Article ID: ISIJINT-2021-565
In this study, the rheological and crystallization behavior of CaO–BaO–Al2O3-based mold slags was investigated through the measurement of the viscosity-temperature relationship and the record of crystallization behavior during the continuous cooling process from 1300 to 600°C applying a modified confocal scanning laser microscopy. Variations of the viscosity, break temperature, initial crystallization temperature and crystallization phases of mold slags with the substitution of SiO2 by Al2O3 and Al2O3 by BaO at a gradient interval of 4 mass% were discussed, and crystallization parameters of average crystallization rate, Ozawa index and effective crystallization activation energy were calculated to explain the crystallization performance. The slag viscosity at 1300°C, the melting and break temperature increased with the substitution of SiO2 (16 to 0 mass%) by Al2O3 (20 to 36 mass%), while those decreased with the substitution of Al2O3 (32 to 16 mass%) by BaO (4 to 20 mass%). With the gradual substitution of SiO2 by Al2O3, the initial crystallization temperature increased from 820 to 1273°C at the cooling rate of 1°C/s, major precipitated phases gradually changed from CaF2 to CaF2, LiAlO2 and BaAl2O4, the average crystallization rate and the Ozawa index fluctuated but had the same tendency. With Al2O3 gradually replaced by BaO, the initial crystallization temperature decreased from 970 to 775°C at the cooling rate of 1°C/s, major precipitated phases changed from CaF2 to CaF2 and BaAl2O4, the crystallization rate of slags was affected by the difference of the nucleation and growth rate of different crystals.
