JPH11353956A - Oxide superconductive twisted wire, conductor for oxide superconductive cable, and manufacture of oxide superconductive twisted wire and conductor for oxide superconductive cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide oxide superconductive twisted wires and a conductor for an oxide superconductive cable having high critical current density, and having the shape of winding a cylindrical core material at the prescribed pitch with element wires composed of an oxide superconductive material or its precursor and silver or a silver alloy covering it. SOLUTION: Plural twisted wires are twisted using element wires composed of an oxide superconductive material or its precursor and silver or a silver alloy covering it. A cylindrical core material 12 is wound with the plural twisted wires at the prescribed pitch, and they are heat-treated to manufacture the oxide superconductive twisted wires. The oxide superconductive twisted wires are assembled on an flexible core material having the same outside diameter as the core material used before the heat-treatment, at the same pitch as before the heat-treatment, to manufacture the conductor for the oxide superconductive cable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconducting stranded wire and a conductor for an oxide superconducting cable using an oxide superconductor or a precursor and a wire covering the same, and a technique for producing the same. In particular, the present invention relates to a technique for providing a conductor for an oxide superconducting stranded wire and an oxide superconducting cable having a high critical current density.

[0002]

2. Description of the Related Art Since an oxide superconducting wire exhibits a superconducting state at liquid nitrogen temperature, it is expected to be applied to superconducting magnets, superconducting cables and the like, and its development is being promoted. In particular, research and development have been conducted on a metal-coated bismuth-based oxide superconducting wire to obtain a high critical current density.

[0003] Regarding the conductor for oxide superconducting cable,
A structure is known in which a tape-shaped silver-coated bismuth-based superconducting wire is spirally wound in multiple layers on a core material. However, in this structure, there is a problem that an AC loss at the time of energization is large because a drift occurs due to a difference in impedance between the inner layer and the outer layer of the conductor. Further, a large AC loss causes a reduction in critical current. As an oxide superconducting cable conductor having a small AC loss, an oxide superconducting cable conductor composed of a stranded sub-cable has been proposed. The AC loss can be reduced by increasing the number of wires in the sub-cable and adopting a multi-strand structure, but the size of the sub-cable increases. In this case, when the strain is applied, the critical current characteristic of the oxide superconducting wire is likely to deteriorate, and the critical current characteristic of the superconducting cable conductor produced by assembling the sub-cables is reduced, and the entire conductor of the oxide superconducting cable is reduced. Has a lower critical current density characteristic.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique for manufacturing a conductor for an oxide superconducting stranded wire and an oxide superconducting cable having excellent critical current characteristics using an oxide superconducting wire. It is in.

[0005]

According to the present invention, an oxide superconducting twisted wire and a conductor for an oxide superconducting cable are manufactured using an oxide superconducting material or a precursor and a wire made of silver or a silver alloy covering the same. A method is provided for doing so. This method comprises the steps of: preparing an oxide superconducting material or a precursor and a wire made of silver or a silver alloy covering the same; and a step of providing an electric insulating layer on the wire, and twisting the wire.
The method includes a step of displacing the strand, and a step of heating and heat-treating the stranded wire to a temperature required for producing an oxide superconducting material.

[0006] As the electric insulating layer of the strand in the production method of the present invention, a coating mainly containing a silicon-based organometallic polymer, a coating mainly containing aluminum phosphate, or the like can be used as the electric insulating layer. . Further, in the manufacturing method according to the present invention, after the strands are twisted, the obtained stranded wire can be formed, for example, so that its cross section becomes a flat or fan shape. Next, the formed stranded wire is heated to a temperature necessary for forming an oxide superconducting material, and heat-treated. By performing a heat treatment after forming the stranded wire in this way, the influence during stranded wire formation is reduced, and a superconducting stranded wire having a high critical current and a high critical current density can be obtained. The formed superconducting stranded wire is useful for forming a compact cable conductor.

The present invention provides a method for manufacturing a conductor for an oxide superconducting cable, comprising a step of winding a plurality of stranded wires obtained by the above-described manufacturing method around a cylindrical core material.

According to the present invention, the above-described plurality of stranded wires are wound around a cylindrical core material, and then heated to a temperature necessary for producing an oxide superconducting material, and heat-treated. On a flexible core material having the same outer diameter as the core material used for the heat treatment, by gathering the stranded wires before heat treatment at the same pitch wound on a cylindrical core material, It is possible to provide an oxide superconducting cable conductor obtained by winding a plurality of stranded oxide superconducting wires around a cylindrical core material.

[0009]

DETAILED DESCRIPTION OF THE INVENTION In the manufacture of an oxide superconductor, for example, a bismuth-based 2223 phase oxide superconductor coated with a metal such as silver or a silver alloy, an oxide superconductor is produced. For example, about 850
Heat treatment is performed at a high temperature of ° C. The oxide superconducting material generated by the heat treatment is relatively vulnerable to bending, and is liable to deteriorate the critical current at a bending strain of, for example, more than 0.3%. Therefore, when a plurality of oxide superconducting wires obtained through the heat treatment step are twisted, bending of the oxide superconducting material occurs due to bending strain, and characteristics such as critical current of the oxide superconducting wire deteriorate. The inventor of the present application prepares an element wire, and after performing a twisting step of twisting the element wire, performs a heat treatment for generating an oxide superconductor, so that an oxide superconducting stranded wire and an oxide exhibiting excellent superconducting properties are obtained. It has been found that a conductor for a superconducting cable can be obtained.

[0010] A predetermined amount of a raw material of the oxide superconducting material is weighed, and the precursor powder 1 of the oxide superconducting material produced by calcining is filled in a silver or silver alloy metal tube 2.
A composite as shown in FIG. 1 is obtained.

The composite material of the precursor powder of the oxide superconductor and the metal is rolled to obtain a tape-like composite material as shown in FIG.

A tape-shaped composite material shown in FIG. 2 is arranged around a silver or silver alloy core wire 3 and inserted into a silver or silver alloy metal tube 5 to perform a diameter reduction such as wire drawing. As a result, a composite material 6 having a multilayer portion 4 made of a powder of a precursor of an oxide superconductor as shown in FIG. 3 is obtained. The amount of the precursor of the oxide superconductor can be adjusted by the amount of winding of the tape-shaped composite material.

As shown in FIG. 4, a plurality of composite materials 6 shown in FIG. 3 are inserted into a silver or silver alloy metal tube 7 and then subjected to a diameter reduction such as a wire drawing to obtain a composite material 6 as shown in FIG. A plurality of the composite materials 6 shown in FIG.
A wire 9 embedded in multiple cores is obtained. Composite material 6 of FIG.
Can control the amount of the precursor of the oxide superconductor. Also, by adjusting the thickness of the metal tube 5 made of silver or silver alloy, by adjusting the interval between the core materials, the interval between the oxide superconductors generated by the heat treatment can be adjusted, and the high critical current can be adjusted. An oxide superconducting wire having a low value and low AC loss can be obtained.

As shown in FIG. 5, an electric insulating layer 10 is formed on the outer periphery of the strand 9. As the electric insulating layer, it has been found that organometallic polymers such as silicon-based organometallic polymers, compounds such as aluminum phosphate, or boron nitride are excellent in terms of resistance to heat treatment, adhesion to strands and strength. . If these materials are used, it is difficult to peel off at the time of twisting, and a coating layer having excellent strength can be formed. By providing an electric insulating layer on the surface of the strand, the coupling current between the strands can be reduced, and the AC loss can be reduced.

The plurality of strands 9 on which the electric insulating layer 10 is formed as described above are twisted to form a stranded wire. At the time of twisting, by subjecting the strand 9 to dislocation,
The drift between the oxide superconductors in the strand can be reduced.

By repeating the twisting step, a secondary or higher order twisted wire can be obtained. FIG. 6 shows an example of a secondary stranded wire in which six strands 9 are primary stranded on a core wire 11 of silver or a silver alloy, and four primary stranded wires are further stranded. The number of twisted wires,
Depending on the twist order, a stranded wire having a large current capacity can be obtained. Also, as the number of twists increases, the effect of dislocation increases, the impedance of the outer and inner layers of the twisted wires can be made uniform, the drift between the twisted wires can be reduced, and the AC loss can be reduced. it can.

Further, by forming the obtained stranded wire into a shape such as a rectangular shape or a fan shape, the packing factor can be increased, a more compact stranded wire can be obtained, and the current density can be improved. FIG. 7 shows an example in which FIG. 6 is formed into a rectangular shape, and a compact formed stranded wire having a small space between the strands and between the stranded wires can be obtained.

As shown in FIG. 8, the stranded wire produced in this manner is wound as a sub-cable 13 around the cylindrical sintering core 12 at a predetermined pitch, and as shown in FIGS. By collecting a plurality of sub-cables 13, a conductor for a superconducting cable can be manufactured. Core material for sintering 1
2 uses a metal tube that can withstand the temperature required for heat treatment of the oxide superconducting material.

The heat treatment for forming the oxide superconductor is performed, for example, at a temperature of 800 to 900 ° C., preferably 840 to 900 ° C.
It is performed at a temperature of 850 ° C. In this way, the cylindrical core material for sintering is wound at a predetermined pitch, and after the stranded wires are assembled, heat treatment is performed to reduce the influence of distortion during stranded wire,
A stranded wire exhibiting high critical current and critical current density characteristics is obtained.

A sub-cable consisting of a plurality of stranded wires is wound around a cylindrical sintering core 12 at a predetermined pitch, and after heat treatment, the winding diameter is enlarged by loosening the twist of the sub-cable or the like. Remove the binding core 12. After that, the core material is replaced with a flexible core material having the same outer diameter as the sintering core material 12, and assembled at the same pitch wound around the cylindrical core material before the heat treatment. A conductor can be obtained. The flexible core material of the superconducting cable conductor can be formed of, for example, copper, aluminum, FRP (fiber reinforced plastic) or the like, and it is preferable to use a copper core material in terms of strength and flexibility.

Further, a sub-cable consisting of a plurality of stranded wires is wound around a cylindrical sintering core material 12 at a predetermined pitch, and after heat treatment, the conductor is disassembled. In this case, the sub-cable is disassembled so as to maintain the wound shape even after disassembly of the conductor, and the sub-cable after disassembly of the conductor is reassembled into a flexible core copper pipe having the same diameter as the sintering core. By assembling on this core material, a conductor for an oxide superconducting cable can be obtained. Also in this case, the material for the core material for sintering and the material for the flexible core material can be selected from the viewpoint of their heat resistance and flexibility.

By assembling the stranded sub-cables in this way, the effect of distortion during the production of the oxide superconducting cable conductor can be reduced. Higher critical current characteristics are obtained as compared to an oxide superconducting cable conductor produced by assembling while winding this stranded wire or an oxide superconducting cable conductor produced by assembling while winding a heat-treated stranded wire. be able to. Hereinafter, the present invention will be described in more detail with reference to examples.

[0023]

EXAMPLES Example 1 Bi ₂ O ₃ , PbO, SrCO ₃ , CaCO ₃ and CuO
Using the powder of Bi: Pb: Sr: Ca: Cu = 1.
Powders having a composition ratio of 8: 0.4: 2: 2: 3 were mixed. This powder was treated at 700 ° C for 12 hours and at 800 ° C for 8 hours for 8 hours.
After calcination for an hour, calcination was further performed at 850 ° C. for 8 hours. This calcined powder was pulverized with a ball mill. After degassing the powder by heating at 800 ° C. for 15 minutes,
Silver pipes were filled as shown in FIG. This silver pipe is 1.
After drawing to 15 mmφ, it was rolled as shown in FIG. 2 to a thickness of 0.2 mm. As shown in FIG. 3, a plurality of rolled tape wire rods are arranged concentrically around a silver bar, and seven oxide superconducting material precursor and silver composite materials are used and fitted to a silver pipe as shown in FIG. Then, wire drawing was performed to 0.9 mmφ to produce a round element wire as shown in FIG. This wire was subjected to a heat treatment at 850 ° C. for 50 hours,
After the electrical insulating layer 10 was provided using an inorganic insulating material based on iO ₂ , a twisting process was performed. Primary stranded wire processing is 0.
Six strands were twisted at a twist pitch of 40 mm with the silver wire 5 of 9 mmφ as the center line. In the secondary stranded wire processing, the four primary stranded wires are twisted at a twist pitch of 80 mm as shown in FIG. 6 and formed into a width of 8 mm and a thickness of 3 mm. Produced.

As shown in FIG. 8, the sub-cable is wound around a stainless steel tube core having an outer diameter of 19 mmφ and an inner diameter of 17 mmφ with a pitch P of 200 mm, bound with a glass tape, and subjected to a heat treatment at 850 ° C. for 100 hours. gave. When Ic was measured in liquid nitrogen while being wound after the heat treatment, Ic was 40 A.

COMPARATIVE EXAMPLE 1 850 was added to the straight secondary stranded wire obtained in Example 1 before the heat treatment.
Heat treatment was performed at 100C for 100 hours. After the heat treatment, a part of the sub-cable was cut out, and the critical current Ic was measured in liquid nitrogen. On the other hand, as shown in FIG. 8, the sub-cable which has been heat-treated in a straight shape is made of a stainless steel core material 12 having an outer diameter of 19 mmφ and an inner diameter of 17 mmφ.
The winding pitch P was set to 200 mm, and Ic was measured in liquid nitrogen in a state of being wound. As a result, Ic was reduced to 12A.

From the above, in the oxide superconducting stranded wire of the present invention of Example 1, the same Ic as that of the heat-treated oxide superconducting stranded wire can be obtained, and the heat-treated stranded wire is used as the core material. It was confirmed that a higher critical current characteristic can be obtained as compared with the wound oxide superconducting stranded wire.

Comparative Example 2 As shown in FIGS. 9 and 10, a copper straight pipe was used as a core material.
The sub-cable 13 obtained in Example 1 was heat-treated, and a single-layer conductor having a length of 5 m was produced using the seven sub-cables. The winding pitch of the sub cable around the core material was 200 mm, and a Mylar tape was wound around the conductor surface. After producing this conductor, the conductor was wound around a drum having a body diameter of 1.6 mφ. When the conductor was rewound from the drum, the conductor was disassembled and the appearance was examined. No buckling or tearing was found in the core material and the sub-cable. This test confirmed that the copper straight pipe had no problem in terms of flexibility as a conductor core material. On the other hand, when a part of the sub-cable after the conductor disassembly was cut out and subjected to Ic measurement, Ic was reduced to 10A. This is because, in addition to the mechanical strain at the time of assembling the sub-cables after the heat treatment, the sub-cable is newly subjected to mechanical strain due to bending when wound around the drum.

Comparative Example 3 A single-layer conductor having a length of 5 m was manufactured using a stainless steel straight pipe as a core material and seven sub-cables before heat treatment prepared in Example 1. The winding pitch of the sub cable around the core material was 200 mm. 850 ° C, 100
After the secondary heat treatment for a time, the conductor was sunk to a diameter of 1.6 mφ.
Wrapped around the drum. Then rewind from the drum,
This conductor was dismantled. A part of the sub-cable after the conductor was disassembled was cut out, and Ic measurement was performed.
It was found that Ic was three times higher than that of A and Comparative Example 2. However, after dismantling, an appearance inspection was performed, and it was found that buckling and tearing occurred in the stainless straight pipe, and the stainless steel straight pipe used was insufficient in flexibility as a conductor core material. I found it.

Example 2 Using a stainless steel straight tube as a core material and seven sub-cables before heat treatment prepared in Example 1, a single-layer conductor of 5 m in length was produced. The winding pitch of the sub cable around the core material was 200 mm. After subjecting this conductor to heat treatment at 850 ° C. for 100 hours, the stainless steel straight tube was pulled out and a copper pipe was inserted at the same time, so that the core material was a single-layer conductor of a copper pipe. Mylar tape was wrapped around the conductor surface for the purpose of protection and fixing. Further, after the conductor was wound around a drum having a body diameter of 1.6 mφ, the conductor was rewound, and a part of the sub-cable after being disassembled was cut out and subjected to Ic measurement.
It was found that Ic was 30 A, which was three times higher than that of Comparative Example 2. In addition, when the conductor was disassembled and the appearance was examined, no buckling or tearing was observed in the outer appearance of the core material and the sub-cable, and it was found that the conductor had no problem in terms of flexibility. As described above, it was found that the conductor manufactured by this method had flexibility and high critical current characteristics.

Example 3 As another example, a single-layer wound conductor having a length of 1 m was produced using a stainless steel straight pipe as a core material and seven sub-cables before heat treatment produced in Example 1. The winding pitch of the sub cable around the core material was 200 mm. After subjecting this conductor to heat treatment at 850 ° C. for 100 hours, the conductor was disassembled. The sub-cable maintained its twisted shape after the conductor was dismantled. After the conductor was disassembled, the seven sub-cables were reassembled using a copper tube having the same diameter (19 mmφ) as the stainless steel tube as a core material to obtain a single-layer wound conductor having a winding pitch of 200 mm. Mylar tape was wrapped around the conductor surface for the purpose of protection and fixing. This conductor was wound around a drum having a body diameter of 1.6 mφ, and then unwound from the drum. A part of the sub-cable after disassembly was cut out and subjected to Ic measurement. As a result, it was found that Ic was 28 A, which was about three times higher than that of Comparative Example 2. Further, when the conductor was disassembled and the appearance was examined, no buckling or tearing was found in the core material and the sub-cable, and it was found that the conductor had no problem in terms of flexibility. As described above, it is possible to temporarily disassemble the sub-cable after the heat treatment and replace the core used for the heat treatment with a flexible core while maintaining the shape of the sub-cable. It was found that the produced conductor had flexibility and high critical current characteristics.

Comparative Example 4 Further, a tape-shaped silver sheath oxide superconducting wire (width 3.5
mm, and a thickness of 0.2 mm) to prepare a conductor for an oxide superconducting cable. Using 14 tape-shaped oxide superconducting wires, the conductor was wound on a stainless steel straight tube at a winding pitch of 200 mm, and two conductors having a length of 1 m were produced. After subjecting this conductor to a second heat treatment at 850 ° C. for 100 hours,
The book conductor was dismantled. The tape-shaped oxide superconducting wire is easily deformed, and it is difficult for the wire after disassembly of the conductor to keep the shape wound around the core. Also, using the remaining one conductor,
When the extraction of the stainless steel tube and the insertion of the copper tube were performed simultaneously, the winding of the oxide superconducting wire was disturbed during the operation. As described above, the technique of replacing the core material cannot be applied to a conductor using a tape-shaped oxide superconducting wire, and is effective in the case of producing a conductor for a superconducting oxide cable using a sub-cable as in the present invention. all right.

[0032]

As described above, according to the present invention, a dislocation is applied to a wire by twisting a wire made of an oxide superconducting material or a precursor and a wire made of silver or a silver alloy covering the same, and a plurality of wires are formed. After the stranded wires are assembled on a cylindrical core material and heat-treated to produce an oxide superconducting stranded wire, the oxidized wire having a shape wound around the cylindrical core material at a predetermined pitch is maintained. By using the superconducting stranded wire as a sub-cable constituting the conductor for an oxide superconducting cable, it is possible to manufacture a stranded oxide superconducting wire and a conductor for an oxide superconducting cable having excellent critical current characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a cross-sectional structure of a composite material comprising a precursor powder of an oxide superconductor and a metal used in the present invention.

FIG. 2 is a schematic view showing a cross-sectional structure of a tape-shaped composite material composed of a precursor powder of an oxide superconductor and a metal used in the present invention.

FIG. 3 is a schematic view showing a cross-sectional structure of a composite material provided with a multilayer portion made of a precursor of an oxide superconductor used in the present invention.

FIG. 4 is a schematic view showing a cross section of a composite material in which a plurality of composite materials of FIG. 3 used in the present invention are inserted into a metal tube.

5 is a schematic diagram of a cross-sectional structure of a wire in which a plurality of composite materials of FIG. 3 are embedded in a silver or silver alloy base material.

FIG. 6 is a schematic diagram showing a cross-sectional structure of a secondary stranded wire used in the present invention.

FIG. 7 is a schematic diagram showing a cross-sectional structure of a formed secondary stranded wire used in the present invention.

FIG. 8 is a perspective view showing a state of a sub-cable wound around a sintering core material at a winding pitch P.

FIG. 9 is a perspective view showing a state in which a sub-cable is wound around a core material in manufacturing an oxide superconducting cable.

FIG. 10 is a schematic view showing a cross-sectional structure of a conductor for an oxide superconducting cable used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Precursor powder of oxide superconductor 2 Metal tube of silver or silver alloy 3 Core wire of silver or silver alloy 4 Multilayer portion composed of precursor powder of oxide superconductor 5 Metal tube of silver or silver alloy 6 Composite material 7 Silver or silver alloy metal tube 8 Base material made of silver or silver alloy 9 Element wire 10 Electrical insulation layer 11 Core material 12 Core material 13 Sub cable

Claims (7)

[Claims] 1. A strand made of an oxide superconducting material or a precursor and a strand made of silver or a silver alloy covering the same and subjected to dislocation, and the strand is heat-treated. Oxide superconducting stranded wire having a shape wound on it at a predetermined pitch 2. The stranded oxide superconducting wire according to claim 1, wherein an electric insulating layer is coated on a surface of said wire. 3. The stranded oxide superconducting wire according to claim 1, wherein said stranded oxide superconducting wire has a multi-strand structure. 4. The stranded oxide superconducting wire according to claim 1, wherein a cross section of the stranded oxide superconducting wire is rectangular or fan-shaped. 5. A strand of an oxide superconducting material or a precursor and a strand of silver or a silver alloy covering the same to perform dislocation on the strand, and a plurality of the strands are placed on a cylindrical core material. And heat-treated to produce an oxide superconducting stranded wire, the oxide superconducting stranded wire having a shape wound at a predetermined pitch on a cylindrical core material is used for an oxide superconducting cable. A conductor for an oxide superconducting cable, characterized in that the conductor is a sub-cable. 6. A dislocation is applied to an element by twisting an element made of an oxide superconducting material or a precursor and silver or a silver alloy covering the element, and disposing the element on a cylindrical core material. A method for producing a stranded oxide superconducting wire, comprising heat-treating in a shape wound at a pitch. 7. A dislocation is applied to a wire made of an oxide superconducting material or a precursor and a wire made of silver or a silver alloy covering the same to apply dislocation to the wire, and a plurality of the stranded wires are placed on a cylindrical core material. At a predetermined pitch, and then heat-treating the oxidized superconducting stranded wire on a flexible core material having the same outer diameter as the core material used for the heat treatment. A method for producing a conductor for an oxide superconducting cable, comprising: assembling wires at the same pitch wound on a cylindrical core material.