IRON MAKING AND STEELMAKING: THEORY AND PRACTICE

Preface xix
Part A GENERAL
1. Introduction 1–23
1.1 Early History of Iron (Steel) 3
1.1.1 Meteoric Iron and Wrought Iron 3
1.1.2 Cast Iron 4
1.1.3 Evolution of Ironmaking in Europe 4
1.1.4 Early History of Steelmaking before the Advent of Modern Processes 6
1.1.5 Iron and Steel Heritage of India 7
1.2 Evolution of Ironmaking Technology Since 1880 8
1.2.1 The Developing Blast Furnace 8
1.2.2 Alternative Ironmaking Processes 11
1.3 Steelmaking Since Henry Bessemer 13
1.3.1 Bessemer Process 13
1.3.2 Open Hearth Process 15
1.3.3 Electric Furnace Steelmaking 15
1.3.4 Basic Oxygen Steelmaking 16
1.3.5 Secondary Steelmaking and Continuous Casting of Steel 17
1.4 Present Status of the World Steel Industry 18
1.4.1 Classification 18
1.4.2 World Production of Steel 19
1.5 Steelmaking in India 19
1.6 Environmental Pollution and Control 20
1.6.1 Steps Taken by the Steel Industry 20
1.6.2 Forms of Pollution 22
1.7 Concluding Remarks 23
References 23
2. Overview of Blast Furnace Ironmaking 24–38
2.1 Introduction 24
2.1.1 Improvements Made in Blast Furnace Technology 25
2.2 Blast Furnace Reactions and Process in a Nutshell 25
vii
Contentsviii • Contents
2.3 General Constructional Features of the Furnace 27
2.3.1 Different Regions within a Blast Furnace 28
2.3.2 Size of Blast Furnace 30
2.4 Performance of Blast Furnace 31
2.5 Blast Furnace Refractory Lining 32
2.6 Charging of Solid Materials from the Top 33
2.7 Blast Furnace Plant and Accessories 37
2.7.1 Hot Blast Stoves 37
References 38
3. Overview of Modern Steelmaking 39–48
3.1 Introduction 39
3.2 Methods Presently Used for Steel Production 39
3.3 Oxygen Steelmaking 40
3.3.1 Top-blown Converter Process 40
3.3.2 Bottom-blown Converters (Q-BOP/OBM) 41
3.3.3 Bath Agitated Processes 42
3.4 Electric Steelmaking 43
3.4.1 Electric Arc Furnace (EAF) 43
3.4.2 Electric Induction Furnaces 44
3.5 Secondary Steelmaking 44
3.5.1 Ladle Stirring 46
3.5.2 Injection Processes 46
3.5.3 Vacuum Processes 46
3.5.4 Reheating Processes 46
3.6 Continuous Casting 47
4. General Physicochemical Fundamentals 49–80
4.1 Introduction 49
4.2 Chemical Equilibrium 49
4.2.1 Activity, Free Energy, Chemical Potential and Equilibrium 50
4.2.2 Free Energy and Equilibrium 52
4.2.3 Oxidation–Reduction Reactions 52
4.3 Activity vs. Composition Relationships 56
4.3.1 Introduction 56
4.3.2 Ideal, Non-ideal and Regular Solutions 57
4.3.3 Activities in Molten Slag Solutions 58
4.3.4 Activity–Composition Relationships in Dilute Solutions 58
4.4 Structure and Physicochemical Properties of Melts 64
4.4.1 Properties of Liquid Iron and Steel 64
4.4.2 Structure and Physicochemical Properties of Slag Melts 66
4.4.3 Slag Basicity and Capacities 69
4.4.4 Slag Models 71
4.5 Kinetics, Mixing and Mass Transfer 73
4.5.1 Introduction 73
4.5.2 Interfacial Chemical Reaction 74
4.5.3 Diffusion 75
4.5.4 Turbulence and Mixing in Fluids 76
4.5.5 Convective Mass Transfer at Interface 76
4.5.6 Enhancement of Process Rates 78
References 80Contents • ix
Part B BLAST FURNACE IRONMAKING
5. Physical Chemistry of Blast Furnace Reactions 83–110
5.1 Thermodynamics of the Carbon–Oxygen Reaction 83
5.1.1 Combustion of Coke in the Tuyere Zone 83
5.1.2 C–CO2–CO Reaction 84
5.2 Gas–Solid Reaction Equilibria in the Blast Furnace Stack 86
5.2.1 The Fe–O System 86
5.2.2 Thermodynamics of Reduction of Iron Oxides by Carbon Monoxide 86
5.2.3 Dissociation of Limestone 89
5.2.4 Reactions of Hydrogen in the Stack 89
5.3 Kinetics of Reactions in the Stack 91
5.3.1 Kinetics of Reduction of Iron Oxides by CO and H2 92
5.3.2 Kinetics of Gasification of Carbon by CO2 95
5.3.3 Kinetics of Reduction of FeO by Carbon 96
5.3.4 Direct and Indirect Reduction in the Blast Furnace 97
5.4 Reactions and Phenomena in the Blast Furnace Bosh and Hearth 99
5.4.1 Blast Furnace Slag—Composition and Viscosity 100
5.4.2 Reaction of Silicon 102
5.4.3 Reaction of Sulphur 106
5.4.4 Reactions of Manganese and Titanium 109
References 110
6. Thermal and Chemical Features of the Blast Furnace 111–125
6.1 Introduction 111
6.1.1 Mass and Heat Balances 111
6.1.2 Regionwise Heat and Mass Balances 114
6.2 Tuyere Flame Temperature 115
6.2.1 RAFT Calculations 116
6.2.2 Tuyere Coal Injection 118
6.3 Thermal and Chemical Reserve Zones 119
6.3.1 Concept of an Ideal Blast Furnace 119
6.3.2 Reichardt’s Diagram and Thermal Reserve Zone 120
6.3.3 Chemical Reserve Zone 121
6.4 The Rist Diagram 122
6.4.1 Rist Diagram Based on Oxygen Balance Only 122
6.4.2 Rist Diagram Based on Mass and Heat Balance 123
6.4.3 Rist Diagram Based on Oxygen and Heat Balance, and Fe–FeXO–Gas Equilibrium 124
References 125
7. Internal Zones and Gas Flow in Blast Furnaces 126–137
7.1 Introduction 126
7.2 The Six Internal Zones 128
7.3 Aerodynamic Features of the Granular Zone 130
7.3.1 Ergun Equation for Packed Beds 130
7.3.2 Bed Fluidisation and Elutriation 132
7.3.3 Gas Flow Through the Granular Zone of a Blast Furnace 132
7.4 Gas Flow in Wet Zones 135
7.5 Concluding Remarks 136
References 137x • Contents
8. Raw Materials I: Coke 138–156
8.1 Introduction 138
8.1.1 Availability of Coking Coal 138
8.1.2 Types of Coal Available 139
8.2 Chemical Characteristics of Coals for Cokemaking 139
8.2.1 Proximate Analysis 139
8.2.2 Ultimate Analysis 141
8.3 Petrographic Characteristics of Coals for Cokemaking 142
8.3.1 Macerals and Mineral Matter 142
8.3.2 Reflectance (Rank) of Coal 142
8.4 Other Important Characteristics 143
8.5 Selection of Coals for Cokemaking 144
8.6 Assessment of Coke Quality 146
8.6.1 Room Temperature Strength 146
8.6.2 High Temperature Characteristics 147
8.7 Processes Used for Cokemaking 148
8.7.1 Conventional By-product Coke Ovens 149
8.7.2 Non-recovery Ovens 151
8.8 Pre-carbonisation Techniques 154
8.8.1 Pre-heating of Coal 154
8.8.2 Briquette Blending of Coal 155
8.8.3 Selective Crushing of Coal 155
8.8.4 Stamp-charging 155
8.9 Alternative Coking Methods 156
References 156
9. Raw Materials II: Iron Ore and Agglomerates 157–178
9.1 Introduction 157
9.2 Occurrence of Iron Ore 157
9.2.1 Iron Ore Reserves of India 158
9.3 Beneficiation of Iron Ore 159
9.4 The Sintermaking Process 159
9.4.1 Bedding and Blending 159
9.4.2 Granulation 160
9.4.3 Sintering 161
9.4.4 Feed Preparation and Product Handling 162
9.5 Fundamentals of Sintering of Iron Ores 162
9.5.1 Sintering Phenomena 162
9.5.2 Heat Transfer during Sintering 164
9.5.3 Sinter Productivity 165
9.5.4 Structure of Sinter 166
9.5.5 Influence of Sinter Chemistry 167
9.6 Pelletisation 167
9.7 Physical and Chemical Characterisation of Lump Ore/Sinter/Pellets 170
9.7.1 Physical Testing 170
9.7.2 Chemical Characterisation 171
9.7.3 Thermal Analysis 171Contents • xi
9.8 Metallurgical Tests 172
9.8.1 Compression and Tumbler Strength 173
9.8.2 Reduction Behaviour 173
9.8.3 Reducibility 174
9.8.4 Reduction under Load 174
9.8.5 Softening–Melting Test 175
9.9 Recycling of Materials in the Blast Furnace 176
References 178
10. Blast Furnace Productivity, Fuel Efficiency and Modern
Developments 179–202
10.1 Introduction 179
10.1.1 Efficiency of Operation 180
10.2 Fundamentals of Blast Furnace Productivity 181
10.2.1 The Concept of Productivity 182
10.2.2 Specific Gas Volume Requirement 182
10.2.3 Gas Flow through the Furnace 183
10.2.4 Furnace Irregularities 184
10.3 Effect of Agglomerated Iron Oxides on Productivity 186
10.3.1 Use of Sinter 186
10.3.2 Use of Pellets in Burden 187
10.3.3 Reducibility 188
10.3.4 Reduction–Degradation Index (RDI) 190
10.3.5 Softening–Melting Characteristics 191
10.4 Coke Quality for Improved Productivity and Fuel Efficiency 192
10.5 High Top Pressure (HTP) Operation 194
10.5.1 Influence of HTP on Productivity and Fuel Efficiency 195
10.5.2 Some Other Performance Improvements through Use of HTP 196
10.6 The Bell-Less Top 197
10.7 Pulverised Coal Injection (PCI) 198
10.8 Concluding Remarks 200
References 201
11. Blast Furnace Products and Their Utilisation 203–211
11.1 Introduction 203
11.2 Composition of Hot Metal 204
11.2.1 Overall Input and Output Considerations 204
11.2.2 Silicon Control 205
11.2.3 Sulphur Control 205
11.2.4 Phosphorus Content of Hot Metal 205
11.3 Handling Hot Metal and Slag 206
11.3.1 Tapping of Hot Metal and Slag 206
11.3.2 Transportation of Hot Metal 207
11.4 Blast Furnace Slag and Its Utilisation 208
11.4.1 Slag Characteristics 208
11.4.2 Usage of Blast Furnace Slag 209
11.5 Blast Furnace Gas and Its Utilisation 209
11.5.1 Cleaning of Blast Furnace Gas 210
Reference 211xii • Contents
12. Blast Furnace Modelling and Control 212–222
12.1 Introduction 212
12.2 General Approach 212
12.3 Process Modelling 214
12.3.1 Blast Furnace Models and Their Purpose 214
12.3.2 Types of Models Available 215
12.4 Steps Involved in Mathematical Modelling 215
12.4.1 General Formulation 215
12.4.2 Identification of Framework 215
12.5 Important Process Models 217
12.5.1 Burden Distribution Model 217
12.5.2 Thermochemical Model 218
12.5.3 Model of the Raceway 219
12.5.4 Freeze-line Model of the Hearth 221
12.6 Real-time Process Simulator 222
Reference 222
Part C ALTERNATIVE IRONMAKING
13. Sponge Ironmaking 225–240
13.1 Introduction 225
13.2 Processes of Making Sponge Iron 225
13.3 Properties of Sponge Iron 226
13.4 Uses of Sponge Iron 227
13.5 Coal-based Sponge Iron Processes 228
13.5.1 Sponge Iron Production in Rotary Kilns 228
13.5.2 Coal-based Processes Using Rotary Hearth Furnaces 230
13.6 Gas-based Processes 231
13.6.1 Reforming of Natural Gas 232
13.6.2 Gas-based Direct Reduction in Fluidised Beds—Finmet Process 232
13.6.3 Gas-based Reduction in Stationary Retorts (HYL Process—Now Referred
to as HYL I) 234
13.6.4 Gas-based Shaft Furnace Processes 235
Reference 240
14. Smelting Reduction 241–262
14.1 Introduction 241
14.2 Raw Materials for Smelting Reduction 241
14.3 Fundamentals of Smelting Reduction 242
14.4 History of Smelting Reduction 244
14.4.1 The Early Stages 244
14.4.2 The Second Stage 244
14.4.3 Commercialisation of SR 244
14.5 SR Process Categorisation 245
14.5.1 Classification Based on the Number of Stages Involved 245
14.5.2 Classification Based on the Type of Furnace Used for Smelting 248Contents • xiii
14.6 Salient Features of Important SR Processes 249
14.6.1 Corex Process 249
14.6.2 Hismelt Process 254
14.6.3 Romelt Process 256
14.6.4 Finex Process 257
14.6.5 Fastmelt Process 258
14.6.6 ITmk3 259
14.6.7 Tecnored Process 260
14.7 Mini Blast Furnace 261
Reference 262
Part D STEELMAKING
15. Physical Chemistry of Primary Steelmaking 265–284
15.1 Introduction 265
15.2 Reactions and Heat Effects 266
15.3 Primary Steelmaking Slags 270
15.3.1 Phase Diagram and Activity-Composition Diagram 270
15.3.2 Other Properties of Primary Steelmaking Slags 274
15.4 The Reaction Equilibria 274
15.4.1 Introduction 274
15.4.2 Oxidation of Iron 275
15.4.3 Reactions of Carbon 275
15.4.4 Oxidation of Silicon 277
15.4.5 Reaction of Phosphorus 277
15.5 Mass Transfer and Kinetics in Steelmaking 282
References 284
16. BOF Plant Practice 285–305
16.1 Introduction 285
16.2 BOF Operation 285
16.3 BOF Shop Layout and Individual Converter Components 286
16.3.1 BOF Vessel Design and Refractory Lining 286
16.3.2 The Lance 288
16.3.3 Gas Cleaning System 288
16.3.4 Engineering Features of BOF Shops 289
16.4 Refining 290
16.5 Major Inputs for BOF Steelmaking 291
16.5.1 Hot Metal 291
16.5.2 Coolants 291
16.5.3 Flux Materials 292
16.5.4 Oxygen 292
16.6 Pre-treatment of Hot Metal Prior to Steelmaking 292
16.6.1 Objectives of Pre-treatment 293
16.6.2 Removal of Silicon 293
16.6.3 Desulphurisation 294
16.6.4 Dephosphorisation 295xiv • Contents
16.7 Reagents Used for Pre-treatment 295
16.7.1 Soda-ash 295
16.7.2 Mixture of Soda-ash and Sodium Sulphate 296
16.7.3 Mill Scale, Sinter Fines, etc. 296
16.7.4 Calcium Carbide and Magnesium Granules 296
16.7.5 Injection of Desulphurising Agents 297
16.8 Hot Metal Pre-treatment Station(s) 301
16.8.1 Desiliconisation 301
16.8.2 Desulphurisation 302
16.9 Simultaneous Removal of Sulphur and Phosphorus 303
16.10 General Comments on Pre-treatment 304
References 305
17. Metallurgical Features of Oxygen Steelmaking 306–326
17.1 Introduction 306
17.2 Interaction of the Oxygen Jet with the Surroundings and the Bath 307
17.2.1 Mechanical Interactions 307
17.2.2 Chemical Interactions between Jet and Bath 309
17.2.3 Chemical–Thermal Interactions of the Jet with the Surroundings 309
17.3 Composition and Temperature Changes During the Blow 310
17.3.1 Slag Path and Lime Dissolution in Slag 312
17.3.2 Kinetics of Lime Dissolution 312
17.4 Kinetics of Carbon–Oxygen Reaction in BOF; Slag–Metal–Gas
Interaction 313
17.4.1 Foams and Emulsions in Basic Oxygen Steelmaking 314
17.4.2 Mechanism of Carbon–Oxygen Reaction 315
17.5 Metallurgical Features of Bath Agitated Processes 316
17.5.1 General 316
17.5.2 Some Process Details 318
17.6 Oxygen Bottom Blown Processes 319
17.7 Comparison of Various Basic Oxygen Processes in Terms of
Composition Control 321
References 326
18. Process Control for Basic Oxygen Steelmaking 327–340
18.1 Introduction 327
18.1.1 Chronology of Developments 327
18.2 Mathematical Models 330
18.2.1 Static Models 330
18.2.2 Dynamic Models 332
18.3 Semi-Dynamic Control 333
18.3.1 The Sub-lance 333
18.3.2 Immersion Carbon Sensor 334
18.3.3 Immersion Oxygen Sensor 335
18.4 Dynamic Control 337
18.4.1 Measurements on Exit Gas 337
18.4.2 Application of Sonic Meter 338
18.5 Concluding Remarks 338
References 340Contents • xv
19. Basic Open Hearth and Electric Arc Furnace Steelmaking 341–361
19.1 Basic Open Hearth Steelmaking 341
19.1.1 The Open Hearth Furnace 342
19.1.2 Steelmaking in Basic Open Hearth Furnaces 344
19.1.3 Transfer of Oxygen and Heat in Open Hearth Furnaces 345
19.1.4 Concluding Remarks 346
19.2 Electric Arc Furnace Steelmaking 346
19.2.1 General 346
19.2.2 The Furnace and the Auxiliaries 347
19.2.3 Conventional EAF Steelmaking Practice 349
19.2.4 Modern Developments in EAF Steelmaking 351
19.3 Performance Assessment of EAF Steelmaking 359
19.3.1 Key Process Performance Indices 359
19.3.2 Operating Costs 360
19.3.3 Steel Quality Control in EAF 360
References 361
20. Secondary Steelmaking 362–396
20.1 Introduction 362
20.2 Inert Gas Purging (IGP) 364
20.3 Deoxidation of Liquid Steel 367
20.3.1 Thermodynamics of Deoxidation of Molten Steel 367
20.3.2 Kinetics of Deoxidation of Molten Steel 370
20.3.3 The Ladle Furnace (LF) 372
20.3.4 Problem of Slag Carryover 373
20.3.5 The CAS-OB Process 374
20.4 Degassing and Decarburisation of Liquid Steel 375
20.4.1 Thermodynamics of Degassing Reactions 375
20.4.2 Kinetics of Desorption and Absorption of Nitrogen by Liquid Steel 376
20.4.3 Vacuum Degassing Processes 377
20.4.4 Manufacture of Ultra-Low Carbon (ULC) Steel by RH-OB Process 380
20.5 Desulphurisation in Secondary Steelmaking 383
20.5.1 Thermodynamic Aspects 383
20.5.2 Kinetic Aspects 385
20.5.3 Injection Metallurgy (IM) 388
20.6 Clean Steel Technology 389
20.6.1 Introduction 389
20.6.2 Cleanliness Control during Deoxidation 389
20.6.3 Cleanliness Control during Teeming 390
20.6.4 Tundish Metallurgy for Clean Steel 391
20.7 Miscellaneous Topics 391
20.7.1 Inclusion Modification 391
20.7.2 Temperature Changes during Secondary Steelmaking 393
20.7.3 Refractories for Secondary Steelmaking 395
References 396xvi • Contents
21. Stainless Steelmaking 397–405
21.1 Introduction 397
21.2 Melting and Refining of Stainless Steels for Scrap and
Ferroalloy-Based Processes 400
21.2.1 Melting 400
21.2.2 The AOD Converter Process 400
21.2.3 Thermodynamics of Reactions in the AOD Process 401
21.3 Other Processes for Stainless Steelmaking 403
21.4 Direct Stainless Steelmaking 404
References 405
Part E CASTING OF LIQUID STEEL
22. Ingot Casting of Steel 409–422
22.1 Introduction 409
22.2 Fundamentals of Solidification 411
22.2.1 Heat Transfer and Solidification Rate in Ingot Casting 411
22.2.2 Segregation and Crystallisation during Solidification 412
22.3 Classification of Steel Ingots 416
22.3.1 Gas Generation during Freezing 416
22.3.2 Types of Ingots 417
22.4 Ingot Defects and Their Remedies 419
22.4.1 Pipe 419
22.4.2 Blow-hole 419
22.4.3 Columnar Structure Effects 420
22.4.4 Segregation 420
22.4.5 Non-metallic Inclusions 421
22.4.6 Internal Fractures and Hairline Cracks 421
22.4.7 Surface Cracks 422
References 422
23. Continuous Casting of Steel 423–447
23.1 Introduction 423
23.2 Heat Transfer and Solidification in Continuous Casting 424
23.2.1 General Considerations 424
23.2.2 Heat Transfer in the Mould 426
23.2.3 Mould Flux 428
23.2.4 Heat Transfer in Secondary Cooling Zone 429
23.3 Metallurgical Comparison of Continuous Casting with Ingot Casting 430
23.4 Modern Tundish Practice 432
23.4.1 Metallurgical Aspects 432
23.4.2 Tundish Design and Operation for Clean Steel 433
23.5 Current State of Continuous Casting Technology for Steel 434
23.5.1 General Features 434
23.5.2 The Mould and Its Operation 434
23.5.3 Electromagnetic Stirring 436Contents • xvii
23.6 Metallurgical Defects and Their Remedies 437
23.6.1 Centreline Macro-segregation and Porosity 437
23.6.2 Cracks 439
23.6.3 Other Defects 441
23.7 Some Special Topics 442
23.7.1 Round Caster and Combination Caster 442
23.7.2 High Speed Casting 443
23.8 Near-Net Shape Casting 444
23.8.1 Thin Slab Casting 445
23.8.2 Strip Casting 446
23.8.3 Beam Blank Casting 446
References 447
Part F MISCELLANEOUS
24. Ironmaking and Steelmaking in India 451–459
24.1 Introduction 451
24.2 Evolution of Global/Indian Steel 452
24.3 India’s Potential in Steel 453
24.4 Growth of the Global Steel Industry 454
24.5 Expansion Plans of Indian Steel Producers 454
24.6 Raw Materials Scenario in India 455
24.6.1 Coal for Ironmaking 455
24.6.2 Iron Ore Scenario 455
24.7 Alternative Ironmaking in India 455
24.7.1 Direct Reduction 456
24.7.2 Smelting Reduction 458
24.7.3 Mini Blast Furnaces (MBFs) 458
24.8 Structure of the Indian Steel Industry 458
24.8.1 The Future 459
24.8.2 Concluding Comments 459
References 459
Appendix I List of Major Iron and Steel Plants in India 461–462
Appendix II Supersonic Jet(s)—Relevance to BOF Steelmaking 463–466
Bibliography 467–468
Index 469–472