JP2022018980A - Reactive sintered silicon carbide sintered compact and method for producing the same - Google Patents

Abstract

To provide a high strength component made of reactive silicon carbide not obtained by the conventional reaction sintering using extrusion molding or cast molding.SOLUTION: Using: silicon carbide powder (a) in which the average particle diameter is 2 to 5 μm and the maximum particle diameter is 10 μm or lower; and silicon carbide powder (b) in which the average particle diameter is 0.1 to 0.5 μm and the maximum particle diameter is 5 μm or lower as silicon carbide raw material powder, as carbon, carbon black (c) in which the average particle diameter is 0.001 to 0.1 μm is added to the silicon carbide powder (a) and the silicon carbide powder (b), an organic binder is added to each powder of (a), (b), (c) and extrusion molding or cast molding is performed to create a desired molded body, and metal silicon powder is impregnated therein to be sintered, thus high strength reactive sintered silicon carbide made of silicon and silicon carbide can be obtained.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a high-strength reaction-sintered silicon carbide sintered body by extrusion molding, and a material composition for producing the sintered body.

In recent years, silicon carbide has excellent properties as a high-temperature structural material and corrosion-resistant material, has features such as high-temperature conductivity and high hardness, and also has high creep resistance and oxidation resistance. Due to these characteristics, it is used in semiconductor manufacturing equipment members, wear-resistant nozzles, mechanical seals, corrosion-resistant reaction tubes, acid treatment jigs, and the like. Further, it is used for a gantry or a roller which is a jig used in a sintering furnace for sintering ceramics. It is also used for rollers, which are jigs for continuous processing furnaces for producing positive electrode materials for lithium-ion batteries.
As a method for obtaining these silicon carbide sintered parts, typical manufacturing processes for silicon carbide include a normal pressure sintering method using a sintering aid, an atmospheric pressure sintering method, a hot press method, and a HIP. Examples include the method and the reaction sintering method.
In particular, in the reaction sintering method (RS method), molten metallic silicon is impregnated into a green compact consisting of silicon carbide (SiC) powder and carbon (C) powder of aggregate, and the reaction of Si + C → SiC is carried out. A dense sintered body can be obtained by forming SiC and filling the pores around the SiC with free silicon (Si).
Therefore, the RS method contains 10 to 40 wt% of free Si in addition to SIC. RS-SiC is a powder sintering method such as normal pressure sintering method, atmospheric pressure sintering method, hot press method, and HIP method. It has been reported that the strength and fracture toughness values are generally lower and the thermal conductivity is higher than that of the SiC prepared in. Also, the RS method is compared with the powder sintering method using a sintering aid. Since the sintering temperature is low and it can be densified without adding an auxiliary agent, low cost and high purity can be expected. Furthermore, there is almost no dimensional change due to sintering, and large complex shaped objects can be sintered into a near net.
For this reason, RS-SiC is often used as a jig for a sintering furnace because the manufacturing cost can be kept low as compared with other construction methods.
However, RS-SiC obtained by the RS method has lower strength than the normal pressure sintering method, atmospheric pressure sintering method, hot press method and HIP method, and is used for a gantry for a sintering furnace. It is necessary to increase the wall thickness, the weight is also heavy, and the manufacturing cost is increased.

Currently, as described in Technical Paper 1 Patent Documents 1 to 4, a mixed powder of silicon carbide having a particle size of 0.1 μm to 10 μm and a carbon powder having an average particle size of 0.005 μm to 1 μm is used. The product is obtained by press molding with the addition of an organic binder. The finer the particle size, the higher the sintering density and the higher the strength, but in extrusion molding and casting molding, it is necessary to increase the amount of binder added, and cracks and swelling during degreasing are likely to occur, so degreasing and drying The time needs to be longer than 24 hours.

Published Patent Publication 2004-35279 Published Patent Publication 2007-22914 Published Patent Publication 2007-55597 Published Patent Publication 2009-190950

Therefore, the present invention uses the optimum silicon carbide powder, carbon powder composition and optimum silicon carbide powder particle size in order to obtain a sound high-strength reaction-sintered silicon carbide sintered body by extrusion molding and casting molding methods. Is the subject.

The present inventors perform casting molding or extrusion molding using a mixture of silicon carbide powder having an adjusted particle size, carbon powder, and an organic binder as a raw material to obtain high-strength reaction sintered silicon carbide. A silicon carbide raw material powder having an average particle size of 2 to 5 μm and a maximum particle size of 10 μm or less, and a silicon carbide powder (a) having an average particle size of 0.1 to 0.5 μm and a maximum particle size of 5 μm or less. A certain silicon carbide powder (b) is used, and an organic binder is used in the powder composition obtained by adding carbon black (c) having an average particle size of 0.001 to 0.1 μm or less as carbon to the silicon carbide powders (a) and (b). By molding, degreasing, and sintering, a high-strength, defect-free sintered body can be obtained.

That is, the silicon carbide powder used in the present invention includes silicon carbide powder (a) having an average particle size of 2 to 5 μm and a maximum particle size of 10 μm or less, and an average particle size of 0.1 to 0.1 to the silicon carbide raw material powder. Using a silicon carbide powder (b) having a maximum particle size of 5 μm or less and a powder consisting of 0.5 μm, carbon black having an average particle size of 0.001 to 0.1 μm or less is used as carbon for the silicon carbide powders (a) and (b). By adding an organic binder to the powder composition to which (c) is added and performing molding, degreasing, and sintering, high-strength, defect-free reactive sintered silicon carbide can be obtained.

In particular, the addition ratio of the silicon carbide powder (a) and the silicon carbide powder (b) is 50 to 90 wt% for the silicon carbide powder (a) and 10 to 50 wt% for the silicon carbide powder (b). Further, the mixing ratio of carbon black is 20 wt% to 40 wt% by weight with respect to the total of the silicon carbide powder (a) and the silicon carbide powder (b), and an organic binder is added to these powder compositions to obtain high strength. Defect-free reaction sintered silicon carbide can be obtained.

According to the powder composition according to the present invention, the amount of binder added can be reduced, and a high-strength reactive silicon carbide sintered body can be obtained by extrusion molding and casting molding.

Extruded parts

In the silicon carbide raw material powder according to the present invention, either or both of β-silicon carbide and α-silicon carbide can be used as a raw material. A powder having an average particle size of 2 to 5 μm and a maximum particle size of 10 μm or less (a) and a powder having an average particle size of 0.1 to 0.5 μm and a maximum particle size of 5 μm or less (b). , And carbon black (c) having an average particle size of 0.001 to 0.1 μm or less is used as carbon for the silicon carbide powders (a) and (b).
A water-soluble polymer material is desirable for the organic binder for molding, and a water-soluble polymer composed of at least one kind of methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, and polyvinyl alcohol is used. Among these water-soluble polymers, methyl celluloses are desirable, and hydroxypropyl methyl cellulose is particularly preferable.
A plasticizer and water are added to these organic binders.
As the plasticizer, an organic material composed of at least one kind such as glycerin and polyoxyethylene monobutyl ether is used.

The particle size of silicon carbide is (a) an average particle size of 2 to 5 μm and (b) an average particle size of 0.1 to 0.5 μm, and the addition ratio of the silicon carbide powder (a) and the silicon carbide powder (b) is the silicon carbide powder. When (a) is 50 to 90 wt% and the silicon carbide powder (b) is 10 to 50 wt%, the strength of the sintered body can be improved. When the amount of the silicon carbide powder (a) added is less than 50 wt%, the amount of binder added is large, and it takes a long time to dry and degreas. Further, when the amount of the silicon carbide powder (a) added is less than 10 wt%, the strength of the sintered body is not sufficiently improved. The desired silicon carbide powder (a) is 60 to 80 wt% and the silicon carbide powder (b) is 20 to 40 wt%.
Further, when the maximum particle size of the silicon carbide powder (a) is larger than 10 μm and the maximum particle size of the silicon carbide powder (b) is larger than 5 μm, the sintering density decreases.

Carbon black (c) having an average particle size of 0.001 to 0.1 μm or less is used as carbon for the silicon carbide powders (a) and (b). The mixing ratio of carbon black to the total of the silicon carbide powder (a) and the silicon carbide powder (b) is 20 wt% to 40 wt% by weight. When the amount of carbon black added is less than 20 wt%, a large amount of unreacted metallic silicon remains in the sintered body, and the strength is lowered. Further, when the amount of carbon black added is more than 40 wt%, a large amount of unreacted carbon remains in the sintered body, and the strength is lowered. When the particle size of carbon black is 0.001 μm or less, it is difficult to disperse carbon uniformly. Further, when the particle size of carbon black is 0.1 μm or more, the reaction with metallic silicon is not uniformly performed in the sintering step, and the strength of the sintered body is not improved.

A water-soluble polymer material is desirable for the organic binder of the present invention, and a water-soluble polymer composed of at least one kind of methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, and polyvinyl alcohol is used. The amount of the water-soluble polymer added is preferably 1 to 10 parts, and more preferably 2 to 5 parts when the amount of silicon carbide and carbon powder is 100 parts. When the amount of the water-soluble polymer added is less than one part, the strength of the molded product is low and deformation is likely to occur during extrusion molding. If the amount of the water-soluble polymer added exceeds 10 parts, thermal decomposition does not proceed sufficiently during heat degreasing, cracks occur in the molded product, and carbides remain.

The amount of the plasticizer added in the present invention is preferably 0.5 to 7 parts, and more preferably 1 to 4 parts. When the amount of the plasticizer added is less than 0.5 part, the molded product is brittle and the fluidity of the molded product is deteriorated. When the amount of the plasticizer added exceeds 7 parts, the extruded molded product becomes soft and it becomes difficult to maintain the shape of the molded product.
The water used in the present invention lowers the viscosity of the molded product and imparts fluidity. The desired amount of water added is 5 to 15 parts, and the desired amount of water added is 7 to 12 parts. When the amount of water added is less than 5 parts, it is difficult to impart fluidity to the molded body, and when the amount of water added exceeds 15 parts, the shape of the molded body can be maintained during extrusion molding. It will be difficult.

The silicon carbide powder of the present invention is added with carbon powder, and a plasticizer and water are added and mixed at room temperature using a kneader such as a Henshell mixer. The mixed material is dispersed with a kneader or three rolls. Let me. If necessary, cure the material for about 1 to 2 days, and then perform extrusion molding into a desired shape using extrusion molding that can be evacuated. A screw type vacuum extrusion molding machine or a piston type vacuum extrusion molding machine is used as the extrusion molding machine.
Cut to the required length and use a dryer to gel the water-soluble polymer and remove the water.

The dried molded product is sintered using a sintering furnace. In sintering, the periphery of the molded product after drying is covered with a metallic silicon powder having a particle size of 0.05 to 1 mm. When the particle size of the metallic silicon powder is less than 0.05 mm, it becomes difficult to remove the metallic silicon adhering from the sintered body, and when the particle size of the metallic silicon is 1 mm or more, the impregnation of the metallic silicon is uniform. This is not done, and the carbon and metallic silicon in the molded body do not react uniformly. Further, when the metal silicon particles become 1 mm or more, the metal particles bite into the molded body, and defects such as cracks and cracks occur on the surface after sintering.
The sintering temperature is 1400 ° C. or higher, preferably 1400 ° C to 1550 ° C, and particularly preferably 1400 to 1500 ° C. Further, it is desirable that the sintering atmosphere is performed under reduced pressure or under an inert gas atmosphere.

As for the sintered body obtained under the above conditions, a sintered body having higher strength as compared with the conventional RS-SiC can be obtained by extrusion molding.

Hereinafter, the invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Example 1]
As the silicon carbide powder, α-silicon carbide (a) having an average particle size of 2 μm was used. The maximum powder particle size was 8 μm or less. And silicon carbide powder (b) having an average particle size of 0.4 μm and a maximum particle size of 4 μm or less is used, and the silicon carbide powders (a) and (b) have an average particle size of 0.05 μm or less as carbon. Carbon black (c) was used.
As the organic binder for molding, an organic material composed of hydroxyethyl methyl cellulose and glycerin and water were used.
The silicon carbide powder was uniformly mixed with carbon black powder, an organic binder and water using a Henschel mixer, and the obtained mixture was kneaded using three rolls. After curing the obtained kneaded product for 24 hours, a round bar having a diameter of 15 mm and a length of 200 mm as shown in the figure was produced using a screw type vacuum extrusion molding machine. The obtained molded product was dried at 50 ° C. and then heated to 120 ° C. to evaporate the water content in the molded product.
The obtained dried molded product was embedded in a metallic silicon powder having a particle size of 0.5 mm and sintered in a carbon tray at 1450 ° C. for 2 hours.

Silicon Carbide Composition Silicon Carbide (a) Average particle size 4 μm 58 wt%
Silicon Carbide (b) Average particle size 0.4 μm 42 wt%

Silicon carbide powder (a) + (b) 70 wt%
Carbon powder 30wt%


Binder composition (total silicon carbide powder (a) + (b) + carbon powder = 100 parts by weight added)
Hydroxyethyl Methyl Cellulose 3.5 parts by weight Glycerin 2.5 parts by weight Water 12 parts by weight

The density of the obtained sintered body was 3.1 g / cm, and it was possible to obtain a dense sintered body with no internal voids. The three-point bending strength of the obtained sintered body is 720 MPa, and the conventional RS-SiC sintered body is about 260 MPa, so that RS-SiC has more than twice the strength of the conventional RS-SiC. An extruded sintered product could be obtained.

[Example 2]
As the silicon carbide powder, β-silicon carbide (a) having an average particle size of 4 μm was used. The maximum powder particle size was 8 μm or less. And silicon carbide powder (b) having an average particle size of 0.4 μm and a maximum particle size of 4 μm or less is used, and the silicon carbide powders (a) and (b) have an average particle size of 0.05 μm or less as carbon. Carbon black (c) was used.
As the organic binder for molding, an organic material composed of hydroxyethyl methyl cellulose and glycerin and water were used.
The silicon carbide powder was uniformly mixed with carbon black powder, an organic binder and water using a Henschel mixer, and the obtained mixture was kneaded using three rolls. After curing the obtained kneaded product for 24 hours, a round bar having a diameter of 15 mm and a length of 200 mm as shown in the figure was produced using a screw type vacuum extrusion molding machine. The obtained molded product was dried at 50 ° C. and then heated to 120 ° C. to evaporate the water content in the molded product.
The obtained dried molded product was embedded in a metallic silicon powder having a particle size of 0.5 mm and sintered in a carbon tray at 1450 ° C. for 2 hours.

Silicon Carbide Composition Silicon Carbide (a) Average particle size 4 μm 60 wt%
Silicon Carbide (b) Average particle size 0.5 μm 40 wt%

Silicon carbide powder (a) + (b) 70 wt%
Carbon powder 30wt%


Binder composition (total silicon carbide powder (a) + (b) + carbon powder = 100 parts by weight added)
Hydroxyethyl Methyl Cellulose 4 parts by weight Glycerin 2.5 parts by weight Water 12 parts by weight

The density of the obtained sintered body was 3.1 g / cm, and it was possible to obtain a dense sintered body with no internal voids. The three-point bending strength of the obtained sintered body is 680 MPa, and the conventional RS-SiC sintered body is about 260 MPa as in Example 1, so that the strength is more than twice that of the conventional RS-SiC. It was possible to obtain an extruded sintered product of RS-SiC having the above.

[Comparative Example 1]
As the silicon carbide powder, β-silicon carbide having an average particle size of 10 μm was used. The maximum powder particle size was 20 μm or less. Carbon black (c) having an average particle size of 0.05 μm or less was used.
As the organic binder for molding, an organic material composed of hydroxyethyl methyl cellulose and glycerin and water were used.
The silicon carbide powder was uniformly mixed with carbon black powder, an organic binder and water using a Henschel mixer, and the obtained mixture was kneaded using three rolls. After curing the obtained kneaded product for 24 hours, a round bar having a diameter of 15 mm and a length of 200 mm as shown in the figure was produced using a screw type vacuum extrusion molding machine. The obtained molded product was dried at 50 ° C. and then heated to 120 ° C. to evaporate the water content in the molded product.
The obtained dried molded product was embedded in a metallic silicon powder having a particle size of 0.5 mm and sintered in a carbon tray at 1450 ° C. for 2 hours.

Silicon Carbide Composition Silicon Carbide (Average Particle Size 10 μm) 100 wt%


Silicon carbide powder (a) + (b) 70 wt%
Carbon powder 30wt%


Binder composition (total silicon carbide powder + carbon powder = 100 parts by weight added)
Hydroxyethyl Methyl Cellulose 4 parts by weight Glycerin 2.5 parts by weight Water 10 parts by weight

The density of the obtained sintered body was 3.0 g / cm, and although no voids could be confirmed inside, the three-point bending strength of the obtained sintered body was 250 MPa, and the conventional RS-SiC. Since the sintered body is about 260 MPa, no improvement in strength can be confirmed as compared with the conventional RS-SiC.

[Comparative Example 2]
As the silicon carbide powder, β-silicon carbide (a) having an average particle size of 4 μm was used. The maximum powder particle size was 8 μm or less. And silicon carbide powder (b) having an average particle size of 0.4 μm and a maximum particle size of 4 μm or less is used, and the silicon carbide powders (a) and (b) have an average particle size of 0.05 μm or less as carbon. Carbon black (c) was used.
As the organic binder for molding, an organic material composed of hydroxyethyl methyl cellulose and glycerin and water were used.
The silicon carbide powder was uniformly mixed with carbon black powder, an organic binder and water using a Henschel mixer, and the obtained mixture was kneaded using three rolls. After curing the obtained kneaded product for 24 hours, a round bar having a diameter of 15 mm and a length of 200 mm as shown in the figure was produced using a screw type vacuum extrusion molding machine. The obtained molded product was dried at 50 ° C. and then heated to 120 ° C. to evaporate the water content in the molded product.
The obtained dried molded product was embedded in a metallic silicon powder having a particle size of 0.5 mm and sintered in a carbon tray at 1450 ° C. for 2 hours.

Silicon Carbide Composition Silicon Carbide (a) Average particle size 4 μm 60 wt%
Silicon Carbide (b) Average particle size 0.5 μm 40 wt%

Silicon Carbide Powder (a) + (b) 90wt%
Carbon powder 10wt%


Binder composition (total silicon carbide powder (a) + (b) + carbon powder = 100 parts by weight added)
Hydroxyethyl Methyl Cellulose 4 parts by weight Glycerin 2.5 parts by weight Water 12 parts by weight

The density of the obtained sintered body was 2.9 g / cm, and voids were formed inside. The three-point bending strength of the obtained sintered body was 230 MPa, and that of the conventional RS-SiC sintered body was about 260 MPa, so that the strength improvement could not be confirmed as compared with the conventional RS-SiC.

[Examples 4 to 9, Comparative Examples 3 to 5]
Furthermore, the experiment was carried out by changing the ratio of the silicon carbide powder and the carbon powder in various ways. The composition of the silicon carbide powder and the carbon powder used is shown at the bottom, and Table 1 shows the results of the sintered body of the extruded product. The kneading conditions, degreasing conditions, and sintering conditions were the same as in Examples 1 to 3. As for the shape of the molded body, the shape shown in FIG. 1 was used.

Silicon Carbide Composition Silicon Carbide (a) Average particle size: 4 μm
Silicon Carbide (b) Average particle size: 0.5 μm

Carbon powder average particle size: 0.03 μm

Organic binder composition table (% by volume)
Hydroxyethyl Methyl Cellulose 4 parts by weight Glycerin 2.5 parts by weight Water 12 parts by weight

In Examples 4 to 9, the density of the sintered body was 3.1 or more, which was dense, and the three-point bending strength was 640 MPa or more, which was a high value. On the other hand, when the ratio of the coarse powder (a) and the fine powder (b) of silicon carbide is out of the range specified by the patent, the bending strength is 250 MPa or less, and the ratio of the fine powder (b) added is large in Comparative Examples 3 and 4. The sintering density was as low as 3.0 g / cm3 or less.

[Examples 10 to 13, Comparative Examples 6 to 8]
Furthermore, the experiment was carried out by changing the particle size of the silicon carbide powder in various ways. The composition of the silicon carbide powder and the carbon powder used is shown at the bottom, and Table 2 shows the results of the sintered body of the extruded product. The kneading conditions, degreasing conditions, and sintering conditions were the same as in Examples 1 to 3. The shape of the molded body was the shape shown in FIG.

Powder material component Silicon carbide (a) Large particle size 60 wt%
Silicon Carbide (b) Small particle size 40 wt%

Silicon Carbide Powder (a) + (b) 90wt%
Carbon powder 30wt%


Organic binder composition table (% by volume)
Hydroxyethyl Methyl Cellulose 4 parts by weight Glycerin 2.5 parts by weight Water 12 parts by weight

In Examples 10 to 13, the density of the sintered body was 3.1 or more, which was dense, and the three-point bending strength was 650 MPa or more, which was a high value. On the other hand, in Comparative Examples 6 to 8 in which the sizes of the coarse powder (a) and the fine powder (b) of silicon carbide were outside the range specified by the patent, the bending strength was 300 MPa or less.

[Examples 14 to 17, Comparative Examples 9 to 12]
Furthermore, the experiment was carried out by changing the addition ratio of the carbon powder in various ways. The composition of the silicon carbide powder and the carbon powder used is shown at the bottom, and Table 1 shows the results of the sintered body of the extruded product. The kneading conditions, degreasing conditions, and sintering conditions were the same as in Examples 1 to 3. The wall thickness of the molded product was the shape shown in FIG.

Silicon Carbide Composition Silicon Carbide (a) Average particle size: 4 μm
Silicon Carbide (b) Average particle size: 0.5 μm

Carbon powder average particle size: 0.03 μm

Organic binder composition table (% by volume)
Hydroxyethyl Methyl Cellulose 4 parts by weight Glycerin 2.5 parts by weight Water 12 parts by weight

By using the present invention, it is possible to obtain an extruded sintered product of a high-strength reaction-sintered silicon carbide sintered body, which has not been obtained in the past. Even if an object that is more than twice as heavy as the conventional one is placed on it as a jig / frame and sintered, it will not bend or break. Especially, by using it for the transfer roller of a continuous furnace, the processing amount per unit time is doubled. Can be increased to a degree.

Claims (7)

Silicon carbide raw material powder, silicon carbide powder (a) having an average particle size of 2 to 5 μm and a maximum particle size of 10 μm or less, and silicon carbide having an average particle size of 0.1 to 0.5 μm and having a maximum particle size of 5 μm or less. Using the silicon powder (b), carbon black (c) having an average particle size of 0.001 to 0.1 μm or less is added as carbon to the silicon carbide powders (a) and (b), and the silicon carbide powders (a) and (b) are added. , (C), an organic binder is added to each powder to prepare a desired molded body, and after drying, metallic silicon is melted in a sintering step and impregnated into the molded body to be composed of silicon and silicon carbide. A method for producing high-strength reaction sintered silicon carbide, which comprises obtaining a composite material. The method for producing high-strength reaction-sintered silicon carbide according to claim 1, wherein in the production method, a desired molded body is produced by casting molding or extrusion molding as a molding method. The claim is characterized in that the addition ratio of the silicon carbide powder (a) and the silicon carbide powder (b) is 50 to 90 wt% for the silicon carbide powder (a) and 10 to 50 wt% for the silicon carbide powder (b). The method for producing high-strength reaction sintered silicon carbide according to claim 1 and claim 2. The invention according to claims 1, 2 and 3, wherein the mixing ratio of carbon black to the total of the silicon carbide powder (a) and the silicon carbide powder (b) is 20 wt% to 40 wt% by weight. A method for producing high-strength reaction sintered silicon carbide. 2. 4. The method for producing high-strength reactive sintered silicon carbide according to 4. The high strength according to claim 1, 2, 3, 4 and 5, wherein the organic binder used in the extrusion molding method contains at least one kind of methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose and polyvinyl alcohol. A method for producing reactive sintered silicon carbide. The invention according to claim 1, 2, 3, 4 and 5, wherein the organic binder used in the casting or extrusion molding method contains at least one kind of methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose and polyvinyl alcohol. A method for producing high-strength reactive sintered silicon carbide.

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