GB575998A - Improvements relating to precious metals and alloys thereof - Google Patents

Abstract

575,998. Obtaining coherent masses from powdered metals; alloys. MIDDLETON, A. B. Oct. 28, 1943, 'No. 17824. Drawings to Specification. [Class 82 (i)] [Also in Group XXII] Metal for use at high temperatures, e.g. for resistance heating furnaces, spark-plug electrodes, thermo-couples, or fuses, is made by sintering a powder consisting of one or more precious metals with or without a smaller proportion of one or more base metals having a high melting point, e.g. over 900‹ C., compressing the product, and finally producing a fibrous structure by cold working, both sintering and compressing being at a 'temperature much below the melting point. Examples of suitable precious metals are platinum, palladium, ruthenium, gold and silver and of base metals are titanium; zirconium, tantalum, columbitun, vanadium, chromium, nickel, copper, molybdenum and tungsten. Platinum containing 4 per cent of tungsten, in powder form, may be sintered at 1200‹ C. and then reduced 98 per cent in cross-section by drawing. The time required for sintering depends on the particle size and the rate of mutual diffusion of the metals concerned. Platinum ammonium chloride may be heated to 400‹ C. to produce platinum sponge which is passed through a sieve having 90 meshes per inch. Tungsten having a particle size of about 1 micron is added and the mixture consolidated under a pressure of 15 tons per square inch, sintered for 3 hours at 1200-1300‹ C., forged in stages of about 10 per cent reduction,. reheating to 1100-1200‹ C. in hydrogen between the stages, until about 75 per cent reduction has been produced, and then rolling in stages of about 10 per cent reduction until a total reduction of 92 per cent has been produced. The final cold working stages may be by drawing. A mixture of platinum 84, palladium 10 and ruthenium 6 per cent may be pressed at 15 tons per square inch in a steel mould to form a bar 2" Î ¢" Î ¢" which is sintered at 1200‹ C. for 3 hours in hydrogen, consolidated :by forging at 1200‹ C., cold rolled and drawn to give a wire of 0.047" diameter. Platinumpalladium alloys are sintered at 1000-1200‹ C. and forged at 700-900‹ C. Specification 556,253 is referred to.