Primer on Flat Rolling

Front Cover......Page 1
Primer on Flat Rolling......Page 4
Copyright Page......Page 5
Table of Contents......Page 8
Preface......Page 16
List of Symbols......Page 19
Advice for Instructors......Page 22
1.1 The Flat Rolling Process......Page 24
1.2 The Hot Rolling Process......Page 25
1.2.1 Reheating furnace......Page 26
1.2.3 Coil box......Page 27
1.2.4 Finish rolling......Page 29
1.2.6 Coiling......Page 30
1.2.8 The Steckel mill......Page 31
1.3 Continuous Casting......Page 32
1.4 Mini-Mills......Page 33
1.5.1 Cold rolling mill configurations......Page 34
1.6 The Warm-Rolling Process......Page 37
1.8 Further Reading......Page 38
1.9 Conclusions......Page 39
2.1 The Flat Rolling Process......Page 40
2.1.2 Mathematical modelling......Page 42
2.1.3 The independent and dependent variables......Page 43
2.2 The Physical Events Before, During and After the Pass......Page 45
2.2.1.2 Homogeneous compression......Page 51
2.3 The Metallurgical Events Before and After the Rolling Process......Page 53
2.4 Limitations of the Flat Rolling Process......Page 55
2.4.1 The minimum rollable thickness......Page 56
2.4.2 Alligatoring and edge-cracking......Page 57
2.5 Conclusions......Page 58
3.1 A Discussion of Mathematical Modelling......Page 59
3.2 A Simple Model......Page 64
3.3.1 The Classical Orowan model......Page 70
3.3.2 Sims’ model......Page 73
3.3.3 Bland and Ford’s model......Page 74
3.4 Refinements of the Orowan Model......Page 75
3.4.1 The deformation of the work roll......Page 78
3.5 The Effect of the Inertia Force......Page 80
3.5.2 A numerical approach......Page 81
3.6 The Predictive Ability of the Mathematical Models......Page 82
3.7 The Friction Factor in the Flat Rolling Process......Page 84
3.7.1 The mathematical model......Page 86
3.7.2.1 Cold rolling of steel......Page 88
3.7.2.2 Distribution of the roll pressure at the contact......Page 91
3.8.1 Structure and terminology......Page 93
3.8.6 Learning......Page 94
3.8.8 Back-propagation neural networks......Page 95
3.8.12 Application of neural networks to predict the roll forces in cold rolling of a low carbon steel......Page 96
3.9 Extremum Principles......Page 97
3.9.1 The upper bound theorem......Page 98
3.11 The Development of the Metallurgical Attributes of the Rolled Strip......Page 101
3.11.1 Thermal–mechanical treatment......Page 103
3.11.1.2 Dynamic and metadynamic recrystallization-controlled rolling......Page 105
3.11.1.4 Controversies regarding the type of recrystallization in strip rolling......Page 106
3.11.2.1 Static changes of the microstructure......Page 107
3.11.2.2 Dynamic softening......Page 111
3.11.2.4 Grain growth......Page 112
3.11.3.3 Tensile strength......Page 113
3.12.1 The forward slip......Page 114
3.12.3 Roll bending......Page 115
3.12.4 Cumulative strain hardening......Page 116
3.12.5 The lever arm......Page 117
3.13.2 Establish the metal’s resistance to deformation......Page 119
3.14 Conclusions......Page 120
4.1 Introduction......Page 122
4.2 Recently Developed Steels......Page 123
4.2.2 Interstitial free (IF) steels......Page 124
4.2.4 TRIP steel......Page 125
4.2.5 High strength low alloy (HSLA) steels......Page 126
4.2.6 Dual-phase (DP) steels......Page 128
4.3 Steel and Aluminum......Page 129
4.4 The Independent Variables......Page 131
4.5.1 Tension tests......Page 132
4.5.2 Compression testing......Page 134
4.5.3 Torsion testing......Page 136
4.6.1 Friction control......Page 137
4.6.2.1 Isothermal conditions......Page 139
4.6.2.2 Monitoring the temperature......Page 140
4.7.1 Low temperatures......Page 141
4.7.2 High temperatures......Page 142
4.8 Mathematical Representation of Stress–Strain Data......Page 144
4.8.1.2 Relations for use in hot rolling......Page 146
4.10 Conclusions......Page 152
5.1 Tribology – A General Discussion......Page 153
5.2.2 The areas of contact......Page 155
5.2.2.1 The relationship of the apparent and the true areas of contact......Page 158
5.2.3 Definitions of frictional resistance......Page 162
5.2.4 The mechanisms of friction......Page 164
5.3.1.1 The embedded pin – transducer technique......Page 165
5.3.1.3 The ring compression test......Page 167
5.3.2.1 Forward slip – coefficient of friction relations......Page 169
5.3.2.2 Empirical equations – cold rolling......Page 173
5.3.2.3 The study of Tabary et al. (1994)......Page 175
5.3.2.4 Empirical equations and experimental data – hot rolling......Page 176
5.3.2.5 Inverse calculations......Page 180
5.3.2.6 Negative forward slip......Page 181
5.3.2.7 The correlation of the coefficient of friction, determined in the laboratory and in industry......Page 182
5.4.1.1 The viscosity......Page 183
5.4.1.2 The viscosity–pressure relationship......Page 184
5.4.1.3 The viscosity–temperature relationship......Page 186
5.4.2 The lubrication regimes......Page 187
5.4.3 A well-lubricated contact in flat rolling......Page 189
5.4.4.1 Roll force and roll torque......Page 190
5.4.4.2 The coefficient of friction......Page 193
5.4.5 Oil-in-water emulsions......Page 194
5.4.5.1 Behaviour of the droplets......Page 195
5.4.5.2 Entrainment of the emulsion......Page 196
5.4.6 A physical model of the contact of the roll and the strip......Page 197
5.4.7 The thickness of the oil film......Page 198
5.4.7.1 Measurement of the thickness of the oil film......Page 199
5.4.7.2 Calculation of the oil film thickness......Page 201
5.5 Dependence of the Coefficient of Friction or the Roll Separating Force on the Independent Variables......Page 202
5.5.1 The dependence of coefficient on reduction......Page 203
5.5.2 The dependence of coefficient on speed......Page 204
5.5.3 The dependence of coefficient on the surface roughness of the roll......Page 206
5.5.4 The dependence of the roll separating force on the lubricant’s viscosity......Page 207
5.5.5.1 The layer of scale......Page 209
5.5.5.2 The effect of the scale thickness on friction......Page 212
5.6 Heat Transfer......Page 213
5.6.1 Estimating the heat transfer coefficient on a laboratory rolling mill......Page 215
5.6.2 Measuring the surface temperature of the roll......Page 217
5.7 Roll Wear......Page 218
5.8 Conclusions......Page 221
5.8.1 Heat transfer coefficient......Page 224
5.8.3 Roll wear......Page 225
5.8.4 What is still missing......Page 226
6.1 The Sensitivity of the Predictions of the Flat Rolling Models......Page 227
6.1.1 The sensitivity of the roll separating force and the roll torque to the coefficient of friction and the reduction......Page 228
6.1.2 The sensitivity of the roll separating force and the roll torque to the strain-hardening co-efficient......Page 230
6.1.3 The dependence of the roll separating force and the roll torque on the entry thickness......Page 231
6.2 A Comparison of the Predictions of Power, Required for Plastic Deformation of the Strip......Page 232
6.3 The Roll Pressure Distribution......Page 233
6.4 The Statically Recrystallized Grain Size......Page 234
6.5 The Critical Strain......Page 236
6.6.1 The shape of the stress–strain curve, as predicted by Shida......Page 237
6.7 Conclusions......Page 239
7.1 The Temper Rolling Process......Page 240
7.2 The Mechanism of Plastic Yielding......Page 241
7.3.1 Yield strength variation......Page 242
7.4.1 The Fleck and Johnson models......Page 243
7.4.2 Roberts’ model......Page 244
7.4.3 The model of Fuchshumer and Schlacher (2000)......Page 246
7.4.5 The model of Domanti et al. (1994)......Page 247
7.4.7 The models of Wiklund (1996a, 1996b, 1999, 2002)......Page 248
7.4.8 The model of Liu and Lee (2001)......Page 249
7.4.9 The studies of Sutcliffe and Rayner (1998)......Page 250
7.4.10 The model of Pawelski (2000)......Page 251
7.6 Conclusions......Page 252
8.1 Introduction......Page 253
8.2.2 Equal channel angular pressing (ECAP)......Page 254
8.2.4 Multiple forging......Page 255
8.2.7 Accumulative roll-bonding (ARB)......Page 256
8.3.2 Preparation and procedure......Page 259
8.4.1 Process parameters......Page 260
8.4.2.2 Yield, tensile strength and ductility......Page 262
8.4.2.4 The cross-section of the roll-bonded strips......Page 263
8.4.2.5 The strength of the bond......Page 264
8.5 The Phenomena Affecting the Bonds......Page 265
8.5.1 Cracking of the edges......Page 266
8.7 A Combination of ECAP and ARB......Page 268
8.7.1 The ECAP process......Page 269
8.7.2 The rolling process......Page 270
8.7.3 The microstructure after ECAP and the rolling passes......Page 271
8.8 Conclusions......Page 274
9.1 Introduction......Page 275
9.2.1 Material......Page 277
9.3 Parameters......Page 278
9.5.2.1 The effect of the speed of rolling......Page 279
9.5.2.2 The effect of the normal pressure......Page 281
9.5.2.3 The effect of the entry temperature – warm bonding......Page 282
9.5.2.4 The effect of the entry temperature – cold bonding......Page 283
9.6.1 Warm bonding......Page 284
9.6.3 Side view of the bond......Page 286
9.7 The Phenomenon of Bonding......Page 287
9.8 Conclusions......Page 290
10.1 Introduction......Page 291
10.2.1 Material......Page 294
10.3.1.1 AISI 1030 steel, cold drawn......Page 295
10.3.1.2 AISI 1008 steel, cold drawn......Page 297
10.3.1.3 Al 6111 aluminum alloy......Page 298
10.4 Predictions of a Simple Model......Page 299
10.5 Strain at Fracture......Page 301
10.6 Conclusions......Page 303
Part 1: Problems......Page 304
Part 2: Solutions......Page 325
References......Page 336
Author Index......Page 357
Subject Index......Page 363
Color plates......Page 366