JPH0664971B2 - Manufacturing method of contact material for vacuum circuit breaker - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a contact for a vacuum circuit breaker, and more particularly to a method for manufacturing a contact material for a vacuum circuit breaker having improved welding resistance and breaking performance.

[Technical Background of the Invention and Problems Thereof] The three basic requirements for contacts for vacuum circuit breakers are:
(1) Less weldability, (2) High withstand voltage,
(3) Good cutoff characteristics are mentioned. In addition to these, it is important that the breaking current value is small, the contact resistance is low and stable, and the wear resistance is good.

However, some of these required characteristics are contradictory. Therefore, in many practical contacts, contact materials suitable for a specific application have been developed by combining two or more elements. There is.

For example, conventionally, as a component that prevents the contact surface from welding due to Joule heat during current interruption or energization, B
Contact materials containing low melting point metals such as i and Te are known (Japanese Patent Publication No. 41-12131 and Japanese Patent Publication No. 23751). However, Bi, Cu, Ag and other highly conductive components,
In contact alloys containing elements with high vapor pressure such as Te, bubbles and pinholes are easily generated in the ingot during the casting process. Further, the contact alloy containing a low melting point metal has a low solid solubility of these components in the matrix phase, and thus segregation easily occurs. For example, as a conventional contact material manufacturing method, a low melting point metal is added after melting Cu, and an inert gas atmosphere such as Ar is added to prevent evaporation of the low melting point metal. There is a method of keeping the pressure in the melting vessel at several Torr to several hundred Torr below.

However, the contact material manufactured by such a method is apt to cause defects such as gas inclusion, generation of voids, and segregation of low melting point metal. If the contact material contains gas, the contact surface will melt due to Joule heat during current interruption or current application, and the gas contained will come out, reducing the degree of vacuum in the vacuum container and impairing the function of the vacuum circuit breaker. U Further, if there is a void or segregation of a low melting point metal in the contact material, the withstand voltage characteristic is significantly deteriorated.

In order to prevent the occurrence of such defects, conventionally, a copper alloy containing a low-melting point metal is once produced by the above-described method, then melted again in a vacuum to remove the contained gas, and after the re-melting, The slow cooling operation prevents voids and segregation of the low melting point metal.

However, in the two-step method of melting in an inert gas atmosphere and remelting in a vacuum as described above, not only a contact material having satisfactory properties can be obtained, but also manufacturing facilities and manufacturing processes are complicated. To do.

[Object of the Invention]

The present invention has been made in view of the above problems,
The purpose of the contact material is to segregate low-melting-point metals, to further improve the breaking characteristics without containing voids and gases, and to further simplify the manufacturing process and equipment. It is intended to provide a manufacturing method.

[Outline of Invention]

The present inventors, in a series of research on contact materials containing a low melting point metal as a welding prevention component, as a result of various studies of specific methods for solving the above-mentioned problems, Ag or (( And) found that by pre-filling a low-melting-point metal in a base material made of Cu, heating and melting it, and then directionally solidifying it, a contact material for a vacuum circuit breaker having excellent properties can be obtained. It was

The present invention is based on the above findings. That is, the method for producing a contact material for a vacuum circuit breaker of the present invention is such that the inside of a base material for a contact material composed of a highly conductive component composed of Cu or (and) Ag is filled with a fusion preventing component composed of a low melting point metal. The contact material base material is heated and melted together with the filled low melting point metal, and then the base material is cooled and solidified along a certain direction while being separated from the heating source.

[Specific Description of the Invention]

 Hereinafter, the present invention will be described in more detail.

FIG. 5 is a front sectional view showing one structural example of a vacuum circuit breaker to which the contact material obtained by the method of the present invention is applied. As shown in FIG. 5, generally, a vacuum circuit breaker has a pair of electrodes 65a, 65b composed of contacts 63a, 63b and energizing shafts 64a, 64b in a vacuum container in which both ends of an insulating container 61 are closed by end plates 62a, 62b. Is provided,
Further, an arc shield 66 is arranged around the contact portion to prevent deposition of arc vapor on the insulating container. On the other hand, the energizing shaft (fixed) 64a and the energizing shaft (movable) 64b are respectively the end plates 62a,
An electric path is formed by hermetically penetrating 62b, and the bellows 67 can open and close the electrode while maintaining a vacuum in the vacuum container.

The contact material obtained in the present invention is the contact 63a,
It is suitable to form both or either of 63b.

Hereinafter, the manufacturing method of the present invention will be described with reference to the accompanying drawings.
In the method of the present invention, first, Cu or (and) Ag
The low-melting-point metal as a welding prevention component is filled in the inside of the base material for a contact material composed of the highly conductive component.

As the base material for the contact material, Cu is generally used as a main component when welding resistance and arc resistance (wear resistance) are important, and Ag is a main component when low contact resistance is important.

On the other hand, as the low melting point metal as the adhesion preventing component,
A metal having a vapor pressure of 10 ⁻³ Torr or more at 800 ° C. is used, and for example, Bi, Te, Se, Sb or an alloy thereof is preferably used.

FIG. 1 schematically shows a cross section of a base material filled with a low melting point metal before heating and melting. As shown in FIG. 1, a granular low melting point metal 12 is charged into a filling hole provided from one end to the other end of a substantially central axis portion of a base material 11 for a contact material having a cylindrical shape. The opening of the hole is closed with a metal stopper 13.

The shape of the base material before melting can be appropriately changed depending on the heating device, container, etc., and the filling hole can be provided in any shape as necessary. The low melting point metal to be charged is the first
As shown in the figure, it may be a granular material, or may be a powdery material or a shape that fits into a hole if necessary.

Various materials can be used as the material of the metal plug that closes the opening of the hole as long as the performance of the contact is not deteriorated. For example, it is made of the same metal as the base material.

It is preferable to fill the low melting point metal in consideration of the volume expansion during heating and melting. The filling amount is preferably such that the content of the low melting point metal in the finally obtained contact material is 0.3 to 0.8% by weight, and for that purpose, the highly conductive component 98.5 to 99.5 is used.
It is desirable to fill the low melting point metal in the range of 0.5 to 1.5 wt% with respect to wt%. Further, the number of holes to be filled is not limited to one as shown in FIG. 1 and may be plural. Further, the volume of the holes can be appropriately changed depending on the manufacturing conditions and the application.

Next, the contact material raw material in which the low melting point metal of the contact material base material is filled as described above is heated and melted. FIG. 2 is a schematic cross-sectional view showing a state in which the above raw material is mounted in an induction heating device as an example. In the example of the induction heating device used in the heating step of this figure, a storage container 22a for storing the object to be heated (raw material made of a base material and a low melting point metal) and its melt, and a movable container for storing the entire storage container 22a 22b and storage container
Heating chamber 21 that houses 22a and movable container 22b therein
And the induction heating coil 23 of the heating source disposed inside the heating chamber.
Consists of.

Further, the inside of the heating chamber 21 is maintained at a high vacuum (for example, 10 ⁻⁵ Torr or less) by exhausting with a vacuum pump 25 via an exhaust pipe 24. The degree of vacuum in the container is measured by the vacuum gauge 26.

The contact material raw material 27 prepared as shown in FIG. 1 is loaded into the storage container 22a, and the container 22b containing the raw material 27 is moved into the movable container 22.
It is housed inside b, a lid 28 is attached to the upper opening of the container 22b, and then the entire movable container 22b is installed in the induction heating coil 23 in the coaxial direction. In this way, preparation for heating is performed.

Next, the coil is energized to melt the raw material in the storage container while maintaining the degree of vacuum in the heating chamber at 10 ^-5 Torr or less. The heating is performed at a temperature at which the base material 11 and the low melting point metal 12 are sufficiently melted. This heating and melting step depends on the type and size of the metal used, but is preferably 60 to 60 in the range of 1100 to 1150 ° C.
120 minutes. In order to exhaust the gas existing in the filling hole to the outside at the melting stage, the base material 11 or the metal stopper 13 may be provided with a vent hole communicating with the outside from the filling hole. For example, the metal plug 13 may be provided with a hole for exhaust, or the side wall of the metal plug may be provided with a fine groove.

In this heating and melting step, the low-melting-point metal having a high vapor pressure is melted in a state of being buried inside the base material 11, so that excessive evaporation of the low-melting-point metal is prevented and the low-melting-point metal in the base material is prevented. The diffusion of can be promoted.

After the gas in the contact material (base material and low melting point metal) 27 is removed by melting in a high vacuum as described above, the movable container 22b is moved in the longitudinal direction (constant direction).
And the molten raw material 27 is separated from the heating source 23. With this transition, the raw material 27 is cooled and solidified. The movable container 22b, the movement of the storage container 22a, it is desirable that the residual gas in the raw material along with the movement, voids, segregation or the like is a speed sufficient to be gradually removed along the traveling direction,
Specifically, it is appropriately selected depending on the shape, size, type, etc. of the raw material, but usually a moving speed of 2 to 6 mm / min is preferable.

Although the induction heating coil of the heating source is fixed in this device example, the present invention is not limited to this example, and the heating source may be moved to cool and solidify the raw material.

The contact material thus obtained is subjected to necessary post-treatments such as cutting and polishing, and then used as a contact for a vacuum circuit breaker.

Example of Invention

Cross-sectional area 3 provided at the center of a Cu base material with an outer diameter of 50 mm and a length of 200 mm 3
A contact material raw material as shown in FIG. 1 was prepared by filling 30 g of Bi particles in a filling hole having a length of 00 mm ² and a length of 50 to 80 mm.
This raw material was heat-melted and cooled / solidified under the following conditions using the apparatus shown in FIG.

Heating temperature 1100 to 1140 ° C Heating time 60 to 120 minutes Vacuum degree 1 to 3 × 10 ^-6 Torr Moving speed of movable container 2 to ⁶ mm / min Bi content in the finally obtained Cu-Bi alloy is 0.6. % By weight. The properties of the contact material thus obtained,
The following tests were conducted in order to evaluate the welding resistance and barrier properties.

(1) Confirmation of Voids The obtained contact material was cut in the longitudinal direction from the center, the cut surface was polished, and the surface structure was observed with an optical microscope, but no voids were observed.

The crystal grains were also well-balanced and good.

(2) Confirmation of Bi segregation The other piece cut in the above (1) was sliced in the longitudinal direction, and each slice was further divided into two equal parts, which were analyzed by atomic absorption spectrometry, The segregation of Bi was investigated. As is clear from the analysis results shown in FIG. 3, the distribution of Bi was almost uniform in the longitudinal direction, and segregation was not observed.

(3) Confirmation of gas content Using the sliced piece prepared in (2) above as a sample, the amount of contained gas was measured using a gas chromatography type two-element analyzer for oxygen, nitrogen, and hydrogen. The measurement was carried out on the most unfavorable O ₂ gas remaining in the vacuum circuit breaker. As shown in the measurement results in Fig. 4, the O ₂ content is about 2p.
It was pm. It should be noted that this is about one-tenth of the value of the contact material obtained by a conventional method, for example, after melting Cu at 1150 ° C., boosting the pressure to 150 Torr with Ar gas and charging a predetermined amount of Bi. .

(4) Confirmation of resistance to welding by energization A disc-shaped contact having an outer diameter of 25 mm and a thickness of 5 mm was prepared from a contact material manufactured by the same method as described in (1) above, and its welding resistance was measured. First, the disc-shaped contact was attached to the tip of a current-carrying shaft having an outer diameter of 25 mm, and the contact facing the same was spherically finished with a tip radius of 100 mm. With a load of 100 g applied to the pair of contacts, both contact surfaces are contacted, and in a vacuum atmosphere of 10 ^-6 Torr, 8KA to 25K.
Current was applied in the range of A, and the tripping force (kg) of the contact surface at this time was measured. Tripping force is 0-10
The value was kg, which was a good value.

(5) Confirmation of current cutoff property A contact material with an outer diameter of 50 mm, a length of 200 mm, and a Bi content of 0.6% was manufactured in the same manner as in (1) above, and then an outer diameter of 30 m
A disk-shaped contact having a thickness of 5 mm and a thickness of 5 mm was prepared and mounted on a vacuum circuit breaker to perform a current interruption test. Current cutoff condition is AC 12K
When set to V and 25KV, the recurrence probability was 1% or less in all cases, and it was about 1/30 of the recurrence probability of the contact manufactured by the conventional method described in (3) above. .

〔The invention's effect〕

As is clear from the results of the above-mentioned examples, the method of the present invention is such that the inside of the contact material base material composed of the highly conductive component is previously filled with a low melting point metal as an anti-welding component, and this is further heated. Since the material is melted and then directionally solidified, it is possible to obtain a contact material having excellent blocking characteristics by preventing inclusion of voids and gas and segregation of low melting point metal by a relatively simple method.

According to the present invention, the contact material base material is cooled and solidified while being separated from the heating source, so that the heating and melting and the cooling and solidification can be continuously performed, and the manufacturing can be efficiently performed.

[Brief description of drawings]

FIG. 1 is a sectional view of a raw material for a contact material in which a low melting point metal is filled in a base material for a contact material, FIG. 2 is a sectional view of an example of a heating device that can be used for heating and melting, and FIG. Fig. 4 is a graph showing the segregation state of Fig. 4, Fig. 4 is a graph showing the analysis result of O ₂ content, and Fig. 5 is a sectional view of the vacuum circuit breaker. 11 ... Substrate, 12 ... Low melting point metal, 13 ... Stopper, 21 ... Heating chamber, 22a ... Storage container, 22b ... Movable container, 23 ... Induction heating coil, 24 ... Exhaust pipe, 25 …… Vacuum pump, 26 …… Vacuum gauge, 27 …… Raw material, 28 …… Lid, 61 …… Insulation container, 62a, 62
b …… End plate, 63a, 63b …… Contact, 64a, 64b …… Conductivity, 65
a, 65b …… electrode, 66 …… arc shield, 67 …… bellows.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyofumi Otobe 1 Toshiba Town Fuchu-shi, Tokyo Inside the Toshiba Fuchu factory (72) Inventor Isao Okutomi 1 Toshiba Town Fuchu-shi inside the Toshiba Fuchu factory (72) Inventor Mikio Okawa 1 Toshiba-cho, Fuchu-shi, Tokyo Inside Toshiba Fuchu factory

Claims (7)

[Claims] 1. A contact material base material composed of a highly conductive component of Cu or / and Ag is filled with an anti-adhesion component composed of a low melting point metal, and used for the contact material together with the filled low melting point metal. A method for producing a contact material for a vacuum circuit breaker, which comprises heating and melting a base material, and then cooling and solidifying the base material while separating the base material from a heating source along a certain direction. 2. The low melting point metal is 10 ⁻³ Tor at 800 ° C.
The method according to claim 1, which is a metal having a vapor pressure of r or more. 3. The low melting point metal is selected from Bi, Te, Se, Sb and alloys of these metals.
The method described in the section. 4. The method according to claim 1, wherein the content of the low melting point metal is 0.5 to 1.5% by weight. 5. The filling of the anti-fusing component is performed by charging the anti-fusing component into at least one filling hole provided in the base material for contact material, and closing the opening of the hole with a metal stopper. The method according to claim 1, which comprises: 6. The method according to claim 1, wherein the induction heating coil of the heating source is moved along a certain direction. 7. The method according to any one of claims 1 to 6, wherein the heat melting and the cooling solidification are performed in a vacuum atmosphere of 10 ^-5 Torr or less.