JPH05169319A - Graphite electrode for electrochemical machining - Google Patents

Abstract

PURPOSE:To provide a graphite electrode for electrochemical machining used in electrochemical-machining and electrochemical-finishing a work made of metal or the like, which can finish a machined surface of a work with high accuracy and be easily handled and will not deteriorate working environment. CONSTITUTION:A coat 30 of pyrolytic carbon or vitreous carbon is formed on the surface of a graphite base material 50 used as an electrode for electrochemical machining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphite electrolytic machining electrode used for electrolytic machining of a work such as metal and electrolytic finishing of a work machined into a three-dimensional shape.

In detail, a work and an electrode having an electrode surface following the work surface of the work are placed in a stationary electrolyte at a predetermined gap, and a pulsed current is applied between the electrodes. The present invention relates to a graphite electrolytic processing electrode used as an electrode in electrolytic finishing for finishing a work on a glossy surface.

[0003]

2. Description of the Related Art Conventionally, an electrode for electrolytic processing has been required to have performances such as easy manufacturing of the electrode, no electrode consumption, and a small roughness of a finished surface of a work. In recent years, graphite has come to be used in place of metal as an electrode material that further satisfies the above-mentioned required performance.

[0004]

However, although graphite is excellent in that it is easy to manufacture and does not consume electrodes, it is originally used as an electrode for electrolytic processing because it is a porous body having many pores. In this case, the shape of the electrode surface was transferred to the work, and there was a limit to the finished surface roughness of the work surface of the work.

Further, since the electrolytic solution permeates into the pores of the graphite electrode and the electrolytic solution components crystallize out after drying, it takes time and effort to clean the graphite electrode after use.
The work environment was deteriorated due to the deposits.

The present invention has been made in view of such circumstances, and an object thereof is to provide the conventional performance that the electrode of the graphite electrode is easy to manufacture and the electrode consumption is poor. However, it is another object of the present invention to provide an electrode for electrolytic machining of graphite that has a highly precise finish on the machined surface of the workpiece, is easy to handle, and does not deteriorate the working environment.

[0007]

According to the invention of claim 1, the means adopted by the present invention in order to solve the above-mentioned problems is that "an electrode used for electrolytic processing and a graphite substrate 5 is used.
The subject is an electrode 10 for electrolytic processing of graphite, which is characterized in that a film 30 of pyrolytic carbon is formed on the surface of 0.

Next, according to the second aspect of the present invention, "It is an electrode used for electrolytic processing, in which a glassy carbon coating 30 is formed on the surface of a graphite base material 50. The subject is an electrolytic machining electrode 10 made of graphite.

[0009]

The film 3 of pyrolytic carbon according to claim 1
0 has a very dense structure with no pores. Therefore, the surface of the porous graphite base material 50 is completely covered, and a smooth electrode surface 11 without irregularities can be obtained. Therefore, when the workpiece 40 is electrolytically finished by using the graphite electrolytic processing electrode 10 coated with the pyrolytic carbon, the processed surface 41 of the workpiece can be finished to be a smooth and glossy surface.

Further, since the graphite electrolytic processing electrode 10 coated with pyrolytic carbon does not have the pores of the graphite base material 50 on the surface of the electrode 10, the electrolytic solution 20 does not penetrate.

Further, the glassy carbon film 30 described in claim 2 has a dense structure like the pyrolytic carbon film 30, and has the same function as described above.

Next, a method for forming the coating film 30 of pyrolytic carbon and glassy carbon on the surface of the graphite substrate 50 will be described. First, as a method for forming the pyrolytic carbon coating 30 on the surface of the graphite substrate 50, various chemical vapor deposition methods (CVD) that are commonly used can be used.
The graphite substrate 50 is heated to 800 to 2600 ° C.,
A graphite base material 50 having a large number of pores by bringing a hydrocarbon into contact with the graphite base material 50 in the presence of hydrogen gas or argon gas.
Form a dense layer of pyrolytic carbon on top. These reactions are carried out under normal pressure or reduced pressure, but considering the uniformity and smoothness of the pyrolytic carbon coating, under reduced pressure, especially 300 Tor.
It is desirable to carry out at r or less. The thickness of the pyrolytic carbon coating is preferably 10 μm to 500 μm. The reason is that if the thickness is 10 μm or less, sufficient smoothness as the electrode surface 11 and the impermeability as the coating film 30 for protecting the graphite base material 50 cannot be obtained. This is because there is a high possibility that cracks will occur.

Further, as a method for forming the glassy carbon coating 30 on the surface of the graphite base material 50, a thermosetting resin having a small flow and foaming during carbonization and a high carbonization yield is dissolved in a solvent. , The solution is applied to the surface of the graphite base material 50 by impregnation, brush coating, spraying, or the like,
After drying and curing, 700-2600 in an inert gas atmosphere
It can be carried out by heat treatment at ℃.

As the thermosetting resin, divinylbenzene resin, furan resin, phenol resin, or copuna resin is used. Copna resin is one or more selected from coal-based or petroleum-based tar, pitch, or naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, acenaphthacene, berylene, coronene and derivatives having these as the main skeletons. The condensed polycyclic aromatic compound consisting of a mixture of the above-mentioned is an aromatic compound (p-xylene dichloride, p having an aromatic ring of one or more rings having at least one group of at least one of a hydroxymethyl group and a halomethyl group). -Xylene glycol (1,4-benzenedimethanol), dimethyl-p-xylene glycol, dimethyl-m-xylene glycol, etc.). Out of these, the Copuna resin has a high carbonization yield for forming the glassy carbon coating 30, and the flow and foaming during carbonization are small, so that good results can be obtained.

The coating 30 made of pyrolytic carbon has a denser structure than the coating 30 made of glassy carbon and can form a smoother electrode surface 11. On the other hand, since the coating film 30 made of glassy carbon is difficult to peel off, the graphite electrolytic processing electrode 10 coated with the glassy carbon can withstand long-term use.

[0016]

EXAMPLES The present invention will be described below based on examples.
A comparative example with respect to the example will also be described. Example 1 First, an isotropic graphite base material is used as the graphite base material 50.
As shown in FIG. 1, a cylindrical product having an outer diameter of 100 mmφ, a height of 50 mm, and a curved portion with a radius of 100 mm at the bottom was manufactured. Next, this was placed in a CVD furnace, heated to 1400 ° C., hydrogen gas was used as a carrier, methane was supplied into the furnace, and a pyrolytic carbon coating having a thickness of 50 μm was formed on the graphite base material 50. An electrode 10 for electrolytic processing was produced.

This electrode 10 is, as shown in FIG.
It is fixed to the electrode fixing device 12 of the electrolytic finishing machine, the work 40 is fixed to the work fixing device 42 in opposition thereto, and the inside of the processing tank 21 is filled with the sodium nitrate solution that is the electrolytic solution 20. Supply a pulsed current at a current density setting of 40 A / square centimeter and remove it 1
Electrolytic finishing of the processed surface 41 of the 00 μm workpiece 40 was performed. As the work material, SKD-61 was used, and the work that had been processed by electric discharge machining up to Rmax 30 μm in advance was used.

The roughness of the machined surface 41 of the workpiece 40 electrolytically machined in this way was measured in order to measure the machining accuracy. Further, the amount of crystals deposited on the electrode surface 11 of the electrolytic electrode 10 made of graphite after use and drying was measured by weight. The results are shown in Table 1.

Example 2 First, a cylindrical material of isotropic graphite material similar to that of Example 1 was produced. Next, benzene-soluble matter (average molecular weight 340) of petroleum pitch having a softening point of 80 ° C. and p-xylene glycol are mixed at a molar ratio of 1: 2, and 1 wt% of p-toluenesulfonic acid is added, Copna resin reacted at 40 ° C for 40 minutes was dissolved in a solvent, and the solution was spray-coated on the cylindrical material, dried and cured at 180 ° C, then placed in a furnace and placed in an argon gas atmosphere at 2000 The electrode 10 for electrolytic processing of graphite having a glassy carbon coating with a thickness of 5 μm was prepared by heat treatment at 0 ° C.

Next, electrolytic finishing was performed under the same conditions as in Example 1, and the same test as in Example 1 was performed. The results are shown in Table 1.

Comparative Example Next, a comparative example to this embodiment will be described. First,
Cylindrical materials of isotropic graphite materials similar to those in Examples 1 and 2 were prepared and subjected to electrolytic finishing under the same conditions as those in Examples 1 and 2 as the electrode 10 for graphite electrolytic processing as it is without surface treatment. The same test as in Examples 1 and 2 was performed. The results are shown in Table 1.

[0022]

From the results shown in Table 1, the graphite electrolytic processing electrodes 10 of Examples 1 and 2 have a smooth and glossy processed surface as compared with the graphite electrolytic processing electrode of the Comparative Example, and The electrolyte solution 20 penetrates into the pores of the graphite base material 50,
No crystal was deposited on the electrode surface 11 when the electrode was dried.

[0024]

As described above, in the graphite electrolytic processing electrode according to the invention described in claim 1 or 2, the surface of the graphite base material constituting the electrode is a pyrolytic carbon coating or glassy carbon. By forming a coating, the electrode surface has a dense surface layer, and the work surface of the workpiece can be finished with high accuracy, and the electrolytic solution penetrates into the graphite electrolytic processing electrode. No crystal was deposited on the electrode surface of the electrode and the working environment was not deteriorated.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a graphite electrolytic processing electrode according to the present invention.

FIG. 2 is a schematic cross-sectional view showing an electrolytic finishing machine using a graphite electrolytic machining electrode according to the present invention.

[Explanation of symbols]

 10 Electrodes for Electrolytic Machining of Graphite 11 Electrode Surface 20 Electrolyte 21 Processing Tank 30 Coating 40 Work 41 Machining Surface 50 Graphite Base Material

Claims (2)

[Claims] 1. An electrode used for electrolytic processing, comprising a graphite base material and a pyrolytic carbon coating formed on the surface of the graphite base material. 2. An electrode used for electrolytic processing, wherein a graphite-like carbon film is formed on the surface of a graphite base material, and the electrode for electrolytic processing is made of graphite.