JPH06104027A - Sleeve material for crimping and connection body - Google Patents

Abstract

PURPOSE:To utilize a connection part for a product for a long period of time in a stable way, since it is of large critical current value, and can be kept in a permanent current mode, by improving a filling rate and making superconducting filaments into contact with one another more closely. CONSTITUTION:For Cu of a stabilizer for connection, a sleeve material adjusted into the outer diameter of 9mm, the hole diameter of 2.2mm, and the entire Hv of approximately 40, is used. Superconducting wires 7, 8 to be connected are of Nb-Ti, and have the diameter of 1.0mm, while 24 filaments 9, 10 of the diameter of 0.078mm are used, and 1060 auxiliary connection filaments 11 of the diameter 0.035mm are used. After the filaments 11 are provided around the filaments 9, 10 in such a way that the filaments 9, 10 are surrounded by them, they are pressed, and the thickness of the Cu sleeve is molded into 6.4mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crimping sleeve for connecting filaments of metallic superconducting wires.

[0002]

2. Description of the Related Art A superconducting wire for connection uses a large number of superconducting element wires (hereinafter referred to as filaments) made of copper (Cu) or aluminum (A).
There is used a superconducting fine multi-wire which is embedded in a stabilizing material such as 1) and is drawn and drawn to a desired outer diameter. Although the soldering method, the brazing method, the crimping method, the welding method and the like have been attempted for the conventionally known connection, all of them have a large electric resistance at the connection portion and generate a large amount of heat when energized. There was a problem in practice.

In order to improve the connection of the superconducting filaments, the exposed filaments are stacked on top of each other and housed in the crimping sleeve as described in JP-A-59-16207. A method is adopted in which an electric conduction state is achieved by pressing pressure through. This connection method involves removing the stabilizer of the superconducting wire to be connected and exposing the exposed superconducting filaments, stacking them on top of each other and storing them in a sleeve for connection, and crimping through the sleeve to store the superconducting wires. The body filaments are crimped and connected to each other.

However, in this connection method, the filaments to be connected to each other contact only the overlapping portions of the outer surfaces thereof, and it is difficult to secure a high critical current value.
Also, the hardness of the sleeve for connection is not considered,
There is a problem that the filament is broken by the sleeve.

In order to further improve the filling rate of the filament of the superconductor, a method for joining superconducting wires has been proposed in Japanese Patent Laid-Open No. 234880/1987. This method is characterized in that the exposed multiple cores of the superconducting wire for connection are sandwiched with each exposed core wire, the sandwiched portion is integrally covered with a metal ring, and this metal ring is pressure-bonded and joined. To do. In that example, the tip of the filament of the connecting superconducting wire is extended to cover the end of each stabilizing material of the superconducting wire, and the end of the metal ring is positioned at the tip of the filament. It is crimped. When the number of superconducting element wires (filaments) is very small as in this example, applying a superconducting filament for connection is effective for improving the filling rate. However, the hardness of the connecting sleeve is not taken into consideration, and there is a drawback that the filament breaks due to the sleeve. In addition, because of the hard sleeve, the adhesion between filaments was not yet sufficient. Due to such a cause, there is a problem that the connection resistance value varies, and there is a defect that the permanent current superconducting wire is not formed.

[0006]

The above-mentioned prior art does not consider the hardness of the stabilizer itself which presses the filament, and therefore the true superconducting wires cannot be connected to each other, resulting in permanent electric conduction. There was also a problem with the characteristics.
That is, although the filaments are pressed and fixed by the sleeve, they have not yet been connected to achieve the proximity effect between filaments and the prevention of shunt loss.

An object of the present invention is to provide a stabilizing sleeve for connection in which filaments are brought close to each other and the filling rate is improved. Further, by using the sleeve, the current attenuation rate is remarkably small and a stable connection is achieved for a long period of time. To provide the body etc.

[0008]

In order to achieve the above-mentioned object, the present invention is to dissolve a superconducting wire in which a plurality of superconducting element wires (filaments) are embedded in a stabilizing material with a chemical, As a result, in the sleeve material in which the exposed filaments are crimped by the crimping sleeve, the crimping sleeve material that has been pretreated to the hardness Hv30 to 60 of the sleeve material that wraps the filaments is provided.

The pressure-bonding sleeve material has a hardness Hv30 to 60 in a range of twice the hole diameter of the portion in contact with the filament.
The sleeve material for pressure bonding has a hardness gradient so that the hardness around it is higher than Hv60.

The present invention also provides a sleeve material for crimping, wherein the sleeve material is made of an aluminum material in the range of twice the hole diameter of the portion in contact with the filament, and the outside is compounded with a copper material. The sleeve material has a hole diameter of about 3
It is necessary to have more than double. The reason is the amount required to restrain the repulsive force of the filament.

Furthermore, the present invention provides a connection body in which the filaments are pressure-bonded and connected by the pressure-bonding sleeve of the present invention described above.

Further, by the crimping sleeve of the present invention, there is provided a connected body in which the filaments and another filament for wrapping the filaments for connection assistance are crimped and connected at the same time.

The connecting body crimped and connected by the crimping sleeve of the present invention has a connection resistance of 10 ^-12 Ω or less and a critical current value of 80% or more of the critical current value of the superconducting wire. It is also a feature of the present invention that it is a connected body.

[0014]

In the connecting portion of the superconducting wire of the present invention, since the superconducting filaments are gathered in the central portion of the stabilizing material by the soft crimping sleeve, the filaments are contacted with each other and the filling rate is improved so that the filaments are closely connected. Sufficient proximity effect between filaments is obtained. Consider how the crimping sleeve works. Insert the filament to be connected, the filament, and the connection-enhancing filament that wraps the filament into the crimp sleeve. Now try the method of crimping with pressing pressure from the vertical direction. A few millimeters of superconducting wire, in which a plurality of superconducting element wires are embedded in a stabilizing material, is inserted into the crimping sleeve, and is pressed and connected together with the filament.

There are various diameters of superconducting wires, but they are 1.0 mm,
Filament is 0.06 mm, and C is used as a stabilizing material for pressure bonding.
Consider the u-sleeve (hole diameter: 2.2 mm). The order of high hardness is filament, superconducting wire, and Cu sleeve. The Cu sleeve is drawn and has a hardness of about 1
It is 10 Hv. A Cu sleeve having a hardness of Hv110 is pressed and first contacts a superconducting wire of 1.0 mm.
The superconducting wire has a superconducting element wire embedded in stabilized Cu and is difficult to be crushed. However, as the pressing pressure increases slightly, the Cu sleeve is the softest in this system, so that the Cu sleeve contacts the filaments while extending in the lateral direction and presses the filaments together.

The inner surface of the Cu sleeve is plastically deformed while pressing the filament, and the hardness gradually increases. The increased hardness pushes the filament toward the center of the sleeve. And as the pressing progresses, a few mm are entered.
A large shear stress will be applied to the 1.0 mm superconducting wire and the nearby filament. The filament diameter is 0.
As a result of the hardened Cu, which is as small as 06 mm, the phenomenon of being driven into a wire breakage appears. On the other hand, if the pressure is reduced so that the filament is not broken, the filling rate of the filament may decrease and the filament may move during use as a component, causing connection resistance.

Therefore, in order not to break the filament,
In addition, in order to improve the contact between filaments and the filling rate of the filaments in the Cu sleeve, Cu is used.
We thought that it was necessary to control the hardness of the sleeve.
The Cu sleeve drawn by drawing with a die is hardened for processing. Cu recrystallizes at 300 ° C. or higher and softens to lower the hardness. As a result of changing the hardness according to the heat treatment temperature and attempting pressure bonding with various hardnesses, it was found that the hardness of the inner surface of the Cu sleeve is preferably Hv30 to 60. It was also found that the elongation rate of stabilized Cu becomes more than double when the hardness becomes about half of the conventional hardness, and the shear stress of the superconducting filament is relieved by this increase in the elongation, and the crimp terminal deforms itself and the filaments The phenomenon that promotes the contact of

The hardness of the Cu sleeve is Hv30-6 as a whole.
It is not necessary that it be 0, rather, it is more preferable that only the area in contact with the filament is soft and the outer circumference is hard. That is, the filament is wrapped by pressing the filament with a soft inner surface, and the repulsive force of the filament is constrained by the hard Cu on the outer periphery. In this way, in order to change the hardness of the inner surface and outer circumference of the sleeve, in the case of Cu material,
This is achieved by subjecting the open inner surface to concentrated heating with a laser, a high frequency wave, an electron beam, or the like and heat treatment. The present invention can also be achieved by applying a composite material in which Al or the like having an Hv of 30 to 50 hardness is clad on the inner surface (Cu or the like on the outer surface) on the inner surface.

The soft range of the inner surface depends on the amount of filaments to be inserted, but as a result of experiments, it has been found that a range corresponding to about twice the hole diameter is suitable. That is, for example,
For a hole diameter of 2.2 mm, it is sufficient to soften the area of 4.4 mm. The diameter of the outer circumference needs to be about three times or more the inner diameter of the sleeve, and good restraining force can be obtained. In order to further stabilize, it is more preferable to apply a shape of about 4 times.

In order to achieve a low resistance connection, it is necessary to make the adhesion between filaments tight. The filament was inserted into the hollow portion of the stabilizing material, and pressure was applied from above and below using a mold that halved, and the relationship between the applied pressure and the filling rate was investigated. Then, when the critical current value of the obtained joint was measured by the 4-terminal method, it was found that a high critical current value could be obtained if the filling rate of the filament was 80% or more. In order to obtain a more stable critical current value, the filling rate is preferably about 90%.

When a current decay test was conducted on the connection portion produced by the present invention as described above, almost no current decay was observed even after 30,000 s, and the calculation result showed 10 ^-13 Ω or less.

As described above, the material of the connecting stabilizing sleeve is important in order to improve the filling rate of the filament and achieve the low resistance connection. Although Cu and Al have been described so far, Au, Ag and the like can also be applied, and the purity thereof needs to be as high as 99.9% or higher.

[0023]

EXAMPLES Examples of the pressure-bonding sleeve material and the connecting body of the present invention will be described below.

The basic structure of the sleeve material for crimping is shown.
FIG. 1 shows a sleeve 2 in which the entire surface of the sleeve 1 is adjusted to Hv 40 to 50 (softening), and a hole 3 for inserting a superconducting wire is provided at the center thereof. FIG. 2 is composed of the softening layer 2 of the sleeve 1 and its outer circumference 4. FIG. 3 shows a sleeve in which the soft material of the sleeve 1 is obtained by clad an Al material 5 corresponding to Hv 30 to 60 with a Cu material 6.

FIG. 4 shows a basic connecting body using a softened Cu sleeve. FIG. 4A shows a sectional state before connection. The superconducting wires 7 and 8 to be connected are inserted into the hole 3 of the softened Cu sleeve 2 by about 3 mm. Beyond that is a filament (superconducting element wire) from which stabilized Cu has been removed in nitric acid, and the filament 9 of the superconducting wire 7 and the filament 10 of the superconducting wire 8 are installed. The connection auxiliary filaments 11 are arranged so as to be wrapped around them. FIG. 4B shows a cross-sectional state after pressing. That is, the superconducting wires 7 and 8 are fixed by the softened sleeve 2 and the filaments 9 and 1
0 and 11 of the auxiliary connecting filaments are also connected and fixed to the center by the softening and stabilizing sleeve 2.

(Example 1) Cu used as the stabilizing material for connection had a diameter of 9 mm and a hole diameter of 2.2 mm, and a sleeve material having a total Hv of about 40 was used. The connected superconducting wire is Nb-
It is a Ti-based material with a diameter of 1.0 mm, and the filament has a diameter of 0.
The number of 075 mm was 24, and the number of connecting auxiliary filaments 11 was 1060 having a diameter of 0.035 mm. After arranging it as shown in Fig. 4 (a), press it to increase the thickness of the Cu sleeve to 6.4m.
Molded into m.

(Example 2) Cu for the stabilizing material for connection has an outer diameter of 9.0 mm and a wall thickness of 4.4 mm, and a softening layer inside thereof is clad with Al of Hv40 and has a hole diameter of 2.2 mm. Using. The conditions and molding thickness of the superconducting wire and filament to be connected are the same as in Example 1.

(Embodiment 3) A sleeve material having an outer diameter of 9 mm, a hole diameter of 2.2 mm, and a total Hv of about 40 was used as the stabilizing material for connection. The superconducting wire to be connected is a Nb-Ti system in stabilized copper with a diameter of 1.0 mm (24 filaments have a diameter of 0.075 mm) and a stabilized Cu-Ni system with a Nb-Ti system with a diameter of 1. A 0 mm filament (600 filaments having a diameter of 0.030 mm) was wrapped with a connecting auxiliary filament (1060 filaments having a diameter of 0.035 mm) 11 and inserted into a connecting sleeve for connection. Connection is shown in Figure 4 (a)
After arranging as described above, pressure was applied to mold the plate thickness of the Cu sleeve to 6.4 mm.

(Comparative Example) The stabilizing material for connection is Cu and has an outer diameter of
9.0 mm, hole diameter 2.4 mm, Hv of the whole sleeve is about 11
0 was used. The conditions and molding thickness of the superconducting wire and filament to be connected are the same as in Example 1.

The connecting sleeve materials used in the above-mentioned Examples and Comparative Examples were combined with the superconducting wires to be connected, and the connecting bodies molded by pressing were observed under a microscopic cross-section. A cross section of the connector produced in Example 1 is shown in FIG. FIG. 5 (a) shows a portion where the superconducting wires 7 and 8 are contained in the sleeve, and FIG.
Shows the connection state of the central part of the sleeve.

As shown in (a), the superconducting wires 7, 8
Stabilizing Cu1 of the sleeve of the present invention surrounds around the. The superconducting wires are also closer to each other, and the void portion 12 is very small. Further, it can be seen that the connection auxiliary filament 11 on the outer peripheral portion enters the inner surface of the sleeve and is more fixed. In (b) filaments 9 and 1
It is clear that 0 is in close proximity, the connection auxiliary filament 11 is in good proximity around it, and there are very few voids so that filament 9 and filament 10 are well connected. Here too, the filament 1 to help connect the outer circumference
It can also be seen that 1 enters the inner surface of the softened stabilizing sleeve and is fixed. In addition, the filling rate of the filament in the connection portion was about 90%. The filament in the vicinity of FIG. 5 (a) did not show any disconnection due to pressing, and had a good connection.

FIG. 6 shows a cross section of the connector produced in the comparative example. FIG. 6 (a) shows a portion where the superconducting wires 7 and 8 are contained in the stabilizing sleeve, and FIG. 6 (b) shows a connection state of the central portion of the sleeve. In (a), void portions 12 are seen around the superconducting wires 7 and 8, and voids 12 are also formed between the filaments. Also in (b), it is apparent that a large number of voids 12 are present between the filament 9 and the filament 10 as compared with Example 1.
The connection auxiliary filament 11 on the outer peripheral portion does not penetrate much into the inner surface of the sleeve. That is, it is considered that the stabilizing sleeve for connection is hard, and the hardness is further increased by pressing, so that there is little intrusion into the sleeve. Further, the filling rate of the filament in the connecting portion was about 70%, which was significantly inferior to the present invention. Further, in the case where the pressure is increased in order to improve the filling rate of the filaments, shear stress acts on the filaments (including the connecting filaments and the connecting auxiliary filaments) in the vicinity of FIG. Observed and not fully connected.

The connection bodies connected in the above Examples and Comparative Examples were subjected to no magnetic field (0T) and no magnetic field (1.0T) in liquid He.
The critical current value at the time of T) was measured. The result is shown in FIG. 7. For measurement, the holder is U-shaped and the distance between the voltage terminals is 1
It was measured at 5 mm. As can be seen from FIG. 7, although the critical current values are different in the examples of the present invention, this is due to variations in manufacturing superconducting wires. Although there are some variations in the same example, this is because the measurement was repeated in the same magnetic field. In any case, compared to the comparative example, the critical current is high and the degree of variation is small. From these results, it can be seen that the connection body using the stabilizing sleeve material for connection of the present invention and connecting by crimping is remarkably excellent.

Further, a permanent current circuit in which a permanent current switch of the connection body was installed was prepared, and an attenuation test of the connection portion was conducted.
The results are shown in Fig. 8. From FIG. 8, it is in Examples 1 and 2 that almost no current attenuation is observed among the Examples, and in Example 3, the permanent current is slightly attenuated as compared with Examples 1 and 2. The goal of the present invention is achieved by showing the modes. Substituting into the formula from the current attenuation tendency of the present invention and calculating, the joints of Examples 1 and 2 were <10 ^−13.
Ω, that of Example 3 was <10 ⁻¹² Ω, and it was revealed that all of them were low resistance joints.

As other stabilizing sleeve materials for connection,
As shown in FIG. 2, even if a stabilizing sleeve material in which the central portion of the Cu material is adjusted to about Hv40 and the outer periphery thereof is adjusted to about Hv90, the connecting body improves the contact of the filaments and improves the filling rate. , The connection part has been confirmed to be <10 ⁻¹² Ω.

Further, in order to bring the filaments into soft contact with each other, it is also within the scope of the present invention to dispose a stabilizing material (core material) between the filaments and press them together.
The core material is Al, Cu, Ag, Au, Pb-S.
An n, In, Bi system or the like can also be applied.

[0037]

According to the pressure-bonding sleeve and the connecting body of the present invention, since the superconducting filaments are brought into closer contact with each other to improve the filling rate, the connecting portion has a large critical current value.
Since it is in the permanent current mode, it can be stably applied to products for a long time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a pressure-bonding sleeve according to the present invention, which is an overall softened sleeve.

FIG. 2 is a cross-sectional view of a stabilizing sleeve material having a hardness gradient formed by softening only the central portion and hardening the others.

FIG. 3 is a cross-sectional view of a composite stabilizing sleeve in which a center portion is made of soft aluminum and the periphery thereof is made of copper.

FIG. 4 is a cross-sectional view showing a state in which a superconducting wire and a filament are connected by the crimping stabilizer of the present invention.

FIG. 5 is a cross-sectional view showing a state in which a superconducting wire and a filament are connected to each other by using the conventional stabilizing material for pressure bonding.

FIG. 6 is a cross-sectional view showing a state in which a superconducting wire and a filament are connected using a conventional crimping stabilizer of a comparative example.

FIG. 7 is a graph showing the critical current characteristics of the connector according to the present invention and the connector according to the comparative example.

FIG. 8 is a graph showing attenuation characteristics of loop current of the connection body according to the present invention and the connection portion according to the comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Crimping sleeve material, 2 ... Softening layer, 3 ... Hole, 4 ... High hardness layer, 5 ... Softening material, 6 ... Hardening material, 7, 8 ... Superconducting wire,
9, 10 ... Filament, 11 ... Connection auxiliary filament, 12 ... Void portion.

Front page continuation (72) Inventor Mitsuo Nakamura 4026 Kujimachi, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Toshiyuki Saito 3-1-1, Saiwaicho, Hitachi City, Ibaraki Hitachi Factory Hitachi Factory

Claims (7)

[Claims] 1. A sleeve material in which a superconducting wire in which a plurality of filaments are embedded in a stabilizing material is melted with a chemical agent, and as a result, the exposed filaments are crimped by a crimping sleeve. A sleeve material for crimping, wherein the sleeve material for wrapping the filament is pre-treated to have a hardness Hv of 30 to 60. 2. The hardness of the sleeve material according to claim 1, wherein the range of twice the hole diameter of the portion in contact with the filament is controlled to have a hardness Hv of 30 to 60, and the circumference thereof has a hardness H.
Crimping sleeve material with hardness gradient higher than v60. 3. The crimping sleeve material according to claim 1, wherein the sleeve material is made of an aluminum material in a range of twice the hole diameter of a portion in contact with the filament, and the outside thereof is compounded with a copper material. 4. The sleeve material for crimping according to claim 1, wherein the sleeve material has an outer diameter shape three times or more the hole diameter. 5. The connection body according to claim 1, 2 or 3, wherein the filament is pressure-bonded and connected by the pressure-bonding sleeve. 6. A connection body in which the filament and another connection-aiding filament that wraps the filament are simultaneously crimped and connected by the crimping sleeve according to claim 1, 2, or 3. 7. The connection body crimped and connected by the crimping sleeve according to claim 4 or 5, has a connection resistance of 10 ⁻¹² Ω or less, and a critical current value of 80% or more of a critical current value of the superconducting wire. A connector having a current value.