Mold wash composition for lost foam mold

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 patterns

[0001] The present invention relates to a mold wash composition for lost foam casting used in lost foam casting.

[0002] Lost foam casting is a casting method in which a synthetic resin foam pattern of the desired shape is replaced with molten metal (hereinafter referred to as "molten metal"). This method offers numerous advantages, including the elimination of cores and complicated mold matching procedures, ease of 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 released during the replacement of a synthetic resin foam pattern with molten metal, resulting in thermal decomposition residues that are entrained 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 or thick-walled products, the removal process becomes complicated, leading to significant problems such as increased labor hours, increased workload for workers, and delayed delivery.

[0003] Examples of wash compositions for vanishing patterns that improve burn-on defects include those disclosed in JP 2003-290869 A, which contain an ore having a DTA endothermic peak temperature (°C) within a specific range; JP 11-285778 A, which discloses a wash using an inorganic or organic fiber material having a length of 6 to 30 mm; and JP 2014-73504 A, which discloses a wash composition for vanishing patterns that contains an ore having a DTA endothermic peak temperature (°C) within a specific range; and JP 2014-73504 A, which discloses a wash composition using an inorganic or organic fiber material having a length of 6 to 30 mm as a refractory aggregate. ２ ) and JP-A No. 2001-334346 discloses a mold wash composition containing one or more selected from calcium bentonite and ammonium nitrate.

[0004] The present invention provides a mold wash composition for evaporative patterns, comprising a 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.

[0005] Schematic diagram showing the shape of the evaporative model used to evaluate the adhesion defects in the examples. Detailed Description of the Invention

[0006] Conventional mold wash compositions are not sufficient in preventing burn-on defects, and further improvements have been required.

[0007] An object of the present invention is to provide a mold wash composition for vanishing patterns that can further suppress burn-on defects.

[0008] The present invention provides a mold wash composition for evaporative patterns, comprising a 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.

[0009] According to the present invention, it is possible to provide a mold wash composition for evaporative models that can further suppress burn-in defects.

[0010] An embodiment of the present invention will be described below.

[0011] <Mold wash composition for evaporative patterns> The mold wash composition for evaporative patterns of this embodiment (hereinafter also simply referred to as "mold 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 mold wash composition for evaporative patterns of this embodiment, it is possible to further suppress burning defects. The reason why the mold wash composition for evaporative patterns of this embodiment exhibits such an effect is partially unknown, but is presumed to be as follows.

[0012] During casting, the wash film 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 of SK1a or higher and SK15 or lower softens and melts with the heat of the molten metal, thereby mitigating the pressure applied to the wash film. Furthermore, the presence of carbon fiber, which is easily dispersed uniformly and functions as a reinforcing material, in the wash film is thought to make it less susceptible to damage and suppress burn-on.

[0013] [Refractory 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), etc., and among these, from the same viewpoint, at least one selected from obsidian, perlite, and mica is preferred.

[0014] 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 burning defects. The content of the refractory aggregate (A) in the refractory aggregate is preferably 60% by mass or less, more preferably 50% by mass or less, from the viewpoint of improving the smoothness of the surface of the casting. 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 burning defects and improving the smoothness of the surface of the casting.

[0015] The refractoriness of the refractory aggregate (A) is SK1a or higher, preferably SK3a or higher, more preferably SK5a or higher, from the viewpoint of suppressing burning defects. The refractoriness of the refractory aggregate (A) is SK15 or lower, preferably SK11 or lower, more preferably SK9 or lower, from the viewpoint of suppressing burning defects. In this specification, the refractoriness refers to the refractoriness (SK value) measured according to JIS R2204:1999 "Testing method for refractoriness of refractories and refractory raw materials."

[0016] The refractory aggregate may contain a refractory aggregate (B) having a refractoriness exceeding SK 15. Examples of the refractory aggregate (B) include silica (SK 35), alumina (SK 37 or higher), mullite (SK 37 or higher), shaft bankets (SK 37 or higher), spinel (SK 37 or higher), magnesia (SK 37 or higher), zircon (SK 37 or higher), and kaolin (SK 35). Among these, at least one selected from silica, mullite, and alumina is preferred from the viewpoints of economy and supply stability.

[0017] The refractory aggregate contains graphite from the viewpoint of improving the releasability of the coated mold from the sand mold. Note that graphite burns in an oxygen-containing environment and therefore cannot be used for the fire resistance measurement according to JIS R2204:1999 "Testing Method for Fire Resistance of Refractories and Refractory Raw Materials." In other words, graphite does not have a fire resistance SK value.

[0018] The graphite content in the refractory aggregate is preferably 5% by mass or more, more preferably 10% by mass or more, from the viewpoint of improving 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, from the viewpoint of improving releasability of the coated mold from the sand mold and suppressing burning defects.

[0019] The content of the refractory aggregate in the vanishing pattern wash composition is preferably 40% by mass or more, 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, 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, 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.

[0020] [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.

[0021] 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 burning defects.

[0022] 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, relative to 100 parts by mass of the refractory aggregate, from the viewpoint of suppressing burn-on defects. 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, relative to 100 parts by mass of the refractory aggregate, from the viewpoint of improving the ease of application 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 parts by mass or less, and even more preferably 0.1 parts by mass or more and 0.4 parts by mass or less, relative to 100 parts by mass of the refractory aggregate, from the viewpoint of suppressing burn-on defects and improving the ease of application to form a uniform coating film.

[0023] The content of the carbon fiber in the mold wash composition for evaporative models is preferably 0.01% by mass or more, 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, more preferably 2.0% by mass or less, from the viewpoint of improving coating workability to form a uniform coating film and from the viewpoint of 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, more preferably 0.05% by mass or more and 2.0% by mass or less, from the viewpoint of suppressing burn-on defects and from the viewpoint of improving coating workability to form a uniform coating film.

[0024] The mold wash composition may contain other components that are typically used in mold washes for evaporative patterns, provided that the effects of this embodiment are not impaired.

[0025] [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, and ethanol is 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.

[0026] 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 the 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 the refractory aggregate, from the viewpoint of improving drying performance. 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 the refractory aggregate, from the viewpoint of improving application workability and drying performance.

[0027] The amount of the dispersion medium in the alcohol-based mold wash composition can be appropriately changed depending on the type of dispersion medium used. For example, when the dispersion medium is a lower alcohol, from the viewpoint of improving application workability, the amount is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, relative to 100 parts by mass of the refractory aggregate. When the dispersion medium is a lower alcohol, from the viewpoint of improving drying properties and preventing coating defects such as cracks, the amount of the dispersion medium in the alcohol-based mold wash composition 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. Furthermore, when the dispersion medium is a lower alcohol, from the viewpoint of improving application workability and forming a sound coating film, the amount of the dispersion medium in the alcohol-based mold wash composition is preferably 10 parts by mass or more and 80 parts by mass or less, more preferably 20 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of the refractory aggregate.

[0028] [Binder] 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.

[0029] [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 part 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. Furthermore, 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. In addition, from the viewpoint of improving the strength of the coating film at high temperatures, the amount of sintering agent added is preferably 0.5 parts by mass or more and 30 parts by mass or less, and more preferably 1.0 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the refractory aggregate.

[0030] Other components that can be blended in the mold wash composition include dispersants such as sodium salt of β-naphthalenesulfonic acid formalin condensate and polyvinylpyrrolidone, surfactants, preservatives, and the like.

[0031] The mold wash composition can be produced by blending the refractory aggregate, the carbon fiber, and other components. The term "blending" includes mixing the components simultaneously or in any order. When the mold wash composition contains carbon fibers of a predetermined length, the carbon fibers may be blended in, or the carbon fibers may be adjusted to the predetermined length by applying shear during mixing.

[0032] The mold wash composition can be used to produce castings by lost foam casting, and more specifically, can be suitably used as a mold wash composition to be adhered to the periphery of a lost foam.

[0033] <Method for manufacturing a lost form pattern for casting> In the method for manufacturing a lost form pattern for casting of this embodiment, a conventional method 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.

[0034] The lost model to which the mold wash composition of this embodiment is applied can be a typical synthetic resin foam model. Examples of the synthetic resin foam include foams of polystyrene, polymethyl methacrylate, copolymers thereof, and the like. 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 effectively achieved. The method for applying the mold wash composition to the lost model to form a mold wash film may be any of conventional methods such as flow coating (spray coating), immersion (hot dip coating), brush coating, and spray coating.

[0035] The lost foam pattern for casting obtained by the method for manufacturing a lost foam pattern for casting of the present embodiment can be suitably used in the manufacturing method of a mold by lost foam casting.

[0036] <Method for manufacturing castings> In the method for manufacturing a casting by the lost foam casting method of this embodiment, a method for manufacturing a casting by a conventional lost foam casting method can be applied. The method for manufacturing a casting of this embodiment is a method for manufacturing a casting using a lost foam pattern for casting obtained by the method for manufacturing 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.

[0037] The molding sand used in the step of embedding the lost pattern for casting in molding sand includes silica sand, which is mainly composed of quartz, as well as new or recycled sand such as zircon sand, chromite sand, synthetic ceramic sand, etc. Molding sand can be used without adding a binder, in which case the filling properties are good, but when a high-strength mold is required, it is preferable to add a conventionally known binder and harden it with a hardener.

[0038] The manufacturing method of a casting in the embodiment in which a binder is added is a manufacturing method of a casting using the lost foam pattern for casting obtained by the manufacturing method of the lost foam pattern for casting, and includes the steps of adding a binder and a curing agent for curing the binder to the molding sand and kneading them to prepare a mixture, embedding the lost foam pattern for casting in the mixture, and casting molten metal into the lost foam pattern for casting embedded in the mixture.

[0039] The binder may be any commonly used binder. Examples of such binders include furan resins, phenolic resins, phenol-furan resins, urethane resins, and alkaline phenolic resins. From the viewpoints of improving mold strength and economic efficiency, the content of the binder 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 viewpoints of improving mold strength and economic efficiency, the content of the binder 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 viewpoints of improving mold strength and economic efficiency, the content of the binder 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.

[0040] In the casting manufacturing method of this embodiment, the pouring temperature varies depending on the metal used, but is generally 1280 to 1480°C for cast iron-based materials, 700 to 750°C for aluminum-based materials, and 1480 to 1680°C for cast steel-based materials. The lost foam casting method of this embodiment can particularly reduce burn-in defects that occur in cast iron-based materials. Furthermore, because burn-in defects are easily suppressed, casting at higher temperatures is possible in order to reduce residual defects.

[0041] When a casting is produced using the aforementioned mold wash composition for a lost pattern, the resulting casting has little burn-on and a beautiful casting surface, and is therefore suitable for applications requiring complex structures, beautiful casting surfaces, etc. Specific examples of castings include components and parts used in automobile dies, machine tools, industrial machinery, hydraulic valves for construction machinery, motors, engine frames, building materials, etc.

[0042] In relation to the above-described embodiments, the present specification further discloses the following compositions, etc.

[0043] <1> A mold wash composition for evaporative patterns, comprising a refractory aggregate and carbon fiber, wherein the refractory aggregate comprises a refractory aggregate (A) having a refractoriness of SK1a or more and SK15 or less, and graphite. <2> The mold wash composition for evaporative patterns according to <1>, wherein the refractoriness of the refractory aggregate (A) is SK1a or more, preferably SK3a or more, more preferably 5a or more, and SK15 or less, preferably SK11 or less, and more preferably 9 or less. <3> The mold wash composition for evaporative patterns 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, and even more preferably 0.4 parts by mass or less, relative to 100 parts by mass of the refractory aggregate. <4> The mold wash composition for evaporative models according to any one of <1> to <3>, wherein the content of the refractory aggregate in the mold wash composition for evaporative models is preferably 40% by mass or more, more preferably 50% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less. <5> The mold wash composition for evaporative models according to any one of <1> to <4>, wherein the content of the carbon fiber in the mold wash composition for evaporative models is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and preferably 10% by mass or less, more preferably 2.0% by mass or less. <6> The mold wash composition for evaporative models 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> The mold wash composition for evaporative patterns 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 evaporative patterns 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 evaporative patterns 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 evaporative patterns according to any one of <1> to <9>, wherein the carbon fibers have an average fiber diameter of preferably 2 μm or more, more preferably 5 μm or more, and preferably 20 μm or less, more preferably 10 μm or less. <11> The mold wash composition for evaporative patterns according to any one of <1> to <10>, further containing water. <12> The mold wash composition for evaporative patterns according to <11>, wherein 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 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> The mold wash composition for a venant pattern according to any one of <1> to <12>, further containing bentonite. <14> The mold wash composition for a venant pattern according to any one of <1> to <13>, further containing a surfactant. <15> A method for producing a venant pattern for casting, having a mold wash film on the surface of the venant pattern, comprising a step of adhering the mold wash composition for a venant pattern 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 venant pattern for casting according to <15>, wherein the venant 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 an evaporative pattern for casting obtained by the production method according to <15> or <16>, comprising the steps of embedding the evaporative pattern for casting in molding sand, and casting molten metal into the evaporative pattern for casting embedded in the molding sand. <18> A method for producing a casting according to <17>, wherein the molding sand is new or recycled 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 refractory aggregate (A) having a refractoriness of SK1a or more and 15 or less, and graphite, for producing a casting by an evaporative pattern casting method.

[0044] Examples that specifically illustrate the present invention will be described below.

[0045] Examples 1 to 10 and Comparative Example 1 Preparation of Mold Wash Compositions 100 parts by mass of a refractory aggregate shown in Table 1 were mixed with carbon fiber, 5 parts by mass of bentonite, 12 parts by mass of a binder, 3 parts by mass of a nonionic surfactant, and 40 parts by mass of ion-exchanged water in the amounts shown in Table 1 to prepare mold wash compositions according to Examples 1 to 10 and Comparative Example 1. The raw materials used were as follows: [Refractory aggregate] Mullite: Cerabeads #1750 manufactured by Itochu Ceratec Co., Ltd. (refractory degree SK37 or higher) Obsidian: Obsidian-80mesh manufactured by Kinseimatec Co., Ltd. (refractory degree SK6a) Mica: Mica KC200 manufactured by Kirara Co., Ltd. (refractory degree SK14) Graphite: Scaly graphite-185 manufactured by Mihara Carbon Co., Ltd. [Fiber] Carbon fiber: SMT-201 manufactured by Morimura Shoji Co., Ltd. (fiber length 2 mm, fiber diameter 7 μm) Glass fiber: Glass chop de Strand SC3J-888 manufactured by Nitto Boseki Co., Ltd. (fiber length 3 mm, fiber diameter 10 μm) Wollastonite fiber: SH-400 manufactured by Kinseimatec Co., Ltd. (fiber length 0.3 mm, fiber diameter 10 μm) [Other] Bentonite: Kunibond manufactured by Kunimine Kogyo Co., Ltd. Binder: Vinyblan 1096 manufactured by Nissin Chemical Industry Co., Ltd. Nonionic surfactant: Emulgen (registered trademark) 106 manufactured by Kao Corporation

[0046] <Evaluation of Burn-In 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 mold wash composition according to each Example and Comparative Example (dry film thickness: 1.0 mm), to prepare a lost form for casting. After the coating was applied, the mold 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 after kneading, 0.8 parts by mass of furan resin (EF-5302, manufactured by Kao-Quaker Corporation) was mixed with 100 parts by mass of the silica sand. The above-mentioned lost form for casting was embedded in the obtained mixed sand, and molten metal was poured from the weir at a speed that did not cause overflow (cast iron: FC-250, pouring temperature: 1470°C). After 24 hours, the mold was disassembled and the casting was taken out. ３ For burn-on defects occurring in the pocket (size: 6 × 10 × 11 cm), the burn-on rate was calculated from the amount of water that entered the pocket using the following formula: Burn-on rate (%) = (660 - amount of water that entered the pocket (g)) / 660 × 100

[0047] The evaluation results are shown in Table 1.

[0048]

Claims

1. A coating composition for lost form patterns, comprising a refractory aggregate and carbon fiber, wherein the refractory aggregate comprises refractory aggregate (A) having a refractoriness of SK1a or more and SK15 or less, and graphite.

2. A coating composition for a evaporative pattern as described in claim 1, wherein the content of the carbon fiber 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.

3. A wash composition for evaporative models as described in claim 1 or 2, wherein the content of the refractory aggregate in the wash composition for evaporative models is 40% by mass or more and 80% by mass or less.

4. A coating composition for evaporative models described in any one of claims 1 to 3, wherein the content of the carbon fiber in the coating composition for evaporative models is 0.01 mass% or more and 10 mass% or less.

5. A coating 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 mass% or more.

6. A wash composition for a vanishing pattern according to any one of claims 1 to 5, wherein the refractory aggregate (A) contains at least one selected from obsidian, perlite, and mica.

7. A coating composition for a lost form pattern according to any one of claims 1 to 6, wherein the content of graphite in the refractory aggregate is 5% by mass or more and 50% by mass or less.

8. A mold wash composition for a evaporative pattern 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.

9. A mold wash composition for a evaporative pattern according to any one of claims 1 to 8, wherein the carbon fibers have an average fiber diameter of 2 μm or more and 20 μm or less.

10. The vanishing pattern wash composition according to any one of claims 1 to 9, further comprising bentonite.

11. The vanishing pattern wash composition according to any one of claims 1 to 10, further comprising a surfactant.

12. A method for producing a lost form pattern for casting, having a mold coating film on the surface of the lost form pattern, comprising a step of adhering a mold coating composition for lost form pattern according to any one of claims 1 to 11 to the periphery of the lost form pattern to form a mold coating film.

13. A method for manufacturing castings using a lost foam pattern for castings obtained by the manufacturing method described in claim 12, comprising the steps of embedding the lost foam pattern for castings in molding sand, and pouring molten metal into the lost foam pattern for castings embedded in the molding sand.

14. Use of a composition containing a refractory aggregate and carbon fiber, wherein the refractory aggregate (A) has a refractoriness of SK1a or more and SK15 or less, and graphite, for producing castings by the lost foam casting method.

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