GB1342599A - Investment casting cores and their method of manufacture - Google Patents

Abstract

1342599 Core moulding processes DOULTON & CO Ltd 3 June 1971 [17 March 1970] 12808/70 Heading B3F [Also in Divisions B5 and C3] In a method of making mould cores for investment casting of metals, a mixture of a ceramic powder and an organic binder is shaped and heated to a temperature insufficient to sinter the ceramic powder but sufficient to remove 48 to 95% by weight of the organic binder and to carbonize the remainder thereby to form a non- thermoplastic body of ceramic powder bonded by carbonaceous residues, the binder being selected so as to decompose during the heating to leave a residue of 0À4 to 14% by weight of the total weight of ceramic powder and carbonaceous residue. The binder, which may be polystyrene, a polyester, polyethylene glycol, or paraffin wax is present in the mixture to be shaped in an amount of 8 to 27% of the total weight. The shaping may be carried out by injection or transfer moulding processes. A sintering flux may be included in the ceramic mixture to be shaped and may be a silica sol., sodium potassium or lithium compound, powdered glass, china or ball clays, or alkaline earth compounds. Ceramic materials mentioned are silica, zirconia, alumina, baria, calcia, magnesia, mullite, calcium phosphate or aluminate, silicon carbide and carbon.