Formation of CaO·TiO2-MgO·DAl2O3 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 CaO·TiO2-MgO·Al2O3 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.