WO2013018393A1 - セラミック中子およびその製造方法 - Google Patents
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- WO2013018393A1 WO2013018393A1 PCT/JP2012/054884 JP2012054884W WO2013018393A1 WO 2013018393 A1 WO2013018393 A1 WO 2013018393A1 JP 2012054884 W JP2012054884 W JP 2012054884W WO 2013018393 A1 WO2013018393 A1 WO 2013018393A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/10—Cores; Manufacture or installation of cores
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/12—Treating moulds or cores, e.g. drying, hardening
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B1/00—Producing shaped prefabricated articles from the material
- B28B1/24—Producing shaped prefabricated articles from the material by injection moulding
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- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C14/00—Glass compositions containing a non-glass component, e.g. compositions containing fibres, filaments, whiskers, platelets, or the like, dispersed in a glass matrix
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Definitions
- the present invention relates to a ceramic core used when casting a casting having a hollow structure, and a manufacturing method thereof.
- Castings having a hollow structure for example, gas turbine blades (turbine blades) made of a Ni-based heat-resistant alloy or the like, have hollow cooling holes formed in the blades with complex and high precision to enhance the cooling effect There is.
- Such a blade can be manufactured by using a ceramic core having a shape corresponding to a hollow cooling hole to be formed by a lost wax precision casting method or the like.
- the ceramic core is exposed to a molten metal at around 1500 ° C. for several hours. Therefore, the ceramic core may be deformed due to thermal deformation or buoyancy due to the molten metal, or may be damaged due to the flow of the molten metal. is there. For this reason, the ceramic core is required to have mechanical strength in a high temperature range around 1500 ° C. and dimensional stability that does not cause dimensional shrinkage or deformation under such casting temperature.
- the ceramic core is eluted and removed using a sodium hydroxide aqueous solution after the completion of casting, elution with respect to an alkaline aqueous solution is also required.
- Patent Document 1 proposes a ceramic core composed of 60 to 85% by mass of fused silica, 15 to 35% by mass of zircon, and 1 to 5% by mass of cristobalite. Yes.
- This ceramic core has sufficient mechanical strength even at a casting temperature of about 1500 ° C., suppresses significant dimensional changes during casting, has excellent dimensional stability, and is likely to elute the ceramic core after casting. ing.
- Patent Document 2 proposes a product manufactured using 60 to 80% by mass of fused silica powder, up to 15% by mass of yttria, and up to 0.2% by mass of alkali metal. .
- This ceramic core has been proposed as having a room temperature strength of a maximum of 12 MPa and a property that hardly deforms even at a high temperature of 1675 ° C., which is considerably higher than 1500 ° C.
- Patent Document 3 proposes a ceramic core manufactured using colloidal silica stabilized with fused silica and sodium. This ceramic core has been proposed as having a room temperature strength of about 7 MPa.
- the ceramic core manufactured using fused silica, zircon, and cristobalite, which is crystalline silica, disclosed in Patent Document 1 described above is an injection molding process in handling at room temperature or in lost wax precision casting. However, there is a problem that it is easy to break when forming a vanishing model. Therefore, it is desirable for this ceramic core to further improve the bending strength at room temperature (25 ° C.).
- the ceramic core manufactured using fused silica, yttria, and alkali metal disclosed in Patent Document 2 described above is hardly deformed even at a considerably high temperature of 1675 ° C.
- this ceramic core has a problem that brittle fracture damage is likely to occur due to the molten metal injected during casting depending on the casting shape. Therefore, it is desirable for this ceramic core to further improve the bending strength in the temperature range around 1500 ° C. during casting. From the viewpoint of shrinkage that occurs when exposed to casting temperature, it is desirable that this ceramic core further improve the dimensional stability during casting.
- the ceramic core manufactured using fused silica which is amorphous silica and colloidal silica stabilized with sodium, which is disclosed in Patent Document 3 described above, has a room temperature strength of about 7 MPa.
- this ceramic core has a problem in bending strength at room temperature, and it is desirable to further improve this.
- this ceramic core has a problem in bending strength in a temperature range around 1500 ° C. at the time of casting as with the ceramic core proposed in Patent Document 1, and further improves this. It is desirable. Furthermore, it is desirable for this ceramic core to further improve dimensional stability during casting.
- the present invention has sufficient bending strength for handling at room temperature after firing, has bending strength and dimensional stability that are difficult to deform and break even when exposed to high temperatures during casting, Furthermore, the ceramic core excellent in the elution property with respect to alkaline aqueous solution is provided. And the manufacturing method is provided.
- the present inventor has studied in detail the bending strength and dimensional stability of the ceramic core at high temperatures, and further the elution of the ceramic core in an aqueous alkaline solution.
- the inventors have found that it is effective to contain an appropriate amount of alumina, and that the optimization of the content of potassium and / or sodium is extremely effective for improving the high-temperature bending strength, and have reached the present invention.
- the ceramic core according to the present invention comprises 0.1 to 15.0% by mass of alumina and at least one of potassium or sodium in an amount of 0.005 to 0.1% by mass, with the balance being silica and inevitable impurities.
- a mixture containing 90% by mass or more of amorphous silica is baked.
- the total amount of the silica is preferably amorphous silica. Further, it is desirable to contain 0.5 to 35.0% by mass of zircon. A ceramic core that is fired to a relative density of 60 to 80% is desirable. Further, it is desirable that the ceramic core is formed such that the bending strength at room temperature (25 ° C.) is 10 MPa or more and the bending strength at 1550 ° C. is 5 MPa or more.
- the total amount of the silica is amorphous silica containing 5 to 30% by mass of coarse particles having a particle size of at least 50 ⁇ m or more, and having an average particle size of 5 to 35 ⁇ m, and 0.1 to 15.0% by mass of alumina. And a mixture comprising 0.5 to 35.0% by mass of zircon is fired to a relative density of 60 to 80%, a bending strength at 25 ° C. of 10 MPa or more, and a bending strength at 1550 ° C. of 5 MPa or more.
- a ceramic core is preferable.
- the above-described ceramic core according to the present invention comprises 0.1 to 15.0% by mass of alumina, 0.005 to 0.1% by mass of at least one of potassium or sodium, the balance being silica and unavoidable
- a mixture containing 90% by mass or more of amorphous silica in 100% by mass of silica is 55 to 75% by volume, and further 25 to 45% by volume of a binder is mixed to form a mixture. Then, the mixture is injected into a mold to form a molded body, and the obtained molded body is degreased at 500 to 600 ° C. and 1 to 10 hours, and then fired at 1200 to 1400 ° C. and 1 to 10 hours. Can be manufactured.
- the total amount of silica contained in the mixture is amorphous silica. Further, it is desirable that 0.5 to 35.0% by mass of zircon is further included in the mixture. Further, it is desirable to bake the relative density to 60 to 80%. Further, it is desirable to bake the bending strength at room temperature (25 ° C.) to 10 MPa or more and the bending strength at 1550 ° C. to 5 MPa or more.
- the total amount of the silica is amorphous silica containing 5 to 30% by mass of coarse particles having a particle size of at least 50 ⁇ m or more, and having an average particle size of 5 to 35 ⁇ m, and 0.1 to 15.0% by mass of alumina. And a mixture containing 0.5 to 35.0% by mass of zircon is made 55 to 75% by volume, and further 25 to 45% by volume of a binder is mixed to make a mixture.
- a production method is preferred in which the resulting molded product is degreased at 500 to 600 ° C. for 1 to 10 hours and then fired at 1200 to 1400 ° C. for 1 to 10 hours. Desirable injection pressure of the mixture into the mold is 1 to 200 MPa. More preferably, the injection pressure of the mixture into the mold is 1 to 80 MPa.
- the present invention after firing, it has a sufficient bending strength for handling at room temperature, and a high temperature range during casting, for example, a temperature of 1400 ° C. to 1600 ° C. of a molten metal made of a heat-resistant alloy such as Fe group or Ni group.
- a temperature of 1400 ° C. to 1600 ° C. of a molten metal made of a heat-resistant alloy such as Fe group or Ni group can provide a ceramic core having excellent bending strength and dimensional stability, and further having excellent dissolution properties with respect to an aqueous alkali solution. Therefore, the present invention can contribute to the development of the industry because it can produce an excellent casting blade when applied to the production of a casting having a hollow structure, for example, the production of a blade for a gas turbine made of a Ni-base heat-resistant alloy or the like.
- An important feature of the present invention is that in a mixture for obtaining a ceramic core mainly composed of a silica component, an appropriate amount of alumina is added to the main silica, and at the same time, potassium, sodium, or both are added.
- the purpose is to optimize the content. Specifically, at least one of potassium and sodium is added to the silica containing 90% by mass or more of amorphous silica in 100% by mass and 0.1 to 15.0% by mass of alumina. It is to contain 0.005 to 0.1% by mass.
- the ceramic core has a high bending strength because a large amount of amorphous silica exists at room temperature after firing, and a large amount of crystalline silica exists at a high temperature during casting, and Since the formation of a liquid phase is suppressed by optimizing the content of potassium and sodium, the composition has high bending strength.
- the ceramic core according to the present invention includes, as a basic composition, silica containing 90% by mass or more of amorphous silica in 100% by mass and 0.1 to 15.0% by mass of alumina.
- silica and alumina as the basic composition, not only becomes a ceramic core having excellent heat resistance, but also a Ni-based heat-resistant alloy-based molten metal that is often applied to blades for gas turbines, etc. It becomes a ceramic core excellent in dimensional stability during casting.
- the silica includes 90% by mass or more of amorphous silica in 100% by mass as described above.
- silica containing 90% by mass or more of amorphous silica it is possible to improve the sinterability when the molded body is sintered to form a ceramic core.
- the ceramic core cooled to room temperature after firing can increase the bending strength at room temperature by adding a large amount of amorphous silica among the silica components, it is desirable that the ceramic core contains a large amount of amorphous silica.
- the bending strength at room temperature (25 ° C) of the ceramic core can be obtained by adding an appropriate amount of non-crystalline silica to the amount of other alumina added separately, potassium, sodium, or both. Of 10 MPa or more.
- alumina is contained in an amount of 0.1 to 15.0% by mass as described above. If the alumina content is controlled within this range, the fire resistance of the alumina can contribute to the improvement of the bending strength at the casting of the ceramic core, that is, in the high temperature range, and the dimensional stability can be enhanced.
- the ceramic core may deviate from the target size by shrinking when exposed to a high temperature during casting. For this reason, the present inventor evaluated the dimensional stability of the ceramic core by the shrinkage rate at the casting temperature of the ceramic core. Ideally, the shrinkage rate is 0%. It was confirmed that 2% which is close to the elongation of is desirable.
- an alumina is about 7 times larger than a zircon as a reduction effect of the shrinkage rate per content. Since the ceramic core containing a large amount of alumina or zircon is difficult to elute into the alkaline aqueous solution, it is essential in the present invention to contain alumina, which has a higher shrinkage reduction effect in the high temperature range.
- the alumina added to the silica is 0.1% by mass or more, the strength related to brittleness and the dimensional stability during casting can be improved, and when the alumina is 15.0% by mass or less, the ceramic
- the alumina was 0.5% by mass
- the shrinkage during casting was 1.0%
- 1.5% by mass was 0.4%.
- it is desirable that the alumina is 0.5% by mass or more and the shrinkage ratio of the ceramic core is 1.0% or less. More desirably, the shrinkage rate of the ceramic core is 0.5% or less by making alumina 1.0% by mass or more.
- the inclusion of 0.005 to 0.1% by mass of at least one of potassium or sodium in the above-described silica and alumina containing material improves the mechanical properties of the ceramic core in the high temperature range. Is especially important for.
- the obtained ceramic core can have a bending strength of 5 MPa or more even at a temperature of 1300 ° C. Further, the bending strength of 5 MPa or more can be maintained even when the ceramic core is in a high temperature range of 1400 ° C. to 1600 ° C., which is a casting temperature of a Ni-base heat-resistant alloy or the like.
- potassium and sodium are not contained in excess of an appropriate amount from the viewpoint of improving the bending strength of the ceramic core at a high temperature.
- the composite oxide promotes densification of the sintered body, it improves the bending strength of the ceramic core at room temperature. Therefore, in the present invention, adding at least 0.005% by mass or more of potassium or sodium is effective because it produces the composite oxide and has an effect as a sintering aid.
- a sintered body that is too dense deteriorates elution, it is desirable that potassium and sodium be suppressed to 0.1% by mass or less.
- the ceramic core of the present invention can contain only potassium, only sodium, or both at the same time, that is, at least one of potassium or sodium is 0.005 to 0.1 mass. % Is important.
- the ceramic core of the present invention has 0.1 to 15.0% by mass of alumina, 0.005 to 0.1% by mass of at least one of potassium or sodium, and the balance is silica.
- a mixture containing 90% by mass or more of amorphous silica in 100% by mass of the silica is calcined.
- the relative density of the ceramic core is preferably adjusted to 60 to 80% in order to have a bending strength at room temperature that is easy to handle and to have a dissolution property with respect to an alkaline aqueous solution.
- the relative density of the ceramic core is higher if it is limited to improvement of mechanical strength, and is lower if it is limited to improvement of elution, and can be adjusted as necessary. As described above, improvement of the mechanical strength and elution of the ceramic core are conflicting demands.
- the relative density of the ceramic core is 75 to 80%, the bending strength at room temperature is further increased.
- the relative density is 60 to 65%, the dissolution property in an alkaline aqueous solution is further increased.
- the relative density is 65% to 75%, the bending strength is increased. It is easy to satisfy both elution properties.
- the relative density of the ceramic core can be adjusted by the amount of binder contained in the molded body, the firing temperature of the molded body, the holding time thereof, and the like.
- the relative density as used in the present invention is synonymous with the relative density defined in JIS-Z2500, and the actual density obtained by dividing the actual mass of the ceramic core by the volume obtained from its dimensions, and the firing of the ceramic core. It is assumed that silica (SiO 2 ) and alumina (Al 2 O 3 ) exist independently in the knot, and the theoretical density obtained from the composition of the raw materials used using these theoretical densities. In other words, the value obtained by dividing the actual density by the theoretical density is expressed as a percentage. Further, when zircon (ZrSiO 4 ) is further included, it is assumed that this also exists independently. In determining the theoretical density, potassium and sodium, which have a lower content than others, are not considered because the influence on the relative density is assumed to be negligible.
- the ceramic core of the present invention comprises 0.1 to 15.0% by mass of alumina, 0.005 to 0.1% by mass of at least one of potassium or sodium, and the balance is silica and inevitable.
- a mixture containing 90% by mass or more of amorphous silica in 100% by mass of silica is calcined.
- the ceramic core of the present invention is basically composed of a mixture of at least one of silica, alumina, potassium or sodium. With respect to this configuration, 0.5 to 35.0% by mass of zircon, which is not as high as alumina as described above but has an effect of reducing the shrinkage rate in the high temperature range of the ceramic core, may be contained.
- zircon coexists with alumina in an appropriate balance, the effect of reducing the shrinkage ratio of the ceramic core in a high temperature range caused by both elements is synergistically improved. Therefore, preferably when the ceramic core contains zircon in an amount of 0.5% by mass or more, the shrinkage rate in the high temperature region of the ceramic core is easily reduced to 1% or less, and further to 0.5% or less.
- the ceramic core it is preferable to contain zircon in the ceramic core according to the present invention.
- the zircon contained in the ceramic core is 35.0% by mass. The following is desirable.
- alumina whose insolubility is inferior to zircon is suppressed to 5.0 mass% or less, and It is preferable to contain 0.0 mass% or more.
- powdered silica powdered alumina, powdered zircon and the like can be used.
- powdered silica powder such as fused silica that is amorphous silica, powder such as cristobalite that is crystalline silica, silica powder in which an amorphous silica component and a crystalline silica component coexist can be used.
- potassium or sodium can be used as a single metal, but is preferably used as a hydroxide such as potassium hydroxide or sodium hydroxide.
- hydroxides can be adjusted in consideration of their contents when they are contained in the powder material described above.
- a composite oxide composed of potassium and / or sodium and silica and / or alumina may also be used.
- the powdered silica preferably has an average particle size of 5 to 35 ⁇ m.
- the thickness is less than 5 ⁇ m, there is a concern about deterioration of dimensional stability during casting due to excessive crystallization and a decrease in bending strength at room temperature. Further, if it exceeds 35 ⁇ m, there is a concern that the bending strength during casting is lowered.
- amorphous silica such as fused silica containing 5-30% by mass of coarse particles having a particle size of at least 50 ⁇ m or more and an average particle size of 5-35 ⁇ m is used. It is preferable to use it.
- the ceramic core is less likely to have an excessive relative density and is likely to have good elution properties with respect to the alkaline aqueous solution.
- the ceramic core tends to have a relative density that tends to decrease the bending strength at room temperature.
- the average particle size of the powdery alumina is preferably 1 to 5 ⁇ m. If the average particle size of the powdered alumina is 1 ⁇ m or more, it contributes to improvement of dimensional stability at the time of casting, but if it exceeds 5 ⁇ m, the relative density of the ceramic core tends to be too small, and the bending strength at room temperature is increased. It tends to decline.
- the average particle size is preferably 5 to 15 ⁇ m. If the average particle size of the powdered zircon is 5 ⁇ m or more, it contributes to improvement of dimensional stability at the time of casting. However, if it exceeds 15 ⁇ m, the relative density of the ceramic core tends to be too small, and the bending strength at room temperature is increased. It tends to decline.
- the average particle diameter referred to in the present invention is a value obtained using a laser diffraction / scattering particle size distribution measuring device (particle size distribution measuring device Microtrac MT3000 manufactured by Nikkiso Co., Ltd.). Specifically, using the light scattering phenomenon obtained by applying laser light to a powdered sample suspended in a dispersion medium, the intensity distribution of scattered light is measured and collected by multiple optical detectors. The obtained scattered light information is A / D converted and then obtained by computer analysis and calculation processing. The particle size distribution is based on volume, and the horizontal axis is the particle size and the vertical axis is the frequency or cumulative output, and the cumulative particle size at 50% is the average particle size. Moreover, the particle size as used in the field of this invention means the diameter of the powder-form individual particle
- the ceramic core according to the present invention can be manufactured by a manufacturing method including a mixture manufacturing process (1), an injection molded body manufacturing process (2), and a degreasing firing process (3). Specifically, in the mixture production step (1), 0.1 to 15.0% by mass of alumina (Al 2 O 3 ) and at least one of potassium (K) or sodium (Na) is added in an amount of 0.001.
- alumina Al 2 O 3
- K potassium
- Na sodium
- the balance being silica (SiO 2 ), and a mixture containing 90% by mass or more of amorphous silica in 100% by mass of silica is 55 to 75% by volume, Further, the main process is to mix 25 to 45% by volume of a binder into a mixture.
- the injection molded body manufacturing step (2) is a step mainly including injecting the mixture obtained in the mixture manufacturing step (1) into a mold to form a molded body, and a degreasing firing step.
- (3) is a step of degreasing the molded body obtained in the injection molded body production step (2) at 500 to 600 ° C. and 1 to 10 hours, and then removing the degreased molded body from 1200 to 1400 ° C. and 1 to 10 hours. It is a process mainly consisting of firing.
- the whole quantity of a silica can be made into an amorphous silica.
- 0.5 to 35.0% by mass of zircon (ZrSiO 4 ) may be further included in the mixture.
- a mixture suitable for setting the relative density of the ceramic core in an appropriate range is such that the mixture is 55 to 75% by volume, and further 25 to 45% by volume of the binder. Is obtained by mixing. Considering the fluidity for injection molding, a mixture composed of a combination of 60 to 70% by volume of the mixture and 30 to 40% by volume of a binder is more preferable. Such a mixture is uniform by, for example, using a mixing stirrer, melting a binder in a container, and then charging various materials related to silica, alumina, potassium and / or sodium, and rotating a stirring blade. It can be obtained by means of stirring until it becomes, or by means of ball mill mixing, kneading or the like.
- raw materials such as the above-mentioned powder can be used for silica, alumina and zircon, and the above-mentioned hydroxides can be used for potassium and sodium.
- the binder for example, one or more of paraffin, styrene thermoplastic elastomer, polyethylene glycol, cetyl alcohol, polypropylene, polystyrene, polybutyl methacrylate, and ethylene vinyl acetate copolymer resin are used. Is good. Furthermore, it is also desirable to mix cellulose fibers, dibutyl phthalate, and the like that contribute to improving the plasticity of the molded body.
- the injection pressure of the softened mixture is preferably 1 to 200 MPa.
- the injection pressure is 1 MPa or more, a necessary amount of the mixture can be filled in the mold, so that a phenomenon called non-rotation hardly occurs.
- the injection pressure exceeds 200 MPa, insertion of the injected mixture into the split part of the mold is likely to occur, so that it becomes difficult to form a molded body without burrs. If the injection pressure is 1 to 150 MPa, it is considered that a generally available injection molding machine can be used without any special modification.
- the degreasing temperature when the molded body is degreased is preferably 500 to 600 ° C.
- degreasing temperature 500 ° C. or higher
- degreasing that is, removal of the binder properly proceeds, and the binder can be sufficiently removed from the molded body.
- defects such as a swelling and a crack in a molded object, can be suppressed as the degreasing temperature is 600 degrees C or less.
- it is preferable to set the degreasing time to 1 to 10 hours. When the degreasing time is 1 hour or more, the removal of the binder is sufficiently advanced, and the degreasing process is performed to sinter the molded body. There is no need.
- the temperature increase rate when degreasing the molded body is from 0.1 ° C. to 100 ° C./h in the temperature range of room temperature to 300 ° C. in consideration of the above-mentioned binder softening and melting temperature range. Is preferably 1 to 10 ° C./h. In the temperature range of more than 300 ° C. and 600 ° C., decomposition proceeds due to the combustion of the binder.
- the firing conditions for forming the degreased molded body into a sintered body are such that the relative density of the ceramic core is suitable, the bending strength in the room temperature region and the high temperature region exceeding 1500 ° C. It is important to improve both the bending strength at the same time.
- a ceramic core having a large amount of amorphous silica in the sintered structure has a high bending strength in a room temperature environment after firing.
- a ceramic core having a large amount of crystalline silica in the sintered structure has a low bending strength under a room temperature environment, but can have a high bending strength under a high temperature environment.
- increasing the bending strength at room temperature and increasing the bending strength at high temperature are in a reciprocal relationship from the viewpoint of the sintered structure. It is important to control the structure and the firing temperature and its holding time.
- the present inventor has promoted the crystallization of amorphous silica in a high temperature environment during casting so that a sintered structure having a large amount of amorphous silica exists in a room temperature environment after firing.
- the firing conditions were examined so as to obtain a structure having a large amount of crystalline silica.
- the firing temperature of the molded body after degreasing is preferably 1200 to 1400 ° C. at which it is considered that the amorphous silica component starts to crystallize. 1 to 10 h is preferable because the core is easily fired to a suitable relative density of 60 to 80%. If the firing temperature is less than 1200 ° C, the structure is likely to be insufficiently sintered, and if it exceeds 1400 ° C, the generation of crystalline silica components such as cristobalite in the sintered structure is promoted, and the ceramic core at room temperature is promoted. Bending strength may decrease. In order to further homogenize the sintered structure of the ceramic core and increase the bending strength, the firing temperature is preferably 1250 ° C. to 1350 ° C.
- the firing time is less than 1 h, sintering of the entire structure of the ceramic core tends to be insufficient, and if it exceeds 10 h, crystallization is promoted and crystal grains grow. Bending strength may decrease.
- the heating rate when firing the molded article is preferably 1 to 300 ° C./h, and if it is 1 ° C./h or more, the productivity is not hindered regardless of the heating time, and 300 ° C. / If it is less than or equal to h, defects such as cracks due to rapid progress of sintering are unlikely to occur.
- the firing atmosphere when firing the molded body is preferably a non-reducing atmosphere that can suppress the decomposition of the constituent oxide, and in the case of a non-reducing atmosphere, nitrogen gas or argon gas in addition to air An inert gas such as can be used.
- the powdered cristobalite used was adjusted to an average particle size of 19.0 ⁇ m.
- As the alumina powdery alumina having an average particle diameter of 2.8 ⁇ m was used.
- potassium or sodium the content in the powdery material described above was taken into account, and the deficiency was supplemented with potassium hydroxide or sodium hydroxide.
- what adjusted the average particle diameter of powdery zircon to 9.5 micrometers was used.
- Each mixture having the composition shown in Table 1 and Table 2 using the above-mentioned materials and a binder made of paraffin and a styrenic thermoplastic elastomer are prepared, and 32% by volume of the binder is mixed with 68% by volume of the mixture.
- the mixture was sufficiently mixed using a stirrer to prepare each mixture.
- each mixture obtained in the above-mentioned mixture production process is injected by applying a pressure of 7 MPa into a mold including a cavity having a volume of 220 cm 3 corresponding to the shape of the ceramic core to be produced, A molded body of was obtained.
- the same handling was applied to both the example and the comparative example.
- each molded body obtained in the injection molded body manufacturing process was held at a temperature of 580 ° C. for 5 hours, thereby substantially degreasing the molded body.
- the temperature rising rate from room temperature to 300 ° C. was 3 ° C./h, and the temperature rising rate from reaching 300 ° C. until reaching 580 ° C. was controlled to 50 ° C./h.
- the molded body was completely degreased in the process of raising the temperature to the firing temperature, and further maintained at the firing temperature shown in Tables 1 and 2 for 2 hours.
- ceramics and the like were fired to obtain ceramic cores shown as Examples 1 to 13 and Comparative Examples 1 to 4.
- the same handling was applied to both the example and the comparative example.
- Each ceramic core was formed so as to have an external shape shown in FIG. 1 corresponding to a hollow rotor blade for a gas turbine.
- the bending strength of the ceramic core was evaluated by producing a test piece of the ceramic core, performing a bending test in accordance with JIS-R1601 for the test in the room temperature range, and in accordance with JIS-R1604 for the test in the high temperature range.
- the test piece shape was set to 3 ⁇ 4 ⁇ 36 mm, the distance between fulcrums: 30 mm, and the test speed was set to a crosshead speed: 0.5 mm / min, at room temperature (25 ° C.) and 1550. It carried out about ° C.
- the dimensional stability of the ceramic core was evaluated by measuring the dimensional value of a predetermined portion of the ceramic core before and after the heat treatment, and evaluating the change rate of the dimension in terms of percentage of shrinkage during casting.
- the heat treatment applied to the ceramic core was a treatment method of holding at a temperature of 1550 ° C. for 2 hours.
- the evaluation of the elution property of the ceramic core with respect to the alkaline aqueous solution is to actually manufacture a mold using the ceramic core, inject a molten metal into the mold and cool it down, and obtain a mold that contains the ceramic core. , Using the template. First, the mold after cooling was immersed in a 30% potassium hydroxide aqueous solution at 160 ° C. for a fixed time (20 h) at 0.3 MPa, and the presence or absence of a ceramic core remaining in the mold after the immersion was examined. And this immersion test was implemented 4 times and evaluated by the possibility of complete dissolution of a ceramic core.
- the ceramic cores (Examples 1 to 7) according to the present invention shown in Table 1 have an alumina content of 0.1 to 15.0 mass% and at least one of potassium or sodium in an amount of 0.005 to 0.1 mass. %, And the balance is composed of silica containing 90% by mass or more of amorphous silica in 100% by mass of silica, and unavoidable impurities, and the bending strength at room temperature (25 ° C.) is 10 MPa or more. The bending strength at high temperature (1550 ° C.) was 5 MPa or more.
- the ceramic core according to the present invention having the composition shown in Table 1 has sufficient bending strength for handling at room temperature after firing, and has high bending strength that can withstand long-time casting. It was confirmed that Further, the ceramic core according to the present invention was not damaged during handling, injection molding, and casting in the evaluation process described above. In addition, all of the ceramic cores according to the present invention had good dissolution properties with respect to the alkaline aqueous solution after casting. In addition, the ceramic core according to the present invention had a casting shrinkage rate of 1.0% or less, and could have dimensional stability in a high temperature range.
- Comparative Example 1 in which the total amount of potassium and sodium was large at 0.870% by mass, the bending strength at high temperature (1550 ° C.) was as low as 1 MPa, and bending strength that could withstand long-time casting could be obtained. There wasn't. Further, Comparative Example 1 had a large shrinkage during casting of 5.5% and could not have dimensional stability in a high temperature range. Further, Comparative Example 2 containing no alumina had a bending strength as low as 3 MPa at a high temperature (1550 ° C.), and could not obtain a bending strength that could withstand long-time casting. Further, Comparative Example 2 had a large shrinkage during casting of 5.0%, and could not have dimensional stability in a high temperature range.
- Comparative Example 3 in which the amorphous silica content in the total silica was small at 78.0% by mass, the bending strength at a high temperature (1550 ° C.) is as low as 3 MPa, and the bending strength that can withstand long-time casting is obtained. Cann't get.
- the ceramic cores according to the present invention shown in Table 2 have an alumina content of 0.1 to 15.0 mass% and at least one of potassium or sodium in an amount of 0.005 to 0.1 mass. %, The balance is 5 to 30% by mass of coarse particles having a particle size of 50 ⁇ m or more, the average particle size is adjusted to 5 to 35 ⁇ m, and unavoidable impurities, and room temperature ( The bending strength at 25 ° C. was 10 MPa or more, and the bending strength at high temperature (1550 ° C.) was 5 MPa or more.
- the ceramic core according to the present invention having the composition shown in Table 2 has sufficient bending strength for handling at room temperature after firing, and high bending strength that can withstand long-time casting. It was confirmed that Further, the ceramic core according to the present invention was not damaged during handling, injection molding, and casting in the evaluation process described above. In addition, all of the ceramic cores according to the present invention had good dissolution properties with respect to the alkaline aqueous solution after casting. In addition, the ceramic core according to the present invention had a casting shrinkage rate of 1.0% or less, and could have dimensional stability in a high temperature range.
- the bending strength at high temperature (1550 ° C.) is as low as 3 MPa in Comparative Example 4 where the powder (coarse particles) with a particle size of 50 to 100 ⁇ m was large at 35% by mass. The bending strength that can withstand long-time casting could not be obtained.
Abstract
Description
また、0.5~35.0質量%のジルコンを含むことが望ましい。
また、相対密度が60~80%に焼成されてなるセラミック中子が望ましい。
また、室温(25℃)における曲げ強度が10MPa以上、1550℃における曲げ強度が5MPa以上に形成されてなる、セラミック中子であることが望ましい。
また、前記混合物にさらに0.5~35.0質量%のジルコンを含ませることが望ましい。
また、相対密度を60~80%に焼成することが望ましい。
また、室温(25℃)における曲げ強度を10MPa以上、1550℃における曲げ強度を5MPa以上に焼成することが望ましい。
また、望ましい前記混合体の金型内への射出圧力は1~200MPaである。
より望ましい前記混合体の金型内への射出圧力は1~80MPaである。
本発明に係るセラミック中子は、基本的な組成として、100質量%中に90質量%以上の非結晶性シリカを含むシリカと、0.1~15.0質量%のアルミナとを含む。基本的な組成を上述のシリカとアルミナとを含むものとすることで、優れた耐熱性を有するセラミック中子となるだけでなく、ガスタービン用ブレードなどに多く適用されるNi基耐熱合金系の溶融金属と反応し難く、鋳造時の寸法安定性に優れたセラミック中子となる。
本発明に係るセラミック中子の原料としては、粉末状シリカや粉末状アルミナ、さらに粉末状ジルコンなどが使用できる。なお、粉末状シリカとしては、非結晶性シリカである溶融シリカなどの粉末、結晶性シリカであるクリストバライトなどの粉末、非結晶性シリカ分と結晶性シリカ分が共存するシリカ粉末などが使用できる。また、カリウムやナトリウムとしては、金属単体での使用も可能と考えられるが、水酸化カリウムや水酸化ナトリウムなどの水酸化物での使用が好適である。水酸化物は、安全性や取扱い性が良いことに加え、これらが上述した粉末素材に含まれる場合には、その含有量を考慮して調整できる。また、カリウムおよび/またはナトリウムとシリカおよび/またはアルミナからなる複合酸化物を使用してもよい。
例えば、粉末状シリカは、その平均粒径を小さくすると、加熱による結晶化により結晶性シリカ分が生成されやすくなり、セラミック中子の高温での曲げ強度が高まる。一方、セラミック中子に非結晶性シリカ分を多く存在させて室温での曲げ強度を高めるには、平均粒径を大きくする方がよい。よって、このような相反関係を考慮し、粉末状シリカは、平均粒径5~35μmが好ましい。なお、5μm未満では、過剰な結晶化による鋳造時の寸法安定性の劣化や、室温での曲げ強度の低下が懸念される。また、35μmを超えると鋳造時の曲げ強度の低下が懸念される。
また、粉末状ジルコンを使用する場合、その平均粒径は5~15μmが好ましい。粉末状ジルコンの平均粒径は、5μm以上であると鋳造時の寸法安定性の向上に寄与するものの、15μmを超えるとセラミック中子の相対密度が過小になりやすくなって室温での曲げ強度が低下しやすい。
また、本発明でいう粒度は、上述の方法で測定された粉末状の個々の粒子の径を意味し、粒径と特段の区別もなく使用される。
本発明に係るセラミック中子は、混合体製造工程(1)、射出成形体製造工程(2)、脱脂焼成工程(3)を含む製造方法によって製造が可能である。具体的には、混合体製造工程(1)は、0.1~15.0質量%のアルミナ(Al2O3)と、カリウム(K)またはナトリウム(Na)のうち少なくとも1種を0.005~0.1質量%と、残部はシリカ(SiO2)であって、該シリカ100質量%中には90質量%以上の非結晶性シリカを含んでなる混合物を55~75体積%とし、さらに25~45体積%のバインダを混合して混合体とすることを主とする工程である。
また、前記バインダとしては、例えば、パラフィン、スチレン系熱可塑性エラストマー、ポリエチレングリコール、セチルアルコール、ポリプロピレン、ポリスチレン、ポリブチルメタクリレート、エチレン酢酸ビニル共重合体樹脂のうち、いずれか1種以上を使用するのがよい。さらに、成形体の可塑性の向上に寄与するセルロース繊維、ジブチルフタレートなどを混合することも望ましい。
焼結組織中に非結晶性シリカ分が多く存在するセラミック中子は、焼成後の室温環境下での曲げ強度は高くなる。一方、焼結組織中に結晶性シリカ分が多く存在するセラミック中子は、室温環境下での曲げ強度は低くなるものの、高温環境下では高い曲げ強度を有することができる。このように、セラミック中子について、室温での曲げ強度を高めることと、高温での曲げ強度を高めることとは、焼結組織の観点からは相反的な関係にあるため、使用するシリカ分の組織や、焼成温度とその保持時間の制御が重要になる。
(混合体製造工程)
混合体製造工程では、実施例および比較例ともに同じ素材を使用した。具体的には、シリカとしては、非結晶性シリカ分として粉末状溶融シリカを、結晶性シリカ分として粉末状クリストバライトを使用した。表1に示す粉末状溶融シリカは、粒度50μm以上の粉末(粗粒)を意図的に加えずに平均粒径を19.0μmに調整したものを使用した。また、粉末状クリストバライトは、平均粒径19.0μmに調整したものを使用した。アルミナとしては、粉末状アルミナの平均粒径2.8μmに調整したものを使用した。カリウムまたはナトリウムとしては、上述した粉末状素材における含有量を考慮した上で、不足分を水酸化カリウムまたは水酸化ナトリウムで補填するようにした。また、ジルコンを加える場合は、粉末状ジルコンの平均粒径9.5μmに調整したものを使用した。
次いで、前記混合体製造工程で得られたそれぞれの混合体を、製造しようとするセラミック中子の形状に対応する体積220cm3のキャビティを含む金型内へ7MPaの圧力を加えて射出し、それぞれの成形体を得た。この工程では、実施例および比較例ともに同様の取扱いとした。
次いで、前記射出成形体製造工程で得られたそれぞれの成形体を580℃の温度で5h保持し、これにより成形体から概ね脱脂した。このとき、室温~300℃までの昇温速度を3℃/hとし、300℃に達してから580℃に達するまでの昇温速度を50℃/hに制御した。そして、焼成温度まで温度を上げる過程で成形体から完全に脱脂し、さらに表1および表2に示す焼成温度で2h保持した。これによりセラミックスなどを焼成し、実施例1~13および比較例1~4として示すセラミック中子を得た。この工程でも、実施例および比較例ともに同様の取扱いとした。なお、いずれのセラミック中子も、ガスタービン用の中空動翼に対応する図1に示す外観形状を有するように形成した。
セラミック中子の曲げ強度は、セラミック中子の試験片を製造し、室温域における試験はJIS-R1601に準じ、高温域における試験はJIS-R1604に準じて曲げ試験を行って評価した。曲げ試験では、試験片については、試験片形状:3×4×36mm、支点間距離:30mm、試験速度については、クロスヘッドスピード:0.5mm/分に設定し、室温(25℃)および1550℃について行った。
セラミック中子の寸法安定性は、セラミック中子の所定箇所の寸法値を熱処理の前後で測定し、その寸法の変化率を百分率で表した鋳造時収縮率で評価した。この場合、セラミック中子に対して施す熱処理は、1550℃の温度で2h保持する処理方法にした。
セラミック中子のアルカリ水溶液に対する溶出性の評価は、実際にセラミック中子を用いて鋳型を製造し、該鋳型に金属溶湯を注入して冷却し、セラミック中子を内包したままの鋳型を得て、該鋳型を用いて行った。まず、冷却後の前記鋳型を、0.3MPaとした中で160℃の30%水酸化カリウム水溶液に一定時間(20h)浸漬し、該浸漬後に鋳型内に残るセラミック中子の有無を調べた。そして、この浸漬試験を4回実施し、セラミック中子の完全溶解の可否で評価した。
また、上述した室温域および高温域での曲げ強度、寸法安定性、溶出性の評価過程において、セラミック中子のハンドリング時、射出成型時、鋳造時における破損の有無を、同時に確認した。
Claims (14)
- 0.1~15.0質量%のアルミナと、カリウムまたはナトリウムのうち少なくとも1種を0.005~0.1質量%と、残部はシリカおよび不可避的不純物であって、前記シリカ100質量%中には90質量%以上の非結晶性シリカを含んでなる混合物が焼成されてなることを特徴とするセラミック中子。
- 前記シリカの全量が非結晶性シリカであることを特徴とする請求項1に記載のセラミック中子。
- 0.5~35.0質量%のジルコンを含むことを特徴とする請求項1または2に記載のセラミック中子。
- 相対密度が60~80%に焼成されてなることを特徴とする請求項1乃至3のいずれかに記載のセラミック中子。
- 室温(25℃)における曲げ強度が10MPa以上、1550℃における曲げ強度が5MPa以上に焼成されてなる、ことを特徴とする請求項1乃至4のいずれかに記載のセラミック中子。
- 前記シリカの全量が、少なくとも粒度50μm以上の粗粒を5~30%質量含み、平均粒径が5~35μmの非結晶性シリカであって、0.1~15.0質量%のアルミナと、0.5~35.0質量%のジルコンとを含んでなる混合物が、相対密度が60~80%、25℃における曲げ強度が10MPa以上、1550℃における曲げ強度が5MPa以上に焼成されてなる、ことを特徴とする請求項1乃至5のいずれかに記載のセラミック中子。
- 請求項1乃至6のいずれか1項に記載のセラミック中子の製造方法であって、0.1~15.0質量%のアルミナと、カリウムまたはナトリウムのうち少なくとも1種を0.005~0.1質量%と、残部はシリカおよび不可避的不純物であって、前記シリカ100質量%中には90質量%以上の非結晶性シリカを含んでなる混合物を55~75体積%とし、さらに25~45体積%のバインダを混合して混合体とし、次いで該混合体を金型内へ射出して成形体とし、得られた該成形体を500~600℃かつ1~10hで脱脂した後に1200~1400℃かつ1~10hで焼成することを特徴とするセラミック中子の製造方法。
- 前記混合物に含むシリカの全量を非結晶性シリカとすることを特徴とする請求項7に記載のセラミック中子の製造方法。
- 前記混合物に0.5~35.0質量%のジルコンを含ませることを特徴とする請求項7または8に記載のセラミック中子の製造方法。
- 相対密度を60~80%に焼成することを特徴とする請求項7乃至9のいずれか1項に記載のセラミック中子の製造方法。
- 室温(25℃)における曲げ強度を10MPa以上、1550℃における曲げ強度を5MPa以上に焼成する、ことを特徴とする請求項7乃至10のいずれかに記載のセラミック中子の製造方法。
- 前記シリカの全量が、少なくとも粒度50μm以上の粗粒を5~30%質量含み、平均粒径が5~35μmの非結晶性シリカであって、0.1~15.0質量%のアルミナと、0.5~35.0質量%のジルコンを含んでなる混合物を55~75体積%とし、さらに25~45体積%のバインダを混合して混合体とし、次いで該混合体を金型内へ射出して成形体とし、得られた該成形体を500~600℃かつ1~10hで脱脂した後に1200~1400℃かつ1~10hで焼成する、ことを特徴とする請求項7乃至11のいずれかに記載のセラミック中子の製造方法。
- 前記混合体の金型内への射出圧力は1~200MPaであることを特徴とする請求項7乃至12のいずれかに記載のセラミック中子の製造方法。
- 前記混合体の金型内への射出圧力は1~30MPaであることを特徴とする請求項13に記載のセラミック中子の製造方法。
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US14/236,671 US9539639B2 (en) | 2011-08-03 | 2012-02-28 | Ceramic core and method for producing same |
EP12819690.4A EP2740550B1 (en) | 2011-08-03 | 2012-02-28 | Ceramic core and method for producing same |
JP2013513468A JP5360633B2 (ja) | 2011-08-03 | 2012-02-28 | セラミック中子およびその製造方法 |
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Cited By (6)
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JP2015054327A (ja) * | 2013-09-10 | 2015-03-23 | 日立金属株式会社 | セラミック中子およびその製造方法、そのセラミック中子を用いた鋳物の製造方法および鋳物 |
WO2015122445A1 (ja) * | 2014-02-13 | 2015-08-20 | 日立金属株式会社 | セラミック焼結体の製造方法およびセラミック焼結体 |
JP2015150574A (ja) * | 2014-02-13 | 2015-08-24 | 日立金属株式会社 | セラミック焼結体の製造方法およびセラミック焼結体 |
JP2016074571A (ja) * | 2014-10-08 | 2016-05-12 | 株式会社ノリタケカンパニーリミテド | 耐火物とその製造方法 |
CN113666763A (zh) * | 2021-08-23 | 2021-11-19 | 深圳市安芯精密组件有限公司 | 雾化芯结构件及其制备方法 |
CN116253575A (zh) * | 2023-03-21 | 2023-06-13 | 东北大学 | 一种镁铬砂镁基陶瓷型芯及其制备方法 |
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CN104086161B (zh) * | 2014-04-29 | 2016-06-01 | 中国科学院金属研究所 | 一种可调节热膨胀系数的硅基陶瓷型芯的制备方法 |
FR3057187B1 (fr) * | 2016-10-12 | 2018-10-19 | Safran Aircraft Engines | Procede de determination du retrait d'un noyau de fonderie lors d'un traitement thermique du noyau |
RU2691435C1 (ru) * | 2018-07-23 | 2019-06-13 | федеральное государственное бюджетное образовательное учреждение высшего образования "Уфимский государственный авиационный технический университет" | Смесь для изготовления литейных керамических стержней полых лопаток из жаропрочных сплавов литьем по выплавляемым моделям |
CN113354422A (zh) * | 2020-03-04 | 2021-09-07 | 中国科学院金属研究所 | 一种用于单晶高温合金叶片的陶瓷型芯及其制备方法 |
KR102411137B1 (ko) * | 2020-12-11 | 2022-06-20 | 한국로스트왁스 주식회사 | 강도 및 리칭성이 우수한 세라믹 코어 및 이의 제조 방법 |
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US9839957B2 (en) | 2013-09-10 | 2017-12-12 | Hitachi Metals, Ltd. | Ceramic core, manufacturing method for the same, manufacturing method for casting using the ceramic core, and casting manufactured by the method |
WO2015122445A1 (ja) * | 2014-02-13 | 2015-08-20 | 日立金属株式会社 | セラミック焼結体の製造方法およびセラミック焼結体 |
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CN113666763A (zh) * | 2021-08-23 | 2021-11-19 | 深圳市安芯精密组件有限公司 | 雾化芯结构件及其制备方法 |
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CN116253575A (zh) * | 2023-03-21 | 2023-06-13 | 东北大学 | 一种镁铬砂镁基陶瓷型芯及其制备方法 |
Also Published As
Publication number | Publication date |
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EP2740550A4 (en) | 2015-05-27 |
JPWO2013018393A1 (ja) | 2015-03-05 |
EP2740550A1 (en) | 2014-06-11 |
EP2740550B1 (en) | 2016-07-20 |
JP5360633B2 (ja) | 2013-12-04 |
US9539639B2 (en) | 2017-01-10 |
US20150321247A1 (en) | 2015-11-12 |
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