JP2853308B2 - Manufacturing method of electrode material - Google Patents

Description

The present invention relates to a method for producing a homogeneous electrode material having a small variation in the distribution of low-melting-point metals, and particularly to a copper-chromium-based electrode material to which bismuth is added. It is preferable.

B. Summary of the Invention An alloy of copper and a low-melting metal and a copper lump are placed on a powder of a high-melting metal, and these are heated and held in a non-oxidizing atmosphere at a temperature equal to or higher than the melting point of copper. This is a method for producing an electrode material in which an alloy of a metal and the copper lump are infiltrated into voids of the high-melting metal, and the low-melting metal is alloyed with copper, thereby evaporating the low-melting metal. While suppressing this, copper and the low melting point metal are infiltrated into the void portion of the high melting point metal so that a homogeneous electrode material having desired performance can be manufactured.

C. Prior Art One of the important performances required as an electrode material of a vacuum interrupter is high current interruption performance.

In recent years, the use of copper-chromium-based materials, which have extremely excellent current interrupting performance, with bismuth added for the purpose of suppressing an increase in contact resistance after current processing, is used as electrode materials for vacuum interrupters. Have been tried.

Conventionally, as a method of producing this bismuth-added copper-chromium-based electrode material, a method of simultaneously sintering a mixed powder of copper, chromium, and bismuth, and a method of producing chromium filled in a container are described. A copper lump is placed on a mixed powder with bismuth and heated in a non-oxidizing atmosphere to a temperature equal to or higher than the melting point of copper so that the copper lump infiltrates voids of chromium and bismuth, or There is known a material in which bismuth is infiltrated into voids of a porous infiltration base material made of sintered copper and chromium.

The composition of the copper-chromium-based electrode material to which bismuth is added is generally in the range of 20 to 98% by weight of copper, 2 to 80% by weight of chromium, and 0.1 to 1.5% by weight of bismuth. Has been adjusted.

D. Problems to be Solved by the Invention Among the conventional production methods for a copper-chromium-based metal material to which bismuth is added, a method in which a mixed powder of copper, chromium and bismuth is sintered at once, and chromium In the method of infiltrating a copper lump into the void portion of bismuth and bismuth, since the vapor pressure of bismuth is high and the melting point is low, the evaporation amount of bismuth having a lower melting point than copper in the heating step of infiltrating the copper lump There is a possibility that the distribution of bismuth in the electrode material manufactured in one container will be extremely uneven and the homogeneity of the product will be impaired, and the ratio of bismuth in the electrode material as designed Difficult to keep.

In the method in which bismuth is infiltrated into the void portion of the sintered body of copper and chromium, although there is no such a problem as described above, in order to produce an electrode material containing a predetermined amount of bismuth, copper is required. It is extremely important to adjust the porosity of the sintered body of chromium and chromium. However, in the conventional method, it is very difficult to adjust the sintered body of copper and chromium to a desired porosity, and the porosity in one sintered body varies widely. And the distribution of bismuth may become non-uniform, thereby impairing the homogeneity of the product.

E. Means for Solving the Problems The method for producing an electrode material according to the present invention comprises the steps of: combining copper and a low-melting metal having a lower melting point than copper on a powder of a high-melting metal constituting a skeleton having a higher melting point than copper. The alloy and the copper lump are placed and heated and held in a non-oxidizing atmosphere at a temperature equal to or higher than the melting point of copper, and the alloy of copper and the low-melting metal and the copper lump are melted in the voids of the high-melting metal. It is characterized in that it is soaked.

In addition, chromium etc. can be mentioned as said high melting point metal. In addition, bismuth or the like can be used as the low melting point metal. Here, in the case where chromium is used as the high melting point metal and bismuth is used as the low melting point metal, if the copper content is less than 20% by weight, the conductivity decreases and the calorific value increases. If the content exceeds 98% by weight, the welding resistance is reduced and the current breaking value is increased. or,
If the chromium content is less than 2% by weight, the cutoff value of the current increases, and if the chromium content exceeds 80% by weight, the current interrupting performance decreases. On the other hand, when bismuth is less than 0.1% by weight, the effect of suppressing the contact resistance value after current interruption is diminished. Conversely, when bismuth exceeds 15% by weight,
It adversely affects the performance as a vacuum interrupter such as withstand voltage characteristics.

Therefore, in the case of using chromium as the high melting point metal and bismuth as the low melting point metal, copper ranges from 20 to 98% by weight, chromium ranges from 2 to 80% by weight, and bismuth ranges from 0.1 to 15% by weight. Respectively.

However, when attention is paid to withstand voltage characteristics and the like as a vacuum interrupter, it is particularly effective to contain bismuth at 1% by weight or less.

When the proportion of the low melting point metal in the alloy of copper and the low melting point metal is less than 0.1% by weight, the use amount of this alloy increases and the cost is increased. In this case, the low melting point metal is remarkably precipitated, and the amount of the low melting point metal in the obtained electrode material may vary. From the above viewpoints, it is desirable that the ratio of the low melting point metal in the alloy of copper and the low melting point metal is in the range of 0.1 to 20% by weight.

F. Action A part of the low-melting-point metal in the alloy of copper and the low-melting-point metal is dissolved in the copper crystal grains. The low melting point metal exceeding the solid solution limit is precipitated at the crystal grain boundary of copper, and the low melting point metal in the precipitated state naturally exists not only on the alloy surface but also inside the alloy.

When an alloy of copper and a low-melting metal in such a state is placed on a powder of a high-melting metal together with a copper lump and heated,
The low-melting-point metal evaporates from the alloy of copper and the low-melting-point metal only from the surface of the alloy of copper and the low-melting-point metal along the copper crystal grain boundaries. Until the copper melts, evaporation of the low melting point metal is suppressed.

Along with this heating operation, gas is released from the voids of the high melting point metal powder, and copper and the low melting point metal infiltrate into the voids of the high melting point metal. The low-melting-point metal lowers the mechanical strength of the electrode material itself, easily deforms the electrode material itself, and suppresses an increase in contact resistance after current interruption.

G. Example A vacuum interrupter is a second example showing a schematic structure thereof.
As shown in the drawing, electrodes 13 and 14 are integrally provided on opposing end surfaces of a pair of lead rods 11 and 12 which are linear with each other. The center of the outer periphery of the cylindrical shield 15 surrounding the electrodes 13 and 14 is held in a state of being sandwiched between a pair of insulating cylinders 16 and 17 surrounding the shield 15. One of the lead rods 11 is airtightly penetrated through a metal end plate 18 joined to one end of one of the insulating cylinders 16, and this metal end plate
It is integrally fixed to 18. The other lead rod 12 connected to a driving device (not shown) is connected via a bellows 20 to the other metal end plate 19 airtightly joined to the other end of the other insulating cylinder 17, and is associated with the operation of the driving device. The movable electrode 14 opens and closes with respect to the fixed electrode 13 so that the movable electrode 14 can reciprocate in the direction opposite to the electrodes 13 and 14.

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

An example of a method for producing this electrode material according to the present invention will be described below with reference to FIG. 1. First, 170 g of chromium powder having a particle size of -100 mesh is placed in a container A made of alumina ceramic having an inner diameter of 68 mm, and 5 g While maintaining the temperature at 1200 ° C. while degassing in a vacuum furnace of × 10 ⁻⁵ Torr, chromium particles are mutually diffused and bonded to obtain a porous infiltration base material B.

On the other hand, copper is melted at 1100 ° C. in a 5 × 10 ⁻⁵ Torr vacuum melting furnace, a predetermined amount of bismuth is added to the copper melt, and these are stirred, and then cooled to contain 0.5% by weight of bismuth. Obtained copper-bismuth alloy.

Thereafter, 170 g of a copper-bismuth alloy C produced by the above-described method and 170 g of a copper lump D are placed on the infiltration base material B formed in the alumina ceramic container A. In this state, the container A is covered with a lid E made of alumina ceramics, and these are heated in a vacuum furnace for 1 hour at 1100 ° C. while being degassed. The copper-bismuth alloy C and the copper lump D are infiltrated, and the obtained electrode material is taken out of the container A and machined into a predetermined shape.

 Thus, an electrode material composed of Cu: 55.00% by weight, Cr: 44.75% by weight, Bi: 0.25% by weight was prepared.

This electrode material was incorporated into the vacuum interrupter shown in Fig. 2 and the current interruption operation at 30 KA was performed 20 times. As a result, the contact resistance value after the interruption operation was 1.8 times the reference value before the interruption operation. Rose only to the extent.

As a comparison, an electrode material not containing bismuth of Cu: 55% by weight and Cr: 45% by weight was prepared by the same infiltration method as the above-mentioned manufacturing method, and this was incorporated into a vacuum interrupter shown in FIG. The current interruption operation was performed 20 times. Based on the contact resistance before the breaking operation according to the above-described embodiment including bismuth of 0.25% by weight, the contact resistance before the breaking operation is 1.4 times with the electrode material in this comparative example, and the contact after the breaking operation is 1.4 times. The resistance reached 3.0 times.

Further, a total of 25 samples were prepared by the manufacturing method of the present embodiment described above, and the ratio of bismuth in the electrode material was examined. As a result, the average value of the bismuth ratio was 0.25% by weight and the standard deviation was 0.02%. It was also found that the variation in the bismuth ratio was very small.

In the above-described embodiment, the chromium powder was sintered in advance, and the copper-bismuth alloy and the copper lump were infiltrated into the infiltration base material obtained by the sintering. A copper-bismuth alloy and a copper lump are placed on the chromium powder, and the inside of the container is heated while being sealed with a lid so that the copper-bismuth alloy and the copper lump infiltrate into the voids of the chromium powder. The same result can be obtained.

H. Effects of the Invention According to the method for producing an electrode material of the present invention, an alloy of copper and a low melting point metal and a copper lump are placed on a high melting point metal constituting a skeleton, and these are heated to form a high melting point metal. Since the alloy of copper and the low melting point metal and the copper lump are infiltrated into the voids, the amount of evaporation of the low melting point metal can be suppressed as compared with the conventional method, and the low melting point metal in the electrode material can be suppressed. And the homogeneity of the product is improved, and the proportion of the low melting point metal in the electrode material can be maintained as designed.

As a result, it is possible to obtain an electrode material in which the characteristics such as the contact resistance value and the current interruption performance after the interruption of the current are entirely improved. In particular, since the contact resistance value is low and stable even after a large number of opening / closing operations, the operating device for opening / closing can be miniaturized and the cubicle can be miniaturized in combination with low heat generation.

In addition, since a copper lump is prepared in addition to the alloy of copper and the low-melting-point metal, the amount of the alloy of copper and the low-melting-point metal used is smaller than when only the alloy of copper and the low-melting-point metal is used. Can be reduced, and a reduction in manufacturing cost accompanying an improvement in productivity can be attempted.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a method for producing an electrode material according to the present invention, and FIG. 2 is a sectional view showing an example of a vacuum interrupter. In the reference numerals in the figure, A is a container, B is an infiltration base material, C is a copper-bismuth alloy, D is a copper lump, E is a lid, 11, 12 are lead rods, and 13, 14
Is an electrode.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-160325 (JP, A) JP-A-60-313442 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01H 33/66 H01H 1/02 H01H 11/04

Claims (3)

(57) [Claims] 1. An alloy of copper and a low melting point metal having a lower melting point than copper is placed on a powder of a high melting point metal constituting a skeleton having a higher melting point than copper, and these are oxidized. Producing an electrode material, wherein the material is heated and held at a temperature equal to or higher than the melting point of copper in an atmosphere, and an alloy of the copper and the low melting point metal and the copper lump are infiltrated into voids of the high melting point metal. Method. 2. The method according to claim 1, wherein the high melting point metal is chromium. 3. The method according to claim 1, wherein the low melting point metal is bismuth.