Effects of fine reactive alumina powders on properties of alumina-magnesia castables with TiO2 additions

The design of alumina-magnesia castables was optimized based on the action mechanism of raw materials. In this study, the effects of fine reactive alumina powders on the properties of alumina-magnesia castables with TiO2 additions were investigated. The phase composition and microstructure of castables with different contents of TiO2 and two fine reactive alumina powders were characterized by X-ray diffraction and scanning electron microscopy. The results of these studies showed that the Na2O/SiO2 ratio of reactive alumina affected on the phase evolution and properties of castables. The changes in the spinel and CA6 content and their solid solubility could account for the comprehensive effect of TiO2 and reactive alumina on the castables. The difference in the expansion of castables with 1 wt% TiO2 addition after calcination at 1350 °C was significant. The permanent linear changes and the apparent porosity of castables first increased and then decreased with increasing the calcination temperature. Castables containing reactive alumina with lower Na2O/SiO2 ratio had higher cold moduli of rupture.