Prediction model for steel/slag interfacial instability in continuous casting process

Abstract

In a continuous casting process, mould powder is typically adopted to cover molten steel, which prevents liquid steel from oxidation by air, preserves heat for the top layer of liquid steel, lubricates the initial shell and so on. However, mould powder may deteriorate the quality of the final product if the entrapment of mould powder forms, which is usually caused by the instability of the steel/slag interface. In the current work, a model to predict the critical point of interfacial instability for liquid–liquid stratified flow was developed based on the Kelvin–Helmholtz instability. To prove the validity of the prediction model, a water model experiment was carried out in a rectangular container. In this experiment, oil and water were used to simulate slag and molten steel respectively. The results of the water model prove that the prediction model is correct. Applying the prediction model to a steel–slag system, the critical velocity of molten steel for mould powder entrapment is 0.463–0.541 m s− 1. When considering the most severe chemical reaction, the critical velocity decreases to 0.29 m s− 1. The lowest critical velocity of molten steel is 0.264 m s− 1 when the viscosity of the slag and steel/slag interfacial tension is extremely low.