

83

55

62

...

65

94

67

...

82

50

56

...

59

91

64

...

80

45

50

...

53

87

62

...

79

40

44

...

46

83

59

...

77

Source: ASTM E 140

Table 13 Approximate equivalent hardness numbers for wrought coppers (>99% Cu, alloys C10200 through C14200) Vickers hardness No.

Knoop hardness No.

Rockwell hardness No.

superficial

Rockwell hardness No.

Rockwell hardness No.

superficial

No. B scale, 100 kgf,

No. F scale, 60 kgf,

15-T scale, 15 kgf,

30-T scale, 30 kgf,

45-T scale, 45 kgf,

in. (1.588 mm) ball, HRF

in. (1.588 mm) ball, HR 15-T

in. (1.588 mm) ball, HR 30-T

in. (1.588 mm) ball, HR 45-T

15-T scale, 15 kgf,

15-T scale, 15 kgf,

30-T scale, 30 kgf,

in. (1.588 mm) ball, HR 15T

in. (1.588 mm) ball, HR 30T

0.020 in. (0.51 mm) strip

0.040 in. (1.02 mm) strip and greater

Brinell hardness No.

500 kgf, 10 mm diameter ball, HBS, 0.080 in. (2.03 mm) strip

20 kgf, 2 mm diameter ball, HBS, 0.040 in (1.02 mm) strip

1 kgf HV

100 gf HV

1 kgf, HK

500 gf, HK

in. (1.588 mm) ball, HR 15T 0.010 in. (0.25 mm) strip

130

127.0

138.7

133.8

...

85.0

...

67.0

99.0

...

69.5

49.0

...

119.0

128

125.2

136.8

132.1

83.0

84.5

...

66.0

98.0

87.0

68.5

48.0

...

117.5

126

123.6

134.9

130.4

...

84.0

...

65.0

97.0

...

67.5

46.5

120.0

115.0

in. (1.588 mm) ball, HRB

124

121.9

133.0

128.7

82.5

83.5

...

64.0

96.0

86.0

66.5

45.0

117.5

113.0

122

121.1

131.0

127.0

...

83.0

...

62.5

95.5

85.5

66.0

44.0

115.0

111.0

120

118.5

129.0

125.2

82.0

82.5

...

61.0

95.0

...

65.0

42.5

112.0

109.0

118

116.8

127.1

123.5

81.5

...

...

59.5

94.0

85.0

64.0

41.0

110.0

107.5

116

115.0

125.1

121.7

...

82.0

...

58.5

93.0

...

63.0

40.0

107.0

105.5

114

113.5

123.2

119.9

81.0

81.5

...

57.0

92.5

84.5

62.0

38.5

105.0

103.5

112

111.8

121.4

118.1

80.5

81.0

...

55.0

91.5

...

61.0

37.0

102.0

102.0

110

109.9

119.5

116.3

80.0

...

...

53.5

91.0

84.0

60.0

36.0

99.5

100.0

108

108.3

117.5

114.5

...

80.5

...

52.0

90.5

83.5

59.0

34.5

97.0

98.0

106

106.6

115.6

112.6

79.5

80.0

...

50.0

89.5

...

58.0

33.0

94.5

96.0

104

104.9

113.5

110.1

79.0

79.5

...

48.0

88.5

83.0

57.0

32.0

92.0

94.0

102

103.2

111.5

108.0

78.5

79.0

...

46.5

87.5

82.5

56.0

30.0

89.5

92.0

100

101.5

109.4

106.0

78.0

78.0

...

44.5

87.0

82.0

55.0

28.5

87.0

90.0

98

99.8

107.3

104.0

77.5

77.5

...

42.0

85.5

81.0

53.5

26.5

84.5

88.0

96

98.0

105.3

102.1

77.0

77.0

...

40.0

84.5

80.5

52.0

25.5

82.0

86.5

94

96.4

103.2

100.0

76.5

76.5

...

38.0

83.0

80.0

51.0

23.0

79.5

85.0

92

94.7

101.0

98.0

76.0

75.5

...

35.5

82.0

79.0

49.0

21.0

77.0

83.0

90

93.0

98.9

96.0

75.5

75.0

...

33.0

81.0

78.0

47.5

19.0

74.5

81.0

88

91.2

96.9

94.0

75.0

74.5

...

30.5

79.5

77.0

46.0

16.5

...

79.0

86

89.7

95.5

92.0

74.5

73.5

...

28.0

78.0

76.0

44.0

14.0

...

77.0

84

87.9

92.3

90.0

74.0

73.0

...

25.5

76.5

75.0

43.0

12.0

...

75.0

82

86.1

90.1

87.9

73.5

72.0

...

23.0

74.5

74.5

41.0

9.5

...

73.0

80

84.5

87.9

86.0

72.5

71.0

...

20.0

73.0

73.5

39.5

7.0

...

71.5

78

82.8

85.7

84.0

72.0

70.0

...

17.0

71.0

72.5

37.5

5.0

...

69.5

76

81.0

83.5

81.9

71.5

69.5

...

14.5

69.0

71.5

36.0

2.0

...

67.5

74

79.2

81.1

79.9

71.0

68.5

...

11.5

67.5

70.0

34.0

...

...

66.0

72

77.6

78.9

78.7

70.0

67.5

...

8.5

66.0

69.0

32.0

...

...

64.0

70

75.8

76.8

76.6

69.5

66.5

...

5.0

64.0

67.5

30.0

...

...

62.0

68

74.3

74.1

74.4

69.0

65.5

...

2.0

62.0

66.0

28.0

...

...

60.5

66

72.6

71.9

71.9

68.0

64.5

...

...

60.0

64.5

25.5

...

...

58.5

64

70.9

69.5

70.0

67.5

63.5

...

...

58.0

63.5

23.5

...

...

57.0

62

69.1

67.0

67.9

66.5

62.0

...

...

56.0

61.0

21.0

...

...

55.0

60

67.5

64.6

65.9

66.0

61.0

...

...

54.0

59.0

18.0

...

...

53.0

58

65.8

62.0

63.8

65.0

60.0

...

...

51.5

57.0

15.5

...

...

51.5

56

64.0

59.8

61.8

64.5

58.5

...

...

49.0

55.0

13.0

...

...

49.5

54

62.3

57.4

59.5

63.5

57.5

...

...

47.0

53.0

10.0

...

...

48.0

52

60.7

55.0

57.2

63.0

56.0

...

...

44.0

51.5

7.5

...

...

46.5

48

57.3

50.3

52.7

61.0

53.5

...

...

39.0

47.5

1.5

...

...

42.0

46

55.8

48.0

50.2

60.5

52.0

...

...

36.0

45.0

...

...

...

41.0

44

53.9

45.9

47.8

59.5

51.0

...

...

33.5

43.0

...

...

...

...

42

52.2

43.7

45.2

58.5

49.5

...

...

30.5

41.0

...

...

...

...

40

51.3

40.2

42.8

57.5

48.0

...

...

28.0

38.5

...

...

...

...

Source: ASTM E 140

Fig. 2 Strength versus density for various engineered materials. Strength is yield strength for metals/alloys and polymers, compressive strength for ceramics (note the broken property envelope lines), tear strength for elastomers, and tensile strength for composites. It should be noted that the tensile strength of engineering ceramics is about 15 times smaller than its compressive strength. Abbreviation key: CFRP, carbon-fiber reinforced polymer; GFRP, glass-fiber reinforced polymer; KFRP, kevlar-fiber reinforced polymer; PMMA, polymethyl methacrylate; Mel, melamines; PP, polypropylene; PC, polycarbonate; PS, polystyrene; PVC, polyvinyl chloride; HDPE, high-density polyethylene; LDPE, low-density polyethylene; PTFE, polytetrafluoroethylene; PU, polyurethane

Table 14 Approximate equivalent hardness numbers for cartridge brass (70% Cu, 30% Zn) Vickers hardness No., HV

Rockwell hardness No.

Brinell hardness No., 500 kgf, 10 mm ball, HBS

scale, kgf,

15-T scale, 15 kgf,

30-T scale, 30 kgf,

45-T scale, 45 kgf,

in. (1.588 mm) ball, HRB

in. (1.588 mm) ball, HRF

in. (1.588 mm) ball, HR 15-T

in. (1.588 mm) ball, HR 30-T

in. (1.588 mm) ball, HR 45-T

196

93.5

110.0

90.0

77.5

66.0

169

194

...

109.5

...

...

65.5

167

192

93.0

...

...

77.0

65.0

166

190

92.5

109.0

...

76.5

64.5

164

188

92.0

...

89.5

...

64.0

162

186

91.5

108.5

...

76.0

63.5

161

184

91.0

...

...

75.5

63.0

159

182

90.5

108.0

89.0

...

62.5

157

180

90.0

107.5

...

75.0

62.0

156

178

89.0

...

...

74.5

61.5

154

176

88.5

107.0

...

...

61.0

152

174

88.0

...

88.5

74.0

60.5

150

172

87.5

106.5

...

73.5

60.0

149

170

87.0

...

...

...

59.5

147

168

86.0

106.0

88.0

73.0

59.0

146

166

85.5

...

...

72.5

58.5

144

B 100

scale, kgf,

F 60

Rockwell superficial hardness No.

164

85.0

105.5

...

72.0

58.0

142

162

84.0

105.0

87.5

...

57.5

141

160

83.5

...

...

71.5

56.5

139

158

83.0

104.5

...

71.0

56.0

138

156

82.0

104.0

87.0

70.5

55.5

136

154

81.5

103.5

...

70.0

54.5

135

152

80.5

103.0

...

...

54.0

133

150

80.0

...

86.5

69.5

53.5

131

148

79.0

102.5

...

69.0

53.0

129

146

78.0

102.0

...

68.5

52.5

128

144

77.5

101.5

86.0

68.0

51.5

126

142

77.0

101.0

...

67.5

51.0

124

140

76.0

100.5

85.5

67.0

50.0

122

138

75.0

100.0

...

66.5

49.0

121

136

74.5

99.5

85.0

66.0

48.0

120

134

73.5

99.0

...

65.5

47.5

118

132

73.0

98.5

84.5

65.0

46.5

116

130

72.0

98.0

84.0

64.5

45.5

114

128

71.0

97.5

...

63.5

45.0

113

126

70.0

97.0

83.5

63.0

44.0

112

124

69.0

96.5

...

62.5

43.0

110

122

68.0

96.0

83.0

62.0

42.0

108

120

67.0

95.5

...

61.0

41.0

106

118

66.0

95.0

82.5

60.5

40.0

105

116

65.0

94.5

82.0

60.0

39.0

103

114

64.0

94.0

81.5

59.5

38.0

101

112

63.0

93.0

81.0

58.5

37.0

99

110

62.0

92.6

80.5

58.0

35.5

97

108

61.0

92.0

...

57.0

34.5

95

106

59.5

91.2

80.0

56.0

33.0

94

104

58.0

90.5

79.5

55.0

32.0

92

102

57.0

89.8

79.0

54.5

30.5

90

100

56.0

89.0

78.5

53.5

29.5

88

98

54.0

88.0

78.0

52.5

28.0

86

96

53.0

87.2

77.5

51.5

26.5

85

94

51.0

86.3

77.0

50.5

24.5

83

92

49.5

85.4

76.5

49.0

23.0

82

90

47.5

84.4

75.5

48.0

21.0

80

88

46.0

83.5

75.0

47.0

19.0

79

86

44.0

82.3

74.5

45.5

17.0

77

84

42.0

81.2

73.5

44.0

14.5

76

82

40.0

80.0

73.0

43.0

12.5

74

80

37.5

78.6

72.0

41.0

10.0

72

78

35.0

77.4

71.5

39.5

7.5

70

76

32.5

76.0

70.5

38.0

4.5

68

74

30.0

74.8

70.0

36.0

1.0

66

72

27.5

73.2

69.0

34.0

...

64

70

24.5

71.8

68.0

32.0

...

63

68

21.5

70.0

67.0

30.0

...

62

66

18.5

68.5

66.0

28.0

...

61

64

15.5

66.8

65.0

25.5

...

59

62

12.5

65.0

63.5

23.0

...

57

60

10.0

62.5

62.5

...

...

55

58

...

61.0

61.0

18.0

...

53

56

...

58.8

60.0

15.0

...

52

54

...

56.5

58.5

12.0

...

50

52

...

53.5

57.0

...

...

48

50

...

50.5

55.5

...

...

47

49

...

49.0

54.5

...

...

46

48

...

47.0

53.5

...

...

45

47

...

45.0

...

...

...

44

46

...

43.0

...

...

...

43

45

...

40.0

...

...

...

42

Source: ASTM E 140

Table 15 Guide to the Unified Numbering System (UNS) for metals and alloys For additional details on the UNS, see the combined ASTM E 527/SAE J1066 standard, "Recommended Practice for Numbering Metals and Alloys." UNS series

Metal/alloy

Nonferrous metals and alloys

A00001-A99999

Aluminum and aluminum alloys

C00001-C99999

Copper and copper alloys

E00001-E99999

Rare earth and rare earth-like metals and alloys

E00001-E00999

Actinium

E01000-E20999

Cerium

E21000-E45999

Mixed rare earths (e.g., mischmetal)

E46000-E47999

Dysprosium

E48000-E49999

Erbium

E50000-E51999

Europium

E52000-E55999

Gadolinium

E56000-E57999

Holmium

E58000-E67999

Lanthanum

E68000-E68999

Lutetium

E69000-E73999

Neodymium

E74000-E77999

Praseodymium

E78000-E78999

Promethium

E79000-E82999

Samarium

E83000-E84999

Scandium

E85000-E86999

Terbium

E87000-E87999

Thulium

E88000-E89999

Ytterbium

E90000-E99999

Yttrium

L00001-L99999

Low-melting-point metals and alloys

L00001-L00999

Bismuth

L01001-L01999

Cadmium

L02001-L02999

Cesium

L03001-L03999

Gallium

L04001-L04999

Indium

L06001-L06999

Lithium

L07001-L07999

Mercury

L08001-L08999

Potassium

L09001-L09999

Rubidium

L10001-L10999

Selenium

L11001-L11999

Sodium

L13001-L13999

Tin

L50001-L59999

Lead

M00001-M99999

Miscellaneous nonferrous metals and alloys

M00001-M00999

Antimony

M01001-M01999

Arsenic

M02001-M02999

Barium

M03001-M03999

Calcium

M04001-M04999

Germanium

M05001-M05999

Plutonium

M06001-M06999

Strontium

M07001-M07999

Tellurium

M08001-M08999

Uranium

M10001-M19999

Magnesium

M20001-M29999

Manganese

M30001-M39999

Silicon

P00001-P99999

Precious metals and alloys

P00001-P00999

Gold

P01001-P01999

Iridium

P02001-P02999

Osmium

P03001-P03999

Palladium

P04001-P04999

Platinum

P05001-P05999

Rhodium

P06001-P06999

Ruthenium

P07001-P07999

Silver

R00001-R99999

Reactive and refractory metals and alloys

R01001-R01999

Boron

R02001-R02999

Hafnium

R03001-R03999

Molybdenum

R04001-R04999

Niobium (Columbium)

R05001-R05999

Tantalum

R06001-R06999

Thorium

R07001-R07999

Tungsten

R08001-R08999

Vanadium

R10001-R19999

Beryllium

R20001-R29999

Chromium

R30001-R39999

Cobalt

R40001-R49999

Rhenium

R50001-R59999

Titanium

R60001-R69999

Zirconium

Z00001-Z99999

Zinc and zinc alloys

Ferrous metals and alloys

D00001-D99999

Specified mechanical properties of steels

F00001-F99999

Cast irons (gray, malleable, and ductile irons)

G00001-G99999

AISI and SAE carbon and alloy steels (except tool steels)

H00001-H99999

AISI and SAE H-steels (carbon, carbon-boron, and alloy H-steels)

J00001-J99999

Cast steels (except tool steels)

K00001-K99999

Miscellaneous steels and ferrous alloys

S00001-S99999

Heat- and corrosion-resistant (stainless) steels

T00001-T99999

Tool steels

Welding filler metals

W00001-W99999

Welding filler metals, covered and tubular electrodes, classified by weld deposit composition

W00001-W09999

Carbon steel with no significant alloying elements

W10000-W19999

Manganese-molybdenum low-alloys steels

W20000-W29999

Nickel low-alloy steels

W30000-W39999

Austenitic stainless steels

W40000-W49999

Ferritic stainless steels

W50000-W59999

Chromium low-alloy steels

W60000-W69999

Copper-base alloys

W70000-W79999

Surfacing alloys

W80000-W89999

Nickel-base alloys

Table 16 SI prefixes--names and symbols Exponential expression

Multiplication factor

Prefix

Symbol

1024

1,000,000,000,000,000,000,000,000

yotta

Y

1021

1,000,000,000,000,000,000,000

zetta

Z

1018

1,000,000,000,000,000,000

exa

E

1015

1,000,000,000,000,000

peta

P

1012

1,000,000,000,000

tera

T

109

1,000,000,000

glga

G

106

1,000,000

meta

M

103

1,000

kilo

k

102

100

hecto(a)

h

101

10

deka(a)

da

100

1

BASE UNIT

10-1

0.1

deci(a)

d

10-2

0.01

centi(a)

c

10-3

0.001

milli

m

10-6

0.000,001

micro

10-9

0.000,000,001

nano

n

10-12

0.000,000,000,001

pico

p

10-15

0.000,000,000,000,001

femto

f

10-18

0.000,000,000,000,000,001

atto

a

10-21

0.000,000,000,000,000,000,001

zepto

z

10-24

0.000,000,000,000,000,000,000,001

yocto

y

(a) Nonpreferred. Prefixes should be selected in steps of 103 so that the resultant number before the prefix is between 0.1 and 1000. These prefixes should not be used for units of linear measurement, but may be used for higher order units. For example, the linear measurement, decimeter, is nonpreferred, but square decimeter is acceptable.

Table 17 Base, supplementary, and derived SI units Measure

Unit

Symbol

Amount of substance

mole

mol

Electric current

ampere

A

Length

meter

m

Luminous intensity

candela

cd

Mass

kilogram

kg

Thermodynamic temperature

kelvin

K

Time

second

s

Plane angle

radian

rad

Solid angle

steradian

sr

Absorbed dose

gray

Gy

Acceleration

meter per second squared

m/s2

Activity (of radionuclides)

becquerel

Bq

Formula

Base units

Supplementary units

Derived units

J/kg

Angular acceleration

radian per second squared

rad/s2

Angular velocity

radian per second

rad/s

Area

square meter

m2

Concentration (of amount of substance)

mole per cubic meter

mol/m3

Current density

ampere per square meter

A/m2

Density, mass

kilogram per cubic meter

kg/m3

Dose equivalent

sievert

Sv

J/kg

Electric capacitance

farad

F

C/V

Electric charge density

coulomb per cubic meter

C/m3

Electric conductance

siemens

S

Electric field strength

volt per meter

V/m

Electric flux density

coulomb per square meter

C/m2

Electric potential, potential difference, electromotive force

volt

V

W/A

Electric resistance

ohm

Ω

V/A

Energy, work, quantity of heat

joule

J

N·m

Energy density

joule per cubic meter

J/m3

Entropy

joule per kelvin

J/K

Force

newton

N

kg · m/s2

Frequency

hertz

Hz

1/s

Heat capacity

joule per kelvin

J/K

Heat flux density

watt per square meter

W/m2

A/V

Illuminance

lux

lx

1m/m2

Inductance

henry

H

Wb/A

Irradiance

watt per square meter

W/m2

Luminance

candela per square meter

cd/m2

Luminous flux

lumen

lm

Magnetic field strength

ampere per meter

A/m

Magnetic flux

weber

Wb

V·s

Magnetic flux density

tesla

T

Wb/m2

Molar energy

joule per mole

J/mol

Molar entropy

joule per mole kelvin

J/mol · K

Molar heat capacity

joule per mole kelvin

J/mol · K

Moment of force

newton meter

N·m

Permeability

henry per meter

H/m

Permittivity

farad per meter

F/m

Power, radiant flux

watt

W

J/s

Pressure, stress

pascal

Pa

N/m2

Quantity of electricity, electric charge

coulomb

C

A·s

Radiance

watt per square meter steradian

W/m2 · sr

Radiant intensity

watt per steradian

W/sr

Specific heat capacity

joule per kilogram kelvin

J/kg · K

Specific energy

joule per kilogram

J/kg

cd · sr

Specific entropy

joule per kilogram kelvin

J/kg · K

Specific volume

cubic meter per kilogram

M3/kg

Surface tension

newton per meter

N/m

Thermal conductivity

watt per meter kelvin

W/m · K

Velocity

meter per second

m/s

viscosity, dynamic

pascal second

Pa · s

Viscosity, kinematic

square meter per second

m2/s

Volume

cubic meter

m3

Wavenumber

1 per meter

1/m

Fig. 3 Fracture toughness versus strength for various engineered materials. Strength is yield strength for metals/alloys and polymers, compressive strength for ceramics (note the broken property envelope lines), tear strength for elastomers, and tensile strength for composites. It should be noted that the tensile strength of engineering ceramics is about 15 times smaller than its compressive strength. Abbreviation key: CFRP, carbon-fiber reinforced polymer; GFRP, glass-fiber reinforced polymer; KFRP, kevlar-fiber reinforced polymer; PMMA, polymethyl methacrylate; Mel, melamines; PP, polypropylene; PC, polycarbonate; PS, polystyrene; PVC, polyvinyl chloride; HDPE, high-density polyethylene; LDPE, low-density polyethylene; PTFE, polytetrafluoroethylene; PU, polyurethane

Table 18 Conversion factors classified according to the quantity/property of interest To convert from

to

multiply by

rad

1.745 329 E-02

Angle

degree

Area

in.2

mm2

6.451 600 E+02

in.2

cm2

6.451 600 E+00

in.2

m2

6.451 600 E-04

ft2

m2

9.290 304 E-02

Bending moment or torque

lbf · in.

N·m

1.129 848 E-01

lbf · ft

N·m

1.355 818 E+00

kgf · m

N·m

9.806 650 E+00

ozf · in.

N·m

7.061 552 E-03

Bending moment or torque per unit length

lbf · in./in.

N · m/m

4.448 222 E+00

lbf · ft/in.

N · m/m

5.337 866 E+01

A/in.2

A/cm2

1.550 003 E-01

A/in.2

A/mm2

1.550 003 E-03

A/ft2

A/m2

1.076 400 E+01

Current density

Electricity and magnetism

gauss

T

maxwell

1.000 000 E-04

Wb

1.000 000 E-02

mho

S

1.000 000 E+00

Oersted

A/m

7.957 700 E+01

Ω· cm

Ω· m

1.000 000 E-02

Ωcircular-mil/ft

μΩ· m

1.662 426 E-03

ft · lbf

J

1.355 818 E+00

Btu (thermochemical)

J

1.054 350 E+03

cal (thermochemical)

J

4.184 000 E+00

kW · h

J

3.600 000 E+06

W·h

J

3.600 000 E+03

ft3/h

L/min

4.719 475 E-01

ft3/min

L/min

2.831 000 E+01

gal/h

L/min

6.309 020 E-02

gal/min

L/min

3.785 412 E+00

lbf

N

4.448 222 E+00

kip (1000 lbf)

N

4.448 222 E+03

tonf

kN

8.896 443 E+00

kgf

N

9.806 650 E+00

lbf/ft

N/m

1.459 390 E+01

lbf/in.

N/m

1.751 268 E+02

Energy (impact, other)

Flow rate

Force

Force per unit length

Fracture toughness

MPa m

1.098 800 E+00

Btu/lb

kJ/kg

2.326 000 E+00

cal/g

kJ/kg

4.186 800 E+00

J/in.

J/m

3.937 008 E+01

kJ/in.

kJ/m

3.937 008 E+01

nm

1.000 000 E-01

μin.

μm

2.540 000 E-02

mil

μm

2.540 000 E+01

in.

mm

2.540 000 E+01

in.

cm

2.540 000 E+00

ft

m

3.048 000 E-01

yd

m

9.144 000 E-01

mile

km

1.609 300 E+00

oz

kg

2.834 952 E-02

lb

kg

4.535 924 E-01

ksi in

Heat content

Heat input

Length

o

A

Mass

ton (short, 2000 lb)

kg

9.071 847 E+02

ton (short, 2000 lb)

kg × 103(a)

9.071 847 E-01

ton (long, 2240 lb)

kg

1.016 047 E+03

oz/in.2

kg/m2

4.395 000 E+01

oz/ft2

kg/m2

3.051 517 E-01

oz/yd2

kg/m2

3.390 575 E-02

lb/ft2

kg/m2

4.882 428 E+00

lb/ft

kg/m

1.488 164 E+00

lb/in.

kg/m

1.785 797 E+01

lb/h

kg/s

1.259 979 E-04

lb/min

kg/s

7.559 873 E-03

lb/s

kg/s

4.535 924 E-01

Mass per unit area

Mass per unit length

Mass per unit time

Mass per unit volume (includes density)

g/cm3

kg/m3

1.000 000 E+03

lb/ft3

g/cm3

1.601 846 E-02

lb/ft3

kg/m3

1.601 846 E+01

lb/in.3

g/cm3

2.767 990 E+01

lb/in.3

kg/m3

2.767 990 E+04

Power

Btu/s

kW

1.055 056 E+00

Btu/min

kW

1.758 426 E-02

Btu/h

W

2.928 751 E-01

erg/s

W

1.000 000 E-07

ft · lbf/s

W

1.355 818 E+00

ft · lbf/min

W

2.259 697 E-02

ft · lbf/h

W

3.766 161 E-04

hp (550 ft · lbf/s)

kW

7.456 999 E-01

hp (electric)

kW

7.460 000 E-01

W/m2

1.550 003 E+03

atm (standard)

Pa

1.013 250 E+05

bar

Pa

1.000 000 E+05

in. Hg (32 °F)

Pa

3.386 380 E+03

in. Hg (60 °F)

Pa

3.376 850 E+03

lbf/in.2 (psi)

Pa

6.894 757 E+03

torr (mm Hg, 0 °C)

Pa

1.333 220 E+02

J/kg · K

4.186 800 E+03

Power density

W/in.2

Pressure (fluid)

Specific heat

Btu/lb · °F

cal/g · °C

J/kg · K

4.186 800 E+03

Stress (force per unit area)

tonf/in.2 (tsi)

MPa

1.378 951 E+01

kgf/mm2

MPa

9.806 650 E+00

ksi

MPa

6.894 757 E+00

lbf/in.2 (psi)

MPa

6.894 757 E-03

MN/m2

MPa

1.000 000 E+00

°F

°C

5/9 · (°F-32)

°R

°K

5/9

°C

5/9

Btu · in./s · ft2 · °F

W/m · K

5.192 204 E+02

Btu/ft · h · °F

W/m · K

1.730 735 E+00

Btu · in./h · ft2 · °F

W/m · K

1.442 279 E-01

cal/cm · s · °C

W/m · K

4.184 000 E+02

in./in. · °C

m/m · K

1.000 000 E+00

in./in. · °F

m/m · K

1.800 000 E+00

Temperature

Temperature interval

°F

Thermal conductivity

Thermal expansion

Velocity

ft/h

m/s

8.466 667 E-05

ft/min

m/s

5.080 000 E-03

ft/s

m/s

3.048 000 E-01

in./s

m/s

2.540 000 E-02

km/h

m/s

2.777 778 E-01

mph

km/h

1.609 344 E+00

rev/min (rpm)

rad/s

1.047 164 E-01

rev/s

rad/s

6.283 185 E+00

poise

Pa · s

1.000 000 E+01

strokes

m2/s

1.000 000 E-04

ft2/s

m2/s

9.290 304 E-02

in.2/s

mm2/s

6.451 600 E+02

in.3

m3

1.638 706 E-05

ft3

m3

2.831 685 E-02

fluid oz

m3

2.957 353 E-05

gal (U.S. liquid)

m3

3.785 412 E-03

m3/s

4.719 474 E-04

Velocity of rotation

Viscosity

Volume

Volume per unit time

ft3/min

ft3/s

m3/s

2.831 685 E-02

in.3/min

m3/s

2.731 177 E-07

nm

1.000 000 E-01

Wavelength

o

A

(a) kg × 103 = 1 metric tonne

Table 19 Alphabetical listing of common conversion factors Conversion factors are written as a number greater than one and less than ten with six or fewer decimal places. This number is followed by the letter E (for exponent), a plus or minus symbol, and two digits that indicate the power of 10 by which the number must be multiplied to obtain the correct value. For example: 3.523 907 E - 02 is 3. 523 907 × 10-2 or 0.035 239 07 An asterisk (*) after the sixth decimal place indicates that the conversion factor is exact and that all subsequent digits are zero. All other conversion factors have been rounded off. To convert from

to

Multiply by

abampere

ampere (A)

1.000 000* E+01

abcoulomb

coulomb (C)

1.000 000* E+01

abfarad

farad (F)

1.000 000* E+09

abhenry

henry (H)

1.000 000* E-09

abmho

siemens (S)

1.000 000* E+09

abohm

ohm (Ω)

1.000 000* E-09

abvolt

volt (V)

1.000 000* E-08

ampere hour

coulomb (C)

3.600 000* E+03

angstrom

meter (m)

1.000 000* E-10

atmosphere, standard

pascal (Pa)

1.013 250* E+0.5

atmosphere, technical (= 1 kgf/cm2)

pascal (Pa)

9.806 650* E+04

bar

pascal (Pa)

1.000 000* E+05

barn

square meter (m2)

1.000 000* E-28

barrel (for petroleum, 42 gal)

cubic meter (m3)

1.589 873 E-01

British thermal unit (International Table)

joule (J)

1.055 056 E+03

British thermal unit (mean)

joule (J)

1.055 87 E+03

British thermal unit (thermochemical)

joule (J)

1.054 350 E+03

British thermal unit (39 °F)

joule (J)

1.059 67 E+03

British thermal unit (59 °F)

joule (J)

1.054 80 E+03

British thermal unit (60 °F)

joule (J)

1.054 68 E+03

Btu (International Table) · ft/(h · ft2 · °F) (thermal conductivity)

watt per meter kelvin [W/(m · K)]

1.730 735 E+00

Btu (thermochemical) · ft/(h · ft2 · °F) (thermal conductivity)

watt per meter kelvin [W/(m · K)]

1.729 577 E+00

Btu (International Table) · in./(h · ft2 · °F) (thermal conductivity)

watt per meter kelvin [W/(m · K)]

1.442 279 E-01

Btu (thermochemical) · in./(h · ft2 · °F) (thermal conductivity)

watt per meter kelvin [W/(m · K)]

1.441 314 E-01

Btu (International Table) · in./s · ft2 · °F) (thermal conductivity)

watt per meter kelvin [W/(m · K)]

5.192 204 E+02

Btu (thermochemical) · in./(s · ft2 · °F) (thermal conductivity)

watt per meter kelvin [W/(m · K)]

5.188 732 E+02

Btu (International Table)/h

watt (W)

2.930 711 E-01

Btu (International Table)/s

watt (W)

1.055 056 E+03

Btu (thermochemical)/h

watt (W)

2.928 751 E-01

Btu (thermochemical)/min

watt (W)

1.757 250 E+01

Btu (thermochemical)/s

watt (W)

1.054 350 E+03

Btu (International Table)/ft2

joule per square meter (J/m2)

1.135 653 E+04

Btu (thermochemical)/ft2

joule per square meter (J/m2)

1.134 893 E+04

Btu (International Table)/(ft2 · s)

watt per square meter (W/m2)

1.135 653 E+04

Btu (International Table)/(ft2 · h)

watt per square meter (W/m2)

3.154 591 E+00

Btu (thermochemical)/(ft2 · h)

watt per square meter (W/m2)

3.152 481 E+00

Btu (thermochemical)/(ft2 · min)

watt per square meter (W/m2)

1.891 489 E+02

Btu (thermochemical)/(ft2 · s)

watt per square meter (W/m2)

1.134 893 E+04

Btu (thermochemical)/(in.2 · s)

watt per square meter (W/m2)

1.634 246 E+06

Btu (International Table)/(h · ft2 · °F) (thermal conductance)

watt per square meter kelvin [W/(m2 · K)]

5.678 263 E+00

Btu (thermochemical)/(h · ft2 · °F) (thermal conductance)

watt per square meter kelvin [W/(m2 · K)]

5.674 466 E+00

Btu (International Table)/(s · ft2 · °F)

watt per square meter kelvin [W/(m2 · K)]

2.044 175 E+04

Btu (thermochemical)/(s · ft2 · °F)

watt per square meter kelvin [W/m2 · K)]

2.042 808 E+04

But (International Table)/lb

joule per kilogram (J/kg)

2.326 000* E+03

Btu (thermochemical)/lb

joule per kilogram (J/kg)

2.324 444 E+03

Btu (International Table)/(lb · °F) (heat capacity)

joule per kilogram kelvin [J/(kg · K)]

4.186 800* E+03

Btu (thermochemical)/(lb · °F) (heat capacity)

joule per kilogram kelvin [J/(kg · K)]

4.184 000* E+03

Btu (International Table)/ft3

joule per cubic meter (J/m3)

3.725 895 E+04

Btu (thermochemical)/ft3

joule per cubic meter (J/m3)

3.723 402 E+04

bushel (U.S.)

cubic meter (m3)

3.523 907 E-02

calorie (International Table)

joule (J)

4.186 800* E+00

calorie (mean)

joule (J)

4.190 02 E+00

calorie (thermochemical)

joule (J)

4.184 000* E+00

calorie (15 °C)

joule (J)

4.185 80 E+00

calorie (20 °C)

joule (J)

4.181 90 E+00

calorie (kilogram, International Table)

joule (J)

4.186800* E+03

calorie (kilogram, mean)

joule (J)

4.190 02 E+03

calorie (kilogram, thermochemical)

joule (J)

4.184 000* E+03

cal (thermochemical)/cm2

joule per square meter (J/m2)

4.184 000* E+04

cal (International Table)/g

joule per kilogram (J/kg)

4.186 800* E+03

cal (thermochemical)/g

joule per kilogram (J/kg)

4.184 000* E+03

cal (International Table)/(g · °C)

joule per kilogram kelvin [J/(kg · K)]

4.186 800* E+03

cal (thermochemical)/(g · °C)

joule per kilogram kelvin [J/(kg · K)]

4.184 000* E+03

cal (thermochemical)/min

watt (W)

6.973 333 E-02

cal (thermochemical)/s

watt (W)

4.184 000* E+00

cal (thermochemical)/(cm2 · s)

watt per square meter (W/m2)

4.184 000* E+04

cal (thermochemical)/(cm2 · min)

watt per square meter (W/m2)

6.973 333 E+02

cal (thermochemical)/(cm2 · s)

watt per square meter (W/m2)

4.184 000* E+04

cal (thermochemical)/(cm · s · °C)

watt per meter kelvin [W/(m · K)]

4.184 000* E+02

cd/in.2

candela per square meter (cd/m2)

1.550 003 E+03

carat (metric)

kilogram (kg)

2.000 000* E-04

centimeter of mercury (0 °C)

pascal (Pa)

1.333 22 E+03

centimeter of water (4 °C)

pascal (Pa)

9.806 38 E+01

centipoise (dynamic viscosity)

pascal second (Pa · s)

1.000 000* E-03

centistokes (kinematic viscosity)

square meter per second (m2/s)

1.000 000* E-06

circular mil

square meter (m2)

5.067 075 E-10

curie

becquerel (Bq)

3.700 000* E+10

degree (angle)

radian (rad)

1.745 329 E-02

degree Celsius

kelvin (K)

TK = t°C + 273.15

degree Fahrenheit

degree Celsius (°C)

t°C = (t°F - 32)/1.8

degree Fahrenheit

kelvin (K)

TK = (t°F + 459.67)/1.8

degree Rankine

kelvin (K)

TK = T°R/1.8

°F · h · ft2/Btu (International Table) (thermal resistance)

kelvin square meter per watt (K · m2/W)

1.761,102 E-01

°F · h · ft2/Btu (thermochemical) (thermal resistance)

kelvin square meter per watt (K · m2/W)

1.762 280 E-01

°F · h · ft2/[Btu (International Table) · in.] (thermal resistivity)

kelvin meter per watt (K · m/W)

6.933 471 E+00

°F · h · ft2/[Btu (thermochemical) · in.] (thermal resistivity)

kelvin meter per watt (K · m/W)

6.938 113 E+00

denier

kilogram per meter (kg/m)

1.111 111 E-07

dyne

newton (N)

1.000 000* E-05

dyne · cm

newton meter (N · m)

1.000 000* E-07

dyne/cm2

pascal (Pa)

1.000 000* E-01

electronvolt

joule (J)

1.602 19 E-19

EMU (electromagnetic units) of capacitance

farad (F)

1.000 000* E+09

EMU of current

ampere (A)

1.000 000* E+01

EMU of electric potential

volt (V)

1.000 000* E-08

EMU of inductance

henry (H)

1.000 000* E-09

EMU of resistance

ohm (Ω)

1.000 000* E-09

ESU (electrostatic units) of capacitance

farad (F)

1.112 650 E-12

ESU of current

ampere (A)

3.335 6 E-10

ESU of electric potential

volt (V)

2.997 9 E+02

ESU of inductance

henry (H)

8.987 554 E+11

ESU of resistance

ohm (Ω)

8.987 554 E+11

erg

joule (J)

1.000 000* E-07

erg/(cm2 · s)

watt per square meter (W/m2)

1.000 000* E-03

erg/s

watt (W)

1.000 000* E-07

faraday (based on carbon-12)

coulomb (C)

9.648 70 E+04

faraday (chemical)

coulomb (C)

9.649 57 E+04

faraday (physical)

coulomb (C)

9.652 19 E+04

fluid ounce (U.S.)

cubic meter (m3)

2.957 353 E-05

foot

meter (m)

3.048 000* E-01

ft2

square meter (m2)

9.290 304* E-02

ft2/h (thermal diffusivity)

square meter per second (m2/s)

2.580 640* E-05

ft2/s

square meter per second (m2/s)

9.290 304* E-02

ft3/min

cubic meter per second (m3/s)

4.719 474 E-04

ft3/s

cubic meter per second (m3/s)

2.831 685 E-02

ft/h

meter per second (m/s)

8.466 667 E-05

ft/min

meter per second (m/s)

5.080 000* E-03

ft/s

meter per second (m/s)

3.048 000* E-01

ft/s2

meter per second squared (m/s2)

3.048 000* E-01

footcandle

lux (lx)

1.076 391 E+01

footlambert

candela per square meter (cd/m2)

3.426 259 E+00

ft · lbf

joule (J)

1.355 818 E+00

ft · lbf/h

watt (W)

3.766 161 E-04

ft · lbf/min

watt (W)

2.259 697 E-02

ft · lbf/s

watt (W)

1.355 818 E+00

ft-poundal

joule (J)

4.214 011 E-02

g, standard free fall

meter per second squared (m/s2)

9.806 650* E+00

gal

meter per second squared (m/s2)

1.00 000* E-02

gallon (Canadian liquid)

cubic meter (m3)

4.546 090 E-03

gallon (U.K. liquid)

cubic meter (m3)

4.546 092 E-03

gallon (U.S. dry)

cubic meter (m3)

4.404 884 E-03

gallon (U.S. liquid)

cubic meter (m3)

3.785 412 E-03

gallon (U.S. liquid) per day

cubic meter per second (m3/s)

4.381 264 E-08

gallon (U.S. liquid) per minute

cubic meter per second (m3/s)

6.309 020 E-05

gallon (U.S. liquid) per hp · h (SFC, specific fuel consumption)

cubic meter per joule (m3/J)

1.410 089 E-09

gauss

tesla (T)

1.000 000* E-04

gilbert

ampere (A)

7.957 747 E-01

grain

kilogram (kg)

6.479 891* E-05

grain/gal (U.S. liquid)

kilogram per cubic meter (kg/m3)

1.711 806 E-02

gram

kilogram (kg)

1.000 000* E-03

g/cm3

kilogram per cubic meter (kg/m3)

1.000 000* E+03

gf/cm2

pascal (Pa)

9.806 650* E+01

hectare

square meter (m2)

1.000 000* E+04

horsepower (550 ft · lbf/s)

watt (W)

7.456 999 E+02

horsepower (boiler)

watt (W)

9.809 50 E+03

horsepower (electric)

watt (W)

7.460 000* E+02

horsepower (metric)

watt (W)

7.354 99 E+02

horsepower (water)

watt (W)

7.460 43 E+02

horsepower (U.K.)

watt (W)

7.457 0 E+02

inch

meter

2.540 000* E-02

inch of mercury (32 °F)

pascal (Pa)

3.386 38 E+03

inch of mercury (60 °F)

pascal (Pa)

3.376 85 E+03

inch of water (39.2 °F)

pascal (Pa)

2.490 82 E+02

inch of water (60 °F)

pascal (Pa)

2.488 4 E+02

in.2

square meter (m2)

6.451 600* E-04

in.3 (volume)

cubic meter (m3)

1.638 706 E-05

in.3/min

cubic meter per second (m3/s)

2.731 177 E-07

in./s

meter per second (m/s)

2.540 000* E-02

in./s2

meter per second squared (m/s2)

2.540 000* E-02

kelvin

degree Celsius (°C)

t°C = TK - 273.15

kilocalorie (International Table)

joule (J)

4.186 800* E+03

Kilocalorie (mean)

joule (J)

4.190 02 E+03

kilocalorie (thermochemical)

joule (J)

4.184 000* E+03

kilocalorie (thermochemical)/min

watt (W)

6.973 333 E+01

kilocalorie (thermochemical)/s

watt (W)

4.184 000* E+03

kilogram-force (kgf)

newton (N)

9.806 650* E+00

kgf · m

newton meter (N · m)

9.806 650* E+00

kgf · s2/m (mass)

kilogram (kg)

9.806 650* E+00

kgf/cm2

pascal (Pa)

9.806 650* E+04

kgf/m2

pascal (Pa)

9.806 650* E+00

kgf/mm2

pascal (Pa)

9.806 650* E+06

km/h

meter per second (m/s)

2.777 778 E-01

kilopond (1 kp = 1 kgf)

newton (N)

9.806 650* E+00

knot (nautical mile per hour)

meter per second (m/s)

5.144 444 E-01

kW · h

joule (J)

3.600 000* E+06

kip (1000 lbf)

newton (N)

4.448 222 E+03

kip/in.2 (ksi)

pascal (Pa)

6.894 757 E+06

lambert

candela per square meter (cd/m2)

1/ * E+04

lambert

candela per square meter (cd/m2)

3.183 099 E+03

liter

cubic meter (m3)

1.000 000* E-03

lm/ft2

lumen per square meter (lm/m2)

1.076 391 E+01

maxwell

weber (Wb)

1.000 000* E-08

mho

siemens (S)

1.000 000* E+00

microinch

meter (m)

2.540 000* E-08

micron (use preferred term micrometer)

meter (m)

1.000 000* E-06

mil

meter (m)

2.540 000* E-05

mile (international)

meter (m)

1.609 344* E+03

mile (U.S. statute)

meter (m)

1.609 347 E+03

mile (international nautical)

meter (m)

1.852 000* E+03

mile (U.S. nautical)

meter (m)

1.852 000* E+03

mi2 (international)

square meter (m2)

2.589 988 E+06

mi2 (U.S. statute)

square meter (m2)

2.589 998 E+06

mi/h (international)

meter per second (m/s)

4.470 400* E-01

mi/h (international)

kilometer per hour (km/h)

1.609 344* E+00

mi/min (international)

meter per second (m/s)

2.682 240* E+01

mi/s (international)

meter per second (m/s)

1.609 344* E+03

millibar

pascal (Pa)

1.000 000* E+02

millimeter of mercury (0 °C)

pascal (Pa)

1.333 22 E+02

minute (angle)

radian (rad)

2.908 882 E-04

oersted

ampere per meter (A/m)

7.957 747 E+01

ohm centimeter

ohm meter (Ω · m)

1.000 000* E-02

ohm circular-mil per foot

ohm meter (Ω · m)

1.662 426 E-09

ounce (avoirdupois)

kilogram (kg)

2.834 952 E-02

ounce (troy or apothecary)

kilogram (kg)

3.110 348 E-02

ounce (U.K. fluid)

cubic meter (m3)

2.841 306 E-05

ounce (U.S. fluid)

cubic meter (m3)

2.957 353 E-05

ounce-force

newton (N)

2.780 139 E-01

ozf · in.

newton meter (N · m)

7.061 552 E-03

oz (avoirdupois)/gal (U.K. liquid)

kilogram per cubic meter (kg/m3)

6.236 023 E+00

oz (avoirdupois)/gal (U.S. liquid)

kilogram per cubic meter (kg/m3)

7.489 152 E+00

oz (avoirdupois)/in.3

kilogram per cubic meter (kg/m3)

1.729 994 E+03

oz (avoirdupois)/ft2

kilogram per square meter (kg/m2)

3.051 517 E-01

oz (avoirdupois)/yd2

kilogram per square meter (kg/m2)

3.390 575 E-02

pint (U.S. dry)

cubic meter (m3)

5.506 105 E-04

pint (U.S. liquid)

cubic meter (m3)

4.731 765 E-04

poise (absolute viscosity)

pascal second (Pa · s)

1.000 000* E-01

pound (lb avoirdupois)

kilogram (kg)

4.535 924 E-01

pound (troy or apothecary)

kilogram (kg)

3.732 417 E-01

lb · ft2 (moment of inertia)

kilogram square meter (kg · m2)

4.214 011 E-02

lb · in.2 (moment of inertia)

kilogram square meter (kg · m2)

2.926 397 E-04

lb/ft · h

pascal second (Pa · s)

4.133 789 E-04

lb/ft · s

pascal second (Pa · s)

1.488 164 E+00

lb/ft2

kilogram per square meter (kg/m2)

4.882 428 E+00

lb/ft3

kilogram per cubic meter (kg/m3)

1.601 846 E+01

lb/gal (U.K. liquid)

kilogram per cubic meter (kg/m3)

9.977 637 E+01

lb/gal (U.S. liquid)

kilogram per cubic meter (kg/m3)

1.198 264 E+02

lb/h

kilogram per second (kg/s)

1.259 979 E-04

lb/hp · h (SFC, specific fuel consumption)

kilogram per joule (kg/J)

1.689 659 E-07

lb/in.3

kilogram per cubic meter (kg/m3)

2.767 990 E+04

lb/min

kilogram per second (kg/s)

7.559 873 E-03

lb/s

kilogram per second (kg/s)

4.535 924 E-01

lb/yd3

kilogram per cubic meter (kg/m3)

5.932 764 E-01

poundal

newton (N)

1.382 550 E-01

poundal/ft2

pascal (Pa)

1.488 164 E+00

poundal · s/ft2

pascal second (Pa · s)

1.488 164 E+00

pound-force (lbf)

newton (N)

4.448 222 E+00

lbf · ft

newton meter (N · m)

1.355 818 E+00

lbf · ft/in.

newton meter (N · m)

1.355 818 E+00

lbf · in.

newton meter (N · m)

1.129 848 E-01

lbf · in./in.

newton meter per meter (N · m/m)

4.448 222 E+00

lbf · s/ft2

pascal second (Pa · s)

4.788 026 E+01

lbf · s/in.2

pascal second (Pa · s)

6.894 757 E+03

lbf/ft

newton per meter (N/m)

1.459 390 E+01

lbf/ft2

pascal (Pa)

4.788 026 E+01

lbf/in.

newton per meter (N/m)

1.751 268 E+02

lbf/in.2 (psi)

pascal (Pa)

6.894 757 E+03

lbf/lb (thrust/weight [mass] ratio)

newton per kilogram (N/kg)

9.806 650 E+00

quart (U.S. dry)

cubic meter (m3)

1.101 221 E-03

quart (U.S. liquid)

cubic meter (m3)

9.463 529 E-04

rad (absorbed dose)

gray (Gy)

1.000 000* E-02

rem (dose equivalent)

sievert (Sv)

1.000 000* E-02

roentgen

coulomb per kilogram (C/kg)

2.58 000* E-04

rpm (r/min)

radian per second (rad/s)

1.047 198 E-01

second (angle)

radian (rad)

4.848 137 E-06

statampere

ampere (A)

3.335 640 E-10

statcoulomb

coulomb (C)

3.335 640 E-10

statfarad

farad (F)

1.112 650 E-12

stathenry

henry (H)

8.987 554 E+11

statmho

siemens (S)

1.112 650 E-12

statohm

ohm (Ω)

8.987 554 E+11

statvolt

volt (V)

2.997 925 E+02

stokes (kinematic viscosity)

square meter per second (m2/s)

1.000 000* E-04

ton (assay)

kilogram (kg)

2.916 667 E-02

ton (long, 2240 lb)

kilogram (kg)

1.016 047 E+03

ton (metric)

kilogram (kg)

1.000 000* E+03

ton (nuclear equivalent of TNT)

joule (J)

4.184 E+09

ton (register)

cubic meter (m3)

2.831 685 E+00

ton (short, 2000 lb)

kilogram (kg)

9.071 847 E+02

ton (long)/yd3

kilogram per cubic meter (kg/m3)

1.328 939 E+03

ton (short)/yd3

kilogram per cubic meter (kg/m3)

1.186 553 E+03

ton (short)/h

kilogram per second (kg/s)

2.519 958 E-01

ton-force (2000 lbf)

newton (N)

8.896 443 E+03

tonne

kilogram (kg)

1.000 000* E+03

torr (mmHg, 0 °C)

pascal (Pa)

1.333 22 E+02

W·h

joule (J)

3.600 000* E+03

W·s

joule (J)

1.000 000* E+00

W/cm2

watt per square meter (W/m2)

1.000 000* E+04

W/in.2

watt per square meter (W/m2)

1.550 003 E+03

yard

meter (m)

9.144 000* E-01

yd2

square meter (in.2)

8.361 274 E-01

yd3

cubic meter (m3)

7.645 549 E-01

yd3/min

cubic meter per second (m3/s)

1.274 258 E-02

Source: Adapted from ASTM E 380, "Standard Practice for Use of the International System of Units (SI)--The Modernized Metric System"

Table 20 Conversion factors for corrosion rates d is metal density in grams per cubic centimeter (g/cm3) Unit

Factor for conversion to

mdd

g/m2/d

μ/yr

mm/yr

mils/yr

in./yr

Milligrams per square decimeter per day (mdd)

1

0.1

36.5/d

0.0365/d

1.144/d

0.00144/d

Grams per square meter per day (g/m2/d)

10

1

365/d

0.365/d

14.4/d

0.0144/d

Microns per year (μm/yr)

0.0274d

0.00274d

1

0.001

0.0394

0.0000394

Millimeters per year (mm/yr)

27.4d

2.74d

1000

1

39.4

0.0394

Mils per year (mils/yr)

0.696d

0.0696d

25.4

0.0254

1

0.001

Inches per year (in./yr)

696d

69.6d

25,400

25.4

1000

1

Table 21 Fundamental physical constants Quantity

Symbol

Numerical value(a)

Units

Speed of light (in vacuum)

c

299,792,458 (exact)

m · s-1

Electronic charge

e

1.6027733 (49)

10-19 C

Planck's constant

h

6.6260755 (40)

10-34 J · s

Avogadro constant (number)

NA

6.0221367 (36)

1023 mol-1

Atomic mass unit

amu or u

1.6605402 (10)

10-27 kg

Electron rest mass

me

9.1093897 (54)

10-31 kg

5.4859903 (13)

10-4 u

1.6726231 (10)

10-27 kg

1.007276470 (12)

u

Proton rest mass

mp

Neutron rest mass

mn

1.6749286 (10)

10-27 kg

1.008664904 (14)

u

Faraday constant

F

9.6485309 (29)

104 C · mol-1

Electron magnetic moment

μe

9.2847701 (31)

10-24 J · T-1

Molar gas constant

R

8.314510 (70)

J · mol-1 · K-1

8.205784 (69)

10-5m3 · atm · mol-1 · K-1

Molar value of ideal gas at STP(b)

Vm

22.41410 (19)

Boltzmann constant

k

1.380658 (12)

10-23 J · K-1

Standard gravity (gravitational acceleration)

g

9.80665

m · s-2

Absolute temperature

T0 °C

273.150 ± 0.010

K

Source: J. Res. National Bureau of Standards, Vol 92 (No. 2), 1987, p 85-95 (a) The numbers in parenthesis are the one-standard-deviation uncertainties in the last digits of the quoted value computed on the basis of internal consistency.

(b) STP = standard temperature and pressure (0 °C at 1 atm, or 760 torr).

Table 22 Greek alphabet Upper and lower cases

Name

Aα

Alpha

Bβ

Beta

γ

Gamma

∆δ

Delta

Eε

Epsilon

Z

Zeta

H

Eta

Theta

I

Iota

K

Kappa

Lambda

M

Mu

N

Nu

Xi

Oo

Omicron

Pi

P

Rho

Sigma

T

Tau

Y

Upsilon

Phi

X

Chi

Psi

Omega

The Chemical Elements Hugh Baker, Consulting Editor, ASM International

THE CHEMICAL ELEMENTS are the basic chemical substances; that is, they cannot be decomposed by chemical change or made by chemical union. These elements follow a periodic pattern related to the atomic mass of each that allows them to be arranged into a convenient table (see the periodic table shown in Fig. 1 and the corresponding Tables 1 and 2). As shown in the periodic table, most of the elements have metallic characteristics, and the table can be used to learn much about the chemical (and physical) nature of each metal. Table 1 Names and symbols for the elements (in alphabetical order) Name

Symbol

Actinium

Ac

Aluminum

Al

Americium

Am

Antimony

Sb(a)

Argon

Ar

Arsenic

As

Astatine

At

Barium

Ba

Berkelium

Bk

Beryllium

Be

Bismuth

Bi

Bohrium

Bh

Boron

B

Bromine

Br

Cadmium

Cd

Calcium

Ca

Californium

Cf

Carbon

C

Cerium

Ce

Cesium

Cs

Chlorine

Cl

Chromium

Cr

Cobalt

Co

Copper(b)

Cu

Curium

Cm

Dubnium

Db

Dysprosium

Dy

Einsteinium

Es

Erbium

Er

Europium

Eu

Fermium

Fm

Fluorine

F

Francium

Fr

Gadolinium

Gd

Gallium

Ga

Germanium

Ge

Gold(c)

Au

Hafnium

Hf

Hassium

Hs

Helium

He

Holmium

Ho

Hydrogen

H

Indium

In

Iodine

I

Iridium

Ir

Iron(d)

Fe

Krypton

Kr

Lanthanum

La

Lawrencium

Lr

Lead(e)

Pb

Lithium

Li

Lutetium

Lu

Magnesium

Mg

Manganese

Mn

Meitnerium

Mt

Mendelevium

Md

Mercury(f)

Hg

Molybdenum

Mo

Neodymium

Nd

Neon

Ne

Neptunium

Np

Nickel

Ni

Niobium(g)

Nb

Nitrogen

N

Nobelium

No

Osmium

Os

Oxygen

O

Palladium

Pd

Phosphorus

P

Platinum

Pt

Plutonium

Pu

Polonium

Po

Potassium(h)

K

Praseodymium

Pr

Promethium

Pm

Protactinium

Pa

Radium

Ra

Radon

Rn

Rhenium

Re

Rhodium

Rh

Rubidium

Rb

Ruthenium

Ru

Rutherfordium

Rf

Samarium

Sm

Scandium

Sc

Seaborgium

Sg

Selenium

Se

Silicon

Si

Silver(i)

Ag

Sodium(j)

Na

Strontium

Sr

Sulfur

S

Tantalum

Ta

Technetium

Tc

Tellurium

Te

Terbium

Tb

Thallium

Tl

Thorium

Th

Thulium

Tm

Tin(k)

Sn

Titanium

Ti

Tungsten(l)

W

Ununnilium

Uun

Unununium

Uuu

Uranium

U

Vanadium

V

Xenon

Xe

Ytterbium

Yb

Yttrium

Y

Zinc

Zn

Zirconium

Zr

(a) Symbol based on the Latin word stibium.

(b) Symbol based on the Latin word cuprum.

(c) Symbol based on the Latin word aurum.

(d) Symbol based on the Latin word ferrum.

(e) Symbol based on the Latin word plumbum.

(f) Symbol based on the Latin word hydrargyrum.

(g) Originally named columbium (Cb). In 1948, IUPAC agreed upon niobium as the official name.

(h) Symbol based on the Latin word kalium.

(i) Symbol based on the Latin word argentum.

(j) Symbol based on the Latin word natrium.

(k) Symbol based on the Latin word stannum.

(l) The origin of the symbol W is wolfram, named after the tungsten mineral wolframite.

Table 2 List of elements in atomic number/atomic weight order At. No.

Symbol

Name

Atomic wt

Notes

1

H

Hydrogen

1.00794(7)

(a)(b)(c)

2

He

Helium

4.002602(2)

(a)(b)

3

Li

Lithium

6.941(2)

(a)(b)(c)(d)

4

Be

Beryllium

9.012182(3)

5

B

Boron

10.811(7)

(a)(b)(c)

6

C

Carbon

12.0107(8)

(a)(b)

7

N

Nitrogen

14.00674(7)

(a)(b)

8

O

Oxygen

15.9994(3)

(a)(b)

9

F

Fluorine

18.9984032(5)

10

Ne

Neon

20.1797(6)

11

Na

Sodium

22.989770(2)

12

Mg

Magnesium

24.3050(6)

13

Al

Aluminum

26.981538(2)

14

Si

Silicon

28.0855(3)

15

P

Phosphorus

30.973761(2)

(a)(c)

(b)

16

S

Sulfur

32.066(6)

(a)(b)

17

Cl

Chlorine

35.4527(9)

(c)

18

Ar

Argon

39.948(1)

(a)(b)

19

K

Potassium

39.0983(1)

(a)

20

Ca

Calcium

40.078(4)

(a)

21

Sc

Scandium

44.955910(8)

22

Ti

Titanium

47.867(1)

23

V

Vanadium

50.9415(1)

24

Cr

Chromium

51.9961(6)

25

Mn

Manganese

54.938049(9)

26

Fe

Iron

55.845(2)

27

Co

Cobalt

58.933200(9)

28

Ni

Nickel

58.6934(2)

29

Cu

Copper

63.546(3)

30

Zn

Zinc

65.39(2)

31

Ga

Gallium

69.723(1)

32

Ge

Germanium

72.61(2)

33

As

Arsenic

74.92160(2)

34

Se

Selenium

78.96(3)

35

Br

Bromine

79.904(1)

36

Kr

Krypton

83.80(1)

(b)

(a)(c)

37

Rb

Rubidium

85.4678(3)

(a)

38

Sr

Strontium

87.62(1)

(a)(b)

39

Y

Yttrium

88.90585(2)

40

Zr

Zirconium

91.224(2)

41

Nb

Niobium

92.90638(2)

42

Mo

Molybdenum

95.94(1)

(a)

43

Tc

Technetium

[98]

(e)

44

Ru

Ruthenium

101.07(2)

(a)

45

Rh

Rhodium

102.90550(2)

46

Pd

Palladium

106.42(1)

(a)

47

Ag

Silver

107.8682(2)

(a)

48

Cd

Cadmium

112.411(8)

(a)

49

In

Indium

114.818(3)

50

Sn

Tin

118.710(7)

(a)

51

Sb

Antimony

121.760(1)

(a)

52

Te

Tellurium

127.60(3)

(a)

53

I

Iodine

126.90447(3)

54

Xe

Xenon

131.29(2)

55

Cs

Cesium

132.90545(2)

56

Ba

Barium

137.327(7)

57

La

Lanthanum

138.9055(2)

(a)

(a)(c)

(a)

(a)

58

Ce

Cerium

140.116(1)

59

Pr

Praseodymium

140.90765(2)

60

Nd

Neodymium

144.24(3)

(a)

61

Pm

Promethium

[145]

(e)

62

Sm

Samarium

150.36(3)

(a)

63

Eu

Europium

151.964(1)

(a)

64

Gd

Gadolinium

157.25(3)

(a)

65

Tb

Terbium

158.92534(2)

66

Dy

Dysprosium

162.50(3)

67

Ho

Holmium

164.93032(2)

68

Er

Erbium

167.26(3)

69

Tm

Thulium

168.93421(2)

70

Yb

Ytterbium

173.04(3)

(a)

71

Lu

Lutetium

174.967(1)

(a)

72

Hf

Hafnium

178.49(2)

73

Ta

Tantalum

180.9479(1)

74

W

Tungsten

184.83(1)

75

Re

Rhenium

186.207(1)

76

Os

Osmium

190.23(3)

77

Ir

Iridium

192.217(3)

78

Pt

Platinum

195.078(2)

(a)

(a)

(a)

79

Au

Gold

196.96655(2)

80

Hg

Mercury

200.59(a)

81

Tl

Thallium

204.3833(2)

82

Pb

Lead

207.2(1)

83

Bi

Bismuth

208.98038(2)

84

Po

Polonium

[209]

(e)

85

At

Astatine

[210]

(e)

86

Rn

Radon

[222]

(e)

87

Fr

Francium

[223]

(e)

88

Ra

Radium

[226]

(e)

89

Ac

Actinium

[227]

(e)

90

Th

Thorium

232.0381(1)

(a)(e)

91

Pa

Protactinium

231.03588(2)

(e)

92

U

Uranium

238.0289(1)

(a)(c)(e)

93

Np

Neptunium

[237]

(e)

94

Pu

Plutonium

[244]

(e)

95

Am

Americium

[243]

(e)

96

Cm

Curium

[247]

(e)

97

Bk

Berkelium

[247]

(e)

98

Cf

Californium

[251]

(e)

99

Es

Einsteinium

[252]

(e)

(a)(b)

100

Fm

Fermium

[257]

(e)

101

Md

Mendelevium

[258]

(e)

102

No

Nobelium

[259]

(e)

103

Lr

Lawrencium

[262]

(e)

104

Rf

Rutherfordium

[261]

(e)(f)

105

Db

Dubnium

[262]

(e)(f)

106

Sg

Seaborgium

[263]

(e)(f)

107

Bh

Bohrium

[262]

(e)(f)

108

Hs

Hassium

[265]

(e)(f)

109

Mt

Meitnerium

[266]

(e)(f)

110

Uun

Ununnilium

[269]

(e)(f)

111

Uuu

Unununium

[272]

(e)(f)

The data were obtained from the IUPAC Commission on Atomic Weights and Isotopic Abundances. More detailed information can be obtained by referring to Pure Appl. Chem., Vol. 68, 1996, p 2339-2359. (a) Geological specimens are known in which the element has an isotopic composition outside the limits for normal material. The difference between the atomic weight of the element in such specimens and that given in the table may exceed the stated uncertainty.

(b) Range in isotopic composition of normal terrestrial material prevents a more precise value being given; the tabulated value should be applicable to any normal material.

(c) Modified isotopic compositions may be found in commercially available material because it has been subject to an undisclosed or inadvertent isotopic fractionation. Substantial deviations in atomic weight of the element from that given in the table can occur.

(d) Commercially available Li materials have atomic weights that range between 6.94 and 6.99; if a more accurate value is required, it must be determined for the specific material.

(e) Element has no stable nuclides. The value enclosed in brackets, for example, [209], indicates the mass number of the longest-lived isotope of the element. However three such elements (Th, Pa, and U) do have a characteristic terrestrial isotopic composition, and for these an atomic weight is tabulated.

(f) The names and symbols for elements 110-111 are under review. The temporary system recommended by J. Chatt, Pure Appl. Chem., Vol 51, 1979, p 381-384 is used above. The names of elements 101 to 109 were confirmed at the IUPAC General Assembly held in Geneva (press release 30 Aug 1997).

Fig. 1 Periodic table of the elements. Values in brackets indicate the mass number of the longest lived isotope of the radioactive element.

In the periodic table (Fig. 1), the elements are arranged in the order of increasing atomic number (the number of protons in the nucleus), but those that have the same number of electrons inhabiting their outermost electron shells (and, therefore, having similar chemical behavior) are grouped under each other; hence, the vertical columns of related elements in the periodic table are called groups. As atomic number increases, more orbital electrons must be accommodated in the shells, and as each outermost shell is filled a new outermost shell (and a new period of the table) is begun. Because the additional shells are larger than the preceding shells, there is room for more electrons and the periods get longer: from two (period 1) to eight and eight (periods 2 and 3), then to eighteen and eighteen (periods 4 and 5), and finally to thirty-two and (probably) thirty-two (periods 6 and 7). Over the years, various conventions have been used to identify each group in the periodic table. For example, the 1948 Edition of the Metals Handbook used a system similar to that adopted by the International Union of Pure and Applied Chemistry (IUPAC) in 1970 in which the left-side and right-side elements in periods 4 through 7 are distinguished by the addition of the letters "A" and "B," respectively (see Fig. 1), the only difference being that the Handbook used small (lower-case) letters with the Roman numerals rather than capital (upper-case) letters. In contrast to the 1970 IUPAC system, which was commonly used in Europe, the Chemical Abstracts Service (CAS) of the American Chemical Society and many other U.S. chemists applied the "B" to the additional groups (groups 3 through 12) in periods 4 through 7 and "A" to the rest. Other conventions that have been occasionally followed in the past are to use "0" instead of VIIIA or VIIIB to identify group 18, and to use Arabic numerals instead of Roman numerals. The most recent (1988) IUPAC recommendation is to eliminate both practices and to use Arabic numerals 1 through 18 instead. Another common practice is to identify groups of similar elements with collective names. For example, the elements lithium, sodium, potassium, rubidium, cesium, and francium in group 1 are called alkali metals from the Arabic for "the ashes" (hydrogen, which is not normally a solid, is not included), and all the elements in group 2 are called alkaline earth metals. While not yet approved by IUPAC, the term pnicogens or pnictides has been applied to the elements in group 15; the term is from the Greek for "stifle, choke, or strangle," which alludes to nitrogen, that is, "burnt air." The term chalcogens has been applied to group 16 elements; the term is from the Greek for "copper," which first alluded to the common occurrence of oxygen and sulfur in many copper ores, but later referred to all these elements that were "ore formers." The term halogens (from the Greek for "salt") has been applied to group 17, and the elements in group 18 are called noble gases or inert gases. Sometimes hydrogen is positioned at the top of the halogen group in addition to its normal position at the top of group 1. Rows of some similar elements are similarly named. For example, the elements in rows 3 through 10, whose atoms have an incomplete d subshell of electrons, are called transition elements or transition metals. IUPAC 1988, however, also includes the atoms in row 11 in the group of transition elements, while other organizations include all the elements between rows 2 and 12. The elements lanthanum through lutetium (atomic numbers 57 through 71) are termed lanthanide elements, lanthanide metals, or simply lanthanides. The lanthanides together with group 3 elements yttrium (atomic number 39) and scandium (atomic number 21) are called rare earth elements, rare earth metals, or simply rare earths. The elements actinium through lawrencium (atomic numbers 89 through 103) are similarly termed actinide elements, actinide metals, or simply actinides (or sometimes second-series rare earths), while those from thorium (atomic number 90) through lawrencium (atomic number 103) are termed actinoids. As stated earlier, most of the chemical elements are metals. (The word "metal" is derived from the Greek "metallon," which is believed to have originated in a verb meaning to seek, search after, or inquire about.) In modern science, a metal is any element that tends to lose electrons from the outer shells of its atoms, with the resulting positive ions held together in a unique crystal structure by the cloud of these free electrons in a mechanism that has been called metallic bonding. This type of atomic bonding is in contrast to ionic bonding and to covalent bonding. In ionic bonding, transfer of valence (outer shell) electrons between dissimilar atoms produces stable outer shells in each and results in positive and negative ions that are mutually attracted by coulombic forces, but do not form a crystal. In covalent bonding, valence electrons are shared, rather than exchanged, and a nonmetallic crystal can form, for example, the diamond form of carbon. The cloud of free electrons in metallic crystals gives rise to the three physical characteristics typical of solid metals: metals are good conductors of electricity, good conductors of heat, and they have a lustrous appearance. In addition, most elemental metals are malleable, ductile, generally denser than other elemental substances, and usually form positive ions. Those elements that do not display the characteristics of the metallic elements are called nonmetals (see the periodic table). However, there are some elements that act as metals under some circumstances and act like nonmetals

underdifferent circumstances. These are now called semimetals, but have been called metalloids (like metals). As shown, the boundaries separating the regions in the periodic table covered by the three classes of elements are not distinct except that nonmetals never form positive ions.

Crystal Structure of Metallic Elements Hugh Baker, Consulting Editor, ASM International

Introduction CRYSTAL STRUCTURE, as defined broadly, is the arrangement of atoms or molecules in the solid state. Crystal structure also involves consideration of defects, or abnormalities, in the idealized atomic/molecular arrangements. The collective arrangement of these atoms on a scale much greater than that of the individual atom is referred to as the microstructure of the material. This article briefly reviews the terms and basic concepts associated with crystal structures that have been widely studied and are of the most importance to metallurgists. More detailed information on the crystal structure of metals can be found in Volume 9, Metallography and Microstructures, of the ASM Handbook and in the Selected References listed at the conclusion of this article.

Crystallographic Terms and Basic Concepts A crystal is a solid consisting of atoms or molecules arranged in a pattern that is repetitive in three dimensions. The arrangement of the atoms or molecules in the interior of a crystal is called its crystal structure. The unit cell of a crystal is the smallest pattern of arrangement that can be contained in a parallelepiped, the edges of which form the a, b, and c axes of the crystal. The three-dimensional aggregation of unit cells in the crystal forms a space lattice, or Bravais lattice (see Fig. 1).

Fig. 1 A space lattice. (Bold lines outline a unit cell.)

Crystal Systems. Seven different crystal systems are recognized in crystallography, each having a different set of axes, unitcell edge lengths, and interaxial angles (see Table 1). Unit-cell edge lengths a, b, and c are measured along the corresponding a, b, and c axes (see Fig. 2). Unit-cell faces are identified by capital letters: face A contains axes b and c, face B contains c and a, and face C contains a and b. (Faces are not labeled in Fig. 2.) Interaxial angle α occurs in face A, angle βin face B, and angle γin face C (see Fig. 2).

Table 1 Relationships of edge lengths and of interaxial angles for the seven crystal systems Crystal system

Triclinic (anorthic)

Monoclinic

Orthorhombic

Edge lengths

Interaxial angles

90°

Examples

HgK

a

b

c

a

b

c

=

= 90°

S; CoSb2

a

b

c

=

=

= 90°

S; Ga; Fe3C (cementite)

= 90°

Sn (white): TiO2

Tetragonal

a=b

c

=

=

Hexagonal

a=b

c

=

= 90°;

Rhombohedral(a)

a=b=c

=

=

= 90°

As; Sb; Bi; calcite

Cubic

a=b=c

=

=

= 90°

Cu; Ag; Au; Fe; NaCl

= 120°

Zn; Cd; NiAs

(a) Rhombohedral crystals (sometimes called trigonal) also can be described by using hexagonal axes (rhombohedral-hexagonal).

Fig. 2 Crystal axes and unit-cell edge lengths. (Unit-cell faces are shown in the illustration, but to avoid confusion, they are not labeled.)

Lattice Dimensions. It should be noted that the unit-cell edge lengths and interaxial angles are unique for each crystalline substance. The unique edge lengths are called lattice parameters. The term lattice constant also has been used for the length of an edge, but the values of edge length are not constant, varying with composition within a phase field and also with temperature due to thermal expansion and contraction. (Reported lattice-parameter values are assumed to be roomtemperature values unless otherwise specified.) Interaxial angles other than 90° or 120° also can change slightly with changes in composition. When the edges of the unit cell are not equal in all three directions, all unequal lengths must be stated to completely define the crystal. The same is true if all interaxial angles are not equal. When defining the unit-cell size of an alloy phase, the possibility of crystal ordering occurring over several unit cells should be considered. Lattice Points. As shown in Fig. 1, a space lattice can be viewed as a three-dimensional network of straight lines. The intersections of the lines (called lattice points) represent locations in space for the same kind of atom or group of atoms of

identical composition, arrangement, and orientation. There are five basic arrangements for lattice points within a unit cell. The first four are: primitive (simple), having lattice points solely at cell corners; base-face centered (end-centered), having lattice points centered on the C faces, or ends of the cell; all-face centered, having lattice points centered on all faces; and innercentered (body-centered), having lattice points at the center of the volume of the unit cell. The fifth arrangement, the primitive rhombohedral unit cell, is considered a separate basic arrangement, as shown in the following section on crystalstructure nomenclature. These five basic arrangements are identified by capital letters as follows: P for the primitive cubic, C for the cubic cell with lattice points on the two C faces, F for all-face-centered cubic, I for innercentered (bodycentered) cubic, and R for primitive rhombohedral. Crystal-Structure Nomenclature. When the seven crystal systems are considered together with the five space lattices, the

combinations listed in Table 2 and shown in Fig. 3 are obtained. These fourteen combinations form the basis of the system of Pearson symbols developed by William B. Pearson, which are widely used to identify crystal types. As can be seen in the table, the Pearson symbol uses a small letter to identify the crystal system and a capital letter to identify the space lattice. To these is added a number equal to the number of atoms in the unit cell conventionally selected for the particular crystal type. When determining the number of atoms in the unit cell, it should be remembered that each atom that is shared with an adjacent cell (or cells) must be counted as only a fraction of an atom. The Pearson symbols for some simple metal crystals are shown in Fig. 4, along with schematics illustrating the atom arrangements in the unit cell. Table 2 The 14-space (Bravais) lattices and their Pearson symbols (see also Fig. 2) Crystal system

Space lattice

Pearson symbol

Triclinic (anorthic)

Primitive

aP

Monoclinic

Primitive

mP

Base centered(a)

mC

Primitive

oP

Base centered(a)

oC

Body centered

oI

Face centered

oF

Primitive

tP

Body centered

tI

Hexagonal

Primitive

hP

Rhombohedral

Primitive

hR

Cubic

Primitive

cP

Orthorhombic

Tetragonal

Body centered

cI

Face centered

cF

(a) The face that has a lattice point at its center may be chosen as the c face (the xy plane), denoted by the symbol C, or as the a or b face, denoted by A or B, because the choice of axes is arbitrary and does not alter the actual translations of the lattice.

Fig. 3 The 14-space (Bravais) lattices illustrated by a unit cell of each: (1) triclinic, primitive; (2) monoclinic, primitive; (3) monoclinic, base centered; (4) orthorhombic, primitive; (5) orthorhombic, base centered; (6) orthorhombic, body centered; (7) orthorhombic, face centered; (8) tetragonal, primitive; (9) tetragonal, body centered; (10) hexagonal, primitive; (11) rhombohedral, primitive; (12) cubic, primitive; (13) cubic, body centered; (14) cubic, face centered

Fig. 4 Unit cells and atom positions for some simple metal crystals. Also listed are the space lattice and crystal system, space- group notation, and prototype for each crystal. The lattice parameters reported are for the prototype crystal. In order to show the atom arrangements more clearly, the atoms in these drawings are shown much smaller than their true effective size in real crystals.

Several of the many possible crystal structures possible are so commonly found in metallic systems that they are often identified by three-letter abbreviations that combine the space lattice with crystal system. For example, bcc for bodycentered cubic (two atoms per unit cell), fcc is used for face-centered cubic (four atoms per unit cell), and cph for closepacked hexagonal (two atoms per unit cell). (The latter space-lattice/crystal system is also commonly referred to as hexagonal close-packed, hcp, in metallurgical literature.) It should be noted that in the schematic representations shown in Fig. 4, the different kinds of atoms in the prototype crystal illustrated are drawn to represent their relative sizes, but in order to show the arrangements more clearly, all the atoms are shown much smaller than their true effective size in real crystals. A more true representation of the effective diameters of the atoms in a unit cell is shown in Fig. 5 for three common crystals.

Fig. 5 Unit cells and atom positions for (a) face-centered cubic, (b) close-packed hexagonal, and (c) body-centered cubic unit cells. The positions of the atoms are shown as dots at the left of each pair of drawings, while the atoms themselves are shown close to their true effective size by spheres or portions of spheres at the right of each pair.

Each atom arrangement shown in Fig. 4 (and all other arrangements) is characterized by efficient atom packing and a high coordination number, which is the number of nearest neighbors surrounding each atom in the cell. Both the fcc and cph structures have a coordination number of 12, while for bcc it is 8 (plus 6 additional neighbors only slightly farther distant). Space-group notation is a symbolic description of the space lattice and symmetry of a crystal. It consists of the symbol for the space lattice followed by letters and numbers that designate the symmetry of the crystal. The space-group notation for each unit cell illustrated in Fig. 4 is identified next to it. To assist in classification and identification, each crystal-structure type is assigned a representative substance (element or phase) having that structure. The substance selected is called the structure prototype for that structure. Generally accepted prototypes for some metal crystals are listed in Fig. 4. Many metals, and some nonmetals, exist in more than one crystalline form, a phenomenon known as polymorphism. When found in elemental solids, the condition is known as allotropy. The prevailing crystal structure depends on both the temperature and external pressure. For example, at atmospheric pressure, iron is bcc at temperatures below 912 °C (1674 °F), fcc between 912 and 1394 °C (1674 and 2541 °F), and above 1394 °C iron reverts to the bcc form until melting at 1538 °C (2800 °F). Titanium, zirconium, and hafnium all exhibit a transition from a cph structure to bcc on heating. Another familiar example is carbon: hexagonal graphite is the stable allotrope at ambient conditions, whereas the fcc allotrope diamond is formed at extremely high pressures. Crystallographic information for the allotropes of the metallic elements can be found in Table 3. Here the data are presented in terms of the Pearson symbol, space group, and prototype of the structure. Low-temperature structures are included for the diatomic and rare gases, which show many similarities with respect to the metallic elements.

Table 3 Crystal structures and lattice parameters of allotropes of the metallic elements Element

Temperature, °C

Pressure(a), GPa

Pearson symbol

Space group

Prototype

Comment, c/a, or

Lattice parameters(b), nm

or a

b

c

Ac

25

atm

cF4

Fm m

Cu

0.5311

...

...

...

Ag

25

atm

cF4

Fm m

Cu

0.40857

...

...

...

Al

25

atm

cF4

Fm m

Cu

0.40496

...

...

...

Al

25

>20.5

hP2

P63/mmc

Mg

0.2693

...

0.4398

1.6331

Am

25

atm

hP4

P63/mmc

0.34681

...

1.1241

2 × 1.621

Am

>769

atm

cF4

Fm m

Cu

0.4894

...

...

...

Am

>1077

atm

cI2

Im m

W

?

...

...

...

Am

25

>15

oC4

Cmcm

0.3063

0.5968

0.5169

...

Ar

< -189.2

atm

cF4

Fm m

0.53109

...

...

...

As

25

atm

hR2

R m

0.41319

...

...

Au

25

atm

cF4

Fm m

0.40782

...

...

...

B

25

atm

hR105

R m

1.017

...

...

a = 65.12°

Ba

25

atm

cI2

Im m

W

0.50227

...

...

...

Ba

25

>5.33

hP2

P63/mmc

Mg

0.3901

...

0.6154

1.5775

Ba

25

>23

?

?

...

...

...

...

...

Be

25

atm

hP2

P63/mmc

Mg

0.22859

...

0.35845

1.5681

La

U

Cu

As

Cu

B

= 65.12°

>1270

atm

cI2

Im m

W

0.25515

...

...

...

BeII

25

>28.3

hP*

...

...

0.4328

...

0.3416

0.7893

Bi

25

atm

hR2

R m

As

0.47460

...

...

= 57.23°

Bi

25

>2.6

mC4

C2/m

Bi

0.6674

0.6117

0.3304

= 110.33°

Bi

25

>3.0

mP4

P21/m

...

0.665

0.420

0.465

Bi

25

>4.3

?

?

...

...

...

...

...

Bi

25

>9.0

cI2

Im m

W

0.3800

...

...

...

Bk

25

atm

hP4

P63/mmc

0.3416

...

1.1069

2 × 1.620

Bk

>977

atm

cF4

Fm m

Cu

0.4997

...

...

...

Br

< -7.25

atm

oC8

Cmca

I2

0.668

0.449

0.874

...

C(graphite)

25

atm

hP4

P63/mmc

C(graphite)

0.24612

...

0.6709

2.7258

C(diamond)

25

>60

cF8

Fa m

C(diamond)

0.35669

...

...

...

Ca

25

atm

cF4

Fm m

Cu

0.55884

...

...

...

Ca

>443

atm

cI2

Im m

W

0.4480

...

...

...

Ca

25

>1.5

?

...

...

...

...

...

...

25

atm

hP2

P63/mmc

Mg

0.29793

...

0.56196

1.8862

Ce

< -177

atm

cF4

Fm m

Cu

0.485

...

...

...

Ce

25

atm

hP4

P63/mmc

0.36810

...

1.1857

2 × 1.611

Ce

>61

atm

cF4

Fm m

0.51610

...

...

...

Be

Cd

La

La

Cu

= 85.33°

Ce

>726

atm

cI2

Im m

'Ce

25

>5.4

oC4

Cmcm

Cf

25

atm

hP4

P63/mmc

Cf

>590

atm

cF4

Fm m

0.412

...

...

...

U

0.3049

0.5998

0.5215

...

La

0.339

...

1.1015

2 × 1.625

Cu

?

...

...

...

< -100.97

atm

oC8

Cmca

I2

0.624

0.448

0.826

...

Cm

25

atm

hP4

P63/mmc

0.3496

...

1.1331

2 × 1.621

Cm

>1277

atm

cF4

Fm m

Cu

0.4382

...

...

...

Co

25

atm

hP2

P63/mmc

Mg

0.25071

...

0.40686

1.6228

Co

>422

atm

cF4

Fm m

Cu

0.35447

...

...

...

Cr

25

atm

cI2

Im m

W

0.28848

...

...

...

'Cr

25

HP

tI2

I4/mmm

0.2882

...

0.2887

1.002

Cs

25

atm

cI2

Im m

W

0.6141

...

...

...

Cs

25

>2.37

cF4

Fm m

Cu

0.6465

...

...

...

'Cs

25

>4.22

cF4

Fm m

Cu

0.5800

...

...

...

Cs

25

>4.27

?

...

...

...

...

...

...

25

atm

cF4

Fm m

Cu

0.36146

...

...

...

'Dy

< -187

atm

oC4

Cmcm

0.3595

0.6184

0.5678

...

Dy

25

atm

hP2

P63/mmc

Mg

0.35915

...

0.56501

1.5732

Dy

>1381

atm

cI2

Im m

W

(0.398)

...

...

...

Cl

Cu

W

La

'Cr

'Dy

25

>7.5

hR3

R m

CdCl2

0.3436

...

2.483

4.5 × 1.606

25

atm

hP2

P63/mmc

Mg

0.35592

...

0.55850

1.5692

Es

25

atm

hP4

P63/mmc

?

...

...

...

Es

?

atm

cF4

Fm m

Cu

?

...

...

...

25

atm

cI2

Im m

W

0.45827

...

...

...

F

< -227.60

atm

mC8

C2/c

F

0.550

0.338

0.728

F

< -219.67

atm

cP16

Pm n

O

0.667

...

...

...

Fe

25

atm

cI2

Im m

W

0.28665

...

...

...

Fe

>912

atm

cF4

Fm m

Cu

0.36467

...

...

...

Fe

>1394

atm

cI2

Im m

W

0.29315

...

...

...

Fe

25

>13

hP2

P63/mmc

Mg

0.2468

...

0.396

1.603

Ga

25

atm

oC8

Cmca

0.45186

0.76570

0.45258

...

Ga

25

>1.2

tI2

I4/mmm

0.2808

...

0.4458

1.588

Ga

-53

>3.0

oC40

Cmcm

1.0593

1.3523

0.5203

...

Gd

25

atm

hP2

P63/mmc

Mg

0.36336

...

0.57810

1.5910

Gd

>1235

atm

cI2

Im m

W

0.406

...

...

...

Gd

25

>3.0

hR3

R m

0.361

...

2.603

4.5 × 1.60

Ge

25

atm

cF8

Fd m

0.56574

...

...

...

Ge

25

>12

tI4

I41/amd

0.4884

...

0.2692

0.551

Dy

Er

Eu

La

Ga

In

Ga

Sm

C(diamond)

Sn

= 102.17°

Ge

25

>12

tP12

P41212

Ge

0.593

...

0.698

1.18

Ge

LT

>12

cI16

Im m

Si

0.692

...

...

...

H

463

atm

tI2

I4/mmm

In

0.33261

...

0.44630

1.3418

Pu

>483

atm

cI2

Im m

W

0.36343

...

...

...

25

atm

cI2

Im m

W

0.5148

...

...

...

Rb

25

atm

cI2

Im m

W

0.5705

...

...

...

Rb

25

>1.08

?

...

...

...

...

...

...

Rb

25

>2.05

?

...

...

...

...

...

...

Re

25

atm

hP2

P63/mmc

Mg

0.27609

...

0.4458

1.6145

Rh

25

atm

cF4

Fm m

Cu

0.38032

...

...

...

Ru

25

atm

hP2

P63/mmc

Mg

0.27058

...

0.42816

1.5824

Pt

Ra

...

= 98.08°

= 101.97°

= 92.13°

S

25

atm

oF128

Fddd

S

1.0464

1.28660

2.44860

S

>95.5

atm

mP64

P21/c

S

1.102

1.096

1.090

= 96.7°

Sb

25

atm

hR2

R m

As

0.45067

...

...

= 57.11°

Sb

25

>5.0

cP1

Pm /m

Po

0.2992

...

...

...

Sb

25

>7.5

hP2

P63/mmc

Mg

0.3376

...

0.5341

1.582

Sb

25

>14.0

mP3

?

...

0.556

0.404

0.422

Sc

25

atm

hP2

P63/mmc

Mg

0.33088

...

0.52680

1.5921

Sc

>1337

atm

cI2

Im m

W

0.373

...

...

...

Se

25

atm

hP3

P3121

0.43659

...

0.49537

1.1346

Si

25

atm

cF8

Fd m

0.54306

...

...

...

Si

25

>9.5

tI4

I41/amd

Sn

0.4686

...

0.2585

0.552

Si

25

>16.0

cI16

Im m

Si

0.6636

...

...

...

Si

25

>16

hP4

P63/mmc

La

0.380

...

0.628

1.653

Sm

25

atm

hR3

R3m

Sm

0.36290

...

2.6207

4.5 × 1.6048

Sm

>734

atm

hP2

P63/mmc

Mg

0.36630

...

0.58448

1.5956

Sm

>922

atm

cI2

Im m

W

?

...

...

...

Sm

25

>4.0

hP4

P63/mmc

0.3618

...

1.166

2 × 1.611

Sn

9.0

tI2

?

0.370

...

0.337

0.91

Sr

25

atm

cF4

Fm m

Cu

0.6084

...

...

...

Sr

>547

atm

cI2

Im m

W

0.487

...

...

...

' Sr

25

>3.5

cI2

Im m

W

0.4437

...

...

...

25

atm

cI2

Im m

W

0.33030

...

...

...

Tb

230

atm

cI2

Im m

W

0.3879

...

...

...

Tl

25

HP

cF4

Fm m

Cu

?

...

...

...

25

atm

hP2

P63/mmc

Mg

0.35375

...

0.55540

1.5700

U

25

atm

oC4

Cmcm

U

0.28537

0.58695

0.49548

...

U

>668

atm

tP30

P42/mnm

U

1.0759

...

0.5656

0.526

U

>776

atm

cI2

Im m

W

0.3524

...

...

...

V

25

atm

cI2

Im m

W

0.30240

...

...

...

W

25

atm

cI2

Im m

W

0.31652

...

...

...

Xe

1478

atm

cI2

Im m

W

(0.407)

...

...

...

Yb

795

atm

cI2

Im m

W

0.444

...

...

...

25

atm

hP2

P63/mmc

Mg

0.26650

...

0.49470

1.8563

Zr

25

atm

hP2

P63/mmc

Mg

0.32316

...

0.51475

1.5929

Zr

>863

atm

cI2

Im m

W

0.36090

...

...

...

Zr

25

HP

hP2

P6/mmm

0.5036

...

0.3109

0.617

Tm

Zn

atm

Ti

Note: Values in parentheses are estimated. Source: Alloy Phase Diagrams, Vol 3, ASM Handbook, ASM International, 1992, p 14-10 to 14-12

(a) HP, high pressure.

(b) The lattice parameter of the unit cells are considered to be accurate ±2 in the last reported digit.

An important source of information on crystal structures for many years was Structure Reports (Strukturbericht in German). In this publication, crystal structures were classified by a designation consisting of a capital letter (A for elements, B for AB-type phases, C for AB2-type phases, D for other binary phases, E for ternary phases, and L for superlattices), followed a number consecutively assigned (within each group) at the time the type was reported. To further distinguish among crystal types, inferior letters and numbers, as well as prime marks, were added to some designations. Because the Strukturbericht designation cannot be conveniently and systematically expanded to cover the large variety of crystal structures currently being encountered, the system is falling into disuse. Relations among Strukturbericht designations and Pearson symbols, space groups, structure prototypes can be found in the Appendix to Volume 3, Alloy Phase Diagrams, of the ASM Handbook. Solid-Solution Mechanisms. There are only two mechanisms by which a metal crystal can dissolve atoms of a different

element. If the atoms of the solute element are sufficiently smaller than the atoms comprising the solvent crystal, the solute atoms can fit into the spaces between the larger atoms to form an interstitial solid solution (see Fig. 6a). The only solute atoms small enough to fit into the interstices of metal crystals, however, are hydrogen, nitrogen, carbon, and boron. (The other small-diameter atoms, such as oxygen, tend to form compounds with metals rather than dissolve in them.) The rest of the elements dissolve in solid metals by replacing a solvent atom at a lattice point to form a substitutional solid solution (see Fig. 6b). When both small and large solute atoms are present, the solid solution can be both interstitial and substitutional. The addition of foreign atoms by either mechanism results in distortion of the crystal lattice and an increase in its internal energy. This distortion energy causes some hardening and strengthening of the alloy called solution hardening. The solvent phase becomes saturated with the solute atoms and reaches its limit of homogeneity when the distortion energy reaches a critical value determined by the thermodynamics of the system.

Fig. 6 Solid-solution mechanisms. (a) Interstitial. (b) Substitutional

Ordered Solutions. As mentioned earlier, some alloy solutions in the ordered state have periodic structures having unit cells

many times larger than in the disordered state, the long period being either along one axis, as in Fig. 7, or along two axes, as in Fig. 8. The length of a superperiod formed by long-period ordering depends on the alloy system and the composition within the system. Figure 7 shows an AuCu II structure having a one-dimensional long-range superlattice, with boundaries between the antiphase domains at intervals of five unit cells of the disordered state. It is orthorhombic when ordered, and face-centered cubic when disordered. Figure 8 shows a two-dimensional long-period superlattice as in certain AB3 alloys (Cu-Pd, Au-Zn, Au-Mn), having antiphase boundaries spaced at intervals M1 and M2 and unit-cell dimensions a, b, and c, in the ordered state. This superlattice is orthorhombic when ordered, and face-centered cubic when disordered.

Fig. 7 AuCu II structure; a one-dimensional, long-period superlattice, having antiphase boundaries spaced at intervals of five unit cells of the disordered state

Fig. 8 Two-dimensional, long-period superlattice, having antiphase boundaries spaced at intervals M1 and M2 and unit-cell dimensions a, b, and c in the ordered state. The palladium atom has different positions in the small cubes in domains I, II, III, and IV.

Crystal Defects and Plastic Flow Crystal defects are important features in all real crystals. Some of the most significant defects are described below. Point defects include vacant atom positions that are occupied in perfect crystals. These vacancies increase in number as

temperature is increased, and by jumping about from one lattice site to another they cause diffusion. Interstitial B atoms are those located between the A atoms of the normal perfect-crystal array; thus, the carbon atoms in bcc ferrite are interstitials in that they fit between the iron atoms of its bcc structure, which is similar to the cI2 type illustrated in Fig. 4. Substitutional B atoms are located at atom positions formerly occupied by A atoms in a normal, perfect-crystal array. A B atom in either substitutional or interstitial solid solution is another common form of point defect. There are also many close pairs and clusters of point defects, such as divacancies, trivacancies, and interstitial-vacancy pairs. Line Defects. Dislocations are line defects that exist in all real crystals. An edge dislocation, which is the edge of an incomplete plane of atoms within a crystal, is represented in cross section in Fig. 9. In this illustration, the incomplete plane extends part way through the crystal from the top down, and the edge dislocation (which is indicated by the standard symbol ( ) is its lower edge.

Fig. 9 A section through an edge dislocation, which is perpendicular to the plane of the illustration and is indicated by the symbol

.

If forces, as indicated by the arrows in Fig. 10, are applied to a crystal, such as the perfect crystal shown in Fig. 10(a), one part of the crystal will slip. The edge of the slipped region, shown as a dashed line in Fig. 10(b), is a dislocation. The portion of the line at the left near the front of the crystal and perpendicular to the arrows, in Fig. 10(b), is an edge dislocation, because the displacement involved is perpendicular to the dislocation.

Fig. 10 Four stages of slip deformation by formation and movement of a dislocation (dashed line) through a crystal

The slip deformation in Fig. 10(b) has also formed another type of dislocation. The part of the slipped region near the right side, where the displacement is parallel to the dislocation, is called a screw dislocation. In this part, the crystal no longer is made of parallel planes of atoms, but instead consists of a single plane in the form of a helical ramp (screw). As the slipped region spreads across the slip plane, the edge-type portion of the dislocation moves out of the crystal leaving the screw-type portion still embedded, as shown in Fig. 10(c). When all of the dislocation finally emerges from the crystal, the crystal is again perfect, but with the upper part displaced one unit cell from the lower part, as shown in Fig. 10(d). Thus, Fig. 10 illustrates the mechanism of plastic flow by the slip process, which is actually flow by dislocation movement. The displacement that occurs when a dislocation passes a point is described by a vector, known as the Burgers vector (b). The direction of the vector with respect to the dislocation line and the length of the vector with respect to the identity distance in the direction of the vector are the fundamental characteristics of a dislocation. The perfection of a crystal lattice is restored after the passage of a dislocation, as indicated in Fig. 10(d), provided no additional defects are generated in the process. Each dislocation that remains in a crystal is the source of local stresses. The nature of these microstresses is indicated by the arrows in Fig. 11, which presents (qualitatively) the stresses acting on small volumes at different positions around the

dislocation at the lower edge of the incomplete plane of atoms. Interstitial atoms usually cluster in regions where tensile stresses make more room for them, as in the lower central part of Fig. 11.

Fig. 11 Crystal containing an edge dislocation, indicating qualitatively the stress (shown by the direction of the arrows) at four positions around the dislocation

Individual crystal grains, which have different lattice orientations, are separated by large-angle boundaries (grain boundaries). In addition, the individual grains are separated by small-angle boundaries (subboundaries) into subgrains that differ very little in orientation. These subboundaries may be considered as arrays of dislocations; tilt boundaries are arrays of edge dislocations, twist boundaries are arrays of screw dislocations. A tilt boundary is represented in Fig. 12 by the series of edge dislocations in a vertical row. Compared with large-angle boundaries, small-angle boundaries are less severe defects, obstruct plastic flow less, and are less effective as regions for chemical attack and segregation of alloying constituents. In general, mixed types of grain-boundary defects are common. All grain boundaries are sinks into which vacancies and dislocations can disappear and may also serve as sources of these defects; they are important factors in creep deformation.

Fig. 12 Small-angle boundary (subboundary) of the tilt type, which consists of a vertical array of edge dislocations

Stacking faults are two-dimensional defects that are planes where there is an error in the normal sequence of stacking of

atom layers. Stacking faults may be formed during the growth of a crystal. They may also result from motion of partial dislocations. Contrary to a full dislocation, which produces a displacement of a full distance between the lattice points, a partial dislocation produces a movement that is less than a full distance.

Twins are portions of a crystal that have certain specific orientations with respect to each other. The twin relationship may

be such that the lattice of one part is the mirror image of that of the other, or one part may be related to the other by a certain rotation about a certain crystallographic axis. Growth twins may occur frequently during crystallization from the liquid or the vapor state, by growth during annealing (by recrystallization or by grain-growth processes), or by the movement between solid phases such as during phase transformation. Plastic deformation by shear may produce deformation twins (mechanical twins). Twin boundaries generally are very flat, appearing as straight lines in micrographs, and are two-dimensional defects of lower energy than large-angle grain boundaries. Twin boundaries are, therefore, less effective as sources and sinks of other defects and are less active in deformation and corrosion than are ordinary grain boundaries. Cold Work. Plastic deformation of a metal at a temperature at which annealing does not rapidly take place is called cold

work, that temperature depending mainly on the metal in question. As the amount of cold work builds up, the distortion caused in the internal structure of the metal makes further plastic deformation more difficult, and the strength and hardness of the metal increases.

Alloy Phase Diagrams and Microstructure Hugh Baker, Consulting Editor, ASM International

Introduction ALLOY PHASE DIAGRAMS are useful to metallurgists, materials engineers, and materials scientists in four major areas: (1) development of new alloys for specific applications, (2) fabrication of these alloys into useful configurations, (3) design and control of heat treatment procedures for specific alloys that will produce the required mechanical, physical, and chemical properties, and (4) solving problems that arise with specific alloys in their performance in commercial applications, thus improving product predictability. In all these areas, the use of phase diagrams allows research, development, and production to be done more efficiently and cost effectively. In the area of alloy development, phase diagrams have proved invaluable for tailoring existing alloys to avoid overdesign in current applications, designing improved alloys for existing and new applications, designing special alloys for special applications, and developing alternative alloys or alloys with substitute alloying elements to replace those containing scarce, expensive, hazardous, or "critical" alloying elements. Application of alloy phase diagrams in processing includes their use to select proper parameters for working ingots, blooms, and billets, finding causes and cures for microporosity and cracks in castings and welds, controlling solution heat treating to prevent damage caused by incipient melting, and developing new processing technology. In the area of performance, phase diagrams give an indication of which phases are thermodynamically stable in an alloy and can be expected to be present over a long time when the part is subjected to a particular temperature (e.g., in an automotive exhaust system). Phase diagrams also are consulted when attacking service problems such as pitting and intergranular corrosion, hydrogen damage, and hot corrosion. In a majority of the more widely used commercial alloys, the allowable composition range encompasses only a small portion of the relevant phase diagram. The nonequilibrium conditions that are usually encountered in practice, however, necessitate the knowledge of a much greater portion of the diagram. Therefore, a thorough understanding of alloy phase diagrams in general and their practical use will prove to be of great help to a metallurgist expected to solve problems in any of the areas mentioned above.

Common Terms Phases. All materials exist in gaseous, liquid, or solid form (usually referred to as a "phase"), depending on the conditions

of state. State variables include composition, temperature, pressure, magnetic field, electrostatic field, gravitational field, and so forth. The term "phase" refers to that region of space occupied by a physically homogeneous material. However, there are two uses of the term: the strict sense normally used by physical scientists and the somewhat less strict sense normally used by materials engineers. In the strictest sense, homogeneous means that the physical properties throughout the region of space occupied by the phase are absolutely identical, and any change in condition of state, no matter how small, will result in a different phase. For example, a sample of solid metal with an apparently homogeneous appearance

is not truly a single-phase material because the pressure condition varies in the sample due to its own weight in the gravitational field. In a phase diagram, however, each single-phase field (phase fields are discussed in a later section) is usually given a single label, and engineers often find it convenient to use this label to refer to all the materials lying within the field, regardless of how much the physical properties of the materials continuously change from one part of the field to another. This means that in engineering practice, the distinction between the terms "phase" and "phase field" is seldom made, and all materials having the same phase name are referred to as the same phase. Equilibrium. There are three types of equilibria: stable, metastable, and unstable. These three are illustrated in a

mechanical sense in Fig. 1. Stable equilibrium exists when the object is in its lowest energy condition; metastable equilibrium exists when additional energy must be introduced before the object can reach true stability; unstable equilibrium exists when no additional energy is needed before reaching metastability or stability. Although true stable equilibrium conditions seldom exist in metal objects, the study of equilibrium systems are extremely valuable, because it constitutes a limiting condition from which actual conditions can be estimated.

Fig. 1 Mechanical equilibria. (a) Stable. (b) Metastable. (c) Unstable

Polymorphism. The structure of solid elements and compounds under stable equilibrium conditions is crystalline, and the

crystal structure of each is unique. Some elements and compounds, however, are polymorphic (multishaped), that is, their structure transforms from one crystal structure to another with changes in temperature and pressure, each unique structure constituting a distinctively separate phase. The term allotropy (existing in another form) is usually used to describe polymorphic changes in chemical elements (see the table contained in Appendix 2 to this article). Metastable Phases. Under some conditions, metastable crystal structures can form instead of stable structures. Rapid

freezing is a common method of producing metastable structures, but some (such as Fe3C, or "cementite") are produced at moderately slow cooling rates. With extremely rapid freezing, even thermodynamically unstable structures (such as amorphous metallic "glasses") can be produced. Systems. A physical system consists of a substance (or a group of substances) that is isolated from its surroundings, a concept used to facilitate study of the effects of conditions of state. By "isolated," it is meant that there is no interchange of mass with its surroundings. The substances in alloy systems, for example, might be two metals such as copper and zinc; a metal and a nonmetal such as iron and carbon; a metal and an intermetallic compound such as iron and cementite; or several metals such as aluminum, magnesium, and manganese. These substances constitute the components comprising the system and should not be confused with the various phases found within the system. A system, however, also can consist of a single component, such as an element or compound. Phase Diagrams. In order to record and visualize the results of studying the effects of state variables on a system, diagrams

were devised to show the relationships between the various phases that appear within the system under equilibrium conditions. As such, the diagrams are variously called constitutional diagrams, equilibrium diagrams, or phase diagrams. A single-component phase diagram can be simply a one- or two-dimensional plot showing the phase changes in the substance as temperature and/or pressure change. Most diagrams, however, are two- or three-dimensional plots describing the phase relationships in systems made up of two or more components, and these usually contain fields (areas) consisting of mixed-phase fields, as well as single-phase fields. The plotting schemes in common use are described in greater detail in subsequent sections of this article. System Components. Phase diagrams and the systems they describe are often classified and named for the number (in

Latin) of components in the system, as shown below:

No. of components

Name of system or diagram

One

Unary

Two

Binary

Three

Ternary

Four

Quaternary

Five

Quinary

Six

Sexinary

Seven

Septenary

Eight

Octanary

Nine

Nonary

Ten

Decinary

The phase rule, first announced by J. Willard Gibbs in 1876, relates the physical state of a mixture to the number of

constituents in the system and to its conditions. It was also Gibbs that first called the homogeneous regions in a system by the term "phases." When pressure and temperature are the state variables, the rule can be written as follows:

f=c-p+2 where f is the number of independent variables (called degrees of freedom), c is the number of components, and p is the number of stable phases in the system.

Unary Diagrams Invariant Equilibrium. According to the phase rule, three phases can exist in stable equilibrium only at a single point on a

unary diagram (f = 1 - 3 + 2 = 0). This limitation is illustrated as point 0 in the hypothetical unary pressure-temperature (PT) diagram shown in Fig. 2. In this diagram, the three states (or phases)--solid, liquid, and gas--are represented by the three correspondingly labeled fields. Stable equilibrium between any two phases occurs along their mutual boundary, and invariant equilibrium among all three phases occurs at the so-called triple point, 0, where the three boundaries intersect. This point also is called an invariant point because at that location on the diagram, all externally controllable factors are fixed (no degrees of freedom). At this point, all three states (phases) are in equilibrium, but any changes in pressure and/or temperature will cause one or two of the states (phases) to disappear.

Fig. 2 Pressure-temperature phase diagram

Univariant Equilibrium. The phase rule says that stable equilibrium between two phases in a unary system allows one

degree of freedom (f = 1 - 2 + 2). This condition, which is called univariant equilibrium or monovariant equilibrium, is illustrated as lines 1, 2, and 3 that separate the single-phase fields in Fig. 2. Either pressure or temperature may be freely selected, but not both. Once a pressure is selected, there is only one temperature that will satisfy equilibrium conditions, and conversely. The three curves that issue from the triple point are called triple curves: line 1 representing reaction between the solid and the gas phases is the sublimation curve; line 2 is the melting curve; and line 3 is the vaporization curve. The vaporization curve ends at point 4, called a critical point, where the physical distinction between the liquid and gas phases disappears. Bivariant Equilibrium. If both the pressure and temperature in a unary system are freely and arbitrarily selected, the

situation corresponds to having two degrees of freedom, and the phase rule says that only one phase can exist in stable equilibrium (p = 1 - 2 + 2). This situation is called bivariant equilibrium.

Binary Diagrams If the system being considered comprises two components, it is necessary to add a composition axis to the PT plot, which would require construction of a three-dimensional graph. Most metallurgical problems, however, are concerned only with a fixed pressure of one atmosphere, and the graph reduces to a two-dimensional plot of temperature and composition (TX) diagram. The Gibbs phase rule applies to all states of matter, solid, liquid, and gaseous, but when the effect of pressure is constant, the rule reduces to:

f=c-p+1 The stable equilibria for binary systems are summarized as follows:

No. of components

No. of phases

Degrees of freedom

Equilibrium

2

3

0

Invariant

2

2

1

Univariant

2

1

2

Bivariant

Miscible Solids. Many systems are composed of components having the same crystal structure, and the components of

some of these systems are completely miscible (completely soluble in each other) in the solid form, thus forming a continuous solid solution. When this occurs in a binary system, the phase diagram usually has the general appearance of that shown in Fig. 3. The diagram consists of two single-phase fields separated by a two-phase field. The boundary between the liquid field and the two-phase field in Fig. 3 is called the liquidus; that between the two-phase field and the solid field is the solidus. In general, a liquidus is the locus of points in a phase diagram representing the temperatures at which alloys of the various compositions of the system begin to freeze on cooling or finish melting on heating; a solidus is the locus of points representing the temperatures at which the various alloys finish freezing on cooling or begin melting on heating. The phases in equilibrium across the two-phase field in Fig. 3 (the liquid and solid solutions) are called conjugate phases.

Fig. 3 Binary phase diagram showing miscibility in both the liquid and solid states

If the solidus and liquidus meet tangentially at some point, a maximum or minimum is produced in the two-phase field, splitting it into two portions as shown in Fig. 4. It also is possible to have a gap in miscibility in a single-phase field; this is shown in Fig. 5. Point Tc, above which phases α1 and α2 become indistinguishable, is a critical point similar to point 4 in Fig. 2. Lines a-Tc and b-Tc, called solvus lines, indicate the limits of solubility of component B in A and A in B, respectively.

Fig. 4 Binary phase diagrams with solid-state miscibility where the liquidus shows (a) a maximum and (b) a minimum

Fig. 5 Binary phase diagram with a minimum in the liquidus and a miscibility gap in the solid state

The configuration of these and all other phase diagrams depends on the thermodynamics of the system, as discussed in the section on "Thermodynamics and Phase Diagrams," which appears later in this article. Eutectic Reactions. If the two-phase field in the solid region of Fig. 5 is expanded so it touches the solidus at some point, as

shown in Fig. 6(a), complete miscibility of the components is lost. Instead of a single solid phase, the diagram now shows two separate solid terminal phases, which are in three-phase equilibrium with the liquid at point P, an invariant point that occurred by coincidence. (Three-phase equilibrium is discussed in the following section.) Then, if this two-phase field in

the solid region is even further widened so that the solvus lines no longer touch at the invariant point, the diagram passes through a series of configurations, finally taking on the more familiar shape shown in Fig. 6(b). The three-phase reaction that takes place at the invariant point E, where a liquid phase freezes into a mixture of two solid phases, is called a eutectic reaction (from the Greek for easily melted). The alloy that corresponds to the eutectic composition is called a eutectic alloy. An alloy having a composition to the left of the eutectic point is called a hypoeutectic alloy (from the Greek word for less than); an alloy to right is a hypereutectic alloy (meaning greater than).

Fig. 6 Binary phase diagrams with invariant points. (a) Hypothetical diagram of the type of shown in Fig. 5, except that the miscibility gap in the solid touches the solidus curve at invariant point P; an actual diagram of this type probably does not exist. (b) and (c) Typical eutectic diagrams for (b) components having the same crystal structure, and (c) components having different crystal structures; the eutectic (invariant) points are labeled E. The dashed lines in (b) and (c) are metastable extensions of the stable-equilibria lines.

In the eutectic system described above, the two components of the system have the same crystal structure. This, and other factors, allows complete miscibility between them. Eutectic systems, however, also can be formed by two components having different crystal structures. When this occurs, the liquidus and solidus curves (and their extensions into the twophase field) for each of the terminal phases (see Fig. 6c) resemble those for the situation of complete miscibility between system components shown in Fig. 3. Three-Phase Equilibrium. Reactions involving three conjugate phases are not limited to the eutectic reaction. For example,

a single solid phase upon cooling can change into a mixture of two new solid phases, or two solid phases can, upon cooling, react to form a single new phase. These and the other various types of invariant reactions observed in binary systems are listed in Table 1 and illustrated in Fig. 7 and 8.

Table 1 Invariant reactions

Fig. 7 Hypothetical binary phase diagram showing intermediate phases formed by various invariant reactions and a polymorphic transformation

Fig. 8 Hypothetical binary phase diagram showing three intermetallic line compounds and four melting reactions

Intermediate Phases. In addition to the three solid terminal-phase fields, α, β, and ε, the diagram in Fig. 7 displays five

other solid-phase fields, γ, δ, δ', n, and σ, at intermediate compositions. Such phases are called intermediate phases. Many intermediate phases have fairly wide ranges of homogeneity, such as those illustrated in Fig. 7. However, many others have very limited or no significant homogeneity range. When an intermediate phase of limited (or no) homogeneity range is located at or near a specific ratio of component elements that reflects the normal positioning of the component atoms in the crystal structure of the phase, it is often called a compound (or line compound). When the components of the system are metallic, such an intermediate phase is often called an intermetallic compound. (Intermetallic compounds should not be confused with chemical compounds, where the type of bonding is different than in crystals and where the ratio has chemical significance.) Three intermetallic compounds (with four types of melting reactions) are shown in Fig. 8. In the hypothetical diagram shown in Fig. 8, an alloy of composition AB will freeze and melt isothermally, without the liquid or solid phases undergoing changes in composition; such a phase change is called congruent. All other reactions are incongruent; that is, two phases are formed from one phase on melting. Congruent and incongruent phase changes, however, are not limited to line compounds: the terminal component B (pure phase ε) and the highest-melting composition of intermediate phase δ' in Fig. 7, for example, freeze and melt congruently, while δ' and ε freeze and melt incongruently at other compositions. Metastable Equilibrium. In Fig. 6(c), dashed lines indicate the portions of the liquidus and solidus lines that disappear into the two-phase solid region. These dashed lines represent valuable information, as they indicate conditions that would exist under metastable equilibrium, such as might theoretically occur during extremely rapid cooling. Metastable extensions of some stable equilibria lines also appear in Fig. 2 and 6(b).

Ternary Diagrams When a third component is added to a binary system, illustrating equilibrium conditions in two dimensions becomes more complicated. One option is to add a third composition dimension to the base, forming a solid diagram having binary diagrams as its vertical sides. This can be represented as a modified isometric projection, such as shown in Fig. 9. Here, boundaries of single-phase fields (liquidus, solidus, and solvus lines in the binary diagrams) become surfaces; single- and two-phase areas become volumes; three-phase lines become volumes; and four-phase points, while not shown in Fig. 9, can exist as an invariant plane. The composition of a binary eutectic liquid, which is a point in a two-component system, becomes a line in a ternary diagram, as shown in Fig. 9.

Fig. 9 Ternary phase diagram showing three-phase equilibrium. Source: Ref 1

While three-dimension projections can be helpful in understanding the relationships in the diagram, reading values from them is difficult. Ternary systems, therefore, are often represented by views of the binary diagrams that comprise the

faces and two-dimensional projections of the liquidus and solidus surfaces, along with a series of two-dimensional horizontal sections (isotherms) and vertical sections (isopleths) through the solid diagram. Vertical sections are often taken through one corner (one component) and a congruently melting binary compound that

appears on the opposite face; when such a plot can be read like any other true binary diagram, it is called a quasi-binary section. One possibility of such a section is illustrated by line 1-2 in the isothermal section shown in Fig. 10. A vertical section between a congruently melting binary compound on one face and one on a different face might also form a quasibinary section (see line 2-3).

Fig. 10 Isothermal section of a ternary diagram with phase boundaries deleted for simplification

All other vertical sections are not true binary diagrams, and the term pseudobinary is applied to them. A common pseudobinary section is one where the percentage of one of the components is held constant (the section is parallel to one of the faces), as shown by line 4-5 in Fig. 10. Another is one where the ratio of two constituents is held constant, and the amount of the third is varied from 0 to 100% (line 1-5). Isothermal Sections. Composition values in the triangular isothermal sections are read from a triangular grid consisting of

three sets of lines parallel to the faces and placed at regular composition intervals (see Fig. 11). Normally, the point of the triangle is placed at the top of the illustration, component A is placed at the bottom left, B at the bottom right, and C at the top. The amount of constituent A is normally indicated from point C to point A, the amount of constituent B from point A to point B, and the amount of constituent C from point B to point C. This scale arrangement is often modified when only a corner area of the diagram is shown.

Fig. 11 Triangular composition grid for isothermal sections; X is the composition of each constituent in mole fraction or percent

Projected Views. Liquidus, solidus, and solvus surfaces by their nature are not isothermal. Therefore, equal-temperature

(isothermal) contour lines are often added to the projected views of these surfaces to indicate the shape of the surfaces (see Fig. 12). In addition to (or instead of) contour lines, views often show lines indicating the temperature troughs (also called "valleys" or "grooves") formed at the intersections of two surfaces. Arrowheads are often added to these lines to indicate the direction of decreasing temperature in the trough.

Fig. 12 Liquidus projection of a ternary phase diagram showing isothermal contour lines. Source: adapted from Ref 1

Reference cited in this section

1. F.N. Rhines, Phase Diagrams in Metallurgy: Their Development and Application, McGraw-Hill, 1956 Thermodynamic Principles The reactions between components, the phases formed in a system, and the shape of the resulting phase diagram can be explained and understood through knowledge of the principles, laws, and terms of thermodynamics, and how they apply to the system. Table 2 Composition conversions The following equations can be used to make conversions in binary systems:

The equation for converting from atomic percentages to weight percentages in higher-order systems is similar to that for binary systems, except that an additional term is added to the denominator for each additional component. For ternary systems, for example:

The conversion from weight to atomic percentages for higher-order systems is easy to accomplish on a computer with a spreadsheet

program.

Internal Energy. The sum of the kinetic energy (energy of motion) and potential energy (stored energy) of a system is called its internal energy, E. Internal energy is characterized solely by the state of the system. Closed System. A thermodynamic system that undergoes no interchange of mass (material) with its surroundings is called a

closed system. A closed system, however, can interchange energy with its surroundings. First Law. The First Law of Thermodynamics, as stated by Julius von Mayer, James Joule, and Hermann von Helmholtz in the 1840s, says that "energy can be neither created nor destroyed." Therefore, it is called the "Law of Conservation of Energy." This law means the total energy of an isolated system remains constant throughout any operations that are carried out on it; that is for any quantity of energy in one form that disappears from the system, an equal quantity of another form (or other forms) will appear.

For example, consider a closed gaseous system to which a quantity of heat energy, Q, is added and a quantity of work, W, is extracted. The First Law describes the change in internal energy, dE, of the system as follows:

dE = Q - W In the vast majority of industrial processes and material applications, the only work done by or on a system is limited to pressure/volume terms. Any energy contributions from electric, magnetic, or gravitational fields are neglected, except for electrowinning and electrorefining processes such as those used in the production of copper, aluminum, magnesium, the alkaline metals, and the alkaline earth metals. With the neglect of field effects, the work done by a system can be measured by summing the changes in volume, dV, times each pressure causing a change. Therefore, when field effects are neglected, the First Law can be written:

dE = Q - PdV Enthalpy. Thermal energy changes under constant pressure (again neglecting any field effects) are most conveniently

expressed in terms of the enthalpy, H, of a system. Enthalpy, also called heat content, is defined by:

H = E + PV Enthalpy, like internal energy, is a function of the state of the system, as is the product PV. Heat Capacity. The heat capacity, C, of a substance is the amount of heat required to raise its temperature one degree, that

is:

However, if the substance is kept at constant volume (dV = 0):

Q = dE and

If, instead, the substance is kept at constant pressure (as in many metallurgical systems):

and

Second Law. While the First Law establishes the relationship between the heat absorbed and the work performed by a

system, it places no restriction on the source of the heat or its flow direction. This restriction, however, is set by the Second Law of Thermodynamics, which was advanced by Rudolf Clausius and William Thomson (Lord Kelvin). The Second Law says that "the spontaneous flow of heat always is from the higher temperature body to the lower temperature body." In other words, "all naturally occurring processes tend to take place spontaneously in the direction that will lead to equilibrium." Entropy. The Second Law is most conveniently stated in terms entropy, S, another property of state possessed by all

systems. Entropy represents the energy (per degree of absolute temperature, T) in a system that is not available for work. In terms of entropy, the Second Law says that "all natural processes tend to occur only with an increase in entropy, and the direction of the process always is such as to lead to an increase in entropy." For processes taking place in a system in equilibrium with its surroundings, the change in entropy is defined as follows:

Third Law. A principle advanced by Theodore Richards, Walter Nernst, Max Planck, and others, often called the Third

Law of Thermodynamics, states that "the entropy of all chemically homogeneous materials can be taken as zero at absolute zero temperature" (0 K). This principle allows calculation of the absolute values of entropy of pure substances solely from heat capacity. Gibbs Energy. Because both S and V are difficult to control experimentally, an additional term, Gibbs energy, G,is introduced, whereby:

G

E + PV - TS

H - TS

and

dG = dE + PdV + VdP - TdS - SdT However,

dE = TdS - PdV Therefore,

dG = VdP - SdT Here, the change in Gibbs energy of a system undergoing a process is expressed in terms of two independent variables-pressure and absolute temperature--which are readily controlled experimentally. If the process is carried out under conditions of constant pressure and temperature, the change in Gibbs energy of a system at equilibrium with its surroundings (a reversible process) is zero. For a spontaneous (irreversible) process, the change in Gibbs energy is less than zero (negative); that is, the Gibbs energy decreases during the process, and it reaches a minimum at equilibrium.

Thermodynamics and Phase Diagrams The areas (fields) in a phase diagram, and the position and shapes of the points, lines, surfaces, and intersections in it, are controlled by thermodynamic principles and the thermodynamic properties of all of the phases that comprise the system. Phase-Field Rule. The phase rule specifies that at constant temperature and pressure, the number of phases in adjacent

fields in a multicomponent diagram must differ by one. Theorem of Le Châtelier. The theorem of Henri Le Châtelier, which is based on thermodynamic principles, says that "if a system in equilibrium is subjected to a constraint by which the equilibrium is altered, a reaction occurs that opposes the constraint, that is, a reaction that partially nullifies the alteration." The effect of this theorem on lines in a phase diagram can be seen in Fig. 2. The slopes of the sublimation line (1) and the vaporization line (3) show that the system reacts to increasing pressure by making the denser phases (solid and liquid) more stable at higher pressure. The slope of the melting line (2) indicates that this hypothetical substance contracts on freezing. (Note that the boundary between liquid water and ordinary ice, which expands on freezing, slopes towards the pressure axis.) Clausius-Clapeyron Equation. The theorem of Le Châtelier was quantified by Benoit Clapeyron and Rudolf Clausius to give

the following equation:

where dP/dT is the slope of the univariant lines in a PT diagram such as those shown in Fig. 2, ∆V is the difference in molar volume of the two phases in the reaction, and ∆H is difference in molar enthalpy of the two phases (the heat of the reaction). Solutions. The shape of liquidus, solidus, and solvus curves (or surfaces) in a phase diagram are determined by the Gibbs

energies of the relevant phases. In this instance, the Gibbs energy must include not only the energy of the constituent components, but also the energy of mixing of these components in the phase. Consider, for example, the situation of complete miscibility shown in Fig. 3. The two phases, solid and liquid, are in stable equilibrium in the two-phase field between the liquidus and solidus lines. The Gibbs energies at various temperatures are calculated as a function of composition for ideal liquid solutions and for ideal solid solutions of the two components, A and B. The result is a series of plots similar to those in Fig. 13(a) to 13(e).

Fig. 13 Use of Gibbs energy curves to construct a binary phase diagram that shows miscibility in both the liquid and solid states. Source: adapted from Ref 2

At temperature T1, the liquid solution has the lower Gibbs energy and, therefore, is the more stable phase. At T2, the melting temperature of A, the liquid and solid are equally stable only at a composition of pure A. At temperature T3, between the melting temperatures of A and B, the Gibbs energy curves cross. Temperature T4 is the melting temperature of B, while T5 is below it. Construction of the two-phase liquid-plus-solid field of the phase diagram in Fig. 13(f) is as follows. According to thermodynamic principles, the compositions of the two phases in equilibrium with each other at temperature T3 can be determined by constructing a straight line that is tangential to both curves in Fig. 13(c). The points of tangency, 1 and 2, are then transferred to the phase diagram as points on the solidus and liquidus, respectively. This is repeated at sufficient temperatures to determine the curves accurately. If, at some temperature, the Gibbs energy curves for the liquid and the solid tangentially touch at some point, the resulting phase diagram will be similar to those shown in Fig. 4(a) and 4(b), where a maximum or minimum appears in the liquidus and solidus curves. Mixtures. The two-phase field in Fig. 13(f) consists of a mixture of liquid and solid phases. As stated above, the

compositions of the two phases in equilibrium at temperature T3 are C1 and C2. The horizontal isothermal line connecting points 1 and 2, where these compositions intersect temperature T3, is called a tie line. Similar tie lines connect the coexisting phases throughout all two-phase fields (areas) in binary and (volumes) in ternary systems, while tie triangles connect the coexisting phases throughout all three-phase regions (volumes) in ternary systems. Eutectic phase diagrams, a feature of which is a field where there is a mixture of two solid phases, also can be constructed from Gibbs energy curves. Consider the temperatures indicated on the phase diagram in Fig. 14(f) and the Gibbs energy curves for these temperatures (Fig. 14a to 14e). When the points of tangency on the energy curves are transferred to the

diagram, the typical shape of a eutectic system results. The mixture of solid α and β that forms upon cooling through the eutectic point 10 has a special microstructure, as discussed later.

Fig. 14 Use of Gibbs energy curves to construct a binary phase diagram of the eutectic type. Source: adapted from Ref 3

Binary phase diagrams that have three-phase reactions other than the eutectic reaction, as well as diagrams with multiple three-phase reactions, also can be constructed from appropriate Gibbs energy curves. Likewise, Gibbs energy surfaces and tangential planes can be used to construct ternary phase diagrams. Curves and Intersections. Thermodynamic principles also limit the shape of the various boundary curves (or surfaces) and

their intersections. For example, see the PT diagram shown in Fig. 2. The Clausius-Clapeyron equation requires that at the intersection of the triple curves in such a diagram, the angle between adjacent curves should never exceed 180°, or alternatively, the extension of each triple curve between two phases must lie within the field of third phase. The angle at which the boundaries of two-phase fields meet also is limited by thermodynamics. That is, the angle must be such that the extension of each beyond the point of intersection projects into a two-phase field, rather than a one-phase field. An example of correct intersections can be seen in Fig. 6(b), where both the solidus and solvus lines are concave. However, the curvature of both boundaries need not be concave. Congruent Transformations. The congruent point on a phase diagram is where different phases of same composition are in

equilibrium. The Gibbs-Konovalov Rule for congruent points, which was developed by Dmitry Konovalov from a thermodynamic expression given by J. Willard Gibbs, states that the slope of phase boundaries at congruent transformations must be zero (horizontal). Examples of correct slope at the maximum and minimum points on liquidus and solidus curves can be seen in Fig. 4. Higher-Order Transitions. The transitions considered in this article up to now have been limited to the common thermodynamic types called first-order transitions, that is, changes involving distinct phases having different lattice

parameters, enthalpies, entropies, densities, and so forth. Transitions not involving discontinuities in composition, enthalpy, entropy, or molar volume are called higher-order transitions and occur less frequently. The change in the magnetic quality of iron from ferromagnetic to paramagnetic as the temperature is raised above 771 °C (1420 °F) is an example of a second-order transition: no phase change is involved and the Gibbs phase rule does not come into play in the transition. Another example of a higher-order transition is the continuous change from a random arrangement of the various kinds of atoms in a multicomponent crystal structure (a disordered structure) to an arrangement where there is some degree of crystal ordering of the atoms (an ordered structure, or superlattice), or the reverse reaction.

References cited in this section

2. A. Prince, Alloy Phase Equilibria, Elsevier, 1966 3. P. Gordon, Principles of Phase Diagrams in Materials Systems, McGraw-Hill, 1968; reprinted by Robert E. Krieger Publishing, 1983

Reading Phase Diagrams Composition Scales. Phase diagrams to be used by scientists are usually plotted in atomic percentage (or mole fraction), while those to be used by engineers are usually plotted in weight percentage. Conversions between weight and atomic composition also can be made using the equations given in Table 2 and standard atomic weights listed in the periodic table (the periodic table and atomic weights of the elements can be found in the article entitled "The Chemical Elements" in this Section). Lines and Labels. Magnetic transitions (Curie temperature and Néel temperature) and uncertain or speculative

boundaries are usually shown in phase diagrams as nonsolid lines of various types. The components of metallic systems, which usually are pure elements, are identified in phase diagrams by their symbols. Allotropes of polymorphic elements are distinguished by small (lower-case) Greek letter prefixes. Terminal solid phases are normally designated by the symbol (in parentheses) for the allotrope of the component element, such as (Cr) or (αTi). Continuous solid solutions are designated by the names of both elements, such as (Cu,Pd) or (βTi, βY). Intermediate phases in phase diagrams are normally labeled with small (lower-case) Greek letters. However, certain Greek letters are conventionally used for certain phases, particularly disordered solutions: for example, βfor disordered body-centered cubic (bcc), or ε for disordered close-packed hexagonal (cph), γ for the γ-brass-type structure, and σ for the σCrFe-type structure. For line compounds, a stoichiometric phase name is used in preference to a Greek letter (for example, A 2B3 rather than δ). Greek letter prefixes are used to indicate high- and low-temperature forms of the compound (for example, αA2B3 for the low-temperature form and βA2B3 for the high-temperature form). Lever Rule. As explained in the section on "Thermodynamics and Phase Diagrams," a tie line is an imaginary horizontal

line drawn in a two-phase field connecting two points that represent two coexisting phases in equilibrium at the temperature indicated by the line. Tie lines can be used to determine the fractional amounts of the phases in equilibrium by employing the lever rule. The lever rule is a mathematical expression derived by the principle of conservation of matter in which the phase amounts can be calculated from the bulk composition of the alloy and compositions of the conjugate phases, as shown in Fig. 15(a).

Fig. 15 Portion of a binary phase diagram containing a two-phase liquid-plus-solid field illustrating (a) application of the lever rule to (b) equilibrium freezing, (c) nonequilibrium freezing, and (d) heating of a homogenized sample. Source: Ref 1

At the left end of the line between α1 and L1, the bulk composition is Y% component B and 100 - Y% component A, and consists of 100% α solid solution. As the percentage of component B in the bulk composition moves to the right, some liquid appears along with the solid. With further increases in the amount of B in the alloy, more of the mixture consists of liquid, until the material becomes entirely liquid at the right end of the tie line. At bulk composition X, which is less than halfway to point L1, there is more solid present than liquid. The lever rule says that the percentages of the two phases present can be calculated as follows:

It should be remembered that the calculated amounts of the phases present are either in weight or atomic percentages, and as shown in Table 3, do not directly indicate the area or volume percentages of the phases observed in microstructures. Table 3 Volume fraction In order to relate the weight fraction of a phase present in an alloy specimen as determined from a phase diagram to its two-dimensional appearance as observed in a micrograph, it is necessary to be able to convert between weight-fraction values and area-fracture values, both in decimal fractions. This conversion can be developed as follows:

The weight fraction of the phase is determined from the phase diagram, using the lever rule.

Volume portion of the phase = (Weight fraction of the phase)/(Phase density)

Total volume of all phases present = Sum of the volume portions of each phase.

Volume fraction of the phase = (Weight fraction of the phase)/(Phase density × total volume)

It has been shown by stereology and quantitative metallography that areal fraction is equal to volume fraction (Ref 6). (Areal fraction of a phase is the sum of areas of the phase intercepted by a microscopic traverse of the observed region of the specimen divided by the total area of the observed region.) Therefore:

Areal fraction of the phase = (Weight fraction of the phase)/(Phase density × total volume)

The phase density value for the preceding equation can be obtained by measurements or calculation. The densities of chemical elements, and some line compounds, can be found in the literature. Alternatively, the density of a unit cell of a phase comprising one or more elements can be calculated from information about its crystal structure and the atomic weights of the elements comprising it as follows:

Total cell weight = Sum of weights of each element

Density = Total cell weight/cell volume

For example, the calculated density of pure copper, which has a fcc structure and a lattice parameter of 0.36146 nm, is:

Phase-Fraction Lines. Reading the phase relationships in many ternary diagram sections (and other types of sections)

often can be difficult due to the great many lines and areas present. Phase-fraction lines are used by some to simplify this task. In this approach, the sets of often nonparallel tie lines in the two-phase fields of isothermal sections (see Fig. 16a) are replaced with sets of curving lines of equal phase fraction (Fig. 16b). Note that the phase-fraction lines extend through the three-phase region where they appear as a triangular network. As with tie lines, the number of phase-fraction lines used is up to the individual using the diagram. While this approach to reading diagrams may not seem helpful for such a simple diagram, it can be a useful aid in more complicated systems. For more information on this topic, see Ref 4 and 5.

Fig. 16 Alternative systems for showing phase relationships in multiphase regions of ternary-diagram isothermal sections. (a) Tie lines. (b) Phase-fraction lines. Source: Ref 4

Solidification. Tie lines and the lever rule can be used to understand the freezing of a solid-solution alloy. Consider the

series of tie lines at different temperature shown in Fig. 15(b), all of which intersect the bulk composition X. The first crystals to freeze have the composition α1. As the temperature is reduced to T2 and the solid crystals grow, more A atoms are removed from the liquid than B atoms, thus shifting the composition of the remaining liquid to composition L2. Therefore, during freezing, the compositions of both the layer of solid freezing out on the crystals and the remaining liquid continuously shift to higher B contents and become leaner in A. Therefore, for equilibrium to be maintained, the solid crystals must absorb B atoms from the liquid and B atoms must migrate (diffuse) from the previously frozen material into subsequently deposited layers. When this happens, the average composition of the solid material follows the solidus line to temperature T4 where it equals the bulk composition of the alloy. Coring. If cooling takes place too rapidly for maintenance of equilibrium, the successive layers deposited on the crystals

will have a range of local compositions from their centers to their edges (a condition known as coring). Development of

this condition is illustrated in Fig. 15(c). Without diffusion of B atoms from the material that solidified at temperature T1 into the material freezing at T2, the average composition of the solid formed up to that point will not follow the solidus line. Instead it will remain to the left of the solidus, following compositions α'1 through α'3. Note that final freezing does not occur until temperature T5, which means that nonequilibrium solidification takes place over a greater temperature range than equilibrium freezing. Because most metals freeze by the formation and growth of "treelike" crystals, called dendrites, coring is sometimes called dendritic segregation. An example of cored dendrites is shown in Fig. 17.

Fig. 17 Copper alloy 71500 (Cu-30Ni) ingot. Dendritic structure shows coring: light areas are nickel-rich; dark areas are low in nickel. 20×. Source: Ref 6

Liquation. Because the lowest freezing material in a cored microstructure is segregated to the edges of the solidifying crystals (the grain boundaries), this material can remelt when the alloy sample is heated to temperatures below the equilibrium solidus line. If grain-boundary melting (called liquation or "burning") occurs while the sample also is under stress, such as during hot forming, the liquefied grain boundaries will rupture and the sample will lose its ductility and be characterized as hot short.

Liquation also can have a deleterious effect on the mechanical properties (and microstructure) of the sample after it returns to room temperature. This is illustrated in Fig. 15(d) for a homogenized sample. If homogenized alloy X is heated into the liquid-plus-solid region for some reason (inadvertently or during welding, etc.), it will begin to melt when it reaches temperature T2; the first liquid to appear will have the composition L2. When the sample is heated at normal rates to temperature T1, the liquid formed so far will have a composition L1, but the solid will not have time to reach the equilibrium composition α1. The average composition will instead lie at some intermediate value such as α'1. According to the lever rule, this means that less than the equilibrium amount of liquid will form at this temperature. If the sample is then rapidly cooled from temperature T1, solidification will occur in the normal manner, with a layer of material having composition α1 deposited on existing solid grains. This is followed by layers of increasing B content up to composition α3 at temperature T3, where all of the liquid is converted to solid. This produces coring in the previously melted regions along the grain boundaries and sometimes even voids that decrease the strength of the sample. Homogenization heat treatment will eliminate the coring, but not the voids. Eutectic Microstructures. When an alloy of eutectic composition is cooled from the liquid state, the eutectic reaction

occurs at the eutectic temperature, where the two distinct liquidus curves meet. At this temperature, both α and β solid phases must deposit on the grain nuclei until all of the liquid is converted to solid. This simultaneous deposition results in microstructures made up of distinctively shaped particles of one phase in a matrix of the other phase, or alternate layers of the two phases. Examples of characteristic eutectic microstructures include spheroidal, nodular, or globular; acicular (needles) or rod; and lamellar (platelets, Chinese script or dendritic, or filigreed). Each eutectic alloy has its own characteristic microstructure, when slowly cooled (see Fig. 18). Cooling more rapidly, however, can affect the microstructure obtained (see Fig. 19). Care must be taken in characterizing eutectic structures because elongated particles can appear nodular and flat platelets can appear elongated or needlelike when viewed in cross section.

Fig. 18 Examples of characteristic eutectic microstructures in slowly cooled alloys. (a) 40Sn-50In alloy showing globules of tin-rich intermetallic phase (light) in a matrix of dark indium-rich intermetallic phase. 150×. (b) Al13Si alloy showing an acicular structure consisting of short, angular particles of silicon (dark) in a matrix of aluminum. 200×. (c) Al-33Cu alloy showing a lamellar structure consisting of dark platelets of CuAl2 and light platelets of aluminum solid solution. 180×. (d) Mg-37Sn alloy showing a lamellar structure consisting of Mg2Sn "Chinese-script" (dark) in a matrix of magnesium solid solution. 250×. Source: Ref 6

Fig. 19 Effect of cooling rate on the microstructure of Sn-37Pb alloy (eutectic soft solder). (a) Slowly cooled sample shows a lamellar structure consisting of dark platelets of lead-rich solid solution and light platelets of tin. 375×. (b) More rapidly cooled sample shows globules of lead-rich solid solution, some of which exhibit a slightly dendritic structure, in a matrix of tin. 375×. Source: Ref 6

If the alloy has a composition different than the eutectic composition, the alloy will begin to solidify before the eutectic temperature is reached. If the alloy is hypoeutectic, some dendrites of will form in the liquid before the remaining liquid solidifies at the eutectic temperature. If the alloy is hypereutectic, the first (primary) material to solidify will be dendrites of . The microstructure produced by slow cooling of a hypoeutectic and hypereutectic alloy will consist of relatively large particles of primary constituent, consisting of the phase that begins to freeze first surrounded by relatively fine eutectic structure. In many instances, the shape of the particles will show a relationship to their dendritic origin (see Fig. 20a). In other instances, the initial dendrites will have filled out somewhat into idiomorphic particles (particles having their own characteristic shape) that reflect the crystal structure of the phase (see Fig. 20b).

Fig. 20 Examples of primary-particle shape. (a) Sn-30Pb hypoeutectic alloy showing dendritic particles of tinrich solid solution in a matrix of tin-lead eutectic. 500×. (b) Al-19Si hypereutectic alloy, phosphorus-modified, showing idiomorphic particles of silicon in a matrix of aluminum-silicon eutectic. 100×. Source: Ref 6

As stated earlier, cooling at a rate that does not allow sufficient time to reach equilibrium conditions will affect the resulting microstructure. For example, it is possible for an alloy in a eutectic system to obtain some eutectic structure in an alloy outside the normal composition range for such a structure. This is illustrated in Fig. 21. With relatively rapid cooling of alloy X, the composition of the solid material that forms will follow line 1 - '4 rather than solidus line to 4. As a result, the last liquid to solidify will have the eutectic composition L4 rather than L3, and will form some eutectic structure in the microstructure. The question of what takes place when the temperature reaches T5 is discussed later.

Fig. 21 Binary phase diagram, illustrating the effect of cooling rate on an alloy lying outside the equilibrium eutectic-transformation line. Rapid solidification into a terminal phase field can result in some eutectic structure being formed; homogenization at temperatures in the single-phase field will eliminate the eutectic structure; phase will precipitate out of solution upon slow cooling into the

-plus-

field. Source: adapted from Ref 1

Eutectoid Microstructures. Because the diffusion rates of atoms are so much lower in solids than liquids, nonequilibrium transformation is even more important in solid/solid reactions (such as the eutectoid reaction) than in liquid/solid reactions (such as the eutectic reaction). With slow cooling through the eutectoid temperature, most alloys of eutectoid composition such as alloy 2 in Fig. 22 transform from a single-phase microstructure to a lamellar structure consisting of alternate platelets of and arranged in groups (or "colonies"). The appearance of this structure is very similar to lamellar eutectic structure (see Fig. 23). When found in cast irons and steels, this structure is called "pearlite"

because of its shiny mother-of-pearl-like appearance under the microscope (especially under oblique illumination); when similar eutectoid structure is found in nonferrous alloys, it often is called "pearlite-like" or "pearlitic."

Fig. 22 Binary phase diagram of a eutectoid system. Source: adapted from Ref 1

Fig. 23 Fe-0.8C alloy showing a typical pearlite eutectoid structure of alternate layers of light ferrite and dark cementite. 500×. Source: Ref 6

The terms, hypoeutectoid and hypereutectoid have the same relationship to the eutectoid composition as hypoeutectic and hypereutectic do in a eutectic system; alloy 1 in Fig. 22 is a hypoeutectoid alloy, while alloy 3 is hypereutectoid. The solid-state transformation of such alloys takes place in two steps, much like freezing of hypoeutectic and hypereutectic alloys except that the microconstituents that form before the eutectoid temperature is reached are referred to as proeutectoid constituents rather than "primary." Microstructures of Other Invariant Reactions. Phase diagrams can be used in a manner similar to that used in the

discussion of eutectic and eutectoid reactions to determine the microstructures expected to result from cooling an alloy through any of the other six types of reactions listed in Table 1. Solid-State Precipitation. If alloy X in Fig. 21 is homogenized at a temperature between T3 and T5, it will reach

equilibrium condition; that is, the portion of the eutectic constituent will dissolve and the microstructure will consist solely of grains. Upon cooling below temperature T5, this microstructure will no longer represent equilibrium conditions, but instead will be supersaturated with B atoms. In order for the sample to return to equilibrium, some of the

B atoms will tend to congregate in various regions of the sample to form colonies of new material. The B atoms in some of these colonies, called Guinier-Preston zones, will drift apart, while other colonies will grow large enough to form incipient, but not distinct, particles. The difference in crystal structures and lattice parameters between the and phases causes lattice strain at the boundary between the two materials, thereby raising the total energy level of the sample and hardening and strengthening it. At this stage, the incipient particles are difficult to distinguish in the microstructure. Instead, there usually is only a general darkening of the structure. If sufficient time is allowed, the regions will break away from their host grains of and precipitate as distinct particles, thereby relieving the lattice strain and returning the hardness and strength to the former levels. While this process is illustrated for a simple eutectic system, it can occur wherever similar conditions exist in a phase diagram; that is, there is a range of alloy compositions in the system for which there is a transition on cooling from a single-solid region to a region that also contains a second solid phase, and where the boundary between the regions slopes away from the composition line as cooling continues. Several examples of such systems are shown schematically in Fig. 24.

Fig. 24 Examples of binary phase diagrams that give rise to precipitation reactions. Source: Ref 6

Although this entire process is called precipitation hardening, the term normally refers only to the portion before much actual precipitation takes place. Because the process takes a while to be accomplished, the term age hardening is often used instead. The rate at which aging occurs depends on the level of supersaturation (how far from equilibrium), the amount of lattice strain originally developed (amount of lattice mismatch), the fraction left to be relieved (how far along the process has progressed), and the aging temperature (the mobility of the atoms to migrate). The precipitate usually takes the form of small idiomorphic particles situated along the grain boundaries and within the grains of phase. In most instances, the particles are more or less uniform in size and oriented in a systematic fashion. Examples of precipitation microstructures are shown in Fig. 25.

Fig. 25 Examples of characteristic precipitation microstructures. (a) General and grain-boundary precipitation of Co3Ti ( ' phase) in a Co-12Fe-6Ti alloy aged 3 × 103 min at 800 °C (1470 °F). 1260×. (b) General precipitation (intragranular Widmanstätten), localized grain-boundary precipitation in Al-18Ag alloy aged 90 h at 375 °C (710 °F), with a distinct precipitation-free zone near the grain boundaries. 500×. (c) Preferential, or localized, precipitation along grain boundaries in a Ni-20Cr-1Al alloy. 500×. (d) Cellular, or discontinuous, precipitation growing out uniformly from the grain boundaries in an Fe-24.8Zn alloy aged 6 min at 600 °C (1110 °F). 1000×. Source: Ref 6

References cited in this section

1. F.N. Rhines, Phase Diagrams in Metallurgy: Their Development and Application, McGraw-Hill, 1956 4. J.E. Morral, Two-Dimensional Phase Fraction Charts, Scr. Metall., Vol 18 (No. 4), 1984, p 407-410 5. J.E. Morral and H. Gupta, Phase Boundary, ZPF, and Topological Lines on Phase Diagrams, Scr. Metall., Vol 25 (No. 6), 1991, p 1393-1396 6. Metallography and Microstructures, Vol 9, 9th ed., ASM Handbook, ASM International, 1985 Examples of Phase Diagrams The general principles of reading alloy phase diagrams are discussed in the preceding section. The application of these principles to actual diagrams for typical alloy systems is illustrated below. The Copper-Zinc System. The metallurgy of brass alloys has long been of great commercial importance. The copper

and zinc contents of five of the most common wrought brasses are:

UNS No.

Common name

Zinc content, %

Nominal Range

Range

C23000

Red brass, 85%

15

14.0-16.0

C24000

Low brass, 80%

20

18.5-21.5

C26000

Cartridge brass, 70%

30

28.5-31.5

C27000

Yellow brass, 65%

35

32.5-37.0

As can be seen in Fig. 26, these alloys encompass a wide range of the copper-zinc phase diagram. The alloys on the highcopper end (red brass, low brass, and cartridge brass) lie within the copper solid-solution phase field and are called brasses after the old designation for this field. As expected, the microstructure of these brasses consists solely of grains of copper solid solution (see Fig. 27a). The strain on the copper crystals caused by the presence of the zinc atoms, however, produces solution hardening in the alloys. As a result, the strength of the brasses, in both the work-hardened and the annealed condition, increases with increasing zinc content.

Fig. 26 The copper-zinc phase diagram, showing the composition range for five common brasses. Source: adapted from Ref 7

Fig. 27 The microstructure of two common brasses. (a) C26000 (cartridge brass, 70Cu-30Zn), hot rolled, annealed, cold rolled 70% and annealed at 638 °C (1180 °F), showing equiaxed grains of copper solid solution. (Some grains are twinned). 75×. (b) C28000 (Muntz metal, 60Cu-40Zn) ingot, showing dendrites of copper solid solution in a matrix of β. 200×. (c) C28000 (Muntz metal), showing feathers of copper solid solution, which formed at β grain boundaries during quenching of all-β structure. 100×. Source: Ref 6

The composition range for those brasses containing higher amounts of zinc (yellow brass and Muntz metal), however, overlaps into the two-phase (Cu)-plus-β field. Therefore, the microstructure of these so-called α-β alloys shows various amounts of βphase (see Fig. 27b and 27c), and their strengths are further increased over those of the αbrasses. The Aluminum-Copper System. Another alloy system of great commercial importance is aluminum-copper.

Although the phase diagram of this system is fairly complicated (see Fig. 28), the alloys of concern in this discussion are limited to the region at the aluminum side of the diagram where a simple eutectic is formed between the aluminum solid solution and the θ(Al2Cu) phase. This family of alloys (designated the 2xxx series) has nominal copper contents ranging from 2.3 to 6.3 wt% Cu, making them hypoeutectic alloys.

Fig. 28 The aluminum-copper phase diagram, showing the composition range for the 2xxx series of precipitation-hardenable aluminum alloys. Source: Ref 7

A critical feature of this region of the diagram is the shape of the aluminum solvus line. At the eutectic temperature (548.2 °C, or 1018.8 °F), 5.65 wt% Cu will dissolve in aluminum. At lower temperatures, however, the amount of copper that can remain in the aluminum solid solution under equilibrium conditions drastically decreases, reaching less than 1% at room temperature. This is the typical shape of the solvus line for precipitation hardening; if any of these alloys are homogenized at temperatures in or near the solid-solution phase field, they can be strengthened by aging at a substantially lower temperature. The Aluminum-Magnesium System. As can be seen in Fig. 29, both ends of the aluminum-magnesium system have solvus lines that are shaped similarly to the aluminum solvus line in Fig. 28. Therefore, both aluminum-magnesium alloys and magnesium-aluminum alloys are age hardenable and commercially important.

Fig. 29 The aluminum-magnesium phase diagram. Source: Ref 7

The Aluminum-Silicon System. Nonferrous alloy systems do not have to be age hardenable to be commercially important. For example, in the aluminum-silicon system (Fig. 30), almost no silicon will dissolve in solid aluminum. Therefore, as-cast hypereutectic aluminum alloy 392 (Al-19% Si) to which phosphorus was added in the melt contains large particles of silicon in a matrix of aluminum-silicon eutectic (see Fig. 20). Aluminum-silicon alloys have good castability (silicon improves castability and fluidity) and good corrosion and wear resistance (because of the hard primary silicon particles). Small additions of magnesium render some aluminum-silicon alloys age hardenable.

Fig. 30 The aluminum-silicon phase diagram. Source: Ref 7

The Lead-Tin System. The phase diagram of the lead-tin system (Fig. 31) shows the importance of the low-melting eutectic in this system to the success of lead-tin solders. While solders having tin contents between 18.3 to 61.9% all have the same freezing temperature (183 °C, or 361 °F), the freezing range (and the castability) of the alloys varies widely.

Fig. 31 The lead-tin phase diagram. Source: Ref 7

The Titanium-Aluminum and Titanium-Vanadium Systems. The phase diagrams of titanium systems are

dominated by the fact that there are two allotropic forms of solid titanium: cph αTi is stable at room temperature and up to 882 °C (1620 °F); bcc βTi is stable from 882 °C to the melting temperature. Most alloying elements used in commercial titanium alloys can be classified as αstabilizer (such as aluminum) or βstabilizers (such as vanadium and chromium), depending on whether the allotropic transformation temperature is raised or lowered by the alloying addition (see Fig. 32). Beta stabilizers are further classified as those that are completely miscible with βTi (such as vanadium, molybdenum, tantalum, and niobium) and those that form eutectoid systems with titanium (such as chromium and iron). Tin and zirconium also are often alloyed in titanium, but instead of stabilizing either phase, they have extensive solubilities in both αTi and βTi. The microstructures of commercial titanium alloys are complicated because most contain more than one of these four types of alloying elements.

Fig. 32 Three representative binary titanium phase diagrams, showing (a) α stabilization (Ti-Al), (b) β stabilization with complete miscibility (Ti-V), and (c) β stabilization with a eutectoid reaction (Ti-Cr). Source: Ref 7

The Iron-Carbon System. The iron-carbon diagram maps out the stable equilibrium conditions between iron and the graphitic form of carbon (see Fig. 33). Note that there are three allotropic forms of solid iron: the low-temperature phase, α; the medium-temperature phase, γ; and the high-temperature phase, δ. In addition, ferritic iron undergoes a magnetic

phase transition at 771 °C (1420 °F) between the low-temperature ferromagnetic state and the higher-temperature paramagnetic state. The common name for bcc Fe is "ferrite" (from ferrum, Latin for "iron"); the fcc γ phase is called "austenite" after William Roberts-Austen; bcc Fe also is commonly called ferrite because (except for its temperature range) it is the same as α-Fe. The main features of the iron-carbon diagram are the presence of both a eutectic and a eutectoid reaction, along with the great difference between the solid solubility of carbon in ferrite and austenite. It is these features that allow such a wide variety of microstructures and mechanical properties to be developed in iron-carbon alloys through proper heat treatment.

Fig. 33 The iron-carbon phase diagram. Source: Ref 7

The Iron-Cementite System. In the solidification of steels, stable equilibrium conditions do not exist. Instead, any

carbon not dissolved in the iron is tied up in the form of the metastable intermetallic compound, Fe3C (also called cementite because of its hardness), rather than remaining as free graphite (see Fig. 34). It is, therefore, the iron-cementite phase diagram, rather than the iron-carbon diagram, that is important to industrial metallurgy. It should be remembered, however, that while cementite is an extremely enduring phase, given sufficient time, or the presence of a catalyzing substance, it will break down to iron and carbon. In cast irons, silicon is the catalyzing agent that allows free carbon (flakes, nodules, etc.) to appear in the microstructure (see Fig. 35).

Fig. 34 The iron-cementite phase diagram and details of the ( Fe) and (

Fe) phase fields. Source: Ref 7

Fig. 35 The microstructure of two types of cast irons. (a) As-cast class 30 gray iron, showing type A graphite flakes in a matrix of pearlite. 500×. (b) As-cast grade 60-45-12 ductile iron, showing graphite nodules (produced by addition of calcium-silicon compound during pouring) in a ferrite matrix. 100×. Source: Ref 6

The boundary lines on the iron-carbon and iron-cementite diagrams that are important to the heat treatment of steel and cast iron have been assigned special designations, which have been found useful in describing the treatments. These lines, where thermal arrest takes place during heating or cooling due to a solid-state reaction, are assigned the letter "A" for arrêt (French for "arrest"). These designations are shown in Fig. 34. To further differentiate the lines, an "e" is added to identify those indicating the changes occurring at equilibrium (to give Ae1, Ae3, Ae4, and Aecm). Also, because the temperatures at which changes actually occur on heating or cooling are displaced somewhat from the equilibrium values, the "e" is replaced with "c" (for chauffage, French for "heating") when identifying the slightly higher temperatures associated with changes that occur on heating. Likewise, "e" is replaced with "r" (for refroidissement, French for "cooling") when identifying those slightly lower temperatures associated with changes occurring on cooling. These designations are convenient terms because they are not only used for binary alloys of iron and carbon, but also for commercial steels and cast irons, regardless of the other elements present in them. Alloying elements such as manganese, chromium, nickel, and molybdenum, however, do affect these temperatures (mainly A3). For example, nickel lowers A3 whereas chromium raises it. The microstructures obtained in steels by slowly cooling are as follows. At carbon contents from 0.007 to 0.022%, the microstructure consists of ferrite grains with cementite precipitated in from ferrite, usually in too fine a form to be visible by light microscopy. (Because certain other metal atoms that may be present can substitute for some of the iron atoms in Fe3C, the more general term, "carbide," is often used instead of "cementite" when describing microstructures). In the hypoeutectoid range (from 0.022 to 0.76% C), ferrite and pearlite grains comprise the microstructure. In the hypereutectoid range (from 0.76 to 2.14% C), pearlite grains plus carbide precipitated from austenite are visible. Slowly cooled hypoeutectic cast irons (from 2.14 to 4.3% C) have a microstructure consisting of dendritic pearlite grains (transformed from hypoeutectic primary austenite) and grains of iron-cementite eutectic (called "ledeburite" after Adolf Ledebur) consisting of carbide and transformed austenite, plus carbide precipitated from austenite and particles of free carbon. For slowly cooled hypereutectic cast iron (between 4.3 and 6.67% C), the microstructure shows primary particles of carbide and free carbon, plus grains of transformed austenite. Cast irons and steels, of course, are not used in their slowly cooled as-cast condition. Instead, they are more rapidly cooled from the melt, then subjected to some kind of heat treatment and, for wrought steels, some kind of hot and/or cold work. The great variety of microconstituents and microstructures that result from these treatments is beyond the scope of a discussion of stable and metastable equilibrium phase diagrams. Phase diagrams are, however, invaluable when designing heat treatments. For example, normalizing is usually accomplished by air cooling from about 55 °C (100 °F) above the upper transformation temperature (A3 for hypoeutectoid alloys and Acm for hypereutectoid alloys). Full annealing is done by controlled cooling from about 28 to 42 °C (50 to 75 °F) above A3 for both hypoeutectoid and hypereutectoid alloys. All tempering and process-annealing operations are done at temperatures below the lower transformation temperature (A1). Austenitizing is done at a temperature sufficiently above A3 and Acm to ensure complete transformation to austenite, but low enough to prevent grain growth from being too rapid.

The Fe-Cr-Ni System. Many commercial cast irons and steels contain ferrite-stabilizing elements (such as silicon,

chromium, molybdenum, and vanadium) and/or austenite stabilizers (such as manganese and nickel). The diagram for the binary iron-chromium system is representative of the effect of a ferrite stabilizer (see Fig. 36a). At temperatures just below the solidus, bcc chromium forms a continuous solid solution with bcc (δ) ferrite. At lower temperatures, the γ-Fe phase appears on the iron side of the diagram and forms a "loop" extending to about 11.2% Cr. Alloys containing up to 11.2% Cr, and sufficient carbon, are hardenable by quenching from temperatures within the loop.

Fig. 36 Two representative binary iron phase diagrams, (a) showing ferrite stabilization (Fe-Cr) and (b) austenite stabilization (Fe-Ni). Source: Ref 7

At still lower temperatures, the bcc solid solution is again continuous bcc ferrite, but this time with α Fe. This continuous bcc phase field confirms that δferrite is the same as αferrite. The nonexistence of γ-Fe in Fe-Cr alloys having more than about 13% Cr, in the absence of carbon, is an important factor in both the hardenable and nonhardenable grades of ironchromium stainless steels. Also at these lower temperatures, a material known as σ phase appears in different amounts from about 14 to 90% Cr. Sigma is a hard, brittle phase and usually should be avoided in commercial stainless steels. Formation of α, however, is time dependent; long periods at elevated temperatures are usually required. The diagram for the binary iron-nickel system is representative of the effect of an austenite stabilizer (see Fig. 36b). The fcc nickel forms a continuous solid solution with fcc (γ) austenite that dominates the diagram, although the α ferrite phase field extends to about 6% Ni. The diagram for the ternary Fe-Cr-Ni system shows how the addition of ferrite-stabilizing chromium affects the iron-nickel system (see Fig. 37). As can be seen, the popular 18-8 stainless steel, which contains about 8% Ni, is an all-austenite alloy at 900 °C (1652 °F), even though it also contains about 18% Cr.

Fig. 37 The isothermal section at 900 °C (1652 °F) of the Fe-Cr-Ni ternary phase diagram, showing the nominal composition of 18-8 stainless steel. Source: Ref 8

The Cr-Mo-Ni System. In addition to its use in alloy and stainless steels and in cobalt- and copper-base alloys, nickel

is also used as the basis of a family of alloys. Many of these nickel-base alloys are alloyed with chromium and molybdenum (and other elements) to improve corrosion and heat resistance. As the chromium and the molybdenum contents in most commercial Ni-Cr-Mo alloys range from 0 to about 30%, the phase diagram shown in Fig. 38 indicates that their microstructures normally consist of a matrix of γ solid solution, although this matrix is usually strengthened by a dispersion of second-phase materials such as carbides. For example, precipitated fcc γ' (Ni3Al,Ti) improves hightemperature strength and creep resistance.

Fig. 38 The isothermal section at 1250 °C (2280 °F) of the Cr-Mo-Ni nickel ternary phase diagram. Source: Ref 9

References cited in this section

6. Metallography and Microstructures, Vol 9, 9th ed., ASM Handbook, ASM International, 1985 7. T.B. Massalski, Ed., Binary Alloy Phase Diagrams, 2nd ed., ASM International, 1990 8. G.V. Raynor and V.G. Rivlin, Phase Equilibria in Iron Ternary Alloys, Vol 4, The Institute of Metals, 1988 9. K.P. Gupta, Phase Diagrams of Ternary Nickel Alloys, Indian Institute of Metals, Vol 1, 1990 Appendix 1 Melting and boiling points of the elements at atmospheric pressure Symbol

Melting point

Boiling point

°C

°K

Error limits

°C

°K

Ac

1051

1324

±50

3200

3473(a)

Ag

961.93

1235.08

...

2163

2436

Al

660.452

933.602

...

2520

2793

Am

1176

1449

...

...

...

Ar

-189.352(T.P.)

83.798(T.P.)

...

-185.9

87.3

As

614(S.P.)

887(S.P.)

...

...

...

At

(302)

(575)

...

...

...

Au

1064.43

1337.58

...

2857

3130

B

2092

2365

...

4002

4275

Ba

727

1000

±2

1898

2171

Be

1289

1562

±5

2472

2745

Bi

271.442

544.592

...

1564

1837

Bk

1050

1323

...

...

...

Br

-7.25(T.P.)

265.90(T.P.)

...

59.10

332.25

C

3827(S.P.)

4100(S.P.)

±50

...

...

Ca

842

1115

±2

1484

1757

Cd

321.108

594.258

...

767

1040

Ce

798

1071

±3

3426

3699

Cf

900

1173

...

...

...

Cl

-100.97(T.P.)

172.18(T.P.)

...

-34.05

239.10

Cm

1345

1618

...

...

...

Co

1495

1768

...

2928

3201

Cr

1863

2136

±20

2672

2945

Cs

28.39

301.54

±0.05

671

944

Cu

1084.87

1358.02

±0.04

2563

2836

Dy

1412

1685

...

2562

2835

Er

1529

1802

...

2863

3136

Es

860

1133

...

...

...

Eu

822

1095

...

1597

1870

F

-219.67(T.P.)

53.48(T.P.)

...

-188.20

84.95

Fe

1538

1811

...

2862

3135

Fm

(1527)

(1800)

...

...

...

Fr

(27)

(300)

...

...

...

Ga

29.7741(T.P.)

302.9241(T.P.)

±0.001

2205

2478

Gd

1313

1586

...

3266

3539

Ge

938.3

1211.5

...

2834

3107

H

-259.34(T.P.)

13.81(T.P.)

...

-252.882

20.268

He

-271.69(T.P.)

1.46(T.P.)

(b)

-268.935

4.215

Hf

2231

2504

±20

4603

4876

Hg

-38.836

234.210

...

356.623

629.773

Ho

1474

1747

...

2695

2968

I

113.6

386.8

...

185.25

458.40

In

156.634

429.784

...

2073

2346

Ir

2447

2720

...

4428

4701

K

63.71

336.86

±0.5

759

1032

Kr

-157.385

115.765

±0.001

-153.35

119.80

La

918

1191

...

3457

3730

Li

180.6

453.8

±0.5

1342

1615

Lr

(1627)

(1900)

...

...

...

Lu

1663

1936

...

3395

3668

Md

(827)

(1100)

...

...

...

Mg

650

923

±0.5

1090

1363

Mn

1246

1519

±5

2062

2335

Mo

2623

2896

...

4639

4912

N

-210.0042(T.P.)

63.1458(T.P.)

±0.0002

-195.80

77.35

Na

97.8

371.0

±0.1

883

1156

Nb

2469

2742

...

4744

5017

Nd

1021

1294

...

3068

3341

Ne

-248.587(T.P.)

24.563(T.P.)

±0.002

-246.054

27.096

Ni

1455

1728

...

2914

3187

No

(827)

(1100)

...

...

...

Np

639

912

±2

...

...

O

-218.789(T.P.)

54.361(T.P.)

...

-182.97

90.18

Os

3033

3306

±20

5012

5285

P(white)

44.14

317.29

±0.1

277

550

P(red)

589.6(T.P.)

862.8(T.P.)

(c)

431

704

Pa

1572

1845

...

...

...

Pb

327.502

600.652

...

1750

2023

Pd

1555

1828

±0.4

2964

3237

Pm

102

1315

...

...

...

Po

254

527

...

...

...

Pr

931

1204

...

3512

3785

Pt

1769.0

2042.2

...

3827

4100

Pu

640

913

±1

3230

3503

Ra

700

973

...

...

...

Rb

39.48

312.63

±0.5

688

961

Re

3186

3459

±20

5596

5869

Rh

1963

2236

...

3697

3970

Rn

-71

202

...

-62

211

Ru

2334

2607

±10

4150

4423

S

115.22

388.37

...

444.60

717.75

Sb

630.755

903.905

...

1587

1860

Sc

1541

1814

...

2831

3104

Se

221

494

...

685

958

Si

1414

1687

±2

3267

3540

Sm

1074

1347

...

1791

2064

Sn

231.9681

505.1181

...

2603

2876

Sr

769

1042

...

1382

1655

Ta

3020

3293

...

5458

5731

Tb

1356

1629

...

3223

3496

Tc

2155

2428

±50

4265

4538

Te

449.57

722.72

±0.3

988

1261

Th

1755

2028

±10

4788

5061

Ti

1670

1943

±6

3289

3562

Tl

304

577

±2

1473

1746

Tm

1545

1818

...

1947

2220

U

1135

1408

...

4134

4407

V

1910

2183

±6

3409

3682

W

3422

3695

...

5555

5828

Xe

-111.7582 (T.P.)

161.3918 (T.P.)

±0.0002

-108.12

165.03

Y

1522

1795

...

3338

3611

Yb

819

1092

...

1194

1467

Zn

419.58

692.73

...

907

1180

Zr

1855

2128

±5

4409

4682

Note: T.P., triple point. S.P., sublimation point at atmospheric pressure. Measurements in parenthesis are approximate. (a) ±300.

(b) There are various triple points.

(c) Red P sublimes without melting at atmosphere pressure.

Appendix 2 Allotropic transformations of the elements at atmospheric pressure Element

Transformation

Temperature, °C

Ag

L

S

0961.93

Al

L

S

660.452

Am

L

1176

1077

769

Ar

L

S

83.798K

Au

L

S

1064.43

B

L

Ba

L

Be

L

2092

S

727

1289

1270

Bi

L

S

271.442

Bk

L

S

1050

Br

L

S

265.9K

Ca

L

842

443

Cd

L

S

321.108

Ce

798

L

726

61

...

Cf

900

L

590

Cl

L

Cm

L

172.16K

S

1345

1277

Co

1495

L

422

Cr

L

S

1863

Cs

L

S

28.39

Cu

L

S

1084.87

Dy

L

1412

1381

'

-187

Er

L

S

1529

Es

L

S

860

Eu

F

L

S

822

53.48K

L

45.55K

Fe

1538

L

1394

912

Ga

L

Gd

L

S

29.7741

1313

1235

Ge

L

S

938.3

H

L

S

13.81K

Hf

L

2231

1743

Hg

L

-38.290

Ho

L

S

1474

I

L

S

113.6

In

L

S

156.634

Ir

L

S

2447

K

L

S

63.71

Kr

L

S

115.65K

La

918

L

865

310

Li

180.6

L

-193

Lu

L

S

1663

Mg

L

S

650

Mn

L

1246

1138

1100

727

Mo

L

N

L

S

2623

63146K

35.61K

Na

97.8

L

-233

Nb

L

Nd

L

S

2469

1021

863

Ne

L

S

24.563K(T.P.)

Ni

L

S

1455

Np

L

639

576

280

O

54.361K

L

43.801K

23.867K

Os

P(white

Pa

L

)

S

3033

L

44.14

L

1572

1170

Pb

L

S

327.502

Pd

L

S

1555

Pm

L

1042

890

Po

L

254

54

Pr

L

931

795

Pt

L

Pu

L

1769.0

S

640

'

483

463

'

320

215

125

Rb

L

S

39.48

Re

L

S

3186

Rh

L

S

1963

Rn

L

S

-71

Ru

L

S

2334

S

L

115.22

95.5

Sb

L

Sc

L

S

630.755

1541

1337

Se

L

S

221

Si

L

S

1414

Sm

1074

L

922

734

Sn

231.9681

L

13

Sr

769

L

547

Ta

L

Tb

L

3020

S

1356

1289

'

Te

L

Th

L

S

-53

449.57

1755

1360

Ti

1670

L

882

Tl

304

L

230

Tm

L

S

1545

U

1135

L

776

668

V

L

S

1910

W

L

S

3422

Xe

L

S

161.918(T.P.)

Y

L

1522

1478

Yb

819

L

795

-3

Zn

L

Zr

L

S

419.58

1855

863

Note: T.P., triple point

Properties of Metals Hugh Baker, Consulting Editor, ASM International

Introduction THE PROPERTIES of materials determine their usefulness. In the context in which it is frequently used, the term "property" connotes something that a material inherently possesses. More properly, a property should be regarded as the response of a material to a given set of imposed conditions (e.g., temperature and/or pressure). Material properties are the link between the basic structure and composition of the material and the service performance of a part or component. A wide variety of properties must be considered when choosing a material and a combination of properties is usually required for a given application. The properties of greatest importance for metals include: • • •

Physical properties, such as mass characteristics, thermal, electrical, magnetic, and optical properties Chemical properties, such as corrosion and oxidation resistance Mechanical properties, such as tensile and yield strength, elongation (ductility), toughness, and hardness

Many of these are discussed in this article. More detailed information can be found in the extensive data compilation on pure metals presented in Volume 2 of the ASM Handbook.

Physical Properties of Metals Mass Characteristics Mass characteristics include atomic weight and density. The atomic weight (or relative atomic mass) is the ratio of the average mass per atom of an element to of the mass of the atom of the nuclide 12C. Atomic weights of the metallic elements are given in the periodic table in the introductory article in this Section entitled "The Chemical Elements." The term density refers to the mass per unit volume of a solid material and is usually expressed in g/cm3 and abbreviated by the Greek letter rho, ρ. For solid materials, density decreases with increasing temperature. Examples of room-temperature density values for various metals can be found in Table 1. Table 1 Some physical properties of metals at room temperature Metal

Density ρd, g/cm3

Specific heat capacity (Cp), kJ/kg · K

Coefficient of linear thermal expansion (α), μm/m · K

Thermal conductivity (k), W/m · K

Electrical resistivity (ρ), nΩ · m

Aluminum

2.6989

0.900

22.8

247

26.2

Antimony

6.697

0.207

8.5 to 10.8

25.9

370

Arsenic

5.778

0.328

5.6

...

260

Barium

3.5

0.26

18

18.4

600

Beryllium

1.848

1.886

9

210

40

Bismuth

9.808

0.122

13.2

8.2

1050

Boron

2.45

1.29

8.3

27.4

18 × 1012

Cadmium

8.642

0.230

31.3

97.5

68.3

Calcium

1.55

0.6315

22.15

196

31.7

Carbon (graphite)(a)

2.25

0.691

0.6-4.3

23.9

13,750

Cerium

8.16

0.192

6.3

11.3

744

Cesium

1.903

0.2016

280

18.42

200

Chromium

7.19

0.4598

6.2

67

130

Cobalt

8.832

0.414

13.8

69.04

52.5

Copper

8.93

0.3846

16.5

398

16.730

Dysprosium

8.551

0.1705

9.9

10.7

926

Erbium

9.066

0.1680

12.2

14.5

860

Europium

5.244

0.1823

35.0

13.9

900

Gadolinium

7.901

0.2359

9.4

10.5

1310

Gallium

5.907

0.3738

18

33.49

150.5

Germanium

5.323

0.3217

5.722

58.6

530 × 106

Gold

19.302

0.128

14.2

317.9

23.5

Hafnium

13.31

0.147

519

23

351

Holmium

8.795

0.1649

11.2

16.2

814

Indium

7.30

0.233

24.8

83.7

84

Iridium

22.65

0.130

6.8

147

53

Iron

7.870

0.4473

11.8

80.4

97.1

Lanthanum

6.146

0.1951

12.1

13.4

615

Lead

11.34

0.1287

26.5

33.6

206.43

Lithium

0.5334

3.3054

56

44.0

93.5

Lutetium

9.841

0.1503

9.9

16.4

582

Magnesium

1.738

1.025

25.2

155

44.5

Manganese

7.43

0.475

21.7

7.79

1440

Mercury

13.546

0.1396

60.7

8.21

958

Molybdenum

10.22

0.276

5

142

52

Neodymium

7.008

0.1900

9.6

16.5

643

Nickel

8.902

0.471

13.3

82.9

68.44

Niobium

8.57

0.27

7.1

52.3

146

Osmium

22.58

0.12973

4.6

...

95

Palladium

12.02

0.245

11.76

70

108

Phosphorus (white)

1.83

0.741

125

0.236

10 × 107

Platinum

21.45

0.132

9.1

71.1

106

Plutonium

19.86

0.142

67

6.5

141.4

Potassium

0.855

0.770

83

108.3

72

Praseodymium

6.773

0.1946

6.7

12.5

700

Promethium

7.264

0.188

11(b)

15(b)

750(b)

Protactinium

15.43

...

9.9

47(b)

150

Rhenium

21.02

0.138

6.6

71.2

193

Rhodium

12.41

0.247

8.3

150

45.1

Rubidium

1.532

0.33489

90

58.3

115.4

Ruthenium

12.45

0.240

5.05

...

76

Samarium

7.520

0.1962

12.7

13.3

940

Scandium

2.989

0.5674

10.2

15.8

562

Selenium

4.809

0.317

49

2.48

100

Silicon

2.3290

0.713

2.616

156

1 × 106

Silver

10.49

0.235

19.0

428

14.7

Sodium

0.9674

1.2220

68.93

131.4

47.7

Strontium

2.6

0.176

...

...

...

Tantalum

16.6

0.1391

6.5

54.4

135.0

Technetium

11.5

...

7.05

50.2

185.0

Tellurium

6.237

0.201

18.2

5.98-6.02

1-50

Terbium

8.230

0.1818

10.3

11.1

1150

Thallium

11.872

0.130

28

47

150

Thorium

11.8

0.11308

10.9

77

157

Thulium

9.321

0.1598

13.3

16.9

676

Tin

5.765

0.205

21

62.8

110

Titanium

4.507

0.5223

8.41

11.4

420

Tungsten

19.254

0.128

3.01-8.87

160

53

Uranium

19.05

0.117

12

27.6

300

Vanadium

6.16

0.498

8.3

31.0

248

Ytterbium

6.903

0.1543

26.3

38.5

250

Yttrium

4.469

0.2981

10.6

17.2

596

Zinc

7.133

0.382

39.7

113

59.16

Zirconium

6.505

0.30

5.85

21.1

450

(a) The electrical resistivity of carbon in diamond form is > 107 nΩ · m.

Thermal Properties Melting and Boiling Points. The melting point is the temperature at which the solid and liquid phases of a pure

material are in equilibrium. The boiling point is the temperature at which the vapor pressure of a liquid equals the pressure of the surroundings: normally this pressure is taken to be 1 atm (760 torr). The melting and boiling points of the chemical elements and the temperatures at which allotropic phase transformations occur are given in Appendices 1 and 2 in the article "Alloy Phase Diagrams and Microstructure" in this Section. Vapor Pressure. The vapor pressure of an element at a given temperature is related to the ratio of that temperature on

the absolute scale to the boiling point of the element, also on the absolute scale. Vapor pressure values for various elements can be found in Table 2. Table 2 Vapor pressures of the elements up to 1 atm (760 mm Hg) Element

Pressure, atm

0.0001

0.001

0.01

0.1

0.5

1.0

°C

°F

°C

°F

°C

°F

°C

°F

°C

°F

°C

°F

Aluminum

1110

2030

1263

2305

1461

2662

1713

3115

1940

3524

2056

3733

Antimony

759

1398

872

1602

1013

1855

1196

2185

1359

2478

1440

2624

Arsenic

308

586

363

685

428

802

499

930

578

1072

610

1130

Bismuth

914

1677

1008

1846

1121

2050

1254

2289

1367

2493

1420

2588

Cadmium

307(a)

585(a)

384(b)

723(b)

471

880

594

1101

708

1306

765

1409

Calcium

688

1270

802(c)

1476(c)

958(b)

1756(b)

1175

2147

1380

2516

1487

2709

Carbon

3257

5895

3547

6417

3897

7047

4317

7803

4667

8433

4827

8721

Chromium

1420(a)

2588(a)

1594(b)

2901(b)

1813

3295

2097

3807

2351

4264

2482

4500

Copper

1412

2574

1602

2916

1844

3351

2162

3924

2450

4442

2595

4703

Gallium

1178

2152

1329

2424

1515

2759

1751

3184

1965

3569

2071

3760

Gold

1623

2953

1839

3342

2115

3839

2469

4476

2796

5065

2966

5371

Iron

1564

2847

1760

3200

2004

3639

2316

4201

2595

4703

2735

4955

Lead

815

1499

953

1747

1135

2075

1384

2523

1622

2952

1744

3171

Lithium

592

1098

707

1305

858

1576

1064

1947

1266

2311

1372

2502

Magnesium

516

961

608(a)

1126(a)

725(b)

1337(b)

886

1627

1030

1886

1107

2025

Manganese

1115(d)

2039(d)

1269(b)

2316(b)

1476

2889

1750

3182

2019

3666

2151

3904

Mercury

77.9(b)

172.2(b)

120.8

249.4

176.1

349.0

251.3

484.3

321.5

610.7

357

675

Molybdenum

2727

4941

3057

5535

3477

6291

4027

7281

4537

8199

4804

8679

Nickel

1586

2887

1782

3240

2025

3677

2321

4210

2593

4699

2732

4950

Platinum

2367

4293

2687

4869

3087

5589

3637

6579

4147

7497

4407

7965

Potassium

261

502

332

630

429

804

565

1051

704

1299

774

1425

Rubidium

223

433

288

550

377

711

497

927

617

1143

679

1254

Selenium

282

540

347

657

430

806

540

1004

634

1173

680

1256

Silicon

1572

2862

1707

3105

1867

3393

2057

3735

2217

4023

2287

4149

Silver

1169

2136

1334

2433

1543

2809

1825

3317

2081

3778

2212

4014

Sodium

349

660

429

804

534

993

679

1254

819

1506

892

1638

Strontium

...

...

(a)

(a)

877(b)

1629(b)

1081

1978

1279

2334

1384

2523

Tellurium

(a)

(a)

509(b)

948(b)

632

1170

810

1490

991

1816

1087

1989

Thallium

692

1277

809

1488

962

1764

1166

2131

1359

2478

1457

2655

Tin

...

...

...

...

...

...

1932 (b)

3510(b)

2163

3925

2270

4118

Tungsten

3547

6417

3937

7119

4437

8019

5077

9171

5647

10197

5927

10701

Zinc

399(a)

750(a)

477(b)

891(b)

579

1074

717

1323

842

1548

907

1665

Source: K.K. Kelley, Bur. Mines Bull., Vol 383, 1935 (a) In the solid state.

(b) In the liquid state.

(c) β.

(d) γ.

Thermal Expansion. Most solid materials expand upon heating and contract when cooled. The change in length with temperature for a solid material can be expressed as follows:

(lf - lo)/lo = α1(Tf - To) or

∆l/lo = α1∆T where lo and lf represent, respectively, the original and final lengths with the temperature change from To to Tf. The parameter α1 is called the linear coefficient of thermal expansion (CTE); it is a material property that is indicative of the extent to which a material expands upon heating and has units of reciprocal temperature (K-1) or μm/m · K. Table 1 lists room-temperature linear CTE values for various metals. With respect to temperature, the magnitude of the CTE increases with rising temperature. In general, CTE values for metals fall between those of ceramics (lower values) and polymers (higher values). Of course, heating or cooling affects all the dimensions of a body, with a resultant change in volume. Volume changes may be determined from:

∆V/Vo = αv∆T

where ∆V and Vo are the volume change and original volume, respectively, and αv represents the volume coefficient of thermal expansion. In many materials, the value of α v is anisotropic; that is, it depends on the crystallographic direction along which it is measured. For materials in which the thermal expansion is isotropic, αv is approximately 3α1. Heat Capacity. A solid material, when heated, experiences an increase in temperature indicating that some energy has

been absorbed. Heat capacity is the property that represents the ability of a material to absorb heat from external surroundings; it is the amount of energy required to produce a unit temperature rise. Heat capacity, C, is expressed as follows:

C = dQ/dT where dQ is the energy required to produce a dT temperature change. Heat capacity is ordinarily specified per mole of material (e.g., J/mol · K). For most practical purposes the quantity used is the specific heat capacity, or specific heat, which is the quantity of heat required to change by one degree the temperature of a body of material of unit mass, expressed as J/kg · K. Lower and higher specific heat values correspond with lower and higher temperatures, respectively.

There are really two ways in which the specific heat can be measured according to the environmental conditions accompanying the transfer of heat. One is the specific heat capacity while maintaining the specimen volume constant, Cv; the other is for constant external pressure, Cp. The magnitude of Cp is always greater than Cv; however, this difference is very slight for most solid materials at room temperature and below. Table 1 lists Cp values for various metallic elements. Thermal Conductivity. Thermal conduction is the phenomenon by which heat is transported/transferred from high- to low-temperature regions of a substance. The property that characterizes the ability of a material to transfer heat is the thermal conductivity, which is defined as:

q = -k(dT/dx) where q denotes the heat flux, or heat flow, per unit time per unit area (area being taken as that perpendicular to the flow direction), k is the thermal conductivity, and dT/dx is the temperature gradient through the conducting medium. The units for q and k are W/m2 and W/m × K, respectively. (Room-temperature k values for various metals are given in Table 1.) It should be noted that the above equation is valid for only steady-state heat flow, that is, for situations in which the heat flux does not change with time. The minus sign in the equation indicates that the direction of heat flow is from hot to cold, or down the temperature gradient. Because the thermal vibration of the free electrons in metallic crystals is a major contributor to the high thermal conductivity of solid metals (along with ionic vibration), the values of the thermal and electrical conductivities of a metal at any given temperature are related. The ratio between the two is called the Wiedemann-Franz ratio (k/σ), which was developed by Gustav Heinrich Wiedemann and Rudolf Franz and is about 1.6 × 10-6 at 20 °C. Further, because electrical resistivity is nearly proportional to the absolute temperature, the value k/σT, called the Lorentz number (after Henrick Anton Lorentz), is approximately constant. A more exact relation between the two conductivities, however, is defined by the Bungardt and Kallenbach equation:

k = A × σT + B × T where A and B are the constants for the free-electron and ionic contributions, respectively, for a given metal. Because of the difficulty involved in measuring thermal conductivity compared to electrical resistivity, this relation is useful in estimating the thermal conductivities of alloys as well as metals. It should be noted that because both electrical and thermal conductivities rely on the migration of free electrons, temperature is not the only factor that affects these properties. Anything that distorts the crystal structure, such as thermal vibrations of the ions, crystal vacancies and dislocations, grain boundaries, interstitial and solute ions, and elastic and plastic strain, will increase resistance to conduction.

Thermal diffusivity is a useful measure of the speed at which heat spreads throughout a metal object, and this property

can be calculated by dividing the thermal conductivity by the product of the specific heat capacity and the density of the metal. The units of thermal diffusivity are m2/s, and the value describes the rate at which the spherical area within the object that is at a given temperature expands from a point heating source. Electrical Properties One of the most important electrical characteristics of a solid material is the ease with which it transits an electric current. Ohm's law (after Georg Simon Ohm) relates the current, I, to the applied voltage, V, as follows:

V = IR where R is the resistance of the material through which the current is passing. The units for V, I, and R are volts (V), amperes (A), and ohms (Ω = V/A). The value of R is influenced by specimen configuration, and for many materials is independent of current. The resistivity, designated ρ, is independent of specimen shape, but related to R through the expression:

ρ= RA/l where l is the distance between the two points at which the voltage is measured, and A is the cross-sectional area perpendicular to the direction of the current. The units for ρ are Ω× m (often given as μmΩ × m or nΩ × m). From the expression for Ohm's law and the previous equation:

ρ= VA/Il Sometimes, electrical conductivity, σ, is used to specify the electrical character of a material. It is simply the reciprocal of the resistivity, or σ= 1/ρ. As shown in Table 1, metals exhibit a wide range of resistivities--from the low resistivity (high conductivity) of silver and copper to the high resistivity (low conductivity) of manganese and bismuth. Resistivity values of metals increase with increasing temperature. Also as shown in Table 1, the semimetals boron, carbon, silicon, white phosphorus, sulfur, germanium, and tellurium have electrical resistivities that are intermediate between those of metal conductors and nonmetal insulators. Therefore, they are called semiconductors. Their resistivities range from about 103 to 1013 Ω· m, and they decrease with increasing temperature over some temperature range. Magnetic Properties All metals have magnetic properties, and these properties are important in many industrial applications. The magnetic moments are generated by the movements of the electrically charged electrons that orbit the atomic nuclei making up the crystal structure of the metal. Each electron generates magnetic moments from two sources, as shown in Fig. 1; one source is its orbiting and the other is its spinning as it orbits. Because these moments have specific directions, the orbital moments of some electron pairs in each individual atom can cancel each other. This also applies to spin moments. The resulting magnetic moment for each atom, then, is the net sum (rather than the total) of the individual moments of its electrons. Therefore, for atoms having completely filled electron shells, there is complete cancellation of electron moments, and the material is not capable of being permanently magnetized.

Fig. 1 Sources of magnetic moments. (a) Orbiting electron. (b) Spinning electron

One measure of the magnetism of a material is its magnetic permeability. Magnetic permeability is a measure of the tendency of magnetic lines of force to pass through a metal in comparison to empty space. Another measure of the magnetism of a material is its magnetic susceptibility. Magnetic susceptibility is the ratio of the intensity of magnetization in a metal to the magnetizing force to which the metal is subjected. Relative permeability and susceptibility are both unitless, but the values of susceptibility in SI units (referred to as meter-kilogram-second or mks units) are 4 greater than the values in cgs-emu (centimeter-gram-second electromagnetic unit) units. (The values of relative permeability are identical in SI and cgs-emu units.) The magnetic susceptibility, , of a material is defined by the equation:

B= H where H is the strength of a magnetic field applied to a material and B is the density of magnetic flux induced in the material. As the applied field is increased, the magnetic flux density also increases until a saturation level for the material is reached (see Fig. 2).

Fig. 2 Magnetization curve for polycrystalline iron

Another property of magnetic materials is its saturation magnetic moment (see Table 3). The value of the saturation magnetic moment of a material is the ratio of the magnetic moment per atom of the material at magnetic saturation to the spin magnetic moment per electron in the material.

Table 3 Magnetic phase transition temperatures of metallic elements Chemical symbol

Atomic number

Allotrope

Phase transition temperature (Tc), K

Type of magnetic ordering(a)

Phase transition temperature (Tc2), K

Type of magnetic ordering(a)

Phase transition temperature (Tc3), K

Type of magnetic ordering(a)

Saturation magnetic moment, B

Ce(b)

58

β-dcph

13.7

AC?

12.5

AC?

...

...

2.61

γ-fcc

14.4

AC?

...

...

...

...

...

AC

...

...

...

...

...

Cm

96

α-dcph

52

Co

27

fcc

1388 °C)

(1115

FM

...

...

...

...

1.715

Cr

24

bcc

312.7 °C)

(39.5

AI

...

...

...

...

0.45

Dy

66

179.0

AI

89.0

FM

...

...

10.33

Er

68

cph

85.0

AI

53

AC

20.0

CF

9.1

Eu

63

bcc

90.4

AC

...

...

...

...

5.9

Fe(c)

26

FM

...

...

...

...

2.216

AC

...

...

...

...

0.75

FM

...

...

...

...

0.75

132.0

AI

20.0

CF

...

...

10.34

-cph

-bcc

1044 °C)

-fcc

67

-cph

293.4 °C)

(771

(20.2

Gd

64

Ho

67

Mn

25

-bcc

100

AC

...

...

...

...

(d)

Nd

60

-dcph

19.9

AI

7.5

AC

...

...

1.84

Ni

28

627.4 (354.2 °C)

FM

...

...

...

...

0.616

Pm

61

98

FM?

...

...

...

...

0.24

cph

fcc

-dcph

Pr

59

-dcph

0.06

AC

...

...

...

...

0.36

Sm

62

-rhomb

106

h, A(e)

13.8

c, A(e)

...

...

0.1

Tb

65

-cph

230.0

AI

219.5

FM

...

...

9.34

Tm

69

58.0

AI

40-32

FI

...

...

7.14

cph

Source: J.J. Rhyne, Bull. Alloy Phase Diagrams, Vol 3 (No. 3), 1982, p 402 (a) FM, transition from paramagnetic to ferromagnetic state; AC, transition to periodic (antiferromagnetic) state that is commensurate with the lattice periodicity (e.g., spins on three atom layers directed up followed by three layers down, etc.); AI, transition to periodic (antiferromagnetic) state that is generally not commensurate with lattice periodicity (e.g., helical spin ordering); CF, transition to conical ferromagnetic state (combination of planar helical antiferromagnetic plus ferromagnetic component); and FI, transition to ferromagnetic periodic structure (unequal number of up and down spin layers).

(b) Ce exists in five crystal structures, two of which are magnetic (γ-fcc; and β-dcph). γCe is estimated to be antiferromagnetic below 14.4 K by extrapolation from fcc Ce-La alloys. (αCe does not exist in pure form below ≈ 100 K.) βCe is thought to exhibit antiferromagnetism on the hexagonal lattice sites below 13.7 K and on the cubic sites below 12.5 K.

(c) Magnetic measurements quoted in table for γFe are for fcc Fe precipitated in copper.

(d) The magnetic moment assignments of Mn are complex.

(e) h, A; c, A; indicate that sites of hexagonal and cubic point symmetry order antiferromagnetically, but at different temperatures.

The magnetic properties of some metallic elements are listed in Tables 3 and 4. It should be noted that there are several types of magnetism found in metals, and the temperatures at which they change from one type to another are also given in Table 3. As seen in the table, iron is not the only metal to exhibit ferromagnetism. Cobalt, nickel, and possibly promethium also exhibit ferromagnetism at room temperature. Gadolinium and a few other rare earth metals are ferromagnetic at very low temperatures. Ferromagnetic materials are those in which, at temperatures below a characteristic temperature called the Curie point (after Pierre Curie), the magnetic moments of atoms or ions tend to be aligned parallel to one another without the presence of an applied field, thereby producing a "permanent" magnetic moment. Above the Curie point, these materials become paramagnetic. Paramagnetic materials are those within which the permanent-magnetic dipole moments of atoms or ions are only partially aligned and the magnetic induction (magnetic flux density) is only slightly greater than the applied magnetic-field strength. The permeability of a ferromagnetic metal can reach values of the order of 106 times that of empty space, while the permeability of a paramagnetic metal is only slightly greater than that of empty space.

Table 4 Room-temperature magnetic susceptibilities for paramagnetic and diamagnetic materials Paramagnetics

Diamagnetics

Material

Susceptibility Xm (volume) (SI units)

Material

Susceptibility Xm (volume) (SI units)

Aluminum

2.07 × 10-5

Copper

-0.96 × 10-5

Chromium

3.13 × 10-4

Gold

-3.44 × 10-5

Molybdenum

1.19 × 10-4

Mercury

-2.85 × 10-5

Sodium

8.48 × 10-6

Silicon

-0.41 × 10-5

Titanium

1.81 × 10-4

Silver

-2.38 × 10-5

Zirconium

1.09 × 10-4

Zinc

-1.56 × 10-5

There are three other types of magnetic materials. Ferrimagnetic materials are those in which the magnetic moments of atoms or ions tend to assume an ordered but nonparallel arrangement in a zero applied field below a characteristic temperature called the Néel point (after Louis E.F. Néel). Antiferromagnetic materials are those in which the magnetic moments of atoms or ions tend to assume an ordered arrangement in a zero applied field, such that the vector sum of the moments is zero below the Néel point. The permeability of antiferromagnetic materials is comparable to that of paramagnetic materials. Above the Néel point, both these materials become paramagnetic. Diamagnetic materials are those within which the magnetic induction is slightly less than the applied magnetic field. For diamagnetic materials, the permeability is slightly less than that of empty space, and the magnetic susceptibility is negative and small. The response of ferromagnetic, paramagnetic, and diamagnetic materials is compared in Fig. 3. Additional information on the magnetic characteristics of metals and alloys can be found in the Section "Special-Purpose Materials" in this Handbook.

Fig. 3 Schematic of the flux density, B, versus magnetic field strength, H, for diamagnetic, paramagnetic, and

ferromagnetic materials

Optical Properties Several optical properties of smooth, bare, unoxidized metal surfaces are important in some applications. Four of these are solar reflectivity (shininess in sunlight), solar absorptivity (warming by sunlight), thermal emissivity (radiation cooling from a warm body), and color. (The word ending "ance" is substituted for "ivity" when the properties are measured on a rough surface.) The reflectivities of metals are high, but their emissivities are low. It should be remembered, however, that the values of these properties apply only to smooth, clean, unoxidized bare surfaces, which are seldom found on metals and alloys in practical applications. Instead, the surfaces of metals are almost always covered with some kind of an oxide layer or paint, both of which have the relatively low reflectance, but high emittance of nonmetallics. Exceptions are the noble metals (see below), which are normally bare. The surface of clean, bare, unoxidized metals is lustrous. The color in all but two instances ranges from silvery gray to various shades of white. The exceptions are the reddish color of copper and the red-yellow of gold, which is the result of their electron configurations. Because of their chemical activities, thin oxides rapidly form on freshly bare surfaces of most metals, and these oxides can affect their appearance (see below). Radiation Properties The properties that describe the transparency or opaqueness of metals to radiation are important in some industries. The transparency to x-rays of light metals is required for the holders of x-ray films, while absorption of x-rays by lead makes possible its use as a shielding material. The thermal-neutron cross section of a metal defines the extent to which that metal absorbs thermal (slow) neutrons from a nuclear reactor, and the low thermal-neutron cross section of zirconium makes it a good canning material for nuclear fuel.

Chemical Properties of Metals The chemical property most important to structural use of a metal is its corrosion behavior. Most metals are basic in chemical behavior (will react with acids). But as stated above, because of the chemical activities of the metallic elements, thin oxides rapidly form on freshly bare surfaces of most metals. Ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold are the exceptions. These eight metals have such low chemical activity that they are called noble metals. The physical and chemical properties of the oxides that form on the nonnoble metals, however, differ from metal to metal. Physically, some oxides cohere tightly to their base metal, while others readily spall or flake off and expose fresh base metal to the air. Also, some oxides are very dense and impervious to diffusion and allow very little oxygen to penetrate to the base metal, while others are quite porous and allow oxidation of the base metal to readily continue. The oxides also differ in their chemical behavior, and this affects their compatibility with various environments (including paints). Many of these oxides are also basic in chemical behavior. The oxides of the alkali metals are strong bases, while those of the alkaline earth metals are moderately strong bases. The oxides of the metals in group 13 of the periodic table, such as aluminum, are amphoteric (react with both strong acids and bases). The oxides of most transition elements are weak bases, but many of these are amphoteric. This includes ferric oxide (Fe2O3), which may react with strong bases. In general, the metals farther to the right of the periodic table form oxides that are increasingly weaker bases. While the metal oxides are protective in many situations, it also should be noted that most bare structural metals are very chemically active, and whenever their protective oxide film breaks down, the reaction to the environment can be quite rapid. General Corrosion Behavior of Metals The general corrosion behaviors of several metals used in construction are discussed below. More detailed information on corrosion characteristics can be found in the Sections of this Handbook that deal with these metals and their alloys. Tin also is protected by a very thin layer of oxide (SnO2) that is relatively impervious, adherent, and quite transparent.

This oxide layer has the good thermal emittance of nonmetallics, but because it is very thin and quite transparent, the surface has almost the same good reflectivity of bare tin.

Copper. The corrosion product predominantly responsible for the protection of copper in aqueous environments is Cu 2O.

This oxide layer is not impervious, but is adherent and provides excellent protection against further corrosion. In marine environments, an attractive and protective green patina forms, which consists of a film of copper chloride or carbonate, sometimes with a inner layer of Cu2O. Aluminum. The oxide that first forms on aluminum is also both quite impervious to diffusion and quite coherent

(although some of the gray oxide will rub off). Therefore, oxidation of the base metal slows almost to a stop while the oxide film is still so thin that it is quite transparent (about 1 nm thick). The corrosion product that forms on the surface of bare metals exposed to air, however, is seldom a simple oxide such as the thin barrier layer of Al2O3 that forms aluminum. In moist air, a more permeable layer of hydrated oxide, Al2O3·3H2O, forms over the oxide layer on aluminum, and it is the chemical properties of these two corrosion products that controls the chemical behavior of aluminum. Titanium. The oxide that typically forms on titanium in aqueous environments is TiO2, but can consist of mixtures of

other oxides, such as Ti2O3 and TiO. The TiO2 film is typically less than 10 nm thick and, therefore, also invisible. Like tin, copper, and aluminum, the oxide surface has both good emittance and good reflectivity. In addition, it is impervious to oxygen (and hydrogen) and is highly chemical resistant and attacked by very few substances. Iron. In contrast to the metals described above, the oxide that forms on iron is much less dense. Therefore, the layer of

iron-oxide rust is rather permeable and builds up fairly rapidly to a thickness that is easily seen (and its reddish color enhances its visibility), and the layer will continue to thicken until all the base metal is converted. The rust also readily flakes and rubs off. This rust, however, consists of hydrated oxides rather than simple oxides, but these hydrated oxides can lose water due to drying and revert to the anhydrous FeO and Fe2O3. In addition, a layer of Fe3O4 (FeO·Fe2)3) often forms between the FeO and Fe2O3, and various crystal forms of FeOOH have also been found to exist in the complicated system of compounds that form on iron (and steel). The composition of this rust film and its corrosion behavior depends on oxygen availability, humidity, temperature, and the levels of atmospheric pollutants present. In aqueous environments, pH affects corrosion of iron and steel. While the rust film offers some protection to iron and steel in alkaline environments, the evolution of hydrogen at low pH tends to diminish this protection. Magnesium. The film that first forms on magnesium is the hydroxide, Mg(OH)2. This hydroxide then reacts with any

carbonic acid in the environment to form various hydrated carbonates, including MgCO3·H2O, MgCO3·5H2O, and 3MgCO3·Mg(OH)2·3H2O. In atmospheres contaminated with sulfur compounds, magnesium sulfites or sulfates such as MgSO4·7H2O may also be present in the film. This gray film is permeable, but also is fairly adhesive and does not readily rub off. Zinc is highly resistant to atmospheric corrosion due to the formation of insoluble basic carbonate films that protect the

metal surface.

Mechanical Properties Elasticity. When a crystal is stressed by an internal or external load, the lattice responds by relative movement of the

atoms (ions) in it in a manner that tends to relieve that stress. The measure of the change in size of the crystal or multicrystalline object caused by the stress is strain. When the load is removed, the crystal or object will return to its original size provided that all the atoms in the crystal or object keep their original neighbors. When this provision is met, the strain is elastic (the crystal or object has sustained elastic deformation) and amount of strain is directly proportional to the amount of stress placed on the crystal or object. This proportionality is called Hooke's law (after Robert Hooke). The relation between applied stress and elastic strain is called the modulus of elasticity of the material. The modulus obtained under unidimensional tension or compression loading is called Young's modulus, E (after Thomas Young), while torsion or shear loading gives the modulus of rigidity or shear modulus, G. Young's modulus and the shear modulus are related by the formula below, which involves the Poisson's ratio, (after Siméon Denis Poisson), which is the ratio of lateral strain to axial strain in a stressed material:

= (E - 2G)/2G Hydrostatic compression causes materials to contract in volume. The ratio of the unit change in volume to the mean normal (perpendicular) compressive stress is called the compressibility, β, of the material. The inverse of compressibility

(the ratio of the mean normal pressure on the material to its unit contraction) is called the bulk modulus, K, of the material. The values of elastic moduli of several metals are listed in Table 5. Table 5 Mechanical properties of selected metals at room temperature Metal

Young's modulus (E), GPa

Shear modulus (G), GPa

Poisson's ratio,

Yield strength, MPa

Tensile strength, MPa

Elongation, %

Aluminum

67

25

0.345

15-20

40-50

50-70

Beryllium

303

142

0.07

262-269

380-413

2-5

Cadmium

55

19.2

0.43

...

69-83

50

Chromium

248

104

0.210

...

83

0

Cobalt

211

80

0.32

758

945

22

Copper

128

46.8

0.308

33.3

209

33.3

Gold

78

27

0.4498

...

103

30

Iron

208.2

80.65

0.291

130

265

43-48

Lead

26.1

5.6

0.44

9

15

48

Magnesium

44

16.3

0.35

21

90

2-6

Molybdenum

325

260

0.293

200

600

60

Nickel

207

70

0.31

59

317

30

Niobium

103

37.5

0.38

...

585

5

Silver

71.0

26

0.37

...

125

48

Tin

44.3

16.6

0.33

9

...

53

Titanium

120

45.6

0.361

140

235

54

Tungsten

345

134

0.283

350

150

40

Zinc

69-138

...

...

...

...

...

Zirconium

49.3

18.3

0.35

230

...

32

Plasticity. When the elastic limit of the bulk material is exceeded and not all of the atoms in a crystal or object under

stress keep their original neighbors (due to slip and/or twinning), a plastic strain increment is added to the elastic strain to make up the total strain on the crystal or object. At this point, the material is said to have begun yielding. Then when the load is removed, the plastic strain remains and the crystal or object has sustained permanent deformation, producing a permanent set. Stress-Strain Curves. Plots of the relation between applied nominal stress (load divided by original cross section) and

resulting strain (unit deformation) that are determined for a material specimen reveal much information about the mechanical properties of that material. Figure 4 shows a tensile stress-strain curve typical of a pure metal. A specimen having a reduced-cross-section "gage" section is prepared, the area of that section is measured, and a standard gage length (often 50 mm, or 2 in.) is marked on the section. Upon initial loading, the metal specimen elongates and laterally contracts (or laterally expands if the load is in compression), and the curve of strain versus stress follows the modulus line until it reaches the proportional limit, which is essentially the same point as the elastic limit. This limit is so low in most metals that it is difficult to determine an accurate value for the modulus of elasticity of the metal from a stress-strain curve. Therefore, this value for metals is often determined instead by a sonic vibrational test.

Fig. 4 Typical tension stress-strain curve for a nonferrous metal

Brittle metals, such as chromium, will fracture upon loading to the elastic limit rather than sustain plastic deformation. Upon loading of ductile metals beyond the elastic limit, the addition of plastic deformation to the elastic strain causes the total strain to increase at a faster rate than before and the plot curves off from the modulus line. Because it also is difficult to determine on a stress-strain curve where yielding begins, an arbitrary definition of "yielding" is used. In many testing standards, the yield strength of most metals is defined as the stress at which a line parallel to the modulus line, but offset from it by 0.2% strain, intersects the curve (see Fig. 4). It should be remembered that the stress applied to the specimen is normally the nominal stress rather than true stress. In the initial portion of the plot, the amount of lateral contraction (thinning) of the specimen is distributed along the entire test length of the specimen and is therefore so small that the nominal and true stress are almost identical. But in the latter portion of the test, necking of a tensile specimen occurs. That is, thinning begins to concentrate near the region where fracture will eventually occur. This necking can often become so pronounced that the nominal stress will decrease upon additional loading, as shown in Fig. 4, even though the true stress continues to increase until fracture occurs. A plot of nominal tension stress versus strain such as shown in Fig. 4 is sometimes called an engineering stress-strain curve to distinguish it from a true stress-strain curve (see also Fig. 5). The high point on an engineering stress-strain curve is defined in test standards as the ultimate tensile strength of the specimen, or simply the tensile strength. The point

of fracture is called the fracture strength or breaking strength. Upon fracture, the elastic energy in the specimen is released and the elastic strain is recovered. The plastic strain remaining in specimen, called the total elongation, is then determined by fitting the broken pieces together and measuring the new distance between the gage marks. The reduction in area of the broken specimen is determined by measuring the dimensions of the necked-down region at the fracture and comparing that cross-sectional area to the original cross section. Besides tensile and compressive stress-strain curves, occasionally torsion and/or bearing curves are determined. Table 5 lists typical strengths and total elongations of several annealed metals.

Fig. 5 True stress-strain curve versus engineering stress-strain curve

Modern design concepts sometimes require better descriptions of stress-strain behavior than afforded by tabular values of modulus, strength, and elongation. Therefore, stress-strain curves themselves are sometimes reproduced, but usually only the portion covering the first few percent of elongation. Other times, strain is not shown on the final plot. Instead, the slope of the stress-strain curve is described by plotting the secant modulus or the tangent modulus. As shown in Fig. 6, the tangent modulus is defined as the slope of a stress-strain curve at a specified point on that curve; the secant modulus is the slope of a line connecting the origin of a stress-strain curve with a specified point on that curve.

Fig. 6 Three types of modulus ratios that can be derived from a stress-strain curve

The stress-strain curves of iron containing even a small amount of carbon are different from those of pure metals. As seen in Fig. 7, the point at which yielding begins, called the yield point or upper yield point, is quite sharply defined. This is because as soon as the stress corresponding to this point is exceeded, the stress required for plastic deformation noticeably drops to a level called the lower yield point. The plot then begins to rise in a curve similar to that for pure metals. The stress at the upper yield point, rather than the lower yield point, is usually reported as the yield strength of these materials.

Fig. 7 Typical tension stress-strain curve for iron containing 0.15% C

Creep is the term used to describe the time-dependent plastic deformation, creep strain, that occurs when a material is

subjected to constant nominal stress. When the non-time-dependent strain that results from the initial loading is added to the creep strain, the result is called total strain. (The thermal expansion that occurs upon heating to the test temperature, however, is not included.) Most creep testing is done under tension and at temperatures that are relatively high for the material being tested, and the terms creep extension and total extension are used. As shown in Fig. 8, the rate of creep strain upon initial loading is fairly rapid, but decreases with time; this is called primary creep. The creep rate then reaches a minimum and a fairly constant rate for a period of time, which is called secondary creep. In third-stage creep or tertiary creep, the creep rate begins to increase again and continues to increase until the specimen breaks (if the test is continued to this point). The relative portions of the total time to rupture taken by these three stages depends on several factors, and in some tests, the secondary stage becomes a point on the graph where it changes from decreasing to increasing curvature.

Fig. 8 The three stages of a creep curve

The results of creep tests are reported in a variety of ways. Sometimes, the results for a given temperature (especially short-time, high-temperature tests) are reported in the form of isochronous stress-strain curves, which are curves constructed from equal-time points on the stress-strain relationships determined in the creep test (see Fig. 9). The elastic portion of such isochronous stress-strain curves is added by using the modulus value for the test temperature determined independently. The stress that causes a specified strain at that temperature is then called the creep strength of the material for those conditions. (The term creep strength is sometimes also used to describe the stress that will cause a specified rate of secondary creep at that temperature.) Other times, equal-strain results for a given temperature are plotted on stress-time graphs.

Fig. 9 Isochronous stress-strain curves for specimens of a material creep tested at a given temperature

When a creep test is continued until the specimen ruptures, the test is often called a creep-rupture or stress-rupture test, and the results are reported on a plot of stress versus time to rupture. Fatigue. The tendency of a material to break under conditions of repeated cyclic stresses is called fatigue. Fatigue

fractures are different from the ductile fractures that usually result from regular tension and creep loading of most metals. Instead, fatigue fracture is caused by the propagation of cracks that initiate at a single point or at a few points in the material, and fatigue fractures are always brittle fractures. Most parts and fatigue specimens contain points of stress concentration, such as surface roughness or changes in part or specimen section, at which stress is concentrated and where fatigue cracking initiates. The amount of concentration can be determined (based on purely elastic behavior) and is reported as the theoretical stress-concentration factor or simply the stress-concentration factor, Kt. The fatigue-strength reduction factor or fatigue-notch factor can be determined by dividing the fatigue strength of smooth (unnotched) specimens by the fatigue strength of notched specimens. Comparing the fatigue-strength reduction factor to the theoretical stress-concentration factor gives a measure of the sensitivity of the material to notches when under cyclic loading; notch sensitivity is the fatigue factor divided by Kt - 1 and often is expressed as a percentage. Several different fatigue tests have been developed, each designed to replicate the loading conditions found in specific industrial applications. The rotating-beam test replicates the loading of a railroad axial; the plate-bending test, a leaf spring; the axial test, connecting rods and chain links. Some tests run under constant load, while others run under constant strain. Therefore, tabular values of fatigue strength or fatigue limit are of value mainly in material selection, rather than useful in actual design calculations. The stress in a fatigue test usually is cycled between a maximum tensile stress and a minimum tensile stress or between a maximum tensile stress and a maximum compression stress. The ratio of these extremes (where compression is considered a negative stress) is called the stress ratio, R. The ratio for fully reversed stress then becomes -1. Other terms used to describe a fatigue stress include mean stress (the stress midway between the extremes), the stress range (the stress variation between the extremes), and the stress amplitude (the stress variation between the mean stress and one of the maximums). The results of fatigue test are usually reported in the form of plots of stress versus number of cycles to fracture, called S-N curves. In these plots, the number of cycles is usually plotted on a logarithmic scale (and sometimes stress is also). Most metals have S-N curves that continually show longer lives at lower stresses, and the fatigue strength of the material must be reported for a given number of cycles (as well as the stress ratio for the test and the stress-concentration factor if the specimen contains a notch). For steels, however, the curve breaks off and becomes essentially horizontal at some stress level called the fatigue limit (see Fig. 10).

Fig. 10 Comparative fatigue curves

Some fatigue tests are conducted using a fracture-mechanics approach. This is described in the Section "Failure Analysis" in this Handbook. Toughness. Generally speaking, toughness is a measure of the amount of energy a material absorbs during straining to fracture. Specimen shape as well as the manner of load application are important in toughness determination. For dynamic (high-strain-rate) loading conditions and when a notch (or point of stress concentration) is present, notch toughness is assessed by using an impact test (see the Section on "Mechanical Testing" in this Handbook). A special measure of toughness is used in linear fracture mechanics called fracture toughness (the ability of a material to resist fracture when a crack is present). This is a scaling factor, also called the critical stress-intensity factor, K, that describes the intensification of applied stress at the tip of a crack of known size and shape at the onset of rapid crack propagation. Details on fracture toughness and fracture mechanics can be found in the Sections "Mechanical Testing" and "Failure Analysis" in this Handbook.

For the static (low-strain-rate) situation, toughness can be determined from the results of a tensile stress-strain test. It is the area under the stress-strain curve up to the point of fracture. Hardness is the resistance of a material to plastic indentation. While the measurement of hardness can involve only a simple scratch test or bounce test, it usually involves the amount of indentation caused by the application of a hard indenter of some standard shape and material. Hardness values are roughly proportional to the strength of a metal (see, for example, the hardness conversion tables for steels in the Section "Glossary of Terms and Engineering Data") and can give an indication of its wear properties (abrasion resistance). Therefore, hardness values can be useful during selection of a suitable material for an application. They also are very useful during quality-control operations, but the values cannot be applied directly during the design of a part. Hardness tests are described in the Section "Mechanical Testing" in this Handbook.

Introduction and Overview of Design Considerations and Materials Selection Introduction ENGINEERING DESIGN can be defined as the creation of a product that satisfies a certain need. A good design should result in a product that performs its function efficiently and economically within the prevailing legal, social, safety, and reliability requirements. To satisfy such requirements, the design engineer has to take into consideration many diverse factors: • •

Function and consumer requirements, such as capacity, size, weight, safety, design codes, expected service life, reliability, maintenance, ease of operation, ease of repair, frequency of failure, initial cost, operating cost, styling, human factors, noise level, pollution, intended service environment, and possibility of use after retirement Material-related factors, such as strength, ductility, toughness, stiffness, density, corrosion resistance, wear

•

resistance, friction coefficient, melting point, thermal and electrical conductivity, processibility, possibility of recycling, cost, available stock size, and delivery time Manufacturing-related factors, such as available fabrication processes, accuracy, surface finish, shape, size, required quantity, delivery time, cost, and required quality

Figure 1 illustrates the relationship among the previously mentioned groups. The figure also shows that there are other secondary relationships between material properties and manufacturing processes, between function and manufacturing processes, and between function and material properties.

Fig. 1 Factors to consider in component design. Source: Ref 1

Figure 2 shows that engineering design is actually part of a much larger process of bringing new products to market. The name that has been coined for the complete process is the product realization process (PRP). As indicated in Fig. 2, engineering design takes place approximately between marketing and manufacturing within the total PRP of a firm. Engineering design, however, is not an isolated activity. It influences, and is influenced by, all other parts of a manufacturing business. Unfortunately, the relationship between design and other sectors of a manufacturing business has not been sufficiently recognized in the past. Recently, however, mostly in response to the pressures of international competitiveness, new approaches to product design and development have arisen to improve quality, drive down cost, and reduce product cycle time. Generally called concurrent engineering, the product uses product development teams of experts from all functions--design, manufacturing, marketing, and so forth--to work together from the start of the product design project. This opens new opportunities for better materials selection and has resulted in the development of new computer-based design tools.

Fig. 2 Engineering design as a part of the product realization process

This introductory article, as well as the other articles that follow on "Design Factors" and "Factors in Materials Selection," discuss the various roles and responsibilities of materials engineers in a product realization organization and suggest new and different ways in which materials engineers can benefit their organizations. The integration of material, process, and product design relies on individuals who are trained in materials selection and can work in a team environment. Often it is the materials engineer/specialist, familiar with the conflicting needs of design, production, and marketing, who can assume the role of mediator to focus on the final product.

Reference 1. M.M. Farag, Selection of Materials and Manufacturing Processes for Engineering Design, Prentice Hall, London, 1989

Key Considerations for Design The Design Process. The role of the materials engineer during the design process can take many paths. The task may simply be to design a "new" part that is nearly identical to an existing part and is expected to be used in similar ways. In this case, it may be possible to use the same material and processing used for the existing part. Alternatively, the task may be to design and select material for a new part. Obviously, this is a much more complex task and requires knowledge of loads, load distributions, environmental conditions, and a host of other performance factors (including customer expectations) and manufacturing-related factors.

In addition to a knowledge of the required performance characteristics, the materials selector is responsible for defining and accounting for manufacturing-induced changes in material properties. Different production methods, as well as controlled and uncontrolled thermal and mechanical treatments, will have varying effects on the performance properties and the cost of the final part or assembly. Often, it is by relating the varying effects of manufacturing processes to customer needs that one manufacturer develops an advantage over another product, using essentially the same material and process combinations. It is critical to understand and accept that the choice of manufacturing processes is frequently not under the direct control of the materials selection expert. In fact, by the time the concept and initial configuration of a design is committed to paper, or to a computer-aided design (CAD) system, the manufacturing processes and sequence of processes required to produce a product cost effectively are normally fixed. They are no longer variables that can be controlled without redesign.

Criteria and Concepts in Design. Material selection involves more than meeting minimum property requirements

for strength, fatigue, toughness, corrosion resistance, or wear resistance. There are numerous options for product design and materials selection, and frequently they cannot be quantified. This precludes the use of mathematical optimization routines and shifts the emphasis to experience. Experience is essential in dealing with these "soft issues" related to qualitative non-property considerations. The design must be producible. This means robust processes must be selected that have known statistical variation and will yield features or complete parts that lie well within the specification limits. This design for manufacturability approach is becoming popular, is an integral part of an integrated product development team's tool box, and has been demonstrated to be effective in improving quality and reducing cost. Designing to minimize the total costs to the consumer during the expected product life (the life cycle cost) is yet another challenge. These costs include raw material, production, use, maintenance (scheduled or otherwise), and disposal or recycling costs. Some of these cost elements are unknown. This is where the combination of the art and skill of engineering faces its most severe test. Similar issues arise when the safety, product liability, and warranty cost exposure aspects of product design and material selection are concerned. In many cases, alternate designs or materials could be chosen with no measurable difference. However, there are also many cases where a particular design and/or material choice could prevent an undesirable product failure mode. An understanding of how a part, assembly, or entire structure can fail and the ramifications of that failure are essential in providing a safe and reliable design. The growing environmental and regulatory demand to consider the entire life cycle of a product could require the manufacturer to recover and recycle the product and process waste materials. This places renewed emphasis on considering all options. Changing the materials or the manufacture of a component involves designing an environmentally friendly product. Changing from chromium plating appears to be environmentally friendly, but today's chrome plating units are being constructed to operate in a zero discharge mode, so there is no obvious gain from eliminating the chrome. The anodizing process can be just as clean. Paint, on the other hand, is suffering severe scrutiny over both emissions during the painting process as well as subsequent mishandling by the consumer. And, changing a part body from metal to plastic is not necessarily a good solution because the recycling infrastructure is not yet adequate on a global level to effectively reclaim the material. Another design factor is the repairability of a product. Automobiles are not intended to have accidents, but they do. Design and material selection only for initial cost and performance factors has led to the widespread use of one-piece plastic parts that are not repairable in many cases. Any product that costs more to repair than the owner finds acceptable will eventually suffer in the marketplace.

Key Considerations for Materials Selection The selection of the correct material for a design is a key step in the process because it is the crucial decision that links computer calculations and lines on an engineering drawing with a working design. Materials and the manufacturing processes that convert the material into a useful part underpin all of engineering design. The enormity of the decision task in materials selection is given by the fact that there are well over 100,000 engineering materials from which to choose. On a more practical level, the typical design engineer should have ready access to information on 50 to 80 materials, depending on the range of applications. The importance of materials selection in design has increased in recent years. The adoption of concurrent engineering methods (see following discussion) has brought materials engineers into the design process at an earlier stage, and the importance given to manufacturing in present day product design has reinforced the fact that materials and manufacturing are closely linked in determining final properties. Moreover, world pressures of competitiveness have increased the general level of automation in manufacturing to the point where cost of materials comprise 50% or more of the cost for most products. Relation of Materials Selection to Design. An incorrectly chosen material can lead not only to failure of the part

but also to unnecessary cost. Selecting the best material for a part involves more than selecting a material that has the properties to provide the necessary performance in service; it is also intimately connected with the processing of the material into the finished part (Fig. 2). A poorly chosen material can add to manufacturing cost and unnecessarily increase

the part cost. Also, the properties of the material can be changed by processing (beneficially or detrimentally), and that may affect the service performance of the part. With the enormous combination of materials and processes to choose from, the task can be done only by introducing simplification and systemization. Design proceeds from concept design, to embodiment (configuration) design, to detail (parametric) design, and the material and process selection then becomes more detailed as the design progresses through this sequence. At the concept level of design, essentially all materials and processes are considered rather broadly. The materials selection methodology and charts developed by Ashby (Ref 2) are highly appropriate at this stage. The decision is to determine whether each design concept will be made from metal, plastics, ceramic, composite, or wood, and to narrow it to a group of materials. The precision of property data needed is rather low. If an innovative material is chosen, it must be done at the conceptual design step because later in the design process too many decisions have been made to allow radical change. At the embodiment or configuration level of design, the emphasis is on determining the shape and approximate size of a part using engineering methods of analysis. Now the designer will have decided on a class of materials and processes, for example a range of aluminum alloys, wrought and cast. The material properties must be known to a greater level of precision. At the detail or parametric design level, the decision will have narrowed to a single material and only a few manufacturing processes. Here the emphasis will be on deciding on critical tolerances, optimizing for robust design, and selecting the best manufacturing process using quality engineering and cost modeling methodologies. Depending on the criticality of the part, materials properties may need to be known to a high level of precision. At the extreme, this requires the development of a detailed data base from an extensive materials testing program. In a more detailed approach to engineering design, Dixon and Poli (Ref 3) suggest a four-level approach to materials selection: • •

•

•

Level I. Based on critical properties, determine whether the part will be made from metal, plastic, ceramic, or composite. Level II. Determine whether metal parts will be produced by a deformation process (wrought) or a casting process; for plastics determine whether they will be thermoplastic or thermosetting setting polymers. Level III. Narrow options to a broad category of material. Metals can be subdivided into categories such as carbon steel, stainless steel, and copper alloys. Plastics can be subdivided into specific classes of thermoplastics and thermosets such as polycarbonates and polyesters. Level IV. Select a specific material according to a specific grade or specification.

Thus material and process selection is a progressive process of narrowing from a large universe of possibilities to a specific material and process selection. Levels I and II are often sufficient for conceptual design. Level III is needed for embodiment (configuration) design and sometimes for conceptual design Level IV usually can be postponed until the detail (parametric) design. For all the stages of engineering design, the problem solving methodology employed is called guided iteration (Ref 3). The steps in the guided iteration process are formulation of the problem, generation of alternative solutions; evaluation of the alternatives; and if these steps are unacceptable, redesign guided by the results of the evaluations. This methodology is fundamental to design processes. It is repeated hundreds or thousands of times during product design. It is used again and again in recursive fashion for the conceptual stage to select materials and processes, to configure parts and to assign numerical values to dimensions and tolerances (i.e., parametric design). Figure 3 summarizes the guided iteration methodology.

Fig. 3 Guided iteration used for conceptual, configuration, and parametric design

Relation of Materials Selection to Manufacturing. The selection of a material must be closely coupled with the

selection of a manufacturing process. This is not an easy task because there are many processes that can produce the same part. The goal is to select the material and process that maximizes quality and minimizes the cost of the part. Figure 4 gives a breakdown of manufacturing processes into nine broad classes.

Fig. 4 The nine classes of manufacturing processes. The first row contains the primary forming (shaping) processes. The processes in the lower vertical column are the secondary forming and finishing processes. Source: Ref 2

In a very general sense, the selection of the material determines a range of processes that can be used to process parts from the material. Table 1 shows the manufacturing methods used most frequently with different metals and plastics (Ref 4). The material melting point and general level of deformation resistance (hardness) and ductility determine these relationships. The next aspect to consider is the minimum and maximum overall size of the part, often expressed by volume, projected area, or weight. Maximum size often is controlled by equipment considerations. Shape is the next factor to consider. The overall guide should be to select a primary process that makes the part as near to final shape as possible (near-net shape forming) without requiring expensive secondary machining or grinding processes. Sometimes the form of the starting material is important. For example, a hollow shaft can be made best by starting with a tube rather than a solid bar. Shape is often characterized by aspect ratio, the surface-to-volume ratio, or the web thickness-to-depth ratio. Closely related to shape is complexity. Complexity is correlated with lack of symmetry. It also can be measured by the information content of the part, that is, the number of independent dimensions that must be specified to describe the shape. Tolerance is the degree of deviation from ideal that is permitted in the dimensions of a part. Closely related to tolerance is surface finish. Surface finish is measured by the root-mean-square amplitude of the irregularities of the surface. Each manufacturing process has the capability of producing a part with a certain range of tolerance and surface finish (Fig. 5).

Table 1 Compatibility between materials and manufacturing processes Process

Cast iron

Carbon steel

Alloy steel

Stainless steel

Aluminum and aluminum alloys

Copper and copper alloys

Zinc and zinc alloys

Magnesium and magnesium alloys

Titanium and titanium alloys

Nickel and nickel alloys

Refractory metals

Thermoplastics

Thermoset plastics

Sand casting

•

•

•

•

•

•

--

•

--

•

--

X

X

Investment casting

--

•

•

•

•

•

--

--

--

•

--

X

X

Die casting

X

X

X

X

•

--

•

•

X

X

X

X

X

Injection molding

X

X

X

X

X

X

X

X

X

X

X

•

--

Structural foam molding

X

X

X

X

X

X

X

X

X

X

X

•

X

Blow molding (extrusion)

X

X

X

X

X

X

X

X

X

X

X

•

X

Blow molding (injection)

X

X

X

X

X

X

X

X

X

X

X

•

X

Rotational molding

X

X

X

X

X

X

X

X

X

X

X

•

X

Impact extrusion

X

•

•

--

•

•

•

--

X

X

X

X

X

Cold heading

X

•

•

•

•

•

--

--

X

--

X

X

X

Casting/molding

Forging/bulk forming

Closed-die forging

X

•

•

•

•

•

X

•

•

--

--

X

X

Pressing (P/M)

X

•

•

•

•

•

X

•

--

•

•

X

X

Hot extrusion

X

•

--

--

•

•

X

•

--

--

--

X

X

Rotary swaging

X

•

•

•

•

--

--

•

X

•

•

X

X

Machining from stock

•

•

•

•

•

•

•

•

--

--

--

--

--

Electrochemical machining

•

•

•

•

--

--

--

--

•

•

--

X

X

Electrical discharge machining (EDM)

X

•

•

•

•

•

--

--

--

•

--

X

X

Wire EDM

X

•

•

•

•

•

--

--

--

•

--

•

X

Sheet metal forming

X

•

•

•

•

•

--

--

--

--

X

X

X

Thermoforming

X

X

X

X

X

X

X

X

X

X

X

•

X

Metal spinning

X

•

--

•

•

•

•

--

--

--

--

X

X

and

sintering

Machining

Forming

•, normal practice; --, less-common practice; X, not applicable.

Source: Adapted from Ref 4

Fig. 5 Approximate values of surface roughness and tolerance on dimensions typically obtained with different manufacturing processes. ECM, electrochemical machining; EDM, electrical discharge machining. Source: Ref 5

References cited in this section

2. M.F. Ashby, Materials Selection in Mechanical Design, Pergamon Press, 1992 3. J.R. Dixon and C. Poli, Engineering Design and Design for Manufacturing, Field Stone Publishers, 1995 4. G. Boothroyd, P. Dewhurst, and W. Knight, Product Design for Manufacture and Assembly, Marcel Dekker, 1994 5. J.A. Schey, Introduction to Manufacturing Processes, McGraw-Hill, 1987 Concurrent Engineering The selection of the material and its processing, product design, cost, availability, recyclability, and performance in final product form have become inseparable. As a result, more and more companies are forming multidisciplinary project teams to ensure that all needed input is obtained concurrently. This is reflected by the increasing use of "concurrent" or "simultaneous" engineering methods (Ref 6, 7). Definition. As defined by the 1986 Institute for Defense Analysis Report R-338 (Ref 6), "concurrent engineering" is a

"systematic approach to the integrated, concurrent design of products and their processes, including manufacture and support. This approach is intended to cause the developers, from the outset, to consider all elements of the product life cycle from concept through disposal, including quality, cost, schedule, and user requirements." Thus, concurrent engineering refers to the philosophic constructs needed to create a synergistic engineering environment that optimizes quality and productivity at a minimum cost. Cross-Functional Design Teams. Today concurrent design proceeds through well-connected cross-functional

integrated product development teams with a common purpose. Information exchange is critical to minimizing error and reducing the development time and costs. Given sufficient priority among a group of projects, an ideal team might be formed with individuals possessing historical, experimental, and fundamental knowledge in the candidate materials, processes, and products. The most effective design teams involve a clearly delineated group of individuals who work full time on the specified product from creation through market introduction. The team comprises not only research and development professionals, but also manufacturing and marketing members, and often members from quality, finance, or

field service. When a team discovers holes in collective knowledge, it may need to rely in part on external sources of information and knowledge (e.g., from key suppliers), as well as to develop new information on its own. Consequently, information transfer both within the team and external to the team are important. References 8, 9, and 10 provide more detailed information on staffing cross-functional design teams and their effectiveness in the implementation of modern design practices and methods. Concurrent Engineering Approach to Materials Processing (Ref 7). Figure 6 shows some of the concepts that

must be addressed for successful concurrent material, process, and product engineering (in this case, for aluminum alloy manufacturing). Typical customer needs are indicated at the left and some typical processes are considered along the top of the figure. It is instructional to locate on this chart the specific types of processing efforts that are often pursued. Process refinement and process control both refer to improvements in a limited set of capabilities of a specific process. Unit process optimization refers to a more comprehensive improvement of the many facets of a particular processing operation. Alloy-process design refers to examining a range of sequential processes but limiting attention to a specific set of evolving product attributes, those with a microstructural origin in this case. Near-net-shape processing is one example of the more general case of eliminating process steps in order to reduce cost. Cost estimation deals with a specific process sequence and assumes that the desired product attributes are achievable.

Fig. 6 Concurrent engineering matrix for aluminum alloy manufacturing. Source: Ref 7

Some of these activities may require historical data (e.g., cost estimation), some may be experimental (e.g., alloy-process design), and some may be model based (e.g., process control). Different forms of information must, therefore, be dealt with in concurrent engineering to maximize knowledge transfer between individuals or subgroups. Improving the quantity, quality, and speed of knowledge transfer is essential because it can improve the effectiveness of the team in understanding and maneuvering within the design space outlined in Fig. 6. However, data transfer itself does not provide an increase in the team's design, optimization, or inverse engineering capabilities. Process modeling and computer simulations can provide such flexibility.

References cited in this section

6. S.N. Dwivedi, A.J. Paul, and F.R. Dax, Ed., Concurrent Engineering Approach to Materials Processing, TMS/AIME, 1992 7. L.A. Lalli, Concurrent Engineering--Simulation Challenges in the Design of Materials, Products, and Processes, Concurrent Engineering Approach to Materials Processing, S.M. Dwivedi, A.J. Paul, and F.R. Dax, Ed., TMS/AIME, 1992 8. P.G. Smith, Cross-Functional Design Teams, Materials Selection and Design, Vol 20, ASM Handbook, ASM International, 1997, p 49-53

9. J.R. Katzenbach and D.L. Smith, The Wisdom of Teams, Harper Business, 1993 10. G.M. Parker, Cross-Functional Teams, Jossey-Bass, 1994 Introduction DESIGN FACTORS described in this article have been somewhat arbitrarily grouped into three categories: functional requirements, analysis of total life cycle, and other major factors; the factors are listed in Tables 1, 2, and 3, respectively. These categories intersect and overlap, which constitutes a major challenge in engineering design. Table 1 Functional requirements in design Performance specifications

Definition of need Risks and consequences of underspecification Consequences of overspecification

Risk and hazard analysis

Failure mode and effect analysis (FMEA) Safety analysis

Design process/configuration

Probabilistic or deterministic statistical approach Stress or load considerations Restrictions on size, weight, or volume Service hazards, such as cyclic loading or aggressive environment Failure anticipation Reliability, maintainability, availability, and repairability Quantity to be produced Value analysis Candidate materials and manufacturing processes

Design for manufacture and assembly (DFMA) Design for quality

Robust design (Taguchi method) Statistical process control (SPC) Total quality management (TQM)

Reliability in design

Quantitative determination Reliability testing

Redesign

Design review Simplification and standardization Functional substitution

Table 2 Total life cycle in design Material selection Producibility Durability Feasibility of recycling Design for recycling Energy requirements

For production During use For reclamation

Environmental compatibility

Effect of product on environment Effect of environment on product

Inspection and quality-assurance testing Handling Packaging Shipping and storage Scrap value

Table 3 Other major factors in design State of the art

Prior knowledge Possible patent infringement Competitive products

Designing to codes and standards

Codes for specific products, such as pressure vessels Safety requirements

Products--Consumer Products Safety Commission

Warnings Unintended uses Labels

Manufacturing--Occupational Safety and Health Administration Environmental requirements--Environmental Protection Agency Industry standards

ANSI ASTM SAE UL ISO

Human factors/ergonomics

Ease of operation Ease of maintenance

Aesthetics Cost

Functional Requirements in Design Performance Specifications It is obvious that any design must necessarily meet performance specifications (Table 1). These specifications must reflect a full and complete analysis of the functions required of the product. An important distinction needs to be made between performance specifications, which enumerate the basic functional requirements of the product, and product specifications, which list requirements for configurations, tolerances, materials, manufacturing methods, and so forth. Performance specifications represent the basic parameters from which the design can be formulated; product specifications are codifications of designs, used for purchase or manufacture of the product. Excellence in design or product specification is not possible without complete and adequate performance specifications. Performance specifications must reflect thorough consideration of the factors listed in Tables 2 and 3. Consequences and risks involved in possible product failures caused by predictable misuse or overload or by imperfections in workmanship or material must be considered in establishing performance specifications (see the discussion on "Risk and Hazard Analysis" ). Situations in which the consequences of product failure would be dire or in which only the very lowest risks of failure can be tolerated dictate the use of stringent performance specifmcations. When product failure does not involve a risk of personal injury and is not likely to result in great financial loss to the user, economic considerations usually imply that performance specifications be no more stringent than necessary to meet functional requirements. Realistic performance specifications result in design and manufacture of products that perform their required functions with little risk of failure, and that at the same time can be produced at the lowest possible cost. As an example of setting performance specifications to suit the application, resistance to corrosion can be specified at any of three levels: (a) avoiding contamination by corrosion products, (b) preventing leaks into or out of closed containers, and (c) maintaining structural integrity and other mechanical and physical properties in spite of corrosive attack. For food-processing equipment, the first of these considerations has paramount importance. For a bridge, the third factor is critical; furthermore, a bridge must retain its structural integrity for many years. In a petrochemical plant, all three considerations are important; chemical process equipment can be designed for continuous operation for two or three years, and any breakdown between scheduled maintenance periods would be extremely expensive. Furthermore, leakage of dangerous chemicals from process equipment is unacceptable. In this case, the cost of a breakdown and the damage caused by leakage can justify use of expensive materials if their performance reduces the probability of leaks or breakdown to very low levels. On an automobile body, low-carbon steel with a corrosion-resistant surface treatment and coating provides corrosion resistance consistent with the anticipated lifetime of the vehicle. Thus, for these various applications, the appropriate criteria for corrosion resistance depend on one or more of the following factors: the degree of contamination permitted by the application, the intended lifetime of the object, the corrosion characteristics of the environment, and the consequences and risks associated with corrosion failure. Example 1: Functional Requirements for an Automotive Exhaust System. The product design specification for the exhaust system must include the following functions: •

Conducting engine exhaust gases away from the engine

• • • • • • •

Preventing noxious fumes from entering the automobile Cooling the exhaust gases Reducing the engine noise Reducing the exposure of automobile body parts to exhaust gases Affecting engine performance as little as possible Helping control undesirable exhaust emissions Having a service life that is acceptably long Having a reasonable cost, both as original equipment and as a replacement part

In its basic form, the exhaust system consists of a series of tubes that collect the gases at the engine and convey them to the rear of the automobile. The size of the tube is determined by the volume of the exhaust gases to be carried away and the extent to which the exhaust system can be permitted to impede the flow of gases from the engine. An additional device, the muffler, is required for noise reduction, and a catalytic converter is required to convert polluting gases to lessharmful emissions. The basic lifetime requirement is that the system must resist the attack of hot, moist exhaust gases for some specified period. In addition, the system must resist attack by the atmosphere, water, mud, and road salt. The location of the exhaust system under the car requires that it be designed as a complex shape that will not interfere with the running gear of the car, road clearance, or the passenger compartment. The large number of automobiles produced each year requires that the material used in exhaust systems be readily available at minimum cost. This system requires numerous material property requirements. The mechanical property requirements are not overly severe: suitable rigidity to prevent excessive vibration and fatigue plus enough creep resistance to provide adequate service life. Corrosion is the limiting factor on life, especially in the cold end, which includes the resonator, muffler, and tail pipe. Several properties of unique interest, that is, where one or two properties dominate the selection of the material, are found in this system. These pertain to the platinum-base catalyst and the ceramic carrier that supports the catalyst. The majority of the tubes and containers that comprise the exhaust system were for years made of readily formed and welded low-carbon steel, with suitable coatings for corrosion resistance. With the advent of greater emphasis on automotive quality and longer life, the material selection has moved to specially developed stainless steels with improved corrosion and creep properties. Ferritic 11% Cr alloys are used in the cold-end components, with 17 to 20% Cr ferritic alloys and austenitic Cr-Ni alloys in the hot end of the system. Risk and Hazard Analysis As described briefly above, product failure and the associated risk of personal injury are critical considerations of the engineering design process. No engineering system/component devised or used can be 100% safe or error free. The objective of risk and hazard analysis is to identify the level of risk and to pinpoint the parts of the system that represent the greatest risk for failure. Then, if the analysis is used properly, steps can be taken to eliminate the cause or reduce the risk to an acceptable minimum. It has been demonstrated that hardware systems approaching a "failure-free" condition can be produced when actions are taken at all levels that are based on: • • • • •

Attention to past experiences with similar systems Availability of risk information for all project personnel A sound, aggressive risk and hazard analysis during all phases Development of suitable corrective action and safety programs based on the analysis A continuous and searching review of all phases of the program efforts

The various analysis techniques have developed from the search for system reliability. Consequently the approach is hardware oriented, with the emphasis on ensuring that hardware is able to perform its intended function. Figure 1 is a flow chart that shows the integration of risk and hazard analysis in the overall design process. Even if designers or design managers are not directly responsible for implementing these analyses, they must be familiar with the methodology so that they understand how they are carried out and how they can respond in terms of design or system changes. Most efforts are best completed during early design phases, and they can be effectively used during design reviews to provide valuable feedback to the design to avoid failures.

Fig. 1 Flow chart showing the integration of risk and hazard analysis into the design process. Source: adapted from Ref 1

Defining Risk. To clarify acceptable risk, Starr et al. (Ref 2) suggest it is useful to recognize the existence of four

different definitions of "risk": • • • •

Real risk is determined by actual circumstances as the future unfolds. Statistical risk is determined from currently available data, based on assumptions that a large number of future systems will, on the average, act the same way as a large number of similar past systems. Predicted risk is based on analysis of system, models, and historical data. Perceived risk is risk seen intuitively by individuals or society.

It should be noted that only "real risk" is a property of hardware. The other three risks represent the concept of risk represented by the system. An important factor in the perception of risk is the probable severity of the consequences if an accident were to occur. A complete assessment of risk requires that the potential effects of an accident be integrated with a probability of its occurrence. Linked closely to severity of consequences in the perception of risk is the episodic nature of consequences. It seems that the size of a potential accident is more important than the probability of occurrence. This truly represents society's value system to a great degree. Activities capable of producing catastrophic accidents, therefore, are seen as a great risk and must be more stringently controlled than high-frequency individual risks. The two methodologies described later in this article can identify possible hazards and possibly identify the resources that are necessary to avoid or reduce the risks; however, whether the resources should be expended to alleviate the perceived risk remains a political-humanistic-management decision. The justification for undertaking these risk and hazard

technological studies is that they give a clearer picture of decisions that must be made to ensure that the functional requirements of a design can be met. More detailed information on quantitative and qualitative risk and hazard analyses is found in Ref 3 and in the section "Human Factors and Safety in Design" in this article. Failure mode and effect analysis (FMEA) was originally developed as a tool to review the reliability of systems

and components. It has been modified over the years to include criticality analysis (CrA) and failure hazard analysis (FHA) to help determine equipment safety requirements. Its intent is still to ensure reliable system function. The objective of FMEA is to expose all potential element failure modes to scrutiny, to classify and quantify their possible causes with their associated probability of occurrence, and to evaluate their impact on the overall system performance. Failure mode and effect analysis normally is implemented as part of a comprehensive reliability program. The analysis is performed at increasing levels of complexity as the design progresses, so that the recommendations resulting from the analysis can be implemented early at minimum cost. The results are used to guide other activities such as design, purchasing, manufacturing, and quality control. Failure mode and effect analysis is a systematic, organized procedure for determining, evaluating, and analyzing all potential failures in an operating system; it is used to supplement and support other reliability or safety activities. The FMEA process involves examining each potential failure mode to assess if the system elements support reliability and to ascertain the consequences of the failure on the entire system. The general process involves the following steps:

1. The probable failure modes of the system are identified, evaluated, assessed, and documented. 2. The documentation of possible failure modes is used to check and verify the safety of the design. 3. Corrective actions are formulated to eliminate or reduce to an acceptable level the consequences of the failure.

The formal procedure (Fig. 2) for preparing an FMEA constitutes the following steps:

1. A functional block diagram or logic diagrams are developed for the system or subsystem. Copies of these diagrams become part of the FMEA documentation. Individual items to be considered are identified by number. 2. All realistic probable failure modes of each element on the diagram are postulated and entered on the FMEA documentation item by item. 3. The probable causes associated with each failure mode are listed beside each failure mode. 4. The immediate consequences of each assumed failure are described and listed beside the failure mode. Symptoms that would affect the function are also listed. 5. Any internal compensating provisions, within the system that either circumvent or mitigate the effect of the failure, are evaluated and noted. 6. The effect of the failure on other components or systems is evaluated and documented. 7. The level of severity of each mode of failure is evaluated in terms of importance and documented as critical, major, or minor. 8. A quantitative probability of occurrence of the failure mode is made. The probability should be expressed numerically (Ref 5), where possible. In some cases, categorizing may be more meaningful if commonly defined categories are used. 9. Finally, remarks and recommendations are documented. Here the analyst provides any additional meaningful data.

Fig. 2 Failure mode and effect analysis flow chart. Source: Ref 4

Safety analysis is the synthesis of other risk/hazard analysis techniques to produce a qualitative systematic analysis

throughout all phases of the project design, development, and implementation, with the objective of preventing accidents. This includes preventing personnel injuries, damage to equipment, and so forth. The techniques are simple but rigorous and time consuming, and to be effective must be continued throughout the life of the system from conception to shutdown and disposal. The method can be applied to any system but from a different point of view than system analysis. The focus of safety analysis is the prevention of hazardous failure. The primary tools of safety analysis are worksheets, a hazard log book, a checklist of hazards, and a system description. A basic requirement is that the practitioners have a willingness to challenge the status quo; they cannot be the same as those committed to the design and implementation of the hardware system. The identification of the hazards is an initial and continuous activity. Identification initiates an iterative process--the preliminary hazard analysis (Fig. 3) that undertakes elimination or reduction of the essential hazardous situations to an acceptable minimum. Design changes, safety devices, warning systems, crew procedures, emergency measures, and so forth, are all recommended. These are carried out to control or resolve the hazard situation. This often requires compromises between the designer and the safety analyst, or even changes in the specification governing the functions and use of the system. At the completion of the preliminary hazard analysis: • • • •

The general hazards of concern are identified. Additional design and operation requirements have been established to forestall or alleviate anticipated hazards. Areas where further improvements with respect to safety are necessary have been identified. A databank has been started that can be used to follow and document potentially hazardous situations.

Fig. 3 Safety analysis flow chart for preliminary hazard analysis. Source: Ref 6

Because no system is perfect, safety analysis cannot stop with the design and production of hardware. The safety analysis evolves into the next stage, operating hazard analysis (OHA) (Fig. 4). This serves to identify solutions where failure that is attributable to operator performance is likely to occur. The techniques of carrying out OHA are the same as for system hazard analysis except that the human operator and his limitations must be considered. The outputs from OHA are operational requirements that compensate for or correct a human limitation. The procedures have to either prevent the hazard or confine and minimize its impact.

Fig. 4 Safety analysis flow chart for operating hazard analysis. Source: Ref 6

The outputs from OHA can be in the form of procedural steps, sequence constraints, caution or warning notes, reference data, or support or standby equipment. The Design Process The design process includes determination of the configuration of the product and various component parts and selection of materials and processes to be used. In its early stages, the process consists of evaluating various combinations of

preliminary configuration, candidate material and potential method of manufacture, and comparing these with previously established performance specifications. The relationship between configuration and material (processed in some specific way) is that every configuration places certain demands on the material, which has certain capabilities to meet these demands. A common specific relationship is a relationship between the stress imposed by the configuration and the strength of the material. Of course, there are other relationships as well. Changes in processing can change the properties of a material, and certain combinations of configuration and material cannot be made by some manufacturing processes. Probabilistic or Deterministic Approach. Quantitative relationships between configurational demands and material capabilities can be established by deterministic methods--the more well known approach--or probabilistic methods. In the former, nominal or average values of stress, dimension, and strength are used in design calculations; appropriate safety factors are used to compensate for expected variations in these parameters and for discontinuities in the material. In the probabilistic approach, each design parameter is accorded a statistical distribution of values. From these distributions and from an allowable limit on probability of failure, minimum acceptable dimensions in critical areas (or minimum strength levels for critical components) can be calculated. Compared with deterministic methods, the probabilistic approach requires greater sophistication on the part of the designer and more elaborate calculations, but offers the potential for more compact parts that use less material. A significant handicap to use of probabilistic methods is the fact that statistical distributions of properties are not widely available and often must be determined before these methods can be applied to a specific design problem.

In either approach to design, the effects of notches and stress concentrations must be considered, because these features increase the vulnerability of all types of parts to failure. However, studies in fracture mechanics have shown that, under some circumstances, notches and discontinuities in the material may be benign, and therefore of little consequence in some design applications. A more detailed description on the use of statistical methods for the prediction of such factors as operating stress, strain, deflection, deformation, wear rate, fatigue strength, creep strength, or service life is found in the Section "Statistical Aspects of Design." Effect of Service Hazards. Cyclic loading, use at extreme temperatures, and the presence of agents that cause either

general corrosion or stress-corrosion cracking are special hazards that must be considered during the materials-selection process. Table 4 lists some common failure modes and the mechanical properties most related to particular modes. Cyclic loading, in particular, is a very common factor in the design of anything that has moving parts; it is also widely recognized that fatigue is responsible for a large portion of all service failures. In 1943, Almen (Ref 7) made an observation that is still valid about fatigue: "Fully 90 percent of all fatigue failures occurring in service or during laboratory and road tests are traceable to design and production defects, and only the remaining 10 percent are primarily the responsibility of the metallurgist as defects in material, material specification, or heat treatment. "Study of fatigue of materials is the joint duty of metallurgical, engineering, and production departments. There is no definite line between mechanical and metallurgical factors that contribute to fatigue. This overlapping of responsibility is not sufficiently understood. "Hence, the engineers are constantly demanding new metallurgical miracles instead of correcting their own faults. Until metallurgists are less willing to look for metallurgical causes of fatigue and insist that equally competent examination for mechanical causes be made, we cannot hope to make full use of our engineering material."

Table 4 Relationships between failure modes and material properties Failure mode

Material property

Ultimate tensile strength

Gross yielding

Yield strength

Compressive yield strength

X

Buckling

Shear yield strength

Fatigue properties

Ductility

Impact energy

Transition temperature

Creep rate

KIc(a)

KIscc(b)

X

X

X

Brittle fracture

X

Fatigue, low cycle

X

X

X

X

X

X

Contact fatigue

X

Fretting

X

X

Corrosion

Stresscorrosion

Electrochemical potential

X

Creep

Fatigue, high cycle

Modulus of elasticity

X

X

X

X

Hardness

Coefficient of expansion

cracking

Galvanic corrosion

Hydrogen embrittlement

X

X

Wear

X

Thermal fatigue

Corrosion fatigue

X

X

X

X

An "X" at the intersection of material property and failure mode indicates that a particular material property is influential in controlling a particular failure mode. (a) Plane-strain fracture toughness.

(b) Threshold stress intensity to produce stress-corrosion cracking

Although Almen spoke specifically about fatigue, his comments can be applied to engineering design on a far broader basis. His comments must not be construed to excuse materials engineers from a proper share of the overall design responsibility, nor to allow them to slacken their efforts to find better materials for specific applications. Almen's comments do imply that all aspects of design must be considered, because even apparently insignificant factors can have far reaching effects. (For example, there is at least one known instance in which fatigue failure of an aircraft in flight was traced to an inspection stamp that was imprinted on a component using too heavy a hammer blow.) Failure Anticipation. Even parts for which loading in service is known accurately and stress analysis is

straightforward, gross design deficiencies can arise from reliance on static load-carrying capacity based solely on tensile and yield strengths. The possibility of failure in other modes, such as fatigue, stress-corrosion cracking, and brittle fracture caused by impact loading, must be considered in the design process. Any discussion of potential failures in service should include careful consideration of the possible consequences of failure. Those failure modes that might endanger life or limb, or destroy other components of the apparatus, should be avoided. Sometimes, a piece of equipment is designed so that one component will fail in a relatively harmless fashion and thus avoid the potentially more serious consequences of the failure of another. For example, a piece of earth-moving equipment might be designed so that the engine will stall if the operator attempts to lift a load so heavy that it might upset the equipment or damage any of the structural components. A blowout plug in a pressure vessel is another example. Conformance to codes and standards, such as those listed in Table 3, can preclude serious consequences of service failure, but designers still must exercise careful judgment in studying (and designing against) the consequences of possible modes of failure. Restrictions on Size, Weight, or Volume. The size and weight of a part can affect the choice of both material and

manufacturing process. Small parts often can be economically machined from solid bar stock, even in fairly large quantities. The material cost of a small part may be far less than the cost of manufacturing it, perhaps making relatively expensive materials feasible. Large parts can be difficult or impossible to heat treat to high-strength levels. There are also limits on size for parts that can be formed by various manufacturing processes. Die castings, investment castings, and powder metallurgy parts are generally limited to a few kilograms. When weight is a critical factor, parts often are made from materials having high strength-to-weight ratios. The quantity of parts to be made can affect all aspects of the engineering design process. Low-quantity production runs can seldom justify the investment in tooling required by production processes, such as forging or die casting, and may limit the choice of materials to those already in the designer's factory or those stocked by service centers. High-quantity production runs may be affected by the capability of materials producers to supply the required quantity. Mass-produced parts sometimes are designed and redesigned, requiring a large expenditure for engineering and evaluation, but providing enough savings, considering the large quantity involved, to make the effort worthwhile. Design for small-quantity parts may be limited to finding the first design and material that serve the required purpose. Other Relationships Influencing the Design Process. Products that can be manufactured in several locations

can present additional problems for designers because the cost and availability of materials can vary from place to place. If the product is to be made in different countries, the nearest equivalent grades of steel, for example, might be different enough to affect service performance. In some areas that have low prevailing labor costs, it may be desirable to design a labor-intensive product; in a high-cost labor market, the designer often attempts to design the product to fit the capabilities of automated manufacturing equipment. It is relatively late in the design process before designers, materials engineers, and manufacturing engineers, by working together, can establish those factors described in "Factors in Material Selection" (for example, Table 1 in the previously mentioned article). Only then can the field of candidate materials and manufacturing processes be narrowed to a manageable number of alternatives. The implications of each of these alternative materials and manufacturing processes can then be evaluated, and any required changes in configuration can be made. One of the complicating factors in materials selection is that virtually all materials properties, including fabricability, are interrelated. Substituting one material for another, or changing some aspect of processing in order to effect a change in one particular property, generally affects other properties simultaneously. Similar interrelations that are more difficult to characterize exist among the various mechanical and physical properties and variables associated with manufacturing processes. For example, cold drawing a wire to increase its strength also increases its electrical resistivity. Steels that have high carbon and alloy contents for high hardenability and strength generally are difficult to machine and weld. Additions

of alloying elements such as lead to enhance machinability generally lower long-life fatigue strength and make welding and cold forming difficult. The list of these relationships is nearly limitless. Value analysis also known as value engineering, is a problem-solving methodology that focuses on identifying the key function(s) of a design so that unnecessary costs can be removed without compromising the quality of the design. Key concepts that must be examined during value analysis include:

• • • • • • • • • •

Is it necessary? Does it do more than is required? Does it cost more than it is worth? Is there something that does the job better? Can it be made by a less-costly method? Can a standard item be used? Considering the quantities used, could a less-costly tooling method be used? Does it cost more than the total of reasonable labor, overhead, material, and profit? Can another manufacturer provide it at less cost without affecting dependability? If it was a personal purchase, would the item be too expensive to purchase?

Value analysis using such criteria can provide both designers and managers with assurance that the final combination of configuration, material, and manufacturing process is a good combination. More detailed information on this topic is found in Ref 8. Design for Manufacture and Assembly With increased awareness of the importance of the interaction between design and manufacture, a new field aimed at formalizing this relationship is evolving, called "design manufacture and assembly" (DFMA) (Ref 9). The DFMA approach examines the product design in all aspects for methods of integrating the product and its processing so that the best match is made between product and process requirements and that the integrated product/process ensures inherent ease of manufacture. A major objective of DFMA is to ensure that the product (including material selection) and the process are designed together. Figure 5 summarizes the steps taken when using DFMA analysis during design. The design-for-assembly (DFA) analysis is conducted first, leading to a simplification of the product structure. Then, early cost estimates for the parts are obtained for both the original design and the new design to make trade-off decisions. During this process, the best materials and processes to be used for the various parts are considered. For example, would it be better to manufacture a cover from plastic or sheet metal? Once the materials and processes have been finally selected, a more thorough analysis for design for manufacture (DFM) can be carried out for the detail design of the parts.

Fig. 5 Typical steps taken when using design for manufacture and assembly (DFMA) analysis during design

Reducing the number of separate parts, thereby simplifying the product, is the greatest improvement provided by DFA (Ref 10). To give guidance in reducing the part count, the DFA software asks the following questions as each part is added to the product during assembly: • •

Is the part or subassembly used only for fastening or securing other items? Is the part or subassembly used only for connecting other items?

If the answer is "yes" to either question, the part or subassembly is not considered theoretically necessary. If the answer is "no" to both questions, the following criteria questions are considered: • • •

During operation of the product, does the part move relative to all other parts already assembled? Must the part be made from a different material than, or be isolated from, all other parts already assembled? Only fundamental reasons concerned with material properties are acceptable. Must the part be separate from all other parts already assembled because the necessary assembly or disassembly of other separate parts would otherwise be impossible?

If the answer to all three criteria questions is "no," the part cannot be considered theoretically necessary. Implementation of DFM analysis helps to quantify cost of parts and allow trade-off decisions to be made for design proposals and material and process selection. Major cost savings are achieved when: • • • • •

The design of products, subassemblies, components, modules, and individual parts are standardized Readily processed materials are used The product design is developed for the particular manufacturing process that will be used to make the part Each part is designed for ease of manufacture Inherently expensive machining operations are eliminated

Of course, engineering designers must design products that not only can be economically manufactured and assembled, but they also must function as intended. This requires selecting and understanding the physical principles by which the product will operate. Moreover, proper function requires special attention to tolerances. These two considerations are called designing for function and fit. However, designers must consider a myriad of other issues as well: installation, maintenance, service, environment, disposal, product life, reliability, safety, and other issues. The phrase "design for X" (DFX) refers to these other issues (Ref 11). Designing for DFM, DFA, minimum parts, function, fit, and DFX is still not all that is required of the engineering designer. Products also must be designed for marketing and profit, that is, for the customer and for the nature of the marketplace. Designers, therefore, need to be aware of what features customers want, and what customers consider to be quality in a product. In addition, marketing considerations should include cost, quality, and, increasingly important, time-that is, when the product will reach the marketplace. Designers also should recognize that the processes by which parts and products are made, and the conditions under which they are used, are variable. As described in the section on "Design for Quality," designing so that products are robust under these variabilities is another design requirement. Design for Quality Robust Design. Variability is the enemy of manufacturing. It is a major cause of poor quality resulting in unnecessary

manufacturing cost, product unreliability, and ultimately, customer dissatisfaction and loss of market share. Variability reduction and robustness against variation of hard-to-control factors are therefore recognized as being of paramount importance in the quest for high-quality products. In a design for quality approach, the design team seeks to design the product and process in such a way that variation in hard-to-control manufacturing and operational parameters is minimal. The ideas behind this approach are largely attributable to the efforts of Genichi Taguchi and the cost-saving approaches to quality control pioneered in Japan. The Taguchi method(s), also known as robust design, is an integrated system of tools and techniques that allow engineers and scientists to reduce product or process performance variability while simultaneously guiding that performance toward the best possible level. Major robust design techniques, tools, and concepts include the quality loss function, parameter design, tolerance design, signal-to-noise ratio, technology development, and orthogonal arrays. Each of these are treated extensively in the literature (see, for example, Ref 12 and 13). Statistical Process Control. Another important tool for quality improvement, advocated by W.E. Deming (Ref 14,

16), and Scherkenbach (Ref 15), is statistical process control (SPC). This is a procedure, using statistical mathematics, which signals that some extraneous factor is affecting the output of a production process. The signal alerts production and quality personnel that a process fault should be looked for and eliminated. In this way, the procedure aids in identifying and correcting the causes of product component defects. Because there are natural random variations in the results of any manufacturing process, the ability to differentiate between these random variations and those caused by some change in process conditions is a critical part of maintaining good control over specified characteristics and dimensions. Broken or worn cutting tools, slipped adjustments, leaks in a pressurized system, and an accidental change to a less-active solder flux are some examples of the kinds of process changes that might otherwise not be noticed, but which may cause a quality deterioration that would be detected by SPC analyses. Additional information about SPC is provided throughout this Handbook. Total Quality Management. Deming also states that 85% of quality problems are caused by systems, procedures, or

management, and only 15% of quality problems are caused by bad workmanship (Ref 16). Blaming workers is not the way to cure quality problems. Incidentally, the 85% of quality problems attributable to management includes problems traceable to weaknesses or errors in the product design. Current thinking on the best managerial approaches to control quality improvement involve heavy worker participation in both the monitoring of quality and the corrective actions taken to solve quality problems. One approach that encompasses worker involvement is total quality management (TQM). Total quality management is more a broad management philosophy and strategy than a particular technique. Referred to earlier as total quality control, it originated in Japan. It involves: • •

A strong orientation toward the customer in matters of quality. Emphasis on quality as a total commitment for all employees and all functions including research, development, design, manufacturing, materials, administration, and service. Employee participation in

• • • •

quality matters is standard at all levels. Suppliers also participate. A striving for error-free production. Perfection is the goal. Use of statistical quality control data and other factual methods rather than intuition to control quality. Prevention of defects rather than reaction after they occur. Continuous improvement.

Total quality management programs usually stress that quality must be designed into the product rather than tested for at the end of the production process. Reference 17 provides additional information. Reliability in Design Definition. Reliability is a measure of the capacity of equipment or systems to operate without failure in the service

environment. The National Aeronautics and Space Administration (NASA) defines reliability as the probability of a device performing adequately for the period of time intended under the operating conditions encountered. Reliability is always a probability, thus its calculation is one form of applied mathematics. Probabilistical and statistical methods, however, like any other forms of mathematics, are aids to, not substitutes for, logical reasoning. Reliability is identified with a state of knowledge, not a state of things. Reliability cannot be used to predict discrete, or individually specific, events; only probabilities, that is averages, are predicted. Probability is a measure of what is expected to happen on the average if the given event is repeated a large number of times under identical conditions. Probability serves as a substitute for certainty. A generalization is made from samples, and the conclusions reached cannot be considered to be absolutely correct. The NASA definition of reliability (and any other definition) includes "adequate performance" of the specific device. There is no general definition of adequate performance. Criteria for adequate performance must be carefully and exactly detailed or specified in advance for each device or system considered. A reliability of 0.99 implies a probability of 1 failure per 100. A reliability of 0.999 does not imply greater accuracy (one more significant figure) but an order of magnitude difference, that is, a probability of failure of 1 per 1000. Reliability Tasks. All general definitions, like the NASA definition, are qualitative. A quantitative definition of

reliability for operating time t is:

R(t) = P(T > t)

(Eq 1)

where R is reliability, P is probability, and T is the time to failure of the device. (T itself is a variable.) The first task in ensuring reliability is to derive and investigate Eq 1. This is first done for a single component. The reliability of an entire system is then determined in keeping with the functions and configuration of the units composing the system. This, in turn, can be a subsystem of a more complex system. The building process continues until the entire system has been treated. The complete system can be so complex that it includes entire organizations, such as maintenance and repair groups with their personnel. The second task, after the system and its reliability are truly understood, is to find the best way of increasing the reliability. The most important methods for doing this are: • • • • •

Reduce the complexity to the minimum necessary for the required functions. Nonessential components and unnecessary complexity increase the probability of system failure, that is, they decrease reliability. Increase the reliability of components in the system. Use parallel redundancy, one or more "hot" spares operate in parallel. If one fails, others still function. Use standby redundancy. One or more "cold" spares is switched to perform the function of a failed component or subsystem. Employ repair maintenance. Failed components are replaced by a technician rather than switched in as with standby redundancy. Replacement is neither automatic nor necessarily immediate.

•

Employ preventive maintenance. Components are replaced periodically by new components even though they may not have failed prior to the time of replacement.

The third task is to maximize system reliability for a given weight, size, or cost. Conversely, the task may be to minimize weight, size, cost or other constraints for a given reliability. Graphic Representation of Reliability. Consider a population of homogeneous components from which a very

large sample is taken and placed in operation at time T = 0. (T is age, in contrast with t, commonly used for operational life or mission time.) The population will initially show a high failure rate. This decreases rapidly as shown in Fig. 6. This period of decreasing failure rate is called various names, such as early life period, infant mortality period, and shakedown period. Failure occurs due to design or manufacturing weaknesses, that is, weak or substandard components.

Fig. 6 Mortality curve; failure rate versus age (schematic). Source: Ref 18

When the substandard components have all failed at age TE, the failure rate stabilizes at an essentially constant rate. This is known as useful life because the components can be used to greatest advantage, Failures during useful life are known as random, chance, or catastrophic because they occur randomly and unpredictably. When components reach age TW, the failure rate again increases. Failures begin to occur from degradation due to aging or wear as the components are approaching their rated life. Early life can be made as short as desired (even eliminated) by proper design, fabrication and assembly, and/or deliberate burn-in periods. For systems that must operate satisfactorily over extended periods, incidence of wear out can be postponed almost indefinitely by replacing units as they fail during useful life and replacing each unit (even if it has not failed or given any indication of imminent failure) no later than at the end of useful life. Reference 19 provides more detailed information on estimating useful life, mean time to failure, and mean time between failures. Reliability Testing. Reliability tests measure or demonstrate the ability of equipment to operate satisfactorily for a

prescribed time period under specified operating conditions. Assuming a system with ten components in series, which must operate for 1000 h with a reliability of 0.99, the characteristic life of a component must be 106 h, or about 115 years. To obtain a state of knowledge to determine this requires more than 115 years of failure-free testing (115 components for 1 year or 1150 components for 6 weeks) for each of 10 components. If the number of parts is several hundred and the desired reliability is 0.999 (not at all uncommon), it is obvious that the required number of tests becomes absurdly impossible. Yet, such products are designed, built, and meet guaranteed performance. Although maximum use is made of past performance data and engineering judgment, it is essential for the designer to know as soon as possible if a design objective for reliability and/or life will be met. To meet a production schedule, it is rarely realistic to test under normal operating conditions. Thus accelerated testing is desired. Three factors control the degree of acceleration: environment, sample size, and testing time. Environment includes any operating condition to which the part is subjected and that may affect its performance and/or durability. Two broad categories of testing are implied: (a) tests to determine which aspects of the environment are truly significant and (b) accelerated tests to determine performance as quickly as possible.

Univariate testing (one parameter at a time) for environmental factors is not always useful because there is no indication of any effect of interaction between two or more factors. Factorial experiments can be used to estimate the main (direct) effect of each "stress," interactions between two (or more) stresses, and experimental error (Ref 20, 21, 22, 23, 24). Related information is contained in the Section "Statistical Aspects of Design," which is contained below. To run a complete factorial experiment, especially for replication, may require a very large number of individual tests or runs. Fortunately, in such a situation, most of the desired information can be obtained by performing only a fraction of the full factorial. In one unusual (and outstanding) situation with 19 variables, a complete full factorial study would have required more than 500,000 samples. A judiciously selected fractional factorial design provided the desired information from a study of only 20 samples (Ref 20, 21, 22, 23, 24, 25). Accelerated testing, which is reducing the time required for testing, can be accomplished by: (a) taking a large sample and testing only part of the sample to failure, (b) magnifying the stress, or (c) sudden-death testing. Alternatives (a) and (c) are especially useful in testing a large number of relatively inexpensive components. Sequential testing is more useful when there are only a few relatively expensive units. If a number of identical units are tested simultaneously, failure will occur in an ordered sequence with the weakest units failing first, and so forth. Such ordering is unique with life testing (Ref 26). The choice of a test involving failure of r units out of n (n > r) rather than the choice of a test involving failure of r out of r units will, in general, permit determination of an estimate of characteristic life in a relatively shorter time. For example, if 20 units have to be operated for 200 h to induce all 20 failures, then on the average, only 46 h are needed to observe the first 10 failures in a sample of 20. Use of magnified loading does reduce testing time and possibly the number of items required for the test. Correlation is a major problem because "normal" needs to be defined and enough overload data must exist to correlate with normal. Rabinowicz et al. (Ref 27) suggested a technique based on cumulative damage. An example of acceleration in fatigue testing was developed by Conover et al. (Ref 28). Intensified loading of programmed fatigue tests developed from field data was used to reduce time to failure in steels for automotive components by a factor of ten. These results were applicable for unnotched specimens, notched specimens, and automotive components. Other useful reliability tests include sudden-death testing (Ref 18, 21), which is especially useful with a large number of relatively inexpensive units, and sequential testing (Ref 18, 21) which is especially useful for tests of a small number of relatively expensive units. Redesign Redesign often can improve performance and reduce cost, and can occur informally during the early stages of design. It may also result from formal design-review procedures. Failure-mode analysis is particularly useful in redesign to reduce the likelihood of further failures. These techniques often have resulted in greatly improved product performance. Standardization and simplification of design can lead to substantial savings without loss of performance. Retaining only the most efficient sizes, types, grades and models of a product is an example; during World War II, the number of "standard" types of steel, brass, and bronze valves in the United States was reduced from 4080 to 2500. Utilization of standard off-the-shelf components can also lead to significant savings. It might be less costly, for example, to use a

-20

bolt 2 in. (50 mm) long, which is a widely stocked size, even though design requirements could be satisfied by a bolt 1 in. (48 mm) long, which would probably be a special order item. Further savings could be realized if the assembly were to be redesigned to allow use of 1 mm) bolts.

in. (38 mm) or 1

in. (44

Functional substitution offers great opportunity for improvement and cost reduction through redesign. The goal of functional substitution is to find a new and different way to meet a design requirement. For example, a bolted assembly might be redesigned for assembly by welding, by pressing mating parts together, or by adhesive bonding. The scope of a

functional redesign program might be rather modest, as in the example just mentioned, or it might entail complete redesign of the product.

References cited in this section

1. J.B. Fussell and D.P. Wagner, Fault Tree Analysis as a Part of Mechanical Systems Design, Engineering Design, Proceedings of the Mechanical Failures Prevention Group, 25th Meeting, NBS 487, National Bureau of Standards, 1976, p 289-308 2. C. Starr et al., The Philosophical Basis for Risk Analysis, Ann. Rev. of Energy, Vol 1, 1976, p 629-662 3. G. Kardos, Risk and Hazard Analysis in Design, Materials Selection and Design, Vol 20, ASM Handbook, ASM International, 1997, p 117-125 4. R.R. Landers, A Failure Mode and Effect Analysis Program to Reduce Mechanical Failures, Engineering Design, Proceedings of the Mechanical Failures Prevention Group, 25th Meeting, NBS 487, National Bureau of Standards, 1976, p 278-288 5. J.J. Hollenback, "Failure Mode and Effect Analysis," Paper 770740, American Society of Agricultural Engineers, 1976 6. H.D. Wolf, Safety Analysis: Qualitative, Quantitative and Cost Effective, Engineering Design, Proceedings of the Mechanical Failures Prevention Group, 25th Meeting, NBS 487, National Bureau of Standards, 1976, p 265-277 7. J.O. Almen, Probe Failures by Fatigue to Unmask Mechanical Causes, SAE Journal, Vol 51, May 1943 8. T.C. Fowler, Value Analysis in Design, Van Nostrand Reinhold, 1990 9. G. Boothroyd, Design for Manufacture and Assembly, Materials Selection and Design, Vol 20, ASM Handbook, ASM International, 1997, p 676-686 10. G. Boothroyd, Assembly Automation and Product Design, Marcel Dekker, 1992 11. D.A. Gatenby, Design for "X"(DFX) and CAD/CAE, Proceedings of the 3rd International Conference on Design for Manufacturability and Assembly, 6-8 June 1988 (Newport, RI) 12. P.J. Ross, Taguchi Techniques for Quality Engineering, McGraw-Hill, 1988 13. L.A. Ealey, Quality by Design: Taguchi Methods and U.S. Industry, 2nd ed., ASI Press and Irwin Professional Publishing, 1994 14. W.E. Deming, Quality, Productivity, and Competitive Position, MIT Center for Advanced Engineering, 1982 15. W.W. Scherkenbach, The Deming Route to Quality and Productivity: Road Maps and Roadblocks, Mercury Press/Fairchild Publications, 1987 16. W.E. Deming, Out of the Crisis, Massachusetts Institute of Technology, 1986 17. D.H. Stamatis, TQM Engineering Handbook, Marcel Dekker, 1997 18. C.O. Smith, Introduction to Reliability in Design, McGraw-Hill, 1976 19. C.O. Smith, Reliability in Design, Materials Selection and Design, Vol 20, ASM Handbook, ASM International, 1997, p 87-95 20. G.E.P. Box, W.G. Hunter, and J.S. Hunter, Statistics for Experimenters, John Wiley & Sons, 1978 21. C. Lipson and N.J. Sheth, Statistical Design Analysis of Engineering Experiments, McGraw-Hill, 1973 22. J.D. Hromi, "Some Aspects of Designing Industrial Test Programs," Paper 690022, Society of Automotive Engineers, Jan 1969 23. W.G. Cochran and G.M. Cox, Experimental Designs, John Wiley & Sons, 1950 24. D.R. Cox, Planning of Experiments, John Wiley & Sons, 1958 25. G.E.P. Box and J.S. Hunter, The 2k-p Fractional Factorial Designs, Technometrics: Part I, Vol 3 (No. 3), Aug 1961, p 311-351; Part II, Vol 3 (No. 4), Nov 1961, p 449-458 26. Epstein and Sobel, Life Testing, J. American Statistical Association, Vol 48 (No. 263), Sept 1953

27. E. Rabinowicz, R.H. McEntire, and R. Shiralkar, "A Technique for Accelerated Life Testing," Paper 70Prod-10, American Society of Mechanical Engineers, April 1970 28. J.C. Conover, H.R. Jaeckel, and W.J. Kippola, "Simulation of Field Loading in Fatigue Testing," Paper 660102, Society of Automotive Engineers, Jan 1966 Statistical Aspects of Design For many years engineers have designed components and structures using best available estimates of material properties, operating loads, and other design parameters. Once established, most of these estimated values have commonly been treated as fixed quantities or constants. This approach is called deterministic, in that each set of input parameters allows the determination of one or more output parameters, where those output parameters may include a prediction of factors such as operating stress, strain, deflection, deformation, wear rate, fatigue strength, creep strength, or service life. In reality, virtually all material properties and design parameters exhibit some statistical variability and uncertainty that influence the adequacy of a design. Fundamentally, designing to prevent service failures is a statistical problem. In simplistic terms, an engineered component fails when the resistance to failure is less than the imposed service condition. Depending on the structure and performance requirements, the definition of failure varies; it could be buckling; permanent deformation; tensile failure; fatigue cracking; loss of cross section due to wear, corrosion; erosion; or fracture due to unstable crack growth. In any of these cases, the failure resistance of a large number of components of a particular design is a random variable, and the nature of this random variable often changes with time. The imposed service condition for these components is also a random variable; it too can change with time. The intersection of these two random variables at any point in time represents the expected failure percentage and provides a measure of component reliability. This section presents some of the statistical aspects of design from an engineer's perspective. Some statistical terms are clarified first because many engineers have not worked in the field of statistics enough to put these terms into day-to-day engineering practice. More detailed information pertaining to the statistical aspects of design is found in Ref 29, 30, 31, 32, 33 and in Volume 8, Mechanical Testing, of the ASM Handbook. Classification of Statistical Terms Random Variables. Any collection of test coupons, parts, components, or structures designed to the same set of

specifications or standards will exhibit some variability in performance between units. Performance can be measured by a wide variety of parameters, or some combination of those parameters. as discussed earlier. In any case, these measures of performance are not controlled, although there is often an attempt to optimize them to maximize performance, within prescribed cost constraints. Because these measures of performance are not controlled and subject to inherent random variability, they are commonly called random variables. The tensile strength of a structural material is a practical example of a random variable. Given a single heat and lot of a material manufactured to a public specification, such as an ASTM, SAE/AMS, or Department of Defense (DoD) specification, repeated tests to determine the tensile strength of that material will produce varied results. This will be true even if the individual tests are performed identically, within the limits of engineering accuracy. Table 5 illustrates that even apparently similar tensile samples tested under identical conditions generally do not produce the same results, producing data scatter or variability. Each observation was based on randomly selected samples from each heat of material.

Table 5 Results of a hypothetical test series to determine the ultimate tensile strength of two heats of material Sample No.

Tensile strength

Heat 1

Heat 2

MPa

ksi

MPa

ksi

1

522

75.7

517

75.0

2

511

74.1

490

71.1

3

489

70.9

499

72.4

4

554

80.3

514

74.6

5

500

72.5

503

72.9

Density Functions. In statistical terms, a density function is simply a function that shows the probability that a random

variable will have any one of its possible values. Consider, for example, the distribution of fatigue lives for a material as shown in Table 6. Assume that these 23 observations were generated from a series of replicate tests, that is, repeated tests under the same simulated service conditions. A substantial range in fatigue lives resulted from these tests, with the greatest fatigue life being more than ten times the lowest observation. Table 6 Representative fatigue data showing variability in cycles to failure Life interval, 106 cycles

Number of failures

Cycles 106 cycles

to

failure,

0.0-0.5

1

0.425

0.5-1.0

5

0.583, 0.645, 0.77, 0.815, 0.94

1.0-1.5

7

1.01, 1.09, 1.11, 1.21, 1.30, 1.41, 1.49

1.5-2.0

4

1.61, 1.70, 1.85, 1.97

2.0-2.5

2

2.19, 2.32

2.5-3.0

2

2.65, 2.99

3.0-3.5

1

3.42

3.5-4.0

0

...

4.0-4.5

0

...

4.5-5.0

1

4.66

Total observations

23

The resulting approximate density function for these data is shown in Fig. 7. This figure shows the number of fatigue life observations within uniform cycles-to-failure intervals. Each interval of the histogram shows the frequency of occurrence of fatigue failures within the interval. It is evident that the probability of occurrence of a fatigue failure for this material and test condition is not constant over the range of possible fatigue lives. If 300 observations were available, instead of 23, the shape of the histogram would tend to stabilize. As the number of observations increase, "bumps" in the frequency diagram (as in Fig. 7) caused by random variations in fatigue life would tend to disappear, and the shape will begin to resemble that of a continuous function. A mathematical representation of such a distribution is called a density function.

Fig. 7 Histogram of fatigue data from Table 6 showing approximate density function

Cumulative Distribution Functions. Plots of experimental data as density functions, as shown in Fig. 7, provide some useful statistical information. Inferences can be made regarding the central tendencies of the data and the overall variability in the data. However, additional information can be obtained from a data sample like the sample summarized in Table 6, by representing the data cumulatively, as in Table 7, and plotting these data on probability paper, as shown in Fig. 8(a). This is done by ranking the observations from lowest to highest and assigning a probability of failure to each ranked value. These so-called median ranks can be obtained from tables of these values from a statistical test (see, for example, Ref 21).

Table 7 Cumulative distribution of fatigue failures from Table 6 Cycle interval × 106

No. of failures

0.0-0.5

0.5-1.0

1.0-1.5

1.5-2.0

2.0-2.5

2.5-3.0

3.0-3.5

3.5-4.0

4.0-4.5

4.5-5.0

1

5

7

4

2

2

1

0

0

1

Fig. 8 Cumulative distribution function for fatigue data from Table 6 based on (a) assumed normal distribution and (b) assumed log-normal distribution

Sample versus Population Parameters. When performing a deterministic analysis, the input parameters are defined to represent the material in some specific way. For example, the input parameter may be the average or typical yield strength of a material or a specification minimum value. The implicit assumption is that, given an infinite number of observations of the strength of this material, the assumed average or minimum values would match the "real" values for this infinite population. Of course, the best that can be done is to generate a finite number of observations to characterize the performance of this material (in this case, yield strength); these observations are considered a statistical sample of this never-attainable, infinite population. Intuitively, an increase in the number of observations (the sample size), should increase the accuracy of the sample estimate of the real, or population material properties. Variability versus Uncertainty. Variability and uncertainty are terms sometimes used interchangeably. However, it

is useful when talking about statistical aspects of design to draw a distinction between them. Uncertainty is defined in most dictionaries as "the condition of being in doubt" or something similar to this. In the context of this discussion, uncertainty can be considered the bounds within which the "true" engineering result, such as the average fatigue life of a component, can be expected to fall. To establish this uncertainty in quantitative terms, it is necessary to identify and quantify all factors that contribute to that uncertainty. Generally speaking, the uncertainty in an engineering result is broad in the early stages of a design, and this uncertainty decreases significantly as more experimentation and analysis work is done. This uncertainty is commonly described in terms of confidence limits, tolerance limits, or prediction limits. Variability is an important element of an uncertainty calculation. The meaning of the term can be drawn directly from its root word, variable. Virtually all elements of a design process can be described as random variables, with some measure of central tendency or average performance and some measure of scatter or variability. For continuous variables, this

variability is generally quantified in terms of a sample standard deviation, or sample variance, which is simply the standard deviation squared, σ2, where σ equals the population standard deviation. Another commonly used measure of variability is the coefficient of variation, which is defined as the sample mean divided by the sample standard deviation and generally is expressed as a percentage. This normalized parameter allows direct comparisons of relative variability of materials or products that display significantly different mean properties. For example, two different aluminum alloys might have tensile strengths that are described statistically as follows:

Aluminum alloy

Average tensile strength, ksi

Standard deviation, ksi

No. 1

70

2.5

No. 2

75

4.0

Alloy No. 1 displays a coefficient of variation (COV) of approximately 3.6%, while alloy No. 2 displays a COV of approximately 5.3%. The higher variability of alloy No. 2, as represented by a COV nearly 50% higher than alloy No. 1, could lead to a higher level of uncertainty in the performance of a structure made from the second alloy in comparison to the first alloy. Precision versus Bias. Precision and bias are statistical terms that are important when considering the suitability of an engineering test method or making a comparison of the relative merits between two or more procedures or processes (Ref 33). A statement concerning the precision of a test method provides a measure of the variability that can be expected between test results when the method is followed appropriately by a competent laboratory. Precision can be defined as the reciprocal of the sample standard deviation, which means that a decrease in the scatter of a test method as represented by a smaller standard deviation of the test results leads directly to an increase in the precision. Conversely, the greater the variability or scatter of the test results, the lower the precision.

The test results of two different processes (e.g.; heat treatments and their effect on tensile strength) can also be statistically compared, and a statement made regarding the precision of one process compared to another. Such a statement of relative precision is only valid if no other potentially significant variables, such as different test machines, laboratories, or machining practices are involved in the comparison. The bias of a set of measurements quantifies the difference in those test results from an accepted reference value or standard. The concept of a bias can also be used to describe the consistent difference between two operators, test machines, testing periods, or laboratories. The term accuracy is sometimes used as a synonym for bias, but it is possible to identify a bias between two sets of measurements or procedures without necessarily having any awareness of which set is most accurate. In order to make quantitative statements about absolute bias or accuracy, it is necessary to have a known baseline or reference point; such fixed points are seldom available in the real world of an engineer. Independent versus Dependent Variables. Many engineering analyses involve the prediction of some outcome

based on a set of predefined input conditions. A very simple example is the prediction of stress in the elastic range for a metal, based on a measured strain and an estimated or measured value for elastic modulus. Another more complex example is the prediction of the fatigue resistance of a part based on estimated local stress or strain amplitudes and experimentally determined fatigue parameters. In general, relationships such as these are developed through a regression analysis, in which the predicted outcome, y, is estimated from a series of terms written as a function of one or more input quantities, xi, and regression parameters, Ai, as follows:

y = A0 + A1f1(x) + A2f2(x). . .

(Eq 2)

In this expression, the predicted result, y, is the dependent variable, while the defined quantity, x, is the independent variable. In some cases, multiple independent variables are needed in combination to realistically estimate the independent variable(s). Why Not Just Assume Normality and Forget the Complications? The first assumption that most engineers

will make when applying statistics to an engineering problem is that the property in question is normally distributed. The normal distribution is relatively simple mathematically, is well understood, and is well characterized. The engineering statistics applications where nonnormal statistical distributions and nonparametric (distribution-free) approaches are used probably do not total the number of applications based on normal statistics. The assumption of normality is reasonable in many cases where only mean trends or average properties are of interest. The importance of verifying this assumption increases when properties removed from the mean or average are being addressed, such as an estimated first percentile value of a design factor or a value 2 or 3 standard deviations below the mean. The assumptions that are made regarding underlying statistical distributions can have a significant impact on the meaningfulness of the answers that result. Statistical Distributions Statistical distributions model various physical, mechanical, electrical, and chemical properties, as well as the number of occurrences of events. There are seven well-known and widely used statistical distributions: normal, log normal, Weibull, and exponential, which are continuous in nature and binomial Poisson and hypergeometric, which are discrete functions. Each of these statistical distributions are briefly described below. References 34, 35, and 36 provide a comprehensive collection of information about numerous statistical distributions used in the development of statistical theory and practice. Reference 21 is a useful layman's source on statistical distributions and their practical application. The normal distribution is the most widely used and best understood statistical distribution. In addition to its

widespread use as an approximation to the distributions of many computed statistics, the normal distribution is frequently used to model various physical, mechanical, electrical, and chemical properties--for example, tensile strength, hardness, conductivity, and elastic modulus. Many properties that scatter randomly about a well-defined mean value, without either positive or negative bias, also tend to follow a normal distribution. The primary limitation associated with the modeling of physical measurements with the normal distribution is its symmetry of average value. Thus, skewed or asymmetric populations are not modeled well by the normal distribution. The main advantage of the normal distribution is the large body of literature available describing procedures for the analysis of normally distributed data. Figure 9 illustrates a histogram that describes the distribution of tensile yield strengths for a particular material. The number of observations in each interval is recorded. Continuous probability density functions are superimposed over the histogram to indicate the conformity of these data to a normal distribution as compared with either a two-parameter or a three-parameter Weibull distribution.

Fig. 9 Histogram of tensile yield strength values with superimposed probability density functions

Log-Normal Distribution. Probably the second most often assumed distribution for engineering random variables is the log-normal distribution. Of course, the log-normal distribution is really just a special case of the normal distribution, where the quantities that are assumed to be normally distributed are the logarithms of the original observations. For example, when the logarithms of the fatigue lives of the material listed in Table 6 were completed and the computed values were ranked and plotted on normal probability paper, a nearly straight line resulted (Fig. 8b). The data trends deviate from linearity only at the very low- and high-fatigue lives. Weibull distribution is used frequently in representing engineering random variables because it is very flexible. It was

originally proposed (Ref 37) to represent fatigue data, but it is now used to represent many other types of engineering data. For the modeling of fatigue strength at a given life, it has been argued that only the Weibull distribution is appropriate (Ref 38). One of the reasons that the Weibull distribution is popular is that data can be plotted on Weibull paper and the conformance of these data to the Weibull distribution can be evaluated by the linearity of the cumulative distribution function in the same way as normal distribution (Fig. 9). Exponential distribution, which is a special case of the Weibull distribution, has been found to be useful in the

analysis of failure rates of complete systems or assemblies, such as light bulbs, water heaters, and automobile transmissions, or where their failures result from chance occurrence alone, such as a wheel hitting a large pothole. Binomial distribution may be applicable where the random variable is discrete and takes on non-negative integer values. It is used commonly in developing sampling plans for periodic inspections of manufacturing or material quality. For example, it is used to model the number of defective items in samples drawn from large lots of items (such as electrical parts) submitted to inspection. Other Discrete Distributions. Two other common variations of the binomial distribution are the hypergeometric and

the Poisson distributions. The hypergeometric distribution is used for the same kinds of applications as the binomial distribution, except that for the binomial, the percentage of defective items is assumed to be constant throughout the experiment. The Poisson distribution differs from the binomial and hypergeometric distributions in that the number of times that an event occurs is not known, but the probability of occurrence of the event is known. Statistical Procedures

Many different statistical techniques can be useful in analysis of mechanical-property data. This section presents brief descriptions of procedures that are used frequently (Ref 39). More detailed descriptions of these and other statistical techniques and tables in their various forms can be found in a number of workbooks and texts (for example, Ref 40). Goodness-of-fit tests can be used to establish whether a sample can realistically be assumed to follow a normal

distribution. The Anderson-Darling goodness-of-fit test for normality can be used to determine whether the density function that fits a given set of data can be approximated by a normal curve. The test involves a numerical comparison of the cumulative distribution function for observed data with that for the fitted normal curve over the entire range of the property being measured. Arithmetic normal probability paper is recommended for graphic illustration of the degree to which a normal distribution fits a set of data. Logarithmic normal probability paper can be used to determine whether the distribution of data could be normalized by a logarithmic transformation. One axis is scaled in units of the property measured, and the other axis is a nonlinear scale of probability. For further information on goodness-of-fit tests, refer to Ref 41 and 42. Tests of significance, which include the F test and t test, are used in determining whether the populations from which

two samples are drawn are identical. The F test is used to determine whether two products differ with regard to their variability. The t test is used to determine whether two products differ with regard to their average properties. If they do, it can be concluded that the two products do not belong to the same population. In making the t test, it is assumed that the variances of two products are nearly equal, as first determined from the F test. If the F test shows that the variances are significantly different, there is no need to conduct the t test. Data Regression Techniques. When it is suspected that the average of one measured value varies linearly or

curvilinearly with some other measured value, a regression analysis is often used to investigate and describe the relationship between the two quantities. Examples are effect of product thickness on tensile strength, effect of temperature on yield strength, and effect of stress on cycles to failure or time to rupture. Reference 43 describes mathematical techniques for performing linear regression computations. Related ASTM Engineering Statistics Standards Table 8 lists standards published by the American Society for Testing and Materials (ASTM) that address statistical issues relevant to engineering design. These standards are maintained by ASTM Committee E11 on Statistical Methods. A primary purpose of this group is to advise other ASTM committees in the area of statistics, and to provide information for general application. Table 8 ASTM standards related to engineering statistics ASTM No.

Title

Statistics terminology

D 4392

"Terminology for Statistically Related Terms"

E 177

"Practice for Use of the Terms Precision and Bias in ASTM Test Methods"

E 456

"Terminology Related to Statistics"

E 1325

"Terminology Relating to Design of Experiments"

E 1402

"Terminology Relating to Sampling"

Statistical conformance with specifications

D 3244

"Practice for Utilization of Test Data to Determine Conformance with Specifications"

E 122

"Practice for Choice of Sample Size to Estimate a Measure of Quality for a Lot or Process"

Statistical control and comparison of test methods

D 4356

"Practice for Establishing Consistent Test Method Tolerances"

D 4853

"Guide for Reducing Test Variability"

D 4855

"Practice for Comparing Test Methods"

E 1323

"Guide for Evaluating Laboratory Measurement Practices and the Statistical Analysis of the Resulting Data"

Statistical analysis of test data

E 178

"Practice for Dealing with Outlying Observations"

E 739

"Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life ( -N) Fatigue Data"

Statistical guidelines for interlaboratory testing programs

D 4467

"Practice for Interlaboratory Testing of a Test Method that Produces Non-Normally Distributed Data"

E 691

"Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method"

Statistical issues in development of sampling plans

D 4854

"Guide for Estimating the Magnitude of Variability from Expected Sources in Sampling Plans"

E 105

"Practice for Probability Sampling of Materials"

E 141

"Practice for Acceptance of Evidence Based on the Results of Probability Sampling"

References cited in this section

21. C. Lipson and N.J. Sheth, Statistical Design Analysis of Engineering Experiments, McGraw-Hill, 1973 29. A.H. Bowker and G.J. Lieberman, Engineering Statistics, Prentice-Hall, 1959 30. A. Hald, Statistical Theory with Engineering Applications, John Wiley & Sons, 1952

31. E.B. Haugen, Probabilistic Approaches to Design, John Wiley & Sons, 1968 32. N.L. Johnson and F.C. Leone, Statistics and Experimental Design in Engineering and the Physical Sciences, Vol I, John Wiley & Sons, 1964 33. "Practice for Use of the Terms Precision and Bias in ASTM Test Methods," E177, Annual Book of ASTM Standards, ASTM 34. S.W. Rust and R.C. Rice, Statistical Distributions, Mechanical Testing, Vol 8, ASM Handbook, ASM International, 1985, p 628-638 35. N.L. Johnson and S. Kotz, Discrete Distributions, Houghton-Mifflin, 1969 36. N.L. Johnson and S. Kotz, Continuous Univariate Distributions--I & II, Houghton-Mifflin, 1970 37. W. Weibull, A Statistical Representation of Fatigue Failures in Solids, Acta Polytech., Mech. Eng. Ser., Vol 1 (No. 9), 1949 38. K.E. Olsson, Weibull Analysis of Fatigue Test Data, Qual. Reliab. Eng. Int., Vol 10, 1994, p 437-438 39. Metallic Materials and Elements for Aerospace Vehicle Structures, MIL-HDBK-5G, Change Notice 1, 1 Dec 1995 40. M.G. Natrella, Experimental Statistics, National Bureau of Standards Handbook 91, 1 Aug 1963 41. J.F. Lawless, Statistical Models and Methods for Lifetime Data, John Wiley & Sons, 1982, p 452-460 42. R.B. D'Agostina and M.A. Stephens, Goodness-of-Fit Techniques, Marcel Dekker, 1987, p 123 43. R.C. Rice, Statistical Aspects of Design, Materials Selection and Design, Vol 20, ASM Handbook, ASM International, 1997, p 72-86 Total Life Cycle in Design It is an accepted principle of engineering to design a product for minimum cost, consistent with fulfilling the functional requirements of the product. It is tempting to define the cost of a product strictly on the basis of component and labor costs (plus allowances for overhead, selling cost, and profit). However, such accounting neglects several important items in the total cost of the product to the user, such as cost of energy to operate the product, cost of maintaining the product, depreciation, and cost of disposal. In addition to the cost of a product to its producer and user, there is the cost to society at large; some of the components of this cost are consumption of raw materials and energy and the impact of the product on the environment. The relative importance of considering the cost to the user and to society during design depends in part on the nature of the product. An automobile, for instance, has considerable user and societal costs; for a bolt, these costs are smaller, harder to identify, and easier to neglect. To a materials engineer, the concept of total life cycle must include the total life of the product, as discussed above and in Table 2, but should also include the total life cycle of the components and materials in the product. Whenever possible, a product should be designed so that components that do not wear out can be reused, or so that the materials in the product can be recycled. Life-cycle analysis (LCA) refers to the "cradle to grave" assessment of the energy requirements and environmental

impacts of a given product design. All aspects of the total life cycle of the product are considered, including raw-material extraction from the earth and product manufacture, use, recycling (including design for recycling), and disposal. Key factors considered in the life-cycle engineering approach are examined in the Section on "Recycling and Life-Cycle Analysis" in this Handbook. Energy Requirements. Reuse of components and materials obviously conserves raw materials, such as the ore from which a metal is made, but it also conserves the energy required to extract the metal from the ore. Basic metal-production operations are highly energy intensive. It has been estimated that 95% of the energy required to manufacture aluminum beverage cans from ore can be saved if metal in the cans is recycled. It may be possible to conserve energy by choosing materials that do not require heat treatment but still have adequate strength. Heavily drafted cold-drawn and stressrelieved steel bars can have yield strengths of 690 MPa (100 ksi); for many purposes, such bars can be used in place of hardened-and-tempered bars. The potential for conservation of scarce resources, particularly those that might be subject to manipulation for economic or political gain, is apparent in these two examples.

As suggested above, the energy required to operate a mechanical device can represent a significant portion of its total lifecycle cost. For example, the cost of electricity used to operate an air conditioner for the duration of the warranty period may be greater than its purchase price. Producibility. The question of producibility affects engineering design at several levels. The most basic question is

whether the technology required to economically produce the desired quantity of the item exists. A product should be designed in accordance with established technological practice whenever possible; working at the limit of technology leads to higher scrap levels and difficulties in production, and advancing the limit of technology requires a developmental program before production can begin. A second question concerns the capability of the factory (or entire industry) to produce the desired number of parts. The third question concerns utilization of existing equipment and personnel. Some of the answers to these questions are managerial prerogatives, but it is usually desirable for designers to analyze the various possibilities and present a set of alternatives, together with possible consequences, advantages, and disadvantages of each, to management. Durability, or intended service lifetime, is one of the parameters on which a design must be based. In general, basic

goals for service lifetime are established for, rather than by, designers. As in the case of producibility, it may be desirable for a designer to develop alternative combinations of material and design that could significantly affect the anticipated service life of the product. Quality assurance should be an integral part of the manufacturing process of any product, especially because the

possible consequences of permitting deficient products to reach the marketplace can be dire. This article does not attempt to describe a quality assurance program, or how to develop such a program; rather, it emphasizes the importance of such a program and points out how design and quality assurance are interrelated. A designer must know the types and severity of discontinuities that can be detected in a quality assurance program and have an appropriate level of confidence in the detection methods. By knowing what can be expected from the quality assurance program, the designer can then provide a margin of safety to compensate for the existence of discontinuities that cannot be detected. This is part of the basic philosophy of fracture mechanics. A similar approach is applicable to design of redundant systems in the product. In either case, the product should be designed with the capabilities and limitations of the quality assurance program in mind. Handling requirements of various products are too frequently neglected in engineering design. Almost without exception, a product is made in one location and used in another. Thus, it is essential to provide means for transporting it from the manufacturer to the seller to the user; the means of transportation can affect the design of the product in several ways. The most obvious concern is to ensure that the product will not be degraded in handling, transit, or storage. Whenever feasible, a product should be designed against the possibility of damage caused by normal handling. A product that can be easily damaged in handling must be carefully (and expensively) protected by packaging or special shipping procedures. It is also important to design a product to minimize shipping and storage space requirements. For example, wastebaskets are usually designed to be nested during handling; many wastebaskets have lugs or other design features that limit nesting in order to permit easy separation. Particularly for consumer products, the design of packages may not be considered a part of product design, but it is still appropriate for a product designer to consider packaging requirements that might result from various design alternatives.

Other Major Factors in Design Besides the functional factors listed in Table 1 and the total life-cycle considerations described in Table 2, several other major factors affect design and materials selection; some of them are listed in Table 3. State of the Art Most of the time, the state of the art in a particular field can be inferred from an engineering evaluation of products currently on the market. Existing products may lack capabilities that could be provided by a new product. The extent of improvement might range from purely cosmetic (which might be the case for a new product intended to capitalize on the market acceptance of an established product) to complete redesign resulting in an entirely new product unlike anything previously produced. The state of the art can be defined not only by existing products but also by industrial and societal standards, technical publications, and patents. Patent infringement is often considered a matter for legal departments, but technical personnel are often able to analyze technological aspects of patents on devices and processes that might be applicable to new products.

Designing to Codes and Standards Many products are subject to either mandatory or voluntary standards. By definition, a "code" is any set of standards set forth and enforced by a local government for the protection of public safety, health, etc., as in the structural safety of buildings (building code), health requirements for plumbing, ventilation, etc. (sanitary or health code), and the specifications for fire escapes or exits (fire code)." "Standard" is defined as "something considered by an authority or by general consent as a basis of comparison; an approved model." As a practical matter, codes tell the user what to do and when and under what circumstances to do it. Codes are often legal requirements that are adopted by local jurisdictions that then enforce their provisions. Standards tell the user how to do it and are usually regarded only as recommendations that do not have the force of law. As noted in the definition for code, standards are frequently collected as reference information when codes are being prepared. It is common for sections of a local code to refer to nationally recognized standards. In many instances, entire sections of the standards are adopted into the code by reference, and then become legally enforceable. A list of such standards is usually given in an appendix to the code. The Need for Codes and Standards. The information contained in codes and standards is of major importance to

designers in all disciplines. As soon as a design problem has been defined, a key component in the formulation of a solution to the problem should be the collection of available reference materials; codes and standards are an indispensable part of that effort. Use of codes and standards can provide guidance to the designer about what constitutes good practice in that field and ensures that the product conforms to applicable legal requirements. The fundamental need for codes and standards in design is based on two concepts: part/component interchangeability and compatibility. Standardization of parts within a particular manufacturing company to ensure interchangeability is only one part of the industrial production problem. The other part is compatibility. What happens when parts from one company, working to their standards, have to be combined with parts from another company, working to their standards? Will parts from company A fit with parts from company B? Yes, but only if the parts are compatible. In other words, the standards of the two companies must be the same. Common Examples of Codes and Standards. Most materials engineers are familiar with the many professional

society codes that have been developed. The American Society of Mechanical Engineers (ASME) publishes the Boiler and Pressure Vessel Code, which has been used as a design standard for many decades. The Society of Automotive Engineers (SAE) publishes hundreds of standards relating to the design and safety requirements for vehicles and their appurtenances. ASTM publishes thousands of standards relating to materials and the methods of testing. These standards are published in a set of 70 volumes divided into 15 separate sections. The standards are developed on a consensus basis with several steps in the review process. Initial publication of a standard is on a tentative basis; such standards are marked with a T until finally accepted. Periodic reviews keep the requirements and methods current. Because designers frequently call out ASTM testing requirements in their materials specifications, the designer should routinely check ASTM listings to make certain the applicable version is being called for. Coordination, approval, and distribution of many domestic standards fall under the auspices of the American National Standards Institute (ANSI), New York, NY. A sponsoring trade association will request that ANSI review its standard. A review group is then formed that includes members of many groups other than the industry. This expands the area of consensus and is an essential feature of the ANSI process. Table 9 gives a partial list of the many organizations that act as sponsors for the standards that ANSI prepares under their consensus format.

Table 9 Sponsoring organizations for standards published by the American National Standards Institute Acronym

Organization

AAMA

American Apparel Manufacturers Association 2500 Wilson Blvd., Arlington, VA 22201 (703) 524-1864

AAMA

American Architectural Manufacturers Association 1540 E. Dundee Rd., Palatine, IL 60067 (708) 202-1350

AAMI

Association for the Advancement of Medical Instrumentation 3330 Washington Blvd., Arlington, VA 22201 (703) 525-4890

AASHTO

American Association of State Highway and Transportation Officials 444 N. Capitol St., N.W., Washington, D.C. 20001 (202) 624-5800

AATCC

American Association of Textile Chemists and Colorists P.O. Box 12215, Research Triangle Park, NC 22709-2215 (919) 549-8141

ABMA

American Bearing Manufacturers Association and Anti-Friction Bearing Manufacturers Association (AFBMA) 1900 Arch St., Philadelphia, PA 19103 (215) 564-3484

...

American Boat and Yacht Council 3069 Solomon's Island Rd., Edgewater, MD 21037-1416 (410) 956-1050

ACI

American Concrete Institute P.O. Box 19150, Detroit, MI 48219 (313) 532-2600

ADA

American Dental Association 211 E. Chicago Ave., Chicago, IL 60611 (312) 440-2500

AGA

American Gas Association 1515 Wilson Blvd., Arlington, VA 22209 (703) 841-8400

AGMA

American Gear Manufacturers Association 1500 King St., Alexandria, VA 22314 (703) 684-0211

AHAM

Association of Home Appliance Manufacturers 20 W. Wacker Dr., Chicago, IL 60606

(312) 984-5800

AIA

Automated Imaging Association 900 Victor's Way, Ann Arbor, MI 48106 (313) 994-6088

AIAA

American Institute of Aeronautics and Astronautics 370 L'Enfant Promenade, S.W., Washington, D.C. 20024 (202) 646-7400

AIIM

Association for Information and Image Management 1100 Wayne Ave., Silver Spring, MD 20910 (301) 587-8202

AISC

American Institute of Steel Construction, Inc 1 E. Wacker Dr., Chicago, IL 60601-2001 (312) 670-2400

ANS

American Nuclear Society 555 N. Kensington Ave., La Grange Park, IL 60525 (708) 352-6611

API

American Petroleum Institute 1220 L St., N.W., Washington, D.C. 20005 (202) 682-8000

ARI

Air-Conditioning and Refrigeration Institute 4301 N. Fairfax Dr., Arlington, VA 22203 (703) 524-8800

ASAE

American Society of Agricultural Engineers 2950 Niles Rd., St. Joseph, MI 49085-9659 (616) 429-0300

ASCE

American Society of Civil Engineers 1015 15th St., N.W., Washington, D.C. 20005 (202) 789-2200

ASHRAE

American Society of Heating, Refrigerating and Air-Conditioning Engineers 1791 Tullie Circle, N.E., Atlanta, GA 30329 (404) 636-8400

ASME

American Society of Mechanical Engineers 345 E. 47th St., New York, NY 10017 (212) 705-7722

ASQC

American Society for Quality Control 611 E. Wisconsin Ave., Milwaukee, WI 53201

(414) 272-8575

ASSE

American Society of Sanitary Engineering P.O. Box 40362, Bay Village, OH 44140 (216) 835-3040

AWS

American Welding Society 550 LeJeune Rd., N.W., Miami, FL 33126 (305) 443-9353

AWWA

American Water Works Association 6666 W. Quincy Ave., Denver, CO 80235 (303) 794-7711

BHMA

Builders Hardware Manufacturers Association 355 Lexington Ave., New York, NY 10017 (212) 661-4261

CEMA

Conveyor Equipment Manufacturers Association 9384-D Forestwood Ln., Manassas, VA 22110 (703) 330-7079

CGA

Compressed Gas Association 1725 Jefferson Davis Highway, Arlington, VA 22202-4100 (703) 412-0900

CRSI

Concrete Reinforcing Steel Institute 933 Plum Grove Rd., Schaumburg, IL 60173 (708) 517-1200

DHI

Door and Hardware Institute 14170 Newbrook Dr., Chantilly, VA 22021-2223 (703) 222-2010

EIA

Electronic Industries Association 2500 Wilson Blvd., Arlington, VA 22201 (703) 907-7550

FCI

Fluid Controls Institute P.O. Box 9036, Morristown, NJ 07960 (201) 829-0990

HI

Hydraulic Institute 9 Sylvan Way, Parsippany, NJ 07054-3802 (201) 267-9700

HTI

Hand Tools Institute 25 North Broadway, Tarrytown, NY 10591 (914) 332-0040

ICEA

Insulated Cable Engineers Association P.O. Box 440, South Yarmouth, MA 02664 (508) 394-4424

IEC

International Electrotechnical Commission Geneva, Switzerland. Communications: c/o ANSI 11 W. 42nd St., New York, NY 10036 (212) 642-4900

IEEE

Institute of Electrical and Electronics Engineers 345 E. 47th St., New York, NY 10017 (212) 705-7900

IESNA

Illuminating Engineering Society of North America 120 Wall St., New York, NY 10005-4001 (212) 248-5000

IPC

Institute for Interconnecting and Packaging Electronic Circuits 2215 Sanders Rd., Northbrook, IL 60062-6135 (708) 509-9700

ISA

Instrument Society of America P.O. Box 12277 Research Triangle Park, NC 27709 (919) 549-8411

ISDI

Insulated Steel Door Institute 30200 Detroit Rd., Cleveland, OH 44145-1967 (216) 899-0010

ISO

International Organization for Standardization Geneva, Switzerland. Communications: c/o ANSI, 11 W. 42nd St., New York, NY 10036 (212) 642-4900

NAAMM

National Association of Architectural Metal Manufacturers 11 S. La Salle St., Chicago, IL 60603 (312) 201-0101

NAPM

National Association of Photographic Manufacturers 550 Mamaroneck Ave., Harrison, NY 10528 (914) 698-7603

NEMA

National Electrical Manufacturers Association 1300 N. 17th St., Rosslyn, VA 22209 (703) 841-3200

NFoPA

National Forest Products Association 1111 19th St., N.W., Washington, D.C. 20036 (202) 463-2700

NFiPA

National Fire Protection Association 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101 (617) 770-3000

NFlPA

National Fluid Power Association 3333 N. Mayfair Rd., Milwaukee, WI 53222-3219 (414) 778-3344

NISO

National Information Standards Organization 4733 Bethesda Ave., Bethesda, MD 20814 (301) 654-2512

NSF

National Sanitation Foundation, International 4201 Wilson Blvd., Arlington, VA 22230 (703) 306-1070

NSPI

National Spa and Pool Institute 2111 Eisenhower Ave., Alexandria, VA 22314 (703) 838-0083

OPEI

Outdoor Power Equipment Institute, Inc. 341 S. Patrick St., Alexandria, VA 22314 (703) 549-7600

RESNA

Rehabilitation Engineering and Assistive Technology Society of North America 1700 N. Moore St., Arlington, VA 22209-1903 (703) 524-6686

RIA

Robotic Industries Association 900 Victors Way, Ann Arbor, MI 48106 (313) 994-6088

RMA

Rubber Manufacturers Association 1400 K St., N.W., Washington, D.C. 20005 (202) 682-4800

SAAMI

Sporting Arms and Ammunition Manufacturers Institute Flintlock Ridge Office Center, 11 Mile Hill Rd., Newtown, CT 06470 (203) 426-4358

SAE

Society of Automotive Engineers 400 Commonwealth Dr., Warrendale, PA 15096 (412) 776-4841

SIA

Scaffold Industries Association 14039 Sherman Way, Van Nuys, CA 91405-2599 (818) 782-2012

SMA

Screen Manufacturers Association 2545 S. Ocean Blvd., Palm Beach, FL 33480-5453 (407) 533-0991

SMPTE

Society of Motion Picture and Television Engineers 595 W. Hartsdale Ave., White Plains, NY 10607 (914) 761-1100

SPI

The Society of the Plastics Industry, Inc. 1275 K St., N.W., Washington, D.C. 20005 (202) 371-5200

TIA

Telecommunications Industries Association 2001 Pennsylvania Ave., N.W., Washington, D.C. 20006-4912 (202) 457-4912

ANSI circulates copies of the proposed standard to all interested parties seeking comments. A time frame is setup for receipt of comments, after which a Board of Standards Review considers the comments and makes what it considers necessary changes. After more reviews, the standard is finally issued and published by ANSI, listed in their catalog, and made available to anyone who wishes to purchase a copy. A similar process is used by the International Standards Organization (ISO), which began to prepare an extensive set of worldwide standards in 1996. Standards published by ISO members are also listed in ANSI catalogs. Standards Information Services. Copies of standards and information about documents published by the more than 350 code- and standard-generating organizations in the United States and several other countries can be obtained from resellers such as Global Engineering Documents, Englewood, CO. They provide information on CD-ROM, magnetic tape, microfilm, or microfiche formats. Similar services exist in many countries throughout the world.

Human Factors and Safety in Design Human factors in design describe the interactions between a device and anyone who uses or maintains it. Examples

of human factors in design include designing the handle of a portable electric drill to fit comfortably into either hand of the user, arranging gages and controls on an automobile dashboard to be easily seen or reached, and designing an ejector to remove the beaters of an electric mixer. Human factors also include operational methods and procedures, testing and evaluating these methods and procedures, job design, development of job aids and training materials, and selection and training of people who will be users. One branch of industrial engineering that deals specifically with human factors is referred to as "ergonomics"; contact with persons involved in such research would be useful to designers. References 44, 45, and 46 include examples of useful references describing human factors in design. Safety in Design. The designer/manufacturer of any product (e.g., consumer product, industrial machinery, tool,

system, etc.) has a major obligation to make the product safe (i.e., reduce the risks associated with the product to an acceptable level). In this context, "safe" means a product with an irreducible minimum of danger (as defined in the legal sense), that is, safe not only with regard to intended use (or uses) but also all unintended, but foreseeable, uses. For example, consider the common flat-tang screw driver. Its intended use is well known. Can anyone say that they have never used such a screwdriver for any other purpose? It must be designed and manufactured to be safe in all these uses. There are three aspects, or stages, in designing for safety:

1. Make the product safe (i.e., design all hazards out of the product). 2. If it is impossible to eliminate all hazards in design, provide guards that eliminate the danger. 3. If it is impossible to provide proper and complete guarding, provide appropriate directions and warnings.

Although the principles or specific guidelines for carrying out these stages in designing for safety are beyond the scope of this article, there is an abundance of literature on safe practices in design (see, for example, Ref 47, 48, 49, 50).

Documents pertaining to safety and control or elimination of workplace hazards can also be obtained from ANSI and the National Safety Council. Aesthetics Aesthetics is an important aspect of the design of almost any product, but it is an aspect that should not be allowed to compromise functional requirements. Some consumer products are sold almost exclusively by aesthetic appeal; design of such products is usually assigned to artists. However, aesthetic appeal is important even for industrial products. A smooth or shiny finish, an artistically pleasing shape, or an appearance of ruggedness and durability may have little or no influence on the ability of the product to perform its function but may, nevertheless, have a considerable effect on the attitude of a potential buyer or on worker acceptance when the item is put into service. Cost Assuming that a product meets the basic functional requirements established for it, the most important single factor in its design and manufacture is cost. The cost of any product must be competitive with the cost of comparable products already on the market. Whether there is a directly comparable product or not, the cost must be low enough to convince a prospective purchaser that the benefits to be derived from the product exceed its cost. Cost-benefit studies almost always precede the purchase of major pieces of manufacturing equipment. Cost generally enters the design process as one of several criteria against which the merit of a design is judged. Whenever a choice exists between different materials, designs, or manufacturing processes, the least costly alternative will be chosen, provided that the basic functional requirements for the product can still be met. In some instances, the possibility of significant cost reduction will justify re-evaluation of basic functional requirements and performance specifications; it may be possible to modify the design goals slightly and thereby significantly reduce costs. However, it is important to remember that any modification of functional requirements and performance specifications can adversely affect utility and marketability.

References cited in this section

44. C.O. Smith, Human Factors in Design, Materials Selection and Design, Vol 20, ASM Handbook, ASM International, 1997, p 126-130 45. M.S. Sanders and E.J. McCormick, Human Factors in Engineering and Design, 7th ed., McGraw-Hill, 1993 46. Ergonomics: International Journal of Research and Practice in Human Factors and Ergonomics, Taylor and Francis 47. C.O. Smith, Safety in Design, Materials Selection and Design, Vol 20, ASM Handbook, ASM International, 1997, p 139-145 48. T.A. Hunter, Engineering Design for Safety, McGraw-Hill, 1992 49. W. Hammer, Product Safety Management and Engineering, Prentice-Hall, 1980 50. W. Hammer, Product Safety Management and Engineering, 2nd ed., American Society of Safety Engineers, 1993

Factors in Materials Selection Introduction THE SELECTION OF ENGINEERED MATERIALS is an integral process that requires an understanding of the interaction between such factors as materials properties, manufacturing and fabrication characteristics, and the design considerations described in the previous article. Two often cited reasons for selecting a certain material for a particular application are (a) the material has always been used in that application and (b) the material has the right properties. Neither reason is evidence of original thinking or even careful analysis of the application. The collective experience gained from common usage of a material in a particular application is useful information, but not justification in itself for selecting a material. The time has passed when each application has its preferred material and a particular material its secure market. In the context in which it is frequently mentioned, the term "property" connotes something that a material inherently possesses. On the contrary, a property should be regarded as the response of the material to a given set of imposed conditions. It must also be recognized that this property should be that of the material in its final available and processed form. Tabulated properties data, such as those available from handbooks, standards organizations, computerized databases, and other sources of materials information summarized in Ref 1 are helpful, but such information must be used judiciously and must be relevant to a particular application. Regardless of specific expertise, every engineer concerned with hardware of any description (and this includes essentially all engineers) must deal constantly with selecting an appropriate material (or combination of materials) for the design. Except in trivial applications, it certainly is not sufficient to indicate that the components should be "steel" or "aluminum" or "plastic". Rather, the engineer must focus attention, knowledge, and skill on the general factors in materials selection listed in Table 1. It is obvious that these are inseparable and interwoven with the factors described in Tables 1 to 3 in the article "Design Factors" in this Section. Table 1 General factors in materials selection Functional requirements and constraints Material properties (see Table 2) Manufacturing process considerations Fabricability (see Table 2) Design configuration Available and alternative materials Corrosion and degradation in service Thermal stability Properties of unique interest

High density High stiffness-to-weight ratio Low melting point Special thermal expansion properties Electrical conductivity/superconductivity Wear resistance Biocompatibility

Cost

In principle, a mathematical expression describing the merit of an engineering design as a function of all these variables, differentiating it with respect to each of the criteria for evaluation, and solving the resulting differential equations to obtain the ideal solution could be written. This is not a reality, however, the principle is valid and should provide a basis for action by the designer. In some instances, a standard, readily available component can be much less costly than, and yet nearly as effective as, a component of optimized, nonstandard design.

Reference

1. J.H. Westbrook, Sources of Materials Property Data and Information, Materials Selection and Design, Vol 20, ASM Handbook, ASM International, 1997, p 491-506

Materials Properties The performance or functional characteristics of a material are expressed chiefly by physical, mechanical, thermal, electrical, magnetic, and optical properties. Material properties are the link between the basic structure and composition of the material and the service performance of the part (Fig. 1).

Fig. 1 The role played by material properties in the selection of materials

An important role of the materials engineer is to assist the designer in making meaningful connections between materials properties and the performance of the part or system being designed. For most mechanical systems, performance is limited, not by a single property, but by a combination of them. Mechanical Properties One question usually asked in selecting materials is whether strength is adequate to withstand the stresses imposed by service loading. Although the primary selection criterion is often strength, it also may be toughness, corrosion resistance, electrical conductivity, magnetic characteristics, thermal conductivity, specific gravity, strength-to-weight ratio, or some other property listed in Table 2. For example, in residential water service, where the water pressure is relatively low, weaker and more expensive copper tubing might be a better choice than stronger steel pipe. Steel pipe comes in sections and is joined by threaded connections with elbows at corners, whereas soft copper can be obtained in coils and can be easily bent around corners. Thus, the lower installation cost of copper can overcome the higher material cost. Also, because of the relatively low water pressure, the strength of copper would be adequate, and the greater strength of steel unnecessary. Furthermore, in the event of freezing, copper usually yields instead of bursting; in many regions of the country, it is more resistant to corrosion by the local water than steel. In general, the usual criterion for selection is not just one property, such as strength, but some combination of properties, manufacturing characteristics, and cost. Table 2 Materials properties that must be considered during the materials selection process Physical properties Crystal structure Atomic weight Density Melting point Boiling point Vapor pressure Viscosity Porosity Permeability Reflectivity Transparency Optical properties Dimensional stability

Electrical properties

Conductivity Resistivity Dielectric constant Hall coefficient (effect) Superconducting temperature

Magnetic properties Magnetic susceptibility Magnetic permeability Coercive force Saturation magnetization Transformation (Curie) temperature Magnetostriction

Nuclear properties Half-life Cross section Stability

Mechanical properties Hardness Modulus of elasticity

Tension Compression

Poisson's ratio Stress-strain curve Yield strength

Tension Compression Shear

Ultimate strength

Tension Shear Bearing

Fatigue properties

Smooth Notched Corrosion fatigue Rolling contact Fretting

Charpy transition temperature Fracture toughness (KIc) High-temperature behavior

Creep Stress rupture

Damping properties Wear properties

Galling Abrasion Erosion

Cavitation Spalling Ballistic impact

Thermal properties Conductivity Specific heat Coefficient of thermal expansion Latent heat of fusion Emissivity Absorptivity Ablation rate Fire resistance

Chemical properties Position in electromotive series

Galvanic corrosion

Corrosion and degradation

Atmospheric Fresh water Salt water Acids Hot gases Ultraviolet

Oxidation Thermal stability Biological stability Stress corrosion Hydrogen embrittlement Hydraulic permeability

Fabrication properties Castability Heat treatability Hardenability Formability Machinability Weldability

Ultimate tensile strength is a commonly measured and widely reported indication of the ability of a material to

withstand loads. However, the direct application of tensile-strength data to design problems is extremely difficult. First of all, the definition of "ultimate tensile strength" is the maximum stress (based on initial cross-sectional area) that a specimen can withstand before failure; it occurs at the onset of plastic instability. Thus, any component loaded to its ultimate tensile strength is likely to fracture immediately. Secondly, if the design is based on a fraction of the ultimate strength, there is the question of what fraction provides adequate strength and safety, together with efficient use of the material. Finally, there seems to be only a rough correlation between tensile strength and material properties such as hardness and fatigue strength at a specified number of cycles, and no correlation whatsoever between tensile strength and properties such as resistance to crack propagation, impact resistance. or proportional limit. Yield strength indicates the lowest measurable stress at which permanent deformation occurs. This information is

necessary to estimate the forces required for forming operations. Yield strength is also useful in considering the effects of a single-application overload; most structures must be designed so that a foreseeable overload will not exceed the yield strength. Hardness is another widely measured material property and is useful for estimating the wear resistance of materials and

estimating approximate strength of steels. Its most widespread application is for quality assurance in heat treating. However, only rough correlation can be made between hardness and other mechanical properties or between hardness and behavior of materials in service. Ductility of a metal, usually measured as the percent reduction in area or elongation that occurs during a tensile test, is

often considered an important factor in material selection. It is assumed that, if a metal has a certain minimum elongation in tensile testing, it will not fail in service through brittle fracture. It is also assumed that if a little ductility is good, a lot is better. Neither of these assumptions is accurate. Metals normally considered very ductile can fail in a seemingly brittle manner, such as under fatigue or stress-corrosion conditions, or when the service temperature is below the ductile-tobrittle transition temperature. How much ductility is actually usable under service conditions and how best to measure it are very controversial. Several estimates of usable ductility (such as the ability of materials to absorb the movement within a large structure that is necessary to equalize the load among all of the members of the structure) fall in the range of 1 to 2% elongation in tensile testing. Larger amounts of ductility only indicate the possibility of more extensive permanent deformation of the structure. In many structures, any permanent deformation destroys the usefulness of the. structure; for example, the aerodynamic efficiency of an aircraft wing can be substantially reduced by only 1 to 1 % deformation. The amount of ductility required for processing may far exceed that actually usable in service. Steel sheet, for example, often must have considerable ductility, far more than a part might need in service, but nevertheless enough to allow the part to be formed to its required shape.

Manufacturing Process Considerations The properties considered in the preceding section relate to the ability of a material to perform adequately in service without failing. But, first the part must be capable of being made, that is it must be producible. There are additional properties and producibility considerations that should be part of the material selection process. For a design to be producible the configuration should not introduce unnecessarily difficult manufacturing challenges. This section will briefly describe the key factors that influence the relationship between materials selection and processing. Reference 2 provides more detailed information on the characteristics of various manufacturing processes. Material Factors In a very general sense the selection of a material determines a range of processes that can be used to produce parts from the material. In the article "Introduction and Overview" in this Section, Fig. 4 shows the common classes of manufacturing processes and Table 4 indicates the manufacturing processes used most frequently with different metals and plastics. The melting point of a material and level of deformation resistance and ductility determine these relationships. Some materials are too brittle to be plastically deformed; other materials are too reactive to be cast or have poor weldability. The melting point of a material determines the casting processes that can be employed. Low-melting-point metals can be used with any of a large number of casting processes, but as the melting point of the material rises, the number of available processes becomes limited. Ashby (Ref 3), has shown a correlation between the size (weight) of a cast part and the melting point of the material (Fig. 2). This plot shows the regions of size that can be handled by different casting and

molding processes and shows how the available number of processes decreases dramatically for materials with highmelting point. This is one of a number of process selection charts, dealing with casting, metalworking, polymer processing, powder fabrication and machining, introduced by Ashby in Ref 3 to aid in the selection of manufacturing process in the conceptual stage of design.

Fig. 2 Ashby process chart for casting. The size in this chart is measured by weight, W. It can be converted to volume via the density, ρ, or to the approximate linear dimension, L, shown on the right-hand axis via L = (W/ρ)1/3. Source: Ref 3

Similarly, yield strength, or hardness, determines the limits in deformation and machining processes. Forging and rolling loads are related to yield strength and tool life (tool load and temperature generation) in machining scales with the hardness of the material being machined. Ultimately the limit of these processes is determined by the workability of the material. See the section "Fabricability" in this article. Shape Factors Each process has associated with it a range of shapes that can be produced. Thus, the first decision in selecting a process is whether it is capable of producing the required shape. A simple classification of shape is as follows:

Two-dimensional (2D)

Profile of product does not change along its length. Examples: wire, pipe, aluminum foil. Many 2D products are used as raw material for processes that make them into 3D shapes.

Three-dimensional (3D)

Profile of the product varies along all three axes. Most products are 3D.

Sheet

Has almost constant section thickness that is small compared with the other dimensions

Bulk

Has a complex shape, often with little symmetry. Solid: has no significant cavities. Hollow: has significant cavities

Whether the process can accommodate shapes with undercuts, or reentrant angles, or parts with an element positioned perpendicular to the main die motion also needs to be determined. For more in-depth considerations of shape and its relationship to process selection, see Ref 2. Process Factors Key manufacturing process factors include cycle time, quality, flexibility, materials utilization, and operating cost. A rating system for evaluating these five process characteristics is given in Table 3. This is applied to rating the most common manufacturing processes in Table 4. Table 3 Scale for rating manufacturing processes Rating

Cycle time

Quality

Flexibility

Materials utilization

Operating costs

1

>15 min

Poor quality, average reliability

Changeover extremely difficult

Waste > 100% of finished component

Substantial machine and tooling costs

2

5 to 15 min

Average quality

Slow changeover

Waste 50 to 100%

Tooling and machines costly

3

1 to 5 min

Average to good quality

Average changeover and setup time

Waste 10 to 50%

Tooling and machines relatively inexpensive

4

20 s to 1 min

Good to excellent quality

Fast changeover

Waste < 10% finished part

Tooling costs low/little equipment

5

1000 °C (1830 °F), the concentration of CO2 is negligible and the total pressure of carbonaceous gases is equal to the partial pressure of carbon monoxide. Between the temperatures of 400 and 1000 °C (750 and 1830 °F), the partial pressures of both the gases are significant. The total gas pressure is usually close to atmospheric at the top of the stack and between 1.3 to 1.5 atm at the tuyere level consisting of ~60 vol% of N2. The temperature conditions and the CO-CO2 balance determines the oxygen potential at any location within the blast furnace. The ability and rate of the furnace to reduce the iron ore depends on the temperature, diffusion of oxygen, amount of volume change upon reduction, availability of hydrogen, onset of slag formation, reduction with solid carbon, presence of gangue, and the use of prereduced sinter material. The top gas analysis in terms of CO/CO2 ratio is a good indicator of blast furnace performance in addition to the temperature and compositions of the hot metal and slag produced.

Composition of Pig Iron Charge Balance. The primary impurities in molten pig iron or hot metal are carbon, sulfur, manganese, silicon, and

phosphorus. While manganese, silicon, and phosphorus are present in the ore as oxides, carbon and sulfur are in the coke of the burden. Silica is also present in the ash of the coke. A typical hot metal has 1.0 to 2.0% Si (determined by the blast furnace operating conditions, slag chemistry, and the steelmaking heat requirements), 0.1 to 0.5% P, 0.04 to 0.07% S, 0.75 to 1.25% Mn, and up to 4.5% C. Carbon is usually dissolved in molten iron close to the solubility limit at the temperature. Carbon is insoluble in slag. Phosphorus oxide is reduced, and phosphorus is dissolved in molten iron. Blast furnace slags are not suitable for removing phosphorus. Sulfur is mostly transferred to the slag as calcium sulfide. A reducing furnace condition, high temperature, and high slag basicity (CaO/SiO2) are conditions that favor sulfur transfer to the slag (Ref 9). Therefore, good desulfurization cannot be achieved during steelmaking as the conditions are highly oxidizing (see the section on steelmaking). Oxygen potential in the system affects the distribution of all the elements that partition themselves between the metal and the slag. Oxygen potentials favorable for sulfur control in hot metal are unsuitable for silicon and manganese removal. For a given carbon activity and carbon monoxide partial pressure in the hearth zone, an increase in temperature helps increase the partitioning of manganese, silicon, and sulfur. The activity of various oxides in the slag and the activity coefficient of different solutes in molten iron are important factors in determining the distribution of impurities in pig iron. Empirical relationships have been established between the slag composition and the activity of oxide components (Ref 10, 11, 12, 13) as well as the sulfide capacity of the slag (Ref 14). An increase in lime and magnesia content of slag increases the sulfide capacity. Higher partitioning of sulfur in the blast furnace is also encouraged by a higher carbon activity in the hot metal. If a low-silicon, low-sulfur hot metal is desired, a pretreatment of hot metal becomes necessary prior to steelmaking (see the section "Hot Metal Pretreatment" ). Use of a low-ash, low-sulfur coke is also desired for making low-sulfur pig iron. Other important solutes that partition between the slag and metal are chromium and titanium. These metals are present as oxides in some ore bodies used for ironmaking. Normally 50 to 60% of the chromium is reduced into the hot metal. Titanium oxide is reduced to titanium carbide and carbonitrides. Sometimes titania-bearing ore is charged in the furnace to protect the hearth from eroding by making the slag and metal viscous. Advances in Blast Furnace Technology Significant improvements have been made over the last forty years in blast furnace productivity in terms of hot metal produced per unit volume of the furnace and the amount of fuel used. These improvements are the result of several advancements. Use of high-strength, super-fluxed sinters permitting the use of higher flame temperatures, coal washing, and blending to lower ash and sulfur; stamp (compression) charging for carbonization and uniform sizing of coke for higher coke strength and furnace permeability; and charging sequence optimization for proper distribution of burden using movable throat armors are some of the developments in charged material management.

High hot-blast temperatures of 1250 °C (2280 °F) are now commonly used in several blast furnaces around the world, which has a direct bearing on the coke rate of the furnace. The ability to use high blast temperatures and the need to control the flame temperature has allowed the use of hydrocarbon fuel injection. This development enhances the reducing power of the bosh gas and in turn lowers the coke rate. Natural gas, coke-oven gas, oil, tar and pulverized coal, or oil-coal slurry have all been effectively used as a fuel supplement to the blast furnace. The discovery of methods to control the flame temperature also allows the enrichment of blast air with oxygen. A 1% increase of oxygen typically improves the furnace productivity by 2 to 4% depending on the burden reducibility. High top-pressure capability has allowed the use of higher wind rates to the furnace without causing burden lifting. There is a corresponding increase in the production rate when the gas inside the furnace is compressed. Approximately 205 MPa (30 psi) top pressures have been successfully used. The development has also necessitated improvements in the off-gas handling system. Hot Metal Pretreatment The blast furnace does not always produce a molten metal with desired compositional levels of sulfur, silicon, and phosphorus due to the fact that process conditions required for desirable partitioning of these elements between the slag and the metal are often conflicting. Higher levels of these solutes may be present in the hot metal due to higher gangue in the ore and/or high sulfur in the coke. Therefore, a pretreatment of the hot metal is carried out before the hot metal can be used for steelmaking. Pretreatment may be carried out at the blast furnace runner, hot-metal ladle, or the mixer because temperature of the metal is different at these three stages. The blast furnace runner also allows a large reaction area between the reagents and the hot metal. The silicon, sulfur, and phosphorus can be lowered by a basic refractory lining of the mixer and by forming a lime-rich oxide slag. An active mixer practice could thus be used by feeding a combined source of iron oxide and lime to the melt in the mixer, such as a fluxed sinter, a mixture of lime and mill scale, or lime and iron-ore fines. Ladle desulfurization has become an important process step due to the demand for ultralow sulfur steels. Soda ash, calcium oxide, calcium carbide, or a mixture of these, is injected with air through a lance immersed in hot-metal ladles. Calcium serves as the desulfurizing agent producing calcium sulfide. Sulfur levels of 0.015 and 0.008% have been reported using lime or calcium carbide as the reagents, respectively (Ref 15). Use of lime-soda ash mixtures is the most economic method where the kinetics of desulfurization can be enhanced mechanically. Alternative Sources of Iron Direct-Reduced Iron. The need to employ low-grade ores and types of fuel unsuitable for blast furnaces has been

driving the search for alternative sources of iron. Processes that produce iron by reduction of iron ore below the melting point of the iron produced are generally classified as direct-reduction processes and the products are known as directreduced iron (DRI) or sponge iron. The processes that produce molten iron, similar to blast furnace hot metal, are classified as smelting-reduction processes. These processes usually split the solid-state reduction steps and the liquid melting and slagging steps into two separate reactors eliminating the need for high-strength prepared burden. Directreduced iron contributes 5 to 6% of the world's total ironmaking capacity with 34 million metric tonnes of DRI produced annually in 1996. Direct-reduced iron is mostly used as a substitute for scrap in steelmaking. Availability of low-cost scrap and the high cost of electricity are deterrents for the use of DRI in industrialized nations, whereas countries endowed with inexpensive natural gas, non-coking coals, hydroelectric power, and access to suitable ore reserves prefer this alternative route to making iron. Chemical reactions for making DRI are similar to those in the blast furnaces. When reduction is carried out below 1000 °C (1830 °F) and H2 gases are primary reductants (generated externally) and the product is porous. Metallic iron also absorbs some carbon to produce 1 to 2.5% iron carbide as cementite when gaseous reduction is carried out. When pure carbon monoxide is used to reduce dense Fe2O3, the reduction stops at 40% at 700 °C (1290 °F) and at 85% at 800 °C (1470 °F), but is completed at higher temperatures (Ref 16). Above 1000 °C (1830 °F), carbon reacts with moisture and CO2 gas producing carbon monoxide and H2, thus renewing the reduction potential of the gas. Processes that produce DRI directly from solid coal without prior gasification of its fixed carbon use temperatures in excess of 1000 °C (1830 °F). In the case of iron oxide reduction with coal, the reactions between carbon and iron oxide particles begin only at the points of contact, but are disrupted once metallic iron is formed in the intermediate phase. Thereafter, the reduction can proceed only as a result of the diffusion of carbon atoms through the metallic iron layer to the residual oxide. Thus, in directreduction processes based on either solid or liquid reductants, it is essential to convert the reductant to a reducing gas.

A temperature of 1200 °C (2190 °F) is considered the upper limit for the direct-reduction processes, above which the metallic iron formed absorbs carbon resulting in fusing and melting of the solid. The direct-smelting processes thus operate with product temperatures >1300 °C (2370 °F), because carbon is absorbed rapidly and a liquid hot metal forms. Table 1 lists the gas-based and coal-based direct-reduction processes as well as the electricity and fuel-based, smeltingreduction processes. A complete description of all these recent developments can be found in Ref 17. Table 1 Classification of available direct-reduction and smelting-reduction processes Direct-reduction processes--reducing gas generated externally from reduction furnace Shaft-furnace processes, moving-bed

Wiberg-Soderfors Midrex HYL III Armco NSC Purofer

Shaft-furnace processes, static-bed

HYL I and II

Fluidized-bed processes

FIOR HIB

Direct-smelting processes Electric-furnace smelting processes

Pig iron electric furnace DLM

Oxyfuel smelting systems

INRED KR Kawasaki CGS

Direct-reduction processes--reducing gas generated from hydrocarbons in reduction furnace Kiln processes

Krup-Renn Krupp-CODIR SL/RN ACCAR DRC

LS-RIOR

Rotary-hearth processes

INMETCO Salem

Retort processes

Hogänäs Kinglor-Metor

Shaft-furnace process, moving-bed

Midrex Electrothermal

Plasma processes Nontransferred arc

Plasmasmelt Plasmared

Transferred arc

ELRED EPP SSP The Toronto system Falling film plasma reactor

Source: Ref 17

The effectiveness of a direct-reduction process is measured through several indices. Percent total iron and percent metallic iron (including cementite) lead to the commercially used index of degree of metallization, which is the percent ratio of total weight of metallic iron to the total weight of iron in the product. The degree of metallization normally ranges between 90 and 95% depending on the reducibility of the original iron oxide and the process chosen. Percent reduction is a measure of the amount of oxygen removed during reduction. The amount of gangue in DRI, the level of sulfur (particularly for coal-based DRI), and the amount of fines affect the productivity of the steelmaking reactor where DRI is used. Both moving- and static-bed shaft furnaces, as well as fluidized-bed processes, are used for making DRI using externally generated reducing gases. Usually a kiln-type furnace, a rotary hearth, or a retort furnace is used when coal is directly used as the fuel in DRI manufacturing. In all coal-based direct-reduction processes, sized ore and a coarse fraction of noncoking coal are fed into the rotary kiln from the inlet end in the required proportions. The growth of gas-based, directreduction processes is more favorable than the coal-based methods due to easier process control, higher availability of

reactor, better energy efficiency, lower sulfur, and higher carbon in the product. In addition, the productivity of a rotary kiln is between 0.3 to 0.5 metric tons/m3 per day compared with over 2 metric tons/m3 per day for a natural gas-based process. Smelting-reduction processes that produce molten iron use low-shaft electric furnaces. A burden of agglomerated

or lump ore, coal, or coke and limestone are directly charged into the furnace. The submerged-arc concept is used with Soderberg self-baking carbon electrodes. As an alternative to the electric-arc furnace, oxyfuel smelting systems are also used for smelting reduction. Flash smelting of the concentrate by coal and oxygen is accomplished in the first stage where close to 90% of the process energy is supplied. In the first stage, the ore is prereduced to FeO. In the second stage, the prereduced and heated material is further reduced mainly by direct reduction with carbon and then smelted. The COREX (or KR) process for smelting reduction conducts the blast furnace functions of preheating and gaseous reduction and smelting in two separate reactors (Fig. 3). Essentially, the process comprises a two-stage operation in which DRI from a shaft furnace is charged without cooling into a connected melter gasifier operating at 3 to 5 atm of pressure.

Fig. 3 Schematic diagram of the COREX smelting-reduction process

Several plasma-arc reduction processes have also been developed to produce molten iron directly from unprepared burden. There are many processes for smelting reduction presently being developed through different stages of commercialization. Several of these rely on the recovery of calorific value of the exhaust process gas to make the technology viable. Although coking is not necessary, some processes are restricted by the ash and volatile contents of coal that can be used. Smelting-reduction processes have significant potential for the production of ferroalloys. Iron Carbide. A promising alternative source of iron has been found in iron carbide, which is produced by the reduction

of iron ore fines by hydrogen gas and subsequent carburization by carbon monoxide gas in a fluidized-bed reactor. The process produces iron carbide powder, which is hard, nonfriable, resistant to oxidation, and has the potential to replace DRI, scrap, or molten iron to produce steel at a lower cost. The process typically operates at a temperature of 600 °C (1110 °F) and pressure of 1.8 atm, producing a 7% C 93% Fe material. The reactions for the production of iron carbide from hematite or magnetite fine ore are:

3Fe2O3 + 11H2 + 2CO Fe3O4 + 5H2 + CO

2Fe3C + 11H2O Fe3C + 5H2O

(Eq 9) (Eq 10)

The combined carbon in iron carbide forms a latent source of energy to the extent that a 1200 °C (2190 °F) preheated iron carbide can constitute 100% of the charge in oxygen steelmaking (Ref 18). Capital cost per annual ton of iron is about one-third that of blast-furnace, coke oven combinations and about one-half that of current DRI plants. Quality steel can be produced because iron carbide does not contain tramp elements and has no sulfur. Equations 9 and 10 indicate that water is the only by-product in iron carbide production.

References cited in this section

1. H.M. Boylston, An Introduction to the Metallurgy of Iron & Steel, John Wiley & Sons, 1936, p 3-31 2. H.H. Campbell, The Manufacture and Properties of Iron & Steel, Hill Publishing Company, 1907, p 2-24 3. W.T. Lankford, Jr., et al., Ed., The Making, Shaping and Treating of Steel, US Steel Publication, 1984, p 124 4. A. Chatterjee and P.V.T. Rao, Ed., Monograph on Coal & Coke at Tata Steel, Tata Steel Publication, 1992, p 69-97 5. P. Reichardt, Arch. F.D. Eisenhuttenw, Vol 1, 1927/1928, p 77-101 6. L. von Bogdandy and H.J. Engell, The Reaction of Iron Oxides, Springer-Verlag, 1971 7. E.T. Turkdogan, Ironmaking Proceedings, AIME, Vol 31, 1972, p 438-458 8. G.D. Elliot and J.A. Bond, Practical Ironmaking, The United Steel Companies, Ltd., Sheffield, UK, 1959, p 97-106 9. C. Bodsworth and H.B. Bell, Physical Chemistry of Iron and Steel Manufacture, Longman Group, Ltd., 1972, p 161-188 10. A.R. Kay and J. Taylor, JISI, 1963, Vol 201, p 68 11. G. Smith and J. Taylor, JISI, Vol 202, 1964, p 577 12. J.C. D'Entremont and J. Chipman, J. Phys. Chem., 1963, Vol 67, p 499 13. J. Taylor, JISI, Vol 202, 1964, p 420 14. K.P. Abraham, M.W. Davies, and F.D. Richardson, JISI, Vol 196, 1960, p 309 15. H.P. Shulz, Stahl Eisen, Vol 89, 1969, p 249 16. A.A. El-Geassy, K.A. Shehata, and S.Y. Ezz, Trans. ISIJ, Vol 17 (No. 11), 1977 17. A. Chatterjee, Beyond the Blast Furnace, CRC Press, 1994, p 19-179 18. F.M. Stefens, Jr., and W.E.J. Williams, Steel Tech. Intl., 1992 Steelmaking In the previous section it was shown that the end product of ironmaking is molten iron produced through large capacity blast furnaces or sponge iron produced through smaller capacity direct- or indirect-reduction processes. Liquid steel is produced as the end product of steelmaking, which is subsequently cast as an ingot or continuously cast. The smeltingreduction or direct steelmaking processes under development will eliminate this sharp distinction, if successfully developed. Steelmaking can be broadly classified into two steps: primary steelmaking in a converter or furnace and secondary steelmaking in a ladle. Ordinary grades of steel may bypass the secondary steelmaking processes. The two most important steelmaking processes are the electric-arc furnace (EAF) process and the basic oxygen furnace (BOF) process or LD (Linz-Donawitz) process. The EAF process accounts for 35 to 40% of the world steel production and BOF produces 55 to 60% of steel. Some other processes, such as the open-hearth furnace, are still practiced in a few countries to produce special steels. Basic Oxygen Steelmaking (Ref 19) Charge Constituents. Oxygen steelmaking uses gaseous oxygen as the primary agent for autothermic generation of heat as a result of the oxidation of dissolved impurities present in hot metal and scrap, such as carbon, silicon, manganese, sulfur and phosphorus, and to some extent, by oxidation of iron. Top blowing is the most common form of oxygen steelmaking, but bottom as well as combined blowing are process variations that are also practiced. In the top-blowing process, oxygen is blown at supersonic velocity with the help of a water-cooled lance inserted through the mouth of the vessel. The vessel is lined with basic refractories like tar-bonded dolomite or carbon magnesite. The charge consists of

steel scrap, hot metal, and flux--all charged through the mouth of the converter. While scrap is added as the source of iron units as well as a coolant, iron ore also provides a source of oxygen and is sometimes charged in the vessel. Lime is the primary flux for making slag but fluorspar and silica can also be added depending on the slag requirements. Typically 10 to 30% of the metallic charge is scrap, which helps control the heat generated by the exothermic oxidation reactions. The flux requirement and the slag volume produced strongly depends on the hot metal composition. Process Description. Figure 4 shows a schematic diagram of a BOF. The converter is tilted approximately 30 to 40°, and the scrap is charged into the vessel using charging buckets. Scrap is usually screened and presorted for compositional consistency. Hot metal is then poured on the scrap. The vessel is then tilted back to an upright position for blowing oxygen. An oxygen lance is gradually lowered to a specified distance from the bath surface, and oxygen is started simultaneously. Within the first five minutes, all the lime is added through mechanized hoppers to flux the oxides of silicon, manganese, and iron. The limesilicate slag formed essentially contains CaO, SiO2, FeO, MnO, and P2O5. After specified periods the lance is gradually lowered to the lowest position where carbon is oxidized to carbon monoxide and carbon dioxide. Only ~10% CO2 is present in the top waste gas, which is collected through hoods placed on top of the vessel mouth during blowing. Total blowing time varies between 17 and 22 min, depending on the impurity content and the lance design. The lance is raised at the end of the blow. Steel is tapped into a ladle between 1650 and 1700 °C (3000 and 3090 °F) and the slag is removed by tilting the converter. Refractories require a preheat only when cold started for the first heat. Subsequent heats are produced on a continuous basis until the vessel is ready for a change of the refractory lining.

Fig. 4 Schematic diagram of the basic oxygen furnace

The typical end-point composition of steel is 0.04-0.06 wt% C, termed "turn-down" carbon; 0.2 wt% Mn, and 0.02 wt% P and S, depending on the composition of the charge materials used. The generation of metal droplets due to the impact of the jet on the metal surface and the evolution of metal and slag composition during the progress of a blow, as well as the kinetics of gas-metal-slag interactions, are important process characteristics which determine the efficiency of the converter. The important gas-metal and gas-slag reactions during steelmaking are: • • •

Oxidation of dissolved impurities in iron such as carbon, silicon, manganese, and phosphorus by gaseous oxygen Reduction of FeO and MnO in the slag by rising CO/CO2 gas bubbles Dissolution of gases such as hydrogen and nitrogen in liquid steel

Figure 5 shows the evolution of bath composition and slag composition in a BOF converter. This figure shows that silicon is oxidized first within the first 3 to 4 min of the blow. However, transfer of sulfur, phosphorus, manganese, and carbon occurs over the entire blow period. As the blow progresses, lime (CaO) gradually dissolves in the slag, and the mass of slag increases over blowing time due to lime and iron oxide dissolution. The temperature of the liquid metal gradually increases from an initial 1250 to 1400 °C (2280 to 2550 °F) to ~1600 to 1700 °C (2910 to 3090 °F) at the end of the blow.

Fig. 5 Composition of (a) steel bath and (b) slag in a basic oxygen furnace converter as a function of blowing time

At the beginning of the blow, the distance of the lance tip from the bath surface is kept high, and after the formation of an initial slag rich in FeO and SiO2, the lance is lowered. The slag starts to foam by around one-third of the blow, and the FeO content of the slag begins to decrease. Beyond three-quarters of the blow, the decarburization rate falls and the FeO content of the slag continuously increases to accommodate most of the oxygen that is not used for carbon oxidation. Toward the end of the blow, the rate of increase of FeO in the slag depends primarily on the lance height and the carbon content of the metal and on the amount of undissolved lime and viscosity of the slag. It can be readily seen that a high level of FeO in the slag directly affects the converter productivity. The equilibrium oxygen activity in liquid steel at tapping temperatures is a function of the turn-down carbon content (Ref 20). At the end of the blow and after the lance is withdrawn, a temperature measurement is taken with an immersion thermocouple and a chemical analysis is done on the bath sample within five minutes. If the bath is too hot, ore or limestone is added as a coolant. A short-period reblow may be necessary if the temperature is too low. Temperature in the BOF is controlled by using a thermally balanced charge of hot metal and scrap such that composition and temperature are achieved at turn down, as desired. The BOF end points are completely computer controlled. Process Capabilities. The basic oxygen process is characterized by (1) use of gaseous oxygen as the sole refining agent, (2) a charge largely composed of molten-blast furnace iron, and (3) rapid chemical reactions in a low surface-tovolume bath, minimizing external heat losses. Basic oxygen furnace steelmaking is an autothermal process, which relies on the oxidation of impurities in hot metal, therefore, a certain amount of hot charge is essential. Important attributes of a tapped steel product are the levels of carbon, oxygen, and other gaseous impurities, as well as the temperature, which affect secondary steelmaking. Control of oxygen and carbon are related to the loss of iron as FeO in the slag, which is undesirable. High levels of silicon in the hot metal require higher amounts of lime for fluxing and lower the converter productivity because larger volume of the converter is occupied by the slag. On the other hand, if low-silicon hot metal is refined, addition of sand can be necessary to create the required volume of slag for refining reactions. Control of sulfur and phosphorus are important for steel properties. Thus, the capabilities of a BOF reactor in terms of productivity are limited by the hot metal composition, scrap rate, desired carbon level, and the finishing temperature.

Electric-Arc Steelmaking (Ref 21)

Furnace Description. The classical blast furnace/BOF integrated steel plants are giving way to modern establishments

of EAF/continuous-caster minimill steel production route. For steelmaking purposes, three-phase, alternating current (ac) direct-arc and direct current (dc) direct-arc furnaces, as well as induction furnaces are commonly used. In three-phase, ac direct-arc processes, current is passed from one electrode down through an arc and the metal charge, then from the charge up through an arc to another electrode. In the dc direct-arc furnaces, current passes from one electrode through an arc and the metal charge to an electrode in the bottom of the furnace. Current is induced in the steel by an oscillating magnetic field in low-, medium-, or high-frequency induction furnaces. Indirect-arc furnaces use radiation heating to heat the charge where the arc is directly struck between the two electrodes. These furnaces are not common for steelmaking. Presently, high-alloy, stainless, bearing, and other high-quality steels as well as low-alloy and plain-carbon steels are produced in EAFs. Figure 6 shows a schematic cross section of an EAF. Commercial EAFs are almost exclusively lined with basic refractories of burned magnesite or direct-bonded, chrome-magnesite bricks with roofs made of high alumina-bricks. All the ingot cast, continuous cast, and most of the foundry-grade steels are produced in basic-lined furnaces, which can melt highly alloyed steel scrap as well as plain-carbon scrap. Basic furnaces can produce steel from a wide range of scrap compositions with the added advantage of refining high-sulfur and high-phosphorus melts. The time required for working the heat due to faster oxidation and the loss of iron in the slag due to lower slag volume are lower in the acid process, which uses a siliceous slag.

Fig. 6 Schematic cross section of a typical electric-arc furnace showing the application of different refractories

Burden Preparation. Segregation of scrap is an important function in burden preparation for electric furnaces. Grade-

wise separation of scrap is done (1) to conserve the valuable alloy content of steel scrap, (2) to use virgin alloys economically, and (3) to ensure that only the desired alloying elements end up in the finished steel product. The segregation is usually done online by spark testing along with accurate chemical analysis using spectrography. Separation of scrap on the basis of size and bulk density is also performed to blend the charge properly. Exclusive use of light scrap (bundles, turnings, punchings, etc.) lowers the productivity by occupying a large volume in the furnace. Light scrap is also prone to oxidation. Light scrap as the initial charge can damage the hearth as the arc can bore through the metallic charge. A charge comprising all heavy scrap (ingots, butts, crops, etc.) is also not suitable as the roof and walls of the furnace are not shielded causing refractory damage. Essentially, the scrap charge is mixed for optimum melting, power utilization, and electrode consumption at minimum operating costs. Direct-reduced iron can be used to partially or fully replace the scrap in an electric furnace charge. Often, DRI is preferred because it has a known uniform composition and contains no residual elements, such as copper, nickel, tin, or chromium. Direct-reduced iron also helps in the formation of a foamy slag due to the presence of carbon and iron oxide. Usually a 30% DRI and 70% scrap charge mix is used depending on the price of the two materials.

Charging Sequence. Electric-arc furnaces have removable roofs so scrap can be quickly and easily charged into the

furnaces. The scrap is charged into the furnace using drop-bottom buckets. Large heavy scrap charges are loaded using magnets and placed slowly on the furnace bottom. Alloying materials which are difficult to oxidize, for example, copper, nickel, and molybdenum, can be charged prior to the melt down. Excess carbon is desired in the bath for meltdown, which is accomplished by oxygen injection or ore addition. If the carbon is low in the metallic charge, coke or scrap electrodes are used as recarburizers to allow ~0.20% higher carbon in the bath at melt down than is required in the finished steel. Oxygen injection is preferred for decarburization rather than mill scale or ore addition. If DRI is used as the metallic charge, it is added over the entire melt-down period through an opening in the furnace roof. Flux is added along with the metallic charge and placed away from the pitch of the electrodes as it is non-conducting. Process Description. The process of making steel in the basic-lined EAF can be divided into (1) the melt-down

period, (2) the oxidizing period, (3) the composition and temperature adjustment period, and (4) the tapping period. Once the charging is complete, the electrodes are lowered to about an inch above the charge material and arcs are struck. Power and electrode consumption are highest during the melt-down period. Melting occurs by direct arcing as well as through radiation from the molten pool of metal collecting in the hearth. Burned or calcined lime as the flux is added toward the end of the melting of the first load of scrap charge. The oxidizing period begins from the time the molten metal forms until the entire charge is in solution. During this period, phosphorus, silicon, manganese, carbon, and iron are oxidized. The sources of oxygen are the injected oxygen, furnace atmosphere, oxides of added alloying elements, and the ore, cinder, and mill scale added to the charge. The oxidizers are added in a controlled fashion to prevent excessive formation of carbon monoxide, which forces the slag to foam and spill out of the furnace. The bubbling action caused by carbon monoxide, called "carbon-boil," stirs the bath and makes it uniform in temperature and composition. Hydrogen and nitrogen are also lowered in the bath during carbon boil. Because electric-furnace steelmaking is not autothermal, that is, it relies on energy from the electric power used, the bath can be made hotter than a BOF. Thus, phosphorus reversal can occur if the slag is not highly basic. Most carbon and low-alloy steel grades are made with a single-slag practice. The steel is finished by adjusting the composition and temperature to the desired value followed by tapping. The oxidizing period overlaps the adjustment period, and further lowering of sulfur and oxygen, if desired, is carried out in the ladles through secondary steelmaking. In the double-slag practice to make high-quality carbon and alloy steels, the first oxidizing slag is removed from the furnace, and a reducing slag is prepared using burned lime, fluorspar, coke, and sand on top of the molten bath. Calcium carbide formed in the slags helps in desulfurization (see the section "Hot Metal Pretreatment" ); however, ladle treatment to lower sulfur is now preferred. The composition is controlled by the slag chemistry as in the BOF. A typical melt-down slag comprises 41% lime, 14% each of iron oxide and silica, 9% magnesia, 4% alumina, and 13% manganous oxide, besides small quantities of phosphorus oxide and sulfur. The electrodes are raised to allow tilting of the furnace for tapping. Stream oxidation is prevented during tapping of steel into ladles. Slag is removed from the furnace before, during, or after steel tapping depending on the practice used. A "wetheel" practice is often used where a small amount of liquid steel is left behind in the furnace for the next heat. This helps in lowering the slag carry-over to the ladle. Sophisticated slide-gate arrangements are used to prevent slag carryover. The main advantage of the arc furnace lies in flexibility in accepting charge materials in any proportion, that is, scrap, molten iron, prereduced material, and pellets, although industrial practice is mostly restricted to scrap and DRI. The control of electric power can be well regulated to impart heat to the bath at different desired rates. This allows a precise control of refining reactions. Oxygen can be blown to speed up the melt-down refining processes. The EAF offers a wide range of possibilities in controlled production of ordinary as well as high-quality special steels. Alloy steels can be made directly with secondary treatments. The process is best suited for the production of higher alloy steel grades, such as tool steels and stainless steels, because of the inherent advantage of process control. Small-capacity EAF can be put into service, whereas small oxygen furnaces are usually uneconomical. Because EAF is primarily scrap based, and the impurity control in scrap is of utmost importance, elements like copper and nickel are hard to remove under the steelmaking conditions. Advances in Steelmaking Technology Oxygen Bottom-Blowing Process. The essential difference from the oxygen top-blowing process, or BOF, is that all

of the required oxygen gas is introduced through the bottom of the vessel with the help of tuyeres (Fig. 7). Lime can be

injected in fine powder form along with oxygen to enhance the rate of dissolution of lime and the formation of a wellmixed homogeneous slag. The oxygen bottom-blowing process is also known as OBM, Q-BOP, or the LWS process depending on the type of tuyere design used for injecting oxygen. Natural gas or oil is used to shroud and protect the tuyeres from the intense heat of oxidation at the tip. The noise generated in bottom-blown processes as well as the turbulence in the bath are low compared with top-blown converters. Because bottom-blown processes operate more closely to the equilibrium conditions, the oxidation potential is much lower than top-blowing processes. This control of slag-metal equilibrium allows lower iron losses as FeO to the slag, higher manganese recoveries, less splashing (slopping) of the furnace, faster blow times, improved phosphorus and sulfur control, and lower dissolved oxygen and nitrogen contents. Bottom-blown converters have about ~2.0% higher yield. Easier process control is available in a Q-BOP as variability due to lance practice does not exist. Also, scrap rate in a bottom-blown process is lower along with a 10% lower oxygen rate than a top-blown process.

Fig. 7 Schematic representation of a bottom-blowing process

In general, less heat is produced in the bottom-blown oxygen steelmaking because less iron and manganese are oxidized for the same turn-down carbon level. Conversion of carbon to carbon dioxide is lower in bottom-blown converters and some of the heat is taken away by the hydrocarbon coolants used to protect the tuyeres. Thus, Q-BOP can melt about 4% less scrap than a top-blown converter. Reproducibility of the thermochemical reactions is much higher in bottom blowing as the absence of an oxygen lance provides better control of the end point. Turned-down steel has slightly higher hydrogen due to the use of hydrocarbons. The levels of carbon, sulfur, and nitrogen in the steel and the amount of FeO in the slag are, however, less in the bottom-blowing process, compared with the top-blowing. Bottom-blown processes typically have a higher bottom-furnace erosion rate and decreased furnace availability due to high heat generation in the vicinity of the tuyeres. Combined-Blowing Process. The advantages and limitations of bottom-blown processes over the top-blown classical BOF led to the development of combined-blowing processes where gases are blown both from the top and bottom of the converter, as shown in Fig. 8. Several patented schemes exist under this broad category of steelmaking, which are different only in the type and amount of gases blown from the top and bottom. Some processes also differ in the style of the tuyeres used, such as small uncooled tuyeres, cooled tuyeres, or permeable elements. Oxygen is typically blown through the top lance with either inert stirring gas (LD-KG, LD-AB, and LBE processes), inert oxidizing gas (LD-OTB, LD-STB, and BSC-BAP processes), or oxygen gas (LD-OB, K-BOP, and OBM processes), blowing through the bottom. Processes, such as Krupp-COIN, and KMS, which have the flexibility to operate on a 100% scrap charge, are also categorized as combined-blowing processes. These methods are characterized by the means employed for increasing the scrap melting rate using a post-combustion lance, scrap preheating, and/or carbon injection.

Fig. 8 Schematic representation of a combined-blowing process

Processes that employ submerged-gas injection to increase bath agitation help increase decarburization efficiency while decreasing oxidation of the metals in the bath. These processes also reduce dissolved oxygen levels and flux consumption while allowing a higher manganese retention. Lower dissolved oxygen in combined blowing through permeable elements at any given carbon level with respect to top-blown processes allows better recovery of the alloying elements and decreases the need for deoxidizers in ladle metallurgy. Lower oxygen is the result of better mixing and near-equilibrium refining of steel in combined-blowing processes. Combined-blown processes have 1.0% higher yield due to less oxidation of iron and manganese and a lower slag rate. Lower oxidation of metallics result in a lower scrap rate for the process. Processes using cooled bottom tuyeres allow the injection of hydrocarbons, powdered lime, or coal to enhance the refining rate and scrap melting. Use of uncooled small tuyeres at the bottom using argon gas injection for stirring is limited due to the cost of argon and the clogging effects at high argon flow rates. Process Control. Significant online computerized process control capabilities are available for steelmaking depending

on the final product mix, decarburization reactions, metallurgical requirements of the plant, and the response time for corrective actions. Carbon removal rate, carbon level, and bath temperature can be continuously monitored. Some measurements use models that call for consistency in the shop practices and quality of materials used, as well as close adherence to the computer recommendations. Online process control results in improved control of carbon, sulfur, and phosphorus amounts and tapping temperature, decreased heat time, increased scrap rate and heat size, decreased flux, coolant, and oxygen consumption, and an overall improved quality of steel. Precise control of the end point carbon and the temperature eliminates time consuming and expensive reblow or cooling procedures. The static-charge model prescribes the proper combination of the charge materials--hot metal, scrap, fluxes, and oxygen-required to meet the desired end point composition and temperature. Part of the calculations are completed in advance, and trimming calculations are done when the actual material balance is available. Calculations also occur during the heat to determine the reblow or cooling requirements to get to the desired end point. Dynamic procedures using in-blow measurements are used for precise control of 100% of the heats in combination with the static charge models. Watercooled sub-lance systems to measure online carbon and temperature, off-gas analysis with continuous recomputing of carbon level, and sonic analysis for carbon level through sound intensity are some of the methods practiced industrially. Immersion thermocouples usually provide the direct temperature measurement. Refractories in Iron and Steelmaking Refractories are the primary materials used by the steel industry in the internal linings of furnaces for making iron and steel, such as blast furnaces, BOF, EAF, etc., and in ladles and tundishes for holding and transporting metals and slags. Thus, the refractories are often required to withstand temperatures in excess of 1700 °C (3090 °F). Refractories affect the quality of the product as well as the energy consumption in iron and steelmaking. Refractories are chosen on the basis of service life and cost. Basic Refractories. The most important group of refractories for the basic steelmaking processes are magnesite-based

and are either natural or synthetic magnesite, brucite, and dolomite. Dense synthetic magnesia is produced from sea water and has a purity of 95 to 99% MgO. Natural magnesite is present as a hydroxide or a carbonate. The double carbonate of dolomite (CaCO3·MgCO3), is found in abundance. High-temperature calcining (firing in kilns to dissociate the

carbonates) is required in all the cases to produce a dense material with minimum impurities. Magnesia-chrome refractory spinels are also commonly used without firing in combination with magnesia refractory. Acid Refractories. The siliceous group of refractories that fall under the "acid" class of materials are beneficiated from quartzite, sandstone, or zircon-type raw materials. Electrical fusion is used to produce special-purpose refractories of fused silica or stabilized zirconia. Several types of fireclays, hydrated aluminosilicates, and kaolin firebricks are usually used for low-temperature refractory needs. The plasticity of fireclays allows it to be used for sealants and grouts. Other Refractories. Alumina refractory bricks, as high-alumina silicates or pure sintered alumina, are common for

high-temperature refractory applications. Carbon bricks and blocks made from petroleum coke, foundry coke, or anthracite coal are extensively used as furnace hearth lining. Silicon carbide and silicon nitride refractories, produced by firing coke and silica mixtures at high temperature, are used in pure form as well as in combination with other refractory materials. In general, refractories are required to withstand a wide range of temperature and sudden changes in temperature to accommodate the thermal shock. Resistance to small compressive stresses, abrasive forces, corrosive actions of molten metal, slag, and process and effluent gases is required. In addition, refractories are required to function as an insulator, heat absorber, or a heat conductor depending on the application. Chemical and physical characteristics of iron and steelmaking refractories, as well as the selection of lining materials for different reactors, have been discussed elsewhere (Ref 22). Fluxes in Iron and Steelmaking The function of fluxes in iron and steelmaking is twofold: (1) to render the high melting refractory oxide impurities or gangue fusible and separable from the molten metal, and (2) to provide a medium with which the impurity elements or compounds would combine in preference to the metal. Practically all of the slag-forming compounds that enter a smelter or refiner can be classified as basic or acid. Silica is the only substance used as a strictly acid flux, although in slags phosphorus oxide behaves in a strongly acidic manner. Neutral fluxes are sometimes added to improve the fluidity or to lower the melting point of the slag for better reaction kinetics and slag handling. Ores contain both acidic and basic oxide impurities with the acidic component predominating. Amphoteric oxides, such as alumina and titania, have a basic or an acidic nature, depending on the slag condition. In acid steelmaking processes, silica is often picked up from the furnace lining itself. In basic processes, such as BOF or EAF, silica is added when excess lime or insufficient silica is present in the system. Primary basic fluxes are either limestone (CaCO3) or dolomite ((Ca, Mg)CO3) and either or both can be used as a blastfurnace flux, depending on the other slag constituents present and the required ability of the slag to remove sulfur. Limestone is preferred for large sulfur removal. The basic oxygen steelmaking process uses burned or calcined lime or burned dolomite to flux silica produced by silicon oxidation. The presence of magnesia in the slag helps protect the magnesite brick lining of the furnace. Limestone and dolomite are precalcined or burned outside the steelmaking vessel, because dissociation of these compounds is endothermic, and an extra heat load on an autothermal process is not desired. Burned lime contains >95% CaO, and the calcined dolomite is comprised of >57% CaO and >40% MgO. Fluorspar or calcium fluoride with >50% CaF2 is used in steelmaking as a more efficient desulfurizer. Quality and quantity of fluxes in iron and steelmaking are important as they occupy a useful volume in the reactors and influence productivity.

References cited in this section

19. B. Deo and R. Boom, Fundamentals of Steelmaking Metallurgy, Prentice Hall, 1993, p 146-187 20. H.W. Kreutzer, Stahl Eisen, Vol 92, 1972, p 716-724 21. W.T. Lankford, Jr., et al., Ed., The Making, Shaping and Treating of Steel, US Steel Publication, 1984, p 627-669 22. W.T. Lankford, Jr., et al., Ed., The Making, Shaping and Treating of Steel, US Steel Publication, 1984, p 42-96

Secondary Steelmaking

Ladle Metallurgy Secondary steelmakings, or ladle metallurgys, is performed to produce clean steel. Clean steels satisfy stringent requirements of surface, internal, and microcleanliness quality and of mechanical properties. The secondary step of ladle metallurgy follows the primary refining in a converter or an EAF, as described in the previous section. Ladle metallurgy has become a routine part of steelmaking due to the growing stringent requirements on the steel composition. Ladle metallurgy is used for deoxidation, decarburization, and adjustment of chemical composition including gases. Refining times in the furnace can often be shortened and production rates increased with an efficient secondary steelmaking practice. Ladle metallurgy also allows the control of teeming temperature, especially required for continuous casting. Steels with as low as 0.002 wt% S can be produced free of oxide or sulfide inclusions. Inclusion shape control is also performed in ladles to improve mechanical properties. Deoxidation and Alloying. Steels are required to meet certain temperature and chemical requirements for proper ladle metallurgy. Toward the end of tapping some amount of furnace slag is carried over into the ladle. Deoxidation and alloying additions can be made during tapping. Intense agitation of the bath caused by the falling stream of liquid metal helps in alloy dissolution, deoxidation, and homogenization. Loss of deoxidizing elements added, such as aluminum and silicon, depends on the amount and composition of the carried-over slag (Ref 23). The loss of deoxidants is minimized as they are expensive, and the entrapment of deoxidation products adversely affects steel cleanliness. Typically, a deoxidant, such as aluminum, would be partly oxidized by the furnace slag and the entrained air. Aluminum is also dissolved in steel depending on the existing equilibrium condition. The primary role of aluminum as a deoxidant is to react with the dissolved oxygen and float up as alumina. However, some of the finer alumina particles are retained in the steel as inclusions. Making low-inclusion steels requires further treatment to float the fine oxide particles. Slag carry-over is minimized to control the hydrogen and nitrogen pick up by the steel as well as the phosphorus reversal due to reduction of P2O5 by deoxidizing agents. Several types of devices are available as slag stoppers. Argon Rinsing and Vacuum Treatment. Stirring treatment with argon gas, also known as online argon rinsing, can be done to homogenize the bath and to promote decarburization by lowering the carbon monoxide partial pressure. Argon rinsing also helps in lowering the nitrogen and hydrogen content, as well as enhancing alloy dissolution and slag-metal reactions due to stirring effects. Exchange treatments with synthetic (low FeO) slags (Ref 24) or conditioned (high CaO) slags (Ref 25) can be carried out during or before tapping followed by argon rinsing to promote deoxidation, desulfurization, and inclusion modification. Methods for argon rinsing are shown schematically in Fig. 9. Although a stopper-rod arrangement is shown in Fig. 9 for teeming the ladle, use of slide-gate systems are more prevalent now.

Fig. 9 Schematic illustrating methods for using the argon-stirring process. (a) The lance method. (b) The porous-plug method

Vacuum treatment is done to facilitate degassing and enhance the kinetics of deoxidation and decarburization. Alloy additions can also be made during the vacuum treatment. Alloy additions susceptible to oxidation, for example, ironniobium, are added after deoxidation. The recovery of expensive alloys is improved by ensuring complete dissolution. Injection treatment in ladles with inert gas, inert gas-oxygen mixtures, or pure oxygen is practiced. Injection of powdered agents of CaSi, CaC2, CaAl, rare earths, and magnesium with an inert gas carrier, or of submerged cored wire with a prior synthetic slag treatment allows for simultaneous deoxidation, desulfurization, and sulfide shape control. If ultra-low

carbon steel grades are to be produced, deoxidation is usually not performed at the time of tapping since dissolved oxygen is later required to react with carbon. Accurate assessment of temperature, chemical composition, and quantity of steel in the ladle must be known for efficient secondary processes. The use of high-quality refractories in the liquid steel handling facilities are desirable to achieve lower oxygen activity when steel is contained in ladles or tundishes. Ladle preheating and temperature control is an integral part of secondary steelmaking as ladles essentially act as heat sinks. Synthetic Slags. Ladle refining to produce ultraclean steels and efficient desulfurization are achieved when steel is

treated under a basic, nonoxidizing slag. These synthetic slags have low oxygen potential, low melting point, moderate fluidity, and high solubility for alumina and sulfur. Processes and Objectives Secondary steelmaking processes define the ways in which the liquid steel is handled in order to achieve the objectives. Table 2 lists the primary methods and equipment used for ladle treatment and their relative capabilities. These methods can be categorized under four major groups (Fig. 10): stirring, injection, vacuum, and heating processes (Ref 26, 27).

Table 2 Relative efficiency of secondary steelmaking processes 0, none; 1, good; 2, better; 3, best Steelmaking processes

Metallurgical functions

Composition control

Temperature control

Deoxidation (O2)

Degassing (H2)

Decarburization

Desulfurization

Microcleanliness

Inclusion morphology

Stream degassing

1

0

1

3

1

0

1

0

D-H degassing

2

2

2

2

2

0

2

1

R-H degassing

2

2

2

2

2

0

2

1

RH-OB degassing

2

2

2

2

3

0

2

1

Ladle refining furnace, reheat only

3

3

3

0

0

1

3

0

Ladle refining furnace, reheat and vacuum degassing

3

3

3

2

2

3

3

1

Argon-oxygen decarburization

1

2

2

1

3

2

1

1

Argon bubbling, CAS

2

1

1

0

0

0

1

0

Argon bubbling, CAB

2

1

2

0

0

2

2

2

Lance powder injection

1

0

2

0

0

3

2

3

Cored-wire injection

2

0

2

0

0

1

2

3

REM canister

1

0

1

0

0

1

1

3

D-H, Dortmund-Horder-Huttenunion; R-H, Ruhrstahl-Heraeus; CAS, composition adjustment by sealed argon bubbling; CAB, capped argon bubbling; REM, rare earth metals

Fig. 10 Processes for secondary steelmaking. Stirring process: (a) bottom injection and (b) lance injection. Injection processes: (c) powder injection and (d) wire feeding. Vacuum processes: (e) stream degassing, (f) RH degassing, and (g) D-H degassing. Heating processes: (h) VOD process, (i) VAD process, and (j) ladle furnace process

Stirring is simple purging or rinsing of liquid steel by inert argon gas passed either through a porous plug or a submerged lance (Fig. 9) to achieve bath homogenization and oxide flotation. Deoxidation and desulfurization by enhancing slagmetal reactions can also be achieved by argon purging if a synthetic slag is used. Alloy additions or deoxidation reagents are introduced either in a powder form through a submerged lance with the help of a carrier gas or by encasing the materials in a wire by injection metallurgy. Vacuum processes are designed to reduce the partial pressure of hydrogen, nitrogen, and carbon monoxide gas in the ambient atmosphere to enable degassing, decarburization, and deoxidation. Vacuum treatments can be broadly classified into vacuum stream degassing, ladle degassing, and recirculation degassing (Table 2 and Fig. 10). The loss in temperature during secondary treatment is compensated by either using a higher superheat in the primary steelmaking or by an additional reheating process, such as the ladle furnace with submerged electrodes. Vacuum-induction melting or vacuum-oxygen degassing are other examples of heating processes. Some of the prominent processes are described in greater detail later in this section and in the section "Processing of Special-Quality Steels." Treatments Degassing. Liquid steel absorbs gases from the atmosphere and from the materials used in steelmaking and can cause

embrittlement, voids, inclusions, etc., in the steel when solidified. The major gases to be eliminated are oxygen, hydrogen, and nitrogen. Oxygen is the principal refining agent in steelmaking and plays a role in determining the final composition and properties of steel and influences the consumption of deoxidizers. The production of rimmed, semikilled, or killed grades of steel essentially refers to oxygen management in liquid steel before solidification. If the oxygen content of molten steel is sufficiently high during vacuum degassing, the oxygen will react with some of the carbon to produce carbon monoxide. The evolved carbon monoxide is removed by the created vacuum, known as vacuum-carbon deoxidation. In undeoxidized steel, the carbon and oxygen contents approach equilibrium at a given temperature and pressure according to:

C+O

CO (gas)

(Eq 11)

(Eq 12) where Keq is the thermodynamic equilibrium constant and pCO is the partial pressure of carbon monoxide. Figure 11 shows the contents of carbon and oxygen in equilibrium at 1600 °C (2910 °F) as a function of partial pressure of carbon monoxide. As the pressure is lowered by vacuum treatments, more and more carbon reacts with oxygen to establish the new carbon monoxide partial pressure, thus making the oxygen unavailable for inclusion formation with the added deoxidizers. Strong deoxidizers, such as aluminum, titanium and silicon, react with oxygen with greater affinity than carbon at atmospheric pressure (Fig. 12) so carbon cannot react with oxygen when vacuum degassed. If not floated properly, oxides of deoxidants can result in inclusions when solidified. Carbon is a stronger deoxidizer than aluminum, titanium, or silicon below a pressure of 0.01 atm.

Fig. 11 Carbon-oxygen equilibrium relationship in liquid steel at 1600 °C (2910 °F) for various partial pressures of CO gas above liquid steel. If carbon and oxygen levels are at 0.04 and 0.05 wt%, respectively, at the start of vacuum treatment (region A), then enough oxygen is available to lower the carbon content to 0.01 wt% at pCO of 0.01 atm. However, for carbon levels greater than 0.05 wt% (region B), an external oxygen source is necessary before vacuum treatment to raise the oxygen level to region O, if 0.01 wt% carbon is desired in the steel at pCO of 0.01 atm. Note that regions A and B are above and below the CO gas stoichiometric line, respectively.

Fig. 12 Equilibrium relationship between the contents of total oxygen and various deoxidizing elements in a steel bath

Hydrogen causes bleeding ingots, embrittlement, low ductility, thermal flaking, and blowholes. Hydrogen is usually picked up from the moisture in the charge and the environment and can be lowered by an effective vacuum treatment, according to Sievert's law:

[%H] = K (pH2)1/2

(Eq 13)

The amount of hydrogen dissolved in molten steel, [%H], is related to the partial pressure of hydrogen gas above molten steel, pH2. The equilibrium consant K is equal to 0.0027 at 1600 °C (2910 °F). Hydrogen removal during vacuum degassing is affected by factors such as surface area exposed to vacuum, degassing pressure, steel composition, extent of prior deoxidation, and hydrogen pickup from alloy additions, slags, and refractories. Nitrogen is particularly harmful for low-carbon steels intended for drawing applications and should be lowered as much as possible. Although nitrogen follows Sievert's law, its removal by argon flushing or vacuum degassing is limited due to the tendency of nitrogen to form stable nitrides. Primary control of nitrogen is attempted during steelmaking practices. Decarburization. It is difficult to produce steel by conventional steelmaking with 2.5. The distribution of phosphorus is also linked to the turn-down carbon level. In general, high basicity and low temperature favor dephosphorization. The addition of fluxes, for example, ilmenite, fluorspar, lime, etc., to lower slag viscosity, also helps to lower the metal phosphorus content. Phosphorus can be essentially captured in the slag during early stages of steelmaking through judicious adjustment of both the blowing practice and hot metal silicon level (Ref 33). Thus, phosphorus control in secondary steelmaking refers to the control of phosphorus reversal occurring through the use of synthetic slags, which is dependent on the activity of P2O5 in the slag and the amount of aluminum and silicon in the metal. The Perrin process was developed for ladle dephosphorization using appropriate synthetic slags. It is important to do a slag-free tapping if synthetic slag-aided deoxidation with aluminum or silicon is carried out. The kinetics of deoxidation by aluminum in an argon-stirred vessel or a R-H degasser has been reported in literature (Ref 34). Inclusion Shape Control If nonmetallic inclusions must remain in the steel, they should be made innocuous to the desired steel properties by changing their shape and/or composition. Steels can be made with more isotropic properties by changing the "stringer" sulfides to globular sulfides by a calcium compound or rare-earth metals treatment. Ladle injection technology, as described earlier, is an appropriate method for adding rare earths by the plunging method. The calcium treatment, primarily carried out for sulfur control, also has a modifying effect on inclusion morphology. A complete modification of type II manganese sulfide inclusions (Fig. 13) takes place when the sulfur content is 730 °C, or 1350 °F) are avoided to prevent carbide coarsening and sticking of coil laps. Adjustment of cooling rate during annealing is practiced to retain some of the carbon in solid solution, which imparts strength to the sheets and strips of ultralow carbon steel. Continuous annealing of lowcarbon materials can be adopted for lower carbon levels of less than 0.02%, whereas batch annealing can be used to process up to 0.05% carbon steels (Ref 55).

Fig. 25 Typical flow diagram for processing low-carbon strip steel

Interstitial-Free Steels Flat-rolled steels with carbon less than 0.003% and manganese below 0.18%, with special emphasis on low nitrogen to prevent aging effects and low hydrogen to prevent flaking, are classified as interstitial-free steel. Lowering of carbon and nitrogen is achieved by niobium, titanium, and boron treatments during secondary steelmaking. A boron-to-nitrogen ratio of 0.8 to 1.0 is beneficial in these steels, because boron has a greater affinity for nitrogen than aluminum, allowing relatively higher coiling temperature. In such steels, titanium carbides raise the recrystallization temperature. Therefore, the steels are finish rolled above 950 °C (1740 °F). Interstitial-free steels are characterized by a high strain ratio of above 2.0, where excellent forming properties can be achieved by continuous annealing. Small additions of phosphorus (rephosphorized steel: up to 0.1% P), manganese, and silicon are sometimes used to impart some strength in interstitialfree steels and are known as interstital-free high-strength steels (IF-HSS). These steels maintain their formability without any impairment of weldability (Ref 56). High-Strength Low-Alloy Steels Both the interstitial-free steels and the ultralow plain carbon steels have low strength due to low carbon and manganese levels (tensile strength below 300 MPa, or 40 ksi) and are not suitable for high-strength applications. These grades have been specifically designed for high formability. However, there is a strong interest in weldable, formable, high-strength flat products in both hot- and cold-rolled conditions. The need to use lighter gages for weight reduction while maintaining a high strength level (yield strengths ranging from 410 to 550 MPa, or 60 to 80 ksi, are common) and structural integrity, has led to the development of a microalloyed class of steel, known as high strength low alloy (HSLA) steels. A minimum tensile strength of 480 MPa (70 ksi) is achieved in some common grades of HSLA steels. Small additions of one or more of the alloying agents, such as vanadium, niobium, titanium, boron, zirconium, chromium, silicon, nitrogen, and/or copper are made to molten steel after ladle deoxidation or during secondary steelmaking to achieve one or more of the following objectives (Ref 57): • • • •

Precipitation strengthening Solid-solution strengthening Ferrite grain-refinement Transformation strengthening

In addition, corrosion resistance, excellent weldability, and high room-temperature and low-temperature notch-toughness values are also desired in HSLA steels for specific applications. The specific role of each of these additions is discussed in

Ref 58. It should be emphasized that lowering the sulfur content in steels is desired for automotive grades, line pipe steels, and corrosion-resistant products (Ref 59). The influence of very small additions of microalloying elements on the properties of HSLA steels is clearly demonstrated in Fig. 26. A good deoxidation practice is essential for HSLA grades so that a high recovery of the alloying additions can be achieved. These steels are produced as flat-rolled sheet, strip, and plate materials as well as structural shapes, for example, line pipe tubulars, gas-container steels, reinforcing bars, coldheading steel, etc.

Fig. 26 Effect of microalloying on yield strength of hot- and cold-rolled steel strips

Ultrahigh Strength Steels Several grades of engineering steels having ultrahigh strengths (over 1000 MPa, or 145 ksi, tensile strength) have been developed either through high-alloy additions of chomium, molybdenum, nickel, vanadium, and manganese in combination with low-carbon contents or through low-to-high alloy additions in combination with medium-to-high carbon levels (>0.40% C). The former type of high-alloy steels with low carbon are used for turbine blades, rings, bolts, and casings, whereas the latter medium-to-high, carbon-bearing steels are needed for high-strength rail steels, bearing steels, forging steels, tool steels, high-speed steels, and high-carbon wire rods. The important properties desired in these grades are high-room and elevated-temperature hardenability (through hardness or surface hardness) in combination with high toughness. Quality of these ultrahigh strength steels has significantly improved with the introduction of vacuum degassing technology as well as inclusion shape control. Argon shrouding of the liquid stream during teeming and casting is practiced to prevent reoxidation and to reduce the non-metallic inclusion content while vacuum induction melting and vacuum arc remelting are common practices for producing exceptionally clean steels (Ref 60). Slag-free tapping, ladle stirring, and the use of high-alumina ladle refractories are some other integral aspects of clean steel production. Inclusion shape control is administered through lead, selenium, tellurium, calcium, bismuth, or rare-earths addition. Niobium, vanadium, or titanium are also added as microadditions for similar property enhancement similar to HSLA steels. Lowsulfur petroleum coke is usually the source for increasing carbon level. The recent commercialization of iron carbide can provide a better source for carburization of steel melts due to its low tramp element level and higher density than petroleum coke. Cold-Rolled Products Cold-rolled finished products include flat bars, cold-rolled strips and sheets, and black plate, which are made from plain carbon steels and alloyed steels, including stainless steels. Tempering, annealing, and edging are associated steps in cold rolling. The chosen processing scheme is dictated entirely by the application. Cold rolling implies passing unheated metal through rolls for thickness reduction, surface finish improvement, and controlled mechanical properties. The metal for cold rolling is generally produced in coiled form in a hot-strip mill. Prior to cold reduction, the hot-rolled coils are uncoiled, pickled, dried, oiled, and recoiled. The coils are reduced at very high speeds by looping the metal from one coil to the other. Heavy reductions of up to 90% may be taken in a single strand reversing mill or a tandem mill. The design of a cold-rolling process is based on the type of mill, power available, steel width, total reduction, steel hardness and tension,

lubrication, and desired surface finish. On multiple-strand mills or a reversing mill, the last pass is primarily used for control of gage thickness, flatness, and surface finish and not for the purpose of reduction (Ref 61). Cold-rolled material is sometimes used in the as-rolled condition to make use of its cold-worked high strength depending on the application. Generally, the metal requires heat treatment to control the mechanical properties. A surface cleaning step, either chemical, electrochemical, or mechanical, is taken before heat treatment. The low-carbon, deep-drawing type steels are usually annealed in a box furnace or a continuous furnace at a low temperature of 675 °C (1250 °F) to encourage recovery and recrystallization while preventing any grain growth. Other types of heat treatments can be performed after cold reduction, for example, to solutionize chromium carbides in stainless steel strips or to form a passive oxide on transformer-grade, silicon-steel sheets. Subsequent to heat treatment, a temper rolling may be necessary to achieve certain features in the product, such as suppression of yield-point elongation that causes Lüder lines (Ref 62), a bright surface finish, and surface flatness and shape improvements. Usually, the reduction achieved during temper rolling is restricted to below 2% to prevent a decrease in ductility. Shearing, side trimming, slitting, and leveling follow temper rolling of cold-rolled products. Some prominent surface defects of cold-rolled products are seams and slivers that have their origin in the inclusions trapped during steel casting. When the steel gage is heavily reduced, nonmetallic inclusions appear on the surface and spall off. In addition, a critical aluminum to nickel balance is required in cold-rolled products for the development of favorable texturing. Thus, it can be readily seen that deoxidation, inclusion control, and nitrogen balance are key steelmaking factors in cold-rolled materials. Fully aluminum-killed steels, cast in wide-end-up molds after argon rinsing and under complete inert shrouding are known to possess enhanced mechanical and surface properties for cold-rolling application. Stainless Steels Iron-chromium steels, with possible additions of nickel and moybdenum, in combination with low carbon contents, are designated as "stainless steels" when a minimum of 12% Cr is present to provide a passive layer of chromium oxide on the surface. This passive layer is responsible for the high corrosion resistance realized in stainless steels. Stainless steel was traditionally made in small EAFs by melting steel scrap, nickel, and ferrochrome before the advent of oxygen refining. The modern practice of making stainless steel is based on a two-stage process. The first stage employs a conventional EAF for the rapid melting of scrap and ferroalloys but uses cheap high-carbon ferrochrome as the main source of chromium. Because stainless steel manufacturing involves more scrap melting and alloying and less refining, EAFs are preferred over the oxygen-based converter processes due to high external energy loads. The high-carbon melt prepared in an EAF is then refined in a second stage, using either AOD or by blowing with oxygen under VOD (see the section "Secondary Steelmaking" ). The AOD process currently produces over 80% of the stainless steel tonnage worldwide. Special desulfurizing slags are used in AOD where intimate metal-slag mixing can be achieved using argon stirring. Oxygen is capable of decarburizing the melt to less than 0.01% C, and hydrogen levels are below 2 to 3 ppm. Sensitization in austenitic stainless steels leading to intergranular corrosion is markedly influenced by the presence of elongated particles or clusters of second phases, such as sulfides or other inclusions. The presence of nitrogen in some niobium-bearing stainless grades leads to carbonitride formation, which also deleteriously influences sensitizaton. Control of gaseous inclusions as well as sulfur are important in refining of stainless steels. Stainless steels require expensive alloying additions of chromium, nickel, and molybdenum. Therefore, recovery of these elements needs special attention. Efficient slag reduction with stoichiometric amounts of silicon or aluminum permits overall recoveries of 97 to 100% for most metallic elements. Chromium recovery averages approximately 97.5%, and nickel and molybdenum recoveries are approximately 100%. Casting is usually done in a continuous caster for better productivity, although ingot casting and primary rolling is still more common for stainless steels than carbon steels. The cost of ferrochrome production affects stainless steel prices directly. Commercial varieties of stainless steels are classified as austenitic (work hardenable), ferritic (work hardenable), austenitic-ferritic (duplex), or martensitic (hardenable by heat treatment). Although this classification is based on microstructure, it relates to two primary roles of alloy additions: (1) the balance between austenite formers (N, C, Ni, Co, Cu, and Mn) and ferrite formers (W, Si, Mo, Cr, V, and Al) controlling the high-temperature microstructure and (2) the overall alloy content, which controls the martensite transformation range, Ms-Mf, and the degree of martensite transformation at ambient temperature. Figure 27 (Ref 63) shows the effect of ferrite-forming (chromium equivalent) and austenite-forming (nickel equivalent) alloy additions on the type of stainless steel produced.

Fig. 27 Modified Schaeffler constitution diagram for stainless steels. The compositions of the ferritic, martensitic, austenitic, and duplex alloys are superimposed on this diagram.

Stainless steels have lower thermal conductivity than carbon or alloy steels below 815 °C (1500 °F) and, therefore, need special attention in heating below 815 °C (1500 °F) to avoid surface burning. In addition, hot-working temperature ranges for stainless steels are narrower than for carbon steels, requiring better temperature control during soaking and rolling. Martensitic grades are slow cooled or annealed after rolling because they are air hardening. Ferritic grades are finish rolled to lower temperatures to prevent grain growth that could lead to tearing and cracking. Austenitic grades require more rolling-mill power because they are stronger than ferritic grades and are also susceptible to grain growth. Sulfur control in reheating furnace atmospheres is important for austenitic grades due to the presence of nickel. Liquid nickel sulfide formation at the grain boundaries during rolling can lead to tears and cracks. Cold rolling of stainless steel has two primary objectives--reduction of hot-rolled gage and cold forming into components. Except the high-carbon grades, all stainless steels are amenable to cold working. Pickling is performed following hot rolling.

References cited in this section

54. D.T. Llewellyn, Low Carbon Strip Steels, Steels: Metallurgy & Applications, Butterworth Heinemann, 1992 55. N. Takahashi, et al., Proc. Metallurgy of Continuous Annealed Sheet Steel, B.L. Bramfitt and P.L. Manganon, Ed., TMS-AIME, 1982, p 133 56. P.J.P. Bordignon, K. Hulka, and B.L. Jones, "High Strength Steels for Automotive Applications," Niobium Technical Report NbTR-06/84, 1984 57. M. Cohen and S.S. Hansen, Proc. HSLA Steels: Metallurgy and Applications (Beijing), J.M. Gray, T. Ko, S. Zhang, B. Wu, and X. Xie, Ed., American Society for Metals, 1985 58. F.B. Pickering, Physical Metallurgy and the Design of Steels, Applied Science Publishers, 1978 59. J.W. Kochera, Proc. of the Low Sulfur Steels Symposium, Workshop II: Oil Country Steels, Amax Matls. Res. Center, 1984, p 41-57 60. "Vacuum Degassing of Steel," Special Report No. 92, The Iron and Steel Institute, 1965 61. W.T. Lankford, Jr., et al., Ed., The Making, Shaping, and Treating of Steel, 10th ed., United States Steel Publication, 1985, p 1102-1168 62. W.L. Roberts, The Cold Rolling of Steel, Marcel-Dekker, Inc., 1978 63. H. Schneider, Foundry Trade J., Vol 108, 1960, p 562 Analytical Techniques for Liquid Steel

It cannot be overemphasized that properties of a steel are primarily determined by its chemical composition and that the steelmaker has no control of the composition once the metal is cast. The computerization of the primary and secondary steelmaking processes and the dramatic reduction in time required to make steel by modern methods has put tremendous pressure on the time available for liquid metal analysis. The chemist must return the chemical composition analysis of liquid steel rapidly so that corrective actions may be taken, if necessary. Unfortunately, the techniques available for rapid and accurate analysis are limited. Chemical analysis is employed to determine whether or not material is within ordered chemical limits and sometimes to check the degree to which elements contained in the steel have segregated. Elemental analysis of carbon, silicon, sulfur, phosphorus, and manganese go hand in hand with oxygen and nitrogen gas measurements as well as the temperature monitoring. Usually, a pyrometer or an immersion thermocouple is employed to accurately measure the temperature. Consumable oxygen sensors are commonly used for on-line total oxygen analysis. However, the rapid determination of concentrations of alloying elements in steels is performed by the optical emission spectroscopy methods. Optical emission spectroscopy can determine major as well as trace elemental constituents qualitatively and quantitatively. Free atoms emit light at a series of narrow wavelength intervals when placed in an energetic environment. These intervals, or emission lines, form a pattern, or the emission spectrum, which is characteristic of the atom producing it. The intensities of the lines are proportional to the number of atoms producing them. The presence of an element in a sample is indicated by the presence in light from the excitation source of one or more of its characteristic lines. The concentration of the element can be determined by measuring line intensities (Ref 64). The characteristic emission spectrum forms the basis for qualitative elemental analysis, whereas the measurement of intensities of the emission lines forms the basis for quantitative analysis. The liquid sample is collected from the steelmaking furnace during the refining period or the ladle during secondary steelmaking and prior to casting. The sample is immediately cast into a form suitable for the spectroscope. Some surface grinding of the active surface may be done prior to analysis. An emission light source is used to decompose the sample into an atomic vapor and then excite the vapor with sufficient efficiency to produce a measurable emission signal. Four types of emission sources are available: arcs, high-voltage sparks, glow discharges, and flames. Each emission source has a set of physical characteristics with accompanying analytical capability and limitations. Spark and glow-discharge emission sources are most common for rapid compositional analysis during steelmaking. Spark-source excitation is the most rapid method for analyzing an alloy sample. Analysis can be done in as little as thirty seconds and usually can be done within a couple of minutes. While flame sources are appropriate for analyzing trace levels of alkali metals down to a few ppm, glow-discharge source is more suited for carbon, phosphorus, and sulfur analysis. Detection limits are as low as 0.002% for sulfur and 0.014% for carbon. Other analytical techniques suitable for chemical analysis of steels include atomic absorption spectroscopy, x-ray fluorescence, and inductively-coupled and direct-current plasma emission spectroscopies. Some of these techniques require the dissolution of samples in a solvent. Qualitative analysis of sulfur and phosphorus is also performed by sulfur and phosphorus prints, but these are not used for rapid analysis.

Reference cited in this section

64. P.B. Farnsworth, Optical Emission Spectroscopy, Metals Handbook, Vol 10, Materials Characterization, 9th ed., American Society for Metals, 1986, p 21-30

Classifications and Designations Carbon and Alloy Steels

of

Introduction WROUGHT CARBON AND ALLOY STEELS with total alloying element contents that do not exceed 5% are considered in this article. Ferrous materials that are cast or made by powder metallurgy methods are not included, but are described elsewhere in this Handbook. The same is true for tool steels, more highly alloyed stainless steels, and steels used primarily for their magnetic or electrical properties (e.g., silicon steels).

Important Terms and Definitions Classification is the systematic arrangement or division of steels into groups on the basis of some common

characteristic. Steels can be classified on the basis of (1) composition, such as carbon or alloy steel; (2) manufacturing method, such as basic oxygen furnace steel or electric-arc furnace steel; (3) finishing method, such as hot-rolled or coldrolled sheet; (4) microstructure, such as ferritic or martensitic; (5) the required strength level, as specified in ASTM standards; (6) heat treatment, such as annealed or quenched-and-tempered; (7) quality descriptors, such as forging quality or structural quality; or (8) product form, such as bar, plate, sheet, strip, tubing, or structural shape. Classification by product form is very common within the steel industry because by identifying the form of a product, the manufacturer can identify the mill equipment required for producing it and thereby schedule the use of these facilities. Common usage has further subdivided these broad classifications. For example, carbon steels are often loosely and imprecisely classified according to carbon content as low-carbon (up to 0.30% C), medium-carbon (0.30 to 0.60% C), or high-carbon (0.60 to 1.00% C) steels. They may be classified as rimmed, capped, semikilled, or killed, depending on the deoxidation practice used in producing them. Alloy steels are often classified according to the principal alloying element (or elements) present. Thus, there are nickel steels, chromium steels, and chromium-vanadium steels, for example. Many other classification systems are in use, the names of which are usually self-explanatory. Grade, type, and class are terms used to classify steel products. Within the steel industry, they have very specific

uses: grade is used to denote chemical composition; type is used to indicate deoxidation practice; and class is used to describe some other attribute, such as strength level or surface smoothness. In ASTM specifications, however, these terms are used somewhat interchangeably. In ASTM A 533, for example, type denotes chemical composition, while class indicates strength level. In ASTM A 515, grade identifies strength level; the maximum carbon content permitted by this specification depends on both plate thickness and strength level. In ASTM A 302, grade connotes requirements for both chemical composition and mechanical properties. ASTM A 514 and A 517 are specifications for high-strength plate for structural and pressure-vessel applications, respectively; each contains several compositions that can provide the required mechanical properties. A 514 type F has the identical composition limits as A 517 grade F. Designation is the specific identification of each grade, type, or class of steel by a number, letter, symbol, name, or suitable combination thereof unique to a particular steel. Chemical composition is by far the most widely used basis for designation, followed by mechanical-property specifications. The most commonly used system of designation in the United States is that of SAE International (formerly the Society of Automotive Engineers) and the American Iron and Steel Institute (AISI). The Unified Numbering System (UNS) is also being used with increasing frequency. A description of each of these designation systems follows. Quality. The steel industry uses the term "quality" in a product description to imply special characteristics that make the

mill product particularly well suited to specific applications or subsequent fabrication operations. The term does not necessarily imply that the mill product is better material, is made from better raw materials, or is more carefully produced than other mill products. A specification is a written statement of attributes that a steel must possess in order to be suitable for a particular

application, as determined by processing and fabrication needs and engineering and service requirements. It generally

includes a list of the acceptable values for various attributes that the steel must possess and, possibly, restrictions on other characteristics that might be detrimental to its intended use. A standard specification is a published document that describes a product acceptable for a wide range of applications and that can be produced by many manufacturers of such items. Even if there is no standard specification that completely describes the attributes required for a steel product to be used in a particular application, it may be preferable to cite the most nearly applicable standard specification and those exceptions necessitated by the particular application. By doing so, the familiarity of both producer and user with the standard specification is retained, while an individualized product can be obtained.

A specification can be advantageously used in purchasing steel (or any other product) by incorporating it into the purchase agreement. The specification clearly states which attributes the product must possess. The use of a designation alone as the basis for purchase indicates that the buyer is specifying only those attributes described in the designation and permitting the supplier the latitude to produce the item according to his usual practice. The distinction between specifications and standard practices follows.

Quality Descriptors The need for communication among producers and between producers and users has resulted in the development of a group of terms known as fundamental quality descriptors. These are names applied to various steel products to imply that the particular products possess certain characteristics that make them especially well suited for specific applications or fabrication processes. The fundamental quality descriptors in common use are listed in Table 1. Table 1 Quality descriptions of carbon and alloy steels Carbon steels Semifinished for forging Forging quality

Special hardenability Special internal soundness Nonmetallic inclusion requirement Special surface

Carbon steel structural sections Structural quality

Carbon steel plates Regular quality Structural quality Cold-drawing quality Cold-pressing quality Cold-flanging quality Forging quality Pressure vessel quality

Hot-rolled carbon steel bars Merchant quality Special quality

Special hardenability Special internal soundness Nonmetallic inclusion requirement

Special surface

Scrapless nut quality Axle shaft quality Cold extrusion quality Cold-heading and cold-forging quality

Cold-finished carbon steel bars Standard quality

Special hardenability Special internal soundness Nonmetallic inclusion requirement Special surface

Cold-heading and cold-forging quality Cold extrusion quality

Hot-rolled sheets Commercial quality Drawing quality Drawing quality special killed Structural quality

Cold-rolled sheets Commercial quality Drawing quality Drawing quality special killed Structural quality

Porcelain enameling sheets Commercial quality Drawing quality Drawing quality special killed

Long terne sheets Commercial quality Drawing quality Drawing quality special killed Structural quality

Galvanized sheets Commercial quality Drawing quality Drawing quality special killed Lock-forming quality

Electrolytic zinc coated sheets Commercial quality Drawing quality Drawing quality special killed

Structural quality

Hot-rolled strip Commercial quality Drawing quality Drawing quality special killed Structural quality

Cold-rolled strip Specific quality descriptions are not provided in cold-rolled strip because this product is largely produced for specific end use

Tin mill products Specific quality descriptions are not applicable to tin mill products

Carbon steel wire Industrial quality wire Cold extrusion wires Heading, forging, and roll-threading wires Mechanical spring wires Upholstery spring construction wires Welding wire

Carbon steel flat wire Stitching wire Stapling wire

Carbon steel pipe

Structural tubing

Line pipe

Oil country tubular goods

Steel specialty tubular products Pressure tubing Mechanical tubing Aircraft tubing

Hot-rolled carbon steel wire rods Industrial quality Rods for manufacture of wire intended for electrical welded chain Rods for heading, forging, and roll-threading wire Rods for lock washer wire Rods for scrapless nut wire

Rods for upholstery spring wire Rods for welding wire

Alloy steels Alloy steel plates Drawing quality Pressure vessel quality Structural quality Aircraft physical quality

Hot-rolled alloy steel bars Regular quality Aircraft quality or steel subject to magnetic particle inspection Axle shaft quality Bearing quality Cold-heading quality Special cold-heading quality Rifle barrel quality, gun quality, shell or armor-piercing shot quality

Alloy steel wire Aircraft quality Bearing quality Special surface quality

Cold-finished alloy steel bars Regular quality Aircraft quality or steel subject to magnetic particle inspection Axle shaft quality Bearing shaft quality Cold-heading quality Special cold-heading quality Rifle barrel quality, gun quality, shell or armor-piercing shot quality

Line pipe

Oil country tubular goods

Steel specialty tubular goods Pressure tubing Mechanical tubing Stainless and head-resisting pipe, pressure tubing, and mechanical tubing Aircraft tubing Pipe

Some of the quality descriptors listed in Table 1, such as forging quality or cold extrusion quality, are self-explanatory. The meaning of others is less obvious: for example, merchant quality hot-rolled carbon steel bars are made for noncritical applications requiring modest strength and mild bending or forming, but not requiring forging or heat treating. The descriptor for one particular steel commodity is not necessarily carried over to subsequent products made from that commodity, for example, standard quality cold-finished bars are made from special quality hot-rolled bars.

The various mechanical and physical attributes implied by a quality descriptor arise from the combined effects of several factors, including: (1) the degree of internal soundness; (2) the relative uniformity of chemical composition; (3) the relative freedom from surface imperfections; (4) the size of the discard cropped from the ingot; (5) extensive testing during manufacture; (6) the number, size, and distribution of nonmetallic inclusions; and (7) hardenability requirements. Control of these factors during manufacture is necessary to achieve mill products having the desired characteristics. The extent of the control over these and other related factors is also conveyed by the quality descriptor. Some, but not all, of the fundamental descriptors can be modified by one or more additional requirements as appropriate: special discard, macroetch test, restricted chemical composition, maximum incidental (residual) alloy, special hardenability, or austenitic grain size. These restrictions could be applied to forging quality alloy steel bars, but not to merchant quality bars. Understanding the various quality descriptors is complicated by the fact that most of the requirements that qualify a steel for a particular descriptor are subjective. Only nonmetallic inclusion count, restrictions on chemical composition ranges and incidental alloying elements, austenitic grain size, and special hardenability are quantified. The subjective evaluation of the other characteristics depends on the skill and experience of those who make the evaluation. Although these subjective quality descriptors might seem imprecise and unworkable, steel products made to meet the requirements of a particular quality descriptor have those characteristics necessary for use in the indicated application or fabrication operation.

Specifications A specification is a written statement of the requirements, both technical and commercial, that a product must meet; it is a document that controls procurement. There are nearly as many formats for specifications as there are groups writing them, but any reasonably adequate specification will provide information about: •

• •

•

•

Scope, which can cover product classification (including size range when necessary), condition, and any comments on product processing deemed helpful to either the supplier or user. An informative title plus a statement of the required form can be used instead of a scope clause. Chemical composition, which can be detailed or indicated by a well-recognized designation based on chemical composition. The SAE-AISI designations are frequently used. The quality statement, which includes any appropriate quality descriptor and whichever additional requirements are necessary. It can also include the type of steel and the steelmaking processes permitted. Quantitative requirements, which identify allowable ranges of the composition and all physical and mechanical properties necessary to characterize the material. Test methods used to determine these properties should also be included, at least by reference to standard test methods. For reasons of economy, this section should be limited to properties that are germane to the intended application. Additional requirements, which can include special tolerances, surface preparation, and edge finish on flat-rolled products, as well as special identification, packaging, and loading instructions.

Engineering societies, associations, and institutes whose members make, specify, or purchase steel products publish standard specifications, many of which have become well known and highly respected. Some of the important specification-writing groups are listed below. It is obvious from the names of some of these that the specifications prepared by a particular group may be limited to its own specialized field:

Organization

Acronym

Association of American Railroads

AAR

American Bureau of Shipbuilding

ABS

American Petroleum Institute

API

American Railway Engineering Association

AREA

American Society of Mechanical Engineers

ASME

American Society for Testing and Materials

ASTM

Society of Automotive Engineers

SAE

Aerospace Material Specification (of SAE)

AMS

The most comprehensive and widely used specifications are those published by ASTM. ASTM specifications pertaining to steel products exist at three distinct levels. ASTM A 6 contains the general requirements for most carbon steel structural products. ASTM A 588, for example, incorporates the general requirements of A 6 and describes the more specific requirements of a family of high-strength low-alloy (HSLA) steels. Other specifications, such as A 231 for alloy steel spring wire, refer to a particular product intended for a specific application. Other specifications for steel products have been prepared by various corporations and United States government agencies to serve their own special needs. They are used primarily for procurement by that corporation or agency, and they receive only limited distribution or use beyond these channels. There is an important difference between specifications and standard practices. As indicated above, a specification is a statement of the requirements that a product must meet. When it is cited by a purchaser and accepted by a supplier, it becomes part of the purchase agreement. Many manufacturers of steel mill products publish compilations of their standard manufacturing practices. These data represent the dimensions, tolerances, and properties that might be expected in the absence of specific requirements that indicate otherwise. The AISI Steel Products Manuals are compilations of the AISI designations for carbon and alloy steels, the standard practices of many steelmakers, and related scientific and technical information that has been reported to the institute. AISI states that the Steel Products Manuals are not specifications; however, they are a good indication of what restrictions and tolerances many producers of steel mill products will accept. Commercial tolerances and practices described in these manuals should, whenever possible, be incorporated into a proprietary specification in order to minimize the additional cost incurred by ordering "nonstandard" steel products.

Chemical Analysis Chemical composition is often used as the basis for classifying steels or assigning standard designations to steels. Such designations are often incorporated into specifications for steel products. Users and specifiers of steel products should be familiar with methods of sampling and analysis. Chemical analyses of steels are usually performed by wet chemical analysis methods or spectrochemical methods. Wet analysis is most often used to determine the composition of small numbers of specimens or of specimens composed of machine tool chips. Spectrochemical analysis is well-suited to the routine determination of the chemical composition of a large number of specimens, as may be necessary in a steel mill environment. Both classical wet chemical and spectrochemical methods for analyzing steel samples are described in detail in Materials Characterization, Volume 10, ASM Handbook. Heat and Product Analysis. During the steelmaking process, a small sample of molten metal is removed from the

ladle or steelmaking furnace, allowed to solidify, and then analyzed for alloy content. In most steel mills, these heat

analyses are performed using spectrochemical methods; as many as 14 different elements can be determined simultaneously. The heat analysis furnished to the customer, however, may include only those elements for which a range or a maximum or minimum limit exists in the appropriate designation or specification. A heat analysis is generally considered to be an accurate representation of the composition of the entire heat of metal. Producers of steel have found that heat analyses for carbon and alloy steels can be consistently held within ranges that depend on the amount of the particular alloying element desired for the steel, the product form, and the method of making the steel. These ranges have been published as commercial practice, then incorporated into standard specifications. Standard ranges and limits of heat analyses of carbon and alloy steels are given in Tables 2, 3, 4, and 5. Table 2 Carbon steel cast or heat chemical limits and ranges Applicable only to semifinished products for forging, hot-rolled and cold-finished bars, wire rods, and seamless tubing Element

Carbon(a)

Manganese

Phosphorus

Sulfur

Maximum specified element, %

0.12

of

Range, %

...

>0.12-0.25 incl

0.05

>0.25-0.40 incl

0.06

>0.40-0.55 incl

0.07

>0.55-0.80 incl

0.10

>0.80

0.13

0.40

0.15

>0.40-0.50 incl

0.20

>0.50-1.65 incl

0.30

>0.40-0.08 incl

0.03

>0.08-0.13 incl

0.05

>0.050-0.09 incl

0.03

>0.09-0.15 incl

0.05

>0.15-0.23 incl

0.07

>0.23-0.35 incl

0.09

Silicon (for bars)(b)(c)

0.08

0.15

>0.15-0.20 incl

0.10

>0.20-0.30 incl

0.15

>0.30-0.60 incl

0.20

Copper

When copper is required, 0.20 minimum is commonly used

Lead(d)

When lead is required, a range of 0.15-0.35 is generally used

Incl, inclusive. Boron-treated fine-grain steels are produced to a range of 0.0005-0.003% B. (a) The carbon ranges shown customarily apply when the specified maximum limit for manganese does not exceed 1.10%. When the maximum manganese limit exceeds 1.10%, it is customary to add 0.01 to the carbon range shown.

(b) It is not common practice to produce a rephosphorized and resulfurized carbon steel to specified limits for silicon because of its adverse effect on machinability.

(c) When silicon is required for rods the following ranges and limits are commonly used: 0.10 max; 0.07-0.15, 0.10-0.20, 0.15-0.35, 0.20-0.40, or 0.30-0.60.

(d) Lead is reported only as a range of 0.15-0.35% because it is usually added to the mold or ladle stream as the steel is poured

Table 3 Carbon steel cast or heat chemical limits and ranges Applicable only to structural shapes, plates, strip, sheets, and welding tubing Element

Carbon(a)(b)

Maximum specified element, %

0.15

of

Range, %

0.05

>0.15-0.30 incl

0.06

>0.30-0.40 incl

0.07

>0.40-0.60 incl

0.08

>0.60-0.80 incl

0.11

>0.80-1.35 incl

0.14

Manganese

Phosphorus

0.20

0.50

>0.050-1.15 incl

0.30

>1.15-1.65 incl

0.35

0.03

0.08

>0.08-0.15 incl

Sulfur

Silicon

Copper

0.05

0.03

0.08

>0.08-0.15 incl

0.05

>0.15-0.23 incl

0.07

>0.23-0.33 incl

0.10

0.08

0.15

>0.15-0.30 incl

0.15

>0.30-0.60 incl

0.30

When copper is required, 0.20% minimum is commonly specified

Incl, inclusive. (a) The carbon ranges shown in the range column apply when the specified maximum limit for manganese does not exceed 1.00%. When the maximum manganese limit exceeds 1.00%, add 0.01 to the carbon ranges shown in the table.

(b) Maximum of 0.12% C for structural shapes and plates

Table 4 Alloy steel heat composition ranges and limits for bars, blooms, billets, and slabs Element

Carbon

Maximum of specified element, %

0.55

Range, %

Open hearth or basic oxygen steels

Electric furnace steels

0.05

0.05

Manganese

Sulfur(a)

Silicon

Chromium

>0.55-0.70 incl

0.08

0.07

>0.70-0.80 incl

0.10

0.09

>0.80-0.95 incl

0.12

0.11

>0.95-1.35 incl

0.13

0.12

0.20

0.15

>0.60-0.90 incl

0.20

0.20

>0.90-1.05 incl

0.25

0.25

>1.05-1.90 incl

0.30

0.30

>1.90-2.10 incl

0.40

0.35

0.015

0.015

>0.050-0.07 incl

0.02

0.02

>0.07-0.10 incl

0.04

0.04

>0.10-0.14 incl

0.05

0.05

0.08

0.08

>0.15-0.20 incl

0.10

0.10

>0.20-0.40 incl

0.15

0.15

>0.40-0.60 incl

0.20

0.20

>0.60-1.00 incl

0.30

0.30

>1.00-2.20 incl

0.40

0.35

0.15

0.15

0.60

0.050

0.15

0.40

Nickel

Molybdenum

Tungsten

>0.40-0.90 incl

0.20

0.20

>0.90-1.05 incl

0.25

0.25

>1.05-1.60 incl

0.30

0.30

>1.60-1.75 incl

(b)

0.35

>1.75-2.10 incl

(b)

0.40

>2.10-3.99 incl

(b)

0.50

0.20

0.20

>0.50-1.50 incl

0.30

0.30

>1.50-2.00 incl

0.35

0.35

>2.00-3.00 incl

0.40

0.40

>3.00-5.30 incl

0.50

0.50

>5.30-10.00 incl

1.00

1.00

0.05

0.05

>0.10-0.20 incl

0.07

0.07

>0.20-0.50 incl

0.10

0.10

>0.50-0.80 incl

0.15

0.15

>0.80-1.15 incl

0.20

0.20

0.20

0.20

>0.50-1.00 incl

0.30

0.30

>1.00-2.00 incl

0.50

0.50

0.50

0.10

0.50

>2.00-4.00 incl

Copper

Vanadium

0.60

0.60

0.20

0.20

>0.60-1.50 incl

0.30

0.30

>1.50-2.00 incl

0.35

0.35

0.05

0.05

0.10

0.10

0.05

0.05

>0.10-0.20 incl

0.10

0.10

>0.20-0.30 incl

0.15

0.15

>0.30-0.80 incl

0.25

0.25

>0.80-1.30 incl

0.35

0.35

>1.30-1.80 incl

0.45

0.45

0.60

0.25

>0.25-0.50 incl

Aluminum

0.10

Element

Steelmaking process

Lowest maximum(c), %

Phosphorus

Basic open hearth, basic oxygen, or basic electric furnace steels

0.035(d)

Basic electric furnace E steels

0.025

Acid open hearth or electric furnace steel

0.050

Basic open hearth, basic oxygen, or basic electric furnace steels

0.040(d)

Basic electric furnace E steels

0.025

Acid open hearth or electric furnace steel

0.050

Sulfur

Incl, inclusive.

(a) A range of sulfur content normally indicates a resulfurized steel.

(b) Not normally produced by open hearth process.

(c) Not applicable to rephosphorized or resulfurized steels.

(d) Lower maximum limits on phosphorus and sulfur are required by certain quality descriptors.

Table 5 Alloy steel heat composition ranges and limits for plates Element

Carbon

Manganese

Sulfur

Maximum of specified element, %

Range, %

Open hearth or basic oxygen steels

Electric furnace steels

0.06

0.05

>0.25-0.40 incl

0.07

0.06

>0.40-0.55 incl

0.08

0.07

>0.55-0.70 incl

0.11

0.10

>0.70

0.14

0.13

0.20

0.15

>0.45-0.80 incl

0.25

0.20

>0.80-1.15 incl

0.30

0.25

>1.15-1.70 incl

0.35

0.30

>1.70-2.10 incl

0.40

0.35

0.02

0.02

>0.060-0.100 incl

0.04

0.04

>0.100-0.140 incl

0.05

0.05

0.25

0.45

0.060

Silicon

Copper

Nickel

Chromium

0.08

0.08

>0.15-0.20 incl

0.10

0.10

>0.20-0.40 incl

0.15

0.15

>0.40-0.60 incl

0.20

0.20

>0.60-1.00 incl

0.30

0.30

>1.00-2.20 incl

0.40

0.35

0.20

0.20

>0.60-1.50 incl

0.30

0.30

>1.50-2.00 incl

0.35

0.35

0.20

0.20

>0.50-1.50 incl

0.30

0.30

>1.50-2.00 incl

0.35

0.35

>2.00-3.00 incl

0.40

0.40

>3.00-5.30 incl

0.50

0.50

>5.30-10.00 incl

1.00

1.00

0.20

0.15

>0.40-0.80 incl

0.25

0.20

>0.80-1.05 incl

0.30

0.25

>1.05-1.25 incl

0.35

0.30

>1.25-1.75 incl

0.50

0.40

0.15

0.60

0.50

0.40

>1.75-3.99 incl

Molybdenum

Vanadium

0.60

0.50

0.05

0.05

>0.10-0.20 incl

0.07

0.07

>0.20-0.50 incl

0.10

0.10

>0.50-0.80 incl

0.15

0.15

>0.80-1.15 incl

0.20

0.20

0.05

0.05

0.10

0.10

0.10

0.25

>0.25-0.50 incl

Incl, inclusive. Boron steels can be expected to contain a minimum of 0.0005% B. Alloy steels can be produced with a lead range of 0.15-0.35%. A heat analysis for lead is not determinable because lead is added to the ladle stream while each ingot is poured.

Because segregation of some alloying elements is inherent in the solidification of an ingot, different portions will have local chemical compositions that differ slightly from the average composition. Many lengths of bar stock can be made from a single ingot; therefore, some variation in composition between individual bars must be expected. The compositions of individual bars might not conform to the applicable specification, even though the heat analysis does. The chemical composition of an individual bar (or other product) taken from a large heat of steel is called the product analysis or check analysis. Ranges and limits for product analyses are generally broader and less restrictive than the corresponding ranges and limits for heat analyses. Such limits used in standard commercial practice are given in Tables 6, 7, and 8. Table 6 Product analysis tolerances for carbon and alloy steel plates, sheet, piling, and bars for structural applications Element

Carbon

Upper limit or maximum specified values, %

0.15

>0.15-0.40 incl

Manganese(a)

0.60

>0.60-0.90 incl

Tolerance, %

Under minimum limit

Over maximum limit

0.02

0.03

0.03

0.04

0.05

0.06

0.06

0.08

Phosphorus

>0.90-1.20 incl

0.08

0.10

>1.20-1.35 incl

0.09

0.11

>1.35-1.65 incl

0.09

0.12

>1.65-1.95 incl

0.11

0.14

>1.95

0.12

0.16

...

0.010

...

(b)

0.04

>0.04-0.15 incl

Sulfur

0.05

...

0.010

Silicon

0.30

0.02

0.03

>0.30-0.40 incl

0.05

0.05

>0.40-2.20 incl

0.06

0.06

0.03

0.03

0.05

0.05

0.04

0.04

0.06

0.06

0.01

0.01

>0.20-0.40 incl

0.03

0.03

>0.40-1.15 incl

0.04

0.04

0.20 minimum only

0.02

...

0.03

0.03

Nickel

1.00

>1.00-2.00 incl

Chromium

0.90

>0.90-2.10 incl

Molybdenum

Copper

0.20

1.00

>1.00-2.00 incl

0.05

0.05

Titanium

0.10

0.01(c)

0.01(c)

Vanadium

0.10

0.01(c)

0.01(c)

>0.10-0.25 incl

0.02

0.02

Minimum only specified

0.01

...

Any

(b)

(b)

Boron

Niobium

0.10

0.01(c)

0.01(c)

Zirconium

0.15

0.03

0.03

Nitrogen

0.030

0.005

0.005

Incl, inclusive. (a)

Manganese product analyses tolerances for bars and bar size shapes:

(b)

Product analysis not applicable.

(c)

If the minimum of the range is 0.01%, the under tolerance is 0.005%.

0.90, ±0.03; >0.90-2.20 incl, ±0.06.

Table 7 Product analysis tolerances for carbon and alloy steel bars, blooms, billets, and slabs Element

Carbon

Manganese

Limit or maximum of specified range, %

Tolerance over the maximum limit or under the minimum limit, %

0.065 m2 (100 in.2)

>0.065-0.129 m2 (100-200 in.2) incl

>0.129-0.258 m2 (200-400 in.2) incl

>0.258-0.516 m2 (400-800 in.2) incl

0.02

0.03

0.04

0.05

>0.25-0.55 incl

0.03

0.04

0.05

0.06

>0.55

0.04

0.05

0.06

0.07

0.03

0.04

0.06

0.07

0.25

0.90

>0.90-1.65 incl

0.06

0.06

0.07

0.08

Phosphorus(a)

Over maximum only,

0.40

0.008

0.008

0.010

0.015

Sulfur(a)

Over maximum only,

0.050

0.008

0.010

0.010

0.015

0.02

0.02

0.03

0.04

>0.35-0.60 incl

0.05

...

...

...

Copper

Under minimum only

0.02

0.03

...

...

Lead(b)

0.15-0.35 incl

0.03

0.03

...

...

Silicon

0.35

Incl, inclusive. Rimmed or capped steels and boron are not subject to product analysis tolerances. Product analysis tolerances for alloy elements in high-strength low-alloy steels are given in Table 8. (a) Because of the degree to which phosphorus and sulfur segregate, product analysis tolerances for those elements are not applicable for rephosphorized and resulfurized steels.

(b) Product analysis for lead applies, both over and under the specified range.

Table 8 Product analysis tolerances for alloy steel bars, blooms, billets, and slabs Element

Carbon

Manganese

Phosphorus

Limit or maximum of specified range, %

Tolerance over the maximum limit or under the minimum limit for size ranges shown, %

0.065 m2 (100 in.2)

>0.065-0.129 m2 (100-200 in.2) incl

>0.129-0.258 m2 (200-400 in.2) incl

>0.258-0.516 m2 (400-800 in.2) incl

0.30

0.01

0.02

0.03

0.04

>0.30-0.75

0.02

0.03

0.04

0.05

>0.75

0.03

0.04

0.05

0.06

0.03

0.04

0.05

0.06

>0.90-2.10 incl

0.04

0.05

0.06

0.07

Over max only

0.005

0.010

0.010

0.010

0.90

Sulfur

Silicon

Over max only(a)

0.005

0.010

0.010

0.010

0.02

0.02

0.03

0.04

0.05

0.06

0.06

0.07

0.03

0.03

0.03

0.03

>1.00-2.00 incl

0.05

0.05

0.05

0.05

>2.00-5.30 incl

0.07

0.07

0.07

0.07

>5.30-10.00 incl

0.10

0.10

0.01

0.10

0.03

0.04

0.04

0.05

>0.90-2.10 incl

0.05

0.06

0.06

0.07

>2.10-3.99 incl

0.10

0.10

0.12

0.14

0.01

0.01

0.02

0.03

>0.20-0.40 incl

0.02

0.03

0.03

0.04

>0.40-1.15 incl

0.03

0.04

0.05

0.06

0.01

0.01

0.01

0.01

>0.10-0.25 incl

0.02

0.02

0.02

0.02

>0.25-0.50 incl

0.03

0.03

0.03

0.03

Min value specified, check under min limit(b)

0.01

0.01

0.01

0.01

0.04

0.05

0.05

0.06

0.08

0.09

0.10

0.12

0.03

...

...

...

0.40

>0.40-2.20 incl

Nickel

Chromium

Molybdenum

Vanadium

Tungsten

1.00

0.90

0.20

0.10

1.00

>1.00-4.00 incl

Aluminum(c)

0.10

Lead(c)

Copper(c)

>0.10-0.20 incl

0.04

...

...

...

>0.20-0.30 incl

0.05

...

...

...

>0.30-0.80 incl

0.07

...

...

...

>0.80-1.80 incl

0.10

...

...

...

0.15-0.35 incl

0.03(d)

...

...

...

0.03

...

...

...

0.05

...

...

...

1.00

>1.00-2.00 incl

Titanium(c)

0.10

0.01(b)

...

...

...

Niobium(c)

0.10

0.01(b)

...

...

...

Zirconium(c)

0.15

0.03

...

...

...

Nitrogen(c)

0.030

0.005

...

...

...

Incl, inclusive. Boron is not subject to product analysis tolerances. (a) Resulfurized steels are not subject to product analysis limits for sulfur.

(b) If the minimum range is 0.01%, the under tolerance is 0.005%.

(c) Tolerances shown apply only to 0.065 m2 (100 in.2) or less.

(d) Tolerance is over and under.

Residual elements usually enter steel products from raw materials used to produce pig iron or from scrap steel used in

steelmaking. Through careful steelmaking practices, the amounts of these residual elements are generally held to acceptable levels. Sulfur and phosphorus are usually considered deleterious to the mechanical properties of steels; therefore, restrictions are placed on the allowable amounts of these elements for most grades. The amounts of sulfur and phosphorus are invariably reported in the analyses of both carbon and alloy steels. Other residual alloying elements generally exert a lesser influence than sulfur and phosphorus on the properties of steel. For many grades of steel, limitations on the amounts of these residual elements are either optional or omitted entirely. Amounts of residual alloying elements are generally not reported in either heat or product analyses, except for special reasons. Silicon Content of Steels. The composition requirements for many steels, particularly plain carbon steels, contain no

specific restriction on silicon content. The lack of a silicon requirement is not an omission, but instead indicates

recognition that the amount of silicon in a steel can often be traced directly to the deoxidation practice employed in making it. Rimmed and capped steels are not deoxidized; the only silicon present is the residual amount left from scrap or raw materials, typically less than 0.05% Si. Specifications and orders for these steels customarily indicate that the steel must be made rimmed or capped, as required by the purchaser; restrictions on silicon content are not usually given. The extent of rimming action during the solidification of semikilled steel ingots must be carefully controlled by matching the amount of deoxidizer with the oxygen content of the molten steel. The amount of silicon required for deoxidation can vary from heat to heat. Thus, the silicon content of the solid metal can also vary slightly from heat to heat. A maximum silicon content of 0.10% is sometimes specified for semikilled steel, but this requirement is not very restrictive; for certain heats, a silicon addition sufficient to leave a residue of 0.10% can be enough of an addition to kill the steel. Killed steels are fully deoxidized during their manufacture; deoxidation can be accomplished by additions of silicon, aluminum, or both, or by vacuum treatment of the molten steel. Because it is the least costly of these methods, silicon deoxidation is frequently used. For silicon-killed steels, a range of 0.15 to 0.30% Si is often specified, providing the manufacturer with adequate flexibility to compensate for variations in the steelmaking process and ensuring a steel acceptable for most applications. Aluminum-killed or vacuum-deoxidized steels require no silicon; a requirement for minimum silicon content in such steel is unnecessary. A maximum permissible silicon content is appropriate for all killed plain carbon steels; a minimum silicon content implies a restriction that the steel must be silicon killed. Silicon is intentionally added to some alloy steels, for which it serves as both a deoxidizer and an alloying element to modify the properties of the steel. An acceptable range of silicon content would be appropriate for these steels. Users and specifiers of steel mill products must realize that the silicon content of these items cannot be established independently of deoxidation practice. In ordering mill products, it is often desirable to cite a standard specification (such as an ASTM specification) where the various ramifications of restrictions on silicon content have already been considered in preparing the specification. In some instances, such as the forming of low-carbon steel sheet, the choice of deoxidation practice can significantly affect the performance of the steel; in such cases, it is appropriate to specify the desired practice.

SAE-AISI Designations As stated above, the most widely used system for designating carbon and alloy steels is the SAE-AISI system. Technically, there are two separate systems, but they are nearly identical and have been carefully coordinated by the two groups. It should be noted, however, that AISI has discontinued the practice of designating steels. Therefore, the reader should consult Volume 1, Materials, of the SAE Handbook for the most up-to-date information. The SAE-AISI system is applied to semi-finished forgings, hot-rolled and cold-finished bars, wire rod and seamless tubular goods, structural shapes, plates, sheet, strip, and welded tubing. Table 9 summarizes the numerical designations used in both SAE and AISI. The fact that a particular steel is listed by SAE or AISI implies only that it has been produced in appreciable quantity. It does not imply that other grades are unavailable, nor that any particular steel producer makes all of the listed grades. Table 9 SAE-AISI system of designations for carbon and alloy steels Numerals and digits

Type of steel and nominal alloy content, %

Carbon steels

10xx(a)

Plain carbon (Mn 1.00 max)

11xx

Resulfurized

12xx

Resulfurized and rephosphorized

15xx

Plain carbon (max Mn range: 1.00-1.65)

Manganese steels

13xx

Mn 1.75

Nickel steels

23xx

Ni 3.50

25xx

Ni 5.00

Nickel-chromium steels

31xx

Ni 1.25; Cr 0.65 and 0.80

32xx

Ni 1.75; Cr 1.07

33xx

Ni 3.50; Cr 1.50 and 1.57

34xx

Ni 3.00; Cr 0.77

Molybdenum steels

40xx

Mo 0.20 and 0.25

44xx

Mo 0.40 and 0.52

Chromium-molybdenum steels

41xx

Cr 0.50, 0.80, and 0.95; Mo 0.12, 0.20, 0.25, and 0.30

Nickel-chromium-molybdenum steels

43xx

Ni 1.82; Cr 0.50 and 0.80; Mo 0.25

43BVxx

Ni 1.82; Cr 0.50; Mo 0.12 and 0.25; V 0.03 min

47xx

Ni 1.05; Cr 0.45; Mo 0.20 and 0.35

81xx

Ni 0.30; Cr 0.40; Mo 0.12

86xx

Ni 0.55; Cr 0.50; Mo 0.20

87xx

Ni 0.55; Cr 0.50; Mo 0.25

88xx

Ni 0.55; Cr 0.50; Mo 0.35

93xx

Ni 3.25; Cr 1.20; Mo 0.12

94xx

Ni 0.45; Cr 0.40; Mo 0.12

97xx

Ni 0.55; Cr 0.20; Mo 0.20

98xx

Ni 1.00; Cr 0.80; Mo 0.25

Nickel-molybdenum steels

46xx

Ni 0.85 and 1.82; Mo 0.20 and 0.25

48xx

Ni 3.50; Mo 0.25

Chromium steels

50xx

Cr 0.27, 0.40, 0.50, and 0.65

51xx

Cr 0.80, 0.87, 0.92, 0.95, 1.00, and 1.05

50xxx

Cr 0.50; C 1.00 min

51xxx

Cr 1.02; C 1.00 min

52xxx

Cr 1.45; C 1.00 min

Chromium-vanadium steels

61xx

Cr 0.60, 0.80, and 0.95; V 0.10 and 0.15 min

Tungsten-chromium steel

72xx

W 1.75; Cr 0.75

Silicon-manganese steels

92xx

Si 1.40 and 2.00; Mn 0.65, 0.82, and 0.85; Cr 0 and 0.65

Boron steels

xxBxx

B denotes boron steel

Leaded steels

xxLxx

L denotes leaded steel

Vanadium steels

xxVxx

(a)

V denotes vanadium steel

The xx in the last two digits of these designations indicates that the carbon content (in hundredths of a percent) is to be inserted.

SAE-AISI Designations for Carbon Steels As shown in Table 9, carbon steels comprise the lxxx groups in the SAE-AISI system and are subdivided into four distinct series as a result of the differences in certain fundamental properties among them. Plain carbon steels (1.00% max Mn) in the 10xx group are listed in Tables 10 and 11; note that ranges and limits

of chemical composition depend on the product form. Designations for merchant quality steels, given in Table 12, include the prefix M. A carbon steel designation with the letter B inserted between the second and third digits indicates the steel contains 0.0005 to 0.003% B. Likewise, the letter L inserted between the second and third digits indicates that the steel contains 0.15 to 0.35% Pb for enhanced machinability. Table 10 Carbon steel compositions Applicable to semifinished products for forging, hot-rolled and cold-finished bars, wire rods, and seamless tubing Designation

Cast or heat chemical ranges and limits(a), %

UNS No.

SAE-AISI No.

C

Mn

P max

S max

G10050

1005

0.06 max

0.35 max

0.040

0.050

G10060

1006

0.08 max

0.25-0.40

0.040

0.050

G10080

1008

0.10 max

0.30-0.50

0.040

0.050

G10100

1010

0.08-0.13

0.30-0.60

0.040

0.050

G10120

1012

0.10-0.15

0.30-0.60

0.040

0.050

G10130

1013

0.11-0.16

0.50-0.80

0.040

0.050

G10150

1015

0.13-0.18

0.30-0.60

0.040

0.050

G10160

1016

0.13-0.18

0.60-0.90

0.040

0.050

G10170

1017

0.15-0.20

0.30-0.60

0.040

0.050

G10180

1018

0.15-0.20

0.60-0.90

0.040

0.050

G10190

1019

0.15-0.20

0.70-1.00

0.040

0.050

G10200

1020

0.18-0.23

0.30-0.60

0.040

0.050

G10210

1021

0.18-0.23

0.60-0.90

0.040

0.050

G10220

1022

0.18-0.23

0.70-1.00

0.040

0.050

G10230

1023

0.20-0.25

0.30-0.60

0.040

0.050

G10250

1025

0.22-0.28

0.30-0.60

0.040

0.050

G10260

1026

0.22-0.28

0.60-0.90

0.040

0.050

G10290

1029

0.25-0.31

0.60-0.90

0.040

0.050

G10300

1030

0.28-0.34

0.60-0.90

0.040

0.050

G10350

1035

0.32-0.38

0.60-0.90

0.040

0.050

G10370

1037

0.32-0.38

0.70-1.00

0.040

0.050

G10380

1038

0.35-0.42

0.60-0.90

0.040

0.050

G10390

1039

0.37-0.44

0.70-1.00

0.040

0.050

G10400

1040

0.37-0.44

0.60-0.90

0.040

0.050

G10420

1042

0.40-0.47

0.60-0.90

0.040

0.050

G10430

1043

0.40-0.47

0.70-1.00

0.040

0.050

G10440

1044

0.43-0.50

0.30-0.60

0.040

0.050

G10450

1045

0.43-0.50

0.60-0.90

0.040

0.050

G10460

1046

0.43-0.50

0.70-1.00

0.040

0.050

G10490

1049

0.46-0.53

0.60-0.90

0.040

0.050

G10500

1050

0.48-0.55

0.60-0.90

0.040

0.050

G10530

1053

0.48-0.55

0.70-1.00

0.040

0.050

G10550

1055

0.50-0.60

0.60-0.90

0.040

0.050

G10590

1059

0.55-0.65

0.50-0.80

0.040

0.050

G10600

1060

0.55-0.65

0.60-0.90

0.040

0.050

G10640

1064

0.60-0.70

0.50-0.80

0.040

0.050

G10650

1065

0.60-0.70

0.60-0.90

0.040

0.050

G10690

1069

0.65-0.75

0.40-0.70

0.040

0.050

G10700

1070

0.65-0.75

0.60-0.90

0.040

0.050

G10740

1074

0.70-0.80

0.50-0.80

0.040

0.050

G10750

1075

0.70-0.80

0.40-0.70

0.040

0.050

G10780

1078

0.72-0.85

0.30-0.60

0.040

0.050

G10800

1080

0.75-0.88

0.60-0.90

0.040

0.050

G10840

1084

0.80-0.93

0.60-0.90

0.040

0.050

G10850

1085

0.80-0.93

0.70-1.00

0.040

0.050

G10860

1086

0.80-0.93

0.30-0.50

0.040

0.050

G10900

1090

0.85-0.98

0.60-0.90

0.040

0.050

G10950

(a)

1095

0.90-1.03

0.30-0.50

0.040

0.050

When silicon ranges or limits are required for bar and semifinished products, the following ranges are commonly used: 0.10% max; 0.10 to 0.20%; 0.15 to 0.35%; 0.20 to 0.40%; or 0.30-0.60%. For rods, the following ranges are commonly used: 0.10 max; 0.07-0.15%; 0.100.20%; 0.15-0.35%; 0.20-0.40%; and 0.30-0.60%. Steels listed in this table can be produced with additions of lead or boron. Leaded steels typically contain 0.15-0.35% Pb and are identified by inserting the letter L in the designation (10L45); boron steels can be expected to contain 0.0005-0.003% B and are identified by inserting the letter B in the designation (10B46).

Table 11 Carbon steel compositions Applicable only to structural shapes, plates, strip, sheets, and welded tubing Designation

Cast or heat ranges and limits(a), %

chemical

UNS No.

SAE-AISI No.

C

Mn

P max

S max

G10060

1006

0.08 max

0.45 max

0.040

0.050

G10080

1008

0.10 max

0.50 max

0.040

0.050

G10090

1009

0.15 max

0.60 max

0.040

0.050

G10100

1010

0.08-0.13

0.30-0.60

0.040

0.050

G10120

1012

0.10-0.15

0.30-0.60

0.040

0.050

G10150

1015

0.12-0.18

0.30-0.60

0.040

0.050

G10160

1016

0.12-0.18

0.60-0.90

0.040

0.050

G10170

1017

0.14-0.20

0.30-0.60

0.040

0.050

G10180

1018

0.14-0.20

0.60-0.90

0.040

0.050

G10190

1019

0.14-0.20

0.70-1.00

0.040

0.050

G10200

1020

0.17-0.23

0.30-0.60

0.040

0.050

G10210

1021

0.17-0.23

0.60-0.90

0.040

0.050

G10220

1022

0.17-0.23

0.70-1.00

0.040

0.050

G10230

1023

0.19-0.25

0.30-0.60

0.040

0.050

G10250

1025

0.22-0.28

0.30-0.60

0.040

0.050

G10260

1026

0.22-0.28

0.60-0.90

0.040

0.050

G10300

1030

0.27-0.34

0.60-0.90

0.040

0.050

G10330

1033

0.29-0.36

0.70-1.00

0.040

0.050

G10350

1035

0.31-0.38

0.60-0.90

0.040

0.050

G10370

1037

0.31-0.38

0.70-1.00

0.040

0.050

G10380

1038

0.34-0.42

0.60-0.90

0.040

0.050

G10390

1039

0.36-0.44

0.70-1.00

0.040

0.050

G10400

1040

0.36-0.44

0.60-0.90

0.040

0.050

G10420

1042

0.39-0.47

0.60-9.90

0.040

0.050

G10430

1043

0.39-0.47

0.70-1.00

0.040

0.050

G10450

1045

0.42-0.50

0.60-0.90

0.040

0.050

G10460

1046

0.42-0.50

0.70-1.00

0.040

0.050

G10490

1049

0.45-0.53

0.60-0.90

0.040

0.050

G10500

1050

0.47-0.55

0.60-0.90

0.040

0.050

G10550

1055

0.52-0.60

0.60-0.90

0.040

0.050

G10600

1060

0.55-0.66

0.60-0.90

0.040

0.050

G10640

1064

0.59-0.70

0.50-0.80

0.040

0.050

G10650

1065

0.59-0.70

0.60-0.90

0.040

0.050

G10700

1070

0.65-0.76

0.60-0.90

0.040

0.050

G10740

1074

0.69-0.80

0.50-0.80

0.040

0.050

G10750

1075

0.69-0.80

0.40-0.70

0.040

0.050

G10780

1078

0.72-0.86

0.30-0.60

0.040

0.050

G10800

1080

0.74-0.88

0.60-0.90

0.040

0.050

G10840

1084

0.80-0.94

0.60-0.90

0.040

0.050

G10850

1085

0.80-0.94

0.70-1.00

0.040

0.050

G10860

1086

0.80-0.94

0.30-0.50

0.040

0.050

G10900

1090

0.84-0.98

0.60-0.90

0.040

0.050

G10950

1095

0.90-1.04

0.30-0.50

0.040

0.050

(a)

When silicon ranges or limits are required, the following ranges and limits are commonly used: up to SAE 1025 inclusive, 0.10% max, 0.100.25%, or 0.15-0.35%. Over SAE 1025, 0.10-0.25% or 0.15-0.35%.

Table 12 Composition ranges and limits for merchant quality steels SAE-AISI No.

Cast or heat ranges and limits(a), %

chemical

C

Mn

P max

S max

M1008

0.10 max

0.25-0.60

0.04

0.05

M1010

0.07-0.14

0.25-0.60

0.04

0.05

M1012

0.09-0.16

0.25-0.60

0.04

0.05

M1015

0.12-0.19

0.25-0.60

0.04

0.05

M1017

0.14-0.21

0.25-0.60

0.04

0.05

M1020

0.17-0.24

0.25-0.60

0.04

0.05

M1023

0.19-0.27

0.25-0.60

0.04

0.05

M1025

0.20-0.30

0.25-0.60

0.04

0.05

M1031

0.26-0.36

0.25-0.60

0.04

0.05

M1044

0.40-0.50

0.25-0.60

0.04

0.05

(a) Merchant quality steel bars are not produced to any specified silicon content.

Free-Machining Grades. Resulfurized carbon steels in the 11xx group are listed in Table 13, and resulfurized and

rephosphorized carbon steels in the 12xx group are listed in Table 14. Both of these groups of steels are produced for applications requiring good machinability. Table 13 Free-machining (resulfurized) carbon steel compositions Applicable to semifinished products for forging, hot-rolled and cold-finished bars, wire rods, and seamless tubing Designation

Cast or heat chemical ranges and limits(a), %

UNS No.

SAE-AISI No.

C

Mn

P max

S

G11080

1108

0.08-0.13

0.50-0.80

0.040

0.08-0.13

G11100

1110

0.08-0.13

0.30-0.60

0.040

0.08-0.13

G11170

1117

0.14-0.20

1.00-1.30

0.040

0.08-0.13

G11180

1118

0.14-0.20

1.30-1.60

0.040

0.08-0.13

G11370

1137

0.32-0.39

1.35-1.65

0.040

0.08-0.13

G11390

1139

0.35-0.43

1.35-1.65

0.040

0.13-0.20

G11400

1140

0.37-0.44

0.70-1.00

0.040

0.08-0.13

G11410

1141

0.37-0.45

1.35-1.65

0.040

0.08-0.13

G11440

1144

0.40-0.48

1.35-1.65

0.040

0.24-0.33

G11460

1146

0.42-0.49

0.70-1.00

0.040

0.08-0.13

G11510

1151

0.48-0.55

0.70-1.00

0.040

0.08-0.13

(a) When lead ranges or limits are required, or when silicon ranges or limits are required for bars or semifinished products, the values in Table 10 apply. For rods, the following ranges and limits for silicon are commonly used: up to SAE 1110 inclusive, 0.10% max; SAE 1117 and over,

0.10% max, 0.10-0.20%, or 0.15-0.35%.

Table 14 Free-machining (rephosphorized and resulfurized) carbon steel compositions Applicable to semifinished products for forging, hot-rolled and cold-finished bars, wire rods, and seamless tubing Designation

Cast or heat chemical ranges and limits(a), %

UNS No.

SAE-AISI No.

C max

Mn

P

S

Pb

G12110

1211

0.13

0.60-0.90

0.07-0.12

0.10-0.15

...

G12120

1212

0.13

0.70-1.00

0.07-0.12

0.16-0.23

...

G12130

1213

0.13

0.70-1.00

0.07-0.12

0.24-0.33

...

G12150

1215

0.09

0.75-1.05

0.04-0.09

0.26-0.35

...

G12144

12L14

0.15

0.85-1.15

0.04-0.09

0.26-0.35

0.15-0.35

(a)

When lead ranges or limits are required, the values in Table 10 apply. It is not common practice to produce the 12xx series of steels to specified limits for silicon because of its adverse effect on machinability.

Plain-Carbon Steels (1.0 to 1.65% Mn). Tables 15 and 16 list steels having nominal manganese content of between 0.9 and 1.5% but no other alloying additions; these steels now have 15xx designations in place of the 10xx designations formerly used.

Table 15 High-manganese carbon steel compositions Applicable only to semifinished products for forging, hot-rolled and cold-finished bars, wire rods, and seamless tubing Designation

Cast or heat chemical ranges and limits(a), %

UNS No.

SAE-AISI No.

C

Mn

P max

S max

G15130

1513

0.10-0.16

1.10-1.40

0.040

0.050

G15220

1522

0.18-0.24

1.10-1.40

0.040

0.050

G15240

1524

0.19-0.25

1.35-1.65

0.040

0.050

G15260

1526

0.22-0.29

1.10-1.40

0.040

0.050

G15270

1527

0.22-0.29

1.20-1.50

0.040

0.050

G15360

1536

0.30-0.37

1.20-1.50

0.040

0.050

G15410

1541

0.36-0.44

1.35-1.65

0.040

0.050

G15480

1548

0.44-0.52

1.10-1.40

0.040

0.050

G15510

1551

0.45-0.56

0.85-1.15

0.040

0.050

G15520

1552

0.47-0.55

1.20-1.50

0.040

0.050

G15610

1561

0.55-0.65

0.75-1.05

0.040

0.050

G15660

1566

0.60-0.71

0.85-1.15

0.040

0.050

(a) When silicon, lead, and boron ranges or limits are required, the values in Table 10 apply.

Table 16 High-manganese carbon steel compositions Applicable only to structural shapes, plates, strip, sheets, and welded tubing Former SAE number

Designation

Cast or heat chemical ranges and limits(a), %

UNS No.

SAE-AISI No.

C max

Mn

P max

S max

G15240

1524

0.18-0.25

1.30-1.65

0.040

0.050

1024

G15270

1527

0.22-0.29

1.20-1.55

0.040

0.050

1027

G15360

1536

0.30-0.38

1.20-1.55

0.040

0.050

1036

G15410

1541

0.36-0.45

1.30-1.65

0.040

0.050

1041

G15480

1548

0.43-0.52

1.05-1.40

0.040

0.050

1048

G15520

1552

0.46-0.55

1.20-1.55

0.040

0.050

1052

(a) When silicon ranges or limits are required, the values shown in Table 11 apply.

H-Steels. Certain steels have hardenability requirements in addition to the limits and ranges of chemical composition.

They are distinguished from similar grades that have no hardenability requirements by the use of the suffix H (Table 17). Hardenability bands for the steels listed in Table 17 can be found in SAE J1268.

Table 17 Composition of carbon and carbon-boron H-steels UNS No.

SAE or AISI No.

Ladle chemical composition, wt%

C

Mn

Si

P, maximum(a)

S, maximum(a)

H10380

1038H

0.34-0.43

0.50-1.00

0.15-0.35

0.040

0.050

H10450

1045H

0.42-0.51

0.50-1.00

0.15-0.35

0.040

0.050

H15220

1522H

0.17-0.25

1.00-1.50

0.15-0.35

0.040

0.050

H15240

1524H

0.18-0.26

1.25-1.75

0.15-0.35

0.040

0.050

H15260

1526H

0.21-0.30

1.00-1.50

0.15-0.35

0.040

0.050

H15410

1541H

0.35-0.45

1.25-1.75

0.15-0.35

0.040

0.050

H15211

15B21H(b)

0.17-0.24

0.70-1.20

0.15-0.35

0.040

0.050

H15281

15B28H(b)

0.25-0.34

1.00-1.50

0.15-0.35

0.040

0.050

H15301

15B30H(b)

0.27-0.35

0.70-1.20

0.15-0.35

0.040

0.050

H15351

15B35H(b)

0.31-0.39

0.70-1.20

0.15-0.35

0.040

0.050

H15371

15B37H(b)

0.30-0.39

1.00-1.50

0.15-0.35

0.040

0.050

H15411

15B41H(b)

0.35-0.45

1.25-1.75

0.15-0.35

0.040

0.050

H15481

15B48H(b)

0.43-0.53

1.00-1.50

0.15-0.35

0.040

0.050

(a) If electric furnace practice is specified or required, the limit for both phosphorus and sulfur is 0.025%, and the prefix E is added to the SAE or AISI number.

(b) These steels contain 0.005 to 0.003% B.

SAE-AISI Designations for Alloy Steels Using the SAE-AISI designation system, a steel is considered an alloy steel when the maximum content range of alloying elements exceeds one or more of the following limits: 1.65% Mn, 0.60% Si, or 0.60% Cu. Also included in the recognized field of alloy steels are steels with a specified or required range or minimum quantity of the following

elements: aluminum, boron, chromium (up to 3.99%), cobalt, niobium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium, or any other alloying element added to increase hardenability in order to optimize mechanical properties and toughness after heat treatment. In some cases, however, alloy additions are used to reduce environmental degradation under certain specified service conditions. In general, total alloy content for SAE-AISI constructional steels does not exceed 5%. Alloy sheet and strip are available as hot-rolled and cold-rolled steel in coils and cut lengths. Other product forms of alloy steel covered by SAE-AISI designations include hot-rolled plate and hot-rolled, cold-rolled, and cold-drawn bar, rod, and wire. In the SAE-AISI system of designations, the major alloying elements in an alloy steel are indicated by the first two digits of the designation (Table 9). The amount of carbon, in hundredths of a percent, is indicated by the last two (or three) digits. The chemical compositions of SAE-AISI standard grades of alloy steels are given in Tables 18 and 19. For alloy steels that have specific hardenability requirements, the suffix H is used to distinguish these steels from corresponding grades that have no hardenability requirement (Table 20). Corresponding hardenability bands for these steels is described in SAE J1268. As with carbon steels, the letter B inserted between the second and third digits indicates that the steel contains boron. The prefix E signifies that the steel was produced by the electric furnace process. Table 18 Alloy steel compositions applicable to billets, blooms, slabs, and hot-rolled and cold-finished bars Ladle chemical composition limits(a), %

Designation

UNS No.

SAE No.

Corresponding AISI No.

C

Mn

P

S

Si

Ni

Cr

Mo

V

G13300

1330

1330

0.280.33

1.601.90

0.035

0.040

0.150.35

...

...

...

...

G13350

1335

1335

0.330.38

1.601.90

0.035

0.040

0.150.35

...

...

...

...

G13400

1340

1340

0.380.43

1.601.90

0.035

0.040

0.150.35

...

...

...

...

G13450

1345

1345

0.430.48

1.601.90

0.035

0.040

0.150.35

...

...

...

...

G40230

4023

4023

0.200.25

0.700.90

0.035

0.040

0.150.35

...

...

...

...

G40240

4024

4024

0.200.25

0.700.90

0.035

0.0350.050

0.150.35

...

...

0.200.30

...

G40270

4027

4027

0.250.30

0.700.90

0.035

0.040

0.150.35

...

...

0.200.30

...

G40280

4028

4028

0.250.30

0.700.90

0.035

0.0350.050

0.150.35

...

...

0.200.30

...

G40320

4032

...

0.300.35

0.700.90

0.035

0.040

0.150.35

...

...

0.200.30

...

G40370

4037

4037

0.350.40

0.700.90

0.035

0.040

0.150.35

...

...

0.200.30

...

G40420

4042

...

0.400.45

0.700.90

0.035

0.040

0.150.35

...

...

0.200.30

...

G40470

4047

4047

0.450.50

0.700.90

0.035

0.040

0.150.35

...

...

0.200.30

...

G41180

4118

4118

0.180.23

0.700.90

0.035

0.040

0.150.35

...

0.400.60

0.080.15

...

G41300

4130

4130

0.280.33

0.400.60

0.035

0.040

0.150.35

...

0.801.10

0.150.25

...

G41350

4135

...

0.330.38

0.700.90

0.035

0.040

0.150.35

...

0.801.10

0.150.25

...

G41370

4137

4137

0.350.40

0.700.90

0.035

0.040

0.150.35

...

0.801.10

0.150.25

...

G41400

4140

4140

0.380.43

0.751.00

0.035

0.040

0.150.35

...

0.801.10

0.150.25

...

G41420

4142

4142

0.400.45

0.751.00

0.035

0.040

0.150.35

...

0.801.10

0.150.25

...

G41450

4145

4145

0.410.48

0.751.00

0.035

0.040

0.150.35

...

0.801.10

0.150.25

...

G41470

4147

4147

0.450.50

0.751.00

0.035

0.040

0.150.35

...

0.801.10

0.150.25

...

G41500

4150

4150

0.480.53

0.751.00

0.035

0.040

0.150.35

...

0.801.10

0.150.25

...

G41610

4161

4161

0.560.64

0.751.00

0.035

0.040

0.150.35

...

0.700.90

0.250.35

...

G43200

4320

4320

0.170.22

0.450.65

0.035

0.040

0.150.35

1.652.00

0.400.60

0.200.30

...

G43400

4340

4340

0.380.43

0.600.80

0.035

0.040

0.150.35

1.652.00

0.700.90

0.200.30

...

G43406

E4340(b)

E4340

0.380.43

0.650.85

0.025

0.025

0.150.35

1.652.00

0.700.90

0.200.30

...

G44220

4422

...

0.200.25

0.700.90

0.035

0.040

0.150.35

...

...

0.350.45

...

G44270

4427

...

0.240.29

0.700.90

0.035

0.040

0.150.35

...

...

0.350.45

...

G46150

4615

4615

0.130.18

0.450.65

0.035

0.040

0.150.25

1.652.00

...

0.200.30

...

G46170

4617

...

0.150.20

0.450.65

0.035

0.040

0.150.35

1.652.00

...

0.200.30

...

G46200

4620

4620

0.170.22

0.450.65

0.035

0.040

0.150.35

1.652.00

...

0.200.30

...

G46260

4626

4626

0.240.29

0.450.65

0.035

0.04 max

0.150.35

0.701.00

...

0.150.25

...

G47180

4718

4718

0.160.21

0.700.90

...

...

...

0.901.20

0.350.55

0.300.40

...

G47200

4720

4720

0.170.22

0.500.70

0.035

0.040

0.150.35

0.901.20

0.350.55

0.150.25

...

G48150

4815

4815

0.130.18

0.400.60

0.035

0.040

0.150.35

3.253.75

...

0.200.30

...

G48170

4817

4817

0.150.20

0.400.60

0.035

0.040

0.150.35

3.253.75

...

0.200.30

...

G48200

4820

4820

0.180.23

0.500.70

0.035

0.040

0.150.35

3.253.75

...

0.200.30

...

G50401

50B40(c)

...

0.380.43

0.751.00

0.035

0.040

0.150.35

...

0.400.60

...

...

G50441

50B44(c)

50B44

0.430.48

0.751.00

0.035

0.040

0.150.35

...

0.400.60

...

...

G50460

5046

...

0.430.48

0.751.00

0.035

0.040

0.150.35

...

0.200.35

...

...

G50461

50B46(c)

50B46

0.440.49

0.751.00

0.035

0.040

0.150.35

...

0.200.35

...

...

G50501

50B50(c)

50B50

0.480.53

0.751.00

0.035

0.040

0.150.35

...

0.400.60

...

...

G50600

5060

...

0.560.64

0.751.00

0.035

0.040

0.150.35

...

0.400.60

...

...

G50601

50B60(c)

50B60

0.560.64

0.751.00

0.035

0.040

0.150.35

...

0.400.60

...

...

G51150

5115

...

0.130.18

0.700.90

0.035

0.040

0.150.35

...

0.700.90

...

...

G51170

5117

5117

0.150.20

0.700.90

0.040

0.040

0.150.35

...

0.700.90

...

...

G51200

5120

5120

0.170.22

0.700.90

0.035

0.040

0.150.35

...

0.700.90

...

...

G51300

5130

5130

0.280.33

0.700.90

0.035

0.040

0.150.35

...

0.801.10

...

...

G51320

5132

5132

0.300.35

0.600.80

0.035

0.040

0.150.35

...

0.751.00

...

...

G51350

5135

5135

0.330.38

0.600.80

0.035

0.040

0.150.35

...

0.801.05

...

...

G51400

5140

5140

0.380.43

0.700.90

0.035

0.040

0.150.35

...

0.700.90

...

...

G51470

5147

5147

0.460.51

0.700.95

0.035

0.040

0.150.35

...

0.851.15

...

...

G51500

5150

5150

0.480.53

0.700.90

0.035

0.040

0.150.35

...

0.700.90

...

...

G51550

5155

5155

0.510.59

0.700.90

0.035

0.040

0.150.35

...

0.700.90

...

...

G51600

5160

5160

0.560.64

0.751.00

0.035

0.040

0.150.35

...

0.700.90

...

...

G51601

51B60(c)

51B60

0.560.64

0.751.00

0.035

0.040

0.150.35

...

0.700.90

...

...

G50986

50100(b)

...

0.981.10

0.250.45

0.025

0.025

0.150.35

...

0.400.60

...

...

G51986

51100(b)

E51100

0.981.10

0.250.45

0.025

0.025

0.150.35

...

0.901.15

...

...

G52986

52100(b)

E52100

0.981.10

0.250.45

0.025

0.025

0.150.35

...

1.301.60

...

...

G61180

6118

6118

0.160.21

0.500.70

0.035

0.040

0.150.35

...

0.500.70

...

0.100.15

G61500

6150

6150

0.480.53

0.700.90

0.035

0.040

0.150.35

...

0.801.10

...

0.15 min

G81150

8115

8115

0.130.18

0.700.90

0.035

0.040

0.150.35

0.200.40

0.300.50

0.080.15

...

G81451

81B45(c)

81B45

0.430.48

0.751.00

0.035

0.040

0.150.35

0.200.40

0.350.55

0.080.15

...

G86150

8615

8615

0.130.18

0.700.90

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86170

8617

8617

0.150.20

0.700.90

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86200

8620

8620

0.180.23

0.700.90

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86220

8622

8622

0.200.25

0.700.90

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86250

8625

8625

0.230.28

0.700.90

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86270

8627

8627

0.250.30

0.700.90

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86300

8630

8630

0.280.33

0.700.90

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86370

8637

8637

0.350.40

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86400

8640

8640

0.380.43

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86420

8642

8642

0.400.45

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86450

8645

8645

0.430.48

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86451

86B45(c)

...

0.430.48

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86500

8650

...

0.480.53

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86550

8655

8655

0.510.59

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G86600

8660

...

0.560.64

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.150.25

...

G87200

8720

8720

0.180.23

0.700.90

0.035

0.040

0.150.35

0.400.70

0.400.60

0.200.30

...

G87400

8740

8740

0.380.43

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.200.30

...

G88220

8822

8822

0.200.25

0.751.00

0.035

0.040

0.150.35

0.400.70

0.400.60

0.300.40

...

G92540

9254

...

0.510.59

0.600.80

0.035

0.040

1.201.60

...

0.600.80

...

...

G92600

9260

9260

0.560.64

0.751.00

0.035

0.040

1.802.20

...

...

...

...

G93106

9310(b)

...

0.080.13

0.450.65

0.025

0.025

0.150.35

3.003.50

1.001.40

0.080.15

...

G94151

94B15(c)

...

0.130.18

0.751.00

0.035

0.040

0.150.35

0.300.60

0.300.50

0.080.15

...

G94171

94B17(c)

94B17

0.150.20

0.751.00

0.035

0.040

0.150.35

0.300.60

0.300.50

0.080.15

...

G94301

94B30(c)

94B30

0.280.33

0.751.00

0.035

0.040

0.150.35

0.300.60

0.300.50

0.080.15

...

(a) Small quantities of certain elements that are not specified or required may be found in alloy steels. These elements are to be considered as incidental and are acceptable to the following maximum amount: copper to 0.35%, nickel to 0.25%, chromium to 0.20%, and molybdenum to 0.06%.

(b) Electric furnace steel.

(c) Boron content is 0.0005-0.003%.

Table 19 Composition ranges and limits for SAE-AISI standard alloy steel plate applicable for structural applications Heat composition ranges and limits(a), %

Designation

SAE-AISI

UNS

C

Mn

Si(b)

Cr

Ni

Mo

1330

G13300

0.27-0.34

1.50-1.90

0.15-0.30

...

...

...

1335

G13350

0.32-0.39

1.50-1.90

0.15-0.30

...

...

...

1340

G13400

0.36-0.44

1.50-1.90

0.15-0.30

...

...

...

1345

G13450

0.41-0.49

1.50-1.90

0.15-0.30

...

...

...

4118

G41180

0.17-0.23

0.60-0.90

0.15-0.30

0.40-0.65

...

0.08-0.15

4130

G41300

0.27-0.34

0.35-0.60

0.15-0.30

0.80-1.15

...

0.15-0.25

4135

G41350

0.32-0.39

0.65-0.95

0.15-0.30

0.80-1.15

...

0.15-0.25

4137

G41370

0.33-0.40

0.65-0.95

0.15-0.30

0.80-1.15

...

0.15-0.25

4140

G41400

0.36-0.44

0.70-1.00

0.15-0.30

0.80-1.15

...

0.15-0.25

4142

G41420

0.38-0.46

0.70-1.00

0.15-0.30

0.80-1.15

...

0.15-0.25

4145

G41450

0.41-0.49

0.70-1.00

0.15-0.30

0.80-1.15

...

0.15-0.25

4340

G43400

0.36-0.44

0.55-0.80

0.15-0.30

0.60-0.90

1.65-2.00

0.20-0.30

E4340(c)

G43406

0.37-0.44

0.60-0.85

0.15-0.30

0.65-0.90

1.65-2.00

0.20-0.30

4615

G46150

0.12-0.18

0.40-0.65

0.15-0.30

...

1.65-2.00

0.20-0.30

4617

G46170

0.15-0.21

0.40-0.65

0.15-0.30

...

1.65-2.00

0.20-0.30

4620

G46200

0.16-0.22

0.40-0.65

0.15-0.30

...

1.65-2.00

0.20-0.30

5160

G51600

0.54-0.65

0.70-1.00

0.15-0.30

0.60-0.90

...

...

6150(d)

G61500

0.46-0.54

0.60-0.90

0.15-0.30

0.80-1.15

...

...

8615

G86150

0.12-0.18

0.60-0.90

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8617

G86170

0.15-0.21

0.60-0.90

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8620

G86200

0.17-0.23

0.60-0.90

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8622

G86220

0.19-0.25

0.60-0.90

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8625

G86250

0.22-0.29

0.60-0.90

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8627

G86270

0.24-0.31

0.60-0.90

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8630

G86300

0.27-0.34

0.60-0.90

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8637

G86370

0.33-0.40

0.70-1.00

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8640

G86400

0.36-0.44

0.70-1.00

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8655

G86550

0.49-0.60

0.70-1.00

0.15-0.30

0.35-0.60

0.40-0.70

0.15-0.25

8742

G87420

0.38-0.46

0.70-1.00

0.15-0.30

0.35-0.60

0.40-0.70

0.20-0.30

Boron or lead can be added to these compositions. Small quantities of certain elements not required may be found. These elements are to be considered incidental and are acceptable to the following maximum amounts: copper to 0.35%, nickel to 0.25%, chromium to 0.20%, and molybdenum to 0.06%. (a) Indicated ranges and limits apply to steels made by the open hearth or basic oxygen processes; maximum content for phosphorus is 0.035% and for sulfur 0.040%. For steels made by the electric furnace process, the ranges and limits are reduced as follows: C to 0.01%; Mn to 0.05%; Cr to 0.05% (1.25%); maximum content for either phosphorus or sulfur is 0.025%.

(b) Other silicon ranges may be negotiated. Silicon is available in ranges of 0.10-0.20%, 0.20-0.30%, and 0.35% maximum (when carbon deoxidized) when so specified by the purchaser.

(c) Prefix "E" indicates that the steel is made by the electric furnace process.

(d) Contains 0.15% V minimum

Table 20 Composition of standard alloy H-steels Ladle chemical composition(a)(b), wt%

H-steel

UNS No.

SAE or AISI No.

C

Mn

Si

Ni

Cr

Mo

V

H13300

1330H

0.27-0.33

1.45-2.05

0.15-0.35

...

...

...

...

H13350

1335H

0.32-0.38

1.45-2.05

0.15-0.35

...

...

...

...

H13400

1340H

0.37-0.44

1.45-2.05

0.15-0.35

...

...

...

...

H13450

1345H

0.42-0.49

1.45-2.05

0.15-0.35

...

...

...

...

H40270

4027H

0.24-0.30

0.60-1.00

0.15-0.35

...

...

0.20-0.30

...

H40280(c)

4028H(c)

0.24-0.30

0.60-1.00

0.15-0.35

...

...

0.20-0.30

...

H40320

4032H

0.29-0.35

0.60-1.00

0.15-0.35

...

...

0.20-0.30

...

H40370

4037H

0.34-0.41

0.60-1.00

0.15-0.35

...

...

0.20-0.30

...

H40420

4042H

0.39-0.46

0.60-1.00

0.15-0.35

...

...

0.20-0.30

...

H40470

4047H

0.44-0.51

0.60-1.00

0.15-0.35

...

...

0.20-0.30

...

H41180

4118H

0.17-0.23

0.60-1.00

0.15-0.35

...

0.30-0.70

0.08-0.15

...

H41300

4130H

0.27-0.33

0.30-0.70

0.15-0.35

...

0.75-1.20

0.15-0.25

...

H41350

4135H

0.32-0.38

0.60-1.00

0.15-0.35

...

0.75-1.20

0.15-0.25

...

H41370

4137H

0.34-0.41

0.60-1.00

0.15-0.35

...

0.75-1.20

0.15-0.25

...

H41400

4140H

0.37-0.44

0.65-1.10

0.15-0.35

...

0.75-1.20

0.15-0.25

...

H41420

4142H

0.39-0.46

0.65-1.10

0.15-0.35

...

0.75-1.20

0.15-0.25

...

H41450

4145H

0.42-0.49

0.65-1.10

0.15-0.35

...

0.75-1.20

0.15-0.25

...

H41470

4147H

0.44-0.51

0.65-1.10

0.15-0.35

...

0.75-1.20

0.15-0.25

...

H41500

4150H

0.47-0.54

0.65-1.10

0.15-0.35

...

0.75-1.20

0.15-0.25

...

H41610

4161H

0.55-0.65

0.65-1.10

0.15-0.35

...

0.65-0.95

0.25-0.35

...

H43200

4320H

0.17-0.23

0.40-0.70

0.15-0.35

1.55-2.00

0.35-0.65

0.20-0.30

...

H43400

4340H

0.37-0.44

0.55-0.90

0.15-0.35

1.55-2.00

0.65-0.95

0.20-0.30

...

H43406(d)

E4340H(d)

0.37-0.44

0.60-0.95

0.15-0.35

1.55-2.00

0.65-0.95

0.20-0.30

...

H46200

4620H

0.17-0.23

0.35-0.75

0.15-0.35

1.55-2.00

...

0.20-0.30

...

H47180

4718H

0.15-0.21

0.60-0.95

0.15-0.35

0.85-1.25

0.30-0.60

0.30-0.40

...

H47200

4720H

0.17-0.23

0.45-0.75

0.15-0.35

0.85-1.25

0.30-0.60

0.15-0.25

...

H48150

4815H

0.12-0.18

0.30-0.70

0.15-0.35

3.20-3.80

...

0.20-0.30

...

H48170

4817H

0.14-0.20

0.30-0.70

0.15-0.35

3.20-3.80

...

0.20-0.30

...

H48200

4820H

0.17-0.23

0.40-0.80

0.15-0.35

3.20-3.80

...

0.20-0.30

...

H50401(e)

50B40H(e)

0.37-0.44

0.65-1.10

0.15-0.35

...

0.30-0.70

...

...

H50441(e)

50B44H(e)

0.42-0.49

0.65-1.10

0.15-0.35

...

0.30-0.70

...

...

H50460

5046H

0.43-0.50

0.65-1.10

0.15-0.35

...

0.13-0.43

...

...

H50461(e)

50B46H(e)

0.43-0.50

0.65-1.10

0.15-0.35

...

0.13-0.43

...

...

H50501(e)

50B50H(e)

0.47-0.54

0.65-1.10

0.15-0.35

...

0.30-0.70

...

...

H50601(e)

50B60H(e)

0.55-0.65

0.65-1.10

0.15-0.35

...

0.30-0.70

...

...

H51200

5120H

0.17-0.23

0.60-1.00

0.15-0.35

...

0.60-1.00

...

...

H51300

5130H

0.27-0.33

0.60-1.10

0.15-0.35

...

0.75-1.20

...

...

H51320

5132H

0.29-0.35

0.50-0.90

0.15-0.35

...

0.65-1.10

...

...

H51350

5135H

0.32-0.38

0.50-0.90

0.15-0.35

...

0.70-1.15

...

...

H51400

5140H

0.37-0.44

0.60-1.00

0.15-0.35

...

0.60-1.00

...

...

H51470

5147H

0.45-0.52

0.60-1.05

0.15-0.35

...

0.80-1.25

...

...

H51500

5150H

0.47-0.54

0.60-1.00

0.15-0.35

...

0.60-1.00

...

...

H51550

5155H

0.50-0.60

0.60-1.00

0.15-0.35

...

0.60-1.00

...

...

H51600

5160H

0.55-0.65

0.65-1.10

0.15-0.35

...

0.60-1.00

...

...

H51601(e)

51B60H(e)

0.55-0.65

0.65-1.10

0.15-0.35

...

0.60-1.00

...

...

H61180

6118H

0.15-0.21

0.40-0.80

0.15-0.35

...

0.40-0.80

...

0.10-0.15

H61500

6150H

0.47-0.54

0.60-1.00

0.15-0.35

...

0.75-1.20

...

0.15

H81451(e)

81B4S5(e)

0.42-0.49

0.70-1.05

0.15-0.35

0.15-0.45

0.30-0.60

0.08-0.15

...

H86170

8617H

0.14-0.20

0.60-0.95

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86200

8620H

0.17-0.23

0.60-0.95

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86220

8622H

0.19-0.25

0.60-9.95

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86250

8625H

0.22-0.28

0.60-0.95

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86270

8627H

0.24-0.30

0.60-0.95

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86300

8630H

0.27-0.33

0.60-0.95

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86301(e)

86B30H(e)

0.27-0.33

0.60-0.95

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86370

8637H

0.34-0.41

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86400

8640H

0.37-0.44

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86420

8642H

0.39-0.46

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86450

8645H

0.42-0.49

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86451(e)

86B45H9(e)

0.42-0.49

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86500

8650H

0.47-0.54

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86550

8655H

0.50-0.60

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H86600

8660H

0.55-0.65

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.15-0.25

...

H87200

8720H

0.17-0.23

0.60-0.95

0.15-0.35

0.35-0.75

0.35-0.65

0.20-0.30

...

H87400

8740H

0.37-0.44

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.20-0.30

...

H88220

8822H

0.19-0.25

0.70-1.05

0.15-0.35

0.35-0.75

0.35-0.65

0.30-0.40

...

H92600

9260H

0.55-0.65

0.65-1.10

1.70-2.20

...

...

...

...

H93100(d)

9310H(d)

0.07-0.13

0.40-0.70

0.15-0.35

2.95-3.55

1.00-1.45

0.08-0.15

...

H94151(e)

94B15H(e)

0.12-0.18

0.70-1.05

0.15-0.35

0.25-0.65

0.25-0.55

0.08-0.15

...

H94171(e)

94B17H(e)

0.14-0.20

0.70-1.05

0.15-0.35

0.25-0.65

0.25-0.55

0.08-0.15

...

H94301(e)

94B30H(e)

0.27-0.33

0.70-1.05

0.15-0.35

0.25-0.65

0.25-0.55

0.08-0.15

...

(a) Small quantities of certain elements may be found in alloy steel that are not specified or required. These elements are to be considered incidental and acceptable to the following maximum amounts: copper to 0.35%, nickel to 0.25%, chromium to 0.20%, and molybdenum to 0.06%.

(b) For open hearth and basic oxygen steels, maximum sulfur content is to be 0.040%, and maximum phosphorus content is to be 0.035%. Maximum phosphorus and sulfur in basic electric furnace steels are to be 0.025% each.

(c) Sulfur content range is 0.035-0.050%.

(d) Electric furnace steel.

(e) These steels contain 0.0005 to 0.003% B.

SAE-AISI Designations for High-Strength Steel Sheet Both SAE and AISI have developed designation systems for high-strength sheet steels (including both structural carbon and HSLA grades). Using these systems, a high-strength steel is defined as a sheet product having a minimum specified yield strength of 240 MPa (35 ksi), without regard to the chemical composition or processing used to achieve that strength level. Excepted from these classification systems are alloy steels and stainless steels. Table 21 compares the SAE and AISI systems.

Table 21 Comparison of the SAE and AISI designation systems for high-strength sheet steel Attribute

SAE

AISI

Yield strength(a), ksi

035

035

040

040

045

045

050

050

055

060

060

065

070

070

080

080

100

120

140

160

190

Chemistry(b)

A

S

B

S

C

S

S

S

W

W

X

X

Y

X

Z

X

D

Carbon level(c)

Deoxidation practice

H

...

L

...

O

O

K

K

F

F

(a) SAE, complete listing of applicable yield strengths shown in ksi. AISI, list of yield strengths is representative; more may be added at producer's option.

(b) A, B, C, and S under SAE represent various combinations of C, Mn, and N, and P content. These are grouped under S in AISI. X, Y, and Z in SAE represent microalloyed steels with 10 ksi, 15 ksi, and 20 ksi respective spreads between yield and tensile strength. These are grouped under X in AISI. The W grades are equivalent. There is no SAE equivalent for the AISI D chemistry.

(c) Value of carbon levels for H and L designations vary with the grade of steel in SAE.

SAE Sheet Designation System. SAE recommended practice J1392 covers high-strength hot-rolled, cold-rolled, and coated sheet steels and has replaced J410c for these particular product forms. The mechanical properties for the various grades covered by practice J1392 are given in Tables 22 and 23.

Table 22 Mechanical properties of hot-rolled high-strength sheet steel specified in SAE J1392 Grade

Yield strength (min)

Tensile strength (min)

Elongation in 2 in. (50 mm) (min)(a), %

ksi

MPa

ksi

MPa

035 A, B, C, S

35

240

(b)

(b)

21

035 X, Y, Z

35

240

(b)

(b)

28

A40 A, B, C, S

40

280

(b)

(b)

20

040 X, Y, Z

40

280

(b)

(b)

27

045 A, B, C, S

45

310

(b)

(b)

18

045 W

45

310

65

450

25

045 X

45

310

55

380

25

045 Y

45

310

60

410

25

045 Z

45

310

65

450

25

050 A, B, C, S

50

340

(b)

(b)

16

050 W

50

340

70

480

22

050 X

50

340

60

410

22

050 Y

50

340

65

450

22

050 Z

50

340

70

480

22

060 X

60

410

70

480

20

060 Y

60

410

75

520

20

070 X

70

480

80

550

17

070 Y

70

480

85

590

17

080 X

80

550

90

620

14

080 Y

80

550

95

650

14

(a) Elongation values are dependent upon specimen geometry (cross-sectional area). Thicker and wider specimens normally result in higher percentages.

(b) Minimum tensile strength normally does not apply.

Table 23 Mechanical properties of cold-rolled and coated high-strength sheet steel specified in SAE J1392 Grade

Yield strength (min)

Tensile strength (min)

ksi

ksi

MPa

MPa

Elongation in 2 in. (50 mm) (min)(a), %

035 A, B, C, S

35

240

(b)

(b)

22

035 X, Y, Z

35

240

(b)

(b)

27

040 A, B, C, S

40

280

(b)

(b)

20

040 X, Y, Z

40

280

(b)

(b)

25

045 A, B, C, S

45

310

(b)

(b)

18

045 W

45

310

65

450

22

045 X

45

310

55

380

22

045 Y

45

310

60

410

22

045 Z

45

310

65

450

22

050 A, B, C, S

50

340

(b)

(b)

16

050 X

50

340

60

410

20

050 Y

50

340

65

450

20

050 Z

50

340

70

480

20

(a) Elongation values are dependent upon specimen geometry (cross-sectional area). Thicker and wider specimens normally result in higher percentages.

(b) Minimum tensile strength normally does not apply.

A six-character code is used to describe strength level, general chemical composition, general carbon level, and the deoxidation/sulfide inclusion control system. The first, second, and third characters give the minimum yield strength in ksi; for example, 035 is 35 ksi, 040 is 40 ksi, and so forth. The fourth character describes the general chemical composition. The letter A means carbon and manganese only; B means carbon, manganese, and nitrogen; C means carbon, manganese, and phosphorus; S means carbon and manganese with nitrogen and/or phosphorus added at producer option; W refers to weathering compositions that include silicon, phosphorus, copper, nickel, and chromium in various combinations; X refers to HSLA compositions that contain niobium, chromium, copper, molybdenum, nickel, silicon, titanium, vanadium, and zirconium added singly or in combination (along with nitrogen and/or phosphorus if desired) and that exhibit a 10 ksi (70 MPa) spread between specified minimum values of yield and tensile strengths; Y refers to the same compositions as X except with a 15 ksi (100 MPa) spread between specified minimal values of yield and tensile strengths; Z refers to the same compositions as X except with a 20 ksi (40 MPa) spread between the specified minimum values of yield and tensile strengths.

The fifth character describes the general carbon level. The letter H refers to the maximum carbon level, and L means 0.13% C maximum. The sixth character describes deoxidation/sulfide inclusion control practices. The letter K means killed and made to a fine-grain practice, F means sulfide-inclusion controlled, killed, and made to a fine-grain practice; and O refers to other than K or F. The AISI designation system of high-strength sheet steels contains three basic components: the minimum yield strength, the chemical composition, and the deoxidation practice. A five-character code is used to describe these components.

The first three characters give the yield strength of a given grade. Yield strength is categorized in 5 ksi (35 MPa) increments from 35 to 60 ksi (241 to 414 MPa), in 10 ksi (70 MPa) increments from 60 to 80 ksi (414 to 550 MPa), in 20 ksi (140 MPa) increments from 80 to 140 ksi (550 to 965 MPa), and in 30 ksi (207 MPa) increments from 160 to 190 ksi (1100 to 1310 MPa). Thus, the designation "050" refers to a steel with a yield strength of 50 ksi (345 MPa). The chemical composition of each grade is designated by a letter classification: S, X, W, or D. The letter S refers to structural-quality steels that contain carbon plus manganese; carbon plus manganese and phosphorus; carbon plus manganese and nitrogen; or carbon plus manganese, phosphorus, and nitrogen. Recovery-annealed steels, except those with the designation X, are included in this category. The letter X refers to low-alloy steel grades containing niobium, chromium, copper, molybdenum, nickel, silicon, titanium, vanadium, and zirconium either singly or in combination. Weathering steels containing silicon, phosphorus, copper, nickel, and chromium in various combinations are indicated by the letter W. Dual-phase steels containing martensite or other transformation products in a ferrite matrix are designated by the letter D. Dual-phase steels exhibit very high work-hardening rates, and, as a result, formed parts have significantly higher strengths than do the original flat-rolled sheets. Consequently, the yield strength of a dual-phase steel is designated as the strength after a 5% strain; for example, an 080D grade exhibits an 80 ksi (550 MPa) yield strength after 5% strain. Deoxidation practice is also designated by a letter classification. The letter F means killed plus sulfide-inclusion controlled, K means killed, and O means nonkilled. For example, the steel designation 040SF would mean a minimum yield strength of 40 ksi (275 MPa), structural quality, killed.

UNS Designations The Unified Numbering System (UNS) has been developed by ASTM and SAE and several other technical societies, trade associations, and United States government agencies. A UNS number, which is a designation of chemical composition and not a specification, is assigned to each chemical composition of a metallic alloy. Available UNS designations are included in the tables in this article. The UNS designation of an alloy consists of a letter and five numerals. The letters indicate the broad class of alloys; the numerals define specific alloys within that class. Existing designation systems, such as the SAE-AISI system for steels, have been incorporated into UNS designations. For example, the UNS prefix letter for carbon and alloy steels is G, and the first four digits are the SAE-AISI designation, for example, G10400. The intermediate letters B and L of the SAEAISI system are replaced by making the fifth digit of the UNS designation 1 and 4 respectively, while the prefix letter E for electric furnace steels is designated in UNS system by making the fifth digit 6. The SAE-AISI steels which have a hardenability requirement indicated by the suffix letter H are designated by the Hxxxxx series in the UNS system. Carbon and alloy steels not referred to in the SAE-AISI system are categorized under the prefix letter K. The UNS designation system is described in greater detail in SAE J1086 and ASTM E 527.

AMS Designations Aerospace Materials Specifications (AMS), published by SAE, are complete specifications that are generally adequate for procurement purposes. Most of the AMS designations pertain to materials intended for aerospace applications; the specifications can include mechanical property requirements significantly more severe than those for grades of steel having similar compositions but intended for other applications. Processing requirements, such as for consumable electrode remelting, are common in AMS steels. Chemical compositions for AMS grades of carbon and steel alloys are given in Tables 24 and 25.

Table 24 Product descriptions and carbon contents for wrought carbon steels covered by AMS designations AMS designation

Product form

Carbon content

Nearest SAE-AISI grade

UNS No.

5010H

Bars (screw machine stock)

...

1112

G12120

5020C

Bars, forgings, tubing

0.32-0.39(a)

11L37

G11374

5022K

Bars, forgings, tubing

0.14-0.20

1117

G11170

5024F

Bars, forgings, tubing

0.32-0.39(b)

1137

G11370

5032D

Wire (annealed)

0.18-0.23

1020

G10200

5036G

Sheet, strip (aluminum coated, low carbon)

...

...

...

5040H

Sheet, strip (deep-forming grade)

0.15 max

1010

G10100

5042H

Sheet, strip (forming grade)

0.15 max

1010

G10100

5044F

Sheet, strip (half-hard temper)

0.15 max

1010

G10100

5045E

Sheet, strip (hard temper)

0.25 max

1020

G10200

5046

Sheet, strip, plate (annealed)

...

1020

G10200

5047C

Sheet, strip (aluminum killed, deep forming grade)

0.08-0.13

1010

G10100

5050H

Tubing (seamless, annealed)

0.15 max

1010

G10100

5053F

Tubing (welded, annealed)

0.15 max

1010

G10100

5060F

Bars, forgings, tubing

0.13-0.18

1015

G10150

5061D

Bars, wire

Low

...

K00802

5062E

Bars, forgings, tubing, plate, sheet, strip

Low

...

K02508

5069D

Bars, forgings, tubing

0.15-0.20

1018

G10180

5070F

Bars, forgings

0.18-0.23

1022

G10220

5075E

Tubing (seamless, cold drawn, stress relieved)

0.22-0.28

1025

G10250

5077D

Tubing (welded)

0.22-0.28

1025

G10250

5080G

Bars, forgings, tubing

0.31-0.38

1035

G10350

5082D

Tubing (seamless, stress relieved)

0.31-0.38

1035

G10350

5085D

Plate, sheet, strip (annealed)

0.47-0.55

1050

G10500

5110E

Wire (carbon, spring temper, cold drawn)

0.75-0.88

1080

G10800

5112H

Wire (spring quality music wire, cold drawn)

0.70-1.00

1090

G10900

5115F

Wire (valve spring quality, hardened and tempered)

0.60-0.75

1070

G10700

5120J

Strip

0.68-0.80

1074

G10740

5121F

Sheet, strip

0.90-1.04

1095

G10950

5122F

Strip (hard temper)

0.90-1.04

1095

G10950

5132G

Bars

0.90-1.30

1095

G10950

(a) Contains 1.5% Mn and 0.025% Pb.

(b) Contains 1.5% Mn

Table 25 Alloy steel product forms and compositions covered by AMS specifications AMS designation

Product form(a)

Nominal composition, %

6250H

Bars, forgings, tubing

6255

Bars, forgings, DVM)

tubing

(P,

C

Cr

Ni

Mo

Other

Nearest proprietary or SAE-AISI grade

UNS No.

0.070.13

1.5

3.5

...

...

3310

K44910

0.160.22

1.45

...

1.0

1.1 Si, 0.08 Al

CBS 600

K21940

6256A

Bars, forgings, DVM)

tubing

(P,

0.100.16

1.0

3.0

4.5

0.08 Al, 0.38 V

CBS 1000M

K71350

6260K

Bars, forgings, (carburizing)

tubing

0.070.13

1.2

3.2

0.12

...

9310

G93106

6263G

Bars, forgings, tubing (carburizing grade, aircraft)

0.110.17

1.2

3.2

0.12

...

9315

...

6264G

Bars, forgings, (carburizing)

0.140.20

1.2

3.2

0.12

...

9317

K44414

6265F

Bars, forgings, CVM)

0.070.13

1.2

3.25

0.12

...

9310

G93106

6266F

Bars, forgings, tubing

0.080.13

0.50

1.82

0.25

0.003 B, 0.06 V

43BV12

K21028

6267C

Bars, forgings, tubing

0.070.13

1.2

3.25

0.12

...

9310

G93106

6270L

Bars, forgings, tubing

0.110.17

0.50

0.55

0.20

...

8615

G86150

6272G

Bars, forgings, tubing

0.150.20

0.50

0.55

0.20

...

8617

G86170

6274K

Bars, forgings, tubing

0.180.23

0.50

0.55

0.20

...

8620

G86200

6275E

Bars, forgings, tubing

0.150.20

0.40

0.45

0.12

0.002 B

94B17

G94171

6276F

Bars, forgings, tubing (CVM)

0.180.23

0.50

0.55

0.2

...

8620

G86200

6277D

Bars, forgings, tubing (VAR, ESR)

0.180.23

0.50

0.55

0.20

...

8620

G86200

6278

Bars, forgings, tubing (for bearing applications; P, DVM)

0.110.15

4.1

3.4

4.2

12. V

...

...

6280G

Bars, forgings, rings

0.280.33

0.50

0.55

0.20

...

8630

G86300

6281F

Tubing (mechanical)

0.280.33

0.5

0.55

0.20

...

8630

G86300

tubing

tubing

(P,

6282F

Tubing (mechanical)

0.330.38

0.50

0.55

0.25

...

8735

G87350

6290F

Bars, forgings (carburizing)

0.110.17

...

1.8

0.25

...

4615

G46150

6292F

Bars, forgings (carburizing)

0.150.20

...

1.8

0.25

...

4617

G46170

6294F

Bars, forgings

0.170.22

...

1.8

0.25

...

4620

G42600

6299C

Bars, forgings, tubing

0.170.23

0.50

1.8

0.25

...

4320H

H43200

6300C

Bars, forgings

0.350.40

...

...

0.25

...

4037

G40370

6302E

Bars, forgings, tubing (low alloy, heat resistant)

0.280.33

1.25

...

0.50

0.65 Si, 0.25 V

17-22A(S)

K23015

6303D

Bars, forgings

0.250.30

1.25

...

0.50

0.65 Si, 0.85 V

17-22A(V)

K22770

6304G

Bars, forgings, tubing (low alloy, heat resistant)

0.400.50

0.95

...

0.55

0.30 V

17-22A

K14675

MAM 6304(b)

Bars, forgings, tubing (low alloy, heat resistant)

0.400.50

0.95

...

0.55

0.30 V

17-22A

K14675

6305A

Bars, forgings, tubing (VAR)

0.400.50

0.95

...

0.55

0.30 V

17-22A

K14675

6308A

Bars, forgings (VAR, ESR)

0.070.13

1.0

2.0

3.2

2.0 Cu, 0.10 V, 0.90 Si

Pyrowear alloy 53

K71040

6312E

Bars, forgings, tubing

0.380.43

...

1.8

0.25

...

4640

K22440

6317E

Bars, forgings (heat treated; 860 MPa tensile strength)

0.380.43

...

1.8

0.25

...

4640

K22440

6320H

Bars, forgings, rings

0.330.38

0.50

0.55

0.25

...

8735

G87350

6321D

Bars, forgings, tubing

0.380.43

0.42

0.30

0.12

0.003 B

81B40

K03810

6322K

Bars, forgings, rings

0.380.43

0.50

0.55

0.25

...

8740

G87400

6323G

Tubing (mechanical)

0.380.43

0.50

0.55

0.25

...

8740

G87400

6324E

Bars, forgings, tubing

0.380.43

0.65

0.70

0.25

...

8740 mod

K11640

6325F

Bars, forgings (heat treated; 725 MPa tensile strength)

0.380.43

0.50

0.55

0.25

...

8740

G87400

6327G

Bars, forgings (heat treated; 860 MPa tensile strength)

0.380.43

0.50

0.55

0.25

...

8740

G87400

6328H

Bars, forgings, tubing

0.480.53

0.50

0.55

0.25

...

8750

K13550

6330D

Bars, forgings, tubing

0.330.38

0.65

1.25

...

...

3135

K22033

6342G

Bars, forgings, tubing

0.380.43

0.80

1.0

0.25

...

9840

G98400

6348A

Bars (normalized)

0.280.33

0.95

...

0.20

...

4130

G41300

6349A

Bars (normalized)

0.380.43

0.95

...

0.20

...

4140

G41400

6350G

Plate, sheet, strip

0.280.33

0.95

...

0.20

...

4130

G41300

6351D

Plate, sheet, (spheroidized)

0.280.33

0.95

...

0.20

...

4130

G41300

6352E

Plate, sheet, strip

0.330.38

0.95

...

0.2

...

4135

G41350

6354C

Plate, sheet, strip

0.100.17

0.62

...

0.2

0.75 Si, 0.10 Zr

NAX AC

6355K

Plate, sheet, strip

0.280.33

0.50

0.55

0.20

...

8630

G86300

6356C

Plate, sheet, strip

0.300.35

0.95

...

0.20

...

4132

K13247

strip

9115-

K11914

6357F

Plate, sheet, strip

0.330.38

0.50

0.5

0.25

...

8735

G87350

6358F

Plate, sheet, strip

0.380.43

0.50

0.55

0.25

...

8740

G87400

6359E

Plate, sheet, strip

0.380.43

0.80

1.8

0.25

...

4340

G43400

6360H

Tubing (seamless, normalized or stress relieved)

0.280.33

0.95

...

0.20

...

4130

G41300

6361B

Tubing (seamless, round; 860 MPa tensile strength)

0.280.33

0.95

...

0.2

...

4130

G41300

6362C

Tubing (seamless; 1035 MPa tensile strength)

0.280.33

0.95

...

0.2

...

4130

G41300

6365G

Tubing (seamless, normalized or stress relieved)

0.330.38

0.95

...

0.20

...

4135

G41350

6370J

Bars, forgings, rings

0.280.33

0.95

...

0.2

...

4130

G41300

6371G

Tubing (mechanical)

0.280.33

0.95

...

0.20

...

4130

G41300

6372G

Tubing (mechanical)

0.330.38

0.95

...

0.20

...

4135

G41350

6373C

Tubing (welded)

0.280.33

0.95

...

0.20

...

4130

G41300

6378C

Bars (die drawn, free machining; 895 MPa yield strength)

0.390.48

0.95

...

0.20

0.015 Te

4142H

K11542

6379A

Bars (die drawn and tempered; 1140 MPa yield strength)

0.400.53

0.95

...

0.20

0.05 Te

4140 mod

G41400

6381D

Tubing

0.380.43

0.95

...

0.20

...

4140

G41400

6382J

Bars, forgings

0.380.43

0.95

...

0.20

...

4140

G41400

6385D

Plate, sheet, strip

0.27-

1.25

...

0.50

0.65 Si, 0.25 V

17-22A(S)

K23015

0.33

6386B(1)

Plate, sheet (heat treated; 620 and 690 MPa yield strength)

0.150.21

0.500.80

...

0.180.28

0.40-0.80 0.15 Zr

Si,

0.05-

...

K11856

6386B(2)

Plate, sheet (heat treated; 620 and 690 MPa yield strength)

0.120.21

0.400.65

...

0.150.25

0.20-0.35 Si, 0.010.03 Ti, 0.03-0.08 V, 0.0005-0.005 B

...

K11630

6386B(3)

Plate, sheet (heat treated; 620 and 690 MPa yield strength)

0.100.20

...

...

1.101.50

0.15-0.30 Si, 0.0010.005 B

...

K11511

6386(4)

Plate, sheet (heat treated; 620 and 690 MPa yield strength)

0.130.20

0.851.20

...

0.150.25

0.20-0.40 Cu, 0.200.35 Si, 0.04-0.10 Ti, 0.0015-0.005 B

...

K11662

6386B(5)

Plate, sheet (heat treated; 620 and 690 MPa yield strength)

0.120.21

...

...

0.450.70

0.20-0.35 Si, 0.0010.005 B

...

K11625

6390B

Tubing (mechanical, special surface quality)

0.380.43

0.95

...

0.20

...

4140

G41400

6395C

Plate, sheet, strip

0.380.43

0.95

...

0.20

...

4140

G41400

6396B

Sheet, strip, plate (annealed)

0.490.55

0.80

1.8

0.25

...

...

K22950

6406C

Plate, sheet, strip (annealed)

0.410.46

2.1

...

0.58

1.6 Si, 0.05 V

X200

K34378

6407D

Bars, forgings, tubing

0.270.33

1.2

2.05

0.45

...

HS-220

K33020

6408

Bars, forgings, tubing (annealed, ESR, CVM, VAR, P)

0.350.45

5.2

...

1.5

1.0 V

...

T20813

6409

Bars, forgings, tubing (normalized and tempered, quality cleanliness)

0.380.43

0.80

1.8

0.25

...

4340

G43400

6411C

Bars, forgings, tubing (CM)

0.280.33

0.85

1.8

0.40

...

4330 mod

K23080

6412H

Bars, forgings

0.350.40

0.80

1.8

0.25

...

4337

G43370

6413G

Tubing (mechanical)

0.350.40

0.80

1.8

0.25

...

4337

G43370

6414E

Bars, forgings, tubing (CVM)

0.380.43

0.80

1.8

0.25

...

4340

G43400

6415L

Bars, forgings, tubing

0.380.43

0.80

1.8

0.25

...

4340

G43400

MAM 6415(b)

Bars, forgings, tubing

0.380.43

0.80

1.8

0.25

...

4340

G43400

6416B

Superseded by AMS 6419

6417C

Bars, forgings, tubing (CM)

0.380.43

0.82

1.8

0.40

1.6 Si, 0.08 V

300M

K44220

6418F

Bars, forgings, tubing, rings

0.230.28

0.30

1.8

0.40

1.3 Mn, 1.5 Si

Hy-tuf

K32550

6419C

Bars, forgings, tubing (CVM)

0.400.45

0.82

1.8

0.40

1.6 Si, 0.08 V

300M

K44220

6421B

Bars, forgings, tubing

0.350.40

0.80

0.85

0.20

0.003 B

98B37 mod

...

6422E

Bars, forgings, tubing

0.380.43

0.80

0.85

0.20

0.003 B

98BV40 mod

K11940

6423C

Bars, forgings, tubing

0.400.46

0.92

0.75

0.52

0.003 B

...

K24336

6424B

Bars, forgings, tubing

0.490.59

0.80

1.8

0.25

...

...

K22950

6426C

Bars, forgings, tubing (CVM)

0.800.90

1.0

...

0.58

0.75 Si

52CB

K18597

6427G

Bars, forgings, tubing

0.280.33

0.85

1.8

0.42

0.08 V

4330 mod

K23080

6428D

Bars, forgings, tubing

0.320.38

0.80

1.8

0.35

0.20 V

4335 mod

K23477

6429C

Bars, forgings, tubing, rings (CVM)

0.330.38

0.78

1.8

0.35

0.20 V

4335 mod

K33517

6430C

Bars, forgings, tubing, rings (special grade)

0.320.38

0.78

1.8

0.35

0.20 V

4335 mod

K33517

6431G

Bars, forgings, tubing (CVM)

0.450.50

1.05

0.55

1.0

0.11 V

D-6ac

K24728

6432A

Bars, forgings, tubing

0.430.49

1.05

0.55

1.0

0.12 V

D-6a

K24728

6433C

Plate, sheet, grade)

0.330.38

0.80

1.8

0.35

0.20 V

4335 mod

K33517

6434C

Plate, sheet, strip

0.330.38

0.78

1.8

0.35

0.20 V

4335 mod

K33517

6435C

Plate, sheet, strip (P, CM, annealed)

0.330.38

0.78

1.8

0.35

0.20 V

4335 mod

K33517

6436B

Plate, sheet, strip (low alloy, heat resistant, annealed)

0.250.30

1.25

...

0.50

0.65 Si, 0.85 V

17-22A(V)

K22770

6437D

Plate, sheet, strip

0.380.43

5.0

...

1.3

0.5 V

H-11

T20811

6438C

Plate, sheet, strip (P, CM)

0.450.50

1.05

0.55

1.0

0.11 V

D-6ac

K24728

6439B

Plate, sheet, strip (annealed, CVM)

0.420.48

1.05

0.55

1.0

0.12 V

D-6ac

K24729

6440J

Bars, forgings, tubing (for bearing applications)

0.981.10

1.45

...

...

...

52100

G52986

6441G

Superseded by AMS 6440

6442E

Bars, forgings (for bearing applications)

0.981.10

0.50

...

...

...

50100

G50986

6443E

Bars, forgings, tubing (CVM)

0.981.10

1.0

...

...

...

51100

G51986

6444G

Bars, wire, forgings, tubing (P, CVM)

0.981.10

1.45

...

...

...

52100

G52986

6445E

Bars, wire, forgings, tubing (CVM)

0.921.02

1.05

...

...

1.1 Mn

51100 mod

K22097

strip

(special

6446C

Bars, forgings (ESR)

0.981.10

1.00

...

...

...

51100

G51986

6447C

Bars, forgings, tubing (ESR)

0.981.10

1.45

...

...

...

52100

G52986

6448F

Bars, forgings, tubing

0.480.53

0.95

...

...

0.22 V

6150

G61500

6449C

Bars, forgings, tubing (for bearing applications)

0.981.10

1.0

...

...

...

51100

G51986

6450E

Wire (spring)

0.480.53

0.95

...

...

0.22 V

6150

G61500

6451A

Wire, spring (oil tempered)

0.510.59

0.65

...

...

1.4 Si

9254

G92540

6454

Sheet, strip, plate (P, CM)

0.380.43

0.80

1.8

0.25

...

4340

G43400

6455F

Plate, sheet, strip

0.480.53

0.95

...

...

0.22 V

6150

G61500

6470H

Bars, forgings, (nitriding)

tubing

0.380.43

1.6

...

0.35

1.1 Al

135 mod

K24065

6471C

Bars, forgings, (nitriding, CVM)

tubing

0.380.43

1.6

...

0.35

1.2 Al

135 mod

K24065

6472B

Bars, forgings (nitriding, heat treated; 770 MPa tensile strength)

0.380.43

1.6

...

0.35

1.1 Al

135 mod

K24065

6475E

Bars, forgings, (nitriding)

0.210.26

1.1

3.5

0.25

1.25 Al

...

K52355

6485

Bars, forgings

0.380.43

5.0

...

1.3

0.50 V

H-11

T20811

6487

Bars, forgings (P, CVM)

0.380.43

5.0

...

1.3

0.50 V

H-11

T20811

6488D

Bars, forgings (P)

0.380.43

5.0

...

1.3

0.50 V

H-11

T20811

6490D

Bars, forgings, tubing (for

0.77-

4.0

...

4.2

1.0 V

M-50

T11350

tubing

bearing applications: P, CVM)

0.85

6491A

Bars, forgings, tubing (for bearing applications; P, DVM)

0.800.85

4.1

...

4.2

1.0 V

M-50

T11350

6512B

Bars, forgings, tubing, rings (annealed)

...

...

18

4.9

7.8 Co, 0.40 Ti, 0.10 Al

Maraging 250

K92890

6514B

Bars, forgings, tubing, rings (annealed, CM)

...

...

18.5

4.9

9.0 Co, 0.65 Ti, 0.10 Al

Maraging 300

K93120

6518A

Sheet, strip, plate (solution treated, DVM)

...

...

19.0

3.0

0.10 Al, 1.4 Ti

...

...

6519A

Bars, forgings, tubing, springs (annealed, DVM)

...

...

19.0

3.0

0.10 Al, 1.4 Ti

...

...

6520B

Plate, sheet, strip (solution heat treated, CM)

...

...

18

4.9

7.8 Co, 0.40 Ti, 0.10 Al

Maraging 250

K92890

6521A

Plate, sheet, strip (solution heat treated, CM)

...

...

18.5

4.9

9.0 Co, 0.65 Ti, 0.10 Al

Maraging 300

K93120

6522

Plate (P, VM)

...

2.0

10.0

1.0

14.0 Co

AF 1410

K92571

6523C

Sheet, strip, plate (annealed, CVM)

0.170.23

0.75

9.0

1.0

0.09 V, 4.5 Co

HP 9-4-20

K91472

6524B

Sheet, strip, plate (annealed, CVM)

0.290.34

1.0

7.5

1.0

0.09 V, 4.5 Co

HP 9-4-30

K91283

6525A

Bars, forgings, tubing, rings (CVM)

0.170.23

0.75

9.0

1.0

0.09 V, 4.5 Co

HP 9-4-20

K91283

6526C

Bars, forgings, tubing, rings (annealed, CVM)

0.290.34

1.0

7.5

1.0

4.5 Co, 0.09 V

HP 9-4-30

K91313

6527

Bars, forgings (P, VM)

0.130.17

2.0

10.0

1.0

14 Co

AF 1410

K92571

6528

Bars (normalized, special aircraft quality cleanliness)

0.280.33

0.95

...

0.20

...

4130

G41300

6529

Bars (normalized, special aircraft quality cleanliness)

0.380.43

0.95

...

0.20

...

4140

G41400

6530H

Tubing (seamless)

0.28-

0.55

0.50

0.20

...

8630

G86300

0.33

6535G

Tubing (seamless)

0.280.33

0.50

0.55

0.20

...

8630

G86300

6543A

Bars, forgings treated, DVM)

0.100.14

2.0

10.0

1.0

8.0 Co

...

K91970

6544A

Plate (solution treated, VM)

0.100.14

2.0

10.0

1.0

8.0 Co

...

K92571

6546C

Plate, sheet, strip (annealed, P, CM)

0.240.30

0.48

8.0

0.48

4.0 Co, 0.09 V

HP 9-4-25

K91122

6550H

Tubing (welded)

0.280.33

0.55

0.50

0.20

...

8630

G86300

(solution

(a) P, premium quality; CVM, consumable vacuum melted; CVAR, consumable vacuum arc remelted; ESR, electroslag remelted; DVM, double vacuum melted; VAR, vacuum arc remelted; CM, consumable electrode remelted; VM, vacuum melted.

(b) MAM, metric aerospace material specifications

ASTM (ASME) Designations As noted previously, the most widely used standard specifications for steel products are those published by ASTM. These are complete specifications, generally adequate for procurement purposes. Many ASTM specifications apply to specific products, such as A 574, for alloy steel socket head cap screws. These specifications are generally oriented toward performance of the fabricated end product, with considerable latitude in chemical composition of the steel used to make the end product. ASTM specifications represent a consensus among producers, specifiers, fabricators, and users of steel mill products. In many cases, the dimensions, tolerances, limits, and restrictions in the ASTM specifications are the same as the corresponding items of the standard practices in the AISI Steel Products Manuals. Many of the ASTM specifications have been adopted by the American Society of Mechanical Engineers (ASME) with little or no modification; ASME uses the prefix "S" and the ASTM designation for these specifications. For example, ASME SA-213 and ASTM A 213 are identical. Steel products can be identified by the number of the ASTM specification to which they are made. The number consists of the letter "A" (for ferrous materials) and an arbitrary, serially assigned number. Citing the specification number, however, is not always adequate to completely describe a steel product. For example, A 434 is the specification for heat treated (hardened and tempered) alloy steel bars. To completely describe steel bars indicated by this specification the grade (SAE-AISI designation in this case) and class (required strength level) must also be indicated. A 434 also incorporates, by reference, two standards for test methods and A 29, the general requirements for bar products. SAE-AISI designations for the compositions of carbon and alloy steels are normally incorporated into the ASTM specifications for bars, wires, and billets for forging. Some ASTM specifications for sheet products include SAE-AISI designations for composition. ASTM specifications for plates and structural shapes generally specify the limits and ranges of chemical composition directly, without the SAE-AISI designations. Table 26 includes a list of some of the ASTM specifications that incorporate SAE-AISI designations for compositions of the different grades of steel.

Table 26 ASTM specifications that incorporate SAE-AISI designations ASTM specifications

Subject

A 29

Carbon and alloy steel bars, hot rolled and cold finished

A 108

Standard quality cold-finished carbon steel bars

A 295

High carbon-chromium ball and roller bearing steel

A 304

Alloy steel bars having hardenability requirements

A 322

Hot-rolled alloy steel bars

A 331

Cold-finished alloy steel bars

A 434

Hot-rolled or cold-finished quenched and tempered alloy steel bars

A 505

Hot-rolled and cold-rolled alloy steel sheet and strip

A 506

Regular quality hot-rolled and cold-rolled alloy steel sheet and strip

A 507

Drawing quality hot-rolled and cold-rolled alloy steel sheet and strip

A 510

Carbon steel wire rods and coarse round wire

A 534

Carburizing steels for antifriction bearings

A 535

Special quality ball and roller bearing steel

A 544

Scrapless nut quality carbon steel wire

A 545

Cold-heading quality carbon steel wire for machine screws

A 546

Cold-heading quality medium-high-carbon steel wire for hexagon-head bolts

A 547

Cold-heading quality alloy steel wire for hexagon-head bolts

A 548

Cold-heading quality carbon steel wire for tapping or sheet metal screws

A 549

Cold-heading quality carbon steel wire for wood screws

A 575

Merchant quality hot-rolled carbon steel bars

A 576

Special quality hot-rolled carbon steel bars

A 646

Premium quality alloy steel blooms and billets for aircraft and aerospace forgings

A 659

Commercial quality hot-rolled carbon steel sheet and strip

A 682

Cold-rolled spring quality carbon steel strip, generic

A 684

Untempered cold-rolled high-carbon steel strip

A 689

Carbon and alloy steel bars for springs

A 711

Carbon and alloy steel blooms, billets, and slabs for forging

A 713

High-carbon spring steel wire for heat-treated components

A 752

Alloy steel wire rods and coarse round wire

A 827

Carbon steel plates for forging and similar applications

A 829

Structural quality alloy steel plates

A 830

Structural quality carbon steel plates

Generic Specifications. Several ASTM specifications, such as A 29, contain the general requirements common to

each member of a broad family of steel products. Table 27 lists several of these generic specifications, which generally must be supplemented by another specification describing a specific mill form or intermediate fabricated product. Table 27 Generic ASTM specifications ASTM specification(a)

Title

A 6/A 6M

General requirements for rolled steel plates, shapes, sheet piling, and bars for structural purposes

A 20/A 20M

General requirements for steel plates for pressure vessels

A 29/A 29M

General requirements for hot-rolled and cold-finished carbon and alloy steel bars

A 450/A 450M

General requirements for carbon, ferritic-alloy, and austenitic alloy tubes

A 505

General requirements for hot-rolled and cold-rolled alloy steel sheet and strip

A 530/A 530M

General requirements for specialized carbon and alloy steel pipe

A 682

General requirements for cold-rolled spring quality high-carbon steel strip

(a) The suffix "M" indicates that a metric version of the specification is available

Sheet Products. Limits and ranges of chemical compositions for carbon steel sheet products with ASTM specifications that do not incorporate SAE-AISI designations are listed in Table 28. ASTM specifications for sheet products that do include SAE-AISI designations are listed in Table 26.

Table 28 Composition ranges and limits for plain carbon sheet and strip (ASTM specifications) ASTM specification

A 611

Description(a)

Composition(b), %

C

Mn

P

S

Other

CR SQ grades A, B, C, E

0.20

0.60

0.04

0.04

(c)

Grade D (type 1)

0.20

0.90

0.04

0.04

(c)

Grade D (type 2)

0.15

0.60

0.20

0.04

(c)

A 366

CR CQ

0.15

0.60

0.35

0.04

(c)

A 109

CR strip tempers 1, 2, 3

0.25

0.60

0.035

0.04

(c)

0.15

0.60

0.035

0.04

(c)

Tempers 4, 5

A 619

CR DQ

0.10

0.50

0.025

0.035

...

A 620

CR DQSK

0.10

0.50

0.025

0.035

(d)

A 570

HR SQ grades 30, 33, 36, and 40

0.25

0.90

0.04

0.05

(c)

0.25

1.35

0.04

0.05

(c)

Grades 45, 50, and 55

A 569

HR CQ

0.15

0.60

0.035

0.040

(c)

A 621

HR DQ

0.10

0.50

0.025

0.035

...

A 622

HR DQSK

0.10

0.50

0.025

0.035

(d)

A 414

Pressure vessel grade A

0.15

0.90

0.035

0.040

(c)

Grade B

0.22

0.90

0.035

0.040

(c)

Grade C

0.25

0.90

0.035

0.040

(c)

Grade D

0.25

1.20

0.035

0.040

(c)(e)

Grade E

0.27

1.20

0.035

0.040

(c)(e)

Grade F

0.31

1.20

0.035

0.040

(c)(e)

Grade G

0.31

1.35

0.035

0.040

(c)(e)

(a) CR, cold-rolled; HR, hot rolled; SQ, structural quality; DG, drawing quality; DQSK, drawing quality, special killed; CQ, commercial quality.

(b) All values are maximum.

(c) Copper when specified as copper-bearing steel: 0.20% min.

(d) Aluminum as deoxidizer usually exceeds 0.010% in the product.

(e) Killed steel can be supplied upon request to the manufacturer for grades D through G. When silicon-killed steel is specified, a range of 0.150.30% Si shall be supplied.

Plate and Structural Shapes. ASTM specifications for plate and structural shapes generally do not incorporate SAEAISI designations. Limits and ranges of chemical composition in ASTM specifications for carbon and alloy structural plate are listed in Table 29.

Table 29 ASTM specifications of chemical composition for structural plate made of alloy steel or carbon steel ASTM specification

Material grade or type

Composition(a), %

C

Mn

P

S

Si

Cr

Ni

Mo

Cu

Others

A

0.150.21

0.80-1.10

0.035

0.04

0.400.80

0.500.80

...

0.180.28

...

Zr, 0.05-0.15; B, 0.0025

B

0.120.21

0.70-1.00

0.035

0.04

0.200.35

0.400.65

...

0.150.25

...

V, 0.03-0.08; Ti, 0.01-0.03; B, 0.0005-0.005

C

0.100.20

1.10-1.50

0.035

0.04

0.150.30

...

...

0.150.30

...

B, 0.001-0.005

E

0.120.20

0.40-0.70

0.035

0.04

0.200.40

1.402.00

...

0.400.60

...

Ti, 0.01-0.10(b); B, 0.001-0.005

F

0.100.20

0.60-1.00

0.035

0.04

0.150.35

0.400.65

0.701.00

0.400.60

0.150.50

V, 0.03-0.08; B, 0.0005-0.006

H

0.120.21

0.95-1.30

0.035

0.04

0.200.35

0.400.65

0.300.70

0.200.30

...

V, 0.03-0.08; B, 0.0005-0.005

J

0.120.21

0.45-0.70

0.035

0.04

0.200.35

...

...

0.500.65

...

B, 0.001-0.005

M

0.120.21

0.45-0.70

0.035

0.04

0.200.35

...

1.201.50

0.450.60

...

B, 0.001-0.005

P

0.120.21

0.45-0.70

0.035

0.04

0.200.35

0.851.20

1.201.50

0.450.60

...

B, 0.001-0.005

Q

0.140.21

0.95-1.30

0.035

0.04

0.150.35

1.001.50

1.201.50

0.400.6

...

V, 0.03-0.08

R

0.150.80

0.85-1.15

0.035

0.04

0.200.35

0.350.65

0.901.10

0.150.25

...

V, 0.03-0.08

S

0.100.20

1.10-1.50

0.035

0.04

0.150.35

...

...

0.100.35

...

B, 0.001-0.005; Nb, 0.06 max(c)

T

0.080.14

1.20-1.50

0.035

0.010

0.400.60

...

...

0.450.60

...

V, 0.03-0.08; B, 0.001-0.005

Alloy steel

A 514

A 709

100, 100W

(equivalent to A 514-A, B, C, E, F, H, J, M, P, Q)

A 710

A

0.07

0.40-0.70

0.025

0.025

0.40

0.600.90

0.701.00

0.150.25

1.001.30

Nb, 0.02 min

B

0.06

0.40-0.65

0.025

0.025

0.150.40

...

1.201.50

...

1.001.30

Nb, 0.02 min

C

0.07

1.30-1.65

0.25

0.25

0.04

...

0.701.00

0.150.25

1.001.30

Nb, 0.02 min

A 36

...

0.29(d)

0.801.20(d)

0.04

0.05

0.150.40(d)

...

...

...

0.20(e)

...

A 131

A

0.26(d)

(f)

0.05

0.05

...

...

...

...

...

...

B

0.21

0.801.10(g)

0.04

0.04

0.3

...

...

...

...

...

D

0.21

0.701.35(d)(g)

0.04

0.04

0.100.35

...

...

...

...

...

E

0.18

0.701.35(g)

0.04

0.04

0.100.35

...

...

...

...

...

CS, DS

0.16

1.001.35(g)

0.04

0.04

0.100.35

...

...

...

...

...

A

0.14

0.90

0.04

0.05

0.04(d)

...

...

...

0.20(e)

...

B

0.17

0.90

0.04

0.05

0.04(d)

...

...

...

0.20(e)

...

C

0.24

0.90

0.04

0.05

0.04(d)

...

...

...

0.20(e)

...

D

0.27

0.90

0.04

0.05

0.04(d)

...

...

...

0.20(e)

...

C

0.36(d)

0.90

0.04

0.05

0.150.40

...

...

...

...

...

D

0.35(d)

0.90

0.04

0.05

0.150.40

...

...

...

...

...

Carbon steel

A 283

A 284

A 529

...

0.27

1.20

0.04

0.05

...

...

...

...

0.20 (e)

...

A 573

58

0.23

0.600.90(g)

0.04

0.05

0.100.35

...

...

...

...

...

65

0.26(d)

0.85-1.20

0.04

0.05

0.150.40

...

...

...

...

...

70

0.28(d)

0.85-1.20

0.04

0.05

0.150.40

...

...

...

...

...

A

0.16

0.90-1.50

0.04

0.05

0.150.50

0.25

0.25

0.08

0.20(e)0.35

...

B

0.20

0.701.60(d)

0.04

0.05

0.150.50

0.25

0.25

0.08

0.20(e)0.35

...

C

0.22

1.00-1.60

0.04

0.05

0.200.50

0.25

0.25

0.08

0.20(e)0.35

...

36

0.27(d)

0.801.20(d)

0.04

0.05

0.150.40(d)

...

...

...

...

...

A 678

A 709

(a) When a single value is shown, it is a maximum limit, except for copper, for which a single value denotes a minimum limit.

(b) Vanadium can be substituted for part or all of the titanium on a one-for-one basis.

(c) Titanium may be present in levels up to 0.06% to protect the boron additions.

(d) Limiting values vary with plate thickness.

(e) Minimum value applicable only if copper-bearing steel is specified.

(f) Plates over 13 mm (

in.) in thickness shall have a minimum manganese content not less than 2.5 times carbon content.

(g) The upper limit of manganese may be exceeded provided C + 1/6 Mn does not exceed 0.40% based on heat analysis.

Pressure-Vessel Plate. Steel plate intended for fabrication into pressure vessels must conform to different

specifications than similar plate intended for structural applications. The major differences between the two groups of specifications are that pressure-vessel plate must meet requirements for notch toughness and has more stringent limits for allowable surface and edge imperfections. Limits and ranges of chemical composition for carbon and alloy steel plate for pressure vessels are given in Table 30.

Table 30 ASTM specifications of chemical compositions for pressure vessel plate made of carbon and alloy steel ASTM specification

Material grade or type

Composition(a), %

C

Mn

P

S

Si

Cr

Ni

Mo

Cu

Others

A

0.17

0.90

0.035

0.04

...

...

...

...

...

...

B

0.22

0.90

0.035

0.04

...

...

...

...

...

...

C

0.28

0.90

0.035

0.04

...

...

...

...

...

...

A 299

...

0.30(b)

0.901.50(b)

0.035

0.04

0.150.40

...

...

...

...

...

A 442

55

0.24(b)

0.801.10(b)

0.035

0.04

0.150.40

...

...

...

...

...

60

0.27(b)

0.801.10(b)

0.035

0.04

0.150.40

...

...

...

...

...

A 455

...

0.33

0.851.20

0.035

0.04

0.10

...

...

...

...

...

A 515

55

0.28(b)

0.90

0.035

0.04

0.150.40

...

...

...

...

...

60

0.31(b)

0.90

0.035

0.04

0.150.40

...

...

...

...

...

65

0.33(b)

0.90

0.035

0.04

0.150.40

...

...

...

...

...

70

0.35(b)

1.20

0.035

0.04

0.150.40

...

...

...

...

...

55

0.26(b)

0.601.20(b)

0.035

0.04

0.150.40

...

...

...

...

...

60

0.27(b)

0.601.20(b)

0.035

0.04

0.150.40

...

...

...

...

...

65

0.29(b)

0.85-

0.035

0.04

0.15-

...

...

...

...

...

Carbon steel

A 285

A 516

1.20

0.40

70

0.31(b)

0.851.20

0.035

0.04

0.150.40

...

...

...

...

...

A 537

Class 1, 2

0.24

0.701.60(b)

0.035

0.04

0.150.50

0.25

0.25

0.08

0.35

...

A 562

...

0.12

1.20

0.035

0.04

0.150.50

...

...

...

0.15 min

Ti min,4 × C

A 612

...

0.29(b)

1.001.50(b)

0.035

0.04

0.150.50(b)

0.25

0.25

0.08

0.35

V, 0.08

A 662

A

0.14

0.901.35

0.035

0.04

0.150.40

...

...

...

...

...

B

0.19

0.851.50

0.035

0.04

0.150.40

...

...

...

...

...

C

0.20

1.001.60

0.035

0.04

0.150.50

...

...

...

...

...

A

0.18

1.001.60

0.035

0.04

0.55

0.25

0.25

0.08

0.35

V, 0.08

B

0.20

1.001.60

0.035

0.04

0.50

0.25

0.25

0.08

0.35

V, 0.08

C

0.22

1.101.60

0.035

0.04

0.200.60

0.25

0.25

0.08

0.35

B, 0.005; V, 0.008

A

0.24

1.60(b)

0.035

0.04

0.150.50

0.25

0.50

0.08

0.35

...

B

0.20

0.901.50

0.030

0.025

0.150.55

0.25

0.25

0.08

0.35

V, 0.08

C

0.20

1.60(b)

0.030

0.025

0.150.55

0.25

0.25

0.08

0.35

V, 0.08

A

0.17

1.051.40

0.035

0.040

0.600.90

0.350.60

...

...

...

...

B

0.25

1.05-

0.035

0.040

0.60-

0.35-

...

...

...

...

A 724

A 738

Alloy steel

A 202

1.40

0.90

0.60

A

0.23(b)

0.80(b)

0.035

0.040

0.150.40

...

2.102.50

...

...

...

B

0.25(b)

0.80(b)

0.035

0.040

0.150.40

...

2.102.50

...

...

...

D

0.20(b)

0.80(b)

0.035

0.040

0.150.40

...

3.253.75

...

...

...

E,F

0.23(b)

0.80(b)

0.035

0.040

0.150.40

...

3.253.75

...

...

...

A

0.25(b)

0.90

0.035

0.040

0.150.40

...

...

0.450.60

...

...

B

0.27(b)

0.90

0.035

0.040

0.150.40

...

...

0.450.60

...

...

C

0.28(b)

0.90

0.035

0.040

0.150.40

...

...

0.450.60

...

...

C

0.25

1.60

0.035

0.040

0.150.40

...

0.400.70

...

...

V, 0.13-0.18

D

0.20

1.70

0.035

0.040

0.100.50

...

0.400.70

...

...

V, 0.10-0.18

A

0.25(b)

0.951.30

0.035

0.040

0.150.40

...

...

0.450.60

...

...

B

0.25(b)

1.151.50

0.035

0.040

0.150.40

...

...

0.450.60

...

...

C

0.25(b)

1.151.50

0.035

0.040

0.150.40

...

0.400.70

0.450.60

...

...

D

0.25(b)

1.151.50

0.035

0.040

0.150.40

...

0.701.00

0.450.60

...

...

A 353

...

0.13

0.90

0.035

0.040

0.150.40

...

8.509.50

...

...

...

A 387

2

0.21

0.550.80

0.035

0.040

0.150.40

0.500.80

...

0.450.60

...

...

A 203

A 204

A 225

A 302

A 517

5

0.15

0.300.60

0.040

0.030

0.50

4.006.00

...

0.450.65

...

...

7

0.15

0.300.60

0.030

0.030

1.00

6.008.00

...

0.450.65

...

...

9

0.15

0.300.60

0.030

0.030

1.00

8.0010.00

...

0.901.10

...

...

11

0.17

0.400.65

0.035

0.040

0.500.80

1.001.50

...

0.450.65

...

...

12

0.17

0.400.65

0.035

0.040

0.150.40

0.801.15

...

0.450.60

...

...

21

0.15(b)

0.300.60

0.035

0.035

0.50

2.753.25

...

0.901.10

...

...

22

0.15(b)

0.300.60

0.035

0.035

0.50

2.002.50

...

0.901.10

...

...

91

0.080.12

0.300.60

0.020

0.010

0.200.50

8.009.50

0.851.05

...

V, 0.18-0.25; Nb, 0.06-0.10; N, 0.030.07; Al, 0.04

A

0.150.21

0.801.10

0.035

0.040

0.400.80

0.500.80

...

0.180.28

...

B, 0.0025

B

0.150.21

0.701.00

0.035

0.040

0.200.35

0.400.65

...

0.150.25

...

B, 0.0005-0.005

C

0.100.20

1.101.50

0.035

0.040

0.150.30

...

...

0.200.30

...

B, 0.001-0.005

E

0.120.20

0.400.70

0.035

0.040

0.200.35

1.402.00

...

0.400.60

...

B, 0.0015, 0.005

F

0.100.20

0.601.00

0.035

0.040

0.150.35

0.400.65

0.701.00

0.400.60

...

B, 0.0005-0.006

H

0.120.21

0.951.30

0.035

0.040

0.200.35

0.400.65

0.300.70

0.200.30

...

B, 0.0005

J

0.120.21

0.450.70

0.035

0.040

0.200.35

...

...

0.500.65

...

B, 0.001-0.005

M

0.12-

0.45-

0.035

0.040

0.20-

...

1.20-

0.45-

...

B, 0.001-0.005

A 533

A 542

A 543

A 553

0.21

0.70

0.35

1.50

0.60

P

0.120.21

0.450.70

0.035

0.040

0.200.35

0.851.20

1.201.50

0.450.60

...

B, 0.001-0.005

Q

0.140.21

0.951.30

0.035

0.040

0.150.35

1.001.50

1.201.50

0.400.60

...

V, 0.03-0.08

S

0.100.20

1.101.50

0.035

0.040

0.150.40

...

...

0.100.35

...

Ti, 0.06; Nb, 0.06

T

0.080.14

1.201.50

0.035

0.010

0.400.60

...

...

0.450.60

...

B, 0.001-0.005; V, 0.03-0.08

A

0.25

1.151.50

0.035

0.040

0.150.40

...

...

0.450.60

...

...

B

0.25

1.151.50

0.035

0.040

0.150.40

...

0.400.70

0.450.60

...

...

C

0.25

1.151.50

0.035

0.040

0.150.40

...

0.701.00

0.450.60

...

...

D

0.25

1.151.50

0.035

0.040

0.150.40

...

0.200.40

0.450.60

...

...

A

0.15

0.300.60

0.025

0.025

0.50

2.002.50

0.40

0.901.10

0.40

V, 0.03

B

0.110.15

0.300.60

0.025

0.15

0.50

2.002.50

0.25

0.901.10

0.25

V, 0.02

C

0.100.15

0.300.60

0.025

0.025

0.13

2.75325

0.25

0.901.10

0.25

V, 0.2-0.3; 0.015-0.035; 0.001-0.003

B

0.23

0.40

0.035

0.040

0.200.40

1.502.00

2.603.25(b)

0.450.60

...

V, 0.03

C

0.23

0.40

0.020

0.020

0.200.40

1.201.80

2.253.25(b)

0.450.60

...

V, 0.03

I

0.13

0.90

0.035

0.040

0.150.40

...

8.509.50

...

...

...

II

0.13

0.90

0.035

0.040

0.150.40

...

7.508.50

...

...

...

Ti, B,

A 645

...

0.13

0.300.60

0.025

0.025

0.200.40

...

4.755.25

0.200.35

...

Al, 0.02-0.12; N, 0.020

A 734

A

0.12

0.450.75

0.035

0.015

0.40

0.901.20

0.901.20

0.250.40

...

Al, 0.06

A 735

...

0.06

1.202.20(b)

0.04

0.025

0.40

...

...

0.230.47

0.200.35(c)

Nb, 0.03-0.09

A 736

A

0.07

0.400.70

0.025

0.025

0.40

0.600.90

0.701.00

0.150.25

1.001.30

Nb, 0.02 min

C

0.07

1.301.65

0.025

0.025

0.40

...

0.701.00

0.150.25

1.001.30

Nb, 0.02 min

A782

...

0.20

0.71.20

0.035

0.040

0.400.80

0.501.00

...

0.200.60

...

Zr, 0.04-0.12

A832

...

0.100.15

0.300.60

0.025

0.025

0.10

2.753.25

...

0.901.10

...

V, 0.20-0.30; Ti, 0.015-0.035; B, 0.001-0.003

A 844

...

0.13

0.90

0.020

0.020

0.150.40

...

8.509.50

...

...

...

(a) When a single value is shown, it is a maximum limit, except where specified as a minimum limit.

(b) Limiting values may vary with plate thickness.

(c) When specified

International Designations and Specifications Most industrialized nations have standards organizations that issue designations and specifications related to steels. Organizations that can assist engineers cross-reference steels from various countries include the American National Standards Institute (ANSI) in the United States and the European Committee for Standardization (CEN) in Brussels, Belgium. The latter is an association of the national standards organizations of 18 countries of the European Union and of the European Free Trade Association. Useful reference sources include: • • • •

A.S. Melilli, Ed., Comparative World Steel Standards, ASTM, 1996 D.L. Potts and J.G. Gensure, International Metallic Materials Cross-Reference, Genium Publishing, 1989 C.W. Wegst, Ed., Stahlschlüssel: Key to Steel, 18th ed., Verlag Stahlschlüssel, 1998 Worldwide Guide to Equivalent Irons and Steels, 3rd ed., ASM International, 1992

Mechanical Properties of Carbon and Alloy Steels Introduction THE PROPERTIES of carbon and alloy steels are dependent on the relationships between chemical composition, processing, and microstructure. In this article, emphasis is placed on the effect of composition (alloying). The role of processing and microstructure on the properties is described in the Section "Structure/Property Relationships in Irons and Steels" in this Handbook. Alloying elements are added to ordinary (plain carbon) steels to modify their behavior during thermal processing (heat treatment or thermomechanical processing), which in turn results in improvement of the mechanical and physical properties of the steel. Specifically, alloying additions are made for one or more of the following reasons: • • • • • • •

Improve tensile strength without appreciably lowering ductility Improve toughness Increase hardenability which permits the hardening of larger sections than possible with plan carbon steels or allows successful quenching with less drastic cooling rates, reducing the hazard of distortion and quench cracking Retain strength at elevated temperatures Obtain better corrosion resistance Improve wear resistance Impart a fine grain size to the steel

A semantic distinction can be made between alloying elements and residual elements; the latter are not intentionally added to the steel, but result from the raw materials and steelmaking practices used to produce the steel. Any particular element can be either alloying or residual. For example, some nickel or chromium could come into steel through alloy steel scrap and so be considered residual; however, if either of these elements must be added to a steel to meet the desired composition range it might be considered an alloying element. Both alloying and residual elements can profoundly affect steel production, manufacture into end products, and service performance of the end product. The effects of one alloying element on a steel may be affected by the presence of other elements; such interactive effects are complex. In addition, the effects of a particular element may be beneficial to steel in one respect but detrimental in others.

Effects of Alloying Elements General effects of various alloying elements commonly found in carbon and low-alloy steels are summarized below. Composition limits or ranges for these elements are tabulated in the article "Classifications and Designations of Carbon and Alloy Steels" in this Section. Additional information on the effects of alloying elements on the performance of steels can be found in a number of articles contained within this Section (see, for example, the articles "Hardenability of Carbon and Alloy Steels," "Service Characteristics of Carbon and Alloy Steels," and "Corrosion Characteristics of Carbon and Alloy Steels") and in the Sections "Tool Steels" and "Stainless Steels" in this Handbook. Carbon is the most important single alloying element in steel. It is essential to the formation of cementite (and other

carbides), pearlite, spheroidite (an aggregate of spherical carbides in a ferrite matrix), bainite and iron-carbon martensite. Microstructures comprising one or more of these components can provide a wide range of mechanical properties and fabrication characteristics. The relative amounts and distributions of these elements can be manipulated by heat treatment to alter the microstructure, and therefore the properties, of a particular piece of steel. Much of ferrous metallurgy is devoted to the various structures and transformations in iron-carbon alloys; many other alloying elements are considered largely on the basis of their effects on the iron-carbon system. Assuming that the comparisons are made among steels having comparable microstructures, the strength and hardness are raised as the carbon content is increased; however, toughness and ductility are reduced by increases in carbon content (workability, weldability, and machinability are also deleteriously affected by higher carbon contents). The influence of

carbon content on mechanical properties is shown in Fig. 1. The hardness of iron-carbon martensite is increased by raising the carbon content of steel, reaching a maximum at about 0.6% C. Increasing the carbon content also increases hardenability.

Fig. 1 Variations in average mechanical properties of as-rolled 25 mm (1 in.) diam bars of plain carbon steels as a function of carbon content

The amount of carbon required in the finished steel limits the type of steel that can be made. As the carbon content of rimmed steel increases, surface quality becomes impaired. Killed steels in approximately the 0.15 to 0.30% C content level may have poorer surface quality and require special processing to obtain surface quality comparable to steels with higher or lower carbon content. Carbon has a moderate tendency to segregate, and carbon segregation is often more significant than the segregation of other elements. Manganese is normally present in all commercial steels. It is important in the manufacture of steel because it deoxidizes

the melt and facilitates hot working of the steel by reducing the susceptibility to hot shortness. Manganese also combines with sulfur to form manganese sulfide stringers, which improve the machinability of steel. It contributes to strength and hardness, but to a lesser degree than does carbon; the amount of increase depends on the carbon content. Manganese has a strong effect on increasing the hardenability of a steel. Manganese has less of a tendency toward macrosegregation than any of the common elements. Steels with more than 0.60% Mn cannot be readily rimmed. Manganese is beneficial to surface quality in all carbon ranges (with the exception of extremely low-carbon rimmed steels. Silicon is on of the principal deoxidizers used in steelmaking. The amount of this element in a steel, which is not always

noted in the chemical composition specifications, depends on the deoxidation practice specified for the product. Rimmed and capped steels contain minimal silicon, usually less than 0.05%. Fully killed steels usually contain 0.15 to 0.30% silicon for deoxidation; if other deoxidants are used, the amount of silicon in the steel may be reduced. Silicon has only a

slight tendency to segregate. In low-carbon steels, silicon is usually detrimental to surface quality, and this condition is more pronounced in low-carbon resulfurized grades. Silicon slightly increases the strength of ferrite, without causing a serious loss of ductility. In larger amounts, it increases the resistance of steel to scaling in air (up to about 260 °C, or 500 °F) and decreases the magnetic hysteresis loss. Such high-silicon steels are generally difficult to process. Copper has moderate tendency to segregate, and in appreciable amounts, it is detrimental to hot-working operations.

Copper adversely affects forge welding, but it does not seriously affect arc or oxyacetylene welding. Detrimental to surface quality, copper exaggerates the surface defects inherent in resulfurized steels. Copper is, however, beneficial to atmospheric corrosion resistance when present in amounts exceeding 0.20%. Steels containing these levels of copper are referred to as weathering steels. Chromium is generally added to steel to increase resistance to corrosion and oxidation, to increase hardenability, to

improve high-temperature strength, or to improve abrasion resistance in high-carbon compositions. Chromium is a strong carbide former. Complex chromium-iron carbides go into solution in austenite slowly; therefore, a sufficient heating time before quenching is necessary. Chromium can be used as a hardening element and is frequently used with a toughening element such as nickel to produce superior mechanical properties. At higher temperatures, chromium contributes increased strength; it is ordinarily used for applications of this nature in conjunction with molybdenum. Nickel, when used as an alloying element in constructional steels, is a ferrite strengthener. Because nickel does not form

any carbide compounds in steel, it remains in solution in the ferrite, thus strengthening and toughening the ferrite phase. Nickel steels are easily heat treated because nickel lowers the critical cooling rate. In combination with chromium, nickel produces alloy steels with greater hardenability, higher impact strength, and greater fatigue resistance than can be achieved in carbon steels. Nickel alloy steels also have superior low-temperature strength and toughness. Molybdenum increases the hardenability of steel and is particularly useful in maintaining the hardenability between

specified limits. This element, especially in amounts between 0.15 and 0.30%, minimizes the susceptibility of a steel to temper embrittlement. Hardened steels containing molybdenum must be tempered at a higher temperature to achieve the same amount of softening. Molybdenum is unique in the extent to which it increases the high-temperature tensile and creep strengths of steel. It retards the transformation of austenite to pearlite far more than it does the transformation of austenite to bainite; thus, bainite can be produced by continuous cooling of molybdenum-containing steels. Vanadium is one of the strong carbide-forming elements. It dissolves to some degree in ferrite imparting strength and

toughness. Vanadium steels show a much finer structure than steels of a similar composition without vanadium. Vanadium also provides increased hardenability where it is in solution in the austenite prior to quenching, a secondary hardening effect on tempering, and increased hardness at elevated temperatures. Niobium. Small additions of niobium increase the yield strength and, to a lesser degree, the tensile strength of carbon

steel. The addition of 0.20% Nb can increase the yield strength of medium-carbon steel by 70 to 100 MPa (10 to 15 ksi). This increased strength may be accompanied by considerably impaired notch toughness unless special measures are used to refine grain size during hot rolling. Grain refinement during hot rolling involves special thermomechanical processing techniques such as controlled-rolling practices, low finishing temperatures for final reduction passes, and accelerated cooling after rolling is completed. Aluminum is widely used as a deoxidizer and for control of grain size. When added to steel in specified amounts, it

controls austenite grain growth in reheated steels. Of all the alloying elements, aluminum is the most effective in controlling grain growth prior to quenching. Titanium, zirconium, and vanadium are also effective grain growth inhibitors; however, for structural grades that are heat treated (quenched and tempered), these three elements may have adverse effects on hardenability because their carbides are quite stable and difficult to dissolve in austenite prior to quenching. Boron is added to fully killed steel to improve hardenability. Boron-treated steels are produced in a range of 0.0005 to

0.003%. Whenever boron is substituted in part for other alloys, it should be done only with hardenability in mind because the lowered alloy content may be harmful for some applications. Boron is most effective in lower carbon steels.

Titanium is primarily used as a deoxidizer and helps to limit grain growth in the fully killed steels. Titanium may be

added to boron steels because it combines readily with any oxygen and nitrogen in the steel, thereby increasing the effectiveness of the boron in increasing the hardenability of the steel. Tungsten increases hardness, promotes a fin-grain structure, and is excellent for resisting heat. At elevated tempering

temperatures, tungsten forms tungsten carbide, which is very hard and stable. The tungsten carbide helps prevent the steel from softening during tempering. Tungsten is used extensively in high-speed tool steels. Zirconium inhibits grain growth and is used as a deoxidizer in killed steels. Its primary use is to improve hot-rolled

properties in high-strength low-alloy (HSLA) steels. Zirconium in solution also improves hardenability slightly. Calcium is sometimes used to deoxidize steels. In HSLA steels it helps to control the shape of nonmetallic inclusions, thereby improving toughness. Steels deoxidized with calcium generally have better machinability than do steels deoxidized with silicon or aluminum. Lead is sometimes added to carbon and alloy steels through mechanical dispersion during teeming for the purpose of

improving the machining characteristics of the steels. These additions are generally in the range of 0.15 to 0.35%. Lead does not dissolve in the steel during teeming but is retained in the form of microscopic globules. At temperatures near the melting point of lead, it can cause liquid-metal embrittlement. Nitrogen increases the strength, hardness, and machinability of steel, but it decreases the ductility and toughness. In aluminum-killed steels, nitrogen forms aluminum nitride particles that control the grain size of the steel, thereby improving both toughness and strength. Nitrogen can reduce the effect of boron on the hardenability of steels.

Effects of Residual Elements Any of the alloying elements mentioned above may inadvertently appear in steel as a result of the presence in raw materials used to make the steel. As such, they would be known as "residual" elements. Because of possible undesired (through not necessarily undesirable) effects of these elements on the finished products, most steelmakers are careful to minimize the amount of these elements in the steel, primarily through separation of steel scrap by alloy content. Several other elements, generally considered to be undesirable impurities, may be introduced into steel from pig iron. For certain specific purposes, however, they may be deliberately added; in this case, they would be considered alloying elements. Phosphorus increases strength and hardness of steel, but severely decreases ductility and toughness. It increases the

susceptibility of medium-carbon alloy steels, particularly straight chromium steels, to temper embrittlement. Phosphorus may be deliberately added to steel to improve its machinability or corrosion resistance. Sulfur. Increased sulfur content lowers transverse ductility and notch impact toughness but has only a slight effect on

longitudinal mechanical properties. Weldability decreases with increasing sulfur content. This element is very detrimental to surface quality, particularly in the lower-carbon and lower-manganese steels. For these reasons only a maximum limit is specified for most steels. The only exceptions is the group of free-machining steels, where sulfur is added to improve machinability; in this case, a range is specified. Sulfur has a greater segregation tendency than do any of the other common elements. Sulfur occurs in steel principally in the form of sulfide inclusions. Obviously a greater frequency of such inclusions can be expected in the resulfurized grades. Oxygen, which is most likely to be found in rimmed steels, can slightly increase the strength of steel, but seriously reduce toughness. Hydrogen dissolved in steel during manufacture can seriously embrittle it. This effect is not the same as the

embrittlement that results from electroplating or pickling. Embrittlement resulting from hydrogen dissolved during manufacture can cause flaking during cooling from hot rolling temperatures. Dissolved hydrogen rarely affects finished mill products, for reheating the steel prior to hot forming bakes out nearly all of the hydrogen. More detailed information on how hydrogen influences the properties of steels can be found in the Section "Failure Analysis" in this Handbook. Tin can render steel susceptible to temper embrittlement and hot shortness.

Arsenic and antimony also increase susceptibility of a steel to temper embrittlement.

Properties of Carbon and Alloy Steels Carbon Steels. The principal factors affecting the properties of the plain carbon steels are carbon content and

microstructure. Each type of microstructure is developed to characteristic property ranges by specific processing routes that control and exploit microstructural changes. Processing technologies not only depend on microstructure but are also used to tailor final microstructures. For example, sheet steel formability depends on the single-phase ferritic microstructures of low-carbon cold-rolled and annealed steel, while high strength and wear resistance are enhanced by carefully developed microstructures of very fine carbides in fine martensite in fine-grained austenite of high-carbon hardened steels. (See the Section "Structure/Property Relationships in Irons and Steels" for further details.) In addition to the predominant effects of carbon content and microstructure, the properties of plain carbon steels may be modified by the effects of residual elements other than the carbon, manganese, silicon, phosphorus, and sulfur that are always present. These incidental elements are usually picked up from the scrap, from the deoxidizers, or from the furnace refractories. The properties of carbon steels may also be affected by the presence of gases, especially oxygen, nitrogen, and hydrogen and their reaction products. The gas content is largely dependent upon the melting, deoxidizing, and pouring practice. The final properties of the plain carbon steels are therefore influenced by the steelmaking practice used in their production. Thus, the factors governing the properties of a plain carbon steel are primarily its carbon content and microstructure, with the microstructure being determined largely by the composition and the final rolling, forging, or heat-treating operations, and secondarily by the residual alloy, non-metallic, and gas content of the steel, which, in turn, depend on the steelmaking practice. Figure 1 illustrates the general effect of carbon content when the microstructure and grain size are held reasonably constant. These data are also representative for hot-rolled sheet and strip products. As this figure shows, hardness, tensile strength, and yield strength increase with increasing carbon content, while the elongation, reduction of area, and Charpy impact values decrease sharply. Tables 1 and 2 show both the effects of carbon content and heat treatment on the properties of carbon steels. Table 1 Mechanical properties of selected carbon and alloy steels in the hot-rolled, normalized, and annealed condition AISI No.(a)

1015

1020

Treatment

Elongation, %

Reduction in area, %

Hardness, HB

45.5

39.0

61.0

126

324.1

47.0

37.0

69.6

121

56.0

284.4

41.3

37.0

69.7

111

448.2

65.0

330.9

48.0

36.0

59.0

143

1600

441.3

64.0

346.5

50.3

35.8

67.9

131

1600

394.7

57.3

294.8

42.8

36.5

66.0

111

Austenitizing temperature

Tensile strength

Yield strength

°C

°F

MPa

ksi

MPa

ksi

As-rolled

...

...

420.6

61.0

313.7

Normalized

925

1700

424.0

61.5

Annealed

870

1600

386.1

As-rolled

...

...

Normalized

870

Annealed

870

1022

1030

1040

1050

1060

1080

1095

As-rolled

...

...

503.3

73.0

358.5

52.0

35.0

67.0

149

Normalized

925

1700

482.6

70.0

358.5

52.0

34.0

67.5

143

Annealed

870

1600

429.2

62.3

317.2

46.0

35.0

63.6

137

As-rolled

...

...

551.6

80.0

344.7

50.0

32.0

57.0

179

Normalized

925

1700

520.6

75.5

344.7

50.0

32.0

60.8

149

Annealed

845

1550

463.7

67.3

341.3

49.5

31.2

57.9

126

As-rolled

...

...

620.5

90.0

413.7

60.0

25.0

50.0

201

Normalized

900

1650

589.5

85.5

374.0

54.3

28.0

54.9

170

Annealed

790

1450

518.8

75.3

353.4

51.3

30.2

57.2

149

As-rolled

...

...

723.9

105.0

413.7

60.0

20.0

40.0

229

Normalized

900

1650

748.1

108.5

427.5

62.0

20.0

39.4

217

Annealed

790

1450

636.0

92.3

365.4

53.0

23.7

39.9

187

As-rolled

...

...

813.6

118.0

482.6

70.0

17.0

34.0

241

Normalized

900

1650

775.7

112.5

420.6

61.0

18.0

37.2

229

Annealed

790

1450

625.7

90.8

372.3

54.0

22.5

38.2

179

As-rolled

...

...

965.3

140.0

586.1

85.0

12.0

17.0

293

Normalized

900

1650

1010.1

146.5

524.0

76.0

11.0

20.6

293

Annealed

790

1450

615.4

89.3

375.8

54.5

24.7

45.0

174

As-rolled

...

...

965.3

140.0

572.3

83.0

9.0

18.0

293

Normalized

900

1650

1013.5

147.0

499.9

72.5

9.5

13.5

293

Annealed

790

1450

656.7

95.3

379.2

55.0

13.0

20.6

192

1117

1118

1137

1141

1144

1340

3140

4130

As-rolled

...

...

486.8

70.6

305.4

44.3

33.0

63.0

143

Normalized

900

1650

467.1

67.8

303.4

44.0

33.5

63.8

137

Annealed

855

1575

429.5

62.3

279.2

40.5

32.8

58.0

121

As-rolled

...

...

521.2

75.6

316.5

45.9

32.0

70.0

149

Normalized

925

1700

477.8

69.3

319.2

46.3

33.5

65.9

143

Annealed

790

1450

450.2

65.3

284.8

41.3

34.5

66.8

131

As-rolled

...

...

627.4

91.0

379.2

55.0

28.0

61.0

192

Normalized

900

1650

668.8

97.0

396.4

57.5

22.5

48.5

197

Annealed

790

1450

584.7

84.8

344.7

50.0

26.8

53.9

174

As-rolled

...

...

675.7

98.0

358.5

52.0

22.0

38.0

192

Normalized

900

1650

706.7

102.5

405.4

58.8

22.7

55.5

201

Annealed

815

1500

598.5

86.8

353.0

51.2

25.5

49.3

163

As-rolled

...

...

703.3

102.0

420.6

61.0

21.0

41.0

212

Normalized

900

1650

667.4

96.8

399.9

58.0

21.0

40.4

197

Annealed

790

1450

584.7

84.8

346.8

50.3

24.8

41.3

167

Normalized

870

1600

836.3

121.3

558.5

81.0

22.0

62.9

248

Annealed

800

1475

703.3

102.0

436.4

63.3

25.5

57.3

207

Normalized

870

1600

891.5

129.3

599.8

87.0

19.7

57.3

262

Annealed

815

1500

689.5

100.0

422.6

61.3

24.5

50.8

197

Normalized

870

1600

668.8

97.0

436.4

63.3

25.5

59.5

197

Annealed

865

1585

560.5

81.3

360.6

52.3

28.2

55.6

156

4140

4150

4320

4340

4620

4820

5140

5150

5160

6150

8620

Normalized

870

1600

1020.4

148.0

655.0

95.0

17.7

46.8

302

Annealed

815

1500

655.0

95.0

417.1

60.5

25.7

56.9

197

Normalized

870

1600

1154.9

167.5

734.3

106.5

11.7

30.8

321

Annealed

815

1500

729.5

105.8

379.2

55.0

20.2

40.2

197

Normalized

895

1640

792.9

115.0

464.0

67.3

20.8

50.7

235

Annealed

850

1560

579.2

84.0

609.5

61.6

29.0

58.4

163

Normalized

870

1600

1279.0

185.5

861.8

125.0

12.2

36.3

363

Annealed

810

1490

744.6

108.0

472.3

68.5

22.0

49.9

217

Normalized

900

1650

574.3

83.3

366.1

53.1

29.0

66.7

174

Annealed

855

1575

512.3

74.3

372.3

54.0

31.3

60.3

149

Normalized

860

1580

75.0

109.5

484.7

70.3

24.0

59.2

229

Annealed

815

1500

681.2

98.8

464.0

67.3

22.3

58.8

197

Normalized

870

1600

792.9

115.0

472.3

68.5

22.7

59.2

229

Annealed

830

1525

572.3

83.0

293.0

42.5

28.6

57.3

167

Normalized

870

1600

870.8

126.3

529.5

76.8

20.7

58.7

255

Annealed

825

1520

675.7

98.0

357.1

51.8

22.0

43.7

197

Normalized

855

1575

957.0

138.8

530.9

77.0

17.5

44.8

269

Annealed

815

1495

722.6

104.8

275.8

40.0

17.2

30.6

197

Normalized

870

1600

939.8

136.3

615.7

89.3

21.8

61.0

269

Annealed

815

1500

667.4

96.8

412.3

59.8

23.0

48.4

197

Normalized

915

1675

632.9

91.8

357.1

51.8

26.3

59.7

183

8630

8650

8740

9255

9310

Annealed

870

1600

536.4

77.8

385.4

55.9

31.3

62.1

149

Normalized

870

1600

650.2

94.3

429.5

62.3

23.5

53.5

187

Annealed

845

1550

564.0

81.8

372.3

54.0

29.0

58.9

156

Normalized

870

1600

1023.9

148.5

688.1

99.8

14.0

40.4

302

Annealed

795

1465

715.7

103.8

386.1

56.0

22.5

46.4

212

Normalized

870

1600

929.4

134.8

606.7

88.0

16.0

47.9

269

Annealed

815

1500

695.0

100.8

415.8

60.3

22.2

46.4

201

Normalized

900

1650

932.9

135.3

579.2

84.0

19.7

43.4

269

Annealed

845

1550

774.3

112.3

486.1

70.5

21.7

41.1

229

Normalized

890

1630

906.7

131.5

570.9

82.8

18.8

58.1

269

Annealed

845

1550

820.5

119.0

439.9

63.8

17.3

42.1

241

Data were obtained from specimens 12.8 mm (0.505 in.) in diameter that were machined from 25 mm (1 in.) rounds. (a) All grades are fine-grained except for those in the 1100 series, which are coarse grained. Heat-treated specimens were oil quenched unless otherwise indicated.

Table 2 Mechanical properties of selected carbon and alloy steels in the quenched-and-tempered condition AISI No.(a)

1030(b)

Elongation, %

Reduction in area, %

Hardness, HB

94

17

47

495

621

90

19

53

401

106

579

84

23

60

302

97

517

75

28

65

255

Tempering temperature

Tensile strength

Yield strength

°C

°F

MPa

ksi

MPa

ksi

205

400

848

123

648

315

600

800

116

425

800

731

540

1000

669

1040(b)

1040

1050(b)

1050

650

1200

586

85

441

64

32

70

207

205

400

896

130

662

96

16

45

514

315

600

889

129

648

94

18

52

444

425

800

841

122

634

92

21

57

352

540

1000

779

113

593

86

23

61

269

650

1200

669

97

496

72

28

68

201

205

400

779

113

593

86

19

48

262

315

600

779

113

593

86

20

53

255

425

800

758

110

552

80

21

54

241

540

1000

717

104

490

71

26

57

212

650

1200

634

92

434

63

29

65

192

205

400

1124

163

807

117

9

27

514

315

600

1089

158

793

115

13

36

444

425

800

1000

145

758

110

19

48

375

540

1000

862

125

655

95

23

58

293

650

1200

717

104

538

78

28

65

235

205

400

...

...

...

...

...

...

...

315

600

979

142

724

105

14

47

321

425

800

938

136

655

95

20

50

277

540

1000

876

127

579

84

23

53

262

650

1200

738

107

469

68

29

60

223

1060

1080

1095(b)

1095

1137

205

400

1103

160

779

113

13

40

321

315

600

1103

160

779

113

13

40

321

425

800

1076

156

765

111

14

41

311

540

1000

965

140

669

97

17

45

277

650

1200

800

116

524

76

23

54

229

205

400

1310

190

979

142

12

35

388

315

600

1303

189

979

142

12

35

388

425

800

1289

187

951

138

13

36

375

540

1000

1131

164

807

117

16

40

321

650

1200

889

129

600

87

21

50

255

205

400

1489

216

1048

152

10

31

601

315

600

1462

212

1034

150

11

33

534

425

800

1372

199

958

139

13

35

388

540

1000

1138

165

758

110

15

40

293

650

1200

841

122

586

85

20

47

235

205

400

1289

187

827

120

10

30

401

315

600

1262

183

813

118

10

30

375

425

800

1213

176

772

112

12

32

363

540

1000

1089

158

676

98

15

37

321

650

1200

896

130

552

80

21

47

269

205

400

1082

157

938

136

5

22

352

1137(b)

1141

1144

1330(b)

315

600

986

143

841

122

10

33

285

425

800

876

127

731

106

15

48

262

540

1000

758

110

607

88

24

62

229

650

1200

655

95

483

70

28

69

197

205

400

1496

217

1165

169

5

17

415

315

600

1372

199

1124

163

9

25

375

425

800

1103

160

986

143

14

40

311

540

1000

827

120

724

105

19

60

262

650

1200

648

94

531

77

25

69

187

205

400

1634

237

1213

176

6

17

461

315

600

1462

212

1282

186

9

32

415

425

800

1165

169

1034

150

12

47

331

540

1000

896

130

765

111

18

57

262

650

1200

710

103

593

86

23

62

217

205

400

876

127

627

91

17

36

277

315

600

869

126

621

90

17

40

262

425

800

848

123

607

88

18

42

248

540

1000

807

117

572

83

20

46

235

650

1200

724

105

503

73

23

55

217

205

400

1600

232

1455

211

9

39

459

315

600

1427

207

1282

186

9

44

402

1340

4037

4042

4130(b)

425

800

1158

168

1034

150

15

53

335

540

1000

876

127

772

112

18

60

263

650

1200

731

106

572

83

23

63

216

205

400

1806

262

1593

231

11

35

505

315

600

1586

230

1420

206

12

43

453

425

800

1262

183

1151

167

14

51

375

540

1000

965

140

827

120

17

58

295

650

1200

800

116

621

90

22

66

252

205

400

1027

149

758

110

6

38

310

315

600

951

138

765

111

14

53

295

425

800

876

127

731

106

20

60

270

540

1000

793

115

655

95

23

63

247

650

1200

696

101

421

61

29

60

220

205

400

1800

261

1662

241

12

37

516

315

600

1613

234

1455

211

13

42

455

425

800

1289

187

1172

170

15

51

380

540

1000

986

143

883

128

20

59

300

650

1200

793

115

689

100

28

66

238

205

400

1627

236

1462

212

10

41

467

315

600

1496

217

1379

200

11

43

435

425

800

1282

186

1193

173

13

49

380

4140

4150

4340

5046

540

1000

1034

150

910

132

17

57

315

650

1200

814

118

703

102

22

64

245

205

400

1772

257

1641

238

8

38

510

315

600

1551

225

1434

208

9

43

445

425

800

1248

181

1138

165

13

49

370

540

1000

951

138

834

121

18

58

285

650

1200

758

110

655

95

22

63

230

205

400

1931

280

1724

250

10

39

530

315

600

1765

256

1593

231

10

40

495

425

800

1517

220

1379

200

12

45

440

540

1000

1207

175

1103

160

15

52

370

650

1200

958

139

841

122

19

60

290

205

400

1875

272

1675

243

10

38

520

315

600

1724

250

1586

230

10

40

486

425

800

1469

213

1365

198

10

44

430

540

1000

1172

170

1076

156

13

51

360

650

1200

965

140

855

124

19

60

280

205

400

1744

253

1407

204

9

25

482

315

600

1413

205

1158

168

10

37

401

425

800

1138

165

931

135

13

50

336

540

1000

938

136

765

111

18

61

282

50B46

50B60

5130

5140

650

1200

786

114

655

95

24

66

235

205

400

...

...

...

...

...

...

560

315

600

1779

258

1620

235

10

37

505

425

800

1393

202

1248

181

13

47

405

540

1000

1082

157

979

142

17

51

322

650

1200

883

128

793

115

22

60

273

205

400

...

...

...

...

...

...

600

315

600

1882

273

1772

257

8

32

525

425

800

1510

219

1386

201

11

34

435

540

1000

1124

163

1000

145

15

38

350

650

1200

896

130

779

113

19

50

290

205

400

1613

234

1517

220

10

40

475

315

600

1496

217

1407

204

10

46

440

425

800

1275

185

1207

175

12

51

379

540

1000

1034

150

938

136

15

56

305

650

1200

793

115

689

100

20

63

245

205

400

1793

260

1641

238

9

38

490

315

600

1579

229

1448

210

10

43

450

425

800

1310

190

1172

170

13

50

365

540

1000

1000

145

862

125

17

58

280

650

1200

758

110

662

96

25

66

235

5150

5160

51B60

6150

81B45

205

400

1944

282

1731

251

5

37

525

315

600

1737

252

1586

230

6

40

475

425

800

1448

210

1310

190

9

47

410

540

1000

1124

163

1034

150

15

54

340

650

1200

807

117

814

118

20

60

270

205

400

2220

322

1793

260

4

10

627

315

600

1999

290

1772

257

9

30

555

425

800

1606

233

1462

212

10

37

461

540

1000

1165

169

1041

151

12

47

341

650

1200

896

130

800

116

20

56

269

205

400

...

...

...

...

...

...

600

315

600

...

...

...

...

...

...

540

425

800

1634

237

1489

216

11

36

460

540

1000

1207

175

1103

160

15

44

355

650

1200

965

140

869

126

20

47

290

205

400

1931

280

1689

245

8

38

538

315

600

1724

250

1572

228

8

39

483

425

800

1434

208

1331

193

10

43

420

540

1000

1158

168

1069

155

13

50

345

650

1200

945

137

841

122

17

58

282

205

400

2034

295

1724

250

10

33

550

8630

8640

86B45

8650

315

600

1765

256

1572

228

8

42

475

425

800

1407

204

1310

190

11

48

405

540

1000

1103

160

1027

149

16

53

338

650

1200

896

130

793

115

20

55

280

205

400

1641

238

1503

218

9

38

465

315

600

1482

215

1392

202

10

42

430

425

800

1276

185

1172

170

13

47

375

540

1000

1034

150

896

130

17

54

310

650

1200

772

112

689

100

23

63

240

205

400

1862

270

1669

242

10

40

505

315

600

1655

240

1517

220

10

41

460

425

800

1379

200

1296

188

12

45

400

540

1000

1103

160

1034

150

16

54

340

650

1200

896

130

800

116

20

62

280

205

400

1979

287

1641

238

9

31

525

315

600

1696

246

1551

225

9

40

475

425

800

1379

200

1317

191

11

41

395

540

1000

1103

160

1034

150

15

49

335

650

1200

903

131

876

127

19

58

280

205

400

1937

281

1675

243

10

38

525

315

600

1724

250

1551

225

10

40

490

8660

8740

9255

9260

425

800

1448

210

1324

192

12

45

420

540

1000

1172

170

1055

153

15

51

340

650

1200

965

140

827

120

20

58

280

205

400

...

...

...

...

...

...

580

315

600

...

...

...

...

...

...

535

425

800

1634

237

1551

225

13

37

460

540

1000

1310

190

1213

176

17

46

370

650

1200

1068

155

951

138

20

53

315

205

400

1999

290

1655

240

10

41

578

315

600

1717

249

1551

225

11

46

495

425

800

1434

208

1358

197

13

50

415

540

1000

1207

175

1138

165

15

55

363

650

1200

986

143

903

131

20

60

302

205

400

2103

305

2048

297

1

3

601

315

600

1937

281

1793

260

4

10

578

425

800

1606

233

1489

216

8

22

477

540

1000

1255

182

1103

160

15

32

352

650

1200

993

144

814

118

20

42

285

205

400

...

...

...

...

...

...

600

315

600

...

...

...

...

...

...

540

425

800

1758

255

1503

218

8

24

470

94B30

540

1000

1324

192

1131

164

12

30

390

650

1200

979

142

814

118

20

43

295

205

400

1724

250

1551

225

12

46

475

315

600

1600

232

1420

206

12

49

445

425

800

1344

195

1207

175

13

57

382

540

1000

1000

145

931

135

16

65

307

650

1200

827

120

724

105

21

69

250

Data were obtained from specimens 12.8 mm (0.505 in.) in diameter that were machined from 25 mm (1 in.) rounds. (a) All grades are fine-grained except for those in the 1100 series, which are coarse grained. Heat-treated specimens were oil quenched unless otherwise indicated.

(b) Water quenched

Alloy steels covered by SAE-AISI designations are not directly produced to specific mechanical properties, but are usually heat treated to achieve the desired properties. For lower strength applications, these steels are usually furnished in the as-rolled, normalized, or annealed condition. Higher strength values may be obtained in the normalized-and-tempered or quenched-and-tempered conditions with the latter heat treatment producing optimal results. Tables 1 and 2 show the effects of heat treatment on the properties of SAE-AISI carbon and alloy steels. Properties of steels produced to meet specific mechanical property requirements (for example ASTM specifications) are discussed in subsequent articles contained in this Section.

Low-Carbon Steel Sheet and Strip

LOW-CARBON STEEL sheet and strip are used primarily in consumer goods. These applications require materials that are serviceable under a wide variety of conditions and that are especially adaptable to low-cost techniques of mass production into articles having good appearance. Therefore, these products must incorporate, in various degrees and combinations, ease of fabrication, adequate strength, excellent finishing characteristics to provide attractive appearance after fabrication, and compatibility with other materials and with various coatings and processes. The steels used for these products are supplied over a wide range of chemical compositions; however, the vast majority are unalloyed, low-carbon steels selected for stamping applications, such as automobile bodies and appliances. For these major applications, typical compositions are 0.03 to 0.10% C, 0.15 to 0.50% Mn, 0.035% P (max), and 0.04% S (max). Generally, rimmed (or capped) ingot cast steel has been used because of its lower price. More recently, these steels have been replaced by killed steels produced by the continuous casting process. This process is inherently suited to the production of killed steels. Where strain aging is to be avoided and/or when exceptional formability is required, steel killed with aluminum, regardless of the method of casting or manufacture, is preferred. Further details regarding steelmaking and deoxidation practice are given in the Section "Steelmaking Practices and Their Influence on Properties" in this Handbook.

The width differentiation between sheet and strip made of plain carbon steel depends on the rolling process. It should be noted that both sheet and strip can be purchased as either cut lengths or coils. The standard dimensional tolerances for plain carbon steel strip are more restrictive than those for sheet. Standard size ranges of plain carbon steel sheet and strip are given in Table 1. Typical characteristics of the various qualities of these products are listed in Tables 2(a) and 2(b). Table 1 Standard sizes of low-carbon sheet and strip Product

Hot-rolled sheet

Hot-rolled strip

Cold-rolled sheet

Thickness

Width

mm

in.

mm

in.

1.2-6.0

0.045-0.230 incl

>300-1200 incl

>12-48 incl

Coils and lengths

1.2-4.5

0.45-0.180 incl

>1200

>48

Coils and lengths

6.012.5

0.230-0.500 incl

>300-1200 incl

>12-48 incl

4.512.5

0.180-0.500 incl

>1200-1800 incl

>48-72 incl

1.2-5.0

0.45-0.203 incl

200

1.2-6.0

0.045-0.229 incl

>200-300 incl

6.012.5

0.230-0.500 incl

0.352.0

0.35

Cold-rolled strip

6.0

Other limitations

Specification symbol (ASTM No.)

Metric units

English units

cut

A 569M, A 621M, or A 622M

A 569, A 621, or A 622

cut

A 569M, A 621M, or A 622M

A 569, A 621, or A 622

Coils only

A 635M

A 635

Coils only

A 635M

A 635

Coils and lengths

cut

A 569M, A 621M, or A 622M

A 569, A 621, or A 622

>6-12 incl

Coils and lengths

cut

A 569M, A 621M, or A 622M

A 569, A 621, or A 622

>200-300 incl

>8-12 incl

Coils only

A 635M

A 635

0.014-0.082 incl

>50-300 incl

>2-12 incl

(a)

A 366M, A 619M, or A 620M

A 366, A 619, or A 620

>0.014

>300

>12

(b)

A 366M, A 619M, or A 620M

A 366, A 619, or A 620

>12-600 incl

>0.50-23.9 incl

(c)

A 109M

A 109

0.250

6

(a) Cold-rolled sheet, coils, and cut lengths, slit from wider coils with cut edge (only) thickness 0.356-2.08 mm (0.014-0.082 in.) and 0.25% C (max) by cost analysis.

(b) When no special edge or finish (other than matte, commercial bright, or luster) is required and/or single-strand rolling of widths under 610 mm (24 in.) is not required.

(c) Width 51-305 mm (2-12 in.) with thicknesses of 0.356-2.08 mm (0.014-0.082 in.) are classified as sheet when slit from wider coils, have a cut edge only, and contain 0.25% C (max) by cost analysis.

Table 2(a) Summary of available types of hot-rolled and cold-rolled plain carbon steel sheet and strip Quality or temper

Applicable basic specification number

SAE-AISE grade designation

Surface finish

Temper-rolled; for exposed parts(a)

Annealed last; for unexposed parts(a)

Description

Symbol

Description

Symbol

As-rolled (black)

A

As-rolled (black)

A

Pickled--dry

P

Pickled--dry

P

Pickled and oiled

O

Pickled oiled

and

O

As-rolled (black)

A

As-rolled (black)

A

Pickled--dry

P

Pickled--dry

P

Pickled and oiled

O

Pickled oiled

and

O

As-rolled (black)

A

As-rolled (black)

A

Pickled--dry

P

Pickled--dry

P

Pickled and oiled

O

Pickled oiled

and

O

As-rolled (black)

A

As-rolled (black)

A

Pickled--dry

P

Pickled--dry

P

Pickled and oiled

O

Pickled oiled

Hot-rolled sheet

Commercial quality

Drawing quality

Drawing quality, special killed

A 569, A 635

A 621

A 622

1008-1012

1006-1008

1006-1008

Hot-rolled strip

Commercial quality

A 569

1008-1012

and

O

Drawing quality

Drawing quality, special killed

A 621

A 622

1006-1008

1006-1008

As-rolled (black)

A

As-rolled (black)

A

Pickled--dry

P

Pickled--dry

P

Pickled and oiled

O

Pickled oiled

and

O

As-rolled (black)

A

As-rolled (black)

A

Pickled--dry

P

Pickled--dry

P

Pickled and oiled

O

Pickled oiled

Matte

E

Matte

U

Commercial bright

B

Luster

L

Matte

E

Matte

U

Commercial bright

B

Luster

L

Matte

E

Matte

U

Commercial bright

B

Luster

L

Matte

1

Matte

1

Regular bright

2

Regular bright

2

and

O

Cold-rolled sheet

Commercial quality

Drawing quality

Drawing quality, special killed

A 366

A 619

A 620

1008-1012

1006-1008

1006-1008

Cold-rolled strip

Temper description numbers 1, 2, 3, 4, 5

A 109

(b)

Best bright

3

Best bright

3

(a) See Table 2(b) for a description of the surface finish listed.

(b) Produced in five tempers with specific hardness and bend test limits; composition subordinate to mechanical properties.

Table 2(b) Selection and specification of surface condition for plain carbon steel sheet Specification symbol

Description of surface

Surface described applicable to

U(a)

Surface finish as normally used for unexposed automotive parts. Matte appearance. Normally annealed last

Cold-rolled sheet

E(b)

Surface finish as normally used for exposed automotive parts that require a good painted surface. Free from strain markings and fluting. Matte appearance. Temper rolled

Cold-rolled sheet

B

Same as above, except commercial bright appearance

Cold-rolled sheet

L

Same as above, except luster appearance

Cold-rolled sheet

1

No. 1 or dull finish (no luster). Especially suitable for lacquer or paint adhesion. Facilitates drawing by reducing the contact friction between the die and the metal

Cold-rolled strip

2

No. 2 or regular bright finish (moderately smooth). Suitable for many applications, but not generally applicable for parts to be plated, unless polished and buffed

Cold-rolled strip

3

No. 3 or best bright finish (relatively high luster). Particularly suitable for parts to be plated

Cold-rolled strip

A

As-rolled or black (oxide or scale not removed)

Hot-rolled sheet and strip

P

Pickled (scale removed), not oiled

Hot-rolled sheet and strip

O

Same as above, except oiled

Hot-rolled sheet and strip

(a) U, unexposed; also designated as class 2, cold-rolled sheet.

(b) E, exposed; also designated as class 1, cold-rolled sheet

Production of Sheet and Strip

Most cold-rolled low-carbon steel sheet is available in two classes (Table 2(a)). Class 1 (temper rolled) is intended for applications where surface appearance is important and where specified surface and flatness requirements must be met. Class 2 is a product intended for applications where appearance is less important. Cold-rolled low-carbon steel strip is available in five hardness tempers ranging from full hard to dead soft (Table 3). Table 3 Mechanical properties of cold-rolled low-carbon steel strip (ASTM A 109) Temper

Bent test requirements(a)

Hardness requirements, HRB

Approximate tensile strength

Elongation in 50 mm (2 in.)(b), %

MPa

ksi

No bending in either direction

550690

80100

...

No. 1 (hard)

90 minimum(c), minimum(d)

No. 2 (halfhard)

70-85(d)

90° bend across rolling direction around a lt radius

380520

55-75

4-16

No. 3 (quarterhard)

60-75(e)

180° bend across rolling direction and 90° bend along rolling direction, both around a lt radius

310450

45-65

13-27

No. 4 rolled)

(skin

65 maximum(e)

Bend flat on itself in any direction

290370

42-54

24-40

No. 5 (dead

55 maximum(e)

Bend flat on itself in any direction

260-

38-50

33-45

84

(a) t = thickness of strip.

(b) For strip 1.27 mm (0.050 in.) thick.

(c) For strip of thickness 1.02-1.78 mm exclusive (0.040-0.070 in. exclusive).

(d) For strip of thickness 1.78-6.35 mm exclusive (0.070-0.250 in. exclusive).

(e) For strip of thickness 1.02-6.35 mm exclusive (0.040-0.250 in. exclusive)

Quality Descriptors for Carbon Steels The descriptors of quality used for hot-rolled plain carbon steel sheet and strip and cold-rolled plain carbon steel sheet include structural quality, commercial quality, drawing quality, and drawing quality, special killed (Table 2(a)). Some of the as-rolled material made to these qualities is subject to surface disturbances known as coil breaks, fluting, and stretcher strains; however, fluting and stretcher strains will not be produced during subsequent forming if the material is temper rolled and/or roller leveled immediately prior to forming. It should be noted that any beneficial effects of roller leveling deteriorate rapidly in nonkilled steel. In addition to the requirements listed below for the various qualities of plain carbon steel sheet and strip, special soundness can also be specified. Commercial quality (CQ) plain carbon steel sheet and strip are suitable for moderate forming; material of this quality has sufficient ductility to be bent flat on itself in any direction in a standard room-temperature bend test. Commercial

quality material is not subject to any other mechanical test requirements, and it is not expected to have exceptionally uniform chemical composition or mechanical properties. However, the hardness of cold-rolled CQ sheet is ordinarily less than 60 HRB at the time of shipment. Drawing Quality. When greater ductility or more uniform properties than those afforded by commercial quality are

required, drawing quality (DQ) is specified. Drawing quality material is suitable for the production of deep-drawn parts and other parts requiring severe deformation. When the deformation is particularly severe or resistance to stretcher strains is required, drawing quality, special killed (DQSK) is specified. Structural quality (SQ), formerly called physical quality (PQ), is applicable when specified strength and elongation

values are required in addition to bend tests (Table 4). Minimum values of tensile strength ranging up to 690 MPa (100 ksi) in hot-rolled sheet and strip and up to 1035 MPa (150 ksi) in cold-rolled sheet are available. Cold-rolled strip, which does not have a quality descriptor, is available in five tempers that conform to specified Rockwell hardness ranges and bend test requirements (Table 3). Table 4 Tensile requirements for structural quality low-carbon steel Class or grade

Yield strength, minimum

Tensile strength, minimum

MPa

MPa

ksi

Elongation in 50 mm (2 in.), minimum, %

ksi

Structural quality hot-rolled sheet and strip in cut lengths or coils (ASTM A 570)(a)

30

205

30

340

49

25.0(b)

33

230

33

360

52

23.0(b)

36

250

36

365

53

22.0(b)

40

275

40

380

55

21.0(b)

45

310

45

415

60

19.0(b)

50

345

50

450

65

17.0(b)

55

380

55

480

70

15.0(b)

Structural quality cold-rolled sheet in cut lengths or coils (ASTM A 611)(a)

A

170

25

290

42

26

B

205

30

310

45

24

C

230

33

330

48

22

D, types 1 and 2

275

40

360

52

20

E

550(c)

80(c)

565

82

...

(a) For coil products, testing by the producer is limited to the end of the coil. Results of such tests must comply with the specified values; however, design considerations must recognize that variation in strength levels can occur throughout the untested portions of the coil, though generally these levels will not be less than 90% of the minimum values specified.

(b) At thickness, t, of 2.5-5.9 mm (0.097-0.230 in.).

(c) On this full-hard product, the yield point approaches the tensile strength; because there is no halt in the gage or drop in the beam, the yield point shall be taken as the stress at 0.5% elongation, under load

Mechanical Properties The commonly measured tensile properties of plain carbon steel sheet and strip are not readily related to their performance in fabrication; the relationship between formability and values of the strain-hardening exponent, n, and the plastic strain ratio, r (determined in tensile testing), is discussed in the Section "Mechanical, Wear, and Corrosion Testing" in this Handbook. The mechanical properties of commercial quality, drawing quality, and drawing quality, special killed sheet and strip are not ordinarily used in specifications unless special strength properties are required in the fabricated product. As a matter of general interest, however, the ranges of mechanical properties typical of sheet produced by three mills in these qualities are shown in Fig. 1. The bands would be wider if the product of the entire industry were represented. It should be noted that the ranges are broader and the sheet harder for the hot-rolled than for the cold-rolled materials.

Fig. 1 Typical mechanical properties of low-carbon steel sheet shown by the range of properties in steel furnished by three mills. Hot-rolled sheet thickness from 1.519 to 3.416 mm (0.0598 to 0.1345 in., or 16 to 10 gage); cold-rolled sheet thickness from 0.759 to 1.519 mm (0.0299 to 0.0598 in., or 22 to 16 gage). All coldrolled grades include a temper pass. All grades were rolled from rimmed steel except the one labeled special killed. See Table 4 for the mechanical properties of structural (physical) quality sheet.

Modified Low-Carbon Steel Sheet and Strip

In addition to the low-carbon steel sheet and strip products already discussed in this article, there are numerous additional products available that are designed to satisfy specific customer requirements. These products are often made with lowcarbon steels having chemical compositions slightly modified from those discussed earlier. For example, in SQ steels, alloying additions of manganese and phosphorus are used to increase strength by substitutional solid-solution strengthening: approximately 3 MPa (0.4 ksi) per 0. 1% Mn, and 7 MPa (1 ksi) per 0.0 1% P. Hot-rolled SQ steels contain from 0.90 to 1.35% max Mn and 0.035% max P. Cold-rolled SQ steels contain 0.60 to 0.90% max Mn and 0.035 to 0.20% P. Carbon contents for SQ steels are generally 0.20 to 0.25%. Interstitial-Free Steels. In IF steels, which are also referred to as extra deep drawing quality (EDDQ), the elimination of interstitials (carbon and nitrogen) is accomplished by adding sufficient amounts of carbide/nitride-forming elements (generally titanium and/or niobium) to tie up carbon and nitrogen completely, the levels of which can be reduced to less than 50 ppm by modem steelmaking/casting practices, including vacuum degassing.

Steels with very low interstitial content exhibit excellent formability with low yield strength (138 to 165 MPa, or 20 to 24 ksi), high elongation (41 to 45%), and good deep drawability. With the addition of carbonitride-forming elements, the deep drawability and the nonaging properties are further improved. Bake-hardening (BH) steels are characterized by their ability to exhibit an increase in yield strength due to carbon

strain aging during paint-baking operations at moderate temperature (125 to 180 °C, or 260 to 355 °F). Bake hardening has little effect on tensile strength. Bake-hardening steels are finding increased usage in automotive outer-body applications (hoods, doors, fenders) to achieve an improvement in dent resistance and, in some cases, a sheet thickness reduction as well. The bake-hardening behavior is dependent on steel chemistry and processing, in addition to the amount of forming strain and paint-baking conditions (temperature and time). Steels that exhibit bake-hardening behavior include plain low-carbon steels (continuously annealed or batch annealed), IF steels (continuously annealed), and dual-phase steels (continuously annealed). Current automotive specifications for BH steels can be categorized according to those that specify a minimum yield strength level or a minimum bake-hardening increment, in the formed (strained) plus baked condition. The conventional test for determining bake-hardenability characteristics involves a 2% tensile prestrain, followed by baking at 175 ± 5 °C (345 ± 10 °F). The resulting increase in yield strength measures the bake hardenability of the material. While all the specifications call for a minimum yield strength level in the as-received (that is, prior to forming) condition, some also require a minimum yield strength after baking the as-received material in the absence of any tensile prestrain. The as-received yield strength is in the range 210 to 310 MPa (30 to 45 ksi) (compared with about 175 MPa, or 25 ksi, for DQSK), while the final yield strength, that is, after 2% prestrain plus bake, ranges between 280 and 365 MPa (40 to 53 ksi) (compared with about 225 MPa, or 33 ksi, for DQSK). Alloy Steel Sheet and Strip

ALLOY STEEL sheet and strip are used primarily for those special applications that require the mechanical properties normally obtained by heat treatment. A sizable selection of the standard alloy steels is available as sheet and strip, either hot rolled or cold rolled. The most commonly available alloys are listed in Table 5. In addition to standard low-alloy steels, high-strength low-alloy (HSLA) and dual-phase steels are available as sheet or strip for applications requiring tensile strengths in the range of 290 to 760 MPa (42 to 110 ksi). These steels are discussed in the article "High-Strength Structural and High-Strength Low-Alloy Steels" in this Section.

Table 5 Standard alloy steels available as sheet and strip SAE or AISI designation

Chemical composition ranges and limits (heat analysis)(a), %

C

Mn

P

S

Si(b)

Ni

Cr

Mo

4118

0.18-0.23

0.70-0.90

0.035

0.040

0.15-0.30

...

0.40-0.60

0.08-0.15

4130

0.28-0.33

0.40-0.60

0.035

0.040

0.15-0.30

...

0.80-1.10

0.15-0.25

4140

0.38-0.43

0.75-1.00

0.035

0.040

0.15-0.30

...

0.80-1.10

0.15-0.25

4340

0.38-0.43

0.60-0.80

0.035

0.040

0.15-0.30

1.65-2.00

0.70-0.90

0.20-0.30

5140

0.38-0.43

0.70-0.90

0.035

0.040

0.15-0.30

...

0.70-0.90

...

5150

0.48-0.53

0.70-0.90

0.035

0.040

0.15-0.30

...

0.70-0.90

...

5160

0.55-0.65

0.75-1.00

0.035

0.040

0.15-0.30

...

0.70-0.90

...

8615

0.13-0.18

0.70-0.90

0.035

0.040

0.15-0.30

0.40-0.70

0.40-0.60

0.15-0.25

(a) The chemical ranges and limits shown are subject to product analysis tolerances. See ASTM A 505.

(b) Other silicon ranges are available. Consult the producer.

Quality Descriptors As it is used for steel mill products, the term "quality" relates to the general suitability of the mill product to make a given class of parts. For alloy steel sheet and strip, the various quality descriptors imply certain inherent characteristics, such as degree of internal soundness and relative freedom from harmful surface imperfections. The quality descriptors used for alloy steel sheet and plate include regular quality, drawing quality, and aircraft quality, which are covered by ASTM specifications. The general requirements for these qualities are covered by ASTM A 505. Additional qualities include bearing quality and aircraft structural quality. Aircraft quality requirements are also covered in AMS specifications.

Mill Heat Treatment Hot-rolled regular-quality alloy steel sheet and strip normally are available from the producer either as rolled or as heat treated. Standard mill heat treated conditions are: annealed, normalized, and normalized and tempered. Cold-rolled regular-quality product normally is available only in the annealed condition. Precoated Steel Sheet

STEEL SHEET frequently is coated in coil form before fabrication either by the steel mills or by specialists called coil coaters. The basic types of precoating include metallic, conversion, preprimed, and prepainted finishing. Metallic coating may be done with zinc, aluminum, tin, terne metal, or combinations of metals such as aluminum and zinc. Conversion coatings are completed with phosphates, and preprimed finishes are done with zinc chromate and zinc-rich coatings. Prepainting consists of applying an organic paint system to steel sheet on a coil coating line either at a mill or at a coil coater.

Zinc Coatings Metallic zinc is applied to iron and steel by one of three processes: hot dip galvanizing, electrogalvanizing, or zinc spraying. Most galvanized steel sheet is coated by the hot dip process. Coating thickness is a key factor in determining coated product performance. In general, thicker coatings provide greater corrosion protection, whereas thinner coatings tend to give better formability and weldability. The amount of coating can also be expressed in terms of mass per unit area. This is determined by weighing a section of the coated product, stripping the coating in an acid solution, and weighing again. Table 6 summarizes coating thickness and mass called for by ASTM specifications. The coating thickness is usually expressed in terms of the coating on one side, whereas the mass is usually given as the sum of the coating on both sides. Table 6 Nominal coating mass and thickness for continuous hot dip coatings on steel sheet Type of coating(a)

Zinc (A 525)

Zinc-iron (A 525)

Coating mass(b), g/m2

Coating thickness(c),

Z1100

1100

78

900

900

64

700

700

50

600

600

42

450

450

32

350

350

25

275

275

19

180

180

13

90

90

6

001

(d)

(d)

ZF180

180

11

Designation

m

Aluminum (A 463) type 1

Aluminum (A 463) type 2

Zn-5Al (A 575)

Zn-55Al (A 792)

120

120

9

100

100

7

75

75

5

001

(d)

(d)

T1 40

120

20

25

75

12

T2 100

305

48

65

195

30

LC

(d)

(d)

ZGF 700

700

48

600

600

41

450

450

31

350

350

24

275

275

19

225

225

15

180

180

12

135

135

9

90

90

6

001

(d)

(d)

AZ 180

180

24

165

165

22

Lead-tin (A 308)

150

150

20

LT 110

336

15

85

259

12

55

168

8

40

122

6

35

107

5

25

76

3

01

(d)

(d)

All values are based on specified triple-spot minima. (a) ASTM specifications as given in Coated Steel Products, Vol 01.06, Annual Book of ASTM Standards, ASTM.

(b) Two sides.

(c) One side. Calculated from densities in g/cm3 as follows: zinc and zinc-iron, 7.07; aluminum type 1, 3.017; aluminum type 2, 3.21; Zn-5Al, 6.87; Zn-55Al, 3.70; lead-tin, 11.08.

(d) No minimum

Hot dip galvanizing is a process in which an adherent, protective coating of zinc and iron-zinc alloys is developed on

the surfaces of iron and steel products by immersing them in a bath of molten zinc. Most zinc coating of steel sheet is done by this process, usually on a continuous galvanizing line. A typical hot dip galvanized coating consists of a series of layers. Starting from the basis steel at the bottom of the coating, each successive layer contains a higher proportion of zinc until the outer layer, which is relatively pure zinc, is reached. There is, therefore, no discrete line of demarcation between the iron and zinc, but a gradual transition through the series of iron-zinc alloys that provide a powerful bond between the basis metal and the coating. Electrogalvanizing. Very thin formable zinc coatings ideally suited for deep drawing or painting can be obtained on

steel products by electrogalvanizing. Zinc is electrodeposited on a variety of mill products, sheet, wire and, in some instances, pipe. Electrogalvanizing of sheet and wire in coil form produces a thin, uniform coating of pure zinc. Electrodeposited zinc coatings are simpler in structure than hot dip galvanized coatings. They are composed of pure zinc, have a homogeneous structure, and are highly adherent. These coatings are not generally as thick as those produced by hot dip galvanizing. However, they do give good corrosion-free service. Coating thicknesses/masses range from 4 to 14 m (30 to 100 g/m2) per side, although the most common coating thicknesses/masses are 8 and 10 m (60 and 70 g/m2). For nonautomotive applications, a thickness/mass of as low as 1.5 m (10 g/m2) can be used. Electrodeposited zinc is considered to adhere to steel as well as any other metallic coating. Because of its excellent adhesion, electrogalvanized coils of steel sheet and wire have good working properties, and the coating remains intact after severe deformation. Good

adhesion depends on very close physical conformity of the coating with the basis metal. Therefore, particular care must be taken during initial cleaning. Electrodeposition also affords a means of applying zinc coatings to finished parts that cannot be predipped. It is especially useful where a high processing temperature could injure the part. One advantage of electrodeposition is that it can be done cold and thus does not change the mechanical properties of the steel. Zinc spraying consists of projecting atomized particles of molten zinc onto a prepared surface. Three types of spraying

pistols are in commercial use today: the molten metal pistol, the powder pistol, and the wire pistol. The sprayed coating is slightly rough and slightly porous; the specific gravity of a typical coating is approximately 6.35, compared with 7.1 for cast zinc. This slight porosity does not affect the protective value of the coating, because zinc is anodic to steel. The zinc corrosion products that form during service fill the pores of the coating, giving a solid appearance. The slight roughness of the surface makes it an ideal basis for paint, when properly pretreated. Chromate Passivation. Several types of finishes can be applied to zinc-coated surfaces to provide extra corrosion

resistance. The simplest type of finish applicable to fresh zinc surfaces is a chromate passivation treatment. It is equally suitable for use on hot dip galvanized, zinc-sprayed, and zinc-plated articles. Usually, the treatment consists of simply cleaning the articles and then dipping them in a chromic acid or sodium dichromate solution at about 20 to 30 °C (68 to 86 °F), followed by rinsing in cold fresh water and drying in warm air. Anodizing of galvanized steel produces a surface that exhibits exceptional resistance to corrosion, wear, heat, and

abrasion. The anodized film is an electrical insulator. The film is formed by immersing finished parts in a simple electrolyte and applying an increasing voltage for up to 10 min. A nonreflective functional coating, anodized zinc demonstrates superior properties when compared with chromate conversion coatings. The anodized zinc coatings range from 25 to 33 m (1.0 to 1.3 mils) in thickness and will not deteriorate at temperatures up to the melting point of zinc. Painting. The selection of galvanized steel as a material for barns, buildings, roofs, sidings, appliances and many

hardware items is based on the sacrificial protection plus the barrier coating afforded the basis metal by zinc coating. For additional protection and pleasing appearance, paint coatings are often applied to the galvanized steel. Weldability. Direct spot welding is recommended for zinc-coated steel, which may be either hot dip galvanized or

electroplated, because the shunting current associated with series welding, when added to the higher-than-normal current needed to weld zinc-coated steel, results in excessive electrode heating and short electrode life. Weldability of thin sheets electroplated with zinc decreases as the coating thickness increases, in the range from 0.005 to 0.025 mm (0.0002 to 0.001 in.). However, as sheet thickness increases above 1.5 mm (0.060 in.), weldability increases regardless of coating thickness. The welding behavior of hot dip galvanized steel is affected by the thickness and uniformity of the zinc-iron alloy layer, as well as the thickness of unalloyed zinc.

Aluminum Coatings Aluminized (aluminum-coated) steel sheet is used for applications where heat resistance, heat reflectivity, or resistance to corrosion are required in an aesthetically pleasing, economical sheet. Aluminum coating is done on continuous lines similar to those used for hot dip galvanizing of steel sheet. Cold rolled steel sheet is hot dipped into molten aluminum or an aluminum alloy containing 5 to 11% Si. The coating consists of two interfacial layers. Between the exterior layer of aluminum-silicon alloy and the steel basis metal, an aluminum-iron-silicon alloy layer is formed. This alloy can significantly affect the ductility, adhesion, uniformity, smoothness, and appearance of the surface and is controlled for optimum properties. Coating Thickness. Two kinds of aluminum coating are produced (Table 6). Type 2 is a thicker coating (typically 30 to 50 m) that is applied by dipping in an unalloyed aluminum bath. This product is used for outdoor construction applications such as roofing, culverts, and silos that require resistance to atmospheric corrosion and have limited formability requirements.

Type 1 aluminum coating is a thinner, aluminum-silicon alloy coating intended primarily for applications requiring formability and resistance to high temperatures, such as automobile exhaust components. Type 1 aluminum coatings are also applied to improve appearance. For most uses, the usual thickness of a Type 1 coating (Class 40) is about 20 to 25 m (0.8 to 1 mil). When maximum formability is a critical requirement, a thinner 12 m (Class 25) coating is specified.

Corrosion Resistance. Aluminum's value as a protective coating for steel sheet lies principally in its inherent

corrosion resistance. In most environments, the long-term corrosion rate of aluminum is only about 15 to 25% of that of zinc. Generally, the protective value of an aluminum coating on steel is a function of coating thickness. The coating tends to remain intact and thus provides long-term protection. Aluminum coatings do not provide sacrificial protection in most environments, particularly in atmospheric exposure. Heat Resistance. Aluminum-coated sheet steel has excellent resistance to high-temperature oxidation. At surface

temperatures above about 510 °C (950 °F), the aluminum coating protects the steel basis metal against oxidation without discoloration. Between 510 and 675 °C (950 and 1250 °F), the coating provides protection to the steel, but some darkening may result from the formation of aluminum-iron-silicon alloy. The alloy is extremely heat resistant, but on long exposure, the coating may become brittle and spall at temperatures above 675 °C (1250 °F) due to a different coefficient of expansion from that of the steel. Weldability. Aluminum-coated steel sheet can be joined by electric resistance welding (spot welding or seam welding). It also can be metal-arc welded, flash welded, or oxyacetylene welded. Thorough removal of grease, oil, paint, and dirt followed by wire brushing is recommended before joining. Special fluxes are required for metal arc and oxyacetylene welding. During spot welding, electrodes tend to pick up aluminum, and the tips must be dressed more frequently than during spot welding of uncoated steel. Also, current density should be higher.

Tin Coatings Tin coatings are applied to steel sheet either by electrolytic deposition or by immersion in a molten bath of tin (hot dip process). Hot dip tin coatings are applied to provide nontoxic, protective and decorative coating of food-handling, packaging, and dairy equipment, and to facilitate soldering of components used in electronic and electrical equipment. In the United States, hot dip tin coating has been replaced by electrolytic tin coating. Electrolytic tin-coated steel sheet is used where solderability, appearance, or corrosion resistance under certain conditions is important, such as in electronic equipment, food-handling and processing equipment, and laboratory clamps. It is generally produced with a matte finish formed by applying the coating to basis metal sheet called "black plate," which has a dull surface texture, and leaving the coating unmelted. It can also be produced with a bright finish formed by applying the coating to basis metal having a smooth surface texture and then melting the coating. Electrolytic tin-coated sheet is usually produced in nominal thicknesses from 0.38 to 0.84 mm (0.015 to 0.033 in.) and in widths from 300 to 910 mm (12 to 36 in.). Tin coatings are of the order of 0.4 to 1.5 m thick, although they are usually expressed in terms of coating mass. Present values range from 0.5 to 11 g/m2 on each surface. In the United States, tin coatings have numbers (Table 7) that designate the total weight of tin (i.e., the weight of the tin on the two sides per base box, a measure of surface area equal to 31,360 in.2, originally defined as 112 sheets, 14 by 20 in.). Presently there is a tendency, for economical and technological reasons, to apply lower-tin coatings, most commonly No. 20 or 25 (2.2 or 2.8 g/m2). Table 7 Electrolytic tin coating weight and mass designations Designation No.

Nominal tin coating weight each surface(a), lb/base box

Minimum average coating weight each surface test value(a)(b), lb/base box

Coating weights per ASTM A 624

10

0.05/0.05

0.04/0.04

20

0.10/0.10

0.08/0.08

25

0.125/0.125

0.11/0.11

35

0.175/0.175

0.16/0.16

50

0.25/0.25

0.23/0.23

75

0.375/0.375

0.35/0.35

100

0.50/0.50

0.45/0.45

D50/25(c)

0.25/0.125

0.23/0.11

D75/25(c)

0.375/0.125

0.35/0.11

D100/25(c)

0.50/0.125

0.45/0.11

D100/50(c)

0.50/0.25

0.45/0.23

D135/25(c)

0.675/0.125

0.62/0.11

Nominal tin coating mass each surface, g/m2

Minimum average coating mass each surface test value(d), g/m2

Coating masses per ASTM A 624M

1.1/1.1

0.9/0.9

2.2/2.2

1.8/1.8

2.8/2.8

2.5/2.5

3.9/3.9

3.6/3.6

5.6/5.6

5.2/5.2

8.4/8.4

7.8/7.8

11.2/11.2

10.1/10.1

D5.6/2.8(c)

5.2/2.5

D8.4/2.8(c)

7.8/2.5

D11.2/2.8(c)

10.1/2.5

D11.2/5.6(c)

10.1/5.2

D15.2/2.8(c)

14.0/2.5

Note: Listed above are the commonly produced coating weights and masses. Upon agreement between the producer and the purchaser, other combinations of coatings may be specified and the appropriate minimum average test values will apply. (a) Base box is a measure of surface area equal to 31,360 in.2.

(b) The minimum value shall be not less than 80% of the minimum average tin coating weight.

(c) The letter D on differentially coated tin plate indicates the coated surface to be marked. For example, the examples indicate that the heavycoated side is marked.

(d) The minimum spot value shall be not less than 80% of the minimum average tin coating mass.

Terne Coatings Long terne steel sheet is carbon steel sheet continuously coated by various hot dip processes with terne metal (lead with 3 to 15% tin). This coated sheet is duller in appearance than conventional tin-coated sheet, hence the name (terne) from the French, which means "dull" or "tarnished." The smooth, dull coating gives the sheet corrosion resistance, formability, excellent solderability, and paintability. The term "long terne" is used to describe terne-coated sheet, while "short terne" is used for terne-coated plate. Because of its unusual properties, long terne sheet has been adapted to a wide variety of applications. Its greatest use is in automotive gasoline tanks. Its excellent solderability and special corrosion resistance makes the product well suited for this application. Long terne sheet is often produced to ASTM A 308. The coatings are designated according to total coating weight on both surfaces as shown in Table 6. For applications requiring good formability, the coating is applied over low-carbon steel sheet of commercial quality, drawing quality, or drawing quality special killed, The terne coating acts as a lubricant and facilitates forming, and the strong bond of the terne metal allows it to be formed along with the basis metal. When higher strength is required, the coating can be applied over low-carbon steel sheet of structural (physical) quality, although at some sacrifice in ductility.

Phosphate Coatings Phosphate coating of iron and steel consists of treatment with a dilute solution of phosphoric acid and other chemicals whereby the surface of the metal, reacting chemically with the phosphoric acid, is converted to an integral layer of insoluble crystalline phosphate compound. This layer is less reactive than the metal surface and at the same time is more absorbent of lubricants or paints. Because the coating is an integral part of the surface, it adheres to the basis metal tenaciously. The chief application for iron phosphate coatings is as a paint base for nongalvanized carbon steel sheet; such a coating is usually applied on coil-coating lines. Manganese phosphate coatings are used chiefly as an oil base on engine parts for break-in and to prevent galling.

Steel Sheet for Porcelain Enameling

PORCELAIN ENAMELS are glass coatings applied primarily to products or parts made of sheet steel, cast iron, or aluminum to improve appearance and to protect the metal surface. Porcelain enamels are distinguished from other ceramic coatings on metallic substrates by their predominantly vitreous nature and the types of applications for which they are used. These coatings are differentiated from paint by their inorganic composition and coating properties. They are fused to the metallic substrate at temperatures above 425 °C (800 °F) during the firing process. Properties of the particular steel sheet should be evaluated before its selection for enameling; some steel sheet is not recommended because of problems that complicate the process of coating the sheet with porcelain enamel. The four major problems are: • • • •

Distortion caused by sag and warpage occurring at the temperatures reached during firing of the enamel Improper surface preparation that causes poor adherence Fishscale imperfections, particularly of the delayed variety, caused by hydrogen evolution Carbon boiling in the enamel coating caused by surface carbides in the steel

Steels for porcelain enameling with a single cover coat (white or colored) have since been developed. These steels, in addition to possessing single-coat coverage, have good sag resistance and freedom from carbon boiling, fishscale formation and the other problems associated with carbon, and internal imperfections. These steels are highly formable and can be drawn into more complex shapes than enameling iron.

Types of Sheet Six types of steel sheet are available for porcelain enameling, These are described below. In most instances, a detailed review should be made with the steel supplier before ordering a particular grade or beginning production. Typical chemical analysis of the steels recommended for enameling are listed in Table 8. Table 8 Compositions of low-carbon steels used for porcelain enameling Type of steel

Composition(a), %

C

Mn

P

S

Al

Ti

Nb

B

Si

Low-carbon enameling steels(b)

0.02-0.04

0.15-0.3

0.015(c)

0.015(c)

0.03-0.07

...

...

0.006

0.015(c)

Decarburized

0.005

0.2-0.3

0.01

0.02

(d)

...

...

...

...

Titanium-stabilized

0.05

0.30

0.01

0.02

0.05

0.30

...

...

...

Interstitial-free

0.005-0.020

0.20

0.01

0.02

...

0.06-0.15

0.10

...

...

(a)

All compositions contain balance of iron.

(b)

Aluminum-killed replacement steel for enameling iron, which was a rimmed ingot-poured product formerly used for porcelain enameling.

(c)

Maximum.

(d)

Some steels may be supplied as aluminum-killed products.

Low-Carbon Enameling Steels (Enameling Iron Replacements). For many years, enameling iron, a rimmed-

ingot poured product with a low metalloid content, was used extensively for porcelain enameling. The enameling characteristics were excellent, with the caveat that the product required a separate ground coat before applying a cover coat. Because enameling iron is a rimmed steel, it cannot be continuously cast. The movement in the steel industry to continuous casting has resulted in the recent withdrawal of the product from the market. A number of highly serviceable enameling iron replacement products are now available for porcelain enameling. These aluminum killed steels have low carbon (0.02 to 0.04 wt%) and low manganese (0.15 to 0.30 wt%), along with 0.015 wt% P max, 0.015 wt% S max, 0.015 wt% Si max, and 0.03 to 0.07 wt% Al. Some contain a boron addition (0.006 wt% max) to aid in grain size control and to help improve resistance to enamel fishscale. The yield strength is 172 to 221 MPa (25 to 32 ksi), the tensile strength is 303 to 338 MPa (44 to 49 ksi), and the elongation is 38 to 46%. Unlike the old enameling iron, these products do not require normalizing; they are either box annealed or continuously annealed. These processing changes result in steels that are more formable than their predecessors. Experience to date indicates that the enameling characteristics are similar to those of enameling iron, and these steels are being used in the same applications. They perform well with both ground-coat and two-coat/two-fire systems. Decarburized Steels. The manufacture of fully decarburized sheet for direct-on cover coat enameling became practical following the development of the open coil annealing process. Different melting and teeming practices may be used to produce decarburized sheets: for instance, ladle aluminum killed-ingot poured and ladle aluminum killedcontinuously cast. These aluminum killed products are not subject to the return of yield point elongation following temper rolling. As killed steels, the hot coiling off the hot strip mill eliminates the possibility of having deep drawability, but in stretch and plane strain conditions, the decarburized products are excellent performers.

Enameling characteristics for decarburized steels are excellent, and these steels are being used in all types of today's enamel systems. The low carbon content eliminates primary boiling and consequent defects such as black specks, pullthrough, and dimples caused by the evolution of carbon monoxide and carbon dioxide through the porcelain enamel coating during firing. These steels have excellent resistance to warpage. They also exhibit good resistance to defects such as fishscale and ground-coat reboiling during firing of the cover coat, both of which are caused by the evolution of hydrogen gas. If overpickled using the acid etch/nickel deposition metal preparation method, ladle killed steels will tend to have a "gassy" enamel surface, and enamel adherence is likely to be substandard. Ladle killing with aluminum and continuously casting is becoming the predominant way to produce these steels. It is expected that all decarburized steels will soon be manufactured by this method. Interstitial-free steels are products in which all of the carbon and nitrogen contained in them are combined with an alloying element. Titanium or niobium (columbium), or a combination of titanium and niobium additions, are used to fully stabilize the steel. Domestically produced IF steels contain from 25-76

>1-3

7

3

5

3

>76

>3

7

4

7

3

7

3

5

3

10

3

10

3

Inside draft

6.35-25.4 -1

>25.4

>1

(a) The minus tolerance is zero.

Fig. 10 Definition of inside and outside draft and limitations on the depth of the cavities between ribs.

Tolerances Forging tolerances, based on area and weight, that represent good commercial practice are listed in Tables 3 and 4. These tolerances apply to the dimensions shown in the illustration accompanying Table 3. In using these tables to determine the size of the forging, the related tolerances, such as mismatch, die wear, and length, should be added to allowance for machining plus machined dimensions. On the average, tolerances listed in Tables 3 and 4 conform to the full process tolerances of actual production parts and yield more than 99% acceptance of any dimension specified from this table. In particular, instances may be found of precise accuracy or rarely as much as ±50% error in the tolerances recommended in Table 4. Table 3 Recommended commercial tolerances on length and location

Maximum length of forging

Tolerance on length or location

mm

in.

mm

in.

150

6

+1.19, -0.79

+0.047, -0.031

380

15

+1.57, -1.19

+0.062, -0.047

610

24

+3.18, -1.57

+0.125, -0.062

910

36

+3.18, -1.57

+0.125, -0.062

1220

48

+3.18, -3.18

+0.125, -0.125

1520

60

+4.75, -3.18

+0.187, -0.125

1830

72

+5.56, -3.18

+0.219, -0.125

Table 4 Recommended commercial tolerances for steel forgings Tolerance

Forging size

Thickness(a)

Area

Weight

Plus

Mismatch(a), plus

Die wear, plus

Minus

103 mm2

in.2

kg

lb

mm

in.

mm

in.

mm

in.

mm

in.

3.2

5.0

0.45

1

0.79

0.031

0.41

0.016

0.41 to 0.79

0.016 to 0.031

0.79

0.031

4.5

7.0

3.2

7

1.57

0.062

0.79

0.031

0.41 to 0.79

0.016 to 0.031

1.57

0.062

6.5

10.0

0.7

1.5

0.79

0.031

0.79

0.031

0.41 to 0.79

0.016 to 0.031

0.79

0.031

7.7

12.0

5.5

12

1.57

0.062

0.79

0.031

0.41 to 0.79

0.016 to 0.031

1.57

0.062

12.9

20.0

0.9

2

1.57

0.062

0.79

0.031

0.41 to 0.79

0.016 to 0.031

1.57

0.062

12.9

20.0

14

30

1.57

0.062

0.79

0.031

0.51 to 1.02

0.020 to 0.040

1.57

0.062

24.5

38.0

2

4.5

1.57

0.62

0.79

0.031

0.41 to 0.79

0.016 to 0.031

1.57

0.062

24.5

38.0

36

80

1.57

0.62

0.79

0.031

0.64 to 1.27

0.025 to 0.050

1.57

0.062

32.3

50.0

3

8

1.57

0.062

0.79

0.031

0.51 to 1.02

0.020 to 0.040

1.57

0.062

32.3

50.0

27

60

1.57

0.062

0.79

0.031

0.51 to 1.02

0.020 to 0.040

1.57

0.062

32.3

50.0

45

100

1.57

0.062

0.79

0.031

0.64 to 1.27

0.025 to 0.050

1.57

0.062

61.3

95.0

5

11

1.57

0.062

0.079

0.031

0.51 to 1.02

0.020 to 0.040

1.57

0.062

85.2

132.0

8

17

1.57

0.062

0.79

0.031

0.64 to 1.27

0.025 to 0.050

1.57

0.062

107

166.0

33

73

2.39

0.094

0.79

0.031

0.76 to 1.52

0.030 to 0.060

2.39

0.094

113

175.0

68

150

2.39

0.094

0.79

0.031

0.76 to 1.52

0.030 to 0.060

2.39

0.094

130

201.0

18

40

1.57

0.062

0.79

0.031

0.64 to 1.27

0.025 to 0.050

1.57

0.062

155

240.0

23

51.5

2.39

0.094

0.79

0.031

0.76 to 1.52

0.030 to 0.060

2.39

0.094

161

250.0

114

250

2.39

0.094

0.79

0.031

0.76 to 1.52

0.030 to 0.060

2.39

0.094

171

265.0

27

60

2.39

0.094

0.79

0.031

0.76 to 1.52

0.030 to 0.060

2.39

0.094

177

275.0

30

65

3.18

0.125

0.79

0.031

1.19 to 2.39

0.047 to 0.094

3.18

0.125

194

300.0

34

75

3.18

0.125

1.57

0.062

1.19 to 2.39

0.047 to 0.094

3.18

0.125

194

300.0

159

350

2.39

0.094

0.79

0.031

0.76 to 1.52

0.030 to 0.060

2.39

0.094

242

375.0

205

450

3.18

0.125

0.79

0.031

1.19 to 2.39

0.047 to 0.094

3.18

0.125

268

415.0

139

306

3.18

0.125

1.57

0.062

1.19 to 2.39

0.047 to 0.094

3.18

0.125

339

525.0

340

750

3.18

0.125

1.57

0.062

1.19 to 2.39

0.047 to 0.094

3.18

0.125

580

900.0

455

1000

3.18

0.125

1.57

0.062

1.19 to 2.39

0.047 to 0.094

3.18

0.125

(a) The illustration in Table 3 shows locations of thickness and mismatch.

The characteristics of die wear are shown graphically in Fig. 11. The part represented was made of 4140 steel, using ten blows in a 11 kN (2500 lbf) board hammer. Tolerances were commercial standard, and the part was later coined to a thickness tolerance of +0.25 mm, -0.000 (+0.010 in., -0.000). The die block, 250 by 455 by 455 mm (10 by 18 by 18 in.), was hardened to 42 HRC. After 30,000 forgings had been produced, the die wore as indicated and the dies were resunk.

Fig. 11 Extent of die wear in a die block hardened to 42 HRC. The block was evaluated for die wear after producing 30,000 forgings of 4140 steel at a rate of 10 blows/workpiece with an 11 kN (2500 lbf) hammer.

Ranges of mismatch tolerance are given in Table 4. The higher values are to be added to tolerances for forgings that need locked dies or involve side thrust on the dies during forging. On forgings heavier than 23 kg (50 lb), it is sometimes necessary to grind out mismatch defects up to 3.18 mm (

in.) maximum.

Flash is trimmed in a press with a trimming die shaped to suit the plan view, outline, and side view contour of the parting

line. The forging may be trimmed with a stated amount of burr or flash left around the periphery at the parting line.

Design of Hot Upset Forgings Hot heading, upset forging, or more broadly, machine forging consists primarily of holding a bar of uniform cross section, usually round, between grooved dies and applying pressure on the end in the direction of the axis of the bar by using a heading tool so as to upset or enlarge the end into an impression of the die. The shapes generally produced include a variety of enlargements of the shank, or multiple enlargements of the shank and "re-entrant angle" configurations. Transmission cluster gears, pinion blanks, shell bodies and many other shaped parts are adapted to production by the upset machine forging process. This process produces a "looped" grain flow of major importance for gear teeth. Simple, headed forgings may be completed in one step, while some that have large, configured heads or multiple upsets may require as many as six steps. Upset forgings are produced weighing from less than 0.45 kg (1 lb) to about 225 kg (500 lb). Machining Stock Allowances. The standard for machining stock allowance on any upset portion of the forging is 2.39 mm (0.094 in.), although allowances vary from 1.58 to 3.18 mm (0.062 to 0.125 in.), depending on size of upset, material and shape of the part (Fig. 12a).

Fig. 12 Machining stock allowances for hot upset forgings. (a) Hot upset forging terminology and standards. (b) Probable shape of shear-cut ends. (c) Variation of corner radius with thickness of upset. These parts are the

simplest forms of upset forgings. Dimensions given in inches

Mismatch and shift of dies are each limited to 0.406 mm (0.016 in.) maximum. Mismatch is the location of the gripper dies with respect to each other. Parting-line clearance is required in gripper dies for tangential clearance in order to avoid undercut and difficulty in removal of the forging from the dies (Fig. 12a). Tolerances for shear-cut ends have not been established. Figure 12(b) shows a shear-cut end on a 31.8 mm (1 in.) diameter shank. Straight ends may be produced by torch cutting, hack-sawing, or abrasive wheel cutoff, at a higher cost than that of shearing. Corner radii should follow the contours of the finished part, with a minimum radius of 1.59 mm ( in.). Radii at the outer diameter of the upset face are not required, but may be specified as desired. Variations in thickness of the upset require variations in radii, as shown in Fig. 12(c), because the source of the force is farther removed and the die cavity is more difficult to fill. When a long upset is only slightly larger than the original bar size, a taper is advisable instead of a radius. Tolerances for all upset forged diameters are generally +1.59 mm, -0 (+

in., -0) except for thin sections of flanges

in., -0). The increase of and upsets relatively large in ratio to the stock sizes used, where they are +2.38 mm, -0 (+ tolerances over the standard +1.59 mm, -0 is sometimes a necessity, because of variations in size of hot rolled mill bars, extreme die wear, or complexity of the part. Draft angles may vary from 1 to 7°, depending on the characteristics of the forging design. Draft is needed to release the forging from the split dies; it also reduces the shearing of face surfaces in transfer from impression to impression. For an upset forged part that requires several operations or passes, the dimensioning of lengths is determined on the basis of the design of each individual pass or operation.

STEEL CASTINGS Introduction STEEL CASTINGS can be made from any of the many types of carbon and alloy steel produced in wrought form. Such castings are produced by pouring molten steel of the desired composition into a mold of the desired configuration and allowing the steel to solidify. The mold material may be silica, zircon, chromite or olivine sand, graphite, metal, or ceramic. Choice of mold material depends on the size, intricacy, and dimensional accuracy of the casting and on cost. While the producible size, surface finish, and dimensional accuracy of castings vary widely with the type of mold, the properties of the cast steel are not affected significantly. Steel castings produced in any of the various types of molds and wrought steel of equivalent chemical composition respond similarly to heat treatment, have the same weldability, and have similar physical, mechanical, and corrosion properties. Cast steels do not exhibit the effects of directionality on mechanical properties that are typical of wrought steels.

Table 1 Summary of specification requirements for various carbon steel castings Unless otherwise noted, all the grades listed in this table are restricted to a phosphorus content of 0.040% max and a sulfur content of 0.045% max. Class or grade

Tensile strength(a)

Yield strength(a)

MPa

MPa

ksi

Minimum elongation in 50 mm (2 in.), %

Minimum reduction in area, %

ksi

Chemical composition(b), %

C

Mn

Si

Other requirements

Condition or applications

specific

ASTM A 27: carbon steel castings for general applications

N-1

...

...

...

. . .

...

...

0.25(c)

0.75(c)

0.80

0.06% S, 0.05% P

Chemical analysis only

N-2

...

...

...

. . .

...

...

0.35(c)

0.60(c)

0.80

0.06% S, 0.05% P

Heat treated but not mechanically tested

U60-30

415

60

205

30

22

30

0.25(c)

0.75(c)

0.80

0.06% S, 0.05% P

Mechanically tested but not heat treated

60-30

415

60

205

30

24

35

0.30(c)

0.60(c)

0.80

0.06% S, 0.05% P

Heat treated and mechanically tested

65-35

450

65

240

35

24

35

0.30(c)

0.70(c)

0.80

0.06% S, 0.05% P

Heat treated and mechanically tested

70-36

485

70

250

36

22

30

0.35(c)

0.70(c)

0.80

0.06% S, 0.05% P

Heat treated and mechanically tested

70-40

485

70

275

40

22

30

0.25(c)

1.20(c)

0.80

0.06% S, 0.05% P

Heat treated and mechanically tested

ASTM A 148: carbon steel castings for structural applications(d)

80-40

550

80

275

40

18

30

(e)

(e)

(e)

0.06% S, 0.05% P

Composition and heat treatment necessary to achieve specified mechanical properties

80-50

550

80

345

50

22

35

(e)

(e)

(e)

0.06% S, 0.05% P

Composition and heat treatment necessary to achieve specified mechanical properties

90-60

620

90

415

60

20

40

(e)

(e)

(e)

0.06% S, 0.05% P

Composition and heat treatment necessary to achieve specified mechanical properties

105-85

725

105

585

85

17

35

(e)

(e)

(e)

0.06% S, 0.05% P

Composition and heat treatment necessary to achieve specified mechanical properties

SAE J435c: see Table 2 for alloy steel castings specified in SAE J435c

0022

...

...

...

. . .

...

...

0.120.22

0.500.90

0.60

187 HB max

Low-carbon steel suitable for carburizing

0025

415

60

207

30

22

30

0.25(c)

0.75(c)

0.80

187 HB max

Carbon steel welding grade

0030

450

65

241

35

24

35

0.30(c)

0.70(c)

0.80

131-187 HB

Carbon steel welding grade

0050A

585

85

310

45

16

24

0.400.50

0.500.90

0.80

170-229 HB

Carbon steel mediumstrength grade

0050B

690

100

485

70

10

15

0.400.50

0.500.90

0.80

207-255 HB

Carbon steel mediumstrength grade

080

550

80

345

50

22

35

...

...

...

163-207 HB

Medium-strength lowalloy steel

090

620

90

415

60

20

40

...

...

...

187-241 HB

Medium-strength lowalloy steel

HA, HB, HC(f)

...

...

...

. . .

...

...

0.250.34

(f)

(f)

See Fig. 1

Hardenability (Fig. 1)

grades

ASTM A 216: carbon steel castings suitable for fusion welding and high-temperature service

WCA

415585

6085

205

30

24

35

0.25

0.70(c)

0.60

(g)

Pressure-containing parts

WCB

485655

7095

250

36

22

35

0.30

1.00(c)

0.60

(g)

Pressure-containing parts

WCC

485655

7095

275

40

22

35

0.25

1.20(c)

0.50

(g)

Pressure-containing parts

0.25

0.70(c)

0.60

(g)(i)(j)

Low-temperature applications

Other ASTM cast steel specifications with carbon steel grades(h)

A 352LCA

415585

6085

205

30

24

35

A 352LCB

450620

6590

240

35

24

35

0.30

1.00

0.60

(g)(j)(k)

Low-temperature applications

A 356grade 1

485

70

250

36

20

35

0.35

0.70(c)

0.60

0.035% P max, 0.030% S max

Castings for valve chests, throttle valves, and other heavy-walled components for steam turbines

A 757A1Q

450

65

240

35

24

35

0.30

1.00

0.60

(j)(k)(l)

Castings for pressurecontaining applications at low temperatures

(a)

Where a single value is shown, it is a minimum.

(b)

Where a single value is shown, it is a maximum.

(c)

For each reduction of 0.01% C below the maximum specified, an increase of 0.04% Mn above the maximum specified is permitted up to the maximums given in the applicable ASTM specifications.

(d)

Grades may also include low-alloy steels; see Table 2 for the stronger grades of ASTM A 148.

(e)

Unless specified by purchaser, the compositions of cast steels in ASTM A 148 are selected by the producer in order to achieve the specified mechanical properties.

(f)

Purchased on the basis of hardenability, with manganese and other elements added as required.

(g)

Specified residual elements include 0.30% Cu max, 0.50% Ni max, 0.50% Cr max, 0.20% Mo max, and 0.03% V max, with the total residual elements not exceeding 1.00%.

(h)

These ASTM specifications also include alloy steel castings for the general type of applications listed in the table.

(i)

Testing temperature of -32 °C (-25 °F).

(j)

Charpy V-notch impact testing at the specified test temperature with an energy value of 18 J (13 ft · lbf) min for two specimens and an average of three.

(k)

Testing temperature of -46 °C (-50 °F).

(l)

Specified residual elements of 0.03% V, 0.50% Cu, 0.50% Ni, 0.40% Cr, and 0.25% Mo, with total amount not exceeding 1.00%. Sulfur and phosphorus content, each 0.025% max

The steel castings discussed in this article are classified into four general groups according to their carbon or alloy contents. Carbon steel castings account for three of these groups: low-carbon steel castings with less than 0.20% carbon,

medium-carbon castings with 0.20 to 0.50% carbon, and high-carbon castings with more than 0.50% carbon. The fourth group, low-alloy steel castings, is generally limited to grades with a total alloy content of less than 8%.

Specifications Steel castings are usually purchased to meet specified mechanical properties, with some restrictions on chemical composition. Tables 1 and 2 list the requirements given in various ASTM specifications and in SAE J435c. Table 1 lists primarily carbon steel castings (with some comparable low-alloy types), while Table 2 lists several low-alloy cast steels and some cast steels with chromium content up to 10.0%. Table 2 Summary of specification requirements for various alloy steel castings with chromium contents up to 10% Material class(a)

Tensile strength(b)

Yield strength(b)

MPa

MPa

ksi

Minimum elongation in 50 mm (2 in.), %

Minimum reduction in area, %

ksi

Composition(c), %

C

Mn

Si

Cr

Ni

Mo

Other

ASTM A 148: steel castings for structural applications(d)

115-95

795

115

655

95

14

30

...

...

...

...

...

...

(e)

135-125

930

135

860

125

9

22

...

...

...

...

...

...

(e)

150-135

1035

150

930

135

7

18

...

...

...

...

...

...

(e)

160-145

1105

160

1000

145

6

12

...

...

...

...

...

...

(e)

165-150

1140

165

1035

150

5

20

...

...

...

...

...

...

(f)

165-150L

1140

165

1035

150

5

20

...

...

...

...

...

...

(f)

210-180

1450

210

1240

180

4

15

...

...

...

...

...

...

(f)

210-180L

1450

210

1240

180

4

15

...

...

...

...

...

...

(f)

260-210

1795

260

1450

210

3

6

...

...

...

...

...

...

(f)

260-210L

1795

260

1450

210

3

6

...

...

...

...

...

...

(f)

SAE J435c: see Table 1 for the carbon steel castings specified in SAEJ435c(g)

0105

725

105

586

85

17

35

...

...

...

...

...

...

(h)

0120

827

120

655

95

14

30

...

...

...

...

...

...

(h)

0150

1035

150

862

125

9

22

...

...

...

...

...

...

(h)

0175

1207

175

1000

145

6

12

...

...

...

...

...

...

(h)

ASTM A 217: alloy steel castings for pressure-containing parts and high-temperature service

WC1

450620

6590

240

35

24

35

0.25

0.500.80

0.60

0.35(i)

0.50(i)

0.450.65

(i)(j)

WC4

485655

7095

275

40

20

35

0.20

0.500.80

0.60

0.500.80

0.701.10

0.450.65

(j)(k)

WC5

485655

7095

275

40

20

35

0.20

0.400.70

0.60

0.500.90

0.601.00

0.901.20

(j)(k)

WC6

485655

7095

275

40

20

35

0.20

0.500.80

0.60

1.001.50

0.50(i)

0.450.65

(i)(j)

WC9

485655

7095

275

40

20

35

0.18

0.400.70

0.60

2.002.75

0.50(i)

0.9-1.20

(i)(j)

WC11

550725

80105

345

50

18

45

0.150.21

0.500.80

0.300.60

1.001.75

0.50(i)

0.450.65

(i)(l)

C5

620795

90115

415

60

18

35

0.20

0.400.70

0.75

4.006.50

0.50(i)

0.450.65

(i)(j)

C12

620795

90115

415

60

18

35

0.20

0.350.65

1.00

8.0010.00

0.50(i)

0.901.20

(i)(j)

ASTM A 389: alloy steel castings (NT) suitable for fusion welding and pressure-containing parts at high temperatures

C23

485

70

275

40

18

35

0.20

0.300.80

0.60

1.001.50

...

0.450.65

(h)(m)

C24

550

80

345

50

15

35

0.20

0.300.80

0.60

1.001.25

...

0.901.20

(h)(m)

ASTM A 487: alloy steel castings (NT or QT) for pressure-containing parts at high temperatures

1A (NT)

585760

85110

380

55

22

40

0.30

1.00

0.80

0.35(n)

0.50(n)

0.25(n)(o)

0.5 Cu(h)(n)

2B (QT)

620795

90115

450

65

22

45

0.30

1.00

0.80

0.35(n)

0.50(n)

0.25(n)(o)

0.5 Cu(h)(n)

1C (NT or QT)

620

90

450

65

22

45

0.30

1.00

0.80

0.35 (n)

0.50(n)

0.25(n)(o)

0.5 Cu(h)(n)

2A (NT)

585760

85110

365

53

22

35

0.30

1.101.40

0.80

0.35(i)

0.50(i)

0.100.30

(i)(p)

2B (QT)

620795

90115

450

65

22

40

0.30

1.101.40

0.80

0.35(i)

0.50(i)

0.100.30

(i)(p)

2C (NT or QT)

620

90

450

65

22

40

0.30

1.101.40

0.80

0.35(i)

0.50(i)

0.100.30

(i)(p)

4A (NT or QT)

620795

90115

415

60

20

40

0.30

1.00

0.80

0.400.80

0.400.80

0.150.30

(k)(p)

4B (QT)

725895

105130

585

85

17

35

0.30

1.00

0.80

0.400.80

0.400.80

0.150.30

(k)(p)

4C (NT or QT)

620

90

415

60

20

40

0.30

1.00

0.80

0.400.80

0.400.80

0.150.30

(k)(p)

4D (QT)

690

100

515

75

17

35

0.30

1.00

0.80

0.400.80

0.400.80

0.150.30

(k)(p)

4E (QT)

795

115

655

95

15

35

0.30

1.00

0.80

0.400.80

0.400.80

0.150.30

(k)(p)

6A (NT)

795

115

550

80

18

30

0.38

1.301.70

0.80

0.400.80

0.400.80

0.300.40

(k)(p)

6B (QT)

825

120

655

95

15

35

0.38

1.301.70

0.80

0.400.80

0.400.80

0.300.40

(k)(p)

7A (QT)(q)

795

115

690

100

15

30

0.20

0.601.00

0.80

0.400.80

0.701.00

0.400.60

(k)(p)(r)

8A (NT)

585760

85110

380

55

20

35

0.20

0.500.90

0.80

2.002.75

...

0.901.10

(k)(p)

8B (QT)

725

105

585

85

17

30

0.20

0.500.90

0.80

2.002.75

...

0.901.10

(k)(p)

8C (QT)

690

100

515

75

17

35

0.20

0.500.90

0.80

2.002.75

...

0.901.10

(k)(p)

9A (NT or QT)

620

90

415

60

18

35

0.33

0.601.00

0.80

0.751.10

0.50(i)

0.150.30

(i)(p)

105

585

85

16

35

0.33

9C (NT or QT)

620

90

415

60

18

35

Composition same as 9A (NT or QT) but with a slightly higher tempering temperature

9D (QT)

690

100

515

75

17

35

0.33

0.601.00

0.80

0.751.10

0.50(i)

0.150.30

(i)(p)

10A (NT)

690

100

485

70

18

35

0.30

0.601.00

0.80

0.550.90

1.402.00

0.200.40

(k)(p)

10B (QT)

860

125

690

100

15

35

0.30

0.601.00

0.80

0.550.90

1.402.00

0.200.40

(k)(p)

11A (NT)

485655

7095

275

40

20

35

0.20

0.500.80

0.60

0.500.80

0.701.10

0.450.65

(p)(s)

11B (QT)

725895

105130

585

85

17

35

0.20

0.500.80

0.60

0.500.80

0.701.10

0.450.65

(p)(s)

12A (NT)

485655

7095

275

40

20

35

0.20

0.400.70

0.60

0.500.90

0.601.00

0.901.20

(p)(s)

12B (QT)

725895

105130

585

85

17

35

0.20

0.400.70

0.60

0.500.90

0.601.00

0.901.20

(p)(s)

13A (NT)

620795

90115

415

60

18

35

0.30

0.801.10

0.60

0.40(t)

1.401.75

0.200.30

(p)(t)

13B (QT)

725895

105130

585

85

17

35

0.30

0.801.10

0.60

0.40(t)

1.401.75

0.200.30

(p)(t)

14A (QT)

8251000

120145

655

95

14

30

0.55

0.801.10

0.60

0.40(t)

1.401.75

0.200.30

(p)(t)

16A (NT)(u)

485655

7095

275

40

22

35

0.12(v)

2.10(v)

0.50

0.20(s)

1.001.40

0.10(s)

(s)(w)

(b) When a single value is shown, it is a minimum.

(c) When a single value is shown, it is a maximum.

0.80

0.751.10

0.150.30

(i)(p)

725

(a) NT, normalized and tempered; QT, quenched and tempered.

0.601.00

0.50(i)

9B (QT)

(d) Unless specified by the purchaser, the compositions of cast steels in ASTM A 148 are selected by the producer and therefore may include either carbon or alloy steels; see Table 1 for the lower-grade steels specified in ASTM A 148.

(e) 0.06% S (max), 0.05% P (max).

(f) 0.020% S (max), 0.020% P (max).

(g) Similar to the cast steel in ASTM A 148.

(h) 0.045% S (max), 0.040% P (max).

(i) When residual maximums are specified for copper, nickel, chromium, tungsten, and vanadium, their total content shall not exceed 1.00%.

(j) 0.50% Cu (max), 0.10% W (max), 0.045% S (max), 0.04% P (max).

(k) When residual maximums are specified for copper, nickel, chromium, tungsten, and vanadium, their total residual content shall not exceed 0.60%.

(l) 0.35% Cu (max), 0.03% V (max), 0.015% S (max), 0.020% P (max).

(m) 0.15-0.25% V.

(n) The specified residuals of copper, nickel, chromium, and molybdenum (plus tungsten), shall not exceed a total content of 1.00%.

(o) Includes the residual content of tungsten.

(p) 0.50% Cu (max), 0.10% W (max), 0.03% V (max), 0.045% S (max), 0.04% P (max).

(q) Material class 7A is a proprietary steel and has a maximum thickness of 63.5 mm (2

in.).

(r) Specified elements include 0.15-0.50% Cu, 0.03-0.10% V, and 0.002-0.006% B.

(s) When residual maximums are specified for copper, nickel, chromium, tungsten, molybdenum, and vanadium, their total content shall not exceed 0.50%.

(t) When residual maximums are specified for copper, nickel, chromium, tungsten, and vanadium, their total content shall not exceed 0.75%.

(u) Low-carbon grade with double austenitization.

(v) For each reduction of 0.01% C below the maximum, an increase of 0.04% Mn is permitted up to a maximum of 2.30%.

(w) 0.20% Cu (max), 0.10% W (max), 0.02% V (max), 0.02% S (max), 0.02% P (max)

In the low-strength ranges, some specifications limit carbon and manganese content, usually to ensure satisfactory weldability. In SAE J435c, carbon and manganese are specified to ensure that the minimum desired hardness and strength are obtained after heat treatment. For special applications, other elements may be specified either as maximum or minimum, depending on the characteristics desired. If only mechanical properties are specified, the chemical composition of castings for general engineering applications is usually left to the discretion of the casting supplier. For specific applications, however, certain chemical compositions limits have been established to ensure the development of specified mechanical properties after proper heat treatment, as well as to facilitate welding, uniform response to heat treatment, or other requirements. Hardness is specified for most grades of SAE J435c to ensure machinability, ease of inspection for high production rate items, or certain characteristics pertaining to wear. SAE J435c includes three grades, HA, HB, and HC, with specified hardenability requirements. Figure 1 plots hardenability requirements, both minimum and maximum, for these steels. Hardenability is determined by the end-quench hardenability test described in the article "Hardenability of Steels" in this Section. Other specifications require minimum hardness at one or two locations on the end-quench specimen. In general, hardenability is specified to ensure a predetermined degree of transformation from austenite to martensite during quenching, in the thickness required. This is important in critical parts requiring toughness and optimal resistance to fatigue.

Fig. 1 End-quench hardenability limits for the hardenability grades of cast steel specified in SAE J435c. The nominal carbon content of these steels is 0.30% C (see Table 1). Manganese and other alloying elements are added as required to produce castings that meet these limits.

Particularly when the purchaser heat treats a part after other processing, a casting will be ordered to compositional limits closely equivalent to the SAE-AISI wrought steel compositions, with somewhat higher silicon permitted. As in other steel castings, it is best not to specify a range of silicon, but to permit the foundry to use the silicon and manganese combination needed to achieve required soundness in the shape being cast. The silicon content is frequently higher in cast steels than for the same nominal composition in wrought steel. A silicon content higher than 0.80% is considered an alloy addition because it contributes significantly to resistance to tempering.

Mechanical Properties General Characteristics. Figure 2 shows the basic trends of the mechanical properties of cast carbon steels as a function of carbon content for four different heat treatments. For a given heat treatment, a higher carbon content generally results in higher hardness and strength levels with lower ductility and toughness values. Because yield strength is a primary design criterion for structural applications, Fig. 3 plots tensile strength, ductility (as measured by elongation), and toughness (based on Charpy V-notch impact energy) versus yield strength for low-alloy cast steels.

Fig. 2 Properties of cast carbon steels as a function of carbon content and heat treatment. (a) Tensile strength and reduction of area. (b) Yield strength and elongation. (c) Brinell hardness. (d) Charpy V-notch impact energy

Fig. 3 Room-temperature properties of cast low-alloy steels. QT, quenched and tempered; NT, normalized and

tempered

Tensile and Yield Strengths. If ferritic steels are compared at a given level of hardness and hardenability, the tensile and yield strengths of cast, rolled, forged, and welded metal are virtually identical, regardless of alloy content. Consequently, where tensile and yield properties are controlling criteria, the designer can interchange rolled, forged, welded, and cast steel. Ductility. The ductility of cast steels is nearly the same as that of forged, rolled, or welded steels of the same hardness.

The longitudinal properties of rolled or forged steel are somewhat higher than the properties of cast steel or weld metal. However, the transverse properties are lower by an amount that depends on the amount of working. When service conditions involve multidirectional loading, the nondirectional characteristic of cast steels may be advantageous. Toughness. The notched-bar impact test is often used as a measure of the toughness of materials and is particularly

useful in determining the transition temperature from ductile to brittle fracture. Nil ductility transition temperature (NDTT) as determined as per method ASTM E 208, lateral expansion values, and the energy absorbed values at specific temperatures are some of the different criteria for evaluating impact properties. The impact properties of wrought steels are usually listed for the longitudinal direction; the values shown are higher than those for cast steels of equivalent composition and thermal treatment. The transverse impact properties of wrought steels are usually 50 to 70% of those in the longitudinal direction above the transition temperature and, in some conditions of composition and degree of working, even lower. Because cast steels are nondirectional, their impact properties usually fall somewhere between the longitudinal and transverse properties of wrought steel of similar composition. Impact properties are controlled by microstructure and, in general, are not significantly affected by microshrinkage or hydrogen. The effect of microstructure, as controlled by chemical composition and heat treatment, is discussed in the article "Service Characteristics of Carbon and Alloy Steels" in this Section (see the sub-section on "Notch Toughness of Steels"). Curves of impact energy versus temperature for casting steels designed specifically for pressure-containing parts for low-temperature service are presented in Fig. 4. These curves illustrate the significant changes in impact properties that can be effected by changes in steel grade and/or heat treatment.

Fig. 4 Effect of temperature on Charpy V-notch impact energy of cast steels for low-temperature service. Steel grades conformed to ASTM A 352. Heat treatments were as follows: grade LCB (0.30% C max, 1.00% Mn max steel), water quenched from 890 °C (1650 °F), tempered at 650 °C (1200 °F) and water quenched, aged 40 h at 425 °C (800 °F), and stress relieved 40 h at 595 °C (1100 °F); grade LC2-1 (Ni-Cr-Mo steel), normalized at 955 °C (1750 °F) and air cooled, reheated to 890 °C (1650 °F) and water quenched, either tempered at 595 °C (1100 °F) and aged 40 h at 425 °C (800 °F) or tempered at 650 °C (1200 °F) and aged 64 h at 425 °C (800 °F). All specimens were taken at locations greater than one-fourth the thickness in from the surface of test blocks 51 by 210 by 229 mm (2 by 8 by 9 in.) having an ASTM grain size of 6 to 8. The curves represent average values for several tests at each test temperature.

Section size also affects the impact properties that are obtained. Figure 5 illustrates this effect for one of the grades of steel castings described in Fig. 4 (grade LCB). When the section size is increased from 25 to 127 mm (1 to 5 in.), the temperature at which the impact energy is reduced to an average of 18 J (13 ft · lbf) is increased by 28 °C (50 °F).

Fig. 5 Effect of section thickness on Charpy V-notch impact curves of grade LCB steel castings. Steel grade conformed to ASTM A 352. Heat treatment was the same as for Fig. 4. All specimens were taken at locations greater than one-fourth the thickness in from the surface of test blocks of four sizes: 25 by 25 by 279 mm (1 by 1 by 11 in.), 51 by 210 by 229 mm (2 by 8 by 9 in.), 76 by 229 by 283 mm (3 by 9 by 11 in.), and 127 by 381 by 381 mm (5 by 15 by 15 in.). The ASTM grain size of the blocks was 6 to 8. The curves represent average values for several tests at each test temperature.

Fatigue Strength. For cast steels, the fatigue strength, or endurance limits, as determined by tests on smooth bars is

generally in the range of 40 to 50% of the tensile strength. Figure 6 compares the fatigue endurance limits of both wrought and cast steels. Although the unnotched fatigue endurance limit or wrought steels is higher, they are much more notch sensitive than are cast steels.

Fig. 6 Fatigue endurance limit versus tensile strength for notched and unnotched cast and wrought steels with various heat treatments. Data obtained in R.R. Moore rotating-beam fatigue tests; theoretical stress concentration factor = 2.2

Section Size and Mass Effects. The size of a cast coupon or casting can have a marked effect on its mechanical properties. This effect reflects the influence of section size on the cooling rates achieved during heat treatment; a larger section has more mass, which slows the cooling rates within the section and thus affects the microstructure and mechanical properties achieved during cooling. The effect of increasing section size on the mechanical properties of a medium-carbon cast steel in the annealed and as-cast condition is shown in Fig. 7. Because of section size effects, the

results of tests on specimens taken from very heavy sections and from large castings are helpful in predicting minimum properties in cast steel parts.

Fig. 7 Effect of section size on tensile strength of medium-carbon steel castings

Low-Carbon Cast Steels Low-carbon cast steels are those with a carbon content of less than 0.20%. Most of the tonnage produced in the lowcarbon classification contains between 0.16 and 0.19% C, with 0.50 to 0.80% Mn, 0.05% P (max), 0.06% S (max), and 0.35% to 0.70% Si. In order to obtain high magnetic properties in electrical equipment, the manganese content is usually held between 0.10 and 0.20%. Low-carbon steel castings are made in two important classes. One may be termed railroad castings, and the other miscellaneous jobbing castings. The railroad castings consist mainly of comparatively symmetrical and well-designed castings for which adverse stress conditions have been carefully studied and avoided. Miscellaneous jobbing castings present a wide variation in design and frequently involve the joining of light and heavy sections. Varying sections make it more difficult to avoid high residual stress in the as-cast shape. Because residual stresses of large magnitude cannot be tolerated in many service applications, stress relieving becomes necessary. Therefore, the annealing of those castings is decidedly beneficial even though it may cause little improvement of mechanical properties. Figure 2 includes the mechanical properties of carbon cast steels with low-carbon contents within the range of about 0.10 to 0.20%. There is very little difference between the properties of the low-carbon

Medium-Carbon Cast Steels The medium-carbon grades of cast steel contain 0.20 to 0.50% C and represent the bulk of steel casting production. In addition to carbon, they contain 0.50 to 1.50% Mn, 0.05% P (max), 0.06% S (max), and 0.35 to 0.80% Si. The mechanical properties at room temperature of cast steels containing from 0.20 to 0.50% C are included in Fig. 2. Steels in this carbon range are always heat treated, which relieves casting strains, refines the as-cast structure, and improves the ductility of the steel. A very large proportion of steel castings of this grade are given a normalizing treatment, followed by a tempering treatment.

High-Carbon Cast Steels Cast steels containing more than 0.50% C are classified as high-carbon steels. This grade also contains 0.50 to 1.50% Mn, 0.05% P (max), 0.05% S (max), and 0.35 to 0.70% Si. The mechanical properties of high-carbon steels at room temperature are shown in Fig. 2. High-carbon cast steels are often fully annealed. Occasionally, a normalizing and tempering treatment is given, and for certain applications an oil quenching and tempering treatment may be used. The microstructure of high-carbon steel is controlled by the heat treatment. Carbon also has a marked influence, for example, giving 100% pearlitic structure at eutectoid composition ( 0.83% carbon). Higher proportions of carbon than eutectoid composition will increase the proeutectoid cementite, which is detrimental to the casting if it forms a network at the grain boundaries because of improper heat treatment (for example, slow cooling from above the Acm temperature). Faster cooling will prevent the formation of this network and, hence, improve the properties.

Low-Alloy Cast Steels

Low-alloy cast steels contain a total alloy content of less than 8%. These steels have been developed and used extensively for meeting special requirements that cannot be met by ordinary plain carbon steels with low hardenability. The addition of alloys to plain carbon steel castings may be made for any of several reasons, such as to provide higher hardenability, increased wear resistance, higher impact resistance at increased strength, good machinability even at higher hardness, higher strength at elevated and low temperatures, and better resistance to corrosion and oxidation than the plain carbon steel castings. These materials are produced to meet tensile strength requirements of 485 to 1380 MPa (70 to 200 ksi), together with some of the above special requirements. Figure 3 shows typical room-temperature mechanical properties of low-alloy steels plotted against yield strength. These properties are, of course, a function of alloy content, heat treatment, and section size.

Bearing Steels Introduction ROLLING-ELEMENT BEARINGS, whether ball bearings or roller bearings with spherical, straight, or tapered rollers, are fabricated from a wide variety of steels. In a broad sense, bearing steels can be divided into two classes: standard bearing steels are intended for normal service conditions (see the discussion which follows); whereas special-purpose bearing steels are used for either extended fatigue life or excessive operating conditions of temperature and corrosion. Bearings for normal service conditions, a category that includes more than 95% of all rolling-element bearings, are applicable when: •

Maximum temperatures are of the order of 120 to 150 °C (250 to 300 °F), although brief excursions to 175 °C (350 °F) may be tolerated. • Minimum ambient temperatures are about -50 °C (-60 °F). • The contact surfaces are lubricated with such materials as oil, grease, or mist. • The maximum Hertzian contact stresses are of the order of 2.1 to 3.1 GPa (300 to 450 ksi).

Bearings used under normal service conditions also experience the effects of vibration, shock, misalignment, debris, and handling. Therefore, the fabrication material must provide toughness, a degree of temper resistance, and microstructural stability under temperature extremes. The material must also exhibit the obvious requirement of surface hardness for wear and fatigue resistance, particularly rolling-contact fatigue resistance.

Bearing Steel Production and Quality Apart from a satisfactory microstructure, which is obtained through the proper combination of steel grade and heat treatment, the single most important factor in achieving levels of rolling-contact fatigue life in bearings is the cleanliness, or freedom from harmful nonmetallic inclusions, of the steel. Bearing steels can be produced by one of these techniques: • • • •

Clean-steel air-melt practices Electroslag remelting Air melting followed by vacuum arc remelting Vacuum induction melting followed by vacuum arc remelting (VIM/VAR)

Cleanliness, cost, and reliability can increase depending on which practice is chosen. Bearing steel cleanliness is most commonly rated by using microscopic techniques, such as those defined in ASTM A 295 for high-carbon steels and A 534 for carburizing steels. The worst fields found in metallographically prepared sections of the steel can be compared with rating charts (J-K charts) according to the type of inclusion: sulfides, stringer-type oxides, silicates, and globular-type oxides.

Bearing steel cleanliness can also be rated by oxygen analysis, the magnetic particle method (AMS 2301, AMS 2300), and ultrasonic methods. Quantified ultrasonic results are supplemented with inclusion imaging and length verification using acoustic microscopy. These tools, along with energy-dispersive or wavelength-dispersive chemical analyses using scanning electron microscopy, have confirmed the aluminum oxide stringers relate directly with bearing fatigue life under operating conditions that promote material fatigue. The size distribution and the total quantity of inclusion stringers in a given group of bearings has been shown to relate to performance (fatigue life) through a summation of the inclusion stringer lengths per unit volume of steel. The total length of inclusion stringers per unit volume is the abscissa on Fig. 1. The steel cleanness range starts with an earlier vacuum carbon deoxidation steel process method to the precipitation-shrouded version of today's air-melt steels and to today's vacuum-arc remelted steel. As shown in Fig. 1, the over-all fatigue life range is more than an order of magnitude. VIM/VAR steel lives exceed even the VAR steel lives so that even though the present-day air-melt steels do give better lives, the vacuum-processed steels are meeting the fatigue life requirements for the extended-life applications.

Fig. 1 Effect of total length of inclusion stringers on the rolling contact fatigue life of a 220 mm (8.7 in.) bore tapered roller bearing inner race as a function of steel cleannesss

Standard Bearing Steels The steel used in rolling bearings for normal requirements such as industrial or automotive applications is an alloy steel with alloy content, in addition to carbon, that runs from 1.5 to 6%, depending on the bearing ring cross section and hardenability requirements. Typical standard bearing steel compositions for high-carbon or through-hardened steels are given in Table 1, and standard bearing steel compositions for low-carbon or carburizing bearing steels are given in Table 2. Both steels are used depending on specific service condition needs. High-carbon steels provide the following advantages: • Ability to carry somewhat higher contact stresses, such as those encountered in point contact loading in ball bearings • A simpler quench and temper heat treatment when compared to carburizing • Potentially greater dimensional stability under temperature extremes because of their characteristically lower content of retained austenite

Table 1 Nominal compositions of high-carbon bearing steels Composition, %

Grade

C

Mn

Si

Cr

Ni

Mo

AISI 52100

1.04

0.35

0.25

1.45

...

...

ASTM A 485-1

0.97

1.10

0.60

1.05

...

...

ASTM A 485-3

1.02

0.78

0.22

1.30

...

0.25

TBS-9

0.95

0.65

0.22

0.50

0.25 max

0.12

SUJ 1(a)

1.02

100 HB) high-silicon-content casting alloys.) Hardness and yield strengths are variously used as approximations of machinability. Chemical milling, the removal of metal by chemical attack in an alkaline or acid solution, is routine for specialized

reductions in thickness. For complex large surface areas in which uniform metal removal is required, chemical milling is often the most economical method. The process is used extensively to etch preformed aerospace parts to obtain maximum strength-to-weight ratios. Integrally stiffened aluminum wing and fuselage sections are chemically milled to produce an optimum cross section and minimum skin thickness. Spars, stringers, floor beams, and frames are frequent applications as well. Formability is among the more important characteristics of aluminum and many of its alloys. Specific tensile and yield

strengths, ductility, and respective rates of work hardening control differences in the amount of permissible deformation. Ratings of comparable formability of the commercially available alloys in various tempers depend on the forming process. Such ratings provide generally reliable comparisons of the working characteristics of metals, but serve as an approximate guide rather than as quantitative formability limits. Choice of temper may depend on the severity and nature of forming operations. The annealed temper may be required for severe forming operations, such as deep drawing, or for roll forming or bending on small radii. Usually, the strongest temper than can be formed consistently is selected. For less severe forming operations, intermediate tempers or even fully hardened conditions may be acceptable. Heat-treatable alloys can be formed in applications for which a high strength-to-weight ratio is required. The annealed temper of these alloys is the most workable condition, but the effects of dimensional change and distortion caused by subsequent heat treatment for property development, and the straightening or other dimensional control steps that may be required, are important considerations. Alloys that are formed immediately following solution heat treatment and quench (T3, T4, or W temper) are nearly as formable as when annealed and can be subsequently hardened by natural or artificial aging. Parts can be stored at low temperatures (approximately -30 to -35 °C, or -20 to -30 °F, or lower) in the W temper for prolonged periods as a means of inhibiting natural aging and preserving an acceptable level of formability. Material that has been solution heat treated and quenched but not artificially aged (T3, T4, or W temper) is generally suitable only for mild forming operations such as bending, mild drawing, or moderate stretch forming if these operations cannot be

performed immediately after quenching. Solution heat-treated and artificially aged (T6 temper) alloys are in general unsuitable for forming operations. Forgeability. Aluminum alloys an be forged into a variety of shapes and types of forgings with a broad range of final part forging design criteria based on the intended application. Aluminum alloy forgings, particularly closed-die forgings, are usually produced to more highly refined final forging configurations than hot-forged carbon and/or alloy steels. For a given aluminum alloy forging shape, the pressure requirements in forging vary widely, depending primarily on the chemical composition of the alloy being forged, the forging process being employed, the forging strain rate, the type of forging being manufactured, the lubrication conditions, and the forging and die temperatures.

As a class of alloys, aluminum alloys are generally considered to be more difficult to forge than carbon steels and many alloy steels. Compared to the nickel/cobalt-base alloys and titanium alloys, however, aluminum alloys are considerably more forgeable, particularly in conventional forging process technology, in which dies are heated to 540 °C (1000 °F) or less. Joining. Aluminum can be joined by a wide variety of methods, including fusion and resistance welding, brazing,

soldering, adhesive bonding, and mechanical methods such as riveting and bolting. Factors that affect the welding of aluminum include: • • • • •

Aluminum oxide coating Thermal conductivity Thermal expansion coefficient Melting characteristics Electrical conductivity

Aluminum oxide immediately forms on aluminum surfaces exposed to air. Before aluminum can be welded by fusion

methods, the oxide layer must be removed mechanically by machining, filing, wire brushing, scraping, or chemical cleaning. If oxides are not removed, oxide fragments may be entrapped in the weld and will cause a reduction in ductility, a lack of fusion, and possibly weld cracking. During welding, the oxide must be prevented from re-forming by shielding the joint area with a nonoxidizing gas such as argon, helium, or hydrogen, or chemically by use of fluxes. Thermal conductivity is a property that most affects weldability. The thermal conductivity of aluminum alloys is

about one-half that of copper and four times that of low-carbon steel. This means that heat must be supplied four times as fast to aluminum alloys as to steel to raise the temperature locally by the same amount. However, the high thermal conductivity of aluminum alloys helps to solidify the molten weld pool of aluminum and, consequently, facilitates out-ofposition welding. The coefficient of linear expansion, which is a measure of the change in length of a material with a change in its

temperature, is another physical property of importance when considering weldability. The coefficient of linear thermal expansion for aluminum is twice that for steel. This means that extra care must be taken in welding aluminum to ensure that the joint space remains uniform. This may necessitate preliminary joining of the parts of the assembly by tack welding prior to the main welding operation. The combination of high coefficient of thermal expansion and high thermal conductivity would cause considerable distortion of aluminum during welding were it not for the high welding speed possible. Melt Characteristics. The melting ranges for aluminum alloys are considerably lower than those for copper or steel.

Melting temperatures and the volumetric specific heats and heats of fusion of aluminum alloys determine that the amount of heat required to enter the welding temperature range is much lower for aluminum alloys. Electrical conductivity has little influence on fusion welding but is a very important property for materials that are to be resistance welded. In resistance welding, resistance of the metal to the flow of welding current produces heat, which causes the portion of the metal through which the current flows to approach or reach its melting point. Aluminum has higher conductivity than steel, which means that much higher currents are required to produce the same heating effect. Consequently, resistance welding machines for aluminum must have much higher output capabilities than those normally

used for steel, for welding comparable sections. Table 4 lists welding, brazing, and soldering characteristics of selected wrought aluminum alloys.

Finishes The natural metallic surface of aluminum is aesthetically pleasing in many product designs even without further finishing. Its natural protective oxide film is transparent and can be thickened by anodizing, for extra protection, without affecting the metal's appearance. But aluminum also accepts a great variety of finishes that can alter its appearance or enhance its surface characteristics as required. Surface textures can be created from rough to matte to mirror-smooth. The metallic hue can be colored by appropriate chemical or anodizing processes. Surface coatings such as paint, lacquer, enamel, electroplating or laminates can be applied.

Applications Aluminum alloys are economical in many applications. They are used in the automotive industry, aerospace industry, in construction of machines, appliances, and structures, as cooking utensils, as covers for housings for electronic equipment, as pressure vessels for cryogenic applications, and in innumerable other areas. Tables 5 and 6 list typical applications for some of the more commonly used wrought and cast alloys, respectively. Table 5 Selected applications for wrought aluminum alloys Alloy

Description and selected applications

1100

Commercially pure aluminum highly resistant to chemical attack and weathering. Low cost, ductile for deep drawing, and easy to weld. Used for high-purity applications such as chemical processing equipment. Also for nameplates, fan blades, flue lining, sheet metal work, spun holloware, and fin stock

1350

Electrical conductors

2011

Screw machine products. Appliance parts and trim, ordnance, automotive, electronic, fasteners, hardware, machine parts

2014

Truck frames, aircraft structures, automotive, cylinders and pistons, machine parts, structurals

2017

Screw machine products, fittings, fasteners, machine parts

2024

For high-strength structural applications. Excellent machinability in the T-tempers. Fair workability and fair corrosion resistance. Alclad 2024 combines the high strength of 2024 with the corrosion resistance of the commercially pure cladding. Used for truck wheels, many structural aircraft applications, gears for machinery, screw machine products, automotive parts, cylinders and pistons, fasteners, machine parts, ordnance, recreation equipment, screws and rivets

2219

Structural uses at high temperature (to 315 °C, or 600 °F). High-strength weldments

3003

Most popular general-purpose alloy. Stronger than 1100 with same good formability and weldability. For general use including sheet metal work, stampings, fuel tanks, chemical equipment, containers, cabinets, freezer liners, cooking utensils, pressure vessels, builder's hardware, storage tanks, agricultural applications, appliance parts and trim, architectural applications, electronics, fin stock, fan equipment, name plates, recreation vehicles, trucks and trailers. Used in drawing and spinning.

3004

Sheet metal work, storage tanks, agricultural applications, building products, containers, electronics, furniture, kitchen equipment, recreation vehicles, trucks and trailers

3105

Residential siding, mobile homes, rain-carrying goods, sheet metal work, appliance parts and trim, automotive parts, building products, electronics, fin stock, furniture, hospital and medical equipment, kitchen equipment, recreation vehicles, trucks and trailers

5005

Specified for applications requiring anodizing; anodized coating is cleaner and lighter in color than 3003. Uses include appliances, utensils, architectural, applications requiring good electrical conductivity, automotive parts, containers, general sheet metal, hardware, hospital and medical equipment, kitchen equipment, name plates, and marine applications

5052

Stronger than 3003 yet readily formable in the intermediate tempers. Good weldability and resistance to corrosion. Uses include pressure vessels, fan blades, tanks, electronic panels, electronic chassis, medium-strength sheet metal parts, hydraulic tube, appliances, agricultural applications, architectural uses, automotive parts, building products, chemical equipment, containers, cooking utensils, fasteners, hardware, highway signs, hospital and medical equipment, kitchen equipment, marine applications, railroad cars, recreation vehicles, trucks and trailers

5056

Cable sheathing, rivets for magnesium, screen wire, zippers, automotive applications, fence wire, fasteners

5083

For all types of welded assemblies, marine components, and tanks requiring high weld efficiency and maximum joint strength. Used in pressure vessels up to 65 °C (150 °F) and in many cryogenic applications, bridges, freight cars, marine components, TV towers, drilling rigs, transportation equipment, missile components, and dump truck bodies. Good corrosion resistance

5086

Used in generally the same types of applications as 5083, particularly where resistance to either stress corrosion or atmospheric corrosion is important

5454

For all types of welded assemblies, tanks, pressure vessels. ASME code approved to 205 °C (400 °F). Also used in trucking for hot asphalt road tankers and dump bodies; also, for hydrogen peroxide and chemical storage vessels

5456

For all types of welded assemblies, storage tanks, pressure vessels, and marine components. Used where best weld efficiency and joint strength are required. Restricted to temperatures below 65 °C (150 °F)

5657

For anodized auto and appliance trim and nameplates

6061

Good formability, weldability, corrosion resistance, and strength in the T-tempers. Good general-purpose alloy used for a broad range of structural applications and welded assemblies including truck components, railroad cars, pipelines, marine applications, furniture, agricultural applications, aircrafts, architectural applications, automotive parts, building products, chemical equipment, dump bodies, electrical and electronic applications, fasteners, fence wire, fan blades, general sheet metal, highway signs, hospital and medical equipment, kitchen equipment, machine parts, ordnance, recreation equipment, recreation vehicles, and storage tanks

6063

Used in pipe railing, furniture, architectural extrusions, appliance parts and trim, automotive parts, building products, electrical and electronic parts, highway signs, hospital and medical equipment, kitchen equipment, marine applications, machine parts, pipe, railroad cars, recreation equipment, recreation vehicles, trucks and trailers

7050

High-strength alloy in aircraft and other structures. Also used in ordnance and recreation equipment

7075

For aircraft and other applications requiring highest strengths. Alclad 7075 combines the strength advantages of 7075 with the corrosion-resisting properties of commercially pure aluminum-clad surface. Also used in machine parts and ordnance

Table 6 Selected applications for aluminum casting alloys Alloy

Representative applications

100.0

Electrical rotors larger than 152 mm (6 in.) in diameter

201.0

Structural members; cylinder heads and pistons; gear, pump, and aerospace housings

208.0

General-purpose castings; valve bodies, manifolds, and other pressure-tight parts

222.0

Bushings; meter parts; bearings; bearing caps; automotive pistons; cylinder heads

238.0

Sole plates for electric hand irons

242.0

Heavy-duty pistons; air-cooled cylinder heads; aircraft generator housings

A242.0

Diesel and aircraft pistons; air-cooled cylinder heads; aircraft generator housings

B295.0

Gear housings; aircraft fittings; compressor connecting rods; railway car seat frames

308.0

General-purpose permanent mold castings; ornamental grilles and reflectors

319.0

Engine crankcases; gasoline and oil tanks; oil pans; typewriter frames; engine parts

332.0

Automotive and heavy-duty pistons; pulleys, sheaves

333.0

Gas meter and regulator parts; gear blocks; pistons; general automotive castings

354.0

Premium-strength castings for the aerospace industry

355.0

Sand: air compressor pistons; printing press bedplates; water jackets; crankcases. Permanent: impellers; aircraft fittings; timing gears; jet engine compressor cases

356.0

Sand: flywheel castings; automotive transmission cases; oil pans; pump bodies. Permanent: machine tool parts; aircraft wheels; airframe castings; bridge railings

A356.0

Structural parts requiring high strength; machine parts; truck chassis parts

357.0

Corrosion-resistant and pressure-tight applications

359.0

High-strength castings for the aerospace industry

360.0

Outboard motor parts; instrument cases; cover plates; marine and aircraft castings

A360.0

Cover plates; instrument cases; irrigation system parts; outboard motor parts; hinges

380.0

Housings for lawn mowers and radio transmitters; air brake castings; gear cases

A380.0

Applications requiring strength at elevated temperature

384.0

Pistons and other severe service applications; automatic transmissions

390.0

Internal combustion engine pistons, blocks, manifolds, and cylinder heads

413.0

Architectural, ornamental, marine, and food and dairy equipment applications

A413.0

Outboard motor pistons; dental equipment; typewriter frames; street lamp housings

443.0

Cookware; pipe fittings; marine fittings; tire molds; carburetor bodies

514.0

Fittings for chemical and sewage use; dairy and food handling equipment; tire molds

A514.0

Permanent mold casting of architectural fittings and ornamental hardware

518.0

Architectural and ornamental castings; conveyor parts; aircraft and marine castings

520.0

Aircraft fittings; railway passenger care frames; truck and bus frame sections

535.0

Instrument parts and other applications where dimensional stability is important

A712.0

General-purpose castings that require subsequent brazing

713.0

Automotive parts; pumps; trailer parts; mining equipment

850.0

Bushings and journal bearings for railroads

A850.0

Rolling mill bearings and similar applications

Alloy and Temper Designation Systems for Aluminum Introduction SYSTEMS FOR DESIGNATING aluminum and aluminum alloys that incorporate the product form (wrought, casting, or foundry ingot), and its respective temper (with the exception of foundry ingots, which have no temper classification) are covered by American National Standards Institute (ANSI) standard H35.1. The Aluminum Association is the registrar under ANSI H35.1 with respect to the designation and composition of aluminum alloys and tempers registered in the United States.

Wrought Aluminum and Aluminum Alloy Designation System A four-digit numerical designation system is used to identify wrought aluminum and aluminum alloys. As shown below, the first digit of the four-digit designation indicates the group:

Aluminum,

99.00%

1xxx

Aluminum alloys grouped by major alloying element(s):

Copper

2xxx

Manganese

3xxx

Silicon

4xxx

Magnesium

5xxx

Magnesium and silicon

6xxx

Zinc

7xxx

Other elements

8xxx

Unused series

9xxx

For the 2xxx through 7xxx series, the alloy group is determined by the alloying element present in the greatest mean percentage. An exception is the 6xxx series alloys in which the proportions of magnesium and silicon available to form magnesium silicide (Mg2Si) are predominant. Another exception is made in those cases in which the alloy qualifies as a modification of a previously registered alloy. If the greatest mean percentage is the same for more than one element, the

choice of group is in order of group sequence: copper, manganese, silicon, magnesium, magnesium silicide, zinc, or others. Aluminum. In the 1xxx group, the series 10xx is used to designate unalloyed compositions that have natural impurity limits. The last two of the four digits in the designation indicate the minimum aluminum percentage. These digits are the same as the two digits to the right of the decimal point in the minimum aluminum percentage when expressed to the nearest 0.01%. Designations having second digits other than zero (integers 1 through 9, assigned consecutively as needed) indicate special control of one or more individual impurities. Aluminum Alloys. In the 2xxx through 8xxx alloy groups, the second digit in the designation indicates alloy modification. If the second digit is zero, it indicates the original alloy; integers 1 through 9, assigned consecutively, indicate modifications of the original alloy. Explicit rules have been established for determining whether a proposed composition is merely a modification of a previously registered alloy or if it is an entirely new alloy. The last two of the four digits in the 2xxx through 8xxx groups have no special significance, but serve only to identify the different aluminum alloys in the group.

Cast Aluminum and Aluminum Alloy Designation System A system of four-digit numerical designations incorporating a decimal point is used to identify aluminum and aluminum alloys in the form of castings and foundry ingot. The first digit indicates the alloy group:

Aluminum,

99.00%

1xx.x

Aluminum alloys grouped by major alloying element(s):

Copper

2xx.x

Silicon, with added copper and/or magnesium

3xx.x

Silicon

4xx.x

Magnesium

5xx.x

Zinc

7xx.x

Tin

8xx.x

Other elements

9xx.x

Unused series

6xx.x

For 2xx.x through 9xx.x (excluding 6xx.x alloys), the alloy group is determined by the alloying element present in the greatest mean percentage, except in cases in which the composition being registered qualifies as a modification of a previously registered alloy. If the greatest mean percentage is common to more than one alloying element, the alloy group is determined by the element that comes first in the sequence.

The second two digits identify the specific aluminum alloy or, for the aluminum (1xx.x) series, indicate purity. The last digit, which is separated from the others by a decimal point, indicates the product form, whether casting or ingot. A modification of an original alloy, or of the impurity limits for unalloyed aluminum, is indicated by a serial letter preceding the numerical designation. The serial letters are assigned in alphabetical sequence starting with A but omitting I, O, Q, and X, the X being reserved for experimental alloys. Explicit rules have been established for determining whether a proposed composition is a modification of an existing alloy or if it is a new alloy. Aluminum Castings and Ingot. For the 1xx.x group, the second two of the four digits in the designation indicate the minimum aluminum percentage. These digits are the same as the two digits to the right of the decimal point in the minimum aluminum percentage when expressed to the nearest 0.01%. The last digit indicates the product form: 1xx.0 indicates castings, and 1xx.1 indicates ingot. Aluminum Alloy Castings and Ingot. For the 2xx.x through 9xx.x alloy groups, the second two of the four digits in the designation have no special significance but serve only to identify the different alloys in the group. The last digit, which is to the right of the decimal point, indicates the produce form: xxx.0 indicates castings, and xxx.1 indicates ingot having limits for alloying elements the same as those for the alloy in the form of castings, except for those listed in Table 1.

Table 1 Alloying element and impurity specifications for ingots that will be remelted into sand, permanent mold, and die castings Alloying element

Composition, wt%

Casting

Sand and permanent mold

Ingot

Die

All

0.15

...

...

Casting -0.03

>0.15-0.25

...

...

Casting -0.05

>0.25-0.6

...

...

Casting -0.10

>0.6-1.0

...

...

Casting -0.2

>1.0

...

...

Casting -0.3

...

Casting -0.3

Iron

...

Magnesium

Zinc

1.3

...

>1.3

...

...

...

0.25-0.60

0.50

...

1.1

Casting +0.05(a)

Casting +0.1(a)

Casting -0.10

...

>0.60

...

Casting -0.1

Source: ANSI H35.1-1997 (a) Applicable only when the specified range for castings is >0.15% Mg.

Designations for Experimental Alloys Experimental alloys also are designated in accordance with the systems for wrought and cast alloys, but they are indicated by the prefix X. The prefix is dropped when the alloy is no longer experimental. During development and before they are designated as experimental, new alloys may be identified by serial numbers assigned by their originators. Use of the serial number is discontinued when the ANSI H35.1 designation is assigned.

Temper Designation System for Aluminum and Aluminum Alloys The temper designation system used in the United States for aluminum and aluminum alloys is used for all product forms (both wrought and cast), with the exception of ingot. The system is based on the sequences of mechanical or thermal treatments, or both, used to produce the various tempers. The temper designation follows the alloy designation and is separated from it by a hyphen. Basic temper designations consist of individual capital letters. Major subdivisions of basic tempers, where required, are indicated by one or more digits following the letter. These digits designate specific sequences of treatments that produce specific combinations of characteristics in the product. Variations in treatment conditions within major subdivisions are identified by additional digits. The conditions during heat treatment (such as time, temperature, and quenching rate) used to produce a given temper in one alloy may differ from those employed to produce the same temper in another alloy. Basic Temper Designations F, As-Fabricated. This is applied to products shaped by cold working, hot working, or casting processes in which no special control over thermal conditions or strain hardening is employed. For wrought products, there are no mechanical property limits. O, Annealed. O applies to wrought products that are annealed to obtain lowest-strength temper and to cast products that

are annealed to improve ductility and dimensional stability. The O may be followed by a digit other than zero. H, Strain-Hardened (Wrought Products Only). This indicates products that have been strengthened by strain

hardening, with or without supplementary thermal treatment to produce some reduction in strength. The H is always followed by two or more digits, as discussed in the section "System for Strain-Hardened Products" in this article. W, Solution Heat-Treated. This is an unstable temper applicable only to alloys whose strength naturally

(spontaneously) changes at room temperature over a duration of months or even years after solution heat treatment. The designation is specific only when the period of natural aging is indicated (for example, W h). See also the discussion of the Tx51, Tx52, and Tx54 tempers in the section "System for Heat-Treatable Alloys" in this article. T, Solution Heat-Treated. This applies to alloys whose strength is stable within a few weeks of solution heat

treatment. The T is always followed by one or more digits, as discussed in the section "System for Heat-Treatable Alloys" in this article. System for Strain-Hardened Products Temper designations for wrought products that are strengthened by strain hardening consist of an H followed by two or more digits. The first digit following the H indicates the specific sequence of basic operations.

H1, Strain-Hardened Only. This applies to products that are strain hardened to obtain the desired strength without

supplementary thermal treatment. The digit following the H1 indicates the degree of strain hardening. H2, Strain-Hardened and Partially Annealed. This pertains to products that are strain-hardened more than the

desired final amount and then reduced in strength to the desired level by partial annealing. For alloys that age soften at room temperature, each H2x temper has the same minimum ultimate tensile strength as the H3x temper with the same second digit. For other alloys, each H2x temper has the same minimum ultimate tensile strength as the H1x with the same second digit, and slightly higher elongation. The digit following the H2 indicates the degree of strain hardening remaining after the product has been partially annealed. H3, Strain-Hardened and Stabilized. This applies to products that are strain-hardened and whose mechanical

properties are stabilized by a low-temperature thermal treatment or as a result of heat introduced during fabrication. Stabilization usually improves ductility. This designation applies only to those alloys that, unless stabilized, gradually age soften at room temperature. The digit following the H3 indicates the degree of strain hardening remaining after stabilization. H4, Strain-Hardened and Lacquered or Painted. This applies to products that are strain-hardened and that are

also subjected to some thermal operation during subsequent painting or lacquering. The number following this designation indicates the degree of strain-hardening remaining after the product has been thermally treated as part of the painting/lacquering cure operation. The corresponding H2x or H3x mechanical property limits apply. Additional Temper Designations. The digit following the designation H1, H2, H3, and H4 indicates the degree of

strain-hardening as identified by the minimum value of the ultimate tensile strength. The numeral 8 has been assigned to the hardest tempers normally produced. The minimum tensile strength of tempers Hx8 can be determined from Table 2 and is based on the minimum tensile strength of the alloy (given in ksi units) in the annealed temper. However, temper registrations prior to 1992 that do not conform to the requirements of Table 2 shall not be revised and registrations of intermediate or modified tempers for such alloy/temper systems shall conform to the registration requirements that existed prior to 1992. Table 2 Minimum tensile requirements for the Hx8 tempers Minimum tensile strength in annealed temper, ksi

6

Increase in tensile strength to Hx8 temper, ksi

8

7-9

9

10-12

10

13-15

11

16-18

12

19-24

13

25-30

14

31-36

15

16

37-42

17

43

Source: ANSI H35.1-1997

Tempers between O (annealed) and Hx8 are designated by numerals 1 through 7 as follows: • • • • •

Numeral 4 designates tempers whose ultimate tensile strength is approximately midway between that of the O temper and that of the Hx8 tempers. Numeral 2 designates tempers whose ultimate tensile strength is approximately midway between that of the O temper and that of the Hx4 tempers. Numeral 6 designates tempers whose ultimate tensile strength is approximately midway between that of the Hx4 tempers and that of the Hx8 tempers. Numerals 1, 3, 5, and 7 designate, similarly, tempers intermediate between those defined above. Numeral 9 designates tempers whose minimum ultimate tensile strength exceeds that of the Hx8 tempers by 2 ksi or more.

The ultimate tensile strength of intermediate tempers, determined as described above, when not ending in 0 or 5, shall be rounded to the next higher 0 or 5. When it is desirable to identify a variation of a two-digit H temper, a third digit (from 1 to 9) may be assigned. The third digit is used when the degree of control of temper or the mechanical properties are different from but close to those for the two-digit H temper designation to which it is added, or when some other characteristic is significantly affected. The minimum ultimate tensile strength of a three-digit H temper is at least as close to that of the corresponding two-digit H temper as it is to either of the adjacent two-digit H tempers. Products in H tempers whose mechanical properties are below those of Hx1 tempers are assigned variations of Hx1. Some three-digit H temper designations have already been assigned for wrought products in all alloys: • • •

Hx11 applies to products that incur sufficient strain hardening after final annealing to fail to qualify as 0 temper, but not so much or so consistent an amount of strain hardening to qualify as Hx1 temper. H112 pertains to products that may acquire some strain hardening during working at elevated temperature and for which there are mechanical property limits. H temper designations assigned to patterned or embossed sheet are listed in Table 3.

Table 3 H temper designations for aluminum and aluminum alloy patterned or embossed sheet Patterned or embossed sheet

Temper of sheet from which textured sheet was fabricated

H114

O

H124

H11

H224

H21

H324

H31

H134

H12

H234

H22

H334

H32

H144

H13

H244

H23

H344

H33

H154

H14

H254

H24

H354

H34

H164

H15

H264

H25

H364

H35

H174

H16

H274

H26

H374

H36

H184

H17

H284

H27

H384

H37

H194

H18

H294

H28

H394

H38

H195

H19

H295

H29

H395

H39

Source: ANSI H35.1-1997

System for Heat-Treatable Alloys The temper designation system for wrought and cast products that are strengthened by heat treatment employs the W and T designations described in the section "Basic Temper Designations" in this article. The W designation denotes an unstable temper, whereas the T designation denotes a stable temper other than F, O, or H. The T is followed by a number from 1 to 10, each number indicating a specific sequence of basic treatments. T1, Cooled from an Elevated-Temperature Shaping Process and Naturally Aged to a Substantially Stable Condition. This designation applies to products that are not cold worked after an elevated-temperature shaping

process such as casting or extrusion and for which mechanical properties have been stabilized by room-temperature aging. It also applies to products that are flattened or straightened after cooling from the shaping process, for which the effects of the cold work imparted by flattening or straightening are not accounted for in specified property limits. T2, Cooled from an Elevated-Temperature Shaping Process, Cold Worked, and Naturally Aged to a Substantially Stable Condition. This variation refers to products that are cold worked specifically to improve

strength after cooling from a hot-working process such as rolling or extrusion and for which mechanical properties have been stabilized by room-temperature aging. It also applies to products in which the effects of cold work, imparted by flattening or straightening, are accounted for in specified property limits. T3, Solution Heat Treated, Cold Worked, and Naturally Aged to a Substantially Stable Condition. T3

applies to products that are cold worked specifically to improve strength after solution heat treatment and for which mechanical properties have been stabilized by room-temperature aging. It also applies to products in which the effects of cold work, imparted by flattening or straightening, are accounted for in specified property limits. T4, Solution Heat Treated and Naturally Aged to a Substantially Stable Condition. This signifies products

that are not cold worked after solution heat treatment and for which mechanical properties have been stabilized by roomtemperature aging. If the products are flattened or straightened, the effects of the cold work imparted by flattening or straightening are not accounted for in specified property limits. T5, Cooled from an Elevated-Temperature Shaping Process and Artificially Aged. T5 includes products

that are not cold worked after an elevated-temperature shaping process such as casting or extrusion and for which mechanical properties have been substantially improved by precipitation heat treatment. If the products are flattened or straightened after cooling from the shaping process, the effects of the cold work imparted by flattening or straightening are not accounted for in specified property limits. T6, Solution Heat Treated and Artificially Aged. This group encompasses products that are not cold worked after

solution heat treatment and for which mechanical properties or dimensional stability, or both, have been substantially improved by precipitation heat treatment. If the products are flattened or straightened, the effects of the cold work imparted by flattening or straightening are not accounted for in specified property limits. T7, Solution Heat Treated and Overaged or Stabilized. T7 applies to wrought products that have been precipitation heat treated beyond the point of maximum strength to provide some special characteristic, such as enhanced resistance to stress-corrosion cracking or exfoliation corrosion. It applies to cast products that are artificially aged after solution heat treatment to provide dimensional and strength stability. T8, Solution Heat Treated, Cold Worked, and Artificially Aged. This designation applies to products that are

cold worked specifically to improve strength after solution heat treatment and for which mechanical properties or

dimensional stability, or both, have been substantially improved by precipitation heat treatment. The effects of cold work, including any cold work imparted by flattening or straightening, are accounted for in specified property limits. T9, Solution Heat Treated, Artificially Aged, and Cold Worked. This grouping is comprised of products that

are cold worked specifically to improve strength after they have been precipitation heat treated. T10, Cooled from an Elevated-Temperature Shaping Process, Cold Worked, and Artificially Aged. T10

identifies products that are cold worked specifically to improved strength after cooling from a hot-working process such as rolling or extrusion and for which mechanical properties have been substantially improved by precipitation heat treatment. The effects of cold work, including any cold work imparted by flattening or straightening, are accounted for in specified property limits. Additional T Temper Variations. When it is desirable to identify a variation of one of the ten major T tempers

described above, additional digits, the first of which cannot be zero, may be added to the designation. Specific sets of additional digits have been assigned to the following wrought products that have been stress relieved by stretching, compressing, or a combination of stretching and compressing:

Product form

Permanent set, %

Plate 1

-3

Rolled or cold-finished rod and bar

1-3

Extruded rod, bar, profiles (shapes), and tube

1-3

Drawn tube -3

Die or ring forgings and rolled rings

1-5

Stress relieved by stretching includes the following.

Tx51 applies specifically to plate, to rolled or cold-finished road and bar, to die or ring forgings, and to rolled rings when stretched to the indicated amounts after solution heat treatment or after cooling from an elevated-temperature shaping process. These products receive no further straightening after stretching. Tx510 applies to extruded rod, bar, shapes and tubing, and to drawn tubing when stretched to the indicated amounts after solution heat treatment or after cooling from an elevated-temperature shaping process. Products in this temper receive no further straightening after stretching. Tx511 applies to extruded rod, bar, profiles (shapes) and tube and to drawn tube when stretched to the indicated amounts after solution heat treatment or after cooling from an elevated temperature shaping process. These products may receive minor straightening after stretching to comply with standard tolerances. Stress relieved by compressing includes the following.

Tx52 applies to products that are stress relieved by compressing after solution heat treatment or after cooling from a hotworking process to produce a permanent set of 1 to 5%.

Stress relieved by combined stretching and compressing includes the following.

Tx54 applies to die forgings that are stress relieved by restriking cold in the finish die. The same digits (51, 52, and 54) can be added to the designation W to indicate unstable solution-heat-treated and

stress-relieved tempers. Temper designations have been assigned to wrought products heat treated from the O or the F temper to demonstrate response to heat treatment. T42 means solution heat treated from the O or the F temper to demonstrate response to heat treatment and naturally aged to a substantially stable condition. T62 means solution heat treated from the O or the F temper to demonstrate response to heat treatment and artificially aged. T7x2 means solution heat treated from the O or F temper and artificially overaged to meet the mechanical properties and corrosion resistance limits of the T7x temper. Temper designations T42 and T62 also may be applied to wrought products heat treated from any temper by the user when such heat treatment results in the mechanical properties applicable to these tempers. System for Annealed Products A digit following the "O" indicates a product in annealed condition having special characteristics. For example, for heattreatable alloys, O1 indicates a product that has been heat treated at approximately the same time and temperature required for solution heat treatment and then air cooled to room temperature; this designation applies to products that are to be machined prior to solution heat treatment by the user. Mechanical property limits are not applicable. Designation of Unregistered Tempers The letter P has been assigned to denote H, T, and O temper variations that are negotiated between manufacturer and purchaser. The letter P follows the temper designation that most nearly pertains. The use of this type of designation includes the following situations: • • • •

The use of the temper is sufficiently limited to preclude its registration. The test conditions are different from those required for registration with the Aluminum Association. The mechanical property limits are not established on the same basis as required for registration with the Aluminum Association. It is used for products such as aluminum metal-matrix composites, which are not included in any registration records. (A proposed nomenclature system for aluminum metal-matrix composites is described in the Section "Special-Purpose Materials" in this Handbook.)

Chemical Compositions International Designations Aluminum Alloys

and for

Introduction MORE THAN 450 ALLOY designations/compositions have been registered by the Aluminum Association Inc. for aluminum and aluminum alloys. Table 1 lists the designations and composition limits of wrought unalloyed aluminum and wrought aluminum alloys. Table 2 lists designations and composition limits for aluminum alloys in the form of castings and ingot. Table 1 Composition limits for wrought aluminum and aluminum alloys AA No.

Composition, wt%

Si

Fe

Cu

Mn

Mg

Cr

Ni

Zn

Ga

V

Specified other elements

Ti

Unspecified other elements

Each

Total

Al, min

1035

0.35

0.6

0.10

0.05

0.05

...

...

0.10

...

0.05

...

0.03

0.03

...

99.35

1040

0.30

0.50

0.10

0.05

0.05

...

...

0.10

...

0.05

...

0.03

0.03

...

99.40

1045

0.30

0.45

0.10

0.05

0.05

...

...

0.05

...

0.05

...

0.03

0.03

...

99.45

1050

0.25

0.40

0.05

0.05

0.05

...

...

0.05

...

0.05

...

0.03

0.03

...

99.50

1060

0.25

0.35

0.05

0.03

0.03

...

...

0.05

...

0.05

...

0.03

0.03

...

99.60

1065

0.25

0.30

0.05

0.03

0.03

...

...

0.05

...

0.05

...

0.03

0.03

...

99.65

1070

0.20

0.25

0.04

0.03

0.03

...

...

0.04

...

0.05

...

0.03

0.03

...

99.70

1080

0.15

0.15

0.03

0.02

0.02

...

...

0.03

0.03

0.05

...

0.03

0.02

...

99.80

1085

0.10

0.12

0.03

0.02

0.02

...

...

0.03

0.03

0.05

...

0.02

0.01

...

99.85

1090

0.07

0.07

0.02

0.01

0.01

...

...

0.03

0.03

0.05

...

0.01

0.01

...

99.90

1100

0.95 Si + Fe

0.050.20

0.05

...

...

...

0.10

...

...

(a)

...

0.05

0.15

99.0

1200

1.00 Si + Fe

0.05

0.05

...

...

...

0.10

...

...

...

0.05

0.05

0.15

99.0

1230

0.70 Si + Fe

0.10

0.05

0.05

...

...

0.10

...

0.05

...

0.03

0.03

...

99.30

1135

0.60 Si + Fe

0.050.20

0.04

0.05

...

...

0.10

...

0.05

...

0.03

0.03

...

99.35

1235

0.65 Si + Fe

0.05

0.05

0.05

...

...

0.10

...

0.05

...

0.06

0.03

...

99.35

1435

0.15

0.02

0.05

0.05

...

...

0.10

...

0.05

...

0.03

0.03

...

99.35

1145

0.55 Si + Fe

0.05

0.05

0.05

...

...

0.05

...

0.05

...

0.03

0.03

...

99.45

1345

0.30

0.40

0.10

0.05

0.05

...

...

0.05

...

0.05

...

0.03

0.03

...

99.45

1350

0.10

0.40

0.05

0.01

...

0.01

...

0.05

0.03

...

0.05 B, 0.02 V + Ti

...

0.03

0.10

99.50

1170

0.30 Si + Fe

0.03

0.03

0.02

0.03

...

0.04

...

0.05

...

0.03

0.03

...

99.70

1175

0.15 Si + Fe

0.10

0.02

0.02

...

...

0.04

0.03

0.05

...

0.02

0.02

...

99.75

1180

0.09

0.01

0.02

0.02

...

...

0.03

0.03

0.05

...

0.02

0.02

...

99.80

1185

0.15 Si + Fe

0.01

0.02

0.02

...

...

0.03

0.03

0.05

...

0.02

0.01

...

99.85

1285

0.08(b)

0.08(b)

0.02

0.01

0.01

...

...

0.03

0.03

0.05

...

0.02

0.01

...

99.85

1188

0.06

0.06

0.005

0.01

0.01

...

...

0.03

0.03

0.05

(a)

0.01

0.01

...

99.88

1199

0.006

0.006

0.006

0.002

0.006

...

...

0.006

0.005

0.005

...

0.002

0.002

...

99.99

2008

0.500.8

0.40

0.71.1

0.30

0.250.50

0.10

...

0.25

...

0.05

...

0.10

0.05

0.15

bal

2009

0.25

0.05

3.24.4

...

1.01.6

...

...

0.10

...

...

(c)

...

0.05

0.15

bal

2010

0.50

0.50

0.71.3

0.100.40

0.401.0

0.15

...

0.30

...

...

...

...

0.05

0.15

bal

0.300.50

0.09

2011

0.40

0.7

5.06.0

...

...

...

...

0.30

...

...

(d)

...

0.05

0.15

bal

2111

0.40

0.7

5.06.0

...

...

...

...

0.30

...

...

(e)

...

0.05

0.15

bal

2012

0.40

0.7

4.05.5

...

...

...

...

0.30

...

...

(f)

...

0.05

0.15

bal

2014

0.501.2

0.7

3.95.0

0.401.2

0.200.8

0.10

...

0.25

...

...

(g)

0.15

0.05

0.15

bal

2214

0.501.2

0.30

3.95.0

0.401.2

0.200.8

0.10

...

0.25

...

...

(g)

0.15

0.05

0.15

bal

2017

0.200.8

0.7

3.54.5

0.401.0

0.400.8

0.10

...

0.25

...

...

(g)

0.15

0.05

0.15

bal

2117

0.8

0.7

2.23.0

0.20

0.200.50

0.10

...

0.25

...

...

...

...

0.05

0.15

bal

2018

0.9

1.0

3.54.5

0.20

0.450.9

0.10

1.72.3

0.25

...

...

...

...

0.05

0.15

bal

2218

0.9

1.0

3.54.5

0.20

1.21.8

0.10

1.72.3

0.25

...

...

...

...

0.05

0.15

bal

2618

0.100.25

0.91.3

1.92.7

...

1.31.8

...

0.91.2

0.10

...

...

...

0.040.10

0.05

0.15

bal

2219

0.20

0.30

5.86.8

0.200.40

0.02

...

...

0.10

...

0.050.15

0.10-0.25 Zr

0.020.10

0.05

0.15

bal

2319

0.20

0.30

5.86.8

0.200.40

0.02

...

...

0.10

...

0.050.15

0.10-0.25 Zr(a)

0.100.20

0.05

0.15

bal

2419

0.15

0.18

5.86.8

0.200.40

0.02

...

...

0.10

...

0.050.15

0.10-0.25 Zr

0.020.10

0.05

0.15

bal

2519

0.25(h)

0.30(h)

5.36.4

0.100.50

0.500.40

...

...

0.10

...

0.050.15

0.10-0.25 Zr

0.020.10

0.05

0.15

bal

2024

0.50

0.50

3.84.9

0.300.9

1.21.8

0.10

...

0.25

...

·

(g)

0.15

0.05

0.15

bal

2124

0.20

0.30

3.84.9

0.300.9

1.21.8

0.10

...

0.25

...

...

(g)

0.15

0.05

0.15

bal

2224

0.12

0.15

3.84.4

0.300.9

1.21.8

0.10

...

0.25

...

...

...

0.15

0.05

0.15

bal

2324

0.10

0.12

3.84.4

0.300.9

1.21.8

0.10

...

0.25

...

...

...

0.15

0.05

0.15

bal

2025

0.501.2

1.0

3.95.0

0.401.2

0.05

0.10

...

0.25

...

...

...

0.15

0.05

0.15

bal

2034

0.10

0.12

4.24.8

0.81.3

1.31.9

0.05

...

0.20

...

...

0.08-0.15 Zr

0.15

0.05

0.15

bal

2036

0.50

0.50

2.23.0

0.100.40

0.300.6

0.10

...

0.25

...

...

...

0.15

0.05

0.15

bal

2037

0.50

0.50

1.42.2

0.100.40

0.300.8

0.10

...

0.25

...

0.05

...

0.15

0.05

0.15

bal

2038

0.501.3

0.6

0.81.8

0.100.40

0.401.0

0.20

...

0.50

0.05

0.05

...

0.15

0.05

0.15

bal

2048

0.15

0.20

2.83.8

0.200.6

1.21.8

...

...

0.25

...

...

...

0.10

0.05

0.15

bal

X2080

0.10

0.20

3.34.1

0.25

1.52.2

...

...

0.10

...

...

0.08-0.25 Zr(i)

...

0.05

0.15

bal

2090

0.10

0.12

2.43.0

0.05

0.25

0.05

...

0.10

...

...

0.08-0.15 Zr(j)

0.15

0.05

0.15

bal

2091

0.20

0.30

1.82.5

0.10

1.11.9

0.10

...

0.25

...

...

0.04-0.16 Zr(k)

0.10

0.05

0.15

bal

2094

0.12

0.15

4.45.2

0.25

0.0250.8

...

...

0.25

...

...

0.04-0.18 Zr(l)

0.10

0.05

0.15

bal

2095

0.12

0.15

3.94.6

0.25

0.250.8

...

...

0.25

...

...

0.04-0.18 Zr(m)

0.10

0.05

0.15

bal

2195

0.12

0.15

3.74.3

0.25

0.250.8

...

...

0.25

...

...

0.08-0.16 Zr(n)

0.10

0.05

0.15

bal

X2096

0.12

0.15

2.33.0

0.25

0.250.8

...

...

0.25

...

...

0.04-0.18 Zr(o)

0.10

0.05

0.15

bal

2097

0.12

0.15

2.53.1

0.100.6

0.35

...

...

0.35

...

...

0.08-0.16 Zr(p)

0.15

0.05

0.15

bal

2197

0.10

0.10

2.53.1

0.100.50

0.25

...

...

0.05

...

...

0.08-0.15 Zr(q)

0.12

0.05

0.15

bal

3002

0.08

0.10

0.15

0.050.25

0.050.20

...

...

0.05

...

0.05

...

0.03

0.03

0.10

bal

3102

0.40

0.7

0.10

0.050.40

...

...

...

0.30

...

...

...

0.10

0.05

0.15

bal

3003

0.6

0.7

0.050.20

1.01.5

...

...

...

0.10

...

...

...

...

0.05

0.15

bal

3303

0.6

0.7

0.050.20

1.01.5

...

...

...

0.30

...

...

...

...

0.05

0.15

bal

3004

0.30

0.7

0.25

1.01.5

0.81.3

...

...

0.25

...

...

...

...

0.05

0.15

bal

3104

0.6

0.8

0.050.25

0.81.4

0.81.3

...

...

0.25

0.05

0.05

...

0.10

0.05

0.15

bal

3204

0.30

0.7

0.100.25

0.81.5

0.81.5

...

...

0.25

...

...

...

...

0.05

0.15

bal

3005

0.6

0.7

0.30

1.01.5

0.200.6

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

3105

0.6

0.7

0.30

0.300.8

0.200.8

0.20

...

0.40

...

...

...

0.10

0.05

0.15

bal

3006

0.50

0.7

0.100.30

0.500.8

0.300.6

0.20

...

0.150.40

...

...

...

0.10

0.05

0.15

bal

3007

0.50

0.7

0.050.30

0.300.8

0.6

0.20

...

0.40

...

...

...

0.10

0.05

0.15

bal

3107

0.6

0.7

0.050.15

0.400.9

...

...

...

0.20

...

...

...

0.10

0.05

0.15

bal

3307

0.6

0.8

0.30

0.500.9

0.30

0.20

...

0.40

...

...

...

0.10

0.05

0.15

bal

3009

1.01.8

0.7

0.10

1.21.8

0.10

0.05

0.05

0.05

...

...

0.10 Zr

0.10

0.05

0.15

bal

3010

0.10

0.20

0.03

0.200.9

...

0.050.40

...

0.05

...

0.05

...

0.05

0.03

0.10

bal

3011

0.40

0.7

0.050.20

0.81.2

...

0.100.40

...

0.10

...

...

0.10-0.30 Zr

0.10

0.05

0.15

bal

3015

0.6

0.8

0.30

0.500.9

0.200.7

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

3016

0.6

0.8

0.30

0.500.9

0.500.8

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

4004

9.010.5

0.8

0.25

0.10

1.02.0

...

...

0.20

...

...

...

...

0.05

0.15

bal

4104

9.010.5

0.8

0.25

0.10

1.02.0

...

...

0.20

...

...

0.02-0.20 Bi

...

0.05

0.15

bal

4008

6.57.5

0.09

0.05

0.05

0.300.45

...

...

0.05

...

...

(a)

0.040.15

0.05

0.15

bal

4009

4.55.5

0.20

1.01.5

0.10

0.450.6

...

...

0.10

...

...

(a)

0.20

0.05

0.15

bal

4010

6.57.5

0.20

0.20

0.10

0.300.45

...

...

0.10

...

...

(a)

0.20

0.05

0.15

bal

4011

6.57.5

0.20

0.20

0.10

0.450.7

...

...

0.10

...

...

0.04-0.07 Be

0.040.20

0.05

0.15

bal

4013

3.54.5

0.35

0.050.20

0.03

0.050.20

...

...

0.05

...

...

(r)

0.02

0.05

0.15

bal

4032

11.013.5

1.0

0.501.3

...

0.81.3

0.10

0.501.3

0.25

...

...

...

...

0.05

0.15

bal

4043

4.56.0

0.8

0.30

0.05

0.05

...

...

0.10

...

...

(a)

0.20

0.05

0.15

bal

4343

6.88.2

0.8

0.25

0.10

...

...

...

0.20

...

...

...

...

0.05

0.15

bal

4543

5.07.0

0.50

0.10

0.05

0.100.40

0.05

...

0.10

...

...

...

0.10

0.05

0.15

bal

4643

3.64.6

0.8

0.10

0.05

0.100.30

...

...

0.10

...

...

(a)

0.15

0.05

0.15

bal

4044

7.89.2

0.8

0.25

0.10

...

...

...

0.20

...

...

...

...

0.05

0.15

bal

4045

9.011.0

0.8

0.30

0.05

0.05

...

...

0.10

...

...

...

0.20

0.05

0.15

bal

4145

9.310.7

0.8

3.34.7

0.15

0.15

0.15

...

0.20

...

...

(a)

...

0.05

0.15

bal

4047

11.013.0

0.8

0.30

0.15

0.10

...

...

0.20

...

...

(a)

...

0.05

0.15

bal

4147

11.013.0

0.8

0.25

0.10

0.100.50

...

...

0.20

...

...

(a)

...

0.05

0.15

bal

4048(s)

9.310.7

0.8

3.34.7

0.07

0.07

0.07

...

9.310.7

...

·.

(a)

...

0.05

0.15

bal

5005

0.30

0.7

0.20

0.20

0.501.1

0.10

...

0.25

...

...

...

...

0.05

0.15

bal

5205

0.15

0.7

0.030.10

0.10

0.61.0

0.10

...

0.05

...

...

...

...

0.05

0.15

bal

5006

0.40

0.8

0.10

0.400.8

0.81.3

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

5010

0.40

0.7

0.25

0.100.30

0.200.6

0.15

...

0.30

...

...

...

0.10

0.05

0.15

bal

5016

0.25

0.6

0.20

0.400.7

1.41.9

0.10

...

0.15

...

...

...

0.05

0.05

0.15

bal

5017

0.40

0.7

0.180.28

0.60.8

1.92.2

...

...

...

...

...

...

0.09

0.05

0.15

bal

5040

0.30

0.7

0.25

0.91.4

1.01.5

0.100.30

...

0.25

...

...

...

...

0.05

0.15

bal

5042

0.20

0.35

0.15

0.200.50

3.04.0

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

5043

0.40

0.7

0.050.35

0.71.2

0.71.3

0.05

...

0.25

0.05

0.05

...

0.10

0.05

0.15

bal

5349

0.40

0.7

0.180.28

0.61.2

1.72.6

...

...

...

...

...

...

0.09

0.05

0.15

bal

5050

0.40

0.7

0.20

0.10

1.11.8

0.10

...

0.25

...

...

...

...

0.05

0.15

bal

5250

0.08

0.10

0.10

0.050.15

1.31.8

...

·

0.05

0.03

0.05

...

...

0.03

0.10

bal

5051

0.40

0.7

0.25

0.20

1.72.2

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

5151

0.20

0.35

0.15

0.10

1.52.1

0.10

...

0.15

...

...

...

0.10

0.05

0.15

bal

5351

0.08

0.10

0.10

0.10

1.62.2

...

...

0.05

...

0.05

...

...

0.03

0.10

bal

5451

0.25

0.40

0.10

0.10

1.82.4

0.150.35

0.05

0.10

...

...

...

0.05

0.05

0.15

bal

5052

0.25

0.40

0.10

0.10

2.22.8

0.150.35

...

0.10

...

...

...

...

0.05

0.15

bal

5252

0.08

0.10

0.10

0.10

2.22.8

...

...

0.05

...

0.05

...

...

0.03

0.10

bal

5352

0.45 Si + Fe

0.10

0.10

2.22.8

0.10

...

0.10

...

...

...

0.10

0.05

0.15

bal

5552

0.04

0.10

0.10

2.22.8

...

...

0.05

...

0.05

...

...

0.03

0.10

bal

5652

0.40 Si + Fe

0.04

0.01

2.22.8

0.150.35

...

0.10

...

...

...

...

0.05

0.15

bal

5154

0.25

0.10

0.10

3.13.9

0.150.35

...

0.20

...

...

(a)

0.20

0.05

0.15

bal

5254

0.45 Si + Fe

0.05

0.01

3.13.9

0.150.35

...

0.20

...

...

...

0.05

0.05

0.15

bal

5454

0.25

0.40

0.10

0.501.0

2.43.0

0.050.20

...

0.25

...

...

...

0.20

0.05

0.15

bal

5554

0.25

0.40

0.10

0.501.0

2.43.0

0.050.20

...

0.25

...

...

(a)

0.050.20

0.05

0.15

bal

5654

0.45 Si + Fe

0.05

0.01

3.13.9

0.150.35

...

0.20

...

...

(a)

0.050.15

0.05

0.15

bal

5754

0.40

0.10

0.50

2.63.6

0.30

...

0.20

...

...

0.10-0.6 Mn + Cr

0.15

0.05

0.15

bal

0.05

0.40

0.40

5954

0.25

0.40

0.10

0.10

3.34.1

0.10

...

0.20

...

...

...

0.20

0.05

0.15

bal

5056

0.30

0.40

0.10

0.050.20

4.55.6

0.050.20

...

0.10

...

...

...

...

0.05

0.15

bal

5356

0.25

0.40

0.10

0.050.20

4.55.5

0.050.20

...

0.10

...

...

(a)

0.060.20

0.05

0.15

bal

5456

0.25

0.40

0.10

0.501.0

4.75.5

0.050.20

...

0.25

...

...

...

0.20

0.05

0.15

bal

5556

0.25

0.40

0.10

0.501.0

4.75.5

0.050.20

...

0.25

...

...

(a)

0.050.20

0.05

0.15

bal

5357

0.12

0.17

0.20

0.150.45

0.81.2

...

...

0.05

...

...

...

...

0.05

0.15

bal

5457

0.08

0.10

0.20

0.150.45

0.81.2

...

...

0.05

...

0.05

...

...

0.03

0.10

bal

5557

0.10

0.12

0.15

0.100.40

0.400.8

...

...

...

...

0.05

...

...

0.03

0.10

bal

5657

0.08

0.10

0.10

0.03

0.61.0

...

...

0.05

0.03

0.05

...

...

0.02

0.05

bal

5180

0.35 Si + Fe

0.10

0.200.7

3.54.5

0.10

...

1.72.8

...

...

0.08-0.25 Zr(a)

0.060.20

0.05

0.15

bal

5082

0.20

0.35

0.15

0.15

4.05.0

0.15

...

0.25

...

...

...

0.10

0.05

0.15

bal

5182

0.20

0.35

0.15

0.200.50

4.05.0

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

5083

0.40

0.40

0.10

0.401.0

4.04.9

0.050.25

...

0.25

...

...

...

0.15

0.05

0.15

bal

5183

0.40

0.40

0.10

0.501.0

4.35.2

0.050.25

...

0.25

...

...

(a)

0.15

0.05

0.15

bal

5086

0.40

0.50

0.10

0.200.7

3.54.5

0.050.25

...

0.25

...

...

...

0.15

0.05

0.15

bal

5091

0.20

0.30

...

...

3.74.2

...

...

...

...

...

(t)

...

0.05

0.15

bal

6101

0.300.7

0.50

0.10

0.03

0.350.8

0.03

...

0.10

...

...

0.06 B

...

0.03

0.10

bal

6201

0.500.9

0.50

0.10

0.03

0.60.9

0.03

...

0.10

...

...

0.06 B

...

0.03

0.10

bal

6301

0.500.9

0.7

0.10

0.15

0.60.9

0.10

...

0.25

...

...

...

0.15

0.05

0.15

bal

6003

0.351.0

0.6

0.10

0.8

0.81.5

0.35

...

0.20

...

...

...

0.10

0.05

0.15

bal

6004

0.300.6

0.100.30

0.10

0.200.6

0.400.7

...

...

0.05

...

...

...

...

0.05

0.15

bal

6005

0.60.9

0.35

0.10

0.10

0.400.6

0.10

...

0.10

...

...

...

0.10

0.05

0.15

bal

6005A

0.500.9

0.35

0.30

0.50

0.400.7

0.30

...

0.20

...

...

0.12-0.50 Mn + Cr

0.10

0.05

0.15

bal

6105

0.61.0

0.35

0.10

0.10

0.450.8

0.10

...

0.10

...

...

...

0.10

0.05

0.15

bal

6205

0.60.9

0.7

0.20

0.050.15

0.400.6

0.050.15

...

0.25

...

...

0.05-0.15 Zr

0.15

0.05

0.15

bal

6006

0.200.6

0.35

0.150.30

0.050.20

0.450.9

0.10

...

0.10

...

...

...

0.10

0.05

0.15

bal

6206

0.350.7

0.35

0.200.50

0.130.30

0.450.8

0.10

...

0.20

...

...

...

0.10

0.05

0.15

bal

6306

0.200.6

0.10

0.050.16

0.100.0

0.450.9

...

...

0.05

...

...

...

0.05

0.05

0.15

bal

6007

0.91.4

0.7

0.20

0.050.25

0.60.9

0.050.25

...

0.25

...

...

0.05-0.20 Zr

0.15

0.05

0.15

bal

6009

0.61.0

0.50

0.150.6

0.200.8

0.400.8

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

6010

0.81.2

0.50

0.150.6

0.200.8

0.61.0

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

6110

0.71.5

0.8

0.200.7

0.200.7

0.501.1

0.040.25

...

0.30

...

...

...

0.15

0.05

0.15

bal

6011

0.61.2

1.0

0.400.9

0.8

0.61.2

0.30

0.20

1.5

...

...

...

0.20

0.05

0.15

bal

6111

0.61.1

0.40

0.500.9

0.100.45

0.501.0

0.10

...

0.15

...

...

...

0.10

0.05

0.15

bal

6013

0.61.0

0.50

0.61.1

0.200.8

0.81.2

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

6113

0.61.0

0.30

0.61.1

0.100.6

0.81.2

0.10

...

0.25

...

...

(u)

0.10

0.05

0.15

bal

6017

0.550.7

0.150.30

0.050.20

0.10

0.450.6

0.10

...

0.05

...

...

...

0.05

0.05

0.15

bal

6151

0.61.2

1.0

0.35

0.20

0.450.8

0.150.35

...

0.25

...

...

...

0.15

0.05

0.15

bal

6351

0.71.3

0.50

0.10

0.400.8

0.400.8

...

...

0.20

...

...

...

0.20

0.05

0.15

bal

6951

0.200.50

0.8

0.150.40

0.10

0.400.8

...

...

0.20

...

...

...

...

0.05

0.15

bal

6053

(v)

0.35

0.10

...

1.11.4

0.150.35

...

0.10

...

...

...

...

0.05

0.15

bal

6253

(v)

0.50

0.10

...

1.01.5

0.040.35

...

1.62.4

...

...

...

...

0.05

0.15

bal

6060

0.300.6

0.100.30

0.10

0.10

0.350.6

0.05

...

0.15

...

...

...

0.10

0.05

0.15

bal

6160

0.300.6

0.15

0.20

0.05

0.350.6

0.05

...

0.05

...

...

...

...

0.05

0.15

bal

6061

0.400.8

0.7

0.150.40

0.15

0.81.2

0.040.35

...

0.25

...

...

...

0.15

0.05

0.15

bal

6162

0.400.8

0.50

0.20

0.10

0.71.1

0.10

...

0.25

...

...

...

0.10

0.05

0.15

bal

6262

0.400.8

0.7

0.150.40

0.15

0.81.2

0.040.14

...

0.25

...

...

(w)

0.15

0.05

0.15

bal

6063

0.200.6

0.35

0.10

0.10

0.450.9

0.10

...

0.10

...

...

...

0.10

0.05

0.15

bal

6463

0.200.6

0.15

0.20

0.05

0.450.9

...

...

0.05

...

...

...

...

0.05

0.15

bal

6763

0.200.6

0.08

0.040.16

0.03

0.450.9

...

...

0.03

...

0.05

...

...

0.03

0.10

bal

6066

0.91.8

0.50

0.71.2

0.61.1

0.81.4

0.40

...

0.25

...

...

...

0.20

0.05

0.15

bal

6070

1.01.7

0.50

0.150.40

0.401.0

0.501.2

0.10

...

0.25

...

...

...

0.15

0.05

0.15

bal

6091

0.400.8

0.7

0.150.40

0.15

0.81.2

0.15

...

0.25

...

...

(u)

0.15

0.05

0.15

bal

6092

0.400.8

0.30

0.71.0

0.15

0.81.2

0.15

...

0.25

...

...

(u)

0.15

0.05

0.15

bal

7001

0.35

0.40

1.62.6

0.20

2.63.4

0.180.35

...

6.88.0

...

...

...

0.20

0.05

0.15

bal

7004

0.25

0.35

0.05

0.200.7

1.02.0

0.05

...

3.84.6

...

...

0.10-0.20 Zr

0.05

0.05

0.15

bal

7005

0.35

0.40

0.10

0.200.7

1.01.8

0.060.20

...

4.05.0

...

...

0.08-0.20 Zr

0.010.06

0.05

0.15

bal

7008

0.10

0.10

0.05

0.05

0.71.4

0.120.25

...

4.55.5

...

...

...

0.05

0.05

0.10

bal

7108

0.10

0.10

0.05

0.05

0.71.4

...

...

4.55.5

...

...

0.12-0.25 Zr

0.05

0.05

0.15

bal

7011

0.15

0.20

0.05

0.100.30

1.01.6

0.050.20

...

4.05.5

...

...

...

0.05

0.05

0.15

bal

7013

0.6

0.7

0.10

1.01.5

...

...

...

1.52.0

...

...

...

...

0.05

0.15

bal

7016

0.10

0.12

0.451.0

0.03

0.81.4

...

...

4.05.0

...

0.05

...

0.03

0.03

0.10

bal

7116

0.15

0.30

0.501.1

0.05

0.81.4

...

...

4.25.2

0.03

0.05

...

0.05

0.05

0.15

bal

7021

0.25

0.40

0.25

0.10

1.21.8

0.05

...

5.06.0

...

...

0.08-0.18 Zr

0.10

0.05

0.15

bal

7029

0.10

0.12

0.500.9

0.03

1.32.0

...

...

4.25.2

...

0.05

...

0.05

0.03

0.10

bal

7129

0.15

0.30

0.500.9

0.10

1.32.0

0.10

...

4.25.2

0.03

0.05

...

0.05

0.05

0.15

bal

7229

0.06

0.08

0.500.9

0.03

1.32.0

...

...

4.25.2

...

0.05

...

0.05

0.03

0.10

bal

7031

0.30

0.81.4

0.10

0.100.40

0.10

...

...

0.81.8

...

...

...

...

0.05

0.15

bal

7039

0.30

0.40

0.10

0.100.40

2.33.3

0.150.25

...

3.54.5

...

...

...

0.10

0.05

0.15

bal

7046

0.20

0.40

0.25

0.30

1.01.6

0.20

...

6.67.6

...

...

0.10-0.18 Zr

0.06

0.05

0.15

bal

7146

0.20

0.40

...

...

1.01.6

...

...

6.67.6

...

...

0.10-0.18 Zr

0.06

0.05

0.15

bal

7049

0.25

0.35

1.21.9

0.20

2.02.9

0.100.22

...

7.28.2

...

...

...

0.10

0.05

0.15

bal

7149

0.15

0.20

1.21.9

0.20

2.02.9

0.100.22

...

7.28.2

...

...

...

0.10

0.05

0.15

bal

7249

0.10

0.12

1.31.9

0.10

2.02.4

0.120.18

...

7.58.2

...

...

...

0.06

0.05

0.15

bal

7050

0.12

0.15

2.02.6

0.10

1.92.6

0.04

...

5.76.7

...

...

0.08-0.15 Zr

0.06

0.05

0.15

bal

7150

0.12

0.15

1.92.5

0.10

2.02.7

0.04

...

5.96.9

...

...

0.08-0.15 Zr

0.06

0.05

0.15

bal

7055

0.10

0.15

2.02.6

0.05

1.82.3

0.04

...

7.68.4

...

...

0.08-0.25 Zr

0.06

0.05

0.15

bal

7064

0.12

0.15

1.82.4

...

1.92.9

0.060.25

...

6.88.0

...

...

0.10-0.50 Zr(x)

...

0.05

0.15

bal

7072

0.7 Si + Fe

0.10

0.10

0.10

...

...

0.81.3

...

...

...

...

0.05

0.15

bal

7472

0.25

0.05

0.05

0.91.5

...

...

1.31.9

...

...

...

...

0.05

0.15

bal

0.6

7075

0.40

0.50

1.22.0

0.30

2.12.9

0.180.28

...

5.16.1

...

...

(y)

0.20

0.05

0.15

bal

7175

0.15

0.20

1.22.0

0.10

2.12.9

0.180.28

...

5.16.1

...

...

...

0.10

0.05

0.15

bal

7475

0.10

0.12

1.21.9

0.06

1.92.6

0.180.25

...

5.26.2

...

...

...

0.06

0.05

0.15

bal

7076

0.40

0.6

0.301.0

0.300.8

1.22.0

...

...

7.08.0

...

...

...

0.20

0.05

0.15

bal

7277

0.50

0.7

0.81.7

...

1.72.3

0.180.35

...

3.74.3

...

...

...

0.10

0.05

0.15

bal

7178

0.40

0.50

1.62.4

0.30

2.43.1

0.180.28

...

6.37.3

...

...

...

0.20

0.05

0.15

bal

7090

0.12

0.15

0.61.3

...

2.03.0

...

...

7.38.7

...

...

1.0-1.9 Co(z)

...

0.05

0.15

bal

7091

0.12

0.15

1.11.8

...

2.03.0

...

...

5.87.1

...

...

0.20-0.60 Co(z)

...

0.05

0.15

bal

7093

0.12

0.15

1.11.9

...

2.03.0

...

0.040.16

8.39.7

...

...

0.08-0.20 Zr(u)

...

0.05

0.15

bal

8001

0.17

0.450.7

0.15

...

...

...

0.91.3

0.05

...

...

(aa)

...

0.05

0.15

bal

8006

0.40

1.22.0

0.30

0.301.0

0.10

...

...

0.10

...

...

...

...

0.05

0.15

bal

8007

0.40

1.22.0

0.10

0.301.0

0.10

...

...

0.81.8

...

...

...

...

0.05

0.15

bal

8009

1.71.9

8.48.9

...

0.10

...

0.10

...

0.25

...

1.11.5

(bb)

0.10

0.05

0.15

bal

8010

0.40

0.350.7

0.100.30

0.100.8

0.100.50

0.20

...

0.40

...

...

...

0.10

0.05

0.15

bal

8111

0.301.1

0.401.0

0.10

0.10

0.05

0.05

...

0.10

...

...

...

0.08

0.05

0.15

bal

8112

1.0

1.0

0.40

0.6

0.7

0.20

...

1.0

...

...

...

0.20

0.05

0.15

bal

8014

0.30

1.21.6

0.20

0.200.6

0.10

...

...

0.10

...

...

...

0.10

0.05

0.15

bal

8015

0.30

0.81.4

0.10

0.100.40

0.10

...

...

0.10

...

...

...

...

0.05

0.15

bal

8017

0.10

0.550.8

0.100.20

...

0.010.05

...

...

0.05

...

...

0.04 B, 0.003 Li

...

0.03

0.10

bal

X8019

0.20

7.39.3

...

0.05

...

...

...

0.05

...

...

(cc)

0.05

0.05

0.15

bal

8020

0.10

0.10

0.005

0.005

...

...

...

0.005

...

0.05

(dd)

...

0.03

0.10

bal

8022

1.21.4

6.26.8

...

0.10

...

0.10

...

0.25

...

0.400.8

(ee)

0.10

0.05

0.15

bal

8030

0.10

0.300.8

0.150.30

...

0.05

...

...

0.05

...

...

0.0010.04 B

...

0.03

0.10

bal

8130

0.15(ff)

0.401.0(ff)

0.050.15

...

...

...

...

0.10

...

...

...

...

0.03

0.10

bal

8040

1.0 Si + Fe

0.20

0.05

...

...

...

0.20

...

...

0.10-0.30 Zr

...

0.05

0.15

bal

8076

0.10

0.60.9

0.04

...

0.080.22

...

...

0.05

...

...

0.04 B

...

0.03

0.10

bal

8176

0.030.15

0.401.0

...

...

...

...

...

0.10

0.03

...

...

...

0.05

0.15

bal

8077

0.10

0.100.40

0.05

...

0.100.30

...

...

0.05

...

...

0.05 B (gg)

...

0.03

0.10

bal

8177

0.10

0.250.45

0.04

...

0.040.12

...

...

0.05

...

...

0.04 B

...

0.03

0.10

bal

8079

0.050.30

0.71.3

0.05

...

...

...

...

0.10

...

...

...

...

0.05

0.15

bal

8280

1.02.0

0.7

0.71.3

0.10

...

...

0.200.7

0.05

...

...

5.5-7.0 Sn

0.10

0.05

0.15

bal

8081

0.7

0.7

0.71.3

0.10

...

...

...

0.05

...

...

18.0-22.0 Sn

0.10

0.05

0.15

bal

8090

0.20

0.30

1.01.6

0.10

0.61.3

0.10

...

0.25

...

...

0.04-0.16 Zr(hh)

0.10

0.05

0.15

bal

Source: Aluminum Association Inc. (a)

0.0008% max Be for welding electrode and filler wire only.

(b)

0.14% max Si + Fe.

(c)

0.6%max O.

(d)

0.20-0.6% Bi, 0.20-0.6% Pb.

(e)

0.20-0.8%Bi, 0.10-0.50% Sn.

(f)

0.20-0.7%Bi, 0.20-0.6% Sn.

(g)

A Zr+ Ti limit of 0.20% max can be used with this alloy designation for extruded and forged products only, but only when the supplier and purchaser have mutually so agreed.

(h)

0.40% max Si + Fe.

(i)

0.005% max Be, 0.20-0.50%O.

(j)

1.9-2.6% Li.

(k)

1.7-2.3% Li.

(l)

0.25-0.6% Ag, 0.7-1.4% Li.

(m) 0.25-0.6% Ag, 0.7-1.5%Li.

(n)

0.25-0.6% Ag, 0.8-1.2%Li.

(o)

0.25-0.6% Ag, 1.3-1.9%Li.

(p)

1.2-1.8% Li.

(q)

1.3-1.7% Li.

(r)

0.6-1.5% Bi, 0.05% max Cd.

(s)

Formerly inactive alloy 4245 reactivated as 4048.

(t)

1.0-1.3% C, 1.2-1.4%Li, 0.20-0.7% O.

(u)

0.05-0.50%O.

(v)

45-65% of actual Mg.

(w)

0.40-0.7% Bi, 0.40-0.7%Pb.

(x)

0.10-0.40% Co, 0.05-0.30%O.

(y)

A Zr + Ti limit of 0.25%max can be used with this alloy designation for extruded and forged products only, but only when the supplier and purchaser have mutually so agreed.

(z)

0.20-0.50% O.

(aa) 0.001% max B, 0.003% max Cd, 0.001% max Co, 0.008% max Li.

(bb) 0.30% max O.

(cc) 3.5-4.5% Ce, 0.20-0.50%O.

(dd) 0.10-0.50% Bi, 0.10-0.25%Sn.

(ee) 0.05-0.20% O.

(ff)

1.0% max Si + Fe.

(gg) 0.02-0.08% Zr.

(hh) 2.2-2.7% Li.

Table 2 Composition limits for unalloyed and alloyed aluminum castings (xxx.0) and ingots (xxx.1 or xxx.2) Designation

Composition, wt%

Others

Al, min

AA No.

Former

Products(a)

Si

Fe

Cu

Mn

Mg

Cr

Ni

Zn

Ti

Sn

Each

Total

100.1

...

Ingot

0.15

0.6-0.8

0.10

(b)

...

(b)

...

0.05

(b)

...

0.03(b)

0.10

99.00

130.1

...

Ingot

(c)

(c)

0.10

(b)

...

(b)

...

0.05

(b)

...

0.03(b)

0.10

99.30

150.1

...

Ingot

(d)

(d)

0.05

(b)

...

(b)

...

0.05

(b)

...

0.03

0.10

99.50

160.1

...

Ingot

0.10(d)

0.25(d)

...

(b)

...

(b)

...

0.05

(b)

...

0.03

0.10

99.60

170.1

...

Ingot

(e)

(e)

...

(b)

...

(b)

...

0.05

(b)

...

0.03(b)

0.10

99.70

201.0

...

S

0.10

0.15

4.0-5.2

0.200.50

0.15-0.55

...

...

...

0.15-0.35

...

0.05 (f)

0.10

bal

201.2

...

Ingot

0.10

0.10

4.0-5.2

0.200.50

0.20-0.55

...

...

...

0.15-0.35

...

0.05 (f)

0.10

bal

A201.0

...

S

0.05

0.10

4.0-5.0

0.200.40

0.15-0.35

...

...

...

0.15-0.35

...

0.03 (f)

0.10

bal

A201.1

A201.2

Ingot

0.05

0.07

4.0-5.0

0.200.40

0.20-0.35

...

...

...

0.15-0.35

...

0.03 (f)

0.10

bal

B201.0

...

S

0.05

0.05

4.5-5.0

0.200.50

0.25-0.35

...

...

...

0.15-0.35

...

0.05 (g)

0.15

bal

203.0

Hiduminium 350

S

0.30

0.50

4.5-5.5

0.200.30

0.10

...

1.3-1.7

0.10

0.5-0.25(h)

...

0.05(i)

0.20

bal

203.2

Hiduminium 350

Ingot

0.20

0.35

4.8-5.2

0.200.30

0.10

...

1.3-1.7

0.10

0.150.25(h)

...

0.05(i)

0.20

bal

204.0

A-U5GT

S, P

0.20

0.35

4.2-5.0

0.10

0.15-0.35

...

0.05

0.10

0.15-0.30

0.05

0.05

0.15

bal

204.2

A-U5GT

Ingot

0.15

0.100.20

4.2-4.9

0.05

0.20-0.35

...

0.03

0.05

0.15-0.25

0.05

0.05

0.15

bal

206.0

...

S, P

0.10

0.15

4.2-5.0

0.200.50

0.15-0.35

...

0.05

0.10

0.15-0.30

0.05

0.05

0.15

bal

206.2

...

Ingot

0.10

0.10

4.2-5.0

0.200.50

0.20-0.35

...

0.03

0.05

0.15-0.25

0.05

0.05

0.15

bal

A206.0

...

S, P

0.05

0.10

4.2-5.0

0.200.50

0.15-0.35

...

0.05

0.10

0.15-0.30

0.05

0.05

0.15

bal

A206.2

...

Ingot

0.05

0.07

4.2-5.0

0.200.50

0.20-0.35

...

0.03

0.05

0.15-0.25

0.05

0.05

0.15

bal

240.0

A240.0, A140

S

0.50

0.50

7.0-9.0

0.30-0.7

5.5-6.5

...

0.30-0.7

0.10

0.20

...

0.05

0.15

bal

240.1

A240.1, A140

Ingot

0.50

0.40

7.0-9.0

0.30-0.7

5.6-6.5

...

0.30-0.7

0.10

0.20

...

0.05

0.15

bal

242.0

142

S, P

0.7

1.0

3.5-4.5

0.35

1.2-1.8

0.25

1.7-2.3

0.35

0.25

...

0.05

0.15

bal

242.1

142

Ingot

0.7

0.8

3.5-4.5

0.35

1.3-1.8

0.25

1.7-2.3

0.35

0.25

...

0.05

0.15

bal

242.2

142

Ingot

0.6

0.6

3.5-4.5

0.10

1.3-1.8

...

1.7-2.3

0.10

0.20

...

0.05

0.15

bal

A242.0

A142

S

0.6

0.8

3.7-4.5

0.10

1.2-1.7

0.150.25

1.8-2.3

0.10

0.07-0.20

...

0.05

0.15

bal

A242.1

A142

Ingot

0.6

0.6

3.7-4.5

0.10

1.3-1.7

0.150.25

1.8-2.3

0.10

0.07-0.20

...

0.05

0.15

bal

A242.2

A142

Ingot

0.35

0.6

3.7-4.5

0.10

1.3-1.7

0.150.25

1.8-2.3

0.10

0.07-0.20

...

0.05

0.15

bal

295.0

195

S

0.7-1.5

1.0

4.0-5.0

0.35

0.03

...

...

0.35

0.25

...

0.05

0.15

bal

295.1

195

Ingot

0.7-1.5

0.8

4.0-5.0

0.35

0.03

...

...

0.35

0.25

...

0.05

0.15

bal

295.2

195

Ingot

0.7-1.2

0.8

4.0-5.0

0.30

0.03

...

...

0.30

0.20

. . .. . .

0.05

0.15

bal

296.0

B295.0, B195

P

2.0-3.0

1.2

4.0-5.0

0.35

0.05

...

0.35

0.50

0.25

...

...

0.35

bal

296.1

B295.1, B195

Ingot

2.0-3.0

0.9

4.0-5.0

0.35

0.05

...

0.35

0.50

0.25

...

...

0.35

bal

296.2

B295.2, B195

Ingot

2.0-3.0

0.8

4.0-5.0

0.30

0.03

...

...

0.30

0.20

...

0.05

0.15

bal

301.0

...

...

9.5-1.5

0.8-1.5

3.0-3.5

0.50-0.8

0.25-0.50

...

1.0-1.5

0.05

0.20

...

0.03

0.10

bal

301.1

...

Ingot(j)

9.5-01.5

0.8-1.2

3.0-3.5

0.50-0.8

0.30-0.50

...

1.0-1.5

0.05

0.20

...

0.03

0.10

bal

302.0

...

...

9.5-10.5

0.25

2.8-3.2

...

0.7-1.2

...

1.0-1.5

0.05

0.20

...

0.03

0.10

bal

302.1

...

Ingot(j)

9.5-10.5

0.20

2.8-3.2

...

0.8-1.2

...

1.0-1.5

0.05

0.20

...

0.03

0.10

bal

303.0

...

...

9.5-10.5

0.8-1.5

0.20

0.50-0.8

0.45-0.7

...

...

0.05

0.20

...

0.03

0.10

bal

303.1

...

Ingot(j)

9.5-10.5

0.8-1.2

0.20

0.50-0.8

0.50-0.7

...

...

0.05

0.20

...

0.03

0.10

bal

308.0

A108

S, P

5.0-6.0

1.0

4.0-5.0

0.50

0.10

...

...

1.0

0.25

...

...

0.50

bal

308.1

A108

Ingot

5.0-6.0

0.8

4.0-5.0

0.50

0.10

...

...

1.0

0.25

...

...

0.50

bal

308.2

A108

Ingot

5.0-6.0

0.8

4.0-5.0

0.30

0.10

...

...

0.50

0.20

...

...

0.50

bal

318.0

...

S, P

5.5-6.5

1.0

3.0-4.0

0.50

0.10-0.6

...

0.35

1.0

0.25

...

...

0.50

bal

318.1

...

Ingot

5.5-6.5

0.8

3.0-4.0

0.50

0.15-0.6

...

0.35

0.9

0.25

...

...

0.50

bal

319.0

319, All Cast

S, P

5.5-6.5

1.0

3.0-4.0

0.50

0.10

...

0.35

1.0

0.25

...

...

0.50

bal

319.1

319, All Cast

Ingot

5.5-6.5

0.8

3.0-4.0

0.50

0.10

...

0.35

1.0

0.25

...

...

0.50

bal

319.2

319, All Cast

Ingot

5.5-6.5

0.6

3.0-4.0

0.10

0.10

...

0.10

0.10

0.20

...

...

0.20

bal

A319.0

...

S, P

5.5-6.5

1.0

3.0-4.0

0.50

0.10

...

0.35

3.0

0.25

...

...

0.50

bal

A319.1

...

Ingot

5.5-6.5

0.8

3.0-4.0

0.50

0.10

...

0.35

3.0

0.25

...

...

0.50

bal

B319.0

SAE 329

S, P

5.5-6.5

1.2

3.0-4.0

0.8

0.10-0.50

...

0.50

1.0

0.25

...

...

0.50

bal

B319.1

...

Ingot

5.5-6.5

0.9

3.0-4.0

0.8

0.15-0.50

...

0.50

1.0

0.25

...

...

0.50

bal

320.0

...

S, P

5.0-8.0

1.2

2.0-4.0

0.8

0.05-0.6

...

0.35

3.0

0.25

...

...

0.50

bal

320.1

...

Ingot

5.0-8.0

0.9

2.0-4.0

0.8

0.10-0.6

...

0.35

3.0

0.25

...

...

0.50

bal

332.0

F332.0, F132

P

8.5-10.5

1.2

2.0-4.0

0.50

0.50-1.5

...

0.50

1.0

0.25

...

...

0.50

bal

332.1

F332.1, F132

Ingot

8.5-10.5

0.9

2.0-4.0

0.50

0.6-1.5

...

0.50

1.0

0.25

...

...

0.50

bal

332.2

F332.2, F132

Ingot

8.5-10.0

0.6

2.0-4.0

0.10

0.9-1.3

...

0.10

0.10

0.20

...

...

0.30

bal

333.0

333

P

8.0-10.0

1.0

3.0-4.0

0.50

0.05-0.50

...

0.50

1.0

0.25

...

...

0.50

bal

333.1

333

Ingot

8.0-10.0

0.8

3.0-4.0

0.50

0.10-0.50

...

0.50

1.0

0.25

...

...

0.50

bal

A333.0

...

P

8.0-10.0

1.0

3.0-4.0

0.50

0.05-0.50

...

0.50

3.0

0.25

...

...

0.50

bal

A333.1

...

Ingot

8.0-10.0

0.8

3.0-4.0

0.50

0.10-0.50

...

0.50

3.0

0.25

...

...

0.50

bal

336.0

A332.0, A132

P

11.013.0

1.2

0.501.5

0.35

0.7-1.3

...

2.0-3.0

0.35

0.25

...

0.05

...

bal

336.1

A332.1, A132

Ingot

11.013.0

0.9

0.501.5

0.35

0.8-1.3

...

2.0-3.0

0.35

0.25

...

0.05

...

bal

336.2

A332.2, A132

Ingot

11.013.0

0.9

0.501.5

0.10

0.9-1.3

...

2.0-3.0

0.10

0.20

...

0.05

0.15

bal

339.0

Z332.0, Z132

P

11.013.0

1.2

1.5-3.0

0.50

0.50-1.5

...

0.50-1.5

1.0

0.25

...

...

0.50

bal

339.1

Z332.1, Z132

Ingot

11.013.0

0.9

1.5-3.0

0.50

0.6-1.5

...

0.50-1.5

1.0

0.25

...

...

0.50

bal

354.0

354

P

8.6-9.4

0.20

1.6-2.0

0.10

0.40-0.6

...

...

0.10

0.20

...

0.05

0.15

bal

354.1

354

Ingot

8.6-9.4

0.15

1.6-2.0

0.10

0.45-0.6

...

...

0.10

0.20

...

0.05

0.15

bal

355.0

355

S, P

4.5-5.5

0.6(k)

1.0-1.5

0.50(k)

0.40-0.6

0.25

...

0.35

0.25

...

0.05

0.15

bal

355.1

355

Ingot

4.5-5.5

0.50(k)

1.0-1.5

0.50(k)

0.45-0.6

0.25

...

0.35

0.25

...

0.05

0.15

bal

355.2

355

Ingot

4.5-5.5

0.140.25

1.0-1.5

0.05

0.50-0.6

...

...

0.05

0.20

...

0.05

0.15

bal

A355.0

...

S, P

4.5-5.5

0.09

1.0-1.5

0.05

0.45-0.6

...

...

0.05

0.04-0.20

...

0.05

0.15

bal

A355.2

...

Ingot

4.5-5.5

0.06

1.0-1.5

0.03

0.50-0.6

...

...

0.03

0.04-0.20

...

0.03

0.10

bal

C355.0

C355

S, P

4.5-5.5

0.20

1.0-1.5

0.10

0.40-0.6

...

...

0.10

0.20

...

0.05

0.15

bal

C355.1

...

Ingot

4.5-5.5

0.15

1.0-1.5

0.10

0.45-0.6

...

...

0.10

020

...

0.05

0.15

bal

C355.2

C355

Ingot

4.5-5.5

0.13

1.0-1.5

0.05

0.50-0.6

...

...

0.05

0.20

...

0.05

0.15

bal

356.0

356

S, P

6.5-7.5

0.6(k)

0.25

0.35(k)

0.20-0.45

...

...

0.35

0.25

...

0.05

0.15

bal

356.1

356

Ingot

6.5-7.5

0.50(k)

0.25

0.35(k)

0.25-0.45

...

...

0.35

0.25

...

0.05

0.15

bal

356.2

356

Ingot

6.5-7.5

0.130.25

0.10

0.05

0.30-0.45

...

...

0.05

0.20

...

0.05

0.15

bal

A356.0

A356

S, P

6.5-7.5

0.20

0.20

0.10

0.25-0.45

...

...

0.10

0.20

...

0.05

0.15

bal

A356.1

...

Ingot

6.5-7.5

0.15

0.20

0.10

0.30-0.45

...

...

0.10

0.20

...

0.05

0.15

bal

A356.2

A356

Ingot

6.5-7.5

0.12

0.10

0.05

0.30-0.45

...

...

0.05

0.20

...

0.05

0.15

bal

B356.0

...

S, P

6.5-7.5

0.09

0.05

0.05

0.25-0.45

...

...

0.05

0.04-0.20

...

0.05

0.15

bal

B356.2

...

Ingot

6.5-7.5

0.06

0.03

0.03

0.30-0.45

...

...

0.03

0.04-0.20

...

0.03

0.10

bal

C356.0

...

S, P

6.5-7.5

0.07

0.05

0.05

0.25-0.45

...

...

0.05

0.04-0.20

...

0.05

0.15

bal

C356.2

...

Ingot

6.5-7.5

0.04

0.03

0.03

0.30-0.45

...

...

0.03

0.04-0.20

...

0.03

0.10

bal

F356.0

...

S, P

6.5-7.5

0.20

0.20

0.10

0.17-0.25

...

...

0.10

0.04-0.20

...

0.05

0.15

bal

F356.2

...

Ingot

6.5-7.5

0.12

0.10

0.05

0.17-0.25

...

...

0.05

0.04-0.20

...

0.05

0.15

bal

357.0

357

S, P

6.5-7.5

0.15

0.05

0.03

0.45-0.6

...

...

0.05

0.20

...

0.05

0.15

bal

357.1

357

Ingot

6.5-7.5

0.12

0.05

0.03

0.45-0.6

...

...

0.05

0.20

...

0.05

0.15

bal

A357.0

A357

S, P

6.5-7.5

0.20

0.20

0.10

0.40-0.7

...

...

0.10

0.04-0.20

...

0.05 (l)

0.15

bal

A357.2

A357

Ingot

6.5-7.5

0.12

0.10

0.05

0.45-0.7

...

...

0.05

0.04-0.20

...

0.03 (l)

0.10

bal

B357.0

...

S, P

6.5-7.5

0.09

0.05

0.05

0.40-0.6

...

...

0.05

0.04-0.20

...

0.05

0.15

bal

B357.2

...

Ingot

6.5-7.5

0.06

0.03

0.03

0.45-0.6

...

...

0.03

0.04-0.20

...

0.03

0.10

bal

C357.0

...

S, P

6.5-7.5

0.09

0.05

0.05

0.45-0.7

...

...

0.05

0.04-0.20

...

0.05 (l)

0.15

bal

C357.2

...

Ingot

6.5-7.5

0.06

0.03

0.03

0.50-0.7

...

...

0.03

0.04-0.20

...

0.03 (l)

0.10

bal

D357.0

...

S

6.5-7.5

0.20

...

0.10

0.55-0.6

...

...

...

0.10-0.20

...

0.05 (l)

0.15

bal

358.0

B358.0, Tens-50

S, P

7.6-8.6

0.30

0.20

0.20

0.40-0.6

0.20

...

0.20

0.10-0.20

...

0.05 (m)

0.15

bal

358.2

B358.2, Tens-50

Ingot

7.6-8.6

0.20

0.10

0.10

0.45-0.6

0.05

...

0.10

0.12-0.20

...

0.05 (n)

0.15

bal

359.0

359

S, P

8.5-9.5

0.20

0.20

0.10

0.50-0.7

...

...

0.10

0.20

...

0.05

0.15

bal

359.2

359

Ingot

8.5-9.5

0.12

0.10

0.10

0.55-0.7

...

...

0.10

0.20

...

0.05

0.15

bal

A359.0

...

...

8.5-9.5

0.25

0.20

0.10

0.40-0.6

...

...

0.05

0.20

...

0.03

0.10

bal

A359.1

...

Ingot(j)

8.5-9.5

0.20

0.20

0.10

0.45-0.6

...

...

0.05

0.20

...

0.03

0.10

bal

360.0(o)

360

D

9.0-10.0

2.0

0.6

0.35

0.40-0.6

...

0.50

0.50

...

0.15

...

0.25

bal

360.2

360

Ingot

9.0-10.0

0.7-1.1

0.10

0.10

0.45-0.6

...

0.10

0.10

...

0.10

...

0.20

bal

A360.0(o)

A360

D

9.0-10.0

1.3

0.6

0.35

0.40-0.6

...

0.50

0.50

...

0.15

...

0.25

bal

A360.1(o)

A360

Ingot

9.0-10.0

1.0

0.6

0.35

0.45-0.6

...

0.50

0.40

...

0.15

...

0.25

bal

A360.2

A360

Ingot

9.0-10.0

0.6

0.10

0.05

0.45-0.6

...

...

0.05

...

...

0.05

0.15

bal

361.0

...

D

9.5-10.5

1.1

0.50

0.25

0.40-0.6

0.200.30

0.200.30

0.50

0.20

0.10

0.05

0.15

bal

361.1

...

Ingot

9.5-10.5

0.8

0.50

0.25

0.45-0.6

0.200.30

0.200.30

0.40

0.20

0.10

0.05

0.15

bal

363.0

363

S, P

4.5-6.0

1.1

2.5-3.5

(p)

0.15-0.40

(p)

0.25

3.04.5

0.20

0.25

(q)

0.30

bal

363.1

363

Ingot

4.5-6.0

0.8

2.5-3.5

(p)

0.20-0.40

(p)

0.25

3.04.5

0.20

0.25

(q)

0.30

bal

364.0

364

D

7.5-9.5

1.5

0.20

0.10

0.20-0.40

0.250.50

0.15

0.15

...

0.15

0.05(r)

0.15

bal

364.2

364

Ingot

7.5-9.5

0.7-1.1

0.20

0.10

0.25-0.40

0.250.50

0.15

0.15

...

0.15

0.05(r)

0.15

bal

369.0

Special K-9

D

11.012.0

1.3

0.50

0.35

0.25-0.45

0.300.40

0.05

1.0

...

0.10

0.05

0.15

bal

369.1

Special K-9

Ingot

11.012.0

1.0

0.50

0.35

0.30-0.45

0.300.40

0.05

0.9

...

0.10

0.05

0.15

bal

380.0(o)

380

D

7.5-9.5

2.0

3.0-4.0

0.50

0.10

...

0.50

3.0

...

0.35

...

0.50

bal

380.2

380

Ingot

7.5-9.5

0.7-1.1

3.0-4.0

0.10

0.10

...

0.10

0.10

...

0.10

...

0.20

bal

A380.0(o)

A380

D

7.5-9.5

1.3

3.0-4.0

0.50

0.10

...

0.50

3.0

...

0.35

...

0.50

bal

A380.1

A380

Ingot

7.5-9.5

1.0

3.0-4.0

0.50

0.10

...

0.50

2.9

...

0.35

...

0.50

bal

A380.2

A380

Ingot

7.5-9.5

0.6

3.0-4.0

0.10

0.10

...

0.10

0.10

...

...

0.05

0.15

bal

B380.0

A380

D

7.5-9.5

1.3

3.0-4.0

0.50

0.10

...

0.50

1.0

...

0.35

...

0.50

bal

B380.1

A380

Ingot

7.5-9.5

1.0

3.0-4.0

0.50

0.10

...

0.50

0.9

...

0.35

...

0.50

bal

C380.0

...

D

7.5-9.5

1.3

3.0-4.0

0.50

0.10-0.30

...

0.50

3.0

...

0.35

...

0.50

bal

C380.1

...

Ingot

7.5-9.5

1.0

3.0-4.0

0.50

0.15-0.30

...

0.50

2.9

...

0.35

...

0.50

bal

D380.0

...

D

7.5-9.5

1.3

3.0-4.0

0.50

0.10-0.30

...

0.50

1.0

...

0.35

...

0.50

bal

D380.1

...

Ingot

7.5-9.5

1.0

3.0-4.0

0.50

0.15-0.30

...

0.50

0.9

...

0.35

...

0.50

bal

383.0

...

D

9.5-11.5

1.3

2.0-3.0

0.50

0.10

...

0.30

3.0

...

0.15

...

0.50

bal

383.1

...

Ingot

9.5-11.5

1.0

2.0-3.0

0.50

0.10

...

0.30

2.9

...

0.15

...

0.50

bal

383.2

...

Ingot

9.5-11.5

0.6-1.0

2.0-3.0

0.10

0.10

...

0.10

0.10

...

0.10

...

0.20

bal

A383.0

...

D

9.5-11.5

1.3

2.0-3.0

0.50

0.10-0.30

...

0.30

3.0

...

0.15

...

0.50

bal

A383.1

...

Ingot

9.5-11.5

1.0

2.0-3.0

0.50

0.15-0.30

...

0.30

2.9

...

0.15

...

0.50

bal

384.0

384

D

10.512.0

1.3

3.0-4.5

0.50

0.10

...

0.50

3.0

...

0.35

...

0.50

bal

384.1

384

Ingot

10.512.0

1.0

3.0-4.5

0.50

0.10

...

0.50

2.9

...

0.35

...

0.50

bal

384.2

384

Ingot

10.512.0

0.6-1.0

3.0-4.5

0.10

0.10

...

0.10

0.10

...

0.10

...

0.20

bal

A384.0

384

D

10.512.0

1.3

3.0-4.5

0.50

0.10

...

0.50

1.0

...

0.35

...

0.50

bal

A384.1

384

Ingot

10.512.0

1.0

3.0-4.5

0.50

0.10

...

0.50

0.9

...

0.35

...

0.50

bal

B384.0

...

D

10.512.0

1.3

3.0-4.5

0.50

0.10-0.30

...

0.50

1.0

...

0.35

...

0.50

bal

B384.1

...

Ingot

10.512.0

1.0

3.0-4.5

0.50

0.15-0.30

...

0.50

0.9

...

0.35

...

0.50

bal

C384.0

...

D

10.512.0

1.3

3.0-4.5

0.50

0.10-0.30

...

0.50

3.0

...

0.35

...

0.50

bal

C384.1

...

Ingot

10.512.0

1.0

3.0-4.5

0.50

0.15-0.30

...

0.50

2.9

...

0.35

...

0.50

bal

385.0

B384.0, 384

D

11.013.0

2.0

2.0-4.0

0.50

0.30

...

0.50

3.0

...

0.30

...

0.50

bal

385.1

B384.1, 384

Ingot

11.013.0

1.1

2.0-4.0

0.50

0.30

...

0.50

2.9

...

0.30

...

0.50

bal

390.0

390

D

16.018.0

1.3

4.0-5.0

0.10

0.450.65(s)

...

...

0.10

0.20

...

0.10

0.20

bal

390.2

390

Ingot

16.018.0

0.6-1.0

4.0-5.0

0.10

0.500.65(s)

...

...

0.10

0.20

...

0.10

0.20

bal

A390.0

A390

S, P

16.018.0

0.50

4.0-5.0

0.10

0.450.65(s)

...

...

0.10

0.20

...

0.10

0.20

bal

A390.1

A390

Ingot

16.018.0

0.40

4.0-5.0

0.10

0.500.65(s)

...

...

0.10

0.20

...

0.10

0.20

bal

B390.0

...

D

16.018.0

1.3

4.0-5.0

0.50

0.450.65(s)

...

0.10

1.5

0.20

...

0.10

0.20

bal

B390.1

...

Ingot

16.018.0

1.0

4.0-5.0

0.50

0.500.65(s)

...

0.10

1.4

0.20

...

0.10

0.20

bal

392.0

392

D

18.020.0

1.5

0.400.8

0.20-0.6

0.8-1.2

...

0.50

0.50

0.20

0.30

0.15

0.50

bal

392.1

392

Ingot

18.020.0

1.1

0.400.8

0.20-0.6

0.9-1.2

...

0.50

0.40

0.20

0.30

0.15

0.50

bal

393.0

Vanasil

S, P, D

21.023.0

1.3

0.7-1.1

0.10

0.7-1.3

...

2.0-2.5

0.10

0.10-0.20

...

0.05 (t)

0.15

bal

393.1

Vanasil

Ingot

21.023.0

1.0

0.7-1.1

0.10

0.8-1.3

...

2.0-2.5

0.10

0.10-0.20

...

0.05 (t)

0.15

bal

393.2

Vanasil

Ingot

21.023.0

0.8

0.7-1.1

0.10

0.8-1.3

...

2.0-2.5

0.10

0.10-0.20

...

0.05 (t)

0.15

bal

408.2(u)

...

Ingot

8.5-9.5

0.6-1.3

0.10

0.10

...

...

...

0.10

...

...

0.10

0.20

bal

409.2(u)

...

Ingot

9.0-10.0

0.6-1.3

0.10

0.10

...

...

...

0.10

...

...

0.10

0.20

bal

411.2(u)

...

Ingot

10.012.0

0.6-1.3

0.20

0.10

...

...

...

0.10

...

...

0.10

0.20

bal

413.0(o)

13

D

11.013.0

2.0

1.0

0.35

0.10

...

0.50

0.50

...

0.15

...

0.25

bal

413.2

13

Ingot

11.013.0

0.7-1.1

0.10

0.10

0.07

...

0.10

0.10

...

0.10

...

0.20

bal

A413.0(o)

A13

D

11.013.0

1.3

1.0

0.35

0.10

...

0.50

0.50

...

0.15

...

0.25

bal

A413.1(o)

A13

Ingot

11.013.0

1.0

1.0

0.35

0.10

...

0.50

0.40

...

0.15

...

0.25

bal

A413.2

A13

Ingot

11.013.0

0.6

0.10

0.05

0.05

...

0.05

0.05

...

0.05

...

0.10

bal

B413.0

...

S, P

11.013.0

0.50

0.10

0.35

0.05

...

0.05

0.10

0.25

...

0.05

0.20

bal

B413.1

...

Ingot

11.013.0

0.40

0.10

0.35

0.05

...

0.05

0.10

0.25

...

0.05

0.20

bal

435.2(v)

...

Ingot

3.3-3.9

0.40

0.05

0.05

0.05

...

...

0.10

...

...

0.05

0.20

bal

443.0

43

S, P

4.5-6.0

0.8

0.6

0.50

0.05

0.25

...

0.50

0.25

...

...

0.35

bal

443.1

43

Ingot

4.5-6.0

0.6

0.6

0.50

0.05

0.25

...

0.50

0.25

...

...

0.35

bal

443.2

43

Ingot

4.5-6.0

0.6

0.10

0.10

0.05

...

...

0.10

0.20

...

0.05

0.15

bal

A443.0

43(0.30 max Cu)

S

4.5-6.0

0.8

0.30

0.50

0.05

0.25

...

0.50

0.25

...

...

0.35

bal

A443.1

43(0.30 max Cu)

Ingot

4.5-6.0

0.6

0.30

0.50

0.05

0.25

...

0.50

0.25

...

...

0.35

bal

B443.0

43(0.15 max Cu)

S, P

4.5-6.0

0.8

0.15

0.35

0.05

...

...

0.35

0.25

...

0.05

0.15

bal

B443.1

43(0.15 max Cu)

Ingot

4.5-6.0

0.6

0.15

0.35

0.05

...

...

0.35

0.25

...

0.05

0.15

bal

C443.0

A43

D

4.5-6.0

2.0

0.6

0.35

0.10

...

0.50

0.50

...

0.15

...

0.25

bal

C443.1

A43

Ingot

4.5-6.0

1.1

0.6

0.35

0.10

...

0.50

0.40

...

0.15

...

0.25

bal

C443.2

A43

Ingot

4.5-6.0

0.7-1.1

0.10

0.10

0.05

...

...

0.10

...

...

0.05

0.15

bal

444.0

...

S, P

6.5-7.5

0.6

0.25

0.35

0.10

...

...

0.35

0.25

...

0.05

0.15

bal

444.2

...

Ingot

6.5-7.5

0.130.25

0.10

0.05

0.05

...

...

0.05

0.20

...

0.05

0.15

bal

A444.0

A344

P

6.5-7.5

0.20

0.10

0.10

0.05

...

...

0.10

0.20

...

0.05

0.15

bal

A444.1

...

Ingot

6.5-7.5

0.15

0.10

0.10

0.05

...

...

0.10

0.20

...

0.05

0.15

bal

A444.2

A344

Ingot

6.5-7.5

0.12

0.05

0.05

0.05

...

...

0.05

0.20

...

0.05

0.15

bal

445.2(u)

B444.2

Ingot

6.5-7.5

0.6-1.3

0.10

0.10

...

...

...

0.10

...

...

0.10

0.20

bal

511.0

F514.0, F214

S

0.30-0.7

0.50

0.15

0.35

3.5-4.5

...

...

0.15

0.25

...

0.05

0.15

bal

511.1

F514.1, F214

Ingot

0.30-0.7

0.40

0.15

0.35

3.6-4.5

...

...

0.15

0.25

...

0.05

0.15

bal

511.2

F514.2, F214

Ingot

0.30-0.7

0.30

0.10

0.10

3.6-4.5

...

...

0.10

0.20

...

0.05

0.15

bal

512.0

B514.0, B214

S

1.4-2.2

0.6

0.35

0.8

3.5-4.5

0.25

...

0.35

0.25

...

0.05

0.15

bal

512.2

B514.2, B214

Ingot

1.4-2.2

0.30

0.10

0.10

3.6-4.5

...

...

0.10

0.20

...

0.05

0.15

bal

513.0

A514.0, A214

P

0.30

0.40

0.10

0.30

3.5-4.5

...

...

1.42.2

0.20

...

0.05

0.15

bal

513.2

A514.2, A214

Ingot

0.30

0.30

0.10

0.10

3.6-4.5

...

...

1.42.2

0.20

...

0.05

0.15

bal

514.0

214

S

0.35

0.50

0.15

0.35

3.5-4.5

...

...

0.15

0.25

...

0.05

0.15

bal

514.1

214

Ingot

0.35

0.40

0.15

0.35

3.6-4.5

...

...

0.15

0.25

...

0.05

0.15

bal

514.2

214

Ingot

0.30

0.30

0.10

0.10

3.6-4.5

...

...

0.10

0.20

...

0.05

0.15

bal

515.0

L514.0, L214

D

0.50-1.0

1.3

0.20

0.40-0.6

2.5-4.0

...

...

0.10

...

...

0.05

0.15

bal

515.2

L514.2, L214

Ingot

0.50-1.0

0.6-1.0

0.10

0.40-0.6

2.7-4.0

...

...

0.05

...

...

0.05

0.15

bal

516.0

...

D

0.30-1.5

0.35-1.0

0.30

0.150.40

2.5-4.5

...

0.250.40

0.20

0.10-0.20

0.10

0.05(w)

...

bal

516.1

...

Ingot

0.30-1.5

0.35-0.7

0.30

0.15-

2.6-4.5

...

0.25-

0.20

0.10-0.20

0.10

0.05 (w)

...

bal

0.40

0.40

518.0

218

D

0.35

1.8

0.25

0.35

7.5-8.5

...

0.15

0.15

...

0.15

...

0.25

bal

518.1

218

Ingot

0.35

1.1

0.25

0.35

7.6-8.5

...

0.15

0.15

...

0.15

...

0.25

bal

518.2

218

Ingot

0.25

0.7

0.10

0.10

7.6-8.5

...

0.05

...

...

0.05

...

0.10

bal

520.0

220

S

0.25

0.30

0.25

0.15

9.5-10.6

...

...

0.15

0.25

...

0.05

0.15

bal

520.2

220

Ingot

0.15

0.20

0.20

0.10

9.6-10.6

...

...

0.10

0.20

...

0.05

0.15

bal

535.0

Almag 35

S

0.15

0.15

0.05

0.100.25

6.2-7.5

...

...

...

0.10-0.25

...

0.05 (x)

0.15

bal

535.2

Almag 35

Ingot

0.10

0.10

0.05

0.100.25

6.6-7.5

...

...

...

0.10-0.25

...

0.05 (y)

0.15

bal

A535.0

A218

S

0.20

0.20

0.10

0.100.25

6.5-7.5

...

...

...

0.25

...

0.05

0.15

bal

A535.1

A218

Ingot

0.20

0.15

0.10

0.100.25

6.6-7.5

...

...

...

0.25

...

0.05

0.15

bal

B535.0

B218

S

0.15

0.15

0.10

0.05

6.5-7.5

...

...

...

0.10-0.25

...

0.05

0.15

bal

B535.2

B218

Ingot

0.10

0.12

0.05

0.05

6.6-7.5

...

...

...

0.10-0.25

...

0.05

0.15

bal

705.0

603, Ternalloy 5

S, P

0.20

0.8

0.20

0.40-0.6

1.4-1.8

0.200.40

...

2.73.3

0.25

...

0.05

0.15

bal

705.1

603, Ternalloy 5

Ingot

0.20

0.6

0.20

0.40-0.6

1.5-1.8

0.200.40

...

2.73.3

0.25

...

0.05

0.15

bal

707.0

607, Ternalloy 7

S, P

0.20

0.8

0.20

0.40-0.6

1.8-2.4

0.200.40

...

4.04.5

0.25

...

0.05

0.15

bal

707.1

607, Ternalloy 7

Ingot

0.20

0.6

0.20

0.40-0.6

1.9-2.4

0.200.40

...

4.04.5

0.25

...

0.05

0.15

bal

710.0

A712.0, A612

S

0.15

0.50

0.350.6

0.05

0.6-0.8

...

...

6.07.0

0.25

...

0.05

0.15

bal

710.1

A712.1, A612

Ingot

0.15

0.40

0.350.6

0.05

0.65-0.8

...

...

6.07.0

0.25

...

0.05

0.15

bal

711.0

C712.0, C612

P

0.30

0.7-1.4

0.350.6

0.05

0.25-0.45

...

...

6.07.0

0.20

...

0.05

0.15

bal

711.1

C712.1, C612

Ingot

0.30

0.7-1.1

0.350.6

0.05

0.30-0.45

...

...

6.07.0

0.20

...

0.05

0.15

bal

712.0

D712.0, D612, 40E

S

0.30

0.50

0.25

0.10

0.500.65(s)

0.40-0.6

...

5.06.5

0.15-0.25

...

0.05

0.20

bal

712.2

D712.2, D612, 40E

Ingot

0.15

0.40

0.25

0.10

0.500.65(s)

0.40-0.6

...

5.06.5

0.15-0.25

...

0.05

0.20

bal

713.0

613, Tenzaloy

S, P

0.25

1.1

0.401.0

0.6

0.20-0.50

0.35

0.15

7.08.0

0.25

...

0.10

0.25

bal

713.1

613, Tenzaloy

Ingot

0.25

0.8

0.401.0

0.6

0.25-0.50

0.35

0.15

7.08.0

0.25

...

0.10

0.25

bal

771.0

Precedent 71A

S

0.15

0.15

0.10

0.10

0.8-1.0

0.060.20

...

6.57.5

0.10-0.20

...

0.05

0.15

bal

771.2

Precedent 71A

Ingot

0.10

0.10

0.10

0.10

0.85-1.0

0.060.20

...

6.57.5

0.10-0.20

...

0.05

0.15

bal

772.0

B771.0, 71B

Precedent

S

0.15

0.15

0.10

0.10

0.6-0.8

0.060.20

...

6.07.0

0.10-0.20

...

0.05

0.15

bal

772.2

B771.2, 71B

Precedent

Ingot

0.10

0.10

0.10

0.10

0.65-0.8

0.060.20

...

6.07.0

0.10-0.20

...

0.05

0.15

bal

850.0

750

S, P

0.7

0.7

0.7-1.3

0.10

0.10

...

0.7-1.3

...

0.20

5.57.0

...

0.30

bal

850.1

750

Ingot

0.7

0.50

0.7-1.3

0.10

0.10

...

0.7-1.3

...

0.20

5.57.0

...

0.30

bal

851.0

A850.0, A750

S, P

2.0-3.0

0.7

0.7-1.3

0.10

0.10

...

0.30-0.7

...

0.20

5.57.0

...

0.30

bal

851.1

A850.1, A750

Ingot

2.0-3.0

0.50

0.7-1.3

0.10

0.10

...

0.30-0.7

...

0.20

5.57.0

...

0.30

bal

852.0

B850.0, B750

S, P

0.40

0.7

1.7-2.3

0.10

0.6-0.9

...

0.9-1.5

...

0.20

5.57.0

...

0.30

bal

852.1

B850.1, B750

Ingot

0.40

0.50

1.7-2.3

0.10

0.7-0.9

...

0.9-1.5

...

0.20

5.57.0

...

0.30

bal

853.0

XC850.0, XC750

S, P

5.5-6.5

0.7

3.0-4.0

0.50

...

...

...

...

0.20

5.57.0

...

0.30

bal

853.2

XC850.2, XC750

Ingot

5.5-6.5

0.50

3.0-4.0

0.10

...

...

Source: Aluminum Association Inc. (a)

D, die casting. P, permanent mold. S, sand. Other products may pertain to the composition shown even though not listed.

(b)

0.025% max Mg +Cr + Ti + V.

(c)

Fe/Si ratio 2.5 min.

(d)

Fe/Si ratio 2.0 min.

(e)

Fe/Si ratio 1.5 min.

(f)

0.40-1.0% Ag.

(g)

0.50-1.0% Ag.

(h)

0.50% max Ti + Zr.

(i)

0.20-0.30%Sb, 0.20-0.30% Co, 0.10-0.30% Zr.

(j)

Primarily used for making metal-matrix composite.

(k)

If Fe exceeds 0.45%, Mg content will not be less than one-half Fe content.

...

...

0.20

5.57.0

...

0.30

bal

(l)

0.04-0.07% Be.

(m)

0.10-0.30%Be.

(n)

0.15-0.30% Be.

(o)

A360.1, A380.1, and A413.1 ingot is used to produce 360.0 and A360.0; 380.0 and A380.0; 413.0 and A413.0 castings, respectively.

(p)

0.8% max Mg +Cr.

(q)

0.25% max Pb.

(r)

0.02-0.04% Be.

(s)

The number of decimal places to which Mg percent is expressed differs from the norm.

(t)

0.08-0.15%V.

(u)

408.2, 409.2, 411.2, and 445.2 are used to coat steel.

(v)

Used with Zn to coat steel.

(w)

0.10% max Pb.

(x)

0.003-0.007%Be, 0.005% max B.

(y)

0.003-0.007%Be, 0.002 max B.

Chemical Compositions International Designations Aluminum Alloys

and for

Cross Referencing Aluminum Alloy Designations Unified Numbering System (UNS) The UNS numbers correlate many nationally used numbering systems currently administered by societies, trade associations, and individual users and producers of metals and alloys. Table 3cross references AA (Aluminum Association) numbers to UNS numbers. Table 3 Unified Numbering System (UNS) numbers corresponding to Aluminum Association(AA) numbers for aluminum and aluminum alloys AA No.

UNS No.

Castings/ingot

100.1

A01001

130.1

A01301

150.1

A01501

160.1

A01601

170.1

A01701

201.0

A02010

201.2

A02012

202.0

A02020

202.2

A02022

203.0

A02030

203.2

A02032

204.0

A02040

204.2

A02042

206.0

A02060

206.2

A02062

208.0

A02080

208.1

A02081

208.2

A02082

213.0

A02130

213.1

A02131

222.0

A02220

222.1

A02221

224.0

A02240

224.2

A02242

238.0

A02380

238.1

A02381

238.2

A02382

240.0

A02400

240.1

A02401

242.0

A02420

242.1

A02421

242.2

A02422

243.0

A02430

243.1

A02431

249.0

A02490

249.2

A02492

295.0

A02950

295.1

A02951

295.2

A02952

296.0

A02960

296.1

A02961

296.2

A02962

305.0

A03050

305.2

A03052

308.0

A03080

308.1

A03081

308.2

A03082

318.0

A03180

318.1

A03181

319.0

A03190

319.1

A03191

319.2

A03192

320.0

A03200

320.1

A03201

324.0

A03240

324.1

A03241

324.2

A03242

328.0

A03280

328.1

A03281

332.0

A03320

332.1

A03321

332.2

A03322

333.0

A03330

333.1

A03331

336.0

A03360

336.1

A03361

336.2

A03362

339.0

A03390

339.1

A03391

343.0

A03430

343.1

A03431

354.0

A03540

354.1

A03541

355.0

A03550

355.1

A03551

355.2

A03552

356.0

A03560

356.1

A03561

356.2

A03562

357.0

A03570

357.1

A03571

358.0

A03580

358.2

A03582

359.0

A03590

359.2

A03592

360.0

A03600

360.2

A03602

361.0

A03610

361.1

A03611

363.0

A03630

363.1

A03631

364.0

A03640

364.2

A03642

369.0

A03690

369.1

A03691

380.0

A03800

380.2

A03802

383.0

A03830

383.1

A03831

383.2

A03832

384.0

A03840

384.1

A03841

384.2

A03842

385.0

A03850

385.1

A03851

390.0

A03900

390.2

A03902

392.0

A03920

392.1

A03921

393.0

A03930

393.1

A03931

393.2

A03932

408.2

A04082

409.2

A04092

411.2

A04112

413.0

A04130

413.2

A04132

435.2

A04352

443.0

A04430

443.1

A04431

443.2

A04432

444.0

A04440

444.2

A04442

445.2

A04452

511.0

A05110

511.1

A05111

511.2

A05112

512.0

A05120

512.2

A05122

513.0

A05130

513.2

A05132

514.0

A05140

514.1

A05141

514.2

A05142

515.0

A05150

515.2

A05152

516.0

A05160

516.1

A05161

518.0

A05180

518.1

A05181

518.2

A05182

520.0

A05200

520.2

A05202

535.0

A05350

535.2

A05352

705.0

A07050

705.1

A07051

707.0

A07070

707.1

A07071

710.0

A07100

710.1

A07101

711.0

A07110

711.1

A07111

712.0

A07120

712.2

A07122

713.0

A07130

713.1

A07131

771.0

A07710

771.2

A07712

772.0

A07720

772.2

A07722

850.0

A08500

850.1

A08501

851.0

A08510

851.1

A08511

852.0

A08520

852.1

A08521

853.0

A08530

853.2

A08532

A201.0

A12010

A201.1

A12011

A201.2

A12012

A206.0

A12060

A206.2

A12062

A242.0

A12420

A242.1

A12421

A242.2

A12422

A305.0

A13050

A305.1

A13051

A305.2

A13052

A319.0

A13190

A319.1

A13191

A333.0

A13330

A333.1

A13331

A355.0

A13550

A355.2

A13552

A356.0

A13560

A356.2

A13562

A356.1

A13561

A357.0

A13570

A357.2

A13572

A360.0

A13600

A360.1

A13601

A360.2

A13602

A380.0

A13800

A380.1

A13801

A380.2

A13802

A383.0

A13830

A383.1

A13831

A384.0

A13840

A384.1

A13841

A390.0

A13900

A390.1

A13901

A413.0

A14130

A413.1

A14131

A413.2

A14132

A443.0

A14430

A443.1

A14431

A444.0

A14440

A444.2

A14442

A444.1

A14441

A535.0

A15350

A535.1

A15351

B201.0

A22010

B237.0

A23570

B319.0

A23190

B319.1

A23191

B356.0

A23560

B356.2

A23562

B357.2

A23572

B380.0

A23800

B380.1

A23801

B384.1

A23841

B390.0

A23900

B390.1

A23901

B413.0

A24130

B413.1

A24131

B443.0

A24430

B443.1

A24431

B535.0

A25350

B535.2

A25352

C355.0

A33550

C355.2

A35522

C355.1

A33551

C356.0

A33560

C356.2

A33562

C357.0

A33570

C357.2

A33572

C380.0

A33800

C380.1

A33801

C384.0

A33840

C384.1

A33841

C443.0

A34430

C443.1

A34431

C443.2

A34432

D357.0

A43570

D380.0

A43800

D380.1

A43801

F356.0

A63560

F356.2

A63562

Wrought alloys

1030

A91030

1035

A91035

1040

A91040

1045

A91045

1050

A91050

1055

A91055

1060

A91060

1065

A91065

1070

A91070

1075

A91075

1080

A91080

1085

A91085

1090

A91090

1095

A91095

1098

A91098

1100

A91100

1110

A91110

1120

A91120

1135

A91135

1145

A91145

1150

A91150

1170

A91170

1175

A91175

1180

A91180

1185

A91185

1188

A91188

1190

A91190

1193

A91193

1198

A91198

1199

A91199

1200

A91200

1230

A91230

1235

A91235

1250

A91250

1260

A91260

1275

A91275

1285

A91285

1345

A91345

1350

A91350

1370

A91370

1385

A91385

1435

A91435

1445

A91445

1450

A91450

2001

A92001

2002

A92002

2003

A92003

2004

A92004

2005

A92005

2006

A92006

2007

A92007

2008

A92008

2009

A92009

2010

A92010

2011

A92011

2014

A92014

2017

A92017

2018

A92018

2020

A92020

2021

A92021

2024

A92024

2025

A92025

2030

A92030

2031

A92031

2036

A92036

2037

A92037

2038

A92038

2048

A92048

2090

A92090

2091

A92091

2117

A92117

2124

A92124

2214

A92214

2218

A92218

2219

A92219

2224

A92224

2304

A92034

2319

A92319

2324

A92324

2419

A92419

2519

A92519

2618

A92618

3002

A93002

3003

A93003

3004

A93004

3005

A93005

3006

A93006

3007

A93007

3008

A93008

3009

A93009

3010

A93010

3011

A93011

3012

A93012

3013

A93013

3014

A93014

3015

A93015

3016

A93016

3017

A93017

3102

A93102

3103

A93103

3104

A93104

3105

A93105

3107

A93107

3203

A93203

3204

A93204

3207

A93207

3303

A93303

3307

A93307

4002

A94002

4004

A94004

4006

A94006

4007

A94007

4008

A94008

4009

A94009

4010

A94010

4011

A94011

4013

A94013

4014

A94014

4015

A94015

4032

A94032

4043

A94043

4044

A94044

4045

A94045

4046

A94046

4047

A94047

4104

A94104

4145

A94145

4147

A94147

4343

A94343

4543

A94543

4643

A94643

5005

A95005

5006

A95006

5010

A95010

5013

A95013

5014

A95014

5016

A95016

5017

A95017

5034

A95034

5039

A95039

5040

A95040

5042

A95042

5043

A95043

5049

A95049

5050

A95050

5051

A95051

5052

A95052

5056

A95056

5058

A95058

5082

A95082

5083

A95083

5086

A95086

5087

A95087

5091

A95091

5110

A95110

5149

A95149

5150

A95150

5151

A95151

5154

A95154

5180

A95180

5182

A95182

5183

A95183

5205

A95205

5210

A95210

5249

A95249

5250

A95250

5251

A95251

5252

A95252

5254

A95254

5280

A95280

5283

A95283

5305

A95305

5310

A95310

5349

A95349

5351

A95351

5352

A95352

5356

A95356

5357

A95357

5451

A95451

5454

A95454

5456

A95456

5457

A95457

5505

A95505

5552

A95552

5554

A95554

5556

A95556

5557

A95557

5605

A95605

5652

A95652

5654

A95654

5657

A95657

5754

A95754

5854

A95854

6002

A96002

6003

A96003

6004

A96004

6005

A96005

6005A

A96005

6006

A96006

6007

A96007

6008

A96008

6009

A96009

6010

A96010

6011

A96011

6012

A96012

6013

A96013

6014

A96014

6015

A96015

6016

A96016

6017

A96017

6053

A96053

6056

A96056

6060

A96060

6061

A96061

6063

A96063

6066

A96066

6070

A96070

6081

A96081

6082

A96082

6090

A96090

6091

A96091

6092

A96092

6101

A96101

6103

A96103

6105

A96105

6106

A96106

6110

A96110

6111

A96111

6113

A96113

6151

A96151

6162

A96162

6181

A96181

6201

A96201

6205

A96205

6206

A96206

6253

A96253

6261

A96261

6262

A96262

6301

A96301

6306

A96306

6351

A96351

6401

A96401

6463

A96463

6763

A96763

6863

A96863

6951

A96951

7001

A97001

7003

A97003

7004

A97004

7005

A97005

7008

A97008

7009

A97009

7010

A97010

7011

A97011

7012

A97012

7013

A97013

7014

A97014

7015

A97015

7016

A97016

7017

A97017

7018

A97018

7019

A97019

7020

A97020

7021

A97021

7022

A97022

7023

A97023

7024

A97024

7025

A97025

7026

A97026

7027

A97027

7028

A97028

7029

A97029

7030

A97030

7031

A97031

7039

A97039

7046

A97046

7049

A97049

7050

A97050

7051

A97051

7055

A97055

7060

A97060

7064

A97064

7070

A97070

7072

A97072

7075

A97075

7076

A97076

7079

A97079

7090

A97090

7091

A97091

7104

A97104

7108

A97108

7109

A97109

7116

A97116

7129

A97129

7146

A97146

7149

A97149

7150

A97150

7175

A97175

7178

A97178

7179

A97179

7229

A97229

7277

A97277

7278

A97278

7472

A97472

7475

A97475

8001

A98001

8004

A98004

8005

A98005

8006

A98006

8007

A98007

8008

A98008

8009

A98009

8010

A98010

8013

A98013

8014

A98014

8015

A98015

8016

A98016

8017

A98017

8018

A98018

8020

A98020

8021

A98021

8022

A98022

8030

A98030

8040

A98040

8050

A98050

8076

A98076

8077

A98077

8079

A98079

8081

A98081

8090

A98090

8091

A98091

8111

A98111

8112

A98112

8130

A98130

8176

A98176

8177

A98177

8211

A98211

8276

A98276

8280

A98280

International Alloy Designations Historically, all major industrialized countries developed their own standard designations for aluminum and aluminum alloys. These are now being grouped under systems of the American National Standards Institute (ANSI), the International Organization for Standardization (ISO), and the European Committee for Standardization (Comité de Normalization, CEN). The International Organization for Standardization has developed its own alphanumeric designation system for

wrought aluminum and its alloys (ISO R209) based on the systems that have been used by certain European countries. The main addition element is distinguished by specifying the required content (middle of range) rounded off to the nearest 0.5:

5052 = Al Mg2.5 5251 = Al Mg2 If required, the secondary addition elements are distinguished by specifying the required content rounded off to the nearest 0.1, for two elements at most:

6181 = Al Si1Mg0.8 The chemical symbols for addition elements should be limited to four:

7050 = Al Zn6CuMgZr If an alloy cannot otherwise be distinguished, a suffix in parentheses is used:

6063 = Al Mg0.7Si 6463= Al Mg0.7Si(B) 6063A = Al Mg0.7Si(A) Note that suffixes (A),(B), and so on should not be confused with suffixes of the Aluminum Association. Table 4 cross references ISO designations with equivalent or similar AA alloy designations. Also included in this table are cross-referenced alloys listed in Austrian, Canadian, French, German, British, Italian, Spanish, and Swiss standards. Additional information is included in the "Registration Record of International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys" (commonly referred to as the blue sheets) published by the Aluminum Association. Table 4 International alloy designations cross referenced to wrought Aluminum Association (AA) alloys The table includes only those alloys that are essentially equivalent in composition to the corresponding AA alloys, but whose composition limits are not necessarily exactly the same as their AA counterparts. International alloy designation

Equivalent/similar AA alloy

ISO R209

Al 99.5

1050A

Al 99.6

1060

Al 99.7

1070A

Al 99.8

1080A

Al 99.0 Cu

1100

Al 99.0

1200

Al 99.3

1230

E-Al 99.5

1350

E-Al 99.7

1370

Al Cu6BiPb

2011

Al Cu4SiMg

2014

Al Cu4SiMg(A)

2014A

Al Cu4MgSi

2017

Al Cu4MgSi(A)

2017A

Al Cu4Mg1

2024

Al Cu4PbMg

2030

Al Cu2.5Mg

2117

Al Cu6Mn

2219

Al Mn1Cu

3003

Al Mn1Mg1

3004

Al Mn1Mg0.5

3005

Al Mn1

3103

Al Mn0.5Mg0.5

3105

Al Si5

4043

Al Si5(A)

4043A

Al Si12

4047

Al Si12(A)

4047A

Al Mg1(B)

5005

Al Mg1.5(C)

5050

Al Mg2.5

5052

Al Mg5Cr

5056

Al Mg5

5056A

Al Mg4.5Mn0.7

5083

Al Mg4

5086

Al Mg3.5

5154

Al Mg3.5(A)

5154A

Al Mg4.5Mn0.7(A)

5183

Al Mg2

5251

Al Mg5Cr(A)

5356

Al Mg3Mn

5454

Al Mg5Mn

5456

Al Mg3Mn(A)

5554

Al Mg3

5754

Al SiMg

6005

Al SiMg(A)

6005A

Al MgSi

6060

Al Mg1SiCu

6061

Al Mg0.7Si

6063

Al Mg0.7Si(A)

6063A

Al Si1MgMn

6082

E-Al MgSi

6101

E-Al MgSi(A)

6101A

Al Si1Mg0.8

6181

Al Mg1SiPb

6262

Al Si1Mg0.5Mn

6351

Al Zn4.5Mg1.5Mn

7005

Al Zn6MgCu

7010

Al Zn4.5Mg1

7020

Al Zn8MgCu

7049A

Al Zn6CuMgZr

7050

Al Zn5.5MgCu

7075

Al Zn7MgCu

7178

Al Zn5.5MgCu(A)

7475

Austria (Austrian Standard M3430)

A199

1200

A199.5

1050

E-Al

1350

AlCuMg1

2017

AlCuMg2

2024

AlCuMg0.5

2117

AlMg5

5056

AlMgSi0.5

6063

E-AlMgSi

6101

AlZnMgCu1.5

7075

Canada (Canadian Standards Association)

990C

1100

CB60

2011

CG30

2117

CG42

2024

CG42 Alclad

Alclad 2024

CM41

2017

CN42

2018

CS41N

2014

CS41N Alclad

Alclad 2014

CS41P

2025

GM31N

5454

GM41

5083

GM50P

5356

GM50R

5056

GR20

5052

GS10

6063

GS11N

6061

GS11P

6053

MC10

3003

S5

4043

SG11P

6151

SG121

4032

ZG62

7075

ZG62 Alclad

Alclad 7075

France (Normes Francaises)

A5/L

1350

A45

1100

A-G1

5050

A-G0.6

5005

A-G4MC

5086

A-GS

6063

A-GS/L

6101

A-M1

3003

A-M1G

3004

A-U4G

2017

A-U2G

2117

A-U2GN

2618

A-U4G1

2024

A-U4N

2218

A-U4SG

2014

A-S12UN

4032

A-Z5GU

7075

Germany (Deutsche Industrie-Norm.)

E-A1995

1350

AlCuBiPb

2011

AlCuMg0.5

2117

AlCuMg1

2017

AlCuMg2

2024

AlCuSiMn

2014

AlMg4.5Mn

5083

AlMgSi0.5

6063

AlSi5

4043

E-AlMgSi0.5

6101

AlZnMgCu1.5

7075

Germany (Werkstoff-Nr.)

3.0257

1350

3.1655

2011

3.1305

2117

3.1325

2017

3.1355

2024

3.1255

2014

3.3547

5083

3.3206

6063

3.2245

4043

3.3207

6101

3.4365

7075

Great Britain (British Standard)

1E

1350

91E

6101

H14

2017

H19

6063

H20

6061

L.80, L.81

5052

L.86

2117

L.87

2017

L.93, L.94

2014A

L.95, L.96

7075

L.97, L.98

2024

2L.55, 2L.56

5052

2L.58

5056

3L.44

5050

5L.37

2017

6L.25

2218

N8

5083

N21

4043

Great Britain (Directorate of Technical Development)

150A

2017

324A

4032

372B

6063

717, 724, 731A

6063

745, 5014, 5084

2618

5090

2024

5100

Alclad 2024

Italy (Unificazione Nazionale Italiana)

P-AlCu4MgMn

2017

P-AlCu4.5MgMn

2024

P-AlCu4.5MgMnplacc.

Alclad 2024

P-AlCu2.5MgSi

2117

P-AlCu4.4SiMnMg

2014

P-AlCu4.4SiMnMgplacc.

Alclad 2014

P-AlMg0.9

5657

P-AlMg1.5

5050

P-AlMg2.5

5052

P-AlSi0.4Mg

6063

P-AlSi0.5Mg

6101

Spain (Una Norma Espanol)

A199.5E

1350

L-313

2014

L-314

2024

L-315

2218

L-371

7075

Switzerland (Verein Schweizerischer Maschinenindustrieller)

Al-Mg-Si

6101

Al1.5Mg

5050

Al-Cu-Ni

2218

Al3.5Cu0.5Mg

2017

Al4Cu1.2Mg

2027

Al-Zn-Mg-Cu

7075

Al-Zn-Mg-Cu-pl

Alclad 7075

Physical Metallurgy of Aluminum Alloys Introduction THE PRINCIPAL CONCERNS in the physical metallurgy of aluminum alloys include the effects of composition, mechanical working, and/or heat treatment on mechanical and physical properties. In terms of properties, strength improvement is a major objective in the design of aluminum alloys because the low strength of pure aluminum limits its commercial usefulness. The two most common methods for increasing the strength of aluminum alloys follow: • •

To disperse second-phase constituents or elements in solid solution and cold work the alloy (non-heattreatable alloys) To dissolve the alloying elements into solid solution and precipitate them as coherent submicroscopic particles (heat-treatable or precipitation-hardening alloys)

The factors affecting these strengthening mechanisms are reviewed in the first half of this article. The use of phase diagrams to better understand the effects of solid-state thermal processing is discussed in the second half of this article.

Alloying and Strengthening Mechanisms The predominant reason for alloying is to increase strength, hardness, and resistance to wear, creep, stress relaxation or fatigue. Effects on these properties are specific to the different alloying elements and combinations of them, and are related to their alloy phase diagrams and to the microstructures and substructures that they form as a result of solidification, thermomechanical history, heat treatment and/or cold working. The tensile yield strength of super-purity aluminum in its annealed (softest) state is approximately 10 MPa (1.5 ksi), whereas those of some heat treated commercial high-strength alloys exceed 550 MPa (80 ksi). When the magnitude of this difference (an increase of over 5000%) is considered, this practical, everyday accomplishment, which is just one aspect of the physical metallurgy of aluminum, is truly remarkable. Higher strengths, up to a yield strength of 690 MPa (100 ksi) and over, may be readily produced, but the fracture toughness of such alloys does not meet levels considered essential for aircraft or other critical-structure applications. The elements that are most commonly present in commercial alloys to provide increased strength--particularly when coupled with strain hardening by cold working or with heat treatment, or both--are copper, magnesium, manganese, silicon, and zinc (Fig. 1). These elements all have significant solid solubility in aluminum, and in all cases the solubility increases with increasing temperature (see Fig. 2).

Fig. 1 The principal aluminum alloys

Fig. 2 Equilibrium binary solid solubility as a function of temperature for alloying elements most frequently added to aluminum

For those elements that form solid solutions, the strengthening effect when the element is in solution tends to increase with increasing difference in the atomic radii of the solvent (Al) and solute (alloying element) atoms. This factor is evident in data obtained from super-purity binary solid-solution alloys in the annealed state, presented in Table 1, but it is evident that other effects are involved, chief among which is an electronic bonding factor. The effects of multiple solutes in solid solution are somewhat less than additive and are nearly the same when one solute has a larger and the other a smaller atomic radius than that of aluminum as when both are either smaller or larger. Manganese in solid solution is highly effective in strengthening binary alloys. Its contribution to the strength of commercial alloys is less, because in these compositions, as a result of commercial mill fabricating operations, the manganese is largely precipitated. Table 1 Solid-solution effects on strength of principal solute elements in super-purity aluminum Element

Difference in atomic radii, rx - rAl, %(a)

Strength/addition values(b)

Yield strength/% addition(c)

Tensile strength/% addition(d)

MPa/at.%

ksi/at.%

MPa/wt%

ksi/wt%

MPa/at.%

ksi/at.%

MPa/wt%

ksi/wt%

Si

-3.8

9.3

1.35

9.2

1.33

40.0

5.8

39.6

5.75

Zn

-6.0

6.6

0.95

2.9

0.42

20.7

3.0

15.2

2.2

Cu

-10.7

16.2

2.35

13.8

2.0

88.3

12.8

43.1

6.25

Mn

-11.3

(e)

(e)

30.3

4.4

(e)

(e)

53.8

7.8

(a) Listed in order of increasing percent difference in atomic radii.

(b) Some property to percent addition relationships are nonlinear. Generally, the unit effects of smaller additions are greater.

(c) Increase in yield strength (0.2% offset) for 1% (atomic or weight basis) alloy addition.

(d) Increase in ultimate tensile strength for 1% (atomic or weight basis) alloy addition.

(e) 1 at.% of manganese is not soluble.

The principal alloys that are strengthened by alloying elements in solid solution (often coupled with cold work) are those in the aluminum-magnesium series, ranging form 0.5 to 6 wt% Mg. These alloys often contain small additions of transition elements, such as chromium or manganese, and less frequently zirconium, to control the grain or subgrain structure, and iron and silicon impurities that usually are present in the form of intermetallic particles. Figure 3 illustrates the effect of magnesium in solid solution on the yield strength and tensile elongation for most of the common aluminummagnesium commercial alloys.

Fig. 3 Correlation between tensile yield, strength elongation, and magnesium content for some commercial aluminum alloys

Elements and combinations that form predominantly second-phase constituents with relatively low solid solubility include iron, nickel, titanium, manganese and chromium, and combinations thereof. The presence of increasing volume fractions of the intermetallic-compound phases formed by these elements and the elemental silicon constituent formed by silicon during solidification or by precipitation in the solid state during postsolidification heating also increases strength and hardness. The rates of increase per unit weight of alloying element added are frequently similar to but usually lower than those resulting form solid solution. This "second-phase" hardening occurs even though the constituent particles are of sizes readily resolved by optical microscopy. These irregularly shaped particles form during solidification and occur mostly along grain boundaries and between dendrite arms. Manganese and chromium are included in the group of elements that form predominantly second phase constituents, because in commercial alloys they have very low equilibrium solid solubilities. In the case of many compositions containing manganese, this is because iron and silicon are also present and form the quaternary phase Al12 (Fe,Mn)3Si. In alloys containing copper and manganese, the ternary phase Al20Cu2Mn3 is formed. Most of the alloys in which chromium is present also contain magnesium, so that during solid-state heating they form Al12Mg2Cr, which also has very low equilibrium solid solubility. The concentrations of manganese and/or chromium held in solid solution in as-cast ingot that has been rapidly solidified and cooled from the molten state greatly exceed the equilibrium solubility. The solid solution is thus supersaturated and metastable. Ingot preheating for wrought commercial alloys containing these elements is designed to cause solid-state precipitation of the complex phase containing one or the other of these elements that is appropriate to the alloy composition. This precipitation does not cause appreciable hardening, nor is it intended that it should. Its purpose is to produce finely divided and dispersed particles that retard or inhibit recrystallization and grain growth in the alloy during subsequent heatings. The precipitate particles of Al12(Fe,Mn)3Si, Al20Cu2Mn3, or Al12Mg2Cr

are incoherent with the matrix, and concurrent with their precipitation the original solid solution becomes less concentrated. These conditions do not provide appreciable precipitation hardening. Changes in electrical conductivity constitute an effective measure of the completeness of these precipitation reactions that occur in preheating. For alloys that are composed of both solid-solution and second-phase constituents and/or dispersoid precipitates, all of these components of microstructure contribute to strength, in a roughly additive manner. This is shown in Fig. 4 for AlMg-Mn alloys in the annealed condition.

Fig. 4 Tensile properties in Al-Mg-Mn alloys in the form of annealed (O temper) plate 13 mm (0.5 in.) thick

Non-Heat-Treatable Alloys By definition, the group of commercial alloys that are classed as non-heat-treatable are those that are not appreciably strengthened by heat treatment--that is, show no effective precipitation hardening. The strengthening mechanisms discussed so far (solid-solution formation, second-phase microstructural constituents and dispersoid precipitates) are those that provide the basis for the non-heat-treatable alloys. Wrought alloys of this type are mainly those of the 3xxx and 5xxx groups containing magnesium, manganese, and/or chromium, and the 1xxx aluminum group and some alloys of the 4xxx group that contain only silicon. Non-heat-treatable casting alloys are of the 4xx.x and 5xx.x groups, containing silicon or magnesium, respectively, and the 1xx.x aluminum group. Strain Hardening. Strain hardening by cold rolling, drawing, or stretching is a highly effective means of increasing the

strength of non-heat-treatable alloys. Work- or strain-hardening curves for several typical non-heat-treatable commercial alloys (Fig. 5) illustrate the increases in strength that accompany increasing reduction by cold rolling of initially annealed temper sheet. This increase is obtained at the expense of ductility as measured by percent elongation in a tensile test and by reduced formability in operations such as bending and drawing. It is frequently advantageous to employ material in a partially annealed (H2x) or stabilized (H3x) temper when bending, forming, or drawing is required, since materials in these tempers has greater forming capability for the same strength levels than does strain-hardened-only (H1x) material (see Table 2 for example). Table 2 Tensile-property data illustrating typical relationship between strength and elongation for non-heattreatable alloys in H1x versus H2x tempers Alloy and temper

Tensile strength

Yield strength

MPa

MPa

ksi

ksi

Elongation, %

3105-H14

172

25

152

22

5

3105-H25

179

26

159

23

8

3105-H16

193

28

172

25

4

Fig. 5 Strain-hardening curves for aluminum (1100), Al-Mn (3003) alloys, and Al-Mg (5050 and 5052) alloys

All mill products can be supplied in the strain-hardened condition although there are limitations on the amounts of strain that can be applied to products such as die forgings and impacts. Even aluminum castings have been strengthened by cold pressing for certain applications.

Heat-Treatable Alloys and Precipitation Hardening Again by definition, heat-treatable alloys are those that can be strengthened by suitable thermal treatment and include compositions used for wrought products as well as alloys for producing castings. Temperature-dependent solid solubility of the type shown for individual solutes in Fig. 1, the solubility increasing with increasing temperature, is a prerequisite. However, this feature alone does not make an alloy capable of precipitation hardening (or heat-treatable). The strengths of most binary alloys containing Mg, Si, Zn, Cr, or Mn alone exhibit little change from thermal treatments regardless of whether the solute is completely in solid solution, partially precipitated, or completed precipitated. In contrast, alloys of the binary Al-Cu system having 3% Cu or more exhibit natural aging (hardening with time at ambient temperatures) after being solution heat treated and quenched. The amounts by which strength and hardness increase become larger with time of natural aging and with the copper content of the alloy from about 3% to the limit of solid solubility (5.65%). Natural aging curves for slowly quenched, high-purity Al-Cu alloys with 1 to 4.5% Cu are shown in Fig. 6. The rates and amounts of the changes in strength and hardness can be increased by holding the alloys at moderately elevated temperatures (for alloys of all types, the useful range is about 120 to 230 °C, or 250 to 450 °F). This treatment is called precipitation heat treating or artificial aging. In the Al-Cu system, alloys with as little as 1% Cu, again slowly quenched, start to harden after about 20 days at a temperature of 150 °C or 300 °F (see Fig. 7). The alloys of this system having less than 3% Cu show little or no natural aging after low-cooling-rate quenching, which introduces little stress.

Fig. 6 Natural aging curves for binary Al-Cu alloys quenched in water at 100 °C (212 °F)

Fig. 7 Precipitation hardening curves for binary Al-Cu alloys quenched in water at 100 °C (212 °F) and aged at 150 °C (300 °F)

The characteristic that distinguishes between the systems having the required temperature to solid solubility relationship that does or does not exhibit precipitation hardening is the type or types of precipitate structures formed. Precipitation hardening is caused by a sequence of submicroscopic structure changes resulting from precipitation reactions that are responsible for the strength changes and can be revealed and analyzed only by such methods as x-ray diffraction and transmission electron microscopy. Room-temperature age hardening (natural aging) is a result of spontaneous formation of Guinier-Preston (G-P) zone structure. Solute atoms either cluster or segregate to selected atomic lattice planes, depending on the alloy system, to form the G-P zones, and this structure is more resistant to movement of dislocations through the lattice and, hence, is stronger. Curves showing the changes in tensile yield strength with time at room temperature (natural aging curves) for three wrought commercial heat-treatable alloys of different alloy systems are shown in Fig. 8. The magnitudes of increase in this property are considerably different for the three alloys, and the differences in rate of change with time are of practical importance. Because 7075 and similar alloys never become completely stable under these conditions, they are rarely used in the naturally aged temper. On the other hand, 2024 is widely used in this condition.

Fig. 8 Natural aging curves for three solution heat-treated wrought aluminum alloys

Precipitation heat treating (or artificial aging) at higher temperatures produces transition, metastable forms of the equilibrium precipitate of the of the particular alloy system. These transition precipitates are still coherent with the solidsolution matrix. The characteristic that determines whether a precipitate phase is coherent or noncoherent is the closeness of match or degree of disregistry between the atomic spacings on the lattice of the matrix and on that of the precipitate. The presence of the precipitate particles, and, even more importantly in most cases, the strain fields in the matrix surrounding the coherent particles, obstruct and retard the movement of dislocations, thus providing increased resistance to deformation--in other words, higher strength. These particles, at the maximum-strength stage, are extremely fine, are resolvable only by transmission electron microscopy (TEM), and constitute a relatively large volume fraction, particularly when the strain fields are considered. With further heating at temperatures that cause strengthening or at higher temperatures, the precipitate particles grow, but even more importantly convert to the equilibrium phases, which generally are not coherent. These changes soften the material and, carried further, produce the softest or annealed condition. Even at this stage, the precipitate particles are still too small to be clearly resolved by optical microscopy, although etching effects are readily observed--particularly in alloys containing copper. Precipitation heat treatment or artificial aging curves for the Al-Mg-Si wrought alloy 6061 are shown in Fig. 9. This is a typical family of curves showing the changes in tensile yield strength that accrue with increasing time at each of a series of temperatures. In all cases, the material has been given a solution heat treatment followed by a quench just prior to the start of the precipitation heat treatment. For detailed presentation of heat treating operations, parameters, and practices see the Section "Heat Treating" in this Handbook.

Fig. 9 Precipitation heat treatment or artificial aging curves for solution heat-treated aluminum alloy 6061

The above description of the precipitation process and its effects on strength and metallurgical structures applies not only to heat treatable binary compositions, none of which is used commercially, but also to the commercial alloys, having generally much greater complexity of composition. As noted before, not only do the mechanical properties change with these heat treatments, and with natural aging, but also physical properties (density and electrical and thermal conductivities) and electrochemical properties (solution potential). On the microstructural and submicroscopic scales, the electrochemical properties develop point-to-point nonuniformities that account for changes in corrosion resistance. Measurements of changes in physical and electrochemical properties have played an important role in completely describing precipitation reactions and are very useful in analyzing or diagnosing whether heat treatable products have been properly or improperly heat treated. Although they may indicate the strength levels of products, they cannot be relied on to determine whether or not the product meets specified mechanical-property limits. Because elements in solid solution are always more harmful to electrical conductivity than the same elements combined with others as intermetallic compounds, thermal treatments are applied to ingots used for fabrication of electrical conductor products. These thermal treatments are intended to precipitate as much as possible of the dissolved impurities. Iron is the principal element involved, and, although the amount precipitated is only a few hundredths of a percent, the effect on electrical conductivity of the wire, cable, or other product made from the ingot is of considerable practical importance. These alloys may or may not be heat treatable with respect to mechanical properties. Electrical conductor alloys 6101 and 6201 are heat treatable.

These alloys are used in tempers in which their strengthening precipitate, the transition form of Mg2Si, is largely out of solid solution to optimize both strength and conductivity. The commercial heat treatable alloys are, with few exceptions, based on ternary or quaternary systems with respect to the solutes involved in developing strength by precipitation. The most prominent systems are: Al-Cu-Mg, Al-Cu-Si, and AlCu-Mg-Si, which are in the 2xxx and 2xx.x groups (wrought and casting alloys, respectively); Al-Mg-Si (6xxx wrought alloys); Al-Si-Mg, Al-Si-Cu, and Al-Si-Mg-Cu (3xx.x casting alloys); Al-Zn-Mg and Al-Zn-Mg-Cu (7xxx wrought and 7xx.x casting alloys); and Al-Li-Cu-Mg (8xxx wrought alloys). In each case, the solubility of the multiple solute elements decreases with decreasing temperatures, as shown in the solvus diagrams in Alloy Phase Diagrams, Volume 3, ASM Handbook. These diagrams show the equilibrium phase (or phases) that precipitates in a particular system. They do not show whether a transition phase occurs, nor do they provide its composition. These multiple alloying additions of both major solute elements and supplementary elements employed in commercial alloys are strictly functional and serve with different heat treatments to provide the many different combinations of properties--physical, mechanical, and electrochemical--that are required for different applications. Some alloys, particularly those for foundry production of castings, contain amounts of silicon far in excess of the amount that is soluble or needed for strengthening alone. The function here is chiefly to improve casting soundness and freedom from cracking, but the excess silicon also serves to increase wear resistance, as do other microstructural constituents formed by manganese, nickel, and iron. Parts made of such alloys are commonly used in gasoline and diesel engines (pistons, cylinder blocks, etc.). Alloys containing the elements silver and lithium are also capable of providing high strength with heat treatment and, in the case of lithium, both increased elastic modulus and lower density, which are highly advantageous--particularly for aerospace applications. Commercial use of alloys containing these elements has been restricted either by cost or by difficulties encountered in producing them. In the case of alloys having copper as the principal alloying ingredient and no magnesium, strengthening by precipitation can be greatly increased by adding small fractional percentages of tin, cadmium, or indium, or combinations of these elements. Alloys based on these effects have been produced commercially but not in large volumes because of costly special practices and limitations required in processing and, in the case of cadmium, the need for special facilities to avoid health hazards from formation and release of cadmium vapor during alloying. Strength at elevated temperatures is improved mainly by solid-solution and second-phase hardening, because, at least for temperatures exceeding those of the precipitation-hardening range-- 230 °C (450 °F)--the precipitation reactions continue into the softening regime. For supersonic aircraft and space vehicle applications subject to aerodynamic heating, the heat treatable alloys of the 2xxx group can be used for temperatures up to 150 °C (300 °F). Aged rapidly solidified powder metallurgy alloys (Al-Fe-V-Si alloys) maintain usable strengths at temperatures as high as 315 °C (600 °F). Effects of Strengthening on Other Mechanical Properties. Resistance to fatigue (from application of dynamic

stresses into the tensile range) increases generally with increasing strength whether from alloying effects alone, from strain hardening, or from heat treatment. This improvement, in terms of either time to initiate cracks or cycles to failure, is generally less than the improvement in static strength, and the highest resistance to fatigue for a given alloy is sometimes provided by a temper having static strength levels lower than the highest strength possible--e.g., 2024-T3x or 2024-T4x versus 2024-T6x or 2024-T8x. This occurs mainly because the resistance to fatigue-crack growth at high levels of stressintensity factor requires good fracture toughness, and this property decreases generally with increasing strength at high levels. As strength, defined as resistance to deformation, increases, the properties of ductility, malleability, ease of forming, and fracture toughness tend to decrease. This inverse relationship between these properties and strength, however, is not universal. As indicated previously, for the non-heat-treatable alloys, the H2x or H3x tempers have advantages over those of the H1x series in the ductility/strength relationship. It is also true that, in the relationship of fracture toughness to yield strength, alloys of the 7xxx group (Al-Zn-Mg-Cu types) are superior to those of the 2xxx and 6xxx groups. All of these properties must be carefully considered in application of alloys to critical engineering structures such as aircraft as well as to products such as truck wheels and other automotive and truck components. Good design, avoiding stress-concentrating features and any features that promote localized corrosion, is in most cases at least as important as good alloy and temper selection.

Other Considerations Involved in Alloy Development. The engineering properties and characteristics that have

immediate effects on the functional behavior of end products is only a partial list of the features that must be considered in alloy design. One of the foremost considerations is that, to be economically viable, an alloy must be capable of being cast and fabricated to the form desired with reasonable freedom from scrap losses resulting from cracking or other inprocess damage. Many alloys and specialty products, including those for extremely large-tonnage items such as beverage cans as well as Alclad products and brazing composites, are tailored to very specific uses, and cost-effective principles apply to the commercial viability of these also. All of these products must compete for markets with other metallic materials as well as polymeric materials, glasses, and ceramics.

Use of Aluminum Alloy Phase Diagrams Although few products are sold and used in their equilibrium condition, equilibrium phase diagrams are an essential tool in understanding effects of composition and both solidification and solid-state thermal processing on microstructure. For aluminum alloys, phase diagrams are used to determine solidification and melting temperatures, the solidification path, and the equilibrium phases that form and their dissolution temperatures. In addition to determining appropriate temperatures for casting and thermal treatments, phase diagrams are used to determine the maximum levels for ancillary element additions of certain elements to prevent the crystallization of coarse primary particles. The most important liquidto-solid transformations for aluminum alloys are the eutectic and the peritectic. Examples of phase diagrams illustrating eutectic and peritectic reactions are discussed in the following paragraphs, and phase diagrams for aluminum alloys are included in the Section "Structure and Properties of Metals" in this Handbook and in Volume 3 of the ASM Handbook. The eutectic reaction is illustrated by the aluminum-copper system (Fig. 10). When the liquidus temperature of aluminum-rich alloys is reached during solidification, the liquid begins to solidify into a solid solution of copper in aluminum ( -aluminum). As temperature approaches the solidus, the -aluminum becomes more enriched with copper. When the temperature falls below the solidus temperature in alloys containing less than the maximum solubility, 5.7% Cu, solidification is complete. At temperatures below the solvus, Al2Cu particles precipitate, depleting the -aluminum of copper. When cooled to room temperature under near-equilibrium conditions, the -aluminum contains little copper, so strength is low. To increase strength, the material must be solution heat treated, quenched, and aged to develop metastable precipitates as described earlier in this article. In alloys containing more than 5.7% Cu, some liquid remains when the eutectic temperature is reached. This liquid solidifies at this temperature by a eutectic reaction to -aluminum and Al2Cu intermetallic particles. On cooling below the eutectic temperature, the -aluminum rejects copper as Al2Cu precipitates. It is important to realize that the eutectic reaction can occur in alloys containing less than the maximum solid solubility under commercial casting conditions, even though the equilibrium phase diagram does not predict that. Consequently, Al2Cu particles form during solidification of most aluminum alloy ingots and shaped castings. Therefore, they are "preheated" or homogenized to dissolve the intermetallic particles.

Fig. 10 Aluminum-copper phase diagram illustrating the eutectic reaction

The peritectic reaction in aluminum alloys is typified by the aluminum-chromium system (Fig. 11). During equilibrium solidification of alloys containing more than the peritectic composition, 0.41% Cr, but less than the maximum solid solubility of 0.77%, an intermetallic compound, Al7Cr, forms when the liquidus temperature is reached. When the temperature falls to the peritectic temperature, 661 °C (1222 °F), the remaining liquid along with the Al7Cr transforms to -aluminum. Under commercial solidification conditions, however, the primary particles of Al7Cr would not have the opportunity to transform to -aluminum, so they would remain. Consequently, maximum chromium limits are established so that all of the chromium remains in supersaturated solid solution in the ingot. It precipitates as chromiumbearing dispersoids during ingot preheat.

Fig. 11 Aluminum-chromium phase diagram illustrating the peritectic reaction

Alloying Effects on Phase Formation All commercial aluminum alloys contain iron and silicon as well as two or more elements intentionally added to enhance properties. The phases formed and the function of the alloying elements are described below. Figure 1 summarizes the most common alloying additions in aluminum alloys. Iron. Virtually all aluminum alloys contain some iron that is an impurity remaining after refining bauxite and smelting.

The phase diagram predicts that during solidification of an aluminum-iron alloy containing a few tenths of a percent of iron, most of the iron remains in the liquid phase until a eutectic of solid solution plus Al3Fe intermetallic constituent particles having a monoclinic crystal structure freezes. Depending on solidification rate and on the presence of other elements such as manganese, constituent particles of the metastable orthorhombic Al6Fe phase can form instead of the equilibrium Al3Fe. The maximum solid solubility of iron in aluminum is 0.05%, but the solubility is much lower in most structural alloys. Silicon. This element is also a ubiquitous impurity in commercial aluminum alloys. Two ternary phases, cubic

Al12Fe3Si and monoclinic -Al9Fe2Si2, form by a eutectic reaction. At low silicon contents, almost all of the iron is present as Al3Fe. With increasing silicon contents, first the - then the -Al-Fe-Si phases appear. Phases in commercial products may not be those predicted by the equilibrium phase diagrams because of the long times at high temperatures required to approach equilibrium. In large amounts, silicon improves castability and fluidity. Consequently, it is used in 4xxx brazing sheet and in 3xx.x and 4xx.x casting alloys. Silicon ranges from about 5 to 20% in casting alloys.

Hypereutectic alloys (those containing >12.6% Si, the eutectic composition) are used for engine blocks because the primary silicon particles are wear resistant. Some 3xx.x casting alloys contain small additions of magnesium to render them capable of being age hardened. Silicon is deliberately added to some alloys containing magnesium to provide precipitation hardening. The Al-Mg-Si system is the basis for the 6xxx alloys. At low magnesium contents, elemental silicon may be present as second-phase particles. As magnesium increases, both silicon particles and equilibrium hexagonal Mg2Si constituents may be present. At higher magnesium contents, only Mg2Si is present. Ternary alloys are strengthened by precipitation of metastable precursors to Mg2Si. With the addition of copper, a complex quaternary Al4CuMg5Si4 phase can form. A precursor to this quaternary phase strengthens Al-Cu-Mg-Si alloys. Manganese. The aluminum-manganese system is the basis for the oldest aluminum alloys. Such alloys, known as 3xxx,

are the most widely used wrought alloys because of their excellent formability and resistance to corrosion. Commercial aluminum-manganese alloys contain both iron and silicon. During solidification of commercial size ingots, some of the manganese forms Al6(Mn,Fe) and cubic Al12(Fe,Mn)Si by eutectic reactions. The remaining manganese remains in solution and is precipitated during the ingot preheat as Al12(Mn,Fe)Si and Al6(Mn,Fe) dispersoids. These dispersoids strengthen the material and control recrystallized grain size. In alloys containing copper, manganese precipitates as Al20Cu2Mn3 dispersoid particles. Effects on strength are minor, but the dispersoids aid in grain size control after solution heat treatment. Magnesium. The aluminum-magnesium system is the basis for the wrought 5xxx and cast 5xx.x non-heat-treatable

aluminum alloys, which provide excellent combinations of strength and corrosion resistance by solid-solution strengthening and work hardening. Although in principle this phase diagram exhibits a positively sloping solvus, a necessary condition for a precipitation-hardening system, difficulty in nucleating the face-centered cubic (fcc) Al3Mg2 precipitates has precluded commercialization of heat-treatable aluminum-magnesium alloys, unless they contain enough silicon, copper, or zinc to form Mg2Si, Al-Cu-Mg, or Al-Zn-Mg precipitates. Copper. The aluminum-copper system is the basis for the wrought 2xxx and cast 2xx.x alloys, and many other heattreatable alloys contain copper. In commercial aluminum-copper alloys, some of the copper chemically combines with aluminum and iron to form either tetragonal Al7Cu2Fe or orthorhombic (Al,Cu,Fe) constituent particles during solidification. These constituents cannot be dissolved during subsequent thermal treatments, but one can transform to the other during thermal treatments of ingots or castings. During heat treatment of aluminum-copper alloys containing little magnesium, Al2Cu precipitates as the strengthening phase.

Adding magnesium to aluminum-rich aluminum-copper alloys results in the formation of the Al2CuMg phase by eutectic decomposition. Metastable precursors to face-centered orthorhombic Al2CuMg precipitates are used to strengthen several structural alloys used in the aerospace industry because they confer a desirable combination of strength, fracture toughness, and resistance to the growth of fatigue cracks. Zinc. This element confers little solid-solution strengthening or work hardening to aluminum, but Al-Zn-Mg precipitates

provide the basis for the 7xxx wrought alloys and the 7xx.x cast alloys. Two phases can form by eutectic decomposition in commercial Al-Zn-Mg alloys: hexagonal MgZn2 and body-centered cubic (bcc) Al2Mg3Zn3. Depending on the zinc/magnesium ratio, copper-free alloys are strengthened by metastable precursors to either MgZn2 or Al2Mg3Zn3. In AlZn-Mg-Cu alloys, copper and aluminum substitute for zinc in MgZn2 to form Mg(Zn,Cu,Al)2. Al2CuMg particles can also form in these alloys by eutectic decomposition and solid-state precipitation. Chromium. In commercial alloys, the solubility can be reduced to such an extent that Al7Cr primary particles can form

by a peritectic reaction at chromium contents lower than that indicated by the binary aluminum-chromium phase diagram. Because coarse primary particles are harmful to ductility, fatigue, and fracture toughness, the upper limits of chromium depend on the amount and nature of the other alloying and impurity elements. In 5xxx alloys, fcc cubic Al18Mg3Cr2 dispersoids precipitate during ingot preheating. In 7xxx alloys, the composition of the dispersoids is closer to Al12Mg2Cr. Chromium dispersoids contribute to strength in non-heat-treatable alloys and control grain size and degree of recrystallization in heat-treatable alloy products. Zirconium. This element also forms a peritectic with aluminum. The phase diagram predicts that the equilibrium Al3Zr phase is tetragonal, but fine dispersoids of metastable cubic Al 3Zr form during ingot preheating treatments. Most 7xxx and some 6xxx and 5xxx alloys developed since the 1960s contain small amounts of zirconium, usually less than 0.15%, to form Al3Zr dispersoids for recrystallization control.

Lithium. This element reduces the density and increases the modulus of aluminum alloys. In binary alloys it forms

metastable Al3Li precipitates and combines with aluminum and copper in Al-Cu-Li alloys to form a large number of AlCu-Li phases. Because of its high cost relative to other alloying elements, lithium alloys have been found to be cost effective thus far only in space and military applications.

Aluminum Wrought Products Introduction COMMERCIAL WROUGHT ALUMINUM PRODUCTS can be divided into two groups. Standardized wrought products include sheet, plate, foil, rod, bar, wire, tube, pipe, and structural forms. Engineered wrought products are those designed for specific applications and include extruded shapes, forgings, and impacts. Typical examples of wrought products include plate or sheet, which is subsequently formed or machined into products such as aircraft or building components, household foil, and extruded shapes such as storm window frames.

Alloys Used for Wrought Products Aluminum alloys are commonly grouped into an alloy designation series, as described in the article "Alloy and Temper Designations for Aluminum" in this Section. The general characteristics of the alloy groups are described below. 1xxx Series. Aluminum of 99.00% or higher purity has many applications, especially in the electrical and chemical

fields. These grades of aluminum are characterized by excellent corrosion resistance, high thermal and electrical conductivities, low mechanical properties, and excellent workability. Moderate increases in strength may be obtained by strain hardening. Iron and silicon are the major impurities. 2xxx Series. Copper is the principal alloying element in 2xxx series alloys, often with magnesium as a secondary

addition. These alloys require solution heat treatment to obtain optimum properties; in the solution heat-treated condition, mechanical properties are similar to, and sometimes exceed, those of low-carbon steel. In some instances, precipitation heat treatment (aging) is employed to further increase mechanical properties. This treatment increases yield strength, with attendant loss in elongation; its effect on tensile strength is not as great. The alloys in the 2xxx series do not have as good corrosion resistance as most other aluminum alloys, and under certain conditions they may be subject to intergranular corrosion. Therefore, these alloys in the form of sheet usually are clad with a high-purity aluminum, a magnesium-silicon alloy of the 6xxx series, or an alloy containing 1% Zn. The coating, usually from 2 to 5% of the total thickness on each side, provides galvanic protection of the core material and thus greatly increases resistance to corrosion. Alloys in the 2xxx series are particularly well suited for parts and structures requiring high strength-to-weight ratios and are commonly used to make truck and aircraft wheels, truck suspension parts, aircraft fuselage and wing skins, structural parts, and those parts requiring good strength at temperatures up to 150 °C (300 °F). 3xxx Series. Manganese is the major alloying element of 3xxx series alloys. These alloys generally are non-heattreatable but have about 20% more strength than 1xxx series alloys. Because only a limited percentage of manganese (up to about 1.5%) can be effectively added to aluminum, manganese is used as a major element in only a few alloys. However, one of these, the popular 3003 alloy, is widely used as a general-purpose alloy for moderate-strength applications requiring good workability. 4xxx Series. The major alloying element in 4xxx series alloys is silicon, which can be added in sufficient quantities (up

to 12%) to cause substantial lowering of the melting range without producing brittleness. For this reason, aluminumsilicon alloys are used in welding wire and as brazing alloys for joining aluminum, where a lower melting range than that of the base metal is required. Most alloys in this series are non-heat treatable, but when used in welding heat-treatable alloys, they pick up some of the alloying constituents of the latter and so respond to heat treatment to a limited extent. The alloys containing appreciable amounts of silicon become dark gray to charcoal when anodic oxide finishes are applied and hence are in demand for architectural applications. Alloy 4032 has a low coefficient of thermal expansion and high wear resistance; thus it is well suited to production of forged engine pistons.

5xxx Series. The major alloying element in 5xxx series alloys is magnesium. When it is used as a major alloying

element or with manganese, the result is a moderate-to-high-strength work-hardenable alloy. Magnesium is considerably more effective than manganese as a hardener, about 0.8% Mg being equal to 1.25% Mn, and it can be added in considerably higher quantities. Alloys in this series possess good welding characteristics and good resistance to corrosion in marine atmospheres. However, certain limitations should be placed on the amount of cold work and the safe operating temperatures permissible for the higher-magnesium alloys (over 3.5% for operating temperatures above 65 °C, or 150 °F) to avoid susceptibility to stress-corrosion cracking. 6xxx Series. Alloys in the 6xxx series contain silicon and magnesium approximately in the proportions required for

formation of magnesium silicide (Mg2Si), thus making them heat treatable. Although not as strong as most 2xxx and 7xxx alloys, 6xxx series alloys have good formability, weldability, machinability, and corrosion resistance, with medium strength. Alloys in this heat-treatable group may be formed in the T4 temper (solution heat treated but not precipitation heat treated) and strengthened after forming to full T6 properties by precipitation heat treatment. 7xxx Series. Zinc, in amounts of 1 to 8%, is the major alloying element in 7xxx series alloys, and when coupled with a

smaller percentage of magnesium results in heat-treatable alloys of moderate to very high strength. Usually other elements, such as copper and chromium, are added in small quantities. Dilute additions of scandium also improve properties. 7xxx series alloys are used in airframe structures, mobile equipment, and other highly stressed parts. Higher strength 7xxx alloys exhibit reduced resistance to stress corrosion cracking and are often utilized in a slightly overaged temper to provide better combinations of strength, corrosion resistance, and fracture toughness. 8xxx series alloys constitute a wide range of chemical compositions. For example, improved elevated-temperature

performance is achieved through the use of dispersion-strengthened Al-Fe-Ce alloys (e.g., 8019) or Al-Fe-V-Si alloys (e.g., 8009) made by powder metallurgy processing. Lower density and higher stiffness can be achieved in lithiumcontaining alloys (e.g., 8090). The latter alloy, which is precipitation hardenable, has replaced medium-to-high strength 2xxx and 7xxx alloys in some aircraft/aerospace applications (e.g., helicopter components).

General Characteristics of Wrought Products Wrought products are those that have been shaped by plastic deformation. This deformation, which is done by hot and cold working processes such as rolling, extruding, forging, and drawing, either singly or in combination, transforms the cast ingot into the desired product form. As the deformation proceeds, the metallurgical structure also changes from a cast structure to a fully wrought structure. In this process, grain size and shape may be radically changed, the final configuration depending on the entire thermomechanical history (including any final annealing stages or heat treatments). During deformation, the second-phase microconstituents present in irregular forms in the ingot are fragmented into more equiaxed particles, which tend to align in the direction of greatest extension. The grains are usually also elongated in this direction and thinned or flattened in flat rolled products, in thin extruded products, and in the flash-plane areas of die forgings. Thus, the wrought metallurgical structure has directionality, the degree of which depends on the directionality of the deformation imposed during shaping of the product. These changes in metallurgical structure are accompanied by changes in properties, particularly mechanical properties, which are generally higher in the wrought products than in the cast ingot from which they originate. The wrought products generally exhibit some pronounced directionality of mechanical properties (i.e., anisotropy), which is negligible in the ingot from which they are produced. The directionality in sheet is not pronounced with respect to tensile properties but can be quite significant with respect to performance in deep drawing or cupping operations. Nonuniformity in different directions in the plane of the sheet causes formation of protuberances called "ears" in circular cups. These are primarily the result of crystallographic texture in the sheet, a nonrandom or preferred orientation of the grains (see the following discussion on "Crystallographic Texture" ). For deep drawing and cupping operations such as those employed in making beverage and food cans, special "non-earing quality" sheet is supplied. Thicker products that can be stressed or tested in three orthogonal directions generally exhibit differences in tensile and compressive properties as well as in resistance to fatigue stresses and stress-corrosion cracking in the three directions. With respect to these characteristics, the longitudinal direction (that in which the product was lengthened or extended most in working, as shown in Fig. 1) generally is superior. In the long-transverse direction (which may be either an extension or compression direction, as shown in Fig. 1, but with less extension or less compression than either of the other two directions), the properties and resistance are intermediate to those of the other directions. In the short transverse direction (direction of greatest compression in working, as shown in Fig. 1), the properties and resistance are generally

lower than in the other directions. In most cases the longitudinal, long-transverse, and short-transverse directions correspond to the greatest, intermediate, and smallest dimensions of product having a rectangular cross section. For products of axisymmetric cross section (round, square, hexagonal, etc.), there is no long- and short-transverse distinction; any direction in the cross-sectional plane is regarded as transverse (Fig. 2).

Fig. 1 Composite of micrographs of flat-rolled 7075-T6 illustrating metallurgical structure directionality. 40×

Fig. 2 Composite of micrographs of 7075-T6 rod illustrating metallurgical structure directionality. 40×

The influence of directionality on mechanical properties is shown in Fig. 3 for two closed-die forgings. Variation in properties is obtained because of the variations in thickness, variations in reduction during forging, and variation in angle between the axis of the test specimen and the direction of grain flow. Both die forgings show markedly lower properties in the short transverse direction than in the longitudinal direction.

Fig. 3 Variation in mechanical properties for two different 7075-T6 aluminum alloy forgings. Both were forged on a 35,000 ton press, solution treated at 470 °C (880 °F) for 3 h, quenched in water at 60 °C (140 °F), and aged at 120 °C (250 °F) for 24 h. Spar forging (shown at top): Cast ingots were received in 17 lots from three sources. Two lots were in 480 mm (19 in.) rounds, and 15 lots were in 250 to 300 mm (10 to 20 in.) squares. Twenty-eight forgings were tested at the locations indicated. Cylinder forging (shown at bottom): All cylinders were forged from 480 mm (19 in.) rounds. Six of the forgings were tested at locations shown.

Fatigue strength of bars cut from forgings is affected in the same manner as tensile strength, yield strength, and elongation. Figure 4 shows the results of fatigue tests of specimens cut from two sample forgings in directions both parallel and transverse to the forging flow lines. Once again, properties are superior in the longitudinal direction.

Fig. 4 Effect of alloy, design, and directionality on the axial fatigue strength of aluminum alloy forgings. Data apply to parts A and B, as shown. Sheet-type fatigue specimens, 3.2 mm (0.125 in.) thick and 6.4 mm (0.250 in.) wide, were cut both parallel and transverse to the forging flow lines. Locations from which specimens were taken are shown on the drawings. Mean stress was 91.7 MPa (13.3 ksi); notch was 1.2 mm (0.047 in.) in diameter hole in center of specimen. Kt = 2.5.

Directionality is considerably affected by whether the grain structure is recrystallized or unrecrystallized, the latter condition generally being more highly directional (see the following discussion on "Grain Structure" ). In the case of heat treated extruded shapes, there is usually a very thin surface or peripheral layer of recrystallized grain structure surrounding an unrecrystallized core. Since the recrystallized grain material is somewhat less resistant to fatigue than the unrecrystallized structure, its thickness should be minimized. For critical applications, a considerable percentage of the length from the rear of the extrusion is discarded to accomplish this, because the recrystallized layer thickness increases from front to rear of the extrusion. In the most critical applications, complete removal of the recrystallized materials by machining or chemical milling may be required. Extrusions, which generally have unrecrystallized structures, exhibit somewhat higher directionality of tensile properties than rolled products of equivalent cross section that also are unrecrystallized. This difference, primarily evidenced by higher longitudinal strength values in the extruded product, which may be as much as 10% higher, is attributed to more pronounced preferred grain orientation generated by the deformation of extrusion. Grain Structure. The grain size of aluminum alloy ingots and castings is typically controlled by the introduction of

inoculants that form intermetallic compounds containing titanium and/or boron. During deformation processing, the grain structure becomes modified. Most aluminum alloy products undergo dynamic recovery during hot working as the dislocations form networks of subgrains. New dislocation-free grains may form between and following rolling passes (static recrystallization) or during deformation processing (dynamic recrystallization). During deformation, the crystal lattice of the aluminum matrix rotates at its interfaces between constituent and coarse precipitate particles. These highenergy sites serve to nucleate recrystallization. This process is termed particle-stimulated nucleation and is an important mechanism in the recrystallization process of aluminum. The particle size that will serve as a nucleus decreases as deformation temperature decreases and strain and strain rate increase. Dispersoid particles retard the movement of highangle grain boundaries. Consequently, hot-worked structures are resistant to recrystallization and often retain the dynamically recovered subgrain structure in the interiors of elongated cast grain boundaries. In heat-treated products containing a sufficient quantity of dispersoids, the unrecrystallized structure of hot-worked plate, forgings, and extrusions can be retained after solution heat treatment. Degree of recrystallization of hot-worked products has an effect on fracture toughness. Unrecrystallized products develop higher toughness than do products that are either partially or completely recrystallized. This behavior is attributed to precipitation on the recrystallized high-angle grain boundaries during the quench. These particles increase the tendency

for low-energy intergranular fracture. Products such as sheet, rods, and tubing that are cold rolled invariably recrystallize during solution heat treatment or annealing to O temper. Decreasing the grain size can increase strength of 5xxx alloy products in the O temper by 7 to 28 MPa (1 to 4 ksi), but grain size is not a major factor in increasing strength of other aluminum alloy products. Several measures of formability are influenced by grain size, however, so grain size is controlled for this reason. One particular use of grain size control is to produce stable, fine grains, which are essential in developing super-plastic behavior in aluminum alloy sheet. Crystallographic Texture. Cast aluminum ingots and shapes generally have a random crystallographic texture; the

orientation of the unit cells comprising each grain are not aligned. With deformation, however, certain preferred crystallographic orientations develop. Many of the grains rotate and assume certain orientations with respect to the direction of deformation. For flat-rolled products and extrusions having a high aspect ratio of width to thickness, the deformation texture is similar to that in pure fcc metals. These orientations are described by using the Miller indices of the planes {nnn} in the grains parallel to the plane of the worked product and directions {nnn} parallel to the working direction. The predominant textures are {110}[112], {123}[634], and {112}[111]. During recrystallization, a high concentration of grains in the {001}[100] or {011}[100] orientations may develop. Alternatively, if particle-stimulated nucleation is present to a large extent, the recrystallized texture will be random. Control of crystallographic texture is particularly important for non-heat-treatable sheet that will be drawn. If texture is not random, ears form during the drawing process. In extruded or drawn rod or bar, the texture is a dual-fiber texture in which almost all grains are aligned so that the grain directions are either [001] or [111]. In heat-treatable alloys, texture has the most potent effect on the properties of extrusions that have the dual-fiber texture. Strengthening by this process is so potent that the longitudinal yield strengths of extruded products exhibiting this texture are about 70 MPa (10 ksi) higher than strength in the transverse direction. If this dual-fiber texture is lost by recrystallization, strength in the longitudinal direction decreases to that in the transverse directions.

Product Forms Table 1 summarizes the various product forms in which commonly used wrought aluminum alloys are available. Recommended tempers are also listed. Temper designations are described in the article "Alloy and Temper Designation Systems for Aluminum" in this Section.

Table 1 Wrought alloy products and tempers Alloy

Sheet

Plate

Tube

Pipe

Drawn

Extruded

Structural profiles (shapes)(a)

Extruded wire, rod, bar, and profiles (shapes)

Rolled or cold-finished

Rod

Bar

Wire

Rivets

Forgings and forging stock

Foil

Fin stock

1050

...

...

...

H112

...

...

...

...

...

...

...

...

...

...

1060

O, H12, H14, H16, H18

O, H12, H14, H112

O, H12, H14, H18, H113

O, H112

...

...

...

H14

...

...

...

...

...

...

1100

O, H12, H14, H16, H18

O, H12, H14, H112

O, H12, H14, H16, H18, H113

O, H112

...

...

O, H112

O, H112, H14, F

O, H112, F

O, H112, H12, H14, H16, H18

O, H14

H112, F

O, H19

O, H14, H18, H19, H25, H111, H113, H211

1145

...

...

...

...

...

...

...

...

...

...

...

...

O, H19

O, H14, H19, H25, H111, H113, H211

1200

...

...

...

H112

...

...

...

...

...

...

...

...

...

...

1235

...

...

...

H112

...

...

...

...

...

...

...

...

O, H19

...

1345

...

...

...

...

...

...

...

...

...

O, H12, H14, H16, H18, H19

...

...

...

...

1350(b)

O, H12, H14,

O,

...

H111

H111

H111

H111

O, H12, H14,

H12,

O, H12, H14, H16,

...

...

...

...

H12,

H16, H18

H14, H112

H16, H22, H24, H26

H111

H19, H22, H24, H26

2011

...

...

T3, T4511, T8

...

...

...

...

T3, T4, T451, T8

T3, T4, T451, T8

T3, T8

...

...

...

...

2014

O, T3, T4, T6

O, T451, T651

O, T4, T6

O, T4, T4510, T4511, T6, T6510, T6511

...

...

O, T4, T4510, T4511, T6, T6510, T6511

O, T4, T451, T6, T651

O, T4, T451, T6, T651

O, T4, T6

...

F, T4, T6, T652

...

...

Alclad 2014

O, T3, T4, T6

O, T451, T651

...

...

...

...

...

...

...

...

...

...

...

...

2017

...

...

...

...

...

...

...

O, H13, T4, T451

O, T4, T451

O, T4

T4

...

...

...

2018

...

...

...

...

...

...

...

...

...

...

...

F, T61

...

...

2024

O, T3, T361, T4, T72, T81, T861

O, T351, T361, T851, T861

O, T3

O, T3, T3510, T3511, T81, T8510, T8511

...

...

O, T3, T3510, T3511, T81, T8510, T8511

O, H13, T351, T4, T6, T851

O, T351, T4, T6, T851

O, H13, T36, T4, T6

T4

...

...

...

Alclad 2024

O, T3, T361, T4, T81, T861

O, T351, T361, T851, T861

...

...

...

...

...

...

...

...

...

...

...

...

Alclad one side 2024

O, T3, T361, T81, T861

O, T351, T361, T851, T861

...

...

...

...

...

...

...

...

...

...

...

...

H13,

O, T3, T361, T81, T861

O, T351, T361, T851, T761

...

...

...

...

...

...

...

...

...

...

...

...

O, T3, T361, T81, T861

O, T351, T361, T851, T861

...

...

...

...

...

...

...

...

...

...

...

...

2025

...

...

...

...

...

...

...

...

...

...

...

F, T6

...

...

2036

T4

...

...

...

...

...

...

...

...

...

...

...

...

...

2117

...

...

...

...

...

...

...

O, H13, H15

...

O, H13, H15

T4

...

...

...

2124

...

T851

...

...

...

...

...

...

...

...

...

...

...

...

2218

...

...

...

...

...

...

...

...

...

...

...

F, T61, T72

...

...

2219

O, T31, T37, T81, T87

O, T351, T37, T851, T87

...

O, T31, T3510, T3511, T81, T8510, T8511

...

...

O, T31, T3510, T3511, T81, T8510, T8511

T851

T851

...

...

F, T852

...

...

Alclad 2219

O, T31, T37, T81, T87

O, T351, T37, T851, T87

...

...

...

...

...

...

...

...

...

...

...

...

2618

...

...

...

...

...

...

...

...

...

...

...

F, T61

...

...

1 % Alclad 2024

1 % Alclad one side 2024

T6,

3003

O, H12, H14, H16, H18

O, H12, H14, H112

O, H12, H14, H16, H18, H25, H113

O, H112

H18, H112

...

O, H112

O, H112, F, H14

O, H112, F

O, H112, H12, H14, H16, H18

O, H14

H112, F

O, H19

O, H14, H18, H19, H25, H111, H113, H211

Alclad 3003

O, H12, H14, H16, H18

O, H12, H14, H112

O, H14, H18, H25, H113

O, H112

...

...

...

...

...

...

...

...

...

...

3004

O, H32, H34, H36, H38

O, H32, H34, H112

O, H34, H36, H38

O

...

...

...

...

...

...

...

...

...

...

Alclad 3004

O, H32, H34, H36, H38

O, H32, H34, H112

...

...

...

...

...

...

...

...

...

...

...

...

3005

O, H12, H14, H16, H18, H19, H26, H28

...

...

...

...

...

...

...

...

...

...

...

...

...

3105

O, H12, H14, H16, H18, H25

...

...

...

...

...

...

...

...

...

...

...

...

...

4032

...

...

...

...

...

...

...

...

...

...

...

F, T6

...

...

5005

O, H12, H14, H16, H18,

O, H12, H14, H32, H34, H112

...

...

...

...

...

O, H12, H14, H16, H22,

...

O, H19, H32

O, H32

...

...

...

H32, H34, H36, H38

H24, H26, H32

5050

O, H32, H34, H36, H38

O, H112

O, H32, H34, H36, H38

...

...

...

...

O, F

O, F

O, H32, H34, H36, H38

...

...

...

...

5052

O, H32, H34, H36, H38

O, H32, H34, H112

O, H32, H34, H36, H38

...

...

...

...

O, F, H32

O, F

O, H32, H34, H36, H38

O, H32

...

O, H19

...

5056

...

...

...

...

...

...

...

O, F, H32

O, F

O, H111, H12, H14, H18, H32, H34, H38, H192, H392

O, H32

...

H19

...

Alclad 5056

...

...

...

...

...

...

...

...

...

H192, H392, H393

...

...

...

...

5083

O, H116, H321

O, H112, H116, H321

...

O, H112

H111,

...

...

O, H111, H112

...

...

...

...

H111, H112, F

...

...

5086

O, H112, H116, H32, H34, H36, H38

O, H112, H116, H32, H34

O, H32, H34, H36

O, H112

H111,

...

...

O, H111, H112

...

...

...

...

...

...

...

5154

O, H32, H34, H36, H38

O, H32, H34, H112

O, H34, H38

O, H112

...

...

O, H112

O, H112, F

O, H112, F

O, H112, H32, H34, H36, H38

...

...

...

...

5252

H24, H25, H28

...

...

...

...

...

...

...

...

...

...

...

...

...

5254

O, H32, H34, H36, H38

O, H32, H34, H112

...

...

...

...

...

...

...

...

...

...

...

...

5454

O, H32, H34

O, H32, H34, H112

H32, H34

O, H112

...

...

O, H111, H112

...

...

...

...

...

...

...

5456

O, H116, H321

O, H112, H116, H321

...

...

...

...

...

...

...

...

...

H112, F

...

...

5457

O

...

...

...

...

...

...

...

...

...

...

...

...

...

5652

O, H32, H34, H36, H38

O, H32, H34, H112

...

...

...

...

...

...

...

...

...

...

...

...

5657

H241, H25, H26, H28

...

...

...

...

...

...

...

...

...

...

...

...

...

6005

...

...

...

T1, T5

...

...

T1, T5

...

...

...

...

...

...

...

6053

...

...

...

...

...

...

...

O, H13

...

O, H13

T61

F, T6

...

...

6061

O, T4, T6

O, T451, T651

O, T4, T6

O, T1, T4, T4510, T4511, T51, T6, T6510, T6511

T6

T6

O, T1, T4, T4510, T4511, T51, T6, T6510, T6511

O, H13, T4, T451, T6, T651

O, T4, T451, T6, T651

O, H13, T4, T6, T89, T913, T94

T6

F, T652

...

...

H111,

T6,

Alclad 6061

O, T4, T6

O, T451, T651

...

...

...

...

...

...

...

...

...

...

...

...

6063

...

...

O, T4, T6, T83, T831, T832

O, T1, T4, T5, T52, T6

T6

...

O, T1, T4, T5, T52, T6

...

...

...

...

...

...

...

6066

...

...

O, T4, T6

O, T4, T4510, T4511, T6, T6510, T6511

...

...

O, T4, T4510, T4511, T6, T6510, T6511

...

...

...

...

F, T6

...

...

6070

...

...

...

T6

...

...

T6

...

...

...

...

...

...

...

6101(b)

...

...

...

T6, T61, T63, T64, T65, H111

T6, T61, T63, T64, T65, H111

T6, T61, T63, T64, T65, H111

T6, T61, T63, T64, T65, H111

...

...

...

...

...

...

...

6105

...

...

...

T1, T5

...

...

T1, T5

...

...

...

...

...

...

...

6151

...

...

...

...

...

...

...

...

...

...

...

F, T6, T652

...

...

6162

...

...

...

...

...

...

T5, T5510, T5511, T6, T6510, T6511

...

...

...

...

...

...

...

6201(b)

...

...

...

...

...

...

...

...

...

T81

...

...

...

...

6262

...

...

T6, T9

T6, T6510, T6511

...

...

T6, T6511

T6, T651, T9

T6, T651, T9

T6, T9

...

...

...

...

T6510,

6351

...

...

...

T4, T6

T4, T6

...

T1, T4, T5, T51, T54, T6

...

...

...

...

...

...

...

6463

...

...

...

...

...

...

T1, T5, T6

...

...

...

...

...

...

...

7005

...

...

...

...

...

...

T53

...

...

...

...

...

...

...

7049

...

...

...

...

...

...

...

...

...

...

...

T73, T7352

...

...

7050

...

T7451(c), T7651

...

...

...

...

T73510, T73511, T74510(c), T74511(c), T76510, T76511

H13

...

H13

T7

T74(c), T7452(c), F

...

...

7072

...

...

...

...

...

...

...

...

...

...

...

...

...

O, H18, H23, H241, H111, H113, H211

7075

T6, T73, T76

O, T651, T7351, T7651

O, T73

O, T6, T6510, T6511, T73, T73510, T73511

...

...

O, T6, T6510, T6511, T73, T73510, T73511, T76, T76510, T76511

O, H13, T6, T651, T73, T7351

O, T6, T651, T73, T735

O, H13, T6, T73

T6, T73

F, T6, T652, T73, T7352

...

...

Alclad 7075

O, T6, T73, T76

O, T651, T7351, T7651

...

...

...

...

...

...

...

...

...

...

...

...

T6,

H14, H19, H24, H25,

Alclad one side 7075

O, T6

O, T651

...

...

...

...

...

...

...

...

...

...

...

...

7008 Alclad 7075

O, T76

O, T651, T7651

...

...

...

...

...

...

...

...

...

...

...

...

7175

...

...

...

...

...

...

...

...

...

...

...

F, T74, T7452(c), T7454(c), T66

...

...

7178

O, T76

T6,

O, T651, T7651

...

...

...

...

O, T6, T6510, T6511, T76, T76510, T76511

O, H13

...

O, H13

T6

...

...

...

Alclad 7178

O, T76

T6,

O, T651, T7651

...

...

...

...

...

...

...

...

...

...

...

...

7475

T61, T761

T651, T7351, T7651

...

...

...

...

...

O

...

...

...

...

...

...

Alclad 7475

T61, T761

T651, T7651

...

...

...

...

...

...

...

...

...

...

...

...

8017

...

...

...

...

...

...

...

H12, H22

...

H212

...

...

...

...

8030

...

...

...

...

...

...

...

H12

...

H221

...

...

...

...

8176

...

...

...

...

...

...

...

H14

...

H24

...

...

...

...

T6,

8177

...

...

...

...

...

...

...

H13, H23

Source: Aluminum Standards and Data 1997, The Aluminum Association Inc., March 1997 (a) Rolled or extruded.

(b) Products listed for these alloys are for electric conductors only.

(c) T74-type tempers, although not previously registered, have appeared in various literature and specifications as T736-type tempers.

...

H221

...

...

...

...

Flat-Rolled Products Flat-rolled products include plate, sheet, and foil. These products are semifabricated to rectangular cross section by sequential reductions in the thickness of cast ingot by hot and cold rolling. Properties in work-hardened tempers are controlled by degree of cold reduction, partial or full annealing, and the use of stabilizing treatments. Plate, sheet, and foil produced in heat-treatable compositions may be solution heat treated, quenched, precipitation hardened, and thermally or mechanically stress relieved. Sheet and foil may be rolled with textured surfaces. Sheet and plate rolled with specially prepared work rolls may be embossed to produce products such as tread plate. By roll forming, sheet in corrugated or other contoured configurations can be produced for such applications as roofing, siding, ducts, and gutters. Plate refers to a product having a thickness greater than 6.3 mm (0.250 in.). Plate up to 200 mm (8 in.) thick is available

in some alloys. Extra-large plates--e.g., 22 mm ( in. thick) by 2.25 m (89 in.) wide by 32 m (105 ft) long--are supplied for construction of the wings of wide-body aircraft. Plate usually has either sheared or sawed edges and can be cut into circles, rectangles or odd-shape blanks. Plate of certain alloys--notably the high-strength 2xxx and 7xxx series alloys--also is available in clad form. The most commonly used plate alloys are 2024, 2124, 2219, 7050, 7178, and 7475 for aircraft structures; 5083, 5086, and 5456 for marine, cryogenic and pressure-vessel applications, and 1100, 3003, 5052, and 6061 for general applications. Table 1 lists the various alloys that are commonly forged. Sheet. When a flat rolled product is over 0.15 through 6.3 mm (0.006 through 0.249 in.) in thickness, it is classified as

"sheet". Sheet edges can be sheared, slit or sawed. Sheet is supplied in flat form, in coils, or in pieces cut to length from coils. Current facilities permit production of a limited amount of extra-large sheet, for example, up to 5 m (200 in.) wide by 25 m (1000 in.) long. Aluminum sheet is available in several surface finishes that range from "mill finishes," which have uncontrolled surface appearance that may vary from sheet to sheet, to bright finishes on one or two sides, to "aircraft skin quality." It may also be supplied embossed, patterned, painted, or otherwise surface treated, and with combinations of such treatments. Special products include corrugated, V-beam, and ribbed roofing and siding, duct sheet, fin stock, recording circles, and computer memory disks. Among standard products are the alclad composites, which consists of heat treated 2xxx or 7xxx alloys clad on either or both sides with an appropriate anodic alloy or with aluminum. For sheet thicknesses, cladding thickness may range from 1 to as much as 10% of sheet thickness, the greater percentages applying to thinner products. A series of products termed "brazing sheet" is available. These products are also composites clad one or both sides with brazing alloy. For architectural uses, clad non-heat-treatable alloys may be supplied. These provide a variety of special finishing characteristics, integral color finishing capability, greater uniformity in appearance, and improved corrosion resistance. With a few exceptions, most alloys in the 1xxx, 2xxx, 3xxx, 5xxx, and 7xxx series are available in sheet form (see Table 1). Along with alloy 6061, they cover a wide range of applications from builders' hardware to transportation equipment and from appliances to aircraft structures. Alloys 6009, 6111, and 6022 are widely used for automobile body panels and hood and deck stampings. Foil is a product up through 0.15 mm (0.006 in.) thick. Most foil is supplied in coils, although it is also available in

rectangular form (sheets). One of the largest end uses of foil is household wrap. There is a wider variety of surface finishes for foil than for sheet. Foil often is treated chemically or mechanically to meet the needs of specific applications. Common foil alloys are 1100, 1145, 1235, 3003, 5052, and 5056 (Table 1). Higher-strength foil of alloy 2024, 5052, or 5056 is used to produce the honeycomb cores used in bonded honeycomb sandwich panels. Bar, Rod, and Wire Bar, rod, and wire are defined as solid products that are extremely long in relation to their cross-section. They differ from each other only in cross-sectional shape and in thickness or diameter. When the cross section is round or nearly round and is over 10 mm ( in.) in diameter, it is called rod. It is called bar when the cross section is square, rectangular, or in the shape of a regular polygon and when at least one perpendicular distance between parallel faces (thickness) is over 10 mm. Wire refers to a product, regardless of its cross-sectional shape, whose diameter or greatest perpendicular distance between parallel faces is 10 mm or less.

Rod and bar can be produced by either hot rolling or hot extruding and brought to final dimensions with or without additional cold working. Wire usually is produced and sized by drawing through one or more dies, although roll flattening also is used. Alclad rod or wire for additional corrosion resistance is available only in certain alloys. Many aluminum alloys are available as bar, rod, and wire; among these alloys, 2011 and 6262 are specially designed for screw-machine products, and 2117 and 6053 for rivets and fittings (Table 1). Alloy 2024-T4 is a standard material for bolts and screws. Alloys 1350, 6101, and 6201 are extensively used as electrical conductors. Alloy 5056 is used for zippers, and alclad 5056 for insect-screen wire. Tubular Products Tubular products include tube and pipe. They are hollow wrought products that are long in relation to their cross section and have uniform wall thickness except as affected by corner radii. Tube is round, elliptical, square, rectangular or regular polygonal in cross section. When round tubular products are in standardized combinations of outside diameter and wall thickness, commonly designated by "nominal pipe sizes" and "ANSI schedule numbers," they are classified as pipe. Tube and pipe may be produced from a hollow extrusion ingot, by piercing a solid extrusion ingot, or by extruding through a porthole die or bridge die. They also may be made by forming and welding sheet. Tube may be brought to final dimensions by drawing through dies. Tube (both extruded and drawn) for general applications is available in such alloys as 1100, 2014, 2024, 3003, 5050, 5086, 6061, 6063, and 7075 (Table 1). For heat-exchanger tube, alloys 1060, 3003, alclad 3003, 5052, 5454, and 6061 are most widely used. Clad tube is available only in certain alloys and is clad only on one side (either inside or outside). Pipe is available in alloy 1350, 3003, 6061, 6063, 6101, and 6351 (Table 1). Shapes Shapes are products that are long in relation to their cross-sectional dimensions and that have cross-sectional shapes other than those of sheet, plate, rod, bar, wire, or tube. Most shapes are produced by extruding or by extruding plus cold finishing; shapes are now rarely produced by rolling because of economic advantages of the extrusion process. Shapes may be solid, hollow (with one or more voids), or semihollow. The 6xxx series (Al-Mg-Si) alloys, because of their easy extrudability, are the most popular alloys for producing shapes. Alloys of the 2xxx and 7xxx series are used in applications requiring higher strength. Standard structural shapes such as I-beams, channels, and angles produced in alloy 6061 are made in different and fewer configurations than similar shapes made of steel; the patterns especially designed for aluminum offer better section properties and greater structural stability than those designed for steel, as a result of more efficient metal usage. The dimensions, weights, and properties of the alloy 6061 standard structural shapes, along with other information needed by structural engineers and designers, are contained in the Aluminum Construction Manual, published by the Aluminum Association, Inc. Most aluminum alloys can be obtained as precision extrusions with good as-extruded surfaces; major dimensions usually do not need to be machined, because tolerances of the as-extruded product often permit manufacturers to complete the part by simple cutoff, drilling, or other minor operations. In many instances, long aircraft structural elements incorporate large attachment fittings at one end. Such elements often are more economical to machine from stepped aluminum extrusions, with two or more cross sections in one piece, rather than from extrusions of uniform cross section that are large enough for the attachment fittings. Aluminum shapes are produced in a great variety of cross-sectional designs that place the metal where it is needed to meet functional and appearance requirements. Full utilization of this capability of the extrusion process depends on the ingenuity of designers in creating new and useful configurations. However, the alloy extruded and the cross-sectional design greatly influence tooling cost, production rate, surface finish, and production cost. Therefore, the extruder should be consulted during the design process to ensure producibility, dimensional control, and finish capabilities that are required for the application. Producibility is limited by metal-flow characteristics and is a function of alloy composition, extrusion temperature, press size, and shape complexity. Shapes are classified with respect to producibility into solid, hollow, and semihollow types and further classified by rules based on the dimensions of the features. The difficulty of extrusion can be estimated from the dimensions, taking into account the alloy to be extruded.

The overall size of the shape affects ease of extrusion and dimensional tolerances. As the circumscribing circle size (smallest diameter that completely encloses the shapes; see Fig. 5) increases, extrusion becomes more difficult. Metal flow is most rapid at the center of the die face. As circle size increases, differences in flow rate from the center to the outside of the shape increase, and die design and construction to counteract this effect are more difficult.

Fig. 5 Illustration of circumscribing circle method of characterizing the size of an extruded shape

Complexity and production difficulty also increase with increasing "shape factor," which is the ratio of the perimeter of a shape to its weight per unit length. Increasing thickness aids extrusion, and shapes having uniform thickness are most easily extruded. Although weight and metal cost decrease with decreasing thickness, the increasing extrusion cost may offset the savings in metal cost. Limits on minimum practical thickness, which depend on circle size, classification, and alloy, are given in Table 2. Table 2 Standard manufacturing limits (in inches) for aluminum extrusions Diameter of circumscribing circle, in.

Minimum wall thickness, in.

1060, 1100, 3003

6063

6061

2014, 5086, 5454

2024, 2219, 5083, 7001, 7075, 7079, 7178

Solid and semihollow shapes, rod and bar

0.5-2

0.040

0.040

0.040

0.040

0.040

2-3

0.045

0.045

0.045

0.050

0.050

3-4

0.050

0.050

0.050

0.050

0.062

4-5

0.062

0.062

0.062

0.062

0.078

5-6

0.062

0.062

0.062

0.078

0.094

6-7

0.078

0.078

0.078

0.094

0.109

7-8

0.094

0.094

0.094

0.109

0.125

8-10

0.109

0.109

0.109

0.125

0.156

10-11

0.125

0.125

0.125

0.125

0.156

11-12

0.156

0.156

0.156

0.156

0.156

12-17

0.188

0.188

0.188

0.188

0.188

17-20

0.188

0.188

0.188

0.188

0.250

20-24

0.188

0.188

0.188

0.250

0.500

Class 1 hollow shapes(a)

1.25-3

0.062

0.050

0.062

...

...

3-4

0.094

0.050

0.062

...

...

4-5

0.109

0.062

0.062

0.156

0.250

5-6

0.125

0.062

0.078

0.188

0.281

6-7

0.156

0.078

0.094

0.219

0.312

7-8

0.188

0.094

0.125

0.250

0.375

8-9

0.219

0.125

0.156

0.281

0.438

9-10

0.250

0.156

0.188

0.312

0.500

10-12.75

0.312

0.188

0.219

0.375

0.500

12.75-14

0.375

0.219

0.250

0.438

0.500

14-16

0.438

0.250

0.375

0.438

0.500

16-20.25

0.500

0.375

0.438

0.500

0.625

Class 2 and 3 hollow shapes(b)

0.5-1

0.062

0.050

0.062

...

...

1-2

0.062

0.055

0.062

...

...

2-3

0.078

0.062

0.078

...

...

3-4

0.094

0.078

0.094

...

...

4-5

0.109

0.094

0.109

...

...

5-6

0.125

0.109

0.125

...

...

6-7

0.156

0.125

0.156

...

...

7-8

0.188

0.156

0.188

...

...

8-10

0.250

0.188

0.250

...

...

(a) Minimum inside diameter is one-half the circumscribing diameter, but never under 1 in. for alloys in first three columns or under 2 in. for alloys in last two columns.

(b) Minimum hole size for all alloys is 0.110 in.2 in area of 0.375 in. in diam.

Alloy selection for extruded shapes has an important effect on producibility and cost as well as on minimum thickness. The extrusion speed possible for a given shape is strongly affected by the composition being extruded and may vary by as much as a factor of 20 (see Table 3). Table 3 Relative extrudability of aluminum alloys Alloy

Extrudability, % of rate for alloy 6063

1350

160

1060

135

1100

135

3003

120

6063

100

6061

60

2011

35

5086

25

2014

20

5083

20

2024

15

7075

9

7178

8

Forgings The term "hand forgings" is applied to most of the open-die forgings produced on flat or contoured dies generally in hydraulic presses with capacities up to 445 MN (50,000 tonf). The most usual are of rectangular or cylindrical cross section and may be produced in economical lengths (multiple length) and later cut into shorter pieces. The general category includes disk-shape parts sometimes referred to as "biscuits" as well as more complicated pieces that may vary in cross section through the length or be bent, curved, or contoured. These forgings fill a frequent need in which the number of pieces required does not justify the time and expense of impression dies. Mandrel-forged rings are another type of open-die-forged product. Forgings of all types, produced on hammers, mechanical presses, or hydraulic presses, range in size from 45 g (0.1 lb) to 1360 kg (3000 lb) or over. Those weighing up to 450 kg (1000 lb) are produced regularly, those weighing between 450 and 900 kg (1000 and 2000 lb) are less common, and pieces weighing more than 900 kg are special items. Most aluminum forgings are produced in closed dies and can vary widely in detail and closeness of approach to the final dimensions desired. The ultimate in shaping parts by forging is represented by "precision forgings," which are essentially net-shape parts requiring little or no machining. The advantage of closed-die forgings is that the metallurgical-structure alignment follows the part contours. This is sometimes called the "grain-flow pattern." This alignment is highly favorable for static strength and fatigue resistance (refer to Fig. 3 and 4). In working operations preliminary to final shaping, the metal may be upset and drawn in ways that further improve final mechanical properties. Particularly for die forgings, which represent engineered products designed to perform specific functions in specific machines or vehicles, the choice of forging process and tooling must be approached on a cost-effective basis involving quantities needed, tooling, forging, and machining costs, and the net effects of these factors. There are great variations in this problem, from the extreme case of simple parts for which tooling costs are inconsequential to parts ordered in large quantities, which usually justify the tooling cost of dies to produce a part with conventional machining allowances or even the higher initial costs of precision forging. The alloy used affects costs, reflecting the relative alloy forgeability (see Fig. 6). This factor, combined with those discussed in the preceding paragraph, may account for a price ratio of up to 10 to 1 for parts of the same weight. Forgings

dies are more expensive than extrusion dies by a factor varying from the ratio 4 to 1 to the ratio 3 to 1, for small and large sections. Factors in formulating decisions as to whether parts should be shaped by machining from bar or plate stock or be produced as hand or die forgings are considered in the section of this article "Product Economics, Selection, and Design." In many cases, a die forging may serve to replace an assembly of parts produced from mill products and stampings or shapes.

Fig. 6 Forgeability vs forging temperature for seven aluminum alloys. Forgeability increases as the arbitrary unit increases.

The alloys most prominent in forgings are of the 2xxx, 6xxx, and 7xxx types; 1xxx, 3xxx, 4xxx, and 5xxx are producible but are used with less frequency (see Table 1). Limitations on controlled strain-hardening capability and on use of strain to produce T8-type tempers influence the use of some of these alloys. The largest forging tonnages in markets other than aerospace are accounted for by automobile and truck wheels of alloy 6061, whereas the aerospace industry uses forgings principally of 2xxx and 7xxx alloys (2014, 2219, 7049, 7050, 7075, and 7175). Mandrel-forged or ring-rolled rings are produced in some forging plants. More information on a variety of representative die forgings, including the alloys and tempers used, the types of forging equipment used, and comments on selection factors, is given in Volume 14, Forming and Forging, of the ASM Handbook. Impacts Impacts are formed in a confining die from a lubricated slug, usually cold, by a single-stroke application of force through a metal punch, causing the metal to flow around the punch or die. The process lends itself to high production rates, with precision parts being produced to exacting quality standards. Impacts involve a combination of cold extrusion and cold forging and, as such, combine most of the advantages of both the forging and extrusion processes. Impacts usually have properties in the longitudinal direction equal to those specified for other product forms of similar composition. There are three basic types of impacting, all of which are used on aluminum. Reverse impacting is used to make shells with forged bases and extruded sidewalls. The slug is placed in a die cavity and struck by a punch, which forces the metal to flow back (upward) around the punch, and then through the opening between the punch and die, to form a simple shell. Forward impacting somewhat resembles conventional extrusion in that the metal is forced through an orifice in the die by the action of a punch, causing the metal to flow in the direction of punch travel. The punch fits the walls of the die so closely that no metal escapes backwards. Forward impacting with a flat-face punch is used to form round, nonround, straight, and ribbed rods, and forward impacting with a stop-face punch is used to form thin-wall tubes with one or both ends open, and with parallel or tapered sidewalls. If the punch is smaller than the die and the die contains an orifice, reverse and forward impacting can be combined to produce a combination impact. A major consideration in designing aluminum impacts is selection of the appropriate alloy. Alloys 1100, 2014, 3003, 6061, 6351, and 7075 are most often utilized in aluminum impacts. These alloys offer a range of mechanical properties that fits most applications. Generally, the stronger the alloy impacted is, the shorter the tool life and the higher the

production costs. Although each part must be considered individually, the stronger alloys generally require greater minimum wall thicknesses. Alloy 1100, which has excellent corrosion resistance in rural, industrial, and marine atmospheres, is commonly impacted to form containers for liquid and semiliquid materials such as food preserves and products sprayed by aerosols. Alloy 3003 is used for many of the same applications as alloy 1100, but it is selected when higher strength than that of 1100 is required. Alloy 6061, which is heat treatable and has excellent corrosion resistance, is widely used in the manufacture of parts for automotive, aircraft, and marine applications, especially where welding is involved or high strength is required. Alloy 6351 is a medium-to-high-strength heat treatable alloy with good corrosion resistance. Alloy 2014 is a heat treatable alloy used for general applications where high tensile and yield strengths, combined with good ductility and good fatigue resistance, are essential. It is widely used in structural applications and in aircraft, automobile, and ordnance parts. Alloy 7075 has the highest strength and hardness of these alloys. This heat treatable alloy is used for many of the same applications as those of alloy 2014, but it is selected where highest stresses are expected or for maximum weight savings. Other Mill Products Fin stock is coiled sheet or foil in specific alloys, tempers, and thickness ranges suitable for manufacture of fins for

heat-exchanger applications. As shown in Table 1, commonly used alloys include 1100, 1145, 3003, 7072. Alclad Products. As described earlier, aluminum products sometimes are coated on one or both surfaces with a

metallurgically bonded, thin layer of pure aluminum or aluminum alloy. If the combination of core and cladding alloys is selected so that the cladding is anodic to the core, it is called alclad. The cladding of alclad products electrochemically protects the core at exposed edges and at abraded or corroded areas. When a corrosive solution is in contact with the product, current from the anodic cladding flows through the electrolyte to the cathodic core, and the cladding tends to dissolve preferentially, thus protecting the core. Sustained protection is dependent on obtaining the optimum quantity of current (which is influenced by the potential difference between the cladding and core), the conductivity of the corroding medium, film formation, and polarization (see the article "Corrosion Resistance of Aluminum and Aluminum Alloys" in this Section). The corrosion potentials of cladding and core alloys are important in selecting a coating that is sufficiently anodic to electrochemically protect the core. Copper in solid solution in aluminum is less anodic as copper content increases. Consequently, pure aluminum is anodic to aluminum-copper-magnesium alloys in the naturally aged T3x and T4x tempers by about 0.154 V and is used as the cladding for most alclad 2xxx products. Increasing zinc in solid solution increases the anodic potential of aluminum alloys, while Mg2Si and manganese have little effect. Alloy 7072, Al-1Zn, has a more anodic potential than pure aluminum and is used as the cladding for Alclad 3003, 5052, 6061, and 7075, as well as others. The most widely used alclad products are sheet and plate, although wire, tube, and other forms are also produced. The most generally accepted method of fabricating alclad sheet and plate consists of hot rolling to pressure weld the cladding slabs to a scalped core ingot. In fabricating alclad products, the temperature and time of thermal treatments should be minimized to avoid extensive diffusion of soluble elements from the core. This is particularly important in the 2xxx alloys, as diffusion of copper in the cladding makes it less anodic. It is less important in alloys containing zinc and magnesium, because these elements make the cladding more anodic. The percentage of cladding thickness is determined principally by the thickness of the finished part. Because the objective is to provide an adequate absolute thickness, the percentage of thicker parts need not be as great as the percentage for thinner parts. A listing of the most widely used alclad products is given in Table 4.

Table 4 Components of clad products Designation

Component alloys(a)

Total specified thickness of composite product, in.

Sides clad

Cladding thickness per side, % composite thickness

Nominal

Alclad 2014 sheet and plate

Alclad 2024 sheet and plate

1

Cladding

2014

6003

2024

max

Both

10

8

...

0.025-0.039

Both

7.5

6

...

0.040-0.099

Both

5

4

...

0.100

Both

2.5

2

3(c)

0.062

Both

5

4

...

0.063

Both

2.5

2

3(c)

2024

1230

0.188

Both

1.5

1.2

3(c)

2024

1230

0.062

One

5

4

...

0.063

One

2.5

2

3(c)

2024

1230

0.188

One

1.5

1.2

3(c)

2219

7072

0.039

Both

10

8

...

0.040-0.099

Both

5

4

...

0.100

Both

2.5

2

3(c)

% Alclad one side 2024 sheet and plate

Alclad 2219 sheet and plate

min

0.024

1230

% Alclad 2024 sheet and plate

Alclad one side 2024 sheet and plate

1

Core

Average(b)

Alclad 3003 sheet and plate

3003

7072

All

Both

5

4

6(c)

Alclad 3003 tube

3003

7072

All

Inside

10

...

...

All

Outside

7

...

...

Alclad 3004 sheet and plate

3004

7072

Alclad 5056 rod and wire

5056

6253

All

0.375

Both

5

4

Outside

20

16

6(c)

(of total cross-sectional area)

Alclad 6061 sheet and plate

6061

7072

Alclad 7050 sheet and plate

7050

7072

7108 Alclad 7050 sheet and plate

Alclad 7075 sheet and plate

2

7075

7108

7072

4

6(c)

0.062

Both

4

3.2

...

0.063

Both

2.5

2

...

0.062

Both

4

3.2

...

0.063

Both

2.5

2

...

0.062

Both

4

3.2

...

0.063-0.187

Both

2.5

2

...

0.188

Both

1.5

1.2

3(c)

7072

0.188

Both

2.5

2

4(c)

7075

7072

0.062

One

4

3.2

...

0.063-0.187

One

2.5

2

...

0.188

One

1.5

1.2

3(c)

7075

7072

0.188

One

2.5

2

4(c)

7075

7008

0.062

Both

4

3.2

...

0.063-0.187

Both

2.5

2

...

0.188

Both

1.5

1.2

3(c)

% Alclad one side 7075 sheet and plate

7008 Alclad 7075 sheet and plate

5

7075 % Alclad 7075 sheet and plate

Alclad one side 7075 sheet and plate

2

7050

Both

All

7011 Alclad 7075 sheet and plate

Alclad 7178 sheet and plate

Alclad 7475 sheet

No. 7 brazing sheet

No. 8 brazing sheet

No. 11 brazing sheet

No. 12 brazing sheet

No. 23 brazing sheet

7075

7178

7475

3003

3003

3003

3003

6951

7011

7072

7072

4004

4004

4343(d)

4343(d)

4045

0.062

Both

4

3.2

...

0.063-0.187

Both

2.5

2

...

0.188

Both

1.5

1.2

3(c)

0.062

Both

4

3.2

...

0.063-0.187

Both

2.5

2

...

0.188

Both

1.5

1.2

3(c)

0.062

Both

4

3.2

...

0.063-0.187

Both

2.5

2

...

0.188-0.249

Both

1.5

1.2

...

0.024

One

15

12

18

0.025-0.062

One

10

8

12

0.063

One

7.5

6

9

0.024

Both

15

12

18

0.025-0.062

Both

10

8

12

0.063

Both

7.5

6

9

0.063

One

10

8

12

0.064

One

5

4

6

0.063

Both

10

8

12

0.064

Both

5

4

6

0.090

One

10

8

12

6951

No. 24 brazing sheet

1100

Clad 1100 reflector sheet

3003

Clad 3003 reflector sheet

4045

1175

1175

0.091

One

5

4

6

0.090

Both

10

8

12

0.091

Both

5

4

6

0.064

Both

15

12

18

0.065

Both

7.5

6

9

0.064

Both

15

12

18

0.065

Both

7.5

6

9

(a) Cladding composition is applicable only to the aluminum or aluminum alloy bonded to the alloy ingot or slab preparatory to processing to the specified composite product. The composition of the cladding may be subsequently altered by diffusion between the core and cladding due to thermal treatment.

(b) Average thickness per side as determined by averaging cladding thickness measurements taken at a magnification of 100 diameters on the cross section of a transverse sample polished and etched for microscopic examination.

(c) Applicable for thicknesses of 0.500 in. and greater.

(d) The cladding component, in lieu of 4343 alloy, may be 5% 1xxx clad 4343.

Specialty mill products include brazing sheet, corrugated sheet for roofing and siding, and heat-exchanger tubing.

These and other specialty mill products are listed in Table 5. Table 5 Specialty mill products Specialty designation

product

Temper

Specialty-product description

Form

Alloy

No. 11 and 12

Sheet

3003 clad with 4343 on one side (No. 11) or on both sides (No. 12)

O, H12, H14

No. 23 and 24

Sheet

6951 clad with 4045 on one side (No. 23) or on both sides (No. 24)

O

Brazing sheet

Reflector sheet

Clad 1100

Sheet

1100 clad with 1175 on one or both sides

...

Clad 3003

Sheet

3003 clad with 1175 on one or both sides

...

Coiled sheet

1100, 3003

O, H12, H14, H16, H18

Coiled sheet

3105

O, H12, H14, H16, H18, H25

Coiled sheet

5005, 5050, 5052

O, H32, H34, H36, H38

Painted sheet

Commercial roofing and siding

roofing

Sheet

3004, Alclad 3004

...

V-beam roofing and siding

Sheet

3004, Alclad 3004

...

Ribbed roofing

Sheet

Alclad 3004

...

Ribbed siding

Sheet

3004, Alclad 3004

...

Duct sheet

Coiled or flat sheet

Alloy and temper with minimum tensile strength of 16.0 ksi

...

Tread plate

Sheet and plate with raised pattern on one surface

6061

O, T4, T6

Heat-exchanger tube

Tube

1060

H14

3003

H14, H25

Alclad 3003

H14, H25

5052

H32, H34

5454

H32, H34

Corrugated and siding

Rigid electrical conduit

Tube

6061

T4, T6

3003

H12

6063

T1

Product Economics, Selection, and Design In the "cost-effective" approach to the problem of material selection, the only valid basis for choosing a particular material is that it will perform all required functions at the lowest overall cost. The material chosen may be the most costeffective because (a) it is lowest in first cost and provides service and durability at least equal to those offered by any alternative material; (b) it is most economical in the long run due to lowest operating or maintenance costs; or (c) it has special characteristics not matched by any alternative material. These considerations at times are "warped" by artificial factors arising from such sources as legislation or the "energy crisis." Also, they may at times be greatly influenced, or even outweighed, by factors of availability or delivery time. The choice between aluminum and some other material on the cost-effective basis is sometimes simple and at other times quite complex; in these cases the choice may shift from one time to another as relative costs change. Machining, joining, or finishing capabilities, as well as physical properties (predominantly density, conductivity, or reflectivity), are foremost considerations in many cases. The competitive position of aluminum in this race is often greatly augmented by the myriad design possibilities offered by aluminum shapes and forged parts. (Aluminum engineered castings also offer many of these advantages.) Product selection is based primarily on shape, dimensional, and mechanical requirements. The piece needed may be required to cover or enclose an area, to fill a certain space, to connect or attach to other pieces, or to conduct or contain a fluid or gas, or it may be limited by weight or other factors. There is seldom any question concerning the best choice in the case of products like foil, wire, tube, or large-area applications for sheet. In other cases, an intelligent choice from among the various products is a complex engineering problem involving many factors in addition to first cost of the product itself. Shapes or die forgings frequently offer the advantage of a single piece having such features as ribs for stiffening, fins for heat dissipation, and bosses or pads for attachment, replacing several pieces that must be cut, formed, and joined. Mechanical-property considerations may be important in some cases, that is such matters as the availability or unavailability of an alloy and temper in a particular product type, the higher longitudinal static strength of extruded versus rolled or forged products, or the matching of metallurgical-structure alignment (or grain-flow pattern) with surface contours, a matter that is characteristic of die forgings. For the most stringent structural applications, the greatest hazards are those posed by dynamic stresses and by combinations of static stresses from assembly interferences or misfits with dynamic applied stresses and corrosive environments. To avoid premature failure from fatigue cracking or stress-corrosion cracking, good mechanical design to minimize such stresses, stress concentrations and exposure to and entrapment of corrosive media are of paramount importance. The type of product and the alloy and temper selected also play a strong role in the design process. Product Dimensions and Dimensional Tolerances The ranges of thickness in which foil, sheet, and plate are available were stated previously. By definition, foil is no greater than 0.15 mm (0.006 in.) thick and for some purposes is as thin as 0.0043 mm (0.00017 in.), sheet ranges from over 0.15 to 6.3 mm (over 0.006 to 0.249 in.) thick, and plate ranges from 6.3 to 200 mm (0.250 to 8 in.) thick. Corresponding width, length, and coil-size limitations are matters for inquiry with producers. Standard dimensional tolerances for all mill products are contained in the American National Standard Institute document H35.2-1993, Annual Book of ASTM Standards, Volume 02.02 and in the Aluminum Association publication Aluminum Standards and Data. These dimensional tolerances on thickness, width, length, diameter, squareness, flatness, straightness, lateral bow, and twist, as applicable, vary with product type and are not tabulated in this Handbook.

The limiting dimensions for extruded products, including rod and bar, and for other solid, hollow, and semihollow shapes, with respect to maximum circumscribing circle size and minimum wall thickness, are alloy dependent, as indicated in Table 2. Various sizes of structural shapes (angles, channels, I-beams, H-beams, Tees, and Zees) produced from alloy 6061-T6 have been established as standard products by the Aluminum Association. Detailed dimensions, weights per lineal foot, and section properties (moment of inertia, section modulus, and radius of gyration) for these standard structural shapes--data which are useful for design--are also tabulated in the Aluminum Association publication Aluminum Standards and Data. These data, as well as those given in the same publication for standard pipe sizes, are not repeated in this Handbook. Limiting dimensions in design of die forgings include total plan area, which may be as great as 0.3 m2 ( 500 in.2) for forgings produced in mechanical presses, 1.9 m2 ( 3000 in.2) for hammer forgings, and 3.2 m2 ( 5000 in.2) for parts made in the largest hydraulic presses. Other limiting design features are web thickness, rib thickness and height, draft angles, and minimum radii for fillets and corners. Cylindrical and other axisymmetric shapes are easiest to produce as impacts, but nonsymmetrical shapes may also be produced. Longitudinal ribs can be incorporated in sidewalls, either inside or outside. Lugs, bosses, grooves, depressions, and even ribs can be incorporated in the end or base configuration. Dimensional limitations apply to maximum diameter (dependent on press size), length-to-diameter ratio (a maximum of 18 to 1, with 12 to 1 more normal), and minimum wall thickness. All of these shape factors are alloy dependent. Effective Design and Use of Wrought Product Capabilities Good design for aluminum can be defined as making the most effective use of its capabilities. An outstanding example of this is the two-piece all-aluminum beverage container. Thin, coiled sheet of relatively high-strength alloys (3004 for the can body; 5182 for the lid), rolled at extremely high speeds, is drawn and ironed to produce the body and formed to produce easy-open ends. Both of these manufacturing operations produce the parts at extremely high rates. The favorable economics of lowest first cost, lower shipping costs (because of low weight), and recyclability combine with functional advantages to make these containers a viable and successful product in a highly competitive market. Such containers are pressure vessels in addition to being subject to considerable abuse from handling, and these factors require the best possible balance among alloy strength, fabricability, and design. Tool design for production of these containers played a key role in making them successful. Roofing and siding for highway freight trailers represent another highly effective, high-volume use of aluminum alloy sheet with advantages in both first and lifetime costs. These applications employ semi-monocoque (stressed skin) construction and moderately high-strength, non-heat-treatable alloys. Skins for aircraft wings, control surfaces, and fuselages (pressure vessels) are likewise effective in both cost and function. These applications employ high-strength, heat treatable alloys, and forming operations ranging from mild to severe. In some cases, the good formability of freshly quenched, very long wing-skin panels is preserved by refrigeration during transcontinental shipment by rail in special cars from mill to aircraft factory. The fact that sheet accounts for such a high percentage of all aluminum mill products produced and shipped annually (nearly 60% in 1996) attests to the versatility and high efficiency of this form in a myriad of applications. Plate is an obvious selection for many purposes. One example is large welded storage tanks used on space vehicles with

formed and welded plate members serving the dual function of containing the fuel and oxidizers (cryogenic liquids) as well as forming the structure of the vehicle. For such applications, as well as for aircraft wings, plate may be extensively machined or chemically milled to form integral stiffening ribs or waffle patterns. When only longitudinal stiffening ribs are required, an alternative product is wide extruded panels with integral ribs. For some designs, machining may be the most economical production technique, because the setup time may account for a large part of the cost of machining. In Fig. 7, for instance, the machined plate was the least expensive method of producing the aluminum part until production reached 600 pieces. At that point, the quantity was sufficient to compensate for the cost of the extrusion die. The built-up design, with skin on both surfaces, was heavier and costlier.

Fig. 7 Cost comparison for producing an alloy 2024-T4 part by three methods

Chemical milling (removal of metal by dissolution in an alkaline or acid solution) is routine for specialized operations on aluminum. For flat parts on which large areas having complex or wavy peripheral outlines are to be reduced only slightly in thickness, chemical milling is usually the most economical method. For sheet metal parts that cannot be formed after machining, chemical milling is the only practical method by which metal can be removed to obtain a waffle-type grid with uniform skin thickness. Even then, allowance must often be made for some springback resulting from metal removal and the consequent redistribution of residual forming stresses. Chemical milling can normally produce a stiffened skin to a thickness tolerance of ±0.13 mm (±0.005 in.), with the cladding left intact on the unmilled surface. Mechanical milling of skins from sheet thicker than 3 mm ( cleanup "skim" cut for flatness on the hold-down surface, because of hold-down limitations.

in.) requires a

Extruded Shapes. Extrusions, with their great design versatility, good surface quality, and precise dimensions,

frequently do not have to be machined extensively; the configuration and dimensional precision of the as-extruded product often permits a manufacturer to complete the part by simple cutoff, drilling, broaching, or other minor machining operations. For any part that can be produced as an extrusion, the cost of the extrusion die is usually written off after a few parts have been produced. Cost of machining may be the only selection consideration. This is illustrated in Fig. 8 by the cost figures for a fuel-tank attachment fitting. The design of this part permitted the use of an extrusion, which required very little machining compared with the same part fabricated from solid bar. After about 100 pieces, the cost per piece decreased substantially.

Fig. 8 Cost of an extruded fuel-tank attachment fitting as a function of quantity. A part completely machined from bar stock is rated 100.

Interconnecting Shapes. It is becoming increasingly common to include an interconnecting feature in the design of an extruded shape to facilitate its assembly to a similar shape or to another product. It can be a simple step to provide a smooth lapping joint or a tongue and groove for a nesting joint (see Fig. 9). Such connections can be secured by any of the common joining methods. Of special interest when the joint is to be arc welded is the fact that lapping and nesting types of interconnections can be designed to provide edge preparation and/or integral backing for the weld (see sketch at bottom right in Fig. 9).

Fig. 9 Four examples of interconnecting extrusions that fit together or fit other products, and four examples of joining methods

Interlocking joints can be designed to incorporate a free-moving hinge (see top sketch in Fig. 10) when one part is slid lengthwise into the mating portion of the next. Panel-type extrusions with hinge joints have found application in conveyor belts and roll-up doors.

Fig. 10 Two examples of extrusions with nonpermanent interconnections

A more common type of interlocking feature used in interconnecting extrusions is the nesting type that requires rotation of one part relative to the mating part for assembly (see bottom sketch in Fig. 10). Such joints can be held together by gravity or by mechanical devices. If a nonpermanent joint is desired, a bolt or other fastener can be used, as illustrated in the bottom sketch in Fig. 10. When a permanent joint is desired, a snapping or crimping feature can be added to interlocking extrusions (see Fig. 11). Crimping also can be used to make a permanent joint between an interlocking extrusion and sheet (Fig. 11). Extrusions also can be provided with longitudinal teeth or serrations, which will permanently grip smooth surfaces as well as surfaces provided with mating teeth or serrations; this is illustrated in the sketch at the bottom of Fig. 11.

Fig. 11 Six examples of interconnecting extrusions that lock together or lock to other products

Applications for interconnecting extrusions include doors; wall, ceiling, and floor panels; pallets; aircraft landing mats; highway signs; window frames; and large cylinders. Die Forgings. The diversity of geometrical possibilities offered by aluminum die forgings frequently makes them

highly advantageous choices in that they can be produced without costly machining, joining, or assembly operations. When compared with alternative methods of achieving the same functions, the integral product is often ahead in a value analysis. Tool (die) costs play a major role in the decision when the choice is between machining parts from bar or plate stock and purchasing die forgings. In other cases, the differences in directionality of wrought structure of the different products, which affect expected resistance to directional stresses and service environments, may be the principal deciding factor. The cost of machining a few parts from a bar or slab is usually less than the cost of making a die and producing the parts by forging. When greater numbers of parts are to be produced, forging usually is the less-expensive method. In borderline cases, a detailed study of machining and die costs is necessary to determine the crossover point. In determining this point, it is necessary to calculate only the original cost of the die, because the supplier of the forging is responsible for die replacements caused by breakage or wear. This replacement cost is included in the price of the forgings. Die cost varies with the size and intricacy of the part. In Fig. 12, a die forging (part A) is compared with a built-up design. Although 75% of the metal was machined away from the rough forging, the machined forging was more economical than the assembly for quantities greater than 125.

Fig. 12 Relative costs of aluminum die forgings and similar components fabricated by other methods. The comparison for Part A is between a built-up design and a die forging. Although the rough forging was machined on all surfaces, a saving in fabrication cost was evident after about 125 forged fittings had been made. Part B is a simpler part, and the costs of forging compared with machining from bar were the same at about the 100th piece. For a more complicated forging (part C), the crossover point where the machined bar became more expensive than the forging occurred at 40 pieces. Part D, a relatively simple fitting, was made as a die forging, an impact extrusion, and a hollowed-out fitting. Forging was the most expensive approach. The cost of extrusion and of machining from plate were about the same for 3000 fittings.

In some large, complicated forgings, the break-even point may be at the first or second forging. It also may be desirable to rough forge the part in relatively inexpensive roughing dies and complete the part by machining if only a few pieces are desired. When this technique is used, the desirable flow of metal induced by forging and the consequent improvement in properties can be obtained at a lower cost than would have to be paid for a part forged to final dimensions. The curves in Fig. 12 compare costs of parts of different size and shape, produced by competitive methods. For the simpler part, B, the crossover point occurs at about 100 pieces. For the complicated forging (part C), the crossover point occurs at 40 pieces. The items considered in determining the costs of these two parts include fabrication-shop learning

curves, unit-run labor, amortized setup, labor, tooling costs (including dies and fixtures), raw materials, and overhead charges. Die forging is not always the cheapest method of producing a large quantity of parts. A relatively simple fitting (part D in Fig. 12) was analyzed for production costs as a die forging, as an impact extrusion, and as a part machined from plate. The machined fitting was more economical for all quantities, because the cost of the finishing operations required for the die forging closely approached the cost of producing the part by machining only. The thin walls and deep crevices of this fitting should have made it ideally suited to impact extrusion. Analysis showed that this method of manufacture was only slightly more expensive than machining for small quantities and identical in cost for quantities greater than 3000 parts. The examples represented by the parts shown in Fig. 12 serve to relate design and cost, and emphasize the necessity for conducting a detailed cost analysis of each of the several methods of fabrication. Precision Forgings. Precision-forged aluminum alloys are a significant commercial forging product form that has undergone major growth in use and has been the subject of significant technological development and capital investment by the forging industry. Precision aluminum forgings normally require no subsequent machining by the purchaser other than, in some cases, the drilling of attachment holes. They are produced with very thin ribs and webs; sharp corner and fillet radii; undercuts, backdrafts, and/or contours; and frequently, multiple parting planes that may optimize grain flow characteristics.

Selection of precision aluminum forging from the candidate methods of achieving a final aluminum alloy shape is based on value analyses for the individual shape in question. Figure 13 presents a cost comparison for a channel-type aluminum alloy part machined from plate, as-machined from a conventional aluminum forging, and produced as a precision forging; costs as a function of production quantity include application of all material, tooling, setup, and fabrication costs. The break-even point for the precision-forging method versus conventional forging occurs with a quantity of 50 pieces, and when compared to the cost of machining the part from plate, the precision forging is always less expensive. Figure 13 also illustrates the potential cost advantages of precision aluminum alloy forgings. It has generally been found that precision aluminum forgings are highly cost effective when alternate fabrication techniques include multiple-axis machining in order to achieve the final part.

Fig. 13 Cost comparison for the manufacture of an aluminum alloy 7075-T73 component

Recent evaluations by the forging industry and users have shown that precision aluminum forgings can reduce final part costs by up to 80 to 90%, in comparison to machined plate, and 60 to 70%, in comparison to machined conventional forgings. Machining labor can be reduced by up to 90 to 95%.

Specifications for Wrought Mill and Engineered Products

In the United States, specifications and standards for wrought aluminum products are issued/published by ASTM, governmental bodies (military and federal specifications), SAE International (Aerospace Materials Specifications, AMS), the American Society of Mechanical Engineers (ASME), and the American Welding Society (AWS). Table 6 provides a cross reference of the various specifications covering wrought aluminum products. Table 6 Aluminum mill product specifications Alloy

1060

1100

Product

Specifications

ASTM

Military

Federal

AMS

ASME

AWS

Sheet and plate

B 209

...

...

...

SB209

...

Wire, rod, and bar: rolled or cold finished

B 211

...

...

...

...

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

SB221

...

Tube: extruded, seamless

B241

...

...

...

SB241

...

Tube: drawn

B 483

...

...

...

...

...

Tube: drawn, seamless

B 210

...

...

...

SB210

...

Tube: condenser

B 234

...

...

...

SB234

...

Pipe: gas and oil transmission

B 345

...

...

...

...

...

Tube: condenser with integral fins

B 404

...

...

...

...

...

Sheet and plate

B 209

...

QQ-A250/1

4001

SB209

...

...

...

...

4003

...

...

Wire, rod, and bar: rolled or cold finished

B 211

...

QQ-A225/1

4102

...

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

SB221

...

Tube: extruded, seamless

B 241

...

...

...

SB241

...

Tube: extruded, coiled

B 491

...

...

...

...

...

Tube: drawn

B 483

...

...

...

...

...

Tube: drawn, seamless

B 210

...

WW-T700/1

4062

...

...

Tube: welded

B 313

...

...

...

...

...

B 547

...

...

...

...

...

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

Spray gun wire

...

MIL-W6712

...

4180

...

...

Forgings and forging stock

B 247

...

...

...

...

...

Welding rod and electrodes: bare

...

...

...

...

A5.10

Impacts

...

MIL-A12545

...

...

...

...

Foil

B 479

...

QQ-A-1876

...

...

...

1145

Foil

B 373, B 479

...

QQ-A-1876

4011

...

...

1235

Foil

B 373, B 479

...

QQ-A-1876

...

...

...

Tube: extruded, coiled

B 491

...

...

...

...

...

Aluminum conductors: steel reinforced

B 232

...

...

...

...

...

B 401

...

...

...

...

...

Bus conductors

B 236

...

...

...

...

...

Rolled redraw rod

B 233

...

...

...

...

...

Stranded conductors

B 231

...

...

...

...

...

B 400

...

...

...

...

...

1350

Wire: H19 temper

B 230

...

...

...

...

...

Wire: H14 temper

B 609

...

...

...

...

...

Wire, rectangular, and square

B 324

...

...

...

...

...

Round solid conductor

B 609

...

Tube: drawn, seamless

B 210

...

...

...

...

...

Wire, rod, and bar: rolled or cold finished

B 211

...

QQ-A225/3

...

...

...

Sheet and plate

B 209

...

...

4029

...

...

...

...

...

4028

...

...

Wire, rod, and bar: rolled or cold finished

B 211

...

QQ-A225/4

4121

SB 211

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

4153

...

...

Tube: extruded, seamless

B 241

...

...

...

...

...

Tube: drawn, seamless

B 210

...

...

...

...

...

Forgings and forging stock

B 247

MIL-A22771

...

4134

SB247

...

...

...

...

4133

...

...

Rings: forged and rolled

...

...

...

4314

...

...

Impacts

...

MIL-A12545

...

...

...

...

Alclad 2014

Sheet and plate

B 209

...

QQ-A250/3

...

...

...

2017

Wire, rod, and bar: rolled or cold finished

B 211

...

QQ-A225/5

4118

...

...

2011

2014

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

2018

Forgings and forging stock

B 247

...

...

4140

...

...

2024

Sheet and plate

B 209

...

QQ-A250/4

4037

...

...

...

...

...

4035

...

...

...

...

...

4192

...

...

...

...

...

4193

...

...

B 211

...

QQ-A225/6

4112

SB211

...

...

...

...

...

...

...

...

...

...

4165

...

...

B221

...

...

4152

SB221

...

...

...

...

4164

...

...

...

...

...

4165

...

...

Tube: extruded, seamless

B 241

...

...

...

...

...

Tube: drawn, seamless

B 210

MIL-T50777

WW-T700/3

4087

...

...

...

...

...

4088

...

...

Tube: hydraulic

...

...

...

4086

...

...

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

Foil

...

MIL-A81596

...

...

...

...

Sheet and plate

B 209

...

QQ-A250/5

4041

...

...

Wire, rod, and bar: rolled or cold finished

Wire, rod, bar, profiles (shapes), and tube: extruded

Alclad 2024

Alclad one side 2024

Sheet and plate

...

...

...

4040

...

...

...

...

...

4194

...

...

...

...

...

4195

...

...

...

...

...

4036

...

...

...

...

...

4077

...

...

2025

Forgings and forging stock

B 247

...

...

4130

...

...

2117

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

2124

Plate

B 209

...

QQ-A250/29

4101

...

...

2218

Forgings and forging stock

B 247

...

...

4142

...

...

2219

Sheet and plate

B 209

...

QQ-A250/30

4031

...

...

Wire, rod, and bar: rolled or cold finished

B211

...

...

...

...

...

Wire, rod, bar, profiles (shapes), and tubes: extruded

B 221

...

...

4162

...

...

...

...

...

4163

...

...

Tube: extruded, seamless

B 241

...

...

4068

...

...

Tube: drawn, seamless

B 210

...

...

4066

...

...

Forgings and forging stock

B 247

MIL-A22771

...

4143

...

...

...

...

...

4144

...

...

Armor plate

...

MIL-A46118

...

...

...

...

Rings: rolled on forged

...

...

...

4313

...

...

Alclad 2219

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

Sheet and plate

B 209

...

...

4094

...

...

...

...

...

4095

...

...

...

...

...

4096

...

...

2319

Welding rod and electrodes: bare

...

...

...

4191

...

A5.10

2618

Forgings and forging stock

B 247

MIL-A22771

...

4132

...

...

3003

Sheet and plate

B 209

...

QQ-A250/2

4006

SB 209

...

...

...

...

4008

...

...

Wire, rod, and bar: rolled or cold finished

B 211

...

QQ-A225/2

...

...

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

SB221

...

Tube: extruded, seamless

B 241

...

...

...

SB241

...

Tube: extruded, coiled

B 491

...

...

...

...

...

Tube: drawn

B 483

...

...

...

...

...

Tube: drawn, seamless

B 210

...

WW-T700/2

4065

SB210

...

...

...

...

4067

...

...

Tube: condenser

B 234

...

...

...

SB 234

...

Tube: condenser with integral fins

B 404

...

...

...

...

...

Tube: welded

B 313

...

...

...

...

...

B 547

...

...

...

...

...

Alclad 3003

3004

Alclad 3004

Pipe

B 241

MIL-P25995

...

...

SB 241

...

Pipe: gas and oil transmission

B 345

...

...

...

...

...

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

Forgings and forging stock

B 247

...

...

...

SB247

...

Foil

...

MIL-A81596

...

4010

...

...

Sheet and plate

B 209

...

...

...

SB209

...

Tube: drawn, seamless

B 210

...

...

...

SB210

...

Tube: extruded

B 221

...

...

...

...

...

Tube: extruded, seamless

B 241

...

...

...

SB241

...

Tube: condenser

B 234

...

...

...

SB234

...

Tube: condenser with integral fin

B 404

...

...

...

...

...

Tube: welded

B 547

...

...

...

...

...

Pipe: gas and oil transmission

B 345

...

...

...

...

...

Sheet and plate

B 209

...

...

...

SB209

...

Tube: extruded

B 221

...

...

...

...

...

Tube: welded

B 313

...

...

...

...

...

B 547

...

...

...

...

...

Sheet and plate

B 209

...

...

...

SB209

...

Tube: welded

B 313

...

...

...

...

...

B 547

...

...

...

...

...

3005

Sheet

B 209

...

...

...

...

...

3105

Sheet

B 209

...

...

...

...

...

4032

Forgings and forging stock

B 247

...

...

...

...

...

4043

Welding rod and electrodes: bare

...

...

...

4190

...

A5.10

Spray gun wire

...

MIL-W6712

...

...

...

...

4045

Brazing filler metal

...

...

...

...

...

...

4047

Brazing filler metal

...

MIL-B20148

...

4185

...

...

Welding rod and electrodes: bare

...

...

...

...

...

A5.10

Brazing filler metal

...

MIL-B20148

...

4184

...

...

Welding rod and electrodes: bare

...

...

...

...

...

A5.10

4343

Brazing filler metal

...

...

...

...

...

...

4643

Welding electrode

...

...

...

4189

...

A5.10

5005

Sheet and plate

B 209

...

...

...

...

...

Wire: H19 temper

B 396

...

...

...

...

...

Stranded conductor

B 397

...

...

...

...

...

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

Rod: rolled

B 531

...

...

...

...

...

Tube: drawn, seamless

B 210

...

...

...

...

...

Tube: drawn

B 483

...

...

...

...

...

Sheet and plate

B 209

...

...

...

SB209

...

4145

5050

5052

Tube: drawn, seamless

B 210

...

...

...

...

...

Tube: drawn

B 483

...

...

...

...

...

Tube: welded

B 313

...

...

...

...

...

B 547

...

...

...

...

...

B 209

...

QQ-A250/8

4015

SB209

...

...

...

...

4016

...

...

...

...

...

4017

...

...

Wire, rod, and bar: rolled or cold finished

B 211

...

QQ-A225/7

4114

...

...

Tube: drawn

B 483

...

...

...

...

...

Tube: drawn, seamless

B 210

...

WW-T700/4

4069, 4070

SB210

...

Tube: hydraulic

...

...

...

4071

...

...

Tube: extruded

B221

...

...

...

...

...

Tube: extruded, seamless

B 241

...

...

...

SB241

...

Tube: condenser

B 234

...

...

...

SB234

...

Tube: condenser with integral fins

B 404

...

...

...

...

...

Tube: welded

B313

...

...

...

...

...

B547

...

...

...

...

...

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

Foil

...

MIL-A81596

...

4004

...

...

Sheet and plate

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

Wire, rod, and bar: rolled or cold finished

B 211

...

...

4182

...

...

Foil

...

MIL-A81596

...

4005

...

...

Alclad 5056

Wire, rod, and bar: rolled or cold finished

B 211

MIL-C-915

...

...

...

...

5083

Sheet and plate

B 209

...

QQ-A250/6

4056

SB209

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

SB221

...

Tube: extruded, seamless

B 241

...

...

...

SB241

...

Tube: drawn, seamless

B 210

...

...

...

...

...

Tube: welded

B547

...

...

...

...

...

Forgings and forging stock

B 247

...

...

...

SB247

...

Pipe: gas and oil transmission

B 345

...

...

...

...

...

Armor plate

...

MIL-A46027

...

...

...

...

Extruded armor

...

MIL-A46083

...

...

...

...

Forged armor

...

MIL-A45225

...

...

...

...

Sheet and plate

B 209

...

QQ-A250/7

...

SB209

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

SB221

...

Tube: extruded, seamless

B 241

...

...

...

SB241

...

Tube: drawn, seamless

B 210

...

WW-T-

...

...

...

5056

5086

700/5

Tube: welded

5154

B 313

...

...

...

...

...

B 547

...

...

...

...

...

Pipe: gas and oil transmission

B 345

...

...

...

...

...

Sheet and plate

B 209

...

...

...

SB209

...

Wire, rod, and bar: rolled or cold finished

B 211

...

...

...

SB221

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

SB210

...

Tube: drawn, seamless

B 210

...

...

...

...

...

Tube: welded

B 313

...

...

...

...

...

B 547

...

...

...

...

...

5183

Welding rod and electrodes: bare

...

...

...

...

...

A5.10

5252

Sheet

B 209

...

...

...

...

...

5254

Sheet and plate

B 209

...

...

...

SB209

...

Tube: extruded, seamless

B 241

...

...

...

...

...

5356

Welding rod and electrodes: bare

...

...

...

...

...

A5.10

5454

Sheet and plate

B 209

...

QQ-A250/10

...

SB209

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

SB221

...

Tube: extruded, seamless

B 241

...

...

...

SB241

...

Tube: condenser

B 234

...

...

...

SB234

...

Tube: condenser with integral fins

B 404

...

...

...

...

...

Tube: welded

B 547

...

...

...

...

...

Sheet and plate

B 209

...

QQ-A250/9

...

SB209

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

SB221

...

Tube: extruded, seamless

B 241

...

...

...

SB241

...

Tube: drawn, seamless

B 210

...

...

...

...

...

Armor plate

...

MIL-A46027

...

...

...

...

Extruded armor

...

MIL-A46083

...

...

...

...

Forged armor

...

MIL-A45225

...

...

...

...

5457

Sheet

B 209

...

...

...

...

...

5554

Welding rod and electrodes: bare

...

...

...

...

...

A5.10

5556

Welding rod and electrodes: bare

...

...

...

...

...

A5.10

5652

Sheet and plate

B 209

...

...

...

SB209

...

Tube: extruded, seamless

B 241

...

...

...

...

...

5654

Welding rod and electrodes: bare

...

...

...

...

...

A5.10

5657

Sheet

B 209

...

...

...

...

...

6005

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

...

...

6053

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

6061

Sheet and plate

B 209

...

QQ-A250/11

4025

SB209

...

5456

...

...

...

4026

...

...

...

...

...

4027

...

...

Tread plate

B 632

...

...

...

...

...

Wire, rod, and bar: rolled or cold finished

B 211

...

QQ-A225/8

4115

SB211

...

...

...

...

4116

...

...

...

...

...

4117

...

...

...

...

...

4128

...

...

B 221

...

...

4150

...

...

...

...

...

4160

...

...

...

...

...

4161

...

...

...

...

...

4172

...

...

...

...

...

4173

...

...

Structural profiles (shapes)

B 308

...

...

4113

SB308

...

Tube: drawn

B 483

...

...

...

...

...

Tube: extruded, seamless

B 241

...

...

...

SB 241

...

Tube: drawn, seamless

B 210

...

WW-T700/6

4079

SB210

...

...

...

...

4080

...

...

...

...

...

4082

...

...

...

...

...

4081

...

...

...

...

...

4083

...

...

Wire, rod, bar, profiles (shapes), and tube: extruded

Tube: hydraulic

Alclad 6061

6063

Tube: condenser

B 234

...

...

...

SB 234

...

Tube: condenser with integral fins

B 404

...

...

...

...

...

Tube: welded

B 313

...

...

...

...

...

B 547

...

...

...

...

...

Pipe

B 241

MIL-P25995

...

...

SB 241

...

Pipe: gas and oil transmission

B 345

...

...

...

...

...

Forgings and forging stock

B 247

MIL-A22771

...

4127

SB247

...

...

...

...

4146

...

...

...

...

...

4248

...

...

Rings: forged or rolled

...

...

...

4312

...

...

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

Impacts

...

MIL-A12545

...

...

...

...

Structural pipe and tube: extruded

B 429

...

...

...

...

...

Foil

...

...

...

4009

...

...

Sheet and plate

B 209

...

...

...

SB209

...

...

...

...

4021

...

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

4156

SB221

...

Tube: extruded, seamless

B 241

...

...

...

SB241

...

Tube: extruded, coiled

B 491

...

...

...

...

...

Tube: drawn

B 483

...

...

...

...

...

Tube: drawn, seamless

B 210

...

...

...

SB210

...

Pipe

B 241

MIL-P25995

...

...

SB241

...

Pipe: gas and oil transmission

B 345

...

...

...

...

...

Structural pipe and tube: extruded

B 429

...

...

...

...

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

...

...

Forgings and forging stock

B 247

...

...

...

...

...

Rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

...

...

Impacts

...

MIL-A12545

...

...

...

...

Pipe: gas and oil transmission

B 345

...

...

...

...

...

6101

Bus conductor

B 317

...

QQ-B-825

...

...

...

6105

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

...

...

6151

Forgings and forging stock

B 247

MIL-A22771

...

4125

...

...

6201

Wire: T81 temper

B 398

...

...

...

...

...

Stranded conductor: T81 temper

B 399

...

...

...

...

...

Wire, rod, and bar: rolled or cold finished

B 211

...

QQ-A225/10

...

...

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

...

...

Tube: drawn, seamless

B 210

...

...

...

...

...

6066

6070

6262

Tube: drawn

B 483

...

...

...

...

...

Pipe: gas and oil transmission

B 345

...

...

...

...

...

Seamless pipe and tube: extruded

B 241

...

...

...

...

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

...

...

6463

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

...

...

7005

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

...

...

7049

Forgings

B 247

MIL-A22771

...

4111

...

...

Extrusion

...

...

...

4157

...

...

Extrusion

...

...

...

4159

...

...

Hand forging

...

...

...

4247

...

...

Forging

...

...

...

4321

...

...

Plate

...

...

...

4200

...

...

Plate

...

...

...

4050

...

...

...

...

...

4201

...

...

...

...

...

4340

...

...

...

...

...

4341

...

...

...

...

...

4342

...

...

B 247

MIL-A22771

...

4107

...

...

...

...

...

4108

...

...

6351

7050

Wire, rod, and bar: extruded

Forgings

Die forgings

...

...

...

4333

...

...

Rivet wire and rod

B 316

...

QQ-A-430

...

...

...

Alclad 7050

Sheet

...

...

...

4243

...

...

7075

Sheet and plate

B 209

...

QQ-A250/12

4024

...

...

...

...

QQ-A250/24

4044

...

...

...

...

...

4045

...

...

...

...

...

4078

...

...

B 211

...

QQ-A225/9

4122

...

...

...

...

...

4123

...

...

...

...

...

4124

...

...

...

...

...

4186

...

...

...

...

...

4187

...

...

B 221

...

...

4154

...

...

...

...

...

4166

...

...

...

...

...

4167

...

...

...

...

...

4168

...

...

...

...

...

4169

...

...

Tube: extruded

B 241

...

...

...

...

...

Tube: drawn, seamless

B 210

...

WW-T700/7

...

...

...

Wire, rod, and bar: rolled or cold finished

Wire, rod, bar, profiles (shapes), and tube: extruded

Forgings and forging stock

Alclad 7075

B 247

MIL-A22771

...

...

...

...

...

...

...

4141

...

...

...

...

...

4126

...

...

...

...

...

4131

...

...

...

...

...

4147

...

...

Hand forgings

...

...

...

4323

...

...

Rings: forged or rolled

...

...

...

4311

...

...

...

...

...

4310

...

...

Impacts

...

MIL-A12545

...

...

...

...

Rivet wire

B 316

...

QQ-A-430

...

...

...

Sheet and plate

B 209

...

QQ-A250/13

...

...

...

...

...

QQ-A250/25

4048

...

...

...

...

QQ-A250/26

4049

...

...

...

...

...

4196

...

...

...

...

...

4197

...

...

Alclad one side 7075

Sheet and plate

B 209

...

QQ-A250/18

4046

...

...

Alclad 7475

Sheet

...

...

...

4100

...

...

...

...

...

4207

...

...

...

...

...

4344

...

...

7175

Extruded

Forgings and forging stock

7178

Alclad 7178

7475

B 247

MIL-A22771

...

4148

...

...

...

...

...

4149

...

...

...

...

...

4179

...

...

B 209

...

QQ-A250/14

...

...

...

...

...

QQ-A250/21

...

...

...

Wire, rod, bar, profiles (shapes), and tube: extruded

B 221

...

...

...

...

...

Rivet wire

B 316

...

...

...

...

...

Tube: extruded, seamless

B 241

...

...

...

...

...

Sheet and plate

B 209

...

QQ-A250/15

4051

...

...

...

...

QQ-A250/22

...

...

...

...

...

QQ-A250/28

...

...

...

...

...

...

4084

...

...

...

...

...

4085

...

...

...

...

...

4089

...

...

...

...

...

4090

...

...

...

...

...

4202

...

...

Sheet and plate

Sheet and plate

Properties of Wrought Aluminum Alloys

Table 1 Nominal densities and specific gravities of wrought aluminums and aluminum alloys Density and specific gravity are dependent on composition, and variations are discernible from one cast to another for most alloys. The nominal values given here should not be specified as engineering requirements but are used in calculating typical values for weight per unit length, weight per unit area, covering area, etc. The density values were derived from metric and subsequently rounded; these values are not to be back-converted to the metric. Alloy

Density, lb/in.3

Specific gravity

1050

0.0975

2.705

1060

0.0975

2.705

1100

0.098

2.71

1145

0.0975

2.700

1175

0.0975

2.700

1200

0.098

2.70

1230

0.098

2.70

1235

0.0975

2.705

1345

0.0975

2.705

1350

0.0975

2.705

2011

0.102

2.83

2014

0.101

2.80

2017

0.101

2.79

2018

0.102

2.82

2024

0.101

2.78

2025

0.101

2.81

2036

0.100

2.75

2117

0.099

2.75

2124

0.100

2.78

2218

0.101

2.81

2219

0.103

2.84

2618

0.100

2.76

3003

0.099

2.73

3004

0.098

2.72

3005

0.098

2.73

3105

0.098

2.72

4032

0.097

2.68

4043

0.097

2.69

4045

0.096

2.67

4047

0.096

2.66

4145

0.099

2.74

4343

0.097

2.68

4643

0.097

2.69

5005

0.098

2.70

5050

0.097

2.69

5052

0.097

2.68

5056

0.095

2.64

5083

0.096

2.66

5086

0.096

2.66

5154

0.096

2.66

5183

0.096

2.66

5252

0.096

2.67

5254

0.096

2.66

5356

0.096

2.64

5454

0.097

2.69

5456

0.096

2.66

5457

0.097

2.69

5554

0.097

2.69

5556

0.096

2.66

5652

0.097

2.67

5654

0.096

2.66

5657

0.097

2.69

6003

0.097

2.70

6005

0.097

2.70

6053

0.097

2.69

6061

0.098

2.70

6063

0.097

2.70

6066

0.098

2.72

6070

0.098

2.71

6101

0.097

2.70

6105

0.097

2.69

6151

0.098

2.71

6162

0.097

2.70

6201

0.097

2.69

6262

0.098

2.72

6351

0.098

2.71

6463

0.097

2.69

6951

0.098

2.70

7005

0.100

2.78

7008

0.100

2.78

7049

0.103

2.84

7050

0.102

2.83

7072

0.098

2.72

7075

0.101

2.81

7178

0.102

2.83

8017

0.098

2.71

8030

0.098

2.71

8176

0.098

2.71

8177

0.098

2.70

Table 2 Typical physical properties of wrought aluminum alloys

Alloy

1060

1100

Average coefficient of thermal expansion(a)

Approximate melting range(b)(c)

m· °C

in./in. · °F

°C

°F

23.6

13.1

645655

11951215

23.6

13.1

643655

11901215

Temper

Thermal conductivity at 25 °C (77 °F)

Electrical conductivity at 20 °C (68 °F), %IACS

Electrical resistivity at 20 °C (68 °F)

W/m · °C

Btu · in./ft2 · h · °F

Equal volume

Equal weight

· mm2/m

· circ mil/ft

O

234

1625

62

204

0.028

17

H18

230

1600

61

201

0.028

17

O

222

1540

59

194

0.030

18

H18

218

1510

57

187

0.030

18

1350

23.75

13.2

645655

11951215

All

234

1625

62

204

0.028

17

2011

22.9

12.7

540643(d)

10051190(d)

T3

151

1050

39

123

0.045

27

T8

172

1190

45

142

0.038

23

O

193

1340

50

159

0.035

21

T4

134

930

34

108

0.0515

31

T6

154

1070

40

127

0.043

26

OH

193

1340

50

159

0.035

21

T4

134

930

34

108

0.0515

31

2014

2017

23.0

23.6

12.8

13.1

507638(e)

513640(e)

9451180(e)

9551185(e)

2018

22.3

12.4

507638(d)

9451180(d)

T61

154

1070

40

127

0.043

26

2024

23.2

12.9

500638(e)

9351180(e)

O

193

1340

50

160

0.035

21

T3, T4, T361

121

840

30

96

0.058

35

T6, T81, T861

151

1050

38

122

0.045

27

2025

22.7

12.6

520640(e)

9701185(e)

T6

154

1070

40

128

0.043

26

2036

23.4

13.0

555650(d)

10301200(d)

T4

159

1100

41

135

0.0415

25

2117

23.75

13.2

555650(d)

10301200(d)

T4

154

1070

40

130

0.043

26

2124

22.9

12.7

500638(e)

9351180(e)

T851

152

1055

38

122

0.045

27

2218

22.3

12.4

505635(e)

9401175(e)

T72

154

1070

40

126

0.043

26

2219

22.3

12.4

543643(e)

10101190(e)

O

172

1190

44

138

0.040

24

T31, T37

112

780

28

88

0.0615

37

T6, T81, T87

121

840

30

94

0.058

35

2618

22.3

12.4

550638

10201180

T6

147

1020

37

120

0.0465

28

3003

23.2

12.9

643655

11901210

O

193

1340

50

163

0.035

21

H12

163

1130

42

137

0.0415

25

H14

159

1100

41

134

0.0415

25

H18

154

1070

40

130

0.043

26

3004

23.9

13.3

630655

11651210

All

163

1130

42

137

0.0415

25

3105

23.6

13.1

635655

11751210

All

172

1190

45

148

0.038

23

4032

19.4

10.8

532570(e)

9901060(e)

O

154

1070

40

132

0.043

26

T6

138

960

35

116

0.050

30

O

163

1130

42

140

0.0415

25

4043

22.1

12.3

575632

10651170

4045

21.05

11.7

575600

10651110

All

172

1190

45

151

0.038

23

4343

21.6

12.0

577613

10701135

All

180

1250

42

158

0.0415

25

5005

23.75

13.2

632655

11701210

All

200

1390

52

172

0.033

20

5050

23.75

13.2

625650

11551205

All

193

1340

50

165

0.035

21

5052

23.75

13.2

607650

11251200

All

138

960

35

116

0.050

30

5056

24.1

13.4

568638

10551180

O

117

810

29

98

0.060

36

H38

108

750

27

91

0.063

38

5083

23.75

13.2

590638

10951180

O

117

810

29

98

0.060

36

5086

23.75

13.2

585640

10851185

All

125

870

31

104

0.055

33

5154

23.9

13.3

593643

11001190

All

125

870

32

107

0.053

32

5252

23.75

13.2

607650

11251200

All

138

960

35

116

0.050

30

5254

23.9

13.3

593643

11001190

All

125

870

32

107

0.053

32

5356

24.1

13.4

570635

10601175

O

117

810

29

98

0.060

36

5454

23.6

13.1

600645

11151195

O

134

930

34

113

0.0515

31

H38

134

930

34

113

0.0515

31

5456

23.9

13.3

568638

10551180

O

117

810

29

98

0.060

36

5457

23.75

13.2

630655

11651210

All

176

1220

46

153

0.038

23

5652

23.75

13.2

607650

11251200

All

138

960

35

116

0.050

30

5657

23.75

13.2

638657

11801215

All

205

1420

54

180

0.0315

19

6005

23.4

13.0

610655(d)

11251210(d)

T1

180

1250

47

155

0.0365

22

T5

190

1310

49

161

0.035

21

O

172

1190

45

148

0.038

23

T4

154

1070

40

132

0.043

26

T6

163

1130

42

139

0.0415

25

O

180

1250

47

155

0.0365

22

T4

154

1070

40

132

0.043

26

T6

167

1160

43

142

0.040

24

O

218

1510

58

191

0.030

18

T1

193

1340

50

165

0.035

21

T5

209

1450

55

181

0.032

19

T6, T83

200

1390

53

175

0.033

20

O

154

1070

40

132

0.043

26

T6

147

1020

37

122

0.0465

28

6053

6061

6063

6066

23

23.6

23.4

23.2

12.8

13.1

13.0

12.9

575650(d)

580650(d)

615655

565645(e)

10701205(d)

10801205(d)

11401210

10451195(e)

6070

...

...

565650(e)

10501200(e)

T6

172

1190

44

145

0.040

24

6101

23.4

13.0

620655

11501210

T6

218

1510

57

188

0.030

18

T61

222

1540

59

194

0.030

18

T63

218

1510

58

191

0.030

18

6105

6151

23.4

23.2

13.0

12.9

600650(d)

590650(d)

11101200(d)

10901200(d)

T64

226

1570

60

198

0.028

17

T65

218

1510

58

191

0.030

18

T1

176

1220

46

151

0.038

23

T5

193

1340

50

165

0.035

21

O

205

1420

54

178

0.0315

19

T4

163

1130

42

138

0.0415

25

T6

172

1190

45

148

0.038

23

6201

23.4

13.0

607655(d)

11251210(d)

T81

205

1420

54

180

0.0315

19

6253

...

...

600650

11001205

...

...

...

...

...

...

...

6262

23.4

13.0

580650(d)

10801205(d)

T9

172

1190

44

145

0.040

24

6351

23.4

13.0

555650

10301200

T6

176

1220

46

151

0.038

23

6463

23.4

13.0

615655

11401210

T1

193

1340

50

165

0.035

21

T5

209

1450

55

181

0.0315

19

T6

200

1390

53

175

0.033

20

O

213

1480

56

186

0.0315

19

T6

198

1370

52

172

0.033

20

6951

23.4

13.0

615655

11401210

7049

23.4

13.0

475635

8901175

T73

154

1070

40

132

0.043

26

7050

24.1

13.4

490630

9101165

T74(f)

157

1090

41

135

0.0415

25

7072

23.6

13.1

640-

1185-

O

222

1540

59

193

0.030

18

655

1215

7075

23.6

13.1

475635(g)

8901175(g)

T6

130

900

3

105

0.0515

31

7175

23.4

13.0

475635(g)

8901175(g)

T74

156

1080

39

124

0.043

26

7178

23.4

13.0

475630(g)

8901165(g)

T6

125

870

31

98

0.055

33

7475

23.2

12.9

475635(g)

8901175(g)

T61, T651

138

960

35

116

0.050

30

T76, T761

147

1020

40

132

0.043

26

T7351

163

1130

42

139

0.0415

25

H12, H22

...

...

59

193

0.030

18

H212

...

...

61

200

0.028

17

8017

23.6

13.1

645655

11901215

8030

23.6

13.1

645655

11901215

H221

230

1600

61

201

0.028

17

8176

23.6

13.1

645655

11901215

H24

230

1600

61

201

0.028

17

(a) Coefficient from 20 to 100 °C (68 to 212 °F).

(b) Melting ranges shown apply to wrought products of 6.35 mm (

in.) thickness or greater.

(c) Based on typical composition of the indicated alloys.

(d) Eutectic melting can be completely eliminated by homogenization.

(e) Eutectic melting is not eliminated by homogenization.

(f) Although not formerly registered, the literature and some specifications have used T736 as the designation for this temper.

(g) Homogenization can raise eutectic melting temperature 10 to 20 °C (20 to 40 °F) but usually does not eliminate eutectic melting.

Table 3 Typical mechanical properties of wrought aluminum and aluminum alloys The following typical properties are not guaranteed, because in most cases they are averages for various sizes, product forms, and

methods of manufacture and may not be exactly representative of any one particular product or size. The data are intended only as a basis for comparing alloys and tempers and should not be specified as engineering requirements or used for design purposes. Alloy and temper

Ultimate tensile strength

MPa

Tensile yield strength

ksi

MPa

Elongation in 50 mm (2 in.), %

ksi

Hardness, HB(a)

1.6 mm ( in.) thick specimen

1.3 mm ( in.) diam specimen

Ultimate Shearing strength

Fatigue endurance limit(b)

Modulus of elasticity(c)

MPa

ksi

MPa

ksi

GPa

106 psi

1060-O

70

10

30

4

43

...

19

50

7

20

3

69

10.0

1060-H12

85

12

75

11

16

...

23

55

8

30

4

69

10.0

1060-H14

95

14

90

13

12

...

26

60

9

35

5

69

10.0

1060-H16

110

16

105

15

8

...

30

70

10

45

6.5

69

10.0

1060-H18

130

19

125

18

6

...

35

75

11

45

6.5

69

10.0

1100-O

90

13

35

5

35

45

23

60

9

35

5

69

10.0

1100-H12

110

16

105

15

12

25

28

70

10

40

6

69

10.0

1100-H14

125

18

115

17

9

20

32

75

11

50

7

69

10.0

1100-H16

145

21

140

20

6

17

38

85

12

60

9

69

10.0

1100-H18

165

24

150

22

5

15

44

90

13

60

9

69

10.0

1350-O

85

12

30

4

...

(d)

...

55

8

...

...

69

10.0

1350-H12

95

14

85

12

...

...

...

60

9

...

...

69

10.0

1350-H14

110

16

95

14

...

...

...

70

10

...

...

69

10.0

1350-H16

125

18

110

16

...

...

...

75

11

...

...

69

10.0

1350-H19

185

27

165

24

...

(e)

...

105

15

50

7

69

10.0

2011-T3

380

55

295

43

...

15

95

220

32

125

18

70

10.2

2011-T8

405

59

310

45

...

12

100

240

35

125

18

70

10.2

2014-O

185

27

95

14

...

18

45

125

18

90

13

73

10.6

2014-T4, T451

425

62

290

42

...

20

105

260

38

140

20

73

10.6

2014-T6, T651

485

70

415

60

...

13

135

290

42

125

18

73

10.6

Alclad 2014O

175

25

70

10

21

...

...

125

18

...

...

72

10.5

Alclad 2014T3

435

63

275

40

20

...

...

255

37

...

...

72

10.5

Alclad 2014T4, T451

420

61

255

37

22

...

...

255

37

...

...

72

10.5

Alclad 2014T6, T651

470

68

415

60

10

...

...

285

41

...

...

72

10.5

2017-O

180

26

70

10

...

22

45

125

18

90

13

72

10.5

2017-T4, T451

425

61

255

37

22

...

...

255

37

...

...

72

10.5

2018-T61

420

61

315

46

...

12

120

270

39

115

17

74

10.8

2024-O

185

27

75

11

20

22

47

125

18

90

13

73

10.6

2024-T3

485

70

345

50

18

...

120

285

41

140

20

73

10.6

2024-T4, T351

470

68

325

47

20

19

120

285

41

140

20

73

10.6

2024-T361(f)

495

72

395

57

13

...

130

290

42

125

18

73

10.6

Alclad 2024O

180

26

75

11

20

...

...

125

18

...

...

73

10.6

Alclad 2024T3

450

65

310

45

18

...

...

275

40

...

...

73

10.6

Alclad 2024-

440

64

290

42

19

...

...

275

40

...

...

73

10.6

T4, T351

Alclad 2024T361(f)

460

67

365

53

11

...

...

285

41

...

...

73

10.6

Alclad 2024T81, T851

450

65

415

60

6

...

...

275

40

...

...

73

10.6

Alclad 2024T861(f)

485

70

455

66

6

...

...

290

42

...

...

73

10.6

2025-T6

400

58

255

37

...

19

110

240

35

125

18

71

10.4

2036-T4

340

49

195

28

24

...

...

...

...

125 (g)

18(g)

71

10.3

2117-T4

295

43

165

24

...

27

70

195

28

95

14

71

10.3

2124-T851

485

70

440

64

...

8

...

...

...

...

...

73

10.6

2218-T72

330

48

255

37

...

11

95

205

30

...

...

74

10.8

2219-O

175

25

75

11

18

...

...

...

...

...

...

73

10.6

2219-T42

360

52

185

27

20

...

...

...

...

...

...

73

10.6

2219-T31, T351

360

52

250

36

17

...

...

...

...

...

...

73

10.6

2219-T37

395

57

315

46

11

...

...

...

...

...

...

73

10.6

2219-T62

415

60

290

42

10

...

...

...

...

105

15

73

10.6

2219-T81, T851

455

66

350

51

10

...

...

...

...

105

15

73

10.6

2219-T87

475

69

395

57

10

...

...

...

...

105

15

73

10.6

2618-T61

440

64

370

54

...

10

115

260

38

125

18

74

10.8

3003-O

110

16

40

6

30

40

28

75

11

50

7

69

10.0

3003-H12

130

19

125

18

10

20

35

85

12

55

8

69

10.0

3003-H14

150

22

145

21

8

16

40

95

14

60

9

69

10.0

3003-H16

180

26

170

25

5

14

47

105

15

70

10

69

10.0

3003-H18

200

29

185

27

4

10

55

110

16

70

10

69

10.0

Alclad 3003O

110

16

40

6

30

40

...

75

11

...

...

...

...

Alclad 3003H12

130

19

125

18

10

20

...

85

12

...

...

69

10.0

Alclad 3003H14

150

22

145

21

8

16

...

95

14

...

...

69

10.0

Alclad 3003H16

180

26

170

25

5

14

...

105

15

...

...

69

10.0

Alclad 3003H18

200

29

185

27

4

10

...

110

16

...

...

69

10.0

3004-O

180

26

70

10

20

25

45

110

16

95

14

69

10.0

3004-H32

215

31

170

25

10

17

52

115

17

105

15

69

10.0

3004-H34

240

35

200

29

9

12

63

125

18

105

15

69

10.0

3004-H36

260

38

230

33

5

9

70

140

20

110

16

69

10.0

3004-H38

285

41

250

36

5

6

77

145

21

110

16

69

10.0

Alclad 3004O

180

26

70

10

20

25

...

110

16

...

...

69

10.0

Alclad 3004H32

215

31

170

25

10

17

...

115

17

...

...

69

10.0

Alclad 3004H34

240

35

200

29

9

12

...

125

18

...

...

69

10.0

Alclad 3004H36

260

38

230

33

5

9

...

140

20

...

...

69

10.0

Alclad 3004H38

285

41

250

36

5

6

...

145

21

...

...

69

10.0

3105-O

115

17

55

8

24

...

...

85

12

...

...

69

10.0

3105-H12

150

22

130

19

7

...

...

95

14

...

...

69

10.0

3105-H14

170

25

150

22

5

...

...

105

15

...

...

69

10.0

3105-H16

195

28

170

25

4

...

...

110

16

...

...

69

10.0

3105-H18

215

31

195

28

3

...

...

115

17

...

...

69

10.0

3105-H25

180

26

160

23

8

...

...

105

15

...

...

69

10.0

4032-T6

380

55

315

46

...

9

120

260

38

110

16

79

11.4

5005-O

125

18

40

6

25

...

28

75

11

...

...

69

10.0

5005-H12

140

20

130

19

10

...

...

95

14

...

...

69

10.0

5005-H14

160

23

150

22

6

...

...

95

14

...

...

69

10.0

5005-H16

180

26

170

25

5

...

...

105

15

...

...

69

10.0

5005-H18

200

29

195

28

4

...

...

110

16

...

...

69

10.0

5005-H32

140

20

115

17

11

...

36

95

14

...

...

69

10.0

5005-H34

160

23

140

20

8

...

41

95

14

...

...

69

10.0

5005-H36

180

26

165

24

6

...

46

105

15

...

...

69

10.0

5005-H38

200

29

185

27

5

...

51

110

16

...

...

69

10.0

5050-O

145

21

55

8

24

...

36

105

15

85

12

69

10.0

5050-H32

170

25

145

21

9

...

46

115

17

90

13

69

10.0

5050-H34

195

28

165

24

8

...

53

125

18

90

13

69

10.0

5050-H36

205

30

180

26

7

...

58

130

19

95

14

69

10.0

5050-H38

220

32

200

29

6

...

63

140

20

95

14

69

10.0

5052-O

195

28

90

13

25

30

47

125

18

110

16

70

10.2

5052-H32

230

33

195

28

12

18

60

140

20

115

17

70

10.2

5052-H34

260

38

215

31

10

14

68

145

21

125

18

70

10.2

5052-H36

275

40

240

35

8

10

73

160

23

130

19

70

10.2

5052-H38

290

42

255

37

7

8

77

165

24

140

20

70

10.2

5056-O

290

42

150

22

...

35

65

180

26

140

20

71

10.3

5056-H18

435

63

405

59

...

10

105

235

34

150

22

71

10.3

5056-H38

415

60

345

50

...

15

100

220

32

150

22

71

10.3

5083-O

290

42

145

21

...

22

...

170

25

...

...

71

10.3

5083-H321, H116

315

46

230

33

...

16

...

...

...

160

23

71

10.3

5086-O

260

38

115

17

22

...

...

160

23

...

...

71

10.3

5086-H32, H116

290

42

205

30

12

...

...

...

...

...

...

71

10.3

5086-H34

325

47

255

37

10

...

...

185

27

...

...

71

10.3

5086-H112

270

39

130

19

14

...

...

...

...

...

...

71

10.3

5154-O

240

35

115

17

27

...

58

150

22

115

17

70

10.2

5154-H32

270

39

205

30

15

...

67

150

22

125

18

70

10.2

5154-H34

290

42

230

33

13

...

73

165

24

130

19

70

10.2

5154-H36

310

45

250

36

12

...

78

180

26

140

20

70

10.2

5154-H38

330

48

270

39

10

...

80

195

28

145

21

70

10.2

5154-H112

240

35

115

17

25

...

63

...

...

115

17

70

10.2

5252-H25

235

34

170

25

11

...

68

145

21

...

...

69

10.0

5252-H38, H28

285

41

240

35

5

...

75

160

23

...

...

69

10.0

5254-O

240

35

115

17

27

...

58

150

22

115

17

70

10.2

5254-H32

270

39

205

30

15

...

67

150

22

125

18

70

10.2

5254-H34

290

42

230

33

13

...

73

165

24

130

19

70

10.2

5254-H36

310

45

250

36

12

...

78

180

26

140

20

70

10.2

5254-H38

330

48

270

39

10

...

80

195

28

145

21

70

10.2

5254-H112

240

35

115

17

25

...

63

...

...

115

17

70

10.2

5454-O

250

36

115

17

22

...

62

160

23

...

...

70

10.2

5454-H32

275

40

205

30

10

...

73

165

24

...

...

70

10.2

5454-H34

305

44

240

35

10

...

81

180

26

...

...

70

10.2

5454-H111

260

38

180

26

14

...

70

160

23

...

...

70

10.2

5454-H112

250

36

125

18

18

...

62

160

23

...

...

70

10.2

5456-O

310

45

160

23

...

24

...

...

...

...

...

71

10.3

5456-H112

310

45

165

24

...

22

...

...

...

...

...

71

10.3

5456-H321, H116

350

51

255

37

...

16

90

205

30

...

...

71

10.3

5457-O

130

19

50

7

22

...

32

85

12

...

...

69

10.0

5457-H25

180

26

160

23

12

...

48

110

16

...

...

69

10.0

5457-H38, H28

205

30

185

27

6

...

55

125

18

...

...

69

10.0

5652-O

195

28

90

13

25

30

47

125

18

110

16

70

10.2

5652-H32

230

33

195

28

12

18

60

140

20

115

17

70

10.2

5652-H34

260

38

215

31

10

14

68

145

21

125

18

70

10.2

5652-H36

275

40

240

35

8

10

73

160

23

130

19

70

10.2

5652-H38

290

42

255

37

7

8

77

165

24

140

20

70

10.2

5657-H25

160

23

140

20

12

...

40

95

14

...

...

69

10.0

5657-H38, H28

195

28

165

24

7

...

50

105

15

...

...

69

10.0

6061-O

125

18

55

8

25

30

30

85

12

60

9

69

10.0

6061-T4, T451

240

35

145

21

22

25

65

165

24

95

14

69

10.0

6061-T6, T651

310

45

275

40

12

17

95

205

30

95

14

69

10.0

Alclad 6061O

115

17

50

7

25

...

...

75

11

...

...

69

10.0

Alclad 6061T4, T451

230

33

130

19

22

...

...

150

22

...

...

69

10.0

Alclad 6061T6, T651

290

42

255

37

12

...

...

185

27

...

...

69

10.0

6063-O

90

13

50

7

...

...

25

70

10

55

8

69

10.0

6063-T1

150

22

90

13

20

...

42

95

14

60

9

69

10.0

6063-T4

170

25

90

13

22

...

...

...

...

...

...

69

10.0

6063-T5

185

27

145

21

12

...

60

115

17

70

10

69

10.0

6063-T6

240

35

215

31

12

...

73

150

22

70

10

69

10.0

6063-T83

255

37

240

35

9

...

82

150

22

...

...

69

10.0

6063-T831

205

30

185

27

10

...

70

125

18

...

...

69

10.0

6063-T832

290

42

270

39

12

...

95

185

27

...

...

69

10.0

6066-O

150

22

85

12

...

18

43

95

14

...

...

69

10.0

6066-T4, T451

360

52

205

30

...

18

90

200

29

...

...

69

10.0

6066-T6, T651

395

57

360

52

...

12

120

235

34

110

16

69

10.0

6070-T6

380

55

350

51

10

...

...

235

34

95

14

69

10.0

6101-H111

95

14

75

11

...

...

...

...

...

...

...

69

10.0

6101-T6

220

32

195

28

15

...

71

140

20

...

...

69

10.0

6262-T9

400

58

380

55

...

10

120

240

35

90

13

69

10.0

6351-T4

250

36

150

22

20

...

...

...

...

...

...

69

10.0

6351-T6

310

45

285

41

14

...

95

200

29

90

13

69

10.0

6463-T1

150

22

90

13

20

...

42

95

14

70

10

69

10.0

6463-T5

185

27

145

21

12

...

60

115

17

70

10

69

10.0

6463-T6

240

35

215

31

12

...

74

150

22

70

10

69

10.0

7049-T73

515

75

450

65

...

12

135

305

44

...

...

72

10.4

7049-T7352

515

75

435

63

...

11

135

295

43

...

...

72

10.4

7050-T73510, T73511

495

72

435

63

...

12

...

...

...

...

...

72

10.4

7050-T7451(h)

525

76

470

68

...

11

...

305

44

...

...

72

10.4

7050-T7651

550

80

490

71

...

11

...

325

47

...

...

72

10.4

7075-O

230

33

105

15

17

16

60

150

22

...

...

72

10.4

7075-T6,

570

83

505

73

11

11

150

330

48

160

23

72

10.4

T651

Alclad 7075O

220

32

95

14

17

...

...

150

22

...

...

72

10.4

Alclad 7075T6, T651

525

76

460

67

11

...

...

315

46

...

...

72

10.4

7175-T74

525

76

455

66

...

11

135

290

42

160

23

72

10.4

7178-O

230

33

105

15

15

16

...

...

...

...

...

72

10.4

7178-T6, T651

605

88

540

78

10

11

...

...

...

...

...

72

10.4

7178-T76, T7651

570

83

505

73

...

11

...

...

...

...

...

71

10.3

Alclad 7178O

220

32

95

14

16

...

...

...

...

...

...

72

10.4

Alclad 7178T6, T651

560

81

490

71

10

...

...

...

...

...

...

72

10.4

7475-T61

565

82

490

71

11

...

...

...

...

...

...

70

10.2

7475-T651

585

85

510

74

...

13

...

...

...

...

...

72

10.4

7475-T7351

495

72

420

61

...

13

...

...

...

...

...

72

10.4

7475-T761

515

75

450

65

12

...

...

...

...

...

...

70

10.2

7475-T7651

530

77

460

67

...

12

...

...

...

...

...

72

10.4

Alclad 7475T61

515

75

455

66

11

...

...

...

...

...

...

70

10.2

Alclad 7475T761

490

71

420

61

12

...

...

...

...

...

...

70

10.2

8176-H24

115

17

95

14

15

...

...

70

10

...

...

69

10.0

(a) 500 kg load and 10 mm ball.

(b) Based on 500,000,000 cycles of completely reversed stress using the R.R. Moore type machine and specimen.

(c) Average of tension and compression moduli. Compression modulus is

(d) 1350-0 wire will have an elongation of

2% greater than tension modulus.

23% in 250 mm (10 in.).

(e) 1350-H19 wire will have an elongation of approximately 1

% in 250 mm (10 in.).

(f) Tempers T361 and T861 were formerly designated T36 and T86, respectively.

(g) Based on 107 cycles using flexural type testing of sheet specimens.

(h) T7451, although not previously registered, has appeared in literature and in some specifications as T73651.

Table 4 Effect of temperature on the tensile strengths of wrought aluminum and aluminum alloys Alloy and temper

Ultimate tensile strength(a), MPa (ksi), at:

-195 °C (320 °F)

-80 °C (112 °F)

-30 °C (18 °F)

24 °C (75 °F)

100 °C (212 °F)

150 °C (300 °F)

205 °C (400 °F)

260 °C (500 °F)

315 °C (600 °F)

370 °C (700 °F)

1100-O

172 (25)

103 (15)

97 (14)

90 (13)

70 (10)

55 (8)

40 (6)

28 (4)

20 (2.9)

14 (2.1)

1100-H14

207 (30)

138 (20)

130 (19)

125 (18)

110 (16)

97 (14)

70 (10)

28 (4)

20 (2.9)

14 (2.1)

1100-H18

235 (34)

180 (26)

172 (25)

165 (24)

145 (21)

125 (18)

40 (6)

28 (4)

20 (2.9)

14 (2.1)

2011-T3

...

...

...

380 (55)

325 (47)

193 (28)

110 (16)

45 (6.5)

21 (3.1)

16 (2.3)

2014-T6, T651

580 (84)

510 (74)

495 (72)

483 (70)

435 (63)

275 (40)

110 (16)

66 (9.5)

45 (6.5)

30 (4.3)

2017-T4, T451

550 (80)

448 (65)

440 (64)

427 (62)

393 (57)

275 (40)

110 (16)

62 (9)

40 (6)

30 (4.3)

2024-T3 (sheet)

585 (85)

503 (73)

495 (72)

483 (70)

455 (66)

380 (55)

185 (27)

75 (11)

52 (7.5)

35 (5)

2024-T4, T351 (plate)

580 (84)

490 (71)

475 (69)

470 (68)

435 (63)

310 (45)

180 (26)

75 (11)

52 (7.5)

35 (5)

2024-T6, T651

580 (84)

495 (72)

483 (70)

475 (69)

448 (65)

310 (45)

180 (26)

75 (11)

52 (7.5)

35 (5)

2024-T81, T851

585 (85)

510 (74)

503 (73)

483 (70)

455 (66)

380 (55)

185 (27)

75 (11)

52 (7.5)

35 (5)

2024-T861

635 (92)

558 (81)

538 (78)

517 (75)

483 (70)

372 (54)

145 (21)

75 (11)

52 (7.5)

35 (5)

2117-T4

385 (56)

310 (45)

303 (44)

295 (43)

248 (36)

207 (30,)

110 (16)

52 (7.5)

32 (4.7)

20 (2.9)

2124-T851

593 (86)

525 (76)

503 (73)

483 (70)

455 (66)

372 (54)

185 (27)

75 (11)

52 (7.5)

38 (5.5)

2218-T61

495 (72)

420 (61)

407 (59)

407 (59)

385 (56)

283 (41)

152 (22)

70 (10)

38 (5.5)

28 (4)

2219-T62

503 (73)

435 (63)

415 (60)

400 (58)

372 (54)

310 (45)

235 (34)

185 (27)

70 (10)

30 (4.4)

2219-T81, T851

572 (83)

490 (71)

475 (69)

455 (66)

415 (60)

338 (49)

248 (36)

200 (29)

48 (7)

30 (4.4)

2618-T61

538 (78)

462 (67)

440 (64)

440 (64)

427 (62)

345 (50)

220 (32)

90 (13)

52 (7.5)

35 (5)

3003-O

228 (33)

138 (20)

117 (17)

110 (16)

90 (13)

75 (11)

59 (8.5)

40 (6)

28 (4)

19 (2.8)

3003-H14

240 (35)

165 (24)

152 (22)

152 (22)

145 (21)

125 (18)

97 (14)

52 (7.5)

28 (4)

19 (2.8)

3003-H18

283 (41)

220 (32)

207 (30)

200 (29)

180 (26)

160 (23)

97 (14)

52 (7.5)

28 (4)

19 (2.8)

3004-O

290 (42)

193 (28)

180 (26)

180 (26)

180 (26)

152 (22)

97 (14)

70 (10)

52 (7.5)

35 (5)

3004-H34

360 (52)

262 (38)

248 (36)

240 (35)

235 (34)

193 (28)

145 (21)

97 (14)

52 (7.5)

35 (5)

3004-H38

400 (58)

303 (44)

290 (42)

283 (41)

275 (40)

215 (31)

152 (22)

83 (12)

52 (7.5)

35 (5)

4032-T6

455 (66)

400 (58)

385 (56)

380 (55)

345 (50)

255 (37)

90 (13)

55 (8)

35 (5)

23 (3.4)

5050-O

255 (37)

152 (22)

145 (21)

145 (21)

145 (21)

130 (19)

97 (14)

62 (9)

40 (6)

27 (3.9)

5050-H34

303 (44)

207 (30)

193 (28)

193 (28)

193 (28)

172 (25)

97 (14)

62 (9)

40 (6)

27 (3.9)

5050-H38

317 (46)

235 (34)

220 (32)

220 (32)

215 (31)

185 (27)

97 (14)

62 (9)

40 (6)

27 (3.9)

5052-O

303 (44)

200 (29)

193 (28)

193 (28)

193 (28)

160 (23)

117 (17)

83 (12)

52 (7.5)

35 (5)

5052-H34

380 (55)

275 (40)

262 (38)

262 (38)

262 (38)

207 (30)

165 (24)

83 (12)

52 (7.5)

35 (5)

5052-H38

415 (60)

303 (44)

290 (42)

290 (42)

275 (40)

235 (34)

172 (25)

83 (12)

52 (7.5)

35 (5)

5083-O

407 (59)

295 (43)

290 (42)

290 (42)

275 (40)

215 (31)

152 (22)

117 (17)

75 (11)

40 (6)

5086-O

380 (55)

270 (39)

262 (38)

262 (38)

262 (38)

200 (29)

152 (22)

117 (17)

75 (11)

40 (6)

5154-O

360 (52)

248 (36)

240 (35)

240 (35)

240 (35)

200 (29)

152 (22)

117 (17)

75 (11)

40 (6)

5254-O

360 (52)

248 (36)

240 (35)

240 (35)

240 (35)

200 (29)

152 (22)

117 (17)

75 (11)

40 (6)

5454-O

372 (54)

255 (37)

248 (36)

248 (36)

248 (36)

200 (29)

152 (22)

117 (17)

75 (11)

40 (6)

5454-H32

407 (59)

290 (42)

283 (41)

275 (40)

270 (39)

220 (32)

172 (25)

117 (17)

75 (11)

40 (6)

5454-H34

435 (63)

317 (46)

303 (44)

303 (44)

295 (43)

235 (34)

180 (26)

117 (17)

75 (11)

40 (6)

5456-O

427 (62)

317 (46)

310 (45)

310 (45)

290 (42)

215 (31)

152 (22)

117 (17)

75 (11)

40 (6)

5652-O

303 (44)

200 (29)

193 (28)

193 (28)

193 (28)

160 (23)

117 (17)

83 (12)

52 (7.5)

35 (5)

5652-H34

380 (55)

275 (40)

262 (38)

262 (38)

262 (38)

207 (30)

165 (24)

83 (12)

52 (7.5)

35 (5)

5456-O

427 (62)

317 (46)

310 (45)

310 (45)

290 (42)

215 (31)

152 (22)

117 (17)

75 (11)

40 (6)

5652-O

303 (44)

200 (29)

193 (28)

193 (28)

193 (28)

160 (23)

117 (17)

83 (12)

52 (7.5)

35 (5)

5652-H34

380 (55)

275 (40)

262 (38)

262 (38)

262 (38)

207 (30)

165 (24)

83 (12)

52 (7.5)

35 (5)

5652-H38

415 (60)

303 (44)

290 (42)

290 (42)

275 (40)

235 (34)

172 (25)

83 (12)

52 (7.5)

35 (5)

6053-T6, T651

...

...

...

255 (37)

220 (32)

172 (25)

90 (13)

38 (5.5)

28 (4)

20 (2.9)

6061-T6, T651

415 (60)

338 (49)

325 (47)

310 (45)

290 (42)

235 (34)

130 (19)

52 (7.5)

32 (4.6)

21 (3)

6063-T1

235 (34)

180 (26)

165 (24)

152 (22)

152 (22)

145 (21)

62 (9)

31 (4.5)

22 (3.2)

16 (2.3)

6063-T5

255 (37)

200 (29)

193 (28)

185 (27)

165 (24)

138 (20)

62 (9)

31 (4.5)

22 (3.2)

16 (2.3)

6063-T6

325 (47)

262 (38)

248 (36)

240 (35)

215 (31)

145 (21)

62 (9)

31 (4.5)

22 (3.2)

16 (2.3)

6101-T6

295 (43)

248 (36)

235 (34)

220 (32)

193 (28)

145 (21)

70 (10)

33 (4.8)

21 (3)

17 (2.5)

6151-T6

393 (57)

345 (50)

338 (49)

330 (48)

295 (43)

193 (28)

97 (14)

45 (6.5)

33 (5)

28 (4)

6262-T651

415 (60)

338 (49)

325 (47)

310 (45)

290 (42)

235 (34)

...

...

...

...

6262-T9

510 (74)

427 (62)

415 (60)

400 (58)

365 (53)

262 (38)

103 (15)

59 (8.5)

32 (4.6)

21 (3)

7075-T6, T651

703 (102)

620 (90)

593 (86)

572 (83)

483 (70)

215 (31)

110 (16)

75 (11)

55 (8)

40 (6)

7075-T73, T7351

635 (92)

545 (79)

525 (76)

503 (73)

435 (63)

215 (31)

110 (16)

75 (11)

55 (8)

40 (6)

7178-T6, T651

730 (106)

648 (94)

627 (91)

607 (88)

503 (73)

215 (31)

103 (15)

75 (11)

59 (8.5)

45 (6.5)

7178-T76, T7651

730 (106)

627 (91)

607 (88)

572 (83)

475 (69)

215 (31)

103 (15)

75 (11)

59 (8.5)

45 (6.5)

(a) These data are based on a limited amount of testing and represent the lowest strength during 10,000 h of exposure at testing temperature under no load; stress applied at 34 MPa/min (5000 psi/min) to yield strength and then at strain rate of 0.05 mm/mm per min (0.05 in./in. per min) to failure. Under some conditions of temperature and time, the application of heat will adversely affect certain other properties of some alloys.

Fig. 1 Smooth and notched axial stress fatigue data for 7050-T7451 plate, 1 to 6 in. (25 to 152 mm) thick, shown in relation to bands established for 7075 wrought products in T6 and T73xx tempers

Fig. 2 Smooth and notched axial stress fatigue data for 7050-T7452 hand forgings, 4 559 × 2133 mm)

× 22 × 84 in. (144 ×

Fig. 3 Smooth and notched axial stress fatigue data for 7050-T7651x extruded shapes, 1.161 in. (29.5 mm) thick

Table 5 Effect of temperature on the yield strengths of wrought aluminum and aluminum alloys Alloy temper

and

0.2% offset yield strength(a), MPa (ksi), at:

-195 °C (320 °F)

-80 °C (112 °F)

-30 °C (18 °F)

24 °C (75 °F)

100 °C (212 °F)

150 °C (300 °F)

205 °C (400 °F)

260 °C (500 °F)

315 °C (600 °F)

370 °C (700 °F)

1100-O

40 (6)

38 (5.5)

35 (5)

35 (5)

32 (4.6)

29 (4.2)

24 (3.5)

18 (2.6)

14 (2)

11 (1.6)

1100-H14

138 (20)

125 (18)

117 (17)

117 (17)

103 (15)

83 (12)

52 (7.5)

18 (2.6)

14 (2)

11 (1.6)

1100-H18

180 (26)

160 (23)

160 (23)

152 (22)

130 (19)

97 (14)

24 (3.5)

18 (2.6)

14 (2)

11 (1.6)

2011-T3

...

...

...

295 (43)

235 (34)

130 (19)

75 (11)

26 (3.8)

12 (1.8)

10 (1.4)

2014-T6, T651

495 (72)

448 (65)

427 (62)

415 (60)

393 (57)

240 (35)

90 (13)

52 (7.5)

35 (5)

24 (3.5)

2017-T4, T451

365 (53)

290 (42)

283 (41)

275 (40)

270 (39)

207 (30)

90 (13)

52 (7.5)

35 (5)

24 (3.5)

2024-T3 (sheet)

427 (62)

360 (52)

352 (51)

345 (50)

330 (48)

310 (45)

138 (20)

62 (9)

40 (6)

28 (4)

2024-T4, T351 (plate)

420 (61)

338 (49)

325 (47)

325 (47)

310 (45)

248 (36)

130 (19)

62 (9)

40 (6)

28 (4)

2024-T6, T651

470 (68)

407 (59)

400 (58)

393 (57)

372 (54)

248 (36)

130 (19)

62 (9)

40 (6)

28 (4)

2024-T81, T851

538 (78)

475 (69)

470 (68)

448 (65)

427 (62)

338 (49)

138 (20)

62 (9)

40 (6)

28 (4)

2024-T861

585 (85)

530 (77)

510 (74)

490 (71)

462 (67)

330 (48)

117 (17)

62 (9)

40 (6)

28 (4)

2117-T4

228 (33)

172 (25)

165 (24)

165 (24)

145 (21)

117 (17)

83 (12)

38 (5.5)

23 (3.3)

14 (2)

2124-T851

545 (79)

490 (71)

470 (68)

440 (64)

420 (61)

338 (49)

138 (20)

55 (8)

40 (6)

28 (4.1)

2218-T61

360 (52)

310 (45)

303 (44)

303 (44)

290 (42)

240 (35)

110 (16)

40 (6)

20 (3)

17 (2.5)

2219-T62

338 (49)

303 (44)

290 (42)

275 (40)

255 (37)

228 (33)

172 (25)

138 (20)

55 (8)

26 (3.7)

2219-T81, T851

420 (61)

372 (54)

360 (52)

345 (50)

325 (47)

275 (40)

200 (29)

160 (23)

40 (6)

26 (3.7)

2618-T61

420 (61)

380 (55)

372 (54)

372 (54)

372 (54)

303 (44)

180 (26)

62 (9)

31 (4.5)

24 (3.5)

3003-O

59 (8.5)

48 (7)

45 (6.5)

40 (6)

38 (5.5)

35 (5)

30 (4.3)

23 (3.4)

17 (2.4)

12 (1.8)

3003-H14

172 (25)

152 (22)

145 (21)

145 (21)

130 (19)

110 (16)

62 (9)

28 (4)

17 (2.4)

12 (1.8)

3003-H18

228 (33)

200 (29)

193 (28)

185 (27)

145 (21)

110 (16)

62 (9)

28 (4)

17 (2.4)

12 (1.8)

3004-O

90 (13)

75 (11)

70 (10)

70 (10)

70 (10)

70 (10)

66 (9.5)

52 (7.5)

33 (5)

20 (3)

3004-H34

235 (34)

207 (30)

200 (29)

200 (29)

200 (29)

172 (25)

103 (15)

52 (7.5)

35 (5)

20 (3)

3004-H38

295 (43)

262 (38)

248 (36)

248 (36)

248 (36)

185 (27)

103 (15)

52 (7.5)

35 (5)

20 (3)

4032-T6

330 (48)

317 (46)

317 (46)

317 (46)

303 (44)

228 (33)

62 (9)

38 (5.5)

22 (3.2)

14 (2)

5050-O

70 (10)

59 (8.5)

55 (8)

55 (8)

55 (8)

55 (8)

52 (7.5)

40 (6)

29 (4.2)

18 (2.6)

5050-H34

207 (30)

172 (25)

165 (24)

165

165 (24)

152 (22)

52 (7.5)

40 (6)

29 (4.2)

18 (2.6)

(24)

5050-H38

248 (36)

207 (30)

200 (29)

200 (29)

200 (29)

172 (25)

52 (7.5)

40 (6)

29 (4.2)

18 (2.6)

5052-O

110 (16)

90 (13)

90 (13)

90 (13)

90 (13)

90 (13)

75 (11)

52 (7.5)

38 (5.5)

21 (3.1)

5052-H34

248 (36)

220 (32)

215 (31)

215 (31)

215 (31)

185 (27)

103 (15)

52 (7.5)

38 (5.5)

21 (3.1)

5052-H38

303 (44)

262 (38)

255 (37)

255 (37)

248 (36)

193 (28)

103 (15)

52 (7.5)

38 (5.5)

21 (3.1)

5083-O

165 (24)

145 (21)

145 (21)

145 (21)

145 (21)

130 (19)

117 (17)

75 (11)

52 (7.5)

29 (4.2)

5086-O

130 (19)

117 (17)

117 (17)

117 (17)

117 (17)

110 (16)

103 (15)

75 (11)

52 (7.5)

29 (4.2)

5154-O

130 (19)

117 (17)

117 (17)

117 (17)

117 (17)

110 (16)

103 (15)

75 (11)

52 (7.5)

29 (4.2)

5254-O

130 (19)

117 (17)

117 (17)

117 (17)

117 (17)

110 (16)

103 (15)

75 (11)

52 (7.5)

29 (4.2)

5454-O

130 (19)

117 (17)

117 (17)

117 (17)

117 (17)

110 (16)

103 (15)

75 (11)

52 (7.5)

29 (4.2)

5454-H32

248 (36)

215 (31)

207 (30)

207 (30)

200 (29)

180 (26)

130 (19)

75 (11)

52 (7.5)

29 (4.2)

5454-H34

283 (41)

248 (36)

240 (35)

240 (35)

235 (34)

193 (28)

130 (19)

75 (11)

52 (7.5)

29 (4.2)

5456-O

180 (26)

160 (23)

160 (23)

160 (23)

152 (22)

138 (20)

117 (17)

75 (11)

52 (7.5)

29 (4.2)

5652-O

110 (16)

90 (13)

90 (13)

90 (13)

90 (13)

90 (13)

75 (11)

52 (7.5)

38 (5.5)

21 (3.1)

5652-H34

248 (36)

220 (32)

215 (31)

215 (31)

215 (31)

185 (27)

103 (15)

52 (7.5)

38 (5.5)

21 (3.1)

5652-H38

303 (44)

262 (38)

255 (37)

255 (37)

248 (36)

193 (28)

103 (15)

52 (7.5)

38 (5.5)

21 (3.1)

6053-T6, T651

...

...

...

220 (32)

193 (28)

165 (24)

83 (12)

28 (4)

19 (2.7)

14 (2)

6061-T6, T651

325 (47)

290 (42)

283 (41)

275 (40)

262 (38)

215 (31)

103 (15)

35 (5)

19 (2.7)

12 (1.8)

6063-T1

110 (16)

103 (15)

97 (14)

90 (13)

97 (14)

103 (15)

45 (6.5)

24 (3.5)

17 (2.5)

14 (2)

6063-T5

165 (24)

152 (22)

152 (22)

145 (21)

138 (20)

125 (18)

45 (6.5)

24 (3.5)

17 (2.5)

14 (2)

6063-T6

248 (36)

228 (33)

220 (32)

215 (31)

193 (28)

138 (20)

45 (6.5)

24 (3.5)

17 (2.5)

14 (2)

6101-T6

228 (33)

207 (30)

200 (29)

193 (28)

172 (25)

130 (19)

48 (7)

23 (3.3)

16 (2.3)

12 (1.8)

6151-T6

345 (50)

317 (46)

310 (45)

295 (43)

275 (40)

185 (27)

83 (12)

35 (5)

27 (3.9)

22 (3.2)

6262-T651

325 (47)

290 (42)

283 (41)

275 (40)

262 (38)

215 (31)

...

...

...

...

6262-T9

462 (67)

400 (58)

385 (56)

380 (55)

360 (52)

255 (37)

90 (13)

40 (6)

19 (2.7)

12 (1.8)

7075-T6, T651

635 (92)

545 (79)

517 (75)

503 (73)

448 (65)

185 (27)

90 (13)

62 (9)

45 (6.5)

32 (4.6)

7075-T73, T7351

495 (72)

462 (67)

448 (6.5)

435 (63)

400 (58)

185 (27)

90 (13)

62 (9)

45 (6.5)

32 (4.6)

7178-T6, T651

648 (94)

580 (84)

558 (81)

538 (78)

470 (68)

185 (27)

83 (12)

62 (9)

48 (7)

35 (5.5)

7178-T76, T7651

615 (89)

538 (78)

525 (76)

503 (73)

440 (64)

185 (27)

83 (12)

62 (9)

48 (7)

38 (5.5)

(a) These data are based on a limited amount of testing and represent the lowest strength during 10,000 h of exposure at testing temperature under no load; stress applied at 34 MPa/min (5000 psi/min) to yield strength and then at strain rate of 0.05 mm/mm per min (0.05 in./in. per min) to failure. Under some conditions of temperature and time, the application of heat will adversely affect certain other properties of some alloys.

Table 6 Effect of temperature on the elongation of wrought aluminum and aluminum alloys Alloy temper

1100-O

and

Elongation(a) in 50 mm (2 in.), %, at:

-195 °C (-320 °F)

-80 °C (112 °F)

-30 °C (-18 °F)

24 °C (75 °F)

100 °C (212 °F)

150 °C (300 °F)

205 °C (400 °F)

260 °C (500 °F)

315 °C (600 °F)

370 °C (700 °F)

50

43

40

40

45

55

65

75

80

85

1100-H14

45

24

20

20

20

23

26

75

80

85

1100-H18

30

16

15

15

15

20

65

75

80

85

2011-T3

...

...

...

15

16

25

35

45

90

125

2014-T6, T651

14

13

13

13

15

20

28

52

65

72

2017-T4, T451

28

24

23

22

18

15

35

45

65

70

2024-T3 (sheet)

18

17

17

17

16

11

23

55

75

100

2024-T4, T351 (plate)

19

19

19

19

19

17

27

55

75

100

2024-T6, T651

11

10

10

10

10

17

27

55

75

100

2024-T81, T851

8

7

7

7

8

11

23

55

75

100

2024-T861

5

5

5

5

6

11

28

55

75

100

2117-T4

30

29

28

27

16

20

35

55

80

110

2124-T851

9

8

8

9

9

13

28

60

75

100

2218-T61

15

14

13

13

15

17

30

70

85

100

2219-T62

16

13

12

12

14

17

20

21

40

75

2219-T81, T851

15

13

12

12

15

17

20

21

55

75

2618-T61

12

11

10

10

10

14

24

50

80

120

3003-O

46

42

41

40

43

47

60

65

70

70

3003-H14

30

18

16

16

16

16

20

60

70

70

3003-H18

23

11

10

10

10

11

18

60

70

70

3004-O

38

30

26

25

25

35

55

70

80

90

3004-H34

26

16

13

12

13

22

35

55

80

90

3004-H38

20

10

7

6

7

15

30

50

80

90

4032-T6

11

10

9

9

9

9

30

50

70

90

5052-O

46

35

32

30

36

50

60

80

110

130

5052-H34

28

21

18

16

18

27

45

80

110

130

5052-H38

25

18

15

14

16

24

45

80

110

130

5083-O

36

30

27

25

36

50

60

80

110

130

5086-O

46

35

32

30

36

50

60

80

110

130

5154-O

46

35

32

30

36

50

60

80

110

130

5254-O

46

35

32

30

36

50

60

80

110

130

5454-O

39

30

27

25

31

50

60

80

110

130

5454-H32

32

23

20

18

20

37

45

80

110

130

5454-H34

30

21

18

16

18

32

45

80

110

130

5456-O

32

25

22

20

31

50

60

80

110

130

5652-O

46

35

32

30

30

50

60

80

110

130

5652-H34

28

21

18

16

18

27

45

80

110

130

5652-H38

25

18

15

14

16

24

45

80

110

130

6053-T6, T651

...

...

...

13

13

13

25

70

80

90

6061-T6, T651

22

18

17

17

18

20

28

60

85

95

6063-T1

44

36

34

33

18

20

40

75

80

105

6063-T5

28

24

23

22

18

20

40

75

80

105

6063-T6

24

20

19

18

15

20

40

75

80

105

6101-T6

24

20

19

19

20

20

40

80

100

105

6151-T6

20

17

17

17

17

20

30

50

43

35

6262-T651

22

18

17

17

18

20

...

...

...

...

6262-T9

14

10

10

10

10

14

34

48

85

95

7075-T6, T651

9

11

11

11

14

30

55

65

70

70

7075-T73, T7351

14

14

13

13

15

30

55

65

70

70

7178-T6, T651

5

8

9

11

14

40

70

76

80

80

7178-T76, T7651

10

10

10

11

17

40

70

76

80

80

(a) These data are based on a limited amount of testing and represent the lowest strength during 10,000 h of exposure at testing temperature under no load; stress applied at 34 MPa/min (5000 psi/min) to yield strength and then at strain rate of 0.05 mm/mm per min (0.05 in./in. per min) to failure. Under some conditions of temperature and time, the application of heat will adversely affect certain other properties of some alloys.

Table 7 Mechanical property limits for non-heat-treatable aluminum alloy sheet and plate Alloy and temper

1060-O

Specified thickness(a)

Tensile strength

Yield strength

Elongation (min)(c), %

Minimum

Maximum

Minimum(b)

Maximum

mm

in.

MPa

ksi

MPa

ksi

MPa

ksi

MPa

ksi

0.15-0.48

0.006-0.019

55

8.0

97

14.0

17

2.5

...

...

15

0.51-1.27

0.020-0.050

55

8.0

97

14.0

17

2.5

...

...

22

1060-H12(d)

1060-H14(d)

1060-H16(d)

1060-H18(d)

1060-H112

1100-O

1100-H12(d)

1.30-76.20

0.051-3.000

55

8.0

97

14.0

17

2.5

...

...

25

0.43-1.27

0.017-0.050

76

11.0

110

16.0

62

9.0

...

...

6

1.30-50.80

0.051-2.000

76

11.0

110

16.0

62

9.0

...

...

12

0.23-0.48

0.009-0.019

83

12.0

117

17.0

69

10.0

...

...

1

0.51-1.27

0.020-0.050

83

12.0

117

17.0

69

10.0

...

...

5

1.30-25.40

0.051-1.000

83

12.0

117

17.0

69

10.0

...

...

10

0.15-0.48

0.006-0.019

97

14.0

131

19.0

76

11.0

...

...

1

0.51-1.27

0.020-0.050

97

14.0

131

19.0

76

11.0

...

...

4

1.30-4.11

0.051-0.162

97

14.0

131

19.0

76

11.0

...

...

5

0.15-0.48

0.006-0.019

110

16.0

...

...

83

12.0

...

...

1

0.51-1.27

0.020-0.050

110

16.0

...

...

83

12.0

...

...

3

1.30-3.25

0.051-0.128

110

16.0

...

...

83

12.0

...

...

4

6.35-12.67

0.250-0.499

76

11.0

...

...

...

...

...

...

10

12.70-25.40

0.500-1.000

69

10.0

...

...

...

...

...

...

20

25.42-76.20

1.001-3.000

62

9.0

...

...

...

...

...

...

25

0.15-0.48

0.006-0.019

76

11.0

107

15.5

24

3.5

...

...

15

0.51-0.79

0.020-0.031

76

11.0

107

15.5

24

3.5

...

...

20

0.81-1.27

0.032-0.050

76

11.0

107

15.5

24

3.5

...

...

25

1.30-6.32

0.051-0.249

76

11.0

107

15.5

24

3.5

...

...

30

6.35-76.20

0.250-3.000

76

11.0

107

15.5

24

3.5

...

...

28

0.43-0.48

0.017-0.019

97

14.0

131

19.0

76

11.0

...

...

3

1100-H14(d)

1100-H16(d)

1100-H18

1100-H112

0.51-0.79

0.020-0.031

97

14.0

131

19.0

76

11.0

...

...

4

0.81-1.27

0.032-0.050

97

14.0

131

19.0

76

11.0

...

...

6

1.30-2.87

0.051-0.113

97

14.0

131

19.0

76

11.0

...

...

8

2.90-12.67

0.114-0.499

97

14.0

131

19.0

76

11.0

...

...

9

12.70-50.80

0.500-2.000

97

14.0

131

19.0

76

11.0

...

...

12

0.23-0.30

0.009-0.012

110

16.0

145

21.0

97

14.0

...

...

1

0.33-0.48

0.013-0.019

110

16.0

145

21.0

97

14.0

...

...

2

0.51-0.79

0.020-0.031

110

16.0

145

21.0

97

14.0

...

...

3

0.81-1.27

0.032-0.050

110

16.0

145

21.0

97

14.0

...

...

4

1.30-2.87

0.051-0.113

110

16.0

145

21.0

97

14.0

...

...

5

2.90-12.67

0.114-0.499

110

16.0

145

21.0

97

14.0

...

...

6

12.70-25.40

0.500-1.000

110

16.0

145

21.0

97

14.0

...

...

10

0.15-0.48

0.006-0.019

131

19.0

165

24.0

117

17.0

...

...

1

0.51-0.79

0.020-0.031

131

19.0

165

24.0

117

17.0

...

...

2

0.81-1.27

0.032-0.050

131

19.0

165

24.0

117

17.0

...

...

3

1.30-4.11

0.051-0.162

131

19.0

165

24.0

117

17.0

...

...

4

0.15-0.48

0.006-0.019

152

22.0

...

...

...

...

...

...

1

0.51-0.79

0.020-0.031

152

22.0

...

...

...

...

...

...

2

0.81-1.27

0.032-0.050

152

22.0

...

...

...

...

...

...

3

1.30-3.25

0.051-0.128

152

22.0

...

...

...

...

...

...

4

6.35-12.67

0.250-0.499

90

13.0

...

...

48

7.0

...

...

9

1350-O

1350-H12

1350-H14

1350-H16

12.70-50.80

0.500-2.000

83

12.0

...

...

34

5.0

...

...

14

50.83-76.20

2.001-3.000

79

11.5

...

...

28

4.0

...

...

20

0.15-0.48

0.006-0.019

55

8.0

97

14.0

...

...

...

...

15

0.51-0.79

0.020-0.031

55

8.0

97

14.0

...

...

...

...

20

0.81-1.27

0.032-0.050

55

8.0

97

14.0

...

...

...

...

25

1.29-6.32

0.051-0.249

55

8.0

97

14.0

...

...

...

...

30

6.35-76.20

0.250-3.000

55

8.0

97

14.0

...

...

...

...

28

0.43-0.48

0.017-0.019

83

12.0

117

17.0

...

...

...

...

3

0.51-0.79

0.020-0.031

83

12.0

117

17.0

...

...

...

...

4

0.81-1.27

0.032-0.050

83

12.0

117

17.0

...

...

...

...

6

1.29-2.87

0.051-0.113

83

12.0

117

17.0

...

...

...

...

8

2.90-12.67

0.114-0.499

83

12.0

117

17.0

...

...

...

...

9

12.70-50.80

0.500-2.000

83

12.0

117

17.0

...

...

...

...

12

0.23-0.30

0.009-0.012

97

14.0

131

19.0

...

...

...

...

1

0.33-0.48

0.013-0.019

97

14.0

131

19.0

...

...

...

...

2

0.51-0.79

0.020-0.031

97

14.0

131

19.0

...

...

...

...

3

0.81-1.27

0.032-0.050

97

14.0

131

19.0

...

...

...

...

4

1.29-2.87

0.051-0.113

97

14.0

131

19.0

...

...

...

...

5

2.90-12.67

0.114-0.499

97

14.0

131

19.0

...

...

...

...

6

12.70-25.40

0.500-1.000

97

14.0

131

19.0

...

...

...

...

10

0.15-0.48

0.006-0.019

110

16.0

145

21.0

...

...

...

...

1

1350-H18

1350-H112

3003-O

3003-H12(d)

0.51-0.79

0.020-0.031

110

16.0

145

21.0

...

...

...

...

2

0.81-1.27

0.032-0.050

110

16.0

145

21.0

...

...

...

...

3

1.29-4.11

0.051-0.162

110

16.0

145

21.0

...

...

...

...

4

0.15-0.48

0.006-0.019

124

18.0

...

...

...

...

...

...

1

0.51-0.79

0.020-0.031

124

18.0

...

...

...

...

...

...

2

0.81-1.27

0.032-0.050

124

18.0

...

...

...

...

...

...

3

1.29-3.25

0.051-0.128

124

18.0

...

...

...

...

...

...

4

6.35-12.67

0.250-0.499

76

11.0

...

...

...

...

...

...

10

12.70-25.40

0.500-1.000

69

10.0

...

...

...

...

...

...

16

25.42-38.1

1.001-1.500

62

9.0

...

...

...

...

...

...

22

0.15-0.18

0.006-0.007

97

14.0

131

19.0

34

5.0

...

...

14

0.20-0.30

0.008-0.012

97

14.0

131

19.0

34

5.0

...

...

18

0.33-0.79

0.013-0.031

97

14.0

131

19.0

34

5.0

...

...

20

0.81-1.27

0.032-0.050

97

14.0

131

19.0

34

5.0

...

...

23

1.30-6.32

0.051-0.249

97

14.0

131

19.0

34

5.0

...

...

25

6.35-76.20

0.250-3.000

97

14.0

131

19.0

34

5.0

...

...

23

0.43-0.48

0.017-0.019

117

17.0

159

23.0

83

12.0

...

...

3

0.51-0.79

0.020-0.031

117

17.0

159

23.0

83

12.0

...

...

4

0.81-1.27

0.032-0.050

117

17.0

159

23.0

83

12.0

...

...

5

1.30-2.87

0.051-0.113

117

17.0

159

23.0

83

12.0

...

...

6

2.90-4.09

0.114-0.161

117

17.0

159

23.0

83

12.0

...

...

7

3003-H14(d)

3003-H16(d)

3003-H18(d)

3003-H112

4.11-6.32

0.162-0.249

117

17.0

159

23.0

83

12.0

...

...

8

6.35-12.67

0.250-0.499

117

17.0

159

23.0

83

12.0

...

...

9

12.70-50.80

0.500-2.000

117

17.0

159

23.0

83

12.0

...

...

10

0.23-0.30

0.009-0.012

138

20.0

179

26.0

117

17.0

...

...

1

0.33-0.48

0.013-0.019

138

20.0

179

26.0

117

17.0

...

...

2

0.51-0.79

0.020-0.031

138

20.0

179

26.0

117

17.0

...

...

3

0.81-1.27

0.032-0.050

138

20.0

179

26.0

117

17.0

...

...

4

1.30-2.87

0.051-0.113

138

20.0

179

26.0

117

17.0

...

...

5

2.90-4.09

0.114-0.161

138

20.0

179

26.0

117

17.0

...

...

6

4.11-6.32

0.162-0.249

138

20.0

179

26.0

117

17.0

...

...

7

6.35-12.67

0.250-0.499

138

20.0

179

26.0

117

17.0

...

...

8

12.70-25.40

0.500-1.000

138

20.0

179

26.0

117

17.0

...

...

10

0.15-0.48

0.006-0.019

165

24.0

207

30.0

145

21.0

...

...

1

0.51-0.79

0.020-0.031

165

24.0

207

30.0

145

21.0

...

...

2

0.81-1.27

0.032-0.050

165

24.0

207

30.0

145

21.0

...

...

3

1.30-4.11

0.051-0.162

165

24.0

207

30.0

145

21.0

...

...

4

0.15-0.48

0.006-0.019

186

27.0

...

...

165

24.0

...

...

1

0.51-0.79

0.020-0.031

186

27.0

...

...

165

24.0

...

...

2

0.81-1.27

0.032-0.050

186

27.0

...

...

165

24.0

...

...

3

1.30-3.25

0.051-0.128

186

27.0

...

...

165

24.0

...

...

4

6.35-12.67

0.250-0.499

117

17.0

...

...

69

10.0

...

...

8

3004-O

3004-H32(d)

3004-H34(d)

3004-H36(d)

12.70-50.80

0.500-2.000

103

15.0

...

...

41

6.0

...

...

12

50.83-76.20

2.001-3.000

100

14.5

...

...

41

6.0

...

...

18

0.15-0.18

0.006-0.007

152

22.0

200

29.0

59

8.5

...

...

...

0.20-0.48

0.008-0.019

152

22.0

200

29.0

59

8.5

...

...

10

0.51-0.79

0.020-0.031

152

22.0

200

29.0

59

8.5

...

...

14

0.81-1.27

0.032-0.050

152

22.0

200

29.0

59

8.5

...

...

16

1.30-6.32

0.051-0.249

152

22.0

200

29.0

59

8.5

...

...

18

6.35-76.20

0.250-3.000

152

22.0

200

29.0

59

8.5

...

...

16

0.43-0.48

0.017-0.019

193

28.0

241

35.0

145

21.0

...

...

1

0.51-0.79

0.020-0.031

193

28.0

241

35.0

145

21.0

...

...

3

0.81-1.27

0.032-0.050

193

28.0

241

35.0

145

21.0

...

...

4

1.30-2.87

0.051-0.113

193

28.0

241

35.0

145

21.0

...

...

5

2.90-50.80

0.114-2.000

193

28.0

241

35.0

145

21.0

...

...

6

0.23-0.48

0.009-0.019

221

32.0

262

38.0

172

25.0

...

...

1

0.51-1.27

0.020-0.050

221

32.0

262

38.0

172

25.0

...

...

3

1.30-2.87

0.051-0.113

221

32.0

262

38.0

172.

25.0

...

...

4

2.90-25.40

0.114-1.000

221

32.0

262

38.0

172

25.0

...

...

5

0.15-0.18

0.006-0.007

241

35.0

283

41.0

193

28.0

...

...

...

0.20-0.48

0.008-0.019

241

35.0

283

41.0

193

28.0

...

...

1

0.51-0.79

0.020-0.031

241

35.0

283

41.0

193

28.0

...

...

2

0.81-1.27

0.032-0.050

241

35.0

283

41.0

193

28.0

...

...

3

1.30-4.11

0.051-0.162

241

35.0

283

41.0

193

28.0

...

...

4

0.15-0.18

0.006-0.007

262

38.0

...

...

214

31.0

...

...

...

0.20-0.48

0.008-0.019

262

38.0

...

...

214

31.0

...

...

1

0.51-0.79

0.020-0.031

262

38.0

...

...

214

31.0

...

...

2

0.81-1.27

0.032-0.050

262

38.0

...

...

214

31.0

...

...

3

1.30-3.25

0.051-0.128

262

38.0

...

...

214

31.0

...

...

4

3004-H112

6.35-76.20

0.250-3.000

159

23.0

...

...

62

9.0

...

...

7

3005-O

0.15-0.18

0.006-0.007

117

17.0

165

24.0

45

6.5

...

...

10

0.20-0.30

0.008-0.012

117

17.0

165

24.0

45

6.5

...

...

12

0.33-0.48

0.013-0.019

117

17.0

165

24.0

45

6.5

...

...

14

0.51-0.79

0.020-0.031

117

17.0

165

24.0

45

6.5

...

...

16

0.81-1.27

0.032-0.050

117

17.0

165

24.0

45

6.5

...

...

18

1.29-6.32

0.051-0.249

117

17.0

165

24.0

45

6.5

...

...

20

0.43-0.48

0.017-0.019

138

20.0

186

27.0

17

17.0

...

...

1

0.51-1.27

0.020-0.050

138

20.0

186

27.0

117

17.0

...

...

2

1.29-2.87

0.051-0.113

138

20.0

186

27.0

117

17.0

...

...

3

2.90-4.09

0.114-0.161

138

20.0

186

27.0

117

17.0

...

...

4

4.11-6.32

0.162-0.249

138

20.0

186

27.0

117

17.0

...

...

5

0.23-0.79

0.009-0.031

165

24.0

214

31.0

145

21.0

...

...

1

0.81-1.27

0.032-0.050

165

24.0

214

31.0

145

21.0

...

...

2

1.29-2.87

0.051-0.113

165

24.0

214

31.0

145

21.0

...

...

3

3004-H38(d)

3005-H12

3005-H14

3005-H16

3005-H18

3005-H19

3005-H25

3005-H26

3005-H27

3005-H28

2.90-6.32

0.114-0.249

165

24.0

214

31.0

145

21.0

...

...

4

0.15-0.79

0.006-0.031

193

28.0

241

35.0

172

25.0

...

...

1

0.81-2.87

0.032-0.113

193

28.0

241

35.0

172

25.0

...

...

2

2.90-6.32

0.114-0.162

193

28.0

241

35.0

172

25.0

...

...

3

0.15-0.79

0.006-0.031

221

32.0

...

...

200

29.0

...

...

1

0.81-3.25

0.032-0.128

221

32.0

...

...

200

29.0

...

...

2

0.15-0.30

0.006-0.012

234

34.0

...

...

...

...

...

...

...

0.33-1.60

0.013-0.063

234

34.0

...

...

...

...

...

...

1

0.15-0.48

0.006-0.019

179

26.0

234

34.0

152

22.0

...

...

1

0.51-0.79

0.020-0.031

179

26.0

234

34.0

152

22.0

...

...

2

0.81-1.27

0.032-0.050

179

26.0

234

34.0

152

22.0

...

...

3

1.29-2.03

0.051-0.080

179

26.0

234

34.0

152

22.0

...

...

4

0.15-0.48

0.006-0.019

193

28.0

248

36.0

165

24.0

...

...

1

0.51-0.79

0.020-0.031

193

28.0

248

36.0

165

24.0

...

...

2

0.81-1.29

0.032-0.050

193

28.0

248

36.0

165

24.0

...

...

3

1.29-2.03

0.051-0.080

193

28.0

248

36.0

165

24.0

...

...

4

0.15-0.48

0.006-0.019

203

29.5

259

37.5

179

26.0

...

...

1

0.51-0.79

0.020-0.031

203

29.5

259

37.5

179

26.0

...

...

2

0.81-1.27

0.032-0.050

203

29.5

259

37.5

179

26.0

...

...

3

1.29-2.03

0.051-0.080

203

29.5

259

37.5

179

26.0

...

...

4

0.15-0.48

0.006-0.019

214

31.0

...

...

186

27.0

...

...

1

3105-O

3105-H12

3105-H14

3105-H16

3105-H18

3105-H25

0.51-0.79

0.020-0.031

214

31.0

...

...

186

27.0

...

...

2

0.81-1.27

0.032-0.050

214

31.0

...

...

186

27.0

...

...

3

1.29-2.03

0.051-0.080

214

31.0

...

...

186

27.0

...

...

4

0.33-0.48

0.013-0.019

97

14.0

145

21.0

34

5.0

...

...

16

0.51-0.79

0.020-0.031

97

14.0

145

21.0

34

5.0

...

...

18

0.81-2.03

0.032-0.080

97

14.0

145

21.0

34

5.0

...

...

20

0.43-0.48

0.017-0.019

131

19.0

179

26.0

103

15.0

...

...

1

0.51-0.79

0.020-0.031

131

19.0

179

26.0

103

15.0

...

...

1

0.81-1.27

0.032-0.050

131

19.0

179

26.0

103

15.0

...

...

2

1.29-2.03

0.051-0.080

131

19.0

179

26.0

103

15.0

...

...

3

0.33-0.48

0.013-0.019

152

22.0

200

29.0

124

18.0

...

...

1

0.51-0.79

0.020-0.031

152

22.0

200

29.0

124

18.0

...

...

1

0.81-1.27

0.032-0.050

152

22.0

200

29.0

124

18.0

...

...

2

1.29-2.03

0.051-0.080

152

22.0

200

29.0

124

18.0

...

...

2

0.33-0.79

0.013-0.031

172

25.0

221

32.0

145

21.0

...

...

1

0.81-1.27

0.032-0.050

172

25.0

221

32.0

145

21.0

...

...

2

1.29-2.03

0.051-0.080

172

25.0

221

32.0

145

21.0

...

...

2

0.33-0.79

0.013-0.031

193

28.0

...

...

165

24.0

...

...

1

0.81-1.27

0.032-0.050

193

28.0

...

...

165

24.0

...

...

1

1.29-2.03

0.051-0.080

193

28.0

...

...

165

24.0

...

...

2

0.33-0.48

0.013-0.019

159

23.0

...

...

131

19.0

...

...

2

5005-O

5005-H12

5005-H14

0.51-0.79

0.020-0.031

159

23.0

...

...

131

19.0

...

...

3

0.81-1.27

0.032-0.050

159

23.0

...

...

131

19.0

...

...

4

1.29-2.03

0.051-0.080

159

23.0

...

...

131

19.0

...

...

6

0.15-0.18

0.006-0.007

103

15.0

145

21.0

34

5.0

...

...

12

0.20-0.30

0.008-0.012

103

15.0

145

21.0

34

5.0

...

...

14

0.33-0.48

0.013-0.019

103

15.0

145

21.0

34

5.0

...

...

16

0.51-0.79

0.020-0.031

103

15.0

145

21.0

34

5.0

...

...

18

0.81-1.27

0.032-0.050

103

15.0

145

21.0

34

5.0

...

...

20

1.29-2.87

0.051-0.113

103

15.0

145

21.0

34

5.0

...

...

21

2.90-6.32

0.114-0.249

103

15.0

145

21.0

34

5.0

...

...

22

6.35-76.2

0.250-3.000

103

15.0

145

21.0

34

5.0

...

...

22

0.43-0.48

0.017-0.019

124

18.0

165

24.0

97

14.0

...

...

2

0.51-0.79

0.020-0.031

124

18.0

165

24.0

97

14.0

...

...

3

0.81-1.27

0.032-0.050

124

18.0

165

24.0

97

14.0

...

...

4

1.29-2.87

0.051-0.113

124

18.0

165

24.0

97

14.0

...

...

6

2.89-4.09

0.114-0.161

124

18.0

165

24.0

97

14.0

...

...

7

4.11-6.32

0.162-0.249

124

18.0

165

24.0

97

14.0

...

...

8

6.35-12.67

0.250-0.499

124

18.0

165

24.0

97

14.0

...

...

9

12.70-50.80

0.500-2.000

124

18.0

165

24.0

97

14.0

...

...

10

0.23-0.79

0.009-0.031

145

21.0

186

27.0

117

17.0

...

...

1

0.81-1.27

0.032-0.050

145

21.0

186

27.0

117

17.0

...

...

2

5005-H16

5005-H18

5005-H32(d)

5005-H34(d)

1.29-2.87

0.051-0.113

145

21.0

186

27.0

117

17.0

...

...

3

2.90-4.09

0.114-0.161

145

21.0

186

27.0

117

17.0

...

...

5

4.11-6.32

0.162-0.249

145

21.0

186

27.0

117

17.0

...

...

6

6.35-12.67

0.250-0.499

145

21.0

186

27.0

117

17.0

...

...

8

12.70-25.40

0.500-1.000

145

21.0

186

27.0

117

17.0

...

...

10

0.15-0.79

0.006-0.031

165

24.0

207

30.0

138

20.0

...

...

1

0.81-1.27

0.032-0.050

165

24.0

207

30.0

138

20.0

...

...

2

1.29-4.11

0.051-0.162

165

24.0

207

30.0

138

20.0

...

...

3

0.15-0.79

0.006-0.031

186

27.0

...

...

...

...

...

...

1

0.81-1.27

0.032-0.050

186

27.0

...

...

...

...

...

...

2

1.29-3.25

0.051-0.128

186

27.0

...

...

...

...

...

...

3

0.43-0.48

0.017-0.019

117

17.0

159

23.0

83

12.0

...

...

3

0.51-0.79

0.020-0.031

117

17.0

159

23.0

83

12.0

...

...

4

0.81-1.27

0.032-0.050

117

17.0

159

23.0

83

12.0

...

...

5

1.29-2.87

0.051-0.113

117

17.0

159

23.0

83

12.0

...

...

7

2.90-4.09

0.114-0.161

117

17.0

159

23.0

83

12.0

...

...

8

4.11-6.32

0.162-0.249

117

17.0

159

23.0

83

12.0

...

...

9

6.35-50.80

0.250-2.000

117

17.0

159

23.0

83

12.0

...

...

10

0.23-0.30

0.009-0.012

138

20.0

179

26.0

103

15.0

...

...

2

0.33-0.79

0.013-0.031

138

20.0

179

26.0

103

15.0

...

...

3

0.81-1.27

0.032-0.050

138

20.0

179

26.0

103

15.0

...

...

4

1.29-2.87

0.051-0.113

138

20.0

179

26.0

103

15.0

...

...

5

2.90-4.09

0.114-0.161

138

20.0

179

26.0

103

15.0

...

...

6

4.11-6.32

0.162-0.249

138

20.0

179

26.0

103

15.0

...

...

7

6.35-12.67

0.250-0.499

138

20.0

179

26.0

103

15.0

...

...

8

12.70-25.40

0.500-1.00

138

20.0

179

26.0

103

15.0

...

...

10

0.15-0.18

0.006-0.007

159

23.0

200

29.0

124

18.0

...

...

1

0.20-0.48

0.008-0.019

159

23.0

200

29.0

124

18.0

...

...

2

0.51-0.79

0.020-0.031

159

23.0

200

29.0

124

18.0

...

...

3

0.81-4.11

0.032-0.162

159

23.0

200

29.0

124

18.0

...

...

4

0.15-0.30

0.006-0.012

179

26.0

...

...

...

...

...

...

1

0.33-0.48

0.013-0.019

179

26.0

...

...

...

...

...

...

2

0.51-0.79

0.020-0.031

179

26.0

...

...

...

...

...

...

3

0.81-3.25

0.032-0.128

179

26.0

...

...

...

...

...

...

4

5005-H39

0.15-1.60

0.006-0.063

193

28.0

...

...

...

...

...

...

1

5005-H112

6.35-12.67

0.250-0.499

117

17.0

...

...

...

...

...

...

8

12.70-50.80

0.500-2.000

103

15.0

...

...

...

...

...

...

12

50.82-76.20

2.001-3.000

100

14.5

...

...

...

...

...

...

18

0.15-0.18

0.006-0.007

124

18.0

165

24.0

41

6.0

...

...

...

0.20-0.48

0.008-0.019

124

18.0

165

24.0

41

6.0

...

...

16

0.51-0.79

0.020-0.031

124

18.0

165

24.0

41

6.0

...

...

18

0.81-2.87

0.032-0.113

124

18.0

165

24.0

41

6.0

...

...

20

5005-H36(d)

5005-H38

5050-O

2.90-6.32

0.114-0.249

124

18.0

165

24.0

41

6.0

...

...

22

6.35-76.20

0.250-3.000

124

18.0

165

24.0

41

6.0

...

...

20

0.43-1.27

0.017-0.050

152

22.0

193

28.0

110

16.0

...

...

4

1.29-6.32

0.051-0.249

152

22.0

193

28.0

110

16.0

...

...

6

0.23-0.79

0.009-0.031

172

25.0

214

31.0

138

20.0

...

...

3

0.81-1.27

0.032-0.050

172

25.0

214

31.0

138

20.0

...

...

4

1.29-6.32

0.051-0.249

172

25.0

214

31.0

138

20.0

...

...

5

0.15-0.48

0.006-0.019

186

27.0

228

33.0

152

22.0

...

...

2

0.51-1.27

0.020-0.050

186

27.0

228

33.0

152

22.0

...

...

3

1.29-4.11

0.051-0.162

186

27.0

228

33.0

152

22.0

...

...

4

0.15-0.18

0.006-0.007

200

29.0

...

...

...

...

...

...

...

0.20-0.79

0.008-0.031

200

29.0

...

...

...

...

...

...

2

0.81-1.27

0.032-0.050

200

29.0

...

...

...

...

...

...

3

1.29-3.25

0.051-0.128

200

29.0

...

...

...

...

...

...

4

5050-H39

0.15-1.60

0.006-0.063

214

31.0

...

...

...

...

...

...

1

5050-H112

6.35-76.20

0.250-3.000

138

20.0

...

...

55

8.0

...

...

12

5052-O

0.15-0.18

0.006-0.007

172

25.0

214

31.0

65

9.5

...

...

...

0.20-0.30

0.008-0.012

172

25.0

214

31.0

65

9.5

...

...

14

0.33-0.48

0.013-0.019

172

25.0

214

31.0

65

9.5

...

...

15

0.51-0.79

0.020-0.031

172

25.0

214

31.0

65

9.5

...

...

16

0.81-1.27

0.032-0.050

172

25.0

214

31.0

65

9.5

...

...

18

5050-H32(d)

5050-H34(d)

5050-H36(d)

5050-H38

5052-H32(d)

5052-H34(d)

5052-H36(d)

5052-H38(d)

5052-H112

1.30-2.87

0.051-0.113

172

25.0

214

31.0

65

9.5

...

...

19

2.90-6.32

0.114-0.249

172

25.0

214

31.0

65

9.5

...

...

20

6.35-76.20

0.250-3.000

172

25.0

214

31.0

65

9.5

...

...

18

0.43-0.48

0.017-0.019

214

31.0

262

38.0

159

23.0

...

...

4

0.51-1.27

0.020-0.050

214

31.0

262

38.0

159

23.0

...

...

5

1.30-2.87

0.051-0.113

214

31.0

262

38.0

159

23.0

...

...

7

2.90-6.32

0.114-0.249

214

31.0

262

38.0

159

23.0

...

...

9

6.35-12.67

0.250-0.499

214

31.0

262

38.0

159

23.0

...

...

11

12.70-50.80

0.500-2.000

214

31.0

262

38.0

159

23.0

...

...

12

0.23-0.48

0.009-0.019

234

34.0

283

41.0

179

26.0

...

...

3

0.51-1.27

0.020-0.050

234

34.0

283

41.0

179

26.0

...

...

4

1.30-2.87

0.051-0.113

234

34.0

283

41.0

179

26.0

...

...

6

2.90-6.32

0.114-0.249

234

34.0

283

41.0

179

26.0

...

...

7

6.35-25.40

0.250-1.000

234

34.0

283

41.0

179

26.0

...

...

10

0.15-0.18

0.006-0.007

255

37.0

303

44.0

200

29.0

...

...

2

0.20-0.79

0.008-0.031

255

37.0

303

44.0

200

29.0

...

...

3

0.81-4.11

0.032-0.162

255

37.0

303

44.0

200

29.0

...

...

4

0.15-0.18

0.006-0.007

269

39.0

...

...

221

32.0

...

...

2

0.20-0.79

0.008-0.031

269

39.0

...

...

221

32.0

...

...

3

0.81-3.25

0.032-0.128

269

39.0

...

...

221

32.0

...

...

4

6.35-12.67

0.250-0.499

193

28.0

...

...

110

16.0

...

...

7

5083-O

5083-H112

5083-H116(e)(f)

5083-H321

5086-O

5086-H32(d)

12.70-05.80

0.500-2.000

172

25.0

...

...

65

9.5

...

...

12

50.83-76.20

2.001-3.000

172

25.0

...

...

65

9.5

...

...

16

1.30-38.10

0.051-1.500

276

40.0

352

51.0

124

18.0

200

29.0

16

38.13-76.20

1.501-3.000

269

39.0

345

50.0

117

17.0

200

29.0

16

76.23-101.60

3.001-4.000

262

38.0

...

...

110

16.0

...

...

16

101.63-127.00

4.001-5.000

262

38.0

...

...

110

16.0

...

...

14

127.03-177.80

5.001-7.000

255

37.0

...

...

103

15.0

...

...

14

177.83-203.20

7.001-8.000

248

36.0

...

...

97

14.0

...

...

12

6.35-38.10

0.250-1.500

276

40.0

...

...

124

18.0

...

...

12

38.13-76.20

1.501-3.000

269

39.0

...

...

117

17.0

...

...

12

0.10-12.67

0.063-0.499

303

44.0

...

...

214

31.0

...

...

10

12.70-31.75

0.500-1.250

303

44.0

...

...

214

31.0

...

...

12

31.78-38.10

1.251-1.500

303

44.0

...

...

214

31.0

...

...

12

38.13-76.20

1.501-3.000

283

41.0

...

...

200

290

...

...

12

4.78-38.10

0.188-1.500

303

44.0

386

56.0

214

31.0

296

43.0

12

38.13-76.20

1.501-3.000

283

41.0

386

56.0

200

29.0

296

43.0

12

0.51-1.27

0.020-0.50

241

35.0

303

44.0

97

14.0

...

...

15

1.30-6.32

0.051-0.249

241

35.0

303

44.0

97

14.0

...

...

18

6.35-50.80

0.250-2.000

241

35.0

303

44.0

97

14.0

...

...

16

0.51-1.27

0.020-0.050

276

40.0

324

47.0

193

28.0

...

...

6

1.30-6.32

0.051-0.249

276

40.0

324

47.0

193

28.0

...

...

8

6.35-50.80

0.250-2.000

276

40.0

324

47.0

193

28.0

...

...

12

0.23-0.48

0.009-0.019

303

44.0

352

51.0

234

34.0

...

...

4

0.51-1.27

0.020-0.050

303

44.0

352

51.0

234

34.0

...

...

5

1.30-6.32

0.051-0.249

303

44.0

352

51.0

234

34.0

...

...

6

6.35-25.40

0.250-1.000

303

44.0

352

51.0

234

34.0

...

...

10

0.15-0.48

0.006-0.019

324

47.0

372

54.0

262

38.0

...

...

3

0.51-1.27

0.020-0.050

324

47.0

372

54.0

262

38.0

...

...

4

1.30-4.11

0.051-0.162

324

47.0

372

54.0

262

38.0

...

...

6

5086-H38(d)

0.15-0.51

0.006-0.020

345

50.0

...

...

283

41.0

...

...

3

5086-H112

4.78-12.67

0.188-0.499

248

36.0

...

...

124

18.0

...

...

8

12.70-25.40

0.500-1.000

241

35.0

...

...

110

16.0

...

...

10

25.43-50.80

1.001-2.000

241

35.0

...

...

97

14.0

...

...

14

50.83-76.20

2.001-3.000

234

34.0

...

...

97

14.0

...

...

14

0.10-6.32

0.063-0.249

276

40.0

...

...

193

28.0

...

...

8

6.35-12.67

0.250-0.499

276

40.0

...

...

193

28.0

...

...

10

12.70-31.75

0.500-1.250

276

40.0

...

...

193

28.0

...

...

10

31.78-50.80

1.251-2.000

276

40.0

...

...

193

28.0

...

...

10

0.51-0.79

0.020-0.031

207

30.0

283

41.0

76

11.0

...

...

12

0.81-1.27

0.032-0.050

207

30.0

283

41.0

76

11.0

...

...

14

1.30-2.87

0.051-0.113

207

30.0

283

41.0

76

11.0

...

...

16

2.90-76.20

0.114-3.000

207

30.0

283

41.0

76

11.0

...

...

18

5086-H34(d)

5086-H36(d)

5086-H116(e)(f)

5154-O

5154-H32(d)

5154-H34(d)

5154-H36(d)

5154-H38(d)

5154-H112

5454-O

5454-H32(d)

0.51-1.27

0.020-0.050

248

36.0

296

43.0

179

26.0

...

...

5

1.30-6.32

0.051-0.249

248

36.0

296

43.0

179

26.0

...

...

8

6.35-50.80

0.250-2.000

248

36.0

296

43.0

179

26.0

...

...

12

0.23-1.27

0.009-0.050

269

39.0

317

46.0

200

29.0

...

...

4

1.30-4.09

0.051-0.161

269

39.0

317

46.0

200

29.0

...

...

6

4.11-6.32

0.162-0.249

269

39.0

317

46.0

200

29.0

...

...

7

6.35-25.40

0.250-1.000

269

39.0

317

46.0

200

29.0

...

...

10

0.15-1.27

0.006-0.050

290

42.0

338

49.0

221

32.0

...

...

3

1.30-2.87

0.051-0.113

290

42.0

338

49.0

221

32.0

...

...

4

2.90-4.11

0.114-0.162

290

42.0

338

49.0

221

32.0

...

...

5

0.15-1.27

0.006-0.050

310

45.0

...

...

241

35.0

...

...

3

1.30-2.87

0.051-0.113

310

45.0

...

...

241

35.0

...

...

4

2.90-3.25

0.114-0.128

310

45.0

...

...

241

35.0

...

...

5

6.35-12.67

0.250-0.499

221

32.0

...

...

124

18.0

...

...

8

12.70-50.80

0.500-2.000

207

30.0

...

...

76

11.0

...

...

11

50.83-76.20

2.001-3.000

207

30.0

...

...

76

11.0

...

...

15

0.51-0.79

0.020-0.31

214

31.0

283

41.0

83

12.0

...

...

12

0.81-1.27

0.032-0.050

214

31.0

283

41.0

83

12.0

...

...

14

1.30-2.87

0.051-0.113

214

31.0

283

41.0

83

12.0

...

...

16

2.90-76.20

0.114-3.000

214

31.0

283

41.0

83

12.0

...

...

18

0.51-1.27

0.020-0.050

248

36.0

303

44.0

179

26.0

...

...

5

5454-H34(d)

5454-H112

5456-O

5456-H112(e)

5456-H116(e)(f)

1.30-6.32

0.051-0.249

248

36.0

303

44.0

179

26.0

...

...

8

6.35-50.80

0.250-2.000

248

36.0

303

44.0

179

26.0

...

...

12

0.51-1.27

0.020-0.050

269

39.0

324

47.0

200

29.0

...

...

4

1.30-4.09

0.051-0.161

269

39.0

324

47.0

200

29.0

...

...

6

4.11-6.32

0.162-0.249

269

39.0

324

47.0

200

29.0

...

...

7

6.35-25.40

0.250-1.000

269

39.0

324

47.0

200

29.0

...

...

10

6.35-12.67

0.250-0.499

221

32.0

...

...

124

18.0

...

...

8

12.70-50.80

0.500-2.000

214

31.0

...

...

83

12.0

...

...

11

50.83-76.20

2.001-3.000

214

31.0

...

...

83

12.0

...

...

15

1.30-38.10

0.051-1.500

290

42.0

365

53.0

131

19.0

207

30.0

16

38.13-76.20

1.501-3.000

283

41.0

358

52.0

124

18.0

207

30.0

16

76.23-127.00

3.001-5.000

276

40.0

...

...

117

17.0

...

...

14

127.03-177.80

5.001-7.000

269

39.0

...

...

110

16.0

...

...

14

177.83-203.20

7.001-8.000

262

38.0

...

...

103

15.0

...

...

12

6.35-38.10

0.250-1.500

290

42.0

...

...

131

19.0

...

...

12

38.13-76.20

1.501-3.000

283

41.0

...

...

124

18.0

...

...

12

1.60-12.67

0.063-0.499

317

46.0

...

...

228

33.0

...

...

10

12.70-31.75

0.500-1.250

317

46.0

...

...

228

33.0

...

...

12

31.78-38.10

1.251-1.500

303

44.0

...

...

214

31.0

...

...

12

38.13-76.20

1.501-3.000

283

41.0

...

...

200

29.0

...

...

12

76.23-101.60

3.001-4.000

276

40.0

...

...

172

25.0

...

...

12

5456-H321

5652-O

5652-H32(d)

5652-H34(d)

4.78-12.67

0.188-0.499

317

46.0

407

59.0

228

33.0

317

46.0

12

12.70-38.10

0.500-1.500

303

44.0

386

56.0

214

31.0

303

44.0

12

38.13-76.20

1.501-3.000

283

41.0

372

54.0

200

29.0

296

43.0

12

0.15-0.18

0.006-0.007

172

25.0

214

31.0

66

9.5

...

...

...

0.20-0.30

0.008-0.012

172

25.0

214

31.0

66

9.5

...

...

14

0.33-0.48

0.013-0.019

172

25.0

214

31.0

66

9.5

...

...

15

0.51-0.79

0.020-0.031

172

25.0

214

31.0

66

9.5

...

...

16

0.81-1.27

0.032-0.050

172

25.0

214

31.0

66

9.5

...

...

18

1.29-2.87

0.051-0.113

172

25.0

214

31.0

66

9.5

...

...

19

2.90-6.32

0.114-0.249

172

25.0

214

31.0

66

9.5

...

...

20

6.35-76.20

0.250-3.00

172

25.0

214

31.0

66

9.5

...

...

18

0.43-0.48

0.017-0.019

214

31.0

262

38.0

159

23.0

...

...

4

0.51-1.27

0.020-0.050

214

31.0

262

38.0

159

23.0

...

...

5

1.29-2.87

0.051-0.113

214

31.0

262

38.0

159

23.0

...

...

7

2.90-6.32

0.114-0.249

214

31.0

262

38.0

159

23.0

...

...

9

6.35-12.67

0.250-0.499

214

31.0

262

38.0

159

23.0

...

...

11

12.70-50.80

0.500-2.000

214

31.0

262

38.0

159

23.0

...

...

12

0.23-0.48

0.009-0.019

234

34.0

283

41.0

179

26.0

...

...

3

0.51-1.27

0.020-0.050

234

34.0

283

41.0

179

26.0

...

...

4

1.29-2.87

0.051-0.113

234

34.0

283

41.0

179

26.0

...

...

6

2.90-6.32

0.114-0.249

234

34.0

283

41.0

179

26.0

...

...

7

6.35-25.4

0.250-1.000

234

34.0

283

41.0

179

26.0

...

...

10

0.15-0.18

0.006-0.007

255

37.0

303

44.0

200

29.0

...

...

2

0.20-0.79

0.008-0.031

255

37.0

303

44.0

200

29.0

...

...

3

0.81-4.1

0.032-0.162

255

37.0

303

44.0

200

29.0

...

...

4

0.15-0.18

0.006-0.007

269

39.0

...

...

221

32.0

...

...

2

0.20-0.79

0.008-0.031

269

39.0

...

...

221

32.0

...

...

3

0.81-3.25

0.032-0.128

269

39.0

...

...

221

32.0

...

...

4

6.35-12.67

0.250-0.499

193

28.0

...

...

110

16.0

...

...

7

12.70-50.80

0.500-2.000

172

25.0

...

...

66

9.5

...

...

12

50.83-76.20

2.001-3.000

172

25.0

...

...

66

9.5

...

...

16

5657-H241(h)

0.76-2.29

0.030-0.090

124

18.0

179

26.0

...

...

...

...

13

5657-H25

0.76-2.29

0.030-0.090

138

20.0

193

28.0

...

...

...

...

8

5657-H26

0.76-2.29

0.030-0.090

152

22.0

207

30.0

...

...

...

...

7

5657-H28

0.76-2.29

0.030-0.090

172

25.0

...

...

...

...

...

...

5

5652-H36(d)

5652-H38(d)

5652-H112

Converted SI (metric) values are for information only and are not to be used for purposes of specification, acceptance, or rejection. (a) Type of test specimen used depends on thickness of material.

(b) Minimum yield strengths are not determined unless specifically requested.

(c) In 50 mm (2 in.) or 4d.

(d) For the corresponding H2 temper, limits for maximum tensile strength and minimum yield strength do not apply.

(e) When tested upon receipt by the purchaser, material in this temper is required to pass the exfoliation corrosion resistance test (ASSET method). The improved resistance to exfoliation corrosion of individual lots is determined by microscopic examination to ensure a microstructure that is predominantly free of a continuous grain-boundary network of aluminum-magnesium precipitate. The microstructure is compared with that in a previously established acceptable reference photomicrograph.

(f) Also applies to material previously designated H117.

(g) This material is subject to some recrystallization and the attendant loss of brightness.

Table 8 Mechanical-property limits for heat treatable aluminum alloy sheet and plate Alloy and temper

Specified thickness

Tensile strength

Yield strength

Elongation (min)(a), %

Minimum

Maximum

Minimum

Maximum

mm

in.

MPa

ksi

MPa

ksi

MPa

ksi

MPa

ksi

0.51-12.67

0.0200.499

...

...

221

32.0

...

...

110

16.0

16

12.7025.40

0.5001.000

...

...

221

32.0

...

...

...

...

10

0.51-0.99

0.0200.039

407

59.0

...

...

241

35.0

...

...

14

1.02-6.32

0.0400.249

407

59.0

...

...

248

36.0

...

...

14

2014-T4 coiled sheet

0.51-6.32

0.0200.249

407

59.0

...

...

241

35.0

...

...

14

2014-T451(b)(c) plate

6.35-12.67

0.2500.499

400

58.0

...

...

248

36.0

...

...

14

12.7025.40

0.5001.000

400

58.0

...

...

248

36.0

...

...

14

25.4350.80

1.0012.000

400

58.0

...

...

248

36.0

...

...

12

50.8376.20

2.0013.000

393

57.0

...

...

248

36.0

...

...

8

2014-T42(d)(e) sheet and plate

0.51-25.40

0.0201.000

400

58.0

...

...

234

34.0

...

...

14

2014-T6 and T62(d)(e) sheet

0.51-0.99

0.0200.039

441

64.0

...

...

393

57.0

...

...

6

2014-O sheet and plate

2014-T3 flat sheet

2014-T62(d)(e) plate

and

T651(b)

2024-O sheet and plate

2024-T3(c) flat sheet

2024-T361(c)(f) flat sheet and plate

1.02-6.32

0.0400.249

441

66.0

...

...

400

58.0

...

...

7

6.35-12.67

0.2500.499

462

67.0

...

...

407

59.0

...

...

7

12.7025.40

0.5001.000

462

67.0

...

...

407

59.0

...

...

6

25.4350.80

1.0012.000

462

67.0

...

...

407

59.0

...

...

4

50.8363.50

2.0012.500

448

65.0

...

...

400

58.0

...

...

2

63.5376.20

2.5013.000

434

63.0

...

...

393

57.0

...

...

2

76.23101.60

3.0014.000

407

59.0

...

...

379

55.0

...

...

1

0.25-12.67

0.0100.499

...

...

221

32.0

...

...

97

14.0

12

12.7044.45

0.5001.750

...

...

221

32.0

...

...

...

...

12

0.20-0.23

0.0080.009

434

63.0

...

...

290

42.0

...

...

10

0.25-0.51

0.0100.020

434

63.0

...

...

290

42.0

...

...

12

0.53-3.25

0.0210.18

434

63.0

...

...

290

42.0

...

...

15

3.28-6.32

0.1290.249

441

64.0

...

...

290

42.0

...

...

15

0.51-1.57

0.0200.062

462

67.0

...

...

345

50.0

...

...

8

1.60-6.32

0.0630.249

469

68.0

...

...

352

51.0

...

...

9

6.35-12.67

0.2500.499

455

66.0

...

...

338

49.0

...

...

9

2024-T4 coiled sheet

2024-T351(b)(c) plate

2024-T42(d)(e) sheet and plate

12.70

0.500

455

66.0

...

...

338

49.0

...

...

10

0.25-0.51

0.0100.020

427

62.0

...

...

276

40.0

...

...

12

0.53-6.32

0.0210.249

427

62.0

...

...

276

40.0

...

...

15

6.35-12.67

0.2500.499

441

64.0

...

...

290

42.0

...

...

12

12.7025.40

0.5001.000

434

63.0

...

...

290

42.0

...

...

8

25.4338.10

1.0011.500

427

62.0

...

...

290

42.0

...

...

7

38.1350.80

1.5012.000

427

62.0

...

...

290

42.0

...

...

6

50.8376.20

2.0013.000

414

60.0

...

...

290

42.0

...

...

4

76.23101.60

3.0014.000

393

57.0

...

...

283

41.0

...

...

4

0.25-0.51

0.0100.020

427

62.0

...

...

262

38.0

...

...

12

0.53-6.32

0.0210.249

427

62.0

...

...

262

38.0

...

...

15

6.35-12.67

0.2500.499

427

62.0

...

...

262

38.0

...

...

12

12.7025.40

0.5001.000

421

61.0

...

...

262

38.0

...

...

8

25.4338.10

1.0011.500

414

60.0

...

...

262

38.0

...

...

7

38.1350.80

1.5012.000

414

60.0

...

...

262

38.0

...

...

6

50.8376.20

2.0013.000

400

58.0

...

...

262

38.0

...

...

4

2219-T62(d)(e) sheet and plate

2219-T81 flat sheet

2219-T851(b) plate

2219-T87 plate

flat

sheet

and

0.51-0.99

0.0200.039

372

54.0

...

...

248

36.0

...

...

6

1.02-6.32

0.0400.249

372

54.0

...

...

248

36.0

...

...

7

6.35-25.40

0.2501.000

372

54.0

...

...

248

36.0

...

...

8

25.4350.80

1.0012.000

372

54.0

...

...

248

36.0

...

...

7

0.51-0.99

0.0200.039

427

62.0

...

...

317

46.0

...

...

6

1.02-6.32

0.0400.249

427

62.0

...

...

317

46.0

...

...

7

6.35-25.40

0.2501.000

427

62.0

...

...

317

46.0

...

...

8

25.4350.80

1.0012.000

427

62.0

...

...

317

46.0

...

...

7

50.8376.20

2.0013.000

427

62.0

...

...

310

45.0

...

...

6

76.23101.60

3.0014.000

414

60.0

...

...

303

44.0

...

...

5

101.63127.00

4.0015.000

407

59.0

...

...

296

43.0

...

...

5

127.03152.40

5.0016.000

393

57.0

...

...

290

42.0

...

...

4

0.51-0.99

0.0200.039

441

64.0

...

...

358

52.0

...

...

5

1.02-6.32

0.0400.249

441

64.0

...

...

358

52.0

...

...

6

6.35-25.40

0.2501.000

441

64.0

...

...

352

51.0

...

...

7

25.4350.80

1.0012.000

441

64.0

...

...

352

51.0

...

...

6

6061-O sheet and plate

6061-T4 sheet

6061-T451(b)(c) plate

50.8376.20

2.0013.000

441

64.0

...

...

352

51.0

...

...

6

76.23101.60

3.0014.000

427

62.0

...

...

345

50.0

...

...

4

101.63127.00

4.0015.000

421

61.0

...

...

338

49.0

...

...

3

0.15-0.18

0.0060.007

...

...

152

22.0

...

...

83

12.0

10

0.20-0.23

0.0080.009

...

...

152

22.0

...

...

83

12.0

12

0.25-0.51

0.0100.020

...

...

152

22.0

...

...

83

12.0

14

0.53-3.25

0.0210.128

...

...

152

22.0

...

...

83

12.0

16

3.28-12.67

0.1290.499

...

...

152

22.0

...

...

83

12.0

18

12.7025.40

0.5001.000

...

...

152

22.0

...

...

...

...

18

25.4376.20

1.0013.000

...

...

152

22.0

...

...

...

...

16

0.15-0.18

0.0060.007

207

30.0

...

...

110

16.0

...

...

10

0.20-0.23

0.0080.009

207

30.0

...

...

110

16.0

...

...

12

0.25-0.51

0.0100.020

207

30.0

...

...

110

16.0

...

...

14

0.53-6.32

0.0210.249

207

30.0

...

...

110

16.0

...

...

16

6.35-25.40

0.2501.000

207

30.0

...

...

110

16.0

...

...

18

25.4376.20

1.0013.000

207

30.0

...

...

110

16.0

...

...

16

6061-T42(d)(e) sheet and plate

6061-T6 and T62(d)(e) sheet

6061-T62(d)(e) plate

and

T651(b)

7075-O sheet and plate

0.15-0.18

0.0060.007

207

30.0

...

...

97

14.0

...

...

10

0.20-0.23

0.0080.009

207

30.0

...

...

97

14.0

...

...

12

0.25-0.51

0.0100.020

207

30.0

...

...

97

14.0

...

...

14

0.53-6.32

0.0210.249

207

30.0

...

...

97

14.0

...

...

16

6.35-25.40

0.2501.000

207

30.0

...

...

97

14.0

...

...

18

25.4376.20

1.0013.000

207

30.0

...

...

97

14.0

...

...

16

0.15-0.18

0.0060.007

290

42.0

...

...

241

35.0

...

...

4

0.20-0.23

0.0080.009

290

42.0

...

...

241

35.0

...

...

6

0.25-0.51

0.0100.020

290

42.0

...

...

241

35.0

...

...

8

0.53-6.32

0.0210.249

290

42.0

...

...

241

35.0

...

...

10

6.35-12.67

0.2500.499

290

42.0

...

...

241

35.0

...

...

10

12.7025.40

0.5001.000

290

42.0

...

...

241

35.0

...

...

9

25.4350.80

1.0012.000

290

42.0

...

...

241

35.0

...

...

8

50.83101.60

2.0014.000

290

42.0

...

...

241

35.0

...

...

6

101.63152.40

4.0016.00(h)

276

40.0

...

...

241

35.0

...

...

6

0.38-12.67

0.0150.499

...

...

276

40.0

...

...

145

21.0

10

12.7050.80

0.5002.000

...

...

276

40.0

...

...

...

...

10

0.20-0.28

0.0080.011

510

74.0

...

...

434

63.0

...

...

5

0.30-0.99

0.0120.039

524

76.0

...

...

462

67.0

...

...

7

1.02-3.18

0.0400.125

538

78.0

...

...

469

68.0

...

...

8

3.21-6.32

0.1260.249

538

78.0

...

...

476

69.0

...

...

8

6.35-12.67

0.2500.499

538

78.0

...

...

462

67.0

...

...

9

12.7025.40

0.5001.000

538

78.0

...

...

469

68.0

...

...

7

25.4350.80

1.0012.000

531

77.0

...

...

462

67.0

...

...

6

50.8363.50

2.0012.500

524

76.0

...

...

441

64.0

...

...

5

63.5376.20

2.5013.000

496

72.0

...

...

421

61.0

...

...

5

76.2388.90

3.0013.500

489

71.0

...

...

400

58.0

...

...

5

88.93101.60

3.5014.000

462

67.0

...

...

372

54.0

...

...

3

7075-T73(i) sheet

1.02-6.32

0.0400.249

462

67.0

...

...

386

56.0

...

...

8

7075-T7351(b)(i) plate

6.35-25.40

0.2501.000

476

69.0

...

...

393

57.0

...

...

7

25.4350.80

1.0012.000

476

69.0

...

...

393

57.0

...

...

6

50.8363.50

2.0012.500

455

66.0

...

...

358

52.0

...

...

6

7075-T6 and T62(d)(e) sheet

7075-T62(d)(e) plate

and

T651(b)

63.5376.20

2.5013.000

441

64.0

...

...

338

49.0

...

...

6

7075-T76(j) sheet

3.18-6.32

0.1250.249

503

73.0

...

...

427

62.0

...

...

8

7075-T7351(b)(i) plate

6.35-25.40

0.2501.000

476

69.0

...

...

393

57.0

...

...

7

25.4350.80

1.0012.000

476

69.0

...

...

393

57.0

...

...

6

50.8363.50

2.0012.500

455

66.0

...

...

358

52.0

...

...

6

63.5376.20

2.5013.000

441

64.0

...

...

338

49.0

...

...

6

7075-T76(j) sheet

3.18-6.32

0.1250.249

503

73.0

...

...

427

62.0

...

...

8

7075-T7651(d)(j) plate

6.35-12.67

0.2500.499

496

72.0

...

...

421

61.0

...

...

8

12.7025.40

0.5001.000

489

71.0

...

...

414

60.0

...

...

6

0.38-12.67

0.0150.499

...

...

276

40.0

...

...

145

21.0

10

12.70

0.500

...

...

276

40.0

...

...

...

...

10

0.38-1.12

0.0150.044

572

83.0

...

...

496

72.0

...

...

7

1.14-6.32

0.0450.249

579

84.0

...

...

503

73.0

...

...

8

6.35-12.67

0.2500.499

579

84.0

...

...

503

73.0

...

...

8

12.7025.40

0.5001.000

579

84.0

...

...

503

73.0

...

...

6

25.4338.10

1.0011.500

579

84.0

...

...

503

73.0

...

...

4

7178-O sheet and plate

7178-T6 and T62(d)(e) sheet

7178-T62(d)(e) plate

and

T651(b)

38.1350.80

1.5012.000

552

80.0

...

...

483

70.0

...

...

3

0.25-12.67

0.0100.499

441

64.0

...

...

345

50.0

...

...

5

12.7076.20

0.5003.000

434

63.0

...

...

345

50.0

...

...

5

2024-T72(d)(e) sheet

0.25-6.32

0.0100.249

414

60.0

...

...

317

46.0

...

...

5

2024-T81 flat sheet

0.25-6.32

0.0100.249

462

67.0

...

...

400

58.0

...

...

5

2024-T851(b) plate

6.35-12.67

0.2500.499

462

67.0

...

...

400

58.0

...

...

5

12.7025.40

0.5001.000

455

66.0

...

...

400

58.0

...

...

5

25.4338.07

1.0011.499

455

66.0

...

...

393

57.0

...

...

5

0.51-1.57

0.0200.062

483

70.0

...

...

427

62.0

...

...

3

1.60-6.32

0.0630.249

489

71.0

...

...

455

66.0

...

...

4

6.35-12.67

0.2500.499

483

70.0

...

...

441

64.0

...

...

4

12.70

0.500

483

70.0

...

...

441

64.0

...

...

4

0.20-0.23

0.0080.009

...

...

207

30.0

...

...

97

14.0

10

0.25-0.81

0.0100.032

...

...

207

30.0

...

...

97

14.0

12

0.84-1.57

0.0330062

...

...

207

30.0

...

...

97

14.0

12

1.60-4.75

0.0630.187

...

...

221

32.0

...

...

97

14.0

12

2024-T62(d)(e) sheet and plate

2024-T861(f) flat sheet and plate

Alclad 2024-O sheet and plate

Alclad 2024-T3(c) flat sheet

Alclad 2024-T361(c)(f) sheet and plate

flat

Alclad 2024-T4 coiled sheet

Alclad 2024-T351(b)(c) plate

4.78-12.67

0.1880.499

...

...

221

32.0

...

...

97

14.0

12

12.7044.45

0.5001.750

...

...

221

32.0(h)

...

...

...

...

12

0.20-0.23

0.0080.009

400

58.0

...

...

269

39.0

...

...

10

0.25-0.51

0.0100.020

407

59.0

...

...

269

39.0

...

...

12

0.53-1.57

0.0210.062

407

59.0

...

...

269

39.0

...

...

15

1.60-3.25

0.0630.128

421

61.0

...

...

276

40.0

...

...

15

3.28-6.32

0.1290.249

427

62.0

...

...

276

40.0

...

...

15

0.51-1.57

0.0200.062

421

61.0

...

...

324

47.0

...

...

8

1.60-4.75

0.0630.187

441

64.0

...

...

331

48.0

...

...

9

4.78-6.32

0.1880.249

441

64.0

...

...

331

48.0

...

...

9

6.35-12.67

0.2500.499

441

64.0

...

...

331

48.0

...

...

9

12.70

0.500

455

66.0(g)

...

...

338

49.0(g)

...

...

10

0.25-0.51

0.0100.020

400

58.0

...

...

248

36.0

...

...

12

0.53-1.57

0.0210.062

400

58.0

...

...

248

36.0

...

...

15

1.60-3.25

0.0630.128

421

61.0

...

...

262

38.0

...

...

15

6.35-12.67

0.2500.499

427

62.0

...

...

276

40.0

...

...

12

Alclad 2024-T42(d)(e) sheet and plate

Alclad 2024-T62(d)(e) sheet and plate

12.7025.40

0.5001.000

434

63.0(g)

...

...

290

42.0(g)

...

...

8

25.4338.10

1.0011.500

427

62.0(g)

...

...

290

42.0(g)

...

...

7

38.1350.80

1.5012.000

427

62.0(g)

...

...

290

42.0(g)

...

...

6

50.8376.20

2.0013.000

414

60.0(g)

...

...

290

42.0(g)

...

...

4

76.23101.60

3.0014.000

393

57.0(g)

...

...

283

41.0(g)

...

...

4

0.20-0.23

0.0080.009

379

55.0

...

...

234

34.0

...

...

10

0.25-0.51

0.0100.020

393

57.0

...

...

234

34.0

...

...

12

0.53-1.57

0.0210.062

393

57.0

...

...

234

34.0

...

...

15

1.60-4.75

0.0630.187

414

60.0

...

...

248

36.0

...

...

15

4.78-6.32

0.1880.249

414

60.0

...

...

248

36.0

...

...

15

6.35-12.67

0.2500.499

414

60.0

...

...

248

36.0

...

...

12

12.7025.40

0.5001.000

421

61.0(g)

...

...

262

38.0(g)

...

...

8

25.4338.10

1.0011.500

414

60.0(g)

...

...

262

38.0(g)

...

...

7

38.1350.80

1.5012.000

414

60.0(g)

...

...

262

38.0(g)

...

...

6

50.8376.20

2.0013.000

400

58.0(g)

...

...

262

38.0(g)

...

...

4

0.25-1.57

0.0100.062

414

60.0

...

...

324

47.0

...

...

5

Alclad 2024-T72(d)(e) sheet

Alclad 2024-T81 flat sheet

Alclad 2024-T851(b) plate

Alclad 2024-T861(f) flat sheet and plate

2036-T4 flat sheet

1.60-4.75

0.0630.187

427

62.0

...

...

338

49.0

...

...

5

4.78-12.67

0.1880.499

427

62.0

...

...

338

49.0

...

...

5

0.25-1.57

0.0100.062

386

56.0

...

...

296

43.0

...

...

5

1.60-4.75

0.0630.187

400

58.0

...

...

310

45.0

...

...

5

4.78-6.32

0.1880.249

400

58.0

...

...

310

45.0

...

...

5

0.25-1.57

0.0100.062

427

62.0

...

...

372

54.0

...

...

5

1.60-4.75

0.0630.187

448

65.0

...

...

386

56.0

...

...

5

4.78-6.32

0.1880.249

448

65.0

...

...

386

56.0

...

...

5

6.35-12.67

0.2500.499

488

65.0

...

...

386

56.0

...

...

5

12.7025.40

0.5001.000

455

66.0(g)

...

...

400

58.0(g)

...

...

5

0.51-1.57

0.0200.062

441

64.0

...

...

400

58.0

...

...

3

1.60-4.75

0.0630.187

476

69.0

...

...

441

64.0

...

...

4

4.78-6.32

0.1880.249

476

69.0

...

...

441

64.0

...

...

4

6.35-12.67

0.2500.499

469

68.0

...

...

427

62.0

...

...

4

12.70

0.500

483

70.0(g)

...

...

441

64.0

...

...

4

0.64-3.18

0.0250.125

290

42.0

...

...

159

23.0

...

...

20

2219-O sheet and plate

0.51-50.83

0.0202.000

...

...

221

32.0

...

...

110

16.0

12

2219-T31(c) flat sheet

0.51-0.99

0.0200.039

317

46.0

...

...

200

29.0

...

...

8

1.02-6.32

0.0400.249

317

46.0

...

...

193

28.0

...

...

10

6.35-50.80

0.2502.000

317

46.0

...

...

193

28.0

...

...

10

50.8376.20

2.0013.000

303

44.0

...

...

193

28.0

...

...

10

76.23101.60

3.0014.000

290

42.0

...

...

186

27.0

...

...

9

101.63127.00

4.0015.000

276

40.0

...

...

179

26.0

...

...

9

127.03152.40

5.0016.000

269

39.0

...

...

172

25.0

...

...

8

0.51-0.99

0.0200.039

338

49.0

...

...

262

38.0

...

...

6

1.02-50.80

0.0402.000

338

49.0

...

...

255

37.0

...

...

6

50.8363.50

2.012.500

338

49.0

...

...

255

37.0

...

...

6

63.5376.20

2.5013.000

324

47.0

...

...

248

36.0

...

...

6

76.23101.60

3.0014.000

310

45.0

...

...

241

35.0

...

...

5

101.63127.00

4.0015.000

296

43.0

...

...

234

34.0

...

...

4

7178-T76(j) sheet

1.14-6.32

0.0450.249

517

75.0

...

...

441

64.0

...

...

8

7178-T7651(b)(j) plate

6.35-12.67

0.2500.499

510

74.0

...

...

434

63.0

...

...

8

2219-T351(b)(c) plate

2219-T37(c) flat sheet and plate

7475-T61 sheet

Alloy and temper

2124-T851(b) plate

12.7025.40

0.5001.000

503

73.0

...

...

427

62.0

...

...

6

1.02-6.32

0.0400.249

490

71.0

...

...

414

60.0

...

...

9

Specified thickness

Axis of test specimen(k)

mm

in.

38.1050.80

1.5002.000

50.8376.20

76.23101.60

101.63127.00

127.03152.40

2.0013.000

3.0014.000

4.0015.000

5.0016.000

Tensile strength

Yield strength

Elongation (min)(a), %

Minimum

Maximum

Minimum

Maximum

MPa

ksi

MPa

ksi

MPa

ksi

MPa

ksi

L

455

66.0

...

...

393

57.0

...

...

6

LT

455

66.0

...

...

393

57.0

...

...

5

ST

441

64.0

...

...

379

55.0

...

...

1.5

L

448

65.0

...

...

393

57.0

...

...

6

LT

448

65.0

...

...

393

57.0

...

...

4

ST

434

63.0

...

...

379

55.0

...

...

1.5

L

448

65.0

...

...

386

56.0

...

...

5

LT

448

65.0

...

...

386

56.0

...

...

4

ST

427

62.0

...

...

372

54.0

...

...

1.5

L

441

64.0

...

...

379

55.0

...

...

5

LT

441

64.0

...

...

379

55.0

...

...

4

ST

421

61.0

...

...

365

53.0

...

...

1.5

L

434

63.0

...

...

372

54.0

...

...

5

LT

434

63.0

...

...

372

54.0

...

...

4

ST

400

58.0

...

...

352

51.0

...

...

1.5

7050-T7451(b)(i) (formerly 7050T73651) plate

6.3550.80

50.8376.20

76.23101.60

101.63127.00

127.03152.40

7050-T7651(b)(j) plate

6.3525.40

25.4338.10

0.2502.000

2.0013.000

3.0014.000

4.0015.000

5.0016.000

0.2501.000

1.0011.500

L

510

74.0

...

...

441

64.0

...

...

10

LT

510

74.0

...

...

441

64.0

...

...

9

ST

...

...

...

...

...

...

...

...

...

L

503

73.0

...

...

434

63.0

...

...

9

LT

503

73.0

...

...

434

63.0

...

...

8

ST

469

68.0

...

...

407

59.0

...

...

2

L

496

72.0

...

...

427

62.0

...

...

9

LT

496

72.0

...

...

427

62.0

...

...

6

ST

469

68.0

...

...

400

58.0

...

...

2

L

489

71.0

...

...

421

61.0

...

...

9

LT

489

71.0

...

...

421

61.0

...

...

5

ST

462

67.0

...

...

393

57.0

...

...

2

L

483

70.0

...

...

414

60.0

...

...

8

LT

483

70.0

...

...

414

60.0

...

...

4

ST

462

67.0

...

...

393

57.0

...

...

2

L

524

76.0

...

...

455

66.0

...

...

9

LT

524

76.0

...

...

455

66.0

...

...

8

ST

...

...

...

...

...

...

...

...

...

L

531

77.0

...

...

462

67.0

...

...

9

LT

531

77.0

...

...

462

67.0

...

...

8

ST

...

...

...

...

...

...

...

...

...

38.1350.80

50.8376.20

7475-T7351 plate

6.3538.10

1.5012.000

2.0013.000

0.2501.500

L

524

76.0

...

...

455

66.0

...

...

9

LT

524

76.0

...

...

455

66.0

...

...

8

ST

...

...

...

...

...

...

...

...

...

L

524

76.0

...

...

455

66.0

...

...

8

LT

524

76.0

...

...

455

66.0

...

...

7

ST

...

...

...

...

...

...

...

...

1.5

L

490

71.0

...

...

414

60.0

...

...

10

LT

490

71.0

...

...

414

60.0

...

...

9

25.4338.10

1.0011.500

ST

462(l)

67.0(l)

...

...

386(l)

56.0(l)

...

...

4(l)

38.1250.80

1.5012.000

L

483

70.0

...

...

400

58.0

...

...

10

LT

483

70.0

...

...

400

58.0

...

...

8

ST

455

66.0

...

...

372

54.0

...

...

4

L

476

69.0

...

...

393

57.0

...

...

10

LT

476

69.0

...

...

393

57.0

...

...

8

ST

448

65.0

...

...

365

53.0

...

...

4

L

469

68.0

...

...

386

56.0

...

...

10

LT

469

68.0

...

...

386

56.0

...

...

8

ST

448

65.0

...

...

365

53.0

...

...

3

L

448

65.0

...

...

365

53.0

...

...

10

LT

448

65.0

...

...

365

53.0

...

...

8

50.8363.50

63.5376.20

76.2388.90

2.0012.500

2.5013.000

3.0013.500

88.93101.60

3.5014.000

ST

448

65.0

...

...

352

51.0

...

...

3

L

441

64.0

...

...

359

52.0

...

...

9

LT

441

64.0

...

...

359

52.0

...

...

7

ST

434

63.0

...

...

345

50.0

...

...

3

Converted SI (metric) values are for information only and are not to be used for purposes of specification, acceptance, or rejection. (a) In 50 mm (2 in.) or 4d.

(b) For stress-relieved tempers, the characteristics and properties other than those specified may differ somewhat from the corresponding characteristics and properties of material in the basic temper.

(c) Upon artificial aging, material in the T3/T31, T37, T351, T36, and T451 tempers is capable of developing the mechanical properties applicable to material in the T81, T87, T851, T861 and T651 tempers, respectively.

(d) These properties usually can be obtained by the user when the material is properly solution heat treated or solution and precipitation heat treated from the O (annealed) or F (as fabricated) temper. These properties also apply to samples of material in the O and F tempers, which are solution heat treated or solution and precipitation heat treated by the producer to determine that the material will respond to proper heat treatment. Properties attained by the user, however, may be lower than those listed if the material has been formed or otherwise cold or hot worked, particularly in the annealed temper, prior to solution heat treatment.

(e) This temper is not available from the material producer.

(f) Tempers T361 and T861 were formerly designated T36 and T86, respectively.

(g) This table specifies properties applicable to test specimens, and, because for plate in thicknesses of 0.500 in. or greater the cladding material is removed during preparation of specimens, the listed properties are applicable to the core material only. Tensile and yield strengths of the composite plate are slightly lower depending on cladding thickness.

(h) The properties given for this thickness apply only to the T651 temper.

(i) When subjected to stress-corrosion testing, material in this temper is capable of exhibiting no evidence of stress-corrosion cracking when exposed for a period of 30 days in the short-transverse direction at a stress level of 75% of the specified yield strength. The stress-corrosion resistance capabilities of individual lots are determined by testing the previously selected tensile-test specimens in accordance with the applicable electrical conductivity acceptance criteria.

(j) Material in this temper, when tested upon receipt by the purchaser, is capable of passing an exfoliation corrosion resistance test and the stresscorrosion criteria of some tests except that the stress level should be 25.0 ksi. The improved resistance to exfoliation corrosion and stresscorrosion cracking of individual lots is determined by testing the previously selected tensile-test specimens in accordance with the applicable electrical conductivity acceptance criteria

(k) L, longitudinal; LT, long transverse; ST, short transverse

(l) Applies to 38.10 mm (1.500 in.) thickness only

Fig. 4 Fatigue-crack-growth rates as functions of stress-intensity factor for two thicknesses of 7050-T7451 plate tested in three directions and in three environments

Table 9 Mechanical property limits for non-heat-treatable aluminum alloy extruded wire, rod, bar, and shapes Alloy and temper

Specified diameter or thickness(a)

Area

Tensile strength

Yield strength (min)

Minimum

Maximum

Elongation (min)(b), %

mm

in.

cm2

in.2

MPa

ksi

MPa

ksi

MPa

ksi

1100-O

All

All

All

All

76

11.0

107

15.5

21

3.0

25

1100-H112

All

All

All

All

76

11.0

...

...

21

3.0

...

3003-O

All

All

All

All

97

14.0

131

19.0

34

5.0

25

3003-H112

All

All

All

All

97

14.0

...

...

34

5.0

...

5083-O

127

5.000

206

32

269

39.0

352

51.0

110

16.0

14

5083-H111

127

5.000

206

32

276

40.0

...

...

165

24.0

12

5083-H112

127

5.000

206

32

269

39.0

...

...

110

16.0

12

5086-O

127

5.000

206

32

241

35.0

317

46.0

97

14.0

14

5086-H111

127

5.000

206

32

248

36.0

...

...

145

21.0

12

5086-H112

127

5.000

206

32

241

35.0

...

...

97

14.0

12

5154-O

All

All

All

All

207

30.0

283

41.0

76

11.0

...

5154-H112

All

All

All

All

207

30.0

...

...

76

11.0

...

5454-O

127

5.000

206

32

214

31.0

283

41.0

83

12.0

14

5454-H111

127

5.000

206

32

228

33.0

...

...

131

19.0

12

5454-H112

127

5.000

206

32

214

31.0

...

...

83

12.0

12

Converted SI (metric) values are for information only and are not to be used for purposes of specification, acceptance, or rejection. (a) The thickness of the cross section from which the tensile-test specimen is taken determines the applicable mechanical properties.

(b) In 50 mm (2 in.) or 4d.

Table 10 Mechanical-property limits for heat-treatable aluminum alloy extruded wire, rod, bar, and shapes Alloy and temper

Specified diameter or thickness(a)

mm

in.

Area

cm2

in.2

Tensile strength

Yield strength

Minimum

Maximum

Minimum

Maximum

MPa

MPa

MPa

MPa

ksi

ksi

ksi

Elongation (min)(b), %

ksi

2014-O

All

All

All

All

...

...

207

30.0

...

...

124

18.0

12

2014-T4, T4510(c)(d) and T4511(c)(d)

All

All

All

All

345

50.0

...

...

241

35.0

...

...

12

2014-T42(e)(f)

All

All

All

All

345

50.0

...

...

200

29.0

...

...

12

All

All

414

60.0

...

...

365

53.0

...

...

7

All

All

441

64.0

...

...

400

58.0

...

...

7

469

68.0

...

...

414

60.0

...

...

7

2014-T6, T6510(c) (c) and T6511

12.67 0.499

12.7019.02

19.05

0.5000.749

0.750

161 25

19.05

2014-T62(e)(f)

0.750

19.02

>161206

>2532

469

68.0

...

...

400

58.0

...

...

6

All

All

414

60.0

...

...

365

53.0

...

...

7

414

60.0

...

...

365

53.0

...

...

7

0.749

19.05

0.750

161 25

19.05

2024-O

2024-T3, T3510(c)(d) T3511(c)(d)

All

0.750

All

6.32

>161206

>2532

414

60.0

...

...

365

53.0

...

...

6

All

All

...

...

241

35.0

...

...

131

19.0

12

All

All

393

57.0

...

...

290

42.0

...

...

12

0.249

6.3519.02

0.2500.749

All

All

414

60.0

...

...

303

44.0

...

...

12

19.0538.07

0.7501.499

All

All

448

65.0

...

...

317

46.0

...

...

10

483

70.0

...

...

358

52.0

...

...

10

469

68.0

...

...

331

48.0

...

...

8

38.10

1.500

161 25

38.10

1.500

>161206

>2532

2024-T42(e)(f)

19.02

All

All

393

57.0

...

...

262

38.0

...

...

12

All

All

393

57.0

...

...

262

38.0

...

...

10

393

57.0

...

...

262

38.0

...

...

10

0.749

19.0538.07

38.10

0.7501.499

1.500

161 25

38.10

2024-T81, T8510(c)and T8511(c)

1.500

>161206

>2532

393

57.0

...

...

262

38.0

...

...

8

1.276.32

0.0500.249

All

All

441

64.0

...

...

386

56.0

...

...

4

6.3538.07

0.2501.499

All

All

455

66.0

...

...

400

58.0

...

...

5

455

66.0

...

...

400

58.0

...

...

5

...

...

221

32.0

...

...

124

18.0

12

290

42.0

...

...

179

26.0

...

...

14

310

45.0

...

...

186

27.0

...

...

14

372

54.0

...

...

248

36.0

...

...

6

372

54.0

...

...

248

36.0

...

...

6

400

58.0

...

...

290

42.0

...

...

6

38.10

1.500

206 32

2219-O

2219-T31 T3510(c)(d)and T3511(c)(d)

All

12.67

All

All

161 0.499

12.7076.17

2219-T62(e)(f)

All

0.5002.999

25.37

25

161 25

161 0.999

25.40

1.000

25

206 32

2219-T81, T8510(c)and T8511(c)

6005-T1

â76.17

161 2.999

12.70

25

All

All

172

25.0

...

...

103

15.0

...

...

16

All

All

262

38.0

...

...

241

35.0

...

...

8

All

All

262

38.0

...

...

241

35.0

...

...

10

0.500

6005-T5

3.15 0.124

3.1825.40

0.1251.000

6061-O

6061-T1

All

All

15.88

All

Al

...

...

152

22.0

...

...

110

16.0

16

All

All

179

26.0

...

...

97

14.0

...

...

16

0.625

6061-T4 T4510(c)(d)and T4511(c)(d)

All

All

All

All

179

26.0

...

...

110

16.0

...

...

16

6061-T42(e)(f)

All

All

All

All

179

26.0

...

...

83

12.0

...

...

16

All

All

241

35.0

...

...

207

30.0

...

...

8

All

All

262

38.0

...

...

241

35.0

...

...

8

All

All

262

38.0

...

...

241

35.0

...

...

10

All

All

...

...

131

19.0

...

...

...

...

18

All

All

117

17.0

...

...

62

9.0

...

...

12

All

All

110

16.0

...

...

55

8.0

...

...

12

All

All

131

19.0

...

...

69

10.0

...

...

14

All

All

124

18.0

...

...

62

9.0

...

...

14

All

All

152

22.0

...

...

110

16.0

...

...

8

All

All

145

21.0

...

...

103

15.0

...

...

8

All

All

152

22.0

207

30.0

110

16.0

172

25.0

8

All

All

207

30.0

...

...

172

25.0

...

...

8

6061-T51

15.88 0.625

6061-T6 T62(e)(f) (c) T6510 and T6511(c)

6.32 0.249

6.35

6063-O

6063-T1

All

0.250

All

12.70 0.500

12.7325.40

6063-T4 and T42(e)(f)

0.5011.000

12.70 0.500

12.7325.40

6063-T5

0.5011.000

12.70 0.500

12.7325.40

6063-T52

0.5011.000

25.40 1.000

6063-T6 and T62(e)(f)

3.15 0.124

3.1825.40

0.1251.000

All

All

207

30.0

...

...

172

25.0

...

...

10

6066-O

All

All

All

All

...

...

200

29.0

...

...

124

18.0

16

6066-T4, T4510(c)(d)and T4511(c)(d)

All

All

All

All

276

40.0

...

...

172

25.0

...

...

14

6066-T42(e)(f)

All

All

All

All

276

40.0

...

...

165

24.0

...

...

14

6066-T6 T6510(c)and T6511(c)

All

All

All

All

345

50.0

...

...

310

45.0

...

...

8

6066-T62(e)(f)

All

All

All

All

345

50.0

...

...

290

42.0

...

...

8

331

48.0

...

...

310

45.0

...

...

6

6070-T6 and T62(e)(f)

76.17

206 2.999

6105-T1

12.70

32

All

All

172

25.0

...

...

103

15.0

...

...

16

All

All

262

38.0

...

...

241

35.0

...

...

8

All

All

255

37.0

...

...

234

34.0

...

...

7

All

All

262

38.0

...

...

241

35.0

...

...

8

0.500

6105-T5

12.70 0.500

6162-T5, T5510(c)and T5511(c)

25.40

6162-T6 T6510(c) and T6511(c)

6.32

6262-T6 T62(e)(f), (c) T6510 and T6511(c)

6351-T54

1.000

0.249

6.3512.67

0.2500.499

All

All

262

38.0

...

...

241

35.0

...

...

10

All

All

All

All

262

38.0

·

...

241

35.0

...

...

10

207

30.0

...

...

138

20.0

...

...

10

117

17.0

...

...

62

9.0

...

...

12

152

22.0

...

...

110

16.0

...

...

8

12.70

129 0.500

6463-T1

12.70

20

129 0.500

6463-T5

12.70

20

129 0.500

20

6463-T6 and T62(e)(f)

3.15

129 0.124

7001-O

7001-T6, T62(e)(f), (c) T6510 and T6511(c)

7005-T53

3.1812.70

0.1250.500

All

All

6.32

207

30.0

...

...

172

25.0

...

...

8

207

...

...

...

172

25.0

...

...

10

20

129 20

All

All

...

...

290

42.0

...

...

179

26.0

10

All

All

614

89.0

...

...

565

82.0

...

...

5

0.249

6.3512.67

0.2500.499

All

All

634

92.0

...

...

579

84.0

...

...

5

12.7050.77

0.5001.999

All

All

648

94.0

...

...

607

88.0

...

...

5

50.8076.17

2.0002.999

All

All

620

90.0

...

...

579

84.0

...

...

5

All

All

345

50.0

...

...

303

44.0

...

...

10

All

All

...

...

276

40.0

...

...

165

24.0

10

All

All

538

78.0

...

...

483

70.0

...

...

7

19.05 0.750

7075-O

7075-T6 T62(e)(f), (c) T6510 and T6511(c)

All

All

6.32 0.249

6.3512.67

0.2500.499

All

All

558

81.0

...

...

503

73.0

...

...

7

12.7038.07

0.5001.499

All

All

558

81.0

...

...

496

72.0

...

...

7

38.1076.17

1.5002.999

All

All

558

81.0

...

...

496

72.0

...

...

7

76.20114.27

3.0004.499

558

81.0

...

...

489

71.0

...

...

7

76.20114.27

3.0004.499

538

78.0

...

...

483

70.0

...

...

6

114.30127

4.5005.000

538

78.0

...

...

469

68.0

...

...

6

129 20

>129206

>2032

206 32

7075-T73(g) T73510(c)(g) T73511(c)(g)

7075-T76(h) T76510(c)(h) T76511(c)(h)

and

and

7178-O

1.576.32

0.0620.249

129

6.3538.07

0.2501.499

161

38.1076.17

1.5002.999

161

76.20114.27

3.0004.499

129

76.20114.27

3.0004.499

3.15

469

68.0

...

...

400

58.0

...

...

7

483

70.0

...

...

421

61.0

...

...

8

476

69.0

...

...

407

59.0

...

...

8

469

68.0

...

...

393

57.0

...

...

7

20

25

25

20

129206

2032

448

65.0

...

...

379

55.0

...

...

7

All

All

496

72.0

...

...

47

62.0

...

...

7

510

74.0

...

...

441

64.0

...

...

7

517

75.0

...

...

448

65.0

...

...

7

517

75.0

...

...

448

65.0

...

...

7

517

75.0

...

...

448

65.0

...

...

7

...

...

276

40.0

...

...

165

24.0

10

565

82.0

...

...

524

76.0

...

...

...

579

84.0

...

...

524

76.0

...

...

5

600

87.0

...

...

538

78.0

...

...

5

593

86.0

...

...

531

77.0

...

...

5

579

84.0

...

...

517

75.0

...

...

5

0.124

3.186.32

0.1250.249

129

6.3512.67

0.2500.499

129

12.7025.40

0.5001.000

129

12.7025.40

0.5001.000

129

All

All

206

20

20

20

20

32

7178-T6, T6510(c) and T6511(c)

All

1.55

Al

0.061

1.586.32

0.0620.249

129

6.3538.07

0.2501.499

161

38.1063.47

1.5002.499

161

38.10-

1.500-

20

25

25

>161-

25-

7178-T62(e)(f)

63.47

2.499

63.5076.17

2.5002.999

206

206

565

82.0

...

...

489

71.0

...

...

5

545

79.0

...

...

503

73.0

...

...

...

565

82.0

...

...

510

74.0

...

...

5

593

86.0

...

...

531

77.0

...

...

5

593

86.0

...

...

531

77.0

...

...

5

579

84.0

...

...

517

75.0

...

...

5

565

82.0

...

...

489

71.0

...

...

5

524

76.0

...

...

455

66.0

...

...

7

531

77.0

...

...

462

67.0

...

...

7

531

77.0

...

...

462

67.0

...

...

7

32

All

1.55

32

All

0.061

7178-T76(h) T6510(d)(h) T76511(d)(h)

and

1.586.32

0.0620.249

129

6.3538.07

0.2501.499

161

38.1063.47

1.5002.499

161

38.1063.47

1.5002.499

63.5076.17

2.5002.999

206

3.186.32

0.1250.249

129

6.3512.67

0.2500.499

129

12.7025.40

0.5001.000

129

20

25

25

>161206

>2532

32

20

20

20

Converted SI (metric) values are for information only and are not to be used for purposes of specification, acceptance, or rejection. (a) The thickness of the cross section from which the tensile-test specimen is taken determines the applicable mechanical properties.

(b) In 50 mm (2 in.) or 4d. For material of such dimensions that a standard test specimen cannot be taken, or for shapes thinner than 0.062 in., the test for elongation is not required.

(c) For stress relieved tempers, the characteristics and properties other than those specified may differ somewhat from the corresponding characteristics and properties of material in the basic temper.

(d) Upon artificial aging, material in the T3/T31, T3510, T3511, T4, T4510, and T4511 tempers is capable of developing the mechanical properties applicable to material in the T81, T8510, T8511, T6, T6510, and T6511 tempers, respectively.

(e) These properties usually can be obtained by the user when the material is properly solution heat treated or solution and precipitation heat treated from the O (annealed) or F (as fabricated) temper. These properties also apply to samples of material in the O and F tempers, which are

solution heat treated or solution and precipitation heat treated by the producer to determine that the material will respond to proper heat treatment. Properties attained by the user, however, may be lower than those listed if the material has been formed or otherwise cold or hot worked, particularly in the annealed temper, prior to solution heat treatment.

(f) This temper is not available from the material producer.

(g) When subjected to stress-corrosion testing, material in this temper is capable of exhibiting no evidence of stress-corrosion cracking when exposed for a period of 30 days in the short-transverse direction at a stress level of 75% of the specified yield strength. The stress-corrosion resistance capabilities of individual lots are determined by testing the previously selected tensile-test specimens in accordance with the applicable electrical conductivity acceptance criteria.

(h) Material in this temper, when tested upon receipt by the purchaser, is capable of passing an exfoliation corrosion resistance test and the stress-

corrosion resistance criteria of note (g) above except that the stress level is to be 25.0 ksi. The improved resistance to exfoliation corrosion and stress-corrosion cracking of individual lots is determined by testing the previously selected tensile-test specimens in accordance with the applicable electrical conductivity acceptance criteria.

Table 11 Mechanical-property limits for aluminum alloy die forgings Alloy and temper

Specified thickness(a)

mm

in.

Hardness, HB(c)

Specimen axis parallel to direction of grain flow

Specimen axis not parallel to direction of grain flow

Tensile strength

Yield strength

Elongation (min), %(b)

Tensile strength

Yield strength

MPa

ksi

MPa

ksi

Coupon

Forging

MPa

ksi

MPa

ksi

76

11.0

28

4.0

25

18

...

...

...

...

...

20

379

55.0

207

30.0

16

11

...

...

...

...

...

100

448

65.0

386

56.0

8

6

441

64.0

379

55.0

3

125

Elongation (min), %(b)(forging)

1100H112(d)

100

4

2014T4

100

4

2014T6

25

1

>2550

>12

448

65.0

386

56.0

(e)

6

441

64.0

379

55.0

2

125

>5075

>23

448

65.0

379

55.0

(e)

6

434

63.0

372

54.0

2

125

>75100

>34

434

63.0

379

55.0

(e)

6

434

63.0

372

54.0

2

125

2018T61

379

55.0

276

40.0

10

7

...

...

...

...

...

100

100

4

2025T6

359

52.0

228

33.0

16

11

...

...

...

...

...

100

100

4

2218T61

100

4

2218T72

100

4

2219T6

100

4

379

55.0

276

40.0

10

7

...

...

...

...

...

100

262

38.0

200

29.0

8

5

...

...

...

...

...

85

400

58.0

262

38.0

10

8

386

56.0

248

36.0

4

100

400

58.0

310

45.0

6

4

379

55.0

290

42.0

4

115

97

14.0

34

5.0

25

18

...

...

...

...

...

25

359

52.0

290

42.0

5

3

...

...

...

...

...

115

290

42.0

152

22.0

...

14

269

39.0

138

20.0

12

...

276

40.0

124

18.0

...

16

269

39.0

110

16.0

14

...

303

44.0

138

20.0

...

16

...

...

...

...

...

...

248

36.0

207

30.0

16

11

...

...

...

...

...

75

262

38.0

241

35.0

10

7

262

38.0

241

35.0

5

80

345

50.0

310

45.0

12

8

...

...

...

...

...

100

303

44.0

255

37.0

14

10

303

44.0

255

37.0

6

90

517

75.0

441

64.0

10

7

490

71.0

421

61.0

3

135

2618T61

100

4

3003H112(d)

100

4

4032T6

100

4

5083H111(d)

100

4

5083H112(d)

100

4

5456H112(d)

100

4

6053T6

100

4

6061T6

100

4

6066T6

100

4

6151T6

100

4

7075T6

25

1

>2550

>12

510

74.0

434

63.0

(e)

7

490

71.0

421

61.0

3

135

>50-

>2-

510

74.0

434

63.0

(e)

7

483

70.0

414

60.0

3

135

75

3

>75100

>34

75

3

>75100

>34

75

3

>75100

>34

7175T74

75

3

7175T7452

75

3

7175T7454

75

3

7075T73

7075T7352

503

73.0

427

62.0

(e)

7

483

70.0

414

60.0

2

135

455

66.0

386

56.0

...

7

427

62.0

365

53.0

3

125

441

64.0

379

55.0

...

7

421

61.0

359

52.0

2

125

455

66.0

386

56.0

...

7

427

62.0

352

51.0

3

125

441

64.0

365

53.0

...

7

421

61.0

338

49.0

2

125

524

76.0

455

66.0

...

7

490

71.0

427

62.0

4

...

503

73.0

434

63.0

...

7

469

68.0

379

55.0

4

...

517

75.0

448

65.0

...

7

483

70.0

421

61.0

4

...

Converted SI (metric) values are for information only and are not to be used for purposes of specification, acceptance, or rejection. (a) As-forged thickness. When forgings are machined prior to heat treatment, the properties given here also will apply to the machined thickness provided that the machined thickness is not less than one-half the original (as forged) thickness.

(b) In 50 mm (2 in.) or 4d.

(c) For information only. Brinell hardness usually is measured on the surface of the heat treated forging using a 500 kg load and a 10 mm penetrator ball.

(d) Properties of forgings in H111 and H112 tempers depend on the equivalent cold work in the forgings. The properties listed should be attainable in any forging within the prescribed thickness range and may be considerably exceeded in some instances.

(e) When separately forged coupons are used to verify acceptability of forgings in the indicated thicknesses, the properties shown for thicknesses up through 1 in., including test-coupon elongation, apply.

Table 12 Minimum and typical room-temperature plane-strain fracture-toughness values for several high-strength aluminum alloys Product form

Alloy and temper

Thickness

Plane-strain fracture toughness (KIc)

L-T direction(a)

Minimum

Plate

7050T7451

7050T7651

7475-

mm

in.

25.4050.80

T-L direction(b)

Typical

Minimum

S-L direction(c)

Typical

Minimum

Typical

MPa

ksi

MPa

ksi

MPa

ksi

MPa

ksi

MPa

ksi

MPa

ksi

1.0002.000

31.9

29.0

37

34

27.5

25.0

33

30

...

...

...

...

50.8376.20

2.0013.000

29.7

27.0

36

33

26.4

24.0

32

29

23.1

21.0

28

25

76.23101.60

3.0014.000

28.6

26.0

35

32

25.3

23.0

31

28

23.1

21.0

28

25

101.63127.00

4.0015.000

27.5

25.0

32

29

24.2

22.0

29

26

23.1

21.0

28

25

127.03152.40

5.0016.000

26.4

24.0

31

28

24.2

22.0

28

25

23.1

21.0

28

25

25.4050.80

1.0002.000

28.6

26.0

34

31

26.4

24.0

31

28

...

...

...

...

50.8376.20

2.0013.000

26.4

24.0

...

...

25.3

23.0

...

...

22.0

20.0

26

24

33.0

30.0

46

42

30.8

28.0

41

37

...

...

...

...

T651

Die forgings

7475T7651

36.3

33.0

47

43

33.0

30.0

41

37

...

...

...

...

7475T7351

41.8

38.0

55

50

35.2

32.0

45

41

27.5

25.0

36

33

7075T651

...

...

29

26

...

...

25

23

...

...

20

18

7075T7651

...

...

30

27

...

...

24

22

...

...

20

18

7075T7351

...

...

32

30

...

...

29

26

...

...

20

18

7079T651

...

...

30

27

...

...

25

23

...

...

18

16

2124T851

26.4

24.0

32

29

22.0

20.0

26

24

19.8

18.0

26

24

2024T351

...

...

37

34

...

...

32

29

...

...

26

24

7050T74, T7452

27.5

25.0

38

35

20.9

19.0

32

29

20.9

19.0

29

26

7175T736, T73652

29.7

27.0

38

35

23.1

21.0

34

31

23.1

21.0

31

28

Hand forgings

Extrusions

7075T7352

...

...

32

29

...

...

30

27

...

...

29

26

7050T7452

29.7

27.0

36

33

18.7

17.0

28

25

17.6

16.0

29

26

7075T73, T7352

...

...

42

38

...

...

28

25

...

...

28

25

7175T73652

33.0

30.0

40

36

27.5

25.0

30

27

23.1

21.0

28

25

2024T852

...

...

26

24

...

...

22

20

...

...

20

18

7050T7651x

...

...

44

40

...

...

31

28

·.

·.

28

25

7050T7351x

...

...

...

...

...

...

...

...

...

...

...

...

7075T651x

...

...

34

31

...

...

22

20

...

...

20

18

7075T7351x

...

...

33

30

...

...

26

24

...

...

22

20

7150T7351x

24.2

22.0

31

28

...

...

...

...

...

...

...

...

7175T7351x

33.0

30.0

40

36

30.8

28.0

34

31

...

...

...

...

(a) L-T, crack plane and growth direction perpendicular to the rolling direction.

(b) T-L, crack plane and growth direction parallel to the rolling direction.

(c) S-L, short transverse fracture toughness

Fig. 5 Minor influences of differing microstructures on fatigue crack growth rate curves: data from twelve 2xxx and 7xxx aluminum alloys with different heat treatments

Fig. 6 Crack growth comparison. Many commercial aluminum alloys show similar fatigue crack propagation rates in air, as indicated.

Table 13 Tensile properties and fracture toughness of aluminum-lithium alloy 2090 2090 temper

Thickness

Specification

Tensile properties

Direction(a)

mm

in.

0.8-3.175

0.032-0.125

Toughness

Ultimate tensile strength

Yield strength

MPa

ksi

MPa

ksi

L

530 (550)

77 (80)

517 (517)

75 (75)

3 (6)

LT

505

73

503

73

45 °

440

64

440

L

483

70

LT

455

45 °

AMS Draft

D89

Elongation in 50 min (2 in.), %

Direction(b) and Kc or KIc(c)

KIc or Kc

MPa

ksi

L-T (Kc)

(44)(d)

(40)(d)

5

...

...

...

64

...

...

...

...

483

70

4

...

...

...

66

455

66

5

...

...

...

385

56

385

56

...

...

...

...

L

495 (525)

72 (76)

455 (470)

66 (68)

3 (5)

L-T (Kc)

49 (71)(d)

45 (65)(d)

LT

475

69

415

60

5

T-L (Kc)

49(d)

45(d)

45 °

427

62

345

50

7

...

...

...

LT

317 min

46 min

214 min

31 min

6 min

...

...

...

Sheet

T83

T83

T84

T3(e)

3.2-6.32

0.8-6.32

...

0.126-0.249

0.032-0.249

...

AMS 4351

AMS 4351

(f)

O

...

...

(f)

LT

213 max

31 max

193 max

28 max

11 min

...

...

...

7075-T6

...

...

...

L

(570)

(83)

(517)

(75)

(11)

L-T (Kc)

(71)(d)

(65)(d)

0.0-3.15(h)

0.000-0.124(h)

AMS Draft

L

517

75

470

68

4

...

...

...

3.175-6.32(h)

0.125-0.249(h)

D88BE

L

545

79

510

74

4

...

...

...

6.35-12.65(h)

0.250-0.499(h)

L

550

80

517

75

5

...

...

...

LT

525

76

483

70

...

...

...

...

(27)

(25)

Extrusions

T86(g)

Plate

7075-T6

...

...

...

L

(565)

(82)

(510)

(74)

(11)

L-T (KIc)

T81

13-38

0.50-1.50

AMS 4346

L

517 (550)

75 (80)

483 (517)

70 (75)

4 (8)

L-T (KIc)

27 (71)

25 (65)

LT

517

75

470

68

3

L-T (KIc)

22

20

Typical values are given in parentheses. Data for alloy 7075-T6 are included for comparison. (a) L, longitudinal; LT, long transverse.

(b) L-T, crack plane and direction perpendicular to the principal direction of metalworking (rolling or extrusion); T-L, crack plane and direction parallel to the direction of metalworking.

(c) Kc, plane-stress fracture toughness; KIc, plane-strain fracture toughness.

(d) Toughness limits based on limited data and typical values (in parentheses) for 405 × 1120 mm (16 × 44 in.) sheet panel.

(e) The T3 temper can be aged to the T83 or T84 temper.

(f) No end user specification.

(g) Temper registration request made to the Aluminum Association.

(h) Nominal diameter or least thickness (bars, rod, wire, shapes) or nominal wall thickness (tube)

Table 14 Tensile properties and fracture toughness of aluminum-lithium alloy 8090 Temper

Product form

Grain structure(a)

Minimum and typical(b) tensile properties

Direction

8090-T81 (underaged)

8090-T8X (peak aged)

8090-78X

8090T8771, 8090-T651 (peak aged)

Damagetolerant bare sheet 2000 (>290) 300 (43.5)

13,800 (2,001) 379 (55)

...

0.67

3,000-14,000 (435-2030) 400-700 (58101.5) 1.23

...

...

Saffil (96% Al2O3-4%SiO2).

(a) (b) (c)

>98% SiC. Transverse rupture strength of bulk

Processing methods for discontinuous aluminum MMCs include various casting processes: liquid-metal infiltration, spray deposition, and powder metallurgy. Each of these processes will be briefly reviewed in the following paragraphs. Effect of Reinforcement on Properties. In MMCs, mechanical properties depend on the amount, size, shape, and

distribution of the dispersed phase (reinforcement), apart from the mechanical properties of the matrix material, and on the nature of the interface. By definition, a composite material generally requires an amount of dispersed phase (>1 vol%) of a size (>1 m) that allows this constituent to be load bearing and not act merely to control the movement of dislocations, as in dispersion-strengthened materials. The shape of the dispersed phase is so important in determining its load-bearing capacity that composites have been classified on this basis: (a) fiber-reinforced composites with both continuous and discontinuous fibers and (b) particle- or whisker-reinforced composites. The aspect ratio generally characterizes the shape. In continuous-fiber composites, the load is applied directly to both the matrix and the fiber. In discontinuous-fiber composites or particle-reinforced composites, the load is transmitted to the dispersoid through the matrix. Property predictions of MMCs can be obtained from mathematical models, which require as input a knowledge of the properties and geometry of the constituents. Information on these mathematical expressions, which include simple rule of mixture models, can be found in the selected references listed at the conclusion of this article. In general, however, the influence of hard particle reinforcement (e.g., SiC) on the relevant mechanical and physical properties of discontinuous aluminum-MMCs can be summarized as follows: •

• • •

Both the ultimate tensile strength and yield strength increase with an increase in reinforcement fraction. (It should be noted that these properties are decreased with an increase in volume fraction of soft particles, e.g., graphite.) The fracture toughness and ductility (percent elongation and strain to failure) decrease with an increase in reinforcement volume fraction. The Young's modulus increases with an increase in reinforcement volume fraction. The thermal and electrical conductivities as well as the coefficient of thermal expansion decrease with increasing reinforcement volume fraction.

Figure 2 illustrates the effects of SiC volume fraction on the properties of discontinuous aluminum MMCs.

Fig. 2 Effect of reinforcement volume fraction on the properties of aluminum metal-matrix composite (MMCs). (a) The ultimate tensile strength (UTS), tensile yield strength (TYS), and strain-to-failure ( f) for 6013/SiC/xxpT6. (b) Fracture toughness as a function of SiC volume fraction. (c) Young's modulus as a function of SiCw and SiCp volume fraction. (d) Thermal conductivity for 2009/SiC/xx-T6. (e) Electrical conductivity for 2009/SiC/xxpT6 and 6061/SiC/xxp-T6. (f) Coefficient of thermal expansion (CTE) for 6061/SiC/xxp-T6.

Cast Aluminum MMCs. In the stir casting (or mixing/vortex), the pretreated and prepared reinforcement filler phase is

introduced in a continuously stirred molten matrix and then cast by sand, permanent mold, or pressure die casting. Melting under an inert gas cover combined with Ar-SF6 gas mixtures for fluxing and degassing is essential to avoid the entrapment of gases. Mixing can be affected ultrasonically or by reciprocating rods, centrifuging, or zero-gravity processing. Matrix alloys include aluminum-silicon compositions specially designed for MMC processing (Table 2). Reinforcements include 10 to 20 m sized SiC or Al2O3 particles in volume fractions ranging from 10 to 20%. Figure 3 shows a typical microstructure. Table 3 lists typical mechanical properties of high-pressure die cast aluminum MMCs. The automotive industry is behind the development of cast aluminum MMCs. Current or potential applications include brake rotors and drums, brake calipers, brake pad backing plates, and cylinder liners.

Table 2 Matrix alloys for discontinuous reinforced aluminum metal-matrix composites Alloy

Composition, wt% Si Fe High-pressure die castings F3D(a) 9.50-10.5 0.80-1.20

Cu

Mn

Mg

Ni

Ti

Zn

Other

Al

3.00-3.50

0.50-0.80

0.30-0.50

1.00-1.50

0.20 max

0.03 max

bal

0.20 max

0.50-0.80

0.50-0.70

...

0.20 max

0.03 max

0.03 max; 0.10 total 0.03 max; 0.10 total

Sand and permanent mold castings F3S(c) 8.50-9.50 0.20 max 0.20 max

...

0.45-0.65

...

0.20 max

...

bal

F3K(d)

...

0.80-1.20

1.00-1.50

0.20 max

...

0.03 max; 0.10 total 0.03 max; 0.10 total

F3N(b)

9.50-10.5

9.50-10.5

0.80-1.20

0.30 max

2.80-3.20

bal

bal

Source: Duralcan USA

(a) (b) (c) (d)

Duralcan F3DxxS composites (xx = volume percent SiC particulate) are general-purpose, diecasting composites. They are similar to 380/SiC/xxp (Aluminum Association MMC nomenclature). Duralcan F3NxxS composites, containing virtually no copper or nickel, are designed for use in corrosion-sensitive applications. They are similar to 360/SiC/xxp. Duralcan F3SxxS composites (xx = volume percent SiC particulate) are general-purpose composites for room-temperature applications. They are similar to 359/SiC/xxp (Aluminum Association MMC nomenclature). Duralcan F3KxxS composites, containing significant amounts of copper and nickel, are designed for use at elevated temperatures. They are similar to 339/SiC/xxp.

Table 3 Typical mechanical properties for high-pressure die cast F3D/SiC composites Material A380-F(b) A390-F(b) F3D.10S-F(c) F3D.10S-O(d) F3D.10S-T5(d) F3D.20S-F(c) F3D.20S-O(d) F3D.20S-T5(e)

Ultimate strength MPa ksi 317 46.0 283 41.0 345 50.0 276 40.0 372 53.9 352 51.0 303 43.9 400 58.0

Yield strength MPa ksi 159 23.1 241 34.9 241 34.9 152 22.0 331 48.0 303 43.9 186 27.0

Elongation(a), % 3.5 1.0 1.2 1.7 0.7 0.4 0.8

(f)

(f)

(f)

Elastic modulus GPa 106psi 71.0 10.3 81.4 11.8 93.8 13.6 93.8 13.6 93.8 13.6 113.8 16.5 113.8 16.5 113.8 16.5

Hardness, HRB 40 76 77 55 84 82 62 87

See Table 2 for composition of matrix alloy.

(a) (b) (c) (d) (e) (f)

Measured by direct reading from stress-strain plot. Handbook values. Cast-to-size tensile bars. Cast-to-size tensile bars, annealed at 343 °C (649 °F) for 4 h. Cast-to-size tensile bars, aged at 177 °C (351 °F) for 5 h. Test bars fractured before yielding.

Impact energy J ft · lbf 3.4 2.5 1.4 1.0 1.4 1.0 2.7 2.0 1.4 1.0 0.7 0.5 1.4 1.0 0.7 0.5

Fig. 3 Typical microstructure of an aluminum-matrix composite containing 20 vol% SiC. 125×

Aluminum MMCs produced by stir casting are also commonly extruded. Wrought composites currently available in extrusion billet include:

Composite 6061/Al2O3/xp 2014/Al2O3/xp 1060/Al2O3/xp 7005/Al2O3/xp 7075/Al2O3/xp

Al2O3 content, vol% 10, 15, or 20 10, 15, or 20 10 10 10

Room-temperature properties of extruded aluminum MMCs are given in Table 4.

Table 4 Room-temperature properties of extruded stir-cast aluminum MMCs in the T6 condition Material

6061/Al2O3/x p

2014/Al2O3/x p

(a)

Al2O3 content , vol % 0 10 15 20 0 10 15 20

Ultimate strength Typical Minimum(a

Yield strength Typical Minimum(a

)

)

MP a

ks i

MPa

ksi

MP a

ks i

MPa

ksi

310 350 365 370 525 530 530 515

45 51 53 54 76 77 77 75

260 325 340 345 470 495 495 485

38 47 49 50 68 72 72 70

275 295 325 350 475 495 505 505

40 43 47 51 69 72 73 73

240 260 290 315 415 455 460 460

35 38 42 46 60 66 67 67

Tensile elongation ,%

20 10 6 4 13 3 2 1

Elastic modulus

Fracture toughness

GP a

106ps i

MPa

ksi

69.0 81.4 89.0 97.2 73.1 84.1 93.8 101

10.0 11.8 12.9 14.1 10.6 12.2 13.6 14.7

29.6 24.0 22.0 21.5 25.3 18.0 18.8 ...

27.0 21.9 20.0 19.6 23.0 16.4 17.1 ...

Values represent 99% confidence interval

Squeeze-Cast Aluminum MMCs. Squeeze casting is a process by which molten metal solidifies under pressure

within closed dies positioned between the plates of a hydraulic press. The applied pressure and the instant contact of the molten metal with the die surface produce a rapid heat transfer condition that yields a pore-free, fine-grain casting with mechanical properties approaching those of a wrought product. Squeeze casting of aluminum MMCs involves placing a porous ceramic preform in the preheated die, which is later filled with the liquid metal; pressure is then applied. The pressure, in this case, helps the liquid metal infiltrate the porous ceramic preform, giving a sound metal-ceramic composite.

Squeeze casting has attracted much attention because the process minimizes material and energy use, produces net shape components, and offers a selective reinforcement capability. Both discontinuous and continuous aluminum-copper, aluminum-silicon, and aluminum-magnesium alloys reinforced with up to 45 vol% SiC have been produced. Rheocast Aluminum MMCs. Rheocasting, also referred to as compocasting, is similar to the metal stirring route, but

instead of the particulates being stirred into a fully liquid metal, it is stirred in the semi-solid (thixotropic) state and subsequently cast under pressure. Particles and discontinuous fibers of SiC, Al2O3, TiC, Si3N4, graphite, mica, glass, slag, magnesium oxide, and boron carbide have been incorporated into vigorously agitated partially solidified aluminum alloy slurries by this technique. Liquid-Metal Infiltration. The Primex pressureless metal infiltration process is based on material and process controls

that allow a metal to infiltrate substantially nonreactive reinforcements without the application of pressure or vacuum. Reinforcement level can be controlled by the starting density of the material being infiltrated. As long as interconnected porosity and appropriate infiltration conditions exist, the liquid metal will spontaneously infiltrate into the preform. Key process ingredients for the manufacture of reinforced aluminum composites include the aluminum alloy, a nitrogen atmosphere, and magnesium present in the system. During heating to infiltration temperature ( 750 °C, or 1380 °F), the magnesium reacts with the nitrogen atmosphere to form magnesium nitride (Mg3N2). The Mg3N2 is the infiltration enhancer that allows the aluminum alloy to infiltrate the reinforcing phase without the necessity of applied pressure or vacuum. During infiltration the Mg3N2 is reduced by the aluminum to form a small amount of aluminum nitride (AlN). The AlN is found as small precipitates and as a thin film on the surface of the reinforcing phase. Magnesium is released into the alloy by this reaction. The pressureless infiltration process can produce a wide array of engineered composites by tailoring of alloy chemistry, particle type, shape, size, and loading. Particulate loading in cast composites can be as high as 75 vol%, given the right combination of particle shape and size. Figure 4 shows a typical microstructure.

Fig. 4 Discontinuous Al/SiC MMC (60 vol% SiC) produced by the liquid-metal infiltration process

The most widely used cast composite produced by liquid-metal infiltration is an Al-10Si-1Mg alloy reinforced with 30 vol% SiC. The 1% Mg present in this alloy is obtained during infiltration by the reduction of the Mg3N2. This composite system is being used for all casting processes except die casting. The composite most used for die casting is based on this system, with the addition of 1% Fe. Alloy modifications can be made to the alloy prior to infiltration or in the crucible prior to casting. The only universal alloy restriction for this composite system is the presence of magnesium to allow the formation of the Mg3N2. For the SiC-containing systems, silicon must also be present in sufficient quantity to suppress the formation of aluminum carbide (Al4C3). Composites consisting of Al2O3-reinforced aluminum that exhibit low excessive wear rates are also produced. An important application area for pressureless molten metal infiltration is Al/SiCp packages, substrates, and support structures for electronic components. Typical requirements include a low coefficient of thermal expansion (CTE) to reduce mechanical stresses imposed on the electronic device during attachment and operation, high thermal conductivity for heat dissipation, high stiffness to minimize distortion, and low density for minimum weight. Compared with conventional aluminum alloys, composites having high loadings of SiC particles feature greatly reduced CTEs and significantly higher elastic moduli, with little or no penalty in thermal conductivity or density (Table 5).

Table 5 Physical properties of an Al/SiC/xxp MMC for electronic applications Property Coefficient of thermal expansion, 10-6/°C (10-6/°F) Thermal conductivity, W/m · K (Btu/h · ft · °F) Density, g/cm3 (lb/in.3) Elastic modulus, GPa (106 psi)

Composite, SiC loading 55 vol% 70 vol% 8.5 (4.7) 6.2 (3.4) 160 (93) 170 (99) 2.95 (0.106) 3.0 (0.0108) 200 (29) 270 (39)

Typical aluminum alloys 22-24 (12-13) 150-180 (87-104) 2.7 (0.097) 70 (10)

Spray deposition involves atomizing a melt and, rather than allowing the droplets to solidify totally as for metal powder manufacture, collecting the semi-solid droplets on a substrate. The process is a hybrid rapid solidification process because the metal experiences a rapid transition through the liquidus to the solidus, followed by slow cooling from the solidus to room temperature. This results in a refined grain and precipitation structure with no significant increase in solute solubility.

The production of MMC ingot by spray deposition can be accomplished by introducing particulate into the standard spray deposition metal spray leading to codeposition with the atomized metal onto the substrate. Careful control of the atomizing and particulate feeding conditions is required to ensure that a uniform distribution of particulate is produced within a typically 95 to 98% dense aluminum matrix. A number of aluminum alloys containing SiC particulate have been produced by spray deposition. These include aluminum-silicon casting alloys and the 2xxx, 6xxx, 7xxx, and 8xxx (aluminum-lithium) series wrought alloys. Significant increases in specific modulus have been realized with SiC-reinforced 8090 alloy (Table 6). Products that have been produced by spray deposition include solid and hollow extrusions, forgings, sheet, and remelted pressure die castings.

Table 6 Properties of conventionally processed aluminum alloys (ingot metallurgy) and spray-deposited aluminum MMCs Material 2014 8090 2014/SiC/15p(a)

(a)

Elastic modulus GPa 106 psi 72 10 80 12 95 14

Density g/cm3 2.8 2.55 2.84

lb/in.3 0.101 0.092 0.103

Specific modulus 25.7 31.4 33.5

Improvement, % 0 22 30

Spray codeposited, extruded, and peak aged

P/M Aluminum MMCs. Powder metallurgy processing of aluminum MMCs involves both SiC particulates and whiskers, although Al2O3 particles and Si3N4 whiskers have also been employed. Processing involves (1) blending of the gas-atomized matrix alloy and reinforcement in powder form; (2) compacting (cold pressing) the homogeneous blend to roughly 80% density; (3) degassing the preform (which has an open interconnected pore structure) to remove volatile contaminants (lubricants and mixing and blending additives), water vapor, and gases; and (4) consolidation by vacuum hot pressing or hot isostatic pressing. The hot-pressed cylindrical billets can be subsequently extruded, rolled, or forged. Whisker-reinforced aluminum MMCs may experience some whisker alignment during extrusion or rolling (Fig. 5). Control of whisker alignment enables production of aluminum MMC product forms with directional properties needed for some high-performance applications. Cross rolling of sheet establishes a more planar whisker alignment, producing a two-dimensional isotropy.

Fig. 5 SiC whisker-reinforced (20 vol% SiC) aluminum alloy sheet with the whiskers aligned in the direction of rolling

The mechanical properties of whisker-reinforced aluminum MMCs are superior to particle-reinforced composites at any common volume fraction (Fig. 6). Tables 7 and 8 show the effects of whisker alignment on the properties of aluminum MMCs. Table 9 lists typical mechanical properties for particle-reinforced aluminum alloys.

Table 7 Typical properties of MMC billet and extruded plate having density of 2.86 g/cm3 (0.103 lb/in.3) to show the effects of SiC whisker alignment MMC material form

Test specimen orientation

305 mm (12 in.) diam cylindrical billet

Longitudinal (axial) Transverse Longitudinal Transverse (long)

13 by 125 mm (

by 5 in.) extrusion

Ultimate tensile

Yield strength(a)

MPa 496 503 737 462

MPa 351 358 448 379

ksi 71.9 72.9 107 67.0

ksi 50.9 51.9 64.9 54.9

Coefficient of thermal expansion ( ) 10-6/K 10-6/°F 16.1 8.95 16.4 9.12 13.0 7.23 19.6 10.9

0.2% offset

(a)

Table 8 Typical properties of SiC whisker-reinforced aluminum alloy sheet Sheet thickness

Test specimen orientation

mm

in.

2.54

0.100

2.54

0.100

Longitudinal (along roll direction) Transverse (90° to roll direction)

Ultimate tensile strength MPa ksi

Yield strength(a) MPa

ksi

718

104

573

83.1

5.3

559

81.0

386

56.4

8.5

Elongation (e), %

Young's, modulus, E

Fracture toughness, Kc MPa

ksi

114

106 psi 16.5

55

50

95

14

59

54

GPa

Material: 2124-T6 reinforced with 15 vol% SiC whiskers. 0.2% offset

(a)

Table 9 Typical mechanical properties of SiC particulate-reinforced aluminum alloy composites Alloy and vol % 6061 Wrought 15

Modulus of elasticity

Yield strength

GPa

106 psi

MPa

ksi

Ultimate tensile strength MPa ksi

68.9 96.5

10 14

275.8 400.0

40 58

310.3 455.1

45 66

Ductility, %

12 7.5

20 25 30 35 40 2124 Wrought 20 25 30 40 7090 Wrought 20 25 30 35 40 7091 Wrought 15 20 25 30 40

103.4 113.8 120.7 134.5 144.8

15 16.5 17.5 19.5 21

413.7 427.5 434.3 455.1 448.2

60 62 63 66 65

496.4 517.1 551.6 551.6 586.1

72 75 80 80 85

5.5 4.5 3.0 2.7 2.0

71.0 103.4 113.8 120.7 151.7

10.3 15 16.5 17.5 22

420.6 400.0 413.7 441.3 517.1

61 58 60 64 75

455.1 551.6 565.4 593.0 689.5

66 80 82 86 100

9 7.0 5.6 4.5 1.1

72.4 103.4 115.1 127.6 131.0 144.8

10.5 15 16.7 18.5 19 21

586.1 655.0 675.7 703.3 710.2 689.5

85 95 98 102 103 100

634.3 724.0 792.9 772.2 724.0 710.2

92 105 115 112 105 103

8 2.5 2.0 1.2 0.90 0.90

72.4 96.5 103.4 113.8 127.6 139.3

10.5 14 15 16.5 18.5 20.2

537.8 579.2 620.6 620.6 675.7 620.6

78 84 90 90 98 90

586.1 689.5 724.0 724.0 765.3 655.0

85 100 105 105 111 95

10 5.0 4.5 3.0 2.0 1.2

Fig. 6 Yield strength comparison between whisker- and particulate-reinforced aluminum MMCs

Continuous Fiber Aluminum MMCs As shown in Fig. 1, aluminum MMCs reinforced with continuous fibers provide the highest performance/strength. Because of their high cost, however, most applications have been limited to the aerospace industry. Aluminum/boron is a technologically mature continuous fiber MMC (Fig. 7). Applications for this composite include tubular truss members in the midfuselage structure of the Space Shuttle orbiter and cold plates in electronic microchip carrier multilayer boards. Fabrication processes for aluminum/boron composites are based on hot-press diffusion bonding of alternating layers of aluminum foil and boron fiber mats (foil-fiber-foil processing) or plasma spraying methods. Selected properties of aluminum/boron composites are given in Table 10.

Table 10 Room-temperature properties of unidirectional continuous-fiber, aluminum-matrix composites Property Fiber content, vol% Longitudinal modulus, GPa (106 psi) Transverse modulus, GPa (106 psi) Longitudinal strength, MPa (ksi) Transverse strength, MPa (ksi)

B/6061 Al 48 214 (31) ... 1520 (220) ...

SCS-2/6061 Al(a) 47 204 (29.6) 118 (17.1) 1462 (212) 86 (12.5)

P100 Gr/6061 Al 43.5 301 (43.6) 48 (7.0) 543 (79) 13 (2)

FP/Al-2Li(b) 55 207 (30) 144 (20.9) 552 (80) 172 (25)

(a) (b)

SCS-2 is a silicon carbide fiber. FP is an alpha alumina (

-Al2O3) fiber

Fig. 7 Cross section of a continuous-fiber-reinforced aluminum/boron composite. Shown here are 142 boron filaments coated with B4C in a 6061 aluminum alloy matrix

m diam

Continuous SiC fibers are often used as replacements for boron fibers because they have similar properties (e.g., a

tensile modulus of 400 GPa, or 60 × 106 psi) and offer a cost advantage. One such SiC fiber is SCS, which can be manufactured with any of several surface chemistries to enhance bonding with a particular matrix, such as aluminum or titanium. The SCS-2 fiber, tailored for aluminum, has a 1 m (0.04 mil) thick carbon rich coating that increases in silicon content toward its outer surface. Hot molding is a low-pressure, hot-pressing process designed to fabricate Al/SiC parts at significantly lower cost than is possible with a diffusion-bonding/solid-state process. Because the SCS-2 fibers can withstand molten aluminum for long periods, the molding temperature can be raised into the liquid-plus-solid region of the alloy to ensure aluminum flow and consolidation at low pressure, thereby eliminating the need for high-pressure die molding equipment. The hot-molding process is analogous to the autoclave molding of graphite-epoxy, in which components are molded in an open-faced tool. The mold in this case is a self-heating, slip-cast ceramic tool that contains the profile of the finished part. A plasma-sprayed aluminum preform is laid into the mold, heated to near molten aluminum temperature, and pressureconsolidated in an autoclave by a metallic vacuum bag. Aluminum/SiC MMCs exhibit increased strength and stiffness as compared with unreinforced aluminum, with no weight penalty. Tensile properties of 6061/SCS-2 composites are given in Table 10. In contrast to the base metal, the composite retains its room-temperature tensile strength at temperatures up to 260 °C (500 °F). Aluminum/graphite MMC development was initially prompted by the commercial appearance of strong and stiff

carbon fibers in the 1960s. Carbon fibers offer a range of properties, including an elastic modulus up to 966 GPa (140 psi × 106) and a negative CTE down to -1.62 × 10-6/°C (-0.9 × 10-6/°F). However, carbon and aluminum in combination are difficult materials to process into a composite. A deleterious reaction between carbon and aluminum, poor wetting of carbon by molten aluminum, and oxidation of the carbon are significant technical barriers to the production of these composites. Two processes are currently used for making commercial aluminum MMCs: liquid metal infiltration of the matrix on spread tows and hot press bonding of spread tows sandwiched between sheets of aluminum. With both precursor wires and metal-coated fibers, secondary processing such as diffusion bonding or pultrusion is needed to make structural elements. Squeeze casting also is feasible for the fabrication of this composite. Precision aerospace structures with strict tolerances on dimensional stability need stiff, lightweight materials that exhibit low thermal distortion. Aluminum/graphite MMCs have the potential to meet these requirements, Unidirectional P100 Gr/6061 aluminum pultruded tube exhibits an elastic modulus in the fiber direction significantly greater than that of steel, and it has a density approximately one-third that of steel. Properties are listed in Table 10. Aluminum/Al2O3 MMCs can be fabricated by a number of methods, but liquid or semi-solid-state processing techniques are commonly used. Aluminum oxide fibers, which include Fiber FP (99.5% Al2O3) and Saffil (96Al2O34SiO2) are inexpensive and provide the composite with improved properties as compared with those of unreinforced aluminum alloys. For example, the composite has an improved resistance to wear and thermal fatigue deformation and a

reduced CTE. Continuous fiber Al/Al2O3 MMCs are fabricated by arranging Al2O3 tapes in a desired orientation to make a preform, inserting the preform into a mold, and infiltrating the preform with molten aluminum via a vacuum assist. Reinforcement-to-matrix bonding is achieved by small additions of lithium to the melt. Table 10 gives the roomtemperature properties of a unidirectional Al-2Li/Al2O3.

Titanium-Matrix Composites Titanium is selected as a matrix metal because of its good specific strength at both room and moderately elevated temperature and its excellent corrosion resistance. Because titanium retains its strength at higher temperatures than aluminum, it has increasingly been used as a replacement for aluminum in aircraft and missile structures as the operating speeds of these items have increased from subsonic to supersonic. Continuous Fiber Titanium MMCs. Silicon carbide fibers are the reinforcement of choice for titanium MMCs. The

SCS-6 fiber is a carbon-cored monofilament that is 142 m in diameter. A tungsten-cored fiber that has a carbon coating has also been developed with a diameter of 127 m. A tungsten-cored monofilament with carbon and titanium diboride coatings that is 102 m in diameter is also available. Fiber contents of 30 to 40 vol% are common (Fig. 8). Conventional matrix alloys include Ti-6Al-4V for low-temperature applications and Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) when higher creep resistance is required or when the temperature is higher than the maximum use temperature for Ti-6Al-4V. The Ti-6242 alloy is used in turbine engine actuator pistons and reinforced fan frames. More recently, titanium aluminide ordered intermetallics such as Ti-22Al-23Nb and Ti-22Al-26Nb have been used as matrix materials. These materials are being developed for rotating blades and impellers. Processing techniques for titanium MMCs used for aerospace applications include fiber-foil-fiber processing and tape casting or wire winding used in conjunction with hot isostatic pressing. Plasma spraying has also been employed to deposit a titanium matrix onto the fibers. Similarly, electron beam physical vapor deposition of metal on fiber has also been demonstrated. Table 11 gives properties for a representative unidirectional SiC/Ti laminate.

Table 11 Room-temperature properties of a unidirectional SiCc/Ti MMC Property Fiber content, vol% Longitudinal modulus, GPa (106 psi) Transverse modulus, GPa (106 psi) Longitudinal strength, MPa (ksi) Transverse strength, MPa (ksi)

SCS-6/Ti-6Al-4V 37 221 (32) 165 (24) 1447 (210) 413 (60)

Fig. 8 Typical fiber array in a SiC-reinforced titanium MMC. Actual fiber diameters are 127 Charles R. Rowe, Atlantic Research Corporation

m. Courtesy of

Particle-Reinforced Titanium MMCs are processed by P/M methods. Although a variety of materials have been studied, the most common combination is Ti-6Al-4V reinforced with 10 to 20 wt% TiC. These composites offer increased hardness and wear resistance over conventional titanium alloys. Properties of unreinforced and reinforced Ti-6Al-4V are compared in Table 12.

Table 12 Properties of TiC particle-reinforced titanium MMCs Property

Ti-6Al-4V

Density, g/cm3 (lb/in.3)

4.43 (0.160)

Tensile strength, MPa (ksi), at: RT 540 °C (1000 °F) Modulus, GPa (106 psi), at: RT 540 °C (1000 °F) Fatigue limit (106 cycles), MPa (ksi) Fracture toughness, MPa (ksi ) Coefficient of linear thermal expansion (RT to 540 °C, or 1000 °F), ppm/°C Hardness, HRC

10 wt% TiC/Ti-6Al4V 4.45 (0.16)

20 wt% TiC/Ti-6Al4V 4.52 (0.162)

896 (130) 448 (65)

999 (145) 551 (80)

1055 (153) 620 (90)

113 (16.5) 89 (13) 517 (75) 55 (50)

133 (19.3) 105 (15.3) 275 (40) 44 (40)

144 (21) 110 (16) ... 32 (29)

8.5

8.1

8.0

34

40

44

RT, room temperature

Other MMCs of Importance Magnesium-matrix composites are being developed to exploit essentially the same properties as those provided by

aluminum MMCs: high stiffness, light weight, and low CTE. In practice, the choice between aluminum and magnesium as a matrix is usually made on the basis of weight versus corrosion resistance. Magnesium is approximately two-thirds as dense as aluminum, but it is more active in a corrosive environment. Magnesium has a lower thermal conductivity, which is sometimes a factor in its selection. Magnesium MMCs include continuous fiber Gr/Mg for space structures, short staple fiber Al2O3/Mg for automotive engine components, and discontinuous SiC or B4C/Mg for engine components and lowexpansion electronic packaging materials. Matrix alloys include AZ31, AZ91, ZE41, QE22, and EZ33. Processing methods parallel those used for the aluminum MMC counterparts. Copper-matrix composites have been produced with continuous tungsten, silicon carbide, and graphite fiber

reinforcements. Of the three composites, continuous graphite/copper MMCs have been studied the most. Interest in continuous graphite/copper MMCs gained impetus from the development of advanced graphite fibers. Copper has good thermal conductivity, but it is heavy and has poor elevated-temperature mechanical properties. Pitch-base graphite fibers have been developed that have room-temperature axial thermal conductivity properties better than those of copper. The addition of these fibers to copper reduces density, increases stiffness, raises the service temperature, and provides a mechanism for tailoring the coefficient of thermal expansion. One approach to the fabrication of graphite/copper MMCs uses a plating process to envelop each graphite fiber with a pure copper coating, yielding MMC fibers flexible enough to be woven into fabric. The copper-coated fibers must be hot pressed to produce a consolidated component. Table 13 compares the thermal properties of aluminum and copper MMCs with those of unreinforced aluminum and copper. Graphite/copper MMCs have the potential to be used for thermal management of electronic components, satellite radiator panels, and advanced airplane structures.

Table 13 Thermal properties of unreinforced and reinforced aluminum and copper Material

Aluminum Copper SiCp/Al P120 Gr/Al P120 Gr/Cu

Reinforcement content, vol% 0 0 40 60 60

Density g/cm3 2.71 8.94 2.91 2.41 4.90

Axial thermal conductivity lb/ft3 169 558 182 150 306

W/m · °C 221 391 128 419 522

Btu/ft · h · °F 128 226 74 242 302

Axial coefficient of thermal expansion 10-6/°C 10-6/°F 23.6 13.1 17.6 9.7 12.6 7 -0.32 -0.17 -0.07 -0.04

Superalloy-Matrix Composites. In spite of their poor oxidation resistance and high density, refractory metal

(tungsten, molybdenum, and niobium) wires have received a great deal of attention as fiber reinforcement materials for use in high-temperature superalloy MMCs. Although the theoretical specific strength potential of refractory alloy fiberreinforced composites is less than that of ceramic fiber-reinforced composites, the more ductile metal fiber systems are more tolerant of fiber-matrix reactions and thermal expansion mismatches. When refractory metal fibers are used to reinforce a ductile and oxidation-resistant matrix, they are protected from oxidation, and the specific strength of the composite is much higher than that of superalloys at elevated temperatures. Fabrication of superalloy MMCs is accomplished via solid-phase, liquid-phase, or deposition processing. The methods include investment casting, the use of matrix metals in thin sheet form, the use of matrix metals in powder sheet form made by rolling powders with an organic binder, powder metallurgy techniques, slip casting of metal alloy powders, and arc spraying. Figure 9 compares the elevated-temperature tensile strength of a nickel-base superalloy (Waspaloy) reinforced with various refractory wires. As this figure indicates, a composite consisting of 50 vol% W-24Re-HfC had the highest strength at 1093 °C (2000 °F).

Fig. 9 Elevated temperature (1093 °C, or 2000 °F) tensile strength of Waspaloy reinforced with 50 vol% refractory metal wire. 218 CS represents potassium-doped tungsten. ST 300 is a W-1.0ThO2 alloy. Comparative data are included for unreinforced MarM 246, a nickel-base superalloy.

Intermetallic-Matrix Composites. One disadvantage of superalloy MMCs is their high density, which limits the

potential minimum weight of parts made from these materials. High melting points and relatively low densities make intermetallic-matrix composites (IMCs) viable candidates for lighter turbine engine materials. Aluminides of nickel, titanium, and iron have received the most attention as matrices for IMCs. Property data on TiB2-reinforced titanium aluminides can be found in the article "Structural Intermetallics" in this Section.

Selected References • • • • • •

Aluminum-Matrix Composites, ASM Specialty Handbook: Aluminum and Aluminum Alloys, J.R. Davis, Ed., ASM International, 1993, p 160-179 D.M. Aylor, Corrosion of Metal-Matrix Composites, Corrosion, Vol 13, ASM Handbook, ASM International, 1987, p 859-863 M.E. Buck and R.J. Suplinskas, Continuous Boron Fiber MMCs, Engineered Materials Handbook, Vol 1, Composites, ASM International, 1987, p 851-857 J.L. Cook and W.R. Mohn, Whisker-Reinforced MMCs, Engineered Materials Handbook, Vol 1, Composites, ASM International, 1987, p 896-902 J.V. Foltz and C.M. Blackman, Metal-Matrix Composites, Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Vol 2, ASM Handbook, ASM International, 1990, p 903-912 D.M. Goddard et al., Continuous Graphite Fiber MMCs, Engineered Materials Handbook, Vol 1,

Composites, ASM International, 1987, p 867-873 J.J. Lewankowski and P.M. Singh, Fracture and Fatigue of Discontinuously Reinforced Aluminum Composites, Fatigue and Fracture, Vol 19, ASM Handbook, ASM International, 1996, p 895-904 J.A. McElman, Continuous Silicon Carbide Fiber MMCs, Engineered Materials Handbook, Vol 1, Composites, ASM International, 1987, p 858-866 P.K. Rohatgi, Y. Liu, and S. Ray, Friction and Wear of Metal-Matrix Composites, Friction, Lubrication, and Wear Technology, Vol 18, ASM Handbook, ASM International, 1992, p 801-811 J.C. Romine, Continuous Aluminum Oxide Fiber MMCs, Engineered Materials Handbook, Vol 1, Composites, ASM International, 1987, p 874-877

• • • •

Structural Intermetallics Introduction ALLOYS based on ordered intermetallic compounds constitute a unique class of metallic material that form long-range ordered crystal structures (Fig. 1) below a critical temperature, generally referred to as the critical ordering temperature (Tc). These ordered intermetallics usually exist in relatively narrow compositional ranges around simple stoichiometric ratio (see the phase diagrams shown in this article).

Fig. 1 Atomic arrangements of conventional alloys and ordered intermetallic compounds. (a) Disordered crystal structure of a conventional alloy. (b) Long-range ordered crystal structure of an ordered intermetallic compound

The search for new high-temperature structural materials has stimulated much interest in ordered intermetallics. Recent interest has been focused on nickel aluminides based on Ni3Al and NiAl, iron aluminides based on Fe3Al and FeAl, and titanium aluminides based on Ti3Al and TiAl. These aluminides possess many attributes that make them attractive for high-temperature structural applications. They contain enough aluminum to form, in oxidizing environments, thin films of alumina (Al2O3) that are compact and protective. They have low densities, relatively high melting points, and good hightemperature strength properties (Tables 1 and 2).

Table 1 Properties of nickel, iron, and titanium aluminides Alloy

Ni3Al NiAl Fe3Al

Crystal structure(a)

L12 (ordered fcc) B2 (ordered bcc) D03 (ordered bcc)

Critical ordering temperature (Tc) °C °F 1390 2535 1640 2985 540 1000

Melting point (Tm) °C 1390 1640 1540

°F 2535 2985 2805

Material density, g/cm3 7.50 5.86 6.72

Young's modulus GPa 179 294 141

106 psi 25.9 42.7 20.4

FeAl Ti3Al TiAl TiAl3

B2 (ordered bcc) B2 (ordered bcc) D019 (ordered hcp) L10 (ordered tetragonal) D022 (ordered tetragonal)

760 1250 1100 1460 1350

1400 2280 2010 2660 2460

1540 1250 1600 1460 1350

2805 2280 2910 2660 2460

... 5.56 4.2 3.91 3.4

... 261 145 176 ...

... 37.8 21.0 25.5 ...

fcc, face-centered cubic; bcc, body-centered cubic; hcp, hexagonal close packed

(a)

Table 2 Attributes and upper use temperature limits for nickel, iron, and titanium aluminides Alloy

Attributes

Ni3Al NiAl

Oxidation, carburization, and nitridation resistance; high-temperature strength High melting point; high thermal conductivity; oxidation, carburization, and nitridation resistance Oxidation and sulfidation resistance Oxidation, sulfidation, molten salt, and carburization resistance Low density; good specific strength

Fe3Al FeAl Ti3Al

Maximum use (°F) Strength limit 1000 (1830) 1200 (2190)

temperature, °C

600 (1110) 800 (1470) 760 (1400)

1100 (2010) 1200 (2190) 650 (1200)

Corrosion limit 1150 (2100) 1400 (2550)

Nickel, iron, and titanium aluminides, like other ordered intermetallics, exhibit brittle fracture and low ductility at ambient temperatures. It has also been found that quite a number of ordered intermetallics, such as iron aluminides, exhibit environmental embrittlement at ambient temperatures. The embrittlement involves the reaction of water vapor in air with reactive elements (aluminum, for example) in intermetallics to form atomic hydrogen, which drives into the metal and causes premature fracture. Thus, the poor fracture resistance and limited fabricability have restricted the use of aluminides as engineering materials in most cases. However, in recent years, alloying and processing have been employed to overcome the brittleness problem of ordered intermetallics. Success in this work has inspired parallel efforts aimed at improving strength properties. The results have led to the development of a number of attractive intermetallic alloys having useful ductility and strength. Figure 2 illustrates the crystal structures showing the ordered arrangements of atoms in several of these aluminides. For most of the aluminides listed in Table 1, the critical ordering temperature is equal to the melting temperature. Others disorder at somewhat lower temperatures, and Fe3Al passes through two ordered structures (D03 and B2) before becoming disordered. Many of the aluminides exist over a range of compositions, but the degree of order decreases as the deviation from stoichiometry increases, Additional elements can be incorporated without losing the ordered structure. For example, in Ni3Al, silicon atoms are located in aluminum sites, cobalt atoms on nickel sites, and iron atoms on either. In many instances, the so-called intermetallic compounds can be used as bases for alloy development to improve or optimize properties for specific applications.

Fig. 2 Crystal structures of nickel, iron, and titanium aluminides

Nickel Aluminides The nickel-aluminum phase diagram shows two stable intermetallic compounds, Ni3Al and NiAl, formed on the nickelrich end (Fig. 3). The compound Ni3Al has an L12 crystal structure, a derivative of the face-centered cubic (fcc) crystal structure; NiAl has a B2 structure, a derivative of the body-centered cubic (bcc) crystal structure (see Fig. 2). Because of the different crystal structures, the two nickel aluminides have quite different physical and mechanical properties.

Fig. 3 The nickel-aluminum phase diagram showing both NiAl and Ni3Al compounds on the nickel-rich end

Ni3Al Aluminides The aluminide Ni3Al is of interest because of its excellent strength and oxidation resistance at elevated temperatures (see Table 2). This intermetallic has long been used as a strengthening constituent in high-temperature, nickel-base superalloys, which owe their outstanding strength properties to a fine dispersion of precipitation particles of the ordered ' phase (Ni3Al) embedded in a ductile disordered matrix. (See the Section "Superalloys" in this Handbook). Single crystals of Ni3Al are ductile at ambient temperatures, but polycrystalline Ni3Al fails by brittle grain-boundary fracture with very little plasticity. This effect persists even in very high-purity materials where no grain-boundary segregation of impurities can be detected. The observation of this characteristic turned attention toward a search for segregants that might act in a beneficial way. Studies of segregants led to the discovery that small ( 0.1 wt%) boron additions not only eliminated the brittle behavior of Ni3Al but converted the material to a highly malleable form exhibiting tensile ductility as high as 50% at room temperature. The beneficial effect of boron is, however, dependent on stoichiometry, and boron is effective in increasing the ductility of Ni3Al only in alloys containing less than 25 at.% aluminum. Since gaining the knowledge that microalloying with boron can ductilize polycrystalline Ni3Al, a number of Ni3Al alloy compositions have been developed. As shown in Table 3, macroalloying additions include chromium, iron, zirconium, and molybdenum. These alloying additions were made to improve strength, castability, hot workability, and corrosion resistance. The effects of these alloying additions are described in the following paragraphs.

Table 3 Nominal compositions of selected Ni3Al alloys Alloy(a) IC-50 IC-74M IC-218 IC-218 LZr IC-221 IC-357 IC-396M

(a)

Composition, wt% Al Cr Fe 11.3 . . . . . . 12.4 . . . . . . 8.5 7.8 . . . 8.7 8.1 . . . 8.5 7.8 . . . 9.5 7.0 11.2 8.0 7.7 . . . Designations

Zr 0.6 ... 0.8 0.2 1.7 0.4 0.8

used

by

Mo ... ... ... ... ... 1.3 3.0

B 0.02 0.05 0.02 0.02 0.02 0.02 0.01

Oak

Ni bal bal bal bal bal bal bal

Ridge

National

Laboratory, Oak Ridge,TN Anomalous Dependence of Yield Strength on Temperature. Ni3Al is one of a number of intermetallic alloys that exhibit an engineering yield strength (0.2% offset) that increases with increasing temperature. This is shown in Fig. 4, which is a plot of yield stress as a function of test temperature. The anomalous yielding effect, which is lower at lower strains, occurs because of the extremely rapid work hardening. The anomalous yielding behavior makes Ni3Al stronger than many commercial solid-solution alloys (such as type 316 stainless steel and Hastelloy alloy X) at elevated temperatures (Fig. 4).

Fig. 4 Yield strength versus test temperature for Ni3Al alloys, two superalloys, and type 316 stainless steel

As with boron-doped Ni3Al, Ni3Al alloys (Table 3) also exhibit rising yield strength with rising temperature. Figure 5 shows that the yield strength of four nickel aluminide alloys tends to rise to a maximum in the temperature range of 400 to 650 °C ( 750 to 1200 °F). Above this temperature range, the yield strength declines.

Fig. 5 Variation of yield strength with test temperature for selected nickel aluminide alloys. Strain rate, 0.5 mm/mm per min. See Table 3 for alloy compositions.

Mechanical Properties. The study of ductility and strength of Ni3Al has led to the development of ductile nickel

aluminide alloys for structural applications with the following composition range (in atomic percent):

Ni-(14-18)Al-(6-9)Cr-(1-4)Mo-(0.01-1.5)Zr/Hf-(0.01-0.20)B

In these aluminide alloys, 6 to 9 at.% Cr is added to reduce environmental embrittlement in oxidizing environments at elevated temperatures. Zirconium and hafnium additions most effectively improve high-temperature strength via solidsolution hardening effects. Molybdenum additions improve strength at ambient and elevated temperatures. Microalloying with boron reduces moisture-induced hydrogen embrittlement and enhances grain-boundary cohesive strength, resulting in sharply increased ductility at ambient temperatures. In some cases, certain amounts (40%) Blend of pigmented soap-fat paste with mineral oil Concentrated sulfochlorinated oil (may contain some fatty oil): Nonemulsifiable Emulsifiable Concentrated chlorinated oil: Nonemulsifiable Emulsifiable

Ease of removal by: WaterDegreasers base or solvents cleaners

Protection against rusting

Very good

Good

Fair

Very good Very good

Very poor Good

Fair Fair

Fair Very good

Poor Good

Fair Fair poor

Poor Good

Very poor Very poor

Good Good

to

Good Very good Good Very good Removal not required

Fair Fair ...

Good Good fair

Very good Good

Fair Fair poor

Fair

Fair

Fair

Poor Good Fair

Good Good Fair

Very poor Very poor Fair

Poor

Poor

Fair

Very poor Good

Fair Fair

Poor Poor

Very poor Good

Fair Fair

Very poor Very poor

to

to

Severity is indicated by the percentage of reduction in diameter in drawing a cylindrical shell.

Direct Redrawing In direct redrawing in a single-action die, the drawn cup is slipped over the punch and is loaded in the die (Fig. 27). At first, the bottom of the cup is wrapped around the punch nose without reducing the diameter of the cylindrical section. The sidewall section then enters the die and is gradually reduced to its final diameter. Metal flow takes place as the cup is drawn into the die so that the wall of the redrawn shell is parallel to, and deeper than, the wall of the cup at the start of the redraw. At the beginning of redrawing, the cup must be supported and guided by a recess in the die or by a blankholder to prevent it from tipping, which would result in an uneven shell.

Fig. 27 Direct and reverse redrawing in single-action and double-action dies

In a single-action redraw, the metal must be thick enough to withstand the compressive forces set up in reducing the cup diameter without wrinkling. Wrinkling can be prevented by the use of an internal blankholder and a double-action press, which usually permits a shell to be formed in fewer operations than by single-action drawing without the use of a blankholder.

Reverse Redrawing In reverse redrawing, the cupped workpiece is placed over a reversing ring and redrawn in the direction opposite to that used for drawing the initial cup. Reverse redrawing can be done with or without a blankholder (Fig. 27). The blankholder serves the same purposes as in direct redrawing. Reverse redrawing can be performed in a progressive die as well as in single-stage dies if the operations are divided to distribute the work and to reduce the severity of each stage. Advantages of reverse drawing as compared with direct redrawing include: • • • •

Metal can be drawn and redrawn in one stroke of a triple-action hydraulic press, or of a double-action mechanical press with a die cushion, which can eliminate the need for a second press. Greater reductions per redraw are possible with reverse redrawing. One or more intermediate annealing operations can often be eliminated by using the reverse technique. Better distribution of metal can be obtained in a complex shape.

In borderline applications, annealing is required between redraws in direct redrawing, but is not needed in reverse redrawing. The disadvantages or reverse drawing are: • •

The technique is not practical for work metal thicker than 6.4 mm ( Reverse redrawing requires a longer stroke than direct redrawing.

in.).

Usually, metals that can be direct redrawn can be reverse redrawn. All of the carbon and low-alloy steels, austenitic and ferritic stainless steels, aluminum alloys, and copper alloys can be reverse redrawn. Reverse redrawing requires more closely controlled processing than direct redrawing. The blanks should be free from nicks and scratches, especially at the edges.

The restraint in reverse redrawing must be uniform and low. For low friction, polished dies and effective lubrication of the work are needed. Friction also is affected by hold-down pressure and by the shape of the reversing ring. Radii of tools should be as large as practical--ten times the thickness of the work metal if possible. Stretch Forming

STRETCH FORMING involves forming sheet, bars, and rolled or extruded sections over a form block of the required shape while the workpiece is held in tension. The work metal is often stretched just beyond its yield point (generally 2 to 4% total elongation) to retain permanently the contour of the form block. The four methods of stretch forming are: stretch draw forming (Fig. 28a and b); stretch wrapping, also called rotary stretch forming (Fig. 28c); compression forming (Fig. 28d); and radial draw forming (Fig. 28e).

Fig. 28 Fundamentals of the techniques involved in the four methods of stretch forming

Applicability Almost any shape that can be produced by other sheet-forming methods can be produced by stretch forming. Drawn shapes that involve metal flow, particularly straight cylindrical shells, and details that result from compression operations such as coining and embossing, cannot be made. However, some embossing is done by the mating-die method of stretch draw forming. Stretch forming is used to form aerospace parts from steel, nickel, aluminum, and titanium alloys and other heat-resistant and refractory metals. Some of these parts are difficult or impossible to form by other methods. Stretch forming is also used to shape automotive body panels, both inner and outer, and frame members that could be formed by other processes but at higher cost. Architectural shapes and aerospace forms that call for compound curves, reverse bends, twists, and bends in two or more planes are also produced by stretch forming.

Machines and Accessories Stretch wrapping, compression forming, and radial-draw forming use rotary tables on which are mounted the form block, a ram gripping and tensioning or wiping device, and a mechanically or hydraulically actuated table gripper (Fig. 28c-e). In stretch wrapping, the workpiece is pulled from one end, wrapping the metal around the form block. In compression

forming, a wiper shoe presses the workpiece against the form block. Radial-draw forming combines both pulling and pressing of the metal. Machines used for these operations have capacities to 8900 kN (1000 tonf). Stretch draw forming is done in three types of machines. In one type, the form block is mounted on a hydraulic cylinder and is pushed into the blank, which is held in tension by a pair of pivoting grippers. In another type, the form block is fixed to the table and a pair of grippers actuated by slides or a hydraulic cylinder draws the blank around it. The third type of machine is a single-action hydraulic press equipped with a two-piece mating die. Grippers pull the blank over the lower die, then the upper die descends to produce the workpiece (Fig. 28b). The hydraulic presses ordinarily used in stretch draw forming have capacities of 1800 to 7100 kN (200 to 800 tonf). Accessory Equipment. Grippers and wiping shoes or rollers are made to conform to the rolled or extruded shape that

is to be stretch formed. Jaws used for gripping sheet in stretch draw forming can be segmented or contoured to apply equal stretch to all parts of the sheet as it is formed. Spinning

SPINNING forms sheet metal or tubing into seamless hollow cylinders, cones, hemispheres, or other circular shapes by a combination of rotation and force. (Tube spinning is discussed in the following article "Forming of Bars, Tubes, and Wire.") The technique falls into two categories: manual spinning and power spinning. Any metal that can be cold formed by other methods can be spun. Most spinning takes place without heating the workpiece; sometimes the metal is preheated to increase ductility or to allow thicker sections to be spun.

Manual Spinning Manual spinning involves no appreciable thinning of the work metal. The operation requires a lathe and it consists of pressing a tool against a circular metal blank that is rotated by the headstock. The blank is usually forced over a mandrel of a predetermined shape, but simple shapes can be spun without a mandrel. Various mechanical devices are used to increase the force that can be applied to the workpiece. Manual spinning is used to form flanges, rolled rims, cups, cones, and double-curved surfaces of revolution (such as bells). Products include light reflectors, tank ends, covers, housings, shields, components for musical instruments, and aircraft and aerospace components (often with mechanical assistance for increased force). The practical maximum thickness of low-carbon steel that can be spun without mechanical assistance is 3.2 mm ( in.). At this thickness, the diameter can be as great as 1.8 m (72 in.). Diameters can be greater when the sheet steel is thinner, but the maximum practical diameter is often limited by the availability of equipment. The upper limit of thickness increases as work metal ductility increases or as strength decreases. For example, the manual spinning of aluminum as thick as 6.4 mm (

in.) is feasible

Equipment for Manual Spinning A typical tool and workpiece setup for manual spinning is shown in Fig. 29(a). A mandrel is mounted on the headstock of a lathe. A circular blank (workpiece) is clamped to the mandrel by a follower block attached to the tailstock of the lathe. The blank is rotated by the headstock, while a friction-type spinning tool is manually pressed against the blank, forcing the blank over the preshaped mandrel. The tool is mounted on a tool rest by a support pin (fulcrum). The operator presses the tool against the blank by pivoting it around the support pin. The tool rest permits the tool to be moved to different positions.

Fig. 29 Manual spinning in a lathe. (a) Setup using a simple hand tool, applied like a pry bar. (b) Setup using scissorlike levers and a roller spinning tool

Figure 29(b) shows a more complex setup for manual spinning. Here, the spinning tools are rollers which are mounted in the fork sections of long levers. The roller is pressed against the workpiece by manipulating the scissor-like levers.

Power Spinning Power spinning is also known as shear spinning, because in this method metal is intentionally thinned by shear forces as high as 3.5 MN (400 tonf). Power spinning is used in two broad areas of application: cone spinning and tube spinning. Virtually all ductile metals can be processed by power spinning. Products range from small hardware items made in large quantities (metal tumblers, for example) to large components for aerospace applications in unit or low-volume production. Blanks as large as 6 m (240 in.) in diameter have been successfully power spun. Plate stock up to 25 mm (1 in.) thick can be power spun without heat. When heated, blanks as thick as 140 mm (5 in.) can be spun. Conical and curvilinear shapes are most commonly produced from flat (or preformed) blanks by power spinning.

Machines for Power Spinning Most power spinning requires machines specially built for the purpose. The primary components of such a machine are shown in Fig. 30. Power spinning machines are usually described by capacity: the diameter and length (in inches) of the largest workpiece that can be spun and the amount of force that can be applied to the work. It is also common practice to specify that the machine can spin a given thickness of metal at a 50% reduction in thickness in one pass.

Fig. 30 Schematic illustration of power spinning in a vertical machine

The capacity of spinning machines, which may be horizontal or vertical, ranges from 455 × 380 mm (18 × 15 in.) at 18 kN (4000 lbf) to machines capable of spinning workpieces as large as 6 m (240 in.) in diameter × 6 m (240 in.) long. Force on the work can be as great as 3.5 MN (400 tonf). Machines have been built that spin steel 140 mm (5

in.) thick.

Machines for power spinning can be automated to various degrees. Automatic spinning machines are available with computer numerical controls (CNC) to automatically perform the spinning operation. Rubber-Pad Forming

RUBBER-PAD FORMING, also known as flexible-die forming, uses two tool halves: a rubber pad or a flexible diaphragm (or bladder), and one solid tool half to form a part to final shape. The solid tool half usually is similar to the punch in a conventional die, but it can be the die cavity. The rubber acts somewhat like hydraulic fluid in exerting nearly equal pressure on all workpiece surfaces as it is pressed around the form block. Rubber-pad forming is used on moderately shallow, recessed parts with simple flanges and relatively simple configurations. Form block height is usually less than 100 mm (3.9 in.). The production rates are relatively high, with cycle times averaging 1 min or less. Flexible-die forming methods fall into three groups: rubber-pad forming, fluid-cell forming, and fluid forming. Specific processes falling into these three categories are described below.

Rubber-Pad Forming The Guerin process is synonymous with the term rubber-pad forming. Other processes, which are essentially modified/improved version of the Guerin process, include the Marform process, the trapped-rubber process, and the ASEA Quintus rubber-pad process. Guerin Process The Guerin process is the oldest and most basic of the production rubber-pad forming processes. Its advantages are simplicity of equipment, adaptation to small-lot production, and ease of changeover. Some metals that are commonly formed by this process are listed in Table 9. Titanium can be formed only if the workpiece and the form block are both heated. The resulting deterioration of the rubber pad often makes the process too costly compared with forming by conventional dies.

Table 9 Metals commonly formed by the Guerin process Maximum thickness(a) mm in.

Metal Mild forming Aluminum alloys 2024-O, 7075-W 2024-T4 Austenitic stainless steels Annealed Quarter hard Titanium alloys Stretch flanging Aluminum alloy 2024-T4 Austenitic stainless steels Annealed

(a) (b) (c) (d)

4.7 1.6

0.187 0.064

1.3 0.8 1.0

0.050(b) 0.032(c) 0.040(d)

1.6

0.064

1.3

0.050

Typical; varies with type of equipment and part design. Up to 2.0 mm (0.078 in.) when compression dams are used. Only very mild forming. When heated to 315 °C (600 °F)

Presses. Almost any hydraulic press can be used for the Guerin process. For maximum forming capability, the force

capacity of the press and the area of the rubber pad must be suitable for the operation under consideration. The rubber pad is generally about the same size as the press ram, but it can be smaller. Tools. The principal tools are the rubber pad and the form block, or punch (Fig. 31). The rubber pad is relatively soft

(about Durometer A 60 to 75) and usually three times as deep as the part to be formed. The pad can consist of a solid block of rubber, or of laminated slabs cemented together and held in a retainer.

Fig. 31 Tooling and setup for rubber-pad forming by the Guerin process. Dimensions given in inches

Procedure. The rubber-pad retainer is fixed to the upper ram of the press; the platen, containing the form block, is

placed on the bed of the press. A blank is placed on the form block and is held in position by two or more locating pins. The pins must be mounted rigidly in the form block so that the rubber will not drive them down into the pinhole or push them out of position. The pins must be no higher than necessary to hold the blank, or they will puncture the rubber pad. In some applications, nests can be used to locate the blank during forming. As the ram descends, the rubber presses the blank around the form block, thus forming the workpiece. The rubber-pad retainer fits closely around the platen, forming an enclosure that traps the rubber as pressure is applied. The pressure produced in the Guerin process is ordinarily 6.9 to 48 MPa (1 to 7 ksi). The pressure can be increased by reducing the size

of the platen. Pressures as high as 140 MPa (20 ksi) have been developed through the use of small platens in highcapacity presses. Marform Process This process was developed to apply the inexpensive tooling of the Guerin process to the deep drawing and forming of wrinkle-free shrink flanges. A blankholder plate and a hydraulic cylinder with a pressure-regulating valve are used with a thick rubber pad and a form block similar to those used in the Guerin process. The blank is gripped between the blankholder and the rubber pad. The pressure-regulating valve controls the pressure applied to the blank while it is being drawn over the form block. For a soft aluminum alloy blank, the diameter can usually be reduced 57%, with reductions as high as 72%. A shell depth equal to the shell diameter is normal when the minimum stock thickness is 1% of the cup diameter. Depths up to three times shell diameter have been reached with multiple-operation forming. The minimum cup diameter is 38 mm (1

in.).

Foil as thin as 0.038 mm (0.0015 in.) can be formed by placing the blank between two aluminum blanks about 0.76 mm (0.030 in.) thick and forming the three pieces as a unit. The inner and outer shells are discarded. Presses. The Marform process is best suited to a single-action hydraulic press in which pressure and speed of operation

can be varied and controlled. Tools. The rubber pad used in Marforming is similar to that used in the Guerin process. It is normally 1

to 2 times as

thick as the total depth of the part, including trim allowance. Drop Hammer Forming with Trapped Rubber Similar to the Guerin process for forming shallow workpieces, the trapped-rubber process uses a drop hammer in place of the hydraulic press; the primary differences are faster forming speed and the impact force of the hammer. ASEA Quintus Rubber-Pad Press ASEA presses, generally designed with force capacities of 50 to 500 MN (5600 to 56,000 tonf), are constructed of wirewound frames and have separate guiding columns. By winding the press frames with prestressed wire, only compressional stresses are present in the large castings or forgings of the yokes and columns, even when subjected to maximum forming pressure. Therefore, when the press is loaded, the frame remains in slight compression, and the major structural components never operate in the tensile mode. The press is equipped with a forged-steel rubber-pad retainer with a replaceable insert to allow for forming at higher pressures. Although the maximum tool height is sacrificed by using these high-pressure inserts, cutting the work area in half doubles the maximum forming pressure of the press when needed. Standard table sizes range from 0.7 × 1.0 m (28 × 39 in.) to 2 × 3 m (79 × 118 in.). Difficult-to-form materials such as titanium, along with the die, can be heated outside the press by an infrared heater; blanks can also be heated by conduction from the table through the heat transferred through the die (Fig. 32).

Fig. 32 Schematic of ASEA Quintus rubber-pad press with provision for heating difficult-to-form materials using infrared heater or heating elements contained in feed table

Fluid-Cell Process Initially developed as the Verson-Wheelon process, this process uses a fluid cell (a flexible bladder, rather than a rubber pad) backed up by hydraulic fluid to exert a uniform pressure directly on the form block positioned on the press table. This process can be classified in terms of the presses used (as for Verson-Wheelon and ASEA Quintus) or as a specialized method (such as the Demarest process) for producing cylindrical and conical parts. The Verson-Wheelon press has cylindrical press housings of laminated, prestressed steel that serve as pressure chambers. The ASEA Quintus press has a forged steel cylinder that is wound with high strength steel wire to create a prestressed press frame with extremely good fatigue properties. Fluid-cell forming can be used for recessed parts that are beyond the capabilities of rubber-pad forming, for all flange configurations (including C-shaped flanges), and for complex parts with reentrant features and intricate joggles. Maximum form block height is 425 mm (16.7 in.), and typical cycle time is 1 to 2 min. Verson-Wheelon Process The Verson-Wheelon process was developed from the Guerin process. It uses higher pressure and is primarily designed for forming shallow parts, using a rubber pad as either the die or punch. A flexible hydraulic fluid cell forces an auxiliary rubber pad to follow the contour of the form block and to exert a nearly uniform pressure at all points. The distribution of pressure on the sides of the form block permits the forming of wider flanges than with the Guerin process. In addition, shrink flanges, joggles, and beads and fibs in flanges and web surfaces can be formed in one operation to rather sharp detail in aluminum, low-carbon steel, stainless steel, heat-resistant alloys, and titanium. Presses. The Verson-Wheelon press has a horizontal cylindrical steel housing, the roof of which contains a hydraulic

fluid cell (Fig. 33). Fluid-cell bladders can be of neoprene or polyurethane composition. Hydraulic fluid is pumped into the cell, causing it to inflate or expand. The expansion creates the force needed to cause the rubber of the work pad to flow downward, over and around the form block and the metal to be formed.

Fig. 33 Principal components of the Verson-Wheelon process

Below the chamber containing the rubber pad and the hydraulic fluid cell is a passage, extending the length of the press, that is wide and high enough to accommodate a sliding table containing form blocks. At each end of the passage is a sliding table that is moved into position for forming. Verson-Wheelon presses are available with forming pressures ranging from 35 to 140 MPa (5 to 20 ksi) and force capacities of 22 to 730 MN (2500 to 82,000 tonf). Sliding tables range in size from 508 × 1270 mm (20 × 50 in.) to 1270 × 4170 mm (50 × 164 in.). The larger machine can form parts having flange widths up to 238 mm (9

in.).

Demarest Process This technique uses an expanding or bulging rubber punch (Fig. 34). It is suitable for cylindrical, somewhat spherical, and conical parts. The punch, equipped with a hydraulic cell, is placed inside the workpiece, which is in turn placed inside the die. Hydraulic pressure expands the punch. After forming, the punch is contracted and removed.

Fig. 34 Forming of a fuel-tank section from a blank using the Demarest process

ASEA Quintus Fluid Cell Process

This is another variation of the Guerin process for deeper and more complex parts. It uses a flexible rubber diaphragm backed up by oil as either the male or female tool half. The pressurized diaphragm forces the blanks to assume the shape of the solid-tool halves. The high, uniform, hydrostatic pressure forms shallow- to medium-depth parts with complex shapes to final shape, practically eliminating the subsequent hand forming usually required to apply the Guerin process. Presses. ASEA Quintus fluid cell presses are available with maximum forming pressures ranging from 100 to 200 MPa

(14 to 29 ksi) and force capacities up to 1400 MN (157,000 tonf). The forming tables range in size from 700 × 2000 mm (27.5 × 78.7 in.) to 2000 × 5000 mm (78.7 × 196.8 in.). The large presses can accommodate tools as high as 425 mm (16.7 in.) and consequently form parts as deep or flanges as wide as 425 mm (16.7 in.).

Fluid Forming In contrast to conventional two-die forming, which produces local stress concentrations in a workpiece, fluid forming (previously classified as rubber-diaphragm forming) is a flexible-die technique that inhibits thinning and crack initiation due to the uniformly distributed pressure. In fluid forming, a rubber diaphragm serves as both the blankholder and a flexible-die member. Fluid forming differs from the rubber-pad and fluid-cell processes in that the forming pressure can be controlled as a function of the draw depth of the part. Fluid forming was initially known as the Hydroform process. The process can use a Verson Hydroform press in which a hydraulic pump delivers fluid under pressure into the pressure-dome cavity. The punch containing the die is driven upward into the cavity against the resistance provided by the fluid, and the workpiece is formed. Fluid forming is intended for punch, cavity, hydroblock, or expansion forming of deep-recessed parts. Cycle time is 15 to 20 s for most parts. Verson Hydroform Process This process differs from those previously described in that the die cavity is not completely filled with rubber, but with hydraulic fluid retained by a 64 mm (2 in.) thick cup-shaped rubber diaphragm. This cavity is termed the pressure dome (Fig. 35). A replaceable wear sheet is cemented to the lower surface of the diaphragm. This method allows more severe draws than in conventional draw dies because the oil pressure against the diaphragm causes the metal to be held tightly against the sides as well as against the top of the punch.

Fig. 35 Fluid-cell forming in a Hydroform press

Reductions in blank diameter of 60 to 70% are common for a first draw. When redrawing is necessary, reductions can reach 40%. Low-carbon steel, stainless steel, and aluminum in thicknesses from 0.25 to 1.65 mm (0.010 to 0.065 in.) are commonly formed. Parts made of heat-resistant alloys and copper alloys are also formed by this process. SAAB Rubber-Diaphragm Method In this variation, hydraulic fluid is used behind a comparatively thin rubber pad or diaphragm. A hydraulic piston compresses the fluid against the rubber and forces the blank into the die (Fig. 36).

Fig. 36 Principals of SAAB rubber-diaphragm (fluid forming) method. The air vents keep trapped air from causing blisters on the workpiece.

ASEA Quintus Fluid Forming Press This is a vertical press with a circular fluid form unit containing the rubber diaphragm and pressure medium. These modular fluid form units serve the same function as the units used in the ASEA Quintus deep-drawing fluid forming press described below. The rigid tool half may be a male block, a cavity die, or an expansion die situated in a movable tool holder. Blanks are loaded onto the tool holder prior to shuttling the holder into the press for the 10 to 50 s forming cycle required to produce the part. ASEA Quintus Deep-Drawing Technique A variation of the SAAB rubber-diaphragm method, ASEA Quintus deep-drawing fluid forming uses two telescopic rams: an outer ram to control dome pressure and an inner ram to regulate the length of the punch draw. Because domes are interchangeable, the user can select a dome of optimal size. Maximum forging pressure can also be increased with smaller domes. Three-Roll Forming

THREE-ROLL FORMING is used to form plate, sheet, bars, beams, angles, or pipe into various shapes (Fig. 37) by passing the work metal between three properly spaced rolls. Any metal that can be cold formed by other processes can be formed in a three-roll machine.

Fig. 37 Typical shapes produced from flat stock by three-roll forming

Machines There are two types of three-roll forming machines: the pinch-roll type and the pyramid-roll type. The rolls on most threeroll machines are positioned horizontally; a few vertical machines are used, primarily in shipyards. An advantage of vertical machines in forming scaly plate is that loose scale is less likely to become embedded in the work metal. Vertical rolls, however, handle wide sections that require careful support to avoid skewness in rolling with difficulty. Most vertical machines have short rolls for fast unloading and are used for bending narrow plate, bars, and structural sections. Conventional pinch-type machines have the roll arrangement shown in Fig. 38. For rolling flat stock up to about 25 mm (1 in.) thick, each roll is of the same diameter. However, on larger machines, the top rolls are sometimes smaller to maintain approximately the same surface speed on both the inside and outside surfaces of the plate being formed. These heavier machines are also supplied with a slip-friction drive on the front roll to permit slip, because of the differential in surface speed of the rolls. Therefore, as work metal thickness increases, the diameter of the top roll is decreased in relation to the diameter of the lower rolls. In general, the smallest cylinder that can be rolled under optimal conditions is 50 mm (2 in.) larger in diameter than the top roll of a pinch-type machine.

Fig. 38 End view of a cylindrical workpiece being rolled in a conventional pinch-type machine. Note large flat area on leading end, and smaller flat area on trailing end.

Shoe-Type Pinch-Roll Machines. One important modification of the three-roll pinch-type machine is the shoe-type machine, which uses the pinch principle with a forming shoe (Fig. 39). Because of the relationship of the two front rolls and the forming shoe to the workpiece, the flat area becomes barely discernible compared with the length of flat area obtained when rolling in a conventional machine (without preforming). This machine is used to manufacture transformer cases and small tanks, such as jackets for hot water tanks.

Fig. 39 End view of a cylindrical workpiece being rolled in a shoe-type machine with two powered rolls

In pyramid-type machines (Fig. 40) the bottom rolls are of equal diameter, but about 50% smaller than the top roll. The bottom rolls are gear driven and are normally fixed; each roll is supported by two smaller rolls. The top roll is adjustable vertically to control the diameter of the cylinder formed. The top roll, which rotates freely, depends on friction with the work metal for rotation. Backup rolls are not used on the top roll.

Fig. 40 Arrangement of rolls in a pyramid-type machine. (a) Entrance of flat workpiece and shape of a nearly finished workpiece, including the flat areas on the leading and trailing ends. (b) Similar, except that the workpiece was prebent to minimize the flat areas on the ends.

As shown in Fig. 40, the work metal is placed on the bottom rolls while the top roll is raised. The top roll is then lowered to contact and bend the work metal a predetermined amount, depending on the diameter of the workpiece to be formed. On a pyramid-type machine, the minimum workpiece diameter is rarely less than 150 mm (6 in.) greater than the top roll. However, more power is required to form sheet or plate into cylinders of minimum diameter than to form cylinders substantially larger than the top roll.

Rolls Rolls for three-roll forming machines are machined from steel forgings having a carbon content of 0.40 to 0.50% and a hardness of 160 to 210 HRB. Plain carbon steel such as 1045 has often been used; when greater strength is needed, rolls are forged from an alloy steel such as 4340. Contour Roll Forming

CONTOUR ROLL FORMING (also known as roll forming or cold roll forming) is a continuous process for forming metal from sheet, strip, or coiled stock into shapes of uniform cross section by feeding the stock through a series of roll stations equipped with contoured rolls (sometimes called roller dies). With two or more rolls per station, most contour roll forming is done by working the stock progressively in two or more stations until the finished shape is produced. The process is suited for large quantities and long lengths to close tolerances and involves a minimum of handling. Auxiliary operations, such as notching, slotting, punching, embossing, curving, and coiling, can be combined with contour roll forming. Contour roll forming is used for parts that were previously manufactured by extrusion processes. This use is limited, however, to parts that can be redesigned to have a constant wall thickness. Industries that use roll-formed products include the automotive; building; office furniture; home appliance and home product; medical; railcar; aircraft; and heating, ventilation, and air conditioning (HVAC) industries. Contour roll forming can be divided into two broad categories: a process using precut lengths of work metal (precut or cut-to-length method), and a process that uses coil stock that is trimmed to size after forming (post-cut method).

Work Materials Any material that can withstand bending to the desired radius can be contour roll formed. Thicknesses of 0.13 to 19 mm (0.005 to in.) and material widths of 3.2 to 1830 mm ( to 72 in.) can be used. Length of the formed part is limited only by the length that can be handled conveniently after forming. In some cases, multiple sections can be formed from a single strip; in other cases, several strips can be fed simultaneously into the machine and combined after forming to produce a composite section. Contour roll forming is almost always

performed at room temperature; however, some materials, such as certain titanium alloys, must be formed at elevated temperatures. This is done on specially designed machines.

Machines The machine most commonly used has a number of individual units, each of which is actually a dual-spindle roll-forming machine mounted on a suitable baseplate to make a multiple-unit machine. The flexibility of this construction permits the user to purchase enough units for immediate needs only. Roll forming machines can be classified according to the method by which the spindles are supported in the unit. Generally, two types exist: inboard (or overhung spindle) machines and outboard machines. Inboard machines (Fig. 41) have spindle shafts supported on one end that are 25 to 38 mm (1 to 1

in.) in diameter and up to 102 mm (4 in.) in length. They are used for forming light-gage moldings, weather strips, and other simple shapes. Material thickness is limited to about 1 mm (0.040 in.), and the top roll shaft is generally geared directly to the bottom shaft. This direct-mesh gearing permits only a small amount of roll redressing (no more than the thickness of the material being formed) on the top and bottom rolls. Tooling changeover is faster on this machine than on the outboard machine.

Fig. 41 Overhung-spindle machine (one roll station) for contour roll forming

Outboard machines (Fig. 42) have housings supporting both ends of the spindle shafts. The outboard housing is generally adjustable along the spindles, permitting shortening of the distance between the supports to accommodate the roll forming of small shapes of heavy-gage material. This also permits the machine to be used as an inboard machine when desired. Outboard machines can be readily designed to accommodate any width of material by making the spindle lengths suit the material width and then mounting the individual units and spindles on a baseplate of suitable width. This

type of machine is built with spindle sizes ranging from 38 to 102 mm (1 to 1830 mm (72 in.).

to 4 in.) diameter and with width capacities up

Fig. 42 Universal contour roll forming machine, with outboard support for roll shafts (rolls not shown)

Tooling Tooling used in roll forming includes the forming rolls and the dies for punching and cutting off the material. Tube mills require some additional tooling to weld, size, and straighten the tubes as they are produced on the machine. Forming Rolls. The rolls actually form the material as it moves through the machine. Several factors must be

considered when designing the rolls to form a particular part. These include the number of required passes, the material width, the "flower" design, the roll design parameters, and the roll material. Flower is the name given to the progressive section contours, starting with the flat material and ending with the desired section profile. Roll Materials. The materials that are most commonly used for contour rolls are: low-carbon steel, turned and polished

but not hardened; gray iron (such as class 30), turned and polished but not hardened; low-alloy tool steel (such as O1 or L6), hardened to 60 to 63 HRC and sometimes chromium plated; high-carbon high-chromium tool steel (such as D2), hardened to 60 to 63 HRC and sometimes chromium plated; and bronze (usually aluminum bronze). Drop Hammer Forming

DROP HAMMER FORMING is a process for producing shapes by the progressive deformation of sheet metal in matched dies under the repetitive blows of a gravity drop hammer or a power drop hammer. Configurations most commonly formed by the process include shallow, smoothly contoured, double-curvature parts; shallow-beaded parts; and parts with irregular and comparatively deep recesses. Small quantities of cup-shape and box-shape parts, curved sections, and contoured flanged parts also are formed.

Advantages and Limitations The main advantages of drop hammer forming are: (a) low cost for limited production; (b) relatively low tooling costs; (c) dies that can be cast from low-melting alloys and that are relatively simple to make; (d) short delivery time of product because of simplicity of toolmaking; and (e) the possibility of combining coining with forming. Against these advantages, the following limitations must be weighed: (a) probability of forming wrinkles; (b) need for skilled operators, specially trained for this process; (c) restriction to relatively shallow parts with generous radii; (d) restriction to relatively thin sheet, from about 0.61 to 1.6 mm (0.024 to 0.064 in.) (thicker sheet can be formed only if the parts are shallow and have generous radii). Drop hammer forming is not a precision forming method; tolerances of less than 0.8 to 1.6 mm ( practical.

to

in.) are not

Hammers for Forming Gravity drop hammers and power drop hammers are comparable to a single-action press. However, they can be used to do the work of a press equipped with double-action dies through the use of rubber pads, beads in the die surfaces, draw rings, and other auxiliary equipment. Because they can be controlled more accurately and because their blows can be varied in intensity and speed, power drop hammers, particularly the air-actuated types, have virtually replaced gravity drop hammers. A typical air drop hammer, equipped for drop hammer forming, is shown in Fig. 43.

Fig. 43 Air-actuated power drop hammer equipped for drop hammer forming

Tooling In general, a tool set consists of a die that conforms to the outside shape of the desired part, and a punch that conforms to the inside contour (see Fig. 43). Tool Materials. Dies are cast from zinc alloy (3.5% Cu, 4% Al, and 0.04% Mg), aluminum alloy, beryllium copper,

ductile iron, or steel. The wide use of zinc alloy as a die material stems from the ease of casting it close to the final shape desired. Its low melting point (381 °C, or 717 °F) also is advantageous. All dies, regardless of die material, are polished. Punches usually are made of lead or a low-melting alloy, although zinc or a reinforced plastic also may be used. The sharpness of the contours to be formed, the production quantity, and the accuracy desired primarily govern the choice of punch material. As a punch material, lead has the advantage of not having to be cast accurately to shape, because it deforms to assume the shape of the die during the first forming trial with a blank.

Lubricants Lubricants are used in drop hammer forming to facilitate deformation by reducing friction and minimizing galling and sticking, and to preserve or improve surface finish. Selection of a lubricant depends primarily on type of work metal, forming temperature, severity of forming, and subsequent processing. Recommendations for lubricants used with steels and aluminum, magnesium, and titanium alloys are given in the section "Selection and Use of Lubricants in Forming Sheet Metal" in this article. Explosive Forming

EXPLOSIVE FORMING changes the shape of a metal blank or preform by the instantaneous high pressure that results from the detonation of an explosive. This discussion deals only with the explosives generally termed high explosives, and not with so-called low explosives. Metal tubing up to 1.4 m (54 in.) in diameter in lengths up to 4.6 m (15 ft) is formed using this process. Tubing with diameters of 1.4 m (54 in.) or less can be as long as 9.1 m (30 ft). Typical domes constructed of 6- to 12-piece gore sections fabricated from explosively formed metal can measure up to 6.1 m (20 ft) in diameter. The process has been used to fabricate gore sections for a 12 m (40 ft) diameter dome.

Confined and Unconfined Systems Systems used for explosive-forming operations are generally classified as either confined or unconfined. Confined systems (Fig. 44) use a die, in two or more pieces, that completely encloses the workpiece. The closed system has distinct advantages for forming thin stock to close tolerances. It has been used for close-tolerance sizing of thin-wall tubing. However, confined systems are generally used only for comparatively small workpieces because economic feasibility decreases as the size of the workpiece increases.

Fig. 44 Confined system for explosive forming

In an unconfined system (Fig. 45) the shock wave from the explosive charge takes the place of the punch in conventional forming. A single-element die is used with a blank held over it, and the explosive charge is suspended over the blank at a predetermined distance (the standoff distance). The complete assembly can be immersed in a tank of water, or a plastic bag filled with water can be placed over the blank.

Fig. 45 Unconfined system for explosive forming

Equipment

The primary equipment for explosive forming in an unconfined system consists of a water tank, a crane, a vacuum pump, and a detonator control (firing) box. The water tank must withstand the repeated impacts of the explosive shock without rupturing. Many tanks are large

enough to reduce the shocks reaching the walls from centrally placed charges. A crane is usually needed to move material around the facility, as well as in and out of the water tank. Ideally, the crane

should be air operated to avoid electric power lines within the firing area. A vacuum pump may be needed for explosive-forming operations in which parts are formed under water. If the firing area is to be maintained with a minimum of electric lines, an entire pump operating on water pressure will work satisfactorily. A mechanical pump driven by an electric motor can be used; the vacuum lines are brought into the firing area from a remote pumping site. An electrically driven mechanical pump is preferred over a venturi pump for its considerably greater capacity and is economy. Detonation Circuit. Under ideal conditions, the firing box for the electric blasting caps in the only electric device that

should be permitted in the area where explosives are handled. A firing box should be constructed on the fail-safe principle so that any malfunction will immediately cause the circuit to be disarmed.

Die Systems and Materials Basic differences between tooling for explosive forming and for conventional forming arise from the type of loading that the die material must withstand. In explosive forming, high-impact loads transmit shock waves through the metal that cause unusual stress patterns within the die materials. Therefore, corners should be eliminated where possible. Shock loading causes the die to fracture along lines from the corners, rather than through the thinnest section, as in static fracture (Fig. 46).

Fig. 46 Modes of fracture of a rectangular die under (a) static load and (b) shock load

Die Materials. Solid dies made from heat-treated alloy steel maintain contour, surface finish, and dimensional accuracy

for a relatively long time. To avoid brittle fracture under overloads, a maximum hardness of 50 HRC is desirable. Electromagnetic Forming

ELECTROMAGNETIC FORMING (EMF) is widely used to both join and shape metals and other materials rapidly and precisely, and without the heat effects and tool marks associated with other techniques. Also known as magnetic pulse forming, EMF uses the direct application of a pressure created in an intense, transient magnetic field. Without mechanical contact, a metal workpiece is formed by the passage of a pulse of electric current through a forming coil.

The major application of EMF is the single-step assembly of metal parts to each other or to other components, although it is also used to shape metal parts. Within the transportation industry, for example, one automotive producer assembles aluminum driveshafts without welding to save a significant amount of weight in light trucks and vans in order to meet requirements for reduced energy consumption. Using the EMF process allows the joining of an impact-extruded aluminum yoke to a seamless tube without creating the heat-affected zone associated with welding. EMF also is used to expand, compress, or form tubular shapes. It is occasionally used to form flat sheet, and it is often used to combine several forming and assembly operations into a single step. In the automotive industry, EMF is used by all three major U.S. manufacturers and several foreign producers to assemble components such as air conditioner accumulators, high-pressure hoses, shock absorber dust covers, rubber boots on constant velocity (CV) joints, oil cooler heat exchangers, steering wheels, gasoline fill tubes, and accessory motor packages.

Process Description In its simplest form, EMF uses a capacitor bank, a forming coil, a field shaper, and an electrically conductive workpiece to create intense magnetic fields to do useful work. This very intense magnetic field, produced by the discharge of a bank of capacitors into a forming coil, lasts only a few microseconds. The resulting eddy current that are induced in the conductive workpiece that is placed close to the coil interact with the magnetic field to cause mutual repulsion between the workpiece and the forming coil. The force of this repulsion is sufficient to cause permanent deformation. The basic circuit (Fig. 47) used for electromagnetic compression forming of a tubular workpiece consists of a forming coil, an energy-storage capacitor, switches, and a power supply of nearly constant current to charge the capacitor. Figure 47(a) shows the flux-density pattern of the magnetic field produced by discharging the capacitor through the forming coil in the absence of an electrically conductive workpiece. The evenly spaced flux lines indicate a uniform flux density within the coil. Figure 47(b) shows the change in field pattern that results when the capacitor is discharged through a forming coil in which a tubular workpiece of highly conductive metal has been inserted. The magnetic field is distorted and the flux density intensified (flux lines are more closely spaced) by confinement to the small annular space between the coil and the workpiece.

Fig. 47 Basic circuit and magnetic field patterns for electromagnetic compression forming of a tubular workpiece. (a) Field pattern in absence of workpiece. (b) Field pattern with workpiece in forming coil. (c) Field pattern when field shaper is used. A, high pressure; B, low pressure.

Field shapers, which are massive current-carrying conductors inductively coupled to the forming coil, concentrate the magnetic field at the point at which forming is desired. This technique most efficiently uses stored energy to produce high

local forming pressures in desired areas. Field shapers also allow the use of a standard forming coil for a variety of applications. The field shaper, which is simpler to make, can be tailored to the specific part to be formed. Figure 47(c) illustrates the use of a field shaper to concentrate the force in certain regions of the workpiece. This technique not only produces high local forming pressures in desired areas, but also lengthens the life of the forming coil by preventing high pressures on weaker parts of the coil. Forming Methods. Electromagnetic forming can usually be applied to three forming methods: compression, expansion,

and contour forming. As shown in Fig. 48(a), a tubular workpiece is compressed by an external coil, usually against a grooved or suitably contoured insert, plug, tube, or fitting inside the workpiece. The tubular workpiece is expanded by an internal coil (Fig. 48b), usually against a collar or other component surrounding the workpiece. Flat stock is almost always contour-formed against a die (Fig. 48c).

Fig. 48 Three basic methods of EMF. (a) Compression. (b) Expansion. (c) Contour forming

Superplastic Forming (SPF)

SUPERPLASTICITY refers to the ability of certain metals to develop extremely high tensile elongations at elevated temperatures and under controlled rates of deformation. The tensile ductility of superplastic metals typically ranges from 200 to 1000% elongation, but ductilities in excess of 5000% have been reported. Elongations of this magnitude are one to two orders greater than those observed for conventional metals and alloys, and they are more characteristic of plastics than metals. Because the capabilities and limitations of sheet metal fabrication are most often determined by the tensile ductility limits, significant advantages potentially are available for forming such materials, provided the high-ductility characteristics observed in the tensile test can be used in production forming processes.

Superplastic Alloys There are several different types of superplasticity in terms of the microstructural mechanisms and deformation conditions, including the following: micrograin superplasticity, transformation superplasticity, and internal stress superplasticity. At this time, only the micrograin superplasticity is of importance in the fabrication of parts. For micrograin superplasticity, the high ductilities are observed under the following conditions:

• • •

Very fine grain size material (approximately 10 m, or 400 in.) Relatively high temperature (greater than about one-half the absolute melting point) A controlled strain rate, usually 0.0001 to 0.01 s-1

Because of these requirements, only a limited number of commercial alloys are superplastic. These include Zn-22Al and the titanium and aluminum alloys listed in Table 10. Other alloys, including some ferrous alloys (e.g., hypereutectoid high-carbon steels), exhibit superplastic behavior, but very few of these have been produced commercially.

Table 10 Superplastic properties of aluminum and titanium alloys Alloy

Aluminum Statically recrystallized Al-33Cu Al-4.5Zn-4.5Ca Al-6 to 10Zn-1.5Mg-0.2Zr Al-5.6Zn-2Mg-1.5Cu-0.2Cr Dynamically recrystallized Al-6Cu-0.5Zr (Supral 100) Al-6Cu-0.35Mg-0.14Si (Supral 220) Al-4Cu-3Li-0.5Zr Al-3Cu-2Li-1Mg-0.2Zr Titanium

Test temperature °C °F

Strain rate, s-1

Strain rate sensitivity, m(a)

Elongation, %

400-500 550 550 516

752-930 1020 1020 961

8 × 10-4 8 × 10-3 10-3 2 × 10-4

0.8 0.5 0.9 0.8-0.9

400-1000 600 1500 800-1200

450 450 450 500

840 840 840 930

10-3 10-3 5 × 10-3 1.3 × 10-3

0.3 0.3 0.5 0.4

1000 900 900 878

840-870 850 900 871 815 815 815 1000

1545-1600 1560 1650 1600 1499 1499 1499 1830

1.3 × 10-4 to 10-3 8 × 10-4 2 × 10-4 2 × 10-4 2 × 10-4 2 × 10-4 2 × 10-4 2 × 10-4

0.75 0.70 0.67 0.63-0.81 0.85 0.53 0.54 0.49

750-1170 700-1100 538 >510 720 670 650 420

815 800 750 800

1499 1470 1380 1470

2 × 10-4 ... ... ...

0.5 ... 0.43 0.60

229 w h). These three basic groups are further divided into subgroups depending on the presence and type of elements subsidiary to the basic shape.

Fig. 11 Classification of forging shapes

This "shape classification" can be useful for estimating costs and predicting preforming steps. However, this method is not entirely quantitative and requires subjective evaluation based on past experience. Parting Line The parting line is the line along the forging at which the dies meet. It can be in a single plane, curved, or irregular. The shape and location of the parting line determine die cost, draft requirements, grain flow, and trimming procedures. In most forgings, the parting line is at the largest cross section of the part because it is easier to spread metal by forging action than to force it into deep die impressions. If the largest cross section coincides with a flat side of a forging, the

parting line could be located along the edges of the flat section, thus placing the entire impression in one die half. This reduces die costs because one die is simply a flat surface. This also prevents mismatch between upper and lower dies and allows forging flash to be trimmed readily. When a die set with one flat die cannot be used, the parting line should be positioned to provide for location of the preform in the finished impression of the forging die and the finished forging in the trimming die. Because part of the metal flow is toward the parting line during forging, the location of the parting line affects the grainflow characteristics of a forged piece. For good internal-flow patterns in, for example, a forging having a vertical wall adjacent to a bottom web section, a parting line on the outer side of the wall should be either adjacent to the web section and near the bottom of the wall, or at the top of the wall. A parting line at any point above the center of the bottom web but below the top of the wall can disrupt the grain flow and cause defects in the forging. Because the dies move only in a straight line, and because the forging must be removed from the die without damage either to the impression or to the forging, die impressions usually can have no undercuts. Frequently, the forging can be inclined with respect to the forging plane to overcome the effect of an undercut. In press forging, "split dies," confined in a holder during forging and opened up for removal of the forged part, allow forging parts with undercuts and complex shapes. Locks and Counterlocks Many forgings require a parting line that is not flat and, correspondingly, die parting surfaces that are neither planar nor perpendicular to the direction of the forging force. Dies that have a change in the plane of their mating surfaces, and that, therefore, mesh ("lock") in a vertical direction when closed, are called locked dies. In forging with locked dies, side or end thrust is frequently a problem. A strong lateral thrust during forging can cause mismatch of the dies or breakage of the forging equipment. To eliminate or control side thrust, forgings can be inclined, rotated, or otherwise placed in the dies to balance the lateral forces (Fig. 12c). Flash can be used to cushion the shock and help absorb the lateral forces. For large production quantities of parts small enough to be forged in multiple-part dies, the impressions can be arranged so the side thrusts cancel each other.

Fig. 12 Locked and counterlocked dies. Locked dies (a) with no means of counteracting side thrust, (b) with counterlock, and (c) requiring no counterlock because the forging has been rotated to minimize side thrust.

Generally, alignment between the upper and lower die impressions can be maintained with proper placement of the impression in the die, using clearance between the guides on the hammer or press to absorb side thrust. When these techniques will not work, side thrust can be counteracted by machining mating projections and recesses, or counterlocks, into the parting surfaces of the dies.

Counterlocks can be relatively simple. A pin lock, consisting of a round or square peglike section with its mating section, may be all that is required to control mismatch. Two such sections, or sections at each corner of the die, may be necessary. A simple raised section with a mating countersunk section running the width and the length of the die can control side and end match. Counterlocks of these types should not be used in long production runs. Counterlocks in high-production dies should be carefully designed and constructed. The height of the counterlock usually is equal to, or slightly greater than, the depth of the locking portion of the die. The thickness of the counterlock should be at least 1.5 times the height to provide adequate strength to resist side thrust. Adequate lubrication of the sliding surfaces is difficult to maintain because of the temperature of the die and the heat radiated from the workpiece. Therefore, the surfaces of the counterlock wear rapidly and need frequent reworking. Because of the cost of constructing and maintaining counterlocks, they should be used only if a forging cannot be produced more economically without them. Size of the Die Block The size of the die block is determined by the width of the finished "platter," including allowance for flash and gutters and allowance for the preforming impressions and for sprues and gates for the blocker and finisher impressions. ("Platter" is defined as the entire workpiece on which the forging equipment performs work, including the flash, sprue, tonghold, and as many forgings as are made at one time.) The impressions in a block should be spaced in such a way that the size of the die face is suitable for the size of the hammer, that flash cannot flow from one impression to another, and that the forging is not pinched in preform impressions that are too narrow. Die pressures vary with different work metals and workpiece shapes. A larger die block usually is needed as die pressure is increased. When standard forged alloy steel rams are used in gravity-drop hammers, the minimum area of the upper die face recommended by one manufacturer is 30% of the ram area for 225 to 1135 kg (500 to 2500 lb) hammers, 35% for 1360 to 2270 kg (3000 to 5000 lb) hammers and 40% for hammers with capacities of 2720 kg (6000 lb) or more. The weight of the upper die should be 25 to 30% of the falling weight. Heavier dies are not recommended for regular practice. For power-drop hammers, the area of the die face should be 50% of the ram area for 455 to 1360 kg (1000 to 3000 lb) hammers, 60% for 1815 to 3630 kg (4000 to 8000 lb) hammers and 70% for hammers with capacities of 4535 kg (10,000 lb) or more. The minimum shut height of the dies should be at least 50 mm (2 in.) greater than the shut height of the hammer or press. The height of the die block determines the maximum impression depth because adequate die material must remain between the bottom of the impression and the bottom face of the die block to provide strength to the die. Relatively small "die inserts" usually are used in mechanical presses. This saves expensive die material and the machining required on large die blocks. The dies are set in recesses in holders fastened to the ram and bed of the press. The dies are held in the recesses by clamps, and screws extending through the holders into the recesses provide for adjustment of die position and hold the die in position. In modern press-forging operations, quick die-change mechanisms are available. Thus, die inserts can be held by hydraulic clamps that hold or release very quickly. Another method is to set up the inserts in an extra die holder outside the press and to change the entire die holder before starting a new production run. Draft Draft, or taper, is added to straight sidewalls of a forging to permit easier removal from the die impression. Forgings having round or oval cross sections or slanted sidewalls form their own draft. Forgings having straight sidewalls, such as square or rectangular sections, can be forged by parting them across the diagonal and tilting the impression in the die so that the parting line is parallel to the forging plane. Another method is to place the parting line at an angle to the forging plane and to machine a straight-wall cavity and a counterlock in each die. The draft used in die impressions normally varies from 3 to 7° for external walls of the forged surfaces that surround holes or recesses having angles ranging from 5 to 10°. More draft is used on walls surrounding recesses to prevent forging sticking in the die as a result of natural shrinkage of the metal as it cools. Flash Allowance

Flash, or excess metal extruded from the finisher impression during forging, acts as a cushion for impact blows and as a pressure-relief valve for the almost incompressible work metal. Also, it restricts the outward flow of the metal so that thin ribs and bosses can be filled in the upper die. The finisher impression generally includes a provision for flash. Figure 13 shows a typical arrangement (flash clearance, flash land, and gutter).

Fig. 13 Section through a forging, die finisher impression showing flash clearance, flash land, and gutter

A small amount of flash clearance in the dies, with an excess volume of work metal in the impression, requires much greater forging load or extra hammer blows to bring the forging to size. This creates excessive wear on the flash land, produces extreme pressures within the impression, and can cause dies to break. Conversely, if the flash clearance is too great, work metal needed to fill the impression flows out through the flash land, and the forging is not properly filled. A balanced condition is needed, with just enough volume of metal to ensure that the flash clearance provided will force the work metal to fill the impression properly without causing excess wear and pressure. The volume, the complexity, and the height-to-weight ratio of the forging, as well as the type of work metal, have an effect on flash thickness. General practice has been to use smaller flash clearance for small forgings than for large forgings. The amount of clearance varies from a minimum of approximately 0.51 mm (0.020 in.) up to a maximum of approximately 9.52 mm (0.375 in.) for forgings weighing up to 90 kg (200 lb). Approximately 3% of the maximum forging thickness is a reasonable guide for flash clearance. The amount of excess work metal extruded from the impression can be too great to permit complete closing of the dies. To ensure complete closing, a gutter is provided for the excess metal after it has passed through the flash land. Locating Impressions The preform and finisher impressions should be positioned across the die block so the forging force is as near the center of the striking force (ram) as possible. This will minimize tipping of the ram, reduce wear on the ram guides, and help to maintain the thickness dimensions of the forging. When the forging is transferred manually to each impression, the impression for the operation requiring the greatest forging force (usually, the finisher) is placed at the center of the die block, and the remaining impressions are distributed as nearly equally as possible on each side of the die block. Symmetrical forgings usually have their centerline along the front-to-back centerline of the die block. For asymmetrical forgings, the center of gravity can be used as a reference for positioning the preform and finisher impressions in the die block. The center of gravity of a forging does not necessarily correspond to the center of the forging force because of the influence of thin sections on the forging force. Because the increase in force is not always directly proportional to the decrease in thickness, both the flash and the location of the thin sections must be considered when locating the impressions in a die block. Evenly distributed flash has little effect on an out-of-balance condition; very thin sections have a marked effect. Often it is necessary to make some calculations in order to determine the center of loading of the finisher impression. Die Inserts Die inserts are used for economy in production of some forgings. In general, they prolong the life of the die block into which they fit. Inserts can decrease production costs when several can be made for the cost of producing one solid die. The time required for changeover or replacement of inserts is brief because a second set of inserts can be made while the

first set is being used. Finally, more forgings can be made accurately in a die with inserts than in a solid die because steel of higher alloy content and greater hardness can be used in inserts than would be safe or economical to use in solid dies. Some commercial drop-hammer forge shops rarely use die inserts. However, nearly all press shops use die inserts. Inserts can contain the impression of only the portion of a forging subjected to greatest wear, or they can contain the impression of a whole forging. An example of the first type of insert is the plug-type insert used for forging deep cavities. Examples of the second type include master-block inserts that permit forging of a variety of shallow parts in a single die block and inserts for replacement of impressions that wear the most rapidly in multiple-impression dies. A plug-type insert (Fig. 14) is usually a projection in the center of the die to forge a hub or cup, for example. In some

impressions, the plug may not be in the center, and more than one plug can be used in a single impression. Although plugs are used in either shallow or deep impressions, the need is usually greater in deep impressions.

Fig. 14 Use of a plug-type insert in combination with a nearly complete insert in the lower die block for making a forging of extreme severity. For forging this workpiece (an automotive axle housing), shown in cross section, an H12 tool steel plug in the upper die block is used in combination with a nearly complete H12 insert in the lower die block.

Plug inserts can be made either from prehardened die steel at a higher hardness than the main part of the die or, for longer life, from one of the hot-work tool steels. For extremely high wear resistance, the plug can be hardfaced. Full inserts are generally used for shallow forgings. The insert can be of high hardness with less danger of breakage

because it has the softer block as a backing. With only the insert made from a higher alloy steel, die costs are low. Changes in die designs are less costly when inserts are used; also, the same die block, or master block, can be used for slightly different forgings by changing inserts (Fig. 15a).

Fig. 15 Two types of die inserts used in hammer forging. (a) Full insert and master block for use in forging of gear blanks in hammers. (b) Multiple-impression insert for use when wear is excessive on one or more impressions. Such an insert is usually secured by a key.

Another application for an insert is in multiple-impression dies in which the impressions wear at different rates. Inserts are used for only the impressions that wear most rapidly. In the multiple-impression die, Fig. 15(b), the blocker and finisher impressions are in the same insert. This technique is not necessarily limited to shallow impressions. If the insert contains a single impression, the impression can be of any practical depth. However, if it contains several impressions, the impression depth is limited to approximately 64 mm (2 in.) or less. Width of the insert must be considered; sufficient wall thickness must be allowed between the edge of the impression and the edge of the insert so the die-block walls are not weakened too greatly.

Die Steels Prehardened and tempered tool steel die blocks are available in a range of compositions and hardnesses. Tool steels are also available for small die blocks, die inserts, and trimming tools. Prehardened die-block steels are usually purchased on a basis of hardness. Hot-work die steels are commonly used for hot-forging dies subjected to temperatures ranging from 315 to 650 °C (600 to 1200 °F). These materials contain chromium, tungsten, and in some cases vanadium or molybdenum or both. These alloying elements induce deep hardening characteristics and resistance to abrasion and softening. These steels are usually hardened by quenching in air or molten salt baths. The chromium-base steels (Table 2) contain approximately 5% Cr. High molybdenum content gives these materials resistance to softening; vanadium increases resistance to abrasion and softening. Tungsten improves toughness and hot hardness; tungsten-containing steels, however, are not resistant to thermal shock and cannot be cooled intermittently with water. The tungsten-base, hot-work die steels contain 9 to 18% W, 2 to 12% Cr, and sometimes small amounts of vanadium. The high tungsten content provides resistance to softening at high temperatures while maintaining adequate toughness, but it also makes water cooling of these steels impossible. Lowalloy proprietary steels are also used frequently as die materials for hot forging. Steels with ASM designations 6G, 6F2, and 6F3 have good toughness and shock resistance with good resistance to abrasion and heat checking. These steels are tempered at lower temperatures (usually 450 to 500 °C, or 840 to 930 °F); therefore, they are more suited for applications that do not result in high die surface temperatures (for example, die holders for hot forging or hammer die blocks).

Table 2 Compositions of tool and die materials for hot forging Nominal composition, % C Mn Si Co Chromium-base AISI hot-work tool steels 0.40 0.40 1.00 . . . H10 0.35 0.30 1.00 . . . H11 0.35 0.40 1.00 . . . H12 0.38 0.30 1.00 . . . H13 0.40 0.35 1.00 . . . H14 0.40 0.30 0.30 4.25 H19 Tungsten-base AISI hot-work tool steels 0.30 0.30 0.30 . . . H21 0.35 0.30 0.30 . . . H22 0.30 0.30 0.30 . . . H23 0.45 0.30 0.30 . . . H24 0.25 0.30 0.30 . . . H25 0.50 0.30 0.30 . . . H26 Low-alloy proprietary steels 0.55 0.80 0.25 . . . ASM 6G 0.55 0.75 0.25 . . . ASM 6F2 0.55 0.60 0.85 . . . ASM 6F3 Designation

Cr

Mo

Ni

V

W

3.30 5.00 5.00 5.25 5.00 4.25

2.50 1.50 1.50 1.50 ... 0.40

... ... ... ... ... ...

0.50 0.40 0.50 1.00 ... 2.10

... ... 1.50 ... 5.00 4.10

3.50 2.00 12.00 3.0 4.0 4.0

... ... ... ... ... ...

... ... ... ... ... ...

0.45 0.40 1.00 0.50 0.50 1.00

9.25 11.00 12.00 15.00 15.00 18.00

1.00 1.00 1.00

0.45 0.30 0.75

... 1.00 1.80

0.10 0.10 0.10

... ... ...

Selection Factors. Die steels are selected according to their ability to harden uniformly, to resist the abrasive action of

the hot metal during forging, to withstand high pressure and heavy shock loads, and to resist cracking and checking caused by heat. Process variables to consider when selecting a die steel include shape, size, and weight of the forging; the metal to be forged; forging temperature; production quantity; and the forging equipment to be used. Further variables in die material selection are cost of the die steel; how the die will be machined (before or after hardening); and forging tolerances (including those specified for draft angles). Typically, the selection also will be determined by previous experience with similar applications and the availability of machining equipment. Additional information on properties and selection of die steels can be found in the Section "Tool Steels" in this Volume. Another excellent information source for die material selection is the Tool Materials, ASM Specialty Handbook, 1995. This Volume provides material selection guidelines for individual forging (hot and cold) and forming operations.

Computer-Aided Design and Computer-Aided Manufacture of Forging Dies Computer analysis is well suited to the design of forging dies. Three-dimensional computer models can simulate metal flow through the die cavities and assist in establishing the best die design. Computer-aided design (CAD) and computeraided manufacture (CAM) techniques are increasingly used in the forging industry. Once the computer determines the detailed dimensions of the die, it can translate them into instructions for numerically controlled machining of the final tooling. Software designed for die design provides a database reference for draft angles, flash dimensioning, and even control of the forging operation. Software now can perform analyses based on sections through the workpiece. The computer can be used to predict forging load, stress concentrations in the die, elastic deformation of the die material, and metal flow of the workpiece. With little effort, these variables can be observed for alternative designs. Flash dimensions can be selected, and initial estimates of blocker or preform sections can be evaluated. Once the die is created on the computer to the designer's satisfaction, the software presents a geometric database to be used to write numerical control instructions for milling the die. More information on computer modeling for forging is available in Forming and Forging, Volume 14, ASM Handbook (see the Section "Computer-Aided Process Design for Bulk Forming," in this Volume). Forging Processes

THIS SECTION reviews specific characteristics of the most common forging processes. Process limitations, advantages, and disadvantages are discussed.

Open-Die Forging Open-die forging--sometimes known as hand, smith, hammer, and flat-die forging--is a process in which the metal workpiece is not confined by dies. The process is typically associated with large parts, although parts can weigh from a few pounds to 150 tons. Probably 80% of all parts forged in open dies weigh between 30 and 1000 lb each. Open-die forging progressively works the starting stock into the final shape, most commonly between flat-faced dies. This process can be selected when the forging is too large to be produced in closed dies. All forgeable metals can be forged in open dies. Shapes Produced Highly skilled hammer and press operators, with the aid of various auxiliary tools, can produce relatively complex shapes in open dies. However, because forging of complex shapes is time consuming and expensive, such forgings are produced only under unusual circumstances. Most open-die forgings are rounds, squares, rectangles, hexagons, and octagons forged from billet stock, either to develop mechanical properties that are superior to those of rolled bars or to provide these shapes in compositions for which the

shapes are not readily available as rolled products. Hubs that have a small diameter adjacent to a large diameter can be produced in small quantities by open-die forging. Open-die forging is used to produce spindles, pinion gears, and rotors that are shaft-like parts with their major or functional diameters either in the center or at one end with one or more smaller diameters extending from one or both sides of the major diameter in shaft-like extensions. Forged and pierced blanks, prior to conversion to rolled rings, are open-die forged. Various basic shapes can be developed between open dies with the aid of "loose" tooling. Hammers and Presses The principles of operation of hammers and presses are discussed in the Section, "Hammers and Presses for Forging." However, open-die forging requires control of the stroke, the position and the speed of the ram, to obtain acceptable precision and quality in the forged part. Therefore, in general, only air or oil-driven power hammers and hydraulic presses are suitable for open-die forging. Modern open-die forging installations use direct-driven hydraulic presses with pulldown frame design and with quick die-changing mechanisms. In this type of press, the cylinder crosshead, which is located below floor level, is rigidly connected to the press columns. This assembly is movable and well guided. The center of gravity of this press is low, with high stiffness. Direct-driven hydraulic presses offer better control of ram speed and ram position. In modern installations this feature is very significant because the press is usually integrated with a manipulator. The stroke position of the press and the motions of the manipulator are computer controlled. As a result, the entire open-die forging operation can be programmed for given initial and final stock shape and workpiece material. Dies Most open-die forgings are produced in a pair of flat dies--one attached to the hammer or to the press ram and the other attached to the anvil. Swage dies (curved), V-dies, and V-die and flat-die combinations are also used (Fig. 16). Occasionally, a combination of a flat die and a swage die is used. Dies are attached to platens and rams or are held on the anvil manually with handles.

Fig. 16 Four types of die sets commonly used in open-die forging

Steels used for dies for open-die forging are often the same as those used for impression dies in closed-die forging--

for example, 6G or 6F2 die-block steels (compositions of these steels can be found in Table 2). Alloy steels such as 4150 give satisfactory results for small dies. Some forgers prefer a higher carbon steel and use a 0.70% carbon, 4300 grade (such as 4370, although this is not a standard steel). The hardness of dies for open-die forging is generally lower than the hardness of impression dies for closed-die forging. For 6G or 6F2, the usual hardness range is 302 to 331 HB. Dies made of 4150 or a similar alloy steel are usually heat treated to 277 to 321 HB. Parallelism. If the faces of a set of dies mounted in a hammer or press are not parallel, the deviation creates a taper on

the forgings that may be out of tolerance. Tolerances for parallelism vary to some extent with the size of the dies. Fairly large dies (dies 965 by 510 mm, or 38 by 20 in., for example) should be parallel within 1.6 mm ( side to side. For smaller dies, closer parallelism can be maintained.

in.) front to back and

Life of dies for open-die forging is longer than that of impression dies for closed-die forging. Because of the wide

variety of forgings produced on the same open dies, life is usually expressed in production hours rather than in number of forgings. It is not unusual for dies to operate in a hammer for 600 h before they require redressing. Dies are usually designed to permit eight to ten redressings, which is equivalent to 4800 to 6000 h total life. Auxiliary Tools To assist in forging production, mandrels, saddle supports, sizing blocks (spacers), ring tools, bolsters, fullers, punches, drifts (expansion tools), and a wide variety of special tools (for producing special shapes) are used. Because most auxiliary tools are exposed to heat, they are usually made from the same steels as the dies.

Closed-Die Forging in Hammers and Presses Closed-die forging, often referred to as impression-die forging, accounts for the bulk of commercial forging production. As the name implies, two or more dies containing impressions of the part shape are brought together causing the workpiece to plastically deform with the metal flow restricted by the die contours. The forging stock, generally round or square bar, is cut to length to provide the volume of metal needed to fill the die cavity, in addition to an allowance for flash and sometimes for a projection for holding the forging. The flash allowance is, in effect, a relief valve for the extreme pressure produced in closed dies. Flash also acts as a brake to slow the outward flow of metal in order to permit complete filling of the desired configuration. Most closed-die forging is performed at elevated temperatures and is known as hot forging. Both the forging stock and the die are preheated prior to forging. Various types of electric and fuel-fired furnaces are used for heating the forging stock, as well as resistance and induction heating. Die heating is discussed in the section "Die Heating." Also in the closed-die category are cold forging and warm forging processes. Cold forging processes technically include such categories as coining, which is covered in the section "Coining." Cold forgings, produced at about room temperature are generally symmetrical and typically weigh less than 11 kg (25 lb). Because of their extreme dimensional precision and fine surface finish they often need little or no further machining. Production rates are very high with long die life. In warm forging, technically and metallurgically similar to cold forging, the workpiece is heated to "a few" hundred degrees above room temperature, but well below hot-forging temperatures. Warm forging may be selected over cold forging for higher carbon grades of steel or to eliminate subsequent annealing. Capabilities of the Process Closed-die forging is used for both low-volume or high-volume production. In addition to producing final, or nearly final, metal shapes, closed-die forging controls grain-flow direction, often improving mechanical properties in the longitudinal direction of the workpiece. Size of forgings produced in closed, impression dies can range from a few ounces to several tons. The maximum size

that can be produced is limited only by the equipment that is available for handling and for forging. Steel forgings weighing as much as 25,400 kg (56,000 lb) have been closed-die forged. Typically, however, more than 70% of the closed-die forgings produced weigh 0.9 kg (2 lb) or less. Shapes. Complex nonsymmetrical shapes that require a minimum number of operations for completion are suitable for closed-die forging. In addition, the process can be used in combination with other processes to produce parts having greater complexity or closer tolerances than are possible by forging alone. Cold coining and the assembly of two or more closed-die forgings by welding are examples of other processes that can extend the useful range of closed-die forging. Forging Materials. Materials selected for closed-die forgings must satisfy two basic requirements. First, the material

strength (or flow stress) must be low to hold die pressures to within the capabilities of practical die materials and constructions. Also, the forgeability of the material (its ability to deform without failure) must be equal to the amount of deformation required in the die. A comparison of the forgeability of various metals and alloys can be found in the article "Forging of Specific Metals and Alloys" later in this Section.

Classification of Closed-Die Forgings Closed-die forgings are generally classified as blocker-type, conventional, and close-tolerance. Blocker-type forgings are produced with generous allowance for finishing. These forgings are produced in relatively inexpensive dies, but their weight and dimensions are somewhat greater than those of counterpart conventional closed-die forgings. Often blocker-type forgings are specified when only a small number of forgings are required and the cost of machining parts to final shape is not excessive.

Blocker-type forgings can be produced in metal die blocks containing cavities of simple shape, or with stops and gages that the forging producer has in stock. These are called "loose" tools because they are not attached to the ram or anvil but are held in position on a bottom flat die by a handle. Loose tooling can be used to produce a variety of simple shapes, on short notice, without the cost of dies. Because they lack the detail and the dimensional accuracy of forgings completed in finisher dies by conventional closeddie forging methods, forgings produced in loose tooling usually require substantially more machining to provide a finished part. Figure 17 shows specific examples.

Fig. 17 Production of six blocker-type forgings with loose tooling in hammers. Dimensions are in inches.

Conventional closed-die forgings are the most common. They can be complex in shape with tolerances that fall within the broad range of general forging practice. Because they are made closer to the shape and dimensions of the final part than blocker-type forgings, they are lighter with more detail. Close-tolerance forgings, obviously, are held to tighter dimensional tolerances than conventional forgings. Little or

no machining is required after forging because close-tolerance forgings are made with less draft and with thinner walls, webs, and ribs. These forgings cost more and require higher forging pressures per unit of plan area than conventional forgings. However, the higher forging cost is sometimes justified by a reduction in machining cost. Additional information on close-tolerance forgings can be found in the subsection "Precision Forging."

Die Impressions. Several different types of can be used in a forging die, each type being designed to serve a specific

function. In a forging sequence that incorporates several types of impressions, each impression should be considered for the specific function that it is to perform, both by itself and in relation to the preceding and succeeding impressions. In particular, the design of each impression should provide for location of the workpiece in the succeeding die impression. Finishers. The finisher impression gives the final overall shape to the workpiece. In this impression excess metal is

forced out into the flash. Despite its name, the finisher impression is not necessarily the last step in the production of a forging. Bending or hot coining sometimes follows to produce the final shape or dimensions to the forged part after it has passed through the finisher impression and the trimming die. Preforming or Roughing. In any form of hammer forging, parts usually are preformed or roughed by one or a

sequence of preliminary steps in impressions called fullers, edgers, rollers, flatteners, benders, splatters, and blockers (Fig. 18). Blockers are also used in press forging.

Fig. 18 Typical multiple-impression hammer dies for closed-die forging

Fullers. This die impression is used to reduce the cross section and to lengthen a portion of the forging stock. In

longitudinal cross section, the fuller is usually elliptical or oval, to obtain optimum metal flow without producing laps, folds, or cold shuts. (Reducing and lengthening forging stock between flat portions of die surfaces is called drawing, rather than fullering.) Fullers are used in combination with edgers or rollers, or as the only impression prior to the blocker or finisher. Because fullering usually is the first step in the forging sequence and generally uses the least amount of forging load, the fuller is almost always placed on the extreme edge of the die (Fig. 18a). Edgers. Used to redistribute and proportion stock for heavy sections to be further shaped in blocker or finisher

impressions, the action of the edger is opposite to that of the fuller. A forged connecting rod, for example, is first reduced in a fuller to prepare the slender central part of the rod and then worked in an edger to proportion the ends for the boss and crank shapes. The edger impression can be open at the side of the die block, Fig. 18(a), or confined, (Fig. 18b). An edger is sometimes used in combination with a bender in a single die impression to reduce the number of forging blows necessary to produce a forging.

Rollers round the stock (for example, from a square billet to a round bar) or redistribute the mass prior to the next

impression. The stock usually is rotated, and two or more blows are needed to roller the stock. The operation of a roller impression is similar to that of an edger, but the metal is partially confined on all sides, with shapes in the top and bottom dies resembling a pair of shallow bowls. Because of the cost of sinking the die impressions, rollering is more expensive than edging when both operations require the same number of blows. Flatteners widen the work metal so it more nearly covers the next impression or, with a 90° rotation, to reduce the

width to within the dimensions of the next impression. The flattener station can be either a flat area on the face of the die or an impression in the die to give the exact size required. Benders. A portion of the die can be used to bend the stock, generally along its longitudinal axis, in two or more planes.

There are two basic designs of bender impressions: free flow and trapped stock. In bending with a free-flow bender, Fig. 18(b), one end or both ends of the forging are free to move into the bender. A single bend is usually made. This type of bending can cause folds or small wrinkles on the inside of the bend. The trapped-stock bender usually creates multiple bends. In trapped-stock bending, the stock is gripped at both ends as the blow is struck and the stock in between is bent. Because the metal is held at both ends, it usually is stretched during bending. There is a slight reduction in cross-sectional area in the bend, and the work metal is less likely to wrinkle or fold than in a free-flow bender. Stock that is to be bent may require preforming by fullering, edging, or rollering. Bulges of extra material can be provided at the bends to prevent formation of kinks or folds in free-flow bending. This is particularly necessary for sharp bends. The bent preform usually is rotated 90° as it is placed in the next impression. Splitters. In making "forked" forgings, part of the work metal is split to conform more closely to the subsequent blocker impression. In splitting, the stock is forced outward from its longitudinal axis by the action of the splitter. Generous radii should be used to prevent formation of cold shuts, laps, and folds. Blockers. The blocker impression is used in both hammer and press forging. The blocker immediately precedes the

finisher impression to refine the shape of the metal. Usually, the blocker omits those details that restrict metal flow in finishing. A blocker may be a streamlined model of the finisher. Streamlining helps the metal to flow around radii, reducing the possibility of cold shuts or other defects. Sometimes, the blocker impression is made by duplicating the finisher impression in the die block and then rounding it off as required for smooth flow of metal. Preferred, however, is to make the blocker impression slightly narrower and deeper than the finisher impression with a volume that is equal to, or only slightly greater than, that of the finisher. This minimizes die wear at the parting line in the finisher impression. For parts that include deep holes or bosses, the blocker can be a gathering operation. It can sink a volume of metal to one side of the forging, which then can be forced through to the other side in the finisher impression to fill a high boss. Blocker impressions are also used to reduce wear on the finisher cavity. Therefore, a blocker is often included in the series of dies for long forging runs, or in production of close-tolerance forgings, to prolong the life of the finisher impression. Process Variables Flashing design, die preheating, and trimming are several characteristics of closed-die forging that must be considered. Flash. Forging pressures are determined in part by flash thickness and flash-land width (Fig. 19). Essentially, forging

pressure increases with decreasing flash thickness and increasing flash-land width. These variables control restriction, frictional forces, and metal temperatures at the flash gap.

Fig. 19 Metal flow and load-stroke curve in closed-die forging. (a) Upsetting. (b) Filling. (c) End. (d) Loadstroke curve

During a typical forging press stroke, loads are relatively low until the more difficult details in the die are partly filled and the metal reaches the flash opening. At this point, two conditions must be fulfilled: a sufficient volume of metal must be trapped within the confines of the die to fill the remaining cavities and extrusion of metal through the narrowing gap of the flash opening must be more difficult than filling of the more intricate detail in the die. As the dies continue to close, the load increases sharply until the die cavity is filled completely. Ideally, at this point, the cavity pressure provided by the flash geometry should be just sufficient to fill the entire cavity, and the forging should be completed. A cavity can be filled with various flash geometries provided that there is always a sufficient supply of material in the die. In general, the flash thickness should increase with increasing forging weight, while the ratio of flash width to flash thickness (w/t) decreases to a limiting value. Die Heating. Dies should be heated to at least 120 °C (250 °F), and preferably to 205 to 315 °C (400 to 600 °F), before

forging begins. "Warmers" (pieces of hot metal) placed between the die faces, or torches, are used. Dies can be heated in ovens before set up in the hammer or press. Temperature-indicating crayons can be used to measure surface temperature. Cold dies can break when a hot billet is placed on them. Trimming. Several processes are used to trim flash after forging. The method used will depend on the production quantity and size of the parts. Trimming can sometimes eliminate a machining operation.

For small quantities or for large forgings, hand grinding, sawing, or machining can be used to remove the flash. In large quantities, most forgings are die trimmed. Cold trimming usually refers to die trimming below 150 °C (300 °F). This method, often used, especially for small forgings, can be done at any time; it need not be a part of the forging sequence. No reheating of the forgings is needed. Another advantage is that the trimming blades can be adjusted to shear the flash to a smooth surface that does not require machining. Almost all of the common forging alloys can be cold trimmed. Some may require annealing or other heat treatment after forging before they can be cold trimmed. As a rule of thumb, a forging can be cold trimmed if, after forging, its tensile strength does not exceed 690 MPa (100 ksi) or hardness not over 207 HB. Cold trimming may require great press capacity, however. Thus, hot trimming may be selected. Hot trimming is done as low as 150 °C, or 300 °F (for nonferrous alloys), and as high as 980 °C (1800 °F) or above for steels and other ferrous alloys. Friction and Lubrication in Forging In forging, friction greatly influences metal flow, pressure distribution, and load and energy requirements. In addition to lubrication effects, the effects of die chilling or heat transfer from the hot material to colder dies must be considered. For example, for a given lubricant, friction data obtained from hydraulic press forging cannot be used for mechanical press or hammer forging even if die and billet temperatures are comparable.

In forging, the ideal lubricant is expected to: • • • • • • • •

Reduce sliding friction between the dies and the forging in order to reduce pressure requirements, to fill the die cavity, and to control metal flow Act as a parting agent and prevent local welding and subsequent damage to the die and workpiece surfaces Possess insulating properties so as to reduce heat losses from the workpiece and to minimize temperature fluctuations on the die surface Cover the die surface uniformly so that local lubricant breakdown and uneven metal flow are prevented Be nonabrasive and noncorrosive so as to prevent erosion of the die surface Be free of residues that would accumulate in deep impressions Develop a balanced gas pressure to assist quick release of the forging from the die cavity; this characteristic is particularly important in hammer forging, in which ejectors are not used Be free of polluting or poisonous components and not produce smoke upon application to the dies

No single lubricant can fulfill all of the requirements listed above; therefore, a compromise must be made for each specific application. Various types of lubricants are used, and they can be applied by swabbing or spraying. The simplest is a high flash point oil swabbed onto the dies. Colloidal graphite suspensions in either oil or water are frequently used. Synthetic lubricants can be employed for light forging operations. The water-base and synthetic lubricants are extensively used primarily because of cleanliness.

Hot Upset Forging Hot upset forging (also called hot heading, hot upsetting, or machine forging) is essentially a process for enlarging and reshaping some of the cross-sectional area of a bar, tube, or other uniform, usually round, section. Basically, the heated forging stock is held between grooved dies while pressure is applied to the end of the stock in the direction of its axis by a heading tool. The tool spreads (upsets) the end by metal displacement (Fig. 20).

Fig. 20 Basic types of upsetter heading tools and dies, showing the extent to which stock is supported. (a) Unsupported working stock. (b) Stock supported in die impression. (c) Stock supported in heading tool recess. (d) Stock supported in heading tool recess and die impression

Applicability Although hot upsetting originally was restricted to single-blow heading of parts such as bolts, present-day machines and tooling permit the use of multiple-pass dies that can produce complex shapes accurately and economically. The process now is widely used for producing finished forgings ranging in complexity from simple headed bolts or flanged shafts to wrench sockets that require simultaneous upsetting and piercing. Parts requiring center (not at bar end) or offset shaping also can be upset. In many instances, hot upsetting is used to prepare stock for subsequent hammer or press forging. Occasionally, hot upsetting is also used as a finishing operation following hammer or press forging, such as in making crankshafts. Because the transverse action of the moving die and longitudinal action of the heading tool can forge in both directions, either separately or simultaneously, hot upset forging is not limited to simple gripping and heading operations. The die motion can be used for swaging, bending, shearing, slitting, and trimming. In addition to upsetting, heading tools are used for punching, internal displacement, extrusion, trimming, and bending. In upset forging, the working stock usually is confined in the die cavities during forging. The upsetting action creates pressure, similar to hydrostatic pressure, which causes the stock to fill the die impressions completely. Thus, a wide variety of shapes can be forged and removed from the dies by this process. Work Material and Size. Although most forgings produced by hot upsetting are of carbon or alloy steel, the process can be used for shaping any forgeable metal. The size or weight of workpiece that can be hot upset is limited only by the capabilities of available equipment; forgings ranging in weight from less than an ounce to several hundred pounds can be produced by this method.

Upset Forging Equipment A typical machine for hot upset forging is mechanically operated from a main shaft with an eccentric drive that operates a main slide, or header slide, horizontally. The action of the header slide is similar to that of the ram in a mechanical press. Power is supplied to a machine flywheel by an electric motor. A flywheel clutch provides for "stop motion" operation, placing movement of the slides under operator control. Forging takes place in three die elements: two gripper dies (one stationary and one moved by the die slide), which have matching faces with horizontal grooves to grip the forging stock and hold it by friction, and a heading tool, or "header," which is carried by the header slide in the plane of the work faces of the gripper dies and aligns with the grooves in these dies (Fig. 21). The travel of the moving die is designated as the "die opening," and its timed relation to the movement of the header slide is such that the dies close during the early part of the header-slide stroke. The part of the forward headerslide stroke that takes place after the dies are closed is known as the "stock gather," and the amount that the returning header slide travels before the moving die starts to open is called the "hold on," or the "hold."

Fig. 21 Basic actions of the gripper dies and heading tools of an upsetter

The die opening determines the maximum diameter of upset that can be formed on a given machine, transferred between the dies and withdrawn through the throat, without pushing the workpiece forward and lifting it out over the top. The diameter of the stock, rather than the stock gather, determines the amount of stock that can be upset; the stock gather, however, has an important bearing on the depth to which internal displacement can be carried. The height of the die determines the number of progressive operations that can be accommodated in one set of dies. Although some forgings are produced by a single stroke of the ram, most shapes require more than one pass to complete. The upsetter dies may incorporate several different impressions or "stations." The stock is moved from one impression (or station) to the next in sequence, to give the forging a final shape. Each move constitutes a "pass." Three or more passes are commonly used to complete the upset, and if flash removal (trimming) is a part of the forging operation, another pass is added. Piercing and shearing passes can also be incorporated in the dies. In single-blow, solid-die machines, the gripper dies are replaced by a shear arm and shear blade. A long heated bar of forging stock is placed in a slot and pushed against a stop. As the machine is actuated, either automatically or by means of a foot pedal, a motion similar to that of a conventional upsetter occurs, except that, instead of the dies closing, a section of the bar is sheared off. While the shear slide is moving, a cam actuates a transfer arm, which moves until it contacts the stock. The stock, now positioned between the shear blade and the transfer arm, is moved into proper position between the punch and the die. As the punch advances and contacts the stock, the shear blade and the transfer arm move apart. The punch continues its advance, and the forging is produced in a single blow. Ejector pins push the forging from the die, and it drops onto an underground conveyor. Another heated bar of forging stock is pushed against the stop, and the cycle is repeated. Tool Materials For short runs, solid dies are made of lower-alloy steels such as 4340, 6G, or 6F3. For runs of approximately 1000 pieces, higher-alloy hot work steels are commonly used for small dies or inserts in large dies. Two important advantages in the use of punch and die inserts are that they can be replaced when worn out and that, in many applications, two or more different parts can be forged with a master block by changing inserts. Die Cooling and Lubrication Normal practice is to keep dies below 205 °C (400 °F) during forging. In some low-production operations, no coolant is required to keep dies below this temperature. In most applications, however, a water spray (sometimes containing a small amount of salt or graphite) is used as a coolant.

Die lubrication slows production and is not widely used in upsetting of steel. Because of the die action in upsetting, parts are less likely to stick than in hammer or press forging. In deep punching and piercing, however, sticking may be encountered, thus requiring a lubricant. An oil-graphite spray is effective and can simultaneously provide adequate cooling. A recirculated suspension of alumina in water is used in some high-production operations.

Roll Forging Roll forging (also known as hot forge rolling) is a process for reducing the cross-sectional area of heated bars or billets by passing them between two driven rolls that rotate in opposite directions and have one or more matching grooves in each roll. The principle involved in reducing the cross-sectional area of the work metal in roll forging is essentially the same as that employed in rolling mills to reduce billets to bars. Applications Any metal that can be forged by other methods can be roll forged. Heating times and temperatures are the same as those used in the forging of metals in open or closed dies. Roll forging can be used either as the sole or main operation in producing a shape. Generally this involves the shaping of long, thin, usually tapered parts. Typical examples are airplane propeller-blade half sections, tapered axle shafts, tapered leaf springs, table-knife blades, hand shovels and spades, various agricultural tools (such as pitchforks), and tradesman's tools (such as chisels and trowels). Roll forging is sometimes followed by the upsetting of one end of the workpiece to form a flange, as in the forging of axle shafts. Roll forging also is used as a preliminary operation to save material and number of hits in subsequent forging in closed dies. Applications in this case include preliminary shaping of stock prior to forging in impression dies in either a press or hammer, thus eliminating a fullering or blocking operation. Crankshafts, connecting rods, and other automotive parts are typical products that are first roll forged from billets to preform stock and then finish forged in a press. Equipment for Roll Forging In machines for roll forging (often called forge rolls, reducer rolls, back rolls, or gap rolls), the driving motor is mounted at the top of the main housing (Fig. 22). The motor drives a large flywheel by means of V-belts. In turn, the flywheel drives the roll shafts, to which the roll dies are attached, through a system of gears. Forging rolls are available in numerous sizes and have the capacity to roll blanks up to 127 mm (5 in.) thick and 1020 mm (40 in.) long.

Fig. 22 Roll-forging machine with outboard housing

Roll dies are bolted to the roll shafts, which rotate in opposite directions during operation. Roll dies (or their effective forging portion) usually occupy about one-half the total circumference; therefore, at least some forging action takes place during half of the revolution. Machines can be operated continuously or stopped between passes, as required. In the roll forging of long tapered workpieces, the more common practice is to operate the machine intermittently.

Roll Dies Roll dies are of three types: flat back, semicylindrical, and fully cylindrical. Each type is shown in Fig. 23(a).

Fig. 23 (a) Dies used in roll forging. (b) Overhang-type roll forger that utilizes fully cylindrical dies

Flat-back dies are primarily used for short-length reductions. They are bolted to the roll shafts and can be easily

changed. Semicylindrical dies are well suited to the forging of medium-length workpieces. Most are true half cylinders (180°),

although some (particularly in large sizes) may encompass up to 220° of a circle to provide sufficient periphery for the specific application. When each die section is no more than 180°, the dies can be made by first machining the flat surfaces of the half rounds for assembly, clamping the half rounds together, and then boring and finishing. Fully cylindrical dies are used to forge long members, sometimes in an overhang-type machine (Fig. 23b). They are built up with rings, with a cutaway portion just large enough to feed in the forging stock. Fully cylindrical dies are sometimes more efficient than semicylindrical or flat-back dies because of the larger periphery available for the forging action. However, one disadvantage of fully cylindrical dies is that the small opening prevents continuous operation; consequently, motion must be controlled by a clutch and a brake. Steels for roll dies do not differ greatly from those used for dies in hammer, press, and upset forging. However,

because roll dies are subjected to less impact than dies in other types of forging, they can be made of die steels that are somewhat higher in carbon content, which is helpful in prolonging die life.

High-Energy-Rate Forging High-energy-rate forging (HERF), sometimes called high-velocity forging, is a closed-die, hot- or cold-forging process in which the stored energy of high-pressure gas is used to accelerate a ram to unusually high velocities to deform the

workpiece. Ideally, the final configuration of the forging is developed in one blow or, at most, a few blows. In HERF, the velocity of the ram, rather than its mass, generates the major forging force. The maximum impact velocity of HERF machines is approximately three to four times that of conventional drop hammers. Typically, the ram velocity at impact in the HERF machine is in the range of 5 to 22 m/s (16 to 72 ft/s); ram velocities range from 4.5 to 9.1 m/s (15 to 30 ft/s) for a power-drop hammer and from 3.6 to 5.5 m/s (12 to 18 ft/s) for a gravity-drop hammer. High-energy-rate machines can be used to hot forge parts of the same general shapes as those produced with conventional hammers and presses. However, the work metal must be capable of undergoing extremely rapid deformation rates as it fills the die cavity without rupturing it. In HERF, the high ram velocities forge parts with thin webs, high-rib, height-towidth ratios, and small draft angles to profiles sufficiently accurate that machining allowance can sometimes be as little as 0.500 mm (0.0197 in.). Even parts made of difficult-to-forge metals can be formed close to finished dimensions in a few blows and often without reheating. Process Advantages and Limitations Advantages. When evaluating high-energy-rate forging in relation to conventional forging, both the machine advantages and process advantages, as a result of the high velocities, must be considered. The machine advantages are beyond dispute. For a given forming capacity, high-speed machines are much smaller than conventional forging machines, and they require much less installation/foundation and therefore a lower capital investment. These advantages arise because the principle used in these machines involves the conversion of the kinetic energy of a ram/platen into forming work. Kinetic energy is proportional to the square of the impact velocity; therefore, a threefold increase in impact speed produces a nine-fold increase in forming energy. High-energy-rate forging machines are typically one-ninth the bulk and weight of equivalent slow-speed machines. Although the finished forging is generally made in one high-speed blow, some machines can be fired two or three times before the work metal has cooled below the forging temperature.

The process advantages are not as obvious as the machine advantages and depend on the particular application under consideration. In general, with HERF, complex parts can be forged in one blow from a billet or a preform. Many metals that are difficult to forge by other methods can be successfully forged by HERF. Dimensional accuracy, surface detail, and, often, surface finish are better with HERF than other techniques. Draft allowances, both internal and external, can be reduced or, in some applications, eliminated. Forgings are made to size or with a minimum of machining allowance. Reduced machining lowers the induced mechanical stress and minimizes the cutting of end grain, which improves the stress-corrosion resistance of some metals, notably aluminum. Deep, thin sections can be HERFed because the rapidity of the blow provides little time for heat transfer to the die walls. Severe deformation possible with HERF provides a high degree of grain refinement in some metals. Limitations. The process, however, does have several limitations. Sharp corners and small radii cannot be forged

without causing undue wear. The process is generally limited to symmetrical parts, although some asymmetrical parts can be forged from preformed billets. High-energy-rate forging part size is limited to approximately 11 to 12 kg (24 to 26 lb) for carbon steel forgings and to lesser weights for forgings made of stainless steel or heat-resistant alloys. The production rate is about the same as in hammer or hydraulic press forging but is slower than in mechanical press forging. However, dies must be carefully designed and fabricated in order to withstand the high impact; compressive prestressing of the die inserts by a shrink ring is a common practice. High-Energy-Rate Forging Equipment and Production Rates As described earlier, the three basic types of HERF machines are ram-and-inner-frame, two-ram, and controlled-energyflow (counterblow) (refer to Fig. 4 and related text). The cycle time for a HERF machine is 12 to 20 s per piece, or a production rate of 180 to 300 parts per hour. Therefore, HERF machines can make parts to close profiles at production rates often comparable to those of drop-hammer and hydraulic presses. Adaptation of automatic transfer equipment to high-energy-rate forging further increases the production rates to levels competitive with manually operated mechanical presses. The machines are readily adaptable to automatic loading and unloading equipment. However, high-production runs or multiple runs of similar parts are needed to justify the cost of automatic handling equipment. Dies

Closed dies and flash-and-gutter impression dies are used in HERF. The closed dies restrict the flow of metal and force it to fill the cavity completely; they are recommended because they require less material in the billet and permit closer dimensional control of the forging. Flash-and-gutter impression dies are generally used for thicker parts with more liberal dimensional tolerances. As in conventional hammer forging, the force of the ram should be completely expended in deforming the workpiece. Impact between the upper and lower tools is potentially destructive. It can be avoided by control of processing conditions that significantly influence metal plasticity (such as temperature, volume, and die temperature and lubrication) and in some cases by selective placement of a protective ring around the upper die. HERF Processing Like conventional forging, HERF is performed over a broad range of temperatures, depending on the specific part, the material, and the design requirements. Three categories of HERF are hot forging, cold forging, and warm forging. Hot Forging. Under the most favorable conditions, hot HERF is used to forge parts that cannot be forged with

conventional machines. Complex parts and components with thin sections have been produced; webs and ribs 3.18 mm (0.125 in.) thick and central ribs 4.76 mm (0.1875 in.) thick are technically feasible. However with pneumatic-hydraulic HERF machines, such results can often be obtained only at the expense of die life in view of their long dwell times. Cold HERF at high speeds improves die lubrication, which lowers the fictional forces, which in turn improves metal flow

and surface finish of the components. The process is practically adiabatic; therefore, with soft materials, such as aluminum and copper, some softening occurs. Forging forces and pressures are generally higher than those obtained at conventional speeds, although energy requirements may well be lower. Warm HERF, in comparison to hot HERF, is free of scale and therefore produces better surface quality, high precision, and improved tool life. In relation to cold HERF, the process significantly lowers tool loads, permitting a wider range of both component sizes and available materials to be forged without appreciable deterioration in component material properties.

Metals HERFed Metals best suited to HERF are those that withstand very high deformation rates without rupturing. High-energy-rate forging is particularly suited to alloys that require high forging temperatures and pressures, especially when thin webs or unusual design features are required. Low-carbon steels, refractory metals, and nickel alloys that have broad forging temperature ranges can be forged. Metals with low ductility under rapid deformation rates, such as magnesium and beryllium alloys, cannot be forged by high-velocity methods. Heating that is caused by rapid deformation, if excessive, may cause incipient melting and serious rupturing when forging to large reductions. The metals affected in this manner include high-carbon steels, high-strength aluminum alloys, and nickel-base, heat-resistant alloys. Increased temperatures during forging can cause -embrittlement in some titanium alloys.

Ring Rolling Ring rolling is used to manufacture seamless annular forgings that are accurately dimensioned and have circumferential grain flow. Ring rolling usually requires less input material than alternative forging methods, and it is applicable to production in any quantity. Operating Principles. In ring rolling (Fig. 24), a heated doughnut-shaped blank, preformed on a press or forging hammer, is placed over a mandrel of slightly smaller diameter than the hole in the blank. The roll gap between the mandrel (undriven) and a larger diameter driven main roll is progressively reduced. Friction between the main roll and the ring causes the ring to rotate, and the ring in turn rotates the bearing-mounted mandrel. As the radial cross section of the ring decreases, circumferential extrusion occurs in the direction of ring rotation, and the ring diameter grows. The work rolls can be plain, producing uniformly rectangular ring cross sections or may have grooves or flanges to produce contoured ring cross sections. Ring height is controlled either by main roll shape or by the use of axial rolls set diametrically across the ring from the mandrel and main roll pass.

Fig. 24 Operational principles of a horizontal ringrolling mill

Products and Applications. Annular components can be ring rolled from any forgeable material. The configuration can range from very flat washer-shaped rings to long sleeve-type rings. Typical materials include carbon and low-alloy steels, copper, brass, aluminum and titanium alloys, and high-strength nickel and cobalt-base alloys, which are very difficult to form. Applications for seamless rolled rings include antifriction bearing races, gear rims, slewing rings, railroad wheel bearings, commutator rings, rotating and nonrotating rings for jet engines and other aerospace applications, nuclear reactor components, bevel ring gears, flanges of all kinds (including weld-neck flanges), sheaves, wheels, valve bodies, food-processing dies, and chain master links. Sizes. About 90% of all rolled rings have outside diameters in the range from 240 to 980 mm (9.5 to 38.6 in.), heights (lengths) ranging from 70 to 210 mm (2.75 to 8.25 in.), and wall thicknesses between 16 and 48 mm (0.63 and 1.9 in.). A significant number of rings, however, are rolled outside the previously mentioned parameters, and it is not unusual to find outside diameters ranging from 75 mm to 8 m (3 in. to 26.25 ft), heights from 15 mm to 2 m (0.6 in. to 6.5 ft), and weights from 0.4 to 82,000 kg (0.9 to 181,000 lb).

Rotary Swaging of Bars and Tubes Rotary swaging is used to reduce the cross-sectional area or otherwise change the shape of bars, tubes, or wires by repeated radial blows with two or more dies. The work is elongated as the cross-sectional area is reduced. The workpiece (starting blank) is usually round, square, or otherwise symmetrical in cross section, although other forms, such as rectangles, can be swaged. Most swaged parts are round, the simplest being formed by reduction in diameter. However, swaging can also produce straight and compound tapers, contours on the inside diameter of tubing, and can change round to square or other shapes. Applicability. Swaging can reduce tubes up to 355 mm (14 in.) in initial diameter and bars up to 100 mm (4 in.) in

initial diameter. Hardness, tensile strength, and reduction in area of the work metal have the most significant effect on swageability. Type and homogeneity of microstructure also influence the ease of swaging and the degree to which a metal can be swaged. Work Metals. Of the plain carbon steels, those with a carbon content of 0.20% or less are the most swageable. These

grades can be reduced up to 70% in a cross-sectional area by swaging. As carbon content or alloy content is increased, swageability is decreased. Alloying elements such as manganese, nickel, chromium, and tungsten increase work metal strength and therefore decrease the ability of the metal to flow. Free-machining additives such as sulfur, lead, and phosphorus cause discontinuities in structure that result in splitting or crumbling of the work metal during swaging. Metal flow during rotary swaging is not confined to one direction. Metal also moves opposite to the direction feed. The

action of the metal moving against the direction of feed is termed "feedback." It results from slippage of the workpiece in the die taper when it is too steep. Unless resisted, the workpiece rotates as the dies close. The speed of rotation is that of the roller cage. If rotation is permitted, swaging occurs in only one position on the workpiece, causing ovaling, flash, and sticking of the workpiece in the die. Resistance to rotation is manual when the swager is hand fed; mechanical means are used with automatic feeds. Swaging Equipment. Rotary swaging machines are classified as standard rotary, stationary-spindle, creeping-spindle,

alternate-blow, and die-closing (Fig. 25). All these machines are equipped with dies that open and close rapidly to provide the impact action that shapes the workpiece. Swagers allow the work to be fed into the taper entrance of the swaging dies.

The amount of diameter reduction per pass is limited by the design of the entrance taper of the dies or the area reduction capability of the machine. The results are expressed in terms of diameter reduction or area reduction.

Fig. 25 Principle machine concepts for rotary swaging. (a) The standard rotary swager is a mechanical hammer that delivers blows (impact swaging) at high frequency, thus changing the shape of a workpiece by metal flow. This machine is used for straight reducing of stock diameter or for tapering round workpieces. (b) With stationary-spindle swagers, the spindle, dies, and work remain stationary while the head and roll rack rotate. These machines are used for swaging shapes other than round. (c) Creeping-spindle swaging employs the principles of both standard and stationary-spindle swaging. The spindle and dies are mounted on a shaft that rotates slowly inside the rapidly rotating roller cage, thus permitting more accurately controlled reciprocation of the dies. (d) Alternate-blow swaging is accomplished by recessing alternate rolls; when two opposing rollers hammer the dies, the rolls 90° away do not. (e) Die-closing swagers are essentially the same as standard rotary swagers. However, die-closing swagers feature a reciprocating wedge mechanism that forces closure of the taper back dies.

Radial Forging Radial forging is performed with four-hammer machines (Fig. 26). The technology of the four-hammer forging machine differs from that of all other hot-forming methods. Conventional presses and hammers, or even rolling mills, use only two tools per forming operation. In the radial forging machine, however, a workpiece is formed at the same time by four hammers arranged in one plane, with maximum forging forces per die of up to 30 MN (3400 tonf). The free spreading that occurs between the two contacting tools in all conventional forging methods is eliminated. A radial press contacts the circumference of the workpiece equally and puts the entire surface of the workpiece under compressive stresses. These compressive stresses prevent the formation of surface cracks during the forging process and improve existing defects.

Fig. 26 Cross section of four-hammer radial forging machine with mechanical drive. (a) Eccentric shaft. (b) Sliding block. (c) Connecting rod. (d) Adjustment housing. (e) Adjusting screw. (f) Hydraulic overload protection. (g) Hammer adjustment drive shafts

Radial forging is sometimes confused in the literature with rotary (orbital) forging. In the rotary forging process described in "Rotary Forging," the axis of the upper die is tilted at a slight angle with respect to the axis of the lower die, and one or both dies rotate. Current applications include bars with round, square, or rectangular cross section starting from ingots or blooms;

stepped solid shafts and axles for locomotives, railroad cars, and trucks; stepped hollow shafts for components in the automotive and aircraft industries; preforms for turbine shafts or for subsequent closed-die forging; thick-wall tubes forged over a water-cooled mandrel; necks and bottoms of steel bottles; and couplings and tool joints. Process advantages include high production rates (approximately four times greater rates for low-alloy steel products

than for hammer or press forging; high-alloy steel production is six times higher), low energy consumption, and close tolerances (machining allowances are approximately 33% of the usual allowances on conventional forged products). Equipment and Process. The four-hammer radial forging machine is basically a short-stroke mechanical press. The

stroke of the forging connecting rods is initiated through eccentric shafts. The eccentric shafts are supported in housings that allow adjustment of the stroke position of the four forging connecting rods. One or two electric motors drive the eccentric shafts through a drive gear, which simultaneously controls the synchronization of the four eccentric shafts. The forging connecting rods can be changed in their stroke position either in unison or in pairs so that round, square, or rectangular cross sections can be forged. Depending on its application, the part-handling system of the machine can be equipped with either one or two workpiece manipulators, which differ widely from conventional forging manipulators. In contrast to press or hammer forging, the workpiece axis in radial forging is always maintained on the forging machine centerline, regardless of the diameter. The manipulator moves only in the longitudinal direction. For exact guidance, the chuck head slides on a machine bed. During the forging of round cross sections, the chuck head rotates the workpiece in cycle with the forging hammers; that is, the rotary movement stops while the hammers are in contact with the workpiece. The rotary movement of the chuck-head spindle is synchronized with the hammer blows, eliminating twisting of the workpiece. The indexing positions of the chuck-head spindle required for forging squares, rectangles, or hexagons can be set automatically. The entire forging process, including loading and unloading, can be performed automatically by computer numerical control (CNC). In radial forging, temperature of the workpiece increases with the deformation rate and the forming resistance of the material. The higher the forming resistance, the higher the temperature increase at each pass. Therefore, the temperature loss of the workpiece (because of heat radiation) can be compensated for by preselecting the deformation rate, forming

the workpiece in temperature ranges with the highest material ductility. In practical terms, this means that all forming can be done in one heat from the ingot to finished bar steel, regardless of the alloy. Chamber furnaces, pit furnaces, and hearth-type furnaces can therefore be replaced by continuously operating furnaces. Equipment for mandrel forging is available in different designs for the hot and cold forging of tubular workpieces. Long tubes with cylindrical bores are forged over a short mandrel, while short tubes are forged over a long mandrel. During hot forging, the mandrel is water cooled while in contact with the workpiece. Tungsten carbide mandrels are often used in cold forging for improved mandrel life.

Rotary Forging Rotary forging, or orbital forging, is a two-die forging process that deforms only a small portion of the workpiece at a time in a continuous manner. Unfortunately, the term rotary forging is sometimes used to describe the process that is more commonly referred to as radial forging, causing some confusion in terminology. Figure 27 illustrates the differences between the two processes. As described in the section "Radial Forging," radial forging is a hot- or cold-forming process that uses two or more radially moving anvils or dies to produce solid or tubular components with constant or varying cross sections along their lengths.

Fig. 27 Differences between rotary and radial forging. (a) In rotary forging, the upper die, tilted with respect to the lower die, rotates around the workpiece. The tilt angle and shape of the upper die result in only a small area of contact (footprint) between the workpiece and the upper die at any given time. Because the footprint is typically only about one-fifth the workpiece surface area, rotary forging requires considerably less force than conventional forging. (b) In radial forging, the workpiece is fed between the dies, which are given a rapid periodic motion as the workpiece rotates. In this manner, the forging force acts on only a small portion of the workpiece at any one time.

In rotary forging (Fig. 27a), the axis of the upper die is tilted at a slight angle with respect to the axis of the lower die, causing the forging force to be applied to only a small area of the workpiece. As one die rotates relative to the other, the contact area between die and workpiece, termed the "footprint," continually progresses through the workpiece, gradually deforming it until a final shape is formed. The tilt angle between the two dies determines the amount of forging force applied to the workpiece. A larger tilt angle results in a smaller footprint; consequently, a smaller amount of force is required to complete the same amount of deformation as compared to a larger contact area. Tilt angles are commonly about 1 to 2°. The larger the tilt angle, however, the more difficult the machine design and maintenance problems are because the drive and bearing system for the tilted die is subjected to large lateral loads and is more difficult to maintain. In addition, a larger tilt angle causes greater frame deflection within the forge, making it difficult to maintain a consistently high level of precision. Process Advantages. The primary advantage of rotary forging is in the low axial force required to form a part. Because only a small area of the die is in contact with the workpiece at any given time, rotary forging requires as little as one-tenth the force required by conventional forging techniques. The smaller forging forces reduce machine and die deformation and die-workpiece friction. This low level of equipment wear makes rotary forging a precision production process that can be used to form intricate parts to a high degree of accuracy.

The average cycle time for a moderately complex part is 10 to 15 s, which is a relatively short time of deformation from preform to final part. A cycle time in the range of 10 to 15 s yields approximately 300 pieces per hour. The resulting piece is also virtually flash free. Therefore, rotary forging results in a much shorter operation from start to finish. Tooling costs for rotary forging are often lower than those for conventional forging. The smaller forging forces allow many parts to be cold forged that would conventionally require hot forging, resulting in decreased die wear and greater ease in handling parts after forging. Machines. Rotary forgers can be broadly classified into two groups. In rotating-die forgers, both dies rotate around their

own axis, but neither die rocks or precesses about the axis of the other die. In rocking-die, or orbital forgers, the upper die rocks across the face of the lower die in a variety of fashions. The most common form is where the upper die orbits in a circular pattern about the axis of the lower die. In this case, the upper die can also either rotate or remain stationary in relation to its own axis. Other examples of rocking-die motion include the rocking of the upper die across the workpiece in a straight, spiral, or planetary pattern. Applications. Rotary forging is generally considered to be a substitute for conventional drop-hammer or press forging. In addition, rotary forging produces parts that would otherwise have to be completely machined because of their shape or dimensions. Currently, approximately one-quarter to one-third of all parts that are either hammer or press forged could be formed on a rotary forge.

Parts made by rotary forging include gears, flanges, hubs, cams, rings, and tapered rollers, as well as thin disks and flat shapes. These parts are axially symmetric and are formed by using an orbital die motion. More complex parts can be forged through the use of such rocking-die motions as straight-line, planetary, and spiral. Straight-line die motion is most commonly used to produce asymmetric pieces, such as T-flanges. Rotary forging is especially effective in forging parts that have high diameter-to-thickness ratios. Thin disks and large flanges are ideally suited to this process because of the ability of rotary forging to produce a higher ratio of lateral deformation per given downward force than conventional forging. There is also very little friction between the dies. Therefore, the lateral movement of workpiece material in rotary forging is as much as 30% more than that in impact forging. Rotary forging is also used to produce intricate features on workpiece surfaces. Parts such as gears, hubs, and hexagonal shapes have traditionally been difficult to produce by conventional forging because die-workpiece friction made it difficult to fill tight spots properly on the dies. Work Materials. Any material, ferrous or nonferrous, that has adequate ductility and cold-forming qualities can be

rotary forged. These materials include carbon and alloy steels, stainless steels, brass, and aluminum alloys. In the past, cold-forged production parts were primarily steels with a Rockwell C hardness in the mid 30s or lower. Generally, harder materials should be annealed before forging or should be warm forged. Warm rotary forging is used for materials with Rockwell C hardness greater than the mid 30s or when an unusually large amount of lateral movement in the workpiece is required. Materials are heated to a point below their recrystallization temperature; for steels, this is generally in the range of 650 to 800 °C (1200 to 1470 °F). Because the working temperature is below the recrystallization temperature, the inherent structure and properties of the metal are preserved. Warm rotary forging increases forgeability, compared to cold rotary forging. However, some disadvantages are inherent in higher temperature forging. The work-hardening effects on the material that are associated with cold working are not as prominent, even though the working temperature is below the recrystallization temperature. In addition, as with any forging process, higher working temperatures result in increased die wear. Dies not only wear at a faster rate but also must be fabricated from more durable, more expensive materials.

Isothermal and Hot-Die Forging Hot-die and isothermal forging are special categories of forging processes in which the die temperatures are significantly higher than those used in conventional hot-forging processes. This has the advantage of reducing die chill, thereby producing near-net and/or net shape parts. Therefore, these processes are also referred to as near-net shape, forging processes. These techniques are primarily used for manufacturing airframe structures and jet-engine components made of titanium and nickel-base alloys, but they have also been used in steel transmission gears and other components.

Isothermal Forging In isothermal forging, the dies are maintained at the same temperature as the forging stock. This eliminates the die chill completely and maintains the stock at a constant temperature throughout the forging cycle. The process uses extremely slow strain rates, thus taking advantage of the strain-rate sensitivity of flow stress for certain alloys. Hot-Die Forging Hot-die forging is characterized by die temperatures higher than those in conventional forging, but lower than those in isothermal forging. Typical die temperatures in hot-die forging are 110 to 225 °C (200 to 400 °F) lower than the temperature of the stock. When compared with isothermal forging, lower die temperature allows wider selection of die materials, but the ability to produce very thin and complex geometries is compromised. Process Advantages The principal criterion for selecting these processes in production is the economic advantage offered because of reduced input material and/or reduced machining. Therefore, they are primarily used for expensive and difficult-to-machine alloys such as titanium and nickel-base alloys. Reduced Material Costs. These near-net shape processes allow the forging to be designed with smaller corner and fillet radii, a smaller draft angle, and a smaller forging envelope. These design features reduce the additional material incorporated to protect the finished part geometry and therefore reduce the weight of the forging considerably. For costly alloys, the reduction in input weight amounts to a significant cost savings. Figure 28 shows an example of this weight reduction for production of titanium alloy forgings.

Fig. 28 Comparison of raw material saved in the production of a Ti-6Al-4V structural forging that was hot-die forged versus a conventionally forged part (see cross-sectional areas and legend)

Reduced Machining. Because near-net shape forgings are produced close to end use weight and configuration, less

material removal is required during machining when compared with conventional forgings. In most cases, no machining is required, or only finish machining cuts are required to produce the final part. The elimination of complex machining can sometimes justify the use of these processes even for less expensive alloys, as in the case of steel gears forged with net tooth geometry. Uniformity of Product. The final product produced by isothermal and hot-die forging has more uniform properties

because of lower or nonexistent thermal gradients within the forging. Process Description In conventional forging operations, the dies are heated to 95 to 205 °C (200 to 400 °F) for hammer operations and to 95 to 425 °C (200 to 800 °F) for press operations. These temperatures are significantly lower than the 760 to 980 °C (1400 to

1800 °F) stock temperature for titanium and the 980 to 1205 °C (1800 to 2200 °F) stock temperature for nickel-base alloys and steels. In addition, these operations are performed at relatively high speeds, resulting in high strain rates. Typical strain rates range to 50 mm/mm per min (50 in./in. per min) for hydraulic presses, 700 mm/mm per min (700 in./in. per min) for screw presses, and exceed 12,000 mm/mm per min (12,000 in./in. per min) for hammers. For titanium and nickel-base alloys, the flow stress in general is highly sensitive to both temperature and strain rate. Therefore, conventional forging for these alloys is characterized by high resistance to deformation, high forging loads, multiple forging operations, and sometimes cracking. The isothermal forging and hot-die forging processes overcome some of these limitations by increasing the die temperature close to the temperature of the forging stock. The die temperatures are maintained at these high levels through continuous heating of the dies during the forge operation using induction heating, gas-fired infrared heating, resistance heating, and so on. The heating arrangement is combined with the press so that heat can be provided to the dies during the forging operation. Another heating arrangement uses gas-fired infrared heaters. Forging Alloys Alloys forged using these processes include titanium alloys, such as Ti-6A1-4V, Ti-6Al-2Sn-4Zr-2Mo, and Ti-10V-2Fe3Al, and superalloys, such as Alloy 100, Alloy 95, Alloy 718 (UNS07718), and WASPALOY (Precision Rings, Inc., Indianapolis, IN). In the case of superalloys such as Alloy 100, the working temperature range is so small that the isothermal and hot-die methods are the only feasible forging processes currently available. In addition, at specific temperatures and strain rates, Alloy 100 exhibits superplasticity. When forged within this temperature range and strain rate range, the alloy can be deformed to large strains at low loads and to fairly complex geometries. Forging Parameters The same factors that affect conventional forging processes also affect near-net shape processes. However, because of tighter forging designs and the requirements for strict uniformity and consistency, stringent controls on parameters such as forge temperature, strain rate, preform microstructure, forging pressure, and dwell time are all important in deciding the degree of dimensional sophistication and the resultant microstructure of the finished part. In general, lower strain rates and increased dwell time increase the potential degree of shape complexity and shape sophistication of the forging, but could influence microstructure due to exposure to high temperatures for long periods of time during and after deformation. In addition, very low strain rates cannot be used in hot-die forging because of the potential decrease in the stock temperature. Preform microstructure has a direct influence on the flow stress and superplasticity of the material, sometimes requiring extruded billet with fine-grain structure as the starting material. Some of the alloys that are forged achieve their final mechanical properties by thermomechanical processing; in this case, the selection of the forge temperature and the amount of deformation are controlled by property requirements. Die Materials Conventional hot-work die steels do not have adequate strength or resistance to creep and oxidation at near-net shape temperatures. Therefore, expensive nickel-base superalloys or molybdenum alloys (e.g., TZM) must be used. Dies are machined by electrical discharge machining. When TZM is used as a die material, a special atmospheric control with either acuum or inert gases is necessary because of the tendency of molybdenum alloys to oxidize severely at temperatures greater than 425 °C (800 °F).

Precision Forging Precision forging does not specify a distinct forging process but rather describes a philosophical approach to forging. The goal of this approach is to produce a net shape, or at least a near-net shape, in the as-forged condition. "Net" indicates that no subsequent machining or finishing of a forged surface is required. Thus, a net shape forging requires no further work on any of the forged surfaces, although secondary operations may be required to produce minor holes, threads, and other such details. A near-net shape forging can be either one in which some but not all of the surfaces are net or one in which the surfaces require only minimal machining or finishing. Precision forging is sometimes described as close-tolerance forging to emphasize the goal of achieving, solely through the forging operation, the dimensional and surface finish tolerances required in the finished part.

Usually, precision forging indicates a hot or warm closed-die forging process that has been upgraded to achieve greater process control. Traditionally, hot forging has not been regarded as a precision process. Due to difficulties in producing close tolerances and acceptable surface finish, hot forgings have traditionally been designed with a generous machining allowance sometimes 3 mm ( in.) or more. The motivation for precision forging is the elimination, or at least the reduction, of the costs associated with this machining allowance. These costs include not only the labor and indirect costs of the machining and finishing operations but also the cost of the excess raw material that is lost during machining (Fig. 28). The material cost savings may not be as obvious as the savings obtained by eliminating machining operations. Material costs are a significant fraction (often more than half) of the total cost of a forging. The weight of a traditional forging is often more than twice the weight of the finished part after machining. Given a geometry that is amenable to precision forging, tolerances of ±0.25 mm (±0.010 in.) typically can be held. In many cases, significantly better tolerances have been demonstrated. Forged surfaces have finishes of 3.20 m (125 in.) root mean square (rms) or better. Forging processes discussed under separate headings in this article that are likely to qualify as "precision forging"

include close-tolerance, closed-die forgings, warm high-energy-rate forging, radial forging, rotary forging, and hot-die and isothermal forging. Cold-forging processes, such as cold heading and cold extrusion (see the following sections) are traditionally precision processes. Similarly, powder forging processes are also classified as precision forging. Powder forging is described in the Section "Ferrous Powder Metallurgy Materials" in this Volume. Work metals commonly precision forged include carbon and alloy steels, stainless steels, copper alloys, aluminum

alloys, titanium alloys, and nickel-base superalloys. Figure 29 compares precision aluminum forging design characteristics with those of conventional aluminum closed-die forging. Precision aluminum forgings are produced with very thin ribs and webs; sharp corner and fillet radii; undercuts, backdraft, and/or contours; and frequently, multiple parting planes that may optimize grain flow characteristics. Similar improvements are possible in other precision forged metals.

Fig. 29 Cross sections of precision (a) and conventional (b) forgings

Cold Forging Cold forging is a very general term that covers processes such as coining/sizing, extrusion, and heading/upsetting. The most widely accepted definition of a cold-forging process is the forming or forging of a bulk material at room temperature. What should be emphasized is that in cold forging, no heating (of either the forging stock or the dies) is required for the actual forming operation. Coining

Coining is a closed-die forging operation, usually performed cold, in which all surfaces of the workpiece are confined or restrained, resulting in a well-defined imprint of the die on the workpiece. It is also a restriking operation, called sizing, that is used to sharpen or change a radius or profile. Preliminary Workpiece Preparation. Full contact between the blank and die surfaces, which is necessary for

coining, usually requires some preliminary meal redistribution by other processes, such as forging or extrusion, because only a small amount of metal redistribution can take place in the coining dies in single-station coining. In progressive-die operations, coining is preceded by other operations such as blanking, drawing, piercing, and bending. Coining is often the final operation in a progressive-die sequence, although blanking or trimming, or both, frequently follow coining. Development of Detail in the Workpiece. In coining dies, the prepared blank is loaded above the compressive

yield strength and is held in this condition during coining. Dwell time under load is important for the development of dimensions in sizing and embossing; it is also necessary for the reproduction of fine detail, as in engraving. Trimming. Flash that develops during coining and any hangers used to carry the blank through coining, especially in

progressive-die coining, must be trimmed from the piece. Applicability. In coining, the surface of the workpiece copies the surface detail in the dies with dimensional accuracy

that is seldom obtained by any other process. It is because of this that the process is used for coin minting. Decorative items, such as patterned tableware, medallions, and metal buttons are also produced by coining. When articles with a design and a polished surface are required, coining is the only practical production method to use. Also, coining is well suited to the manufacture of extremely small items, such as interlocking-fastener elements. Many automotive components are sized by coining. Sizing is usually done on semifinished products and provides significant savings in material and labor costs relative to machining. Workpiece Size. Practical limits on workpiece size are mainly imposed by available press capacities and properties of

the die material. For example, work metal with a compressive yield strength of 690 MPa (100 ksi) loaded in a press of 22 MN (2500 tonf) capacity can be coined in a maximum surface area of 0.032 m2 (50 in.2). As the yield strength increases, the area that can be coined using the same press decreases proportionately. However, an increase in strength of the workpiece must be limited so that plastic failure of the die does not occur. Coining Equipment. In coining, the workpiece is squeezed between the dies so that the entire surface area is

simultaneously loaded above the yield strength. To achieve metal deformation, the load determined from the compressive yield strength must be increased three to five times. Because of the area loading requirement and the great stress needed to ensure metal movement, press loading for coining is very severe, frequently approaching the capacity of the equipment used, with consequent danger of overloading. Some coining equipment, such as drop hammers, cannot be readily overloaded, but presses (especially mechanical presses) can be severely overloaded. This is most likely to happen if more than one blank is fed to the coining dies at a time. Such overloading can break the press and the dies, and it will certainly shorten the life of the dies. Coining can be performed in any type of press that has the required capacity. Drop hammers and knuckle-type and eccentric-driven mechanical presses are extensively used in coining. High-speed hydraulic presses also are well adapted for coining, especially when progressive dies are used. Large-capacity hydraulic presses are ideal for coining and sizing operations on large workpieces. Conversely, when it is feasible to coin large numbers of small, connected parts, as in a continuous strip of work metal, roll coining is the most economical method. Die Materials. Tool steels for dies for striking high-quality coins and medals are selected for machinability,

hardenability, distortion in hardening, hardness, wear resistance, and toughness. In dies used for decorative coining, materials that can be through hardened to produce a combination of good wear resistance, high hardness, and high toughness are preferred. A smooth, polished background surface on the die is required for striking proof-type coins and medals. Massive undissolved carbides or nonmetallic inclusions make it more difficult to obtain this smooth background. Work Materials. Steels that are most easily coined include carbon and alloy grades with carbon content up to

approximately 0.30%. Malleable iron castings are frequently sized by coining. Stainless steels of types 301, 302, 304,

305, 410, and 430 are preferred for coining. Free-machining type 303Se (selenium-bearing) is sometimes coined. Types 301, 302, and 430 are used in coining of spoons and forks. Type 305 coins well but is not widely used because of cost. Stainless steels are preferred in the soft annealed condition, in the hardness range of 75 to 85 HRB. Copper, silver, gold, and their alloys have excellent coinability and are widely used in coin and medallion manufacture. The pure metals are sufficiently soft and coinable to allow extreme deformation in coining, but even after such deformation they are too soft to wear well. As a consequence, important coining metals are prepared by alloying; thus, a relatively wide range of hardness is obtainable. Cold Heading Cold heading is a cold-forging process in which the force developed by one or more strokes (blows) of a heading tool is used to upset (displace) the metal in a portion of a wire or rod blank in order to form a section of different contour or, more commonly, of larger cross section than the original. The process is widely used to produce a variety of small- and medium-sized hardware items, such as bolts and rivets. Cold heading, however, is not limited to the cold deformation of the ends of a workpiece nor to conventional upsetting; metal displacement can be imposed at any point, or at several points, along the length of the workpiece and may incorporate extrusion in addition to upsetting. In cold heading, the cross-sectional area of the initial material is increased as the height of the workpiece is decreased. Advantages of the process over machining of the same parts from suitable bar stock include: • • •

Almost no waste material Increased tensile strength from cold working Controlled grain flow

Suitable Work Metals. Most cold heading is done on low-carbon steel wire with hardness ranging from Rockwell B

75 to 87. This is the type of material for which most machines are rated. Copper, aluminum, stainless steel, and some nickel alloys are also cold headed. Titanium, beryllium, magnesium, and refractory metals are less formable at room temperature and are likely to crack when cold headed; these metals are sometimes warm headed. Rating Formability. Metals and alloys are rated for cold heading on the basis of the length of stock, in terms of

diameter, that can be successfully upset. Equipped with flat-end punches, most cold-heading machines can upset to approximately two diameters of low-carbon steel wire per stroke. If the unsupported length is increased beyond approximately two diameters, the stock is likely to fold onto itself, as shown in Fig. 30. For more formable metals, such as copper and some copper alloys, the length of upset per stroke may be up to four diameters. Punches and dies can, however, be designed to increase the headable length of any work metal. For example, with a coning punch (Fig. 31) or a bulbing punch, it is possible to head as much as six diameters of low-carbon steel stock in two strokes.

Fig. 30 Typical folding effect with a flat-end punch when heading low-carbon steel wire with unsupported length of more than two diameters

Fig. 31 Use of a coning punch in the first blow of a two-blow heading operation, which enables a low-carbon steel workpiece to be upset to a length of up to six diameters in two strokes

Machines. Standard cold headers are classified according to whether the dies open and close to admit the work metal or

are solid, and according to the number of strokes (blows) the machine imparts to the workpiece during each cycle. The die in a single-stroke machine has one mating punch; in a double-stroke machine, the die has two punches. The two punches usually reciprocate so that each contacts the workpiece during a machine cycle. Tools used in cold heading consist principally of punches or hammers and dies. The dies can be made as one piece (solid

dies) or as two pieces (open dies), as shown in Fig. 32.

Fig. 32 Solid (one-piece) and open (two-piece) cold heading dies. (a) Solid die. (b) Open dies

Solid dies (known also as closed dies) consist of a cylinder of metal with a hole through the center (Fig. 32a). Solid dies can be made entirely from one material or may be made with the center portion surrounding the hole as an insert of a different material. Open dies (also called two-piece dies) consist of two blocks with matching grooves in their faces (Fig. 32b). When the grooves in the blocks are put together, they match to form a die hole as in a solid die. The die blocks have as many as eight grooves on various faces, so that as one wears, the block can be turned to make use of a new groove. Tool Materials. The shock loads imposed upon cold heading tools must be considered in selecting tool materials. For optimum tool life it is essential that both punches and dies have hard surfaces (preferably Rockwell C 60 or higher). However, with the exception of tools for cold heading of hard materials, the interior portions of the tools must be softer (Rockwell C 40 to 50, and sometimes as low as Rockwell C 35 for larger tools) or breakage is likely.

To meet these conditions, shallow-hardening tool steel such as W1 or W2 is used extensively for punches and open dies and for solid dies made without inserts. Lubrication. Although some of the more ductile metals can be successfully cold headed to moderate severity without a

lubricant, most metals to be cold headed are lubricated to prevent galling of the work metal or the dies, sticking in the dies, and excessive die wear. Lubricants used include lime coating, phosphate coating, stearates and oils, and plating with softer metals such as copper, tin, or cadmium. The ultimate in lubrication for steel to be cold headed is a coating of zinc phosphate with stearate soap--the same as is used for cold extrusion of steel. Cold Extrusion Cold extrusion is so called because the slug or preform enters the die at room temperature or at a temperature appreciably below the recrystallization temperature. Any subsequent rise in temperature, which may amount to several hundred degrees Fahrenheit, is caused by the thermomechanical effects of plastic deformation and friction. Cold extrusion involves backward or forward, or combined backward-and-forward, displacement of metal by plastic flow under steady, though not uniform, pressure. Backward displacement from a closed die is in the direction opposite to punch travel, as shown in Fig. 33(a). Workpieces are often cup-shaped and have wall thickness equal to the clearance between the punch

and die. In forward extrusion, the work metal is forced in the direction of the punch travel, as shown in Fig. 33(b). Sometimes these two basic methods of extrusion are combined so that some of the work metal flows backward and some forward, as shown in Fig. 33(c).

Fig. 33 Displacement of metal in cold extrusion. (a) Backward. (b) Forward. (c) Combined backward and forward

Metals Cold Extruded. Aluminum and aluminum alloys, copper and copper alloys, low-carbon and medium-carbon steels, modified carbon steels, low-alloy steels, and stainless steels are the metals most commonly cold extruded. This listing is in the order of decreasing extrudability. Extrusion ratio R is determined by dividing the original area undergoing deformation by the final deformed area of the

workpiece:

Because volume remains constant during extrusion, the extrusion ratio can also be estimated by increase in length. An extrusion ratio of 4 to 1 indicates that the length has increased by approximately a factor of four. The metal being extruded has a large effect on the maximum ratio that is practical. Some typical approximate maximum extrusion ratios are 40 for aluminum alloy 1100, 5 for 1018 steel, and 3.5 for type 305 stainless steel and similar austenitic grades. Extrusion pressure increases with extrusion ratio. Figure 34 shows that extrusion ratio has a larger effect on ram pressure in the forward extrusion of carbon steel than either carbon content or type of annealing treatment. Figure 35 illustrates the effect of tensile strength on extrudability in terms of ram pressure for both the backward and forward extrusion of lowcarbon and medium-carbon steels of the 1000, 1100, and 1500 series at different extrusion ratios.

Fig. 34 Effect of carbon content, type of annealing treatment, and extrusion ratio on maximum ram pressure in forward extrusion of the carbon steel part shown from the preformed slug shown

Fig. 35 Effect of tensile strength of steel being extruded on ram pressure required for backward and forward extrusion at different ratios

Presses and Headers. Hydraulic presses, mechanical presses, special knuckle-joint presses for cold extrusion, special cold forging machines, and cold heading machines are employed for cold extrusion. Most presses used for cold extrusion are essentially the same as those used for sheet metal forming.

Most cold extrusion operations are performed on mechanical presses or cold heading machines. Of the two, mechanical presses are used more often because of their adaptability to other types of operations. Mechanical presses are generally less costly and are capable of higher speeds than are hydraulic presses of similar capacity. The ram pressure that must be borne during the stroke is a function of the workpiece strength (as affected by composition, state of cold work, anneal, etc.) and the extrusion ratio, as shown in Fig. 34 and 35. Tooling. The components of a typical tool assembly used for backward extrusion of steel parts are identified in Fig. 36.

There is considerable variation in tooling practice and in the design details of tool-assembly components.

Fig. 36 Nomenclature of tools comprising a typical setup for backward extrusion

Tool Materials. Compressive strength of the punch and tensile strength of the die are important considerations when

selecting material for cold extrusion tools. Because the die is invariably prestressed in compression by the pressure of the inner and outer shrink rings, the principal requirement for a satisfactory die is a combination of tensile yield strength and prestressing that will prevent failure. Punches must have enough compressive strength to resist upsetting without being hazardously brittle. Thus, almost without exception, and particularly for extruding steel, the primary tools in contact with the workpiece must be made of steels that will harden through the section in the sizes involved. (This is notably different from cold heading tools, for which a hard case and soft core are usually desired.) Among the relatively few exceptions are small dies made of a water-hardening tool steel and bore quenched. As the bore hardens, the remainder of the die cools and shrinks, placing the bore in compression. The degree of strength required for the tools is influenced by workpiece shape, composition and hardness of the metal being extruded, and production requirements. Preparation of Slugs. Despite the loss of metal, sawing and cutting off in a machine, such as an automatic bar

machine, are widely used methods of producing slugs. The advantages of these methods include dimensional accuracy, freedom from distortion, and minimal work hardening. Shearing is an economical means of producing slugs. Variation in the sizes of the slugs is a major disadvantage of shearing. If slugs are allowed to vary in size, die design must allow for the escape of excess metal in the form of flash. An alternative to die adjustment in some applications is to compensate for the distortion and other discrepancies in sheared slugs by coining the slugs to desired dimensions. Lubricants for Steel. In most instances, the starting metal surface is given a conversion coating such as zinc phosphate

to facilitate lubrication. A soap lubricant gives best results. Slugs are immersed in a dilute (45 to 120 kg/m3, or 16 oz/gal) soap solution at 60 to 90 °C (145 to 190 °F) for three to five minutes. Some soaps are formulated to react chemically with a zinc phosphate coating, resulting in a layer of water-insoluble metal soap (zinc stearate) on the surfaces of the slugs. This coating has a high degree of lubricity and maintains a film between the work metal and tools at the high pressures and temperatures developed during extrusion. Other soap lubricants, such as high-titer sodium tallow soaps, with or without filler additives, can be used effectively for mild extrusion of steel. This type of lubricant is absorbed by a phosphate coating, rather than reacting with it. Although the lubricant obtained by reaction of soap and zinc phosphate is best for extruding steel, its use demands precautions. If soap builds up in the dies, workpieces will not completely fill out. Best practice is to vent all dies so that the soap can escape and also to keep a coating of mineral seal oil (applied as an air-oil mist) on the dies to prevent adherence of the soap. When steel extrusions are produced directly from coiled wire (similar to cold heading), the usual practice is to coat the coils with zinc phosphate. This practice, however, has one deficiency; because only the outside diameter of the work metal is coated, the sheared ends are uncoated at the time of extrusion. This deficiency is partly compensated for by constantly flooding the work with sulfochlorinated oil.

Lubricants for Aluminum. Aluminum and aluminum alloys can be successfully extruded with lubricants such as

high-viscosity oil, grease, wax, tallow, and sodium-tallow soap. Zinc stearate, applied by dry tumbling, is an excellent lubricant for extruding aluminum. The lubricant should be applied to clean metal surfaces, free from foreign oil, grease, and dirt. Preliminary etching of the surfaces increases the effectiveness of the lubricant. For the most difficult aluminum extrusions (less extrudable alloys or greater severity, or both), the slugs should be given a phosphate-treatment followed by application of a soap that reacts with the surface to form a lubricating layer similar to that formed when extruding steel. Impact extrusion, often simply called impacting, is similar to backward, forward, and combination extrusion except

that faster speeds, shorter strokes, and shallower dies are employed. Cold impacting is used extensively for the easy extrusion of nonferrous metals having low melting points and good ductility, such as lead, tin, zinc, aluminum, copper, and alloys of these metals.

Hot Extrusion Hot extrusion involves pushing a heated billet of metal through a die. The temperature at which extrusion is performed depends on the material being extruded (Table 3). The extruded product can be hollow or solid, and the cross section can vary from a simple round to a complicated shape. Direct (forward) extrusion, wherein the metal is forced under pressure through a die opening of the desired cross-sectional area and shape, is most widely employed. The die is located in the end of the cylinder opposite the ram. In the less-used indirect (backward) extrusion process, the die is mounted on a hollow ram and is pushed through the metal instead of the metal being pushed through the die. The principal differences between direct and indirect extrusion are illustrated in Fig. 33.

Table 3 Typical billet temperatures for hot extrusion Material Lead alloys Magnesium alloys Aluminum alloys Copper alloys Titanium alloys Nickel alloys

Billet temperature °C °F 90-260 200-500 340-430 650-800 340-510 650-950 650-1100 1200-2000 870-1040 1600-1900 1100-1260 2000-2300

Process Variations The three basic types of hot extrusion are nonlubricated, lubricated, and hydrostatic (Fig. 37).

Fig. 37 Schematics of the (a) nonlubricated, (b) lubricated, and (c) hydrostatic extrusion processes

Nonlubricated Hot Extrusion. As the name implies, this extrusion method uses no lubrication on the billet,

container, and die, and it can produce very complex sections, with mirror surface finishes and close dimensional tolerances. Generally, aluminum alloys are extruded without lubrication. In lubricated hot extrusion, a suitable lubricant (usually ground or powdered glass or grease) is placed between the

extruded billet and the die. The choice between grease and glass lubricants is based mainly on extrusion temperature. Below 1000 °C (1830 °F), grease lubricants are used; above this temperature glass is employed. Steels, titanium alloys, nickel alloys, and copper alloys require a lubricant during extrusion. In hydrostatic extrusion, a fluid film present between the billet and die exerts pressure on the deforming billet. The

hydrostatic extrusion process is primarily used when conventional lubrication is inadequate--for example, in the extrusion of brittle alloys (including beryllium and TZM molybdenum), composites, or clad materials. For all practical purposes, hydrostatic extrusion can be considered an extension of the lubricated hot extrusion process. Presses and Tooling for Hot Extrusion Horizontal and vertical presses are used for hot extrusion. Horizontal presses are the most common (Fig. 38). Most modern extrusion presses are driven hydraulically, but mechanical drives are used in some applications, such as the production of small tubes. Two basic types of hydraulic drives are available: direct and accumulator. In the past, accumulator presses were the most widely used, but today direct-drive presses are used more extensively.

Fig. 38 Schematic of a horizontal extrusion press showing a hydraulically powered ram forcing the heated billet through the die

The container, which receives the hot billet to be extruded, is a heated cylinder that is almost always fitted with a liner.

The liner must resist the abrasive action of the billet during extrusion and should maintain relatively high hardness at elevated temperatures. The container and liner should be made of materials with high fracture toughness and good resistance to low-cycle fatigue.

The ram, also referred to as the stem, operates within the liner and transmits pressure from the press cylinder to the billet. The ram must sustain high cyclic compressive loading. The material used for the ram should have good resistance to upsetting, work hardening, thermal shock, and rapidly applied stress. The dummy block is a block of steel that is inserted between the ram and the billet to absorb the heat and erosion that

otherwise would be imposed directly on the ram. The dummy block should resist indentation by the billet at temperatures approaching the billet temperature. The die or die assembly is the area through which the billet is pushed to form the extruded bar or shape. A die

assembly typically consists of the following component parts (see Fig. 39): •

A die, which is usually a circular steel block with a cut pattern of the transverse section of the shape to

• • • •

be produced A die ring (die holder), which is a steel ring located in front of the container that contains the die and the backer A die backer, which is a circular steel block placed behind an extrusion die for support. The hole in the backer is slightly larger than the hole in the die to allow for clearance of the extrusion. One or more bolsters, which are circular steel blocks used adjacent to the backer to reinforce the die and backer against billet pressure A tool carrier (die slide or housing)

The die itself must have high toughness combined with resistance to wear and softening at elevated temperatures. The other components of the die assembly should be high in both strength and toughness.

Fig. 39 Typical extrusion die assembly, showing relative positions of components in a tool carrier

The mandrel is a rod used to produce the cavity in a hollow shape while it is being extruded. Mandrels should be high

in hot hardness, abrasion resistance, fracture toughness, and yield strength. Press Operation. With the ram retracted, a hot billet or slug is placed in the container. A dummy block is inserted

between the ram and billet; then the hot billet is pushed into the container liner and advanced under high pressure against the die. The metal is squeezed through the die opening, assuming the desired shape, and is severed from the remaining stub by sawing or shearing.

Selected References • • • • • •

T. Altan et al., Ed., Forging Equipment, Materials, and Practices, Battelle-Columbus Laboratories, Metalworking Division, 1973 T.G. Byrer, Ed., Forging Handbook, Forging Industry Association and American Society for Metals, 1984 D. Lange, Ed., Handbook of Metal Forming, McGraw-Hill, 1985 Forging Processes, An Internet publication with executive summary, Forging Institute of America, 1997 Hot Forging, Tool and Manufacturing Engineers' Handbook, Vol 2, Forming, 4th ed., C. Wick, J.T. Benedict, and R.F. Veilleux, Ed., Society of Manufacturing Engineers, 1984 Open Die Forging Manual, 3rd ed., Forging Institute of America, 1992

Powder Metallurgy Erhard Klar, Consultant

Introduction POWDER METALLURGY (P/M) is a small but important branch of metallurgy that comprises the manufacture of metal powders and articles from powders through forming and sintering. In its most basic and widely used form, it consists of pressing a powder to the desired shape, followed by heating at an elevated temperature below its melting point. The beginning of modern P/M is attributed to Wollaston (Ref 1) who, early in the 19th century, described a press-sinter forging technique for making fully dense platinum, a metal which, at that time, could not be melted because of its high melting point. Early in the 20th century, high melting point metals like tungsten and molybdenum were formed by P/M processing into articles for the electrical industry. Powder metallurgy processing was also used for the manufacture of composite electrical contacts. Cemented carbides and porous bronze bearings followed in the 1920s, friction materials in the 1930s, and several refractory metals and so-called structural parts in the 1940s. The latter application evolved parallel to the growth of the automotive industry, and, to the present day, overall use of powder metallurgy in fully industrialized countries is strongly dependent on the automotive industry (Fig. 1).

Fig. 1 Powder metallurgy parts markets for North America, 1995. Source: Metal Powder Industries Federation

In the 1950s and 1960s the structural parts segment of the P/M industry expanded toward higher and full density processes and products. This led to increasing competition of the P/M industry with wrought metals. Examples of this evolution include powder forged steels, hot isostatically pressed tool steels, nickel-base superalloys, and high specific stiffness aluminum aircraft alloys Although early uses were based on the ability of P/M to form articles of high melting point metals without melting and, later, to produce unique structures such as porous oil-impregnated bearings and composite materials, the success of the structural parts segment of P/M is largely based on economic advantages. These include energy efficient, environmentally acceptable, and nearly scrap-free mass production of parts by pressing and sintering, often without any subsequent machining or other secondary treatments. Powder metallurgy is a dynamic technology. Advances in powder making, new processing equipment, and new P/M processes continue to emerge. Over the years, many variants of the basic compaction and sintering process have been developed. In addition to new and stronger alloys, the high and full density processes (i.e., warm compaction, hot isostatic pressing, powder forging, powder injection molding, powder rolling, and powder extrusion) combined with excellent control of microstructure and the innate capability of P/M to produce composite materials, allow the manufacture of conventional and unique materials possessing a wide property spectrum of the highest quality. In spite of the many attractive attributes of P/M, there are limitations The basic and economic press-and-sinter technique, employing mechanical and hydraulic presses for the compaction of the powders, has shape and size limitations. Because

of the generally higher cost of powders in comparison to ingots and the high cost of tooling, presses, and sintering furnaces, the manufacture of large part numbers, at least 1,000 to 10,000, is usually essential if competition with alternate manufacturing processes, such as machining, die and investment casting, die forging, fine blanking, and stamping, is to be successful. This explains the preferred use of P/M in industries requiring large part numbers, especially the automotive industry. Manufacturing processes ("freeform powder molding") that allow for the production of small lot sizes of P/M components without resorting to expensive hand tooling are under development (Ref 2). Figure 2 shows total metal powder shipments of iron, copper and copper alloys, and stainless steel powders in North America back to their initial uses. The high initial growth rate of iron powders slowed down to a more sustainable annual rate of approximately 3 % around 1970, a rate only moderately higher than the U.S. gross domestic product. This is related in part to the still increasing usage of P/M parts in the automobile. The compound annual growth rate of stainless steel powders and parts is still around 5%. This is attributed to improvements in the corrosion resistance of sintered stainless steels and their uses in more demanding applications such as in antilock brake system (ABS) sensor rings and automobile exhaust system components. The growth rate of copper powders, because their consumption was recorded in the 1940s and 1950s, exhibits a stagnant consumption over the past 50+ years. This is attributed largely to the relatively high cost and price volatility of copper and its partial or full substitution with less expensive materials such as iron and plastics.

Fig. 2 Powder production in North America. Source: Metal Powder Industries Federation

In the following, some basic P/M terms are briefly explained, and after a discussion of powder properties, an overview of general and individual powder production processes is presented. Consolidation of powders by pressing and sintering as well as high density methods are treated similarly. Emphasized are distinguishing features of powders, their manufacturing processes, compacting processes, and consolidated part properties. This information forms a basis for selecting the optimum P/M approach in the design of a product. Actual properties of P/M parts are found in the Sections dealing with the individual alloy product classes in this Handbook. For more details, refer to Powder Metal Technologies and Applications, Volume 7, ASM Handbook, 1998; to general textbooks on P/M (Ref 3 and 4); and to the Selected References listed at the conclusion of this Section.

References

1. W.H. Wollaston, Phil. Trans. Roy. Soc., Vol 119, 1828, p 1-8 2. S.J. Rock, C.R. Gilman, and W.Z. Misiolek, Freeform Powder Molding: From CAD Model to Part without Tooling, Int. J. Powder Metall., Vol 33 (No. 6), 1997, p 37-44 3. F.V. Lenel, Powder Metallurgy--Principles and Applications, Metal Powder Industries Federation, 1980 4. R.M. German, Powder Metallurgy Science, 2nd ed., Metal Powder Industries Federation, 1994

P/M Definitions Definitions of key powder metallurgy terms, which are used in the following sections, are given here. Additional terms related to P/M technology can be found in the "Glossary of Metallurgical and Metalworking Terms" in this Handbook. •

•

•

activated sintering •

A sintering process in which the rate of sintering is increased, for example by addition of a substance to the powder

apparent density •

The weight of a unit volume of powder. It is related to particle shape; the more irregular the shape of a powder particle, the lower the apparent density.

cold isostatic pressing •

The densification of a material under isostatic pressure conditions at room temperature using a flexible mold and a high pressure hydrostatic pressure in a hydraulic chamber

•

compressibility

•

cross contamination

• •

A measure of the ability of a powder to densify under pressure Contamination of a material with material of a different (chemical) composition as a result of the (sequential) manufacture of different materials using the same processing equipment

•

dimensional change

•

double-action pressing

•

• •

•

• •

•

• •

• •

The shrinkage or growth of a part as a result of sintering Method by which a powder is pressed in a die between two punches moving from opposite directions into the die cavity

flow rate •

The time required for a powder sample of standard weight to flow through an orifice in a standard instrument according to a specified procedure

green part •

The pressed part

green strength •

A measure of the ability of a green (i.e., pressed) compact to maintain size and shape during handling prior to sintering

hot isostatic pressing •

A process combining temperature and high pressure gas to densify a material into a net-shape component using a pressure-tight outer envelope

metal injecting molding •

A process in which a mixture of a metal powder and plastic binder is injection molded

powder forging •

Hot densification by forging of an unsintered, presintered, or sintered preform made from powder (also known as P/M forging or known as P/M hot forming)

powder metallurgy •

The branch of metallurgy related to the manufacture of metal powders and articles fabricated from powders by the application of forming and sintering processes

preform •

A compact blank intended to be subjected to deformation and densification involving change of shape.

premix •

A lubricated powder mixture ready for compaction

•

prior particle boundaries •

Precipitates present on the surfaces of powder particles, or precipitates forming on the surfaces during processing. These boundaries are usually visible by metallography and responsible for low ductility and deterioration of other properties of parts made from such powders.

•

punch

•

single-action pressing

• •

Part of a die or compacting tool set that is used to transmit pressure to the powder in the die cavity Method by which a powder is pressed in a stationary die between one moving and one fixed punch

•

sintering

•

withdrawal process

• •

The bonding of neighboring particles in a mass of powder (as in a compact) by heating Operation by which a die descends over a fixed lower punch to free the compact

Powder Characteristics For a powder to be suitable to P/M processing, it must possess powder properties that are tailored to the particular compacting and sintering process used, and it must provide the end or performance properties required in the finished P/M part. It must also be cost effective and, increasingly, powder specifications are becoming stricter and narrower in the interest of improving quality and consistency of P/M parts. The most significant fundamental powder characteristics include particle size, particle size distribution, particle shape, and purity of a powder. Engineering-type powder properties such as apparent density, flow rate, green strength, and compressibility depend on several of the fundamental powder properties in a more complex way. Quantitative relationships between the two types of properties are still of an empirical nature. Particle Size. Powders suitable for conventional P/M processing are typically called -80 mesh powders, that is, powders

with an upper particle size of approximately 177 m. This upper particle size limit arises from the need of porous sintered parts to have a surface texture that is pleasing to the eye and to assure adequate mechanical properties. Also, many powders are mixtures of several components that alloy with each other during sintering by solid-state diffusion. In the presence of large particles, the sintering times of such systems would be unacceptably long. The lower end of the particle size spectrum of typical P/M powders is approximately 1 m. Most P/M powders have -325 mesh (0.6 T) produce large intraparticle pores and small specific surface area powders with good compressibility.

Fig. 17 Sponge iron particles. (a) Cross section. (b) Scanning electron micrograph. Both 180×. Source: Ref 5

The most important commercial process for oxide-reduced iron powder, the Höganäs process, is based on the direct reduction of a high-purity magnetite ore. Beneficiation and magnetic separation reduce the level of silicon dioxide to approximately 0.2%. Because of this, the powder is mainly used in low and medium density P/M applications where the deleterious effects of oxide inclusions are overshadowed by the effect of pores. Oxide reduced powders of high purity made from high purity oxides include iron, copper, tungsten, and molybdenum. Oxide-reduced powders, because of their superior green strength characteristics, are often preferred in applications where green strength is important (i.e., friction parts) and where compressibility is of lesser importance. Sponge powders, as a result of their porous structure and larger surface area, shrink more than atomized powders during sintering, and they are sometimes added to atomized powders to modify and/or adjust the shrinkage characteristics of a powder. Precipitation from Solution. Production of metal powders by hydrometallurgical processing is based on leaching an ore or ore concentrate, followed by precipitating the metal from the leach solution by electrolysis, cementation, or chemical reduction. In the Sherritt-Gordon process, copper, nickel, and cobalt are separated and precipitated from salt solutions by reduction with hydrogen. Hydrogen pressure, solution pH, and solution temperature must be controlled for successful reduction and differ for different metals. Through the use of additives and control of nucleation, powders with a wide range of particle sizes, particle density, and particle shape may be produced.

Through co-precipitation or successive precipitation of different metals, alloyed and composite powders can be produced. Thermal Decomposition. Of the group of thermally decomposed powders, those produced by thermal decomposition

of carbonyls are the most important. Both iron and nickel are produced by decomposition of their carbonyls. Carbonyls are obtained by passing carbon monoxide over sponge metal at specific temperatures and pressures. Powder is produced by boiling the carbonyls in heated vessels at atmospheric pressure. The powder can be milled and annealed in hydrogen. The chemical purity of the powder can be high (over 99.5%) with the principal impurities being carbon, nitrogen, and oxygen. Particle size can be controlled very closely. Iron carbonyl powder is usually spherical in shape and less than 10 m in diameter. Nickel carbonyl powder is usually available as a fine spiky, a fine filamentary, and fine or coarse, high density powder. Electrochemical Processes. Copper, iron, manganese, and silver are the main metals produced commercially by

electrodeposition. Depending on the electrochemical polarization characteristics of a metal, it can be deposited as a

loosely adhering, powdery deposit on the cathode, or as a smooth, dense, and brittle deposit, which subsequently is milled into powder. In metals where the deposition potential varies little with current density, such as copper, silver, zinc, and cadmium, powdery deposits form. Iron, nickel, manganese, and cobalt require a large change in cathode potential for a small change in current density. These deposits are dense. Their brittleness can be controlled to some extent by proper adjustment of the electrolytic cell conditions. The singularly outstanding quality of electrolytic powders is high purity. Before the advent of atomized powders, electrolytic iron and copper powders were widely used in the manufacture of electrical and magnetic P/M parts and also for high density parts because the high purity of the metals provided superior electrical, magnetic, or high compressibility characteristics. The relatively high purity of atomized powders has bridged this gap to a considerable extent. In addition, the high processing cost of electrolytic powders, in part related to environmental factors, has widened the cost differential between electrolytic and other types of metal powders. Particle shape and size of loosely deposited electrolytic powders depends on the electrolytic cell conditions and can be additionally controlled through the use of addition agents to the electrolyte. Subsequent annealing can be used to stabilize the powders against oxidation and to broaden the range of powder characteristics. Commercial electrolytic copper powders have particle shapes from dendritic to equiaxed irregular and apparent densities from less than 1 g/cm3 to over 3 g/cm3. The particle shape of electrolytic iron powder, as a result of milling, is irregular and flaky, with fairly rough surfaces. Table 1 compares chemical and physical properties of typical compacting-grade iron powders made by electrolysis, oxide reduction, and atomization.

Table 1 Chemical and physical properties of compacting-grade iron powder Constituent or property Chemical analysis, % Total iron Insolubles Carbon Hydrogen loss Manganese Sulfur Phosphorus Physical properties Apparent density, g/cm3 Flow rate, s/50 g Sieve analysis, % +100 -100 + 150 -150 + 200 -200 + 325 -325 Compacting properties(a) Green density, g/cm3 Green strength, MPa (psi)

Electrolytic

Reduced

Atomized

99.61 0.02 0.02 0.29 0.002 0.01 0.002

98.80 0.10 0.04 0.30 ... 0.007 0.010

99.15 0.17 0.015 0.16 0.20 0.015 0.01

2.31 38.2

2.40 30.0

3.00 24.5

0.5 13.1 22.6 29.4 34.4

0.1 7.0 22.0 17.0 27.7

2.0 17.0 28.0 22.0 22.0

6.72 19.7 (2800)

6.51 19.0 (2700)

6.72 8.4 (1200)

Source: Ref 5

(a)

At 414 MPa (30 tsi) with 1% zinc stearate.

Reference cited in this section

5. Powder Metallurgy, Vol 7, Metals Handbook, 9th ed., American Society for Metals, 1984 Powder Treatments Most powders receive one or more treatments prior to compaction. These treatments are tailored to the use of a powder and may include particle size distribution adjustment through screening and/or air classifying, annealing for the purpose

of improving compacting properties, lubricant addition for compacting grade powders, mixing of different powders for premixes, and blending of powders and powder mixes to homogenize their various components. These treatments are usually performed by the powder producer. The quality of these treatments can greatly affect the uniformity and consistency of sintered part properties. With increasing emphasis on zero-defect manufacture, the treatments have received more attention in recent years. Classifying/Screening. Many powder production processes yield relatively broad particle size distributions, and

because of the many manufacturing variables, the distributions and average particle sizes may exhibit marked lot-to-lot variations, which contribute to the variation of important powder and sintered part properties. Classifying and screening are used to render the particle size distributions of powders more uniform with well-defined, upper particle size limits. Powder producers often manufacture series of powders that differ only in particle size distribution. Such powders exhibit "graded" differences in dimensional change during sintering. For filter manufacture, classifying and screening is used to generate narrowly sized powder fractions for controlled pore size in filters and flow restrictors. Powder Mixtures and Segregation of Powders. Most P/M metal powders are multicomponent systems and,

therefore, are subject to segregation. Segregation is even possible in a one-component metal powder if, for instance, coarse and fine powder particles "demix" as a result of vibration. The opportunity for powder segregation exists in processes such as shipping and filling of hoppers and compaction dies, where individual components, on account of differences in particle size, shape, density, surface roughness, and other properties, exhibit different flow rates. The most widely used P/M compacting grade powders are mixtures of iron with graphite, copper, nickel, and/or molybdenum. The preferred use of powder mixtures rather than of prealloyed powders is related to several factors. The most important factor is that elemental powder mixtures generally possess significantly higher compressibilities than their prealloyed counterparts. Secondly, powder mixtures are usually less expensive than prealloyed powders. And thirdly, powder mixtures more often can be formulated to provide transient liquid phases during sintering, which can reduce sintering times and improve mechanical properties. In most powder mixtures, the base powder typically comprises 90% or more of the powder mixture. As the other components are present in only small amounts, and their alloying effects are powerful, it is very important that they are uniformly distributed and that the homogeneity of the powder is preserved during shipping of the powders and during handling at the parts producer's site until compaction is completed. Without such precautions, the properties of the sintered parts are not optimal and the standard deviation, that is, the scatter of the properties, can be quite large. Stabilization of Multicomponent Powder Mixtures. Because of the wide use of powder mixtures and their

sensitivity toward demixing, much work has been done toward the stabilization of powder mixtures. Stabilizers. A powder mixture is optimally mixed if its components approach a random (statistical) distribution that is free of agglomeration (Fig. 18). The quality of mixing can be measured by the number of particle contacts (in green compacts) between identical or different powder components as illustrated in Fig. 19 for iron-copper mixtures, or by the chemical analysis of appropriate samples taken from the powder mixture.

Fig. 18 Schematic representation of particle patterns in a powder mixture. (a) Ordered. (b) Agglomerated. (c)

Statistical (random) distribution. (d) Demixed or segregated. Source: Ref 6

Fig. 19 Effect of stabilizer on iron-iron contact formation in binary iron-copper system. Source: Ref 6

Blenders and mixers that rely mainly on gravity (tumblers) are suitable for powders that mix readily. More intense mixing is accomplished with low-shear, agitated-type blenders that use ribbons, slow-speed paddles, screw-type augers, or other means of motion. Figure 20 illustrates how spherical powders mix quite readily, but also are subject to demixing or overblending. Consequently, mixing should be stopped once a near-random distribution has been achieved. The variability coefficient in Fig. 20 represents the standard deviation of the measured degree of mixing divided by the average value of the measured property. The quality of the mixture improves with decreasing variability coefficient.

Fig. 20 Effect of particle size and shape of components of 90%Fe-10%Cu mixtures on degree of blending. Quality of blending improves as variability coefficient decreases. Particle size and shape for components: (a) Cu, 200 to 300 m; Fe, 10,000 $100

Powder forging Steel

Fig. 26 Variation of sintered density and compact properties with the degree of sintering as represented by the sintering temperature. Source: Ref 4

Conventional Pressing and Sintering Conventional compaction and sintering is the most widely employed technique for producing P/M parts. Figure 27 shows the processing steps.

Fig. 27 General steps in the P/M process. Source: Ref 7

Compaction of Powders. As a metal powder deforms during compaction, its hardness increases (work hardening), and its rate of densification decreases with increasing compaction pressure, as shown in Fig. 28. Cold welding and interlocking of particles provides compact green strength. Densities above 90% of theoretical are difficult to attain for many metal powders because of the increasing work hardening. High compressibility powders are, therefore, preferred in systems that require high compacting pressures, such as iron, stainless steel, and tool steel powders. Typical and maximum compaction pressures employed in the industry for these powders are in the range of 550 to 827 MPa (40 to 60 tsi).

Fig. 28 Key steps during compaction and effect of compacting pressure on green density. Source: Ref 4

Density increases up to approximately 95% of theoretical can be obtained by repressing after sintering. The attainment of a high density by sintering at a high temperature and/or for a long period of time usually requires repressing of the sintered part in order to restore acceptable dimensional tolerances. In the most common compaction technique, double action compaction pressure is applied along one vertical axis, from both top and bottom, as shown in Fig. 29. The punches provide compression forces while the die provides lateral support to the powders. To press parts of identical weight, it is important that the apparent density of a powder and its flow and packing properties are constant.

Fig. 29 Tool motions during a powder compaction cycle, showing the sequence of powder fill, pressing, and ejection. Source: Ref 4

In spite of the use of lubricants, residual friction between die walls and powder and within the powder itself and the nonisotropic application of pressure result in nonuniform density throughout the part. Figure 30 shows the density distribution (lines of constant density in g/cm3) of a cylinder pressed from nickel powder from only one direction, at a pressure of 690 MPa (100 ksi). The low density near the bottom of the compact explains the widespread use of double action compaction. The density differences (and the implicit variations in stresses and contact geometries) are the main reason why compacts, upon sintering, do not shrink uniformly and why sintering of such compacts is, therefore, performed under conditions that result in only small dimensional changes. With substantial shrinkage, dimensional tolerances deteriorate rapidly and require sizing.

Fig. 30 Density distribution in a cylindrical nickel powder compact. Source: Ref 5

Design Limitations. The vertical compaction motion and the requirement that a part be automatically ejected from the die impose size and shape limitations. Additional limitations arise from the necessity that die components resist fracture and that the flow of powder into the die must be possible for uniform density. Generally, the wall thickness of a part is not less than 1.5 mm (0.060 in.). A maximum length-to-wall thickness ratio of 8 to 1 ensures reasonable density uniformity. Simple steps or level changes not exceeding 15% of the overall part height can be formed by face contours in the punches. This requires a draft of at least 5° for proper ejection.

Spherical parts require a flat area around a major diameter to allow the punch to terminate in a flat section (Fig. 31). Parts that must fit into ball sockets are repressed after sintering to remove the flats. Through holes in the pressing direction are produced with core rods extending through the punches.

Fig. 31 Proper design of spherical shapes in P/M parts. Source: Ref 7

Chamfers are preferred rather than radii on part edges to prevent burrs. Figures 32 and 33 show examples of unacceptable, acceptable, and preferred design features.

Fig. 32 Chamfer (a) and edge radii (b) design features. Source: Ref 7

Fig. 33 Examples of undesirable design features and preferred alternatives for P/M parts. Source: Ref 7

Reference 8 provides more details on designing for P/M. The limitations of shape complexity in the conventional press and sinter technique can be overcome in part by so-called multiple part assembly through sinter bonding, brazing, or welding. With a large press ( 1000 tons capacity) and a high compressibility powder, commercially produced parts can weigh around 2 kg (4.4 lb), with a compaction area of approximately 160 cm2 (62.99 in2), and a part thickness of approximately 75 mm (2.96 in.) although larger and heavier parts have been produced on conventional equipment. Springback of a part, that is, expansion after ejection from the die as a result of the release of elastic stresses, must be included in die design. Springback is usually less than 0.3% of the die dimension. Dies are typically made from tool steel or cemented carbide. The latter are used in high volume production. Powder metallurgy parts are classified by their complexity in terms of the number of their so-called levels or thicknesses and pressing directions (single or double action). Multiple level parts are the most difficult to press as each level requires separate punches for independent motion in order to minimize density differences between the various levels, (Fig. 34). Figure 35 illustrates the capabilities of the P/M press and sinter process in terms of the four compaction classes.

Fig. 34 The multiple tool components needed to compact a two-level gear. Source: Ref 4

Fig. 35 Collection of P/M components demonstrating the variety of possible shapes and the four compaction classes. (a) Class 1. (b) Class 2. (c) Class 3. (d) Class 4. Courtesy of Randall M. German, The Pennsylvania State University

P/M presses can be of the hydraulic, mechanical, pneumatic, rotary, or isostatic type. Hydraulic presses have press

capacities from less than 100 tons (896 kN to over 2000 tons, or 17,920 kN). Ejection of a pressed part from the die may be by the lower punches or by the so-called withdrawal type tooling. Rotary presses are cam-operated, high-speed presses. They are used for compacting small parts and can produce small bearings at rates of several 100 per min. Small mechanical presses (up to approximately 20 tons, or 179 kN) can produce parts up to approximately 100 per min, larger presses (>100 tons, or 896 kN) can produce up to approximately 25 parts per min. Hydraulic presses are controlled by compacting load, and mechanical presses are controlled by compact dimensions. If, therefore, the apparent density of a powder fluctuates toward a higher value, a hydraulically pressed part is bound to be of slightly larger height, while a mechanically pressed part will have a slightly higher density. Herein lies the importance of uniform apparent density of a powder lot to assure uniform parts for the entire powder lot. Hydraulic presses are slower than mechanical presses, but they allow more uniform densities and more independent controls. Complex shapes involving undercuts or large length-to-diameter ratios can be formed by cold isostatic pressing. Using this process, a flexible mold is filled with powder and pressurized isostatically (at ambient temperature), using a fluid such as oil or water. Compacting pressures ranging from 210 to 410 MPa (30 to 60 ksi) are most commonly employed, although pressures as high as 1400 MPa (200 ksi) have been used. Sintering. Sintering is the process through which the particle contacts achieved during compaction grow (Fig. 36) and

the physical and mechanical properties of a part are developed. Frequently, it is accompanied by shrinkage of the part. Sintering can also involve alloying and homogenization of mixed powder parts, often accompanied by growth.

Fig. 36 Scanning electron micrographs of the neck formation due to sintering. The spheres (33 m diam) were sintered at 1030 °C for 30 min in vacuum. Courtesy of Randall M. German, The Pennsylvania State University

Sintering is performed at temperatures around of the absolute melting point of the material, typically for 20 to 60 min and under a protective atmosphere. Widely used furnace atmospheres include endothermic gas, exothermic gas, dissociated ammonia, hydrogen, hydrogen-nitrogen mixtures, and vacuum. The main function of the atmosphere is to protect a part from oxidation or nitridation, as might occur when heating in air. Frequently, however, critical aspects of a sintering atmosphere also include reducing and carbonizing power and capability for efficient removal of the lubricant. Some sintering furnaces contain so-called rapid burn-off zones for rapid and efficient removal of the lubricant. This usually entails an atmosphere with a higher oxidation potential, that is, a higher concentration of gases such as steam and carbon dioxide. Steel parts with defined levels of carbon require that the furnace atmosphere has the correct concentration of carbonizing components, that is, CO, CH4, and C3H8, in order to assure the correct carbon level and its uniform distribution throughout the part. Endothermic atmospheres (mixtures of hydrogen, nitrogen, and carbon monoxide) are used for this purpose. For some materials, the sintering process must be carefully controlled for developing optimum properties. The following are examples: • • •

•

Aluminum alloys are most widely sintered in very low dew point nitrogen Tool steels are sintered in a very narrow temperature range to achieve densification through liquid phase sintering without excessive grain growth and carbide coarsening. For best corrosion resistance, stainless steels are preferably sintered at high temperature (1180 to 1290 °C, or 2250 to 2350 °F) in low dew point hydrogen or under vacuum, followed by rapid cooling. Sintering in dissociated ammonia increases strength, but corrosion resistance is only modest because of the formation of chromium nitrides and attendant sensitization. Furthermore, the chloride corrosion resistance of sintered stainless steels goes through a minimum at a density of approximately 7.0 g/cm3, as a result of crevice corrosion due to the presence of pores. Corrosion resistance in acids improves steadily with increasing density. Soft magnetic steels are sintered at high temperatures in low dew point hydrogen to reduce their interstitials (carbon, nitrogen, and oxygen) and to maximize the magnetic properties.

The majority of parts require at least some reducing gases in the furnace atmosphere because of the ever present surface oxides on most metal powders, which, without their removal, would interfere with sintering. As the sintering process is driven mainly by the surface energy of the powder particles, it is evident that a fine powder sinters more rapidly than a coarse powder. This is the reason why metal injection molding (MIM) employs very fine powders, 5 to 20 m, which under normal sintering conditions shrink to nearly full density.

Sintering theory describes the evolution of the pore structure in terms of solid state atomic transport (diffusion) events. Theoretical approaches are useful for estimating the effects of the many process variables. In the early stage of sintering, bonds form at the particle contacts. During intermediate stage sintering, in the density range of approximately 70 to 92% of theoretical, the rate of sintering decreases, grain growth occurs, and pores become isolated. In the final stage, spherical and isolated pores shrink only slowly by vacancy diffusion to grain boundaries. In liquid phase sintering, a liquid coexists with the solid phase during part or the entire sintering process. The presence of the liquid, through a solution-reprecipitation process, enables more rapid sintering and much faster densification than is typical for a solid state system. Thus, with a liquid phase sintering system, it is possible to achieve a high sintered density without the use of a fine powder. Commercially, widely used liquid phase sintering systems include bronze (for porous bearings), copper steels, tool steels, cemented carbides, iron-phosphorous and tungsten-nickel. In activated sintering, a small amount of an additive is used to improve the diffusion rate during sintering. Examples include palladium added to tungsten and hydrogen chloride added to hydrogen atmospheres for sintering iron compacts. Apart from the development of strength during sintering, a critical property is the control of dimensional change. In the press and sinter technique, the sintering cycle with its many variants is usually controlled to produce close to zero dimensional change. Shrinkage is usually less than 2.5%. This results in dimensional tolerances of approximately +0.07 to 0.10% for 1 in. diameter parts. The tolerances in the axial directions are approximately +0.5% for a 1 in. long part. Sizing can be used to further improve dimensional tolerances. Further improvements by P/M equipment manufacturers and powder producers also will result in further improvements of this important property. Liquid phase sintering typically produces more distortion and liquid phase sintered parts, even when shrinkage is absent, which are often sized to improve the final tolerances of a part. Sintering Furnaces. Structural parts are typically sintered in continuous belt, pusher, or walking beam furnaces. For

economic reasons, batch-type furnaces are often used for refractory metal powder parts and their alloys as well as for cemented carbide compacts. Vacuum furnaces can be used for all of the above. Still other furnaces are used for hot pressing, hot extrusion, and hot forging. Some refractory materials are sintered by directly passing electrical current through them. Belt furnaces operate up to approximately 1177 °C (2150 °F). They are widely used for sintering the bulk of structural parts. Pusher and walking beam furnaces are operated at temperatures up to approximately 1371 °C (2500 °F), and vacuum furnaces up to 3000 °C (5432 °F). The various heating elements used in these furnaces (nichrome, kanthal, silicon carbide, molybdenum, and graphite) determine the maximum operating temperatures and the atmospheres (reducing, oxidizing, carbonizing, and inert) under which they are used. Most furnaces are designed to contain a preheat and delubrication zone, a hot zone, and a cooling zone, as shown schematically in Fig. 37.

Fig. 37 The sequence of operations occurring in a sintering furnace. The lower diagram shows the timetemperature profile typical of metal powder sintering. Source: Ref 4

Warm Compaction. In warm compaction both powder and die are heated under a protective atmosphere and the

compacted. This process produces parts with densities up to approximately 95% of theoretical, that is, similar to those

obtained by double pressing, but at a lower cost. Green strength is also significantly higher so that parts can be machined in the green condition. Full Density Processes Commercial full density processes include powder forging (P/F), metal injection molding (MIM), hot isostatic pressing (HIP), roll compacting, hot pressing, extrusion, and spray forming. In these processes, porosity is eliminated and physical and mechanical properties are improved to the level of wrought materials and sometimes beyond. Strengthening a part through alloying additions is less limited in the full density processes than it is in the press and sinter process. In the latter, high compressibility is important to achieve high pressed densities. In P/F, MIM, and HIP, the compressibility of a powder plays only a minor role. It is for this reason that the press and sinter process often employs powder mixtures and relies on alloying during sintering, while the full density processes in general prefer the harder prealloyed powders. Several of the full density processes offer complex shape capability and attractive advantages regarding material utilization, energy efficiency, and precision, in comparison to conventional wrought materials. These advantages are, however, obtained through the use of more expensive processing. High or full density alone is not sufficient to achieve superior properties. Most full density processes use "clean" powders, and any nonreducible surface oxides are limited to very small amounts and, if present, are broken up and homogeneously distributed through shear deformation. Fully dense P/M materials can exceed the properties of wrought materials of the same composition through control of the microstructure, that is, control of various defects, homogeneity of structure, and the smaller grain size typical of most P/M materials. It is, therefore, important to determine the properties needed in a given application and then select the most economic process that can achieve the desired properties. Full dense processing is currently used to manufacture high fatigue strength structural parts for automotive uses; superalloy components; high-temperature, light-weight composites; wear resistant materials; cutting tools; permanent magnets; and dispersion-strengthened copper. Figure 38 compares schematically some of the options of high and full density processing with respect to density, part size, and level of performance. The range of properties for a given density (cross-hatched area) arises from alloying and heat treatment effects, as well as from morphological differences. Tables 3 and 4 compare several performance and other properties of the major full density processes.

Fig. 38 Three of the variables that influence the selection of a powder metallurgy processing method: component size, density, and performance (as a percentage of that of a wrought material). That behavior corresponds to ferrous based P/M systems formed from coarse powder, but is representative of many powder metallurgy materials. The symbols are press and sinter, P/S; press, sinter, and repress, reP; press, sinter, and forge, P/S + F; cold isostatically press and sinter, CIP + S; hot isostatically press, HIP; hot isostatically press and forge, HIP + F. Source: Ref 4

Powder Forging. In P/F a so-called preform, made by conventional pressing and sintering of a forging grade powder, is forged by a simple blow in a confined die at an elevated temperature (800 to 1200 °C, or 1450 to 2200 °F, for ferrous parts). In hot upsetting, the preform undergoes a significant amount of lateral material flow; in hot repressing, material flow is mainly in the direction of pressing. Hot upsetting with its large amount of shear stresses is effective in breaking up

powder particle oxide films, which improves metallurgical bonding between particle interfaces and enhances dynamic mechanical properties. Weight distribution within the preform is carefully controlled to obtain full density without tool breakage. Although P/F involves less handling, fewer dies and processing steps, and produces less scrap than conventional forging of cast materials, it is presently primarily used for the high volume production of automotive parts. This is attributed to the high cost for developing preforms and maintaining forging tools and automated production systems. In hot upsetting, the design of the preform is critical in that densification and shaping through the application of a uniaxial force occur simultaneously and must occur without bulging and cracking of the preform. Forging windows (computer-aided design) describe the amounts of fracture-free permissible straining. Figure 39 shows a few of the many possible operating layouts of a powder forging process line. For the forging steps, the heated preform is removed from the furnace, usually by a robotic manipulator, and located in the die cavity for forging at high pressure (690 to 965 MPa, or 100 to 140 ksi). The preform can also be coated with graphite to minimize its oxidation during reheating and transfer to the forging die.

Fig. 39 A powder forging process line. Source: Ref 9

Metal Injection Molding. In MIM, a uniform mixture of metal powder and binder is injected into a mold (Fig. 40), the

binder is removed, and the part sintered to more or less full density. This process permits the manufacture of very complex metallic shapes with less expensive forming equipment than the equipment used in the press and sinter process. The powders suitable for MIM are, however, very fine with an average particle size of less than approximately 20 m, and they can cost over twice as much as the coarser powders used in the conventional press and sinter process. The high surface area of the fine powders provide the surface energy necessary to achieve full densification during sintering. Widely used powders include carbonyl iron and nickel powders and other fine and more or less spherically shaped powders made by other processes. Near spherically shaped powders provide desirable high packing densities. The large amount of binder used in MIM, up to 40%, must be removed carefully through solvent or capillary extraction and/or through thermal debinding. The large amount of shrinkage (20% linear) taking place during sintering is mainly isotropic, and therefore dimensional tolerances, although somewhat inferior to pressed and sintered parts, are acceptable.

Fig. 40 Schematic of the metal injection molding process. Source: Ref 4

Metal injection molding is mostly used for the manufacture of relatively small parts, usually less than lb, of complex geometries. Typical products include rechargeable batteries, orthodontic brackets, capacitors, filters, and catalytic substrates. Forming methods that use similar metal powders and binders similar to MIM include various types of slip casting, extrusion, and freeze drying. Hot Isostatic Pressing. In HIP, or "hipping," a powder is filled into a gas-tight metal or ceramic container and then

heated and vacuum degassed to remove volatile contaminants. This is followed by further heating and pressurizing with gas (Ar or N2) in a HIP vessel. Temperatures up to 2200 °C (4000 °F) and pressures up to 200 MPa (30 ksi) are in use. Because of the isotropic pressure, the consolidated powder is in the shape of the original container except for the smaller size. The container can be stripped from the consolidated part by machining or by chemical dissolution. Hot isostatic pressing allows the production of large parts with very good shape complexity but modest dimensional tolerances and low production rate. The dimensional tolerances are over an order of magnitude inferior to conventional die compaction and to P/F. For these reasons, HIP is mainly used for the consolidation of expensive metals, preferably of large size, such as superalloys, titanium, stainless and tool steels, and composites. Hot isostatic pressing is also applied to P/M materials with densities over 92%. In this case, no container is necessary because at such densities there exists no open porosity. Cemented carbides, wear materials, and titanium implants are manufactured this way. Because of the hydrostatic stresses in HIP, powder consolidation occurs with only little shear on the particle surfaces. This mandates the use of very clean and oxide-free powders. Roll Compaction. In roll compaction or powder rolling, conventional rolling technology is employed to compact a

powder at room temperature into a porous (60 to 90% of theoretical) strip. The powder is gravity fed into the gap of two rolls. The flexible green strip enters a sintering furnace followed by hot rolls to complete densification to theoretical

density. Roll compaction of powders is used in the manufacture of high purity metals, soft magnetic alloys, composite, and other specialty materials. Hot pressing can be performed in a rigid die using uniaxial pressure, similar to die compaction. A protective

atmosphere protects the powder from becoming oxidized. Alternatively, the powder can be encapsulated in a container. Graphite, refractory metals, or ceramics can be used as die materials. Hot pressing is a slow process because of the large thermal mass of the tooling. Typical maximums for temperature and pressure are 2200 °C (4000 °F) and 50 MPa (7.3 ksi). Hot pressing under vacuum minimizes contamination. Hot pressing is used industrially for the manufacture of diamond tool and friction materials and beryllium. Extrusion. In extrusion, a powder is typically canned, degassed, and then extruded at elevated temperature (over two-

thirds of the absolute melting point of the material. For full densification and crack-free extrusion, reduction rates greater than ten are used. Temperature is the main control variable to achieve good product quality and acceptable tooling life. The high level of shear present in powder extrusion is very effective in breaking up prior particle boundaries of highly alloyed metals. This results in superior microstructures and superior mechanical properties. Extrusion is used commercially for the manufacture of stainless steel tubing, oxide-dispersion strengthened metals, composites, and other specialty materials. Spray Forming. In spray forming, inert gas atomized powder is directed onto a substrate. With proper process control,

the atomized droplets reach the substrate surface in semisolid condition and splat deform to full or nearly full density. Rapid heat extraction results in minimal segregation in even complex alloys and in very good homogeneity. Deposition rates of up to 2 kg/s are possible. Spray forming is currently being applied to nickel, copper, and aluminum alloys.

References cited in this section

4. R.M. German, Powder Metallurgy Science, 2nd ed., Metal Powder Industries Federation, 1994 5. Powder Metallurgy, Vol 7, Metals Handbook, 9th ed., American Society for Metals, 1984 7. H.I. Sanderow, Design for Powder Metallurgy, in Materials Selection and Design, Vol 20, ASM Handbook, 1997, p 745-753 8. Powder Metallurgy Design Manual, 2nd ed., Metal Powder Industries Federation, 1995 9. W.B. James, M.J. Dermott, and R.A. Powell, Powder Forging, in Forming and Forging, Vol 14, ASM Handbook, 1988, p 188-211

Secondary Operations Sometimes sintered parts require special treatments, known as secondary and/or finishing operations, to meet final application requirements. They include heat treatments, joining, repressing and sizing, machining, and various kinds of surface treatments. The presence of residual porosity requires special precautions in some of these processes. Heat treatments serve to increase the surface hardness of a part to improve wear resistance or to increase the hardness

of the entire part to improve strength. Powder metallurgy parts with residual porosity are heat treated in carburizing and nitriding gases or in noncorrosive liquids (quench oils). Porosity in P/M parts increases the depth of carburization (Fig. 41). Therefore, parts to be case carburized should have a density of at least 7.2 g/cm3 to avoid penetration of the carbonizing gas into the part interior. Lower density parts are sometimes copper infiltrated to meet that requirement.

Fig. 41 Hardness, in terms of the Vickers hardness number, versus depth below the surface for three P/M steels following vacuum carburization at 925 °C (1695 °F). The higher the porosity the deeper the carbon penetration because of permeation through the open pore network. Below approximately 8% porosity, the carburization process is largely by solid-state diffusion. Source: Ref 4

The hardenability of P/M parts is reduced due to the presence of pores, which reduce thermal conductivity and cooling rate. This is illustrated in Fig. 42 for two porosity levels. Although manganese and chromium significantly improve hardenability, their use is limited to very low dew point atmospheres, which prevent the oxidation of these elements.

Fig. 42 Hardenability, as measured by Jominy end-quench hardness traces, for two porosity levels in sintered steel. The lower porosity gives better heat conduction with concomitantly greater depth of a high hardness. Source: Ref 4

Porous steel parts can be steam treated to improve wear and corrosion resistance and to provide low-pressure, leak tightness. The treatment is performed at low temperature in superheated steam. The steam oxidizes the surface pores, which close through formation of an adherent layer of bluish to black iron oxide (Fe3O4). Joining. At low porosity levels (5 line pairs/mm

(a) (b)

Real-time radiography(a)

2.5 line pairs/mm

Computed tomography or digital radiography(b) 0.2-4.5 line pairs/mm

5

20

99

2

8

95

0.5

2

80

Scatter, poor photon statistics 200-1000 Poor, requires film scanner

Scatter, poor photon statistics 500-2000 Moderate to good; typically 8 bit data

Moderate; affected by structure visibility and variable radiographic magnification

Moderate to poor; affected by structure visibility, resolution, variable radiographic magnification, and optical distortions

Minimal scatter Up to 1 × 106 Excellent; typically 16 bit data Excellent; affected by resolution, enhanced by low contrast detectability

General characteristics of real-time radiography with fluorescent screen-TV camera system or an image intensifier. Digital radiographic imaging performance with discrete element detector arrays is comparable to computed tomography performance values.

Can be improved with microfocus x-ray source and geometric magnification

(c)

The detectors used in digital radiography include scintillator photodetectors, phosphor photodetectors, photomultiplier tubes, and gas ionization detectors. Scintillator and phosphor photodetectors are compact and rugged, and they are used in flying-spot and fan-beam detector arrangements. Photomultiplier tubes are fragile and bulky, but do provide the capability of photon counting when signal levels are low. Gas ionization detectors have low detection efficiencies but better longterm stability than scintillator- and phosphor-photodetector arrays. A typical phosphor-photodetector array for the radiographic inspection of welds consists of 1024 pixel elements with 25 m (1 mil) spacing, covering 25 mm (1 in.) in length perpendicular weld seam. The linear photodiode array is covered with a fiberoptic faceplate and can be cooled in order to reduce noise. For the conversion of the x-rays to visible light, fluorescent screens are coupled to the array by means of the fiber optics. A linear collimator parallel to the array is arranged in front of the screen. The resolution perpendicular to the array is defined by the width of this slit and the speed of the manipulator. A second, single-element detector is provided to detect instabilities of the x-ray beam. Using 100 kV radiation, a spatial resolution of 0.1 mm (0.004 in.) can be achieved with a scanning speed of 1 to 10 mm/s (0.04 to 0.4 in./s). The data from the detector system are digitized and then stored in a fast dual-ported memory. This permits quasisimultaneous access to the data during acquisition. Before the image is stored in the frame buffer and displayed on the monitor, simple preprocessing can be done, such as intensity correction of the x-ray tube by the data of the second detector and correction of the sensitivity for different array elements. If further image processing or automatic defect evaluation is required, the system can be equipped with fast image-processing hardware. All standard devices for digital storage can be utilized. Image Processing. Because real-time systems generally do not provide the same level of image quality and contrast as radiographic film, image processing is often used to enhance the images from image intensifiers, fluorescent screens, and detector arrays. With image processing, the video images from real-time systems can compete with the image quality of film radiography. Moreover, image processing also increases the dynamic range of real-time systems beyond that of film (which typically has a dynamic range of about 1000 to 1).

Images can be processed in two ways: as an analog video signal and as a digitized signal. An example of analog processing is to shade the image after the signal leaves the camera. Shading compensates for irregularities in brightness across the video image due to thickness or density variations in the testpiece. This increases the dynamic range (or latitude) of the system, which allows the inspection of parts having larger variations in thickness and density. After analog image processing, the images can be digitized for further image enhancement. This digitization of the signal may involve some detector requirements. In all real-time radiological applications, the images have to be obtained at low dose rates (around 20 R/s). In digital x-ray imaging, however, the most often used dose is around 1 mR, in order to reduce the signal fluctuations that would result from a weak x-ray flux. This means that only a short exposure time (of the order of a few milliseconds) and a frequency of several images can be used if kinetic (motion) blurring is to be avoided. The resulting requirements for the x-ray detector are therefore: • • •

The capability of operating properly in a pulsed mode, which calls for a fast temporal response An excellent linearity, to allow the use of the simplest and most efficient form of signal processing A wide operating dynamic range in terms of dose output (around 2000 to 1)

Once the image from the video camera has been digitized in the image processor, a variety of processing techniques can be implemented. The image-processing techniques may range from the relatively simple operation of frame integration to more complex operations such as automatic defect evaluation. Radiation Gaging. Radiation-measuring instruments do not produce images. The output from these instruments is a

meter reading or a strip chart, which records the radiation transmitted through a test piece in terms of roentgens. Many of these instruments are routinely used to check areas surrounding a radiographic-inspection site for excessive radiation. Radiation gaging can be applied to certain automated processes, such as thickness gaging of materials or determination of liquid levels in sealed containers. In these applications, it may not be necessary to actually measure the amount of

radiation passing through the material, but only to detect changes in the level of radiation--in other words, for a "go, nogo" type of inspection. When a highly absorbing material such as thick lead or concrete must be inspected for voids and when usual radiographic techniques are impractical, radiation gaging can be used effectively. Voids can be located in these materials by noting increases in the readings of radiation-detecting instruments. Computed Tomography. Cross-sectional images of an inspection object can be obtained by a series of radiation attenuation measurements all around the object. Typically, a fan beam of radiation about 1 or 2 mm in height is used along with a bank of detectors on the opposite side of the object. The attenuation data permit a computer reconstruction showing density differences in the cross section of the object (Fig. 9a).

Fig. 9 Comparison of (a) computed tomography (CT) and (b) radiography. A high-quality digital radiograph (b) of a solid rocket motor igniter shows a serious flaw in a carefully oriented tangential shot. A CT image (a) at the height of the flaw shows the flaw in more detail and in a form an inexperienced viewer can readily recognize.

X-ray computed tomography has many of the same benefits and limitations as film and real-time radiography. The primary difference is the nature of the radiological image. Radiography (Fig. 9b) compresses the structural information from a three-dimensional volume into a two-dimensional image. This is useful in that it allows a relatively large volume to be interrogated and represented in a single image. This compression, however, limits the information and reduces the sensitivity to small variations. Radiographic images also can be difficult to interpret because of shadows from overlying and underlying structures superimposed on the features of interest. In contrast, the CT method provides sufficient information to localize a feature (Fig. 9a). Some of the performance characteristics of radiography and computed tomography are compared in Table 5. One of the limitations of CT inspection is that the CT image provides detailed information only over the limited volume of the cross-sectional slice. Full inspection of the entire volume of a component with computed tomography requires many slices, limiting the inspection throughput of the system. Therefore, CT equipment is often used in a digital

radiography (DR) mode during production operations, with the CT imaging mode used for specific critical areas or to obtain more detailed information on indications found in the DR image. Digital radiography capabilities and throughput can be significant operational considerations for the overall system usage. Computed tomography systems generally provide a DR imaging mode, producing a two-dimensional radiographic image of the overall testpiece.

Characteristics of X-Ray Film Three general characteristics of film--speed, gradient, and graininess--are primarily responsible for the performance of the film during exposure and processing and for the quality of the resulting image. Film speed, gradient, and graininess are interrelated; that is, the faster the film, the larger the graininess and the lower the gradient--and vice versa. Film speed and gradient are derived from the characteristic curve for a film emulsion, which is a plot of film density versus the exposure required for producing that density in the processed film. Graininess is an inherent property of the emulsion, but can be influenced somewhat by the conditions of exposure and development. The selection of radiographic film for a particular application is generally a compromise between the desired quality of the radiograph and the cost of exposure time. This compromise occurs because slower films generally provide a higher film gradient and a lower level of graininess and fog. Film Types. The classification of radiographic film is complicated, as evidenced by changes in ASTM standard practice

E 94. The 1988 edition (and subsequent editions) of ASTM E 94 references an ASTM E 746, which describes a standard test method for determining the relative image-quality response of industrial radiographic film. Careful study of ASTM E 746 is required to arrive at a conclusive classification index suitable for the given radiographic film requirements of a facility. Earlier editions (1984 and prior) of ASTM E 94 contained a table listing the characteristics of industrial films grouped into four types. Table 6 summarizes the general characteristics of these four types. This relatively simple classification method is referenced by many codes and specifications, which may state only that a type 1 or 2 film can be used for their specification requirements. However, because of this relatively arbitrary method of classification, many film manufacturers may be reluctant to assign type numbers to a given film. Moreover, the characteristics of radiographic films can vary within a type classification of Table 6 because of inherent variations among films produced by different manufacturers under different brand names and because of variations in film processing that affect both film speed and radiographic density. These variations make it essential that film processing be standardized and that characteristic curves for each brand of film be obtained from the film manufacturer for use in developing exposure charts.

Table 6 General characteristics of the four types of radiographic film specified in the earlier (1984) edition of ASTM E 94 Film type 1 2 3 4(a)

(a) (b) (c) (d)

Film characteristic Speed Gradient Low Very high Medium High High Medium Very high(b) Very high(b)

Graininess Very fine Fine Coarse (c)

Normally used with fluorescent screens. When used with fluorescent screens. Graininess is mainly a characteristic of the fluorescent screens. When used for direct exposure or with lead screens. These groupings are given only for qualitative comparisons. For a more detailed discussion on film classification, see the section "Film Types" in this article.

Because the variables that govern the classification of film are no longer detailed in ASTM E 94, it is largely the responsibility of the film manufacturer to determine the particular type numbers associated with his brand names. Some manufacturers indicate the type number together with the brand name on the film package. If there is doubt regarding the type number of a given brand, it is advisable to consult the manufacturer. Most manufacturers offer a brand of film characterized as very low speed, ultrahigh gradient, and extremely fine grain.

Film selection for radiography is a compromise between the economics of exposure (film speed and latitude) and the

quality desired in the radiograph. In general, fine-grain, high-gradient films produce the highest-quality radiographs. However, because of the low speed typically associated with these films, high-intensity radiation or long exposure times are needed. Other factors affecting radiographic quality and film selection are the type and thickness of the testpiece and the photon energy of the incident radiation. Although the classification of film is more complex than the types given in Table 6, a general guide is that better radiographic quality will be promoted by the lowest type number in Table 6 that economic and technical considerations will allow. In this regard, Table 7 suggests a general comparison of film characteristics for achieving a reasonable level of radiographic quality for various metals and radiation-source energies. It should be noted, however, that the film types are only a qualitative ranking of the general film characteristics given in Table 6. Many radiographic films, particularly those designed for automatic processing, cannot be adequately classified according to the system in Table 6. This compounds the problem of selecting film for a particular application.

Table 7 Guide to the selection of radiographic film for steel, aluminum, bronze, and magnesium in various thicknesses Thickness mm in. Steel 0-6

Type of film(a) for use with these x-ray tube voltages, or radioactive isotopes: 50-80 80-120 120-150 150-250 Ir-192 250-400 1 Co-60 2 MeV kV kV kV kV kV MeV

Ra

6-31 MeV

3

3

2

1

...

...

...

...

...

...

...

4

3

2

2

...

1

...

...

...

...

...

...

4

3

2

2

2

1

...

1

2

...

... ... ... ...

... ... ... ...

... ... ... ...

3 4 ... ...

2 3 ... ...

2 4 4 ...

1 2 3 ...

2 2 3 ...

1 2 2 3

2 3 3 ...

1 1 2 2

1

1

...

...

...

...

...

...

...

...

...

2

1

1

1

...

...

...

...

...

...

...

2

1

1

1

...

1

...

...

...

...

...

3 4 ... ...

2 3 4 ...

2 2 3 ...

1 2 3 ...

1 1 2 4

1 2 3 ...

... ... ... ...

... ... ... ...

... ... ... ...

... ... ... ...

... ... ... ...

4

3

2

1

1

1

1

...

...

...

...

...

3

2

2

2

1

1

...

1

...

...

...

4

4

3

2

2

1

2

1

2

...

... ... ... ...

... ... ... ...

4 ... ... ...

4 ... ... ...

3 3 ... ...

3 4 ... ...

1 2 3 ...

2 3 3 ...

1 2 2 3

2 3 ... ...

1 1 2 2

1

1

...

...

...

...

...

...

...

...

...

1

1

1

...

...

...

...

...

...

...

...

2

1

1

...

1

...

...

...

...

...

...

2 3 ... ...

1 2 3 ...

1 2 2 ...

1 1 2 4

1 2 3 ...

... ... ... ...

... ... ... ...

... ... ... ...

... ... ... ...

... ... ... ...

... ... ... ...

06-13 13-25 25-50 50-100 100-200 >200 Aluminum 0-6

-1 1-2 2-4 4-8 >8

06-13 13-25 25-50 50-100 100-200 >200 Bronze 0-6

-1 1-2 2-4 4-8 >8

06-13 13-25 -1 1-2 25-50 2-4 50-100 100-200 4-8 >8 >200 Magnesium 0-6 06-13 13-25 -1 1-2 25-50 2-4 50-100 100-200 4-8 >8 >200

(a)

These recommendations represent a usually acceptable level of radiographic quality and are based on the qualitative classification of films defined in Table 6. Optimum radiographic quality will be promoted by use of the lowest-number film type that economic and technical considerations will allow. The recommendations for type 4 film are based on the use of fluorescent screens.

Exposure Factors Exposure is the intensity of radiation multiplied by the time during which it acts; that is, the amount of energy that reaches a particular area of the film and that is responsible for producing a particular density on the developed film. Density is the quantitative measure of blackening of a photographic emulsion. Density, measured directly with an instrument called a densitometer, is the logarithm of the ratio of the light intensity incident on the film to that transmitted by the film. Therefore, a film with a density of 1.0 will transmit only 10% of the light, a film with a density of 2.0 will transmit only

of the light, and so on.

There are two kinds of density: (a) the density associated with transparent-base radiographic film, called transmission density, and (b) the density associated with opaque-base imaging material such as radiographic paper, called reflection density. The exposure time in film radiography depends mainly on film speed, the intensity of radiation at the film surface, the characteristics of any screens used, and the desired level of photographic density. In practice, the energy of the radiation is first chosen to be sufficiently penetrating for the type of material and thickness to be inspected. The film type and the desired photographic density are then selected according requirements for contrast sensitivity (as discussed below). Once these factors are fixed, then the source strength, the source-to-film distance, and the characteristics of any screens used determine the exposure time. With a given type of film and screen, the exposure time to produce the desired photographic density can be determined. Because intensity is inversely proportional to the square of distance from the source, the reciprocity law for equivalent exposures with an x-ray tube can be written as:

where i is the tube current, t is the exposure time, L is the source-to-film distance, and the subscripts refer to two different combinations that produce images with the desired photographic density. The parallel expression that applies to exposures made with a -ray source is:

where a is the source strength in gigabecquerel (Curies). Contrast sensitivity refers to the ability of responding to and displaying small variations in subject contrast. Contrast sensitivity depends on the characteristics of the image detector and on the level of radiation being detected (or on the amount of exposure for films). The relationship between the contrast sensitivity and the level of radiation intensity (or film exposure) can be illustrated by considering two extremes. At low levels of radiation intensity, the contrast sensitivity of the detectors is reduced by a smaller signal-to-noise ratio, while at high levels, the detectors become saturated. Consequently, contrast sensitivity is a function of dynamic range (see below).

In film radiography, the contrast sensitivity is:

where D is the smallest change in photographic density that can be observed when the film is placed on an illuminated screen. The factor GD is called the film gradient or film contrast. The film gradient is the inherent ability of a film to record a difference in the intensity of the transmitted radiation as a difference in photographic density. It depends on film type, development procedure, and film density. For all practical purposes, it is independent of the quality and distribution of the transmitted radiation. Contrast sensitivity in real-time systems is determined by the number of bits (if the image is digitized) and the signal-tonoise ratio (which is affected by the intensity of the radiation and the efficiency of the detector). The best contrast sensitivity of digitized images from fluorescent screens is about 8 bits (or 256 gray levels). Another way of specifying the contrast sensitivity of fluorescent screens is with a gamma factor, which is defined by the fractional unit change in screen brightness, B/B, for a given fractional change in the radiation intensity, I/I. Most fluorescent screens have a gamma factor of about one, which is not a limiting factor. At low levels of intensity, however, the contrast is reduced because of quantum mottle (which is a form of screen unsharpness). Unsharpness may reduce the contrast depending on flaw size (Fig. 10).

Fig. 10 Effect of geometric unsharpness on image contrast. (a) Flaw size, d, is larger than the unsharpness, then full contrast occurs. (b) Flaw size, d, is smaller than the unsharpness, then contrast is reduced.

Dynamic range, or latitude, describes the ability of the imaging system to produce a suitable signal over a range of

radiation intensities. The dynamic range is given as the ratio of the largest signal that can be measured to the precision of the smallest signal that can be discriminated. A large dynamic range allows the system to maintain contrast sensitivity over a wide range of radiation intensities or testpiece thicknesses. Film radiography has a dynamic range of up to 1000 to 1, while digital radiography with discrete detectors can achieve 100,000 to 1. The latitude, or dynamic range, of film techniques is the range of testpiece thickness that can be recorded with a single exposure. High-gradient films generally have narrow latitude, that is, only a narrow range of testpiece thickness can be imaged with optimum density for interpretation. If the testpiece is of nonuniform thickness, more than one exposure may have to be made (using different x-ray spectra or different exposure times) for complete inspection of the piece. The number of exposures, as well as the exposure times, can often be reduced by using a faster film of lower gradient but wider latitude, although there is usually an accompanying reduction in ability to image small flaws.

Exposure Charts for X-Ray Radiography. Equipment manufacturers usually publish exposure charts for each type

of x-ray generator that they manufacture. These published charts, however, are only approximations; each particular unit and each installation is unique. Radiographic density is affected by such factors as radiation spectrum, film processing, setup technique, amount and type of filtration, screens, and scattered radiation. Although published exposure charts are acceptable guides for equipment selection, more accurate charts that are prepared under normal operating conditions are recommended for each x-ray machine. A simple method for preparing accurate exposure charts is as follows:

1. Make a series of radiographs of a calibrated multiple-thickness step wedge, using several different values of exposure at each of several different tube voltage settings. 2. Process the exposed films together under conditions identical to those that will be used for routine application. 3. From the several densities corresponding to different thicknesses, determine which density (and thickness) corresponds exactly with the density desired for routine application. This step must be done with a densitometer because no other method is accurate. If the desired density does not appear on the radiograph, the thickness corresponding to the desired density can be found by interpolation. 4. Using the thickness determined in step 3 and the tube voltage (kilovoltage) and exposure (milliamp second or milliamp min) corresponding to that piece of film, plot the relation of thickness to exposure on semilogarithmic paper with exposure on the logarithmic scale. 5. Draw lines of constant tube voltage through the corresponding points on the graph.

Spectral Sensitivity. The shape of the characteristic curve of a given x-ray film is for all practical purposes unaffected by the wavelength distribution in the x-ray or gamma-ray beam used for the exposure. However, the sensitivity of the film in terms of roentgens required to produce a given density is strongly affected by radiation energy (beam spectrum of a given kilovoltage or given gamma-ray source).

Figure 11 shows the exposure required for producing a density of 1.0 on type 4 radiographic film developed in an x-ray developer (made from powder) for 5 min at 20 °C (68 °F). The exposures were made directly, without screens. The spectral-sensitivity curves for all x-ray films have approximately the same general features as the curves shown in Fig. 11.

Fig. 11 Spectral-sensitivity curves for a type 4 radiographic film, showing exposure required to produce a density of 1.0

The classification of radiographic film is complicated; however, a relatively simple classification has been adopted by ASTM. According to the classification in ASTM E 94, radiographic films are grouped into four types. The general characteristics of these four types are summarized in Table 6. The relative image quality of x-ray film can also be determined in a quantitative manner using a multihole test piece as described in ASTM E 746. Screens are often used with x-ray films during exposure. Metal screens, typically used at x-ray energies of over 150 kV, intensify the image by emission of photoelectrons and help reduce the effects of scatter by attenuating the lower-energy scattered radiation. Lead is typically used. Fluorescent screens are used in some situations to help reduce exposure times.

Image Quality. The quality level of an industrial radiograph is governed by the radiographic sensitivity exhibited on

the radiograph itself. Radiographic sensitivity is determined through the use of penetrameters or image-quality indicators (IQI). Penetrameters, or IQIs, are of known size and shape, and have the same attenuation characteristics as the material in the test piece. They are placed on the test piece or on a block of identical material during setup and are radiographed at the same time as the test piece. Penetrameters preferably are located in regions of maximum test-piece thickness and greatest test-piece-to-film distance, and near the outer edge of the central beam of radiation. The degree to which features of the penetrameter are visible in the developed image is a measure of the quality of that image. The image of the penetrameter that appears on the finished radiograph is evaluated during interpretation to ensure that the desired sensitivity, definition, and contrast have been achieved in the developed image. Penetrameters of different designs have been developed by various standards-making organizations. Common types are plaques containing holes and a second type containing a series of wires. Plaque-type penetrameters consist of strips of material of uniform thickness with holes drilled through them specified by ASTM E 142. Wire-type penetrameters are widely used in Europe (see German standard DIN 54109). They are also used in the U.S. and are described in ASTM standard E 747. The sensitivity of a wire-type penetrameter is expressed in terms of wire diameter divided by object thickness.

Neutron Radiography Neutron radiography is a form of nondestructive inspection that uses a specific type of particulate radiation, called neutrons, to form a radiographic image of a test piece. The geometric principles of shadow formation, variation of attenuation with test-piece thickness, and many other factors that govern the exposure and processing of a neutron radiograph are similar to those for radiography using x-rays or gamma rays. The section deals mainly with the characteristics that differentiate neutron radiography from x-ray or gamma-ray radiography. The application of neutron radiography is described, especially in terms of its advantages for improved contrast on low-atomic-number materials, discrimination between isotopes, or inspection of radioactive specimens. Neutrons are subatomic particles that are characterized by relatively large mass and a neutral electric charge. The attenuation of neutrons differs from the attenuation of x-rays in that the processes of attenuation are nuclear rather than processes that depend on interaction with electron shells surrounding the nucleus. Neutrons are produced by nuclear reactors, accelerators, or certain radioactive isotopes, all of which emit neutrons of relatively high energy (fast neutrons). Because most neutron radiography is performed with neutrons of lower energy (thermal neutrons), the sources are usually surrounded by a "moderator," which is a material that reduces the kinetic energy of the neutrons by scattering. Neutron radiography differs from conventional radiography in that the attenuation of neutrons as they pass through the test piece is more related to the specific isotope present than to density or atomic number. X-rays are attenuated more by elements of high atomic number than by elements of low atomic number, and this effect varies relatively smoothly with atomic number. Also, x-rays are generally attenuated more by materials of high density than they are by materials of low density. For thermal neutrons, the attenuation tends to decrease with increasing atomic number, although the trend is by no means a smooth relationship. In addition to the high attenuation of several light elements (hydrogen, lithium, and boron), certain medium to heavy elements (especially cadmium, samarium, europium, gadolinium, and dysprosium) and certain specific isotopes have exceptionally high capabilities for absorbing thermal neutrons. This means that neutron radiography is capable of detecting these highly attenuating elements or isotopes when present in a structure of lower absorption capability. Using neutrons, it is possible to radiographically detect certain isotopes--for instance, certain isotopes of hydrogen, cadmium, or uranium. Some neutron-image-detection methods are insensitive to gamma rays or x-rays and can be used to inspect radioactive materials such as reactor fuel elements. The high attenuation of hydrogen, in particular, opens many application possibilities, including inspection of assemblies for detection of adhesives, explosives, lubricants, water, hydrides, corrosion, plastic, or rubber. Neutron Sources

The excellent discrimination capabilities of neutrons generally refer to neutrons of low energy--that is, thermal neutrons. Characteristics of neutron radiography corresponding to various ranges of neutron energy are summarized in Table 8. Although any of these energy ranges can be used for radiography, this article emphasizes the thermal-neutron range, which is the most widely used for inspection.

Table 8 Characteristics of neutron radiography at various neutron-energy ranges Type of neutrons Cold

Energy range Below 0.01 eV

Thermal

0.01 to 0.3 eV 0.3 eV to 10 keV 10 keV to 20 MeV

Epithermal Fast

Characteristics High-absorption cross sections decrease transparency of most materials, but also increase efficiency of detection. An advantage is reduced scatter at energies below the Bragg cutoff, where neutrons can no longer undergo Bragg reflection. Good discrimination between materials and ready availability of sources. Excellent discrimination for particular materials by working at energy of resonance. Greater transmission and less scatter in samples containing materials such as hydrogen and enriched reactor fuels. Good point sources are available. At low-energy end of spectrum, fast-neutron radiography may be able to perform many inspections done with thermal neutrons, but with a panoramic technique. Good penetration capability because of low-absorption cross sections in all materials. Poor material discrimination

In thermal-neutron radiography, an object (test piece) is placed in a thermal-neutron beam in front of an image detector. The neutron beam may be obtained from a nuclear reactor, a radioactive source, or an accelerator. Several characteristics of these sources are summarized in Table 9. For thermal-neutron radiography, fast neutrons emitted by these sources must first be moderated and then collimated. The radiographic intensities listed in Table 9 typically do not exceed 10-5 times the total fast-neutron yield of the source. Part of this loss is incurred in moderating the neutrons, and the remainder in bringing a collimated beam out of a large-volume moderator.

Table 9 Several characteristics of thermal-neutron sources Type of source

Radioisotope Accelerator Subcritical assembly Nuclear reactor

(a)

Typical radiographic intensity(a) 101-104

Resolution

103-106 104-106

Poor medium Medium Good

105-108

Excellent

to

Exposure time

Characteristics

Long

Stable operation, low to medium investment cost, possibly portable

Average Average

On-off operation, medium cost, possibly transportable Stable operation, medium to high investment cost, movement difficult Medium to high investment cost, movement difficult

Short 2

Neutrons per cm per second

Collimation is necessary for thermal-neutron radiography because there are no useful point sources of low-energy neutrons. Good collimation in thermal-neutron radiography is comparable to small focal-spot size in conventional radiography; the images of thick objects will be sharper with good collimation. Conversely, it should be noted that available neutron intensity decreases with increasing collimation. Neutron Detection Methods Detection methods for neutron radiography generally make use of photographic or x-ray films. In the direct-exposure method, film is exposed directly to the neutron beam, with a conversion screen or intensifying screen providing secondary radiation that actually exposes the film. Alternatively, film can be used to record an autoradiographic image from a radioactive, image, carrying screen in a technique called the transfer method. Direct-Exposure Method. Conversion screens of thin gadolinium foil or a scintillator have been most widely used in

the direct-exposure method. When bombarded with a beam of neutrons, some of the gadolinium atoms absorb neutrons and promptly emit gamma rays and internal conversion electrons. Scintillators are fluorescent screens, often made of zinc sulfide crystals that also contain a specific isotope such as 3Li6 or 5B10. Gadolinium oxysulfide, a scintillator originally developed for x-ray radiography, has been widely used for neutron radiography.

Scintillators provide useful images with total exposures as low as 5 × 105 neutrons per cm2. The high speed and favorable relative response make scintillators attractive for use with nonreactor neutron sources. Gadolinium screens provide greater uniformity and image sharpness (high-contrast resolution of 10 m has been reported), but an exposure about 30 or more times that of a scintillator is required, even with fast films. Transfer Method. In the transfer method, a thin sheet of metal, typically of indium or dysprosium, is exposed to the

neutron beam transmitted through the specimen. Neutron capture induces radioactivity--indium having a half-life of 54 min and dysprosium a half-life of 2.35 h. The "radiograph" to be interpreted is made by placing the radioactive transfer screen in contact with a sheet of film. Beta-particles and gamma-rays from the transfer screen expose the film. The transfer method is especially valuable for inspection of a radioactive specimen. Although radiation emitted by the specimen (especially gamma rays) causes heavy film fogging during x-ray radiography or direct-exposure neutron radiography, the same radiation will not induce radioactivity in a transfer screen. Thus, a clear image of the specimen can be obtained even when there is a high level of background radiation. In comparing the two primary detection methods, the direct-exposure method offers high speed, indefinite imageintegration time and the best spatial resolution. The transfer method offers insensitivity to gamma rays emitted by the specimen and greater contrast because of lower amounts of scattered and secondary radiation. Real-time imaging, in which light from a scintillator is observed by a television camera, also can be used for neutron

radiography. Because of low brightness, most real-time neutron radiographic images are enhanced by an image-intensifier tube, which may be separate or integral with a television camera. This method can be used for applications such as the study of fluid flow in a closed system such as a heat pipe or engine or the study of metal flow in a mold during casting. Applications Various applications that are discussed in ASTM STP 586 emphasize the value of neutron radiography for inspection of ordnance, explosive, aerospace, and nuclear components. The presence, absence, or correct placement of explosives, adhesives, O-rings, plastic components, and similar materials can be verified. The presence of fluids or corrosion can be detected. Nuclear fuel and control materials can be inspected to determine distribution of isotopes and to detect foreign or imperfect material. Hydride deposition in metals and diffusion of boron in heat treated boron-fiber composites can be observed. The characteristics of neutron radiography complement those of conventional x-radiography; one radiation provides a capability lacking or difficult for the other.

Thermal Inspection Introduction THERMAL INSPECTION comprises inspection by all methods in which heat-sensing devices or substances are used to detect irregular temperatures. Thermal inspection of workpieces can be used to detect flaws and to detect undesirable distribution of heat during service. There are several methods of thermal inspection and many types of temperaturemeasuring devices and substances. This article, however, is limited mainly to the discussion of: • •

Thermography, which is the mapping of isotherms, or contours of equal temperature, over a test surface Thermometry, which is the measurement of temperature.

These techniques are separated into two categories: (a) direct contact, in which a thermally sensitive device or material is placed in physical and thermal contact with the test piece; and (b) noncontact techniques that depend on thermally generated electromagnetic energy radiated from the test piece.

Contact Thermographic Inspection

Contact thermographic inspection consists of coating the surface of the test piece with a material that reacts to a change in temperature by changing color or other aspect of appearance. The reaction may be permanent or reversible. Many coatings having reversible reactions can be recovered for reuse. The most commonly used materials for contact thermographic inspection can be classified as heat-sensitive paints, heatsensitive papers, thermal phosphors, liquid crystals, and other temperature-sensitive coatings. Material coatings are relatively low in cost and simple to apply, but they may have the disadvantage of providing qualitative temperature measurements (the exception is coatings with liquid crystals, which can be calibrated to show relatively small changes in temperature). Another disadvantage of coatings is that they may change the thermal characteristics of the surface. Cholesteric liquid crystals are greaselike substances that can be blended to produce compounds having color

transition ranges at temperatures from -20 to 250 °C (-5 to 480 °F). Liquid crystals can be selected to respond in a temperature range for a particular test and can have a color response for temperature differentials of 1 to 50 °C (2 to 90 °F). When illuminated with white light while in their color response range, liquid crystals will scatter the light into its component colors, producing an iridescent color that changes with the angle at which the crystals are viewed. Outside this color response range, liquid crystals are generally colorless. The response time for the color change varies from 30 to 100 ms. This is more than adequate to allow liquid crystals to show transient changes in temperature. The spatial resolution obtainable can be as small as 0.02 mm (0.0008 in.). In addition, because the color change is generally reversible, anomalies can be evaluated by repeating the test as many times as needed. Techniques for applying liquid crystals are relatively straightforward once the proper blend of compounds is selected. Because liquid crystals function by reflecting light, they are more readily seen when used against a dark background. Therefore, if the specimen is not already dark, covering the surface with a removable, flat-black coating is strongly recommended before application. The crystals can then be applied by pouring, painting, spraying, or dipping. Care must be taken that the specimen or the coating is not attacked by the solvent base used with the liquid crystals. The applied film of liquid crystals must be of uniform thickness to prevent color irregularities caused by thickness differences rather than temperature differences. A good film thickness is about 0.02 mm (0.0008 in.). Successive layers used to build up the film thickness should not be allowed to dry between coats. A coating of proper thickness will have a uniform, low-gloss appearance when viewed with oblique illumination. Thermally quenched phosphors are organic compounds that emit visible light when excited by ultraviolet light. The

brightness of a phosphor is inversely proportional with temperature over a range from room temperature to about 400 °C (750 °F), as indicated in Fig. 1. Some phosphors exhibit a change in brightness of as much as 25%/°C (14%/°F). An individual phosphor should be selected to cover the temperature range used for a particular inspection. The coating is applied by painting a well-agitated mixture of the phosphor onto the surface to a thickness of about 0.12 mm (0.0047 in.).

Fig. 1 Relative brightness of four thermally quenched phosphors (U.S. Radium Radelin phosphor numbers) as a function of temperature

Heat-sensitive paints that are effective from 40 to 1600 °C (about 100 to 2900 °F) are available. Some of these paints

undergo several color transitions as their temperature is increased, and, under favorable conditions, an accuracy of ±5 °C

(±9 °F) is attainable with them. These paints have been used effectively for monitoring isotherms in heat-affected zones during welding, for monitoring preheating prior to welding, and for inspecting castings for porosity. Heat-Sensitive Papers. Several types of heat-sensitive papers have been used in nondestructive inspection. They are

applied by bonding directly to the surface of the test piece, or by means of a vacuum holddown arrangement. One type consists of a porous paper coated with an organic compound. A finely divided white pigment is applied to a highly absorptive black paper in a binder soluble in a solvent that does not dissolve the pigment. When the melting temperature of the pigment is reached, the paper absorbs the coating and the initial white color is replaced by a black appearance. These papers are used to indicate when a specific temperature has been reached.

Noncontact Thermographic Inspection A large number of devices will respond to the radiant energy in the infrared bandwidth produced by an object at a temperature above absolute zero and convert it to a proportional electric signal that then may be displayed. Infrared imaging equipment is available with a wide range of capabilities. The simplest systems are responsive to the near-infrared portion of the optical spectrum. These include night-vision devices and vidicon systems with silicon or lead sulfide sensors. Silicon sensors provide sensitivity for temperatures above 425 °C (800 °F), while lead sulfide sensors respond to temperatures above 200 °C (400 °F). There are two basic types of infrared detectors: photon-effect devices and thermal devices. The response of the photoneffect devices depends on the wavelength of the received radiation; therefore, the output signal depends on the wavelength of the infrared signal. Thermal detectors respond only to the heating caused by the incoming radiation, and the output signal is largely independent of the radiation wavelength. At certain wavelengths, the photon-effect devices will produce a much larger signal than thermal detectors. Hand-held infrared scanners are portable imaging systems capable of responding in the far-infrared portion of the

optical spectrum (wavelengths of 8 to 12 m). This range is emitted by objects at or near room temperature. In general, hand-held scanners have poor imaging qualities and are not suitable for the accurate measurement of local temperature differences. However, they can be useful for detecting hot spots, such as over-heated components, thermal runaway in an electronic circuit, or unextinguished fires. High-resolution infrared imaging systems are required for most part inspection applications. These systems use

either pyroelectric vidicon cameras with image-processing circuitry or cryogenically cooled mechanical scanners to provide good-quality image resolution (150 pixels, or picture elements, per scan line) temperature sensitivity to 0.1 °C (0.2 °F). In addition to good image resolution and temperature sensitivity, response times of the order of 0.1 s or less facilitate the detection of transient temperature changes or differentials. These imaging systems will use either a gray scale or a color scale correlated to temperature ranges to depict the temperature distribution within the image. Thermal wave interferometer systems combine modulated laser excitation with rapid phase and amplitude

sensing that can be scanned across a surface to produce an image. One application for this type of system is the inspection of plasma-sprayed coatings. The system senses the interaction between the thermal waves of the laser and the thermal variations from coating defects and thickness variations.

Contact Thermometric Inspection There are several basic thermal detectors: bolometers, thermistors, thermocouples, and thermopiles. For the most part, they can be used either in direct contact with the test item or as radiation detectors (noncontact applications). These devices can detect infrared radiation of both short and long wavelengths, and very low-temperature or low-radiation levels without cryogenic cooling. Bolometers are thermal detectors that are based on the principle that the resistance of a material changes as it is heated.

The bolometer allows the radiation to impinge on a very fine wire or a thin metallic film, blackened to increase absorption. The change in resistance is then a direct function of the radiation absorbed. The temperature coefficient of a bolometer is from 0.3 to 0.5%/°C. Thermocouples. A thermocouple consists of a junction of two dissimilar metals. As the junction temperature is raised,

a thermoelectric electromotive force is produced. Thermocouples are always used in pairs in a bridge circuit so that the

measured temperature is a direct function of the electromotive force produced by the sensing thermocouple as subtracted from the electromotive force produced by a reference thermocouple held at a known temperature. Thermopiles. A thermopile is merely a series of thermocouple junctions; it produces an increase in electromotive force as a direct function of the number of junctions. Meltable Substances. Waxlike crayons that melt at temperatures in the range of 38 to 1760 °C (100 to 3200 °F) are

commercially available. Such a crayon has a melting point within a nominal tolerance of ±1% of its rated temperature value. These crayons are normally used by making a mark with one or more of them on a surface before it is heated.

Noncontact Thermometric Inspection The temperature-measuring devices used in noncontact thermometric inspection depend on response of a thermal detector to infrared radiation. They are particularly useful when it is necessary to monitor or measure surface temperatures remotely. Radiometers are instruments used to measure incident radiation. They consist of some type of hollow cavity with an

aperture in one end and a thermal detector mounted internally. The thermal detector is so located that the radiation is focused on it. Because thermal detectors have a uniform response without regard to infrared wavelength, a radiometer is often used to measure total radiation. If the radiometer has a lens system, it will be restricted to the infrared-transmission characteristics of the lenses. Pyrometers (or infrared thermometers) are used in nondestructive testing in much the same way as are infrared

scanning devices. These instruments have less accuracy than other scanning devices, but they are simpler, more rugged, more portable, and less expensive. A wide variety of this type of equipment is commercially available, with a corresponding variety of performance.

Applicability Thermal methods can be useful in the detection of subsurface flaws or voids, provided the depth of the flaw is not large compared to its diameter. Thermal inspection becomes less effective in the detection of subsurface flaws as the thickness of an object increases because the possible depth of the defects increases. Thermal inspection is applicable to complex shapes or assemblies of similar or dissimilar materials and can be used in the one-sided inspection of objects. Moreover, because of the availability of infrared sensing systems, thermal inspection can also provide rapid, noncontact scanning of surfaces, components, or assemblies. Thermal inspection does not include those methods that use thermal excitation of a test object and a nonthermal sensing device for inspection. For example, thermally induced strain in holography or the technique of thermal excitation with ultrasonic or acoustic methods does not constitute thermal inspection.

Holography Introduction HOLOGRAPHY is basically a two-step process for creating a whole image--that is, a three-dimensional image--of a diffusely reflecting object having some arbitrary shape. In the first step, both the amplitude and phase of any type of coherent wave motion emanating from the object are recorded by encoding this information in a suitable medium. This recording is called a hologram. At a later time, the wave motion is reconstructed from the hologram by a coherent beam in a process that results in the regeneration of an image having the true shape of the object. The utility of holography for nondestructive inspection of metal components and metal-containing structures lies in the fact that this regenerated image can then be used as a kind of three-dimensional template against which any deviations in the shape or dimensions of the object can be observed and measured.

In principle, holography can be performed with (a) any wave radiation encompassed in the entire electromagnetic spectrum, (b) any particulate radiation, such as neutrons and electrons, that possesses wave-equivalent properties; and (c) nonelectromagnetic wave radiation, such as sound waves. The two methods currently available for practical nondestructive inspection are optical holography, using visible light waves, and acoustical holography, using ultrasonic waves.

Optical Holography Optical holographic interferometry has been successfully used both in research and testing applications as a noncontacting tool for displacement, strain and vibration studies, depth-contour mappings, and transient/dynamic phenomena analyses. Specific applications of optical holography in nondestructive evaluation include: • • • •

Detection of debonds within honeycomb-core sandwich structures Detection of unbonded regions within pneumatic tires and other laminates Detection of cracks in hydraulic fittings Qualitative evaluation of turbine blades

Applicability The advantages of using optical holographic interferometry for nondestructive inspection include the following:

•

• • •

•

•

•

•

It can be applied to any type of solid material--ferromagnetic or nonferromagnetic; metallic, nonmetallic, or composite; electrically or thermally conductive or nonconductive; and optically transparent or opaque It can be applied to test objects of almost any size and shape, provided a suitable mechanism exists for stressing or otherwise exciting the object. Pulsed-laser techniques allow the inspection of test objects in unstable or hostile environments. It has an inherent sensitivity to the displacement or deformation of at least one-half an optical wavelength, or about 125 nm (1250 ). This permits the use of low levels of stress during inspection. Further, special analysis techniques can provide improved sensitivity of almost 1000 fold. It does not rely on data acquisition by either point-by-point determinations or scanning processes; instead, three-dimensional images of interference fringe fields are obtained of the entire surface (front, back, and internal, if desired) or a large fraction thereof. It allows flexibility of readout. For example, in flaw detection applications, the images can be examined purely qualitatively for localized fringe anomalies within the overall fringe field. If, conversely, the application involves the strain analysis of an object subjected to a specific type of stress, the image can be analyzed to yield a highly quantitative point-by-point map of the resulting surface displacements. It permits comparison of the responses of an object to two different levels of stress or other excitation. The frame of reference for this differential measurement is usually, but not always, the unstressed or natural state of the test object. This differential type of measurement contrasts with absolute types, which are made without a frame of reference, and with comparative measurements, in which a similar but different object is used as a frame of reference. The interferograms can be reconstructed at any later time to produce three-dimensional replicas of the previously recorded test results.

The disadvantages of using optical holographic interferometry for nondestructive inspection include the following:

•

•

Although no physical contact with the test object is required to effect the interaction of the coherent light with either the test object or the photographic plate, it is often necessary to provide fixturing not only for the test object but also for the stressing source. The success of a holographic inspection procedure depends largely on the adequacy of design and the practical performance of both the fixturing and the stress-imparting mechanisms. It is limited to test objects with wall or component thicknesses that will offer sufficiently large

• •

•

•

•

•

displacements without requiring stressing forces that will cause rigid-body movement or damage to the object. For sandwich structures, the thickness of the skin is the limiting factor; the maximum skin thickness that can be tested is a function of the stressing method. Holographic methods are best suited to diffusely reflecting surfaces with high reflectivity. Removable coatings are often sprayed onto strongly absorbing materials and specularly reflecting surfaces Although holographic interferometry is capable of accurately locating a flaw within the surface area of the test object being inspected, the cross-sectional size of the flaw can often be only approximately determined, and information concerning the depth of the flaw, when obtainable at all, is qualitative in nature. Where visual interpretation of interferograms is to be performed, holographic interferometry may be limited in its dynamic range for some applications. However, electronic methods for fringe interpretation have been used to provide increased sensitivity and dynamic range. Test results sometimes cannot be analyzed because of the localization of the interference fringes in space rather than on the surface of the test object (in real-time holographic interferometry) or on the reconstructed image of the object (in double-exposure holographic interferometry). With the exception of holographic-contouring applications, holographic interferometry is currently limited to differential tests, in which the object is compared to itself after it has been subjected to changes in applied stress. Comparative tests, in which a given object can be compared to a standard object, are not feasible with holographic interferometry because of inherent random variations in test object surfaces. Personnel performing holographic inspection must be properly trained. The greater the sophistication of the equipment, the greater the required operating skill.

Optical Holography Method Holographic Recording. When visible lightwaves are used, the hologram is recorded with an optical system called a

holocamera (see Fig. 1a). A monochromatic laser beam of phase-coherent light is divided into two beams by a variable beam splitter. One beam, the object beam, is expanded by a spatial filter into a divergent beam directed to illuminate the object uniformly. A portion of the laser light reflected from the object is intercepted by a high-resolution photographic plate, as shown in Fig. 1(a). The second beam, the reference beam, originating from the beam splitter is directed by a mirror, diverges from a second spatial filter, and is directed onto the photographic plate by a second mirror. With either object beam or reference beam absent, a uniformly exposed photographic plate will result. However, with both coherent beams falling on the plate simultaneously, an interference pattern is generated as a result of the coherent interaction of the two beams, and this pattern is recorded by the photographic emulsion.

Fig. 1 Schematic diagrams of the basic optical systems used in continuous-wave holography: (a) holocamera used to record hologram of an object on a photographic plate and (b) optical system for reconstructing a virtual image of the object from the hologram on the photographic plate

Holographic Reconstruction. In the reconstruction process, which is illustrated in Fig. 1(b), the hologram is used as a diffraction grating. When it is illuminated with the reference beam only, three beams emerge--a zero-order, or undeflected, beam and two first-order diffracted beams. The diffracted beams produce the real and virtual images of the object to complete the holographic process. The real image is pseudoscopic, or depth inverted, in appearance. Hence, the virtual image (also referred to as the true, primary, or nonpseudoscopic image) is the image that is of primary interest in practical applications of holography. In Fig. 1(b), only the first-order diffracted beam that yields the virtual image is shown, the other two beams having been omitted from the figure for the sake of clarity. If the original object is threedimensional, the virtual image is a genuine three-dimensional replica of the object, possessing both parallax and depth of focus. However, if the configuration of the optical system or the wavelength of light used during reconstruction differs from that used during recording, distortion, aberration, and changes in magnification can occur. (The holographic recording and reconstruction systems can be designed to minimize these effects.) Interferometric Techniques of Inspection. When optical holography is applied to inspection of parts, generation

of a three-dimensional image of the object, per se, is of little value. Furthermore, for opaque materials, optical holography is strictly limited to surface observations. Hence, if optical holography is to be used for nondestructive inspection, supplementary means must be used to either stress or otherwise excite test objects to produce surface manifestations of the feature of interest. It is for measurement of such manifestations that the techniques of optical holography have been further developed to form the subfield of holography termed optical holographic interferometry. As in conventional interferometry, holographic interferometric measurements can be made with great accuracy (to within a fraction of the wavelength of the light being used). Whereas conventional interferometry is usually restricted to the examination of objects having highly polished surfaces and simple shapes, holographic interferometry can be used to examine objects of arbitrary shape and surface condition. Because holographic interferometry produces a three-

dimensional fringe-field image, which can be examined from many different perspectives (limited only by the size of the hologram), a single holographic interferogram is equivalent to a series of conventional two-dimensional interferograms. In contrast to conventional interferometry, which must be performed in real time, holographic interferometry can be performed either in real time or at two different times (time-lapse technique). In the time-lapse technique, advantage is taken of the fact that more than one hologram may be made on the same recording medium. Examples of this approach include the double-exposure, multiple-exposure, and continuous-exposure techniques.

Acoustical Holography Acoustical holography is the extension of holography into the ultrasonic domain. The principles of acoustical holography are the same as those of optical holography because the laws of interference and diffraction apply to all forms of radiation obeying the wave equation. Differences arise only because the methods for recording and reconstructing the hologram must accommodate the form of radiation used. This need to accommodate the form of radiation restricts the practical range of sound-wave frequency that can be used in acoustical holography. At present, only two types of basic systems for acoustical holography are available--the liquid-surface type and the scanning type. These utilize two different detection methods, and these methods in turn dictate the application of the systems to nondestructive inspection. Neither of these two types of systems relies on the interferometric techniques of optical holographic inspection, where information on flaws at or near the surface of a test object is obtained from the pattern formed by interference between two nearly identical holographic images that are created while the object is differentially stressed. Instead, systems for acoustical holography obtain information on internal flaws directly from the image of the interior of the object. Liquid-Surface Acoustical Holography. The basic system for liquid-surface acoustical holography is similar to the

basic system for optical holography, except for the method of read out. In liquid-surface systems, two separate ultrasonic transducers supply the object beam and reference beam, which are usually pulsed. The two transducers and the test object are immersed in a water-filled tank. The test object is positioned in the object plane of an acoustic (ultrasonic) lens, which also is immersed in the tank. The practical limits for the object-beam transducer in a commercial system are a wave frequency of 1 to 10 MHz, a pulse length of 50 to 300 microseconds, and a pulse-repetition rate of 60 to 100 per second. This transducer is placed so that its beam passes through the test object. As the object beam passes through the test object, it is modified by the object. The modification is generally in both amplitude and phase. The object beam then passes through an acoustic lens, which focuses the image of the test object at the liquid surface. This image contains a wave front nearly identical to that emanating from the test object. The reference-beam transducer is connected to the same oscillator as the object-beam transducer so that it emits a second wave front coherent with the wave front from the object-beam transducer. The reference-beam transducer is aimed at the same region of the liquid surface as the object beam, where the wave fronts interfere. The image is reconstructed from the hologram by reflecting a beam of coherent light from the ripple pattern in the isolation tank. Scanning Acoustical Holography. The basic system for scanning acoustical holography is shown in Fig. 2. No

reference-beam transducer is required in this system because electronic phase detection is used to produce the hologram: that is, the required interaction (mixing) between the piezoelectrically detected object-beam signal and the simulated reference-beam signal occurs in the electronic domain. A pulser circuit--consisting of a continuous-wave oscillator and a pulse gate that is triggered by an electronic clock--and a power amplifier feed a single focused ultrasonic transducer that is scanned over an area above the test object while alternately transmitting and receiving the ultrasonic signals. The transducer and the test object are immersed in a water-filled tank, as in Fig. 2(b), or they are coupled by a water column.

Fig. 2 Diagrams of the basic system used in nondestructive inspection by scanning acoustical holography. See text for description. (a) Ultrasonic and light portions of systems. (b) Scanning and recording portions of system

The signal is pulsed so that time gating can be used to reject undesired surface echoes. The pulse length may be set to any desired value from a few periods of the wave frequency to an upper limit of 50% of the time between successive pulses. Long pulse lengths are used to examine regions lying deep within the metal, while short pulse lengths are required for the regions near the surface so that transmitted energy is not mixed with reflected energy. The practical limits of the transducer in a commercial system are a wave frequency of 1 to 10 MHz, a pulse length of 5 to 20 microseconds, and a pulse-repetition rate of 500 to 1000 per second. The frequency band of a given transducer is relatively narrow (±5% of the mean frequency). The echo from the flaw is received by the transducer and processed by a time-interval counter or a pair of balanced mixers in quadrature. The resulting data are digitized and entered into the computer. As the transducer scans a rectangular area, a matrix of complex numbers accumulates in the computer. This matrix represents the phase and amplitude of the reflected wave taken on a set of sample points. Comparison of Liquid-Surface and Scanning Systems. The outstanding feature of the liquid-surface system of

acoustical holography is that it provides a real-time image, whereas the image provided by the scanning system requires reconstruction. The real-time feature makes the liquid-surface system suitable for rapid inspection of large amounts of material on a continuous basis. In contrast, inspection with the scanning system is relatively slow. Photographic or videotape records for later study may be made with either system. The outstanding feature of the scanning system is its ability to determine accurately the position and dimensions of flaws lying deep in opaque test objects, especially when only one side of the object is accessible. (In contrast to the scanning system, the liquid-surface system is usually operated in the transmission mode, which requires access to both sides of the test object.) Although both systems offer about the same resolution, the sensitivity of the scanning system is greater by a factor of about 106. The excellent flaw-measuring ability of the scanning system can be used to characterize accurately the flaws detected previously by faster inspection methods, such as scanning with a conventional ultrasonic search unit.

Another important feature of the scanning system is that the commercial equipment for this system is usually transportable, whereas liquid-surface equipment is usually stationary. In addition, scanning transducers can be coupled to very large test objects by water columns, whereas inspection by the liquid-surface system usually requires that the test objects be small enough to be placed in a water-filled tank and completely immersed. A useful advantage of the scanning system is its capability of selectively producing either longitudinal or shear waves in the volume of metal under examination, by adjustment of the angle of incidence of the incoming ultrasonic beam.

Mechanical Testing Hardness Testing

HARDNESS is a term that has different meanings to different people: it is resistance to penetration to a metallurgist, resistance to wear to a lubrication engineer, a measure of flow stress to a design engineer, resistance to scratching to a mineralogist, and resistance to cutting to a machinist. Although these various definitions of hardness appear to differ significantly in character, they are all related to the plastic flow stress of the material. Table 1 lists the major types of hardness testers, which can be either portable instruments or laboratory devices. Only static indentation and rebound testing are discussed in this article. These two methods account for virtually all routine hardness testing in the metalworking industry. Static indentation hardness testing is the more widely used of the two methods, although rebound testing is extensively employed, particularly for hardness measurements on large workpieces or for applications in which visible or sharp impressions in the test surface cannot be tolerated.

Table 1 Classification of hardness testers Method Indentation: standard operation Vickers Rockwell Brinell Indentation: nonstandard operation Rockwell Vickers Brinell Indentation: equivalent hardness Static

Dynamic Other indentation methods UCI method Comparative hardness method Dynamic Reaction force Rebound

Type Macroindentation or microindentation Macroindentation Macroindentation Low-load Low-load Calibrated pin system (static or dynamic) "Press-and-read" type (mechanical or electronic) "Scissors" type Clamp type Cylinder type ... Cylinder type Horizontal bar type Piezo-electric crystal principle Mechanical Electronic (EQUO) method

Source: P.F. Aplin, Classification and Solution of Portable Hardness-Testing Equipment, Non-Destructive Testing, Vol 1, Elsevier

Brinell Hardness Testing The Brinell hardness test is basically simple, and it consists of applying a constant load, usually 500 to 3000 kg, on a hardened steel ball-type indenter, 10 mm in diameter, to the flat surface of a workpiece (Fig. 1). The 500 kg load is usually used for testing nonferrous metals, such as copper and aluminum alloys, whereas the 3000 kg load is most often used for testing harder metals, such as steels and cast irons. The load is held for a specified time (10 to 15 s for iron or steel and about 30 s for softer metals), after which the diameter of the recovered indentation is measured in millimeters. This time period is required to ensure that plastic flow of the work metal has stopped.

Fig. 1 Sectional view of a Brinell indenter, showing the manner in which the application of force by the indenter causes the metal of the workpiece to flow

Hardness is evaluated by taking the mean diameter of the indentation (two readings at right angles to each other) and calculating the Brinell hardness number (HB) by dividing the applied load by the surface area of the indentation according to the following formula:

HB = L/( D/2)[D - (D2 - d2)1/2] where L is the load, in kilograms; D is the diameter of the ball, in millimeters; and d is the diameter of the indentation, in millimeters. It is not necessary, however, to make the calculation for each test. Such calculations are available in table form for all diameters of indentations in Section 1 of this Handbook. Highly hardened steel (or other very hard metals) cannot be tested by a hardened steel ball by the Brinell method, because the ball will flatten during penetration and a permanent deformation will take place. This problem is recognized in specifications for the Brinell tests. Tungsten carbide balls are recommended for Brinell testing materials of hardness from 444 HB up to about 627 HB (indentation of 2.45 mm in diameter). However, higher Brinell values will result when using carbide balls instead of steel balls because of the difference in elastic properties. Surface Preparation. The degree of accuracy that can be attained by the Brinell hardness test can be greatly

influenced by the surface smoothness of the workpiece being tested. The surface of the workpiece on which the Brinell indentation is to be made must be filed, ground, machined, or polished with emery paper (3/0 emery paper is suitable) so that the indentation diameter is clearly enough defined to permit its measurement. There should be no interference from tool marks. Indentation Measurement. The diameter of the indentation is measured by a microscope to the nearest 0.05 mm

(0.002 in.). This microscope contains a scale, and usually a built-in light, to facilitate easy reading. The indentations produced in Brinell hardness tests may exhibit different surface characteristics. These have been carefully studied and analyzed. In some instances there is a ridge around the indentation extending above the original surface of the workpiece. In other instances the edge of the indentation is below the original surface. Sometimes there is no difference at all. The first phenomenon is called a "ridging" type of indentation and the second a "sinking" type. Cold worked metals generally have the former type of indentation, and annealed metals the latter type.

Brinell Hardness Testers. Several types of testers that exert the prescribed force on the indenter are in general use.

The two general types are hydraulic analog testers and newer digital hardness testers. Digital hardness testers have better resolution than analog testers. The resolution of digital testers reduces or eliminates the need for extrapolation, but they are not as durable as analog testers. In statistical process control of Brinell testing, there is no adequate way to achieve high process capability indices (C p and Cpk values) without making the investment in state of the art optics that utilize frame grabbers to read the impression. It is possible to take several impressions on pieces and take the average of these impressions to get a point in a subgroup, but this method requires larger sample sizes and inspection costs increase. Many analog Brinell testers are typically manually operated hydraulic instruments like the one show in Fig. 2. The workpiece is placed on the anvil and raised, by means of the elevating screw, to a position near the indenter. Fingertip rotation of the control knob allows a selected force (in kilograms), indicated on the gage, to be applied. This force is held for a pre-established length of time and then released. The specimen is removed and the indentation measured. The entire cycle, including indenting and measurement, requires approximately one minute.

Fig. 2 Analog Brinell hardness tester

Portable Brinell Hardness Testers. Conventional Brinell hardness testers have limited use, for two reasons: (a) the workpieces to be tested must be brought to the testers, and (b) size and design of the workpieces must be such that they can be placed between the anvil and the indenter.

Some of the problems posed by these limitations can often be solved by use of a portable hardness tester. Hydraulic portable testers like the general design shown in Fig. 3 weigh no more than about 25 lb and can be easily transported to the workpieces. Smaller, digital testers are also available.

Fig. 3 Hydraulic, manually operated portable Brinell hardness tester

Spacing of Indentations. To ensure accurate results, indentations should not be made too close to the edge of the workpiece being tested. Lack of sufficient supporting material on one side of the workpiece will cause the resulting indentation to be large and unsymmetrical. It is generally agreed that the error in a Brinell hardness number is negligible

if the distance from the center of the indentation is not less than 2 indentation from any edge of the workpiece.

times (and preferably 3 times) the diameter of the

Similarly, indentations should not be made too close to one another. If indentations are too close together, the work metal may be cold worked by the first indentation, or there may not be sufficient supporting material for the second indentation. The latter condition would produce too large an indentation, whereas the former may produce too small an indentation. To prevent this, the distance between centers of adjacent indentations should be at least three times the diameter of the indentation. General Precautions. To avoid misapplication of Brinell hardness testing, the fundamentals and limitations of the test

procedure must be clearly understood. Further, to avoid inaccuracies, some general rules should be followed. Such rules include the following:

1. 2. 3. 4.

Indentations should not be made on a curved surface having a radius of less than 1 in. Spacing of indentations should be correct, as outlined above under "Spacing of Indentations." The load should be applied steadily to avoid overloading caused by inertia of the weights. The load should be applied in such a way that the direction of loading and the test surface are perpendicular to each other within 2°. 5. The thickness of the workpiece being tested should be such that no bulge or mark showing the effect of the load appears on the side of the workpiece opposite the indentation. In any event, the thickness of the specimen shall be at least ten times the depth of indentation. 6. The surface finish of the workpiece being tested should be such that the indentation diameter is clearly outlined.

Limitations. The Brinell hardness test has three principal limitations:

1. Size and shape of the workpiece must be capable of accommodating the relatively large indentations. 2. Because of the relatively large indentations, the workpiece may not be usable after testing.

3. The limit of hardness range--about 11 HB with the 500 kg load to 627 HB with the 3000 kg load--is generally considered the practical range.

Rockwell Hardness Testing Rockwell hardness testing is the most widely used method for determining hardness. There are several reasons for this distinction. The Rockwell test is simple to perform and does not require highly skilled operators. By use of different loads and indenters, Rockwell hardness testing can be used for determining hardness of most metals and alloys, ranging from the softest bearing materials to the hardest steels. A reading can be taken in a matter of seconds with conventional manual operation and in even less time with automated setups. No optical measurements are required (all readings are direct). Rockwell hardness testing differs from Brinell hardness testing in that the hardness is determined by the depth of indentation made by a constant load impressed upon an indenter. Although a number of different indenters are use for Rockwell hardness testing, the most common type is a diamond ground to a 120° cone with a spherical apex having a 0.2 mm radius, which is known as a Brale indenter (Fig. 4a).

Fig. 4 Rockwell indenter. (a) Diamond-cone Brale indenter (show at about 2×). (b) Comparison of old and new U.S. diamond indenters. The angle of the new indenter remains at 120° but has a larger radius closer to the average ASTM specified value of 200 m; the old indenter has a radius of 192 m. The indenter with the larger radius has a greater resistance to penetration of the surface.

The shape of the Rockwell diamond indenter most widely used in the United States is different from indenters in the rest of the world. The ASTM specification calls for a diamond cone radius of 200 ± 10 m (0.0079 in.), but in practice, it is closer to 192 m (0.0076 in.). While not out of tolerance, the old U.S. standard indenter is at the low end of the specification. In the United States, the diamond was first set at 192 m to match the nominal values of the hardness test blocks. However, the rest of the world has used a diamond size closer to 200 m (0.0079 in.). A comparison of the old (192 m) U.S. standard diamond indenter and the current (200 m tip) U.S. indenter is shown in Fig. 4(b). The larger radius increases the indenter's resistance to penetration into the surface of the testpiece. At higher HRC hardness, most of the indenter travel is along the radius; whereas at the lower hardnesses, more indenter travel is along the angle. This is why the hardness shift from old to new has been most significant in the HRC 63 range and not the HRC 25 range. Methods

As shown in Fig. 5, the Rockwell hardness test consists of measuring the additional depth to which an indenter is forced by a heavy (major) load (Fig. 5b) beyond the depth of a previously applied light (minor) load (Fig. 5a). Application of the minor load eliminates backlash in the load train and causes the indenter to break through slight surface roughness and to crush particles of foreign matter, thus contributing to much greater accuracy in the test. The basic principle involving minor and major loads illustrated in Fig. 5 applies to steel-ball indenters as well as to diamond indenters.

Fig. 5 Indentation in a workpiece made by application of (a) the minor load, and (b) the major load, on a diamond Brale indenter in Rockwell hardness testing. The hardness value is based on the difference in depths of indentation produced by the minor and major loads.

The minor load is applied first, and a reference or "set" position is established on the measuring device of the Rockwell hardness tester. Then the major load is applied at a prescribed, controlled rate. Without moving the workpiece being tested, the major load is removed and the Rockwell hardness number is automatically indicated on the dial gage. The entire operation takes from 5 to 10 s. Diamond indenters are used mainly for testing materials, such as hardened steels and cemented carbides. Steel-ball indenters available with diameters of aluminum alloys, and bearing metals.

,

,

, and

in., are used for testing materials, such as soft steel, copper alloys,

Rockwell Testers. There are two basic types of Rockwell hardness testers--regular and superficial. Both testers have

similar basic mechanical principles and significant components. Rockwell testers generally come with two different resolutions. The standard Rockwell analog tester (Fig. 6), which has been the industrial workhorse for years, has a resolution of 1.0 HRC. Many operators think they can improve resolution to 0.5 HRC or even 0.1 HRC by extrapolation, but this is not true. Extrapolation of readings only increases measurement error when several operators are checking parts.

Fig. 6 Principal components of a regular (normal) Rockwell hardness tester. Superficial Rockwell testers are similarly constructed.

As with Brinell testing, better resolution can be achieved by investing in digital testing equipment. The newer digital Rockwell testers (Fig. 7) have a resolution of 0.1 HRC, and they eliminate the need for extrapolation (guessing). Similar resolution can be obtained on portable digital testers.

Fig. 7 A digital Rockwell hardness tester

Regular Rockwell Hardness Testing. In regular Rockwell hardness testing, the minor load is always 10 kg. The

major load, however, can be 60, 100, or 150 kg. No Rockwell hardness value is expressed by a number alone. A letter has been assigned to each combination of load and indenter, as shown in Table 2. Each number is suffixed by first the letter H (for hardness), then the letter R (for Rockwell), and finally the letter that indicates the scale used. For example, a value of 60 on the Rockwell C scale is expressed as 60 HRC, and so on. Regardless of the scale used, the "set" position is the same; however, when the diamond Brale indenter is used, the readings are taken from the black divisions on the dial gage. When testing with any of the ball indenters, the readings are taken from the red divisions.

Table 2 Rockwell-hardness-scale designations for combinations of type of indenter and major load Scale designation

Indenter Type Diam, in. Regular Rockwell tester Ball B ... ... ...

Major load, kg

Dial figure

100

Red

150 60 100 100

Black Black Black Red

C A D E

Brale Brale Brale Ball

F

Ball

60

Red

G

Ball

150

Red

H

Ball

60

Red

K

Ball

150

Red

L

Ball

60

Red

M

Ball

100

Red

P

Ball

150

Red

R

Ball

60

Red

S

Ball

100

Red

V

Ball

150

Red

15 30 45 15

... ... ... ...

Superficial Rockwell Tester N Brale . . . 15N N Brale . . . 30N Brale ... 45N Ball 15T 30T

Ball

30

...

45T

Ball

45

...

15W

Ball

15

...

30W

Ball

30

...

45W

Ball

45

...

15X

Ball

15

...

30X

Ball

30

...

45X

Ball

45

...

15Y

Ball

15

...

30Y

Ball

30

...

45Y

Ball

45

...

One Rockwell number represents an indentation of 0.002 mm (0.00008 in.). Therefore, a reading of 60 HRC indicates indentation from minor to major load of (100 - 60) × 0.002 mm = 0.080 mm, or 0.0032 in. A reading of 80 HRB indicates an indentation of (130 - 80) × 0.002 mm = 0.100 mm, or 0.004 in. Superficial Rockwell hardness testing employs a minor load of 3 kg, but the major load can be 15, 30, or 45 kg.

Just as in regular Rockwell testing, the indenter may be either a diamond or a steel ball, depending mainly on the nature of the metal being tested. Regardless of load, the letter N designates use of the superficial Brale, and the letters T, W, X, and Y designate use of steel-ball indenters. Scale and load combinations are presented in Table 2. Superficial Rockwell

hardness values are always expressed with the number suffixed by a number and a letter that show the load/indenter combination. For example, if a load of 30 kg is used with a diamond indenter and a reading of 80 is obtained, the result is reported as 80 HR30N (where H means hardness, R means Rockwell, 30 means a load of 30 kg, and N indicates use of a diamond indenter). All tests are started from the "set" position. One Rockwell superficial hardness number represents an indentation of 0.001 mm or 0.00004 in. Therefore, a reading of 80 HR30N indicates indentation from minor to major load of (100 - 80) × 0.001 mm = 0.020 mm, or 0.0008 in. Dials on the superficial hardness testers contain only one set of divisions, which is used with all types of superficial indenters. Selection of Rockwell Scale Where no specification exists or there is doubt abut the suitability of a specified scale, an analysis should be made of those factors that influence the selection of the proper scale. These influencing factors are found in the following four broad categories: • • • •

Type of work metal Thickness of work metal Width of area to be tested Scale limitation

Influence of Type of Work Metal. The types of work metal normally tested using the different regular Rockwell hardness scales are given in Table 3. This information also can be helpful when one of the superficial Rockwell scales may be required. For example, note that the C, A, and D scales--all with diamond indenters--are used on hard materials, such as steel and tungsten carbide. Any material in this hardness category would be tested with a diamond indenter. The choice to be made is whether the C, A, D, or the 45N, 30N, or 15N scale is applicable. Whatever the choice, the number of possible scales has been reduced to six. The next step is to find a scale, either regular or superficial, that will guarantee accuracy, sensitivity, and repeatability of testing.

Table 3 Typical applications of regular Rockwell hardness scales Scale(a) B C A D E F G H K, L, M, P, R, S, V

(a)

Typical applications Copper alloys, soft steels, aluminum alloys, malleable iron Steel, hard cast irons, pearlitic malleable iron, titanium, deep case-hardened steel, and other materials harder than 100 HRB Cemented carbides, thin steel, and shallow case-hardened steel Thin steel and medium case-hardened steel and pearlitic malleable iron Cast iron, aluminum and magnesium alloys, bearing metals Annealed copper alloys, thin soft sheet metals Phosphor bronze, beryllium copper, malleable irons. Upper limit is 92 HRG to avoid flattening of ball. Aluminum, zinc, lead Bearing metals and other very soft or thin materials. Use smallest ball and heaviest load that do not give anvil effect. The N scales of a superficial hardness tester are used for materials similar to those tested on the Rockwell C, A, and D scales but of thinner gage or case depth. The T scales are used for materials similar to those tested on the Rockwell B, F, and G scales but of thinner gage. When minute indentations are required, a superficial hardness tester should be used. The W, X, and Y scales are used for very soft materials

Influence of Thickness of Work Metal. The metal immediately surrounding the indentation in a Rockwell hardness

test is cold worked, The depth of material affected during testing is on the order of ten times the depth of the indentation. Therefore, unless the thickness of the metal being tested is at least ten times the depth of the indentation, an accurate Rockwell hardness test cannot be expected.

The depth of indentation for any Rockwell hardness test can easily be computed; in practice, however, computation is not necessary, because tables of minimum thicknesses are available (for example, see Table 4). The values for minimum thickness do follow the 10-to-1 ratio in some ranges, but they are actually based on experimental data accumulated on various thicknesses of low-carbon steels and of steel strip that has been hardened and tempered.

Table 4 Minimum work-metal hardness values for testing various thicknesses of metals with regular and superficial Rockwell hardness testers Metal thickness, in.

0.005 0.006 0.008 0.010 0.012 0.014 0.015 0.016 0.018 0.020 0.022 0.024 0.025 0.026 0.028 0.030 0.032 0.034 0.035 0.036 0.038 0.040

Minimum hardness for superficial hardness testing Diamond Brale indenter Ball indenter, in. 15N 30N 45N 15T 30T 45T (15 kg) (30 kg) (45 kg) (15 kg) (30 kg) (45 kg) ... ... ... 93 ... ... 92 ... ... ... ... ... 90 ... ... ... ... ... 88 ... ... 90 87 ... 83 82 77 ... ... ... 76 80 74 ... ... ... ... ... ... 78 77 77 68 74 72 ... ... ... (a) 66 68 ... ... ... (a) (a) 57 63 58 62 (a) 47 58 ... ... ... (a) (a) 51 ... ... ... (a) (a) ... ... ... 26 (a) (a) 37 ... ... ... (a) (a) 20 ... ... ... (a)

(a)

(a)

(a)

(a)

(a)

(a)

(a)

(a)

(a)

(a)

(a)

... ...

... ...

... ...

...

...

...

(a)

(a)

(a)

(a)

(a)

(a)

(a)

(a)

(a)

... ...

... ...

... ...

(a)

(a)

(a)

(a)

(a)

(a)

Minimum hardness for regular hardness testing Diamond Brale indenter Ball indenter, in. A D C F B G (60 kg) (100 kg) (150 kg) (60 kg) (100 kg) (150 kg) ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 86 ... ... ... ... ... 84 ... ... ... ... ... 82 77 ... 100 ... ... 78 75 69 ... ... ... 76 72 67 ... ... ... ... ... ... 92 92 90 71 68 65 ... ... ... 67 63 62 ... ... ... 60 58 57 67 68 69 (a) 51 52 ... ... ... (a) 43 45 ... ... ... (a) ... ... ... 44 46 (a) (a) 37 ... ... ... (a) (a) 28 ... ... ... (a) (a) (a) 20 20 22

These values are approximate only and are intended primarily as a guide: see test for example of use. Materials thinner than shown may be tested on a Tukon microhardness tester. The thickness of the workpiece should be at least 1 indentation when using a Vickers indenter, and at least

(a)

times the diagonal of the

times the long diagonal when using a Knoop indenter.

No minimum hardness for metal of equal or greater thickness.

To use the values in Table 4, assume that it is necessary to check the hardness of a strip of steel 0.014 in. thick, of an approximate hardness of 63 HRC. According to Table 4, material having a hardness of 63 HRC must be approximately 0.028 in. thick for an accurate test using the C scale. Therefore, this steel strip should not be tested on the C scale. At this point, check the approximate converted hardness on the other Rockwell scales equivalent to 63 HRC. These values taken from a conversion table are 83 HRA, 70 HR45N, 80 HR30N, and 91 HR15N. Referring again to Table 4 for hardened 0.014 in. thick material, there are only three Rockwell scales to choose: 45N, 30N, and 15N. The 45N scale is not suitable because the material should be at least 74 HR45N. On the 30N scale, 0.014 in. thick material must be at least 80 HR30N, and the material at hand is 80 HR30N. On the 15N scale, the material must be at least 76 HR15N, and this material is 91.5 HR15N. Therefore, either the 30N or 15N scale may be used. After all limiting factors have been eliminated, and a choice exists between two or more scales, the scale applying the heavier load should be used. The heavier load will produce a larger indentation, covering a greater portion of the material, and a Rockwell hardness number more representative of the material as a whole will be obtained. In addition, the heavier the load, the greater the sensitivity of the scale. Checking any conversion table and comparing the 15N scale to the 30N scale will show that in the hard-steel range a difference in hardness of one point on the 30N scale represents a difference of only 0.5 point on the 15N scale. Therefore, smaller differences in hardness can be detected when using the 30N scale.

This approach would also apply in determining which scale should be used to measure the hardness of a case of known approximate depth and hardness. Influence of Test-Area Width. In addition to the limitation of indentation depth for a workpiece of given thickness and hardness, there is a limiting factor on the minimum width of material. If the indentation is placed too close to the edge of a workpiece, the edge will deform outward and the Rockwell hardness number will be decreased accordingly.

Experience has shown that the distance from the center of the indentation to the edge of the workpiece must be at least 2 times the diameter of the indentation to ensure an accurate test. Therefore, the width of a narrow test area must be at least five indentation diameters when the indentation is placed in the center. Limitations of Rockwell Scales. The potential range of each Rockwell scale can be determined readily from the dialgage divisions on the tester: the black scale (for diamond indenter) on all regular hardness-tester dial gages is numbered from 0 to 100, with 100 corresponding to the "set" position; the red scale (for ball indenters) is numbered from 0 to 130, with 130 being the "set" position. On the superficial hardness tester, the dial gage has only one set of divisions, numbered from 0 to 100.

Use of the diamond indenter when readings fall below 20 is not recommended, because there is loss of sensitivity when indenting this far down the conical section of the indenter. Brale indenters are not calibrated below values of 20; and if used on soft materials, there is no assurance that there will be the usual degree of agreement in results when replacing the indenters. Support for Workpiece. A fundamental requirement of the Rockwell hardness test is that the surface of the workpiece

being tested be approximately normal to the indenter and that the workpiece must not move or slip in the slightest degree as the major load is applied. The depth of indentation is measured by the movement of the plunger rod holding the indenter; therefore, any slipping or moving of the workpiece will be followed by the plunger rod and the motion transferred to the dial gage, causing an error to be introduced into the hardness test. As one point of hardness represents a depth of only 0.00008 in., a movement of only 0.001 in., could cause an error of over 10 Rockwell numbers. The support must be of sufficient rigidity to prevent its permanent deformation in use. Standardized Hardness Values In 1990, after several meetings between the American Society for Testing and Materials (ASTM) and standards groups from Europe and Asia, the U.S. government agreed to provide hardness standards for U.S. manufacturers. The reason for the change is that hardness, though based on traceable parameters, has had no absolute numbers. For example, the loads on a tester can be verified with a traceable load cell, but the hardness values themselves are empirical. The result is a value that is not directly traceable to any standard, national or otherwise. In the future, the values will be absolute, and will be traceable to a government standard. The hardness program at the National Institute of Standards and Technology (NIST) involves traceable Standard Reference Materials (SRMs) blocks. The hardness standards are to be calibrated at NIST by means of a dead weight tester. Only two of these machines exist in the world. Other primary machines exist in other countries, but the only exact duplicate of the NIST machine is located at IMGC, which is the NIST equivalent in Italy. The new NIST traceable blocks, at a nominal size of 60 mm (2.36 in.) diam and 15 mm (0.6 in.) thick, are larger than the typical Rockwell hardness test blocks. They are made of steel in the appropriate HRC range and have a polished mirrorlike surface. Although most ASTM type HRC Rockwell test blocks are labeled ±0.5 HRC on the high end (60 HRC range), the NIST blocks will have much tighter tolerances (down to 0.1). Test locations will be indicated on the block; associated hardness numbers and statistical information will be listed on the certificate, enabling the user to find more than the just arithmetic mean of the hardness. The very first blocks for Rockwell tests will be Hardness Rockwell C (HRC). The blocks should appear for sale in the near future. However, it is possible that not all the Rockwell scales will be represented. Which scales are needed will be decided by the scientists at NIST.

Vickers Hardness Testing

In 1925, Smith and Sandland of the United Kingdom developed a new indentation test for metals that were too hard to evaluate by the Brinell test, whose hardened steel ball was limited to steels with hardnesses below 450 HBS ( 48 HRC). In designing the new indenter, they chose a square-based diamond pyramid (Fig. 8) geometry that would produce hardness numbers nearly identical to Brinell numbers within the range of both. This decision was very wise, as it made the Vickers test very easy to adopt.

Fig. 8 Schematic representation of the square-base pyramidal diamond indenter used in a Vickers hardness tester and the resulting indentation in the workpiece

The ideal d/D ratio (d = impression diameter, D = ball diameter) for a spherical indenter is 0.375. If tangents are drawn to the ball at the impression edges for d/D = 0.375, they meet below the center of the impression at an angle of 136°, the angle chosen for the Vickers indenter. The use of a diamond indenter allows the Vickers test to evaluate any material and, furthermore, has the very important advantage of placing the hardness of all materials on one continuous scale. The lack of a continuous scale is a major disadvantage of Rockwell type tests, for which 15 standard and 15 superficial scales were developed. Not one of these scales can cover the full hardness range. The HRA scale covers the broadest hardness range, but it is not commonly used. In the Vickers test, the load is applied smoothly, without impact, and held in place for 10 or 15 s. The physical quality of the indenter and the accuracy of the applied load (defined in ASTM E 384) must be controlled to get the correct results. After the load is removed, the two impression diagonals are measured, usually with a filar micrometer, to the nearest 0.1 m, and then averaged. The Vickers hardness (HV) is calculated by:

HV = 1854.4L/d2 where the load L is in grams-force, and the average diagonal d is in expressed in units of kgf/mm2 rather than the equivalent gf/ m2).

m (although the hardness number units are

The original Vickers testers were developed for test loads of 1 to 120 kgf, which produce rather large indents. Recognizing the need for lower test loads, the National Physical Laboratory (U.K.) experimented with lower test loads in 1932. The first low-load Vickers tester was described by Lips and Sack in 1936. Because the shape of the Vickers indentation is geometrically similar at all test loads, the HV value is constant, within statistical precision, over a very wide test load range, as long as the test specimen is reasonably homogeneous. However, studies of microindentation hardness test results conducted over the, past several years on a wide range of loads have shown that results are not constant at very low loads. This problem, called the "indentation size effect" (ISE), has been attributed to fundamental characteristics of the material. In fact, the same effect is observed at the low-load test range of bulk Vickers testers. Procedure. As noted, the Vickers hardness test follows the Brinell principle, in that an indenter of definite shape is

pressed into the material to be tested, the load removed, and the diagonals of the resulting indentation measured. The indenter is made of diamond and is in the form of a square-base pyramid having an angle of 136° between faces (Fig. 8). This indenter has angle across corners, or so-called edge angle, of 148° 6' 42.5''. The facets are highly polished and free

from surface imperfections, and the point is sharp. The loads applied vary from 1 to 120 kg; the standard loads are 5, 10, 20, 30, 50, 100, and 120 kg. For most hardness testing, 50 kg is maximum. With the Vickers indenter, the depth of indentation is about one-seventh of the diagonal length of the indentation. For certain types of investigation, there are advantages to such a shape. The Vickers hardness number (HV) is the ratio of the load applied to the indenter to the surface area of the indentation. By formula:

HV = 2P sin( /2)/d2 where P is the applied load, in kilograms; d is the mean diagonal of the indentation, in millimeters; and between opposite faces of the diamond indenter (136°).

is the angle

Equipment for determining the Vickers hardness number should be designed to apply the load without impact, and

friction should be reduced to a minimum. The actual load on the indenter should be correct to less than 1%, and the load should be applied slowly, because the Vickers is a static test. Some standards require that the full load be maintained for 10 to 15 s. To obtain the greatest accuracy in hardness testing, the applied load should be as large as possible, consistent with the dimensions of the workpiece. Loads of more than 50 kg are likely to fracture the diamond, especially when used on hard materials. The accuracy of the micrometer microscope should be checked against a stage micrometer, which consists of ruled lines, usually 0.1 mm apart, that have been checked against certified length standards. The average length of the two diagonals is used in determining the hardness value. The comers of the indentation provide indicators of the length of the diagonals. The area must be calculated from the average of readings of both diagonals. The indentations are usually measured under vertical illumination with a magnification of about 125 diameters. The included angle of the diamond indenter should be 136° with a tolerance of less than ±0.50°, which is readily obtainable with modem diamond-grinding equipment. This would mean an error of less than 1% in the hardness number. The indenters must be carefully controlled during manufacture so that in use the indentations produced will be symmetrical. Tables are available for converting the values of the diagonals of indentation in millimeters to the Vickers hardness number. Vickers Hardness Testers. Several types of Vickers hardness testers are available. The principal component of a

basic Vickers tester is shown schematically in Fig. 9(a). A modern Vickers tester is shown in Fig. 9(b). Current equipment may include image analysis peripherals and other features for more automated handling and testing. Automation methods include motorized stage capabilities where long or repetitive hardness traverses are required. These can be programmed so that little operator involvement is required during the indentation mode. Digital display of the measured diagonals and automatic calculation of the hardness from the diagonals also simplify measurement but still require the operator to peer into the microscope portion of the tester. Some systems include a closed circuit television system to the tester so that the operator can look at the magnified image on the TV screen and measure the diagonals. This is easier on the operators, but resolution of the system may not be as high.

Fig. 9 Vickers hardness testers. (a) Principal components of a mechanical type. (b) Modern Vickers tester with digital readout of diagonal measurements and hardness values

Scleroscope Hardness Testing The Scleroscope hardness test is essentially a dynamic indentation hardness test, wherein a diamond-tipped hammer is dropped from a fixed height onto the surface of the material being tested. The height of rebound of the hammer is a measure of the hardness of the metal. The Scleroscope scale consists of units that are determined by dividing the average rebound of the hammer from a quenched (to maximum hardness) and untempered water-hardening tool steel into 100 units. The scale is continued above 100 to permit testing of materials having hardnesses greater than that of fully hardened tool steel. Testers. Two types of Scleroscope hardness testers are shown in Fig. 10. The Model C Scleroscope consists of a

vertically disposed barrel containing a precision-bore glass tube. A base-mounted version of a Model C Scleroscope is shown in Fig. 10(a). The scale is graduated from 0 to 140. It is set behind and is visible through the glass tube. Hardness is read from the vertical scale, usually with the aid of the reading glass attached to the tester, A pneumatic actuating head, affixed to the top of the barrel, is manually operated by a rubber bulb and tube. The hammer drops and rebounds with the glass tube.

Fig. 10 Principal components of two types of base-mounted Scleroscope hardness testers

The Model D Scleroscope hardness tester (Fig. 10b) is a dial-reading tester. The tester consists of a vertically disposed barrel that contains a clutch to arrest the hammer at maximum height of rebound, which is made possible because of the short rebound height. The hammer is longer and heavier than the hammer in the Model C Scleroscope and develops the same striking energy while dropping a shorter distance. Both models of the Scleroscope hardness tester may be mounted on various types of bases. The C-frame base, which rests on three points and is for bench use in hardness testing small workpieces, has a capacity about 3 in. high by 2 in. deep. A swing arm and post is also for bench use but has height and reach capacities of 9 and 14 in., respectively. Another type of base is used for mounting the Scleroscope hardness tester on rolls and other cylindrical objects having a minimum diameter of 2 in., or on flat, horizontal surfaces having a minimum dimension of 3 by 5 in. The Model C Scleroscope hardness tester is commonly used unmounted. However, when the hardness tester is unmounted, the workpiece should have a minimum weight of 5 lb. The Model D Scleroscope hardness tester should not be used unmounted. Workpiece Surface-Finish Requirements. As with other metallurgical hardness testers, certain surface-finish

requirements on the workpiece must be met for Scleroscope hardness testing to make an accurate hardness determination.

An excessively coarse surface finish will yield erratic readings. Hence, when necessary, the surface of the workpiece should be filed, machined, ground, or polished to permit accurate, consistent readings to be obtained. Limitations on Workpiece and Case Thickness. Case-hardened steels having cases as thin as 0.010 in. can be accurately hardness tested provided the core hardness is no less than 30 Scleroscope. Softer cores require a minimum case thickness of 0.015 in. for accurate results.

Thin strip or sheet may be tested, with some limitations, but only when the Scleroscope hardness tester is mounted in the clamping stand. Ideally, the sheet should be flat and without undulation. If the sheet material is bowed, the concave side should be placed up to preclude any possibility of erroneous readings due to spring effect. The minimum thicknesses of sheet in various categories (in inches) that may be hardness tested are as follows:

Hardened steel Cold finished steel strip Annealed brass strip Half-hard brass strip

0.005 0.010 0.015 0.010

Test Procedure. To perform a hardness test with either the Model C or the Model D Scleroscope hardness tester, the

tester should be held or set in a vertical position, with the bottom of the barrel in firm contact with the workpiece. The hammer is raised to the elevated position and then allowed to fall and strike the surface of the workpiece. The height of rebound is then measured, which indicates the hardness. When using the Model C Scleroscope hardness tester, the hammer is raised to the elevated position by squeezing the pneumatic bulb. The hammer is released by again squeezing the bulb. When using the Model D Scleroscope hardness tester, the hammer is raised to the elevated position by turning the knurled control knob clockwise until a definite stop is reached. The hammer is allowed to strike the workpiece by releasing the control knob. The reading is recorded on the dial Spacing of Indentations. Indentations should be at least 0.50 mm (0.020 in.) apart and only one at the same spot. Flat

workpieces with parallel surfaces may be hardness tested within

in. (6 mm) of the edge when properly clamped.

Taking the Readings. Experience is necessary to interpret the hardness readings accurately on a Model C Scleroscope hardness tester. Thin materials or those weighing less than 5 lb must be securely clamped to absorb the inertia of the hammer. The sound of the impact is an indication of the effectiveness of the clamping: a dull thud indicates that the workpiece has been clamped solid, whereas a hollow ringing sound indicates that the workpiece is not tightly clamped or is warped and not properly supported. Five hardness determinations should be made and their average taken as representative of the hardness of a particular workpiece. Advantages of the Scleroscope hardness test are summarized as follows:

1. Tests can be made very rapidly. Over 1000 tests per hour are possible. 2. Operation is simple and does not require highly skilled technicians. 3. The Model C Scleroscope tester is portable and may be used unmounted for hardness testing workpieces of unlimited size: rolls, large dies, and machine-tool ways. 4. The Scleroscope hardness test is a nonmarring test; no crater is left, and only in the most unusual instances would the tiny hammer mark be objectionable on a finished workpiece. 5. A single scale accommodates the entire hardness range from the softest to the hardest metals.

Limitations of the Scleroscope hardness test are summarized as follows:

1. The hardness tester must be in a vertical position, or the free fall of the hammer will be impeded and result in erratic readings. 2. Scleroscope hardness tests are more sensitive to variations in surface conditions than some other hardness tests.

3. Because readings taken with the Model C Scleroscope hardness tester are those observed from the maximum rebound of the hammer on the first bounce, even the most experienced operators may disagree among themselves by one or two points in the reading.

Microhardness Testing The term "microhardness" usually refers to indentation hardness tests made with loads not exceeding 1 kg. Such hardness tests have been made with a load as light as 1 g, although the majority of microhardness tests are made with loads of 100 to 500 g. In general, the term is related to the size of the indentation rather than the load applied. Fields of Application Microhardness testing is capable of providing information regarding the hardness characteristics of materials that cannot be obtained with hardness tests, such as the Brinell, Rockwell, or Scleroscope. Because of the required degree of precision for both equipment and operation, microhardness testing is usually, although not necessarily, performed in a laboratory. Such a laboratory, however, is often a process-control laboratory and may be located close to production operations. Microhardness testing is recognized as a valuable method for controlling numerous production operations in addition to its use in research applications. Specific fields of application of microhardness testing include: • • • • • •

Measuring hardness of precision workpieces that are too small to be measured by the more common hardness-testing methods Measuring hardness of product forms, such as foil or wire, that are too thin or too small in diameter to be measured by the more convenient methods Monitoring of carburizing or nitriding operations, which is usually accomplished by hardness surveys taken on cross sections of test pieces that accompanied the workpieces through production operations Measuring hardness of individual microconstituents Measuring hardness close to edges, thus detecting undesirable surface conditions, such as grinding bum and decarburization Measuring hardness of surface layers, such as plating or bonded layers

Indenters Microhardness testing is performed with either the Knoop or the Vickers indenter. The Knoop indenter is more widely used in the United States; the Vickers indenter is more widely used in Europe. Knoop indentation testing is performed with a diamond ground to pyramidal form that produces a diamond-shape indentation having an approximate ratio between long and short diagonals of 7 to 1 (Fig. 11). The pyramidal shape employed has an included longitudinal angle of 172° 30' and an included transverse angle of 130°. The depth of indentation is about one thirtieth of its length. Because of the shape of the indenter, indentations of accurately measurable lengths are obtained with light loads.

Fig. 11 Schematic representation of a pyramidal Knoop indenter and the resulting indentation in the workpiece

The Knoop hardness number (HK) is the ratio of the load applied to the indenter to the unrecovered projected area of indentation. By formula:

HK = P/A = P/CL2 where P is the applied load, in kilograms; A is the unrecovered projected area of indentation, in square millimeters; L is the measured length of the long diagonal, in millimeters; and C is 0.07028, a constant of the indenter relating projected area of the indentation to the square of the length of the long diagonal. Figure 12 presents a comparison of the indentations made by the Knoop and Vickers indenters. Each has some advantages over the other. For example, the Vickers indenter penetrates about twice as far into the workpiece as does the Knoop indenter, and the diagonal of the Vickers indentation is about one-third of the total length of the Knoop indentation. Therefore, the Vickers indenter is less sensitive to minute differences in surface conditions than is the Knoop indenter. However, the Vickers indentation, because of the shorter diagonal, is more sensitive to errors in measurement than is the Knoop indentation.

Fig. 12 Comparison of indentations made by Knoop and Vickers indenters in the same work metal and at the same loads

The shortcoming of the Knoop indent is that the three-dimensional indent shape changes with test load and, consequently, HK varies with load. In fact, HK values may be reliably converted to other test scales only for HK values produced at the standard load, generally 500 gf, that was used to develop the correlations. However, at high loads the variation is not substantial. Note that all hardness scale conversions are based on empirical data; consequently, conversions are not precise but are estimates. Microhardness Testers Several types of microhardness testers are available. The most accurate operate through the direct application of load by dead weight or by weights and lever. The Tukon tester is widely used for microhardness testing. Several different designs of this microhardness tester are available; they vary mainly in load range, but all can accommodate both Knoop and Vickers indenters. The Tukon microhardness tester shown in Fig. 13 has a load range of 1 to 1000 g. Loads are applied by dead weight. The microscope is furnished with three objective lenses having magnifications of about 150, 300, and 600 diameters.

Fig. 13 Principal components of a Tukon microhardness tester

Sources of tester error include inaccuracy in loading, vibration, rate of load application, duration of contact period, and impact. To limit the shock that can occur when the operator removes the load (this generally has an adverse effect on indentations made with loads below 500 g), an automatic test cycle is built into the Tukon microhardness tester. With this automatic test cycle, the load is applied at a constant rate, maintained in the work for 18 s, and smoothly removed. Thus, the operator does not need to touch the tester while the load is being applied and removed. The design of microhardness testers will vary from one type to another, but it is essential to remove the applied load without touching the tester if clearcut indentations are to be obtained. A movable stage to support the workpiece is an essential component of a microhardness tester. In many applications the indentation must be in a selected area, usually limited to a few thousandths of a square millimeter. In testing with the type of Tukon microhardness tester shown in Fig. 13, first the required area is located by looking through the microscope and moving the mechanical stage until the desired location is centered within the optical field of view. The stage is then indexed under the indenter, and the automatic indentation cycle is initiated by tripping the handle. After the cycle is completed, signaled by a telltale light, the stage is again indexed back under the objective for indentation measurement. Optical equipment used in microhardness testers for measuring the indentation must focus on both ends of the

indentation at the same time, as well as be rigid and free from vibration. Lighting is also important. Complete specifications of measurement, including the mode of illumination, are necessary in microhardness-testing techniques. Polarized light, for instance, results in larger measurements than does unpolarized light. Apparently, this is caused by the reversal of the diffraction pattern; that is, the indentation appears brighter than the background. When test data are recorded, it is recommended that both the magnification and the type of illumination used be reported. In measuring the indentation, the proper illumination to obtain optimum resolution is essential, and the appropriate objective lens should be selected. In operation, the ends of the indentation diagonals should be brought into sharp focus. With the Knoop indenter, one leg of the long diagonal should not be more than 20% longer than the other. If this is not apparent or if the ends of the diagonal are not in focus, the surface of the workpiece should be checked to make sure it is normal to the axis of the indenter. With the Vickers indenter, both diagonals should be measured and the average used for calculating the Vickers hardness number (HV). Preparing and Holding the Specimen Regardless of whether the metal being tested for microhardness is an actual workpiece or a representative specimen, surface finish is of prime importance. To permit accurate measurement of the length of the Knoop indentation or diagonals of the Vickers indentation, the indentation must be clearly defined. In general, as the test load decreases, the surface-finish requirements become more stringent. When the load is 100 g or less, a metallographic finish is recommended.

Specific Applications of Microhardness Testing Microhardness testing is used extensively in research and for controlling the quality of manufactured products, as well as for solving shop problems. Testing of small workpieces is an important use of microhardness testing. Many manufactured products, notably in the instrument and electronics industries, are too small to be tested for hardness by the more conventional methods. Many such workpieces can be tested without impairing their usefulness, generally by means of various types of holding and clamping fixtures.

Microhardness testing is also applied to product forms that cannot be tested by other means. Thin foils and small-diameter wires are typical examples. Monitoring of Surface-Hardening Operations. Microhardness testing is the best method in present use for

accurately determining case depth and certain case conditions of carburized or nitrided workpieces, using the hardnesssurvey procedure. In most instances this is accomplished by use of test coupons that have accompanied the actual workpiece through the heat treating operation. The coupons are then sectioned and usually mounted for testing. To ensure accurate readings close to the edge of the cross section, the 100 g is most often used, although a 500 g load is sometimes preferred. If the 100 g load is used, a metallographic finish is essential. Readings are taken at pre-established intervals (commonly, 0.004 or 0.005 in.), usually beginning at least 0. 001 in. from the edge of the workpiece. Accuracy, Precision, and Bias. Many factors (Table 5) can influence the quality of microindentation test results. In

the early days of low-load ( 0. Deformation will be uniform and stable when d /dA < 0. Because /A is negative in tension, stable deformation in tension occurs when d /dA 0. Therefore, from Eq 17, the condition for stable, uniform tensile deformation is:

+m

(Eq 18)

1

Necking is involved with the interplay between the applied stress and the flow resistance of the material. As the specimen elongates under a given load the area decreases and the stress increases. If necking is not to occur, the material's strength must increase through strain hardening ( ) and strain-rate hardening (m). For room-temperature deformation, m occurs for

0 and the instability criterion reduces to

d /d If the true-stress/true-strain curve is given by

1. Thus, stable tensile deformation

(Eq 19) = K a, then

d /d = nK

n-1

=

=K

n

and necking occurs when

=n

(Eq 20)

Because n in tension rarely exceeds 0.5, the available uniform strain in the tension test is limited.

Elongation Measurements in Tension Testing The measured elongation depends on the gage length or the dimensions of the cross section of the specimen. This is because the total extension consists of two components, the uniform extension up to the point of necking and the localized extension after necking (Fig. 16). The extent of uniform extension will depend on the metallurgical condition of the material (through n) and the effect of specimen size and shape on the development of a neck.

Fig. 16 Local elongation measured at positions away from fracture in tension specimens for two aluminum alloys

However,

Lf - L0 = a + euL0

(Eq 21)

where a is the local necking extension and euL0 is the uniform extension. We then have

(Eq 22)

which clearly indicates that the total elongation is a function of the gage length. Numerous attempts to rationalize the strain distribution in the tension test have been made, dating back to 1850. Following Barba's law, which states that geometrically similar specimens develop geometrically similar necks, it is usually assumed that the local extension at the neck is proportional to the linear dimension of the cross-sectional area, a = becomes:

, so that the elongation equation

(Eq 23)

This equation for elongation clearly shows the rationale for the use of fixed ratios of gage length to diameter or gage length to square root of cross-sectional area in specifying tensile-specimen dimensions. It also reinforces the importance of stating the gage length over which the measurement was made when reporting elongation values. In the United States, the standard tensile specimen is 0.505 in. (12.83 mm) in diameter and 2 in. (50.8 mm) in gage length, so 1/D 4. However, the testing standards in other countries specify different gage lengths for the measurement of elongation (Table 6).

Table 6 Dimensional relationships for specimens used in different countries for measurement of elongation Type of specimen Sheet Round bar

Dimensional relationship L0/ L0/D0

United Kingdom Before Current 1962 4.0 5.65

United States (ASTM) 4.5

11.3

3.54

4.0

10.0

5.0

Germany

To compare the ductilities of different metals by elongation measurements, the gage length should be adjusted as a function of the cross-sectional area of the test specimen. However, when flat specimens are cut from sheet or plate primarily to determine whether quality of individual lots meets specifications, it is usual to use fixed gage lengths, because of the lower cost of preparing and testing a large number of such specimens. The effect of specimen geometry on total elongation is of particular concern in testing of sheet-metal specimens. Although the Unwin equation (Eq 23) may be obeyed (within considerable scatter), a simpler equation due to Templin is possibly in better agreement with the results:

ef = C(A)b

(Eq 24)

Analysis of the results showed that the exponent b in Templin's equation depends on both uniform strain and localized fracture strain. Thus it will vary with processing and heat-to-heat differences in the metal, and it cannot be considered to be a real constant of the metal. A general trend was shown to exist between the exponent b in Templin's equation and the logarithm of the ratio of the zero-gage-length (fracture-strain) elongations to the infinite-gage-length (uniform-strain) elongations. Although (even after 100 years of study) opinions differ in detail concerning the effect of specimen geometry on elongation, there is general agreement concerning the validity and importance of one factor--the ratio . Even here it appears to be better validated for round bars than for rectangular specimens. However, if sufficient data on the influence of specimen size on elongation are not available, the elongation of a specimen of arbitrary size can be estimated by using the concept that a constant elongation is obtained if

is maintained constant, as suggested by Eq 23.

Then, at a constant value of elongation, + , where A and L are the areas and gage lengths of two different specimens, 1 and 2, of the same metal. To predict the elongation in length L2 on a specimen with area A2 from measurements on a specimen with area A1, it is only necessary to adjust the gage length of specimen 1 to conform to L1 = L2

. As an example, suppose that sheet

in. (3.2 mm) thick is available, and it is desired to predict the

elongation in 2 in. (50.8 mm) in identical material 0.080 in. (2.03 mm) thick. Using sheet specimens

in. (12.7 mm)

wide, it is predictable that a test specimen with L = 2 = 2.5 in. (63.5 mm) from the in. (3.2 mm) sheet would give the same elongation as a 2 in. (50.8 mm) gage length in sheet 0.080 in. (2.0 mm) thick. The usefulness of this procedure is shown in Fig. 17, where solid lines are experimental and points indicate predicted elongations for specimens of different areas.

Fig. 17 Calculated variation of elongation in 2 in. (50.8 mm) with specimen cross-sectional area. Source: E.G. Kula and N.N. Fahey, Mat. Res. Std., Vol 1, 1961, p 631

This discussion indicates that the measures of ductility available with the tension test leave a great deal to be desired in providing quantitative values. The main difficulty arises from the necking of the specimen. The occurrence of uniform and localized deformation makes the percentage elongation at fracture of little value as a quantitative measure of ductility, although it is usually required in metallurgical specifications. Reduction of area is a better measure of ductility, but its quantitative use is made difficult by the poorly defined triaxial stress state introduced by the formation of a neck.

Plane-Strain Tension Test A special type of tension-test specimen has been designed to give maximum plastic constraint so as to emphasize the differences in fracture behavior of nominally ductile materials (Fig. 18). The deep grooves in the specimen restrict the deformation to the grooved region. The ratio B/L is large enough so that approximately plane-strain conditions are achieved in the test section. Thus, strain occurs in the thickness and length directions but not in the width direction. The true strain is given:

= ln h0/h

(Eq 25)

where h0 is the initial thickness of the reduced section and h is the thickness at any time after deformation has begun. However, the ratio L/h is large enough so that there is no notch effect, and thus a specimen designed to the specification in Fig. 18 is an unnotched plane-strain specimen. Thus, the true stress can be determine from the load divided by the area (h × B).

Fig. 18 Plane-strain tension specimen where B = 1 in.; L =

in.; h = 0.080 in.; r =

in.

The plane-strain tension specimen described in Fig. 18 has the disadvantage that it may not be practical to machine such a specimen in a thin sheet. Also, because deformation is confined to the notch region, it may be difficult to make axialstrain measurements in those limited confines. A special clip-on fixture allows a regular sheet specimen to be converted to a plane-strain specimen. This plane-strain tension specimen is 38 mm wide and 200 mm long. The specimen contains two circular edge notches with a 19 mm radius. A special fixture containing four knife edges is clamped to the surface of the specimen. The knife edges run parallel to the tensile axis of the specimen and fall just inside the reduced cross section. These knife edges prevent any deformation in the width direction. As a result, necking and failure occur perpendicular to the tensile axis.

Summary The tension test is a "benchmark test" or "reference test" that provides much basic information about the mechanical state of a material. This test provides information on the flow of a material and its ductility. The flow resistance is evaluated on the basis of yield stress. The yield stress is variously determined by the first deviation from linear elastic behavior, or more precisely by the stress corresponding to the intersection with the stress-strain curve at an offset strain of 0.002 (the 0.2% offset yield strength). If the stress-strain curve can be expressed by Eq 5, then the yield stress corresponding to a particular cold reduction, expressed as reduction of area, RA, is given by the following equation:

(Eq 26)

This shows that a high strain-hardening exponent n leads to higher flow stress. In addition, with high n values, the deformation is spread out and local points of weakness, which can lead to thinning or fracture, are minimized. At elevated temperatures, strain-rate sensitivity becomes important, and strain hardening becomes less important. Elongation and reduction of area in the tension test cannot be calculated from each other because the occurrence of necking prevents the constant-volume relationship (A0L0 = A1L1) from being invoked over a distance containing the necked region. While elongation and reduction of area usually vary in the same way--for example, as a function of test temperature or alloy content--this is not always the case. Generally speaking, elongation and reduction of area measure different types of material behavior. Elongation measurements in the tension test are chiefly influenced by uniform

elongation (except when the gage length is very short) and thus depend on the strain-hardening capacity of the material. Reduction of area is more a measure of the deformation required to produce fracture. It is the most structure-sensitive ductility parameter. Compression Testing

THE CONCEPTS of uniaxial tensile and compressive loading are quite similar. In both cases, a strain is produced parallel to the applied load that has the same sign as the applied load, and two-transverse strains are produced that are opposite in sign to the applied load. Below the proportional limit, the strain in the load direction, in both cases, can be calculated using a single value of Young's modulus. Similarly, the transverse strain can be calculated using a second material constant, Poisson's ratio ( ): transverse

=

axial

Compression testing is an extremely valuable testing procedure, which is often overlooked because it is not properly understood. One of the main advantages of the compression test is that tests can be performed with a minimum of material, and thus mechanical properties can be obtained from specimens that are too small for tension testing. Compression tests are also very helpful for predicting the bulk formability of materials (behavior in forging, extrusion, rolling, etc.). In compression testing, the material does not neck as in tension, but undergoes barreling; failure occurs by different mechanisms and therefore there is no ultimate tensile strength (UTS). In general, ductile materials do not fail in compression but tend to flow in response to the imposed loads. Brittle cylindrical specimens loaded in compression fail in shear on a plane inclined to the load, and therefore actually break into two or more pieces. In this case, an ultimate (compressive) stress can be defined. In comparison with tension testing, several difficulties are encountered in conducting compression tests and interpretation of the experimental data. For example, maintaining complete axiality of the applied load is important. In tension testing, self-aligning grips make this relatively simple to accomplish. In compression testing, if the specimen is tall in relation to its diameter, this can present a major difficulty. Nonaxiality of the load induces a bending load in the specimen, in addition to the axial load, that potentially will cause buckling. Alignment of the loading platens to impose strict uniaxial loading is easier if the specimen contact area is large, but this in turn introduces other difficulties. Frictional forces exist at the specimen/platen interface that tend to restrict the increase in diameter of the specimen as it decreases in height. These forces are directly related to the coefficient of friction, , and thus care must be given to minimizing . P is the compressive load. Due to these frictional forces, loading on the specimen is not uniaxial. The effect of these frictional forces is two fold; an analysis indicates that the magnitude of the applied stress is increased over what it would be if the specimen were loaded uniaxially (i.e., the situation if equals 0), and diametral expansion is hindered near the platens, but not in material well removed from the platen, so that the specimen becomes barrel shaped (Fig. 19). Because of the increased magnitude of the applied stress, deformation at midheight is plastic, whereas it is still elastic near the specimen/platen interface. The ratio of the elastically strained material to the plastically strained material increases as the specimen height decreases, so that barreling increases during the course of a test. The unfortunate consequence of barreling is that specimens selected for easy axial alignment are the same specimens that show extensive barreling and for which the internal stresses in the material have a large biaxial component. Therefore, some compromise must be made in selecting specimen dimensions. A height-to-diameter ratio of about 3 to 1 often is selected to minimize buckling that occurs due to bending loads generated by nonaxial alignment of the load.

Fig. 19 Elastically loaded region and barreling in a compression specimen for two different height-to-width ratios

Because of the increasing contact area and the elastically strained material near the platen, the load-deflection curve bends upward as the specimen decreases in height (Fig. 20). A dramatic increase in load occurs if the elastically strained regions of Fig. 19 overlap.

Fig. 20 Load-deflection curves. (a) Curves illustrating the relationship of compression load to height reduction for various d0/h0 ratios. (b) Replot of curves for extrapolation to d0/h0=0. d0 is initial diameter; h0 is initial height.

Due to the presence of frictional forces, the pressure distribution across the specimen is not uniform, as shown in Fig. 21. The pressure distribution is given:

p=

0

exp[(2 /h)(r-x)]

where p is pressure, 0 is yield stress, is coefficient of friction, r is cylinder radius, x is distance from center of cylinder to data point on x-axis, and h is cylinder height.

Fig. 21 Line-loaded compression disk

Figure 20 also shows how the pressure distribution changes as the height decreases and as the coefficient of friction changes. The load needed to deform the cylinder can be estimated by multiplying the average pressure on the specimen by the contact area. Figure 20 indicates that the load required to deform materials increases dramatically as the diameterto-height ratio becomes greater and also increases with rise in the coefficient of friction. Without overload protection on the load cell, precautions must be taken so that the large loads required to cause plastic flow do not damage the load cell by exceeding its capacity, especially at the large plastic strains characteristics of forming processes. Coefficients of friction are kept as low as possible to minimize barreling and the development of large loads by providing lubrication at the platen/specimen interface. Two possibilities are the use of lubricating oil and oil grooves in the specimen or platen, or thin Teflon (E.I. DuPont de Nemours & Co., Inc., Wilmington, DE) sheet between the platen and the specimen. An alternative procedure to minimize friction effects and the attendant barreling phenomenon is the sequential loading of the specimen; that is, to load until plastic deformation just starts, unload, determine the change in dimensions and relubricate, then reload again until plastic flow initiates. This locus of points is then connected to provide a constructed stress-strain curve (Fig. 20). A tedious but accurate way to determine a true uniaxial compression stress-strain curve is to use a series of specimens having varying l/D ratios. The stress at a given height reduction is then determined for each l/D ratio, plotted as a function of l/D ratio, and extrapolated to an l/D ratio of 0. This might be done at only one value of offset (i.e., corresponding to 0.2% strain) to provide a true flow stress, or a complete curve could be constructed.

Line-Loaded Compression Testing For the line-loaded test, a flat disk is loaded (Fig. 21). If the disk is of brittle material so that fracture occurs before plastic flow initiates, the thickness of the disk does not affect the calculated stress to cause fracture. The tensile stress at fracture for this case is calculated:

s = 2P/ Dt

where s is maximum tensile stress, P is applied load, D is specimen diameter, and t is specimen thickness. This test is known as the "Brazilian test" and is routinely applied to determine the tensile strength of rocks.

Plain-Strain Compression Testing The common forming operations--rolling, swaging, and forging--are forming operations in which there is little or no change in dimension in one direction. For example, in rolling, a decrease in thickness is converted into an increase in length with little increase in width. Such a state of strain is then two dimensional; it is planar strain. Plane-strain deformation is referred to when the development of a local neck is discussed; and in that case, the plane-strain deformation occurred due to an internal state of strain in the body. Two loading situations that develop plane-strain deformation are illustrated here; one in which the plane-strain deformation is developed due to external constraint on the flowing material, and a second, in which the constraint is developed internally in the material. In Fig. 22(a), metal can flow in the x and z directions due to the applied stress in the z direction, but cannot flow in the y direction because of the die wall. In Fig. 22(b), the load P causes flow in the z and y directions, but flow occurs in the x direction if the x dimension or the width-to-thickness ratio of the sheet is large. This is because the material not under the die has no load imposed on it and, therefore, has no tendency to spread in either the x or y direction. Therefore, this unloaded material restrains flow of the material in the x direction (but not the y direction) under the die. There is net flow, in the y direction, because the unloaded material is simply pushed out by the expanding material under the die. Planestrain conditions are realized when the width-to-thickness ratio is about 10 to 1. Because of frictional forces under the die, the b/t ratio should be held to between 2 to 1 and 4 to 1. If large decreases in thickness are obtained in the test, sequential loading with a change in die dimension is necessary to maintain this ratio. In any event, it is again possible to construct a stress-strain curve.

Fig. 22 Plane-strain compression. (a) Plane-strain compression of a block in a die. (b) Indenting dies for planestrain compression testing. Source: R.N. Parkins, Mechanical Treatment of Metals, Elsevier, 1968, p 22

Because the strains are large, true stresses and strains frequently are calculated rather than the nominal stresses and strains. The stress and strain developed in the plane-strain compression test are then given:

and

T=ln (t/t0) Although not derived here, the mean stresses and the strain in the load direction in plane-strain deformation are related to the stress and strain developed in a uniaxial compression test of a cylinder: plane strain=1.15

uniaxial compression

and plane strain=1.15 uniaxial compression

Therefore, stresses and strains measured in the plane-strain compression test must be divided by the factor 1.15 if an equivalent curve for uniaxially loaded material is to be constructed or if the data are to be compared with data obtained in a uniaxial test.

Upset Testing Bulk forming processes, such as forging, extrusion, and rolling, are also evaluated for formability by upset testing. In the simplest form of this test, a short cylinder is flattened (upset) into a pancake shape. The bulging at the edges produces tensile stresses that cause fractures. Workability is evaluated by determining the largest deformation that can be achieved without producing edge cracking. More typical, however, is use of the hot upset test over a range of temperatures to establish the working temperature that minimizes fracture. A precision upset test has been developed to determine the three-dimensional analog of the forming-limit diagram. If grid lines are electroetched on the surfaces of small cylinders, then the compressive axial strain ( z) and the tensile hoop strain ( ) at which fracture occurs can be determined. By varying the length-to-diameter ratios (l/D) of the cylinders and the lubrication at the cylinder ends, a wide range of stress states can be developed. By observing the strain in the upset cylinder at which surface fracture just occurs for each of the stress states, a fracture-locus line can be established (Fig. 23). For any combination of strains below the fracture-locus line, fracture has not yet occurred and the condition is safe. When the strain path crosses the fracture line, surface fracture has occurred. This procedure is helpful in predicting the bulk formability of metals.

Fig. 23 Fracture-locus lines

Dynamic Fracture Testing

THE MOST IMPORTANT fracture tests can be grouped into two categories: impact (dynamic-fracture) tests and fracture-toughness tests. However, the variety of service circumstances--different types of materials, differing crack morphologies, differing environments and loading rates, effects of size--have spawned a large number of fracture tests, some highly specialized. The most common impact tests are the Charpy test and the Izod test. Both are used primarily for low- and mediumstrength materials (typically steels). These materials may break at stresses either above or below yield, depending on the circumstances (temperature, size of crack, etc.). Fracture-toughness tests are intended primarily for medium- and highstrength materials that may break at below-yield stresses, if a crack or other sharp flaw--often quite small--is present. Fracture-toughness tests are based on the theoretical developments of fracture mechanics and give results that can be directly used in calculations relating the size of cracks to applied loads and stresses. In fracture-toughness tests, unlike in impact tests, loads are normally applied relatively slowly--at about the same rate as in an ordinary tension test--and temperature need not be of concern. Although fracture-toughness tests can be conducted in a tension-test machine, the specimen looks quite different. Generally, it is a plate containing a crack grown from a machined notch, rather than the smooth round bar used in tension testing. Impact tests feature a high but generally indeterminate rate of loading, typically generated by a swinging pendulum or falling weight. The results are not directly related to the stresses and deformations normally calculated during the course of engineering analysis and design, although the results may relate to the temperatures experienced in service. In general, impact-test results have significance based on empirical correlations with service experience, or as a means of comparing materials. The Charpy test is most commonly used to evaluate the effects of metallurgical processes on dynamic mechanical properties. Another test, the Izod impact test, employs a cantilevered specimen hit by a swinging pendulum.

Charpy Tests Specimens used for Charpy tests come in several different configurations. Two examples are the V-notch test specimen, containing a shallow 45° machined notch as a stress concentrator, and the Charpy keyhole specimen, with a stress raiser that looks something like a keyhole (Fig. 24a and b). The V-notch test is the more common of the two tests.

Fig. 24 Notched-bar impact-test specimens. (a) Simple beam V-notch Charpy specimen. (b) Simple beam keyhole-notch Charpy specimen. (c) Cantilever beam notched Izod specimen. Source: Notched Bar Impact Testing of Metallic Materials, E 23-81, ASTM, 1981

Charpy tests have the virtue of being simple and inexpensive. Furthermore, the specimen is small--also one of the limitations of the test--and Charpy testing machines are widely available. The principal application is for delineating the transition-temperature region in low- and medium-strength steels; in the common test sequence, a series of nominally

identical specimens is broken at different temperatures. (Occasionally this test is used for materials other than low- and medium-strength steel.) Material specifications often include required levels of Charpy test performance, but the results of the test have limited fundamental significance. Results only have meaning in terms of correlations with ductile or brittle behavior under service conditions based on actual experience. However, because Charpy tests have been employed for so many years, a good deal of this experience is available in the form of general rules that can be exploited by designers. Figure 25 illustrates the Charpy bar supported at its ends and struck on the surface opposite the notch so that the loading is three-point bending. The source of the blow is a heavy, swinging pendulum with a range of 35 to 325 J (25 to 240 ft · lb) of energy at impact. The weight and height of the pendulum striking head may be modified to produce various joules (foot-pounds) of energy. Testing-machine and specimen details for Charpy tests, together with test procedures, are standardized, as described in ASTM E 23.

Fig. 25 Setup and specimen for Charpy impact testing

Machining of specimens should be controlled to provide specimen uniformity. The orientation of the bars, with respect to the rolling direction, often has considerable effect on impact behavior. In its simplest form, a Charpy test is conducted by inserting a specimen into the machine, cocking the pendulum, and releasing it to fracture the test bar. Typically, a series of tests is performed at different temperatures. Charpy machines should be periodically checked against standardized specimens to determine their accuracy. In addition to data on energy absorbed, two other quantities are commonly determined for each impact-test specimen. First, the percentage of fibrous fracture area visible on the cross section of the broken specimen is compared with the percentage of cleavage area. Second, the lateral contraction of the broken bar at the root of the notch is measured. Figure 26 shows a series of fracture surfaces from Charpy V-notch tests at different temperatures. The fracture surface is entirely fibrous in appearance above the transition-temperature region, indicating ductile behavior; it is entirely cleavage below. In the transition region, small decreases in temperature increase the percentage of cleavage fracture. As Fig. 26 shows, the texture difference between fibrous and cleavage regions makes identification straightforward for specimens (such as annealed low-carbon steel), which fail by cleavage at low temperatures. The percentages can be estimated visually or, if more precision is needed, the fracture surfaces can be photographed and further analyzed. Note that in the transition region, cleavage takes place in the center of the specimen, with fibrous fracture near the outer surfaces of the bar. This is a result of the differing states of stress in the interior and near the surface. The inner material is constrained against plastic deformation and more likely to fracture by cleavage.

Fig. 26 Series of fractographs of Charpy V-notch specimens of 4340 steel tested at different temperatures, showing the change in appearance and estimated percentages of fibrous fracture. Source: Army Materials and Mechanics Research Center, Watertown Arsenal

Notch-root contraction is also a direct indication of fracture behavior--in this case, of the amount of plastic deformation accompanying the fracture. The contraction is usually easiest to measure with a micrometer caliper. The thickness of the unbroken specimen at the notch root should be measured before the test.

The energy absorbed and the fracture-surface appearance are the most commonly specified results of the Charpy test. For example, steels for certain applications may be required to have a certain minimum level of energy absorption--15 or 20 J (10 or 15 ft · lb) are common values--at the lowest expected service temperature. Alternately, some minimum percentage of fibrous fracture (e.g., 50%) may be required. Again, note that such requirements have no intrinsic significance and can only be defined based on correlations with service experience. The energy absorbed in impact, percentage of fibrous fracture, and notch-root contraction can be plotted against temperature to determine the ductile-to-brittle transition temperature. However, the particular definition of the ductile-tobrittle transition temperature must be clearly specified in the data report. The standard Charpy impact test yields direct readings only of the energy absorbed. "Instrumented" tests make use of testing machines with auxiliary sensors to acquire other data, typically load data. A specially made striking tup instrumented with strain gages can give a load-time history that allows initiation of the crack from the machined notch to be distinguished from propagation of that crack through the specimen. This is a relatively specialized test utilized for specific limited applications. The advantages of the basic Charpy test, small specimen size, and low cost, are retained, while allowing fracture-mechanics parameters, such as toughness, to be estimated under specific circumstances.

The Izod Test The Izod test is a cantilever-beam test as compared to the simple-beam Charpy test. As shown in Fig. 27, the Izod specimen is held in a fixture wit, the V-notch facing the striking anvil of the pendulum. The center of the V-notch is in the same plane as, and parallel to, the supporting fixture. The actual fracture test is performed in the same manner as the Charpy test, and data on energy consumed are reported in joules (foot-pounds). The Izod test does not lend itself to variable-temperature testing because of the appreciable time required to place and clamp the specimen, which results in rapid temperature change due to specimen and fixture contact. Izod tests are generally specified for materials tested at room temperature and where the engineering part is designed to operate under cantilever loading.

Fig. 27 Setup and specimen for Izod impact testing

Dynamic Tear Tests Dynamic tear tests and drop-weight tear tests come in several varieties, two of which have been standardized by ASTM. All are similar to the Charpy test in the use of the kinetic energy of a swinging pendulum (or occasionally a failing weight) to break an artificially notched test specimen. In essence, they are larger versions of the Charpy test, with test specimens that are both thicker and wider to represent the fracture behavior of thick-section structural materials. While the Charpy test is used almost exclusively to investigate the transition-temperature behavior of low- and medium-strength steels, dynamic tear (DT) tests can be used as well for high-strength steels and for aluminum and titanium alloys. When such materials are broken in a Charpy machine, the energy absorbed is typically so low, compared to the testing machine's capacity, that little meaningful information can be obtained. The larger DT specimen allows different alloys and heat treatments to be more reliably compared.

Typical DT specimens are shown in Fig. 28. The larger specimen is used only where full-thickness tests representative of actual structures must be undertaken.

Fig. 28 Two sizes of the standard specimen for the Naval Research Laboratory standardized dynamic tear test. In the specimens, a crack with a sharp tip is produced by making a brittle electron beam weld or by pressing with a knife edge. With either method of providing the crack tip, and with either size of specimen, maximumconstant conditions are attained. Dimensions are in inches.

As in a Charpy test, the basic information obtained from a DT test is the energy absorbed in breaking the specimen, although fracture-surface appearance and the extent of plastic deformation near the fracture can also be useful. The two varieties of ASTM standard dynamic tear or drop-weight tests have the designations E 436 ("Drop-Weight Tear Tests for Ferritic Steels") and E 604 ("Dynamic Tear Testing of Metallic Materials"). As the names imply, the purposes are quite different, even though the general features are similar. The E 436 drop-weight tear test uses a specimen, normally of the actual thickness of the steel plate being investigated, with an easily produced, pressed notch (see ASTM E 436 for details). The test is used only for steel and indicates the transition temperature between ductile and brittle behavior. To this end, specimens are tested at increasing (or decreasing) temperatures until the crack propagates as a fully developed fibrous fracture away from the notch (it makes no difference if the crack initiates by a cleavage mechanism). This is determined by visual examination of the fractured specimen; no quantitative data need be gathered. Thus, the test is simple and inexpensive. It is used primarily for quality control purposes on structural steels, notably for pipeline applications. The ASTM E 604 test differs in two fundamental ways: the energy absorbed in fracturing the specimen is measured, and the test can be used on materials other than steels. The standard dimensions of the specimen are less than for either of the specimens shown in Fig. 28; the notch is machined, and the specimen is always 15.9 mm ( in.) thick. Tests can be conducted at a fixed temperature to compare several materials; or over a range of temperatures to investigate transition-temperature effects. Considerable effort has gone into correlating DT test results with plane-strain fracture-toughness values, because the more sophisticated testing procedures required for the latter are more costly and time consuming. In some cases, the DT test can be used to estimate plane-strain toughness.

Drop Weight Test As the name implies, in a drop weight test (DWT) the specimen is broken by a falling weight rather than by a pendulum. However, the essential difference between this test and those described earlier is that it provides the operational definition of an important parameter termed the nil-ductility temperature (NDT). The NDT is the highest temperature at which a particular steel is likely to fracture in brittle fashion by cleavage. Above this temperature, the fracture will be accompanied by some macroscopic plastic flow associated with fibrous fracture and a microvoid-coalescence process on the microscale. The DWT procedure does not, however, require interpretation of the fracture appearance, nor must any

quantitative data be gathered beyond the temperature of the specimen. As the definition of the term NDT implies, the test is used only for low- and medium-strength steels that show a cleavage-fibrous transition as the temperature is increased. The DWT also has been standardized by ASTM (E 208). The specimen is a flat plate with a hard-surfacing weld bead deposited on one side, as shown in Fig. 29. The brittle weld is notched to act as a crack starter. The fixture for DWT tests holds the specimen with the notched weld facing downward so that the falling weight will load the specimen in bending. The weld is thus on the tensile surface, and the specimen is backed up so that it can bend only a limited amount (approximately 5°). Well below the NDT, a DWT will produce complete fracture (Fig. 29). Well above the NDT, the specimen will bend elastically and plastically but will not break. The NDT, as defined by this test, is the temperature at which a crack starting at the notched hard-surfacing weld propagates to one or both edges of the tensile surface of the specimen. To conduct a DWT series, specimens are tested over a range of temperatures; the operationally defined NDT is the highest of these temperatures at which the specimen "breaks," according to this definition. The NDT is a widely applied parameter for structural steels and is referenced, for example, in the ASME Boiler and Pressure Vessel Code.

Fig. 29 Fracture appearance of drop weight nil-ductility transition specimens

Fracture Toughness Testing

FRACTURE TOUGHNESS is defined as a "generic term for measures of resistance to extension of a crack" (ASTM E 616). The term fracture toughness is usually associated with the fracture mechanics methods that deal with the effect of defects on the load-bearing capacity of structural components. Fracture toughness is an empirical material property that is determined by one or more of a number of standard fracture toughness test methods. In the United States, the standard test methods for fracture toughness testing are developed by the American Society for Testing and Materials (ASTM). These standards are developed by volunteer committees and are subjected to consensus balloting. This means that all objecting points of view to any part of the standard must be addressed. Other industrial countries have equivalent standards writing organizations that develop fracture toughness test standards. In addition, international bodies, such as the International Organization for Standardization (ISO), develop fracture toughness test standards that have an influence on products intended for the intentional market. In this review of fracture toughness testing, the ASTM approach will be emphasized to give the article a consistent point of view. The standard fracture toughness test methods have been written mostly with metals in mind. Toughness testing of nonmetals is also an important consideration. For many nonmetals, the equivalent standard for metals is adapted with some possible modification. Fracture toughness test methods that are written specifically for a particular nonmetal are mostly in preparation. Therefore, this review emphasizes those standards written for metals without intending to make them apply exclusively to metals.

Fracture Toughness Behavior Fracture toughness is the resistance to the propagation of a crack. This propagation is often thought to be unstable, resulting in a complete separation of the component into two or more pieces. Actually, the fracture event can be stable or unstable, With unstable crack extension, often associated with a brittle fracture event, the fracture occurs at a well defined point and the fracture characterization can be given by a single value of the fracture parameter. With stable fracture, often associated with a ductile fracture process, the fracture is an ongoing process that cannot be readily described by a point. This fracture process is characterized by a crack growth resistance curve or R-curve. This is a plot of a fracture parameter

versus the ductile crack extension, a. An example K-based R-curve is shown in Fig. 30(a). Sometimes a single point is chosen on the R-curve to describe the entire process; this is mostly done for convenience and does not give a complete quantitative description of the fracture process.

Fig. 30 Plane-strain fracture toughness (KIc) test. (a) Schematic of K-based crack resistance (R) curve with definition of KIc. (b) Specimens used in the KIc test as defined in ASTM E 399

Whether the fracture is ductile or brittle does not directly influence the deformation process that a component or specimen might undergo during the measurement of toughness. The deformation process is generally described as being linearelastic or nonlinear. This determines which parameter is used in the fracture toughness test characterization. All loading begins as linear-elastic. For this, the primary fracture parameter is the well known crack tip density factor, K, originally defined by Irwin. If the toughness is relatively high, the loading may progress from linear-elastic to nonlinear during the toughness measurement, and a nonlinear parameter is needed. The nonlinear parameters that are most often used in toughness testing are the J-integral, labeled J, and the crack tip opening displacement (CTOD), labeled . Because all loading starts as linear-elastic, the nonlinear parameters are all written as a sum of a linear component incorporating K and a nonlinear component.

Test Methods Fracture toughness test methods include linear-elastic and nonlinear loading, slow and rapid loading, crack initiation, and crack arrest. The development of the test methods follows a chronological pattern; that is, a standard was written for a particular technology soon after that technology was developed. Standards written in this matter tend to become exclusive to a particular procedure or parameter. Because most fracture toughness tests use the same specimens and procedures, this

exclusive nature of each new standard did not allow much flexibility in the determination of a toughness value. The newer approach is to write standards to encompass all parameters and measures of toughness into a single test procedure. This approach is labeled the common method approach and is being developed by ASTM as well as standards organizations in other countries. The standards for fracture toughness testing are periodically revised, and several new ones are often in development. Volume 3.01 of the Annual Book of ASTM Standards should be consulted for the current tests or new test standards. The fracture toughness test is generally conducted on a test specimen containing a preexisting defect; usually the defect is a sharp crack introduced by fatigue loading and called the precrack. The test is conducted on a machine that loads the specimen at a prescribed rate. Measurements of load and a displacement value are taken during the test. The data resulting from this are subjected to an analysis procedure to evaluate the desired toughness parameters. These toughness results are then subjected to qualification procedures (or validity criteria) to see if they meet the conditions for which the toughness parameters are accepted. Values meeting these qualification conditions are labeled as acceptable standard measures of fracture toughness. The standard fracture toughness test then has these ingredients: test specimens, types, and preparation; loading and instrumentation requirements taken; data analysis; and qualification of results. Linear-Elastic Fracture Toughness Testing Fracture mechanics and fracture toughness testing began with a strictly linear-elastic methodology using the crack-tip stress-intensity factor, K. Later, nonlinear parameters were developed. However, the first test methods developed used the linear-elastic parameters and were based on K. These methods are described first in this article. Plane-Strain Fracture Toughness (KIc)Test The first fracture toughness test that was written as a standard was the KIc test method, ASTM E 399. This test measures fracture toughness that develops under predominantly linear-elastic loading with the crack-tip region subjected to nearplane-strain constraint conditions through the thickness. The test was developed for essentially ductile fracture conditions, but can also be used for brittle fracture. As a ductile fracture test, a single point to define the fracture toughness is desired. To accomplish this, a point where the ductile crack extension equals 2% of the original crack length is identified. This criterion is illustrated schematically with a K-R curve in Fig. 30(a). This criterion gives a somewhat size-dependent measurement, and so validity criteria are chosen to minimize the size effects as well as restrict the loading to essentially linear-elastic regime. The details of this test can be found in ASTM E 399. Test Specimen Selection. The first element of the test is the selection of a test specimen. Five different specimen

geometries are allowed (Fig. 30b). These are the single edge-notched bend specimen, SE(B); compact specimen, C(T); arc-shape tension specimen, A(T); disk-shape compact specimen, DC(T); and the arc-shape bend specimen, A(B). Many of these specimen geometries are used in the other standards besides ASTM E 399. The bend and compact specimens are traditional fracture toughness specimens used in nearly every fracture toughness test method. The other three are special geometries that represent special component structural forms. Therefore, most fracture toughness tests are conducted with either the edge-notched bend or compact specimens. The choice between the bend and compact specimen is based on the following: • • •

The amount of material available (the bend takes more) Machining capabilities (the compact has more detail and costs more to machine) The loading equipment available for testing

All of the specimens for the KIc test must be precracked in fatigue before testing. The choice of the specimen also requires a choice of the size. Because the validity criteria depend on the size of the specimen, it is important to select a sufficient specimen size before conducting the test. However, the validity criteria cannot be evaluated until the test is completed; therefore, choosing the correct size is a guess that may turn out to be wrong. There are guidelines in ASTM E 399 for choosing a correct size, but no guarantee that the chosen size will pass the validity requirement. The test specimen must also be chosen so that the proper material is sampled. This means that the location in the material source and the orientation of the sample must be correct and accounted for. As the specimens

are prepared, requirements for tolerances on such things as locations of surfaces, size and location of the notch and pin holes, and surface finishes must be followed. Loading Machines and Instrumentation. Most tests are conducted on either closed-loop servo-hydraulic machines or a constant-rate crosshead drive machine. The first machine allows load, displacement, or other transducer control, but it is more expensive. It is preferred for precracking, which is usually done at a constant load range so load control is desired. The second type of loading machine is less expensive and may give more stability, but it allows only crosshead control. Because this is required in most of the fracture toughness tests, this type of machine is quite satisfactory for the actual fracture toughness testing but is not so good for precracking.

Loading fixtures must be designed for the test. Two types can be used, choice of loading fixture depends on the test specimen chosen. The bend specimens SE(B) and A(B) use a bend fixture. The tension specimens C(T), DC(T), and A(T) require a pin-and-clevis loading. For the KIc test, a continuous measurement of load and displacement is required during the test. The load is measured by a load cell, which should be on all loading machines. The measurement of displacement is usually done with a strain-gaged clip gage that is positioned over the mouth of the crack in the specimen. The ASTM E 399 standard gives guidelines for the working requirements of the load and displacement gages used in the tests. The loading of the specimen is done at a prescribed rate. It must be done fast enough so that any environmental or temperature interactions are not a problem. On the other hand, it must be done slowly enough so that it is not considered a dynamically loaded test. For the KIc test, the load must be applied at a rate so that the increase in K is given by the range 0.55 to 2.75 MPa /s. The loading is done in displacement control, which usually means test machine crosshead control. During the loading, the load and displacement are measured continuously either autographically or digitally. Test Data and Analysis. The load-and-displacement record provides the basic data of the test. The data are then

analyzed to determine a provisional KIc value labeled KQ. This provisional value is determined from a provisional load, PQ, and the crack length. The PQ value is determined with a secant slope on the load-and-displacement record (Fig. 31). The PQ value determined by drawing the original loading slope of the load-versus-displacement record. A slope of 5% less than the original slope is then drawn from the origin. For a monotonically increasing load, the PQ is taken where the 5% secant intersects the load-versus-displacement curve, this is shown as type I in Fig. 31. For other records in which an instability or other maximum load is reached before the 5% secant, the maximum load reached up to and including the possible intersection of the 5% secant is the PQ. Type II shown in Fig. 31 is an example of one of the other types of loadversus-displacement records. The 5% secant corresponds to about 2% ductile crack extension; this may be physical crack extension or effective crack extension related to plastic zone development. Unstable failure before reaching the 5% offset also marks a measurement point for PQ at the maximum load reached at the point of instability.

Fig. 31 Typical load-versus-displacement record for the KIc test, two types

The PQ value is used to determine the corresponding KQ value, which is calculated:

K = P f(a/W)/B where P is load, B and W are specimen thickness and width, and f(a/W) is a calibration function that depends on the ratio of crack length to specimen width, a/W, and is given in the standard. For the calculation of K, a crack length value, a, is required. This comes from a physical measurement on the fracture surface of a broken specimen half. The specimen must be fractured into halves if it is not already that way from the test. The crack length is measured to the tip of the precrack using an averaging formula in the test standard. This value of crack length normalized with width, W, is used in the calibration function f(a/W) to determine the KQ value. The KQ is provisional K value that may be the KIc if it passes the validity requirements. The two major validity requirements are to ensure that crack resistance does not increase significantly with crack growth and that linear-elastic loading and plane-strain thickness are achieved. The first of these two requirements is quantified:

which limits the R-curve behavior to an essentially flat trend and ensures that some physical crack extension. The second requirement is:

which guarantees linear-elastic loading and plane-strain thickness, Pmax is the maximum value of load reached during the test. An example of Pmax is shown in Fig. 31; ys is the 0.2% offset yield strength. Values of KQ that pass these validity requirements are labeled as valid KIc and are reported as such in a standard prescribed reporting of test results. Fatigue precracking should be done in accordance with ASTM E 399. The K level used for precracking each

specimen should not exceed about two-thirds of the intended starting K-value for a given environmental exposure. This prevents fatigue damage, or residual compressive stress at the crack tip, which may alter the fracture toughness behavior, particularly when testing at a K-level near the KQ value for the specimen. Chevron notches are sometimes used to facilitate starting such mechanical precracks. These modifications also may be necessary to control fatigue precracking of some materials. Rapid-Load KIc(t) A value of fracture toughness labeled KIc(t) can be determined for a rapid-load test. Details of this method are given in a special annex to the method E 399. For the static loading rate KIc value, the maximum loading rate is defined as 2.75 MPa /s. Anything faster than that is labeled as a rapid-load fracture toughness. The specimen apparatus and procedure are much the same as for the regular KIc test. Special instructions are given to ensure that the instrumentation can handle the rapidly changing signals. The interpretation of results must be based on a dynamic value of the yield stress, YD. An equation for YD is given in the Annex to E 399. Results are reported KIc(t), where the loading time of the test is written in parentheses after the measured toughness value. K-R Curve (ASTM E 561) Ductile fracture toughness behavior is measured by a crack growth resistance curve or "R-curve," which is defined as "a plot of crack-extension resistance as a function of slow-stable crack extension." Although many ductile fracture processes can be measured as a single point, such as with KIc, the R-curve is a more complete description of the fracture toughness. When the R-curve increases significantly, a single-point measurement is even less descriptive of the actual fracture toughness. Steeply rising R-curves occur in many metallic materials but especially in thin plate or sheet materials. The

steeply rising R-curve makes the single-point definition more size- and geometry-dependent and does not lend to structural evaluation. The K-R curve is a good method for fracture toughness characterization in cases where the R-curve is steeply rising but the fracture behavior occurs under predominantly linear-elastic loading conditions. The K-R curve procedure is given by ASTM E 561. The objective of the method is to develop a plot K, the resistance parameter, versus effective crack extension, ae. The method allows three different test specimens: the compact, C(T); the center-cracked tension panel, M(T); and the crack-line-wedge-loaded specimen, C(W). The compact specimen is the same as the compact type in ASTM E 399 for KIc tests (Fig. 30b). The center-cracked tension panel and the crack-line-wedge-loaded specimens are shown in Fig. 32(a) and 32(b), respectively. The first two specimens use a conventional loading machine with fixtures that are specified in the test method. The C(W) specimen is wedge loaded to provide a stiff, displacement-controlled loading system (Fig. 32b). The can prevent rapid, unstable failure of the specimen under conditions where the R-curve toughness is so low that the Rcurve can be measured to larger values of ae. All specimens must be precracked in fatigue.

Fig. 32 Specimens for crack growth resistance testing. (a) Center-cracked tension specimen, M(T). (b) Crackline-wedge-loaded compact specimen, C(W), in loading fixture

The instrumentation required on the specimens is similar to that for the KIc test, except for the case of the C(W) specimen. The basic test result is a plot of load versus displacement measured across the specimen mouth. From this, an effective crack length is determined from secant offset slopes to the load-versus-displacement record (Fig. 33). An effective crack extension is the difference between the original and effective crack lengths. Effective crack length is determined from the slope of the secant offset using the appropriate compliance function, which relates this slope to crack length. The K is determined as a function of the load and corresponding effective crack length:

K = Pf(ae/W)/B The resulting plot of K versus effective crack length is the desired K-R curve fracture toughness. The result is subjected to a validity requirement that limits the amount of plasticity. For the C(T) and C(W) specimens:

b = (W - a)

(4/ )(Kmax/

ys)

2

where b is the uncracked ligament length, ys is the 0.2% offset yield strength, and Kmax is the maximum level of K reached in the test. For the M(T) specimen, the net section stress based on the physical crack size must be less than the yield strength.

Fig. 33 Secant offset measurement of effective crack length

For the C(W) specimen, a load is not measured. The data collected are a series of displacement values taken at two different points along the crack line, one near the crack mouth and one nearer the crack tip. From the two different displacement values, an effective crack length can be determined from the ratio of the two displacement values and from calibration values given in a table in E 561. From the crack length and displacement, a K-value can be determined and the K-R curve constructed. The toughness result is then a curve of K versus ae, somewhat similar to the one in Fig. 30. Crack Arrest, KIa(ASTM E 1221) This procedure allows a toughness value to be determined based on the arrest of a rapidly growing crack, which may be lower than the initiation value. The specimen and procedure are somewhat different from the previously discussed toughness test methods that determine initiation toughness values only. The specimen for crack arrest testing is called the compact-crack-arrest compact specimen (Fig. 34). It is similar to the crack-line-wedge-loaded specimen, C(W), of the KR curve method and requires wedge loading in order to provide a very stiff loading system to arrest the crack. The notch preparation is different from the other standards in that the specimen has a notch with no precrack. Generally, a brittle weld bead is placed at the notch tip to start the running crack, although other methods are allowed. The running crack advances rapidly into the test material and must be arrested by the test material to produce a KIa result. The only instrumentation on the specimen is a displacement gage. A load cell is placed on the loading wedge, but it does measure the load on the specimen. The displacements at the beginning of the unstable crack extension and at the crack arrest position are measured and converted to K values. To eliminate effects of non-linear deformation, which cannot be directly measured with only a displacement gage, a series of loads and unloads are conducted on the specimen until the unstable cracking occurs. When the specimen is unloaded, the crack tip can be marked by a procedure called "heat tinting." Heat tinting consists of marking the physical crack extension by heating the specimen until oxidation occurs on the crack. The specimen is then broken open, and the crack extension measured on the fracture surface.

Fig. 34 Crack-line-wedge-loaded compact-crack-arrest specimen

The value of KIa is determined from a displacement value and the crack length at the arrest point. Validity is determined from the size criterion:

W-a

1.25(K/

YD)

2

where YD is a dynamic yield strength. To complete a successful KIa test, careful attention must be paid to the instructions in E 1221. Nonlinear Fracture Toughness Testing Linear-elastic parameters are used to measure fracture toughness for relatively low toughness materials that fracture under or near the linear loading portion of the test. For many materials used in structures, it is desirable to have high toughness, a value at least high enough so that the structure would not reach fracture toughness before significant yielding occurs. For these materials, it is necessary to use the nonlinear fracture parameters to measure fracture toughness properties. The two leading nonlinear fracture parameters are J and . For high toughness materials, fracture is often by a ductile mechanism, but this is not necessarily the case for all materials. JIc Testing (ASTM E 813). One of the first tests developed using the J parameter is the JIc test per ASTM E 813. In

this test, an R-curve is developed using J versus a pairs and a point near the beginning of the R curve is defined as JIc "a value of J near the onset of stable crack extension" (ASTM E 813). The specimens for the JIc test are the bend SE(B) and compact C(T). These specimens are similar to the ones used for KIc testing; however, the compact specimen for J testing has a cutout on the front face so that a displacement gage can be mounted directly on the load line; that is, in the line of the applied loads. The loading fixtures required are the bend fixture for the bend and the pin-and-clevis for the compact. Again, a clevis with a loading flat at the bottom of the pin hole in the clevis is essential to get free rotation of the specimen. The instrumentation required is the load cell and a displacement measuring clip gage. If the electrical potential system is used additional instrumentation is required. The clip gage for the JIc test requires more resolution than that for the KIc test if a single specimen test method is used. For the bend specimen, a loadline clip gage is needed to measure J. Additionally, a second clip gage can be used over the crack mouth if a single specimen method is used. The basic output of the test is a plot of J versus physical crack extension ( a). (Unlike the K-R curve method, which uses effective crack extension, the JIc test uses physical crack extension.) To obtain the required J versus a data measurements of load, displacement and physical crack length are required during the test. There are two techniques used to develop these data. The first is the multiple-specimen test method, in which each specimen develops a single value of J and a but no special crack monitoring equipment is needed during the test. Crack extension is measured on the fracture surface at the conclusion of the test. However, for this technique a number of specimens are required to develop the plot of J versus a values needed for the result. The other method is the single specimen test from which all the J versus a

values are developed from one test. To accomplish this, a method of crack length monitoring is needed during the test. The primary method for crack length monitoring during the test is called the elastic unloading compliance method, in which crack length is measured from an elastic slope. The measurement of the elastic slope requires only a clip gage that measures displacement. The compact specimen uses the gage mounted on the load line. The bend specimen could use two gages: one on the loadline to measure J and one over the crack mouth to measure slope. The second single-specimen method is the electrical potential crack monitoring system, in which the electrical resistivity of the specimen is measured and correlated with crack length during the test. This is a secondary method to measure crack length and is not described in detail in the E 813. It requires some additional expertise on the part of the tester to use. The test procedure depends on the method of crack length monitoring. For the multiple-specimen test, five or more specimens are loaded to prescribed displacement values that are thought to give some physical crack extension but not complete separation of the specimen. This results in a number of individual load-versus-displacement records, as shown in Fig. 35. When the prescribed displacement is reached, the specimen is unloaded and the crack tip is marked by heat tinting.

Fig. 35 Load versus displacement for multiple-specimen tests

The single-specimen method using elastic compliance is initially loaded in the same way; however, during the test partial unloadings are taken to develop elastic slopes from which crack length can be evaluated using compliance relationships (Fig. 36). The compliance relationships are given in E 813. For the electrical potential method, the load, displacement, and potential change are measured simultaneously. Potential changes are related to crack length through either an analytical or empirical correlation.

Fig. 36 Load versus displacement with unloading slopes

From these test results, J is evaluated from the load-versus-loadline displacement record. The J is calculated from a linear combination of an elastic term and a plastic term:

where K is the stress-intensity factor, E is elastic modulus, is Poisson's ratio, P is load, pl is plastic displacement, B is specimen thickness, b is specimen uncracked ligament (W - a, where W is specimen width), and pl = 2 + 0.522b/W for the compact specimen. This equation is the basic J formula for the case of a nongrowing crack. It is based on a K equivalence for the elastic component of J and an area term for the plastic component of J. Alternate J formulas are given in E 813 for the growing crack. The crack length is used to determine a = a - a0, where a0 is the original crack length at the beginning of the test. The J versus a results form a part of the J-R curve and are the basic data of the JIc method. The objective is to get J versus a values in a certain restricted range. These data are then subjected to a prescribed evaluation scheme to choose a point on the J-R curve that is near the initiation of stable cracking. The method for developing the JIc is somewhat complicated, and the details are given in E 813. Basically, the J versus a pairs are evaluated to see which fall in a prescribed range. The pairs falling in the correct range are fitted with a power-law equation:

J = C1( a) where C1 and C2 are constants. A construction line is drawn, and the intersection of this with the fitted line is the evaluation point for a candidate JIc value. This candidate value is labeled JQ. The candidate JQ value is subjected to qualification criteria to see if it comprises an acceptable value. The basic one is to guarantee a sufficient specimen size:

b,B where

Y

25(JQ/

Y)

is an effective yield strength and Y

=(

ys

+

uts)/2

where ys and uts are the yield strength and ultimate tensile strength, respectively. If the qualification requirements are met, the JQ is JIc, and the results are reported following the prescribed format in E 813. A more complete evaluation of fracture toughness for ductile fracture based on J is the J-R curve procedure in ASTM E 1152. This standard uses the same specimens, instrumentation, and test procedures as the JIc test. The JIc and J-R curve methods are very similar, hence a combined J standard is being prepared. Crack Tip Opening Displacement (CTOD) (ASTM E 1290). The crack tip opening displacement method of

fracture toughness measurement was the first one that used a nonlinear fracture parameter to evaluate toughness. The first CTOD standard was written by the British Standards Institution (BS 5762, 1979). Subsequently, ASTM E 1290 was written as the U.S. version of this test method. The basic idea of the test method is to evaluate a fracture toughness point for brittle fracture or to evaluate a safe point for the case of ductile fracture. The primary measurements of toughness are at unstable fracture before significant ductile crack extension, labeled c; unstable fracture after significant crack extension, u; or the point of maximum load in the test, m. The method originally had a point near the beginning of stable crack extension, i, that was measured as a point on an R-curve in a similar manner to JIc. This point was subsequently removed from the test method. The CTOD standard uses the same bend and compact specimens that are used in the JIc test; thus, the same loading fixtures are used. The method requires measurement of load and displacement during the test. The formulas for calculation use a combination of an elastic and a plastic component for :

= K2(1 -

2

)/2

ysE

+ rp(W - a0)

p/[rp(W

- a) + a0 + z]

In this equation, the elastic component of is based on an equivalent K and the plastic component is based on a rigid plastic rotation of the specimen about a neutral stress point at rp(W - a0) from the crack tip. In the equation, is Poisson's ratio, ys is the yield strength, rp is a rotation factor, p is a plastic component of displacement, W - a0 is the uncracked ligament length, and z is the position of the clip gage from the crack measurement position.

For many years, the CTOD test was the only one that measured toughness for a brittle, unstable fracture event using a nonlinear fracture parameter. In addition, the method allows the measurement of toughness after a "popin," which is described as a discontinuity in the load-versus-displacement record usually caused by a sudden, unstable advance of the crack that is subsequently arrested. New Test Methods The development of standard fracture toughness test methods is an ongoing process. Some new test methods for fracture toughness testing include: • • • •

The combined J standard (ASTM E 1737-96) The common test method (ASTM E 1820-96) The transition fracture toughness standard The standard for testing of weldments

The latter two methods will likely become test standards in the near future. Fatigue Life Testing

FATIGUE TESTS can be classified as crack initiation or crack propagation tests. In crack initiation testing, specimens or parts are subjected to the number of stress (or strain-controlled) cycles required for a fatigue crack to initiate and to subsequently grow large enough to produce failure. In crack propagation testing, fracture mechanics methods are used to determine the crack growth rates of pre-existing cracks under cyclic loading. Both methods can be used in a benign environment, or by the combined effects of cyclic stresses and an aggressive environment (corrosion fatigue). This section focuses on fatigue life test methods and general fatigue life data. In general, fatigue life (crack initiation) testing is stress controlled (SN) or strain controlled ( -N). The test specimens (Fig. 37) are described primarily by the mode of loading, such as direct (axial) stress, plane bending, rotating beam, alternating torsion, and combined stress.

Fig. 37 Typical fatigue life test specimens. (a) Torsional specimen. (b) Rotating cantilever beam specimen. (c) Rotating beam specimen. (d) Plate specimen for cantilever reverse bending. (e) Axial loading specimen. The design and type of specimen used depend on the fatigue testing machine used and the objective of the fatigue study. The test section in the specimen is reduced in cross section to prevent failure in the grip ends and should be proportioned to use the upper ranges of the load capacity of the fatigue machine (i.e., avoiding very low load amplitudes where sensitivity and response of the system are decreased).

Test Methods Testing machines are defined by several classifications: the controlled test parameter (load, deflection, strain, twist, torque, etc.); the design characteristics of the machine (direct stress, plane bending, rotating beam, etc.) used to conduct the specimen test; or the operating characteristics of the machine (electromechanical, servohydraulic, electromagnetic, etc.). Machines range from simple devices that consist of a cam run against a plane cantilever beam specimen in constantdeflection bending to complex servohydraulic machines that conduct computer-controlled spectrum load tests. Axial and rotating-bending machines are most commonly used for fatigue tests. Surface preparation of specimens is critical in all fatigue life tests. Axial Fatigue Life Tests. ASTM E 466 specifies specimens to be used in axial fatigue tests. The specific dimensions of specimens depend on the objective of the experimental program, machine to be used, and available material. ASTM does not specify dimensions but details preparation techniques and reporting techniques. In reporting, a sketch of the

specimen, with dimensions, should be given. The surface-roughness and out-of-flatness dimensions should be included. Specimens should not be subjected to any surface treatment. For axial loading, ASTM E 466 states that regardless of the machining, grinding, or polishing method used, the final metal removal should be in a direction approximately parallel to the longitudinal axis of the specimen. Improper preparation methods can greatly bias the results. Hence, preparation techniques should be carefully developed; if a change in the preparation technique is made, it has to be demonstrated that it does not introduce any bias in the results. Rotating-bending fatigue tests of the simple beam type are performed in testing machines such as that shown in

Fig. 38, sometimes called the R.R. Moore testing machine. In operation, an electric motor rotates a cylindrical specimen, usually at 1800 rpm or higher, while a simple mechanical counter records the number of cycles. Loads are applied to the center of the specimen by a system of bearings and dead weights. A limit switch stops the test when the specimen breaks and the weights descend.

Fig. 38 Loading arrangement for a rotating-beam fatigue-testing machine. S, specimen; P, load

The weights produce a moment that causes the specimen to bend. A strain gage placed on the specimen shows compressive stresses on the top and tensile stresses when the gage is rotated to the bottom. Stresses range from maximum tension to maximum compression during each revolution of the testing machine. Bending moments can be converted to stress by assuming that they are elastic and by employing the flexure formula:

= MC/I For circular specimens, I = C4/4, where C is the specimen radius. The maximum stress at the outer fiber, proportional to the bending moment, M. This moment is the product of the moment arm and the force.

, is

The specimen is machined from the material to be tested and is fastened into the bearing housing with special cap screws. The effective dead weight of the R.R. Moore machine and weighing apparatus is 4.54 kg (10 lb), which is deducted from the total weight required and added to the weight pan (Fig. 38) to provide the desired stress:

18.22 kg - 4.54 kg = 13.68 kg (40.13 lb - 10 lb = 30.13 lb) When the drive motor is actuated, a counter records the number of revolutions. If the specimen breaks, the bearing housing descends and actuates a switch that shuts off the drive motor. If the specimen does not break (carbon and lowalloy steels may achieve a million or more cycles), the stress is at or below the endurance limit. Next, the machine is shut off and another specimen is run at a higher stress level. A series of tests is performed to provide sufficient data at varying stress levels. For cantilever-beam rotating-bending machines of the White-Souther type (Fig. 39), a different bending moment is used in stress calculation. A weight, P, is supported by fixture to a ball-bearing housing at the free end of the specimen. This produces a bending moment, M, that equals P × L, which is the distance of the specimen from the center of the applied load, 75 mm (3 in.). The stress in the outer fiber is

The weight added to the weight pan is the calculated weight minus the weight of the weighing apparatus.

Fig. 39 Loading arrangement for a cantilever-beam fatigue machine for rotating-bending testing. S, specimen; P, load

Plate-Bending Machines. In rotating-bending tests, the mean or average stress is always zero. The effect of mean stress, which is very important in fatigue, is evaluated by cantilever bending machines that are used to test plate materials. In these machines, sometimes called Kraus plate-bending machines, specimens are loaded with constant deflection by means of an eccentric crank (Fig. 40). Stresses can be calculated by assuming that they are elastic. In many cases this is not a good assumption, because, when tested, some soft materials may involve small amounts of plastic stress.

Fig. 40 Reciprocating-bending fatigue-testing machine, and typical specimen (at lower left) for testing of sheet

Specimens are usually tapered to provide a constant-stress test area. The approximate stress, S, is given by:

where y is the specimen deflection, t is the thickness of the specimen, E is the elastic modulus, and l is the distance from load application to the back of the specimen. Constant-deflection beam-type machines are used to test both strip and plate. A typical specimen is shown at lower left in Fig. 40. Resonant-Testing Machines. Machines for resonant testing are basically spring-mass, vibrating systems. The frame

design is based on a resonant, spring-mass system that consists of two masses linked by the specimen and grip string and that oscillates as a dipole. The system is excited by an electromagnet housed in the machine base. The masses and load

string are positioned in the vertical frame, which is suspended and guided on leaf springs. The eight springs are arranged in a special configuration to make a unique and compact design without the need for a heavy seismic block. Mean load is applied by a motor located in the base of the system. The motor drives the four comer gearboxes through two shafts and applies mean loads in both tension and compression. The mean-load force is carried by the box-type structure of springs, and the level either is adjusted by a hand-held controller or is maintained at a level preset by the controller. The magnet air gap is maintained automatically by the action of the gap servomotor driving a wedge beneath the electromagnet. A linear variable displacement transformer (LVDT) constantly monitors the air gap, and control is maintained even when the mean load is changed while the machine is running. A manually operated drive located in the upper mass permits major adjustment of specimen spacing. The electromagnet excites the dual-mass system at its natural frequency by means of pulse excitation. This feature enables a simple switch to replace the conventional power amplifier, thus providing high reliability at low cost and, in addition, eliminating the need to tune an oscillator to the natural frequency of the system. Closed-loop amplitude control is achieved by controlling the pulse power to the magnet from the error between the actual and demanded load amplitudes, thereby providing fast response to changing load demands. A strain-gaged load cell provides accurate load monitoring and digital indication of peak dynamic load, mean load, and frequency. Ultrasonic fatigue testing involves cyclic stressing of material at frequencies typically in the range of 15 to 25 kHz.

The major advantage of using ultrasonic fatigue is its ability to provide near-threshold data within a reasonable length of time. High-frequency testing also provides rapid evaluation of the high-cycle fatigue limit of engineering materials as described in the article "Ultrasonic Fatigue Testing" in Mechanical Testing, Volume 8, Metals Handbook, 9th edition. 5

9

Corrosion Fatigue Life Testing. High-cycle corrosion fatigue tests (performed in the range of 10 to 10 cycles to

failure) are typically done at a relatively high frequency of 25 to 100 Hz to conserve time. Multiple, inexpensive rotatingbend machines are often dedicated to these experiments. Low-cycle corrosion fatigue tests (in the regime where plastic strain, p, dominates) follow from the ASTM standard for low-cycle fatigue testing in air (ASTM E 606). For aqueous media, the typical cell for corrosion fatigue life testing includes an environmental chamber of glass or plastic that contains the electrolyte. The specimen is gripped outside of the test solution to preclude galvanic effects. The chamber is sealed to the specimen, and solution can be circulated through the environmental cell. The setup should include reference electrodes and counter electrodes to enable specimen (working electrode) polarization with standard potentiostatic procedures. Care should be taken to uniformly polarize the specimen, to account for voltage drop effects, and to isolate counter electrode reaction products. If potential is controlled, control of the oxygen content of the solution may not be necessary, although highly deaerated solutions are considered prudent. Environmental containment for high-cycle and low-cycle corrosion fatigue life testing is similar, but the overall setup for low-cycle (strain-controlled) testing is more complicated because gage displacement must be measured. For straincontrolled fatigue life, testing in simple aqueous environments, diametral or axial displacement is measured by a contacting but galvanically insulated extensometer, perhaps employing pointed glass or ceramic arms extending from an extensometer body located outside of the solution. Hermetically sealed extensometers or linear-variable-differential transducers can be submerged in many electrolytes over a range of temperatures and pressures. Alternately, the specimen can be gripped in a horizontally mounted test machine and be half submerged in the electrolyte with the extensometer contacting the dry side of the gage. For simple and aggressive environments, grip displacement can be measured external to the cell-contained solution, such as for high-temperature water in a pressurized autoclave. It is necessary to conduct low-cycle fatigue tests in air (at temperature), with an extensometer mounted directly on the specimen gauge, to relate grip displacement and specimen strain.

Fatigue Life Data It has long been recognized that fatigue data, when resolved into elastic and plastic terms, can be represented as linear functions of life on a logarithmic scale. Figure 41 schematically shows this representation of elastic and plastic components, which together define the total fatigue life curve of a material. The general fatigue-life relation, expressed in terms of the strain range ( , where is the strain change from cyclic loading), is as follows:

=

e

+

p

(Eq 27)

where

e

is the elastic strain range,

p

is the plastic strain range, and where:

(Eq 28)

(Eq 29)

Therefore, the total strain amplitude (or half the total strain range,

/2) can be expressed as the sum of Eq 28 and 29:

(Eq 30)

where 'f is the fatigue ductility coefficient, 'f is the fatigue strength coefficient, b is the fatigue strength exponent, c is the fatigue ductility exponent, and Nf is the number of cycles to failure.

Fig. 41 Schematic of fatigue life curve with the Manson four-point criteria for the elastic and plastic strain lines. D is the tensile ductility, f is the fracture stress (load at fracture divided by cross-sectional area after fracture), and UTS is conventional ultimate tensile strength.

These four empirical constants (b, c, 'f, 'f) form the basis of modeling strain-life behavior for many alloys, although it must be noted that some materials (such as some high-strength aluminum alloys and titanium alloys) cannot be represented by Eq 30. For many steels and other structural alloys, substantial data have been collected for the four parameters in Eq 30. In many cases, the four fatigue constants have been defined by curve fitting of existing fatigue life data. A collection of this data is tabulated in Fatigue and Fracture, Volume 19, ASM Handbook. The four fatigue constants can also be estimated from monotonic tensile properties. With the availability of extensive data, however, these techniques are not widely used. Nonetheless, the "four-point method" is a method to estimate fatigue life behavior from tensile properties. This method can be used to compare fatigue and tensile properties. In addition, it should also be mentioned that the four fatigue constants are also related to the following parameters:

(Eq 31) n' = b/c

(Eq 32)

where K' is the cyclic strength coefficient and n' is the cyclic strain hardening exponent in the power-law relation for a log-log plot of the completely reversed stabilized cyclic true stress ( ) versus true plastic strain ( p), such that = K'( n' p) . The use of power-law relationship is not based on physical principles, although the relationships in Eq 31 and 32 may be convenient for mathematical purposes. The parameters K' and n' are usually obtained from a curve fit of cyclic stressstrain data. Four-Point Method Numerous studies have been devoted to the development of techniques for estimating strain-controlled fatigue characteristics (per Eq 30). For the most part, these studies dealt with data generated under completely reversed strain cycling (i.e., R = -1, or A = ) and usually attempted to relate fatigue properties with tensile properties. Extensions of these studies have carried the estimating procedures a step further, addressing the correlation of fatigue data obtained at various strain ratios (R). Two common methods for approximating the shape of a fatigue curve are the "method of universal slopes" and the "fourpoint correlation" method. These two methods have been known for many years. The method of universal slopes, first proposed by Manson, is based on the relation:

(Eq 33) where UTS is ultimate strength, E is modulus of elasticity, and

f

is true fracture ductility, or ln [1/(1 - RA)].

This approximation thus requires only tensile strength, modulus, and reduction in area (RA). However, note that it is based on strain range ( ) rather than strain amplitude ( /2). The four-point method also allows construction of fatigue life curves from more readily available handbook data (i.e., monotonic tensile data). This method can be compared with the traditional strain-based approach (Fig. 41) or a stressbased approach. In both cases, the four-point method is based on the premise that total fatigue life per Eq 30 can be estimated as the sum of elastic strain (Eq 28) and plastic strain (Eq 29) components. The step-by-step process for locating points on the plastic- and elastic-strain-life lines is described below for both strain-based and stress-based data. Strain-Based Four-Point Method. The four-point method initially was developed in terms of strain range by

Manson (Fig. 41). The four points in Fig. 41 are determined as follows: •

• • •

Point P1 on the elastic strain line is positioned at Nf = 0.25 cycles (where a monotonic test is of one fatigue cycle) and at an elastic strain range of 2.5 f /E (where f is the fracture stress in a tensile test and E is the elastic modulus). Point P2 on the elastic strain line is positioned at Nf = 10 cycles and at an elastic strain range of 0.9 UTS/E, where UTS is the conventional ultimate tensile strength. Point P3 on the plastic strain line is positioned at Nf = 10 cycles, where the plastic strain range is 0.25D3/4 and D is the conventional logarithmic ductility (also known as f). Point P4 on the plastic strain line is positioned at Nf = 104 cycles, where the plastic strain range is given 4 4 by p (at 10 cycles) = 0.0069 - 0.525 e (at 10 cycles), where the elastic strain-range line at Nf = 4 4 10 cycles; ( e at 10 ) is shown as *e in Fig. 41.

Point P1 depends on fracture stress, which is not readily available in literature. However, fracture stress (which is the load at fracture divided by the area as measured after fracture) can be estimated by means of the following approximate relationship among fracture stress, ultimate tensile stress, and fracture ductility, thus, f

= UTS(1 + D)

(Eq 34)

This relation follows from Fig. 42, where each point is fixed by the data for one material.

Fig. 42 Fracture stress versus tensile ductility

On the basis of the approximate equality in Eq 34, Manson noted that when E is known, only two tensile properties-ultimate tensile strength (UTS) and the reduction in area (to give D)--are needed to position the lines in Fig. 41 and thus obtain a prediction of fatigue behavior. Figure 43 shows a convenient graphical solution by Manson for locating the four points. For example, if UTS/E is 0.01 and the reduction in area is 50% (D = 0.694), the value of P2 from the right-hand scale is 0.009 and that of P3 from the top scale is 0.18. Locating the point with the coordinates UTS/E = 0.01 and reduction in area equal to 50% gives values for P1 and P4 of 0.042 and 0.0009, respectively. These points will locate the two strain-range lines, and the total strain-range curve can then be positioned to relate and Nf for the material in question.

Fig. 43 Graphical solution to obtain the four points (P1, P2, P3, and P4, in Fig. 41) to position the elastic and plastic strain-range lines.

Stress-Based Four-Point Method. The four-point also applies to the construction of a stress-based S-N fatigue

curve, as shown in Fig. 44. The four points A, B, C, and D in Fig. 44 can be defined in terms of either stress or strain. In terms of strain, the points are identical to points P1, P2, P3, and P4 in Fig. 41. For construction of an S-N fatigue curve, the points are determined as described below.

Fig. 44 Schematic summary of four-point method for estimating fatigue strength or strain life

Point A (in terms of stress) is simply the ultimate tensile strength of the metal, plotted on the vertical axis of the graph at

N = . As in the strain-based approach, this assumes that the simple tensile test represents one-fourth of a single, completely reversed fatigue cycle--the peak positive value of the applied stress.

Point B, the right-hand locator of the elastic curve, is defined as the fatigue-endurance limit, if the metal has one;

otherwise, point B is the endurance strength. Some ferrous alloys have an endurance limit, that is, a stress level below which fatigue failure will never occur, regardless of number of cycles. This is generally around 107 or 106 cycles, at which point the fatigue curve approaches zero-slope, or a horizontal line. Many metals, particularly those that do not work harden, have no detectable endurance limit. Their long-life fatigue curves never become truly horizontal. For these metals, a pseudo-endurance limit, called endurance strength, is reported. Usually, this value is defined as the failure stress at some large number of cycles, for example, 107 to 1010. Point B can also be obtained from tensile-test data--a virtue of this technique, as handbook values for fatigue-endurance strengths or limits are often not available. Figure 45 is used to find the fatigue-endurance value from yield strength and true ultimate tensile strength for the material. The "ductility parameter" is simply calculated from handbook tensile data using the equation on the horizontal axis of the graph. Then find the "endurance-to-yield" strength ratio for the appropriate material. Multiply this ratio by "yield strength" to find the endurance value, which is point B.

Fig. 45 Plot for estimating fatigue-endurance limits (point B in Fig. 44) for common structural alloy groups

Beyond point B, the ratio of ultimate tensile strength to yield strength can be used to approximate the slopes of the longlife portion of the fatigue curve. According to many researchers, a ratio greater than 1.2 suggests that the material strain hardens sufficiently to produce a pronounced endurance limit value, and the curve assumes a zero slope. For ratios less than 1.2, however, the curve will continue to drop beyond point B. The lower the ratio below 1.2, the further the fatigue curve deviates from a horizontal, zero-slope line beyond point B. Because both endurance strength and endurance limit are reported in terms of stress, this value must be divided by Young's modulus for the metal if the fatigue curve is being constructed in terms of strain. Point C is a value known as "fracture ductility." If natural, or true, strain at fracture for a simple tension test is known

(which would be the distance between gage points at fracture divided by initial gage length), fracture ductility is the natural log of this value. In most cases, however, reduction of area for a simple tensile test is given in handbooks. As before in the discussion on the universal slopes method, fracture ductility, f, is estimated.

(Eq 35)

where RA is percentage reduction of area.

Because fracture ductility is in units of strain, this value must be multiplied by Young's modulus to obtain point C in terms of stress. In all cases, point C is also plotted at N =

. 4

Point D is defined as the intersection of the plastic and elastic curves at 10 cycles. (According to the theory of 4

"universal slopes," elastic and plastic strain curves intersect at N = 10 ). Thus, locate point D on the elastic curve and draw the plastic curve between points C and D. Now the fatigue curve can be drawn as the arithmetic summation of the elastic and plastic lines. Comparison with Data for Steel, Aluminum, and Copper Alloys. To demonstrate the validity of the method

described here, actual fatigue test results for various steel, aluminum, and copper alloys were compared with curves approximated from handbook data (P. Weihsmann, Mater. Eng., March 1980, p 53). In addition, a more recent analysis by J.H. Ong (Int. J. Fatigue, Vol 15, 1993, p 13-19) on 49 steels demonstrates that the predicted values by the four-point correlation method and the universal slopes method give satisfactory agreement with experimental data. The analysis by Ong shows that the four-point method gives the best estimates for predicting fatigue properties from uniaxial tension tests. Of the six comparisons shown (Fig. 46), fatigue data for steels and aluminum were taken from published sources. The measurements for copper fatigue are original, taken from tests on simulated squirrel-cage rotor, bar-to-end ring joints for induction motors.

Fig. 46 Comparison of actual fatigue test results (open circles) with fatigue curves constructed by the fourpoint method from tensile data. Total fatigue life is a solid line and elastic and plastic components are dashed lines constructed from tensile data point (shown by Xs). (a) 4340 steel. (b) Alloy steel plate (Lukens 80). (c) 7075-T6 aluminum. (d) Electrolytic-tough-pitch (ETP) copper. (e) Brass. (f) Beryllium-copper alloy

Because these parts had been brazed prior to testing, the copper fatigue test data were assumed to represent essentially annealed material. Traceability of the data is not "ideal" in these cases, as handbook tensile data for the approximated curves were selected for truly annealed materials. Nevertheless, correlation between fatigue test data and the curves drawn from annealed tensile data is quite good, indicating that this technique appears to be perfectly acceptable for copper alloys as well. Figures 46(a) to (f) were prepared from actual fatigue-test data (open circles) and from handbook tensile data (Xs). Fatigue curves constructed according to the techniques outlined in this article are shown in solid curves. Elastic and

plastic strain curves used in the construction of the fatigue curves are dashed. While this is no substitute for thorough, conventional fatigue testing, reasonable correlation between the actual fatigue data and the simulated curves indicates that this technique can be a quick shortcut for approximating fatigue-life information. Fatigue Crack Growth Testing

TESTING OF SMOOTH OR NOTCHED SPECIMENS generally characterizes the overall fatigue life of a specimen material. This type of testing, however, does not distinguish between fatigue crack initiation life and fatigue crack propagation life. With this approach, pre-existing flaws or crack-like defects, which would reduce or eliminate the crack initiation portion of the fatigue life, cannot be adequately addressed. Therefore, testing and characterization of fatigue crack growth is used extensively to predict the rate at which subcritical cracks grow due to fatigue loading. For components that are subjected to cyclic loading, this capability is essential for life prediction, for recommending a definite accept/reject criterion during nondestructive inspection, and for calculating in-service inspection intervals for continued safe operation.

Fracture Mechanics in Fatigue Linear elastic fracture mechanics is an analytical procedure that relates the magnitude and distribution of stress in the vicinity of a crack tip to the nominal stress applied to the structure; to the size, shape, and orientation of the crack or cracklike imperfection; and to the crack growth and fracture resistance of the material. The procedure is based on the analysis of stress-field equations, which show that the elastic stress field in the region of a crack tip can be described by a single parameter, K, called the stress-intensity factor. This same procedure is also used to characterize fatigue crack growth rates (da/dN) in terms of the cyclic stress-intensity range parameter ( K). When a component or a specimen containing a crack is subjected to cyclic loading, the crack length (a) increases with the number of fatigue cycles, N, if the load amplitude ( P), load ratio (R), and cyclic frequency ( ) are held constant. The crack growth rate, da/dN, increases as the crack length increases during a given test. The da/dN is also higher at any given crack length for tests conducted at higher load amplitudes. Thus, the following functional relationship can be derived from these observations:

where the function f is dependent on the geometry of the specimen, the crack length, the loading configuration, and the cyclic load range. The general nature of fatigue-crack growth and its description using fracture mechanics can be briefly summarized by the example data shown in Fig. 47. This figure shows a logarithmic plot of the crack growth per cycle, da/dN, versus the stress-intensity-factor range, K, corresponding to the load cycle applied to a specimen. The da/dN-versus- K plot shown is from five specimens of ASTM A 533 B1 steel tested at 24 °C (75 °F). A plot of similar shape is expected with most structural alloys; the absolute values of da/dN and K are dependent on the material. Results of fatigue-crackgrowth-rate tests for nearly all metallic structural materials have shown that the da/dN-versus- K curves have the following characteristics: a region at low values of da/dN and K in which fatigue cracks grow extremely slowly or not at all below a lower limit of K called the threshold of K, Kth; an intermediate region of power-law behavior described by the Paris equation:

where C and n are material constants; and an upper region of rapid, unstable crack growth with an upper limit of corresponds either to KIc or to gross plastic deformation of the specimen.

K that

Fig. 47 Fatigue-crack-growth behavior of ASTM A 533 B1 steel with a yield strength of 470 MPa (70 ksi). Test conditions: R = 0.10; ambient room air; 24 °C (75 °F)

Test Methods Testing procedures for measuring fatigue-crack-growth rates are described in ASTM method E 647. This method applies to medium-to-high crack-growth rates--that is, above 10-8 m/cycle (3.9 × 10-7 in./cycle). For applications involving fatigue lives of up to about 108 load cycles, the procedures of E 647 can be used. Fatigue lives greater than about 106 cycles correspond to growth rates below 10-8 m/cycle, and these require special testing procedures, which are related to the threshold of fatigue-crack growth shown in Fig. 47. ASTM method E 647 describes the use of center-cracked specimens and compact specimens. The specimen thickness-towidth ratio, B/W, is smaller than the 0.5 value for KIc tests; the maximum B/W values for center-cracked and compact specimens are 0.125 and 0.25, respectively. With the thinner specimens, it is feasible to use crack-length measurements on the sides of the specimens as representations of through-thickness crack-growth behavior. The specimens are loaded in the same general manner as for KIc testing. For tension-tension fatigue loading, the KIc loading fixtures often can be used. For this type of loading, both the maximum and minimum loads are tensile, and the load ratio, R = Pmin/Pmax, is in the range 0 < R < 1. A ratio of R = 0.1 is commonly used. Tension-compression loading can be performed with the compact specimen, but it is a more complex type of loading and requires more care. Testing normally is performed in laboratory air at room temperature; however, any gaseous or liquid environment and temperature of interest may be used in order to determine the effect of corrosion or other chemical reaction on cyclic loading. Cyclic loading may involve various wave forms for constant-amplitude loading, spectrum loading, or random loading. For constant-amplitude loading, a set of crack-length-versus-elapsed-cycle data (a versus N) is collected, with the specimen loading, Pmax and Pmin, generally held constant. The minimum crack length increment a, between data points is required by ASTM E 647 to be larger than a certain measurement of erroneous growth rates from a group of data points

that are too closely spaced relative to the precision of data measurement and relative to the scatter of the data. The growth rates may be calculated by either of two methods. The secant method is simply the slope of the straight line connecting two adjacent data points. This method, although simpler, results in more scatter in measured crack-growth rate. The polynomial method fits a second-order polynomial expression (parabola) to typically 5 to 7 adjacent points, and the slope of this expression is the growth rate. The polynomial method, particularly when used with a large number of adjacent points, eliminates some of the scatter in growth rate, which is inherent in fatigue testing. The measured values of growth rate typically are plotted as in Fig. 47, where K is calculated from P = Pmax - Pmin (for tension-tension loading) using a K expression. The measured growth-rate data are represented by an equation of the form of the Paris equation:

where the material constants C and n apply only within a certain range of da/dN and K values. Other relationships based on the Paris equation, such as the commonly used Forman equation, are used to represent the variation of da/dN with other key variables, including load ratio, R, and the critical K value, Kc, at which fast fracture of the specimen occurs. The Forman equation is:

where C and n are material constants of the same types as those in the Paris equation, but of different values. An advantage of the Forman equation is that it describes the type of accelerate da/dN behavior that is often observed at high values of K and is not described by the Paris equation. For example, for zero-to-tension loading (in which R = Pmin/Pmax = 0), as K approaches Kc in the Forman equation, da/dN increases rapidly, and this is often observed in tests. In addition, the Forman equation describes the often-observed decrease in da/dN associated with an increase in R from zero toward one. So when it is necessary to describe the effect of K approaching Kc, or the effect of R on da/dN, the Forman equation can be used to represent the da/dN behavior. When only K, the primary variable affecting da/dN, is involved, the less complex Paris equation may be used. Cyclic crack growth rate testing in the low-growth regime (region 1 in Fig. 47) complicates acquisition of

valid and consistent data, because the crack growth behavior becomes more sensitive to the material, environment, and testing procedures in this regime. Within this regime, the fatigue mechanisms of the material that slow the crack growth rates are more significant (see the article "Fatigue Crack Threshold Behavior and Analysis" in Fatigue and Fracture, Volume 19, ASM Handbook). It is extremely expensive to obtain a true definition of Kth, and in some materials a true threshold may be nonexistent. Generally, designers are more interested in the fatigue crack growth rates in the near-threshold regime, such as the K that corresponds to a fatigue crack growth rate of 10-8 to 10-10 m/cycle (3.9 × 10-7 to 10-9 in./cycle). Because the duration of the tests increases greatly for each additional decade of near-threshold data (10-8 to 10-9 to 10-10, etc., m/cycle), the precise design requirements should be determined in advance of the test. Although the methods of conducting fatigue crack threshold testing may differ, ASTM E 647 addresses these requirements. In all areas of crack growth rate testing, the resolution capability of the crack measuring technique should be known; however, this becomes considerably more important in the threshold regime. The smallest amount of crack length resolution as possible is desired, because the rate of decreasing applied loads (load shedding) is dependent on how easily the crack length can be measured. The minimum amount of change in crack growth that is measured should be ten times the crack length measurement precision. It is also recommended that for noncontinuous load shedding testing, where (P -P )/P > 0.02, the reduction in the maximum load should not exceed 10% of the previous maximum load, and the minimum crack extension between load sheds should be at least 0.50 mm (0.02 in.). In selecting a specimen, the resolution capability of the crack measuring device and the K-gradient (the rate at which K is increased or decreased) in the specimen should be known to ensure that the test can be conducted appropriately. If the measuring device is not sufficient, the threshold crack growth rate may not be achieved before the specimen is separated

in two. To avoid such problems, a plot of the control of the stress intensity (K versus a) should be generated before selection of the specimen. When a new crack-length measuring device is introduced, a new type of material is used, or any other factor is different from that used in previous testing, the K-decreasing portion of the test should be followed with a constant load amplitude (K-increasing) to provide a comparison between the two methods. Once a consistency is demonstrated, constant-load amplitude testing in the low crack growth rate regime is not necessary under similar conditions. Creep, Stress-Rupture, and Stress-Relaxation Testing

THE FLOW or plastic deformation of a metal held for long periods of time at stresses below the normal short-time yield strength is known as creep. Although we normally think of creep as occurring only at elevated temperatures, room temperature can be high enough for creep to occur in some metals. In lead, for example, creep at room temperature is common. In many cases, lead pipes must be supported to prevent sagging under their own weight. The development of steam turbines and jet engines has greatly increased interest in creep because, in these, the metal parts must withstand high loads at high temperatures for long times. The high centrifugal loads tend to cause certain parts to elongate or distort. Tolerances must be kept close to be efficient; yet if the metal parts deform too much, this spacing will be eliminated and failure will occur. In most cases, the parts cannot be made sufficiently heavy to prevent all creep because the weight penalty would reduce efficiency too much. Many such parts are therefore designed for a certain expected life span. For this, accurate data are needed to determine how much the metal part can be expected to deform under the conditions of stress and temperature to be encountered in service. Tests that measure the deformation of a metal as a function of time at constant load and temperature are known as creep tests.

Creep Phenomena A typical creep curve is shown in Fig. 48. The vertical (y) axis is creep strain and the horizontal (x) axis is time plotted on logarithmic coordinate. The curve consists of three parts: primary, secondary, and tertiary creep, or first-, second-, and third-stage creep. The strain shown is plastic or permanent strain. When a creep specimen is loaded, there will be some elastic extension of the specimen, but this is not shown in this curve. In the primary stage, the initial creep rate shows a continuous decrease with time. In second-stage creep, the creep rate is considered essentially constant. In the third stage, the strain rate increases rapidly to fracture. This increase in the third stage is due, in part, to the reduction in crosssectional area and thus the increasing true stress. Measurements made of specimen cross section during third-stage creep indicate that the increase in strain rate is not due only to necking or reduction in cross-sectional area, however.

Fig. 48 Idealized creep curve

Although, in the idealized creep curve shown in Fig. 48, the creep rate is shown as constant in the second stage, this does not occur in practice. If the test is long enough to show all stages of creep, the curve will show a continually diminishing

rate of creep to a point where the curve inverts and the creep rate starts to increase again (Fig. 49). The change in rate may be very slight over time; in some cases, the curve may approach a straight line.

Fig. 49 Creep curve with minimum creep rate and point of inversion

Rupture Tests The rupture test is valuable in determining tendencies of materials that may have to break under an overload. It finds much use in selection of materials for applications where dimensioned tolerances are not critical but rupture could not be tolerated. The rupture test is similar to a creep test except that no strain measurements are made during the test. The specimen is stressed under a constant load at constant temperature as in the creep test, and the time for fracture to occur is measured. Measurements are also made of the elongation and reduction in area of the broken specimen. Stresses are higher than those used for creep tests. An example of a typical application of the rupture test would be for testing boiler pipes. This test is also called the stress-rupture test, or time-to-rupture test.

Relaxation Tests The relaxation test is somewhat similar to the creep test, but the load continually decreases instead of remaining constant. This test is primarily of value in evaluating bolt materials. When a bolt is drawn up tight, a tensile load is present in the bolt and the bolt is elongated slightly. This causes a clamping load on whatever the bolt is mounted on. If the bolt creeps (extends or relaxes), this clamping load will be reduced. If the bolt elongates sufficiently to remove all tension, it no longer fulfills its function. In a relaxation test, the load is reduced at intervals in order to maintain a constant elongation (strain). A relaxation curve thus takes the general shape shown in Fig. 50. Note that the y-axis in this curve is stress or load rather than strain (elongation) as in the creep curve.

Fig. 50 Relaxation curve

Typical Procedure for Making a Creep Test Selection and Preparation of Specimen. The same precautions used in selecting and preparing a specimen for a short-time tension test apply to specimens for creep testing. The specimen should be selected to be truly representative of that which it is supposed to represent. Machining and grinding should follow procedures to produce a surface as nearly stress-free as possible. There should be no undercutting at the fillets, and the gage length should be uniform in cross section or very slightly smaller at the center of the gage length.

The specimen is carefully identified in as much detail as is appropriate--type of metal, heat number, vendor, etc.--and this information is recorded with the specimen's measurements. Sometimes gage marks, for measuring total extension, are made on the specimen. Such marks or scribe lines must be used with care, because the depressions or scribe lines can cause premature failure on some materials. Any operation, such as stamping the ends of the specimen, must be used with care to avoid any damage to the specimen. Loading. In mounting the specimen in the adapters and load train, care is needed to avoid straining of the specimen in

handling. Strain can occur when threading the specimen into the adapters and when handling the load train with the specimen in place, especially if the specimen is very small or brittle. The load train (specimen adapters or grips, pull rods, etc.) with the specimen in place should be carefully examined for any misalignment that will cause bending of the specimen under load. The upper load train should be suspended from the lever arm and the compensating weight adjusted so that the lever arm balances. The strain-measuring clamps and extensometer or the platinum strips are attached to the specimen, and the load train is inserted into the furnace with the specimen centered. The specimen must be stabilized at temperature before being loaded, Also, the extensometer should be adjusted and zeroed. Loading of the weight pan should be done smoothly and without excessive shock. If the specimen is to be step loaded, the weight is placed on the weight pan in measured increments and the strain corresponding to each step of loading is recorded. The loading curve thus obtained is used in determining the elastic modulus. If step loading is not used, a method of applying the load smoothly must be used. Smooth application can be done by having a support such as a scissors jack under the load pan during loading. When all weights are in place, the supporting jack is smoothly lowered from under the weight pan. Data Collection. Reading of strain should be made frequently enough to define the curve well. This diligence will

necessitate much more frequent readings during the early part of the test than later. The elastic portion of the stress-strain curve can be obtained by measurement of the instantaneous contraction when the load is removed at the end of the test if the specimen has not broken. Temperature Control. In bringing the specimen to temperature, it is important that the specimen not be

overtemperatured. A common practice is to bring the specimen up to about 30 °C (50 °F) below the desired temperature in about 1 to 4 h, and then take considerably longer in bringing the specimen to the desired temperature and adjusting for good stabilization. It should be understood that a period of time above the desired temperature is not cancelled in effect by an equal period at a temperature the same amount below the desired temperature. Any rise in temperature above the desired temperature of more than a small amount (such as defined by ASTM Recommended Practice for Conducting Creep and Time for Rupture Tension Tests of Materials) should be rejected. The limits specified in this recommendation are ±1.7 °C (±3 °F) up to 980 °C (1800 °F) and ±2.8 °C (±5 °F) above 980 °C (1800 °F). At temperatures very much above 1095 °C (2000 °F), the limits are broadened somewhat. Variation of temperature along the specimen from the nominal test temperature should vary no more than these limits at these temperatures. These limits refer to indicated variations in temperature according to the temperature recorder. Every effort should be made to ensure that the indicated temperature is as close to true temperature as possible. There is the possibility of both thermocouple error and instrument error. Thermocouples, especially base-metal thermocouples, drift in calibration with use or because of contamination. Other possible errors can result from incorrect lead wires or incorrect connection of lead wires, direct radiation on the thermocouple bead, or other causes. Representative thermocouples should be calibrated from each lot of wires used for base-metal thermocouples, and, except at low temperatures, base-metal thermocouples should not be re-used without slipping back to remove the wire exposed to high temperatures and rewelding. Noble-metal couples are generally more stable. However, they are also subject to error due to contamination and need to be annealed periodically. Annealing can be done by connecting a variable transformer to the two wires and sending enough current through the wire to make it incandescent.

When the thermocouple is attached to the specimen, the junction must be kept in intimate contact with the specimen. The bead at the junction should be as small as possible, and there must be no twisting of the thermocouple elsewhere that could cause shorting. Any other metal contact across the two wires will cause shorting and erroneous readings. Many authorities recommend shielding the thermocouple junction from radiant heating. Temperature-measuring, controlling, and recording instruments must be calibrated periodically against some standard. The calibration is usually done by connecting a precision potentiometer to the thermocouple terminals on the instrument and feeding in millivoltages corresponding to the output of the thermocouple at each of several temperatures. Tables of millivolt output for various types of thermocouples are readily available from manufacturers of precision potentiometers. Most creep and rupture machines are equipped with a switch that automatically shuts off the timer when the specimen breaks. In creep tests, the load is usually selected low enough so that rupture does not occur. The microswitch that shuts off the timer also shuts off or lowers the temperature of the furnace on many other creep-rupture units. In some furnaces, the life of the heating element is severely reduced if the furnace is shut off after each test; so for some furnaces the temperature is lowered to some lower control temperature, such as 540 or 650 °C (1000 or 1200 °F). Interrupted Tests. Sometimes, because of a power failure or other problem, it becomes necessary to interrupt a test, for instance, the specimen is cooled, then reheated. For many materials, this change appears to have little effect on either creep properties or time to rupture if the times of cooling and heating are not very great. It cannot be stated, however, that such treatment will not affect any materials. Any interruption of a test should be reported.

Presentation of Data Creep. The usual method for presenting creep data is in the form of a curve showing percent creep strain as the vertical

axis and time as the horizontal axis. Time is usually plotted on a log scale to show the early part of the curve in good detail and yet prevent the curve from being excessively long. Sometimes a whole family of curves is plotted on the same coordinates to show the effect of different temperatures or different stresses on one material. Other methods for plotting data include time to reach a given percent of creep versus load at a constant temperature or time to reach a given percent of creep versus temperature at constant load. The loading curve, showing the strain versus load as the specimen is loaded, is plotted separately and is used in computing the elastic modulus of the material at temperature. Rupture. Rupture data are presented in several types of graphs. One type has stress as the vertical axis versus log of

time-to-rupture (at constant temperature) on the horizontal axis. Usually, stress-rupture data are presented by means of a parameter plot. Stress is plotted against a parameter value that relates to both time and temperature. Several different parameters have been used. A widely used one, the Larson-Miller parameter, follows the formula P = (T + 460) (log t + c).This means that the parameter value P equals the Rankine temperature (460 + the temperature, T, in degrees Fahrenheit) times the log (base 10) of the time, t, in hours plus a constant c. The constant (c) has various values depending on the material but usually runs from about 17 to 23 for most materials tested. The value of c is determined by plotting log of time versus 1/[T(°F) + 460] using rupture data from several tests at constant stress but different temperatures on the same material. This produces a series of straight lines convering as on a single point. At this point log t = c, and this constant is theoretically the best constant to use for the data involved. Shear Testing

IN GENERAL, the amount of existing shear-strength data is seriously less than the published data available for other mechanical properties. Stores of data that deal with mechanical properties, such as tensile and yield strength, hardness, and ductility for virtually all metals and metal alloys, and in a wide variety of conditions, are readily obtainable. At least two reasons can be identified to explain the scarcity of shear-strength data. First, the demand is low, because the number of components that are loaded in shear under service conditions is far less than that of components loaded in tension, compression, bending, or torsion. Probably the primary reason for the lack of published data on shear strength is the difficulty in obtaining accurate test data. Shear testing inherently involves a number of variables; thus, the tests are less reproducible than testing for properties, such as tensile or yield strength. Therefore, most shear testing has been

performed by means of nonstandard equipment and procedures operating on arbitrary bases, thus producing results that are empirical. The greatest needs for shear-test data are in the designing of structures that are riveted, pinned, or bolted together and where service stresses are actually in shear. Notable examples of such structures are found in the aerospace industry. The required standardization is given by ASTM B 565.

Single- and Double-Shear Testing In the many tests that have been devised for evaluating shear strength, both single- and double-shear testing have been used. The double-shear technique is far more accurate, however, making those results more reproducible than results for the single-shear technique. Compression-type loading for a shear fixture is shown in Fig. 51, with a specimen being tested in double shear. This type of fixture may also be used for single-shear tests.

Fig. 51 Shear test fixture of the compression loading type used for single or double shear test. Courtesy Tinius Olsen Testing Machine Company

Procedure. The test specimen is assembled in the fixtures, per ASTM B 565, and loaded in tension until complete

failure occurs. Crosshead speed during the test should not exceed 19.1 mm/min (0.750 in./min), and loading rate should not exceed 690 MPa/min (100 ksi/min). The maximum load in double shear is determined by the direct reading on the testing machine.

Calculation of Shear Stress The calculation of stress in double shear is a simple mater of dividing the machine load by the area of the cross section ( D2/4). It follows, then, that single-shear stress is one-half of this value, or:

where P is load in kilograms (pounds), and D is diameter in millimeters (inches). As previously stated, shear testing is more vulnerable to the effects of variables than certain other mechanical tests, such as tests for tensile or yield strength. Even when the fixtures and test specimens meet specified tolerances, some variations are bound to exist in the test-jig assembly that will be reflected as variables in the results. The presence or absence of lubricant on the surfaces of the specimens and test fixtures can be responsible for substantial variations in the results. For example, a lubricated specimen may cause a reduction in shear strength of as much as 3%.

To minimize this variable, it is recommended that the test fixtures and specimens be carefully cleaned prior to testing, preferably by means of ultrasonic cleaning in a suitable solvent. Torsion Testing

IN THE TORSION TEST, a specimen is subjected to twisting or torsional loads to simulate service stresses for such parts as axles, crankshafts, twist drills, and spring wire. The test has not been standardized and is rarely specified. However, the torsion test provides information such as modulus of elasticity in shear (sometimes called modulus of rigidity), the shearing yield strength, and the modulus of rupture (apparent ultimate shear strength). The torsion test may also be performed as a high-temperature twist test on materials such as tool steels to determine forgeability. The test does not provide meaningful results for very brittle materials such as cast irons, because these materials would fail in diagonal tension before the shear-strength limit was reached.

General Procedure In torsion testing, the specimen is clamped in clamping heads so that the specimen remains as straight as possible during testing. The test specimen is then twisted at a slow, uniform rate until it breaks, or until a specified number of turns is obtained. The number of turns is recorded. If the number of turns falls within an acceptable range, the test specimen is considered to have passed the test. Results of the torsion test are largely comparative and have no standardized values. Torsion testing is frequently employed to assess the quality of brazed joints for sheet-metal products. A T-joint of sufficient length is brazed and then subjected to two full turns in torsion. Visual examination is made to determine if failure has occurred in the brazed joint. One of the only standardized applications of the torsion test applies to torsion testing of wire (ASTM E 558). An example of a torsion-testing machine is presented in Fig. 52.

Fig. 52 Close-up of a 10,000 in. · lb (1100 N · m) torsion-testing machine with special tooling for Phillips screwdriver bits. Courtesy of Tinius Olsen Testing Machine Company

Data Torsion data are usually presented as torque-twist curves, in which the applied torque is plotted against the angle of twist. Torsion produces a state of stress known as pure shear, and the shear stress at yielding can be calculated from the torque at yielding and the specimen dimensions. The maximum stress for a cylindrical specimen (at the surface) can be calculated from the following relation:

where S is maximum shear stress in MPa (ksi), T is torque in N · m (lb · in.), and d is specimen diameter in cm (in.). This formula holds only when the strain is proportional to stress, but it is commonly used for computing higher stresses and for determining modulus of rupture (apparent ultimate shear strength). The total torsional deformation is measured as angular twist of one end of the gage length in relation to the other. In order to obtain the angular twist per inch of gage length, the total angular twist is divided by the gage length. The angular twist per inch of gage length can then be converted into shear strain, in inches per inch, by multiplying by half the diameter of the specimen. Es, the modulus of elasticity in shear (sometimes called the modulus of rigidity), can be calculated from the following formula:

where S is maximum shear stress, in MPa (ksi); L is the gage length of the specimen, in cm (in.); r is the distance from the axis of the specimen to the outermost fiber (half the diameter), in cm (in.); and is the angle of twist, expressed in radians, in length L. The yield strength is generally defined as the maximum stress developed by a torque producing an offset of 0.2% from the original modulus line, analogous to the method used for determining tensile yield strength.

Comparison of Torsional and Tension Data From the torque-twist diagram it is simple to obtain a shear stress-shear strain diagram. The great advantage of the torsion test over the tension test is that large values of strain can be obtained without complications such as necking. One problem of torsional tests is that the stress is not constant throughout the cross section. This problem can be circumvented by using tubular specimens. If the results of a tension test and a torsion test are plotted for the same low-carbon steel, the two curves will be markedly different. However, if the two curves are normalized by converting the normal stress and longitudinal strain in the uniaxial test and the shear stress and strain in the torsion test into effective stress and strain, the two curves come into close correspondence. The effective streses and strains are determined by well-known equations (for instance, Eq. 1.67 and 1.81 in Mechanical Metallurgy: Principles and Applications, by M.A. Meyers and K.K. Chawla, Prentice-Hall, 1984). These results show that the work hardening of the material is a function of the amount of plastic strain and does not depend on the state of stress. Such is not the case for all materials, however. Differences in texture due to different constraints can be responsible for substantial differences in the effective stress-strain curve. Formability Testing

FORMABILITY is the technical term used to describe the ease with which a metal can be shaped through plastic deformation. Usually, it is synonymous with the term "workability." The evaluation of the formability of a metal involves both measurement of resistance to deformation (strength) and determination of the extent of plastic deformation that is possible before fracture (ductility). The emphasis in most formability tests, however, is on the amount of deformation required to cause fracture. Because of the diverse geometries of the tools and workpieces and the various ways that forces of deformation are applied, different metalworking processes produce varying stress states. These can be divided into two broad categories: bulk-deformation processes, such as forging, extrusion, and rolling, where the stress state is three-dimensional, and sheetforming processes, such as deep drawing and stretch forming, where the stress state is two-dimensional and lies in the plane of the sheet. The tests that simulate bulk-formability testing are given in the section "Compression Testing" in this article.

Bend Tests

Bend tests are among the most frequently used tests for evaluating the ductility of a metal or welded joint by measuring its ability to resist cracking during bending. Bending is the process by which a straight length is transformed into a curved length. The fibers of the metal on the outer (convex) surface of the bend are stretched, thus inducing tensile stresses. Simultaneously, the fibers on the inner (concave) surface of the bend are placed in compression. ASTM methods E 190, E 290, and E 855 provide descriptions of the various procedures. General Methods Bend Radius. For a given bending operation, the bend radius, R, cannot be made smaller than a certain value, or the

metal cracks on the outer (tensile) surface. Usually, this minimum bend radius (Rmin) is expressed in terms of multiples of the specimen thickness, t. Thus, a material with a 3t minimum bend radius can be bent without cracking through a radius equal to three times the specimen thickness. It follows, then, that a material with a minimum bend radius of 1t has greater formability; whereas a minimum bend radius of 5t indicates a less formable material. Test Specimens. Bend-test specimens are usually in the form of a rectangular beam. Wherever possible, as with a plate

or a sheet, the full thickness of the material should be used. Generally, the specimen thickness should not exceed 40 mm (1 in.). When using a machined specimen of reduced thickness, the as-fabricated surface should be retained as a surface of the bend specimen. This surface should be oriented in the bend fixture as the tensile surface. For specimens cut from plate material, the width should be twice the thickness, but no less than 20 mm ( in.). For thin specimens cut from sheet, the width should exceed eight times the thickness. The ratio of width to thickness affects the stress state produced in bending and, therefore, the ductility measured in the test. For this reason, bend-test results made on thin sheet should not be compared with those obtained with thicker plate to avoid erroneous conclusions about the formability of the materials. The length of a bend-test specimen must be of some minimum that varies with thickness. Length, however, is not critical if the specimen is long enough to accomplish the bending operation. The edges of the specimen may be rounded to a radius not to exceed 1.6 mm ( in.) to minimize edge cracking. Flame-cut surfaces should be machined to remove heataffected metal. Sheared edges should be machined or smoothed on an abrasive belt to remove the sheared edge. Although bend testing usually is performed with specimens of rectangular cross section, round specimens may also be used. Bend specimens may be cut from sheet or plate to evaluate the basic formability of the material or test the formability of an as-fabricated surface. Because most fabricated products have mechanical properties that are directional (anisotropic), directionality is an important consideration in making the test. Figure 53 shows the orientation of the bend-test specimen with the rolling direction for a longitudinal orientation and a transverse orientation. The transverse orientation generally shows lower ductility, because the tensile bending stresses are oriented perpendicular to the fiber structure developed by the rolling deformation.

Fig. 53 Relative orientations of specimens for longitudinal and transverse bend tests. Arrows indicate direction of rolling. Source: Semi-Guided Bend Test for Ductility of Metallic Materials, ASTM E 290-80

The quality of welds often is evaluated by bend testing (ASTM E 190). A specimen is cut from the welded assembly with the weld in the center of the specimen. The weld may be either transverse or parallel to the length of the specimen. Free Bend Tests

A free bend test is one in which the curvature of the bend is left "free" to take its natural shape. As shown in Fig. 54, the specimen is given a preliminary bend in a bending fixture (Fig. 54a) and then is transferred to a free bend fixture (Fig. 54b) where the bend is completed.

Fig. 54 Free bend tests. (a) A partial bend is made with the specimen in a horizontal position. (b) The specimen is positioned vertically, and the two knurled jaws are forced together until the specimen fractures or makes a 180° U-bend.

For moderately ductile materials, the formability is evaluated by the bend angle ( ) that can be achieved before cracking occurs on the tensile face (outside surface) of the bend. For a highly ductile material that can be bent flat on itself ( = 80°), the ductility is evaluated on the thickest specimen for which this can be done without cracking. Restricted (Controlled) Bend Tests A restricted bend test is one in which the test specimen is made to bend closely around a predetermined radius, R. Various examples of this test are shown in Fig. 55. The test shown in Fig. 55(a) usually is called a guided-bend test. The need for a test fixture sometimes may be eliminated by using a soft metal support to accommodate the punch, as in Fig. 55(b). For thin sheet metal, the bending force may be applied by a hand-operated lever, or alternatively, the sheet may be hammered over the bending die with a plastic or rawhide mallet (Fig. 55c). ASTM E 290 describes this test in detail.

Fig. 55 Restricted bend tests. (a) Guided bend test wherein the test material is forced through a fixture of predetermined radius. (b) Modification of guided bend test using soft metal for the fixture. (c) Method of clamping the specimen while bending it over a predetermined radius

Ordinarily, a grid pattern is lightly scribed on the tensile surface of the bend specimen before the restricted bend test. This surface is observed during the test, either with a mirror or by bending in small increments, to determine when the cracks first appear. At this point, the angle of bend is recorded, or the elongation of the tensile surface is determined from the

grid network. Alternatively, the minimum bend radius that will permit bending through a fixed bend angle is determined as the measure of formability. Bend Tests on Very Ductile Materials Bend tests on very ductile materials are less controlled than those discussed earlier, but they are more severe tests. For a sheet, the basic test is to determine whether the sheet can be bent flat on itself through 180° without cracking. A further test of ductility is to cross fold the sheet once again across the first fold (Fig. 56a). Bend tests are made on tubes by first flattening the tube, as shown in Fig. 56(b). This applies two separate transverse bends of nearly 180°. Subsequently, the flattened tube can be folded along its longitudinal axis (Fig. 56c).

Fig. 56 Fold tests on ductile sheet or tube (see text)

Sheet-Formability Tests Several tests have been developed to evaluate the formability of sheet metal, Most complex sheet-forming operations can be resolved into a combination of bending plus stretching and drawing. In a pure stretch-forming operation, the edges of the blank strip are clamped, and the shape is produced by multidirectional stretching over the contours of the deforming tool or punch. Sheet-metal drawing, usually called deep drawing, utilizes the radial drawing of the sheet-metal blank into the die under the action of the punch. In deep drawing, the outer portion of the blank shrinks in diameter under circumferential compression. To prevent the blank from buckling, the blankholder must exert sufficient pressure to prevent wrinkling but not enough pressure to restrict the sheet from drawing into the die. Thus, in deep drawing, no deformation occurs in the central region of the punch directly under the punch; whereas in stretch forming, the maximum deformation occurs in this region. Figure 57 shows the essential differences between stretching and drawing.

Fig. 57 Two operations that simulate stamping: (a) deep drawing and (b) stretching

The ability of the metal to undergo stretching is enhanced by a high value of strain hardening. Thus, a high value of strain-hardening exponent minimize failure in stretch forming. The ability to withstand deformation in deep drawing, without failure, derives from the crystallographic texture of the metal sheet produced during rolling. The desired texture is such that the slip systems are aligned to give higher strength in the thickness of the sheet than in the plane of the sheet. As the plastic-strain ratio, r, becomes greater, the limiting draw ratio, LDR, becomes larger. The plastic-strain radio is obtained by taking a tensile specimen and straining it to the point of necking. The longitudinal, thickness, and lateral (with-direction) strains are determined and are, respectively, l, t, and w. The plastic-strain ratio is defined as:

ASTM E 517 describes the test used to determine r. The limiting draw ratio (LDR) is the largest ratio of blank diameter to punch diameter for which the blank can be drawn into a cup of diameter Dp without tearing. Many laboratory tests have been developed to measure and control the formability characteristics of sheet metals. Some, such as the hydraulic bulge test, are fundamental tests, while others attempt to simulate actual sheet-forming operations. Finally, the forming of actual parts on which a grid of circles has been imprinted in combination with the forming-limit curves (or Keeler-Goodwin curves) can be used to measure the formability of a given sheet metal. In the hydraulic bulge test, metal is tested under uniaxial tension in the tension test and under local compression in the hardness test. In a typical press-forming operation, the metal is deformed under biaxial tension or biaxial tensioncompression, in which the metal is strained simultaneously in two directions in the plane of the sheet. The hydraulic bulge test can be used to measure the properties of sheet metal when strained under biaxial conditions. In the bulge test, a circular sheet is clamped at the edge and deformed by hydraulic pressure into a dome. For an isotropic sheet, essentially uniform biaxial stress and strain exist over an appreciable region at the center of the diaphragm. Failure eventually occurs in this central region. Another sheet-formability test is the stretch bend test, which measures the ability of a sheet metal to be bent around a sharp radius under tension. It is a more severe test than the simple bend test and, in addition, can be used to measure the sensitivity of a metal to tearing from a stretched cut edge (a major problem in components with hole or stretch flanges). In the stretch bend test, a sheared strip specimen of the material to be tested is clamped firmly between jaws and bent under tension, burr side outward, over a radiused punch. Normally, an autographic record of punch load and punch travel is obtained during the test. The punch travel--either at maximum load when cracks start to run into the material from the sheared edges, or at failure--is taken as the measure of specimen formability.

Ball Punch Deformation Test (Olsen and Erichsen Tests) The Olsen test simulates sheet-metal performance under stretching conditions. It is a simple test in which the sheet metal is clamped rigidly in a blankholder, then stretched over a small hemispherical punch 22.2 min ( in.) in diameter. The stretchability of the sheet is then assessed by measuring the height to which the sheet can be stretched before fracture occurs. In a typical Olsen tester, both the punch travel and punch load are recorded, and the fracture point is established by noting the point at which the load suddenly decreases. Figure 58 shows sheet specimens that were subjected to four different formability tests.

Fig. 58 Results typical of ductility tests on sheet-metal blanks. (a) Olsen and Erichsen tests. (b) Deep draw cup test. (c) Fukui test. (d) Hole-expansion test. Courtesy of Tinius Olsen Testing Machine Co.

The Olsen test has been replaced by the "ball punch deformation test" standardized by ASTM (ANSI/ASTM E 543). In this test, many of the test parameters that previously were left to the discretion of the individual performing the test are normalized. The standardized test applies to specimens with thicknesses between 0.2 and 2.0 mm. The machine to which the tooling is attached should have the capability of holding down the specimen (pressure between the top and bottom die) with a force of at least 10,000 N (2200 lbf). Because the punch surface and the sheet-metal surface are in contact during this test, the friction between the two surfaces has a large effect on the test conditions. To maintain standard friction conditions from one test to the next, the lubricant is standardized. Commercial available petroleum jelly is applied to the punch only. ASTM E 643 also states that other lubrication systems (e.g., polyethylene sheet plus oil) may be used as agreed between supplier and user. The speed of the penetrator shall be between 0.08 and 0.4 mm/s (0.2 and 1 in./min). The end of the test corresponds to the drop-in load, which is caused by necking of the sheet. If the machine is not equipped with a load indicator, the end point will be either visible necking or fracture of the test specimen in the dome. The cup height is measured at this point and is the penetrator (punch) displacement. The Erichsen test, which is common in Europe where it was standardized, is similar to the Olsen test in principle--that is, the test simulates sheet-metal performance under stretching conditions. The punch diameter for the Erichsen test is slightly smaller than the punch used for the Olsen test (20 mm, or 0.79 in.). The Erichsen test may be performed with or without lubrication, but the use of lubrication introduces a new variable, as described in the above discussion of the Olsen test. A portable instrument for performing the Erichsen test is available and has been widely used for control of formability or drawability in sheet-metal working, especially for quality control of incoming material. Limiting Dome Height Test In the Erichsen, Olsen, and bulge tests, fracture occurs at conditions that are close to equibiaxial strain (when the strain is the same in the two perpendicular directions). In the uniaxial tension test, fracture occurs at a combination of tensile strain plus a small amount of contraction strain in the width direction. In practical press-forming operations, most fractures occur at close to plane-strain conditions, such as a tensile strain in one direction with zero strain in the other direction-which is somewhere between the, conditions in the Olsen, Erichsen, and bulge tests on the one hand and conditions in the tension test on the other. The limiting dome height test has been developed to simulate more effectively the fracture conditions found in most parts. In this test, a large-diameter hemispherical punch, usually 100 mm (4 in.) in diameter, is used, and strips of sheet steel of

varying widths are clamped and then stretched over the punch. The strips are marked with a grid of small circles, 2.5 mm (0.1 in.) in diameter, and the width strain at fracture is measured from the circle closest to the fracture. The width strain increases as the width of the sheet becomes greater. The advantage of the limiting dome height test is that it more closely simulates the fracture conditions in a practical pressforming operation. It is a complex and time-consuming test, however, and the results are critically dependent on sheet thickness. In this test, lubrication is not critical; the standard practice is to perform the test dry (without lubricant). Swift Cup Test This test simulates the drawing operation and involves drawing of a small flat- or hemispherical-bottom, parallel-side cup. The sheet is held under a blankholder, as shown in Fig. 59, but is well lubricated with polyethylene and oil to ensure that the blank can be drawn in under the blankholder. Typical Swift cup test forming tools are available in 19, 32, and 50 mm diameters for use with specimens ranging in thickness from 0.3 to 1.24, 0.32 to 1.30, and 0.45 to 1.86 mm, respectively. For drawing 40 mm square cups from 80 mm diam round specimens from 0.2 to 2 mm thick, a 40 mm square forming tool is recommended.

Fig. 59 Swift cut test. Punch diameter is 50 or 32 mm (2 or 1.3 in.).

The drawability of the metal is estimated by drawing a series of blanks of increasing diameter. The maximum blank size that can be drawn without fracture occurring over the punch nose is used to calculate the limiting draw ratio. For example, forming a 66 mm diam disk using a 33 mm forming tool provides an LDR of 2.0. Because the condition of the edge of each blank can have an important effect on the test result, the blank edges usually are turned in a lathe to ensure strainfree, burr-free edges. The results of this test correlate well with the performance of sheet metal in deep-drawn components, but, because of shape and alignment, reproducibility between laboratories is not good. The main problem with this test, however, is that it is time consuming, and a large number of blanks of different sizes must be tested to obtain a reliable result. Apart from measuring drawability, this test also can be used as a quality control check to measure the tendency toward earing of the sheet metal. In this case, a blank of fixed diameter is drawn, and the height between the peaks and troughs in the cup wall are measured. The Englehardt or draw fracture test is a variation of the Swift cup test for measuring drawability that overcomes the problems of complexity and time involved in that test. The draw fracture test involves drawing of a cup to the point of maximum drawing load, then clamping the flange and continuing the punch travel to fracture. A load-penetration curve similar to that in Fig. 60 is obtained and the Englehardt value, T, is calculated from the maximum draw and fracture loads, Pd and Pf:

This result depends on strip thickness and usually is corrected, using an empirical relationship, to a nominal thickness. Because of its simplicity of operation and reproducibility, the draw fracture test is the most suitable for testing of drawability on a routine basis.

Fig. 60 Draw fracture test. A and B: drawing. C and D: clamping and fracture

Fukui Conical Cup Test The Fukui conical cup drawing test (Fig. 61) was developed to assess the performance of a material during forming operations involving both drawing and stretching. The advantage of this test is that no holddown is necessary if the correct relationship between sheet thickness and blank diameter is maintained.

Fig. 61 Fukui conical cup test

A blank of the appropriate size is laid over a 30° conical entry die and forced into the cavity by a flat-bottom or hemispherical punch. The height of the cup at failure is used as a measure of formability. The test requires various tooling for different sheet thicknesses, and the result is thickness dependent. It has been demonstrated that the Fukui cup depth is influenced mainly by stretchability, but with some dependence on drawability. Thus, this test does not correlate as highly with uniform elongation and r-values as do other tests that are predominately stretch or draw, which may explain why the conical cup test has not been as widely accepted as other simulative tests. Typical tooling commercially available for the Fukui test includes a cutting ring, cutting ram, and ball indenter available for specimen thicknesses from 0.5 to 1.6 mm.

Forming-Limit Curves The poor correlation often found between results of the common "cupping" test and actual metal performance led investigators to look at some more fundamental parameters. Localized necking requires a critical combination of major and minor strains (along two perpendicular directions in the sheet plane). This concept led to the development of diagrams known as the Keeler-Goodwin or forming-limit curves. The forming-limit curve (FLC) is an important addition to formability testing techniques.

Each type of steel, aluminum, brass, or other sheet metal can be deformed only to a certain level before local thinning (necking) and fracture occur. This level depends principally on the combination of strains imposed, that is, the ratio of major and minor strains. The lowest level occurs at or near plane strain, that is, when the minor strain is zero. This information was first represented graphically as the forming limit diagram, which is a graph of the major strain at the onset of necking for all values of the minor strain that can be realized. Figure 62 shows a typical forming limit diagram for steel. The diagram is used in combination with strain measurements, usually obtained from circle grids, to determine how close to failure (necking) a forming operation is or whether a particular failure is due to inferior work material or to a poor die condition.

Fig. 62 Typical forming limit diagram for steel

For most low-carbon steels, the forming limit diagram has the same shape as the one shown in Fig. 62, but the vertical position of the curve depends on the sheet thickness and the n value. The intercept of the curve with the vertical axis, which represents plane strain and is also the minimum point on the curve, has a value equal to n in the (extrapolated) zero thickness limit. The intercept increases linearly with thickness to a thickness of about 3 mm (0.12 in.). The rate of increase is proportional to the n value up to n = 0. 2, as shown in Fig. 63. Beyond these limits, further increases in thickness and n value have little effect on the position of the curve. The level of the forming limits also increases with the m value.

Fig. 63 Effect of thickness and n value on the plane-strain intercept of a forming limit diagram

The shape of the FLC for aluminum alloys, brass, and other materials differs from that in Fig. 62 and varies from alloy to alloy within a system. The position of the curve also varies and rises with an increase in the thickness, n value, or m value, but at rates that are generally not the same as those for low-carbon steel. The forming limit diagram is also dependent on the strain path. The standard FLC is based on an approximately uniform strain path. Diagrams generated by uniaxial straining followed by biaxial straining, or the reverse, differ considerably from the standard diagram. Therefore, the effect of the strain path must be taken into account when using the diagram to analyze a forming problem. These FLCs provide helpful guidelines for press-shop formability. Coupled with circle-grid analysis, they can serve as a guide in modifying the shapes of stampings. Circle-grid analysis consists of photoprinting a circle pattern on a blank and stamping it, thereby determining the major and minor strains in its critical areas. This is then compared with the FLC to verify the available safety margin. The strain pattern can be monitored with changes in lubrication, hold-down pressure, and size and shape of drawbeads and the blank; this can lead to changes in experimental procedure. Circle-grid analysis also serves, in conjunction with the FLC, to indicate whether a certain alloy might be replaced by another one, possibly cheaper or lighter. During production, the use of occasional circle-grid stampings provides valuable help with respect to wear, faulty lubrication, and changes in hold-down pressure. Wear Testing Peter J. Blau, Metals and Ceramics Division, Oak Ridge National Laboratory

Introduction WEAR is mechanically-induced surface damage that results in the progressive removal of material. Because different types of wear occur in machinery, many different types of wear tests have been developed to evaluate its effects on materials and surface treatments. Consequently, the selection of the right type of wear test for each investigation is important in order to achieve useful and meaningful engineering data. More than one type of wear can attack the same part, such as sliding wear and impact wear in printing presses, or erosive wear and abrasive wear on extrusion machine screws for plastics. Sometimes wear can operate in the presence of corrosive or chemically-active environments, and synergistic chemo-mechanical effects are possible. Selection of appropriate wear test methods begins with an assessment of the type of wear involved in each problem area. Having a structure to classify wear types can make this process easier, and one such structure is provided in this article. Wear testing is performed for one or more of the following reasons: to screen materials, surface treatments, or lubricants for a certain application; to help develop new, wear-resistant materials, surface treatments, or lubricants; to establish the relationship between the manufacturing, processing, or finishing methods applied to a certain machine part and its wear performance; or to better understand and model the fundamental nature of a certain type of wear. Surprising to some, the wear resistance of a given material is not a basic material property, like elastic modulus or yield strength. Rather, a material's wear behavior depends on the conditions of its use. Therefore, the first step in wear testing is to recognize how the results of the work will be used. Only then can the appropriate test method(s), testing parameters, and a useful format for reporting the results be selected. While this strategy may seem straightforward, its implementation in practice is not necessarily so. A test intended to mimic the environment seen by a particular machine component is called a tribosimulation. The initial challenge in designing a tribosimulation is identifying the major wear-causing factors and finding a test that will produce the same type of wear response from test coupons as for operating parts. Conducting a tribosystem analysis involves gathering as much data as possible from the field, consulting the component designers, if possible, and attempting to define the relevant contact conditions (mechanical, thermal, and chemical) accurately. Deciding which test to use and then selecting the proper variables and controls for that test often involves an iterative process of testing, analyzing the results, examining the worn surfaces, and possibly adjusting the testing parameters to better establish the usefulness and repeatability of the results. Because the subject of wear testing encompasses a wide variety of machine designs and testing strategies, this article focuses principally on the basic principles of wear test selection and use. The selected references listed in the bibliography provide additional detailed information, particularly when there is a need to screen materials for specific, wear-critical applications.

German standard DIN 50-322 elucidates a convenient method for grouping types of wear tests. The six levels of wear testing are as follow: (1) field testing (e.g., a truck for hauling rock), (2) full-scale machine test stand trials (e.g., the truck carrying a known load running on a wheel dynamometer stand), (3) machine subassembly test stand trials (e.g., the transmission of the truck on a dynamometer), (4) sub-scale tests (e.g., a small version of the transmission on a dynamometer), (5) component tests (e.g., a gear-testing machine), and (6) simple specimen tests (e.g., a simple curved specimen sliding on another curved specimen). Most laboratory wear tests, including a number of ASTM standard wear test methods, fall into categories (5) or (6). These bench-type tests are the focus of this article.

Wear Mechanisms Before describing specific types of tests, it will be helpful to identify the major forms of wear. Different classification schemes for wear have been developed, because those developing wear classification schemes have come from different backgrounds and experiences with wear. No one scheme is universally accepted, but most of them have reasonably similar features. Figure 1 shows an approach to wear classification; here, wear is classified by the type of relative motion. Note that galling, scratching, scoring, and damage from the impact of a foreign body are not strictly forms of wear because material is not necessarily removed (it may instead be displaced to one side), and even if some material is removed, the process is not repetitive and progressive. Rather, these latter phenomena are referred to as "surface damage."

Fig. 1 Major categories of wear

Forms of Wear The three categories of contact depicted in Fig. 1 are tangential motion (sliding), impact, and rolling. There are a number of subcategories. Formal definitions for the important types of wear, such as those shown in Fig. 1, have been compiled from a variety of sources in the Glossary of Friction, Lubrication, and Wear Technology, Volume 18, ASM Handbook. The Glossary also contains reviews of each major form of wear and detailed discussions of both wear mechanisms and wear control. An abbreviated summary of the characteristics of the wear types shown in Fig. 1 follows. Sliding wear is the consequence of relative tangential motion between solid surfaces being pressed together. If one of

the surfaces is much harder and contains sharp points that plow or cut through the other surface, possibly producing thin chips, then two-body abrasive wear is said to occur. An example of this is sandpaper abrading wood. In contrast, threebody abrasive wear is produced by foreign particles trapped between relatively-moving solid surfaces. An example of this is the accelerated wear of a bushing by hard particles (grit) that have somehow found their way into the lubricant. It is possible that what starts out as a sliding wear situation can become a three-body abrasive wear situation after a period of time due to the generation and abrasive action of work hardened wear debris particles. Adhesive wear is a somewhat archaic term, based on a proposed mechanism for the severe wear of metals, in which material from one surface is observed to adhere to the other at high spots (asperities) that are subsequently sheared off. While factors other than adhesion may be involved, it is so historically ingrained in the tribology literature that it will be

used here for convenience to describe sliding wear other than the other than abrasive, fretting, fatigue, and polishing wear. Repeated stressing of a surface by sliding contact can cause cracks to nucleate and grow, producing the flake-like delaminations and pitting that are associated with fatigue wear. Fretting wear is a special case of reversed oscillating sliding wear in which the relative displacements between bodies are quite small (1.2 m, or 0.05 mil) than a decorative deposit, but not necessarily harder.

o

hard drawn o

o

hardenability o

o

Wear-resistant materials available as bare welding rod, flux-coated rod, long-length solid wires, long-length tubular wires, or powders that are deposited by hardfacing.

hard metal o

o

The application of a hard, wear-resistant material to the surface of a component by welding, spraying, or allied welding processes to reduce wear or loss of material by abrasion, impact, erosion, galling, and cavitation. See also surfacing .

hardfacing alloys o

o

Increasing hardness of metals by suitable treatment, usually involving heating and cooling. When applicable, the following, more specific terms should be used: age hardening , case hardening , flame hardening , induction hardening , precipitation hardening , and quench hardening .

hardfacing o

o

An alloy rich in one or more alloying elements that is added to a melt to permit closer control of composition than is possible by the addition of pure metals, or to introduce refractory elements not readily alloyed with the base metal. Sometimes called master alloy or rich alloy.

hardening o

o

The relative ability of a ferrous alloy to form martensite when quenched from a temperature above the upper critical temperature. Hardenability is commonly measured as the distance below a quenched surface at which the metal exhibits a specific hardness (50 HRC, for example) or a specific percentage of martensite in the microstructure.

hardener o

o

An imprecise term applied to drawn products, such as wire and tubing, that indicates substantial cold reduction without subsequent annealing. Compare with light drawn .

A collective term that designates a sintered material with high hardness, strength, and wear resistance and is characterized by a tough metallic binder phase and particles of carbides, borides, or nitrides of the refractory metals. The term is in general use abroad, while for the carbides the term cemented carbide is preferred in the U.S., and the boride and nitride materials are usually categorized as cermets .

hardness o

A measure of the resistance of a material to surface indentation or abrasion; may be thought of as a function of the stress required to produce some specified type of surface deformation. There is no absolute scale for hardness; therefore, to express hardness quantitatively, each type of test has its own scale of arbitrarily defined hardness. Indentation hardness can be measured by Brinell, Rockwell, Vickers, Knoop, and Scleroscope hardness tests.

o

hard solder

o

hard surfacing

o o o

The bottom portions of certain furnaces, such as blast furnaces, air furnaces, and other reverberatory furnaces, that support the charge and sometimes collect and hold molten metal.

heat o

o

The upsetting of wire, rod, or bar stock in dies to form parts that usually contain portions that are greater in cross-sectional area than the original wire, rod, or bar.

hearth o

o

Carbon, carbon-boron, or alloy steel produced to specified limits of hardenability; the chemical composition range may be slightly different from that of the corresponding grade of ordinary carbon or alloy steel.

heading o

o

A four-electrode cell for measurement of electrolyte resistance and electrode polarization during electrolysis.

H-band steel o

o

Same as full hard temper.

Haring cell o

o

See preferred terms surfacing or hardfacing .

hard temper o

o

A term erroneously used to denote silver-base brazing filler metals.

A stated tonnage of metal obtained from a period of continuous melting in a cupola or furnace, or the melting period required to handle this tonnage.

heat-affected zone (HAZ)

o o

heat check o

o

A pattern of parallel surface cracks that are formed by alternate rapid heating and cooling of the extreme surface metal, sometimes found on forging dies and piercing punches. There may be two sets of parallel cracks, one set perpendicular to the other.

heat-resistant alloy o

o

That portion of the base metal that was not melted during brazing, cutting, or welding, but whose microstructure and mechanical properties were altered by the heat.

An alloy developed for very-high-temperature service where relatively high stresses (tensile, thermal, vibratory, or shock) are encountered and where oxidation resistance is frequently required.

heat sink o

A material that absorbs or transfers heat away from a critical element or part.

o

heat tinting

o

heat treatable alloy

o o

Coloration of a metal surface through oxidation by heating to reveal details of the microstructure. An alloy that can be hardened by heat treatment.

o

heat treating film

o

heat treatment

o o

o

A block or plate usually mounted on or attached to a lower die in a forming or forging press that serves to prevent or minimize the deflection of punches or cams.

hemming o

o

Synonymous with base .

heel block o

o

A sintered tungsten alloy with nickel, copper, and/or iron, the tungsten content being at least 90 wt% and the density being at least 16.8 g/cm3.

heel o

o

Heating and cooling a solid metal or alloy in such a way as to obtain desired conditions or properties. Heating for the sole purpose of hot working is excluded from the meaning of this definition.

heavy metal o

o

A thin coating or film, usually an oxide, formed on the surface of a metal during heat treatment.

A bend of 180° made in two steps. First, a sharp-angle bend is made; next the bend is closed using a flat punch and a die.

HERF o

A common abbreviation for high-energy-rate forging or high-energy-rate forming .

o

herringbone pattern

o

high-conductivity copper

o o o

A closed-die hot- or cold-forging process in which the stored energy of high-pressure gas is used to accelerate a ram to unusually high velocities in order to effect deformation of the workpiece. Ideally, the final configuration of the forging is developed in one blow or, at most, a few blows. In high-energy-rate forging, the velocity of the ram, rather than its mass, generates the major forging force. Also known as HERF processing, high-velocity forging, and high-speed forging.

high-energy-rate forming o

o

Fatigue that occurs at relatively large numbers of cycles. The arbitrary, but commonly accepted, dividing line between high-cycle fatigue and low-cycle fatigue is considered to be about 104 to 105 cycles. In practice, this distinction is made by determining whether the dominant component of the strain imposed during cyclic loading is elastic (high cycle) or plastic (low cycle), which in turn depends on the properties of the metal and on the magnitude of the nominal stress.

high-energy-rate forging (HERF) o

o

Copper that, in the annealed condition, has a minimum electrical conductivity of 100% IACS as determined by ASTM test methods.

high-cycle fatigue o

o

Same as chevron pattern .

A group of forming processes that applies a high rate of strain to the material being formed through the application of high rates of energy transfer. See also explosive forming , highenergy-rate forging , and electromagnetic forming .

high frequency resistance welding

o o

highlighting o

o

o

HIP

o

hob

o o

Machining a part from bar stock, plate, or a simple forging in which much of the original stock is removed. A pressurized plate designed to hold the workpiece down during a press operation. In practice, this plate often serves as a stripper and is also called a stripper plate. In heat treating of metals, that portion of the thermal cycle during which the temperature of the object is maintained constant.

holding furnace o

o

A rotary cutting tool with its teeth arranged along a helical thread, used for generating gear teeth or other evenly spaced forms on the periphery of a cylindrical workpiece. The hob and the workpiece are rotated in timed relationship to each other while the hob is fed axially or tangentially across or radially into the workpiece. Hobs should not be confused with multiplethread milling cutters, rack cutters, and similar tools, where the teeth are not arranged along a helical thread.

holding o

o

See hot isostatic pressing .

holddown plate (pressure pad) o

o

Contraction where the shape will not permit a metal casting to contract in certain regions in keeping with the coefficient of expansion.

hogging o

o

A loss of strength and ductility of steel by high-temperature reaction of absorbed hydrogen with carbides in the steel resulting in decarburization and internal fissuring.

hindered contraction o

o

Steels designed to provide better mechanical properties and/or greater resistance to atmospheric corrosion than conventional carbon steels. They are not considered to be alloy steels in the normal sense because they are designed to meet specific mechanical properties rather than a chemical composition (HSLA steels have yield strengths greater than 275 MPa, or 40 ksi). The chemical composition of a specific HSLA steel may vary for different product thicknesses to meet mechanical property requirements. The HSLA steels have low carbon contents (0.05 to 0.25% C) in order to produce adequate formability and weldability, and they have manganese contents up to 2.0%. Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium, and zirconium are used in various combinations.

high-temperature hydrogen attack o

o

High-productivity machining processes that achieve cutting speeds in excess of 600 m/min (2000 sfm) and up to 18,000 m/min (60,000 sfm).

high-strength low-alloy (HSLA) steels o

o

Deoxidized copper with residual phosphorus present in amounts (usually 0.013 to 0.04%) generally sufficient to decrease appreciably the conductivity of the copper.

high-speed machining o

o

Buffing or polishing selected areas of a complex shape to increase the luster or change the color of those areas.

high residual phosphorus copper o

o

A group of resistance welding process variations that uses high frequency welding current to concentrate the welding heat at the desired location.

A furnace into which molten metal can be transferred to be held at the proper temperature until it can be used to make castings.

holding temperature o

In heat treating of metals, the constant temperature at which the object is maintained.

o

holding time

o

hole expansion test

o o

o

Time for which the temperature of the heat treated metal object is maintained constant. A simulative test in which a flat metal sheet specimen with a circular hole in its center is clamped between annular die plates and deformed by a punch, which expands and ultimately cracks the edge of the hole.

hole flanging

o o

holidays o

o

A heat treating practice whereby a metal object is held at high temperature to eliminate or decrease chemical segregation by diffusion.

honing o

o

Use of a carburizing process to convert a low-carbon ferrous alloy to one of uniform and higher carbon content throughout the section.

homogenizing o

o

Discontinuities in a coating (such as porosity, cracks, gaps, and similar flaws) that allow areas of substrate to be exposed to any corrosive environment that contacts the coated surface.

homogeneous carburizing o

o

The forming of an integral collar around the periphery of a previously formed hole in a sheet metal part.

A low-speed finishing process used chiefly to produce uniform high dimensional accuracy and fine finish, most often on inside cylindrical surfaces. In honing, very thin layers of stock are removed by simultaneously rotating and reciprocating a bonded abrasive stone or stick that is pressed against the surface being honed with lighter force than is typical of grinding.

Hooke's law o

A generalization applicable to all solid material, which states that stress is directly proportional to strain and is expressed as:

o

where E is the modulus of elasticity or Young's modulus. The constant relationship between stress and strain applies only below the proportional limit. See also modulus of elasticity .

o

Hoopes process

o

horn

o o

o

A die casting machine in which the metal chamber under pressure is immersed in the molten metal in a furnace. The chamber is sometimes called a gooseneck, and the machine is sometimes called a gooseneck machine.

hot-cold working o

o

In foundry practice, resin-base (furan or phenolic) binder process for molding sands similar to shell coremaking; cores produced with it are solid unless mandrelled out.

hot chamber machine o

o

The distance between adjacent surfaces of the horns of a resistance welding machine.

hot box process o

o

A mechanical metal forming press equipped with or arranged for a cantilever block or horn that acts as the die or support for the die, used in forming, piercing, setting down, or riveting hollow cylinders and odd-shaped work.

horn spacing o

o

(1) In a resistance welding machine, a cylindrical arm or beam that transmits the electrode pressure and usually conducts the welding current. (2) A cone-shaped member that transmits ultrasonic energy from a transducer to a welding or machining tool. See also ultrasonic impact grinding and ultrasonic welding .

horn press o

o

An electrolytic refining process for aluminum, using three liquid layers in the reduction cell.

(1) A high-temperature thermomechanical treatment consisting of deforming a metal above its transformation temperature and cooling fast enough to preserve some or all of the deformed structure. (2) A general term synonymous with warm working .

hot corrosion o

An accelerated corrosion of metal surfaces that results from the combined effect of oxidation and reactions with sulfur compounds and other contaminants, such as chlorides, to form a molten salt on a metal surface that fluxes, destroys, or disrupts the normal protective oxide. See also gaseous corrosion .

o

hot crack

o

hot-die forging

o

A crack that develops in a weldment or casting during solidification.

o

o

hot dip o

o

A metallic coating obtained by dipping the substrate into a molten metal.

hot extrusion o

o

Covering a surface by dipping the surface to be coated into a molten bath of the coating material. See also hot dip coating .

hot dip coating o

o

A hot forging process in which both the dies and the forging stock are heated; typical die temperatures are 110 to 225 °C (200 to 400 °F) lower than the temperature of the stock. Compare with isothermal forging .

A process whereby a heated billet is forced to flow through a shaped die opening. The temperature at which extrusion is performed depends on the material being extruded. Hot extrusion is used to produce long, straight metal products of constant cross section, such as bars, solid and hollow sections, tubes, wires, and strips, from materials that cannot be formed by cold extrusion.

hot forging o

(1) A forging process in which the die and/or forging stock are heated. See also hot-die forging and isothermal forging . (2) The plastic deformation of a pressed and/or sintered powder compact in at least two directions at temperatures above the recrystallization temperature.

o

hot forming

o

hot isostatic pressing

o o

o

(1) A process for simultaneously heating and forming a compact in which the powder is contained in a sealed flexible sheet metal or glass enclosure and the so-contained powder is subjected to equal pressure from all directions at a temperature high enough to permit plastic deformation and sintering to take place. (2) A process that subjects a component (casting, powder forgings, etc.) to both elevated temperature and isostatic gas pressure in an autoclave. The most widely used pressurizing gas is argon. When castings are hot isostatically pressed, the simultaneous application of heat and pressure virtually eliminates internal voids and microporosity through a combination of plastic deformation, creep, and diffusion.

hot mill o

o

See hot working .

A production line or facility for hot rolling of metals.

hot press forging o

Plastically deforming metals between dies in presses at temperatures high enough to avoid strain hardening.

o

hot pressing

o

hot pressure welding

o o

o

A solid-state welding process that produces coalescence of materials with heat and application of pressure sufficient to produce macrodeformation of the base material. Vacuum or other shielding media may be used. See also diffusion welding and forge welding . Compare with cold welding .

hot quenching o

o

Simultaneous heating and forming of a powder compact. See also pressure sintering .

An imprecise term for various quenching procedures in which a quenching medium is maintained at a prescribed temperature above 70 °C (160 °F).

hot shortness o

A tendency for some alloys to separate along grain boundaries when stressed or deformed at temperatures near the melting point. Hot shortness is caused by a low-melting constituent, often present only in minute amounts, that is segregated at grain boundaries.

o

hot tear

o

hot top

o o

A fracture formed in a metal during solidification because of hindered contraction . (1) A reservoir, thermally insulated or heated, that holds molten metal on top of a mold for feeding of the ingot or casting as it contracts on solidifying, thus preventing formation of pipe or voids. (2) A refractory-lined steel or iron casting that is inserted into the tip of the mold and is supported at various heights to feed the ingot as it solidifies.

o

hot trimming

o

hot upset forging

o

The removal of flash or excess metal from a hot part (such as a forging) in a trimming press.

o

A bulk forming process for enlarging and reshaping some of the cross-sectional area of a bar, tube, or other product form of uniform (usually round) section. It is accomplished by holding the heated forging stock between grooved dies and applying pressure to the end of the stock, in the direction of its axis, by the use of a heading tool, which spreads (upsets) the end by metal displacement. Also called hot heading or hot upsetting. See also heading and upsetting .

o

hot-worked structure

o

hot working

o o

o

(1) The plastic deformation of metal at such a temperature and strain rate that recrystallization takes place simultaneously with the deformation, thus avoiding any strain hardening. Also referred to as hot forging and hot forming. (2) Controlled mechanical operations for shaping a product at temperatures above the recrystallization temperature. Contrast with cold working .

hubbing o

o

The structure of a material worked at a temperature higher than the recrystallization temperature.

The production of forging die cavities by pressing a male master plug, known as a hub, into a block of metal.

Hull cell o

A special electrodeposition cell giving a range of known current densities for test work.

o

hydraulic hammer

o

hydraulic-mechanical press brake

o o o

A mechanical press brake that uses hydraulic cylinders attached to mechanical linkages to power the ram through its working stroke.

hydraulic press o

o

A gravity-drop forging hammer that uses hydraulic pressure to lift the hammer between strokes.

A press in which fluid pressure is used to actuate and control the ram. Hydraulic presses are used for both open- and closed-die forging.

hydrodynamic machining o

Removal of material by the impingement of a high-velocity fluid against a workpiece. See also waterjet/abrasive waterjet machining .

o

hydrogen-assisted cracking (HAC)

o

hydrogen-assisted stress-corrosion cracking (HSCC)

o o o

A term sometimes used to denote brazing in a hydrogen-containing atmosphere, usually in a furnace; use of the appropriate process name is preferred.

hydrogen damage o

o

The formation of blisters on or below a metal surface from excessive internal hydrogen pressure. Hydrogen may be formed during cleaning, plating, or corrosion.

hydrogen brazing o

o

See hydrogen embrittlement .

hydrogen blistering o

o

See hydrogen embrittlement .

A general term for the embrittlement, cracking, blistering, and hydride formation that can occur when hydrogen is present in some metals.

hydrogen embrittlement o

A process resulting in a decrease of the toughness or ductility of a metal due to the presence of atomic hydrogen. Hydrogen embrittlement has been recognized classically as being of two types. The first, known as internal hydrogen embrittlement, occurs when the hydrogen enters molten metal which becomes supersaturated with hydrogen immediately after solidification. The second type, environmental hydrogen embrittlement, results from hydrogen being absorbed by solid metals. This can occur during elevated-temperature thermal treatments and in service during electroplating, contact with maintenance chemicals, corrosion reactions, cathodic protection, and operating in high-pressure hydrogen. In the absence of residual stress or external loading, environmental hydrogen embrittlement is manifested in various forms, such as blistering, internal cracking, hydride formation, and reduced ductility. With a tensile stress or stress-intensity factor exceeding a specific threshold, the atomic hydrogen interacts with the metal to induce subcritical crack growth leading to fracture. In the absence of a corrosion reaction (polarized cathodically), the usual term used is hydrogen-assisted cracking (HAC) or hydrogen stress cracking (HSC). In the presence of active corrosion, usually as pits or crevices (polarized anodically), the cracking is generally called stress-corrosion cracking (SCC), but should more properly be called hydrogenassisted stress-corrosion cracking (HSCC). Thus, HSC and electrochemically anodic SCC can

operate separately or in combination (HSCC). In some metals, such as high-strength steels, the mechanism is believed to be all, or nearly all, HSC. The participating mechanism of HSC is not always recognized and may be evaluated under the generic heading of SCC. o

hydrogen-induced cracking (HIC) o

o

hydrogen-induced delayed cracking o

o

A term sometimes used to identify a form of hydrogen embrittlement in which a metal appears to fracture spontaneously under a steady stress less than the yield stress. There is usually a delay between the application of stress (or exposure of the stressed metal to hydrogen) and the onset of cracking. Also referred to as static fatigue.

hydrogen loss o

o

Same as hydrogen embrittlement .

The loss in weight of metal powder or a compact caused by heating a representative sample according to a specified procedure in a purified hydrogen atmosphere. Broadly, a measure of the oxygen content of the sample when applied to materials containing only such oxides as are reducible with hydrogen and no hydride-forming element.

hydrogen overvoltage o

In electroplating, overvoltage associated with the liberation of hydrogen gas.

o

hydrogen stress cracking (HSC)

o

hydrometallurgy

o o o

Industrial winning or refining of metals using water or an aqueous solution.

hydrostatic extrusion o

o

See hydrogen embrittlement .

A method of extruding a billet through a die by pressurized fluid instead of the ram used in conventional extrusion.

hydrostatic pressing o

A special case of isostatic pressing that uses a liquid such as water or oil as a pressure transducing medium and is therefore limited to near room-temperature operation.

o

hydrostatic tension

o

hypereutectic alloy

o o

o

The phenomenon of permanently absorbed or lost energy that occurs during any cycle of loading or unloading when a material is subjected to repeated loading.

I

IACS o

o

The lag of the magnetization of a substance behind any cyclic variation of the applied magnetizing field.

hysteresis (mechanical) o

o o

In an alloy system exhibiting a eutectoid, any alloy whose composition has an excess of base metal compared with the eutectoid composition and whose equilibrium microstructure contains some eutectoid structure.

hysteresis (magnetic) o

o

In an alloy system exhibiting a eutectic, any alloy whose composition has an excess of base metal compared with the eutectic composition and whose equilibrium microstructure contains some eutectic structure.

hypoeutectoid alloy o

o

In an alloy system exhibiting a eutectoid, any alloy whose composition has an excess of alloying element compared with the eutectoid composition, and whose equilibrium microstructure contains some eutectoid structure.

hypoeutectic alloy o

o

In an alloy system exhibiting a eutectic, any alloy whose composition has an excess of alloying element compared with the eutectic composition and whose equilibrium microstructure contains some eutectic structure.

hypereutectoid alloy o

o

Three equal and mutually perpendicular tensile stresses.

International annealed copper standard; a standard reference used in reporting electrical conductivity. The conductivity of a material, in %IACS, is equal to 1724.1 divided by the electrical resistivity of the material in n · m.

ideal critical diameter (DI)

o

o

idiomorphic crystal o

o

Under an ideal quench condition, the bar diameter that has 50% martensite at the center of the bar when the surface is cooled at an infinitely rapid rate (that is, when H = , where H is the quench severity factor or Grossmann number ). An individual crystal that has grown without restraint so that the habit planes are clearly developed. Compare with allotriomorphic crystal .

immersed-electrode furnace o

A furnace used for liquid carburizing of parts by heating molten salt baths with the use of electrodes immersed in the liquid. See also submerged-electrode furnace .

o

immersion cleaning

o

immersion coating

o o o

A form of erosion-corrosion generally associated with the local impingement of a high-velocity, flowing fluid against a solid surface.

impingement erosion o

o

Corrosion associated with turbulent flow of liquid. May be accelerated by entrained gas bubbles. See also erosion-corrosion and impingement corrosion .

impingement corrosion o

o

A process resulting in a continuing succession of impacts between liquid or solid particles and a solid surface.

impingement attack o

o

Wear of a solid surface resulting from repeated collisions between that surface and another solid body. The term erosion is preferred in the case of multiple impacts and when the impacting body or bodies are very small relative to the surface being impacted.

impingement o

o

A test for determining the energy absorbed in fracturing a test piece at high velocity, as distinct from static test. The test may be carried out in tension, bending, or torsion, and the test bar may be notched or unnotched. See also Charpy test , impact energy , and Izod test .

impact wear o

o

A measure of the resiliency or toughness of a solid. The maximum force or energy of a blow (given by a fixed procedure) that can be withstood without fracture, as opposed to fracture strength under a steady applied force.

impact test o

o

An especially severe shock load such as that caused by instantaneous arrest of a falling mass, by shock meeting of two parts (in a mechanical hammer, for example), or by explosive impact, in which there can be an exceptionally rapid buildup of stress.

impact strength o

o

A blemish on a drawn sheet metal part caused by a slight change in metal thickness. The mark is called an impact line when it results from the impact of the punch on the blank; it is called a recoil line when it results from transfer of the blank from the die to the punch during forming, or from a reaction to the blank being pulled sharply through the draw ring.

impact load o

o

The process (or resultant product) in which a punch strikes a slug (usually unheated) in a confining die. The metal flow may be either between punch and die or through another opening. The impact extrusion of unheated slugs is often called cold extrusion.

impact line o

o

The amount of energy, usually given in joules or foot-pound force, required to fracture a material, usually measured by means of an Izod test or Charpy test. The type of specimen and test conditions affect the values and therefore should be specified.

impact extrusion o

o

Depositing a metallic coating on a metal immersed in a liquid solution, without the aid of an external electric current. Also called dip plating.

impact energy o

o

A coating produced in a solution by chemical or electrochemical action without the use of external current.

immersion plating o

o

Cleaning in which the work is immersed in a liquid solution.

Loss of material from a solid surface due to liquid impingement. See also erosion .

impregnation

o

o

impression-die forging o

o

(1) Elements or compounds whose presence in a material is undesirable. (2) In a chemical or material, minor constituent(s) or component(s) not included deliberately; usually to some degree or above some level, undesirable.

inclinable press o

o

A forging that is formed to the required shape and size by machined impressions in specially prepared dies that exert three-dimensional control on the workpiece.

impurities o

o

(1) Treatment of porous castings with a sealing medium to stop pressure leaks. (2) The process of filling the pores of a sintered compact, usually with a liquid such as a lubricant. (3) The process of mixing particles of a nonmetallic substance in a cemented carbide matrix, as in diamondimpregnated tools.

A press that can be inclined to facilitate handling of the formed parts. See also open-back inclinable press .

inclusion o

(1) A physical and mechanical discontinuity occurring within a material or part, usually consisting of solid, encapsulated foreign material. Inclusions are often capable of transmitting some structural stresses and energy fields, but to a noticeably different degree than from the parent material. (2) Particles of foreign material in a metallic matrix. The particles are usually compounds, such as oxides, sulfides, or silicates, but may be of any substance that is foreign to (and essentially insoluble in) the matrix. See also exogenous inclusion , indigenous inclusion , and stringer .

o

inclusion count

o

incomplete fusion

o o o

In hardness testing, a solid body of prescribed geometry, usually chosen for its high hardness, that is used to determine the resistance of a solid surface to penetration.

indigenous inclusion o

o

(1) The resistance of a material to indentation. This is the usual type of hardness test, in which a pointed or rounded indenter is pressed into a surface under a substantially static load. (2) Resistance of a solid surface to the penetration of a second, usually harder, body under prescribed conditions. Numerical values used to express indentation hardness are not absolute physical quantities, but depend on the hardness scale used to express hardness. See also Brinell hardness test , Knoop hardness test , nanohardness test , Rockwell hardness test , and Vickers hardness test .

indenter o

o

In welding, fusion that is less than complete.

indentation hardness o

o

Determination of the number, kind, size, and distribution of nonmetallic inclusions in metals.

An inclusion that is native, innate, or inherent in the molten metal treatment. Indigenous inclusions include sulfides, nitrides, and oxides derived from the chemical reaction of the molten metal with the local environment. Such inclusions are small and require microscopic magnification for identification. Compare with exogenous inclusion .

indirect-arc furnace o

An electric arc furnace in which the metallic charge is not one of the poles of the arc.

o

indirect (backward) extrusion

o

induction brazing

o o o

An alternating current electric furnace in which the primary conductor is coiled and generates, by electromagnetic induction, a secondary current that develops heat within the metal charge.

induction hardening o

o

A brazing process in which the heat required is obtained from the resistance of the workpieces to induced electric current.

induction furnace o

o

See extrusion .

A surface-hardening process in which only the surface layer of a suitable ferrous workpiece is heated by electromagnetic induction to above the upper critical temperature and immediately quenched.

induction heating

o o

induction melting o

o

Heating by combined electrical resistance and hysteresis losses induced by subjecting a metal to the varying magnetic field surrounding a coil carrying alternating current. Melting in an induction furnace.

induction soldering o

A soldering process in which the heat required is obtained from the resistance of the workpieces to induced electric current.

o

induction tempering

o

induction welding

o o

o

The inductor used when induction heating and melting as well as induction welding, brazing, and soldering.

inductor o

o

A welding process that produces coalescence of metals by the heat obtained from the resistance of the workpieces to the flow of induced high-frequency welding current with or without the application of pressure. The effect of the high-frequency welding current is to concentrate the welding heat at the desired location.

induction work coil o

o

Tempering of steel using low-frequency electrical induction heating.

A device consisting of one or more associated windings, with or without a magnetic core, for introducing inductance into an electric circuit.

industrial atmosphere o

An atmosphere in an area of heavy industry with soot, fly ash, and sulfur compounds as the principal constituents.

o

inert anode

o

inert gas

o o

o

An anode that is insoluble in the electrolyte under the conditions prevailing in the electrolysis. (1) A gas, such as helium, argon, or nitrogen, that is stable, does not support combustion, and does not form reaction products with other materials. (2) In welding, a gas that does not normally combine chemically with the base metal or filler metal. See also protective atmosphere .

infiltration o

The process of filling the pores of a sintered or unsintered compact with a metal or alloy of lower melting temperature.

o

infrared brazing

o

infrared soldering

o

infrared spectroscopy

o o o

o

A brazing process in which the heat required is furnished by infrared radiation. A soldering process in which the heat required is furnished by infrared radiation. The study of the interaction of material systems with electromagnetic radiation in the infrared region of the spectrum. The technique is useful for determining the molecular structure of organic and inorganic compounds by identifying the rotational and vibrational energy levels associated with the various molecules. See also electromagnetic radiation .

ingate o

Same as gate .

o

ingot

o

ingot iron

o o o

Commercially pure iron.

inhibitor o

o

A casting of simple shape, suitable for hot working or remelting.

A substance that retards some specific chemical reaction, e.g., corrosion. Pickling inhibitors retard the dissolution of metal without hindering the removal of scale from steel.

inoculant o

Material that, when added to molten metal, modifies the structure and thus changes the physical and mechanical properties to a degree not explained on the basis of the change in composition resulting from their use. Ferrosilicon-base alloys are commonly used to inoculate gray irons and ductile irons.

o

inoculation

o

insert

o

The addition of a material to molten metal to form nuclei for crystallization. See also inoculant .

o

o

insert die o

o

A quantitative metallographic technique in which the desired quantity, such as grain size or inclusion content, is expressed as the number of times per unit length a straight line on a metallographic image crosses particles of the feature being measured.

interconnected porosity o

o

Quenching in which the quenching medium is cooling the part at a rate at least two and a half times faster than still water. See also Grossmann number .

intercept method o

o

An impact test in which the load on the specimen is continually recorded as a function of time and/or specimen deflection prior to fracture.

intense quenching o

o

Cutters having replaceable blades that are either solid or tipped and are usually adjustable.

instrumented impact test o

o

A relatively small die that contains part or all of the impression of a forging and that is fastened to a master die block.

inserted-blade cutters o

o

(1) A part formed from a second material, usually a metal, which is placed in the molds and appears as an integral structural part of the final casting. (2) A removable portion of a die or mold.

A network of connecting pores in a sintered object that permits a fluid or gas to pass through the object. Also referred to as interlocking or open porosity.

intercritical annealing o

Any annealing treatment that involves heating to, and holding at, a temperature between the upper and lower critical temperatures to obtain partial austenitization, followed by either slow cooling or holding at a temperature below the lower critical temperature.

o

intercrystalline

o

intercrystalline corrosion

o

intercrystalline cracking

o o o o

Between the crystals, or grains, of a polycrystalline material. See intergranular corrosion . See intergranular cracking .

interdendritic corrosion o

Corrosive attack that progresses preferentially along interdendritic paths. This type of attack results from local differences in composition, such as coring commonly encountered in alloy castings.

o

interdendritic porosity

o

interface

o o o

Voids occurring between the dendrites in cast metal. The boundary between any two phases. Among the three phases (gas, liquid, and solid), there are five types of interfaces: gas-liquid, gas-solid, liquid-liquid, liquid-solid, and solid-solid.

interfacial tension o

The contractile force of an interface between two phases.

o

intergranular

o

intergranular corrosion

o o o

Corrosion occurring preferentially at grain boundaries, usually with slight or negligible attack on the adjacent grains. See also interdendritic corrosion .

intergranular cracking o

o

Between crystals or grains. Also called intercrystalline. Contrast with transgranular .

Cracking or fracturing that occurs between the grains or crystals in a polycrystalline aggregate. Also called intercrystalline cracking. Contrast with transgranular cracking .

intergranular fracture o

Brittle fracture of a polycrystalline material in which the fracture is between the grains, or crystals, that form the material. Also called intercrystalline fracture. Contrast with transgranular fracture .

o

intergranular penetration

o

intergranular stress-corrosion cracking (IGSCC)

o o

In welding, the penetration of a filler metal along the grain boundaries of a base metal. Stress-corrosion cracking in which the cracking occurs along grain boundaries.

o

intermediate annealing

o

intermediate electrode

o

intermediate phase

o o o o

Same as bipolar electrode . In an alloy or a chemical system, a distinguishable homogeneous phase whose composition range does not extend to any of the pure components of the system.

intermetallic compound o

o

Annealing wrought metals at one or more stages during manufacture and before final treatment.

An intermediate phase in an alloy system, having a narrow range of homogeneity and relatively simple stoichiometric proportions; the nature of the atomic binding can be of various types, ranging from metallic to ionic.

intermetallic phases o

Compounds, or intermediate solid solutions, containing two or more metals, which usually have compositions, characteristic properties, and crystal structures different from those of the pure components of the system.

o

intermittent weld

o

internal friction

o o

A weld in which the continuity is broken by recurring unwelded spaces. The conversion of energy into heat by a material subjected to fluctuating stress.

o

internal grinding

o

internal oxidation

o o

o

Plating in which the flow of current is discontinued for periodic short intervals to decrease anode polarization and elevate the critical current density. It is most commonly used in cyanide copper plating.

interrupted quenching o

o

Aging at two or more temperatures, by steps, and cooling to room temperature after each step. See also aging , and compare with progressive aging and step aging .

interrupted-current plating o

o

In a multiple-pass weld, the temperature (minimum or maximum as specified) of the deposited weld metal before the next pass is started.

interrupted aging o

o

See preferred term residual stress .

interpass temperature o

o

A void or network of voids within a casting caused by inadequate feeding of that section during solidification.

internal stress o

o

The formation of isolated particles of corrosion products beneath the metal surface. This occurs as the result of preferential oxidation of certain alloy constituents by inward diffusion of oxygen, nitrogen, sulfur, and so forth. Also called subscale formation.

internal shrinkage o

o

Grinding an internal surface such as that inside a cylinder or hole.

A quenching procedure in which the workpiece is removed from the first quench at a temperature substantially higher than that of the quenchant and is then subjected to a second quenching system having a different cooling rate than the first.

interstitial solid solution o

A type of solid solution that sometimes forms in alloy systems having two elements of widely different atomic sizes. Elements of small atomic size, such as carbon, hydrogen, and nitrogen, often dissolve in solid metals to form this solid solution. The space lattice is similar to that of the pure metal, and the atoms of carbon, hydrogen, and nitrogen occupy the spaces or interstices between the metal atoms. See also substitutional solid solution .

o

intracrystalline

o

intracrystalline cracking

o o o

See transgranular cracking .

inverse chill o

o

Within or across the crystals or grains of a metal; same as transcrystalline and transgranular.

The condition in a casting section in which the interior is mottled or white, while the other sections are gray iron. Also known as reverse chill, internal chill, and inverted chill.

inverse segregation

o o

investing o

o

o

A mixture of a graded refractory filler, a binder, and a liquid vehicle, used to make molds for investment casting.

investment precoat o

o

(1) Casting metal into a mold produced by surrounding, or investing, an expendable pattern with a refractory slurry coating that sets at room temperature, after which the wax or plastic pattern is removed through the use of heat prior to filling the mold with liquid metal. Also called precision casting or lost wax process . (2) A part made by the investment casting process.

investment compound o

o

A flowable mixture, or slurry, of a graded refractory filler, a binder, and a liquid vehicle that, when poured around the patterns, conforms to their shape and subsequently sets hard to form the investment mold.

investment casting o

o

In investment casting, the process of pouring the investment slurry into a flask surrounding the pattern to form the mold.

investment o

o

A concentration of low-melting constituents in those regions of an alloy in which solidification first occurs.

An extremely fine investment coating applied as a thin slurry directly to the surface of the pattern to reproduce maximum surface smoothness. The coating is surrounded by a coarser, cheaper, and more permeable investment to form the mold. See also dip coat and investment casting .

investment shell o

Ceramic mold obtained by alternately dipping a pattern set up in dip coat slurry and stuccoing with coarse ceramic particles until the shell of desired thickness is obtained. See also investment casting .

o

An atom, or group of atoms, which by loss or gain of one or more electrons has acquired an electric charge. If the ion is formed from an atom of hydrogen or an atom of a metal, it is usually positively charged; if the ion is formed from an atom of a nonmetal or from a group of atoms, it is usually negatively charged. The number of electronic charges carried by an ion is termed its electrovalence. The charges are denoted by superscripts that give their sign and number; for example, a sodium ion, which carries one positive charge, is denoted by Na+; a sulfate ion, which

ion

carries two negative charges, by o

ion carburizing o

o

A part made of cast iron.

ironing o

o

A generic term applied to atomistic film deposition processes in which the substrate surface and/or the depositing film is subjected to a flux of high-energy particles (usually gas ions) sufficient to cause changes in the interfacial region or film properties.

iron casting o

o

A method of surface hardening in which nitrogen ions are diffused into a workpiece in a vacuum through the use of high-voltage electrical energy. Synonymous with plasma nitriding or glowdischarge nitriding.

ion plating o

o

The process of modifying the physical or chemical properties of the near surface of a solid (target) by embedding appropriate atoms into it from a beam of ionized particles.

ion nitriding o

o

The reversible interchange of ions between a liquid and solid, with no substantial structural changes in the solid.

ion implantation o

o

A method of surface hardening in which carbon ions are diffused into a workpiece in a vacuum through the use of high-voltage electrical energy. Synonymous with plasma carburizing or glowdischarge carburizing.

ion exchange o

o

.

An operation used to increase the length of a tube or cup through reduction of wall thickness and outside diameter, the inner diameter remaining unchanged.

iron rot

o

Deterioration of wood in contact with iron-base alloys.

o

iron soldering

o

irradiation

o o o

o o

A type of impact test in which a V-notched specimen, mounted vertically, is subjected to a sudden blow delivered by the weight at the end of a pendulum arm. The energy required to break off the free end is a measure of the impact strength or toughness of the material. Contrast with Charpy test .

J

jaw crusher o

A machine for the primary disintegration of metal pieces, ores, or agglomerates into coarse powder.

o

A mechanism for holding a part and guiding the tool during machining or assembly operation.

jig jig boring o

o

The condition of having the same values of properties in all directions.

Izod test o

o o

Having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.

isotropy o

o

A diagram that shows the isothermal time required for transformation of austenite to begin and to finish as a function of temperature. Same as time-temperature-transformation (TTT) diagram or S-curve.

isotropic o

o

A change in phase that takes place at a constant temperature. The time required for transformation to be completed, and in some instances the time delay before transformation begins, depends on the amount of supercooling below (or superheating above) the equilibrium temperature for the same transformation.

isothermal transformation (IT) diagram o

o

A hot-forging process in which a constant and uniform temperature is maintained in the workpiece during forging by heating the dies to the same temperature as the workpiece. Compare with hot-die forging .

isothermal transformation o

o

Austenitizing a ferrous alloy, then cooling to and holding at a temperature at which austenite transforms to a relatively soft ferrite-carbide aggregate. See also austenitizing .

isothermal forging o

o

A process for forming a powder metallurgy compact by applying pressure equally from all directions to metal powder contained in a sealed flexible mold. See also cold isostatic pressing and hot isostatic pressing .

isothermal annealing o

o

Having the same crystal structure. This usually refers to intermediate phases that form a continuous series of solid solutions.

isostatic pressing o

o

A graph or chart that shows constant corrosion behavior with changing solution (environment) composition and temperature.

isomorphous o

o

The exposure of a material or object to x-rays, gamma rays, ultraviolet rays, or other ionizing radiation.

isocorrosion diagram o

o

A soldering process in which the heat required is obtained from a soldering iron .

Boring with a single-point tool where the work is positioned upon a table that can be located so as to bring any desired part of the work under the tool. Thus, holes can be accurately spaced. This type of boring can be done on milling machines or jig borers.

J-integral o

A mathematical expression; a line or surface integral that encloses the crack front from one crack surface to the other, used to characterize the fracture toughness of a material having appreciable plasticity before fracture. The J-integral eliminates the need to describe the behavior of the material near the crack tip by considering the local stress-strain field around the crack front; JIc is the critical value of the J-integral required to initiate growth of a preexisting crack.

o

joint o

o

joint clearance o

o

The distance between the faying surfaces of a joint. In brazing, this distance is referred to as that which is present before brazing, at the brazing temperature, or after brazing is completed.

joint efficiency o

o

The location where two or more members are to be or have been fastened together mechanically or by welding, brazing, soldering, or adhesive bonding.

The ratio of the strength of a welded joint to the strength of the base metal, expressed in percent.

jolt ramming o

Packing sand in a mold by raising and dropping the sand, pattern, and flask on a table. Jolt-type, jolt squeezers, jarring machines, and jolt rammers are machines using this principle. Also called jar ramming.

o

Jominy test

o o

K

o

See end-quench hardenability test.

karat o

A unit for designating the fineness of gold in an alloy. In this system, 24 karat (24 k) is 1000 fine or pure gold. The most popular jewelry golds are:

Karat designation Gold content

o

kerf

o

keyhole

o o

10k

10/24ths, or 41.67% Au

The width of the cut produced during a cutting process. A technique of welding in which a concentrated heat source, such as a plasma arc, penetrates completely through a workpiece forming a hole at the leading edge of the molten weld metal. As the heat source progresses, the molten metal fills in behind the hold to form the weld bead. A type of specimen containing a hole-and-slot notch, shaped like a keyhole, usually used in impact bend tests. See also Charpy test and Izod test . Steel treated with a strong deoxidizing agent such as silicon or aluminum in order to reduce the oxygen content to such a level that no reaction occurs between carbon and oxygen during solidification. A large furnace used for baking, drying, or burning firebrick or refractories, or for calcining ores or other substances.

KIscc o

Abbreviation for the critical value of the plane strain stress-intensity factor that will produce crack propagation by stress-corrosion cracking of a given material in a given environment.

kish o

o

14/24ths or 58.33% Au

kiln o

o

14k

killed steel o

o

18/24ths, or 75% Au

keyhole specimen o

o

18k

A standard test casting, for steel and other high-shrinkage alloys, consisting of a rectangular bar that resembles the keel of a boat, attached to the bottom of a large riser, or shrinkhead. Keel blocks that have only one bar are often called Y-blocks; keel blocks having two bars, double keel blocks. Test specimens are machined from the rectangular bar, and the shrinkhead is discarded.

o

o

100% Au (99.5% min)

keel block o

o

24k

Free graphite that forms in molten hypereutectic cast iron as it cools. In castings, the kish may segregate toward the cope surface, where it lodges at or immediately beneath the casting surface.

knife-line attack

o o

knockout o

o

o

o

A number related to the applied load and to the projected area of the permanent impression made by a rhombic-based pyramidal diamond indenter having included edge angles of 172° 30' and 130° 0' computed from the equation:

o

where P is applied load, kgf; and d is the length of the long diagonal of the impression, mm. In reporting Knoop hardness numbers, the test load is stated.

Knoop hardness test

A heavy short-stroke press in which the slide is directly actuated by a single toggle joint that is opened and closed by a connection and crack. It is used for embossing, coining, sizing, heading, swaging, and extruding.

knurling o

o

An indentation hardness test using calibrated machines to force a rhombic-based pyramidal diamond indenter having specified edge angles, under specified conditions, into the surface of the material under test and to measure the long diagonal after removal of the load.

knuckle-lever press o

o

(1) Removal of sand cores from a casting. (2) Jarring of an investment casting mold to remove the casting and investment from the flask. (3) A mechanism for freeing formed parts from a die used for stamping, blanking, drawing, forging, or heading operations. (4) A partially pierced hole in a sheet metal part, where the slug remains in the hole and can be forced out by hand if a hole is needed.

Knoop hardness number (HK)

o

o

Intergranular corrosion of an alloy, usually stabilized stainless steel, along a line adjoining or in contact with a weld after heating into the sensitization temperature range.

Impressing a design into a metallic surface, usually by means of small, hard rollers that carry the corresponding design on their surfaces.

Kroll process o

A process for the production of metallic titanium sponge by the reduction of titanium tetrachloride with a more active metal, such as magnesium or sodium. The sponge is further processed to granules or powder.

o o

L

o

lack of penetration (LOP)

lack of fusion (LOF) o o

o

A condition in a welded joint in which fusion is less than complete. A condition in a welded joint in which joint penetration is less than that specified.

ladle o

Metal receptacle frequently lined with refractories used for transporting and pouring molten metal.

o

ladle metallurgy

o

lamellar tearing

o o

o

Occurs in the base metal adjacent to weldments due to high through-thickness strains introduced by weld metal shrinkage in highly restrained joints. Tearing occurs by decohesion and linking along the working direction of the base metal; cracks usually run roughly parallel to the fusion line and are steplike in appearance.

laminate o

o

Degassing processes for steel carried out in a ladle.

(1) A composite metal, usually in the form of flat sheets, composed of two or more metal layers so bonded that the composite metal forms a structural member. (2) To form a metallic product of two or more bonded layers.

lamination o

(1) A type of discontinuity with separation or weakness generally aligned parallel to the worked surface of a metal. May be the result of pipe, blisters, seams, inclusions, or segregation elongated and made directional by working. Laminations may also occur in powder metallurgy compacts.

(2) In electrical products such as motors, a blanked piece of electrical sheet that is stacked up with several other identical pieces to make a stator or rotor. o

lancing o

o

o

o

land o

(1) For profile-sharpened milling cutters, the relieved portion immediately behind the cutting edge. (2) For reamers, drills, and taps, the solid section between the flutes. (3) On punches, the portion adjacent to the nose that is parallel to the axis and of maximum diameter.

o

A surface imperfection, with the appearance of a seam, caused by hot metal, fins, or sharp corners being folded over and then being rolled or forged into the surface but without being welded.

lap lapping o

o

(1) A press operation in which a single-line cut is made in strip stock without producing a detached slug. Chiefly used to free metal for forming, or to cut partial contours for blanked parts, particularly in progressive dies. (2) A piercing (cutting) process carried out by metal powder cutting or oxyfuel gas cutting.

A finishing operation using fine abrasive grits loaded into a lapping material such as cast iron. Lapping provides major refinements in the workpiece including extreme accuracy of dimension, correction of minor imperfections of shape, refinement of surface finish, and close fit between mating surfaces.

laser o

A device that produces a concentrated coherent light beam by stimulating electronic or molecular transitions to lower energy levels. Laser is an acronym for light amplification by stimulated emission of radiation.

o

laser alloying

o

laser beam cutting

o o

o

A welding process that produces coalescence of materials with the heat obtained from the application of a concentrated coherent light beam impinging upon the joint.

laser hardening o

o

Use of a highly focused monofrequency collimated beam of light to melt or sublime material at the point of impingement on a workpiece.

laser beam welding (LBW) o

o

A thermal cutting process that severs materials by melting or vaporizing them with the heat obtained from a laser beam, with or without the application of gas jets to augment the removal of material.

laser beam machining o

o

See laser surface processing .

A surface-hardening process that uses a laser to quickly heat a surface. Heat conduction into the interior of the part will quickly cool the surface, leaving a shallow martensitic layer.

laser surface processing o

The use of lasers with continuous outputs of 0.5 to 10 kW to modify the metallurgical structure of a surface and to tailor the surface properties without adversely affecting the bulk properties. The surface modification can take the following three forms. The first is transformation hardening in which a surface is heated so that thermal diffusion and solid-state transformations can take place. The second is surface melting, which results in a refinement of the structure due to the rapid quenching from the melt. The third is surface (laser) alloying, in which alloying elements are added to the melt pool to change the composition of the surface. The novel structures produced by laser surface melting and alloying can exhibit improved electrochemical and tribological behavior.

o

latent heat

o

lateral extrusion

o o o

An operation in which the product is extruded sideways through an orifice in the container wall.

lath martensite o

o

Thermal energy absorbed or released when a substance undergoes a phase change.

Martensite formed partly in steels containing less than approximately 1.0% C and solely in steels containing less than approximately 0.5% C as parallel arrays of packets of lath-shape units 0.1 to 0.3 m thick.

lattice constants o

See lattice parameter .

o

lattice parameter o

o

o

o

The length of any side of a unit cell of a given crystal structure. The term is also used for the fractional coordinates x, y, and z of lattice points when these are variable.

launder o

(1) A channel for transporting molten metal. (2) A box conduit conveying particles suspended in water.

o

Direction of predominant surface pattern remaining after cutting, grinding, lapping, or other processing.

lay lead o

(1) The axial advance of a helix in one complete turn. (2) The slight bevel at the outer end of a face cutting edge of a face mill.

o

lead angle

o

lead burning

o

leak testing

o o o

o

An imprecise term, applied to drawn products such as wire and tubing, that indicates a lesser amount of cold reduction than for hard drawn products. A filler-metal electrode used in arc welding, consisting of a metal wire with a light coating, usually of metal oxides and silicates, applied subsequent to the drawing operation primarily for stabilizing the arc. Contrast with covered electrode .

light metal o

o

An induction melting process in which the metal being melted is suspended by the electromagnetic field and is not in contact with a container.

lightly coated electrode o

o

(1) Separation of fine powder from coarser material by forming a suspension of the fine material in a liquid. (2) A means of classifying a material as to particle size by the rate of settling from a suspension.

light drawn o

o

Flattening of rolled sheet, strip, or plate by reducing or eliminating distortions. See also stretcher leveling and roller leveling.

levitation melting o

o

Lines on sheet or strip running transverse to the direction of roller leveling. These lines may be seen upon stoning or light sanding after leveling (but before drawing) and can usually be removed by moderate stretching.

levigation o

o

Slow cooling rates associated with a hot vapor blanket that surrounds a part being quenched in a liquid medium such as water. The gaseous vapor envelope acts as an insulator, thus slowing the cooling rate.

leveling o

o

A cutter all of whose flutes twist away in a counterclockwise direction when viewed from either end.

leveler lines o

o

The eutectic of the iron-carbon system, the constituents of which are austenite and cementite. The austenite decomposes into ferrite and cementite on cooling below Ar1, the temperature at which transformation of austenite to ferrite or ferrite plus cementite is completed during cooling.

Leidenfrost phenomenon o

o

A nondestructive test for determining the escape or entry of liquids or gases from pressurized or into evacuated components or systems intended to hold these liquids. Leak testing systems, which employ a variety of gas detectors, are used for locating (detecting and pinpointing) leaks, determining the rate of leakage from one leak or from a system, or monitoring for leakage.

left-hand cutting tool o

o

A misnomer for welding of lead.

ledeburite o

o

In cutting tools, the helix angle of the flutes.

One of the low-density metals, such as aluminum, magnesium, titanium, beryllium, or their alloys.

limiting current density

o o

limiting dome height (LDH) test o

o

The change per unit length due to force in an original linear dimension. An increase in length is considered positive.

liner o

o

A method of fracture analysis that can determine the stress (or load) required to induce fracture instability in a structure containing a cracklike flaw of known size and shape. See also fracture mechanics and stress-intensity factor.

linear (tensile or compressive) strain o

o

(1) Deviations from perfect alignment of parallel arms of a columnar dendrite as a result of interdendritic shrinkage during solidification from a liquid. This type of deviation may vary in orientation from a few minutes to as much as two degrees of arc. (2) A type of substructure consisting of elongated subgrains.

linear elastic fracture mechanics o

o

A mechanical test, usually performed unlubricated on sheet metal, that simulates the fracture conditions in a practical press-forming operation.

lineage structure o

o

The maximum current density that can be used to obtain a desired electrode reaction without undue interference such as from polarization.

(1) The slab of coating metal that is placed on the core alloy and is subsequently rolled down to clad sheet as a composite. (2) In extrusion, a removable alloy steel cylindrical chamber, having an outside longitudinal taper firmly positioned in the container or main body of the press, into which the billet is placed for extrusion.

line reaming o

Simultaneous reaming of coaxial holes in various sections of a workpiece with a reamer having cutting faces or piloted surfaces with the desired alignment.

o

lip-pour ladle

o

liquation

o o

o

Ladle in which the molten metal is poured over a lip, much as water is poured out of a bucket. (1) The separation of a low-melting constituent of an alloy from the remaining constituents, usually apparent in alloys having a wide melting range. (2) Partial melting of an alloy, usually as a result of coring or other compositional heterogeneities.

liquation temperature o

The lowest temperature at which partial melting can occur in an alloy that exhibits the greatest possible degree of segregation.

o

liquid carburizing

o

liquid honing

o o o

A nitrocarburizing process (where both carbon and nitrogen are absorbed into the surface) utilizing molten liquid salt baths below the lower critical temperature.

liquid penetrant inspection o

o

A method of surface hardening in which molten nitrogen-bearing, fused-salt baths containing both cyanides and cyanates are exposed to parts at subcritical temperatures.

liquid nitrocarburizing o

o

Catastrophic brittle failure of a normally ductile metal when in contact with a liquid metal and subsequently stressed in tension. See also solid metal embrittlement .

liquid nitriding o

o

Producing a finely polished finish by directing an air-ejected chemical emulsion containing fine abrasives against the surface to be finished.

liquid metal embrittlement (LME) o

o

Surface hardening of steel by immersion into a molten bath consisting of cyanides and other salts.

A type of nondestructive inspection that locates discontinuities that are open to the surface of a metal by first allowing a penetrating dye or fluorescent liquid to infiltrate the discontinuity, removing the excess penetrant, and then applying a developing agent that causes the penetrant to seep back out of the discontinuity and register as an indication. Liquid penetrant inspection is suitable for both ferrous and nonferrous materials, but is limited to the detection of open surface discontinuities in nonporous solids.

liquid phase sintering o

Sintering of a compact or loose powder aggregate under conditions where a liquid phase is present during part of the sintering cycle.

o

liquid shrinkage

o

liquidus

o o

o

A molding material consisting of sand, silt, and clay, used over brickwork or other structural backup material for making massive castings, usually of iron or steel.

local action o

o

(1) In cutting, building up of a cutting tool back of the cutting edge by undesired adherence of material removed from the work. (2) In grinding, filling the pores of a grinding wheel with material from the work, usually resulting in a decrease in production and quality of finish. (3) In powder metallurgy, filling of the die cavity with powder.

loam o

o

(1) The lowest temperature at which a metal or an alloy is completely liquid.(2) In a phase diagram, the locus of points representing the temperatures at which the various compositions in the system begin to freeze on cooling or finish melting on heating. See also solidus .

loading o

o

The reduction in volume of liquid metal as it cools to the liquidus.

Corrosion due to the action of "local cells," that is, galvanic cells resulting from inhomogeneities between adjacent areas on a metal surface exposed to an electrolyte.

local cell o

A galvanic cell resulting from inhomogeneities between areas on a metal surface in an electrolyte. The inhomogeneities may be of physical or chemical nature in either the metal or its environment.

o

local current density

o

localized corrosion

o

localized precipitation

o o o

o

o

An arrangement of hot rolling stands such that a hot bar, while being discharged from one stand, is fed into a second stand in the opposite direction. Refers to an area in a formed panel that is not stiff enough to hold its shape, may be confused with oil canning.

lost foam casting o

o

See transverse direction .

loose metal o

o

The making of a resistance seam weld in a direction essentially parallel to the throat depth of a resistance welding machine.

looping mill o

o

A magnetic field that extends within a magnetized part from one or more poles to one or more other poles and that is completed through a path external to the part.

long transverse o

o

That direction parallel to the direction of maximum elongation in a worked material. See also normal direction and transverse direction .

longitudinal resistance seam welding o

o

In forging, a condition in which the flash line is not entirely in one plane. Where two or more plane changes occur, it is called compound lock. Where a lock is placed in the die to compensate for die shift caused by a steep lock, it is called a counterlock.

longitudinal field o

o

Precipitation from a supersaturated solid solution similar to continuous precipitation , except that the precipitate particles form at preferred locations, such as along slip planes, grain boundaries, or incoherent twin boundaries.

longitudinal direction o

o

Corrosion at discrete sites, for example, crevice corrosion, pitting, and stress-corrosion cracking.

lock o

o

Current density at a point or on a small area.

An expendable pattern process in which an expandable polystyrene pattern surrounded by the unbonded sand, is vaporized during pouring of the molten metal.

lost wax process o

An investment casting process in which a wax pattern is used.

o

(1) A specific amount of material produced at one time using one process and constant conditions of manufacture, and offered for sale as a unit quantity. (2) A quantity of material that is thought

lot

to be uniform in one or more stated properties such as isotopic, chemical, or physical characteristics. (3) A quantity of bulk material of similar composition whose properties are under study. Compare with batch . o

low-alloy steels o

o

low-cycle fatigue o

o

(1) The reduction of frictional resistance and wear, or other forms of surface deterioration, between two load-bearing surfaces by the application of a lubricant. (2) Mixing or incorporating a lubricant with a powder to facilitate compacting and ejecting of the compact from the die cavity; also, applying a lubricant to die walls and/or punch surfaces.

Lüders lines o

o

(1) Any substance interposed between two surfaces in relative motion for the purpose of reducing the friction or wear between them. (2) A material applied to dies, molds, plungers, or workpieces that promotes the flow of metal, reduces friction and wear, and aids in the release of the finished part.

lubrication o

o

Deoxidized copper with residual phosphorus present in amounts (usually 0.004 to 0.012%) generally too small to decrease appreciably the electrical conductivity of the copper.

lubricant o

o

A covered arc welding electrode that provides an atmosphere around the arc and molten weld metal that is low in hydrogen.

low-residual-phosphorus copper o

o

The part of a pneumatic or hydraulic press that is moving in a lower cylinder and transmits pressure to the lower punch.

low-hydrogen electrode o

o

Fatigue that occurs at relatively small numbers of cycles (0 and is taken to be zero when the load ratio is 0.

minus sieve o

o

In fatigue, the stress having the lowest algebraic value in the cycle, tensile stress being considered positive and compressive stress negative.

minimum stress-intensity factor (Kmin) o

o

The minimum radius over which a metal product can be bent to a given angle without fracture.

Nominal stress at fracture in a bend test or torsion test. In bending, modulus of rupture is the bending moment at fracture divided by the section modulus. In torsion, modulus of rupture is the torque at fracture divided by the polar section modulus.

Mohs hardness o

The hardness of a body according to a scale proposed by Mohs, based on ten minerals, each of which would scratch the one below it. These minerals, in decreasing order of hardness, are:

Diamond

10

Corundum

9

Topaz

8

Quartz

7

Othoclase (feldspar) 6

o

5

Fluorite

4

Calcite

3

Gypsum

2

Talc

1

mold o

o

Apatite

(1) The form, made of sand, metal, or refractory material, that contains the cavity into which molten metal is poured to produce a casting of desired shape. (2) A die.

mold cavity o

The space in a mold that is filled with liquid metal to form the casting upon solidification. The channel through which liquid metal enters the mold cavity (sprue, runner, gates) and reservoirs for liquid metal (risers) are not considered part of the mold cavity proper.

o

molding machine

o

molding press

o

molding sands

o o o

A machine for making sand molds by mechanically compacting sand around a pattern. A press used to form powder metallurgy compacts. Foundry sands containing more than 5% natural clay, usually between 8 and 20%.

o

mold jacket

o

mold wash

o o o

An isothermal reversible reaction in a binary system, in which a liquid on cooling decomposes into a second liquid of a different composition and a solid. It differs from a eutectic in that only one of the two products of the reaction is below its freezing range.

monotropism o

o

A process for extracting and purifying nickel. The main features consist of forming nickel carbonyl by reaction of finely divided reduced metal with carbon monoxide, then decomposing the nickel carbonyl to deposit purified nickel on small nickel pellets.

monotectic o

o

The liquid state of a weld prior to solidification as weld metal.

Mond process o

o

An aqueous or alcoholic emulsion or suspension of various materials used to coat the surface of a casting mold cavity.

molten weld pool o

o

Wood or metal form that is slipped over a sand mold for support during pouring of a casting.

The ability of a solid to exist in two or more forms (crystal structures), but in which one form is the stable modification at all temperatures and pressures. Ferrite and martensite are a monotropic pair below the temperature at which austenite begins to form, for example, in steels. Alternate spelling is monotrophism.

morphology o

The characteristic shape, form, or surface texture or contours of the crystals, grains, or particles of (or in) a material, generally on a microscopic scale.

o

mosaic structure

o

mottled cast iron

o o o

In crystals, a substructure in which adjoining regions have only slightly different orientations. Iron that consists of a mixture of variable proportions of gray cast iron and white cast iron; such a material has a mottled fracture appearance.

mounting

o o

mounting resin o

o

The mixing and kneading of foundry molding sand with moisture and clay to develop suitable properties for molding.

multiaxial stresses o

o

For any alloy system, the temperature at which martensite starts to form on cooling. See transformation temperature for the definition applicable to ferrous alloys.

mulling o

o

Thermosetting or thermoplastic resins used to mount metallographic specimens.

Ms temperature o

o

A means by which a specimen for metallographic examination may be held during preparation of a section surface. The specimen can be embedded in plastic or secured mechanically in clamps.

Any stress state in which two or three principal stresses are not zero.

multiple o

A piece of stock for forging that is cut from bar or billet lengths to provide the exact amount of material for a single workpiece.

o

multiple-pass weld

o

multiple-slide press

o o o

A weld made by depositing filler metal with two or more successive passes. A press with individual slides, built into the main slide or connected to individual eccentrics on the main shaft, that can be adjusted to vary the length of stroke and the timing. See also slide .

multiple spot welding o

Spot welding in which several spots are made during one complete cycle of the welding machine.

o

m-value

o o

N

o

nanohardness test o

o

An indentation hardness testing procedure, usually relying on indentation force versus tip displacement data, to make assessments of the resistance of surfaces to penetrations of the order of 10 to 1000 nm deep.

native metal o

o

See strain-rate sensitivity .

(1) Any deposit in the earth's crust consisting of uncombined metal. (2) The metal in such a deposit.

natural aging o

Spontaneous aging of a supersaturated solid solution at room temperature. See also aging . Compare with artificial aging .

o

natural strain

o

NDE

o

NDI

o o o

See true strain . See nondestructive evaluation . See nondestructive inspection .

o

NDT

o

near-net shape

o o o

See nondestructive testing . See net shape .

necking o

(1) The reduction of the cross-sectional area of a material in a localized area by uniaxial tension or by stretching. (2) The reduction of the diameter of a portion of the length of a cylindrical shell or tube.

o

necking down

o

net shape

o o

o

Localized reduction in area of a specimen during tensile deformation. The shape of a powder metallurgy part, casting, or forging that conforms closely to specified dimensions. Such a part requires no secondary machining or finishing. A near-net shape part can be either one in which some but not all of the surfaces are net or one in which the surfaces require only minimal machining or finishing.

Neumann band

o o

neutral flame o

o

(1) A gas flame in which there is no excess of either fuel or oxygen in the inner flame. Oxygen from ambient air is used to complete the combustion of CO2 and H2 produced in the inner flame. (2) An oxyfuel gas flame in which the portion used is neither oxidizing nor reducing. See also carburizing flame , oxidizing flame , and reducing flame .

neutron embrittlement o

o

Mechanical twin in ferrite.

Embrittlement resulting from bombardment with neutrons, usually encountered in metals that have been exposed to a neutron flux in the core of the reactor. In steels, neutron embrittlement is evidenced by a rise in the ductile-to-brittle transition temperature.

nibbling o

Contour cutting of sheet metal by use of a rapidly reciprocating punch that makes numerous small cuts.

o

nip angle

o

nitriding

o o

o

A potential more cathodic (positive) than the standard hydrogen potential.

no-draft (draftless) forging o

o

(1) A metal whose potential is highly positive relative to the hydrogen electrode. (2) A metal with marked resistance to chemical reaction, particularly to oxidation and to solution by inorganic acids. The term as often used is synonymous with precious metal .

noble potential o

o

The positive direction of electrode potential, thus resembling noble metals such as gold and platinum.

noble metal o

o

Any of several processes in which both nitrogen and carbon are absorbed into the surface layers of a ferrous material at temperatures below the lower critical temperature and, by diffusion, create a concentration gradient. Nitrocarburizing is performed primarily to provide an antiscuffing surface layer and to improve fatigue resistance. Compare with carbonitriding .

noble o

o

Introducing nitrogen into the surface layer of a solid ferrous alloy by holding at a suitable temperature (below Ac1 for ferritic steels) in contact with a nitrogenous material, usually ammonia or molten cyanide of appropriate composition. Quenching is not required to produce a hard case. See also bright nitriding and liquid nitriding .

nitrocarburizing o

o

See angle of bite .

A forging with extremely close tolerances and little or no draft that requires minimal machining to produce the final part. Mechanical properties can be enhanced by closer control of grain flow and by retention of surface material in the final component.

nodular graphite o

Graphite in nodular (rounded) form as opposed to flake form (see flake graphite ). See also ductile iron and spheroidal graphite .

o

nodular iron

o

nominal stress

o o

o

The stress at a point calculated on the net cross section without taking into consideration the effect on stress of geometric discontinuities, such as holes, grooves, fillets, and so forth. The calculation is made using simple elastic theory.

nondestructive evaluation (NDE) o

o

See preferred term ductile iron.

Broadly considered synonymous with nondestructive inspection (NDI) . More specifically, the quantitative analysis of NDI findings to determine whether the material will be acceptable for its function, despite the presence of discontinuities. With NDE, a discontinuity can be classified by its size, shape, type, and location, allowing the investigator to determine whether or not the flaw(s) is acceptable. Damage tolerant design approaches are based on the philosophy of ensuring safe operation in the presence of flaws.

nondestructive inspection (NDI) o

A process or procedure, such as ultrasonic or radiographic inspection, for determining the quality or characteristics of a material, part, or assembly, without permanently altering the subject or its

properties. Used to find internal anomalies in a structure without degrading its properties or impairing its serviceability. o

nondestructive testing (NDT) o

Broadly considered synonymous with nondestructive inspection (NDI).

o

nonmetallic inclusions

o

normal direction

o o o

That direction perpendicular to the plane of working in a worked material. See also longitudinal direction and transverse direction .

normalizing o

o

See inclusions .

Heating a ferrous alloy to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range.

normal segregation o

Concentration of alloying constituents that have low melting points in those portions of a casting that solidify last. Compare with inverse segregation .

o

normal solution

o

normal stress

o o o

A mechanical press used for notching internal and external circumferences and also for notching along a straight line. These presses are equipped with automatic feeds because only one notch is made per stroke.

notch rupture strength o

o

Cutting out various shapes from the edge of a strip, blank, or part.

notching press o

o

Ratio of the resilience determined on a plain specimen to the resilience determined on a notched specimen.

notching o

o

A test specimen that has been deliberately cut or notched, usually in a V-shape, to induce and locate point of failure.

notch factor o

o

The percentage reduction in area after complete separation of the metal in a tensile test of a notched specimen.

notched specimen o

o

The distance from the surface of a test specimen to the bottom of the notch. In a cylindrical test specimen, the percentage of the original cross-sectional area removed by machining an annular groove.

notch ductility o

o

Susceptibility of a material to brittle fracture at points of stress concentration. For example, in a notch tensile test, the material is said to be notch brittle if the notch strength is less than the tensile strength of an unnotched specimen. Otherwise, it is said to be notch ductile.

notch depth o

o

Relates to the severity of the stress concentration produced by a given notch in a particular structure. If the depth of the notch is very small compared with the width (or diameter) of the narrowest cross section, acuity may be expressed as the ratio of the notch depth to the notch root radius. Otherwise, acuity is defined as the ratio of one-half the width (or diameter) of the narrowest cross section to the notch root radius.

notch brittleness o

o

The radius of the rounded portion of the cutting edge of a tool.

notch acuity o

o

The stress component that is perpendicular to the plane on which the forces act. Normal stress may be either tensile or compressive.

nose radius o

o

An aqueous solution containing one gram equivalent of the active reagent in 1 L of the solution.

The ratio of applied load to original area of the minimum cross section in a stress-rupture test of a notched specimen.

notch sensitivity o

The extent to which the sensitivity of a material to fracture is increased by the presence of a stress concentration, such as a notch, a sudden change in cross section, a crack, or a scratch. Low notch

sensitivity is usually associated with ductile materials, and high notch sensitivity is usually associated with brittle materials. o

notch strength o

The maximum load on a notched tension-test specimen divided by the minimum cross-sectional area (the area at the root of the notch). Also called notch tensile strength.

o

nuclear grade

o

nucleation

o o o

The initiation of a phase transformation at discrete sites, with the new phase growing on the nuclei. See also nucleus (2) .

nucleus o

o

Material of a quality adequate for use in nuclear application.

(1) The heavy central core of an atom, in which most of the mass and the total positive electric charge are concentrated. (2) The first structurally stable particle capable of initiating recrystallization of a phase or the growth of a new phase and possessing an interface with the parent metallic matrix. The term is also applied to a foreign particle that initiates such action.

nugget o

(1) A small mass of metal, such as gold or silver, found free in nature. (2) The weld metal in a spot, seam, or projection weld.

o

n-value

o o

O

o

offhand grinding o

o

The distance along the strain coordinate between the initial portion of a stress-strain curve and a parallel line that intersects the stress-strain curve at a value of stress (commonly 0.2%) that is used as a measure of the yield strength. Used for materials that have no obvious yield point.

offset yield strength o

o

Grinding where the operator manually forces the wheel against the work, or vice versa. It often implies casual manipulation of either grinder or work to achieve the desired result. Dimensions and tolerances frequently are not specified, or are only loosely specified; the operator relies mainly on visual inspection to determine how much grinding should be done. Contrast with precision grinding .

offset o

o

See strain-hardening exponent .

The stress at which the strain exceeds by a specific amount (the offset) an extension of the initial, approximately linear, proportional portion of the stress-strain curve. It is expressed in force per unit area.

oil canning o

See canning .

o

oil quenching

o

Olsen ductility test

o o

o

A cupping test in which a piece of sheet metal, restrained except at the center, is deformed by a standard steel ball until fracture occurs. The height of the cup at the time of fracture is a measure of the ductility.

open-back inclinable press o

o

Hardening of carbon steel in an oil bath.

A vertical crank press that can be inclined so that the bed will have an inclination generally varying from 0 to 30°. The formed parts slide off through an opening in the back. It is often called an OBI press.

open-die forging o

The hot mechanical forming of metals between flat or shaped dies in which metal flow is not completely restricted. Also known as hand or smith forging. See also hand forge (smith forge) .

o

open dies

o

open hearth furnace

o o

o

Dies with flat surfaces that are used for preforming stock or producing hand forgings. A reverberatory melting furnace with a shallow hearth and a low roof. The flame passes over the charge on the hearth, causing the charge to be heated both by direct flame and by radiation from the roof and sidewalls of the furnace. See also reverberatory furnace .

open rod press

o o

optical emission spectroscopy o

o

A hydraulic press in which the slide is guided by vertical, cylindrical rods (usually four) that also serve to hold the crown and bed in position. Pertaining to emission spectroscopy in the near-ultraviolet, visible, or near-infrared wavelength regions of the electromagnetic spectrum. See also electromagnetic radiation .

orange peel o

A surface roughening in the form of a pebble-grained pattern that occurs when a metal of unusually coarse grain size is stressed beyond its elastic limit. Also called pebbles and alligator skin.

o

orbital forging

o

ordered structure

o

o

o

o

The crystal structure of a solid solution in which the atoms of different elements seek preferred lattice positions. Contrast with disordered structure .

o

A natural mineral that may be mined and treated for the extraction of any of its components, metallic or otherwise, at a profit.

ore ore dressing o

o

A condition wherein a metal curves upward on leaving the rolls because of the higher speed of the lower roll.

overhead-drive press o

o

Bending metal through a greater arc than that required in the finished part to compensate for springback.

overdraft o

o

Aging under conditions of time and temperature greater than those required to obtain maximum change in a certain property, so that the property is altered in the direction of the initial value.

overbending o

o

A small high-speed metal forming press in which the die and punch move horizontally with the strip during the working stroke. Through a reciprocating motion, the die and punch return to their original positions to begin the next stroke.

overaging o

o

The physical crack size at the start of testing.

oscillating die press o

o

Arrangements in space of the axes of the lattice of a crystal with respect to a chosen reference or coordinate system. See also preferred orientation .

original crack size (ao) o

o

Same as mineral dressing .

orientation o

o

See rotary forging .

A mechanical press with the driving mechanism mounted in or on the crown or upper parts of the uprights.

overheating o

Heating a metal or alloy to such a high temperature that its properties are impaired. When the original properties cannot be restored by further heat treating, by mechanical working, or by a combination of working and heat treating, the overheating is known as burning.

o

overlap

o

oversize powder

o

overstressing

o o o o

Powder particles larger than the maximum permitted by a particle size specification. In fatigue testing, cycling at a stress level higher than that used at the end of the test.

oxidation o

o

In resistance seam welding, the area in a given weld remelted by the succeeding weld.

(1) A reaction in which there is an increase in valence resulting from a loss of electrons. Contrast with reduction . (2) A corrosion reaction in which the corroded metal forms an oxide; usually applied to reaction with a gas containing elemental oxygen, such as air. Elevated temperatures increase the rate of oxidation. (3) A chemical reaction in which one substance is changed to another by oxygen combining with the substance. Much of the dross from holding and melting furnaces is the result of oxidation of the alloy held in the furnace.

oxidation losses

o o

oxidative wear o

o

(1) A corrosive wear process in which chemical reaction with oxygen or oxidizing environment predominates. (2) A type of wear resulting from the sliding action between two metallic components that generates oxide films on the metal surfaces. These oxide films prevent the formation of a metallic bond between the sliding surfaces, resulting in fine wear debris and low wear rates.

oxidized steel surface o

o

Reduction in the amount of metal or alloy through oxidation.

Surface having a thin, tightly adhering oxidized skin (from straw to blue in color), extending in from the edge of a coil or sheet.

oxidizing agent o

A compound that causes oxidation, thereby itself being reduced.

o

oxidizing atmosphere

o

oxidizing flame

o o o

A furnace atmosphere with an oversupply of oxygen that tends to oxidize materials placed in it. A gas flame produced with excess oxygen in the inner flame that has an oxidizing effect. See also neutral flame and reducing flame .

oxyacetylene cutting o

An oxyfuel gas cutting process in which the fuel gas is acetylene.

o

oxyacetylene welding

o

oxyfuel gas cutting

o o

o

An oxyfuel gas welding process in which the fuel gas is acetylene. Any of a group of processes used to sever metals by means of chemical reaction between hot base metal and a fine stream of oxygen. The necessary metal temperature is maintained by gas flames resulting from combustion of a specific fuel gas such as acetylene, hydrogen, natural gas, propane, propylene, or Mapp gas (stabilized methylacetylene-propadiene).

oxyfuel gas welding (OFW) o

Any of a group of processes used to fuse metals together by heating them with gas flames resulting from combustion of a specific fuel gas such as acetylene, hydrogen, natural gas, or propane. The process may be used with or without the application of pressure to the joint, and with or without adding any filler metal.

o

oxygas cutting

o

oxygen arc cutting

o o

o

An oxygen cutting process used to sever metals with oxygen supplied through a consumable lance; the preheat to start the cutting is obtained by other means.

oxygen probe o

o

A length of pipe used to convey oxygen either beneath or on top of the melt in a steelmaking furnace, or to the point of cutting in oxygen lance cutting.

oxygen lance cutting o

o

Oxygen cutting in which a bevel or groove is formed.

oxygen lance o

o

Electrolytic copper free from cuprous oxide, produced without the use of residual metallic or metalloidal deoxidizers.

Oxygen gouging o

o

A group of cutting processes used to sever or remove metals by means of the chemical reaction between oxygen and the base metal at elevated temperatures. In the case of oxidation-resistant metals, the reaction is facilitated by the use of a chemical flux or metal powder. See also chemical flux cutting , metal powder cutting , oxyfuel gas cutting , oxygen arc cutting , and oxygen lance cutting .

oxygen-free copper o

o

An oxygen cutting process used to sever metals by means of the chemical reaction of oxygen with the base metal at elevated temperatures. The necessary temperature is maintained by an arc between a consumable tubular electrode and the base metal.

oxygen cutting o

o

See preferred term oxygen cutting .

P

An atmosphere-monitoring device that electronically measures the difference between the partial pressure of oxygen in a furnace or furnace supply atmosphere and the external air.

o

pack carburizing o

o

A method of surface hardening of steel in which parts are packed in a steel box with a carburizing compound and heated to elevated temperatures. This process has been largely supplanted by gas and liquid carburizing processes.

pack nitriding o

A method of surface hardening of steel in which parts are packed in a steel box with a nitriding compound and heated to elevated temperatures.

o

pack rolling

o

pancake forging

o o o

The appearance of a metal particle, such as spherical, rounded, angular, acicular, dendritic, irregular, porous, fragmented, blocky, rod, flake, nodular, or plate.

particle size o

o

An imprecise term used to denote a treatment given cold-worked metallic material to reduce its strength to a controlled level or to effect stress relief. To be meaningful, the type of material, the degree of cold work, and the time-temperature schedule must be stated.

particle shape o

o

A process used to recover precious metals from lead and based on the principle that if 1 to 2% Zn is stirred into the molten lead, a compound of zinc with gold and silver separates out and can be skimmed off.

partial annealing o

o

A property exhibited by substances that, when placed in a magnetic field, are magnetized parallel to the field to an extent proportional to the field (except at very low temperatures or in extremely large magnetic fields). Compare with ferromagnetism .

Parkes process o

o

(1) A material whose specific permeability is greater than unity and is practically independent of the magnetizing force. (2) Material with a small positive susceptibility due to the interaction and independent alignment of permanent atomic and electronic magnetic moments with the applied field. Compare with ferromagnetic material .

paramagnetism o

o

A metallic structure in which the lengths and widths of individual grains are large compared to their thicknesses.

paramagnetic material o

o

A rough forged shape, usually flat, that can be obtained quickly with minimal tooling. Considerable machining is usually required to attain the finish size.

pancake grain structure o

o

Hot rolling a pack of two or more sheets of metal; scale prevents their being welded together.

The controlling lineal dimension of an individual particle as determined by analysis with screens or other suitable instruments. See also sieve analysis and sieve classification .

particle size distribution o

The percentage, by weight or by number, of each fraction into which a powder or sand sample has been classified with respect to sieve number or particle size.

o

particle sizing

o

parting

o o

o

A material dusted or sprayed on foundry (casting) patterns to prevent adherence of sand and to promote easy separation of cope and drag parting surfaces when the cope is lifted from the drag.

parting line o

o

(1) In the recovery of precious metals, the separation of silver from gold. (2) The zone of separation between cope and drag portions of the mold or flask in sand casting. (3) A composition sometimes used in sand molding to facilitate the removal of the pattern. (4) Cutting simultaneously along two parallel lines or along two lines that balance each other in side thrust. (5) A shearing operation used to produce two or more parts from a stamping.

parting compound o

o

Segregation of granular material into specified particle size ranges.

(1) The intersection of the parting plane of a casting or plastic mold or the parting plane between forging dies with the mold or die cavity. (2) A raised line or projection on the surface of a casting, plastic part, or forging that corresponds to said intersection.

parting plane

o o

parting sand o

o

The coating, usually green, that forms on the surface of metals such as copper and copper alloys exposed to the atmosphere. Also used to describe the appearance of a weathered surface of any metal.

pattern o

o

Same as stretcher leveling .

patina o

o

In wiremaking, a heat treatment applied to medium- or high-carbon steel before drawing of wire or between drafts. This process consists of heating to a temperature above the transformation range and then cooling to a temperature below Ae1 in air or in a bath of molten lead or salt.

patent leveling o

o

A condition in which a piece of metal, because of an impervious covering of oxide or other compound, has a potential much more positive than that of the metal in the active state.

patenting o

o

A corrosion cell in which the anode is a metal in the active state and the cathode is the same metal in the passive state.

passivity o

o

(1) A metal corroding under the control of a surface reaction product. (2) The state of the metal surface characterized by low corrosion rates in a potential region that is strongly oxidizing for the metal.

passive-active cell o

o

(1) A reduction of the anodic reaction rate of an electrode involved in corrosion. (2) The process in metal corrosion by which metals become passive. (3) The changing of a chemically active surface of a metal to a much less reactive state. Contrast with activation .

passive o

o

(1) A single transfer of metal through a stand of rolls. (2) The open space between two grooved rolls through which metal is processed. (3) The weld metal deposited in one trip along the axis of a weld. See also weld pass .

passivation o

o

In foundry practice, a fine sand for dusting on sand mold surfaces that are to be separated.

pass o

o

(1) In forging, the dividing line between dies. (2) In casting, the dividing line between mold halves.

(1) A form of wood, metal, or other material around which molding material is placed to make a mold for casting metals. (2) A form of wax- or plastic-base material around which refractory material is placed to make a mold for casting metals. (3) A full-scale reproduction of a part used as a guide in cutting.

pearlite o

A metastable lamellar aggregate of ferrite and cementite resulting from the transformation of austenite at temperatures above the bainite range.

o

pearlitic malleable

o

pearlitic structure

o o o

See malleable iron . A microstructure resembling that of the pearlite constituent in steel. Therefore, it is a lamellar structure of varying degrees of coarseness.

peeling o

The detaching of one layer of a coating from another, or from the substrate, because of poor adherence.

o

peel test

o

peening

o o o

A destructive method of inspection that mechanically separates a lap joint by peeling. Mechanical working of metal by hammer blows or shot impingement.

penetrant o

A liquid with low surface tension used in liquid penetrant inspection to flow into surface openings of parts being inspected.

o

penetrant inspection

o

penetration

o

See preferred term liquid penetrant inspection .

o

o

penetration hardness o

o

Same as indentation hardness .

percussion welding o

o

(1) In founding, an imperfection on a casting surface caused by metal running into voids between sand grains; usually referred to as metal penetration . (2) In welding, the distance from the original surface of the base metal to that point at which fusion ceased.

A resistance welding process that produces coalescence of abutting surfaces using heat from an arc produced by a rapid discharge of electrical energy. Pressure is applied percussively during or immediately following the electrical discharge.

perforating o

The punching of many holes, usually identical and arranged in a regular pattern, in a sheet, workpiece blank, or previously formed part. The holes are usually round, but may be any shape. The operation is also called multiple punching. See also piercing .

o

peripheral milling

o

peritectic

o o o

o

o

(1) The passage or diffusion (or rate of passage) of a gas, vapor, liquid, or solid through a material (often porous) without physically or chemically affecting it; the measure of fluid flow (gas or liquid) through a material. (2) A general term used to express various relationships between magnetic induction and magnetizing force. These relationships are either "absolute permeability," which is a change in magnetic induction divided by the corresponding change in magnetizing force, or "specific (relative) permeability," the ratio of the absolute permeability to the permeability of free space. (3) In metal casting, the characteristics of molding materials that permit gases to pass through them. "Permeability number" is determined by a standard test.

pewter o

A tin-base white metal containing antimony and copper. Originally, pewter was defined as an alloy of tin and lead, but to avoid toxicity and dullness of finish, lead is excluded from modern pewter. These modern compositions contain 1 to 8% Sb and 0.25 to 3% Cu.

o

The negative logarithm of the hydrogen-ion activity; it denotes the degree of acidity or basicity of a solution. At 25 °C (77 °F), 7.0 is the neutral value. Decreasing values below 7.0 indicates increasing acidity; increasing values above 7.0, increasing basicity. The pH values range from 0 to 14.

pH

phase o

o

The deformation remaining after a specimen has been stressed a prescribed amount in tension, compression, or shear for a specified time period and released for a specified time period. For creep tests, the residual unrecoverable deformation after the load causing the creep has been removed for a substantial and specified period of time. Also, the increase in length, expressed as a percentage of the original length, by which an elastic material fails to return to its original length after being stressed for a standard period of time.

permeability o

o

A metal, graphite, or ceramic mold (other than an ingot mold) of two or more parts that is used repeatedly for the production of many castings of the same form. Liquid metal is usually poured in by gravity.

permanent set o

o

A ferromagnetic alloy capable of being magnetized permanently because of its ability to retain induced magnetization and magnetic poles after removal of externally applied fields; an alloy with high coercive force. The name is based on the fact that the quality of the early permanent magnets was related to their hardness.

permanent mold o

o

An isothermal reversible reaction in which a solid phase reacts with a second solid phase to produce a single (and different) solid phase on cooling.

permanent magnet material o

o

An isothermal reversible reaction in metals in which a liquid phase reacts with a solid phase to produce a single (and different) solid phase on cooling.

peritectoid o

o

Milling a surface parallel to the axis of the cutter.

A physically homogeneous and distinct portion of a material system.

phase change

o o

phase diagram o

o

Forming an adherent phosphate coating on a metal by immersion in a suitable aqueous phosphate solution. Also called phosphatizing. See also conversion coating .

phosphorized copper o

o

The maximum number of phases (P) that may coexist at equilibrium is two, plus the number of components (C) in the mixture, minus the number of degrees of freedom (F): P + F = C + 2.

phosphating o

o

A graphical representation of the temperature and composition limits of phase fields in an alloy or ceramic system as they actually exist under the specific conditions of heating or cooling. A phase diagram may be an equilibrium diagram, an approximation to an equilibrium diagram, or a representation of metastable conditions or phases. Synonymous with constitution diagram. Compare with equilibrium diagram .

phase rule o

o

The transition from one physical state to another, such as gas to liquid, liquid to solid, gas to solid, or vice versa.

General term applied to copper deoxidized with phosphorus. The most commonly used deoxidized copper.

photoelasticity o

An optical method for evaluating the magnitude and distribution of stresses, using a transparent model of a part, or a thick film of photoelastic material bonded to a real part.

o

photomacrograph

o

photomicrograph

o o o

Properties of a material that are relatively insensitive to structure and can be measured without the application of force; for example, density, electrical conductivity, coefficient of thermal expansion, magnetic permeability, and lattice parameter. Does not include chemical reactivity. Compare with mechanical properties .

physical testing o

o

The science and technology dealing with the properties of metals and alloys, and of the effects of composition, processing, and environment on those properties.

physical properties o

o

In fracture mechanics, the distance from a reference plane to the observed crack front. This distance may represent an average of several measurements along the crack front. The reference plane depends on the specimen form, and it is normally taken to be either the boundary or a plane containing either the load line or the centerline of a specimen or plate.

physical metallurgy o

o

A micrograph produced by photographic means.

physical crack size (ap) o

o

A macrograph produced by photographic means.

Methods used to determine the entire range of the material's physical properties of a material. In addition to density and thermal, electrical, and magnetic properties, physical testing methods may be used to assess simple fundamental physical properties such as color, crystalline form, and melting point.

physical vapor deposition (PVD) o

A coating process whereby the deposition species are transferred and deposited in the form of individual atoms or molecules. The most common PVD methods are sputtering and evaporation. Sputtering, which is the principal PVD process, involves the transport of a material from a source (target) to a substrate by means of the bombardment of the target by gas ions that have been accelerated by a high voltage. Evaporation, which was the first PVD process used, involves the transfer of material to form a coating by physical means alone, essentially vaporization. Physical vapor deposition coatings are used to improve the wear, friction, and hardness properties of cutting tools and as corrosion-resistant coatings.

o

pickle liquor

o

pickle stain

o o o

A spent acid-pickling bath. Discoloration of metal due to chemical cleaning without adequate washing and drying.

pickling

o

o

pickoff o

o

The chemical removal of surface oxides (scale) and other contaminants such as dirt from iron and steel by immersion in an aqueous acid solution. The most common pickling solutions are sulfuric and hydrochloric acids. An automatic device for removing a finished part from the press die after it has been stripped.

pickup o

(1) Transfer of metal from tools to part or from part to tools during a forming operation. (2) Small particles of oxidized metal adhering to the surface of a mill product.

o

Pidgeon process

o

piercing

o o

o

o o

A process for production of magnesium by reduction of magnesium oxide with ferrosilicon. The general term for cutting (shearing or punching) openings, such as holes and slots, in sheet material, plate, or parts. This operation is similar to blanking; the difference is that the slug or pierce produced by piercing is scrap, while the blank produced by blanking is the useful part.

piezoelectric effect o

The reversible interaction, exhibited by some crystalline materials, between an elastic strain and an electric field. The direction of the strain depends on the polarity of the field or vice versa. Compare with electrostrictive effect .

o

A metal casting used in remelting.

pig pig iron o

(1) High-carbon iron made by reduction of iron ore in the blast furnace. (2) Cast iron in the form of pigs.

o

Pilger tube-reducing process

o

pin (for bend testing)

o o

o

Porosity consisting of numerous small gas holes (pinholes) distributed throughout the metal; found in weld metal, castings, and electrodeposited metal.

Piobert lines o

o

A test for determining the ability of a tube to be expanded or for revealing the presence of cracks or other longitudinal weaknesses, made by forcing a tapered pin into the open end of the tube.

pinhole porosity o

o

The trimming of the edge of a tubular metal part or shell by pushing or pinching the flange or lip over the cutting edge of a stationary punch or over the cutting edge of a draw punch.

pin expansion test o

o

A pass of sheet metal through rolls to effect a very small reduction in thickness.

pinch trimming o

o

Surface disturbances on metal sheet or strip that result from rolling processes and that ordinarily appear as fernlike ripples running diagonally to the direction of rolling.

pinch pass o

o

The plunger or tool used in making semiguided, guided, or wraparound bend tests to apply the bending force to the inside surface of the bend. In free bends or semiguided bends to an angle of 180°, a shim or block of the proper thickness may be placed between the legs of the specimen as bending is completed. This shim or block is also referred to as a pin or mandrel. See also mandrel .

pinchers o

o

See tube reducing .

See Lüders lines .

pipe o

(1) The central cavity formed by contraction in metal, especially ingots, during solidification. (2) An imperfection in wrought or cast products resulting from such a cavity. (3) A tubular metal product, cast or wrought. See also extrusion pipe .

o

pipe tap

o

pipe threads

o o o

pit

A tap for making internal pipe threads within pipe fittings or holes. Internal or external machine threads, usually tapered, of a design intended for making pressuretight mechanical joints in piping systems.

o o

pitting o

o

An arc cutting process that severs metals by melting a localized area with heat from a constricted arc and removing the molten metal with a high-velocity jet of hot, ionized gas issuing from the plasma torch.

plasma arc welding (PAW) o

o

Producing a smooth finish on metal by a rapid succession of blows delivered by highly polished dies or by a hammer designed for the purpose, or by rolling in a planishing mill.

plasma arc cutting o

o

Producing flat surfaces by linear reciprocal motion of work and the table to which it is attached, relative to a stationary single-point cutting tool.

planishing o

o

A method of measuring grain size in which the grains within a definite area are counted.

planing o

o

In linear elastic fracture mechanics, the value of the crack-extension resistance at the instability condition determined from the tangency between the R-curve and the critical crack-extension force curve of the specimen. See also stress-intensity factor .

planimetric method o

o

The stress condition in linear elastic fracture mechanics in which the stress in the thickness direction is zero; most nearly achieved in loading very thin sheet along a direction parallel to the surface of the sheet. Under plane-stress conditions, the plane of fracture instability is inclined 45° to the axis of the principal tensile stress.

plane-stress fracture toughness (Kc) o

o

The crack extension resistance under conditions of crack-tip plane strain. See also stress-intensity factor .

plane stress o

o

The stress condition in linear elastic fracture mechanics in which there is zero strain in a direction normal to both the axis of applied tensile stress and the direction of crack growth (that is, parallel to the crack front); most nearly achieved in loading thick plates along a direction parallel to the plate surface. Under plane-strain conditions, the plane of fracture instability is normal to the axis of the principal tensile stress.

plane-strain fracture toughness (KIc) o

o

(1) Forming small sharp cavities in a surface by corrosion, wear, or other mechanically assisted degradation. (2) Localized corrosion of a metal surface, confined to a point or small area, that takes the form of cavities.

plane strain o

o

A small, regular or irregular crater in the surface of a material created by exposure to the environment, for example, corrosion, wear, or thermal cycling. See also pitting .

An arc welding process that produces coalescence of metals by heating them with a constricted arc between an electrode and the workpiece (transferred arc) or the electrode and the constricting nozzle (nontransferred arc). Shielding is obtained from hot, ionized gas issuing from an orifice surrounding the electrode and may be supplemented by an auxiliary source of shielding gas, which may be an inert gas or a mixture of gases. Pressure may or may not be used, and filler metal may or may not be supplied.

plasma-assisted chemical vapor deposition o

A chemical vapor deposition process that uses low-pressure glow-discharge plasmas to promote the chemical deposition reactions. Also called plasma-enhanced chemical vapor deposition.

o

plasma carburizing

o

plasma nitriding

o o o

Same as ion nitriding .

plasma spraying o

o

Same as ion carburizing .

A thermal spraying process in which a nontransferred arc of a plasma torch is utilized to create a gas plasma that acts as the source of heat for melting and propelling the surfacing material to the substrate.

plaster molding o

Molding in which a gypsum-bonded aggregate flour in the form of a water slurry is poured over a pattern, permitted to harden, and, after removal of the pattern, thoroughly dried. This technique is used to make smooth nonferrous castings of accurate size.

o

plastic deformation o

o

plastic flow o

o

Martensite formed partly in steel containing more than approximately 0.5% C and solely in steel containing more than approximately 1.0% C that appears as lenticular-shape plates (crystals).

platen o

o

A flat-rolled metal product of some minimum thickness and width arbitrarily dependent on the type of metal. Plate thicknesses commonly range from 6 to 300 mm (0.25 to 12 in.); widths from 200 to 2000 mm (8 to 80 in.).

plate martensite o

o

In formability testing of metals, the ratio of the true width strain to the true thickness strain in a sheet tensile test, r = w t. A formability parameter that relates to drawing, it is also known as the anisotropy factor. A high r-value indicates a material with good drawing properties.

plate o

o

The property of a material that allows it to be repeatedly deformed without rupture when acted upon by a force sufficient to cause deformation and that allows it to retain its shape after the applied force has been removed.

plastic-strain ratio (r-value) o

o

The phenomenon that takes place when metals are stretched or compressed permanently without rupture.

plasticity o

o

The permanent (inelastic) distortion of materials under applied stresses that strain the material beyond its elastic limit.

(1) The sliding member, slide, or ram of a metal forming press. (2) A part of a resistance welding, mechanical testing, or other machine with a flat surface to which dies, fixtures, backups, or electrode holders are attached and that transmits pressure or force.

plating o

Forming an adherent layer of metal on an object; often used as a shop term for electroplating. See also electrodeposition and electroless plating .

o

plating rack

o

plug

o o

o

A fixture used to hold work and conduct current to it during electroplating. (1) A rod or mandrel over which a pierced tube is forced. (2) A rod or mandrel that fills a tube as it is drawn through a die. (3) A punch or mandrel over which a cup is drawn. (4) A protruding portion of a die impression for forming a corresponding recess in the forging. (5) A false bottom in a die.

plug tap o

A tap with chamfer extending from three to five threads.

o

plug weld

o

plumbage

o o o

Grinding wherein the only relative motion of the wheel is radially toward the work.

plus mesh o

o

A special quality of powdered graphite used to coat molds and, in a mixture of clay, to make crucibles.

plunge grinding o

o

A weld made in a circular hole in one member of a joint, fusing that member to another member.

The powder sample retained on a screen of stated size, identified by the retaining mesh number. See also sieve analysis and sieve classification .

plus sieve o

The portion of a sample of a granular substance (such as metal powder) retained on a standard sieve of specified number. Contrast with minus sieve . See also sieve analysis and sieve classification .

o

plymetal

o

P/M

o o

Sheet consisting of bonded layers of dissimilar metals. The acronym for powder metallurgy .

o

pneumatic press

o

point angle

o

A press that uses air or a gas to deliver the pressure to the upper and lower rams.

o o

In general, the angle at the point of a cutting tool. Most commonly, the included angle at the point of a twist drill, the general-purpose angle being 118°.

Poisson's ratio ( ) o

The absolute value of the ratio of transverse (lateral) strain to the corresponding axial strain resulting from uniformly distributed axial stress below the proportional limit of the material.

o

polarity (welding)

o

polarization

o o

o

A substantially vitreous or glassy, inorganic coating (borosilicate glass) bonded to metal by fusion at a temperature above 425 °C (800 °F). Porcelain enamels are applied primarily to components made of sheet iron or steel, cast iron, aluminum, or aluminum-coated steels.

pore o

o

Loss of small portions of a porcelain enamel coating. The usual cause is outgassing of hydrogen or other gases from the substrate during firing, but pop-off may also occur because of oxide particles or other debris on the surface of the substrate. Usually, the pits are minute and cone shaped, but when pop-off is the result of severe fishscale the pits may be much larger and irregular.

porcelain enamel o

o

A general term for the ability of a solid to exist in more than one form. In metals, alloys, and similar substances, this usually means the ability to exist in two or more crystal structures, or in an amorphous state and at least one crystal structure. See also allotropy , enantiotropy , and monotropism .

pop-off o

o

Pertaining to a solid comprised of many crystals or crystallites, intimately bonded together. May be homogeneous (one substance) or heterogeneous (two or more crystal types or compositions).

polymorphism o

o

(1) Smoothing metal surfaces, often to a high luster, by rubbing the surface with a fine abrasive, usually contained in a cloth or other soft lap. Results in microscopic flow of some surface metal together with actual removal of a small amount of surface metal. (2) Removal of material by the action of abrasive grains carried to the work by a flexible support, generally either a wheel or a coated abrasive belt. (3) A mechanical, chemical, or electrolytic process or combination thereof used to prepare a smooth, reflective surface suitable for microstructural examination that is free of artifacts or damage introduced during prior sectioning or grinding. See also electrolytic polishing and electropolishing .

polycrystalline o

o

A stereoscopic projection of a polycrystalline aggregate showing the distribution of poles, or plane normals, of a specific crystalline plane, using specimen axes as reference axes. Pole figures are used to characterize preferred orientation in polycrystalline materials.

polishing o

o

(1) A means of designating the orientation of a crystal plane by stereographically plotting its normal. For example, the north pole defines the equatorial plane. (2) Either of the two regions of a permanent magnet or electromagnet where most of the lines of induction enter or leave.

pole figure o

o

A plot of current density versus electrode potential for a specific electrode-electrolyte combination.

pole o

o

(1) The change from the open-circuit electrode potential as the result of the passage of current. (2) A change in the potential of an electrode during electrolysis, such that the potential of an anode becomes more noble, and that of a cathode more active, than their respective reversible potentials. Often accomplished by formation of a film on the electrode surface.

polarization curve o

o

See direct current electrode negative and direct current electrode positive .

(1) A small opening, void, interstice, or channel within a consolidated solid mass or agglomerate, usually larger than atomic or molecular dimensions. (2) A minute cavity in a powder metallurgy compact, sometimes added intentionally. (3) A minute perforation in an electroplated coating.

porosity o

(1) Fine holes or pores within a solid; the amount of these pores is expressed as a percentage of the total volume of the solid. (2) Cavity-type discontinuities in weldments formed by gas

entrapment during solidification. (3) A characteristic of being porous, with voids or pores resulting from trapped air or shrinkage in a casting. See also gas porosity and pinhole porosity . o

postheating o

o o

Heating weldments immediately after welding, for tempering, for stress relieving, or for providing a controlled rate of cooling to prevent formation of a hard or brittle structure. See also postweld heat treatment .

postweld heat treatment o

Any heat treatment that follows the welding operation.

o

(1) A vessel for holding molten metal. (2) The electrolytic reduction cell used to make such metals as aluminum from a fused electrolyte.

pot

o

pot annealing

o

potential

o o o

Same as box annealing . (1) Any of various functions from which intensity or velocity at any point in a field may be calculated. (2) The driving influence of an electrochemical reaction .

poultice corrosion o

A term used in the automotive industry to describe the corrosion of vehicle body parts due to the collection of road salts and debris on ledges and in pockets that are kept moist by weather and washing. Also called deposit corrosion or attack.

o

pouring

o

pouring basin

o o o

The transfer of molten metal from furnace to ladle, ladle to ladle, or ladle into molds. In metal casting, a basin on top of a mold that receives the molten metal before it enters the sprue or downgate.

powder o

An aggregate of discrete particles that are usually in the size range of 1 to 1000 m.

o

powder cutting

o

powder flame spraying

o

powder forging

o o o o

A shaped object that has been formed from metal powders and sintered by heating below the melting point of the major constituent. A structural or mechanical component made by the powder metallurgy process. A metallic powder composed of two or more elements that are alloyed in the powder manufacturing process and in which the particles are of the same nominal composition throughout.

precious metals o

o

See powder forging .

prealloyed powder o

o

The technology and art of producing metal powders and utilizing metal powders for production of massive materials and shaped objects.

powder metallurgy part o

o

In powder metallurgy, an agent or component incorporated into a mixture to facilitate compacting and ejecting of the compact from its mold.

powder metallurgy forging o

o

The plastic deformation of a powder metallurgy compact or preform into a fully dense finished shape by using compressive force; usually done hot and within closed dies.

powder metallurgy (P/M) o

o

A thermal spraying process variation in which the material to be sprayed is in powder form.

powder lubricant o

o

See preferred terms chemical flux cutting and metal powder cutting .

Relatively scarce, highly corrosion resistant, valuable metals found in periods 5 and 6 (groups VIII and Ib) of the periodic table. They include ruthenium, rhodium, palladium, silver, asmium, iridium, platinum, and gold. See also noble metal .

precipitation o

In metals, the separation of a new phase from solid or liquid solution, usually with changing conditions of temperature, pressure, or both.

o

precipitation hardening o

Hardening in metals caused by the precipitation of a constituent from a supersaturated solid solution. See also age hardening and aging .

o

precipitation heat treatment

o

precision casting

o o o

Artificial aging of metals in which a constituent precipitates from a supersaturated solid solution. A metal casting of reproducible, accurate dimensions, regardless of how it is made. Often used interchangeably with investment casting .

precision forging o

A forging produced to closer tolerances than normally considered standard by the industry. With precision forging, a net shape, or at least a near-net shape, can be produced in the as-forged condition. See also net shape .

o

precision grinding

o

precoat

o o

o

A machine tool having a stationary bed and a slide or ram that has reciprocating motion at right angles to the bed surface, the slide being guided in the frame of the machine. See also hydraulic press , mechanical press , and slide .

press brake o

o

Heating a powder metallurgy compact to a temperature below the final sintering temperature, usually to increase the ease of handling or shaping of a compact or to remove a lubricant or binder (burnoff) prior to sintering.

press o

o

(1) Heating before some further thermal or mechanical treatment. For tool steel, heating to an intermediate temperature immediately before final austenitizing. For some nonferrous alloys, heating to a high temperature for a long time, in order to homogenize the structure before working. (2) In welding and related processes, heating to an intermediate temperature for a short time immediately before welding, brazing, soldering, cutting, or thermal spraying. (3) In powder metallurgy, an early stage in the sintering procedure when, in a continuous furnace, lubricant or binder burnoff occurs without atmosphere protection prior to actual sintering in the protective atmosphere of the high heat chamber.

presintering o

o

(1) The initial pressing of a metal powder to form a compact that is to be subjected to a subsequent pressing operation other than coining or sizing. (2) Preliminary forming operations, especially for impression-die forging.

preheating o

o

A condition of a polycrystalline aggregate in which the crystal orientations are not random, but rather exhibit a tendency for alignment with a specific direction in the bulk material, commonly related to the direction of working. See also texture .

preforming o

o

A mechanical test specimen that is notched and subjected to alternating stresses until a crack has developed at the root of the notch.

preferred orientation o

o

Mill products that have a metallic, organic, or conversion coating applied to their surfaces before they are fabricated into parts.

precracked specimen o

o

(1) In investment casting, a special refractory slurry applied to a wax or plastic expendable pattern to form a thin coating that serves as a desirable base for application of the main slurry. See also investment casting . (2) To make the thin coating. (3) The thin coating itself.

precoated metal products o

o

Machine grinding to specified dimensions and low tolerances.

An open-frame single-action press used to bend, blank, corrugate, curl, notch, perforate, pierce, or punch sheet metal or plate.

press-brake forming o

A metalforming process in which the workpiece is placed over an open die and pressed down into the die by a punch that is actuated by the ram portion of a press brake. The process is most widely used for the forming of relatively long, narrow parts that are not adaptable to press forming and for applications in which production quantities are too small to warrant the tooling cost for contour roll forming.

o

pressed density

o

press forming

o o o

An oxyfuel gas welding process that produces coalescence simultaneously over the entire area of abutting surfaces by heating them with gas flames obtained from combustion of a fuel gas with oxygen and by application of pressure, without the use of filler metal.

pressure sintering o

o

A resistance welding process variation in which a number of spot or projection welds are made with several electrodes functioning progressively under the control of a pressure-sequencing device.

pressure gas welding o

o

(1) Making castings with pressure on the molten or plastic metal, as in die casting, centrifugal casting, cold chamber pressure casting, and squeeze casting. (2) A casting made with pressure applied to the molten or plastic metal.

pressure-controlled welding o

o

A quench in which hot dies are pressed and aligned with a part before the quenching process begins. Then the part is placed in contact with a quenching medium in a controlled manner. This process avoids part distortion.

pressure casting o

o

A rupture in a green powder metallurgy compact that develops during ejection of the compact from the die. Sometimes referred to as a slip crack.

press quenching o

o

The clear distance (left to right) between housings, stops, gibs, gibways, or shoulders of strain rods, multiplied by the total distance from front to back on the bed of a metalforming press. Sometimes called working area.

pressing crack o

o

Any sheet metalforming operation performed with tooling by means of a mechanical or hydraulic press.

pressing area o

o

The weight per unit volume of an unsintered compact. Same as green density .

A hot-pressing technique that usually employs low loads, high sintering temperatures, continuous or discontinuous sintering, and simple molds to contain the powder. Although the terms pressure sintering and hot pressing are used interchangeably, distinct differences exist between the two processes. In pressure sintering, the emphasis is on thermal processing; in hot pressing, applied pressure is the main process variable.

pressure welding o

See preferred terms cold welding , diffusion welding , forge welding , hot pressure welding , pressure-controlled welding , pressure gas welding , and solid-state welding .

o

primary creep

o

primary crystals

o o

The first, or initial, stage of creep, or time-dependent deformation. The first type of crystals that separate from a melt during solidification.

o

primary metal

o

primary mill

o o o

A mill for rolling ingots or the rolled products of ingots to blooms, billets, or slabs. This type of mill is often called a blooming mill and sometimes called a cogging mill.

principal stress (normal) o

o

Metal extracted from minerals and free of reclaimed metal scrap. Compare with native metal .

The maximum or minimum value of the normal stress at a point in a plane considered with respect to all possible orientations of the considered plane. On such principal planes the shear stress is zero. There are three principal stresses on three mutually perpendicular planes. The state of stress at a point may be (1) uniaxial, a state of stress in which two of the three principal stresses are zero, (2) biaxial, a state of stress in which only one of the three principal stresses is zero, and (3) triaxial, a state of stress in which none of the principal stresses is zero. Multiaxial stress refers to either biaxial or triaxial stress.

process annealing o

A heat treatment used to soften metal for further cold working. In ferrous sheet and wire industries, heating to a temperature close to but below the lower limit of the transformation range and subsequently cooling for working. In the nonferrous industries, heating above the

recrystallization temperatures at a time and temperature sufficient to permit the desired subsequent cold working. o

process metallurgy o

o

proeutectoid phase o

o

The greatest stress a material is capable of developing without a deviation from straight-line proportionality between stress and strain. See also elastic limit and Hooke's law .

protective atmosphere o

o

(1) A specified stress to be applied to a member or structure to indicate its ability to withstand service loads. (2) The stress that will cause a specified small permanent set in a material.

proportional limit o

o

A predetermined load, generally some multiple of the service load, to which a specimen or structure is submitted before acceptance for use.

proof stress o

o

(1) To test a component or system at its peak operating load or pressure. (2) Any reproduction of a die impression in any material; often a lead or plaster cast. See also die proof .

proof load o

o

A resistance welding process that produces coalescence of metals with the heat obtained from resistance to electric current through the work parts held together under pressure by electrodes. The resulting welds are localized at predetermined points by projections, embossments, or intersections.

proof o

o

Sequential forming at consecutive stations with a single die or separate dies.

projection welding o

o

A die with two or more stations arranged in line for performing two or more operations on a part; one operation is usually performed at each station.

progressive forming o

o

Aging by increasing the temperature in steps or continuously during the aging cycle. See also aging and compare with interrupted aging and step aging .

progressive die o

o

Any operation that produces an irregular contour on a workpiece, for which a tracer or templatecontrolled duplicating equipment usually is employed.

progressive aging o

o

Particles of a phase in ferrous alloys that precipitate during cooling after austenitizing but before the eutectoid transformation takes place. See also eutectoid .

profiling o

o

The science and technology of winning metals from their ores and purifying metals; sometimes referred to as chemical metallurgy. Its two chief branches are extractive metallurgy and refining.

(1) A gas or vacuum envelope surrounding the part to be brazed, welded, or thermal sprayed, with the gas composition controlled with respect to chemical composition, dew point, pressure, flow rate, and so forth. Examples are inert gases, combusted fuel gases, hydrogen, and vacuum. (2) The atmosphere in a heat treating or sintering furnace designed to protect the parts or compacts from oxidation, nitridation, or other contamination from the environment.

pseudobinary system o

(1) A three-component or ternary alloy system in which an intermediate phase acts as a component. (2) A vertical section through a ternary diagram.

o

puckering

o

pull cracks

o o o

In a casting, cracks that are caused by residual stresses produced during cooling and that result from the shape of the object.

pulverization o

o

Wrinkling or buckling in a drawn shell in an area originally inside the draw ring.

The process of reducing metal powder particle sizes by mechanical means; also called comminution or mechanical disintegration.

punch o

(1) The male part of a die--as distinguished from the female part, which is called the die. The punch is usually the upper member of the complete die assembly and is mounted on the slide or in a die set for alignment (except in the inverted die). (2) In double-action draw dies, the punch is the inner portion of the upper die, which is mounted on the plunger (inner slide) and does the

drawing. (3) The act of piercing or punching a hole. Also referred to as punching . (4) The movable tool that forces material into the die in powder molding and most metalforming operations. (5) The movable die in a trimming press or a forging machine. (6) The tool that forces the stock through the die in rod and tube extrusion and forms the internal surface in can or cup extrusion. o

punching o

o

(1) The die shearing of a closed contour in which the sheared out sheet metal part is scrap. (2) Producing a hole by die shearing, in which the shape of the hole is controlled by the shape of the punch and its mating die. Multiple punching of small holes is called perforating . See also piercing .

punch press o

(1) In general, any mechanical press. (2) In particular, an endwheel gap-frame press with a fixed bed, used in piercing.

o

punch radius

o

push bench

o o o

Equipment used for drawing moderately heavy-gage tubes by cupping sheet metal and forcing it through a die by pressure exerted against the inside bottom of the cup.

pusher furnace o

o

The radius on the end of the punch that first contacts the work, sometimes called nose radius .

A type of continuous furnace in which parts to be heated are periodically charged into the furnace in containers, which are pushed along the hearth against a line of previously charged containers thus advancing the containers toward the discharge end of the furnace, where they are removed.

push welding o

Spot or projection welding in which the force is applied manually to one electrode, and the work or backing plate takes the place of the other electrode.

o

pyramidal plane

o

pyrometallurgy

o o

In noncubic crystals, any plane that intersects all three axes. High-temperature winning or refining of metals.

o

pyrometer

o

pyrophoric powder

o o o o

quality

In a ternary or higher-order system, a linear composition series between two substances each of which exhibits congruent melting, wherein all equilibria, at all temperatures or pressures, involve only phases having compositions occurring in the linear series, so that the series may be represented as a binary on a phase diagram.

quasi-cleavage fracture o

o

A temper of nonferrous alloys and some ferrous alloys characterized by tensile strength about midway between that of dead soft and half hard tempers.

quasi-binary system o

o

Determination of specific characteristics of a microstructure by quantitative measurements on micrographs or metallographic images. Quantities so measured include volume concentration of phases, grain size, particle size, mean free path between like particles or secondary phases, and surface-area-to-volume ratio of microconstituents, particles, or grains.

quarter hard o

o

(1) The totality of features and characteristics of a product or service that bear on its ability to satisfy a given need (fitness-for-use concept of quality). (2) Degree of excellence of a product or service (comparative concept). Often determined subjectively by comparison against an ideal standard or against similar products or services available from other sources. (3) A quantitative evaluation of the features and characteristics of a product or service (quantitative concept).

quantitative metallography o

o

A powder whose particles self-ignite and burn when exposed to oxygen or air.

Q o

o

A device for measuring temperatures above the range of liquid thermometers.

A fracture mode that combines the characteristics of cleavage fracture and dimple fracture. An intermediate type of fracture found in certain high-strength metals.

quench-age embrittlement

o

Embrittlement of low-carbon steels resulting from precipitation of solute carbon at existing dislocations and from precipitation hardening of the steel caused by differences in the solid solubility of carbon in ferrite at different temperatures. Quench-age embrittlement usually is caused by rapid cooling of the steel from temperatures slightly below Ac1 (the temperature at which austenite begins to form), and can be minimized by quenching from lower temperatures.

o

quench aging

o

quench annealing

o o o

(1) Hardening suitable - alloys (most often certain copper to titanium alloys) by solution treating and quenching to develop a martensitic-like structure. (2) In ferrous alloys, hardening by austenitizing and then cooling at a rate such that a substantial amount of austenite transforms to martensite.

quenching o

o

Fracture of a metal during quenching from elevated temperature. Most frequently observed in hardened carbon steel, alloy steel, or tool steel parts of high hardness and low toughness. Cracks often emanate from fillets, holes, corners, or other stress raisers and result from high stresses due to the volume changes accompanying transformation to martensite.

quench hardening o

o

Annealing an austenitic ferrous alloy by solution heat treatment followed by rapid quenching.

quench cracking o

o

Aging induced by rapid cooling after solution heat treatment.

Rapid cooling of metals (often steels) from a suitable elevated temperature. This generally is accomplished by immersion in water, oil, polymer solution, or salt, although forced air is sometimes used. See also brine quenching , caustic quenching , direct quenching , fog quenching , forced-air quenching , hot quenching , intense quenching , interrupted quenching , oil quenching , press quenching , selective quenching , spray quenching , time quenching , and water quenching .

quenching crack o

A crack formed in a metal as a result of thermal stresses produced by rapid cooling from a high temperature.

o

quenching oil

o o

R

o

racking

o

rabbit ear o o

o

Lines on a fracture surface that radiate from the fracture origin and are visible to the unaided eye or at low magnification. Radial marks result from the intersection and connection of brittle fractures propagating at different levels. Also known as shear ledges. See also chevron pattern . A general term for the alteration of properties of a material arising from exposure to ionizing radiation (penetrating radiation), such as x-rays, gamma rays, neutrons, heavy-particle radiation, or fission fragments in nuclear fuel material. See also neutron embrittlement .

radioactive element o

o

A process using two or more moving anvils or dies for producing shafts with constant or varying diameters along their length or tubes with internal or external variations. Often incorrectly referred to as rotary forging .

radiation damage o

o

The forming of sheet metals by the simultaneous application of tangential stretch and radial compression forces. The operation is done gradually by tangential contact with the die member. This type of forming is characterized by very close dimensional control.

radial marks o

o

A term used to describe the placing of metal parts to be heat treated on a rack or tray. This is done to keep parts in a proper position to avoid heat-related distortions and to keep the parts separated.

radial forging o

o

Recess in the corner of a metalforming die to allow for wrinkling or folding of the blank.

radial draw forming o

o

Oil used for quenching metals during a heat treating operation.

An element that has at least one isotope that undergoes spontaneous nuclear disintegration to emit positive particles, negative particles, or rays.

radioactivity

o

o

radiograph o

o

A surface imperfection on a casting, occurring as one or more irregular lines, caused by expansion of sand in the mold. Compare with buckle (2).

reaction sintering o

o

Rate of change of true stress with respect to true strain in the plastic range.

rattail o

o

Lines or markings on a fatigue fracture surface that results from the intersection and connection of fatigue fractures propagating from multiple origins. Ratchet marks are parallel to the overall direction of crack propagation and are visible to the unaided eye or at low magnification.

rate of strain hardening o

o

Progressive cyclic inelastic deformation (growth, for example) that occurs when a component or structure is subjected to a cyclic secondary stress superimposed on a sustained primary stress. The process is called thermal ratcheting when cyclic strain is induced by cyclic changes in temperature, and isothermal ratcheting when cyclic strain is mechanical in origin (even though accompanied by cyclic changes in temperature).

ratchet marks o

o

A group of 17 chemically similar metals that includes the elements scandium and yttrium (atomic numbers 21 and 39, respectively) and the lanthanide elements (atomic numbers 57 through 71).

ratcheting o

o

The cooling or quenching of liquid (molten) metals at rates that range from 104 to 108 °C/s.

rare earth metal o

o

The algebraic difference between the maximum and minimum stress in one cycle--that is, Sr = Smax - Smin.

rapid solidification o

o

A longitudinal welding sequence wherein the weld-bead increments are deposited at random to minimize distortion.

range of stress (Sr) o

o

(1) Packing foundry sand, refractory, or other material into a compact mass. (2) The compacting of molding (foundry) sand in forming a mold.

random sequence o

o

The moving or falling part of a drop hammer or press to which one of the dies is attached; sometimes applied to the upper flat die of a steam hammer. Also referred to as the slide .

ramming o

o

The angular relationship between the tooth face, or a tangent to the tooth face at a given point, and a given reference plane or line.

ram o

o

The radius of the cylindrical surface of the pin or mandrel that comes in contact with the inside surface of the bend during bending. In the case of free or semiguided bends to 180° in which a shim or block is used, the radius of bend is one-half the thickness of the shim or block.

rake o

o

A method of nondestructive inspection in which a test object is exposed to a beam of x-rays or rays and the resulting shadow image of the object is recorded on photographic film placed behind the object, or displayed on a viewing screen or television monitor (real-time radiography). Internal discontinuities are detected by observing and interpreting variations in the image caused by differences in thickness, density, or absorption within the test object. See also real-time radiography .

radius of bend o

o

A photographic shadow image resulting from uneven absorption of penetrating radiation in a test object. See also radiography .

radiography o

o

(1) The property of the nuclei of some isotopes to spontaneously decay (lose energy). Usual mechanisms are emission of , , or other particles and splitting (fissioning). Gamma rays are frequently, but not always, given off in the process. (2) A particular component from a radioactive source, such as radioactivity.

The sintering of a metal powder mixture consisting of at least two components that chemically react during the treatment.

reactive metal

o

o

real-time radiography o

o

An operation in which a previously formed hole is sized and contoured accurately by using a rotary cutting tool (reamer) with one or more cutting elements (teeth). The principal support for the reamer during the cutting action is obtained from the workpiece.

recalescence o

o

A method of nondestructive inspection in which a two-dimensional radiographic image can be immediately displayed on a viewing screen or television monitor. This technique does not involve the creation of a latent image; instead, the unabsorbed radiation is converted into an optical or electronic signal, which can be viewed immediately or can be processed in near real time with electronic and video equipment. See also radiography .

reaming o

o

A metal that readily combines with oxygen at elevated temperatures to form very stable oxides, for example, titanium, zirconium, and beryllium. Reactive metals may also become embrittled by the interstitial absorption of oxygen, hydrogen, and nitrogen.

(1) The increase in temperature that occurs after undercooling, because the rate of liberation of heat during transformation of a material exceeds the rate of dissipation of heat. (2) A phenomenon, associated with the transformation of iron to iron on cooling (supercooling) of iron or steel, that is revealed by the brightening (reglowing) of the metal surface owing to the sudden increase in temperature caused by the fast liberation of the latent heat of transformation. Contrast with decalescence .

recarburize o

(1) To increase the carbon content of molten cast iron or steel by adding carbonaceous material, high-carbon pig iron, or a high-carbon alloy. (2) To carburize a metal part to return surface carbon lost in processing; also known as carbon restoration.

o

recess

o

recovery

o o

o

A groove or depression in a surface. (1) The time-dependent portion of the decrease in strain following unloading of a specimen at the same constant temperature as the initial test. Recovery is equal to the total decrease in strain minus the instantaneous recovery. (2) Reduction or removal of work-hardening effects in metals without motion of large-angle grain boundaries. (3) The proportion of the desired component obtained by processing an ore, usually expressed as a percentage.

recrystallization o

(1) The formation of a new, strain-free grain structure from that existing in cold-worked metal, usually accomplished by heating. (2) The change from one crystal structure to another, as occurs on heating or cooling through a critical temperature. (3) A process, usually physical, by which one crystal species is grown at the expense of another or at the expense of others of the same substance but smaller in size. See also crystallization .

o

recrystallization annealing

o

recrystallization temperature

o o o

Equipment for transferring heat from gaseous products of combustion to incoming air or fuel. The incoming material passes through pipes surrounded by a chamber through which the outgoing gases pass.

red mud o

o

(1) The grain size developed by heating cold-worked metal. The time and temperature are selected so that, although recrystallization is complete, essentially no grain growth occurs. (2) In aluminum and magnesium alloys, the grain size after recrystallization, without regard to grain growth or the recrystallized conditions. See also recrystallization .

recuperator o

o

The approximate minimum temperature at which complete recrystallization of a cold-worked metal occurs within a specified time.

recrystallized grain size o

o

Annealing cold-worked metal to produce a new grain structure without phase change.

A residue, containing a high percentage of iron oxide, obtained in purifying bauxite in the production of alumina in the Bayer process.

redox potential o

This potential of a reversible oxidation-reduction electrode measured with respect to a reference electrode, corrected to the hydrogen electrode, in a given electrode.

o

redrawing o

o

reducing agent o

o

(1) A material (usually an inorganic, nonmetallic, ceramic material) of very high melting point with properties that make it suitable for such uses as furnace linings and kiln construction. (2) The quality of resisting heat.

refractory alloy o

o

Melting of an electrodeposit followed by solidification. The surface has the appearance and physical characteristics of a hot dipped surface (especially tin or tin alloy plates). Also called flow brightening .

refractory o

o

The branch of process metallurgy dealing with the purification of crude or impure metals. Compare with extractive metallurgy .

reflowing o

o

In materials characterization, a material of definite composition that closely resembles in chemical and physical nature the material with which an analyst expects to deal; used for calibration or standardization. See also standard reference material .

refining o

o

A nonpolarizable electrode with a known and highly reproducible potential used for potentiometric and voltammetric analyses. See also calomel electrode .

reference material o

o

Transverse breaks or ridges on successive inner laps of a coil that results from crimping of the lead end of the coil into a gripping segmented mandrel. Also called reel kinks.

reference electrodes o

o

(1) A spool or hub for coiling or feeding wire or strip. (2) To straighten and planish a round bar by passing it between contoured rolls.

reel breaks o

o

The difference between the original cross-sectional area of a tensile specimen and the smallest area at or after fracture as specified for the material undergoing testing. Also known as reduction of area.

reel o

o

A pot or tank in which either a water solution of a salt or a fused salt is reduced electrolytically to form free metals or other substances.

reduction in area (RA) o

o

(1) In cupping and deep drawing, a measure of the percentage decrease from blank diameter to cup diameter, or of diameter reduction in redrawing. (2) In forging, rolling, and drawing, either the ratio of the original to final cross-sectional area or the percentage decrease in cross-sectional area. (3) A reaction in which there is a decrease in valence resulting from a gain in electrons. Contrast with oxidation .

reduction cell o

o

(1) A gas flame produced with excess fuel in the inner flame. (2) A gas flame resulting from combustion of a mixture containing too much fuel or too little air. See also neutral flame and oxidizing flame .

reduction o

o

(1) A furnace atmosphere that tends to remove oxygen from substances or materials placed in the furnace. (2) A chemically active protective atmosphere that at elevated temperature will reduce metal oxides to their metallic state. Reducing atmosphere is a relative term and such an atmosphere may be reducing to one oxide but not to another oxide.

reducing flame o

o

(1) A compound that causes reduction, thereby itself becoming oxidized. (2) A chemical that, at high temperatures, lowers the state of oxidation of other batch chemicals.

reducing atmosphere o

o

The second and successive deep-drawing operations in which cup-like shells are deepened and reduced in cross-sectional dimensions. See also deep drawing .

(1) A heat-resistant alloy. (2) An alloy having an extremely high melting point. See also refractory metal . (3) An alloy difficult to work at elevated temperatures.

refractory metal o

A metal having an extremely high melting point and low vapor pressure; for example, niobium, tantalum, molybdenum, tungsten, and rhenium.

o

regenerator o

o

regulator o

o

A soldering process in which the heat required is obtained from the resistance to electric current flow in a circuit of which the workpiece is a part.

resistance spot welding o

o

A resistance welding process that produces coalescence at the faying surfaces of overlapped parts progressively along a length of a joint. The weld may be made with overlapping weld nuggets, a continuous weld nugget, or by forging the joint as it is heated to the welding temperature by resistance to the flow of the welding current.

resistance soldering o

o

A brazing process in which the heat required is obtained from the resistance to electric current flow in a circuit of which the workpiece is a part.

resistance seam welding o

o

(1) Coating material used to mask or protect selected areas of a substrate from the action of an etchant, solder, or plating. (2) A material applied to prevent flow of brazing filler metal into unwanted areas.

resistance brazing o

o

A grinding wheel bonded with a synthetic resin.

resist o

o

(1) The amount of energy per unit volume released on unloading. (2) The capacity of a material, by virtue of high yield strength and low elastic modulus, to exhibit considerable elastic recovery on release of load.

resinoid wheel o

o

(1) The stress existing in a body at rest, in equilibrium, at uniform temperature, and not subjected to external forces. Often caused by the forming or thermal processing curing process. (2) An internal stress not depending on external forces resulting from such factors as cold working, phase changes, or temperature gradients. (3) Stress present in a body that is free of external forces or thermal gradients. (4) Stress remaining in a structure or member as a result of thermal or mechanical treatment or both. Stress arises in fusion welding primarily because the weld metal contracts on cooling from the solidus to room temperature.

resilience o

o

Small quantities of elements unintentionally present in an alloy.

residual stress o

o

The application of pressure to a previously pressed and sintered powder metallurgy compact, usually for the purpose of improving some physical or mechanical property or for dimensional accuracy.

residual elements o

o

The magnetic induction remaining in a magnetic circuit after removal of the applied magnetizing force. Sometimes called remanent induction.

repressing o

o

Buffing or other abrasive treatment of the high points of an embossed metal surface to produce highlights that contrast with the finish in the recesses.

remanence o

o

A quantitative measure of the ability of a product or service to fulfill its intended function for a specified period of time.

relieving o

o

A device for controlling the delivery of welding or cutting gas at some substantially constant pressure.

reliability o

o

Same as recuperator except that the gaseous products or combustion heat brick checkerwork in a chamber connected to the exhaust side of the furnace while the incoming air and fuel are being heated by the brick checkerwork in a second chamber, connected to the entrance side. At intervals, the gas flow is reversed so that incoming air and fuel contact hot checkerwork while that in the second chamber is being reheated by exhaust gases.

A resistance welding process that produces coalescence at the faying surfaces of a joint by the heat obtained from resistance to the flow of welding current through the workpieces from electrodes that serve to concentrate the welding current and pressure at the weld areas.

resistance welding

o

o

resistance welding electrode o

o

A furnace in which the flame used for melting the metal does not impinge on the metal surface itself, but is reflected off the walls of the root of the furnace. The metal is actually melted by the generation of heat from the walls and the roof of the furnace.

reverse-current cleaning o

o

A vessel used for distillation of volatile materials, as in separation of some metals and in destructive distillation of coal.

reverberatory furnace o

o

(1) The striking of a trimmed but slightly misaligned or otherwise faulty forging with one or more blows to improve alignment, improve surface condition, maintain close tolerances, increase hardness, or effect other improvements. (2) A sizing operation in which coining or stretching is used to correct or alter profiles and to counteract distortion. (3) A salvage operation following a primary forging operation in which the parts involved are rehit in the same forging die in which the pieces were last forged.

retort o

o

Any external mechanical force that prevents a part from moving to accommodate changes in dimension due to thermal expansion or contraction. Often applied to weldments made while clamped in a fixture. Compare with constraint .

restriking o

o

The part(s) of a resistance welding machine through which the welding current and, in most cases, force are applied directly to the work. The electrode may be in the form of a rotating wheel, rotating bar, cylinder, plate, clamp, chuck, or modification thereof.

restraint o

o

A group of welding processes that produce coalescence of metals with resistance heating and pressure. See also flash welding , projection welding , resistance seam welding , and resistance spot welding .

Electrolytic cleaning in which a current is passed between electrodes through a solution, and the part is set up as the anode. Also called anodic cleaning .

reverse drawing o

Redrawing of a sheet metal part in a direction opposite to that of the original drawing.

o

reverse polarity

o

reverse redrawing

o o o

o

o

o

Casting of a continuously stirred semisolid metal slurry. The process involves vigorous agitation of the melt during the early stages of solidification to break up solid dendrites into small spherulites. See also semisolid metal forming .

o

A long V-shaped or radiused indentation used to strengthen large sheet metal panels. (2) A long, usually thin protuberance used to provide flexural strength to a forging (as in a rib-web forging).

rib rigging

A low-carbon steel containing sufficient iron oxide to give a continuous evolution of carbon monoxide while the ingot is solidifying, resulting in a case or rim of metal virtually free of voids. Sheet and strip products made from rimmed steel ingots have very good surface quality.

ring and circle shear o

o

The engineering design, layout, and fabrication of pattern equipment for producing castings; including a study of the casting solidification program, feeding and gating, risering, skimmers, and fitting flasks.

rimmed steel o

o

A second drawing operation in a direction opposite to that of the original drawing.

rheocasting

o

o

See preferred term direct current electrode positive (DCEP) .

A cutting or shearing machine with two rotary-disk cutters driven in unison and equipped with a circle attachment for cutting inside circles or rings from sheet metal, where it is impossible to start the cut at the edge of the sheet. One cutter shaft is inclined to the other to provide cutting clearance so that the outside section remains flat and usable. See also circle shear and rotary shear .

ring rolling o

The process of shaping weldless rings from pierced disks or shaping thick-wall ring-shaped blanks between rolls that control wall thickness, ring diameter, height, and contour.

o

riser o

o

riser blocks o

o

A type of guillotine shear that utilizes a curved blade to shear sheet metal progressively from side to side by a rocker motion.

Rockwell hardness number o

o

A fracture that exhibits separated-grain facets; most often used to describe an intergranular fracture in a large-grained metal.

rocking shear o

o

(1) A copper electrodeposit obtained from copper cyanide plating solution to which Rochelle salt (sodium potassium tartrate) has been added for grain refinement, better anode corrosion, and cathode efficiency. (2) The solution from which a Rochelle copper electrodeposit is obtained.

rock candy fracture o

o

An extra cathode or cathode extension that reduces the current density on what would otherwise be a high-current-density area on work being electroplated.

Rochelle copper o

o

Heating an ore to effect some chemical change that will facilitate smelting.

robber o

o

Joining of two or more members of a structure by means of metal rivets, the unheaded end being upset after the rivet is in place.

roasting o

o

A term used in fractography to describe a characteristic pattern of cleavage steps running parallel to the local direction of crack propagation on the fracture surfaces of grains that have separated by cleavage.

riveting o

o

(1) Plates or pieces inserted between the top of a metalforming press bed or bolster and the die to decrease the height of the die space. (2) Spacers placed between bed and housings to increase shut height on a four-piece tie-rod straight-side press.

river pattern o

o

A reservoir of molten metal connected to a casting to provide additional metal to the casting, required as the result of shrinkage before and during solidification.

A number derived from the net increase in the depth of impression as the load on an indenter is increased from a fixed minor load to a major load and then returned to the minor load. Various scales of Rockwell hardness numbers have been developed based on the hardness of the materials to be evaluated. The scales are designated by alphabetic suffixes to the hardness designation. For example, 64 HRC represents the Rockwell hardness number of 64 on the Rockwell C scale. See also Rockwell superficial hardness number .

Rockwell hardness test o

An indentation hardness test using a calibrated machine that utilizes the depth of indentation, under constant load, as a measure of hardness. Either a 120° diamond cone with a slightly rounded point or a 1.6 or 3.2 mm (

o

o

o

The same test as used to determine the Rockwell hardness number except that smaller minor and major loads are used. In Rockwell testing, the minor load is 10 kgf, and the major load is 60, 100, or 150 kgf. In superficial Rockwell testing, the minor load is 3 kgf, and major loads are 15, 30, or 45 kgf. In both tests, the indenter may be either a diamond cone or a steel ball, depending principally on the characteristics of the material being tested. A solid round metal section 9.5 mm ( relation to its diameter.

in.) or greater in diameter, whose length is great in

rod mill o

o

Like the Rockwell hardness number, the superficial Rockwell number is expressed by the symbol HR followed by a scale designation. For example, 81 HR30N represents the Rockwell superficial hardness number of 81 on the Rockwell 30N scale.

rod o

o

in.) diam steel ball is used as the indenter.

Rockwell superficial hardness test o

o

or

Rockwell superficial hardness number

(1) A hot mill for rolling rod. (2) A mill for fine grinding, somewhat similar to a ball mill, but employing long steel rods instead of balls to effect grinding.

roll bending

o

Curving sheets, bars, and sections by means of rolls. See also bending rolls .

o

roll compacting

o

roller hearth furnace

o o

o

Obvious transverse breaks usually about 3 to 6 mm ( to in.) apart caused by the sheet metal fluting during roller leveling. These will not be removed by stretching.

roller leveler lines o

o

A modification of the pusher-type continuous furnace that provides for rollers in the hearth or muffle of the furnace whereby friction is greatly reduced and lightweight trays can be used repeatedly without risk of unacceptable distortion and damage to the work. See also pusher furnace .

roller leveler breaks o

o

Progressive compacting of metal powders by use of a rolling mill.

Same as leveler lines .

roller leveling o

Leveling by passing flat sheet metal stock through a machine having a series of small-diameter staggered rolls that are adjusted to produce repeated reverse bending.

o

roller stamping die

o

roll flattening

o o o

Repeated stressing of a solid surface due to rolling contact between it and another solid surface or surfaces. Continued rolling-contact fatigue of bearing or gear surfaces may result in rollingcontact damage in the form of subsurface fatigue cracks and/or material pitting and spallation.

rolling mills o

o

The reduction of the cross-sectional area of metal stock, or the general shaping of metal products, through the use of rotating rolls. See also rolling mills .

rolling-contact fatigue o

o

Metalforming through the use of power-driven rolls whose contour determines the shape of the product; sometimes used to denote power spinning.

rolling o

o

A process of shaping stock between two driven rolls that rotate in opposite directions and have one or more matching sets of grooves in the rolls; used to produce finished parts or preforms for subsequent forging operations.

roll forming o

o

The flattening of metal sheets that have been rolled in packs by passing them separately through a two-high cold mill with virtually no deformation. Not to be confused with roller leveling .

roll forging o

o

An engraved roller used for impressing designs and markings on sheet metal.

Machines used to decrease the cross-sectional area of metal stock and to produce certain desired shapes as the metal passes between rotating rolls mounted in a framework comprising a basic unit called a stand. Cylindrical rolls produce flat shapes; grooved rolls produce rounds, squares, and structural shapes. See also four-high mill , Sendzimir mill , and two-high mill .

roll straightening o

The straightening of metal stock of various shapes by passing it through a series of staggered rolls, the rolls usually being in horizontal and vertical planes, or by reeling in two-roll straightening machines.

o

roll threading

o

roll welding

o o o

A crack in either the weld or heat-affected zone at the root of a weld.

rosette o

o

Solid-state welding in which metals are heated, then welded together by applying pressure, with rolls, sufficient to cause deformation at the faying surfaces. See also forge welding .

root crack o

o

See preferred term thread rolling .

(1) Rounded configuration of microconstituents in metals arranged in whorls or radiating from a center. (2) Strain gages arranged to indicate at a single position strains in three different directions.

rotary forging

o

o

rotary furnace o

o

A bulk forming process for reducing the cross-sectional area or otherwise changing the shape of bars, tubes, or wires by repeated radial blows with one or more pairs of opposed dies.

rouge finish o

o

A swaging machine consisting of a power-driven ring that revolves at high speed, causing rollers to engage cam surfaces and force the dies to deliver hammerlike blows on the work at high frequency. Both straight and tapered sections can be produced.

rotary swaging o

o

A sheet metal cutting machine with two rotating-disk cutters mounted on parallel shafts driven in unison.

rotary swager o

o

A continuous-type furnace in which the work advances by means of an internal spiral, which gives good control of the retention time within the heated chamber.

rotary shear o

o

A machine for forming powder metallurgy parts that is fitted with a rotating table carrying multiple die assemblies in which powder is compacted.

rotary retort furnace o

o

A circular furnace constructed so that the hearth and workpieces rotate around the axis of the furnace during heating. Also called rotary hearth furnace.

rotary press o

o

A process in which the workpiece is pressed between a flat anvil and a swiveling (rocking) die with a conical working face; the platens move toward each other during forging. Also called orbital forging. Compare with radial forging .

A highly reflective finish produced with rouge (finely divided, hydrated iron oxide) or other very fine abrasive, similar in appearance to the bright polish or mirror finish on sterling silver utensils.

rough blank o

A blank for a metalforming or drawing operation, usually of irregular outline, with necessary stock allowance for process metal, which is trimmed after forming or drawing to the desired size.

o

rough grinding

o

roughing stand

o o o

(1) Relatively finely spaced surface irregularities, the heights, widths, and directions of which establish the predominant surface pattern. (2) The microscopic peak-to-valley distances of surface protuberances and depressions. See also surface roughness .

rubber forming o

o

Machining without regard to finish, usually to be followed by a subsequent operation.

roughness o

o

The first stand (or several stands) of rolls through which a reheated billet passes in front of the finishing stands. See also rolling mills and stand .

rough machining o

o

Grinding without regard to finish, usually to be followed by a subsequent operation.

Forming a sheet metal wherein rubber or another resilient material is used as a functional die part. Processes in which rubber is employed only to contain the hydraulic fluid are not classified as rubber forming.

rubber-pad forming o

A sheet metal forming operation for shallow parts in which a confined, pliable rubber pad attached to the press slide (ram) is forced by hydraulic pressure to become a mating die for a punch or group of punches placed on the press bed or baseplate. Also known as the Guerin process . Variations of the Guerin process include the fluid-cell process , fluid forming , and Marforming process .

o

rubber wheel

o

runner

o o

o

A grinding wheel made with a rubber bond. (1) A channel through which molten metal flows from one receptacle to another. (2) The portion of the gate assembly of a casting that connects the sprue with the gate(s). (3) Parts of patterns and finished castings corresponding to the portion of the gate assembly described in (2).

runner box o

A distribution box that divides molten metal into several streams before it enters the casting mold cavity.

o

runout o

(1) The unintentional escape of molten metal from a mold, crucible, or furnace. (2) An imperfection in a casting caused by the escape of metal from the mold.

o

rupture stress

o

rust

o o o o

The stress at failure. Also known as breaking stress or fracture stress . A visible corrosion product consisting of hydrated oxides of iron. Applied only to ferrous alloys. See also white rust .

S

sacrificial protection o

Reduction of corrosion of a metal in an electrolyte by galvanically coupling it to a more anodic metal; a form of cathodic protection.

o

saddling

o

sag

o

o

Forming a seamless metal ring by forging a pierced disk over a mandrel (or saddle).

o

An increase or decrease in the section thickness of a casting caused by insufficient strength of the mold sand of the cope or of the core.

salt bath heat treatment o

o

Heat treatment for metals carried out in a bath of molten salt.

salt fog test o

An accelerated corrosion test in which specimens are exposed to a fine mist of a solution usually containing sodium chloride, but sometimes modified with other chemicals. Also known as salt spray test.

o

salt spray test

o

sample

o o

o

See salt fog test . (1) One or more units of a product (or a relatively small quantity of a bulk material) withdrawn from a lot or process stream and then tested or inspected to provide information about the properties, dimensions, or other quality characteristics of the lot or process stream. (2) A portion of a material intended to be representative of the whole.

sand o

A granular material naturally or artificially produced by the disintegration or crushing of rocks or mineral deposits. In casting, the term denotes an aggregate, with an individual particle (grain) size of 0.06 to 2 mm (0.002 to 0.08 in.) in diameter, that is largely free of finer constituents, such as silt and clay, which are often present in natural sand deposits. The most commonly used foundry sand is silica; however, zircon, olivine, aluminum silicates, and other crushed ceramics are used for special applications.

o

sandblasting

o

sand casting

o

sand hole

o o o

Abrasive blasting with sand. See also blasting or blast cleaning and compare with shotblasting . Metal castings produced in sand molds. A pit in the surface of a sand casting resulting from a deposit of loose sand on the surface of the mold.

o

sandwich rolling

o

satin finish

o o o

In saw manufacture, grinding away of punch marks or milling marks in the gullets (spaces between the teeth) and, in some cases, simultaneous sharpening of the teeth; in reconditioning of worn saws, restoration of the original gullet size and shape.

sawing o

o

A diffusely reflecting surface finish on metals, lustrous but not mirrorlike. One type is a butler finish.

saw gumming o

o

Rolling two or more strips of metal in a pack, sometimes to form a roll-welded composite.

Using a toothed blade or disk to sever parts or cut contours.

scab o

A defect on the surface of a casting that appears as a rough, slightly raised surface blemish, crusted over by a thin porous layer of metal, under which is a honeycomb or cavity that usually

contains a layer of sand; defect common to thin-wall portions of the casting or around hot areas of the mold. o

scale o

o

scale pit o

o

Surface oxidation, consisting of partially adherent layers of corrosion products, left on metals by heating or casting in air or in other oxidizing atmospheres. (1) A surface depression formed on a forging due to scale remaining in the dies during the forging operation. (2) A pit in the ground in which scale (such as that carried off by cooling water from rolling mills) is allowed to settle out as one step in the treatment of effluent waste water.

scaling o

(1) Forming a thick layer of oxidation products on metals at high temperature. Scaling should be distinguished from rusting, which involves the formation of hydrated oxides. See also rust . (2) Depositing water-insoluble constituents on a metal surface, as in cooling tubes and water boilers.

o

scalping

o

scanning Auger microscopy (SAM)

o o

o

The hardness of a metal determined by the width of a scratch made by drawing a cutting point across the surface under a given pressure.

screen o

o

(1) Products that are discarded because they are defective or otherwise unsuitable for sale. (2) Discarded metallic material, from whatever source, that may be reclaimed through melting and refining.

scratch hardness o

o

(1) A wet or dry cleaning process involving mechanical scrubbing. (2) A wet or dry mechanical finishing operation, using fine abrasive and low pressure, carried out by hand or with a cloth or wire wheel to produce satin or butler-type finishes.

scrap o

o

(1) The formation of severe scratches in the direction of sliding. (2) The act of producing a scratch or narrow groove in a surface by causing a sharp instrument to move along that surface. (3) The marring or scratching of any formed metal part by metal pickup on the punch or die. (4) The reduction in thickness of a material along a line to weaken it intentionally along that line.

scouring o

o

Oxidation, in the presence of fluxes, of molten lead containing precious metals, to partly remove the lead in order to concentrate the precious metals.

scoring o

o

A dynamic indentation hardness test using a calibrated instrument that drops a diamond-tipped hammer from a fixed height onto the surface of the material being tested. The height of rebound of the hammer is a measure of the hardness of the material.

scorification o

o

A number related to the height of rebound of a diamond-tipped hammer dropped on the material being tested. It is measured on a scale determined by dividing into 100 units the average rebound of the hammer from a quenched (to maximum hardness) and untempered AISI W-5 tool steel test block.

Scleroscope hardness test o

o

Cutting surface areas of metal objects, ordinarily by using an oxyfuel gas torch. The operation permits surface imperfections to be cut from ingots, billets, or the edges of plate that are to be beveled for butt welding. See also chipping .

Scleroscope hardness number (HSc or HSd) o

o

An analytical technique that measures the lateral distribution of elements on the surface of a material by recording the intensity of their Auger electrons versus the position of the electron beam.

scarfing o

o

Removing surface layers from an ingot, billet, or slab.

(1) The woven wire or fabric cloth, having square openings, used in a sieve for retaining particles greater than the particular mesh size. U.S. standard, ISO, or Tyler screen sizes are commonly used. (2) One of a set of sieves, designated by the size of the openings, used to classify granular aggregates such as sand, ore, or coke by particle size. (3) A perforated sheet placed in the gating system of a mold to separate impurities from the molten metal.

screw dislocation

o o

screw press o

o

See dislocation . A high-speed press in which the ram is activated by a large screw assembly powered by a drive mechanism.

scuffing o

(1) Localized damage caused by the occurrence of solid-phase welding between sliding surfaces, without local surface melting. (2) A mild degree of galling that results from the welding of asperities due to frictional heat. The welded asperities break, causing surface degradation.

o

seal coat

o

sealing

o o

o

Any weld designed primarily to provide a specific degree of tightness against leakage.

seam o

o

(1) Closing pores in anodic coatings to render them less absorbent. (2) Plugging leaks in a casting by introducing thermosetting plastics into porous areas and subsequently setting the plastic with heat.

seal weld o

o

Material applied to infiltrate the pores of a thermal spray deposit.

(1) On a metal surface, an unwelded fold or lap that appears as a crack, usually resulting from a discontinuity. (2) A surface defect on a casting related to but of lesser degree than a cold shut . (3) A ridge on the surface of a casting caused by a crack in the mold face.

seam weld o

A continuous weld made between or upon overlapping members, in which coalescence may start and occur on the faying surfaces, or may have proceeded from the outer surface of one member. The continuous weld may consist of a single weld bead or a series of overlapping spot welds.

o

seam welding

o

season cracking

o o

See arc seam weld and resistance seam welding . An obsolete historical term usually applied to stress-corrosion cracking of brass.

o

secondary alloy

o

secondary creep

o

secondary ion mass spectroscopy (SIMS)

o o o

o

A die made of parts that can be separated for ready removal of the workpiece. Synonymous with split die . (1) Nonuniform distribution of alloying elements, impurities, or microphases in metals and alloys. (2) A casting defect involving a concentration of alloying elements at specific regions, usually as a result of the primary crystallization of one phase with the subsequent concentration of other elements in the remaining liquid. Microsegregation refers to normal segregation on a microscopic scale in which material richer in an alloying element freezes in successive layers on the dendrites (coring) and in constituent network. Macrosegregation refers to gross differences in concentration (for example, from one area of a casting to another). See also inverse segregation and normal segregation .

segregation banding o

o

The removal of a conveniently sized, representative specimen from a larger sample for metallographic inspection. Sectioning methods include shearing, sawing (using hacksaws, band saws, and diamond wire saws), abrasive cutting, and electrical discharge machining.

segregation o

o

Metal recovered from scrap by remelting and refining.

segment die o

o

An analytical technique that measures the masses of ions emitted from the surface of a material when exposed to a beam of incident ions. The incident ions are usually monoenergetic and are all of the same species, for example, 5 keV Ne+ ions.

sectioning o

o

See creep.

secondary metal o

o

Any alloy whose major constituent is obtained from recycled scrap metal.

Inhomogeneous distribution of alloying elements aligned in filaments or plates parallel to the direction of working.

seizing

o o

The stopping of a moving part by a mating surface as a result of excessive friction.

seizure o

The stopping of relative motion as the result of interfacial friction. Seizure may be accompanied by gross surface welding. The term is sometimes used to denote scuffing .

o

Sejournet process

o

selective heating

o o o

Corrosion in which one element is preferentially removed from an alloy, leaving a residue (often porous) of the elements that are more resistant to the particular environment. Also called dealloying or parting. See also decarburization , decobaltification , denickelification , dezincification , and graphitic corrosion .

selective quenching o

o

Intentionally heating only certain portions of a workpiece.

selective leaching o

o

See Ugine-Sejournet process .

Quenching only certain portions of an object.

self-diffusion o

Thermally activated movement of an atom to a new site in a crystal of its own species, as, for example, a copper atom within a crystal of copper.

o

self-hardening steel

o

self-lubricating material

o o o

Preliminary operations performed prior to finishing.

semiguided bend o

o

An impression in a series of forging dies that only approximates the finish dimensions of the forging. Semifinishers are often used to extend die life or the finishing impression, to ensure proper control of grain flow during forging, and to assist in obtaining desired tolerances.

semifinishing o

o

A solid crystalline material whose electrical resistivity is intermediate between that of a metal conductor and an insulator, ranging from about 10-3 to 108 · cm, and is usually strongly temperature dependent.

semifinisher o

o

Plating in which prepared cathodes are mechanically conveyed through the plating baths, with intervening manual transfers.

semiconductor o

o

Arc welding with equipment that controls only the filler metal feed. The advance of the welding is manually controlled.

semiautomatic plating o

o

Any solid material that shows low friction without application of a lubricant.

semiautomatic arc welding o

o

See preferred term air-hardening steel .

The bend obtained by applying a force directly to the specimen in the portion that is to be bent. The specimen is either held at one end and forced around a pin or rounded edge or is supported near the ends and bent by a force applied on the side of the specimen opposite the supports and midway between them. In some instances, the bend is started in this manner and finished in the manner of a free bend.

semikilled steel o

Steel that is incompletely deoxidized and contains sufficient dissolved oxygen to react with the carbon to form carbon monoxide and thus offset solidification shrinkage.

o

semipermanent mold

o

semisolid metal forming

o o

o

A permanent mold in which sand cores or plaster are used. A two-step casting/forging process in which a billet is cast in a mold equipped with a mixer that continuously stirs the thixotropic melt, thereby breaking up the dendritic structure of the casting into a fine-grained spherical structure. After cooling, the billet is stored for subsequent use. Later, a slug from the billet is cut, heated to the semisolid state, and forged in a die. Normally the cast billet is forged when 30 to 40% is in the liquid state. See also rheocasting .

sensitization o

In austenitic stainless steels, the precipitation of chromium carbides, usually at grain boundaries, on exposure to temperatures of about 540 to 845 °C (about 1000 to 1550 °F), leaving the grain

boundaries depleted of chromium and therefore susceptible to preferential attack by a corroding medium. Welding is the most common cause of sensitization. Weld decay (sensitization) caused by carbide precipitation in the weld heat-affected zone leads to intergranular corrosion. o

sensitizing heat treatment o

o

Sendzimir mill o

o

(1) Separation of solids from suspension in a fluid of lower density, solely by gravitational effects. (2) A process for removing iron from liquid magnesium alloys by holding the melt at a low temperature after manganese has been added to it.

severity of quench o

o

Resistance welding in which two or more spot, seam, or projection welds are made simultaneously by a single welding transformer with three or more electrodes forming a series circuit.

settling o

o

A type of cluster mill with small-diameter work rolls and larger-diameter backup rolls, backed up by bearings on a shaft mounted eccentrically so that it can be rotated to increase the pressure between the bearing and the backup rolls. Used to roll precision and very thin sheet and strip.

series welding o

o

A heat treatment, whether accidental, intentional, or incidental (as during welding), that causes precipitation of constituents at grain boundaries, often causing the alloy to become susceptible to intergranular corrosion or intergranular stress-corrosion cracking. See also sensitization .

Ability of quenching medium to extract heat from a hot steel workpiece; expressed in terms of the Grossmann number (H).

shadowing o

Directional deposition of carbon or a metallic film on a plastic replica so as to highlight features to be analyzed by transmission electron microscopy. Most often used to provide maximum detail and resolution of the features of fracture surfaces.

o

shakeout

o

shaker-hearth furnace

o o o

See flake .

shaving o

o

Producing flat surfaces using single-point tools. The work is held in a vise or fixture or is clamped directly to the table. The ram supporting the tool is reciprocated in a linear motion past the work.

shatter crack o

o

A group of metallic materials that demonstrate the ability to return to some previously defined shape or size when subjected to the appropriate thermal procedure.

shaping o

o

A cutter having a straight or tapered shank to fit into a machine-tool spindle or adapter.

shape memory alloys o

o

(1) The portion of a die or tool by which it is held in position in a forging unit or press. (2) The handle for carrying a small ladle or crucible. (3) The main body of a lathe tool. If the tool is an inserted type, the shank is the portion that supports the insert.

shank-type cutter o

o

A continuous type furnace that uses a reciprocating shaker motion to move the parts along the hearth.

shank o

o

Removal of castings from a sand mold. See also knockout .

(1) As a finishing operation, the accurate removal of a thin layer of a work surface by straightline motion between a cutter and the surface. (2) Trimming parts such as stampings, forgings, and tubes to remove uneven sheared edges or to improve accuracy.

shear o

(1) The type of force that causes or tends to cause two contiguous parts of the same body to slide relative to each other in a direction parallel to their plane of contact. (2) A machine or tool for cutting metal and other material by the closing motion of two sharp, closely adjoining edges; for example, squaring shear and circular shear. (3) An inclination between two cutting edges, such as between two straight knife blades or between the punch cutting edge and the die cutting edge, so that a reduced area will be cut each time. This lessens the necessary force, but increases the

required length of the working stroke. This method is referred to as angular shear. (4) The act of cutting by shearing dies or blades, as in shearing lines. o

shear angle o

o

shear bands o

o

The angle that the shear plane, in metal cutting, makes with the work surface. (1) Bands of very high shear strain that are observed during rolling of sheet metal. During rolling, these form at approximately 35° to the rolling plane, parallel to the transverse direction. They are independent of grain orientation and at high strain rates traverse the entire thickness of the rolled sheet. (2) Highly localized deformation zones in metals that are observed at very high strain rates, such as those produced by high velocity (100 to 3600 m/s, or 330 to 11,800 ft/s) projectile impacts or explosive rupture.

shear fracture o

A mode of fracture in crystalline materials resulting from translation along slip planes that are preferentially oriented in the direction of the shearing stress.

o

shear ledges

o

shear lip

o o

o

The tangent of the angular change, caused by a force between two lines originally perpendicular to each other through a point in a body. Also called angular strain.

shear stress o

o

A confined zone along which shear takes place in metal cutting. It extends from the cutting edge to the work surface.

shear strain o

o

The ratio of shear stress to the corresponding shear strain for shear stresses below the proportional limit of the material. Values of shear modulus are usually determined by torsion testing. Also known as modulus of rigidity.

shear plane o

o

A narrow, slanting ridge along the edge of a fracture surface. The term sometimes also denotes a narrow, often crescent-shaped, fibrous region at the edge of a fracture that is otherwise of the cleavage type, even though this fibrous region is in the same plane as the rest of the fracture surface.

shear modulus (G) o

o

See radial marks .

(1) The stress component tangential to the plane on which the forces act. (2) A stress that exists when parallel planes in metal crystals slide across each other.

sheet o

A flat-rolled metal product of some maximum thickness and minimum width arbitrarily dependent on the type of metal. It has a width-to-thickness ratio greater than about 50. Generally, such flat products under 6.5 mm ( and over are called plates.

o

The plastic deformation of a piece of sheet metal by tensile loads into a three-dimensional shape, often without significant changes in sheet thickness or surface characteristics. Compare with bulk forming .

shelf roughness o

o

in.) thick

sheet forming o

o

in.) thick are called sheets, and those 6.5 mm (

Roughness on upward-facing surfaces where undissolved solids have settled on parts during a plating operation.

shell o

(1) A hollow structure or vessel. (2) An article formed by deep drawing. (3) The metal sleeve remaining when a billet is extruded with a dummy block of somewhat smaller diameter. (4) In shell molding, a hard layer of sand and thermosetting plastic or resin formed over a pattern and used as the mold wall. (5) A tubular casting used in making seamless drawn tube. (6) A pierced forging.

o

shell core

o

shell hardening

o o

A shell-molded sand core. A surface-hardening process in which a suitable steel workpiece, when heated through and quench hardened, develops a martensite layer or shell that closely follows the contour of the

piece and surrounds a core of essentially pearlitic transformation product. This result is accomplished by a proper balance among section size, steel hardenability, and severity of quench. o

shelling o

o

shell molding o

o

o

shift

o

shim

o o

A casting imperfection caused by mismatch of cope and drag or of cores and molds. A thin piece of material used between two surfaces to obtain a proper fit, adjustment, or alignment. See flat edge trimmer .

shock load o

o

(1) Protective gas used to prevent atmospheric contamination during welding. (2) A stream of inert gas directed at the substrate during thermal spraying so as to envelop the plasma flame and substrate; intended to provide a barrier to the atmosphere in order to minimize oxidation.

shimmy die o

o

An arc welding process that produces coalescence of metals by heating them with an arc between a covered metal electrode and the workpieces. Shielding is obtained from decomposition of the electrode covering. Pressure is not used, and filler metal is obtained from the electrode. Also commonly referred to as stick welding.

shielding gas o

o

A metal arc cutting process in which metals are severed by melting them with the heat of an arc between a covered metal electrode and the base metal.

shielded metal arc welding (SMAW) o

o

A foundry process in which a mold is formed from thermosetting resin-bonded sand mixtures brought in contact with preheated (150 to 260 °C, or 300 to 500 °F) metal patterns, resulting in a firm shell with a cavity corresponding to the outline of the pattern. Also called Croning process .

shielded metal arc cutting o

o

(1) A term used in railway engineering to describe an advanced phase of spalling. (2) A mechanism of deterioration of coated abrasive products in which entire abrasive grains are removed from the coating that holds the abrasive to the backing layer of the product.

The sudden application of an external force that results in a very rapid buildup of stress--for example, piston loading in internal combustion engines.

shoe o

(1) A metal block used in a variety of bending operations to form or support the part being processed. (2) An anvil cap or sow block.

o

Shore hardness test

o

short-circuiting transfer

o o

o

Same as Scleroscope hardness test . In consumable electrode arc welding, a type of metal transfer similar to globular transfer, but in which the drops are so large that the arc is short circuited momentarily during the transfer of each drop to the weld pool. Compare with globular transfer and spray transfer .

shortness o

A form of brittleness in metal. It is designated as cold shortness or hot shortness to indicate the temperature range in which the brittleness occurs.

o

short transverse

o

shot

o o o

Blasting with metal shot; usually used to remove deposits or mill scale more rapidly or more effectively than can be done by sandblasting.

shot peening o

o

(1) Small, spherical particles of metal. (2) The injection of molten metal into a die casting die. The metal is injected so quickly that it can be compared to the shooting of a gun.

shotblasting o

o

See transverse direction .

A method of cold working metals in which compressive stresses are induced in the exposed surface layers of parts by the impingement of a stream of shot, directed at the metal surface at high velocity under controlled conditions.

shotting

o o

shrinkage o

o

Diffusing silicon into solid metal, usually low-carbon steels, at an elevated temperature in order to improve corrosion or wear resistance.

silky fracture o

o

Embrittlement of iron-chromium alloys (most notably austenitic stainless steels) caused by precipitation at grain boundaries of the hard, brittle intermetallic phase during long periods of exposure to temperatures between approximately 560 and 980 °C (1050 and 1800 °F). Sigmaphase embrittlement results in severe loss in toughness and ductility and can make the embrittled material susceptible to intergranular corrosion. See also sensitization .

siliconizing o

o

A hard, brittle, nonmagnetic intermediate phase with a tetragonal crystal structure, containing 30 atoms per unit cell, space group, P4/mnm, occurring in many binary and ternary alloys of the transition elements. The composition of this phase in the various systems is not the same, and the phase usually exhibits a wide range in homogeneity. Alloying with a third transition element usually enlarges the field homogeneity and extends it deep into the ternary section.

sigma-phase embrittlement o

o

That portion of a powder sample that passes through a sieve of specified number and is retained by some finer mesh sieve of specified number. See also sieve analysis .

sigma phase o

o

The separation of powder into particle size ranges by the use of a series of graded sieves. Also called screen analysis.

sieve fraction o

o

A method of determining particle size distribution, usually expressed as the weight percentage retained upon each of a series of standard screens of decreasing mesh size.

sieve classification o

o

A standard wire mesh or screen used in graded sets to determine the mesh size or particle size distribution of particulate and granular solids. See also sieve analysis .

sieve analysis o

o

Milling with cutters having peripheral and side teeth. They are usually profile sharpened but may be form relieved.

sieve o

o

For a metalforming press, the distance from the top of the bed to the bottom of the slide with the stroke down and adjustment up. In general, it is the maximum die height that can be accommodated for normal operation, taking the bolster plate into consideration. See also bolster .

side milling o

o

A protective, refractory-lined metal-delivery system to prevent reoxidation of molten steel when it is poured from ladle to tundish to mold during continuous casting.

shut height o

o

A measuring ruler with graduations expanded to compensate for the change in the dimensions of the solidified casting as it cools in the mold.

shroud o

o

Cracks that form in metal as a result of the pulling apart of grains by contraction before complete solidification. See also hot tear .

shrinkage rule o

o

A void left in cast metal as a result of solidification shrinkage. Shrinkage cavities can appear as either isolated or interconnected irregularly shaped voids. See also casting shrinkage .

shrinkage cracks o

o

(1) The contraction of metal during cooling after hot forging. Die impressions are made oversize according to precise shrinkage scales to allow the forgings to shrink to design dimensions and tolerances. (2) See casting shrinkage .

shrinkage cavity o

o

The production of shot by pouring molten metal in finely divided streams. Solidified spherical particles are formed during descent in a tank of water.

A metal fracture in which the broken metal surface has a fine texture, usually dull in appearance. Characteristic of tough and strong metals. Contrast with crystalline fracture and granular fracture .

silver soldering

o o

single-action press o

o

Nonpreferred term used to denote brazing with a silver-base filler metal. See preferred terms furnace brazing , induction brazing , and torch brazing . A metalforming press that provides pressure from one side.

single impulse welding o

A resistance welding process variation in which spot, projection, or upset welds are made with a single impulse.

o

single-point tool

o

single-stand mill

o o

A cutting tool having one face and one continuous cutting edge. A rolling mill designed such that the product contacts only two rolls at a given moment. Contrast with tandem mill .

o

single welded joint

o

sinkhead

o

sinking

o o o o

In foundry practice, a gating arrangement designed to prevent the passage of slag and other undesirable materials into a casting. Removing or holding back dirt or slag from the surface of the molten metal before or during pouring.

skin o

o

The starting stock for making welded pipe or tubing; most often it is strip stock of suitable width, thickness, and edge configuration.

skimming o

o

(1) Secondary forming or squeezing operations needed to square up, set down, flatten, or otherwise correct surfaces to produce specified dimensions and tolerances. See also restriking . (2) Some burnishing, broaching, drawing, and shaving operations are also called sizing. (3) A finishing operation for correcting ovality in tubing. (4) Final pressing of a sintered powder metallurgy part to obtain a desired dimension.

skim gate o

o

Effect of the dimensions of a piece of metal on its mechanical and other properties and on manufacturing variables such as forging reduction and heat treatment. In general, the mechanical properties are lower for a larger size.

skelp o

o

The bonding of adjacent surfaces of particles in a mass of powder or a compact by heating. Sintering strengthens a powder mass and normally produces densification and, in powdered metals, recrystallization. See also liquid phase sintering and solid-state sintering .

sizing o

o

The quotient of the mass (weight) over the volume of the sintered body expressed in grams per cubic centimeter.

size effect o

o

(1) The operation of machining the impression of a desired forging into die blocks. (2) See tube sinking .

sintering o

o

Same as riser .

sintered density o

o

In arc and gas welding, any joint welded from one side only.

A thin outside metal layer, not formed by bonding as in cladding or electroplating, that differs in composition, structure, or other characteristics from the main mass of metal.

skin lamination o

In flat-rolled metals, a surface rupture resulting from the exposure of a subsurface lamination by rolling.

o

skin pass

o

skiving

o o

See temper rolling . (1) Removal of a material in thin layers or chips with a high degree of shear or slippage, or both, of the cutting tool. (2) A machining operation in which the cut is made with a form tool with its face so angled that the cutting edge progresses from one end of the work to the other as the tool feeds tangentially past the rotating workpiece.

o

skull o

o

slab o

o

(1) A layer of solidified metal or dross on the walls of a pouring vessel after the metal has been poured. (2) The unmelted residue from a liquated weld filler metal. A flat-shaped semifinished rolled metal ingot with a width not less than 250 mm (10 in.) and a cross-sectional area not less than 105 cm2 (16 in.2).

slabbing mill o

A primary mill that produces slabs.

o

slab milling

o

slack quenching

o o

o

(1) A material of extremely fine particle size encountered in ore treatment. (2) A mixture of metals and some insoluble compounds that forms on the anode in electrolysis.

slip o

o

The main reciprocating member of a metalforming press, guided in the press frame, to which the punch or upper die is fastened; sometimes called the ram . The inner slide of a double-action press is called the plunger or punch-holder slide; the outer slide is called the blankholder slide. The third slide of a triple-action press is called the lower slide, and the slide of a hydraulic press is often called the platen.

slime o

o

A type of fracture in metals, typical of plane-stress fractures, in which the plane of separation is inclined at an angle (usually about 45°) to the axis of applied stress.

slide o

o

(1) Slag or dross entrapped in a metal. (2) Nonmetallic solid material entrapped in weld metal or between weld metal and base metal.

slant fracture o

o

A nonmetallic product resulting from the mutual dissolution of flux and nonmetallic impurities in smelting, refining, and certain welding operations (see, for example, electroslag welding ). In steelmaking operations, the slag serves to protect the molten metal from the air and to extract certain impurities.

slag inclusion o

o

The incomplete hardening of steel due to quenching from the austenitizing temperature at a rate slower than the critical cooling rate for the particular steel, resulting in the formation of one or more transformation products in addition to martensite.

slag o

o

See preferred term peripheral milling .

Plastic deformation by the irreversible shear displacement (translation) of one part of a crystal relative to another in a definite crystallographic direction and usually on specific crystallographic plane. Sometimes called glide.

slip band o

A group of parallel slip lines so closely spaced as to appear as a single line when observed under an optical microscope. See also slip line .

o

slip direction

o

slip flask

o o

o

The crystallographic plane in which slip occurs in a crystal.

slitting o

o

Visible traces of slip planes on metal surfaces; the traces are (usually) observable only if the surface has been polished before deformation. The usual observation on metal crystals (under a light microscope) is of a cluster of slip lines known as a slip band .

slip plane o

o

A tapered flask that depends on a movable strip of metal to hold foundry sand in position. After closing the mold, the strip is refracted and the flask can be removed and reused. Molds thus made are usually supported by a mold jacket during pouring.

slip line o

o

The crystallographic direction in which the translation of slip takes place.

sliver

Cutting or shearing along single lines to cut strips from a metal sheet or to cut along lines of a given length or contour in a sheet or workpiece.

o o

slot furnace o

o

A foundry flask hinged on one corner so that it can be opened and removed from the mold for reuse before the metal is poured.

snap temper o

o

(1) The product formed by twisting and bending of hot metal rod prior to its next rolling process. (2) Any crooked surface imperfection in a plate, resembling a snake. (3) A flexible mandrel used in the inside of a shape to prevent flattening or collapse during a bending operation.

snap flask o

o

(1) Heavy stock removal of superfluous material from a workpiece by using a portable or swing grinder mounted with a coarse grain abrasive wheel. (2) Offhand grinding on castings and forgings to remove surplus metal such as gate and riser pads, fins, and parting lines.

snake o

o

A reaction product sometimes left on the surface of a metal after pickling, electroplating, or etching.

snagging o

o

See hand forge (smith forge) .

smut o

o

Thermal processing wherein chemical reactions take place to produce liquid metal from a beneficiated ore.

smith forging o

o

A hollow casting usually made of an alloy with a low but wide melting temperature range. After the desired thickness of metal has solidified in the mold, the remaining liquid is poured out. Considered an obsolete practice.

smelting o

o

The act of adding a separate piece or pieces of material in a joint before or during welding that results in a welded joint not complying with design, drawing, or specification requirements.

slush casting o

o

(1) A short piece of metal to be placed in a die for forging or extrusion. (2) A small piece of material produced by piercing a hole in sheet material. See also blank .

slugging o

o

An experimental technique for evaluating susceptibility to stress-corrosion cracking. It involves pulling the specimen to failure in uniaxial tension at a controlled slow strain rate while the specimen is in the test environment and examining the specimen for evidence of stress-corrosion cracking.

slug o

o

Cutting a narrow aperture or groove with a reciprocating tool in a vertical shaper or with a cutter, broach, or grinding wheel.

slow strain rate technique o

o

A common batch furnace for heat treating metals where stock is charged and removed through a slot or opening.

slotting o

o

An imperfection consisting of a very thin elongated piece of metal attached by only one end to the parent metal into whose surface it has been worked.

A precautionary interim stress-relieving treatment applied to high-hardenability steels immediately after quenching to prevent cracking because of delay in tempering them at the prescribed higher temperature.

S-N curve o

A plot of stress (S) against the number of cycles to failure (N). The stress can be the maximum stress (Smax) or the alternating stress amplitude (Sa). The stress values are usually nominal stress; i.e., there is no adjustment for stress concentration. The diagram indicates the S-N relationship for a specified value of the mean stress (Sm) or the stress ratio (A or R) and a specified probability of survival. For N a log scale is almost always used. For S a linear scale is used most often, but a log scale is sometimes used. Also known as S-N diagram.

o

soak cleaning

o

soaking

o o

Immersion cleaning without electrolysis. In heat treating of metals, prolonged holding at a selected temperature to effect homogenization of structure or composition. See also homogenizing .

o

soft magnetic material o

A ferromagnetic alloy that becomes magnetized readily upon application of a field and that returns to practically a nonmagnetic condition when the field is removed; an alloy with the properties of high magnetic permeability, low coercive force, and low magnetic hysteresis loss.

o

soft soldering

o

soft temper

o o

See preferred term soldering . Same as dead soft temper.

o

solder

o

solderability

o

solder embrittlement

o o o o

The relative ease and speed with which a surface is wetted by molten solder. Reduction in mechanical properties of a metal as a result of local penetration of solder along grain boundaries.

soldering o

o

A filler metal used in soldering that has a liquidus not exceeding 450 °C (840 °F).

A group of processes that join metals by heating them to a suitable temperature below the solidus of the base metals and applying a filler metal having a liquidus not exceeding 450 °C (840 °F). Molten filler metal is distributed between the closely fitted surfaces of the joint by capillary action. See also solder .

soldering flux o

See flux .

o

soldering iron

o

solid cutters

o o o

A soldering tool having an internally or externally heated metal bit usually made of copper. Cutters made of a single piece of material rather than a composite of two or more materials.

solidification o

The change in state from liquid to solid upon cooling through the melting temperature or melting range.

o

solidification range

o

solidification shrinkage

o o o

A sintering procedure for compacts or loose powder aggregates during which no component melts. Contrast with liquid phase sintering.

solid-state welding o

o

A single, solid, homogeneous crystalline phase containing two or more chemical species.

solid-state sintering o

o

The occurrence of embrittlement in a material below the melting point of the embrittling species. See also liquid metal embrittlement .

solid solution o

o

Any solid used as a powder or thin film on a surface to provide protection from damage during relative movement and to reduce friction and wear.

solid metal embrittlement o

o

A crack that forms, usually at elevated temperature, because of the internal (shrinkage) stresses that develop during solidification of a metal casting. Also termed hot crack.

solid lubricant o

o

The reduction in volume of metal from beginning to end of solidification. See also casting shrinkage .

solidification shrinkage crack o

o

The temperature between the liquidus and the solidus.

A group of welding processes that join metals at temperatures essentially below the melting points of the base materials, without the addition of a brazing filler metal. Pressure may or may not be applied to the joint. Examples include cold welding , diffusion welding , forge welding , hot pressure welding , and roll welding .

solidus o

(1) The highest temperature at which a metal or alloy is completely solid. (2) In a phase diagram, the locus of points representing the temperatures at which various compositions stop freezing upon cooling or begin to melt upon heating. See also liquidus .

o

solute o

o

The component of either a liquid or solid solution that is present to a lesser or minor extent; the component that is dissolved in the solvent.

solution heat treatment o

Heating an alloy to a suitable temperature, holding at that temperature long enough to cause one or more constituents to enter into solid solution, and then cooling rapidly enough to hold these constituents in solution.

o

solution potential

o

solvent

o o o

A gaseous environment containing hydrogen sulfide and carbon dioxide in hydrocarbon reservoirs. Prolonged exposure to sour gas can lead to hydrogen damage, sulfide-stress cracking, and/or stress-corrosion cracking in ferrous alloys.

sow block o

o

A fine mixture of ferrite and cementite produced either by regulating the rate of cooling of steel or by tempering steel after hardening. The first type is very fine pearlite that is difficult to resolve under the microscope; the second type is tempered martensite.

sour gas o

o

In a phase or equilibrium diagram, the locus of points representing the temperature at which solid phases with various compositions coexist with other solid phases, that is, the limits of solid solubility.

sorbite (obsolete) o

o

The component of either a liquid or solid solution that is present to a greater or major extent; the component that dissolves the solute.

solvus o

o

Electrode potential where half-cell reaction involves only the metal electrode and its ion.

A block of heat-treated steel placed between the anvil of the hammer and the forging die to prevent undue wear to the anvil. Sow blocks are occasionally used to hold insert dies. Also called anvil cap.

space lattice o

A regular, periodic array of points (lattice points) in space that represents the locations of atoms of the same kind in a perfect crystal. The concept may be extended, where appropriate, to crystalline compounds and other substances, in which case the lattice points often represent locations of groups of atoms of identical composition, arrangement, and orientation.

o

spade drill

o

spalling

o o

See preferred term flat drill . (1) Separation of particles from a surface in the form of flakes. The term spalling is commonly associated with rolling-element bearings and with gear teeth. Spalling is usually a result of subsurface fatigue and is more extensive than pitting. (2) The spontaneous chipping, fragmentation, or separation of a surface or surface coating. (3) A chipping or flaking of a surface due to any kind of improper heat treatment or material dissociation.

o

spangle

o

spark testing

o o

o

The characteristic crystalline form in which a hot dipped zinc coating solidifies on steel strip. A method used for the classification of ferrous alloys according to their chemical compositions, by visual examination of the spark pattern or stream that is thrown off when the alloys are held against a grinding wheel rotating at high speed.

spatter o

The metal particles expelled during arc or gas welding. They do not form part of the weld.

o

spatter loss

o

specific energy

o o o

In cutting or grinding, the energy expended or work done in removing a unit volume of material.

specimen o

o

The metal lost due to spatter.

A test object, often of standard dimensions and/or configuration, that is used for destructive or nondestructive testing. One or more specimens may be cut from each unit of a sample.

speed of travel

o o

speiss o

o

Metallic arsenides and antimonides that result from smelting metal ores such as those of cobalt or lead.

spheroidal graphite o

o

In welding, the speed with which a weld is made along its longitudinal axis, usually measured in meters per second or inches per minute.

Graphite of spheroidal shape with a polycrystalline radial structure. This structure can be obtained, for example, by adding cerium or magnesium to the melt. See also ductile iron and nodular graphite .

spheroidite o

An aggregate of iron or alloy carbides of essentially spherical shape dispersed throughout a matrix of ferrite.

o

spheroidized structure

o

spheroidizing

o o

A microstructure consisting of a matrix containing spheroidal particles of another constituent. Heating and cooling to produce a spheroidal or globular form of carbide in steel. Spheroidizing methods frequently used are: (1) Prolonged holding at a temperature just below Ae1. (2) Heating and cooling alternatively between temperatures that are just above and just below Ae1. (3) Heating to a temperature above Ae1 or Ae3 and then cooling very slowly in the furnace or holding at a temperature just below Ae1. (4) Cooling at a suitable rate from the minimum temperature at which all carbide is dissolved to prevent the reformation of a carbide network, and then reheating in accordance with method 1 or 2 above. (Applicable to hypereutectoid steel containing a carbide network.)

o

spiegeleisen (spiegel)

o

spindle

o o o

A form of metal characterized by a porous condition that is the result of the decomposition or reduction of a compound without fusion. The term is applied to forms of iron, titanium, zirconium, uranium, plutonium, and the platinum-group metals.

sponge iron o

o

A segmented punch or a set of punches in a powder metallurgy forming press that allow(s) a separate positioning for different powder fill heights and compact levels in dual-step and multistep parts. See also stepped compact .

sponge o

o

A die made of parts that can be separated for ready removal of the workpiece. Also known as segment die.

split punch o

o

Any of a series of longitudinal, straight projections on a shaft that fit into slots on a mating part to transfer rotation to or from the shaft.

split die o

o

A fine, homogeneous mixture of two phases that form by the growth of composition waves in a solid solution during suitable heat treatment. The phases of a spinodal structure differ in composition from each other and from the parent phase, but have the same crystal structure as the parent phase.

spline o

o

The forming of a seamless hollow metal part by forcing a rotating blank to conform to a shaped mandrel that rotates concentrically with the blank. In the typical application, a flat-rolled metal blank is forced against the mandrel by a blunt, rounded tool; however, other stock (notably, welded or seamless tubing) can be formed. A roller is sometimes used as the working end of the tool.

spinodal structure o

o

(1) Shaft of a machine tool on which a cutter or grinding wheel may be mounted. (2) Metal shaft to which a mounted wheel is cemented.

spinning o

o

A pig iron containing 15 to 30% Mn and 4.5 to 6.5% C.

A coherent, porous mass of substantially pure iron produced by solid-state reduction of iron oxide (mill scale or iron ore).

spot drilling

o o

spotfacing o

o

Making an initial indentation in a work surface, with a drill, to serve as a centering guide in a subsequent machining process. Using a rotary, hole-piloted end-facing tool to produce a flat surface normal to the axis of rotation of the tool on or slightly below the workpiece surface.

spot weld o

A weld made between or upon overlapping members in which coalescence may start and occur on the faying surfaces or may proceed from the surface of one member. The weld cross section is approximately circular.

o

spot welding

o

spray quenching

o o

o

(1) Before finishing to final dimensions, repeatedly heating a ferrous or nonferrous part to or slightly above its normal operating temperature and then cooling to room temperature to ensure dimensional stability in service. (2) Transforming retained austenite in quenched hardenable steels, usually by cold treatment. (3) Heating a solution-treated stabilized grade of austenitic stainless steel to 870 to 900 °C (1600 to 1650 °F) to precipitate all carbon as TiC, NbC, or TaC so that sensitization is avoided on subsequent exposure to elevated temperature.

stack cutting o

o

A hybrid liquid metal forging process in which liquid metal is forced into a permanent mold by a hydraulic press.

stabilizing treatment o

o

A machining tool, used for cutting sheet metal or plate, consisting essentially of a fixed cutting knife (usually mounted on the rear of the bed) and another cutting knife mounted on the front of a reciprocally moving crosshead, which is guided vertically in side housings. Corner angles are usually 90°.

squeeze casting o

o

Making square holes by means of a specially constructed drill made to rotate and also to oscillate so as to follow accurately the periphery of a square guide bushing or template.

squaring shear o

o

The bombardment of a solid surface with a flux of energetic particles (ions) that results in the ejection of atomic species. The ejected material may be used as a source for deposition. See also physical vapor deposition .

square drilling o

o

(1) The mold channel that connects the pouring basin with the runner or, in the absence of a pouring basin, directly into which molten metal is poured. Sometimes referred to as downsprue or downgate. (2) Sometimes used to mean all gates, risers, runners, and similar scrap that are removed from castings after shakeout.

sputtering o

o

A temper of nonferrous alloys and some ferrous alloys characterized by tensile strength and hardness about two-thirds of the way from full hard to extra spring temper.

sprue o

o

(1) The elastic recovery of metal after stressing. (2) The extent to which metal tends to return to its original shape or contour after undergoing a forming operation. This is compensated for by overbending or by a secondary operation of restriking. (3) In flash, upset, or pressure welding, the deflection in the welding machine caused by the upset pressure.

spring temper o

o

In consumable-electrode arc welding, a type of metal transfer in which the molten filler metal is propelled across the arc as fine droplets. Compare with globular transfer and short-circuiting transfer .

springback o

o

A quenching process using spray nozzles to spray water or other liquids on a part. The quench rate is controlled by the velocity and volume of liquid per unit area per unit of time of impingement.

spray transfer o

o

See arc spot weld and resistance spot welding .

Thermal cutting of stacked metal plates arranged so that all the plates are severed by a single cut.

stack molding

o

o

staggered-tooth cutters o

o

The general term used to denote all sheet metal pressworking. It includes blanking, shearing, hot or cold forming, drawing, bending, or coining.

stand o

o

Fastening two parts together permanently by recessing one part within the other and then causing plastic flow at the joint.

stamping o

o

Any of several steels containing at least 10.5% Cr as the principal alloying element; they usually exhibit passivity in aqueous environments.

staking o

o

Milling cutters with alternate flutes of oppositely directed helixes.

stainless steel o

o

A foundry practice that makes use of both faces of a mold section, one face acting as the drag and the other as the cope. Sections, when assembled to other similar sections, form several tiers of mold cavities, all castings being poured together through a common sprue.

A piece of rolling mill equipment containing one set of work rolls. In the usual sense, any pass of a cold- or hot-rolling mill. See also rolling mills .

standard electrode potential o

The reversible potential for an electrode process when all products and reactions are at unit activity on a scale in which the potential for the standard hydrogen half-cell is zero.

o

standard gold

o

standard reference material

o o o

A type of drop hammer in which the ram is raised for each stroke by a double-action steam cylinder and the energy delivered to the workpiece is supplied by the velocity and weight of the ram and attached upper die driven downward by steam pressure. The energy delivered during each stroke can be varied.

steam treatment o

o

A condition of brittleness that causes transcrystalline fracture in the coarse grain structure that results from prolonged annealing of thin sheets of low-carbon steel previously rolled at a temperature below about 705 °C (1300 °F). The fracture usually occurs at about 45° to the direction of rolling.

steam hammer o

o

A hard structural constituent of cast iron that consists of a binary eutectic of ferrite, containing some phosphorus in solution, and iron phosphide (Fe3P). The eutectic consists of 10.2% P and 89.8% Fe. The melting temperature is 1050 °C (1920 °F).

Stead's brittleness o

o

A term sometimes used to identify a form of hydrogen embrittlement in which a metal appears to fracture spontaneously under a steady stress less than the yield stress. There almost always is a delay between the application of stress (or exposure of the stressed metal to hydrogen) and the onset of cracking. More properly referred to as hydrogen-induced delayed cracking .

steadite o

o

A complete description of the stresses within a homogeneously stressed volume or at a point. The description requires, in general, the knowledge of the independent components of stress.

static fatigue o

o

A complete description of the deformation within a homogeneously deformed volume or at a point. The description requires, in general, the knowledge of the independent components of strain.

state of stress o

o

A thin sheet of metal used as the cathode in electrolyte refining.

state of strain o

o

A reference material, the composition or properties of which are certified by a recognized standardizing agency or group.

starting sheet o

o

A gold alloy containing 10% Cu; at one time used for legal coinage in the United States.

The treatment of a sintered ferrous part in steam at temperatures between 510 and 595 °C (950 to 1100 °F) in order to produce a layer of black iron oxide (magnetite, or ferrous-ferric oxide, FeO·Fe2O3) on the exposed surface for the purpose of increasing hardness and wear resistance.

Steckel mill

o

o

A cold reducing mill having two working rolls and two backup rolls, none of which is driven. The strip is drawn through the mill by a power reel in one direction as far as the strip will allow and then reversed by a second power reel, and so on until the desired thickness is attained.

steel o

An iron-base alloy, malleable in some temperature ranges as initially cast, containing manganese, usually carbon, and often other alloying elements. In carbon steel and low-alloy steel, the maximum carbon is about 2.0%; in high-alloy steel, about 2.5%. The dividing line between lowalloy and high-alloy steels is generally regarded as being at about 5% metallic alloying elements. Steel is said to be differentiated from two general classes of "irons": the cast irons, on the highcarbon side and the relatively pure irons such as ingot iron, carbonyl iron, and electrolytic iron, on the low-carbon side. In some steels containing extremely low carbon, the manganese content is the principal differentiating factor, steel usually containing at least 0.25% and ingot iron considerably less.

o

step aging o

o

Aging of metals at two or more temperatures, by steps, without cooling to room temperature after each step. See also aging , and compare with interrupted aging and progressive aging .

stepped compact o

A powder metallurgy compact with one (dual step) or more (multistep) abrupt cross-sectional changes, usually obtained by pressing with split punches, each section of which uses a different pressure and a different rate of compaction. See also split punch .

o

stepped extrusion

o

step fracture

o

stereoscopic micrographs

o o o

o

See extrusion . Cleavage fractures that initiate on many parallel cleavage planes. A pair of micrographs (or fractographs) of the same area, but taken from different angles so that the two micrographs when properly mounted and viewed reveal the structures of the objects in their three-dimensional relationships.

sterling silver o

A silver alloy containing at least 92.5% Ag, the remainder being unspecified but usually copper. Sterling silver is used for flat and hollow tableware and for various items of jewelry.

o

stick electrode

o

stick welding

o

sticker breaks

o o o o

A general term used to refer to a supply of metal in any form or shape and also to an individual piece of metal that is formed, forged, or machined to make parts. A material used on the surfaces adjacent to the joint to limit the spread of soldering or brazing filler metal. See also resist .

stopper rod o

o

(1) The rate of stress with respect to strain; the greater the stress required to produce a given strain, the stiffer the material is said to be. (2) The ability of a material or shape to resist elastic deflection. For identical shapes, the stiffness is proportional to the modulus of elasticity. For a given material, the stiffness increases with increasing moment of inertia, which is computed from cross-sectional dimensions.

stopoff o

o

Arc-shaped coil breaks, usually located near the center of sheet or strip.

stock o

o

See preferred term shielded metal arc welding .

stiffness o

o

A shop term for covered electrode .

A device in a bottom-pour ladle for controlling the flow of metal through the nozzle into a mold. The stopper rod consists of a steel rod, protective refractory sleeves, and a graphite stopper head.

stopping off o

(1) Applying a resist. (2) Depositing a metal (copper, for example) in localized areas to prevent carburization, decarburization, or nitriding in those areas. (3) Filling in a portion of a mold cavity to keep out molten metal.

o

stradle milling

o

straightening

o o

Face milling a workpiece on both sides at once using two cutters spaced as required. (1) Any bending, twisting, or stretching operation to correct any deviation from straightness in bars, tubes, or similar long parts or shapes. This deviation can be expressed as either camber (deviation from a straight line) or as total indicator reading (TIR) per unit of length. (2) A finishing operation for correcting misalignment in a forging or between various sections of a forging. See also roll straightening .

o

straight polarity

o

strain

o o

o

An increase in hardness and strength of metals caused by plastic deformation at temperatures below the recrystallization range. Also known as work hardening.

strain-hardening coefficient o

o

The potential energy stored in a body by virtue of elastic deformation, equal to the work that must be done to produce this deformation.

strain hardening o

o

(1) Aging following plastic deformation. (2) The changes in ductility, hardness, yield point, and tensile strength that occur when a metal or alloy that has been cold worked is stored for some time. In steel, strain aging is characterized by a loss of ductility and a corresponding increase in hardness, yield point, and tensile strength.

strain energy o

o

A loss in ductility accompanied by an increase in hardness and strength that occurs when lowcarbon steel (especially rimmed or capped steel) is aged following plastic deformation. The degree of embrittlement is a function of aging time and temperature, occurring in a matter of minutes at about 200 °C (400 °F), but requiring a few hours to a year at room temperature.

strain aging o

o

The unit of change in the size or shape of a body due to force. Also known as nominal strain. The term is also used in a broader sense to denote a dimensionless number that characterizes the change in dimensions of an object during a deformation or flow process. See also engineering strain and true strain .

strain-age embrittlement o

o

See preferred term direct current electrode negative (DCEN) .

See strain-hardening exponent .

strain-hardening exponent o

The value of n in the relationship:

=K o

o

The time rate of straining for the usual tensile test. Strain as measured directly on the specimen gage length is used for determining strain rate. Because strain is dimensionless, the units of strain rate are reciprocal time.

strain-rate sensitivity (m-value) o

o

where is the true stress, is the true strain, and K, which is called the strength coefficient, is equal to the true stress at a true strain of 1.0. The strain-hardening exponent, also called "nvalue," is equal to the slope of the true stress/true strain curve up to maximum load, when plotted on log-log coordinates. The n-value relates to the ability of as sheet metal to be stretched in metalworking operations. The higher the n-value, the better the formability (stretchability).

strain rate o

o

n

The increase in stress ( ) needed to cause a certain increase in plastic strain rate ( ) at a given level of plastic strain ( ) and a given temperature (T):

strain rods

o o

strain state o

o

Preferential attack of areas under stress in a corrosive environment, where such an environment alone would not have caused corrosion.

stress-corrosion cracking (SCC) o

o

A multiplying factor for applied stress that allows for the presence of a structural discontinuity such as a notch or hole; Kt equals the ratio of the greatest stress in the region of the discontinuity to the nominal stress for the entire section. Also called theoretical stress concentration factor.

stress corrosion o

o

On a macromechanical level, the magnification of the level of an applied stress in the region of a notch, void, hole, or inclusion.

stress concentration factor (Kt) o

o

One-half the algebraic difference between the maximum and minimum stresses in one cycle of a repetitively varying stress.

stress concentration o

o

The intensity of the internally distributed forces or components of forces that resist a change in the volume or shape of a material that is or has been subjected to external forces. Stress is expressed in force per unit area. Stress can be normal (tension or compression) or shear. See also compressive stress , engineering stress , mean stress , nominal stress , normal stress , residual stress , shear stress , tensile stress , and true stress .

stress amplitude o

o

Corrosion resulting from direct current flow through paths other than the intended circuit. For example, by an extraneous current in the earth.

stress o

o

(1) Current flowing through paths other than the intended circuit. (2) Current flowing in electrodeposition by way o an unplanned and undesired bipolar electrode that may be the tank itself or a poorly connected electrode.

stray-current corrosion o

o

A composite filler metal electrode consisting of stranded wires that may mechanically enclose materials to improve properties, stabilize the arc, or provide shielding.

stray current o

o

A generic term describing continuous casting of one or more elongated shapes such as billets, blooms, or slabs; if two or more shapes are cast simultaneously, they are often of identical cross section.

stranded electrode o

o

See state of strain .

strand casting o

o

(1) Rods sometimes used on gapframe metalforming presses to lessen the frame deflection. (2) Rods used to measure elastic strain and thus stresses, in frames of metalforming presses.

A cracking process that requires the simultaneous action of a corrodent and sustained tensile stress. This excludes corrosion-reduced sections that fail by fast fracture. It also excludes intercrystalline or transcrystalline corrosion, which can disintegrate an alloy without applied or residual stress. Stress-corrosion cracking may occur in combination with hydrogen embrittlement.

stress-intensity factor o

A scaling factor, usually denoted by the symbol K, used in linear-elastic fracture mechanics to describe the intensification of applied stress at the tip of a crack of known size and shape. At the onset of rapid crack propagation in any structure containing a crack, the factor is called the critical stress-intensity factor, or the fracture toughness. Various subscripts are used to denote different loading conditions or fracture toughnesses:

Kc

Plane-stress fracture toughness. The value of stress intensity at which crack propagation becomes rapid in sections thinner than those in which plane-strain conditions prevail.

KI

Stress-intensity factor for a loading condition that displaces the crack faces in a direction normal to the crack plane (also known as the opening mode of deformation).

KIc

Plane-strain fracture toughness. The minimum value of Kc for any given material and condition

KId Dynamic fracture toughness. The fracture toughness determined under dynamic loading conditions; it is used as an approximation of KIc for very tough materials. KIscc Threshold stress-intensity factor for stress-corrosion cracking. The critical plane-strain stress intensity at the onset of stress-corrosion cracking under specified conditions. KQ

Provisional value for plane-strain fracture toughness.

Kth Threshold stress intensity for stress-corrosion cracking. The critical stress intensity at the onset of stresscorrosion cracking under specified conditions. K

o

stress-intensity factor range ( K) o

o

Design features (such as sharp corners) or mechanical defects (such as notches) that act to intensify the stress at these locations.

stress range o

o

In fatigue, the variation in the stress-intensity factor in a cycle, that is, Kmax - Kmin. See also fatigue crack growth rate .

stress raisers o

o

The range of the stress-intensity factor during a fatigue cycle. See also fatigue crack growth rate .

See range of stress .

stress ratio (A or R) o

The algebraic ratio of two specified stress values in a stress cycle. Two commonly used stress ratios are: (1) the ratio of the alternating stress amplitude to the mean stress, A = Sa/Sm; and (2) the ratio of the minimum stress to the maximum stress, R = Smin/Smax.

o

stress relaxation

o

stress-relaxation curve

o o o

Cracking in the heat-affected zone or weld metal that occurs during the exposure of weldments to elevated temperatures during postweld heat treatment, in order to reduce residual stresses and improve toughness, or high-temperature service.

stress-relief heat treatment o

o

A plot of the remaining or relaxed stress as a function of time. The relaxed stress equals the initial stress minus the remaining stress. Also known as stress-time curve.

stress-relief cracking o

o

The time-dependent decrease in stress in a solid under constant constraint at constant temperature.

Uniform heating of a structure or a portion thereof to a sufficient temperature to relieve the major portion of the residual stresses, followed by uniform cooling.

stress relieving o

Heating to a suitable temperature, holding long enough to reduce residual stresses, and then cooling slowly enough to minimize the development of new residual stresses.

o

stress-rupture strength

o

stress-rupture test

o o

See creep-rupture strength . See creep-rupture test .

o

stress state

o

stress-strain curve

o o

o

The leveling of a piece of sheet metal (that is, removing warp and distortion) by gripping it at both ends and subjecting it to a stress higher than its yield strength.

stretcher straightening o

o

A graph in which corresponding values of stress and strain from a tension, compression, or torsion test are plotted against each other. Values of stress are usually plotted vertically (ordinates or y-axis) and values of strain horizontally (abscissas or x-axis). Also known as deformation curve and stress-strain diagram.

stretcher leveling o

o

See state of stress .

A process for straightening rod, tubing, and shapes by the application of tension at the ends of the stock. The products are elongated a definite amount to remove warpage.

stretcher strains

o

o

stretch former o

o

(1) Removing a coating from a metal surface. (2) Removing a foundry pattern from the mold or the core box from the core.

structural shape o

o

A punch that serves as the top or bottom of a metalforming die cavity and later moves farther into the die to eject the part or compact. See also ejector rod and knockout(3) .

stripping o

o

A plate designed to remove, or strip, sheet metal stock from the punching members during the withdrawal cycle. Strippers are also used to guide small precision punches in close-tolerance dies to guide scrap away from dies and to assist in the cutting action. Strippers are made in two types: fixed and movable.

stripper punch o

o

(1) A flat-rolled metal product of some maximum thickness and width arbitrarily dependent on the type of metal; narrower than sheet. (2) A roll-compacted metal powder product. See also roll compacting . (3) Removal of a powder metallurgy compact from the die. An alternative to ejecting or knockout.

stripper o

o

A continuous weld bead made without appreciable transverse oscillation (weaving motion). Contrast with weave bead .

strip o

o

In wrought materials, an elongated configuration of microconstituents or foreign material aligned in the direction of working. The term is commonly associated with elongated oxide or sulfide inclusions in steel.

stringer bead o

o

Those areas on the faces of a set of metalforming dies that are designed to meet when the upper die and lower die are brought together. The striking surface helps protect impressions from impact shock and aids in maintaining longer die life.

stringer o

o

Electrodepositing, under special conditions, a very thin film of metal that will facilitate further plating with another metal or with the same metal under different conditions.

striking surface o

o

(1) A thin electrodeposited film of metal to be overlaid with other plated coatings. (2) A plating solution of high covering power and low efficiency designed to electroplate a thin, adherent film of metal.

striking o

o

A fatigue fracture feature, often observed in electron micrographs, that indicates the position of the crack front after each succeeding cycle of stress. The distance between striations indicates the advance of the crack front across that crystal during one stress cycle, and a line normal to the striations indicates the direction of local crack propagation. See also beach marks .

strike o

o

The extension of the surface of a metal sheet in all directions. In stretching, the flange of the flat blank is securely clamped. Deformation is restricted to the area initially within the die. The stretching limit is the onset of metal failure.

striation o

o

The shaping of a metal sheet or part, usually of uniform cross section, by first applying suitable tension or stretch and then wrapping it around a die of the desired shape.

stretching o

o

(1) A machine used to perform stretch forming operations. (2) A device adaptable to a conventional press for accomplishing stretch forming.

stretch forming o

o

Elongated markings that appear on the surface of some sheet materials when deformed just past the yield point. These markings lie approximately parallel to the direction of maximum shear stress and are the result of localized yielding. See also Lüders lines .

A piece of metal of any of several designs accepted as standard by the structural branch of the iron and steel industries.

structure

o

o

stud arc welding o

o

A portion of a crystal or grain, with an orientation slightly different from the orientation of neighboring portions of the same crystal.

submerged arc welding (SAW) o

o

An annealing treatment in which a steel is heated to a temperature below the A1 temperature, then cooled slowly to room temperature. See also transformation temperature .

subgrain o

o

A network or low-angle boundaries, usually with misorientations less that 1° within the main grains of a microstructure.

subcritical annealing o

o

An expendable pattern of foamed plastic, especially expanded polystyrene, used in manufacturing castings by the lost foam process. See also lost foam casting .

subboundary structure (subgrain structure) o

o

A general term for joining a metal stud or similar part to a workpiece. Welding may be accommodated by arc, resistance, friction, or other processes with or without external gas shielding.

styrofoam pattern o

o

An arc welding process that produces coalescence of metals by heating them with an arc between a metal stud, or similar part, and the other workpiece. When the surfaces to be joined are properly heated, they are brought together under pressure. Partial shielding may be obtained by the use of a ceramic ferrule surrounding the stud. Shielding gas or flux may or may not be used.

stud welding o

o

As applied to a crystal, the shape and size of the unit cell and the location of all atoms within the unit cell. As applied to microstructure, the size, shape, and arrangement of phases. See also unit cell .

An arc welding process that produces coalescence of metals by heating them with an arc or arcs between a bare metal electrode or electrodes and the workpieces. The arc and molten metal are shielded by a blanket of granular, fusible material on the workpieces. Pressure is not used, and filler metal is obtained from the electrode and sometimes from a supplemental source (welding rod, flux, or metal granules).

submerged-electrode furnace o

A furnace used for liquid carburizing of parts by heating molten salt baths with the use of electrodes submerged in the ceramic lining. See also immersed-electrode furnace .

o

subsieve fraction

o

subsieve size

o o o

See preferred term subsieve fraction .

substitutional element o

o

Particles that will pass through a 44 m (325 mesh) screen.

An alloying element with an atomic size and other features similar to the solvent that can replace or substitute for the solvent atoms in the lattice and form a significant region of solid solution in the phase diagram.

substitutional solid solution o

A solid solution in which the solvent and solute atoms are located randomly at the atom sites in the crystal structure of the solution. See also interstitial solid solution .

o

substrate

o

substructure

o o o

Formation of isolated particles of corrosion products beneath a metal surface. This results from the preferential reactions of certain alloy constituents to inward diffusion of oxygen, nitrogen, or sulfur.

sulfidation o

o

Same as subboundary structure .

subsurface corrosion o

o

The material, workpiece, or substance on which the coating is deposited.

The reaction of a metal or alloy with a sulfur-containing species to produce a sulfur compound that forms on or beneath the surface on the metal or alloy.

sulfide stress cracking (SSC) o

Brittle fracture by cracking under the combined action of tensile stress and corrosion in the presence of water and hydrogen sulfide. See also environmental cracking .

o

sulfur dome o

o

sulfur print o

o

Heat-resistant alloys based on nickel, iron-nickel, or cobalt that exhibit high strength and resistance to surface degradation at elevated temperatures.

superconductivity o

o

Synthetically produced diamond and cubic boron nitride (CBN) used in a wide variety of cutting and grinding applications.

superalloys o

o

A macrographic method of examining for distribution of sulfide inclusions by placing a sheet of wet acidified photographic paper in contact with the polished sheet surface to be examined.

superabrasives o

o

An inverted container, holding a high concentration of sulfur dioxide gas, used in die casting to cover a pot of molten magnesium to prevent burning.

A property of many metals, alloys, compounds, oxides, and organic materials at temperatures near absolute zero by virtue of which their electrical resistivity vanishes and they become strongly diamagnetic.

supercooling o

Cooling of a substance below the temperature at which a change of state would ordinarily take place without such a change of state occurring, for example, the cooling of a liquid below its freezing point without freezing taking place; this results in a metastable state.

o

superficial hardness test

o

superfines

o o o

The portion of a metal powder that is composed of particles smaller than a specified size, usually 10 m.

superfinishing o

o

See Rockwell superficial hardness test .

A low-velocity abrading process very similar to honing; however, unlike honing, superfinishing processes focus primarily on the improvement of surface finish and much less on correction of geometric errors (dimensional accuracy). Also known as microhoning.

superheating o

(1) Heating of a substance above the temperature at which a change of state would ordinarily take place without a change of state occurring, for example, the heating of a liquid above its boiling point without boiling taking place; this results in a metastable state. (2) Any increment of temperature above the melting point of a metal; sometimes construed to be any increment of temperature above normal casting temperatures introduced for the purpose of refining, alloying, or improving fluidity.

o

superlattice

o

superplastic forming (SPF)

o o

o

Rods or pins of precise length used to support the overhang of irregularly shaped punches in metal forming presses.

support plate o

o

A metastable solution in which the dissolved material exceeds the amount the solvent can hold in normal equilibrium at the temperature and other conditions that prevail.

support pins o

o

The ability of certain metals (most notably aluminum- and titanium-base alloys) to develop extremely high tensile elongations at elevated temperatures and under controlled rates of deformation.

supersaturated o

o

A strain rate sensitive sheet metal forming process that uses characteristics of materials exhibiting high tensile elongation. During superplastic forming, gas pressure is imposed on a superplastic sheet, causing the material to form into the die configuration. See also superplasticity .

superplasticity o

o

See ordered structure .

A plate that supports a draw ring or draw plate in a sheet metal forming press. It also serves as a spacer. See also draw plate and draw ring .

surface alterations o

Irregularities or changes on the surface of a material due to machining or grinding operations. The types of surface alterations associated with metal removal practices include mechanical (for

example, plastic deformation, hardness variations, cracks, etc.), metallurgical (for example, phase transformations, twinning, recrystallization, and untempered or overtempered martensite), chemical (for example, intergranular attack, embrittlement, and pitting), thermal (heat-affected zone, recast, or redeposited metal, and resolidified material), and electrical surface alterations (conductivity change or resistive heating). o

surface checking

o

surface damage

o o

o

Same as checks . In tribology, damage to a solid surface resulting from mechanical contact with another substance, surface, or surfaces moving relatively to it and involving the displacement or removal of material. In certain contexts, wear is a form of surface damage in which material is progressively removed. In another context, surface damage involves a deterioration of function of a solid surface even though there is no material loss from that surface. Surface damage may therefore precede wear.

surface finish o

(1) The geometric irregularities in the surface of a solid material. Measurement of surface finish shall not include inherent structural irregularities unless these are the characteristics being measured. (2) Condition of a surface as a result of a final treatment. See also roughness .

o

surface grinding

o

surface hardening

o o

o

Tapering bar, rod, wire, or tubing by forging, hammering, or squeezing; reducing a section by progressively tapering lengthwise until the entire section attains the smaller dimension of the taper. See also rotary swaging .

swarf o

o

(1) The operation of reducing or changing the cross-sectional area of stock by the fast impact of revolving dies. (2) The tapering of bar, rod, wire, or tubing by forging, hammering, or squeezing; reducing a section by progressively tapering lengthwise until the entire section attains the smaller dimension of the taper.

swaging o

o

A type of weld composed of one or more stringer or weave beads deposited on an unbroken surface to obtain desired properties or dimensions.

swage o

o

The deposition of filler metal (material) on a base metal (substrate) to obtain desired properties or dimensions, as opposed to making a joint. See also buildup , buttering , cladding , coating , and hardfacing .

surfacing weld o

o

The roughness, waviness, lay, and flaws associated with a surface. See also lay .

surfacing o

o

Fine irregularities in the surface texture of a material, usually including those resulting from the inherent action of the production process. Surface roughness is usually reported as the arithmetic roughness average, Ra, and is given in micrometers or microinches.

surface texture o

o

The alteration of surface composition or structure by the use of energy or particle beams. Two types of surface modification methods commonly employed are ion implantation and laser surface processing.

surface roughness o

o

A generic term covering several processes applicable to a suitable ferrous alloy that produces, by quench hardening only, a surface layer that is harder or more wear resistant than the core. There is no significant alteration of the chemical composition of the surface layer. The processes commonly used are carbonitriding, carburizing, induction hardening, flame hardening, nitriding, and nitrocarburizing. Use of the applicable specific process name is preferred.

surface modification o

o

Producing a plane surface by grinding.

Intimate mixture of grinding chips and fine particles of abrasive and bond resulting from a grinding operation.

sweat soldering o

A soldering process variation in which two or more parts that have been precoated with solder are reheated and assembled into a joint without the use of additional solder.

o

sweep o

o

Swift cup test o

o

A grinding machine suspended by a chain at the center point so that it may be turned and swung in any direction for grinding of billets, large castings, or other heavy work. Principal use is removing surface imperfections and roughness.

synthetic cold-rolled sheet o

o o

Equipment for continuously hot reducing ingots, blooms, or billets to square flats, rounds, or rectangles by the crank-driven oscillating action of paired dies.

swing frame grinder o

o

A simulative test for determining formability of sheet metal in which circular blanks of various diameters are clamped in a die ring and deep drawn into a cup by a flat-bottomed cylindrical punch. The ratio of the largest blank diameter that can be drawn successfully to the cup diameter is known as the limiting drawing ratio (LDR) or deformation limit.

swing forging machine o

o

A type of foundry pattern that is a template cut to the profile of the desired mold shape that, when revolved around a stake or spindle, produces that shape in the mold.

A hot-rolled pickled sheet given a sufficient final temper pass to impart a surface approximating that of cold-rolled steel.

T

tacking o

Making tack welds.

o

tack weld

o

tailings

o

tandem mill

o o o

o

o

o

A rolling mill consisting of two or more stands arranged so that the metal being processed travels in a straight line from stand to stand. In continuous rolling, the various stands are synchronized so that the strip can be rolled in all stands simultaneously. Contrast with single-stand mill . See also rolling mills . Arc welding in which two or more electrodes are in a plane parallel to the line of travel.

tangent bending o

The forming of one or more identical bends having parallel axes by wiping sheet metal around one or more radius dies in a single operation. The sheet, which may have side flanges, is clamped against the radius die and then made to conform to the radius die by pressure from a rocker-plate die that moves along the periphery of the radius die. See also wiper forming (wiping) .

o

A cylindrical or conical thread-cutting tool with one or more cutting elements having threads of a desired form on the periphery. By a combination of rotary and axial motions, the leading end cuts an internal thread, the tool deriving its principal support from the thread being produced.

tap

tap density o

o

The discarded portion of a crushed ore, separated during concentration.

tandem welding o

o

A weld made to hold parts of a weldment in proper alignment until the final welds are made.

The apparent density of a powder, obtained when the volume receptacle is tapped or vibrated during loading under specified conditions.

tapping o

(1) Producing internal threads with a cylindrical cutting tool having two or more peripheral cutting elements shaped to cut threads of the desired size and form. By a combination of rotary and axial motion, the leading end of the tap cuts the thread while the tap is supported mainly by the thread it produces. See also tap . (2) Opening the outlet of a melting furnace to remove molten metal. (3) Removing molten metal from a furnace.

o

tarnish

o

teapot ladle

o o o

Surface discoloration of a metal caused by formation of a thin film of corrosion product. A ladle in which, by means of an external spout, metal is removed from the bottom rather than the top of the ladle.

teeming o

Pouring molten metal from a ladle into ingot molds. The term applies particularly to the specific operation of pouring either iron or steel into ingot molds.

o

temper o

(1) In heat treatment, reheating hardened steel or hardened cast iron to some temperature below the eutectoid temperature for the purpose of decreasing hardness and increasing toughness. The process also is sometimes applied to normalized steel. (2) In tool steels, temper is sometimes used, but inadvisedly, to denote the carbon content. (3) In nonferrous alloys and in some ferrous alloys (steels that cannot be hardened by heat treatment), the hardness and strength produced by mechanical or thermal treatment, or both, and characterized by a certain structure, mechanical properties, or reduction in area during cold working. (4) To moisten green sand for casting molds with water.

o

temper brittleness

o

temper carbon

o o

o

Light cold rolling of sheet steel to improve flatness, to minimize the formation of stretcher strains, and to obtain a specified hardness or temper.

tensile strength o

o

In heat treatment, reheating hardened steel to some temperature below the eutectoid temperature to decrease hardness and/or increase toughness.

temper rolling o

o

Embrittlement of low-alloy steels caused by holding within or cooling slowly through a temperature range (generally 300 to 600 °C, or 570 to 1110 °F) just below the transformation range. Embrittlement is the result of the segregation at grain boundaries of impurities such as arsenic, antimony, phosphorus, and tin; it is usually manifested as an upward shift in ductile-tobrittle transition temperature. Temper embrittlement can be reversed by retempering above the critical temperature range, then cooling rapidly. Compare with tempered martensite embrittlement .

tempering o

o

Embrittlement of high-strength alloy steels caused by tempering in the temperature range of 205 to 370 °C (400 to 700 °F); also called 350 °C or 500 °F embrittlement. Tempered martensite embrittlement is thought to result from the combined effects of cementite precipitation on prioraustenite grain boundaries or interlath boundaries and the segregation of impurities at prioraustenite grain boundaries. It differs from temper embrittlement in the strength of the material and the temperature exposure range. In temper embrittlement, the steel is usually tempered at a relatively high temperature, producing lower strength and hardness, and embrittlement occurs upon slow cooling after tempering and during service at temperatures within the embrittlement range. In tempered martensite embrittlement, the steel is tempered within the embrittlement range, and service exposure is usually at room temperature.

temper embrittlement o

o

The decomposition products that result from heating martensite below the ferrite-austenite transformation temperature.

tempered martensite embrittlement o

o

A surface or subsurface layer in a steel specimen that has been tempered by heating during some stage of the metallographic preparation sequence (usually grinding). When observed in a section after etching, the layer appears darker than the base material.

tempered martensite o

o

A thin, tightly adhering oxide skin (only a few molecules thick) that forms when steel is tempered at a low temperature, or for a short time, in air or a mildly oxidizing atmosphere. The color, which ranges from straw to blue depending on the thickness of the oxide skin, varies with both tempering time and temperature.

tempered layer o

o

Clusters of finely divided graphite, such as that found in malleable iron, that are formed as a result of decomposition of cementite, for example, by heating white cast iron above the ferriteaustenite transformation temperature and holding at these temperatures for a considerable period of time. Also known as annealing carbon.

temper color o

o

See temper embrittlement .

In tensile testing, the ratio of maximum load to original cross-sectional area. Also called ultimate strength . Compare with yield strength .

tensile stress

o o

A stress that causes two parts of an elastic body, on either side of a typical stress plane, to pull apart. Contrast with compressive stress .

tensile testing o

See tension testing .

o

tension

o

tension testing

o o

o

A method of determining the behavior of materials subjected to uniaxial loading, which tends to stretch the material. A longitudinal specimen of known length and diameter is gripped at both ends and stretched at a slow, controlled rate until rupture occurs. Also known as tensile testing.

terminal phase o

o

The force or load that produces elongation.

A solid solution having a restricted range of compositions, one end of the range being a pure component of an alloy system.

terminal solid solution o

In a multicomponent system, any solid phase of limited composition range that includes the composition of one of the components of the system. See also solid solution .

o

ternary alloy

o

ternary system

o

terne

o o o

o

A group of cutting processes that melts the metal (material) to be cut. See also air carbon arc cutting , arc cutting , carbon arc cutting , electron beam cutting , laser beam cutting , metal powder cutting , oxyfuel gas cutting , oxygen arc cutting , oxygen cutting , and plasma arc cutting . (1) The decomposition of a compound into its elemental species at elevated temperatures. (2) A process whereby fine solid particles can be produced from a gaseous compound. See also carbonyl powder .

thermal electromotive force o

o

A method for determining transformations in a metal by noting the temperatures at which thermal arrests occur. These arrests are manifested by changes in slope of the plotted or mechanically traced heating and cooling curves. When such data are secured under nearly equilibrium conditions of heating and cooling, the method is commonly used for determining certain critical temperatures required for the construction of phase diagrams.

thermal decomposition o

o

Exposure of a material or component to a given thermal condition or a programmed series of conditions for prescribed periods of time.

thermal cutting o

o

In a polycrystalline aggregate, the state of distribution of crystal orientations. In the usual sense, it is synonymous with preferred orientation , in which the distribution is not random. Not to be confused with surface texture . See also fiber .

thermal analysis o

o

See creep .

thermal aging o

o

An alloy of lead containing 3 to 15% Sn, used as a hot dip coating for steel sheet or plate. The term long terne is used to describe terne-coated sheet, whereas short terne is used for terne-coated plate. Terne coatings, which are smooth and dull in appearance (terne means dull or tarnished in French), give the steel better corrosion resistance and enhance its ability to be formed, soldered, or painted.

texture o

o

The complete series of compositions produced by mixing three components in all proportions.

tertiary creep o

o

An alloy that contains three principal elements.

The electromotive force generated in a circuit containing two dissimilar metals when one junction is at a temperature different from that of the other. See also thermocouple .

thermal embrittlement o

Intergranular fracture of maraging steels with decreased toughness resulting from improper processing after hot working. Thermal embrittlement occurs upon heating above 1095 °C (2000 °F) and then slow cooling through the temperature range of 980 to 815 °C (1800 to 1500 °F), and

has been attributed to precipitation of titanium carbides and titanium carbonitrides at austenite grain boundaries during cooling through the critical temperature range. o

thermal fatigue o

o

thermal inspection o

o

Fracture resulting from the presence of temperature gradients that vary with time in such a manner as to produce cyclic stresses in a structure. A nondestructive test method in which heat-sensing devices are used to measure temperature variations in components, structures, systems, or physical processes. Thermal methods can be useful in the detection of subsurface flaws or voids, provided the depth of the flaw is not large compared to its diameter. Thermal inspection becomes less effective in the detection of subsurface flaws as the thickness of an object increases, because the possible depth of the defects increases.

thermally induced embrittlement o

See embrittlement .

o

thermal-mechanical treatment

o

thermal shock

o o o

See thermomechanical working . The development of a steep temperature gradient and accompanying high stresses within a material or structure.

thermal spraying o

A group of coating or welding processes in which finely divided metallic or nonmetallic materials are deposited in a molten or semimolten condition to form a coating. The surfacing material may be in the form of powder, rod, or wire. See also electric arc spraying , flame spraying , plasma spraying , and powder flame spraying .

o

thermal stresses

o

thermal wear

o o

o

A device for measuring temperatures, consisting of lengths of two dissimilar metals or alloys that are electrically joined at one end and connected to a voltage-measuring instrument at the other end. When one junction is hotter than the other, a thermal electromotive force is produced that is roughly proportional to the difference in temperature between the hot and cold junctions.

thermomechanical working o

o

Heat treatment for steels carried out in a medium suitably chosen to produce a change in the chemical composition of the object by exchange with the medium.

thermocouple o

o

Removal of workpiece material--usually only burrs and fins--by exposure to hot fuel gases that are formed by igniting an explosive, combustible mixture of natural gas and oxygen. Also known as the thermal energy method.

thermochemical treatment o

o

A welding process that produces coalescence of metals by heating them with superheated liquid metal from a chemical reaction between a metal oxide and aluminum, with or without the application of pressure. Filler metal is obtained from the liquid metal.

thermochemical machining o

o

Strongly exothermic self-propagating reactions such as that where finely divided aluminum reacts with a metal oxide. A mixture of aluminum and iron oxide produces sufficient heat to weld steel, the filler metal being produced in the reaction. See also thermit welding .

thermit welding o

o

Removal of material due to softening, melting, or evaporation during sliding or rolling. Thermal shock and high-temperature erosion may be included in the general description of thermal wear. Wear by diffusion of separate atoms from one body to the other, at high temperatures, is also sometimes denoted as thermal wear.

thermit reactions o

o

Stresses in a material resulting from nonuniform temperature distribution.

A general term covering a variety of metalforming processes combining controlled thermal and deformation treatments to obtain synergistic effects, such as improvement in strength without loss of toughness. Same as thermal-mechanical treatment.

thief o

A racking device or nonfunctional pattern area used in the electroplating process to provide a more uniform current density on plated parts. Thieves absorb the unevenly distributed current on

irregularly shaped parts, thereby ensuring that the parts will receive an electroplated coating of uniform thickness. See also robber . o

thin-wall casting o

A term used to define a casting that has the minimum wall thickness to satisfy its service function.

o

threading

o

thread rolling

o o o

The bending of a piece of metal or a structural member in which the object is placed across two supports and force is applied between and in opposition to them. See also V-bend die .

threshold stress o

o

A temper of nonferrous alloys and some ferrous alloys characterized by tensile strength and hardness about midway between those of half hard and full hard tempers.

three-point bending o

o

The production of threads by rolling the piece between two grooved die plates, one of which is in motion, or between rotating grooved circular rolls. Also known as roll threading.

three-quarters hard o

o

Producing external threads on a cylindrical surface.

Threshold stress for stress-corrosion cracking. The critical gross section stress at the onset of stress-corrosion cracking under specified conditions.

throwing power o

(1) The relationship between the current density at a point on a surface and its distance from the counterelectrode. The greater the ratio of the surface resistivity shown by the electrode reaction to the volume resistivity of the electrolyte, the better is the throwing power of the process. (2) The ability of a plating solution to produce a uniform metal distribution on an irregularly shaped cathode. Compare with covering power .

o

tiger stripes

o

TIG welding

o

tilt boundary

o o o o

Continuous bright lines on sheet or strip in the rolling direction. Tungsten inert-gas welding; see preferred term gas tungsten arc welding . A subgrain boundary consisting of an array of edge dislocations.

tilt mold o

A casting mold, usually a book (permanent) mold, that rotates from a horizontal to a vertical position during pouring, which reduces agitation and thus the formation and entrapment of oxides.

o

tilt mold ingot

o

time quenching

o o o

An ingot made in a tilt mold . A quench in which the cooling rate of the part being quenched must be changed abruptly at some time during the cooling cycle.

time-temperature curve o

A curve produced by plotting time against temperature.

o

time-temperature-transformation (TTT) diagram

o

tinning

o o o

A polymorphic modification of tin that causes it to crumble into a powder known as gray tin. It is generally accepted that the maximum rate of transformation occurs at about -40 °C (-40 °F), but transformation can occur at as high as about 13 °C (55 °F).

tint etching o

o

Coating metal with a very thin layer of molten solder or brazing filler metal.

tin pest o

o

See isothermal transformation (IT) diagram .

Immersing metallographic specimens in specially formulated chemical etchants in order to produce a stable film on the specimen surface. When viewed under an optical microscope, these surface films produce colors that correspond to the various phases in the alloy. Also known as color etching.

tin tossing o

Oxidizing impurities in molten tin by pouring it from one vessel to another in air, forming a dross that is mechanically separable.

o

toggle press

o

tolerance

o o o

The specified permissible deviation from a specified nominal dimension, or the permissible variation in size or other quality characteristic of a part.

tolerance limits o

o

A mechanical press in which the slide is actuated by one or more toggle links or mechanisms.

The extreme values (upper and lower) that define the range of permissible variation in size or other quality characteristic of a part.

tonghold o

The portion of a forging billet, usually on one end, that is gripped by the operator's tongs. It is removed from the part at the end of the forging operation. Common to drop hammer and presstype forging.

o

tooling

o

tool steel

o o

o

A process for separating copper and nickel, in which their molten sulfides are separated into two liquid layers by the addition of sodium sulfide. The lower layer holds most of the nickel.

torch o

o

The chamfered cutting edge of a face milling blade, to which a flat is sometimes added to produce a shaving effect and to improve finish.

top-and-bottom process o

o

(1) A projection on a multipoint tool (such as on a saw, milling cutter, or file) designed to produce cutting. (2) A projection on the periphery of a wheel or segment thereof--as on a gear, spline, or sprocket, for example--designed to engage another mechanism and thereby transmit force or motion, or both. A similar projection on a flat member such as a rack.

tooth point o

o

Any of a class of carbon and alloy steels commonly used to make tools. Tool steels are characterized by high hardness and resistance to abrasion, often accompanied by high toughness and resistance to softening at elevated temperature. These attributes are generally attained with high carbon and alloy contents.

tooth o

o

A generic term applying to die assemblies and related items used for forming and forging metals.

See preferred terms cutting torch (arc) , cutting torch (oxyfuel gas) , welding torch (arc) , and welding torch (oxyfuel gas) .

torch brazing o

A brazing process in which the heat required is furnished by a fuel gas flame.

o

torch soldering

o

torsion

o o

o

A soldering process in which the heat required is furnished by a fuel gas flame. (1) A twisting deformation of a solid or tubular body about an axis in which lines that were initially parallel to the axis become helices. (2) A twisting action resulting in shear stresses and strains.

torsional moment o

In a body being twisted, the algebraic sum of the couples or the moments of the external forces about the axis of twist, or both.

o

total carbon

o

total elongation

o o o

The sum of the free carbon and combined carbon (including carbon in solution) in a ferrous alloy. The total amount of permanent extension of a test piece broken in a tensile test usually expressed as a percentage over a fixed gage length. See also elongation, percent .

toughness o

Ability of a material to absorb energy and deform plastically before fracturing. Toughness is proportional to the area under the stress-strain curve from the origin to the breaking point. In metals, toughness is usually measured by the energy absorbed in a notch impact test. See also impact test .

o

tough pitch copper

o

tracer milling

o

Copper containing from 0.02 to 0.04% O, obtained by refining copper in a reverberatory furnace.

o o

tramp alloys o

o

Duplication of a three-dimensional form by means of a cutter controlled by a tracer that is directed by a master form. Residual alloying elements that are introduced into steel when unidentified alloy steel is present in the scrap charge to a steelmaking furnace.

tramp element o

Contaminant in the components of a furnace charge, or in the molten metal or castings, whose presence is thought to be either unimportant or undesirable to the quality of the casting. Also called trace element.

o

transcrystalline

o

transcrystalline cracking

o o o

A phenomenon, occurring chiefly in certain highly alloyed steels that have been heat treated to produce metastable austenite or metastable austenite plus martensite, whereby, on subsequent deformation, part of the austenite undergoes strain-induced transformation to martensite. Steels capable of transforming in this manner, commonly referred to as TRIP steels, are highly plastic after heat treatment, but exhibit a very high rate of strain hardening and thus have high tensile and yield strengths after plastic deformation at temperatures between about 20 and 500 °C (70 and 930 °F). Cooling to 195 °C (320 °F) may or may not be required to complete the transformation to martensite. Tempering usually is done following transformation.

transformation ranges o

o

Heat treatment of steels comprising austenitization followed by cooling under conditions such that the austenite transforms more or less completely into martensite and possibly into bainite.

transformation-induced plasticity o

o

Cracking or fracturing that occurs through or across a crystal. Also termed intracrystalline cracking.

transformation hardening o

o

See transgranular .

Those ranges of temperature within which austenite forms during heating and transforms during cooling. The two ranges are distinct, sometimes overlapping but never coinciding. The limiting temperatures of the ranges depend on the composition of the alloy and on the rate of change of temperature, particularly during cooling. See also transformation temperature .

transformation temperature o

The temperature at which a change in phase occurs. This term is sometimes used to denote the limiting temperature of a transformation range. The following symbols are used for irons and steels:

Accm

In hypereutectoid steel

Ac1

The temperature at which austenite begins to form during heating.

Ac3

The temperature at which transformation of ferrite to austenite is completed during heating.

Ac4

The temperature at which austenite transforms to

ferrite during heating.

Aecm, Ae1, Ae3, The temperatures of phase changes at equilibrium Ae4 Arcm

In hypereutectoid steel

Ar1

The temperature at which transformation of austenite to ferrite or to ferrite plus cementite is completed during cooling.

Ar3

The temperature at which austenite begins to transform to ferrite during cooling.

Ar4

The temperature at which

Ar'

The temperature at which transformation of austenite to pearlite starts during cooling.

Mf

The temperature at which transformation of austenite to martensite is completed during cooling.

Ms(or Ar'')

The temperature at which transformation of austenite to martensite starts during cooling.

ferrite transforms to austenite during cooling.

o o

transgranular o

o

A metal in which the available electron energy levels are occupied in such a way that the d-band contains less than its maximum number of ten electrons per atom, for example, iron, cobalt, nickel, and tungsten. The distinctive properties of the transition metals result from the incompletely filled d-levels.

transition phase o

o

An unstable crystallographic configuration that forms as an intermediate step in a solid-state reaction such as precipitation from solid solution or eutectoid decomposition.

transition metal o

o

Fracture through or across the crystals or grains of a material. Also called transcrystalline fracture or intracrystalline fracture. Contrast with intergranular fracture .

transition lattice o

o

Cracking or fracturing that occurs through or across a crystal or grain. Also called transcrystalline cracking. Contrast with intergranular cracking .

transgranular fracture o

o

Through or across crystals or grains. Also called intracrystalline or transcrystalline.

transgranular cracking o

o

NOTE: All these changes, except formation of martensite, occur at lower temperatures during cooling than during heating, and depend on the rate of change of temperature.

A nonequilibrium state that appears in a chemical system in the course of transformation between two equilibrium states.

transition point o

At a stated pressure, the temperature (or at a stated temperature, the pressure) at which two solid phases exist in equilibrium--that is, an allotropic transformation temperature (or pressure).

o

transition structure

o

transition temperature

o o

o

Literally, "across," usually signifying a direction or plane perpendicular to the direction of working. In rolled plate or sheet, the direction across the width is often called long transverse; the direction through the thickness, short transverse.

transverse rolling machine o

o

(1) An arbitrarily defined temperature that lies within the temperature range in which metal fracture characteristics (as usually determined by tests of notched specimens) change rapidly, such as the ductile-to-brittle transition temperature (DBTT). The DBTT can be assessed in several ways, the most common being the temperature for 50% ductile and 50% brittle fracture (50% fracture appearance transition temperature, or FATT), or the lowest temperature at which the fracture is 100% ductile (100% fibrous criterion). (2) Sometimes used to denote an arbitrarily defined temperature within a range in which the ductility changes rapidly with temperature.

transverse direction o

o

In precipitation from solid solution, a metastable precipitate that is coherent with the matrix.

Equipment for producing complex preforms or finished forgings from round billets inserted transversely between two or three rolls that rotate in the same direction and drive the billet. The rolls, carrying replaceable die segments with appropriate impressions, make several revolutions for each rotation of the workpiece.

transverse rupture strength (TRS) o

The stress, calculated from the bending stress formula, required to break a powder metallurgy specimen of a given dimension. The specimen is supported near its ends with a load applied midway between the fixed centerline of the supports. From the value of the break load, the TRS can be calculated using:

o

where F is the load at fracture, L is the span between supports, and W and H are the width and height of the test bar, respectively.

o

trees

o

trepanning

o

Visible projections of electrodeposited metal formed at sites of high current density.

o

o

triaxiality o

o

In a triaxial stress state, the ratio of the smallest to the largest principal stress, all stresses being tensile.

triaxial stress o

o

A machining process for producing a circular hole or groove in solid stock, or for producing a disk, cylinder, or tube from solid stock, by the action of a tool containing one or more cutters (usually single-point) revolving around a center.

A state of stress in which none of the three principal stresses is zero. See also principal stress (normal) .

tribology o

(1) The science and technology of interacting surfaces in relative motion and of the practices related thereto. (2) The science concerned with the design, friction, lubrication, and wear of contacting surfaces that move relative to each other (as in bearings, cams, or gears, for example).

o

trimmer blade

o

trimmer die

o o o

The upper portion of the trimmer that contacts the forging and pushes it through the trimmer blades; the lower end of the trimmer punch is generally shaped to fit the surface of the forging against which it pushes.

trimmers o

o

The punch press die used for trimming flash from a forging.

trimmer punch o

o

The portion of the trimmers through which a forging is pushed to shear off the flash.

The combination of trimmer punch, trimmer blades, and perhaps trimming shoe used to remove the flash from the forging.

trimming o

(1) In forging, removing any parting-line flash or excess material from the part with a trimmer in a trim press; can be done hot or cold. (2) In drawing, shearing the irregular edge of the drawn part. (3) In casting, the removal of gates, risers, and fins.

o

trimming press

o

trimming shoe

o o o

The holder used to support trimmers. Sometimes called trimming chair.

triple-action press o

o

A power press suitable for trimming flash from forgings.

A mechanical or hydraulic press having three slides with three motions properly synchronized for triple-action drawing, redrawing, and forming. Usually, two slides--the blankholder slide and the plunger--are located above and a lower slide is located within the bed of the press. See also hydraulic press , mechanical press , and slide .

triple point o

(1) A point on a phase diagram where three phases of a substance coexist in equilibrium. (2) The intersection of the boundaries of three adjoining grains, as observed in a metallographic section.

o

TRIP steel

o

troostite (obsolete)

o o

A commercial steel product exhibiting transformation-induced plasticity . A previously unresolvable, rapidly etching, fine aggregate of carbide and ferrite produced either by tempering martensite at low temperature or by quenching a steel at a rate slower than the critical cooling rate. Preferred terminology for the first product is tempered martensite; for the latter, fine pearlite.

o

Troy ounce

o

true current density

o o o

See preferred term local current density .

true strain o

o

A unit of weight for precious metals that is equal to 31.1034768 g (1.0971699 oz avoirdupois).

(1) The ratio of the change in dimension, resulting from a given load increment, to the magnitude of the dimension immediately prior to applying the load increment. (2) In a body subjected to axial force, the natural logarithm of the ratio of the gage length at the moment of observation to the original gage length. Also known as natural strain.

true stress

o o

truing o

o

The formation of localized corrosion products scattered over the surface in the form of knoblike mounds called tubercles. The formation of tubercles is usually associated with biological corrosion.

tube reducing o

o

The removal of the outside layer of abrasive grains on a grinding wheel for the purpose of restoring its face.

tuberculation o

o

The value obtained by dividing the load applied to a member at a given instant by the crosssectional area over which it acts.

Reducing both the diameter and wall thickness of tubing with a mandrel and a pair of rolls. See also spinning .

tube sinking o

Drawing tubing through a die or passing it through rolls without the use of an interior tool (such as a mandrel or plug) to control inside diameter; sinking generally produces a tube of increased wall thickness and length.

o

tube stock

o

tumbling

o o

o

Four undriven working rolls, arranged in a square or rectangular pattern, through which metal strip, wire, or tubing is drawn to form square or rectangular sections.

turning o

o

tuyere

o

twin

o o

o

Rotating workpieces, usually castings or forgings, in a barrel partly filled with metal slugs or abrasives, to remove sand, scale, or fins. It may be done dry, or with an aqueous solution added to the contents of the barrel. See also barrel finishing .

Turk's-head rolls o

o

A semifinished tube suitable for subsequent reduction and finishing.

Removing material by forcing a single-point cutting tool against the surface of a rotating workpiece. The tool may or may not be moved toward or along the axis of rotation while it cuts away material. An opening in a cupola, blast furnace, or converter for the introduction of air or inert gas. Two portions of a crystal with a definite orientation relationship; one may be regarded as the parent, the other as the twin. The orientation of the twin is a mirror image of the orientation of the parent across a twinning plane or an orientation that can be derived by rotating the twin portion about a twinning axis. See also annealing twin and mechanical twin .

twin bands o

Bands across a crystal grain, observed on a polished and etched section, where crystallographic orientations have a mirror-image relationship to the orientation of the matrix grain across a composition plane that is usually parallel to the sides of the band.

o

twist boundary

o

two-high mill

o o o

U-bend die A die, commonly used in press-brake forming, that is machined horizontally with a square or rectangular cross-sectional opening that provides two edges over which metal is drawn into a channel shape.

Ugine-Sejournet process o

o

Any of a series of alloys containing lead (58.5 to 95%), antimony (2.5 to 25%), and tin (2.5 to 20%) used to make printing type. Small amounts of copper (1.5 to 2.0%) are added to increase hardness in some applications.

U o

o

A type of rolling mill in which only two rolls, the working rolls, are contained in a single housing. Compare with four-high mill and cluster mill.

type metal o

o o

A subgrain boundary consisting of an array of screw dislocations.

A direct extrusion process for metals that uses molten glass to insulate the hot billet and to act as a lubricant.

ultimate elongation

o o

The elongation at rupture.

ultimate strength o

The maximum stress (tensile, compressive, or shear) a material can sustain without fracture; determined by dividing maximum load by the original cross-sectional area of the specimen. Also known as nominal strength or maximum strength.

o

ultimate tensile strength

o

ultrahard tool materials

o o

The ultimate or final (highest) stress sustained by a specimen in a tension test. Very hard, wear-resistant materials--specifically, polycrystalline diamond and polycrystalline cubic boron nitride--that are fabricated into solid or layered cutting tool blanks for machining applications.

o

ultrahigh-strength steels

o

ultraprecision finishing

o o

o

Structural steels with minimum yield strengths of 1380 MPa (200 ksi). Machining processes used to alter surface characteristics such as finish, waviness, roundness, etc., with substantial removal of the work material. Examples include lapping and polishing of optical lenses, computer chips, or magnetic heads, and honing of cylinder liners.

ultrasonic beam o

A beam of acoustical radiation with a frequency higher than the frequency range for audible sound--i.e., above about 20 kHz.

o

ultrasonic cleaning

o

ultrasonic frequency

o o o

See ultrasonic inspection .

ultrasonic welding o

o

A soldering process variation in which high-frequency vibratory energy is transmitted through molten solder to remove undesirable surface films and thereby promote wetting of the base metal. This operation is usually accomplished without a flux.

ultrasonic testing o

o

Material removal by means of the ultrasonic vibration of a rotating diamond core drill or milling tool. The process does not involve an abrasive slurry; instead, the diamond tool contacts and cuts the workpiece. Compare with ultrasonic impact grinding .

ultrasonic soldering o

o

A nondestructive method in which beams of high-frequency sound waves are introduced into materials for the detection of surface and subsurface flaws in the material. The sound waves travel through the material with some attendant loss of energy (attenuation) and are reflected at interfaces. The reflected beam is displayed and then analyzed to define the presence and location of flaws or discontinuities. Most ultrasonic inspection is done at frequencies between 0.1 and 25 MHz--well above the range of human hearing, which is about 20 Hz to 20 kHz.

ultrasonic machining o

o

A form of abrasive grinding in which a nonrotating tool vibrating at ultrasonic frequency causes a grit-loaded slurry to impinge on the surface of a workpiece, and thereby remove material. Compare with ultrasonic machining .

ultrasonic inspection o

o

A frequency, associated with elastic waves, that is greater than the highest audible frequency, generally regarded as being higher than 20 kHz.

ultrasonic impact grinding o

o

Immersion cleaning aided by ultrasonic waves that cause microagitation.

A solid-state welding process in which materials are welded by locally applying high-frequency vibratory energy to a joint held together under pressure.

underbead crack o

A crack in the heat-affected zone of a weld generally not extending to the surface of the base metal.

o

undercooling

o

underdraft

o o o

Same as supercooling . A condition wherein a metal curves downward on leaving a set of rolls because of higher speed in the upper roll.

underfill

o

o

underfilm corrosion o

o

Applying a cyclic stress lower than the endurance limit. This may improve fatigue life if the member is later cyclically stressed at levels above the endurance limit.

uniaxial stress o

o

Corrosion that occurs under organic films in the form of randomly distributed threadlike filaments or spots. In many cases this is identical to filiform corrosion .

understressing o

o

(1) In weldments, a depression on the face of the weld or root surface extending below the surface of the adjacent base metal. (2) A portion of a forging that has insufficient metal to give it the true shape of the impression.

A state of stress in which two of the three principal stresses are zero. See also principal stress (normal) .

uniform corrosion o

(1) A type of corrosion attack (deterioration) uniformly distributed over a metal surface. (2) Corrosion that proceeds at approximately the same rate over a metal surface. Also called general corrosion.

o

uniform elongation

o

uniform strain

o o o

A combination of four hydraulic presses arranged in one plane equipped with billet manipulators and automatic controls, used for radial or draw forging.

universal mill o

o

The net amount of power required during machining or grinding to remove a unit volume of material in unit time.

universal forging mill o

o

A parallelepiped element of crystal structure, containing a certain number of atoms, the repetition of which through space will build up the complete crystal.

unit power o

o

The strain occurring prior to the beginning of localization of strain (necking); the strain to maximum load in the tension test.

unit cell o

o

The elongation at maximum load and immediately preceding the onset of necking in a tensile test.

A rolling mill in which rolls with a vertical axis roll the edges of the metal stock between some of the passes through the horizontal rolls.

upset o

(1) The localized increase in cross-sectional area of a workpiece or weldment resulting from the application of pressure during mechanical fabrication or welding. (2) That portion of a welding cycle during which the cross-sectional area is increased by the application of pressure. (3) Bulk deformation resulting from the application of pressure in welding. The upset may be measured as a percent increase in interfacial area, a reduction in length, or a percent reduction in thickness (for lap joints).

o

upset forging

o

upsetting

o o o

A resistance welding process in which the weld is produced, simultaneously over the entire area of abutting surfaces or progressively along a joint, by applying mechanical force (pressure) to the joint, then causing electrical current to flow across the joint to heat the abutting surfaces. Pressure is maintained throughout the heating period.

V

vacancy o

o

The working of metal so that the cross-sectional area of a portion or all of the stock is increased. See also heading .

upset welding o

o o

A forging obtained by upset of a suitable length of bar, billet, or bloom.

A structural imperfection in which an individual atom site is temporarily unoccupied.

vacuum arc remelting (VAR) o

A consumable-electrode remelting process in which heat is generated by an electric arc between the electrode and the ingot. The process is performed inside a vacuum chamber. Exposure of the droplets of molten metal to the reduced pressure reduces the amount of dissolved gas in the metal. See also consumable-electrode remelting .

o

vacuum carburizing o

o

A high-temperature gas carburizing process using furnace pressures between 13 and 67 kPa (0.1 to 0.5 torr) during the carburizing portion of the cycle. Steels undergoing this treatment are austenitized in a rough vacuum, carburized in a partial pressure of hydrocarbon gas, diffused in a rough vacuum, and then quenched in either oil or gas.

vacuum casting o

A casting process in which metal is melted and poured under very low atmospheric pressure; a form of permanent mold casting in which the mold is inserted into liquid metal, vacuum is applied, and metal is drawn up into the cavity.

o

vacuum degassing

o

vacuum deposition

o

vacuum furnace

o o o o

A process for remelting and refining metals in which the metal is melted inside a vacuum chamber by induction heating. The metal can be melted in a crucible and then poured into a mold. Melting in a vacuum to prevent contamination from air and to remove gases already dissolved in the metal; the solidification can also be carried out in a vacuum or at low pressure.

vacuum nitrocarburizing o

o

A method of processing materials (especially metal and ceramic powders) at elevated temperatures, consolidation pressures, and low atmospheric pressures.

vacuum melting o

o

A furnace using low atmospheric pressures instead of a protective gas atmosphere like most heattreating furnaces.

vacuum induction melting (VIM) o

o

Deposition of a metal film onto a substrate in a vacuum by metal evaporation techniques.

vacuum hot pressing o

o

The use of vacuum techniques to remove dissolved gases from molten alloys.

A subatmospheric nitrocarburizing process using a basic atmosphere of 50% ammonia/50% methane, containing controlled oxygen additions of up to 2%.

vacuum refining o

Melting in a vacuum to remove gaseous contaminants from the metal.

o

vacuum sintering

o

vapor degreasing

o o

o

Deposition of a metal or compound on a heated surface by reduction or decomposition of a volatile compound at a temperature below the melting points of the deposit and the base material. The reduction is usually accomplished by a gaseous reducing agent such as hydrogen. The decomposition process may involve thermal dissociation or reaction with the base material. See also vacuum deposition .

V-bend die o

o

See chemical vapor deposition , physical vapor deposition , and sputtering .

vapor plating o

o

Degreasing of work in the vapor over a boiling liquid solvent, the vapor being considerably heavier than air. At least one constituent of the soil must be soluble in the solvent. Modifications of this cleaning process include vapor-spray-vapor, warm liquid-vapor, boiling liquid-warm liquid-vapor, and ultrasonic degreasing.

vapor deposition o

o

Sintering of ceramics or metals at subatmospheric pressure.

A die commonly used in press-brake forming, usually machined with a triangular cross-sectional opening to provide two edges as fulcrums for accomplishing three-point bending.

vent o

A small opening in a foundry mold for the escape of gases.

o

vermicular graphite iron

o

vibratory finishing

o o o

Same as compacted graphite iron . A process for deburring and surface finishing in which the product and an abrasive mixture are placed in a container and vibrated.

Vickers hardness number (HV)

o

o

A number related to the applied load and the surface area of the permanent impression made by a square-based pyramidal diamond indenter having included face angles of 136°, computed from:

o

where P is applied load (kgf), d is mean diagonal of the impression (mm), and of the indenter (136°).

Vickers hardness test o

o

walking-beam furnace

Deformation of metals at elevated temperatures below the recrystallization temperature. The flow stress and rate of strain hardening are reduced with increasing temperature; therefore, lower forces are required than in cold working. See also cold working and hot working .

warpage o

o

A distinct pattern of intersecting sets of parallel lines, sometimes producing a set of V-shaped lines, sometimes observed when viewing brittle fracture surfaces at high magnification in an electron microscope. Wallner lines are attributed to interaction between a shock wave and a brittle crack front propagating at high velocity. Sometimes Wallner lines are misinterpreted as fatigue striations.

warm working o

o

A continuous-type heat treating or sintering furnace consisting of two sets of rails, one stationary and the other movable, that lift and advance parts inside the hearth. With this system, the moving rails lift the work from the stationary rails, move it forward, and then lower it back onto the stationary rails. The moving rails then return to the starting position and repeat the process to advance the parts again.

Wallner lines o

o

A molding (casting) process in which the sand is held in place in the mold by vacuum. The mold halves are covered with a thin sheet of plastic to retain the vacuum.

W o

o

(1) A shrinkage cavity produced in castings or weldments during solidification. (2) A term generally applied to paints to describe holidays, holes, and skips in a film.

V process o

o o

Same as primary metal .

void o

o

A microindentation hardness test employing a 136° diamond pyramid indenter (Vickers) and variable loads, enabling the use of one hardness scale for all ranges of hardness--from very soft lead to tungsten carbide. Also known as diamond pyramid hardness test. See also microindentation and microindentation hardness number .

virgin metal o

o

(1) Deformation other than contraction that develops in a casting between solidification and room temperature. (2) The distortion that occurs during annealing, stress relieving, and hightemperature service.

wash o

(1) A coating applied to the face of a mold prior to casting. (2) An imperfection at a cast surface similar to a cut (3) .

o

wash metal

o

waterjet/abrasive waterjet machining

o o

o

is the face angle

Molten metal used to wash out a furnace, ladle, or other container. A hydrodynamic machining process that uses a high-velocity stream of water as a cutting tool. This process is limited to the cutting of nonmetallic materials when the jet stream consists solely of water. However, when fine abrasive particles are injected into the water stream, the process can be used to cut harder and denser materials. Abrasive waterjet machining has expanded the range of fluid jet machining to include the cutting of metals, glass, ceramics, and composite materials.

water quenching o

A quench in which water is the quenching medium. The major disadvantage of water quenching is its poor efficiency at the beginning or hot stage of the quenching process. See also quenching .

o

waviness o

o

wax pattern o

o

Damage to a solid surface, generally involving progressive loss of material, due to a relative motion between that surface and a contacting surface or substance. Compare with surface damage .

wear debris o

o

A precise duplicate, allowing for shrinkage, of the casting and required gates, usually formed by pouring or injecting molten wax into a die or mold. See also investment casting .

wear o

o

A wavelike variation from a perfect surface, generally much larger and wider than the roughness caused by tool or grinding marks.

Particles that become detached in a wear process.

wear pad o

In forming, an expendable pad of rubber or rubberlike material of nominal thickness that is placed against the diaphragm to lessen the wear on it. See also diaphragm (2) .

o

weathering

o

weathering steels

o o o

Copper-bearing high-strength low-alloy steels that exhibit high resistance to atmospheric corrosion in the unpainted condition.

weave bead o

o

Exposure of materials to the outdoor environment.

A type of weld bead made with transverse oscillation.

web o

(1) A relatively flat, thin portion of a forging that effects an interconnection between ribs and bosses; a panel or wall that is generally parallel to the forging plane. See also rib . (2) For twist drills and reamers, the central portion of the tool body that joins the lands. (3) A plate or thin portion between stiffening ribs or flanges, as in an I-beam, H-beam, or other similar section.

o

weight percent

o

weld

o o

o

A localized coalescence of metals or nonmetals produced either by heating the materials to suitable temperatures, with or without the application of pressure, or by the application of pressure alone with or without the use of filler metal.

weldability o

o

Percentage composition by weight. Contrast with atomic percent .

The capacity of a material to be welded under the imposed fabrication conditions into a specific, suitably designed structure and to perform satisfactorily in the intended service.

weld bead o

A deposit of filler metal from a single welding pass.

o

weld crack

o

weld decay

o o

o

A crack in weld metal. Intergranular corrosion, usually of stainless steels or certain nickel-base alloys, that occurs as the result of sensitization in the heat-affected zone during the welding operation. See also sensitization .

welding o

(1) Joining two or more pieces of material by applying heat or pressure, or both, with or without filler material, to produce a localized union through fusion or recrystallization across the interface. The thickness of the filler material is much greater than the capillary dimensions encountered in brazing. (2) May also be extended to include brazing and soldering. (3) In tribology, adhesion between solid surfaces in direct contact at any temperature.

o

welding current

o

welding cycle

o o

The current in the welding circuit during the making of a weld. The complete series of events involved in the making of a weld.

o

welding electrode

o

welding ground

o o

See electrode (welding) . Same as work lead .

o

welding leads

o

welding machine

o o o

The electrical cables that serve as either work lead or electrode lead of an arc welding circuit. Equipment used to perform the welding operation. For example, spot welding machine, arc welding machine, seam welding machine, etc.

welding rod o

A form of filler metal used for welding or brazing that does not conduct the electrical current, and which may be either fed into the weld pool or preplaced in the joint.

o

welding sequence

o

welding stress

o

welding tip

o o o o

A form of welding filler metal, normally packaged as coils or spools, that may or may not conduct electrical current depending on the welding process with which it is used. See also electrode (welding) and welding rod . The interface between weld metal and base metal in a fusion weld, between base metals in a solid-state weld without filler metal, or between filler metal and base metal in a solid-state weld with a filler metal and in a braze.

weld line o

o

A device used in oxyfuel gas welding, torch brazing, and torch soldering for directing the heating flame produced by the controlled combustion of fuel gases. See also oxyfuel gas welding .

weld interface o

o

A device used in the gas tungsten and plasma arc welding processes to control the position of the electrode, to transfer current to the arc, and to direct the flow of shielding and plasma gas. See also gas tungsten arc welding and plasma arc welding .

welding wire o

o

A welding torch tip designed for welding.

welding torch (oxyfuel gas) o

o

Residual stress caused by localized heating and cooling during welding.

welding torch (arc) o

o

The order in which the various component parts of a weldment or structure are welded.

See preferred term weld interface .

weldment o

An assembly whose component parts are joined by welding.

o

weld metal

o

weld nugget

o o o

That portion of a weld that has been melted during welding. The weld metal in spot, seam or projection welding. See also nugget and resistance spot welding .

weld pass o

A single progression of a welding or surfacing operation along a joint, weld deposit, or substrate. The result of a pass is a weld bead, layer, or spray deposit.

o

weld pool

o

weld puddle

o o

The localized volume of molten metal in a weld prior to its solidification as weld metal. See preferred term weld pool .

o

weld reinforcement

o

Wenstrom mill

o o o

A rolling mill similar to a universal mill but where the edges and sides of a rolled section are acted on simultaneously.

wet blasting o

o

Weld metal in excess of the quantity required to fill a joint.

A process for cleaning or finishing by means of a slurry of abrasive in water directed at high velocity against the workpieces.

wetting o

(1) The spreading, and sometimes absorption, of a fluid on or into a surface. (2) A condition in which the interface tension between a liquid and a solid is such that the contact angle is 0° to 90°. (3) The phenomenon whereby a liquid filler metal or flux spreads and adheres in a thin continuous layer on a solid base metal.

o

wetting agent o

o

whisker o

o

A cast iron that is essentially free of graphite, and most of the carbon content is present as separate grains of hard Fe3C. White iron exhibits a white, crystalline fracture surface because fracture occurs along the iron carbide platelets.

white layer o

o

See malleable iron .

white iron o

o

A surface layer in a steel that, as viewed in a section after etching, appears whiter than the base metal. The presence of the layer may be due to a number of causes, including plastic deformation induced by machining or surface rubbing, heating during a metallographic preparation stage to such an extent that the layer is austenitized and then hardened during cooling, and diffusion of extraneous elements into the surface.

whiteheart malleable o

o

(1) A short single crystal fiber or filament used as a reinforcement in a matrix. Whisker diameters range from 1 to 25 m, with aspect ratios (length to diameter ratio) generally between 50 and 150. (2) Metallic filamentary growths, often microscopic, sometimes formed during electrodeposition and sometimes spontaneously during storage or service, after finishing.

white-etching layer o

o

(1) A substance that reduces the surface tension of a liquid, thereby causing it to spread more readily on a solid surface. (2) A surface-active agent that produces wetting by decreasing the cohesion within the liquid.

(1) Compound layer that forms in steels as a result of the nitriding process. (2) In tribology, a white-etching layer, typically associated with ferrous alloys, that is visible in metallographic cross sections of bearing surfaces. See also Beilby layer .

white metal o

(1) A general term covering a group of white-colored metals of relatively low melting points based on tin or lead. (2) A copper matte of about 77% Cu obtained from smelting of sulfide copper ores.

o

white rust

o

Widmanstätten structure

o o

o

Method of curving sheet metal sections or tubing over a form block or die in which this form block is moved relative to a wiper block or slide block.

wiping effect o

o

A joint made with solder having a wide melting range and with the heat supplied by the molten solder poured onto the joint. The solder is manipulated with a hand-held cloth or paddle so as to obtain the required size and contour.

wiper forming, wiping o

o

A hot dipped galvanized coating from which virtually all free zinc is removed by wiping prior to solidification, leaving only a thin zinc-iron alloy layer.

wiped joint o

o

Recovering a metal from an ore or chemical compound using any suitable hydrometallurgical, pyrometallurgical, or electrometallurgical method.

wiped coat o

o

A condition that exists when molten metal, during cooling, evolves so much gas that it becomes violently agitated, forcibly ejecting metal from the mold or other container.

winning o

o

A structure characterized by a geometrical pattern resulting from the formation of a new phase along certain crystallographic planes of the parent solid solution. The orientation of the lattice in the new phase is related crystallographically to the orientation of the lattice in the parent phase. The structure was originally observed in meteorites, but is readily produced in many alloys, such as titanium, by appropriate heat treatment.

wildness o

o

Zinc oxide; the powder product of corrosion of zinc or zinc-coated surfaces.

wire

Activation of a metal surface by mechanical rubbing or wiping to enhance the formation of conversion coatings, such as phosphate coatings.

o

o

wire bar o

o

A cast shape, particularly of tough pitch copper, that has a cross section approximately square with tapered ends, designed for hot rolling to rod for subsequent drawing into wire.

wire drawing o

o

(1) A thin, flexible, continuous length of metal, usually of circular cross section, and usually produced by drawing through a die. The size limits for round wire sections range from approximately 0.13 mm (0.005 in.) to 25 mm (1 in.). Larger rounds are commonly referred to as bars. See also flat wire . (2) A length of single metallic electrical conductor, it may be of solid, stranded or tinsel construction, and may be either bare or insulated.

Reducing the cross section of wire by pulling it through a die.

wire flame spraying o

A thermal spraying process variation in which the material to be sprayed is in wire or rod form. See also flame spraying .

o

wire rod

o

wiring

o o o

Hot-rolled coiled stock that is to be cold drawn into wire. Formation of a curl along the edge of a shell, tube, or sheet and insertion of a rod or wire within the curl for stiffening the edge. See also curling .

woody structure o

A macrostructure, found particularly in wrought iron and in extruded rods of aluminum alloys, that shows elongated surfaces of separation when fractured.

o

work hardening

o

working electrode

o

work lead

o o o o

Same as strain hardening . The test or specimen electrode in an electrochemical cell. The electrical conductor connecting the source of arc welding current to the work. Also called work connection, welding ground, or ground lead.

worm o

An exudation (sweat) of molten metal forced through the top crust of solidifying metal by gas evolution. See also zinc worms .

o

wrap forming

o

wrinkling

o o

o

A commercial iron consisting of slag (iron silicate) fibers entrained in a ferrite matrix.

X

x-ray o

o

A wavy condition obtained in deep drawing of sheet metal, in the area of the metal between the edge of the flange and the draw radius. Wrinkling may also occur in other forming operations when unbalanced compressive forces are set up.

wrought iron o

o o

See stretch forming .

A penetrating electromagnetic radiation, usually generated by accelerating electrons to high velocity and suddenly stopping them by collision with a solid body. Wavelengths of x-rays range from about 10-1 to 10-2 , the average wavelength used in research being about 1 . Also known as roentgen ray or x-radiation. See also electromagnetic radiation .

x-ray diffraction (XRD) o

An analytical technique in which measurements are made of the angles at which x-rays are preferentially scattered from a sample (as well as of the intensities scattered at various angles) in order to deduce information on the crystalline nature of the sample--its crystal structure, orientations, and so on.

o

x-ray fluorescence

o

x-ray map

o o o

Emission by a substance of its characteristic x-ray line spectrum on exposure to x-rays. An intensity map (usually corresponding to an image) in which the intensity in any area is proportional to the concentration of a specific element in that area.

x-ray photoelectron spectroscopy (XPS)

o o

An analytical technique that measures the energy spectra of electrons emitted from the surface of a material when exposed to monochromatic x-rays.

x-ray spectrometry o

Measurement of wavelengths of x-rays by observing their diffraction by crystals of known lattice spacing.

o

x-ray spectrum

o

x-ray topography

o o

The plot of the intensity or number of x-ray photons versus energy (or wavelength). A technique that comprises topography and x-ray diffraction. The term topography refers to a detailed description and mapping of physical (surface) features in a region. In the context of the x-ray diffraction, topographic methods are used to survey the lattice structure and imperfections in crystalline materials.

o o

Y

o

yellow brass

Y-block o o

o

zinc worms Surface imperfections, characteristic of high-zinc brass castings, that occur when zinc vapor condenses at the mold/metal interface, where it is oxidized and then becomes entrapped in the solidifying metals.

zincrometal o

o

A term used synonymously with modulus of elasticity. The ratio of tensile or compressive stresses to the resulting strain. See also modulus of elasticity .

Z o

o

The stress level of highly ductile materials at which large strains take place without further increase in stress.

Young's modulus o

o o

The stress at which a material exhibits a specified deviation from proportionality of stress and strain. An offset of 0.2% is used for many materials, particularly metals. Compare with tensile strength .

yield stress o

o

In materials that exhibit a yield point, the difference between the elongation at the completion and at the start of discontinuous yield.

yield strength o

o

The first stress in a material, usually less than the maximum attainable stress, at which an increase in strain occurs without an increase in stress. Only certain materials--those that exhibit a localized, heterogeneous type of transition from elastic to plastic deformation--produce a yield point. If there is a decrease in stress after yielding, a distinction may be made between upper and lower yield points. The load at which a sudden drop in the flow curve occurs is called the upper yield point. The constant load shown on the flow curve is the lower yield point.

yield point elongation o

o

(1) Evidence of plastic deformation in structural materials. Also known as plastic flow or creep. See also flow . (2) The ratio of the number of acceptable items produced in a production run to the total number that were attempted to be produced. (3) Comparison of casting weight to the total weight of metal poured into the mold.

yield point o

o

A name sometimes used in reference to the 65Cu-35Zn type of brass.

yield o

o

A single keel block .

A steel coil-coated product consisting of a mixed-oxide underlayer containing zinc particles and a zinc-rich organic (epoxy) topcoat. It is weldable, formable, paintable, and compatible with commonly used adhesives. Zincrometal is used to protect outer body door panels in automobiles from corrosion.

zone melting o

Highly localized melting, usually by induction heating, of a small volume of an otherwise solid metal piece, usually a metal rod. By moving the induction coil along the rod, the melted zone can be transferred from one end to the other. In a binary mixture where there is a large difference in composition on the liquidus and solidus lines, high purity can be attained by concentrating one of the constituents in the liquid as it moves along the rod.

Copyright © 2001 ASM International®. All Rights Reserved.