Tundish Technology For Clean Steel Production

Contents......Page 6
Preface......Page 12
1. Introduction......Page 14
1.1 Ingot and Continuous Casting of Steel......Page 16
1.2 The Role of Tundish in the Continuous Casting Process......Page 21
1.3 The Need for Clean Steel......Page 25
References......Page 27
2.1 Introduction......Page 30
2.2.1.1 Definition of macro inclusions......Page 31
2.2.1.2 Origins of exogenous macro inclusions......Page 32
2.2.1.3 Constitution of exogenous inclusions......Page 34
2.2.2.1 Thermodynamics of deoxidation reaction......Page 37
2.2.2.2 Sequence of oxide inclusion formation......Page 43
2.2.2.3 Primary, secondary, and tertiary inclusions......Page 47
2.2.2.5 The deoxidation process......Page 49
2.3.1 Size distribution of inclusions......Page 51
2.3.2.1 Relative deformability of inclusions during hot rolling......Page 54
2.3.2.2 Classification of inclusions by shape after deformation of steel matrix......Page 55
2.4 Influence of Inclusions on Steel Properties......Page 56
2.5 Measures to Reduce Inclusions......Page 59
2.5.1 Maximizing inclusion removal in ladle refining......Page 60
2.5.2 Minimizing pickup of macro inclusions......Page 66
2.5.3.1 The dominant mechanism of inclusion removal......Page 67
2.5.3.2 Characteristics and modeling of the formation and removal of Al2O3 clusters......Page 68
2.5.3.3 Influence of flow and temperature of melt on the removal of alumina clusters......Page 75
2.5.4.1 Design criteria for inclusion removal......Page 80
2.5.4.2 Effect of dimensions and profile of the tundish on inclusion removal......Page 83
2.5.5 Remarks on modeling......Page 86
References......Page 89
3.2 Fluid Flow Regimes......Page 92
3.3 Newton’s Law of Viscosity......Page 93
3.3.1 Viscosity......Page 95
3.4 Dimensionality of Flow......Page 96
3.5.1 Viscous or diffusive momentum transport......Page 97
3.5.2 Convective momentum transport......Page 98
3.6 Equations of Continuity and Motion......Page 99
3.7 Stokes’ Law......Page 100
3.8 Turbulent Flow......Page 101
3.8.1 The eddy size spectrum......Page 103
3.8.3 Turbulent shear stress......Page 105
3.10 Heat and Mass Transfer......Page 107
3.11 Turbulence Models......Page 108
References and Further Reading......Page 110
4.2 Stimulus-Response Techniques......Page 112
4.2.2 Pulse input and C-curve......Page 114
4.3 Characterization of Flow Systems......Page 115
4.3.1 Plug flow......Page 116
4.3.2 Well-mixed flow......Page 118
4.4 Characterization of Actual Systems......Page 120
4.4.1 Longitudinal dispersion model......Page 121
4.4.1.1 Step input and F-curve......Page 123
4.4.1.2 Pulse input and C-curve......Page 124
4.4.1.3 Closed vessel......Page 125
4.4.1.4 Open vessel......Page 126
4.4.1.6 Mean and variance of the residence time distribution......Page 127
4.4.2 Tanks-in-series model......Page 130
4.4.3 Combined or mixed models......Page 131
4.4.3.1 Active region......Page 132
4.4.3.2 Dead region......Page 133
4.4.3.3 Application of a combined model to melt flow in tundish......Page 136
4.4.3.4 An example of tundish melt flow characterization......Page 138
References......Page 140
5.1 Introduction......Page 142
5.2 Physical Modeling......Page 143
5.2.1.2 Kinematic similarity......Page 144
5.2.1.3 Dynamic similarity......Page 145
5.2.2 Similarity criteria......Page 147
5.2.3 Isothermal system......Page 149
5.2.4 Non-isothermal system......Page 155
5.2.5.1 Inclusion flotation......Page 159
5.2.6 Water modeling procedure......Page 165
5.2.7 Effect of tracer density on melt flow characterization......Page 168
5.3.1 Turbulent flow field and heat transfer......Page 172
5.3.3 Numerical solution procedure......Page 173
5.3.4 Tracer dispersion......Page 174
5.3.6 Commercial software codes......Page 175
5.4.1 Case study # 1......Page 176
5.4.2 Case study # 2......Page 177
5.4.3 Case study # 3......Page 181
References......Page 185
6.1 Introduction......Page 186
6.2 Reoxidation During Ladle to Tundish Melt Transfer......Page 187
6.3 Slag Entrainment and Sensing Technologies......Page 189
6.4 The Effect of Tundish Size......Page 194
6.5 The Effect of Flow Control Devices......Page 201
6.6 Gas Injection in Tundishes......Page 208
6.7 Role of Tundish Flux......Page 214
6.7.1 Basicity of slag......Page 218
6.7.2 Alumina dissolution rate......Page 221
6.7.3 Slag viscosity......Page 222
6.7.5 Metallic Al in tundish fluxes......Page 224
6.8 Calcium Addition......Page 225
6.9.1 Use of grade separators and strand links......Page 230
6.9.2 Casting of different grades using the same tundish......Page 234
6.10 Tundish Refractory......Page 236
6.11 Recycling of a Hot Tundish......Page 237
6.11.1 Slag crystallization and build-up......Page 240
6.11.2 Temperature drop of tundish......Page 241
6.12.1 Starting a sequence......Page 242
6.12.2 Ending a sequence......Page 245
6.13.1 Melt delivery system from the tundish to the mold......Page 248
6.13.2 Clogging of the tundish nozzle, slide plate hole, and the SEN......Page 250
6.14 Concluding Remarks......Page 254
References......Page 255
7.2 Melt Temperature Variation......Page 260
7.3 Temperature Measurement Devices......Page 265
7.4 The Need for Superheat Control......Page 268
7.5 External Heating (Plasma Systems)......Page 272
7.5.1 DC arc plasma system......Page 273
7.5.2 Mobile plasma arc system......Page 277
7.5.2.2 Mobile plasma arc generation......Page 278
7.5.3 AC arc plasma system......Page 281
7.5.3.2 Effect of gas composition and flow rate......Page 283
7.5.3.3 Cold- and hot-run trials......Page 285
7.5.3.4 Heating efficiency and temperature control......Page 286
7.6 External Heating (Induction Systems)......Page 288
7.6.1 Heating efficiency and temperature control......Page 289
7.7 External Cooling......Page 291
References......Page 293
8.1 Introduction......Page 296
8.2 Advances of the H-Shaped Tundish......Page 298
8.3 The Centrifugal Flow Tundish (CF Tundish)......Page 300
8.4 Argon Bubbling in a Tundish......Page 305
8.5 Electromagnetic Control of Melt Flow......Page 307
8.6 Tundish Heaters......Page 312
8.7 Hot Cycling with a Single Tundish Reheated Under Inert Atmosphere......Page 317
8.8 Improved Argon Shrouding of the Melt Stream from the Ladle to the Tundish......Page 320
8.9 Concluding Remarks......Page 322
References......Page 324
Subject Index......Page 326