JPH04292805A - Manufacture of oxide superconductive wire - Google Patents

Abstract

PURPOSE:To improve the critical current density by inserting a plurality of element wires in which an oxide super conductor is coated with a metal sheath into a metal tube after the element wires are processed to come into a flat rectangular section shape, and plastic-processing the metal tube. CONSTITUTION:A mixture of Bi2O3, PbO, SrCO3, CaCO3, and CuO in a prescribed ratio is heated, pulverized, and degassed to obtain submicron powder. A silver pipe of 12mm diameter is filled with the powder, the pipe is drawn to become an element wire having 1mm diameter, and the element wire is flat rolled to obtain a flat rectangular section shape element wire 1 composed of an oxide superconductor 4 and the silver sheath 5. Ninety element wires 1 are inserted into a silver pipe 2 having 12mm outer diameter and 10mm inner diameter tightly and a silver rod 3 of 2mm outer diameter is placed in the center of the pipe 2. Drawing process, primary, and secondary flat rolling, and sintering are carried out to make the diameter 1.45mm. Consequently the resulting wire has multicores and the critical current density can be heightened.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an oxide superconducting wire, and more particularly to a method for manufacturing an oxide superconducting wire in which oxide superconductors are multicore.

0002

[Description of related applications] The present applicant has, for example,
No. 87052 proposes an oxide superconducting wire in which oxide superconductors are multicore.

Multi-core oxide superconductors in such an oxide superconductor wire make it possible to reduce the thickness of each oxide superconductor. Reducing the thickness of the oxide superconductor means that a high degree of plastic working is applied to the oxide superconductor, which improves the density of the oxide superconductor and improves crystal orientation. This is effective in realizing a high critical current density.

[0004] Oxide superconductors generally have the disadvantage that their critical current density decreases due to strain such as bending, but by reducing their thickness, the strain resistance of the critical current density can be improved to some extent. can be done.

In the above-mentioned earlier application, as a method for manufacturing an oxide superconducting wire in which oxide superconductors are multicore, a plurality of oxide superconductors each coated with a metal sheath having a circular cross section is used. It is disclosed that a wire material having a circular cross section is inserted into a metal tube having a circular cross section, and plastic working is applied in that state.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an oxide superconducting wire that can provide an even higher critical current density, based on the manufacturing method disclosed in the earlier application as described above. The aim is to provide the following.

[0007]

[Means for Solving the Problems] The present invention includes the steps of preparing a plurality of wires each coated with an oxide superconductor in the form of a metal sheath, processing each wire into a rectangular shape, and processing the wire into a rectangular shape. The method includes a step of inserting a plurality of wire rods into a metal tube, and a step of subjecting the metal tube into which the plurality of wire rods are inserted to plastic working.

[0008]

[Operation] In the present invention, the density of the oxide superconductor is improved and the crystal orientation is improved by subjecting the wire material to rectangular processing. In other words, the oxide superconductor has already become densified and its crystal grains have become oriented before it is inserted into the metal tube. The degree of their densification and orientation is increased.

[0009]

Therefore, according to the present invention, an oxide superconducting wire exhibiting a high critical current density can be obtained.

0010

[Example] Bi2 O3, PbO, SrCO3, C
Using aCO3 and CuO, Bi:Pb:Sr:
Ca:Cu=1.85:0.41:2.01:2.19
: These were blended so that the composition ratio was 2.98. This blend was heated to 750℃ in the atmosphere for 12 hours.
time, then at 800℃ for 8 hours, and then in a reduced pressure atmosphere of 1T.
orr for 8 hours at 760°C. In addition, after each heat treatment, pulverization was performed, respectively. The powder obtained through such heat treatment is further processed into
It was ground using a ball mill to obtain submicron powder. For this powder, 1 at 800°C in a reduced pressure atmosphere
Degassing treatment was performed for 0 minutes.

The obtained powder was filled into a silver pipe with a diameter (outer diameter) of 12 mm, and wire-drawn to a diameter of 1 mm. In this way, a wire material was obtained.

[0012] Thereafter, in an example according to the present invention, the wire material was subjected to flat roll rolling so that the plate thickness reduction rate was 80%. As shown in FIG. 1, the rectangular wire material 1 obtained in this way has an outer diameter of 12 mm and an inner diameter of 10 mm.
90 pieces were inserted tightly into silver pipe 2. A silver rod 3 having an outer diameter of 2 mm was placed at the center of the cross section of the silver pipe 2. In addition, in FIG. 1, 4 is an oxide superconductor, and 5 is a silver sheath.

On the other hand, as a comparative example, the above-mentioned wire material was
The wire was further drawn to a diameter of 0.91 mm. As shown in FIG. 2, the thus obtained wire material 1 with a circular cross section
1 into a silver pipe 12 with an outer diameter of 12 mm and an inner diameter of 10 mm,
90 tubes were inserted tightly. A silver rod 13 having an outer diameter of 0.91 mm was placed at the center of the cross section of the silver pipe 12. In addition, in FIG. 2, 14 is an oxide superconductor, and 15 is a silver sheath.

The composite obtained in the above example and the composite obtained in the comparative example were each wire-drawn to a diameter of 1.45 mm, and then both were wire-drawn at a thickness reduction rate of 70%. After being subjected to flat roll rolling, it was heated at 845°C for 50 hours.
Secondary sintering was performed, then secondary flat roll rolling was performed at a plate thickness reduction rate of 20%, and further secondary sintering was performed at 840° C. for 50 hours.

When the critical current density of the oxide superconducting wire obtained in this manner was measured at liquid nitrogen temperature,
The example showed a value of 4.0 x 104 A/cm2, and the comparative example showed a value of 2.0 x 104 A/cm2. Therefore, it can be seen that according to the present invention, an oxide superconducting wire exhibiting a higher critical current density can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a state in which a plurality of rectangular wire materials 1 are inserted into a silver pipe 2 according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a plurality of wire materials 11 each having a circular cross section are inserted into a silver pipe 12 in a comparative example of the present invention.

[Explanation of symbols]

1. Wire material 2 Silver pipe (metal pipe) 4 Oxide superconductor 5 Silver sheath (metal sheath)

Claims (1)

[Claims] 1. A plurality of strands of oxide superconductor covered with a metal sheath are prepared, each of the strands is processed into a rectangular shape, and the plurality of strands processed into a rectangular shape are inserted into a metal tube. A method for manufacturing an oxide superconducting wire, comprising the steps of: performing plastic working on the metal tube into which a plurality of the wire elements are inserted.