JPH08102225A - Superconductive element wire, superconductive cable, and composite superconductive conductor - Google Patents

Abstract

PURPOSE: To obtain a superconductive element wire covered with a cover film with its small coupling loss, a superconductive cable for which this superconductive element wire is molded and twisted, and a composite superconductive coductor for which a plurality of these superconductive cables are bundled. CONSTITUTION: Cu3 or a Cu-Sn matrix 23 in which a plurality of Nb3 Sn thin wires 2 are embedded is covered with a Sn-In cover film 6 or 26, a superconductive element wire 1 or 21 is constituted, a plurality of these superconductive element wires are bundled and twisted, and a superconductive cable is constituted. A cable in conduit type composite superconductive conductor is constituted from this superconductive cable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting wire in which a plurality of superconducting conductor thin wires are embedded in a conductor and the surface is covered with a film, a superconducting cable formed by forming and twisting the superconducting wires, and a superconducting cable. The present invention relates to a composite superconducting conductor formed by bundling a plurality of bundles, and particularly to a superconducting element wire, a superconducting cable, and a composite superconducting conductor using a coating having a small coupling loss.

[0002]

2. Description of the Related Art Conventionally, as a superconducting element wire, there has been known a superconducting element wire in which a plurality of superconducting thin wires are bundled and embedded in a conductor. FIG. 9 shows a cross-sectional structure of a superconducting element wire manufactured by this method. In the superconducting element wire 31 shown in FIG. 9, a stabilizing Cu material 34 having a circular cross-sectional shape is arranged in the central portion, and a plurality of superconducting conductor thin wires 3 are provided outside thereof.
2 are arranged, these are embedded in a Cu matrix 33, and the surface thereof is covered with a Sn film 36. A diffusion barrier 37 is formed on the surface of the stabilized Cu material 34. Also, the superconducting conductor thin wire 3
Nb is used as the material of No. 2, and Nb is obtained by heat-treating after processing into a predetermined size as described above.
A superconducting thin wire 32 of 3 Sn is generated. In addition to this structure, heat treatment may be performed after Al2 O3 is applied to the surface of the Sn coating (Masao Shimada, "Research and development of AC (powder method Nb3 Sn) wire", energy environment comprehensive technology). Developed "Superconducting Electric Power Applied Technology" Proceedings of 1993 Research Results Presentation Meeting (See Superconducting Power Generation Equipment, Material Technology Research Association Super-GM, 1994). When manufacturing a superconducting cable which conducts a large current, as shown in FIG.
A core material 38 made of —Ni alloy is arranged and twisted to form the superconducting cable 35.

[0003]

However, in the above-mentioned conventional superconducting cable in which the superconducting element wires are bundled, a large coupling loss occurs due to a coupling current flowing between the superconducting element wires. Coupling loss is generally proportional to the time constant τ, which indicates the rate at which the coupling current decays. The time constant τ is expressed by the following equation τ = μo / 2r (lp / 2π) 2 ... (1). In the above formula (1), μo represents the magnetic permeability of vacuum, r represents the resistance value of the coupling current path (hereinafter referred to as “equivalent resistance value”), and lp represents the twist pitch.

The equivalent resistance value r is a value determined by the contact resistance between the wires, the contact area, or the resistance value of the intervening material. When only the Sn plating is applied to the surface like the conventional superconducting element wire, the specific resistance value is small, the equivalent resistance value is small, and the time constant τ is decreased, so that the coupling loss becomes large. In particular, the coupling loss becomes large when pulse energization or AC energization is performed. If this coupling loss becomes larger than a certain value, there is an increased possibility that the superconducting coil formed by winding the superconducting cable will be quenched.

When Al2 O3 is applied to the surface of the Sn coating, the coupling loss can be reduced, but when twisted, Al2 O3 peels off and the Al2 O3 portion becomes non-uniform. Since the resistance decreases, the coupling current easily flows between the superconducting element wires, and the coupling loss increases.

Therefore, an object of the present invention is to provide a superconducting element wire coated with a film having a small coupling loss, a superconducting cable formed by forming and twisting the superconducting element wire, and a composite superconducting conductor obtained by bundling a plurality of the superconducting cables. It is in.

[0007]

In order to solve the above-mentioned problems, the superconducting element wire according to the first invention of the present invention comprises a conductor in which a plurality of Nb3 Sn wires are buried, and is covered with a film. In the superconducting element wire, the coating film is made of an alloy in which In is added to Sn.

A superconducting cable according to a second aspect of the present invention is a superconducting cable in which a plurality of superconducting element wires are formed and twisted, and the superconducting element wires are embedded with a plurality of Nb3Sn wires. The conductor is formed by being coated with a film formed by adding In to Sn.

The composite superconducting conductor according to the third aspect of the present invention is a composite superconducting conductor in which a superconducting cable consisting of a plurality of superconducting element wires is housed in stabilized Cu and embedded in solder. The superconducting element wire is composed of a plurality of Nb3
The Sn wire-embedded conductor is covered with a film formed by adding In to Sn.

In the above description, when the weight ratio of In is x percent (0 <x ≦ 17), the coating film is composed of Sn having a weight ratio of (100-x) and In having a weight ratio of x percent. You may do it.

[0011]

According to the present invention having the above-mentioned structure, as a coating film for coating the surface of the superconducting element wire, instead of the conventional Sn,
Since the Sn-In alloy in which In is added to Sn is used,
The specific resistance at 4.2K becomes large. As a result, the equivalent resistance value increases and the time constant of the coupling loss decreases, so that the coupling loss of the superconducting element wire is reduced.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross-sectional structure of a superconducting element wire which is a first embodiment of the present invention. As shown in FIG. 1, this superconducting element wire 1 has a stabilized Cu of circular cross-section at the center.
The material 4 is arranged and a plurality of Nb3S is provided outside the material.
A superconducting conductor thin wire 2 made of n is arranged, and these are Cu
Is embedded in the matrix 3 and the surface thereof is covered with the coating film 6. The coating film 6 is composed of an alloy in which In is added to Sn. A diffusion barrier 7 is formed on the surface of the stabilized Cu material 4.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 shows a cross-sectional structure of a superconducting cable that is a second embodiment of the present invention. As shown in FIG. 2, this superconducting cable 5 has Cu-Ni at the center.
A core material 8 made of an alloy and having a circular cross-sectional shape is arranged, a plurality of superconducting element wires 1 are arranged on the outer side thereof, and these are formed and stranded.

Next, a procedure for manufacturing the above-mentioned superconducting element wire 1 and superconducting cable 5 will be described. First, a stabilized Cu material 4 having a circular cross-sectional shape with a diffusion barrier 7 formed on the surface thereof is arranged at a central position, and an Nb core is arranged inside the Cu matrix 3 on the outside thereof to form a composite. Next, this composite is processed into a superconducting element wire 1 having a diameter of about 0.5 mm by hydrostatic extrusion and die drawing. After twisting this superconducting element wire 1 to a pitch of 10 mm, Sn-In
The alloy is plated to form a coating 6 made of Sn—In alloy on the surface. Next, as shown in FIG.
A plurality of superconducting element wires 1 are arranged around a core material 8 made of an i alloy to form a stranded wire. Then, a heat treatment is performed at a temperature of 600 ° C. for 100 hours to generate Nb 3 Sn thin wires 2 from the Nb thin wires.

Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a cross-sectional structure of a superconducting element wire according to a third embodiment of the present invention. As shown in FIG. 3, this superconducting element wire 11 is provided with a stabilizing Cu material 14 having a circular cross section having a diffusion barrier 17 formed on the surface in the central portion thereof, and is made of a plurality of Nb3 Sn outside thereof. Superconducting conductor fine wires 12 are arranged, and these are Cu-Sn.
It is embedded in an alloy matrix 13 and its surface is a coating 1.
It is constituted by being coated with 6. Coating 16
Is formed by adding In to Sn.

Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows a cross-sectional structure of a superconducting cable which is a fourth embodiment of the present invention. As shown in FIG. 4, this superconducting cable 15 has a Cu-N
A core material 18 made of an i alloy and having a circular cross-sectional shape is arranged, and a plurality of superconducting wires 11 are arranged outside the core material 18,
These are formed by forming a twisted wire.

Next, the procedure for manufacturing the superconducting element wire 11 and the superconducting cable 15 formed from the superconducting element wire 11 will be described. First, a stabilized Cu material 14 having a circular cross-sectional shape with a diffusion barrier 17 formed on the surface thereof is arranged at a central position, and the Cu—Sn alloy matrix 1 on the outside thereof is arranged.
Place the Nb core in 3 to form the complex. next,
This composite is processed into a superconducting element wire 11 having a diameter of about 0.5 mm by hydrostatic extrusion and die wire drawing. After twisting this superconducting element wire 11 at a pitch of 10 mm, Sn
The -In alloy is plated to form the coating film 16 made of the Sn-In alloy on the surface. Next, a plurality of superconducting element wires 11 are arranged around a core material 18 made of a Cu-Ni alloy and twisted. After that, by performing heat treatment at a temperature of 600 ° C. for 100 hours, Nb thin wire to Nb 3 Sn thin wire 12
Is generated.

Next, a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 5 shows a cross-sectional structure of a composite superconducting conductor which is a fifth embodiment of the present invention. As shown in FIG. 5, the composite superconducting conductor 21 is a “cable-in-conduit” type composite superconducting conductor, and one is contained in a hollow tubular conduit 26 made of SuS (stainless steel).
Two U-shaped stabilizing Cu materials 24a and two stabilizing C materials
The u-material 24b is disposed, and the superconducting cable 25 housed in the space surrounded by these stabilizing Cu materials is the solder 23.
Stabilized Cu material 24a embedded in the U-shape
The superconducting cable 25 is maintained in the superconducting state by forcibly flowing the supercritical helium into the groove 29.

Further, the superconducting cable 25 has the above-mentioned second structure.
The structure is similar to that of the superconducting cable of the embodiment or the fourth embodiment.

Since the composite superconducting conductor 21 uses stainless steel as the conduit material, the mechanical strength of the conductor is improved.

The solder 23 is a solder composed of Sn-In alloy.

A procedure for manufacturing the composite superconducting conductor 21 will be described. First, a core material (not shown) is arranged in the central portion, and a plurality of superconducting element wires 22 are arranged around the core material to produce a twisted superconducting cable 25. Next, flux is applied to the surface of the superconducting cable 25 and the wall surfaces of the stabilizing Cu materials 24a and 24b to be soldered. Next, the plurality of superconducting cables 25 are housed in the housing space formed by the stabilized Cu materials 24a and 24b to produce a housing. Next, a plurality of superconducting cables 25 in the storage space of the storage body are embedded in the solder 23 by filling the storage space of the storage body with the solder 23 heated to 230 ° C. and melted.

Next, the results of measuring the specific resistance of the Sn-In alloy formed by adding In to Sn as described above will be described. The specific resistance was measured by the specific resistance measuring device shown in FIG. As shown in FIG. 6, the resistivity measuring device 60 includes a bottomed tubular first container 61, a bottomed tubular second container 62 arranged to accommodate the first container 61,
A third container 63 having a bottomed tubular shape and arranged to house the second container 62 is provided.

A ring-shaped background magnet 66 is arranged in the first container 61, and a support 68 having a tip end of a subject 67 for measuring the specific resistance is wound around the background magnet 66 in a central opening. Has been inserted inside. The inside of the first container 61 is filled with liquid helium 64, and the subject 67 and the background magnet 6 are
6 is immersed in liquid helium 64. First container 6
A lid 73 having a good heat insulating property is attached to the first opening.
Therefore, the first container 61, the second container 62, and the third container 6
3 and the lids 73 and 74 form a heat insulating container.

The side surface of the second container 62 has a double structure, and the inside thereof is filled with liquid nitrogen 65. A vacuum layer 69 is provided between the first container 61 and the second container 62 and between the second container 62 and the third container 63. A lid 74 having good heat insulation is attached to the openings of the second container 62 and the third container 63.

A conductor wire 75 is connected to one end of a subject 67 wound in a coil on the tip of the support 68, and a conductor wire 76 is connected to the other end. A power source 72 is connected to the conductor wire 76, and the conductor wire 76 is connected to the power source 72 via a shunt resistor 71. An XY recorder 70 is connected to both ends of the shunt resistor 71.

Next, the measuring method will be described. First, a current is supplied from the power source 72 to the subject 67 via the lead wires 75 and 76. The voltage at this time is measured by the XY recorder 70 from both ends of the shunt resistor 71. The generated voltage is V (unit: V) when the maximum energizing current value is I (unit: A)
And the length of the subject 67 is L (unit: m) and the cross-sectional area of the subject 67 is S, the specific resistance ρ (unit: Ωm)
Is expressed by the following equation ρ = V · S / I · L (2) The specific resistance measurement was performed when the energizing current value I was 10 A, and the values at 4.2 K and 4.3 T were obtained.

The measurement results are shown in FIG. As shown in FIG. 7, in this measurement, the specific resistance in the case where 0 to 17 w% In was added to Sn was determined.

As a result, 0 to 10% by weight (hereinafter, "w
% ”. Up to), increasing the concentration of In added increases the resistivity compared to the case where In is not added, but 10w%
It was found that the resistivity decreases when the added concentration is increased at the boundary of. If the specific resistance increases, the equivalent resistance value increases,
As a result, the time constant of the coupling loss is reduced, so that the coupling loss of the superconducting element wire is reduced.

However, even if the concentration of added In is increased beyond the boundary point, the value of the specific resistance must be at least twice as large as the value when In is not added (the value on the vertical axis in FIG. 7). I understand. Therefore, the added concentration x of In is 0
It was found that the range of <x ≦ 17 w% is an effective range for increasing the specific resistance.

When the concentration of In added is x (w%), I
It is necessary to reduce the composition ratio of Sn by the amount of adding n.
Therefore, the alloy produced has a weight ratio (100-x).
Percent Sn and x weight percent In.

From the above results, it is considered that the effect of reducing the coupling loss is effective not only when the element added to Sn is one type (In) but also when it is two or more types. As a result of the trial, for example, Sb is set to a weight ratio of 1 w% or less, Cu is set to a weight ratio of 0.08 w% or less, and Cd is set to 0.
Bi: Zn: Fe: Al
Examples include Sn—In alloys added so that the total weight ratio of Al and As is 0.35 w% or less.

Next, the result of measuring the bond loss of the alloy formed by adding In to Sn as described above will be described. The coupling loss was measured by the coupling loss measuring device shown in FIG. As shown in FIG. 8, this coupling loss measuring device includes a bottomed cylindrical heat insulating container 81, and a ring-shaped background magnet 84 is arranged in the heat insulating container 81 to measure the coupling loss. A pickup coil 86 wound around the sample 85 and the sample is inserted into the central opening of the background magnet 84. Liquid helium 82 is filled in the heat insulating container 81, and the subject 85, the pickup coil 86, and the background magnet 84 are immersed in the liquid helium 82. A lid 83 having a good heat insulating property is attached to the opening of the heat insulating container 81.

A conductor 88 is connected to one end of the pickup coil 86 wound around the subject 86, and a conductor 89 is connected to the other end. The other end of each conductor 88, 89 is connected to a shunt resistor 90. The tap output line of the shunt resistor 90 is connected to the integrator 87. A power supply (not shown) and a control device are connected to the background magnet 84.

Next, the measuring method will be described. First, the background magnetic field of the background magnet 84 is changed by a power supply and a control device (not shown). The voltage induced in the subject 85 by this magnetic field fluctuation is detected by the pickup coil 86. Pickup coil 8
The current detected at 6 is conducted to the shunt resistor 90 by the conductors 88 and 89, and is input to the integrator 87 as a voltage. The integrator 87 converts the magnetic flux into the input to obtain the coupling loss of the subject 85.

The measurement results are shown in Table 1.

[Table 1]

As shown in Table 1, when the coating is Sn-In plating, the value of the coupling loss is smaller than the value when In is not added to Sn, and it is proved that it is reduced by about 70%. It was

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same function and effect can be realized by the present invention. It is included in the technical scope of the invention.

[0039]

As described above, according to the present invention,
Since a Sn-In alloy in which In is added to Sn is used as a coating for covering the surface of the superconducting element wire so as to reduce the coupling loss of the superconducting element wire, the superconducting coil formed by winding the superconducting element wire is quenched. Can reduce the likelihood of Further, in the cable-in-conduit type composite superconducting conductor, the Cr plating on the surface of the superconducting element wire, which has been conventionally performed in order to reduce the coupling current time constant between the element wires, is not necessary, and therefore expensive Cr plating is required. It is possible to reduce the cost required for, and it is economically advantageous.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a cross section of a superconducting element wire according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a cross-sectional structure of a superconducting cable that is a second embodiment of the present invention.

FIG. 3 is a perspective view showing a cross-sectional structure of a superconducting element wire according to a third embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of a cross section of a superconducting cable which is a fourth embodiment of the present invention.

FIG. 5 is a perspective view showing a cross-sectional structure of a composite superconducting conductor which is a fifth embodiment of the present invention.

FIG. 6 is a diagram illustrating a method for measuring the specific resistance of the superconducting element wires shown in FIGS. 1 to 5.

FIG. 7 is an S forming the superconducting element wire shown in FIGS.
It is a characteristic view which shows the specific resistance in 4.2K of an n-In alloy, and 4.3T.

FIG. 8 is a diagram illustrating a method of measuring the coupling loss of the superconducting element wires shown in FIGS. 1 to 5.

FIG. 9 is a cross-sectional view showing a configuration of a conventional example of a superconducting wire.

FIG. 10 is a cross-sectional view showing a configuration of a conventional example of a superconducting cable.

[Explanation of symbols]

 1 superconducting element wire 2 superconducting conductor thin wire 3 matrix 4 stabilizing Cu material 5 superconducting cable 6 coating 7 diffusion barrier 8 core material 11 superconducting element wire 12 superconducting conductor thin wire 13 matrix 14 stabilizing Cu material 15 superconducting cable 16 coating 17 diffusion barrier 18 Core material 21 Composite superconducting conductor 22 Superconducting element wire 23 Solder 24a, 24b Stabilizing Cu material 25 Superconducting cable 26 Conduit 29 Groove 31 Superconducting element wire 32 Superconducting conductor fine wire 33 Matrix 34 Stabilizing Cu material 35 Superconducting cable 36 Coating 37 Diffusion barrier 38 Core material 60 Specific resistance measuring device 61 First container 62 Second container 63 Third container 64 Liquid helium 65 Liquid nitrogen 66 Background magnet 67 Specimen 68 Supporting tool 69 Vacuum layer 70 XY recorder 71 Shunt resistance 72 Power source 73 , 74 Lid 75 to 78 Conductive wire 80 Coupling loss measuring device 81 Insulation container 82 Liquid helium 83 Lid 84 Background magnet 85 Subject 86 Pickup coil 87 Integrator 88,89 Conductor 90 Shunt resistance

Claims (4)

[Claims] 1. A superconducting element wire comprising a conductor in which a plurality of Nb3Sn wires are embedded is covered with a coating, wherein the coating is made of an alloy containing Sn and In added thereto. . 2. A superconducting cable in which a plurality of superconducting element wires are formed and twisted, and the superconducting element wires are formed by coating a conductor in which a plurality of Nb3 Sn wires are embedded with a film formed by adding In to Sn. A superconducting cable characterized by being configured as follows. 3. A composite superconducting conductor in which a superconducting cable composed of a plurality of superconducting element wires is housed in stabilized Cu and embedded in solder, wherein the superconducting element wire is a conductor in which a plurality of Nb3 Sn wires are embedded. , Sn is coated with a film formed by adding In to the composite superconducting conductor. 4. The weight ratio of In is x percent (0 <
When x ≦ 17), the coating film has a weight ratio (100−).
The superconducting element wire according to claim 1, wherein x) percent Sn and x weight percent In are included.