Continuous Casting of Steel
W. R. Irving
FInstP, MIM, CEng
CONTENTS
SUMMARY
1 INTRODUCTION
1.1 Historical background
1.2 Description of the Continuous Casting Process and the
Evolution of Machine Design
1.2.1 Brief Description and Basic Principles of the
Continuous Casting Process
1.2.2 Evolution of Machine Design
1.3 Advantages of Continuous Casting over Ingot Casting
1.3.1 Improved Yield
1.3.2 Reduced Energy Consumption
2 LIQUID STEEL SUPPLY
2.1 General details
2.2 Compositional Control
2.2.1 Carbon Removal for Low Carbon Strip Grades
2.2.2 Hydrogen Removal
2.2.3 Sulphur Removal and Control
2.2.4 Nitrogen Removal and pickup
2.2.5 Oxygen Control
2.3 Temperature Control in Ladle and Tundish
2.4 Tundish Technology
2.5 Ladle to Tundish Teeming
2.6 Tundish to Mould Teeming
3 MACHINE COMPONENTS, HEAT TRANSFER AND
STRAND SOLIDIFICATION
3.1 Mould Technology
3.1.1 Mould Design Details
3.1.1.1 Mould length
3.1.1.2 Mould Materials
3.1.1.3 Mould Oscillation
3.1.1.4 Variable Width Moulds
3.1.1.5 Moulds for twin and triple casting
3.1.2 Mould Heat Transfer
3.1.2.1 Affect of Cooling Water Flow Rate
vii
xi
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1
7
7
13
18
19
20
22
22
22
24
24
24
25
26
28
30
32
33
37
37
37
40
40
40
43
44
44
51viii Continuous Casting of Steel
3.1.2.2 Affect of Mould Lubrication 51
3.1.2.3 Affect of Carbon Content 52
3.1.2.4 Affect of Casting Speed 54
3.1.2.5 Temperature Distribution in Copper Plates 55
3.1.2.6 Heat Transfer Measurements on a
Slab Mould 55
3.2 Strand Support Systems and Secondary Cooling 58
3.2.1 Strand Support System Details for Various
Machine Types 58
3.2.1.1 Below Mould Support System for Slabs 59
3.2.1.2 Main Strand Support Systems for
Slab Casters 60
3.2.2 Secondary Cooling 62
3.2.2.1 Spray Cooling with Water Only 66
3.2.2.2 Spray Cooling with Water and Air
(Air Mist) 67
3.2.3 Roller Design and Performance 68
3.3 Strand Straightening and Strand Withdrawal 72
3.3.1 Strand straightening 72
3.3.1.1 Strand Completely Solidified 73
3.3.1.2 Straightening with a liquid core 73
3.3.1.3 Straightener design \74
3.3.2 Strand Bending 76
3.3.3 Withdrawal Units 78
3.4 Computer Simulation Models 79
3.4.1 The Strand Solidification Model 80
3.4.2 Strand Deformation Model 82
3.4.2.1 Critical Strain Levels 87
3.4.3 Roller Temperature and Deflection Models 87
4 PRODUCT REQUIREMENTS AND FACTORS AFFECTING
AS-CAST QUALITY 93
4.1 Categorisation of Final Products and the As-cast
Quality Requirements 93
4.2 Affect of Chemical, Process and Engineering Parameters on
Surface Defects 95
4.2.1 Categorisation of Surface Defects 95
4.2.2 Compositional Factors 96
4.2.2.1 Peritectic Grades 96
4.2.2.2 Grain Refined Steels 98Contents ix
4.2.2.3 Affect of Residuals such as sulphur
and phosphorus 100
4.2.3 Mould Parameters 103
4.2.3.1 Mould Level Control 105
4.2.3.2 Mould Lubrication 106
4.2.3.3 Mould Oscillation 112
4.2.4 Secondary Cooling 118
4.2.4.1 Below Mould Cooling 118
4.2.4.2 Hard and Soft Cooling for Production of
Grain Refined Steels 119
4.2.5 Machine Geometry 120
4.2.5.1 Machine Alignment 120
4.2.5.2 Strand Straightening 120
4.3 Effect of Chemical, Process and Engineering Parameters on
Internal Quality 120
4.3.1 Categorisation of Internal Defects 120
4.3.2 Casting Temperature 122
4.3.2.1 Effect on Steel Cleanness 122
4.3.2.2 Effect on Internal Structures 122
4.3.3 Electromagnetic Stirring (EMS) 129
4.3.3.1 EMS on Billet sand Blooms 130
4.3.3.2 EMS on Slabs 135
4.3.4 Compositional Factors 138
4.3.5 Machine Geometry 140
4.3.5.1 Affect on Inter Columnar Segregation 141
4.3.5.2 Affect on Centreline Segregation 143
4.3.6 Secondary Cooling 147
4.3.7 Casting Speed 149
4.4 Geometrical Defects 150
5 SPECIAL PROCESSES AND EMERGING TECHNOLOGIES 156
5.1 Horizontal Casting 158
5.2 Beam Blank Casting 162
5.3 Thin Slab Casting 165
5.4 Strip Casting 173
6 PROCESS CONTROL AND ANCILLARY EQUIPMENT 177
6.1 Automatic On-line Process Control Systems 179
6.1.1 Tundish Level Control 179
6.1.2 Automatic Mould Level Control 179
6.1.3 Secondary Cooling Water Control 182x Continuous Casting of Steel
6.1.4 Automatic Start of Casting 185
6.1.5 Automatic Mould Powder Feeding 186
6.2 On-Line Monitoring Systems 186
6.2.1 Detection of Slag from the Ladle 186
6.2.2 Continuous Tundish Temperature Measurement 187
6.2.3 Mould Thermal Monitoring (MTM) and Sticker
Breakout Prediction 188
6.2.4 Mould Oscillation Monitoring 195
6.2.5 Spray Water Monitoring 196
6.3 Off-Line Measuring Systems 196
6.3.1 Mould Geometry Measurements 196
6.3.2 Strand Condition and Spray Water
Distribution Monitoring 196
6.3.2.1 Measuring head 197
6.3.2.2 Computer Hardware 197
6.3.2.3 Computer Software 197
6.4 Quality Control Systems 197
6.4.1 On-line Hot Surface Inspection 199
6.4.2 On-line Quality Prediction Systems 201
INDEX 2051.
INDEX
Index Terms Links
A
Air ingress 33 34
Air gap formation 8 49 50
Air mist cooling 63 66 67
Argon Shrouding 33 48
Argon Stirring 24 26 28
Automation 177
mould metal level 179 182
on-line predictive grading 201
powder feeding 186
secondary cooling 182
start of casting 185
tundish metal level 179
B
Basic oxygen steelmaking (BOS) 13 16 24
Beam blanks 156 162
Bending 3 13 15 76
multi point 78
Billet and/or bloom casting 2 10 15 35
38 48 50 59
130 149
Breakout 13 41 114 193
194Index Terms Links
Break ring 158 160
Bulging 8 59 68 82
142 144
C
Calcium
aluminates 28
sulphides 28
treatment 26 27
Carbon 23 24
effect on heat transfer 53 54 97
effect on internal cracks 124 139
effect on longitudinal facial cracks 97
Casting powders 53 95 97 108
affect on heat transfer 53 107
affect on longitudinal facial cracks 95 97
Central porosity 121 127 129
Centreline segregation
macrosegregation 126 129 144
semi-macrosegregation (or’V’
segregation) 128 129 135
Chemical composition 22 95 96
aluminium 34 98 99
carbon 23 24 52 54
97 102 117 124
131 135 139 193
manganese/sulphur ratio 101 102 119 139
niobium 98 99
phosphorus 23 100
silicon 23Index Terms Links
Chemical composition (Cont.)
sulphur 23 24 25 34
100 101 102
vanadium 99
Cleanness 23 26 30
Columnar structure 121 124
Cracks
centerline 121 144
intercolumnar (or interdendritic) 121 139 142
longitudinal corner 95 151
longitudinal facial 95 97 101 103
104 111 119 150
star 95
transverse corner 95 99
transverse facial 95 99 105
triple point 121
D
Definitions
beam blanks 162
billet 2
bloom 2
cast strip 169
slab 2
thin slab 165
Dendritic structure (see columnar structure)
Deoxidation 24 25 26 33
Diagonal cracks 151Index Terms Links
Direct charging (see hot changing)
Dual spray system 67
Dummy bar 11 12 197
E
Electromagnetic brake (EMBR) 137 138
Electromagnetic stirring (EMS) 129
billets and blooms 130
horizontal casting 161 162
slabs 134
Energy 19 20 44
Equiaxed structure 121 135 136
Evolution of machine design 13 14 15
F
Ferrostatic pressure 8 58 69
Foot rolls 58 151
Free cutting steels 24
G
Grain refined steels 98 99 119
H
Hazelett process 157 166 168
Heal time (negative strip) 3 7 41 44
49 112 113 195
Heat transfer
convective 62
mould 7 44Index Terms Links
Heat transfer (Cont.)
radiative 62
secondary cooling 8 63
support rols 69 70
Horizontal casting 15 156 158
Hot charging 20 167
Hydrogen 24 32
Hydrogen-induced cracking (HIe) 137
I
Ingot casting 1 18 19 20
In-line rolling 167
Inclusions 26 27 28 48
95 96 103 121
129 136 137 138
Internal cracks 121 139 151
L
Ladle 9 10 28 32
car 9 10
changing 10
furnace 23 24 28 29
turret 9 10
Liquid core length 17 81
Liquidus temperature 81 122 136
Longitudinal facial cracks 96 97 101 103
104 119
Longitudinal corner cracks 95 151Index Terms Links
M
Mini-ingot formation 127
Mould
construction 38
cooling 8
copper 8 40 41
design 37 38
friction 13 78 160
geometry 196
heat transfer 7 37 44
length 40
lives 39
maintenance 39
materials 40 41 160
metal level control 35 105
multi stage 58
oscillation 40 41 42 48
112
oscillation monitoring 195
powders 48 53 91 95
97 107
plating 40
thermal monitoring 188
taper 43 44 49
tubular 38
twin/triple 17 44
variable width 16 43 44
Multi-nozzle system 66
Multi-roll drive 77 78Index Terms Links
N
Negative strip (or heal time) 3 7 41 44
112 113 195
Nitrogen 23 25 35 98
99
Nitrogen pick-up 25 33
Nozzle clogging 28 34
Nozzles
metering 33 35 48 182
spray 8 60 63
submerged entry 11 22 31 34
44 47 48
O
Oscillation 40 41 42 48
112
Oscillation marks 114
Ovality 150
Oxygen 26
P
Partition coefficients 140
Pinch roll unit 77
Pinholes 104 105 107 134
Plate mould 38 40
Pouring stream shrouding 9 10 32
Process control computer system 178
Production rate 16 17 44Index Terms Links
R
Rape seed oil 7 107 109
Reduction in area 98 99
Refractory materials 21 24 27 32
34
Reoxidation 27 28 33 34
103
Rhomboidity 150
Roll
alignment 85 86 141
cooling 69 70
designs 68 69 88 89
friction 78
gap measuring device 142 197 198
material 71
measurements 197
Permanent bending 69 90
Rotation transducers 197
split (or divided) 61
wear 72
S
Secondary cooling
air mist 63 67
design 65
heat flux 65
impact density 64
multi-nozzle 66 148
single nozzle 66 148
spray nozzles 8 63Index Terms Links
Secondary cooling (Cont.)
twin nozzle 66 148
water only 63 66
Segregation
centerline macrosegregation 129 140 144
intercolumnar (or interdendritic)
macrosegregation 140 142 143
microsegregation 129
negative segregation (or white
bands) 132 133
V segregation (or spot segregation) 128 135 140 144
Sequence casting 10 22
Shape defect 150 151
Sheet 135
Shrinkage cavity 121 127 129
Shrouding 9 10 11 32
tube 9 32 33
gas 11 35
Slag detection 186 187
Slag spots 104 105 106
Sliding gates 9 32 33
Slitting 17
Soft reduction 127 129 137 144
147
Solidification 11
columnar (or dendritic) structure 121 125 127 128
equiaxed structure 121 135 136
solidification constant 16
solidification model 16 18 80 184
solidification rate 16 80 81Index Terms Links
Spray Cooling (see secondary cooling)
Star cracks 96
Starting chain (see dummy bar)
Stirring systems (see electromagnetic
stirring)
Stopper rod 10
Strand
friction 78
guide section 58 59
machine cooling water 63
maintenance 61
secondary cooling 8 62
straightening 11 13 14 72
support grids, plates 59
support, slab strands 59 60 61
taper 127 129 137 144
145
walking beam supports 59
with air mist 63 67
withdrawal force 79
withdrawal 77
Straightening 11 13 14 72
continuous 75
multi point 13 75 76
single point 13 75 76
strains/strain rates 73
Strains
bulging 82
misalignment 82
straightening 73 87Index Terms Links
Strip casting 156 169
Stroke length 112 113
Submerged entry nozzle (SEN) 11 22 31 33
34 44 47 48
Sulphur 23 24 25 34
100 101 103
Superheat 121 122 125 133
136
Support rolls 8 58 68 87
Surface defects 95
T
Taper
mould 43 44 49 196
strand 127 129 137 144
145
Temperature control
ladle 28
surface 100 120 182
tundish 28
Thin slabs 156 165
Torch cutting 11 18
Transverse cracks 98 99 105 119
Tubular moulds 38
Tundish 10 30
bath level 35 179
changing on-the-fly 10
flow control 33 34 179 180
flow patterns in tundish 31
influence on cleanness 30 31Index Terms Links
Tundish (Cont.)
metering nozzles 35 182
refractory lining 32
size 30
sliding gates 33 35
stopper rods 10 31 33 34
35
weirs and dams 30
Twin and Triple casting 17 44
V
Vacuum degassing 23 24 25 26
28
V-segregation (or spot segregation) 128 135 144
Variable width mould 16 43 44
W
Walking beams 59
Water
cooling channels 37 38 50 51
impact density 64
machine 63
mould cooling 37 50 52
roll cooling 63 68 88
secondary cooling 62
sprays nozzles 8 62 148
velocity 37 38
water quality 37
Wide flange beams 162Index Terms Links
Withdrawal rolls 9 11 77 78
Withdrawal forces 79
Y
Yield 19 44
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