Formation conditions of Mg2Ti04 and MgAI204 in Ti-Mg-AI complex deoxidation of molten iron

It is important to study the complex deoxidation equilibrium of molten iron in Ti-Mg-AI system from the view point of inclusion control. The equilibrium experiments between molten iron and TiO_x-MgO-AI₂0 ₃ slag and the thermodynamic calculation on the complex deoxidation are conducted at 1 973 K in the present study. The liquid phase region of TiO_x-MgO-AI₂0₃ system in equilibrium with molten iron is clarified at 1 973 K. The equilibrium compounds which are coexisted with the slag on the liquidus curve in the system are identified to be Mg₂Ti0₄ and MgAI₂0₄. The equilibrium relation between the deoxidation products (Mg₂Ti0 ₄ or MgAI₂0₄) and the composition of solute elements in steel is investigated, and the conditions that Mg ₂Ti0₄ forms instead of MgAI₂0₄ nor Al₂0₃ are examined in the complex deoxidation of Ti-Mg-AI system. When the aluminum content of molten iron is under 4 mass ppm, Mg ₂Ti0₄ forms over the wide concentration range. The concentration range of MgAI₂0₄ formation widens as the aluminum content of molten iron increases. It is necessary to increase Mg content and to decrease Al content in order to form Mg₂Ti0 ₄ in the Ti-Mg-AI complex deoxidation of molten iron in the range Ti<0.01 mass%. However, it is difficult in the range of Ti>0.01 mass% to form Mg₂Ti0₄.