JP2001118444A - Oxide superconductive wire and method for fabrication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of fabricating an oxide superconductive wire that improves Jc at low cost without performing a positive tape-shaping process. SOLUTION: An oxide superconductive core filament 11 is coated with a metal coating 12 to form a wire element 10. Two wire elements 10 are arranged adjacent to each other to form a first wire collection 17, which is radially compressed for the wire element to flow into a first space S1 inside a first imaginary circle C1 to produce a first composite wire 18 of circular cross section. A plurality n of first composite wires are arranged adjacent to one another to form a second wire collection 22 with the vertically bisectional lines 24 of the division line 23 intersecting the center of a second imaginary circle C2 tangent to the first composite wires. The second wire collection is radially compressed for the first composite wires to flow into a second space S2 inside the second imaginary circle C2 to produce a second composite wire 25 of circular cross section, which is imparted with superconductivity by heat treatment to obtain an oxide superconductive wire 27.

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 a superconducting wire suitable for use in superconducting coils, superconducting cables, and other applications.

[0002]

2. Description of the Related Art An oxide superconducting wire in which an oxide superconductor filament composed of an oxide superconductor is coated with a metal such as silver or a silver alloy has been developed. Up to now, oxide superconducting wires generally have a tapered cross section. This is because the density of the oxide superconductor can be improved by molding the wire into a tape shape,
The contact area between the coated metal and the oxide superconductor can be increased,
Further, since the interface between the coating metal and the oxide superconductor can be smoothed, a high critical current density (hereinafter, referred to as “Jc”) can be realized.

[0003] The reason for this is that, for example, as described in the 56th Spring Meeting of the 1997 Society of Low Temperature Engineering and Superconductivity, P22, the oxide superconducting wire is formed into a tape shape during the heat treatment for superconductivity for exhibiting superconductivity. At the interface between the coating metal silver or silver alloy and the oxide superconductor,
This is because a good degree of orientation is obtained in the crystal structure of the oxide superconductor, and as a result, Jc of the oxide superconducting wire increases.

[0004] However, when the oxide superconducting wire is tape-shaped, it is difficult to control the thickness and dimensions in manufacturing the superconducting coil and the like, and there is a difficulty in forming a solenoid-shaped coil and the like.

Therefore, recently, an oxide superconducting wire having a round cross section and a high Jc has been desired.

Hitherto, a method for producing an oxide superconducting wire having a round cross section has been proposed.

As a first method, a metal tube of silver or the like is filled with an oxide superconducting precursor powder, subjected to diameter reduction by extrusion or wire drawing, and then subjected to a superconducting heat treatment or a metal tube. A composite billet is prepared by filling the oxide superconducting precursor powder inside, and a plurality of this composite billet is further incorporated into another metal tube such as silver, and these are subjected to diameter reduction processing by extrusion or drawing. Then, a method of performing a superconducting heat treatment has been proposed. (For example, 53rd
Of the 1995 Low Temperature Engineering and Superconductivity Society of Japan
77, 57th Fall Meeting of 1997 Low Temperature Engineering and Superconductivity Society P82).

[0008] As a second manufacturing method, a plurality of oxide superconducting precursor powders coated with a metal and processed into a tape shape are laminated and incorporated into a metal tube, and then extruded or drawn. A method has been proposed in which Jc is improved by performing diameter reduction processing and then performing a superconducting heat treatment (Japanese Patent Laid-Open No. 9-223418).

[0009]

However, in the above-mentioned first manufacturing method of the prior art, the density of the oxide superconductor is low, and the oxide superconductor has a small smooth area at the interface with the coating metal. Jc of the superconducting wire was still low. Further, in the second manufacturing method, although Jc of the oxide superconducting wire can be secured to some extent, a step of processing into a tape in the manufacturing process is indispensable, and a great deal of time and cost are required for producing the oxide superconducting wire. I was

Accordingly, the present invention solves the above-mentioned disadvantages of the prior art, and does not require an aggressive tape-like processing step.
It is an object of the present invention to provide a method for manufacturing an oxide superconducting wire and an oxide superconducting wire capable of improving the resistance.

[0011]

According to the first aspect of the present invention, two or more wires each having a coating metal provided on the outer periphery of one or more oxide superconductor core filaments and having a substantially circular cross section are arranged adjacently. Then, a first aggregated wire rod is formed, and then one of the element wires is placed in a first space formed by a first imaginary circle in contact with the two wire surfaces and two adjacent wire surfaces. The first aggregated wire is reduced in diameter so as to allow the material to flow through the portion to produce a first composite wire having a circular cross-section, and then n pieces of the first composite wire are arranged adjacent to each other to form a first composite wire. In this case, the two bisected wires are used. At this time, the perpendicular bisectors of the dividing lines between the original wires in each of the first composite wires are formed in all the n lines along the longitudinal direction of the first composite wire. Set so that it always passes through the center of the second virtual circle that is in contact with the surface of the first composite wire of The second aggregated wire is reduced in diameter so that a part of the first composite wire flows through a second space formed by the second virtual circle and the surfaces of the n first composite wires. A second composite wire having a circular cross section is produced, and thereafter, the second composite wire is subjected to a superconducting heat treatment to produce an oxide superconducting wire.

According to a second aspect of the present invention, in the first aspect of the present invention, when forming the second aggregated wire, each of the n first composite wires constituting the second aggregated wire is provided. In the case where the twist of the same pitch is applied, the perpendicular bisector of the dividing line between the original wires in each of these first composite wires is formed on the surface of all n first composite wires. The first composite wire was set to pass through the center of the imaginary second imaginary circle to perform the initial alignment of the first composite wire, and then the first composite wire was matched with the twist pitch of the first composite wire itself. The second aggregated wire is formed by twisting at a pitch.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the diameter reduction processing of each of the first aggregated wire and the second aggregated wire has a cross-sectional reduction rate of 70% or more. The aspect ratio of the oxide superconductor core filament of the first composite wire is 1.5 or more, and the aspect ratio of the oxide superconductor core filament of the second composite wire is 3.0 or more. It is.

The invention described in claim 4 is the first to third aspects of the present invention.
In the invention described in any one of the above, after the diameter reduction of the second aggregated wire, a superconducting heat treatment is performed on the second composite wire produced by the diameter reduction.

[0015] The invention according to claim 5 provides the invention according to claims 1 to 4.
In the invention described in any one of the above, the superconducting heat treatment is performed at a temperature of 700 to 950 ° C. and an oxygen partial pressure of 0.01 to 10
It is performed in an atmosphere of atm.

[0016] The invention according to claim 6 is the invention according to claims 1 to 5.
In the invention described in any one of the above, the oxide superconductor core filament is a Bi-2212 phase or a Bi-2223 phase having Bi, Sr, Ca, and Cu.

[0017] The invention according to claim 7 is the invention according to claims 1 to 6.
In the invention described in any one of the above, the main oxide superconductor of the oxide superconductor core filament is Bi, P
It is a Bi-2212 phase or Bi-2223 phase comprising b, Sr, Ca and Cu.

[0018] The invention according to claim 8 is the first grouping in which one or a plurality of oxide superconductor core filaments are provided with a coating metal on the outer periphery and two adjacent wires having a substantially circular cross section are arranged adjacent to each other. Then, a part of the wire is caused to flow into a first space formed by a first virtual circle in contact with the two wire surfaces and two adjacent wire surfaces. The first aggregated wire is reduced in diameter to produce a first composite wire having a circular cross section. Next, n pieces of the first composite wire are arranged adjacent to each other to form a second aggregated wire. At this time, the perpendicular bisectors of the division lines between the original wires in each of the first composite wires are formed in all of the n first composite wires over the longitudinal direction of the first composite wires. It is set so that it always passes through the center of the second virtual circle that is in contact with the surface of the wire, The second aggregated wire is reduced in diameter so as to allow a part of the first composite wire to flow into a second space formed by the virtual circle and the surfaces of the n first composite wires, and is traversed. A second composite wire having a face circle shape is produced, and thereafter, the second composite wire is subjected to a heat treatment for superconductivity, thereby producing the composite wire.

According to a ninth aspect of the present invention, in the invention of the eighth aspect, when forming the second aggregated wire, each of the n first composite wires constituting the second aggregated wire is provided. In the case where the twist of the same pitch is applied, the perpendicular bisector of the dividing line between the original wires in each of these first composite wires is formed on the surface of all n first composite wires. The initial alignment of the first composite wire is set so as to always pass through the center of the second imaginary circle that is in contact with the first composite wire, and then the first composite wire is matched with the twist pitch of the first composite wire itself. The second aggregated wire is formed by twisting at a different pitch.

According to a tenth aspect of the present invention, in the invention of the eighth or ninth aspect, the diameter reduction of each of the first aggregated wire and the second aggregated wire is performed by a cross-sectional reduction rate of 70%.
The aspect ratio of the oxide superconductor core filament of the first composite wire is 1.5 or more, and the aspect ratio of the oxide superconductor core filament of the second composite wire is 3.0 or more. Is what you do.

According to an eleventh aspect of the present invention, in the invention according to any one of the eighth to tenth aspects, after the second aggregated wire is subjected to the diameter reducing process, the second aggregated wire rod is manufactured by the diameter reducing process. The composite wire is subjected to a heat treatment for superconductivity.

According to a twelfth aspect of the present invention, in the invention according to any one of the eighth to eleventh aspects, the superconducting heat treatment is performed at a temperature of 700 to 950 ° C. and an oxygen partial pressure of 0.01 to 0.01.
It is performed in an atmosphere of 10 atm.

According to a thirteenth aspect of the present invention, in the invention according to any one of the eighth to twelfth aspects, the oxide superconductor core filament has a Bi-2212 phase comprising Bi, Sr, Ca and Cu. Alternatively, it is a Bi-2223 phase.

According to a fourteenth aspect of the present invention, in the invention according to any one of the eighth to thirteenth aspects, the main oxide superconductor of the oxide superconductor core filament is Bi,
Bi-2212 comprising Pb, Sr, Ca and Cu
Phase or Bi-2223 phase.

The first, fourth, sixth to eighth, eleventh, thirteenth, and fourteenth aspects of the invention have the following effects.

The first aggregated wire rod is made to flow a part of the wire into a first space formed by the first virtual circle contacting the two wire surfaces and the two adjacent wire surfaces. Since the diameter is reduced to produce the first composite wire with a circular cross section,
At the time of this diameter reduction processing, a part of the material of the strand flows uniformly into the first space, so that the aspect ratio of the oxide superconductor core filament in the first composite wire can be made larger than before the diameter reduction processing.

Further, n first composite wires are arranged adjacent to each other to form a second aggregated wire, and at this time, a perpendicular bisector of a dividing line between the original wires in each of the first composite wires is provided. Is set so as to always pass through the center of the second imaginary circle in contact with the surface of all n first composite wires over the longitudinal direction of the first composite wire. The second aggregated wire is reduced in diameter so as to allow a part of the first composite wire to flow into a second space formed by the surfaces of the n first composite wires, and the second cross-sectionally circular second shape is formed. Since the composite wire is manufactured, a part of the material of the first composite wire uniformly flows into the second space during the diameter reduction processing, so that the aspect ratio of the oxide superconductor core filament in the second composite wire is reduced. It can be larger than before diameter machining.

From these facts, the density of the oxide superconductor core filament in the second composite wire can be increased, and the surface (interface) where the oxide superconductor core filament in the second composite wire contacts the coated metal.
And the area of the smooth surface can be increased. As a result, the crystal structure of the oxide superconducting core filament in the oxide superconducting wire after the superconducting heat treatment of the second composite wire is improved, especially in the vicinity of the interface with the coated metal, and the degree of orientation is improved. The Jc of the oxide superconducting wire can be improved without requiring a processing step.

The second and ninth aspects of the invention have the following effects.

When the n first composite wires constituting the second aggregated wire are twisted at the same pitch, the dividing line between the original wires in each of the first composite wires is used. Is set to always pass through the center of the second imaginary circle that is in contact with the surface of all n first composite wires to perform the initial alignment of the first composite wire,
Next, since the first composite wire is twisted at a pitch that matches the twist pitch of the first composite wire itself to form a second aggregated wire, the initial position of the first composite wire is , Does not change in the longitudinal direction of each first composite wire. Therefore, even when the first composite wire is twisted, the aspect ratio in the oxide superconductor core filament of the second composite wire composed of the n first composite wires is set to the first composite wire. It can be larger. Therefore, also in this case, the degree of orientation of the crystal structure of the oxide superconducting core filament in the oxide superconducting wire can be improved, and an active tape-like processing step is not required. Can be improved.

The third and tenth aspects of the invention have the following effects.

If the reduction rate of the cross section of the first aggregated wire and the second aggregated wire is less than 70%, the first or second space is not completely filled even by the material flow of the element wire or a part of the first composite wire. There is a possibility that the aspect ratio and densification of the oxide superconductor core filament become insufficient and J
c cannot be expected to improve, but the cross-sectional reduction rate is 70%.
% Or more, the above problem can be solved.

The invention according to claims 5 and 12 has the following effects.

The superconducting heat treatment is performed at a temperature (preferably 700 to 950 ° C.) at which a liquid phase is formed in at least a part of the oxide superconductor core filament, and an oxygen partial pressure of 0.
Since the heat treatment was performed in an atmosphere of 01 to 10 atm, the oxide superconductor material or a precursor thereof became a liquid phase by such heat treatment, and then nucleated from the contact surface with the coating metal to grow along the surface. To form a crystalline structure with a good degree of orientation,
The aspect ratio of the oxide superconductor core filament can be improved, and the smooth surface of the interface between the core filament and the coating metal can be increased.

[0035]

Embodiments of the present invention will be described below with reference to the drawings. [A] First Embodiment (FIGS. 1 and 2) FIG. 1 is a process chart showing a first embodiment of a method for manufacturing an oxide superconducting wire according to the present invention.

(1) First, two wires 10 each having an oxide superconductor core filament 11 coated with a coating metal 12 are prepared. This wire 10 is a silver or silver alloy pipe 1
5 is filled with an oxide superconducting precursor powder 14 to form a composite billet 13, or a single-core filament obtained by reducing the diameter of the composite billet 13, or
A bundle of a plurality of such wires 10 may be inserted into another silver or silver alloy pipe, and may be any of so-called multifilament wires obtained by reducing the diameter of the pipes.

(2) Next, these wires 10 are not processed into a tape shape, that is, while the cross-sectional shapes of the wires 10 and the oxide superconductor core filaments 11 are kept substantially circular. Then, two pieces are inserted into another silver or silver alloy pipe 16 to form a first aggregated wire rod 17.
At this time, the wire 10 is symmetrically arranged adjacent to the inside of the pipe 16. However, the outer diameter of the wire 10 and the pipe It is preferable to select 16 inner diameters.

At this time, the first space S1 formed by the first imaginary circle C1 (that is, the inner surface of the pipe 16) in contact with the surface of the wire 10 and the surface of two adjacent wires 10 has the following reduced diameter. By processing (procedure (3)), an area large enough to allow a part of the wire 10 to flow through the material in a cross-sectional direction substantially perpendicular to the longitudinal direction of the wire 10 is secured.

(3) Next, the first aggregated wire rod 17 is reduced in diameter by a usual method such as drawing to produce a first composite wire rod 18 having a circular cross section. This diameter reduction processing is performed in the first space S1 formed by the first virtual circle C1 (or the inner surface of the pipe 16) and the surfaces of the two adjacent wires 10, substantially perpendicular to the longitudinal direction of the wires 10. A part of the element wire 10 is caused to flow in a material in a cross section direction. This material flow results in deformation of each of the oxide superconductor core filaments 11 having a substantially circular cross section into a semicircle or a rectangular shape, and at the same time, a coating metal 19 around each oxide superconductor core filament 11. To cover.

By appropriately selecting (for example, 70% or more) the cross-section reduction rate by the diameter reduction processing, the aspect ratio of the oxide superconductor core filament 11 of the strand 10 of the strand 10 in the first composite wire 18 is determined. The major axis length / minor axis length in the cross section of the core filament 11) can be set to 1.5 or more by this surface reduction processing. As a result, compared to a wire having an aspect ratio of approximately 1 and having a normal circular cross section, a larger smooth surface of the oxide superconductor core filament 11 can be secured, and the denseness of the core filament 11 can be increased. .

(4) Next, in order to further increase the aspect ratio of the oxide superconductor core filament 11, n (n
= 2 to 19) The first (three in this embodiment) first composite wire 18 is inserted into another silver or silver alloy pipe 20 while keeping its cross-sectional shape substantially circular. They are aggregated to form a second aggregated wire rod 22. At this time, the dividing line 23 between the original strands 10 in each of the first composite wires 18
Are perpendicular to each other, and all n (three) of the first composite wires 1 extend along the longitudinal direction of the first composite wire 18.
8 is set so as to always pass through the center O of the second virtual circle C2 in contact with the surface of the second virtual circle C2.

When the first composite wire 18 is not twisted, the alignment of the first composite wire 18 is performed in such a manner that the division line 23 between the original wires 10 in the first composite wire 18 is perpendicular to the second composite wire 18. This is realized by performing initial alignment so that the dividing line 24 passes through the center O of the second virtual circle C2, and holding this initial position along the longitudinal direction of the first composite wire 18.

(5) Next, while holding the position of each first composite wire 18 in the second aggregated wire 22 at the position shown in the above procedure (4), the second aggregated wire 22 is drawn. Perform diameter reduction processing such as. Due to this diameter reduction processing, a part of the material of each first composite wire 18 is formed in the second space S2 formed by the inner surface of the pipe 20 as the second virtual circle C2 and the surface of each first composite wire 18. To form a second composite wire 25 having a circular cross section.

At this time, the cross-sectional reduction rate (that is, the area reduction rate) in the above-mentioned diameter reduction processing is set to 70% or more. When the area reduction ratio is less than 70%, the second space S2 in the second aggregated wire rod 22 may not be completely filled by a part of the first composite wire rod 18, and the aspect ratio of the oxide superconductor core filament 11 may be reduced. Ratio improvement (for example, an aspect ratio of 3.
0 or more) or the denseness of the oxide superconductor core filament 11 becomes insufficient, so that an improvement in Jc cannot be expected.

In the second composite wire 25 produced by this diameter reducing process, the oxide superconductor core filament 11 is deformed into an elliptical or rectangular shape, and the periphery of each oxide superconductor core filament 11 is covered with a coating metal. 19 and the pipe 20 are covered with a covering metal 26 formed by deformation.

(6) Finally, the second composite wire 25 produced in the step (5) is subjected to a superconducting heat treatment, so that the oxide superconducting precursor of the oxide superconducting core filament 11 is converted to an oxide superconducting material. To the desired oxide superconducting wire 2
Get 7.

One example of the heat treatment for superconductivity is performed at a temperature (preferably 700 to 950 ° C.) at which a liquid phase is generated in at least a part of the oxide superconductor core filament 11 and in an atmosphere having an oxygen partial pressure of 0.01 to 10 atm. It is preferable to carry out in. This is because, by such a heat treatment, the oxide superconducting precursor becomes a liquid phase, then nucleates from the interface with the coating metal 26, grows along the surface, and forms a crystal structure with a good degree of orientation. This is because the effect of increasing the aspect ratio of the oxide superconductor core filament 11 and increasing the smooth surface of the core filament 11 at the interface with the coating metal 26 is thereby significantly increased.

That is, the crystal structure 28 in the oxide superconductor core filament 11 after the heat treatment for superconductivity is shown in FIG.
As shown in (A), the degree of orientation becomes good near the interface in contact with the coating metal 26, and as a result, Jc of the oxide superconducting wire 27 can be improved.

Therefore, according to the above embodiment, the following effects are obtained.

The first imaginary circle C1 in contact with the surface of the two wires 10 and the surface of the two adjacent wires 10 are formed into a first space S1 formed by the first virtual circle C1 so that a part of the wires 10 flows in the first space S1. Since the diameter of the aggregated wire 17 is reduced to produce the first composite wire 18 having a circular cross section,
Since a part of the material of the wire 10 flows uniformly in the first space S1, the aspect ratio of the oxide superconductor core filament 11 in the first composite wire 18 can be made larger than before the diameter reduction processing.

Further, the n first composite wires 18 are arranged adjacent to each other to form a second aggregated wire 22, and at this time, the division lines 23 between the original wires 10 in each of the first composite wires 18 are formed. The perpendicular bisector 24 is the first composite wire 1
8 is set so as to always pass through the center O of the second imaginary circle C2 in contact with the surface of all n first composite wires 18 over the longitudinal direction of the second composite wire 18, and then the second imaginary circle C2 and n The second aggregated wire rod 22 is reduced in diameter so that a part of the first composite wire rod 18 flows into the second space S2 formed between the first composite wire rod 18 and the surface of the first composite wire rod 18 to form a second cross-sectional circle. Double composite wire 2
5 is manufactured, a part of the material of the first composite wire 18 flows uniformly into the second space S2 during the diameter reduction processing. The ratio can be made larger than before the diameter reduction processing.

From these facts, the density of the oxide superconductor core filament 11 in the second composite wire 25 can be increased, and the oxide superconductor core filament 11 in the second composite wire 25
The smoothness of the surface (interface) in contact with 6 can be enhanced, and the area of this smooth surface can be increased. As a result, the crystal structure 28 of the oxide superconducting core filament 11 in the oxide superconducting wire 27 after the superconducting heat treatment of the second composite wire 25 has a good degree of orientation, particularly near the interface with the coating metal 26, The Jc of the oxide superconducting wire 27 can be improved at low cost without requiring an active tape-like processing step.

When the reduction rate of the cross section of the first aggregated wire 17 and the second aggregated wire 22 is less than 70%, the first space S1 or the second space S2 is a part of the material of the strand 10 or the first composite wire 18. There is a possibility that the oxide superconductor core filament 11 may not be completely buried even by the flow, and the improvement of the aspect ratio and the densification of the oxide superconductor core filament 11 become insufficient, so that the improvement of Jc cannot be expected. Since the ratio is set to 70% or more, the above problem can be solved.

The heat treatment for superconductivity is performed at a temperature (preferably 700 to 950 ° C.) at which a liquid phase is generated in at least a part of the oxide superconductor core filament 11 and in an atmosphere having an oxygen partial pressure of 0.01 to 10 atm. From
By such a heat treatment, the oxide superconducting precursor becomes a liquid phase, and then nucleates from the contact surface with the coating metal 26 and grows along the surface to form a crystal structure 28 with a good degree of orientation. The aspect ratio of the body core filament 11 can be improved, and the smooth surface of the oxide superconductor core filament 11 at the interface with the coating metal 26 can be increased.

[B] Second Embodiment (FIG. 3) FIG. 3 is a process chart showing a second embodiment of the method for producing an oxide superconducting wire according to the present invention. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
In the second embodiment, procedures (2) and (4) in the manufacturing process of the first embodiment are different from those of the first embodiment.

That is, in the present embodiment, the procedure (2) corresponding to the production procedure (2) of the first embodiment is described.
In a), the wire 10 is not processed into a tape shape, that is, the wire 10 and the oxide superconductor core filament 11 are not processed.
The two strands 10 are arranged adjacent to each other and twisted together while keeping the cross-sectional shape of each of them substantially circular to form the first aggregated wire rod 31.

At this time, the first space S3 formed by the first imaginary circle C3 in contact with the surface of the two wires 10 and the surface of the two adjacent wires 10 has the following diameter reduction processing ( According to the procedure (3)), a part of the wire 10 is subjected to material flow in a cross-sectional direction substantially perpendicular to the longitudinal direction of the wire 10.

In this embodiment, a procedure (4) corresponding to the procedure (4) of the manufacturing process of the first embodiment is described.
In a), n (n = 2 to 19) (3 in this embodiment)
The second composite wire rod 32 is formed by twisting the first composite wire rod 18 of the present invention while keeping its cross-sectional shape substantially circular. At this time, the perpendicular bisector 24 of the dividing line 23 between the original wires 10 in each of the first composite wires 18 is n (three) in the longitudinal direction of the first composite wire 18.
Are set so as to always pass through the center Oa of the second virtual circle C4 in contact with the surfaces of all the first composite wires 18.

Since the first composite wire 18 is twisted, the first composite wire 18 is first aligned with the split lines 2 between the original wires 10 in each of n (three) wires.
3 is the center O of the second virtual circle C4.
a, and then pass these n
The first (3) first composite wires 18 are combined with the first composite wire 1
By twisting at a pitch that matches the twist position of the wire itself, the initial position is held and realized along the longitudinal direction of the first composite wire.

In this case, in the next step (5) of reducing the diameter of the second aggregated wire 32, the second aggregated wire 32 is formed between the adjacent n (three) wires 10 surfaces. Part of the material of the strand 10 flows into the second space S4 to be formed, and the second composite wire 25 is produced.

Therefore, according to the above embodiment, in addition to the same effects as those of the first embodiment, the following effects can be obtained.

[0062] The n (3
In the case where the first composite wires 18 are twisted at the same pitch, the perpendicular bisector 24 of the dividing line 23 between the original wires 10 in each of the first composite wires 18 is used. However, the position of the first composite wire 18 is set so as to always pass through the center Oa of the second virtual circle C4 in contact with the surface of all n (three) first composite wires 18, and the next alignment is performed. The second composite wire 18 is formed by twisting the first composite wire 18 at a pitch that matches the twist pitch of the first composite wire 18 itself. The position does not change over the longitudinal direction of each first composite wire 18. Therefore, even when the first composite wire 18 is twisted, these n
The aspect ratio of the second composite wire 25 composed of the three (three) first composite wires 18 in the oxide superconductor core filament 11 can be made larger than that of the first composite wire 18. Therefore, also in this case, similarly to the effect of the first embodiment, the degree of orientation of the crystal structure 28 of the oxide superconducting core filament 11 in the oxide superconducting wire 27 can be improved, and aggressive tape-like processing can be performed. The Jc of the oxide superconducting wire 27 can be improved at low cost without requiring any process.

Here, in the first and second embodiments, the oxide superconductor core filament 11, the element wire 1
The term “substantially circular” that defines the cross-sectional shape of 0 and the first and second composite wires 18 and 25 is a concept that includes not only a circle but also a symmetric N-gon (N is 6 or more).

The oxide superconductor core filament 1
1 is Bi-2 comprising Bi, Sr, Ca and Cu
212 phase or Bi-2223 phase, or Bi, S
It is preferably a Bi-2212 phase or a Bi-2223 phase containing r, Pb, Ca and Cu.

Hereinafter, examples of the present invention will be described together with comparative examples.

Here, since Example 1 corresponds to the first embodiment and Examples 2 and 3 correspond to the second embodiment, the description of Example 1 refers to FIG. Reference is made to FIG. 3 in the description of Examples 2 and 3. Example 1 Each powder of Bi ₂ O ₃ , SrCo ₃ , CaCo ₃ , and CuO was mixed so that Bi ₂ Sr ₂ CaCu ₂ O _X was obtained as a composition, and this was heated to 820 ° C. in the air. After performing a heat treatment for maintaining this heating state for 20 hours, it was pulverized to prepare a powder 14 of a Bi-2212 phase oxide superconducting precursor. On the other hand, the outer diameter 15
mm, an inner diameter of 11 mm, and a length of 1000 mm were prepared. The composite billet 13 was formed by tapping and filling the powder 14 into a pipe 15. The composite billet 13 was drawn to an outer diameter of 5.4 mm to obtain a strand 10.

The wire 10 was cut into a predetermined length, two of which were assembled into the same silver pipe 16 as described above, and were further drawn to an outer diameter of 4.6 mm to produce a first composite wire 18. The obtained first composite wire 18 is cut into a predetermined length, and is cut into a pipe 20 similar to the above, and the original wire 10 is cut.
The perpendicular bisector 24 of the dividing line 23 between the first composite wire 1
8 in the longitudinal direction of the virtual circle C2 so as to always pass through the center of the virtual circle C2.
The second composite wire 25 was manufactured by drawing.

Similarly, the obtained first composite wire 18 is cut into a predetermined length, and as shown in a comparative example shown in FIG. The vertical bisector 24 of the dividing line 23 between the element wires 10 is assembled and arranged so as not to pass through the center of the virtual circle 41 in contact with the surfaces of the three first composite wires 18. 2mm diameter
Then, the second composite wire 42 was manufactured.

Each of the second composite wires 25 and 42 is cut into a length of about 30 mm, and heated and maintained at 882 ° C. for 10 minutes in an atmosphere with an oxygen partial pressure of 1 atm, and then at a cooling rate of 5 ° C./h at 830 ° C. Then, it was kept for 1 hour, and cooled in a furnace to perform a superconducting heat treatment.

The oxide superconducting wire 27 (Example 1) produced from the second composite wire 25 and the oxide superconducting wire 43 (Comparative Example 1) produced from the second composite wire 42 were placed in liquid helium and externally. In the absence of a magnetic field, the critical current is 1 μV /
It was measured in terms of cm. As a result, the former is 1600 A /
mm ² , and the latter was Jc of 1000 A / mm ² .

In the oxide superconducting wire 27 of Example 1, the aspect ratio of the oxide superconducting core filament 11 was about 3.0, whereas in the oxide superconducting wire 43 of Comparative Example 1, the oxide superconducting wire 43 The aspect ratio of the body core filament 44 was about 1.5 on average. In the oxide superconductor core filament 11 of the first embodiment, the cross-sectional shape with respect to the longitudinal direction is arranged so that the aspect ratio is increased in any portion, whereas the oxide superconductor core of the first comparative example is arranged. The filament 11 has a portion having a non-uniform cross section and a small aspect ratio.

For this reason, in FIG. 2 showing the state of the crystal structure of the oxide superconductor core filament after the heat treatment for superconductivity, in the oxide superconducting wire 27 of Example 1, the crystal structure of the oxide superconductor core filament 11 is shown. 28
In the oxide superconducting wire rod 43 of Comparative Example 1, the degree of orientation of the crystal structure 45 of the oxide superconducting core filament 11 is larger in some places, whereas the degree of orientation is good near the contact portion with the silver coating. Was inferior. As a result, it is considered that Example 1 obtained higher Jc than Comparative Example 1. [Example 2] As Bi ₂ Sr ₂ CaCu ₂ O _X is obtained as a _{composition, Bi 2 O 3, SrCo 3} , Ca 2 Co 2, Cu
Each powder of O is mixed, heated to 820 ° C. in the air, and subjected to a heat treatment for maintaining the heating state for 20 hours, and then crushed to obtain a powder of Bi-2212 phase oxide superconducting precursor. 14 were prepared. On the other hand, a silver pipe 15 having an outer diameter of 15 mm, an inner diameter of 11 mm, and a length of 1000 mm was prepared. The composite billet 13 was formed by tapping and filling the powder 14 into a pipe 15. The composite billet 13 was drawn to an outer diameter of 1.3 mm to produce a strand 10.

Two strands of the obtained wires 10 were twisted and further drawn to an outer diameter of 1.7 mm to produce a first composite wire 18. The twist pitch of the first composite wire 18 was 30 mm. Next, this first composite wire 18 is
This arrangement, the initial twist pitch is set to 30 mm and twisted, and further drawn to an outer diameter of 2 mm to form the second composite wire 25
Was prepared.

Similarly, three first composite wires 18 are twisted, the initial twist pitch is set to 50 mm, the first composite wire 18 is twisted at a twist pitch different from 30 mm, and further expanded to an outer diameter of 2 mm. The wire was drawn to produce a second composite wire 42.

Each of the second composite wires 25 and 42 was cut to a length of about 30 mm, and was subjected to a superconducting heat treatment under the same conditions as in Example 1.

The oxide superconducting wire 27 manufactured from the second composite wire 25 (Example 2) and the oxide superconducting wire 43 manufactured from the second composite wire 42 (Comparative Example 2) were mixed in liquid helium. Critical current of 1μV without external magnetic field
/ Cm. As a result, the former is 2300A
/ Mm ² , and the latter was Jc of 1600 A / mm ² .

The reason for the difference between the two Jc's is that, in the second embodiment, as in the first embodiment and the first comparative example, the perpendicular bisector of the dividing line 23 between the original strands 10 is used. 24 is a second virtual circle C2 extending in the longitudinal direction of the first composite wire rod 18.
And the stranded wire pitch of the first composite wire 18 itself and the second aggregated wire 32
Since the stranded wire pitch of the first composite wire 18 is the same, the oxide superconductor core filament 11 of the second composite wire 25 has a uniform cross section at any position in the longitudinal direction of the second composite wire 25. While the aspect ratio of the oxide superconductor core filament 11 can be increased, in Comparative Example 2, the oxide superconductor core filament 11 of the second composite wire 42 has a cross section at each position in the longitudinal direction of the second composite wire 42. The shape is uneven, and consequently,
This is because the average aspect ratio is small. Example 3 Bi _1.84 Pb _0.34 Sr _1.9 Ca _2.2 Cu _3.1
Powder 14 of an oxide superconducting precursor having an O _x composition was prepared.
On the other hand, the silver pipe 15 has an outer diameter of 15 mm and an inner diameter of 11 m
m and a length of 1000 mm were prepared. The powder 14 is tapped and filled into a pipe 15 to form a composite billet 13.
Was formed. The composite billet 13 was drawn to an outer diameter of 1.3 mm to produce a strand 10.

Two strands of the obtained wire 10 were twisted and further drawn to an outer diameter of 1.7 mm to produce a first composite wire 18. The twist pitch of the first composite wire 18 was 30 mm. Three of the first composite wires 18 were arranged, twisted at an initial twist pitch of 30 mm, and further drawn to an outer diameter of 2 mm to produce a second composite wire 25.

Similarly, three first composite wires 18 are twisted together, the initial twist pitch is set to 50 mm, the first composite wire 18 is twisted at a twist pitch different from 30 mm, and further expanded to an outer diameter of 2 mm. The wire was drawn to produce a second composite wire 42.

The two second composite wires 25 and 42 are placed in air for 84
After heating to 5 ° C. and baking while maintaining this heating state for 50 hours, these are drawn to an outer diameter of 1.8 mm, and further heated to 845 ° C. in air and held for 50 hours for baking. By performing such a superconducting heat treatment, Bi-2223 phase oxide superconducting wires 27 and 43 were produced. The former wire 27 is referred to as Example 3 and the latter wire 43 is referred to as Comparative Example 3.

The critical current Ic of each of these oxide superconducting wires 27 and 43 was measured in liquid nitrogen without an external magnetic field under the definition of 1 μV / cm. As a result, the former is 85
A / mm ^2, the latter was the Jc of 60A / mm ^2. This difference in Jc is the same as in Example 2 and Comparative Example 2.

As described above, the present invention has been described based on the above embodiment and the above example, but the present invention is not limited to this.

For example, in both the embodiments and the examples, the method of manufacturing the wire 10 having a substantially circular cross section is not only the powder-in-tube method as described above, but also the dip coating method, the doctor blade method, and the like. Method, coating method,
An organic acid salt method, a thermal spraying method, a plasma spraying method, a screen printing method, a vapor deposition method, a CVD method, a sputtering method, a jelly roll method by a laser ablation method, or a combination thereof may be used.

The materials of the oxide superconductor core filament 11 and the coating metal 26 of the oxide superconducting wire 27 are not limited to one kind in the wire structure, but may be a combination of a plurality of materials. .

The oxide superconductor core filament 1
As the kind of the oxide superconductor constituting 1, not only 2212 and 2223 phases containing at least Bi but also 2212, 2223, 1201 and 121 containing at least Tl
12, 1234, ReBa ₂ Cu ₃ O _y phase (where Re = Y, La, Nd, Eu, Dy, Gd, Ho, E
r, Tm, Yb, Lu) and at least Hg 22
12, 2223, 1201, 1212, 1223, 12
It may be 34 phases.

Further, as the material of the coating metal 26, silver or a silver alloy is preferably used because of its many achievements so far, but any material that does not react with the oxide superconductor (eg, gold, platinum, palladium or copper) Can be used without any problems. Any material that reacts with the oxide superconductor may be used as long as it has a reaction inhibitor such as zirconia or magnesium oxide.

Examples of applications of the oxide superconducting wire 27 include superconducting devices such as magnets, coils, cables, bus bars, current leads, magnetic shields, current limiters, and permanent current switches. In this case, the method of manufacturing the superconducting device using the oxide superconducting wire 27 is as follows:
Either the "act &Wind" method or the "Wind &React" method may be used.

[0088]

As described above, according to the method for manufacturing an oxide superconducting wire according to the present invention, a coating metal is provided on the outer periphery of one or more oxide superconducting core filaments, and the cross section of the core filament is substantially circular. A first space formed by two strands arranged adjacent to each other to form a first aggregated wire rod, and then formed by a first virtual circle in contact with the two strands and two adjacent strands. The first aggregated wire is reduced in diameter so as to allow a part of the element wire to flow therein, thereby producing a first composite wire having a circular cross section. Are arranged adjacent to each other to form a second aggregated wire. At this time, a perpendicular bisector of a division line between the original wires in each of the first composite wires extends in the longitudinal direction of the first composite wire. Always pass through the center of the second imaginary circle in contact with the surface of all n first composite wires. Then, the second composite wire is made to flow partially into the second space formed by the second virtual circle and the surfaces of the n first composite wires. The diameter of the aggregated wire is reduced to produce a second composite wire having a circular cross section, and then the second composite wire is subjected to a superconducting heat treatment to produce an oxide superconducting wire. Jc can be inexpensively improved without the need for a tape-like processing step.

According to the oxide superconducting wire according to the invention of claim 8, two or more wires having a coating metal provided on the outer periphery of one or more oxide superconductor core filaments and having a substantially circular cross section are provided. The first wire bundle is arranged adjacent to the first wire rod, and then the first wire is formed in a first space formed by a first virtual circle in contact with two wire surfaces and two adjacent wire surfaces. The first aggregated wire is reduced in diameter so that a part of the wire flows through the material to produce a first composite wire having a circular cross section. Next, n pieces of the first composite wire are arranged adjacent to each other. The second composite wire rod, the vertical bisector of the dividing line between the original strands in each of the first composite wire, in the longitudinal direction of the first composite wire, Always pass through the center of the second imaginary circle in contact with the surface of all n first composite wires. Then, the second composite wire is caused to flow partially into the second space formed by the second virtual circle and the surfaces of the n first composite wires. The diameter of the aggregated wire was reduced to produce a second composite wire having a circular cross section, and then the second composite wire was subjected to superconducting heat treatment. Jc can be inexpensively improved without a process.

[Brief description of the drawings]

FIG. 1 is a process chart showing a first embodiment of a method for producing an oxide superconducting wire according to the present invention.

FIG. 2 is a view showing a crystal structure of an oxide superconducting core filament of the oxide superconducting wire manufactured by the method for manufacturing an oxide superconducting wire of FIG. 1 and a comparative example.

FIG. 3 is a process chart showing a second embodiment of the method for producing an oxide superconducting wire according to the present invention.

FIG. 4 is a process chart showing some manufacturing steps of a comparative example in a method for manufacturing an oxide superconducting wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Element wire 11 Oxide superconductor core filament 12 Coated metal 16 Pipe 17 First aggregated wire 18 First composite wire 20 Pipe 22 Second aggregated wire 23 Split line 24 Vertical bisector 25 Second composite wire 27 Oxidation Object superconducting wire 31 first aggregated wire 32 second aggregated wire C1 first virtual circle C2 second virtual circle S1 first space S2 second space O center C4 second virtual circle S4 second space Oa center

Claims (14)

[Claims] 1. A first aggregated wire comprising two or more strands each having a coating metal provided on the outer periphery of one or more oxide superconductor core filaments and having a substantially circular cross section and being adjacent to each other. The first aggregated wire rod to allow a part of the wire to flow into a first space formed by a first virtual circle in contact with the wire surface and two adjacent wire surfaces. The diameter is reduced to produce a first composite wire having a circular cross section. Next, n pieces of the first composite wire are arranged adjacent to each other to form a second aggregated wire, and at this time, the first composite wire is used. The perpendicular bisector of the dividing line between the original strands in each of the wires is
Along the longitudinal direction of the first composite wire, the center is set so as to always pass through the center of the second imaginary circle in contact with the surfaces of all n first composite wires. The second aggregated wire is reduced in diameter so as to allow a part of the first composite wire to flow into a second space formed between the first composite wire and the surface of the first composite wire. A method for producing an oxide superconducting wire, comprising producing a second composite wire, and thereafter performing a superconducting heat treatment on the second composite wire to produce an oxide superconducting wire. 2. In forming the second aggregated wire, if each of the n first composite wires constituting the second aggregated wire is twisted at the same pitch, the first composite wire is The vertical bisector of the dividing line between the original wires in each of the composite wires is set so as to pass through the center of the second imaginary circle in contact with the surface of all n first composite wires. Performing the initial alignment of one composite wire, and then forming the second aggregated wire by twisting these first composite wires at a pitch that matches the twist pitch of the first composite wire itself. The method for producing an oxide superconducting wire according to claim 1, wherein: 3. The diameter reduction processing of each of the first aggregated wire and the second aggregated wire is a cross-sectional reduction rate of 70% or more,
The aspect ratio of the oxide superconductor core filament of the first composite wire is 1.5 or more, and the aspect ratio of the oxide superconductor core filament of the second composite wire is 3.0 or more. 3. The method for producing an oxide superconducting wire according to 1 or 2. 4. After reducing the diameter of the second aggregated wire rod,
The method for producing an oxide superconducting wire according to any one of claims 1 to 3, wherein a superconducting heat treatment is performed on the second composite wire produced by the diameter reducing process. 5. The superconducting heat treatment is performed at a temperature of 700-9.
The method for producing an oxide superconducting wire according to any one of claims 1 to 4, wherein the method is performed in an atmosphere at 50 ° C and an oxygen partial pressure of 0.01 to 10 atm. 6. The Bi-2212 wherein the oxide superconductor core filament comprises Bi, Sr, Ca and Cu.
The method for producing an oxide superconducting wire according to any one of claims 1 to 5, wherein the oxide superconducting wire is a phase or a Bi-2223 phase. 7. The main oxide superconductor of the oxide superconductor core filament is Bi, Pb, Sr, Ca and C.
Bi-2212 phase or Bi-222 comprising u
The method for producing an oxide superconducting wire according to any one of claims 1 to 6, wherein the superconducting wire has three phases. 8. One or more oxide superconductor core filaments are provided with a coating metal on the outer periphery thereof, and two adjacent wires having a substantially circular cross section are arranged adjacent to each other to form a first aggregated wire. The first aggregated wire rod so as to allow a part of the wire to flow into a first space formed by a first virtual circle in contact with two wire surfaces and two adjacent wire surfaces. Is reduced in diameter to produce a first composite wire having a circular cross section. Next, n pieces of the first composite wire are arranged adjacent to each other to form a second aggregated wire. The perpendicular bisector of the dividing line between the original wires in each of the composite wires is in contact with the surface of all n first composite wires over the longitudinal direction of the first composite wire. It is set so as to always pass through the center of the virtual circle. Next, the second virtual circle and the n The diameter of the second aggregated wire is reduced to allow a part of the first composite wire to flow into the second space formed by the surface of the one composite wire, and the second composite wire having a circular cross section is formed. An oxide superconducting wire manufactured by subjecting the second composite wire to a superconducting heat treatment. 9. When forming the second aggregated wire rod, if each of the n first composite wire rods constituting the second aggregated wire strand is twisted at the same pitch, the first composite wire rods may have the first pitch. The vertical bisector of the dividing line between the original wires in each of the composite wires is set so as to always pass through the center of the second imaginary circle in contact with the surface of all n first composite wires. The initial alignment of the first composite wire is performed, and then the first composite wire is twisted at a pitch that matches the twist pitch of the first composite wire itself to form the second aggregated wire. The oxide superconducting wire according to claim 8, wherein: 10. The diameter reduction processing of each of the first aggregated wire and the second aggregated wire is 70% or more in cross-sectional reduction rate, and the aspect ratio of the oxide superconductor core filament of the first composite wire is 1. 10. The oxide superconducting wire according to claim 8, wherein the oxide superconducting core filament of the second composite wire has an aspect ratio of 3.0 or more. 11. A superconducting heat treatment is performed on the second composite wire produced by the diameter reducing process after the diameter reducing process of the second aggregated wire material.
The oxide superconducting wire according to any one of the above. 12. The superconducting heat treatment is performed at a temperature of 700 to 700.
The oxide superconducting wire according to any one of claims 8 to 11, wherein the heat treatment is performed in an atmosphere at 950 ° C and an oxygen partial pressure of 0.01 to 10 atm. 13. The Bi-221, wherein the oxide superconductor core filament comprises Bi, Sr, Ca and Cu.
The oxide superconducting wire according to any one of claims 8 to 12, wherein the wire is a two-phase or Bi-2223 phase. 14. A Bi-2212 phase or Bi-22 in which the main oxide superconductor of the oxide superconductor core filament contains Bi, Pb, Sr, Ca and Cu.
The oxide superconducting wire according to any one of claims 8 to 13, wherein the superconducting wire has 23 phases.