JPH0711212A - Adhesive for use at extremely low temperature - Google Patents

Abstract

PURPOSE:To obtain an adhesive capable of keeping high adhesivity and increasing the strength, resistant to cracking and having high thermal conductivity at an extremely low temperature. CONSTITUTION:A two-pack type adhesive liquid is mixed with at least one kind of filler selected from glass beads, hollow glass beads, highly heat- conductive material, highly heat-conductive ceramic and aluminum nitride. The adhesive having the above composition is applied to the bonding part 7 of a shield plate 3 of a cryostat 2 and cured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic adhesive for adhering a shield plate in a cryostat for cooling a superconducting electromagnet, for example.

[0002]

2. Description of the Related Art Conventionally, there are many kinds of adhesives, and there are liquid adhesives, powders, and rod-shaped solid adhesives.
It also depends on the bonding temperature, and there are room-temperature curing adhesives and heat-curing adhesives. Further, they are classified as a solvent adhesive, a pressure sensitive adhesive, a heat sensitive adhesive, and a reactive adhesive.

There are natural adhesives and synthetic adhesives, and synthetic adhesives are generally widely used. Furthermore, inorganic adhesives such as sodium silicate are used for bonding glass and ceramics.

As described above, there are various kinds of adhesives depending on their uses. However, generally, adhesives used at extremely low temperatures have low adhesive strength, and most of them are cracked after bonding. Therefore, the cryogenic adhesive used for the purpose of preventing the adherend to be peeled off, which is used at room temperature, is hardly known, and is used only as a space filler under the present circumstances.

[0005]

Conventionally, known adhesives have extremely weak adhesive strength at extremely low temperatures, lack strength and are easily cracked, and have insufficient airtight sealability and thermal conductivity. There are some problems such as being small.

The present invention has been made in order to solve the above problems, and provides an adhesive for cryogenic use which has a large adhesive force at an extremely low temperature, has an increased strength, does not easily crack, and has a large thermal conductivity. To do.

[0007]

According to the present invention, at least one of glass beads, hollow glass beads, high thermal conductive material, high thermal conductive ceramics and aluminum nitride is mixed as a filler in a two-liquid mixed type adhesive liquid. It is characterized by

[0008]

In the adhesive used at a very low temperature, a solid substance is mixed as a filler. As the adhesive, a two-liquid mixed type such as an epoxy type or a polyurethane type (preferably, an acrylic type, a nylon type, a polyamide type) may be used.

Although the material, particle size, and amount of mixture differ depending on the use, 5 to 60% of solid matter having a diameter of 1 μm to 1 mm is mixed. Since it is a two-liquid mixture type, it does not matter whether it is mixed in one side first or in use.

Glass beads are used as a filler when strength is important, and hollow glass beads are used when weight reduction is required. When it is desired to increase the thermal conductivity, aluminum nitride is mixed. The surface treatment of the filler must be performed according to the type of filler and adhesive.

By mixing such a filler,
Conventionally, the adhesive alone had cracks and the adhesive itself was broken, but the cracks do not enter (difficult to enter), the adherend does not separate, and the so-called "sticking" state occurs.

In this case, the adhesive force between the non-adhesive and the adhesive does not increase, but the apparent adhesive force is increased due to the increased strength (holding) of the adhesive itself. It is getting bigger.

Further, unlike mechanical connection such as bolts and rivets, it is possible to seal a gap between non-adhesive objects. As a result, it becomes possible to use it even at a joint where airtightness is required. The use of a high thermal conductivity material for the filler results in good heat transfer at the bond.

[0014]

EXAMPLE A first example of the cryogenic adhesive according to the present invention will be described with reference to FIG. FIG. 1 is a sectional view showing an example in which the cryogenic adhesive according to the present invention is applied to a shield plate 3 in a cryostat 2 having a superconducting magnet 1 built therein.

That is, a cylindrical shield side plate 6 is adhered to a shield upper plate 4 and a shield lower plate 5 each having a flat plate with a "flange" at a joint portion 7 with an epoxy adhesive (not shown). . The joint portion 7 is a portion which is conventionally fixed with a screw or a rivet.

In this embodiment, the shield upper plate 4, the shield lower plate 5 and the shield side plate 6 are made of aluminum, but with the same shape and usage, both are made of copper or one is made of copper and the other is made of aluminum. It is also possible to use a material or a material in which FRP and aluminum are adhered. Note that reference numeral 8 in FIG. 1 indicates a helium container.

The joint portion 7 of the shield plate 3 as in the present embodiment
In the case of using an adhesive as described above, since it is preferable that the adhesive itself has a high thermal conductivity, aluminum nitride particles were mixed into the epoxy adhesive.

The particle size is nominally 100 μm,
There is a variation of several tens of μm. The mixing ratio is 50% (calculated value) in terms of volume percentage. It is adhered to the entire surface (collar part) that contacts each other.

However, although there is a gap of about 1 mm between the shield upper plate and the shield side plate or the shield lower plate, the gap is filled with the adhesive of this embodiment. All shield plates were joined together without peeling even at extremely low temperatures, and in the case of FRP and aluminum plates, the heat transfer coefficient was equal to or higher than that of riveting even in the portion where the gap was 0.5 mm.

There was no problem in strength, and not only the weight of the shield plate could be supported, but also the shield plate was so strong that it would not come off even if the shield plate was deformed by hanging the cryostat.

Further, the workability is also improved, and the bolts and holes for rivets are not formed in the shield plate, so that the material cost is reduced. Furthermore, since it is not necessary to pinch indium, which is generally used for rivets and bolt tightening, the cost of indium is low, and the mounting work is the same as the conventional one.
It became possible in less than / 10 time.

Next, a second embodiment of the cryogenic adhesive according to the present invention will be described with reference to FIG. FIG. 2 is an example in which the present invention is used for a dissimilar metal joint portion of a low temperature pipe. The second embodiment is applied to the cryostat 2 having the superconducting magnet 1 as in the first embodiment.

That is, the shield plate 3 is cooled by the cooling pipe 10 through which the liquid nitrogen refrigerant flows. The shield plate 3 is made of aluminum, and the cooling pipe 10 is also made of aluminum.
A vacuum space 12 is provided between the shield upper plate 4 and the stainless steel vacuum container 11 for heat insulation.
It is shielded from the atmosphere outside. Since the liquid nitrogen of the refrigerant is supplied from the atmosphere side, the cooling pipe 10 is connected to the atmosphere and the vacuum space.
The vacuum container 11 must be penetrated while ensuring the airtightness with the vacuum container 12.

For this reason, metal welding is performed at the weld 13 between the cooling pipe 10 and the vacuum container 11. Welding stainless steel and aluminum is difficult, so this part of the cooling pipe is also stainless steel. Therefore, an airtight dissimilar metal joint 14 of stainless steel and aluminum is required in the vacuum space 12, and the adhesive of the present invention is used here. This joint portion 14 is a portion that has been conventionally pressure-bonded. Reference numeral 15 in FIG. 2 is a pipe / plate joint.

After the portion of the vacuum container 11 is welded at the welded portion 13, it is adhered with an epoxy adhesive. Hollow glass beads are used as the filler. The cooling pipes 10 are butt-bonded to each other, and by simply providing a bent portion on the aluminum pipe side, the cooling pipes 10 can withstand the force due to heat shrinkage and are bonded without peeling. Since the bonding is the final step, it suffices to perform the alignment only by the bending condition of the bent portion, which facilitates the production.

Further, in the second embodiment, the adhesive according to the present invention is also used for the pipes of the shield plate 3 and the cooling pipe 10, and the plate joint portion 15. Since this cooling pipe 10 is for cooling the shield plate 3, the two must be closely joined so that the heat transfer is as high as possible.

Therefore, although it is generally joined by aluminum welding, due to the welding, the shield plate is distorted and it is considerably difficult to weld the entire circumference of the cooling pipe, and it takes time. . Further, in order to enhance heat transfer, the thinner the thickness of the cooling pipe 10, the better, but welding becomes difficult.

By using the present invention in such a place, the shield plate 3 is not deformed, and
It can be joined in no time. High thermal conductivity ceramics as a filler, for example, when using aluminum nitride, not only the heat transfer rate is increased,
The electrical insulation is also enhanced. Similarly, when copper, silver, or the like is mixed in for the purpose of increasing the thermal conductivity, the specific gravity becomes about 8.9 to 1.
Since it is as large as 0.5, the bonded portion becomes heavy.

Since the specific gravity of aluminum nitride is about 3.3, it does not become much heavier than adhesives and glass.
When hollow glass is used, it is almost the same as the adhesive.
The specific gravity is about 5.

Crimping parts, O-ring seals and the like have been used in the parts where the sealing property is required, but since the sealing property is maintained by adhesion, expensive crimping parts and large flanges are not required. Therefore, the parts are smaller than the flange and the like, the heat insulation performance is improved correspondingly, the manufacturing is easy, and the entire apparatus is easily downsized. Of course, the price will also drop. Further, depending on the device, the work becomes easy.

[0031]

EFFECTS OF THE INVENTION According to the present invention, the adhesive strength is great under cryogenic temperature, the airtight sealing property is kept good, and the thermal conductivity can be increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment in which an adhesive according to the present invention is applied to a shield plate in a cryostat for a superconducting magnet.

FIG. 2 is a side view showing a second embodiment in which the adhesive according to the present invention is applied to a dissimilar metal joint portion of a low temperature pipe.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Superconducting magnet, 2 ... Cryostat, 3 ... Shield plate, 4 ... Shield upper plate, 5 ... Shield lower plate, 6 ... Shield side plate, 7 ... Joint part, 8 ... Helium container, 9 ... Liquid helium, 10 ... Cooling piping , 11 ... vacuum container, 12 ... vacuum space, 13
… Welded part, 14… Joint part, 15… Piping, plate joint part.

Claims (1)

[Claims] 1. A cryogenic temperature characterized by mixing at least one of glass beads, hollow glass beads, high thermal conductive material, high thermal conductive ceramics, and aluminum nitride as a filler in a two-liquid mixed type adhesive liquid. Adhesive.