JPH04312724A - Contact material of vacuum valve - Google Patents

Abstract

PURPOSE:To improve the current-chopping characteristic and current-breaking characteristic of the contact material of a vacuum valve by specifying a highly conductive component made of an element selected from Ag or/and Cu and an arc-resisting component made of WC respectively to have xwt.% and ywt.% and having Cr or V carbide of zwt.% against WC contained in the arc-resisting component. CONSTITUTION:The contact material is formed out of 20 to 50wt.% of a highly conductive component selected from Ag or/and Cu, and an arc-resisting component made of 50 to 80wt.% of WC. At this time, at least one of 1 to 10wt.% of Cr or V carbide against WC is contained in the arc-resisting component while also an auxiliary component made of one or more elements selected from Fe, Co and Ni is contained in a contact material. Contacts 13a, 13b worked out of this contact material are soldered to electrodes 7, 8, respectively and then the electrodes 7, 8 are soldered respectively to conductive rods 5, 6. The current-chopping characteristic and current-breaking characteristic of the contact material of the vacuum valve can thus be improved so as to sufficiently lower the high-frequency arc-extinguishing characteristic thereof.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact material for a vacuum valve having excellent current cutting characteristics and high frequency arc extinguishing characteristics.

0002

2. Description of the Related Art The contacts of a vacuum valve, which cuts off current in a high vacuum by utilizing arc diffusivity in a vacuum, are composed of two opposing fixed and movable contacts. When this vacuum valve is used to cut off the current in an inductive circuit such as a motor load, an excessive abnormal surge voltage is generated.
There is a risk of damaging the load equipment. The cause of this abnormal surge voltage is, for example, a rupture phenomenon that occurs when a small current is interrupted in a vacuum (current is forcibly interrupted without waiting for the natural zero point of the AC current waveform), or a high-frequency arc extinction phenomenon. etc. The abnormal surge voltage value Vs due to the cutting phenomenon is the product of the circuit surge impedance Zo and the current cutting value Ic, that is, Vs = Zo・Ic
It is expressed as Therefore, in order to lower the abnormal surge voltage Vs, the current cutoff value Ic must be lowered.

In response to the above requirements, tungsten carbide (
A vacuum switch using a contact made of a composite alloy of WC) and silver (Ag) has been developed (Japanese Patent Application No. 42-68447, US Pat. No. 3,683,138), and this has been put into practical use. This Ag-WC alloy contact has the following characteristics. (1) Intervention of WC facilitates electron emission. (2) Promote evaporation of the contact material based on heating of the electrode surface due to collision of field emission electrons. (3) The carbide of the contact material is decomposed by the arc, producing a charged body and connecting the arc.

Bismuth (Bi) is another contact material that exhibits low cutting current characteristics (low chopping characteristics).
) and copper (Cu), and this material has been put to practical use in vacuum valves (Japanese Patent Publication No. 35-14
No. 974, U.S. Patent No. 2975256, Special Publication No. 4
1-12131, US Pat. No. 3,246,979)
. Among these alloys, one containing 10% by weight (hereinafter referred to as wt%) of Bi (Japanese Patent Publication No. 35-14974) exhibits low cutting current characteristics due to its moderate vapor pressure characteristics. In addition, Bi containing 0.5 wt% (Japanese Patent Publication No. 12131/1986) segregates at grain boundaries, embrittles the alloy itself, achieves low welding external force, and has excellent large current interrupting properties. ing. Another contact material that obtains low breaking current characteristics is a Ag:Cu ratio of approximately 7:3.
An Ag-Cu-WC alloy has been proposed (JP-A-58-157015). It is stated that this alloy exhibits stable cutting current characteristics because the ratio of Ag and Cu is selected in an unprecedentedly limited manner. Furthermore, Japanese Patent Publication No. 62-077439 states that setting the grain size of the arc-resistant material (for example, the grain size of WC) to 0.2 to 1 μm is effective in improving low shredding current characteristics. Suggested.

[0005]

[Problem to be solved by the invention] In recent years, vacuum valves have
With the increasing number of applications being applied to inductive circuits such as electric motors, and the emergence of high surge impedance loads, it is of course desirable to have even more stable and low breaking current characteristics, as well as high-frequency arc-extinguishing characteristics (high-frequency current It is also necessary to satisfy the requirements (blocking ability). This is because it has been found that in addition to surges caused by current interruption, surges caused by repeated high-frequency re-ignition pose a threat to load insulation. There has been no contact material for conventional vacuum valves that satisfies both of these characteristics at the same time.

That is, surge (overvoltage) due to current interruption
can be improved by reducing the current cutoff value. However, in surges caused by repeated high-frequency re-ignition, when dielectric breakdown occurs between electrodes after current interruption, the high-frequency current flowing depending on the circuit conditions is interrupted, increasing the recovery voltage value, and further causing dielectric breakdown between the electrodes. By repeating the process that occurs, the recovery voltage value increases and an excessive surge voltage is generated. In this case, the surge is generated to extinguish the high-frequency current, and by improving the high-frequency arc-extinguishing characteristics to reduce the surge voltage, the generated surge can be reduced. It is necessary to improve and stabilize arc characteristics. Alloy contact made of composite of WC and Ag (Japanese Patent Application No. 68447/1989,
In U.S. Pat. No. 3,683,138), not only is the breaking current value itself insufficient, but no consideration is given to improving the high frequency arc extinction characteristics.

[0007] An alloy containing 10 wt% of Bi and Cu (Japanese Patent Publication No. 35-14974, US Pat. No. 297
No. 5256), the amount of metal supplied to the interelectrode space decreased as the number of openings and closings increased, deterioration of low cutting current characteristics appeared, and deterioration of withstand voltage characteristics depending on the amount of high vapor pressure elements was also pointed out. There is. Furthermore, the high-frequency arc-extinguishing characteristics are not fully satisfied. An alloy containing 0.5wt% Bi and Cu (
Japanese Patent Publication No. 41-12131, U.S. Patent No. 32469
No. 79) has insufficient low breaking current characteristics.

[0008] Furthermore, the weight ratio of Ag and Cu is approximately 7:
3 Ag-Cu-WC alloy (JP-A-58-1570
No. 15) and an alloy in which the grain size of the arc-resistant material is 0.2 to 1 μm (Japanese Patent Application Laid-open No. 62-077439) do not fully satisfy high frequency arc extinguishing properties. An object of the present invention is to provide a contact material for a vacuum valve that has both excellent low breaking current characteristics and high frequency arc extinguishing characteristics. [Structure of the invention]

[0009]

[Means and effects for solving the problems] In order to achieve the above object, the present invention provides that the content of the highly conductive component is Ag or/
The total content of We and Cr3C2 or/and Vc is 50 to 80wt%, and the content of the arc-resistant components is 50 to 80wt%, and the content of the arc-resistant components is 50 to 80wt%.
The amount of r3 C2 or/and Vc is 1 to 1 to the amount of Wc.
By containing 10 wt%, current cutting characteristics and high frequency arc extinguishing characteristics are improved.

0010

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a vacuum valve, and FIG. 2 is an enlarged view of an electrode portion of the vacuum valve.

In FIG. 1, a shutoff chamber 1 includes an insulating container 2 formed of an insulating material into a substantially cylindrical shape, and metallic lids 4a and 4 provided at both ends of the container through sealing fittings 3a and 3b.
b and is constructed in a vacuum-tight manner.

A pair of electrodes 7 and 8 attached to opposite ends of conductive rods 5 and 6 are arranged in the breaker chamber 1, with the upper electrode 7 being a fixed electrode and the lower electrode 8 being a movable electrode. It is used as an electrode. A bellows 9 is attached to the electrode rod 6 of the electrode 8 to allow the electrode 8 to move in the axial direction while keeping the interior of the breaker chamber 1 vacuum-tight. A metal arc shield 10 is provided above the bellows 9 to prevent the bellows 9 from being covered with arc vapor. An arc shield 11 is provided to prevent the insulating container 2 from being covered with arc vapors. Further, the electrode 8 is fixed to the conductive rod 6 by a brazing portion 12, as shown in an enlarged view in FIG. 2, or is crimped and connected by caulking. Contact 13a is attached to electrode 8 by brazing 14. Note that the contact 13b is attached to the electrode 7 by brazing.

In general, in order to improve the current cutting characteristics, it is extremely important not only to maintain the current cutting itself at a lower value but also to reduce the width of its dispersion. The above-mentioned current cutting phenomenon is said to be closely related to the amount of vapor between the contacts (material properties include vapor pressure and heat conduction), electrons emitted from the contact material, etc. According to the inventors' experiments, the former It turned out that the contribution was larger. Therefore, it has been found that the current cutting phenomenon can be alleviated by making it easier to supply steam or by making contacts from materials that are easier to supply. The aforementioned Cu-Bi
Based on this point of view, the alloys have low shear values. However, a fatal drawback is that due to the low melting point (271°C) of Bi, during baking at around 600°C or silver brazing at 800°C, which is usually carried out in a vacuum valve, the melting of Bi results in movement and aggregation. , the presence of Bi, which should maintain current cutting characteristics, becomes non-uniform. For this reason, a phenomenon is observed in which the width of variation in the current cutoff value increases.

On the other hand, in the Ag-arc-resistant material alloy represented by Ag-WC, although it depends on the amount of Ag vapor at the boiling point of the arc-resistant material (WC in this case), on the other hand, the above-mentioned C
The vapor pressure of Ag is significantly lower than the vapor pressure of Bi in the u-Bi system, so depending on where in the contact point (Ag or arc-resistant material) the arc foot sticks, it can lead to insufficient temperature, ie, insufficient steam. There is. As a result, it was confirmed that there was a wide variation in the current cutoff value. It was thought that it was already possible to prevent the rapid temperature drop of the contact surface at the end of the current rupture using an alloy made only of a combination of Ag and an arc-resistant material and to maintain the arc. Furthermore, in order to improve the performance, we came to the conclusion that it is necessary to add some kind of auxiliary technology. As one idea for this improvement, the above-mentioned Japanese Patent Application Laid-Open No. 58-157015 suggests a technique of finely distributing crystal grains by forming a highly conductive component into an alloy of Ag and Cu. This technology has stabilized the characteristics. The location where the arc mainly sticks may be in the arc-resistant component or in the Ag-Cu alloy, and in both cases, the current cutting phenomenon is alleviated (improved) by supplying Ag-Cu vapor. , some variation occurred when it adhered to the arc-resistant component.

On the other hand, by making the arc-resistant component more fine, the variation width can be improved. Therefore, it is suggested that the particle size of the arc-resistant component plays an important role in the current cutting phenomenon, and segregation of the arc-resistant component was observed at approximately 10 to 20 times the initial particle size. Combined with observations showing significant variation in contact materials, this suggests a specific range of particle sizes.

However, Japanese Patent Application Laid-Open No. 58-157015
As in the publication, in order to improve the cutting current characteristics by controlling the amounts of Ag and Cu and the particle size of WC to predetermined values,
Although important technological advances have been made, these technologies have not been able to achieve even lower breaking current characteristics, ensure high-frequency arc-extinguishing characteristics, and in particular have not improved high-frequency arc-extinguishing characteristics.

As mentioned above, surges caused by repeated high-frequency re-ignition can be caused by cutting off the high-frequency current that flows depending on the circuit conditions when dielectric breakdown occurs between the electrodes after the current is cut off, and the recovery voltage value increases. The recovery voltage value increases due to repetition of the process in which dielectric breakdown occurs between the electrodes, and an excessive surge voltage is generated. In order to suppress excessive surge voltage, it is desirable to allow the high-frequency current discharge that flows at the time of dielectric breakdown in the microelectrode gap to continue arcing until the commercial frequency load current rises, without extinguishing the high-frequency current discharge.

When this commercial frequency load current rises, by the time it reaches the next current zero point, the breaker has been opened to a sufficient electrode difference length, so after this current zero point there is a gap between the electrodes. The disconnection is completed without any dielectric breakdown or repetition. Therefore, no excessive surge voltage is generated as described above.

Furthermore, even if a subsequent arc does not occur, by reducing the high frequency arc extinguishing ability, the surge due to high frequency re-ignition can be reduced. That is, it is only necessary to improve the continuation characteristics of high-frequency current discharge in a small gap between electrodes. In order to improve this continuation arc characteristic, many measures have been considered by various researchers, but the effectiveness of the measures has not yet been clarified due to the problem of correlation with other factors. This invention focuses on reducing the amount of gas contained in the contact alloy. That is, the insulation between the electrodes is destroyed by a large amount of gas suddenly released into the electrode space from the arced part heated to a high temperature by the arc when the arc is cut off. The restriking phenomenon is induced depending on conditions such as the electrode surface or the state of the space. The source of the gas in this case is gas contained or adsorbed in the contact alloy. Some of these gases include gases released when arc-induced decomposition of compounds (e.g. oxides) with gases existing inside or on the surface of the contacts, so multidimensional management and reduction of gases at the contacts is required. It is necessary to Generally, Ag-W
If the melting point of one material (in this case WC) is extremely high, such as C and C, it is impossible to manufacture a contact at a temperature higher than the melting temperature of both materials, and at least one of the materials melts. It is manufactured at a temperature below that temperature, ie by a sintering method. On the other hand, when the melting temperatures of both materials are low, such as the aforementioned Cu-Bi, the material is manufactured at a temperature higher than the melting temperature of both materials, that is, by a melting method. Normally, the amount of gas in a contact material produced by the sintering method is several to several hundred times greater than that produced by the melting method. The gas at the contact point by the sintering method is mainly gas originating from raw material powder (mainly WC),
Examples include gases caused by sintering technology such as the atmosphere during sintering. The gas related to the former raw material powder can be kept at a stable value by sufficiently controlling the process from the half crushing process to the storage process, and further controlling the particle size degassing process. Regarding gases related to the latter sintering technology, it is effective to manage the sintering furnace and the tools used, but the temperature during sintering or infiltration is particularly important, and it is better to select a high temperature. This tends to be advantageous for reducing gas emissions. Therefore, the sintering or infiltration temperature is selected to be high within the allowable range after controlling the above-mentioned conditions that can be controlled.

However, in the sintering process of the WC skeleton during the production of Ag-EWC, setting the sintering temperature to a high level is extremely effective in reducing the gas content of the WC skeleton, as described above. It was not possible to maintain the required porosity in the skeleton, and as a result, it became impossible to secure the amount of Ag required in the infiltration process, resulting in a shortage of highly conductive components as a contact material, and the desired material It interferes with performance.

[0021] If the temperature in the infiltration process is high, the evaporation loss of Ag will also be large, which will also cause fluctuations in the composition of the contact material, but the selection of the sintering temperature during the production of the WC skeleton will improve the composition. important for

Therefore, in the present invention, the ratio of the highly conductive component to the arc-resistant component, that is, the Ag or/and C
The amount of u is 20 to 50 wt%, and the remainder is WC and C or/
and V carbide. Due to this requirement, even if the sintering temperature during the manufacture of the WC skeleton is set to a temperature that is advantageous for low gasification, the porosity in the WC skeleton will not be reduced below a predetermined value, and therefore the amount of gas contained in the contact will be reduced. It is possible to secure the desired amount of highly conductive components (Ag and/or Cu) while reducing the amount. As a result, a predetermined amount of Cv3 C2 or/
The presence of V and Vc limits the excessive progress of sintering of WC during sintering, and reduces the amount of highly conductive components in the contact and the amount of gas in the contact, which are important contact characteristics. This contributes to improving the vacuum valve characteristics, which is the objective of the improvement mentioned above. Next, among the methods of manufacturing this vacuum valve, particularly the method of manufacturing the contact material will be described. Prior to manufacturing, arc-resistant components and auxiliary components are classified by required particle size. The classification operation can be carried out using a combination of sieving and sedimentation, for example, to easily obtain powder of a predetermined particle size. First, WC of a predetermined particle size
, Cr3C2, Vc in a predetermined amount and a predetermined amount of Ag or/and Cu with a predetermined particle size are prepared, and these are mixed,
Thereafter, a powder compact is obtained by pressure molding. Fe if necessary
, Co, and Ni may be mixed. Next, this powder compact is heated at a predetermined temperature, e.g.
Temporary sintering is performed at 50°C for 1 hour to obtain a temporary sintered body.Next, a predetermined amount and ratio of Ag or/and Cu is added to the remaining pores of this temporary sintered body at 1150°C for 1 hour. Infiltrated Ag or/
and obtain a Cu-WC-Cr3C or/and Vc alloy. Infiltration is primarily carried out in vacuum, but is also possible in hydrogen. The ratio of conductive components in the alloy (Ratio of Ag or/and Cu to WC-Cr3C or/and Vc was controlled as follows. For example, Ag or/and Cu
was vacuum melted at a temperature of 1200° C. and a degree of vacuum of 1.3×10 −2 Pa, cut, and used as a material for infiltration. When making a WC sintered body, a predetermined amount of Ag or/and a part of Cu is mixed in the WC in advance, and the remaining Ag is added afterwards.
A contact alloy with a desired composition can also be obtained by infiltrating Cu). Next, the evaluation method and evaluation conditions for obtaining specific example data, which will be described later, will be described. (1) Current cutting characteristics

[0023] A prefabricated vacuum valve with each contact attached and evacuated to 10-3 Pa or less was manufactured, and this device was installed at a height of 0.8 m.
The breaker current was measured when the electrode was opened at an opening speed of /second and a small current was cut off with a delay. Breaking current is 20A (effective value)
, 50Hz. The opening phase was randomly determined and the cutting current was measured for three contacts when the contacts were cut off 500 times, and the average and maximum values are shown in Table 1. Note that the numerical values are shown as relative values when the average value of the cutting current values of Example 2 in the same table is set to 1.0. (2) High frequency arc extinction characteristics

When a small current with a lagging power factor is switched on and off, if an overvoltage is generated on the load side due to current interruption, the difference between the overvoltage and the power supply voltage is applied between the poles of the vacuum valve. If the voltage between the electrodes exceeds the withstand voltage value of the contact spacing, dielectric breakdown occurs and discharge occurs, causing excessive high-frequency current to flow through the contacts. When this high-frequency current is cut off, the process returns to the initial stage and an overvoltage appears, which again causes a discharge in the contact gap, and the process repeats. Such a repeated phenomenon is well known as a multiple firing phenomenon. In circuit breakers with high high-frequency arc extinguishing ability, such as vacuum circuit breakers, large surge voltages can be generated due to multiple re-ignitions depending on the circuit conditions, which can threaten the insulation of load equipment (motors and transformers). Generally, it is said that the smaller the high-frequency arc extinguishing ability, the more difficult it is to repeat the re-ignition and the smaller the generated surge.

In order to examine the high frequency arc extinguishing characteristics of each contact, we manufactured a vacuum valve to which each contact was attached and evacuated to 10-3 Pa or less. A load current interruption test was conducted on a single-phase transformer. The length between the breaker and the transformer is 10
0m 6.6kV single core CV cable (conductor cross section 200
mm2). Load current is 10A (effective value),
The opening speed of the breaker was 0.8 m/sec (average), the opening phase of the breaker was controlled, and the circuit breaker was disconnected at a phase where multiple re-ignition occurred. The transient high-frequency current that flows through the contacts during multiple re-ignitions is caused by the inductance around the breaker, the power supply side,
The frequency of the transient high-frequency current is determined by the stray capacitance on the load side, and in this test, the frequency of the transient high-frequency current was approximately 10
It was 0kHz. To measure the high-frequency arc-extinguishing ability, 20 breaking tests were performed for each contact, and the average value of the high-frequency arc-extinguishing ability after 1 ms had elapsed after the contact was opened was determined. The values in Table 1 are shown as relative values when the average value of the high frequency arc extinguishing ability of Example 2 is set as 100. (3) Contents of the contact under test

Table 1 shows the material contents of the test contacts and their corresponding characteristic data along with comparative examples. As shown in the table, Ag or/and Cu-WC-Cr3 C or/and V
The amount of highly conductive components in the c alloy is 12.7wt% to 80.
5wt%, the amount of WC is 19.5wt to 87.3wt%,
In addition, the amount of Cr3C2 and/or Vc was varied within a range of 0 to 20% relative to the amount of WC. Furthermore, contacts using arc-resistant components (WC) having particle sizes of 0.1 μm to 44 μm were evaluated, and the results were studied. Table 1 shows these conditions and the corresponding results.

[0027]

[Table 1] Examples 1-4, Comparative Examples 1-4

WC powder with an average particle size of 0.7 μm and 3μ of Cr
3 Prepare C2 and Vc. Molding is performed while appropriately selecting a molding pressure in the range of 0 to 8 tons/cm2 so as to adjust the amount of voids remaining after sintering. In this case, in Example 3 (Ag = 50 wt%) and Comparative Example 2 (Ag = 72.2 wt%), which have a large amount of highly conductive components in the alloy, the molding pressure may be particularly low or the A method is adopted in which a mixed powder is obtained by mixing a part of (Ag+Cu) with WC and this is molded. After molding these mixed powders, Example 1 and Comparative Example 1
For example, Ag-
A WC sintered body is obtained. In Examples 2 to 3 and Comparative Example 2, sintered bodies are obtained by sintering at a lower sintering temperature. In this way, Ag is infiltrated into the voids of the sintered bodies with different void amounts, and the final Ag content in the Ag alloy is 12 to 72 wt% (Comparative Examples 1 to
2. Obtain the alloys of Examples 1 to 3). After processing these contact materials into predetermined shapes, the cutting characteristics and high-frequency arc-extinguishing characteristics were evaluated using the evaluation method and conditions described above.

As mentioned above, the evaluation of the cutting characteristics was 5.
A comparison was made based on the characteristics when cut off 00 times. As shown in Comparative Examples 1-2 and Examples 1-3 in Tables 1-2, A in the alloy
The average value of the cut value in terms of g amount is that of Example 2 (Ag=36.6
wt%) is 1.0, 2.0
Although the increase is less than double (deterioration of characteristics), Ag=1
2.7wt% (Comparative Example 1) and Ag=72.2wt%
In (Comparative Example 2), the maximum value is increasing, whereas A
When g is 20 to 50 wt% (Examples 1 to 3), the comparative value is stable at 2.0 times or less (good characteristics). Especially Ag=
The breaking characteristics of a contact with a small amount of Ag, such as 12.7wt% (Comparative Example 1), decreases to about 20% by cutting more times.
It can be seen that the cutting characteristics deteriorate from around 00 times of opening and closing.

On the other hand, when evaluating the high-frequency arc-extinguishing characteristics, when similarly examining the relative values with the characteristics of Example 2 as the standard,
Stable characteristics are shown when the Ag amount is 20 to 50 wt% (Examples 1 to 3), but when the Ag amount is 12.7 wt% (Comparative Example 1)
At 72.2 wt% (Comparative Example 2), the relative value tends to increase (deterioration of characteristics), and it is recognized that the relative value exceeds 200. Therefore Ag-WC-Cr3 C2
Or/and the amount of Ag in the Vc alloy is preferably in the range of 20 to 50 wt% from the viewpoint of both cutting characteristics and high frequency arc extinction characteristics.

Although the highly conductive component was shown to be Ag, (A
g+Cu), the amount is 20 to 50 wt as described above.
It is outside the range of %. Comparative example 3 (Ag+Cu=13.5w
Comparative Example 4 (Ag+Cu=80.5wt%) is inferior in both the cutting properties and high frequency arc extinction properties, but Example 4 (Ag+Cu=37.5wt%) which is within the above range
), both characteristics are preferable. Examples 5-9, Comparative Examples 5-8

In Examples 1 to 4 and Comparative Examples 1 to 4 described above, the amounts of Cr3 C2 and Vc as arc-resistant components other than WC were kept constant (the amount of Cr3 C2 relative to the amount of WC was 4.
5wt%, the amount of Vc relative to the amount of WC is 2.5wt%)
However, the contact used in the vacuum valve of the present invention is based on the amount of WC.
The amount of V2 is 1 to 10 wt% (Examples 5 to 6), and the amount of V
The amount of c in the range of 1 to 10 wt% (Examples 7 to 8) is also within a preferable range for both properties. On the other hand, Cr3 C2
The amount of Vc is 20wt% (Comparative Example 6), and the amount of Vc is also 20wt%.
% (Comparative Example 7), the current cutting characteristics are good, but the high frequency arc extinguishing characteristics in particular are markedly deteriorated, which is not preferable. Furthermore, in Comparative Example 8 where the total amount of Cr3 C2 and Vc is 1 wt% or less, the same deterioration in characteristics as described above is observed, but the total amount of Cr3 C2 and Vc is 1 wt% (Example 9).
In the case of , the maximum current cutoff value is stable at 2.0 or less, and the high frequency arc extinguishing characteristic is also stable at 200 or less. Examples 9-13, 15

In Examples 1 to 8 and Comparative Examples 1 to 8 described above, Ag and/or Cu were used as highly conductive components, and WC and Cr3 C2 or/and Vc were used as arc-resistant components at the contacts of the vacuum valve of the present invention. Although no other auxiliary materials are used, less than 1 wt% of Fe, Co is added to the above material system.
, Ni addition (Ag or/and Cu and WC, Cr3C
2 or/and Vc), stable characteristics are exhibited as shown in Examples 10 to 12 and 15. Stable characteristics were exhibited even when 1% of Fe, Co, and Ni (Example 13) coexisted. Example 14, Comparative Example 9

The average particle diameter of the WC particles of the contact material used in the vacuum valve of the present invention is 0.1 μm (Comparative Example 7) to 3 μm.
(Example 7), the average particle size of WC was within the preferable range even if it was 6 μm (Example 14), but when the average particle size of WC was 44 μm (comparison Example 9) The deterioration of the current cutting characteristics, especially the maximum value, varies considerably. As in the embodiments described above, Ag
or/and Cu, the total amount of the highly electric material consisting of Cu is controlled to a predetermined value, and the average particle size of WC is set to 6 μm or less, preferably 1 μm or less, and Cr3 C2 or/
and Vc, the current cutting characteristics can be maintained low and variations can be managed to be small, and the high frequency arc extinguishing characteristics can also be maintained sufficiently low at the same time.

[0035]

Effects of the Invention As described in detail above, according to the present invention, the current cutting characteristics can be maintained low and can be managed with little variation, and the high frequency arc extinguishing characteristics can also be maintained sufficiently low at the same time. We can provide contact materials for valves. Therefore, if the contact material according to the present invention is used for a vacuum valve contact, a vacuum valve with good current cutting characteristics and breaking characteristics can be obtained, resulting in a vacuum valve that further improves the stability of current cutting characteristics.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a vacuum valve showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the electrode part in FIG. 1.

[Explanation of symbols]

Claims (2)

[Claims] [Claim 1] 20 selected from Ag or/and Cu
~50% by weight of highly conductive component and 50-80% by weight of W
A contact material for a vacuum valve comprising an arc-resistant component consisting of carbon, characterized in that the arc-resistant component contains at least one of Cr or V carbide in an amount of 1 to 10% by weight based on WC. material. 2. The contact material for a vacuum valve according to claim 1, further comprising 1% by weight or less of an auxiliary component consisting of at least one of Fe, Co, and Ni.