Formation Conditions of Ti2O3, MgTi2O4, Mg2TiO4, and MgAl2O4 in Ti-Mg-Al Complex Deoxidation of Molten Iron

The relationships of the compounds in the Mg-Ti-Al-O system in equilibrium with molten iron are investigated at temperatures ranging from 1873 to 1973 K, and the thermodynamic calculations are conducted in avoiding Al2O3 or spinel MgAl2O4 formation and for inclusion control. The equilibrium relations between the compounds (Mg2TiO4, MgTi2O4, or MgAl2O4) and the composition of solutes in steel are clarified. The conditions are shown that the transformation of the stable compound from Mg-Ti spinel to Mg-Al spinel occurs at Mg contents ranging from 1 to 10 ppm by mass. It is also found, on the Mg-Ti spinel, the stable compound is transformed from inverse-spinel Mg2TiO4 to normal-spinel MgTi2O4 at Ti = about 60 ppm by mass. In addition, the stable compound is transformed from MgTi2O4 to Ti2O3 at Ti about 1000 ppm by mass.