JP2742421B2 - Superconducting wire and its manufacturing method - Google Patents

Description

The present invention is suitable as a wire for a superconducting magnet used in a particle accelerator or a magnetic resonance diagnostic apparatus, and has a particularly high critical current density. The present invention relates to a superconducting wire having high mechanical strength and a method for manufacturing the same.

"Conventional technology" In a superconducting wire, heat may be generated due to the movement of a quantum flux line, and in such a case, buds of normal conduction are partially generated in the superconducting wire, and the entire superconducting wire is May be transposed to a normal conduction state. Therefore, in order to stabilize the superconducting wire by preventing such magnetic instability, normal conduction dislocation, and the like, conventionally, the following technology has been adopted.

A superconductor is buried in a stable base material of good conductivity such as copper. In particular, the stabilizing matrix is formed from high-purity copper.

The superconductor is refined into a filament having a diameter of several μm to several tens μm.

Twist multi-core wire.

Adopt a braided or formed stranded wire structure.

When a superconducting wire is used for alternating current, a stabilizing base material is formed from a high-resistance metal material such as a Cu-Ni alloy to suppress a coupling current generated between superconducting filaments.

Since superconducting characteristics of a superconductor made of a compound or the like deteriorate when mechanical strain is applied, a reinforcing material is added to the superconducting wire to prevent mechanical strain from being applied.

From such a background, conventionally, a superconducting wire A having a structure shown in FIG. 2 has been provided as a compound superconducting wire for alternating current.

The superconducting wire A shown in FIG. 2 constitutes a superconducting wire 2 by arranging a large number of compound superconducting filaments inside a stabilized base material made of copper, and prepares a plurality of superconducting wires 2. Each superconducting element wire 2 is brazed to a brazing metal 4 such as a solder by adding a twisted wire around a stabilizing material 3 made of oxygen-free copper.
Thus, the structure is fixed to the stabilizer 3. That is, in the superconducting wire A having this structure, the stabilizing material 3 stabilizes the superconducting wires 2 and also serves as a reinforcing material for the superconducting wires 2.

[Problems to be Solved by the Invention] By the way, when the conventional superconducting wire A shown in FIG. 2 is manufactured, when the superconducting wire 2 is twisted around the stabilizing material 3, the brittle superconducting wire 2 There is a problem that stress is applied to the superconducting wire 2 and the superconducting properties of the superconducting wire 2 are deteriorated. Further, since the superconducting wire 2 itself is brittle and has low strength, it is necessary to sufficiently reinforce it. Therefore, the superconducting wire A shown in FIG. 2 has a structure in which the stabilizing material 3 also serves as a reinforcing material. However, when the reinforcing member 3 is made large, there is a problem that the entire sectional area increases and the conductor becomes large.

The present invention has been made to solve the above problems, and provides a compound-based superconducting wire having high stability of superconducting characteristics, high critical current density, high mechanical strength, and compact structure, and a production thereof. The purpose is to do.

"Means for Solving the Problems" The present invention provides, in order to solve the above problems, a plurality of stabilizing base materials made of a good conductive metal material, and a diffusion prevention layer individually covering these stabilizing base materials. A shielding layer that covers the plurality of stabilizing base materials with the diffusion preventing layer in a state where they are separately spaced from each other, a core part including a diffusion preventing layer that covers the shielding layer, and the core part. It is characterized by comprising a superconducting portion provided so as to cover and formed by arranging a superconducting filament inside a metal base.

In addition, the invention according to claim 2 creates an in-situ wire in which dendrites composed of one or more elements are arranged inside a metal matrix among a plurality of elements constituting a superconducting intermetallic compound. , A stabilizing material is formed by covering a diffusion prevention tube made of Ta, Nb, etc. and a high resistance metal cladding tube on the outside of a stabilizing base material made of a good conductive metal material such as copper,
A plurality of these stabilizing materials are assembled, inserted into a diffusion prevention tube, and reduced in diameter, so that a plurality of stabilizing base materials made of a good conductive metal material and a diffusion preventing material that individually covers these stabilizing base materials. A composite layer comprising: a layer; a high-resistance metal shielding layer that covers the plurality of stabilizing base materials with the diffusion preventing layer in a state where they are separately spaced; and a diffusion preventing layer that covers the shielding layer. A member is formed, a plurality of the in-situ wires are arranged on the outer periphery of the composite member, and a diameter of the entire in-situ wire is reduced to form a composite wire. Forming a coating layer made of the remaining elements among the elements, and further performing a heat treatment to diffuse the elements of the coating layer into the inside of the compact formed of in-situ wire to produce a superconducting intermetallic compound. Things.

[Operation] Since the stabilizing base material is covered with the diffusion preventing layer, contamination of the stabilizing base material by unnecessary elements is prevented. Further, since the stabilizing base materials are individually separated by the shielding layer made of a high-resistance metal material, the AC loss is reduced, and the stability of the superconducting wire is improved. Further, since the superconducting portion is manufactured based on the in-situ wire, a superconducting wire having high mechanical strength and high critical current density can be obtained.

In addition, a plurality of stabilizing base materials are provided and individually covered with the diffusion preventing layer, and the shielding layer outside the diffusion preventing layer is further covered with the diffusion preventing layer outside the diffusion preventing layer. And the contamination by the diffusion element during the diffusion heat treatment is prevented, and the shielding layer is also covered by the diffusion prevention layer. Therefore, the contamination of the shielding layer by the diffusion element during the diffusion heat treatment is also prevented. Further, diffusion of the element of the shielding layer made of a high-resistance metal material to the stabilizing base material side is also prevented.

Next, according to the method of the present invention, it is possible to obtain a superconducting wire having the above-described excellent action.

 Hereinafter, the present invention will be described in more detail.

FIGS. 1A to 1I are views for explaining an example in which the present invention is applied to a method for manufacturing an Nb ₃ Sn-based superconducting wire.
In order to manufacture a superconducting wire by carrying out the present invention, first, as shown in FIG. 1 (a), a diffusion preventing material such as Nb or Ta is formed on the outer periphery of a rod-shaped stabilizing base material 10 made of oxygen-free copper. The composite material 13 is obtained by covering the layer 11 and further covering the outer periphery thereof with a cladding tube 12 made of a Cu-Ni alloy.

Here, Ta or Nb was selected as a constituent material of the diffusion prevention tube 11 because Ni contained in the cladding tube 12 diffuses to the stabilizing base material 10 side during a diffusion heat treatment performed in a later step. Ta or Nb was selected for the purpose of preventing contamination of the stabilized base material 10 by preventing the occurrence of unnecessary compounds and preventing the formation of unnecessary compounds between the constituent elements of the stabilized base material 10 during the diffusion heat treatment. Further, the alloy constituting the cladding tube 12 is made of Ni or Ti, Zr, Hf or the like which increases the electric resistance of copper.
An alloy is used in which at least one of Group IIIa elements and Group IIIb elements of the Periodic Table III such as Al, Ga, and In is added to copper.

Next, the diameter of the composite material 13 is reduced by a diameter reducing method such as a groove roll process or a forging process to obtain a stabilized material 14 shown in FIG. 1 (b).

Next, a plurality of the stabilizing materials 14 (seven in the drawing) are assembled, and a diffusion prevention tube 15 made of Ta or Nb and a pure copper tube body
As shown in FIG. 1 (c), the composite member 17 shown in FIG.
Get.

On the other hand, the in-situ ingot 20 shown in FIG.
Create The in-situ ingot 20 is made by melting a predetermined component of a Cu-Nb alloy, and has a structure in which a myriad of dendrites composed of Nb are dispersed inside a metal base made of Cu. After the in-situ ingot 20 is created, the diameter of the in-situ ingot 20 is reduced to create an in-situ line 21 shown in FIG.

Next, a plurality of in-situ wires are provided around the outer periphery of the composite member 17.
21 is arranged and further inserted into a copper tube 22 as shown in FIG. 1 (f), and the diameter thereof is reduced. Thus, as shown in FIG. 1 (g), a composite wire 25 comprising a core portion 23 formed by consolidating and reducing the diameter of the composite member 17 and a compacted body 24 of an in-situ wire 21 surrounding the core portion is obtained. Next, a coating layer 26 made of Sn is further formed on the outer periphery by plating or the like to form a coating composite wire 27 shown in FIG. 1 (g).

Next, the coated composite wire 27 was heated to a melting point of Sn (231
C.), and more preferably, a first heat treatment for heating at 180 to 220 ° C. for several tens to several hundred hours. By this first heat treatment, Sn in the coating layer 26 diffuses into the inside of the coating composite wire 27 and the coating layer 26 disappears. During this heat treatment, Sn
When heated at a temperature higher than the melting point, the coating layer 26 is undesirably melted off.
It is not preferable because it takes time to diffuse n. Then, preferably, the wire is subjected to a heat treatment of heating to 300 to 450 ° C. for several tens to several hundred hours to promote the diffusion of Sn and prevent the generation of unnecessary compounds.

Next, a diffusion heat treatment of heating the wire to 500 to 700 ° C. for several tens to several hundreds hours is performed, and Sn diffused to the inner side of the compact 24 is formed.
And the Nb filament react to generate a filament of the Nb ₃ Sn superconducting intermetallic compound to obtain a superconducting wire B shown in FIG. 1 (h). The superconducting wire B is connected to the superconducting portion 28 on the outer peripheral side.
And a core 23 provided at the center thereof.

The cross-sectional structure of the core portion 23 is as shown in FIG.
A diffusion preventing layer 31 made of Ta or Nb is formed inside an inner coating layer 30 made of copper, and a shielding layer 33 made of Cu-Ni is filled therein. Inside the shielding layer 33, a diffusion preventing layer 34 is formed. The structure has a structure in which a stabilized base material 35 made of pure copper surrounded by is dispersed. Note that Sn diffused from the coating layer 26 into the coated composite wire 24 during the heat treatment passes through the pipe 22 and diffuses to the inside of the compacted body 24 made of an in-situ wire. The diffusion is prevented by the diffusion prevention layer 31 existing in the core portion 23, and the diffusion of Sn into the inside of the core portion 23 is prevented. Also,
Since the stabilizing base material 35 has a structure that is double-covered by the diffusion preventing layer 31 and the diffusion preventing layer 34, the diffusion of Sn during the diffusion heat treatment is completely prevented. It is not preferable that Sn diffuses into the inside of the core portion 23 and the stabilized base material 35 is contaminated with Sn because the electric resistance of the stabilized base material 35 at an extremely low temperature increases.
In addition, the stabilizing base material 35 is individually shielded by the diffusion prevention layer 34.
33, the Ni contained in the shielding layer 33
Is also prevented from contaminating the stabilized base material 35.

Since the superconducting wire B manufactured as described above is manufactured based on the in-situ wire 21, it has excellent critical current characteristics,
It is also excellent in mechanical strength, such as little deterioration of superconductivity even when subjected to mechanical strain. Further, the superconducting wire B has a structure in which the core portion 23 is provided at the center thereof, so that the superconducting wire B has a structure reinforced by the core portion 23 and has a high mechanical strength. Therefore, the superconducting wire B does not require a special reinforcing material unlike the conventional superconducting wire A shown in FIG. 2, so that the entire conductor can be made more compact than before.

The superconducting wire B is used in a state where the superconducting wire B is cooled to an extremely low temperature by a coolant such as liquid helium. When a part of the superconducting portion 28 attempts to transpose to the normal conducting state for some reason, a current flows through the core portion 23 to prevent heat generation.

When the superconducting wire B is used for alternating current and a part of the superconducting portion 28 tries to transpose to the normal conducting state, an alternating current flows through the stabilizing base materials 35. Since the structure is separated by the shielding layer 33 made of high resistance Cu-Ni, the AC loss that is likely to occur between the stabilizing base materials 35 can be reduced. Therefore, superconducting wire B exhibits extremely excellent stability for AC use.

By the way, in the above example, the structure of the present invention was applied to the structure of the Nb ₃ Sn superconducting wire, but the structure of the present invention was applied to a compound such as V ₃ Ga, Nb ₃ Ge, Nb ₃ Al. Of course, the present invention can be applied to the structure of a superconducting wire based on an alloy, and can also be applied to a superconducting wire based on an alloy such as Nb-Ti. Further, the method of the present invention can be applied as a method for producing a general compound-based superconducting wire such as a V ₃ Ga-based as well as an Nb ₃ Sn-based.

In addition, in the above-described example, the structure of the superconducting wire in which one core portion 23 is disposed inside the superconducting portion 28 has been described. However, the superconducting wire having the structure in which the plurality of core portions 23 are disposed inside the superconducting portion 28 has Of course, the invention may be applied.

"Example" A rod-shaped in-situ ingot having a composition of Cu-30 wt% Nb and a diameter of 50 mm was melted and subjected to forging, extrusion and drawing to obtain an in-situ wire having a diameter of 2 mm.
In addition, a 99.9% pure oxygen-free copper rod has an outer diameter of 15 mm,
Nb tube with inner diameter of 14mm, composition of Cu-30wt% Ni, outer diameter of 20mm
A stabilizing material having a diameter of 1.1 mm was obtained by drawing a wire over a tube having an inner diameter of 16 mm.

Next, 91 stabilizing materials were assembled to form an outer diameter of 15 mm and an inner diameter of 14
It was inserted into a Ta tube having a diameter of 1 mm, further inserted into an oxygen-free copper tube having an outer diameter of 18 mm and an inner diameter of 16 mm, and then reduced in diameter to obtain a composite member having a diameter of 11 mm.

Next, the composite member is arranged at the center of an oxygen-free copper tube having an outer diameter of 18 mm and an inner diameter of 16 mm, and the above-mentioned 18 in-situ wires are arranged around the tube. I got In the middle of the diameter reduction processing, twist processing was performed so that the pitch became 10 mm at the stage of the wire diameter of 0.3 mm. Further, a Sn plating layer having a thickness of 8 μm was formed on the outer periphery by an electroplating method to obtain a plated composite wire.

Next, the plated composite wire was heated at 180 ° C. for 4 days, then heated at 400 ° C. for 2 days, and further heat-treated by heating the tube at 550 ° C. for 5 days to produce a current-carrying wire.

When the obtained superconducting wire was cooled to 4.2 K with liquid helium under a magnetic field of 10 T (tesla) and the critical current density was measured, it showed an excellent value of 1.5 × 10 ⁵ A / cm ² .

When the inside of the superconducting wire was analyzed with an X-ray microanalyzer, it was found that Sn had diffused from the surface of the wire to about 50 μm to 60 μm. It was also confirmed that the stabilized base metal at the center was not contaminated by Ni present around it.

[Effects of the Invention] As described above, the present invention provides a plurality of stabilizing base materials made of a good conductive metal material, a diffusion preventing layer individually covering the stabilizing base materials, and a stabilizing base material separated from each other. A shielding layer that covers the shielding layer in a state where it is disposed, a core portion including a diffusion prevention layer that covers the shielding layer, and a filament that is provided to cover the core portion and that is provided with a superconductor filament inside the metal base. With the superconducting part formed, the stabilizing base material is prevented from being contaminated during the diffusion heat treatment, and further, the AC loss of the stabilizing base material is reduced by the shielding layer made of a high-resistance metal. Therefore, it has a feature that the critical current density is high and the AC current is excellent. Furthermore, since the shielding layer is covered with the diffusion preventing layer in addition to the stabilizing base material, elemental contamination of the shielding layer during the diffusion heat treatment can be prevented, and the stabilized base material is covered twice with the diffusion preventing layer. Therefore, elemental contamination of the stabilized base material during the diffusion heat treatment can be completely eliminated. Further, the constituent elements of the shielding layer do not contaminate the stabilized base material during the diffusion heat treatment. Therefore, it is possible to provide a superconducting wire suitable for AC with high stability and high critical current density. In addition, since the core is provided, it is mechanically strong and has a compact structure. Therefore, the superconducting wire of the present invention is extremely excellent as an AC superconducting wire.

According to the method of the present invention, the critical current density is high because of having the superconducting portion manufactured from the in-situ wire,
A superconducting wire having high strength with little deterioration of superconducting characteristics due to mechanical strain can be manufactured. Further, a plurality of stabilizing base materials made of a good conductive metal material, a diffusion preventing layer individually covering these stabilizing base materials, and a plurality of the stabilizing base materials with the diffusion preventing layers are separately arranged. Since it has a structure including a shielding layer made of a high-resistance metal and a diffusion preventing layer covering the shielding layer, contamination of the stabilized base material during diffusion heat treatment can be prevented. Since the structure is such that the AC loss is reduced by covering the stabilizing base material with the shielding layer made of a resistance metal, there is an effect that a superconducting wire having a high critical current density for AC can be manufactured. Furthermore, since the shielding layer is covered with the diffusion preventing layer in addition to the stabilizing base material, elemental contamination of the shielding layer during the diffusion heat treatment can be prevented, and the stabilized base material is covered twice with the diffusion preventing layer. Therefore, elemental contamination of the stabilized base material during the diffusion heat treatment can be completely eliminated. Further, there is no danger that the constituent elements of the shielding layer will diffuse to the stabilized base material side during the diffusion heat treatment. Therefore, a superconducting wire having high stability and high critical current density can be provided. Further, since the core is disposed inside, a superconducting wire having a high mechanical strength and a compact structure can be manufactured.

[Brief description of the drawings]

FIGS. 1 (a) to 1 (i) are for explaining an example of the present invention, and FIG. 1 (a) is a cross-sectional view showing a coated state of a stabilizing base material, and FIG. FIG. 1 (b) is a sectional view showing a stabilizing material, FIG. 1 (c) is a sectional view showing an assembled state of the stabilizing material, FIG. 1 (d) is a sectional view showing an in-situ ingot, and FIG. Sectional view showing in-situ line, first
FIG. 1 (f) is a sectional view showing an assembled state of the stabilizing material and the in-situ wire, FIG. 1 (g) is a sectional view showing a composite wire, FIG. 1 (h) is a sectional view of a superconducting wire, FIG. i) is an enlarged cross-sectional view showing the central structure of the superconducting wire shown in FIG.
FIG. 2 is a sectional view showing one structural example of a conventional compound superconducting wire. B: superconducting wire, 10: stabilizing base material, 15: anti-diffusion tube, 20: in-situ ingot, 21: in-situ wire, 23: core, 24: compacted body, 26: coating layer , 27 ... plated composite wire, 28 ... superconducting part, 31 ... diffusion prevention layer, 33 ... shielding layer, 34 ... diffusion prevention layer, 35 ... stabilized base material.

Continued on the front page (72) Inventor Nobuyuki Sadakata 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Electric Wire Co., Ltd. (72) Inventor Takashi Saito 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (56) References JP-A-60-250513 (JP, A) JP-A-60-250506 (JP, A) JP-A-62-243745 (JP, A) JP-A-62-252012 (JP, A)

Claims (2)

(57) [Claims] 1. A plurality of stabilizing base materials made of a good conductive metal material, a diffusion preventing layer individually covering these stabilizing base materials,
A core comprising: a shielding layer covering the plurality of stabilizing base materials with the diffusion preventing layer in a state where they are separately arranged; a diffusion preventing layer covering the shielding layer; and a core covering the core. And a superconducting portion formed by arranging a superconducting filament inside a metal base. 2. An in-situ wire in which dendrites composed of one or more elements among a plurality of elements constituting a superconducting intermetallic compound are arranged inside a metal matrix, and a good conductive material such as copper is formed. A stabilizing material is formed by covering a diffusion prevention tube made of Ta, Nb, etc. and a high-resistance metal cladding tube outside the stabilizing base material made of a conductive metal material. A plurality of stabilizing base materials made of a good conductive metal material, a diffusion preventing layer individually covering these stabilizing base materials, Forming a composite member comprising a high-resistance metal shielding layer that covers the plurality of stabilizing base materials in a state where they are separately spaced from each other, and a diffusion prevention layer that covers the shielding layer. On the outer circumference, arrange a plurality of the in-situ wires, and further reduce the entire diameter After forming the joining wire, of the plurality of elements constituting the superconducting intermetallic compound, forming a coating layer composed of the remaining elements on the outer periphery of the composite wire, and further performing a heat treatment to convert the elements of the coating layer from the in-situ wire. A method for producing a superconducting wire, characterized in that a superconducting intermetallic compound is generated by diffusing the compound into the inside of a compact.