JPH1040761A - Contact material for vacuum circuit breaker, its manufacture, and vacuum circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the contact resistance and improve a large current breaking property, withstand voltage, and melting and depositing resistance by adjusting surface roughness of a contact material to have specified values as the maxi mum height and the mathematical average roughness, respectively. SOLUTION: Respective contact materials 13a, 13b are vacuum-brazed in the center parts of the end faces of electrodes 7, 8, respectively. The roughness of the contact materials is controlled to be 12μm or lower as the maximum height Ry defined as JIS B0601 and 4μm or lower as the mathematical average roughness Ra. In the case the surface roughness exceeds 12μm (Ry) or 4μm (Ra), the contact resistance of the contact points increases and due to excess Joule heat generation, the large current breaking property is deteriorated. Moreover, an electric field is concentrated on a part where a projected part is formed and withstand voltage is therefore decreased and at the same time, partial melting and deposition easily occur and thus the melting and depositing resistance of the contact points is deteriorated and a vacuum circuit breaker having excellent durability is obtained.

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 the like, and in particular, when used as a contact (contact) of a vacuum circuit breaker, greatly improves a large current breaking property, pressure resistance and welding resistance. The present invention relates to a contact material for a vacuum circuit breaker, a method of manufacturing the same, and a vacuum circuit breaker.

[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, 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.

The above-mentioned contact member must have arc resistance (arc resistance) or welding resistance so as not to be welded by an arc generated when the contacts are frequently opened and closed, while maintaining 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
System, Ag-Cu material, Ag-CdO material, 30% C
u-W materials, 50% Cu-Cr materials and the like are used. Particularly, Cu-W-based contact materials have excellent conductivity, while Cu-Cr-based contact materials have excellent withstand voltage characteristics. Therefore, Cu-W-based contact materials have become widespread particularly as contact materials 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, this contact material has a disadvantage that the welding resistance is poor. Therefore, a contact material obtained by adding a welding prevention metal such as Bi or Te as a third component to a conventional Cu-Cr-based contact material is also widely used.

[0009]

However, Cu-
In a contact material in which a welding prevention metal such as Bi or Te is added as a third component to a Cr-based material, there is a problem that the pressure resistance is significantly deteriorated. Therefore, at present, contact materials of various component systems are selectively used according to the application in accordance with the degree of demand for welding property and pressure resistance.

[0010] These Cu-Cr-based contact materials are expected to be used more and more in the future as materials for forming contacts (contacts) of vacuum circuit breakers. In addition, technical requirements for miniaturization of the vacuum circuit breaker are also increasing, and further improvement in pressure resistance, large current interrupting property and welding resistance is required. However, as miniaturization progresses, density, type,
Even when using contact materials with the same composition ratio, crystal structure, impurities, etc., variations in the performance of each vacuum circuit breaker vary greatly from contact material to mass production of vacuum breakers with stable performance. There is a problem that it becomes difficult.

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, a large current interrupting property, a pressure resistance and a welding resistance can be greatly improved, and the interrupting performance is improved. An object of the present invention is to provide a contact material for a vacuum circuit breaker capable of mass-producing a stable vacuum circuit breaker.

[0012]

Means for Solving the Problems In order to achieve the above object, the present inventors have paid attention to the properties of the contact surfaces of a pair of contact materials which are arranged to face each other in a vacuum circuit breaker. That is, as a result of earnestly studying the influence of the presence or absence of unevenness generated during the surface processing of the contact material on the current interruption characteristics of the contact material, the following findings were obtained.

That is, in the vacuum circuit breaker, the surface roughness of the contact material has a close relationship with the contact resistance of the contact. That is, if the surface of the contact material has many irregularities and large surface roughness, the contact resistance of the contact increases, Joule heat is generated, and the large current interrupting ability of the circuit breaker deteriorates. On the other hand, if protrusions are formed on the surface of the material, electric field concentration occurs at that portion, withstanding voltage decreases, and furthermore, local melting of the contact is more likely to occur, so that welding resistance deteriorates. It turned out to be.

It is also considered that the increase in load current per unit area accompanying the recent miniaturization of the contact material has made the adverse effects caused by the unevenness of the contact material surface more remarkable.

The inventors of the present invention can greatly improve the breaking characteristics, withstand voltage characteristics and welding resistance of the contact material by further smoothing the roughness of the contact surface of the contact material as compared with the conventional one. I got the knowledge. More specifically, the contact material is made to have a surface roughness of 12 μm or less in maximum height (Ry) or 4 μm or less in arithmetic average roughness (Ra) specified in Japanese Industrial Standards (JIS B0601). It has been found that the characteristics of circuit breakers using materials can be greatly improved. Further, by making the surface roughness of the contact material 12 μm or less at the maximum height (Ry) and at the same time 4 μm or less at the arithmetic mean roughness (Ra), when the contact material is used for a circuit breaker, the circuit breaks further. It has also been found that the characteristics can be improved. 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 copper as a highly conductive component and chromium as an arc resistant component, and has a surface roughness of JIS B 0601. The maximum height (Ry) specified by the formula (1) is 12 μm or less. The contact material for a vacuum circuit breaker is composed of copper as a highly conductive component and chromium as an arc-resistant component. The surface roughness of the contact material has an arithmetic average roughness (R) defined by JIS B0601.
In a), it is 4 μm or less. Further, the present invention is a contact material for a vacuum circuit breaker comprising copper as a highly conductive component and chromium as an arc-resistant component, and has a surface roughness of 1 at a maximum height (Ry) specified in JIS B 0601.
2 μm or less and 4 μm in arithmetic average roughness (Ra)
It is characterized by the following. Further, the chromium content as an arc-resistant component is 10 to 80% by weight.

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 10 to 80% by weight. Is done. If the content is less than 10 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.

Further, Cu as a high conductive component has a high conductivity and is contained in an amount of 90 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, when the content exceeds 90 wt%, the content of the arc resistant component relatively decreases, and the arc (electric arc) generated during the contact opening / closing operation causes the contacts to be easily welded, resulting in reduced wear resistance. .

Here, the Cu powder may be Cu powder produced by an electrolytic method or 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, infiltration or melting using the above-mentioned Cu powder and Cr powder as raw materials. It is manufactured by processing the surface to a predetermined surface roughness by a cutting method, a polishing method, a blast method or the like.

In the powder metallurgy method, a step of preparing a raw material mixture by using a mechanical mixer such as a ball mill with a Cr powder as an arc resistant component and a 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.

On the other hand, the infiltration method is a method in which molten Cu is infiltrated into pores of a porous Cr calcined body to form a Cu—Cr alloy material. The melting method is a method in which a Cr material and a Cu material are melted and then solidified to form a Cu—Cr alloy material.

The surface roughness of the contact material is a factor that greatly affects the breaking characteristics of the vacuum circuit breaker.
12 μm at the maximum height (Ry) specified by SB0601
m or 4 μm or less in arithmetic average roughness (Ra). This surface roughness is 12 μm (Ry) or 4 μm (R
When the value exceeds a), the contact resistance of the contact increases, and excessive Joule heat is generated, so that the large current interrupting ability of the circuit breaker is reduced. In addition, electric field concentration occurs at the portion where the protrusions are formed, and the withstand voltage characteristics are reduced, welding is also likely to occur partially, the welding resistance of the contacts is deteriorated, and a vacuum circuit breaker with excellent durability is obtained. I can't. Therefore, the surface roughness of the contact material is in the above range.

The processing method for obtaining the surface roughness as described above is not particularly limited, but the following cutting method, polishing method or blasting method can be employed.

That is, when the surface is processed by the cutting method, the feed speed of the cutting tool as a cutting tool, the cutting allowance (cut allowance), the rotation speed of the contact material as the work, the material and shape of the cutting tool, etc. are optimized. Thereby, a predetermined surface roughness is obtained. Generally, in order to obtain a smooth surface having a small surface roughness, the feed rate may be reduced and the cutting allowance may be reduced. Therefore, by cutting the cut surface of the contact material and cutting at a low temperature, machinability is improved, and workability and productivity of the contact material can be improved.

On the other hand, according to the polishing method of polishing while spraying a polishing liquid on the surface of the contact material, a predetermined smooth surface can be easily obtained. However, if the polishing liquid remains on the surface of the contact material, there is a high risk that the polishing liquid components volatilize during the shut-off operation, thereby significantly deteriorating the shut-off performance of the vacuum circuit breaker. Therefore,
It is important to remove the polishing liquid component from the contact material as much as possible after the polishing process.

A blast method in which high-hardness abrasive particles are sprayed onto the surface of the contact material at high speed together with an injection medium such as air is also effective as a method for adjusting the surface roughness. However, even in the blast method, it is necessary to remove the abrasive component as much as possible so as not to remain on the surface of the contact material after the treatment.

It has been confirmed by experiments by the present inventors that it is extremely effective to use dry ice flakes as high hardness fine particles used in the blast method. After blasting using dry ice strips, dry ice is completely vaporized (sublimated)
Therefore, there is little possibility that foreign matter remains on the surface of the contact material.

According to the contact material for a vacuum circuit breaker according to the above configuration, the surface roughness is 12 μm or less at the maximum height (Ry) specified by JIS B0601, or the arithmetic average roughness (R).
Since it is 4 μm or less in a), when used as a contact member of a vacuum circuit breaker, the contact resistance at the contact is reduced, and the large current interrupting property, voltage resistance, and welding resistance can be significantly improved. 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.

[0030]

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

Examples 1 to 12 The composition ratios of Cr powder as an arc resistant component having an average particle size of 110 μm and electrolytic Cu powder as a highly conductive component having an average particle size of 50 μm are shown in Table 1. Were weighed as follows. The Cr powder and the electrolytic Cu powder weighed together with the mixing balls were put into a ball mill pot, and the mixture was rotated and mixed in an inert gas atmosphere to obtain a raw material mixture. Next, this raw material mixture was filled in a mold press machine, and 700M
Press molding was performed with a pressing force of Pa to obtain a Cu-Cr molded body. Furthermore, this Cu-Cr compact was inserted into a heating furnace,
The molded body was heated to 1050 ° C. in a nitrogen gas atmosphere, held for 3 hours, fired, cooled in a furnace, and taken out of the heating furnace.

Next, the surface of the Cu-Cr sintered body taken out is cut and polished by a cutting method or a polishing method so as to have the surface roughness shown in Table 1, and further cut into a predetermined contact shape. Thereby, many contact materials according to Examples 1 to 12 were prepared.

Conventional Examples 1 to 3 The surfaces of the Cu—Cr sintered bodies prepared in Examples 1 , 5 and 9 were polished to a surface roughness shown in Table 1 using a polishing method. Many contact materials according to Examples 1 to 3 were prepared.

Comparative Examples 1 to 6 C prepared in Examples 3, 4, 7, 8, 11, and 12
The surface of the u-Cr sintered body was polished by using a polishing method so as to have a surface roughness shown in Table 1, and each of Comparative Examples 1 to
Many contact materials according to No. 6 were prepared.

In order to evaluate the breaking characteristics of the contact materials according to the examples, the conventional examples and the comparative examples thus prepared, 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, each contact member 13a, 13b according to each embodiment, conventional example, and comparative example is
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 to assemble vacuum circuit breakers as shown in FIG. 1, and the quality of the breaking characteristics was compared. That is, the minimum value of the re-ignition current when the circuit of a predetermined voltage value was cut off was measured.

In addition, a mirror-finished N
While the i-needle is used as the anode, each mirror-finished contact material is used as the cathode, the gap between both electrodes is set to 0.5 mm, and the voltage is gradually increased in vacuum to measure the voltage value when a spark is generated Then, a static withstand voltage value was obtained.

Further, a disk-shaped contact material having a diameter of 25 mm and a pressure rod having the same diameter are arranged opposite to each other, and a constant load (1
After applying a predetermined current (20 KA) for 20 milliseconds in vacuum in a contact state with a pressing force of
The tensile force required to separate the contact material and the pressure rod was measured, and the welding resistance was evaluated. In addition, the above-mentioned respective characteristic values are relatively shown with the characteristic value in the case of using the contact materials having the respective composition ratios shown in Conventional Examples 1 to 3 as the reference value 1.0. Table 1 below shows the measured values.

[0039]

[Table 1]

As is clear from the results shown in Table 1 above,
The vacuum circuit breaker corresponding to each embodiment incorporating the contact material whose surface roughness is adjusted within a predetermined range and finished smoothly is compared with the conventional circuit breaker using the contact material having a rough surface. Since the variation in the frequency of occurrence of restriking was small and the tripping force after energization was significantly reduced, it was demonstrated that the welding resistance was significantly improved.

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

[0042]

As described above, according to the contact material for a vacuum circuit breaker according to the present invention, the surface roughness is 12 μm or less in maximum height (Ry) or 4 μm or less in arithmetic average roughness (Ra). When used as a contact member of a vacuum circuit breaker, the contact resistance at the contact decreases,
Voltage resistance and welding resistance can be greatly improved. 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.

[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;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Isolation 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 Brazing parts 13a, 13b Contact member 14 Brazing material (Ag brazing material)

Claims (8)

[Claims] 1. A contact material for a vacuum circuit breaker comprising copper as a highly conductive component and chromium as an arc-resistant component, wherein the contact material has a surface roughness of 12 μm at a maximum height (Ry) specified by JIS B0601. A contact material for a vacuum circuit breaker, comprising: 2. A contact material for a vacuum circuit breaker comprising copper as a highly conductive component and chromium as an arc-resistant component, wherein the contact material has an arithmetic average roughness (Ra) defined by JIS B0601. A contact material for a vacuum circuit breaker, which is 4 μm or less. 3. A contact material for a vacuum circuit breaker comprising copper as a highly conductive component and chromium as an arc-resistant component, wherein the contact material has a surface roughness of 12 μm at a maximum height (Ry) specified in JIS B0601. A contact material for a vacuum circuit breaker, wherein the contact material has an arithmetic average roughness (Ra) of 4 μm or less. 4. The chromium content as an arc-resistant component is 10%.
4 to 80% by weight.
The contact material for a vacuum circuit breaker according to any one of the above. 5. A vacuum circuit breaker which opens and closes an electric circuit by opening and closing a pair of contacts arranged in a vacuum vessel so as to face each other, wherein said contacts are made of copper as a highly conductive component and chromium as an arc resistant component. And the surface roughness is JIS B 0
A vacuum circuit breaker comprising a contact material having a maximum height (Ry) specified in 601 of 12 μm or less. 6. A vacuum circuit breaker which opens and closes an electric circuit by opening and closing a pair of contacts arranged in a vacuum vessel so as to face each other, wherein said contacts are made of copper as a highly conductive component and chromium as an arc resistant component. And the surface roughness is JIS B 0
A vacuum circuit breaker comprising a contact material having an arithmetic average roughness (Ra) specified in 601 of 4 μm or less. 7. A step of mixing a chromium powder as an arc-resistant component and a copper powder as a highly conductive component to prepare a raw material mixture; and forming the raw material mixture to form a molded body; The step of sintering the obtained molded body in a non-oxidizing atmosphere and the surface roughness of the obtained sintered body were measured according to JIS B 060
Machining the contact material to have a maximum height (Ry) of 12 μm or less or an arithmetic mean roughness (Ra) of 4 μm or less. 8. The method for producing a contact material for a vacuum circuit breaker according to claim 7, wherein the average particle size of the copper powder is 1/20 to 1/3 of the average particle size of the chromium powder.