GB586895A - Improvements in and relating to the manufacture of sintered metal products - Google Patents

Abstract

In a process for the manufacture of a sintered body of iron or iron alloy powder and copper powder from a highly compressed mixture of the powders, the temperature of sintering is intermediate the melting points of the two metals and the duration of sintering is such as to ensure that a sufficient proportion of the lower melting-point metal is brought to the liquid phase to alloy with the iron and substantially eliminate voids. The iron may contain alloying constituents such as nickel, manganese, chromium, carbon, silicon in amounts of not more than 5 per cent. by weight. The powders are thoroughly mixed in a ball mill either dry or in a liquid such as acetone and are compacted at a pressure of from 20-50 tons per square inch, which may be applied before or during sintering. After sintering the product may be mechanically worked. As the alloy possesses age-hardening properties, the hardness and tensile strength may be altered by controlling the sintering temperature and also the rate of cooling which may vary from sudden quenching to slow cooling over a period of twelve hours. The powders may contain one or both metals in the form of oxide, carbonate or chloride which is converted to the metal as by heating in a hydrogen atmosphere. As a specific example a mixture containing 25 per cent. copper was annealed at 600 DEG C. in a hydrogen atmosphere for one or two hours, compressed at 30 tons per square inch and sintered for two hours at 1130 DEG C.