JP5441387B2 - Manufacturing method of casting manufacturing structure, casting manufacturing structure, and casting manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a structure such as a mold used in manufacturing a casting, a structure for manufacturing a casting obtained by the method, and a method of manufacturing a casting using the structure.

  For castings, in general, a mold having a cavity is formed with casting sand based on a wooden mold or a mold, and a core is disposed in the cavity as needed, and then a molten metal is supplied to the cavity. Manufactured.

  Wooden molds and molds require skill in processing and expensive equipment, and have disadvantages such as expensive and heavy waste, and waste disposal problems, and are difficult to use in addition to mass production castings. Also, sand molds that use foundry sand add a binder to ordinary sand and harden it to retain its shape, so reusing the sand requires a regeneration process step and during the regeneration process. There is also a problem that waste such as dust is generated. In addition, when the core is manufactured in a sand mold, the workability is poor due to the mass of the core itself in addition to the above problems, and furthermore, the conflicting performance of maintaining the strength during casting and removing the core after casting is present. Required.

  As a technique for solving such a problem, a technique for obtaining a structure for producing a casting containing organic fibers, inorganic fibers, inorganic particles, and a thermosetting resin, which is excellent in moldability and shape retention is known. Furthermore, in addition to organic fibers, inorganic fibers, and thermosetting resins, as a technique for obtaining a structure for producing castings that has been accurately shaped even in a complicated shape, it contains thermally expandable particles, A technique (see Patent Documents 1 and 2) for obtaining a casting manufacturing structure is disclosed.

JP 2006-346747 A JP 2007-144511 A

  Although the techniques of Patent Documents 1 and 2 have an effect on strength retention during casting and core removability after casting, when a casting is manufactured using a complex-shaped casting manufacturing structure, Gas defects may occur in castings. Therefore, a means that can improve this problem has been strongly desired.

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to produce a casting manufacturing structure that is excellent in moldability even in a complicated shape and can reduce gas defects in the casting. An object of the present invention is to provide a manufacturing method of a casting manufacturing structure, a casting manufacturing structure obtained thereby, and a casting manufacturing method using the casting manufacturing structure.

  The present invention relates to a method for producing a casting manufacturing structure that uses a slurry-like composition containing inorganic particles, inorganic fibers, thermosetting resin, thermally expandable particles, a water-soluble polymer compound, and a dispersion medium, and is thermoformed. Further, the present invention relates to a method for manufacturing a casting manufacturing structure in which the boiling point (° C.) of a dispersion medium is equal to or higher than the expansion start temperature (° C.) of thermally expandable particles.

  Moreover, this invention relates to the structure for casting manufacture obtained by the manufacturing method of the said invention, Comprising: Air permeability is 6-120.

  Moreover, this invention relates to the manufacturing method of a casting which comprises the casting process which casts a molten metal using the structure for casting manufacture of the said invention.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a complicated shape, it is excellent in a moldability and can manufacture the structure for casting manufacture which can reduce the gas defect of a casting, The manufacturing method of the structure for casting manufacture, and the casting obtained by it A manufacturing structure and a casting manufacturing method using the casting manufacturing structure are provided.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
<Slurry composition>
The slurry composition of the present invention contains inorganic particles, inorganic fibers, thermosetting resin, thermally expandable particles, a water-soluble polymer compound and a dispersion medium.

(I) Inorganic particles Examples of the inorganic particles used in the slurry composition according to the present invention include graphite, obsidian, mica, mullite, silica, and magnesia. These inorganic particles can be used alone or in combination of two or more. From the viewpoint of reducing gas defects in castings, graphite is preferable, and among graphite, at least one selected from earth graphite and artificial graphite is preferable, and artificial graphite is more preferable.

  The average particle diameter of the inorganic particles is preferably 80 μm or more, more preferably 100 μm or more, and further preferably 150 μm or more from the viewpoint of reducing gas defects in the casting. The average particle diameter of the inorganic particles is preferably 2000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less, from the viewpoint of the hot strength of the structure for producing castings. From this viewpoint, the average particle diameter of the inorganic particles is preferably 80 to 2000 μm, more preferably 100 to 1000 μm, and still more preferably 150 to 500 μm.

  Here, the average particle diameter of the inorganic particles is measured by the following first measurement method. When the calculated average particle diameter is 200 μm or more, the value is taken as the average particle diameter, and the calculated average particle diameter is 200 μm. In the case of less than, it can be determined by measuring by the following second measuring method.

[First measurement method]
Measured based on the method specified in JIS Z2601 (1993) “Testing Method of Foundry Sand” Annex 2, and the average particle diameter was defined as 50% mass accumulation. The mass accumulation is calculated by regarding the particles on each sieve surface as “average diameter Dn (mm)” shown in JIS Z2601 (1993) explanatory table 2.

[Second measurement method]
It is an average particle diameter of 50% of volume accumulation measured using a laser diffraction type particle size distribution measuring apparatus (LA-920 manufactured by Horiba Seisakusho). The analysis conditions are as follows.
・ Measurement method: Flow method ・ Refractive index: Varies depending on inorganic particles (Refer to the manual attached to LA-920)
-Dispersion medium: mixed with ion-exchanged water + sodium hexametaphosphate 0.1%-Dispersion method: stirring, built-in ultrasonic wave 3 minutes-Sample concentration: 2 mg / 100 cm ³

  The content of the inorganic particles in the slurry-like composition according to the present invention is such that the inorganic particles, the inorganic fibers, the thermosetting resin, the thermally expandable particles, and the like from the viewpoint of improving the hot strength of the structure for casting production. The total mass of the water-soluble polymer compound (hereinafter referred to as “inorganic particles, inorganic fibers, thermosetting resin, thermally expandable particles and water-soluble polymer compound” is referred to as “solid material of slurry-like composition”), Preferably it is 30-90 mass%, More preferably, it is 40-85 mass%, More preferably, it is 50-80 mass%.

(Ii) Inorganic fiber Examples of the inorganic fiber used in the slurry composition according to the present invention include artificial mineral fibers such as carbon fiber and rock wool, ceramic fibers, and natural mineral fibers. These inorganic fibers can be used alone or in combination of two or more. Among these, carbon fiber is preferable, pitch-based or polyacrylonitrile (PAN) -based carbon fiber is more preferable, and PAN-based carbon fiber is more preferable from the viewpoint of suppressing shrinkage accompanying carbonization of the thermosetting resin.

  The inorganic fiber has an average fiber length of preferably 0.5 mm or more, more preferably 1 mm or more, and further preferably 2 mm or more, from the viewpoint of the hot strength of the structure for producing castings. Further, from the viewpoint of moldability of the structure for producing castings, the average fiber length is preferably 15 mm or less, more preferably 8 mm or less, and further preferably 5 mm or less. From this viewpoint, the average fiber length of the inorganic fibers is preferably 0.5 to 15 mm, more preferably 1 to 8 mm, and still more preferably 2 to 5 mm.

  The inorganic fiber has a major axis / minor axis ratio of preferably 1 to 5000, more preferably 10 to 2000, from the viewpoint of the hot strength of the structure for casting production and the moldability of the structure for casting production. More preferably, it is 50-1000.

  The content of the inorganic fiber in the slurry composition according to the present invention is preferably 1% by mass with respect to the total mass of the solid content material of the slurry composition from the viewpoint of the hot strength of the structure for casting production. As mentioned above, More preferably, it is 2 mass% or more, More preferably, it is 5 mass% or more. Further, from the viewpoint of moldability of the structure for producing castings, the total mass of the solid material of the slurry-like composition is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 15% by mass or less. It is. From this viewpoint, it is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and still more preferably 5 to 15% by mass with respect to the total mass of the solid content material of the slurry composition.

(Iii) Thermosetting resin Examples of the thermosetting resin used in the slurry-like composition according to the present invention include a phenol resin, an epoxy resin, and a furan resin. Among these, the generation amount of pyrolysis gas during casting is small, there is a combustion suppressing effect, the residual carbon ratio after pyrolysis (carbonization) is as high as 25% or more, and carbonization occurs when the structure is used as a mold. Phenol resin is preferably used from the viewpoint that a good cast surface can be obtained by forming a film.

  Examples of the phenol resin include novolak phenol resins, resol type phenol resins, modified phenol resins modified with urea, melamine, epoxy, and the like. Among them, by using a resol type phenolic resin, it is possible to reduce odor during molding of the structure and casting defects when the structure is used as a mold without the need for curing agents such as acids and amines. ,preferable.

  The content of the thermosetting resin in the slurry composition according to the present invention is preferably 1 with respect to the total mass of the solid content material of the slurry composition from the viewpoint of the hot strength of the structure for casting production. It is at least 5% by mass, more preferably at least 2% by mass, even more preferably at least 5% by mass. Further, from the viewpoint of the gas defect reduction effect of the casting, the thermosetting resin is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably based on the total mass of the solid content material of the slurry composition. Is 15% by mass or less. From this viewpoint, the content of the thermosetting resin is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and still more preferably 5 to 5% by mass with respect to the total mass of the solid content material of the slurry composition. 15% by mass.

(Iv) Thermally expandable particles In the present invention, thermally expandable particles whose expansion start temperature (° C) is not higher than the boiling point (° C) of the dispersion medium are used. As a result, it is possible to obtain a casting manufacturing structure with high accuracy and high air permeability, and to greatly reduce gas defects in the casting. Furthermore, from the viewpoint of reducing gas defects in the casting by obtaining the moldability of the complex shape of the structure for producing castings and high air permeability, the thermal expansion particles have an expansion start temperature of the thermal expansion particles described above. Preferably it is 5-100 degreeC low with respect to the boiling point of a dispersion medium, More preferably, it is 10-80 degreeC low, More preferably, it is 10-70 degreeC low.

  Here, the expansion start temperature (° C.) of the thermally expandable particles is the volume change start temperature in JP-A No. 11-2615 (see paragraph 0012 of JP-A No. 11-2615). This refers to the volume change start temperature when the temperature is raised at a rate of temperature rise of 10 ° C./min.

  When the volume change start temperature of the thermally expandable particle has a range, the minimum value of the volume change start temperature is regarded as the expansion start temperature of the thermally expandable particle.

  Examples of the thermally expandable particles include particles in which a thermoplastic resin is used as a shell wall and low boiling point hydrocarbons are encapsulated (microencapsulated).

  Examples of the thermoplastic resin include acrylonitrile copolymer, vinylidene chloride / acrylonitrile copolymer, polypropylene, propylene / ethylene copolymer, propylene / butene copolymer, polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid. Ester copolymer, ethylene / acrylic acid copolymer, polystyrene resin, acrylonitrile / styrene copolymer (AS resin), acrylonitrile / conjugated diene / styrene copolymer (ABS resin), methacrylate ester / styrene copolymer ( MS resin), methacrylic acid ester / conjugated diene / styrene copolymer (MBS resin), styrene / maleic anhydride copolymer (SMA resin), styrene / conjugated diene copolymer and hydrogenated resins thereof (SBS, SIS, SEBS, SEPS), Ste Emissions based elastomer) polyamide resin (polyamide, polyamide elastomers), polyester resins (polyesters, polyester elastomers), polyurethane resins, polyvinyl resins, such as polycarbonate resins. The thermoplastic resin is preferably an acrylonitrile copolymer from the viewpoint of moldability of the structure for producing castings.

  Examples of the low boiling point hydrocarbon include isobutane, normal butane, normal pentane, isopentane, hexane, cyclohexane, heptane, petroleum ether, neopentane, propane, propylene, and butene. The low-boiling compound is preferably a hydrocarbon compound having a carbon number of 6 or less and a boiling point of less than 80 ° C. from the viewpoint of the effect of reducing gas defects in the casting (improving the air permeability of the structure for casting production). These thermally expandable particles can be used alone or in combination of two or more.

  The thermally expandable particles are expanded by heat, and the average diameter before expansion is preferably 1 to 60 μm, more preferably 2 to 50 μm, and further preferably 5 to 30 μm from the viewpoint of moldability. Moreover, when it heats at 80-200 degreeC, what expands 3-10 times in diameter is preferable.

  The content of the thermally expandable particles in the slurry-like composition according to the present invention is a slurry-like composition from the viewpoint of obtaining a casting manufacturing structure that is precisely shaped even if it has a complicated shape. Preferably it is 0.1 mass% or more with respect to the total mass of solid content material of this, More preferably, it is 0.5 mass% or more. The content of the thermally expandable particles is preferably 15% by mass or less, more preferably 10% by mass with respect to the total mass of the solid content material of the slurry-like composition, from the viewpoint of excellent gas defect reduction effect of the casting. Hereinafter, it is more preferably 5% by mass or less. From such a viewpoint, the content of the heat-expandable particles is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, further based on the total mass of the solid content material of the slurry-like composition. Preferably it is 0.5-5 mass%.

(V) Water-soluble polymer compound In the present invention, a water-soluble polymer compound is added to a slurry-like composition that is a raw material for producing a casting production structure from the viewpoint of improving the moldability of the casting production structure. Is essential. Here, the water-soluble polymer compound means one having 1 g or more dissolved in 100 g of water at 25 ° C. and having a weight average molecular weight of 10,000 to 10,000,000, and 10,000 to 5,000,000. preferable.

  The water-soluble polymer includes natural polymer gum arabic, tragacanth gum, xanthan gum, guar gum, locust bean gum, gellan gum, alginic acid, carrageenan, semi-synthetic polymer methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl hydroxypropyl. Cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, cationized cellulose, synthetic polymer polyacrylic acid, poly-α-hydroxyacrylic acid, acrylic acid copolymer, acrylate ester copolymer, methacrylate ester, nonion Polyacrylamide, anionic polyacrylamide, cationic polyacrylamide, polyaminoalkyl methacrylate, acrylamide / acrylic Copolymer, polyvinyl sulfonic acid, polystyrene sulfonic acid, sulfonated maleic acid, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, may be mentioned polyvinyl methyl ether, polyether-modified silicone, or the like modified products thereof. These may be salts. These water-soluble polymers can be used alone or in combination of two or more. Among these, from the viewpoint of thickening action against water and moldability of the structure for casting production, semi-synthetic polymers, among them, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylhydroxypropylcellulose, ethylhydroxyethylcellulose, Cellulose derivatives such as carboxymethylcellulose or a salt thereof and cationized cellulose are preferred, and carboxymethylcellulose or a salt thereof is more preferred.

  The content of the water-soluble polymer in the slurry-like composition according to the present invention is preferably 20% by mass or less based on the total amount of the solid content material of the slurry-like composition from the viewpoint of the gas defect reduction effect of the casting. More preferably, it is 10 mass% or less, More preferably, it is 5 mass% or less. In addition, the content of the water-soluble polymer is preferably 0.1% by mass or more, more preferably, based on the total amount of the solid material of the slurry-like composition, from the viewpoint of moldability of the structure for producing castings. It is 0.5 mass% or more, More preferably, it is 1 mass% or more. From such a viewpoint, the content of the water-soluble polymer is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and still more preferably based on the total amount of the solid material of the slurry composition. Is 1 to 5% by mass.

(Vi) Dispersion medium In the slurry composition according to the present invention, a dispersion medium having a boiling point equal to or higher than the expansion start temperature of the thermally expandable particles is used. Examples of the dispersion medium include water and other solvents such as ethanol, methanol, dichloromethane, acetone, and xylene. These can be used individually or in mixture of 2 or more. Among these, water is preferable from the viewpoint of ease of handling.

  The dispersion medium is a structure for manufacturing a casting having a complicated shape and has a high air permeability. From the viewpoint of reducing gas defects in the casting, the boiling point of the dispersion medium is The expansion start temperature of the thermally expandable particles is preferably 5 to 100 ° C higher, more preferably 10 to 80 ° C higher, still more preferably 10 to 70 ° C higher. That is, the difference between the boiling point of the dispersion medium and the expansion start temperature of the thermally expandable particles [boiling point of dispersion medium (° C.) − Expansion start temperature of thermally expandable particles (° C.)] is preferably 5 to 100 ° C. More preferably, it is 10-80 degreeC, More preferably, it is 10-70 degreeC.

  The slurry composition according to the present invention preferably contains a dispersion medium in an amount of 30 to 80% by mass, more preferably 40 to 70% by mass, and still more preferably 45 to 65% by mass.

(Vii) Others In the slurry-like composition according to the present invention, the mixing ratio of the inorganic particles and the thermally expandable particles is such that the inorganic particles / the thermally expandable particles / = 40 / 15-80 / 0.1 (mass ratio) is preferable.

  In the slurry-like composition according to the present invention, the compounding ratio (mass ratio) of the inorganic particles, the inorganic fibers, the thermosetting resin, the thermally expandable particles, and the water-soluble polymer compound is a structure for producing castings. From the viewpoint of the hot strength of steel and the effect of reducing gas defects in the casting, preferably the inorganic particles / the inorganic fibers / the thermosetting resin / the thermally expandable particles / the water-soluble polymer compound = 40 to 90/1. 20 / 1-30 / 0.1-15 / 0.1-20 (mass ratio), more preferably 55-85 / 2-18 / 2-18 / 0.5-12 / 0.5-10 (mass) Ratio), more preferably 50 to 80/5 to 15/5 to 15 / 0.5 to 5/1 to 5 (mass ratio) (however, the sum of the numerical values of the components used for the mass ratio is 100). is there.).

  The slurry-like composition according to the present invention preferably has a lower organic fiber content from the viewpoint of moldability in a more complex-shaped structure for casting production and a gas defect reduction effect of the casting. From this viewpoint, the mixing ratio (mass ratio) of the total amount of the organic fiber and the solid material of the slurry composition is preferably the total amount of the organic fiber / slurry composition solid material = 0.1 (mass ratio). ) Or less, more preferably 0.05 (mass ratio) or less. Furthermore, it is even more preferable that the slurry composition does not contain organic fibers.

<Manufacturing method of casting structure>
The method for producing a casting manufacturing structure according to the present invention includes a slurry-like composition containing the inorganic particles, the inorganic fibers, the thermosetting resin, the thermally expandable particles, the water-soluble polymer compound, and the dispersion medium. Is a method for producing a structure for producing a casting, which includes a step of filling a mold and heat-molding, wherein the boiling point (° C) of the dispersion medium is equal to or higher than the expansion start temperature (° C) of the thermally expandable particles. It is.

  The molding die used in the method for manufacturing a structure for manufacturing a casting according to the present invention includes, for example, a main mold having a cavity corresponding to the hollow rod-shaped product shown in FIG. 1 and a core material forming a hollow. The temperature of the mold is heated to about 120 to 250 ° C. in consideration of evaporation of the dispersion medium, curing of the thermosetting resin, and expansion of the thermally expandable particles. The molding die is filled with the slurry-like composition by providing a gate opening / closing means. The filling pressure is preferably about 0.5 to 3 MPa when air pressure is used as the means.

  The method for producing a structure for producing a casting according to the present invention is such that the slurry-like composition is filled in a mold and heat-molded, and preferably the slurry-like composition is heated to 120 to 250 ° C. in the step of heat-molding. Heat to cure the thermosetting resin.

  Next, the slurry-like composition according to the present invention filled in the mold is dried while releasing the vapor derived from the dispersion medium generated by heating the mold and the gas derived from the thermosetting resin to the outside of the mold. Then, after cooling, the structure for casting production according to the present invention can be manufactured by performing trimming, applying a chemical agent, or the like as necessary.

<Cast manufacturing structure>
The casting production structure obtained by the production method of the present invention contains inorganic particles, inorganic fibers, thermosetting resins, thermally expandable particles, and water-soluble polymer compounds.

  The air permeability of the structure for producing a casting of the present invention is preferably 6 or more from the viewpoint of excellent gas defect reduction effect of the casting, more preferably 10 or more, further preferably from the viewpoint of manifesting the gas defect reduction effect of the stable casting. Is 15 or more. In addition, the air permeability of the structure for producing a casting of the present invention is preferably 120 or less, more preferably from the viewpoint of excellent gas defect reduction effect of the casting and the structure having sufficient hot strength even during casting. 100 or less, more preferably 80 or less. From this viewpoint, the air permeability of the structure for manufacturing a casting is preferably 6 to 120, more preferably 10 to 100, and still more preferably 15 to 80.

  The air permeability of the structure for producing castings is, for example, (1) reducing the density of the structure for producing castings, (2) the expansion start temperature of the thermally expandable particles is 5 with respect to the boiling point of the dispersion medium. By selecting one having a temperature lower by -100 ° C. (adjusting the expansion start temperature of the thermally expandable particles and the boiling point of the dispersion medium), the numerical value can be increased, that is, the air permeability can be improved. Furthermore, appropriate adjustment of the expansion start temperature of the thermally expansible particles and the boiling point of the dispersion medium has a greater effect on the air permeability than lowering the density of the casting production structure. The air permeability can be obtained by the measurement method described in the examples.

  The thickness of the structure for producing a casting according to the present embodiment can be appropriately set according to the use and the portion of the structure, but the thickness at the portion in contact with the molten metal is preferably 0.2 to 5 mm. Preferably it is 0.2-4 mm, More preferably, it is 0.4-3 mm. If the thickness is equal to or greater than the lower limit value, the shape function of the casting manufacturing structure can be maintained at the time of casting. Less likely to occur.

  The structure for casting production obtained by the present invention is used for a main mold having a casting product-shaped cavity on the inner surface, a core used in the main mold, or a pouring system member such as a runner, a filter holder, etc. Although it can be applied, the structure for producing a casting of the present invention is excellent in surface smoothness, and a casting having a good casting surface can be obtained. Therefore, application to a main mold and a core is preferable. In particular, the structure for producing a casting according to the present invention is excellent in the gas defect reduction effect of the casting, and is therefore suitable for application to a core that is covered with a molten metal during casting and is likely to generate a gas defect. More suitable for application to.

<Manufacturing method of casting>
Next, a casting manufacturing method using the casting manufacturing structure of the present invention will be described based on its preferred embodiment. In the casting manufacturing method of the present embodiment, the casting manufacturing structure obtained as described above is embedded in a predetermined position in the casting sand to form a mold. As the foundry sand, a conventional one that has been conventionally used for producing this type of casting can be used without any particular limitation.

  Then, the molten metal is poured from the pouring gate and cast. At this time, since the structure of the present invention maintains the hot strength and the thermal contraction accompanying the thermal decomposition of the casting production structure is small, the cracks of each casting production structure and the casting production structure itself Breakage is suppressed, and insertion of molten metal into a casting structure or adhesion of foundry sand is less likely to occur.

  After the casting is finished, the casting is cooled to a predetermined temperature, the casting frame is disassembled to remove the casting sand, and the casting manufacturing structure is removed by blasting to expose the casting. At this time, since the curable resin is thermally decomposed, it is easy to remove the casting manufacturing structure. Thereafter, post-processing such as trimming is performed on the casting as necessary to complete the manufacturing of the casting.

  A more preferable method for producing a casting is an embodiment in which the casting production structure of the present invention is used as a hollow core. The hollow core is opened in the mold, and at least one of the openings of the hollow core is opened outside the mold. And then pouring molten metal into the mold.

  Specifically, as shown in FIG. 3, the hollow core of FIG. 1 is arranged in the main mold, the hollow core is supported by keren, and one of the openings of the hollow core is opened outside the mold. And a method of casting a molten metal by pouring molten metal into a mold. As a method for arranging one of the openings of the hollow core so as to open to the outside of the mold, a method of providing the main mold with an opening so as to communicate with the hollow part of the hollow core may be used.

Examples 1-7 and Comparative Examples 1-7
<Preparation of slurry composition>
By stirring and mixing solid material 100 g of a slurry-like composition whose composition and blending ratio (mass ratio) of inorganic particles, inorganic fibers, thermosetting resin, water-soluble polymer compound and thermally expandable particles are shown in Table 1. After the preparation, 140 g of a dispersion medium is added to the solid content material of the slurry-like composition, and stirred at 2000 rpm for 10 minutes at 20 to 40 ° C., so that the solid content concentration of the slurry-like composition is 41.7% by mass ( In the slurry composition, a slurry having a solid content of 41.7% by mass) and a dispersion medium concentration of 58.3% by mass (in the slurry composition, the dispersion medium is 58.3% by mass). A composition was prepared. In addition, each component shown in Table 1 is as follows.

[Inorganic particles]
Artificial graphite: “G-30” manufactured by Chuetsu Graphite Co., Ltd. Average particle size: 210 μm
Soil graphite: “AE-1” manufactured by Chuetsu Graphite Co., Ltd. Average particle size: 425 μm

[Inorganic fiber]
Carbon fiber: PAN carbon fiber (Mitsubishi Rayon Co., Ltd., trade name “Pyrofil chopped fiber”, average fiber length 3 mm)

[Thermosetting resin]
Phenol resin: (Bellpearl S-890, manufactured by Air Water Co., Ltd.) Resole type

[Water-soluble polymer compound]
CMC: sodium carboxymethyl cellulose (“Serogen MP-60” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., weight average molecular weight: 370,000 to 400,000, dissolved in 3 g or more in 100 g of water at 25 ° C.)

[Thermal expandable particles]
Thermally expandable particles 1: Matsumoto Yushi Seiyaku Co., Ltd., trade name “Matsumoto Microsphere F-36” (expansion start temperature: 75 ° C.)
Thermally expandable particles 2: manufactured by Matsumoto Yushi Seiyaku Co., Ltd., trade name “Matsumoto Microsphere F-105D” (expansion start temperature: 130 ° C.)

[Dispersion medium]
Water: tap water Boiling point: 100 ° C
Xylene: Wako Pure Chemical Industries, Ltd. Standard: Reagent grade 1 Boiling point: 140 ° C
Acetone: Wako Pure Chemical Industries, Ltd. Standard: Wako first grade Boiling point: 56.5 ° C
Dichloromethane: Wako Pure Chemical Industries, Ltd. Standard: Wako first grade Boiling point: 40.2 ° C

<Manufacture of casting structures>
To the mold having the main mold having a cavity corresponding to the hollow rod-shaped product shown in FIG. 1 and the core material forming the hollow, the slurry-like composition prepared above is heated to 160 ° C. at an air pressure of 1 MPa. Filled. By heating for 5 minutes, a hollow rod-shaped product (structure for casting production) shown in FIG. 1 having an outer diameter of 11 mm (hollow part diameter: 5 mm) × length of 380 mm was obtained.

<Measurement method of air permeability of casting manufacturing structure>
“5. Standard test method for disappearance model coating agent” (March 1996, Kansai Branch, Japan Foundry Engineering Society) defined based on JIS Z2601 (1993) “Testing method of foundry sand”. According to the method of measuring the air permeability, the air permeability was measured using a device having the same principle as the air permeability measuring device (compressor air ventilation method) described in the publication (FIG. 5-2 on page 24). The air permeability P is expressed by “P = (h / (a × p)) × v”. In the formula, h: specimen thickness (cm), a: specimen cross-sectional area (cm ² ), p: ventilation resistance (cmH ₂ O), and v: air flow rate (cm ³ / min).

  Here, the thickness of the test piece is the thickness of the hollow rod-shaped product (casting structure), that is, “(outer diameter−hollow part diameter) / 2”, and the cross-sectional area of the test piece is “hollow part diameter × circumferential ratio × Length ".

  At the time of measurement, as shown in FIG. 2, the air permeability tester is attached with a rubber tube and a connection jig (packing) so that it can be connected to the hollow portion of the hollow rod-shaped product without leakage, and further, the air permeability tester is attached to one end of the hollow portion of the hollow rod-shaped product. The connecting jig was connected without a gap, and the other end was closed with packing to prevent air leakage, and measurement was performed.

<Casting of castings>
As shown in FIG. 3, a casting having the following form was cast by injecting the following molten metal using a mold in which the hollow rod-shaped product (hollow core) of FIG.
Molten metal: Cast iron JIS FC300 equivalent, molten metal temperature 1400 ° C
Form of casting: hollow rod mold (main mold) with outer diameter of 54mm, length of 280mm, hollow part diameter of 11mm (upper and lower molds)

<Evaluation of casting>
The defects on the casting surface obtained above were evaluated with a score. The score was divided into 16 divided areas in the axial direction, and the scores were totaled and compared for each area according to the presence or absence of defects occurring on the upper mold side surface, the lower mold side surface, and the cross section. The score in each area was 1 point for each defect (1) to (9) below, and -1 point for each defect if it existed. As a result, each area has a maximum of 9 points, and the entire casting is 9 × 16 = 144 points. Here, the total score was multiplied by 100/144, and the rating was given so that the entire casting became 100 points. The results are shown in Table 1.
[Upper mold side surface]
(1) Sand burning defect (2) Pinhole defect (spherical of 1 mm or more)
(3) Crater-like defects (shallow dents of 3 mm or more)
[Lower mold side surface]
(4) Sand burning defect (5) Pinhole defect (spherical of 1 mm or more)
(6) Crater-like defects (shallow dents of 3 mm or more)
〔cross section〕
(7) Sand burning defect (8) Pinhole defect (spherical of 1 mm or more)
(9) Crater-like defects (shallow dents of 3 mm or more)

  As shown in Table 1, in Examples 1 to 7 in which the boiling point of the dispersion medium is equal to or higher than the expansion start temperature of the thermally expandable particles, the hollow rod-shaped product (structure for manufacturing a casting) has appropriate air permeability. It can be seen that a casting in which defects (sand burning defects, pinhole defects, crater-like defects) due to gas defects are significantly reduced is obtained. On the other hand, in Comparative Examples 1 to 7 in which the boiling point of the dispersion medium is equal to or lower than the expansion start temperature of the thermally expandable particles, the air permeability of the hollow rod-shaped product (structure for casting production) is not sufficient, and thus the obtained casting It can be seen that the occurrence of defects in can not be sufficiently reduced. In the results in Table 1, the air permeability and the casting score are not completely correlated with the difference in pouring temperature, pouring time, and weather conditions (especially humidity) during casting, but the air permeability is high. By doing (increasing the numerical value of air permeability), it can be read that the casting score tends to improve.

It is a perspective view which shows typically the hollow rod-shaped goods manufactured by the Example and the comparative example. This is a method for measuring the air permeability of a hollow bar-shaped product used in Examples and Comparative Examples. It is the schematic which shows the casting_mold | template used by the Example and the comparative example. It is the schematic which shows the location which divided the casting into 16 for the axial direction for the defect evaluation of a casting surface.

Claims (7)

A structure for casting production comprising a step of filling a mold with a slurry-like composition containing inorganic particles, inorganic fibers, thermosetting resin, heat-expandable particles, a water-soluble polymer compound and a dispersion medium, and heat-molding the mold. A manufacturing method of
The heat-expandable particles are selected from isobutane, normal butane, normal pentane, isopentane, hexane, cyclohexane, heptane, petroleum ether, neopentane, propane, propylene, and butene with acrylonitrile copolymer, which is a thermoplastic resin, as the shell wall. These are thermally expandable particles that contain low-boiling hydrocarbons.
The heat-expandable particles are heat-expandable particles that have an average diameter of 1 to 60 μm before expansion and expand to a diameter of 3 to 10 times by heating at 80 to 200 ° C.
The boiling point (℃) is Ri der expansion starting temperature (℃) or more heat-expandable particles,
The expansion start temperature of the thermally expandable particles is a volume change start temperature when the temperature is increased at a temperature increase rate of 10 ° C./min.
A method for manufacturing a casting manufacturing structure.   The structure for casting production according to claim 1, wherein a blending ratio of the inorganic particles and the thermally expandable particles is the inorganic particles / the thermally expandable particles / = 40/15 to 80 / 0.1 (mass ratio). Manufacturing method.   The method for producing a structure for producing a casting according to claim 1 or 2, wherein the inorganic particles are at least one selected from earthy graphite and artificial graphite.   The manufacturing method of the structure for casting manufacture as described in any one of Claims 1-3 which heats the said slurry-like composition to 120-250 degreeC in the process of thermoforming, and hardens the said thermosetting resin. The manufacturing method of the structure for casting manufacture as described in any one of Claims 1-4 whose expansion start temperature of a thermally expansible particle is 5-100 degreeC lower than the boiling point of a dispersion medium. A casting production structure obtained by the production method according to any one of claims 1 to 5 , wherein the air permeability defined below is 6 to 120.
<Air permeability of the casting manufacturing structure>
Air permeability P = (h / (a × p)) × v
In the formula, h: test piece thickness (cm), a: test piece cross-sectional area (cm ² ), p: ventilation resistance (cmH ₂ O), v: air flow rate (cm ³ / min). A casting manufacturing method comprising a casting step of casting molten metal into the casting manufacturing structure according to claim 6 .

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