Effect of Al2O3–SiO2–MnO inclusions on precipitation of MnS in Si–Mn-killed 304 stainless steels

Abstract

ABSTRACTLaboratory experiments and thermodynamic calculation were conducted to investigate the precipitation of MnS inclusions in Si–Mn-killed 304 stainless steels with various Al and S concentrations. Three types of MnS-contained inclusions were detected: MnS phase dissolved in the MnO–SiO2 inclusion, the Al2O3-rich core phase surrounded by a MnS out layer, and the individual MnS. In steel with less than 0.001% Al, the liquid SiO2–MnO-rich inclusions can hardly influence the precipitation of MnS inclusions during the cooling process of 304 stainless steels. With the increase of Al in steel, more solid Al2O3-rich inclusions are formed, which can act as nucleation agents for MnS inclusions and dramatically promote the precipitation of MnS inclusions during the cooling process of Si–Mn-killed 304 stainless steels.