JPH0765646A - Oxide superconducting cable and manufacture of strand - Google Patents

Abstract

PURPOSE:To provide an oxide superconducting cable excellent in laying workability with a good flexibility and hard to generate decrease in superconducting characteristic, e.g. critical current and the like owing to stranded conditions of oxide superconducting wire as well as low temp. cooling of cable. CONSTITUTION:Around the outer circumference of a cable former 1 composed of a spiral pipe, spiral strands 2, 3 composed of an oxide superconducting wire having a metal sheath are disposed. To produce the strands 2, 3 for the oxide superconducting cable, strand material of oxide superconducting wire having a metal sheath is spirally wound around a heat resistant pipe with the bending distortion difference within 0.1 of the bending distrotion in the case of spirally winding onto the cable former 1, and it is heat treated to form the spiral strands 2, 3. With such a method, a former with an arbitral outer dia. can be used through avoiding the winding process to the former 1, thereby providing a compact 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 cable having good layability suitable for a power cable and the like, and a method for manufacturing the above-mentioned cable strand having excellent superconducting characteristics.

[0002]

2. Description of the Related Art A system for realizing high current transmission with a compact power cable by utilizing the characteristics of an oxide superconductor has been studied.

Conventionally, as a power cable used in such a system, there has been known one in which an oxide superconducting wire having a metal sheath is spirally wound around the outer circumference of a cable former made of a metal pipe. However, when cooled to a low temperature to form a superconducting state, characteristics such as critical current are deteriorated, and it is difficult to bend the cable, and the flexibility is poor and workability at the time of laying is poor.

Further, by spirally winding an oxide superconducting wire around a cable former, there is also a problem that the superconducting characteristics, and in particular, the critical current is greatly reduced as compared with the case where the oxide superconducting wire is in a straight line state before being twisted. It was

[0005]

DISCLOSURE OF THE INVENTION The present invention shows good flexibility and excellent workability for laying, and the critical current can be obtained by cooling the cable to a low temperature and twisting the oxide superconducting wire. It is an object to obtain an oxide superconducting cable in which characteristics such as

[0006]

According to the present invention, an oxide superconducting cable is characterized in that a cable former made of a spiral tube has a spiral element wire made of an oxide superconducting wire having a metal sheath on the outer periphery thereof. , And an oxide superconducting stranded wire having a metal sheath, which is spirally wound around the outer periphery of the heat-resistant pipe with a bending strain difference of 0.1% or less when the spiral winding is performed on the cable former. The present invention provides a method for manufacturing an element wire for an oxide superconducting cable, which comprises heat-treating the element to form the above-mentioned helical element wire.

[0007]

By using the spiral tube as the cable former, it is possible to prevent the characteristics such as the critical current from being deteriorated when the cable is cooled to a low temperature, and the good flexibility due to the good deformability of the spiral tube. It is possible to obtain a cable having excellent laying workability. In order to prevent the deterioration of characteristics due to the low temperature cooling, the difference in thermal deformation due to the difference in expansion coefficient between the wire and the cable former during low temperature cooling is deformed by reducing the diameter of the spiral tube, etc. It is thought that this is because the stress-strain generated in the oxide superconducting wire forming the twisted wire is reduced by absorbing the shrinkage of the wire due to.

On the other hand, the oxide superconducting wire spirally provided on the outer circumference of the cable former is formed in advance as an element wire having a predetermined spiral state, so that the outer circumference of the cable former made of a metal pipe, a spiral tube or the like is formed. It is possible to prevent the occurrence of bending strain due to the spiral winding, and to prevent the deterioration of the characteristics such as the critical current due to the twisting of the oxide superconducting wire, thereby providing a cable having excellent superconducting characteristics. In addition, it is possible to avoid the need to wind the oxide superconducting wire around the former and to avoid problems such as cracking due to the winding process, and it is possible to use a former with a smaller outer diameter to improve compactness. You can

[0009]

EXAMPLE The oxide superconducting cable of the present invention comprises a cable former made of a spiral tube and a spiral strand made of an oxide superconducting wire having a metal sheath on the outer circumference. An example thereof is shown in FIG. Reference numeral 1 is a cable former, 2 is a first-layer strand, and 3 is a second-layer strand.

The spiral tube used as the cable former in the present invention may be any suitable one depending on the oxide superconducting cable to be formed. Generally, width 2-10m
For example, a plate-shaped wire rod having a thickness of 1 to 5 mm and a thickness of 1 to 5 mm is spirally wound into a tubular shape having an outer diameter of 10 to 30 mm.

As the material for forming the spiral tube, metals such as stainless steel, silver and copper or plastics, or FRP using carbon fibers or glass fibers are generally used. For forming a cable for AC power transmission, a spiral tube made of FRP or the like is advantageous because power loss is small.

The cable former used in the present invention may be a spiral tube provided with a polymer layer on the outer periphery thereof. In such a polymer layer, the oxide superconducting wire forming the stranded wire is in a state of being partially in contact with the spiral tube due to the gap of the spiral tube, and local strain due to a stress difference occurs in the oxide superconducting wire due to bending and extension of the cable. It is provided for the purpose of guaranteeing the contact for the purpose of preventing the deterioration of the characteristics. Therefore, when the strands made of oxide superconducting wires are superposed to form a multi-layer winding structure, they can be provided also between the layers.

The polymer layer can be formed, for example, by a method in which a film or tape made of a polymer is wound around the outer circumference of the spiral tube without leaving a gap to cover it. As the polymer, for example, polyester or polyimide, and above all, a fluororesin having good sliding property and low temperature embrittlement resistance can be preferably used.

The oxide superconducting cable can be formed, for example, by spirally winding a linear oxide superconducting wire around the outer circumference of the cable former, or by previously forming a strand of the spiral oxide superconducting wire. It can also be carried out by a method of forming the above and mounting it on the outer circumference of the cable former. The former is able to wind the oxide superconducting wire around the former with good adhesion and is advantageous in preventing the deterioration of superconducting properties due to loosening, etc.The latter is the deterioration of superconducting properties due to bending strain when winding the oxide superconducting wire. It is advantageous for prevention of

The above-mentioned spiral element wire made of the oxide superconducting wire has a bending strain amount of 0.1% or less when spirally winding an oxide superconducting stranded wire material having a metal sheath on a cable former. It can be manufactured by, for example, a method of spirally winding the heat-resistant tube around the outer circumference of the heat-resistant tube due to the difference in bending strain, and heat-treating it.

The oxide superconducting stranded wire material having a metal sheath, which is spirally wound around the outer periphery of the heat resistant tube, may be an oxide superconducting wire obtained by finishing the sintering of the superconducting layer. Generally, the oxide superconductor inside the metal sheath before sintering is in a powder state, or the state in which the formed superconducting layer is crushed by pre-sintering it and pressing it. . The press treatment is intended to stabilize or improve the quality, and is performed twice or more if necessary, and in that case, a heating step is usually provided between the press treatment before and after the press treatment.

The stranded wire material may be made of an oxide superconducting wire having a metal sheath or a single core of the forming material thereof, or a composite material obtained by making the single wire multicore by an appropriate method. May be. The stranded wire material has a width of 2 to 5
In general, a flat shape such as a tape shape or a rectangular shape having a thickness of about 0.1 mm and a thickness of 0.1 to 0.3 mm is used, but it has an appropriate cross-sectional shape such as a round wire shape and other polygonal shapes. May be.

To form the stranded wire material, for example, a powder of oxide superconductor is filled in a metal tube, and the wire is made long by an appropriate wire drawing means such as a die or pinch roll, a rolling means, and a swaging means. It can be performed by an arbitrary method such as a method of treatment, flattening processing, or forging processing. The metal tube is processed into a metal sheath. The multifilamentary wire can be obtained by, for example, a method of filling a metal tube with a plurality of wire rods and thinning or flattening it to make it composite a plurality of times as necessary. The particle size of the oxide superconductor powder to be used is generally 100 μm or less, preferably 0.1 to 10 μm, and the powder can be obtained by, for example, a method of pulverizing a sintered body of the oxide superconductor. .

As a material for forming the metal sheath in the oxide superconducting stranded wire material, for example, silver, gold, platinum, stainless steel, alloys containing such metals such as silver-magnesium alloy, especially silver-platinum alloy, silver -A noble metal-based material such as a high melting point alloy such as a palladium alloy is generally used, but is not limited thereto.

There is no particular limitation on the type of components forming the oxide superconductor inside the metal sheath. Examples thereof include Bi ₂ Sr ₂ CaCu ₂ O _y and Bi _2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _y.
Bi-based oxide superconductors such as YBa ₂ Cu ₃ O _y and YBa ₂ C
Y-based oxide superconductors such as u ₄ O _y , Ba _- based oxide superconductors such as Ba _1-x K _x BiO ₃ , Nd _- based oxide superconductors such as Nd _2-x Ce _x CuO _y , Tl ₂ Ba Examples include Tl-based oxide superconductors such as ₂ Ca ₂ Cu ₃ O _y , other La-based oxide superconductors, Pb-based oxide superconductors, and the like.

Further, the above-mentioned components such as Bi are substituted with other rare earth elements, the components such as Sr are substituted with other alkaline earth metals, or the O component is substituted with F. To be Furthermore, the thing containing the pinning center etc. is mentioned. The pinning center-containing oxide superconductor has the advantage of exhibiting a large critical current density even under a high magnetic field due to the effect of pinning the magnetic flux by the pinning center. The oxide superconductor containing the pinning center is, for example, the MPMG method (Melt
Powdering Melt Growth) and the like.

In the present invention, the heat-resistant tube used for forming the spiral element wire is intended to enable the element wire obtained after the heat treatment to be removed therefrom, and accordingly, the oxide superconducting stranded wire material can be removed by the heat treatment. The tube may be made of a suitable material such as a tube made of ceramic such as alumina that does not become inseparable by being adhered to and a coated tube such as a stainless steel tube coated with ceramic. The heat-resistant tube may be formed as an assembled split mold or the like to facilitate the removal of the wire.

The winding condition of the oxide superconducting stranded wire around the heat-resistant tube is within 0.1% of the bending strain when spirally wound around the cable former to be used, preferably 0.05. The spiral winding condition is that the difference in bending strain is within%. If the bending strain amount difference exceeds 0.1%, the superconducting property is significantly deteriorated when applied to a cable former.

The bending strain amount (ε) is calculated by the equation: ε = t
・ Can be calculated from cos ² β / 2r. Note that t is the thickness of the oxide superconducting stranded wire material, r is the radius based on the outer diameter of the heat resistant tube or cable former, and β is the angle of spiral winding with respect to the heat resistant tube or cable former.

Therefore, from the viewpoint of efficiently forming the strands while satisfying the above-mentioned difference in bending strain, a heat-resistant tube having a diameter larger than that of the cable former to be used is used, and an oxide superconducting stranded wire material is used. It is advantageous to spirally wind the with a narrow pitch. However, in the spiral winding, lap winding is avoided so that the wire materials do not adhere to each other during the heat treatment. The relationship between the pitch (P) and the angle (β) of the spiral winding is
Formula represented by ^{cosβ = 2r / √ (4r 2} + P 2/4).

In addition, in the above, since the strand according to the present invention can be provided as a superposed layer of two or more layers on the outer circumference of the cable former, when forming the strand of the second layer or more, the cable wire is formed. The bending strain amount difference is determined based on the outer diameter of the mer having a stranded wire layer as a lower layer such as the first layer or the second layer.

The heat treatment of the spirally wound oxide superconducting wire material with a predetermined bending strain amount on the outer periphery of the heat-resistant tube is carried out by heating the spiral superconducting wire having an oxide superconducting wire having a superconducting layer in a sintered state. Intended for formation. Therefore, the heating conditions can be appropriately determined according to the conventional type according to the type of oxide superconductor. Generally, heat treatment is performed at a temperature of 700 to 1200 ° C.

The obtained spiral strand is removed from the heat resistant tube and mounted on a predetermined cable former to obtain an intended oxide superconducting cable. In that case, the wire may be single-phase winding or multi-layer winding. The multilayer winding is generally 10 layers or less, but is not limited to this. When obtaining an electric power cable, it is preferable to have a power transmission capacity of 1000 A or more from the viewpoint of reducing power transmission loss. In that case, a multilayer winding structure is generally used.

In the case of the multi-layer winding structure, it is advantageous to reverse the spiral direction of the wire up and down in order to improve the flexibility of the cable. When using the strands manufactured according to the present invention, as the cable former, a regular pipe having no spiral structure may be used in addition to the spiral pipe.

Example 1 Powder of Bi _1.7 Pb _0.3 Sr ₂ Ca ₂ Cu ₃ O _y type oxide superconductor having a particle size of 0.1 to 10 μm was filled in a silver tube having a thickness of 1.0 mm and a diameter of 7.0 mm. Then, after rolling it with a pinch roll to form a tape body with a width of 3 mm and a thickness of 0.2 mm (thickness of the superconducting portion is 100 μm), the tape body is straightened to 820 to 820.
Heat treatment was performed at 860 ° C. for about 50 hours to obtain an oxide superconducting wire.

Next, the above oxide superconducting wire is wound around a cable former consisting of a spiral tube having an outer diameter of 20 mm, which is formed by spirally winding a copper plate having a width of 5 mm and a thickness of 2 mm in a cylindrical shape with a gap of 2 mm. The first layer was formed by spirally winding at a pitch of 50 mm, then the spiral direction was reversed on the second layer to form the second layer, and an oxide superconducting cable having a length of about 400 mm was obtained. 20 oxide superconducting wires were used for forming the first layer and the second layer, respectively. Therefore, a total of 40 oxide superconducting wires are wound around the outer circumference of the cable former.

Example 2 A tape body was spirally wound on an outer circumference of an alumina tube having an outer diameter of 50 mm at a pitch of 5 mm and heat-treated at 820 to 860 ° C. for about 50 hours to form a spiral strand of oxide superconducting wire. Got
Next, the above-mentioned wire was removed from the alumina tube so that bending stress was not applied as much as possible, and it was attached to the outer periphery of the cable former according to Example 1 so that bending stress was not applied as much as possible. Got the cable.

Example 3 An oxide superconducting cable was obtained in the same manner as in Example 2 except that a copper pipe having a wall thickness of 2 mm and having a regular shape with no gap was used for the cable former.

Comparative Example An oxide superconducting cable was obtained in the same manner as in Example 1 except that the copper pipe of Example 3 was used as the cable former.

Evaluation Test Flexibility When the cables obtained in Examples and Comparative Examples were supported on one side and a load of 10 kg was applied to the other end, the amount of bending at the other end was examined.

Superconducting Properties The cables obtained in Examples and Comparative Examples were cooled with liquid nitrogen, and the critical currents in the linear state and the bent state with a diameter of 1 m were examined.

The above results are shown in the table below.

[0038]

INDUSTRIAL APPLICABILITY The cable of the present invention, in which the former is a spiral tube, has excellent superconducting properties such as critical current during low temperature cooling, exhibits good flexibility, and is excellent in laying workability. Further, according to the wire according to the present invention, it is possible to prevent the occurrence of bending strain due to the spiral winding mounting on the former, and to obtain a cable having excellent superconducting characteristics such as critical current, and to avoid winding treatment on the former to arbitrarily A former with a different outer diameter can be used, and a more compact cable can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory side view of an oxide superconducting cable.

[Explanation of symbols]

 1: Cable former 2, 3: Helical wire made of oxide superconducting wire

Claims (4)

[Claims] 1. An oxide superconducting cable, characterized in that a spiral former made of an oxide superconducting wire having a metal sheath is provided on the outer periphery of a cable former made of a spiral tube. 2. A spiral wound on the outer circumference of the heat resistant tube with a bending strain amount difference of 0.1% or less of the bending strain amount when spirally winding an oxide superconducting stranded wire having a metal sheath on a cable former. A method for manufacturing an element wire for an oxide superconducting cable, which comprises rotating and heating the material to form a spiral element wire made of the oxide superconducting wire. 3. The oxide superconducting cable according to claim 1, wherein the spiral wire is manufactured by the method according to claim 2. 4. The oxide superconducting cable according to claim 1, which comprises a cable former having a polymer layer on the outer circumference of the spiral tube.