Control of inclusion composition in calcium treated aluminum killed steels

Abstract

Inclusions in slab samples with various total calcium, oxygen and sulfur content were investigated in low carbon aluminum killed steel (LCAK steel) with low sulfur content based on industrial experiments and the relationship between steel and inclusions was studied by analyzing inclusions characteristic being detected by SEM-EDS. It is found that T.Ca/T.O could better replace dissolved Ca to evaluate the extent of modification of alumina inclusions by Ca. Inclusions changed from Al2O3 based inclusions to Al2O3-CaS inclusions and finally to CaO-CaS inclusions with the increase of T.Ca/T.O in steel for slab samples and MgO and Al2O3 content in inclusions almost linearly decreased with T.Ca/T.O in steel. Increasing T.Ca/S in steel could improve the modification extent of alumina by Ca further increased CaS content of inclusions for slab samples with Al2O3-CaS inclusions. In addition, the formation mechanism of inclusions including Al2O3 based inclusions, Al2O3-CaS inclusions and CaO-CaS inclusions was discussed.