JPH04292879A - How to join superconducting wires - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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, busbars, power leads, coils, 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 for coil applications, persistent current bonding is required. This persistent current bonding is achieved by directly bonding superconductors to each other and passing a superconducting current, but mechanical strain may occur in this bonded portion and the critical current may decrease.

Particularly, when a plurality of layers of tape-shaped superconducting wires are bonded in a superposed state, the critical current decreases significantly at such a bonded portion.

[0007] An object of the present invention is to provide a method for joining tape-shaped superconducting wires having a plurality of stacked layers, which can suppress such a decrease in critical current.

[0008]

[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 a state in which multiple layers are stacked one on top of the other, and includes the following two steps.

One step is to peel off the metal coating on one side of the joint part of the tape-shaped superconducting wires to be joined from the superconductor to expose the superconductor, and also to separate the joint parts of the superconducting layers of each layer in the longitudinal direction. This is a step of arranging each layer of superconducting wire between multiple layers of tape-shaped superconducting wires to be joined, so that the superconducting wires are in sequentially shifted positions.

[0010] Another step is to stack the exposed superconductors on each other in their respective layers, and to bond the tape-shaped superconducting wires stacked in multiple layers.

[0011] In order to bond the superconducting wires of each layer, the superconductors are stacked on top of each other with the metal coating partially removed or turned over, subjected to plastic processing or press processing, and then heat treated to bond the superconductors together. Can be done.

[0012] The removal and peeling of the metal coating is preferably carried out after removing only the portions of the metal coating on both sides in the width direction of the end of the tape-shaped superconducting wire.

[0013]

Effects of the Invention In the joining method of the present invention, each layer is bonded between the tape-shaped superconducting wires to be joined, which are stacked in multiple layers, so that the joining portions of the superconducting layers of each layer are sequentially shifted in the longitudinal direction. Superconducting wires are installed. For this reason,
The joint parts, which are slightly thicker than other parts, are distributed in the longitudinal direction of each tape-shaped superconducting wire, dispersing strain during pressing when joining the superconductors. be able to. As a result, according to the present invention, it is possible to suppress a decrease in critical current.

According to the present invention, it is possible to flow a superconducting current, and it can be used as a persistent current junction of coils or a junction of large current conductors. Therefore, the cable,
It can be used as a superconducting wire bonding method that is ideal for various applications such as bus bars, power leads, and magnets. It is particularly effective for joining wire rods for magnets in persistent current mode.

[0015]

[Example] Bi:Pb:Sr:Ca:Cu=1.80:
Oxide or carbonate is mixed to have a composition of 0.41:2.01:2.18:3.02, and by heat treatment,
A powder consisting mainly of 2212 phase and 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 wire-drawn to a diameter of 1 mm and rolled to a thickness of 0.17 mm. This wire was heat treated at 845° C. for 50 hours and sintered.

FIG. 1 is a perspective view showing the wire obtained in this manner. Referring to FIG. 1, a tape-shaped superconductor 10a is constructed by providing a metal coating 12 around a superconductor 11.

FIG. 2 is a perspective view showing a state in which a plurality of tape superconducting wires shown in FIG. 1 are stacked with the metal coating on the ends thereof peeled off. Referring to FIG. 2, the metal coating at the end joint of the tape-shaped superconducting wire in the state shown in FIG. 1 was peeled off to expose superconductor 11a. Next, four tape-shaped superconducting wires 20a, 30a, 40a, and 50a whose ends had been treated in the same manner were stacked one on top of the other while shifting their joints in the longitudinal direction, resulting in a state as shown in FIG. .

[0019] In the same manner as described with reference to FIG.
The other bundle of tape-shaped superconducting wires to be joined was prepared, and the tape superconducting wires were overlapped as shown in FIG. 3. Referring to FIG. 3, tape-shaped superconducting wire 10 of each layer
a, 20a, 30a, 40a and 50a are respectively the other counterpart tape-shaped superconducting wires 10b, 20b,
30b, 40b and 50b. In this state, the superconductors at the joints of the tape-shaped superconducting wires are superimposed on each other.

[0020] In this state, it was pressed with a pressure of 20 tons so that the entire thickness was 0.75 mm.

[0021] The wire rod obtained as a bundle of multiple layers of tape-shaped superconducting wires obtained as described above was heat-treated at 840°C for 50 hours. When we measured the critical current at the joint of this wire, we found that
The critical temperature was 90 to 100 A at liquid nitrogen temperature. This value was almost the same as the critical current of this wire at liquid nitrogen temperature, and no decrease in critical current was observed at the joint.

[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 a state in which the metal coating at the end of the tape-shaped superconducting wire of FIG. 1 is peeled off and multiple layers are stacked.

FIG. 3 is a perspective view showing a state in which multiple layers of tape-shaped superconducting wires shown in FIG. 2 are overlapped and bonded together.

[Explanation of symbols]

10a-50a, 10b-50b Tape-shaped superconducting wire 11a Superconductor 12a Metal coating

Claims (1)

[Claims] Claim 1: A method for joining tape-shaped superconducting wires made of metal-coated oxide superconductors in a state in which multiple layers are stacked, the metal on one side of the joining portion of the tape-shaped superconducting wires to be joined. The coating is peeled off from the superconductor to expose the superconductor, and the tape-shaped superconducting wires to be joined are stacked in multiple layers so that the joining portions of the superconducting wires of each layer are at positions sequentially shifted in the longitudinal direction. A method for joining superconducting wires, comprising the steps of: arranging superconducting wires in each layer; overlapping the exposed superconductors in each layer; and joining the tape-shaped superconducting wires stacked in multiple layers.