GB625397A - Improvements in or relating to powdered metal compositions - Google Patents

Abstract

A modification of the composition of the powder mixture of the parent Specification, the modified mixture having the following composition: Ni above 8 per cent and up to 25 per cent, Mn 0.2 to 1.4 per cent, graphite 0.08 to 1.0 per cent, soft iron and the usual impurities forming the remainder. The Mn content may be added in the form of manganese carbonate. The particles of the constituents, other than iron, should preferably pass through a 300 mesh sieve. In a further modification of the invention of the parent case, articles are manufactured from powder mixtures containing 2-25 per cent Ni by first compacting and then sintering the mixture, for example compacting at a pressure upwards of 20 tons per square inch and sintering at temperatures above 1100 DEG C. Sintering is preferably carried out in a non-oxidizing atmosphere comprising 75 per cent hydrogen and 25 per cent nitrogen. The compacted and sintered mixture may be coined at pressures up to 60 tons per square inch with or without subsequent sintering at up to 1350 DEG C. or heat treatment as normally applied to wrought steel. The powder mixtures of the present invention containing above 8 per cent of Ni may, alternatively, be formed into articles by a simultaneous compacting and sintering operation.