JP2000200520A - Manufacturing method of oxide superconducting wire - Google Patents

Abstract

(57) [Problem] To provide a method for manufacturing an inexpensive oxide superconducting wire, which can improve Jc without requiring an active tape processing step. In a method for manufacturing an oxide superconducting wire having a plurality of oxide superconductor core filaments and a metal coating covering the oxide superconductor core filament, one or more oxide superconductor core filaments are provided. N-element wires (n = 2 to 12) having a metal coating provided on the outer periphery thereof and having a substantially circular cross section are arranged symmetrically adjacent to each other, and adjacent to the inner surface of the virtual cylinder in contact with the n-element surfaces. A surface reduction process is performed so that a part of the wire flows into a space formed by two matching wire surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an oxide superconducting wire, and more particularly to a method for producing an oxide superconducting wire suitable for a superconducting coil, a superconducting cable, and other uses.

[0002]

2. Description of the Related Art An oxide superconducting wire in which an oxide superconducting filament is coated with a metal coating made of 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 forming the wire into a tape shape, the contact area between the metal coating and the oxide superconductor can be increased, and the interface between the metal coating and the oxide superconductor can be improved. This is because smoothing can be performed and a high critical current density (hereinafter, referred to as Jc) can be realized. That is, for example, as described in the 56th Spring Meeting of the 1997 Society of Low Temperature Engineering and Superconductivity, p22, the oxide superconductivity at the interface with silver or silver alloy as the metal coating during the heat treatment for superconductivity for developing superconducting properties. This is because an oriented structure of the material constituting the body is obtained, and as a result, Jc is increased.

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

[0004] Therefore, recently, the cross section has a round shape and a high Jc.
Oxide superconducting wires have been long-awaited.

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

[0006] As a first production 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 to a metal tube. A plurality of tubes filled with oxide superconducting precursor powder are further incorporated into another metal tube such as silver,
A method has been proposed in which these are subjected to diameter reduction processing by extrusion or wire drawing, and then subjected to a superconducting heat treatment (for example, the 53rd Spring Meeting of the 1995 Society of Low Temperature Engineering and Superconductivity, p77, and the 57th Fall 1997 Fall Meeting). Proceedings of the Society of Low Temperature Engineering and Superconductivity Society p82).

[0007] As a second manufacturing method, a plurality of oxide superconducting precursors coated with a metal and processed into a tape form are bundled, further assembled in a metal tube, and subjected to diameter reduction such as extrusion or wire drawing. Then, a method of improving Jc by performing a superconducting heat treatment has also been proposed (Japanese Patent Application Laid-Open No. 9-1997).
223418).

[0008]

However, Jc was still low in the above-mentioned first manufacturing method of the prior art. Further, in the second manufacturing method, although a certain level of Jc can be secured, a step of processing into a tape shape in the manufacturing process is indispensable, and there has been a problem that it takes time and cost to manufacture a wire.

Accordingly, the present invention provides an inexpensive method for manufacturing an oxide superconducting wire which solves the above-mentioned drawbacks of the prior art and can improve Jc without requiring an aggressive tape-like processing step. The purpose is to do.

[0010]

According to the present invention, there is provided an oxide superconducting wire having a plurality of oxide superconductor core filaments and a metal coating covering the oxide superconductor core filament. In the manufacturing method, one or a plurality of oxide superconductor core filaments and a metal coating provided on the outer periphery thereof, and n round wires (n = 2 to 12) substantially circular in cross section are symmetrically adjacent to each other. A method for producing an oxide superconducting wire rod which is arranged and subjected to a surface reduction process so that a part of a wire is caused to flow through a space formed by an inner surface of a virtual cylinder in contact with the surface of n wires and two adjacent wire surfaces. I will provide a.

The present invention also relates to a method for manufacturing an oxide superconducting wire having a plurality of oxide superconductor core filaments and a metal coating covering the oxide superconductor core filaments, Or n wires (n = 2 to 12) having a plurality of wires and a metal coating provided on the outer periphery thereof and having a substantially circular cross section
Are arranged symmetrically adjacent to each other, and by reducing the diameter thereof, a part of the element wire is caused to flow in a cross-sectional direction substantially perpendicular to the longitudinal direction of the element wire, and the aspect ratio of each of the oxide superconductor core filaments is reduced. Provided is a method for manufacturing an oxide superconducting wire having a larger diameter than before reducing.

Further, the present invention relates to a method for producing an oxide superconducting wire having a plurality of oxide superconductor core filaments and a metal coating covering the oxide superconductor core filaments. Are accommodated in a metal pipe in a state in which n wires (n = 2 to 12) having a substantially circular cross section are arranged symmetrically adjacent to each other in a cross section, and these are subjected to diameter reduction processing. A method of manufacturing an oxide superconducting wire material in which a part of the element wire is caused to flow in a cross-sectional direction substantially perpendicular to the longitudinal direction of the wire and the aspect ratio of each of the oxide superconductor core filaments is made larger than before the diameter reduction processing. I do.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing an oxide superconducting wire according to the present invention will be described below.

First, two or three strands of metal coated with an oxide superconductor core filament are prepared. This wire may be a single-core filament wire filled with a powder of an oxide superconducting precursor in a silver or silver alloy pipe, or a bundle of a plurality of such wires may be replaced with another silver or silver alloy. Any of so-called multifilament strands obtained by inserting the pipes into a pipe made of stainless steel and reducing the diameter of the pipes may be used. These wires are not subjected to tape-like processing, that is, the cross-sectional shape of the wires and the cross-sectional shape of each of the oxide superconductor core filaments are kept different from each other while maintaining a substantially circular shape. Inserted into an alloy pipe. At this time, these strands are symmetrically arranged in the pipe,
It is preferable to select the outer diameter of the strand or the inner diameter of the pipe so that the inner surface of the virtual cylinder that is in contact with the surface of the strand substantially matches the inner surface of the pipe. At this time, the space formed by the inner surface of the virtual cylinder (preferably the inner surface of the pipe) in contact with the surface of the wire and the surface of the two adjacent wires is formed in the cross-sectional direction substantially perpendicular to the longitudinal direction by the next diameter reduction processing step. Make sure that there is enough space to allow a part of the wire to flow through the material.

Next, these are extruded and reduced in diameter by a usual method such as drawing. In this diameter reduction processing, a part of the wire is inserted into a space formed by the inner surface of the virtual cylinder (preferably the inner surface of the pipe) and two adjacent wire surfaces in a cross-sectional direction substantially perpendicular to the longitudinal direction of the wire. Let the material flow. This material flow results in a wire having a substantially circular cross section, a semicircular shape for two wires, and an interior angle of approximately 12 for three wires.
When the number of element wires is four, the shape is changed to a fan shape with 0 degrees and an inner angle of approximately 90 degrees. If the number of wires is 12, the shape is changed to a fan shape having an inner angle of approximately 30 degrees.

By appropriately selecting the cross-sectional reduction rate by the diameter reduction processing, that is, the area reduction rate, the aspect ratio of the oxide superconductor core filament inside each strand (long axis length / short axis length in the cross section of the filament) is obtained. Can be set to 1.5 or more by this surface reduction processing. This makes it possible to secure more smooth surfaces of the filaments and to increase the denseness of the filaments as compared with a wire having an ordinary aspect ratio of approximately 1 and having a circular cross section. Next, a desired oxide superconducting wire is obtained by performing a superconducting heat treatment under ordinary conditions.

Since the present invention is a production method as described above, a filament having a high aspect ratio is used as a starting material, and a high aspect oxide superconductor core filament is formed without using a tape-like processing. Can be manufactured.

In the present invention, the reduction rate of the diameter reduction processing is 70%.
% Is preferable. If this is less than 70%,
There is a possibility that the initial space may not be completely filled even by the material flow of a part of the strand, and the improvement of the aspect ratio and the densification of the oxide superconductor core filament become insufficient, and the Jc
This is because improvement of the quality cannot be expected.

One example of the superconducting heat treatment is performed in an atmosphere 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 0.01 to 10 atm. It is preferable to carry out in. This is because when such heat treatment causes the oxide superconductor material or its precursor to generate a liquid phase,
This is because nuclei are generated from the contact surface with the metal coating and are grown along the surface to form a texture with a good degree of orientation. This is because the effect of improving the aspect ratio and increasing the smooth surface is significantly increased.

[0020] In the finally obtained oxide superconducting wire, the minor axis length of the oxide superconductor core filament is preferably 1 to 50 µm. If the short axis length is too long, that is, if the filament is too thick, surface growth by superconducting heat treatment will not occur, while if the short axis length is too short, that is, if the filament is too thin, the diameter during the diameter reduction processing This is because problems such as breakage of the filament in the longitudinal direction due to sausaging and the like occur.

Here, in the present invention, the term “substantially circular” that defines the cross-sectional shape of the oxide superconductor core filament, the element wire, and the wire is not limited to a circle but also a symmetric N-gon (N is 6 or more). It is a concept that also includes Further, the oxide superconductor core filament has at least Bi, Sr, Ca,
2212 phase or Bi-22 consisting of and Cu
At least one of the 23 phases, or at least B
Bi-221 consisting of i, Sr, Pb, Ca and Cu
It is preferable to use two phases, but the present invention is not limited to these.

[0022]

Embodiments of the present invention will be described below.

Example 1 The composition was Bi ₂ Sr ₁ Ca
Bi ₂ O ₃ and SrC to obtain ₂ Cu ₂ O _x
O ₃ , Ca ₂ CO ₃ , and CuO powders were mixed and subjected to a heat treatment at 820 ° C. for 20 hours in the air, and then pulverized to prepare a Bi-2212 phase oxide superconducting precursor powder. . On the other hand, as a silver pipe, outer diameter 15mm, inner diameter 11m
m and a length of 1000 mm were prepared. The precursor powder was tap-filled into the silver pipe to form a composite billet. The composite billet was drawn to an outer diameter of 4.6 mm. The obtained composite wire is 1000 mm long.
Then, three of them were assembled in the same silver pipe as described above, and were further drawn to an outer diameter of 2 mm.

Similarly, the same precursor powder was prepared, and the same silver pipe was tap-filled to form a composite billet. The composite billet was drawn to a diameter of 3.5 mm. The obtained composite wire was cut into a length of 1000 mm, and seven such wires were assembled into the same pipe as described above, followed by drawing to an outer diameter of 2 mm.

Each of the obtained wires is cut into a length of about 30 mm, kept at 880 ° C. for 10 minutes in the atmosphere at 1 atm, gradually cooled to 830 ° C. at a cooling rate of 5 ° C./hour, and further kept for 1 hour. And cooled the furnace. The former sample was named Example 1 and the latter was Comparative Example 1. Both samples were subjected to a critical current Ic of 1 μV /
Measured in cm. As a result, the obtained Jc was 1600 A / mm ^{2 in} the example material 1 and 800 A / mm ^{2 in the} comparative example material 1.
Met.

FIGS. 1 and 3 show cross-sectional views of the wires of Example 1 and Comparative Example 1, respectively. In the figure, 1 is an oxide superconductor core filament and 2 is a silver coating.

In the example material 1, the aspect ratio of the oxide superconductor core filament 2 was about 1.5, whereas the comparative example material 1 was almost 1. 2 and 4 are schematic diagrams showing the state of the crystal structure 3 in the oxide superconductor core filament 1 after the heat treatment for superconductivity. In the example material 1 shown in FIG. 2, the degree of orientation of the crystal structure is good near the contact portion with the silver coating, whereas in the comparative example material 1 shown in FIG. 4, the degree of orientation of the crystal structure is significantly inferior. Was. For this reason, it is considered that the example material 1 obtained a higher Jc.

FIG. 5 is a schematic explanatory view showing a main part of a manufacturing process of the material 1 of the embodiment. As shown in FIG. 5 (a), the deformation occurring in the three composite strands 21 incorporated in the silver pipe 22 by the diameter reduction processing (drawing processing) is caused by the surface of two adjacent composite strands and these composite strands. From the relationship between the porosity of the space S formed by the inner surface of the silver pipe in contact with the surface of the strand and the ease of deformation of the composite strand 21 due to the material flow, the direction of the arrow A in FIG. The deformation mainly causes the material to flow partially in the cross-sectional direction substantially perpendicular to the direction (see FIG. 5B). In this way, the aspect ratio of the oxide superconductor afilament can be increased by the diameter reduction processing as shown in FIG. 5C.

[Example 2] A composite wire rod obtained by drawing the same composite billet as in Example 1 to an outer diameter of 5.4 mm is cut into a predetermined length, which is cut into a silver pipe similar to that described above. And two pieces were further drawn to an outer diameter of 4.6 mm. The obtained composite wire is placed on the same silver pipe as above.
This was assembled and further drawn to an outer diameter of 2 mm. The obtained wire was cut into a length of about 30 mm and heat-treated as in Example 1. This sample was used as Example Material 2, and Jc was measured in the same manner as in Example 1. As a result, the obtained Jc was 20
It was 00 A / mm ² .

FIG. 6 shows a cross sectional view of the material 2 of the embodiment. J
The reason why c was improved from that of the example material 1 was that the aspect ratio of the oxide superconductor core filament 1 was about 2.5 as shown in the figure.
It is because it became larger than Example material 1.

Example 3 Bi-2212 phase main phase Bi
An oxide superconducting precursor powder having a composition of _1.84 Pb _0.34 Sr _1.9 Ca _2.2 Cu _3.1 O _x was prepared. This powder was tap-filled into the same silver pipe as in Example 1 to form a composite billet. The composite billet was drawn to an outer diameter of 4.6 mm. The obtained composite wire is 1000 mm long.
Then, three of the silver pipes were assembled into the same silver pipe as described above, and were further drawn to an outer diameter of 2 mm. 845 in air
After firing at 50 ° C. for 50 hours, the wire was drawn to an outer diameter of 1.8 mm, and further fired in air at 845 ° C. for 50 hours to obtain Bi-2223.
A wire having a phase oxide superconductor core filament was prepared. This wire was named Example Material 3.

Similarly, the same precursor powder was prepared, and the same silver pipe was tapped and filled to form a composite billet. The composite billet was drawn to a diameter of 3.5 mm. The obtained composite wire was cut into a length of 1000 mm, and seven such tubes were assembled into the same silver pipe as described above, and were further drawn to an outer diameter of 2 mm. Next, firing, drawing and firing were performed in the same manner as in Example Material 3 to produce a wire having a Bi-2223 phase oxide superconductor core filament. This wire was used as Comparative Example Material 3.

Jc for both samples in the same manner as in Example 1.
Was measured. As a result, the obtained Jc was 8 in Example Material 3.
0 A / mm ² , and 40 A / mm ² for Comparative Example Material 3. This difference in Jc is due to the same reason as in the first embodiment.

Example 4 The same composite billet as in Example 3 was drawn to an outer diameter of 4.6 mm. The obtained composite wire was cut into a length of 1000 mm, and three of them were assembled in the same silver pipe as described above, and further drawn to an outer diameter of 1.2 mm. The obtained composite wire was cut into a predetermined length, and 61 of the same were assembled into the same silver pipe as described above, followed by wire drawing and heat treatment in the same manner as in Example 3 to obtain Bi-222.
A wire having a three-phase oxide superconductor core filament was produced. This wire was designated as Example material 4.

Similarly, the same precursor powder was prepared, and the same silver pipe was tap-filled to form a composite billet. The composite billet was drawn to an outer diameter of 1.2 mm. The obtained composite wire was cut into a predetermined length, 61 of which were assembled into the same silver pipe as above, and further drawn to an outer diameter of 2 mm. Next, a wire rod having a Bi-2223 phase oxide superconductor core filament was prepared by performing wire drawing and heat treatment in the same manner as described above. This wire was used as Comparative Example Material 4.

Jc for both samples in the same manner as in Example 1.
Was measured. As a result, the obtained Jc was 9 in Example Material 4.
0 A / mm ² , and 50 A / mm ² for Comparative Example Material 4.

[Example 5] In the same manner as in Example 1, the obtained composite wire was cut into a length of 1000 mm, and 61 pieces were assembled in the same silver pipe as described above, and the outer diameter was further 4.6 mm.
It was pulled out and added. The obtained composite wire was cut into a predetermined length, and three pieces were assembled in the same silver pipe as described above, and were further drawn to an outer diameter of 2 mm.

In the same manner, the same precursor powder was prepared and the same silver pipe was tap-filled to form a composite billet. The composite billet was drawn to a diameter of 1.2 mm. The obtained composite wire was cut into a predetermined length, 61 of the same were assembled into a pipe similar to the above, and further drawn to an outer diameter of 2 mm.

Each of the obtained wires was cut into a length of about 30 mm and heat-treated in the same manner as in Example 1. The former sample was named Example 5 and the latter was Comparative Example 5. Jc was measured for both samples in the same manner as in Example 1. As a result, the obtained Jc was 1900 A / mm ² for Example Material 5 and 1000 A / mm ² for Comparative Example Material 5.

Example 6 After the same composite billet as in Example 1 was drawn to an outer diameter of 4.4 mm, the obtained composite wire was cut into a length of 1000 mm and cut into an outer diameter of 15 mm. 4mm inside a silver pipe 11mm inside diameter and 1000mm long
This was assembled, and further drawn to an outer diameter of 2 mm.

In the same manner, the same precursor powder is prepared, and the same silver pipe is tapped and filled to form a composite billet. The composite billet is drawn to a diameter of 3.5 mm. Seven wires were assembled into a pipe having the same length as that described above, and were further drawn to an outer diameter of 2 mm.

Each of the obtained wires has a length of about 30 mm.
And heat-treated in the same manner as in Example 5. The former was named Example 6 and the latter was Comparative Example 6. Jc was measured for both samples in the same manner as in Example 1. As a result, the former is 12
The Jc value was 00 A / mm ² , and the latter was 800 A / mm ² .

In the example material 6, the aspect ratio of the oxide superconductor core filament 1 was about 1.5, whereas the comparative example material 6 was almost 1. Further, in Example Material 6, the core filament had a good degree of orientation of the crystal structure in the vicinity of the contact portion with the silver coating, whereas Comparative Example Material 6 had a significantly poor degree of orientation of the crystal structure. Therefore, Example Material 6
Is considered to indicate a higher Jc value.

FIG. 6 is a schematic explanatory view showing the waist in the manufacturing process of the sixth embodiment. The deformation that occurs in the four composite wires 21 incorporated in the silver pipe 22 by wire drawing is shown in FIG.
As shown in (a), the porosity of the space S formed by the surface of two adjacent composite wires and the inner surface of the silver pipe in contact with the surfaces of the composite wires, and the deformation of the composite wires 21 due to the material flow. Due to easiness, the deformation mainly causes a part of the wire to flow in the direction of arrow A in the figure, that is, the cross-sectional direction substantially perpendicular to the longitudinal direction of the composite wire 21 (see FIG. (B)). Thus, the aspect ratio of the oxide superconductor core filament can be increased by reducing the diameter.

Example 7 After the same composite billet as in Example 1 was drawn to an outer diameter of 4.0 mm, the obtained composite wire was cut to a length of 1000 mm, and the resulting composite wire was cut to an outer diameter of 15 mm. 5mm inside a silver pipe 11mm inside diameter and 1000mm long
This was assembled and further drawn to an outer diameter of 2 mm.

The obtained wire was cut into a length of about 30 mm, heat-treated in the same manner as in the fifth embodiment to obtain the seventh embodiment material, and Jc was measured in the same manner as in the sixth embodiment. As a result, 1200A
Jc / mm ² was obtained. The aspect ratio of the oxide superconductor was about 1.5.

FIG. 8 is a schematic explanatory view showing the waist in the manufacturing process of this embodiment. As shown in FIG. 8A, the deformation that occurs in the five composite wires 21 incorporated in the silver pipe 22 is caused by a cross-sectional direction substantially perpendicular to the longitudinal direction of the composite wire 21 (the circumferential direction of the cross-section). ) Mainly causes deformation of a part of the element wire. In this case, a deformation that causes a part of the element wire to flow in the direction of the center of the cross section also occurs (the direction of arrow b in the figure).
Therefore, the aspect ratio of the core filament can be increased.

[Embodiment 8] An outer diameter 4.4 similar to that of Embodiment 3 is used.
mm composite wire was cut into a length of 1000 mm, and four of them were assembled into a silver pipe with an outer diameter of 15 mm, an inner diameter of 11 mm, and a length of 1000 mm, and were drawn to an outer diameter of 2 mm. After firing at 845 ° C. for 50 hours, the wire was drawn to an outer diameter of 1.8 mm, and further fired in air at 845 ° C. for 50 hours to produce a Bi-2223 wire. This wire was named Example Material 8. Jc of this example material 8 is 70 A / mm ²
Met.

Example 9 A similar composite wire obtained in Example 4 was cut into a length of 1000 mm, 61 of which were assembled into a silver pipe as described above, and further reduced to an outer diameter of 4.0 mm. It was drawn. The obtained wire was cut into a predetermined length, five of which were assembled into a silver pipe in the same manner as described above, further drawn to an outer diameter of 2 mm, cut into a length of 30 mm, and cut at 880 ° C. After holding for 1 minute, the sample was cooled to 830 ° C. at a cooling rate of 5 ° C./hour, and further held for 1 hour to cool the furnace. The Jc of the obtained wire was measured in the same manner as described above, and it was 1800 A / mm ² .

The composite wire obtained in the same manner was cut into a predetermined length, 61 of which were assembled in the same pipe as described above, and were further drawn to an outer diameter of 2 mm. The sample was cut into a length of 30 mm, heat-treated in the same manner as described above, and cooled in a furnace. When Jc was measured in the same manner as described above using this sample as Comparative Example 7, it was 1000 A / mm ² .

As is apparent from the above description of the embodiments, according to the method for manufacturing an oxide superconducting wire of the present invention, one or more oxide superconducting core filaments and a metal coating provided on the outer periphery thereof are provided. And two substantially linear element wires (n = 2 to 12), which are substantially circular in cross section, are symmetrically arranged adjacent to each other and the inner surface of the virtual cylinder in contact with the n element wires. Since the surface reduction processing is performed so that a part of the element wire flows through the space formed by the above, the aspect ratio of the oxide superconductor core filament can be increased, and the conventional oxide superconductor core filament having an aspect ratio of almost 1 The number of planes increases and the compactness becomes higher as compared with. Therefore, the orientation of the crystal structure of the oxide superconductor core filament in the vicinity of the contact portion with the metal coating is promoted by the superconducting heat treatment, and the Jc of the obtained oxide superconducting wire can be greatly improved.

Regarding the structure of the wire, not only a so-called single filament type having a structure in which a single oxide superconductor core filament is embedded in a metal coating, but also a plurality of oxide superconductor core filaments in a metal coating. It is clear that the effects of the present invention can be obtained even with a so-called multifilament type having a structure embedded in the substrate.

In the present invention, as a method for producing a wire having a substantially circular cross section, not only the powder-in-tube method as in the above embodiment, but also a dip coating method, a doctor blade method, a coating method, an organic acid salt, and the like. 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.

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

The type of the oxide superconductor includes not only 2212 and 2223 phases containing at least Bi but also 2212, 2223 and 120 containing at least Tl.
1, 1212, 1234, ReBa ₂ Cu ₃ O _y
Phase (where Re = Y, La, Nd, Eu, Dy, Gd,
Ho, Er, Tm, Yb, Lu) and at least Hg
2212, 2223, 1201, 1212, 12 including
23, 1234 phases.

On the other hand, silver or a silver alloy is widely used as the material for the metal coating, and is preferably used. However, any material that does not react with gold or other oxide superconductors can be used without any problem. Even if the material reacts with the oxide superconductor,
It does not matter if it is provided with a reaction inhibitor such as zirconia or magnesium oxide.

Further, in the structure of the wires, as described above, the number of the oxide superconductor core filaments in the metal coating is not limited, but the number of the oxide superconductor core filaments crosses n (n = 2 to 12) wires. It goes without saying that a method of symmetrically adjoining the surface may be a straight shape or a spiral shape.

The oxide superconducting wire obtained by the production method of the present invention can be used as a conductor by itself or as a conductor obtained by assembling a plurality of such superconducting wires, for example, a spiral or straight stranded wire. Further, a configuration in which these conductors are combined with other members may be adopted. Examples of applications include superconducting devices such as magnets, coils, cables, bus bars, current leads, magnetic shields, current limiters, and permanent current switches.

Further, in the case of using the above-mentioned application, the production method may be either the React & Wind method or the Wind & React method.

Although the obtained oxide superconducting wire has a substantially circular cross section in the present invention, it can be further processed into a rectangular wire or a tape wire as required.

[0061]

According to the manufacturing method of the present invention, it is possible to provide an inexpensive method for manufacturing an oxide superconducting wire that can improve Jc without requiring an active tape processing step. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of an oxide superconducting wire obtained by a production method of the present invention.

FIG. 2 is a schematic diagram showing a crystal structure in an oxide superconductor core filament in the example of FIG.

FIG. 3 is a cross-sectional view showing an example of an oxide superconducting wire obtained by a conventional manufacturing method.

FIG. 4 is a schematic view showing a crystal structure in an oxide superconductor core filament in the conventional example of FIG.

FIG. 5 is a schematic explanatory view showing a main part of a manufacturing process according to one embodiment of the present invention.

FIG. 6 is a cross-sectional view showing another embodiment of the oxide superconducting wire obtained by the manufacturing method of the present invention.

FIG. 7 is a schematic explanatory view showing a main part of a manufacturing process according to a sixth embodiment of the present invention.

FIG. 8 is a schematic explanatory view showing a waist in a manufacturing process according to a seventh embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Oxide superconductor core filament 2, 12 Silver coating 21 Composite strand 22 Pipe

Claims (10)

[Claims] 1. A method for manufacturing an oxide superconducting wire having a plurality of oxide superconductor core filaments and a metal coating covering the oxide superconductor core filament, wherein one or more of the oxide superconductor core filaments are provided. And an inner surface of an imaginary cylinder having a metal coating provided on the outer periphery thereof and symmetrically adjacent to n wires (n = 2 to 12) having a substantially circular cross section and contacting the surfaces of the n wires. A method for producing an oxide superconducting wire, wherein the surface of the wire is reduced so that a part of the wire flows into a space formed between the wire and two adjacent wire surfaces. 2. A method for producing an oxide superconducting wire having a plurality of oxide superconductor core filaments and a metal coating covering the oxide superconductor core filament, wherein one or more of the oxide superconductor core filaments are provided. And n metal wires (n = 2 to 12) having a substantially circular shape in cross section and having a metal coating provided on the outer periphery thereof are arranged symmetrically adjacent to each other, and the diameters of these wires are reduced. Part of the element wire is caused to flow in a cross-section direction substantially perpendicular to the longitudinal direction, and the aspect ratio of each of the oxide superconductor core filaments is made larger than before the diameter reduction processing. Production method. 3. A method for manufacturing an oxide superconducting wire having a plurality of oxide superconductor core filaments and a metal coating covering the oxide superconductor core filament, wherein the method is provided on an oxide superconductor core filament and an outer periphery thereof. The metal wire is provided in a metal tube in a state in which n wires (n = 2 to 12) having a substantially circular cross section are arranged symmetrically adjacent to each other in a cross section, and these wires are reduced in diameter to form the wire. Characterized in that a part of the element wire is caused to flow in a cross-sectional direction substantially perpendicular to the longitudinal direction of the material, and the aspect ratio of each of the oxide superconductor core filaments is made larger than before the diameter reduction processing. Manufacturing method. 4. The method for producing an oxide superconducting wire according to claim 1, wherein the number n of adjacently arranged wires is two or three. 5. The method for producing an oxide superconducting wire according to claim 1, wherein a superconducting heat treatment is performed after the diameter reduction processing. 6. A process according to claim 2, wherein said diameter reducing processing is processing for reducing the cross-sectional reduction rate to 70% or more and for setting the aspect ratio of each of the oxide superconductor core filaments to 1.5 or more. 5. The method for producing an oxide superconducting wire according to 3 or 4. 7. The superconducting heat treatment at a temperature at which a liquid phase is formed in at least a part of the oxide superconductor core,
The method for producing an oxide superconducting wire according to claim 5, wherein the method is performed in an atmosphere having an oxygen partial pressure of 0.01 to 10 atm. 8. The superconducting heat treatment temperature is from 700 to 95.
The method for producing an oxide superconducting wire according to claim 7, wherein the temperature is 0 ° C. 9. The oxide superconductor core filament according to claim 1, wherein
Bi composed of at least Bi, Sr, Ca, and Cu
The method for producing an oxide superconducting wire according to any one of claims 1 to 3, wherein the oxide superconducting wire is at least one of a -2212 phase and a Bi-2223 phase. 10. The oxide superconductor core filament is a Bi-2212 phase or Bi-2223 composed of at least Bi, Sr, Pb, Ca, and Cu. 5. The method for producing an oxide superconducting wire according to any one of the above.