A mathematical model was developed to study the effects of the flow control devices and the gas curtain on the steel cleanness in a single-strand tundish. The Eulerian–Lagrangian approach was applied to investigate the bubble flow and the behavior of the non-metallic inclusions in the system. Two modelling approaches were considered: (i) one-way coupling, where the influence of the micro-inclusion on the molten steel flow is neglected; and (ii) two-way coupling, where the momentum exchange between the molten steel and the bubbles is modelled. The model verification and validation (V&V) were carried out in order to establish confidence in the model predictions. Four different tundish configurations and the effect of various parameters, such as the inclusion size, the inclusion density and the gas flow rate, were investigated at the normal casting conditions. The results show that the flow control devices and the gas curtain reduce the extent of the dead volumes in the tundish and thus enhance the removal efficiency of the inclusions. Controlling the gas stirring intensity is important for tundish operation with the aim of removing the inclusions. Theoretical analysis suggests that small bubbles are preferable to increase the inclusion removal rate in industrial operations.
Natural convection of molten steel flow in a tundish occurs due to the temperature variation of the inlet stream and heat losses through top surface and refractory walls. A computational fluid dynamics (CFD) model was applied to study the effect of thermal buoyancy on fluid flow and residence-time distribution in a single-strand tundish. The CFD model was first validated with the experimental data from a non-isothermal water model and then applied to both scale-down model and prototype. The effects of flow control devices, including weir, dam and turbulence inhibitor, were compared and analyzed. Parameter studies of different heat losses through the top surface were performed. The results show that thermal buoyancy has a significant impact on the flow pattern and temperature distributions of molten steel in the tundish. The increase of heat loss through the top surface shortens the mean residence time of molten steel in the tundish, leading to an increase in dead volume fraction and a decrease in plug flow volume fraction.
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