JPH09190730A - Manufacture of contact member for vacuum circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a contact member for use in a vacuum circuit breaker, capable of enhancing the reliability of operation of the vacuum circuit breaker since it can prevent time vacuum circuit breaker from deteriorating in interruption and pressure resistance performance because of its small contents of oxygen and metal impurities in the contact member. SOLUTION: Chromium powders as arc-resisting components and copper powders as a high-conductivity components are mixed to prepare a mixture of raw materials, which is molded into a copper-chromium molding. The copper- chromium molding is heated to temperatures less than sintering starting temperature in a hydrogen atmosphere and then heated and baked in a vacuum atmosphere. In this case, the process of heating it in the hydrogen atmosphere and that of heating and baking it in the vacuum atmosphere are performed continuously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a contact member for a vacuum circuit breaker, and particularly to a vacuum circuit breaker having a small content of oxygen and metal impurities and capable of preventing deterioration of the circuit breaker performance and pressure resistance performance. The present invention relates to a method for manufacturing a contact member for a vacuum circuit breaker capable of improving the operational reliability of the 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 high vacuum of about 10 ^-4 Pa
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, a shut-off chamber 1 in which the contact is 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. As a specific contact constituent material satisfying both the arc resistance and the high conductivity, for example, Ag is used.
System, Ag-Cu system material, Ag-CdO system material, 30% C
u-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.

Generally, contact members are required to be highly purified, and in particular gaseous impurity components such as oxygen and Na, K, Ba, which cause instability of the arc and deterioration of the breaking performance, are contained.
It is a major technical issue to reduce the content of metal impurities that have a small work relationship and deteriorate the withstand voltage performance by electron radiation as much as possible.

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

Particularly, in the powder metallurgy method, it is possible to form a shape close to the final product, and it is possible to reduce the raw material cost, and at the same time, it is possible to increase the mixing accuracy of the composition ratio of the Cu component and the Cr component. There are advantages. On the other hand, in the powder metallurgy method, since the sintered body is formed by solid phase sintering, the melting point of the material having the lowest melting point (Cu in the case of Cu-Cr based material) among the constituent materials of the contact member. Above, there is a restriction that can not be heated. Therefore, it is more difficult to remove impurities by volatilization, as compared with the dissolution method or the infiltration method. As a result, there is a drawback that the purity of the contact member is greatly influenced by the purity of each raw material powder. Therefore, in the manufacturing process by the conventional general powder metallurgy method, in order to remove the impurities mixed in the material by recontamination, after taking measures to prevent recontamination of the contact material due to oxygen and metal impurities. The molded body is sintered in a hydrogen reducing atmosphere, or the molded body is sintered in a vacuum atmosphere.

[0011]

However, in the conventional manufacturing method, it is difficult to say that oxygen and metal impurities contained in the contact member have been sufficiently reduced to a level not technically required. there were. This is because
In the sintering process of the compact, the temperature rising rate is set so high that the sintering start temperature is reached while oxygen and metal impurities are not sufficiently removed, so compaction of the compact is started early. This is because a large amount of oxygen and metal impurities remain in the sintered body. Further, it is extremely difficult to completely remove oxygen and metal impurities remaining inside the sintered body at the end of the sintering process. Furthermore, when sintering is performed in a hydrogen atmosphere, if a large amount of pores remain in the sintered body, the proportion of hydrogen trapped in the pores after sintering increases, and the hydrogen component becomes a vacuum. There is also a problem that the breaking performance of the breaker is deteriorated.

In any case, it is extremely difficult to sufficiently reduce oxygen and metal impurities in the conventional method of manufacturing a contact member by powder metallurgy, and a vacuum circuit breaker is formed using this contact member. In some cases, it was difficult to obtain sufficient breaking characteristics and pressure resistance performance.

The present invention has been made to solve the above-mentioned problems, and the content of oxygen and metal impurities in the contact member is small, so that it is possible to prevent deterioration of the breaking performance and pressure resistance of the vacuum circuit breaker, and thus the vacuum circuit breaker can be prevented. It is an object of the present invention to provide a method of manufacturing a contact member for a vacuum circuit breaker, which can improve the operation reliability of the above.

[0014]

In order to achieve the above object, the present inventors have researched a method for removing oxygen and metal impurities remaining in a contact member, and particularly, atmospheric conditions, heating temperature, The following findings were obtained as a result of various experiments conducted by variously changing the conditions such as the heating time and the effect of these conditions on the breaking performance and pressure resistance of the circuit breaker using the contact member. That is, in order to reduce the amount of impurities remaining in the contact member as a sintered body as much as possible, a temperature lower than the sintering start temperature at which the densification of the Cu—Cr compact (compacted powder) is started is performed. We have found that it is essential to sufficiently remove oxygen and metal impurities in the temperature range. In particular, it was found that oxygen can be effectively removed in a highly reducing hydrogen atmosphere, and that hydrogen components and residual metal impurities mixed in the compact from the atmosphere can be efficiently removed in a vacuum atmosphere. . That is, it was found that a contact member having a low impurity content can be obtained by changing the heating atmosphere in two stages for the same Cu-Cr molded body and heating it under a predetermined temperature condition. The present invention has been completed based on the above findings.

That is, the method for manufacturing a contact member for a vacuum circuit breaker according to the present invention comprises 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 the above raw material mixture. Forming a copper-chromium compact to form a copper-chromium compact, heating the copper-chromium compact to a temperature lower than the sintering start temperature in a hydrogen atmosphere, and vacuum-heating the copper-chromium compact And a step of heating and firing in a vacuum atmosphere, and the step of heating in the hydrogen atmosphere and the step of heating and firing in a vacuum atmosphere are continuously performed. Further, the step of heating in a hydrogen atmosphere and the step of heating and baking in a vacuum atmosphere may be performed in the same heating furnace without exposing the compact to an oxidizing atmosphere. The heating temperature in the hydrogen atmosphere is 100 to 750 ° C.
Is set to Furthermore, the heating time in a hydrogen atmosphere is 0.5 hours or more. The step of heating the molded body in a hydrogen atmosphere is characterized in that the molded body is kept at a predetermined heating temperature for 0.5 hours or more after the inside of the heating furnace is heated to a uniform temperature. Further, the content of chromium powder in the raw material mixture is set to 20
It is advisable to set it in the range of up to 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 continuously heating and firing a molded body formed of a raw material mixture composed of Cu powder and Cr powder by changing the atmospheric condition from a hydrogen atmosphere to a vacuum atmosphere in two stages. It

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. To be 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, 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. .

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 becomes coarse so as to exceed 1/3 of the average particle size of the Cr powder, it becomes difficult to uniformly deposit and arrange the Cu powder on the surface of the Cr powder. On the other hand, when the fine powder is less than 1/20, re-aggregation of the Cu powder is likely to occur, and in any case, it becomes difficult to obtain a state in which each component is uniformly dispersed. A more preferable particle size ratio is in the range of 1/10 to 1/5.

In the step of preparing the raw material mixture, the Cu
The powder is mixed with Cr powder while applying a predetermined energy (impact force) by a mechanical mixer such as a ball mill.
As in the case of the electrolytic Cu powder, the predetermined energy is larger than the energy at which the Cu powder can be attached to the surface of the Cr powder with a weak bonding force by utilizing the ductility of Cu, and The energy is set to be smaller than the energy for agglomeration / coarsening or crushing Cr powder. The magnitude of this energy can be adjusted by changing the pot material, rotation speed, rotation time, ball diameter, etc. of the ball mill, and is optimized in consideration of the particle size and morphology of the Cu powder in the raw material mixture.

By the above mixing step, finely divided Cu powder is introduced between the particles of the Cr powder, and the Cr powders do not aggregate with each other, so that a raw material mixture having a uniform composition can be obtained. Even when the mold of the molding machine is filled with this raw material mixture, the Cr
Fine Cu crushed powder adheres to the peripheral surface of each particle of the powder, or evenly adheres so as to cling to each other, so that re-separation of Cu powder and Cr powder can be effectively prevented. .

Next, the prepared raw material mixture is filled in a mold of a press molding machine and press-molded under a pressure of about 600 to 1000 MPa to prepare a Cu-Cr molded body having a predetermined shape.

Next, the Cu-Cr compact thus obtained is heated in a hydrogen atmosphere to a temperature lower than the sintering start temperature to remove oxygen and metal impurities. Where Cu-Cr
In the sintering operation of the contact member made of a system material, the solid phase sintering of Cu having a melting point lower than the sintering temperature of Cr is mainly used. The sintering start temperature of Cu is about 650-75.
Since the temperature is 0 ° C, the operation for removing oxygen and metal impurities is 7
It is carried out in a temperature range of 50 ° C. or lower. The atmosphere temperature at the time of removing the impurities is not particularly limited as long as it is lower than the sintering start temperature of Cu, and if it is 100 ° C. or higher, the impurity removing action proceeds to some extent. However, when the temperature becomes lower, the treatment time becomes longer and the removal amount decreases, and further, the problem that the setting of the hydrogen atmosphere conditions becomes complicated in a general-purpose firing facility becomes remarkable, so that the temperature of 550 to 750 ° C. is practically used. Range, more preferably 600 to
It is desirable to process in the temperature range of 650 ° C.

The hydrogen atmosphere conditions differ depending on the amount of oxygen and the amount of impurities contained in the compact, but the heating temperature is 650.
The conditions under which oxygen and metal impurities can be effectively removed when the temperature is set to around ℃ are described below. That is, 650 ° C
In order to allow the reduction reaction of the Cu oxide to proceed smoothly in the vicinity temperature range, hydrogen is introduced into the atmosphere so that the partial pressure ratio P _H2 / P _H20 between hydrogen and water vapor in the hydrogen atmosphere is 10 ⁴ or more. It is essential to do this. When the partial pressure ratio is less than 10 ⁴ , it becomes difficult to reduce the Cu oxide to hydrogen, resulting in a contact member having a high oxygen content.

The heating time in the hydrogen atmosphere varies depending on the size of the contact member and the content of impurities, but it is required to be 0.5 hours or more. If the heating time is less than 0.5 hours, it is difficult to remove impurities sufficiently. The preferred range of heating time is 2 to 5 hours. Particularly, in the step of heating the molded body in a hydrogen atmosphere, first, the temperature inside the heating furnace is made uniform, and then the molded body is heated to the predetermined heating temperature of 0.
By holding the molded product for 5 hours or more, the molded product can be uniformly heated, and a molded product with less unevenness can be obtained.

Next, a sintering step of firing the Cu-Cr compact which has been heat-treated at a temperature lower than the sintering start temperature is started. That is, the obtained Cu-Cr compact has a vacuum degree (vacuum pressure).
Is heated to 900 to 1082 ° C. in a firing furnace adjusted to a vacuum atmosphere in the range of 10 ⁻³ Pa to 10 ⁻⁷ Pa,
It is fired under a holding condition of 0.5 hours or more to form a Cu-Cr sintered body.

Under a low vacuum with the degree of vacuum exceeding 10 ^-3 Pa, it becomes difficult to remove metal impurities and hydrogen that has penetrated into the pores. On the other hand, under high vacuum with a degree of vacuum of less than 10 ^-7 Pa, C
The evaporation of u is likely to occur. Therefore, the degree of vacuum is 10
It is set in the range of ^-3 to 10 ^-7 Pa, but 10 ^-4 to 10 ^-7
The range of Pa is more preferable.

It should be noted that oxygen and metal impurities can be removed at the same time if both the reducing atmosphere condition with hydrogen and the vacuum atmosphere condition can be realized at the same time. However, in reality, in order to prevent hydrogen from remaining in the holes, the atmosphere is reduced. Temperature is 600-650 ℃
To reduce the Cu oxides in a hydrogen atmosphere to remove oxygen impurities, and then the temperature inside the firing furnace is set to 10
^A suitable means is to remove the metal impurities in a vacuum atmosphere of about ⁻⁴ to 10 ⁻⁷ Pa.

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, if the sintering temperature exceeds the melting point of copper (about 1084 ° C),
It becomes virtually 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, and a contact member having a uniform structure cannot be obtained. Therefore, the processing temperature in the sintering step is set to 900 ° C to a temperature just below the melting point of copper and the holding time is set to 0.5 hours or more, but the processing temperature is set to 1050 ° C or more and the holding time is set to 2 to 5 hours. It is more preferable to set to.

By carrying out the step of heating in a hydrogen atmosphere and the step of heating and baking in a vacuum atmosphere in the same heating furnace without exposing the compact to an oxidizing atmosphere, Cu containing a smaller amount of impurities can be obtained. It is preferable because a -Cr sintered body can be obtained.

The Cu--Cr sintered body thus prepared was processed into a predetermined shape to form a contact member, and the contact member was joined to the end faces of the opposing electrodes by using a brazing material, and further the contact members were joined together. By joining the electrodes to the ends of the conductive rod, a vacuum circuit breaker as shown in FIGS. 2-3 is assembled.

According to the method of manufacturing a contact member for a vacuum circuit breaker having the above-mentioned structure, first, the molded body is heated in a hydrogen atmosphere at a temperature lower than the sintering start temperature to reduce the oxide contained in the molded body. Effectively removes oxygen impurities. Thereafter, the molded body is heated and fired in a vacuum atmosphere to volatilize and remove metal impurities, and at the same time, the hydrogen that has penetrated into the pores of the molded body when heated in a hydrogen atmosphere is effectively removed. As a result, it is possible to obtain a high-purity contact member having a small content of oxygen and metal impurities and a small amount of residual hydrogen. Therefore, by forming a vacuum circuit breaker using this contact member, it is possible to form a highly reliable vacuum circuit breaker with stable characteristics and less deterioration in breaking performance and pressure resistance.

[0033]

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 110 μm and electrolytic Cu powder as a highly conductive component having an average particle size of 50 μm were weighed at a weight ratio of 50:50. .
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 die press and press-molded under a pressure of 700 MPa to obtain a Cu-Cr compact. further,
This Cu—Cr compact was inserted into a heating furnace and heated to a temperature of 600 ° C. in a vacuum atmosphere as shown in FIG. Next, the inside of the heating furnace was replaced with a hydrogen atmosphere so that the partial pressure ratio P _H2 / P _{H20 of} hydrogen and water vapor was 10 ^4, and the temperature was kept at 600 ° C. for 4 hours. After that, hydrogen was exhausted from the heating furnace, a vacuum atmosphere was adjusted so that the degree of vacuum was about 2 × 10 ⁻⁴ Pa, and the temperature was kept at 600 ° C. for 4 hours. Thereafter, the molded body was heated to a temperature of 1050 ° C. in a vacuum atmosphere having a degree of vacuum of about 3 × 10 ⁻¹ Pa, held for 3 hours, baked, cooled in a furnace, and taken out from the heating furnace. By processing the taken out contact material into a predetermined contact shape, Example 1
A large number of contact members according to the present invention were prepared.

Comparative Example 1 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 were weighed at a weight ratio of 50:50, respectively. .
Then, the weighed Cr powder and Cu powder were uniformly mixed with a ball mill to obtain a raw material mixture. Next, the raw material mixture was filled in a die pressing machine and press-molded under a pressure of 700 MPa to obtain a Cu-Cr compact as in Example 1. Furthermore, without heating this Cu—Cr compact in a hydrogen atmosphere, the degree of vacuum is 5 × 5 in a vacuum atmosphere of 3 × 10 ⁻¹ Pa.
The sample was heated to a temperature of 1050 ° C. at a temperature rising rate of ° C./min, held for 3 hours, baked, cooled in the furnace, and taken out from the heating furnace. A large number of contact members according to Comparative Example 1 were prepared by processing the taken out contact material into a predetermined contact shape.

Comparative Example 2 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 were weighed at a weight ratio of 50:50. Then, the mixture was uniformly mixed with a ball mill to obtain a raw material mixture. Next, the raw material mixture was filled in a die press and press-molded under a pressure of 700 MPa to obtain a Cu-Cr compact similar to that in Example 1. Further, this Cu-Cr compact is heated to a temperature of 1050 ° C at a temperature rising rate of 5 ° C / min in a hydrogen atmosphere having a hydrogen / steam partial pressure ratio P _H2 / P _H20 of 530, and held for 3 hours. After firing, the furnace was cooled and taken out of the heating furnace. A large number of contact members according to Comparative Example 2 were prepared by processing the taken out contact material into a predetermined contact shape.

Regarding the contact members according to the examples and the comparative examples thus prepared, an ICP emission spectrometer (SEIKO) was used.
Ba content is measured using SPS-1100A manufactured by Co., Ltd., while Na and K contents are measured using a flame atomic absorption spectrometer (Model 3100 manufactured by Perkin Elmer Co., Ltd.), and an infrared absorption spectrometer is further used. (LECO Co., Ltd. TC-436) is used to measure the oxygen content, and the content of each impurity in the compact (compacted powder) before the sintering step is measured, and the sintering is performed with respect to the value before the sintering step. The ratio of the values after the binding step was calculated as the effect of reducing impurities. The calculation results are shown in Table 1 below.

As shown in FIG. 3, the prepared contact members 13a and 13b according to the example and the comparative example were vacuum-brazed to the center portions of the end faces of the electrodes 7 and 8 using Ag brazing material 14, respectively. . 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, 10 vacuum circuit breakers as shown in FIG. 2 were assembled using the electrodes 7 and 8 in which the contact members 13a and 13b were brazed and joined, and the quality of the breaking characteristics was compared. That is, the variation width (minimum value-maximum value) of the frequency of re-ignition when a circuit having a predetermined voltage and current value was interrupted 20,000 times was measured, and the results shown in Table 1 below were obtained.

[0039]

[Table 1]

As is clear from the results shown in Table 1 above,
In the contact member manufactured by dividing the heating and firing atmosphere into two stages according to the manufacturing method according to Example 1, the effect of reducing oxygen and metal impurities is remarkable, and the amount of remaining impurities is larger than that of each comparative example. It was reduced to 1/10 or less, and it was revealed that the purity was extremely high.

On the other hand, in the contact member according to Comparative Example 1 in which the heat treatment was not performed in the hydrogen reducing atmosphere, the oxygen removal rate was 3%.
It is about 5 to 50%. In the contact member according to Comparative Example 2 in which the heat treatment was not performed in the vacuum atmosphere, Na,
It was again confirmed that the effect of reducing metallic impurities such as K and Ba was small.

Although Table 1 exemplifies Na, K, and Ba, which have a large influence as a metal impurity on contact characteristics and have a small work function, other materials can be used according to the manufacturing method of this embodiment. It was confirmed that the same reduction effect can be obtained for the impurity element.

Further, it can be confirmed that the vacuum circuit breakers incorporating the contact members according to the examples have very few variations in the re-ignition occurrence frequency as compared with the vacuum circuit breakers incorporating the contact members according to the respective comparative examples. , The stability of the arc and the breaking performance were dramatically improved.

In the above-described embodiment, as shown in FIG. 1, the hydrogen atmosphere and the vacuum atmosphere are held in the predetermined temperature range below the sintering start temperature for 4 hours, respectively. As shown in, the heating may be performed from room temperature to a predetermined sintering temperature at a constant heating rate.

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

[0046]

As described above, according to the method for manufacturing a contact member for a vacuum circuit breaker according to the present invention, the compact is first heated in a hydrogen atmosphere at a temperature lower than the sintering start temperature and contained in the compact. The resulting oxide is reduced to effectively remove oxygen impurities. Thereafter, the molded body is heated and fired in a vacuum atmosphere to volatilize and remove metal impurities, and at the same time, the hydrogen that has penetrated into the pores of the molded body when heated in a hydrogen atmosphere is effectively removed. As a result, it is possible to obtain a high-purity contact member having a small content of oxygen and metal impurities and a small amount of residual hydrogen. Therefore, by forming a vacuum circuit breaker using this contact member, it is possible to form a highly reliable vacuum circuit breaker with stable characteristics and less deterioration in breaking performance and pressure resistance.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between heating time and heating temperature in the method of the present invention.

FIG. 2 is a sectional view showing the structure of a vacuum circuit breaker using a contact member manufactured by the method of the present invention.

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

[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)

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

Claims (6)

[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. A hydrogen atmosphere, the step of heating the copper-chromium compact to a temperature lower than the sintering start temperature, and the step of heating and baking the copper-chromium compact in a vacuum atmosphere; A method of manufacturing a contact member for a vacuum circuit breaker, which comprises continuously performing a step of heating in a vacuum and a step of heating and firing in a vacuum atmosphere. 2. The method according to claim 1, wherein the step of heating in a hydrogen atmosphere and the step of heating and firing in a vacuum atmosphere are carried out in the same heating furnace without exposing the molded body to an oxidizing atmosphere. A method for manufacturing a contact member for a vacuum circuit breaker. 3. The heating temperature in a hydrogen atmosphere is 100.
It is -750 degreeC, The manufacturing method of the contact member for vacuum circuit breakers of Claim 1 characterized by the above-mentioned. 4. The heating time in a hydrogen atmosphere is 0.5.
The method for producing a contact member for a vacuum circuit breaker according to claim 1, wherein the contact time is not less than time. 5. The step of heating the molded body in a hydrogen atmosphere is characterized in that the molded body is kept at a predetermined heating temperature for 0.5 hours or more after the inside of the heating furnace is heated to a uniform temperature. A method for manufacturing a contact member for a vacuum circuit breaker according to claim 1. 6. The content of chromium powder in 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.