New Deoxidation Method of Titanium Using Metal Filter in Molten Salt

Metallic Ti has a strong affinity for O at high temperatures, and methods for removing O directly from Ti are limited. Recently, the authors developed a new sintering process that removes O from Ti using Y metal as a deoxidizing agent in molten salt. However, Y contaminated the sintered Ti body. To address this problem, the authors developed a new Ti deoxidation process using a metal filter. In this process, a Ti green made of Ti powder and Y metal are introduced with molten salt into the respective sides of a room divided by a Ti filter. O removed from the Ti green passes through the Ti filter and reacts with the Y metal. Meanwhile, the small solubility and diffusion coefficient of Y in beta-Ti are expected to kinetically prevent Y contamination of the sintered Ti body. It was experimentally demonstrated that a sintered Ti product with a low-O-concentration (< 250 mass ppm O) can be produced while suppressing Y contamination (< 120 mass ppm Y) in the new process. The establishment of this process enables low-cost production of highly functional Ti products and the recycling of Ti scraps in the future.