JPH0574284A - Contact material for vacuum valve - Google Patents

Abstract

PURPOSE:To improve the current-chopping characteristics by constructing a structure containing respective specified percentages of a high-conduction component, an arc resisting material, and a sintering-promoter agent, which high- conduction component, arc resisting material and sintering-promoter agent have their respective specified proportions. CONSTITUTION:A vacuum bulb contact material is constructed of a high- conduction component consisting of one or more of Ag and Cu, an arc resisting material consisting of at least one selected from the group consisting of WC, MO2C, TaC, Cr2C3, and Ti, and a sintering-promoter agent consisting of at least one selected from the group consisting of Fe, Co, and Ni. In this contact material, the high-conduction component is 20 to 65vol.%, the Ag therein being set at 30wt% or more, while the sintering-promoter agent is set at 1wt% or more. The structure of this contact material is composed of a first region where the arc resisting material having a particle size of 3mum or less is finely and uniformly dispersed in the high-conduction component, and a second region consisting mainly of the high-conduction component having a width or particle size of 10mum or more, and the rate of the first region with respect to the total structure is set at 80vol.% or more.

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 which has excellent current cutting characteristics.

[0002]

2. Description of the Related Art The contact point of a vacuum valve for interrupting a current in a high vacuum by utilizing arc diffusivity in a vacuum is composed of two opposed and fixed 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 may occur and destroy load equipment. The cause of this abnormal surge voltage is, for example, a cutting phenomenon that occurs when a small current is cut off in a vacuum (the current is forcibly cut off without waiting for the natural zero point of the AC current waveform), or a high-frequency arc extinction phenomenon. Etc. The value Vs of the abnormal surge voltage due to the cutting phenomenon is determined by the surge in peace dance Zo · Ic of the circuit.
It is represented by. Therefore, in order to reduce the abnormal surge voltage Vs, the current cut value Ic must be reduced.

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

As another contact material exhibiting a low cutting current characteristic, an alloy composed of bismuth (Bi) and copper (Cu) is manufactured, and this material is put to practical use in a vacuum valve (special feature). Japanese Patent Publication 35-14974, U.S. Patent No. 29
75256, Japanese Patent Publication No. 41-12131, and U.S. Pat. No. 3,246,979). 10% by weight of Bi in this alloy
(Hereinafter, wt%) (Japanese Patent Publication No. 35-14974)
No. 4) has an appropriate vapor pressure characteristic, and thus exhibits a low cutting current characteristic, and a Bi content of 0.5 wt% (Japanese Patent Publication No. 41-12131) is segregated at the grain boundaries. As a result, the alloy itself becomes brittle and a low welding pull-off force is realized, which is excellent in blocking large currents.

As another contact material for obtaining a low cutting current characteristic, Ag-C in which the ratio of Ag and Cu is approximately 7: 3.
There is a u-WC alloy. In this alloy, since the ratio of Ag and Cu which is not limited to the conventional one is selected, 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 is also known to be effective in improving the low cutting current characteristic.

[0006]

A vacuum circuit breaker is required to have a low surge characteristic, 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 a more stable low cutting characteristic. Is becoming desired. The contact of the alloy in which WC and Ag are compounded (US Pat. No. 3,683,138) cannot be said to have a sufficiently low cutting current.

An alloy composed of 10 wt% of Bi and Cu (Japanese Patent Publication No. 35-14974, US Pat. No. 2,975,2).
No. 56), the amount of metal vapor supplied to the electrode space decreases as the number of switching circuits increases, and the low chopping current characteristic deteriorates. It is also pointed out that the withstand voltage characteristic deteriorates depending on the high vapor pressure element amount. .. Alloy in which 0.5 wt% of Bi and Cu are compounded (Japanese Patent Publication No. Sho 41-12131, US Pat. No. 3,246,97).
No. 9) also has insufficient low cutting current characteristics.

The weight ratio of Ag to Cu is about 7:
In the Ag-Cu-WC alloy described in No. 3 and the arc-resistant material having a particle size of 0.2 to 1 μm, the average current cutting characteristics are improved to some extent, but when opened and closed many times. The consideration of the maximum value of the cutting current value is insufficient.

The present invention has been made based on the above-mentioned background, and an object of the present invention is to provide a contact material for a vacuum circuit breaker having an extremely low current cutting characteristic, and a demand for a vacuum circuit breaker which becomes severe. Is to respond to.

[0011]

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

[0012]

In a composite material contact such as a sintered contact material, its current cutting characteristic is greatly influenced not only by the material composition but also by its structure. It is considered that the current cutting phenomenon is a phenomenon caused by the collapse of the balance of energy and matter in an extremely small area called a cathode spot.
In the case of a contact material represented by the present invention, which is represented by a contact material such as Ag-WC-Co, the diameter of the cathode spot is reduced to about 10 μm at the instant of current cutting. Therefore, if the material structure is not completely homogeneous up to this order, the cutting characteristics will vary depending on the composition of the place where the cathode point was present during 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, it is necessary to miniaturize the structure of the contact material to at least this order. That is, in most of the surface of the contact material, the internal composition with a diameter of 10 μm falls within the composition range shown in the claims.
It is necessary to control the 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, the 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 organization so that such unevenly distributed 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 is composed of an insulating container 2 formed of an insulating material in a substantially cylindrical shape, and metallic lids 4a and 4 provided on both ends of the insulating container 2 with sealing metal fittings 3a and 3b interposed therebetween.
It is vacuum-tightly constructed with b. A pair of electrodes 7 and 8 attached to opposite ends of the conductive rods 5 and 6 are arranged in the shutoff 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 so that the electrode 8 can be moved in the axial direction while keeping the inside of the blocking chamber 1 vacuum-tight. An arc shield 10 made of metal 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 arc vapor. Further, as shown in an enlarged view in FIG. 2, the electrode 8 is fixed to the conductive rod 6 by a brazing portion 12 or is crimp-connected by caulking. The contact 13a is brazed to the electrode 8 by brazing 14.
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 manufacturing, the arc resistant component and auxiliary component are classified according to the required particle size. The classification work is performed, for example, by using a sieving method and a sedimentation method together to easily obtain a powder having a predetermined particle size. First, WC and Co and / or C having a predetermined particle size
A predetermined amount of Ag and a predetermined amount of Ag having a predetermined particle size are partially prepared, and these are mixed and then pressure-molded to obtain a powder compact. Then, the powder compact is temporarily sintered in a hydrogen atmosphere having a dew point of −50 ° C. or lower or 1.3 × 10 ⁻¹ Pa or lower at a predetermined temperature, for example, 1150 ° C. for 1 hour, and then calcined. Get a union.

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

The ratio of the amount of conductive components in the alloy Ag / (A
The control of g + Cu) was performed 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 vacuum degree 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
A contact alloy having a desired composition can also be obtained by previously mixing a predetermined amount of a part in WC when forming the pre-sintered body.

The average inter-particle distance of WC is determined by the total amount of conductive components, the amount of conductive components preliminarily blended with WC during pre-sintering (hereinafter referred to as "preliminary blending amount"), WC particle size, and Co content. It is controlled by adjusting.

Next, the method for evaluating the current cutting characteristics and the evaluation conditions for obtaining the data of the embodiment of the present invention will be described. A prefabricated valve in which each contact was attached and which was evacuated to 10 ^-3 Pa or less was manufactured, and this device was opened at an opening speed of 0.8 m / sec to measure the cutting current when a delayed small current was cut off. The breaking current was 20 A (effective value) and 50 Hz. The opening phase was performed randomly, and the cutting current when interrupted 500 times was measured for three contact points, and the average value and maximum value thereof are shown in Tables 1 to 4. The numerical values are shown as relative values when the average cutting current value of Example 3 was set to 1.0, and when the maximum cutting current value was 3.5 or less, it was judged to be good. First, the composition conditions are fixed, and the tissue conditions are considered as parameters. 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.
o is about 0.7 wt%, the arc resistant material is WC, and the composition conditions are constant, and the arc resistant material having a particle size of 0.8 μm is finely and uniformly dispersed in the high conductive component. The cutting property was examined by changing the ratio of the first region to the entire tissue.

As a result, as shown in Tables 1 and 2, in Examples 1 to 3 in which the ratio of the first region is 80 vol% or more,
While the maximum cutting current value is 2.5 or less, which is good, in Comparative Examples 1 and 2 in which the cutting current value is 80 vol% or less, the maximum value is extremely high although the average value is relatively low. Is becoming It is presumed that this is because the current cutting is highly likely to occur in the second region, which is coarse and mainly contains the conductive component and has poor local cutting characteristics. Examples 4 to 6 and Comparative Example 3

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.
o is about 0.7 wt%, the arc resistant material is WC, and the first region in which the arc resistant material is finely and uniformly dispersed in the highly conductive component occupies 82 to 87 area% of the entire tissue. 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 cutting current value is 3.0 or less, which is good. In Comparative Example 3 of 9 μm, although the average value is 1.2, which is relatively low, the maximum value is 6.0, which is significantly high.
Such an extremely high cutting current value is presumed to occur on a coarse arc resistant material having poor cutting characteristics.

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

The ratio of Ag in the conductive component is 72 wt.
%, The Co content is 0.7 wt%, and only the total amount of the conductive component is changed.
As shown in Table 1 and Table 2, the conductive component amount 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 in both the average value and the maximum value. It is a value. This is because the amount of the arc resistant material is small and the effect of the addition thereof cannot be sufficiently obtained. On the other hand, in Comparative Example 5 in which the amount of the conductive component is about 17 vol%, the maximum value of the cutting current value is extremely high although the average value of the cutting current value is not so high. This is because the arc-resistant materials are so close to each other that the conductive component evaporates and is consumed due to repeated discharge, and the coarseness thereof has the same characteristics as the WC particles. Examples 10-12, Comparative Examples 6-7

The cutting characteristics when the conductive component amount is about 50 vol% and the Co content is 0.7 wt% and only the ratio of Ag in the conductive component is changed will be shown.
As shown in Tables 1 and 2, in Examples 10 to 12 in which the proportion of Ag is 30 wt% or more, the maximum cutting current value is 3.4.
The following is good, but this is 30 wt% or less of Comparative Example 6
At ~ 7, the cutting current value is high in both the average value and the maximum value. Examples 13 to 15 and Comparative Example 8

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

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

The amount of the conductive component, the ratio of Ag in the conductive component, the content of the sintering auxiliary component, and the WC, which are almost the same as those in Example 3,
In Examples 18 and 19 in which the sintering aids were Ni and Fe in particle size, the maximum 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 is used.
A highly conductive component composed of at least one of WC, Mo ₂
At least one of C, TaC, Cr ₂ C ₃ and TiC
In a contact material for a vacuum valve, which comprises an arc-resistant material made of one or more and a sintering aid made of at least one of Fe, Co, and Ni, the highly conductive component is 20 to 65 vol.
%, Of which the proportion of Ag is 30 wt% or more, the sintering aid is 1 wt% or less, and the organization is that the arc resistant material having a particle size of 3 μm or less is fine and uniform in the highly conductive component. The dispersed first region and the width or grain size is 10 μm
Since the above-mentioned second region is mainly composed of the high-conductivity component, and the ratio of the first region in the whole tissue is 80 vol% or more, the vacuum having stable and excellent current cutting property is obtained. A contact material for a valve can be obtained.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view of the electrode components of FIG.

[Fig. 3] Current cutting value of a typical contact material for vacuum valve-
Frequency characteristic diagram.

[Explanation of symbols]

 7, 8 ... Electrodes, 13a, 13b ... Contacts.

Claims (1)

[Claims] 1. A highly conductive component comprising at least one of Ag and Cu, and WC, Mo ₂ C, TaC and Cr.
_{In the} vacuum valve contact material comprising an arc resistant material made of at least one or more of ₂ C ₃ and TiC and a sintering aid made of at least one or more of Fe, Co and Ni, the high conductivity The composition is 20 to 65 vol%, the Ag proportion is 30 wt% or more, the sintering aid is 1 wt% or less, and the organization is that the particle size is 3 μm.
The first region in which the arc-resistant material of m or less is finely and uniformly dispersed in the highly conductive component, and the width or particle size is 10 μm.
The second region is mainly composed of the highly conductive component of m or more, and the ratio of the first region to the entire tissue is 80 vol.
% Or more contact material for vacuum valve.