JPH0788543B2 - Contact alloy for vacuum valve - Google Patents

Description

The present invention relates to a vacuum valve, and more particularly to a contact alloy for a vacuum valve having improved temperature rising characteristics and contact resistance characteristics.

(Prior Art) The characteristics required for a contact material for a vacuum valve are that there are three basic requirements indicated by each performance against welding resistance, withstand voltage, and breaking, and that temperature rise and contact resistance are low and stable. Is an important requirement. However, due to conflicting requirements, it is not possible to meet all requirements with a single metal species.
Therefore, in many practical contact materials,
We have developed contact materials that combine two or more elements that complement each other's lacking performance and that are suitable for specific applications such as for large currents or high voltages, and have excellent characteristics as such. Although materials have been developed, the reality is that no contact material for vacuum valves has yet been obtained that sufficiently satisfies the requirements for higher breakdown voltage and higher current.

For example, a Cu-Bi alloy containing an anti-fusing component such as Bi in an amount of 5% or less is known as a contact material aimed at increasing the current (Japanese Patent Publication No. 41-12131). Since the solubility of Bi in the phase is extremely low, segregation often occurs, surface roughness after cutting is large, and work forming is difficult.

In addition, as another contact material aimed at increasing the current, Cu-Te
Alloys are also known (Japanese Patent Publication No. 44-23751). Although this alloy alleviates the above problems of the Cu-Bi alloy, it is more sensitive to the atmosphere than the Cu-Bi alloy and lacks stability such as contact resistance. In addition, these Cu
-As a common feature of contacts such as Te, Cu-Bi, etc., although it has excellent welding resistance, even if the withstand voltage characteristics are sufficient for application to the conventional medium voltage class, It has become clear that the above application is not always satisfactory.

On the other hand, Cu (or
Sintered alloys of highly conductive components such as Ag) and Cr are known.
However, since Cr is a metal that is extremely easily oxidized, it is needless to say that the control of the powder or the molded body is important, but the conditions of the atmosphere during calcination and infiltration also influence the material properties. For example, even in the case of Cu-Cr alloys obtained by adequately controlling the temperature and time during pre-sintering and infiltration, there are variations and instabilities in the contact resistance or temperature rise characteristics. Those that are stable are desired.

As a means for solving these problems, conventionally, a technique of forming a thin layer of Cu or Ag on the contact surface of a Cu-Cr alloy contact by plating, or Cr particles exposed on the contact surface of the contact. Techniques for removing such are being implemented.

(Problems to be solved by the invention) In the conventional technique of forming a thin layer of Cu or the like on the surface of a contact, stable contact resistance characteristics can be obtained when the thickness is sufficient, but Stabilization of temperature rise characteristics cannot be achieved only by formation.

Since the above-mentioned findings and instability of properties are also found to be correlated with the production lot of Cu-Cr material, considering these together,
It is suggested that the contact material has a great influence.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a contact alloy material for a vacuum valve, which can stabilize both contact resistance characteristics and temperature rise characteristics.

[Structure of Invention]

(Means and Actions for Solving Problems) The contact alloy for a vacuum valve according to the present invention is Mo, W, V, N.
C containing at least 50% by weight of at least one selected from b and Ta
r and the balance Cu or / and Ag, and the amount of Cr solid-dissolved in the Cu or / and Ag is 0.01 to 0.35 wt% based on 100 wt% of the Cu or / and Ag. There is.

As described above, the contact alloy according to the present invention is Cu (or / and A
g) -Cr group (50 wt% or less with respect to Cr, 0.2 wt% or more of Mo,
Cu in the alloy containing at least one of W, V, Nb and Ta)
(Or / and Ag) 0.01 ~ 0.35
Since the content is limited to the wt% range, stable temperature rise characteristics and contact resistance characteristics can be obtained when this alloy is used as a contact alloy for vacuum valves.

Furthermore, in the present invention, the use of Cr containing 10 ppm or less, 20 ppm or less, 10 ppm or less, and 10 ppm or less of Al, Si, V, and Ca in the raw material Cr further promotes the stabilization of the above characteristics. be able to.

(Specific Description of the Invention) The contact alloy for a vacuum valve according to the present invention will be described in more detail below.

In the present invention, Cu (or / and Ag) -Cr alloys containing at least one of Mo, W, V, Nb and Ta in a predetermined amount are collectively referred to as Cu (or / and Ag) -Cr. Use as the base contact material.

Studies have shown that the instability of Cu-Cr based contact materials is
It was found to depend on the compositional variation in the Cu-Cr based alloy, the particle size of Cr particles, the viscosity distribution, the degree of segregation, and the degree of vacancies present in the alloy. And these solutions are raw materials
Although it was recognized that the selection of Cr and the control of the sintering technology are effective, in order to improve the maintenance of stability further, in addition to the above ,,, and more detailed material and sintering technology management I found it necessary. That is, it was found that the instability of the above properties is correlated with the difference in the amount of Cr slightly contained in the Cu phase. That is, the amount of Cr contained in the Cu portion in the Cu-Cr-based alloy is estimated by a semi-quantitative method by the method described below, the Cu-Cr-based alloy showed an unstable value of the characteristics, generally 0.5 ~ 0.2 wt% Cu that exhibits stable characteristics according to the present invention described later, while varying in the range of
That of the --Cr-based alloy showed a value near 0.2%. In a Cu (or / and Ag) -Cr-based contact material containing a predetermined amount of at least one of Mo, W, V, Nb and Ta
The amount of Cr that forms a solid solution in the Cu portion is within the specified range, that is, 0.01 to 0.35
It has been found that the strict limitation to the weight% is extremely effective for improving the temperature rise characteristic and the contact resistance characteristic or reducing the variation width.

In other words, the reduction of re-ignition phenomenon and re-ignition phenomenon of the vacuum valve has been attracting attention because of the effect of suppressing the amount of Al and Si in the alloy, but these values are kept at a certain level, for example, 10 ppm.
Even if kept at ~ 20ppm or less, the total reliability of the vacuum valve still remains uncertain about the stabilization of the temperature rise characteristic and the contact resistance characteristic, and the present inventors have been overlooked in the past. The attention was paid to the influence of the amount of Cr, which is the other main element contained in the Cu phase in the alloy, that is, to the total amount of Cr (20 to 80 wt%) contained in the alloy. Sufficient properties were not obtained, rather the above-mentioned Cu
We have found that it is important to pay attention to the amounts of these main component elements, Cr, which are present in trace amounts in the phase. According to the knowledge of the present inventors, the amount of Cr in the Cu phase in the alloy is the raw material used.
Cr originally contained in Cu, other main component Cr
Depends on Cr penetrating into Cu from Cu. As a measure to reduce these Cr in the Cu phase as much as possible, for the former, adopt a raw material Cu containing as few impurity elements as possible, or
For ordinary raw material Cu, it is effective to make it highly purified in advance by the zone melting method, and for the latter, Cu
Whether to lower the temperature of high temperature treatment in the alloying process of Cr and Cr,
It is effective to shorten the time and it is effective to rationally control the cooling process after the alloying process.

With a vacuum valve, generally, when a predetermined current value is given,
It is desired that the temperature rise at the valve terminal portion be below a certain value, which is mentioned as one of the important characteristics.

The temperature rise value is mainly determined by the energization current value, the thermal conductivity of the main circuit, the heat radiation efficiency, the electric resistance, etc., but the electric resistance value is an important factor. The electrical resistance is composed of the resistance of the conductive shaft (usually Cu, specific resistance = 1.7 μΩcm) and the resistance of the contact (in the present invention, 20-80% Cu-Cr alloy), but a film is formed on the contact surface. It is necessary to add the contact resistance when there is such a thing, the contact resistance depending on the load to be selected, etc. If there is a magnetic field generating coil (usually Cu), this resistance is also added It becomes resistance. Here, the resistance of the conductive shaft can be set to a fixed value depending on the design size, and the contact resistance can also be a stable fixed value if a sufficient contact load is applied, and the magnetic field generating coil can also be designed. It depends on the above dimensions and can be a constant value. Therefore, the electrical resistance between the main circuits is considered to be due to the excessive variation in the resistance of the material of the contact material itself of the present invention, and the degree of this variation is the Cu-Cr value described above.
It has been found by experiments by the present inventors that it correlates with the amount of Cr in the Cu phase in the base contact material.

(Example) Next, a contact alloy according to an example of the present invention will be described more specifically including a manufacturing method.

The raw material used in the present invention comprises an arc-resistant material consisting of Cr and Mo, W, V, Nb or Ta which has been thoroughly degassed and whose surface has been cleaned, and / or Cu and / or Ag. And a conductive material. In addition, these Cr, C
In addition to u, Ag, Te, Bi, Sb of about 10% or less depending on the contact application
A welding resistant material such as or Fe or Co may be added as an auxiliary component. If the grain size of Cr exceeds 250 μm, the probability of contact between pure Cu and Ag parts is high, which is not preferable from the viewpoint of welding resistance, but there is a lower limit of grain size for exhibiting the effect of the present invention. Instead, the lower limit may be determined from the viewpoint of handling such as increase in activity.

Further, the heating conditions for obtaining the contact alloy may be either a method of completing at a melting point of Cu or Ag or lower, and a method of heating at a melting point of Cu or Ag or higher and infiltrating it. Also in the method, Cr in the Cu member (or Ag member) in the alloy
Controlling the amount of is very important for achieving the above-mentioned object of the present invention.

On the other hand, the skeleton is made of Cr containing at least one of Mo, W, V, Nb, and Ta, or is mixed with a small amount of Cu or / and Ag in advance, and the contact material of the present invention A similar effect can be obtained.

As the raw material Cu, it is preferable to use, for example, electrolytic Cu that has been crushed and sieved in an inert atmosphere such as argon gas.

Regarding the raw materials Cr, Mo, W, V, Nb, and Ta, it is preferable to use impurities containing as little impurities as possible, such as Al, Si, and Ca.

The contact resistance characteristic and the temperature rise characteristic in the present invention are obtained as follows.

The contact resistance is 50mm in diameter with a surface roughness of 5μm.
10 ^-5 Torr with a flat electrode and a convex electrode with the same surface roughness and a radius of curvature of 100 R facing each other
Attach the electrode in the inside of the detachable vacuum container and apply a load of 3 kg. Then, the contact resistance is obtained from the potential effect when an alternating current is applied to both electrodes 10A. The contact resistance value is a value that includes the resistance or contact resistance of the wiring material, switch, measuring instrument, etc. that form the measurement circuit as a circuit constant.

On the other hand, the temperature rise characteristics are as follows: electrodes with the same electrode conditions as above facing each other and a contact force of 500 kg in a vacuum container of 10 ^-5 Torr
The maximum temperature when 00A was continuously energized for 1 hour was determined at the movable shaft. The temperature is a comparative value including the ambient temperature of about 25 ° C. and the influence of the heat capacity of the holder to which the electrode is attached.

In addition, the contact resistance values are 1.8 to 2.5 μΩ for the shaft of the removable vacuum switchgear itself and 5.2 for the magnetic field generating coil.
It contains 6.0 μΩ, and the rest is the contact point (contact alloy resistance, same contact resistance) value.

In addition, the content of Cr in the Cu phase in the Cu-Cr-based contact material was determined as follows (note that since each Cu-Cr-based contact material was determined by almost the same method, a typical example is shown here). Shown).

That is, Cu-Cr base contact material was cut to prepare powder, 1g of which was placed in a beaker and 50 ml of 3N nitric acid was added and heated at 100 ° C for 30 minutes, and after cooling, the solution was filtered to obtain undecomposed Cr particles. Cu
The phases were separated, and the filtrate was diluted with distilled water to obtain a test solution for determining impurities in the Cu phase, which was determined by inductively coupled plasma emission spectroscopy under the conditions shown in Table 1 below. Table 1 (Measurement conditions of inductively coupled plasma emission spectroscopy) Frequency 27.12MHz High frequency output 1.3KW Cooling gas 16.5l / min Nebulizer gas 0.4l / min Plasma gas 0.8l / min Measurement wavelength Cr: 267.7nm First, contact 125 μm on average for the entire alloy manufacturing process
A molded body obtained by molding Cr at a pressure of 2 ton / cm ² is housed in a carbon container and temporarily sintered at 1000 ° C. for 1 hour in vacuum. An infiltrant made of Cu (oxygen-free copper) is placed under the temporary sintered body, and then the infiltration process is performed at a vacuum temperature of 1200 ° C. for 1 hour. Next, after completing the infiltration process, contact alloy material 12
Cool from 00 ° C at 0.6 to 6 ° C / min.

Cu containing about 40 wt% Cr and about 10 wt% Mo-
In the Cr-based contact material, various amounts of Cr in the Cu phase are selected,
After processing into a predetermined contact shape, each alloy sample was attached to the detachable test device and subjected to an electrification test under the predetermined conditions. As can be seen from the results in Table 2 below, as the Cr content in the Cu phase increases, the temperature rises, but especially the Cr content is 0.35%.
In the following (Examples 1 to 4), the temperature rise value of the movable shaft portion was 70 ° C. or lower, whereas it was 0.59% (Comparative Example 2) when cooled at a rate of 6.5 ° C./min. , The temperature rise value
It was found to exceed 70 ° C (Table 2). Although it is difficult to make a precise explanation to distinguish at 70 ° C, the assembled switchgear used in this experiment has a thermal configuration (arrangement of members and heat capacity, etc.) that is very close to that of a general vacuum valve. Because
It can be considered that a certain degree of correspondence has been obtained. In other words, with a normal vacuum valve, an increase of 65 ° C is one standard, and according to the experimental conversion, it is 70% of this detachable switchgear.
C corresponds approximately.

The above tendency is the result of investigation on the contact in which the total Cr in the Cu—Cr based contact material is about 40%, but the amount of Cr is 55.2%, and the amount of Mo is almost 10% (Example 5), 69.2% and Mo. Is increased to about 10% (Example 6), when the amount of Cr in the Cu phase is within about 0.35%, a stable temperature rise characteristic is seen, but Cu-Cr
In the contact alloy in which the total amount of Cr in the base contact material is 80.7% and the amount of Mo is almost 10% (Comparative Example 3), the amount of Cr in the Cu member is 0.35.
% Or less (Comparative Example 3), stable temperature characteristics cannot be secured. Regarding the contact resistance characteristics, the low contact resistance value is maintained when the amount of Cr in the Cu phase is 0.35% or less (Examples 1 to 4), but in Comparative Example 2 with 0.35% or more, high contact resistance characteristics are obtained. Show.

In addition, Examples 1 to 4 in which the amount of Cr is about 40% and the amount of Mo is about 10%,
And the withstand voltage characteristics of the Cu-Cr based contact material shown in Comparative Example 2 are about the same as those of the Cu-Cr contact material containing no Mo (Comparative Example 1).
30% excessive, superior. This tendency is shown in Examples 5 and 6 (Cr
The amount is about 50-70%, and the amount of Mo is about 10%). Further, as in Example 7, the superiority is recognized even if the Co amount is excessive by 0.1%. In the present invention, the presence of Mo in the arc resistant material is effective from the viewpoint of withstand voltage, and the Co amount is Example 9
It is also effective for Cu-Cr-based contact materials that are present in larger amounts as shown in (Table 2).

Although the above was shown for the Cu-Cr-Mo contact material, the main point of the contact material of the present invention is that the Cu or / and Ag phases
When suppressing the Cr content in the Cr phase within a predetermined value, that is, within 0.35 wt%, another Cu—Cr-based contact material, that is, as shown in Table 3, Cu—Cr—W (Example 10), The same effect was observed in Cu-Cr-Ta (Example 13) -based contact materials (Examples 10 to 18).

Further, even if Ag is used as the highly conductive material, the same effect can be obtained when the amount of Cr in the Ag phase is controlled within a predetermined amount (Examples 17 to 18).

As described above, in the Cu-Cr-based and Ag-Cr-based contact alloy materials of the present invention, the amount of Cr in the high-conductivity material (Cu or / and Ag phase) is high in both temperature rise characteristics and contact resistance characteristics. Good characteristics are exhibited by controlling within a predetermined amount. The lower limit of the amount of arc resistant material is often determined from other aspects such as contact wear resistance and welding resistance and cutoff characteristics, but especially Cu
Or / and Ag highly conductive material, if less than 20%,
Sufficient cut-off characteristics cannot be secured, and if it is 80% or more, it becomes insufficient from the viewpoint of wear resistance and withstand voltage characteristics.

Also, Cr and other arc resistant materials (ie W, Mo, V,
The amount of Nb, Ta) is the above-mentioned highly conductive material (Cu or / and Ag).
Is the residual amount of these, but these ratios (W, Mo, V, Nb,
As for the ratio of at least one of Nb and Ta to Cr), it is essential that Cr is present in an amount of 50% or more, particularly from the viewpoint of securing a large capacity breaking performance.

Due to the above, Cu in Cu and / or Ag-Cr based contact materials
Or, and / or the upper limit of the amount of Cr in the Ag phase is 0.35 wt%, and the lower limit is preferably lower, but some intrusion during production (sintering and / or infiltration) Inevitable, 0.
About 01 wt% exists inevitably, and this is considered to be the practical lower limit.

Incidentally, Al in the raw material Cr, the amount of Si and Ca also has an important influence on the reduction of re-ignition characteristics, for example Al in Cr used in this example is 100 ppm or less, preferably 10 ppm or less, Si is 20 ppm or less and Ca is 10 ppm or less, and the effect of the present invention is further promoted by setting such an upper limit.

〔The invention's effect〕

As can be understood from the results of the above examples, the vacuum valve welding point alloy according to the present invention has an excellent effect in stabilizing both contact resistance characteristics and temperature rise characteristics.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mikio Okawa 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Fuchu factory, Toshiba Corp. (56) Reference JP 61-124542 (JP, A) JP 61-6218 ( JP, A) JP 60-197840 (JP, A)

Claims (2)

[Claims] 1. A Cr containing 50% by weight or less of at least one selected from Mo, W, V, Nb, and Ta, and the balance Cu or / and
Cr made of Ag and solid-dissolved in the above Cu and / or Ag
Is 0.01 based on the Cu or / and Ag as 100% by weight.
Contact alloy for vacuum valves, characterized in that it is ~ 0.35% by weight. 2. The contact alloy for a vacuum valve according to claim 1, wherein Cu and / or Ag is 20% by weight or more and less than 80% by weight of the total weight.