JPH03281692A - Preparation of starting powder for carbonaceous material - Google Patents

Abstract

PURPOSE:To obtain a starting powder for a carbonaceous material with a higher bulk density and improved electrical discharge machining characteristics by pulverizing a product which is obtained by subjecting a coal tar-based raw material to heat treatment and has specific physical properties. CONSTITUTION:A starting powder for a carbonaceous material is formed by pulverizing a product which is obtained by subjecting a coal tar-based raw material to heat treatment and has an average grain size after grinding of 15 to 20mum, a volatile content of 3 to 20wt.%, a toluene-soluble content of 1 to 10wt.%, and a difference between the quinoline-soluble content and the toluene-soluble content of 2wt.% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing raw material powder useful for high-density special carbon materials. More specifically, the present invention relates to a method for producing raw material powder for special carbon materials that has high density and good electrical discharge machining properties.

[Conventional technology]

Conventionally, special carbon materials are produced by heating and mixing grains and powder of pitch coke and petroleum coke in a predetermined ratio, adding an appropriate amount of binder pitch, adding acid, and forming. Furthermore, this formed body is fired, graphitized, and then processed to produce a special carbon material product. Furthermore, a method has recently been reported in which a special carbon material is produced by molding mesocarbon microbeads obtained by heat-treating pitch and then treating it with a solvent.

[Problem to be solved by the invention]

These methods have problems such as insufficient product properties such as low bulk density and low strength, and complicated processes and high manufacturing costs.The emergence of special carbon materials with low cost and good properties. was desired.

In recent years, carbon materials have been attracting attention for their use as electrodes for electrical discharge machining, and demand is rapidly increasing. There is a need for carbon materials that have a low wear rate over time. Furthermore, carbon materials manufactured from mesocarbon are expensive due to complicated processes, and there is a demand for materials with low manufacturing costs and high properties.

[Means for solving cia] Therefore, in view of this situation, the present inventor conducted intensive studies to produce a special carbon material with high strength and good discharge characteristics. The present invention was achieved based on the discovery that a product with high properties can be obtained by pulverizing the raw material and molding it into a product.

That is, the gist of the present invention is a product obtained by heat-treating a coal tar-based raw material, which is crushed to have an average particle size of 1.
Volatile content (VM) of 5 to 20μ is 20% by weight or less and 3% by weight or more, and toluene soluble content (TS)
Cr-resin) is 10% by weight or less and 1% by weight or more, and the quinoline soluble content (QS) and toluene soluble content (TS
) is pulverized into powder having a difference of 2% by weight or less.

The present invention will be explained in detail below.

First, the coal tar-based raw material in the present invention is coal tar produced as a by-product during coal carbonization or coal tar pitch obtained therefrom, and its VM may exceed 30% by weight, but if it exceeds 30% by weight, the target The VM of the raw material is preferably 30% by weight or less because it takes a long time to adjust the physical properties, reduces processing capacity, and increases cost.

Furthermore, if the amount of argon in these raw materials is too high, a large amount of low-boiling fractions will be fused, resulting in poor heat treatment efficiency, so the amount of argon in these raw materials is preferably 30% by weight or less.

These coal tar-based raw materials are usually heated to 350 to 48
It is produced by heat treatment at 0°C for about 1 to 72 hours.

In the present invention, the heat treatment of coal tar-based raw materials is usually carried out by
The treatment is carried out at 200 to 350° C. for about 0.5 to 48 hours, but it is more effective to apply mechanical energy to ensure uniform treatment. Examples of methods for applying mechanical energy include stirring and ultrasonic waves. The heat treatment may be performed in an inert gas (argon, nitrogen, etc.) under autogenous pressure, but is preferably performed in the presence of air.

The target heat-treated product of the present invention has a VM of 20% by weight after being pulverized to an average particle size of 15 to 2.0μ.
3% by weight or more, and TS is 10% by weight or less and 1% or more by weight, and the difference between QS and TSO (QS-T
S) is less than or equal to 2% by weight.

That is, first of all, if the VM of the heat-treated product exceeds 20%, the weight loss during firing is too large and the properties deteriorate;
If it is less than %, the sinterability will be poor and the properties will deteriorate. Furthermore, if the amount of TS (argon) in the pulverized product exceeds 10% or more, the molded product will foam and crack during firing. If it is less than 1%, the sintered component will be small and the properties will deteriorate.

Furthermore, if the difference between QS and TSO exceeds 2% by weight, the structure of the molded article will become non-uniform and its properties will deteriorate. If the difference between QS and TS is 2% by weight or less, the molded product structure will be homogeneous and the molded product properties will be improved.

In the present invention, the product thus obtained is pulverized to obtain raw material powder. In order to obtain a good molded product, the average particle size of the raw material powder is preferably 50μ or less, but in order to further improve the uniformity of the product structure, it is preferably 30μ or less, more preferably 20μ or less, and most preferably 10μ.
It is preferable to pulverize the powder to a fine powder.

For forming to obtain a molded article, ordinary molding, cold isostatic pressing, etc. are used. Calcining can be done either in an inert gas or in a coke pleat.
It is done at a temperature of 00°C. Furthermore, conventional methods can be used for graphitization (Tammann furnace, Acheson furnace, induction heating), and usually 200
It is made at 0-3000°C.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

In addition, in the examples, % means weight %.

Example I A coal tar-based raw material having a VM of 20.5% and a T resin amount of 24.4% was heat-treated at 230° C. for 80 minutes while applying mechanical energy in the presence of air. When the average particle size of the product was 16μ, the VM was 15.2% and the amount of argon was 5.2%. The quinoline soluble content was 6.6%, and the difference between QS and TS was 1.4%.

This finely pulverized product was molded using a mold press. This compact was fired to 1000° C. in a coke shower to prevent oxidation, and then graphitized to 2800° C. in a Tammann furnace to obtain a product. The bulk density of the graphite molded body was 1.88, and the consumption rate during electrical discharge machining was 1.2%.

Example 2 25% of raw material with VM of 20.6% and γ resin of 21.1%
Heat treated at 0°C for 70 minutes in the same manner as in Example 1 to obtain an average particle size of 1.
A product was obtained in which the VM at 7μ was 14.9% and the amount of γ resin was 5.5%. The quinoline soluble content of this product was 5.4%, and the difference between QS and TSO was -0.1%. A molded body was produced from this finely pulverized product in the same manner as in Example 1. Its bulk density was 1.89, and its wear rate during electrical discharge machining was 0.7%.

Comparative Example 1 The same raw material as in Example 1 was heat-treated to obtain V with an average particle size of 17μ.
A product was obtained in which M was 14.6% and the amount of γ resin was 6.9%.

The quinoline soluble content of this product was 10.5%, QS
The difference between TS and TS was 3.6%. A molded body was produced from this finely pulverized product in the same manner as in Example 1. Its bulk density is 1.
77, the wear rate during electrical discharge machining was 3.8%.

Comparative Example 2 The same raw material as in Example 2 was heat-treated to obtain V at an average particle size of 16μ.
A product containing 14.4% M and 7.4% T resin was obtained.

The quinoline soluble content of this product was 17.9%, QS
The difference between TS and TS was 10.5%.

A molded body was produced from this finely pulverized product in the same manner as in Example 1. Its bulk density is 1.79, and its wear rate during electrical discharge machining is 9.
It was 7%.

Comparative Example 3 The bulk density and wear rate during electrical discharge machining of a commercially available product were simultaneously measured and found to be 1.84 and 4.4% by weight, respectively.

〔Effect of the invention〕

The carbon material using the raw material powder produced by the method of the present invention has a high bulk density and has very good electrical discharge machining characteristics (low wear rate).

Claims (1)

[Claims] (1) A product obtained by heat-treating a coal tar-based raw material, which is pulverized to an average particle size of 15 to 20 μm and has a volatile content (VM) of 20% by weight or less and 3% by weight or more, and toluene. The soluble content (TS) is 10% by weight or less and 1% by weight or more, and the difference between the quinoline soluble content (QS) and toluene soluble content (TS) is 2% by weight or less. A method for producing raw material powder for carbon materials, which is characterized by: