Improved process for making moulds for 'cire-perdue' precision casting

摘要

742,361. Moulding processes. REGIE NATIONALE DES USINES RENAULT. July 9, 1952 [Aug. 30, 1951], No. 17347/52. Class 83 (1). A wax pattern precoated with a refractory powder in a solution of alkaline silicate is rendered insoluble, before investing with a mixture of sand, binder and water, by treating with a solution of a volatilizable acid, or a salt of ammonium, or of a weak organic base which is easily hydrolysable, in a solvent which does not dissolve the alkaline silicate. The substance should leave no residue on heating and may comprise a salt of a weak base, e.g. hydrochloric acid in equal parts of ethyl alcohol and water, or ammonium nitrate in methyl alcohol. Acetic, oxalic and nitric acids are also mentioned. The solution is applied to the dried precoated pattern by spraying or dipping.