Formation Conditions of Mg(2)TiO(4) and MgAI(2)0(4) in Ti-Mg-Al Complex Deoxidation of Molten Iron

It is important to study the complex deoxidation equilibrium of molten iron in Ti-Mg-Al system from the view point of inclusion control. The equilibrium experiments between molten iron and TiO(x)-MgO-AI(2)O(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-AI(2)O(3) 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 Mg(2)TiO(4) and MgAI(2)O(4). The equilibrium relation between the deoxidation products (Mg(2)TiO(4) or MgAI(2)O(4)) and the composition of solute elements in steel is investigated, and the conditions that Mg(2)TiO(4) forms instead of MgAI(2)O(4) nor AI(2)O(3) are examined in the complex deoxidation of Ti-Mg-Al system. When the aluminum content of molten iron is under 4 mass ppm, Mg(2)TiO(4) forms over the wide concentration range. The concentration range of MgAI(2)O(4) 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 Mg(2)TiO(4) in the Ti-Mg-Al 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 Mg(2)TiO(4).