Optimization Of Flow Field Of Slab Mold Using Numerical And Physical Simulation Method

With the rapid development of continuous casting technology and increasingly high requirements on steel quality, mold metallurgy has got much more attention. Mold is the final metallurgical vessel which makes steel clean in the process of continuous casting. The fluid flow field in mold affects inclusion removal, slag entrapment, solidified shell formation and solidification structure greatly. To optimization of the flow field in mold is important for improving the quality of slab and operation performance.In the thesis, the flow field in slab mold of super-low-head continuous caster in Nanjing Steel Plant has been studied through numerical simulation by using computational fluid dynamics commercial software, FLUENT6.2.16 and physical simulation with scale factorλ=0.6. The effects of the casting speed, the structure and immersion depth of submerged entry nozzle, the eccentricity of nozzle on the flow field have been investigated, and the following conclusions are obtained.(1) It is indicated by numerical and physical simulation that for higher casting speed, the original operating parameters with submerged entry nozzle A will increase the impact of molten steel flow on mold narrow face and the depth of steel liquid flow, which cause the fluctuation of molten steel surface and slag entrapment.(2) Increasing the immersion depth of the submerged entry nozzle, the exit inclination of nozzle and the nozzle diameter is favorable to decrease the velocity and fluctuation of molten steel surface and the probability of slag entrapment, whereas increase the impact depth of molten steel flow, which is unfavorable for the shell growth and the removed of impurity and bubble.(3) The eccentricity of submerged nozzle will remarkably destroy the symmetry of the flow field, increase the fluctuation of molten steel surface and the probability of slag entrapment, destroy the uniform and symmetrical growth of shell and worsen the slab quality.(4) It is found by physical simulation that increasing the exit area of the submerged entry nozzle can improve the flow field for higher casting speed. With the nozzle immersion depth of 200mm and the optimized nozzle J, the casting speed can be increased from 1.3m/min and 1.25m/min to 1.5m/min and 1.45m/min respectively for the two slab mold (1000×180mm2 and 1200×180mm2). The structure for the prototype of submerged entry nozzle is: 50mm diameter,18°exit inclination and exit area of R=25mm and H=20mm.