JPS61168567A - Manufacture of silicon carbide sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a silicon carbide sintered body, and particularly the present invention relates to a method for manufacturing a silicon carbide sintered body having excellent oxidation resistance.

Silicon carbide has chemical and physical properties such as high strength, good wear resistance, good oxidation resistance, good corrosion resistance, good thermal conductivity, low coefficient of thermal expansion, high thermal shock resistance and high strength at high temperatures. Mechanical seals have excellent properties, such as wear-resistant materials, refractory materials for high-temperature furnaces, heat-resistant structural materials such as heat exchangers, combustion tubes, and highly corrosive solutions such as acids and alkalis. This material can be widely used as a corrosion-resistant material for pump parts, etc.

[Conventional technology]

By the way, silicon carbide has been known as a material that is difficult to sinter. In other words, until recently, it was difficult and rare to obtain a high-density sintered body of this material using the pressureless sintering method, which is generally used to produce oxide ceramics, in which the material is molded at room temperature and then sintered under no pressure. . However, recently, various pressureless sintering methods have been proposed in which a mixed powder consisting of silicon carbide powder and sintering aids such as boron-containing additives and carbonaceous additives is compacted and sintered in an inert atmosphere. has been done.

For example, according to the invention described in JP-A-50-78609, (a) silicon carbide;
forming a homogeneous dispersion of submicron powder consisting of a boron-containing compound in an amount corresponding to % boron and a carbonaceous additive in an amount corresponding to 0.1 to 1.0% by weight carbon; (b) shaping the powder mixture into a green body, and (C) shaping the green body from 1900 to 2100
A method of making a high-density silicon carbide ceramic is disclosed that includes sintering in an inert atmosphere at a temperature of 500 ℃ for a sufficient time to obtain a ceramic article having a density of at least 85% of the theoretical density.

According to the invention described in JP-A-54-67599, an organosilicon polymer compound whose main skeleton components are silicon and carbon is heated to 1600 to 2200 in vacuum or an inert gas atmosphere.
A powder mainly composed of β-8iC is obtained by thermal decomposition at a temperature of
After heating to a temperature of 0C, it is treated with an acid containing at least hydrofluoric acid to dissolve and remove impurities to obtain a powder made of high-purity β-8iC, and carbon and boron are added to each raw material powder in the mixture. The mixture was added until the content was 0.1 to 5% by weight, and the mixture was molded into a predetermined shape.
A method for producing a silicon carbide sintered body is disclosed, which comprises sintering at a temperature of 0 to 2300 C for a sufficient time to have a density of at least 2.60 C or more.

According to the invention described in JP-A-56-169181,
In a method for producing a silicon carbide sintered body in which silicon carbide fine powder, a boron-containing additive, and a carbonaceous additive are mixed, molded, and then sintered without pressure, 85% by weight or more of β-type crystal silicon carbide and the remainder are 100 parts by weight of silicon carbide fine powder consisting essentially of 2H-type crystalline silicon carbide and 0.1 to 3 parts by weight of boron-containing it.
．． A first step of homogeneously mixing 0 parts by weight of a boron-containing additive and a carbonaceous additive of more than 1.0 parts by weight and less than 4.0 parts by weight in terms of fixed carbon content; A second step of forming the formed body; a step of sintering the formed body at 2050 to 2200 C in a gas atmosphere consisting of at least one selected from argon, helium, neon, krypton, xenon, and hydrogen; 3rd step; consists of a combination of the above 1st to 3rd steps and produces 50 to 50 β-type crystals.
85% by weight, residual free carbon of 1., more than 0% by weight3.
0 weight or less; 3. A method for producing a high-strength silicon carbide sintered body having a density of Qi/cm3 or more is disclosed.

[Problems to be Solved by the Invention] By the way, according to the invention described in JP-A-50-78609, boron is used as a sintering aid to reduce silicon carbide to zero.
．． Since it is contained in a relatively large amount of 3 to 3.0% by weight, the resulting sintered body has a drawback of poor oxidation resistance.

Furthermore, according to the invention described in JP-A-54-67599, the method uses extremely expensive β-8iC powder obtained by thermally decomposing an organosilicon polymer compound as a starting material. The drawback is that it is difficult to use widely as a material.

The invention described in JP-A-56-169181 is an invention filed by the applicant, and its purpose is to improve the pressureless sintering method of silicon carbide and to obtain a high-strength sintered body. By adding the quality additive in excess of the amount required by the oxidation content of the silicon carbide fine powder and actively incorporating it in the form of free carbon into the silicon carbide sintered body, the
The phase transformation to the type crystal is optimized, and the β-type crystal becomes coarse and fine crystals as it changes to the α-type. However, the invention described in the above publication requires silicon carbide of which 85% by weight or more consists of β-type crystals as a starting material in order to obtain a high-strength sintered body, and the addition of boron or carbon as a sintering aid is necessary. It has the disadvantage of being subject to various restrictions.

The present invention eliminates the drawbacks of the previously known pressureless sintering methods for silicon carbide as described above, and is particularly suitable for use under harsh conditions such as gas turbine parts, high temperature heat exchangers, and furnace structural materials. It is an object of the present invention to provide a method that can inexpensively and easily produce a pressureless sintered body of silicon carbide having high density and excellent oxidation resistance.

[Means to solve the problem]

According to the present invention, in a method for producing a silicon carbide sintered body in which silicon carbide fine powder is sintered without pressure, the method contains 50% by weight or more of β-type silicon carbide having an average crystal lattice constant of 4,3584 A or more. 100 parts by weight of silicon carbide fine powder, 0.01 to 0.25 parts by weight of a boron-containing additive in terms of boron content, and 0.3 to 5.0 parts by weight of carbonaceous material in terms of fixed carbon content. After homogeneously mixing with the additives, it is molded into a formed product having an arbitrary shape, and then heated for 1700~
The above object can be achieved by a method for producing a silicon carbide sintered body, which is characterized by sintering at 2300 C and producing a silicon carbide sintered body having a density of 2.8 or more.

Next, the present invention will be explained in detail.

Conventionally, according to a pressureless sintering method of silicon carbide, a sintered body is manufactured by mixing silicon carbide powder with boron and carbon and sintering the mixture. By the way, since the boron remains in the sintered body and lowers the melting point of the silica on the surface of the sintered body, thereby deteriorating the oxidation resistance of the sintered body, it is desirable that the amount added is as small as possible. However, according to the conventionally known pressureless sintering method of silicon carbide, some specific silicon carbide fine powders, such as the organosilicon polymer compound described in JP-A-54-67599, cannot be thermally decomposed. The extremely expensive β-type silicon carbide powder obtained by
It is difficult to obtain a high-density non-pressure sintered body of silicon carbide with a small amount of boron added, except for silicon carbide fine powder that is essentially made of mold crystals, and the minimum value of the amount of boron added is Both amounts were 0.1% by weight, which was not a very small amount.

The present inventors found that the average value of the crystal lattice constant was 4.3584.
& The silicon carbide fine powder mainly composed of β-type silicon carbide has extremely excellent sinterability, and can be used as a starting material in the pressureless sintering method.

A large number of necks can be uniformly generated between silicon carbide particles with an extremely small amount of boron added, and a silicon carbide sintered body with a high density and uniform microstructure and excellent oxidation resistance can be obtained. We discovered something new.

According to the present invention, the silicon carbide fine powder contains 50% by weight of β-type silicon carbide having an average crystal lattice constant of 4.3484 or more.
It is necessary that the content is as follows. The reason for this is that β-type silicon carbide whose m crystal has an average lattice constant of 4.3584 or more has extremely excellent sinterability;
This is because by using silicon carbide fine powder containing 50% by weight or more of type silicon carbide as a starting material, a high-density sintered body can be obtained with an extremely small amount of boron added. A silicon carbide fine powder containing the above amount is particularly advantageous.

The β-type silicon carbide used in the present invention is preferably β-type silicon carbide obtained by firing silica and carbon at a high temperature as starting materials, and is an invention previously filed by the present applicant in Japanese Patent Publication No. 57 The product manufactured using the manufacturing apparatus described in Japanese Patent No. 48485 is economically advantageous.

The reason why β-type silicon carbide with an average crystal lattice constant of 4.3584 i or more has excellent sintering properties is as follows.
β-type silicon carbide with an average crystal lattice constant of 4.3584 & above has a high probability of forming necks between particles during neck formation during the sintering process, and elemental diffusion through grain boundaries is easy. This is thought to be due to

The average value of the lattice constant of the crystal used in the present invention is 4
．． The β-type silicon carbide of 3584 & above can be produced by dissolving aluminum as a solid solution during the silicon carbide production reaction.1 For example, silica, carbon, and an aluminum-containing additive added as necessary are used as starting materials. 18
It can be produced by firing at a high temperature range of 0.00 to 2200 °C.

As the aluminum-containing additive, various aluminum-containing salts and metallic aluminum can be used, including alumina (aluminum oxide).

It is advantageous to use mullite or the like.

According to the present invention, the β-type silicon carbide is alumina A 2
It is preferable that the content is 0.02 to 1.0% by weight. The reason for this is that if it is less than 0.02% by weight, it is difficult to make the crystal lattice constant larger than 4.3584 A, while if it is more than 1.0% by weight, aluminum is not dissolved in silicon carbide. This is because abnormal grain growth of plate crystals is likely to occur during sintering, which not only makes it difficult to obtain a high-density sintered body, but also deteriorates the high-temperature properties of the sintered body. However, a range of 0.1 to 0.5 weight f% is more advantageous.

By the way, the present applicant previously disclosed the following invention in Japanese Unexamined Patent Publication No. 57-17465.

"In a method for manufacturing a silicon carbide sintered body in which silicon carbide fine powder is sintered without pressure, aluminum is added in an amount of O01 to 1.0% by weight.
Silicon carbide fine powder containing 90 units or more of silicon carbide in the / type crystal and 0.1 to 100% in terms of boron content
A first step of homogeneously mixing 3.0 parts by weight of a boron-containing additive and a carbonaceous additive in an amount exceeding 1.0 parts by weight and not more than 4.0 parts by weight in terms of fixed carbon content; A second step of molding into a green body having the shape; the green body is heated with argon.

190 in a gas atmosphere consisting of at least one selected from helium, neon, krypton, xenon, and hydrogen.
3rd step of sintering at 0 to 2100 C; 80 to 95% of at least one of the 4H type crystal or 6H type crystal formed by the combination of the first to 3rd steps, the remainder mainly consisting of β type crystal, Contains more than 1.0% by weight and less than 3.0% residual free carbon, and at least 3.0% by weight. O1i1
"A method for producing a high-strength silicon carbide sintered body having a density of -/crn3".

However, the invention described in the above publication uses silicon carbide fine powder containing 90% or more of β-type crystal silicon carbide as a starting material, and phase-transforms most of the crystals into α-type crystal silicon carbide during sintering. In contrast, the present invention produces a high-strength silicon carbide sintered body containing 80 to 95% of This is a method for producing a high-density silicon carbide sintered body with excellent oxidation resistance with an extremely small amount of added boron by using silicon carbide fine powder containing teIJ or more as a starting material, and in accordance with the purpose and structure of the invention. Thick and different.

According to the present invention, it is preferable that at least 20% by weight of the resulting silicon carbide sintered body is β-type silicon carbide. The reason for this is that when the β-type silicon carbide contained in the obtained silicon carbide sintered body is less than 20% by weight, the phase transformation accompanying sintering is significant, and the abnormal grain growth of plate-like crystals is remarkable due to the phase transformation. This is because it becomes difficult to obtain a high-density sintered body.

According to the present invention, the silicon carbide fine powder has a specific surface area of 5 to 5.
It is preferable that it is 0 m2/9-. The reason for this is that if silicon carbide, which has a specific surface area smaller than 5In"/9-, is used as a starting material, there will be fewer necks formed in the initial stage of sintering, and shrinkage during sintering will be uneven. On the other hand, fine silicon carbide powder with a specific surface area larger than 50m"/9- has many neck points and is considered to have excellent sinterability, but such fine silicon carbide powder is difficult to obtain. It is from.

According to the present invention, the silicon carbide fine powder has an oxygen content of 0.
It is preferably 1 to 1.0 weight iL%. Oxygen contained in the preflamed silicon fine powder reacts with carbon during sintering and is removed by the mechanism shown in the following equation.

8i0z + C-+SiO+ COfl)SiO+
2C→SiC+ CO(2) Therefore, the oxygen is 1
．． If the amount is greater than 0% by weight, not only will a large amount of carbonaceous additive have to be used, but also boron as a sintering aid will be oxidized and a large amount of CO gas will be generated, making it difficult to sinter. This is because sintering becomes difficult, such as the need for degassing during sintering. On the other hand, fine silicon carbide powder containing less than 0.1 liters of oxygen can be obtained, for example, by treatment with a mixed acid of hydrofluoric acid and nitric acid. Silicon carbide fine powder is extremely active and easily oxidizes even at room temperature when dried in an air atmosphere, so in order to maintain a low oxygen content, the atmosphere after acid treatment must be kept non-oxidizing. This is because it would be impractical to do so.

According to the present invention, the boron-containing additive is 0.01 to 0 in terms of boron content per 100 parts by weight of silicon carbide fine powder.
．． It is necessary to add 25 parts by weight.

The boron content of the boron-containing additive is 0.0
The reason why the amount is 1 to 0.25 parts by weight is that if it is less than 0.01 parts by weight, the adhesive effect during neck formation is insufficient and it is difficult to achieve high density.On the other hand, if it is more than 0.25 parts by weight, This is because boron remaining in the sintered body lowers the melting point of the silica layer on the surface of the sintered body, thereby degrading the oxidation resistance of the sintered body. As the boron-containing additive, it is preferable to use at least one selected from, for example, boron, boron carbide, or a mixture thereof.

According to the present invention, a silicon carbide sintered body particularly excellent in oxidation resistance can be obtained when the amount of the boron-containing additive added is less than 0.1 parts by weight in terms of boron content.

According to the present invention, the carbonaceous additive is converted into a fixed carbon content of 0.3 to 5.0 per 100 gram weight of silicon carbide fine powder.
It is necessary to add parts by weight. The carbonaceous additive is used to remove oxygen contained in the silicon carbide fine powder and to be interposed between the silicon carbide particles to optimize the diffusion of SiC. Therefore, it is advantageous to add the carbonaceous additive at least in an amount that matches the oxygen content, and further in an amount sufficient to be uniformly interposed between silicon carbide particles.

The reason why the amount of the carbonaceous additive added is 0.3 to 5.0 parts by weight in terms of fixed carbon content is that if it is less than 0.3 parts by weight, most of the carbonaceous additive will be consumed by oxygen. This is because the effect of optimizing the diffusion of 8iC cannot be sufficiently exerted due to the amount of carbon content, and on the other hand, if the amount exceeds 5.0 parts by weight, excessive carbon exists between silicon carbide particles, which significantly inhibits sintering. .

The carbonaceous additive is present at least 100 m at the beginning of sintering.
``Preferably, it has a specific surface area of 7%.

The reason is that the specific surface area at the start of sintering is too
If 2/P is also smaller, the effect of optimizing the diffusion of SiC will be weak. Therefore, in order to fully exhibit the effect of optimizing the diffusion of SiC, it must be added in large quantities, and it may cause interference in the sintered body. This is because the number of layers increases, making it difficult to obtain a high-strength sintered body.

As the carbonaceous additive, any material that can cause carbon to be present at the start of sintering can be used, such as phenolic resin, lignin sulfonate, polyvinyl alcohol, cornstarch, molasses, coal tar pitch, alginate, and polyphenylene. Various organic substances or
Carbon black.

Pyrolytic carbon such as acetylene black can be advantageously used.

According to the present invention, silicon carbide fine powder, a boron-containing additive, and a carbonaceous additive are homogeneously mixed, and then molded into a formed body having an arbitrary shape, and then heated to a temperature of 1,700 to 2
Sintered at 300 C, 2.8? A silicon carbide sintered body having a density higher than the original density is produced.

According to the present invention, it is advantageous that the non-oxidizing atmosphere is a gas atmosphere consisting of at least one selected from argon, helium, neon, krypton, xenon, and hydrogen.

By the way, during sintering in the present invention, as described above, CO gas is generated according to the above formulas (1) and (2+).If the CO gas is present in a large amount, the reaction of the above formula is suppressed, and the silica on the surface of silicon carbide is Film removal becomes insufficient,
Sufficient sintering shrinkage cannot be obtained, and if the silica film remains, it will form an intervening phase within the silicon carbide sintered body and deteriorate the physical properties, especially the mechanical strength, of the sintered body, so CO gas must be removed from the furnace. No. Therefore, according to the present invention, it is advantageous to provide the above-mentioned gas flow atmosphere inside the furnace. It is advantageous to maintain the CO gas partial pressure in the furnace atmosphere during the sintering to 10 KPa or less.

According to the present invention, the formed body is heated at a temperature of 1700 to 2300C.
It is necessary to sinter within the range of The reason for this is that if the sintering temperature is as low as 1700 C, the sintering temperature of the present invention is 2.8? /FF
It is difficult to obtain a sintered body with a density of 13 or more, and conversely, at temperatures higher than 2300 C, crystal grains grow significantly and the physical properties of the sintered body, such as mechanical strength, decrease. In order to obtain a sintered body with a fine microstructure and high strength, it is advantageous to sinter at a temperature within the range of 1900 to 2100 tel'.

According to the present invention, one of the heating steps leading to the sintering temperature
Within the temperature range of 500 to 1700 t:', maintain the partial pressure of CO gas lower than IKPa in the temperature range for a sufficient period of time to allow the silica film removal reaction to proceed quickly and the neck formation reaction to occur uniformly. It is advantageous to do so.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Example 1 Silica sand powder (8i02 = 99.6%, total AA = 0.
1%, 80 mesh or less), anthracite powder (C=
87.8%, total M = 0.4% + 325 mesh or less) and pitch powder (C = 50.41.200
Below mesh, 7% by weight of silica sand) is added to C/5i
02 molar ratio was 3.8, and the mixture was placed in a vertical screw mixer and mixed for 10 minutes. ＃C in the compound raw materials
Molding was performed using a dish-type granulator while spraying an aqueous solution of MC005.

After sifting with a sieve and burr grizzly, drying to obtain an average particle size of I
A molding raw material of Q, 5 m, and bulk specific gravity of 0.6 was obtained. Next, the forming raw material was charged from the top of a manufacturing apparatus similar to that described in Japanese Patent Publication No. 57-48485.

The SiC formation reaction was carried out at a temperature of about 1900 C by indirect electric heating. Furthermore, the obtained product was purified and classified for particle size to prepare silicon carbide fine powder.

The silicon carbide fine powder has 96.7% β-type crystals and the remainder is 2H.
The lattice constant of β-type crystal is 4.3609.
A and 0.31% by weight aluminum.

It contained 0.32 wt. free carbon, 0.18 wt. oxygen, and had a specific surface area of 15.8 m"/).

The lattice constant of the β-type crystal was determined from the (420) diffraction line.

The silicon carbide fine powder has a specific surface area of 99.9 i and 27.8 m.
”/? boron carbide powder 0.1? and fixed carbon content 5t
, 150 d of acetone was added to the mixture with 2.1 tJ of novolac type phenolic resin, and the mixture was mixed for 2 hours using a vibration mill. The mixture slurry was discharged from the vibrating mill and spray-dried.

The average particle size is 0.091111, the powder bulk density is 3s% (x
, 12V-) were obtained.

Take an appropriate amount of these granules and use a gold W4 mold to
．． Preliminary molding was performed at a pressure of 15 t/m2, and then 1. Molding was carried out at a pressure of Bt/c-. The density of the formed body obtained by the above molding was 61 inches (1,95 cm).
Plon) to 6! If': + got.

The formed body was placed in a Tammann type sintering furnace and sintered in an argon gas stream under atmospheric pressure. The heating process is normally fi ~
1650 C is 5 C/min, 40 at 1650 C
After holding for a minute, the temperature was further increased at a rate of 5 C/min and held at a maximum temperature of 2000 G for 30 minutes. C during sintering
O gas partial pressure is 5 KPa or less at room temperature to 1650G, 16
0.5KPa or less when held at 50C, 1650
The argon gas flow rate was appropriately adjusted so that the temperature was 5 KPa or less in the higher temperature range than C.

The obtained sintered body contained 0.31% by weight of aluminum and 1.0% by weight of free carbon, and had a density of 3.12 Van 3 (relative theoretical density rate 98.0%). Further, as a result of powder X-ray diffraction measurement of this sintered body, this sintered body has a 92.
It was found that 1% was β-type crystals.

The sintered body was processed into a plate shape of 30 x 30 x 1 m, and washed with acetone to prepare a sample for oxidation resistance test. The sample was treated for 20 hours in a heating furnace maintained in an air atmosphere of 14,000 °C, and the weight increase before and after the treatment was measured, and the weight increase was 0.02 cm/cm2 compared to before the treatment, indicating that the oxidation resistance was recognized as being excellent.

Example 2, Comparative Example 1 Same as described in Example IK, but using oil coke powder with different aluminum content as shown in Table 1 instead of anthracite powder and at the temperature shown in Table 1. Silicon carbide fine powder was prepared.

The physical properties of the obtained silicon carbide fine powder are shown in Table 1.

Using the silicon carbide fine powder shown in Table 1 above, sintered bodies were obtained in the same manner as in Example 1, except that the amount of boron carbide added was changed as shown in Table 1. The physical properties of the obtained sintered body are as shown in Example 1.
The results are shown in Table 1.

According to Table 1, although actual examples 2-1 and 2-2 have different total U amounts, they both yield high-density sintered bodies, and -1 has excellent oxidation resistance. It can be seen that In addition, in Example 2-3, the SiC formation reaction temperature was set at 21%.
In this example, the lattice constant of the silicon carbide powder obtained is 4.3618 A, and the sintered body produced from this powder has a particularly high density and has the best oxidation resistance. Ta. In Examples 2-4 and 2-5, the silicon carbide powder used in Example 1 was used, but the amount of boron carbide added was 0.05 L each. , 0.151i- to produce a sintered body. All of the obtained sintered bodies had high density and excellent oxidation resistance.

On the other hand, in Comparative Example 1, the average value of the lattice constant of the silicon carbide powder crystal is 4.3580 The chemical properties were also extremely poor compared to the examples.

The silicon carbide fine powder described in Example IK as a starting material 99.
9p and the boron carbide powder described in Example 1 were further classified by particle size, and the specific surface area was 47.8 m2/Ba1 made boron carbide o, i y, average particle size 21ON, specific surface area 128 m
For a mixture with 2/9 carbon black 1.5i, acetone 150d, polyethylene glycol Q, 7a
After ball milling for 10 hours, the slurry was spray dried. An appropriate amount of this dry powder was collected and a green body was prepared in the same manner as in Example 1 to obtain a sintered body.

The density of the obtained sintered body is 3.01? /cn13 high.

It was found that 94.0% were β-type crystals.

Further, the weight increase in the oxidation resistance test measured in the same manner as in Example 1 was as small as 0.03 mti/cm2, indicating excellent oxidation resistance.

Example 4 Same as Example 1, but α-type silicon carbide fine powder produced by crushing, refining, and particle size classification of commercially available α-type silicon carbide was added to 60 parts by weight of the silicon carbide fine powder described in Example 1 as a starting material. 4
A sintered body was obtained using silicon carbide fine powder mixed in a proportion of 0 parts by weight.

Note that the α-type silicon carbide fine powder has a specific surface area of 14.8 m2.
/? It contained 0.01% by weight of aluminum, 0.3% by weight of free carbon, and 0.02% by weight of oxygen.

The density of the obtained sintered body was 2.90 i/C'ff13, and the content of β-type silicon carbide was 40.4 i/C'ff13.

Also, the weight increase in the oxidation resistance test measured in the same manner as in Example 1 was 0.04 mg/at? It had excellent oxidation resistance.

As described above, according to the present invention, a pressureless sintered body of silicon nine carbide having high density and excellent oxidation resistance can be produced at low cost.

Claims (1)

[Claims] 1. A method for producing a silicon carbide sintered body by pressure-free sintering of silicon carbide fine powder, comprising 50% by weight or more of β-type silicon carbide having an average crystal lattice constant of 4.3584 Å or more. It contains 100 parts by weight of silicon carbide fine powder, a boron-containing additive of 0.01 to 0.25 parts by weight in terms of boron content, and 0.01 to 0.25 parts by weight in terms of fixed carbon content.
After homogeneously mixing with 3 to 5.0 parts by weight of a carbonaceous additive, it is molded into a formed body having an arbitrary shape, and then sintered at 1700 to 2300°C in a non-oxidizing atmosphere to produce 2.8 g/c
A method for producing a silicon carbide sintered body, comprising producing a silicon carbide sintered body having a density of m^3 or more. 2. The method according to claim 1, wherein the β-type silicon carbide is a β-type silicon carbide obtained by firing silica and carbon at a high temperature as starting materials. 3. The β-type silicon carbide contains aluminum in an amount of 0.02 to 1.
The method according to claim 1 or 2, which contains 0% by weight. 4. The silicon carbide fine powder has a specific surface area of 5 to 50 m^2/g
The method according to any one of claims 1 to 3. 5. The method according to any one of claims 1 to 4, wherein the silicon carbide fine powder has an oxygen content of 0.1 to 1.0% by weight. 6. The method according to any one of claims 1 to 3, wherein the boron-containing additive is at least one selected from boron, boron carbide, or a mixture thereof. 7. The carbonaceous additive is at least 100 m^ at the beginning of sintering.
The method according to any one of claims 1 to 6, which has a specific surface area of 2/g. 8. The method according to any one of claims 1 to 7, wherein at least 20% by weight of the silicon carbide sintered body is β-type silicon carbide.