JP3106605B2 - 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]

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]

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 had an irregular shape due to a high cooling rate.

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 molded under pressure, and the obtained molded body is heated and sintered in an inert atmosphere,
In addition, the alloy powder of copper and chromium obtained by the water atomization method is subjected to pressure molding, the obtained molded body is heated in an inert atmosphere, pre-sintered, and subsequently pressed at a higher pressure. 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 an irregular shape, so that press molding is easy. In addition, since the surface area is large, sintering at a low heating temperature (1000 to 1050 ° C.) can be performed.

[0014]

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 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 weighing device 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 weighing device 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 production of an electrode material for a vacuum interrupter using the above-mentioned 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 atomizing method has an irregular shape, a strong compact can be obtained.

Next, the obtained compact was placed in a vacuum furnace (5 × 10
⁽⁻⁵ Torr) at 1050 ° C. for 30 minutes for sintering. 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 0.1%.

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. As a result of measuring the breaking performance, 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 a water atomizing method is described below.

The copper-chromium alloy powder obtained by the water atomizing method is placed in a mold having a diameter of 42 mm and placed at 343 MPa (35
Pressure molding was performed at a pressure of 00 kgf / cm ² ) to obtain a compact (compact).

The obtained molded body was placed in a vacuum furnace (5 × 10 ⁻⁵ Tor).
Heating was performed at 900 ° C. for 60 minutes in sintering to perform sintering (pre-sintering).

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 3050 at 1050 ° C. in a vacuum furnace (5 × 10 ⁻⁵ Torr).
After heating for a minute, sintering (main sintering) was performed.

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 0.07%. That is, by performing sintering in two stages, the density and conductivity after sintering can be improved, and the oxygen content can be 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 to measure the breaking performance. As a result, 7.2 KV-12.5 KA
It was confirmed that the performance was satisfied.

In addition to the above, the sintering temperature of the compact is 1000 to 1050 ° C., and the compacting pressure is 196 to 588 MPa (2000 to 6000 kg).
f / cm ² ), and a sintering atmosphere other than vacuum, such as a gas atmosphere such as Ar or H ₂ .

[0033]

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 subjected to pressure molding, and the obtained molded body is heated in an inert atmosphere. Sintering makes it possible to obtain an electrode material in which chromium with a fine particle size is uniformly dispersed in a copper matrix.Also, the alloy powder has an irregular shape, so press molding is easy. And sintering at a lower temperature than before can be performed by increasing the surface area. Further, by performing sintering in two stages, the density and conductivity after sintering can be improved.

[Brief description of the drawings]

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

FIG. 2 is a cross-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-53-146904 (JP, A) JP-A-57-67141 (JP, A) JP-A-63-174535 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01H 11/04 C22C 9/00 H01H 33/66

Claims (1)

(57) [Claims] 1. An alloy powder of copper and chromium obtained by a water atomizing method is subjected to pressure molding, and the obtained molded body is heated in an inert atmosphere to perform preliminary sintering, and then to a higher pressure. A method for producing an electrode material, comprising: performing heat treatment at a higher temperature than during pre-sintering after pressing.