Direct Oxygen Removal from Titanium by Utilizing Vapor of Rare Earth Metals

To promote the recycling of Ti scrap, it is essential to develop new technologies that can efficiently remove oxygen impurities from the Ti scrap. However, the direct removal of oxygen dissolved in solid Ti is extremely difficult, and currently, there are no effective deoxidation methods that can be used industrially. In this study, we experimentally verified a new deoxidation technique for Ti using the vapor of rare earth metals with high vapor pressures, such as Sm, Eu, Tm, and Yb. It was confirmed that Eu did not decrease the oxygen concentration in the Ti samples below 1000 mass ppm O. On the other hand, it was shown that the vapor of Sm, Tm, and Yb decreased the oxygen concentration in the Ti samples through their oxide formation reactions. In particular, it was demonstrated that Tm vapor can deoxidize Ti at or below the oxygen concentration of the Ti sponge produced by the Kroll process (∼500 mass ppm O).