GB635959A - Improvements in precision casting - Google Patents

Abstract

635,959. Mould materials; moulding processes. DUESBURY, W. H., and ATKINS, C. Dec. 11, 1947, No. 32648. [Class 83 (i)] In a process of moulding, a pattern is coated with a high refractory material bound by ethyl silicate with the addition of a condensing agent and is then invested in a refractory material which is bound by cement and which is waterborne. The investment material comprises 75 to 96 per cent by weight of a refractory material such as charp, chammotte, silica flour, molochite or the like mixed with 4 to 25 per cent of ordinary cement or alumina cement. The coating comprises ethyl silicate with 1 to 5 per cent of a condensing agent such as piperidine or monoethanolamine and if desired a wetting agent with or without a volatile solvent miscible with ethyl silicate, such as alcohol, the whole being mixed with refractory material such as a mixture of potter's flint and china clay. The coating may be applied to the pattern by spraying, painting or dipping. After drying and firing, the ethyl silicate forms pure silica. In certain cases it may be desirable to apply the refractory mixed with ethyl silicate separately from the condensing agent in order to avoid gelling prior to application. This may conveniently be done by spraying simultaneously through different nozzles. After the investment has been settled by vibrators, the top liquid is poured off, the mould allowed to stand for the cement to set and the wax pattern is then melted or burnt out and the mould is fired.