Physical And Numerical Simulation On Fluid Flow In Slab Mold For Continuous Casting

As the last vessel of purifying steel in continuous casting process, molten steel flow in slab molds has a great influence on inclusion removal, slag entrainment, formation of solidified shell and microscopic solidification structure of the slab. The structural improvement of submerged nozzle structure has important significance for improving continuous casting productivity and slab quality. The reasonable flow field makes steel surface becoming stable and prevents slag entrapment, which plays a very important role in improving the purity of the liquid steel and avoiding the slab surface defects and internal defects.The slab mold in an industrial continuous caster was token as the object for investigation in this thesis, based on the commercial software FLUENT, and the three-dimensional mathematical model for the flow in the mold was set up according to the theory of computational fluid dynamics. The flow field and the temperature field in the mold under the conditions of different technological parameter were calculated. The influence of immersion depth, section width, SEN side area on the flow field and temperature field of the molten steel in the mold were studied. The influence on the inclusion removal under different parameters was also discussed.For the mold with 230mm×1300mm and 230mm×1930mm section, the SEN structure and operation parameters were optimized at 1.3 m/min cast rate and 0.1 m3/h gas flow rate in the model molds. Under the conditions of 230mm×1300mm mold and 130mm immersion depth, the level fluctuation of the original SEN was 0.57cm, and slag entrapment phenomenon was obvious. The level fluctuation reduced to 0.38cm by using the optimum 5# SEN, the free surface is smooth and the slag entrapment phenomenon is reduced.5# SEN was reasonable at 1.3m/min casting speed, and the immersion depth of SEN was 130mm-160mm from this investigation.In the mathematical simulation, the maximum free surface flow velocity reduced from 0.5m/s to 0.4m/s in 230mm×1300mm mold, and the maximum free surface flow velocity reduced from 0.6m/s to 0.48m/s in 230mm× 1930mm mold, by using 5# SEN. The temperature of molten steel in the narrow side wall was 1790K by using 1# SEN, and the temperature reduced to 1785K by suing the 5# SEN.Behavior of inclusions in the molds was investigated with numerical simulation. The numbers of inclusions had less effect on the inclusion removal rate. The larger the diameter, the smaller density and the nearer to submerged entry nozzle wall, the easier the inclusions were removed. The smaller the immersion depth of nozzle was and the narrower the mold section was, the easier the inclusions were removed.