Evolution of inclusions in Ti stabilized ultra low carbon steel(Ti-IF) steel

The morphologies evolution of various types of inclusions in Ti-IF steel were observed by a special depth erosion method,and the formation and evolution process were discussed.The results showed that the main inclusions were FeO·xMnO before Al deoxidization and the ratio of integrated oxygen and free oxygen was in ranged of 0.3 to 0.4.In present study,the main effect factors on the morphologies of Al;O;inclusions were [Al]/[O];（soluble aluminum divide free oxygen） and initial free oxygen;cluster Al;O;was formed easily with high free oxygen([O];) and low[Al]/[O]（blew 3 in present study）.Otherwise,the dendritic Al;O;was formed;coral-like Al;O;was the mixture of the dendrite Al;O;and spherical Al;O;.Some Al;O;·TiO;inclusions appeared because a high[Ti]concentration region existed around 70TiFe（containing 70 percent titanium） particles after 70TiFe addition.The maximum sizes of Al;O;reached 800μm when 3 min aluminum was added;as the time past,the large size Al;O;decreased significantly;the maximum size of Al;O;was blew 100μm and 50μm in calming sample and tundish sample respectively.