JPH04240022A - Manufacture of graphite material for electric discharge machining electrode - Google Patents

Abstract

PURPOSE:To provide a graphite material suitable for forming various kinds of parts of the electrode, etc., of an electric discharge machining device, excellent in wear resistance at high density and high strength, by making a starting raw material only as a mesophase raw material, also specifying the item thereof, executing carbonization after forming in the specified shape body, and graphitizing this. CONSTITUTION:A graphite material for electric discharge machining electrode is manufactured by using the mesophase material of a raw material mesocarbon micro bead or bulk mesophase pulverized material, etc. In this case, that which has 20-30% beta resin component, <=0.15% ash, 0.15-0.79% moisture, 8.8-15.1% volatile component, 86-91.5% fixed carbon and <=15.0mum mean grain diameter by a laser diffraction type grain size meter, is used. This is formed in a cold press, a carbonization treatment is executed within the temperature range at 2400-3000 deg.C at the specified rise temperature on this formed body, a graphitizing treatment is executed within the temperature range at 2400-3000 deg.C on this carbonized body, and a graphite material for electric discharging electrode is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing graphite material, and in particular to a graphite material that has high strength, high density, and low consumption and is suitable for electrodes employed in electric discharge machining equipment. This relates to a method for producing a certain graphite material. [0002] For example, electrodes used in electric discharge machining equipment are generally made of graphite material, but this manufacturing method basically involves mixing carbonaceous aggregate and binder pitch. It is then formed. However, in this method, the carbonaceous aggregate must be finely pulverized in order to homogenize the product. For example, when needle coke is finely pulverized, a large amount of binder is required to cover the fine powder. It is inevitable. If the binder component increases, it may thermally decompose and polycondense during the carbonization process, creating pores, or the carbonaceous aggregate and binder may exhibit different shrinkage characteristics, making it impossible to obtain high strength. It is something. However, unless this graphite material is made to have high density and high strength, good discharge performance and durability cannot be obtained. Therefore, recently, this type of graphite material has been manufactured by adopting various manufacturing methods such as those proposed in Japanese Patent Publication No. 1-23405 or Japanese Patent Publication No. 1-58125. It was. [0003] In the ``method for producing a carbon molded body'' proposed in Japanese Patent Publication No. 1-23405, it is clear from the claims of the above publication that ``a coal-based binder pitch or a petroleum-based binder pitch is used. , when producing a carbon molded body by mixing with carbonaceous aggregate and firing, bulk mesophase is added in advance to the binder pitch or carbonaceous aggregate, or to the mixture of the binder pitch and carbonaceous aggregate. "A method for manufacturing a carbon molded body, which is characterized by adding carbonaceous aggregate in advance," but this manufacturing method basically involves mixing carbonaceous aggregate and binder pitch. However, in this method, the carbonaceous aggregate must be finely pulverized in order to homogenize the product. For example, when needle coke is finely pulverized, a large amount of binder is required to cover the fine powder. It is inevitable. If the binder component increases, it may thermally decompose and polycondense during the carbonization process, creating pores, or the carbonaceous aggregate and binder may exhibit different shrinkage characteristics, making it impossible to obtain high strength. As mentioned above, it is a thing. [0004] For this purpose, as shown in the above-mentioned Japanese Patent Publication No. 1-58125, it is necessary to
The temperature is raised to 400 to 530 °C under reduced pressure of orr or while blowing heated steam at 400 to 600 °C, and low molecular components and cracked oil are removed.
Carbon content: 92% by weight or more, volatile content up to 900℃: 7
~13% by weight, a raw material with a linear shrinkage rate of 6% or less when heated to 500°C, is pulverized to an average particle size of 10 μm or less, then molded and fired. High strength and high density. It has also been proposed to adopt a method called ``method for manufacturing carbon materials''. However, this manufacturing method does not specify anything regarding the ash content in the pitch, which can have a large effect when used as an electrode, and the carbon material manufactured by this method can be used as is for electrodes, etc. of electrical discharge machining equipment. It cannot be used as a material for constructing. [0005] Therefore, the inventors of the present invention have conducted various studies on how to produce the best graphite material for constructing electrodes, etc. of electric discharge machining equipment, and as a result, they have completed the present invention. It is. OBJECTS TO BE SOLVED BY THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object to be solved is to further increase the density and increase the density of graphite materials for electrical discharge machining electrodes. Strengthening and reducing wear and tear. [0007]An object of the present invention is to provide a method for producing a high-density, high-strength, and hard-to-consume graphite material suitable for forming electrodes, etc. of electrical discharge machining equipment. It is in. [Means and effects for solving the problems] In order to solve the above problems, the means taken by the present invention is to use mesophase materials such as mesocarbon microbeads or bulk mesophase pulverized products as raw materials. A method for producing a graphite material for an electrical discharge machining electrode, wherein the mesophase material includes: (a) a β resin component of 20 to 30%, (b) an ash content of 0.15% or less, and (c) a moisture content of 0.15 to 30%. 0.79% (d) Volatile content: 8.8 to 15.1% (e) Fixed carbon: 86 to 91.5% (f) Average particle diameter measured by a laser diffraction granulometer is 15.
Using a material with a diameter of 0 μm or less, this is formed by cold pressing,
The maximum temperature for this molded product is 840 to 1 at a predetermined temperature increase.
This is a method for producing a graphite material for electrical discharge machining electrodes by performing carbonization treatment in a temperature range of 200°C, and then graphitizing the carbide in a temperature range of 2400 to 3000°C. That is, the production method of the present invention uses only mesophase materials such as mesocarbon microbeads or bulk mesophase pulverized products as raw materials, and this type of mesophase materials have an average particle size of 10 to 1
Graphite material using 5μm mesocarbon microbeads as raw material (bulk density 1.90g/cm3, bending strength 1000
kg/cm2) and bulk mesophase pulverized products (bulk density 1.94g/cm3, bending strength 750kg/cm2). The properties of this mesophase material are specified as (a) to (f) above because the graphite material formed by the manufacturing method of the present invention constitutes the electrodes etc. of the electrical discharge machining device. High enough strength,
This is to have high density and wear resistance,
Specifically, the reasons are as follows. Regarding (a), the necessity of having 20 to 30% of the β-resin component, that is, a component that does not dissolve in benzene but dissolves in quinoline, is due to the adhesion of the particles during firing and the generation of thermal decomposition. This is because it is necessary to prevent the formation of pores caused by volatilization from objects. Regarding (b), ash content causes so-called pit holes;
If these pit holes exist in the graphite used in electrodes for electrical discharge machining equipment, they not only significantly impede the discharge characteristics, but also cause the discharge points to concentrate and accelerate the wear of the electrode. It is. For this reason, it is ideal that the ash content contained in the raw material be zero, but it is nearly impossible to reduce the ash content to zero. Therefore, if an upper limit is set that is acceptable as a graphite material for electrical discharge machining electrodes and is possible at a low cost using current technology, the above-mentioned range will be the optimum one. In other words, by setting the maximum ash content in the raw material to 0.15%, electrodes, etc. for electrical discharge machining equipment for graphite materials can be improved, at least when compared to those in which this ash content is not specified. This can further improve the functionality of the system. Regarding (c), water is completely unnecessary after the graphite material is completed, but a certain amount of water must be contained in the raw material before molding. The reason for this is that in order to mold the pulverized raw material into a certain shape before firing, moisture is required to allow the raw material to maintain its shape. However, if there is too much moisture, it is impossible to achieve close packing for molding, so an upper limit is naturally determined. [0015] Therefore, in order to form a graphite material for electrical discharge machining electrodes, the optimum water content of the mesophase material, which has been pulverized to an average particle size of 15.0 μm or less, is 0.15 to 0.79%. It will become. With such a moisture content, sufficient molding can be performed, and high-density filling and high-density products can be achieved. Regarding (d), similarly to (a), if the volatile content of (d) is too small, the fusion properties of the particles will decrease and a high-strength material will not be obtained. If it is too large, pores will be created in the graphite material due to gas generated by thermal decomposition, making it impossible to obtain a high-density material. Regarding (e), the fixed carbon content is 10 because this is the graphite material.
Ideally, it should exist at 0%, but in order to mold the fine powder raw material into a certain shape and fire it, other ingredients must be included to cause the material to shrink, so it should fall within this range. It is something. In other words, if the fixed carbon content in the raw material is lower than 86%, it means that the total volatile content, ash content, and moisture content is 14% or more. If the volatile content is too large, a high-density material cannot be obtained due to the gas generated by thermal decomposition as described above. High ash content causes pit holes. If there is a lot of moisture, it is not possible to pack the raw material powder close to each other. On the other hand, if it is 91.5% or more, the fusion properties of the particles decrease and a high-strength material cannot be obtained. Regarding (f), the average particle diameter of the raw material determines the firing conditions when firing it to form a certain product. In other words, if the particle size of the raw material is small, it will take a considerable amount of time to bake, while if the particle size is too large and it is used as an electrode for electric discharge machining, the surface of the electric discharge machining will become rough and the electrode will wear out. big. Therefore, in order to ensure the high density and high strength necessary for a graphite material for electrical discharge machining electrodes, it is optimal to set the average particle diameter of the starting material as described above. The raw materials as described above are used and solidified into a shape for, for example, an electrode. That is, it is molded, and this molding can be carried out easily and reliably if the raw material satisfies the above-mentioned conditions. The reason why this raw material is formed by cold pressing is to minimize the anisotropy ratio of the graphite material, and also because it can be formed into a shape close to the product shape of the electrode, reducing processing loss. . Next, the molded product as described above is first subjected to carbonization treatment. The mesophase raw material here has a fixed carbon content of 86 to 91.5%, and still contains moisture, volatile matter, and ash. What is the carbonization treatment mentioned here?
It is heated at a maximum temperature range of 840 to 1200 degrees Celsius to volatilize most of the moisture and volatile components, shrink, and become denser.
The aim is to increase the strength. [0021] Then, the material subjected to the carbonization treatment in this manner is subjected to a graphitization treatment. This treatment can remove the ash that causes pit holes, as well as the volatile matter and moisture that were not removed in the carbonization treatment. Also,
Graphitization reduces the hardness and makes it easier to process into electrode shapes. Further, by adjusting the graphitization temperature, a graphite material having an optimal electrical resistivity for an electrical discharge machining electrode can be obtained. For this purpose, electrode materials for electrical discharge machining are manufactured by heating to 2400 to 3000°C in a non-oxidizing atmosphere. [Example] Next, the case where a graphite material for an electric discharge machining electrode is manufactured by employing the manufacturing method of the present invention as described above will be explained based on an example. First, a bulk mesophase pulverized product was used as a mesophase material as a starting material, and its specifications were adjusted as follows. [0024] β resin component → 25.6% ash content → 0.00
5% Moisture → 0.29% Volatile content → 10.8% Fixed carbon content → 88.95% Average particle diameter → 9.18 μm [0025] Approximately 200 g of such raw materials were pressed at a pressure of 1300 kg/cm2 by cold pressing. The graphite material for electrical discharge machining electrodes is made by molding it into a predetermined shape, carbonizing it at an average heating rate of 17°C to 920°C, and then heating it to about 2800°C for 4.5 hours to graphitize it. Obtained. When the physical properties of the obtained graphite material for electrical discharge machining electrodes were measured, the following results were obtained. Note that the numerical values in parentheses indicate the range of each value obtained when the specifications of the raw material are determined according to the method according to the present invention. [0027] Apparent density → 1.96 g/cm3 (1.93
~1.97) Electrical specific resistance → 1190μΩ・cm (1160~1230
) Bending strength → 900 kg/cm2 (770 to 990) Shore hardness → 70 (65 to 72) [0028] Then, electrodes were formed using this graphite material for electrical discharge machining electrodes, and other graphite materials currently on the market were used. When we measured and compared the characteristics with electrodes formed from different materials, we found that
The results shown in Table 1 below were obtained. [Table 1] [0030] According to the results, when electrodes are formed using graphite material for electrical discharge machining electrodes formed by the method according to the present invention, the electrode wear rate is lower than that of other comparative examples. This makes it an extremely suitable material. In addition, electrode wear rate is electrode depth/electrode reduction dimension x
In Table 1, Comparative Examples 1 and 2 are electrode materials made using commercially available coke and pitch, and Comparative Examples 3 and 4 are electrode materials made using commercially available mesophase raw materials. This is an electrode material made using all of these materials. [0031] As described in detail above, in the production method according to the present invention, first, the starting material is only the mesophase raw material, and its specifications are set as described above, and then this is After forming into a shape, carbonizing it, and then graphitizing it, it has high density, high strength, and wear resistance, making it suitable for forming various parts such as electrodes for electrical discharge machining equipment. It is possible to produce graphite material with excellent properties.

Claims (1)

[Claims] 1. A method for producing a graphite material for electrical discharge machining electrodes using a mesophase material such as mesocarbon microbeads or a bulk mesophase pulverized product as a raw material, the mesophase material comprising: (a) a β-resin component; (b) Ash content is 0.15% or less (c) Moisture content is 0.15-0.79% (d) Volatile content is 8.8-15.1% (e) Fixed carbon is 86-30% 91.5% (f) The average particle diameter measured by a laser diffraction granulometer is 15.5%.
Using a material with a diameter of 0 μm or less, this is formed by cold pressing,
The maximum temperature for this molded product is 840 to 1 at a predetermined temperature increase.
A method of manufacturing a graphite material for electrical discharge machining electrodes by carbonizing the carbide in a temperature range of 200°C and graphitizing the carbide in a temperature range of 2400 to 3000°C.