JPH0765643A - Oxide superconducting wire - Google Patents

Abstract

PURPOSE:To improve the mechanical strength of an oxide superconducting wire produced by the Ag sheath method. CONSTITUTION:In an Ag sheath layer 3 a tension member 1 is arranged which is composed of a high strength metal core 11 and an Ag cover layer formed thereon. A superconducting part 2 made of sintered body of oxide superconducting powder is arranged in a gap between the member 1 and the Ag sheath layer 3. By the use of tension member 1 with the Ag cover layer 12, the mechanical strength of the wire is improved without degrading in the superconducting characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of mechanical strength of oxide superconducting wire produced by Ag sheath method.

[0002]

2. Description of the Prior Art One of the methods for forming oxide superconductor wire is
There is a g sheath method. This method is used as the Ag sheath layer
g A raw material powder or synthetic powder of oxide superconductor is filled in a pipe, wire drawing or rolling is performed to make a wire, and then heat treatment is performed to sinter the superconducting powder to obtain an oxide superconducting wire. Is. Therefore, the oxide superconducting wire manufactured by the Ag sheath method is composed of an Ag sheath layer and a sintered layer of oxide superconducting powder loaded inside the Ag sheath layer.

[0003]

Ag used as the sheath layer of the above wire has the advantage that it does not undergo an oxidation reaction with the superconducting powder, but it is a soft metal by nature, and the heating that is performed to form the superconducting phase. Since the treatment further promotes the softening, the obtained wire has a drawback that the mechanical strength is very weak, and there is a drawback that the wire is easily broken when stress is applied.

Therefore, an object of the present invention is to improve the mechanical strength of an oxide superconducting wire produced by the Ag sheath method.

[0005]

In the oxide superconducting wire according to the present invention, a tension member having an Ag coating layer on the surface is arranged inside an Ag sheath layer, and oxidation occurs in a gap between the Ag sheath layer and the tension member. The oxide superconducting wire material loaded with the superconducting powder is heat-treated, and preferably the second sheath layer made of high-strength metal is provided outside the Ag sheath layer.

[0006]

By arranging the tension member inside the Ag sheath layer, the mechanical strength such as tensile strength of the wire can be improved. Further, simply disposing a high-strength metal that can be used as a tension member causes a new problem that the superconducting powder is adversely affected by the diffusion reaction with the superconducting powder. In the present invention, however, an Ag coating layer is formed on the surface of the tension member. Since it is provided, such a problem does not occur, and the presence of the Ag coating layer can keep the crystal orientation of the superconducting phase excellent.

Further, by providing the second sheath layer on the outside of the Ag sheath layer, it is possible to improve the resistance to external damage and the mechanical strength of the wire.

[0008]

The oxide superconducting wire of the present invention will be described below in detail with reference to the drawings. 1 and 2 show an embodiment of the present invention. In the figure, reference numeral 1 denotes a tension member, which is formed by providing an Ag coating layer 12 on the surface of a high-strength metal core material 11. Reference numeral 3 denotes an Ag sheath layer, and 2 denotes a superconducting portion made of a sintered body of oxide superconducting powder, which is loaded in a gap between the tension member 1 and the Ag sheath layer 3. In the embodiment shown in FIG. 2, the second sheath layer 4 made of high-strength metal is provided directly on the Ag sheath layer 3.

As the high-strength metal core material 11 used for the tension member 1, a material having high rigidity and high tensile strength and preferably made of a non-magnetic metal can be used. Examples thereof include stainless steel, Hastelloy, Inconel, tungsten and molybdenum. Also, these metals can be used as the second sheath layer 4.

A provided on the surface of the high-strength metal core material 11
As the g coating layer 12 and the Ag sheath layer 3, Ag or A
The g alloy can be used, and examples of the Ag alloy include Ag-Pt alloy, Ag-Pd alloy, Ag-Cu alloy and the like. The thickness of the Ag coating layer 12 is determined in consideration of the degree of wire drawing, etc., but is 10 μm to 300 μm after wire drawing.
m, preferably about 20 μm to 100 μm. A
If the g coating layer 12 is too thin, the effect of suppressing the above diffusion reaction is weakened, and if it is too thick, the Ag sheath layer 3
The ratio of the volume of the tension member 1 to the internal volume of 1 increases, and the superconducting phase decreases, which is not preferable.

In consideration of the problem of the decrease of the superconducting phase, it is necessary to select the thickness of the core material 11, so that the diameter of the tension member 1 becomes larger than the inner diameter of the Ag sheath layer 3.
The setting of about 4/5 to 1/15, preferably about 3/5 to 1/10 does not impair the mechanical strength reinforcing effect of the tension member 1 and does not reduce the superconducting phase so much. Is preferred.

The superconducting portion 2 is composed of a sintered body of oxide superconductor powder. The oxide superconductor powder used is, for example, a composition for superconducting prepared by an appropriate method such as a solid phase method or a coprecipitation method, which is subjected to a sintering treatment, and has a particle size of 100 μm or less, particularly 0.1 to 10 μm. It can be obtained by a method such as pulverizing to a powder of a certain degree. There is no particular limitation on the type of oxide superconductor. As an example, Bi ₂ Sr ₂ Ca
Bi-based oxide superconductors such as Cu ₂ O _y and Bi _2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _y , YBa ₂ Cu ₃ O _y and Y
Y-based oxide superconductor such as Ba ₂ Cu ₄ O _y , Ba
Ba-based oxide superconductors such as _1-x K _x BiO ₃ , Nd
Nd-based oxide superconductors such as _2-x Ce _x CuO _y , other La-based oxide superconductors, Tl-based oxide superconductors, P
Examples thereof include b-based oxide superconductors.

Further, the above-mentioned components such as Bi are substituted with other rare earth elements, the components such as Sr are substituted with other alkaline earth metals, and the O components are substituted with F and the like. To be Furthermore, the thing containing the pinning center etc. are mentioned. The pinning center-containing oxide superconductor has the advantage of exhibiting a large critical current density even under a high magnetic field due to the effect of pinning the magnetic flux by the pinning center. The oxide superconductor containing the pinning center can be obtained by, for example, the MPMG method.

The oxide superconducting wire of the present invention is, for example, Ag.
The tension member 1 is arranged near the center in the Ag tube which becomes the sheath layer 3, the gap between the tube and the tension member 1 is charged with the above oxide superconducting powder, and then this is wire-drawn to an appropriate outer diameter. Then, an oxide superconducting wire material is produced, and finally the material is heat-treated to sinter the built-in oxide superconducting powder.

The wire drawing can be carried out by an appropriate method such as a swaging method, a groove roll method, a die method. When drawing wire, if necessary,
For example, by adding a rolling process through a pinch roll or the like, it can be formed into an appropriate cross-sectional shape such as a tape shape according to the purpose of use.

The above heat treatment is for bulking the oxide superconducting powder in the Ag sheath layer 3 to integrate it. The temperature is appropriately determined according to the oxide superconducting powder used and the like, and is generally 700 to 1200 ° C. The heat treatment may be performed in a pressurized atmosphere, for example, by storing the object to be sintered in a closed heat-resistant pressure-resistant container. The pressurized atmosphere acts as an external pressure that prevents sintering swelling.

A large number of the above-mentioned oxide superconducting wire materials are prepared, bundled and loaded into an appropriate metal tube,
The above heat treatment may be performed after the wire drawing process.

[0018]

As described above, according to the oxide superconducting wire of the present invention, since the tension member is incorporated in the Ag sheath layer, the mechanical strength of the wire can be improved. Therefore, it is advantageous for laying a portion where a strong stress is applied to the wire. Further, since the Ag coating layer is provided on the surface of the tension member, a diffusion reaction does not occur, and the presence of this Ag coating layer keeps the orientation of the superconducting phase excellent,
The mechanical strength can be improved without deteriorating the superconducting property.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an oxide superconducting wire according to the present invention.

FIG. 2 is a cross-sectional view showing another example of the oxide superconducting wire according to the present invention.

[Explanation of symbols]

 1 Tension member 11 High-strength metal core material 12 Ag coating layer 2 Superconducting part 3 Ag sheath layer 4 Second sheath layer

Claims (2)

[Claims] 1. A material for an oxide superconducting wire in which a tension member having an Ag coating layer on the surface is arranged inside an Ag sheath layer, and an oxide superconductor powder is loaded in a gap between the Ag sheath layer and the tension member. Oxide superconducting wire made by heat treatment. 2. The oxide superconducting wire according to claim 1, wherein a second sheath layer made of a high-strength metal is provided outside the Ag sheath layer.