JP2000086374A - Boron carbide-silicon carbide complex carbon material having oxidation resistance, crucible for sintering, crucible for vacuum deposition, die for continuous casting, crucible for melting metal, roller for transporting glass, uniformly heating pipe for annealing steel wire material, jig for high-temperature burning and jig for hot press using the complex carbon material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a B4C-SiC complex carbon material having an economically formed dense SiC layer having excellent oxidation resistance and abrasion resistance at a fixed part (the whole face or a part) of the surface layer part of a carbon base by a simpler method than a CVD method or a CVR method. SOLUTION: This boron carbide-silicon carbide complex carbon material has an outermost surface layer part containing B4C-SiC in 3-20 μm thickness on the surface layer part of a carbon base and forms a SiC-containing layer in >=1 mm thickness on a SiC-containing complex layer. The boron carbide-silicon carbide complex carbon material having oxidation resistance is applied to the whole or part of the surface of a crucible for sintering, a crucible for vacuum deposition, a die for continuous casting, a crucible for melting a metal, a roller for transporting glass, a uniformly heating pipe for annealing a steel wire material, a jig for high-temperature burning and a jig for hot press.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the sintering with excellent boron carbide over silicon carbide composite carbon material (hereinafter B ₄ C-SiC composite carbon material) and its oxidation resistance which can be used in a high temperature atmosphere The present invention relates to a crucible, a crucible for vacuum evaporation, a die for continuous casting, a roller for conveying a glass tube, a soaking tube for annealing a steel wire, a jig for high-temperature firing, and a jig for hot pressing.

[0002]

2. Description of the Related Art Carbon materials have excellent thermal conductivity, abrasion resistance, chemical resistance, and mechanical properties at high temperatures. Widely used for crucibles for vacuum deposition, crucibles for vacuum evaporation, dies for continuous casting, crucibles for molten metal, rollers for conveying glass tubes, soaking tubes for annealing steel wire rods, jigs for high-temperature firing, jigs for hot pressing, etc. However, the carbon substrate alone is liable to be oxidized, and there are problems such as deterioration in strength due to oxidative consumption and short life due to deterioration in accuracy.

[0003] To solve the above problem, the surface of the carbon substrate,
Silicon carbide with excellent oxidation resistance and good compatibility with carbon (hereinafter referred to as S
Means for coating iC) is considered to be effective, and chemical vapor deposition (CVD), conversion (CVR), and the like are well known as general techniques for SiC coating.

[0004] The SiC layer formed by the CVD method is very dense and has excellent gas impermeability, and is effective for improving oxidation resistance. Since they are only attached and have a different coefficient of thermal expansion from the carbon substrate, there is a drawback that when subjected to a thermal shock, peeling of the layers and microcracks occur. Therefore, a carbon base material having a thermal expansion coefficient close to that of SiC must be used. In addition, there is also a problem that it is difficult to partially coat the inside of the hole or to uniformly cover the inside of the hole due to the manufacturing method, and the manufacturing cost is high.

On the other hand, the CVR method is a method in which a Si or SiO gas is reacted with a carbon substrate to convert the surface layer or the entire surface of the substrate into SiC. Unlike the CVD method, the SiC layer is formed chemically. Therefore, the problem such as peeling of the SiC layer can be solved. However, there is also a problem that the production cost is increased due to the production method, which is not so effective in improving the oxidation resistance, and the production cost is high as in the CVD method. Have.

The present invention has been made in view of the above problems, and has as its object the purpose of the present invention is to provide a CVD method or a CV method.
Compared to the R method, a simple SiC layer is excellent in oxidation resistance and abrasion resistance by a simple method and is economically formed on a predetermined portion (entire or partial) of a surface layer portion of a carbon base material. B ₄ CS
iC composite carbon material and crucible for sintering, crucible for vacuum deposition, continuous casting die, crucible for molten metal using the same,
An object of the present invention is to provide a glass tube conveying roller, a steel wire rod annealing tube, a high-temperature firing jig, and a hot pressing jig.

[0007]

The present inventors first applied a slurry containing Si powder, B ₄ C powder, a thermoplastic resin, and a solvent for the resin to the surface of a carbonaceous substrate, and dried the slurry. after, by heat treatment at 1500 ° C. or higher in a non-oxidizing atmosphere, dense and oxidation resistance, it has proposed an excellent novel B ₄ C-SiC composite carbon material and a method for manufacturing the wear resistance (JP-7 No. 144982). The present inventors have subsequently found out, as a result of trial and error, an excellent oxidation resistance, a specific composition ratio necessary for having abrasion resistance, and the thickness of each layer, thereby completing the present invention. .

According to the first aspect of the present invention, a Si layer having a thickness of 1 mm or more is formed on a predetermined portion (whole or part) of a surface portion of a carbon base material.
A C-containing composite layer having a thickness of 1 to
An oxidation-resistant boron carbide-silicon carbide composite carbon material comprising an outermost surface layer containing 50 μm of B ₄ C—SiC.

According to a second aspect of the present invention, in the first aspect, the composition ratio of the two components of B ₄ C—SiC in the outermost surface layer is B ₄ C
2. The boron carbide-silicon carbide composite carbon material according to claim 1, wherein the composite material is formed of / SiC = 1 to 22/78 to 99. 3.

A third aspect of the present invention is the boron carbide-silicon carbide composite carbon material according to the first aspect, wherein the silicon carbide conversion rate in the SiC-containing composite layer is substantially uniform in a depth direction. .

According to a fourth aspect of the present invention, there is provided a sintering crucible comprising a part or all of the surface layer of the composite carbon material according to any one of the first to third aspects.

According to a fifth aspect of the present invention, there is provided a crucible for vacuum deposition using a part or all of the surface layer of the composite carbon material according to any one of the first to third aspects.

According to a sixth aspect of the present invention, there is provided a continuous casting die using a part or all of the surface layer portion of the composite carbon material according to any one of the first to third aspects.

According to a seventh aspect of the present invention, there is provided a molten metal crucible using a part or all of the surface layer of the composite carbon material according to any one of the first to third aspects.

[0015] The invention of claim 8 is a glass tube transporting roller using a part or all of the surface layer portion of the composite carbon material according to any one of claims 1 to 3.

According to a ninth aspect of the present invention, there is provided a soaking tube for annealing a steel wire rod, wherein the composite carbon material according to any one of the first to third aspects is used for part or all of a surface layer.

A tenth aspect of the present invention is a high-temperature firing jig using the composite carbon material according to any one of the first to third aspects for part or all of a surface layer portion.

According to an eleventh aspect of the present invention, there is provided a hot press jig using the composite carbon material according to any one of the first to third aspects for a part or all of a surface layer portion.

The outermost surface layer portion of the B ₄ C—SiC composite carbon material of the present invention must contain at least the B ₄ C component, and is necessarily homogeneously mixed with the surrounding SiC. It does not need to be distributed in a state. B ₄ C in the outermost surface layer is easily oxidized, and forms B ₂ O ₃ in a high-temperature oxidizing atmosphere. By forming vitreous B ₂ O ₃ , the eutectic temperature with Si decreases. finally SiO ₂ -B ₂ O ₃ -based glassy is formed, the glass further covers the outermost surface layer, will form a dense oxide protective coating. Therefore, a state in which a dense oxide protective film having excellent gas impermeability is formed on the outermost layer is obtained.

If the outermost layer having such a function is too thick, cracks and chippings are likely to occur. Therefore, the outermost layer is formed to have a thickness of 3 to 20 μm, preferably 5 to 15 μm. By setting the thickness of the outermost surface layer in this way, the oxidation resistance effect of B ₂ O ₃ can be sufficiently exerted, while at the same time eliminating unnecessary manufacturing costs for forming the outermost surface layer more than necessary. In addition, an increase in product cost can be prevented.

SiC and B_FourThe composition ratio of C is
78-99% by weight, B_FourC component is 1 to 22% by weight
Some are desirable. Binary compositions (Si
C, B _FourThe SiC layer having the outermost surface layer portion containing C) is shaped
Is most efficiently provided with oxidation resistance.
B_FourBecause it can be a C-SiC composite carbon material
It is. Furthermore, B_FourC is preferably 3 to 20% by weight.
New In promoting the formation of the SiC-containing composite layer,
3% by weight or more is preferable, and the outermost surface layer is
When oxidized, the outermost layer_Two─B_Two O_Three
B only forms vitreous system_FourTen if C exists
Minutes, considering this point, the upper limit is 20% by weight.
This is because the following is preferable.

The SiC-containing composite layer following the outermost surface layer described above needs to contain at least SiC. This S
The iC-containing composite layer imparts oxidation resistance. Even if the outermost surface layer portion of the SiO ₂ ─B ₂ O ₃ vitreous oxidation protective film disappears, the oxidation progress of the carbonaceous substrate is suppressed by the SiC of the SiC-containing composite layer. Therefore, the SiC-containing composite layer having such a function needs to have a thickness of 1 mm or more, and the SiC-C layer formed with the thickness of 1 mm or more is formed almost uniformly in the thickness direction. desirable. This is because the oxidation resistance in the thickness direction does not change. Here, “substantially uniform in the thickness direction” means that the ratio of the silicidation ratio at the shallow portion to the deep portion of the SiC-containing composite layer is 0.8.
It is within.

Such a deep and uniform SiC layer can be easily formed for the following reasons. B contained in the outermost layer surface
₄ C does not penetrate into the interior base material, in some action, for example, catalytic activity, there is work to infiltrate Si into the carbon base material,
As a result, Si diffuses in the carbon substrate in the depth direction by 1 mm or more, so that a SiC layer having a uniform thickness of 1 mm or more can be formed in the SiC-containing composite layer.

The carbon substrate used in the present invention is not particularly limited, and is a carbon material consisting essentially of carbon or a graphitized product containing carbon as a main component, for example, a high density isotropic graphite material. It is desirable to use a carbon substrate obtained by processing a carbon substrate having an average pore radius of 1 μm or more measured by a mercury intrusion method into a product shape.

When a carbon substrate having an average pore radius smaller than 1 μm is used, when a slurry in which Si and B ₄ C are mixed is applied to the carbon substrate, the slurry penetrates into the fine pores of the carbon substrate. It is not so desirable because it becomes difficult. The upper limit of the average pore radius of the carbon substrate is not particularly limited, and the carbon substrate having a large average pore radius such as a carbon fiber reinforced carbon composite material is such that the slurry permeates deep inside the carbon substrate. After heat treatment, almost the whole is composited.

First, a slurry comprising an Si powder having an average particle size of 10 to 100 μm, a B ₄ C powder having an average particle size of 5 to 100 μm, a thermoplastic resin and a solvent for the resin is prepared. As the thermoplastic resin used here, a resin having a high film-forming property and a low residual carbon ratio is used. For example, a resin selected from polyamideimide, polyvinyl alcohol, and a polyamide resin is particularly preferable. Among them, polyamide is more preferable, and is used by dissolving it in a solvent such as dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methyl-2-pyrrolidone and the like.

However, when a resin having a high residual carbon ratio, for example, a thermosetting resin such as furfuryl alcohol or phenol resin is used as the resin, the resin will not adhere to the surface of the carbon substrate when a high-temperature heat treatment is performed in a later step. Carbide, Si and B
It is not preferable because the reaction product with ₄ C is sometimes fixed and cannot be easily removed.

The mixing ratio when mixing the Si powder and the B ₄ C powder is desirably 3 to 20% by weight of the B ₄ C powder with respect to 80 to 97% by weight of the Si powder. If the B ₄ C powder is less than 3% by weight, the effect of mixing the B ₄ C powder is small. Specifically, by mixing B ₄ C powder,
_Some action by ₄ C, for example, a catalytic action effect appears. That is, when the content is less than 3% by weight, this effect is not so much exhibited, and the molten Si does not completely penetrate into the pores in the carbon substrate even after the high-temperature heat treatment, and is fixed as metallic Si on the surface of the carbon substrate after cooling. Will remain. Conversely, when the content is 3% by weight or more, the molten Si penetrates deeply into the pores,
This is because the reaction with the carbon base material proceeds to form SiC, and the effect of easily forming a uniform SiC layer in the depth direction with the thickness according to claim 1 is obtained.

In this case, there is no residue as metal Si on the surface of the carbon substrate, and the carbide of the resin used, Si
Although the residue of the components C and B ₄ C remains, in the present invention, it is sufficient to add the B ₄ C powder to such an extent that the residue can be left. Therefore, the upper limit of the B ₄ C powder is about 20% by weight. desirable. Of course, according to the required specifications, more than 20% of B ₄ C powder is added to form a deeper SiC layer to further improve oxidation resistance and abrasion resistance and other properties. Products.

The slurry prepared as described above is applied to the entire surface or a necessary portion by a suitable means such as brushing and spatula coating. Moreover, you may immerse in a slurry. The thickness applied at this time can be any thickness, but is preferably 1 to 2 mm from the surface of the carbon substrate. 1
If it is less than 00 μm, the formation of the SiC layer becomes shallow, which is not preferable. Thereafter, by drying from about 80 ° C. to 200 ° C. for 5 hours, the solvent is volatilized, and the resin is completely cured. The material thus obtained is subjected to a high-temperature heat treatment in a vacuum of 10 Torr or less. The heating rate is 400 ° C./hour, and the temperature is maintained at about 1600 to 1800 ° C. for 1 hour. The heating means is not particularly limited, and may be performed by an appropriate means.
By this operation, the Si component is melted, penetrates into the pores of the carbon substrate through the carbonized layer of the resin, reacts with the carbon, and reacts with the carbon.
Convert to C.

After obtaining the above series of treatments, finally, the surface portion of the carbon base material corresponding to the portion to which the slurry was applied is S
A B ₄ C—S structure having a structure in which a dense outermost layer containing a B ₄ C component is formed on the surface while being converted into an iC layer.
An iC composite carbon material can be obtained.

In the case of a B ₄ C—SiC composite carbon material having such a structure, even if it is oxidized at a high temperature, a melt of SiO ₂ ─B ₂ O ₃ system glass is generated on the outermost surface layer, An object enters and covers the voids in the outermost surface layer, and a new oxidation protective film is formed. This oxidation protective film functions to suppress the subsequent oxidation. As a result, Si obtained by the CVD method
A dense protective film having excellent gas impermeability comparable to the C film can be formed. Moreover, in the case of the B ₄ C—SiC composite carbon material according to the present invention, it is easy to form the SiC layer on a part or the whole of the surface layer of the carbon base material, and as a result, it has excellent oxide resistance. It is possible to provide a carbon composite material in which a SiC layer is economically formed at any given site.

A specific application example using the B ₄ C—SiC composite carbon material according to the present invention will be described below.

First, an example of application to a sintering crucible will be described. Conventionally, the carbon substrate of sintering crucibles is mainly made of isotropic high-density graphite in a reduction furnace, but when exchanging sintered products, the crucible surface is exposed to the atmosphere, Atmospheric moisture and the like are adsorbed on the carbon substrate. Also, a small amount of water is generated in the reduction furnace due to the reaction between hydrogen gas and oxygen. There is a problem that the water or the like becomes an oxidizing source, oxidizes the carbon material, and the gas generated at that time reacts with the sintered product in the crucible, thereby contaminating the processed product with impurities.

These problems can be solved by applying the B ₄ C—SiC composite carbon material of the present invention to all or a part of the surface of the sintering crucible. Sintering crucible 1 comprises a crucible 2 and the upper lid 3 has a shape shown in FIG. 1, the outer surface in direct contact with the air, formed by B ₄ C-SiC composite carbon material. Specifically, the mating surface 2c of the crucible side 2a, the bottom surface 2b and the upper lid 3, and the upper surface 3a and the side 3b of the upper lid 3
And the mating surface 3c of the crucible 2 with the B ₄ C-
It is formed of a SiC composite carbon material.

Since the outer surfaces 2a, 2b, 2c of the crucible 1 and the outer surfaces 3a, 3b, 3c of the upper lid are formed of a B ₄ C—SiC composite carbon material which is a gas-impermeable oxidation protective film, The effect of extending the life of the crucible itself, preventing intrusion of impurity gas from the outside of the crucible, and maintaining the purity of the sintering metal powder inside the crucible can be obtained.

Next, an example of application to a crucible for vacuum evaporation will be described. Conventionally, crucibles for vacuum deposition are usually pitch impregnated so that molten metal does not penetrate into the pores of the carbon substrate,
A carbon material obtained by repeating steps such as firing is used. For example, in the case of a metal that reacts with a carbon material such as aluminum, treatments such as impregnation with a salt solution of an inorganic material and calcination are further performed, but there is a problem that the reaction with the metal cannot be completely prevented.

These problems can be solved by applying the B ₄ C—SiC composite carbon material of the present invention to all or part of the surface of the crucible for vacuum evaporation, particularly to the inner surface. As shown in FIG. 2, the crucible for vacuum evaporation 11 of the present invention has a bulk density of 1.90 g / cm ³ or more and a specific resistance of 1200 μΩ as a carbon substrate.
cm or less of isotropic graphite, after machining the graphite into the shape shown in the figure, brushing the slurry according to the present invention on the crucible inner surface 11a which is a surface in contact with the molten metal for vapor deposition,
It is formed by forming a B ₄ C—SiC composite carbon material. The crucible for vacuum evaporation obtained by the present invention has improved oxidation resistance, can suppress the reaction with the molten metal for evaporation in the crucible, and can improve the life of the crucible.

Next, an example of application to a continuous casting member will be described. As a material for continuous casting, carbon substrates with excellent physical properties such as high-temperature mechanical properties, thermal conductivity, and lubricity have been used in many cases, but carbon substrates alone are extremely oxidized and wear-resistant. However, there is a drawback that the life is very short, for example, the strength is deteriorated due to oxidative consumption, leading to early breakage.

These problems can be solved by applying the B ₄ C—SiC composite carbon material of the present invention to all or a part of the surface of the continuous casting member, particularly to the casting surface. As shown in FIG. 3, the continuous casting member 21 has a bulk density of 1.75 g / cm ³ or more, an average pore radius of 2.0 μm or less, and a bending strength of 400 kgf / cm ² or more as a carbon base material. Isotropic graphite having a thermal conductivity of 80 kcal / hrm ° C or more,
It is processed into split dies 22 and 23. The average pore radius is a value measured by a mercury intrusion method (a contact angle of 1 between mercury and a sample).
41.3 °, half the cumulative pore volume at a maximum pressure of 1000 kg / cm ² ). Next, the slurry is performed only brushing the casting surface 25 in contact with the molten metal and ingot 24 to form a B ₄ C-SiC composite carbon material according to the invention only the partial.

By the way, the surface immediately after the composite treatment is rougher than the surface of the carbon substrate before the treatment, and when such a surface is used as a die, the cooled and solidified ingot is used. When it is pulled out intermittently, a large frictional force acts between them, and the inner surface of the die is damaged by the ingot,
This is because the scratch may be transferred to the ingot and roughen the surface of the ingot. Therefore, the inner surface of the continuous casting member is always mirror-finished. There is no particular limitation on the mirror finishing means, and examples thereof include a wet polishing method using die abrasive grains. The final polishing degree may be 0.75 μm or less in JIS average surface roughness (Ra). The heat conductivity of the mirror-finished surface (SiC conversion layer) is approximately 50 kc
If al / hrm ° C is secured, the cooling and solidifying ability of the metal is sufficient.

As described above, the member for continuous casting obtained by the present invention is characterized in that the portion of the carbon substrate in contact with the molten metal and the ingot is S
After the coating layer of iC is formed deeper, a structure in which B ₄ C-SiC composite layer subjected to mirror surface processing is provided. Therefore, by covering the surface of the carbon substrate with B ₄ C-SiC composite layer, the improvement object of the oxidation resistance and wear resistance are of the present invention, can in some reliably effective. As a result, the life of the continuous casting member can be further extended, and at the same time, an ingot with a smooth casting surface can be stably and reliably produced for a long time.

Next, an example of application to a crucible for molten metal will be described. Crucibles for molten metal are often made of isotropic high-density graphite as a carbon substrate, but most of them are used in normal pressure atmosphere, so they are oxidized by the atmosphere or the inside of the crucible reacts with the molten metal. There is such a problem.

These problems can be solved by applying the B ₄ C—SiC composite carbon material of the present invention to all or part of the surface of the molten metal crucible, particularly to the inner surface. As shown in FIG. 4, the molten metal crucible 31 of the present invention is obtained by processing a carbon base material into the shape shown in the drawing, and forming a B ₄ C—SiC composite carbon material according to the present invention on the crucible inner surface 32 in contact with the molten metal. Be done.

By forming the CB ₄ C—SiC composite layer according to the present invention on the inner surface of the crucible, the reaction with the molten metal can be suppressed, and the life of the crucible can be extended.

Next, an example of application to a glass tube conveying roller will be described. Although cast iron was used for the glass tube transport roller, there were problems in that the glass tube, which is a product, was damaged, and that the shaping accuracy was reduced due to oxidative deterioration. Therefore, carbon materials have been used in place of cast iron in order to prevent damage to the product.However, carbon materials alone have problems such as deterioration in strength due to oxidative consumption and deterioration in shaping accuracy of glass tubes. There is a demand for a carbon material having excellent oxidation resistance.

These problems can be solved by applying the B ₄ C—SiC composite carbon material of the present invention to all or part of the surface of the glass tube transporting roller, particularly to the casting surface. As shown in FIG. 5, the glass tube transporting roller 41 of the present invention includes:
The carbon base material is processed into the shape shown in the figure in which two disks are attached to one shaft, and preferably, the B ₄ C-
An SiC composite carbon material is formed.

By forming the B ₄ C—SiC composite layer on the entire surface, the oxidation of the surface layer by the glass is suppressed, so that the deterioration of the shaping accuracy due to the oxidation can be prevented and the life of the roller can be extended.

Next, an example of application to a soaking tube for annealing a steel wire rod will be described. Conventionally, in the process of annealing steel wire,
The wire rod has been moved and processed in a soaking tube made of stainless steel alone with sliding. At that time, there are many problems that the product wire is damaged due to welding between the stainless steel soaking tube and the wire, and as a preventive measure, a carbon tube is inserted into the stainless steel soaking tube to prevent welding of the wire. However, in this case, problems such as oxidative consumption of the carbon tube and carburization of the wire material newly arise, and a material for a soaking tube for annealing a steel wire material instead of the carbon material is demanded.

The B ₄ C—SiC composite carbon material of the present invention is
It is formed on the entire inner surface of the carbon tube inserted into the soaking tube for annealing a steel wire rod. FIG. 6 is a schematic cross-sectional view of an example of a soaking tube for annealing a steel wire rod. By forming the B ₄ C—SiC composite layer of the present invention on the inner surface, preferably the entire surface, of the carbon tube 52,
The oxidation resistance is improved and the carbon tube 52 of the steel wire 53 is improved.
Welding can be prevented, and in addition, carburization of the steel wire rod 53 can be prevented. Further, the excellent lubricity of the product of the present invention prevents the wire from being damaged, thereby stabilizing the quality of the steel wire and greatly improving the yield.

Next, an example of application to a high-temperature firing jig will be described. The high-temperature firing jig is a jig used in a high-temperature atmosphere such as a firing furnace shelf, a metal brazing jig, and the like, and a graphite material or a stainless steel material has been used. However, as described above, when a graphite material is used in a high-temperature atmosphere, there is a problem of oxidation and a problem of carburization of a treated surface, and in the case of a stainless steel material, the shape changes with time due to thermal distortion and the like. There were problems such as deterioration of the accuracy of product dimensions.

The B ₄ C—SiC composite material of the present invention is formed at a portion in contact with the treated surface under a high temperature atmosphere. Thus, the above problem can be solved, and a carbon high-temperature firing jig having no change in shape over time and excellent in oxidation resistance can be obtained.

Next, an example of application to a hot press jig will be described. Dies used for hot pressing,
For the jigs such as the upper and lower punches, graphite is often used conventionally because of the excellent high-temperature characteristics of graphite. In that case,
It was necessary to apply a release agent to the surface of the jig in order to prevent welding with the processed product. This release agent causes impurities to be mixed into the processed product.

Therefore, by forming the B ₄ C—SiC composite material of the present invention on the upper and lower punches and the die surface of the hot press, it is possible to prevent the surface from being oxidized and to mix impurities into the treated surface. And the amount of release agent can be minimized. As shown in FIG. 7, the jig for hot pressing is an integrated or split die 6.
1 and upper and lower punches 62 and 63.

[0055]

The present invention will be specifically described below with reference to examples. (Example 1) As carbon substrate, bulk density 1.77 g / cm
³ , average pore radius is 1.5μm, bending strength is 400kg
f / cm ² isotropic graphite (manufactured by Toyo Tanso Co., Ltd.)
A crucible having the shape shown in FIG. An 8% solution of polyvinyl alcohol (manufactured by Nippon Gosei Sangyo Co., Ltd.) as a binder was used as a dispersion medium. Silicon powder (manufactured by Wako Pure Chemical Industries, Ltd., average particle size: 40 μm) and boron carbide powder (manufactured by Kyoritsu Ceramics Co., Ltd., average particle size: 20 μm) are mixed in a weight ratio of 80:20, and mixed and dispersed in a dispersion medium. This was made into a slurry.

The slurry is applied to a crucible, which is an outer surface directly in contact with the atmosphere, and a predetermined portion of an upper lid by a brush, and then the solvent is evaporated at 200 ° C. in a dryer.
Further, in a 3 Torr nitrogen gas atmosphere, the temperature was raised to 1600 ° C. for 4 hours in a vacuum heating furnace, held for 1 hour, cooled, and taken out. The thickness of the silicified portion was 3 mm.
The outermost surface layer containing B ₄ C was 10 μm. In addition, the ratio of the silicidation rate at the shallow part of the silicide part to that at the deep part
0.8.

(Comparative Example 1) Using isotropic graphite (manufactured by Toyo Tanso Co., Ltd.) of the same material as in Example 1, it was processed into the shape shown in FIG. 1 to obtain a crucible for sintering for testing.

Using the test sintering crucibles obtained in Example 1 and Comparative Example 1, a sintering test of tungsten carbide was performed in a state where graphite powder and tungsten powder were mixed as sintering metals.

Example 2 As a carbon substrate, a bulk density of 1.
9 g / cm ³ , an average pore radius of 0.4 μm, a bending strength of 650 kgf / cm ² and a specific resistance of 1200 μΩcm or less isotropic graphite (manufactured by Toyo Tanso Co., Ltd.) were added to a crucible having the shape shown in FIG. Processed, crucible inner surface 6 in contact with molten metal
In accordance with the same procedure as in Example 1, a crucible for test vacuum deposition which was subjected to a silicidation treatment was obtained. The thickness of the silicified part is 2m
m. The outermost surface layer containing B ₄ C was 8 μm. In addition, the ratio of the silicidation rate at the shallow portion of the silicide portion to that at the deep portion was 0.8.

(Comparative Example 2) Using isotropic graphite (manufactured by Toyo Tanso Co., Ltd.) of the same material as in Example 2, it was processed into the shape shown in FIG. 2 to obtain a crucible for vacuum deposition for testing.

Using the crucible for test vacuum evaporation obtained in Example 2 and Comparative Example 2, a vacuum evaporation test was conducted using aluminum as the molten metal for evaporation.

(Example 3) As a carbon substrate, a bulk density of 1.
An isotropic graphite (manufactured by Toyo Tanso Co., Ltd.) having an average pore radius of 87 g / cm ³ , an average pore radius of 1.5 μm, a bending strength of 650 kgf / cm ² and a thermal conductivity of 120 kcal / hm ° C. This was processed into a rectangular die, and a continuous casting die for test was prepared by subjecting the casting surface to a silicidation treatment in the same procedure as in Example 1. The thickness of the silicified portion was 2 mm. The surface was polished to Ra = 0.75 μm using an abrasive to obtain a continuous casting die for testing.

Comparative Example 3 An isotropic graphite base material (manufactured by Toyo Tanso Co., Ltd.) of the same material and the same shape as in Example 3 was subjected to the same polishing treatment as in Example 3 for the test. A continuous casting die was obtained.

Using the crucible for continuous casting for test obtained in Example 3 and Comparative Example 3, a continuous casting test was performed using a copper alloy.

Example 4 As a carbon substrate, a bulk density of 1.
82 g / cm ³ , average pore radius 1 μm, flexural strength 7
80 kgf / cm ² isotropic graphite (manufactured by Toyo Tanso Co., Ltd.)
Is processed into a crucible having the shape shown in FIG. 4, and on the inner surface of the crucible in contact with the molten metal, in the same procedure as in Example 1,
A crucible for a molten metal for a test subjected to a silicidation treatment was obtained. The thickness of the silicified portion was 3 mm. The outermost surface layer containing B ₄ C was 8 μm. In addition, the ratio of the silicidation rate at the shallow portion of the silicide portion to that at the deep portion was 0.8.

(Comparative Example 4) Using isotropic graphite (manufactured by Toyo Tanso Co., Ltd.) of the same material as in Example 4, it was worked into the shape shown in FIG. 4 to obtain a crucible for a molten metal for testing.

Using the crucible for molten metal for test obtained in Example 4 and Comparative Example 4, iron was dissolved and a melting test was performed.

Example 5 As a carbon substrate, a bulk density of 1.
90 g / cm ³ , an average pore radius of 0.2 μm, a bending strength of 950 kgf / cm ² , isotropic graphite (Toyo Carbon Co., Ltd.)
Was processed into the shape shown in FIG. 5, and a silicification-treated glass transporting roller was obtained in the same procedure as in Example 1 over the entire surface. The thickness of the silicified portion was 1 mm. The outermost surface layer containing B ₄ C was 10 μm.

(Comparative Example 5) Using isotropic graphite (manufactured by Toyo Tanso Co., Ltd.) of the same material as in Example 5, it was processed into the shape shown in FIG. 5 to obtain a roller for transporting a glass tube for testing. .

(Example 6) As a carbon substrate, a bulk density of 1.
FIG. 6 shows isotropic graphite (manufactured by Toyo Tanso Co., Ltd.) having 82 g / cm ³ , an average pore radius of 1.5 μm, a bending strength of 550 kgf / cm ² and a thermal conductivity of 120 kcal / hm ° C. A tube having an outer diameter of 40 mm and a wall thickness of 5 mm was processed, and the entire surface thereof was subjected to the same procedure as in Example 1 to obtain a test steel wire rod soaking tube for silicidation. The thickness of silicide is 2mm
Met.

(Comparative Example 6) An isotropic graphite substrate (manufactured by Toyo Tanso Co., Ltd.) of the same material as in Example 6 was used, and an outer diameter of 40 mm as shown in FIG. The tube was processed into a tube having a thickness of 5 mm to obtain a soaking tube for annealing a test steel wire rod.

(Embodiment 7) As an example of a jig for high-temperature firing, a jig for high-temperature firing will be described using a shelf plate for a firing furnace as an example. 1.77 g / c bulk density as carbon substrate
m ³ , average pore radius 1.5 μm, flexural strength 400 k
gf / cm ² of isotropic graphite (manufactured by Toyo Tanso Co., Ltd.)
It was processed into a shape of 50 × 350 × 4.0 mm, and silicidation was performed on the entire surface in the same procedure as in Example 1 to obtain a shelf for a test firing furnace. 2.0mm thickness of silicide
Met. The outermost surface layer containing B ₄ C was 10 μm.

(Comparative Example 7) Using isotropic graphite (manufactured by Toyo Tanso Co., Ltd.) of the same material as in Example 7, processed into the same shape as in Example 7, and obtained a shelf plate for a firing furnace for testing. Was.

Example 8 As a carbon substrate, a bulk density of 1.
An isotropic graphite (manufactured by Toyo Tanso Co., Ltd.) having 85 g / cm ³ , an average pore radius of 1.7 μm, a bending strength of 530 kgf / cm ² , and a thermal conductivity of 110 kcal / hm ° C. was manufactured by using the shape shown in FIG. A hot press die and a die for silicification were obtained in the same procedure as in Example 1. The thickness of the silicified part is 3.0
mm. The outermost surface layer containing B ₄ C was 10 μm.

Comparative Example 8 An isotropic graphite substrate (manufactured by Toyo Tanso Co., Ltd.) of the same material and the same shape as in Example 8 was used to obtain a test hot press die.

Each of the test products obtained in Examples 1 to 8 and Comparative Examples 1 to 8 was subjected to a test suitable for each use. Table 1 shows the test results.

[0077]

[Table 1]

As is clear from Table 1, Examples 1 to 8
Can withstand the production of a good product for a long time with respect to those of Comparative Examples 1 to 8.

[0079]

According to the present invention, the carbonaceous substrate, the boron carbide-silicon carbide-composite carbon layer having a thickness of 1 to 50 μm on the outermost surface layer, and the SiC-containing composite layer have a thickness of It is based on forming an oxidation-resistant boron carbide-silicon carbide composite carbon material in which a silicon carbide-containing layer having a thickness of 1 mm or more is formed, and includes a conventional CVD method, a conversion method, a sintering method, and the like. Unlike, relatively easy to form anywhere and overall surface portion of the carbonaceous substrate, dense equivalent to the coating layer obtained by a CVD method, B ₄ C having excellent oxidation resistance
—SiC composite carbon material. In the B ₄ C—SiC composite carbon material of the present invention, the SiC / B ₄ C ratio (% by weight) of the outermost surface layer is set as follows: SiC / B ₄ C = 78.
９９99/1 to ２２22, and a uniform layer can be formed in the depth direction. Therefore, the above-mentioned effects can be surely exerted while considering economy.

Further, according to the present invention, the B ₄ C—SiC composite carbon material according to the present invention is formed on the outer surface of a sintering crucible, so that the outer surface of the crucible is removed. By coating with a protective film, the life of the crucible itself can be prolonged, the effect of preventing the intrusion of impurity gas from the outside of the crucible, and the effect of maintaining the purity of the sintering metal inside the crucible can be obtained. .

The invention according to claim 5 is characterized in that the B ₄ C—SiC composite carbon material according to the present invention is formed on the inner surface of a crucible as a crucible for vacuum vapor deposition, so that the oxidation resistance is improved, and Can be suppressed from reacting with the molten metal for vapor deposition, and the life can be prolonged.

The invention according to claim 6 is to form the B ₄ C—SiC composite carbon material according to the present invention as a continuous casting die on the casting surface in contact with the molten metal and the ingot on the inner surface of the die. is there. As a result, the improvement of the oxidation resistance and wear resistance of the continuous casting member is ensured, and the life of the continuous casting member can be further extended, and at the same time, the cooling and solidifying ability of the metal is sufficient. As a result, an ingot with a smooth casting surface can be stably and reliably produced for a long time.

The invention according to claim 7 is characterized in that the B ₄ C—SiC composite carbon material according to the present invention is formed on the inner surface of a crucible as a crucible for molten metal, so that oxidation resistance is improved and molten metal is improved. Reaction can be suppressed, and the effect of extending the life can be obtained.

Further, according to the invention of claim 8, the B ₄ C—SiC composite carbon material according to the present invention is formed on the entire surface of the glass tube transporting roller, thereby deteriorating the strength due to oxidative consumption and shaping the glass tube. It is possible to prevent the deterioration of accuracy, and it is possible to extend the life of the roller in accordance with the effect of improving the shaping accuracy of the glass tube.

Further, according to the ninth aspect of the present invention, the B ₄ C—SiC composite carbon material according to the present invention is formed on the entire surface of the soaking tube for annealing a steel wire, thereby welding the steel wire to the soaking tube. In addition to the above, the excellent lubricity of the product of the present invention prevents the wire rod from being damaged, thereby stabilizing the quality of the steel wire rod and improving the yield.

The invention according to claim 10 provides a jig for high-temperature firing of the B ₄ C—SiC composite carbon material according to the present invention,
For example, by forming a jig for metal brazing or a jig for heat treatment used in a high-temperature atmosphere such as a shelf plate for a firing furnace, the carburizing of the processed product is suppressed, and the The shape change can be suppressed, and the product dimensional accuracy of the processed product can be kept constant.

Further, according to the invention, the B ₄ C—SiC composite carbon material according to the present invention is formed on a hot press jig, thereby suppressing oxidation of the jig and forming a die or a punch. It is excellent in the releasability between the product and the processed product, and the use of the release agent can be minimized.

[Brief description of the drawings]

FIG. 1 is a schematic view of a sintering crucible used in Examples.

FIG. 2 is a schematic view of a crucible for vacuum evaporation used in Examples.

FIG. 3 is a schematic perspective view of a continuous casting die used in Examples.

FIG. 4 is a schematic view of a crucible for melting metal used in Examples.

FIG. 5 is a schematic view of a glass tube transport roller used in the examples.

FIG. 6 is a schematic view of a soaking tube for annealing a steel wire rod used in an example.

FIG. 7 is a schematic diagram of a hot press jig used in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crucible for sintering 11 Crucible for vacuum evaporation 21 Die for continuous casting 31 Crucible for melting metal 41 Roller for conveying glass tube 52 Heat equalizing tube for annealing steel wire rod 61 Dice for hot pressing

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C21D 9/52 103 C21D 9/52 103A C23C 14/24 C23C 14/24 A (72) Inventor Takashi Takatsu Kagawa (72) Inventor Masatoyo Okazaki, Onohara-cho, Mitoyo-gun, Kagawa Prefecture Toyo Carbon Co., Ltd. Co., Ltd. (54) [Title of the Invention] Oxidation-resistant boron carbide-silicon carbide composite carbon material and crucible for sintering, crucible for vacuum deposition, continuous casting die, crucible for molten metal, glass using the same Roller for pipe transfer, soaking tube for annealing steel wire, jig for high temperature firing, jig for hot press

Claims (11)

[Claims] 1. A boron carbide-silicon carbide-containing composite layer having a thickness of 3 to 20 μm on which a silicon carbide-containing composite layer having a thickness of 1 mm or more is formed on a surface layer of a carbonaceous substrate. An oxidation-resistant boron carbide-silicon carbide composite carbon material characterized by being formed with: 2. The composition ratio (% by weight) of the two components of boron carbide and silicon carbide in the boron carbide-silicon carbide-containing composite layer is silicon carbide / boron carbide = 78 to 99 /
The boron carbide-silicon carbide composite carbon material according to claim 1, which is 1 to 22. 3. The boron carbide-silicon carbide composite carbon material according to claim 1, wherein the silicon carbide conversion ratio in the silicon carbide-containing composite layer is substantially uniform in a depth direction. 4. A sintering crucible using the composite carbon material according to any one of claims 1 to 3 for a part or all of a surface layer portion. 5. A crucible for vacuum vapor deposition using the composite carbon material according to claim 1 for a part or all of a surface layer portion. 6. A continuous casting die using the composite carbon material according to claim 1 for a part or all of a surface layer portion. 7. A molten metal crucible using the composite carbon material according to claim 1 for a part or all of a surface layer portion. 8. A roller for transporting a glass tube, wherein the composite carbon material according to claim 1 is used for a part or all of a surface layer portion. 9. A soaking tube for annealing a steel wire rod, wherein the composite carbon material according to claim 1 is used for a part or all of a surface layer portion. 10. A high-temperature firing jig using the composite carbon material according to claim 1 for part or all of a surface layer. 11. A hot press jig using the composite carbon material according to claim 1 for a part or all of a surface layer portion.