Influence of stepped expansion of tundish capacity on molten steel flow behavior

The application of fiow control devices in continuous casting tundishes is a common strategy to extend molten steel residence time and optimize fiow and temperature fields. However, rational expansion of tundish capacity offers an alternative means to achieve comparable metallurgical benefits. To systematically investigate the effect of tundish capacity on molten steel transport characteristics, based on the adjustment of tundish longitudinal width, a novel stepwise expansion method was proposed. A six-strand T-type tundish was used as the research subject. Four geometrically scaled configu-rations with capacities ranging from 22 to 34 t were created through proportional width expansion. Computational fiuid dynamics simulations were employed to track the evolution of molten steel fiow patterns. The results demonstrated that expanding the capacity from 22 to 30 t increased the mean residence time of the molten steel from 349.14 to 626.91 s, corresponding to a 79.6% increase. The dead zone volume fraction decreased from 30.16% to 24.18%, while the surface velocity declined from 0.06399 to 0.05814 m/s. Additionally, the maximum temperature difference across strands was reduced from 2.52 to 1.39 K, representing a 45% decrease. However, the 34 t tundish exhibited reduced metallurgical performance compared with that of the 30 t design. Furthermore, when the casting speed of the 30 t tundish increased to 3.2 m/min, the mean residence time decreased by 58.26 s. However, it remained 219.51 s longer than that of the prototype tundish, and the dead zone volume fraction achieved a 5.98% reduction.