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

With the increase in demand for titanium, the usage of titanium scrap has increased. It is necessary to develop a new technology to efficiently remove oxygen impurities in titanium scrap. However, it is extremely difficult to remove oxygen directly from a solid solution of oxygen and titanium; thus, there is no effective deoxidation method for titanium at the industrial scale. In this study, the authors thermodynamically analyzed and considered the feasibility of a new technology to remove oxygen dissolved in titanium by utilizing the vapor of rare earth metals which have high vapor pressures at high temperatures, such as samarium, europium, thulium, and ytterbium. It was elucidated that titanium with oxygen levels of < 500 mass ppm could be obtained by exploiting the deoxidation ability of samarium, thulium, and ytterbium combined with their ability to form oxychlorides. The oxygen level achieved through the proposed technology is lower than that obtained using metallic calcium vapor. Based on thermodynamic considerations, a new process to efficiently remove oxygen in titanium using rare earth metals with high vapor pressure based on their oxyhalide formation is proposed.

Automated summary

This study presents a new technology for removing oxygen from titanium using rare earth metal vapor, and its feasibility is analyzed thermodynamically. The results show that titanium with oxygen levels of less than 500 ppm can be obtained by exploiting the deoxidation ability of samarium, thulium, and ytterbium combined with their oxychloride formation.