GB1346576A - Method of making a mould or mould piece - Google Patents

Abstract

1346576 Foundry moulding processes DEFENCE SECRETARY OF STATE FOR 19 April 1971 [3 April 1970] 15817/70 Heading B3F [Also in Division B5] A foundry mould block is prepared by coating an expendable layer 13 on to a pattern 14, applying refractory material to the thus-coated pattern (14, 13) to form a block 11, removing the expendable layer 13, separating the block 11 from the pattern 14 by a distance 15 and injecting between the block 11 and pattern 14 a facing composition of a finely-divided refractory material dispersed in a wax. The block 11 with its facing is removed from the pattern 14 and fired in a kiln to evaporate the wax and harden the facing. After casting, the facing is removed from the block 11 with the casting so that the block 11 may be refaced for further use. Before moulding the pattern 14 is covered with an expandable layer 13 of wax, plaster, modelling clay, selfadhesive wax sheet, rubber or thermoplastic sheet and the block 11 is moulded by pouring a refractory cement-like mixture over the coated pattern 14 (see Division B5) or by tamping a refractory aggregate/Na silicate mixture around the pattern 14 and hardening with CO 2 . To provide chilling regions in the mould, SiC or chrome iron ore may be added locally to the block 11 and to provide heat-insulated areas bubble Al 2 O 3 or porous grog may be added locally to the block 11. After moulding the expendable layer 13 is fired away and the pattern 14 and flash sides, but not the block surface covered with parting agent. The pattern 14 is spaced from the block 11 by a distance of 2-3 mm. for patterns of area up to 1000 cm.<SP>2</SP>, up to 4 mm. for larger patterns, and a liquid wax/refractory composition injected between the pattern 14 and block 11 to form a facing layer (see Division B5). After separating the faced block 11 from the pattern it is fired to drive off wax and to preheat the mould to pre-casting temperature. Facing compositions suitable for use with steels and other high temperature alloys and for use with aluminium, copper and other lower temperature alloys are disclosed in the Specification. Cores may be made by injecting a liquid wax/ refractory composition about an insert and stoving the moulded core to drive off the wax and to assist hardening.