JPH0670888B2 - Method for manufacturing contact material for vacuum circuit breaker - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a contact material for an electric circuit switch that opens and closes a large current, especially a vacuum switch, a contact material for a circuit breaker, and a method for manufacturing the same, and in particular, it emits less gas. The present invention relates to a method for manufacturing a sintered type or infiltration type contact.

[Technical background of the invention and its problems]

The vacuum circuit breaker has advantages such as small size, no maintenance, no pollution, etc. compared to other circuit breakers, so its application range has been gradually expanded in recent years, and the circuit voltage is expected to be applied from 36KV to 72KV or more. It became. Increasing the breakdown voltage depends on the properties of the contact material. Empirically, if a low melting point, high vapor pressure material (such as Bi) was used as a constituent element of the contact, such as the Cu-Bi system that was manufactured by the melting method, there were some difficulties in increasing the withstand voltage. .

Therefore, powder such as Cu-W, Cu-Cr, or W, Cr
Cu was infiltrated into the porous skeleton to produce the contact. However, since the powder has a large surface area compared to its volume, a large amount of gas adheres to the surface thereof, and the step of eliminating this adsorbed gas has had an important influence on the properties of the contact. Conventionally, as a process of removing the adsorbed gas, a sintering process in a vacuum (for example, the process described in JP-A-59-94320),
Alternatively, treatment in a hydrogen atmosphere (see, for example, JP-A-59-171421)
The process described in Japanese Patent Publication) is known.

However, Cu, W, etc., which have excellent welding resistance of the contacts, have a strong gas adsorption force and cannot sufficiently absorb the adsorbed gas by the above-mentioned treatment.

For example, it is known that O (oxygen) atoms physically adsorbed on W cannot be removed even if heated at 2500 ° C. in a reducing gas such as CO.

On the other hand, the temperature at the cathode point of the arc is considered to be about 3,000 K to 3,500 K, so a large amount of gas was released during current interruption, impairing the high current interruption performance.

For example, a Cu-Cr contact manufactured by a conventional manufacturing method has a gas content of about 500 to 2000 ppm. It was difficult to raise the processing temperature to 2000K or higher to remove the adsorbed gas because of the equipment price and the vapor pressure of the contact material.

[Object of the Invention]

In view of the above-mentioned circumstances, it is an object of the present invention to provide a method for manufacturing a contact material for a vacuum circuit breaker, which produces a small amount of free gas when an arc occurs while maintaining desired welding prevention performance and high pressure resistance performance.

[Outline of Invention]

In the production of Cu-Cr contact material, the processable temperature of Cr, which adsorbs a large amount of gas, was 1,200 ° C at most due to its vapor pressure characteristic, and the gas content of the contact obtained under these conditions was about 400 to 700 ppm.

In the contact manufacturing method used in the present invention, impurities adhering to the surface of the powder or fibrous body, such as oil and fat, and desorption of adsorbed gas can be sufficiently excited even at low temperature by exciting active gas and reducing gas. The ionization state was used.

First, the water adsorbed on the surface of the powder is about 200 ℃ to 5 ℃ in vacuum.
It is removed by heating at 00 ℃. Deposits such as oil on the surface can be removed by exposing the powder to a gas discharge atmosphere in Ar gas containing CF ₄ , for example. O (oxygen atoms) that are more strongly adsorbed and bonded on the powder surface can be almost completely removed by exposing the powder to a gas discharge atmosphere in Ar gas containing H ₂ or CO.

After such a treatment, the material of the contact is manufactured by sintering or infiltration.

〔The invention's effect〕

According to the production method of the present invention, the gas analysis results in a gas (mainly O ₂ and N ₂ ) content of about 10 ppm, and a value almost the same as that of the contact material produced by the melting method, for example, Cu-Bi material, is obtained. Was given.

Since the degassing treatment of the present invention can be performed at a lower temperature than hydrogen treatment and vacuum treatment, it is possible to perform the sintering and infiltration temperatures at a low temperature.

In the case of contact materials manufactured by powder metallurgy, in order to improve the welding resistance of high conductivity materials such as Al, Ag and Cu, powders or fibrous materials with high melting points such as Cr, Mo and W are mixed with high conductivity materials. To do.
Therefore, it is desirable that the high melting point powder or fibrous material does not diffuse into the high conductivity material to form a solid solution or an intermetallic compound. For this reason, it is advantageous to sinter and infiltrate at a low temperature.

In the method of manufacturing by mixing the powder of the high-conductivity material and the powder of the high-melting-point material or the fibrous body in advance and then sintering,
The degassing treatment method of the present invention is particularly effective. Also, for metal borides, low temperature sintering and infiltration are particularly important. When a high-conductivity material and a metal boride are mixed and kept at a high temperature, boron (B) in the boride diffuses into the high-conductivity material to generate new boride, which lowers the electrical conductivity of the contact. Let

As described above, according to the contact manufacturing method of the present invention, not only the free gas in the contact can be removed almost completely, but also the contact can be manufactured at a low temperature and the decrease in the electric conductivity of the contact can be prevented. .

Example of Invention

 FIG. 1 shows an example of an apparatus for carrying out the present invention.

The vacuum furnace 1 is evacuated to a vacuum by an exhaust device (EX) 3 through a valve (V ₅ ) 2. The contact material 4 is placed in the boat 5. A device (not shown) for stirring powder or fibrous material is connected to the boat through a connecting rod 6. A material heating heater 7 is provided at the bottom of the boat 5, and the heater is connected to a power source (PS ₁ ) 8. Electrode 9
Is installed facing the material 4 in the boat. A discharge power supply 10 is connected between the electrode 9 and the material or boat.

The gas supply system consists of three gas reservoirs (GR ₁ ) 11, (GR ₂ ) 12,
The (GR ₃ ) 13 stores an inert gas such as a rare gas, a gas containing a halogen element such as CF ₄ , and a reducing gas such as H ₂ and CO. These gases are used for valves (V ₁ ) 14, (V ₂ ) 15,
It is supplied into the vacuum furnace through (V ₃ ) 16 and valve (V ₄ ) 17.

First, raw materials, for example, powders or fibrous bodies such as Cu, Cr, Mo and Ti are mixed and placed in a boat. The valves (V ₁ ) to (V ₄ ) are closed, and the vacuum furnace is evacuated to a pressure of 1 × 10 ⁻⁴ Torr or less by the exhaust device EX.

The material 4 is heated to 200 to 500 ° C. by the heater 7 to remove H ₂ O (water) and the like adhering to the surface of the material.

Next, in order to remove oils and fats that could not be sufficiently removed by pretreatment of the material, for example, Freon cleaning, mix the inert gas and the gas containing halogen element from the gas reservoirs (GR ₁ ) and (GR ₂ ) at an appropriate mixing ratio. Introduced into the vacuum furnace, discharge power supply (PS
₂ ) Turn on 10 to generate uniform discharge between the material 4 and the electrode 9. This discharge excites or ionizes the gas, and the gas has a much higher energy than the thermally heated state. By bringing the gas in this state into contact with the surface of the material, the surface layer can be easily removed. The removed substance is discharged to the outside as a halide gas through the exhaust device (EX) 3. When the surface of the material is covered with an oxide layer, the inert gas and the reducing gas are mixed from the gas reservoirs (GR ₁ ) and (GR ₂ ) into the vacuum furnace at an appropriate mixing ratio, and the discharge power source ( Turn on PS ₂ ) to cause discharge. In order to improve the contact between the exciting gas and the surface of the material, the material is well stirred by the stirring device. It depends on the nature of the material whether to perform both the gas discharge treatment of the halide and the gas discharge treatment of the reducing gas, or whether only one treatment is completed.

The discharge may use microwave discharge without electrodes. After the treatment by discharge is completed, the inside of the vacuum furnace is evacuated to a high vacuum, or thereafter, the inert gas is filled to 100 Torr or less.

Next, the temperature of the heater is raised to sinter the raw material to complete the production of the contact material.

Concretely, Cr will be described as a representative raw material.

Usually, the amount of raw material gas is 1000 to 7000 ppm. By applying the technique of the present invention to this, as shown in Table 1, it becomes 50 to 100 ppm, which is reduced to 1/20 to 1/70. This raw material
50% Cu-Cr obtained by infiltrating copper into the remaining pores of a Cr skeleton obtained by sintering Cr for about 1 hour in a vacuum at 950 ° C.
The amount of O ₂ gas in the alloy was 10 to 30 ppm.

In order to clarify the effect of the present invention, as an experiment to be compared with this, using Cr powder which does not give the technique of the present invention, the sintering,
The same heat treatment as the infiltration condition was performed to obtain a 50% Cu-Cr alloy. The amount of O ₂ gas in this alloy was 400 to 3000 ppm, and the gas in the 50% Cu—Cr alloy to which the technique of the present invention was applied was 1/40 to 1/100 of that in the case where it was not applied. (Example -1) other _{Ti, Cr 3 C 2, TiC} , CrB 2, TiB 2, CrN, TiN ( Example 2
With respect to 8), the same effect as shown in Table 1 was obtained.

When the probability of re-ignition occurrence is investigated using the contacts obtained in this way, the occurrence frequency is 1 /
It has decreased to 2 to 1/5.

The above-mentioned effects can be recognized for any of the above-mentioned material groups other than the materials shown in Example 1-8. In addition, in Example 1-8, although an example of Cu was shown as the high-conductivity material, the same effect can be obtained with Ag, Cu-Ag alloy, Al, or the like.

A typical condition for gas excitation is a total gas pressure of 1 Torr and a direct current discharge (discharge current density 10 mA / cm ³ ) for about 20 minutes in a CCl ₄ mixed gas of about 10% (pressure ratio) in argon gas, Again, the same discharge as before was carried out for about 1 hour in a CO mixed gas of about 10% (pressure ratio) in argon at a total gas pressure of 1 Torr.

The gas flow rate was high immediately after the start of the treatment, and was narrowed down near the end of the treatment.

[Other Embodiments of the Invention]

In Fig. 1, discharge was used to excite and ionize the gas. However, when an excimer laser is used as a laser beam, especially as a light source in the ultraviolet region, gas molecules and atoms for degassing excite multiphoton absorption,
Ionized. Further, since the laser beam also activates the surface of the material 4, the degassing action by the excited gas is efficiently performed. The outline of the apparatus is shown in FIG. The beam emitted from the laser oscillator 18 is expanded by a beam expander 19 to an appropriate angle, reflected by a reflecting mirror 20, and introduced into a vacuum furnace through a beam irradiation window 21 provided in the upper part of the vacuum furnace 1. Irradiation window 21 is preferably made of quarantine, sapphire, etc. that allows light in the ultraviolet range to pass through. However, when a gas containing a halogen element is used for the degassing treatment, the life of the window material becomes longer if the inside of the irradiation window is coated with a protective film.

Fig. 1 and Fig. 2 show the method of mixing and sintering the material of the contact at a predetermined mixing ratio. The method of infiltrating Al, Ag, Cu, etc. into the powder or fibrous material of the high melting point material. However, the degassing treatment of the powder or fibrous body can be basically performed by the method shown in FIG. 1 or 2.

[Brief description of drawings]

FIG. 1 is a block diagram of a contact material processing apparatus according to the present invention, and FIG.
The figure is a block diagram of an apparatus showing another embodiment of the present invention. 1 ... vacuum furnace, 5 ... material loading boat 6 ... stirring device, 7 ... heating device 11 ... inert gas source, 12 ... gas source containing halogen element 13 ... reducing gas source, 9 ... … Discharge electrode 18 …… Laser oscillator

Claims (4)

[Claims] 1. A contact alloy for a vacuum valve produced by sintering or infiltration using at least one powder or fibrous material selected from the group of metals, carbides, borides, nitrides and silicates as a raw material. In the above, the raw material powder or fibrous body is treated in advance in an atmosphere of an excited or ionized state of a reducing gas such as hydrogen or carbon monoxide or a gas containing a halogen element as a component. Method of manufacturing contact material for equipment. 2. A means for producing an excited and ionized state of gas,
The method for producing a contact material for a vacuum circuit breaker according to claim 1, wherein at least one of DC or AC gas discharge and laser light is used. 3. The method according to claim 1, wherein the powder or the fibrous body is treated while being heated to 200 ° C. or higher.
Item 2. A method for manufacturing a contact material for a vacuum circuit breaker according to Item 2 or Item 2. 4. The powder or fibrous material is Ag, Cu, Ti, V, Cr, Zr, N.
b, Mo, Hf, Ta, W, TiC, VC, Cr ₃ C ₂ , ZrC, NbC, MoC, HfC, TaC, WC, B
₄ C, TiN, ZrN, CrN, HfN, TaN, TiB ₂ , VB ₂ , CrB ₂ , ZrB, NbB ₂ , M
oB ₂ , TaB, WB ₂ , TiSi ₂ , Cr ₃ Si, ZrSi ₂ , NbSi ₂ , MoSi ₂ , Ta
The method for producing a contact material for a vacuum circuit breaker according to claim 1, characterized in that it comprises at least one of Si ₂ and WSi ₂ .