JPS5947406B2 - Method for manufacturing aluminum-coated multicore superconducting wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of multicore superconducting wires using aluminum as a stabilizing material.

A superconductor maintains its superconductivity even in a high magnetic field, but a single superconducting wire reacts sensitively to changes in magnetic flux and thermal fluctuations, losing its superconducting properties and transitioning to a normal conductor. The part that has transitioned to a normal conductor has a finite electrical resistance and generates heat, further causing a transition to normal conductivity to the adjacent part, and eventually superconducting damage occurs over the entire length. For this reason, for practical use, superconducting wires are stabilized by coating them with good electrical and thermal conductors at low temperatures, such as copper, aluminum, silver, etc., and in order to further increase stability, superconducting wires are coated with thin multi-core conductors. It is desirable to turn it into something new and twist it. For superconductor materials using copper as a stabilizing material, the technology for increasing the number of thin wires has been established.
Although it has been put into practical use, the processing technology for thin multi-core superconducting wire using aluminum as a stabilizing material has not yet been established.

The reason for this is due to the difference in workability between the superconducting material and aluminum, and a so-called aluminum flow phenomenon occurs in which only the surface aluminum is processed, making it difficult to reduce the area of the superconducting material as an integral part.

It is well known that this flow phenomenon can be prevented by coating the metal that causes it with a harder metal. Therefore, the present invention aims to obtain an aluminum-stabilized multi-core superconducting wire by utilizing this well-known technology, and the outer periphery of the superconducting wire (or wire) is coated with aluminum and a metal or metal having higher deformation resistance than aluminum is coated on the outer periphery of the superconducting wire (or wire). A process of sequentially applying coatings made of alloys such as aluminum alloys, copper, copper alloys, etc., and then removing coatings made of metals or alloys that have higher deformation resistance than aluminum from the resulting composite wire, and converging them to form aluminum alloys. From the process of inserting a metal or alloy with high deformation resistance into a pipe and reducing its surface area, and the process of twisting the obtained multi-core composite wire and removing the aluminum coating on the outer periphery of the metal or alloy with high deformation resistance. This is a method characterized by As seen in Figure 1, superconducting materials such as Nb-T
A relatively thick wire 1 made of i-Zr alloy is inserted into an aluminum pipe 2, its outer periphery is covered with a copper pipe 3, and then the area is reduced by a known method such as rolling or drawing. Copper coating 31 on the outer periphery by chemical treatment
It was obtained by removing .

This superconducting wire 11 may be a multicore superconducting wire as shown in FIG. 4.

Reference numeral 4 denotes a pipe that encloses a bundle formed by collecting the superconducting wires 11 obtained in this way without twisting them, and this pipe is made of copper like the pipe 3, and the superconducting wires 11 are
Together with the bundle, the area is reduced by a method known now.

In this case, the copper pipe used may be circular, but if a hexagonal one is used, the superconducting wire 11 will not move, and a more preferable result will be obtained.

Since there is a gap 5 in the bundle and between the bundle and the pipe 4 at the beginning of the area reduction process, it is unavoidable that the aluminum coating 21 will flow into the gap 5 until the pipe 4 becomes thin, or it will stop at a certain point. The superconducting wires 11 are in contact with each other, the gaps 5 disappear, and the overall wire diameter is reduced, resulting in a multi-stop composite wire having a cross-sectional structure as shown in FIG.

The multi-core composite wire is then twisted with the copper sheath 41 still in place, and the copper sheath 41 is removed by a known chemical process to form a large number of wires in the aluminum matrix 22, as seen in FIG. A desired multicore superconducting wire in which the superconducting thin wires 12 are embedded is obtained.

The aluminum coatings in the multi-core composite wire are crimped to each other by area reduction processing, but since the twisting is done before the copper coating 41 is removed, separation of the crimping in the next process can be prevented to ensure a good result. can get. According to the experience of the inventors, the method of the present invention can be carried out if the cross-sectional area ratio of aluminum to superconducting material is 5/1 or less, and it has been found that a ratio of 3/1 or less is particularly good.

Therefore, in practice, the multi-core superconducting wire produced by the method of the present invention is further coated with aluminum by known methods such as extrusion, drawing, braiding, etc., or twisted with aluminum wire to increase the aluminum cross-sectional area. It is necessary to do so.

Generally, stabilized aluminum is considered to have a purity of about 99.99%, but it is difficult to obtain aluminum of high purity industrially, and it is thought that the purity will be slightly lower for practical use.

In terms of processing, the higher the purity, the more difficult it becomes.
Even if approximately 5% aluminum is used, there may be difficulties depending on the aluminum cross-sectional area ratio, so it is desirable to use aluminum with a purity of 99.5% or higher. Of course, when blocking a multi-core composite wire, the superconducting wire 11
It is also possible to increase the cross-sectional area ratio of aluminum by coating the outer periphery of the bundle with aluminum wire, in which a part of the bundle is replaced with aluminum wire.

Next, examples of this invention will be shown.

Outer diameter 10.5Tfr1n1 Length 1m<7) Nb-Ti-
Zr wire, outer diameter 17571im1 wall thickness 3T1r! l, a 99.99% pure aluminum tube with a length of 1 m,
Copper tubes with an outer diameter of 21.5 WL1, a wall thickness of 1.5 m, and a length of 1 m were prepared, and after degreasing and cleaning, they were assembled concentrically, and then subjected to die wire drawing processing to make wire rods with an outer diameter of 5.2 Tfrm. .

In order to incorporate the obtained wire rod into an aluminum pipe as a multi-core wire, 37 wire rods each having a length of 1 m were obtained by cutting to a fixed length.The copper coating of each wire rod was dissolved and removed using nitric acid, washed with water, and then dried. As a result, an aluminum coated wire with an outer diameter of 4.37 m was obtained, and the core wire diameter was 3.17 m. Next, each of the obtained wires was degreased and cleaned, with a diagonal of 30.61LW and an opposite side of 26.5LW.
Incorporated into a high-purity (99.99%) aluminum tube with an outer diameter of 37 m and a length of 1 wn, which has a hexagonal inner shape in cross section,
The outer circumference of the aluminum tube has an outer diameter of 41TfWL1 and a wall thickness of 1.
A copper tube with a length of 5wn and a length of 1m was fitted to form a composite body, and this composite body was reduced in area to an outer diameter of 2Tfr1ft by die wire drawing. After that, it was twisted with a pitch of 30 WI, and further, in order to correct the streaks and undulations caused by twisting on the wire surface, the wire was drawn in one pass to an outer diameter of 1.81 mm, and then the copper on the outer periphery was dissolved and removed (with nitric acid), washed with water, Dry. This results in an outer diameter of 0.1
A multicore superconducting wire with an outer diameter of 1.7 wL was obtained in which 37 Nb-Ti-Zr wires were independently dispersed in an aluminum material.

As described above, according to the present invention, it is possible to manufacture an aluminum-coated multicore superconducting wire, which was previously considered impossible. Moreover, since twisting is performed with the metal or alloy coating still attached, which has higher deformation resistance than aluminum after area reduction processing, it has the advantage of preventing separation of aluminum in the next process, which increases its industrial value. There is something big about it.

[Brief explanation of the drawing]

1 to 4 show cross sections of a wire at each step of an embodiment of the method according to the present invention. 1, 11 and 12...superconducting wire, 2 aluminum pipe, 3 and 4...copper pipe, 5...
...Gap, 21...Aluminum coating, 22.
...Aluminum matrix, 31 and 41.
...Copper coating.

Claims (1)

[Claims] 1 The process of obtaining a single-fiber composite wire by applying an aluminum coating and a metal or alloy coating with higher deformation resistance than aluminum to the outer periphery of a superconducting wire (or rod), and reducing the surface area of the single-core composite wire. The process of removing the coating from a metal or alloy with high deformation resistance, the single core wires from which the coating has been removed are bundled and inserted into a metal or alloy pipe with higher deformation resistance than aluminum, and the pipe is subjected to an area reduction process together with the pipe. A process of twisting the multi-core composite wire to obtain a multi-core composite wire, and a step of removing a metal or alloy coating having higher deformation resistance than aluminum from the surface of the twisted multi-core composite wire. A method for manufacturing aluminum-coated multicore superconducting wire.