Investigation on the Convection Pattern of Liquid Steel in the Continuous Casting Tundish by Theoretical Analysis, Water Model Experiment and CFD Simulation D. Y. Sheng Lage Jonsson Process Metallurgy Department, MEFOS, S 97125, Lulea, Sweden Tel: 0046-920-201934 Fax: 0046-920-255832 Email: sheng@mefos.se MEFOS PHOENICS User Conference

Process Introduction MEFOS Tundish Metallurgy Function of Tundish: Ladle with clean steel 40 ppm O tot Slag 20-30 ppm Stirring Shroud Stopper (Ar-bubbling) 10-20 ppm Nozzle Mould Slag+casting powder Slag+cover powder Tundish Blow-Holes (Ar+Al 2 3 ) BOF EAF BF Function of Tundish: Tradition: 1, Steel distribution vessel Modern: 2, Inclusion removal 3, Alloy trimming 4, Superheat control 5, Homogenisation Tundish Metallurgy MEFOS PHOENICS User Conference

Objective Problem Arisement MEFOS Two different opinions: The steel flow in tundish is: Objective 1, Forced Convection System? OR 2, Mixed Convection System? Thermal conditions: 1, Heat loss 2, External heating and cooling 3, Variation of inlet temperature MEFOS PHOENICS User Conference

CFD Causes to This Study ! Two different flow pattern are on my screen Is this true ? MEFOS PHOENICS User Conference

Theoretical Consideration F gl u l Gr bouyancy inertia ~ ( ) * / Re Dr 3 2 r m . T ul g s 4 74 = @ bD n b D w 00 Dimensional Anaysis: Tundish Water Model (1) Even one degree temperature difference in the tundish, buoyancy can not be ingored. (2) Water model can be used to simulate the convection pattern due to similar of this dimensionless number. MEFOS PHOENICS User Conference

Water Model Experiment 1 1 l a d l e ( 1 ) t h e r m o c o u p l e I n t e r f a c e c a m e r a 3 6 7 2 1 5 t u n d i s h ( 2 ) 1 9 4 8 M i c r o c o m p u t e r o u t l e t ( 3 ) MEFOS PHOENICS User Conference

Experimental measurements PHOENICS User Conference MEFOS Experimental measurements 50 100 150 200 250 300 350 10 15 20 25 30 35 Time, (s) Temperature, (¡æ) 7 8 Time, (s) 1 2 3 4 5 6 Temperature, (¡æ) 50 100 150 200 250 300 350 10 15 20 25 30 35 Time, (s) Temperature, (¡æ) 9 10 50 100 150 200 250 300 350 15 20 25 30 35 Temperature, (¡æ) a Time, (s) b c d

CFD Simulation MEFOS Modeling description 1. 3-D Navier-Stokes equations. 2. S tandard k- e two equations model 3. F ree surface is k ept at a fixed level. 4. Fluid flow and temperature are coupled PHOENICS 3.1, Sun Enterprise 4000, 6 CPU 350 MHz MEFOS PHOENICS User Conference

Hotter Incoming (1) MEFOS PHOENICS User Conference

Cooler Incoming (1) MEFOS PHOENICS User Conference

Schematic of flow pattern a, equal temperature inlet b, hotter inlet c, cooler inlet MEFOS PHOENICS User Conference

Verification (1) MEFOS No.6 No.10 No.9 No.4 PHOENICS User Conference 30 60 90 120 150 180 210 240 270 300 330 282 284 286 288 290 292 294 296 298 302 CFD model Physical model Temperature, (K) Time, (s) 30 60 90 120 150 180 210 240 270 300 330 282 284 286 288 290 292 294 296 298 302 CFD model Physical model Temperature, (K) Time, (s) 30 60 90 120 150 180 210 240 270 300 330 282 284 286 288 290 292 294 296 298 302 CFD model Physical model No.6 No.10 Temperature, (K) CFD model Physical model Temperature, (K) Time, (s) 30 60 90 120 150 180 210 240 270 300 330 282 284 286 288 290 292 294 296 298 302 Time, (s) No.9 No.4

Hotter Incoming (2) MEFOS PHOENICS User Conference

Cooler Incoming (2) MEFOS PHOENICS User Conference

Future work MEFOS (1) Turbulence model of the transition region (2) Use the CFD model for real tundish simulation (3) Considersing the heat loss surrounding and additional heat source (4) Time dependent inlet temperature variation will be considered. MEFOS PHOENICS User Conference

Conclusion MEFOS (1) Dimensionless number Gr/Re can be used to 2 can be used to set up thermal similarity between water model and actual tundish (2) Thermal buoyancy driven flow is obvious in the non-isothermal water model (3) CFD simulation keeps good agreement with mesurement (4) The tundish is a mixed convection system MEFOS PHOENICS User Conference