JPH04292876A - Junction method of superconductive wire - Google Patents

Abstract

PURPOSE:To manufacture a junction part of superconductive wire capable of permanent current junction, uniform superconductive characteristic in the junction part, and preventing the deterioration of superconductive characteristic by the influence of the atmosphere and a coolant. CONSTITUTION:One-side metal coats 2, 5 on the junction part of tape superconductive wires 3 to be joined are peeled from superconductors 1, 4 to expose the superconductors 1, 4. The exposed superconductors 1, 4 are mutually superposed, and the circumference is covered with a silver foil 7. The superposed part of the superconductors covered with the silver foil is subjected to plastic work or pressing work followed by thermal treatment to conduct the junction.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method for joining superconducting wires using oxide high-temperature superconducting materials.

0002

2. Description of the Related Art In recent years, ceramic-based, ie, oxide-based superconductors have attracted attention as superconducting materials exhibiting higher critical temperatures. Among them, yttrium is 90K.
, the bismuth type has a high critical temperature of about 110K, and the thallium type has a high critical temperature of about 120K, and their practical use is expected.

[0003] These high-temperature superconducting materials are considered to be applied to cables, bus bars, power leads, magnets, and the like.

0004

[Problems to be Solved by the Invention] However, when applying these high-temperature superconducting materials, it is not only necessary to obtain long wires with stable characteristics, but also to conduct bonding while maintaining a large current. It is necessary to stabilize or make it superconducting. Particularly in coil applications, persistent current bonding is required.

[0005] An object of the present invention is to provide a method for joining superconducting wires that enables persistent current joining and has uniform superconducting characteristics even at the joined portion.

[0006]

[Means for Solving the Problems] The joining method of the present invention includes:
This is a method for joining tape-shaped superconducting wires made of metal-coated oxide superconductors, in which the metal coating on one side of the joining part of the tape-shaped superconducting wires to be joined is peeled off from the superconductor, and the superconducting The method includes a step of exposing the body, a step of overlapping the exposed superconductors and coating the surroundings with metal, and a step of joining the overlapped portions of the superconductors coated with metal.

[0007] The metal covering the overlapped portion of the superconductor may be the same as the metal covering the superconducting wire;
Alternatively, silver or the like can be used.

[0008] The overlapped portions of superconductors coated with metal are subjected to, for example, plastic working or pressing, and then heat treated to bond the superconductors together.

[0009] At the joint portion of the superconducting wires, it is preferable that the unnecessary portions where the metal coating is present in the width direction are removed and then the superconducting wires are overlapped.

0010

Effects of the Invention In the joining method of the present invention, the overlapping portions of superconductors are coated with metal, and then the superconductors are joined together. Since the joint portion is coated with metal in this way, the influence of the external environment on the superconductor can be blocked by this metal coating. Therefore, when sintering is performed thereafter, the sintering atmosphere is the same for the parts other than the bonded parts, and uniform superconducting properties can be obtained throughout.

[0011] Furthermore, the influence of the atmosphere or coolant after sintering can be blocked, thereby preventing the superconducting properties from deteriorating.

The joining method of the present invention can be effectively used for cables, bus bars, power leads, magnets, and the like.

[0013]

[Example] Example 1 Bi:Pb:Sr:Ca:Cu=1.80:0.41:
Oxides or carbonates are mixed so that the composition becomes 2.01:2.18:3.02, and by heat treatment, mainly 221
A powder consisting of two phases and a non-superconducting phase was prepared.

This powder was subjected to degassing treatment at 800° C. for 2 hours in the atmosphere. This powder was covered with a silver pipe having an outer diameter of 12 mm and an inner diameter of 8 mm, which was drawn to a wire diameter of 1 mm and rolled to a thickness of 0.17 mm. This wire rod is 8
It was heat-treated at 45° C. for 50 hours and sintered.

FIG. 1 is a diagram showing the tape-shaped superconducting wire thus obtained. Referring to FIG. 1, a tape-shaped superconducting wire 3 is constructed by providing a metal coating 2 around a superconductor 1.

The metal coating 2 at the end of the tape-shaped superconducting wire shown in FIG. 1 was peeled off to expose the superconductor 1. FIG. 2 shows this state.

FIG. 3 shows a tape-shaped superconducting wire whose end portions have been treated in the same manner as shown in FIG. 2 in a superposed state.

As shown in FIG. 3, another tape-shaped superconducting wire 6 is arranged so that the superconductor 4 and the superconductor 1 overlap. The metal coating 5 of the tape-shaped superconducting wire 6 is placed on the tape-shaped superconductor 3, while the metal coating 2 of the tape-shaped superconducting wire 3 is placed on the tape-shaped superconducting wire 6. A silver foil 7 is further wrapped around this overlapping portion as shown by a chain line. The silver foil used was 30 μm thick, 10 mm wide, and 20 mm long.
mm. Superconductor 4 and superconductor 1 are overlapped with a length of 10 mm.

In the state shown in FIG. 3, pressing was performed at a pressure of 30 tons until the entire thickness was 0.35 mm. This wire was heat treated at 840°C for 50 hours.

[0020] When the critical current of the joint portion of the obtained wire was measured, the critical current in liquid nitrogen was 20 to 30 A. This value is equivalent to the critical current of this wire at liquid nitrogen temperature.

Example 2 Bi:Pb:Sr:Ca:Cu=1.82:0.43:
Oxides or carbonates are mixed so that the composition becomes 2.00:2.07:3.00, and heat treatment mainly produces 221
A powder consisting of two phases and a non-superconducting phase was prepared.

This powder was subjected to degassing treatment at 800° C. for 2 hours in the atmosphere. This powder has an outer diameter of 12 mm,
It was covered with a silver pipe having an inner diameter of 8 mm, wire-drawn to a diameter of 1 mm, and then rolled to a thickness of 0.17 mm. This wire was heat treated at 850°C for 50 hours.

As shown in FIG. 4, the silver coating 12 on one side of the superconducting wire obtained as described above was stripped off within a length of 10 mm to expose the superconductor 11. This tape-shaped superconducting wire 13 was joined to a similar tape-shaped superconducting wire.

FIG. 5 is a perspective view showing this state. The superconductor 11 of the tape-shaped superconducting wire 13 and the superconductor 14 of the tape-shaped superconducting wire 16 were overlapped so that they overlapped, and the metal coatings 12 and 15 were positioned on both sides thereof. Furthermore, silver foil was coated around this overlapped portion. The silver foil used was 30 μm thick and 10 μm wide.
mm, and the length is 20 mm. Silver foil 17 like this
With the joint sandwiched and covered, a load of 40 tons was applied and pressed to a thickness of 0.20 mm, and this was heated at 840°C.
When the critical current at the bonded portion of the wire obtained by bonding the superconductors together by heat treatment for 50 hours was measured, the critical current at liquid nitrogen temperature was 20 to 30 A. This value is equivalent to the critical current of this wire in liquid nitrogen.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a tape-shaped superconducting wire used in an embodiment of the present invention.

FIG. 2 is a perspective view showing the tape-shaped superconducting wire in FIG. 1 with the metal coating on the end thereof peeled off.

3 is a perspective view showing a state in which the tape-shaped superconducting wires in the state shown in FIG. 2 are overlapped and joined together; FIG.

FIG. 4 is a perspective view showing a tape-shaped superconducting wire used in another embodiment of the present invention with the metal coating on the end portion removed.

FIG. 5 is a perspective view showing a state in which the tape-shaped superconducting wires in the state shown in FIG. 4 are overlapped and joined together.

[Explanation of symbols]

1,4 Superconductor 2,5 Metal coating 3,6 Tape-shaped superconducting wire 11,14 Superconductor 12,15 Metal coating 13, 16 Tape-shaped superconducting wire 7,17 Silver foil

Claims (1)

[Claims] 1. A method for joining tape-shaped superconducting wires made of metal-coated oxide superconductors, the metal coating on one side of the joining portion of the tape-shaped superconducting wires to be joined being superconducting. The superconductor is peeled from the body to expose the superconductor, the exposed superconductors are overlapped and the surroundings are coated with metal, and the overlapped portions of the metal-coated superconductors are joined. A method for joining superconducting wires.