Physical And Numerical Simulation On Flow Field Of Bloom Continuous Casting

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 bloom and operation performance.A company plans to produce three section blooms at 350mm×320mm,350mm× 250mm,220mm×220mm. The experiment is mainly based on physical simulation and numerical simulation for different section blooms to determine reasonable processing parameters and electromagnetic stirring parameters, design appropriate nozzle structure. The main conclusions are as follows:(1) It will increase the depth of steel liquid flow for increasing casting speed. When casting speed is greater than 0.9m/s and the nozzle immersion depth is 100nim for producing section blooms at 350mm×320mm, it causes the fluctuation of molten steel surface and slag entrapment.(2) When casting speed is 0.8 m/s for producing section blooms at 350mmX 320mm, increasing the immersion depth of the submerged entry nozzle, it is favorable to decrease the fluctuation of molten steel surface, whereas increases the impact depth of molten steel flow, which is unfavorable for the removed of impurity and bubble. In order to obtain reasonable flow field, it is recommended that the immersion depth of the submerged entry nozzle controls between 80-120mm.(3) Increasing the nozzle diameter, it is not obvious impact to fluctuation of molten steel surface, but decreases the impact depth of molten steel flow.(4) When casting speed is 0.8 m/s and the nozzle immersion depth is 100mm for producing section blooms at 350mm×320mm, with the pass-through nozzle, it is small impact to fluctuation of molten steel surface, but increases the impact depth of molten steel flow. With bilateral nozzle, liquid surface is active, serious impact on the wall, and steel leakage accident happens more easily.(5) The pass-through nozzle which nozzle diameter is 45mm is used to produce section blooms at 350mm×320mm,350mmX 250mm. The pass-through nozzle which nozzle diameter is 25mm is used to produce section bloom at 220mm × 220mm(6) With electromagnetic stirring, flow filed in mold are improved obviously, the fluctuation of molten steel surface becomes more active, and decrease the impact depth of molten steel flow and ratio of equiaxial crystal, reduce the center segregation and center loose, improve the quality of bloom.(7) When casting speed is 0.8 m/s and the nozzle immersion depth is 100mm and parameters of the electromagnetic stirring are 400A and 3Hz, the maximum tangential velocity in central cross-section is 0.45m/s, which can produce enough centrifugal force and shear force to break dendrite and clean the front face of solidification. The maximum tangential velocity at free surface is 0.041 m/s, at which the fluctuation of molten steel surface is reasonable, and the molten slag is good.