JPH1031942A - Contact material for vacuum circuit breaker and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heavy-current interrupting property, withstand voltage and fusion resistance in the use as the contact of a vacuum circuit-breaker by setting the oxygen content in the chromium phase of a contact material for vacuum circuit-breaker formed of chromium phase and copper phase to a ratio within a specified range. SOLUTION: Each contact member 13a, 13b is brazed to the end surface center parts of electrodes 7, 8, respectively by use of Ag brazing filler metal 14. The electrodes 7, 8 are integrally bonded to the end surfaces of conductive bars 5, 6 through brazing parts. Further, the electrodes 7, 8 are arranged so as to be opposite to each other, whereby a vacuum circuit-breaker is assembled. In this contact material for vacuum circuit-breaker, oxygen content in chromium is 200-1000ppm. The oxygen component contained in chromium phase is present as chromium oxide. Further, the content of chromium as arc resisting component is 20-80wt.%.

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 circuit breaker and a method of manufacturing the same, and particularly when used as a contact (contact) of a vacuum circuit breaker, the frequency of re-ignition can be reduced and the breaking characteristics can be greatly improved. The present invention relates to a contact material for a vacuum circuit breaker that can be improved and a method for manufacturing the same.

[0002]

2. Description of the Related Art Circuit breakers open and close electric circuits in a normal state,
Widely used in power equipment, substation equipment, high-speed railway vehicles, etc. to automatically and instantaneously cut off the electric circuit when combined with an overcurrent relay that detects the failure state when an abnormality such as a grounding accident or short circuit accident occurs. Have been. In particular, vacuum circuit breakers
Container (vacuum valve) maintained at a high vacuum of about 10 ^-4 Pa
The electric circuit is opened and closed by opening and closing a pair of contact members disposed opposite to each other.

FIG. 1 is a sectional view showing an example of the structure of a general vacuum circuit breaker. In FIG. 1, a shut-off chamber 1 in which contact opening and closing operations are performed includes an insulating container 2 made of an insulating material and formed in a substantially cylindrical shape, and sealing metals 3 a at upper and lower ends of the insulating container 2.
It is partitioned and formed by metal lids 4a and 4b provided via the base 3b, and is formed in a vacuum-tight manner. A pair of conductive rods 5 and 6 are arranged in the blocking chamber 1 so as to face each other in the axial direction, and a pair of electrodes 7 and 8 are attached to opposing ends of the conductive rods 5 and 6. . In the figure, the upper electrode 7 is a fixed electrode, while the lower electrode 8 is a movable electrode. A telescopic bellows 9 is mounted on the conductive rod 6 of the movable electrode 8 to enable the movable electrode 8 to reciprocate in the axial direction while the interior of the shut-off chamber 1 is maintained in a vacuum-tight manner. An arc shield 10 made of metal is provided on the bellows 9 to prevent the bellows 9 from being covered with the arc vapor by the arc shield 10.

A metal arc shield 11 is disposed in the cut-off chamber 1 so as to cover the pair of electrodes 7 and 8 facing each other. The arc shield 11 covers the insulating container 2 with arc vapor. Is prevented.

As shown in FIG. 2 in an enlarged manner, the electrode 8 is fixed to a brazing portion 12 formed at the end of the conductive rod 6 by heat bonding or crimped by crimping. The contact member 13a is integrally fixed to the center of the end face of the electrode 8 via a brazing material 14. The fixed-side contact member 13b shown in FIG. 2 is also integrally joined to the end face of the fixed electrode 7 via a brazing material.

According to the vacuum circuit breaker having the above structure, 10 ^-7 To
The contact is opened and closed in a high vacuum atmosphere of about rr to cut off the load current. Since a high dielectric strength in a high vacuum can be used, the opening and closing stroke of the contact member facing the contact can be shortened. Vacuum circuit breakers are smaller and lighter than other circuit breakers, such as oil-filled circuit breakers, magnetic circuit breakers, and air / gas circuit breakers, and are maintenance-free. Due to its excellent characteristics, such as good, there is a tendency in recent years to expand its applicable range.

The contact member incorporated in the above-mentioned vacuum circuit breaker is required to have arc resistance (arc resistance), voltage resistance and welding resistance so as not to be welded by an arc generated when the contacts are frequently opened and closed. On the other hand, in order to maintain the low contact resistance, it is indispensable to have high conductive properties. Specific contact forming materials satisfying both the arc resistance and the high conductivity include, for example, Ag-based materials, Ag-based materials, and the like.
-Cu-based materials, Ag-CdO-based materials, 30% Cu-W-based materials, 50% Cu-Cr-based materials and the like are used.
In particular, Cu-W based contact materials have excellent conductivity,
Since the u-Cr-based contact material has excellent withstand voltage characteristics, it is widely used particularly as a contact material for high-output electrical equipment.

This Cu-Cr contact material is mainly composed of copper (Cu) having high conductivity and chromium (Cr) having a high melting point and excellent arc resistance and pressure resistance. It is a contact material that achieves both high withstand voltage and large current interrupting properties. However, in order to expand this contact material to other application fields, it is necessary to further improve the characteristics such as the above-mentioned high breaking property, voltage resistance, and welding resistance.

Conventionally, as one method for improving the characteristics of the contact material, it has been considered desirable to reduce the impurity gas component contained in the contact material as much as possible.
It has been reported that by removing the impurity gas component, the contact material can be made higher in withstand voltage and the restriking phenomenon can be reduced. That is, the contact members are required to be highly purified, and in particular, gaseous impurity components such as oxygen, which cause instability of the arc and deterioration of the breaking performance, and work-related components such as Na, K, and Ba. It has been a great technical problem to reduce as much as possible the content of metal impurities that cause a reduction in the withstand voltage performance due to electron emission.

[0010]

However, the Cu-Cr-based contact materials obtained up to now, including the contact material having a reduced amount of impurities as described above, have a breaking performance and a re-ignition frequency. At present, sufficient characteristics have not been obtained so as to be applicable to a wide range of fields.

[0011] The use of these Cu-Cr-based contact materials is expected to increase in the future as a material constituting a contact (contact) of a vacuum circuit breaker. In addition, technical requirements for miniaturization of vacuum circuit breakers are increasing, and further reduction in occurrence frequency of re-ignition and improvement in pressure resistance, large current interruption, and welding resistance are required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and when used as a contact of a vacuum circuit breaker, the frequency of occurrence of re-ignition is reduced, and a large current interrupting property, pressure resistance and welding resistance are achieved. It is an object of the present invention to provide a contact material for a vacuum circuit breaker capable of mass-producing a vacuum circuit breaker whose breakability can be greatly improved and whose breaking performance is stable, and a method of manufacturing the same.

[0013]

Means for Solving the Problems To achieve the above object, the inventors of the present invention have determined the amounts of various components that were conventionally considered to deteriorate the conductivity and the breaking characteristics of the contact material. As a result of re-investigating the effect of the presence form in the material on the characteristics of the contact material, the following findings were obtained.

That is, a contact material is formed by using a copper powder and a chromium powder containing a predetermined amount of oxygen, and the contained oxygen component is present in the contact material as a compound such as chromium oxide. It has been found that the arc resistance can be improved by increasing the melting point of, and the breaking characteristics as a contact material can be greatly improved. Further, since the boiling point of the contact material is also increased, the amount of metal vapor generated at the time of opening and closing the contact is reduced, and an excessive arc is suppressed. As a result, it has been found that the breaking characteristics of the contact material are improved and the contact characteristics themselves are stabilized, so that the frequency of occurrence of restriking can be significantly reduced. The present invention has been completed based on the above findings.

That is, the contact material for a vacuum circuit breaker according to the present invention is a contact material for a vacuum circuit breaker comprising a chromium phase as an arc-resistant component and a copper phase as a highly conductive component. Is 200 to 1000 ppm. Further, the oxygen component contained in the chromium phase is present as chromium oxide. Further, the chromium content as an arc-resistant component is 20 to 80% by weight.

Further, the method for producing a contact material for a vacuum circuit breaker according to the present invention is characterized in that copper powder and oxygen as highly conductive components are added in 100 parts.
Mixing a chromium powder as an arc-resistant component containing up to 2000 ppm to prepare a raw material mixture, forming the raw material mixture to form a copper-chromium compact, And heat sintering to form a copper-chromium sintered body. Alternatively, a copper-chromium sintered body formed by heat sintering may be further infiltrated with copper.

A step of forming and sintering a chromium powder as an arc-resistant component containing 100 to 2000 ppm of oxygen to form a calcined chromium body; And a step of infiltrating copper as the above.

Here, Cr as an arc-resistant component is a component that is excellent in arc resistance and welding resistance and extends the life of the contact, and is contained in the raw material mixture in the range of 20 to 80% by weight. Is done. If the content is less than 20 wt%, the arc resistance is reduced and it is difficult to extend the life of the contact. On the other hand, when the content exceeds 80% by weight, the content of Cu as a high conductive component described later is relatively reduced, and the contact function is reduced due to an increase in contact resistance.

Cu as a high conductive component has a high conductivity, and is contained in an amount of 80 to 20% by weight (wt%) as a residual component excluding the Cr component in order to reduce the contact resistance value of the contact. If the Cu content is less than 20% by weight, the conductivity decreases, the contact resistance increases, and the function as a contact material decreases. On the other hand, if the content exceeds 80 wt%, the content of the arc resistant component relatively decreases, and the arc (electric arc) generated at the time of the contact opening / closing operation causes the contacts to be easily welded, resulting in reduced wear resistance. .

The Cr powder used as a raw material of the Cu—Cr contact material according to the present invention contains 100 to 2000 p
It is desirable to use a chromium powder containing pm. The oxygen component contained in the Cr powder is present as a compound such as chromium oxide in the contact material as described later, and has an effect of improving the breaking characteristics of the contact material and reducing the frequency of restriking. . The preferred oxygen content of the Cr powder also varies depending on the mixing ratio with the Cu powder described below and the presence or absence of an oxidation step during production. When the oxygen content in the Cr powder is less than 100 ppm, the effect of improving the cutoff characteristics and the frequency of occurrence of restriking becomes insufficient. On the other hand, when the oxygen content exceeds 2000 ppm, a gas is generated at the time of breaking the contact, or the conductivity of the contact is lowered to deteriorate the breaking characteristics. Therefore, the oxygen content in the Cr powder is 100 to 2000 ppm. And

On the other hand, the above-mentioned Cu powder includes Cu powder produced by an electrolytic method and C powder produced by an atomizing method.
u powder can be used. The Cu powder obtained by these manufacturing methods has a high purity, and is generally a Cu powder material suitable for a contact member requiring characteristics as a high-purity material. The average particle size of the Cu powder used here is in the range of 1/20 to 1/3 of the average particle size of the Cr powder, and by adjusting to this particle size range, the Cu powder and the Cr powder can be uniformly formed. A dispersed raw material mixture is easily obtained. That is, when the average particle size of the Cu powder after the mixing operation is so coarse that it exceeds one-third of the average particle size of the Cr powder, it is difficult to uniformly attach and arrange the Cu powder on the surface of the Cr powder. On the other hand, in the case of a fine powder of less than 1/20, reagglomeration of the Cu powder is likely to occur, and in any case, it is difficult to obtain a state in which the components are uniformly dispersed. A more preferred particle size ratio is in the range of 1/10 to 1/5.

The contact material for a vacuum circuit breaker according to the present invention is prepared by preparing a Cu-Cr material by powder metallurgy or infiltration using the above-mentioned Cu powder and Cr powder as raw materials.
It is manufactured by processing a Cr material into a predetermined shape.

In the powder metallurgy method, a step of preparing a raw material mixture by using a mechanical mixer such as a ball mill with Cr powder as an arc-resistant component and Cu powder as a highly conductive powder; A step of filling the raw material mixture into a mold of a press molding machine and press-molding the same under a pressure of about 600 to 1000 MPa to form a Cu-Cr molded body having a predetermined shape; Heating and sintering at a temperature of 900 to 1050 ° C. for 0.5 to 3 hours in a non-oxidizing atmosphere such as an active gas.

It is also effective to further infiltrate the pores of the Cu—Cr sintered body prepared by the powder metallurgy method with copper as described above to further densify the contact material and improve the conductivity. is there.

On the other hand, the infiltration method is a method in which molten Cu is infiltrated into pores of a porous calcined Cr body to form a Cu—Cr alloy material.

According to the above manufacturing method, Cr as an arc-resistant component
A contact material comprising a phase and a Cu phase as a highly conductive component is prepared.

Here, the amount of oxygen contained in the Cr phase of the contact material is adjusted in the range of 200 to 1000 ppm. The oxygen is present as a compound such as chromium oxide (Cr ₂ O ₃ ) in the Cr phase, and is effective for improving the breaking characteristics of the contact material and reducing the frequency of restriking. That is, the melting point of chromium oxide (1990 ° C.) is
60 ° C.) and the boiling point of chromium oxide (3000).
C.) also becomes higher than the boiling point of metal chromium (2672 ° C.), and by containing these high-melting point compounds, the melting point of the contact material itself increases and the arc resistance can be improved.

Further, since the boiling point of the contact material also increases, the amount of metal vapor generated at the time of opening and closing the contact is reduced, so that excessive arc generation can be suppressed. As a result, the breaking characteristics of the contact material are improved, and the frequency of restriking is reduced because the contact characteristics are stabilized.

Here, the oxygen content in the Cr phase is 200 pp.
If it is less than m, the effect of improving the cutoff characteristics and the effect of reducing the frequency of restriking will be insufficient. On the other hand, when the oxidized content exceeds 1000 ppm, gas is easily generated at the time of opening / closing of the contacts, the pressure resistance is reduced, the conductivity of the contact material is reduced, and the electrical resistance of the contacts is generated. The contact temperature rises due to the generated Joule heat, which leads to abnormal generation of component vapors and gases, which rather deteriorates the cutoff characteristics.

As described above, by including a predetermined amount of oxygen in the Cr phase of the contact material, the breaking characteristics of the vacuum circuit breaker can be improved, and the application range of the circuit breaker can be expanded.
Reliability can be improved.

According to the contact material for a vacuum circuit breaker according to the above construction, since a predetermined amount of oxygen is contained in the chromium phase constituting the contact material, a large current interruption when used as a contact member of the vacuum circuit breaker. Performance, voltage resistance and welding resistance can be greatly improved, and the occurrence of restriking can be effectively reduced. Therefore, even in a miniaturized vacuum circuit breaker, it is possible to mass-produce a vacuum circuit breaker having good breaking performance and excellent durability and reliability.

Further, the breaking performance is improved as compared with the conventional contact material, and the re-ignition phenomenon can be greatly reduced.
The reliability of the circuit breaker is improved, and the applicable range of the circuit breaker can be greatly expanded.

[0033]

Next, an embodiment of the present invention will be described.
This will be described with reference to the following examples.

Examples 1 to 5 A Cr powder as an arc-resistant component containing an amount of oxygen shown in Table 1 and having an average particle size of 100 μm, and an electrolytic Cu powder as a highly conductive component having an average particle size of 50 μm were prepared. Were weighed so that the composition ratio (weight ratio) shown in Table 1 was obtained. Then, C weighed together with the mixing balls into a ball mill pot
The r powder and the electrolytic Cu powder were charged and rotationally mixed in an inert gas atmosphere to obtain a raw material mixture. Next, this raw material mixture was charged into a mold press, and press-formed at a pressure of 800 MPa to obtain a Cu-Cr formed body. Furthermore, this Cu
-Insert the Cr compact into a heating furnace, and heat the compact in a nitrogen gas atmosphere at a temperature increase rate of 5 ° C / min at a temperature of 1050 ° C.
After heating for 3 hours and firing, the furnace was cooled and taken out of the heating furnace.

Next, the Cu—Cr sintered body taken out was cut into a predetermined contact shape to obtain a first contact example.
Many contact materials according to Nos. To 5 were prepared.

Conventional Example 1 A contact material according to Conventional Example 1 was prepared by preparing, molding and sintering a raw material mixture under the same conditions as in Example 1 except that a Cr powder having an oxygen content as low as 90 ppm was used. A number of materials were prepared.

Comparative Examples 1-3 Preparation of a raw material mixture under the same conditions as in Example 1 except that a Cr powder having an excessive oxygen content of 1500 ppm was used.
A number of contact materials according to Comparative Example 1 were prepared by performing molding and sintering. Cr having an oxygen content as low as 90 ppm
Except for using powder, preparation, molding, and sintering of a raw material mixture were performed under the same conditions as in Examples 4 and 5, respectively, to prepare a number of contact materials according to Comparative Examples 2 and 3, respectively.

In order to evaluate the breaking characteristics of the contact materials according to the examples, the conventional examples, and the comparative examples prepared as described above, each contact member was incorporated in a vacuum valve, and a vacuum circuit breaker as shown in FIGS. Each was manufactured.

That is, as shown in FIG. 2, the contact members 13a and 13b according to each embodiment, the conventional example, and the comparative example are
g Using a brazing material 14, the electrodes 7 and 8 were vacuum-brazed at the center of the end faces. On the other hand, the electrodes 7, 8 were integrally joined to the end surfaces of the conductive rods 5, 6 via a brazing portion 12. Further, the electrodes 7, 8 to which the respective contact members 13a, 13b were brazed were arranged so as to face each other, and ten vacuum circuit breakers as shown in FIG. 1 were assembled, and the quality of the breaking characteristics was compared. That is, a predetermined voltage (6 Kv),
The minimum re-ignition current and the range of variation of the re-ignition occurrence frequency (minimum value to maximum value) when the circuit having the current value (500 A) was interrupted 20,000 times were measured.

The breaking performance was measured and evaluated as follows. That is, after the contact surface is cooled by baking, voltage aging, or the like to make the conditions constant, 7.2K is applied.
The maximum value of the current at the cutoff limit was measured while increasing the current by 1 KA at 50 Hz and 50 Hz. In addition, each characteristic value is relatively shown with the characteristic value when the contact material according to Conventional Example 1 is used as a reference value 1.0. Each characteristic value is shown in Table 1 below.

[0041]

[Table 1]

As is clear from the results shown in Table 1 above,
The vacuum circuit breaker corresponding to each embodiment in which a contact material containing oxygen within a predetermined range in the Cr phase is incorporated is compared with the circuit breaker according to the conventional example and the comparative example using the conventional contact material. The occurrence frequency of ignition is small, the minimum re-ignition current is high, and the welding resistance is greatly improved.

In particular, the variation range of the frequency of occurrence of restriking is extremely small, the variation in arc stability and breaking performance is small, and a small-sized vacuum circuit breaker with stable characteristics can be mass-produced.

[0044]

As described above, according to the contact material for a vacuum circuit breaker according to the present invention, since a predetermined amount of oxygen is contained in the chromium phase constituting the contact material, it can be used as a contact member of the vacuum circuit breaker. When used, large current interrupting property, voltage resistance and welding resistance can be significantly improved, and the occurrence of restriking can be effectively reduced. Therefore, even in a miniaturized vacuum circuit breaker, it is possible to mass-produce a vacuum circuit breaker having good breaking performance and excellent durability and reliability.

Further, the breaking performance is improved as compared with the conventional contact material, and the re-ignition phenomenon can be greatly reduced.
The reliability of the circuit breaker is improved, and the applicable range of the circuit breaker can be greatly expanded.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structural example of a vacuum circuit breaker to which a contact material according to the present invention is applied.

FIG. 2 is an enlarged sectional view showing a contact and an electrode unit shown in FIG. 1;

[Description of Signs] 1 Shutoff chamber 2 Insulating container 3a, 3b Sealing metal 4a, 4b Lid 5 Conductive rod 6 Conductive rod 7 Electrode (fixed electrode) 8 Electrode (movable electrode) 9 Bellows 10 Arc shield 11 Arc shield 12 Wax Attachment parts 13a, 13b Contact member 14 Brazing material (Ag brazing material)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01H 1/02 B22F 3/14 101B (72) Inventor Junichi Sato 1 Toshiba-cho, Fuchu-shi, Tokyo Stock (72) Inventor Kenji Watanabe 1 Toshiba-cho, Fuchu-shi, Tokyo In-house Fuchu factory

Claims (8)

[Claims] 1. A contact material for a vacuum circuit breaker comprising a chromium phase as an arc-resistant component and a copper phase as a highly conductive component,
The oxygen content in the chromium phase is 200 to 1000 ppm
A contact material for a vacuum circuit breaker, characterized in that: 2. The contact material for a vacuum circuit breaker according to claim 1, wherein the oxygen component contained in the chromium phase exists as chromium oxide. 3. The chromium content as an arc-resistant component is 20.
2. The contact material for a vacuum circuit breaker according to claim 1, wherein the content is from about 80% by weight. 4. The method according to claim 1, wherein copper powder and oxygen as highly conductive components are added in an amount of 10%.
Mixing a chromium powder as an arc-resistant component containing 0 to 2000 ppm to prepare a raw material mixture, and forming the raw material mixture to form a copper-chromium molded body;
A step of heating and sintering the copper-chromium molded body to form a copper-chromium sintered body. 5. A copper-chromium sintered body formed by heat sintering, wherein copper is further infiltrated.
A method for producing the contact material for a vacuum circuit breaker according to the above. 6. The method according to claim 4, wherein the average particle size of the copper powder is 1/20 to 1/3 of the average particle size of the chromium powder. 7. A step of forming and sintering a chromium powder as an arc-resistant component containing 100 to 2000 ppm of oxygen to form a calcined body of chromium, A method of infiltrating copper as a component. 8. A chromium phase comprising a chromium phase as an arc-resistant component and a copper phase as a highly conductive component and having an oxygen content of 20 in the chromium phase.
A vacuum circuit breaker having a contact of 0 to 1000 ppm.