To investigate the effect of magnesium on TiN liquid precipitation in titanium microalloyed steel,the steel was melted in a vacuum induction furnace.The changes in inclusion composition and size in magnesium-treated steel at different billet positions were analyzed by SEM-EDS and imaging software and were compared with untreated steel.FactSage software was used to calculate inclusion formation.The results revealed that TiN inclusions form in the liquid phase at the solidification front.Higher nitrogen content increases TiN precipitation temperature and amount,and affects Ti4C2S2 and MnS precipitation.Without magnesium treatment,the average sizes of TiN are 2.48 and 2.11 μm in the quarter and center of slab,respectively.After magnesium treatment,the sizes decrease to 1.50,1.45,1.48,and 1.38 μm,respectively,with increased number density.Traces of Mg enable the stable existence of MgO·Al2O3,serving as TiN solidification cores,aiding dispersion and reducing the formation of large-size TiN during steel cooling.
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