JP7152151B2 - Manufacturing method of ceramic core - Google Patents

Description

The present invention relates to a method for manufacturing a ceramic core.

Industrial gas turbine moving and stationary vanes (turbine blades), jet engines, turbochargers, and other heat-resistant structural parts used in high-temperature environments (e.g., 1100°C or higher) are made of Ti-based alloys, Ni-based alloys, Co-based alloys, etc. of superalloys are widely used. Among these heat-resistant structural members, it is known that turbine blades, for example, are provided with hollow holes, which are air flow paths, which are designed intricately and with high precision in order to enhance the cooling effect while maintaining the strength of the blade. ing. A heat-resistant structural component having such a hollow hole is molded using a ceramic core having a shape corresponding to the hollow hole to be formed. The ceramic core is eluted and removed using a chemical or the like after molding of the heat-resistant structural component. Patent document 1 is mentioned as a prior art regarding this kind of ceramic core. Patent document 2 is a technical document related to 3D additive manufacturing.

JP 2015-226935 A JP-A-2005-144870

In recent years, in order to achieve higher efficiency in heat-resistant structural parts such as turbine blades, there has been a growing demand for heat-resistant structural parts having product shapes such as hollow holes that are designed more complicatedly. there is Therefore, a ceramic core having a complicated internal shape is desired so that a product shape such as a hollow hole designed more complicatedly can be formed. However, the ceramic core generally needs to be molded by an injection molding method in which a high-temperature fluidized ceramic core-forming slurry is injected into a mold or by a cast molding method in which the slurry is poured into the mold, and then removed from the mold. , the internal shape cannot be complicated. In other words, there is a drawback that it is difficult to manufacture a ceramic core with a complicated shape due to restrictions on the internal shape. Regarding this point, Patent Document 1 proposes manufacturing a ceramic core of a desired shape using a 3D additive manufacturing technique. However, with such a technique, the outer surface of the ceramic core becomes gradual due to the lamination steps, and it may not be possible to mold a heat-resistant structural component having a good casting surface.

The present invention has been made in view of the above points, and a main object thereof is to provide a ceramic core manufacturing method capable of obtaining a ceramic core having a complicated internal shape.

In order to achieve the above object, the present invention provides a method of manufacturing a ceramic core having a predetermined internal shape. This manufacturing method includes forming a modeled object having a shape corresponding to the internal shape using modeling powder containing an inorganic material and a water-soluble organic material (modeling step). Also, the shaped article is placed in a mold having a cavity corresponding to the outer shape of the ceramic core, and the ceramic core forming material is poured into the cavity formed by the die and the shaped article and solidified. (solidification step). Furthermore, it includes obtaining a ceramic core having the internal shape by eliminating the shaped object contained in the solidified product (elimination step). According to the manufacturing method of this aspect, a ceramic core having a complicated internal shape can be manufactured.

In a preferred aspect of the method for manufacturing a ceramic core disclosed herein, the step of removing the shaped article includes a treatment of removing the shaped article by immersing it in water. According to such a configuration, it is possible to easily and efficiently remove the modeled object contained in the solidified product.

In a preferred aspect of the ceramic core manufacturing method disclosed herein, the step of eliminating the shaped object includes a process of applying ultrasonic vibration to the shaped object. By doing so, it is possible to efficiently eliminate a modeled object having a more complicated shape.

In a preferred aspect of the ceramic core manufacturing method disclosed herein, the frequency of the ultrasonic vibration is 20 kHz or more and 50 kHz or less. When the frequency of the ultrasonic vibration is within such a range, it becomes easier to remove the molded object contained in the solidified material.

In a preferred aspect of the method for manufacturing a ceramic core disclosed herein, the step of shaping the shaped article includes mixing a shaping liquid containing water with at least a part of the layer of the shaping powder filled in layers. It includes a process of solidifying and repeatedly laminating the solidified layers. According to such a configuration, it is possible to efficiently model a layered product having a complicated shape.

In a preferred embodiment of the ceramic core manufacturing method disclosed herein, the inorganic material is an oxide containing at least one element selected from the group consisting of Al, Zr, Ti, Zn, Ni, Fe and Si. is composed mainly of By using oxides containing these metal elements or metalloid elements, the mechanical strength of the shaped article obtained in the shaping process can be improved, and deformation of the shaped article before the solidification process can be suppressed.

In a preferred embodiment of the ceramic core manufacturing method disclosed herein, the water-soluble organic material is mainly composed of at least one selected from the group consisting of thermoplastic resins, thermosetting resins and polysaccharides. there is By using any one of thermoplastic resins, thermosetting resins and polysaccharides, the above effects can be exhibited more effectively.

It is a figure which shows the manufacturing flow of the ceramic core which concerns on one Embodiment. It is a figure which shows the manufacturing process of the ceramic core which concerns on one Embodiment. It is a figure which shows the manufacturing process of the ceramic core which concerns on one Embodiment. 3 is a map of an laminate and a ceramic core according to an example. It is a map which shows the manufacturing process of the ceramic core which concerns on an Example. It is a graph which shows the relationship between the volume ratio of PVA, and the intensity|strength of a laminate-molded article.

Preferred embodiments of the present invention are described below. Matters other than those specifically mentioned in this specification, which are necessary for carrying out the present invention, can be grasped as design matters by those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field.

The ceramic core disclosed herein is a core for precision casting used in the manufacture of heat-resistant structural parts used in high-temperature environments such as industrial gas turbine moving and stationary vanes (turbine blades), jet engines, and turbochargers. , has a predetermined internal shape. The procedure for manufacturing the ceramic core will be described below with reference to FIG. FIG. 1 is a flow chart showing the manufacturing process. The manufacturing method of this embodiment has a modeling step (step S10), a solidifying step (step S20), and a disappearing step (step S30).
Here, the modeling step of step S10 includes modeling a modeled object having a shape corresponding to the internal shape using a modeling powder containing an inorganic material and a water-soluble organic material. In the solidification step of step S20, the shaped article is placed in a mold having a cavity corresponding to the outer shape of the ceramic core, and the cavity formed by the die and the shaped article is filled with a ceramic core forming material. It involves pouring the material and allowing it to solidify (typically solidify). The disappearing step of step S30 includes obtaining a ceramic core having the internal shape by removing the shaped object contained in the solidified material. In this way, through each step of the shaping process, the solidifying process, and the disappearing process, it is possible to manufacture a ceramic core having excellent surface smoothness and a complicated internal shape. Each step will be described in more detail below.

<Molding process>
In the modeling step of step S10, a modeling powder containing an inorganic material and a water-soluble organic material is used to model a modeled object having a shape corresponding to the internal shape of the ceramic core. In this embodiment, a layered manufacturing powder containing an inorganic material and a water-soluble organic material is prepared, and a layered article is formed by a powder adhesion type layering method using the layered manufacturing powder.

The inorganic material does not undergo a hydration reaction (typically the formation of hydrates or hydroxides) when water contacts the particles (inorganic particles) made of the inorganic material, or even if it does occur. It is limited only to the microscopic range of the surface of the particles, and there is no particular limitation as long as the majority of the particles is a non-hydratable inorganic material that does not substantially react with water. For example, inorganic particles mainly composed of oxides, nitrides, carbides, etc. containing any element belonging to Groups 4 to 14 of the periodic table can be suitably used. Among them, inorganic particles mainly composed of oxides (ceramics), nitrides, carbides containing any one of the metal elements or metalloid elements selected from Al, Zr, Ti, Zn, Ni, Fe and Si. preferable. Alternatively, inorganic particles mainly composed of a metal containing an element belonging to any one of Groups 4 to 13 of the periodic table or alloys thereof may be employed. Among them, inorganic particles mainly composed of a metal containing any one of the metal elements of Al, Zr, Ti, Zn, Ni and Fe or an alloy thereof are preferable.

Specifically, aluminum oxide (e.g. alumina) particles, zirconium oxide (e.g. zirconia) particles, titanium oxide (e.g. titania) particles, silicon oxide (e.g. silica) particles, zinc oxide particles, iron oxide particles, nickel oxide particles, oxide Oxide particles such as cerium (e.g. ceria) particles, magnesium oxide (e.g. magnesia) particles, chromium oxide particles, manganese dioxide particles, barium titanate particles, calcium carbonate particles, barium carbonate particles; aluminum particles, nickel particles, iron particles, etc. Nitride particles such as silicon nitride particles and boron nitride particles; Carbide particles such as silicon carbide particles and boron carbide particles; One type of inorganic particles may be used alone, or two or more types may be used in combination. Among them, alumina particles, zirconia particles, titania particles, silica particles, zinc oxide particles, barium titanate particles, aluminum particles, nickel particles, and iron particles are preferable because they can form a high-strength shaped article. Among them, alumina particles, zirconia particles, titania particles, and silica particles are more preferable, and alumina particles are particularly preferable.

In this specification, the phrase “mainly composed of A” with respect to the composition of the inorganic particles means that the proportion of A in the inorganic particles (purity of A) is 90% or more (preferably 95%) on a mass basis. above, more preferably 97% or more, still more preferably 98% or more, for example 99% or more).

The shape (outer shape) of the inorganic particles may be spherical or non-spherical. From the viewpoint of mechanical strength, ease of manufacture, etc., substantially spherical inorganic particles can be preferably used. The average particle size of the inorganic particles is not particularly limited, but may be, for example, 5 μm or more and 60 μm or less. If the average particle size of the inorganic particles is too small, the powder for layered manufacturing will be difficult to flow, which may reduce moldability when the powder is filled in a thin layer during modeling. The average particle size of the inorganic particles is preferably 10 μm or more, more preferably 20 μm or more, and particularly preferably 30 μm or more (for example, 40 μm or more) from the viewpoint of moldability. In addition, the average particle size of the inorganic particles is approximately 60 μm or less. If the average particle size of the inorganic particles is too large, the powder tends to flow easily after being filled in a thin layer during modeling, which may cause lamination displacement in each layer of the laminate-molded product. The average particle size of the inorganic particles is preferably 55 μm or less, more preferably 50 μm or less, and particularly preferably 45 μm or less from the viewpoint of suppressing lamination misalignment. For example, inorganic particles having an average particle diameter of 10 μm≦X≦50 μm (typically 30 μm≦X≦50 μm) are suitable from the viewpoint of achieving both moldability and suppression of lamination misalignment.

In the present specification, unless otherwise specified, the "average particle size" is the particle size at an integrated value of 50% in the particle size distribution measured based on a particle size distribution measuring device based on the laser scattering/diffraction method, i.e., 50% It means the volume average particle size (D50 size). More specifically, it is a 50% volume average particle diameter measured dry using a laser diffraction/scattering particle size distribution analyzer without dispersing the particles with compressed air.

The content of the inorganic particles (inorganic material) in the powder for additive manufacturing is not particularly limited. The content of the inorganic particles is usually 50 parts by mass or more when the total amount of the additive manufacturing powder is 100 parts by mass, and is preferably 60 parts by mass or more, more preferably 60 parts by mass or more, from the viewpoint of improving mechanical strength. is 70 parts by mass or more. In one aspect, the content of the inorganic particles may be, for example, 75 parts by mass or more, typically 80 parts by mass or more. The upper limit of the content of the inorganic particles is not particularly limited, but is preferably 95 parts by mass or less, more preferably 92 parts by mass or less, and may be, for example, 88 parts by mass or less.

The powder for additive manufacturing disclosed here contains a water-soluble organic material (typically in the form of particles) in addition to the inorganic materials described above. Particles made of a water-soluble organic material (water-soluble organic particles) can be a component that dissolves in water and adheres inorganic particles to each other when mixed with a water-containing modeling liquid.

The material and properties of the water-soluble organic particles are not particularly limited. For example, water-soluble organic particles mainly composed of any one of thermoplastic resins, thermosetting resins, polysaccharides and water-soluble waxes are preferably used.

Preferred examples of thermoplastic resins include vinyl alcohol resins, isobutylene resins, polyamide resins, polyester resins, and the like. A vinyl alcohol-based resin is typically a resin (PVA) containing a vinyl alcohol unit as the main repeating unit. In the resin, the ratio of the number of moles of vinyl alcohol units to the number of moles of all repeating units is usually 50% or more (for example, 50% to 90%), preferably 65% or more, more preferably 75% or more. , for example 85% or more. All repeating units may consist essentially of vinyl alcohol units. In PVA, the type of repeating units other than vinyl alcohol units is not particularly limited, and may be, for example, vinyl acetate units. Anion-modified PVA such as carboxyl group-modified PVA, sulfonic acid group-modified PVA, and phosphate group-modified PVA, cation-modified PVA, or ethylene, vinyl ethers, vinyl esters, (meth)acrylamides, alpha olefins having long-chain alkyl groups, etc. Polymerized modified PVA; and the like may also be used. Although the polymerization degree of PVA is not particularly limited, it may be, for example, 100 to 5000 (preferably 500 to 3000). The isobutylene-based resin may be an isobutylene homopolymer or a copolymer of isobutylene and another monomer (isobutylene copolymer). In the isobutylene copolymer, other monomers to be copolymerized with isobutylene are not particularly limited. Examples thereof include monomers having an ethylenic double bond. Examples of monomers having an ethylenic double bond include ethylenically unsaturated carboxylic acids such as (anhydrous) maleic acid, acrylic acid, methacrylic acid, (anhydrous) phthalic acid, and (anhydrous) itaconic acid. A chemically modified isobutylene copolymer may also be used. Although the molecular weight of the isobutylene copolymer is not particularly limited, it can be, for example, 3×10 ³ to 2×10 ⁵ (preferably 5×10 ³ to 1.7×10 ⁵ ). Examples of polyamide-based resins include water-soluble nylons obtained by chemically modifying nylons such as polycaproamide (nylon-6). Examples of polyester-based resins include water-soluble polyesters in which a component having a hydrophilic group is introduced into polyester as a copolymer component. Among these thermoplastic resins, vinyl alcohol-based resins and isobutylene-based resins are preferably used because of their strong adhesion.

Preferred examples of thermosetting resins include, for example, melamine resins. The melamine-based resin may be a melamine resin obtained by a polymerization reaction of melamine and aldehyde, or a monomer (or its initial polymer) used to form the melamine resin and other monomers (or its It may be a copolymer resin with an initial polymer). In the melamine resin, the aldehyde polymerized with melamine is not particularly limited. For example, a melamine resin obtained by polymerization reaction of melamine and formaldehyde can be preferably used.

Preferred examples of polysaccharides include cellulose derivatives such as hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, carboxymethylcellulose; gum arabic, xanthan gum, curdlan, starch, dextrin. , glucomannan, agarose, carrageenan, guar gum, locust bean gum, tragacanth gum, quinseed gum, pullulan, agar, konjac mannan; sucrose, dextrose, fructose, lactose, sugar, xylitol, chitosan, cyclodextran, Modified starch; is exemplified. Among them, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, methylcellulose, ethylcellulose, gum arabic, and xanthan gum are preferably used from the viewpoint of adhesiveness and the like.

Water-soluble waxes include animal waxes and vegetable waxes. The term “wax” as used herein refers to an oil-like organic substance (wax) that is solid at room temperature (eg, 25° C.) and has a melting point lower than the boiling point of water (100° C.). Waxes are typically esters of higher fatty acids and monohydric or dihydric higher alcohols, and the concept includes neutral fats, higher fatty acids, and hydrocarbons. Preferable examples of vegetable waxes include Japan wax such as haze wax and sumac wax (main component: palmitic acid glyceride); carnauba wax (main component: myricyl cerotate, myricyl alcohol); sugarcane wax (main component: myricyl palmitate). ); palm wax (main component: myricyl palmitate); candelilla wax; Suitable examples of animal waxes include beeswax (main components: cerotic acid, myricyl palmitate); spermaceti (main component: myricyl palmitate); sperm whale oil (components: oleic acid, cetyl alcohol, palmitic acid, etc.); beard whale oil (ingredients: oleyl alcohol, cetyl alcohol, etc.); privet wax; wool wax (ingredients: ceryl alcohol, myristic acid, etc.);

Other examples of water-soluble organic particles that can be contained in the additive manufacturing powder disclosed herein include polyethylene glycol, polyethylene oxide, polyacrylic acid, partially neutralized sodium polyacrylate, styrenated polyacrylic acid, sulfone A water-soluble water-soluble substance composed mainly of a modified polyester polymer, sulfonated polystyrene, sorbitose, polyvinylpyrrolidone, a copolymer of polyvinylpyrrolidone, sodium polyacrylate, a copolymer of sodium polyacrylate, sodium alginate, gelatin, pectin; Organic particles can be mentioned. The water-soluble organic particles described above may be used singly or in combination of two or more.

In the present specification, the phrase “mainly composed of A” with respect to the composition of the water-soluble organic particles means that the proportion of A in the water-soluble organic particles (purity of A) is 90% or more on a mass basis ( preferably 95% or more, more preferably 97% or more, still more preferably 98% or more, for example 99% or more).

In a preferred embodiment, the water-soluble organic material may have a solubility in water of 20% or more at 20°C. The solubility is preferably 30% or higher, more preferably 50% or higher, still more preferably 70% or higher, and particularly preferably 90% or higher. Although the upper limit of the solubility is not particularly limited, it is generally 99% or less. The solubility of the water-soluble organic particles may be, for example, 98% or less, typically 95% or less. The technology disclosed herein can be preferably implemented in a mode using water-soluble organic particles having a solubility of 30% or more and 95% or less (further, 50% or more and 92% or less). The term "solubility" as used herein refers to the percentage by mass of the water-soluble organic material relative to the saturated aqueous solution (water + water-soluble organic material) when the maximum amount of the water-soluble organic material is dissolved in water.

Although not particularly limited, the average particle size of the water-soluble organic particles is usually 0.1 μm or more, preferably 1 μm or more. The upper limit of the average particle size of the water-soluble organic particles is suitably about 250 μm or less, preferably 200 μm or less.

Although the volume ratio X of the water-soluble organic particles to the total volume of the powder for additive manufacturing (the volume excluding the gaps between particles) is not particularly limited, it is generally 20% by volume or more. From the viewpoint of obtaining a stronger shaped article, the volume ratio X of the water-soluble organic particles is preferably 25% by volume or more, more preferably 30% by volume or more, and even more preferably 35% by volume or more. Moreover, it is suitable that the volume ratio X of the water-soluble organic particles is approximately 60% by volume or less. From the standpoint of obtaining a model with higher strength, the volume ratio X of the water-soluble organic particles is preferably 50% by volume or less, more preferably 45% by volume or less, and even more preferably 40% by volume or less.

In the technology disclosed herein, the water-soluble organic particles and the inorganic particles may exist as independent particles without adhering to each other. Since the water-soluble organic particles and the inorganic particles exist as independent particles in this way, the desired powder for layered manufacturing can be easily realized. Alternatively, water-soluble organic particles may be adhered to the surfaces of inorganic particles. That is, a part or all of the inorganic particles may be covered (coated) with the water-soluble organic particles. As a result, a required amount of the water-soluble organic particles is surely present between the inorganic particles, so that the water in which the water-soluble organic particles are dissolved efficiently spreads among the inorganic particles. Therefore, the effect of improving the strength of the model can be exhibited more effectively.

The powder for additive manufacturing disclosed herein contains known additives that can be used for powder for additive manufacturing, such as dispersants, thickeners, and printing aids, within the range that does not impair the effects of the present configuration. It may be further contained as necessary. The content of the additive may be appropriately set according to the purpose of addition, and detailed description is omitted because it does not characterize the present invention.

The method for preparing the powder for additive manufacturing is not particularly limited. For example, each component contained in the powder for additive manufacturing may be mixed using a well-known mixing method such as a V-type mixer, a rocking mixer, or a tumbler mixer. The manner in which these components are mixed is not particularly limited. For example, all the components may be mixed at once, or they may be mixed in an appropriately set order.

A modeling liquid, typically containing water, is mixed with the above powder for layered modeling to form a modeled object.

The solvent used for the said modeling liquid should just contain water. As the solvent, pure water, ultrapure water, ion-exchanged water (deionized water), distilled water, or the like can be preferably used. If necessary, the modeling liquid disclosed herein may further contain an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water. Generally, water is preferably 40% by volume or more of the solvent contained in the modeling liquid, and more preferably 50% by volume or more (typically 50 to 100% by volume) is water. Such a modeling liquid can be mixed at a ratio of, for example, 20 to 80 parts by mass (typically 40 to 60 parts by mass) with respect to 100 parts by mass of the powder for additive manufacturing during modeling.

The modeling liquid disclosed herein may contain known additives that can be used in the modeling liquid, such as dyes, organic pigments, inorganic pigments, wetting agents, flow-increasing agents, etc., as long as they do not impair the effects of the present configuration. It may be further contained as necessary. The content of the additive may be appropriately set according to the purpose of addition, and detailed description is omitted because it does not characterize the present invention.

There are no particular limitations on the method of forming a modeled object using the powder for layered modeling. For example, a modeled object can be modeled by forming a layer of the powder using the powder for layered modeling and then supplying a modeling liquid containing water to a predetermined region of the layer. This modeling can be performed, for example, using a 3D printer that models a three-dimensional object based on three-dimensional data or the like corresponding to a layered product to be modeled. Such a 3D printer can have an inkjet that drops a modeling liquid containing water, and a placement table on which powder for layered modeling is placed.

Then, by repeating the following operations 1 to 3, layered solids are successively layered to form a layered product.
Operation 1: Fill (deposit) the powder for layered manufacturing in layers on a table so that each layer of the layered product to be modeled has a thickness (for example, 0.01 mm to 0.3 mm) corresponding to each layer. do.
Operation 2: Modeling including water from an inkjet head to the portion to be cured (that is, the portion corresponding to a part of the layered product to be modeled) of the layered powder for layered manufacturing (deposit) Drop the liquid. Then, by dissolving the water-soluble adhesive particles contained in the dropping portion and bonding the non-hydration reaction base material particles, a hardened layer (layered solid matter) is formed.
Operation 3: The setting table is lowered vertically by a thickness corresponding to each layer of the laminate-molded article.

After that, the laminate-molded article is completed by finally removing the laminate-molding powder that has not been cured. Such laminates are formed by adhering a large number of non-hydrated reaction matrix particles with dissolved water-soluble adhesive particles, and may have a porous structure. After modeling, the laminate-molded article obtained may be naturally dried. Although the drying time is not particularly limited, it is approximately 1.5 hours to 24 hours, preferably 2 hours to 10 hours.

<Solidification process>
In the solidification step of step S20, a mold having a cavity corresponding to the outer shape of the ceramic core is prepared, and the molded object obtained in the molding step is placed in the mold. Then, the ceramic core forming material is poured into the cavity formed by the mold and the shaped article and allowed to solidify.

The ceramic core-forming material may contain ceramic particles that form the main skeleton of the ceramic core, and a binder component.

The composition of the ceramic that constitutes the ceramic particles is not particularly limited. Such ceramics are, for example, silica ( _SiO2 ), alumina _{( Al2O3} ) _, zirconia (ZrO2), magnesia (MgO), titania _{( TiO2} ), ceria ₍ CeO2), yttria ( _Y2O3 ). , hafnia (HfO ₂ ), barium titanate (BaTiO ₃ ), manganese dioxide (MnO ₂ ), lime (CaO), zinc oxide (ZnO), red iron oxide (Fe ₂ O ₃ ), zircon (ZrSiO ₄ ), mullite (Al ₆ O ₁₃ Si ₂ ), aluminum silicate and other oxide-based ceramics, silicon nitride (Si ₃ N ₄ ), boron nitride (BN), aluminum nitride (AlN), silicon carbide (SiC), A non-oxide ceramic such as boron carbonitride may be used, or a composite material containing at least one of these ceramics may be used. Any one of these ceramics can be used alone, or two or more of them can be used in combination, depending on the application of the ceramic core and the properties required. Among them, silica, alumina, zircon, hafnia, yttria, zirconia and the like are preferably used because of their excellent flame retardancy. The chemical formula shown in parentheses after the name of the substance above indicates a representative composition of the substance, and the actual ceramic composition is not intended to be limited to such a chemical formula.

As the binder component, various materials that are insoluble or sparingly soluble in water and that can be used in this type of molding method can be used. Examples of binder components include polyamide, polyether ketone, polyether sulfone, polyether polyether block amide, polyethylene, polyethylene terephthalate, polyethylene glycol, polyolefin, polycarbonate, polycyclohexylene methylene terephthalate, polystyrene, polysulfone, and polyvinylidene fluoride. , polyvinyl chloride, polyvinyl butyral, polyphenylsulfone, polyphenylene ether, polyphenylene sulfide, polyphthalamide, polybutylene terephthalate, polypropylene, polymethyl methacrylate, polylactide, methyl cellulose, urea-formaldehyde polycondensate, petroleum wax, and the like. be.

An example of a binder component is a solid in a normal temperature range (e.g., less than 45°C, typically 25 ± 5°C), melted (softened) by heating to a predetermined temperature less than 45°C, and 45 C. or higher and can exhibit high fluidity in a molten state. Examples of such binder components include petroleum waxes. Various waxes specified in JIS K 2235 (1991) can be used as the petroleum wax. Specifically, as the petroleum wax, paraffin wax separated and refined from vacuum distilled oil and microwax (microcrystalline wax) separated and refined from vacuum distilled residual oil or heavy distillate oil are suitable. Examples include: Such petroleum waxes are not particularly limited, but paraffin waxes having a weight average molecular weight of 500 or less and microwaxes having a weight average molecular weight of 1000 or less are easily melted by heating at a relatively low temperature. preferred because it can

The petroleum wax may have a relatively low melting point. It can be said that it is expensive. In addition, the petroleum-based wax described above may be a substance with poor compatibility because of its extremely simple molecular structure compared to common solvents such as water and organic solvents. Therefore, the binder component may contain a water-insoluble polyoxyethylene-type nonionic surfactant together with the petroleum wax. By adding such a water-insoluble polyoxyethylene-type nonionic surfactant to the petroleum-based wax, the melting point of the petroleum-based wax is lowered while uniformly mixing with the petroleum-based wax, resulting in sufficient fluidity. can be given.

Such a water-insoluble polyoxyethylene-type nonionic surfactant can be used without any particular limitation as long as it can be uniformly mixed with the petroleum wax and can sufficiently lower the melting point of the petroleum wax. For example, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene/polyoxypropylene decyl ether, polyoxyethylene behenyl ether, polyoxyethylene cholesteryl ether, polyoxyethylene Polyoxyethylene alkyl ethers such as ethylene isocetyl ether, polyoxyethylene isostearyl ether, polyoxyethylene octyldodecyl ether, polyoxyethylene decyltetradecyl ether, polyoxyethylene hydrogenated dimer dilinoleyl ether, polyoxyethylene distyrene Ether-type POE-type nonionic surfactants such as polyoxyalkylene derivatives such as polyphenyl ether; polyoxyethylene hydrogenated castor oil, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene lauryl stearate Ester type (ether ester type) POE type nonionic surfactants such as ethers, polyoxyethylene lauryl ether isostearate, polyoxyethylene cetyl ether stearate, and polyoxyethylene stearyl ether stearate; polyoxyethylene alkylamines, etc. Nitrogen-containing POE type nonionic surfactants.

In addition to the ceramic powder and the binder component, optional additives can be added to the ceramic core forming material, although they are not essential. Typical examples of such optional additives include coupling agents, lubricants, plasticizers, release agents, carbon and the like. Such optional additives can be added in a proportion of, for example, 10% by mass or less of the ceramic core-forming material, as long as the features of the present invention are not impaired.

The above ceramic core forming material is heated (for example, in a temperature range where the binder component melts, typically 50° C. or higher, eg, 50° C. to 150° C., preferably 50° C. to 100° C.) to melt. The heating temperature for melting the binder can be appropriately changed according to the type of binder contained in the mixed material. The heat treatment for melting the mixed material may be performed while kneading using a roll mill, a mixer, or the like. This makes it possible to obtain a composite material in which the ceramic powder is suitably dispersed.

Next, as shown in FIG. 2, a mold 20 having a cavity 10 corresponding to the outer shape of the ceramic core is prepared, and a molded object 30 obtained in the molding process is placed in the mold 20 . Then, as shown in FIG. 3 , a molten ceramic core forming material 40 is poured into a cavity 10 formed by the mold 20 and the model 30 . In this process, after the ceramic core forming material 40 is melted, the molten ceramic core forming material 40 may be injected into the cavity 10 by applying pressure using any injection molding machine. . Alternatively, the molten ceramic core forming material 40 may be poured into the cavity 10 .
Mold 20 is then maintained at a temperature such that the binder component cures. As a result, the melted ceramic core forming material 40 that has been poured is heat-radiated and solidified (or cooled and solidified). As a result, a solidified material (typically a solidified material) having a shape corresponding to the cavity 10 of the mold 20 is obtained.

<Disappearance process>
In the disappearing step of step S30, the solidified material is removed from the mold 20, and the modeled object 30 contained in the solidified material is eliminated. The disappearing step may include, for example, a process of dissolving and removing the laminate-molded article included in the solidified article in water. Specifically, the solidified product is preferably immersed in water together with the laminate-molded product. As a result, the water-soluble organic material in the laminate-molded article included in the solidified material dissolves in water, and the molded article collapses.
In a preferred embodiment, the disappearing step includes a process of applying ultrasonic vibrations to the laminate-molded article immersed in water. The more complicated the shape of the laminate-molded article, the more difficult it is to remove. However, the laminate-molded article can be efficiently removed by applying ultrasonic vibrations in water as described above. There are no particular restrictions on the means for applying ultrasonic vibrations to the laminate-molded article. For example, an appropriate ultrasonic device may be used to apply ultrasonic vibrations to the laminate-molded article immersed in water. Conditions for ultrasonic waves are not particularly limited, but the frequency of ultrasonic waves is preferably 10 kHz to 100 kHz, preferably 15 kHz to 80 kHz, and more preferably 20 kHz to 50 kHz. The preferred power of ultrasound can be 50W-600W, preferably 100W-500W.

Thus, by immersing the laminate-molded article contained in the solidified article in water to make it disappear, a ceramic core having a desired internal shape can be obtained. If necessary, the ceramic core may be subjected to a degreasing treatment to remove the binder component from the ceramic core after molding. Specifically, the ceramic core is heated to a temperature at which the material constituting the binder component is thermally decomposed. The heating conditions (temperature, time) in this degreasing treatment can be appropriately changed according to the type and content of the binder component. Also, the ceramic core may be sintered after degreasing. The heating conditions (temperature, time, atmosphere) in the firing treatment can be appropriately changed according to the type and particle size of the ceramic powder, the desired density of the ceramic core, and the like. For example, the firing temperature may be set to 1000° C. to 1500° C. (preferably 1100° C. to 1300° C.). Also, the atmosphere during firing is preferably set to an oxidizing atmosphere or an inert atmosphere. This can form a stronger ceramic core.

The ceramic core disclosed herein is produced by a molding step of molding a molded object having a shape corresponding to the internal shape of the ceramic core using molding powder containing an inorganic material and a water-soluble organic material, and an external shape of the ceramic core. A solidification step of placing the shaped article in a mold having a cavity corresponding to and solidifying by pouring a ceramic core forming material into the cavity formed by the mold and the shaped article, and and a disappearing step of obtaining a ceramic core having the above internal shape by removing the encapsulated shaped object. Therefore, the obtained ceramic core can have an excellent outer surface smoothness and a complicated inner shape. Such a ceramic core can be preferably used as a ceramic core used for manufacturing various heat-resistant structural parts having a product shape such as a hollow hole designed intricately and with high precision.

Several examples relating to the present invention are described below, but are not intended to limit the present invention to those shown in the examples.

<Test Example 1>
In this example, a ceramic core with a complex internal shape was produced. Specifically, alumina particles as an inorganic material and polyvinyl alcohol (PVA) as a water-soluble organic material are mixed to prepare a powder for additive manufacturing, and a shape corresponding to the internal shape is produced using a 3D printer. was modeled (see FIG. 4(A)). As PVA, one having a solubility in water of 90% at 20° C. was used. Also, the volume ratio X of PVA in the powder for layered manufacturing was set to 50% by volume.
Next, a mold having a cavity corresponding to the outer shape of the ceramic core was prepared, and the laminate-molded article was placed in the mold (see FIG. 5). Then, while heating the mold, the ceramic core forming material was injected into the cavity formed by the mold and the laminate-molded article, and cooled and solidified. As the material for forming the ceramic core, silica particles and zircon particles as ceramic particles were heated and mixed with wax as a binder component so as to have fluidity suitable for injection molding. The obtained solidified product was taken out from the mold, and the solidified product was immersed in water together with the laminate-molded product and subjected to ultrasonic vibration. The ultrasonic frequency was set between 20 kHz and 50 kHz. This removed the laminate-molded article included in the solidified material. Thus, the ceramic score shown in FIG. 4(B) was obtained.

<Test Example 2>
In this example, the following test was conducted in order to confirm the influence of the frequency of ultrasonic vibration on the solubility of the modeled object. Alumina particles as an inorganic material and PVA particles as a water-soluble organic material are mixed to prepare powder for layered modeling, and a 3D printer is used to produce a layered product (4 mm long x 40 mm wide x 3 mm high) ( A test piece) was shaped. The PVA has a solubility in water of 90% at 20°C (hereinafter referred to as “PVA1”) and a PVA with a solubility in water of 30% at 20°C (hereinafter referred to as “PVA2”). It was used. Further, the volume ratio X of PVA in the powder for layered manufacturing in each example was set to 50% by volume.

The laminate-molded article obtained above was immersed in water, ultrasonic vibration was applied, and the dissolution time until the laminate-molded article collapsed was measured. As an ultrasonic device, one of "W-113" and "WDX-1200-I" manufactured by Honda Electronics Co., Ltd., and "ASU-10D" manufactured by AS ONE Corporation was used. Table 1 shows the type of PVA used, the frequency of ultrasonic vibration, the output, and the dissolution time for the powder for additive manufacturing of each example.

As shown in Table 1, when comparing Examples 1 to 8 in which PVA1 was used as the water-soluble organic material, Examples 2 to 8 in which ultrasonic vibration was applied to the laminate-molded article did not apply ultrasonic vibration. Better results were obtained with shorter dissolution times compared to Example 1. Further, in Examples 2, 3, 5 to 7 in which the frequency of ultrasonic vibration was 20 kHz to 50 kHz, the dissolution time was further shortened compared to Examples 4 and 8. When comparing Examples 9 to 16 in which PVA2 was used as the water-soluble organic material, Examples 10 to 16 in which ultrasonic vibration was applied to the layered product had a longer dissolution time than Example 9 in which ultrasonic vibration was not applied. was shorter and gave better results. Further, in Examples 10, 11, 13 to 15 in which the frequency of ultrasonic vibration was 20 kHz to 50 kHz, the dissolution time was further shortened compared to Examples 12 and 16. From these results, from the viewpoint of solubility of the laminate-molded article, it is preferable to immerse the laminate-molded article in water while applying ultrasonic vibration. Further, it is preferable that the frequency of the ultrasonic vibration is 20 kHz to 50 kHz.

<Test Example 3>
In this example, the following test was conducted in order to confirm the effect of the volume ratio of the water-soluble organic material in the powder for layered manufacturing on the strength of the layered product. Alumina particles as an inorganic material and PVA as a water-soluble organic material are mixed to prepare a powder for layered modeling, and a 3 mm long x 3 mm wide x 30 mm high layered product (test piece) was shaped. Table 2 summarizes the content of the inorganic material (alumina particles), the content of the water-soluble organic material (PVA), and the volume ratio X in the powder for layered manufacturing used for the layered product according to each example.

The three-point bending strength of the test piece of each example was measured by a method conforming to JIS R 1601. The results are shown in the "Strength" column of Table 2 and in FIG. FIG. 6 is a graph showing the relationship between the volume ratio X of PVA in the powder for additive manufacturing and the strength.

As shown in Table 2 and FIG. 6, Examples 19 to 22 in which the volume ratio X of PVA in the powder for additive manufacturing is 30% to 50% by volume are 3 points compared to Examples 17, 18, and 23. Good results were obtained in flexural strength. A laminate-molded article having high strength does not lose its shape easily, for example, when a ceramic core-forming material is poured into a mold in which the molded article is placed and solidified. Therefore, it is preferable in that the ceramic core disclosed herein can be stably formed.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

For example, in the above-described embodiment, in the step of removing the modeled article, the case of removing the modeled article by immersing it in water was exemplified, but the method of removing the modeled article is not limited to this. For example, the shaped article may be heated and burned away. That is, the solidified object containing the modeled object may be heated to a temperature range in which the modeled object is burned off and the solidified object is not burned away, thereby removing the encapsulated modeled object. Even in this case, a ceramic core with a desired internal shape can be obtained. However, from the viewpoint of dimensional stability and production stability, it is preferable to immerse the modeled article in water to remove it, as in the above-described embodiment.

10 Cavity 20 Mold 30 Laminated product 40 Ceramic core forming material

Claims (4)

A method of manufacturing a ceramic core having a predetermined internal shape, comprising:
An oxide containing at least one element selected from the group consisting of Al, Zr, Ti, Zn, Ni, Fe and Si, a nitride containing at least one selected element, or at least one selected The internal shape is obtained by using a molding powder that independently contains inorganic particles made of an inorganic material mainly composed of a carbide containing a seed element and water-soluble organic particles made of a water-soluble organic material. forming a model having a shape corresponding to
placing the shaped article in a mold having a cavity corresponding to the outer shape of the ceramic core, and pouring a ceramic core forming material into the cavity formed by the die and the shaped article and solidifying; and obtaining a ceramic core having the internal shape by eliminating the shaped object contained in the solidified solidified product;
encompasses
The step of forming the modeled object includes a process of mixing a modeling liquid containing water with at least a part of the layers of the modeling powder filled in layers to solidify the layers, and repeatedly stacking the solidified layers,
The step of disappearing the model includes a process of immersing the model in water and applying ultrasonic vibrations.
A method for manufacturing a ceramic core. The method for manufacturing a ceramic core according to claim 1 , wherein the frequency of the ultrasonic vibration is 20 kHz or more and 50 kHz or less. 3. The inorganic material according to claim 1 , wherein the inorganic material is mainly composed of an oxide containing at least one element selected from the group consisting of Al, Zr, Ti, Zn, Ni, Fe and Si. A method for manufacturing a ceramic core. The ceramic according to any one of claims 1 to 3 , wherein the water-soluble organic material is mainly composed of at least one selected from the group consisting of thermoplastic resins, thermosetting resins and polysaccharides. How the score is produced.

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