JPH079777B2 - Contact material for vacuum valve - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a contact material for a vacuum valve capable of reducing the re-ignition occurrence rate.

[Technical Background of the Invention and Problems Thereof] The characteristics required for a contact for a vacuum valve are welding resistance, withstand voltage, and high breaking property.

However, it is difficult to make these three requirements ideally compatible because they are required to have contradictory physical properties. Therefore, the priority requirement of the circuit to be applied is set to the first and other requirements are sacrificed slightly. It is the current situation.

For example, in the conventional high-voltage, large-capacity vacuum breaker,
It is known that an electrode contact is provided with a Cu alloy containing 5% by weight or less of a deposition preventing component (Bi, Te, Pb, etc.) as in the invention described in JP-B-41-12131.

However, with respect to the recent demand for higher voltage, it is not sufficient in terms of withstand voltage. That is, the vacuum circuit breaker is small and lightweight,
It has superior features compared to other circuit breakers such as maintenance-free and environmentally friendly. Therefore, in the vacuum circuit breaker, the range of application has been expanded from the conventionally used circuit of 36 kV or less to the circuit of higher voltage, and the demand for opening and closing special circuits, for example, capacitor circuits is also rapidly increasing. Therefore, higher withstand voltage is required.

The re-ignition phenomenon and the re-ignition phenomenon are mentioned as one of the important factors that are problematic in order to increase the withstand voltage of the vacuum circuit breaker. The re-ignition phenomenon improves the reliability of the product. Although it is regarded as important from the viewpoint of, the preventive technology as well as the direct cause has not been clarified.

Further, with the increase in the withstand voltage, the contact material is also required to have a higher withstand voltage and a characteristic that the re-ignition phenomenon does not occur frequently. In this case, high withstand voltage of contact material,
In order to achieve non-re-ignition, the amount of fragile anti-adhesion components that are defective in pressure resistance itself should be minimized, excessive concentration should be avoided, and gas impurities and pinholes should be minimized. It is desirable to increase the strength of the contact alloy itself.

Therefore, from these viewpoints, the above-mentioned Cu-Bi alloy is not satisfactory.

On the other hand, Cu-Cr alloy may be applied as a contact material in a field requiring high breakdown voltage and large current interruption. Since this Cu-Cr alloy has no vapor pressure difference between constituent materials as much as other contact materials, it has an advantage that uniform performance can be expected, and its characteristics can be fully utilized depending on the usage.

However, the occurrence of the re-ignition phenomenon has not yet been sufficiently mitigated, and there is a need for improvement in view of downsizing of the vacuum valve.

By the way, since this Cu-Cr alloy is generally manufactured by a powder metallurgy method, the physical and chemical states of the raw material powder,
It is considered that the contact alloy sintering technology is particularly involved in the occurrence of re-ignition. For the former raw material powder,
The present inventors have made detailed observations on the total amount of gas released in the process of heating the contact material and the morphology of the release, and there is an important correlation between these factors and the occurrence of the re-ignition phenomenon. It has been found that the re-ignition phenomenon can be effectively suppressed by controlling the release of these gases, particularly the release of gas that is suddenly generated near the melting point, for each of the raw materials that make up the contact material.

That is, when the contact material is heated, most of the adsorbed gas is degassed below the melting point and the solid solution gas is released near the melting point. Although it is (for example, about several milliseconds), a pulse-like burst gas release (several to hundreds of bursts) is observed.

These burst gases contain some C ₂ H ₂ , CH _4, etc.,
Entity from CO, it is the CO _2, O oxygen-based, such as _2, these sudden gas is thought to be released by the decomposition of the oxide mixed in the contact material.

According to the research conducted by the present inventors, the contact material that frequently causes the re-ignition phenomenon also releases a large amount of sudden gas.

Therefore, based on the above knowledge, it is considered that the re-ignition phenomenon is prevented by holding the contact material at a temperature equal to or higher than its melting point and releasing the sudden gas in advance. Also, impurities such as oxides that have an oxide form from the beginning and are mixed in the raw material powder are mainly removed by sieving using the difference in particle size from the raw material powder. It was also confirmed that the re-ignition phenomenon could be mitigated by carrying out the infiltration process from one direction when infiltrating the highly conductive material to collect and remove impurities such as oxides in one place. There is.

However, impurities such as oxides present in the raw material cannot be removed by sieving or infiltration process, and it is considered that they are a factor of potential re-ignition. However, the raw material powder (Cr
It was confirmed that the re-ignition phenomenon tends to be further reduced by carefully examining the powder) and selecting the raw material powder with less inclusions. Thus, although the selection of the raw material powder mainly containing less oxide was found to be effective in reducing the re-ignition phenomenon, it was found that there was still room for improvement when rigorous experiments were carried out. That is, a lot in which inclusions in the Cr powder are not substantially recognized is selected, this is used as a Cr raw material, and a lot that has been thoroughly examined for Cu is also used as a raw material, and Cu-Cr alloys are manufactured using each. As a result, an alloy in which the presence of inclusions was found in the Cr powder and an alloy in which the presence of inclusions was not found were produced, and re-ignition occurred with the vacuum valve using the former alloy with inclusions. It turns out that a lot has occurred. After all, this is presumed to be the inclusions formed by the reaction between certain elements that were solid-soluted in the Cu powder and the atmosphere during sintering, and therefore the re-ignition characteristics were dramatically improved. In order to do so, pay attention to a certain element that is particularly solid-soluted in the raw material (impurity cannot be detected and confirmed microscopically) in addition to impurities such as oxides that are simply mixed in the raw material. Suggest that there is a need to do so.

As a result of microanalysis, it was confirmed that the above-mentioned certain elements were Al and Si, which produced Al ₂ O ₃ and SiO ₂ after sintering and infiltration, and inclusions that enable microscopic observation. Was confirmed to have been formed.

[Object of the Invention] The present invention has been made based on the above-mentioned findings, and an object of the present invention is to provide a highly reliable contact material for vacuum valves capable of dramatically reducing the frequency of re-ignition. There is.

[Summary of the Invention] The contact material for a vacuum valve of the present invention is Al contained in Cr.
Amount 0.0001-0.01wt%, Si amount 0.0001-0.01wt%
%, Similarly, 20 to 80 wt% of Cr that satisfies the condition that the total amount of Al and Si is 0.0002 to 0.015 wt%, and the balance is made of an alloy of one or both of Cu and Ag.

[Embodiment of the Invention] FIG. 1 is a front sectional view showing a structural example of a vacuum valve to which a contact material according to the present invention is applied, and FIG. 2 is an enlarged view of a main part thereof.

In FIG. 1, a shut-off chamber 1 is composed of an insulating container 2 formed of an insulating material such as ceramic in a substantially cylindrical shape, and metal lids 4 and 5 provided at both ends of the insulating container 2 via sealing mechanisms 3 and 3a.
And it is hermetically sealed with vacuum. Further, in the shut-off chamber 1, fixed electrodes 8 and movable electrodes 9 are arranged at the ends of the pair of electrode rods 6, 7 facing each other. Further, a bellows 10 is attached to the electrode rod 7 of the movable electrode 9, and the pair of electrodes 8 and 9 can be opened and closed by the reciprocating movement of the electrode 9 while keeping the inside of the blocking chamber 1 airtight.
The bellows 10 is covered with a hood to prevent the deposition of arc vapor, and a cylindrical metal container 12 is further provided in the shutoff chamber 1 to prevent the deposition of arc vapor on the insulating container 2. ing.

On the other hand, the movable electrode 9 is fixed to the electrode rod 7 by a brazing material 13 or is crimped (not shown) by caulking, as shown in FIG. The movable contact 14 is joined by a brazing material 15.
The fixed electrode 8 is also almost the same except that the direction is reversed, and a fixed contact 14a is provided on this.

The contact material according to the present invention is suitable for forming both and / or one of the contacts 14 and 14a as described above.

The Cr used to make the contact material of the present invention is very different from that of the prior art.

That is, the gas adsorbed on the Cr powder in the process of crushing Cr, the foreign substances mixed in, and the like can be sufficiently removed by the heat treatment and crushing in a restricted atmosphere, and the sieving process. Further, Cr powder containing oxides as impurities can also be microscopically separated. However, Al and Si, which are in solid solution in Cr, cannot be separated microscopically (as described above, they form undesired oxides by reaction with sintering and infiltration atmosphere). ), This is the point that requires the most attention in order to dramatically improve the characteristics of the restriking phenomenon.

An example of manufacturing the contact material according to the present invention is as follows. That is, having a particle size of about 100 to 400 mesh average particle size, and with respect to the amount of solid solution Al and Si, using a Cr powder that satisfies the conditions carefully selected, a predetermined amount of Cr powder and a predetermined amount of Cu (or
The mixed powder with Ag) is pressure-molded at a pressure of about 4 ton / cm ² . The molded body thus obtained is pre-sintered or main-sintered at a temperature of 1000 ° C. or higher in a vacuum state of hydrogen or higher than about 1 × 10 ⁻³ mmHg. As for the pre-sintered body, hydrogen or Cu is infiltrated into the holes in the skeleton in a vacuum higher than about 1 × 10 ^-3 mmHg (1100 ° C or higher for Cu, 1000 ° C for Ag). Or higher temperature).
If necessary, Cu or Ag or Cu and Ag containing an anti-fusing component (Bi, Pb, Te, Sb, etc.) can be infiltrated to obtain a contact material.

These processes use a crucible or container in a well-controlled state to prevent impurities and gases from entering and diffusing into the contact material from the crucible, which may cause the generation of sudden gas. The point is to delete the factor.

In that sense, it is important to burn the crucible and the like in advance under predetermined conditions in order to manage it in an excellent condition.

In addition to managing the condition of crucibles, selection of the material is also an important technique for reducing sudden gas.

Under severely controlled conditions, carbon, quartz, etc. can also be maintained at an explosive gas below a specified value, but BN, AlN, Si ₃ N _4, etc., which have the property of sublimation, are especially considered to maintain a clean surface. The effect is easily obtained. A crucible, a boat, etc. are important as a supporting technique for sufficiently exhibiting the effect as the contact material according to the present invention. That is, for the container material such as the crucible, the boat, and the plate that accommodates the contact material at the time of temporary sintering, main sintering, and infiltration, use a material whose contact state is sufficiently clean so that the contact material with less sudden gas is used. It is an effective support technology to obtain. If necessary, the contact material thus obtained is subjected to processing such as cutting and polishing, or if possible, subjected to plastic working such as forging rolling to obtain a contact having a desired shape.

Incidentally, the Cr powder satisfying the above-mentioned carefully selected conditions in the present invention means that there are two requirements that the amount of gas in Cr in the powder state is small and that Al and Si which are solid-solved in Cr are small. Means to meet at the same time.

Currently, Cr that is industrially supplied is FeCr ₂ O ₄ or MgCr ₂ O ₄
Cr ore such as is reduced with other metal such as Al or Si
Mainly, a method of obtaining Cr and a method of dissolving the Cr ore to separate undissolved non-metallic impurities and a metal other than Cr, and electrolyzing this as an electrolytic solution to obtain metallic Cr. However, the Cr by the former method contains a few thousand ppm to 10,000 ppm of impurities such as Al, Si, and Fe, while the amount of gas (oxygen, nitrogen) is about 1,000 ppm, and by the latter method. On the contrary, Cr has a gas amount (oxygen, nitrogen) of 1,000p.
Although it is remarkably large as pm to 10,000 ppm, impurities such as Al are small, and for example, it is common to contain only a few hundred ppm or less. That is, when comparing the Cr by the above two methods, the Cr by the former method has a small gas amount,
The latter is characterized by the fact that there are many impurities, whereas the latter has a completely opposite relationship. Nevertheless, the Cr raw material as the contact material for the vacuum valve in the present invention is required to have both the amount of gas and the impurities limited to a certain level or less.

Therefore, the Cr powder satisfying the carefully selected conditions in the present invention is prepared, for example, as follows. That is, first, metallic Cr is obtained from a Cr ore having a Cr content as high as possible. Next, this metal Cr is subjected to vacuum heat treatment and hydrogen heat treatment as needed, and then crushed in a non-oxidizing atmosphere, and Al ₂ O ₃ , SiO ₂ , FeO and other non-metal particles that are still mixed as particles are mixed. This process prepares Cr powder with desired particle size by removing oxygen, nitrogen, hydrogen gas mainly by appropriate combination of heat treatment in hydrogen and heat treatment in vacuum while removing by means such as flotation. For example, a mixture of Al ₂ O ₃ , SiO ₂ , FeO and the like in a particle state is sufficiently removed, but Al, Si and the like existing in a solid solution state in Cr are, of course, difficult to remove. Therefore, the selection of Cr ore at the start is important for the restriction of the amount of Al and Si in the solid solution state. The amount of gas in the raw material Cr used for the contact material of the present invention thus obtained is 100 ppm or several 100 ppm, which is significantly less than 1,000 ppm, which is the value of the industrially supplied normal Cr shown above. Secured.

Hereinafter, the present invention will be described in more detail with reference to sample tests.

The contact materials were evaluated based on the re-ignition occurrence probability shown below.

A disc-shaped contact piece with a diameter of 30 mm and a thickness of 5 mm was attached to a demountable vacuum valve, and the frequency of re-ignition was measured when the circuit of 6 kV x 500 A was interrupted 2000 times, and two breakers were measured. (6 bulbs) variation width (maximum and minimum)
Indicated by. When installing the contacts, use baking heat (45
(0 ° C., 30 minutes) only, and no brazing material was used and the heating associated therewith was not performed.

Here, the results of the sample test are shown in Table-1.

High-purity Cu is put into a graphite crucible and heated in a vacuum at about 1500 ° C. for 1 hour for directional solidification to prepare a Cu mass for an infiltrant.

A plurality of types of Cr powders are prepared, and the Si and Al contents present in each Cr powder are distinguished by size, and a Cr powder (raw material) satisfying the above-mentioned carefully selected conditions is selected.

After containing Cr powder satisfying the above-mentioned carefully selected conditions in a graphite container preheated at 2000 ° C. in vacuum, the degree of vacuum is 5 × 10 ⁻⁶ Torr.
Sinter at 1200 ° C for 1 hour to obtain a Cr skeleton. Each Cr skeleton thus obtained was brought into contact with the Cu mass for infiltration material, and in an integrated state, they were housed in a graphite container preheated at 2000 ° C. in a vacuum, and the degree of vacuum was 5 × 10 ⁻ again. By heating at 1150 ° C for 1 hour in ⁶ Torr, Cu is infiltrated into the pores in the Cr skeleton to obtain a Cu-Cr alloy.

In Table 1, Comparative Examples 1 to 5, Examples 1 to 3 and Example 6 are produced at the sintering temperature of 1200 ° C. and the infiltration temperature of 1150 ° C. as described above. About 6 tons before storing Cr powder that satisfies the carefully selected conditions in a graphite container for sintering
Pressure molding at 1 / cm ² and sintering at 1380 in a vacuum of 2 × 10 ^-6 Torr
℃ × 1 hour, infiltration at a vacuum degree of 5 × 10 ^-6 Torr 1150 ℃ × 1
It was heated for an hour. Further, in Example-5, Cr powder satisfying the carefully selected conditions was pressure-molded at about 4 ton / cm ² and sintered at 1200 ° C. for 1 hour at a vacuum degree of 5 × 10 ⁻⁶ Torr,
It was heated at 1150 ° C. for 1 hour in a vacuum degree of 5 × 10 ⁻⁶ Torr to infiltrate Cu. Further, Example-6 is Cu for infiltrant.
In addition to the lumps, prepare Cu powder of equal or higher quality. this
The same amount of Cu powder and Cr powder satisfying the above-mentioned carefully selected conditions were mixed, and the mixed powder was placed in the preheated graphite container.
A skeleton was obtained by heating in hydrogen at 00 ° C for 1 hour and melted in the remaining pores by heating the Cu ingot for the infiltrant at a vacuum degree of 5 × 10 ^-6 Torr at 1150 ° C for 1 hour. It is soaked.

Example-7 is the case where a 99.99% Ag ingot is further vacuumed for about 135
After heating in a graphite crucible for 1 hour at 0 ° C., directional solidification is carried out to obtain an Ag ingot for the infiltrant. Cr is a powder of Cr satisfying the above-mentioned carefully selected conditions in a Si ₃ N ₄ crucible at a vacuum degree of 4 × 10 ^-6 Torr and 1000 ° C ×
After heating for 1 hour, the prepared skeleton and the Ag lump are integrated and housed in a Si ₃ N ₄ crucible at a vacuum degree of 5 × 10 ^-6 Torr.
It was heated at 0 ° C for 1 hour to infiltrate Ag into the pores in the skeleton to obtain an Ag-Cr alloy.

Table 1 compares the amount of Al and Si present in the Cr particles in each test contact material (Cu-Cr alloy, Cu-Ag-Cr alloy, Ag-Cr alloy) with the probability of restriking occurrence. I showed it.

Here, the amount of Al and Si, Cu-Cr alloy containing a known amount of Cr using an ion micro-analyzer as a standard sample, is determined by strength comparison, and Cu in the Cu-Cr alloy is pickled It was removed by the method to obtain only Cr, and Al in Si and Si were quantitatively analyzed by the emission spectroscopic analysis method for comparison and confirmation.

The raw material Cr is, of course, free of non-metallic contaminants such as Al ₂ O ₃ and SiO ₂ , but according to the microscopic observation, the Cr
It was also confirmed that no non-metallic inclusions such as Al ₂ O ₃ and SiO ₂ were present in the particles.

The amount of Al present in the Cr particles in the contact material is approximately 400 ppm, 1
At 400 ppm, 2100 ppm, and 5700 ppm (Comparative Examples-3, 2, 5, and 1), 0.4% or more of the high re-ignition probability was shown, and the variation range among the six evaluation valves also tended to be large. . In addition, although the same amount of Al was 40 ppm, which was extremely small, when the amount of Si was extremely large (Comparative Example-4), a high probability of re-ignition occurred.

On the other hand, as shown in Examples 1 to 3, the Al amount is <10 pp.
m, 20ppm, 98ppm or less 100ppm or less, Si amount is <5ppm,
When the concentration was 100 ppm or less, such as 70 ppm and 50 ppm, the re-ignition probability was extremely low. Examples 1 to 3 described above
And Comparative Examples 1 to 5 contained about 50 wt% Cr.
As for the results for Cu-Cr, as shown in Examples-4 to 6, the same was true for the Cr contents of about 79%, 40% and 20%.
When the amount of Si and the amount of Si were less than 100ppm, a low probability of re-ignition occurred. Furthermore, the above Examples 1 to 6 and Comparative Examples 1 to 1
5 shows the Cu-Cr alloy, but even if the high conductive material is Ag instead of Cu (Example-7), Cu-Ag is also used.
Even if it is an alloy (Example-8), the amount of Al and the amount of Si are 100 ppm.
It showed a low probability of re-ignition when:

From the above experimental results, it is found that when the Al and Si contents in the Cr particles in the test contact material are within 100 ppm, the re-ignition probability is low. However, if it is 1 ppm or less, the lower limit amount is 1 ppm, which is a practical value, because the measurement accuracy and the technology for limiting the content are not industrial.

The raw material Cr used in producing each of the test contact materials shown in Examples 1 to 8 (Table 1) was the same as in the high purity hydrogen described above before being subjected to the sintering / infiltration treatment. At 400 ° C or higher, preferably 1000 ° C or higher, and 800 ° C or higher in high vacuum,
Preferably given in appropriate combination with a heat treatment of 1000 ℃ or more,
Moreover, it is performed so as not to come into contact with the reactive atmosphere (for example, in the air) when transferring from one heat treatment to another heat treatment. As mentioned above, A in the raw material Cr
When l and Si are contained in the range of several hundred ppm or less, the gas content is generally several 1,000 to 10,000 ppm, and also in the cases of Examples 1 to 8, the above-mentioned heat treatment in hydrogen and heat treatment in vacuum are performed. The amount of gas in Cr at the raw material level is adjusted by. The effect is that, as in Examples 9, 10 and 11 shown in Table 2, the amount of gas in Cr (before sintering / infiltration) at the time of raw material (in the case of the present invention, particular attention should be paid to oxygen and nitrogen). Good luck) but 1,00
When it is 0 ppm or less (Examples 2 and 11), the effect of suppressing the occurrence of restriking is superior to the samples (Examples 9 and 10) in which the amount is higher than this. Therefore, it can be said that it is desirable to control the gas in the raw material Cr in addition to the control of the amounts of Al and Si in the contact alloy when a particularly strict design is performed to suppress re-ignition.

In addition, the gas amount evaluation in Table-2 shows that about 100 mesh Cr powder was extracted by heating in a carbon crucible at 2400 ° C. in vacuum for the gas amount in the raw material Cr. Regarding the gas amount, the contact was cut into a size of about 5 mm ³ and this was extracted by heating in a carbon crucible at 2400 ° C. in a vacuum.

[Effects of the Invention] As described above, according to the present invention, it is contained in Cr.
Al content is 0.0001-0.01wt%, Si content is 0.0001-0.01wt%
%, Also 20 to 80 wt% of Cr satisfying the condition that the total amount of Al and Si is 0.0002 to 0.015 wt% and the balance of one or both of Cu and Ag is adopted as a contact for a vacuum valve. It is possible to provide a highly reliable contact material for a vacuum valve, which can drastically reduce the firing frequency.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structural example of a vacuum valve employing a contact material according to the present invention, and FIG. 2 is an enlarged view of a main part thereof. 1 ... Shut-off chamber, 2 ... Insulation container, 6,7 ... Electrode rod, 8
...... Fixed electrode, 9 ...... Movable electrode, 14,14a ...... Contact, 13,1
5 ... brazing material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaoru Sekiguchi 8 Shinshinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Kanagawa Yokohama Metal Factory (56) Reference JP-A-59-186218 (JP, A)

Claims (1)

[Claims] 1. The amount of Al contained in Cr is 0.0001 to 0.01 wt.
%, Similarly Si content is 0.0001 to 0.01 wt%, and similarly, the total amount of Al and Si is 0.0002 to 0.015 wt% Cr, which is 20 to 80 w
A contact material for a vacuum valve, which is made of an alloy of t% and the balance of one or both of Cu and Ag.