Influence of Large-Scale Vortex Movement in Lower Recirculation Zone on Instable Flow Field in the Mold

Abstract

During continuous casting of slab, the flow field in the mold is unstable, which will lead to defects in final products. To investigate the instability of molten steel in the mold, an unsteady Reynolds-average (URAN) method is used to study the unstable flow of molten steel in the mold. The results show that the large-scale vortex movement in the lower recirculation zone is a major factor causing the instability of flow field. These vortexes change the outflow of molten steel in the lower recirculation zone. Molten steel discharging from one side of the nozzle outlet reaches a certain depth, it refluxes to the bottom of nozzle, while it discharging from the other outlet flows deep into the liquid pool. This will cause an asymmetric distribution of internal defects in the casting productions. These vortexes also affect the meniscus level fluctuations of molten steel. They change the reverse flow direction and pressure field in the lower recirculation zone, which affect the position and the angle of stream impinging on the narrow face. The paper could provide a basis for stabilizing the flow field in the mold.