JPH10199380A - Manufacture of vacuum bulb - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a required function, save high-temperature heat treatment in reductive atmosphere to be performed before plating for tissue re- crystallization, add nickel plating or further corrosive plating by performing heat treatment within a specific temperature range after plating of austenite- based stainless steel constituting a vacuum bulb. SOLUTION: Fixed size and movable metal end plates 2, 3, a bellows 9, a bellows cover 13, a shield 10, and a shielding fixing bracket 12 are made of an austenite-based stainless steel. This material is free of stress corrosion split or particle boundary corrosion split in a vacuum container, a part exposed to air is nickel-plated, and liquid treatment is not required. To remove processing strain and hydrogen, heating is performed at 270 to 400 deg.C for more than 30 minutes during drying after plating. By specifying the pH value of a watt bath for wet-type nickel plating made of austenite-based stainless steel and Fe-Ni alloy or inconnel in place thereof is 3.0 to 4.2, thereby sticking property is improved, and inflating is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a vacuum valve, and more particularly to a surface treatment and a heat treatment method applied to a metal part.

[0002]

2. Description of the Related Art Generally, a vacuum valve is constructed as shown in FIG. In FIG. 1, reference numeral 1 denotes a cylindrical insulating cylinder made of a ceramic insulating material. Openings at both ends are closed by a fixed-side metal end plate 2 and a movable-side metal end plate 3 to form a vacuum container 4. I have. A fixed contact energizing shaft 7 is fixedly penetrated through the fixed-side metal end plate 2, and a movable contact energizing shaft 8 is movably penetrated through the bearing 11 through the movable-side metal end plate 3 so as to face the fixed contact energizing shaft 7. I have. And
A fixed contact (fixed electrode) 5 is attached to the fixed contact energizing shaft 7 in the facing portion, and a movable contact (movable electrode) 6 is attached to the movable contact energizing shaft 8. A metal bellows 9 is provided so as to allow the movable contact energizing shaft 8 to move in the axial direction with respect to the movable metal end plate 3. The upper end of the bellows 9 is joined to the upper lower surface of an inverted U-shaped bellows cover 13 whose upper end is joined to the movable contact energizing shaft 8. Reference numeral 10 denotes a shield, which is provided so as to surround the fixed contact 5 and the movable contact 6. 12 is the shield 1
This is a shield fixing bracket for fixing 0. In the mounting structure of each member as described above, each energized shaft 7, 8 and its corresponding fixed contact 5 and movable contact 6, fixed-side metal end plate 2 and fixed contact energized shaft 7, movable contact energized shaft 8 and bellows 9 , The other end of the movable-side metal end plate 3 and the bellows 9, and the respective joining portions of the metal end plates 2 and 3 and the insulating cylinder 1 are joined by brazing or welding.

The movable contact energizing shaft 8 is driven in the axial direction by an operating mechanism (not shown) so that the movable contact 6 comes into contact with and separates from the fixed contact 5.

When such a vacuum valve is used in a pole switch or the like, it may be used not only in a polluted atmosphere but also in an extremely corrosive atmosphere. For this reason, when an alloy such as an iron-nickel alloy is used for the fixed metal end plate 2 and the movable metal end plate 3 which are the metal exterior parts exposed to the outside, the outer surface is made of an epoxy resin of a corrosion-resistant organic material. A coating film is formed by a paint to take anticorrosion measures, and a stainless steel material having good corrosion resistance is used.
Further, the fixed-side metal end plate 2, the movable-side metal end plate 3, the bellows 9, the shield 10, and the shield fixing bracket 12 are formed by nickel plating on a metal base material such as austenitic stainless steel, iron-nickel alloy, and inconel. We use what we gave. The austenitic stainless steel is subjected to high-temperature heat treatment in a reducing atmosphere gas after processing to obtain a required shape to achieve recrystallization of the structure. The heat-treated austenitic stainless steel, iron-nickel alloy, and inconel material are plated with nickel to obtain functions such as improved brazing wettability, corrosion protection, and oxidation prevention. A high-temperature heat treatment is performed in a reducing atmosphere for the purpose of ensuring the adhesion between the material and the nickel plating. Using metal parts that have undergone such treatment, bonding such as brazing is performed in a vacuum or in a reducing atmosphere, and particularly when high airtightness must be maintained, the treatment is performed under high vacuum and high temperature. Is going.

[0005]

As described above, austenitic stainless steel is subjected to a reducing atmosphere (hydrogen gas or the like) in order to recrystallize its structure before nickel plating. The heat treatment is performed at a high temperature exceeding 1000 ° C. Performing this heat treatment in a reducing atmosphere has the function of preventing oxidation and nitridation, and further, has the function of removing an oxide film and impurities (oil and the like) formed before the treatment from the base material. Diffusion of large amounts of hydrogen molecules into the metal may cause embrittlement, particularly at welded places such as shields.Furthermore, since there is a treatment in an acid bath in the next nickel plating step, It may promote conversion. In addition, nickel plating is applied to austenitic stainless steel, iron-nickel alloy (sealing alloy), and inconel material, which are subjected to heat treatment before plating to increase the number of processes compared to the processing of other base materials. Because of forming a strong oxide film from the nature of, after removing this film,
After activation and simultaneous processing of etching and thin film formation, nickel plating is performed. Since the plating process is performed on a special material, the process is complicated and there are many factors affecting the process, and plating defects such as blistering tend to occur more easily than the generally applied electroplating process. Thereafter, washing with water (including pure water washing) is performed (they also have an effect of relaxing the tensile stress of plating), and draining (water removal) and drying are performed in the air (they also have an effect of preventing hydrogen embrittlement by baking).
Next, a high-temperature heat treatment is performed in a reducing atmosphere such as a hydrogen gas for the purpose of further ensuring adhesion between the nickel plating and the base material and facilitating determination of plating defects. For this reason, there is a possibility that hydrogen molecules diffuse into the nickel plating and further into the base metal and become brittle. In addition, since the processing temperature is different from the heat treatment in the reducing atmosphere described above,
If a furnace is used, control is required. The above members are joined by brazing or the like in a high vacuum or in a neutral gas atmosphere.

[0006] The present invention has been made in view of the above,
First, it is possible to provide the necessary function as a metal component of a vacuum valve without performing high-temperature heat treatment in a reducing atmosphere before plating of austenitic stainless steel, and secondly, to function due to defects in nickel plating. A plating adhesion test that eliminates a portion of insufficient adhesion, which is particularly problematic, and confirms whether the performance is reliable can be performed during the manufacturing process. It is an object of the present invention to provide a method of manufacturing a vacuum valve that can surely perform joining such as brazing without performing high-temperature heat treatment in an atmosphere.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is to provide an austenitic stainless steel constituting a vacuum valve after plating from 270 to 40%.
The gist is that the heat treatment is performed at a temperature of 0 ° C. With this configuration, austenitic stainless steel should be nickel-plated when used in a high vacuum or when used in the atmosphere, and nickel-plated + rust-proof painted when used in a severe corrosive environment. Thus, the present invention can be applied as a metal component of a vacuum valve without performing a high-temperature solution heat treatment for recrystallization of a structure. However, since it is a material that is easily affected by heat, it is necessary to remove the processing strain generated during the processing even when the solution heat treatment is not performed, and by performing the heat treatment at a temperature of 270 to 400 ° C., the nickel plating by the wet method is performed. In addition, the processing distortion is removed together with the drying and baking for removing hydrogen in the case of applying. Nickel oxidation proceeds at 500 ° C. or higher, and even if the treatment is performed in a vacuum, the wettability during brazing deteriorates. However, the upper limit of the heat treatment temperature is set to 400 ° C. with a sufficient margin. If the temperature is lower than 270 ° C., the removal of processing strain becomes insufficient.

A second aspect of the present invention is to make the pH value of the watt bath for nickel plating of austenitic stainless steel, iron-nickel alloy and inconel constituting the vacuum valve 3.0 to 4.2. And With this configuration, when the pH value of the watt bath is 4.5 or more, the current density distribution is affected by the unevenness of the current density distribution in a complex shape having irregularities, R portions, and the like, and blisters are easily generated. pH value is 3.
If it is less than 0, the throwing power of the plating is poor and pits are likely to occur. For this reason, since the pH value increases during the treatment, the upper limit is set to 4.2 in view of the safety side,
By setting the H value to 3.0 to 4.2, it becomes possible to prevent blistering while maintaining good throwing power.

According to a third aspect of the present invention, in the method for manufacturing a vacuum valve according to the second aspect, the austenitic stainless steel, the iron-nickel alloy and the inconel after nickel plating are dried by heating at a temperature of 270 to 400 ° C. The gist of the present invention is to perform a plating adhesion non-destructive test, a baking for removing hydrogen and a treatment for strengthening the adhesion between the base metal and the nickel plating simultaneously with the heating and drying. With this configuration, for the austenitic stainless steel, in addition to obtaining the action described in the first aspect of the present invention, any metal component can be surely confirmed if there is a blister, so that it is non-destructive. A plating adhesion test can be performed, and at the same time, a baking action for removing hydrogen for preventing hydrogen embrittlement and an action for further ensuring the adhesion between the base metal and the nickel plating can be obtained.

According to a fourth aspect of the present invention, there is provided the method of manufacturing a vacuum valve according to the second or third aspect, wherein the nickel-plated austenitic stainless steel, the iron-nickel alloy, and the inconel are joined by brazing.
400 to 7 in the heating process before reaching the brazing temperature
The gist is to maintain the temperature at 50 ° C. for at least 10 minutes. With this configuration, the holding temperature and the temperature rise until the brazing temperature is reached further cause interdiffusion between the base metal and the nickel plating before the melting reaction of the brazing material, thereby obtaining a strong bond.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a vacuum valve according to the present invention will be described below with reference to the drawings.

First, the configuration of the present embodiment will be described. In the vacuum valve shown in FIG. 3, the insulating cylinder is made of ceramic (mainly alumina), and a portion to be joined to the fixed metal end plate and the movable metal end plate is metallized (Mo-Mn + nickel plating) on the ceramic. ing. The fixed metal end plate and the movable metal end plate are made of an iron-nickel alloy (40
-42 wt% Ni) or austenitic stainless steel (SUS304, SUS304L), bellows are austenitic stainless steel or inconel material, bellows cover is austenitic stainless steel, shield and shield fixing metal are austenitic stainless steel, and nickel plating is applied. I am giving.

Plating method: Degreasing-water-pickling (Hc
1, normal temperature)-Rinse-Nickel strike (Nicl ₂
Hcl, room temperature)-Rinse-Nickel plating (Nicl ₂
40~50g / l NiSO ₄ 280~380g / l
H ₃ BO ₃ 30~40g / l, humidifier 55 ± 3 ° C. p
H3.0-4.2)-Rinse (including pure water)-Dry (27
0 to 400 ° C., 0.5 h or more), plating thickness 15 μm or more.

Brazing: The brazing material is eutectic silver brazing (BAg
-8 Ag72-Cu28), silver brazing (Ag60-Cu)
40), palladium solder (Ag58-Cu32-Pd1)
0) etc., and the method of increasing the temperature is as shown in FIG.
1 at 400-750 ° C before reaching brazing temperature
Keep the temperature for at least 0 minutes.

Next, the manufacturing method and operation of this embodiment will be described.

Austenitic stainless steel is a chromium carbide (Cr, Fe) ₂₃ depending on the use environment.
Precipitation of C _{6 at the} grain boundaries may cause stress corrosion cracking and grain boundary corrosion cracking. For this reason, SUS30
For No. 4, recovery of the metal structure by applying a low-carbon material or performing solution treatment (about 1050 ° C., rapid cooling) →
Although it is recommended to recrystallize, the inside of the vacuum vessel is a particularly excellent environment, so that the above-mentioned corrosion does not occur. No conversion processing is required. As is well known, austenitic stainless steel is a material that is easily affected by heat, so even if solution treatment is not performed, it is necessary to remove the processing strain generated during processing, and if nickel plating is performed by wet plating Must remove water. For this purpose, the drying after the nickel plating is performed by using a drying furnace at 270 to 400 ° C. for 0.5 h or more, thereby simultaneously removing the processing strain and baking for removing the hydrogen.

Nickel plating for forming a protective film (oxidation resistance, etc.) mainly for improving the wettability of the brazed portion with respect to austenitic stainless steel, iron-nickel alloy, and Inconel members, that is, obtaining bonding strength. Has been given.
Generally, these members have a protective function due to a dense oxide film generated on these members without forming a protective film such as plating, and a surface treatment is intentionally performed. Then, it is necessary to form a plating film after removing the protective film that has been generated, and it is more difficult to perform random treatment on the same line than a normally performed treatment (corresponding to special plating, which is equivalent to a component. The shape is complicated such as bellows). When nickel plating is formed through a complicated and difficult process, the characteristics of the vacuum valve (especially airtight parts)
When a plating defect, particularly a blister portion of a member having a blister, is joined by brazing, the joint portion becomes defective. In particular, when this phenomenon occurs in the hermetic part for maintaining a high vacuum state,
In addition to the adverse effect on the wettability of the brazing material, there is a possibility that the same phenomenon as the intrusion of foreign matter occurs (voids or the like) and the airtightness maintaining function is lost. In order to prevent swelling of nickel plating from occurring, it is important to control the watt bath (a general name for the composition of the solution used for nickel plating). Pretreatment (alkaline degreasing-water washing-pickling (use of hydrochloric acid, activation and neutralization of base material surface)-water washing-nickel strike (equivalent to wood bath)
-Water bath (nickel chloride 40-50 g / l, nickel sulfate 2)
80-380 g / l, boric acid 30-40 g / l)
When H is 5.0 or more, blistering and peeling are likely to occur (internal stress increases). Conventional baths have a pH of 4.2-
Although it was in the middle of 4.8 (high and low), when the pH was 4.5 or more, blistering was liable to occur due to the non-uniformity of the current density distribution in a complicated shape (unevenness, R portion). p
If it is less than H3, the throwing power is poor and pits tend to occur. For this reason, the pH is controlled at 3 to 4.2 (the pH rises during the treatment and is set to 4.2 in view of the safety side) (humidification is 55 ± 3 ° C. and nickel plating is 15 μm or more). In this way, by heating in a low pH watt bath, it is possible to prevent blistering while maintaining good plating throwing power as shown in Table 1. In addition, according to a general definition, a low pH bath has a pH of 1.5 to
4.5, the high pH bath has a pH of 4.5-6.0.

The austenitic stainless steel, iron-nickel alloy, and inconel member are subjected to the above-mentioned plating treatment, washing with water (including pure water washing), and then moisture removal drying. The function described above by performing drying in an air furnace at 270 to 400 ° C. × 0.5 h or more (nickel oxidation proceeds at 500 ° C. or more and wettability deteriorates even when treated in vacuum). In addition to the above, a nickel plating adhesion test (non-destructive) of any member can be performed. As described above, a problem arises when a member having blisters, which is a defect of nickel plating, is applied to a product. In the plating process, blisters can be eliminated, and in the main drying process, an adhesion test (which can be surely confirmed if blisters are present) can be performed nondestructively to serve as an inspection. Further, it has a baking action for removing hydrogen (particularly preventing hydrogen embrittlement at the welded portion of the arc shield), and further has an action for further ensuring the adhesion between the base metal and the nickel plating. In this case, the mutual diffusion for improving the adhesion between the base metal and the nickel plating is about 1 μm or less. Conventionally, after the draining and drying after the plating treatment is performed at about 200 ° C., the heat treatment is performed at a high temperature of 800 to 900 ° C. in a reducing atmosphere (hydrogen), but this step becomes unnecessary. As shown in FIG. 1, the temperature is maintained at 400 to 750 ° C. before the brazing temperature is reached for 10 minutes or more, and the temperature is raised until the brazing temperature is reached. Interdiffusion occurs between the nickel platings, resulting in a strong bond.

As described above, according to the present embodiment,
The following effects are produced. First, firstly, if it is used in a high vacuum or used in the atmosphere, if nickel plating is used, and if it is used in a more severe corrosive environment, nickel plating + rust prevention coating is applied, Austenitic stainless steel can be applied as a member without performing solution heat treatment for recrystallization of the structure. Austenitic stainless steel is a material that is susceptible to thermal effects (thermal expansion and shrinkage), so it is necessary to remove the processing strain at the member stage before brazing, and this action involves nickel plating-water washing (including pure water washing). ) It is carried out at the time of subsequent drying (the dimensional accuracy is equivalent to the conventional product).

Second, austenitic stainless steel,
When nickel plating is applied to an iron-nickel alloy or an Inconel member, a plating film can be formed by a method that does not easily cause blistering, which is a plating defect, and drying after washing with water can also serve as a non-destructive adhesion test.

Third, the above-described drying can improve the baking for removing hydrogen and the adhesion between the base metal and the nickel plating. Nickel plating used conventionally
There is no need to perform high-temperature heat treatment in a reducing atmosphere after rinsing and draining. When the temperature rises during brazing,
Before the brazing material is melted, mutual diffusion of the base metal and nickel plating occurs and has a strong adhesion. Even when the brazing material is melted and solidified (cooled) and the joining is completed, the mechanical properties of the conventional process are maintained. No difference is seen. FIG. 2 shows a comparison between the process of this embodiment and the conventional process. Tables 2, 3, and 4 show the characteristics of the process of the present embodiment and those of the conventional process in comparison. From Tables 2, 3 and 4, the product of the present embodiment has the same performance as the conventional product.

[0022]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[0023]

As described above, according to the first aspect of the present invention, since the austenitic stainless steel constituting the vacuum valve is heated at a temperature of 270 to 400 ° C. after plating, the austenitic stainless steel is heated. Even without performing a high-temperature solution heat treatment in a reducing atmosphere before plating stainless steel, it is possible to remove the processing strain together with baking of hydrogen removal to prevent hydrogen embrittlement and drying when wet nickel plating is applied. This can be performed to provide a necessary function as a metal component of the vacuum valve. Therefore, the number of steps for using the hydrogen furnace can be reduced, and energy saving and safety can be improved.

According to the second aspect of the present invention, the pH value of the watt bath for nickel plating of austenitic stainless steel, iron-nickel alloy and inconel constituting the vacuum valve is set to 3.0 to 4.2. Even if nickel plating for these metal components is processed in the same process,
It is possible to prevent blistering while maintaining good throwing power of the plating, and it is possible to prevent occurrence of defects in the joints of the component members due to brazing or the like.

According to the third aspect of the present invention, the austenitic stainless steel, the iron-nickel alloy, and the inconel after the nickel plating are heated and dried at a temperature of 270 to 400 ° C. The test, the baking for removing hydrogen, and the treatment for strengthening the adhesion between the base metal and the nickel plating are performed.
In addition to obtaining the effects described in the described invention, any metal component can be surely confirmed if there is a blister, so that a non-destructive plating adhesion test can be performed, and at the same time, hydrogen embrittlement Baking of hydrogen removal for prevention and adhesion between the base metal and the nickel plating can be further ensured.

According to the fourth aspect of the present invention, at the time of the brazing of the nickel-plated austenitic stainless steel, the iron-nickel alloy and the inconel by the brazing process, the temperature is raised to 400 ° C. before reaching the brazing temperature.
750 ° C. for at least 10 minutes. Therefore, even if a high-temperature heat treatment in a reducing atmosphere after nickel plating is not performed, the mutual exchange between the base metal and the nickel plating can be performed before the melting reaction of the brazing material. Diffusion occurs and a strong bond can be obtained, and joining such as brazing can be reliably performed.

[Brief description of the drawings]

FIG. 1 is a view for explaining a method of increasing a temperature during a brazing step in an embodiment of a method of manufacturing a vacuum valve according to the present invention.

FIG. 2 is a diagram showing processing steps of the above-described embodiment in comparison with a conventional technique.

FIG. 3 is a longitudinal sectional view showing a configuration of a conventional vacuum valve.

[Explanation of symbols]

2 Fixed-side metal end plate using austenitic stainless steel or iron-nickel alloy 3 Moving-side metal end plate using austenitic stainless steel or iron-nickel alloy 9 Bellows using austenitic stainless steel or Inconel 10 Austenitic Shield using stainless steel 12 Shield fixing bracket using austenitic stainless steel 13 Bellows cover using austenitic stainless steel

Claims (4)

[Claims] 1. A method of manufacturing a vacuum valve, comprising: subjecting an austenitic stainless steel constituting a vacuum valve to a heat treatment at a temperature of 270 to 400 ° C. after plating. 2. The production of a vacuum valve, wherein the pH value of a watt bath for nickel plating of austenitic stainless steel, iron-nickel alloy and inconel constituting the vacuum valve is 3.0 to 4.2. Method. 3. The austenitic stainless steel, nickel-nickel alloy and inconel after nickel plating
A method of heating and drying at a temperature of 70 to 400 [deg.] C., and simultaneously performing the heating and drying, performing a plating adhesion non-destructive test, a baking for removing hydrogen, and a treatment for strengthening the adhesion between base metal and nickel plating. 3. The method for manufacturing a vacuum valve according to 2. 4. During the joining process by brazing the nickel-plated austenitic stainless steel, iron-nickel alloy and Inconel, the temperature is maintained at a temperature of 400 to 750 ° C. for at least 10 minutes before the brazing temperature is reached. The method for manufacturing a vacuum valve according to claim 2, wherein