JP2006228684A - Contact point material for vacuum valve, the vacuum valve, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact point material for vacuum valves which can improve the smooth state of contact surfaces, therefor, which is superior in withstand voltage characteristics, as well as in current-cutting properties, and also to provide a vacuum valve that uses the contact point material, a manufacturing method of the vacuum valve, and thereby, a low-surge vacuum breaker having superior characteristics. <P>SOLUTION: A contact material for vacuum valves is made by having 0.02-1.0% by mass of Ag<SB>2</SB>Te contained in an Ag-WC based contact material, and the Ag<SB>2</SB>Te exists in a form of a coat layer or particles having sizes (diameters or thicknesses) of 0.01-0.2 um on an interface between Ag and WC, consisting of the matrix of contact points 13a, 13b, as well as in a form of an Ag<SB>2</SB>Te precipitate that is precipitated in Ag constituting the matrix. When contact points 13a, 13b are used as the contact points of vacuum valves, an Ag<SB>2</SB>Te coat, which is deposited slightly; when heated by current switching or current breaking, covers the contact surfaces to maintain smoothness, and thus, for improving the withstand voltage characteristics. By including Ag<SB>2</SB>Te in an Ag-WC base contact point material at the predetermined rate, smoothness on contact points is maintained, even after current switching or current breaking has been processed, and then the withstand voltage characteristics can be improved. Accordingly, a vacuum breaker using the contact point material can improve withstand voltage characteristics to achieve high reliability, in keeping the same superior current-cutting characteristics as the conventional Ag-WC base contact points have. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a contact material having excellent cutting characteristics and improved withstand voltage characteristics, a low surge type vacuum valve equipped with the contact material, and a manufacturing method thereof.

  A vacuum circuit breaker that is used for high-voltage power receiving equipment and installed for the purpose of opening and closing the circuit in the normal state as well as in the abnormal state, especially in the short-circuit state, has two contact points that can be opened and closed: an opposing fixed contact and movable contact The electric circuit is opened and closed in vacuum by opening and closing the contacts in the vacuum valve. This vacuum circuit breaker utilizes the excellent arc extinguishing force and insulation performance of the arc in a vacuum, and since the arc generated at the time of opening spreads in the vacuum at a high speed, it can easily interrupt a large current. In addition, since the insulation capacity is excellent, the distance between the contacts can be reduced, so that it is small and lightweight.

  On the other hand, the vacuum circuit breaker may cause surge due to a sudden current change at the time of current interruption, the so-called current cutting phenomenon, and this surge has an effect on the system and load. It was a problem. In particular, when it is used in a circuit having a high surge impedance load such as a motor, a large surge is generated, so that the influence on the load equipment is further concerned. For this reason, in order to protect a load apparatus from a surge, a surge protection device is often used in combination with a vacuum circuit breaker. However, such surge protection devices generally contain oil, which hinders the advantages of the vacuum circuit breaker such as environmental harmony and incombustible structure.

  Therefore, in recent years, a low surge type vacuum circuit breaker having a small current drop (cutting current value) at the moment of current interruption has been developed and used in the field of 7.2 kV class. Patent Documents 1 to 3 disclose contact materials for vacuum valves suitable for use in low surge type vacuum circuit breakers.

  For example, Patent Document 1 discloses a vacuum sealer using a contact of an alloy in which tungsten carbide (WC) and silver (Ag) are combined. The contact using this Ag-WC alloy is said to exhibit excellent cutting characteristics due to the thermal electron emission effect due to the presence of WC.

  Further, in Patent Document 2, as a material having both low cutting characteristics and low contact resistance characteristics, the content, ratio, and existence state of Ag and copper (Cu) are optimal for an Ag-Cu-WC-based contact material. In addition, there is disclosed a vacuum valve contact material in which the particle diameter of the arc-resistant component WC is refined. In the contact material disclosed in Patent Document 2, it acts with Ag of the matrix due to the presence of Cu, and the matrix forms a eutectic structure of AgCu, and the cutting characteristics and the breaking characteristics are greatly improved by the effect of the refined structure. It is supposed to be improved.

Further, Patent Document 3 proposes an Ag-WC-C-based contact material as a contact material having excellent cutting characteristics and re-ignition characteristics. The contact material disclosed in Patent Document 3 contains 0.005 to 0.2% of carbon (C) having a diameter of 0.01 to 5 μm that is not solid-solved in Ag-WC and does not form a compound. Therefore, it is said that the cutoff characteristic is improved.
US Pat. No. 3,683,138 Patent No. 2768721 Specification Bulletin Japanese Patent Laid-Open No. 10-245652

  In recent years, the low surge type vacuum circuit breaker using the contact material as described above for the contact of the vacuum valve has come to be used in the class of 7.2 kV class or higher. Therefore, as a contact material of a vacuum valve used for a vacuum circuit breaker, it has been desired that not only the cutting characteristics are excellent but also the withstand voltage characteristics are excellent.

  In this regard, in the contact material disclosed in Patent Document 1, the contact surface after current switching or current interruption loses a smooth state due to selective evaporation of Ag, and a decrease in withstand voltage characteristics is seen. It was necessary to improve the withstand voltage characteristics when incorporated in a vacuum valve that repeatedly shuts off.

  In the contact material disclosed in Patent Document 2, AgCu eutectic produced by acting on Ag in the matrix due to the presence of Cu is present in the matrix composed of Ag and Cu contained as a highly conductive component. Existing. The melting point of this AgCu eutectic is 779 ° C., which is lower than the brazing temperature (about 820 ° C.) when the contact material is fixed to the electrode of the vacuum valve by brazing. For this reason, the AgCu eutectic melts in the Ag brazing process, the contact surface loses a smooth state, and a decrease in the withstand voltage characteristic is seen. With respect to the withstand voltage characteristic when used as a vacuum circuit breaker attached to a vacuum valve It was something that needed improvement.

  Furthermore, the contact material disclosed in Patent Document 3 contains 0.005 to 0.2% of C (carbon) having a diameter of 0.01 to 5 μm that does not form a solid solution in Ag-WC and does not form a compound. Therefore, when it is intended to be used for a higher voltage power receiving facility or the like, the withstand voltage characteristics are not sufficient due to the active thermionic emission phenomenon from the C portion.

  As described above, all of the conventional contact materials for vacuum valves are not sufficient in withstand voltage characteristics when used by being attached to a vacuum valve, and need to be improved.

  The present invention is intended to solve the problems of such conventional contact materials, can improve the smooth state of the contact surface, and thus has excellent cutting characteristics as well as resistance to damage. We provide contact materials for vacuum valves with excellent voltage characteristics, together with vacuum valves using the contact materials for vacuum valves and their manufacturing methods, thereby realizing a low surge type vacuum circuit breaker with superior characteristics. It is intended to do.

  The contact material for a vacuum valve of the present invention that achieves the above object contains 20 to 60% by mass of Ag, 0.02 to 1.0% by mass of silver telluride, and the balance is made of tungsten carbide.

  The contact material for a vacuum valve of the present invention may have a composition in which the tungsten carbide is replaced with one or more selected from molybdenum carbide, tungsten and molybdenum. Furthermore, 1 type chosen from Co, Ni, and Fe can be contained at 5 mass% or less.

Further, the vacuum valve of the present invention comprises a contact made of the above-mentioned vacuum valve contact material, and the manufacturing method of this vacuum valve is a vacuum valve contact material containing Ag, silver telluride and tungsten carbide. the sintering of the raw material, and performing at a cooling rate of more than 10 ° C. / sec conditions in the temperature range from the melting temperature of the Ag 2 _Te to the melting temperature -200 ° C. of Ag 2 _Te during the cooling after sintering, sintered The contact obtained by molding after bonding is bonded to the electrode of the vacuum valve by brazing, the contact heating time is within 30 minutes, and the melting temperature of Ag ₂ Te from the bonding temperature during cooling after bonding— And a step of performing a cooling rate in a temperature range up to 200 ° C. under a condition of 10 ° C./second or more.

The contact material for a vacuum valve of the present invention has a composition in which Ag ₂ Te is present in a predetermined ratio in an Ag—WC contact material, so that smoothness is maintained even after current switching or current interruption. Therefore, the withstand voltage characteristic is improved. Therefore, it is possible to provide a highly reliable vacuum circuit breaker with improved withstand voltage while maintaining the excellent cutting characteristics of the conventional Ag-WC contacts.

  Hereinafter, the contact material for a vacuum valve of the present invention will be described more specifically.

As an example of the components of the contact material for a vacuum valve of the present invention, Ag contains 20 to 60% by mass, silver telluride contains 0.02 to 1.0% by mass, and the balance is made of tungsten carbide. Since this component system has Ag ₂ Te, when it is attached to a vacuum valve of a vacuum circuit breaker and used as a contact point, it is about 0.1 to 5 μm by heating at the time of current switching and current interruption. The slightly adhered Ag ₂ Te covers the contact surface and maintains smoothness. If the thickness is less than 0.1 μm, the effect is not clear, and if it exceeds 5 μm, the withstand voltage characteristic becomes conversely unstable. Thereby, the withstand voltage characteristic is improved.

The Ag amount is in the range of 20 to 60% by mass. Ag is contained in order to maintain conductivity as a contact for a vacuum valve. If the Ag content in the AgWC contact material to which Ag ₂ Te is added is less than 20% by mass, the breaking characteristics, temperature characteristics, and contact resistance characteristics cannot be sufficiently secured, which is not preferable.

On the other hand, when the Ag amount in the Ag-WC contact point to which Ag ₂ Te is added exceeds 60%, the amount of WC in the Ag-WC contact point material to which Ag ₂ Te of the present invention is added becomes insufficient, and the cutting characteristics The WC effect of maintaining wear resistance is not fully exhibited and the cutting characteristics are reduced, that is, the cutting current value is increased, causing surge generation, and the wear resistance is also reduced. It is not preferable.

Tungsten carbide (WC) maintains the cutting characteristics and wear resistance by adjusting the ratio with Ag in the Ag-WC-based contact material to which Ag ₂ Te of the present invention is added. If the amount of WC is too small, the effect of maintaining the cutting characteristics and wear resistance is lowered, which is not preferable. On the other hand, if the amount of WC is too large, the amount of Ag becomes insufficient, and the interruption characteristics, temperature characteristics, and contact resistance characteristics cannot be secured sufficiently, which is not preferable. Therefore, the amount of WC is the amount of the balance containing 20 to 60% by mass of Ag and 0.02 to 1.0% by mass of Ag ₂ Te.

Ag ₂ Te is contained in the range of 0.02 to 1.0% by mass. Ag ₂ Te has a structure in a dispersed form in an Ag—WC alloy, and is present in the form of an Ag ₂ Te precipitate or an Ag ₂ Te coating at the interface between Ag and WC constituting the matrix. It also precipitates in Ag constituting the same, and is also present in the form of an Ag ₂ Te precipitate. This Ag ₂ Te selectively evaporates when the contact current is opened or closed or when the current is cut off, and the deposited film of Ag ₂ Te slightly adhered by the heat at the time of opening or closing the current covers the contact surface, thereby improving smoothness. As a result, the withstand voltage characteristic is prevented from lowering, which is useful for further improvement of the characteristic.

If the amount of Ag ₂ Te is less than 0.02% by mass, the effect of improving the smooth state of the contact surface after current switching or current interruption is small, and there is no effect in improving the withstand voltage characteristics as a vacuum circuit breaker. When the amount of Ag ₂ Te exceeds 1.0% by mass, the manufacturing method will be described later, but the cooling rate when passing through the range from the melting temperature of Ag ₂ Te after melting the contact to the melting temperature of −200 ° C. Even when the temperature is controlled at 10 ° C./second or more, the Ag ₂ Te particles are coarsened, and when used as a vacuum valve contact, the Ag ₂ Te particles drop off more, and the smoothness is significantly impaired. The characteristic deterioration is large, which is not preferable.

  The melting temperature of Te is 452 ° C., which is significantly lower than the normal brazing temperature performed at a temperature around 820 ° C. Therefore, if this Te is contained in an Ag-WC alloy and used as a contact for a vacuum valve, Te is removed from the joining surface in a brazing process for joining the contact to the electrode of the vacuum valve. It may flow out, and the smoothness of the contact will be impaired.

On the other hand, the melting temperature of Ag ₂ Te contained in the present invention is about 925 ° C., which is sufficiently higher than the brazing temperature at about 820 ° C. above, so that in the joining step (brazing step) The phenomenon of flowing out from the joint surface is not seen. Also in this respect, the component system of the contact material of the present invention is advantageous.

Moreover, the contact surface used for the vacuum valve of the conventional low surge type vacuum circuit breaker loses smoothness on the contact surface heated excessively at the time of current switching or current interruption, and the withstand voltage characteristic is lowered. In this regard, in the contact material of the present invention, when it is excessively heated at the time of current switching or current interruption, a selective evaporation phenomenon of Ag ₂ Te is observed, and is slightly adhered by the heat at the time of current switching or current interruption. The deposited film of Ag ₂ Te covers the contact surface and maintains smoothness. As a result, the withstand voltage characteristic is prevented from being lowered.

As described above, the contact material of the present invention and the contact of the vacuum valve made of this contact material have a structure in which Ag ₂ Te is dispersed in the form of a precipitate or a film in an Ag—WC alloy. As described above, Ag ₂ Te is finely and uniformly dispersed in the structure, so that the contact material of the present invention improves the maintenance of smoothness when used for the contact of the vacuum valve, and thus the withstand voltage characteristic. It contributes to.

In the range of 0.02 to 1.0% by mass, which is the Ag ₂ Te amount of the contact material of the present invention, the size, ie, diameter, length (in the case of a precipitate) or thickness of Ag ₂ Te. In many cases, the diameter, length or thickness is preferably 1 μm or less (in the case of a form as a coating), and the value should be suppressed to 5 μm or less in order to maintain and improve the withstand voltage characteristics. is there. By setting the diameter or thickness of Ag ₂ Te to 2 μm or less, stable withstand voltage characteristics and cutting current characteristics are obtained. A suitable range is 0.01 to 2 μm.

The size of the above preferable range is, for example, a cooling rate of 10 when passing through a temperature range from the melting temperature of Ag ₂ Te to the melting temperature of −200 ° C. after sintering or infiltration in manufacturing the contact. In addition to controlling the temperature to at least ° C./second, in the manufacture of a vacuum valve, the holding time when heating the contact for brazing the contact should be 30 minutes or less, and the melting of Ag ₂ Te after the contact is brazed This can be achieved by controlling the cooling rate when passing through the temperature range from the temperature to the melting temperature of −200 ° C. to 10 ° C./second or more.

As described above, the two working conditions affect the conditions of the cooling process after the sintering or infiltration of the contact described above, the heating and holding time in the brazing process, and the cooling conditions in the brazing process. At the same time, since the size and distribution of the Ag ₂ Te precipitates are determined, it cannot be uniquely estimated and designed, and is also related to the withstand voltage characteristics, so that it is difficult to predict. Furthermore, the situation where the contact flows out from the contact surface and the smoothness of the contact surface are also involved in the withstand voltage characteristics. Therefore, the withstand voltage characteristic and current chopping characteristic of the _Ag-WC-Ag 2 Te of the present invention, _Ag 2 Te precipitates amount and _Ag 2 Te precipitate size, i.e. the manufacturing conditions and material conditions of the contacts both surfaces This is achieved when both are optimized.

  Next, an example of another component system of the contact material for a vacuum valve of the present invention will be described.

  The contact material for a vacuum valve of the present invention includes WC in a contact material for a vacuum valve comprising 20 to 60% by mass of Ag and 0.02 to 1.0% by mass of silver telluride, with the balance being tungsten carbide. , Molybdenum carbide (MoC), tungsten (W) and molybdenum (Mo) selected from one or more selected component composition ranges.

  When MoC, W and Mo are contained in the contact material for a vacuum valve, the same function as in the case of the WC is exhibited and the same effect is obtained. Moreover, also about content, the same effect can be acquired in the range of the same amount as the case of the said WC. Therefore, in the contact material for a vacuum valve of the present invention, WC is set to a component composition range in which one or two or more selected from molybdenum carbide (MoC), tungsten (W), and molybdenum (Mo) are substituted. It can be done.

In the contact material for a vacuum valve of the present invention, the silver telluride contained for improving the smooth state of the contact surface is Ag ₇ Te ₄ , Ag ₁₂ Te ₇ , Ag ₃ Te _{2 in} addition to Ag ₂ Te. Or one or more tellurium-silver compounds selected from AgTe may be used.

When silver telluride is produced from Ag and Te, in addition to the most stable Ag ₂ Te as a compound, one or more selected from Ag ₇ Te ₄ , Ag ₁₂ Te ₇ , Ag ₃ Te ₂ , AgTe Of tellurium-silver compounds. One or two or more tellurium-silver compounds selected from Ag ₇ Te ₄ , Ag ₁₂ Te ₇ , Ag ₃ Te ₂ , and AgTe are 20 in total with respect to the total silver telluride including Ag ₂ Te. Even when silver telluride mixed at a ratio of less than mass% is used, the expected effect as the contact material for a vacuum valve of the present invention can be obtained.

That is, when one or more of Ag ₇ Te ₄ , Ag ₁₂ Te ₇ , Ag ₃ Te ₂ , AgTe is mixed in a part of silver telluride in excess of 20% by mass, these compounds melt. Since the temperature is lower than the melting temperature of Ag ₂ Te of about 925 ° C. and lower than the brazing temperature at about 820 ° C., it is not preferable for the brazing operation, and unevenness is seen on the contact surface and the withstand voltage characteristic is lowered. It can be seen. There is no problem if one or more of Ag ₇ Te ₄ , Ag ₁₂ Te ₇ , Ag ₃ Te ₂ , and AgTe is 20% by mass or less.

  The contact material for a vacuum valve of the present invention may contain 5% or less of one of Co, Ni, and Fe in addition to the above-described component systems.

That is, since Co, Ni, and Fe all have an effect as a sintering aid when manufacturing a contact material for a vacuum valve, in the present invention, sinterability between Co and WC In order to improve the wettability by obtaining the improvement effect, Ag—WC-based material containing Ag ₂ Te or this WC was substituted with MoC, W, or Mo for one type selected from Co, Ni, and Fe It can be contained in a component material. By containing Co, Ni or Fe, a sintered body having a high density can be obtained, and the wear resistance can be further improved. In particular, it is useful when an Ag-WC contact is manufactured under conditions such that the sintering temperature exceeds approximately 1000 ° C. If the amount of Co, Ni or Fe exceeds 5% by mass, the cutting property of the Ag-WC contact point is deteriorated (the cutting current value is increased), which is not preferable.

Next, the manufacturing method of the contact material for vacuum valves of this invention is demonstrated. In the following, a contact valve material for a vacuum valve having a component system of Ag—Ag ₂ Te—WC will be described as a representative, but the same applies to a contact material for a vacuum valve having other components of the present invention.

(Manufacture of raw materials)
First, in order to produce Ag ₂ Te as a raw material, when the raw materials of Ag and Te are in a lump shape, they are weighed in a ratio in which Ag is 2 and Te is 1 in an atomic ratio, and in a non-oxidizing atmosphere, for example, a predetermined amount Of Ag ₂ Te ingot which is dissolved with sufficient stirring in a reduced pressure or vacuum atmosphere at about 1050 ° C. and has no change in the composition ratio, or Ag ₂ Te powder obtained by pulverizing this, can be used as a raw material. .

Also, when the raw materials of Ag and Te are powdery, respectively, weighed at a ratio in which Ag is 2 and Te is 1, and both are sufficiently mixed while being pulverized by a mixer to mix Ag and Te. Get powder. After the mixed powder is easily molded to a mass, it is heated to about 500 to 900 ° C. to produce an Ag ₂ Te ingot or an Ag ₂ Te powder obtained by pulverizing this, and may be used as a raw material.

There are various methods as described below for producing the vacuum valve contact of the present invention using Ag ₂ Te thus obtained.

For heating in a non-oxidizing atmosphere, WC powder and Ag ₂ Te powder prepared in advance are sealed in a vacuum vessel, for example, heated to about 900 ° C., and part or the entire surface of the WC powder In addition, WC powder coated with Ag ₂ Te with no change in composition ratio can be obtained and used as a raw material. Ag ₂ Te is scattered in the form of particles on a part of the surface of the WC powder depending on the pressure in the vacuum volume and the heating time, or is extremely thin on the entire surface. This is mixed with Ag powder and sintered. Since Ag ₂ Te has a relatively high vapor pressure, it is desirable to heat it in a sealed container in order to reduce evaporation loss.

In the case of using the _Ag 2 Te masses instead of _Ag 2 Te powder, and heating the _Ag 2 Te mass prepared in advance and WC powder to about the melting temperature of the vacuum encapsulated _Ag 2 Te into the vacuum vessel, on the surface A WC powder coated with Ag ₂ Te that does not vary in composition ratio may be obtained and used as a raw material. This is mixed with Ag powder and sintered.

Further, by using the Ag powder instead of WC powder, and this in the case of manufacturing the Ag powder and the raw material from the _Ag 2 Te powder, vacuum-sealed and _Ag 2 Te powder previously prepared and Ag powder in a vacuum chamber 900 It is possible to use Ag as a raw material by heating to about 0 ° C. to obtain Ag powder whose surface is coated with Ag ₂ Te whose composition ratio does not vary. This is mixed with WC powder and sintered.

In the case of using the _Ag 2 Te masses instead of _Ag 2 Te powder, and heating the _Ag 2 Te mass prepared in advance and Ag powder at about the melting temperature of the vacuum encapsulated _Ag 2 Te into the vacuum vessel, on the surface the composition ratio may be used as starting materials to obtain a Ag powder coated with no Ag 2 _Te fluctuation. This is mixed with WC powder and sintered.

Ag powder, WC powder, and Ag ₂ Te powder prepared in advance are vacuum-sealed in a vacuum vessel, heated to about 900 ° C., and Ag powder and WC powder coated with Ag ₂ Te on which the composition ratio does not vary A mixed powder may be obtained and used as a raw material. This raw material is sintered.

Further, the Ag powder and WC powder and previously prepared _Ag 2 Te mass is heated to about the melting temperature of the vacuum encapsulated _Ag 2 Te in the vacuum vessel was covered with no _Ag 2 Te fluctuation in proportion to the surface Ag A mixed powder of powder and WC powder may be obtained and used as a raw material. This raw material is sintered.

In these methods, WC powder as a raw material to be mixed prior to sintering, Ag 2 _Te powder in the case of using a powder as Ag powder and Ag 2 _Te, in order to uniformly mix, the average particle size of approximately the same It is preferable that For example, the particle size can be about 3 μm for WC powder, about 5 μm for Ag powder, and about 5 μm for Ag ₂ Te powder.

Prepared by the _Ag 2 Te and WC, Ag, and sintering method _Ag-WC-Ag 2 Te contact ratio according to the present invention known by or sintered infiltration method described above.

The production conditions during production by the sintering method or the sintering infiltration method can be appropriately selected according to a known method. For example, the heating temperature can be about 860 to 960 ° C. When the heating temperature is higher than the melting temperature of Ag ₂ Te, liquid phase sintering is performed. When the heating temperature is lower than the melting temperature of Ag ₂ Te, solid phase sintering is performed. Either solid phase sintering or liquid phase sintering is performed. Can also be implemented. The heating time can be about 1 to 3 hours. Moreover, the applied pressure at the time of shaping | molding can be about 1-4 t / cm < ² >. Of course, it can be manufactured under conditions other than these manufacturing conditions.

Further, when heating by the sintering method or the sintering infiltration method, heating is performed in a non-oxidizing atmosphere in order to prevent oxidation. For example, when heating in a reduced pressure or vacuum atmosphere, the pressure of the atmosphere in the vacuum vessel can be 10 ⁻⁴ torr or less. Moreover, it can also heat in a hydrogen atmosphere as a non-oxidizing atmosphere instead of the heating in a vacuum vessel. In the case of heating in a hydrogen atmosphere, heating may be performed at atmospheric pressure.

Be carried out at a cooling rate of 10 ° C. / sec or more conditions in the temperature range from the melting temperature of the Ag 2 _Te during the cooling after the sintering to the melting temperature -200 ° C. of Ag 2 _Te is, Ag in the contact for a vacuum valve ₂ Te is preferable in order to make the size of 0.01 to ₂ μm.

  Next, the vacuum valve of the present invention will be described. The vacuum valve of the present invention comprises a contact formed from the contact material for a vacuum valve described so far. An example of such a vacuum valve will be described with reference to FIGS.

  FIG. 1 is a cross-sectional view of an embodiment of a vacuum valve to which a contact material for a vacuum valve of the present invention is applied. In FIG. 1, the vacuum valve has a shut-off chamber 1 adapted to maintain an airtight and vacuum state. The shut-off chamber 1 includes an insulating container 2 formed in a substantially cylindrical shape by an insulating material, and metal lids 4a and 4b provided at both ends of the insulating container 2 via sealing fittings 3a and 3b, respectively. It is a space composed of

In the blocking chamber 1, a conductive bar 5 fixed to the lid 4a and an electrode bar 6 provided so as to be movable in the axial direction with respect to the lid 4b are one of the conductive bars 5. And one end of the electrode rod 6 are provided so as to face each other. In addition, a pair of electrodes 7 and 8 are disposed at the end portions of the conductive rod 5 and the electrode rod 6 which are opposed to each other, and the electrodes 7 disposed on the fixed conductive rod 5 are fixed electrodes. The electrode 8 arranged on the electrode rod 6 movable in the axial direction is called a movable electrode. A bellows 9 is attached to the electrode rod 6 that can move in the axial direction, and the inside of the blocking chamber 1 when the electrode 8 moves in the axial direction by the bellows 9 is kept vacuum and airtight. It is possible. A metal arc shield 10 is provided on the top of the bellows 9 to prevent the bellows 9 from being covered with arc vapor. Further, a metal arc shield 11 is provided in the shut-off chamber 1 so as to cover the electrodes 7, 8, and the arc shield 11 prevents the insulating container 2 from being covered with arc vapor.

  FIG. 2 is an enlarged cross-sectional view of the vicinity of the electrode 8. The electrode 8 is fixed to the electrode rod 6 by brazing. In the figure, a brazing portion 12 formed between the electrode 8 and the electrode rod 6 is shown. The electrode 8 may be fixed to the electrode rod 6 by caulking instead of brazing. And the contact 13a is being fixed to the front-end | tip part of this electrode 8 by brazing. In the figure, a brazing portion 14 formed between the electrode 8 and the electrode rod 6 is shown. Similarly, the contact 13b is fixed to the tip of the electrode 7 by brazing.

  The vacuum valve is normally energized when both contacts 13a and 13b are connected. When the movable electrode rod 6 is moved in the axial direction so that the contact 13a is separated from the contact 13b in order to cut off the current from this state (moving downward in the drawing of FIG. 1), the movable contact 13a is fixed. Is separated from the contact 13b on the side, and an arc is generated between the two contacts. This arc is maintained by the generation of metal vapor from the cathode (for example, movable contact 13a) side. When the current reaches the zero point (zero point), the generation of metal vapor stops and the arc cannot be maintained, and the interruption is completed. By such an operation, the vacuum valve performs current opening / closing or current interruption.

  A contact material having a component and composition according to the present invention is brazed to the tip portions of the electrodes 7 and 8 at about 820 ° C. using, for example, Ag as a brazing material. The contact material having the components and composition according to the present invention does not cause a phenomenon that the components constituting the contact material melt and flow out of the contact surface at such a brazing temperature, so that the smoothness of the contact surface is maintained, Does not adversely affect the withstand voltage characteristics.

In order to set the size of Ag ₂ Te in the contact to 0.01 to ₂ μm, the holding time when heating the contact for brazing is preferably 30 minutes or less. Later, it is preferable to control the cooling rate when passing through the temperature range from the melting temperature of Ag ₂ Te to the melting temperature of −200 ° C. to 10 ° C./second or more.

The best mode for developing a low surge type vacuum circuit breaker with excellent cutting characteristics and improved withstand voltage characteristics is the cooling rate after heating during manufacturing or brazing, for example, in an Ag ₂ Te-Ag-WC contact The cooling rate when passing through the −200 ° C. range from the melting temperature of Ag ₂ Te is about 100 ° C./second, and the size of the Ag ₂ Te precipitates is controlled to a diameter or length of 1 μm or less to be coarsened This is a contact made of 0.1 mass% Ag ₂ Te-40 mass% Ag-remainder WC, and is a vacuum valve on which this is mounted.

Contacts having various component compositions and Ag ₂ Te sizes shown in Table 1 including the best mode were manufactured by a known sintering method or sintering infiltration method.

Table 1 shows the size and characteristic evaluation and overall evaluation of Ag ₂ Te in the obtained Ag-WC-Ag ₂ Te contact.

(Evaluation methods and conditions):
The cutting current characteristics are evaluated by manufacturing a contact having a diameter of 20 mm and a thickness of 4 mm, one of which is a flat surface and the other of which is a curved surface having a curvature radius of 50 mm, and is attached to a detachable cutting current evaluation device. The degree of vacuum is 10 ⁻³ Pa. After evacuating below and cleaning the contact surface by baking, the voltage of the shunt that inserted the cutting current value in series at the opening speed of 0.8 m / sec. It is obtained by measuring the descent. The evaluation criteria are as follows.

  A case where all cutting current values during opening and closing 2000 times are 1 A or less (Evaluation A), and a measurement value of 1 A or less is mixed by about 1%, but the remainder exceeds 1 A and is 1.5 A or less (Evaluation) B) A case where the measured value of 1.5A or less is mixed by about 1% but the remaining is 1.5 to 2A is defined as (Evaluation C), and both are acceptable ranges.

  On the other hand, the case where the measured value of 2A or less is mixed by about 1% but the remaining is 2A to 2.5A (Evaluation X), the case of 2.5A to 3A or less (Evaluation Y), 3A or more (Evaluation Z), and both are in the range of failure.

  Withstand voltage characteristics, one side is a flat contact with a diameter of 30 mm and a thickness of 5 mm, and the other is a curved contact with a tip having a radius of curvature of 5 mm, and a voltage is gradually applied between the opposing contacts. -The voltage at the time of squeezing was taken as the static withstand voltage value. Since the withstand voltage value varies widely, five undischarged portions were selected and measured for each of the three contacts, and the variation width was shown.

The withstand voltage value of the contact of Example 2 in which the amount of Ag ₂ Te was 0.1% was used as a reference (Evaluation B). A case where a high withstand voltage value of 1.2 times or more of the value of Example 1 is shown (Evaluation A), and a case where a withstand voltage value of 0.9 to less than 1.0 times is shown (Evaluation C). Both are acceptable ranges.

  On the other hand, less than 0.9 times to 0.8 times the withstand voltage value of the reference contact of Example 2 (Evaluation X), less than 0.8 times to 0.6 times or more (Evaluation Y), 0.6 times Less than was made into (evaluation Z), and all were made into the range of rejection.

The size of Ag ₂ Te shown for reference was determined by observation at a magnification of 10,000 times or more using a scanning electron microscope. The size of the Ag 2 _Te is of its diameter in the case of the particulate, in the case of the film-like was its thickness.

[Examples 1 to 4], [Comparative Examples 1 to 3]
In an Ag-WC-Ag ₂ Te contact, after making a contact with a constant Ag of 40% by mass, a Ag ₂ Te of 0% by mass, and a contact with 0.01 to 3% by mass, the Ag ₂ Te A contact having a size in the range of 0.01 to 0.2 μm was selected and used as a test contact. Note that most of Ag ₂ Te was observed in a thin film state or a lump state at the interface between the WC and the Ag matrix by observation with a scanning electron microscope. The evaluation results were arranged by relative values based on the characteristics of Example 2 in which the Ag ₂ Te amount was 0.1% by mass.

When the Ag ₂ Te amount is 0.02% by mass (Example 1), the withstand voltage characteristic is (Evaluation AB), but when the Ag ₂ Te amount is 1% by mass (Example 4), the withstand voltage characteristic is Although it becomes (evaluation C) of the tendency of a fall rather than the said (Example 1), all are the ranges of a pass. On the other hand, when the amount of Ag ₂ Te is increased to 3% by mass (Comparative Example 3), the cutting current characteristic shows (Evaluation A to B) and is in the acceptable range, but the withstand voltage characteristic is ( Evaluation Y to Z) show a variation as well as a decrease.

Conversely, when the amount of Ag ₂ Te is decreased to 0.01% by mass (Comparative Example 2), the cutting current characteristic shows (Evaluation C) and is in the pass range, but the withstand voltage characteristic is (Evaluation C to X ). The amount of Ag ₂ Te is not preferable because it is not significantly different from zero (Comparative Example 1).

As described above, the Ag ₂ Te amount in the Ag—WC—Ag ₂ Te contact is preferably in the range of 0.02 to 1% by mass (Examples 1 to 4).

[Examples 5 to 7], [Comparative Examples 4 to 6]
In Examples 1 to 4 and Comparative Examples 1 to 3, the contact amount where the Ag amount in the Ag-WC-Ag ₂ Te contact is constant at 40% by mass is shown. However, the Ag amount of the contact to which the present invention is applied is The presence effect of Ag ₂ Te is exhibited without being limited to 40% by mass.

  That is, even in the case where the Ag amount is 20 mass percent, 30 mass%, and 60 mass% (Examples 5 to 7), the withstand voltage characteristics show (Evaluation A to B, B) and are good. Cutting current characteristics are also shown (Evaluations B and B to C), and both characteristics are compatible.

  On the other hand, in the case where the Ag amount is 10% by mass (Comparative Example 4), the withstand voltage characteristic is good indicating (Evaluation A to B), but the cutting current characteristic is reduced to (Evaluation C to X). Both characteristics cannot be achieved.

  Further, in the case where the Ag amount is 70% (Comparative Example 5), the withstand voltage characteristics are good (evaluation B to C), but the cutting current characteristics are reduced to (evaluation X to Y), and both characteristics are Coexistence cannot be achieved.

  Further, even when the Ag amount is 85% (Comparative Example 6), the withstand voltage characteristic shows (Evaluation C) and is in the acceptable range, but the cutting current characteristic is lowered to (Evaluation Y to Z), and both characteristics are Coexistence cannot be achieved.

From the above, the Ag amount in the Ag-WC-Ag ₂ Te contact is preferably in the range of 20 to 60% (Examples 5 to 7).

[Examples 8 to 9], [Comparative Example 7]
In Examples 1 to 7 and Comparative Examples 1 to 6, the contact point in which the size of Ag ₂ Te in the Ag-WC-Ag ₂ Te contact point is set to 0.01 to 0.2 μm is shown, but the present invention is applied. The size of Ag ₂ Te of the contact to be achieved is not limited to 0.01 to 0.2 μm, and the object of the present invention is achieved.

That is, in the case the size of the _Ag 2 Te is 0.1 [mu] m, 1 [mu] m (Example 8-9), withstand voltage characteristic is good shows (evaluation B, B-C). The cutting current characteristic also shows (Evaluation B), and both characteristics are compatible.

On the other hand, in the case where the size of Ag ₂ Te is 5 μm or more (Comparative Example 7), the cutting current characteristic is good indicating (Evaluation B), but the withstand voltage characteristic is lowered to (Evaluation X to Z). However, both characteristics cannot be achieved.

As described above, the size of Ag ₂ Te in the Ag-WC-Ag ₂ Te contact is preferably in the range of 0.01 to ₂ μm, and more preferably in the range of 0.1 to 1 μm (Example 8). ~ 9).

[Examples 10 to 14], [Comparative Example 8]
In Examples 1 to 9 and Comparative Examples 1 to 7, the Ag—WC—Ag ₂ Te contacts are shown for contacts that do not have auxiliary components such as Co, Ni, and Fe. However, in the contacts to which the present invention is applied, auxiliary contacts are used. The object of the present invention is achieved even when Co, Ni, and Fe in a predetermined amount range exist as components.

  That is, in the case where Co is 0.1% by mass, 1% by mass, and 5% by mass (Examples 10 to 12) as the auxiliary component, the withstand voltage characteristics are (Evaluation A, A to B, B) and good. . Cutting current characteristics are also shown (Evaluations B and B to C), and both characteristics are compatible.

  Even when Ni or Fe is used in place of Co, the withstand voltage characteristics are (evaluation A to B) and are good. The cutting current characteristics also show (B to C), and both characteristics are compatible (Examples 13 to 14).

  On the other hand, in the case where Co is 10% by mass (Comparative Example 7) as an auxiliary component, the withstand voltage characteristic is (Evaluation B) and good, but the cutting current characteristic is (Evaluation Z) and is rejected. Both characteristics cannot be achieved.

As described above, the amount of Co, Ni, or Fe as an auxiliary component in the Ag—WC—Ag ₂ Te contact is preferably in the range of 5% or less (Examples 9 to 11).

[Examples 15 to 17]
In Examples 1 to 14 and Comparative Examples 1 to 8, the Ag-WC-Ag ₂ Te contact is shown for WC. However, the contact to which the present invention is applied is not limited to the WC, and the object of the present invention is achieved. .

  That is, even in the case of Examples 15 to 17 containing MoC, W, and Mo instead of WC, the withstand voltage characteristics are (evaluation B, AB) and are good. The cutting current characteristic also shows (C), and both characteristics are compatible.

It is sectional drawing of one Embodiment of the vacuum valve to which the contact material for vacuum valves of this invention is applied. It is a cross-sectional enlarged view of the electrode vicinity of FIG.

Explanation of symbols

5 ... electrode rod, 6 ... electrode rod, 7 ... electrode, 8 ... electrode, 13a ... contact, electrode 13b ... contact

Claims (7)

  A contact material for a vacuum valve comprising 20 to 60% by mass of Ag, 0.02 to 1.0% by mass of silver telluride, and the balance being tungsten carbide.   2. The contact material for a vacuum valve according to claim 1, wherein the silver telluride has a size of 0.01 to 2 [mu] m.   The contact material for a vacuum valve according to claim 1 or 2, wherein the tungsten carbide has a composition in which one or more selected from molybdenum carbide, tungsten and molybdenum are substituted. The silver telluride contains, in addition to Ag ₂ Te, one or more tellurium-silver compounds selected from Ag ₇ Te4, Ag ₁₂ Te ₇ , Ag ₃ Te ₂ and AgTe. 2. The contact material for a vacuum valve according to claim 1, wherein the contact material is a vacuum valve.   Furthermore, 1 type chosen from Co, Ni, and Fe is contained at 5 mass% or less, Contact material for vacuum valves given in any 1 paragraph chosen from Claims 1-4 characterized by the above-mentioned.   A vacuum valve comprising a contact made of the contact material for a vacuum valve according to any one of claims 1 to 5. Sintering of the raw material of the contact material for the vacuum valve containing Ag, silver telluride and tungsten carbide is performed at a temperature range from the melting temperature of Ag ₂ Te to the melting temperature of Ag ₂ Te at −200 ° C. during cooling after sintering. A step of performing a cooling rate at 10 ° C./second or more under the conditions;
The contact obtained by forming after sintering is joined to the electrode of the vacuum valve by brazing, the contact holding time is within 30 minutes, and the melting temperature of Ag ₂ Te from the joining temperature during cooling after joining A step of performing a cooling rate in a temperature range up to -200 ° C under a condition of 10 ° C / second or more,
A method for manufacturing a vacuum valve, comprising:

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