JPS63183105A - Production of electrode material - Google Patents

Abstract

PURPOSE:To improve the formability of a temporarily infiltrated base material and to obtain an electrode material having improved electrical conductivity by mixing metal powder with powder of the same metal as the metal of an infiltrating material, press-forming the powdery mixture and infiltrating the infiltrating material into the formed bodies. CONSTITUTION:Powder of a metal such as Mo or Cr is mixed with 1-30 wt.% powder of the same metal as the metal of an infiltrating material, e.g., electrolytic copper. The powdery mixture is filled into dies and press-formed. The press-formed bodies 12 are arranged in a vessel 11 and the infiltrating material is put on the bodies 12. Formed discoid copper blocks 13 may be used as the infiltrating material. After a lid 14 is fitted, the vessel 11 is put in a vacuum furnace and held at about 1000 deg.C for about 60 min to bond the Mo or Cr particles to the copper particles by diffusion as well as to carry out degassing. The resulting porous base material to be infiltrated is then held at a temp. between the m.p. of copper and the m.p. of Mo or Cr to melt and infiltrate the copper blocks 13 into the base material. Thus, an electrode material is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing an electrode material made of an infiltrated composite metal, which is used, for example, as an electrode for a vacuum interrupter.

B. Summary of the invention By mixing metal powder of the same material as the infiltration material and metal powder forming the infiltration base, the formability of the temporary infiltration base is improved, and the electrical conductivity is improved and stabilized. The aim is to

C2 Conventional technology JP-A-59-274 as electrode material for vacuum interrupter
Mo-Cr-C11 composite metal, which is an infiltration type composite metal material disclosed in Publication No. In addition to having good properties, it is also known to have excellent electrical properties such as current interrupting ability and dielectric strength.

FIG. 3 shows an example of a conventional manufacturing method for manufacturing the Mo-Cr-Cu composite metal.

In Fig. 3, a mixed powder 2 of molybdenum and chromium, which has a higher melting point than copper, is filled in a container 1 made of alumina ceramics, which does not react with copper and is stable even at high temperatures. A ceramic lid 4 is placed on the lid 4 and these are heated in a non-oxidizing atmosphere at a temperature below the melting point of copper to first form a porous sintered body of molybdenum and chromium inside the container 1, and then degassed. While heating these in a non-oxidizing atmosphere at a temperature above the melting point of copper and below the melting points of molybdenum and chromium, the copper ingot 3 is infiltrated into the porous sintered body to form the Mo-Or-Cu composite metal. was manufacturing.

These heat treatments in a non-oxidizing atmosphere are typically performed in a vacuum furnace.

D. Problems to be Solved by the Invention If the rate of temperature rise or fall is accelerated during heat treatment in a vacuum furnace, the alumina ceramic container may break due to thermal stress. If cracks or the like occur in the container in this way, the mixed powder of molybdenum and chromium will spill out of the container and copper will flow out, resulting in a high possibility that the inside of the vacuum furnace will be contaminated by these.

Further, since the Mo-Cr-Cu composite metal ingot is in close contact with the entire inner wall of the container, it is often difficult to remove the ingot from the container, resulting in damage to the container.

Furthermore, if the copper remaining without being infiltrated during the infiltration work is bonded to the container, especially if the copper is bonded to the inner peripheral surface of the container, Mo-C
It is almost difficult to take out the r-Cu composite metal ingot from the container, and even if it is possible to take it out, chips are often formed on the inner peripheral surface of the container.

Mo recommends that containers with such chips be used again.
Since a portion of the -Cr-Cu composite metal ingot fills the chipped portion of the container, it becomes impossible to take out the ingot unless the container is destroyed.

In any case, the conventional method is a very simple method in that it forms an infiltration type electrode material in a container, but when looking at it including removal from the container and damage to the container, etc. However, productivity could not necessarily be said to be good.

Means for Solving Problem E1 In order to improve the performance as an electrode and improve productivity, the present inventors added metal powder when obtaining a porous sintered body to be used as an infiltration base material. An attempt was made to form a temporary molded body of the infiltration base material by pressure molding, and then sinter this to infiltrate with the infiltrant. In addition, since the electrodes of the vacuum interrupter are used in a vacuum, the following points were taken into consideration.

(1) Forming a temporary molded body by pressurizing only metal powder without using any binder that may contaminate the inside of the vacuum furnace and vacuum interrupter.

(2) Since the temporary formed body is sintered and becomes porous before being infiltrated with an infiltrant material such as copper alloy or copper alloy, it has a predetermined void inside which the infiltrant material can infiltrate; Pressure molding should be performed at the lowest possible pressure to ensure the specified conductivity.

(3) However, in consideration of the work of taking out the temporary molded body from the mold of the molding machine and placing the infiltration material, the temporary formed body after molding must be pressure-formed to a strength that can be handled by hand. To be there.

(4) No cracks will occur in the temporarily formed body after pressurization.

The experimental conditions were as follows: Molybdenum powder and chromium powder each having a particle size of -100 mesh (149 μm or less) were mixed mechanically at a weight ratio of Mo=Or=3:1, and a gold powder with an inner diameter of 60 mm was mixed mechanically. Pour about 100g into the mold and 1
The pressure was maintained for minutes to obtain a temporary molded body with a diameter of 6 (1 m) and a thickness of about 10 mm.

As a result, it was found that a pressure of less than 400 kg/c11 causes deformation during hand-held work, and that a pressure of 500 kg/d or more is required.

Therefore, based on the above results, we decided to
After placing the copper ingot on the temporary molded body pressurized with a pressure of 100 kg/c11 and sintering the temporary formed body in a vacuum furnace,
The surface of the electrode material obtained by infiltrating the copper ingot into the infiltration base material was cut, and its conductivity was measured. The measurement points were a total of 5 points, including the center and peripheral areas of the disk surface, and the conductivity (IAC3
%), and it was found that the conductivity at the center tended to be lower than at the periphery.

In this way, if electrodes are made of a material that tends to have low conductivity in the center and high conductivity in the periphery, arcs are likely to occur in the periphery where the conductivity is high when interrupting current, which may affect current interrupting performance. This is one of the causes of negative effects. In other words, if the arc is localized to the outer periphery of the electrode, the electrode area will not be used effectively when the current is cut off, causing local heating of the electrode and roughening the electrode surface, causing re-ignition. be.

In addition, in a vacuum interrupter that applies a vertical magnetic field, the magnetic field effect weakens especially immediately after firing, resulting in a decrease in current interrupting performance.

The present inventors discovered that because the temporary molded body of metal powder is formed by applying sudden pressure, the metal powder in the center of the mold is crushed and densified, which causes melting. It was surmised that copper was difficult to infiltrate into the center of the immersed base material.

Therefore, if a predetermined amount of metal powder of the same material as the infiltration material is mixed into the metal powder forming the temporary compact, the infiltration material such as copper can be mixed with other infiltration base materials such as molybdenum and chromium. Since it is softer than metal, it can act as a lubricant and cushioning material during pressure molding, and will improve the ability of molybdenum powder and chromium powder to come into contact with each other and be crushed, contributing to improving the conductivity distribution. Experiments were conducted using dendrite-like electrolytic copper powder without changing other experimental conditions.

The results of this experiment are shown in Table 1.

Table 1 As is clear from Table 1, it is not possible to improve the electrical conductivity when the amount of copper powder mixed into the mixed powder of molybdenum and chromium is about 0.5% by weight, and when it is more than 30% by weight, it is difficult to improve the conductivity. It was found that the strength was not improved (40 kg/cd or less) because the bonding with the four members was not sufficient.

Therefore, the amount of copper powder to be mixed is 1 to 30% by weight based on the mixed powder of molybdenum and chromium to form a temporary compact, and the rope is infiltrated into the compact.In this case, the tensile strength is 45 to 50 kg/aIl, JP-A-59-2
Compared to the method disclosed in Japanese Patent No. 7418, similar results were obtained up to a stiffening pressure of 5000 kg/cj.

The present invention has been made based on the above results, and includes mixing at least one type of metal powder with a melting point higher than that of the infiltrant and a metal powder of the same material as the infiltrant, and also a metal powder having the same material as the infiltrant. The material metal powder is set in a range of 1% to 30% by weight relative to the other metal powders, this mixed powder is pressure-molded into a predetermined shape to form a temporary compact, and this temporary compact is After forming the infiltration base material by sintering the temporary formed body while heating at a temperature below the melting point of the infiltration material and degassing in a non-oxidizing atmosphere, the infiltration base material is The infiltrant material placed on the infiltration base material is heated and maintained at a temperature equal to or higher than the melting point of the infiltration material in a non-oxidizing atmosphere to infiltrate the infiltration material into the infiltration base material. It is characterized by the following.

As the metal powder, it is sufficient to use a metal having a melting point higher than that of copper, which is an infiltration material, such as any combination of molybdenum, chromium, tungsten, iron p-cobalt, niobium, and stainless steel. Similar results can be obtained up to a maximum of 160 meshes.

F Function Metal powder of the same material as the infiltrant is mixed into the metal powder constituting the temporary compact, and this is pressure-molded to form the temporary compact. Since the powder is softer than other metal powders that have a higher melting point than the infiltrant, the center part of the mixed powder filled in the mold acts as a lubricant and M impact during pressure molding. In particular, the occurrence of densification is reduced, and since it is made of the same material as the infiltration material, the electrical conductivity of this central portion is improved.

Example G First, -100 mesh molybdenum, chromium, and electrolytic copper powders were prepared, and the weight ratio was Mo: Cr = 3.
= 1, prepare 100 g and further 5 g of copper, and mix them mechanically.

Then, prepare a mold with a shape larger than the desired electrode shape (inner diameter 60 nm), attach this mold to a pressure molding machine, fill the above-mentioned mixed powder into the mold, and then press The molding machine is operated to produce 1100 kg/al of these mixed powders.
Compression molding is carried out by about 1 degree with a pressure of 1 liter.

As shown in FIG. 1, one or more of the temporary molded bodies obtained in this way are placed spaced apart from each other in a container 11 made of alumina ceramics, etc. The formed copper ingot 13 is placed thereon, a lid 14 made of the same material as the container 11 is placed on the container 11, and the container 11 is inserted into a vacuum furnace. and 5X1.333 mPa (5X10 mH
g) A temperature of about 1000°C (below the melting point of steel) is maintained in a vacuum of about 60 minutes to degas the temporary formed body 12 and diffuse bond the molybdenum particles, chromium particles, and copper particles. Obtain a porous infiltration matrix.

After that, the copper ingot 13 is kept at a temperature of about 30 degrees above the melting point of copper and below the melting point of the metal powder (about 1100°C).
Infiltrate into the voids of the infiltrated base material. Note that the amount of copper ingot 13 is necessary to match the pore volume of the infiltrated base material,
If there is too much, there is a risk that it will spread over the entire bottom surface of the container 11.

These infiltration operations, degassing treatments, and sintering operations may be performed in a non-oxidizing atmosphere such as hydrogen gas, argon gas, or nitrogen gas other than a vacuum atmosphere.

When the surface of the electrode material obtained in this way was cut and the electrical conductivity was examined, the central part was 63% (IAC5) and the peripheral part was up to 61%.
We were able to confirm the experimental results mentioned above.

Further, this electrode material was processed into an electrode with an outer diameter of 50 mm and a thickness of 4 mm, and as a result of testing by incorporating it into a vacuum incluctor, a current interrupting performance similar to that of the conventional electrode was obtained. In particular, the withstand voltage characteristics are improved by approximately 10%, and the contact resistance value is increased by 10%.
A result of ~15% reduction was obtained.

Effects of the Invention According to the method for manufacturing an electrode material of the present invention, metal powder of the same material as the infiltration material is mixed into the metal powder forming the temporary compact, and the temporary compact is press-molded. The metal powder made of the same material as the infiltration material acts as a lubricant and a buffer material for other metal powders during pressure forming of the temporary compact, which improves the uniform conductivity distribution and improves the distribution of conductivity between the periphery of the electrode and It would be possible to reduce the difference in conductivity between the center and the center.

Moreover, since the strength has been improved, the voltage characteristics of '#4 can be improved overall.For example, when used as an electrode material for a vacuum interrupter for switching capacitors, there is less roughness on the contact surface due to the input current when the current is applied, and the re-ignition The probability can be significantly reduced. This makes it possible to reduce the distance between the electrodes and reduce the opening/closing speed of the electrodes, thereby making it possible to reduce the size of the vacuum interrupter and its operating device itself.

In addition, it is possible to handle the mixed powder by solidifying it, and this mixed powder can be formed into any shape.
It is possible to minimize the machining allowance for the electrode shape after infiltration, and it is possible to improve productivity by 1.5 to 2 times compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an infiltration operation according to an embodiment of the manufacturing method according to the present invention, and FIG. 2 is a conceptual diagram of an operation of an example of a conventional manufacturing method. Also, in the figures, 11 is a container, 12 is a temporary infiltration matrix, and 13 is a container.
is a copper ingot, and 14 is a lid.

Claims (2)

[Claims] (1) At least one type of metal powder having a higher melting point than the infiltrant and a metal powder of the same material as the infiltrant are mixed, and the metal powder of the same material as the infiltrant is mixed with the other metal powder. This mixed powder is pressure-molded into a predetermined shape to form a temporary compact, and this temporary compact is heated at a temperature below the melting point of the infiltrant. After sintering the temporary compact while degassing in a non-oxidizing atmosphere to form the infiltrated base material, the infiltrated base material is placed on the infiltrated base material. A method for manufacturing an electrode material, characterized in that the infiltrating material is infiltrated into the infiltrating base material by heating and holding the infiltrating material together with the material in a non-oxidizing atmosphere at a temperature equal to or higher than the melting point of the infiltrating material. (2) The method for manufacturing an electrode material according to claim 1, wherein the metal powder made of the same material as the infiltrant to be mixed with the metal powder is in a dendrite shape.