Microstructure and enhanced slag resistance of Al2O3-SiC-C refractory castables with addition of ammonium metatungstate

The present study aims to clarify the influence of ammonium metatungstate (AMT) on composition, micro -structural evolution and properties of Al2O3-SiC-C (ASC) refractory castables. Castables with different AMT contents were prepared using brown corundum, white corundum, silicon carbide, calcium aluminate cement, and AMT as major raw materials. The results show that hot modulus of rupture, thermal shock resistance and slag resistance were significantly improved for castables with addition of AMT (lower than 1.0 wt%), due to the optimized microstructure from the formation and development of mullite and SiC whiskers in castables. Along with the in-situ formed whiskers in pores, formation of Fe7W6 from the reaction between W ions in castables and Fe ions in the penetrated molten slag led to the enhanced slag viscosity and inhibited continuous penetration (penetration index decreased from 30.5% to 20.2%) for castables with AMT ranging from 0 to 0.5 wt%. The research of this work provides a new insight into microstructure and high-temperature properties enhancement of ASC refractory castables.