The corrosion and microstructure relationship for cement-bonded spinel refractory castables

Due to the lack of studies addressing the relationship between chemical and microstructural features and the corrosion resistance of castables containing pre-formed and in situ spinel (MgAl2O4), the main aspects related to the different wear rates of these compositions when in contact with steel ladle slags have not been properly stated. Considering this scenario, this work presents the slag resistance analysis of castables designed by different spinel incorporation routes (in situ formation, pre-formed spinel addition and both). A high-iron oxide containing industrial slag was used and the results indicated that the role of the distinct CA6 (CaO·6Al2O3) distribution in the castable's microstructure before the slag attack was more relevant than the spinel ability as an ion trapper. The location of CA6 crystals in the in situ spinel-forming castable led to a suitable physico-chemical protection of both, the tabular alumina aggregates and the matrix, during the experiment. For the pre-formed spinel-containing castable, the former CA6 presence only in the matrix resulted in a high dissolution of alumina from the aggregates into the liquid during the corrosion test and a great amount of CA6 crystals was formed. Cracks were then generated and followed by further cycles of penetration and chemical reactions, which spoiled the refractory's performance.