JPH01246733A - Contact for vacuum circuit breaker, manufacture thereof and vacuum breaker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a contact for a vacuum circuit breaker having high voltage resistance and excellent welding resistance, a method for manufacturing the same, and a vacuum circuit breaker.

[Conventional technology]

Various materials have been developed for electrode contacts for vacuum circuit breakers. Typical main materials include Cu-based molten alloys (Cu-Pb, Cu-
B1. Cu-Co-B1Pb, etc.) or JP-A-5
W C made by powder metallurgy such as No. 4-73284
-Ag and Cr-Cu based infiltration alloys as disclosed in Japanese Patent Publication No. 45-35101 are known.

Against this background, recently there has been an increasing demand for vacuum circuit breakers to be able to provide higher voltage and large current interruption, and currently the latter type of Cr-C
A large number of U-based materials or improved materials thereof are being proposed. In particular, the demand for this Cr-Cu material is increasing because its raw materials are cheap and the I2 manufacturing method is simple.

However, in recent years, as high-output power generation equipment such as nuclear power and nuclear fusion has become widespread, power circuit breakers with even higher capacity have become necessary.

Traditionally, gas circuit breakers have been used for high voltage applications, but vacuum circuit breakers are expected to be used in the future as they are compact, can interrupt large currents, are noiseless, and are maintenance-free. For this purpose, conventional electrode contact materials such as those described above are beginning to reach their limits in terms of withstand voltage and welding resistance.

Currently, various materials of the Cr-Cu-ceramic type made by powder metallurgy are disclosed as high voltage withstand materials specifically proposed. For example, JP-A-61-
No. 148726, No. 61-253730, No. 51-1
No. 16981, No. 59-58723, No. 60-131
No. 723, No. 60-197840, No. 52-1203
No. 71, No. 55-143731, No. 60-89020
No. 60-180026 and No. 60-180026 are considered to be relatively promising materials due to their welding resistance and the ability to reduce cutting surge depending on the type of ceramic powder. However, since all of the above materials contain Cu, there is a limit to their withstand voltage. In other words, although Cr-Cu-ceramic materials can be expected to have some improvement over Cr-Cu materials, as long as they contain Cu, their withstand voltage characteristics are controlled by the amount of Cu. .

[Problem to be solved by the invention]

In conventional electrode materials, Cr, which is brittle and easily peels off, is dispersed in order to provide welding resistance.

Or it was used as a skeleton. However, even with repeated interruptions of large currents, welding of the electrically connected surfaces was still unavoidable. When this is forcibly peeled off, the surface of the electrically connected portion progresses to roughness, and countless protrusions are formed that cause electric field concentration, which tends to gradually deteriorate the voltage resistance.

Furthermore, materials containing various types of ceramics in the Cr-Cu system have been disclosed, and it is true that materials to which even a small amount of ceramics are added tend to have improved welding resistance. However, conventional materials always contained more or less Cu. Since this Cu does not have a very high melting point,
Repeated interrupted arc heat promoted surface roughness.

Therefore, as long as Cu is included, as mentioned above, Cu itself does not have good withstand voltage, so there is a limit to achieving higher withstand voltage and larger current.

On the other hand, it is not enough to simply include ceramics. That is, in a vacuum circuit breaker, a large current is constantly applied and the current is repeatedly interrupted. Therefore, unless the electrical conductivity of the electrically connected portion is always good, the contact resistance will increase, causing heat generation, which will also be a major cause of surface roughness.

An object of the present invention is to provide a contact for a vacuum circuit breaker that can improve the welding resistance of conventional materials as described above and at the same time exhibit excellent voltage resistance and current interrupting performance. It is also an object of the present invention to provide a method for manufacturing such a contact and a vacuum circuit breaker.

[Means to solve the problem]

In order to achieve the above object, the vacuum circuit breaker contact according to the present invention is made of an intermetallic compound having a higher melting point than copper and conductive ceramics. The vacuum circuit breaker is provided with the above-mentioned contacts, and the amount of the conductive ceramic is preferably in the range of 1 to 20% by weight. Furthermore, examples of conductive ceramics include borides, carbides, nitrides, and silicides of Ti, Zr, Mo, or W, and examples of intermetallic compounds include NiAl, Ni, and AQ. That is, NiAu-TiB2. NiAl
- Composite materials such as TiN, NiAl-TiC, etc.

Specifically, the intermetallic compounds include NiAQ, Ni, AQ, and Ni2AQ.
3 y F e A Q HF e A Q 2 *
F e z A Q s + F e A Q 3
s COA I2 tCozA Q,, Cr,A Q
tl, Cr, A Q9. There are CrAQ, etc. All of these melting points are higher than Cu and Ag<Mo, W,
It is lower than Ta etc.

One or a mixture of two or more of these may be used. In addition, specific examples of the conductive ceramics include TiB2. Z
rBz+ HfB2. VB2. NbBzeT a B
2 # Cr B z HM o B 21 W2 B
HT x N pZ rN, HfN, VN, NbN,
TaN, Cr2N, Mo, N, WN, TiSi,,Z
rSi,.

HfSi,,VSi2. NbSi2. TaSi2゜Cr
Si2. MoSi,,wsi,'ric,ZrC.

HfC, NbC, TaC, Cr3G2. Mo2C.

It is composed of one or more types of WC.

The method for manufacturing contacts for vacuum circuit breakers includes the steps of mixing powders of intermetallic compounds and conductive ceramics, molding, sintering, and then depressurizing and degassing, and one or more of the above steps. After passing through the steps, the manufacturing method includes a step of densifying the material by applying pressure treatment such as hot isostatic pressing (HIP), cold isostatic pressing (CIP), or hot pressing (HP). be.

[Effect]

In composite materials, intermetallic compounds such as NiAl have particularly good electrical conductivity and are high melting point substances,
It has a high melting point of around 1600℃.

Therefore, it has good heat resistance, and the contact fiJ1 is less likely to melt due to bare arc heat than conventional Cu or Ag base materials, and welding is less likely to occur. NiAl compounds also have low electrical resistance, approximately 15 to 20 IAC8% when converted to electrical conductivity.
(100IAC8% is 1.7X when converted to electrical resistance value
10-'Ω·■), and can be used as is as a contact material.

Further, various conductive ceramics dispersed around particles of intermetallic compounds such as NiA1 are themselves conductors and have a higher melting point than intermetallic compounds such as NiA1. For this reason.

Not only can it prevent contact welding due to arc heat, but it can also reduce roughness of the electrical contact surface and maintain a smooth surface at all times. Therefore, since there are few protrusions that cause electric field concentration, the voltage resistance is high and stable.

In addition, all of the constituent materials forming the contact material have electrical conductivity, and their thermionic emission is not as large as that of W, Mo, and Ta, so they have great advantages in that they have good insulation recovery characteristics and excellent large current interrupting performance.

Note that since borides and nitrides themselves are substances with low work-related properties, if the weight ratio of these conductive ceramics is about 10%, thermionic emission increases and the blocking performance decreases accordingly. However, along with this phenomenon, the cutting surge also tends to decrease, so by selecting an appropriate amount of conductive ceramics, it is possible to exhibit the electrode characteristics of a variety of VCBs (vacuum circuit breakers). In other words, it is known that high withstand voltage and large current and low surge are usually contradictory to each other.

Until now, there has been no electrode material that simultaneously satisfies both characteristics to a high degree. However, according to the material of the present invention, a wide range of electrode characteristics can be brought out by appropriately selecting the ratio of high melting point intermetallic compound to conductive ceramic.

To summarize the above, VCB electrodes with conductive ceramics of 1 to 10% by weight exhibit high withstand voltage and welding resistance, and 10 to 20% by weight of conductive ceramics to exhibit low surge properties. . Therefore, the content of conductive ceramics is 1~
The range is 20% by weight.

Next, the method for manufacturing a vacuum circuit breaker contact according to the present invention is:
Because it includes a pressure treatment process such as IP treatment, it is a material that has covalent bonds with intermetallic compounds and conductive ceramics, so it is highly effective even for materials with poor self-sintering properties such as ordinary metal powder. Can be densified.

〔Example〕

Examples of the present invention will be shown below.

Example 1 High-frequency vacuum melted NiA1 alloy (compound composition; Ni-
31.5wt%Al) was crushed into 200mesh
powder was obtained. By the process shown in Fig. 1, this NiAl
The powder, TiB, and powder were mixed for 30 minutes using an automatic mortar, and then the mixed powder was molded into a mold with a diameter of 50 mm and a thickness of 30 mm using a hydraulic press.The molded body was then slightly reduced. In order to have sex (A r + 4 v o
Temporary sintering was performed at 1400° C. for 1 hour in a mixed gas atmosphere of 1% H, ). Furthermore, this molded body is encapsulated with mild steel at a temperature of 300°C.

The capsule was sealed under reduced pressure while degassing at a pressure of 10-2 to 1 O-'torr, and the capsule was heated at a temperature of 1400°C and a pressure of 2000°C.
HIP treatment was performed under the condition of kg/cd. As a result, each capsule of the pre-sintered body was forcibly compressed, and a dense composite material having a density of 98 to 99% of the theoretical density was obtained.

Next, the mild steel capsule of this HIP treated material is peeled,
Diameter 20I (with ball R30), thickness 5 using an electric discharge machine
A pair of electrode contacts were collected from the cabinet.

A vacuum valve shown in FIG. 2 was used to test the breaking characteristics of various electrode contacts. This vacuum valve consists of a cylindrical ceramic insulation case 1, a stainless steel terminal plate 2,
3 constitutes a container, and the inside is 10-6 to 1
It is maintained at a high vacuum of 0-"torr level. Inside this container, there are a pair of electrodes, namely a fixed electrode 4 and a bellows 6.
A movable electrode 5 is provided which is movable through the . Further, a cylindrical shield 7 is provided to surround the electrode 4.5, and this shield 7 prevents the electrode components from adhering to the inner wall of the insulating case 1 when they are evaporated or scattered due to the interruption arc. It has the role of prevention. Electrode 4
, 5 are soldered with silver to an auxiliary electrode plate 8.9 made of Cu. 10.11 is the holder, 12 is the bellows shield,
Reference numeral 13 indicates an exhaust pipe, that is, the electrode contact in this example has a diameter of 20 mm.

It is used as a chip contact with a thickness of 5 mm.

In various electrical performance tests, the withstand voltage test method is to cut off AC 300A 10 times, then increase the impulse voltage to 5k.
Apply increasing voltage in V steps.

This is to measure the discharge voltage value at which the gap between electrodes reaches dielectric breakdown. The interrupting performance test was conducted using an electrode with a diameter of 20IIfi.
The purpose is to cut off the alternating current in 50OA steps and find the limit current value at which the cutoff becomes impossible. Furthermore,
In the cutting current test, the cutting current generated when a small current of 2 to 8 A AC was interrupted was measured 100 times, and the maximum value and average value were determined.゛Table 1 shows the results of measuring the vCB electrode characteristics using the above contacts. In Example 1, NiA1 compound powder and various Ti conductive powders (boride, nitride, silicide, carbide) were mainly used. We took up composite materials with.

In the table, as a comparison with conventional materials, Cu-Co-B1Pb,
Although Cr--Cu alloys are mentioned, it can be seen that the material of the present invention is particularly excellent in voltage resistance.

In other words, all [NiAl-conductive ceramics] composite materials have a withstand voltage of 100 kV or more, which is higher than that of Cu.
-2 to 2.5 times that of the Go-BiPb melted alloy, Cr-
It was found that it has a high voltage resistance that is approximately 30% higher than that of Cu infiltrated alloys.

Although the dielectric strength is effective even if 1 to 5 wt % of conductive ceramics is added to NiA1, it reaches a maximum at approximately 10 vt %, and tends to decrease when the amount exceeds that amount. However, when 10 to 20 wt% of ceramics is added, the cutting current characteristics are improved, and low surge characteristics of approximately 1 to 2 A are obtained. Also, when looking at the current interrupting performance, all of them are 8~
It is in the range of 10KA, and this value is also in the range of conventional Cu-Go-B.
It can be said that it has a high blocking ability that is comparable to that of iPb and Cr-Cu alloys.

Example 2 Table 2 shows other Ni and At compounds.

Composites of AI with Ti boride and Ti nitride, NiAl compounds and other conductive ceramics such as Mo, W, and Zr borides, nitrides,
This is the result of examining various composite materials with silicide and carbide. The test method was the same as in Example 1.

As is clear from the table, all of them had the same tendency as Example 1, had excellent voltage resistance and high interrupting ability, and also exhibited low surge properties as the amount of conductive ceramic increased.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a contact for a vacuum circuit breaker which has improved withstand voltage characteristics as compared to conventional electrode contacts and is also excellent in both large current interrupting performance and anti-welding performance. In addition, by including approximately 20% by weight of conductive ceramics, a low-surge type contact can be obtained.

According to the manufacturing method of the present invention, even if ceramics or the like with poor self-sintering property is used as a raw material, it is possible to easily increase the density and obtain a contact point.

Furthermore, since the vacuum circuit breaker according to the present invention includes the above-mentioned contacts, reliability is improved and it is possible to meet the demands for high voltage and large current interruption.

Table 1 Table 2

[Brief explanation of the drawing]

FIG. 1 is a process diagram of the method for manufacturing an electrode contact of the present invention. FIG. 2 shows a sectional view of the vacuum valve for a vacuum circuit breaker according to the present invention. 4... Fixed electrode (contact), 5... Movable electrode (contact)
.

Claims (1)

[Claims] 1. A contact for a vacuum circuit breaker characterized by being made of an intermetallic compound with a higher melting point than copper and conductive ceramics. 2. The contact for a vacuum circuit breaker according to claim 1, wherein the conductive ceramic is 1 to 20% by weight, and the remainder is an intermetallic compound and unavoidable impurities. 3. The contact for a vacuum circuit breaker according to claim 2, wherein the conductive ceramic is a boride, carbide, nitride or silicide of Ti, Zr, Mo or W, and the intermetallic compound is NiAl or Ni_3Al. 4. The process consists of mixing and molding the intermetallic compound and conductive ceramic powder, sintering it, and then degassing it by reducing the pressure. After passing through one or more of the above steps, pressurizing 1. A method of manufacturing a contact for a vacuum circuit breaker, comprising a step of processing and densification. 5. A vacuum circuit breaker comprising the vacuum circuit breaker contact according to claim 1.