Effect of TiO₂ in Refining Slag on Inclusions in Ti-Ferritic Stainless Steel

The effect of TiO₂ in the refining slag on the inclusions in Ti-containing stainless steel was investigated under laboratory conditions during Al deoxidation.The results indicate that the inclusions initial Al₂O₃ forms then change into MgO-Al₂O₃ type inclusions with the dimention of 4 μm when the top slag does not contain TiO₂.In the case of TiO₂-bearing slag,the inclusion composition is migrated firstly to the high TiO_x region,then to MgO-Al₂O₃ types.Finally,TiO₂-MgO-Al₂O₃ forms in average size of 2～3 μm.The inclusion size is decreased with the addition of TiO₂.And the presentence of TiO₂ in top slag can prevent the oxidation of Ti in molten steel by increasing the activity of TiO₂ in slag phase.Meanwhile,TiN precipitation is enhanced both in amount and size,which also lowers the Nb content around TiN.Thus,NbC participation becomes smaller then that participate in the sample refined by the slag without TiO₂.