JP2010097902A - PRECURSOR FOR MANUFACTURING Nb3Sn SUPERCONDUCTIVE WIRE, AND Nb3Sn SUPERCONDUCTIVE WIRE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal diffusion method-based Nb<SB>3</SB>Sn superconductive wire capable of reducing AC loss to the utmost while maintaining high critical current density Jc by lessening a diameter of a Nb<SB>3</SB>Sn superconductive filament as much as possible and applying to a NMR magnet, and to provide a precursor used for the same. <P>SOLUTION: In the precursor obtained by making into a wire a compound tube having a cylindrical diffusion barrier layer with a stabilized copper layer on its outer periphery and inserted by a group of multiple wires in the cylindrical diffusion barrier layer, the group of multiple wires are formed of a plurality of Cu/Nb element wires where an Nb or Nb-based alloy core is buried in Cu or a Cu-based alloy matrix, and a plurality of Cu/Sn element wires where Sn or Sn-based alloy core is buried in Cu or a Cu-based alloy matrix. The plurality of Cu/Nb element wires are arranged so as to divide into a plurality of zones by the plurality of Cu/Sn element wires connected and arranged with each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a precursor (precursor for producing a superconducting wire) for producing an Nb ₃ Sn superconducting wire by an internal diffusion method, and an Nb ₃ Sn superconducting wire produced by such a precursor, in particular, a superconducting magnet. The present invention relates to a Nb ₃ Sn superconducting wire useful as a material for the above and a precursor thereof.

  Among the fields where superconducting wires are put into practical use, there are superconducting magnets used in high-resolution nuclear magnetic resonance (NMR) analyzers, fusion devices, accelerators, and the like. In particular, for superconducting magnets used in NMR analyzers (hereinafter sometimes referred to as “NMR magnets”), high magnetic field and compact size are required due to the demand for improved resolution of NMR signals and shortened data acquisition. It has been demanded.

To increase the magnetic field and size of an NMR magnet, it is essential to improve the performance of the superconducting wire used in the magnet, but it has been used as the wire for the innermost coil of the NMR magnet. Development of a new superconducting wire that surpasses the characteristics of the bronze Nb ₃ Sn superconducting wire is required.

In the above bronze method, a core wire made of a plurality of Nb or Nb base alloys is embedded in a Cu—Sn base alloy (bronze) matrix to form a composite wire, and the composite wire is reduced in diameter by extrusion or wire drawing. The core material is reduced in diameter to form an Nb-based filament, and a plurality of composite wires made of the Nb-based filament and bronze are bundled to form a wire group, and copper for stabilization (stabilized copper) is formed on the outer periphery thereof. ), The diameter is further reduced. Subsequently, the wire group after the diameter reduction is heat-treated (diffusion heat treatment) at about 600 ° C. or more and 800 ° C. or less, so that an Nb ₃ Sn compound phase (Nb ₃ Sn superconducting phase) is formed at the interface between the Nb-based filament and the bronze matrix. Is a method of generating

However, in this method, there is a limit to the Sn concentration that can be dissolved in bronze (15.8% by mass or less), the thickness of the produced Nb ₃ Sn compound phase is thin, and the crystallinity is deteriorated. There is a drawback that a high critical current density Jc cannot be obtained. The NMR magnet can be made more compact as the critical current density Jc of the wire is higher.

As a method for producing the Nb ₃ Sn superconducting wire, in addition to the bronze method, a powder method using powdered Sn or Sn-based alloy and an internal diffusion method are also known. In these methods, since there is no limit on the Sn concentration due to the solid solubility limit as in the bronze method, the Sn concentration can be set as high as possible, and a high-quality Nb ₃ Sn compound phase can be generated, so that a high critical current density Jc is obtained. Is expected to be. In the superconducting wire by the above bronze method, the Cu—Sn alloy undergoes work hardening during cold working, and thus requires multiple annealing (strain relief annealing). In particular, in the internal diffusion method, Cu, Nb, Sn, etc. Since the precursor (precursor for producing a superconducting wire) is composed of a material having excellent workability, there is an advantage that it is not necessary to perform annealing during processing, and the production time of the precursor can be shortened.

In the internal diffusion method (also referred to as “internal Sn method”), as shown in FIG. 1 (schematic diagram of the basic configuration of the precursor for producing the internal diffusion method Nb ₃ Sn superconducting wire), Cu or a Cu-based alloy (hereinafter, “ A core material made of Sn or an Sn-based alloy (hereinafter sometimes referred to as “Sn core material”) 3 is embedded in the central portion of 4 (sometimes referred to as a “Cu matrix”), and around the Sn core material 3. In the Cu matrix 4, a core material (hereinafter sometimes referred to as “Nb core material”) 2 made of a plurality of Nb or Nb-based alloys is arranged so as not to contact each other, and a precursor (for superconducting wire manufacturing) Precursor 1 is drawn and processed, and then Sn in the Sn core material 3 is diffused by heat treatment (diffusion heat treatment) and reacted with the Nb core material 2 to generate an Nb ₃ Sn compound phase in the wire. It is a method to make it.

  Further, in the precursor as described above, as shown in FIG. 2, a diffusion barrier layer 6 is provided between the portion where the Nb core material 2 and the Sn core material 3 are disposed and the stabilizing copper layer 4a outside thereof. The arranged configuration (precursor 5) may be employed. The diffusion barrier layer 6 has a cylindrical shape (cylindrical diffusion barrier layer), and is composed of, for example, an Nb layer or a Ta layer (including each alloy layer), or two layers of an Nb layer and a Ta layer. In this case, Sn in the Sn core material 3 is prevented from diffusing to the outside, and the effect of increasing the Sn concentration near the Nb core in the superconducting wire is exhibited.

  In the configuration of the precursor shown in FIGS. 1 and 2, the Nb core material 2 is used for producing such a precursor (precursor for producing a superconducting wire) because the Sn core material 3 is arranged in the central portion of the wire. It is necessary to prepare a composite pipe composed of an outer cylinder for arranging and an inner cylinder for arranging the Sn core material 3.

In producing an Nb ₃ Sn superconducting wire by an internal diffusion method, various proposals have been made for the structure of a precursor that exhibits good superconducting properties (particularly high critical current density Jc). As such a technique, for example, as shown in FIG. 3, a plurality of Cu / Nb element wires in which a Nb or Nb base alloy core (Nb core material 2 shown in FIGS. 1 and 2) is embedded in a Cu or Cu base alloy matrix. 7 and a Sn or Sn-based alloy core (Sn core material 3 shown in FIGS. 1 and 2) is formed into a composite wire group by a plurality of Cu / Sn element wires 8 embedded in a Cu or Cu-based alloy matrix. In the group, the periphery of the Cu / Sn element wire 8 is dispersed and arranged so as to surround the Cu / Nb element wire 7 (precursor 10).

  In such a configuration, the Cu / Nb element wire 7 and the Cu / Sn element wire 8 are arranged so as to contact each other. In the configuration shown in FIG. 3, the cylindrical diffusion barrier layer 6 and the stabilized copper layer 4a are also disposed. Hereinafter, the configuration of the precursor shown in FIG. 3 may be referred to as a “dispersion type internal diffusion method superconducting wire precursor”. In such a dispersion type internal diffusion method superconducting wire precursor, the superconducting characteristics can be further enhanced as compared with the precursor shown in FIGS. Since a Cu composite pipe made of is not required, the manufacturing process is simplified.

  FIG. 4 is a cross-sectional view schematically showing a detailed configuration of the Cu / Nb element wire 7 which is a constituent element of the dispersion type internal diffusion method superconducting wire precursor. In this Cu / Nb element wire 7, the Nb or Nb base alloy core (Nb core 2) is inserted into a pipe made of Cu or Cu base alloy, and subjected to diameter reduction processing such as extrusion or wire drawing, and the cross-sectional shape Is a hexagonal composite (Nb single core wire), and a plurality (37 in this figure) are bundled and inserted into a pipe 9 made of Cu or a Cu-based alloy [FIG. 4 (a)]. The cross-sectional shape is formed in a hexagonal shape by performing diameter reduction processing such as extrusion and wire drawing [FIG. 4B]. The pipe 9 made of Cu or a Cu-based alloy forms the Cu matrix 4 after the diameter reduction processing (the same applies to the Cu / Sn element wire 8 shown in FIG. 5).

  FIG. 5 is a cross-sectional view schematically showing a detailed configuration of the Cu / Sn element wire 8 serving as a component of the distributed internal diffusion method superconducting wire precursor. In this Cu / Sn element wire 7, an Sn or Sn-based alloy core (Sn core material 3) is inserted into a pipe 9 made of Cu or a Cu-based alloy [FIG. 5 (a)], and extrusion, wire drawing, etc. By reducing the diameter, the cross-sectional shape is formed in a hexagonal shape (FIG. 5B).

  The conventional dispersion type internal diffusion superconducting wire precursor (FIG. 3) is configured by arranging the Cu / Nb element wire 7 and the Cu / Sn element wire 8 shown in FIGS. 4 and 5 so as to contact each other. . The Cu / Nb element wire 7 and the Cu / Sn element wire 8 are generally combined in a hexagonal cross section (FIGS. 4B and 5B). a), an appropriate diameter reduction process may be applied from the stage shown in FIG. 5A, and the cross-sectional shape may be combined in a circular stage.

Heat treatment (diffusion heat treatment) is applied to such a precursor, and Nb or Nb base alloy core in the Cu / Nb element wire and diffusion reaction of Sn or Sn base alloy core in the Cu / Sn element wire _A superconducting wire is formed by generating a ₃ Sn superconducting phase. In the superconducting wire manufactured with such a dispersion type internal diffusion method superconducting wire precursor, the Cu / Nb element wires are in contact with each other in the form of a mesh at the precursor stage, and Nb ₃ The Sn superconducting phase is also formed in a network.

However, during the Nb ₃ Sn superconducting phase generation heat treatment, the volume expansion of the Nb core due to the reaction of Nb + 3Sn → Nb ₃ Sn occurs, and a Cu-Sn part with a very large amount of Sn is generated, and the melting point of this part is very high Therefore, a phenomenon occurs in which the Nb core portion formed by the Nb ₃ Sn superconducting phase is present in the Cu—Sn liquid phase. Even in such a state, the generation of Nb ₃ Sn proceeds, but the movement of the Nb core in the state of floating in the liquid phase (spotted in the liquid phase) cannot be suppressed, and the surrounding Nb The cores touch each other, and after the heat treatment is completed, most of the Nb ₃ Sn bonds to each other, resulting in an apparently very large Nb ₃ Sn filament.

In the case of a wire having a large Nb ₃ Sn filament size, it is expected to cause electromagnetic instability (flux jump), an increase in AC loss for AC use, and the like. An NMR magnet using such a superconducting wire is very difficult to put into practical use.

In order to solve such a problem, a general bronze method Nb ₃ Sn superconducting wire is subjected to strong processing so that the filament diameter is 10 μm or less. In the internal diffusion method, for example, As shown in Patent Document 1, it has been proposed to arrange Nb cores radially.

However, the technology proposed so far has realized that the apparent filament diameter can be reduced while taking advantage of the fact that the process can be simplified by configuring the dispersion type internal diffusion method superconducting wire precursor. In fact, when applied to an NMR magnet, an Nb ₃ Sn superconducting wire that can reduce AC loss as much as possible while maintaining a high critical current density Jc has not been realized.
JP 2006-32190 A

The present invention has been made under such circumstances, and its purpose is to reduce the AC loss as much as possible while maintaining a high critical current density Jc by reducing the diameter of the Nb ₃ Sn superconducting filament as much as possible. An object of the present invention is to provide an internal diffusion Nb ₃ Sn superconducting wire that can be applied to an NMR magnet and a precursor therefor.

The precursor for producing a superconducting wire of the present invention that has achieved the above-mentioned object is,
The precursor used when manufacturing Nb ₃ Sn superconducting wire by the internal diffusion method has a cylindrical diffusion barrier layer provided with a stabilized copper layer on the outer periphery, and a composite wire group is inserted into the cylindrical diffusion barrier layer A precursor obtained by converting the composite pipe made into a wire,
The composite wire rod group is
A plurality of Cu / Nb element wires in which an Nb or Nb-based alloy core is embedded in a Cu or Cu-based alloy matrix;
The Sn or Sn base alloy core consists of a plurality of Cu / Sn element wires embedded in a Cu or Cu base alloy matrix,
The plurality of Cu / Nb element wires have a gist in that they are arranged so as to be divided into a plurality of regions by the plurality of Cu / Sn element wires connected to each other.

  In the precursor for producing a superconducting wire according to the present invention, (a) the plurality of Cu / Nb element wires and the plurality of Cu / Sn element wires have a cross-sectional shape formed in a hexagon, (b) The plurality of Cu / Nb element wires are divided so as not to be continuously arranged in the circumferential direction. (C) In the divided Cu / Nb element wires, the Cu / Sn elements are separated. (D) The ratio (A: B) of the number A of the plurality of Cu / Nb element wires to the number B of the plurality of Cu / Sn element wires is as follows: It is preferable to satisfy requirements such as 5: 1.0 to 3.0: 1.0.

A Nb ₃ Sn superconducting wire exhibiting desired characteristics (high critical current density Jc, reduced AC loss) can be produced by heat treatment using the above-described precursor for superconducting wire production. The structure of the superconducting wire reflects the structure of the precursor, and is produced by a diffusion reaction between the Nb or Nb base alloy core in the Cu / Nb element wire and the Sn or Sn base alloy core in the Cu / Sn element wire. The Nb ₃ Sn superconducting phase region is divided by the portion where the Cu / Sn element wire was disposed before the heat treatment.

In the precursor for producing a superconducting wire according to the present invention, a composite wire group as a constituent element of the precursor, a plurality of Cu / Nb element wires in which an Nb or Nb base alloy core is embedded in a Cu or Cu base alloy matrix, and Sn Alternatively, the plurality of Cu / Sn elements are composed of a plurality of Cu / Sn element wires in which an Sn-based alloy core is embedded in Cu or a Cu-based alloy matrix, and the plurality of Cu / Nb element wires are connected to each other. Since it is arranged to be divided into a plurality of regions by the wire, a distributed internal diffusion method Nb ₃ Sn superconducting wire that can reduce AC loss while maintaining high critical current density Jc characteristics is realized did it.

  The structure of the precursor for manufacturing a superconducting wire according to the present invention (hereinafter sometimes simply referred to as “precursor”) will be described with reference to the drawings. FIG. 6 is a cross-sectional view schematically showing a configuration example of the precursor 15 of the present invention. In the structure of the precursor of the present invention, a Cu / Nb element wire 7 (a plurality of Nb or Nb base alloy cores are embedded in a Cu or Cu base alloy matrix) as shown in FIG. A composite wire group is formed from a Cu / Sn element wire 8 as shown in FIG. 5 (one Sn or Sn base alloy core is embedded in a Cu or Cu base alloy matrix). In the configuration shown, a plurality of Cu / Sn element wires 8 that are linearly connected to each other are arranged in three locations radially from the center. By adopting such a configuration, the plurality of Cu / Nb element wires 7 are divided into a plurality of (six locations in the circumferential direction in FIG. 6) regions by a plurality of Cu / Sn element wires 8 (disposed radially). The Cu / Nb element wire 7 is divided so as not to be continuously arranged all around in the circumferential direction (not connected once in the circumferential direction). In such a configuration, the Cu / Nb element wire 7 is not continuously arranged in the circumferential direction, which contributes to reduction of AC loss. From such a viewpoint, it is preferable that the number divided in the circumferential direction is three or more.

  FIG. 7 is a cross-sectional view schematically showing another configuration example of the precursor 16 of the present invention. In this configuration, the Cu / Nb element wires 7 are arranged radially and connected in a hexagonal shape. By adopting such a configuration, a plurality of Cu / Nb element wires 7 are divided into a plurality of regions (12 in FIG. 7) by a plurality of Cu / Sn element wires 8 (arranged radially and hexagonally). Will be.

  In the precursors 15 and 16 of the present invention, the Cu / Nb element wire 7 is basically divided into a plurality of regions as described above. If the hexagonal shape is merely arranged, there may be a region that is insufficient as a Sn supply source. Considering these points, the Cu / Sn element wire 8a may be partially (individually or linearly) dispersed in the region of the divided Cu / Nb element wire 7 as necessary. However, there may be a region of the Cu / Nb element wire 7 in which the Cu / Sn element wire 8a is not partially arranged, such as near the outer periphery of the precursor 16 shown in FIG.

  In the precursors 15 and 16 shown in FIGS. 6 and 7, the cross-sectional shape is a hexagonal Cu / Nb element wire 7 and a Cu / Sn element wire 8 combined to form a wire group. The / Nb element wire 7 and the Cu / Sn element wire 8 are not limited to hexagonal cross-sections, and have a circular cross-section as shown in FIGS. 4 (a) and 5 (b). Also good. However, the cross-sectional shape is preferably a hexagon in consideration of workability and the porosity during assembly.

The ratio (A: B) of the number A of the plurality of Cu / Nb element wires and the number B of the plurality of Cu / Sn element wires is 1.5: 1.0 to 3.0: 1.0. Is preferred. When the number A of Cu / Nb element wires decreases so that the value of A with respect to B is smaller than 1.5, the superconducting characteristics deteriorate due to the decrease in the Nb core, and the Cu / Sn element increases so as to exceed 3.0. When the number B of wires is reduced, the amount of Nb ₃ Sn produced decreases due to Sn shortage and superconducting characteristics deteriorate.

  Also in the precursor of the present invention, the diffusion barrier layer 6 and the stabilized copper layer 4a are disposed as in the prior art. For example, the diffusion barrier layer 6 may be a layer made of Nb or an Nb base alloy and / or a layer made of Ta or a Ta base alloy (a layer made of Nb or an Nb base alloy or a single layer made of Ta or a Ta base alloy, or These multilayers) can be used.

The configuration for dividing the Cu / Nb element wire 7 into a plurality of wire groups is not limited to the configurations shown in FIGS. 6 and 7, but various other configurations are assumed. Even after the heat treatment for generating the Nb ₃ Sn phase, unlike the conventional example (configuration shown in FIG. 3), a wire material in which the Nb ₃ Sn phase is divided as originally arranged can be obtained. As a result, the diameter of the Nb ₃ Sn phase filament can be reduced, and the AC loss can be reduced while maintaining a high critical current density Jc. The AC loss (P _h ) is calculated by the following equation (1). It can be seen that maintaining the Nb ₃ Sn filament diameter small is effective in reducing the AC loss.

P _h = (8 / 3π) × f × λ × Jc × d _f × B _m (1)
Where f: frequency of externally varying magnetic field (Hz)
λ: Nb ₃ Sn space factor in superconducting wire Jc: critical current density (A / m ² )
d _f : Filament diameter (m)
B _m : indicates the amplitude (T) of the externally varying magnetic field.

In the present invention, excellent superconducting properties (critical current density Jc) are exhibited by using the precursor 15 as described above and performing diffusion heat treatment (typically about 200 ° C. or more and less than about 800 ° C.) including bronzing heat treatment. Nb ₃ Sn superconducting wire can be obtained. Specifically, after performing a bronzing heat treatment (diffusion of Sn into Cu) in a temperature range of 180 to 600 ° C., heat treatment for generating Nb ₃ Sn for about 100 to 300 hours in a temperature range of 650 to 750 ° C. To do. The bronzing heat treatment may be a combination of multi-stage heat treatments such as about 180 to 200 ° C. for about 50 hours, about 340 ° C. for about 50 hours, and about 550 ° C. for about 50 to 100 hours.

  The precursor of the present invention basically includes a Cu / Nb element wire 7 in which a core material (Nb core material 2) made of Nb or Nb base alloy is embedded in a Cu or Cu base alloy matrix, and Sn or Sn base. The core material made of an alloy (Sn core material 3) is composed of Cu / Sn element wire 8 embedded in Cu or a Cu-based alloy matrix, but as a Cu-based alloy used as a material of the Cu matrix, Cu containing an element such as Ni (up to about 5% by mass) can be used. As the Nb-based alloy used as the Nb core material 2, an alloy containing an additive element such as Ti, Ta, Zr, Hf or the like up to about 8% by mass can be used. Furthermore, as the Sn-based alloy used as the Sn core material 3, it is possible to use an alloy in which an additive element such as Ti or Ta is contained in Sn to such an extent that the workability is not hindered (3% by mass or less).

A Nb ₃ Sn superconducting wire exhibiting desired characteristics (high critical current density Jc, reduced AC loss) can be produced by heat treatment using the above-described precursor for superconducting wire production. The structure of the superconducting wire reflects the structure of the precursor, and is produced by a diffusion reaction between the Nb or Nb base alloy core in the Cu / Nb element wire and the Sn or Sn base alloy core in the Cu / Sn element wire. The Nb ₃ Sn superconducting phase region is divided by the portion where the Cu / Sn element wire was disposed before the heat treatment. The Nb ₃ Sn superconducting wire contributes to high magnetic field and compactness of the NMR magnet.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example 1
According to the following procedure, the precursor whose cross-sectional shape was shown in FIG. 6 was produced. First, an Nb core having an outer diameter of 28.0 mm was inserted into a Cu pipe having an outer diameter of 32.8 mm and an inner diameter of 29.0 mm, and then Cu / Nb having a hexagonal cross-sectional shape of 4 mm opposite side length by wire drawing. A composite single core wire was produced. This is straightened and cut, bundled in 37, inserted into a Cu pipe (outer diameter: 32.8 mm, inner diameter: 29.0 mm), and drawn by a hexagonal cross-section (hexagon opposite side: 2.0 mm) Cu / An Nb composite multifilamentary wire (Cu / Nb element wire 7) was prepared, and after correction, cut into a length of 2 m.

  On the other hand, a Sn-2 mass% Ti rod having a diameter of 20.6 mm was inserted into a Cu pipe having an outer diameter of 24.0 mm and an inner diameter of 21.0 mm, and the opposite side length was 2.0 mm by wire drawing. A Cu / Sn composite single core wire (Cu / Sn element wire 8) having a cross-sectional shape was prepared, and after correction, cut into a length of 2 m.

  Next, as shown in FIG. 6, the Cu / Nb element wire 7 is made up of the Cu / Nb element wire 7: 162 and the Cu / Sn element wire 8: 91, as shown in FIG. Arranged and bundled so as to be divided into six parts to form a composite wire group (A: B≈1.8: 1.0).

In a Cu pipe (outer diameter: 45.0 mm, inner diameter: 38.0 mm), a Nb sheet with a thickness of 0.2 mm wound three times was inserted and brought into close contact with the inner surface of the Cu pipe. The composite wire group was inserted into this Cu pipe (in which the Nb sheet was adhered to the inner surface) and then drawn to prepare a precursor for producing an Nb ₃ Sn superconducting wire having an outer diameter of 1.0 mm. Diameter of Nb filament (Nb core material) in Cu / Nb element wire 7 at this stage (per one): 7.5 to 8.0 μm, Sn filament in Cu / Sn element wire 8 (Sn core material) Diameter: 45 to 50 μm.

The obtained precursor (with an outer diameter of 1.0 mm) was subjected to heat treatment (Nb ₃ Sn superconducting phase generation heat treatment) of 210 ° C. × 50 hours + 350 ° C. × 100 hours + 670 ° C. × 100 hours to obtain Nb ₃ Sn A superconducting wire was used. The resulting Nb ₃ Sn superconducting wire, by the method described below, was determined in terms of critical current density Jc, and AC loss.

[Measurement of critical current density Jc]
In liquid helium (temperature 4.2K), a sample (superconducting wire) is energized under an external magnetic field of 12T (Tesla), and the generated voltage is measured by the 4-terminal method. This value is an electric field of 0.1 μV / cm. The critical current density Jc was determined by measuring the current value (critical current Ic) at which the current occurred and dividing this current value by the cross-sectional area per non-Cu portion of the wire.

[AC loss measurement]
AC loss (mJ / cm ³ : loss per volume of superconducting part) was measured in a magnetic field of ± 3T (Tesla) in liquid helium (temperature 4.2K) by the pickup coil method (the calculation formula is Street).

(Example 2)
According to the following procedure, the precursor whose cross-sectional shape was shown in FIG. 7 was prepared. First, an Nb core having an outer diameter of 28.0 mm was inserted into a Cu pipe having an outer diameter of 32.8 mm and an inner diameter of 29.0 mm, and then Cu / Nb having a hexagonal cross-sectional shape of 4 mm opposite side length by wire drawing. A composite single core wire was produced. This is straightened and cut, bundled in 37, inserted into a Cu pipe (outer diameter: 32.8 mm, inner diameter: 29.0 mm), and drawn by a hexagonal cross-section (hexagon opposite side: 2.0 mm) Cu / An Nb composite multifilamentary wire (Cu / Nb element wire 7) was prepared, and after correction, cut into a length of 2 m.

  On the other hand, a Sn-2 mass% Ti rod having a diameter of 20.6 mm was inserted into a Cu pipe having an outer diameter of 24.0 mm and an inner diameter of 21.0 mm, and the opposite side length was 2.0 mm by wire drawing. A Cu / Sn composite single core wire (Cu / Sn element wire 8) having a cross-sectional shape was prepared, and after correction, cut into a length of 2 m.

  Next, the Cu / Nb element wires 7: 162 and the Cu / Sn element wires 8: 91 are connected to the Cu / Sn element wires 8 as shown in FIG. Arranged and bundled so as to be divided into places to form a composite wire group.

In a Cu pipe (outer diameter: 45.0 mm, inner diameter: 38.0 mm), a Nb sheet with a thickness of 0.2 mm wound three times was inserted and brought into close contact with the inner surface of the Cu pipe. The composite wire group was inserted into this Cu pipe (in which the Nb sheet was adhered to the inner surface) and then drawn to prepare a precursor for producing an Nb ₃ Sn superconducting wire having an outer diameter of 1.0 mm. Diameter of Nb filament (Nb core material) in Cu / Nb element wire 7 at this stage (per one): 7.5 to 8.0 μm, Sn filament in Cu / Sn element wire 8 (Sn core material) Diameter: 45 to 50 μm.

The obtained precursor (with an outer diameter of 1.0 mm) was subjected to heat treatment (Nb ₃ Sn superconducting phase generation heat treatment) of 210 ° C. × 50 hours + 350 ° C. × 100 hours + 670 ° C. × 100 hours to obtain Nb ₃ Sn A superconducting wire was used. The resulting Nb ₃ Sn superconducting wire, was determined in terms of critical current density Jc, and the ac loss in the same manner as in Example 1.

(Comparative Example 1)
According to the following procedure, a precursor (conventional precursor for manufacturing a distributed superconducting wire) having a sectional shape shown in FIG. 3 was prepared. First, an Nb core having an outer diameter of 28.0 mm was inserted into a Cu pipe having an outer diameter of 32.8 mm and an inner diameter of 29.0 mm, and then Cu / Nb having a hexagonal cross-sectional shape of 4 mm opposite side length by wire drawing. A composite single core wire was produced. This is straightened and cut, bundled in 37, inserted into a Cu pipe (outer diameter: 32.8 mm, inner diameter: 29.0 mm), and drawn by a hexagonal cross-section (hexagon opposite side: 2.0 mm) Cu / An Nb composite multifilamentary wire (Cu / Nb element wire 7) was prepared, and after correction, cut into a length of 2 m.

  On the other hand, a Sn-2 mass% Ti rod having a diameter of 20.6 mm was inserted into a Cu pipe having an outer diameter of 24.0 mm and an inner diameter of 21.0 mm, and the opposite side length was 2.0 mm by wire drawing. A Cu / Sn composite single core wire (Cu / Sn element wire 8) having a cross-sectional shape was prepared, and after correction, cut into a length of 2 m.

  Next, the Cu / Nb element wire: 162 and the Cu / Sn element wire: 91, and the Cu / Sn element wire 8 is the Cu / Nb element wire 7 as shown in FIG. 3 (conventional example). Were dispersed and arranged so as to surround them to form a composite wire group.

In a Cu pipe (outer diameter: 45.0 mm, inner diameter: 38.0 mm), a Nb sheet with a thickness of 0.2 mm wound three times was inserted and brought into close contact with the inner surface of the Cu pipe. The composite wire group was inserted into this Cu pipe (in which the Nb sheet was adhered to the inner surface) and then drawn to prepare a precursor for producing an Nb ₃ Sn superconducting wire having an outer diameter of 1.0 mm.

The obtained precursor (with an outer diameter of 1.0 mm) was subjected to heat treatment (Nb ₃ Sn superconducting phase generation heat treatment) of 210 ° C. × 50 hours + 350 ° C. × 100 hours + 670 ° C. × 100 hours to obtain Nb ₃ Sn A superconducting wire was used. The resulting Nb ₃ Sn superconducting wire, was determined in terms of critical current density Jc, and the ac loss in the same manner as in Example 1.

Table 1 below collectively shows the critical current density Jc and the AC loss of the superconducting wires obtained in Examples 1 and 2 and Comparative Example 1. The critical current density Jc needs to be at least 1200 A / mm ² or more, and the AC loss needs to be 1000 mJ / cm ³ or less.

  As can be seen from the results, in Examples 1 and 2 that satisfy the requirements defined in the present invention, the reduction of AC loss is achieved while maintaining a high critical current density Jc. On the other hand, in the conventional dispersion type internal diffusion method superconducting wire (Comparative Example 1), it can be seen that although the critical current density Jc is good, the AC loss is increased.

It is sectional drawing which showed typically the example of a basic composition of the precursor for superconducting wire manufacturing applied to an internal diffusion method. It is sectional drawing which showed typically the other structural example of the precursor for superconducting wire manufacturing applied to the internal diffusion method. It is sectional drawing which showed typically the example of a structure of the precursor for superconducting wire manufacturing in a prior art (dispersion type internal diffusion method superconducting wire precursor). It is sectional drawing which shows typically the detailed structure of the Cu / Nb element wire used as the component of a dispersion type internal diffusion method superconducting wire precursor. It is sectional drawing which shows typically the detailed structure of the Cu / Sn element wire used as the component of a dispersion type internal diffusion method superconducting wire precursor. It is sectional drawing which showed typically the example of a structure of the precursor for superconducting wire manufacture of this invention. It is sectional drawing which showed typically the example of another structure of the precursor for superconducting wire manufacturing of this invention.

Explanation of symbols

1,5,10,13,15,16 Precursor 2 for manufacturing superconducting wire 2 Nb or Nb-based alloy core (Nb core material)
3 Sn or Sn-based alloy core (Sn core material)
4 Cu matrix 4a Stabilized copper layer 6 Diffusion barrier layer (tubular diffusion barrier layer)
7 Cu / Nb element wire 8 Cu / Sn element wire

Claims (6)

The precursor used when manufacturing Nb ₃ Sn superconducting wire by the internal diffusion method has a cylindrical diffusion barrier layer provided with a stabilized copper layer on the outer periphery, and a composite wire group is inserted into the cylindrical diffusion barrier layer A precursor obtained by converting the composite pipe made into a wire,
The composite wire rod group is
A plurality of Cu / Nb element wires in which an Nb or Nb-based alloy core is embedded in a Cu or Cu-based alloy matrix;
The Sn or Sn base alloy core consists of a plurality of Cu / Sn element wires embedded in a Cu or Cu base alloy matrix,
The Nb ₃ Sn superconducting wire manufacturing method, wherein the plurality of Cu / Nb element wires are arranged so as to be divided into a plurality of regions by the plurality of Cu / Sn element wires connected to each other. Precursor. 2. The precursor for producing an Nb ₃ Sn superconducting wire according to claim 1, wherein the plurality of Cu / Nb element wires and the plurality of Cu / Sn element wires are formed in a hexagonal cross section. The precursor for producing a Nb ₃ Sn superconducting wire according to claim 1 or 2, wherein the plurality of Cu / Nb element wires are divided so as not to be continuously arranged in the circumferential direction. The precursor for producing a Nb ₃ Sn superconducting wire according to any one of claims 1 to 3, wherein the Cu / Sn element wire is partially arranged in a region of the divided Cu / Nb element wire. . The ratio (A: B) of the number A of the plurality of Cu / Nb element wires to the number B of the plurality of Cu / Sn element wires is 1.5: 1.0 to 3.0: 1.0. Item 5. A precursor for producing a Nb ₃ Sn superconducting wire according to any one of Items 1 to 4. An Nb or Nb-based alloy core in a Cu / Nb element wire and an Sn or Sn-based alloy in a Cu / Sn element wire by heat-treating the precursor for producing a superconducting wire according to any one of claims 1 to 5. the core is diffusion reaction, resulting Nb ₃ Sn superconducting phase region, the portion where Cu / Sn-element wire before the heat treatment had been arranged, Nb ₃ Sn superconducting wire which is characterized in that which has been divided.