Influence of Mg/Ti complex addition on evolution and thermodynamics of the inclusion in Al-killed steel

Abstract

To reveal the effects of magnesium and titanium on the behavior of inclusions in Al-killed steels, four types of experimental steel with different magnesium and titanium contents were prepared. Subsequently, the samples extracted from the steels were polished and analyzed by field emission scanning electron microscopy. The results show that titanium and magnesium can control efficiently the inclusions size and morphology. The number of Mg–Al–Ti–O inclusions in high-Mg and low-Ti steel was large, but their size was small. The Mg–Al–Ti–O inclusions were nearly spherical, unlike the Mg–Al–O spinel. According to the phase stability diagram, the MgO · Ti2 O3 phase is not stable, unless the ratio of log[a Mg ] and log[a Ti ] of molten steel is lower than 0.654. As for the production practice, the addition amount of magnesium and titanium should be considered simultaneously to modify inclusions in molten steel.