JP2007002337A - Method for producing electrode for discharge surface treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce an electrode for discharge surface treatment in which the variation of film components is eliminated, so as to realize their uniformization, and capable of performing the formation of a thick film which has been difficult heretofore. <P>SOLUTION: The invention is a method for producing an electrode used for discharge surface treatment where pulselike discharge is generated between an electrode and a work in a working liquid, and a film of the electrode material is formed on the surface of the work by the discharge energy, or a film of a substance obtained by the reaction of the electrode material by the discharge energy is formed on the surface of the work. The method is provided with: a stage where an alloy material is dissolved or pulverized; a stage where the particle diameter of the pulverized alloy powder is made uniform through a filter; and a stage where the alloy powder whose particle diameter is made uniform is subjected to compression molding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a substance in which a pulsed discharge is generated between an electrode having an alloy powder as an electrode material and a work, and a film of the electrode material is formed on the work surface by the discharge energy or the electrode material reacts by the discharge energy. In particular, the present invention relates to a method for producing an electrode used for the discharge surface treatment.

  A technique for improving the corrosion resistance and wear resistance by coating the surface of a metal material by a submerged electric discharge machining method is already known. An example of the technique is as follows.

  For example, in Japanese Patent Application Laid-Open No. 5-148615, this electrode material is deposited on a workpiece by performing pulse discharge in liquid using an electrode formed by mixing WC (tungsten carbide) and Co powder and compression molding, and thereafter A method is disclosed in which remelting electric discharge machining is performed with a plurality of electrodes (for example, copper electrode, graphite electrode) to obtain higher hardness and higher adhesion. That is, using a WC-Co mixed green compact electrode, the workpiece (base material S50C) is subjected to electrical discharge machining in a liquid, WC-Co is deposited on the workpiece (primary machining), and then a copper electrode or the like. Remelting processing (secondary processing) is performed with electrodes that are not so consumed. As a result, with the primary processing, the deposited structure had a hardness (Vickers hardness Hv) of about Hv = 1410, and there were many cavities, but the secondary processing remelt processing eliminated the cavities of the coating layer, Hardness is also improved with Hv = 1750. By this method, a coating layer that is hard and has good adhesion to a steel material as a workpiece can be obtained.

  However, in the above-described method, it is difficult to form a coating layer having strong adhesion on the surface of a sintered material such as a cemented carbide as a workpiece. In this regard, according to the study by the present inventors, when a material such as Ti that forms hard carbide is used as an electrode and a discharge is generated between the workpiece and the workpiece, a strong hard film is formed on the workpiece without remelting. It was found that it can be formed on a metal surface. This is because TiC is generated by the reaction between the electrode material consumed by the discharge and carbon C, which is a component in the working fluid.

Japanese Patent Laid-Open No. 9-192937 uses a material such as Ti when a discharge is generated between a workpiece and a compact of a metal hydride such as TiH ₂ (titanium hydride) as an electrode. A technique capable of forming a hard film faster and with better adhesion than the case is disclosed. Furthermore, when a discharge is generated between the workpiece and a compact, which is a mixture of hydride such as TiH ₂ (titanium hydride) with other metals or ceramics, various properties such as hardness and wear resistance are obtained. There is also disclosed a technique capable of quickly forming a hard coating having a thickness.

  As another technique, Japanese Patent No. 3227454 discloses that a surface-treated electrode having high strength can be produced by preliminary sintering. That is, when manufacturing an electrode for discharge surface treatment comprising a powder obtained by mixing WC powder and Co powder, a green compact obtained by mixing and compressing WC powder and Co powder is obtained by mixing WC powder and Co powder. Although it may be only compression molded, if the molding is performed after the wax is mixed, the moldability of the green compact is improved.

  In this case, the wax is an insulating substance, and if it remains in the electrode in large quantities, the electrical resistance of the electrode increases and the discharge performance deteriorates. Therefore, the wax is removed by heating the green compact electrode in a vacuum furnace. is doing. At this time, if the heating temperature is too low, the wax cannot be removed, and if the temperature is too high, the wax becomes soot and deteriorates the purity of the electrode. It is necessary to keep below.

Then, the green compact in the vacuum furnace is heated by a high-frequency coil or the like to give a strength that can withstand machining, and is fired to a hardness of, for example, white ink so as not to be hardened (this is a pre-sintered state) Called). In this case, bonding proceeds at the contact portion between the carbides, but the bonding is weak because the sintering temperature is relatively low and the main sintering is not achieved. It has been found that when the discharge surface treatment is performed with such an electrode, a dense and homogeneous film can be formed.
JP-A-5-148615 Japanese Patent Laid-Open No. 9-192937 Japanese Patent No. 3227454

  However, in the above-described conventional discharge surface treatment, as an electrode, powder of a material to be coated is mixed, for example, Co powder 107, Cr powder 108, Ni powder 109 as shown in FIG. 5, and the mixed powder is compression-molded. A green compact or a green compact subjected to heat treatment is used. In another example, when forming a cemented carbide (WC-Co-Cr) component film, WC (tungsten carbide) powder, Co (cobalt) powder and Cr (chromium) powder The electrode is a green compact obtained by mixing and compression-molding the mixed powder, or a compact subjected to heat treatment thereafter.

  A dense film can be formed by discharging the green compact electrode. However, since it is an electrode manufactured by mixing powder, when the film is observed microscopically, Due to the mixing variation and the variation in melting caused by the size of the powder particle size, a uniform component film is not obtained. The degree of this micro variation is inevitable as long as the mixed powder is discharged as an electrode. In a normal film, the variation of this component does not become a problem, but it may become a problem in a special environment, for example, when used in a high temperature environment such as an aircraft engine.

  Further, in the conventional discharge surface treatment as described above, since the focus was on forming a hard coating, the electrode material may be a hard ceramic material or an oil component in the machining fluid depending on the energy of discharge. The main component is a material that chemically reacts with certain C (carbon) to form a hard carbide. However, hard materials generally have characteristics such as a high melting point and poor thermal conductivity, and thin films of about 10 μm can be densely formed, but it is extremely difficult to form dense thick films of several hundred μm or more. there were.

  Based on the research of the present inventors ("Formation of thick film by electric discharge surface treatment (EDC)" Akihiro Goto et al., Mold Technology, (1999), Nikkan Kogyo Shimbun) WC-Co (9: 1) It has been shown that a thick film of about 3 mm could be formed using an electrode, but the film formation was not stable and difficult to reproduce. As described above, there are problems such as the fact that the material of the coating varies depending on the particle size of the original powder, and this is a practically difficult level.

  The present invention has been made in view of the above, and an object of the present invention is to provide a discharge surface treatment electrode and a discharge surface treatment method in which variations in coating film components, which has been difficult in the past, are eliminated and made uniform.

  In addition, the present invention has been made in view of the above, and an object of the present invention is to provide a method for manufacturing a discharge surface treatment electrode for forming a thick film, which has been difficult in the past by conventional submerged pulse discharge machining. .

  In order to achieve the above object, a method for manufacturing an electrode for discharge surface treatment according to the present invention generates a pulsed discharge in a machining fluid between an electrode and a workpiece, and a coating of an electrode material is applied to the workpiece by the discharge energy. In a manufacturing method of an electrode for discharge surface treatment used for discharge surface treatment in which a film of a substance formed on the surface or reacted with an electrode material by discharge energy is formed on a workpiece surface, a step of dissolving or pulverizing the alloy material, And a step of compressing and forming the alloy powder having the same particle size.

  According to this invention, an electrode for discharge surface treatment using an alloy powder as an electrode material can be efficiently produced.

Embodiment 1 FIG.
Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a simplified configuration diagram of a discharge surface treatment electrode manufacturing apparatus according to Embodiment 1 of the present invention. In FIG. 1, in a space surrounded by the upper punch 103 of the mold, the lower punch 104 of the mold, and the die 105 of the mold, for example, stellite (Cr (chromium), Co (cobalt), Ni (nickel), etc. Alloy) powder 101 is filled. Then, a compact is formed by compressing the alloy powder 101, or a heated compact is formed. In the discharge surface treatment, the green compact or one obtained by heating the green compact is used as the discharge electrode.

  Here, the alloy powder 101 is a powder made by melting and grinding an alloy (for example, stellite) made by mixing Co (cobalt), Cr (chromium), Ni (nickel), etc., and this powder is a filter. It is a powder with a uniform particle size. That is, each powder particle is an alloy.

  In FIG. 1, the alloy powder 101 is compression molded by a die 105 and punches 103 and 104. In some cases, heat treatment is then performed to increase the strength of the electrode. Using such an electrode, a pulsed discharge is generated in the oil in the working fluid.

  FIG. 2 is a simplified diagram of a discharge surface treatment apparatus showing a state during discharge. In FIG. 2, an electrode 202 is a green compact of alloy powder grains 201, and the electrode 202 and a work 203 are arranged to face each other in a working fluid 204 that is oil, A pulsed voltage is applied between the workpiece 203 and a pulsed discharge is generated to form a discharge arc column 206, and a film is formed on the workpiece 203.

  FIG. 3 shows a voltage waveform and a pulsed discharge current waveform applied between the electrode 202 and the work 203. The discharge is performed with a negative polarity on the electrode 202 side and a positive polarity on the work 203 side.

  The electrode material is supplied to the workpiece side for each discharge. Since the electrode material is made of a single kind of alloy and is a uniform component, a coating without variations in components can be formed.

Embodiment 2. FIG.
Next, a second embodiment will be described. In the first embodiment described above, the powder of the electrode 202 is an alloy powder, but in this second embodiment, the component composition of the alloy is specified.

  According to the experiments by the present inventors, it has been found that the coating can be made thicker as a material that does not form carbide or does not easily form carbide is added to the component of the electrode material. Conventionally, a large proportion of materials that easily form carbides are included. For example, when a material such as Ti is included in the electrode, a chemical reaction occurs due to discharge in oil, and the coating is called TiC (titanium carbide). It becomes hard carbide. As the surface treatment progresses, the material of the workpiece surface changes from steel (when processing into steel) to TiC, which is ceramic, and along with that, characteristics such as heat conduction and melting point change. However, when a material that is not carbonized or hardly carbonized is added to the electrode, the film does not become a carbide, and a phenomenon occurs in which the material that remains in the film as a metal increases. And, it has been found that the selection of the electrode material has a great significance for thickening the coating. In this case, it is a matter of course that the hardness, denseness, and uniformity are satisfied, and it is a premise for forming a thick film.

  FIG. 4 shows the film thickness for the components of an alloy made by mixing Co (cobalt), Cr (chromium), Ni (nickel), and the like. Here, Co (cobalt) and Ni (nickel) which are hard to be carbonized are shown. ) And the thickness of the coating.

  In expressing this relationship, the discharge pulse conditions used are as follows: in FIG. 3, the peak current value ie = 10 A, the discharge duration (discharge pulse width) te = 64 μs, the rest time to = 128 μs, and the electrode with an area of 15 mm × 15 mm. A film was formed. The processing time is 15 minutes.

Due to the discharge in oil, some of the Cr in the electrode becomes carbide, such as Cr ₃ C ₂ (chromium carbide), but Co (cobalt) and Ni (nickel), which are difficult to carbonize, remain as they are. It becomes a component of the film. As the amount of Co (cobalt) and Ni (nickel) in the electrode increases, the coating becomes thicker. That is, when the electrode contains a metal material in which 50% by weight or more of the carbide is not formed in the film or is hard to form carbide by discharge, the film becomes very thick. According to FIG. 4, the Co and Ni contents are low. Although the film thickness was about 10 μm, it gradually became thicker from about 30% Co and Ni content, and increased to about 10,000 μm after the Co and Ni content exceeded 50%.

  In this case, in forming the pressure film, the electrode powder is made of an alloy, so that a uniform film can be formed without causing non-uniform components in the film. The alloy has been described by taking stellite as an alloy, but it can also be applied to Inconel, which is an alloy of Ni, Cr, and Fe with a Ni content of 50% by weight or more.

It is a simplified block diagram of the electrode manufacturing apparatus for discharge surface treatment concerning this invention. It is the simplification figure of the discharge surface treatment apparatus which showed the mode during discharge. It is a voltage and current waveform diagram at an electrode. It is a characteristic diagram which shows the relationship of Ni and Co weight% with respect to a film thickness. It is a simplified block diagram of the electrode manufacturing apparatus for discharge surface treatment for showing the conventional green compact.

Claims (5)

A pulsed discharge is generated in the machining fluid between the electrode and the workpiece, and a coating of the electrode material is formed on the workpiece surface by the discharge energy, or a coating of a substance that reacts with the electrode material is formed on the workpiece surface by the discharge energy. In the manufacturing method of the discharge surface treatment electrode used for the discharge surface treatment to
Melting or grinding the alloy material;
A step of aligning the particle size of the ground alloy powder;
Compressing and forming an alloy powder having a uniform particle size with a predetermined mold;
A method for manufacturing an electrode for discharge surface treatment, comprising: The method for producing an electrode for discharge surface treatment according to claim 1, wherein heat treatment is performed after the compression molding. 3. The method for producing an electrode for discharge surface treatment according to claim 1, wherein the alloy powder is an alloy containing at least 30 wt% of either Co or Ni. 3. The method for producing an electrode for discharge surface treatment according to claim 1, wherein the alloy powder is made by mixing Co, Cr, and Ni. 3. The method for manufacturing an electrode for discharge surface treatment according to claim 1, wherein the alloy powder is an alloy of Ni, Cr, and Fe.

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