Effect of TiO2 addition to LF refining slag on the Ti, Al, and cleanliness of Ti-stabilized stainless steel

The influence of TiO2 addition to LF refining slag on Ti-stabilized stainless steel was evaluated using a vacuum induction furnace at 1873 K. The effect of CaO-SiO2-MgO-Al2O3 basic slags with different TiO2 contents on the titanium loss, aluminum loss and total oxygen content in the steel was studied. It was observed that the oxidation rate of Ti first decreases and then increases with the increase in the content of TiO2 in slag and reaches the minimum when 8%TiO2 is added to the slag. However, the change in the oxidation rate of Al shows the opposite tendency. The total oxygen in the molten steel remains unchanged with time when 8%TiO2 is added to the slag, and the total oxygen of the others increases monotonically with time. The activities of TiO2 and Al2O3 from the calculation of the ion and molecule coexistence theory (IMCT) in the initial slag present the same change tendency, and both first increase and then decrease with the gradual increase in TiO2 in the slag and reach the maximum when 8%TiO2 is added to the slag. The results of a kinetic analysis showed that the rate-determining step of the oxidation of Ti in the steel is the mass transfer on the slag side, and the rate-determining step of the oxidation of Al in the steel is the mass transfer on the metal side.