JPH11203957A - Oxidic superconductive wire and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a.c. loss in carrying alternating current by increasing the resistance of the surface of a superconductive conductor and retaining eddy current within the superconductive conductor in carrying alternating current. SOLUTION: This oxidic superconductive wire is composed of multiple superconductive conductors 13, each of which is formed by placing multiple superconductive cores 11 in a sheath 12, by placing around a pipe-like former; a superconductive layered product is formed by winding the superconductive conductors 13 around the former, and current-carrying among the superconductive conductors 13 is restrained in the superconductive layers product, so that an increased-resistance layer 14 is formed by an increased-resistance material having electric resistivity higher than that of a sheath material forming the sheath 12 on the surface of the superconductive conductor 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconducting wire and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as an example of an oxide superconducting wire,
As shown in FIGS. 5 to 7, an oxide superconducting wire 1 in which a superconducting conductor 3 is spirally wound around a pipe-shaped former 2 made of copper or the like is known. As shown in FIG. 6A, the superconducting conductor 3 includes a plurality of superconducting cores 4.
Is covered with a sheath 5 made of silver or the like, and a superconducting laminate 8 is formed by winding the superconducting conductor 3 on the pipe-shaped former 2 in a plurality of layers. The oxide superconducting material used for the superconducting core 4 is B
i ₂ Sr ₂ Ca ₁ Cu ₂ O _x (Bi-based 2212 phase), Bi ₂ S
r ₂ Ca ₂ Cu ₃ O _y (Bi-based 2223 phase), Bi _1.6 Pb
_0.4 Sr ₂ Ca ₂ Cu ₃ O _x , Tl ₂ Ba ₂ Ca ₂ Cu ₃ O _y ,
Those having such a composition are used. Among them, Bi
A system, in particular, a Bi-based 2223 phase oxide superconducting material is applied to the superconducting core 4 as a stable material having a high critical temperature.

Hereinafter, a method for manufacturing such an oxide superconducting wire will be described with reference to FIG. [Raw material processing step: S1] A raw material powder of a Bi-based oxide superconducting material, for example, a Bi compound powder such as Bi ₂ O ₃ ,
Pb compound powder such as PbO, Sr such as SrCO ₃
Compound powder, Ca compound powder such as CaCO ₃ , C
A mixture of a compound powder of Cu such as uO is mixed. [Filling step: S2] The powder mixed in the raw material powder processing step S1 is filled in a sheath material pipe such as Ag,
A sheath material composite (Ag sheath composite) is formed. [Single Wire Drawing (Drawing) Processing Step: S3] The Ag sheath composite formed in the filling step S2 is drawn to a predetermined wire diameter to form a superconducting single core elementary conductor (single core wire). I do. [Multi-core process: S4] A plurality of superconducting single-core elementary conductors formed in single wire drawing process S3 are assembled and inserted into a pipe made of a covering material such as Ag, and then drawn to form a superconducting multi-conductor. A core element conductor (multi-core wire) is formed. [Rolling Step: S5] The above multifilamentary wire is formed into, for example, a tape-shaped superconducting conductor (tape material) by roll rolling. [Heat treatment step: S6] Heat treatment is performed on the tape-shaped superconducting element conductor (tape material). Thereafter, the rolling (or pressing) in the rolling step S5 and the heat treatment in the heat treatment step S6 are repeated a plurality of times to form the superconducting conductor 3 having a predetermined size as shown in FIG. [Conducting Step: S7] As shown in FIG. 5, the superconducting conductor 3 is wound around a pipe-shaped former 2 to form a plurality of superconducting laminates 8 in a laminated state, thereby forming the oxide superconducting wire 1. Molding.

[0004]

However, in the above-described oxide superconducting wire 1, when an alternating current is applied to the oxide superconducting wire 1, as shown in FIG.
In each superconducting conductor 3, an eddy current F is generated by the influence of a self-magnetic field due to an alternating current flowing in a direction perpendicular to the plane of FIG. 6B. At this time, the sheath 5 is made of Ag having a low electric resistivity (for Ag, 1.63 μΩc at 20 ° C.).
6C), the eddy current F1 is conducted to the sheath 5 of the adjacent superconducting conductor 3, as shown in FIG. 6C. As a result, as shown in FIG. 7, since the eddy current F2 is conducted across the superconducting laminate 8, the eddy current F2 becomes dominant throughout the oxide superconducting wire 1 and the AC loss increases. there were.

The present invention has been made in view of the above circumstances, and aims to achieve the following objects. To increase the resistance of the superconducting conductor surface. To reduce eddy currents flowing between superconducting conductors in a superconducting laminate by retaining eddy currents in the superconducting conductor at the time of alternating current. To reduce AC loss when AC is applied.

[0006]

In an oxide superconducting wire according to the present invention, a plurality of superconducting conductors formed by arranging a plurality of superconducting cores inside a sheath are arranged around a pipe-shaped former. An oxide superconducting wire comprising: a superconducting laminate formed by winding the superconducting conductor around a former; and a surface of the superconducting conductor having a higher electrical resistivity than a sheath material forming a sheath. A high resistance layer for suppressing eddy current is formed by the resistance material. Superconducting core of the superconducting _{conductor, Bi 2 Sr 2 Ca 1 Cu} 2 O x (Bi221
Bi-phase), Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _y (Bi 2223)
Phase), Bi _1.6 Pb _0.4 Sr ₂ Ca ₂ Cu ₃ O _x , Tl ₂ Ba ₂
It has a composition represented by Ca ₂ Cu ₃ O _y , etc., and it is particularly preferable to select a Bi-based superconducting material of Bi-based 2223 phase or Bi-based 2212 phase.
It is preferable that the sheath is made of a noble metal such as Ag, Pt, or Au. The electrical resistivity of the high-resistance material is preferably three times or more the electrical resistivity of the sheath material. As the high-resistance material, zinc or titanium is preferably selected. Preferably, the former is made of stainless steel. In the method for manufacturing an oxide superconducting wire, a raw material powder processing step of mixing the raw material powder of the oxide superconducting material, and filling the mixed raw material powder into a sheath material pipe, forming a sheath material composite And a step of drawing (drawing out) a single-core wire by drawing the formed sheath material composite to a predetermined wire diameter to form a superconducting single-core elementary conductor (single-core wire). And multi-core forming a superconducting multi-core element conductor (multi-core wire) by assembling a plurality of formed superconducting single-core element conductors inside a pipe made of a coating material and then drawing to a predetermined wire diameter A step of rolling the superconducting multi-conductor element into a tape-shaped superconducting element conductor (tape material) by rolling, and a heat treatment step of heat-treating the superconducting element conductor a plurality of times to obtain a predetermined size Rolling to Form Superconducting Conductor (Tape Material) A processing repetition step, a high-resistance step of forming a high-resistance layer made of a high-resistance material having a higher electrical resistivity than the sheath material over the surface of the superconducting conductor, And forming a superconducting laminate by winding around the conductor. Zinc is selected as the high resistance material, and a high resistance layer is formed by zinc plating in the high resistance step. Titanium was selected as the high resistance material, and RF was used in the high resistance process.
The formation of the high resistance layer is performed by physical vapor deposition such as sputtering.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an oxide superconducting wire according to the present invention and a method for producing the same will be described below with reference to the drawings. 1 to 3, reference numeral 10 denotes an oxide superconducting wire, 11 denotes a superconducting core, 12 denotes a sheath, 13
Is a superconducting conductor, 14 is a high resistance layer, 15 is a former, 1
6 is a superconducting laminate.

In the oxide superconducting wire 10, as shown in FIG. 2, for example, a cylindrical superconducting laminate 16 is formed by winding a plurality of superconducting conductors 13 around a pipe-shaped former 15. ing. In such an oxide superconducting wire 10, as shown in FIG. 2, for example, the superconducting conductor 1 wound on the surface of a pipe-shaped former 15 is used.
The third layer 16A is wound in the direction of so-called S (from the right), and the second layer 16B of the superconducting conductor 13 wound around the first layer 16A is wound in the direction of the so-called Z (from the left).
Spiral winding in the SZ direction, which is wound in the opposite direction for each layer, such as winding in the direction of S, or spiral winding in the SS direction, which is wound in a direction overlapping S Is used to form a plurality of superconducting laminates 16 in a laminated state. The former 15 is made of, for example, stainless steel, and a semiconductor layer, an insulating layer, and / or a sealing layer (not shown) are formed outside the oxide superconducting wire 10.

The superconducting conductor 13 has a width of 0.5 mm to 5 mm.
And a thickness of about 0.05 mm to 0.7 mm in a tape shape, for example, a width of 4.0 mm and a thickness of 0.2.
0 mm. As shown in FIGS. 1 and 2, the superconducting conductor 13 is formed by arranging a plurality of superconducting cores 11 inside the sheath 12, and suppresses the conduction between the superconducting conductors 13 in the superconducting laminate 16. On the surface of the superconducting conductor 13, a high-resistance layer 14 is formed of a high-resistance material having a higher electrical resistivity than the sheath material forming the sheath 12. The superconducting core 11 of the superconducting conductor 13 is Bi ₂
Sr ₂ Ca ₁ Cu ₂ O _x (Bi 2212 phase), Bi ₂ Sr ₂
Ca ₂ Cu ₃ O _y (Bi 2223 phase), Bi _1.6 Pb _0.4 S
It has a composition represented by r ₂ Ca ₂ Cu ₃ O _x , Tl ₂ Ba ₂ Ca ₂ Cu ₃ O _y , and the like.
A three-phase Bi-based oxide superconducting material is selected. Sheath 1
Reference numeral 2 denotes a sheath material made of a precious metal such as Ag, Pt, or Au or an alloy thereof, and is, for example, Ag. The high-resistance layer 14 is formed of a high-resistance material and has a thickness in the range of 5 μm to 50 μm, and the electrical resistivity of the high-resistance material is 3% of the electrical resistivity of the sheath material in the sheath 12.
It is preferably at least three times, and preferably in the range of about three to thirty times. For example, when the sheath 12 is made of Ag (having an electrical resistivity of 1.63 μΩcm at 20 ° C.) or the like, zinc (20 ° C.) having about three times the electrical resistivity of the sheath material (Ag) is used as the high-resistance material. Has an electrical resistivity of 5.96 μΩcm) or a sheath material (Ag) of 3
Titanium having an electrical resistivity of about 0 (electrical resistivity is 55 μΩcm at 20 ° C.) or the like is applied.

Hereinafter, a method for producing an oxide superconducting wire according to the present invention will be described with reference to FIG. [Raw material processing step: S1] Raw material powder of oxide superconducting material, for example, Bi ₂ O ₃ , PbO, SrCO ₃ , CaC
O ₃ and CuO are converted to Bi: Pb: Sr: C
a: Cu: mixing so that the mixing ratio becomes 1.8: 0.4: 2.2: 3.0, and heat treatment (calcination) performed under a temperature condition of 780 ° C. to 820 ° C. and the calcining Is repeated several times. Here, the raw material powder to be mixed may be any of oxides and carbonates of each element of Bi, Pb, Sr, Ca, and Cu in addition to the above. [Filling step: S2] The powder pulverized in the raw material powder processing step S1 is formed into, for example, a cylindrical shape by CIP (cold isostatic pressing) molding or the like, and filled and sealed inside a pipe of a sheath material such as Ag. A complex (Ag complex) is formed. [Single Wire Drawing (Drawing) Processing Step: S3] The sheath material composite (Ag sheath composite) formed in the filling step S2 is drawn to a predetermined wire diameter with a die or the like, and the superconducting single core is formed. An elementary conductor (single core wire) is formed. [Multi-core process: S4] A predetermined number of superconducting single-core element conductors formed in the single-core wire drawing process S3 (for example, 37, 55
, Or 61) are assembled inside a coating pipe made of a coating material such as Ag, sealed, and then drawn to a predetermined wire diameter with a die or the like to obtain a superconducting multicore element conductor (multiple). Core wire). [Rolling heat treatment repetition step: S5, S6] The superconducting multi-core element conductor is formed into a tape-shaped superconducting element conductor (tape material) by rolling such as roll rolling. (Rolling process: S5)
The superconducting element conductor is housed inside an electric furnace or the like in a state of being wound around a heat treatment drum, for example, at a temperature of 825 ° C to 8 ° C.
The heat treatment is performed at a temperature in the range of 40 ° C. and a treatment time in the range of 10 hours to 100 hours. (Heat treatment step: S6)
Further, the rolling (or pressing) in the rolling step S5 and the heat treatment in the heat treatment step S6 are repeated a plurality of times to form a superconducting conductor (tape material) having a predetermined size. [High Resistance Step: SR] As shown in FIG. 1A, the high resistance layer 14 made of a high resistance material having a higher electrical resistivity than the sheath material, covering the surface of the superconducting conductor (tape material). To form Here, for example, zinc is selected as the high resistance material, and the high resistance layer 14 is formed by zinc plating in the high resistance step. [Molding Step: S7] The formed superconducting conductor 13 is
As shown in (1), the oxide superconducting wire 10 is formed by being wound around a pipe-shaped former 15 to form a superconducting laminate 16 having a plurality of laminated states, for example, five layers.

The case where an alternating current is applied to the oxide superconducting wire manufactured by the above manufacturing method will be described below.

When an alternating current is applied to the oxide superconducting wire 10, as shown in FIG. 1 (b), each superconducting conductor 13 generates a self-current due to the alternating current flowing in a direction perpendicular to the plane of FIG. 1 (b). An eddy current F is generated by the influence of the magnetic field. At this time, the sheath 12 has a low electric resistivity A
g (having an electrical resistivity of 1.63 μΩcm at 20 ° C.), but the high-resistance layer 14 around the sheath 12 is made of zinc having a high electrical resistivity (at 20 ° C., the electrical resistivity is 5.63 μΩcm).
96 μΩcm), the surface of the superconducting conductor 13 has a high resistance, and as shown in FIG.
Does not conduct to the sheath 12 of the adjacent superconducting conductor 13, and the eddy current remains inside each superconducting conductor 13. As a result, as shown in FIG. 3, in the superconducting laminate 16, since the conduction of the eddy current F <b> 3 is suppressed, the eddy current does not become dominant as a whole of the oxide superconducting wire 10, and the AC loss is reduced. It becomes possible.

In another embodiment of the present invention, for example, titanium is selected as the high-resistance material. At this time, in the resistance increasing step SR in the above-described manufacturing method, the resistance increasing layer 14 is formed by physical vapor deposition such as RF sputtering. Further, the high resistance layer 1 is made of Ti.
4, when the electrical resistivity of titanium is 20 ° C.
In this case, the surface of the superconducting conductor 13 is further increased in resistance because it is 55 μΩcm, which is higher than that of zinc, and the eddy current F1 can be conducted to the sheath 12 of the adjacent superconducting conductor 13 as shown in FIG. As a result, the eddy current stays inside each superconducting conductor 13. As a result, as shown in FIG. 3, in the superconducting laminate 16,
Since the conduction of the eddy current F3 is suppressed, the eddy current does not become dominant in the entire oxide superconducting wire 10, and the AC loss can be further reduced.

[0014]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples.

(Example 1) Bi ₂ O ₃ , PbO, SrCO
₃ , CaCO ₃ , CuO, Bi: Pb: Sr: Ca:
A plurality of heat treatments (calcination) performed at a temperature of 800 ° C. and pulverization after the calcination are performed by mixing the Cu so that the mixing ratio of Cu becomes 1.8: 0.4: 2.2: 3.0. This was repeated twice to obtain a raw material powder. This raw material powder is CIP
(Cold isostatic press) Formed into a cylindrical shape with an outer diameter of 1
An Ag pipe having a diameter of 3 mm and an inner diameter of 8 mm was filled and sealed to obtain an Ag sheath composite. The Ag sheath composite is drawn to a wire diameter of 2.0 mm with a die or the like to form a single core wire, and the single core wire is formed into an outer diameter of 21 mm and an inner diameter of 1 mm.
55 pieces were assembled in an 8.5 mm Ag pipe, filled and sealed, and then drawn to a wire diameter of 2.0 mm with a die or the like to obtain a multi-core wire. The tape material obtained by rolling the multi-core wire by roll rolling is subjected to a heat treatment at a temperature of 840 ° C. and a processing time of 45 hours.
This rolling (or pressing) and heat treatment were repeated a plurality of times to obtain a tape material having a width of 4.0 mm and a thickness of 0.2 mm.

Next, Zn ₃ (PO ₄ ) _{2 was} added to this tape material.
・ Zinc plating is performed by electro-zinc plating using a 4H ₂ O (tertiary zinc phosphate) aqueous solution, and the film thickness is 5
A superconducting conductor was obtained by forming a high-resistance layer of μm to 50 μm.

The superconducting conductor is insulated by attaching a Kapton tape to the surface, and has an outer diameter of 30 mm and a length of 10 m.
Was wound around a pipe-shaped former made of a stainless steel corrugated tube at a pitch of 50 cm to form a superconducting laminate having a five-layer structure to obtain an oxide superconducting wire.

(Example 2) In the same manner as in Example 1,
A tape material was produced. Next, 99.0 Ti is vapor-deposited on the produced tape material by RF sputtering at a temperature condition of 250 ° C., an RF power of 300 W and a processing time of 2 hours, and a high-resistance layer having a thickness of 5 μm to 50 μm is formed on the tape material surface. Thus, a superconducting conductor was obtained.

The superconducting conductor is insulated by attaching a Kapton tape to the surface, and has an outer diameter of 30 mm and a length of 10 m.
Was wound around a pipe-shaped former made of a stainless steel corrugated tube at a pitch of 50 cm to form a superconducting laminate having a five-layer structure to obtain an oxide superconducting wire.

Comparative Example A tape material was produced in the same manner as in the above example. Next, 25 pieces of the produced tape material are wound at a pitch of 50 cm around a pipe-shaped former made of a stainless steel corrugated pipe having an outer diameter of 30 mm and a length of 10 m, which is insulated by attaching a Kapton tape to the surface. A superconducting laminate was formed as a five-layer structure to obtain an oxide superconducting wire.

Measurement experiments were performed on the oxide superconducting wires obtained in Examples 1 and 2 and the oxide superconducting wires obtained in Comparative Examples under the following conditions. External magnetic field: 0 T Temperature: 77 K AC cycle: 30 Hz AC current value: 10 A AC loss of the oxide superconducting wire in Example 1: Lz AC loss of the oxide superconducting wire in Example 2: Lt AC loss of the oxide superconducting wire in Comparative Example AC loss: Ln Lt / Ln = 0.7 Lz / Ln = 0.8 As a result, when the high resistance layer is formed, the AC of the oxide superconducting wire is higher than when the high resistance layer is not formed. It was measured that the loss was reduced by 15% to 30%.

[0022]

According to the oxide superconducting wire of the present invention and the method for producing the same, the following effects can be obtained. (1) In the oxide superconducting wire according to the present invention, a superconducting conductor in which a plurality of superconducting cores are arranged inside a sheath and covered with a high-resistance layer is wound around a plurality of formers. An eddy current that is to be generated between the superconducting conductors can be suppressed by the high-resistance layer on the surface of the superconducting conductor, so that an AC loss during AC conduction can be reduced. (2) Since a high-resistance layer is formed on the surface of the superconducting conductor using zinc, titanium, or the like, the eddy current during alternating-current conduction is reliably retained in the superconducting conductor, and the eddy current flowing between the superconducting conductors in the superconducting laminate. , It is possible to reduce the AC loss at the time of AC energization. (3) Obtaining an oxide superconducting wire rod in which the eddy current flowing between the superconducting conductors in the superconducting laminate is reduced and the AC loss during AC conduction is reduced by implementing the manufacturing method according to the present invention. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a state when an AC current is applied to a superconducting conductor in an embodiment of an oxide superconducting wire and a method for manufacturing the same according to the present invention.

FIG. 2 is a perspective view showing an oxide superconducting wire according to an embodiment of the present invention and a method for manufacturing the same.

FIG. 3 is a cross-sectional view showing a superconducting laminate according to one embodiment of the oxide superconducting wire and the method for producing the same according to the present invention.

FIG. 4 is a flowchart showing one embodiment of a method for manufacturing an oxide superconducting wire according to the present invention.

FIG. 5 is a perspective view showing a conventional oxide superconducting wire.

FIG. 6 is a schematic cross-sectional view showing a state of a conventional superconducting conductor when an alternating current is applied.

FIG. 7 is a sectional view showing a conventional superconducting laminate.

FIG. 8 is a flowchart showing a conventional method for manufacturing an oxide superconducting wire.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... oxide superconducting wire, 11 ... superconducting core, 12 ... sheath, 13 ... superconducting conductor, 14 ... high resistance layer, 15 ... former, 16 ... superconducting laminated body, 16A ... first layer, 16B
… Second layer, F… eddy current, F3… eddy current

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takashi Saito 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Co., Ltd.

Claims (4)

[Claims] 1. An oxide superconducting wire comprising a plurality of superconducting conductors formed by arranging a plurality of superconducting cores inside a sheath around a pipe-shaped former, wherein the superconducting conductor is wound around the former. By turning, a superconducting laminate is formed, and on the surface of the superconducting conductor, a high-resistance layer for suppressing eddy current is formed by a high-resistance material having a higher electrical resistivity than the sheath material forming the sheath. An oxide superconducting wire, characterized in that: 2. The oxide superconducting wire according to claim 1, wherein the electrical resistivity of the high-resistance material is at least three times the electrical resistivity of the sheath material. 3. The oxide superconducting wire according to claim 1, wherein zinc or titanium is selected as the high-resistance material. 4. A method for producing an oxide superconducting wire comprising a plurality of superconducting conductors formed by arranging a plurality of superconducting cores inside a sheath around a pipe-shaped former, the method comprising: A raw material powder processing step of mixing the raw material powders, and a filling step of filling the mixed raw material powder into a sheath material pipe to form a sheath material composite,
The formed sheath material composite is drawn to a predetermined wire diameter to form a superconducting single-core elementary conductor, and the formed superconducting single-core elementary conductor is coated with a pipe of a covering material. After a plurality of pieces are assembled inside, a multi-core forming step of forming a superconducting multi-core element by drawing to a predetermined wire diameter, and rolling the super-conducting multi-element element into a tape-shaped superconducting element conductor by rolling. Forming, performing a heat treatment on the superconducting element conductor, a rolling heat treatment repeating step of forming a superconducting conductor of a predetermined size by repeating this rolling and heat treatment a plurality of times, and covering the surface of the superconducting conductor, from a sheath material. A high-resistance step of forming a high-resistance layer made of a high-resistance material having a large electric resistivity,
A step of winding the formed superconducting conductor around a former to form a superconducting laminate, and forming a superconducting laminate.