JPH04269471A - Joint part of superconducting wire - Google Patents

Abstract

PURPOSE:To ensure a large current and stabilize the characteristic by mutually superposing and connecting superconductors of superconducting wires to be connected. CONSTITUTION:The powder of a high temperature superconducting material containing Bi, Pb, Sr, Ca and Cu is covered with silver, subjected to drawing and rolling, and then thermally treated followed by sintering to form a wire material having a metal coat 2 around an oxide high temperature superconductor 1. The coat 2 on the terminal of this wire material is partially removed to expose a conductor 1, which is mutually superposed and pressurized, and then thermally treated. In this case, it is essentially required to mutually connect the superconductors through no other material and through the same material, and the connecting length is desirably 5 mm or more. Thus, a superconductive current can be sent, and this connection is stable, and can be applied to the permanent current connection in a coil and the connection of large current conductors.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a superconducting wire joint using an oxide high-temperature superconducting material.

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.
, bismuth type has a high critical temperature of about 110K, and thallium type has a high critical temperature of about 120K, and their practical use is expected. Applications of these high-temperature superconducting materials to cables, busbars, power leads, coils, etc. are being considered.

0003

[Problems to be Solved by the Invention] However, when applying these high-temperature superconducting materials, it is not only necessary to obtain a long wire with stable characteristics, but also to ensure a large current and a stable junction. In particular, for coil applications, persistent current bonding is required. Persistent current bonding requires superconducting wires to be bonded together and superconducting current to flow.

[0004] An object of the present invention is to ensure such a large current and to provide a stable junction.

[0005]

[Means for Solving the Problems] The joint of the present invention is a joint of superconducting tape wires made of metal-coated oxide superconductors, in which the superconductors of opposing superconducting wires to be joined overlap each other. This is a joint of superconducting wires characterized in that they are joined together.

[0006] These joints can be manufactured by overlapping superconducting tape wires made of metal-coated superconductors, or by placing superconductors taken from the same wire in the middle. A method is used in which a metal coating material is placed on the outside, plastic working or pressing is performed, and then heat treatment is performed to bond the superconductors together, but the method is not limited to this, and various methods can be used.

However, in the present invention, it is essential that the superconductors of the superconducting wire are joined to each other without any other material or through the same wire material.

[0008] When joining, it is desirable that the joining length be 5 mm or more. The superconducting wire of this invention is in the form of a tape-like wire and is used for cables, busbars, power leads, coils, etc.

[0009] As the wire of the high temperature superconductor, a metal-coated wire is preferred from the viewpoint of stability, and is used in the present invention.

[0010] As for the type of metal, a metal with low resistivity that does not react with the high-temperature superconductor, has good workability, and functions as a stabilizing material is preferred, and silver and silver alloys are used. These metals are used to coat high temperature superconductors or as intermediate layers. When used as an intermediate layer, another metal such as copper, aluminum, nickel, stainless steel or an alloy thereof is further coated thereon.

[0011] As the high temperature superconductor, for example, yttrium-based, bismuth-based, or thallium-based ones are used. Bismuth-based materials are preferred because of their critical temperature (110 K), low critical current density, low toxicity, and no need for rare earth elements.

0012

[Operations and Effects of the Invention] The joint of the present invention is a joint of superconducting tape wires made of metal-coated oxide superconductors, and the superconductors of opposing superconducting tape wires to be joined are overlapped. Since this is a joint of superconducting wires that is characterized by being joined, it is possible to flow a superconducting current, is stable, and can be used as a persistent current joint of a coil or a joint of a large current conductor. therefore,
It is possible to provide superconducting wire joints that are optimal for various uses. That is, it can be used for cables, busbars, power leads, magnets, etc.

[0013]

[Example] Example 1 Bi:Pb:Sr:Ca:Cu=1.80:0.41:
Oxides and carbon salts are mixed to have a composition of 2.01:2.18:3.02, a powder consisting mainly of 2212 phase and non-superconducting phase is prepared by heat treatment, and this is placed in a reduced pressure atmosphere of 6 torr. Degassing treatment was performed at 760°C for 3 hours. These powders were coated with silver having an outer diameter of 12 mm and an inner diameter of 8 mm,
The wire was drawn to a thickness of 1 mm and rolled to a thickness of 0.18 mm.

[0014] This wire was heat treated at 845°C for 50 hours and sintered. The obtained wire is shown in FIG. As shown in FIG. 1, a metal coating 2 is provided around the oxide high temperature superconductor 1.

Each end of this wire was treated as shown in FIG. 2 to expose the oxide high temperature superconductor 1. The terminals treated as shown in FIG. 2 were stacked so that one portion of the oxide high temperature superconductor overlapped by 8 mm, and pressed with a pressure of 20 tons so that the overall thickness was 0.15 mm.

[0016] This wire was heat treated at 840°C for 50 hours. When the critical current of the joint of this wire was measured, the critical current was 30 to 40 A at liquid nitrogen temperature. It was found that the critical current 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 and carbon salts are mixed to have a composition of 2.00:2.07:3.00, a powder consisting mainly of 2212 phase and non-superconducting phase is prepared by heat treatment, and this is placed in a reduced pressure atmosphere of 8 torr. Degassing treatment was performed at 760°C for 2 hours. These powders were coated with silver having an outer diameter of 12 mm and an inner diameter of 8 mm,
The wire was drawn to a thickness of 1 mm and rolled to a thickness of 0.18 mm.

[0018] This wire was heat treated at 850°C for 50 hours. Using two of these wires, the silver on one side was peeled off to a length of 10 mm to expose the superconductor, and a thin tape with a thickness of 30 μm taken from the bismuth-based superconductor at the center of the superconducting tape wire was interposed between them. I let it happen. This structure was pressed with a load of 30 tons and heated to 840°C.
, heat treated for 50 hours. When the critical current of the joint of this wire was measured, the critical current was 30 to 40 A at liquid nitrogen temperature. It was found that the critical current is equivalent to the critical current of this wire at liquid nitrogen temperature.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a superconducting wire manufactured in an example of the present invention, and is a diagram showing a state before a metal coating is stripped off.

FIG. 2 is a perspective view showing a superconducting wire manufactured in an embodiment of the present invention, with the metal coating removed before joining.

[Explanation of symbols]

1 Oxide high temperature superconductor 2 Metal coating

Claims (1)

[Claims] [Claim 1] A joining portion of superconducting tape wires made of metal-coated oxide superconductors, characterized in that the superconductors of opposing superconducting tape wires to be joined are overlapped and joined. Junction of superconducting wire.