JPH04324220A - Manufacture of electrode material - Google Patents

Abstract

PURPOSE:To optionally adjust the mixing ratio of a high-melting-point metal with the distributional dispersion of a low-melting-point metal reduced by placing an alloy of copper and the low-melting-point metal on an infiltration base material, composed of the copper and the high-melting-point metal, to be infiltrated under a specific condition. CONSTITUTION:An alloy C of copper and a low-melting-point metal, such as bismuth having a melting point lower than that of the copper, is placed on an infiltration base material B composed by mixing copper powder and powder of a high-melting-point metal such as chromium having a melting point higher than that of the copper. The infiltration base material B and the alloy C are heated to the melting point or more of the alloy C in a non-oxidizing atmosphere to be kept, and the alloy C is infiltrated into the gap portions of the base material B. This restrains the evaporation of the low-melting-point metal and also reduces distributional dispersion in the gap portions, and on the other hand, enables the mixing ratio of the high-melting-point metal to be optionally changed by previously containing the copper into the high-melting-point metal.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing an electrode material that has little variation in the distribution of low-melting point metals and can arbitrarily change the proportion of high-melting point metals.
It is suitable for application to chromium-based electrode materials.

0002

2. Description of the Related Art One of the important properties required of electrode materials for vacuum interrupters is high current interrupting performance.

[0003] In recent years, copper-chromium materials, which have excellent current interrupting performance, have been added with low melting point metals such as bismuth in order to suppress the increase in contact resistance after current interrupting. Attempts have been made to use it as an electrode material for interrupters.

Conventionally, methods for manufacturing bismuth-added copper-chromium electrode materials include sintering a mixed powder of copper, chromium, and bismuth all at once;
A copper ingot is placed on a mixed powder of chromium and bismuth filled in a container, and heated above the melting point of copper in a non-oxidizing atmosphere, infiltrating the copper ingot into the voids of chromium and bismuth. An alloy of copper and bismuth is placed on top of chromium powder filled in a container or a container, and the alloy is heated to above its melting point in a non-oxidizing atmosphere to fill the voids in the chromium. Those in which copper and bismuth are infiltrated are known.

[0005] Generally, the composition of a copper-chromium based electrode material to which bismuth is added is copper in the range of 20 to 98% by weight, chromium in the range of 2 to 80% by weight, and bismuth in the range of 2 to 15% by weight. It has been adjusted to a range of %.

[0006]

[Problems to be Solved by the Invention] Among the conventional manufacturing methods for copper-chromium metal materials added with bismuth, a method in which a mixed powder of copper, chromium, and bismuth is sintered all at once, and chromium In the method of infiltrating copper ingots into the voids of bismuth, since bismuth has a high vapor pressure and a low melting point, the amount of evaporation of bismuth, which has a lower melting point than copper, is reduced during the heating process of infiltrating the copper ingots. There is a risk that the distribution of bismuth in the electrode material manufactured in one container may become extremely uneven, impairing the homogeneity of the product. Difficult to maintain.

[0007]Also, although the method of infiltrating an alloy of copper and bismuth into the voids of chromium does not have the above-mentioned problems, it is necessary to infiltrate the alloy of copper and bismuth into the voids of chromium. Moreover, the volume ratio of chromium must be kept to about 50% to ensure a void area, making it difficult to arbitrarily set the ratio of chromium in the electrode material.

[0008]

[Object of the invention] The present invention provides an electrode material that has less variation in the distribution of low-melting point metals and can arbitrarily adjust the mixing ratio of high-melting point metals, particularly a copper-chromium based electrode material to which bismuth is added. The purpose is to provide a method.

[0009]

[Means for Solving the Problems] The method for manufacturing an electrode material according to the present invention is to infuse copper onto an infiltrated base material made by mixing copper powder and powder of a high-melting point metal that has a higher melting point than the copper. An alloy with a low melting point metal that has a lower melting point than that of copper is placed, and these are heated and maintained above the melting point of the alloy in a non-oxidizing atmosphere, and the alloy is infiltrated into the voids of the infiltration base material. This feature is characterized in that it allows the user to

[0010] The high melting point metal may include chromium and the like. Moreover, bismuth etc. can be mentioned as said low melting point metal. Here, in a product that uses chromium as a high melting point metal and bismuth as a low melting point metal, if the copper content is less than 20% by weight, the electrical conductivity will decrease and the calorific value will increase; If it exceeds 98% by weight, the welding resistance will decrease and the current cutoff value will increase. Furthermore, if the chromium content is less than 2% by weight, the current interrupting value increases, whereas if the chromium content exceeds 80% by weight, the current interrupting performance decreases. On the other hand, if the bismuth content is less than 2% by weight, the effect of suppressing the contact resistance value after current interruption will be diminished, and if the bismuth content exceeds 15% by weight, the performance as a vacuum interrupter such as withstand voltage characteristics will be affected. have a negative impact on

Therefore, in the case where chromium is used as the high melting point metal and bismuth is used as the low melting point metal, copper is in the range of 20 to 98% by weight, chromium is in the range of 2 to 80% by weight, and bismuth is in the range of 2 to 80% by weight. It is desirable that each content is in the range of 15% by weight.

However, as shown in FIG. 2, which shows the relationship between the proportion of bismuth in the electrode material and the cutting current value, when the proportion of bismuth is 2% by weight, the cutting current value is 2A.
(Ampere) or less, but even in the case of 6% by weight, the breaking current value can be secured to be 1A or less, so the proportion of bismuth may be set to 6% by weight or more, and conversely, if it exceeds 12% by weight, However, there is a risk that the low melting point metal will significantly precipitate, causing variations in the amount of the low melting point metal in the resulting electrode material, and it will not be very effective in reducing the cutting current value. From the above viewpoint, it is particularly effective to keep the proportion of bismuth in the alloy of copper and bismuth within the range of 6 to 12% by weight.

[0013]

[Operation] A part of the low melting point metal in the alloy of copper and the low melting point metal is solidly dissolved in the copper crystal grains. A low melting point metal that exceeds the solid solution limit precipitates at the grain boundaries of copper, but naturally this precipitated low melting point metal exists not only on the alloy surface but also inside the alloy.

When copper and low melting point metal in such a state are placed on a mixed powder of copper and high melting point metal and heated, the low melting point metal evaporates from the alloy of copper and low melting point metal. This occurs only from the surface of the alloy of copper and low-melting point metal along the grain boundaries of copper, and evaporation of the low-melting point metal is suppressed until the copper in the alloy of copper and low-melting point metal melts. The state will be as follows.

With this heating operation, gas is released from the voids of the mixed powder of copper and high melting point metal, and the alloy of copper and low melting point metal infiltrates into the voids of the copper and high melting point metal. The low melting point metal lowers the mechanical strength of the electrode material itself, making the electrode material itself easily deformable and suppressing an increase in contact resistance after current interruption.

[0016]

[Embodiment] A vacuum interrupter is as shown in FIG. 3, which shows an example of its schematic structure.A pair of lead rods 11 and 12 that are in a straight line are provided with electrodes 13 and 14 on opposite end surfaces, respectively. are provided integrally. These electrodes 1
A central portion of the outer periphery of a cylindrical shield 15 surrounding the shields 3 and 14 is held between a pair of insulating cylinders 16 and 17 surrounding the shield 15. One of the lead rods 11
is integrally fixed to the metal end plate 18 joined to one end of one of the insulating tubes 16 in a state where it hermetically penetrates 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 that the electrodes 13 and 14 can reciprocate in opposing directions.

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

An example of the method for manufacturing this electrode material according to the present invention will be described below based on FIG.
A chromium powder with a particle size of 50 mesh accounts for 80% of the total, and a copper powder with a particle size of -325 mesh accounts for 80% of the total. These are uniformly stirred and mixed so that the powder content is 75% by weight.

Then, 130 g of this mixed powder was placed in a container A made of alumina ceramics with an inner diameter of 70 mm, and it was heated for 11 hours while degassing in a vacuum furnace at 5 x 10-4 Torr.
The mixture is heated and maintained at 30° C. for 1 hour to diffusely bond the chromium particles and copper particles to each other to obtain a porous infiltrated base material B.

On the other hand, copper was melted at 1100°C in a vacuum melting furnace at 5 x 10-5 Torr, a predetermined amount of bismuth was added to the molten copper, and the mixture was stirred and then cooled until the amount of bismuth was 18% by weight. % copper bismuth alloy is obtained.

Thereafter, 120 g of copper-bismuth alloy C made by the method described above is placed on the infiltration base material B formed in the alumina ceramic container A, and in this state, the container A is Covered with a lid D made of alumina ceramics, these were heated to 1130°C for 30 minutes while degassing in a 5 x 10-4 Torr vacuum furnace, and copper-bismuth was added to the voids of the porous infiltration base material B. Alloy C is infiltrated, and the resulting electrode material is taken out of container A and machined into a predetermined size and shape.

[0022] In this way, Cu: 71.43% by weight Cr: 19.92% by weight Bi: 8.65% by weight An electrode material consisting of

This electrode material was assembled into the vacuum interrupter shown in FIG. 3, and the cutting current value was measured, and it was confirmed that the current value was 1A or less.

In the above-mentioned embodiment, the mixed powder of copper and chromium was sintered in advance, and the resulting infiltration base material was infiltrated with the copper-bismuth alloy. A copper-bismuth alloy is placed on top of the mixed powder of copper and chromium, and the inside of the container is heated while being sealed with a lid to infiltrate the copper-bismuth alloy into the voids of the copper and chromium powder. However, similar results can be obtained.

[0025]

[Effects of the Invention] According to the method for manufacturing an electrode material of the present invention,
An alloy of copper and a low melting point metal is placed on a mixture of copper and a high melting point metal, and these are heated to melt the alloy of copper and a low melting point metal into the voids between the copper and the high melting point metal. By immersing the material in the electrode material, it is possible to suppress the amount of evaporation of the low melting point metal compared to conventional methods, and the distribution of the low melting point metal in the electrode material becomes uniform, improving the homogeneity of the product. It is possible to maintain the proportion of low melting point metal in the design.

Furthermore, by mixing copper with the high melting point metal in advance, even if the proportion of the high melting point metal in the electrode material is set higher than in the conventional case, the copper and low melting point metal will not be present in these voids. It becomes possible to reliably infiltrate the alloy of
The proportion of the high melting point metal in the electrode material can be set arbitrarily.

As a result, it is possible to obtain an electrode material whose properties such as contact resistance after current interruption and current interruption performance are generally improved. In particular, since the contact resistance value is low and stable even after many times of opening and closing operations, it is possible to downsize the operating device for opening and closing, and together with the fact that less heat is generated, the cubicle can be downsized.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the method for manufacturing an electrode material according to the present invention.

FIG. 2 is a graph showing the relationship between the proportion of bismuth in the electrode material and its cutting current value.

FIG. 3 is a sectional view showing an example of a vacuum interrupter.

[Explanation of symbols]

A is a container, B is an infiltration base material, C is a copper-bismuth alloy, D is a lid, 11 and 12 are lead rods, and 13 and 14 are electrodes.

Claims (3)

[Claims] Claim 1: An alloy of copper and a low melting point metal having a lower melting point than the copper is deposited on an infiltration base material made by mixing copper powder and a powder of a high melting point metal having a higher melting point than the copper. A method for manufacturing an electrode material, characterized in that the alloy is placed in a non-oxidizing atmosphere and heated to a temperature higher than the melting point of the alloy, and the alloy is infiltrated into the voids of the infiltration base material. . 2. The method for producing an electrode material according to claim 1, wherein the high melting point metal is chromium. 3. The method for producing an electrode material according to claim 1, wherein the low melting point metal is bismuth.