Development of Method for Direct Deoxidation of Titanium using Mixtures of Magnesium Chloride and Rare-Earth Chlorides

¹ The Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505, Japan
² Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

^* t-ouchi@iis.u-tokyo.ac.jp

Abstract

To decrease the cost of Ti sponge, Ti scrap is added during the remelting process to produce an ingot. However, the use of Ti scrap as an additive during this process is limited because Ti scrap is contaminated by oxygen (O) and iron (Fe), which are not removable during the remelting process. Here we introduce a new electrochemical deoxidation process for Ti scrap using a mixture of magnesium chloride (MgCl₂) and rare-earth chlorides (RECl₃, RE: Y and Ho) as a flux. Ti and carbon were used as the cathode and anode, respectively. Mg is deposited on the Ti cathode and reduces the oxygen in the Ti to oxide ions (O²). The activity of the generated O²” in the system, a_Qi-, is maintained at a low level through the formation of rare-earth oxy chloride (REOCl), and is further decreased by the formation of carbon oxides on the anode. During this process, the concentration of oxygen in the Ti is effectively decreased to 100 mass ppm in the MgCl₂-YCl₃ flux at 1,200 K. This new deoxidation method is considered applicable to the recycling process of Ti scrap containing large amounts of oxygen.