WO2026018762A1 - Mold wash composition for lost foam mold - Google Patents

Abstract

The present invention provides a mold wash composition for a lost foam mold, the mold wash composition containing a refractory aggregate and carbon fibers. The refractory aggregate contains graphite and a refractory aggregate (A) having a fire resistance SK of 1a to 15. The present invention successfully provides a mold wash composition for a lost foam mold said composition being capable of better suppressing burns.

Description

Wash composition for evaporative model

The present invention relates to a mold wash composition for lost foam casting used in lost foam casting.

Lost foam casting is a casting method in which a synthetic resin foam pattern of the same shape as the product is replaced with molten metal (hereinafter referred to as "molten metal"). It offers numerous benefits, including no need for cores, no need for complicated work like mold matching, easy design changes, and short delivery times. However, issues remain, such as reducing residue defects and burn-in defects, and various research efforts are being conducted to improve the process. Residual defects occur when thermal decomposition gases are not sufficiently discharged when a synthetic resin foam pattern is replaced with molten metal, resulting in thermal decomposition residue that becomes trapped in the upper part of the product. Burn-in defects occur when the molten metal breaks down the mold coating and leaks into the sand mold. Preventing burn-in defects is particularly important; when they occur in large products or thick product parts, the work of removing them becomes complicated, causing major problems such as increased labor hours, increased burden on workers, and delayed delivery.

Examples of wash compositions for vanishing patterns that improve burn-in defects include a wash composition for vanishing patterns containing an ore whose DTA endothermic peak temperature (°C) is within a specific range in JP 2003-290869 A, a wash using an inorganic or organic fibrous material having a length of 6 to 30 mm in JP 11-285778 A, a wash containing wollastonite (CaO.SiO ₂ ) as a refractory aggregate in JP 2014-73504 A, and a wash composition containing one or more selected from calcium bentonite and ammonium nitrate in JP 2001-334346 A.

The present invention provides
Contains refractory aggregate and carbon fiber,
The refractory aggregate (A) has a refractoriness of SK1a or more and SK15 or less, and the refractory aggregate (A) contains graphite.

Schematic diagram showing the shape of the evaporative model used to evaluate the adhesion defects in the examples.

Detailed Description of the Invention

Conventional coating compositions were not sufficient to prevent burn-on defects, and further improvements were needed.

The object of the present invention is to provide a mold wash composition for lost-mold models that can further suppress burn-in defects.

The present invention provides
Contains refractory aggregate and carbon fiber,
The refractory aggregate (A) has a refractoriness of SK1a or more and SK15 or less, and the refractory aggregate (A) contains graphite.

The present invention provides a mold wash composition for lost-mold models that can further suppress burn-in defects.

The following describes one embodiment of the present invention.

<Mold wash composition for vanishing patterns>
The vanishing pattern wash composition of this embodiment (hereinafter also simply referred to as "vanishing pattern wash composition") contains a refractory aggregate and carbon fiber, and the refractory aggregate contains a refractory aggregate (A) having a refractoriness of SK1a or more and 15 or less, and graphite. According to the vanishing pattern wash composition of this embodiment, it is possible to further suppress burning defects. The reason why the vanishing pattern wash composition of this embodiment exhibits such an effect is partially unknown, but is presumed to be as follows.

During casting, the coating is subjected to the thermal expansion of the foundry sand and the pressure of the molten metal, so it needs to have physical properties that can withstand severe pressure differences. Refractory aggregate (A) with a refractoriness rating of SK1a or higher and 15 or lower softens and melts with the heat of the molten metal, mitigating the pressure on the coating. Furthermore, the presence of carbon fiber, which is easily dispersed uniformly and can easily function as a reinforcing material, in the coating makes it less susceptible to damage and is thought to help prevent burning.

[Fire-resistant aggregate]
From the viewpoint of suppressing sintering defects, the refractory aggregate contains a refractory aggregate (A) having a refractoriness of SK1a or more and 15 or less. Examples of the refractory aggregate (A) include mica (SK14), obsidian (SK6a), perlite (SK6a), colophonite (SK5a), orthoclase (SK9), albite (SK9), nepheline (SK10), anorthite (SK9), and the like. Among these, from the same viewpoint, at least one selected from obsidian, perlite, and mica is preferred.

The content of the refractory aggregate (A) in the refractory aggregate is preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 30% by mass or more, from the viewpoint of suppressing burn-in defects. The content of the refractory aggregate (A) in the refractory aggregate is preferably 60% by mass or less, and more preferably 50% by mass or less, from the viewpoint of improving the smoothness of the casting surface. The content of the refractory aggregate (A) in the refractory aggregate is preferably 1% by mass or more and 60% by mass or less, more preferably 10% by mass or more and 50% by mass or less, and even more preferably 30% by mass or more and 50% by mass or less, from the viewpoint of suppressing burn-in defects and improving the smoothness of the casting surface.

The fire resistance of the refractory aggregate (A) is SK1a or higher, preferably SK3a or higher, and more preferably 5a or higher, from the viewpoint of suppressing burning defects. The fire resistance of the refractory aggregate (A) is SK15 or lower, preferably SK11 or lower, and more preferably SK9 or lower, from the viewpoint of suppressing burning defects. In this specification, fire resistance refers to the fire resistance (SK value) measured in accordance with JIS R2204:1999 "Test methods for fire resistance of refractories and refractory raw materials."

The refractory aggregate may contain refractory aggregate (B) having a refractoriness exceeding SK15. Examples of the refractory aggregate (B) include silica (SK35), alumina (SK37 or higher), mullite (SK37 or higher), shaft bankets (SK37 or higher), spinel (SK37 or higher), magnesia (SK37 or higher), zircon (SK37 or higher), and kaolin (SK35). Of these, at least one selected from silica, mullite, and alumina is preferred from the standpoints of economy and supply stability.

The refractory aggregate contains graphite to improve the releasability of the coated sand mold. Note that graphite burns when subjected to fire resistance testing in an oxygen-present environment according to JIS R2204:1999 "Test methods for fire resistance of refractories and refractory raw materials." This means that it does not have a fire resistance SK value.

The graphite content in the refractory aggregate is preferably 5% by mass or more, and more preferably 10% by mass or more, from the viewpoint of improving the releasability of the coated mold from the sand mold. The graphite content in the refractory aggregate is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of suppressing burning defects. The graphite content in the refractory aggregate is preferably 5% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 30% by mass or less, even more preferably 5% by mass or more and 20% by mass or less, and even more preferably 10% by mass or more and 20% by mass or less, from the viewpoint of improving the releasability of the coated mold from the sand mold and suppressing burning defects.

The content of the refractory aggregate in the vanishing pattern wash composition is preferably 40% by mass or more, and more preferably 50% by mass or more, from the viewpoints of drying properties and prevention of defects in the paint film such as cracks. The content of the refractory aggregate in the vanishing pattern wash composition is preferably 80% by mass or less, and more preferably 70% by mass or less, from the viewpoints of application workability. The content of the refractory aggregate in the vanishing pattern wash composition is preferably 40% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 70% by mass or less, from the viewpoints of drying properties and prevention of defects in the paint film such as cracks, and application workability.

[Carbon fiber]
The average fiber length of the carbon fibers is preferably 0.1 mm or more, more preferably 0.2 mm or more, from the viewpoint of suppressing burning defects. The average fiber length of the carbon fibers is preferably 10 mm or less, more preferably 5 mm or less, from the viewpoint of suppressing burning defects. The average fiber length of the carbon fibers is preferably 0.1 mm or more and 10 mm or less, more preferably 0.2 mm or more and 5 mm or less, from the viewpoint of suppressing burning defects.

From the viewpoint of suppressing burning defects, the average fiber diameter of the carbon fibers is preferably 2 μm or more, more preferably 5 μm or more. From the viewpoint of suppressing burning defects, the average fiber diameter of the carbon fibers is preferably 20 μm or less, more preferably 10 μm or less. From the viewpoint of suppressing burning defects, the average fiber diameter of the carbon fibers is preferably 2 μm or more and 20 μm or less, more preferably 5 μm or more and 10 μm or less.

From the viewpoint of suppressing burn-on defects, the content of the carbon fiber is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, per 100 parts by mass of the refractory aggregate. From the viewpoint of improving application workability to form a uniform coating film, the content of the carbon fiber is preferably 4.5 parts by mass or less, more preferably 1.0 part by mass or less, and even more preferably 0.4 parts by mass or less, per 100 parts by mass of the refractory aggregate. From the viewpoint of suppressing burn-on defects and improving application workability to form a uniform coating film, the content of the carbon fiber is preferably 0.03 parts by mass or more and 4.5 parts by mass or less, more preferably 0.05 parts by mass or more and 1.0 part by mass or less, and even more preferably 0.1 parts by mass or more and 0.4 parts by mass or less, per 100 parts by mass of the refractory aggregate.

The content of the carbon fiber in the mold wash composition for evaporative models is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more, from the viewpoint of suppressing burn-on defects. The content of the carbon fiber in the mold wash composition for evaporative models is preferably 10% by mass or less, and more preferably 2.0% by mass or less, from the viewpoint of improving application workability to form a uniform coating film and suppressing burn-on defects. The content of the carbon fiber in the mold wash composition for evaporative models is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.05% by mass or more and 2.0% by mass or less, from the viewpoint of suppressing burn-on defects and improving application workability to form a uniform coating film.

The mold wash composition may contain other components typically used in mold washes for evaporative patterns, provided that the effects of this embodiment are not impaired.

[Dispersion medium]
The mold wash composition may contain a dispersion medium commonly used in vanishing pattern washes. When the mold wash composition is an aqueous mold wash composition, water serves as the main dispersion medium. When the mold wash composition is an alcohol-based mold wash composition, lower alcohols such as methanol, ethanol, and isopropyl alcohol are preferred, with ethanol being more preferred, from the viewpoint of improving drying properties. In the case of an alcohol-based mold wash composition, an aromatic solvent or a hydrocarbon solvent may be used as an auxiliary dispersion medium.

In the case of an aqueous mold-wash composition, the amount of water in the aqueous mold-wash composition is preferably 10 parts by mass or more, and more preferably 20 parts by mass or more, per 100 parts by mass of refractory aggregate, from the viewpoint of improving application workability. In the case of an aqueous mold-wash composition, the amount of water in the aqueous mold-wash composition is preferably 80 parts by mass or less, and more preferably 70 parts by mass or less, per 100 parts by mass of refractory aggregate, from the viewpoint of improving drying workability. Furthermore, in the case of an aqueous mold-wash composition, the amount of water in the aqueous mold-wash composition is preferably 10 parts by mass or more and 80 parts by mass or less, and more preferably 20 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of refractory aggregate, from the viewpoint of improving application workability and drying workability.

The amount of dispersant in the alcohol-based mold wash composition can be varied as appropriate depending on the type of dispersant used. For example, if the dispersant is a lower alcohol, the amount is preferably 10 parts by mass or more, and more preferably 20 parts by mass or more, per 100 parts by mass of refractory aggregate, from the viewpoint of improving application workability. If the dispersant is a lower alcohol, the amount of dispersant in the alcohol-based mold wash composition is preferably 80 parts by mass or less, and more preferably 70 parts by mass or less, per 100 parts by mass of refractory aggregate, from the viewpoint of improving drying speed and preventing coating defects such as cracks. Furthermore, if the dispersant is a lower alcohol, the amount of dispersant in the alcohol-based mold wash composition is preferably 10 to 80 parts by mass, and more preferably 20 to 70 parts by mass, per 100 parts by mass of refractory aggregate, from the viewpoint of improving application workability and forming a sound coating film.

[Binding agent]
The mold wash composition may contain a binder commonly used in mold washes for evaporative patterns. Examples of binders that can be used in aqueous systems include water-soluble polymers such as sodium polyacrylate, starch, methyl cellulose, polyvinyl alcohol, sodium alginate, and gum arabic, as well as various resin emulsions. Furthermore, in alcohol systems, it is preferable to add various resins that are soluble or dispersible in alcohol in order to improve the strength of the mold wash film. From the viewpoints of improving the coating film strength and economic efficiency, the content of the binder is preferably 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the refractory aggregate.

[Sintering agent]
The mold wash composition may contain a sintering agent typically used in mold washes for evaporative patterns, provided that the effects of this embodiment are not impaired. Examples of such sintering agents include bentonites such as sodium bentonite and calcium bentonite, clays such as kibushi clay, and ethyl silicate. Among these, bentonite is preferred because it functions not only as a binder but also as a sintering agent at high temperatures. The amount of sintering agent added is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, per 100 parts by mass of the refractory aggregate, from the viewpoint of improving the strength of the mold wash at high temperatures. The amount of sintering agent added is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, per 100 parts by mass of the refractory aggregate, from the viewpoint of improving the strength of the mold wash at high temperatures. The amount of sintering agent added is preferably 0.5 parts by mass or more, more preferably 30 parts by mass or less, more preferably 15 parts by mass or less, per 100 parts by mass of the refractory aggregate, from the viewpoint of improving the strength of the mold wash at high temperatures. The amount of sintering agent added is preferably 0.5 parts by mass or more, but not more than 30 parts by mass, more preferably 1.0 parts by mass or more, per 100 parts by mass of the refractory aggregate, from the viewpoint of improving the strength of the mold wash at high temperatures.

Other components that can be incorporated into the mold wash composition include dispersants such as sodium salt of β-naphthalenesulfonic acid formalin condensate and polyvinylpyrrolidone, surfactants, preservatives, etc.

The mold wash composition can be produced by blending the refractory aggregate, the carbon fiber, and other ingredients. The term "blending" includes mixing the ingredients simultaneously or in any order. When carbon fibers of a predetermined length are to be included in the mold wash composition, the carbon fibers of the predetermined length may be blended in, or the carbon fibers may be adjusted to the predetermined length by applying shear during mixing.

The above-mentioned mold wash composition can be used to produce castings using the lost foam casting method, and more specifically, it can be suitably used as a mold wash composition to be adhered to the periphery of a lost foam.

<Method of manufacturing a lost foam pattern for casting>
In the method for manufacturing a lost form pattern for casting of this embodiment, conventional methods for manufacturing a lost form pattern for casting can be applied. The method for manufacturing a lost form pattern for casting of this embodiment is a method for manufacturing a lost form pattern for casting having a mold wash film around the periphery of the lost form pattern, and includes a step of adhering the mold wash composition for the lost form pattern to the periphery of the lost form pattern to form a mold wash film.

A typical synthetic resin foam model can be used as the lost model to which the mold wash composition of this embodiment is applied. Examples of synthetic resin foams include foams of polystyrene, polymethyl methacrylate, and copolymers thereof. When the lost model to which the mold wash composition of this embodiment is applied is expanded polystyrene, the effects of the mold wash composition of this embodiment can be more pronounced. The method for applying the mold wash composition to the lost model to form a mold wash film can be any of the conventional methods, such as flow coating (spray coating), immersion (dip dipping), brush coating, and spray coating.

The lost foam pattern for casting obtained by the method for manufacturing a lost foam pattern for casting of this embodiment can be suitably used in the manufacturing of a casting mold using the lost foam casting method.

<Casting manufacturing method>
The method for producing a casting by the lost foam casting method of this embodiment can be applied to the method for producing a casting by the conventional lost foam casting method. The method for producing a casting of this embodiment is a method for producing a casting using the lost foam pattern for casting obtained by the method for producing a lost foam pattern for casting, and includes the steps of embedding the lost foam pattern for casting in molding sand and casting molten metal into the lost foam pattern for casting embedded in the molding sand.

The molding sand used in the process of embedding the lost casting pattern in molding sand includes silica sand, which is primarily composed of quartz, as well as new or recycled sand such as zircon sand, chromite sand, and synthetic ceramic sand. Molding sand can also be used without the addition of a binder, in which case it has good packing properties, but if a high-strength mold is required, it is preferable to add a conventionally known binder and harden it with a hardener.

The manufacturing method for castings in the embodiment in which the binder is added is a manufacturing method for castings using the lost form fabrication pattern obtained by the manufacturing method for the lost form fabrication pattern for casting, and includes the steps of adding a binder and a hardener for hardening the binder to the molding sand and kneading them to prepare a mixture, embedding the lost form fabrication pattern for casting in the mixture, and pouring molten metal into the lost form fabrication pattern for casting embedded in the mixture.

The binder may be any binder that is commonly used. Examples of binders that can be used include furan resin, phenol resin, phenol-furan resin, urethane resin, and alkaline phenol resin. From the standpoints of improving mold strength and economic efficiency, the binder content is preferably 0.1 parts by mass or more, and more preferably 0.4 parts by mass or more, per 100 parts by mass of molding sand. From the standpoints of improving mold strength and economic efficiency, the binder content is preferably 5.0 parts by mass or less, and more preferably 2.0 parts by mass or less, per 100 parts by mass of molding sand. From the standpoints of improving mold strength and economic efficiency, the binder content is preferably 0.1 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.4 parts by mass or more and 2.0 parts by mass or less, per 100 parts by mass of molding sand.

In the casting manufacturing method of this embodiment, the pouring temperature varies depending on the metal used, but is generally 1280-1480°C for cast iron, 700-750°C for aluminum, and 1480-1680°C for cast steel. The lost foam casting method of this embodiment is particularly effective in reducing burn-in defects that occur in cast iron. Furthermore, because burn-in defects are easily suppressed, casting at higher temperatures is possible in order to reduce residual defects.

When castings are produced using the aforementioned mold wash composition for lost patterns, castings with little burn-in and beautiful casting surfaces are obtained, making it suitable for applications requiring complex structures or beautiful casting surfaces. Specific examples of castings include components and parts used in automobile molds, machine tools, industrial machinery, hydraulic valves for construction machinery, motors, engine frames, building materials, etc.

In relation to the above-described embodiments, this specification further discloses the following compositions, etc.

<1>
Contains refractory aggregate and carbon fiber,
The refractory aggregate (A) has a refractoriness of SK1a or more and SK15 or less, and the refractory aggregate (A) contains graphite.
<2>
The fire resistance of the fire-resistant aggregate (A) is SK1a or more, preferably SK3a or more, more preferably SK5a or more, and SK15 or less, preferably SK11 or less, more preferably SK9 or less.
<3>
The mold wash composition for a evaporative pattern according to <1> or <2>, wherein the content of the carbon fiber is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and preferably 4.5 parts by mass or less, more preferably 1.0 part by mass or less, even more preferably 0.4 parts by mass or less, relative to 100 parts by mass of the refractory aggregate.
＜4＞
The wash composition for evaporative patterns according to any one of <1> to <3>, wherein the content of the refractory aggregate in the wash composition for evaporative patterns is preferably 40% by mass or more, more preferably 50% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less.
<5>
The content of the carbon fiber in the evaporative pattern wash composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and is preferably 10% by mass or less, more preferably 2.0% by mass or less.
<6>
The mold wash composition for evaporative patterns according to any one of <1> to <5>, wherein the content of the refractory aggregate (A) in the refractory aggregate is preferably 1% by mass or more, more preferably 10% by mass or more, even more preferably 30% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less.
＜７＞
<6> The wash composition for a vanishing pattern according to any one of <1> to <6>, wherein the refractory aggregate (A) contains at least one selected from obsidian, perlite, and mica.
＜8＞
The mold wash composition for a evaporative pattern according to any one of <1> to <7>, wherein the content of graphite in the refractory aggregate is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less.
＜９＞
The mold wash composition for a evaporative pattern according to any one of <1> to <8>, wherein the carbon fibers have an average fiber length of preferably 0.1 mm or more, more preferably 0.2 mm or more, and preferably 10 mm or less, more preferably 5 mm or less.
<10>
The mold wash composition for a evaporative pattern according to any one of <1> to <9>, wherein the average fiber diameter of the carbon fibers is preferably 2 μm or more, more preferably 5 μm or more, and preferably 20 μm or less, more preferably 10 μm or less.
<11>
<10> The vanishing pattern wash composition according to any one of <1> to <10>, further containing water.
<12>
The amount of water in the mold wash composition is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, relative to 100 parts by mass of the refractory aggregate.
<13>
<13> The vanishing pattern wash composition according to any one of <1> to <12>, further containing bentonite.
<14>
<14> The vanishing pattern wash composition according to any one of <1> to <13>, further comprising a surfactant.
＜15＞
A method for manufacturing a lost form pattern for casting having a coating film on the surface of the lost form pattern, comprising:
<14> A method for producing a venant pattern for casting, comprising a step of adhering the venant pattern wash composition according to any one of <1> to <14> to the periphery of the venant pattern to form a mold wash film.
<16>
The method for producing a lost form pattern for casting according to <15>, wherein the lost form pattern is a model of a synthetic resin foam, and the synthetic resin foam is a foam of polystyrene, polymethyl methacrylate, or a copolymer thereof.
＜17＞
A method for producing a casting using a lost foam for casting obtained by the production method according to <15> or <16>,
A method for manufacturing a casting, comprising the steps of: embedding the evaporative pattern for casting in molding sand; and pouring molten metal into the evaporative pattern for casting embedded in the molding sand.
＜18＞
<17> The method for producing a casting according to <17>, wherein the molding sand is new or recycled sand of silica sand, zircon sand, chromite sand, or synthetic ceramic sand.
＜19＞
Use of a composition containing a refractory aggregate and carbon fiber, wherein the refractory aggregate contains a refractory aggregate (A) having a refractoriness of SK1a or more and SK15 or less, and graphite, for producing a casting by an lost foam casting method.

The following describes examples that specifically demonstrate the present invention.

<Examples 1 to 10 and Comparative Example 1>
[Preparation of Mold Wash Composition]
100 parts by mass of the refractory aggregate shown in Table 1 was mixed with 5 parts by mass of carbon fiber, 12 parts by mass of binder, 3 parts by mass of nonionic surfactant, and 40 parts by mass of ion-exchanged water in the amounts shown in Table 1 to prepare the mold wash compositions of Examples 1 to 10 and Comparative Example 1. The raw materials used are as follows:
[Fire-resistant aggregate]
Mullite: Cerabeads #1750 (refractory grade SK37 or higher) manufactured by Itochu Ceratec Co., Ltd.
Obsidian: Kinseimatec Co., Ltd. Obsidian - 80 mesh (fire resistance SK6a)
Mica: Kirara Co., Ltd. Mica KC200 (fire resistance SK14)
Graphite: Scaly graphite-185 manufactured by Mihara Carbon Co., Ltd.
[fiber]
Carbon fiber: SMT-201 (fiber length 2 mm, fiber diameter 7 μm) manufactured by Morimura Shoji Co., Ltd.
Glass fiber: Glass Chopped Strand SC3J-888 (fiber length 3 mm, fiber diameter 10 μm) manufactured by Nitto Boseki Co., Ltd.
Wollastonite fiber: SH-400 (fiber length 0.3 mm, fiber diameter 10 μm) manufactured by Kinseimatec Co., Ltd.
[others]
Bentonite: manufactured by Kunimine Kogyo Co., Ltd. Kunibond binder: manufactured by Nissin Chemical Industry Co., Ltd., Vinyblan 1096
Nonionic surfactant: Emulgen (registered trademark) 106, manufactured by Kao Corporation

<Evaluation of burn-on defects>
A lost form for casting, having the shape shown in FIG. 1 , was prepared using expanded polystyrene (expansion ratio: 60). The surface of this lost form was coated with the wash composition of each Example and Comparative Example (dry film thickness: 1.0 mm), to prepare a lost form for casting. After the wash application, the casting was dried for 12 hours under conditions of 50°C and 25% RH. Then, 0.32 parts by mass of an organic sulfonic acid curing agent (TK-2, manufactured by Kao-Quaker Corporation) was added to 100 parts by mass of Fremantle silica sand (No. 5), and the mixture was kneaded. Then, 0.8 parts by mass of furan resin (EF-5302, manufactured by Kao-Quaker Corporation) was mixed with the 100 parts by mass of the silica sand. The lost form for casting was embedded in the resulting mixed sand, and molten metal was poured through a weir at a rate that would prevent overflow (cast iron: FC-250, pouring temperature: 1470°C). After 24 hours, the mold was disassembled and the casting was removed. For burn-on defects occurring in the pockets (volume 660 cm ³ : 6×10×11 cm) of the resulting castings, the burn-on rate was calculated from the amount of water that entered the pockets using the following formula.
Adhesion rate (%) = (660 - amount of water in the pocket (g)) / 660 x 100

The evaluation results are shown in Table 1.

 

Claims (14)

Contains refractory aggregate and carbon fiber,
The refractory aggregate (A) has a refractoriness of SK1a or more and SK15 or less, and the refractory aggregate (A) contains graphite. The mold wash composition for evaporative patterns according to claim 1, wherein the carbon fiber content is 0.03 parts by mass or more and 4.5 parts by mass or less per 100 parts by mass of the refractory aggregate. The wash composition for evaporative patterns according to claim 1 or 2, wherein the content of the refractory aggregate in the wash composition for evaporative patterns is 40% by mass or more and 80% by mass or less. The evaporative pattern wash composition according to any one of claims 1 to 3, wherein the carbon fiber content in the evaporative pattern wash composition is 0.01% by mass or more and 10% by mass or less. The wash composition for evaporative patterns according to any one of claims 1 to 4, wherein the content of the refractory aggregate (A) in the refractory aggregate is 1% by mass or more. The wash composition for evaporative patterns according to any one of claims 1 to 5, wherein the refractory aggregate (A) contains at least one selected from obsidian, perlite, and mica. The wash composition for evaporative patterns according to any one of claims 1 to 6, wherein the graphite content in the refractory aggregate is 5% by mass or more and 50% by mass or less. The mold wash composition for evaporative patterns according to any one of claims 1 to 7, wherein the carbon fibers have an average fiber length of 0.1 μm or more and 10 mm or less. The mold wash composition for evaporative patterns according to any one of claims 1 to 8, wherein the average fiber diameter of the carbon fibers is 2 μm or more and 20 μm or less. The wash composition for evaporative patterns according to any one of claims 1 to 9, further containing bentonite. The vanishing pattern wash composition according to any one of claims 1 to 10, further comprising a surfactant. A method for manufacturing a lost form pattern for casting having a coating film on the surface of the lost form pattern, comprising:
A method for producing a venant pattern for casting, comprising a step of adhering the venant pattern wash composition according to any one of claims 1 to 11 to the periphery of the venant pattern to form a mold wash film. A method for manufacturing a casting using the lost foam for casting obtained by the manufacturing method according to claim 12,
A method for manufacturing a casting, comprising the steps of: embedding the evaporative pattern for casting in molding sand; and pouring molten metal into the evaporative pattern for casting embedded in the molding sand. Use of a composition containing refractory aggregate and carbon fiber, wherein the refractory aggregate contains refractory aggregate (A) having a refractoriness of SK1a or more and SK15 or less, and graphite, for the production of castings by the lost foam casting method.