JP2878718B2 - Contact material for vacuum valve - Google Patents

Description

The present invention relates to a contact material for a vacuum valve, and more particularly to a contact material for a vacuum valve having improved welding resistance and withstand voltage characteristics.

(Prior art) The characteristics required for the contact material for a vacuum valve are the three basic requirements indicated by the performances for welding resistance, withstand voltage, and breaking, and in addition, the temperature rise and contact resistance are low and stable. Is an important requirement. However, because some of these requirements are conflicting, it is impossible to satisfy all requirements with a single metal species. For this reason, in many contact materials that are in practical use, a combination of two or more elements that can mutually compensate for the insufficient performance, and a contact suitable for a specific application such as for large current or high voltage Materials have been developed, and materials with excellent properties have been developed.However, the contact materials for vacuum valves that sufficiently satisfy the demands for higher withstand voltage and higher current have not yet been obtained. It is a fact.

For example, a Cu-Bi alloy material containing a welding prevention component such as Bi in an amount of 5% or less as a contact material aimed at increasing the current is known (Japanese Patent Publication No. 41-12131). Since the solubility of Bi in water is extremely low, segregation often occurs, the surface roughness after interruption is large, and there is a problem that working and forming are difficult.

In addition, Cu-
Te alloy materials are also known (JP-B-44-23751). Although this alloy mitigates the above problems of the Cu-Bi alloy material, it is more sensitive to the atmosphere than the Cu-Bi alloy material and thus lacks stability such as contact resistance.

Furthermore, as a common feature of these contact materials such as Cu-Te and Cu-Bi, even though they have excellent welding resistance, even if their withstand voltage characteristics are sufficient for application to the conventional medium-voltage class, this is not the case. It has become clear that application to the high voltage field is not always satisfactory.

On the other hand, a Cu-Cr alloy material containing Cr is known as a contact material for a vacuum valve. This contact material exhibits excellent thermal characteristics of Cr and Cu at high temperatures, and thus has excellent characteristics for high withstand voltage and large current. That is, the Cu-Cr alloy material is frequently used as a contact capable of achieving both high withstand voltage characteristics and high capacity breaking.

However, the Cu-Cr alloy material is significantly inferior in the welding resistance to the Cu-Bi alloy material to which Bi is added in an amount of about 5% or less, which is generally used as a contact material for circuit breakers.

The welding phenomenon means that the contact material is melted by the Joule heat generated at the contact surfaces of the contacts and then solidified, and the contact material is vaporized by the arc discharge generated at the moment of opening and closing and then solidified. Occurs at Cu−
In any of the Cr alloy materials, Cr and
Cu forms fine particles of 1 μm or less and forms a layer of several μm to several hundred μm in a state where they are disturbed with each other.

Generally, ultra-fine structure is one of the factors contributing to the improvement of the strength of a material, and this case is no exception. Thus, even when the strength of the ultrafine Cu-Cr layer is excellent in the strength of the matrix of the Cu-Cr alloy material and the matrix strength exceeds the designed tripping force, welding occurs.

Therefore, an operating mechanism for driving a vacuum valve using a Cu-Cr material needs to be designed to have a larger tripping force than Cu-Bi, and is difficult in terms of miniaturization and economy.

Also, as a contact with improved welding resistance of Cu-Cr material,
A Cu-Cr-Bi contact in which Bi is added to a Cu-Cr contact is known (Japanese Patent Publication No. 61-41091). This contact is typically C
Although effective in improving the welding resistance of the u-Cr material, it has the disadvantage that the material is significantly embrittled due to the effect of Bi, causing a reduction in the pressure resistance and an increase in the probability of occurrence of re-arcing.

(Problems to be Solved by the Invention) As mentioned above, Cu-Cr-Bi contact materials are generally
Compared to Cu-Cr contact materials, the welding resistance is improved,
Problems remain in terms of withstand voltage and occurrence of re-arcing.

Accordingly, the present invention provides a vacuum valve contact material that minimizes a decrease in withstand voltage and a reduction in the probability of occurrence of re-ignition while maintaining the welding resistance of the Cu-Cr-Bi contact material for a vacuum valve. With the goal.

[Constitution of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides Cu, Bi and Cr.
Comprising 20 to 60% by weight of Cr, and
Bi content (ratio of Cu plus Bi to Bi) is 0.
0.05 to 1.0% by weight, and as an arrangement for controlling the Bi present at the crystal grain boundaries of the Cu matrix, the average crystal grain size of the Cu matrix is set to 0.7 mm or more so as to include Cr particles. Material for a vacuum valve.

Further, in the crystal grains of the Cu matrix containing Cu as a main component containing Cr particles, Bi alone or / and Bi containing Bi as a main component are contained.
2. The vacuum valve contact material according to claim 1, wherein an alloy is present.

(Operation) As described above, in the Cu-Cr-Bi contact material,
By setting the average crystal grain size of the conductive material containing Cr particles to 0.7 mm or more, the withstand voltage and re-pointing almost the same as the Cu-Cr contact material while maintaining the welding resistance of the Cu-Cr-Bi contact. Can be the probability of spawning.

 That is, the operation is specifically described.

Bi exists in the Cu-Cr-Bi contact material in the following four forms. It exists at the interface between the solid-dissolved Cr particles in Cu and the conductive material (Cu matrix) containing Cu as a main component. It exists at the Cu matrix crystal grain boundaries. It exists in the Cu matrix crystal grains. The presence of Bi in the crystal grain boundaries of Cu matrix has the strongest effect on the contact strength among these existing forms. The present inventors have found that encouraging the probability of the occurrence of ignition is promoted.

According to the experiments of the present inventors, solid solution in Cu and Cr particles
The amount of Bi present at the Cu matrix interface is almost constant when the same raw material is used, but the amount of Bi present at the Cu matrix grain boundaries and the amount of Abundances to the different. That is, Cu
When the matrix crystal grain size is small, Bi tends to be present at the Cu matrix crystal grain boundaries. Conversely, when the Cu matrix crystal grain size is large, the amount of Bi present in the Cu matrix crystal grains is large, There are few.

Due to the above factors, the strength of the contact base material is stronger when the crystal grain size of the Cu matrix is larger, and the withstand voltage characteristics and the probability of occurrence of re-arcing are comparable to those of the conventional Cu-Cr contact.

(Example) Hereinafter, an example of the present invention will be described based on a specific embodiment. First, the configuration of a vacuum valve to which the contact material of the present invention is applied will be described with reference to FIGS. 1 and 2. I do.

FIG. 1 shows an example of the configuration of a vacuum valve to which the contact material of the present invention is applied. In FIG. 1, reference numeral 1 denotes a shut-off chamber, and this shut-off chamber 1 is formed in a substantially cylindrical shape from an insulating material. The insulated container 2 and the metallic lids 4a and 4b provided at both ends thereof with sealing fittings 3a and 3b are formed in a vacuum-tight manner. Thus, a pair of electrodes 7, 8 attached to opposing ends of the conductive rods 5, 6 are arranged in the shut-off chamber 1,
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 movable electrode 8 to enable the electrode 8 to move in the axial direction while keeping the inside of the shutoff chamber 1 vacuum-tight. Shield 10 is provided and bellows 9
Is prevented from being covered with arc vapor. Reference numeral 11 denotes a metallic arc shield provided in the shut-off chamber 1 so as to cover the upper air electrodes 7 and 8, and prevents 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 fixed to the electrode 8 by brazing. In FIG. 1, reference numeral 13b denotes a fixed contact.

The contact material according to the present invention includes the contacts 13a, 13 as described above.
It is suitable for constituting both or any one of b.

Next, a method for manufacturing a contact material according to the present invention will be described. The method for producing a Cu-Cr-Bi contact material according to the present invention is roughly classified into two, one of which is an infiltration method and the other is a solid phase method.

 First, an example of the infiltration method will be described.

A powder compact is obtained by press-molding a Cr powder having a predetermined particle size.
Next, this powder compact is subjected to a hydrogen atmosphere having a dew point of −50 ° C. or less or a vacuum degree of 1 × 10 ⁻³ Torr or less at a predetermined temperature, for example.
Temporarily sintered at 950 ° C. × 1 hour to obtain a temporarily sintered body.

Next, a predetermined Bi%
Is infiltrated at, for example, 1100 ° C. for 30 minutes, and then cooled and solidified by a predetermined cooling method to obtain a Cu—Cr—Bi alloy material. The infiltration is performed mainly in vacuum, but can also be performed in hydrogen.

Here, when the sintering heat treatment and / or the infiltration heat treatment temperature is selected to be higher, the evaporation of Cu and Bi is intense, and it is important to control the amounts of the components. However, since the heat treatment temperature varies depending on the furnace performance or the amount, size, heat capacity, etc. of the material to be heat treated at one time, it is impossible to express that temperature universally. For example, a method of directly determining and managing by X-ray method can be adopted,
Generally, the choice of temperature above 1300 ° C reduces the presence of Cu,
It has proven unfavorable.

On the other hand, the lower limit temperature is 600 ° C. or more, preferably 900 ° C. in the sintering heat treatment, from the viewpoint of degassing of the raw material or the compact.
C. or higher, and in the infiltration heat treatment, at least 1100 ° C. is required due to the need to degas the skeleton and melt Cu.

Further, the cooling rate after infiltration is important in terms of the crystal grain size of the Cu matrix. According to the findings of the present inventors, a water cooling mechanism is provided below the port during infiltration, and the cooling rate of the infiltrant is adjusted by the cooling water temperature and the flow rate of water to adjust the crystal grain size of the Cu matrix. Was possible.

 Next, an example of the solid phase sintering method will be described.

After mixing the specified Cr powder Cu powder and Bi powder, the green compact is formed by a press machine, and then sintered in a hydrogen atmosphere having a dew point of -50 ° C or less or a vacuum atmosphere of 1 × 10 ^-3 Torr or less. I do. This pressing step and sintering step are repeated a plurality of times to obtain the desired Cu-Cr-Bi contact material.

What should be noted here is the working ratio by the pressing pressure after sintering, and the sintering conditions. According to the study of the present inventors, the factor that determines the crystal grain size of the Cu matrix, which is a feature of the present invention, is the pressing and sintering conditions in the final step, for example, processing strain (deposition change) due to pressing in the final step. ) Is about several percent, and the sintering condition is that the crystal grain size of the Cu matrix can be reduced to 0.7 mm by holding at 1000 ° C. × 2 hours (time).

The contact material manufactured in this way has a Cu matrix crystal grain size of 1 mm or more, and from the distribution of Bi in the contacts, the pressure resistance characteristics are equivalent to those of the Cu-Cr contacts without Bi added. Ideal as a material.

Next, each contact material manufactured as described above is shown in comparison with a comparative example. The conditions and methods for evaluation in each of the examples are as follows.

(1) Welding resistance A pair of disk-shaped specimens with an outer diameter of 25 mmφ has a tip with an outer diameter of 25 mmφ of 10
A pressure rod having a spherical surface of 0R is opposed, a load of 100 kg is applied, a current of 50 Hz, 20 KA is applied in a vacuum of 10 ^-5 mmHg for 20 milliseconds, and the force required for tripping between the sample and the rod at that time Was measured to determine the welding resistance. The evaluation was made based on a relative value when the welding and peeling force of the Cu-Cr alloy material after infiltration shown in Comparative Example 2 was 1.00. Each table shows the variation width in the measured values of the three contact points.

(2) Withstand voltage characteristics Ni that is mirror-finished by buffing for each contact alloy
The needle is used as the anode, each mirror-finished sample is used as the cathode, the gap between the two electrodes is set to 0.5 mm, and the voltage is gradually increased in a vacuum of 10 ^-6 mmHg to measure the voltage value when spark is generated Then, a static withstand voltage value was obtained. The measurement data shown in Table 2 indicates that the static withstand voltage of the infiltrated Cu-Cr alloy was 1.00, including the variation when three repetitive tests were performed.
(Comparative Example 1 shown in Table 1) is shown as a relative value.

(3) Re-ignition characteristics A disk-shaped contact piece with a diameter of 30 mm and a thickness of 5 mm is attached to a demountable vacuum valve, and the frequency of re-ignition when a circuit of 6 KV x 500 A is cut off 2,000 times is measured. And the variation width (maximum and minimum) of two circuit breakers (six valves)
Indicated by Baking heating (45
(0 ° C., 30 minutes) only, and no brazing material was used and no accompanying heating was performed.

Examples 1-2, Comparative Example-2 Cu content about 50 wt%, Bi / Cu + Bi content 0.5 wt% (wt%), infiltration temperature constant at 1100 ° C, only cooling conditions were changed, and the average crystal grain size of the Cu matrix was 3 mm. , 0.7mm, Cu-Cr different from 100μm
-Bi contacts were manufactured (Examples 1 and 2, Comparative Example-
3). As shown in Table 1, the characteristics of the welding resistance were Bi
Is significantly better than the Cu-Cr contact to which Cu is not added (Comparative Example-1), but the withstand voltage characteristics and the probability of occurrence of re-dotting decrease as the crystal grain size becomes smaller. In Comparative Example-3), the probability of occurrence of re-incarnation greatly increased,
The status was determined to be unusable. From the above results, Cu
The matrix is desirably a crystal grain of 0.7 mm or more.

Examples 2 to 4 and Comparative Examples 3 to 4 A Cu-Cr-Bi contact was manufactured by changing the Bi content to 0.01, 0.05, 0.48, 1.0 and 5.3 while keeping the Cu content at 50 wt%, the infiltration temperature and the cooling conditions constant. (Comparative Example-3, Examples-3, 2, 4, and Comparative Example-4, respectively). As shown in Table 1, those having a low Bi content (Comparative Example-3) had a good probability of occurrence of re-arcing of the withstand voltage characteristics, but showed little improvement in the welding resistance. Bi
In the case where the content was large (Comparative Example-4), the probability of occurrence of restriking and the decrease in withstand voltage characteristics were remarkable as in the case where the Cu crystal grains were thin. From the above, it can be said that the Bi / Cu + Bi amount is suitably 0.05 to 1.0.

Example 5 The mutual effect of the infiltration temperature and the cooling condition is examined. Infiltration temperature 1300 ° C, cooling condition is 10 ° C x 3 / min.
An average crystal grain size of 0.7 mm was obtained. As for these characteristics, favorable characteristics were obtained in all of the welding resistance characteristics, the withstand voltage characteristics, and the probability of occurrence of re-arcing.

From these results, it was reconfirmed that it is necessary to control the amount of Bi and the crystal grain size of the Cu matrix in order to satisfy all of the welding resistance characteristics, the withstand voltage characteristics, and the probability of occurrence of re-arcing.

Up to now, the infiltration method has been used as an example. In the case of the infiltration method, the most influential factor on the Cu crystal grain size is the cooling conditions during solidification of Cu, which, in consideration of natural cooling by cutting off the heat source, besides the heat capacity inside the furnace, There is also a place to see it as a characteristic. But suppose it is obtained by cutting off the heat source
If the furnace has characteristics such that the average crystal grain size of the Cu matrix is less than 0.7 mm, the cooling condition is controlled by gradually lowering the heat input rather than cutting off the heat source. Things are possible.

 An example of the solid phase sintering method will be described.

Comparative Example-5-6, Example-6 100 μm Cu depending on the processing rate and sintering conditions in the final step
Bi-free Cu-Cr contacts with crystal grain size obtained (Comparative Example-5)
And a Cu-Cr-Bi contact (Comparative Example-6) having a Cu crystal grain size of 100 µm and a 1-mm Cu-Cr-Bi contact (Example-6).

The solid-state Cu-Cr contacts containing no Bi (Comparative Example-5) show a slight improvement in welding resistance as compared with the infiltrated Cu-Cr contacts, but are still not satisfactory. The Cu—Cr—Bi contact having a Cu matrix average crystal grain size of 100 μm (Comparative Example-6) has a defect in the withstand voltage and the probability of occurrence of re-crossing, although the welding resistance is improved. On the other hand, the Cu-Cr-Bi contact having a Cu matrix average crystal grain size of 1 mm (Example-6) showed good characteristics.

From the above, it has been proved that the present invention is applicable not only to the infiltration method but also to the solid phase sintering method.

Examples 7 to 8 and Comparative Examples 7 to 8 The effective range of the Cr content is examined. Cr content is 10.6, 20.
5,39.3,85.6 wt% Cu-Cr-Bi contacts were manufactured (Comparative Example-7, Examples-7,8, Comparative Example-8). When the various properties were evaluated, the welding resistance properties were all good.

However, in terms of withstand voltage, the Cr content was 10.6 wt% (Comparative Example-
Contact point 7) had a remarkable decrease in withstand voltage because the amount of Cu was too large. However, there was no problem in terms of re-incarnation. In the contact with 85.6 wt% Cr (Comparative Example-8), the material was further embrittled due to the large amount of Cr, and good results were not obtained with respect to the withstand voltage characteristic and the probability of occurrence of re-arcing. On the other hand, Cr content
20.5,59.3wt% contacts all showed good results.

 From the above results, it is desirable that the Cr% is 20 to 60 wt%.

In the embodiment described above, the average crystal grain size of the Cu matrix in the infiltration method and the solid phase sintering method is 0.7 mm or more Cu-Cr
Although a manufacturing example of a -Bi contact is shown, it is clear that the same characteristics can be obtained even if a similar contact is manufactured using another method not described here.

[Effects of the Invention] According to the present invention described above, Cu-Cr-Bi for vacuum valves is used.
It is possible to provide a contact material for a vacuum valve in which the withstand voltage characteristics and the probability of occurrence of restriking do not decrease while maintaining the welding resistance of the contact material.

[Brief description of the drawings]

FIG. 1 is a sectional view of a vacuum valve to which the present invention is applied, and FIG.
The figure is an enlarged sectional view of the contact portion. 1 ... shut-off room, 2 ... insulating container, 3a ... sealing fitting, 3b ...
... Seal fitting, 4a ... Lid, 4b ... Lid, 5 ... Conductive rod,
6 ... conductive rod, 7 ... fixed electrode, 8 ... fixed electrode, 9 ...
... bellows, 10 ... arc shield, 11 ... arc shield, 12 ... brazing part, 13a ... movable side contact, 13b ... fixed side contact, 14 ... brazing part.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Atsushi Yamamoto 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Toshiba Fuchu Plant, Inc. (72) Inventor Shigeo Soma 1-Toshiba-cho, Fuchu-shi, Tokyo (72) Inventor Kadan Sekiguchi 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside Toshiba Yokohama Office (56) References JP-B-61-41091 (JP, B2) (58) Fields surveyed (Int. Cl. ⁶ , DB name) C22C 9/00-9/10 C22C 27/06 H01H 33/66

Claims (2)

(57) [Claims] (1) It comprises Cu, Bi and Cr, wherein the content of Cr is 20 to 60% by weight, and the content of Bi (based on Bi)
The ratio of the sum of Cu and Bi) is 0.05 to 1.0% by weight. As a configuration for controlling the Bi present at the crystal grain boundary of the Cu matrix, the average crystal grain of the Cu matrix is included so as to include Cr particles. Contact material for vacuum valves characterized in that the diameter is 0.7 mm or more. 2. The vacuum according to claim 1, wherein the single crystal of Bi and / or the Bi alloy containing Bi as a main component are present in the crystal grains of the Cu matrix containing Cu as a main component and containing Cr particles. Contact material for valves.