JPH05242773A - Vacuum interrupter electrode material - Google Patents

Abstract

PURPOSE:To provide an electrode material produced by molding and sintering metal powder and having spiral grooves which prevents chips or cracks from being generated after molding to eliminate the need of excess care in handling and provides a sufficient electric conductivity after sintering. CONSTITUTION:Mixed powder of copper and fireproof metal (for example, chrome) containing 50wt.% or more of copper is filled in an electrode metal mold and pressurized and molded such that the density of the resultant compact is 65% or more of the theoretical density and the generated compact is sintered. The sintered compact is used as an electrode without further processing.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrode material for a vacuum interrupter having a groove.

[0002]

2. Description of the Related Art Generally, as a vacuum interrupter electrode, a shape in which an arc is diffused by magnetic drive (hereinafter referred to as a spiral shape) is used as shown in FIG. Such an electrode 1 has been obtained mainly by machining a material (surface processing spiral groove processing).
In the figure, 2 is a spiral groove and 3 is a pedal.

However, since machining causes an increase in price, as a method for producing an electrode material aiming at non-processing by powder metallurgy and reducing the price, Japanese Patent Laid-Open Publication No. 53-53 is available.
The one disclosed in Japanese Patent Publication No. 149676 is provided.
In this method, a metal powder material is pressure-molded into a spiral electrode shape, and this is sintered.

[0004]

However, as a result of attempting to manufacture an electrode by mixing various powders by the above-mentioned powder metallurgy method, the electrode has the groove 2, so that the following problems occur. I understood it.

(1) Since the shape of the electrode is the irregular spiral shape as shown in FIG. 1, when the powder is compression-molded, the contact area between the die and the powder or the molded body is large and the friction is large. Therefore, it is easy for the powder and the like to be easily scraped.

(2) When the above-mentioned galling occurs, the life of an expensive mold is shortened, and the cost is rather increased.
In particular, when the molded body 5 is removed from the mold 4 as shown in FIG. 2, the force is concentrated on the root 4b of the groove forming portion 4a of the mold 4, and the mold 4 may be damaged. Therefore, the groove 2 of the electrode cannot be deepened.

(3) Further, when the molded body 5 is taken out from the mold 4, if the frictional force is greater than the strength of the pedal tip of the molded body,
As shown in FIG. 3, chipping or cracking 6 occurs at the tip of the pedal, making it unusable as an electrode.

(4) As an electrode shape which does not cause the above-mentioned defects, for example, as shown in FIG. 4, a groove 2 of the pedal 3 is shallow and an R portion 7 at the tip is large. Becomes shorter, the driving of the arc becomes insufficient, and the breaking performance deteriorates.

(5) In order to solve this problem, as a result of molding with a small applied pressure, chipping could be prevented, but another problem that the pedal was easily broken during handling after taking out the molded body occurred. That is, as shown in FIG. 5, since a force is applied to the base portion of the pedal 3 during handling, there is a risk of damage at this portion. In the figure, 8 is a damaged part.

(6) Further, when the molding pressure is small, the shrinkage after sintering becomes large. Since the spiral shape is irregular,
The shrinkage does not have a similar shape to that at the time of molding, so that the shape of the electrode after sintering becomes different from the desired shape. Further, each pedal is deformed, the arc drive at the time of breaking is different, and breaking becomes unstable.

(7) Further, in the powder metallurgy method, in order to reduce the frictional force, a small amount (about 0.1% by weight) of a lubricant such as zinc stearate is generally mixed. If the lubricant cannot be removed, the barrier performance will be significantly reduced.

[0012]

In view of the above problems, attention is paid to the composition and molding density of the starting materials for electrodes, the electrode materials are molded by changing these, and the presence or absence of damage during handling after molding The conductivity and the like when used as an electrode after binding were examined. The results are shown in Table 1. The one shown in Table 1 uses a mixed powder of copper (hereinafter, Cu) powder and chromium (hereinafter, Cr) powder as an example of a refractory metal, and has a molding density of 6
By setting it to 5% or more, problems such as breakage during handling disappeared. If Cu is 50% by weight or less, the conductivity and the density after sintering become low, and Cu cannot be used as an electrode material.

That is, the electrode material for the interrupter for vacuum according to the present invention is formed by pressure molding a mixed powder of Cu containing 50 wt% or more of Cu and a refractory metal so that the molding density becomes 65% or more of the theoretical density. Then, the obtained molded body is heated and sintered at a temperature equal to or lower than the melting point of Cu.

[0014]

[Table 1]

[0015]

EXAMPLE Next, a method for manufacturing an electrode material according to an example of the present invention will be described. As starting material, powder size 100
Cu powder having a particle diameter of 150 μm or less and Cr powder having a particle diameter of 150 μm or less are sufficiently mixed in a V-type mixer for 1 hour at various weight ratios to obtain mixed powder. As the Cu powder, those obtained by an electrolysis method are preferable because the powder is easily entangled and easily crushed during pressure molding.

Next, the mixed powder obtained as described above was filled in a spiral mold and pressure-molded while changing the molding density to obtain a molded body having a diameter of 63 mm and a thickness of 8 mm. next,
The obtained molded body was subjected to Cu (5 × 10 ⁻⁵ Torr) in a vacuum.
Was heated at a temperature of 1060 ° C. just below the melting point for 2 hours to obtain a sintered body. The obtained sintered body is used as an electrode as it is. The characteristics after molding and after sintering are as shown in Table 1.

As can be seen from Table 1, by setting the molding density after molding to 65% or more of the theoretical density, it is possible to prevent the molding from being damaged during handling of the molding. Table 2 shows, as an example, the relationship between the molding density of the 80Cu-20Cr compact and the bending stress of the sintered compact. If the molding density is 65% or more, sufficient bending stress can be obtained.

[0018]

[Table 2]

As shown in FIG. 6, the sintered bodies 21 and 22 having a composition of 80Cu-20Cr and a compacting density of 80% are brazed to the lead rods 23 and 24 as electrodes to form a vacuum interrupter 25, which is cut off. As a result of the test, a good blocking performance was confirmed. Further, the device was attached to the operation mechanism and the open / close life test was performed 20000 times, but no abnormality such as chipping or cracking occurred on the electrode.

The above example uses Cr as the refractory metal, but in addition to this, Mo, W, Ti, SUS, F
One kind or two or more kinds of e, Ta, Nb, etc. can be adopted. However, when two or more kinds are included, it is necessary that the refractory metals be a combination of those that do not form a solid solution, diffuse, or form an intermetallic compound.

[0021]

According to the electrode material of the present invention, a mixed powder of Cu containing 50 wt% or more of Cu and a refractory metal is pressed so that the compact density is 65% or more of the theoretical density. To obtain a molded body without chipping or cracks, and further a sintered body by specifying the starting material and the density at the time of molding, such as molding and sintering the obtained molded body to obtain an electrode material. You can

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view of a vacuum interrupter electrode having a spiral groove.

FIG. 2 is a partial explanatory view showing the occurrence of defects during molding.

FIG. 3 is an explanatory diagram of chips and cracks generated at the tip of the pedal.

FIG. 4 is a plan view of an example of a molded body having a shallow groove.

FIG. 5 is an explanatory diagram of a damaged portion occurring at the base of the pedal.

FIG. 6 is a cross-sectional view of a vacuum interrupter using the electrode material obtained according to the present invention.

[Explanation of symbols]

 1 Electrode 2 Spiral groove 3 Pedal 21,22 Sintered body 23,24 Lead rod

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichigo Yanagisawa 2-17-1 Osaki, Shinagawa-ku, Tokyo Meiden Koshisha

Claims (1)

[Claims] 1. A mixed powder of copper and a refractory metal containing 50% by weight or more of copper is pressure-molded so that the molding density is 65% or more of the theoretical density, and the obtained molded body is below the melting point of copper. An electrode material for a vacuum interrupter, which is characterized by being heated and sintered at the above temperature.