GB354216A - Improvements in or relating to alloys of palladium, silver and copper - Google Patents

Abstract

Alloys having a high resistance to tarnish and corrosion and particularly suitable for dental purposes and for heat and electricity conductors consist of about 25-98 per cent of palladium, about 1-50 per cent of copper, and not less than 1 per cent of silver which substantially constitutes the remainder. The alloy is substantially free from iron and analogous metals that impair the ductility, but small amounts of other elements may be present. For example, castings may be improved by the presence of a dioxidizer such as manganese, zinc, silicon, boron, magnesium or calcium or compounds thereof, such as about 0,2 per cent of calcium boride. A method of heat treating the alloy comprises heating it above 700 DEG C. and below the melting-point and quickly cooling, or alternatively annealing above 700 DEG C. and cooling in a medium such as diatomaceous earth or the material known under the registered Trade Mark "Silocel." The alloys may be age-hardened by water quenching from above 700 DEG C. and heating at 350-550 DEG C., 450 DEG C., for 15-60 minutes followed by slow cooling. The Specification as open to inspection under Sect. 91 (3) (a) describes also alloys containing less than 25 per cent of palladium and alloys which contain, in addition to the palladium, copper, and silver, small amounts of noble metals such as gold, platinum, and rhodium and up to 4 per cent of base metals such as nickel and cobalt. This subject-matter does not appear in the Specification as accepted. Alloys containing less than 25 per cent of palladium with copper and silver constituting principally the remainder now form the subject of Specification 354,239.