JP4458797B2 - Bonding materials for vacuum valves - Google Patents

Description

  The present invention relates to a bonding material for a vacuum valve, and more particularly to a bonding material used for partial assembly of a vacuum valve such as bonding of a contact material and an electrode material, bonding of a shield and a support.

A normal vacuum valve is configured as shown in FIG. In FIG. 1, reference numeral 1 denotes an insulating container in which an insulating material such as ceramics is formed in a cylindrical shape, and the end faces of the opening portions at both ends are hermetically sealed with a fixed-side sealing fitting 2a and a movable-side sealing fitting 2b. The vacuum vessel 3 having an internal pressure of 1 × 10 ⁻² Pa or less is formed. Inside the vacuum vessel 3, a fixed energizing shaft 4a serving as one electric circuit, a fixed side contact 5a fixed to the end thereof, a movable energizing shaft 4b serving as the other electric circuit, and a movable side fixed to the end thereof A contact point 5b is provided, and the fixed side contact point 5a and the movable side contact point 5b are arranged so as to be detachable. A coil electrode 6a and a coil electrode 6b are provided behind the fixed contact 5a and the movable contact 5b, respectively. The movable energizing shaft 4b is fixed to the other end of the bellows 7 having one end fixed to the movable side sealing fitting 2b, and can move in the axial direction while maintaining the vacuum degree of the vacuum vessel 3. I have to. Further, in order to prevent the inside of the vacuum vessel 3 from lowering the insulation resistance due to the metal vapor generated from both contacts when the fixed side contact 5a and the movable side contact 5b are opened and closed attached to the inner wall of the insulating vessel 1, A metal shield 8 that surrounds the fixed contact 5a and the movable contact 5b is provided by hooking a joined body with the support 9 to a protrusion inside the insulating container 1.

  Further, as shown in an enlarged view in FIG. 2, the contact 5b and the electrode 6b are fixed to the conductive shaft 4b by a brazing portion 10b or are crimped and connected by caulking. The contact 5b is fixed to the electrode 6b with a brazing portion 11b.

  This vacuum valve is usually assembled in a two-step brazing process, which is a partial assembly process for manufacturing a contact / electrode assembly and a shield / support assembly, and an entire sealing process for joining an insulating container and a sealing fitting. Manufacture. The melting temperature of the brazing material used in the first partial assembly process is higher than the melting temperature of the brazing material used in the final overall sealing process, and the former is usually palladium brazing (Ag—Cu—Pd), In that case, eutectic silver solder (Ag-28 wt% Cu) is usually used for the latter.

  That is, the brazing material used for the brazing part 11 to be joined in the partial assembly process is usually a palladium brazing (see, for example, Patent Document 1). BPd-2 of palladium brazing has a solidus temperature of 825 ° C and a liquidus temperature of 850 ° C. It is very useful when manufacturing vacuum valves at 890 ° C for partial assembly and 820 ° C for overall sealing. It is a brazing material suitable for. However, since this brazing material contains expensive Pd as a constituent element, it is expensive, and furthermore, it is difficult to purchase at a stable price due to price fluctuation of Pd.

  On the other hand, vacuum valves are required to maintain and improve welding resistance, withstand voltage characteristics, cutoff characteristics, cutting characteristics, wear resistance, contact resistance characteristics, temperature rise characteristics, and the like. In addition, severe mechanical shocks, electrical shocks, and thermal shocks can be applied repeatedly over a long period of time alone or in combination. When such severe various impact stresses are applied singly or simultaneously, for example, dropping or peeling (related to bonding characteristics) is observed at the contact portion between the electrode and the connection portion between the electrode and the current-carrying shaft. .

According to the microscopic observation in the vicinity of these connecting portions, generation of displacement and generation of fine cracks are observed in any joint interface. In order to ensure the reliability of the vacuum valve, a joining technique that suppresses the above-described interface shift and crack generation is required.

  However, the impact stress applied to each component in the vacuum valve is not constant depending on the frequency of current interruption and current switching, the magnitude of current and voltage, the location, material and size of each component. For this reason, it is difficult to predict the extent of crack formation and dropout and the time until it. Therefore, the above-mentioned required characteristics are to be satisfied as much as possible by selecting standard bonding materials with proven results such as Ag—Cu, Cu—Mn, and Ag—Cu—Mn.

  However, in addition to the generation of cracks and dropouts due to electrical shock and mechanical shock, especially when a large current is interrupted and opened / closed, the arc generated by the interruption moves to a portion of the contact electrode where the arc voltage is low. Stagnation, concentration and overheating, or conversely, overheating of the local parts of these members due to the thermal shock caused by the arc when the shield, bellows, bellows cover surface and insulating cylindrical surface are ignited. The joint portion is also indirectly overheated, causing crack formation and dropout of the joint portion (the joint has a joint strength of a predetermined value or more). In addition, abnormal movement of metal particles and metal vapor caused by the arc moving to the contacts, electrodes, and shields, and stagnation and concentration there, or overheating the brazed parts also causes contact of the brazing material components, electrodes, There is a phenomenon of sticking to the shield. These are factors that cause a significant decrease in the withstand voltage characteristics and the cutoff characteristics of the vacuum valve. That is, it is suggested that stabilization of the joint portion over a long period is extremely important.

  Conventionally, as a technique for joining the constituent members of the vacuum valve, in addition to using the above-described expensive palladium brazing (see, for example, Patent Document 1), Patent Document 2 includes an Ag—Cu—Sn brazing material. In joining by joining, the joining technique etc. which coat | cover an Sn layer on the surface of a joining member are disclosed.

  Patent Document 3 discloses a joining technique using a brazing material composed of 15 to 35% Mn, 0.5 to 15% Zn, 0.05 to 0.25% Ti, and the remaining Cu as a general joining technique. ing.

  In Patent Document 4, as a joining technique for SUS, a brazing material composed of 1 to 10% Sn, 2.5 to 10% Cu and the balance Ag, 1 to 10% Sn, 2.5 to 10% Cu, 6 The joining technique by the brazing material which consists of Mn of% or less and remainder Ag is disclosed.

Patent Document 5 discloses two regions of 1 to 15% Mn, 5 to 15 Sn, the remaining X region consisting of AgCu, and 0.05 to 10% Mn, 1 to 10% Sn and the remaining Y region consisting of AgCu. The joining technique by the brazing | wax material comprised by this is disclosed.
Japanese Examined Patent Publication No. 64-8412 (pages 2 and 3) JP 59-175521 (pages 3 to 4) Japanese Examined Patent Publication No. 52-29692 (first page, Fig. 7) JP 2002-361478 A (pages 3 to 4) JP 2001-357760 A (page 6)

In the above disclosed technique related to the joining of the components of the vacuum valve, the crack is generated or dropped from the severe mechanical shock, electrical shock, or thermal shock that the vacuum valve receives when a large current is repeatedly interrupted for a long period of time. Such a situation could not be avoided completely. In addition, even with the above general joining technique, it has not been possible to completely avoid the generation and dropping of cracks in the joint. It is a problem to avoid these problems and improve various electrical characteristics such as withstand voltage characteristics of the vacuum valve.

  Moreover, in the joining technique of patent document 2, the process of providing a Sn layer is required.

  The joining technique of Patent Document 3 has a drawback of contaminating the object to be joined or the furnace interior with Mn and Zn.

  The joining techniques of Patent Document 4 and Patent Document 5 also have a drawback that the object to be joined and the inside of the furnace are contaminated by Mn.

  As described above, in the above-described conventional disclosed technique related to the joining of the constituent members of the vacuum valve, the joint portion is subjected to severe mechanical shock, electrical shock, and thermal shock that the vacuum valve receives when a large current is repeatedly interrupted for a long period of time. It has not been possible to completely avoid the generation and removal of cracks in the furnace and contamination in the furnace.

  An object of the present invention is to provide a vacuum valve bonding material capable of improving the various electric characteristics such as the withstand voltage characteristics of a vacuum valve without using these, and using noble metal elements other than Ag. And

The vacuum valve bonding material according to the present invention is a vacuum valve bonding material used for partial assembly of a vacuum valve, and does not contain noble metal elements other than Ag as constituent elements, and the component is Cu-10 to 55 wt% Ag . And the solid phase ratio determined from thermodynamic data and equilibrium diagram curve is 20% or more at a temperature of 820 ° C.

  According to the present invention, various electrical characteristics such as the withstand voltage characteristics of the vacuum valve can be improved without using a noble metal element other than Ag. That is, for example, if the vacuum valve bonding material according to the present invention is used for partial assembly of the vacuum valve such as bonding of a contact material and an electrode material, bonding of a shield and a support, the second heat treatment in manufacturing the vacuum valve. Sometimes, the contact point does not drop off from the electrode, and the junction between the shield and the support does not dissociate, and the electrical characteristics such as the withstand voltage characteristic of the vacuum valve can be improved.

  As described above, at the time of the second heat treatment when manufacturing the vacuum valve, it is necessary that the contact does not drop off from the electrode, and the joint between the shield and the support does not dissociate. For that purpose, it is necessary to satisfy “the solid phase ratio of the brazing filler metal at 820 ° C. being 20% or more”.

  In this case, the brazing material is in a solid-liquid coexistence state, and the contact does not fall off if the solid phase ratio is more than a certain level.

  Here, the solid phase ratio indicates the ratio of the solid phase at a certain temperature of the brazing material. For example, when the solid phase ratio is 0%, a complete liquid phase state is obtained, and when the solid phase ratio is 100%, the solid phase ratio is complete. When the solid phase ratio is larger than 0% and smaller than 100%, a solid-liquid coexisting state is indicated. The calculation method of the solid phase ratio can be obtained from the thermodynamic data and the equilibrium diagram curve by solidification simulation. For further confirmation, the structure was rapidly cooled after being held at the obtained temperature for a long time.

  According to the present invention, the contact can be prevented from falling off the electrode and the shield and the support can be separated from each other, and the withstand voltage performance can be stabilized.

  A manufacturing method and test results of a vacuum valve using the vacuum valve bonding material according to the present invention will be described with reference to FIG. In the test results, the bondability (shield / support or contact / electrode bondability) is expressed in three stages by observing the inside of the vacuum valve with X-rays after manufacturing the vacuum valve (see the outside of FIG. 3), and withstand voltage. The characteristic was expressed as a relative value with a target value of 1.

(Comparative Examples 1-2, Examples 1-3)
In Comparative Example 1, as a result of using BPd-2 (Ag-31.5Cu-10Pd) containing 10 wt% of the precious metal element Pd as the brazing material, the shield / support did not fall off and was joined and withstand voltage characteristics Was 1.2 times the target value.

  In Comparative Example 2, when Cu-60Ag was used as the brazing material, the solid phase ratio at 820 ° C. was 15% according to the simulation, and when the vacuum bulb was manufactured and the inside was observed with X-rays, the shield was dropped. Was.

  In Examples 1 to 3, when Cu-55Ag, Cu-40Ag, and Cu-10Ag were used as brazing materials, the solid phase ratios at 820 ° C. were 20%, 50%, and 98%, respectively, and the test results were shielded. / The support was joined without falling off, and the withstand voltage characteristic was 1.1 times the target value.

  As described above, it was found that the solid phase ratio should satisfy 20% or more so that the shield / support bonded by partial assembly does not fall off.

(Examples 4 to 5)
In Example 4, Cu-39Ag-1Sn was used as the brazing material, and in Example 5, Ag-39Cu-5Ni was used. As a result, the shield / support did not fall off and the test was conducted and the withstand voltage characteristics were also targeted. It was 1.1 times the value.

  In Examples 4 and 5, Sn and Ni have been described as additive elements, but the same effect can be expected by adding two or more of four kinds of elements including In and Ti. In particular, if the total amount of additive elements is 10 wt% or less, a decrease in strength of the brazing filler metal itself can be suppressed, so that the effect can be expected to be even greater.

(Examples 6 to 8)
In Comparative Example 1 and Examples 1 to 5, examples where the bonding atmosphere is in a vacuum have been described, but the gist of the present invention is not limited thereto.

  In Examples 6 to 8, when the bonding atmosphere was carried out in an inert atmosphere such as a hydrogen atmosphere, an argon atmosphere, and a nitrogen atmosphere, results that satisfy both the bonding property and the withstand voltage characteristics were obtained. Furthermore, the appearance of the brazing material part was good and showed a metallic luster.

(Examples 9 to 14)
In Comparative Example 1 and Examples 1 to 8, the example of joining of stainless steels called shield / support joining was described, but the gist of the present invention is not limited to this.

  In Example 9, as a result of joining the Cu-50Cr contact and the Cu electrode, a result satisfying both the joining property and the withstand voltage characteristic was obtained.

  In Examples 10 to 13, as a result of joining the Cu electrode with the contacts as Cu-Bi, Cu-Te-Se, Cu-W, and Ag-WC, respectively, results that satisfy both the joining property and the withstand voltage characteristics were obtained. .

  In Example 14, as a result of joining the Cu-25Cr contact and the Cu-2Cr electrode, a result satisfying both the joining property and the withstand voltage characteristic was obtained.

  As shown by the above results, according to the present invention, it is possible to provide a vacuum valve that is inexpensive, has high bonding reliability, and has excellent withstand voltage characteristics.

  ADVANTAGE OF THE INVENTION According to this invention, the joining material for vacuum valves which improved joinability and the withstand voltage characteristic can be provided.

Sectional drawing which shows the structural example of the vacuum valve to which the joining material for vacuum valves which concerns on this invention is applied. The expanded sectional view of the contact and electrode part of the vacuum valve shown in FIG. The table | surface which shows the conditions and test result of the Example of the joining material for vacuum valves which concerns on this invention, and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulation container 2a, 2b ... Sealing metal fitting 3 ... Vacuum container 4a, 4b ... Current supply shaft 5a, 5b ... Contact 6a, 6b ... Electrode 7 ... Bellows 8 ... Shield 9 ... Support 10b, 11b ... Brazing part

Claims (2)

A joining material for a vacuum valve used for partial assembly of a vacuum valve, which does not contain noble metal elements other than Ag as constituent elements, and that the component is Cu-10 to 55 wt% Ag , and thermodynamic data and an equilibrium diagram curve A bonding material for a vacuum valve, characterized in that the solid phase ratio determined from the above is 20% or more at a temperature of 820 ° C.   2. The vacuum valve according to claim 1, wherein the additive element contains at least one of Sn, Ni, In, and Ti, and the total content of the additive elements is 10 wt% or less. Bonding material.

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