GB556253A - Improvements relating to sparking plug electrodes - Google Patents

Abstract

556,253. Platinum alloys; heat treatment. MOND NICKEL CO., Ltd., and PFEIL, L. B. May 15, 1942, No. 6647. [Classes 72 and 82 (i)] [Also in Groups XXVII and XXII] Sparking-plug electrodes 1, 8 resistant to attack by lead are made of alloys composed principally of one or more metals of the platinum group, of which at least the unsupported parts have a fibrous microstructure when they are assembled in the plugs and ready for service. Suitable alloys containing 4 per cent. to 5 per cent. tungsten, 20 per cent. iridium, 10 per cent. rhodium or 2 per cent. molybdenum, or platinum-tin alloys, or ruthenium may be added to a platinumtungsten alloy. The alloy is subjected to severe cold working to produce a wire of fibrous microstructure, and re-crystallization due to heating of at least the part of the wire which forms the unsupported part of the electrode is prevented during the production of the wire and its essembly in the plug, e.g. by keeping the temperature below about 950‹ C. In an example, platinum-tungsten alloy is reduced hot to a rod 0.2 inches square, annealed at 1050‹ C. for 15 minutes, and reduced in stages by cold working to 0.046 inch diameter round wire; the alloy may be held at a temperature of 800‹ for 10-15 minutes at 0.09 inches prior to further reduction in size. The electrode 8 is spot-welded to the plug body 10 and the electrode 1 is set in a metal 4 having a melting-point no higher than that of silver, a glass seal 7 being provided around the metal wire 5.