Effects of Fine Alumina Addition and Sintering Temperature on Mechanical Properties of Alumina-Magnesia Monolithic Refractories

Abstract

Alumina-magnesia monolithic refractories are mainly used to line the inner wall of steel ladles. The refractories are damaged by the thermal shock while using on its wall and the spalling of them occurs. Therefore, it is very important to evaluate the thermal shock resistance of refractories. The effective fracture energy (γ_eff) is known as the parameter which affects to the thermal shock resistance. The objective of this study is to identify the effect of adding fine particles on the γ_eff. The samples were prepared by changing the fraction of fine alumina (average particle size is 3.4 µm) against coarse alumina (average particle size is 550 µm) and the effect of adding fine particles on the γ_eff was evaluated. The γ_eff was measured by Work of Fracture method. The value of γ_eff was enhanced to a maximum when the fine alumina fraction was 20-30 mass%. The reason could be explained by the apparent porosity and the roughness of the surface. Adding appropriate amount of fine alumina brought lower apparent porosity and rougher surface, leading to higher γ_eff.