| 摘要 |
The object of this method is to provide a mixture having a better fluidity, so that it flows easily into the mould or the core and matches its shape more exactly. To foundry sand are added approximately 1.8 % of a hardenable formaldehyde resin in an aqueous solution, 0.2 % of an organosiloxane, and 1 % of a surfactant in aqueous solution, in order to obtain a mixture containing approximately 1.5 % of water. By mixing, the liquid phase of the mixture is made to foam, after which an acid hardener of the resin is added, the mixture is poured into a mould or core box, without tucking (settling) and the mixture is left to set. The hardener must be added after the other ingredients, otherwise the mixture is only half as fluid.
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