Publication Information and Contributors Forming and Forging was published P1

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

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

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

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

• 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

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

Nonlubricated hot extrusion

Lubricated direct hot extrusion

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)

Linear stretch forming (stretch forming)

Linear roll forming (roll forming)

Spinning (and roller flanging)

Reference cited in this section

1 T Altan, S.I Oh, and H.L Gegel, Metal Forming: Fundamentals and Applications, American Society for Metals, 1983

Note cited in this section

* Sheet forming is also referred to as forming In the broadest and most accepted sense, however, the term forming is used to described bulk as well as sheet forming processes

Introduction to Forming and Forging Processes

S.L Semiatin, Battelle Columbus Division

Types of Metalworking Equipment

The various forming processes discussed above are associated with a large variety of forming machines or equipment, including the following (Ref 1):

• Rolling mills for plate, strip, and shapes

• Machines for profile rolling from strip

• Ring-rolling machines

• Thread-rolling and surface-rolling machines

• Magnetic and explosive forming machines

• Draw benches for tube and rod; wire- and rod-drawing machines

• Machines for pressing-type operations (presses)

Among those listed above, pressing-type machines are the most widely used and are applied to both bulk and sheet forming processes These machines can be classified into three types: load-restricted machines (hydraulic presses), stroke-restricted machines (crank and eccentric, or mechanical, presses), and energy-restricted machines (hammers and screw presses) The significant characteristics of pressing-type machines comprise all machine design and performance data that are pertinent to the economical use of the machine These characteristics include:

• Characteristics for load and energy: Available load, available energy, and efficiency factor (which equals the energy available for workpiece deformation/energy supplied to the machine)

• Time-related characteristics: Number of strokes per minute, contact time under pressure, and velocity under pressure

• Characteristics for accuracy: For example, deflection of the ram and frame, particularly under off-center loading, and press stiffness

Reference cited in this section

1 T Altan, S.I Oh, and H.L Gegel, Metal Forming: Fundamentals and Applications, American Society for Metals, 1983

Introduction to Forming and Forging Processes

S.L Semiatin, Battelle Columbus Division

Recent Developments in Metalworking

Over the last 20 years, metalworking practice has seen advances with regard to the development of new processes and new materials, the understanding and control of material response during forming, and the application of sophisticated process design tools Some of these technological advances will be summarized in the following sections in this article

New Processes

A number of processes have recently been introduced or accepted These include a variety of forging processes, such as radial, precision, rotary, metal powder, and isothermal forging, as well as sheet forming processes, such as superplastic forming Laser cutting and abrasive waterjet cutting of sheet and plate materials are also finding increased use Each of these processes is described in greater detail in subsequent articles in this Volume

Radial forging is a technique that is most often used to manufacture axisymmetrical parts, such as gun barrels Radial forging machines (Fig 1) use the radial hot- or cold-forging principle with three, four, or six hammers to produce solid or hollow round, square, rectangular, or profiled sections The machines used for forging large gun barrels are of a horizontal type and can size the bore of the gun barrel to the exact rifling that is machined on the mandrel Products produced by radial forging often have improved mechanical and metallurgical properties as compared to those produced

by other, more conventional techniques

Fig 1 Workpiece and tooling configurations for radial forging Source: Ref 2

Rotary, 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 As shown in Fig 2, 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 (called the footprint) continually progresses through the workpiece until the final shape is obtained The tilt angle between the two dies has a major effect on the size of the footprint and therefore on the amount of forging force applied to the workpiece Rotary forging requires as little as one-tenth the force needed for conventional forging processes The smaller forging forces result in lower die and machine deflections and therefore in the ability to make intricate parts to a high degree of accuracy