Takanari Ouchi

Abstract:

Titanium (Ti) is the ninth-most abundant element of the Earth’s crust. Ti and its alloys have excellent characteristics, such as high specific strength and high corrosion resistance; however, their use is currently limited in specific areas because of their high production costs. Feeding Ti scraps with virgin Ti for ingot production is an approach to reduce these costs. In this process, scrap dosages are limited to avoid increasing the O concentration of the ingot. Reducing the concentration of O in Ti and its alloys is a significant challenge due to high affinity of Ti for O and high solubility of O in Ti. To increase scrap dosage, we developed a new deoxidation process for Ti and its alloys. In this work, Ti and Ti alloys were deoxidized in a molten salt electrolyte using rare-earth metals (e.g., Y, La, and Ho) as reducing agents[1–10]. By utilizing the formation of rare-earth oxyhalides, we demonstrated that the O concentration in Ti could be decreased to less than 100 mass ppm, lower than that in the virgin metals (Sponge Ti). Therefore, we named this process the “upgrade recycling process,” and have implemented it for Ti alloys. We believe this new method is a promising technique to promote the recycling of Ti and its alloys, lowering the price of Ti products in the future.