JP2669225B2 - Airtight attachment method for stainless steel parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hermetically sealing stainless steel parts, and more particularly to a method for hermetically sealing stainless steel parts used in electronic tubes and the like which require a high vacuum.

[0002]

2. Description of the Related Art Electron tubes such as microwave tubes and transmitter tubes are used in a wide range of fields from communication to television broadcasting, radar, industrial heating, nuclear fusion, etc., and in recent years their importance has been increasing. There is.

The inside of the electron tube must be maintained at a high vacuum of (10 ^-4 to 10 ^-6 ) Pa or less so as not to hinder the movement of electrons, molecules or ions. For this reason, the vacuum envelope of the electron tube needs to be assembled by hermetically sealing individual parts, and using a brazing material made of gold, silver, copper, or an alloy thereof having a relatively high melting point, and brazing. Is air-tightly sealed.

[0004] Stainless steel is used as a component of a vacuum envelope of an electron tube because stainless steel has high mechanical strength and excellent corrosion resistance and is inexpensive as compared with other materials. Since stainless steel contains chrome, which is easy to participate in, conventional airtight sealing of stainless steel parts has a vacuum atmosphere of a vacuum degree of 10 ^-2 Pa or less for the purpose of preventing oxidation of stainless steel and obtaining a reliable joint. Alternatively, it is performed by heating and melting the brazing material in a reducing atmosphere having a dew point of -60 ° C or lower.

[0005]

In this conventional method for hermetically sealing stainless steel parts, since brazing is performed in a vacuum atmosphere, it takes a long time to exhaust the air to reach the vacuum atmosphere, and brazing. Since parts are heated by radiant heat, there is a drawback that heating takes a long time, and there is a problem that mass production is difficult.

When brazing is performed in a reducing atmosphere, the dew point is -60 ° C. or lower (moisture content is 0.1 × 10 ^-4).
% Or less) in a highly pure reducing atmosphere. However, there has been a problem that it is difficult to always maintain a dew point of −60 ° C. or less due to the influence of degassing from brazing parts and gas released from the furnace wall.

An object of the present invention is to provide a method for hermetically sealing stainless steel parts, which enables reliable joining in a short time.

[0008]

According to the present invention, a stainless steel part and a metal part of the same kind or different kind from the stainless steel part are joined by heating in a reducing atmosphere through a brazing material. in hermetic sealing method of a stainless parts, = C-SO ₂ - structure and first organic compound having, in the C = O and C = C and C≡C and C = N and C≡N structures A step of forming a nickel layer on the surface of the stainless steel component by electrolytic plating in a nickel plating solution containing a second organic substance having any one of the structures; and the metal on the nickel layer via a brazing material. Bonding the parts.

[0009]

FUNCTION Nickel does not oxidize even in a reducing atmosphere with a dew point of + 30 ° C. Therefore, in the hermetic sealing method of the present invention, since the surface of the stainless steel component is covered with the nickel plating layer and then brazed, a vacuum atmosphere or a highly pure reducing atmosphere (dew point −60 ° C. or less) as in the conventional method is used.
You don't have to.

[0010] The first and the second in the nickel plating solution are used.
The organic compound of the nickel plating layer is deposited into a layer,
It is necessary to suppress the diffusion of the stainless steel (especially chromium), which is the underlying metal, into the nickel plating layer in the high-temperature step during brazing. In the nickel plating solution that does not contain these organic compounds, the plating layer has a columnar structure,
Chromium in the base metal, stainless steel, easily diffuses through the grain boundaries of the plating layer.

Further, when the content of the organic compound in the plating solution is large, the amount of carbon or sulfur that co-folds in the plating layer is large, and blistering of the nickel plating layer occurs during the high temperature brazing process. Can not be hermetically sealed.

In order to prevent the above-mentioned problems, it is desirable that the content of the organic compound in the plating solution is in the range of 1 to 5 g / l. The nickel plating layer deposited from the plating solution has a layered structure and the content of carbon or sulfur is 0.05% or less. Therefore, the diffusion of chromium in the stainless steel as the base metal is prevented, and the nickel plating layer does not bulge during the high-temperature brazing process.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a cavity portion for a klystron for explaining an embodiment of the present invention.

In the first embodiment, as shown in FIG.
The envelope component A1, the envelope component B2, and the support plate 3 are made of Su.
S304 stainless steel material, and as shown in Table 1, the surface of these parts has a structure of = C-SO ₂ -1.5 g of sodium 1.5 naphthalene-disulfonate 3 g /
The nickel plating layer 4 having a thickness of 10 μm was formed using a nickel plating solution obtained by mixing 0.5 g / l of 2-butyne-1.4diol having a structure of 1 and C≡C.

[0016]

[Table 1]

Next, a drift tube component 5 made of oxygen-free copper material and a brazing material 6 made of 28% copper and 72% silver were assembled.

Next, the brazing material 6 was melted by heating to 800 ° C. in a dry hydrogen atmosphere having a dew point of −30 ° C. and hermetically sealed, and no leak was confirmed by a helium leak detector.

For comparison, a nickel plating solution not mixed with an organic compound was used and air-sealing was performed under the same conditions as in the above-mentioned embodiment except that the other conditions were the same. The surfaces of the container component A1, the envelope component B2, and the support plate 3 were oxidized, and were poorly compatible with the brazing material 6, and could not be hermetically sealed.

In the second embodiment, assembling was carried out as shown in FIG. 1 by using the same parts as in the first embodiment and nickel plating solutions having the same mixing amount shown in Table 1. The thickness of the nickel plating layer 4 was the same 10 μm.

The brazing material is immersed in wet hydrogen at a dew point of + 30 ° C. for 80 minutes.
When heated to 0 ° C. to melt the brazing material and hermetically sealed, a leak test was conducted with a helium leak detector, and no leak was detected.

In the third embodiment, various organic compounds shown in Table 2 were used and hermetically sealed under the same conditions as in the second embodiment. The inorganic components (nickel sulfate, nickel chloride, boric acid) of the nickel plating solution were the same as those in Table 1.

[0023]

[Table 2]

When a leak test was performed with a helium leak detector, it was confirmed that no leak was caused when any organic compound was used.

When the total content of these organic compounds is less than 1 g / l, diffusion into the nickel plating layer of the stainless steel component easily occurs, and oxidation occurs during the brazing process. If it exceeds 5 g / l, the carbon or sulfur that is folded together in the nickel layer causes blistering of the plating during the brazing process. Therefore, the content of the organic compound is
It is desirable that the total amount be 1 to 5 g / l.

[0026]

As described above, according to the present invention, since the nickel plating layer having the layered structure is provided on the surface of the stainless component, even if the brazing is performed in the reducing atmosphere with the dew point of + 30 ° C. Oxidation does not occur, and there is an effect that reliable hermetic sealing can be performed.

Therefore, the heating time of the brazed parts can be reduced and the brazing can be performed under normal pressure, as compared with the conventional case of brazing in a vacuum atmosphere.
I could improve.

Further, the yield of the brazing process is about 10% of the conventional one.
I could improve.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a klystron cavity portion for explaining an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 envelope component A 2 envelope component B 3 support plate 4 nickel plating layer 5 drift tube 6 brazing filler metal

Claims (1)

(57) [Claims] 1. A method for hermetically sealing a stainless steel component, which comprises heating a stainless steel component and a metal component of either the same kind or different kind as the stainless steel component through a brazing material in a reducing atmosphere to join them. Wherein a first organic compound having a structure of ＣC—SO ₂ — and one of the structures of C ＝ O, C ＝ C, C≡C, CＮN, and C≡N A step of forming a nickel layer on the surface of the stainless steel component by electrolytic plating in a nickel plating solution containing the second organic substance, and a step of joining the metal component on the nickel layer via a brazing material A method for hermetically sealing stainless steel parts, which is characterized in that