Effects of S Content on Inclusion Formation in the Al and Ti–Mg Complex Deoxidized Steel

Abstract

Two groups of Al and Ti–Mg complex deoxidized steels with different S contents are designed, and inclusion characteristics of two groups of steel samples are observed by field‐emission scanning electron microscopy–energy‐dispersive spectroscopy. The results show that there are single TiS inclusions, MgAl2O4 (Al2O3)–TiS, and MgAl2O4–TiN–TiS complex inclusions in No. 1 steel (low‐sulfur content) and No. 2 steel (high‐sulfur content). However, there are also complex inclusions containing MnS in the No. 2 steel but not in No. 1 steel. In order to reveal the precipitation mechanism of MnS, equilibrium phase of inclusion from 1873 K to liquidus temperature is further analyzed, and the mass fractions of different inclusions from liquidus to solidus temperature are quantitatively calculated using the element segregation model combined with FactSage 7.2 thermodynamic software. Furthermore, the mismatch values between different crystal planes of MnS, TiS, and TiN are calculated. The results show that MnS (110) is most likely to precipitate on TiS (001), which is consistent with the observation that there is TiS–MnS interface in the complex inclusions containing MnS in No. 2 steel. This study could be helpful to the controlling sulfide precipitation in Al and Ti–Mg complex deoxidized steel.