GB606119A - Improvements in or relating to moulding materials - Google Patents

Abstract

A shaped article is made by mixing together sodium silicofluoride, sodium silicate having a silica-sodium oxide ratio not less than 3.3:1, and a filler inert to sodium silicate, allowing the product to set, and then heating to expel water and effect hardening. The mix may be made by adding the filler to a solution of sodium silicate and adding the sodium silicofluoride when the required consistency has been obtained; adding a mixture of filler and sodium silicofluoride to a solution of sodium silicate to form a slurry; or by adding the filler and sodium silicofluoride to powdered sodium silicate and then adding sufficient water. The mix may be poured or rammed according to the consistency and the desired product. The filler used is determined by the intended use of the product, e.g. sand for production of articles such as patterns, core trays, mould parts or the like to withstand temperatures up to 350 DEG C.; fused silica, graded if desired, or a mixture of silica and zirconia or zirconium silicate for high-temperature purposes; asbestos, alumina, or mica for heat-insulating purposes; graphite when electric conducting properties are required; oxidizing substances such as manganese dioxide, or such substances as calcium carbonate or sodium fluoride for use in degassing, cleaning, and refining metals; a heat-producing mixture, e.g. of iron oxide and aluminium for the purpose of keeping a metal liquid in a mould; or sawdust or like combustible material or a chemical containing water of crystallization for introducing a gas into a molten metal.