JP3168630B2 - 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 water atomization method, and more particularly to a method for producing an electrode material for a vacuum interrupter. It is suitable for use.

[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 interruption performance.

A copper (Cu) -chromium (Cr) alloy is known as an electrode material having a very excellent current interrupting 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.

[0010]

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

The atomizing method includes a gas atomizing method using a high-pressure gas and a water atomizing method using pressurized water. The copper-chromium alloy powder obtained by both methods was examined.
The alloy powder produced by the water atomization method has the disadvantage that it is cooled by water and therefore has a high oxygen content, while the cooling rate is high and the shape is irregular, resulting in excellent moldability.

The present invention has been made by paying attention to such characteristics of a copper-chromium alloy powder obtained by a water atomization method, and has a structure comprising an alloy powder of copper and chromium obtained by a water atomization method. Is heated and pulverized in a reducing atmosphere,
The obtained alloy powder is molded under pressure, and the obtained molded body is heated and sintered in an inert atmosphere, and
The alloy powder of copper and chromium obtained by the water atomization method is heated and pulverized in a reducing atmosphere, the obtained alloy powder is compacted, and the obtained compact is heated in an inert atmosphere and pre-sintered. Then, after further pressurizing at a higher pressure, a heat treatment is performed at a higher temperature than during pre-sintering.

[0013]

The copper-chromium alloy powder obtained by the water atomizing method has a large oxygen content as it is because it is cooled by water.
The alloy powder can be finely divided and the oxygen content can be reduced.

The obtained fine alloy powder is pressed and sintered to obtain an electrode material having a structure in which fine chromium is uniformly dispersed. The chromium particle size in the copper matrix can be adjusted by the sintering temperature and time.

[0015]

FIG. 2 shows a vacuum interrupter as 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.

The copper-chromium alloy fine powder for producing the electrode material for the electrodes 13 and 14 is obtained by a water atomizing method. FIG. 1 shows the method.

Reference numeral 21 denotes a melting furnace in which oxygen-free copper having an amount of 80% copper and 20% chromium and shot chrome having a size of 5 to 6 mm are melted at 1750 ° C. The temperature of the molten metal is controlled.

Reference numeral 22 denotes a water atomizing device, and a tundish 2 for receiving a molten metal is provided on an upper portion of a drum-shaped device main body 23.
4 is provided, and a water injection nozzle 25 is provided at an outlet of the molten metal in the apparatus main body 23. Water 31 is stored in a lower part of the apparatus main body 23, and a collection container 27 is connected to a lower outlet 26.

At the outlet side of the collection container 27, a heater 2 is provided.
8, a classifier 29, a weigher 30 and the like are provided.

The molten mixture of copper and chromium is first poured into a tundish 24 of a water atomizer 22. The molten metal falls from the lower part of the tundish 24 by gravity. At this time, 9.8 MPa (100 kgf /
Water pressurized to cm ² ) is sprayed on the melt, and the melt is pulverized. The powdered molten metal is cooled by the water 31 in the apparatus main body 23. The cooled powder is collected in a collection container 27 from the lower part of the apparatus main body 23, dried by the heater 28, and then weighed by the weigher 30 through the classifier 29.

The particle size of the obtained copper-chromium alloy fine powder is 1
50 μm or less, and its component ratio is also equivalent to the ratio of the original mixture of copper and chromium (Cu: 80 to 95% by weight, C
r: 5 to 20% by weight). As a result of observing the copper-chromium alloy fine powder with an electron microscope, it was confirmed that chromium particles of 5 μm or less were uniformly dispersed in the copper matrix. Further, since the cooling rate is high, the powder itself has an irregular shape.

The above-mentioned copper-chromium alloy powder is not used as it is, but is placed in an alumina container and placed in a hydrogen atmosphere at 900 ° C. for 2 hours.
After heating for an hour, it was further pulverized mechanically and sieved to obtain a copper-chromium alloy atomized powder of 100 μm or less.

The heat treatment temperature is not limited to 900 ° C. For example, a particle diameter of 100 μm or less, an average particle diameter of 60 μm
In this case, an appropriate temperature is selected in the range of 500 to 1000 ° C. The maximum temperature is a temperature at which the sintering reaction of the atomized powder does not significantly proceed. This is because if sintering proceeds, the subsequent pulverization step takes time and there is a possibility that impurities may be mixed. The minimum temperature is the temperature at which outgassing is active. When the particle size of the powder is small, the sintering proceeds easily, so that the heat treatment temperature needs to be lowered. The heat treatment is performed in a reducing atmosphere such as the above-described hydrogen or vacuum.

The method for producing an electrode material for a vacuum interrupter using the above-mentioned atomized copper-chromium alloy powder is performed as follows.

First, a copper-chromium alloy powder is placed in a mold having a diameter of 42 mm, and molded under pressure at a pressure of 490 MPa (5000 kgf / cm ² ) to obtain a compact (compact). At this time, since the copper-chromium alloy powder obtained by the water atomization method and further mechanically pulverized has an irregular shape,
A strong molded body can be obtained.

Next, the obtained molded body is placed in a vacuum furnace (vacuum pressure:
It was heated at 1050 ° C. for 30 minutes in 5 × 10 ⁻⁵ Torr) and sintered. Since the copper-chromium alloy powder has an irregular shape and a large surface area, it can be sintered at a temperature lower than the melting point of copper.

The packing ratio (ratio to the theoretical density) of the sintered body thus obtained is 95%, and the conductivity is 50%.
% IACS, oxygen content was 0.07%. That is, the oxygen content decreases as compared with the case where the water atomized powder is used as it is.

The sintered body was machined into an electrode shape having a diameter of 40 mm, and the electrodes 13 and 14 of the vacuum interrupter shown in FIG. 2 were used to measure the breaking performance. As a result, 7.2 KV-12.5 KA
It was confirmed that the performance was satisfied.

Another electrode manufacturing method using a copper-chromium alloy powder obtained by heating and pulverizing a copper-chromium alloy powder obtained by a water atomizing method in a reducing atmosphere such as hydrogen will be described below.

The copper-chromium alloy powder was placed in a mold having a diameter of 42 mm, and was molded under pressure at a pressure of 343 MPa (3500 kgf / cm ² ) to obtain a compact (compact).

The obtained molded body was placed in a vacuum furnace (vacuum pressure: 5 × 1).
It was heated for 60 minutes at 900 ° C. in 0 ^-5 Torr) and allowed to sinter (presintering).

The sintered body obtained by the preliminary sintering is again
After pressurizing at a pressure of 0 MPa (5000 kgf / cm ² ), the pressure was increased to 1050 in a vacuum furnace (vacuum pressure: 5 × 10 ⁻⁵ Torr).
C. for 30 minutes to perform sintering (main sintering).

The packing ratio (ratio to the theoretical density) of the obtained sintered body was 98%, the conductivity was 55% IACS, and the oxygen content was 0.05%. That is, by performing sintering in two stages, the density and conductivity after sintering can be improved, and the oxygen content can be further reduced.

The sintered body was machined into an electrode shape having a diameter of 40 mm, and the electrodes 13 and 14 of the vacuum interrupter shown in FIG. 2 were used.
It was confirmed that the performance was satisfied.

In addition to the above, the sintering temperature of the compact is 1000 to 1080 ° C., and the compacting pressure is 196 to 588 MPa (2000 to 6000 kg).
f / cm ² ), and an atmosphere of Ar, H _2, etc. other than vacuum is employed as the sintering atmosphere.

[0036]

According to the method for producing an electrode material according to the present invention, an alloy powder of copper and chromium obtained by a water atomization method is heated and pulverized in a reducing atmosphere, and the obtained alloy powder is subjected to pressure molding. Since the obtained molded body is heated and sintered in an inert atmosphere, it is possible to obtain an electrode material in which the oxygen content is extremely low and chromium having a fine particle diameter is uniformly dispersed in a copper matrix. In addition, since the alloy powder has an irregular shape, strong press molding is easy, and sintering can be performed at a lower temperature than before because of the increase in surface area. Further, by performing the sintering in two stages, the density and conductivity after sintering can be improved, and the oxygen content can be further reduced.

[Brief description of the drawings]

FIG. 1 is a schematic process diagram of production of a copper-chromium alloy powder by a water atomizing method.

FIG. 2 is a sectional view illustrating an example of a vacuum interrupter.

[Explanation of symbols]

 11, 12 Lead rod 13, 14 Electrode 22 Water atomizing device 24 Tundish 25 Water injection nozzle 27 Recovery container 28 Heater

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-67141 (JP, A) JP-A-63-137101 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22F 5/00 H01H 11/04 H01H 33/66

Claims (2)

(57) [Claims] 1. A obtained by water atomization, 5 [mu] m or less
The lower chromium particles are evenly dispersed in the copper matrix,
An irregularly shaped alloy powder of copper and chromium was heated in a reducing atmosphere and mechanically pulverized, and the resulting irregularly shaped alloy powder was pressed and obtained. A method for producing an electrode material, wherein a compact is heated and sintered in an inert atmosphere. 2. The method according to claim 1, wherein said powder is obtained by a water atomizing method ,
The lower chromium particles are evenly dispersed in the copper matrix,
An irregularly shaped alloy powder of copper and chromium was heated in a reducing atmosphere and mechanically pulverized, and the resulting irregularly shaped alloy powder was pressed and obtained. A method for producing an electrode material, comprising: performing pre-sintering by heating a molded body in an inert atmosphere; subsequently, pressurizing at a higher pressure; and then performing heat treatment at a temperature higher than that during pre-sintering.