Formation of CaO-TiO₂-MgO-Al₂O₃ dual phase inclusion in Ti stabilized stainless steel

The formation of CaO-TiO₂-MgO-Al₂O₃ dual phase inclusion in 321 stainless steel was investigated in the laboratory. The result indicated that the condition for the formation of CaOTiO₂-MgOAl₂O₃ in 321 steel is [Ca]>0.001wt%, [Ti]>0.1wt%, and [Al]>0.01wt%. The mechanism is the following: Al₂O₃ inclusion turns into CaO-Al₂O₃ after Ca-Si wire is fed into the molten steel; [Mg] is then obtained by reducing MgO in slag or crucible wall by [Al] and [Ti]; finally CaO-Al₂O₃ inclusion is changed into CaO-TiO₂-MgO-Al₂O₃ by the reaction with [Mg], [Ti], and [O] in the molten steel simultaneously.