Corrosion resistance of alumina-magnesia castable to slag in steel ladle lining

Abstract

The corrosion resistance of alumina-magnesia castable to a basic slag was evaluated to find the highly-resistive castable composition for steel processing. Stable solid phases were CA6, alumina and spinel after firing of the castable of Al₂O₃–MgO–CaO–SiO₂ system. The slag corrosion was simulated thermodynamically for CA6, alumina, spinel and castables. The solubility of each oxide component is expected in the order of MgAl₂O₄ > CA6 > Al₂O₃ at 1600°C because of the formation of CA2 on CA6 and the formation of CA2 and CA6 on alumina, suggesting the protection of castable from slag. However, CA2 and CA6 disappear at 1800°C and the solubility changes in the order of CA6 > Al₂O₃ > MgAl₂O₄. Although the protection of castable by CA6 is also expected, the CA6 disappears at a large amount of slag and a high temperature. The solubility of castable decreases with increasing MgO/CaO ratio owing to spinel formation. The practical immersion test demonstrated the high corrosion resistance of high MgO/CaO castable against slag, exhibiting the importance of spinel formation.