Aluminothermic reduction of tungstic oxide

Abstract

A method for the preparation of massive tungsten metal by aluminothermic reduction of its trioxide in a closed, magnesia-lined reactor, with provision for the formation of a low melting "Al₂O₃-Al₂S₃" slag, has been developed. The presence of a small amount of a mixture of calcium and sulphur was found to be necessary in the charge to trigger the reaction at the relatively low temperature of about 450dgC (outer wall temperature of the bomb). Using 200 g of tungstic oxide and stoichiometric amounts of aluminium, the yield, with and without the formation of the low melting slag, was 72 and 64%, respectively. The influence of the reductant on the yield and quality of the metal was also studied. In a typical run, the tungsten metal obtained by using stoichiometric amount of aluminium contained 1400 p.p.m. of the reductant; this was reduced to about 30 p.p.m. by subjecting the metal to non-consumable arc-melting. The microstructure, hardness and density of the arc-melted sample indicated that tungsten metal could be obtained by the above process in a pure form.