1996 Volume 36 Issue Suppl Pages S140-S143
Inclusions of CaO-SiO2-Al2O3-MgO-TiO2 in type 304 stainless steel were found to be formed by Al and Ti deoxidation on nucleation sites of suspended AOD slag droplets in molten steel. The crystallized phases in inclusions, i.e., MgO·Al2O3 spinel, CaO·TiO2 (perovskite) and TiO2 (rutile), showed very high melting temperature and formed in parallel to the decrease in molten steel temperature. The major factors affecting MgO·Al2O3 spinel crystallization are aluminum content in steel and weight fraction of MgO in AOD slag. Also, decreasing the AOD slag basicity (%CaO/%SiO2) is the most effective way to reduce the crystallization of the harmful CaO·TiO2 phase in inclusions.