Slag entrainment in the mold of a continuous caster

The entrainment of slag in the mold of a continuous caster is one of the most common sources of surface and internal defects in continuously cast steel. Unfortunately, very little is understood concerning this problem. Very little work has been done to examine the effect of physical properties, geometrical factors, or operational practices on the entrainment phenomenon.; The goal of this work is to provide an understanding of the entrainment phenomenon. An explanation of the mechanism of entrainment in the mold of a continuous caster will be given. This work focuses on the determination of the operational parameters necessary to continuously cast steel without slag entrainment occurring.; Entrainment studies were conducted using water models. Silicon oil and water were used to model slag and steel respectively. Experiments were conducted in a vortexing tank, a laboratory entrainment model, a model of a billet caster, a model of a bloom caster, and a model of a slab caster.; A laser technique for the measurement of two dimensional fluid velocities was developed. The critical velocity necessary to cause entrainment was measured to be 11.6 cm/s for a silicon oil and water system. Similitude was applied to the critical velocity necessary to entrain to produce a critical velocity necessary to entrain in a slag and steel system of 45.9 cm/s.; Experiments were conducted to determine the influence of density, viscosity, and interfacial tension on the entrainment phenomenon. From this data an equation was derived to predict the critical velocity necessary to cause entrainment in immiscible fluids. This equation is validated through its comparison to the work of others.; Curves were determined to show the relationship between the physical properties of the fluids, the geometrical factors of the models, and the operational procedures used during casting. Parameters such as casting speed, submersion depth, submerged entry nozzle design, argon purging, mold level control, clogging, and slag foaming are related to each other and explained.; It is hoped that this work will produce results that when coupled with the existing mathematical models can be used to set up and operate a continuous caster more efficiently.