JP3106610B2 - Manufacturing method of electrode material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrode material using fine metal powder as a raw material by an atomizing method in which a metal having a lower melting point than copper is added to a copper-chromium alloy, and more particularly to an electrode for a vacuum interrupter. It is suitable for use.

[0002]

2. Description of the Related Art One of the important performances required as an electrode material of a vacuum interrupter is a high current breaking performance.

[0003] A copper (Cu) -chromium (Cr) alloy is known as an electrode material having a very excellent current breaking performance. Conventionally, a copper powder produced by an electrolytic method or the like and a pulverization method or the like are used. A method of powder metallurgy in which a mixture of chromium powder produced by the above method and a mixture thereof is compression-pressed and sintered at a high temperature is generally used.

In this copper-chromium alloy, chromium is dispersed in a copper matrix. When attention is paid to the electrical characteristics as an electrode material, fine chromium is uniformly dispersed in the copper matrix. Is more preferred.

However, in the case of a conventional copper-chromium alloy produced by powder metallurgy, the width of the particle size distribution of chromium powder obtained by mechanical pulverization by a pulverization method is very large, and the average particle diameter is large. Since it reaches about 40 μm, there is a drawback that when mixing the copper powder and the chromium powder, uniform mixing is difficult due to the difference in specific gravity, the particle size of the powder, or the difference in particle size distribution. As a result, chromium in the copper matrix after sintering was not finely and uniformly dispersed, and the electrical characteristics were not as good as expected.

Therefore, it is conceivable to further mechanically pulverize the chromium powder to reduce its particle size. In this case, the surface of the chromium powder is oxidized during the pulverization process and during storage, and contains oxygen. There is also a problem that the sinterability is reduced as the amount increases. It is also conceivable to classify the chromium powder obtained by the pulverization method by sieving and use only the chromium powder having a fine diameter. However, in this method, the yield is extremely deteriorated and the production cost is increased.

For these reasons, the present inventors have manufactured a fine powder of a copper-chromium alloy by an atomizing method without using a mechanical pulverization method of chromium, which is difficult to make fine and has a problem of surface oxidation. , A method for producing an electrode material by sintering the same, by obtaining copper-chromium in which chromium having a fine particle diameter is uniformly dispersed in a copper matrix, can obtain copper-chromium by a conventional sintering metallurgy method or the like. It has become possible to provide an electrode material having a significantly improved breaking current value as compared with a chromium alloy.

[0008]

Even when a copper-chromium alloy whose current breaking performance can be improved by using a raw material obtained by the atomizing method and manufacturing it by a sintering method, other electrodes can be used. Compared with the material, it cannot be said that it is still sufficient in terms of contact resistance value and welding resistance.

Therefore, a powder of a low melting point metal such as bismuth (Bi), which can lower the contact resistance and improve the welding resistance, is mixed with the fine powder of the copper-chromium alloy produced by the atomizing method. By heating and sintering, an attempt was made to obtain an electrode material having a large breaking current value, a low contact resistance value, and an excellent welding resistance.

However, according to this method, the low melting point metal evaporates and scatters during the heating step during sintering. When mixing the fine powder of the copper-chromium alloy and the powder of the low melting point metal by the atomization method, the low melting point metal is used. It is necessary to set these ratios in anticipation of scattering of the melting point metal. In addition, since the mixing ratio of the low melting point metal to the fine powder of the copper-chromium alloy is several percent or less, it is very difficult to mix them uniformly without variation, and the manufacturing process becomes complicated. Further, it has been found that the reproducibility of the ratio of the low melting point metal in the electrode material obtained by this method is poor, and it is difficult to keep the quality constant.

[0011]

An object of the present invention is to provide a method for easily and reproducibly producing an electrode material having a low contact resistance value and a good welding resistance by adding a low melting point metal to a copper-chromium alloy. The purpose is to:

[0012]

Means for Solving the Problems The present inventors made an alloy material fine powder of copper and chromium by an atomizing method, and then heated and sintered in a non-oxidizing atmosphere to produce an electrode material. Focusing on the feasibility, manufacturing of electrode materials by atomizing copper, chromium, and a metal with a lower melting point than copper by alloying and heating and sintering this in a non-oxidizing atmosphere. It was investigated whether or not it was possible.

[0013] Therefore, the refractory copper ingot is charged.
Put the crucible in argon (Ar) gas or nitrogen (N _Two) Gas or vacuum
Heated to 1200 ° C in a non-oxidizing atmosphere of
To dissolve the copper in the refractory crucible. Next, a very small
Rick chrome is poured into this refractory crucible and
Is heated to 1700 ° C. in a non-oxidizing atmosphere. This
After completely dissolving the chromium,
Put into the refractory crucible, copper-chromium-bismuth alloy
Of molten metal was obtained.

The molten metal is rapidly cooled and solidified by a gas atomizing method using argon gas at a pressure of 5 to 8 MPa (megapascals) to form a fine powder, and a fine powder of a copper-chromium-bismuth alloy in which chromium is dispersed in a copper matrix. A powder was obtained.

In carrying out the above method, the weight ratio of copper, chromium and bismuth before melting was set to 80: 20: 1. If the proportion of chromium is more than 20% by weight, copper dispersed in a chromium matrix is formed, and a target copper-chromium-bismuth alloy powder cannot be obtained. Is less than 5% by weight, it is hardly expected to improve current breaking performance due to the addition of chromium.

When copper, chromium and bismuth are melted, copper, chromium and bismuth having a low oxygen content are selected in order to reduce the oxygen content of the molten metal. To reduce the oxygen content to 1000 ppm or less. In this case, unavoidable impurities such as iron (F
e) and the presence of nickel (Ni) were allowed.

The particle size of the copper-chromium-bismuth alloy fine powder thus obtained was found to be 150 μm or less, and it was found by chemical analysis that the proportion of bismuth was 0.5% by weight. In addition, as a result of observing the copper-chromium-bismuth alloy fine powder with an electron microscope, it was confirmed that chromium particles of 5 μm or less were uniformly dispersed in the copper matrix.

Next, this copper-chromium-bismuth alloy fine powder was filled in a mold having a diameter of 50 mm, and pressed into a disk with a pressing force of 3.5 ton / cm ² , and this was pressed into a mold. × 10 ^-5 To
It was heated to 1080 ° C. for 30 minutes in a vacuum of rr to obtain a disc-shaped sintered body. Table 1 shows the results of measuring the content of bismuth contained in this sintered body for each of the 10 samples as the method of the present invention.

As a comparison, a copper-chromium alloy fine powder obtained by the same method as the above-mentioned atomizing method and a bismuth powder in a ratio of 0.5% by weight with respect to the copper-chromium alloy fine powder were mixed. This was filled into a mold having a diameter of 50 mm, and pressed into a disk with a pressing force of 3.5 ton / cm ² , and then pressed in a vacuum of 5 × 10 ⁻⁵ Torr for 30 minutes.
Table 1 shows the results obtained by measuring the content of bismuth contained in the sintered body of each of the 10 samples in the case of heating and sintering at 80 ° C (hereinafter, this manufacturing method is referred to as a powder addition method) for each of the 10 samples. Show.

Further, a copper powder, a chromium powder and a bismuth powder in a ratio of 0.5% by weight thereof are mixed, and the resulting mixed powder of copper, chromium and bismuth has a diameter of 50 mm. 3.5 tons / cm ²
After being press-formed into a disk with a pressing force of
^In the case of sintering at 1080 ° C. for 30 minutes in a vacuum of ^-5 Torr (hereinafter, this manufacturing method is referred to as a conventional method), the content of bismuth contained in the sintered body was set to 10 for each of the samples Table 1 also shows the measurement results.

[0021]

[Table 1]

As is evident from the above results, it was found that the method of the present invention was less likely to scatter bismuth than the powder addition method and the conventional method, and the variation in the bismuth ratio was smaller.

The method for producing an electrode material according to the present invention is based on the above considerations. Copper, chromium, and a metal having a lower melting point than copper are alloyed into fine powder by an atomizing method. Is heated and sintered in a non-oxidizing atmosphere.

Here, a metal having a lower melting point than copper and capable of lowering the contact resistance value of the electrode material and improving the welding resistance (hereinafter, referred to as a metal).
This is referred to as a low melting point metal). In addition to the aforementioned bismuth, antimony (Sb), tellurium (Te), selenium (Se), lead
It is possible to employ one or more of (Pb)
The ratio of these low melting metals to copper and chromium is 0.1.
It is desirable to be within the range of 02 to 3.0% by weight.

The ratio of the low melting point metal is 0.02.
%, It is almost impossible to expect a decrease in contact resistance and an improvement in welding resistance due to the addition of these low-melting metals. Also, when the amount of the low-melting-point metal exceeds 3.0% by weight, the current breaking performance is rapidly deteriorated.

[0026]

The alloy fine powder of copper-chromium-low-melting-point metal obtained by the atomizing method has chromium having a fine particle diameter uniformly dispersed in a copper matrix. By pressing this into a predetermined shape and heating it, the metal crystal particles are densely sintered and integrated without coarsening in a state where evaporation of the low melting point metal is suppressed.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A vacuum interrupter is shown in FIG. 1 which shows an example of a schematic structure of the vacuum interrupter. Electrodes 13 and 14 are respectively provided on opposing end surfaces of a pair of lead rods 11 and 12 which form a straight line. It is provided integrally via a brazing material (not shown). A central portion of the outer periphery of a cylindrical shield 15 surrounding the electrodes 13 and 14 is held in a state sandwiched between a pair of insulating cylinders 16 and 17 surrounding the shield 15.

The one lead rod 11 is integrally fixed to the metal end plate 18 in a state where it penetrates the metal end plate 18 joined to one end of the one insulating cylinder 16 in an airtight manner.
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 hermetically joined to the other end of the other insulating cylinder 17 so as to be able to reciprocate in a direction facing the electrodes 13 and 14 with the operation of the driving device. The movable electrode 14 opens and closes with respect to the fixed electrode 13.

The electrodes 13 and 14 in this embodiment are:
It is composed of a copper-chromium-lead alloy obtained by sintering a raw material by an atomizing method.

An example of a method of manufacturing the electrodes 13 and 14 according to the present invention will be described below. A refractory crucible into which a copper ingot has been charged is heated to 1200 ° C. in a non-oxidizing atmosphere such as a vacuum, thereby producing a refractory crucible. The copper in the crucible was dissolved.
Next, very small brick-like chromium is charged into the refractory crucible, and these are placed in a non-oxidizing atmosphere such as vacuum for 17 hours.
Heat to 00 ° C. After the chromium was completely dissolved in this way, 0.7% by weight of lead was further charged into the refractory crucible to obtain a molten copper-chromium-lead alloy.

Then, the molten metal is rapidly cooled and solidified by a gas atomizing method using argon gas at a pressure of 5 to 8 MPa to obtain fine powder of a copper-chromium-lead alloy in which chromium is dispersed in a copper matrix. I made it.

The particle diameter of the copper-chromium-lead alloy fine powder thus obtained was found to be 150 μm or less, and it was found by chemical analysis that the proportion of lead was 0.5% by weight.
In addition, as a result of observing the copper-chromium-lead alloy fine powder with an electron microscope, it was confirmed that chromium particles of 5 μm or less were uniformly dispersed in the copper matrix.

Next, this copper-chromium-lead alloy fine powder was filled in a mold having a diameter of 50 mm, and pressed into a disk with a pressing force of 3.5 ton / cm ² , and this was pressed into a disk. It was heated to 1080 ° C. for 30 minutes in a vacuum of × 10 ⁻⁵ Torr to obtain a disc-shaped sintered body. Table 2 shows the results of measuring the content of lead contained in this sintered body for each of the 10 samples as the method of the present invention.

As a comparison, a copper-chromium alloy fine powder obtained by the atomizing method and a lead powder having a ratio of 0.5% by weight with respect to the copper-chromium alloy fine powder were mixed, and the powder addition method described above was used. As a result, a sintered body of a copper-chromium-lead alloy was obtained, and the results of measurement of the content of lead contained in the sintered body for 10 samples are also shown in Table 2.

Further, copper powder, chromium powder and 0.5% by weight of lead powder are mixed with each other, and the resulting mixed powder of copper, chromium and lead is mixed with the above-mentioned conventional method. As a result, a sintered body of a copper-chromium-lead alloy was obtained, and the results of measurement of the content of lead contained in the sintered body for 10 samples are also shown in Table 2.

[0036]

[Table 2]

As is clear from the above results, in the present embodiment employing lead as the low melting point metal, the amount of scattered lead is much smaller than in the case of the powder addition method and the conventional method, and the lead ratio is not uniform. It turned out to be less.

In the above-described embodiment, lead was used as the low-melting metal. However, another example of the method of manufacturing the electrodes 13 and 14 according to the present invention using tellurium as the low-melting metal will be described below. A melt of a copper-chromium-tellurium alloy is obtained in exactly the same manner as described above, and this melt is rapidly solidified by a gas atomizing method using argon gas at a pressure of 5 to 8 MPa to fine powder, and chromium is dispersed in a copper matrix. Thus, a fine powder of a copper-chromium-tellurium alloy was obtained.

The copper-chromium-tellurium alloy fine powder thus obtained had a particle size of 150 μm or less, and the chemical analysis revealed that the proportion of tellurium was 0.5% by weight. Further, as a result of observing the copper-chromium-tellurium alloy fine powder with an electron microscope, it was confirmed that chromium particles of 5 μm or less were uniformly dispersed in the copper matrix.

Next, this copper-chromium-tellurium alloy fine powder was filled in a mold having a diameter of 50 mm, and pressed into a disk with a pressing force of 3.5 ton / cm ^2. × 10 ^-5 Torr
Was heated at 1080 ° C. for 30 minutes in a vacuum of to obtain a disc-shaped sintered body. Table 3 shows the results of measuring the tellurium content of the sintered body for each of the 10 samples as the method of the present invention.

For comparison, a copper-chromium alloy fine powder obtained by the atomizing method and a tellurium powder having a ratio of 0.5% by weight with respect to the copper-chromium alloy fine powder were mixed.
A sintered body of a copper-chromium-tellurium alloy was obtained by the powder addition method described above, and the content of tellurium contained in the sintered body was reduced to 10%.
Table 3 also shows the results of the measurements for each sample.

Further, copper powder, chromium powder and tellurium powder in a ratio of 0.5% by weight thereof were mixed,
The mixed powder of copper, chromium, and tellurium thus obtained was obtained as a sintered body of a copper-chromium-tellurium alloy by the above-described conventional method, and the content of tellurium contained in the sintered body was measured for each of 10 samples. The results are shown in Table 3.

[0043]

[Table 3]

As is clear from the above results, even when tellurium is used as the low melting point metal, the method of the present invention has a much smaller amount of tellurium scattered than the powder addition method and the conventional method, and has a variation in tellurium ratio. Turned out to be less.

Next, each of the above-mentioned samples was machined as a spiral electrode having a diameter of 40 mm, and incorporated into the vacuum interrupter shown in FIG. Tested. In this case, the contact resistance value is a value when the electrodes 13 and 14 are pressed with a force of 500 N (Newton), and the welding force is a peak current of 35 kA when the electrodes 13 and 14 are pressed with a force of 500 N. This is a static value after two cycles of alternating current.

Table 4 shows the contact resistance values corresponding to the samples shown in Table 1, and Table 5 shows the welding force. Table 6 shows the contact resistance values corresponding to the samples in Table 2 and Table 7 shows the welding force. Further, Table 8 shows the contact resistance values corresponding to the samples in Table 3 and Table 9 shows the welding force.

[0047]

[Table 4]

As is clear from the above results, it was found that when bismuth was used as the low melting point metal, the method of the present invention could reduce the contact resistance value as compared with the powder addition method and the conventional method.

[0049]

[Table 5]

As is clear from the above results, it was found that when bismuth was used as the low melting point metal, the method of the present invention can reduce the welding force as compared with the powder addition method and the conventional method.

[0051]

[Table 6]

As is clear from the above results, it was found that when lead was used as the low melting point metal, the method of the present invention can reduce the contact resistance value as compared with the powder addition method and the conventional method.

[0053]

[Table 7]

As is evident from the above results, it has been found that when lead is used as the low melting point metal, the method of the present invention can reduce the welding force as compared with the powder addition method and the conventional method.

[0055]

[Table 8]

As is apparent from the above results, when tellurium is used as the low melting point metal, it was found that the method of the present invention can reduce the contact resistance value as compared with the powder addition method and the conventional method.

[0057]

[Table 9]

As is clear from the above results, it has been found that when tellurium is used as the low melting point metal, the method of the present invention can reduce the welding force as compared with the powder addition method and the conventional method.

[0059]

According to the method for producing an electrode material of the present invention,
Copper, chromium, and at least one of bismuth, antimony, tellurium, selenium, and lead having a lower melting point than copper are alloyed into fine powders by the atomizing method, and then heated and sintered in a non-oxidizing atmosphere. As a result, the scattering amount of the low melting point metal is suppressed as compared with the conventional method, so that the ratio of the low melting point metal can be controlled with relatively high accuracy. In comparison, it is possible to provide an electrode material having a higher breaking current value, a lower contact resistance value, and an excellent welding resistance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a vacuum interrupter.

[Explanation of symbols]

 11 and 12 are lead rods, and 13 and 14 are electrodes.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Nobuhisa Suzuki 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Inside Meidensha Co., Ltd. (56) References JP-A-3-47931 (JP, A) JP 57-67141 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01H 11/00 C22C 9/00 H01H 33/66

Claims (2)

(57) [Claims] An electrode characterized in that copper, chromium, and a metal having a lower melting point than copper are atomized by an atomizing method and are heated and sintered in a non-oxidizing atmosphere. Material manufacturing method. 2. The method according to claim 1, wherein the low melting point metal is at least one of bismuth, antimony, tellurium, selenium, and lead.