JP2013206532A - PRECURSOR FOR MANUFACTURING Nb3Sn SUPERCONDUCTING WIRE ROD BY INTERNAL Sn METHOD, Nb3Sn SUPERCONDUCTING WIRE ROD, AND MANUFACTURING METHODS THEREFOR - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive precursor by suppressing disconnection in the diameter reduction working.SOLUTION: A precursor 1 (precursor for manufacturing NbSn superconducting wire rod by internal Sn method) has a stabilized copper layer 2, a diffusion barrier layer 3 arranged on the inner peripheral side of the stabilized copper layer 2, and a superconducting matrix 5 arranged on the inner peripheral side of the diffusion barrier layer 3. The superconducting matrix 5 has an Sn segment wire rod 10, and an Nb segment wire rod 20 arranged so as to surround the periphery of the Sn segment wire rod 10. The Sn segment wire rod 10 has an Sn core rod 12 arranged on the inner peripheral side of a Cu matrix 11. The Nb segment wire rod 20 has an Nb single core wire rod 30 and a Ti single core wire rod 40. The Nb single core wire rod 30 has an Nb core rod 32 on the inner peripheral side of a Cu matrix 31. The Ti single core wire rod 40 has an Nb layer 42 arranged on the inner peripheral side of a Cu matrix 41 and a Ti core rod 43 arranged on the inner peripheral side of the Nb layer 42.

Description

The present invention relates to a precursor for producing an Nb ₃ Sn superconducting wire produced by an internal Sn method, an Nb ₃ Sn superconducting wire, and methods for producing them.

Patent Document 1 describes a conventional Nb ₃ Sn superconducting wire. This superconducting wire is used as a winding of a coil of a superconducting magnet. This superconducting magnet is used in nuclear magnetic resonance (NMR) analyzers, physical property evaluation apparatuses, power storage, fusion reactors, and the like.

Conventionally, it is known that the critical current density in a high magnetic field can be increased by including Ti in the Nb ₃ Sn superconducting phase of the Nb ₃ Sn superconducting wire. In the technique described in Patent Document 1, an SnTi alloy is used as a Ti supply source ([0052] of Patent Document 1).

JP 2006-4684 A

However, the technique described in Patent Document 1 has the following problems. The SnTi alloy includes SnTi particles (compound) in Sn. This SnTi particle reduces the workability of the wire formed of the SnTi alloy. Therefore, the wire is likely to break during the diameter reduction process for producing the precursor for producing the Nb ₃ Sn superconducting wire.

  Moreover, in order to suppress this disconnection, there exists a technique which refines | miniaturizes SnTi particle | grains and disperses SnTi particle | grains in Sn. However, a SnTi alloy in which SnTi particles are refined and dispersed is difficult to manufacture and is expensive.

Accordingly, an object of the present invention is to provide a precursor for producing an internal Sn method Nb ₃ Sn superconducting wire that is inexpensive and capable of suppressing disconnection during diameter reduction processing, and a method for producing the same.

The precursor for producing the internal Sn method Nb ₃ Sn superconducting wire of the present invention includes a stabilized copper layer, a diffusion barrier layer disposed on the inner peripheral side of the stabilized copper layer, and an inner peripheral side of the diffusion barrier layer. And a superconducting matrix disposed. The superconducting matrix includes an Sn segment wire and an Nb segment wire arranged so as to surround the periphery of the Sn segment wire. The Sn segment wire includes an Sn core disposed on the inner peripheral side of the Cu matrix. The Sn core material is formed of a Sn alloy composed of a metal other than Ti and Sn, or pure Sn. The Nb segment wire includes an Nb single core wire and a Ti single core wire. The said Nb single core wire is equipped with the Nb core material arrange | positioned at the inner peripheral side of Cu matrix. The Ti single-core wire includes an Nb layer disposed on the inner peripheral side of the Cu matrix, and a Ti core disposed on the inner peripheral side of the Nb layer. The Ti core material is formed of pure Ti or NbTi alloy.
The method for producing a precursor for producing an internal Sn method Nb ₃ Sn superconducting wire according to the present invention comprises a step of preparing a Ti core formed of pure Ti or an NbTi alloy, and an Nb layer on the inner peripheral side of the Cu matrix. And arranging the Ti core material on the inner circumference side of the Nb layer to produce a Ti single core wire material, and arranging the Nb core material on the inner circumference side of the Cu matrix to produce an Nb single core wire material. A step of producing a Nb segment wire by combining the step, the Ti single core wire and the Nb single core wire, and an Sn core formed of Sn alloy (alloy made of metal other than Ti and Sn) or pure Sn A step of preparing a material, a step of producing an Sn segment wire by arranging the Sn core material on the inner peripheral side of the Cu matrix, and arranging the Nb segment wire so as to surround the periphery of the Sn segment wire A step of producing a conductive matrix, a step of arranging a diffusion barrier layer on the inner peripheral side of the stabilizing copper layer and a step of arranging the superconductive matrix on the inner peripheral side of the diffusion barrier layer to produce a composite, and the composite And a step of reducing the diameter of the body.

  It is possible to suppress disconnection during the diameter reduction processing and to reduce the cost of the precursor.

It is sectional drawing of a precursor.

With reference to FIG. 1, the precursor 1 (precursor for manufacturing an internal Sn method Nb ₃ Sn superconducting wire) according to an embodiment of the present invention, a manufacturing method thereof, and the like will be described. First, a superconducting wire (Nb ₃ Sn superconducting wire) manufactured using the precursor 1 will be described.

A superconducting wire (Nb ₃ Sn superconducting wire) is manufactured by subjecting the precursor 1 to diffusion heat treatment to form an Nb ₃ Sn-based superconducting phase (hereinafter also simply referred to as “superconducting phase”). This superconducting wire is manufactured by the dispersed Sn internal Sn method (described later). The structure of the superconducting wire at right angles to the cross section (cross section perpendicular to the axial direction, cross section viewed from the axial direction) is almost the same as the structure of the cross section perpendicular to the axis of the precursor 1 described later (hereinafter, the cross section perpendicular to the axis is simply Also called “cross section”).

Precursor 1 (precursor for producing an internal Sn method Nb ₃ Sn superconducting wire) is a precursor at a stage before performing diffusion heat treatment (Nb ₃ Sn generation heat treatment). The precursor 1 is a precursor at a stage after the diameter reduction processing of a “composite” described later. The cross section of the precursor 1 is, for example, circular (or rectangular). The precursor 1 includes a stabilized copper layer 2, a diffusion barrier layer 3, and a superconducting matrix 5 in order from the outer peripheral side (radially outer side).

  The stabilized copper layer 2 is a layer for preventing an overcurrent from flowing through the superconducting phase and burning the superconducting phase when the superconducting wire is changed from the superconducting state to the normal conducting state. The stabilized copper layer 2 is disposed on the outermost peripheral side of the precursor 1.

  The diffusion barrier layer 3 is a layer that suppresses the diffusion of Sn in the superconducting matrix 5 to the outer peripheral side (stabilized copper layer 2 side) during the diffusion heat treatment. The diffusion barrier layer 3 is disposed on the inner peripheral side (radially inner side) of the stabilizing copper layer 2 and is disposed on the outer peripheral side of the superconducting matrix 5. The diffusion barrier layer 3 includes at least one of an Nb layer and a Ta layer. The innermost layer (the portion in contact with the superconducting matrix 5) of the diffusion barrier layer 3 is preferably a Ta layer. The reason is that when the innermost layer of the diffusion barrier layer 3 is not a Ta layer but an Nb layer, the Nb layer of the diffusion barrier layer 3 reacts with Sn in the superconducting matrix 5 during the diffusion heat treatment. This is because a superconducting phase is formed in the vicinity of the barrier layer 3, the effective filament diameter of the superconducting wire is increased, and the AC loss may be increased.

The superconducting matrix 5 is a part where a superconducting phase is formed after diffusion heat treatment (after Nb ₃ Sn generation heat treatment). Superconducting matrix 5 is arranged at the center of the cross section of precursor 1. The superconducting matrix 5 includes a plurality of Sn segment wires 10 and a plurality of Nb segment wires 20. The superconducting matrix 5 may include a wire other than the Sn segment wire 10 and the Nb segment wire 20, for example, a reinforcing wire (not shown). In the superconducting matrix 5, the Nb segment wire 20 is arranged so as to surround the Sn segment wire 10 (except for the outer peripheral end of the superconducting matrix 5). Preferably, the Nb segment wire 20 is disposed so as to surround the entire periphery of the Sn segment wire 10. Specifically, for example, six Nb segment wires 20 having a hexagonal cross section are arranged so as to surround the entire periphery of one Sn segment wire 10 having a hexagonal cross section.

The Sn segment wire 10 is a supply source of the Sn component of the Nb ₃ Sn superconducting wire. The Sn segment wire 10 has a hexagonal (regular hexagonal) cross section, for example (the same applies to the Nb segment wire 20, the Nb single core wire 30, and the Ti single core wire 40).

The Sn segment wire 10 includes a Cu matrix 11 and a Sn core material disposed on the inner peripheral side of the Cu matrix 11. Then, the Sn component and the Cu component in the superconducting matrix 5 are arranged separately until a bronzing heat treatment (described later) is performed. That is, the superconducting wire is manufactured by the internal Sn method. Therefore, the critical current density (Jc) of the superconducting wire manufactured by the precursor 1 can be made larger than that of the superconducting wire manufactured by the bronze method.
The bronze method is a method for manufacturing a superconducting wire using a precursor including bronze (Cu—Sn alloy). There is a limit (about 16% by weight) in the Sn concentration in the bronze. If the Sn concentration is insufficient, the reaction between Nb and Sn is insufficient, the superconducting phase is not sufficiently formed, and the critical current density may not be sufficiently high. On the other hand, in the internal Sn method, the Sn concentration has no limit as described above. Therefore, the superconducting phase can be sufficiently formed, and as a result, the critical current density of the superconducting wire can be increased.

  Further, the plurality of Sn segment wire rods 10 are dispersed in the superconducting matrix 5 (the Sn segment wire rods 10 are not adjacent to each other). That is, the superconducting wire is manufactured by the distributed Sn method (DT method, Distributed Tin method). Since the Sn segment wire 10 is dispersedly arranged, the Sn component in the superconducting matrix 5 is dispersed, the reaction between Sn and Nb occurs uniformly, and the superconducting phase is uniformly formed.

  The Cu matrix 11 is a member in which the Sn core material 12 is disposed on the inner peripheral side. The cross section of the Cu matrix 11 is formed, for example, such that the outer periphery is a hexagon (regular hexagon) and the inner periphery is a circle. The Cu matrix 11 facilitates the diameter reduction processing of the Sn segment wire 10. This is because Cu forming the Cu matrix 11 is excellent in lubricity with a diameter reducing tool (for example, a wire drawing die) and can prevent seizure or the like (this effect and the above-mentioned cross section). The same applies to the Cu matrices 31 and 41).

  The Sn core material 12 is made of Sn alloy or pure Sn. This “pure Sn” may contain less than 0.5% by weight of impurities (other than Ti). This “Sn alloy” is an alloy composed of a metal (additive element) other than Ti and Sn. This Sn alloy contains, for example, about 0.5 wt% to 10 wt% of additive elements such as Ta, Zr, and Hf. The upper limit of the ratio of the additive element in the Sn alloy is set to a value that does not hinder the workability of the Sn segment wire 10 (precursor 1). Further, the Sn core material 12 is disposed at the center of the cross section of the Sn segment wire 10. The Sn core material 12 has, for example, a circular cross section (the same applies to the cross-sectional shapes of the Nb core material 32 and the Ti core material 43).

  The Nb segment wire 20 is a combination of the Nb single core wire 30 and the Ti single core wire 40. The Nb segment wire 20 includes, for example, 36 Nb single-core wires 30 arranged, and, for example, a Ti single-core wire 40 arranged in the center. In addition, the Nb segment wire 20 shown in FIG. 1 is a state in which the Cu matrices 31 and 41 are integrated by a diameter reduction process.

The Nb single core wire 30 is a Nb supply source of Nb ₃ Sn superconducting wire. The plurality of Nb single core wires 30 are arranged in a dispersed manner in the Nb segment wire 20. The Nb single core wire 30 includes a Cu matrix 31 and an Nb core material 32 disposed on the inner peripheral side of the Cu matrix 31.

  The Nb core material 32 is formed of pure Nb or Nb alloy. This “pure Nb” may contain a trace amount (for example, less than 0.5% by weight) of impurities. This “Nb alloy” is an alloy containing about 0.5 wt% to 10 wt% of additive elements (for example, Ta, Hf, Zr, Ti, etc.). The Nb core material 32 is disposed at the center of the cross section of the Nb single core wire 30.

The Ti single core wire 40 is a supply source of Ti component to the Nb ₃ Sn superconducting phase. The Ti single core wire 40 includes a Cu matrix 41, an Nb layer 42, and a Ti core material 43 in order from the outer peripheral side.

  The Nb layer 42 is formed of an Nb alloy not containing Ti or pure Nb. The Nb layer 42 is a layer disposed on the inner peripheral side of the Cu matrix 41. The Nb layer 42 is a layer disposed on the outer peripheral side of the Ti core material 43. The Nb layer 42 is a Ti diffusion barrier layer that prevents the Ti component from diffusing from the Ti core material 43 to the outer peripheral side during the diameter reduction processing (particularly during annealing performed during the diameter reduction processing). . When the Nb layer 42 is sufficiently thinned by processing, the Ti component can be diffused from the Ti core material 43 to the outer peripheral side by a long-time heat treatment (details will be described later). The thickness of the Nb layer 42 is appropriately set according to the temperature and time of the heat treatment so that the above function can be realized. Specifically, the thickness of the Nb layer 42 is desirably set to 0.1 to 2.0% of the diameter of the Ti core material 43.

  The Ti core material 43 is formed of pure Ti or NbTi alloy. This pure Ti may contain less than 0.5% by weight of impurities. The Nb component in the NbTi alloy is, for example, about 0.5 to 60% by weight. This NbTi alloy may contain additional elements other than Nb and Ti. The Ti core material 43 is disposed at the center of the cross section of the Ti single core wire 40.

  Next, the amount and arrangement of the Ti single core wire 40 will be described. The amount of the Ti single core wire 40 is adjusted so that the ratio of the Ti component to the Nb component in the superconducting matrix 5 is 0.1 to 5.0% by weight. The Ti single core wire 40 is uniformly arranged in the Nb segment wire 20. For example, as described above, one Ti single core wire 40 is disposed at the center of the cross section of the Nb segment wire 20. Further, for example, a plurality of Ti single core wires 40 may be dispersed (at least not adjacent to each other) in the Nb segment wire 20. For example, the number of Ti single core wires 40 may be increased as the Ti core material 43 is thinner. Further, for example, the Ti single core wire 40 may be increased as the Ti component in the Ti core material 43 formed of the NbTi alloy decreases.

(Manufacturing method)
Next, the manufacturing method of the precursor 1 and a superconducting wire is demonstrated. This manufacturing method includes a step of producing an Nb segment wire 20, a step of producing an Sn segment wire 10, a step of producing a composite (precursor 1 before diameter reduction processing) and reducing the diameter, and a precursor 1. And a step of producing a superconducting wire by heat treatment. In addition, below, the member name in the stage of the precursor 1 may be described in parentheses.

  (Preparation of Nb segment wire 20) The manufacturing method of the Nb segment wire 20 includes the steps of manufacturing the Ti single core wire 40, the step of manufacturing the Nb single core wire 30, the Ti single core wire 40 and the Nb single core wire 30. And a step of combining the two.

  The Ti single core wire 40 is manufactured as shown in the following (a) to (g). (A) A Ti billet (Ti core material 43) formed of pure Ti or an NbTi alloy is prepared. (B) An Nb sheet (Nb layer 42) is disposed on the inner peripheral side of the Cu pipe (Cu billet) (Cu matrix 41). (C) A Ti billet (Ti core material 43) is disposed on the inner peripheral side of the Nb sheet (Nb layer 42). In addition, the order of each process can be changed variously. For example, an Nb sheet (Nb layer 42) wound around a Ti billet (Ti core material 43) may be inserted into the inner peripheral side of the Cu tube (Cu matrix 41). The same applies to the subsequent steps in that the order of each step can be changed in various ways. (D) Both ends in the axial direction of the billet (Ti single core wire 40) produced in the above (a) to (c) are welded in a vacuum state. (E) The billet welded in (d) above is hot extruded. (F) The extruded material extruded in (e) above is reduced in diameter to have a hexagonal cross-sectional shape. In addition, you may anneal in the middle of a multiple diameter reduction process. (G) Cut into a predetermined length (fixed length) after correcting the dimensions and shape. Thereby, the Ti single core wire 40 is produced.

  The Nb single core wire 30 is produced as shown in the following (h) and (i). (H) An Nb billet (Nb core material 32) is disposed (inserted) on the inner peripheral side of the Cu tube (Cu matrix 31). (I) The diameter reduction process etc. are carried out similarly to said (d)-(g). Thereby, the Nb single core wire 30 is produced.

  The Nb segment wire 20 is produced as in the following (j) to (l). (J) A combination of the Ti single core wire 40 and the Nb single core wire 30 is inserted into the Cu tube. (K) The amount of the Ti single core wire 40 in (j) is adjusted so that the ratio of the Ti component to the Nb component in the superconducting matrix 5 is 0.1 to 5.0% by weight. (L) A diameter reduction process or the like is performed in the same manner as in the above (d) to (g). Thereby, the Nb segment wire 20 is produced.

  (Production of Sn segment wire 10) The Sn segment wire 10 is produced as the following (m) to (o). (M) An Sn rod (Sn core material 12) made of Sn alloy or pure Sn is prepared. (N) An Sn rod (Sn core material 12) is disposed on the inner peripheral side of the Cu tube (Cu matrix 11). (O) The rod produced in (n) is subjected to diameter reduction processing by cold drawing or the like. Thereby, the Sn segment wire 10 is manufactured.

  (Production of composite and reduction in diameter) The method for producing the composite (precursor 1 before diameter reduction) includes a step of producing superconducting matrix 5 and a step of combining superconducting matrix 5 with another member.

  The superconducting matrix 5 is manufactured as in the following (p) and (q). (P) The superconducting matrix 5 is produced by combining the Sn segment wire 10 and the Nb segment wire 20. (Q) In the case of (p) above, the Nb segment wire 20 is arranged so as to surround the periphery of the Sn segment wire 10.

  The composite (precursor 1 before diameter reduction processing) is produced as in the following (r) to (t). (R) On the inner peripheral side of the Cu tube (stabilized copper layer 2), for example, a layer (diffusion barrier layer 3) in which an Nb sheet is overlaid is disposed (attached). (S) Superconducting matrix 5 is arranged on the inner peripheral side of the Nb sheet (diffusion barrier layer 3). Thereby, a composite is produced. (T) The composite is subjected to diameter reduction processing by cold drawing or the like. Thereby, the precursor 1 is manufactured.

(Heat Treatment) A superconducting wire is manufactured by subjecting the precursor 1 to a diffusion heat treatment. The diffusion heat treatment includes (u) bronzing heat treatment and (v) Nb ₃ Sn generation heat treatment.

  The bronzing heat treatment (u) is performed as follows. For example, the precursor 1 is heated at a temperature of 200 ° C. to 600 ° C. for several tens of hours or several hundred hours. As a result, the Sn component of the Sn core material 12 is diffused into the Cu matrices 31 and 41 of the Nb segment wire rod 20, and bronze (Cu—Sn alloy) is generated.

The Nb ₃ Sn generation heat treatment (v) is performed as follows. The precursor 1 that has undergone the bronzing heat treatment (u) is heated, for example, at a temperature of 600 ° C. to 800 ° C. for tens of hours or hundreds of hours. As a result, an Nb ₃ Sn superconducting phase is formed at the boundary between the bronze generated in (u) and the Nb single-core wire 30.

During these heat treatments (u) and (v), the Ti component of the Ti core material 43 is uniformly diffused into the surrounding Nb ₃ Sn superconducting phase. Thereby, the Nb ₃ Sn superconducting wire of the present invention is manufactured. The reason why the Ti component can diffuse as described above is that the Nb layer 42 is sufficiently thinned by the diameter reduction processing (the above (e), (f), (l), and (t)), and the heat treatment (the above (u) and This is because (v)) is a long time. On the other hand, in the processing stage of the precursor 1, the annealing time is short (it can be annealed during the above (f) and (l)), and the Nb layer 42 is not sufficiently thin, so Ti is as described above. Difficult to diffuse.

(Experiment)
Superconducting wires of Examples of the present invention, Comparative Example 1 and Comparative Example 2 were produced. And about each superconducting wire, the critical current density and the frequency | count of disconnection were measured.

The superconducting wire of Example was produced by the manufacturing method provided with the process of said (a)-(v).
(Ti single core wire 40) The Cu pipe (Cu matrix 41) used in the step (b) has an outer diameter of 140 mmφ and an inner diameter of 110 mmφ. The Nb sheet (Nb layer 42) used in the same process has a thickness of 0.2 mm. The Ti billet (Ti core material 43) used in the step (c) is made of an Nb-47 wt% Ti alloy (Ti is 47 wt%) and has an outer diameter of 109 mmφ. The opposite side length (shortest distance between two parallel sides of a regular hexagonal cross section) of the Ti single core wire 40 produced in the steps (a) to (g) is 4.3 mm.
(Nb single core wire 30) The Cu pipe (Cu matrix 31) used in the step (h) has an outer diameter of 68 mmφ and an inner diameter of 61 mmφ. The Nb billet (Nb core material 32) used in the same process has an outer diameter of 60.8 mmφ. The opposite side length of the Nb single core wire 30 produced in the steps (h) and (i) is 4.3 mm.
(Nb segment wire 20) The Cu pipe used in the step (j) has an outer diameter of 34 mmφ and an inner diameter of 30 mmφ. One Nb segment wire 20 produced in the steps (j) to (l) includes one Ti single core wire 40 and 36 Nb single core wires 30 as shown in FIG. It is. The opposite side length of this Nb segment wire 20 is 1.7 mm.
(Sn segment wire 10) The Cu pipe (Cu matrix 11) used in the step (n) has an outer diameter of 24 mmφ and an inner diameter of 21 mmφ. The Sn rod (Sn core material 12) used in the step (m) is made of pure Sn and has an outer diameter of 20.6 mmφ. The opposite side length of the Sn segment wire 10 produced in the steps (m) to (o) is 1.7 mm.
(Composite) In the steps (p) and (q), the entire periphery of one Sn segment wire 10 is arranged so as to surround the six Nb segment wires 20. Moreover, the superconducting matrix 5 was produced by combining 138 Nb segment wires 20 and 73 Sn segment wires 10. The Cu pipe (stabilized copper layer 2) used in the step (r) has an outer diameter of 34 mmφ and an inner diameter of 30 mmφ. The Nb sheet (diffusion barrier layer 3) used in the same process is a roll of 0.2 mm thickness. The precursor 1 produced in the steps (a) to (s) has a diameter of 1.0 mmφ.
(Heat treatment) The bronzing heat treatment (u) was performed at 210 ° C. for 50 hours and at 350 ° C. for 100 hours. The Nb ₃ Sn generation heat treatment (v) was performed at 670 ° C. for 100 hours.
In the superconducting wire of the example, the ratio of the Ti component to the Nb component in the superconducting matrix 5 was 1.1% by weight. This ratio was unified between the example and the comparative example 1.

The superconducting wire of Comparative Example 1 is different from the superconducting wire of the example in the following points and is identical in other points.
The superconducting wire precursor (1) of Comparative Example 1 does not include the Ti single core wire 40. That is, the precursor (1) of the superconducting wire of Comparative Example 1 is obtained by replacing the Ti single core wire 40 of the example with the Nb single core wire 30.
Moreover, although Sn core material 12 of an Example was formed with pure Sn, Sn core material (12) of the comparative example 1 was formed with Sn-2 wt% Ti alloy.

  The superconducting wire of Comparative Example 2 is produced by the bronze method.

  The critical current density was determined as follows. The critical current of each superconducting wire was measured by the four-terminal method in liquid helium (temperature 4.2 K) under an external magnetic field of 16 T (Tesla). The critical current density was calculated by dividing the measured critical current by the area of the non-Cu portion.

  The number of disconnections was measured as follows. The number of disconnections at the time of diameter reduction when manufacturing the precursor 1 having a length of 5000 m was measured. Also, the number of breaks during diameter reduction of each wire constituting the precursor 1, such as the Sn segment wire 10 and the Nb segment wire 20, and the number of breaks during diameter reduction of the composite (precursor 1 before heat treatment), The total number of times was measured. In addition, since the structure of the precursor 1 is greatly different between the example (and comparative example 1) manufactured by the internal Sn method and the comparative example 2 manufactured by the bronze method, the number of disconnections between the example and the comparative example 2 is compared. Is omitted.

(result)
The experimental results are shown in Table 1. The “Jc characteristic” in the table is the critical current density.

The critical current density was almost equal between the example and the comparative example 1. This is because the ratio of the Ti component to the Nb component in the superconducting matrix 5 is unified in the example and the comparative example 1.
Further, the critical current density in the example was larger than that in the comparative example 2. This is because the Sn concentration in the superconducting matrix 5 is higher in the example (internal Sn method) than in the comparative example 2 (bronze method), and as a result, the superconducting phase can be sufficiently formed.

  The number of disconnections was smaller in Example than in Comparative Example 1. The reason is as follows. In the precursor (1) of Comparative Example 1, the Sn core material (12) was formed of a SnTi alloy, and this SnTi alloy deteriorated the workability of the diameter reduction processing. On the other hand, in the precursor 1 of an Example, Sn core material 12 does not contain a SnTi alloy. Further, in the precursor 1 of the example (before the heat treatment), the diffusion of Ti from the Ti single core wire 40 is hindered by the Nb layer 42, so that no SnTi alloy is generated. Therefore, disconnection was able to be suppressed more in the Example than in Comparative Example 1.

(Effect 1)
Next, effects of the precursor 1 and the like of the present invention will be described. Precursor 1 (precursor for producing internal Sn method Nb ₃ Sn superconducting wire) includes stabilized copper layer 2, diffusion barrier layer 3 disposed on the inner peripheral side of stabilized copper layer 2, and diffusion barrier layer 3. And a superconducting matrix 5 disposed on the inner peripheral side. Superconducting matrix 5 includes Sn segment wire 10 and Nb segment wire 20 arranged so as to surround the periphery of Sn segment wire 10. The Sn segment wire 10 includes an Sn core material 12 disposed on the inner peripheral side of the Cu matrix 11. The Sn core material 12 is formed of a Sn alloy composed of a metal other than Ti and Sn, or pure Sn. The Nb segment wire 20 includes an Nb single core wire 30 and a Ti single core wire 40. The Nb single core wire 30 includes an Nb core material 32 disposed on the inner peripheral side of the Cu matrix 31. The Ti single core wire 40 includes an Nb layer 42 disposed on the inner peripheral side of the Cu matrix 41, and a Ti core member 43 disposed on the inner peripheral side of the Nb layer 42. The Ti core material 43 is formed of pure Ti or NbTi alloy.

(Effect 1-1)
The Nb segment wire 20 includes an Nb layer 42 and a Ti core 43 disposed on the inner peripheral side of the Nb layer 42. Therefore, the Ti component of the Ti core material 43 is prevented from diffusing to the outer peripheral side of the Nb layer 42 during the diameter reduction process for manufacturing the precursor 1 (particularly during annealing during the diameter reduction process). . Therefore, it can suppress that this Ti component and the Sn component in the superconducting matrix 5 form the SnTi alloy which causes a disconnection. Therefore, it can suppress that a wire (The precursor 1 before diameter reduction processing, and the Sn segment wire 10) breaks at the time of diameter reduction processing for manufacturing the precursor 1. FIG.
In addition, if the precursor 1 is subjected to heat treatment for a long time in a state where the Nb layer 42 is sufficiently thin by the diameter reduction processing, the Ti component of the Ti core material 43 is diffused to the surroundings. As a result, this Ti component is diffused in the Nb3sn superconducting phase. Therefore, the superconducting characteristics (critical current density in a high magnetic field) can be improved.

(Effect 1-2)
The Ti core material 43 is formed of pure Ti or NbTi alloy. Since pure Ti and NbTi alloy have better workability than SnTi alloy, it is possible to suppress disconnection of the wire during diameter reduction processing for manufacturing the precursor 1. In addition, since pure Ti and NbTi alloys are easier to obtain and cheaper than SnTi alloys in which SnTi particles are miniaturized (alloys that improve workability as described above), the precursor 1 can be manufactured at a low cost.

(Effects 2 and 5)
The amount of the Ti single core wire 40 is adjusted so that the ratio of the Ti component to the Nb component in the superconducting matrix 5 is 0.1 to 5.0% by weight. Since the said ratio is 0.1 weight% or more, a critical current density can be made high enough. Since the said ratio is 5.0 weight% or less, the deterioration of workability (workability of diameter reduction process) by having too many Ti components can be suppressed.

(Effects 3 and 6)
The Nb ₃ Sn superconducting wire of the present invention is obtained by subjecting the precursor 1 to diffusion heat treatment to form an Nb ₃ Sn-based superconducting phase (the method for producing the Nb ₃ Sn superconducting wire of the present invention is a precursor). 1 is subjected to diffusion heat treatment to form a Nb ₃ Sn-based superconducting phase). This superconducting wire has the above effects.

(Effect 4)
The manufacturing method of the precursor 1 (precursor for manufacturing an internal Sn method Nb ₃ Sn superconducting wire) includes a step of preparing a Ti core 43 formed of pure Ti or an NbTi alloy, and Nb on the inner peripheral side of the Cu matrix 41. And a step of arranging the Ti core material 43 on the inner peripheral side of the Nb layer 42 and producing the Ti single core wire 40 while arranging the layer 42. Further, this manufacturing method combines Nb core material 32 by arranging Nb core material 32 on the inner peripheral side of Cu matrix 31, and Ti single core wire 40 and Nb single core wire 30 in combination. A step of producing the segment wire 20. Furthermore, this manufacturing method includes the steps of preparing an Sn core material 12 formed of Sn alloy (an alloy made of metal other than Ti and Sn) or pure Sn, and an Sn core material 12 on the inner peripheral side of the Cu matrix 11. And manufacturing the Sn segment wire rod 10. Further, in this manufacturing method, the Nb segment wire 20 is disposed so as to surround the Sn segment wire 10 and the superconducting matrix 5 is produced, and the diffusion barrier layer 3 is disposed on the inner peripheral side of the stabilized copper layer 2. And a step of producing a composite (precursor 1 before diameter reduction processing) by disposing the superconducting matrix 5 on the inner peripheral side of the diffusion barrier layer 3 and a step of diameter reduction processing of the composite.
With this configuration, the same effect as the above (Effect 1) can be obtained.

(Modification)
The precursor 1 and the like may be modified as follows. For example, in the above embodiment, the precursor 1 has a circular cross section. However, the cross section of the precursor 1 may be, for example, an ellipse or a rectangle (including a rectangle having four rounded corners). When the cross section of the precursor 1 is rectangular, when a coil is formed using the superconducting wire manufactured using the precursor 1 as a winding, the dead space between the superconducting wires can be reduced.

1 Precursor (Internal Sn Method Nb ₃ Sn Precursor for Superconducting Wire Production)
2 Stabilized copper layer 3 Diffusion barrier layer 5 Superconducting matrix 10 Sn segment wire 11 Cu matrix 12 Sn core material 20 Nb segment wire 30 Nb single core wire 31 Cu matrix 32 Nb core material 40 Ti single core wire 41 Cu matrix 42 Nb layer 43 Ti core material

Claims (6)

A stabilized copper layer;
A diffusion barrier layer disposed on the inner peripheral side of the stabilizing copper layer;
A superconducting matrix disposed on the inner peripheral side of the diffusion barrier layer,
The superconducting matrix is
Sn segment wire,
Nb segment wire disposed so as to surround the periphery of the Sn segment wire,
The Sn segment wire includes an Sn core disposed on the inner peripheral side of the Cu matrix,
The Sn core material is formed of a Sn alloy composed of a metal other than Ti and Sn, or pure Sn,
The Nb segment wire comprises an Nb single core wire and a Ti single core wire,
The Nb single-core wire includes an Nb core material disposed on the inner peripheral side of the Cu matrix,
The Ti single core wire is
An Nb layer disposed on the inner peripheral side of the Cu matrix;
Ti core material disposed on the inner peripheral side of the Nb layer,
The Ti core material is formed of pure Ti or an NbTi alloy.
Precursor for producing internal Sn method Nb ₃ Sn superconducting wire. 2. The internal Sn method Nb ₃ according to claim 1, wherein the amount of the Ti single-core wire is adjusted such that the ratio of the Ti component to the Nb component in the superconducting matrix is 0.1 to 5.0 wt%. Precursor for producing Sn superconducting wire. Respect precursor of claim 1 or 2, to form the _Nb 3 Sn based superconducting phase is subjected to diffusion heat treatment, _Nb 3 Sn superconducting wire. Preparing a Ti core formed of pure Ti or NbTi alloy;
A step of arranging a Nb layer on the inner peripheral side of the Cu matrix and arranging the Ti core material on the inner peripheral side of the Nb layer to produce a Ti single core wire;
A step of arranging an Nb core material on the inner peripheral side of the Cu matrix to produce an Nb single core wire;
A step of producing an Nb segment wire by combining the Ti single core wire and the Nb single core wire;
A step of preparing a Sn alloy composed of a metal other than Ti and Sn, or a Sn core formed of pure Sn;
Arranging the Sn core material on the inner peripheral side of the Cu matrix to produce a Sn segment wire;
Arranging the Nb segment wire so as to surround the Sn segment wire and producing a superconducting matrix;
A step of disposing a diffusion barrier layer on the inner peripheral side of the stabilized copper layer and disposing the superconducting matrix on the inner peripheral side of the diffusion barrier layer to produce a composite;
Reducing the diameter of the composite;
A method for producing a precursor for producing an internal Sn method Nb ₃ Sn superconducting wire. 5. The internal Sn method Nb ₃ according to claim 4, wherein the amount of the Ti single-core wire is adjusted such that the ratio of the Ti component to the Nb component in the superconducting matrix is 0.1 to 5.0% by weight. The manufacturing method of the precursor for Sn superconducting wire manufacturing. Against progenitors produced by the method according to claim 4 or 5, comprising forming the Nb 3 _Sn based superconducting phase is subjected to diffusion heat treatment, Nb 3 _Sn method of manufacturing a superconducting wire.