Comparison of microstructure, thermo-mechanical property and corrosion resistance of bauxite-corundum refractory castables reinforced by two approaches

Abstract To achieve better performance of bauxite-corundum refractory castables in the steelmaking industry, we developed two reinforcement approaches (i.e. by removing microsilica or replacing cement with microsilica) for this refractory in this work. Besides, a comparison of their microstructures, thermo-mechanical properties and corrosion resistance was carried out. The abundant generation of liquids and big pores in the matrix is the leading cause of the lower thermo-mechanical and corrosion resistance of the conventional bauxite-corundum castable. The microsilica-free castable showed no liquids but a strong corundum-CA6 network structure in the matrix, which greatly enhanced the hot strength. Unfortunately, this refractory exhibited poor green strength because of a lower volume fraction of flowable components during preparation. Moreover, some coarse cracks were produced due to violent slag-matrix interaction. In contrast, the ultralow cement (1 wt%) castable with high microsilica content (7 wt%) not only created a stronger and more uniform corundum-mullite network but also showed excellent stability and infiltration resistance during corrosion because of its smaller pore sizes and the formation of a dense protective layer.