JPWO2006057053A1 - Discharge surface treatment electrode, discharge surface treatment method, and discharge surface treatment apparatus - Google Patents

Abstract

A pulsed discharge is generated between a workpiece and a molded electrode formed by molding a metal powder, a metal compound powder, or a ceramic powder, and the energy of the electrode material or electrode material on the workpiece surface depends on the discharge energy. In the discharge surface treatment to form a film made of the reacted substance, a liquid mixed powder is obtained by mixing a metal powder, a metal compound powder, or a ceramic powder in water or an organic solvent liquid to which a dispersant is added. A step of forming, pouring the mixed powder into a mold, removing the liquid by volatilization or absorption into the mold to form a powder molded body, and heating the powder molded body to a temperature at which conductivity is obtained. The electrode for discharge surface treatment is manufactured by the process.

Description

In the present invention, a pulsed discharge is generated between a metal powder, a metal compound powder, or a molded body electrode formed by solidifying a ceramic powder and a workpiece, and the energy is applied to the electrode material on the workpiece surface. Or it is related with the discharge surface treatment which forms the film which consists of the substance which electrode material reacted with discharge energy, and is related with a molded object electrode manufacture especially.

A technique for improving the corrosion resistance and wear resistance by coating the surface of a metal material by submerged electric discharge machining is disclosed in, for example, WC (tungsten carbide) and Co as disclosed in JP-A-5-148615. This electrode material is deposited on the workpiece by performing pulse discharge in liquid with an electrode formed by mixing and compacting the powder of this material, and then remelting discharge machining with another electrode (for example, copper electrode, graphite electrode). A method has been established to obtain higher hardness and higher adhesion. (See Patent Document 1)
Further, as disclosed in Japanese Patent Laid-Open No. 9-192937, when a discharge is generated between a workpiece and a compact of a metal hydride such as TiH2 (titanium hydride) as an electrode, a material such as Ti A technique capable of forming a hard film faster and with better adhesion than in the case of using a coating has been established. (See Patent Document 2)
Moreover, as shown in Japanese Patent No. 3227454, a high-strength surface-treated electrode manufacturing technique has been established by preliminary sintering. (See Patent Document 3).
In addition, the literature based on the study by the present inventors shows that a thick film of about 3 mm can be formed using a WC-Co (9: 1) electrode (see Non-Patent Document 1). The formation of the film was not stable and difficult to reproduce, and at first glance it seemed dense with a metallic luster, but it was a brittle film with many pores, and it was so weak that it was removed when rubbed strongly with a metal piece.

JP-A-5-148615 Japanese Patent Laid-Open No. 9-192937 Japanese Patent No. 3227454 "Formation of thick film by discharge surface treatment (EDC)" Akihiro Goto et al., Mold Technology, (1999), Nikkan Kogyo Shimbun

As the electrode used for the surface treatment, the inventors have found that when a predetermined amount or more of a material that does not easily become carbide is mixed in the electrode material, a dense thick film can be formed. Co (cobalt), Ni ( It has been found that a thick film can be obtained by increasing the material such as nickel) or Fe (iron).
However, in the case of the aforementioned thin hard film and thick film, the electrode is produced mainly by compression molding in which powder is put into a mold and pressed.
In the method of compression molding by pressing, it is possible to produce small electrodes uniformly. However, as the electrode size increases, it becomes difficult to produce uniform electrodes by pressing.
For example, when manufacturing an electrode by pressing a Co alloy powder containing Co as a main component, since the Co alloy powder is pressed to press the powder from above and below in a predetermined mold, the size of the electrode to be manufactured This is because as the distance from the upper and lower press surfaces increases, the pressure is not transmitted and the central portion is not sufficiently compressed.
In addition, when the discharge surface treatment is performed using an electrode that is not uniformly compressed and varies in quality as described above, the quality of the coating cannot be stably maintained.

  The present invention has been made in view of the above, and an object thereof is to establish a technique for uniformly and stably producing an electrode for discharge surface treatment by a discharge pulse in a liquid regardless of the size. .

  The discharge surface treatment electrode according to the present invention generates a pulsed discharge between a metal powder, a metal compound powder, or a molded electrode obtained by molding a ceramic powder, and the energy of the work. In the discharge surface treatment for forming a coating made of an electrode material or a material in which the electrode material reacts with discharge energy on the surface, a metal powder, a metal compound powder, or water in an organic solvent liquid to which a dispersant is added, or A step of mixing a ceramic powder to prepare a liquid mixed powder, a step of pouring the mixed powder into a mold, removing the liquid by volatilization or absorption into the mold, and forming a powder compact, and the powder molding And heating the body to a temperature at which electrical conductivity is obtained.

The discharge surface treatment electrode according to the present invention can improve the uniformity of the electrode and can improve the film formation.
In addition, since a large-shaped electrode can be easily formed, even when a small electrode is required, it can be cut out from the large electrode, and the productivity of the electrode can be increased.

It is explanatory drawing for description of the electrode for discharge surface treatment. This is a process for manufacturing an electrode for discharge surface treatment. The relationship between the heating temperature when a powder compact made of Co alloy powder is heated for 1 hour and the electrical resistance value after heating at that temperature is shown. It is a figure which shows a mode that discharge surface treatment is performed. It is a figure which shows the relationship between the voltage and electric current in discharge surface treatment.

Embodiment 1 FIG.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram for explaining manufacture of an electrode for discharge surface treatment in Embodiment 1 of the present invention.
In the figure, acetone, which is an organic solvent to which a dispersing agent 2 is added in a container 1, and a Co alloy powder to be a discharge surface treatment electrode are mixed to produce a mixed powder liquid.
Here, as an example, a description will be given of the case where Co alloy powder is mixed with acetone, but it goes without saying that other electrode materials may be used.
The electrode material may be, for example, an alloy powder material such as Ni alloy or Fe alloy, Co, Ni, Fe single metal powder, conductive ceramics, or a mixed powder of a plurality of metals / ceramics. The metal element is not limited to these materials.
In order to form a thick film, a predetermined amount, that is, 40% by volume or more, more desirably 50% by volume or more, is included in a metal that does not form carbide or is hard to be carbonized, such as Co, Ni, Fe, and the like. It is good to have.

The volume% of the material in the alloy is difficult to define, but here, the ratio of the value obtained by dividing the weight of each powder to be mixed by the density of each material is defined as volume%.
For example, in the case of an alloy of Co (cobalt) and Cr (chromium), the volume percent of Co (cobalt) is ((weight percent of Co) / (specific gravity of Co)) ÷ (((weight percent of Cr) / (Specific gravity of Cr)) + ((% by weight of Co) / (specific gravity of Co))).
Needless to say, if the material to be mixed as an alloy has a material with a specific gravity close to that of the original material, it is almost the same as the weight%.
On the other hand, the liquid to be mixed with the powder is not limited to acetone, but may be an organic solvent such as alcohol or toluene, or water if it is a material that is difficult to oxidize, such as ceramics or a metal such as Co.

FIG. 2 shows a process for manufacturing an electrode for discharge surface treatment according to the present embodiment.
In the figure, 3 is a mold made of a porous material such as gypsum, and 4 is a powder compact formed by removing an organic solvent from the mixed powder liquid 2.
Next, the process for manufacturing the electrode for discharge surface treatment will be described.
The process for manufacturing the powder compact 4 is roughly composed of the following steps.
1) Prepare mold 3 made of plaster.
Here, if the split mold is used, the powder compact can be easily taken out.
2) In a mold 3 made of gypsum, a Co alloy powder having an average particle size of 1 to 2 μm or less, and a mixture 2 of an organic solvent and a dispersant are placed. Here, as a dispersing agent, stearic acid is added about 3 wt% of the Co alloy.
3) A drying step for removing the solvent from the mixed powder liquid 2.
Decrease due to volatilization or absorption into the mold 4) When most of the organic solvent is not volatilization / absorption into the mold, the Co alloy solidifies.
5) The powder compact can be taken out by splitting the split mold.
If necessary, the surface of the molded electrode is polished.

Depending on the material and particle size of the powder, there may be cases where the powder compact 4 has good electrical conductivity and can be used as an electrode for discharge surface treatment, but in most cases, the electrical resistance is too high and the strength is weak. In many cases, it is difficult to use the electrode as it is.
Therefore, the powder molded body 4 is heated so that it can be used as an electrode for discharge surface treatment.
Since the powder compact 4 is made of a powder material, it is in a state where it is easily oxidized.
For this reason, if the powder is simply heated, the powder will oxidize and adversely affect the conductivity of the electrode. Therefore, it is desirable to heat in a non-oxidizing atmosphere such as a vacuum furnace or an argon furnace.

FIG. 3 shows the relationship between the heating temperature when the powder compact 4 made of Co alloy powder is heated for 1 hour and the electrical resistance value after heating at that temperature.
Although the electric resistance value before heating varies depending on the material and the like, it is usually a value of 10Ω or more, and is not in a state where it can be used as a discharge surface treatment electrode.
However, the electrical resistance can be lowered by heating the powder compact 4.
Here, if the heating temperature is too high, the powder molded body 4 becomes too hard and becomes a so-called sintered state, and the electric resistance is reduced, but it cannot be used as an electrode for discharge surface treatment. The temperature at which the electrical resistance drops below 1Ω and does not become too hard is the optimum heating temperature of the powder compact 4.
Of course, heating is not always necessary when there is sufficient conductivity without heating.

FIG. 4 shows a state where the discharge surface treatment is performed by the electrode manufactured by the above method.
As shown in the figure, the electrode 11 and the workpiece 12 are placed in a working liquid 14 such as oil with a predetermined gap therebetween, and a discharge is generated by applying a pulsed voltage from the power supply 14 for discharge surface treatment. In the figure, reference numeral 15 denotes an arc column of discharge that is generated at the moment when the discharge occurs.
The discharge surface treatment power source 13 has a negative electrode polarity, and generates a pulsed discharge having a pulse width te of about several μm to several tens of μm as shown in FIG.

The film formed by the above method is uniform even if the location of the electrode changes, and is a film having a constant performance.
Moreover, even when the electrode size is increased, variations in electrode hardness, electrical resistance, and the like are reduced, and the quality of the coating can be stabilized.
According to the present embodiment, it is possible to improve the uniformity of the electrode in the case of a carbide-based thin hard coating, and in particular, the uniformity of an electrode including a metal material that is difficult to form carbides such as Co, Ni, and Fe. Can be improved.
In addition, according to the present method, a large-shaped electrode can be easily formed, so that even when a small electrode is necessary, it can be cut out from the large electrode and used, thereby increasing the productivity of the electrode.

  The present invention relates to an electrode manufacturing technique used for discharge surface treatment.

Claims (9)

A pulsed discharge is generated between a workpiece and a molded electrode formed by molding a metal powder, a metal compound powder, or a ceramic powder, and the energy of the electrode material or electrode material on the workpiece surface depends on the discharge energy. In discharge surface treatment to form a film made of the reacted material,
A step of mixing a metal powder, a metal compound powder, or a ceramic powder with water or an organic solvent liquid to which a dispersant is added, to create a liquid mixed powder;
Pouring the mixed powder into a mold, removing the liquid by volatilization or absorption into the mold, and forming a powder compact;
Heating the powder compact to a temperature at which electrical conductivity is obtained;
An electrode for discharge surface treatment, which is manufactured from   2. The discharge surface treatment electrode according to claim 1, wherein the powder material contains 40% by volume or more of a metal material which does not form carbide or is difficult to form.   3. The discharge surface treatment electrode according to claim 2, wherein the metal material which does not form or hardly forms carbide is Co, Ni, or Fe. A pulsed discharge is generated between a workpiece and a molded electrode formed by molding a metal powder, a metal compound powder, or a ceramic powder, and the energy of the electrode material or electrode material on the workpiece surface depends on the discharge energy. In discharge surface treatment to form a film made of the reacted material,
A step of mixing a metal powder, a metal compound powder, or a ceramic powder with water or an organic solvent liquid to which a dispersant is added, to create a liquid mixed powder;
Pouring the mixed powder into a mold, removing the liquid by volatilization or absorption into the mold, and forming a powder compact;
Heating the powder compact to a temperature at which electrical conductivity is obtained;
A method for producing an electrode for discharge surface treatment comprising:   5. The method for producing an electrode for discharge surface according to claim 4, wherein the powder material contains 40% by volume or more of a metal material which does not form carbide or is difficult to form.   6. The discharge surface treatment method according to claim 5, wherein the metal material that does not form or hardly forms carbide is Co, Ni, or Fe. In a liquid of water or an organic solvent to which a dispersant has been added, a metal powder, a metal compound powder, or a liquid mixed powder obtained by mixing ceramic powder is poured into a mold, and the liquid is volatilized or absorbed by the mold. After removing to form a powder compact, an electrode manufactured by heating the powder compact to a temperature at which conductivity is obtained;
A machining fluid supply device for immersing the electrode and the workpiece in a machining fluid or supplying a machining fluid between the electrode and the workpiece;
And a power supply device that generates a pulsed discharge by applying a voltage to the machining fluid between the electrode and the workpiece, and the electrode component or a component in which the electrode component is changed by the discharge on the workpiece surface is a main component. Discharge surface treatment apparatus for forming a film.   8. The discharge surface treatment apparatus according to claim 7, wherein the electrode component contains 40% by volume or more of a metal material which does not form carbide or is difficult to form.   9. The discharge surface treatment apparatus according to claim 7, wherein the metal material that does not form or hardly forms carbide is Co, Ni, or Fe.

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