Basic slag attack of spinel-containing refractory castables

Abstract

The better performance of spinel-containing refractory castables when in contact with basic slag is mainly associated with their higher corrosion resistance. Although the literature has shown various studies related to this subject, only few of them evaluated the overall microstructural effect on the corrosion resistance. Considering this aspect, four different compositions were produced, in order to evaluate the binder source influence (calcium aluminate cement or hydratable alumina), the silica fume addition and spinel incorporation method (in situ or pre-formed) effects. Based on the physical properties (apparent porosity, linear thermal expansion and pore size diameter distribution) and also on the phases generated (detected by SEM, before and after corrosion), a basic slag corrosion mechanism, for the set conditions, is proposed. The results pointed out that lower penetration can be attained by reducing the pore size diameters, whereas chemical corrosion resistance is a consequence of higher content of fine alumina, lower amount of calcium aluminates and the lack of liquid phase in the castable matrix. This study stresses that the castable formulation design and the proper raw material selection are of utmost importance to understand and master the performance of this class of refractory castables.