Brief review of removal effect of hydrogen-plasma arc melting on refining of pure titanium and titanium alloys

In this study, the effect of hydrogen-plasma arc melting (HPAM) on the removal of metallic and gaseous impurities from pure titanium and titanium alloys is briefly reviewed according to the previous results and a newly added experiment. The highest removal degree (RD) of metallic impurities from pure titanium by HPAM with an Ar-20 vol.% of H2 gas is 84.8%. In the titanium alloys, the RD values of the metallic impurities of the TiNi, TiMo, TiAl, and Ti6Al4V alloys regarding HPAM with an Ar-20 vol.% of H2 gas are 82.6%, 86.2%, 49.1%, and 76.6%, respectively. The total amount of gaseous impurities such as O, N, C, and H was decreased to 962 ppm from 2697 ppm, whereby a high RD value of 64.6% is shown despite the strong affinity of titanium regarding gaseous elements. It is suggested that HPAM exerts a dramatic effect on the removal of metallic impurities from pure titanium and titanium alloys, and it is appropriate for the refining of titanium alloys whereby a significant weight loss needs to be avoided. Thereby, HPAM process can be applied to industrial refining of commercial titanium and titanium alloys.