Slag resistance mechanism of CaO·6Al2O3 refractory and its effect on inclusions of aluminum deoxidized steel

In order to verify the advantage of CaO·6Al2O3 (CA6)‐based refractories on the inclusions of aluminum deoxidized steel, the five refractories, CA6, alumina, spinel, and CA6‐alumina and CA6‐spinel composition refractories were prepared into crucibles, and then the laboratory smelting experiments were conducted. After experiment, the slag resistance of the crucible and the variation on inclusions in steel were characterized and discussed. A dense CaO·2Al2O3 (CA2) layer, which was produced by CA6 reacting with the slag, was distributed between the original bricklayer and the slag layer, improving the slag resistance of refractories. Meanwhile, the 12CaO·7Al2O3 (C12A7), generated by the reaction between CA2 and refining slag, would release much Ca into the molten steel. The Ca would react with inclusions to produce low melting point substance to float up and remove, contributing to the reduction of the proportion of large size inclusions. In addition, typical inclusions in steel smelted with CA6 crucible were small‐sized MgO·Al2O3 inclusions, whereas those of other crucibles are MnS–MgO·Al2O3 composite inclusions with MgO·Al2O3 as the core, implying CA6 may absorb sulfur during the smelting process.