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. The relationships of the compounds in the Mg-Ti-Al-O system in equilibrium with molten iron are clarified 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. It is shown that the equilibrium relations between those compounds and the composition of solutes in steel at 1973 K.