Effect of Al on the Evolution of Non-metallic Inclusions in the Mn-Si-Ti-Mg Deoxidized Steel During Solidification: Experiments and Thermodynamic Calculations

The effect of Al on the evolution of non-metallic inclusions in the Mn-Si-Ti-Mg deoxidized steels during solidification were investigated based on the experiments and thermodynamic calculations. The inclusions belonged to the MgO-TiO2-Ti2O3-Al2O3 + MnS + TiN system. In particular, the major oxide inclusion was the Mg-Ti-Al-O spinel phase of which composition was continuously changed from the Mg-Ti-O to MgAl2O4 with the concentration Al in steels. The spinel compositions calculated from thermodynamic databases are in good agreement with experimental results. TiN was only observed on the surface of MnS. MgAl2O4 aggregates were also observed at high Al concentration. In general, the evolution of inclusions is well explained by thermodynamic calculations.