Publication Information and Contributors Forming and Forging was published P1

ASM
INTERNATIONAL ®
Publication Information and Contributors

Forming and Forging was published in 1988 as Volume 14 of the 9th Edition Metals Handbook. With the third printing
(1993), the series title was changed to ASM Handbook. The Volume was prepared under the direction of the ASM
Handbook Committee.
Volume Chair
The Volume Chair was S.L. Semiatin.
Authors and Reviewers
• Rafael Nunes UFRGS
• Ibrahim Abbas Westinghouse Electric Corporation
• Leo L. Algminas Klein Tools, Inc.
• Taylan Altan The Ohio State University
• H. Alsworth USC Corporation
• D. Ashok Universal Energy Systems Knowledge Integration Center
• Robert A. Ayres General Motors Corporation
• R. Bajoraitis Boeing Commercial Airplane Company
• James A. Bard Johnson Matthey Company
• R.A. Barry Cincinnati Inc.
• M. Baxi Ullrich Copper, Inc.
• James R. Becker Cameron Forge Company

• K.H. Beseler Girard Associates, Inc.
• R. Beswick Enheat Aircraft Division (Canada)
• Deborah A. Blaisdell The U.S. Baird Corporation
• R.L. Bodnar Bethlehem Steel Corporation
• George P. Bouckaert Nooter Corporation
• Bruno J. Brazaukas Fine-Blanking Company, Inc.
• John Breedis Olin Corporation
• John D. Bryzgel Fenn Manufacturing Company
• G.C. Cadwell Rohr Industries, Inc.
• Glenn Calmes Harris Calorific Division Emerson Electric Company
• Robert A. Campbell Mueller Brass Company
• R.F. Cappellini Bethlehem Steel Corporation
• M.B. Cenanovic Ontario Hydro (Canada)
• Arthur C.P. Chou Dyna East Corporation
• P.C. Chou Drexel University
• M.D. Conneely The Timken Company
• E. Cook Douglas Aircraft Company
• Thomas D. Cooper Air Force Wright Aeronautical Laboratories
• W.H. Couts Wyman-Gordon Company
• Richard J. Cover LTV Steel Company
• Ed Craig AGA Gas, Inc.
• Jack Crane Olin Corporation
• Thomas J. Culkin Lumonics Materials Processing Corporation
• C.V. Darragh The Timken Company
• James H. DeBord Technical Consultant
• Phillipe Delori SMS Sutton, Inc.
• George E. Dieter University of Maryland
• A.E. Doherty Explosive Fabricators, Inc.
• S.M. Doraivelu Universal Energy Systems Knowledge Integration Center
• J.R. Douglas Eaton Corporation

• Joseph A. Douthett Armco Inc.
• Earl Drollinger Buffalo Forge Company
• L.J. Duly The Timken Company
• E. Erman Bethlehem Steel Corporation
• H.D. Erzinger Liquid Carbonic Corporation
• D.A. Evans The Evans Findings Company, Inc.
• L. Ewert McDonnell Douglas Corporation
• Lynn Ferguson Deformation Control Technology
• Brownell N. Ferry LTV Steel Corporation
• Brian J. Finn Laser Lab Sales Inc.
• Robert J. Fiorentino Battelle Columbus Division
• Blaine Fluth Diversico Industries
• Charles W. Frame Chambersburg Engineering Company
• R. Fuquen The Timken Company
• T. Furman Ladish Company, Inc.
• R. Gagne Army Materials and Mechanics Research Center
• H.L. Gegel Air Force Wright Aeronautical Laboratories/Materials Laboratory
• A.K. Ghosh Rockwell International
• J.W. Giffune Jernberg Forgings Company
• R.A. Giles SACO Defense Inc.
• Jude R. Gleixner Keystone Carbon Company
• S. Gopinath Universal Energy Systems Knowledge Integration Center
• Larry A. Grant Electrofusion Corporation
• W.G. Granzow Armco Inc.
• V.S. Gunaskera Ohio University
• Gene Hainault Fansteel
• C.H. Hamilton Washington State University
• Thomas Harris Armco Inc.
• K. Hasegawa Joseph T. Ryerson & Son, Inc.
• A. Hayes Ladish Company, Inc.

• H.J. Henning Forging Industry Association
• K. Herbert Murdock, Inc.
• V. Sam Hill Dow Chemical Company
• Franz Hofer American GFM Corporation
• Albert L. Hoffmanner Braun Engineering Company
• Hans Hojas Gesellschaft fur Fertigungstechnik und Maschinbau mbH (West Germany)
• H. Hollenbach Murdock, Inc.
• William H. Hosford University of Michigan
• T.E. Howson Wyman-Gordon Company
• Louis E. Huber, Jr. Cabot Corporation
• P.A. Hughes The Timken Company
• B. Huthwaite Troy Engineering
• F. Infield Erie Press Systems
• Natraj C. Iyer Westinghouse R&D Center
• Sulekh C. Jain General Electric Company
• V.K. Jain University of Dayton
• W. Brian James Hoeganaes Corporation
• D.M. Jankowski The Timken Company
• L.L. Jenney Universal Energy Systems Knowledge Integration Center
• B. Jewell Heintz Corporation
• C.A. Johnson National Forge Company
• Serope Kalpakjian Illinois Institute of Technology
• R.S. Kaneko Lockheed-California Company
• S. Kedzierski Talon, Inc.
• Stuart Keeler The Budd Company Technical Center
• C.R. Keeton Ajax Rolled Ring Company
• E.W. Kelley Haynes International
• John Kerr Fenn Manufacturing Company
• Ashok K. Khare National Forge Company
• B.W. Kim Northrup Corporation

• H. Joseph Klein Haynes International
• A.A. Knapp Canadian Copper & Brass Development Association (Canada)
• F. Koeller Technical Consultant
• P.K. Kropp The Timken Company
• Robert Krysiak Scot Forge
• G.W. Kuhlman Aluminum Company of America
• Howard A. Kuhn University of Pittsburgh
• G.D. Lahoti The Timken Company
• J.A. Laverick The Timken Company
• D. Lee Rensselaer Polytechnic Institute
• Peter W. Lee The Timken Company
• J. Linteau AMAX Specialty Metals
• Roger W. Logan Los Alamos National Laboratory
• Mark Lynch Oneida Ltd.
• Mike Maguire Colorado School of Mines
• S.A. Majlessi Rensselaer Polytechnic Institute
• J.C. Malas Air Force Wright Aeronautical Laboratories/Materials Laboratory
• Frank Mandigo Olin Corporation
• Norman Margraff Verson Allsteel Press Company
• A. Marquis Masco Corporation
• J. Marshall Naval Ordnance Station
• D.L. Mayfield McDonnell Douglas Corporation
• Ron McCabe American GFM Corporation
• Michael J. McDermott Hoeganaes Corporation
• N.M. Medei Bethlehem Steel Corporation
• Wilfred L. Mehling Ajax Manufacturing Company
• Edward E. Mild Timet Inc.
• Clarence J. Miller Abbey Etna Machine Company
• K.L. Miller The Timken Company
• M.E. Miller Molloy Manufacturing Corporation

• Virginia Mouch Electronic Data Systems Corporation
• Elliot S. Nachtman Tower Oil & Technology Company
• John R. Newby Consultant
• Stefan Nilsson ASEA Pressure Systems, Inc.
• Reuben Nystrom Cincinnati Inc.
• Gerald A. O'Brien General Motors Corporation Saginaw Division
• Linus J. O'Connell Aluminum Company of America
• N.T. Olson Maxwell Laboratories
• Ramjee Pathak Federal-Mogul Corporation
• W. Peters Grumman Aircraft Systems
• L.J. Pionke McDonnell Douglas Corporation
• George D. Pirics National Machinery Company
• Michael M. Plum Maxwell Laboratories, Inc.
• Robert A. Powell Hoeganaes Corporation
• S.H. Pratt The Timken Company
• Eugene Priebe Armco Inc.
• P.S. Raghupathi Battelle Columbus Division
• Christopher W. Ramsey Colorado School of Mines
• E. Raymond Cameron Iron Works, Inc.
• L.K. Repp The Timken Company
• C.E. Rodaitis The Timken Company
• H.C. Rogers Drexel University
• H.H. Ruble Inco Alloys International
• P.A. Russo RMI Company
• R. Sanders Laserdyne
• J.A. Schey University of Waterloo (Canada)
• John Schley Ontario Technologies Corporation
• J. Schlosser Schlosser Forge Company
• S.L. Semiatin Battelle Columbus Division
• W.C. Setzer Aluminum Company of America

• Sanjay Shah Wyman-Gordon Company
• William F. Sharp Explosive Fabricators Inc.
• V.A. Shende Universal Energy Systems Knowledge Integration Center
• R.J. Shipley Textron, Inc.
• Rajiv Shivpuri The Ohio State University
• John Siekirk General Motors Technical Center
• Gregg P. Simpson Peerless Saw Company
• Don Smith FMC Corporation
• James K. Solheim Metal Bellows Division Parker Bertea Aerospace Company
• M. Spinelli Aluminum Precision Products
• Lee Spruit Autodie Corporation
• S.K. Srivastava Haynes International
• George W. Stacher Rockwell International
• Robin Stevenson General Motors Corporation
• Jack D. Stewart, Sr. Stewart Enterprises, Inc.
• P. Stine Metallurgical Laboratories
• D.J. Stuart National Forge Company
• J. Gerin Sylvia University of Rhode Island
• Brian Taylor General Motors Corporation
• Eric Theis Herr-Voss Corporation
• R. Thompson Inland Steel Company
• Steven W. Thompson Colorado School of Mines
• Don Tostenson LTV Steel Corporation
• John Turn Brush Wellman Inc.
• John Uccellini Controls Corporation of America
• D. Van Aernum Union Fork & Hoe Corporation
• Chester J. Van Tyne Lafayette College
• J.H. Vogel Rensselaer Polytechnic Institute
• F. Walker General Electric Company
• R. Wallies Cameron Iron Works, Inc.

• J. Walters Cameron Iron Works, Inc.
• P.T. Wardhammer Carmet Company
• Robert Wattinger Manco/Ameco Automation
• Michael W. Wenner General Motors Research Laboratory
• Robert A. Westerkamp Cincinnati, Inc.
• C. White Ladish Company, Inc.
• G. White Coherent General
• Ronald H. Williams Air Force Wright Aeronautical Laboratories
• R.H. Witt Grumman Aircraft Systems
• H.W. Wolverton Quanex Corporation
• William G. Wood Kolene Corporation
• S.J. Woszczynski The Timken Company
Foreword
Forming and forging processes are among the oldest and most important of materials-related technologies. Volume 14 of
the 9th Edition of Metals Handbook describes these processes comprehensively, with accuracy and clarity.
Today, industry must continuously evaluate the costs of competitive materials and the operations necessary for converting
each material into finished products. Manufacturing economy with no sacrifice in quality is paramount. Therefore,
"precision" forming methods, net and near-net shape processing, and modern statistical and computer-based process
design and control techniques are more important than ever. This book serves as an invaluable introduction to this new
technology, and also provides a strong foundation with regard to more standard, well-established metalworking
operations.
This is the second of three volumes in the 9th Edition devoted to the technologies used to form metal parts. Volume 7,
Powder Metallurgy, was published in 1984; Volume 15, Casting, will follow the present volume. The combination of
these significant contributions to the metallurgical literature will provide Handbook readers with unprecedented coverage
of metal forming methods.
A successful Handbook is the culmination of the time and efforts of hundreds of contributors. To those individuals listed
in the next several pages, we extend our sincere thanks. The Society is especially indebted to Dr. S.L. Semiatin for his
tireless efforts in organizing and editing this volume. Finally, we are grateful for the support and guidance provided by the
ASM Handbook Committee and the skill of an experienced editorial staff. As a result of these combined efforts, the
tradition of excellence associated with the Metals Handbook continues.

William G. Wood
President, ASM International
Edward L. Langer
Managing Director, ASM International
Preface
Metalworking is one of the oldest of materials-related technologies and accounts for a large percentage of fabricated
metal products. The usefulness of the deformation processes that comprise metalworking technology is indicated by the
wide variety of parts of simple and complex shape with carefully tailored mechanical and physical properties that are
made routinely in industry. It is difficult to imagine what our lives would be like without such products.
The 8th Edition of Metals Handbook treated various aspects of metalworking in two separate volumes: forging was
addressed in the volume Forging and Casting, and sheet forming in the one on Forming. In the present 9th Edition, the
decision was made to bring all this information together in one Handbook.
During the editing process, all of the articles from the 8th Edition volumes were reviewed for technical content. Some
required only minor revision, others were totally rewritten. A section on other bulk forming processes was added to
provide a balance to the extensive collection of articles on forging. In this new section, topics such as conventional hot
extrusion; hydrostatic extrusion; wire, rod, and tube drawing; and flat, bar, and shape rolling are discussed.
In addition, approximately 20 new articles have been added to describe advances in metalworking technology that have
occurred since publication of the 8th Edition. These advances can be broadly grouped in the categories of new processes,
new materials technologies, and new methods of process design and control. New processes include isothermal and hot-
die forging, precision forging, and superplastic forming of sheet metals. New materials technologies center on the
development and widespread use of thermal-mechanical processing, particularly for aerospace alloys, and concepts of
metal workability and formability. In the area of process design and control, several articles were written to summarize
the powerful mathematical and statistical methods that have been developed to take metalworking from an experienced-
based art into the realm of scientific technology. These techniques have allowed forming engineers to design dies and
preforms for single and multistage processes without actually constructing tooling or tying up expensive production
equipment. With the development of user-friendly computer programs and low-cost computers, such techniques are
finding increasing acceptance by manufacturers worldwide.
Thanks are due to the various individuals who organized, wrote, edited, and reviewed various sections and articles in this
Handbook; their voluntary contributions of time and expertise are invaluable in a project such as this. We would also like
to extend thanks to the ASM Handbook staff. The amount of careful and devoted work that the staff put into the

Handbook cannot really be appreciated until one actually works with them on one of these volumes.
S.L. Semiatin
Chairman
General Information
Officers and Trustees of ASM International
Officers
• William G. Wood President and Trustee Kolene Corporation
• Richard K. Pitler Vice President and Trustee Allegheny Ludlum Corporation (retired)
• Raymond F. Decker Immediate Past President and Trustee University Science Partners, Inc.
• Frank J. Waldeck Treasurer Lindberg Corporation
Trustees
• Stephen M. Copley University of Southern California
• Herbert S. Kalish Adamas Carbide Corporation
• H. Joseph Klein Haynes International, Inc.
• William P. Koster Metcut Research Associates, Inc.
• Robert E. Luetje Kolene Corporation
• Gunvant N. Maniar Carpenter Technology Corporation
• Larry A. Morris Falconbridge Limited
• William E. Quist Boeing Commercial Airplane Company
• Daniel S. Zamborsky Aerobraze Corporation
• Edward L. Langer Managing Director ASM International
Members of the ASM Handbook Committee (1987-1988)
• Dennis D. Huffman (Chairman 1986-; Member 1983-) The Timken Company
• Roger J. Austin (1984-) Astro Met Associates, Inc.
• Roy G. Baggerly (1987-) Kenworth Truck Company
• Peter Beardmore (1986-) Ford Motor Company
• Robert D. Caligiuri (1986-) Failure Analysis Associates
• Richard S. Cremisio (1986-) Rescorp International, Inc.
• Thomas A. Freitag (1985-) The Aerospace Corporation
• Charles David Himmelblau (1985-) Lockheed Missiles & Space Company, Inc.

• J. Ernesto Indacochea (1987-) University of Illinois at Chicago
• Eli Levy (1987-) The De Havilland Aircraft Company of Canada
• Arnold R. Marder (1987-) Lehigh University
• L.E. Roy Meade (1986-) Lockheed-Georgia Company
• Merrill I. Minges (1986-) Air Force Wright Aeronautical Laboratories
• David V. Neff (1986-) Metaullics Systems
• David LeRoy Olson (1982-) Colorado School of Mines
• Ned W. Polan (1987-) Olin Corporation
• Paul E. Rempes (1986-) Williams International
• E. Scala (1986-) Cortland Cable Company, Inc.
• David A. Thomas (1986-) Lehigh University
Previous Chairmen of the ASM Handbook Committee
• R.S. Archer (1940-1942) (Member, 1937-1942)
• 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)
• 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)
• J.L. McCall (1982) (Member, 1977-1982)
• W.J. Merten (1927-1930) (Member, 1923-1933)
• 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 Kathleen M. Mills, Manager of
Editorial Operations; Joseph R. Davis, Senior Editor; James D. Destefani, Technical Editor; Theodore B. Zorc, Technical
Editor; Heather J. Frissell, Editorial Supervisor; George M. Crankovic, Assistant Editor; Alice W. Ronke, Assistant
Editor; Diane M. Jenkins, Word Processing Specialist; and Karen Lynn O'Keefe, Word Processing Specialist. Editorial
assistance was provided by J. Harold Johnson, Robert T. Kiepura, Dorene A. Humphries, and Penelope Thomas. The
Volume was prepared under the direction of Robert L. Stedfeld, Director of Reference Publications.
Conversion to Electronic Files
ASM Handbook, Volume 14, Forming and Forging was converted to electronic files in 1998. The conversion was based
on the fourth printing (1996). 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, Robert Braddock, Alexandra Hoskins, and Erika Baxter. 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 © 1988 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, April 1988
Second printing, December 1989
Third printing, November 1993
Fourth printing, April 1996
ASM Handbook is a collective effort involving thousands of technical specialists. It brings together in one book 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, are given in connection with the accuracy or completeness of this publication, and no responsibility
can be taken for any claims that may arise.
Nothing contained in the ASM Handbook 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 the ASM Handbook 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.
Includes bibliographies and indexes.
Contents: v. 1. Properties and selection--[etc.]-- v. 9 Metallography and microstructures--[etc.]-- v. 14. Forming and
forging.
1. Metals--Handbooks, manuals, etc. 1. ASM INTERNATIONAL. Handbook Committee.
TA459.M43 1978 669 78-14934
ISBN 0-87170-007-7 (v. 1)
SAN 204-7586
Introduction to Forming and Forging Processes
S.L. Semiatin, Battelle Columbus Division

Introduction
METALWORKING consists of deformation processes in which a metal billet or blank is shaped by tools or dies. The
design and control of such precesses depend on an understanding of the characteristics of the workpiece material, the
conditions at the tool/workpiece interface, the mechanics of plastic deformation (metal flow), the equipment used, and the
finished-product requirements. These factors influence the selection of tool geometry and material as well as processing
conditions (for example, workpiece and die temperatures and lubrication). Because of the complexity of many
metalworking operations, models of various types, such as analytic, physical, or numerical models, are often relied upon
to design such processes.
This Volume presents the state of the art in metalworking processes. Various major sections of this Volume deal with

descriptions of specific processes, selection of equipment and die materials, forming practice for specific alloys, and
various aspects of process design and control. This article will provide a brief historical perspective, a classification of
metalworking processes and equipment, and a summary of some of the more recent developments in the field.
Introduction to Forming and Forging Processes
S.L. Semiatin, Battelle Columbus Division

Historical Perspective
Metalworking is one of three major technologies used to fabricate metal products; the others are casting and powder
metallurgy. However, metalworking is perhaps the oldest and most mature of the three. The earliest records of
metalworking describe the simple hammering of gold and copper in various regions of the Middle East around 8000 B.C.
The forming of these metals was crude because the art of refining by smelting was unknown and because the ability to
work the material was limited by impurities that remained after the metal had been separated from the ore. With the
advent of copper smelting around 4000 B.C., a useful method became available for purifying metals through chemical
reactions in the liquid state. Later, in the Copper Age, it was found that the hammering of metal brought about desirable
increases in strength (a phenomenon now known as strain hardening). The quest for strength spurred a search for alloys
that were inherently strong and led to the utilization of alloys of copper and tin (the Bronze Age) and iron and carbon (the
Iron Age). The Iron Age, which can be dated as beginning around 1200 B.C., followed the beginning of the Bronze Age
by some 1300 years. The reason for the delay was the absence of methods for achieving the high temperatures needed to
melt and to refine iron ore.
Most metalworking was done by hand until the 13th century. At this time, the tilt hammer was developed and used
primarily for forging bars and plates. The machine used water power to raise a lever arm that had a hammering tool at one
end; it was called a tilt hammer because the arm tilted as the hammering tool was rised. After raising the hammer, the
blacksmith let it fall under the force of gravity, thus generating the forging blow. This relatively simple device remained
in service for some centuries.
The development of rolling mills followed that of forging equipment. Leonardo da Vinci's notebook includes a sketch of a
machine designed in 1480 for the rolling of lead for stained glass windows. In 1945, da Vinci is reported to have rolled
flat sheets of precious metal on a hand-operated two-roll mill for coin-making purposes. In the following years, several
designs for rolling mills were utilized in Germany, Italy, France, and England. However, the development of large mills
capable of hot rolling ferrous materials took almost 200 years. This relatively slow progress was primarily due to the
limited supply of iron. Early mills employed flat rolls for making sheet and plate, and until the middle of the 18th century,

these mills were driven by water wheels.
During the Industrial Revolution at the end of the 18th century, processes were devised for making iron and steel in large
quantities to satisfy the demand for metal products. A need arose for forging equipment with larger capacity. This need
was answered with the invention of the high-speed steam hammer, in which the hammer is raised by steam power, and the
hydraulic press, in which the force is supplied by hydraulic pressure. From such equipment came products ranging from
firearms to locomotive parts. Similarly, the steam engine spurred developments in rolling, and in the 19th century, a
variety of steel products were rolled in significant quantities.
The past 100 years have seen the development of new types of metalworking equipment and new materials with special
properties and applications. The new types of equipment have included mechanical and screw presses and high-speed
tandem rolling mills. The materials that have benefited from such developments in equipment range from the ubiquitous
low-carbon steel used in automobiles and appliances to specialty aluminum-, titanium-, and nickel-base alloys. In the last
20 years, the formulation of sophisticated mathematical analyses of forming processes has led to higher-quality products
and increased efficiency in the metalworking industry.

Introduction to Forming and Forging Processes
S.L. Semiatin, Battelle Columbus Division

Classification of Metalworking Processes
In metalworking, an initially simple part--a billet or a blanked sheet, for example--is plastically deformed between tools
(or dies) to obtain the desired final configuration. Metal-forming processes are usually classified according to two broad
categories:
• Bulk, or massive, forming operations
• Sheet forming operations
*

In both types of process, the surfaces of the deforming metal and the tools are in contact, and friction between them may
have a major influence on material flow. In bulk forming, the input material is in billet, rod, or slab form, and the surface-
to-volume ratio in the formed part increases considerably under the action of largely compressive loading. In sheet
forming, on the other hand, a piece of sheet metal is plastically deformed by tensile loads into a three-dimensional shape,
often without significant changes in sheet thickness or surface characteristic.

Processes that fall under the category of bulk forming have the following distinguishing features (Ref 1):
• The deforming material, or workpiece, undergoes large plastic (permanent) deformation, resulting in an
appreciable change in shape or cross section
• The portion of the workpiece undergoing plastic deformation is generally much larger than the portion
undergoing elastic deformation; therefore, elastic recovery after deformation is negligible
Examples of generic bulk forming processes are extrusion, forging, rolling, and drawing. Specific bulk forming processes
are listed in Table 1.
Table 1 Classification of bulk (massive) forming processes
Forging
Closed-die forging with flash
Closed-die forging without flash
Coining
Electro-upsetting
Forward extrusion forging
Backward extrusion forging
Hobbing
Isothermal forging
Nosing
Open-die forging
Rotary (orbital) forging
Precision forging
Metal powder forging
Radial forging
Upsetting

Rolling
Sheet rolling
Shape rolling
Tube rolling
Ring rolling

Rotary tube piercing
Gear rolling
Roll forging
Cross rolling
Surface rolling
Shear forming
Tube reducing

Extrusion
Nonlubricated hot extrusion
Lubricated direct hot extrusion
Hydrostatic extrusion

Drawing
Drawing
Drawing with rolls
Ironing
Tube sinking

Source: Ref 1
The characteristics of sheet metal forming processes are as follows (Ref 1):
• The workpiece is a sheet or a part fabricated from a sheet
• The deformation usually causes significant changes in the shape, but not the cross-sectional area, of the
sheet.
• In some cases, the magnitudes of the plastic and the elastic (recoverable) deformations are comparable;
therefore, elastic recovery or springback may be significant.
Examples of processes that fall under the category of sheet metal forming are deep drawing, stretching, bending, and
rubber-pad forming. Other processes are listed in Table 2.
Table 2 Classification of sheet metal forming processes
Bending and straight flanging

Brake bending
Roll bending

Surface contouring of sheet
Contour stretch forming (stretch forming)
Androforming
Age forming
Creep forming
Die-quench forming
Bulging
Vacuum forming