GB337160A - Improvements in and relating to the manufacture of tungsten - Google Patents

Abstract

337,160. Gray, J., (Pacz, A.). Oct. 3, 1929. Vacuum tubes.-In the preparation of tungsten suitable for use in making filaments for wireless valves, &c., freedom of the tungsten ingots from residual oxygen is ensured by intimately mixing tungsten, powder with a more volatile metal such as silver, compacting the mixture, and then sintering and volatilizing all the added metal, leaving an unworhed pure tungsten ingot. The mixture to be compacted may be formed by reducing by hydrogen an intimate mixture of tungstic oxide and a reducible silver compound such as silver chloride: or solutions of silver nitrate and sodium tungstate may be added simultaneously to dilute hydrochloric acid, and the mixed precipitate may be reduced: or silver nitrate solution may be added to sodium tungstate solution and the precipitate treated with hydrochloric acid. The product may be made to contain over 1.5 per cent of thoria, and in such case a mixture of tungsten, silver, and thoria is compacted, and sintered at such a temperature as to volatilize the silver and sinter the tungsten, and the resulting ingot is swaged and drawn; or thorium nitrate solution may be added to the mixture of tungstic oxide and silver chloride prior to reduction by hydrogen. The amount of silver added may be about equal to the thoria content and may be about 0.5-10 per cent of the tungsten. Specifications 3162/13 and 5150/13, [both in Class 39 (ii), Electric lamps, Incandescent], are referred to.