METHOD FOR MAKING NIOBIUM HIGH-PURITY BY ELECTRON BEAM MELTING

摘要

PURPOSE:To efficiently obtain high purity Nb suitable for superconducting acceleration cavity by means of electron beam melting by using a raw material in which the weight proportion of O+N+C is specified and carrying out final melting at specific degree of vacuum while increasing melting energy. CONSTITUTION:In the final melting in electron beam melting, an Nb material in which the sum total of O, N, and C is regulated to =250ppm by weight proportion is used. The final melting is carried out while regulating the melting energy determined by electron beam output and melting velocity to =10KWh/kg and also regulating the degree of vacuum at melting to =5X10-4Torr. When melting energy is increased, the surface characteristics of an ingot can be improved and defects, such as lateral cracks and dimples, can be reduced. Owing to the synergistic effect of these effects and highly purifying effect due to low degree of vacuum, the making high-purity of Nb in electron beam melting can be effectively attained.