JPS6172610A - Production of high-density graphite material - Google Patents

Abstract

PURPOSE:Aggregate and binder are kneaded with heat, roughly crushed, then heat-treated at a specific temperature, further crushed into particles of specific particle sizes, formed, roasted to effect graphitization whereby high-density graphite which is used to produce electrodes for electrical discharge machining and nozzle for continuous casting is obtained. CONSTITUTION:Aggregate consisting of coke powder, graphite powder and oil smoke, preferably less than 15 micrometer average particle size and a binder consisting of tar pitch, coal tar, phenolic resin (preferably containing more than 35% solid carbon and 25-60wt% of the binder are heat-kneaded, preferably 150-300 deg.C, crushed into particles of less than 10mm maximum particle size. Then, the crude particles are heat-treated at 300-550 deg.C. The heat treatment is effected so that the volatile content is reduced to 5-20wt%. Then, the product is crushed so that the average particle size becomes more than 1.05 time the average particle size of the aggregate but less than 18 micrometers. Then, the particles are formed, roasted and graphitized to give the objective high- density graphite material.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing graphite material with high density.

(Prior art and its problems) High-density graphite materials are usually made by heating and kneading aggregates such as coke powder, graphite powder, and oil smoke with the addition of coagulating agents such as tar pitch, cove tar, and phenolic resin. The molded powder obtained by crushing the extruded and kneaded material and adjusting the particle size is molded into a predetermined shape by means such as pressure molding or isostatic pressing to obtain a molded product, which is then heated in a matzuru furnace, tunnel furnace, etc. It is provided at about 1000°C in a firing furnace. This fired product is then impregnated with pitch and fired again. A method is used in which the pitch impregnation and re-firing steps are performed a necessary number of times and then graphitized at a temperature of about 3000'C. This pinch impregnation work is a batch work, it takes time to remove the pitch around the fired product after impregnation, and there is no need for a long process for re-firing. I was worried that this would be a problem, such as high cost and long time required.

Therefore, recently, a production method using HIP (hot isostatic pressing) using calcined coke as a raw material and a production method using Ruimen carbon microbeads have been developed. However, H
The method using IP requires the use of expensive equipment, and the method using all mesocarbon microbeads requires high raw material costs because the production of the microbeads is complicated, and it is difficult to fire large products, resulting in a high defect rate. There were few disadvantages such as high

(Object of the Invention) An object of the present invention is to provide a method for producing a high-density graphite material that solves the above-mentioned problems.

(Structure of the Invention) The present invention involves heating and kneading aggregate and a binder and coarsely pulverizing the mixture to a maximum particle size of 10 μm or less, heat-treating the mixture at a temperature of 300 to 550°C, and then 1.0 of the average particle size of
The present invention relates to a method for producing a high-density graphite material, which comprises pulverizing it to 18 μm or less by a factor of 5 times or more, followed by forming 1w8 and graphitizing it.

The aggregate in the present invention is coke powder or graphite powder.

9. Inorganic material powder such as oil smoke. Binding materials include tar pitch, coal tar, and phenol 4U1. Furfuryl alcohol, etc. The average particle size of the aggregate is preferably 15 μm or less. If it exceeds 15 μm, the pore size in the structure becomes large, which is disadvantageous for achieving high density. The bonding material preferably has fixed carbon of 35i1J or more. If it is less than 35% by weight, a large amount of volatile matter will be released and it will be disadvantageous to increase the density. The ratio of the binder is preferably 25 to 6 degrees in terms of N amount. If it is less than 25%, it is not sufficient for high density.

If it exceeds 60%, kneading tends to be insufficient.

The aggregate and binder are first thoroughly mixed using a V-type mixer or the like, or are thoroughly mixed during kneading.

This mixture is kneaded using a double-arm kneader, a continuous kneader, etc., and the kneading temperature is set so that the kneaded material has an optimum viscosity. This kneading temperature is not limited to 9%, but is generally 150 to 300°C.

Kneading should be carried out sufficiently so that the aggregate and binder are uniform and the binder covers the aggregate well. Since the kneaded material obtained in this way is in the form of lumps, it is necessary to coarsely grind the material to a maximum particle size of 10 mm or less. If there is a kneaded material that exceeds the 10 mark,
This is because volatile matter is difficult to remove during heat treatment, and volatile matter is not released uniformly between the inside and the surface.

The kneaded material thus obtained was heat treated at a temperature of 300 to 5
Heat treatment is performed at 50°C. If the heat treatment temperature is less than 300°C, the release of volatile matter will take a long time.

On the other hand, if the temperature exceeds 50°C'jr, the sinterability of the kneaded material will almost disappear and the desired product will not be obtained. Is heat treatment possible even in an oxidizing atmosphere, or is the treatment temperature 350℃?
If the treatment time exceeds 40 minutes, oxidation will become significant and the physical properties will deteriorate.

A non-oxidizing atmosphere is preferred. The heat treatment is preferably carried out so that the volatile content of the kneaded product is 5 to 20% by weight. If the volatile content is less than 5%, the physical properties of the graphite material will not be sufficient;
This is because if it exceeds this, blisters and cracks are likely to occur.

The kneaded material after the heat treatment is pulverized by a pulverizer.

As a crusher, there are ball mills and vibrating ball mills.

Examples include jet mills, turbo mills, bottle mills, etc., but are not particularly limited. What is the average particle size of the crushed powder?

It is required to be at least 1.05 times the aggregate particle diameter and at most 18 μm. If r'A is less than 1.05 times, the amount of binding material on the surface of the aggregate is insufficient, the binding strength is reduced, and a high-density material cannot be obtained. Also,
If the average particle size of the pulverized powder exceeds 18 μrn't, the pore size in the structure becomes large and a high-density material cannot be obtained.

This pulverized powder is molded into a predetermined shape by known means such as pressure molding or isostatic pressing to obtain a molded body, which is then fired in a known method in a kiln furnace such as a manful furnace or tunnel furnace. Graphitization is carried out at a temperature of 2500° C. or higher, but there are no particular limitations on these methods.

(Example) Next, an example will be explained.

Example 1 To 50 parts by weight of pitch coke powder having an average particle size of 3 μm, 50 parts by weight of tar pitch powder ground to an average particle size of 35 μm was added, and the mixture was thoroughly mixed using a type 2 mixer. This mixed powder was sufficiently kneaded using a double-arm kneader while heating at a temperature of 200°C, and after cooling, it was coarsely ground to a maximum particle size of 44 or less. This was heated at 450° C. for 10 minutes in a nitrogen atmosphere to reduce the volatile content to 14% by weight. This kneaded material was coarsely crushed, then crushed in a ball mill until the average particle size became powder of 10 μm, and the molded body obtained by pressure molding was fired in a non-oxidizing atmosphere width of about 1000 ° C.
It was graphitized at about 3000°C. The physical characteristics at this time are fJ1
Shown in the table.

Example 2 45 parts by weight of tar pitch powder pulverized to an average particle size of 35 μm was added to 55 parts by weight of pinch coke powder having an average particle size of 3 μm, and thoroughly mixed in a V-type mixer. This mixed powder was sufficiently kneaded while being heated at a temperature of 170° C. using a continuous kneading machine, and after cooling, it was coarsely ground to a maximum particle size of 4 mm or less. This was heated at 400°C for 10 minutes in a nitrogen atmosphere to remove 1 volatile content.
The content was 6% by weight. After coarsely pulverizing this kneaded material, it was pulverized with a jet mill until the average particle size became 8 μm, and the resulting molded product was firstly pressure-molded and then fired in a non-oxidizing atmosphere width of about 1000°C, and then heated at about 3000°C. Graphitization was performed. The physical properties at this time are shown in Table 1.

Example 3 55 parts by weight of tar pitch powder pulverized to an average particle size of 10 μm was added to 45 parts by weight of carbon black having an average particle size of 20 μm, and thoroughly mixed using a V-type mixer. This mixed powder was thoroughly kneaded using a double-arm kneader while heating at a temperature of 190°C, and after cooling, it was coarsely pulverized to obtain coarse particles having a maximum particle size of 4 mm or less. This was heated at 450° C. for 25 minutes in a nitrogen atmosphere to reduce the volatile content to 12% by weight. This kneaded material was pulverized with a vibration mill until the average particle size became 6 μm, and this powder was pressure-molded, and the resulting compact was fired in a non-oxidizing atmosphere width of about 1000°C, and graphitized at about 3000°C. I did it. The physical properties at this time are shown in Table 1.

Comparative Example 1 35 parts by weight of crushed tar pitch powder was added to 65 parts by weight of pinch coke powder with an average particle size of 25 μm.

The mixture was thoroughly mixed using a V-type mixer. This mixed powder was kneaded for 3 hours while being heated at a temperature of 200° C. using a double-arm kneader. This kneaded material was pulverized to give an average particle size of 35 μm. Volatile matter was filtered at 9%, molded and baked in the same manner as in Example 1.
Graphitization was performed. The physical properties are shown in Table 1.

Comparative Example 2 The fired body obtained in Comparative Example 1 was impregnated with pitch, and after re-firing, it was graphitized in the same manner as in Example 1. Their physical properties are shown in Table 1.

Example 4 To 60 parts by weight of pitch coke powder having an average particle size of 10 μm, 40 parts by weight of tar pitch powder crushed to an average particle size of 35 μm was added and thoroughly mixed using a mixer.

This mixed powder was sufficiently kneaded in a continuous kneading machine while heating at a temperature of 220 DEG C., cooled, and coarsely ground to obtain coarse particles having a maximum particle size of 4 mm or less. This was heated in the atmosphere at 350° C. for 25 minutes to reduce the volatile content to 11% by weight.

This kneaded material was pulverized with a vibration mill until the average particle size became 12 μm, and the pulverized powder was press-molded and placed in a non-oxidizing atmosphere with a width of about 100 μm.
It was fired at 0°C and graphitized at a temperature of about 3000°C. Table 1 shows the values of the physical properties at this time.

As is clear from the first side of Table 1, the graphite material of the example has a greater bulk density than the comparative graphite material, and also has greater bending strength and shore hardness.

(Effects of the Invention) According to the present invention, it is possible to economically obtain a high-density graphite material with crushed characteristics without pitch impregnation9 and without using expensive equipment9. graphite for electrical discharge machining electrodes, continuous casting nozzles, etc. that require Manufacture method of density graphite material 3, conflict with case of person making amendment Patent applicant name (4451 Hitachi Chemical Co., Ltd. 4, agent)
Person 5, Detailed explanation of the invention in the specification subject to amendment 6, Contents of amendment

Claims (1)

[Claims] 1. Aggregate and binder are heated and kneaded, and the kneaded material is coarsely ground to a maximum particle size of 10 mm or less, and then heat treated at a temperature of 300 to 550°C, and then the average particle size is the average of the aggregate. A method for producing a high-density graphite material, which comprises pulverizing the material to a particle size of 1.05 times or more and 18 μm or less, followed by molding, firing, and graphitization. 2. The method for producing a high-density graphite material according to claim 1, wherein the aggregate has an average particle size of 15 μm or less. 3. The method for producing a high-density graphite material according to claim 1, wherein the heat treatment is a heat treatment to reduce the volatile content of the kneaded material to 5 to 20% by weight.