GB585875A - Improved method of making porous metal articles - Google Patents

Abstract

585,875. Centrifugal moulding of powdered metal. GENERAL MOTORS CORPORATION. June 28, 1944, No. 12266. Convention date, July 10, 1943. Addition to 554,110, [Group XXII]. [Class 87 (ii)] [Also in Groups II and XXII] A method of forming porous metal articles comprises distributing into a cylindrical shape a mixture of metal powder, a binder and a volatile solvent, driving off the solvent while rotating the charge so distributed and then sintering the shaped article. The centrifuge comprises a cylindrical body 20 rotated by a shaft 22 and having a bore with a part 26 of greater diameter than the inner portion 27. A cover 28 has a central aperture 30 of the same diameter as the portion 27. Into the bore part 26 is inserted a backing shell 32 of metal, a refractory non-metallic material such as graphite or in some cases a material such as asbestos paper. A mixture of metal powder, binder and a highly volatile solvent in the form of a thick slurry is poured on to the rotating shell from a hopper 33 and levelled with a blade 38. The solvent is evaporated by warm air after which the shell and powder mass can be removed and sintered to form a coherent body. The binder is preferably a substance that will decompose on heating, such as pyroxylin dissolved in an organic solvent. If the metal powder comprises a mixture of 90 per cent. copper and 10 per cent. tin, a temperature between 1550 and 1750‹F. should be used for sintering, whilst for a mixture of 90-95 per cent. iron and 10-5 per cent. copper a temperature of 2050‹F. would be suitable. A temperature of 2000‹F. should be used for copper nickel alloys in which nickel is present to approximately 60 per cent. A reducing atmosphere is employed and the sintering should be carried out for 15-30 mintues. If making a composite bearing a shell 32 of metal is inserted into the centrifuge and the powder bonded to it during sintering. For other articles the slurry may be poured on to a removable shell. If the shell comprises asbestos paper, this would be destroyed during the sintering process leaving only the porous sleeve.