JPH0143971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a contact material for a vacuum shield breaker which has excellent large current shearing characteristics and high voltage resistance.

[Conventional technology]

Vacuum sheath breakers have advantages such as maintenance-free, non-polluting, and excellent sheath breaker performance, so the scope of their application is rapidly expanding. Additionally, along with this, demands for higher withstand voltage and larger shear current capacity are becoming more severe. On the other hand, the performance of a vacuum shield breaker is determined to a large extent by the contact material inside the vacuum container.

Satisfactory characteristics of contact materials for vacuum shield disconnectors include (1) large shield breaking capacity, (2) high withstand voltage, (3) low contact resistance, and (4) low welding force. (5) low contact wear, (6) low cutting current, (7) good workability, and (8) sufficient mechanical strength.

In actual contact materials, it is quite difficult to satisfy all of these properties, and in general, materials are used that satisfy particularly important properties depending on the application, sacrificing other properties to some extent. This is the actual situation. For example, the copper-tungsten contact material described in JP-A-55-78429 has excellent withstand voltage performance. However, it has the disadvantage of poor current conduction and breaking performance.

On the other hand, for example, copper as described in JP-A-54-71375
Chrome contact materials are often used because they have very good damping performance, but they are inferior to the copper-tungsten contact materials in terms of withstand voltage performance.

In addition to the above-mentioned contact materials for vacuum shields and disconnectors, examples of contact materials generally used in air, oil, etc. are listed in literature such as "Powder Metallurgy" (published by Nikkan Kogyo Shimbun). However, for example, powder metallurgy P229~
When the silver-molybdenum contact materials and copper-molybdenum contact materials described in 230 are used for vacuum insulation and disconnection contacts, the withstand voltage performance is inferior to the copper-tungsten contact materials described above, and the current resistance and disconnection performance are inferior to those described above. Because it is inferior to copper-chromium contact materials, it is rarely used at present.

[Problem that the invention seeks to solve]

Conventional contact materials for vacuum shields and disconnectors have been used by taking advantage of their respective characteristics as described above, but in recent years, the demands for larger currents and higher voltages for vacuum shields and disconnectors have become stricter. It is becoming difficult to fully satisfy the required performance with contact materials such as these. or,
There is a need for contact materials with even better performance in reducing the size of vacuum shields and disconnectors.

This invention was made in order to solve the problems of the conventional products as described above, and it is an object of the present invention to provide a contact material for vacuum shields and breakers that has excellent large current breaking characteristics and high withstand voltage performance. The purpose is

[Means for solving problems]

The contact material for a vacuum shield breaker according to the present invention contains copper and chromium as another component.
Molybdenum boride ranges from 0.2 to 10 to 38% by weight
% by weight.

[Effect]

The contact material for vacuum shields and breakers containing boride of copper, chromium, and molybdenum in this invention is as follows:
Borides of chromium and molybdenum are uniformly and finely distributed in the copper, demonstrating excellent cleaving performance and high pressure resistance.

〔Example〕

The inventors prototyped materials made by adding various metals, alloys, and intermetallic compounds to copper, incorporated them into vacuum shields and disconnectors, and conducted various experiments. As a result, it was found that the contact material containing copper and borides of chromium and molybdenum had very excellent welding performance.

An embodiment of the present invention will be described below.

(Preparation of contact material) The contact material was prepared using two methods: an atmospheric pressure sintering method and a pressure sintering method using a powder metallurgy method.

The first pressureless sintering method for manufacturing contact materials is based on particle size.
Chromium powder with a particle size of 70μm or less and MoB with a particle size of 40μm or less
The powder and the copper powder having a particle size of 40 μm or less were each weighed in predetermined proportions, and then mixed for about 2 hours. continue,
This mixed powder was filled into a mold with an inner diameter of φ30 and press molded. Next, this compact was sintered for about 2 hours in a hydrogen atmosphere just below the melting point of copper to obtain a contact material.

The second pressure sintering method for manufacturing contact materials is based on particle size.
Chromium powder with a particle size of 70μm or less and MoB with a particle size of 40μm or less
The powder and the copper powder having a particle size of 40 μm or less were each weighed in predetermined proportions, and then mixed for 2 hours. Next, this mixed powder was filled into a carbon die with an inner diameter of φ30.5, and heated at 1000 to 1050 in a vacuum using a hot press machine.
C. for 2 hours, during which time a pressure of 100 to 300 Kg/cm ² (for example, 200 Kg/cm ^{2 )} was applied to obtain a mass of contact material. Alternatively, the mixed powder may be filled into a mold with an inner diameter of φ30 and press-molded, and then the molded product may be hot-pressed in a hot press to obtain a contact material. The cold press-formed body was vacuum-sealed in a stainless steel container and heated in argon to just below the melting point of copper for 2 hours.
Contact materials were also obtained by applying hydrostatic pressure at 2 tons/cm ² .

The first pressureless sintering method also yields a contact material with a theoretical density of 95% or more, but the second pressureless sintering method achieves a contact material with a theoretical density of almost 99% or more. A contact material was obtained, and the electrical conductivity and hardness were slightly better with the pressure sintering method.

Figure 1 shows a Cu-Cr-
A micrograph of the metallographic structure of the MoB alloy contact material at a magnification of 100 is shown. This is made by weighing chromium powder, MoB powder, and copper powder at a weight ratio of 25:5:70, mixing for 2 hours, press-forming at a pressure of 3 tons/ ^cm2 , and molding this compact with an inner diameter of φ30.5. filled into a carbon die, heated in a vacuum for 2 hours just below the melting point of copper,
φ30.5 obtained by applying a pressure of 200Kg/cm ² during this time
×10t Cu-Cr-MoB alloy. In Figure 1, Cu
It can be seen that Cr and MOB are uniformly and finely distributed inside.

FIG. 4 shows a micrograph of the metal structure of a conventional Cu-Cr alloy contact material at a magnification of 100 as a comparative example.
This involves weighing Cr powder with a particle size of 70 μm or less and copper powder with a particle size of 40 μm or less in a ratio of 25:75, mixing for 2 hours, and then filling a mold with an inner diameter of φ30 with this mixed powder. This is a Cu-Cr alloy obtained by press forming at a pressure of 3 ton/cm ² and then heating this compact for 2 hours in a hydrogen atmosphere just below the melting point of copper.

(Properties of contact materials, experiments) The above contact materials manufactured by each method have a diameter of 20 mm.
After machining the electrode into a mm-thick electrode, it was assembled into a vacuum shield and disconnector, and its electrical characteristics were measured.

Figures 2 and 3 both show the shearing performance of the contact material according to an embodiment of the present invention, and the shearing performance of the conventional Cu-25Cr weight% alloy is set to 1. This figure shows the shearing performance of the contact material according to the invention. This evaluation of shearing performance was determined from the results of synthetic shearing tests with various DC components and arc times.
A test was conducted on a 25% by weight Cr product and a reference value was determined. Next, the test for the product of the present invention was started from the level of the conventional product, and the shearing performance was measured. Since the details of the data in the range below that of conventional products are unknown, they are indicated by broken lines in the figure.

Figure 2 shows the amount of Cr (weight%) in the alloy at 12, 15,
It shows the relationship between the amount of MoB added and the shearing performance when fixed at 20 and 25, and when the amount of Cr is 12% by weight or more, the addition of MoB improves the shearing performance. When Cr content is 25% by weight, MoB is 5% by weight.
However, when the amount of MoB was less than 0.2% by weight, no effect was observed at all. On the other hand, the amount of MoB is 10
If it exceeds % by weight, the shear cutting performance will deteriorate.

Figure 3 shows the amount of Cr (weight%) in the alloy: 25, 30,
It shows the relationship between the amount of MoB added and the shearing performance when fixed at 35 and 38, and when the amount of Cr is 38% by weight or less, an improvement in the shearing performance is seen by adding MoB. Therefore, as a contact material for vacuum shields and disconnectors,
Cr content ranges from 12 to 38% by weight, and MoB content ranges from 0.2 to 10
It is desirable to contain it in a range of % by weight.

It was also confirmed that the addition of MoB tends to improve the withstand voltage performance.

In the above examples, the borides of copper, chromium, and molybdenum are each a single metal, an alloy of three or two metals, an intermetallic compound of three or two metals, or an intermetallic compound of three or two metals.
Or, it is thought that they are distributed as a complex.

In addition, although MoB was used as the boride of Mo in the above embodiment, MoB ₂ , Mo ₂ B
Similar effects were obtained using other Mo borides such as However, from the experimental results, as Mo boride,
The shearing performance was most effectively improved when at least one of MoB and MoB ₂ was contained.

Although not shown, the above alloy includes Bi, Te,
Low melting point metals such as Sb, Tl, Pb, Se, Ce, and Ca, their alloys, their intermetallic compounds, and at least one of their oxides are added in an amount of 10% by weight or less. It has been confirmed that, in the case of the disconnection contact as well, the present invention has the effect of increasing the insulating performance and withstand voltage performance in the same manner as in the above embodiments.

Note that when 10% by weight or more of at least one of low melting point metals, alloys thereof, intermetallic compounds thereof, and oxides thereof was added, the shearing performance was significantly reduced. Also, the low melting point metal is Ce,
Or, in the case of Ca, the characteristics were slightly degraded.

〔Effect of the invention〕

As described above, according to the present invention, it contains copper and 12 to 38% by weight of chromium as other components.
Since it contains molybdenum boride in the range of 0.2 to 10% by weight, it is effective to obtain a contact material for a vacuum shield breaker having excellent shearing performance and high withstand voltage performance.

[Brief explanation of drawings]

Figure 1 shows a Cu-25wt%Cr-
Figure 2 shows a micrograph of the metal structure of a 5 wt% MoB contact material at a magnification of 100 times.
A characteristic diagram showing the relationship between MoB addition amount and shearing performance when the MoB content is fixed at 15, 20, and 25. Figure 3 shows the relationship between the MoB addition amount and the shearing performance when the weight ratio of Cr in the contact material according to an embodiment of the present invention is fixed at 25, 30, 35, When fixed at 38
Figure 4 is a characteristic diagram showing the relationship between the amount of MoB added and the shearing performance. It is a figure showing a micrograph.

Claims (1)

[Claims] 1. Contains copper, and also contains chromium in a range of 12 to 38% by weight and molybdenum boride as other components.
A contact material for vacuum shields and disconnectors, characterized in that the content ranges from 0.2 to 10% by weight. 2. The contact material for a vacuum shield or breaker according to claim 1, wherein the molybdenum boride is at least one of MoB and _MoB2 . 3 Bismuth, tellurium, antimony, thallium,
At least one of the low melting point metals of lead, selenium, cerium, and calcium, their alloys, their intermetallic compounds, and their oxides.
The contact material for a vacuum shield or breaker according to claim 1 or 2, characterized in that it contains not more than % by weight.