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TAPER PREDICTION IN SLAB AND THIN SLAB CASTING MOLDS. Claudio Ojeda Department of Mechanical Engineering University of Illinois at Urbana-Champaign October 15, 2002. Introduction. Taper plays an important role to ensure good contact and heat exchange between mold wall and shell surface. - PowerPoint PPT Presentation
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University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 1
TAPER PREDICTION IN SLAB AND THIN SLAB CASTING
MOLDS
Claudio Ojeda
Department of Mechanical Engineering University of Illinois at Urbana-Champaign
October 15, 2002
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 2
Introduction
Taper plays an important role to ensure good contact and heat exchange between mold wall and shell surface.– Shell growth uniformity
Problems– Excessive taper causes:
Narrow face wearing. Extra tensile stress causes transverse cracking. Buckling of the shell wide face, causes “gutter” and longitudinal
cracks.– Insufficient taper causes:
Breakouts in the steel shell. Bulging below mold causing subsurface longitudinal cracks.
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 3
Objectives
Calculate ideal taper including the effects of:– Shell shrinkage– Mold distortion– Flux layer thickness– Funnel extra length (thin slabs)
Investigate the effect of heat flux profile on Ideal Taper in conventional and thin slabs as affected by
– Heat flux profile– Casting speed– Steel grade– Powder type– Mold length
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 4
Model description Finite difference heat transfer and solidification model
(CON1D). 2D Finite element elastic-viscoplastic thermal-stress
model (CON2D). 1D slice-domain representing the behavior of a
longitudinal slice through the centerline of the shell moving down the mold.
Heat flux boundary condition is applied in the shell surface.
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 5
Model description
Narrow face
Wide
Shell
face
liquidsteel
Liquidsteel
SolidifyingShell
Shell surface
Insulated
Constant uAlong this edge
t
y
x
F
qx
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 6
Definition of ideal taper
Billet moldsIT= Shell shrinkage(z) – (Mold distortion(z) – Mold distortion meniscus)
Slab moldsIT= Shell shrinkage(z) – (Mold distortion(z) – Mold distortion meniscus)
– (flux thickness(z) – flux thickness meniscus)
Thin slab moldsIT= Shell shrinkage(z) – (Mold distortion(z) – Mold distortion meniscus)
– (flux thickness(z) – flux thickness meniscus) – (funnel extra length meniscus – funnel extra length(z))
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 7
Billet Mold distortion
Billet casting operating conditions Samarasekera, Brimacombe,
Ironmaking and Steel making, 1982, Vol. 9, Issue 1, pp 1-15
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DISTANCE BELOW MENISCUS (mm)
DIS
PLA
CEM
ENT
(mm
)
0 100 200 300 400 500 600 700 800 900 1000-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Total shell shrinkage strainMold distortionIdeal Taper|
0.27%C, 1.0 m/min
Mold geometrySlab width 120 mmSlab thickness 120 mmMold height 1100 mmCu plate thickness 10.15 mm
Copper propertiesThermal conductivity 360 W m-1K-1
Elastic modulus 117 GpaPoisson ratio 0.343Thermal expansion coefficient 16.0*10-6K-1
Density 8940 kg m-3
Operating conditionsPour temperature 1540 CWater slot heat transfer coefficient 35 kW m-2K-1
Water temperature, Tw 30 CAmbient temperature 25 CMeniscus level (below top mold) 100 mm
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 8
Slab Mold distortion
Mold distortion = Wide face expansion + Narrow face distortion
– Wide face expansion Transmitted by clamping forces Linearized temperatures of hot and cold plate faces
– Narrow face distortion Linearized temperatures of hot and cold plate faces Water jacket stiffness
222hotcoldhotmencoldmen
moldWFTTTTmoldwidthx
2
12
__
3xLx
Kt
ttTTx
cold
coldhotcoldhotcoldhot
NF
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 9
Validation of Thin-slab mold distortion
Thin Slab operating conditions Heat flux profile
1. Joong Kil Park, Brian G. Thomas, Indira V. Samarasekera, and U. Sok Yoon, Metallurgical and Materials Transactions B, 2002, vol. 33B, pp 425-436.
2. Joong Kil Park, Brian G. Thomas, Indira V. Samarasekera, and U. Sok Yoon, Metallurgical and Materials Transactions B, 2002, vol. 33B, pp 437-449.
Mold geometrySlab width 1260 mmSlab thickness 75 mmMold height 1000 mmCu plate thickness 60 mmWater slot depth – shallow slots 35 mmWater slot thickness 5 mmDistance between most slots 4.6 mmCopper propertiesThermal conductivity 350 W m-1K-1
Elastic modulus 115 GpaPoisson ratio 0.34Thermal expansion coefficient 17.7*10-6K-1
Density 8960 kg m-3
Operating conditionsWater slot heat transfer coefficient 38.45 kW m-2K-1
Water temperature, Tw 37.8 CAmbient temperature 35 CMeniscus level (below top mold) 100 mm
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 10
Validation of Thin-slab Mold distortion
Wide face temperature Wide face expansion
DISTANCE FROM TOP OF MOLD (mm)
WID
EFA
CE
EXP
AN
SIO
N(m
m)
0 100 200 300 400 500 600 700 800 900 1000
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Wide face expansion from Con1d resultsWide face expansion from 3D simulation
meniscus
DISTANCE BELOW TOP OF MOLD (mm)
TEM
PER
ATU
RE
(C)
0 100 200 300 400 500 600 700 800 900 10000
100
200
300
400
500
600Hot face temperatureCold face temperatureHot face linearized temperatureCold face linearized temperature
y = -0.269x + 444.17
y = -0.0495x + 116.57
meniscus
Thot
Tcold
Tref
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 11
Validation conventional slab mold distortion
Conventional Slab operating cond. Heat flux profile
B.G.Thomas, G. Li, A. Moitra and D. Habing: ISS transactions, October 1998, pp 125-143.
zq 084.09.3168.2 0.0<z<0.084m 084.058.268.2 zq 0.084<z<0.7m
Mold geometrySlab width 914 mmSlab thickness 220 mmMold height 700 mmCu plate thickness 60 mmWater slot depth – shallow slots 25 mmWater slot thickness 5 mmDistance between most slots 35 mmCopper propertiesThermal conductivity 374 W m-1K-1
Elastic modulus 117 GpaPoisson ratio 0.343Thermal expansion coefficient 17.7*10-6K-1
Density 8940 kg m-3
Operating conditionsWater slot heat transfer coefficient 35 kW m-2K-1
Water temperature, Tw 15 CAmbient temperature 35 CMeniscus level (below top mold) 84 mm
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 12
Validation conventional slab mold distortion
Wide face temperature Narrow face temperature
DISTANCE BELOW TOP OF THE MOLD (mm)
TEM
PER
ATU
RE
(C)
0 100 200 300 400 500 600 7000
50
100
150
200
250
300
Hot face temperatureCold face temperatureLinearized hot face temperatureLinearized cold face temperature
y = -0.1678x + 220.98
y = -0.032x + 59.535
Thot
Tcold
meniscus
DISTANCE BELOW TOP OF THE MOLD (mm)
TEM
PER
ATU
RE
(C)
0 100 200 300 400 500 600 7000
50
100
150
200
250
300
350
400
Hot face temperatureCold face temperatureLinearized hot face temperatureLinearized cold face temperature
y = -0.2489x + 320.42
y = -0.0769x + 95.16
Tcold
ThotTref
meniscus
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 13
Validation conventional slab mold distortion
Wide face expansion + Narrow face distortion
DISTANCE BELOW TOP OF THE MOLD (mm)
MO
LDD
ISTO
RTI
ON
(mm
)
0 100 200 300 400 500 600 700-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
Narrow face distortion calculated in the 3D simulationAnalitical calculation of the mold distortion
meniscus
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 14
Shell shrinkage
Heat flux profile– Importance of changes in meniscus area
Casting speed– Increasing casting speed increases instantaneous and average
heat flux but decreases time for shrinkage. Mold length
– For the same conditions higher mold length causes higher shrinkage
Steel grade– Differences between low, peritectic and high carbon content steels
Mold Powder composition– Differences in solidification temperature
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 15
Effect of heat flux profile Shell shrinkage controlled by heat flux profile. Higher heat flux causes more shrinkage. Shell shrinkage sensitive to minor changes specially near the
meniscus. Mean heat flux determined with*:
QG is the mean heat flux (MW/m2), is the powder viscosity at 1300 oC, (Pa-s), Tflow is the melting temperature of the mold flux (oC), Vc is the casting speed (m/min), and %C is the carbon content
– *C. Cicutti, M. Valdez and T. Perez, "Mould Thermal Evaluation in a Slab Continuous Casting Machine," 85th Steelmaking Conference, (Nashville, TE, USA), Iron and Steel Society, Inc. (USA), Vol. 85, 2002, 97-107.
2
47.019.109.06
027.0%107.0exp152.011063.4 CVTQ CflowG
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 16
Effect of heat flux
DISTANCE BELOW MENISCUS (mm)
HEA
TFL
UX
(MW
/m2)
0 100 200 300 400 500 600 700 8000
1
2
3
4
5
6
Higher Meniscus heat fluxHigher mold exit heat flux
Heat flux average = 1.466 MW/m20.08%C, 1.5 m/min
DISTANCE BELOW MENISCUS (mm)
SHEL
LSH
RIN
KAG
E(m
m)
0 100 200 300 400 500 600 700 8000
1
2
3
4
5
Higher meniscus heat fluxHigher mold exit heat flux
Heat Flux Average=1.466 MW/m20.08%C, 1.5 m/min
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 17
Effect of casting speed
– Higher casting speed causes higher heat flux (more shrinkage) but less dwell time (less shrinkage).
Net effect: less shrinkage
DISTANCE-BELOW-MENISCUS(mm)
SHEL
LSU
RFA
CE
TEM
PER
ATU
RE
(C)
0 100 200 300 400 500 600 700 800
1000
1100
1200
1300
1400
1500
1.1 m/min1.5 m/min1.9 m/min
0.07%C, Flux E
TIME BELOW MENISCUS (mm)
HEA
TFL
UX
(MW
/m2 )
0 10 20 30 40 50 600
1
2
3
4
5
6
7
High heat flux q=6.5(t+1)-0.5
Width: 200 mm
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 18
Effect of casting speed
DISTANCE-BELOW-MENISCUS(mm)
TOTA
LSH
ELL
SH
RIN
KAG
EST
RAI
N(%
)
0 100 200 300 400 500 600 700 8000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.1 m/min1.5 m/min1.9 m/min
0.07%C, Flux E
DISTANCE BELOW MENISCUS (mm)
SH
ELL
THIC
KNE
SS(m
m)
0 100 200 300 400 500 600 700 8000
2
4
6
8
10
12
14
16
18
1.1 m/min1.5 m/min1.9 m/min
0.07%C, Flux E
Width: 200 mmWidth: 200 mm
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 19
Effect of casting speed
Effect of casting speed on Ideal taper
DISTANCE BELOW MENISCUS (mm)
IDE
AL
TAP
ER
(%)
0 100 200 300 400 500 600 700 800-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.1 m/min1.5 m/min1.9 m/min
0.07%C, Flux E
Width: 200 mm
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 20
Effect of casting speed
Peritectic steels High carbon steels
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DISTANCE BELOW MENISCUS (mm)
IDE
ALTA
PER
(%)
0 100 200 300 400 500 600 700 800-0.1
0
0.10.2
0.3
0.4
0.5
0.6
0.70.8
0.9
11.1
1.21.31.41.5
0.27 % Carbon Content, 1.2 m/min Casting Speed0.27 % Carbon Content, 1.5 m/min Casting Speed0.47 % Carbon Content, 1.04 m/min Casting Speed0.47 % Carbon Content, 1.3 m/min Casting Speed|
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DISTANCE BELOW MENISCUS (mm)
IDE
ALTA
PER
(%)
0 100 200 300 400 500 600 700 800-0.1
0
0.10.2
0.3
0.4
0.5
0.6
0.70.8
0.9
11.1
1.21.31.41.5
0.13 % Carbon Content, 1.2 m/min Casting Speed0.13 % Carbon Content, 1.5 m/min Casting Speed0.16 % Carbon Content, 1.18 m/min Casting Speed0.16 % Carbon Content, 1.5 m/min Casting Speed|
Width: 200 mmWidth: 200 mm
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 21
Effect of casting speed
Cases 0B 1B 2B 3B 4B 5B 6B 7B 8B 9B 10B 11B 12B
Grade peritectic medium carbon medium carbon high carbonTliquidus 1527 1521 1517 1490Carbon content 0.08% 0.13% 0.16% 0.27% 0.47%%Mn, %Si 0.42%, 0.01% .57%, .22% .87%, .14% .75%, .22%%P, %S .07%, .07% .07%, .07% .007%, .005% .018%, .007%Powder type E (220) E (220) C (666) C (666) E(220) E (220)Viscosity (Pa-s) 0.083 0.083 0.192 0.192 0.083 0.083sol. Temp ( C ) 1120 1120 1215 1215 1120 1120Casting Speed (m/min) 1.1 1.5 1.9 1.3 1.45 1.2 1.5 1.18 1.5 1.2 1.5 1.04 1.3Tundish temp (C) 1567 1555 1555 1559 1559 1542Heat Flux (MW/m2)Heat Average (MW/m2) 1.70 1.94 2.13 1.83 1.94 1.77 1.94 1.76 1.94 1.77 1.94 1.67 1.83Surf Temp (exit (C) 1016 1032 1044 1005 1010 1001 1012 1006 1018 1006 1018 972 984Shrinkage (mm) CON1D 13.18 12.36 11.74 8.98 8.68 8.30 7.84 11.03 10.47 8.64 8.16 8.09 7.17Shrinkage 50mm CON2D 2.40 1.84 1.41 2.47 2.27 2.87 2.47 2.36 1.96 1.94 1.56 1.81 1.46Shrinkage (mm) CON2D 6.80 6.29 5.92 6.98 6.81 7.42 7.08 6.79 6.44 6.29 5.96 6.05 5.73Taper (%/mold) CON2D 1.36 1.26 1.18 1.40 1.36 1.48 1.42 1.36 1.29 1.26 1.19 1.21 1.15Flux layer (mm) 1.47 1.25 1.14 1.39 1.33 2.34 2.07 2.23 1.91 1.99 1.76 1.99 1.76Mold distortion+expansion (mm) -0.43 -0.55 -0.65 -0.49 -0.55 -0.46 -0.55 -0.46 -0.55 -0.46 -0.55 -0.41 -0.49Ideal NF (mm) 5.70 5.60 5.45 6.05 6.05 5.55 5.55 5.00 5.10 4.75 4.75 4.50 4.45Ideal NF (%) 1.14 1.12 1.09 1.21 1.21 1.11 1.11 1.00 1.02 0.95 0.95 0.90 0.89
high carbon
.3%, .03%
.01%, .007%
low carbon15270.07%
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 22
Effect of casting speed
Higher casting speed causes higher heat flux (more shrinkage) but less dwell time (less shrinkage).
Measured data of heat flux*Net effect: no change in shrinkage
*C. Cicutti, M. Valdez and T. Perez, "Mould Thermal Evaluation in a Slab Continuous Casting Machine," 85th Steelmaking Conference, (Nashville, TE, USA), Iron and Steel Society, Inc. (USA), Vol. 85, 2002, 97-107.
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X
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XX
X X X X X X X X X X X
DISTANCE BELOW MENISCUS (mm)
HEA
TFL
UX
(MW
/m2 )
0 100 200 300 400 500 600 700 8000
1
2
3
4
5
6
7
8
0.07%C, 1.1 m/min, avg q: 1.39 MW/m2
0.07%C, 1.5 m/min, avg q: 1.61 MW/m2
0.07%C, 1.9 m/min, avg q: 1.8 MW/m2
0.08%C, 1.3 m/min, avg q: 1.48 MW/m2
0.08%C, 1.45 m/min, avg q: 1.56 MW/m2|
X
Flux ESlab width: 1000 mmSlab thickness: 200 mmWorking mold length: 800 mmPouring temperature: 1567oC
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X
X
X
X
X
X
X
X
X
X
X
XX
XX
XX
X X X X X X X X X X X X
DISTANCE-BELOW-MENISCUS(mm)
TEM
PER
ATU
RE(
C)
0 100 200 300 400 500 600 700 8001100
1150
1200
1250
1300
1350
1400
1450
1500
1550
Flux E, 0.07%C, 1.1 m/minFlux E, 0.07%C, 1.5 m/minFlux E, 0.07%C, 1.9 m/minFlux E, 0.08%C, 1.3 m/minFlux E, 0.08%C, 1.45 m/min
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DISTANCE-BELOW-MENISCUS(mm)
TOTA
LSH
ELL
SHR
INKA
GE
STR
AIN
(%)
0 100 200 300 400 500 600 700 8000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
Flux E, 0.07, 1.1 m/minFlux E, 0.07, 1.5 m/minFlux E, 0.07, 1.9 m/minFlux E, 0.08, 1.3 m/minFlux E, 0.08, 1.45 m/min
|X
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 23
Effect of mold length
Mold length– For the same conditions (including heat flux), shell
shrinkage strains for different mold lengths can be approximated with the same curve
– Shell shrinkage for different mold lengths can be obtained truncating the curves at the desired working mold length
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 24
Effect of mold length
DISTANCE-BELOW-MENISCUS(mm)
TOTA
LSH
ELL
SH
RIN
KAG
ES
TRAI
N(%
)
0 100 200 300 400 500 600 700 8000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.1 m/min1.5 m/min1.9 m/min
0.07%C, Flux E
TIME BELOW MENISCUS (s)
HEA
TFL
UX
(MW
/m2 )
0 10 20 30 40 50 600
1
2
3
4
5
6
7
q=6.5(t+1)-0.5
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 25
Effect of steel grade
Steel grade effect Low carbon steels (>0.08%C)– Higher plastic strain– Higher thermal expansion
Peritectic steels (0.1%)– Deeper oscillation marks causes
lower heat flux– Higher thermal expansion– Final result the smallest shell
shrinkages High carbon steels (>0.2%)
– Shallow oscillation marks Higher heat flux
– Small inelastic strain Thermal strain
– Heat flux and shell shrinkage similar to low carbon steels
Temperature (oC)
Ther
mal
Line
arEx
pans
ion
(m/m
)
800 1000 1200 1400 1600-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
0.003%C0.044%C0.1%C0.27%C0.44%C
Reference Temperature = Solidus
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 26
Effect of steel grade
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X
XX
XX
XX
X X X X X X X X X
DISTANCE BELOW MENISCUS (mm)
HEA
TFL
UX
(MW
/m2)
0 100 200 300 400 500 600 700 8000
1
2
3
4
5
0
1
2
3
4
5
0.07%C, Flux E0.08%C, Flux E0.13%C, Flux C0.16%C, Flux C0.47%C, Flux E
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X
Casting speed: 1.5 m/min
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X
X
X
X
X
X
XX
XX X X X X X X X X X X X X X X
DISTANCE-BELOW-MENISCUS(mm)
SH
ELL
SU
RFA
CE
TEM
PER
ATU
RE
(C)
0 100 200 300 400 500 600 700 8001100
1150
1200
1250
1300
1350
1400
1450
1500
1550
0.07%C, Flux E0.08%C, Flux E0.13%C, Flux C0.16%C, Flux C0.47%C, Flux E
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X
Casting speed: 1.5 m/min
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 27
Effect of steel grade
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X
X
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XX
XX X X X X X X X X X X X X
DISTANCE-BELOW-MENISCUS(mm)
TOTA
LSH
ELL
SH
RIN
KAG
EST
RA
IN(%
)
0 100 200 300 400 500 600 700 8000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
0.07%C, Flux E0.08%C, Flux E0.13%C, Flux C0.16%C, Flux C0.47%C, Flux E
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X
Casting speed: 1.5 m/min
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XX
XX
XX
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X
DISTANCE BELOW MENISCUS (mm)
SH
ELL
THIC
KNE
SS(m
m)
0 100 200 300 400 500 600 700 8000
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0.07%C, Flux E0.08%C, Flux E0.13%C, Flux C0.16%C, Flux C0.47%C, Flux E
|
X
Casting speed: 1.5 m/min
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 28
Effect of steel grade
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XX
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X
DISTANCE BELOW MENISCUS (mm)
IDE
ALTA
PER
(%)
0 100 200 300 400 500 600 700 800-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
0.07 %C, Flux E0.08 %C, Flux E0.13 %C, Flux C0.16 %C, Flux C0.47 %C, Flux E
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X
Casting speed: 1.5 m/min
CARBON CONTENT (%)
TOTA
LSH
ELL
SH
RIN
KAG
ES
TRAI
N(%
)
0 0.1 0.2 0.3 0.4 0.50
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
Powder E, meniscus to mold exitPowder C, meniscus to mold exitPowder E, 50 mm to mold exitPowder C, 50 mm to mold exit
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 29
Effect of steel gradeGrade low carbon peritectic medium carbon medium carbon high carbonTliquidus 1527 1527 1521 1517 1490Carbon content 0.07% 0.08% 0.13% 0.16% 0.47%%Mn, %Si .3%, .03% 0.42%, 0.01% .57%, .22% .87%, .14% .75%, .22%%P, %S .01%, .007% .07%, .07% .07%, .07% .007%, .005% .018%, .007%Powder type E (220) E (220) C (666) C (666) E (220)viscosity (Pa-s) 0.083 0.083 0.192 0.192 0.083sol. Temp (C) 1120 1120 1215 1215 1120Flux comsumption rate (kg/t) 0.245 0.245 0.245 0.245 0.05Solid flux velocity ratio (V/Vc) 0.02 0.0185 0.0026 0.0091 0.009Oscilation mark depth (mm) 0.24 0.24 0.34 0.34 0.05Casting Speed (m/min) 1.5 1.5 1.5 1.5 1.5Tundish temp (C) 1567 1567 1567 1567 1567Heat flux average (MW/m2) 1.61 1.59 1.29 1.37 1.64Surf Temp (exit (C) 1126.7 1134.3 1250.2 1218 1114.7Shrinkage (mm) CON1D 9.40 5.96 3.12 6.52 4.96Shrinkage 50mm CON2D 2.73 2.62 1.43 1.33 2.31Shrinkage (mm) CON2D 6.21 6.04 3.72 3.74 4.61Taper (%/mold) CON2D 1.24 1.21 0.74 0.75 0.92Flux layer (mm) 1.30 1.31 1.98 1.97 1.51Narrow face distortion (mm) -1.54 -1.51 -1.32 -1.35 -1.71Wide face expansion (mm) 1.07 1.06 0.96 1.01 1.45Ideal NF (mm) 5.37 5.19 2.09 2.11 3.36Ideal NF (%) 1.0737 1.037 0.418 0.421 0.672
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 30
Effect of mold flux composition
Study of the effect of Powder composition in shell shrinkage– Mold powder viscosity
Slight changes in shell shrinkage
– Mold powder Solidification temperature Higher solidification temperature causes a lower heat flux
and consequently lower shell shrinkage
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 31
Effect of mold flux composition
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DISTANCE BELOW MENISCUS (mm)
IDE
ALTA
PER
(%)
0 100 200 300 400 500 600 700 800-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
Flux solidification temperature: 1040oCFlux solidification temperature: 1120oCFlux solidification temperature: 1160oCFlux solidification temperature: 1215oC|
0.07%C, 1.5 m/min
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DISTANCE-BELOW-MENISCUS(mm)
TOTA
LSH
ELL
SH
RIN
KAG
ES
TRAI
N(%
)
0 100 200 300 400 500 600 700 8000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
Flux solidification temperature: 1040oCFlux solidification temperature: 1120oCFlux solidification temperature: 1160oCFlux solidification temperature: 1215oC|
0.07%C, 1.5 m/min
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 32
Effect of mold flux compositionGrade low carbonTliquidus 1527Carbon content 0.07%%Mn, %Si .3%, .03%%P, %S .01%, .007%Powder type A (RB1 - B) C (666) D (155) E (220)viscosity (Pa-s) 0.225 0.192 0.115 0.083sol. Temp (C) 1160 1215 1040 1120Flux comsumption rate (kg/t) 0.25 0.25 0.25 0.25Solid flux velocity ratio (V/Vc) 0.008 0.015 0.011 0.020Oscillation mark depth (mm) 0.24 0.24 0.24 0.24Casting Speed (m/min) 1.5 1.5 1.5 1.5Tundish temp (C) 1567 1567 1567 1567Heat Flux average (MW/m2) 1.41 1.36 1.71 1.61Surf Temp (exit (C) 1202.1 1220 1090 1126.7Shrinkage (mm) CON1D 7.72 7.24 10.36 9.40Shrinkage 50 mm CON2D 2.12 1.88 3.08 2.73Shrinkage (mm) CON2D 4.98 4.64 6.82 6.21Taper (%/mold) CON2D 1.00 0.93 1.36 1.24Flux layer (mm) 1.59 1.73 1.12 1.30Narrow face distortion (mm) -1.36 -1.29 -1.65 -1.54Wide face expansion (mm) 0.94 0.88 1.17 1.07Ideal NF (mm) 3.81 3.32 6.15 5.37Ideal NF (%) 0.76 0.66 1.23 1.07
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 33
Conclusions
More taper is needed near the top of the mold to compensate the more shrinkage of the steel shell.
As casting speed increases, shrinkage decreases. Shell shrinkage depends mainly of the heat flux profile
which depends of the casting speed and interface conditions.
Peritectic steels generally requires smaller taper (due to the lower heat flux caused by bigger oscillation marks).
Mold powders with higher solidification temperatures require less taper (due to lower heat flux).
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 34
Extra length in Funnel
In thin slab casting there is a taper induced by the change in perimeter of the wide face, because of the funnel shape.
abaab
bbaEL 22
122 2sin
22
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 35
Extra length in funnel
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 36
Thin slab casting ideal taper
Higher casting speeds than conventional slab casting.
Funnel shape effect.IT= Shell shrinkage(z) – (Mold distortion(z) – Mold distortion meniscus) – (flux thickness(z) – flux thickness meniscus) – (funnel extra length meniscus – funnel extra length(z))
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 37
Thin slab casting conditions
Operating Conditions.
Mold geometrySlab thickness 49.78 mmMold Heigth 1100 mmCu plate thickness 121 mmFunnelFunnel width: a 1020 mmFunnel depth at top: b 60 mmFunnel heigth 750 mm
Description Carbon Content Casting Speed Mold Width Meniscus levelDifficult to cast low carbon 0.04% 4.5 m/min 1280 mm 83 mmLow Carbon 0.06% 4.7 m/min 1100 mm 83 mmApproximately Peritectic 0.074% 3.9 m/min 1020 mm 83 mmHigh Carbon 0.83% 4 m/min 1020 mm 58 mm
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 38
Thin slab casting ideal taper
Heat flux and surface temperatures
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DISTANCE BELOW MENISCUS (mm)
HEA
TFL
UX
(MW
/m2 )
0 100 200 300 400 500 600 700 800 900 10000
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0.04% C, 4.5 m/min Casting speed, 1280 mm Mold Width0.055% C, 4.7 m/min Casting speed, 1105 mm Mold Width0.074% C, 3.9 m/min Casting speed, 1020 mm Mold Width0.83% C, 3.7 m/min Casting Speed, 1021 mm Mold Width|
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DISTANCE-BELOW-MENISCUS(mm)
SHE
LLS
UR
FAC
ETE
MPE
RA
TUR
E(C
)
0 100 200 300 400 500 600 700 800 900 10001000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
0.04% C, 4.5 m/min Casting Speed, 1020 mm Mold Width0.055% C, 4.7 m/min Casting Speed, 1105 mm Mold Width0.074% C, 3.9 m/min Casting Speed, 1020 mm Mold Width0.83% C, 3.7 m/min Casting Speed, 1021 mm Mold Width|
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 39
Thin slab casting ideal taper
Solidified steel shell thickness
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DISTANCE BELOW MENISCUS (mm)
SH
ELL
THIC
KN
ESS
(mm
)
0 100 200 300 400 500 600 700 800 900 10000
1
2
3
4
5
6
7
8
9
10
0.04% C, 4.5 m/min, 1280 mm Mold Length0.055% C, 4.7 m/min, 1105 mm Mold Length0.074% C, 3.9 m/min, 1020 mm Mold Length0.83% C, 4.0 m/min, 1021 mm Mold Length|
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 40
Thin slab casting ideal taper
Difficult to cast low carbon
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DISTANCE BELOW MENISCUS (mm)
DIS
TAN
CE
(mm
)
0 100 200 300 400 500 600 700 800 900 1000-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
Steel shell shrinkageMold narrow face distortionMold flux layer thicknessFunnel extra lengthIdeal Taper|
0.04% Carbon Content, 4.5 m/min Casting Speed1280 mm Mold Width
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 41
Thin slab casting ideal taper
Common low carbon steel
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DISTANCE BELOW MENISCUS (mm)
DIS
TAN
CE
(mm
)
0 100 200 300 400 500 600 700 800 900 1000-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
Steel shell shrinkagemold narrow face distortionMold flux layer thicknessFunnel extra lengthIdeal Taper|
0.055 % Carbon Content, 4.7 m/min Casting Speed1100 mm Mold Width
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 42
Thin slab casting ideal taper
Approximately peritectic steel
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DISTANCE BELOW MENISCUS (mm)
DIS
TAN
CE
(mm
)
0 100 200 300 400 500 600 700 800 900 1000-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
Steel shell shrinkageMold narrow face distortionMold flux layer thicknessFunnel extra lengthIdeal Taper|
0.074% Carbon Content, 3.9 m/min Casting Speed1020 mm Mold Width
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 43
Thin slab casting ideal taper
High carbon steel
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DISTANCE BELOW MENISCUS (mm)
DIS
TAN
CE
(mm
)
0 100 200 300 400 500 600 700 800 900 1000-3.5
-3-2.5
-2-1.5
-1-0.5
00.5
11.5
22.5
33.5
44.5
55.5
6
Steel shell shrinkageMold distortionMold flux layer thicknessEnter-XY DataIdeal Taper|
0.83% Carbon Content, 3.7 m/min Casting Speed1020 mm Mold Width
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 44
Thin slab casting ideal taper
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DISTANCE BELOW MENISCUS (mm)
IDE
ALTA
PER
(%)
0 100 200 300 400 500 600 700 800 900 1000-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.04%C, 4.5 m/min0.055%C, 4.7 m/min0.074%C, 3.9 m/min0.83%C, 3.7 m/min|
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 45
Thin slab casting ideal taper
ResultsCase (carbon content %)
Recorded T (°C)
Recorded Heat Flux (kW/m2)
Computed T (°C)
Computed Heat Flux (kW/m2)
Suggested Taper from Calculations (%/mold)
Taper used currently (%/mould)
0.04 11.66 2732.48 9.44 2346 0.23 0.85
0.055 8.33 2310 9.79 2355 0.0 0.95
0.074 7.22 2177 8.67 2152 -0.01 0.95
0.83 7.88 2310 7.98 2149 -0.42 1.2
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 46
Thin slab casting ideal taper
Results– The shell shrinks more on the top of the mold than in
the bottom of the mold, so it is difficult to match the shrinkage of the shell shell with a linear Taper.
– Mold distortion, flux layer thickness and extra length of funnel significantly affect the Ideal taper.
– The Ideal Taper predicted is for all cases smaller than the taper used currently.
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 47
Effect of ferrostatic pressure
DISTANCE-BELOW-MENISCUS(mm)
TOTA
LSH
ELL
SHR
INK
AGE
STR
AIN
(%)
0 100 200 300 400 500 600 700 800 900 10000
0.1
0.2
0.30.4
0.5
0.6
0.7
0.8
0.9
11.1
1.2
1.3
1.41.5
1.6
Without ferrostatic pressureWidth: 120 mm with Ferrostatic pressureWidth: 200 mm with ferrostatic pressure
University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Claudio Ojeda 48
Conclusions
More taper is needed near the top of the mold, such as achieved using parabolic taper.
As casting speed increases, shrinkage decreases (for same conditions and heat flux profile).
Mold length affects the taper only by extending the nonlinear curve (for the same conditions and heat flux profile).
Mold taper depends mainly on the heat flux profile, which in turn depends on the casting speed and interface conditions (powder, steel grade, etc.).
Peritectic steels generally require slightly less taper than either low or high carbon steels, owing to their lower heat flux.
Mold powders with higher solidification temperature have lower heat flux (compared with both oil lubrication or low solidification temperature powders) and consequently have less shrinkage and less ideal taper (other conditions staying the same).
Flux layer thickness, mold distortion and extra length of funnel (thin slabs) make important contributions to Ideal Taper.