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

The refining effect of Ar/Ar-H-2 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-H-2 PAM down to a few mass ppm levels, and the purities of respective Mo metals refined by Ar/Ar-20%H-2 PAM were improved up to 4N(99.9943%) and 5N(99.9996%). It is also found that Ar-H-2 PAM provides excellent decarburization, deoxidation, and denitrogenization. This confirmed that the refining effect is chemically induced by activated hydrogen atoms during Ar-H-2 PAM. (C) 2010 Elsevier B.V. All rights reserved.