ASM - Extrusion

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EXTRUSION

SECOND EDITION

Editors

M. Bauser

G. Sauer

K. Siegert

Translated from German by

A.F. Castle

ASM International姞 Materials Park, Ohio 44073-0002

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Copyright䉷 2006 by ASM International威

Originally published as Strangpressen 䉷 2001 Aluminium-Verlag, Du¨sseldorf, Germany

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 2006

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 or 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 LIA-BLE 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 end-use 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 repro-duction, 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.

Prepared under the direction of the ASM International Technical Books Committee (2006–2007), James Foley, Chair.

ASM International staff who worked on this project include Scott D. Henry, Senior Product Manager; Charles Moosbrugger; Editor, Diane Grubbs, Editorial Assistant; Bonnie Sanders, Production Manager; Madrid Tram-ble, Senior Production Coordinator; Diane Wilkoff, Production Coordinator; Pattie Pace, Production Coor-dinator; Kathryn Muldoon, Production Assistant

Library of Congress Cataloging-in-Publication Data Extrusion / editors, M. Bauser, G. Sauer, K. Siegert. — 2nd ed.

p. cm.

Includes bibliographical references and index. ISBN-13: 978-0-87170-837-3

ISBN-10: 0-87170-837-X

1. Metals—Extrusion. 2. Aluminum alloys. I Bauser, M. (Martin) II. Sauer, G. (Gu¨nther) III. Siegert, Klaus. TS255.E78 2006 671.3⬘4—dc22 2006050365 SAN: 204-7586 ASM International威 Materials Park, OH 44073-0002 www.asminternational.org Printed in the United States of America

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iii

8.2.2 Introduction of a QMS ...552 8.2.3 Process Chain ...553 8.2.4 Product Liability ...555 8.2.5 Economics ...556 8.3 Quality Control ...556 8.3.1 Organization ...556 8.3.1.1 Process Organization ...557 8.3.2 Responsibilities ...558 8.3.2.1 General Requirements ...558 8.3.3 Audits ...558 8.3.3.1 QMS Audit ...559

8.3.3.2 Environmental System Audit ...560

8.3.3.3 Process Audit ...560

8.3.3.4 Product Audit ...560

8.3.3.5 Inspector Audit ...561

8.3.4 Testing ...561

8.3.4.1 Failure Modes and Effect Analysis ...561

8.3.4.2 Inspection Planning ...561

8.4 Outlook ...563

Appendix A List of Formula Symbols ...565

Appendix B Approximate Composition of Materials ...567

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Foreword

The book Extrusion: Processes, Equipment, Tooling, edited by Kurt Laue and Helmut Stanger, was published in 1976 by the Aluminium-Verlag GmbH, Du¨sseldorf. The excellent, wide, and often deep overview enabled experienced engineers as well as students and academics to understand ex-trusion processes, equipment, and tooling. For a long time, this book, which was also translated into English, was the standard reference on extrusion.

Because it has been out of print for several years, it made sense to republish the book Extrusion in a fully updated version. The editors have attempted to retain the character of the book as an overview of the processes, equipment, and tooling. Extruded products have been discussed in more detail to demonstrate the range of applications of extrusion and to stimulate the industrial application of extrusion beyond that used today.

In addition, the metallurgical fundamentals of the extrusion process are covered in detail, because the editors believe that extrusion can only be optimized by taking the materials technology into account.

The discussions on extrusion equipment, plant, and tooling attempt to extend the overview with application examples. Actual applications, however, require the cooperation of the customer, extruder, tool maker and equipment manufacturer.

The book Extrusion is intended for both students and research engineers as well as engineers in extrusion plants, manufacture of machinery and plant, tool manufacture, as well as the designers, process developers, and managers of automotive companies, building industries, and plant manufac-ture. The book should give an introduction to and an overview of extrusion. More detailed discussions and the latest research results can be found in the technical literature.

The authors thank the co-authors of this book and the numerous companies that have helped in its realization by providing the material for the figures and technical discussions. Specific mention should be made of the support from Wieland-Werke AG, Ulm, and by the companies Alusuisse Neuhausen and Alusingen. We should also thank the members of the “Extrusion Technical Com-mittee” in the DGM for the valuable information they provided. These include, in particular, Dr. J. Baumgarten, Dr. G. Fischer, and Dipl.-Ing. Rethmann. Thanks are also due to Y. Ismailoglu of IFU-Stuttgart and A. Schug of Wieland-Werke Ulm for the preparation and production of numerous photographs, drawings, tables, and diagrams.

The editors also give special thanks to the Aluminium Verlag for fulfilling the requests and re-quirements of the editors and the authors and for the careful preparation of the contributions for printing.

Sadly, one of the three editors, our dear colleague and friend, Professor Dr. Ing. Gu¨nther Sauer, died on October 7, 2000. He gave a great deal of commitment and effort to the realization of this book and completed all of his promised contributions to it before his sudden death. Unfortunately, he was not allowed the pleasure of seeing this book in its final format. We would like to express our sincere thanks for being a good colleague and a friend.

We hope this book fulfills the expectations of the reader and contributes to the further development of extrusion.

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Authors

Dr. Rudolf Akeret, Neuhausen, Switzerland Adolf Ames, Duchtlingen bei Singer (Hohentwiel) Dr. rer. nat. Martin Bauser, Senden bei Ulm Dr. rer. nat. Amit K. Biswas, Kaarst Dipl.-Ing. Wolfgang Eckenbach, Iserlohn Dr. rer. nat. Adolf Frei, Neu-Ulm Horst H. Groos, Mettmann Willi Johnen, Simmerath Dr.-Ing. Klaus Mu¨ller, Berlin Dr. Josef Putz, Simmerath

Prof. Dr.-Ing. Gu¨nther Sauer, Kronberg/Ts. Dr.-Ing. Gu¨nther Scharf, Bonn

Prof. Dr.-Ing. Wolfgang Schneider, Bonn

Dr.-Ing. Gottfried Schreiter, Kleinwaltersdorf bei Freiberg Prof. Dr.-Ing. Dr. H.C. Klaus Siegert, Stuttgart

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Extrusion, Second Edition

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Terms of Use. This publication is being made available in PDF format as a benefit to members and customers of ASM International. You may download and print a copy of this publication for your personal use only. Other use and distribution is prohibited without the express written permission of ASM International.

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. As with any material, evaluation of the material under end-use conditions prior to specification is essential. Therefore, specific testing under actual conditions is recommended. Nothing contained in this publication 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 publication shall be construed as a defense against any alleged infringement of letters patent,

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CHAPTER 1 Introduction*

Fig. 1.1 Extrusion processes. (a) Direct extrusion. (b) Indirect extrusion. 1, extrusion; 2, die; 3, billet; 4, dummy block; 5, container; 6, stem; 7, dummy block with die; 8, sealing tool

1.1 Basic Principles of Extrusion

THE EXTRUSION OF METALS, in which a billet, usually round, is pressed by a stem at high pressure through a tool of the desired shape, the die, to one or more lengths, first achieved its important position in the semi-finished product industry in the twentieth cen-tury. The process was used mainly for the pro-duction of bar, wire, tubes, and sections in aluminum alloys and copper alloys. However, stainless steel tubes, steel sections, and semifin-ished products in other metals also are produced in small quantities by extrusion.

Figure 1.1 illustrates the two most important types of extrusion:

● In direct extrusion, a stem, usually with a

pressure pad in front, pushes the billet in a stationary container through a tool of the de-sired shape, the die. Relative movement takes place between the billet and the con-tainer.

● In contrast, in indirect extrusion, the die is

located in front of a hollow stem and pushed against the billet by the forward movement of the container closed at the back. There is, therefore, no relative movement between the billet and the container.

During extrusion, a compressive stress state is developed within the billet, which enables large deformations to be achieved with a low risk of cracking. The ratio of the billet cross-sectional area to that of the extruded section is known as the extrusion ratio. It usually falls in the range 10 to 100. In special cases—for ex-ample, brass wire—the extrusion ratio can be as high as 1000. However, this requires the mate-rial’s being extruded to have a low flow stress

*Historic Development of Extrusion, Martin Bauser

in addition to a high specific press pressure of

up to 1000 N/mm2. Extrusion is therefore

nor-mally carried out at a high temperature:

alumi-num alloys usually in the range 400 to 500⬚C,

copper alloys between 600 and 900 ⬚C, and

stainless steels and special materials up to

1250⬚C.

Mention should also be made of the special processes of hydrostatic extrusion, the conform process, and cable sheathing also described in this book.

In hydrostatic extrusion (Fig. 1.2), the billet is surrounded by a pressurized fluid. This has the advantage of negligible liquid friction be-tween the billet and the container. The only fric-tion that has to be taken into considerafric-tion is between the material and the die. Because the

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Fig. 1.3 Conform process. 1, extrusion; 2, die; 3, feedstock; 4, shoe; 5, friction wheel; 6, groove

Fig. 1.2 Hydrostatic extrusion. 1, extrusion; 2, die; 3, seal; 4, billet; 5, container; 6, stem; 7, hydrostatic medium

Fig. 1.4 Bramah’s lead piston press, 1797. A, melting cham-ber; B, piston; C, tube support; D, tube mandrel; E, extruded tube

process is difficult to operate and the pressurized fluid can withstand only relatively low tempera-tures, which restricts the extrusion ratios that can be achieved, the process has only limited appli-cations in spite of initial great hopes.

In the conform process (Fig. 1.3), a contin-uous feedstock is extruded through the die by a rotating friction wheel with a groove that is closed by a semicircular shoe. Small cross sec-tions and relatively low deformation ratios are possible. Only a few applications are known.

The standard processes, i.e., direct and indi-rect extrusion, have step by step reached high levels of productivity and quality combined with a simultaneous reduction in operating personnel associated with improvements in machine tech-nology and upstream and downstream

equip-ment, modern control technology, and the opti-mization of tooling materials and tooling design. Knowledge of the fundamental principles of metallurgy, as well as the basics of deformation technology, machinery, and tooling, is needed to understand the extrusion process. All these as-pects are discussed in this book.

Historic Development of

Extrusion*

Martin Bauser

Joseph Bramah described in a patent in 1797 a “press for the production of pipes of a specific diameter and length without joints in lead and other soft metals” (Fig. 1.4). Joseph Bramah used liquid lead forced from a melting vessel A

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Fig. 1.6 First bridge die by I. and C. Hanson (1837) Fig. 1.5 First hydraulic lead press (Th. Burr, 1820). A,

con-tainer; B, die; C, extrusion stem with machined dummy block and threaded mandrel; D, extruded tube by the piston B through a valve into the cylinder. The liquid material is then pushed by the piston as split metal streams through annularly located openings in the mandrel support so that the metal streams combine and solidify in the an-nular gap formed by the tube mandrel D and the tube support C to form a tube E.

Pure lead melts at 327 ⬚C, and most of its

alloys at an even lower temperature, so that this material can be formed with low loads even at 80 ⬚C. Therefore, lead was the only important extruded material up to the end of the nineteenth century. Many of the important elements of the process used today were, however, developed during this period.

The first known design of a (vertical) hydrau-lic extrusion press for lead tube was developed by the Englishman Thomas Burr in 1820 (Fig. 1.5). It had a container A, an extrusion stem with a machined-in pressure pad, a threaded mandrel, and a replaceable die B.

England played a leading role in extrusion as well as in many engineering fields. Lead pipes were used there relatively early for water supply pipes. English inventions from the nineteenth century include the bridge die, the hydraulic ac-cumulator, the gas-heated container, and the in-direct extrusion process. Specific mention should be made of the invention of I. and C.

Hanson, who, as early as 1837, were producing lead tubes from a solid billet through a multipart bridge die with a replaceable fixed pressure pad (Fig. 1.6).

The first two-piece container heated with gas was developed by Hammon in 1867.

The start of electrification opened a new mar-ket for lead as a cable sheathing material. The first cable sheathing press was built by Borell in 1879 in which lead was extruded directly onto the cable core. The process was improved in 1882 by Werner von Siemens.

Alexander Dick, who lived in England, suc-ceeded in developing from lead extrusion the processing of metals with higher melting points. He is therefore quite correctly considered to be the “father of extrusion.”

In 1894, Dick registered a patent for an extru-sion press designed specifically for brass rod (Fig. 1.7) [Dic 94]. His idea was to cast liquid metal into the vertically orientated container and to let it solidify. After rotating the container into the horizontal position, the product was extruded from this initial heat through a replaceable die, F. Direct water pressure pushed the stem for-wards. A pressure pad protected it from the billet heat and prevented back extrusion of the metal. The die and die holder, E, were sealed against the cross head by two wedges, D. These were

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Fig. 1.9 Bridge die by A. Dick (1897) Fig. 1.8 Hydraulic extrusion press (1895)

Fig. 1.7 First brass extrusion press. D, wedges; E, die and die holder; F, replaceable die (A. Dick, 1894) opened at the end of the extrusion process, and the die discard and pressure pad ejected using the stem (Fig. 1.8).

Because the one-piece container made from cast iron or steel tended to crack under the ther-mal stresses developed by the casting of the hot metal, a multipiece container was introduced in 1896. However, the individual cylinders were not prestressed but merely insulated from each other by powdered graphite and borax.

The time-consuming process copied from lead pipe extrusion of filling the container with liquid metal was soon replaced by the use of preheated cast billets. Alexander Dick described over a period of time many important details in numerous patents: the loose pressure pad, vari-ous mandrel designs for tubes, dies for multihole extrusion, and even a hollow section die. The three-piece bridge die patented by Alexander Dick in 1897 is shown in Fig. 1.9 [Dic 97]. The billet is divided into six streams that weld to-gether in the shape forming aperture.

The manufacture of extrusion presses with press capacities of more than 7 MN enabled larger billets to be used, thus giving an economic

production. The water hydraulic extrusion press was powered by a pressurized water system con-sisting of pumps and accumulators. The hot bil-lets were manually loaded into the container us-ing tongs. Hand-operated valves were used to control the operating sequence of the extrusion press. The extruded products had to be handled manually with tongs.

Rapid developments at the start of the twen-tieth century resulted in the extrusion process completely replacing the previously standard process for the production of bars, sections, and wire in copper alloys of section by rolling of cast billets. More than 200 extrusion presses, mostly for brass, had been built by 1918 (mainly by the German company Krupp-Gruson). However, even steel sections were being extruded by 1914. Although it was possible to produce tubes on standard presses by the development of “floating mandrels,” which were a loose fit in the hollow billet and were heavily tapered toward the die, this was replaced—following a patent by Arnold Schwieger in 1903—by a piercing system lo-cated behind the main cylinder (Fig. 1.10).

The mandrel holder passing through the main cylinder carries the mandrel at its tip, which can pierce the solid billet. This then forms the inter-nal contour of the tube in the die. These presses, which can naturally also be used to extrude solid bars by removal of the mandrel, were built up to the 1950s. Then the internal piercer enabled the press length to be shortened and the align-ment of the mandrel to be improved (Fig. 1.11).

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Fig. 1.10 First rod and tube press (Arnold Schwieger, 1903) In the 1920s, experience showed that that the concentricity of internal and external tube walls was better on vertical hydraulic presses because of the favorable influence of gravity. The man-drel was rigidly screwed to the stem and pre-pierced billets used. In the 1950s, numerous ver-tical tube presses were built (by the companies Schloemann and Hydraulik) but now with in-dependent mandrel movement and automatic operation for the production of copper and brass tubes. The manufacture of vertical presses stopped around 1965 when it became possible

to improve the alignment of the press centerline, the guiding of the container, stem, and mandrel to such an extent that tubes with adequate con-centricity were produced on horizontal presses. In spite of the high cycle speeds, the presses with a maximum capacity of 16 MN did not have sufficient power to process billets of sufficient size.

Around 1933, the vertical mechanical tube presses patented by Singer started to mass pro-duce steel tubes. These vertical tube presses with a high number of strokes per minute for the mass production of steel tubes have been largely re-placed by rolling processes that operate more economically with a higher productivity.

Containers, which had for a long time been produced as multipiece units but without any in-terference fit could operate only with specific press extrusion pressures of approximately 300

N/mm2_{. It was only the introduction of two- or}

three-piece prestressed containers that enabled higher extrusion pressures to be used. Movable containers enabled the billet loading and the re-moval of the discard to be improved. The intro-duction of electric container heating (resistance and later induction heating) in 1933 replaced the previously used gas or coal heating and enabled aluminum to be processed (Fig. 1.12).

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Fig. 1.12 Three-piece container with induction heating

The rapid expansion of extrusion technology since 1925 gave rise to intensive investigation into the flow processes and deformation tech-nology theories. These resulted in new devel-opments in press construction and tooling tech-nology.

For a long time it was standard practice to design each press from new to meet the needs of the application and the customer. Around 1960, multipurpose extrusion presses that could be used universally were developed in Europe.

Fig. 1.13 Complete aluminum extrusion plant (SMS Hasenclever)

Although Alcan has processed aluminum on horizontal presses since 1918, the breakthrough in aluminum extrusion came with the construc-tion of airships and aircraft. Difficult-to-extrude high-strength aluminum alloys were developed in the 1930s (aluminum copper), and large prod-uct cross sections required powerful presses. The largest extrusion presses built up to 1945 had a press power of 125 MN. Around 1950, the preassembled short stroke press with variable di-rect oil drive (mounted above the press), and die slide or die rotate for rapid die changing, was developed in the United States. This enabled short dead cycles to be developed. These presses for aluminum alloys were built with press loads from 10 to 30 MN. They provided optimal pro-duction in combination with a high-speed gas-fired billet furnace in front of the press and a handling system with stretcher and saw for the profiles after the press. Aluminum profiles for windows and curtain walling could then be pro-duced economically. The full layout of an alu-minum extrusion plant is shown in Fig. 1.13.

Although experiments by R. Genders (1921, in England) into indirect extrusion resulted in the manufacture of theses presses by 1925, the breakthrough of this process came with the in-direct extrusion of brass wire (Hydraulik Co.). Improved designs and the application to difficult-to-extrude aluminum alloys ensured the increasing application of this indirect extrusion process. In contrast, the hydrostatic extrusion process has succeeded in only very specialized applications in spite of extensive research and numerous publications. One example is the ex-trusion of composite materials.

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REFERENCES

[Bau 82]: M. Bauser and E. Tuschy,

Strang-pressen—Heutiger Stand und Entwicklung-stendenzen (Extrusion—Present Position and Development Trends), Z. Metallkd., Vol 73, 1982, p 411–419

[Bis 73]: A. Biswas and F.J. Zilges, Direktes,

indirektes und hydrostatisches Strangpres-sen—Verfahrensbeschreibung und geschicht-liche Entwicklung (Direct, Indirect and Hy-drostatic Extrusion Process Description and Historic Development), Aluminium, Vol 49, 1973, p 296–299

[Dic 94]: A. Dick, Deutsches Patent 83388,

1894

[Dic 97]: A. Dick, Deutsches Patent 99405,

1897

[Nus 90]: A.J. Nussbaum, Extrusion of Metals:

The First Hundred Years, Light Met. Age, Vol 48, 1990, p 8–33

[Pea 61]: C.E. Pearson and R.N. Parkins, The

Extrusion of Metals, Chapman & Hall, 1960

[Pet 59]: E. Petsch, Neues

indirekt-Strang-preßverfahren fu¨r Metalldraht (New Indirect Extrusion Process for Metal Wire), Z.

Me-tallkd., Vol 50, 1959, p 629–637

[Wei 66]: F. Weitzel, Die Entwicklung der

Strangpresse (The Development of the Extru-sion Press), Edelstahlwerke Buderus AG,

Wetzlar, 1966

[Wie 70]: H. Wieland, Die Geschichte des

Strangpressens im Blicke der Wieland-werke

(The History of Extrusion from the Viewpoint

of Wielandwerke), Wielandwerke AG, Ulm,

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CHAPTER 2 Extruded Products

Gu¨nther Sauer*

THE HOT-WORKING PROCESS extrusion is used to produce semifinished products in the form of bar, strip, and solid sections as well as tubes and hollow sections. The high mean com-pressive stresses in the deformation zone of the container enable materials to be worked that cannot be processed into semifinished products by other hot-working processes, for example rolling, because of their limited workability. The extrusion process also enables semifinished products to be produced from powder metal-lurgy-based materials, composite materials, and the production of semifinished products from clad composites with material combinations in-cluding aluminum/copper and aluminum/steel using the cladding process. Finally, the sheath-ing of electrical cables with lead or aluminum alloys using the transverse extrusion process has been a standard process for a long time, as has the production of multicore solders with inte-grated flux cores using the same process.

The pushing of the material being extruded through the shape-forming aperture of the extru-sion die enables cross-sectional shapes to be pro-duced that cannot be manufactured by any other hot-working process. The favorable deformation conditions with nonferrous metals such as tin and lead alloys as well as magnesium and alu-minum alloys with good welding properties and working temperatures that can be withstood by the tool materials also enable the billet to be di-vided into several metal streams, and then re-welded in the shape-forming region of the ex-trusion die to form tubes and hollow sections. The production of hollow sections is one of the

*Extruded Products from Materials with a Working Temperature Range of 600 to 1300⬚C, Martin Bauser

main applications of extrusion. This process can also be used for certain copper alloys; however, the materials used for the extrusion tooling can-not withstand the thermo-mechanical stresses. Billet-on-billet extrusion enables coiled tubes of long length to be produced, for example, alu-minum alloy heat exchanger tubes and tin and lead alloy multicore solders.

The extrusion process generally produces a semifinished product close to the finished size with materials with working temperatures up to 600 ⬚C. This occurs in one production step in contrast to other processes used to form semifin-ished products. Therefore, the design of the cross section of the semifinished product can practically ignore any limitations associated with subsequent processing operations. The most suitable cross-sectional geometry can be freely selected for the specific application. Sim-ple matching of the cross-sectional geometry of the extrusion to the static, dynamic, and geo-metric requirements combined with the wide range of joining methods in assembly character-ize the high functionality of the products pro-duced by this working process.

2.1 Tin and Lead Extruded

Products with a Deformation

Temperature Range of 0 to 300

⬚C

Tin alloy extruded products are mainly soft solders with or without flux cores for use in elec-trical engineering and electronics. Tin alloys are significantly more common than are lead alloys.

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Fig. 2.1 Soft solder with one or more flux cores (tube solder), extruded and drawn to the finished dimensions and coiled on plastic spools. Source: Collin

Fig. 2.2 Extruded sections and tubes in lead base and tin al-loys for use as anodes for the electrochemical coat-ing, supply tubes for aggressive media, materials for seals and radiation protection, etc. Source: Collin

They are produced on horizontal presses and drawn, coiled, or wound to the customers’ de-sired finished sizes on multispindle wire draw-ing machines as shown in Fig. 2.1. The produc-tion processes are described in secproduc-tion 5.3. Other extruded products are anodes used for electro-chemical plating with tin, for example, tin plat-ing for corrosion protection. Tin alloy extruded products are also used in the manufacture of chemical equipment.

Lead alloy products have lost a large part of their market since World War II because of the toxic properties of these alloys. Even in the 1950s, extruded lead alloys were still used for water supply pipes up to the fittings on sinks. These materials were also used for extruded wa-ter waste pipes. This has changed completely. Lead alloys may no longer come into contact with food products because they can form very poisonous lead salts. Drinking water counts as a food and, therefore, lead drinking water pipes are no longer permitted. Nevertheless, lead loys offer a range of advantages that make al-ternative materials difficult or even impossible to find. Lead alloys have good resistance to fluoric and sulfuric acids as well as phosphoric acid, ammonia, chlorine, and soda. They are therefore useful alloys for the chemical industry.

The high density makes lead alloys particularly suitable for radiation and noise protection. Good workability combined with low melting points means that lead alloys are also used for the man-ufacture of soft solder, which is described in sec-tion 5.3. Lead alloys, similar to tin alloys, are also suitable for the production of custom shaped anodes as shown in Fig. 2.2 for electro-chemical plating. An example is the approxi-mately 20 lm thick and soft running surface in plain bearings such as bearing shells and bushes. Although the use of specific lead alloys for the production of cable sheaths cannot be classified as environmentally harmful, the cable industry prefers alternative plastic and aluminum-base materials. High-voltage cables are still sheathed in lead. Spacers for double glazing (Fig. 2.3) are also extruded from lead alloys. Fishing nets and curtains are usually weighted with lead lines produced by horizontal extrusion. Some exam-ples are shown in Fig. 2.3.

Lead alloys can be made relatively resistant to corrosion by the addition of tin. They can also be recycled relatively easily. However, the en-vironmental political pressure will affect the cur-rent applications because of the toxic properties of this material.

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Fig. 2.3 Extruded solder with several flux cores, lead sheathed cable, and window spacer sections in lead alloys for double glazed windows, as well as lead lines for fishing nets and curtain weights. Source: Collin

Fig. 2.4 From left to right: Section in MgAl2Zn for the pro-duction of pencil sharpeners, two sections in MgAl3Zn for warp knitting machine, and test arm sections for disc magazines. Source: Fuchs-Metallwerke

2.2 Magnesium and Aluminum

Extruded Products with a Working

Temperature Range of

300 to 600

⬚C

2.2.1 Magnesium Alloy Extruded Products

Magnesium alloys are light materials with useful mechanical properties. Their density of

approximately 0.0018 kg/m3 _{is about 36% less}

than that of the aluminum alloys. The Young’s modulus (E) is approximately 45 GPa and, therefore, about 65% of the E-modulus of alu-minum alloys. For this reason, they are, in prin-ciple, more interesting than aluminum alloys as a construction material for light components. However, the corrosion resistance of magnesium components is not usually as good as that of alu-minum components. They, therefore, have to be given more surface protection. The corrosion sensitivity of magnesium alloys can be lowered significantly by reducing the trace element con-tent of copper, iron, manganese, and nickel into the ppm region. The corrosion behavior of high-purity magnesium alloys approaches that of alu-minum alloys. This has considerably increased the interest in magnesium alloys as construction materials. However, the mechanical behavior of magnesium components is very directional

de-pendent because of the hexagonal lattice struc-ture. In addition, any partial cold working of magnesium components, as is necessary, for ex-ample, for the aluminum alloy side door beam in Fig. 2.24, in the section “Passenger Cars,” is practically impossible because of this hexagonal lattice structure. Magnesium alloys naturally have good machining characteristics. Unlike aluminum alloys, they do not need any chip-breaking alloying additions such as lead and

bis-muth. Consequently, extruded semifinished

products are eminently suited to the production of turned components including ones in daily use, for example, pencil sharpeners. A typical profile can be seen in Fig. 2.4 [Fuc 96]. In the past, the market for extruded magnesium alloy products was limited in spite of the products’ good properties, in particular, their low density. The reason for this is both the lattice-related poor cold-working properties, and the hot-work-ing properties that are very alloy dependent. The main application for magnesium alloys is, there-fore, still cast components. The most well-known application is the engine and gearbox housing used after World War II in the air-cooled flat twin engine in the Volkswagen Beetle.

Basically, magnesium products are used where the weight saving, e.g., components with a low mass, has high priority. The main areas of application are automobile and machine manu-facture. The extruded products shown in Fig. 2.5 and 2.6 are suited primarily for machine com-ponents subjected to high acceleration and brak-ing, for example, in textile machine components [Fuc 96]. These products are also used in the aerospace industry and in military applications.

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Fig. 2.5 Extruded section in MgAl3Zn for textile machines. Source: Fuchs-Metallwerke

Fig. 2.6 Hollow section in MgAl3Zn for the external rotor of a turbocharger for automobile engines. Source: Fuchs-Metallwerke

Magnesium alloys are being developed fur-ther because of their suitability for light com-ponents with the intention of achieving higher static and dynamic mechanical properties as well as improving the working properties [Tec 96/97/ 98, Gar 93]. Interest in magnesium alloy com-ponents is increasing, particularly in the auto-mobile industry.

In the past, hot-worked semifinished products in the form of magnesium alloy sheet and

ex-truded products were used to a significant degree in the period before World War II. Complete fu-selages in hot-rolled and section-reinforced magnesium sheets were produced for small air-craft [Bec 39]. Bus trailers were manufactured almost entirely from hot-worked magnesium al-loys, including a welded frame of extruded mag-nesium tubes clad with magmag-nesium sheet [Bec 39]. Welded seat frames for passenger aircraft were made from extruded magnesium tubes.

The increasing interest by the automobile in-dustry in light extruded products in order to save energy by reducing vehicle weight has resulted in increasing examination of extruded semifin-ished products in magnesium alloys. This will gain in importance if the further development of the magnesium alloys results in higher values of static and dynamic strength and improved work-ing and corrosion properties. It can, therefore, be assumed that magnesium alloys will also be used to an increasing extent for load-carrying components as well as safety components, which require a good proof stress and elonga-tion. Magnesium alloys are, moreover, as easily recycled as aluminum alloys.

The extrusion of magnesium alloys is de-scribed in section 5.5.

2.2.2 Aluminum Alloy Extruded Products

The main application of the hot-working pro-cess extrusion is in the general production of bars, tubes, and wire in aluminum alloys and, in particular, the manufacture of aluminum sec-tions. No other material is used as a semifinished product to the same extent in practically all areas of technology. Acceptable materials properties and modulus of elasticity, weight saving from the low-density, good surface quality, good di-mensional accuracy and minimum subsequent machining, and ease of recycling make alumi-num alloys both economically and environmen-tally interesting. These properties, as well as the largely unrestricted shape of the cross-section geometry, are the basis for the trend to the de-velopment of ever more functional components with good appearance and corrosion resistance. The reason for the predominance of alumi-num profiles in extrusion is due to the moderate working temperatures of the aluminum alloys. The extrusion tooling can then withstand the thermo-mechanical stresses. In general, the working temperature of aluminum alloys is be-low the annealing temperature of the hot-work-ing tool steels normally used to manufacture