Effect of partial substitution of calcium alumino-titanate for bauxite on the microstructure and properties of bauxite-SiC composite refractories

Calcium alumino-titanate (CAT) is obtained by processing titanium-iron slag in an industrial process that involves melting, homogenization, de-ironing, and silicon reduction. The correlation between CAT addition and the microstructures, phase compositions, thermo-mechanical properties, and alkali resistance of bauxite-SiC refractories were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), as well as by thermodynamic analysis. The results show that CAT can react with SiO₂ to form a low-melting-point phase (anorthite), causing the CA₆, CA₂, and CaTiO₃ phases to disappear. In addition, the formation of the liquid phase in the Al₂O₃-TiO₂-CaO-SiO₂ system at high temperatures deteriorates the properties of the composite. The strength and refractoriness under load of the composite decrease with the addition of CAT. Moreover, the thermal shock resistance of the composite first increase and then decrease with the addition of CAT. For CAT concentrations ≤10.8 wt%, the composite demonstrates good alkali resistance. The alkali resistance of the CAT-containing bauxite-SiC composite is mainly dependent on the external dense regions.