JPS63216279A - Connecting method for superconductive wire - Google Patents

Abstract

PURPOSE:To reduce the heat generation at a connection section by sticking the inner periphery of the circular joint connector on the outer periphery of end sections of superconductive wires to be connected and connecting the superconductive wires. CONSTITUTION:A superconductive wire 10 has a structure that many superconductive fiber materials 11 to be converted into superconductive fibers when heat-treated are arranged in a stabilizing materiel 12. To connect such superconductive wires 10, 10, end sections of the superconductive wires 10, 10 are inserted into a tubular joint connector 13, and the inner periphery of the connector 13 is brought into contact with the outer periphery of the end sections of the superconductive wires 10, 10. Next, the connector 13 is pressed to the superconductive wires 10, 10, and the connector 13 is stuck by pressure to the end sections of the superconductive wires 10, 10. The connector 13 is made of one or more base meterials formed with superconductive fiber materials to be converted into superconductive fibers when heat-treated. Accordingly, the contact resistance can be reduced, and the heat generation at the connection section can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a connection structure for superconducting wires used in FL for nuclear fusion toroidal magnets, particle accelerator magnets, superconducting generator magnets, and the like.

U. Prior Art As a conventional method for connecting superconducting wires, the connecting method shown in FIGS. 5 and 6 is known.

In the conventional connection method shown in FIGS. 5 and 6, the ends of the superconducting wires 1.1 to be connected are butted against each other, and the superconducting wires 1.1 are placed around the abutted portions. A plurality of short superconducting wires 2 for connection are arranged so as to be in contact with I, and a metal adhesive 3 is applied around them while the ends of the superconducting wire 1.1 are surrounded by the plurality of superconducting wires 2 for connection. This is a method of filling and fixing.

Further, as another conventional example of a method for connecting superconducting wires, methods shown in FIGS. 7 and 8 are known.

In the connection method shown in FIGS. 7 and 8, when connecting a superconducting wire 7 in which a superconducting filament 6 is arranged inside a stabilizing material 5 made of copper, the stabilizing material 5 at the end of the superconducting wire 7 is The required length of superconducting filaments 6 are removed to expose the superconducting filaments 6, and the exposed superconducting filaments 6 are interwoven or tied together, and then the outer periphery is covered with a steel pipe (or copper plate) 8, and the surroundings of the copper plate or the inside of the steel pipe are covered. This is a method of connecting by filling the metal adhesive with the metal adhesive.

"Problems to be Solved by the Invention" Although the conventional connection method explained based on FIGS. 5 and 6 is applicable to both alloy-based superconducting wires and compound-based superconducting wires, Since the superconducting conductors of the superconducting wires to be connected are not completely metallically bonded to each other, but are connected via the metal adhesive 3, there is a problem in that heat generation occurs.

In order to reduce this heat generation, it is necessary to make the connecting superconducting wire 2 as long as possible to reduce the contact resistance, but this has the problem of increasing material costs and taking time for the joining operation.

On the other hand, in the conventional method explained based on FIG. 7 and FIG. Although it is applicable to superconducting wires, there is a problem that the superconducting filament after heat treatment is brittle and cannot be applied to connection of compound-based superconducting wires, which are difficult to process.

Furthermore, when connecting alloy superconducting wires having processable superconducting filaments, the braided portion is covered with copper tube 8 after the superconducting filaments 6 are braided. There is a problem in that it is difficult to completely cover the exposed superconducting filaments 6 due to gaps between them.

The present invention has been made in view of the above-mentioned problems, and allows superconducting wires to be connected more easily than conventional connection methods, generates less heat at the connecting portion, does not cause deterioration of superconducting properties, and The purpose of this invention is to provide a method that can connect wires or alloy superconducting wires to each other at a lower cost than before.

``Means for Solving the Problems J'' In order to solve the above-mentioned problems, the present invention provides one or more bases formed by forming a superconducting fiber material that becomes a superconducting fiber by heat treatment inside the base. Using an annular joint connector made of material, the ends of both superconducting wires to be connected are butted together, covered with a joint connector, and the outer circumferential surface of the end of the superconducting wire is tightly attached to the inner circumferential surface of the joint connector. This is used to connect superconducting wires together.

``Operation'' Insert the end of the superconducting wire into the annular joint connector,
By connecting the superconducting wire while avoiding contact of the entire inner surface of the joint connector with the end of the superconducting wire, the contact area of the connecting portion is made larger than before, and heat generation at the connecting portion is reduced.

Since the contact area of the connecting portion can be increased compared to the conventional one, the connecting portion can be made shorter than the conventional one, and the cost can be reduced. Furthermore, superconducting fibers produced by heat-treating the joint connector contact and connect both superconducting wires, thereby connecting the superconducting wires without generating heat.

Embodiment J FIGS. 1 and 2 are for explaining one embodiment of the present invention. The superconducting wire 10 shown in FIG. The superconducting wire 10 used in this example has Nb fibers dispersed inside the base made of copper. It has a blended structure and is manufactured using an in-situ method in which an in-situ rod is produced by melting a Cu--Nb alloy with the required components and then subjected to a wire drawing process.

Note that the superconducting wire 10 of this example is made of Sn as described later.
By applying plating and further performing diffusion heat treatment to diffuse Sn, NbaSn superconducting fibers are formed inside, and a superconducting wire is completed.

To connect the superconducting wire 10.10, the superconducting wire IO
The end of the superconducting wire 10.10 is inserted into a tubular joint connector 13 having an inner diameter slightly larger than the diameter of the joint connector 13, and the inner peripheral surface of the joint connector 13 is brought into contact with the outer peripheral surface of the end of the superconducting wire 10. do. Next, the joint connector 13 is pressed against the superconducting LIQ 10 using a crimping jig, and the joint connector 13 is crimped onto the end of the superconducting wire 10.10.

The joint connector 13 is obtained by processing an ingot 14 when an ingot I4 shown in FIG. 3(a) is manufactured by melting a Cu--Nb alloy having the required components. Three-sided ingot! 4 is a base 15 made of copper
It has a structure in which Nb dendrites 16 are dispersed inside,
By subjecting this ingot I4 to wire drawing, it is possible to obtain an in-situ rod 19 in which a large number of Nb fibers 118 are closely distributed inside the base 17, as shown in FIG. 3(b). , a tubular joint connector 13 is manufactured by drilling a hole in the center of an in-situ rod 19 having a required length.

Superconducting wire 10.1 using the joint connector 13
After connecting 0, connect S to the surface of joint connector 13.
Apply n plating to form a Sn layer, superconducting wire 10.10
NNb35n inside by diffusion heat treatment! Generate an i-conductive conductor. In addition, diffusion heat treatment is 700 to 800
C. for 20 to 100 hours.

By performing the heat treatment, the joint connector 13
Sn diffuses and reacts with the Nb fibers 9a18 inside the
b3Sn is generated, and the joint connector 13 becomes a superconductor. In addition, in order to heat the joint connector 13 and the superconducting wire 10.10 at high temperature for a long time by the diffusion heat treatment, the joint connector 13 and the superconducting wire 10.
Copper atoms diffuse at the contact surface of 0, and the inner circumferential surface of the joint connector I3 and the outer circumferential surface of the superconducting wire 10.10 become molecularly bonded and welded, improving the bonding strength.

When joining using the joint connector 13 as described above, the joint connector! Since 3 itself is a superconductor, there is no problem of heat generation in the joint connector 13, and the inner peripheral surface of the joint connector 13 and the outer peripheral surface of the superconducting wire 10 and 10 are welded together by diffusion heat treatment. Because of this, there is less resistance at the bonding surface and less heat generation than before. Also, compared to the conventional method shown in Fig. 6, in which the superconducting wire for connection was connected by gluing it to the outer peripheral side of the end of the superconducting wire, joint connector I3 and superconducting wire! 0. Because the contact area with IQ is large,
The joint connector 13 can be made shorter than the conventional superconducting wire for connection, and there is an effect that the connection can be made at low cost.

By the way, when connecting the compound-based superconducting wire after diffusion heat treatment with the joint connector 13, it is necessary to use the joint connector 13 instead of the crimping method because crimping the joint connector 13 to the end of the superconducting wire will damage the brittle superconductor. , adhere with metal adhesive. The joint connector 13 used in this case is made by forming Sn plating on the surface and performing diffusion heat treatment to generate superconducting fibers inside.
No diffusion heat treatment shall be performed after bonding.

When joining using a metal adhesive in this way, the metal adhesive can become a heat generating part, but the joint connector 1
3 inner peripheral surface and superconducting wire 10. Since the outer circumferential surface of the to is in full contact with the outer peripheral surface of the to, the contact area is much larger than that of the conventional structure shown in FIG. 6, and the heat generation at the bonded portion is also reduced.

FIG. 4 shows a joint connector 20 according to a second embodiment of the present invention.
The joint connector 20 of this embodiment has 2
It is composed of base materials 21, 21 each having a split cylindrical shape.

The base material 21 has an internal structure similar to that of the joint connector 13 used in the embodiment described above, and has a structure in which superconducting fiber materials are dispersed inside a Cu base.

The base materials 21, 21 cover the ends of the superconducting wires to, to which are to be connected, and are bonded to the superconducting wires +0.10 to form a cylindrical shape, thereby connecting the superconducting wires to, to.

By the way, the joint connector 13 having the above structure is Nb,
When used for connecting Ge-based superconducting wires, Sn is added to the superconducting wires.
The above structure may be applied by applying Ge plating instead of plating, performing diffusion heat treatment, and using superconducting wire. Also,
Of course, the connection method using the tied connector 13 can be applied to the connection of alloy superconducting wires. Note that the joint connector I3 may have a rectangular tube shape.

"Manufacturing Example I" A shaft hole with a diameter of 20 mm was formed in a 150 mm straight cylindrical in-situ ingot made of Cu-40%Nb manufactured by an in-situ method, and an oxygen-free steel rod covered with a Ta pipe was inserted into this shaft hole. inserted. Subsequently, swaging, intermediate annealing, and wire drawing were performed to create a wire with a diameter of 1 m.
A wire rod with a length of about 0.5 km was obtained.

A Sn plating layer with a thickness of 30 μm was formed on the surface of this wire by electroplating. The thickness of this Sn plating layer is determined by applying diffusion heat treatment to the inside of the wire as described below.
When diffused, the tin concentration in the entire wire is 16 m5
The thickness is determined to be approximately the same.

The length of the wire is approximately 0.5 km, but in order to manufacture a coil obtained by winding a wire with a total length of 2 km, it is necessary to connect four of the wires.

Therefore, the wires are connected using a joint connector having the structure shown in FIGS. 1 and 2. To manufacture this joint connector, first, a Cu-40%Nb in-situ ingot with a diameter of 50 mm manufactured by the in-situ method is reduced to a diameter of 5 mm, cut to the required length, and a 3.5-mm diameter ingot is placed in the center. A shaft hole is formed using a drill.

Next, reduce the diameter of this tube to an outer diameter of 2 mm and an inner diameter of 1.2+
If it is n+n, it is cut to a total length of 40 mm to obtain a joint connector. A 70 μm thick Sn plating layer was formed on the surface of this joint connector.

Next, the ends of the four wires are butted together, and the joint connectors are passed through the butted parts so that the joint connectors are in contact with the lengths of 20II and 11II, and the ends of the joint connectors are crimped with a crimping jig. Each wire was connected by crushing it. Note that, prior to connection, the surface of each wire was covered with a glass yarn braided layer and subjected to insulation treatment.

Next, the wire rods connected as described above were heat-treated at 200° C. for 50 hours to diffuse and eliminate Sn in the Sn plating layer, and then coil winding was performed.

Next, the coil was subjected to a diffusion heat treatment of heating at 550° C. for 100 hours to produce a Nb3Sn superconducting coil.

After immersing this superconducting coil in liquid helium,
A current of 0 A was applied, and a magnetic field of 5 T (Tesla) from a backup coil was applied to generate an IOT magnetic field. At this time, no heat generation was observed at the connection, and the normal superconducting state was maintained.

"Example 2" An ultra-fine multicore Nb5Sn superconducting wire with stabilized copper was manufactured by an internal plating method, and a wire diameter of 1.4 mm was heat-treated at 800° C. for 50 hours to complete a Nb3Sn superconducting wire.

Next, a joint connector was made by connecting two of these superconducting wires to be used for winding a coil.

The joint connector is manufactured by an in-situ method. An in-situ ingot with a diameter of 50 mm is reduced to a diameter of 3 mm. After forming a Sn plating layer with a thickness of 100 μm on the surface, the joint connector is cut into a length of 30 mm. ．．
A 5 mm shaft hole was formed and a diffusion heat treatment was performed to heat the product to 575° C. for 100 hours.

In order to connect the two Nb3Sn superconducting wires, the ends of the two superconducting wires are inserted into the joint connector, the ends of the superconducting wires are butted together, and they are fixed with solder. After this, the whole is subjected to coil processing. A superconducting coil was manufactured.

The completed superconducting coil was immersed in liquid helium for 400 min.
A magnetic field of 5 T was generated independently by applying a current of A.

Furthermore, by placing a backup coil outside the IOT, we succeeded in generating a magnetic field for the IOT. At that time, no heat generation or voltage generation occurred at the connection.

"Effects of the Invention" As explained above, the present invention uses an annular shifted connector in which a superconducting fiber material is arranged inside the base, and the inner circumferential surface of the joint connector is attached to the outer circumferential surface of the end of the superconducting wire to be connected. In order to connect the superconducting wires by coating the superconducting wires, the contact resistance is reduced by increasing the contact area between the superconducting wires and the joint connector compared to the conventional method in which the connecting superconducting wires are connected vertically. It is possible to eliminate heat generation at the connection part. Furthermore, since the contact resistance is low, the connecting portion can be made shorter than before, which has the effect of making the connection inexpensive. Furthermore, when the superconducting wire and the joint connector are heat-treated, the inner circumferential surface of the joint connector and the outer circumferential surface of the superconducting wire form intermolecular bonds, which improves the bonding strength, reduces contact resistance, and suppresses heat generation. It has the effect of Furthermore, when a joint connector is bonded to a superconducting wire, there is a risk of heat generation at the bonded part, but compared to the conventional method in which the connecting superconducting wire is connected vertically, it is easier to connect the joint connector on the superconducting wire. Since the contact area is large, it has the effect of reducing heat generation at the bonded part.

[Brief explanation of the drawing]

Figures 1 to 3 illustrate an embodiment of the present invention.
Figure 1 is a longitudinal cross-sectional view of the connection part using a joint connector, Figure 2 is a cross-sectional view of the connection part, and Figure 3 is a cross-sectional view of the connection part using a joint connector.
Figure (a) is a cross-sectional view of the ingot, Figure 3 (b) is a cross-sectional view of the in-situ rod, Figure 4 is a cross-sectional view of a two-piece joint connector, and Figure 5 is a conventional example of a connection structure. FIG. 6 is a cross-sectional view of the conventional example shown in FIG. 5, and FIGS. 7 and 8 are for explaining other conventional examples. FIG. 8 is a sectional view showing a state in which the connecting portion is covered with a steel pipe. IO...Superconducting wire, 11...Superconducting fiber material, 12...Stabilizing material, 13.20...Joint connector.

Claims (4)

[Claims] (1) In a method for connecting compound-based superconducting wires or alloy-based superconducting wires that generate superconducting conductors through heat treatment, a superconducting fiber material that becomes superconducting fibers through heat treatment is formed inside the base. Using an annular joint connector made of one or more base materials, the ends of each superconducting wire to be connected are butted together and covered with a joint connector, and the outer circumferential surface of the end of the superconducting wire is brought into close contact with the inner circumferential surface of the joint connector. A method for connecting superconducting wires, characterized in that the superconducting wires are connected to each other by using the same method. (2) Claim 1, characterized in that a joint connector for connecting a superconducting wire in which a superconducting conductor is arranged inside a stabilizing material is fixed to the superconducting wire with a metallic adhesive.
How to connect superconducting wires as described in section. (3) When connecting superconducting wires in which a superconducting material that becomes a superconducting conductor through heat treatment is arranged inside a stabilizing material, a joint connector is crimped onto the superconducting wire before heat treatment to connect the superconducting wires. A method for connecting superconducting wires according to claim 1, characterized in that: (4) A method for connecting superconducting wires according to claim 1, characterized in that a joint connector constructed by joining two halves of a semi-cylindrical body is used.