JPH09161583A - Manufacture of contact member for vacuum circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce influence of a brazing material, allow exertion of stable breaking characteristics, and enhance the reliability of a vacuum breaker even in case it is assembled by joining contact members using a brazing material. SOLUTION: Chromium powder as an arc-resisting component is mixed with copper powder as a high conductivity component so that a mixture as crude material is prepared, and the obtained material is shaped to produce a copper- chromium molding, and in the condition that this is in contact with a copper material having a thickness below 0.5mm, they are heated to a temp. between 900 and 1080 deg.C and kept for 0.5hr or more. Thereby the copper-chromium molding is baked to form a sintered body, and at the same time, copper material is diffused in the surface of the sinter and joined fast so that a copper layer 15 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a contact member for a vacuum circuit breaker, and particularly when a vacuum circuit breaker is assembled by joining the contact member with a brazing material, the influence of the brazing material is reduced and the stability is improved. The present invention relates to a method of manufacturing a contact member for a vacuum circuit breaker, which can exhibit the above-mentioned breaking characteristics and can improve the reliability of the vacuum circuit breaker.

[0002]

2. Description of the Related Art Circuit breakers open and close electric circuits in a normal state,
Widely used in electric power equipment, substation equipment, high-speed railway vehicles, etc. to automatically and instantaneously cut off the power line in combination with an overcurrent relay that detects a fault condition in the event of a grounding accident or short-circuit accident. Has been done. In particular, vacuum circuit breakers
Container (vacuum valve) maintained at high vacuum of about 10 ^-7 Torr
The electric circuit is opened and closed by opening and closing a pair of contact members that are arranged inside to face each other.

FIG. 2 is a sectional view showing a structural example of a general vacuum circuit breaker. In FIG. 2, the shutoff chamber 1 in which the contacts are opened and closed includes an insulating container 2 made of an insulating material and formed into a substantially cylindrical shape, and a sealing metal 3 at the upper and lower ends of the insulating container 2.
It is partitioned and formed by metal lids 4a and 4b provided via a and 3b to be vacuum-tight. Isolation room 1
Inside, a pair of conductive rods 5, 6 are arranged so as to face each other in the axial direction, and a pair of electrodes 7, 8 are attached to the ends of the conductive rods 5, 6 facing each other. 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.

Further, as shown in an enlarged manner in FIG. 3, the electrode 8 is fixed to the brazing portion 12 formed at the end of the conductive rod 6 by heat bonding or is crimped by caulking. 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, since a high dielectric strength in a high vacuum can be utilized, the opening and closing stroke of the opposed contact member can be shortened.

As the above-mentioned contact member, arc resistance (arc resistance) and welding resistance are indispensable so as not to be welded by an arc generated when a contact is frequently opened and closed, while maintaining low contact resistance. It is an essential requirement to have high conductivity characteristics. Specific contact constituent materials include, for example, Ag-based materials, Ag-Cu-based materials, and Ag-CdO.
Based materials, 30% Cu-W based materials, 50% Cu-Cr based materials, etc. are used. In particular, the Cu-W-based contact material has excellent conductivity, while the Cu-Cr-based contact material has excellent withstand voltage characteristics, and thus is widely used as a contact material for high-power electric devices.

Among the above-mentioned contact materials, Cu-Cr based contact materials which are particularly suitable as contact materials for high-power equipment are, for example, formed by a powder metallurgy method as a sintered body of a mixture of Cr powder and Cu powder. A porous Cr calcined body formed by infiltrating Cu is used as the infiltrant.

In the powder metallurgy method, the series of processing steps are simple, and there is an advantage that the contact member can be manufactured easily and inexpensively. Moreover, since several percent by volume of pores remain inside the sintered body which is the contact member manufactured by the powder metallurgy method, compared with the contact member manufactured by infiltrating Cu into the Cr calcined body. Especially, since it has excellent welding resistance, it is in great demand as a contact member for a circuit breaker of a high current / high breakdown voltage class.

[0010]

However, in a circuit breaker in which a contact member manufactured by a powder metallurgy method is joined to an electrode by a brazing process, since there are holes in the contact member, the brazing material melted during the joining process is There is a tendency to seep into the inside of the contact member through the holes due to the capillary phenomenon, and in some cases, it may seep out to the surface of the contact member. This phenomenon causes re-ignition phenomenon and welding phenomenon of the contact member, and further increases destabilization in the whole breaking characteristics such as breakable current characteristics and withstand voltage characteristics, which causes a specific decrease. Is a factor that reduces the reliability of the vacuum circuit breaker itself.

In order to suppress the above-described phenomenon of the brazing filler metal bleeding to a minimum, it has been conventionally attempted to strictly control and adjust the amount of the brazing filler metal used at the time of joining and the heat treatment conditions. It is complicated and it is still difficult to completely avoid the above phenomenon of bleeding.

[0012] In the future, in order to meet the increasing demand for circuit breakers of high current and high withstand voltage class using Cu-Cr type contact members, it is particularly desired to prevent the above-mentioned bleeding phenomenon and improve reliability. It is rare.

On the other hand, when the contact members are joined by the conventional brazing method, the joining surface tends to be insufficient and the joining strength tends to be insufficient. Particularly, the Cu--Cr system manufactured by the powder metallurgy method is used. In the case of a high-current / high-voltage class circuit breaker that uses contact members, it is a major issue to improve the joint strength.

The present invention has been made to solve the above problems. Even when a vacuum circuit breaker is assembled by joining contact members with a brazing material, the effect of the brazing material is reduced and stable breaking characteristics are obtained. It is an object of the present invention to provide a method for manufacturing a contact member for a vacuum circuit breaker, which is capable of exhibiting the above-mentioned effects and improving the reliability of the vacuum circuit breaker.

[0015]

In order to achieve the above object, a method of manufacturing a contact member for a vacuum circuit breaker according to the present invention comprises:
Mixing chromium powder as an arc-resistant component and copper powder as a highly conductive component to prepare a raw material mixture; molding the raw material mixture to form a copper-chromium compact;
The copper-chromium compact is fired by heating the copper-chromium compact to a temperature of 900 to 1080 ° C. in a state where the copper-chromium compact is in contact with a copper material having a thickness of 0.5 mm or less and holding it for 0.5 hour or more. And forming a copper layer by diffusing and bonding a copper material to the surface of the sintered body. In addition, the content of chromium powder in the raw material mixture is 20 to
It may be set in the range of 80% by weight.

That is, the Cu--Cr to which the method of the present invention is directed
The system contact member is manufactured by sintering a molded body formed of a mixed powder of Cr powder and Cu powder according to a processing procedure of powder metallurgy in a state of being in contact with a copper material.

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 range of 20 to 80% by weight. 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, the content is 80% by weight
If it exceeds, the content of Cu as a highly conductive component, which will be described later, is relatively decreased, and the contact resistance is increased, so that the energizing function as a contact is deteriorated.

Cu, which has a high conductivity, 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 arc-resistant component has an average particle size of 30 to 20.
A Cr powder of about 0 μm and a spherical Cu powder having an average particle diameter of about the same as that of the Cr powder are uniformly mixed in the above predetermined ratio to prepare a raw material mixture. Next, the prepared raw material mixture is used to press-mold with a pressing force of about 600 to 1000 MPa by a die press or the like to prepare a Cu-Cr molded body having a predetermined shape.

Next, the sintering step of firing the obtained Cu-Cr compact is started. In the method of the present invention, in this sintering step, the Cu—Cr compact and the copper material having a thickness of 0.5 mm or less are brought into contact with each other and heated to a temperature of 900 to 1080 ° C.
By holding for 5 hours or more, the molded body is made into a sintered body and the copper material is diffusion-bonded to the surface of the sintered body to be alloyed to form a contact member having a dense copper layer formed on the surface of the sintered body. Is a major feature.

When brazing a contact member, the copper layer functions as a barrier layer that prevents the brazing material from bleeding up, and also improves the uniformity of the surface of the contact member to improve brazing strength (bonding strength). It improves the mechanical characteristics of the valve of the vacuum circuit breaker.

The reason why the thickness of the copper material for forming the copper layer is set to 0.5 mm or less is as follows. That is, when the thickness of the copper material exceeds 0.5 mm, diffusion bonding does not proceed sufficiently under the conditions that the processing temperature in the sintering step is 900 to 1080 ° C. and the holding time is less than 0.5 hours, and the copper layer Since the adhesion strength is deteriorated, the reliability of the contact is deteriorated. Therefore, the thickness of the copper material is 0.5 mm
Although it is set as follows, it is more preferable to use a foil-shaped copper material having a thickness of 0.1 mm or less.

When the sintering temperature is lower than 900 ° C.,
Even if the holding time is set to 0.5 hours or more, it becomes difficult to sufficiently proceed the solid phase sintering of the contact member. On the other hand, when the sintering temperature exceeds 1080 ° C, the melting point of copper is 10
Since it is 83 degreeC, it becomes practically impossible to perform solid phase sintering. If the holding time is less than 0.5 hours, solid-phase sintering of the contact member does not proceed sufficiently, a uniform contact member cannot be obtained in terms of structure, and copper diffusion bonding becomes insufficient. Unable to achieve the intended purpose. Therefore, the treatment temperature in the sintering step is set in the range of 900 to 1080 ° C. and the holding time is set to 0.5 hours or more, but the treatment temperature is set to 1050 ° C. or more and the holding time is set to a range of 2 to 3 hours. , And more preferable.

According to the method of manufacturing a contact member for a vacuum circuit breaker having the above structure, a dense copper layer having no holes is formed on the surface of the contact member. This copper layer functions as a barrier to the molten brazing material when the contact member is brazed to the electrode. Therefore, it is possible to effectively prevent the brazing material from soaking into the inside and the surface of the contact member, which contributes to the stabilization of the electric circuit interruption characteristic of the contact member.

Further, since a uniform and smooth copper layer is formed on the surface of the contact member, the brazing strength (bonding strength) of the contact member
Will increase significantly. Therefore, the reliability and durability of the vacuum circuit breaker using the above contact member can be greatly improved.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described.
A description will be given with reference to the following examples.

Example 1 Cr powder as an arc-resistant component having an average particle size of 100 μm and Cu as a highly conductive component having an average particle size of 50 μm
The powder and the powder were uniformly mixed at a weight ratio of 50:50 to obtain a raw material mixture. Next, the raw material mixture was filled in a die press machine,
A Cu-Cr molded body was obtained by press molding with a pressure of 800 MPa. Furthermore, this Cu-Cr compact is made to have a thickness of 50 μm.
m at a temperature of 1 at a heating rate of 5 ° C./min in a vacuum atmosphere while being placed in contact with an oxygen-free copper foil as a copper material.
The mixture was heated to 050 ° C., held for 3 hours for firing, and the copper material was diffusion-bonded, then cooled in a furnace and taken out from the heating furnace. A large number of contact members according to Example 1 were prepared by processing the taken out contact material into a predetermined contact shape.

Example 2 Cr powder as an arc-resistant component having an average particle size of 100 μm and Cu as a highly conductive component having an average particle size of 50 μm
The powder and the powder were uniformly mixed at a weight ratio of 50:50 to obtain a raw material mixture. Next, the raw material mixture was filled in a die press machine,
A Cu-Cr molded body was obtained by press molding with a pressure of 800 MPa. Furthermore, this Cu-Cr compact is made to have a thickness of 50 μm.
m at a temperature of 9 at a temperature rising rate of 5 ° C./min in a vacuum atmosphere while being placed in contact with an oxygen-free copper foil as a copper material.
The mixture was heated to 00 ° C., held for 3 hours for firing, and diffusion-bonded with a copper material, followed by furnace cooling and removal from the heating furnace. A large number of contact members according to Example 2 were prepared by processing the extracted contact material into a predetermined contact shape.

Comparative Example 1 Cr powder as an arc-resistant component having an average particle size of 100 μm and Cu as a highly conductive component having an average particle size of 50 μm.
The powder and the powder were uniformly mixed at a weight ratio of 50:50 to obtain a raw material mixture. Next, the raw material mixture was filled in a die press machine,
A Cu-Cr molded body was obtained by press molding with a pressure of 800 MPa. Furthermore, this Cu-Cr molded body is 1 mm thick.
At a temperature rise rate of 5 ° C / min in a vacuum atmosphere while being placed in contact with the oxygen-free copper foil as the copper material of
It was heated to 50 ° C., held for 3 hours to be fired, and the copper material was diffusion-bonded, then cooled in a furnace and taken out from the heating furnace. A contact member according to Comparative Example 1 was prepared by processing the extracted contact material into a predetermined contact shape.

Comparative Example 2 Cr powder as an arc-resistant component having an average particle size of 100 μm and Cu as a highly conductive component having an average particle size of 50 μm.
The powder and the powder were uniformly mixed at a weight ratio of 50:50 to obtain a raw material mixture. Next, the raw material mixture was filled in a die press machine,
A Cu-Cr molded body was obtained by press molding with a pressure of 800 MPa. Furthermore, this Cu-Cr compact is made to have a thickness of 50 μm.
m at a temperature of 8 at a heating rate of 5 ° C./min in a vacuum atmosphere while being placed in contact with an oxygen-free copper foil as a copper material.
The mixture was heated to 00 ° C., held for 3 hours for firing, and diffusion-bonded with a copper material, followed by furnace cooling and removal from the heating furnace. A contact member according to Comparative Example 2 was prepared by processing the taken out contact material into a predetermined contact shape.

Comparative Example 3 Cr powder as an arc-resistant component having an average particle size of 100 μm and Cu as a highly conductive component having an average particle size of 50 μm.
The powder and the powder were uniformly mixed at a weight ratio of 50:50 to obtain a raw material mixture. Next, the raw material mixture was filled in a die press machine,
A Cu-Cr molded body was obtained by press molding with a pressure of 800 MPa. Furthermore, this Cu-Cr molded body is 1 mm thick.
At a temperature rise rate of 5 ° C / min in a vacuum atmosphere while being placed in contact with the oxygen-free copper foil as the copper material of
The mixture was heated to 50 ° C., held for 20 minutes for firing, and diffusion-bonded with a copper material, followed by furnace cooling and removal from the heating furnace. A contact member according to Comparative Example 3 was prepared by processing the taken out contact material into a predetermined contact shape.

Comparative Example 4 Cr powder as an arc-resistant component having an average particle size of 100 μm and Cu as a highly conductive component having an average particle size of 50 μm.
The powder and the powder were uniformly mixed at a weight ratio of 50:50 to obtain a raw material mixture. Next, the raw material mixture was filled in a die press machine,
A Cu-Cr molded body was obtained by press molding with a pressure of 800 MPa. Further, this Cu-Cr compact was heated in a vacuum atmosphere at a temperature of 1050 ° C at a temperature rising rate of 5 ° C / min.
After heating for 3 hours and firing, the furnace was cooled and taken out of the heating furnace. A contact member according to Comparative Example 4 was prepared by processing the extracted contact material into a predetermined contact shape.

As shown in FIG. 1, each contact member 13 according to the example and the comparative example prepared in this manner is used as an electrode 8 by using an Ag brazing material 14 with the side on which the copper layer 15 is formed as a joint surface.
Was vacuum brazed to the center part of the end face. On the other hand, the electrode 8 was integrally joined to the end face of the conductive rod 6 via the brazing portion 12.
Then, the cross-sectional structures of the contact members after brazing were compared and observed, and the occurrence rate of the "bleeding up" phenomenon of the brazing material was measured. The average bonding strength of each contact member was also measured. In addition, the average bonding strength is shown relative to the reference value of Comparative Example 4.

Further, a vacuum circuit breaker as shown in FIG. 2 was assembled using the electrodes 7 and 8 in which the respective contact members 13 were brazed and joined, and the quality of the breaking characteristics was compared. That is, the frequency of re-ignition when a circuit having a predetermined voltage and current value was cut off 20,000 times was measured, and the results shown in Table 1 below were obtained.

[0035]

[Table 1]

As is clear from the results shown in Table 1,
In the contact members according to the respective examples manufactured under the predetermined treatment conditions specified by the method of the present invention, since the dense copper layer is formed, there is no bleeding of the brazing material inside or on the surface of the contact member. Moreover, the joint strength of the contact members is also high. When the bonding strength of the contact members of Examples 1 and 2 was measured, breakage occurred in the base material portion. Therefore, the frequency of re-ignition when operating the vacuum circuit breaker is
It was confirmed that the vacuum circuit breaker was significantly reduced in comparison with Comparative Example 4 showing the conventional example, and the reliability and durability of the vacuum circuit breaker were significantly improved.

On the other hand, when the thickness of the copper material is excessive (Comparative Example 1), the sintering temperature is low (Comparative Example 2), or the holding time in the sintering process is too short (Comparative Example 3), copper is used. It was found that the diffusion bonding of the materials became insufficient, and the bonding strength of the contact member decreased, and it could not be put to practical use. Further, in Comparative Example 4, 2% of the brazing filler metal was soaked up to the half position in the thickness direction of each contact member, and 2% of the brazing filler metal reached the surface.

In the above embodiment, as shown in FIG. 2, the contact members 13a and 13b manufactured in each embodiment are brazed to the pair of electrodes 7 and 8 facing each other to form a vacuum circuit breaker. Although it was formed, it was confirmed that similarly high breaking characteristics are exhibited even when the contact member according to this example is joined to only one electrode.

[0039]

As described above, according to the method for manufacturing a contact member for a vacuum circuit breaker according to the present invention, a dense copper layer having no holes is formed on the surface of the contact member. This copper layer functions as a barrier against the molten brazing material when the contact member is brazed to the electrode. Therefore, it is possible to effectively prevent the brazing material from soaking into the inside and the surface of the contact member, which contributes to the stabilization of the electric circuit interruption characteristic of the contact member.

Further, since a uniform and smooth copper layer is formed on the surface of the contact member, the brazing strength (joint strength) of the contact member
Will increase significantly. Therefore, the reliability and durability of the vacuum circuit breaker using the above contact member can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a contact member manufactured by the method of the present invention is joined to an electrode of a vacuum circuit breaker.

FIG. 2 is a sectional view showing the structure of a vacuum circuit breaker.

FIG. 3 is an enlarged cross-sectional view showing an electrode portion shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Breaking chamber 2 Insulating container 3a, 3b Sealing metal 4a, 4b Lid body 5 Conductive rod 6 Conductive rod 7 Electrode (fixed electrode) 8 Electrode (movable electrode) 9 Bellows 10 Arc shield 11 Arc shield 12 Brazing part 13, 13a , 13b Contact member 14 Brazing material (Ag brazing material) 15 Copper layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiromichi Horie Inventor Hiromichi Horie 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Toshiba Corporation Yokohama Office

Claims (2)

[Claims] 1. A step of preparing a raw material mixture by mixing chromium powder as an arc-resistant component and copper powder as a highly conductive component, and forming the raw material mixture to form a copper-chromium compact. Process, the above-mentioned copper-chromium compact and thickness 0.5mm
Temperature 900 to 1080 in the state of contacting with the following copper materials
By heating to ℃ and holding for 0.5 hours or more, copper-
And a step of forming a copper layer by diffusing and bonding a copper material to the surface of the sintered body at the same time as baking the chrome compact to form a sintered body. 2. The chromium powder content of the raw material mixture is 20 to
The range of 80% by weight is set.
A method for manufacturing a contact member for a vacuum circuit breaker according to claim 1.