High Alumina Refractory Material with Improved Thermal Shock Resistance and Hot Properties for Hollowware

摘要

Refractory products for ingot casting normally require good thermal shock and corrosion resistance. These properties are normally achieved by Refractories of the alumina-silica systems. However, these products are based on natural raw materials which also contain some impurities, e.g. Fe_2O_3, TiO_2 and alkali that are responsible for the formation of liquid phase in critical operation conditions. In addition, the free silica present in the refractory as glassy silicate phase decreases the thermal shock and can react with Mn containing steels, which turns the refractory corrosion into a potential source of non metallic inclusions. To address these problems, a hollowware material was developed, based on a special refractory aggregate and a pure matrix, so that the thermal shock and erosion resistance were optimized together. This material, which contains 84% AI_2O_3, is characterized by a low amount of impurities. Laboratory results have shown an increase of 150°C in the RUL T05 of this material in comparison with bauxite based bricks (85% Al_2O_3). Superior thermal shock was also obtained, observed by the higher residual mechanical strength after 10 thermal cycles. This new hollowware material can be used whenever strong operational conditions take place, like high casting temperature and Mn containing steels.