JPH0753137B2 - Method for manufacturing metallic vacuum double structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a metal vacuum double structure such as a thermos bottle and a vacuum double pipe.

(Prior Art) In order to improve the heat retaining property of a metallic vacuum double structure, for example, a vacuum double container such as a thermos bottle, increase the degree of vacuum between the inner container and the outer container and remove it from the inner container. It is important to block radiant heat transfer to the container.

In order to increase the degree of vacuum, it is not only possible to enhance the vacuum evacuation processing capability and seal it to a high vacuum, but also to prevent the release of stored gas from the outer surface of the inner container or the inner surface of the outer container after sealing. It is especially necessary. Therefore, conventionally, a method of degreasing the outer surface of the inner container and the inner surface of the outer container and further pickling with nitric hydrofluoric acid, a method of heating in a furnace during exhaust treatment to discharge the stored gas together with air, and a getter are used. There is a method of adsorbing the occluded gas which is released from the metal surface, but usually all of these methods are used.

Further, as a method of preventing radiant heat transfer, conventionally, at least a method of forming a plating layer on the outer surface of the inner container by electrolytic plating or silver mirror reaction, or as shown in JP-A-61-31111, the outer surface of the inner container There is a method of covering with a thin plate of copper or aluminum.

On the other hand, as a vacuum sealing method after the vacuum evacuation treatment, a method of brazing a closing member to an exhaust port formed on the bottom surface of the outer container (hereinafter referred to as a brazing method) and an exhaust gas provided on the bottom surface of the outer container. There is a method of sandwiching the tip tube for use (hereinafter referred to as the tip tube method).

In the above brazing method, when flux is used for brazing of the closing member, gas flows into the vacuum spaces of both the inner and outer containers to lower the degree of vacuum, so it is necessary to braze without using flux.

For this reason, for example, in a vacuum double container made of stainless steel, it is necessary to flush the surface thereof at a high temperature and use a brazing material having a melting point of about 900 to 1070 ° C. such as nickel brazing. Moreover, when stainless steel is added to a high temperature or cooled from a high temperature, solid solution carbon precipitates as a carbide in a certain temperature range (generally, about 450 to 850 ° C), and becomes sensitive to intergranular corrosion. Is likely to occur and corrosion resistance is reduced, so avoid the dangerous temperature range for sensitization.
When performing vacuum evacuation treatment and brazing at a temperature of 850 ° C or higher, and when cooling from a high temperature, an inert gas must be supplied into the vacuum heating furnace for rapid cooling.

On the other hand, since the brazing material is not used in the tip tube method,
The vacuum exhaust treatment is performed at a temperature lower than the sensitization region, that is, 400 to 450 ° C.

By the way, during vacuum evacuation processing, it is necessary to heat the double container to clean the metal surface and release the stored gas.However, if heated during the evacuation processing, the plating surface and the like will oxidize. After pre-evacuating to a vacuum higher than 1 × 10 ^-2 Torr (1.33 Pa), 850 to 950 ℃ by brazing method
In addition, the tip tube method is designed to heat at 400 to 450 ° C.

The above method of increasing the degree of vacuum, the method of preventing radiant heat transfer, and the method of vacuum containment are also applied to the manufacture of a vacuum double pipe used as a water supply pipe for freeze prevention.

Generally, regarding the degree of vacuum, when the pressure is 10 ^-3 Torr or more, low vacuum, 10 ^-5 to 10 ^-3 Torr range are high vacuum, 10 ^-8 to 10 ^-5 Torr range are ultra high vacuum, 10 ^{Since -8} Torr or less is called an ultrahigh vacuum, it is also referred to in this specification.

(Problems to be Solved by the Invention) However, when pre-evacuating to a vacuum higher than 1 × 10 ^-2 Torr as in the conventional case, air which is a convective heat transfer medium is diluted, and a space between the outer container and the inner container is reduced. The heat transfer is extremely poor. Therefore, even if the inner container is heated after preliminary evacuation, the temperature rise of the inner container is significantly delayed compared to the outer container that receives the furnace heat directly.As a result, the vacuum evacuation process takes a long time and degassing from the outer surface of the inner container is insufficient. Therefore, there is a problem that the stored gas remaining after the vacuum containment is released, the degree of vacuum is lowered, the heat insulating property is changed with time, and the heat retaining property is gradually lowered.

Further, in the brazing method in particular, since it is heated at a high temperature in a high vacuum, there is a problem that the plating evaporates or the quality is deteriorated and the heat insulating property is impaired.

The above problem similarly occurs in the production of the vacuum double pipe.

The present invention has been made in view of such a problem, and a metal vacuum double structure capable of achieving sufficient degassing from the inner wall in a short vacuum exhaust processing time and stabilizing heat insulation. It is intended to provide a manufacturing method.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention has an extremely excellent heat insulating property under a high vacuum of 1 × 10 ⁻⁴ Torr or less in the relationship between the degree of vacuum and the heat insulating property. Is well known in the art, but attention is paid to the fact that this change in adiabaticity changes abruptly when the vacuum degree is in the order of 10 ^-1 to 10 ^-3 Torr (see Material for Heat Transfer Engineering, edited by the Japan Society of Mechanical Engineers). The heat degassing is carried out in a vacuum in which the heat insulating property does not appear remarkably and the heat transfer property is somewhat good, that is, in a low vacuum of the order of 10 ^-2 Torr or more.

That is, the present invention relates to a method for manufacturing a metal vacuum double structure in which a double wall structure is formed by an inner wall and an outer wall, and a space between the inner wall and the outer wall is subjected to an exhaust treatment to be vacuum-sealed. As shown in Fig. 1, in the first step I, pre-evacuation to a low vacuum of the order of 10 ^-2 Torr or more is performed, and in the second step II, heating is performed for a predetermined time to perform degassing, and then in the third step III, the heating temperature is increased. Maintained at 10 ^-4 Tor
Exhaust to a high vacuum of r order or less, and the 4th step IV
It is to be sealed in vacuum.

When the material of the inner wall or the outer wall is austenitic stainless steel such as SUS304, it is preferable to carry out the heat degassing at a temperature lower than or above the sensitization region of the stainless steel.

The vacuum sealing method can be either a conventional tip tube method or a brazing method. However, when the material of the inner wall or the outer wall is austenitic stainless steel, the tip tube method is a sensitized region of the stainless steel. The hot degassing should be performed at a lower temperature, and the brazing method should be performed at a temperature above the sensitization region.

In addition to the air, an inert gas such as nitrogen (N ₂ ) or argon (Ar) can be sealed in the space between the inner wall and the outer wall. However, in the case of air, the wall surface is oxidized by oxygen (O ₂ ) in the air, but the probability of collision between oxygen (O ₂ ) and hydrogen (H ₂ ) which is the main component of degassing increases, Oxygen and hydrogen are easily combined to be released as water vapor (H ₂ O), which has the advantage of being economical from the viewpoint of activation.

(Operation) When pre-evacuating to a low vacuum of the order of 10 ^-2 Torr or more in the first step I, the heat transfer between the inner wall and the outer wall is reduced and heat insulation is generated, but at the order of 10 ^-2 Torr , Heat transfer is not so bad.

For this reason, when heating in the second step II, the heat of the outer wall directly receiving the heat of the furnace is quickly transferred to the inner wall by radiation, conduction, and convection, and the temperature of the inner wall rises in a short time. Therefore, the occluded gas is liberated from the wall surface of the inner wall as well as the outer wall, and the degassing is sufficiently performed in a short time.

Then, in the third step III, if exhaust processing is performed to the order of 10 ⁻⁴ Torr or less, the free gas is discharged to the outside together with air.

After the exhaust process is completed, vacuum sealing is performed by the tip tube method or the brazing method in the fourth step IV to obtain a high vacuum vacuum double structure.

When the inner wall or the outer wall is austenitic stainless steel such as SUS304 and vacuum sealing is performed by the tip tube method, by heating degassing at a temperature lower than the sensitization region of the stainless steel in the second step II, There is no risk of deterioration of corrosion resistance due to sensitization.

Further, when the inner wall or the outer wall is austenitic stainless steel and vacuum sealing is performed by a brazing method, heating degassing is performed at a temperature exceeding the sensitization region of the stainless steel in the second step II, As with the tip tube method, there is no risk of deterioration in corrosion resistance.

(Example) Next, the Example of this invention is described according to an accompanying drawing.

(1) Manufacturing method of vacuum double container i) First embodiment FIG. 4 shows a double container 1 for vacuum bottles before vacuum evacuation treatment, which is manufactured by the method according to the present invention, and includes upper part 2a and lower part 2b. Two
The inner container 3 made of stainless steel is inserted into the outer container 2 made of stainless steel, which is formed in a divided manner.
The upper part 2a of the outer container 2 is joined to the upper part 2a of the outer container 2 by the mouth Y.
The lower part 2b and the lower part 2b are joined at the X part to form a double wall structure, and the tip tube 4 for exhaust is provided on the bottom part of the outer container 2.

On the other hand, in order to improve the heat retaining property of the double container 1 after the vacuum exhaust treatment, at least the outer surface of the inner container 3 forming the vacuum space 5, at least the outer surface of the inner container 3, is subjected to electrolytic plating or silver mirror reaction. A copper or silver plating layer is formed. For example, the inner container 3 is previously set to 250 to 550 in an oxidizing atmosphere.
A space formed between the tip tube 4 and the inner container 3 and the outer container 2 after firing at a temperature of several minutes to several hours to form an oxide film on the outer surface of the double container 1. A known silver mirror reaction solution is injected into 5 to carry out a silver mirror reaction to form a silver mirror layer on the outer surface of the inner container 3, followed by washing with water and drying.

Further, a getter is attached to the wall surface of the space 5 by a holding member (not shown) so as to adsorb the gas released after the vacuum sealing to complete the heat insulation.

Next, a vacuum evacuation process and a vacuum sealing method of the vacuum double container 1 having the above configuration will be described.

The double container 1 is put in a heating furnace and the tip tube 4 is connected to a vacuum pump.

Then, as shown in FIG. 2, in the first step 21, the inner container 3
The space 5 between the outer container 2 and the outer container 2 is pre-evacuated to a low vacuum of 1 × 10 ^-2 Torr.

In the second step 22 in this low vacuum state, heating is performed at 400 to 450 ° C. At this time, the outer container 2 directly heated by the furnace heat
The heat of the inner container 3 is generated by the radiant heat transfer, the heat transfer of the mouth portion Y, and the convective heat transfer performed through the residual gas in the space 5.
Be transmitted to. Although the first step 21 is evacuated to a low vacuum of 1 × 10 ^-2 Torr, convective heat transfer due to the residual gas in the space 5 becomes dominant at this degree of vacuum, and the outer container 2 to the inner container 3 The heat transfer to is not so bad. Therefore, the heat of the outer container 2 is quickly transferred to the inner container 3, and the inner container 3 is
Heat up in about 20 minutes. Therefore, the occluded gas is released into the space 5 from the outer surface of the outer container 2 as well as the outer surface of the inner container 3, so that degassing is sufficiently performed in a short time. Since the heating in the second step 22 is performed at a temperature lower than that of the sensitized region of stainless steel, there is no fear of deterioration of corrosion resistance due to sensitization.

Then, while maintaining the temperature of the second step 22, the gas is further evacuated in the third step 23 to obtain a high vacuum of 1 × 10 ⁻⁴ Torr. At this time, the residual gas and the free gas in the space 5 are collected in the tip tube 4
The getter is activated while being discharged to the outside through.

Next, while maintaining this high vacuum state, it is cooled in the fourth step 24, and in the fifth step 25, the chip tube 4 is pinched off and vacuum sealed.

The vacuum double container manufactured by the above process is the second process.
At 22, the outer container 2 as well as the inner container 3 is sufficiently degassed, so that the stored gas is less released after the vacuum containment, and the heat insulation is stabilized. In this example,
Although the getter is mounted in the space 5, the amount of getter can be reduced when the exhaust process is performed within the same time because the degassing is sufficiently performed during the manufacturing process as described above.

ii) Second Embodiment FIGS. 5 and 6 show a double container 10 for a thermos bottle manufactured by a method according to another embodiment of the present invention.
In place of the tip tube 4 of the outer container 2, an opening 4a is formed, and an exhaust port edge member 7 having an exhaust port 6 in the center is fitted and joined to the opening 4a. Exhaust port closing member 8
Are substantially the same except that they are installed via the brazing filler metal 9. Corresponding parts are designated by the same reference numerals and description thereof is omitted.

The double container 1a is inverted, and as shown in FIG. 6, an annular corrugated brazing material 9 is installed on the outer peripheral edge of the haiku opening 6, and the exhaust port closing member 8 is placed on the brazing material 9. After that, it is set in a vacuum heating furnace. A getter is attached to the inside of the exhaust port edge member 7 by a holding member (not shown).

Then, as shown in FIG. 3, in the first step 31, 1 × 10 ^-2 Torr is obtained as in the first step 21 of the manufacturing method according to the first embodiment.
Is preliminarily evacuated to a low vacuum, and heated in the second step 32 to 850 to 950 ° C. for degassing, and then evacuated to a high vacuum of 1 × 10 ⁻⁴ Torr in the third step 33. Next, when the fourth step 34 is heated to around 1000 ° C. while maintaining this high vacuum state, the brazing filler metal 9 is melted and the exhaust port closing member 8 descends onto the exhaust port edge member 7 by the action of gravity. While closing the exhaust port 6, the getter is activated. Then, in the fifth step 35, when it is rapidly cooled, the brazing filler metal 9
Rapidly solidifies, and the space between the exhaust port edge member 7 and the exhaust port closing member 8 is completely sealed as shown in FIG. 5 while maintaining a high vacuum in the space 5 between the inner and outer containers.

In the manufacturing method according to the second embodiment, 1 × is used in the first step 31.
10 ⁻² Torr Since it is pre-evacuated to a low vacuum, the heating degassing in the second step 32 is sufficiently performed in a short time, and the third step 33 is performed, as in the manufacturing method according to the first embodiment. The vacuum evacuation processing time in 2 is also short. Further, in the second step 32, heating is performed at a temperature exceeding the sensitization region of the stainless steel and quenching is performed in the fifth step 35, so that the time period during which the stainless steel is exposed to the sensitization region is extremely short, and the sensitization reduces corrosion resistance. There is no fear.

Further, in the second step 32, since it is heated to a high temperature of 850 to 950 ° C., the plating on the outer surface of the inner container 3 may evaporate or deteriorate. However, since the space 5 is not a high vacuum but a low vacuum of 1 × 10 ^-2 Torr and some gas remains, the evaporated plating metal atoms collide with the molecules of the residual gas to prevent diffusion. As a result, the evaporation of plating is suppressed. In addition, since such a low vacuum is sufficiently reached by a mechanical pump without using a diffusion pump, hydrocarbon (HC), which is one of the causes of alteration of plating, may flow in if a mechanical pump is used. Therefore, the deterioration of the plating is suppressed.

In addition, in the above-mentioned example, 1 × 10
^Although pre-evacuation to ^-2 Torr is not limited to this value, it is sufficient to exhaust to a low vacuum of the order of 10 ^-2 Torr to 100 Torr. Also, the degree of vacuum in the third step 23, 33 is not limited to 1 × 10 ^-4 Torr, but 10 ^-4 Tor
A high vacuum region on the order of rr or less may be used.

iii) Confirmation test The present inventors conducted a test for confirming the heat retaining property of the stainless steel vacuum double container manufactured by the method according to the present invention.

In this heat retention test, under the conditions shown in Table 1, a stainless steel vacuum double container manufactured by the method according to the present invention, in which the inner container was covered with copper foil having different wall thickness instead of plating, was used. Five samples each were used as test samples.

For comparison with this, as shown in Table 2, a stainless steel vacuum double container sample manufactured by a conventional method was prepared.

No getter was used in any of the samples.

And, for each sample, initial: immediately after production, after being placed in a 95 ° C atmosphere for 1 week after production, then for 2 weeks (more than 1 week) after production, after being placed in a 95 ° C atmosphere for 4 weeks (more than 2 weeks) After placing in a 95 ° C atmosphere, 3 months after production (more February) After placing in a 95 ° C atmosphere, April after production (more January) After placing in a 95 ° C atmosphere, In the 6 steps, put hot water of 95 ℃ in the inner container 1 and 20 ℃
Thermal retention was tested by measuring the temperature of the hot water after 24 hours in the atmosphere.

Among these test results, those of the test sample of the present invention are shown in Table 3, and those of the conventional comparative sample are shown in FIGS. 7a to 7d.
In Figures 7a to 7d, the temperature curve is 95 ° C above and below.
It is possible to know the temperature drop of the hot water after 24 hours of heat retention, that is, the magnitude of the 24-hour heat retention power, and it is possible to know the decrease of the vacuum degree due to aging, that is, the magnitude of the vacuum maintenance power, from the decreasing gradient of the temperature curve. Further, by comparing the figures for the same type of material, for example, A ₂ , A ₃ , and A ₄ , it is possible to know the influence of the short duration of the exhaust time during manufacturing.

The results of this test confirmed the following items regarding heat retention and exhaust time.

As is clear from the average value of each sample I and II in Table 3, the vacuum maintenance power decreased by 1 ° C. after one week in sample I,
Sample II dropped 0.8 ° C after 1 week and 0.2 more after 2 weeks
C., and in the case of Sample III, the temperature decreases only 2.3.degree. C. after one week, and thereafter tends to increase or level off. Therefore, according to the method of the present invention, the vacuum maintaining force is level and does not extremely decrease.

Note that the 24-hour heat retention of Samples I and II (around 67 ° C) is the same as Sample III.
Is greater than the 24-hour heat retention (around 45 ° C) of
This is due to the radiation heat transfer prevention function and the gas absorption function of the copper foil.

As is clear from the comparison between sample I in Table 3 and sample B _{3 in} FIG. 7c under the same conditions, the decrease in the vacuum maintaining power of sample I is about 1 ° C., while the vacuum maintaining of sample B ₃ is maintained. The force is reduced by about 3 ° C. after 2 weeks. Therefore, according to the method of the present invention, the vacuum maintaining power is improved as compared with the conventional method.

As is clear from a comparison between sample I in Table 3 and sample B _{1 in} FIG. 7a, both have the same 24-hour heat retention and the vacuum retention tends to level off. The evacuation time for sample B ₁ is 100 minutes, whereas the time is 50 (10 + 40) minutes. Therefore, according to the method of the present invention,
The exhaust time can be shortened by 50 minutes compared to the conventional method.

No. 7 in Table 3 under the same conditions except Sample III and exhaust method
As can be seen by comparing sample D _{3 in} Figure c, the initial 24
Both of them have the same heat retention, but after that, Sample III
In the sample D ₃ , the temperature curve is almost horizontal and the vacuum maintaining power is flat, whereas in the sample D ₃ , the temperature curve tends to decrease and the vacuum maintaining power is decreased, and the peak becomes low at about 3 weeks.
Therefore, according to the method of the present invention, both the vacuum maintaining ability and the 24-hour heat retaining ability are superior to the conventional method with the same evacuation time.

(2) Example of manufacturing method of vacuum double pipe FIG. 8 shows a vacuum double pipe used for a water supply pipe for freeze prevention, etc., and roughly includes a water supply pipe 10, an outer cylinder 11, a connecting member 13, It is composed of 14 and.

The water supply pipe 10 is a stainless pipe having an inner diameter of 22 mm and a thickness of 1 mm, and a portion where the outer cylinder 11 is packaged is covered with a copper foil or a copper or silver plating layer is formed. The gap between the outer cylinder 11 and the outer cylinder 11 is kept constant, and the outer cylinder 11 and the water supply pipe are
An appropriate spacer may be provided so as to prevent thermal contact with 10 as much as possible. The outer cylinder 11 is a stainless steel pipe having an inner diameter of 42 mm and a thickness of 1.2 mm, and is adapted to be externally mounted on the water supply pipe 10, and a copper tip tube 12 is attached to the outer peripheral portion on the upstream side. The connecting members 13 and 14 are ring members having a U-shaped cross section formed of a stainless material, which are inserted into the water supply pipe 10 and welded all around the outer surface of the water supply pipe 10 and the end of the outer cylinder 11 to form the water supply pipe 10. A space between the outer cylinders 11 is covered.

Then, this space is heated and exhausted through the chip tube 12, and the chip tube 12 is sandwiched so as to be vacuum-sealed.

Further, caps 15 and 16 made of stainless steel are attached to both ends of the outer cylinder 11 and outside of the connecting members 13 and 14, respectively, and sealing agents 17 and 17 are provided between the caps 15 and 16 and the connecting members 13 and 14, respectively. Each chip tube 12 is injected, and the tip tube 12 is covered with the downstream side of the cap 16 and another cap 18 and is appropriately sealed with a sealant or the like. As shown in the drawing, the tip tube 12 may be covered with the cap 19 and the inside thereof may be filled with the sealant 17.

In this vacuum double pipe, instead of sandwiching the chip tube 12 and vacuum-sealing, an opening is formed as in the second embodiment of the vacuum double container, and the opening is closed by a closing member. You may contact them by brazing.

In order to manufacture the vacuum double pipe having the above structure, first, as shown in FIG. 9, the connecting member 13 is provided on the downstream side of the water supply pipe 10 with its U-shaped inner surface facing the downstream side. A
The points indicated by are welded all around, the connecting member 14 is installed at the upstream end of the outer cylinder 11 with its U-shaped inner surface facing the upstream side, and the points indicated by the arrow B are welded all around.

Then, the outer cylinder 11 is installed from the upstream side of the water supply pipe 10, the points indicated by arrows C and D are welded all around, and the space surrounded by the outer cylinder 11 and the connecting members 13 and 14 is provided outside the water supply pipe 10. To form a part. When the outer cylinder 11 is mounted on the water supply pipe 10, the tips of the water supply pipe 10 and the outer cylinder 11 are connected to each other by a connecting member.
Since it does not come in contact with 14,13, it can be done easily and comfortably. Further, the copper foil or the plating layer provided on the outer surface of the water supply pipe 10 is not damaged.

Next, the heating and exhausting process and the vacuum sealing process of the space portion between the water supply pipe 10 and the outer cylinder 11 are performed, and the method is the same as the method in the first embodiment of the vacuum double container, and its operation Since the effect is the same, the description is omitted.

In this manufacturing process, when the material is put into the furnace from room temperature and heated, first, the temperature of the outer cylinder 11 rises, and then the temperature of the water supply pipe 10 rises later. The expansion amount of 11 is large, and the outside and the inside of the connecting members 13 and 14 are deformed by receiving forces in the directions of arrows a and b in FIG. 8, respectively.

On the contrary, when the cooling is started, the outer cylinder 11 is cooled faster than the water supply pipe 10, so that the contraction amount of the outer cylinder 11 is large at the time of cooling. , 14 are deformed by receiving forces in the directions of arrows a'and b ', respectively.

In this way, the connecting members 13 and 14 receive forces in completely opposite directions during heating and cooling, but the connecting members 13 and 14 are
Since the intermediate connecting portion is substantially perpendicular to the inner ring portion and the outer ring portion and has a degree of freedom in both directions, no excessive stress is applied at the time of deformation and no damage occurs.

The present inventors conducted a confirmation test on a vacuum double pipe manufactured by the method according to the present invention, and as a result, kept the upper and lower portions of the antifreezing pipe in an atmosphere of 5 ° C. and kept a space between them. It was found that the internal water does not freeze for about 80 hours even when exposed to a low temperature of -30 ° C.

(Effects of the Invention) As is apparent from the above description, according to the present invention, before exhausting to a high vacuum, the inner wall is quickly heated by heating under a low vacuum that does not impair the heat transfer property. Therefore, in particular, degassing from the inner wall is sufficiently performed in a short time, the overall heating and exhausting treatment time is shortened, the manufacturing process is shortened, and the heat insulating property is stabilized.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process by a method for manufacturing a metal vacuum double structure according to the present invention, and FIGS. 2 and 3 are respectively a suntenless steel vacuum chamber 2 by a tip tube method and a brazing method of the present invention. The figure which shows the manufacturing process of a heavy structure, FIG. 4 is sectional drawing of the double container manufactured by the method which concerns on this invention by the chip tube method,
5 is a sectional view of a double container manufactured by the method according to the present invention by a brazing method, and FIG. 6 is a partially enlarged sectional view of FIG.
7a to 7d are diagrams showing the test results regarding the heat retaining property of the vacuum double container manufactured by the conventional method, and FIG. 8 is a half of the vacuum double pipe manufactured by the method according to the present invention by the tip tube method. A sectional view, FIG. 9 is a half sectional view showing a state in the middle of manufacturing the vacuum double pipe. 1 ... Double container, 2 ... Outer container, 3 ... Inner container, 5 ... Space.

Claims (1)

[Claims] 1. A form a double wall structure with inner and outer walls, in the method for producing a metal-made vacuum double structure of containment vacuum evacuated processing space between the inner and outer walls, 10 ^-2 Torr After pre-evacuating to a low vacuum of the order of 10 ^-4 Torr or more, degassing by heating for a predetermined time, and then evacuating to a high vacuum of the order of 10 ^-4 Torr or less while maintaining the heating temperature and vacuum-sealing. A method for manufacturing a metal vacuum double structure, comprising: