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

¹ State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, P.R. China
e-mail: qianguoyu_yejin@126.com
² Xingtai Iron and Stee1 Corp.LTD, Xingtai Hebei, Hebei 54027, P.R. China

Received: 12 January 2014
Accepted: 18 June 2014

Abstract

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.