JP3168635B2 - Manufacturing method of electrode material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrode material using a copper (Cu) -chromium (Cr) alloy powder obtained by a gas atomizing method, and more particularly to a method for producing an electrode material for a vacuum interrupter. It is suitable.

[0002]

2. Description of the Related Art One of the important performances required as an electrode material of a vacuum interrupter is a high current breaking performance.

[0003] A copper (Cu) -chromium (Cr) alloy is known as an electrode material having a very excellent current breaking performance. Conventionally, a copper powder produced by an electrolytic method or the like and a pulverization method or the like are used. A method of powder metallurgy in which a mixture of chromium powder produced by the above method and a mixture thereof is compression-pressed and sintered at a high temperature is generally used.

[0004] In addition, an infiltration method in which chromium is infiltrated into voids of the compression-pressed copper powder, or a mixed powder of copper and chromium is compression-pressed and fired at a low temperature. After sintering, a method of infiltrating copper into the voids or a method of casting has been attempted.

[0005]

In this copper-chromium alloy, chromium is dispersed in a copper matrix. However, when attention is paid to the electrical characteristics as an electrode material, fine chromium is contained in the copper matrix. It is preferable that they are uniformly dispersed.

However, in the case of a conventional copper-chromium alloy produced by powder metallurgy, the width of the particle size distribution of chromium powder obtained by mechanical pulverization by a pulverization method is very large, and the average particle diameter is large. Since it reaches about 40 μm, there is a drawback that when mixing the copper powder and the chromium powder, uniform mixing is difficult due to the difference in specific gravity, the particle size of the powder, or the difference in particle size distribution. As a result, chromium in the copper matrix after sintering was not finely and uniformly dispersed, and the electrical characteristics were not as good as expected.

[0007] Therefore, it is conceivable to further mechanically pulverize the chromium powder to reduce its particle size. In this case, the surface of the chromium powder is oxidized during the pulverization process and during storage, and oxygen-containing powder is contained. There is also a problem that the sinterability is reduced as the amount increases. It is also conceivable to classify the chromium powder obtained by the pulverization method by sieving and use only the chromium powder having a fine diameter. However, in this method, the yield is extremely deteriorated and the production cost is increased.

[0008] On the other hand, conventional copper produced by the infiltration method
In the case of a chromium alloy, chromium powder is easily oxidized, so it is necessary to thoroughly control its quality, and chromium powder having an oxidized surface has poor wettability with copper and has a disadvantage that it cannot be infiltrated.

In the case of a conventional copper-chromium alloy produced by a casting method, chromium particles in a copper matrix grow due to a low cooling rate during solidification, and uniform and fine chromium is dispersed. In addition to the difficulty, there is a disadvantage that the quality of the obtained copper-chromium alloy is apt to vary due to the tendency of solidification segregation.

The present inventors have obtained a fine powder of a copper-chromium alloy by an atomizing method without using a mechanical crushing method of chromium, which is difficult to miniaturize and has a problem of surface oxidation.

As a method for producing powder by the atomizing method, there are a gas atomizing method using gas as a medium and a water atomizing method using water.

Gas atomized powder is suitable as an electrode material for a vacuum interrupter because of its low gas content.
The powder has a spherical shape. Therefore, when the electrode material is manufactured by press molding, the powder is less deformable due to small deformation of the powder, and as shown in FIG. Will occur.

On the other hand, water atomized powder has good formability due to its irregular shape, but because it is obtained by spraying water, water tends to remain in the powder, causing surface oxidation of the powder. There is. For this reason, when water atomized powder is used as a raw material, sufficient drying and reduction treatment are required after spraying.

[0014]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has been made to provide a method of manufacturing an electrode material having good moldability while utilizing the characteristics of gas atomized powder. Is to add an electrolytic copper powder having a particle size of 150 μm or less in a ratio of 5% by weight or more and 50% by weight or less to an alloy powder having a composition of 80 to 95% by weight of copper and 5 to 20% by weight of chromium obtained by gas atomization Then, the obtained mixed powder is subjected to pressure molding, and the obtained molded body is heated and sintered in an inert atmosphere.

[0015]

The copper-chromium alloy powder obtained by the gas atomization method has a low oxygen content, but has poor moldability. By mixing electrolytic copper powder with this alloy powder, the formability is improved due to its irregular shape. Therefore, by shaping and heating and sintering the mixed powder, it is possible to obtain an electrode material in which fine chromium is uniformly dispersed and has excellent breaking performance and the like.

[0016]

FIG. 1 shows a vacuum interrupter which is an example of an application example of an electrode material obtained by the method according to the present invention. Electrodes 13 and 14 are provided integrally on opposite ends of a pair of lead rods 11 and 12 which are linear with each other via a brazing material (not shown). These electrodes 13, 1
The central portion of the outer periphery of the cylindrical shield 15 surrounding the shield 4 is held between the pair of insulating tubes 16 and 17 surrounding the shield 15. The one lead bar 11 is integrally fixed to the metal end plate 18 in a state where the lead rod 11 air-tightly penetrates the metal end plate 18 joined to one end of the one insulating cylinder 16. The other lead rod 12 connected to a drive device (not shown) is connected via a bellows 20 to the other metal end plate 19 airtightly joined to the other end of the other insulating cylinder 17, and is driven by the operation of the drive device. The movable electrode 14 opens and closes with respect to the fixed electrode 13 so that the movable electrode 14 can reciprocate in the direction opposite to the electrodes 13 and 14.

A copper-chromium alloy powder, which is a starting material for producing electrode materials for the electrodes 13 and 14, is obtained by a gas atomizing method.

For example, after a mixture of 80% by weight of copper and 20% by weight of chromium is heated and dissolved in a vacuum, the
It is produced by spraying with a gas at a pressure of 5 to 8 MPa.

In the above gas atomization, the weight ratio of copper and chromium in the mixture of copper and chromium before melting is set to 4: 1. If the weight ratio of chromium is higher than this, copper dispersed in a chromium matrix is generated, and a target copper-chromium alloy powder cannot be obtained.

When the mixture of copper and chromium is melted, copper and chromium having a low oxygen content are selected in order to reduce the oxygen content of the molten metal, while melting in a non-oxidizing atmosphere as described above. Or deoxidize to an oxygen content of 10
Keep below 00ppm.

The particle size of the copper-chromium alloy powder thus obtained was 150 μm or less, and its component ratio was equivalent to that of the original mixture of copper and chromium. Also, this copper
As a result of observing the chromium alloy fine powder with an electron microscope, 5μ
It was confirmed that chromium particles of m or less were uniformly dispersed in the copper matrix.

The copper-chromium alloy powder obtained by the above-mentioned process is coated with electrolytic copper having a particle size of 50 μm in an amount of 5% by weight to 50% by weight.
Mix in the following range to obtain a mixed powder.

The mixed powder is filled in a mold having a diameter of 40 mm,
Pressure molding is performed at a pressure of 〜490 MPa (1000 to 5000 kgf / cm ² ) to obtain a molded body (compact). Since the electrolytic copper powder having good moldability is mixed with the gas atomized powder, the molding at this time is easily and firmly performed, and there is no fear of occurrence of cracks and chips.

Next, the obtained molded body is placed in a vacuum furnace (vacuum pressure:
In 5 × 10 ⁻⁵ Torr), heat treatment is performed just below the melting point to obtain a sintered body. FIGS. 2 and 3 show the relationship between the packing density and conductivity of the obtained electrode material and the amount of electrolytic copper powder added.

As can be seen from FIGS. 2 and 3, both the packing density and the electrical conductivity increase with an increase in the amount of the electrolytic copper powder added.
In particular, when 10 to 25% by weight of copper powder is added, the highest breaking current value is exhibited. In addition, the moldability is as follows.
It was improved by adding 0% by weight or more. Therefore, the addition amount of the copper powder is in the range of 5% by weight to 50% by weight, and preferably in the range of 10% by weight to 25% by weight. In this sintering step, the particle size of chromium in the copper matrix can be adjusted by changing the sintering temperature and time.

The obtained sintered body was machined into a spiral electrode shape having a diameter of 40 mm, and the results of testing the breaking performance and contact resistance are shown in FIGS. 4 and 5. As is clear from the figure,
Good performance was obtained as compared with the case where the gas atomized powder of the copper-chromium alloy was used as it was (the black spot in the figure).

[0027]

According to the method for producing an electrode material according to the present invention, the copper-chromium alloy powder obtained by the gas atomization method is not used as it is, but the electrolytic copper powder is added and the mixture is molded and sintered as a mixed powder. Therefore, an electrode material having excellent breaking performance without chipping or cracking can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a vacuum interrupter.

FIG. 2 is a graph showing the relationship between the amount of copper powder added and the packing density.

FIG. 3 is a graph showing the relationship between the amount of copper powder added and the conductivity.

FIG. 4 is a graph showing a relationship between an added amount of copper powder and a breaking current value.

FIG. 5 is a graph showing a relationship between an added amount of copper powder and a contact resistance value.

FIG. 6 is an external view showing a state in which a molded body has a chip or the like.

[Explanation of symbols]

 11,12 Lead rod 13,14 Electrode

Continuation of the front page (56) References JP-A-57-67141 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22F 5/00 C22C 9/00 H01H 11/04 H01H 33 / 66

Claims (1)

(57) [Claims] [Claim 1] 80 to 80 obtained by a gas atomizing method
Alloy powder 95 wt% of copper-5-20 wt% chromium composition, particle size less electrolytic copper powder 150 [mu] m 5 wt% or more 5
A method for producing an electrode material, comprising adding at a ratio of 0% by weight or less, press-molding the obtained mixed powder, and heating and sintering the obtained compact in an inert atmosphere.