Deoxidation of Titanium Using Cerium–Chloride Flux for Upgrade Recycling of Titanium Scraps

Abstract

The fabrication process of titanium (Ti) ingots generates a large number of Ti scraps contaminated by oxygen (O). In the past, various direct deoxidation methods from Ti for recycling of the Ti scraps have been developed, although they have not been industrialized yet. In this study, we developed a novel deoxidation process utilizing cerium (Ce), which is an inexpensive and abundant rare-earth element, as a deoxidant for Ti. Based on the thermodynamic analysis utilizing the available thermochemical data with some theoretical assumptions for cerium oxychloride (CeOCl), it is expected that the production of Ti with extremely low oxygen concentration is feasible by a deoxidation reaction of Ti through the formation of CeOCl. In this study, we demonstrated that Ti samples can be deoxidized by Ce metal in KCl fluxes to 1000 mass ppm O or less through the formation of CeOCl. Furthermore, we also demonstrated that Ti samples were deoxidized by Ce metal in CeCl₃ fluxes down to 100 mass ppm O or less under the Ce/CeOCl/CeCl₃ equilibrium. In some experiments, Ti samples without physical contact with Ce metal and CeCl₃ fluxes were also deoxidized. This result suggests the possibility of developing a new deoxidation process by supplying the deoxidant and flux through the gas phase. This new deoxidation technique using Ce metal and chloride fluxes enables Ti scraps containing a large number of oxygen impurities to be recycled.