Structure for cast production

Abstract

The structure for cast manufacturing of the present invention contains an organic component of which at least a part is an organic fiber. The mass reduction rate of the structure after heating at 1000°C for 30 minutes under a nitrogen atmosphere is 1 mass% or more and less than 20 mass%. The structure for cast manufacturing contains inorganic particles. The structure for cast manufacturing contains, as the inorganic particles, first inorganic particles having at least one of a prescribed shape and physical properties and second inorganic particles having at least one of a prescribed shape and physical properties different from those of the first inorganic particles. In addition to or instead of this, the maximum bending stress of the structure for cast manufacturing measured in accordance with JIS K7017 is 9 MPa or more and the bending strain at the maximum bending stress is 0.6% or more.

Description

Technical Field

[0001] This invention relates to structures for casting manufacturing. Background Technology

[0002] Molds used for casting are typically made of wood, metal, or sand. Regarding these molds, there is a desire to improve formability and shape retention, reduce weight, and lower waste disposal costs. The applicant has proposed a structure for casting manufacturing containing inorganic fibers, layered clay minerals, and inorganic particles other than the layered clay minerals, with the organic content below a specified amount (Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: US 2020346279 A1 Summary of the Invention

[0006] This invention relates to structures for casting manufacturing.

[0007] In one embodiment, the structure contains organic components.

[0008] In one embodiment, at least a portion of the organic components in the above structure are organic fibers.

[0009] In one embodiment, the mass reduction rate of the above-described structure after heating at 1000°C for 30 minutes under a nitrogen atmosphere is more than 1% by mass and less than 20% by mass.

[0010] In one embodiment, it contains inorganic particles.

[0011] In one embodiment, the inorganic particles include a first inorganic particle and a second inorganic particle, wherein the first inorganic particle is not a layered particle and the second inorganic particle is a layered particle.

[0012] In one embodiment, the inorganic particles comprise a first inorganic particle with a melting point above 1200°C and a second inorganic particle with a melting point below 1200°C.

[0013] In one embodiment, the maximum bending stress measured according to JIS K7017 is 9 MPa or more.

[0014] In one embodiment, the bending strain at the maximum bending stress, as measured according to JIS K7017, is 0.6% or more. Detailed Implementation

[0015] While the structure described in Patent Document 1 has high formability and shape retention, there is still room for improvement in terms of improving operability such as processing and assembly of the structure during mold manufacturing, reducing gas defects in the casting caused by combustion gases from organic materials contained in the structure during casting, and reducing sand adhesion on the surface of the casting.

[0016] Therefore, the present invention relates to a structure for casting manufacturing that combines improved operability, reduced gas defects, and reduced sand adhesion on the casting surface.

[0017] The present invention will now be described based on preferred embodiments.

[0018] The casting manufacturing structure of the present invention (hereinafter also referred to as "structure") is suitable for use as a segmented mold or casting mold for casting.

[0019] In this specification, depending on the context, "structure for casting" or "structure" refers to a component that forms part of a mold, such as a segmented mold, and the mold itself.

[0020] Unless otherwise specified, “mass%” in this specification refers to the mass ratio relative to the overall mass of the structure used in casting.

[0021] In the following description, for ease of explanation, the components of the mold itself, i.e., the structure for casting manufacturing, which is not subject to the coating process described later, will be explained. Where this structure has multiple components or is formed by multiple layers, the following description applies to any component or layer.

[0022] The structure preferably contains organic fibers as an organic component. Organic fibers are fibrous materials composed of organic components. Because organic fibers are softer than inorganic fibers (described later), they have the function of improving the toughness of the structure by having these fibers intertwine with each other or by combining with other materials that can be included in the structure.

[0023] Organic fibers are preferably dispersed at least on the surface of the structure, and more preferably dispersed on the surface and inside the structure.

[0024] By dispersing organic fibers on the surface of the structure, a fibrous network structure is formed on the surface. Compared with existing structures, the strength and toughness of the structure are significantly improved, preventing accidental breakage or damage caused by impact, bending, or cracking. Therefore, when the structure is cut to the required length, damage such as crack initiation or propagation can be suppressed. Even during processing and assembly, breakage is less likely, improving operability.

[0025] The term "organic component" in this specification refers to natural substances or compounds that have hydrocarbon groups in their molecular structure. Therefore, materials such as carbon fibers, which are composed solely of carbon or of carbon and nitrogen, do not constitute organic components or materials containing organic components in this invention. Carbon fibers are classified as inorganic components, as described later.

[0026] Whether a structure contains organic components can be determined by the presence of peaks corresponding to C=C, CH, C=O, and OH bonds obtained by solid-state NMR. If at least a CH bond or a C=O bond is present, the material being measured is determined to contain organic components.

[0027] Furthermore, whether the structure contains organic fibers can be determined using the aforementioned solid-state NMR, as well as by observing the surface and interior of the structure using micro-FT-IR and a microscope (manufactured by Keyence Ltd., model: VHX-500; all microscopes in this manual are of this type). Specifically, the location of functional groups originating from organic matter is identified under micro-FT-IR; if organic fibers are observed at these locations using a microscope, it is determined that the structure contains organic fibers.

[0028] From the viewpoint that it is easier to form a network structure of organic fibers, the content of organic components containing organic fibers in the structure is preferably more than 5% by mass, more preferably 5.5% by mass or more, and even more preferably 6% by mass or more.

[0029] From the same point of view as above, the content of organic fibers in the structure is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more.

[0030] Furthermore, from the viewpoint of reducing gas generation during casting, the content of organic components, including organic fibers, is preferably less than 20% by mass, more preferably less than 15% by mass, and even more preferably less than 13% by mass, based on their total amount. Within this range, the amount of gas flowing into the target casting is reduced, improving the quality of the casting. It also suppresses the undesirable situation of sand adhering to the organic components from the structure after thermal decomposition, etc., which are fixed to the molten metal. Moreover, it can suppress the backflow of gas generated when the molten liquid flows in during casting, preventing molten metal from being blown back from the inlet end face, thus improving the safety of the casting operation.

[0031] From the same point of view as above, the content of organic fibers in the structure is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2.5% by mass or less.

[0032] The content of organic components in structures used for casting manufacturing can be determined by following these steps when analyzing such structures.

[0033] As a pretreatment, a sample formed by pulverizing and uniformly mixing the structure used for casting manufacturing, which will be the object of the measurement, is subjected to FT-IR analysis. Furthermore, the content of inorganic components consisting solely of carbon, such as carbon fibers, in the structure is quantified by comparing the detection intensity of peaks originating from C=C bonds. Subsequently, the sample is heated at a temperature above 1300°C under a nitrogen atmosphere to carbonize the organic components, and the mass loss is measured. Next, the carbonized sample is subjected to FT-IR analysis to quantify the content of residual carbon components. Finally, the difference between the carbon component content of the sample before carbonization and the carbon component content of the sample after carbonization, plus the mass loss, is calculated, and this total value is taken as the content of organic components in this invention.

[0034] Organic fibers include natural fibers, synthetic fibers, regenerated fibers, semi-synthetic fibers, and recycled fibers. They can be used alone or in combination of two or more.

[0035] Natural fibers include pulp fibers, animal fibers, etc.

[0036] Pulp fibers include wood pulp and non-wood pulp.

[0037] Wood pulp includes mechanical pulp made from coniferous or broadleaf trees, as well as natural cellulose fibers made from coniferous or broadleaf trees.

[0038] Non-wood pulps include cotton pulp, cottonseed lint pulp, hemp, cotton, bamboo, wheat straw, and natural cellulose fibers made from them.

[0039] Animal fibers include proteins such as wool, goat hair, cashmere, and feathers.

[0040] Synthetic fibers can be exemplified by fibers containing synthetic resins such as polyolefin resins, polyester resins, polyamide resins, poly(meth)acrylic resins, polyvinyl resins, polyimide resins, and aromatic polyamide resins. These resins can be used individually or in combination to form a single fiber.

[0041] Examples of polyolefin resins include polyethylene or polypropylene.

[0042] Examples of polyester resins include polyethylene terephthalate or polybutylene terephthalate, polybutylene naphthalate, polyhydroxybutyric acid, polyhydroxyalkanoate, polycaprolactone, polybutylene succinate, polylactic acid resins, etc.

[0043] Examples of polylactic acid resins include polylactic acid and lactic acid-hydroxycarboxylic acid copolymers.

[0044] Examples of poly(meth)acrylic resins include polyacrylic acid, polymethyl methacrylate, polyacrylate, polymethacrylic acid, and polymethacrylate.

[0045] Examples of polyethylene-based resins include polyvinyl chloride, polyvinylidene chloride, vinyl acetate resin, vinylidene chloride resin, polyvinyl alcohol, polyvinyl acetal, polyvinyl butyral, and polystyrene.

[0046] Examples of regenerated fibers include cupra and rayon.

[0047] Examples of semi-synthetic fibers include, for example, acetate fiber.

[0048] Examples of recycled fibers include pulp fibers obtained by cutting and fibrillating fibers such as waste paper and clothing.

[0049] Among these, from the viewpoint of improving the toughness and operability of the structure and easily reducing defects on the surface of the structure during manufacturing and casting, pulp fibers, as well as at least one of fibers containing polyester resin and fibers containing aramid resin are preferred as organic fibers.

[0050] From the viewpoint of improving the formability and operability of the structure, it is preferable that the structure also contains other organic components besides organic fibers.

[0051] Examples of materials containing such other organic components include starch, thermosetting resins, colorants, and thermally expandable particles. They can be used alone or in combination of two or more.

[0052] From the viewpoint of suppressing combustion of the structure during casting and improving the shape retention of the structure, thermosetting resins are preferred.

[0053] Thermosetting resins include phenolic resins, modified phenolic resins, epoxy resins, melamine resins, furan resins, etc.

[0054] Phenolic resins include phenolic varnish type and methyl phenolic resin type.

[0055] Modified phenolic resins include resins that have been modified with urea, melamine, and epoxy resins.

[0056] They can be used individually or in combination of two or more.

[0057] Among these, from the viewpoint of reducing gas generation during casting and easily obtaining castings with high dimensional stability and surface smoothness, phenolic resin is preferred as an other organic component.

[0058] The structure preferably also contains inorganic components, and more preferably, it also contains inorganic particles as inorganic components. By including inorganic components in the structure, the heat resistance of the structure can be improved, as well as the strength, dimensional stability, and shape retention of the structure during casting.

[0059] When the structure contains inorganic particles, it is preferable that the inorganic particles are present at least on the surface of the structure, and more preferably on both the surface and the interior of the structure.

[0060] When inorganic particles are included, the inorganic particles preferably have a melting point of 1200°C or higher, more preferably 1500°C or higher. By using inorganic particles with such melting points, the shape retention of the structure is excellent even under the high-temperature conditions during casting.

[0061] This includes inorganic particles whose melting point is actually below 2500℃.

[0062] If the melting point of the inorganic particles is within the above range, the structure used for casting will not melt significantly during casting, thus suppressing the generation of gas defects or sand adhesion in the casting.

[0063] The melting point of the inorganic particles was determined using the following method. A thermogravimetric differential thermal analysis-mass spectrometry (TG-DTA / MS) apparatus manufactured by Nippon Steel Technology Co., Ltd. was used. The structure for casting was heated from 30°C to 1500°C at a rate of 20°C / min under a nitrogen atmosphere, and then cooled to 30°C at a rate of 20°C / min after 30 minutes. The melting point was then determined based on the measurement results.

[0064] Furthermore, the structure preferably comprises one or more compounds selected from oxides, carbides, and nitrides, wherein the oxides, carbides, and nitrides are oxides, carbides, and nitrides of elements selected from aluminum, zirconium, silicon, and iron. That is, the structure preferably comprises one or more compounds selected from aluminum oxide, silicon dioxide, iron(II), iron(III), aluminum nitride, zirconium oxide, silicon nitride, and silicon carbide.

[0065] By including such compounds in the structure, the heat resistance of the structure is improved even under high-temperature conditions during casting, and the shape retention of the structure is excellent.

[0066] The presence of these compounds in the structure essentially means that the structure contains inorganic particles.

[0067] The presence of the aforementioned compounds in the structure can be determined by X-ray diffraction. Specifically, the structure of the object to be measured is subjected to X-ray diffraction under conditions of tube voltage 30 kV, tube current 15 mA, goniometer scanning angle 5–70°, and goniometer scanning speed 10° / min, thereby determining the presence and type of the aforementioned compounds.

[0068] In addition to inorganic particles that can have the above-mentioned melting points, it can also contain clay minerals. Clay minerals typically have melting points below 1200°C.

[0069] By further utilizing clay minerals with such melting points, the clay minerals melt and fill the spaces between the inorganic particles as molten metal flows in, preventing the inorganic particles from separating from each other. As a result, the strength and shape of the structure can be maintained.

[0070] Inorganic particles have independent shapes and can be spherical, polyhedral, scaly, layered, spindle-shaped, fibrous, amorphous, or a combination thereof.

[0071] Inorganic particles can be used alone or in combination of two or more.

[0072] In the following description, the case of using two types of inorganic particles, namely a first inorganic particle and a second inorganic particle, as examples of inorganic particles that can be included in the structure will be used. The first inorganic particle and the second inorganic particle are defined to have at least one different shape and physical property from each other.

[0073] In one embodiment, the first inorganic particle is preferably a non-layered particle (i.e., a particle having a shape other than layered). Furthermore, in one embodiment, the second inorganic particle is preferably a layered particle.

[0074] In another embodiment, the melting point of the first inorganic particle is preferably 1200°C or higher. Furthermore, in another embodiment, the melting point of the second inorganic particle is preferably lower than 1200°C.

[0075] In another embodiment, the first inorganic particle is more preferably a particle with a melting point preferably above 1200°C and is a non-layered particle. Furthermore, in yet another embodiment, the second inorganic particle is more preferably a particle with a melting point preferably below 1200°C and is a layered particle. Thus, by using a variety of inorganic particles, each possessing multiple physical properties and with each property being different, the strength and operability of the structure can be improved.

[0076] Unless otherwise specified, the following description applies to the descriptions in the above embodiments.

[0077] Regarding the first inorganic particle, from the viewpoint of further improving the heat resistance of the structure, it is preferable to use one or more of graphite, mullite, obsidian, zirconium, silica, fly ash, and alumina as the first inorganic particle, and more preferably, at least graphite and mullite. Mullite contains alumina, silica, and iron oxide.

[0078] Generally, graphite is divided into naturally occurring graphite, such as flake graphite or amorphous graphite, and artificial graphite, which is manufactured using raw materials such as petroleum coke, carbon black, or pitch. Among these, flake graphite is preferred from the viewpoint of improving the formability of structures.

[0079] Regarding the average particle size of the first inorganic particles, from the viewpoint of improving the air permeability of the structure and suppressing gas defects in the casting, it is preferably 1 μm or more, and more preferably 10 μm or more.

[0080] Furthermore, regarding the average particle size of the first inorganic particles, from the viewpoint that the structure can maintain sufficient thermal strength even during casting, it is preferably 1000 μm or less, and more preferably 500 μm or less.

[0081] In order to ensure that the average particle size of inorganic particles is within the above-mentioned range, the inorganic particles used as raw materials can be screened, or further pulverized using known pulverizing equipment such as dry pulverizing or wet pulverizing.

[0082] The average particle size of the first inorganic particles can be obtained, for example, by measuring the particle size distribution using a laser diffraction / scattering particle size distribution measuring device (LA-950V2, manufactured by Horiba Manufacturing Co., Ltd.). In the particle size distribution measurement, a dry cell unit is used to measure the particle size of the inorganic particles in a powder state dispersed by compressed air. Regarding the measurement conditions, the compressed air pressure is set to 0.20 MPa, the flow rate to 320 L / min, and the sample input is adjusted to ensure the laser absorbance is 95%–99%. The median particle size is calculated based on the obtained volumetric particle size distribution and defined as the average particle size.

[0083] When a second inorganic particle is included as an inorganic particle, the second inorganic particle is preferably a layered clay mineral. That is, it is preferable that the structure includes layered particles as the second inorganic particle, and more preferably layered particles including clay minerals.

[0084] Layered clay minerals swell due to the presence of water, resulting in a thickening effect, thus facilitating the uniform mixing of the various raw materials during the fabrication of the structure. Furthermore, during drying, the layered clay minerals lose the water molecules present between their unit crystalline layers, causing the inorganic particles and organic fibers to form a dense structure and solidify. This leads to increased strength and workability of the structure at room temperature, and effectively imparts thermal strength to the casting during manufacturing. In addition, it maintains the machinability and shape retention of the structure, and the resulting casting exhibits high surface smoothness, reducing the incidence of gas defects.

[0085] From the viewpoint of creating a structure that combines heat resistance and strength, exhibiting excellent operability, dimensional stability, and shape retention during structure manufacturing, operation, and casting, it is preferable to use a combination of spherical and layered particles as inorganic particles. More specifically, it is preferable to use a combination of first inorganic particles and layered clay mineral particles as second inorganic particles, wherein the first inorganic particle is a non-layered particle such as a spherical particle, and the second inorganic particle is a layered particle.

[0086] To confirm that the structure contains spherical and layered particles, the shape of the particles can be determined by observing the surface of the structure using a scanning electron microscope (SEM).

[0087] Layered clay minerals used as the second inorganic particles impart shapeability to the structure mainly by being interbedded between organic fibers or other materials, and have the function of further improving room temperature strength and thermal strength.

[0088] As layered clay minerals, crystalline inorganic compounds with a layered structure, such as layered silicate minerals, can be used. Layered clay minerals can be natural products or artificially manufactured products.

[0089] Specific examples of layered clay minerals include those represented by the kaolinite, smectite, and mica groups. These various layered clay minerals can be used alone or in combination of two or more.

[0090] Examples of clay minerals belonging to the kaolinite group include kaolinite. Examples of clay minerals belonging to the montmorillonite group include montmorillonite, bentonite, saponite, lithium montmorillonite, bedesite, magnesia, and chlorodiasite.

[0091] Clay minerals belonging to the mica group include, for example, vermiculite, halloysite, and tetrasilicicmica.

[0092] In addition, hydrotalcite, which is a layered polyhydric hydroxide, can also be used.

[0093] Among the aforementioned layered clay minerals, montmorillonite or bentonite exhibits strong adhesion to its components in a hydrated state, making them suitable for use from the perspective of shape imparting properties during the molding process in the manufacture of structures.

[0094] In addition, from the viewpoint of heat resistance during casting, kaolinite or montmorillonite is preferred.

[0095] Regarding the average particle size of the second inorganic particles, from the viewpoint of improving the permeability of the structure and thus suppressing gas defects in the casting, it is preferably 0.1 μm or more, and more preferably 1 μm or more.

[0096] From the viewpoint of improving the strength, formability and shape retention of the structure, the average particle size of the second inorganic particles is preferably 500 μm or less, more preferably 200 μm or less.

[0097] When using layered clay minerals as the second inorganic particle, the average particle size of the layered clay minerals can be within the above-mentioned range.

[0098] The average particle size of the second inorganic particle can be determined using the same method as the method described above for determining the average particle size of the first inorganic particle.

[0099] The mass reduction rate of the structure under high-temperature conditions during casting is within the specified range. The mass reduction rate of the structure is related to the gas generation rate due to organic components in the structure during casting. Specifically, there is a tendency for a lower mass reduction rate to have a lower gas generation rate.

[0100] Therefore, a lower mass reduction rate means that the thermal strength of the structure can be maintained more stably, and it is superior in maintaining the dimensional accuracy of the casting, reducing gas defects caused by gas generated during casting mixed into the casting, and reducing sand adhesion of the structure to the casting surface.

[0101] Specifically, the mass reduction rate of the structure after heating at 1000°C for 30 minutes under a nitrogen atmosphere is preferably less than 20%, more preferably less than 15% by mass, and even more preferably less than 9% by mass. If the mass reduction rate is within this range, the amount of gas generated when flowing into the high-temperature molten liquid during casting is reduced, and the amount of gas flowing into the casting is also reduced, thus further improving the quality of the casting. It also suppresses the undesirable situation of sand adhering to parts of the organic components originating from the structure after thermal decomposition, etc., by the molten metal. Furthermore, it can suppress the backflow of gas generated when flowing into the molten liquid during casting, which could cause molten metal to blow back from the inlet end face, thereby improving the safety of the casting operation.

[0102] In addition, in order to effectively reduce the gas generation rate, the lower the mass reduction rate mentioned above, the better. However, from the viewpoint of fully realizing the prevention of structural disintegration by improving the structural toughness with the use of organic fibers, it is preferable to be 1% by mass or more, more preferably 3% by mass or more, and even more preferably more than 5% by mass.

[0103] To achieve such a mass reduction rate, for example, the content of organic components containing organic fibers and the content of each inorganic particle can be set to the above-mentioned appropriate range, or heat treatment can be performed after molding in the manufacturing process of the structure to remove the gas-generating components.

[0104] Regarding the mass reduction rate, a thermogravimetric analyzer (manufactured by Seiko Instruments Inc., STA7200RVTG / DTA) was used. The casting structure to be tested was heated from 30°C to 1000°C in a nitrogen atmosphere at a heating rate of 20°C / min, and held at 1000°C for 30 minutes. The change in mass at 1000°C was measured as a function of temperature, using the mass of the structure at 30°C as a baseline (100%). The mass reduction rate (%) was calculated as the percentage of the mass of the structure at 1000°C relative to the mass of the structure at 30°C.

[0105] Regarding the structure, the maximum bending stress, which is one of the indicators of the structure's toughness, is preferably 9 MPa or more, and more preferably 12 MPa or more. By having such a maximum bending stress, the structure becomes a highly tough structure, which can prevent the structure from disintegrating, cracking, or fracturing, and improve the structure's operability, shape retention, and dimensional stability.

[0106] Furthermore, regarding the maximum bending stress of the structure, from the viewpoint of balancing the operability of the structure and the operability during casting, it is preferably 50 MPa or less, more preferably 40 MPa or less, and even more preferably 30 MPa or less.

[0107] Furthermore, regarding the structure, the bending strain (hereinafter also referred to as "bending strain") at the maximum bending stress, which is measured as one of the indicators of the structure's toughness, is preferably 0.6% or more, and more preferably 0.65% or more. By having such a bending strain, the structure becomes a highly tough structure, which can prevent the structure from disintegrating or cracking, and improve the structure's operability, shape retention, and dimensional stability.

[0108] In addition, although the greater the bending strain of the structure, the better, in practice it is preferred to be 8% or less, more preferably 6% or less, and even more preferably 4% or less.

[0109] The bending strain and maximum bending stress of the structure can be measured using a measuring device (Shimadzu Corporation, AGX-plus universal testing machine) according to the three-point bending test of JIS K7017. At this time, a plate-shaped sample with a longitudinal length of 60 mm × a transverse length of 15 mm × a thickness of 2 mm is cut from the structure to be used as the test specimen for measurement.

[0110] The maximum bending stress is a physical property value calculated by dividing the moment (product of load and distance) applied to the sample during a three-point bending test by the section modulus of the sample. Depending on the dimensions of the structure being measured, samples of any size can be cut for measurement when the aforementioned plate-shaped sample cannot be produced.

[0111] The casting structure with the above-described composition, by containing organic fibers, can improve the intertwining and bonding of organic fibers with each other or with other materials by utilizing the moderate softness and elasticity of the organic fibers, thereby enhancing the toughness of the structure. As a result, resistance to brittle fracture is improved, and the formation of surface or internal breakage defects, cracks, or fractures can be suppressed under various conditions, such as during manufacturing, transportation, processing, assembly, or high-temperature loads during casting, thus improving the operability of the structure. Furthermore, it can prevent accidental breakage or fracture of the gating point, which serves as the flow path for molten metal flowing into the mold during casting. In particular, the presence of organic fibers on the surface of the structure, where the organic fibers intertwine to form a mesh structure, acts as a mesh covering the structure, thus effectively suppressing the formation of surface breakage defects, cracks, or fractures.

[0112] Furthermore, even if minor defects such as cracks or disintegration are accidentally generated during the manufacturing, transportation, processing, assembly, or casting of the structure, the presence of the organic fiber network structure can inhibit the further development of these defects, and the structure exhibits high shape retention.

[0113] Furthermore, by incorporating inorganic particles into the structure, a structure with high heat resistance capable of withstanding casting is achieved. As a suitable form of inorganic particles, by combining materials other than clay minerals with clay minerals, the structure exhibits excellent heat resistance, resulting in high room temperature strength and thermal strength, while also possessing excellent workability due to the high toughness derived from organic fibers.

[0114] In addition, by controlling the mass reduction rate of the structure within a specific range, when using the structure as a mold for casting, it is possible to effectively reduce casting defects such as sand adhesion or gas defects on the casting surface. As a result, castings with excellent dimensional accuracy and surface smoothness can be manufactured, and the manufacturing cost of castings can be reduced.

[0115] The structure also requires improved maneuverability during processing and assembly. When the structure has low toughness, cutting it to specified dimensions or other machining processes can easily lead to cracks, gaps, or breaks. For structures prone to defects, casting them can result in disintegration starting from the defective areas, or molten metal leaking out of the structure. Consequently, such structures have poor maneuverability, leading to low casting efficiency.

[0116] In this regard, the structure of the present invention, due to its excellent toughness, can be easily cut using a cutter or similar tool to adjust its size and use. Furthermore, even after cutting, it is difficult for the structure to develop cracks, gaps, or other defects. Moreover, even when multiple structures are connected or assembled into a single mold, it is difficult for individual structures to develop cracks, gaps, or other defects. As a result, the structure of the present invention offers excellent operability during processing and assembly.

[0117] From the viewpoint of improving the toughness of the structure, more effectively suppressing the formation of disintegration defects or cracks on the surface of the structure, and thus improving the operability during use, the structure preferably contains organic fibers on the surface of the structure, and preferably the number of organic fibers per unit area of ​​the surface of the structure is above a specified value.

[0118] Specifically, organic fibers are preferably present in the structure at 100 mm intervals on the surface of the structure. 2 The presence of 50 or more, more preferably 70 or more, and even more preferably 100 or more.

[0119] In addition, every 100mm of the surface of the structure 2 The actual number of organic fibers present is less than 300.

[0120] Regarding the number of organic fibers present on the surface of the structure, firstly, the fibrous structures on the surface of the structure were determined to be organic fibers using the aforementioned solid-state NMR, micro-FT-IR, and microscopic methods. Subsequently, the surface of the structure containing organic fibers was observed using a microscope or SEM. The obtained fiber observation image data was processed using image processing software (WinROOF, manufactured by Mitani Corporation; all image processing software in this manual is of this type). The 100mm... 2 The area is taken as one field of view, and the arithmetic mean of the number of roots when measuring more than three fields of view is calculated.

[0121] When determining the number of organic fibers, the area to be measured can be observed in 100mm increments at a time. 2 The area can be determined by observing the area, or the observation can be divided into multiple observations of 100mm.2 The area, for example, observing 10mm 10 times. 2 Area, etc.

[0122] From the viewpoint that a single fiber can easily come into contact with multiple other fibers or materials, improve the intertwining of fibers or their bonding with other materials, further improve the toughness of the structure, and improve the operability of the structure, the average fiber length L1 of the organic fibers present on the surface of the structure is preferably 0.5 mm or more, more preferably 1 mm or more.

[0123] From the viewpoint of improving the formability of the structure during manufacturing and improving the dimensional uniformity of the structure during manufacturing and casting, the average fiber length L1 of the organic fibers present on the surface of the structure is preferably 7 mm or less, more preferably 5 mm or less, and even more preferably 4 mm or less.

[0124] The average fiber length L1 of organic fibers can be obtained by observing the surface of the structure using a microscope or SEM. For the obtained fiber observation image data, image processing software is used to measure the length of the fiber from one end to the other using 50 fibers as the object. The arithmetic mean of the measured length is taken as the average fiber length.

[0125] From the viewpoint of increasing the contact area with other fibers or materials by increasing the surface area of ​​the fibers, improving the intertwining of fibers with each other or the bonding with other materials, further improving the toughness of the structure, and improving the operability of the structure, the average fiber diameter D1 of the organic fibers present on the surface of the structure is preferably 8 μm or more, more preferably 10 μm or more.

[0126] From the viewpoint of improving the formability of the structure during manufacturing and improving the dimensional uniformity of the structure during manufacturing and casting, the average fiber diameter D1 of the organic fibers present on the surface of the structure is preferably less than 40 μm, more preferably less than 35 μm, and even more preferably less than 30 μm.

[0127] Regarding the average fiber diameter D1 of organic fibers, the surface of the structure can be observed using a microscope or SEM. For the obtained fiber observation image data, image processing software is used to select 50 fibers as objects, and the lengths of the object fiber orthogonal to the length direction are measured at 5 points on each fiber. The arithmetic mean of these measurements is taken as the average fiber diameter.

[0128] From the viewpoint of improving the intertwining of fibers or their bonding with other materials, and further improving the rigidity and strength of the structure, the ratio of the average fiber length (in mm) of the organic fibers present on the surface of the structure to the average fiber diameter (in mm), that is, the ratio of the average fiber length L1 (in mm) to the average fiber diameter D1 (in μm) divided by 1000, "1000 × average fiber length L1 / average fiber diameter D1", is preferably 10 or more, more preferably 30 or more, further preferably 50 or more, and even more preferably 100 or more.

[0129] From the viewpoint of improving the formability of the structure during manufacturing and improving the dimensional uniformity of the structure during manufacturing and casting, the ratio of "1000 × average fiber length L1 / average fiber diameter D1" is preferably 260 or less, and more preferably 230 or less.

[0130] Within the scope that enables the effects of the present invention, the structure for casting manufacturing may further include inorganic fibers.

[0131] In the case of inorganic fibers, the inorganic fibers mainly have the function of not burning during manufacturing and casting, thereby maintaining the shape of the structure.

[0132] The inorganic fibers that can be used include man-made mineral fibers, ceramic fibers, and natural mineral fibers.

[0133] Man-made mineral fibers include PAN-based carbon fibers and pitch-based carbon fibers, as well as asbestos.

[0134] These inorganic fibers can be used alone or in combination of two or more.

[0135] Among these, carbon fiber is preferred from the viewpoint of maintaining the shape and strength of the structure under the high temperature environment during casting.

[0136] Carbon fiber is a fiber that contains no hydrocarbon groups in its structure and contains carbon double bonds. Carbon fiber is typically composed of only carbon.

[0137] Whether a structure contains inorganic fibers can be determined by the following methods.

[0138] First, focusing on the fibrous material present on the surface of the structure, elemental distribution and analysis were performed using scanning electron microscopy (SEM-energy dispersive X-ray spectroscopy (EDX) or microscopic FT-IR analysis. Based on these analyses, the types and amounts of elements contained in the fibrous material were determined. If fibrous material containing C=C bonds was observed, and this fibrous material did not simultaneously contain metallic and oxygen elements, or if fibrous material lacking CH, C=O, or OH bonds was observed, the fibrous material was determined to be an inorganic fiber.

[0139] When the structure contains inorganic fibers, from the viewpoint of improving the formability and uniformity of the structure for casting manufacturing, the average fiber length of the inorganic fibers is preferably 0.5 mm or more, and more preferably 1 mm or more.

[0140] Furthermore, regarding the average fiber length of the inorganic fibers, from the viewpoint of improving the formability of the structure, it is preferably 15 mm or less, more preferably 8 mm or less, and even more preferably 5 mm or less.

[0141] Regarding the average fiber length of inorganic fibers, firstly, fibrous materials existing on the surface of the structure are identified as inorganic fibers using the method described above. Then, these inorganic fibers are observed under a microscope or SEM at 50x magnification. At least 30 fibers are randomly selected from this two-dimensional image, and their length from one end to the other is measured. The arithmetic mean of these measurements is taken as the average fiber length.

[0142] When the structure contains inorganic fibers, from the viewpoint of improving the formability and uniformity of the structure for casting manufacturing, the average fiber diameter of the inorganic fibers is preferably 5 μm or more, and more preferably 10 μm or more.

[0143] Furthermore, regarding the average fiber diameter of the inorganic fibers, from the viewpoint of improving the formability of the structure and improving the dimensional uniformity of the structure during manufacturing and casting, it is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less.

[0144] Regarding the average fiber diameter of inorganic fibers, after determining the presence of inorganic fibers in the same way as the above-mentioned method for determining inorganic fibers, more than 30 randomly selected inorganic fibers are taken as objects, and the lengths of five points orthogonal to the length direction of each fiber are measured. The arithmetic mean of the measurements at this time is taken as the average fiber diameter.

[0145] Without impairing the effects of the present invention, the structure for casting manufacturing may be coated with a molding agent in addition to the above-described components. In this case, the structure for casting manufacturing includes: a base material having the above-described structure, and a surface layer formed on the surface of the base material by applying a molding agent or the like.

[0146] The purpose of the molding compound is to improve anti-sticking properties, surface smoothness, and release properties.

[0147] As a molding compound, examples include materials commonly used in sand casting or shell casting, such as materials that are mainly composed of refractory particles and contain thermosetting resins or silicones as organic components.

[0148] Furthermore, even when the structure for casting manufacturing of the present invention does not form a surface layer by applying a molding agent, it exhibits excellent anti-sand adhesion, surface smoothness, and demolding properties.

[0149] The following describes the manufacturing method of the structure for casting. This manufacturing method generally consists of the following steps: a step of mixing organic components containing organic fibers and inorganic components such as inorganic particles or inorganic fibers, as needed, with a dispersion medium to prepare a precursor for the structure; and a step of heating and pressing the precursor for the structure using a stamping die to solidify and shape the precursor for the structure.

[0150] In the following description, as a preferred method, a method for preparing a structural precursor by mixing organic components containing organic fibers with inorganic particles is illustrated.

[0151] First, organic components containing organic fibers, inorganic components such as inorganic particles, and a dispersion medium are mixed to create a precursor for the structure (mixing process).

[0152] Specifically, organic fibers, thermosetting resins, various inorganic particles, and dispersion media are uniformly mixed to produce a precursor for the structure.

[0153] The precursor of the structure contains organic fibers and thermosetting resins as organic components, various inorganic particles and dispersion media, and is in the form of dough.

[0154] Dough is defined as a fluid substance that is easily deformed by external forces, and in which the various organic and inorganic components and the dispersion medium it contains do not easily separate.

[0155] The mixing of various organic components, inorganic particles, and dispersion media can be carried out by adding them all at once, or by adding them sequentially in any order. From the viewpoint of mixing uniformity, it is preferable to first dry mix the various organic components and inorganic particles, and then add the dispersion media for mixing.

[0156] The precursor of the structure can be made by mixing, for example, manually or using known mixing equipment.

[0157] When using a mixing device, a universal mixer, kneader, or pressure kneader suitable for mixing high-viscosity materials such as slurry or dough is preferred.

[0158] When using a mixing apparatus, this can be done, for example, by using a pressure kneader (manufactured by Nihon Spindle Manufacturing Co., Ltd.) at 6.1 rpm for 30 minutes.

[0159] Examples of aqueous dispersion media include solvents such as water, ethanol, and methanol, or mixtures thereof.

[0160] From the perspective of improving the dispersion stability and ease of handling of various materials, water is preferred as the dispersion medium.

[0161] The amount of water or other dispersion medium added is preferably 10 to 70 parts by mass relative to 100 parts by mass of the solid mixture consisting of various organic components and various inorganic particles.

[0162] In the case where layered clay minerals are contained as inorganic particles, although the layered clay minerals are granular or powdery in their dry state, when mixed with water, water molecules hydrate with the cations contained in the interlayer of the unit crystal of the layered clay minerals and enter the interlayer.

[0163] Regarding layered clay minerals in a wet state, the distance between unit crystal layers in layered clay minerals increases due to water molecules, causing swelling and turning them into viscous fluids.

[0164] Layered clay minerals possess both fluidity and viscosity, allowing them to easily penetrate between other components such as organic fibers or inorganic particles, functioning as a binder that holds them together.

[0165] From the viewpoint of improving the formability and toughness of the manufactured structure, improving the operability of the obtained structure, and reducing defects in the structure, the content of organic fiber in the structure precursor is preferably 0.3% by mass or more, and more preferably 0.5% by mass or more, relative to the total content of solid components.

[0166] From the viewpoint of reducing gas generation during casting and thus reducing defects in castings when using the obtained structure for casting, the content of organic fiber is preferably 10% by mass or less, more preferably 5% by mass or less.

[0167] The average fiber length and average fiber diameter of the organic fibers used can be within the ranges mentioned above.

[0168] From the viewpoint of ensuring good shape retention, surface smoothness, and demolding properties during the manufacturing and casting of the structure, the content of the first inorganic particles in the structure precursor is preferably 40% by mass or more, and more preferably 60% by mass or more, relative to the content of the solid component.

[0169] Furthermore, from the viewpoint of effectively exhibiting the toughness of the structure and improving the operability of the obtained structure, the content of inorganic particles in the structure precursor is preferably 90% by mass or less, and more preferably 85% by mass or less, relative to the content of solid components.

[0170] The average particle size of the first inorganic particles used can be within the above-mentioned range.

[0171] When the structure contains second inorganic particles, from the viewpoint of ensuring good formability of the structure for casting, the content of the second inorganic particles in the structure precursor is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, relative to the content of solid components.

[0172] Furthermore, from the viewpoint of suppressing the amount of gas generated from the structure during casting and reducing the incidence of gas defects in the casting when using the obtained structure for casting, the content of the second inorganic particles in the structure precursor is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, relative to the content of solid components.

[0173] When layered clay minerals are used as the second inorganic particle, the content of the layered clay minerals can be set within the range described above.

[0174] The average particle size of the second inorganic particles used can be within the above-mentioned range.

[0175] Inorganic fibers may be absent from the structure, meaning the content of inorganic fibers in the structure is 0% by mass, or inorganic fibers may be included in the structure. When inorganic fibers are included, from the viewpoint of improving the formability during manufacturing and the shape retention during casting, the content of inorganic fibers is preferably more than 0% by mass and less than 20% by mass, more preferably less than 16% by mass, further preferably less than 5% by mass, and even more preferably less than 3% by mass.

[0176] In cases involving multiple inorganic fibers, the content of inorganic fibers is based on total amount.

[0177] The average fiber length and average fiber diameter of the inorganic fibers used can be within the ranges mentioned above.

[0178] When carbon fiber is included as an inorganic fiber, from the viewpoint of improving the formability during the manufacture of the structure and the shape retention during casting, the carbon fiber content is preferably 1% by mass or more, and more preferably 2% by mass or more.

[0179] Furthermore, the carbon fiber content is preferably 20% by mass or less, more preferably 16% by mass or less.

[0180] From the perspective of improving the formability of the structure, the dough-like structural precursor can be supplied to an external force-applying mechanism for stretching to form a sheet (stretching process).

[0181] As an external force-applying mechanism, there are no particular restrictions as long as it can stretch the precursor of the structure into a sheet-like form. For example, the precursor of the structure can be supplied between a pair of stretching rollers or between a stretching roller and a flat plate for stretching.

[0182] Before and after this process, the precursor of the structure remains in a state that is easily deformed by external forces.

[0183] Next, the dough-like or sheet-like structural precursor is heated and pressed using a stamping die. While the precursor is drying and curing, it is molded into a structural body with the desired casting shape (molding process). This results in a structural body with at least organic fibers on its surface.

[0184] The stamping die has a shape corresponding to the external shape of the structure to be formed in the casting. By heating and pressing the precursor of the structure using the stamping die, the shape of the stamping die is transferred onto the precursor of the structure. While dehydrating and drying the precursor of the structure to cure it, a structure with the desired casting shape is formed. At the same time, a thermosetting resin that can be contained as an organic component is cured.

[0185] The structure after this process becomes less susceptible to deformation by external forces. The formed structure can be molded with a cavity that opens to the outside, consisting of two molds combined into a set of segmented molds, known as a casting mold, or it can be a one-piece molded structure.

[0186] By removing moisture from the precursor of the structure through heating and pressing, the layered clay minerals contained in the precursor lose the dispersion medium molecules such as water that exist between their unit crystal layers. By losing the dispersion medium molecules, the layered clay minerals shrink and solidify while forming a tight structure inside the structure together with inorganic components such as organic fibers and inorganic particles.

[0187] As a result, shear forces are generated between organic fibers, layered clay minerals and other inorganic particles, making them less susceptible to deformation by external forces and effectively maintaining the shape of the structure.

[0188] Regarding the fiber length and diameter of organic fibers, the particle size of various inorganic particles, and the fiber length and diameter of inorganic fibers as needed, even after mixing, swelling, drying, heating, and pressing between the fabrication of the precursor and the molding process, the fiber length, fiber diameter, and particle size remain almost unchanged. Therefore, the fiber length and diameter of various fibers used as raw materials, as well as the particle size of various particles, are basically the same as the fiber length and diameter of various fibers and the particle size of various particles present in the structure.

[0189] Regarding the heating temperature in the molding process, from the viewpoint of easily removing the dispersion medium such as water from the precursor of the structure, it is preferably 70°C or higher, and more preferably 100°C or higher.

[0190] The heating temperature in the molding process is preferably below 250°C, and more preferably below 200°C.

[0191] Regarding the heating time in the molding process, from the point of view of manufacturing efficiency, under the condition of the above-mentioned heating temperature range, it is preferred to set it to 1 minute or more, and more preferably to set it to 60 minutes or less.

[0192] Regarding the pressure applied during the molding process, from the viewpoint of improving the formability of the structure, it is preferably 0.5 MPa or more, and more preferably 1 MPa or more.

[0193] Furthermore, from the viewpoint of improving the formability of the structure, the pressure is preferably 20 MPa or less, and more preferably 10 MPa or less.

[0194] In the structure for casting manufacturing, from the viewpoint of reducing gas defects in the casting caused by vapors originating from dispersion media such as water, the water content is preferably set to 5% by mass or less, more preferably 3% by mass or less.

[0195] The moisture content in the structure used for casting can be adjusted through the above-mentioned molding process, or it can be adjusted by performing a drying process in addition to the heating and pressing process.

[0196] When performing a drying process, known thermostatic baths or hot air drying devices can be used.

[0197] In addition, the heating temperature and heating time in the drying process can be the same as those described above.

[0198] When a casting mold is formed by combining two structures that constitute a set of segmented molds, the structure is manufactured in the manner described above as a set of segmented molds, and then the segmented molds are further joined with the cavity side as the inner side, thereby enabling the manufacture of the target casting mold.

[0199] As a method of joining segmented molds, for example, joining can be achieved using joining components such as screws or clamps, or general adhesives, or sand molds covering a set of segmented molds.

[0200] The thickness of the structure for casting can be appropriately set according to the shape of the target casting. From the viewpoint of obtaining sufficient thermal strength and shape retention during casting, the thickness of at least the part in contact with the molten metal is preferably 0.2 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more.

[0201] Furthermore, from the viewpoint of improving the ease of operation of the structure and reducing the amount of gas generated, it is preferable to have a thickness of 10 mm or less, and more preferably 5 mm or less.

[0202] The thickness of the structure can be adjusted by appropriately changing the shape and pressure of the molding die.

[0203] The casting structure produced through the above processes contains organic fibers, making it lightweight and highly tough. This helps to suppress the disintegration, cracking, or breakage of the structure, resulting in excellent workability. Furthermore, by including inorganic particles in the casting structure, it becomes lightweight, exhibits the desired toughness, and improves heat resistance, thus achieving a casting structure that combines high room temperature strength, high thermal strength, and high shape retention.

[0204] It can also effectively reduce casting defects such as sand adhesion and gas defects on the casting surface. As a result, castings with excellent dimensional accuracy and surface smoothness can be manufactured.

[0205] The ability to manufacture castings with excellent dimensional accuracy and surface smoothness means that post-processing can be reduced to achieve the desired shape and dimensional accuracy of the castings, thereby reducing the manufacturing cost of the castings.

[0206] The casting of a part using a casting manufacturing structure can be carried out using a conventional casting method. That is, molten metal is poured into the gating system formed by the casting manufacturing structure. After casting, the metal is cooled to a predetermined temperature, the casting manufacturing structure is removed, and the casting is exposed. Then, post-processing such as finishing can be performed on the casting as needed.

[0207] The present invention has been described above based on preferred embodiments, but the present invention is not limited to the above embodiments and the various components can be combined appropriately.

[0208] [Example]

[0209] The present invention will now be described in more detail through embodiments. However, the scope of the present invention is not limited to these embodiments.

[0210] [Example 1]

[0211] Organic fibers (mechanical pulp) and thermosetting resins (phenolic resin, methyl phenolic resin) are used as organic components, mullite (spherical, average particle size of 30 μm) is used as the first inorganic particle, and layered clay mineral particles (montmorillonite, Kunimine Industries Co., Ltd., Kunipia F, average particle size of 145 μm) are used as the second inorganic particle.

[0212] In addition, PAN-based carbon fiber (manufactured by Mitsubishi Chemical Corporation, PYROFILTR03CM A4G) is used as an inorganic fiber.

[0213] The materials were mixed according to the ratios shown in Table 1 below to create a precursor for the structure, and the structure for casting was manufactured according to the method described above. The resulting structure for casting was produced in two shapes: a flat plate with a thickness of 2 mm and a cylindrical shape with an outer diameter of 50 mm, a length of 300 mm, and a thickness of 2 mm. Furthermore, the flat plate structure was used to evaluate the maximum bending stress and bending strain at maximum bending stress, the reduction in mass, the average fiber length on the structure surface, and the average fiber diameter, as described later. The cylindrical structure was used to evaluate the operability, casting performance, and surface finish of the casting, as described later.

[0214] The amount of water added is 50 parts by mass relative to 100 parts by mass of the mixture. The heating temperature and heating time of the precursor structure are set to 140°C and 10 minutes, and the pressure in the molding process is set to 5 MPa.

[0215] The "Total Organic Components" in the table represents the content of organic components in the structure used for casting. In this embodiment, the structure is not coated or treated, and therefore does not have a surface layer.

[0216] [Example 2]

[0217] As organic fibers, fibers containing aramid resin (manufactured by Toray Industries, Inc., Kevlar (registered trademark) chopped fibers, 100% by mass of aramid resin) are used instead of mechanical pulp, and inorganic fibers are not used. Otherwise, the materials are mixed in the proportions shown in Table 1 below to manufacture a casting structure in the same manner as in Example 1.

[0218] [Example 3]

[0219] In addition to using waste newspaper pulp from which pulp fibers were extracted through water pulping as organic fibers, mechanical pulp was used instead of organic pulp. Otherwise, the materials were mixed in the proportions shown in Table 1 below to manufacture a structure for casting in the same manner as in Example 1.

[0220] [Example 4]

[0221] Mechanical pulp and thermosetting resin (phenolic resin, methyl phenolic resin) are used as organic components, while obsidian (Kinsei Matec Co., Ltd., polyhedral, Nice Catch Flour #330) with an average particle size of 27 μm is used as the first inorganic particle. Obsidian contains aluminum oxide, silicon dioxide, and iron oxide.

[0222] Furthermore, PAN-based carbon fiber (Mitsubishi Chemical Corporation, PYROFIL TR03CMA4G) is used as an inorganic fiber.

[0223] In addition, the materials are mixed in the proportions shown in Table 1 below to manufacture a casting structure in the same manner as in Example 1.

[0224] [Example 5]

[0225] As organic fibers, fibers containing polyester resin (fiber diameter 11 μm, fiber length 5 mm, polyester resin 100% by mass) are used instead of mechanical pulp, and inorganic fibers are not used. Otherwise, the materials are mixed in the proportions shown in Table 1 below to manufacture a structure for casting in the same manner as in Example 1.

[0226] [Example 6]

[0227] As an organic fiber, a fiber containing polyester resin (fiber diameter 11 μm, fiber length 5 mm, polyester resin 100% by mass) was used instead of mechanical pulp. Otherwise, the materials were mixed in the proportions shown in Table 1 below to manufacture a structure for casting in the same manner as in Example 1.

[0228] [Comparative Example 1]

[0229] Except for the absence of organic fibers as organic components, the materials are mixed in the proportions shown in Table 1 below to manufacture a casting structure in the same manner as in Example 1.

[0230] [Comparative Example 2]

[0231] As an organic component, only newspaper pulp is used instead of the combination of mechanical pulp and newspaper pulp. Otherwise, the materials are mixed in the proportions shown in Table 1 below to manufacture the structure for casting in the same manner as in Example 1.

[0232] [Evaluation of maximum bending stress and bending strain at maximum bending stress]

[0233] For the casting structures of the embodiments and comparative examples, plate-shaped test samples were taken according to the above method, and the maximum bending stress (MPa) and bending strain (%) at the maximum bending stress were measured on the samples according to the three-point bending test method of JIS K7017. Maximum bending stress and bending strain are indicators of the toughness of the casting structure; the higher the values ​​of maximum bending stress and bending strain, the higher the toughness of the structure and the better its operability. The results are shown in Table 1.

[0234] [Evaluation of quality reduction rate]

[0235] Regarding the evaluation of the mass reduction rate of the casting structures of the embodiments and comparative examples, a thermogravimetric analyzer (manufactured by Seiko Instruments Inc., STA7200RV TG / DTA) was used. The casting structures of each embodiment and comparative example were heated from 30°C to 1000°C at a heating rate of 20°C / min under a nitrogen atmosphere. The change in mass was measured as a function of temperature, and the mass reduction rate (%) was calculated based on the mass at 30°C. The results are shown in Table 1.

[0236] [Evaluation of average fiber length and average fiber diameter on the surface of the structure]

[0237] The average fiber length and average fiber diameter of the organic fibers present on the surface of the structure for casting manufacturing in the examples and comparative examples were evaluated according to the method described above. The results are shown in Table 1.

[0238] [Evaluation of the number of fibers on the surface of the structure]

[0239] The number of organic fibers present on the surface of the structure for casting manufacturing in the examples and comparative examples was evaluated according to the method described above. The results are shown in Table 1.

[0240] [Evaluation of the operational feasibility of the structure]

[0241] The operability of the casting structures of the embodiments and comparative examples was evaluated according to the following method. Specifically, a hand saw with a cutting edge thickness of 1 mm and a longitudinal cutting edge was used to cut at a position 50 mm away from the end face of the structure, and the length (mm) of the influence range of cracks or defects generated during cutting was measured from the cut end face. The shorter the influence range length, the better the operability of the structure. The results are shown in Table 1 below.

[0242] [Evaluation of casting (blowback height)]

[0243] Using the casting manufacturing structures of the examples and comparative examples as molds, 25 kg of molten metal containing cast iron at 1350°C was poured into the mold over 20 seconds to manufacture castings. At this time, the backflush height (mm) of the molten metal from the inlet face of the molten metal was measured. A lower backflush height means better suppression of gas generation from the casting manufacturing structure during molten metal inflow, reduced gas defects in the casting, and higher safety of the casting operation. The results are shown in Table 1 below.

[0244] [Surface quality evaluation of castings]

[0245] Using the casting structures of the embodiments and comparative examples as molds, molten metal containing cast iron at 1350°C was poured into the molds to manufacture castings. The area ratio of the sand-adhered portion formed at this time was calculated, and the surface properties of the casting surface were evaluated.

[0246] Specifically, on the surface of the casting at the contact point between the structure for casting and the resulting casting, the portion where the flowing molten metal damages and adheres to the structure for casting, or the portion where it carries and adheres to deposits from casting sand, is considered as a sand-adhering portion, and its presence and extent are visually determined.

[0247] Next, for the range of sand-adhered portions determined by the above method, sheets with a fixed weight per unit area are cut out corresponding to the shape of each sand-adhered portion. The total mass of the cut sheets is divided by the weight per unit area of ​​the sheet to calculate the area of ​​the sand-adhered portion.

[0248] In addition, regarding the surface area of ​​the casting, a sheet with a fixed weight per unit area is used to cover the surface of the casting in a way that the sheets do not overlap. The mass of the sheet used for covering is divided by the weight per unit area of ​​the sheet, thereby calculating the surface area of ​​the casting.

[0249] Then, the area ratio of the sand-adhered portion is calculated as a percentage (%) of the area of ​​the sand-adhered portion relative to the surface area of ​​the casting.

[0250] A lower area ratio of sand-adhered portions indicates less sand adhering to the casting surface, resulting in better dimensional accuracy and surface smoothness of the casting. The results are shown in Table 1 below.

[0251] [Table 1]

[0252]

[0253] As shown in Table 1, the casting manufacturing structure of the embodiment, by containing a specified amount of organic components including organic fibers, exhibits higher maximum bending stress and bending strain compared to the casting manufacturing structure of the comparative example, resulting in improved toughness and thus improved operability. Furthermore, the casting manufacturing structure of the embodiment, by containing a specified amount of organic components including organic fibers, has a mass reduction rate of less than a specified value, thus effectively reducing gas defects in the obtained casting. Moreover, the area ratio of sand-adhered portions in the casting manufacturing structure of the embodiment is also equal to or less than that of the comparative example, thus effectively reducing sand adhesion to the casting surface and resulting in castings with excellent dimensional accuracy and surface smoothness.

[0254] Therefore, the structure for casting manufacturing of the present invention has excellent operability and can reduce gas defects and sand adhesion on the surface of the casting.

[0255] In particular, the casting manufacturing structures of Examples 1, 3 and 4, by combining inorganic fibers with a small amount of organic fibers, can suppress the amount of gas generated and improve bending stress.

[0256] In addition, the casting structure of Example 5 can fully meet the bending characteristics using only organic fibers, while significantly reducing the manufacturing cost of the structure.

[0257] Industrial availability

[0258] According to the present invention, a structure for casting manufacturing is provided that has excellent operability and can reduce gas defects in castings and sand adhesion on the surface of castings.

Claims

1. A structure for manufacturing castings, comprising more than 5% by mass and less than 20% by mass of organic components. At least a portion of the organic component is organic fiber. The organic fiber comprises one or more selected from pulp fiber, as well as fibers containing polyester resin and fibers containing aromatic polyamide resin. The mass reduction rate of the structure used in casting after heating at 1000°C for 30 minutes under a nitrogen atmosphere is greater than 1% and less than 20% by mass. The thickness of the structure used for casting is between 0.2 mm and 10 mm. The organic fibers are distributed per 100 mm on the surface of the structure used for casting. 2 There are more than 50. The structure for casting manufacturing satisfies at least one of the following (1), (2) and (3): (1) Contains inorganic particles, wherein the inorganic particles include a first inorganic particle and a second inorganic particle, wherein the first inorganic particle is not a layered particle and the second inorganic particle is a layered particle. (2) Contains inorganic particles, wherein the inorganic particles include a first inorganic particle with a melting point of 1200°C or higher and a second inorganic particle with a melting point of less than 1200°C. (3) The maximum bending stress measured according to JIS K7017 is 9 MPa or more and the bending strain at the maximum bending stress is 0.6% or more. The first inorganic particle is selected from one or more of graphite, mullite, obsidian, zirconium, silicon dioxide, fly ash, and alumina. The second inorganic particle is selected from one or more layered clay minerals of the kaolinite group, montmorillonite group, and mica group. Of the total 100 parts by mass of the solid component consisting of the organic component and the inorganic particles, the content of the organic fiber is 0.3% by mass to 10% by mass, the content of the first inorganic particles is 40% by mass to 90% by mass, and the content of the second inorganic particles is 1% by mass to 50% by mass.

2. The structure for casting manufacturing as described in claim 1, wherein, The mass reduction rate is less than 15% of the mass.

3. The structure for casting manufacturing as described in claim 1, wherein, The mass reduction rate is between 1% and 9.69% of mass.

4. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The mass reduction rate is 3% or more.

5. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The maximum bending stress is above 9 MPa.

6. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The maximum bending stress is below 50 MPa.

7. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The bending strain at the maximum bending stress is 0.6% or more.

8. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The bending strain at the maximum bending stress is 0.65% or more.

9. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The bending strain at the maximum bending stress is less than 8%.

10. The structure for manufacturing castings as described in any one of claims 1 to 3, wherein, It contains inorganic particles, which include one or more of the following: alumina, silicon dioxide and iron oxide.

11. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The first inorganic particle is a spherical particle, and the second inorganic particle is a layered clay mineral particle.

12. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The organic fibers are distributed per 100 mm on the surface of the structure used for casting. 2 There are more than 70.

13. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The organic fibers are distributed per 100 mm on the surface of the structure. 2 There are fewer than 300.

14. The structure for casting manufacturing as described in claim 12, wherein, The average fiber length L1 of the organic fibers present on the surface is 0.5 mm or more.

15. The structure for casting manufacturing as described in claim 12, wherein, The average fiber length L1 of the organic fibers present on the surface is less than 7 mm.

16. The structure for casting manufacturing as described in claim 12, wherein, The average fiber diameter D1 of the organic fibers present on the surface is less than 40 μm.

17. The structure for casting manufacturing as described in claim 12, wherein, The average fiber diameter D1 of the organic fibers present on the surface is greater than 8 μm.

18. The structure for casting manufacturing as claimed in claim 12, wherein, The ratio of the average fiber length to the average fiber diameter of the organic fibers present on the surface is 10 or more, calculated as 1000×L1 / D1.

19. The structure for casting manufacturing as described in claim 18, wherein, The ratio is less than 260 when calculated as 1000×L1 / D1.

20. The structure for manufacturing castings as described in any one of claims 1 to 3, wherein, It also contains other organic components besides the organic fibers.

21. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The inorganic fiber content contained in the structure for casting is between 0% and 20% by mass.

22. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The organic component content in the structure used for casting is 5.5% by mass or more.

23. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The organic content in the structure used for casting is less than 15% by mass.

24. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The content of the organic component comprising the organic fiber is more than 7.0% by mass and less than 14.0% by mass.

25. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The thickness of the structure used for casting is between 0.5 mm and 10 mm.

26. The structure for casting manufacturing as described in any one of claims 1 to 3, wherein, The organic fiber content in the structure used for casting is between 0.5% and 10% by mass.

27. A method for manufacturing a casting, which uses the casting manufacturing structure according to any one of claims 1 to 26.

28. A method for manufacturing a casting mold, which uses the casting manufacturing structure according to any one of claims 1 to 26.

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