Hydrogen effect on refining of Mo metal by Ar–H2 plasma arc melting

The refining effect of Ar/Ar–H2 plasma arc melting (PAM) was investigated and the purity of Mo metals was evaluated by glow discharge mass spectrometry (GDMS). Most impurities in the Mo metals except for W were removed by Ar/Ar–H2 PAM down to a few mass ppm levels, and the purities of respective Mo metals refined by Ar/Ar–20%H2 PAM were improved up to 4N(99.9943%) and 5N(99.9996%). It is also found that Ar–H2 PAM provides excellent decarburization, deoxidation, and denitrogenization. This confirmed that the refining effect is chemically induced by activated hydrogen atoms during Ar–H2 PAM.