JP3032771B2 - Superconducting coil manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a superconducting coil.
But about the superconducting particularly an oxide superconductor
The present invention relates to a method for manufacturing a coil .

[0002]

2. Description of the Related Art A superconducting coil is often manufactured by superposing a tape-like superconducting wire on an insulator and winding it tightly.

[0003] than the alloy superconductor represented by Nb-Ti, intermetallic compound superconductor represented by Nb ₃ Sn has a large change due to the distortion. Oxide-based superconductors developed in recent years belong to ceramics, and their behavior against strain is close to that of intermetallic compound-based superconductors. Since the alloy-based superconductor has a small change due to strain, it is possible to form a superconductor and then wind the coil on a coil. Therefore, the so-called R & W method (react-
A superconducting coil can be manufactured by an and-wind process.

[0004] An intermetallic compound-based superconductor having a large change due to strain is formed by densely winding a coil before forming a superconductor, a so-called W & R method (wind-and-react method).
process). This method is also used for oxide-based superconductors (for example, a presentation from Furukawa Electric Co., Ltd. at the Society of Low Temperature Engineering and Superconductivity in November 1990).

[0005] Among oxide-based superconductors, Bi-based superconductors have high reactivity at high temperatures. Therefore, heat treatment for forming the superconductor after forming the coil reacts with many substances except silver and gold. , Lose superconductivity. In order to prevent this, a method of previously covering the periphery of the superconductor with a silver sheath has been used.

[0006]

However, when a coil is formed by a W & R method using an oxide superconductor, there is no suitable insulator to be wound between the superconductor tapes. This is because the heat treatment when manufacturing an oxide superconducting coil by the W & R method requires a higher temperature (800 ° C. or higher) than that of an intermetallic compound superconductor, and the insulator itself withstands the heat treatment temperature. At the same time
This is because it is required that the superconductor and the insulator do not deteriorate due to the reaction with the superconductor.

The present invention provides an oxide superconducting coil using an insulator similar to an alloy superconducting coil or an intermetallic compound superconducting coil, and an oxide superconducting coil which requires high-temperature treatment after coil formation. It is an object of the present invention to realize a superconducting coil that can be manufactured at low cost by the W & R method while using a body or the like.

Further, the present invention realizes a method of manufacturing an oxide-based superconducting coil using an insulator similar to an alloy-based superconducting coil and an intermetallic compound-based superconducting coil. It is an object of the present invention to realize a method for inexpensively manufacturing a superconducting coil using a necessary oxide-based superconductor by a W & R method.

[0009]

According to the present invention, an insulator similar to an alloy-based superconducting coil or an intermetallic compound-based superconducting coil is used, or an oxide-based superconductor that requires high-temperature treatment after coil formation is used. In order to realize an oxide-based superconducting coil which can be manufactured at low cost by the W & R method, a material such as silver which does not substantially react with the oxide-based superconductor even at a high temperature is used as a support, and at least one surface thereof includes an organic binding medium. A strip having a layer made of oxide-based superconductor powder dispersed therein is wound to form a coil. Or,
A strip having a layer made of an oxide-based superconductor powder, and an insulator, a coil wound by being overlapped so as to be adjacent,
Constitute.

Further, according to the present invention, an alloy superconducting coil,
Using the same insulator as the intermetallic compound superconducting coil,
In order to realize a method for manufacturing an oxide-based superconducting coil, and to realize a method for inexpensively manufacturing a superconducting coil using an oxide-based superconductor or the like that requires a high-temperature treatment after forming the coil by heat treatment, A coil formed by winding a wire configured to generate superconductivity so as to form an appropriate gap in the radial direction is formed, the coil is heat-treated, and after the heat treatment, an insulator is inserted into the gap between the wires, thereby forming a wire. And insulators form coils that are radially adjacent to each other,
A superconducting coil made of an oxide superconductor or the like is manufactured.
After inserting the insulator in the gap between the wires, the gap may be reduced by winding the coil as necessary.

When the heat treatment temperature is low, an insulator may be inserted between the wires before the heat treatment, or a superconducting wire may be wound together with the insulator. By superposing and winding two or more superconducting wires so as to keep a gap therebetween, multiple superconducting coils can be manufactured, and a coil having a small number of turns and a coil having a large number of effective turns can be obtained. In this case, two or more superconducting wires may be wound with a gap in the radial direction, and inserted into the gap to combine them to form a multiple coil. The diameters of the individual coils to be combined and the gaps between the wires are preferably close to each other. Otherwise, the degree of deformation required when assembling the coils increases, causing stress in the coils and impairing the superconducting characteristics.

In the case of manufacturing an oxide-based superconducting coil, at least one surface of a support made of a material such as silver which does not substantially react with the oxide-based superconductor at high temperatures, the oxide-based superconducting material dispersed in an organic binding medium is used. A layer made of body powder is provided to form a strip-shaped wire, and the wire is wound so as to form a predetermined gap in a radial direction to form a coil. After the coil is formed, an insulator is inserted into the gap between the wires. A method of forming a coil in which the strip and the insulator are adjacent to each other in the radial direction is useful.

The layer of the oxide-based superconductor dispersion may be on only one side of the strip or on both sides. The thickness of each surface of the strip was 200 μm after drying.
m or less. Some of the superconductor particles may be exposed on the surface of the layer of the dispersion, or the surface of the layer may be covered with an organic binding medium or another insulating material.

In order to form a layer in which the oxide-based superconductor powder is dispersed in the organic binding medium, a support made of a material such as silver which does not substantially react with the oxide-based superconductor even at a high temperature is provided by: A method of applying a dispersion liquid in which the oxide-based superconductor powder is dispersed in a solution of an organic binding medium by dip coating, doctor blade coating, or the like can be used.

The support for forming the layer in which the oxide-based superconductor powder is dispersed in the organic binding medium is made of a substance that does not substantially react with the oxide-based superconductor even at a high temperature. Such materials are silver, gold and the like.

As an insulator, the temperature of liquid helium (4.
2K) that does not cause cracking is preferable, and can be selected from insulators commonly used for alloy superconducting coils and intermetallic compound superconducting coils. For example, polyethylene terephthalate, polytetrafluoroethylene, alumina, magnesia and the like can be used.

The above-described method for manufacturing a superconducting coil can also be applied to the case where heat treatment is not required after coil formation. That is, a coil is formed by winding at least one superconducting wire so as to form an appropriate gap in the radial direction, and an insulator is inserted into the gap of the superconducting wire at the same time as or after the coil is formed, and a superconductor is formed. Can form coils radially adjacent to the insulator. Silver sheath method, CV
This method can also be applied to a superconducting wire formed by a method D, a sputtering method or the like.

At the time of assembling the coil, members other than the oxide superconducting wire and the insulator, such as a metal superconducting wire, a normal conducting wire, a wire used for observation and monitoring, a reinforcing material, and the like may be inserted. Absent. In addition, when assembling a coil by combining a plurality of coiled wires, the order of inserting an insulator or the like in the gap between the wires may be such that the insulator is arranged in one coiled wire in advance, or the order may be multiple. An insulator may be inserted after the coil is formed.

[0020]

[0021]

According to the method of manufacturing an oxide-based superconducting coil of the present invention, a coil formed by winding a wire configured to generate superconductivity by heat treatment so as to form an appropriate gap in a radial direction is formed. By heat treating the coil,
A coil of superconducting wire is formed. After the heat treatment, an insulator is inserted into the gap between the superconducting wires to form a coil in which the wire and the insulator are adjacent to each other in the radial direction, and a superconducting coil can be manufactured. Since heat treatment at a high temperature necessary for imparting superconductivity to the oxide can be performed without contacting the insulator, an oxide superconducting coil or the like can be manufactured at low cost by the W & R method. After the superconducting wire is configured,
Since the superconducting coil is manufactured by being wound on the insulator, the oxide superconducting coil can be easily manufactured using the same insulator as the alloy superconducting coil and the intermetallic compound superconducting coil.

[0022]

The present invention will be described more specifically with reference to the following examples. Embodiment 1 FIG. 1 shows a typical example of a superconducting coil according to the present invention. In the superconducting coil shown in FIG.
Are coated with an oxide-based superconducting layer 2 and are wound spirally with an insulator 3 interposed therebetween. The silver tape 1 has a thickness of 50 μm and a width of 13 mm. The oxide superconducting layer 2 is made of Bi ₂ Sr ₂ CaCu ₂ O, as described later.
A slurry dispersion of the calcined powder of _X was applied, dried, and heat-treated, and the thickness was 35 μm. Insulator 3
Is an alumina powder packed layer having a thickness of 0.38 mm. The outside of the entire coil is solidified with an epoxy resin (not shown).
Although the actual number of turns of the coil is 50 turns, FIG. 1 shows only a portion of 4 turns. The inner diameter of the coil of this embodiment is 13 mm, and the outer diameter is 63 mm.

This superconducting coil was manufactured as follows. As shown in FIG. 2A, the oxide Bi ₂ Sr ₂ CaCu
The ₂ O _X of the calcined powder 21 was mixed with polyvinyl butyral 22, the solvent 23 (trichlorethylene and 2-butanol) was added to the mixture, in a slurry dispersion 24 obtained by stirring as shown in FIG. 2B As shown in FIG. 2C, the silver tape 1 was passed at a speed of 1 m / min, and the liquid films 24a were attached to both surfaces of the silver tape 1 and air-dried for several hours.
The thickness of the oxide layer after drying is 100 μm. 0.2 thickness
A 5 mm polyethylene sheet (not shown) is overlapped and wound in a pancake shape to form a coil. At 150 ° C for 1
After annealing (annealing) for a period of time, the polyethylene sheet is removed, and as shown in FIG.
As shown in FIG. 2E, a heat treatment of heating to a temperature at which the oxide is partially melted and then gradually cooling is performed in the electric furnace 26 while maintaining the gap at 0.25 mm. The details of the heat treatment are as follows.

First, in an electric furnace, at 500 ° C.
And heated to 885 ° C for 90 minutes,
After maintaining at 885 ° C. for 10 minutes, the temperature is lowered to 840 ° C. at a rate of 5 to 10 ° C./hour and kept at this temperature for 1 hour. The electric furnace current was cut off and allowed to cool to room temperature in 5 hours. By this heat treatment, the thickness of the oxide layer was reduced, and a pancake coil having a gap of 0.38 mm between the wires was obtained.

By the heat treatment, the superconductor crystal grows and orients, and at the same time, the bonding with the silver tape is strengthened. Observation of the cross section of the coil with a scanning electron microscope revealed that the oxide particles were oriented along the silver tape.

After the heat treatment, an electrode (not shown) is attached to the end of the coil, and as shown in FIG. 2F, the gap between the wires 25 is filled with alumina powder 27 as the insulator 3, and the whole is solidified with epoxy resin. Complete the superconducting coil.

The pancake type superconducting coil manufactured in this manner was subjected to an electric current test in a liquid helium (4.2 K) temperature and a magnetic field of 12 T. The external magnetic field was parallel to the central axis of the coil. When the resistance was calculated from the cross-sectional area of the tape wire after the heat treatment, and the superconducting threshold value was defined as 1 × 10 ⁻¹³ Ωm, the critical current value (Ic) was 230 A. After the test in the magnetic field, 230 A was supplied to the sample coil in a state where the external magnetic field was removed, and the center magnetic field B _O generated by the coil was measured using a Hall element, and it was 3800 G.
This value almost coincides with the theoretical value, and indicates that the insulation between the superconducting wires is sufficient and that there is no defect in the length direction of the superconducting wire.

Example 2 A coil of a coiled wire manufactured through the same materials and processes as in Example 1 until heat treatment was inserted into a gap between the wires by inserting a polyethylene terephthalate tape having a thickness of 0.12 mm. Was wound into a coil having an inner diameter of 13 mm, an outer diameter of 45 mm, and a number of turns of 64, and the whole was solidified with epoxy resin to obtain a superconducting coil.

The obtained coil was subjected to an energization test in the same manner as in Example 1, and the critical current value (Ic) was obtained.
Is 230A as in the case of Example 1, and a coil wound more densely could be manufactured without deteriorating the superconducting characteristics of the wire.

After the energization test in the magnetic field, the external magnetic field was removed, 230 A was supplied to the coil, and the center magnetic field B ₀ generated by the sample coil was measured by the Hall element.
It was a B ₀ = 6000G. This indicates that the number of turns increases for the same wire, and that the shape factor of the coil works more advantageously.

Third Embodiment Another example of a superconducting coil according to the present invention is shown in FIG. In the superconducting coil shown in FIG. 3, the silver tapes 1a, 1b, 1c, 1d are respectively coated on both sides with an oxide superconducting layer 2, and are wound spirally with an insulator 3 interposed therebetween. Silver tape 1a, 1b, 1
Each of c and 1d has a thickness of 50 μm and a width of 13 mm. The oxide-based superconducting layer 2 is made of Bi ₂ S as in the first embodiment.
This is a layer having a thickness of 35 μm, to which a slurry-like dispersion of calcined powder of r ₂ CaCu ₂ O _X is applied, dried, and then heat-treated. Silver tapes 1a, 1b covered with superconducting layer 2;
1c and 1d are replaced by superconducting wires 31a, 31b and 3 respectively.
Shown as 1c and 31d. Insulators 32a, 32b, 32
c and 32d are polyethylene terephthalate tapes having a thickness of 0.15 mm. The outside of the entire coil is hardened with epoxy resin (not shown).

Although the actual number of turns of the coil is 64 turns, FIG. 3 shows only a portion of 8 turns. The inner diameter (diameter) of the coil of this embodiment is 13 mm, and the outer diameter (diameter) is 45 mm.

This superconducting coil was manufactured as follows. In the same manner as in Example 1, Bi ₂ Sr ₂ CaCu ₂ O
_In a slurry dispersion of the calcined powder of _X , a thickness of 50 μm,
A liquid film was adhered to the surface of the silver tape 1a and the like through a silver tape 1a and 1b having a width of 13mm and a length of 7.5m and dried. The thickness of the superconducting layer 2 after drying is 100 μm. The obtained composite tape is cut into five pieces each having a length of 1.5 m, and then superposed on a polyethylene sheet having a thickness of 1.7 mm, and wound into a pancake shape to form a coil. After annealing (annealing) each at 150 ° C. for 1 hour, the polyethylene sheet was removed, and as shown in FIG. 2, while maintaining the wires of each coil at a distance of 1.7 mm from each other, the oxide was partially removed. Heat to a temperature at which it is gradually melted and then gradually cooled. The conditions of the heat treatment are the same as in the first embodiment. The silver tapes 1a, 1b, 1c, 1d covered with the superconducting layer 2 are superconducting wires 31a, 31b, 3 respectively.
1c and 31d.

The dimensions of the pancake-like coils thus obtained were 13 mm in inner diameter, 63 mm in outer diameter, and 1 turn.
In 2.5 turns, a gap of 1.85 mm is left between the wires.

After the electrodes are attached to the four coiled wires, the gaps between the coiled superconducting wires 31a are
Four polyethylene terephthalate tapes 32a, 32b, 32c, 32d each having a thickness of 0.12 mm are inserted. The superconducting wire 31c is inserted between two sheets 32b and 32c inside the four polyethylene terephthalate tapes. The insertion situation is shown in FIGS. However, illustration of the polyethylene terephthalate tape is omitted for convenience. FIG.
A shows the superconducting wires 31a and 31c before insertion, FIG. 4B shows a state during insertion, and FIG. 4C shows a state after insertion.

Similarly, the superconducting wire 31b is inserted between the two polyethylene terephthalate tapes 32a and 32b located inside the superconducting wire 31c.
The superconducting wire 31d is inserted between the polyethylene terephthalate tapes 32c and 32d located outside the superconducting wire 31c. By inserting such a superconducting wire, 4
A heavy coil is obtained. Thereafter, the entire quadruple coil is wound and tightened to form a coil having an inner diameter of 13 mm and an outer diameter of 45 mm.
By winding the coil, the number of turns of the coil becomes 16 turns, that is, a total of 64 turns in four rows. The whole is hardened with cryogenic grease (Apiezon wax).

Finally, four rows of coils are connected in series to complete the coil. For the purpose of performance comparison, a plurality of polyethylene terephthalate tapes were stacked in the gap between one coiled wire rod that had been prepared and left before, and the thickness was 1.8 mm.
Then, the whole was solidified with cryogenic grease (Apiezon wax) as it was to prepare.

The quadruple and single pancake type superconducting coils thus manufactured were subjected to an electric current test in a liquid helium (4.2 K) temperature and a magnetic field of 12 T. The external magnetic field was parallel to the central axis of the coil. The resistance is calculated from the cross-sectional area of the tape wire after heat treatment, and the superconducting threshold value is set to 1 ×
When defined as 10 ^-13 Ωm, both critical current values (Ic) were 230A. This indicates that the coil was not deteriorated by the tightening.

After the test in the magnetic field, 230 A was applied to the sample coil except for the external magnetic field, and the center magnetic field B _O generated by the coil was measured using a Hall element.
000G, the single coil was 950G. The ratio of the value of the magnetic field of the quadruple coil to the value of the magnetic field of the single coil is greater than 4, which is due to the increase in the number of turns due to tightening (from 12.5 to 16)
And a change in the shape factor due to a decrease in the coil outer diameter (from 63 mm to 45 mm). These values almost coincide with the theoretical values, indicating that the insulation between the wires is sufficient and that there is no degraded portion in the length direction of the superconducting wire.

[0040]

[0041]

According to the method of manufacturing a superconducting coil of the present invention , an inexpensive oxide superconducting coil can be realized using the same insulator as the alloy superconducting coil and the intermetallic compound superconducting coil. .

According to the method for producing a superconducting coil of the present invention, an oxide-based superconducting coil can be easily produced using the same insulator as the alloy-based superconducting coil and the intermetallic compound-based superconducting coil. Further, an oxide superconducting coil or the like can be manufactured at low cost by the W & R method.

Further, according to the method for manufacturing a superconducting coil of the present invention, when the whole wound coil is tightened, the amount of deformation of each coil is reduced. By being within the allowable strain range of the superconducting wire, even if an oxide superconducting wire having poor strain resistance is used, it can be tightly wound. Therefore, the number of turns of the coil increases for the same wire length. By further tightening, the outer diameter of the coil becomes smaller, and the shape of the coil becomes more advantageous for generating a magnetic field.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a cross section of an embodiment of a superconducting coil according to the present invention.

FIGS. 2A to 2E are explanatory diagrams of one embodiment of a method for manufacturing a superconducting coil according to the present invention.

FIG. 3 is an explanatory view showing a cross section of another embodiment of the superconducting coil according to the present invention.

4A to 4C are explanatory views of another embodiment of the method for manufacturing a superconducting coil according to the present invention.

[Explanation of symbols]

1, 1a, 1b, 1c, 1d Silver tape 2 Oxide-based superconducting layer 3 Insulator 21 Bi ₂ Sr ₂ CaCu ₂ O _X calcined powder 22 Polyvinyl butyral 23 Solvent 24 Slurry dispersion liquid 24a Liquid film 25 Coiled wire 26 Electric furnace 27 Insulator 31a, 31b, 31c, 31d Superconducting wire 32a, 32b, 32c, 32d Insulator or polyethylene terephthalate tape

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Kumakura 1-2-1, Sengen, Tsukuba, Ibaraki Pref., National Institute of Science and Technology Tsukuba Branch (72) Inventor Jin Kitaguchi, Sengen 1, Tsukuba, Ibaraki Tsukuba Branch, National Institute of Science and Technology, Metal Science and Technology Agency (72) Inventor Hiroshi Maeda Tsukuba Branch, Metallic Materials Research Institute, National Institute of Metals, 1-2-1 Sengen, Tsukuba, Ibaraki Prefecture (72) Inventor Junichiro Kase 1150 Hazawa-cho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Inside Asahi Glass Co., Ltd. Central Research Laboratory (72) Inventor Junichi Shimoyama 1150 Hazawa-cho, Kanagawa-ku, Yokohama City, Kanagawa Prefecture Asahi Glass Co., Ltd. Central Research Laboratory (72) Inventor Go Morimoto 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd., Central Research Laboratory (72) Inventor Katsumi Nomura Tsuchiura, Ibaraki Prefecture 3550 Kida Yomachi Hitachi Research Center, Ltd. Advanced Research Center (72) Inventor Masahiro Seito 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Advanced Research Center (56) References JP-A-63-294615 (JP, a) JP Akira 63-294620 (JP, a) JP Akira 55-76598 (JP, a) JP Akira 52-95049 (JP, a) (58 ) investigated the field (Int.Cl. ⁷ , DB name) H01F 6/06 H01B 12/06

Claims (4)

(57) [Claims] 1. A structure in which heat treatment produces superconductivity.
So that the formed wire forms a predetermined gap in the radial direction.
Forming a coil wound around the coil , heat- treating the coil , inserting an insulator into the gap after the heat treatment, if necessary,
The diameter of the coil is reduced so that the wire and the insulator have a radius
Forming coils adjacent to each other in the direction
Manufacturing method of a superconducting coil. 2. A superconducting wire forms a predetermined gap in a radial direction.
At least two of which are wound to form
Coils are inserted by inserting the coils into the gap
And at least two of said superconducting wires,
A multiplex superconducting coil having a gap is formed, and an insulator is inserted into the gap of the multiplex superconducting coil.
The diameter of the coil is reduced as necessary, and the superconducting wire is reduced.
And said insulator form coils adjacent to each other in a radial manner
A method for manufacturing a superconducting coil. 3. Substantially reacting with an oxide-based superconductor at a high temperature.
On at least one side of a strip-shaped support made of a material
Oxide-based superconductor powder dispersed in organic binding medium?
Forming a wire, forming at least one of said wires with a predetermined gap in the radial direction.
A coil is formed by winding to form a coil, and an insulator is provided in the gap at or after the coil formation.
A method for manufacturing a superconducting coil , comprising inserting a coil in which the strip and the insulator are radially adjacent to each other by inserting. 4. The method according to claim 1, wherein at least one strip-shaped superconducting wire is half
Wind the coil to form an appropriate gap in the radial direction and
At the same time as the coil is formed in the gap between the superconducting wires.
Insert the insulator after the coil is formed, and the superconductor and the insulator
A method for manufacturing a superconducting coil, comprising forming coils adjacent to each other in a radial direction .