JP3206336B2 - Contact of vacuum circuit breaker and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact used in a vacuum circuit breaker and having a low breaking current value and good current breaking performance.

[0002]

2. Description of the Related Art FIG. 3 is a schematic sectional view showing a main part of a vacuum valve used in a vacuum circuit breaker. In FIG. 3, a vacuum valve is formed by hermetically joining a metal upper flange 2a and a lower flange 2b to both ends of a ceramic or glass insulating cylinder 1 for ensuring insulation properties. I have. In this container, a pair of contacts capable of performing contact and separation, that is, a movable contact 3a
And the fixed contact 4a. One end of a movable-side energizing rod 3b having a T-shaped cross section is attached to the movable contact 3a, and the other end of the movable-side energizing rod 3b is connected to an upper flange 2a.
Through the center of the bellows 5 joined to the outside of the vacuum vessel from the upper flange 2a, the movable contact 3a
The movable contact 3 is formed with the movable-side conducting rod 3b.

The fixed contact 4a has one end of a fixed-side energizing rod 4b having an I-shaped cross section attached thereto, and the other end of the fixed-side energizing rod 4b passes through the lower flange 2b and is joined to the lower flange 2b outside the container. The fixed contact 4 is formed by the fixed contact 4a and the fixed-side energizing rod 4b. The movable contact 3a can be brought into contact with and separated from the fixed contact 4b in a state where the container holds a vacuum, and current can be supplied and cut off through the movable contact 3 and the fixed contact 4 . Bellows 5
A bellows cover 6 provided between the lower end of the bellows and the movable side conducting rod 4a protects the bellows 5 from being damaged by an arc at the time of opening and closing the current. An arc shield 7 provided on the inner wall of the vacuum vessel is provided. Is bellows cover 6
This is for protecting the insulating tube 1 in the same manner as described above.

[0004] The vacuum vessel of the vacuum valve having such a configuration is provided with an exhaust pipe 8 which is attached through a part of any of the upper flange 2a, the lower flange 2b, the movable energizing rod 3b, and the fixed energizing rod 4b. While the entire container is heated, a vacuum pump (not shown) is used to evacuate the container to a pressure of 10 ⁻² Pa (Pascal) or less.
FIG. 3 shows an example in which the exhaust pipe 8 is attached to the fixed-side energizing rod 4b and the container is evacuated to a vacuum. After the evacuation, the evacuation pipe 8 is sealed at a predetermined location outside the container, thereby completing the vacuum valve. In this way, the manufactured vacuum valve maintains a high vacuum,
The movable contact 3a and the fixed contact 4a can be contacted and separated by the extendable bellows 5.

The movable contact 3a and the fixed contact 4a used here are the most important components of the vacuum valve,
The contact material constituting these contacts is required to have the following characteristics. Excellent current interruption characteristics. Low breaking current value.

[0006] It has excellent arc and welding resistance. Excellent withstand voltage characteristics. Low contact resistance and large current carrying capacity. The amount of stored gas is small. The manufacturing method is simple and inexpensive.

However, since some of these required properties require properties of contradictory contact materials, a single metal cannot satisfy these required properties. Or more multi-element alloys are used. In addition, contact materials are properly used depending on the use of the vacuum circuit breaker.
Various alloys such as a Cu-based alloy, a Cu-W-based alloy, and a Wc-Ag-based alloy have been used.

[0008] Among these alloys, Cu-Bi alloy and Cu-Cr-B are used as contact materials for a low surge type vacuum circuit breaker which secures current breaking characteristics and has a low current breaking value.
i-alloy, Cu-Bi-Te alloy or the like is used. Some low-melting metals include Pb and Se in addition to Bi and Te. When such an alloy is manufactured by a normal vacuum melting method, there is a problem that the content of the low-melting-point metal decreases due to volatilization in the manufacturing process, and the low-melting-point metal volatilizes to cause fouling of the heating furnace. to avoid this, when prepared by a sintering method of a temperature lower than the vacuum melting method, vacancies alloy remaining true density is not obtained, et al. The holes remaining in the alloy are easy to adsorb gas when processing into the contact shape, and when manufacturing a vacuum valve using the contact material that adsorbed the gas, release the adsorbed gas from the contact material and release this gas. Because of the necessity of elimination, it takes a considerable time to stabilize the degree of vacuum inside the vacuum valve.

Therefore, Cu-Bi alloys and Cu-Cr-B containing a large amount of low melting point metals such as Bi, Te, Pb, Se, etc.
In order to produce an i-alloy or the like in a completely dense state having a desired composition and having no pores, a hot isostatic press [hereinafter, referred to as HIP (Ho), which provides a synergistic effect of high temperature and high pressure.
abbreviation of t Isostatic Pressing) is effective. HIP is a widely known technique, and its outline will be described with reference to FIG.

FIG. 4 is a schematic cross-sectional view showing the configuration of a main part of the HIP processing apparatus, and the supply path of the inert gas is indicated by an arrow.
In FIG. 4, the apparatus includes a heat insulating material 1 in a high-pressure vessel 9.
0 and a heater 11 are arranged, the whole of which is housed in an external structure 12. The object 13 is placed on a table placed on a lid 14 of a high-pressure container 9, and the high-temperature and high-pressure gas is Heating and pressurizing is performed depending on the atmosphere. In general, pressurization is performed by filling an inert gas 15 such as Ar or N ₂ into the high-pressure container 9 by pressurizing the gas with a gas compressor 16 and pressurizing the container 9. At the same time high pressure vessel 9
By the heating of the heater 11 inside, the pressure can be further increased by the expansion of the inert gas 15 filled therein. The feature of the HIP processing is that since the gas pressure is used, an isotropic pressure can be applied to the object 13 having an arbitrary shape. Therefore, the object to be processed 1 is placed in a metal container, evacuated to vacuum, and subjected to HIP processing.
3 can be densified to the true density.

[0011]

However, a contact having a true density must be joined to and integrated with a current-carrying rod in order to form a contact.
There are issues that need to be resolved. The joining method includes a method of directly brazing the contact and the current-carrying rod, and a method of mechanically joining the contact and the current-carrying rod by plastically processing a part of the contact and the current-carrying rod. 5 (a) and 5 (b) are schematic cross-sectional views of a contact portion showing a joining state of a contact and an energizing rod, FIG. 5 (a) shows a case of joining by brazing, and FIG. ) Shows the case of joining by caulking, respectively, but here, for convenience of explanation, the movable contact and the fixed contact are not distinguished.

FIG. 5 (a) shows the contact 17a and the energizing rod 1
8a is directly brazed to form a brazing layer 19, but when brazing a contact 17a having a low melting point and containing a large amount of Bi or Te which tends to weaken the metal, Since these metal components which have been in a liquid phase before the material is in a liquid phase penetrate into the brazing material when the brazing material is melted, the brazing layer 19 becomes brittle, and the opening and closing vibration of the vacuum circuit breaker, The contact when the large current is cut off causes the contact 17a to fall off, causing a fatal defect in the vacuum valve.

On the other hand, FIG. 5 (b) shows a state in which the contact 17b and a part of the conducting rod 18b are plastically worked, and these are caulked and mechanically joined to form the caulked portion 20. In this case, when caulking lightly, the caulking portion 20 of the current-carrying rod 18b which has been subjected to plastic working and hardened causes the caulking portion 20 to be 400 to 500 at the time of heating and evacuation in the manufacturing process of the vacuum valve.
C., the high-purity Cu rod generally used as a material for the current-carrying rod 18b is completely annealed, and the strength of the caulked portion 20 is reduced. The contact having reduced bonding strength is loosened between the contact 17b and the energizing rod 18b due to the opening and closing vibration of the vacuum circuit breaker. Also, if swaged too strongly, the contact 17b itself may be damaged.
The crimping conditions must be set strictly.

The present invention has been made in view of the above points, and an object of the present invention is to provide a contact of a vacuum circuit breaker having a desired composition and a true density, which can be firmly joined to an energizing rod. is there.

[0015]

In order to solve the above-mentioned problems, a contact point of a vacuum circuit breaker of the present invention is a method in which a powder compact is made of H.
Made by IP processing, and after processing, put powder compact
A contact is formed as a composite material leaving a part of the u-made metal container, and an energizing rod is brazed to the remaining metal container. Through
The time for brazing the electric rod is after the HIP treatment,
Remove even after removing the brazed part of the container
It may be before.

[0016]

As described above, since the contacts of the vacuum circuit breaker of the present invention are manufactured by HIP processing, a desired alloy composition and a true density can be obtained. Therefore, since the brazing is performed between the original conductive materials, the contact point of the contactor and the current-carrying rod are in a strong joint state.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. The contact of the present invention is produced by subjecting a powder compact to HIP processing. The process will be described with reference to the schematic cross-sectional views of FIGS. 1 (a) to 1 (c). First, Cu-25Cr-20B in weight ratio
A compact 21a obtained by press-molding the powder mixed at a ratio of i at about 294 MPa is filled in a metal container 22 made of Cu.
At this time, the thickness of the bottom surface of the metal container 22 is larger than the thickness of the side surface. For example, it is appropriate that the thickness of the bottom surface is approximately 3 mm and the thickness of the side surface is approximately 1/2. This is for preventing the bottom portion from being deformed by the HIP process, because it becomes difficult to braze the current-carrying rod.
Separately, a metal pipe 23 is attached and the section is T
A lid 24 having a letter shape is prepared, and the lid 24 is joined to the upper part of the metal container 22 filled with the molded body 21a [FIG.
(A)].

Next, the metal container 22 to which the lid 24 is attached
Is charged into an electric furnace (not shown), and while heating to 200 to 300 ° C., the inside of the metal container 22 is evacuated from the metal pipe 23 using a vacuum evacuation device (not shown). The inner surface is pressure-bonded with a part of the pipe 23 to form the sealing portion 25. In this process, the heating temperature is set to 200 to 30.
The reason why the temperature is set to 0 ° C. is that the gas contained in the molded body 21a cannot be sufficiently removed at a temperature of 200 ° C. or less, and therefore, when the inside of the vacuum valve using the obtained contact is evacuated, a stable This is because it takes a long time to reach the degree of vacuum. If the temperature exceeds 300 ° C., Bi volatilizes, causing a change in the alloy composition ratio, and a desired alloy composition cannot be obtained [FIG. (B)].

Next, this is charged into the high pressure vessel 26 of the HIP processing apparatus, and the temperature is 500 to 1000 ° C. in an Ar atmosphere.
The pressure is maintained at about 69 to 196 MPa for 30 to 120 minutes. Here, the temperature of 500 to 1000 ° C.
If the Bi powder is melted and solidified at a temperature of 500 ° C. or less, the breaking current value of the vacuum valve using the obtained contact is almost the same as that of a temperature of 500 ° C. or more at an average value because the obtained powder is extremely fine. However, this is because a value considered to be an abnormal value occurs several times in 100 measurements, and when the temperature exceeds 1000 ° C., Cu as the main component of the molded body 21a or the metal container 22 made of Cu This is because there is a risk of melting. HIP
After the processing is completed, the metal container 22 and the sintered alloy 21b are taken out of the high-pressure container 26. Arrows in the high-pressure vessel 26 indicate that pressure is applied to the sintered alloy 21b isotropically. When the molded body 21a containing Cu as a main component and the metal container 22 made of Cu are brought into contact with each other and heated or pressed, the atoms of both become easy to diffuse. However, since the HIP treatment has a synergistic effect of high temperature and high pressure as described above, The interdiffusion of atoms becomes extremely remarkable, and after a lapse of a predetermined time, the contact portions integrally have sufficient strength. [FIG. 1 (c)].

In a normal HIP process, after the metal container and the object to be processed are taken out, the metal container is removed by cutting or the like.
Normally, only the object to be processed is used as a dense and high-strength member, but the present invention is characterized in that a part of the metal container 22 is left as it is and used as a brazing surface. That is, the contact of the present invention is formed as a clad-type composite material in which a Cu plate is bonded to a sintered alloy by HIP processing and post-processing, and brazing with a current-carrying rod is performed at a portion corresponding to the Cu plate. It has a special feature.

FIG. 2 is a schematic sectional view showing this state.
FIG. 2A shows a state in which the current-carrying rod is brazed and FIG.
(B) shows a state in which this is processed, but also here, for convenience, the movable contact and the fixed contact are not distinguished. FIG.
(A) Cu-25Cr-20B with lid 24 attached
FIG. 2B shows a state in which the metal container 22 containing the i-sintered alloy 21b and the energizing rod 27 are brazed with silver to form a brazing layer 28. FIG. This indicates that the metal container 22 at the portion serving as the electrical contact surface was cut and removed to form a contact. In this step, first, the sintered alloy 21b and the metal container 22 may be cut and then brazed to the energizing rod 27 and silver. However, in this case, since a part of the surface of the sintered alloy 21b remains exposed, there may be a problem such as a shift in composition due to evaporation of Bi at a silver brazing temperature or contamination of a brazing furnace. In practice, it is often advantageous to perform cutting after silver brazing.

As described above, at the end of production, the contact of the present invention is formed by integrating an extremely high-density sintered alloy with Cu, which is a conductive material which is originally a wrought material, on the Cu side. Since the brazing is performed with the current-carrying rod, it is possible to obtain a contact having very strong contacts. Next, regarding the contact of the present invention thus produced, Cu-2
When the density of the 5Cr-20Bi sintered alloy was measured, it reached 99.8% or more with respect to the true density. This is because powder mixing → pressure molding (294 to 491 MPa) → sintering (5
The density of the conventional sintered alloy obtained in the process of (00 to 900 ° C.) is 96.5 to 98.5% with respect to the true density, and even when a pressure of 491 to 785 MPa is applied,
The increase in density is a sufficient value compared to a very small increase. When the cross-sectional structure of the sintered alloy of the contact point of the present invention was observed with a microscope having a magnification of about 100, no voids were observed at all, or very minute voids were slightly observed due to the HIP treatment. It was also confirmed that it was nothing more than mere. In addition, according to the composition analysis, the content of Bi, which is a low-melting metal, has not changed from the initial blending value.

Next, using the contact shown in FIG.
Although the vacuum valve shown in FIG. 3 was assembled, the time required for the degree of vacuum inside the vacuum valve to stabilize in the evacuation step was determined by the contact vacuum valve using a sintered alloy manufactured by a conventional powder metallurgy method. Is about 1/2 to 1/5. This is because the type of gas released in the evacuation process is
Moisture is mainly contained, but the amount is extremely small compared to the conventional one.The contact of the present invention is dense, there is almost no gas occluded inside, and after the gas adsorbed on the contact surface is removed, The degree of vacuum inside the vacuum valve is due to a stable state immediately. Then, for the vacuum valve that has been completely evacuated, a breaking test was performed at 7.2 KV / 20 KA, and a breaking current value was measured when 10 A was energized after the breaking test. As a result, both the breaking performance and the breaking current value were abnormal. There was no change in the degree of vacuum before and after the cutoff test.

Further, after completion of the series of tests, the vacuum valve was disassembled and the contact was abnormal, that is, Cu-25Cr.
-20Bi sintered alloy 21b falling off or loose, metal container 22
An investigation was made of an abnormality at the silver brazing portion between the electrode and the current-carrying rod 27, but no abnormality was found. In the contact of the present invention, the sintered alloy 21b is already integrated with Cu on the brazing surface from the beginning at the time of the HIP processing. Therefore, the sintered alloy 21b is directly brazed to the current-carrying rod 27 without Cu. Also, no defects are observed.

[0025]

As the contact material of the vacuum valve of the vacuum circuit breaker having a low breaking current value and good breaking performance, an alloy containing a large amount of low melting point metal is used. In order to obtain a dense sintered alloy having no pores, it is effective to perform HIP processing. However, in the present invention, the metal container used for HIP processing is C
Since the metal container made of u is formed integrally with the sintered alloy after the HIP treatment, the portion corresponding to the bottom surface of the metal container is used as a brazing surface for the current-carrying rod. The contact of the vacuum valve can be manufactured. Therefore, a contact in which the contact was extremely firmly joined was obtained without causing a defect in the brazing layer between the contact and the current-carrying rod, and as a result, a large current such as an opening / closing vibration of a vacuum valve and a short-circuit current was cut off. Even at this time, loosening of the contact junction and dropping of the contact do not occur, and the reliability of the vacuum valve can be improved.

[Brief description of the drawings]

FIG. 1 shows HIP processing steps used in the present invention, wherein (a) shows a state in which a molded article is charged into a container and a lid is placed,
(B) is a schematic cross-sectional view showing a state in which it is evacuated and sealed, and (c) is a state in which it is further heated and pressurized in a high-pressure container.

FIGS. 2A and 2B show a process of fabricating a contact using the contact of the present invention. FIG. 2A shows a state where the contact is formed by brazing to a current-carrying rod while HIP processing is performed, and FIG. Schematic sectional view showing the state

FIG. 3 is a schematic cross-sectional view illustrating a main configuration of a vacuum valve for a vacuum circuit breaker.

FIG. 4 is a schematic sectional view showing a configuration of a main part of the HIP processing apparatus.

FIGS. 5A and 5B are partial schematic cross-sectional views showing contacts in which a contact and an energizing rod are joined, wherein FIG. 5A shows a case of brazing and FIG. 5B shows a case of caulking;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Insulation cylinder 2a Upper flange 2b Lower flange 3 Movable contact 3a Movable contact 3b Movable side conducting rod 4 Fixed contact 4a Fixed contact 4b Fixed side conducting rod 5 Bellows 6 Bellows cover 7 Arc shield 8 Exhaust pipe 9 High pressure vessel 10 Heat insulating material DESCRIPTION OF SYMBOLS 11 Heater 12 External structure 13 Object to be processed 14 Lid 15 Inert gas 16 Gas compressor 17a Contact 17b Contact 18a Energizing rod 18b Energizing rod 19 Brazing layer 20 Caulked part 21a Molded body 21b Sintered alloy 22 Metal container 23 Metal Pipe 24 Lid 25 Sealing part 26 High-pressure vessel 27 Current-carrying rod

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-202813 (JP, A) JP-A-6-39957 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01H 33/66

Claims (4)

(57) [Claims] 1. A hot isostatic pressure in which a powder compact containing Cu as a main component and containing at least one low-melting-point metal is placed in a Cu metal container and sealed, and isotropically applied a high pressure with an inert gas. A contact of a vacuum circuit breaker that has been subjected to press processing,
Leaving a portion of the Cu-made metal container <br/> used for the hot isostatic pressing treatment is formed as a composite material, the Cu metal
A contact point for a vacuum or breaker, characterized in that a current-carrying rod is brazed to the bottom of the composite material leaving a part of the container . 2. The contact according to claim 1, wherein the thickness of the bottom surface of the metal container made of Cu is larger than the thickness of the side wall. 3. A process for the powder compact comprising at least one as a main component low-melting-point metal to seal this by taking into Cu metal container Cu, Cu metal contents of the powder compact
A hot isostatic pressing treatment step of adding isotropically high pressure sealed while in an inert gas atmosphere to a vessel, current supply rods on one end of the Cu metal containers sealed and hot isostatic pressing the powder compact After brazing, at least this Cu
The C leaving brazed portion of the energizing rod manufacturing metal containers
A method for manufacturing a contact point of a vacuum or a breaker, comprising a step of removing a u-made metal container . 4. A process for the powder compact comprising at least one as a main component low-melting-point metal to seal this by taking into Cu metal container Cu, Cu metal contents of the powder compact
A hot isostatic pressing treatment step of adding isotropically high pressure sealed while in an inert gas atmosphere vessel of at least energizing rod Cu metal containers sealed and hot isostatic pressing the powder compact Cu-made metal leaving brazing part
A method for producing a contact point of a vacuum or breaker, comprising a step of brazing an energizing rod to a brazing portion of the energizing rod of a Cu metal container after removing the container .