Numerical simulation on the multiphase flow and reoxidation of the molten steel in a two-strand tundish during ladle change

In the current study, a three-dimensional mathematical model was proposed to investigate the molten steel-slag-air multiphase flow in a two-strand slab continuous casting (CC) tundish during ladle change, focusing on the exposure of the molten steel and the subsequent occurrence of reoxidation. The exposure of the molten steel was calculated using the coupled realizable k-ε model, volume of fluid (VOF) model. The diffusion of dissolved oxygen was calculated by solving the user defined scalar (UDS) equation. And the user defined function (UDF) was used to define the source term in the UDS equation, determined the oxidation rate and oxidation position. The effect of the refilling speed on the molten steel exposure and dissolved oxygen content was discussed. Increasing the refilling speed during ladle change led to a reduction in both the refilling time and the exposure duration of the molten steel. However, the higher refilling speed resulted in the enlargement of slag eyes and an increase in the average dissolved oxygen content within the tundish, thereby exacerbating the reoxidation phenomenon. Additionally, the time required for the molten steel with a high dissolved oxygen content to exit the tundish varied with the refilling speed. Under refilling conditions with an inlet speed of 3.0 m/s during ladle change, the molten steel with a high dissolved oxygen content exited the outlet in a short period, reaching a maximum dissolved oxygen content of 0.000525wt%. Conversely, when the inlet speed was 1.8 m/s, the maximum dissolved oxygen content was 0.000382wt%. It was recommended to appropriately decrease the refilling speed during ladle change process to minimize reoxidation effects and enhance the quality of the steel product.