JP2644244B2 - Method for producing oxide-based superconducting wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a method for manufacturing an oxide-based superconducting wire.

(Prior Art) Recently, an oxide-based compound superconductor having a composition represented by Y—Ba—Cu—O has been attracting attention. Many of these oxide-based compound superconductors have a critical temperature higher than the temperature of liquid nitrogen. For this reason, it is not necessary to use expensive and difficult-to-handle liquid helium as a refrigerant, and it is expected that the superconducting technology will be drastically developed.

Incidentally, in order to expand the applicability of the oxide-based compound superconductor, it is necessary to obtain a wire material such as a normal lead wire. Oxide-based compound superconductors are so-called pottery and are very brittle. Therefore, it is very difficult to convert the oxide-based compound superconductor into a wire. For this reason, various proposals for making a wire rod have been conventionally made.

In these proposals, a silver pipe serving as a sheath was filled with a powder raw material capable of synthesizing an oxide-based compound superconductor, subjected to surface reduction processing, and then heat-treated in an oxygen atmosphere. There is a method of synthesizing a compound superconductor. In this method, necessary circuit elements are formed by thin wires formed by surface reduction processing, and then heat-treated in an oxygen atmosphere to synthesize a compound superconductor from the powder raw material. In this case, the silver pipe, that is, the silver sheath, facilitates the penetration of oxygen into the interior during the heat treatment, and facilitates the formation of the compound superconductor layer. According to this method, there is no need to apply an external force to the wire after the heat treatment, so that there is no risk of damaging the formed compound superconductor layer. Therefore, it is possible to manufacture a substantially long wire.

However, the conventional manufacturing method described above has the following problems. That is, according to the research so far, the superconductivity of the synthesized oxide-based compound superconductor largely depends on the supply amount of oxygen during the heat treatment. That is, as the supply amount of oxygen increases, a material exhibiting superior superconductivity can be synthesized. In the conventional manufacturing method,
Oxygen diffuses inside the silver sheath and is supplied to the inside. Silver is more permeable to oxygen than other metals. However, a certain thickness is required to exert the function as a sheath. As the thickness increases, the amount of permeated oxygen decreases. For this reason, the conventional manufacturing method has reached the limit in improving the superconductivity.

(Problems to be Solved by the Invention) As described above, in the conventional silver sheath method, it was essentially difficult to improve the superconducting characteristics.

Accordingly, an object of the present invention is to provide a manufacturing method that can easily manufacture an oxide-based superconducting wire having high superconducting characteristics while employing a silver sheath method.

[Structure of the Invention] (Means for Solving the Problems) In the manufacturing method according to the present invention, a silver pipe serving as a sheath is filled with a raw material capable of synthesizing an oxide-based compound superconductor, and reduced. A step of forming a thin line by performing surface processing, and a step of forming a thin line obtained by this step into a rectangular wire;
The above-mentioned object is achieved by a step of forming localized thin-walled portions along the longitudinal direction in the obtained rectangular silver sheath and a step of subsequently heat-treating the compound superconductor in an oxygen atmosphere. doing.

(Operation) When heat treatment is performed in an oxygen atmosphere, a large amount of oxygen penetrates into the inside through local thin portions scattered and formed in the silver sheath. Therefore, it is possible to supply a larger amount of oxygen to the raw material than the conventional manufacturing method without impairing the function of the sheath, and as a result, it is possible to improve the superconductivity.

(Example) Hereinafter, an example is described with reference to drawings.

FIG. 1 is a view for explaining an intermediate step of the manufacturing method of the present invention. That is, in the figure, reference numeral 1 denotes a thin line formed by filling a silver pipe serving as a sheath with a raw material and subjecting the raw material to surface reduction processing. In this example, a mixture of yttrium oxide powder, barium carbonate powder, and copper oxide powder mixed at a molar ratio of 0.5: 1.0: 3.0 is used as a raw material.

The thin wire 1 is guided to a forming machine 3 composed of a pair of rotating pressure rollers 2a and 2b, and is formed into a rectangular wire 4. The rectangular wire 4 is formed by coating a raw material 5 with a thin silver sheath 6 as shown in the cross section in FIG. Pressing machines 7a and 7b are arranged on both sides of the flat wire 5 on the lower grain side of the molding machine 3. These pressurizing machines 7a and 7b use a flat wire 4
The shafts 8a and 8b are provided so as to be perpendicular to the moving direction of the rectangular wire 4 and opposed to both sides in the thickness direction of the flat wire 4, and are driven to rotate in the direction of the arrow in the embodiment by a driving source (not shown).
And pressing pins 9a and 9b projecting from the outer peripheral surfaces of the shafts 8a and 8b and pressing the silver sheath 6 at the distal end with the distal end positioned in the thickness direction of the flat wire 4 at the distal end. Therefore, when the flat wire 4 passes through the position where the pressurizers 7a and 7b are provided, as shown in FIG. 2, the thin portions 11 are arranged in a line in the silver sheath 6 located in the thickness direction. Will be formed.

In this embodiment, as described above, the thin portion 11
After forming a coil with the rectangular wire 4 in which scattered dots were formed, heat treatment was performed in an oxygen atmosphere at 920 ° C. for 5 hours, and a compound superconductor was synthesized in the raw material 5 by this heat treatment.

When the characteristics of the oxide-based superconducting wire thus manufactured were examined, it was confirmed that the critical current density was improved by 50% as compared with the case where the thin portion 11 was not provided. This is because the thin portion 11 provided with oxygen in the silver sheath 6 during the heat treatment.
It is thought to be the result of a large amount of permeation into the interior through.

The present invention is not limited to the above embodiment. That is, the raw material for synthesizing the oxide-based compound superconductor is not limited to the yttrium-based one.

[Effects of the Invention] As described above, according to the manufacturing method of the present invention, a large amount of oxygen can be supplied at the time of heat treatment without leaking the raw material out of the sheath. Superconducting wire can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment in an intermediate step of the manufacturing method of the present invention, and FIG. 2 is a local sectional view of a flat wire after the intermediate step. 1 ... fine wire after surface reduction, 3 ... molding machine, 4 ... rectangular wire, 5 ...
… Raw material, 6… silver sheath, 7a, 7b …… pressing machine, 11… thin section.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akira Murase 1 Toshiba-cho, Komukai, Koyuki-ku, Kawasaki City, Kanagawa Prefecture (56) References JP-A-63-298918 (JP, A) JP-A-63-298918 JP-A-1-163910 (JP, A) JP-A-64-71006 (JP, A) JP-A-1-112609 (JP, A)

Claims (2)

(57) [Claims] 1. A step of filling a silver pipe serving as a sheath with a material capable of synthesizing an oxide-based compound superconductor, performing a surface reduction process on the raw material, and thinning the thin line. Into a rectangular wire, a step of forming localized thin portions along the longitudinal direction in the obtained silver sheath of the rectangular wire, and then a heat treatment in an oxygen atmosphere to form the compound superconductor. A method for producing an oxide-based superconducting wire, comprising the steps of: 2. The oxide-based superconducting wire according to claim 1, wherein said raw material is capable of synthesizing a compound superconductor represented by Y—Ba—Cu—O. Production method.