Metal Cutting Metal Cutting Fourth Edition Edward M. Trent Department of Metallurgy and Materials University of Birmingham, England Paul K. Wright Department of Mechanical Engineering University of California at Berkeley, U.S. Boston Oxford Auckland Johannesburg Melbourne New Delhi Copyright © 2000 by Butterworth–Heinemann A member of the Reed Elsevier group All rights reserved. No part of this publication 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 prior written permission of the publisher. Recognizing the importance of preserving what has been written, Butterworth–Heinemann prints its books on acid-free paper whenever possible. Butterworth–Heinemann supports the efforts of American Forests and the Global ReLeaf program in its campaign for the betterment of trees, forests, and our environment. Library of Congress Cataloging-in-Publication Data Trent, E. M. (Edward Moor) Metal cutting / Edward M. Trent, Paul K. Wright.– 4th ed. p. cm. Includes bibliographical references and index. ISBN 0-7506-7069-X 1. Metal-cutting. 2. Metal-cutting tools. I. Wright, Paul Kenneth. II. Title. TJ1185.T73 2000 671.5’3—dc21 99-052104 The publisher offers special discounts on bulk orders of this book. For information, please contact: Manager of Special Sales Butterworth–Heinemann 225 Wildwood Avenue Woburn, MA 01801–2041 Tel: 781-904-2500 Fax: 781-904-2620 For information on all Butterworth–Heinemann publications available, contact our World Wide Web home page at: http://www.bh.com 10 9 8 7 6 5 4 3 2 1 Printed in the United States of America TABLE OF CONTENTS Foreword ix Preface xi Acknowledgements xv Chapter 1 Introduction: Historical and Economic Context 1 The Metal Cutting (or Machining) Process 1 A Short History of Machining 2 Machining and the Global Economy 4 Summary and Conclusion 7 References 8 Chapter 2 Metal Cutting Operations and Terminology 9 Introduction 9 Turning 9 Boring Operations 12 Drilling 13 Facing 14 Forming and Parting Off 14 Milling 14 Shaping and Planing 16 Broaching 18 Conclusion 19 References 19 Bibliography (Also see Chapter 15) 19 Chapter 3 The EssentialFeaturesof MetalCutting 21 Introduction 21 vi The Chip 23 Techniques for Study of Chip Formation 24 Chip Shape 25 Chip Formation 26 The Chip/tool Interface 29 Chip Flow Under Conditions of Seizure 40 The Built-up Edge 41 Machined Surfaces 47 Summary and Conclusion 47 References 55 Chapter 4 Forces and Stresses in Metal Cutting 57 Introduction 57 Stress on the Shear Plane 58 Forces in the Flow Zone 60 The Shear Plane and Minimum Energy Theory 62 Forces in Cutting Metals and Alloys 74 Stresses in the Tool 79 Stress Distribution 80 Conclusion 95 References 95 Chapter 5 Heat in Metal Cutting 97 Introduction 97 Heat In the Primary Shear Zone 98 Heat at the Tool/work Interface 102 Heat Flow at the Tool Clearance Face 112 Heat in Areas of Sliding 113 Methods of Tool Temperature Measurement 114 Measured Temperature Distribution in Tools 121 Relationship of Tool Temperature to Speed 126 Relationship of Tool Temperature to Tool Design 128 Conclusion 130 References 130 Chapter 6 Cutting Tool Materials I: High Speed Steels 132 Introduction and Short History 132 Carbon Steel Tools 133 High Speed Steels 138 Structure and Composition 140 Properties of High Speed Steels 144 Tool Life and Performance of High Speed Steel Tools 149 Tool-life Testing 163 Conditions of Use 166 vii Further Development 167 Conclusion 173 References 173 Chapter 7 Cutting Tool Materials II: Cemented Carbides 175 Cemented Carbides: an Introduction 175 Structures and Properties 176 Tungsten Carbide-Cobalt Alloys (WC-Co) 177 Tool Life and Performance of Tungsten Carbide-Cobalt Tools 186 Tungsten-Titanium-Tantalum Carbide Bonded with Cobalt 202 Performance of (WC+TiC+TaC) -Co Tools 205 Perspective: “Straight” WC-Co Grades versus the “Steel-Cutting” Grades 209 Performance of “TiC Only” Based Tools 210 Performance of Laminated and Coated Tools 211 Practical Techniques of Using Cemented Carbides for Cutting 215 Conclusion on Carbide Tools 224 References 225 Chapter 8 Cutting Tool Materials III: Ceramics, CBN Diamond 227 Introduction 227 Alumina (Ceramic) Tools 227 Alumina-Based Composites (Al O + TiC) 229 2 3 Sialon 231 Cubic Boron Nitride (CBN) 236 Diamond, Synthetic Diamond, and Diamond Coated Cutting Tools 239 General Survey of All Tool Materials 245 References 249 Chapter 9 Machinability 251 Introduction 251 Magnesium 252 Aluminum and Aluminum Alloys 254 Copper, Brass and Other Copper Alloys 258 Commercially Pure Iron 269 Steels: Alloy Steels and Heat-Treatments 269 Free-Cutting Steels 278 Austenitic Stainless Steels 290 Cast Iron 293 Nickel and Nickel Alloys 296 Titanium and Titanium Alloys 303 Zirconium 307 Conclusions on Machinability 307 References 309 viii Chapter 10 Coolants and Lubricants 311 Introduction 311 Coolants 313 Lubricants 322 Conclusions on Coolants and Lubricants 334 References 337 Chapter 11 High Speed Machining 339 Introduction to High Speed Machining 339 Economics of High Speed Machining 340 Brief Historical Perspective 341 Material Properties at High Strain Rates 343 Influence of Increasing Speed on Chip Formation 348 Stainless Steel 352 AISI 4340 359 Aerospace Aluminum and Titanium 360 Conclusions and Recommendations 363 References 368 Chapter 12 Modeling of Metal Cutting 371 Introduction to Modeling 371 Empirical Models 373 Review of Analytical Models 374 Mechanistic Models 375 Finite Element Analysis Based Models 382 Artificial Intelligence Based Modeling 397 Conclusions 404 References 406 Chapter 13 Management of Technology 411 Retrospective and Perspective 411 Conclusions on New Tool Materials 412 Conclusions on Machinability 414 Conclusions on Modeling 416 Machining and the Global Economy 417 References 422 Chapter 14 Exercises For Students 425 Review Questions 425 Interactive Further Work on the Shear Plane 434 Bibliography and Selected Web-sites 435 Index 439 FOREWORD Dr. Edward M. Trent who died recently (March, 1999) aged 85, was born in England, but was taken to the U.S.A. as a baby when his parents emigrated to Pittsburgh and then to Philadelphia. Returning to England, he was a bright scholar at Lansdowne High School and was accepted as a student by Sheffield University in England just before his seventeenth birthday, where he studied metallurgy. After his first degree (B.Sc.), he went on to gain his M.Sc. and Ph.D. and was awarded medals in 1933 and 1934 for excellence in Metallurgy. His special research subject was the machining process, and he continued in this work with Wickman/Wimet in Coventry until 1969. Sheffield University recognized the importance of his research, and awarded him the degree of D.Met. in 1965. Prior to the 1950’s, little was known about the factors governing the life of metal cutting tools. In a key paper, Edward Trent proposed that the failure of tungsten carbide tools to cut iron alloys at high speeds was due to the diffusion of tungsten and carbon atoms into the workpiece, producing a crater in the cutting tool, and resulting in a short life of the tool. Sceptics disagreed, but when tools were covered with an insoluble coating, his ideas were confirmed. With the practical knowledge he had gained in industry, and his exceptional skill as a metallographer, Edward Trent joined the Industrial Metallurgy Department at Birmingham University, England in 1969 and was a faculty member there until 1979. Just before his retirement, he was awarded the Hadfield Medal by the Iron and Steel Institute in recognition of his contribution to metallurgy. Edward Trent was thus a leading figure in the materials science aspects of deformation and metal cutting. As early as 1941, he published interesting photomicrographs of thermoplastic shear bands in high tensile steel ropes that were crushed by hammer blows. One of these is reproduced in Fig- ure 5.6 of this text. Such studies of adiabatic shear zones naturally led him onward to the metal cutting problem. It is an interesting coincidence that also in the late 1930s and early 1940s, another leader in materials science, Hans Ernst, curious about the mechanism by which a cutting tool removes metal from a workpiece, carried out some of the first detailed microscopy of the process of chip formation. He employed such methods as studying the action of chip formation through the x FOREWORD microscope during cutting, taking high-speed motion pictures of such, and making photomicro- graphs of sections through chips still attached to workpieces. As a result of such studies, he arrived at the concept of the “shear plane” in chip formation, i.e. the very narrow shear zone between the body of the workpiece and the body of the chip that is being removed by the cutting tool, which could be geometrically approximated as a plane. From such studies as those by Ernst, Trent and others, an understanding emerged of the geometrical nature of such shear zones, and of the role played by them in the plastic flows involved in the chip formation process in metal cutting. That understanding laid the groundwork for the development, from the mid-1950s on, of analytical, physics-based models of the chip formation process by researchers such as Merchant, Shaw and others. These fundamental studies of chip formation and tool wear, and the metal cutting technology resulting from it, are still the base of our understanding of the metal cutting process today. As the manufacturing industry builds on the astounding potential of digital computer technology, born in the 1950s, and expands to Internet based collaboration, the resulting global enterprises still depend on the “local” detailed fundamental metal cutting technology if they are to obtain increasingly precise products at a high quality level and with rapid throughput. However, one of the most important strengths that the computer technology has brought to bear on this situation is the fact that it provides powerful capability to integrate the machining performance with the per- formance of all of the other components of the overall system of manufacturing. Accomplish- ment of such integration in industry has enabled the process of performing machining operations to have full online access to all of the total database of each enterprise’s full system of manufac- turing. Such capability greatly enhances both the accuracy and the speed of computer-based engineering of machining operations. Furthermore, it enables each element of that system (prod- uct design, process and operations planning, production planning and control, etc.), anywhere in the global enterprise to interact fully with the process of performing machining and with its tech- nology base. These are enablements that endow machining technology with capability not only to play a major role in the functioning and productivity of an enterprise but also to enable the enterprise as a whole to utilize it fully as the powerful tool that it is. M. Eugene Merchant and Paul K. Wright, June 1999