GB456743A - Improvements in or relating to precious metal alloys - Google Patents

Abstract

Alloys containing 50-75 per cent of gold, 40-15 of platinum and 5-25 of palladium, more than 5 of palladium being present when there is more than 65 of gold, are hardened by annealing them at a temperature above 1005 DEG C. but below their melting point and then either quenching and reheating to 500-750 DEG C. for a time sufficient to produce the desired hardness, e.g. 1/4 to 1 hour, the subsequent quenching beng followed, if desired, by cold working or cooling slowly to a temperature within the range 500-750 DEG C. and then quenching. The hardening may be carried out by rolling an ingot, subjecting it to a prolonged homogenizing annealing, e.g. for 1-2 hours, then to short anneals, e.g. for 1-5 minutes at intervals in the rolling process, each anneal being followed by quenching and then to a final heating at 500-750 DEG C. for a time sufficient to produce the desired hardness, e.g. 1- 1/2 hour. The amount of reduction in thickness produced by the rolling is from 20 to 90 per cent. In an example, an alloy contains 70 per cent of gold, 20 of platinum and 10 of palladium. Specification 361,893 is referred to.