JP2986191B2 - Method of manufacturing sand core for casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the invention]

(Industrial application field) The present invention relates to obtaining a cast product having a hollow portion.
The present invention relates to a method for manufacturing a sand core for casting, which is used for manufacturing a core to be an internal mold corresponding to a portion to be the hollow portion. (Prior Art) Conventionally, when manufacturing the above-described core, for example, resin-coated sand (a fire-resistant sand generally coated with a phenol resin and a curing agent while kneading at a high temperature) is heated to a high temperature (for example, A shell core molding method in which air is blown into a mold at a temperature of about 250 to 300 ° C at an air pressure of about 4 to 5 kgf / cm ² , and a refractory and a resin binder (typically phenol / formalin resin) are used as a hardener and The cold box method was used in which the mixture was kneaded with the catalyst at room temperature and then blown into the air and formed or hand-molded (for example, the “Revised 4th Edition Metal Handbook”, Showa 57)
Published on December 20, 2012, edited by The Japan Institute of Metals, page 1504 to page 1527, "13.5 Special Casting Method". ). (Problems to be Solved by the Invention) However, in the above-mentioned shell core molding method, there is a problem in dimensional accuracy, especially in the case of a core used for a component having a complicated shape because molding is performed at a high temperature. In the box method, although the dimensional accuracy is improved because it is at room temperature, the thick part of the core is cast at a relatively low temperature of about 700 ° C, such as aluminum alloy, in any of the above methods. In the casting to be inserted, the thermal decomposition of the binder hardly occurs inside the core,
In addition, carbonization may occur due to insufficient oxygen supply,
There has been a problem that the disintegration after casting may not be very good. (Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and has good dimensional accuracy, easily obtains strength required as a core, and has good disintegration after casting. It is an object of the present invention to provide a method for producing a sand core for casting which can obtain a core.

Configuration of the Invention

(Means for Solving the Problems) The present invention uses a water-soluble ultraviolet-curable resin as a binder and a mold that can transmit ultraviolet light as a molding die when manufacturing a sand core for casting. A resin-coated sand coated with the water-soluble UV-curable resin on the surface thereof is molded in a mold capable of transmitting the ultraviolet rays, and is irradiated with ultraviolet rays from the outside of the mold to be cured, and then removed from the mold. It is characterized in that it is configured to obtain a sand core for casting, and in an embodiment, it is characterized in that it is configured to use a water-soluble ultraviolet curable resin imparted with anaerobic. The configuration of the method of manufacturing the core is used as means for solving the above-mentioned conventional problems. In the method for producing a sand core for casting according to the present invention,
The foundry sand applied here is not particularly limited, and for example, is appropriately selected and used from various kinds such as silica sand, olivine sand, zircon sand and the like. As a binder (binder) for such a sand core for casting, a water-soluble UV-curable resin is used. A resin that cures within (for example, seconds) is composed of a monomer, a prepolymer (also called an oligomer), a photopolymerization initiator, a stabilizer, and the like. Generally, monomers and prepolymers have acryloyl groups (CH ₂ CHCH—CO) and methacryloyl groups (C
_{H 2 = C (CH 3)} CO-), a vinyl group (CH ₂ = CH-), having one or several photopolymerizable functional groups such as carboxyl group (-COOH), a hydroxy group (-OH) And those containing unsaturated bonds in the molecular chain, such as polybutadiene and unsaturated polyester. A typical example of the former monomer is 2
-Ethylhexyl, 2-hydroxyethyl acrylate, 2
Monofunctional, such as hydroxyethyl acryloyl phosphate, tetrahydrofurfuryl acrylate,
1,4-butanediol diacrylate, 1,6-hexiondiol diacrylate, diethylene glycol diacrylate, polyethylene glycol 400 diacrylate,
There are polyfunctional ones such as trimethylolpropane triacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate. Examples of the latter prepolymer include polyester acrylate, epoxy acrylate, and polyurethane acrylate. Furthermore, the photopolymerization initiator absorbs ultraviolet rays to start a polymerization reaction, and is 300 to 450 nm (nanometer).
Chemical compounds are carbonyl compounds, sulfur compounds, azo compounds, organic peroxides, biacetyl, acetophenone, benzophenone, benzyl, benzoyl, benzoyl peroxide, methylbenzoyl formate, etc. There is. In some cases, amines such as triethylamine and diethylaminomethacrylate are used as a sensitizer for the photopolymerization initiator. A composition using the above-described monomer or prepolymer forms a cured product by irradiation with ultraviolet light, but in this state, shows a property insoluble in water. The ultraviolet-curable resin used in the present invention is a composition in a liquid state, which is exposed to ultraviolet light for a short time (for example, in seconds).
It must be hardened to form a core and be soluble in water after the casting is completed. The composition used in the present invention is obtained by methoxylating acrylate of polyethylene glycol, for example, methoxy polyethylene glycol acrylate [CH
_{2 = CH-CO- (OCH 2} -CH 2) n-OCH 3], or N- vinyl-2-pyrrolidone They have been found to be photopolymerizable and soluble in water. In the present invention, the above-mentioned compounds can be used alone, but also in combination with a fat-soluble resin such as polyvinyl alcohol, pomvinylpyrrolidone, a combination with a water-soluble resin soluble in the above composition, and photopolymerization. As the initiator, those listed above can be used. It is desirable that such a water-soluble ultraviolet curable resin is added in an amount of 3% by weight or more based on the sand core for casting. (Effect of the Invention) In the method for manufacturing a sand core for casting according to the present invention, a water-soluble ultraviolet-curable resin is used as a binder for the sand core for casting. The resin-coated sand obtained by kneading is molded into a predetermined shape in a mold capable of transmitting ultraviolet light, and is cured by irradiating a laser beam or the like having a wavelength similar to ultraviolet light or ultraviolet light from the outside of the mold to a predetermined shape. By doing so, it becomes a casting sand core held in a predetermined shape, and because it uses ultraviolet rays or laser beams for curing, it has good dimensional accuracy and casting sand with the dimensional accuracy and strength required for a core. Become a core. After casting, the core disintegration due to submersion or the like is remarkably improved, and the core elutes well. (Embodiment) In this embodiment, a case in which a sand core 2 for casting having a shape shown in FIG. 2 is used as an internal mold when casting a compressor housing 1 for a turbocharger having a shape shown in FIG. Shown for example. The foundry sand used here is silica sand No. 8, and the water-soluble ultraviolet curable resin has the compounding ratio shown in Table 1 and has the properties shown in Table 2. Therefore, when manufacturing the sand core 2 for casting having the shape shown in FIG. 2, as shown in FIG. 3 (a), the mixing ratio shown in Table 1 and the properties shown in Table 2 were used. The water-soluble UV-curable resin 3 is weighed, and as shown in FIG. 3 (b), a molding sand 4 made of silica sand is prepared. Then, as shown in FIG. 4, the molding sand 4 is mixed in a mixer 5 with the molding sand 4 as a resin binder.
The resin-coated sand 6 in which the surface of the molding sand 4 was coated with the water-soluble ultraviolet-curable resin 3 was obtained by mixing the water-soluble ultraviolet-curable resin 3 with 0% by weight and then kneading with a mixer. Next, as shown in FIG. 5, the resin-coated sand 6 was blown into the transparent acrylic mold 7 capable of transmitting ultraviolet rays by air pressure of 4.0 kgf / cm ² and blow-molded. As shown in Fig. 7, ultraviolet light having a wavelength (λ) of 375 nm was irradiated for 10 minutes by an ultraviolet light irradiator 8 to be cured. At the time of this curing, it has been found that an anaerobic state (vacuum treatment) is preferable if necessary in order to sufficiently cure the inside. Subsequently, as shown in FIG. 7, the mold was removed from the transparent acrylic mold 7 to obtain a sand core for casting 2 having baseboards 2a, 2b and 2c. Next, using the casting sand core 2 as an inner mold,
Casting the turbocharger compressor housing 1 having the shape shown in the figure, and submerging it after casting to dissolve the water-soluble UV-curable resin and sanding out, the core molding sand is remarkably easily eluted, It was recognized that workability was greatly improved.

【The invention's effect】

In the method for manufacturing a sand core for casting according to the present invention, in manufacturing a sand core for casting, a water-soluble ultraviolet-curable resin is used as a binder, and a mold capable of transmitting ultraviolet light is used as a molding die. A resin-coated sand in which the water-soluble ultraviolet-curable resin is coated on the surface of sand is molded in a mold capable of transmitting the ultraviolet rays, and is cured by irradiating ultraviolet rays from the outside of the mold and then demolding. Is performed to obtain a sand core for casting, so that a resin-coated sand obtained by kneading molding sand and a water-soluble UV-curable resin was molded into a predetermined shape in a molding die capable of transmitting ultraviolet light. By irradiating ultraviolet rays from the outside of the mold in a state, it is possible to obtain a casting sand core hardened into a predetermined shape, and it can be cured at room temperature by ultraviolet irradiation. It is possible to obtain a sand core for casting that has high dimensional accuracy and sufficient strength as a core, and because of its extremely good stopping and disintegration property with water, The core sand is easily eluted from the cast product, and a remarkable effect that the productivity of the cast product having a hollow portion can be significantly improved is brought about.

[Brief description of the drawings]

FIG. 1 is a perspective explanatory view showing an example of a casting manufactured using a sand core for casting, and FIG. 2 shows an example of a sand core for casting used to manufacture the casting of FIG. Explanation of slope, 3rd
FIG. 7 to FIG. 7 are explanatory diagrams sequentially showing the steps of manufacturing the sand core for casting shown in FIG. 2 ... sand core for casting, 3 ... water-soluble ultraviolet curing resin,
4 Casting sand 6 Resin coated sand 7
Mold capable of transmitting ultraviolet rays, 8 ... UV irradiator.

Continuation of the front page (56) References JP-A-3-207548 (JP, A) JP-B-51-10813 (JP, B2) JP-B-54-13412 (JP, B2) (58) Fields investigated (Int) .Cl. ⁶ , DB name) B22C 1/22 B22C 9/10

Claims (1)

(57) [Claims] In producing a sand core for casting, a water-soluble UV-curable resin is used as a binder, and a molding die capable of transmitting UV light is used. A resin-coated sand coated with a cured resin is molded in a mold capable of transmitting the ultraviolet light, and after being irradiated with ultraviolet light from the outside of the mold and cured, the mold is released and a sand core for casting is formed. A method for producing a sand core for casting.