JPH10287470A - Firing jig containing carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon fiber-containing firing jig enhanced in the dispersibility of carbon fibers, increased in the binding strength of the carbon fibers to a matrix, improved in the strength and toughness of raw material and in the life of the jig, and prevented in generation of cracks, by using a graphite and ceramic composite material comprising a graphitic raw material, SiC, SiO2 , BN as another component, and the carbon fibers. SOLUTION: This carbon fiber-containing firing jig comprises a graphite and ceramic composite material comprising 5-20 wt.% of a graphite raw material, 10-70 wt.% of SiC, 1-30 wt.% of SiO2 , 1-5 wt.% of BN and 0.1-2 wt.% of carbon fibers. The dispersing of the carbon fibers whose surfaces are coated with a thermosetting resin improves the binding force of the fibers on their surfaces, enhances their binding strength to the matrix, expresses the large pulling resistance of the fibers and improves the strength and breaking toughness of the raw material. The carbon fibers to be compounded comprise either of PAN-based carbon fibers and pitch-based carbon fibers, and has a length of 2-30 mm. The coating resin is used for maintaining the binding force also after calcination, and the graphitic raw material comprises natural graphite, artificial graphite or kish graphite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon / ceramic composite material containing carbon fibers which can be used as a jig for reduction firing and non-oxidation firing.

[Prior art]

Conventionally, graphite materials, ceramic materials such as silicon carbide, silicon nitride, and alumina, and graphite-ceramic composite materials are used as firing jigs used in reduction firing and non-oxidation firing, and in particular, as sheath materials for firing. ing. Graphite materials are excellent in heat resistance, non-reactivity, processing, and the like, but wear due to oxidation is a major problem. In the case of ceramics, there is almost no oxidation consumption, but there are problems of cracking due to thermal shock, embrittlement of the structure due to transformation of the structure due to heating, and processing cost. On the other hand, graphite-ceramic composite materials have better oxidation resistance than graphite materials, have better thermal shock resistance than ceramic materials, and have lower reactivity with fired products. Conceivable. However, since this material has low fracture toughness, it often breaks due to overturning or dropping during work handling, and in that respect, its reliability as a material is low. In order to solve this problem, carbon fibers or inorganic fibers, whiskers, etc. are dispersed in the material at the time of kneading the raw materials. In some cases, a method for improving the performance is performed. Carbon fiber is a fiber having a very high modulus of elasticity with little reaction and deterioration even at high temperatures. It is also relatively inexpensive. However, it does not bond with the components in the material, and the wettability between the carbon fiber and the binder is poor. Therefore, the adhesive strength between the fiber surface and the material matrix is low, and microcracks are generated between the matrix and the matrix, which is a factor that lowers the physical strength. On the other hand, the costs of inorganic fibers and whiskers are much higher than those of carbon fibers. Is not always practical. Further, it is difficult to uniformly disperse the fibers at the time of kneading, and in many cases, fibers are formed or the fibers are dispersed in a spherical state due to rotational stress during kneading and do not contribute to the drawing effect. The present invention is to uniformly disperse carbon fibers and improve the strength and toughness of the material at low cost.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide graphite and
By mixing carbonized fiber coated with thermosetting resin in ceramic composite material, the dispersibility of carbon fiber is increased, and at the same time, the bonding strength between matrix and carbon fiber is increased, and the strength and toughness of the material are improved. The purpose is to prevent chipping and cracking during handling and to improve the life as a firing jig.

[0004]

The present invention relates to a graphitic raw material 5 to 5.
30 wt%, SiC10~70 wt%, SiO ₂ 1 to 3
It is a graphite refractory which is a graphite-ceramic composite material containing 0% by weight and BN of 1 to 5% by weight and carbon fibers of 0.1 to 2% by weight, and its surface is coated with a thermosetting resin.
By dispersing the carbon fibers, the bonding strength on the fiber surface is improved, the bonding strength with the matrix is increased, and the pull-out resistance of the fiber is exhibited, thereby improving the strength and fracture toughness of the material. Further, under an oxygen-containing atmosphere, the ceramic component in the material reacts with oxygen in the atmosphere to form SiO ₂ and B ₂ O ₃ glass phases on the surface of the refractory and in the pores of the material, and the oxygen and graphite components An object of the present invention is to prevent the contact and prevent the oxidation of the graphite component.

[0005] The carbon fiber to be blended can be either PAN type or pitch type, depending on the cost and required characteristics. From the viewpoint of molding yield and characteristic values, the carbon fiber can be blended in a length of 2 to 30 mm and in a blending amount of 0.1 to 2% by weight. As the resin coated on the carbon fiber, a thermosetting resin is used in order to maintain the bonding force after firing. In this case, the use of a resin of the same type as the resin used as the binder of the raw material itself improves the adhesiveness with the matrix and improves the bonding strength with the fiber. As the type of thermosetting resin, phenol resin is most effective, but furan, melanin and the like can also be used. As the graphite raw material, natural graphite powder excellent in oxidation resistance, spoiling resistance, corrosion resistance, and slipperiness is mainly used, but is not limited thereto, and artificial graphite powder and quiche graphite powder may be used. . SiC, SiO ₂ , and BN are blended as ceramic components. SiC has excellent heat resistance and is a low-reactive substance. This has the effect of suppressing the oxidation reaction of the carbon component by partially forming SiO ₂ in an oxidizing atmosphere. In order to increase the ratio of dispersion in the entire refractory and increase the amount of SiO ₂ formed by oxidation, it is desirable to use particles having a particle size of 1 mm or less. S to mix
At high temperatures, iO ₂ has the effect of forming a glass phase and suppressing the oxidation reaction of the carbon component. In order to increase the ratio of dispersion in the entire refractory and improve the antioxidant effect, it is desirable to use one having a particle size of 1 mm or less. As the SiO ₂ glass, E - B - like it can be added components, also simple to change the SiO ₂ was oxidized as Si containing SiO _2.
BN has a low coefficient of friction and forms a B ₂ O ₃ glass phase in an oxidizing atmosphere. It is desirable to use one having a particle size of 1 mm or less in order to increase the dispersion ratio and improve the antioxidant effect.

[0006]

When the carbon fiber is contained in the refractory material, resistance to pulling out between the fiber and the matrix occurs depending on the material, so that strength and toughness are improved. In this case, the fiber is required to have high elastic modulus, high heat resistance, low reactivity, and the like. Carbon fiber has a high modulus of elasticity and specific strength in both PAN-based and pitch-based,
Under a non-oxidizing atmosphere, the fiber is stable up to 3000 ° C. and has low reactivity with other substances. Therefore, the characteristics can be exhibited without any change at the stage of firing the raw material and at the time of using it as a product. However, carbon fibers rarely react with other substances and have poor wettability with a binder, so that microcracks may occur at the interface between other materials and the carbon fibers. In order to prevent this, the same type of thermosetting resin as the binder of the material is coated on the carbon fiber surface.
To increase the bonding strength with the matrix. This increases the fiber pullout resistance and improves the strength and fracture toughness of the material. If the added amount of carbon fiber is 0.1% by weight or less, no toughness effect is exhibited. If the content is 2% by weight or more, the dispersibility of the fibers during kneading becomes poor, and the fibers are unevenly distributed, causing defects in the molding material, and as a result, the strength and toughness of the material decrease. At the same time, a return phenomenon occurs during molding pressurization, and the structure of the molded body is destroyed. As a result, strength, thermal shock resistance, and yield are reduced. The fiber length is 30
In the case of more than 1 mm, the dispersibility of the fibers is deteriorated and the fibers are unevenly distributed, so that defects occur in the material, and the strength, the thermal shock resistance and the yield are reduced. When the length is shorter than 2 mm, the effect of pulling out is small, so that the effect on fracture toughness is small.

[0007] The proportion of the resin to be coated is calculated assuming that the resin is in a dry state,
It can be used in a range of up to 0% by weight. If the fiber is not coated with a resin, the fiber gradually becomes granular due to the rotational stress of kneading. For this reason, even if the carbon fibers are dispersed, they do not remain in a linear fiber shape, so that pullout resistance does not appear when stress is applied, and the effect of carbon fiber blending is not exhibited. On the other hand, when the resin is coated at an appropriate concentration, the carbon fiber is reinforced by the resin film, so that the fiber strength is improved. Therefore, even if a rotational stress is applied during kneading, the fibers do not become granular. As a result, the fibers can be dispersed while maintaining their shape, so that the strength and toughness can be improved by the pull-out resistance of the carbon fibers. The concentration of resin coated on carbon fiber is 5
When the content is less than 10% by weight, the bonding strength with the matrix decreases, and the effect on strength and toughness is small. In addition, since the strength of the fiber is low, it is granulated. On the other hand, when the content is 60% by weight or more, the bonding between the coated fibers is strong,
At the time of kneading, the fibers do not separate from each other, the dispersibility of the fibers is reduced, and the fibers are agglomerated. Therefore, the fiber agglomeration diameter becomes nonuniform, which causes a variation as a material and a stress concentration. Therefore, strength and toughness are not improved. In addition, thermal shock resistance is also reduced.

Although graphite is weak against oxidation, it is chemically stable, has high heat resistance, high thermal conductivity, low coefficient of thermal expansion, and is excellent in thermal shock resistance and workability. If the amount of the graphite material is less than 5% by weight, the characteristics of graphite cannot be exhibited, and the thermal shock resistance, lubricity, and workability are greatly reduced. On the other hand, when the content is 30% by weight or more, the oxidation resistance decreases, and the wear due to oxidation increases. SiC is chemically stable and has excellent oxidation resistance due to the formation of SiO ₂ on the surface in a high-temperature oxidizing atmosphere, but has a low thermal shock resistance and is very hard as compared with graphite, and therefore has extremely poor workability. In an oxidizing atmosphere, oxidation gradually starts at 400 ° C. or higher, and is affected by some oxygen partial pressure in the furnace or at the entrance and exit of the furnace to form a SiO ₂ glass phase by a reaction of SiC + O ₂ → SiO ₂ + CO. S formed
Since iO ₂ is in a liquid phase, it diffuses into the surface and pores of the material, and the diffusion suppresses the contact area between carbon and oxygen, thereby suppressing the oxidation of the carbon part. Therefore, if the content of SiC is less than 10% by weight, SiO ₂
And wear due to oxidation increases. On the other hand, when the content is 71% by weight or more, thermal shock resistance, lubricity, and workability are significantly reduced. SiO ₂ forms a liquid phase from 600 ° C. or higher. When inserted into a furnace as a jig, it melts and becomes a liquid phase, and diffuses into the surface and pores of the material. Due to this diffusion, the contact area between carbon and oxygen is suppressed, so that oxidation of the carbon part is suppressed. If it is less than 1% by weight, the absolute amount of the glass phase formed on the refractory decreases, and the oxidation of the carbon part increases. If it is 30% by weight or more, the elastic modulus increases and the thermal conductivity decreases, so that the thermal shock resistance decreases. In addition, since the particles are very hard, the processability is reduced and the cost is increased.

SiO ₂ undergoes cristobalite transformation when heated to 1000 ° C. or higher, and returns to its original state when cooled.
At this time, since a large volume change occurs, if the thermal history is repeated many times, the structure becomes brittle, and the strength and thermal shock resistance of the composite material are greatly reduced. Therefore, it is not preferable to add 30% by weight or more. BN has excellent heat resistance and lubricity, and is a low-reactive substance. When oxidized, it has the effect of forming B ₂ O ₃ and suppressing the oxidation reaction of the carbon component. It is desirable to use a particle having a particle size of 1 mm or less in order to increase the dispersion ratio in the entire refractory, increase the amount of B ₂ O ₃ formed for preventing oxidation, and improve the lubricity of the material. However, the wettability with the binder is poor, and if it is excessively mixed, the strength cannot be obtained. Also, since the cost of the raw material itself is very high, it is not desirable to mix 5% or more.

[0010]

The present invention will be described in detail with reference to the following examples. The evaluation test materials were prepared according to the compounding ratios shown in Tables 1 to 3. The production was performed using common raw materials and production machines. As a manufacturing process, natural graphite, ceramics, and phenol resin
The carbon fibers were mixed in a dry manner. A phenol resin was used as the resin for coating the carbon fiber, and Bellpar S-890 manufactured by Kanebo Co., Ltd. was used. The coating method of the resin on the carbon fiber is as follows.
After dissolving 890, the carbon fiber was immersed in the prepared resin solution, taken out and air-dried. This carbon fiber was cut into a predetermined length for use. When the amount of the coating resin was small, this operation was repeated several times. 10% by weight of a phenol resin for binding the raw material was added to the raw material mixed powder, and the mixture was kneaded at room temperature by a double-armed kneader, and then molded at 500 kg / cm ² by a hydraulic press. A molded article was prepared. This molded body is placed in a non-oxidizing atmosphere for 20 minutes.
The temperature was raised at a rate of 100 ° C./hr, followed by firing at a maximum temperature of 1000 ° C. to obtain a graphite / ceramic composite material.

The average particle size of each raw material used is 200 graphite.
μ, silicon carbide 10 μ, and silicon oxide 20 μBN 10 μ. The carbon fiber is T-30 made by Toho Rayon having a length of 20 mm.
0 equivalent (fiber diameter 15 μ) was used.

Hereinafter, the molding results of the raw materials and the firing properties are shown in the respective tables.
The evaluation results are shown. With respect to the evaluation items, the molding results were confirmed by visually observing the molded body after molding and by the presence or absence of cracks. In the thermal shock resistance test, a test piece of 150 × 50 × 50 mm was cut, heated to 1200 ° C. in an electric furnace, and immediately put into water three times. After this, check for cracks,
Judgment was made based on the presence or absence of cracks. For comparison of toughness values, Charpy-impact test values were measured. Regarding the oxidation test, a test piece cut into a size of 30 × 30 × 30 mm was set in an electric furnace in an air atmosphere, and a weight loss rate after 100 hours was measured. The test temperatures were 700 ° C and 900 ° C. Table 1 shows Examples and Comparative Examples to which carbon fibers were added. By blending the carbon fibers as shown in Examples 1 to 5, the effect of drawing out the carbon fibers occurs and the Charpy
The impact test value has improved. Compared to the pure graphite material of Comparative Example 1 (MS-G manufactured by SSC), it is equal to or more than that.
On the other hand, with respect to the resistance to sparkling, the decrease in the weight of oxidized oxide was significantly reduced compared to Comparative Example 1 without any problem. Comparative Example 2 shows an example in which no carbon fiber is blended, and has no toughness because there is no carbon fiber. Comparative Example 3 shows an example in which the carbon fiber content is more than 2% by weight. If the fiber distribution amount is large, a return phenomenon occurs during molding, and cracks occur. Thereby, the strength, the elasticity value, etc. are also reduced. Comparative Example 4 is an example using a carbon fiber without resin coating. As compared with the examples, the strength and the toughness are inferior.

[Table 1] Table 2 shows examples in which the amounts of graphite and ceramics are changed. Examples 6 to 9 show that the constitutional ratio of each component is within the range of the present invention, and there is no problem in both moldability and adiabatic impact, and good results are shown in oxidation. On the other hand, Comparative Example 5 contains less than 5% by weight of graphite and is inferior in thermal shock resistance. Comparative Example 6 contains more than 30% by weight of graphite and has a large oxidative consumption. Comparative Example 7 contains more than 70% by weight of SiC and Comparative Example 8 contains more than 30% by weight of SiO _2, but all have inferior thermal shock resistance. Comparative Example 9 has less than 1% by weight of BN.
In this case, the coefficient of friction increases.

[Table 2] Table 3 shows Examples 10 to 13 in which the amount of the carbon fiber coating resin is within the range of the present invention, all of which have no problem in moldability and thermal shock resistance, and show good results with respect to oxidation. ing. Comparative Example 10 shows the results with a low carbon fiber coating resin amount. When the concentration is lower than 5% by weight, the effect of improving the strength is low due to insufficient bonding between the carbon fiber and the matrix. Comparative Example 11 shows the result of a large carbon fiber coating resin. If the amount of the carbon fiber coating resin is more than 60% by weight, it is difficult to uniformly separate the fibers during kneading because the fibers are strongly bonded to each other by the resin. For this reason, uneven dispersion of fibers occurs, which causes cracks during molding or causes stress concentration.

[Table 3]

[0013]

As described above, the jig made of the carbon-ceramic composite material containing the resin-coated carbon fiber according to the present invention is a conventional graphite material and graphite / jig.
It has the same oxidation resistance, thermal shock resistance, etc. as compared to ceramic composite material jigs, and has better strength and toughness. Therefore, the present invention greatly contributes to an industry having a heat treatment step.

Claims (5)

[Claims] 1. A graphite raw material of 5 to 30% by weight, SiC10
A carbon fiber comprising a graphite / ceramic composite material containing 70 to 70% by weight, 1 to 30% by weight of SiO2, and 1 to 5% by weight of BN as other components and 0.1 to ₂ % by weight of carbon fiber. Included firing jig 2. The graphite raw material according to claim 1, wherein the raw material is one of natural graphite, artificial graphite and quiche graphite.
The firing jig containing the carbon fiber described in the above. 3. The firing jig containing carbon fibers according to claim 1, wherein the carbon fibers are made of PAN or pitch. 4. The firing jig containing carbon fibers according to claim 1.3, wherein the length of the carbon fibers is 2 to 30 mm. 5. The firing jig containing carbon fibers according to claim 1.3.4, wherein the surface of the carbon fibers is coated with a thermosetting resin.