GB598423A - Improvements in a method of compacting metal powder into complicated shapes - Google Patents

Abstract

Articles such as screw-threaded rods, spur and spiral gears and generally having a complicated external shape are obtained from metal powder by compacting the powder into a hollow mass, compressing the hollow mass against the walls of a die of the required shape by an expansible core inserted into the hollow (see Group V), and subjecting the compact thus formed to any known suitable sintering process. The compact may be made solid (before sintering) by compacting additional powder within the hollow. Large compacts may be built up from a plurality of shells one within the other produced as above. The powder size referred to is 100 to less than 1 micron diameter and in an example pure iron powder of size corresponding to 325 mesh is first compacted into hollow form in a die in successive half inch layers under a pressure of 1-2 tons/sq. inch. An expansible member is then inserted in the hollow and expanded to force the powder into the detail of the mould, without additional compacting with a pressure of 1-2 tons/sq. inch, or with additional compacting in an approximate ratio of 1:2 with a pressure of 4-5 tons/sq. inch. The radial or wall thickness of a compact moulded in one stage in this way is given as 1/2 inch to 5/8 inch before the additional compacting (if any) by the pressure exerted internally.