Microstructures and slag resistance of Al2O3-SiO2-SiC-C refractories

The slag resistance and microstructure of Al2O3-SiO2-SiC-C refractories using Al, Si, Si3N4, BN, B2O3 and B4C as additives were studied in both reducing and oxidizing atmospheres. The carbon content dominates the slag penetration resistance and the viscosity of the liquid phase affects the slag penetration when the carbon contents are close in reducing atmosphere. Si and Si3N4 have a negative effect on the slag penetration resistance due to indirect oxidation of carbon to form SiC. B4C and B2O3 also have a negative effect on the slag penetration resistance due to formation of a more fluid boron-containing liquid, especially B4C addition. There is no significant effect of 5 wt% Al and 5 wt% BN addition on the slag penetration resistance. Carbon and BN hardly react with the slag, and SiC partially reacts with slag to lead to the deposition of carbon, whereas corundum is readily dissolved by slag. The oxidation resistance of carbon and SiC dominate the slag resistance in oxidizing atmosphere.