KR101823940B1 - Method for manufacturing electrode using in electric discharge machining - Google Patents

Abstract

The present invention relates to a method to manufacture an electrode for electric discharge machining, capable of manufacturing an electronic device for electric discharge machining equivalent to a graphite electrode at low costs. According to the present invention, the method comprises: a first step of finding a carbonization condition capable of growing a graphite crystal of the electrode for electric discharge machining to a set size in a carbonization process by changing an increase rate of carbonization temperature, and the amount of coal tar pitch or graphite mixed with a phenol resin; a second step of mixing the phenol resin with the coal tar pitch or graphite as much as an amount required for the carbonization condition, and waste carbon fiber to make a mixture; a third step of heating and pressing the mixture to make a formed body; a fourth step of carbonizing the formed body at the increase temperature required to make a carbonized body; and a fifth step of processing the carbonized body in the shape of an electrode for electric discharge machining.

Description

[0001] METHOD FOR MANUFACTURING ELECTRODE USING IN ELECTRIC DISCHARGE MACHINING [0002]

The present invention relates to a method of manufacturing an electrode for electric discharge machining.

Electric discharge machining utilizes the heat of the spark generated when the anode and the cathode of the electricity come into contact with each other, and melts or vaporizes the material to process the material.

Electrodes for electric discharge machining used in electric discharge machining are made of brass, graphite, silver-tungsten, copper-tungsten, copper-tungsten, iron, copper, zinc, phosphor bronze and aluminum.

Among them, electrodes for electric discharge machining (hereinafter referred to as " graphite electrodes ") made of graphite have low electrode consumption and excellent discharge stability, and can be selected and used depending on applications ranging from roughing to finishing and ultra- Which is easier to work than other metal electrodes.

Due to such excellent properties, the use of graphite electrodes as electrodes for electric discharge machining has been rapidly increasing.

However, since graphite electrodes are complicated in their manufacturing process and require a great deal of cost for constructing a manufacturing facility, they are all imported.

Korea registered patent (10-1439177)

An object of the present invention is to provide a method for manufacturing an electrode for electric discharge machining that is comparable to a graphite electrode at a low cost, while replacing a graphite electrode which is complicated in manufacturing process and requires a large cost for constructing a manufacturing facility.

A method of manufacturing an electrode for electric discharge machining for achieving the above object,

The carbonization condition in which the graphite crystal of the electrode for electric discharge machining can be grown to a predetermined size in the carbonization process is changed by changing the carbonation temperature rise rate and the amount of the coal tar pitch mixed with the phenol resin or the amount of the graphite to be mixed with the phenol resin, step;

A second step of mixing a phenolic resin with a coal tar pitch or graphite in an amount required in the carbonization condition and a waste carbon fiber to prepare a mixture;

A third step of heating and pressurizing the mixture to form a molded body;

A fourth step of carbonizing the formed body to a carbonized body at a carbonation temperature rise rate required in the carbonization condition; And

And a fifth step of machining the carbonized body to make it into the shape of an electrode for electric discharge machining.

The present invention is characterized in that the optimum carbonization condition in which the graphite crystal of the electrode for electric discharge machining can be grown to a predetermined size in the carbonization step is defined as the carbonation temperature rise rate, the amount of the coal tar pitch mixed with the phenol resin, In exchange, the electrode for electric discharge machining is found out before it is manufactured in earnest. The carbonization condition thus found is an important condition having a critical meaning that determines the performance of the electrode for electric discharge machining. The electrode for electric discharge machining manufactured by applying such carbonization condition can have a performance equivalent to that of the conventional graphite electrode.

The present invention relates to a method for producing a carbon fiber, which comprises mixing carbon fiber discarded during carbon fiber spinning or carbon fiber cut off during the production of CFRP into phenol resin, coal tar pitch or phenol resin and graphite, It is made into a working electrode. The carbon fiber which is discarded in the carbon fiber spinning or the carbon fiber which is cut off in the production of the CFRP is not different in quality from the new carbon fiber and when the electrode for electric discharge machining is manufactured with such carbon fiber, An electrode for electric discharge machining can be produced. In addition, the carbon fiber discarded in the carbon fiber spinning process or the carbon fiber discarded in the CFRP process can be recycled to produce the electrode for electric discharge machining, thereby reducing the manufacturing cost of the electrode for electric discharge machining.

Therefore, by using the present invention, it is possible to produce an electrode for electric discharge machining that is comparable to a graphite electrode at low cost, while replacing the graphite electrode, which is complicated in manufacturing process and requires a lot of cost for constructing a manufacturing facility.

1 is a flowchart showing a method of manufacturing an electrode for electric discharge machining according to an embodiment of the present invention.
FIG. 2 is a graph showing the TGA results obtained by changing the carbonation temperature rise rate at 2 ° C./min, 5 ° C./min, and 10 ° C./min while the amount of coal tar pitch mixed in the phenolic resin was fixed at 5 wt% .
3 is a graph showing TGA results obtained by changing the carbonation temperature rise rate at 2 ° C / min, 5 ° C / min, and 10 ° C / min while keeping the amount of coal tar pitch mixed with phenol resin fixed at 10 wt% .
4 is a graph showing TGA results obtained by changing the carbonization temperature rise rates at 2 ° C / min, 5 ° C / min, and 10 ° C / min while the amount of graphite mixed in the phenolic resin was fixed at 5 wt%.
5 is a graph showing TGA results obtained by changing the carbonation temperature rise rate at 2 ° C / min, 5 ° C / min, and 10 ° C / min while the amount of graphite mixed in the phenolic resin was fixed at 10 wt%.

Hereinafter, a method for manufacturing an electrode for electric discharge machining according to an embodiment of the present invention will be described.

As shown in FIG. 1, a method of manufacturing an electrode for electric discharge machining according to an embodiment of the present invention,

The carbonization condition in which the graphite crystal of the electrode for electric discharge machining can be grown to a predetermined size in the carbonization process is changed by changing the carbonation temperature rise rate and the amount of the coal tar pitch mixed with the phenol resin or the amount of the graphite to be mixed with the phenol resin, Step S11;

A second step (S12) of mixing a phenolic resin with a coal tar pitch or graphite in an amount required in the carbonization condition and waste carbon fiber to prepare a mixture;

A third step (S13) of heating and pressing the mixture to form a molded body;

A fourth step (S14) of carbonizing the molded body to a carbonized body at a carbonation temperature rise rate required in the carbonization condition; And

And a fifth step (S15) of machining the carbonized body to form an electrode for electric discharge machining.

The first step S11 will be described below.

In the carbonization process, the optimal carbonization condition is determined so that the graphite crystal of the discharge electrode can be grown to a predetermined size.

The carbonization process refers to the fourth step (S11).

The set size is the size of the graphite crystal which can have the performance equivalent to the performance of the conventional graphite electrode. The size of the graphite crystal differs depending on the graphite electrode depending on the application (roughing, finishing, super-precision machining) of the graphite electrode. The size of the graphite crystal can be determined by actually measuring it.

The performance of the graphite electrode means that it has less electrode consumption, excellent discharge stability, and can be selected depending on the application, from roughing to finishing and ultra-precision processing, and is light in workability compared with other metal electrodes.

The larger the carbonization yield is, the larger the graphite crystal grows, and the graphite crystal can be easily made to the set size.

The optimum carbonization condition with the highest carbonization yield is found by changing the rate of carbonization temperature rise, the amount of coal tar pitch mixed with phenol resin, or the amount of graphite mixed with phenol resin.

Hereinafter, the experimental results of finding the optimum carbonization condition will be described.

[Experiment 1]

In order to find the optimal carbonization condition in which the graphite crystal of the electrode for electric discharge machining can be grown to a set size in the carbonization process, as shown in Fig. 2, the amount of the coal tar pitch mixed with the phenol resin And the TGA analysis (thermogravimetric analysis) is carried out while varying the rate of carbonization temperature rise at 2 캜 / min, 5 캜 / min, and 10 캜 / min.

As a result of TGA analysis, the carbonization yield was 56.7% at a carbonization temperature rise rate of 2 ° C / min. The carbonization yield was 53.7% at a carbonization temperature rise rate of 5 캜 / min. The carbonization yield was 52.5% at a carbonization temperature rise rate of 10 ° C / min.

[Experiment 2]

In order to find the optimal carbonization condition in which the graphite crystal of the electrode for electric discharge machining can be grown to a set size in the carbonization process, as shown in Fig. 3, the amount of coal tar pitch mixed in the phenol resin is fixed at 10 wt% TGA analysis is carried out by varying the rate of carbonization temperature increase at 2 캜 / min, 5 캜 / min, and 10 캜 / min.

As a result of TGA analysis, the carbonization yield was 57.7% at a carbonization temperature rise rate of 2 ° C / min. The carbonization yield was 54.9% at a carbonization temperature rise rate of 5 ° C / min. The carbonization yield was 53.1% at a carbonization temperature rise rate of 10 ° C / min.

[Experiment 3]

In order to find the optimal carbonization condition in which the graphite crystal of the electrode for electric discharge machining can be grown to a predetermined size in the carbonization process, as shown in Fig. 4, the amount of graphite mixed in the phenol resin is fixed at 5 wt% And the TGA analysis (thermogravimetric analysis) is carried out while varying the rate of carbonization temperature rise at 2 캜 / min, 5 캜 / min, and 10 캜 / min.

As a result of TGA analysis, the carbonization yield was 58.2% at a carbonization temperature rise rate of 2 ° C / min. The carbonization yield was 54.1% at a carbonization temperature rise rate of 5 캜 / min. The carbonization yield was 52.2% at a carbonization temperature rise rate of 10 ° C / min.

[Experiment 4]

In order to find the optimal carbonization condition in which the graphite crystal of the electrode for electric discharge machining can be grown in the predetermined size in the carbonization process, as shown in Fig. 5, the amount of graphite mixed in the phenol resin was fixed at 10 wt% TGA analysis is carried out by changing the rate of temperature rise at 2 캜 / min, 5 캜 / min, and 10 캜 / min.

As a result of TGA analysis, the carbonization yield was 58.5% at a carbonization temperature rise rate of 2 ° C / min. The carbonization yield was 55.2% at a carbonization temperature rise rate of 5 ° C / min. The carbonization yield was 53.6% at a carbonization temperature rise rate of 10 ° C / min.

[Experiments 1] to [Experiment 4] As a result, it can be seen that the optimum carbonization conditions are carbonization temperature rise rate 2 ° C / min, which is the greatest with a carbonization yield of 58.5%, and amount of graphite to be mixed with phenol resin 10wt%. Therefore, the optimum carbonization condition is set at a carbonization temperature rise rate of 2 占 폚 / min and the amount of graphite to be mixed with phenol resin is 10 wt%.

The optimum carbonization condition thus determined is an important condition having a critical meaning that determines the performance of the electrode for electric discharge machining according to the present invention.

In order to set the optimal carbonization conditions beforehand in advance of the preparation of the electrodes for electrical discharge machining in such a manner that the carbonation temperature rise rate, the amount of the coal tar pitch mixed with the phenol resin, or the amount of the graphite to be mixed with the phenol resin is changed, It is an important feature that only the invention has.

Further, in order to further increase the hydrocarbon yield, the present invention finds optimum carbonization conditions by adding a coal tar pitch or graphite to the phenol resin. This is an important feature of the present invention. As a result, the test results show that the phenol resin alone does not exceed the maximum carbonization yield of 56.1%.

The second step S12 will be described below.

(10 wt%) of graphite and waste carbon fiber are mixed with phenol resin in an amount required in the carbonization condition selected to make a mixture.

Waste carbon fibers are carbon fibers which are cut off when carbon fiber is spun or CFRP is produced. These carbon fibers have a qualitative difference with respect to carbon fiber obtained by pyrolysis of CFRP (Carbon Fiber Reinforced Plastic) which has been used for a long time.

That is, the carbon fiber which is discarded when the carbon fiber is spun or is cut off when the CFRP is manufactured is not different from the new carbon fiber in quality, and the performance of the discharge electrode is improved by forming the electrode for electric discharge machining with such carbon fiber. This is an important feature of the present invention only.

Particularly, since the carbon fibers that are cut and discarded during the production of CFRP are PAN-based carbon fibers having a diameter of 7 μm and a length of 6 mm or less, if the electrodes for electric discharge machining are formed by orienting the PAN-based carbon fibers in one direction, It is possible to produce an electrode for electric discharge machining having a performance equivalent to that of the graphite electrode of the class 5 μm in average particle size.

The third step S13 will be described below.

The mixture is put into a mold having the shape of an electrode for electric discharge machining, pressed by a press, and heated by a heater to form a molded body. The pressure to be pressed by the press is 3 to 5 MPa, and the heating temperature is 120 to 180 ° C.

The fourth step S14 will be described below.

At a carbonization temperature rise rate of 10 ° C / min required under the selected carbonization condition, the formed body is carbonized to form a carbonized body.

The fifth step S15 will be described below.

The carbonized body is polished with a diamond grinder to perform precision machining in the form of an electrode for electric discharge machining.

Through the first step (S11) to the fifth step (S15), an electrode for electric discharge machining having a performance equivalent to that of a graphite electrode is manufactured.

Claims (5)

delete delete A first step of changing the carbonization condition in which the graphite crystal of the electrode for electric discharge machining can be grown to a predetermined size in the carbonization process by changing the carbonation temperature rise rate and the amount of graphite mixed with phenol resin or graphite mixed with phenol resin;
A second step of mixing a phenolic resin with a coal tar pitch or graphite in an amount required in the carbonization condition and a waste carbon fiber to prepare a mixture;
A third step of heating and pressurizing the mixture to form a molded body;
A fourth step of carbonizing the formed body to a carbonized body at a carbonation temperature rise rate required in the carbonization condition; And
And a fifth step of processing the carbonized material to form an electrode for electric discharge machining,
In the first step, the carbonation temperature rise rates at 2 占 폚 / min and 5 占 폚 / min, the amounts of graphite pitch mixed in the phenol resin, and the amounts of graphite to be mixed with the phenol resin are set at 0 wt%, 5 wt% and 10 wt% After combining, TGA analysis was performed to find the carbonization condition,
Wherein the optimum carbonization condition among the carbonization conditions is a carbonization temperature rise rate of 2 占 폚 / min and an amount of graphite to be mixed with the phenol resin is 10wt%. delete A first step of changing the carbonization condition in which the graphite crystal of the electrode for electric discharge machining can be grown to a predetermined size in the carbonization process by changing the carbonation temperature rise rate and the amount of graphite to be mixed with phenol resin or graphite mixed with phenol resin;
A second step of mixing a phenolic resin with a coal tar pitch or graphite in an amount required in the carbonization condition and a waste carbon fiber to prepare a mixture;
A third step of heating and pressurizing the mixture to form a molded body;
A fourth step of carbonizing the formed body to a carbonized body at a carbonation temperature rise rate required in the carbonization condition; And
And a fifth step of processing the carbonized material to form an electrode for electric discharge machining,
In the second step,
The waste carbon fiber is carbon fiber discarded when carbon fiber is spun, or carbon fiber cut off when CFRP is manufactured,
Wherein the carbon fibers cut and discarded when the CFRP is manufactured are PAN fibers having a diameter of 7 占 퐉 or less and a length of 6 mm or less.

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