| 摘要 |
1,185,748. Making moulds for metal casting. SWISS ALUMINIUM Ltd. 18 Oct., 1968 [20 Oct., 1967 (2)], No. 49494/68. Heading B5A. [Also in Division C3] A self-hardening mould for metal castings is made by applying to the surface of a pattern coated with a parting agent a rapid-hardening slurry comprising a binder, hardener, solvent and a refractory powder which does not sinter at the temperature of the molten metal with which the mould is to be used, and before this first layer has completely hardened, applying over the first layer, a thicker second layer of a hardenable sand mixture containing an additive to slow the rate of hardening. The same binder may be used for both layers and a reinforcing mesh may be embedded in the surface of the sand layer, a supporting structure optionally being attached to this mesh. The parting agent may be paraffin, glycerol, kerosene or a silicone oil, the binder is preferably sodium silicate, the refractory powder talcum, graphite, quartz or zirconium oxide, the solvent water and the rapid acting hardener one of anhydrous aluminium sulphate, aluminium diphosphate, glyoxal, titanium silicofluoride, cement, gypsum, ferrosilicon powder, calcium silicon powder and aluminium powder. The sand mixture preferably comprises coarse quartz sand sodium silicate solution and one of sodium silicofluoride, sodium aluminate, dicalcium silicate and sodium zirconium silicate as the slow hardening material. The binder may also be cement, alcoholic ethyl silicate, a silicic acid sol or an organic binder such as a phenol or furan resin. |
