Thermal cycle degradation of alumina-silica refractories exposed to molten Al-5Mg alloy

Abstract

In this study, degradation by so-called “Obake” , an advanced stage of an external corundum growth on alumina-silica refractory surfaces, was investigated. The Obake was successfully recreated by melting Al-5%Mg in the alumina-silica crucible under thermal cycle conditions. The thermal test temperatures were chosen at 1000°C or 1150°C. It was confirmed that internal degradation occurred by formation of spinel (MgAl2O4) where the refractory was in touch with molten Al-5Mg and by corundum growth at completely separate location that is at or in the vicinity of the melt line of the refractory surface where the following reaction would take place.