Comparison study on effect of nano-sized Al2O3 addition on the corrosion resistance of microporous magnesia aggregates against tundish slag

Abstract The microporous magnesia aggregates show a promising application prospect as tundish lining, due to the excellent thermal insulation. In this study, the effect of nano-sized Al2O3 addition on the corrosion resistance of microporous magnesia aggregates against tundish slag is explored. The results show that the addition of nano-sized Al2O3 deteriorates the slag resistance of microporous magnesia aggregates, which is mainly because that the apparent porosity of aggregates increases with the addition of nano-sized Al2O3. Furthermore, MgO·Al2O3 spinel is formed in situ at the grain boundaries of Al2O3-bearing aggregates and the dissolution of MgO·Al2O3 spinel into molten slag damages the structure of aggregates. For the Al2O3-free microporous magnesia aggregates, as expected, the penetration of high basicity slag (CaO/SiO2 = 9, mass ratio) into refractory is slighter than that of low basicity slag (CaO/SiO2 = 4, mass ratio). But, for the Al2O3-bearing microporous magnesia aggregates, the corrosion of refractory by high basicity slag is severer. This is mainly because that MgO·Al2O3 spinel is more unstable in high basicity slag. Therefore, it is not suitable to add nano-sized Al2O3 for the preparation of microporous magnesia as tundish lining.