JP4822534B2 - Manufacturing method of ceramics - Google Patents

Description

  The present invention relates to a method for producing a carbon-containing silicon carbide ceramic that is a composite ceramic of silicon carbide and carbon.

  Ceramics are excellent in heat resistance, strength, hardness, wear resistance, corrosion resistance, and the like as compared with metals, and are lightweight, and in recent years, they have been developed and put into practical use as high-temperature structural materials. For example, silicon carbide, one of which has many advantages such as low strength deterioration at high temperatures, excellent corrosion resistance and wear resistance, and high thermal conductivity. Therefore, automotive engine parts, mechanical seals, bearings, Application to parts that require corrosion resistance, wear resistance, and high-temperature strength such as mold materials and precision sliding members such as magnetic heads and sliders has been studied.

  On the other hand, a metal, glass, plastic, or the like has been formed by a method in which a heated raw material is sandwiched between molds and pressed into a predetermined shape. Since the mold used for such molding is repeated several tens of thousands of times at a high temperature, materials having excellent heat resistance and mechanical strength such as cemented carbide, silicon carbide, and silicon nitride have been used.

  However, although commonly used cemented carbide has the advantage of being easier to machine than ceramics, it can cause chemical reactions by touching high temperature raw materials that are heated and melted, and oxygen and water vapor mixed in the molding atmosphere. As a result, problems such as oxidation of the main component tungsten carbide occur.

  Further, since the surface of silicon carbide or silicon nitride is oxidized to silicon oxide when heated, there is a problem that the raw material is fused to the mold surface depending on the type of the raw material. In order to improve this, a method has been adopted in which the molding atmosphere is replaced with an inert gas such as nitrogen, or a release layer containing carbon such as diamond-like carbon is formed on the surface of ceramics or cemented carbide. , Has become the current mainstream.

  As a method for forming the release layer, a sputtering method, a vacuum deposition method, an ion plating method, a high-frequency plasma CVD method, or the like is employed. However, forming a release layer on a mold is not suitable for mass production because the process becomes complicated. Furthermore, there is also a drawback that the release layer is peeled off after repeating tens of thousands of moldings.

  Therefore, Patent Document 1 discloses a technique of using a composite ceramic of silicon carbide and carbon as a forming die for the purpose of improving the releasability of raw materials without forming a release layer. Moreover, as a manufacturing method, after granulating the raw material mixture after calcining as desired, a block is formed by a CIP method (COLD ISOSTATIC PRESS) or the like, and if necessary, machining is performed from the block to form a molded body of a mold A method of making is disclosed.

JP 2006-188415 A

  However, the ceramic molding method described in Patent Document 1 is one-stage molding (CIP is used in the examples) in which molding is performed in a single process, and the particle size is not controlled by granulation or the like. . Therefore, it has been found that when a mold is actually manufactured by this molding method, mechanical strength is insufficient or pores are generated on the surface of the mold.

  Such surface pores are directly transferred to the object to be molded, which poses a problem for molds of various materials. In addition, the generation of pores on the surface also affects the mechanical strength, wear resistance, slidability, and the like of the ceramic structural material, and thus becomes a problem not only for the mold but also for various ceramic members.

  Therefore, an object of the present invention is to provide a method for producing carbon-containing silicon carbide ceramics that can improve mechanical strength such as durability as a mold and can sufficiently suppress the generation of surface pores.

  When manufacturing carbon-containing silicon carbide ceramics, the present inventors use a granulated product having a specific particle size distribution as a raw material powder, and by molding and firing, it excels in mechanical strength such as durability, The inventors have found that a mold having no pores on the surface can be mass-produced, and completed the present invention.

  That is, the method for producing a carbon-containing silicon carbide ceramic of the present invention comprises a step of granulating a raw material mixture X containing silicon carbide, a carbon raw material and a sintering aid, and molding the granulated product obtained in the step. A method for producing carbon-containing silicon carbide ceramics having a step of firing, wherein D10 in the volume-based particle size distribution of the granulated product is 30 to 60 μm, D50 is 50 to 85 μm, and D90 is 90 to 135 μm. Features. In addition, the various physical-property values in this invention are values specifically measured by the method as described in an Example.

  According to the method for producing a carbon-containing silicon carbide ceramic of the present invention, for example, mechanical strength such as durability as a mold can be improved and generation of pores on the surface can be sufficiently suppressed.

Hereinafter, embodiments of the present invention will be described in detail.
The production method of the present invention relates to a method for producing a carbon-containing silicon carbide ceramic, and is particularly useful as a method for producing a mold comprising a carbon-containing silicon carbide ceramic. The carbon-containing silicon carbide ceramics (hereinafter, also simply referred to as “ceramics”) of the present invention is a silicon carbide-carbon composite ceramic containing silicon carbide and carbon. It has the characteristics of wear resistance and high durability. Here, releasability refers to releasability when used as a mold.

  According to the ceramic of the present invention, the material itself is excellent in releasability, and there is an advantage that the mold can be easily processed and molded. That is, by including carbon in the silicon carbide-based ceramics, it is possible to impart excellent releasability as compared with a mold only made of silicon carbide-based ceramics.

  The molding die refers to a die (mold) used for various moldings and includes a concept used as a part of the die. For example, either a die or a punch of a die composed of a die and a punch may be used as the molding die obtained in the present invention. Or it is good also considering only the vicinity containing the raw material contact surface of a die | dye and / or punch as a shaping | molding die obtained by this invention.

  Examples of molding objects include glass, resin, metal, ceramics, and composites thereof.

  The production method of the present invention comprises a step of granulating a raw material mixture X containing silicon carbide, a carbon raw material and a sintering aid, and a step of forming and firing the granulated product obtained in the step. In the method for producing silicon carbide ceramics, a granulated product having a predetermined particle size distribution is used. In the present invention, a molded product can be obtained by firing the granulated product, but in the present invention, CIP molding and firing are performed from the viewpoint of improving mechanical strength such as durability and sufficiently suppressing the generation of pores on the surface. Is preferred.

[Raw material powder]
The granulated product used in the present invention has D10 of 30 to 60 μm, D50 of 50 to 85 μm, and D90 of 90 to 135 μm in the volume-based particle size distribution. In the present invention, D10 is 35 to 50 μm, D50 is 50 to 80 μm, and D90 is 90 from the viewpoint of improving the durability of the mold and suppressing the generation of pores on the surface of the mold. It is preferable that D10 is 35 to 50 μm, D50 is 55 to 80 μm, D90 is 95 to 130 μm, D10 is 40 to 50 μm, D50 is 65 to 80 μm, and D90 is 105 to 130 μm. More preferably it is.

  The raw material powder for producing the ceramic of the present invention is obtained by granulating a mixture of raw materials containing silicon carbide, a carbon raw material and a sintering aid (hereinafter referred to as “mixture X”). By forming and baking such a granulated product, the ceramic of the present invention is obtained.

  The mixture X can be obtained, for example, by mixing and pulverizing raw materials including silicon carbide, a carbon raw material, and a sintering aid. The mixing or pulverization of the raw materials may be performed dry or wet. Moreover, after mixing raw materials, there are a case where the mixture is calcined and then pulverized (aspect 1), and a case where mixing and pulverization are performed simultaneously (aspect 2). In the present invention, when the particle size distribution of the granulated product is adjusted to the above range, in any embodiment, it is preferable to granulate the mixture X, and it is more preferable to classify after granulation.

  In the case of the aspect 1, since the silicon carbide and carbon in the ceramic obtained after firing become close, the relative density of the ceramic can be improved. Moreover, in the case of the aspect 2, for example, when the average particle diameter of the particles constituting the mixture X is 0.05 to 3 μm, a ceramic having excellent density and strength may be obtained without passing through the calcination step. For this reason, the calcination step is not necessary, and therefore the manufacturing process can be simplified, which is more preferable. That is, in the present invention, it is preferable that the step of preparing the granulated product includes a step of simultaneously mixing and crushing raw materials including silicon carbide, a carbon raw material, and a sintering aid.

  The silicon carbide used in the production method of the present invention may be either α or β crystal type. The purity of silicon carbide is not particularly limited, but is preferably 90% from the viewpoint of imparting good sintered body density, strength, and fracture toughness to ceramics and improving mechanical properties such as Young's modulus. % Or more, more preferably 95% by weight or more. The form of silicon carbide is preferably a powder having an average particle size of 5 μm or less, and more preferably a powder having a size of 0.1 to 3 μm because of good sintering properties.

  The carbon raw material used in the production method of the present invention is an organic substance having a conversion rate to carbon after firing of 50 to 95% by weight, and when used for wet mixing, it is soluble or has good dispersibility in a solvent. If it shows, it will not specifically limit. The conversion rate of the carbon raw material to carbon after firing is preferably 50 to 90% by weight from the viewpoint of improving the relative density of the ceramic.

  From the same viewpoint, the average particle size is preferably 5 to 200 μm. As the carbon raw material, an aromatic hydrocarbon is preferred because of its high conversion rate to carbon after firing. Examples of the aromatic hydrocarbon include furan resin, phenol resin, coal tar pitch, etc. Among them, phenol resin and coal tar pitch are more preferably used. In addition, the conversion rate to carbon after baking of a carbon raw material means the weight% of fixed carbon in the carbon raw material measured based on JISK2425.

The sintering aid used in the production method of the present invention is not particularly limited as long as it is usually selected as a sintering aid in the production of ceramics, and any one may be used. it can. Examples of the sintering aid include boron compounds such as B and B ₄ C, aluminum compounds, and yttria compounds. Specific examples of aluminum compounds and yttria compounds include Al ₂ O ₃ and Y ₂ O. ₃ or the like.

Examples of other components that can be used as raw materials in the production method of the present invention include additives usually used in the production of ceramics, such as TiC, TiN, Si ₃ N ₄ , and AlN.

  From the viewpoint of improving the relative density and bending strength of ceramics, the ratio of silicon carbide to carbon in the ceramics is preferably 6 to 50 parts by weight with respect to 100 parts by weight of silicon carbide, and 10 to 40 parts by weight of carbon. More preferably, it is more preferably 15 to 35 parts by weight of carbon.

  Accordingly, the mixing ratio of silicon carbide, carbon raw material, and sintering aid when mixing the mixture X is calculated so that the obtained ceramic satisfies the above content ratio, and the carbon raw material and silicon carbide are sintered. It is preferable to use it with an auxiliary agent.

  As a usage-amount of a sintering auxiliary agent, Preferably it is 0.1-15 weight part with respect to 100 weight part of silicon carbide, More preferably, it is 0.2-10 weight part, More preferably, it is 0.5-5 weight Parts, even more preferably 1-3 parts by weight. When other components are used, a predetermined amount may be mixed when mixing.

  Further, from the viewpoint of improving the relative density and bending strength of the ceramic, the content of silicon carbide in the ceramic is preferably 54 to 94% by weight, more preferably 60 to 90% by weight, and still more preferably 65 to 85% by weight. is there.

  In aspect 1, the method of mixing the raw materials may be any method such as dry mixing, wet mixing, or hot kneading, but wet mixing is preferable from the viewpoint of dispersibility of the carbon raw material.

  As the solvent used for the wet mixing, either water or an organic solvent may be used, but from the viewpoint of dispersibility of the carbon raw material and oxidation prevention of silicon carbide, it is preferable to use an organic solvent, from the viewpoint of maintaining the environment. Is preferably water.

  As the organic solvent, for example, alcohol solvents such as methanol, ethanol and propanol, aromatic hydrocarbon solvents such as benzene, toluene and xylene, ketone solvents such as methyl ethyl ketone, and the like can be used.

  As the mixing device, a general mixer can be used. Examples of the mixer include a pot mill such as a ball mill and a vibration mill, a stirring mill such as a sand mill and an attritor mill, and a continuous mill thereof, but are not limited thereto.

  Next, the obtained mixture is preferably calcined from the viewpoint of obtaining a stable sintering effect. When wet mixing is performed, it is preferable to remove the solvent by a known method before calcination. The calcination is preferably 200 to 600 ° C., more preferably 300 to 500 ° C., further preferably 400 to 500 ° C., preferably 0.5 to 12 hours, more preferably 1 to 10 hours, preferably non-oxidizing. Perform in an atmosphere. In the case of calcining at a temperature of 200 ° C. or higher, the volatile components are appropriately volatilized, so that the porosity of the ceramic obtained after firing can be reduced. In addition, when calcining at a temperature of 600 ° C. or lower, since the carbon sintering ability can be maintained, a dense sintered body can be obtained. The non-oxidizing atmosphere may be any of nitrogen gas, argon gas, helium gas, carbon dioxide gas, a mixed gas thereof, or vacuum, and in some cases, calcination may be performed under pressure with a gas.

  The calcined body obtained by the calcining is preferably pulverized by dry or wet pulverization, but the average particle size after pulverization improves the durability of the mold and generates pores on the surface of the mold. From a viewpoint of suppressing, 0.2-0.6 micrometer is preferable, 0.3-0.5 micrometer is more preferable, 0.35-0.45 micrometer is still more preferable.

  The wet pulverization may be performed using a known pulverizer such as a ball mill, a vibration mill, or a planetary mill attritor. As the solvent used in that case, for example, water is preferable in consideration of the environment, but aromatic solvents such as benzene, toluene and xylene, alcohol solvents such as methanol and ethanol, or ketone solvents such as methyl ethyl ketone, etc. Can also be used. As other solvents, a mixed solvent of water and the organic solvent or the like can be used. Usually, the solvent may be used in an amount of about 50 to 200% by weight based on 100% by weight of the raw material mixture.

  In aspect 2, it is preferable to grind | pulverize the mixture of raw materials so that it may become an average particle diameter comparable as the aspect 1 by performing mixing and grinding | pulverization of said raw material simultaneously. The mixing and pulverization may be either a dry method or a wet method, but is preferably performed in a wet manner from the viewpoint of dispersibility of the carbon raw material. As the solvent used for wet mixing and pulverization, either water or an organic solvent may be used. From the viewpoint of the dispersibility of the carbon raw material and the prevention of oxidation of silicon carbide, it is preferable to use an organic solvent. From the viewpoint, it is preferable to use water. As an organic solvent, the thing similar to what is used for the wet mixing of aspect 1 can be used. Examples of the apparatus for performing mixing and pulverization simultaneously include, but are not limited to, a pot mill such as a ball mill and a vibration mill, a stirring mill such as a sand mill and an attritor mill, and a continuous mill thereof. It is not a thing.

  That is, in the production method of the present invention, in the mixture X that can be prepared as described above, the average particle size of the particles constituting the mixture X improves the durability of the mold and generates pores on the surface of the mold. From the viewpoint of suppression, 0.15 to 0.50 μm is preferable, 0.25 to 0.40 μm is more preferable, and 0.30 to 0.35 μm is still more preferable.

  In the present invention, the average particle diameter means D50, that is, a particle diameter at which the integrated particle size distribution (volume basis) from the small particle size side is 50%. The average particle diameter can be measured by a laser diffraction / scattering method.

  The means for adjusting the average particle diameter of the particles constituting the mixture X to be within a desired particle diameter range is not particularly limited, and for example, adjusting the setting conditions of the pulverizing apparatus can be mentioned. For example, when a vibration mill is used as an apparatus for pulverization, pulverization may be performed using zirconia balls as pulverization media.

  In the present invention, it is preferable to granulate the mixture X to obtain a granulated product in which the particles are bound together. The granulation method is not particularly limited as long as it can be classified as necessary to prepare the raw material powder having the above particle size distribution. For example, a spray dryer (spray drying granulator), a spray cooling granulator, a flow Examples thereof include a granulating apparatus such as a bed granulating apparatus, a rolling fluidized bed granulating apparatus, a high-speed stirring granulating apparatus, a rolling granulating apparatus, and an ultrasonic granulating apparatus. In the present invention, it is particularly preferable to perform granulation using a spray dryer from the viewpoint of obtaining a dense sintered body having no pores while performing suitable granulation and molding.

  During granulation, a binder is added as necessary. From the viewpoint of stably preparing the raw material powder having the particle size distribution, it is preferable to add a binder. In addition, from the viewpoint of filling into the mold, the shape of the granule obtained after granulation is preferably a spherical shape with high fluidity.

  Examples of the binder to be used include wax, emulsion, polyvinyl alcohol, polyvinyl acetate, cellulose derivative, etc., and excellent solubility in ethanol, which is a preferred solvent during granulation, while performing suitable granulation and molding, From the viewpoint of obtaining a dense sintered body having no pores, polyvinyl alcohol (Poval) is preferable.

  The addition amount of the binder is preferably 1 to 15 parts by weight with respect to 100 parts by weight of the mixture X from the viewpoint of obtaining a dense sintered body without pores while performing suitable granulation and molding. Part by weight is more preferred.

  Water can be used as the liquid medium when using a spray dryer, but from the viewpoint of evaporability (volatility), alcoholic solvents such as methanol and ethanol, and aromatic solvents such as benzene, toluene and xylene. It is preferable to use a solvent or a ketone solvent such as methyl ethyl ketone.

  Further, from the viewpoint of obtaining dense ceramics, the content of volatile components (including binder, plasticizer, lubricant, etc.) in the mixture X is preferably 0.1 to 10% by weight, more preferably 0.2 to 8%. % By weight, more preferably 0.3 to 8% by weight. When the content of the volatile component in the mixture X is 0.1% by weight or more, since the sintering ability derived from carbon can be sufficiently exhibited during firing, a dense sintered body can be obtained. In addition, when the content of the volatile component in the mixture X is 10% by weight or less, the generation of cracks due to the volatilization of the volatile component during firing and the occurrence rate of residual pores after firing can be reduced. A sintered body can be obtained. As a means for adjusting the content of the volatile component, calcining can be mentioned, and the content can be reduced by calcining.

  In addition, in this invention, content of the volatile component in the mixture X is calculated | required as follows. That is, the mixture X was dried at 130 ° C. for 16 hours for the purpose of removing the solvent, filled in a mold (φ60 mm), and molded to a thickness of 9 mm under a pressure of 147 Mpa. The body weight and the weight of the sintered body obtained by firing the compact at 2150 ° C. for 4 hours are measured using an analytical balance, and are calculated by the following formula.

Volatile component content (% by weight) = (Molded body weight−Sintered body weight) / Molded body weight × 100
[CIP molding]
In the present invention, it is preferable to perform CIP molding (COLD ISOSTATIC PRESS). CIP molding is also called isostatic pressing, and is a method in which molding is performed by applying isotropic pressure. Specifically, for example, a granulated product or a preformed product is put into a mold made of rubber or the like, and pressure is applied isotropically through a pressure medium such as water or oil.

  The pressure for CIP molding is preferably 90 to 300 MPa, more preferably 140 to 250 MPa, from the viewpoint of obtaining a dense sintered body without pores while performing suitable molding. The pressurization time is preferably 0.5 to 3 minutes and more preferably 1 to 2 minutes from the viewpoint of obtaining a dense sintered body having no pores while performing suitable molding. Although heating may be performed during CIP molding, it is usually not necessary to perform heating.

  When preforming, the pressure to be applied is preferably 10 to 70 MPa, more preferably 25 to 70 MPa, and still more preferably 35 to 70 MPa. Heating may be performed during the preforming, but usually it is not necessary to perform heating. Preliminary molding can be performed by mold molding, cast molding, injection molding, or the like using an appropriate molding die.

[Post-process]
In this invention, post processes, such as degreasing | defatting, baking, shape processing, and surface polishing, can be implemented as needed.

  Degreasing is performed as necessary, and is performed in a non-oxidizing atmosphere. The non-oxidizing atmosphere gas is the same as that used in the calcination step. The degreasing temperature is usually preferably from 300 to 1400 ° C.

  Firing refers to a heat treatment necessary for sintering the particles constituting the mixture X. Although it does not specifically limit as a baking method, Preferably it carries out by a normal pressure with the baking temperature of 1900-2300 degreeC. The firing time is usually 0.5 to 8 hours. By setting the firing temperature within the range of 1900 to 2300 ° C., the ceramic of the present invention can be obtained as a dense and strong sintered body. The atmosphere during firing is preferably a vacuum or a non-oxidizing atmosphere similar to the above. As the firing method, a hot press, a HIP (HOT ISOSTATIC PRESS) method, or the like may be used to increase the density of the ceramic.

  In the present invention, it is preferable to perform shape processing after firing in processing the mold to a desired size. Any shape processing can be adopted as long as it is used for shape processing of ceramics, but for example, cutting using an NC processing machine, a cutting tool, a wire cut electric discharge machine or the like can be performed.

  When producing a member that requires surface smoothness, it is preferable to perform polishing for surface smoothing. The polishing method is not particularly limited, but since ceramic is a high-hardness material, polishing with abrasive grains other than diamond requires a long time, so it is preferable to polish with diamond abrasive grains. From the viewpoint of ensuring the surface smoothness of the surface in contact with the raw material of the mold, the average particle diameter of the diamond abrasive used is preferably 2 μm or less.

From the viewpoint of improving the mechanical strength such as the durability of the molding die and sufficiently suppressing the generation of pores on the surface of the molding die, the molding die obtained as described above has a bulk density of 2.6 g / cm. It is preferably ³ or more, more preferably 2.65 g / cm ³ or more, still more preferably 2.68 g / cm ³ or more.

  The mold produced according to the present invention has excellent wear resistance and very little reactivity with raw materials. Moreover, it is excellent in releasability, and the raw material after molding has a surface smoothness to the extent that post-polishing is substantially unnecessary. Furthermore, even after repeated use over a long period of time, the surface of the mold does not become rough and mold release defects do not occur, and high durability is exhibited. Therefore, according to the shaping | molding die of this invention, shaping | molding costs, such as a metal, glass, a plastic, can be reduced.

  Examples and the like specifically showing the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

(1) Particle size distribution, average particle size The particle size distribution is determined by the laser diffraction / scattering method by HORIBA, Ltd. LA-750, D10 (10% particle size based on volume), D50 (50% particle size based on volume), D90 (90% particle size by volume) was measured. At that time, water was used as a dispersion medium, and a polyacrylic acid dispersant “Poise 530” (manufactured by Kao Corporation) was added as a dispersant by 0.5% by weight to the slurry, and the sample concentration was set in the apparatus. It adjusted so that it might become the range of the predetermined | prescribed transmittance | permeability. The above average D50 was adopted.

(2) Bulk density The bulk density of the mold was measured by the Archimedes method using water.

(3) Durability Using the produced mold, this was used as upper and lower molds, and soda-lime glass was press-molded at a temperature of 600 ° C. (melting point or higher) and a pressure of 50 MPa. At that time, the number of times until the mold was damaged was evaluated as durability. In Table 1, ◎ indicates 20,000 times or more, ◯ indicates 10,000 times or more and less than 20,000 times, Δ indicates 500 times or more and less than 10,000 times, and × indicates durability of less than 500 times.

(4) Porosity generation rate The surface of the mold (N = 20) after surface polishing was observed with a microscope at a magnification of 200 times, and the number of pores existing on the surface of the mold was counted, and the surface pores were counted. The incidence was evaluated.

(5) Content of Volatile Component A pulverized product (corresponding to the mixture X) obtained by pulverization with an attritor mixer was dried at 130 ° C. for 16 hours, and then filled in a mold (φ60 mm), and a pressure of 147 Mpa. The weight of the molded body obtained by molding to a thickness of 9 mm below and the weight of the sintered body obtained by firing the molded body at 2150 ° C. for 4 hours were measured using an analytical balance, It is calculated by the following formula.

Volatile component content (% by weight) = (Molded body weight−Sintered body weight) / Molded body weight × 100
Examples 1-7
43 parts by weight of coal tar pitch (average particle diameter of 1 mm or less) with a carbon fixation rate of 58% is carbonized as a sintering aid for 100 parts by weight of silicon carbide with an average particle diameter of 0.69 μm (purity 99% or more). 2 parts by weight of boron (purity 99% by weight or more) is mixed, water is added so that the solid content is 35% by weight, and Celna D735 (manufactured by Chukyo Yushi Co., Ltd.) is added as a dispersant to the solid content to 0.1%. The mixture was mixed by weight and mixed for 2 hours 30 minutes with an attritor mixer.

  The obtained mixed slurry was dried at 130 ° C. for 16 hours, cooled to room temperature, and coarsely pulverized by a jaw crusher. The coarsely pulverized product was calcined at 495 ° C. for 9 hours in a nitrogen atmosphere, and then ethanol was added to a solid content of 50% by weight, followed by pulverization with an attritor mixer for 4 hours to obtain a mixture X (average particle size 0.41 μm). And 6% by weight of volatile components). 1 part by weight of binder (Povar) was added to 100 parts by weight of the solid content, and spray drying was performed with a spray dryer to obtain a molding powder. The obtained molding powder was classified with a sieve to prepare a granulated product having a particle size distribution shown in Table 1.

  These granulated materials were subjected to CIP molding (pressurization time: 1 minute) at the pressure shown in Table 1 to prepare a molded body of 90 × 90 × 20 mm.

  Thereafter, the compact was degreased at 500 ° C. to volatilize the binder component, and then fired at 2200 ° C. in an argon atmosphere for 4 hours. The obtained fired body was processed into a disk shape of φ75 × 15 mm with an NC processing machine and polished with diamond abrasive grains having an average particle diameter of 0.5 μm so as to have a surface roughness of 1 μm or less to obtain a mold. Table 1 shows the results of the above evaluations using this mold.

Examples 8-12
28 parts by weight of coal tar pitch (average particle diameter of 20 μm or less) having a carbon fixation rate of 87.6% and sintering aid for 100 parts by weight of silicon carbide having an average particle diameter of 0.69 μm (purity 99% by weight or more) 2 parts by weight of boron carbide (purity 99% by weight or more) was mixed, and ethanol was mixed so that the solid content was 50% by weight. Mixing and pulverization were simultaneously performed with an attritor mixer for 3 hours to obtain a mixture X (average particle size 0.32 μm, volatile component 6% by weight). Thereafter, 2 parts by weight of a binder (popal) was added to 100 parts by weight of the solid content, and spray drying was performed with a spray dryer to obtain a molding powder. The obtained molding powder was classified with a sieve to prepare a granulated product having a particle size distribution shown in Table 1.

  These granulated materials were subjected to CIP molding (pressurization time: 1 minute) at the pressure shown in Table 1 to prepare a molded body of 90 × 90 × 20 mm.

  Thereafter, the compact was degreased at 500 ° C. to volatilize the binder component, and then fired at 2200 ° C. in an argon atmosphere for 4 hours. The obtained fired body was processed into a disk shape of φ75 × 15 mm with an NC processing machine and polished with diamond abrasive grains having an average particle diameter of 0.5 μm so as to have a surface roughness of 1 μm or less to obtain a mold. Table 1 shows the results of the above evaluations using this mold.

Comparative Examples 1-4
In Example 1, CIP molding was performed under exactly the same conditions except that the raw material powder having the particle size distribution shown in Table 1 was used to obtain a molding die. Table 1 shows the results of the above evaluations using this mold.

  In addition, the raw material powder with such a small particle size could be obtained by collecting the fine powder generated by the spray dryer in the production methods shown in Examples 1 to 7.

  As a result, in Examples 1 to 7, no generation of pores was observed on the surface of the mold, and even when the molding was repeated 500 times or more, the mold was not damaged and the glass was not fused. In particular, in the molds of Examples 1 and 3 to 5 in which the particle size distribution of the raw material powder was more suitable, the mold was not damaged and the glass was not fused even when the molding was repeated 20000 times or more. In addition, in the molds of Examples 8 to 12 using the mixture X obtained by mixing and pulverizing the raw materials at the same time, the calcining step is not necessary, and even if the molding is repeated more than 20000 times, No breakage or glass fusing occurred.

  Compared with this, in Comparative Examples 1 to 4 in which the particle size distribution is not appropriate, pores were generated on the surface of the mold, and the durability was evaluated and was damaged by molding less than 500 times.

Claims (3)

A method for producing carbon-containing silicon carbide ceramics, comprising: a step of granulating a mixture X of raw materials containing silicon carbide, a carbon raw material and a sintering aid; and a step of molding and firing the granulated product obtained in the step. There,
A method for producing a carbon-containing silicon carbide ceramic in which D10 is 35 to 50 μm , D50 is 50 to 85 μm, and D90 is 90 to 135 μm in the volume-based particle size distribution of the granulated product.   The method for producing carbon-containing silicon carbide ceramics according to claim 1, wherein the ratio of silicon carbide to carbon in the carbon-containing silicon carbide ceramics is 6 to 50 parts by weight of carbon with respect to 100 parts by weight of silicon carbide. The method for producing a carbon-containing silicon carbide ceramics according to claim 1 or 2, wherein in the step of granulating the mixture X of raw materials, the raw materials are mixed and pulverized simultaneously.