KR820000167B1 - Method of manufacture for a vaccume breacker - Google Patents

Abstract

This invention is a manufacturing method for a predominant vacuum breaker to withstand high voltage. Its manufacturing method is composed of a process mixing chrome(Cr) powder and copper(Cu) powder, a process sintering its mixture in a non-oxidn. atmosphere after mixing, a process forming point contact in sintered alloy, and a process forming the part of point contact by a couple of point contacts.

Description

Manufacturing method of vacuum breaker

1 is a photograph of a microscopic view of a contact material made of a Cu-Cr alloy obtained by the present invention.

2 is a characteristic diagram showing the relationship between the amount of copper and chromium and the conductivity.

3 is a characteristic diagram showing a relationship between a copper amount and a contact resistance.

4 is a characteristic diagram showing the relationship between the amount of copper and the surface hardness.

5 is a characteristic diagram showing a relationship between a copper amount and a breakdown voltage.

6 is a characteristic diagram showing a relationship between a motion amount and a breaking current.

7 is a characteristic diagram showing the relationship between the amount of agreement and welding.

8 is a characteristic diagram showing the relationship between the average particle diameter of chromium and the withstand voltage.

9 is a characteristic diagram showing the relationship between the average particle diameter of copper, the hydrogen reduction loss, and the content of lead (Pb).

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a vacuum circuit breaker excellent for high withstand voltage.

As the contact characteristics of the vacuum circuit breaker,

(1) High blocking performance, (4) Low welding force,

(2) High withstand voltage, (5) Low interruption current value is required.

(3) Low contact resistance

In practice, however, it is difficult to satisfy all of these characteristics as a contact material, and generally satisfies a particularly important characteristic depending on the use and sacrifices other characteristics to some extent.

The present invention provides a vacuum circuit breaker having a novel contact that satisfies the above-mentioned characteristics (1), (2) and (3) because of its purpose to provide a vacuum circuit which is used as a circuit having a high voltage and a large current capacity. It is.

The inventors have noted that chromium has a high withstand voltage in vacuum as an advantageous contact material at high voltages.

However, since this chromium is a heat-resistant metal, it has a strong thermoelectron radiation characteristic, so that a large blocking performance cannot be obtained by itself. In addition, since the conductivity is small and the contact resistance is large, the temperature rise occurs as a circuit breaker with a large current capacity as it is, and thus cannot be used.

In the present invention, as described below, it is possible to provide a method for manufacturing a vacuum circuit breaker suitable for the above purpose by effectively removing the defects of chromium and using the advantage of high withstand voltage of chromium.

In the present invention, firstly, copper should be eliminated by adding copper.

The present invention describes an embodiment of manufacturing the contact junction of the present invention by powder metallurgy in a powder of copper and chromium.

The conventional casting method is described in that there is a drawback that the chromium is non-uniformly dispersed.

The conventional casting method has the drawback that chromium is not uniformly dispersed, and according to the powder metallurgy method, a Cu-Cr alloy in which chromium is uniformly dispersed in a copper matrix can be easily obtained. This fact is evident in the tissue picture of FIG. Moreover, in this invention, the copper powder of 5 micrometers or more of average particle diameters is used.

By using the copper powder of such a particle size, it compares with copper of about 3 micrometers of average particle diameters, and there is little hydrogen reduction reduction, and there are few low boiling point impurities. Moreover, such a contact material was very excellent as a vacuum circuit breaker for high voltage and high current.

In addition, when manufacturing a contact material, it is necessary to prevent the effect of metal dust on the human body. In this regard, when compared with copper having an average particle diameter of about 3 μm, it is better to use copper powder having an average particle diameter of 5 μm or more. It is advantageous.

In other words, it is advantageous to prevent metal dust and prevent floating.

In addition, the present invention provides a method for producing such a Cu-Cr alloy by sintering in a non-oxidizing atmosphere composed of vacuum or hydrogen halide such as hydrogen, internal temperature and argon.

Chromium has a drawback that is extremely easy to oxidize, which is difficult in a general casting method, but the present invention can sufficiently prevent oxidation because it is sintered in a vacuum or in an atmosphere having a strong reducing ability.

In addition, all contact materials using copper having an average particle diameter of about 3 μm have difficulties in terms of oxygen content and low boiling point impurity content, as described above. The high temperature vacuum treatment is performed.

Here, since the vacuum furnace operates while maintaining a high vacuum state, the operation efficiency is low, uniform heating is difficult, the cost is high, and the cost of the contact point is also high.

The inventors tested the hydrogen sintering method using copper of an average particle diameter of about 3 micrometers by experiment.

Experiments showed difficulties in terms of oxygen content and low boiling point impurity content.

When copper of 5 µm or more in average particle diameter was used, good alloys could be obtained.

In the vacuum sintering method, good results were obtained in terms of oxygen content and low boiling point impurity content even in a copper having an average particle diameter of 3 µm. In this way, the average particle diameter of 5 µm or more makes it possible to manufacture the contact materials inexpensively by increasing the operation efficiency of the sintering furnace since there are unreasonable shortcomings in terms of oxygen content and low boiling point impurity content even when sintering in non-oxidizing atmosphere such as oxygen sintering method is applied. I could. In the present invention, chromium powder having an average particle diameter of 100 µm or less is used.

Since chromium needs to be uniformly dispersed in the copper matrix in order to exhibit high breakdown performance in chromium, the smaller the particle size of chromium is, the better.

As a result of examining the upper limit of the average particle diameter of chromium in the breakdown voltage resistance, etc., it became clear that the average particle size was 100 µm or less.

This will be understood in the characteristics shown.

Hereinafter, an embodiment of the present invention will be described in detail.

The Cu-Cr-based alloy herein is sintered at a temperature of 1030 ° C. in a hydrogen atmosphere of about −20 ° C. with a Cu-Cr powder material premixed and molded at a predetermined ratio as an example.

In such a hydrogen atmosphere, these unnecessary substances can be removed by heating a small amount of the low boiling point material contained in the copper or chromium powder as impurities before sintering in a high-temperature vacuum atmosphere in advance.

As a result, the withstand voltage was improved.

In order to effectively reduce and remove oxides of copper and chromium powders, the dew point of the hydrogen atmosphere needs to be sufficiently low. However, when the dew point is about -20 ° C, the oxygen gas content can be suppressed to below 3500PPM weight ratio and the oxygen gas content to 3500PPM weight ratio or less can be required and sufficient performance as Cu-Cr alloy alloy contact material for vacuum breaker.

The accelerated test again validated the vacuum life at the top of 30-50 years. In addition, it is preferable that the density ratio with respect to theoretical density becomes higher as a contact material for a vacuum circuit breaker, but since this Cu-Cr alloy can block several 10KV and several 10KA at 90% or more of density ratio, the consumption by a current opening and closing is also no problem and is small. It was confirmed.

In the case of hydrogen sintering, when the solid powder is sintered at a temperature at which the copper powder does not melt, hydrogen gas penetrates into the contacts, thereby effectively reducing and removing oxides of copper and chromium. By liquid phase sintering at the melting temperature, it was confirmed that required density can be obtained in a shorter time than in the case of solid phase sintering.

FIG. 1 is a micrograph of a Cu-Cr (weight ratio 75%, chromium 25%) based material obtained according to an embodiment of the present invention. Indicates.

2-8 show the characteristic of the Cu-Cr system material by this invention.

2 shows the relationship between the same amount and the conductivity, indicating that the conductivity increases with the amount of agreement.

3 shows the relationship between the amount of copper and the contact resistance.

4 shows the relationship between the copper amount and the surface hardness (Rockwell F scale), indicating that the hardness decreases with the copper amount.

The results of FIG. 3 are interpreted as a result of the increase of the synergistic effect as the synergistic effect of FIG. 2 and FIG.

5 shows the relationship between the breakdown voltage and the same amount after opening and closing a current of about 200 A 50,000 times.

5 shows that the withstand voltage decreases with the same amount.

6 shows the relationship between the same amount and the breaking current.

The breaking current shows a low curve with respect to the same quantity, and averages less than 3.3A between 20-80% of the quantity.

The characteristics of the breaking current value of the contact obtained by the embodiment of the present invention are that, for example, the average value is considerably lower than that of the Cu-Bi system, the width of the distribution is good, and it does not change very much even after switching the current.

In addition, the cut-off current value of the contact with the low boiling point material, which is not limited to the Cu-Bi system, has a relatively large distribution with respect to the current switching frequency.

In FIG. 7, the relationship between the copper amount and the welding characteristic is shown.

This data shows the maximum current value that can be tripped with a force of 100 kg after applying a current of 20 kg to the contact point of the model pipe and letting a predetermined current flow.

Is the current which is not welded, and is the current to be welded.

8 shows the relationship between the chromium particle size and the breakdown voltage, and it can be seen that constant breakdown voltage performance can be obtained when the average grain size of chromium is 100 μm or less.

Fig. 9 shows the relationship between the average particle diameter of copper, the hydrogen reduction loss and the purity, in particular the content of lead (Pb).

Compared with the copper reduction reduction of about 3 mu m in average particle diameter, the one having an average particle diameter of 5 mu m is 50% or less.

Thus, compared with content of lead (Pb), it becomes 10% or less.

The present inventors have also verified the relationship between other properties, such as% of copper, surface hardness, contact resistance, breaking current, and arc time at blocking of 40 KArms, but all exhibited excellent characteristics.

Claims (1)

A process of mixing chromium powder and copper powder, a process of sintering in a non-oxidizing atmosphere after mixing, a process of forming a contact from an alloy formed by sintering, a process of forming a contact portion by injecting a pair of the above contacts, and the like. Method for manufacturing a vacuum circuit breaker provided.

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