Effect of Physicochemical Properties of Slag on the Removal Rate of Alumina Inclusions in the Ruhrstahl-Heraeus (RH) Refining Conditions

Abstract

The effect of physicochemical properties of iron-bearing calcium aluminate (Ruhrstahl-Heraeus, RH-type) slag on the removal rate of alumina inclusions in Al-killed steel melts has been investigated by considering the interfacial reaction between steel melts and the slag layer at high temperature. The total oxygen content in the steel decreases as soon as the Fe-Al alloy is added to the steel melts. The apparent rate constant of oxygen removal reaction increases with increasing content of iron oxide and CaO/Al2O3 ratio in the slag due to a decrease in the viscosity of the slag. However, the apparent rate constant of oxygen removal reaction is not fully proportional to the physicochemical properties of the slag because the oxygen is continuously transferred from slag to bulk steel melts due to the reoxidative interfacial reaction between steel and slag melts. Alumina-rich inclusions in the steel sample were observed using scanning electron microscopy combined with automatic feature analysis to characterize the inclusions based on reaction time and slag composition. It was revealed that the inclusion removal rate, which is obtained from the decrease in the mass pct of alumina inclusion, is strongly proportional to the physicochemical properties of the slag. Furthermore, the oxygen behavior in the steel has been investigated using a computational simulation considering the inclusion removal rate as well as metal-slag chemical reaction kinetics in a commercial RH operation scale.