Effect of alumina-chrome slag with different Na2O content on the slag corrosion resistance of corundum spinel castables

Alumina-chrome (AC) slag from aluminothermic reduction has potential applications in corundum-spinel castables and can significantly lower costs. However, the stability of using AC slag remains unclear due to the fluctuating impurities such as sodium oxide. The purpose of this work is to evaluate the feasibility of using two types of AC slag with different Na₂O impurity contents in traditional corundum-spinel castables. The results indicated that the slag corrosion resistance of corundum-spinel castables is extremely sensitive to the Na₂O impurities in AC slag. AC slag with a low Na₂O content (0.29 wt%) can potentially replace tabular alumina aggregates without significantly compromising the slag corrosion resistance of the castables. Nevertheless, the slag corrosion resistance of the castables is deteriorated sharply as the Na₂O content in AC slag reaches 1.39 wt%. The dissolution of sodium oxide impurities from alumina chrome waste residual into the slag not only increases the liquid phase amount of the slag, but also decreases its viscosity at high temperatures. These changes can make the slag more aggressive towards the castables, thereby promoting the slag penetration and limiting the formation of protective layer at the interface.