Effect of firing atmosphere on the microstructure and properties of Al2O3–SiC–C castables

Abstract Al2O3–SiC–C (ASC) castables were performed using brown fused alumina as aggregates, silicon carbide, white fused alumina, ultrafine α-Al2O3, microsilica, calcium aluminate cement, silicon powder and ball pitch as matrixes. Microstructural observations and analysis of the effects of firing atmosphere and Si powder addition were investigated in this paper. The results show that the strength and strain tolerance of ASC castables with Si powder addition were significantly improved, but their thermal shock resistance was slightly degraded. Compared with the samples after firing in air atmosphere, cold strength and thermal shock resistance of samples after firing in reducing atmosphere were improved, and hot strength of samples tested in reducing atmosphere was little affected by the pretreatment conditions. The difference in properties was closely related to the phase composition and microstructure of ASC castables fired in air atmosphere and reducing atmosphere. The growth process of SiC whiskers was also discussed in detail.