JP3243288B2 - Carbon jig for sintering - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon jig used for sintering a molded article made of powder and / or fiber such as metal and ceramics by heat treatment.

[0002]

2. Description of the Related Art Sintered ceramics or nickel,
An alloy sintered body of copper or the like is manufactured by sintering a green compact by performing a high-temperature heat treatment. In the sintering process, generally, a method is employed in which a green compact is placed on a plate-shaped susceptor made of carbon or ceramics, or is placed in a sintering furnace with a case placed thereon, and heat-treated. . For this reason, a jig for sintering is required to have high heat resistance and chemical stability that does not cause a chemical reaction with a material to be sintered.

Conventionally, plate jigs of this type include silicon carbide and graphite (Japanese Patent Application Laid-Open No. 49-17805), carbon (Japanese Patent Application Laid-Open No. 59-8671), molybdenum, tantalum, and the like.
There is known a material in which a ceramic layer is coated on a refractory metal surface such as tungsten (JP-A-56-84374). However, a plate made of a ceramic material such as silicon carbide is susceptible to thermal shock and has a disadvantage that cracks and breakage are likely to occur during the sintering process. In addition, when the high melting point metal plate is coated with a ceramic layer, the jig material itself becomes extremely expensive, and in addition, cracks occur in the coating layer due to a difference in thermal expansion between the coating layer and the base material during the heat treatment process, thereby ending the service life. There is. On the other hand, a plate made of carbon or graphite material has excellent material properties such as good workability and high resistance to thermal shock. In addition to the decrease in the retention, the smoothness and the thickness accuracy of the surface of the sintered body are reduced.

[0004]

As described above, the conventional carbon jig made of carbon or graphite has excellent material characteristics, but causes a phenomenon in which the sintered body is fused to the plate surface. Sex was not enough. This tendency becomes more remarkable as the size of the sintered body increases, and there is also a problem in the material strength of the plate under severe sintering conditions.

[0005] The present invention was developed as a result of a multifaceted study of the material and characteristics of the plate constituting the jig in order to solve the problems of these carbon jigs. We provide a carbon jig for sintering that does not cause the fusion phenomenon of the sintered body during sintering and can perform sintering with a high yield without impairing surface smoothness and thickness accuracy even for large size Is to do.

[0006]

The carbon jig for sintering according to the present invention for achieving the above object has a surface roughness of R.
max 5μm or less, surface pore size of 5μm or less, having a bulk specific gravity of 1.48g / cc or more, Shore hardness of 90 or less, thermal conductivity of 3W / m ° K or more, glassy It is characterized in that it is composed of a plate-shaped glassy carbon composite material having a composite structure in which a filler of carbon powder is homogeneously dispersed in a carbon matrix. In addition to these properties, a jig having a bending strength of 900 kgf / cm ² or more and a thickness accuracy of ± 0.05 mm is more preferable.

The numerical values of each property used in the present invention are based on the following measuring methods. Surface roughness is JIS
B0601 (1982) "Definition and Display of Surface Roughness", the size of surface pores is measured with an optical microscope or a scanning electron microscope. The bulk specific gravity is measured according to JISR7222 (1979) "Physical test method for high-purity graphite material", the Shore hardness is measured by a D-type Shore hardness meter, and the thermal conductivity is measured at room temperature in the thickness direction of the material by a laser flash method. In addition, the bending strength was evaluated according to JIS K6911 (1982) “General thermosetting plastic test method”, and the thickness accuracy was measured at 10 or more locations of the material.

The glassy carbon composite material constituting the carbon jig for sintering of the present invention refers to a composite structure in which a filler of carbon powder is homogeneously dispersed in a glassy carbon matrix. Usually, glassy carbon is produced by carbonization of thermosetting resin, and in addition to its properties such as high strength and gas impermeability, it has material characteristics such as lower surface wettability compared to other carbon materials. is there. For this reason, although it exhibits the function of preventing fusion with the sintered body, the temperature distribution during heat treatment tends to be non-uniform due to the low thermal conductivity of the glassy carbon alone, and sintering does not proceed uniformly . Moreover, since it is a brittle material, it is easily damaged by an impact during handling. The glassy carbon composite material according to the present invention has a composite structure in which a filler of carbon powder is uniformly dispersed in the skeleton of glassy carbon, so that the thermal conductivity is improved while maintaining low wettability, and the brittleness is improved. It becomes a suitable material with increased mechanical strength and toughness.

Among the properties specified in the present invention, the surface properties of the plate having a surface roughness Rmax of 5 μm or less and a surface pore size of 5 μm or less give an excellent surface state to the sintered body after the heat treatment. If the surface properties exceed the above values, the surface of the sintered body will be rough and the thickness accuracy will be deteriorated. Bulk specific gravity of glassy carbon composite material is 1.48
If it is less than g / cc, the surface structure becomes coarse and dense, and the smoothness of the surface of the sintered body is impaired. If the Shore hardness becomes less than 90, cracks and cracks occur in the jig. The thermal conductivity is an important requirement for uniform sintering, and if it is less than 3 w / m ° K, the yield of the sintered body decreases. Therefore, satisfying all these properties is a plate requirement for obtaining a good sintered body with good yield, but in addition to this, the bending strength is 900 k
If the gf / cm ² or more and the thickness accuracy are ± 0.05 mm, a better jig is obtained.

The carbon jig for sintering of the present invention having the above-described properties can be manufactured as follows.
First, a thermosetting resin and carbon powder are mixed at a predetermined mixing ratio, and then kneaded using a kneader or the like. As the thermosetting resin, a resin having a high residual carbon ratio such as a phenol resin, a furan resin, and a polyimide resin is generally used. The carbon powder is appropriately selected and used from graphite powder, coke powder, carbon black, glassy carbon powder and the like.
The kneaded material is formed into a plate shape by a method such as compression molding or roll molding, cured, and then fired and carbonized in a non-oxidizing atmosphere. The carbonization temperature is generally 800-1500 ° C., but if necessary, it is graphitized at a high temperature of 2000 ° C. or more. The carbonization operation is performed using an electric furnace replaced with an inert gas such as nitrogen or argon, or a combustion gas heating type furnace such as a reed hammer type continuous furnace.

In the above-mentioned process, a carbon jig for sintering having the property characteristics of the present invention is manufactured by appropriately adjusting the manufacturing conditions. Generally, control of bulk specific gravity, strength, hardness, thermal conductivity, and the like is ensured by appropriately adjusting the type, particle size, and blending ratio of raw materials, and setting kneading conditions appropriately. For example, when the amount of carbon powder increases, high bulk specific gravity, hardness and thermal conductivity are imparted, but it is difficult to secure strength and the low surface wettability inherent to glassy carbon is lost. Adjustment of kneading conditions and curing conditions is an important condition for the surface pores. If degassing is not sufficient at the time of kneading the raw materials, air will be incorporated into the material, resulting in a porous body including the surface pores. The surface roughness and thickness accuracy mainly depend on the molding conditions, and predetermined characteristics can be secured by using an appropriate method. For example, in the case of compression molding, a method of using a mold having a predetermined surface roughness and accuracy,
In the case of roll forming, a method using a roll forming machine having predetermined surface accuracy is adopted.

The carbon jig material of the present invention is used alone or in a state mounted on a high melting point metal plate, a graphite plate or a ceramic plate. In terms of handling, a lightweight and highly heat-resistant graphite plate is preferable. The green compact before sintering is manufactured by an appropriate method such as doctor blade method, slip casting method, molding method, etc., packed in a heat treatment furnace while placed on a plate-like carbon jig, and sintered. Processing is performed. The molded body placed on the jig may be covered with a case for the purpose of preventing deformation if necessary. Heat treatment furnaces include single furnaces and tunnel furnaces.
It is selected according to requirements such as production volume and quality. Conditions such as temperature and atmosphere during the heat treatment are set according to the type and quality of the material to be sintered.

[0013]

By using the carbon jig for sintering of the present invention, it is possible to produce a sintered body having a high yield in which the quality of the product surface such as smoothness and thickness accuracy is greatly improved in the sintering process of metal or ceramics. Becomes possible. This is due to the fact that, in addition to the inherent properties such as low surface wettability of the glassy carbon composite material, all the specified properties are effective. That is, since the surface wettability is low, the phenomenon that the sintered body is fused to the jig surface during the sintering is prevented, and the sintered state is made uniform by the high thermal conductivity.

Further, since the surface pores are small, the surface roughness is small, and the thickness accuracy is good, the smoothness and the thickness accuracy of the sintered body surface are improved, and the bulk specific gravity, Shore hardness, bending strength and the like are improved. These properties function to enhance the strength and toughness of the jig and extend the life greatly. Although these action mechanisms are slightly improved only by satisfying the individual characteristics, remarkable yield and quality improvement effects as in the present invention cannot be obtained. As described above, all the other characteristic elements are added to the inherent properties of the glassy carbon composite material to act synergistically, so that the intended purpose can be achieved.

[0015]

Hereinafter, examples of the present invention will be described in comparison with comparative examples.

Examples 1-2, Comparative Examples 1-5 A graphite powder having an average particle size of 15 μm and a liquid phenol resin (PR940, manufactured by Sumitomo Durez Co., Ltd.) were mixed and kneaded with a resin kneading kneader. A primary compact was produced by a 50 Torr mold press. This primary formed body was formed into a plate by a roll forming machine. The plate compact is sandwiched between aluminum plates via release paper, cured at 180 ° C in an electric dryer, sandwiched between graphite plates, packed in an electric furnace, and surrounded by coke powder at 1000 ° C. For a carbonization treatment. In this process, graphite powder content, molding conditions,
By controlling the curing conditions and the like, a glassy carbon composite material having a plate shape of 700 mm in length and 1 mm in thickness with different properties was produced. Table 1 shows properties of the manufactured glassy carbon composite material.

[0017]

[Table 1]

Next, alumina was added to the silicon nitride powder and dispersed in ethanol to form a slurry. The slurry was formed by a doctor blade method and dried to produce a ceramic green sheet 700 mm in length and 0.8 mm in thickness. Further, the nickel carbonyl powder was molded under pressure to obtain a green sheet having the same size as above. These green sheets were placed on a sintering carbon jig prepared by the above-described method, and sintering was performed. The sintering is performed at 1750 ° C. for 4 hours in a nitrogen atmosphere in the case of the ceramic sintering, and at 1100 ° C. in a nitrogen atmosphere containing 10% hydrogen gas in the case of the nickel sintering. Set to time conditions. Table 2 shows the yield and other results during sintering of silicon nitride, and Table 3 shows the yield and other results during sintering of nickel.

[0019]

[Table 2]

[0020]

[Table 3]

As is apparent from a consideration of Tables 1 to 3, in the examples satisfying the property characteristics requirements of the present invention, even if a large-sized sintered body is used, there is no fusing phenomenon during sintering, so that the product yield is high. The properties of the sintered body and the state of the jig were also good, but in the comparative examples in which any of the properties of the present invention were deviated, no satisfactory results were obtained.

[0022]

As described above, according to the present invention, there is provided a high-performance sintering carbon jig capable of producing a fired body having always excellent surface characteristics and accuracy with a high yield.
Therefore, it is suitable for applications such as electronic material heating shelves that require high step precision and smoothness, and electrode plates for molten carbonate fuel cells, and has extremely high industrial utility.

Claims (2)

(57) [Claims] 1. A surface having a surface roughness Rmax of 5 μm or less and a surface pore size of 5 μm or less, and a bulk specific gravity of 1.
48g / cc or more, Shore hardness 90 or less, thermal conductivity 3W /
have a m ° K or more properties of glassy carbon Matori'
Composite in which carbon powder filler is homogeneously dispersed in
A carbon jig for sintering, comprising a plate-shaped glassy carbon composite material having a weave . 2. The carbon jig for sintering according to claim 1, which has a bending strength of 900 kgf / cm ² or more and a thickness accuracy of ± 0.05 mm.