CN117102435A

CN117102435A - Structure for casting production

Info

Publication number: CN117102435A
Application number: CN202310374114.1A
Authority: CN
Inventors: 益子雄行; 石川雅隆; 木部义幸; 池永春树
Original assignee: Kao Corp
Current assignee: Kao Corp
Priority date: 2022-05-23
Filing date: 2023-04-10
Publication date: 2023-11-24

Abstract

The present application relates to a structure (3) for producing castings, comprising a main body (31) and a surface layer (32) covering at least a part of the main body (31), wherein the main body (31) contains organic fibers, inorganic fibers, first inorganic particles having an average particle diameter of more than 1 [ mu ] m and less than 50 [ mu ] m, and a binder, and the surface layer (32) contains second inorganic particles having an average particle diameter of more than 1 [ mu ] m and less than 100 [ mu ] m, a clay mineral, and 7 parts by mass to 40 parts by mass of the same binder as the binder or a different type of binder relative to 100 parts by mass of the second inorganic particles.

Description

Structure for casting production

Technical Field

The present application relates to a structure for casting production.

Background

The present inventors have previously proposed a structure for casting production having a surface layer on the surface of a structure containing organic fibers, inorganic particles, and a binder (see patent document 1). The surface layer of the structure for casting production is a layer containing refractory inorganic particles, clay minerals and a binder. According to such a structure for casting production, there is an advantage that the mixing of gas generated at the time of casting production into the casting can be suppressed by the surface layer. Therefore, according to this structure for casting production, it is possible to improve the gas induced defect which is one of the serious defects of castings.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2012-02841

Disclosure of Invention

The present invention relates to a structure for casting production, which has a main body portion and a surface layer covering at least a part of the main body portion.

In one embodiment, the main body preferably contains organic fibers, inorganic fibers, first inorganic particles having an average particle diameter of more than 1 μm and less than 50 μm, and a first binder.

In one embodiment, the surface layer preferably contains second inorganic particles having an average particle diameter of 1 μm or more and 100 μm or less, clay minerals, and a second binder of the same or different type from the first binder, and the second binder is preferably contained in an amount of 7 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the second inorganic particles.

Drawings

Fig. 1 is a schematic cross-sectional view showing an embodiment of the structure for producing castings according to the present invention.

Fig. 2 (a) to (d) are schematic cross-sectional views showing other embodiments of the structure for producing castings according to the present invention.

Fig. 3 is a schematic view showing a mold using the structure for producing a casting of the present invention.

Detailed Description

The structure for producing castings described in patent document 1 can be easily cut by containing organic fibers or the like, and therefore can be cut into any size before use, and can be easily adapted to the shape of the target casting and the shape of the melt flow path. There is room for improvement in preventing cracking due to forces applied during cutting and in resisting sand weight during casting. The structure for casting production described in this document also has room for improvement in terms of strength for preventing the surface layer from peeling.

The present invention relates to a structure for producing castings, in which the strength of both a main body portion and a surface layer is enhanced and breakage is less likely to occur.

Hereinafter, the present invention is described based on preferred embodiments and with reference to the accompanying drawings.

Fig. 1 shows a structure (hereinafter also simply referred to as "structure") 3 for producing a casting, which is one preferred embodiment of the present invention. The structure 3 is cylindrical as shown in fig. 1. The "tubular shape" of the present invention includes a shape having a bending portion in an axial direction partially shown in fig. 2 (a), a shape having an arc shape in an axial direction entirely shown in fig. 2 (b), a shape having a branching portion shown in fig. 2 (c) and (d), and the like.

As shown in fig. 1 and 2, the structure 3 has a main body 31 and a surface layer 32 covering at least a part of the main body 31.

The structure 3 preferably forms a surface layer 32 on at least the surface of the portion of the main body 31 that is in contact with the molten metal when it is used. That is, in the state where the surface layer 32 is formed on the surface of the body 31, it is preferable that the surface layer 32 is present on the side contacting the molten metal from the viewpoint of improving the gas induced defects of the casting. The surface layer 32 preferably covers 50% or more, more preferably 80% or more, still more preferably 90% or more, and still more preferably substantially 100% of the surface of the body 31 on the side contacting the molten metal.

The main body 31 contains organic fibers, inorganic fibers, first inorganic particles having an average particle diameter of more than 1 μm and less than 50 μm, and a binder (hereinafter also referred to as "first binder"). The main body 31 can be formed by, for example, preparing a slurry composition (hereinafter, referred to as a raw material slurry) containing organic fibers, inorganic fibers, first inorganic particles, a first binder, and a dispersion medium, molding the intermediate molded body of the main body 31 using a molding die for molding, and then heating and drying the intermediate molded body using a die, but the present invention is not limited to this method. Hereinafter, each component contained in the main body 31 will be described.

(i) Organic fiber

The organic fibers form a skeleton in the main body 31 in a state before the use thereof for casting, and at the time of casting, a part or all of the organic fibers are burned by heat of the molten metal, so that a cavity is formed in the main body 31 after the casting is manufactured.

The organic fiber may contain, in addition to wood pulp, a fibrillated synthetic fiber, a regenerated fiber (e.g., rayon fiber), or the like, and may contain one or a mixture of two or more of them. Among them, paper fibers are preferably contained. The reason for this is that the molded article can be molded into various forms by papermaking, and the wet strength performance of the dehydrated and dried molded article is excellent, and the paper fiber is easily obtained, stable and economical. In addition, in addition to wood pulp, cotton pulp, linter pulp (linter pulp), bamboo, straw, and other non-wood pulp may be included in the paper fiber. As the wood pulp, virgin pulp or recycled pulp (recycled product) may be used singly or in combination. The recycled pulp is preferably contained in view of availability, environmental protection, reduction in manufacturing cost, and the like. The organic fiber preferably contains waste paper (newspaper or the like) from the viewpoints of improving the moldability and the ease of supply of the structure and economic efficiency.

The average fiber length of the organic fibers is preferably 0.8mm or more, more preferably 0.9mm or more. When the average fiber length of the organic fibers is equal to or greater than the lower limit, it is possible to prevent cracks from occurring on the surface of the main body 31 and to secure mechanical properties such as impact strength.

The average fiber length of the organic fibers is preferably 10mm or less, more preferably 7mm or less, and still more preferably 5mm or less. When the upper limit value is less than or equal to the above, uneven wall thickness of the body 31 is less likely to occur, and the surface smoothness is also good.

From the viewpoint of improving toughness and usability, the main body 31 preferably contains 8 mass% or more, more preferably 10 mass% or more, and still more preferably 13 mass% or more of organic fibers relative to the entire mass of the main body. The upper limit of the content of the organic fiber in the main body 31 may be, for example, 30 mass% or less, particularly 25 mass% or less, and may be 20 mass% or less. The usability means that when cutting in an arbitrary size before use, cracking is not easily generated by the force applied during cutting, or breakage is not easily generated by the weight of sand during casting.

(ii) Inorganic fiber

The inorganic fiber mainly forms its skeleton in the structure in a state before being used for casting, and maintains its shape at the time of casting without burning by the heat of the molten metal. In particular, when an organic binder is used as the first binder to be described later, the inorganic fibers can suppress thermal shrinkage caused by thermal decomposition of the organic binder due to heat of the molten metal.

The inorganic fibers may contain, for example, artificial mineral fibers such as carbon fibers and rock wool, ceramic fibers, glass fibers, and natural mineral fibers, and may contain one or two or more of them in combination. Among them, carbon fibers, which are materials having high strength even at high temperatures of metal melting, are preferably contained from the viewpoint of suppressing the above-mentioned heat shrinkage. Further, from the viewpoint of suppressing the manufacturing cost, it is preferable to contain rock wool and/or glass fiber.

The average fiber length of the inorganic fibers is preferably 0.1mm or more, more preferably 0.25mm or more, and still more preferably 0.4mm or more. When the average fiber length of the inorganic fibers is equal to or greater than the lower limit, the drainage is good, and the occurrence of defective dehydration during the production of the main body 31 can be prevented. Further, the thick body 31 (particularly, hollow three-dimensional body such as bottle) can be made to have good shapability.

On the other hand, the average fiber length of the inorganic fibers is preferably 10mm or less, more preferably 8mm or less, and still more preferably 4mm or less. When the average fiber length of the inorganic fibers is equal to or less than the upper limit, the body 31 having a uniform wall thickness can be obtained, and the hollow structure can be easily manufactured.

The main body 31 preferably contains 0.5 mass% or more, more preferably 1 mass% or more, still more preferably 1.5 mass% or more, still more preferably 2 mass% or more of the inorganic fibers based on the total mass of the main body 31. When the content of the inorganic fibers is equal to or more than the lower limit value, strength at the time of casting of the main body 31 can be ensured, and this effect is particularly remarkable when the main body 31 uses an organic binder. Further, the occurrence of shrinkage, cracking, wall peeling (a phenomenon in which the wall surface of the main body 31 separates into an inner layer and an outer layer) and the like of the main body 31 due to carbonization of the organic binder can be prevented. Further, it is easy to suppress the occurrence of defects in the part of the main body 31 or the molding sand (foundry sand) mixed into the product part (casting).

The main body 31 preferably contains 80 mass% or less, more preferably 40 mass% or less, still more preferably 35 mass% or less, and still more preferably 20 mass% or less of the inorganic fibers based on the mass of the entire main body 31. When the content of the inorganic fibers is less than the upper limit, the moldability of the main body 31, particularly in the papermaking step and the dewatering step, is improved, and the fluctuation in the raw material cost of the fibers to be used is reduced.

The mass ratio of the organic fiber to the inorganic fiber (inorganic fiber/organic fiber) is preferably 0.1 or more, more preferably 0.2 or more, and still more preferably 0.5 or more when the inorganic fiber is a carbon fiber. Further, it is preferably 50 or less, more preferably 30 or less, further preferably 1 or less, further preferably 0.8 or less, particularly preferably 0.7 or less.

When the inorganic fiber is rock wool or glass fiber, the inorganic fiber/organic fiber is preferably 10 or more, more preferably 20 or more. Further, it is preferably 90 or less, more preferably 80 or less.

When the mass ratio is less than or equal to the upper limit of the above range, the moldability in the molding or the dehydration molding of the structure is good, and the strength of the structure after dehydration is sufficient, so that breakage or the like of the structure at the time of removal from the molding can be prevented. When the mass ratio is equal to or greater than the lower limit of the above range, shrinkage of the structure due to thermal decomposition of the organic fiber and an organic binder described later can be suppressed.

The long axis/short axis ratio of the inorganic fiber is more preferably 10 to 2000, still more preferably 50 to 1000, from the viewpoint of improving the heat strength of the structure for casting production and the moldability of the structure for casting production.

(iii) First inorganic particles

The first inorganic particles may include aggregate particles of refractory materials such as graphite, mullite, obsidian, zirconia, zircon, mica, silica, hollow ceramics, fly ash, and alumina. The first inorganic particles may be contained alone or two or more of them may be selected to be contained. Hollow ceramic refers to hollow particles contained in fly ash, and can be obtained by floating fly ash with water.

In the structure 3, the average particle diameter of the first inorganic particles is preferably within a specific range.

Specifically, the average particle diameter of the first inorganic particles is preferably less than 50 μm, more preferably 40 μm or less, further preferably 35 μm or less, further preferably 25 μm or less. By setting the average particle diameter of the first inorganic particles within the upper limit, the density of the first inorganic particles in the main body 31 can be increased, and the strength of the main body 31 can be improved. Further, since the surface roughness of the body 31 can be reduced, a coating liquid composition described later can be uniformly applied to the inner surface of the body 31. Specifically, it is possible to avoid the occurrence of an extremely thin portion in the surface layer 32 formed by applying the coating liquid composition described later to the inner surface of the main body portion. By setting the first inorganic particles to be small, specifically, setting the average particle diameter of the first inorganic particles within the above upper limit, the void size between the first inorganic particles of the main body portion 31 can be reduced. This improves the strength of the structure 3, and suppresses shrinkage of the main body 31 during casting production. Therefore, leakage of molten metal due to cracking of the structure 3 can be prevented, and combustion can be suppressed. Further, the inter-particle distance of the main body 31 can be reduced, and the gaps between the first inorganic particles in the main body 31 can be reduced. In this way, when the molten metal contacts the body 31, burning caused by the molten metal passing through the first inorganic particles of the body 31 and contacting the molding sand can be prevented. By suppressing the burn-in, the molding sand can be suppressed from being mixed into the molten metal. In general, when a casting is manufactured, a portion of a product formed by solidification of molten metal in a cavity of a sand mold and a portion other than the product formed by solidification of molten metal in a melt flow channel pipe can be obtained. By suppressing the mixing of molding sand into the molten metal, parts other than the product can be easily reused. Further, since the step for removing the molding sand from the molten metal obtained by remelting the part other than the product can be omitted, the cost can be suppressed, and the quality of the molten metal obtained by remelting the part other than the product can be stabilized.

Further, the average particle diameter of the first inorganic particles is preferably larger than 1 μm, more preferably 5 μm or more, still more preferably 10 μm or more, still more preferably 15 μm or more, from the viewpoint of improving the moldability of the main body 31. By setting the average particle diameter of the first inorganic particles within this lower limit, when the intermediate molded body of the main body 31 is produced by papermaking, it is possible to prevent the first inorganic particles from passing through the papermaking net and reducing the yield, and thus it is possible to improve the moldability of the main body 31. Further, since the drainage property of the intermediate molded body of the main body 31 can be improved, dehydration and drying can be easily performed, and the moldability of the main body 31 can be improved.

These lower limits may be combined with any of the upper limits described above.

The average particle diameter of the first inorganic particles can be measured by the following method.

[ method for measuring average particle diameter ]

The average particle diameter of the present invention was determined to be 50% by volume cumulative average particle diameter measured by a laser diffraction particle size distribution measuring apparatus (LA-920 manufactured by horiba, inc.). The analysis conditions are as follows:

measurement method: flow process

Refractive index: specific to various inorganic particles (refer to the handbook attached to LA-920)

Dispersion medium: using dispersion media corresponding to the various inorganic particles

Dispersion method: stirring and ultrasonic wave (22.5 kHz) built in for 3 minutes

Sample concentration: 2mg/100cm ³

The specific gravity of the first inorganic particles is preferably 0.5 or more and 5 or less from the viewpoint of dispersibility of the raw materials, more preferably 1 or more and 4 or less, still more preferably 1.5 or more and 3.5 or less from the viewpoint of further weight reduction. By setting the specific gravity of the first inorganic particles to be within the above range, the dispersibility of the raw material in the step of kneading when the dispersion medium is water is improved. The composition of the main body 31 may be determined in consideration of the apparent specific gravity of the first inorganic particles and also in consideration of the bulk specific gravity. The bulk specific gravity is the mass per unit volume obtained by measuring the amount of particles added to a container after the particles are placed in a container of constant volume to reach a steady state.

The first inorganic particles may be hollow. By using hollow particles, the bulk specific gravity of the inorganic particles having a large specific gravity can be reduced.

The content of the first inorganic particles is preferably 40 mass% or more, more preferably 45 mass% or more, and still more preferably 50 mass% or more, based on the entire mass of the main body, from the viewpoint of improving the heat strength.

The content is preferably 80% by mass or less, more preferably 75% by mass or less, still more preferably 70% by mass or less, still more preferably 65% by mass or less, and particularly preferably 60% by mass or less.

(iv) First adhesive

In the present invention, the first binder may contain at least one of an organic binder and an inorganic binder. From the viewpoint of excellent removability after casting, it is preferable to contain an organic binder. Examples of the organic binder include thermosetting resins such as phenolic resins, epoxy resins, and furan resins. Among them, the phenolic resin is preferably contained in view of the low amount of inflammable gas generated, the combustion suppressing effect, the high carbon residue after thermal decomposition (carbonization), and the like.

Examples of the phenolic resin include linear phenolic resins, resols such as resols, and modified phenolic resins modified with urea, melamine, epoxy resins, and the like. Among them, the inclusion of the resol resin is preferable because it does not require a curing agent such as an acid or an amine, and therefore can reduce odor during molding of the main body 31 and casting defects during use of the main body 31 as a mold.

When a phenolic novolac resin is contained, it is preferably used in combination with a curing agent. Since the curing agent is easily soluble in water, it is preferable that the surface of the main body 31 is dehydrated and then coated. The curing agent preferably contains, for example, hexamethylenetetramine.

Examples of the inorganic binder include a phosphoric acid binder, water glass such as silicate, gypsum, sulfate, silica binder, and silicon binder. The organic binder may be contained alone or in combination of two or more, or may be used in combination with the inorganic binder.

In the first binder, the reduction ratio (TG thermography measurement) at a temperature of 1000 ℃ in a nitrogen atmosphere is preferably 50 mass% or less, particularly preferably 45 mass% or less, from the viewpoint of firmly bonding the organic fibers, the inorganic fibers, and the first inorganic particles when the molded part is dried and molded before casting.

From the viewpoint of improving the strength and further exhibiting the effect of suppressing the gas generation amount, the main body 31 preferably contains 5 mass% or more, more preferably 10 mass% or more, and still more preferably 15 mass% or more of the first binder with respect to the mass of the entire main body.

Further, from the viewpoint of improving heat resistance, preventing the reduction of the content of the matrix component and the frame during molding, and improving shape retention, the main body 31 preferably contains 50 mass% or less, more preferably 40 mass% or less, and still more preferably 25 mass% or less of the first binder with respect to the mass of the entire main body. Particularly when the first binder contains an organic binder, the effect of improving heat resistance is more remarkable by controlling the content of the first binder within the above-mentioned range.

(v) Other ingredients

In addition to the organic fibers, the inorganic fibers, the first inorganic particles, and the first binder, a paper strength enhancer (paper strength enhancer) may be added to the main body portion 31. When the intermediate formed body of the main body 31 is impregnated with the first binder (described later), the paper strength reinforcing agent has an effect of preventing swelling of the intermediate formed body.

Examples of the paper strength reinforcing agent include latex, acrylic emulsion, polyvinyl alcohol, carboxymethyl cellulose (CMC), polyacrylamide resin, and polyamide epichlorohydrin resin.

The content of the paper strength enhancer in terms of solid content is preferably 0.01 mass% or more and 2 mass% or less, more preferably 0.02 mass% or more and 1 mass% or less, relative to the entire mass of the main body 31. When the amount of the paper strength enhancer is 0.01 mass% or more, it is sufficient to prevent swelling and to fix the added powder to the fiber appropriately. On the other hand, when the content is 2 mass% or less, the molded body of the body 31 is less likely to adhere to the mold.

The main body 31 may further contain a component such as a coagulant or a colorant.

The thickness of the main body 31 may be set according to the purpose of use, and is preferably 0.2mm or more, more preferably 0.8mm or more, and still more preferably 1.2mm or more. When the thickness of the main body 31 is above this lower limit value, the strength as a structure will be sufficient to enable the structure to maintain a desired shape and function in a state unaffected by the sand pressure.

The thickness of the main body 31 is preferably 5mm or less, more preferably 3.5mm or less, and still more preferably 2.1mm or less. When the thickness of the main body 31 is equal to or less than the upper limit value, the air permeability is appropriate, and the raw material cost can be reduced, the molding time can be shortened, and the manufacturing cost can be suppressed.

When the main body 31 is produced by a wet process using a raw material slurry, the water content of the main body 31 before use (before use for casting) is preferably 10 mass% or less, more preferably 8 mass% or less. The reason for this is that the lower the water content, the lower the gas generation amount due to thermal decomposition in the casting process. It is preferable to have this water content even after the surface layer 32 is formed. Therefore, the water content of the casting production structure 3 of the present invention is preferably 10 mass% or less, more preferably 8 mass% or less.

The density of the main body 31 is preferably 3g/cm ³ Hereinafter, more preferably 2g/cm ³ The following is given. The reason for this is that when the density is small, the weight is reduced, and the handling and processing of the structure 3 are facilitated.

As described above, the structure 3 has the surface layer 32. The surface layer 32 contains second inorganic particles having an average particle diameter of 1 μm or more and 100 μm or less, a clay mineral, and a binder (hereinafter also referred to as "second binder"). The second adhesive is the same or a different kind of adhesive from the first adhesive. The surface layer 32 can be formed by applying a coating liquid composition containing second inorganic particles, clay minerals, and a second binder to the inner peripheral surface of the main body portion 31.

The components contained in the surface layer 32 are explained below.

(vi) Second inorganic particles

From the viewpoint of improving heat resistance at the time of casting, the surface layer 32 preferably contains 40 mass% or more, more preferably 60 mass% or more, and still more preferably 70 mass% or more of the second inorganic particles with respect to the entire mass of the surface layer.

Further, from the viewpoint of improving the strength of the surface layer 32 at the time of casting, the second inorganic particles are preferably contained in an amount of 93 mass% or less, more preferably 90 mass% or less, and still more preferably 80 mass% or less, relative to the mass of the entire surface layer.

From the viewpoint of both, it is preferably 40% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 90% by mass or less, and still more preferably 70% by mass or more and 89% by mass or less.

The average particle diameter of the second inorganic particles is 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, still more preferably 15 μm or more from the viewpoints of sealing property of the surface of the body 31, adhesion between the body 31 and the surface layer 32, and the like.

The second inorganic particles have an average particle diameter of 100 μm or less, preferably 80 μm or less, more preferably 70 μm or less, still more preferably 50 μm or less, still more preferably 35 μm or less, and particularly preferably 25 μm or less, from the viewpoint of suppressing transfer of the thermally decomposed gas generated from the main body 31 to the molten metal side during casting.

The average particle diameter of the second inorganic particles can be obtained in the same manner as the method for measuring the average particle diameter of the first inorganic particles.

In the structure 3, the ratio D1/D2 of the average particle diameter D1 of the first inorganic particles to the average particle diameter D2 of the second inorganic particles is preferably 0.1 or more, more preferably 0.5 or more, and still more preferably 1 or more from the viewpoints of improving the sealing property of the surface of the main body 31 and improving the gas barrier property.

Further, D1/D2 is preferably 2.5 or less, more preferably 2 or less, and still more preferably 1.8 or less, from the viewpoint of preventing the second inorganic particles from entering the gaps between the first inorganic particles in the main body portion 31, being easily distributed on the surface of the main body portion 31 formed of the first inorganic particles, and being easily forming a uniform surface layer 32 on the surface of the main body portion 31.

The second inorganic particles preferably have fire resistance. The second inorganic particles have fire resistance, which means that the melting point is preferably 1500 ℃ or higher, more preferably 1600 ℃ or higher, and still more preferably 1700 ℃ or higher. From this point of view, examples of the second inorganic particles include particles selected from metal oxides and metal silicates. Specifically, the second inorganic particles include refractory inorganic particles such as mullite, zircon, zirconia, alumina, olivine, shosapiner (trade name, fused spinel), magnesia, chromite, and the like. From the viewpoint of improving the gas-induced defects of the casting even when a molten metal having a higher temperature is used, mullite, zircon, and alumina are preferably contained. The second inorganic particles may be selected to contain one or more of them alone. In cast steel (0.03 to 1.7% C) having a carbon content lower than that of cast iron (1.7 to 6.67% C), aggregate particles other than carbonaceous materials are preferably used, and zircon, mullite, and alumina having a high melting point and low wettability with molten metal are more preferably contained.

(vii) Clay mineral

The surface layer 32 further contains clay minerals from the viewpoint of improving the heat strength and imparting viscosity at the time of coating. By adding the clay mineral to the dispersion liquid (coating liquid composition) for obtaining the surface layer, the dispersion liquid is given a moderate viscosity, so that the sedimentation of the raw material in the dispersion liquid is prevented, and the dispersibility of the raw material is improved. Examples of the clay mineral include a layered silicate mineral and a multi-chain structure mineral, which may be natural or synthetic. Examples of the layered silicate mineral include clay minerals belonging to the group of montmorillonite, kaolin and illite, such as bentonite, montmorillonite, hectorite, activated clay, spinodal clay, zeolite, and the like. Examples of the multi-chain mineral include attapulgite, sepiolite, and palygorskite. From the viewpoint of improving the heat strength and ensuring the viscosity at the time of coating, it is preferable to contain one or more selected from attapulgite, sepiolite, bentonite and montmorillonite. More preferably, the material is one or more selected from attapulgite and sepiolite. In this regard, since the clay mineral has a layered structure or a multi-chain structure, it is distinguished from, for example, a second inorganic particle mainly comprising a hexagonal closest packed structure and generally having no layered structure or multi-chain structure. That is, the second inorganic particles have neither a layered structure nor a multi-chain structure.

From the viewpoint of improving the hardness of the surface layer 32 and improving the peeling resistance of the surface layer 32 in the pre-casting state, the surface layer 32 preferably contains 1.5 parts by mass or more, more preferably 2 parts by mass or more, still more preferably 2.2 parts by mass or more, relative to 100 parts by mass of the second inorganic particles.

Further, from the viewpoint of improving heat resistance at the time of casting, the clay mineral is preferably contained in an amount of 50 parts by mass or less, more preferably 25 parts by mass or less, and still more preferably 10 parts by mass or less.

The surface layer 32 preferably contains 1.2 mass% or more, more preferably 1.6 mass% or more, and still more preferably 2 mass% or more, of the clay mineral, from the viewpoint of improving the heat strength and imparting viscosity at the time of coating, provided that the ratio of the clay mineral and the second inorganic particles satisfies the above-described relationship.

Further, from the viewpoint of improving heat resistance at the time of casting, the clay mineral is preferably contained in an amount of 50 mass% or less, more preferably 25 mass% or less, and still more preferably 10 mass% or less.

(viii) Second adhesive

From the viewpoint of improving the heat strength, the surface layer 32 further contains a second binder. From the viewpoint of improving the room temperature strength and heat resistance of the structure for casting production, the second binder is preferably used in forming the surface layer 32. The second adhesive may be any of an adhesive that is solid before the production of the structure 3, and an adhesive that is liquid before the production of the structure 3 and is converted into a solid during the production of the structure 3.

As the second binder that is solid before production from the structure 3, an organic binder and an inorganic binder can be used. Examples of the organic binder include a novolac resin, a resol resin, a polyethylene resin, a polypropylene resin, a polyester resin, and a polyimide resin. Examples of the inorganic binder include various sols such as sulfate, silicate, phosphate, lithium silicate, zirconia sol, colloidal silica, and alumina sol, and the inorganic binder is preferably an inorganic binder, more preferably at least one selected from the group consisting of colloidal silica and aluminum phosphate, and still more preferably colloidal silica. The above binders may be used alone or in combination of two or more kinds, or an organic binder and an inorganic binder may be used in combination. From the viewpoint of improving the heat strength, an inorganic binder is particularly preferably used as the second binder.

As the second binder which is liquid before the structure 3 is manufactured and is converted into a solid during the manufacturing process of the structure 3, an organic binder and an inorganic binder can be used.

Examples of the organic binder include a solution of resol, epoxy, furan, water-soluble alkyd, water-soluble butyral, polyvinyl alcohol, water-soluble acrylic, water-soluble polysaccharide, vinyl acetate, or a copolymer thereof dissolved in a solvent.

Examples of the inorganic binder include water glass such as silicate, tetramethyl orthosilicate, and tetraethyl orthosilicate.

The second binder may be the same as the first binder, but is preferably a different material from the first binder in terms of further improving the heat strength.

In the structure 3, the content of the second inorganic particles preferably has a specific relationship with the content of the second binder.

Specifically, from the viewpoint of improving the strength of the surface layer 32, the surface layer 32 preferably contains 7 parts by mass or more, more preferably 8 parts by mass or more, and still more preferably 9 parts by mass or more of the second binder with respect to 100 parts by mass of the second inorganic particles.

Further, from the viewpoint of improving heat resistance at the time of casting, the surface layer 32 preferably contains 40 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less of the second binder per 100 parts by mass of the second inorganic particles. These upper values may be combined with any of the lower values described above.

The surface layer 32 preferably contains 5 mass% or more, more preferably 7 mass% or more, and still more preferably 8 mass% or more of the second binder, from the viewpoint of improving the heat strength, provided that the ratio of the second inorganic particles to the second binder satisfies the above-described relationship.

Further, from the viewpoint of improving heat resistance at the time of casting, the second binder is preferably 40% by mass or less, more preferably 30% by mass or less, and still more preferably 20% by mass or less.

The shape of the second binder is not particularly limited, but is preferably granular. When the second binder is in the form of particles, the second binder is liable to enter between the second inorganic particles in the surface layer 32, and the voids between the second inorganic particles can be reduced. By reducing the gaps between the second inorganic particles, the gas barrier property of the surface layer 32 can be improved. The average particle diameter D3 of the second binder is preferably 10% or less, more preferably 5% or less, and even more preferably 1% or less of the average particle diameter D2 of the second inorganic particles, from the viewpoint of making the effect more remarkable. The lower limit value of the proportion of the average particle diameter D3 of the second binder to the average particle diameter D2 of the second inorganic particles may be, for example, 0.1%. The average particle diameter of the second binder can be obtained in the same manner as the measurement method of the average particle diameter of the first inorganic particles.

The specific gravity of the second binder is preferably lower than that of the second inorganic particles, from the viewpoint of reducing the voids between the second inorganic particles and improving the gas barrier property of the surface layer 32. From the viewpoint of making this effect more remarkable, the ratio of the specific gravity of the second binder to the specific gravity of the second inorganic particles (specific gravity of the second binder/specific gravity of the second inorganic particles) is preferably 0.05 or more, more preferably 0.1 or more, further preferably 0.15 or more, and preferably 1 or less, more preferably 0.9 or less, further preferably 0.8 or less, and preferably 0.05 or more and 1 or less, more preferably 0.1 or more and 0.9 or less, further preferably 0.15 or more and 0.8 or less.

The mass reduction rate of the surface layer 32 is preferably 10% or less, more preferably 7% or less, and even more preferably 5% or less, from the viewpoint of reducing the gas generation amount at the time of casting and preventing occurrence of gas-induced defects in the casting. The lower limit of the mass reduction rate of the surface layer 32 may be 0% or more, for example, 0.5% or more.

The mass reduction rate can be measured by the following method.

< method for measuring Mass reduction Rate >

The surface layer was scraped from the casting structure using a cutter or the like so as not to include the main body portion, and a sample was obtained.

Then, the above-mentioned sample was heated from 30℃to 1000℃at a heating rate of 20℃/min under a nitrogen atmosphere by using a thermogravimetric measuring device (STA 7200RV TG/DTA, manufactured by Seiko Instruments Co., ltd.), the change in mass was measured as a function of the temperature, and the percentage of the mass of the sample at 1000℃relative to the mass of the sample at 30℃was calculated as a mass reduction rate (%).

In addition, from the viewpoint of preventing the gas generated during casting from being mixed into the molten metal flowing in the structure 3 and avoiding occurrence of gas-induced defects in the cast product produced, the porosity of the surface layer 32 is preferably equal to or less than a predetermined upper limit value.

The thickness of the surface layer 32 (the layer thickness of the surface layer 32 formed on the surface of the main body 31 after drying) is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 20 μm or more, still more preferably 100 μm or more, and particularly preferably 200 μm or more, from the viewpoint of exhibiting the effect of reducing the gas induced defects as the quality of castings and improving the sagging property of the surface layer 32.

In addition, from the viewpoint of improving workability, the thickness of the surface layer 32 is preferably 1000 μm or less, more preferably 900 μm or less, still more preferably 800 μm or less, still more preferably 700 μm or less, still more preferably 600 μm or less.

The thickness of the surface layer 32 can be obtained by a measurement method described in the embodiment described later.

In the structure 3, the air permeability of the main body 31 is preferably higher than the air permeability of the surface layer 32. In this way, the gas shielded by the surface layer 32 can be effectively discharged from the surface where the surface layer 32 is not formed, and the gas generated during casting can be effectively prevented from being mixed into the molten metal flowing in the structure 3. The air permeability can be measured according to JIS P8117. The air permeability of the body 31 alone is preferably equal to or higher than a predetermined lower limit value and the air permeability of the surface layer 32 alone is preferably equal to or lower than a predetermined upper limit value, from the viewpoint of more effectively preventing the gas generated during casting from being mixed into the molten metal flowing in the structure 3. From the same point of view, the air permeability of the structure 3 is preferably equal to or higher than a predetermined lower limit value and equal to or lower than a predetermined upper limit value.

In the structure 3, the proportion of the surface layer 32 is preferably 10 mass% or more and 80 mass% or less, more preferably 20 mass% or more and 80 mass% or less, still more preferably 30 mass% or more and 70 mass% or less, still more preferably 38 mass% or more and 60 mass% or less, based on the mass of the structure 3.

The maximum bending stress of the structure 3 is preferably 10MPa or more, more preferably 13MPa or more, and even more preferably 15MPa or more. When the maximum bending stress is equal to or higher than the lower limit, the molding sand is less likely to be deformed by being squeezed, and the function as the structure 3 can be maintained.

The maximum bending stress of the structure 3 can be measured by a three-point bending test according to JIS K7017 using a measuring device (Universal test machine AGX-plus manufactured by Shimadzu corporation). As the specimen for measuring the maximum bending stress, a plate-like specimen having dimensions of 60mm in length by 15mm in width cut from a structure for casting production was used. The sample is sampled so as to include both the body 31 and the surface layer 32.

Maximum bending stress sigma _h The physical property value calculated by dividing the moment (product of load and distance) applied to the sample in the three-point bending test by the section coefficient of the sample is calculated by the following formula (1).

Maximum bending stress

In formula (1), P _h The maximum bending load, L, is the distance between the fulcrums, b is the lateral length of the specimen, and h is the thickness of the specimen.

When the plate-like sample cannot be cut based on the size of the structure to be measured, a sample having an arbitrary size may be cut for measurement.

Next, a method for manufacturing the structure 3 will be described. The structure 3 can be manufactured by, for example, forming the surface layer 32 on the inner surface of the main body 31 manufactured after the main body 31 is manufactured. The method of manufacturing the main body 31 will be described below.

< method for producing body portion 31 >

The main body 31 can be manufactured by a molding method having a molding step. Such a molding method is described in, for example, japanese patent application laid-open No. 2012-02841.

Specifically, first, a raw material slurry containing organic fibers, inorganic fibers, first inorganic particles, and a first binder in a predetermined ratio is prepared. The raw material slurry is prepared by dispersing organic fibers, inorganic fibers, first inorganic particles, and a first binder in a predetermined dispersion medium. The first binder may be impregnated into the body 31 instead of being formulated into the raw material slurry.

Examples of the dispersion medium include solvents such as ethanol, methanol, methylene chloride, acetone, and xylene, in addition to water. These dispersion media may be used singly or in combination of two or more. Among them, water is preferable from the viewpoint of ease of handling.

The proportions of the organic fibers, the inorganic fibers, the first inorganic particles, and the first binder in the raw material slurry are appropriately adjusted to have the composition of the target body 31.

Additives such as a paper strength enhancer, a coagulant, and a preservative may be added to the raw material slurry as needed.

Next, the intermediate molded body of the main body 31 is molded using the raw material slurry.

In the intermediate molding step, a molding die for molding by dehydration is used in which a cavity having a shape corresponding to the outer shape of the intermediate molding is formed by closing two split molds (split molds), for example. Then, a predetermined amount of the raw material slurry is injected into the cavity under pressure from the upper opening of the mold. Thereby pressurizing the cavity to a predetermined pressure. Each parting mold is provided with a plurality of communication holes for communicating the outside thereof with the mold cavity in advance, and the inner surface of each parting mold is covered with a net having a prescribed mesh size. In the case of pressurizing and injecting the raw material slurry, for example, a pressurizing pump is used. The pressurized injection pressure of the raw material slurry is preferably 0.01 to 5MPa, more preferably 0.01 to 3MPa, and still more preferably 0.1 to 0.5 MPa.

As described above, since the cavity is pressurized, the dispersion medium in the raw material slurry is discharged to the outside of the mold through the communication hole. On the other hand, the solid content in the raw material slurry is deposited on the mesh covering the cavity, and a fiber laminate is uniformly formed on the mesh. In the fiber laminate thus obtained, the organic fibers and the inorganic fibers are entangled with each other, and the binder is present between the fibers, so that even if the fiber laminate has a complicated shape, high shape retention can be achieved after dry molding. Further, since the cavity is pressurized, even when a hollow intermediate molded body is formed, the raw material slurry can flow in the cavity so that the raw material slurry is stirred. Thus, the slurry concentration in the die cavity becomes uniform, and the fiber laminate is uniformly deposited on the above-mentioned web.

After the fiber laminate is formed, the pressurized injection of the raw material slurry is stopped, air is pressed into the cavity, and the fiber laminate is pressurized and dehydrated. Then, the air supply is stopped, the cavity is sucked through the communication hole, and a hollow core (elastic core) which is elastic and can be freely extended and contracted is inserted into the cavity. The core is preferably formed of polyurethane, fluororubber, silicone rubber, elastomer, or the like excellent in tensile strength, rebound resilience, stretchability, and the like.

Then, a pressurized fluid is supplied into the elastic core inserted into the cavity to expand the elastic core, and the fiber laminate is pressed against the inner surface of the cavity by the expanded elastic core. The fiber laminate is thereby pressed against the inner surface of the cavity, and the shape of the inner surface of the cavity is transferred to the outer surface of the fiber laminate, while the fiber laminate is dewatered.

As the pressurized fluid for expanding the elastic core, for example, compressed air (heated air), oil (heated oil), and other various liquids can be used. In view of the efficiency of producing the molded article, the supply pressure of the pressurized fluid is preferably 0.01MPa or more and 5MPa or less, more preferably 0.1MPa or more and 3MPa or less, and still more preferably 0.1MPa or more and 0.5MPa or less, from the viewpoint of efficient production. When the pressure is 0.01MPa or more, the drying efficiency of the fiber laminate is good, the surface properties and the transferability are sufficient, and when the pressure is 5MPa or less, a good effect can be achieved, and the device can be miniaturized.

In this way, since the fiber laminate is pressed from the inside thereof to the inner surface of the cavity, even if the shape of the inner surface of the cavity is complex, the shape of the inner surface of the cavity can be transferred to the outer surface of the fiber laminate with high accuracy. In addition, even if the molded article to be produced has a complicated shape, the bonding step of each part is not required, and the finally obtained member does not have joints and thickened portions due to bonding.

When the inner surface shape of the cavity is sufficiently transferred to the outer surface of the fiber laminate and the fiber laminate can be dehydrated to a predetermined water content, the pressurized fluid in the elastic core is pumped out to automatically shrink the elastic core to the original size. Then, the shrunken elastic core is taken out from the cavity, the mold is opened, and the fiber laminate having a wet state with a predetermined moisture content is taken out. The extrusion and dehydration of the fiber laminate using the elastic core may be omitted, and the fiber laminate may be dehydrated and molded by only pressing and dehydrating the fiber laminate with air being compressed into the cavity.

Next, the fiber laminate after dehydration molding is transferred to a heating and drying step.

In the heating and drying step, a mold for drying and molding is used in which a cavity having a shape corresponding to the outer shape of the intermediate molded body is formed. Then, the mold is heated to a predetermined temperature, and the wet fiber laminate after dehydration molding is filled in the mold.

Next, an elastic core similar to the elastic core used in the papermaking step is inserted into the fiber laminate, a pressurized fluid is supplied into the elastic core to expand the elastic core, and the fiber laminate is pressed against the inner surface of the cavity by the expanded elastic core. It is preferable to use an elastic core surface-modified with a fluorine-based resin, a silicone-based resin, or the like. The supply pressure of the pressurized fluid is preferably the same as that in the dehydration step. In this state, the fiber laminate is heated, dried, and dried to form the intermediate molded body.

The heating temperature (mold temperature) of the mold for dry molding is preferably 100 ℃ or higher and 300 ℃ or lower, more preferably 150 ℃ or higher and 250 ℃ or lower, and still more preferably 190 ℃ or higher and 240 ℃ or lower, from the viewpoint of improving the surface properties, shortening the drying time, and the like. The heat treatment time varies depending on the heating temperature, and therefore cannot be generalized, but is preferably from 0.5 minutes to 30 minutes, more preferably from 1 minute to 10 minutes, from the viewpoint of improving quality and productivity. When the heating temperature is 300 ℃ or lower, the surface properties of the intermediate molded product are good, and when it is 100 ℃ or higher, the drying time of the intermediate molded product can be shortened.

When the fiber laminate is sufficiently dried, the pressurized fluid in the elastic core is extracted, and the core is contracted and removed from the fiber laminate. Then, the mold is opened and the intermediate molded body is taken out. The intermediate molded body is used as the main body 31 by curing a thermosetting resin by heat treatment.

Since the body portion 31 thus obtained is pressed by the elastic core, the smoothness of the inner and outer surfaces is high. Therefore, the molding accuracy is high, and even when the fitting portion and the screw portion are provided, a structure with high accuracy can be obtained. Therefore, the structure connected by these fitting portions and screw portions can reliably suppress leakage of the molten metal, and the molten metal can smoothly flow therein. Further, since the heat shrinkage rate of the main body 31 at the time of casting is still less than 5%, leakage of molten metal due to cracks, deformation, and the like of the structure can be prevented without any problem.

The resulting intermediate formed body may also be impregnated with some or all of the first binder. On the other hand, when the first binder is impregnated in the intermediate formed body instead of being contained in the raw material slurry, the treatment of the raw material slurry and the rinse water (white water) is made simple. When a thermosetting adhesive is used as the first adhesive, the intermediate-formed body is dried by heating at a predetermined temperature, and the thermosetting adhesive is thermally cured, thereby completing the manufacture of the main body portion 31.

< method for producing Structure 3 >

The structure 3 can be manufactured by forming the surface layer 32 on the surface of the main body 31 manufactured by the above manufacturing method.

As a method of forming the surface layer 32, there is mentioned a coating method using a coating liquid composition, for example, a method such as brushing, spraying, electrostatic coating, baking paint, sputtering, dipping, and French coating (French pole), and as a result, it is considered that dip coating is most preferable when the uniformity, effectiveness, and economy of the thickness of the surface layer are studied intensively. When the surface layer 32 is formed by dip coating the inner surface of the body portion 31 whose inside is hollow, the surface layer 32 may be formed by filling the coating liquid composition into the hollow portion of the body portion 31 and contacting the body portion (hereinafter referred to as method 1). When the method 1 is performed on the body portion 31 having the hollow portion in an open state, for example, the open portion of at least a part of the hollow portion may be closed to be in a state where the coating liquid composition can be held in the hollow portion, and the coating liquid composition is preferably allowed to flow into the hollow portion so as to fill the hollow portion, and preferably is allowed to stand for a predetermined time, and then the coating liquid composition is discharged to form the surface layer 32. In any of the coating methods, the temperature of the coating liquid composition is preferably in the range of 5 ℃ to 40 ℃, more preferably 15 ℃ to 30 ℃, and most preferably the apparatus is set in the range of 20 ℃ to 30 ℃ and set at a constant temperature. In dip coating, particularly in the case of method 1, the standing time is preferably in the range of 1 second to 60 seconds from the viewpoint of productivity, and may be batchwise or continuously performed. In either method, vibration may be applied to the body portion 31 to which the coating liquid composition is applied by a vibration table or the like in order to adjust the film thickness of the surface layer 32. In order to make the second inorganic particles more firmly adhere to the surface of the main body 31, it is preferable to perform a drying step. Examples of the drying method include, but are not limited to, hot air drying using a heater, far infrared drying, microwave drying, superheated steam drying, and vacuum drying. When drying is performed by using a hot air dryer, the drying temperature in the center part of the drying furnace is preferably in the range of 100 ℃ to 500 ℃, and most preferably in the range of 105 ℃ to 300 ℃ from the viewpoint of further reducing the influence of thermal decomposition of organic substances, binders and the like and securing safety against ignition. The dispersion medium of the coating liquid composition includes water, alcohol, and the like, and water is preferable. The dispersion medium is preferably used in an amount of 5 parts by mass or more and 100 parts by mass or less, more preferably 10 parts by mass or more and 80 parts by mass or less, and still more preferably 10 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the solid content in the coating liquid composition.

The structure for producing castings of the present invention can be disposed in molding sand and spare particles (sand blasting balls and other particles instead of molding sand), and is useful as a melt runner (casting system) or an overflow runner, etc., for producing castings having improved gas-induced defects as casting defects, and is particularly suitable for producing steel castings liable to develop gas-induced defects.

The use of the structure for casting according to the present invention is applicable to the above-mentioned casting mold having a cavity, or to a so-called full-mold casting method using a foaming resin (styrene) mold, or a lost foam casting method using no adhesive, or to a casting field such as a main mold for forming a casting mold, a core, or other fields requiring heat resistance, and the like, and the structure according to the present invention is suitable for use as a runner for a gate, a runner for an exhaust gas, or the like, or a core.

< method for producing cast article >

Next, a method for producing a casting using the structure for producing a casting according to the present invention will be described based on preferred embodiments. In the casting production method according to the present embodiment, the structure for producing a casting of the present invention obtained as described above is embedded in a predetermined position in molding sand, for example, and is molded. The molding sand is not particularly limited, and conventional molding sand generally used in the production of such castings can be used. The method of embedding the casting structure is not particularly limited, and for example, the casting structure may be arranged at a predetermined position and then molding sand may be arranged at a predetermined position, or the casting structure may be arranged after molding sand is arranged at a predetermined state.

Then, molten metal is poured into the mold to cast. Specifically, molten metal is poured from a pouring gate to cast. In this case, since the cast structure of the present invention maintains the heat strength and the thermal shrinkage accompanying thermal decomposition is small, cracking of each cast structure and breakage of the cast structure itself are suppressed, and infiltration of molten metal into the cast structure, adhesion of molding sand, and the like is less likely to occur.

After casting, the mold frame is disassembled after cooling to a predetermined temperature, molding sand is removed, and the casting is exposed by removing the structure for casting by sand blasting. At this time, the thermosetting resin is thermally decomposed, so that the removal treatment of the structure for casting production is easily completed. Thereafter, after-treatment such as finishing treatment is performed on the casting as necessary, and the casting is completed.

When a casting is produced using the structure 3 according to the present embodiment, a cavity may be provided in at least one of the openings 33 provided in the structure 3, and the structure 3 may be buried in a predetermined position in molding sand to form a sand mold. When the sand mold is formed, the structure 3 may be buried while keeping a part of the openings 33 (i.e., at least one opening 33) among the openings 33 provided in the structure 3. In this case, the opening 33 that is not buried may be entirely outside the molding sand, or a part of the opening 33 that is not buried may remain in the molding sand.

Examples

The invention will be further illustrated by the following examples. The scope of the invention is not limited to such embodiments.

Example 1

After a fiber laminate was prepared using the following raw material slurry, the fiber laminate was dehydrated and dried to obtain a runner 1 for a gate shown in fig. 3 (size in mm in the drawing). The flow channel 1 includes straight cylindrical body portions (hereinafter also referred to as "straight pipes") 11, 12 and elbow-shaped body portions (hereinafter also referred to as "bent pipes") 14, 16. The composition of the main body is shown in table 1.

< preparation of raw stock slurry >

The organic fibers and the inorganic fibers in the following proportions were dispersed in water to prepare an aqueous slurry of about 1 mass% (1 mass% of the total mass of the organic fibers and the inorganic fibers relative to the aqueous slurry), and then, the first inorganic particles, the first binder, the coagulant, and the paper strength enhancer were added to the slurry so that the main body described in table 1 could be obtained, thereby preparing raw material slurries. The coagulant was added to the slurry in an amount of 0.625 parts by mass and the paper strength enhancer in an amount of 0.025 parts by mass (in terms of solid content), based on 100 parts by mass (in terms of solid content) of the total of the organic fibers, the inorganic fibers, the first inorganic particles and the first binder. The components shown in table 1 are as follows:

< organic fiber >

Organic fiber: waste newspaper (average fiber length 1mm, drainage (freeness) 150 cc)

< inorganic fiber >

Inorganic fibers: carbon fiber [ fiber length 3mm, fiber width 11 μm (major axis/minor axis ratio=273) ]

< first inorganic particles >

Mullite: average particle diameter 21 μm, specific gravity 3.1

< first adhesive >

Phenolic resin (resole): the decrement of the catalyst at 1000℃under nitrogen was 44% (TG thermography)

< coagulant >

Coagulant: polyamide epichlorohydrin

< paper Strength enhancer >

Paper strength enhancer: carboxymethyl cellulose 1 mass% aqueous solution

< dispersion Medium >

Dispersion medium: water and its preparation method

< step of papermaking and dehydration >

As the molding die, a die having a cavity forming surface corresponding to the main body (straight pipe and curved pipe) is used. A net of a predetermined mesh is disposed on a cavity forming surface of the mold, and a large number of communication holes are formed to communicate the cavity forming surface with the outside. The mold is composed of a pair of split molds. The raw material slurry is circulated by a pump, a predetermined amount of the slurry is injected under pressure into the papermaking mold, and water in the slurry is removed through the communication holes, whereby a predetermined fiber laminate is deposited on the surface of the web. After the injection of the predetermined amount of the raw material slurry is completed, pressurized air is injected into the papermaking mold, and the fiber laminate is dehydrated. The pressure of the pressurized air was 0.2MPa and the time required for dehydration was about 30 seconds.

< drying Process >

As the drying mold, a mold having a cavity forming surface corresponding to the main body (straight pipe and curved pipe) is used. The mold is formed with a plurality of communication holes for communicating the cavity forming surface with the outside. The mold is composed of a pair of split molds. The above-mentioned fiber laminate was taken out of the papermaking mold, transferred and assembled into a drying mold heated to 200 ℃. Then, a bag-shaped elastic core is inserted from an upper opening of the drying mold, pressurized air (0.2 MPa) is injected into the elastic core in the closed drying mold, the elastic core is inflated, the fiber laminate is pressed against an inner surface of the drying mold by the elastic core, and an inner surface shape of the drying mold is transferred to a surface of the fiber laminate and dried. After the compression drying (60 seconds), the compressed air in the elastic core was evacuated, the elastic core was contracted and taken out of the drying mold, and the molded article was taken out of the drying mold and cooled to obtain a thermally cured body.

< preparation of coating liquid composition comprising second inorganic particles as the main ingredient >

The solid materials having the compositions and the blending ratios (mass ratios) of the second inorganic particles, the clay mineral, and the second binder shown in table 1 were stirred with a water stirrer for 15 minutes to obtain a coating liquid composition containing the second inorganic particles as a main component. The components shown in table 1 are as follows. The water amount was adjusted to the solid content concentration (mass%) shown in table 1.

< second inorganic particles >

Mullite: average particle diameter 20.0 μm, specific gravity 3.1

< clay mineral >

Attapulgite clay

< second adhesive >

Colloidal silica: average particle diameter of 22nm

< formation of surface layer >

The heat-cured body parts (straight pipe and bent pipe) were each closed at one open end, and the prepared coating liquid composition was poured into the inside of each body part until the coating liquid composition was left to stand for 10 minutes, and then turned upside down to discharge the coating liquid composition. After natural drying, the resultant was dried by a hot air dryer at a temperature of 200℃for 30 minutes to obtain a structure for casting production having a surface layer formed thereon.

Example 2

A casting structure was obtained in the same manner as in example 1, except that the compositions and thicknesses of the main body portion and the surface layer were changed as shown in table 1. The components shown in table 1 are as follows.

< first inorganic particles >

Obsidian: average particle diameter 30 μm, specific gravity 2.4

Example 3

< first inorganic particles >

Spherical silica: spherical, with an average particle diameter of 14 μm and a specific gravity of 2.2

Examples 4 and 5

A casting structure was obtained in the same manner as in example 1, except that the compositions and thicknesses of the main body portion and the surface layer were changed as shown in table 1.

Examples 6 and 7

Comparative example 1

The composition and thickness of the body portion were changed as shown in table 1, and the surface of the resulting body portion was not formed with a surface layer. The body thus obtained was used as a structure for casting production in comparative example 1.

Comparative example 2

< first inorganic particles >

Spherical silica: spherical shape with an average particle diameter of 80 μm and a specific gravity of 2.2

Comparative example 3

A casting structure was obtained in the same manner as in example 1, except that the compositions and thicknesses of the main body portion and the surface layer were changed as shown in table 1. In comparative example 3, the surface layer contained no viscosity mineral and no second binder. The components shown in table 1 are as follows.

< second inorganic particles >

Colloidal silica: average particle diameter of 22nm

Comparative example 4

< first inorganic particles >

Spherical silica: spherical shape with an average particle diameter of 37 μm and a specific gravity of 2.2

< measurement of thickness of surface layer >

The thickness of the surface layer formed on the surface of the body portion is obtained by measuring the thickness of the casting structure after the surface layer is formed and the thickness of the body portion before the surface layer is formed, and then by measuring the difference between the thickness and the thickness. The thickness of the body before the formation of the surface layer was obtained by measuring the thickness of the marked portion at any 10 places by using a gauge (dial caliper gauges) (model No.209-611, model DCGO-50 RL) and taking the average value thereof, and the thickness of the casting structure after the formation of the surface layer was obtained by measuring the thickness of the portion corresponding to the marked portion at any 10 places in the body by using a gauge (model No.209-611, model DCGO-50 RL) and taking the average value thereof.

The strength of the cast structure and the surface layer of the cast structures of examples and comparative examples were evaluated as follows. The results are shown in Table 1.

< evaluation of strength of Structure for casting production >

The strength of the structure for casting production was evaluated by the maximum bending strength.

Plate-like test pieces having dimensions of 60mm in length by 15mm in width were cut out from the structures for casting production of examples and comparative examples, and the test pieces were evaluated according to the three-point bending test method of JIS K7017 to determine the maximum bending strength (N). The distance between the fulcrums at the time of measurement was 40mm, and the press-in speed was 1.0 mm/sec.

< evaluation of surface layer Strength of Structure for casting production >

According to JIS K5600-5-4: in 1999, "paint routine test method. Scratch hardness (pencil method)", measurements were made. Scratch hardness (pencil method) was measured by pressing a pencil (fixed angle 45 °, load 750 g) against the surface layer. The scratch hardness is used as the pencil hardness of the surface layer. The pencil hardness of the surface layer is used as an index of the surface layer strength.

TABLE 1

From the results shown in Table 1, it can be seen that: the structures for casting production of examples 1 to 5 have sufficient strength relative to comparative examples 1 to 4, both the structures for casting production themselves and the surface layers.

The cast-producing structures of example 1 and comparative example 1 were evaluated for burn-up properties as follows.

< evaluation of burn-up Property >

The casting manufacturing structures of example 1 and comparative example 1 were used as casting molds, the casting manufacturing structures were buried in molding sand, and molten metal including cast steel at 1540 ℃ was cast to prepare castings. After the casting production was completed, the produced casting was taken out, and the burn-in property was evaluated based on whether or not the casting had a burn-in portion formed. Specifically, the contact portion between the casting and the casting manufacturing structure in the surface of the manufactured casting was used as an evaluation site. The burn-up property was evaluated based on whether or not the surface of the casting, which is the evaluation site, had a portion where molten metal flowing in at the time of casting production damaged and adhered to the casting structure and a portion where the adhering substance from the molding sand was trapped and adhered.

The casting manufactured using the casting manufacturing structure of example 1 had no burned portion. On the other hand, the cast product produced using the cast product production structure of comparative example 1 had a burned portion. From this, it can be seen that: the casting manufacturing structure of example 1 can suppress burn-in casting manufacturing.

Industrial applicability

According to the present invention, there is provided a structure for casting production in which the strength of both the main body portion and the surface layer is enhanced and breakage is less likely to occur.

Claims

1. A structure for casting production having a main body portion and a surface layer covering at least a part of the main body portion, characterized in that:

the main body part contains organic fibers, inorganic fibers, first inorganic particles with an average particle diameter of more than 1 mu m and less than 50 mu m and a first binder,

the surface layer contains second inorganic particles having an average particle diameter of 1 [ mu ] m or more and 100 [ mu ] m or less, a clay mineral, and a second binder of the same type as or different from the first binder, and contains 7 parts by mass or more and 40 parts by mass or less of the second binder with respect to 100 parts by mass of the second inorganic particles.

2. The structure for casting production according to claim 1, wherein:

the first inorganic particles have an average particle diameter of more than 1 μm and 30 μm or less,

the main body portion contains 40 mass% to 80 mass% of the first inorganic particles.

3. The structure for casting production according to claim 1 or 2, characterized in that:

The first inorganic particles have an average particle diameter of 5 μm or more and 30 μm or less.

4. The structure for casting production according to any one of claims 1 to 3, wherein:

the main body contains 45 mass% to 65 mass% of the first inorganic particles with respect to the entire mass of the main body.

5. The structure for producing castings according to any one of claims 1 to 4, wherein:

the clay mineral is contained in an amount of 1.5 to 50 parts by mass based on 100 parts by mass of the second inorganic particles.

6. The structure for casting production according to any one of claims 1 to 5, wherein:

the ratio D1/D2 of the average particle diameter D1 of the first inorganic particles to the average particle diameter D2 of the second inorganic particles is 0.1 to 2.5.

7. The structure for producing castings according to any one of claims 1 to 6, wherein:

the mass reduction rate of the surface layer is 0% or more and 10% or less.

8. The structure for casting production according to any one of claims 1 to 7, wherein:

the second binder comprises an inorganic binder.

9. The structure for casting production according to any one of claims 1 to 8, wherein:

The second binder comprises one or more selected from sulfate, silicate, phosphate, lithium silicate, zirconia sol, colloidal silica, and alumina sol.

10. The structure for casting production according to any one of claims 1 to 9, wherein:

the surface layer contains 40 mass% or more and 90 mass% or less of the second inorganic particles with respect to the mass of the entire surface layer.

11. The structure for casting production according to any one of claims 1 to 10, wherein:

the main body contains 8 to 30 mass% of organic fibers based on the mass of the entire main body.

12. The structure for casting production according to any one of claims 1 to 11, wherein:

the second binder is in the form of particles, and the average particle diameter of the second binder is 10% or less of the average particle diameter of the second inorganic particles.

13. The structure for casting production according to any one of claims 1 to 12, wherein:

the second binder has a specific gravity lower than that of the second inorganic particles.

14. The structure for casting production according to any one of claims 1 to 13, wherein:

The porosity of the surface layer is not less than a predetermined value.

15. The structure for casting production according to any one of claims 1 to 14, wherein:

the organic fibers comprise wood pulp.

16. The structure for casting production according to any one of claims 1 to 15, wherein:

as the inorganic fibers, carbon fibers are included.

17. The structure for casting production according to any one of claims 1 to 16, wherein:

the main body contains 1.5 mass% to 35 mass% of the inorganic fibers with respect to the mass of the entire main body.

18. The structure for casting production according to any one of claims 1 to 17, wherein:

the mass ratio of the inorganic fibers to the organic fibers is 0.1 to 0.8 in terms of inorganic fibers/organic fibers, when the inorganic fibers are carbon fibers.

19. The structure for casting production according to any one of claims 1 to 18, wherein:

as the first inorganic particles, one or two or more kinds selected from graphite, mullite, obsidian, zirconia, zircon, mica, silica, hollow ceramics, fly ash, and alumina are contained.

20. The structure for casting production according to any one of claims 1 to 19, wherein:

as the first binder, a thermosetting resin selected from the group consisting of a phenolic resin, an epoxy resin, and a furan resin is included.

21. The structure for casting production according to any one of claims 1 to 20, wherein:

the main body portion contains 16 mass% or more and 40 mass% or less of the first binder with respect to the mass of the entire main body portion.

22. The structure for casting production according to any one of claims 1 to 21, wherein:

the second inorganic particles comprise one or more of zircon, mullite, and alumina.

23. The structure for casting production according to any one of claims 1 to 22, wherein:

the clay mineral contains one or more selected from attapulgite and sepiolite.

24. The structure for casting production according to any one of claims 1 to 23, wherein:

the surface layer contains 1.6 mass% or more and 25 mass% or less of the clay mineral.

25. The structure for casting production according to any one of claims 1 to 24, wherein:

The surface layer contains 7 mass% or more and 30 mass% or less of the second binder.

26. The structure for casting production according to any one of claims 1 to 25, wherein:

the first inorganic particles have an average particle diameter of 10 μm or more and 35 μm or less,

the second inorganic particles have an average particle diameter of 15 μm or more and 25 μm or less,

the ratio D1/D2 of the average particle diameter D1 of the first inorganic particles to the average particle diameter D2 of the second inorganic particles is 0.5 to 1.8,

in the main body portion of the present invention,

the first inorganic particles are contained in an amount of 50 to 60 mass% based on the mass of the entire body,

the organic fiber is contained in an amount of 10 to 20 mass% based on the mass of the entire body,

the inorganic fiber is contained in an amount of 2 to 20 mass% based on the mass of the entire body,

the inorganic fibers may comprise carbon fibers and,

the mass ratio of the inorganic fibers to the organic fibers is 0.5 to 1 by mass of the inorganic fibers/organic fibers,

the first binder is contained in an amount of 15 to 25 mass% based on the mass of the entire body,

The thickness of the main body part is more than or equal to 0.8mm and less than or equal to 5mm,

in the surface layer of the material in question,

the clay mineral is contained in an amount of 2.2 to 10 parts by mass based on 100 parts by mass of the second inorganic particles,

the mass reduction rate is 0.5% or more and 5% or less,

the second inorganic particles are contained in an amount of 70 to 90 mass% relative to the mass of the entire surface layer,

contains 2 to 10 mass% of the clay mineral,

the second binder is contained in an amount of 8 to 30 parts by mass based on 100 parts by mass of the second inorganic particles,

containing 8 to 20 mass% of the second binder,

the thickness of the surface layer is 200 [ mu ] m or more and 700 [ mu ] m or less.

27. The use of a structure for casting production, characterized in that:

the structure for producing castings according to any one of claims 1 to 26, which is used as a melt flow path or an overflow flow path in casting of cast steel.

28. A method for manufacturing a mold for casting steel, comprising:

a step of embedding the structure for casting production according to any one of claims 1 to 26 in molding sand while leaving a part of the openings of the structure for casting production.

29. A method of manufacturing a cast steel casting, comprising:

a casting mold manufacturing step of embedding the casting mold manufacturing structure according to any one of claims 1 to 26 in molding sand while leaving a part of the openings of the casting mold manufacturing structure; and

and a casting step of casting a molten metal into the mold.