Corrosion of spinel clinker by CaO–Al2O3–SiO2 ladle slag

Three different grades of sintered spinel clinker were used containing 47, 69 and 94 wt.% Al2O3, respectively, i.e. MgO-rich, stoichiometric and Al2O3-rich. Based on these clinkers, the corrosion mechanism of each spinel clinker by CaO–Al2O3–SiO2 slag was investigated and the corrosion and penetration behavior of castables containing powdered spinel clinker examined. A layer of MgO·(Al, Fe)2O3 complex spinel formed at the slag-refractory interface was proportional to the MgO content of the spinel clinkers, and it depressed the slag corrosion. The free MgO and spinel minerals in each spinel clinker mainly trapped Fe2O3 from the slag. CaO–Al2O3 compounds were formed at the slag-clinker interface by the reaction between free Al2O3 in the Al2O3-spinel clinker and CaO from slag. Slag penetration into the spinel clinkers was retarded by these compounds. As a result of adding fine spinel powder to the matrix of Al2O3-based castables, it was observed that higher content of MgO in spinel clinker showed better resistance to slag corrosion but lower resistance to slag penetration.