JP3106609B2 - 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 fine powder of a copper-chromium alloy as a main raw material by an atomizing method, and is particularly suitable for use as an electrode of a vacuum interrupter.

[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 are used. In general, a powder metallurgy method is used in which a mixture of chromium powder produced by the above method and the like is compression-pressed and sintered at a high temperature.

[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]

This copper-chromium alloy has chromium 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.

[0010] Moreover, although the above-mentioned copper-chromium alloy is excellent in current breaking performance, it cannot be said that compared with other well-known electrode materials, sufficient satisfaction is obtained in terms of contact resistance value and welding resistance. I could not say it.

[0011]

An object of the present invention is to provide a method for producing an electrode material having good contact resistance and good welding resistance based on a high quality copper-chromium alloy in which fine chromium is uniformly dispersed in a copper matrix. The purpose is to do.

[0012]

SUMMARY OF THE INVENTION The present inventors have manufactured a fine powder of a copper-chromium alloy by an atomizing method without using a mechanical pulverizing method of chromium, which is difficult to miniaturize and has a problem of surface oxidation. Then, it was examined whether or not it was possible to manufacture an electrode material based on this.

Therefore, a mixture of copper and chromium is melted in a non-oxidizing atmosphere such as a vacuum, and the molten metal is melted at 5 to 8 MPa.
The powder was rapidly solidified by a gas atomizing method using an argon (Ar) gas at a pressure of (megapascal) to obtain a fine powder of a copper-chromium alloy in which chromium was dispersed in a copper matrix.

In carrying out the above method, the weight ratio of copper and chromium in the mixture of copper and chromium before melting was set to 4: 1. If the weight ratio of chromium is larger 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. Alternatively, deoxidation treatment was performed to reduce the oxygen content to 1000 ppm or less. In this case, the presence of unavoidable impurities, such as iron (Fe) and nickel (Ni), mixed in the raw materials and the like was allowed.

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

Next, 300 g of the copper-chromium alloy fine powder was charged into an alumina ceramic container having an inner diameter of 70 mm, and heated to about 1080 ° C. in a vacuum of 5 × 10 ⁻⁵ Torr. It turned out to be possible enough.

The method for producing an electrode material according to the present invention has been made in view of the above-mentioned knowledge, and it has been found that an alloy fine powder of copper and chromium obtained by an atomizing method and a powder of a metal having a lower melting point than the copper are used. And sintering them by heating them in a non-oxidizing atmosphere.

Here, a metal having a lower melting point than copper and capable of lowering the contact resistance value of the electrode material and improving the welding resistance (hereinafter, referred to as a metal).
Bismuth (B
i), antimony (Sb), tellurium (Te), selenium (Se), and lead (Pb) can be used. It is desirable that these ratios be within the range of 0.02 to 3.0% by weight.

The ratio of these low melting point metals is 0.02.
%, It is almost impossible to expect a decrease in contact resistance and an improvement in welding resistance due to the addition of these low-melting metals. Also, when the amount of the low-melting-point metal exceeds 3.0% by weight, the current breaking performance is rapidly deteriorated.

[0021]

In the copper-chromium alloy fine powder obtained by the atomization method, chromium having a small particle diameter is uniformly dispersed in a copper matrix. By mixing this with a low melting point metal powder and heating, these metal crystal particles are densely sintered and integrated without becoming coarse.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A vacuum interrupter is shown in FIG. 1 which shows an example of a schematic structure of the vacuum interrupter. Electrodes 13 and 14 are respectively provided on opposing end surfaces of a pair of lead rods 11 and 12 which are linear with each other. They are integrally joined via a brazing material (not shown). A central portion of the outer periphery of a cylindrical shield 15 surrounding the electrodes 13 and 14 is held in a state sandwiched between a pair of insulating cylinders 16 and 17 surrounding the shield 15.

The one lead rod 11 is integrally fixed to the metal end plate 18 in a state where it penetrates the metal end plate 18 joined to one end of the one insulating cylinder 16 in an airtight manner. Further, the other lead rod 12 connected to a driving device (not shown) is connected via a bellows 20 to the other metal end plate 19 air-tightly connected to the other end of the other insulating cylinder 17 to operate the driving device. Accordingly, the movable-side electrode 14 opens and closes with respect to the fixed-side electrode 13 so as to reciprocate in the direction in which the electrodes 13 and 14 face each other.

The electrodes 13 and 14 in this embodiment are:
The main part is made of a copper-chromium alloy obtained by sintering a mixture of a low melting point metal and a raw material by an atomizing method.

An example of the method for producing the electrodes 13 and 14 according to the present invention is as follows. Bismuth powder having a particle size of -275 mesh was uniformly mixed at a ratio of 0.5% by weight to 3.5 µm). Then, the mixed powder was filled in a mold having a diameter of 50 mm, and pressed into a disk at a pressure of 3.5 ton / cm ² , and then pressed in a vacuum furnace of 5 × 10 ⁻⁵ Torr for 1080. C. for 30 minutes to sinter.

The thus obtained sintered body contains 0.19% by weight of bismuth, which is a low-melting-point metal, which evaporates during sintering. A spiral electrode having a diameter of 40 mm was machined and assembled into the vacuum interrupter shown in FIG. 1 to measure the breaking current value, contact resistance value, and welding force. As a result, the results shown in Sample A in Table 1 were obtained. Was done.

A lead powder having a particle size of -275 mesh and a particle size of -275 mesh were uniformly mixed with the same atomized powder of copper and chromium as used in the sample A. , This mixed powder is filled in a mold having a diameter of 50 mm,
After being press-formed into a disk at a pressure of 3.5 ton / cm ² , this was pressed at 1080 ° C. in a vacuum furnace of 5 × 10 ^-5 Torr for 3 hours.
Heated for 0 minutes and sintered.

The sintered body thus obtained contains 0.45% by weight of lead due to the evaporation of lead occurring during sintering, and this is used as a sample B as a spiral having a diameter of 40 mm. The electrode was machined and assembled into the vacuum interrupter shown in FIG. 1 to measure the breaking current value, the contact resistance value, and the welding force. As a result, the results shown in Sample B of Table 1 were obtained.

Similarly, tellurium powder having a particle size of -275 mesh at a ratio of 0.5% by weight with respect to the same atomized powder composed of copper and chromium as used in Samples A and B was used. Mix evenly and mix this powder with 50mm diameter
And press-molded into a disk at a pressure of 3.5 ton / cm ² , and then heated at 1080 ° C. for 30 minutes in a 5 × 10 ⁻⁵ Torr vacuum furnace, and sintered. I let it.

The sintered body thus obtained contained 0.45% by weight of lead due to the evaporation of lead generated during sintering, and this was used as a sample C to form a spiral having a diameter of 40 mm. The electrode was machined and assembled into the vacuum interrupter shown in FIG. 1 to measure the breaking current value, the contact resistance value, and the welding force. As a result, the results shown in Sample C of Table 1 were obtained.

On the other hand, as comparative examples, copper powder having a particle size of 100 μm, chromium powder having a particle size of 80 μm, and
79.75: 19.75 by weight ratio with 5 mesh bismuth powder
Mix uniformly at a ratio of 0.5.
m, and press-molded into a disk at a pressure of 3.5 tons / cm ² , and then heated at 1080 ° C. for 30 minutes in a 5 × 10 ⁻⁵ Torr vacuum furnace, and fired. Tied.

The sintered body thus obtained was machined into a spiral electrode having a diameter of 40 mm as a comparative example, and was incorporated into a vacuum interrupter shown in FIG. 1 to measure the breaking current value, contact resistance value and welding force. As a result of each measurement, the results as shown in Comparative Examples in Table 1 were obtained.

[0033]

[Table 1]

The breaking current value in these tests is a value obtained when an arc generation time is set to 0.4 cycle with an AC voltage of 7.2 kV, and
The welding force is a value obtained when two cycles of an alternating current having a peak current of 35 kA were performed while the electrodes 13 and 14 were pressed against each other with a force of 500 N. It is a static value.

As is clear from Table 1, in the electrode material according to the present invention, the low melting point metal and the chromium having a fine particle diameter are uniformly dispersed in the copper matrix. It was found that the diffusion was performed smoothly and the current interruption performance was improved as compared with the conventional manufacturing method. Further, by adding the low melting point metal, the contact resistance and the welding resistance could be reduced.

In the above-described embodiment, bismuth, lead and tellurium are used alone as the low-melting-point metal. In addition, antimony or selenium may be used alone, or when two or more of these are mixed, the above-mentioned case may be used. It is possible to obtain an electrode material having the same performance as described above.

[0037]

According to the method for producing an electrode material of the present invention,
The alloy fine powder of copper and chromium obtained by the atomization method and the powder of the low melting point metal were mixed and heated and sintered in a non-oxidizing atmosphere. A copper-chromium alloy electrode material in which the melting point metal and chromium with a fine particle size are uniformly dispersed can be obtained. Compared with the conventional sinter metallurgy method, the breaking current value is larger and the contact resistance is higher. An electrode material having a low value and excellent in welding resistance and the like can be provided.

[Brief description of the drawings]

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

[Explanation of symbols]

 11 and 12 are lead rods, and 13 and 14 are electrodes.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Nobuhisa Suzuki 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Inside Meidensha Co., Ltd. (56) References JP-A-3-47931 (JP, A) JP 57-67141 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01H 11/04 H01H 33/66 C22C 9/00

Claims (2)

(57) [Claims] An alloy fine powder of copper and chromium obtained by an atomizing method, and a powder of a metal having a lower melting point than said copper.
From 0.02 to 3.
A method for producing an electrode material , comprising mixing at a ratio of 0% by weight and heating them in a non-oxidizing atmosphere for sintering. 2. The low melting point metal is bismuth, antimony,
2. The method according to claim 1, wherein the material is at least one of tellurium, selenium, and lead.