Composition for forming sand moulds and cores for casting metals

摘要

A composition for making moulds and cores for casting metals by the shell moulding process comprises foundry sand, about 5 to 10 per cent. by weight of the sand of a solid fusible thermosetting resin and about 0.1 to 1.0 per cent. by weight of the sand of an alkyl, aryl or aralkyl ortho-silicate or polysilicate. The resin may be a phenol-, urea-, or melamineformaldehyde resin. The cured moulds and cores have a more uniform resin distribution than those from compositions not containing the organic silicate. In examples: (1) 10,000 parts of 100-mesh foundry sand, 50 parts of tetra ethyl silicate and 600 parts of a 200-mesh dry phenol formaldehyde resin were mixed and a test bar moulded from the mixture. (2) As in (1) with the order of adding the ingredients in the mixing changed. (3) As in (1) but using 6 parts of butyl ortho-silicate, and using the mixture to make a shell mould for a gate-valve plug. (4) 10,000 parts sand, 700 parts urea-formaldehyde resin and 30 parts of a mixed phenyl-cresyl orthosilicate were mixed and used to make a shell mould for a gate-valve plug.