JPH0736306B2 - Vacuum valve contact alloy - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a vacuum valve (switch), and more particularly to a contact alloy for a vacuum valve having improved current interruption characteristics.

[Technical background of the invention]

The contact point of a vacuum valve that cuts off a current in a high vacuum by utilizing arc diffusivity in a vacuum is composed of two opposing fixed and movable contacts. In particular, when the current is cut off by an induction circuit such as a motor load, excessive surge voltage may be generated, which may damage the load equipment. The cause of this abnormal surge voltage is due to the current interruption phenomenon that occurs on the low current side during interruption in vacuum (forced current interruption without waiting for the natural zero point of the AC current waveform). . The value Vs of the abnormal surge voltage is the product of the circuit surge impedance Zo and the current interruption value Ic, that is, Vs =
Represented by 2Zo Ic. Therefore, in order to reduce the abnormal surge voltage Vs, the current interruption value Ic must be reduced.

In response to the above requirements, a vacuum switch whose contacts are made of an alloy of WC and Ag has been put into practical use (Japanese Patent Application No. 42-6844).
No. 7). In this alloy contact, (1) intervening WC facilitates electron emission, (2) promotes evaporation of contact material due to heating of the electrode surface due to collision of field emission electrons, (3) carbide in contact material Shows an excellent current interruption characteristic in that it is decomposed by an arc to generate a charged body and connect the arc.

Also, as another contact having the above current interruption characteristics, Bi and
An alloy compounded with Cu has been produced, and this material has been put to practical use in a vacuum valve (Japanese Patent Publication Nos. 35-14974 and 41-12131). This alloy has the following characteristics: (1) Bi with a weight ratio of about 10% has an appropriate vapor pressure characteristic, so it exhibits low breaking current characteristics (Japanese Patent Publication No.
35-1494).

(2) Bi having a weight ratio of about 0.5% is unevenly present in the grain boundaries, and as a result, the alloy itself becomes brittle, a low welding external force is realized, and it is excellent in large current interruption (Japanese Patent Publication No. 41- No. 12131).

[Problems of background technology]

However, in recent years, the number of cases where a vacuum valve is applied to an inductive circuit has increased more than before, and a high impedance load has also appeared. Therefore, it is desired for the vacuum valve to have more stable current interruption characteristics, and cost reduction. Is desired.

For such requirements, the contact alloys Ag-WC, Cu-B
For i, the breaking current value was at a high level or lacked in stability. That is, Ag-WC contact alloy has Ag
Since the difference in vapor pressure between WC and WC is extremely large, it causes remarkable selective evaporation of Ag due to arc heat and the like, resulting in instability of current cutting characteristics and fluctuation of contact resistance.

On the other hand, Cu-Bi contact alloy has a problem that the melting point of Bi is as low as 271 ° C, which is an essential problem, and causes Bi to agglomerate during vacuum valve baking or silver brazing heating, leading to poor bonding. .

[Object of the Invention]

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a contact alloy for a vacuum valve, in which the stability of the current cutting characteristic is further improved.

[Outline of Invention]

The present invention is a contact alloy for a vacuum valve, which is characterized by comprising a conductive material containing at least one of silver and copper and an auxiliary material consisting of 0.5 to 20% by weight of zinc telluride. is there.

Example of Invention

An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of the structure of a vacuum breaker to which the contact alloy of the present invention is applied. In FIG. 1, reference numeral 1 denotes a breaking chamber, and this breaking chamber 1 is formed of an insulating material into a substantially cylindrical shape. The insulating container 2 and the metallic lids 4a and 4b provided on both ends of the insulating container 2 via the sealing metal fittings 3a and 3b are vacuum-tight. Then, a pair of electrodes 7 and 8 attached to opposite ends of the conductive rods 5 and 6 are arranged in the shut-off chamber 1, and the upper electrode 7 is a fixed electrode and the lower electrode 8 is movable. It is used as an electrode.
Further, a bellows 9 is attached to the electrode rod 6 of the movable electrode 8 to enable the electrode 8 to move in the axial direction while keeping the blocking chamber 1 vacuum-tight. Further, a metallic arc shield 10 is provided above the bellows 9,
Are protected from being covered with arc vapor. Also 11 is
A metallic arc shield provided in the interrupting chamber 1 so as to cover the electrodes 7 and 8 prevents the insulating container 2 from being covered with arc vapor. 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 by caulking. Contact 13a
Are brazed to the electrode 8 by brazing 14. Reference numeral 13b is a fixed side contact, which is attached by brazing similarly to the fixed side electrode 8.

Here, the consideration for obtaining the contact alloy of the present invention will be described. In order to improve the current cutoff characteristic, it is extremely important to reduce the variation width in addition to maintaining the current cutoff value itself at a lower value. It is said that the current interruption phenomenon is closely related to the amount of vapor between contacts (vapor pressure, heat conduction), thermoelectrons emitted from the contact material, etc. According to the experiments conducted by the inventors, the former contributes more. It turned out to be Therefore, it has been found that the current interruption phenomenon can be alleviated by making the supply of steam easy or by making the contact with a material which is easy to supply. The Cu-Bi alloy has a low threshold value from this viewpoint, but the fatal drawback is that the low melting point (271 ° C) of Bi normally causes baking at a temperature of around 600 ° C or 800 ° C, which is usually performed by a vacuum valve. During the silver brazing operation at ℃, as a result of the movement and agglomeration of Bi due to melting, the existence of Bi that should maintain the current cutoff characteristic becomes non-uniform. Therefore, it was confirmed that the variation range of the current cutoff value increases.

On the other hand, in Ag-refractory alloys represented by Ag-WC, Ag (or Cu) at the boiling point of the refractory material (WC in this case)
However, depending on which position of the contact point (whether the refractory material is Ag) the arc foot sticks, it is sometimes lower than the vapor pressure of Bi in the Cu-Bi system. Causes insufficient temperature, that is, insufficient steam.
As a result, it was confirmed that the variation range of the current threshold value appears. In this way, it is already considered to be the limit to prevent the sudden temperature drop of the contact surface at the end of the current interruption with the alloy consisting only of the combination of the refractory material and Ag (or Cu), and to connect the arc. Has led to the conclusion that the presence of auxiliary materials is necessary.

As described above, the two consideration results of the Cu-Bi alloy and the Ag-WC alloy (Ag-refractory material system) indicate that a new auxiliary material is required as a contact with stable current cutting characteristics, and the condition is steam It is suggested that it is indispensable to have stability in heat treatment such as baking, in addition to having the ability to supply.

Therefore, in the present invention, as described above, the auxiliary material having a certain condition is positively contained to improve the current cutting characteristic. Therefore, in order to obtain a low breaking current characteristic, the present invention provides an alloy of Cu, Cu-refractory material, Cu-Co or Fe (wherein Cu is partially or entirely replaced with Ag) 0.5 to 2
0% ZnTe is added as an auxiliary material. Te in this ZnTe
Is about 66 Wt%, but a slight deviation of Te or Zn can coexist as a Cu-Zn solid solution containing Zn and a Cu alloy containing a Cu-Te compound. In such a state, the metal alloy vaporizes by heating with a relatively small amount of energy and a suitable amount of metal vapor enters the arc space. This acts as a reduction of the current interruption phenomenon, and as a result, practically satisfactory contact alloys for vacuum valves. It was confirmed that

Next, an example of a method for manufacturing this contact alloy will be described. Prior to production, about 100 mesh Te and Zn powder was put into a pot filled with argon gas and mixed for about 12 hours to form a mixed powder at 4 ton / cm ² , and then at 900 ° C. in a hydrogen stream. Sinter for 24 hours to obtain ZnTe lumps. This ZnTe is 100
Grind to ~ 200 mesh and use as raw material.

Next, the manufacturing process will be described.

First, manufacture of Cu-ZnTe contact material; a part of the required amount of Cu was prepared as powder, and ZnTe powder prepared with this was mixed in a pot for about 12 hours and molded at 2 ton / cm ² , 900 ℃ in hydrogen
Sinter for 4 hours. The residual material of the required amount of Cu is infiltrated in hydrogen at 1120 ° C into the residual holes of the skeleton obtained as above to obtain a contact material. Alternatively, the Cu powder corresponding to the total amount of the required Cu and the ZnTe powder are mixed for about 12 hours to obtain 4 ton / cm ²
After molding at, sinter in hydrogen at 95 ℃ to obtain contact material.

Second, manufacture of Cu-ZnTe, refractory materials (W, Mo, Ta, Nb, Zr, Ti, Cr) and contact materials of any one of these carbides and borides; unit material powder of about 100 mesh and After the ZnTe powder is mixed and molded, a skeleton is obtained by sintering. Next, Cu is infiltrated into the remaining holes in the skeleton to obtain a contact material.

Third, manufacture of Cu-ZnTe-Fe (Co) contact material; powder of either 100 Fe or Co of about 100 mesh and ZnTe powder are mixed and molded, and then skeleton is obtained by sintering. Next, Cu is infiltrated into the remaining holes in the skeletal to obtain a contact material.

As described above, the auxiliary materials (ZnTe; W, Mo, Ta, Nb, Zr, Ti, Cr) are added to the conductive materials (Cu, Ag) as shown in Tables 1 and 2.
Each contact alloy containing a refractory material) is manufactured.

Next, each of the contact alloys produced above will be considered and the best content ratio will be determined.

Currently, it is a comparative material as a contact alloy with low current cutting characteristics.
Ag-70% WC and Cu-15% Bi alloys shown in 2 and 3 are in practical use. This is because the current breaking characteristic is improved as compared with pure Cu (Comparative Material-1), but especially in the Cu-Bi system (Comparative Material-3), the characteristics (increase in the breaking current value) are significantly increased by increasing the number of switching to degrade.

On the other hand, in the Cu-ZnTe system, when the ZnTe content is 0.12% (comparative material-4), the current cutting characteristic shows a quantitative characteristic, and the ZnTe content is required to be at least 0.5% (implementation material-1) and a maximum of 20% ( Implementation material-
The range of 3) is necessary. In this range, both the average value and the maximum value of the current cutoff value are low and stable. When the amount of ZnTe exceeds 30%, it is not related to the current cutoff property, but the cutoff characteristics after the cutoff at a voltage of 7.2 kv are significantly deteriorated (Comparative Example-5). Therefore, the amount of ZnTe is 0.5 to 20.
In the range of%, the change in the breaking property is also slight compared with the property of the Ag-70WC system, and the degree of decrease is slight, which is practical and the best. Therefore, the amount of ZnTe is set in the range of 0.5 to 20%.

The above is not limited to the Cu-ZnTe pseudo-binary system, but similar effects can be obtained even if ZnTe is present in the matrix composed of Cu and the refractory material (W, Mo, Ta, Nb, Zr, Ti, Cr). Has been obtained. This is clarified by comparing the working materials-5 to 19 with the comparative materials-6 to 9.

Furthermore, the conductive material is not limited to Cu, but is not limited to the material used in Example-4,1.
As shown in 6,17, the same effect is obtained even when Ag is used or when Cu and Ag coexist.

In addition, when Te is present in the Cu matrix as shown in Example Material-20, it is added to the Cu matrix as shown in Example Material-21.
Even if Zn is present, the same effect is obtained. In this case, the matrix Zn or Te (actually Cu ₂ T
e) exists because ZnTe, which is the material of the present invention, has an ideal T
This occurs due to the alloying of the remaining Zn or Te with Cu when the content of 66% e deviates slightly to Zn rich or Te rich. This is usually well recognized in industrial production considering economy, but as the contact material, the range should be controlled to about 2% or less, and the presence of more than this is not preferable in the bonding process. It should be avoided.

As shown above, the greatest feature of the contact containing ZnTe is not only that it shows a low current breaking characteristic, but also that there is little fluctuation (the breaking current value increases) after opening and closing a predetermined number of times. It is in the place where the characteristics can be obtained with almost no reduction in the cutting performance. It is considered that the cause is that, as described above, there are few changes such as decomposition, migration, and aggregation with respect to heat received in the baking or silver brazing process. Therefore, the above-mentioned ZnTe
2% remaining Zn or Te deviated from (66% Te)
May be consumed mainly by evaporation due to arc heat due to current switching or current interruption. Therefore,
The larger this amount is, the larger the fluctuation range of the current breaking value or the breaking characteristic with respect to the number of times of switching increases and decreases, which is not preferable, and Zn and Te are preferably controlled with 2% as a guide.

The evaluation conditions are as follows. Breaking current: The breaking current value in the table is the voltage drop of the coaxial shunt inserted in series with the contact under test, observed with a synchroscope. In other words, the average value of the breaking current values after 500 experiments were given by applying an alternating current with an effective value of 44 A through the LC circuit. The sample is baked and discharged aged for measurement. If the aging is insufficient, the threshold value increases with the number of measurements, so heating and discharging should be performed sufficiently. The sample morphology has a diameter of 20 mm, a thickness of 4 mm, one is flat, the other is 20 mmR and the contact pressure is 10 kg.

Cut-off evaluation: The cut-off limit was comparatively evaluated by increasing the current by 1 KA at 7.2 kv 50 Hz after incorporating it into an experimental valve for a cut-off test facing a diameter of 20 mm and a cap of 2.5 mm and applying baking and voltage aging.

As described above, in the above-described one embodiment, copper or a conductive material containing zinc or a refractory material, silver, or the like in copper, and a vapor pressure and a thermal conduction between the vacuum valve contacts which are stable to heat treatment in the conductive material. Since it is a contact material containing zinc telluride as an auxiliary material that can be easily supplied, the following effects can be obtained. In other words, stable current interruption characteristics can be obtained with little deterioration due to heat received during manufacturing of contact alloys or during manufacture of vacuum valves such as baking and silver brazing.
Further, the breaking property can sufficiently maintain the conventional contact material property. Therefore, when the contact material of the present invention is used for a vacuum valve contact, a vacuum valve having excellent current interruption characteristics and interruption characteristics can be obtained.

〔The invention's effect〕

As described in detail above, according to the present invention, it is possible to provide a contact alloy for a vacuum valve in which the stability of the current cutting characteristic is further improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a vacuum valve to which an embodiment of a contact alloy for a vacuum valve of the present invention is applied, and FIG. 2 is an enlarged configuration diagram of an electrode portion of the vacuum valve shown in FIG. 1 ... Shut-off room, 2 ... Insulation container, 5,6 ... Conductive rod, 13
a, 13b …… Contact point.

Claims (4)

[Claims] 1. A vacuum valve contact alloy comprising a conductive material containing at least one of silver and copper and an auxiliary material composed of 0.5 to 20% by weight of zinc telluride. . 2. The auxiliary material is Te in zinc telluride.
At 66% by weight, the conductive material is any one of copper or a copper solid solution containing less than 2% by weight of zinc or a copper alloy containing less than 2% by weight of a copper-terel compound. A contact alloy for a vacuum valve according to the item 1). 3. The auxiliary material is about 66% by weight of terer in zinc telluride, and the conductive material is any one of tungsten, molybdenum, tantalum, niubilam, zirconium, titanium, chromium, chromium carbide, and boride. Claim (1) consisting of refractory material and copper
The contact alloy of the vacuum valve according to the item. 4. The auxiliary material is a refractory material in which the tellurium content in zinc telluride is approximately 66% by weight, the conductive material is either iron or cobalt, and copper or a copper solid solution containing less than 2% by weight zinc. The contact alloy for a vacuum valve according to claim (1), which comprises any one of copper alloys containing less than 2% by weight of a copper-tellur compound.