Coated sand, manufacturing method for same, and manufacturing method for mold

Abstract

Purposes of the present invention are to provide a dry coated sand having a high degree of fluidity at the room temperature, a method of advantageously producing the coated sand, and a method of producing a casting mold having excellent properties, by using the coated sand. The dry coated sand is obtained by mixing an aqueous solution of a water glass used as a binder, with a heated refractory aggregate, whereby water in the aqueous solution is evaporated, and a coating layer of the binder is formed on surfaces of the refractory aggregate. A moisture percentage in the thus obtained dry coated sand is controlled so as to be not more than 0.5% by mass. The intended casting mold is obtained by filling a molding cavity of a forming mold, with the dry coated sand, and passing a steam through the coated sand, to solidify or cure the coated sand.

Description

technical field [0001] The present invention relates to coated sand, its manufacturing method, and the manufacturing method of casting moulds, and in particular, to dry coated sand having fluidity at room temperature, its manufacturing method, and casting castings using such coated sand. type of manufacturing method. Background technique [0002] Conventionally, as one of the casting molds used in molten metal casting, coated sand obtained by coating casting sand containing refractory aggregate with a predetermined binder and molded into the desired shape has been used. For example, in the "Foundry Engineering Handbook" edited by the Japan Foundry Engineering Society, pages 78-90 ("Foundry Engineering Handbook" pages 78-90) clarified that as such bonding materials, in addition to cement, water In addition to inorganic binders such as glass, organic binders using resins such as phenolic resins, furan resins, and polyurethane resins can also be used, and the method of molding...

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Problems solved by technology

[0006] However, studies by the inventors of the present invention have clarified that in such a binder-coated refractory, a coating layer of a binder containing a water-soluble inorganic compound such as water glass or sodium chloride is formed as a solid coating layer. On the surface of the refractory aggregate, the fluidity may not be sufficiently ensured, and the strength of the mold obtained by using it may not be sufficient

In addition, it has been clarified that when the refractory aggregate is coated with such a water-soluble inorganic compound (bonding material), the water-soluble inorganic compound is used in the form of an aqueous solution in a state dissolved in water. The state of the coating changes according to the amount of moisture contained in it, so the physical properties of the binder-coated refractory also change

That is, when the above-mentioned amount of moisture is small, it cannot be coated uniformly, and when the amount of moisture is large, it cannot be dried sufficiently. Therefore, when such a binder is used to coat the refractory, the moldability and physical properties will be reduced, or it will become incomplete. In addition, the characteristics of the bonding material-coated refractory formed by the water-soluble inorganic compound are also quite different, and there is also an inherent problem that even if you want to manufacture the bonding material-coated refractory under the same conditions, There are also problems such as uneven physical properties and difficulty in optimizing manufacturing conditions.

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