Optimization Of SEN Structure In Slab Continuous Casting Mold For Low Carbon Aluminium-killed Steel

Mold is the final procedure of molten steel’s solidification and a very important part of continuous casting machine in the process of continuous casting production. As the last step of purifying steel, the mold’s performance directly affects the production process of continuous casting and slab quality. The structure of submerged entry nozzle(SEN) has a great influence on flow field of molten steel in mold and its design is the key to optimize the flow field. Reasonable flow filed of molten steel in mold can accelerate inclusion floating and inhibit slag entrapment. It has important practical significance on improving molten steel purity and quality of continuous casting product.This theme took section 230mm×1930mm and section 230mm×1300mm molds as the research objects. The SEN immersion depth, bottom structure and side hole area ratio were investigated by means of physical simulation experiment to explore the influence on flow field in mold. Additionally, the numerical simulation was applied to analyze the temperature field and the flow field and to verify the results in physical simulation experiment. On this basis, the optimal parameters of SEN were determined.In physical simulation, the modeling experiments were conducted in a 1:2.3 mold model under the conditions of 230mm×1930mm and 230mm×1300mm molds with 1.20m/min and 1.35m/min casting speed, respectively. Gas flow rate was 0.10m3/h in physical modeling experiments. Through the physical simulation experimental analysis,5# SEN was confirmed as the optimum SEN and the suitable immersion depth is 57 mm to 70 mm (130mm-160mm in the prototypes). In section 230mm×1930mm mold, when the immersion depth was 57mm (120mm in the prototypes), the average wave height of surface was 0.159 cm and the impact depth was 210 mm with former 13# SEN, and there was slight slag entrapment on the surface. After using the optimum 10# SEN, the average wave height of surface dropped down to 0.142 cm and the impact depth dropped down to 190 mm at the same immersion depth, and the surface was smooth and steady with no slag entrapment phenomenon.In the numerical simulation, the impact depth of 10# SEN increased along with increasing immersion depth in section 230mm×1930mm mold. This was consistent with the results in physical simulation experiments. When the immersion depth was 130 mm, on the surface the temperature was 1787K, increasing 3K compared with the former 13# SEN. And in the lower recirculation zone the temperature was 1793K, reducing 3K compared with former 13# SEN. This was beneficial to the growth of the casting slab solidification shell. In the same conditions, the numerical simulation of inclusions with the discrete phase model indicated that when inclusion particles was injected, the inclusion removal rate of optimum 10# SEN was higher than that of former 13# SEN.