GB661780A - Improvements in or relating to moulds - Google Patents

Abstract

661,780. Making moulds. SINTERED PRODUCTS, Ltd. June 21, 1950 [March 28, 1949], No. 8406/49. Class 83 (ii) and 83 (iv). [Also in Group V] Powder metallurgy.-A porous metal mould suitable for moulding pottery and articles such as egg trays made from wood fibre is made by filling a master mould with dry powder of copper, nickel, aluminium or alloys thereof, sintering the powder at 800-900‹ C. in a reducing atmosphere, cooling while still in a protective atmosphere and removing the sintered mass from the master mould. Uniform filling of the master mould may be effected by vibration. The porous mould may be made partly of solid metal to which the porous portion is joined during the sintering or may be wholly of porous metal but of different compositions, for example, the face of bronze and the back of copper. The powder used to form the face of the mould may be finer than that used for the backing and this may be effected by painting the master mould with a thin paste of fine powder and then filling with a coarser powder or by first sintering a layer of fine powder and then adding a backing of coarser powder or thirdly, by vibrating the master mould so that the finer particles of between 200 and 250 mesh penetrate through the mass of the powder of between 30 and 50 mesh to the face. In a specific example, bronze powder containing 10 per cent by weight of tin and consisting substantially of spherical particles was pressed into a master mould by hand and sintered in cracked ammonia for four hours at 800‹ C. After cooling and stripping, the porous mould may be polished and electroplated with chromium as described in Specification 603,762.