Metal Cutting

464 Pages·2000·34.35 MB·English

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
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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
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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