JPS625525A - Contact material for vacuum valve - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a contact material for a vacuum valve that can reduce the incidence of restriking.

[Technical background of the invention and its problems] The characteristics required of a contact for a vacuum valve are welding resistance, withstand voltage, and high interrupting property.

However, these three requirements require contradictory physical properties, so it is difficult to ideally balance them, so prioritize the requirements of the applied circuit first and sacrifice other requirements slightly. This is the current situation.

For example, in conventional high-voltage, large-capacity vacuum breakers,
As in the invention described in Japanese Patent Publication No. Sho 41-12131, an electrode contact comprising a Cu alloy containing 5% or less of welding prevention components (Bi, Te, Pb, etc.) is known.

However, it is not sufficient in terms of withstand voltage to meet the recent demand for higher voltage. In other words, the vacuum breaker is small and lightweight;
It has superior features compared to other circuit breakers, such as being maintenance-free and environmentally friendly.

Therefore, the scope of application of vacuum breakers has expanded from the conventionally commonly used circuits of 36 kV or less to even higher voltage circuits, and the demand for opening and closing special circuits, such as capacitor circuits, is also rapidly increasing. Therefore,
There is a need for even higher voltage resistance.

Now, one of the important factors that poses a problem when trying to make vacuum breakers withstand high voltages is the re-ignition phenomenon. Despite the fact that it is considered important from the perspective of the above, not only prevention techniques but also the direct cause of its occurrence have not yet been clarified.

In addition, with the increase in voltage resistance, contact materials are required to have even higher voltage resistance and characteristics that reduce the frequency of restriking. In this case, increasing the voltage resistance of the contact material,
In order to achieve non-restriking, it is necessary to minimize the amount of fragile welding prevention components that can cause defects in terms of pressure resistance, avoid excessive concentration, and minimize gas impurities, pinholes, etc. It is desirable to increase the strength of the contact alloy itself.

Therefore, from these points of view, the above-mentioned Cu-B
1 alloy is not satisfactory.

On the other hand, in fields that require high voltage resistance and large current interruption, Qu-Cr alloys are sometimes used as contact materials. Unlike other contact materials, this Cu-Cr alloy has the advantage that it can be expected to exhibit uniform performance because there is no difference in vapor pressure between the constituent materials, and its characteristics can be fully utilized depending on how it is used. .

However, the occurrence of the restriking phenomenon has not yet been sufficiently alleviated, and improvements are needed, particularly from the viewpoint of downsizing the vacuum valve.

By the way, since this Cu-Cr alloy is generally manufactured using a powder metallurgy method, the physical and chemical conditions of the raw powder, the sintering technology of the contact alloy, etc. are the items that are particularly involved in the occurrence of restriking. Conceivable. Regarding the former raw material powder, the present inventors made detailed observations of the total amount of gas released during the process of heating the contact material and the form of release, and found that these factors and the occurrence of the restriking phenomenon were There is an important correlation between the two, and by controlling the release of these gases, especially the release of gases that suddenly occur near the melting point, it is possible to effectively suppress the restriking phenomenon, especially for each of the raw materials that make up the contact material. We found that it is possible to suppress the

In other words, when the contact material is heated, most of the adsorbed gas is degassed below the melting point, and the gas dissolved in solid solution near the melting point is released. However, if the contact material is further heated above the melting point, it will degas for a very short time. (for example, on the order of several milliseconds), but pulse-like sudden gas emissions (several to hundreds of bursts) are observed.

These sudden gases contain a small amount of C2H2, CH4, etc., but since they are mainly oxygen-based such as Co, CO2, 02, etc., these sudden gases are released by the decomposition of oxides mixed in the contact material. It is considered that

According to the research conducted by the present inventors, contact materials that frequently cause restriking phenomena also release a large amount of sudden gas.

Therefore, based on the above findings, it is possible to prevent the restriking phenomenon by holding the contact material at a temperature higher than its melting point and releasing this sudden gas in advance. In addition, impurities such as oxides that are in the form of oxides 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, but they are removed in advance in the skeleton. It has been confirmed that when infiltrating a highly conductive material into a metal, the restriking phenomenon can be reduced by performing the infiltration process from one direction to collect and remove impurities such as oxides in one place. There is.

However, impurities such as oxides present in the raw materials cannot be removed by sieving or infiltration processes, and are considered to be one of the causes of potential restriking. However, as a means of solving this problem, by carefully examining the raw material powder (Cr powder) and selecting a raw material powder with fewer inclusions, the restriking phenomenon tends to be reduced by -S. It was confirmed. Although the selection of raw material powder with less oxide content was found to be effective in reducing the restriking phenomenon, rigorous experiments revealed that there was still room for improvement. In other words, a lot in which virtually no inclusions are observed in the Cr powder is selected, and this is
When Cu-Cr alloys were produced using lots that had been carefully examined for Qu as raw materials, some alloys were found to have inclusions in the Cr powder, while others were found to have inclusions in the Cr powder. It was found that restriking occurred more often in vacuum valves using the former alloy with inclusions. In the end, this is Q
It is assumed that the inclusions are generated by the reaction between the elements dissolved in the U powder and the atmosphere during sintering. Therefore, in order to dramatically improve the restriking characteristics, it is necessary to In addition to impurities such as oxides that are simply mixed into raw materials, it is necessary to pay attention to certain elements that are dissolved in solid solution in raw materials (which cannot be detected microscopically because they are in a solid solution state). Suggests.

As a result of microanalysis, the above-mentioned elements are AJl and Si.
It was confirmed that this was Af203 after sintering and infiltration.
and S+02, and it was also confirmed that inclusions that could be observed microscopically were formed.

[Object of the Invention] The present invention was made based on the above-mentioned knowledge, and has an object to provide a highly reliable contact material for a vacuum valve that can dramatically reduce the frequency of restriking occurrences. [Summary of the Invention] In order to achieve the above object, the contact material for a vacuum valve of the present invention contains 20 to 80% Cr and the remainder is OLI.

In an alloy consisting of one or both of Ag, Al contained in Cr in the alloy is 0.01 wt% or less (0.00
0.01wt% or more), and Si is limited to 0.01wt% or more
The content is limited to below Q (0,0001 wt% or more).

[Embodiments of the Invention] FIG. 1 is a front cross-sectional view showing an example of the structure of vacuum pulp to which the contact material according to the present invention is applied, and FIG. 2 is an enlarged view of the main parts thereof.

In FIG. 1, a breaking point 1 consists of an insulating container 2 formed of an insulating material such as ceramic into a substantially cylindrical shape, and metal lids 4 and 5 provided at both ends of the container via sealing mechanisms 3 and 3a. Vacuum-tightly sealed. Furthermore, the connection is broken 1
Inside, a fixed electrode 8 and a movable electrode 9 are arranged at mutually opposing ends of a pair of electrode rods 6.7, respectively.

A bellows 1o is attached to the electrode rod 7 of the movable electrode 9, and allows the pair of electrodes 8.9 to open and close by reciprocating the electrode 9 while keeping the inside of the breaker 1 vacuum-tight. This bellows 10 is covered with a hood 11,
A cylindrical metal container 12 is further provided within the breaker 1 to prevent arc vapor from adhering to the insulating container 2.

On the other hand, as the enlarged structure of the movable electrode 9 is shown in FIG. A movable contact 14 is joined by a brazing material 15. Further, the fixed electrode 8 is also substantially the same except that the direction is reversed, and a fixed contact 14a is provided thereon.

The contact material according to the invention is suitable for contact 14.1 as described above.
This is suitable for configuring either or both of 4a.

Cr used for manufacturing the contact material of the present invention is
It is very different from the conventional one.

That is, in the process of pulverizing Cr, gas adsorbed to Cr powder, foreign substances mixed in, etc. can be sufficiently removed by heat treatment, pulverization, and sieving steps in a restricted atmosphere. In addition, C containing oxides etc. as impurities
R powder can also be separated microscopically. However, A, which is in solid solution in Cr,! , Si is impossible to fractionate microscopically (as mentioned earlier, it forms undesirable oxides by reaction with the sintering and infiltration atmosphere), and dramatically improves the restriking properties. This is the point that requires the most attention in order to improve.

An example of manufacturing a contact material according to the invention is as follows. That is, using Cr powder that has an average particle size of about 100 to 400 meshes and satisfies the above-mentioned carefully selected conditions regarding the amount of Al and Si dissolved in solid solution, a predetermined amount of Cr powder and Cr powder are used.
4 tons/cr of mixed powder with a predetermined amount of u (or Ao)
Pressure mold with a pressure of about i. The thus obtained molded body is heated with hydrogen or I
Perform preliminary sintering or final sintering. For the pre-sintered body, hydrogen or CIJ is infiltrated into the pores in the skeleton in a vacuum higher than 1 Xl 0' mHg (1100°C in the case of Cu)
(1000°C or higher for AQ). Furthermore, if necessary, a welding prevention component (B
i, Pb, Te, Sb, etc.) containing C1l or A
Contact materials can also be obtained by infiltrating a or CIJ and AQ.

These processes use crucibles or containers under well-controlled conditions to prevent impurities and gas from entering and diffusing into the contact material, which may cause sudden gas generation. The key is to remove factors.

In this sense, it is important to dry-fire the crucible under predetermined conditions in advance in order to maintain an excellent state.

In addition to controlling the condition of the crucible, the selection of its material is also an important technique for reducing sudden gas emissions.

Under strictly controlled conditions, carbon, quartz, etc. can be maintained at below a specified level of explosive gas, but BN, AJIN, St 3 N4, etc., which have sublimation properties, are particularly effective in keeping their surfaces clean. can be easily obtained.

Crucibles, boats, etc. are important as support technologies for fully demonstrating the effect of the contact material according to the present invention. In other words, by using container materials such as crucibles, boats, and plates that house the contact material during pre-sintering and sintering and infiltration, the contact materials with less sudden gas can be used by using materials that are kept in a sufficiently clean condition. It is an effective support technique for gaining. Contacts having a desired shape can be obtained by subjecting the thus obtained contact material to processing such as cutting and polishing, if necessary, or, if possible, to plastic processing such as forging and rolling.

In addition, the Cr powder that satisfies the carefully selected conditions in the present invention mentioned above has two requirements: a small amount of gas in Cr in the powder state, and a small amount of AJl and Si dissolved in Cr. It means to satisfy at the same time.

Currently, Cr that is industrially supplied is Fe Cr 2
04, M(l Qr 204 etc.)
Alternatively, a method of obtaining metal Cr by reduction with other metals such as Si, and a method of dissolving the Cr ore, separating undissolved non-metallic impurities, separating metals other than Cr, and electrolyzing this as an electrolytic solution. The main method is to obtain metal Cr.

However, the amount of gas (oxygen, nitrogen)
is about 1.000 ppm, whereas AJl, St
.

The number of impurities such as Fe is 1. OOOppm ~10.00
01] Contains Dm, and Cr produced by the latter method is, on the contrary, a gas! (oxygen, nitrogen) is 1,000 ppm to 1
0,0001)I)Ill, but impurities such as Af are generally contained in a small amount, for example, only several hundred ppm or less. In other words, when comparing Cr produced by the above two methods, Cr produced by the former method has a small gas layer and many impurities, whereas the latter has a completely opposite relationship. There is. Nevertheless, the Cr raw material used as the contact material for the vacuum valve in the present invention is required to have both the gas amount and impurities within a certain level.

Therefore, the preparation of Cr powder that satisfies the carefully selected conditions in the present invention is as follows, for example. That is, first, metal Cr is obtained from a Cr ore with as much Cr content as possible. Next, this metal Cr is subjected to vacuum heat treatment and hydrogen heat treatment as necessary, and then pulverized in a non-oxidizing atmosphere, and Al2O3
, Si 02 .

Non-metallic particles such as FeO that are still mixed in the form of particles are removed by means such as flotation, and heat treatment in hydrogen is performed.
Mainly oxygen,
Nitrogen and hydrogen gas are removed to produce Cr powder with the desired particle size. This process produces, for example, AJ1203 in the particle state.

A mixture of SiO2, FeO, etc. is sufficiently removed, but A-!, which exists in solid solution in Cr! , Si, etc., are of course difficult to remove.

Therefore, the constraints on AJ, Si l in solid solution state are as follows:
The selection of Cr ore at the start is important. The amount of gas in the raw material Cr used in the contact material of the present invention obtained in this way is significantly lower than the value of 1,000ppm, which is the value of normal industrially supplied Cr shown above.
PM or several hundred ppm was secured.

The present invention will be explained in more detail below using sample tests.

The contact materials were evaluated based on the restrike probability shown below.

A disc-shaped contact piece with a diameter of 30 m and a thickness of 5 shoes was attached to a demount pull type vacuum valve, and the frequency of re-ignition was measured when a 6 kV x 500 A circuit was interrupted 2000 times.
It is shown by the variation width (maximum and minimum) of the circuit breakers (6 pulps) on the table. When attaching the contacts, only baking heating (450° C., 30 minutes) was performed, and no brazing material or accompanying heating was performed.

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

High-purity CLI is placed in a graphite crucible and the vacuum width is approximately 1500℃.
Directional solidification is performed by heating for 1 hour to prepare a Cu lump for use as an infiltrant.

A plurality of types of Cr powder are prepared, and the Si and Al contents present in each Cr powder are differentiated according to the size, and a Cr powder (raw material) that satisfies the carefully selected conditions is selected.

After storing Cr powder that satisfies the above-mentioned carefully selected conditions in a graphite container that has been pre-heat-treated at 2000°C in a vacuum, the vacuum level is 5x1.
Sintered at 1200°C for 1 hour in O-IITCr
Get a skeleton. Each of the Qr skeletons thus obtained and the CLI lump for infiltration material were brought into contact with each other, and the integral state was stored in a graphite container that had been preheated at 2000°C in a vacuum, and then heated again at a vacuum degree of 5X 10-'. Under Torr? 1
By heating at 150°C for 1 hour, GO 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 have a sintering temperature of 1200°C and an infiltration temperature of 11°C as described above.
In Example 4, Cr powder that met carefully selected conditions was press-molded at approximately 6 tons/d before being stored in a graphite container for sintering, and the sintering was performed at a vacuum degree. 2X 10
Infiltration was carried out by heating at 1150° C. for 1 hour in a vacuum of 5×10 −” Torr for 1 hour at 1380” C. In addition, for Example-5, Cr powder that met carefully selected conditions was pressure-molded at about 4 tons/d,
After sintering at 1200℃ for 1 hour at a vacuum level of 5xl O''8 Torr, 115
It was heated at 0°C for 1 hour to infiltrate Cu.

Furthermore, in Example 6, Cu powder having the same or higher quality is prepared in addition to the Cu lump for the infiltration material. This Cu powder and the Cr powder that satisfies the carefully selected conditions are mixed in equal amounts, and this mixed powder is placed in the preheated graphite container and heated in hydrogen at 1200°C for 1 hour to form a skeleton. Then, the remaining pores are filled with a vacuum degree of 5×1 by the Cu lump for the infiltration material.
It was infiltrated by heating at 1150° C. for 1 hour at 0-” Torr.

In Example 7, a 99.99% AIJ ingot was further heated in a graphite crucible at a vacuum width of about 1350° C. for 1 hour, and then subjected to directional solidification to obtain an AQ lump for use as an infiltrant. For Cr, Cr powder that satisfies the carefully selected conditions is heated in a Si 3 N4 crucible at a vacuum level of 4 x 10-' Torr at 1000°C for 1 hour, and the prepared skeleton and the Ag lump are integrated, and then heated in a Si 3 N4 crucible. Store inside and vacuum level 5x10
``''' Heating at 1050° C. for 1 hour at Torr infiltrated A(+ into the pores in the skeleton to obtain an Aa-Cr alloy.

Each test contact material (C1-Cr alloy, Cu-Ag-C
Table 1 shows a comparison of the Af and Si1 present in the C particles in the R alloy and the A-C alloy and the restriking probability characteristics.

Here, AJl and Sit are determined by comparing the strength of a Cu-Cr alloy containing a known amount of Cr using an ion micro analyzer as a standard sample, and by removing Cu in the Cu-Cr alloy by pickling. Remove Cr
Quantitative analysis of Af and Si in Cr was carried out by emission spectrometry and comparative confirmation was made.

Of course, the raw material Cr is free of nonmetallic contaminants such as Af203 and Si02, but according to microscopic observation,
Among the Cr particles in the test contact material, Afz 03
It has also been confirmed that there are no non-metallic inclusions such as SiO2.

The amount of Al present in the Cr particles in the contact material is approximately 40
0ppm, 1400apl, 2100ppm.

570013pII (Comparative Examples-3, 2, 5, and 1) all showed a high restrike probability of 0.4% or more, and the variation among the six evaluation bulbs also tended to be large. In addition, even though the amount of Al is extremely small at 40 ppm, the amount of Sin is extremely large (comparative example -
4) also showed a high restrike probability.

On the other hand, as shown in Examples 1 to 3, the amount of Al is <
10f) I) l , 2 Qppm , 981) I)
1001) l) ffi or less and Sit is <
5pu, 70ppl.

In the case of 100 ppm or less, such as 50 ppII, the probability of restriking occurrence was extremely low. Regarding Examples 1 to 3 and Comparative Examples 1 to 5 described above, the results are for Cu-Cr containing about 50 wt% Cr, but as shown in Examples 4 to 6, the amount of Cr is Approximately 79%, 40
% and 20%, the AJl amount and Sin are 10
01)l) Throat below 1 showed a low probability of restriking. Furthermore, the above-mentioned Examples 1 to 6 and Comparative Examples 1 to 5 are C
This is shown for the IJ-Cr gold alloy, but even if the highly conductive material is Ag instead of Cu (Example 7), C
Even with the u-AQ alloy (Example 8>, when the AJl amount and Sil are 1001)l or less, a low restriking probability was exhibited.

From the above experimental results, it is clear that Cr exists in the Cr particles in the test contact material. It can be seen that when l and Sil are within 100 ppm, the probability of restriking is low. But i
Below pp+i, the lower limit is 1 p due to the lack of industrial technology for measurement accuracy and content constraints.
pm becomes the actual value.

The raw material Qr used in producing each of the test contact materials shown in Examples 1 to 8 (Table 1) was prepared in the aforementioned high-purity hydrogen solution before being subjected to sintering and infiltration treatment. heat treatment at 400°C or higher, preferably 1000°C or higher, and 8°C in high vacuum.
Heat treatment at 00°C or higher, preferably 1000°C or higher, in appropriate combinations, with care taken to avoid contact with a reactive atmosphere (e.g., air) when transferring from one heat treatment to another. It is. As mentioned earlier, Aj! in the raw material Cr! , when the St content is about several 100 pH or less, the gas content is about several 1,000 to 10.
It is common to contain OOOppm, and Examples 1 to
In the case of No. 8, the amount of gas in Cr at the raw material level was also adjusted by the above-mentioned heat treatment in hydrogen and heat treatment in vacuum. The effect is as shown in Example 9.10.11 shown in Table 2, the amount of gas in Cr at the time of raw material (before sintering and infiltration) (
In the case of the present invention, particular attention should be paid to oxygen and nitrogen), but
1. The effect of suppressing the occurrence of restriking when the amount is less than OOO ppm (Examples 2 and 11) is better than that of samples where the amount is more than this (Examples 9 and 10). Therefore, when performing a particularly strict design to suppress restriking, it is desirable to control the gas in the raw material Cr used in addition to controlling AJl and s+m in the contact alloy.

In addition, the gas evaluation in Table 2 is based on raw material Cr, and the amount of gas in it is extracted by heating approximately 100 mesh of Cr powder in a carbon crucible in a vacuum at 2400°C. Regarding the amount of gas, cut out the contact into a size of about 5 IML3 and place it in a carbon crucible in vacuum for 2400 min.
It is extracted by heating at ℃.

[Effects of the Invention] As explained above, according to the present invention, Cr is 20 to 80
wt%, and the balance is Cu and/or A(l), and the AJL contained in Cr in the alloy is 0.
01 wt% or less (but 0,0001 wt% or more)
and Si to o, oi wt% or less (however, 0
. can.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the configuration of a vacuum valve employing the contact material according to the present invention, and FIG. 2 is an enlarged view of the main parts thereof. DESCRIPTION OF SYMBOLS 1... Breaking/crossing, 2... Insulating container, 6.7... Electrode rod, 8... Fixed electrode, 9... Movable electric bridge, 14.1
4a... Contact, 13.15... Brazing metal.

Claims (2)

[Claims] (1) In an alloy consisting of 20 to 80 wt% Cr and the balance being one or both of Cu and Ag, the Al contained in Cr in the alloy is 0.01 wt% or less (however, 0.0001 wt% or less).
A contact material for a vacuum valve, characterized in that Si is limited to 0.01 wt% or less (but not less than 0.0001 wt%). (2) The contact material for a vacuum valve according to claim 1, wherein the total amount of oxygen and nitrogen gas in the Cr in the alloy at the time of raw material is less than 1000 ppm.