GB1173014A - Improvements in or relating to the Purification of Metals - Google Patents

Abstract

1,173,014. Purifying metals and alloys. AIR REDUCTION CO. Inc. Nov. 1, 1966, No.48825/66. Heading C7D. In a method for the production of a highly purified refractory metal (V, Nb, Ta, Mo, W, Zr, Hf, Re), lanthanide rare earth metal, actinide rare earth metal, or alloy thereof, from a mixture of the metal with an impurity which cannot be separated from the metal by vaporization at a reduced pressure without causing vaporization of the metal, the mixture is heated in an electron beam furnace at a pressure of not more than 1000 microns Hg to form a molten pool, the molten pool is contacted with oxygen or a C 1-3 hydrocarbon gas which reacts with the impurity to form a vaporizable compound, and the latter is vaporized without vaporizing the metal. The process may be effected on intermediate products resulting from treatment of metal oxide raw material with reducing agents such as disclosed in Specification 1,173,015. As shown, metal oxide plus reducing agent in iron boxes 16 are melted in region 18 of furnace 10 by the action of electron beam guns 36. Volatile impurities and iron are vaporized off and condensed, and the melt then flows into region 20 in which heating is effected by electron beam guns 38 to vaporize further impurities. Reactive gas is then introduced through pipes 80, 82 further to purify the melt which then flows into region 22 to form ingots in mould 94. Pressures are preferably maintained at 1-1,000 microns Hg in region 18, and at not more than 2 microns Hg in regions 20, 22, by pumps 30, 32, 34. The examples relate to the purification of Nb, Mo, U, Ta - 10% W, and Ta.