| 摘要 |
A molding material, a foundry molding material mixture and a manufacturing method of a mold or molding parts are provided to obtain excellent flowage and even packing density for molded article caused by improved shape accuracy by using partially solubilized amorphous SiO2. A molding material or a molding part consists of 1-10% of alkaline silicate based binder, 1-10% by weight of micelle of amorphous silicon dioxide and the rest of silica of which particle size is 0.01-5mm, wherein the particles of the amorphous silicon dioxide have spherical shape, respectively, and particles corresponding to at most 1.5% by weight have diameter of at least 45mum; the surface of the amorphous silicon dioxide has swelling phase having thickness of 0.5-1% with respect to mean particle diameter. The mean particle diameter of the amorphous silicon dioxide is 10-45mum, and the purity of the amorphous silicon dioxide is over 85%. Binder bridges are formed between alkaline silicon dioxide and the silica through additional binding centers. The binder comprises 0.01-0.50% of iron, aluminum and/or cadmium. A manufacturing method of a mold or molding parts using the molding material comprises steps of: placing partially solubilized amorphous spherical SiO2 of which particle size is at least 45mum in a suspension comprising 20-70% of silica dioxide for solid content, of which pH is adjusted to 9-14 as a micelle; subjecting the amorphous silicon dioxide in an alkaline treatment for at least 4 minutes until a swelling phase is formed on the surface of the silicon dioxide; mixing the silicon dioxide with molding sand and binder homogeneously while a ratio of binder/SiO2 to molding sand in the mixture is maintained at 1-10 to 90; and suiting the silicon dioxide together with the molding sand and the binder in a mold box and drying the product for forming finished core. The surface of the amorphous silicon dioxide is partially solubilized, the mean particle diameter of the silicon dioxide is extended to 2%, and a swelling phase is formed on the surface.
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