Purification of cobalt, nickel, and titanium by cold-crucible induction melting in ultrahigh vacuum

Three separate charges of cobalt 9.2 kg in weight, 3.0 kg nickel and 1.6 kg titanium have been melted in ultrahigh vacuum (UHV) using cold-crucible induction melting (CCIM) furnace, in which UHV of better than 1 x 10 -7 Pa is attainable. The effects of CCIM in UHV on the purification of these metals due to the removal of gaseous impurities, and the characteristics of CCIM in UHV have been investigated by the analysis of the melting conditions such as the total pressure and the mass spectra of gases during CCIM, and analytical results of these ingots. CCIM in the present UHV degree and quality is found to be very effective for the purification due to the removal of gaseous impurities in cobalt and nickel, in particular, for the decrease in oxygen, and very important for melting of ultrahigh-purity titanium without any contamination by gaseous impurities, in particular, oxygen.