Effect of ZnO Addition on Effective Fracture Energy of Alumina-Magnesia Castable Refractory

Abstract

Alumina-magnesia castable refractory is used for the inner wall of molten steel ladle. The main cause of damage to this refractory is thermal shock caused by a sudden temperature change when putting in and out molten steel. Therefore, there is a thermal shock damage resistance coefficient R'''' as a parameter that represents the resistance of refractory materials to thermal shock, and the evaluation of effective fracture energy is important for improving R''''. The purpose of this study is to evaluate the effect of ZnO addition on the effective fracture energy of alumina-magnesia castable refractories. ZnO is reported to improve the mechanical properties of spinel (MgAl₂O₄). Samples containing 0 to 3 mass% ZnO were prepared, and the effective fracture energy, crystalline phase, microstructure, and apparent porosity were evaluated. The effective fracture energy increased with the increase of the amount of ZnO added. The apparent porosity shows a constant value regardless of the amount of ZnO added, and the promotion of spinel sintering and the increase of spinel amount by the solid solution of zinc oxide contributed to the improvement of the effective fracture energy.