Effect of Casting Speed on Slag Entrainment Behaviour During Ingot Filling

Slag entrainment compromises ingot quality. Investigating its behaviour during ingot casting is crucial for enhancing product quality. In this study， a 9 t octagonal ingot was selected as the research object and a VOF（Volume of Fluid） multiphase flow model was established to systematically analyze the behaviour of molten steel filling flow fields， variations in Weber number， liquid surface fluctuations， and steel-slag interface behavior under different casting speeds. The results show that a casting speed of 20 kg/s represents the critical maximum casting speed at which slag entrainment occurs in this ingot. Below this speed， the Weber number near the central flow stream remains lower than the critical value， indicating stable flow patterns and mild surface fluctuations， with a central wave height of 0.06 m. The steel-slag interface remains stable， and slag entrainment does not occur. When the casting speed exceeds this threshold， the Weber number near the central flow stream exceeds the critical value， reducing flow stability. The height of the central surface hump and the turbulent kinetic energy of the central jet increase， raising the central wave height to about 0.08 m. The residence time of slag eye becomes longer， intensifying surface fluctuations and destabilizing the steel-slag interface. Consequently， the residual slag phase content in the molten steel increases sharply， with the residual rate rising from 0% at 15 kg/s to 74.3% at 25 kg/s.