GB575734A - Improvements in or relating to moulds for casting of metals or metal alloys - Google Patents

Abstract

In making moulds or cores for casting magnesium or other metal, sand &c. is mixed to the usual consistency, moulding with a binder liquid consisting of a hardenable organic silicon compound, e.g. hydrolysed silicon ester with between one and four molecular proportions of water, as described in Specification 575,752, and a gelling accelerator. This may consist of hydrochloric acid, lime, or magnesia, but preferably an accelerator, such as piperidine, is used which also condenses the binder to form a polymerized resinous body. The accelerator and water may be mixed with the binder or with the material bound. The mixture may be used for making cores, one-piece moulds, about an easily fusible pattern, or two-part moulds, by tamping and vibrating or by high pressure, e.g. 200-1000 lbs. per square inch, or for lining a metal mould or one made from sand, slip or other cheap materials. Reinforcing material, such as wire, woven cloth, or asbestos p cloth wetted with a slurry of fine aggregate and bonding liquid, may be inserted in the mass while filling a mould box. The pattern and, if desired, the sides of the box are removed when gelling has taken place, say within half an hour, and the mould is then dried at room temperature for, say, eight hours and heated to 700-1000 DEG C. in an hour or more. Semi-permanent moulds may be made thus, using refractory powders bonded as described. For low temperature castings the refractory is replaced by plaster of Paris, magnesium oxychloride or cement fondu, the mould preferably lined with fine aggregate also bonded as described.