Inclusion Removal from Steel Casterccc.illinois.edu/s/2002_Presentations... · Fluid density...

1University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Lifeng Zhang (2002)

Inclusion Removal fromSteel Caster

Inclusion Removal fromSteel Caster

Lifeng Zhang

Department of Mechanical &. Industrial EngineeringUniversity of Illinois at Urbana-Champaign

March 10, 2002

Lifeng Zhang

Department of Mechanical &. Industrial EngineeringUniversity of Illinois at Urbana-Champaign

March 10, 2002


Acknowledgements

! Professor B.G.Thomas! Accumold! AK Steel! Allegheny Ludlum Steel! Columbus Stainless Steel! Hatch Associates! LTV Steel! Fluent Inc.! National Science Foundation! National Center for Supercomputing Applications

! Professor B.G.Thomas! Accumold! AK Steel! Allegheny Ludlum Steel! Columbus Stainless Steel! Hatch Associates! LTV Steel! Fluent Inc.! National Science Foundation! National Center for Supercomputing Applications


Objectives

! Fluid flow and inclusion clogging simulation in SEN! Fluid flow and inclusion removal from continuous

casting mold (trajectory calculation model, lumpedcollision model)

! Similarity criteria for particle motion in water and inliquid steel

! Fluid flow and inclusion clogging simulation in SEN! Fluid flow and inclusion removal from continuous

casting mold (trajectory calculation model, lumpedcollision model)

! Similarity criteria for particle motion in water and inliquid steel


Background—Review on SteelCleanliness and Inclusions

Background—Review on SteelCleanliness and Inclusions


Metallographical Microscope Observation (MMO);Image Analysis (IA);Sulfur Print;Slime (Electrolysis);Electron Beam melting (EB);Cold Crucible (CC) melting;Scanning Electron Microscopy (SEM);Electron Probe Micro Analyzer (EPMA)Optical Emission Spectrometry (OES-PDA)Mannesmann Inclusion Detection (MIDAS)Laser-Diffraction Particle Size Analyzer (LDPSA)Conventional Ultrasonic Scanning (CUS)Cone Sample ScanningFractional Thermal Decomposition (FTD)Laser Microprobe Mass Spectrometry (LAMMS)X-ray Photoelectron Spectroscopy (XPS)Auger Electron Spectroscopy (AES)Photo Scattering MethodCoulter Counter AnalysisLiquid Metal Cleanliness Analyzer (LIMCA)Ultrasonic Techniques for Liquid System

Metallographical Microscope Observation (MMO);Image Analysis (IA);Sulfur Print;Slime (Electrolysis);Electron Beam melting (EB);Cold Crucible (CC) melting;Scanning Electron Microscopy (SEM);Electron Probe Micro Analyzer (EPMA)Optical Emission Spectrometry (OES-PDA)Mannesmann Inclusion Detection (MIDAS)Laser-Diffraction Particle Size Analyzer (LDPSA)Conventional Ultrasonic Scanning (CUS)Cone Sample ScanningFractional Thermal Decomposition (FTD)Laser Microprobe Mass Spectrometry (LAMMS)X-ray Photoelectron Spectroscopy (XPS)Auger Electron Spectroscopy (AES)Photo Scattering MethodCoulter Counter AnalysisLiquid Metal Cleanliness Analyzer (LIMCA)Ultrasonic Techniques for Liquid System

Direct Evaluation Methods of Steel CleanlinessDirect Evaluation Methods of Steel Cleanliness

Total oxygen measurementNitrogen pick-upDissolved aluminum loss measurementSlag composition measurementSubmerged entry nozzle (SEN) clogging

Total oxygen measurementNitrogen pick-upDissolved aluminum loss measurementSlag composition measurementSubmerged entry nozzle (SEN) clogging

Direct MethodsDirect Methods Indirect MethodsIndirect Methods


"""" No single ideal method can evaluate steel cleanliness."""" Several methods should be coupled together"""" No single ideal method can evaluate steel cleanliness."""" Several methods should be coupled together

Steel Cleanliness EvaluationSteel Cleanliness Evaluation

1) Nippon Steel Co.: T.O measurement and EB melting for small inclusions, Slimemethod and EB-EV for large inclusions;

2) Usinor: T.O measurement with FTD, OES-PDA, IA and SEM for small inclusions,Electrolysis and MIDAS for large inclusions.

3) Baosteel: T.O measurement, Metallographical Microscope Observation, XPS, andSEM for small inclusions; Slime and SEM for large inclusions; nitrogen pickup; slagcomposition analysis.

1) Nippon Steel Co.: T.O measurement and EB melting for small inclusions, Slimemethod and EB-EV for large inclusions;

2) Usinor: T.O measurement with FTD, OES-PDA, IA and SEM for small inclusions,Electrolysis and MIDAS for large inclusions.

3) Baosteel: T.O measurement, Metallographical Microscope Observation, XPS, andSEM for small inclusions; Slime and SEM for large inclusions; nitrogen pickup; slagcomposition analysis.


Effect of Stirring Power on Steel CleanlinessEffect of Stirring Power on Steel Cleanliness

100 101 102 103 10410-3

10-2

10-1

100

KO (min - 1)

d[O]/dt=Ko [O][O]: ppmt: min

KO: min - 1

Ar gas bubblingASEA-SKF (I)ASEA-SKF (II)VOD (NK-PERM)VOD (Convent.)RH (NK-PERM)RH (Convent.)

ε (Watt/ton)

" Stirring helps to lower oxygen contents

" Too vigorous stirring is even bad for inclusion removal.

" Stirring helps to lower oxygen contents

" Too vigorous stirring is even bad for inclusion removal.


Deeper Tundish Lowers InclusionsDeeper Tundish Lowers Inclusions


-0.3 -0.2 -0.1 0 0.1 0.2 0.30

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050(m)

0.2m/s:Speed (m/s)

(m)

From the SEN clogging (N—inclusion numberindex by the methods of MIDAS)From the SEN clogging (N—inclusion numberindex by the methods of MIDAS)

Asymmetrical flow pattern in mold caused by:1) Nozzle clogging2) Turbulence

Asymmetrical flow pattern in mold caused by:1) Nozzle clogging2) Turbulence

Asymmetrical Mold Flow Pattern Lowers Steel CleanlinessAsymmetrical Mold Flow Pattern Lowers Steel Cleanliness

Stopper rodStopper rodInflowInflow

PowderPowder CloggingClogging SENSEN

CloggingCloggingMoldMold

Asymmetrical Flow PatternAsymmetrical Flow Pattern

Nar

row

face

Nar

row

face

Nar

row

face

Nar

row

face

From transient behavior of fluid flowFrom transient behavior of fluid flow


Inclusion Attachment to BubbleInclusion Attachment to Bubble

" Good for inclusion removal if bubbles float out;

" Bad for steel cleanliness if bubbles was entrapped by the solidifying shell

" Good for inclusion removal if bubbles float out;

" Bad for steel cleanliness if bubbles was entrapped by the solidifying shell

Observed inclusions number attached todifferent size bubbles for LCAK steel slabObserved inclusions number attached todifferent size bubbles for LCAK steel slab

Magnification factor: 500Magnification factor: 500

Example of inclusion captured by a bubbleExample of inclusion captured by a bubble


“Elephant skin”“Elephant skin”

Casting disruption, automatic

level control outage

Casting disruption, automatic

level control outage

Casting length (m)Casting length (m)

Number of defectsNumber of defects

Variation in cleanliness at the start of casting withaccidental disruption of automatic level controlVariation in cleanliness at the start of casting withaccidental disruption of automatic level control

The surface level change can beinduced by" Oscillation of mold" Cast speed change" Too much gas injection" Asymmetrical flow in mold

The surface level change can beinduced by" Oscillation of mold" Cast speed change" Too much gas injection" Asymmetrical flow in mold

Level Control Variations Cause DefectsLevel Control Variations Cause Defects

Trace investigation at WISCO(China): inclusions from slagentrainment in slab, 5.17% from ladleslag, 40.4% from tundish flux and13.52% from mold powder.

Trace investigation at WISCO(China): inclusions from slagentrainment in slab, 5.17% from ladleslag, 40.4% from tundish flux and13.52% from mold powder.


Inclusion Entrapment to SENLining Walls

Inclusion Entrapment to SENLining Walls


UniformInlet condition

5000Particle density (kg/m3)

10, 20, 48, 90, 200,300Particle size (diameter) (mm)

9.54 ×10-7Fluid kinetic viscosity (m2/s)

7020Fluid density (kg/m3)

0.02Casting speed (m/s)

0.0065Liquid steel flow rate (m3/s)

10Bottom well depth (mm)

15 degPort angle (down)

30Port thickness (mm)

65 × 80Port width× port height (mm × mm)

300SEN submergence depth (mm)

717SEN length (mm)

80SEN bore diameter (mm)

ValueParameters

SEN Simulation Parameters (Case C)SEN Simulation Parameters (Case C)

Random-Walk, 15000 particles each sizeInclusion motion model

k-ε two equation, FluentTurbulence


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

(m)

-0.1-0.0500.050.1

(m)

X Y

Z

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

(m)

-0.0500.05

(m)

Y

Z

X

-0.1-0.0500.050.1

(m)

-0.05

0

0.05

(m)

ZX

Y

Geometry of SEN (Case C)Geometry of SEN (Case C)


Mesh for Fluid Flow and Inclusion Motion Simulation in SENMesh for Fluid Flow and Inclusion Motion Simulation in SEN


1.501.401.301.201.101.000.900.800.700.600.500.400.300.200.100.00

speed (m/s)

1.501.401.301.201.101.000.900.800.700.600.500.400.300.200.100.00

Speed (m/s)

Velocity Distribution in SENVelocity Distribution in SEN


wall-I

wall-II

wall-III

10 1000.00

0.05

0.10

0.15

0.20

0.25

0.30

Without lift forceWalls: I II III

With lift forceWalls: I II III

Fra

ctio

nto

wal

ls

dp (µm)

Inclusion Entrapment to Walls of SENInclusion Entrapment to Walls of SEN

180000 inclusions to different places:

Nozzle Bottom: 4%

Nozzle Port Walls:10%

Nozzle bore wall: 17%

Total: 31%

Inclusions fraction towalls is independent oninclusions sizes.


Most particles are entrapped at bottom.

Nozzle Clogging SimulationNozzle Clogging Simulation


Assumptions:

1) Once inclusions collide with wall, they are entrapped;

2) Uniform clog distribution along each SEN surface;

3) Total oxygen entering nozzle is 30ppm.

Assumptions:

1) Once inclusions collide with wall, they are entrapped;

2) Uniform clog distribution along each SEN surface;

3) Total oxygen entering nozzle is 30ppm.

Estimate Clog Growth RateEstimate Clog Growth Rate

0 200 400 600 800 10000

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

Nozzle bottomNozzle Port wallNozzle bore wall

Min

imum

thic

knes

sof

clog

mat

eria

ls(m

m)

cast steel (tonne)

310]T.O[

Thickness −××

××=S

W

pρα

Thickness: m

T.O: total oxygen, ppm

W: Casting weight, tonne

α: Fraction of inclusions collide with walls

ρp: Inclusion density, 3500kg/m3

S, surface area of SEN inner walls, m2

Thickness: m

T.O: total oxygen, ppm

W: Casting weight, tonne

α: Fraction of inclusions collide with walls

ρp: Inclusion density, 3500kg/m3

S, surface area of SEN inner walls, m2

Conclusion: The current inclusion entrapment model (once collidingwith wall inclusions are entrapped) overpredict the effect ofentrapment of inclusion to SEN walls.

Conclusion: The current inclusion entrapment model (once collidingwith wall inclusions are entrapped) overpredict the effect ofentrapment of inclusion to SEN walls.


Fluid Flow and Inclusion Motionin Continuous Casting Mold

Fluid Flow and Inclusion Motionin Continuous Casting Mold


Nozzle simulation resultInlet condition

5000/2700Particle density (kg/m3)

0.5-300Particle size (diameter) (µm)




0.00325Average inlet flow rate (half mold) (m3/s)

2.55/1.3/0.25Domain height/width/thickness (m)

0.3Submergence depth (m)

26o (down)Inlet jet angle

15o (down)Nozzle angle

0.065×0.080Inlet port size ( width× height) (m × m)

ValuesParameters

Parameters for Mold (Case C)Parameters for Mold (Case C)

Escape from top surface and open bottom,trapped at narrow and wide face walls

Boundary condition for inclusions

Random walk model , by FluentInclusion motion model

k-ε, by FluentTurbulence model


X

Z

Y

0

0.5

1

1.5

2

2 .5

Dom

ain

dept

h(m

)

0 0 .1 0.2 0 .3 0 .4 0 .5 0.6

H alf m o ld w idth (m )

1 .501 .401 .301 .201 .101 .000 .900 .800 .700 .600 .500 .400 .300 .200 .100 .00

Speed (m /s)

Mesh and Velocity Vector Distribution in MoldMesh and Velocity Vector Distribution in Mold


Inclusion Removal by TrajectoryCalculation

Inclusion Removal by TrajectoryCalculation


Inclusion Size Distribution in SteelInclusion Size Distribution in Steel

Number density distributionNumber density distribution Mass fraction size distributionMass fraction size distribution

1) Total oxygen content: Mold 31.4ppm, Slab surface27.2ppm, Slab other places: 24.4ppm

2) The inclusion size distribution of tundish sample aboveoutlet is used as the mold inlet inclusion size distribution.

0 20 40 60 80 100 120 140-1

0

1

2

3

4

5

6

7 Tundish sample above outletSlab (surface 20mm)Slab (mean of innerand outer radius)

Al2O3 amount (ppm)

dp (µm)0 20 40 60 80 100 120 140

100

102

104

106

108

1010

1012

Number of Al2O3 inclusion (1/m3)

Tundish sample above outletSlab (surface 20mm)Slab (mean of innerand outer radius)

dp (µm)


0 20 40 60 80 100 120

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

dp (µm)30012249110.5

Fra

ctio

nto

top

surf

ace,

η T

time (s)

Fraction of Inclusion to Top SurfaceFraction of Inclusion to Top Surface

1) For the inclusions smaller than 50 µm, the fraction to the top surface isindependent on inclusion size, and this fraction is around 6% after40seconds.;

2) Beyond that, the removal to top surface increases with size increasing.

1) For the inclusions smaller than 50 µm, the fraction to the top surface isindependent on inclusion size, and this fraction is around 6% after40seconds.;

2) Beyond that, the removal to top surface increases with size increasing.


0 20 40 60 80 100 120

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

dp (µm)30012249110.5

Fra

ctio

nto

narr

owfa

ce,η

N

time (s)

0 20 40 60 80 100 120

0.00

0.05

0.10

0.15

0.20

0.25

0.30

dp (µm)30012249110.5

Fra

ctio

nto

wid

efa

ce,η

W

time (s)

Fraction of Inclusion to Narrow Face and Wide FaceFraction of Inclusion to Narrow Face and Wide Face

Inclusions captured by the wide face and narrow is independent on inclusion sizes.

28% inclusions are captured by narrow face, and 22% are captured by wide face.

Inclusions captured by the wide face and narrow is independent on inclusion sizes.

28% inclusions are captured by narrow face, and 22% are captured by wide face.


13.244%Remaining in domain

6.622%Wide Face

8.428%Narrow Face

1.86%Top surface

T.OFractions

T.O entering mold: 30ppmT.O entering mold: 30ppm

Inclusion Fractions by Trajectory CalculationInclusion Fractions by Trajectory Calculation


Inclusion Removal by LumpedCollision Model

Inclusion Removal by LumpedCollision Model

SNNNNdt

dN i

jjijjij

ijjiji

i −+−= ∑∑−

=−−

∞

=

1

1,

1 21 βφβφ

S is the source term for inclusion floating removalrate, which is decided by trajectory calculations.S is the source term for inclusion floating removalrate, which is decided by trajectory calculations.


0 50 100 150 20010121416182022242628303234363840

Removal to top surface and shell

Only removal to shell

Only removal to top surface

No removal

T.O

(ppm

)

t (s)

Total Oxygen as Function of Time by Collision ModelTotal Oxygen as Function of Time by Collision Model

When considering only removal to topsurface, T.O. is around 27ppm after severalhundreds seconds; When considering bothremoval to top surface and entrapment tosolidifying shell, T.O. is asymptotic to14ppm. Industrial T.O measurement of slabis 24.4ppm. Thus the real inclusion removalcurve should be between the two cases.Thus the current entrapment to solidifyingshell overpredict the inclusion removal.

When considering only removal to topsurface, T.O. is around 27ppm after severalhundreds seconds; When considering bothremoval to top surface and entrapment tosolidifying shell, T.O. is asymptotic to14ppm. Industrial T.O measurement of slabis 24.4ppm. Thus the real inclusion removalcurve should be between the two cases.Thus the current entrapment to solidifyingshell overpredict the inclusion removal.


Inclusion Size Distribution as Function of Collision ModelInclusion Size Distribution as Function of Collision Model

0 20 40 60 80 100 120 140 160 180100

103

106

109

1012t=0s

t=100sNo removalOnly removal to top surfaceOnly removal to shellRemoval to top surface and shell

Incl

usio

nnu

mbe

rde

nsity

(m-

3st

eel)

dp (µm)

31University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Lifeng Zhang (2002)Nozzle simulation result

5000

300

0.954 ×10-6

7020

0.02

0.00325

2.55/1.3/0.25

0.3

26o (down)

15o (down)

0.065××××0.080

Case C

LES simulation of nozzleInlet condition

2700/5000Particle density (kg/m3)

300Particle size (diameter) (µm)




0.00344Average inlet flow rate (half mold) (m3/s)

4.0/1.83/0.238Domain height/width/thickness (m)

0.15Submergence depth (m)

25o (down)Inlet jet angle

25o (down)Nozzle angle

0.051××××0.056Inlet port size ( width× height) (m × m)

Case AParameters

Inclusion Removal for Two CasesInclusion Removal for Two Cases

Escape from top surface and open bottom, trappedat narrow and wide face walls


Random walk model, by FluentInclusion motion model

15000Inclusions number injected



Inclusion Removal for Two CasesInclusion Removal for Two Cases

Because case C has a shorter domain height and largersubmergence depth, thus inclusions fraction to outlet (bottom) ishigher than case A. The inclusion fraction entrapped to wideface is much lower than case A. Thus, the real difference mightnot be so large.

Because case C has a shorter domain height and largersubmergence depth, thus inclusions fraction to outlet (bottom) ishigher than case A. The inclusion fraction entrapped to wideface is much lower than case A. Thus, the real difference mightnot be so large.

Inclusions density: 5000 kg/m3Inclusions density: 5000 kg/m3

top narrow wide bottom remain0

5

10

15

20

25

30

35

40

45

50

0-10s

Incl

usio

nfr

actio

nto

face

s(%

)

Case ACase C


10

20

30

40

50

60

70

0-100sCase ACase C

Incl

usio

nfr

actio

nto

face

s(%

)


Effect of Inclusion Density on Inclusion RemovalEffect of Inclusion Density on Inclusion Removal

Smaller density inclusions more easily float out to the topsurface, larger density inclusion more easily escape from bottom(outlet).

Smaller density inclusions more easily float out to the topsurface, larger density inclusion more easily escape from bottom(outlet).


5

10

15

20

25

30

35

40

45

50Inclusion density

2700 kg/m3

5000 kg/m3

0-10s

Incl

usio

nfr

actio

nto

face

s(%

)


10

20

30

40

50

60

70

0-100s

Inclusion density

2700 kg/m3

5000 kg/m3

Incl

usio

nfr

actio

nto

face

s(%

)Case ACase A


The Accuracy of the SimilarityCriterion of Stokes Velocity forthe Particle Motion in Waterand in Liquid Steel

The Accuracy of the SimilarityCriterion of Stokes Velocity forthe Particle Motion in Waterand in Liquid Steel


Simulation Parameters for Water System and Steel SystemSimulation Parameters for Water System and Steel System

[1] Yuan, Q., S.P. Vanka, and B.G. Thomas. Large Eddy Simulatios of Turbulence Flow and InclusionsTransport in Continuous Casting of Steel. Turbulence and Shear Flow Phenomena Second InternationalSymposium, June 27-29. 2001: KTH, Stockholm

[1] Yuan, Q., S.P. Vanka, and B.G. Thomas. Large Eddy Simulatios of Turbulence Flow and InclusionsTransport in Continuous Casting of Steel. Turbulence and Shear Flow Phenomena Second InternationalSymposium, June 27-29. 2001: KTH, Stockholm

LES pipe simulation results[1]Inlet condition

0.954 ×10-61.0 ×10-6Fluid kinetic viscosity (m2/s)


0.01520.0152Casting speed (m/s)

0.003440.00344Average inlet flow rate (m3/s)

0.2380.238Mold/Domain thickness (m)

1.831.83Mold/Domain width (m)

2.1522.152Mold/Domain height (m)

0.1500.150Submergence depth (m)

25o25oInlet jet angle

25o25oNozzle angle

0.051×0.0560.051×0.056Nozzle port size/ Inlet port size (x×y) (m)

Liquid SteelWater


Two holes on lower part of one wide faceOutlet

9882700Particle density (kg/m3)

3.8mm473 µm, 300 µm,200 µm

Particle size

1.0×10 - 60.954×10-6Viscosity (m2/s)

Same (The previous water model case)Mold Geometry

Water ModelSteel Caster

Escape from top surface and open bottom,reflected off walls


Random walk model, by FluentInclusion motion model

15000Inclusions number injected


Model and Parameters for Water System and Steel SystemModel and Parameters for Water System and Steel System


( )g

dV PP

s µρρ

18

2−=

VS: Stokes velocity, m/s

ρ, ρp, liquid and particle density, kg/m3

dp, particle diameter, m

µ, liquid viscosity, kg/m.s

g, gravitational acceleration, m/s2

VS: Stokes velocity, m/s

ρ, ρp, liquid and particle density, kg/m3

dp, particle diameter, m

µ, liquid viscosity, kg/m.s

g, gravitational acceleration, m/s2

Particle Stokes Terminal Rising Velocity in LiquidParticle Stokes Terminal Rising Velocity in Liquid

10-6 10-5 10-4 10-3 10-210-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Liquid steel system:

ρp=2700kg/m3

ρ=7020kg/m3

µ=0.0067kg/m.s

Water model system:

ρp=988kg/m3

ρ=998kg/m3

µ=0.001kg/m.s

Sto

kes

velo

sity

ofpa

rtic

les

(m/s

)

dp (m)


The removal fraction of the 200µm inclusion in liquid steel isalmost similar with the mentioned 3.8mm particle in watermodel.

The removal fraction of the 200µm inclusion in liquid steel isalmost similar with the mentioned 3.8mm particle in watermodel.

Comparison of Particle Removal in Water Model andLiquid Steel

Comparison of Particle Removal in Water Model andLiquid Steel

top surface outlet0

10

20

30

40

50

60

70

80

90dp=473µm, ρp=2700 kg/m3

in liquid steel (Stokes)

dp=300µm, ρp=2700 kg/m3

in liquid steel (Allen)

dp=200µm, ρp=2700 kg/m3

in liquid steel

dp=3.8mm, ρp=988 kg/m3

in water

Fra

ctio

nin

100s

(%)

0-10s 10-20s 20-30s0

10

20

30

40

50

rem

oval

frac

tion

toto

psu

rfac

e(%

)

dp=473µm, ρp=2700 kg/m3

in liquid steel (Stokes)

dp=300µm, ρp=2700 kg/m3

in liquid steel (Allen)

dp=200µm, ρp=2700 kg/m3

in liquid steel

dp=3.8mm, ρp=988 kg/m3

in water


Conclusions

1) Of inclusions entering nozzle, 31% collide with nozzle surfaces (18%with SEN walls, 4% with bottom, 9% with port walls).

2) For the inclusions smaller than 50 µm, the fraction to the top surface isindependent of inclusion size, and this fraction is around 6%. For theinclusions larger than 50 µm, their removal to top surface increaseswith increasing size.

3) Inclusion fraction captured by the wide and narrow face is independentof inclusion size.

4) 28% of inclusions are captured by narrow face, and 22% are capturedby wide face.

5) Smaller density inclusions more easily float out to the top surface,larger density inclusion more easily escape from bottom (outlet).

6) The current entrapment model at the walls overpredicts inclusionremoval.

7) Standard similarity criteria for particle motion in water model and inliquid steel (Stoke and Allen) are not accurate enough.

1) Of inclusions entering nozzle, 31% collide with nozzle surfaces (18%with SEN walls, 4% with bottom, 9% with port walls).

2) For the inclusions smaller than 50 µm, the fraction to the top surface isindependent of inclusion size, and this fraction is around 6%. For theinclusions larger than 50 µm, their removal to top surface increaseswith increasing size.

3) Inclusion fraction captured by the wide and narrow face is independentof inclusion size.

4) 28% of inclusions are captured by narrow face, and 22% are capturedby wide face.

5) Smaller density inclusions more easily float out to the top surface,larger density inclusion more easily escape from bottom (outlet).

6) The current entrapment model at the walls overpredicts inclusionremoval.

7) Standard similarity criteria for particle motion in water model and inliquid steel (Stoke and Allen) are not accurate enough.


Further Investigations

1 The transient fluid flow simulation for the steel caster mold.

2 The suitable entrapment model of inclusion to the solidifiedshell.

3 The inclusions collision and coagulation simulation and itscontribution to inclusion size growth and removal.

4 The interaction between inclusions and bubbles and itscontribution to inclusion motion (removal) from mold.

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