JP2005213558A - Electrode for electrical discharge surface treatment and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a green compact electrode for use in surface treatment, which is easily formed into optional shape and is easily handled. <P>SOLUTION: An electrical discharge surface treatment is carried out by generating pulse discharge between a green compact electrode prepared by compacting metal powder, metal compound powder or ceramic powder and a work, and depositing a coating comprising the electrode material or a substance produced by the reaction of the electrode material with discharge energy on the work surface. In the surface treatment, the electrode is prepared by depositing the electrode powder which results in the coating by the above surface treatment on an electrode core having rigidity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, a metal powder, a metal compound powder, a green compact obtained by compression molding a ceramic powder, or a green compact obtained by heat-treating the green compact is used as an electrode in a working fluid or in the air. The present invention relates to a discharge surface treatment in which a pulsed discharge is generated between an electrode and a workpiece, and a film made of an electrode material or a substance obtained by reacting the electrode material with discharge energy is formed on the workpiece surface by the energy.

Conventionally, as a technique for coating the surface of a workpiece to impart corrosion resistance and wear resistance, for example, Japanese Patent Application Laid-Open No. 5-148615 uses a green compact electrode made of WC powder and Co powder. A discharge surface treatment method is disclosed in which primary processing (deposition processing) is performed, and then secondary processing (remelting processing) is performed by replacing the electrode with a relatively low electrode consumption such as a copper electrode.
This technique is an excellent method for forming a hard coating with a high hardness and a thickness of about several tens of μm on the steel material, but it has to be performed in two steps. It is difficult to form a hard film having strong adhesion on the surface of a sintered material such as a cemented carbide.

Japanese Patent Application Laid-Open No. 9-192937 discloses a discharge surface treatment method in which a hard coating having a thickness of several μm to several tens of μm is formed on a cemented carbide by using a compact electrode of TiH ₂ powder. Is disclosed.

  In addition, as a method for producing an electrode for discharge surface treatment, International Publication WO 00/29155 discloses that a metal mold, a metal compound, or the like is filled in a female die of a discharge surface treatment target mold, An electrode manufacturing method is disclosed in which a material powder in a female mold is pressed by a male mold.

JP-A-5-148615 Japanese Patent Laid-Open No. 9-192937 International Publication WO00 / 29155

The conventional discharge surface treatment using a green compact electrode has the advantage that the electrode components are easily melted by the discharge energy and a film is easily formed on the surface of the workpiece, but the green compact electrode is brittle and easily broken.
Accordingly, it has been extremely difficult to perform machining for matching the electrode to the shape of the workpiece or molding a small portion such as a screw hole for fixing the electrode to the apparatus.
In order to increase the rigidity of the electrode, it is conceivable that the green compact electrode is used as a metal electrode by sintering it. However, the electrode after the main sintering is subjected to removal processing and cannot deposit a film.
Similarly, since the green compact electrode is fragile and easily broken, it is difficult to form a practical size electrode.
That is, in order to mold an electrode to a practical size used for surface treatment of a mold or the like, the press capability must be dramatically increased, and pressure is applied to the inside of the material during compression molding of the powder material. Non-uniform propagation increases density non-uniformity and causes defects such as cracking.
Therefore, since the hard coating formed on the workpiece has variations, it is a factor that deteriorates the quality.
Furthermore, regarding the electrode manufacturing, even if the electrode powder is put into a female mold and pressed by a male mold, the discharge surface treatment can be performed uniformly along the mold surface if the electrode is of an appropriate size.
However, when the male mold is thin, there is a problem that the male mold is deformed during pressure molding and a desired surface cannot be obtained.

  In other words, in the conventional electrode manufacturing method, when a round bar electrode having an outer diameter of Φ1 mm or less or a flat plate electrode having a thickness of 1 mm or less is manufactured, the pressed electrode is broken when it is put into the furnace or removed from the furnace, or the electrode is held. In addition to being able to manufacture small and thin electrodes, there is a limit to the shape of the electrodes that can be manufactured.

  The present invention has been made to solve the above-described problems in the discharge surface treatment, and provides a method capable of manufacturing electrodes of any shape.

  The discharge surface treatment electrode according to the present invention generates a pulsed discharge between a metal powder, a metal compound powder, or a green compact electrode obtained by compression molding a ceramic powder, and the workpiece. In discharge surface treatment that forms a coating made of an electrode material or a material that reacts with the discharge energy of the electrode material on the workpiece surface by energy, the electrode powder that becomes the coating in the surface treatment is disposed on the core of the rigid electrode. Is.

  According to the present invention, since it is possible to manufacture a green compact electrode shape that could not be manufactured in the past, it becomes possible to form a coating on the inner surface of a small hole or the surface of a narrow groove. There are effects such as improvement of heat exchange efficiency by expanding the surface area.

Embodiment 1 FIG.
First, the principle of discharge surface treatment using a green compact electrode formed by compressing and forming a metal powder of several μm will be described with reference to FIG.
In addition, the electrode uses what heat-processed, after compression-molding the metal powder of several micrometers.
An electrode and a workpiece are arranged in the working fluid, the electrode is used as a cathode, the workpiece is used as an anode, and the main shaft generates a discharge in a servo-controlled state so that they do not come into contact with each other.
A part of the electrode is melted and vaporized by the heat of the discharge, and the electrode lump is released by the blast and electrostatic force generated by the discharge, and is deposited on the workpiece to form a film.

The green compact electrode used here is manufactured through an electrode manufacturing process shown in FIG.
The metal powder on the market is converted into a metal powder having a desired particle size through pulverization, drying and sieving processes.
In addition, a wax such as paraffin is added to the spherical powder of metal or ceramics with an average particle size of several μm to improve the transmission of the pressure of the press to the inside of the electrode during pressing. mixing.
In addition, when mixed with wax such as paraffin, the powder covers the surroundings of the powder, and the liquid is agglomerated by the action of intermolecular force or electrostatic force to form a large lump. Need to be sifted.
The powder that has passed through the sieve is molded with a compression press, and then heated in a vacuum furnace or a furnace in an atmosphere of nitrogen or an inert gas to produce a conductive green compact electrode.

The green compact electrode is manufactured by the process of FIG. 2, but as described above, it is difficult to form the electrode manufactured by the process of FIG. 2 into a desired shape.
Therefore, in the present embodiment, the electrode manufacturing process shown in FIG. 3 is performed.
In addition, the state of the press in the manufacturing process is shown in FIG.
In the figure, 1 is a Co (cobalt) powder having a particle size of about 1 μm, 2 is a punch above the mold, 3 is a punch below the mold, 4 is a mold die, and 5 is a mixture of paraffin and Co powder 1 This is a Co round bar obtained by press-molding the body at a high pressure (about 300 MPa).
Here, the Co powder 1 was mixed with 3% by weight of paraffin.
Thereafter, in order to decompose the agglomerated material, the powder mixed with paraffin was passed through a sieve having a mesh size of 0.05 mm.
Then, an appropriate amount of a mixture of paraffin and Co powder 1 is put into a mold, and a Co round bar 5 is embedded therein.
Thereafter, the Co powder 1 is placed so as to cover the Co round bar 5 so that the round bar does not come into contact with the mold wall surface, and is pressed by applying pressure with a punch.
By applying a predetermined pressing pressure to the powder, the powder becomes a solid and becomes a green compact.
The pressure applied here is about 90 MPa, which is lower than when the Co round bar 5 is manufactured.
In addition, in order to improve the transmission of the pressure of the press to the inside of the powder at the time of pressing, when the wax such as paraffin is mixed in the powder by about 1% to 10% by weight, the moldability can be improved. As the remaining amount of wax increases, the electrical conductivity deteriorates. Therefore, when the wax is mixed, it is desirable to remove the wax in a later step.

After that, the compression-molded green compact can be used as it is as an electrode for discharge surface treatment as long as a predetermined hardness is obtained by compression, but the strength can be increased by heating.
In the case of Co, the electrode is held at 300 ° C. for 1 hour to increase the strength of the electrode.
At this time, the Co round bar 5 molded with a large breath pressure has a strong bond between the powder and the rigidity.
In addition, the Co powder 1 around the Co round bar 5 has a strength enough to be separated by discharge and become a film.
Further, when wax is mixed during compression molding, it is necessary to remove the wax by heating the electrode, and therefore, the temperature is maintained at 200 ° C. for 30 minutes in a vacuum furnace.
When heated, the wax that has reached the melting point oozes from the electrode to the surface.
Thereafter, when heated to 300 ° C., the exuded wax reaches the boiling point and vaporizes.
In addition, there exists a part maintained at about 100 degreeC in the furnace, and the wax which vaporized there is trapped and returns to a liquid.
In such a process, the wax is removed from the electrode.

Next, FIG. 5 shows a state in which a discharge surface treatment is performed on the inner surface of a narrow hole by using an electrode 11 composed of Co powder 1 having an average particle diameter of 1 μm and a Co rod 5.
The electrode 11 and the workpiece 12 are disposed in the machining liquid 13, and discharge can be generated between the electrode side surface and the hole side surface based on the discharge surface treatment power source 14, and the discharge surface treatment can be performed on the inner surface of the narrow hole. .

In the conventional method for producing an electrode for discharge surface treatment, an electrode having an outer diameter of Φ2 mm could not be produced, so that the coating could not be treated on the inner wall or entrance of the fine hole.
However, according to the present embodiment, a Co powder 1 having an average particle diameter of 1 μm is placed about 30 mm from the bottom into a mold having a size of Φ2 mm × 50 mm, and a Co rod 5 having a diameter of Φ1 mm × 40 mm is inserted therein, and the average particle diameter is further increased. Co powder 1 of 1 μm is added, compression molding is performed at a press pressure of 2 MPa, and the electrode is heated in a vacuum furnace to be manufactured.
In addition, the handling of the electrode manufactured by this Embodiment is as easy as a metal bar.
That is, according to this embodiment, a thin electrode having a diameter of about 2 mm can be manufactured.

Using the electrodes manufactured as described above, the inner wall of a hole of Φ2.5 mm × 100 mm was actually coated.
The discharge pulse conditions used were negative on the electrode side, positive polarity on the work side, peak current value ie = 5 to 20 A, and discharge duration (discharge pulse width) te = about 4 to 100 μs.
During processing, the electrode was rotated and further swung.
Under either condition, a film of about 0.05 mm could be deposited on the inner wall of the cylinder.
According to the present invention, when the hole diameter or the hole tip is worn by some influence, it can be repaired to the original dimension.

Although Co has been described in the present embodiment, Ni or Ag may be used as the material of the round bar.
Since Co, Ni, and Ag are materials that are difficult to oxidize, the oxide film formed on the surface is thin.
Therefore, the oxide film on the surface is easily broken by pressing, and the bonding between the powders becomes strong, and a high-rigidity round bar can be manufactured only by pressing.
Furthermore, since the strength is remarkably improved at a low temperature, it is possible to give a strength close to that of a metal rod at a heating temperature for increasing the strength of the powder around the round bar.
For example, in order to form a TiC (titanium carbide) film, it is necessary to cover the Co core with TiC powder and to heat at about 1000 ° C. At 1000 ° C., TiC has an optimum hardness for forming a coating, and the Co core material has a strength almost similar to that of a metal rod.

Even if a metal rod is used as the core material, a high-strength thin electrode can be manufactured. However, when pressed, the bonding strength between the powder covering the rod and the metal rod is lowered.
In the round bar of powder and green compact, since the surface area which contacts is large, it becomes big joint strength.

Further, Co or Ni powder may be used for the core material, and the metal or alloy powder or ceramic powder may be used for the powder to be the coating.
When the contamination of the coating is disliked, the material of the core rod and the coating powder may be unified as in this embodiment.

Embodiment 2. FIG.
Although the thin electrode has been described in the first embodiment, a large electrode cannot be manufactured by the conventional method for manufacturing a discharge surface treatment electrode.
The electrode used in the discharge surface treatment is an aggregate of particles, and each particle remains in the shape of being joined by point contact and is not completely dissolved. Therefore, the strength of the electrode is very small, and when the electrode becomes large, the electrode is broken by its own weight.

FIG. 6 shows the appearance of manufacturing the electrode for discharge surface treatment according to the present embodiment.
In the same manner as in the first embodiment, 3% by weight of paraffin is mixed with Co powder 1 having a particle size of 1 μm, and after agglomeration, the mixture is passed through a sieve having a mesh size of 0.05 mm. A bottomed round bar 6 having a Co protrusion is embedded therein.
The round bar 6 is a green compact of the powder 1, but is molded by applying a high pressure.
By pressing with a predetermined pressure by a punch, the powder 1 is solidified into a green compact.

As in the first embodiment, in order to improve the transmission of the pressure of the press into the powder during pressing, wax such as paraffin is mixed in the powder at a weight ratio of about 1% to 10% to improve the moldability. However, as the remaining amount of wax in the electrode increases, the electrical conductivity deteriorates. Therefore, when the wax is mixed, it is desirable to remove the wax in a later step.
The compression-molded green compact can be used as it is as an electrode for discharge surface treatment as long as a predetermined hardness is obtained by compression, but the strength can be increased by heating.
Further, when wax was mixed during compression molding, it was necessary to remove the wax by heating the electrode, so the electrode was molded by heating to 300 ° C. in a vacuum furnace.
At this time, the Co round bar 6 molded with a large breath pressure has a strong bond between the powder and the rigidity.
Further, the Co powder 1 around the Co round bar 6 is separated by electric discharge and has a strength enough to form a film.

In the conventional method for manufacturing an electrode for discharge surface treatment, an electrode of 200 mm × 200 mm × 200 mm could not be manufactured.
However, according to the present embodiment, Co powder 1 having an average particle diameter of 1 μm is put into a mold having dimensions of 200 mm × 200 mm × 200 mm, and a Co rod of 180 mm × 180 mm × 150 mm (the upper part is 200 mm × 200 mm × 30 mm) 6 was inserted and compression molded at a press pressure of 2 MPa. The electrode was placed in a vacuum furnace and held at 300 ° C. for about 1 hour to produce an electrode.
It should be noted that handling of the electrode manufactured according to the present embodiment is as easy as metal lump.
In other words, the present embodiment made it possible to manufacture 200 mm × 200 mm × 200 mm electrodes.

Even if the electrode is actually processed, a film of about 0.05 mm can be formed on the inner surface of 205 mm × 205 mm × 200 mm. Conventionally, when surface processing of a large area is performed, it is repeatedly performed with a small electrode. Since the processing that had to be performed can be performed with minimum tool change and the like, the work efficiency of film formation is improved.
In addition, since a large electrode can be formed, it is possible to process a workpiece having a three-dimensional shape, and it is possible to obtain an effect that a large number of surfaces can be processed simultaneously.

Embodiment 3 FIG.
Next, the process for manufacturing the electrode for discharge surface treatment in Embodiment 3 will be described with reference to FIG.
In the above-described embodiment, the case where Co green compact is used as the core of the green compact electrode has been described. However, in order to manufacture a relatively thin film-like electrode, in this embodiment, an ABS network is used as the core. 7 is used.
Specifically, after the paraffin is mixed into the Co powder 1 having a particle diameter of 1 μm in the same manner as in the above-described embodiment, it is passed through a sieve having a mesh size of 0.05 mm in order to decompose the agglomerated material, and an appropriate amount is put into a mold. The net 7 is embedded inside.
Thereafter, a mixture of Co powder 1 is further added, and pressing is performed by applying a predetermined pressure by a punch, whereby the powder is solidified and becomes a green compact.
It is the same as in the above-described embodiment that wax is added during pressing and the wax is removed in the subsequent steps.
The compression-molded green compact can be used as it is as an electrode for discharge surface treatment as long as a predetermined hardness is obtained by compression, but the strength can be increased by heating.
Further, when wax was mixed during compression molding, it was necessary to remove the wax by heating the electrode, so the electrode was molded by heating to 300 ° C. in a vacuum furnace.

In the conventional manufacturing method of the electrode for discharge surface treatment, an electrode of 100 mm × 100 mm × 5 mm could not be manufactured.
However, a mixture of Co powder 1 and paraffin having an average particle diameter of 1 μm is placed in a mold having dimensions of 100 mm × 100 mm × 5 mm, an ABS net 7 of 90 mm × 90 mm × 2 mm is inserted therein, and Co having an average particle diameter of 1 μm is further inserted. The powder 1 mixture was added, compression-molded at a press pressure of 2 MPa, the electrode was placed in a vacuum furnace, and held at 300 ° C. for about 1 hour to produce an electrode.
It should be noted that handling of the electrode manufactured according to the present embodiment is as easy as metal lump.
In other words, this embodiment made it possible to manufacture an electrode of 100 mm × 100 × 5 mm.

Even if the electrode is actually processed, a film of about 0.05 mm can be formed on the inner surface of the groove having a narrow gap of 105 mm × 105 mm × 10 mm, and a film can be formed at a place where the conventional treatment could not be performed.
If the electrode obtained in this embodiment is used for a slit of a heat exchanger or the like, the surface area can be increased due to the surface roughness of the coating, and the efficiency of heat exchange can be increased.

In this embodiment, the case where an ABS net is used as the core of the electrode has been described, but a flat plate has the same effect.
However, a mesh is better because the bonding strength between the powder and the flat plate is small.
The material is not limited to ABS or metal, but may be glass or plastic or resin that does not deform at high temperatures.
When a material having a low melting point is used for the mesh as in this embodiment, the mesh is evaporated by the heat of discharge.
If a high melting point material is used for the mesh, it will not melt even with the heat of discharge.
If it does not melt, the surface becomes the discharge surface, but since the mesh material is not conductive, the discharge cannot be performed or the electrode collides with the workpiece.
However, since those having a low melting point are not evaporated, even if a core appears during processing, the coating is not adversely affected.
If Zn, which is a metal with a low melting point, is used, there is no need to worry about the above problems.
Further, when a hard material having a high melting point is used, the material cannot be supplied from the electrode, and thus the deposited film is removed.
ABS and plastic melt and precipitate carbon, but since the processing fluid is originally treated with oil in a carbon-rich environment, the coating is not soiled.

It is a figure which shows the phenomenon of a discharge surface treatment. It is a flowchart of a general electrode manufacturing process of a green compact electrode. It is a flowchart of the electrode manufacturing process in this Embodiment. It is a figure which shows the mode of the press in an electrode manufacturing process. It is a phenomenon figure which processes using the electrode of this Embodiment. It is a figure which shows the mode of the press in an electrode manufacturing process. It is a figure which shows the mode of the press in an electrode manufacturing process.

Explanation of symbols

  1 Co powder, 2 top punch, 3 bottom punch, 4 molds, 5 round bar, 6 round bar with bottom, 7 mesh.

Claims (18)

A pulsed discharge is generated between the electrode of a green powder, a powder of a metal powder or a metal compound, or a green compact obtained by compression molding a ceramic powder, and the work is used to generate an electrode material or electrode material on the work surface. In the discharge surface treatment to form a film made of a substance reacted by the discharge energy,
An electrode for discharge surface treatment, characterized in that an electrode powder that becomes a film by the surface treatment is disposed on a rigid electrode core. The electrode for discharge direction treatment according to claim 1, wherein the electrode core is made of the same material as the electrode powder that becomes a film in the surface treatment. 3. The discharge surface treatment electrode according to claim 1 or 2, wherein a material that is not easily oxidized, such as Ag, Ni, or Co, is used for the core of the electrode. The electrode for discharge surface treatment according to any one of claims 1 to 3, wherein the core of the electrode is embedded in the green compact electrode. The electrode for discharge surface treatment according to claim 4, wherein the core of the electrode has a net structure. The electrode for discharge surface treatment according to any one of claims 1 to 3, wherein the electrode core has a bottomed shape having a protrusion embedded in the green compact electrode. The electrode for discharge surface treatment according to any one of claims 1 to 6, wherein the core of the electrode is made of a material having rigidity and a low melting point. 8. The discharge surface treatment electrode according to claim 7, wherein a resin having a rigidity and a low melting point is made of a resin such as Zn, ABS, or acrylic. The electrode for discharge surface treatment according to claim 7, wherein the shape of the material having rigidity and low melting point is a net shape or a porous shape. Putting metal powder or metal compound powder, or ceramic powder into a mold having a desired shape;
Placing a rigid electrode core in the electrode material powder; and
In a state where the powder of the electrode material and the electrode core are arranged in the mold, a predetermined pressure is applied, and the green compact electrode is press-molded,
The manufacturing method of the electrode for discharge surface treatment provided with this. 11. The method for producing an electrode for discharge direction treatment according to claim 10, wherein the electrode core is made of the same material as the electrode powder that becomes a film in the surface treatment. The method for manufacturing an electrode for discharge direction treatment according to claim 10 or 11, wherein a material that is not easily oxidized, such as Ag, Ni, or Co, is used for the core of the electrode. 13. The method for producing an electrode for discharge surface treatment according to claim 10, wherein the core of the electrode is embedded in the green compact electrode. 14. The method for manufacturing an electrode for discharge surface treatment according to claim 13, wherein the core of the electrode has a net structure. The method for producing an electrode for discharge surface treatment according to any one of claims 10 to 12, wherein the electrode core has a bottomed shape having a protrusion embedded in the green compact electrode. The method for manufacturing an electrode for discharge surface treatment according to any one of claims 10 to 15, wherein the core of the electrode is made of a material having rigidity and a low melting point. The method for producing an electrode for discharge direction treatment according to claim 16, wherein a resin having a rigidity and a low melting point is used, such as a resin such as Zn, ABS, or acrylic. The method for producing an electrode for discharge surface treatment according to claim 16, wherein the shape of the material having rigidity and low melting point is a net shape or a porous shape.

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