JP2904452B2 - Contact material for vacuum valve - Google Patents

Description

DETAILED DESCRIPTION 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.

[0002]

2. Description of the Related Art The contacts of a vacuum valve for interrupting a current in a high vacuum by utilizing arc diffusivity in a vacuum are composed of two fixed and movable contacts facing each other. When the current of an inductive circuit such as a motor load is cut off by using this vacuum valve, an excessive abnormal surge voltage may be generated to destroy the load device. The cause of the abnormal surge voltage is, for example, a cutting phenomenon that occurs when a small current is interrupted in a vacuum (current interruption is performed without waiting for a natural zero point of an AC current waveform) or a high-frequency arc extinguishing phenomenon And so on. The value of the abnormal surge voltage Vs due to the cutting phenomenon is the surge impulse dance Zo · Ic of the circuit.
It is represented by Therefore, in order to lower the abnormal surge voltage Vs, the current cutoff value Ic must be reduced.

In response to the above requirements, a vacuum switch using a contact made of an alloy of a composite of tungsten carbide (WC) and silver (Ag) has been developed (US Pat. No. 3,683,138).
No.) has been put to practical use. The contact of the Ag-WC alloy has the following characteristics. (1) The presence of WC facilitates electron emission. (2) The evaporation of the contact material based on the heating of the electrode surface by the collision of the field emission electrons is promoted. (3) The carbide of the contact material is decomposed by the arc to generate a charged body and connect the arc.

Further, as another contact material exhibiting a low cutting current characteristic, an alloy in which bismuth (Bi) and copper (Cu) are compounded has been manufactured, and this material has been put to practical use in a vacuum valve (see, for example, Japanese Patent Application Laid-Open No. H11-157556). No. 35-14974, U.S. Pat. No. 29
No. 75256, Japanese Patent Publication No. 41-12131, U.S. Pat. No. 3,246,979). 10% by weight of Bi in this alloy
(Hereinafter referred to as wt%) (Japanese Patent Publication No. 35-14974).
No.) has a low cutting current characteristic since it has an appropriate vapor pressure characteristic, and the one in which Bi is 0.5 wt% (Japanese Patent Publication No. 41-12131) is segregated at crystal grain boundaries. As a result, the alloy itself is embrittled to realize a low welding pull-off force, and is excellent in large current interrupting properties.

[0005] As another contact material for obtaining low cutting current characteristics, Ag-C, in which the ratio of Ag to Cu is approximately 7: 3, is used.
There is a u-WC alloy. In this alloy, a ratio of Ag and Cu, which has never been limited, is selected, so that stable cutting current characteristics are exhibited. Further, by setting the grain boundary of the arc-resistant material (for example, the grain boundary of WC) to 0.2 to 1 μm,
It has also been found that it is effective for improving low cutting current characteristics.

[0006]

The vacuum circuit breaker is required to have a low surge property, and for that purpose, a low cutting current characteristic is required.

However, in recent years, the vacuum valve has been more and more applied to inductive circuits such as large-capacity electric motors, and a high surge impedance load has appeared. Therefore, the vacuum valve has more stable and low cutting characteristics. It has come to be desired. In the case of an alloy contact made of a composite of WC and Ag (US Pat. No. 3,683,138), the cutting current is not sufficiently low.

An alloy in which 10 wt% of Bi and Cu are compounded (Japanese Patent Publication No. 35-14974, US Pat.
No. 56), it is pointed out that the supply amount of metal vapor to the electrode space decreases with the increase in the switching circuit, and the low cutting current characteristics deteriorate, and the withstand voltage characteristics deteriorate depending on the high vapor pressure element amount. . Alloy containing 0.5 wt% of Bi and Cu (Japanese Patent Publication No. 41-12131, U.S. Pat. No. 3,246,976)
No. 9) also has insufficient low cutting current characteristics.

The weight ratio of Ag to Cu is approximately 7:
In the case of Ag-Cu-WC alloy and the alloy whose arc-resistant material has a particle size of 0.2 to 1 μm, although the average current cutting characteristics are improved to some extent, when the alloy is opened and closed many times, Of the maximum cutting current value is insufficient.

The present invention has been made on the basis of the above background, and has as its object to provide a contact material for a vacuum circuit breaker having extremely low current cutting characteristics, and to meet a demand for a severer vacuum circuit breaker. It is to respond to.

[0011]

In order to achieve the above-mentioned object, the present invention provides a high-conductivity component comprising Ag and / or Cu and at least one of WC, Mo ₂ C, TaC, Cr ₂ C ₃ and TiC. One or more arc resistant materials, Fe, C
o, a sintering aid composed of at least one of Ni, the composition of which is 20 to 65 v
ol%, and the ratio of Ag in the high conductive component is 30 w
t% or more, and the sintering aid is 1 wt% or less, and its structure is that the arc-resistant material having a particle size of 3 μm or less is finely and uniformly dispersed in the highly conductive component. The second region is mainly composed of a region and a conductive component having a width or a particle size of 10 μm or more, and the ratio of the first region to the whole tissue is 80%.
It is a contact material for a vacuum valve in which the content is at least vol.

[0012]

In a composite material contact such as a sintered contact material, the current cutting characteristics are greatly affected by not only the material composition but also the organization thereof. This is considered to be because the current cutting phenomenon is a phenomenon that occurs due to the collapse of the energy and material balance in a very small area called the cathode spot.
For example, in the case of a contact material such as a contact material such as Ag-WC-Co as shown in the present invention, the diameter of the cathode spot is reduced to about 10 μm at the moment of current cutting. For this reason, if the material structure is not completely homogeneous to this order, the cutting characteristics will differ depending on the composition of the place where the cathode spot was present at the time of current cutting, and the statistical distribution form of the cutting current value is As shown in FIG. 3, a composite distribution of several distributions results. Therefore, in order to generate a sufficiently low and stable cutting current value, the structure of the contact material must be miniaturized to at least this order. That is, in most parts of the surface of the contact material, the composition inside the 10 μm diameter is in the composition range shown in the claims.
You need to control that organization.

The contact material having the composition shown in the present invention is:
The cutting current value is reduced on average by adding an appropriate amount of a high melting point arc-resistant material to the conductive component. Therefore, a portion where the conductive component is unevenly distributed and the arc-resistant material is relatively low is disadvantageous in cutting characteristics. That is, as shown in the present invention, it is important to control the structure so that such an uneven distribution region of the conductive component is reduced.

[0014]

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

In FIG. 1, a shut-off chamber 1 comprises an insulating container 2 formed of an insulating material in a substantially cylindrical shape, and metal lids 4a, 4a provided at both ends thereof through sealing fittings 3a, 3b.
and b. A pair of electrodes 7 and 8 attached to the opposite ends of the conductive rods 5 and 6 are provided in the shut-off chamber 1, and the upper electrode 7 is a fixed electrode and the lower electrode 8 is a movable electrode. . A bellows 9 is attached to the electrode rod 6 of the electrode 8 to enable the electrode 8 to move in the axial direction while keeping the inside of the shut-off 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. Further, a metal arc shield 11 is provided in the shut-off chamber 1 so as to cover the electrodes 7 and 8, thereby preventing the insulating container 2 from being covered with the arc vapor. Further, as shown in an enlarged manner in FIG. 2, the electrode 8 is fixed to the conductive rod 6 by a brazing portion 12 or is connected by crimping by crimping. The contact 13a is attached to the electrode 8 by brazing.
The contact 13b is attached to the electrode 7 by brazing.

Next, an example of a method for manufacturing the contact material will be described. Prior to production, the arc resistant components and auxiliary components are classified according to the required particle size. The classification operation is performed by using, for example, a sieving method and a sedimentation method in combination to easily obtain a powder having a predetermined particle size. First, WC of a predetermined particle size and Co and / or C
A predetermined amount of Ag and a predetermined amount of Ag having a predetermined particle size are prepared, mixed, and then pressed to obtain a powder compact. Then, the powder compact is temporarily sintered under a hydrogen atmosphere having a dew point of −50 ° C. or less or 1.3 × 10 ⁻¹ Pa or less at a predetermined temperature, for example, 1150 ° C. for 1 hour. Get the unity.

Then, a predetermined amount and a predetermined ratio of Ag-Cu are infiltrated into the remaining pores of the temporary sintered body at 1150 ° C. for 1 hour to obtain an Ag-Cu-Co-WC alloy. The infiltration is performed mainly in a vacuum, but is also possible in hydrogen.

The ratio Ag / (A) of the amount of the conductive component in the alloy is
g + Cu) was controlled as follows. For example, an ingot having a predetermined ratio of Ag / (Ag + 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. Another method of controlling the ratio Ag / (Ag + Cu) of the conductive component is as follows.
When preparing a pre-sintered body, a contact alloy having a desired composition can be obtained by previously mixing a predetermined amount of a part in WC.

The average distance between WC particles is defined as the total amount of the conductive component, the amount of the conductive component preliminarily blended into the WC at the time of preliminary sintering (hereinafter referred to as the preblended amount), the WC particle size, and the Co content. Is controlled by adjusting.

Next, a description will be given of an evaluation method and evaluation conditions of the current cutting characteristics obtained from the data of the embodiment of the present invention. An assembling valve evacuated to 10 ⁻³ Pa or less with each contact attached was manufactured, and this device was opened at an opening speed of 0.8 m / sec, and the cutting current when the delay small current was cut off was measured. The breaking current was 20 A (effective value) and 50 Hz. The opening phase was performed randomly, and the cutting current when the circuit was cut off 500 times was measured for three contacts, and the average and maximum values are shown in Tables 1 to 4. The numerical values are shown as relative values when the average value of the cutting current values in Example 3 was set to 1.0, and when the maximum value of the cutting current values was 3.5 or less, it was judged to be good. First, the composition condition is fixed, and the organization condition is considered as a parameter. Examples 1-3, Comparative Examples 1-2

The total amount of the conductive component is about 50 vol%, the ratio of Ag in the conductive component is about 72 wt%, and the sintering aid is C
The arc-resistant material having a particle size of 0.8 μm is finely and uniformly dispersed in the high-conductivity component under the conditions that the composition conditions are constant, with about 0.7 wt% in o and the arc-resistant material being WC. The ratio of the first region to the whole tissue was changed, and the cutting characteristics were examined.

As a result, in Examples 1 to 3 in which the ratio of the first region is 80 vol% or more as shown in Tables 1 and 2,
The maximum value of the cutting current value is 2.5 or less, which is good. On the other hand, in Comparative Examples 1 and 2 in which the maximum value is 80 vol% or less, the maximum value is extremely high although the average value is relatively low. Has become. This is presumed to be due to the high probability of current cutting occurring in the second region, which is coarse and mainly composed of conductive components, and has poor local cutting characteristics. Examples 4 to 6, Comparative Example 3

The total amount of the conductive component is about 50 vol%, the proportion of Ag in the conductive component is about 72 wt%, and the sintering aid is C
o is about 0.7 wt%, the arc-resistant material is WC, and the ratio of the first region where the arc-resistant material is finely and uniformly dispersed in the highly conductive component to the entire tissue is 82 to 87 area%. And the cutting characteristics were evaluated using the particle size of the arc-resistant material as a parameter.

As a result, as shown in Tables 1 and 2, in Examples 3 to 6 in which the WC particle size is 3 μm or less, the maximum value of the cutting current value is 3.0 or less, which is good. In Comparative Example 3 where this is 9 μm, although the average value is relatively low at 1.2, the maximum value is significantly high at 6.0.
It is estimated that such an extremely high cutting current value is generated on a coarse arc-resistant material having poor cutting characteristics.

Next, cutting characteristics when the composition conditions were changed and the composition was changed were examined. First, the sintering aid is C
o, Ag / Cu-WC-Co contact material system using WC as the arc resistant material was studied. The constant composition condition is WC
The particle size was 0.8 μm, and the first region where the arc-resistant material was finely and uniformly dispersed in the conductive component was 80% by area. Examples 7 to 9, Comparative Examples 4 to 5

The proportion of Ag in the conductive component is 72 wt.
% And the Co content is 0.7 wt%, and the cutting characteristics are shown when only the total amount of the conductive components is changed.
As shown in Tables 1 and 2, the amount of the conductive component is 20 to 65 vol.
%, The cutting current value is good at 2.9 or less, but in Comparative Example 4 in which the amount of the conductive component is about 71 vol%, the cutting current value is high both in the average value and the maximum value. Value. This is because the effect of the addition cannot be sufficiently obtained because the amount of the arc-resistant material is small. On the other hand, in Comparative Example 5 in which the amount of the conductive component is about 17 vol%, the maximum value is extremely high even though the average value of the cutting current value is not so high. This is because the distance between the arc-resistant materials became very close, and the portion where the conductive component was evaporated and consumed by the repeated discharge had coarseness similar to that of the WC particles. Examples 10 to 12, Comparative Examples 6 and 7

The cutting characteristics when the amount of the conductive component is about 50 vol%, the Co content is 0.7 wt%, and only the ratio of Ag in the conductive component is changed are shown.
As shown in Tables 1 and 2, in Examples 10 to 12 in which the ratio of Ag was 30 wt% or more, the maximum value of the cutting current value was 3.4.
Comparative Example 6 where the content is 30 wt% or less.
In Nos. To 7, the cutting current value is a high value for both the average value and the maximum value. Examples 13 to 15 and Comparative Example 8

The cutting characteristics when the amount of the conductive component is about 50 vol%, the ratio of Ag in the conductive component is about 72 wt%, and only the Co content is changed are shown.
As shown in Tables 1 and 2, in Examples 13 to 15 in which the Co content is 1 wt% or less, the maximum value of the cutting current value is 3.4 or less, which is good. However, Comparative Example 8 in which this is 1.9 wt%. In the figure, the cutting current value is a high value for both the average value and the maximum value. Next, Tables 3 and 4 show cutting characteristics when Mo ₂ C and TaC are used as arc-resistant materials and when Ni and Fe are used as sintering aids. Examples 16 to 17

The amounts of the conductive components, the proportion of Ag in the conductive components, the Co content, and the particle size of the arc-resistant material were almost the same as those in Example 3, and the components of the arc-resistant material were Mo ₂ C, TaC, Cr ₂ C ₃ and In Examples 16, 17, 18 and 19 of TiC, the maximum values of the cutting current values were 2.6, 2.3, 2.5 and 2.8, respectively, and all showed good current cutting characteristics. Examples 18 to 19

The amount of the conductive component, the ratio of Ag in the conductive component, the content of the sintering auxiliary component, and
In Examples 18 and 19 in which the sintering assisting components were Ni and Fe in terms of particle size, the maximum values of the cutting current values were 2.5 and 2.6, respectively, and both showed good current cutting characteristics.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

As described above, according to the present invention, Ag or Cu
A highly conductive component comprising at least one of the following: WC, Mo ₂
At least one of C, TaC, Cr ₂ C ₃ and TiC
In a vacuum valve contact material comprising at least one arc-resistant material and at least one of Fe, Co, and Ni, a high conductive component is 20 to 65 vol.
% Of which is 30% by weight or more, the sintering aid is 1% by weight or less, and the structure is such that an arc-resistant material having a particle size of 3 μm or less is finely and uniformly dispersed in a highly conductive component. A dispersed first region and a width or particle size of 10 μm
Since the above-described high-conductivity component is mainly composed of the second region, and the ratio of the first region to all the tissues is 80 vol% or more, the vacuum having stable and excellent current cutting characteristics is obtained. A valve contact material can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of an electrode component shown in FIG.

FIG. 3 shows current cutting values of typical contact materials for vacuum valves.
Frequency characteristic diagram.

[Explanation of symbols]

 7, 8 ... electrodes, 13a, 13b ... contacts.

Continuation of front page (56) References JP-A-2-228438 (JP, A) JP-A-62-77439 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01H 33 / 66

Claims (1)

(57) [Claims] 1. A highly conductive component comprising at least one of Ag or Cu, WC, Mo ₂ C, TaC, Cr
_{2. A} vacuum valve contact material comprising: an arc-resistant material made of at least one of ₂ C ₃ and TiC; and a sintering aid made of at least one of Fe, Co, and Ni. The components are 20 to 65 vol%, of which the ratio of Ag is 30 wt% or more, the sintering aid is 1 wt% or less, and the organization is as follows:
m and a first region in which the arc-resistant material of not more than m is finely and uniformly dispersed in the highly conductive component, and a width or a particle size of 10 μm.
m or more of the high-conductivity component is composed of the second region mainly composed of 80 vol.
% Of a contact material for a vacuum valve.