Prediction of the effect of additives on slag resistance of Al2O3---SiO2---SiC---C bond phases in air

A comparison is made of predictions of the structural evolution of Al2O3---SiO2---SiC---C refractories during firing and under slag attack made with the FACT computation package, and experimental observations including the development of a decarburised zone, relative wear of different materials and phases present as determined by microstructural and X-ray examination. The corrosion tests were carried out under oxidising conditions and with slags both containing and free of iron oxide. Two different base refractory compositions were used, one containing clay and one without. The additives considered included 5% Al, 10% Si, 5% B4C, 5% BN, 5%B2O3, and 15% Si3N4. Experimentally, good wear resistance was associated with the predicted content of SiC in the refractory in the as-fired condition. The most effective additives were silicon and B4C, whilst the most deleterious was B2O3. These results are interpreted in terms of the thermochemical predictions, including the variation in oxygen potential with slag attack and it is shown that the materials can be ranked in the same order as observed in the wear tests.