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 Al 2 O 3 addition on the corrosion resistance of microporous magnesia aggregates against tundish slag is explored. The results show that the addition of nano-sized Al 2 O 3 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 Al 2 O 3 . Furthermore, MgO·Al 2 O 3 spinel is formed in situ at the grain boundaries of Al 2 O 3 -bearing aggregates and the dissolution of MgO·Al 2 O 3 spinel into molten slag damages the structure of aggregates. For the Al 2 O 3 -free microporous magnesia aggregates, as expected, the penetration of high basicity slag (CaO/SiO 2 = 9, mass ratio) into refractory is slighter than that of low basicity slag (CaO/SiO 2 = 4, mass ratio). But, for the Al 2 O 3 -bearing microporous magnesia aggregates, the corrosion of refractory by high basicity slag is severer. This is mainly because that MgO·Al 2 O 3 spinel is more unstable in high basicity slag. Therefore, it is not suitable to add nano-sized Al 2 O 3 for the preparation of microporous magnesia as tundish lining.