Mechanism of Alumina Adhesion to Continuous Caster Nozzle with Reoxidation of Molten Steel

Abstract

Basic experiments were conducted on the adhesion of Al₂O₃ in molten steel when molten FeO is present in the molten steel. It was found that the adhesion and coalescence of Al₂O₃ particles are promoted when molten FeO is present in the molten steel, that FeO and FeAl₂O₄ are observed in the bond between the Al₂O₃ particles, and that this observed result agrees with the pattern of Al₂O₃ adhesion to the continuous caster nozzle when the molten steel is reoxidized. Based on these experimental results, a study was made of the mechanism whereby Al₂O₃ adheres to the continuous caster nozzle when the molten steel is reoxidized. When the oxygen concentration in the molten steel is locally raised by the reoxidation of the molten steel, the adhesion force of the Al₂O₃ particles due to the liquid bridge force of the molten FeO is far greater than the adhesion force of the Al₂O₃ particles due to the van der Waals force or the surface tension of the molten steel. The adhesion of Al₂O₃ to the nozzle interface is thus considered to proceed mainly with the molten FeO serving as binder. Since the molten FeO binder changes into a solid bridge of FeAl₂O₄ in a short time, the Al₂O₃ particles adhering to the nozzle interface are considered to integrate to form a network of Al₂O₃ particles faster than possible with solid-phase sintering.