JPH02117028A - Electrode material of vacuum interrupter and its manufacture - Google Patents

Abstract

PURPOSE:To make it possible to maintain the current chopping value and the contact resistance value at a low value by fusing and spreading copper and bismuth at the clearances of chromium, and after that, quenching them to deposit the bismuth at the interfaces between the chromium and the copper. CONSTITUTION:The electrode material consists of chromium to compose the skeleton, copper filled in the skeleton of the chromium, and bismuth filled in the skeleton together with the copper and deposited at the interfaces between the chromium and the copper filled in the skeleton. When it is manufactured, by fusing and spreading the copper and the bismuth in the powder of chromium, and quenching them to deposit the bismuth at the interfaces between the chromium and the copper, the current chopping value and the contact resistance value can be maintained at a low value.

Description

[Detailed Description of the Invention] Industrial Application The present invention relates to a four-pole material for a vacuum interrupter that can maintain low current cutoff value and contact resistance over a long period of time, and a method for manufacturing the same. .

B. Summary of the invention A copper-bismuth alloy is placed on chromium powder, heated to infiltrate copper and bismuth into the voids of the chromium, and then rapidly cooled to precipitate bismuth at the interface between the chromium and copper. This is an electrode material for a vacuum interrupter that can maintain a low current cutoff value and contact resistance value for a long period of time.

C. Conventional technology In general, the main performances required for electrode materials for vacuum incretors include (1) good welding resistance (high 21JJ flow cutoff performance), (3) low current cutoff value, etc. can be mentioned.

However, since increasing the current cutting performance and lowering the current cutting value of an electrode material are due to mutually contradictory physical properties, it is not possible to satisfy all of the above characteristics with a single electrode material. However, the current situation is to select the electrode material that best meets the specifications of the vacuum interrupter.

For example, the copper-bismuth alloy disclosed in Japanese Patent Publication No. 41-12131 is made by adding 0.5% by weight of bismuth (Bi), which has a high vapor pressure and a low melting point, to steel (Cu).
It is well known that it has good welding resistance and current interrupting performance. In addition, the tungsten steel sintered metal disclosed in Japanese Patent Publication No. 54-36121 etc. is made by adding 20% by weight of copper to tungsten (W), which has a low vapor pressure and high melting point, and has a low current cutoff value. has advantages. As an electrode material with a particularly low current cut-off value,
There is a steel-bismuth alloy disclosed in Japanese Patent No. 74, that is, an alloy in which 20% by weight of bismuth is added to copper.

D. Problems to be Solved by the Invention Copper-bismuth alloys containing 0.5% by weight of bismuth have good current cutting performance, but on the other hand, the current cutting value is as high as, for example, IOA, and a cutting surge occurs when cutting the current. There are things to do.

For this reason, it is difficult to cut off the delayed small current in a good manner, which may cause dielectric breakdown of the electrical equipment on the load side.

In addition, tungsten steel sintered metal and copper-bismuth alloy containing 20% by weight of bismuth have a low current cutoff value, but
It has poor current cutting performance and cannot cut off large currents such as short circuit current. In particular, this copper-bismuth alloy is shown in Figure 9, which shows a secondary electron image of its metal structure taken by an X-ray microanalyzer, Figure 10, which shows an X-ray image of the copper distribution state in this sample, and an X-ray image of the bismuth distribution state. The first representing
As shown in FIG. 1, since bismuth is hardly dissolved in copper, the copper crystal grains become large and bismuth precipitates between the copper crystal grains.

For this reason, when the electrodes of the vacuum interrupter are frequently opened and closed, bismuth is not stably supplied to the electrode surface, and the current cutoff value becomes unstable. Moreover, when the inside of the vacuum interrupter is evacuated during the process of manufacturing the vacuum interrupter, bismuth melts and precipitates in a spherical shape on the electrode surface due to the heating operation, which deteriorates the welding resistance of the electrode material and increases the contact resistance value. There was a risk that he would be invited. Note that the white parts in FIGS. 10 and 11 are locations where each metal element exists.

E. Means for solving the problem In recent years, copper chromium alloys with excellent withstand voltage characteristics and current interrupting performance are being adopted as *ti for vacuum interrupters, but the current interrupting value is not necessarily satisfactory. Therefore, it may be possible to add bismuth, a well-known low-melting point material, to a copper-chromium alloy to improve the current cutoff value without impairing the withstand voltage characteristics or current cutoff performance. In this case, since chromium alloys have conventionally been manufactured by an infiltration method, it is considered difficult to finely disperse bismuth into a copper chromium alloy by simply adding bismuth to a copper chromium alloy. In other words, the present inventors focused on the fact that conventional copper-bismuth alloys are made by a melting method, and in this melting method, bismuth is mutually exposed to high temperature heat loads for a long time. It was thought that it would precipitate between the crystal grains and that it would be difficult to uniformly disperse it.

Therefore, when producing copper chromium bismuth, instead of using the conventional melting method, we tried an infiltration method that requires high-temperature heat load in a short time.

That is, a copper-bismuth alloy was infiltrated into a skeleton of chromium powder to obtain a copper-chromium-bismuth composite metal.

As a result, due to the presence of chromium powder, it was found that when copper and bismuth were infiltrated into the chromium skeleton, bismuth precipitated in a dispersed state around the chromium particles and was hardly present between the copper grains. did.

The present invention has been made based on the above-mentioned findings,
The electrode material of the vacuum interrupter according to the present invention includes chromium constituting the skeleton, copper filled in the chromium skeleton, and the copper filled in the skeleton together with the copper and dispersed at the interface between the chromium and the copper. It consists of bismuth.

In this way, in order to precipitate bismuth in a dispersed state at the interface between chromium and copper, the method for manufacturing the electrode material for a vacuum interrupter according to the present invention involves placing a copper-bismuth alloy on chromium powder and depositing bismuth vapor on top of the copper-bismuth alloy. After heating and holding above the melting point of the steel-bismuth alloy in a non-oxidizing atmosphere containing copper and bismuth to infiltrate into the voids of the chromium,
It is characterized by rapid cooling.

In addition, it is desirable that the cooling operation after infiltration be continued at a cooling rate of about 10 to 20 degrees per minute to at least about 800 degrees Celsius, so that bismuth is effectively precipitated in a dispersed state at the interface between chromium and copper. be able to.

Here, if the steel content is less than 20% by weight, the electrical conductivity will decrease and the amount of heat generated will increase, while if the copper content exceeds 70% by weight, the welding resistance will decrease and the current cutoff value will increase. bring. Furthermore, if the chromium content is less than 2% by weight or if the bismuth content is less than 1% by weight, the current cutoff value will increase. Furthermore, if chromium exceeds 75% by weight,
Current interrupting performance deteriorates. On the other hand, bismuth is 2
If it exceeds 0% by weight, the durability as a Bi electrode and a vacuum interrupter will decrease rapidly. Therefore, copper is 20 to 70
Desirably, the weight percent range is 2 to 75 weight percent for chromium and 1 to 20 weight percent for bismuth.

F action By heating, the chromium powder first diffuses and bonds with each other to become porous, and copper and bismuth infiltrate into the voids of the chromium (by rapid cooling after infiltration, bismuth Since bismuth precipitates not between the crystal grains of steel but at the interface between chromium and copper, the distribution state of bismuth is finely dispersed as a whole.

G Embodiment The vacuum interrupter is as shown in FIG. 8, which shows an example of its schematic structure.A pair of glue rods 11 and 12, which are in a straight line, are provided with electric current l' on their opposite end surfaces, respectively. l
13 and 14 are integrally provided. These electrodes 13.1
The central part of the outer periphery of the cylindrical shield 15 surrounding the shield 15 has a pair of absolute fi[16] surrounding the shield 15.

It is held between 17.

One of the lead rods 11 is integrally fixed to the metal end plate 18 joined to one end of the insulating tube 16 while airtightly passing through the metal end plate 18 . The other lead rod 12, which is connected to a drive device (not shown), is connected via a bellows 20 to the other metal end plate 19, which is hermetically joined to the other end of the other insulating tube 17. The movable electrode 14 is configured to open and close with respect to the fixed electrode 13 so as to be able to reciprocate in the opposite direction of the electrodes 13 and 14.

The electrodes 13 and 14 are made of chromium (Cr) and copper (Cu).
And, at the interface between these chromium and copper, bismuth (
It is composed of a composite metal consisting of Bi).

An example of the manufacturing method of this electrode material is as follows: -1
00 mesh chromium powder with an inner diameter of 68!111
Approximately 40% of copper-bismuth alloy was placed on top of the chromium powder in a container made of alumina ceramics.
The lid is placed on the container with the chromium particles placed on it, and heat treatment is performed as shown in Fig. 7 while degassing in a vacuum furnace. obtain.

Thereafter, copper and bismuth are infiltrated into the voids of the infiltrated base material, but at this time, the inside of the container becomes an atmosphere containing a large amount of bismuth vapor. Then, the obtained electrode material is taken out of the container and machined into a predetermined size and shape.

In this way, an electrode material consisting of Cr: 38% by weight, Bi: 12% by weight, Cu: the remainder was prepared as a first sample, and the state of its metallographic structure was examined using an X-ray microanalyzer. A preliminary examination of the secondary metallographic structure is shown in Figure 1, an X-ray image showing the distribution of copper in this sample is shown in Figure 2, an Xg image showing the distribution of chromium is shown in Figure 3, and an X-ray image showing the distribution of bismuth in this sample is shown in Figure 1. X-ray images representing the distribution state are shown in FIG. In Figures 2 to 4, the white areas are the locations where each metal element exists, and copper and bismuth infiltrate into the voids of the porous infiltration base material made of chromium, and bismuth forms the interface between chromium and copper. In other words, as is clear from FIG. 1, it can be seen that the chromium particles are finely dispersed and precipitated around the chromium particles.

In addition to the above first sample, a second sample consisting of Cr: 35% by weight, Bi: 15% by weight, Cu: remainder, and a third sample consisting of Cr: 32% by weight, Bi: 18% by weight, Cu: remainder, were prepared, Each is processed into a disk shape with a diameter of 50 mm and a thickness of 6.5 m, and 4
A rounded material with a radius of curvature of 1 ml was incorporated as the electrodes 13 and 14 of a vacuum interrupter shown in FIG. 7, and the welding resistance, current interrupting performance, and current interrupting value were examined.

Regarding contact resistance, t, T 1. ? , the vacuum interrupter is loaded and closed at 200V and 120A, and the applied force at this time is 15
As a result of calculating the contact resistance values after 100, 1,000, -0,000, and 100,000 cycles under the condition of 0 kgf, as shown in Figure 5, there is almost no difference from the initial value even after 100,000 cycles. , 15μ
The value was as low as Ω. Note that ω represents the change in the contact resistance values of the first sample, Kagami the second sample, and Tohe the third sample. For comparison, the case of a copper-chromium alloy in which 50% by weight of chromium is added to copper is shown in [Mo].

Regarding current cutting performance, the first sample can cut off a current of 26 kA (r, ms,) under a voltage condition of 7.2 kV, and the second sample can cut off a current of 24 kA (r, ILs,).
In the third sample, the current was 22 kA (r,
ts, ) could be cut off.

On the other hand, the current cutoff value is 200V.

The vacuum interrupter was loaded and closed at 120A, and the current cutoff values after 100, 1,000, -0,000, and 100,000 cycles were calculated, and as shown in Figure 6, even after 100,000 cycles, IA The following good results were obtained. Note that the O mark shown in FIG.

The Δ mark and the X mark each represent the average value of 50 measurements, and σ( indicates the change in the current cutoff value for the first sample, xi indicates the second sample, and toi indicates the change in the current cutoff value for the third sample.

H Effects of the Invention According to the electrode material for a vacuum interrupter and the manufacturing method thereof of the present invention, copper and bismuth are infiltrated into chromium powder,
By rapidly cooling these to disperse and precipitate bismuth at the interface between chromium and copper, the vacuum can maintain the current cutoff value below IA and the contact resistance at a low value of about 15 μΩ even after 100,000 times of opening and closing. Can provide an interrupter.

In addition, the contact resistance value is low and stable even after multiple opening/closing operations, so the operating device for opening/closing can be made smaller, and combined with the fact that it generates less heat, the cubicle can be made smaller. be.

[Brief explanation of drawings]

FIG. 1 is a micrograph showing a secondary electron image of the metal structure taken with an X-ray microanalyzer in one embodiment of the electrode material for a vacuum interrupter according to the present invention, FIG. 2 is a micrograph showing the distribution state of copper, Figure 3 is a microscopic photograph showing the distribution of chromium, Figure 4 is a microscope photograph showing the distribution of bismuth, and Figure 5 is a contact between the copper chromium alloy and this example when the present invention is applied to a vacuum interrupter. A graph comparing the resistance values, Fig. 6 is a graph showing the characteristics of the current cutoff value when the present invention is applied to a vacuum interrupter, Fig. 7 is a graph showing the process of heat treatment according to this embodiment, Fig. 8 is a cross-sectional view showing an example of the vacuum interrupter, Fig. 9 is a micrograph showing a secondary electron image of the metal structure of a conventional copper-bismuth alloy taken with an X-ray microanalyzer, and Fig. 10 shows the distribution state of copper! 11 is a micrograph showing the distribution state of bismuth. In the figure, the reference numbers 11 and 121 represent electrodes, and 13° and 14 represent electrodes. Patent applicant Meidensha Co., Ltd. Agent

Claims (2)

[Claims] (1) A vacuum interrupter consisting of chromium constituting a skeleton, copper filled in the chromium skeleton, and bismuth filled in the skeleton together with the copper and dispersed at the interface between the chromium and the copper. electrode material. (2) Place the copper-bismuth alloy on the chromium powder, heat and maintain the alloy above the melting point of the copper-bismuth alloy in a non-oxidizing atmosphere containing bismuth vapor, and place copper and bismuth into the voids of the chromium. A method for producing an electrode material for a vacuum interrupter, which comprises infiltrating and then rapidly cooling.