GB564905A - Improvements relating to metal compositions - Google Patents

Abstract

564,905. Composite metal. SIMS, F. R., and COMPOUND ELECTRO METALS, Ltd. March 17, 1943, No. 4360. [Class 82 (i)] [Also in Group XXII] Metal, of high electrical and thermal conductivity and of great hardness under conditions of prolonged high temperature and high mechanical pressure, is produced by permeating a porous mass of tungsten, molybdenum, silicon, boron or other hard heat-resistant metal with a metal such as silver or copper, this operation being carried out at a temperature below the melting point of the hard metal. The composite metal is employed in the manufacture of parts such as the arcing tips of contact assemblies of high-rupturing capacity switch-gear and die-facings for the electrodes of large flash-welding machines. In one method, short lengths of scrap tungsten rod are passed three times through a sledge mill and the product is sieved to isolate particles of from 1.168 to 2.362 mm. size which are placed loosely in a graphite mould which is then heated in a reducing atmosphere to 1300‹ C. or 1200‹ C. if copper or silver respectively is used as the permeating metal. After 15 minutes heating, strips of copper &c. are placed from time to time on top of the mould until a surplus remaining on the surface indicates that all the interstices have been filled, the resulting conglomerate being slowly cooled in an atmosphere of nitrogen. In another method, tungsten powder of less than 200 mesh is waxed pressed and sintered from 1250‹ to 1300‹ C. The product is crushed by pestle and mortar and particles as above are sifted out and treated as before. The resulting product may be crushed and again treated in a graphite mould as in the first method. In a further modification, the tungsten may be in the form of fine filaments. These may be pressed either along or with powdered tungsten formed in situ in the mass by reducing an oxide. Permeation of copper &c. thus takes place as before. An intimate mixture of copper and tungsten &c. may be formed prior to heating to melt the copper and in this case also the tungsten may be reduced in the mixture.