Nb3Sn SUPERCONDUCTING WIRE PRECURSOR, AND Nb3Sn SUPERCONDUCTING WIRE

Abstract

This Nb3Sn superconducting wire precursor comprises a cylindrical stabilized copper layer, a cylindrical first Sn diffusion barrier layer provided inside the copper layer, and a superconducting element group precursor housed inside the barrier layer. The superconducting element group precursor includes a plurality of Sn-based reinforced element wires and a plurality of Nb-based superconducting element wire precursors. The reinforced element wires include a Cu or Cu-based alloy first stabilization matrix, a plurality of Sn-based filaments that are Sn or Sn-based alloys and that are embedded in the first stabilization matrix, and a plurality of reinforcement-material multi-core wires that are configured from a plurality of metal or alloy-made reinforcement filaments. The wire precursors comprise a second stabilization matrix of Cu or a Cu-based alloy, and an Nb-based superconducting filament precursor that is Nb or an Nb-based alloy and that is embedded in the second stabilization matrix.

Description

Precursor for Nb3Sn superconducting wire and Nb3Sn superconducting wire

[0001] The present disclosure relates to Nb ３ Sn superconducting wire precursor and Nb ３ This relates to Sn superconducting wire.

[0002] Conventionally widely used Nb ３ The manufacturing method of Sn superconducting wire is to heat treat a wire having a structure in which a plurality of Nb filaments are embedded in a Cu-Sn-based alloy (bronze) matrix, and to diffuse the Sn in the bronze matrix into the Nb filaments, thereby forming the Nb superconducting phase. ３ There is a bronze process that produces Sn.

[0003] However, in the bronze process, there is an upper limit (solubility limit) to the Sn concentration that can be dissolved in bronze, so the Nb that can be produced ３ There is a limit to the area of ​​Sn, and as a result, there is a limit to the improvement of the critical current density Jc of the superconducting wire.

[0004] In addition, Nb ３ In addition to the bronze method, there is also a method called the internal tin method (internal diffusion method) for manufacturing Sn superconducting wires. In the internal tin method, a wire having a structure in which Nb-based alloy filaments and Sn-based alloy filaments are embedded in a Cu-based alloy matrix is ​​heat-treated, so that Sn in the Sn-based alloy filaments is diffused into the Nb-based alloy filaments, and Nb is formed at the interface between the Nb-based alloy filaments and the Cu-based alloy matrix. ３ Sn is produced.

[0005] The internal tin method is not affected by the solid solubility limit of Sn in Cu-Sn-based alloys, which is a problem in the bronze method. ３ The area where Sn is generated can be increased, and a high critical current density Jc can be obtained. In addition, the internal tin method can increase the Sn concentration compared to the bronze method, so high-quality Nb ３ Sn can be produced.

[0006] Nb produced by the internal tin method ３ The Sn superconducting wire is often used not as a single wire but as a stranded wire in which a plurality of wires are twisted together.

[0007] As mentioned above, in the internal tin method, the amount of Sn is increased to ３ Increasing the area where Sn is generated improves the critical current density Jc. Therefore, in order to maximize the amount of Sn in the wire, it is necessary to minimize the amount of Cu around the Sn-based alloy filaments.

[0008] For example, Patent Document 1 describes a method for suppressing deterioration of wire drawing processability due to an increase in the Sn content, in which a precursor for superconducting wire has an Nb element in which Nb is embedded in a Cu matrix and an Sn element in which Sn filaments are embedded in Cu, and multiple Sn filaments are arranged in the Sn element.

[0009] However, in the precursor for superconducting wire described in Patent Document 1, Sn filaments with low strength are arranged in a group in the Sn element, which causes a large difference in strength between the Sn element and the Nb element, resulting in a problem that the arrangement of the elements becomes disordered during twisting. When the arrangement of the elements becomes disordered, the distance between the Sn element and the Nb element becomes uneven, and the Nb element for diffusing Sn throughout the wire becomes insufficient. ３ It becomes necessary to extend the Sn generation heat treatment time. ３ The crystal grains of Sn become coarse, and the critical current density Jc decreases.

[0010] In addition, Nb ３ Sn wire with Nb ３ When the Sn-producing heat treatment is performed, Sn diffuses, causing cavities to form in the areas that were previously Sn filaments. In the precursor for superconducting wire described in Patent Document 1, aggregates of cavities are formed within the Sn elements. This causes problems such as a decrease in the strength of the wire and an accelerated decrease in the critical current density (Jc) due to electromagnetic stress.

[0011] JP 2014-32930 A

[0012] The object of the present disclosure is to provide a method for producing a superconducting wire rod having good strength and capable of maintaining a high critical current density Jc even after being subjected to a twisting process. ３ Sn superconducting wire precursor and Nb ３The object of the present invention is to provide a Sn superconducting wire.

[0013] [1] A superconducting element group precursor comprising: a cylindrical stabilizing copper layer provided on an outer periphery; a cylindrical first Sn diffusion barrier layer provided inside the stabilizing copper layer; and a superconducting element group precursor housed inside the first Sn diffusion barrier layer, wherein the superconducting element group precursor comprises a plurality of Sn-based strengthened element wires and a plurality of Nb-based superconducting element wire precursors, wherein the plurality of Sn-based strengthened element wires comprise: a first stabilizing matrix made of Cu or a Cu-based alloy; a plurality of Sn-based filaments embedded in the first stabilizing matrix and made of Sn or a Sn-based alloy; and a plurality of reinforced multifilamentary wires embedded in the first stabilizing matrix and made of a plurality of reinforced filaments made of a metal or an alloy, and the plurality of Nb-based superconducting element wire precursors comprise: a second stabilizing matrix made of Cu or a Cu-based alloy; and one or more Nb-based superconducting filament precursors embedded in the second stabilizing matrix and made of Nb or a Nb-based alloy. ３ Precursor for Sn superconducting wire. [2] The Nb ３ In a cross section perpendicular to the axial direction of the precursor for a Sn superconducting wire, in each of the plurality of Sn-based reinforcement element wires, a reinforcement multi-filamentary wire assembly in which the plurality of reinforcement multi-filamentary wires are assembled is arranged in the center, and a Sn-based filament assembly in which the plurality of Sn-based filaments are assembled is arranged on the periphery. ３ [3] The Sn-based reinforcing element wire is a precursor for a Sn superconducting wire. ３ The Nb superconducting wire precursor according to the above [1] or [2] further comprises a second Sn diffusion barrier layer, which is provided between the reinforcing material multifilamentary wire assembly and the Sn-based filament assembly in a cross section perpendicular to the axial direction of the Sn superconducting wire precursor and is made of Ta or Nb metal or an alloy containing at least one of Ta and Nb. ３ [4] The Nb superconducting wire precursor according to any one of [1] to [3] above, wherein the reinforcing filament is made of a metal selected from Nb, Ta, Ti, V, W, Mo, Fe, and Hf, or an alloy containing at least one element selected from Nb, Ta, Ti, V, W, Mo, Fe, and Hf.３ [5] A precursor for a Sn superconducting wire, comprising: a cylindrical stabilizing copper layer provided on an outer periphery; a cylindrical first Sn diffusion barrier layer provided inside the stabilizing copper layer; and a superconducting element group housed inside the first Sn diffusion barrier layer, wherein the superconducting element group comprises a plurality of strengthening element wires and a plurality of Nb-based superconducting element wires, the plurality of strengthening element wires comprising a first stabilizing matrix made of Cu or a Cu-based alloy and a plurality of strengthening multifilamentary wires embedded in the first stabilizing matrix and composed of a plurality of strengthening filaments made of a metal or an alloy, and the plurality of Nb-based superconducting element wires comprising a second stabilizing matrix made of Cu or a Cu-based alloy and a plurality of Nb-based superconducting element wires embedded in the second stabilizing matrix. ３ and a single or multiple superconducting filaments having a compound superconducting phase made of Sn, ３ Sn superconducting wire.

[0014] According to the present disclosure, there is provided a method for producing a superconducting wire rod having good strength and capable of maintaining a high critical current density Jc even after being subjected to a twisting process, comprising the steps of: ３ Sn superconducting wire precursor and Nb ３ It is possible to provide a Sn superconducting wire.

[0015] FIG. 1 shows the Nb ３ 2 is a cross-sectional view showing an example of a precursor for a Sn superconducting wire. ３ Nb superconducting wire precursor obtained by heating ３ 3 is a cross-sectional view showing an example of a Sn superconducting wire rod according to the first embodiment; ３ 4 is a cross-sectional view showing another example of an Nb-based superconducting element wire precursor constituting a precursor for an Sn superconducting wire. ３ Nb superconducting wire precursor obtained by heating ３ 5 is a cross-sectional view showing an example of a Sn superconducting wire rod. ３ 6 is a cross-sectional view showing another example of an Nb-based superconducting element wire precursor constituting a precursor for an Sn superconducting wire. ３ Nb superconducting wire precursor obtained by heating ３7 is a cross-sectional view showing an example of a Sn superconducting wire rod. ３ 8 is a cross-sectional view showing another example of an Nb-based superconducting element wire precursor constituting a precursor for an Sn superconducting wire. ３ Nb superconducting wire precursor obtained by heating ３ 9 is a cross-sectional view showing an example of a Sn superconducting wire rod. ３ 10 is a cross-sectional view showing an example of a precursor for a Sn superconducting wire. ３ Nb superconducting wire precursor obtained by heating ３ 11 is a cross-sectional view showing an example of a Sn superconducting wire rod. ３ 12 is a cross-sectional view showing an example of a precursor for a Sn superconducting wire. ３ Nb superconducting wire precursor obtained by heating ３ FIG. 2 is a cross-sectional view showing an example of an Sn superconducting wire.

[0016] Hereinafter, a detailed description will be given based on an embodiment.

[0017] The present inventors have found that Nb ３ Sn superconducting wire precursor and Nb ３ As a result of extensive research into Sn superconducting wire, it was discovered that the strength of Sn-based reinforced element wire is improved by providing a reinforced multi-core wire consisting of multiple reinforcing filaments, thereby reducing the difference in strength between the Sn-based reinforced element wire and the Nb-based superconducting element wire precursor or the Nb-based superconducting element wire. This prevents the Sn-based reinforced element wire from deforming significantly during twisting, which would cause the arrangement of the elements to become distorted, and therefore a high critical current density Jc can be maintained even after twisting. This discovery led to the completion of the present disclosure.

[0018] Nb in the embodiment ３The Sn superconducting wire precursor includes a cylindrical stabilizing copper layer provided on the outer periphery, a cylindrical first Sn diffusion barrier layer provided inside the stabilizing copper layer, and a superconducting element group precursor housed inside the first Sn diffusion barrier layer. The superconducting element group precursor includes a plurality of Sn-based strengthening element wires and a plurality of Nb-based superconducting element wire precursors. The plurality of Sn-based strengthening element wires include a first stabilizing matrix made of Cu or a Cu-based alloy, a plurality of Sn-based filaments embedded in the first stabilizing matrix and made of Sn or a Sn-based alloy, and a plurality of reinforcement multifilamentary wires embedded in the first stabilizing matrix and made of a plurality of reinforcement filaments made of a metal or alloy. The plurality of Nb-based superconducting element wire precursors include a second stabilizing matrix made of Cu or a Cu-based alloy, and one or more Nb-based superconducting filament precursors embedded in the second stabilizing matrix and made of Nb or a Nb-based alloy.

[0019] Nb in the embodiment ３ The Sn superconducting wire comprises a cylindrical stabilizing copper layer provided on the outer periphery, a cylindrical first Sn diffusion barrier layer provided inside the stabilizing copper layer, and a superconducting element group housed inside the first Sn diffusion barrier layer. The superconducting element group comprises a plurality of strengthening element wires and a plurality of Nb-based superconducting element wires. The plurality of strengthening element wires comprises a first stabilizing matrix made of Cu or a Cu-based alloy, and a plurality of strengthening multifilamentary wires embedded in the first stabilizing matrix and composed of a plurality of strengthening filaments made of a metal or an alloy. The plurality of Nb-based superconducting element wires comprises a second stabilizing matrix made of Cu or a Cu-based alloy, and a plurality of Nb-based superconducting element wires embedded in the second stabilizing matrix. ３ and one or more superconducting filaments having a compound superconducting phase made of Sn.

[0020] (First embodiment) FIG. 1 shows the Nb ３ 1 is a cross-sectional view showing an example of a precursor for a Sn superconducting wire; ３ The cross-sectional view of the precursor 1 for Sn superconducting wire is ３ 1 is a cross section perpendicular to the axial direction (longitudinal direction) of the precursor 1 for a Sn superconducting wire.３ The Sn superconducting wire precursor 1 includes a cylindrical stabilizing copper layer 10 , a cylindrical first Sn diffusion barrier layer 20 , and a superconducting element group precursor 30 .

[0021] Nb ３ The stabilizing copper layer 10 constituting the precursor 1 for the Sn superconducting wire is cylindrical, and ３ The stabilizing copper layer 10 is provided on the outer periphery of the Sn superconducting wire precursor 1, and covers the first Sn diffusion barrier layer 20 from the outside. The stabilizing copper layer 10 is made of Cu or a Cu alloy.

[0022] Nb ３ The first Sn diffusion barrier layer 20 constituting the precursor 1 for a Sn superconducting wire is cylindrical and provided inside the stabilizing copper layer 10. The first Sn diffusion barrier layer 20 is preferably made of a metal selected from Ta and Nb, or an alloy containing at least one of Ta and Nb.

[0023] The first Sn diffusion barrier layer 20 is made of Nb ３ During the heat treatment for producing the compound superconducting phase 73 made of Sn, the Sn in the Sn-based filaments 42 is prevented from diffusing into the stabilizing copper layer 10 and bronzing the stabilizing copper layer 10, thereby preventing a decrease in superconducting properties such as the residual resistivity ratio, and also reacting with the Nb-based superconducting filament precursor 53 to form Nb ３ The amount of Sn necessary for generating Sn is held inside the first Sn diffusion barrier layer 20 .

[0024] Nb ３ The superconducting element group precursor 30 constituting the Sn superconducting wire precursor 1 is housed inside the first Sn diffusion barrier layer 20. The superconducting element group precursor 30 includes a plurality of Sn-based strengthened element wires 40 and a plurality of Nb-based superconducting element wire precursors 50.

[0025] Each of the plurality of Sn-based reinforcing element wires 40 includes a first stabilizing matrix 41, a plurality of Sn-based filaments 42, and a plurality of reinforcing multifilamentary wires 44. The first stabilizing matrix 41 is made of Cu or a Cu-based alloy.

[0026] The Sn-based filaments 42 are made of Sn or an Sn-based alloy and are embedded in the first stabilizing matrix 41. By carrying out a heat treatment for generating a compound superconducting phase 73 (described later), Sn in the Sn-based filaments 42 reacts with the Nb-based superconducting filament precursor 53 in the Nb-based superconducting element wire precursor 50 to form Nb ３ A compound superconducting phase 73 made of Sn is formed. ３ When the precursor 1 for the Sn superconducting wire is subjected to heat treatment, Sn diffuses from the Sn-based filaments 42, so that the Sn-based filaments 42 no longer exist as filaments, and Nb ３ In the Sn superconducting wire 2, a cavity V is formed in a part of the reinforcing element wire 40a.

[0027] The reinforcement multifilamentary wire 44 is composed of a plurality of reinforcement filaments 43 made of a metal or alloy and is embedded in the first stabilizing matrix 41. The reinforcement filaments 43 are preferably made of a metal selected from Nb, Ta, Ti, V, W, Mo, Fe, and Hf, or an alloy containing at least one of Nb, Ta, Ti, V, W, Mo, Fe, and Hf. The reinforcement multifilamentary wire 44 has a strength greater than that of the Sn-based filaments 42. Therefore, the strength of the Sn-based reinforcement element wire 40 including the reinforcement multifilamentary wire 44 is greater than that of a Sn-based element wire without the reinforcement multifilamentary wire 44.

[0028] Each of the plurality of Nb-based superconducting element wire precursors 50 includes a second stabilizing matrix 51 and one or more Nb-based superconducting filament precursors 53. The second stabilizing matrix 51 is made of Cu or a Cu-based alloy. The Nb-based superconducting filament precursors 53 are made of Nb or an Nb-based alloy and are embedded in the second stabilizing matrix 51.

[0029] 1 shows an example in which each of the plurality of Nb-based superconducting element wire precursors 50 includes only a plurality of Nb-based superconducting filament precursors 53. However, each of the plurality of Nb-based superconducting element wire precursors 50 may include only a single Nb-based superconducting filament precursor 53, or may include a mixture of a plurality of Nb-based superconducting filament precursors 53 and a single Nb-based superconducting filament precursor 53.

[0030] By carrying out a heat treatment for generating the compound superconducting phase 73 described later, all or part of the Nb-based superconducting filament precursor 53 reacts with Sn diffused from the Sn-based filament 42 to form Nb ３ A filament-shaped compound superconducting phase 73 made of Sn is formed.

[0031] Thus, Nb ３ The Sn superconducting wire precursor 1 includes the Sn-based reinforced element wire 40 and the plurality of reinforcement multi-core wires 44, which reduces the difference in strength between the Sn-based reinforced element wire 40 and the Nb-based superconducting element wire precursor 50, thereby preventing the Sn-based reinforced element wire 40 from deforming significantly during stranding, thereby preventing the arrangement of the elements from becoming distorted. As a result, a high critical current density Jc can be maintained even after stranding.

[0032] Next, Nb ３ The heat treatment for generating the compound superconducting phase 73 made of Sn is performed ３ Nb obtained by applying to the precursor 1 for Sn superconducting wire ３ The Sn superconducting wire 2 will be described. ３ The precursor for Sn superconducting wire 1 is heated to form Nb ３ 2 is a cross-sectional view showing an example of a Sn superconducting wire 2. FIG.

[0033] As shown in FIG. ３ Nb, which is a heating product of the precursor 1 for Sn superconducting wire ３ The Sn superconducting wire 2 includes a cylindrical stabilizing copper layer 10 , a cylindrical first Sn diffusion barrier layer 20 , and a group of superconducting elements 60 .

[0034] Nb ３ The stabilizing copper layer 10 and the first Sn diffusion barrier layer 20 of the Sn superconducting wire 2 are made of Nb３ The structure is the same as that of the stabilizing copper layer 10 and the first Sn diffusion barrier layer 20 of the precursor 1 for a Sn superconducting wire.

[0035] The superconducting element group 60 is housed inside the first Sn diffusion barrier layer 20. The superconducting element group 60 includes a plurality of strengthening element wires 40a and a plurality of Nb-based superconducting element wires 70.

[0036] Each of the plurality of reinforcing element wires 40a includes a first stabilizing matrix 41 and a plurality of reinforcing multifilamentary wires 44. ３ The first stabilizing matrix 41 and the plurality of reinforcing multifilamentary wires 44 of the Sn superconducting wire 2 are made of Nb ３ The structure is similar to that of the first stabilizing matrix 41 and the plurality of reinforcing multifilamentary wires 44 of the precursor 1 for a Sn superconducting wire.

[0037] Each of the plurality of reinforcing element wires 40a has a cavity V formed therein. ３ When applied to the precursor 1 for Sn superconducting wire, Nb ３ The Sn in the Sn-based filaments 42 provided in the Sn-based strengthening element wire 40 of the Sn superconducting wire precursor 1 diffuses to form the voids V. The position of the voids V in the strengthening element wire 40a corresponds to the position of the Sn-based filaments 42 in the Sn-based strengthening element wire 40.

[0038] Each of the plurality of Nb-based superconducting element wires 70 includes a second stabilizing matrix 51 and one or more superconducting filaments 80. ３ The second stabilizing matrix 51 of the Sn superconducting wire 2 is made of Nb ３ The second stabilizing matrix 51 has the same structure as the second stabilizing matrix 51 of the Sn superconducting wire precursor 1. The superconducting filaments 80 are embedded in the second stabilizing matrix 51. Each of the plurality of superconducting filaments 80 is made of Nb ３ It has a compound superconducting phase 73 made of Sn.

[0039] 2 shows an example in which each of the plurality of Nb-based superconducting element wires 70 includes only a plurality of superconducting filaments 80. However, each of the plurality of Nb-based superconducting element wires 70 may include only a single superconducting filament 80, or may include a mixture of a single superconducting filament 80 and a plurality of superconducting filaments 80.

[0040] 2 and the following figures show Nb-based superconducting element wires 70, 70a, 70b, and 70c manufactured by the internal tin method. ３ Sn superconducting wire precursor 1 to Nb ３ When heat treatment is performed to generate the compound superconducting phase 73 made of Sn, ３ Sn diffused from the Sn-based filaments 42 of the Sn superconducting wire precursor 1 reacts with Nb on the surface of the Nb-based superconducting filament precursor 53, forming the compound superconducting phase 73 of Nb. ３ Sn filaments can be produced. ３ In the Sn superconducting wire 2, there are no Sn-based filaments 42, and voids V are formed. ３ The heat treatment of the Sn superconducting wire precursor 1 is carried out in an inert gas atmosphere such as argon or nitrogen.

[0041] In addition, the Nb-based superconducting element wires 70, 70a, 70b, and 70c shown in FIG. 2 and the following figures show examples in which the Nb-based superconducting filament precursor 53 in the central portion that remains without reacting with Sn is present in the superconducting filament 80. However, Nb ３ Depending on the amount of Sn contained in the Sn-based filaments 42 of the precursor 1 for Sn superconducting wire and the diameter size of the Nb-based superconducting filament precursor 53, the Nb-based superconducting filament precursor 53 may not be present in the superconducting filament 80, i.e., the superconducting filament 80 may consist of a compound superconducting phase 73.

[0042] Thus, Nb ３In the Sn superconducting wire 2, the strengthening element wire 40a is provided with a plurality of reinforcement multi-core wires 44, which reduces the difference in strength between the strengthening element wire 40a and the Nb-based superconducting element wire 70, thereby preventing the strengthening element wire 40a from deforming significantly during twisting, thereby preventing the arrangement of the elements from becoming disarrayed. As a result, a high critical current density Jc can be maintained even after twisting.

[0043] Nb ３ The heat treatment for generating Sn is usually carried out after the process of twisting the wire material, so that some or all of the reinforcing filaments 43 react with the Sn diffused from the Sn-based filaments 42 to form Nb. ３ The reinforcing element wire 40a of the Sn superconducting wire 2 is made of Nb ３ Even if Sn is formed, the effect of suppressing the disorder of the element arrangement during twisting can be maintained. ３ The formation of Sn results in Nb ３ Nb contained in the Sn superconducting wire 2 ３ Since the amount of Sn increases, the critical current density Jc can be further improved.

[0044] Furthermore, since the reinforcing multi-filamentary wires 44 are arranged between the plurality of cavities V, the strength of the reinforcing element wires 40a can be further improved. ３ The Sn superconducting wire 2 can further reduce the deterioration of the critical current density Jc due to electromagnetic stress.

[0045] FIG. 3 shows the Nb ３ 4 is a cross-sectional view showing another example of the Nb-based superconducting element wire precursor constituting the Sn superconducting wire precursor 1. ３ Nb superconducting wire precursor obtained by heating ３ FIG. 2 is a cross-sectional view showing an example of an Sn superconducting wire.

[0046] 3 , each of the plurality of Nb-based superconducting element wire precursors 50 a includes a second stabilizing matrix 51, a plurality of Nb-based reinforcing filaments 52, and a plurality of Nb-based superconducting filament precursors 53. The plurality of Nb-based reinforcing filaments 52 and the plurality of Nb-based superconducting filament precursors 53 are both made of Nb or an Nb-based alloy and are embedded in the second stabilizing matrix 51.

[0047] The diameter of the Nb-based superconducting filament precursor 53 is larger than the diameter of the Nb-based reinforcing filament 52. For example, the diameter of the Nb-based reinforcing filament 52 is 0.04 μm or more and 0.30 μm or less, and the diameter of the Nb-based superconducting filament precursor 53 is 1 μm or more and 10 μm or less.

[0048] In addition, Nb ３ In a cross section perpendicular to the axial direction of the Sn superconducting wire precursor 1, the ratio of the total area of ​​the plurality of Nb-based reinforcing filaments 52 to the area of ​​an Nb-based reinforcing filament assembly 52a in which the plurality of Nb-based reinforcing filaments 52 are aggregated is smaller than the ratio of the total area of ​​the plurality of Nb-based superconducting filaments 52 to the area of ​​an Nb-based superconducting filament assembly precursor 53a in which the plurality of Nb-based superconducting filament precursors 53 are aggregated. For example, the ratio of the total area of ​​the plurality of Nb-based reinforcing filaments 52 to the area of ​​the Nb-based reinforcing filament assembly 52a is 0.1 or more and 0.5 or less, and the ratio of the total area of ​​the plurality of Nb-based superconducting filament precursors 53 to the area of ​​the Nb-based superconducting filament assembly precursor 53a is 0.6 or more and 0.9 or less. Here, the Nb-based reinforcing filament assembly 52a is defined as including a plurality of Nb-based reinforcing filaments 52, as well as a second stabilizing matrix 51 present between the plurality of Nb-based reinforcing filaments 52, but not including any second stabilizing matrix 51 that is not sandwiched between the plurality of Nb-based reinforcing filaments 52. Also, the Nb-based superconducting filament assembly precursor 53a is defined as including a plurality of Nb-based superconducting filament precursors 53, as well as a second stabilizing matrix 51 present between the plurality of Nb-based superconducting filament precursors 53, but not including any second stabilizing matrix 51 that is not sandwiched between the plurality of Nb-based superconducting filament precursors 53.

[0049] In this way, by providing a plurality of Nb-based reinforcing filaments 52 in the Nb-based superconducting element wire precursor 50a, Nb ３ Sn superconducting wire precursor 1 and Nb ３ The Sn superconducting wire 2 has high mechanical strength against axial tensile stress. ３ The decrease in the critical current density Jc of the Sn superconducting wire 2 can be further suppressed. ３ Sn superconducting wire precursor 1 and Nb ３ When a radial compressive stress is applied to the Sn superconducting wire 2, the second stabilizing matrix 51 in the portion where the Nb-based reinforcing filaments 52 are embedded, in other words, the second stabilizing matrix 51 of the Nb-based reinforcing filament aggregate 52a, is preferentially deformed. Therefore, damage to the superconducting filaments during twisting or rolling is further reduced, and the Nb ３ It is possible to further suppress a decrease in the critical current density Jc of the Sn superconducting wire 2. In this way, damage to the superconducting filament precursor due to the twisting process or rolling process can be further suppressed, and therefore the superconducting filaments are protected. ３ The Sn superconducting wire 2 can fully exhibit a high critical current density Jc.

[0050] Furthermore, both the Nb-based reinforcing filament 52 and the Nb-based superconducting filament precursor 53 are made of Nb or an Nb-based alloy, which makes it possible to avoid deterioration in workability due to adjacent members with different mechanical properties.

[0051] In addition, as shown in FIG. ３ In a cross section perpendicular to the axial direction of the Sn superconducting wire precursor 1, in each of the plurality of Nb-based superconducting element wire precursors 50a, it is preferable that an Nb-based reinforcing filament assembly 52a in which a plurality of Nb-based reinforcing filaments 52 are aggregated is arranged in the center, and an Nb-based superconducting filament assembly precursor 53a in which a plurality of Nb-based superconducting filament precursors 53 are aggregated is arranged on the periphery. ３ The Nb-based superconducting element wire precursor 50a is disposed at the center of the Nb-based superconducting element wire precursor 50a in the cross section of the Sn-based superconducting wire precursor 1.３ The annular Nb-based superconducting filament assembly precursor 53a arranged around the entire outer periphery of the Nb-based superconducting element wire precursor 50a in the cross section of the Sn superconducting wire precursor 1 covers the periphery of the Nb-based reinforcing filament assembly 52a. ３ When the Sn superconducting wire precursor 1 is subjected to the treatment, the Sn diffused from the Sn-based filaments 42 reacts preferentially with the plurality of Nb-based superconducting filament precursors 53 arranged on the outer periphery of the Nb-based superconducting element wire precursor 50a, thereby forming high-quality Nb. ３ The Sn compound superconducting phase 73 is easily formed.

[0052] As shown in FIG. 4, the Nb ３ The precursor for Sn superconducting wire 1 is heated to form Nb ３ In the Sn superconducting wire 2, the superconducting element group 60 housed inside the first Sn diffusion barrier layer 20 includes a plurality of strengthening element wires 40a and a plurality of Nb-based superconducting element wires 70a.

[0053] Each of the plurality of Nb-based superconducting element wires 70a includes a second stabilizing matrix 51, a plurality of Nb-based reinforcing filaments 52 made of Nb or an Nb-based alloy, and a plurality of superconducting filaments 80. Both the plurality of Nb-based reinforcing filaments 52 and the plurality of superconducting filaments 80 are embedded in the second stabilizing matrix 51.

[0054] Each of the plurality of superconducting filaments 80 is made of Nb ３ The superconducting filaments 80 have a compound superconducting phase 73 made of Sn. The diameter of the superconducting filaments 80 is larger than the diameter of the Nb-based reinforced filaments 52. For example, the diameter of the Nb-based reinforced filaments 52 is 0.04 μm or more and 0.30 μm or less, and the diameter of the superconducting filaments 80 is 1 μm or more and 10 μm or less.

[0055] In addition, Nb ３In a cross section perpendicular to the axial direction of the Sn superconducting wire 2, the ratio of the total area of ​​the plurality of Nb-based reinforced filaments 52 to the area of ​​an Nb-based reinforced filament assembly 52a in which the plurality of Nb-based reinforced filaments 52 are aggregated is smaller than the ratio of the total area of ​​the plurality of superconducting filaments 80 to the area of ​​a superconducting filament assembly 80a in which the plurality of superconducting filaments 80 are aggregated. For example, the ratio of the total area of ​​the plurality of Nb-based reinforced filaments 52 to the area of ​​the Nb-based reinforced filament assembly 52a is 0.1 or more and 0.5 or less, and the ratio of the total area of ​​the plurality of superconducting filaments 80 to the area of ​​the superconducting filament assembly 80a is 0.6 or more and 0.9 or less. Here, the superconducting filament assembly 80a is defined as including the plurality of superconducting filaments 80 and second stabilizing matrices 51 present between the plurality of superconducting filaments 80, but excluding second stabilizing matrices 51 that are not sandwiched between the plurality of superconducting filaments 80.

[0056] Thus, Nb ３ The Sn superconducting wire 2 has a high mechanical strength against tensile stress in the axial direction because the Nb-based superconducting element wire 70a includes a plurality of Nb-based reinforcing filaments 52. ３ When a compressive stress in the radial direction is applied to the precursor 1 for a Sn superconducting wire, the second stabilizing matrix 51 in the portion where the Nb-based reinforcing filaments 52 are embedded is preferentially deformed. ３ Nb during twisting and rolling of Sn superconducting wire precursor 1 ３ Since the superconducting filaments 80 of the Sn superconducting wire 2 are less damaged, the decrease in the critical current density Jc can be further suppressed. ３ Even if the precursor 1 for the Sn superconducting wire is subjected to twisting or rolling, the Nb ３ The Sn superconducting wire 2 can fully exhibit a high critical current density Jc.

[0057] Furthermore, both the Nb-based reinforcing filament 52 and the Nb-based superconducting filament precursor 53 are made of Nb or an Nb-based alloy, which further prevents deterioration in workability due to adjacent members with different mechanical properties.

[0058] In addition, Nb shown in FIG. ３ In a cross section perpendicular to the axial direction of the Sn superconducting wire 2, in each of the plurality of Nb-based superconducting element wires 70a, an Nb-based reinforcing filament assembly 52a in which a plurality of Nb-based reinforcing filaments 52 are aggregated is arranged in the center, and a superconducting filament assembly 80a in which a plurality of superconducting filaments 80 are aggregated is arranged on the periphery. In this case, the annular superconducting filament assembly 80a arranged around the entire periphery of the Nb-based superconducting element wire 70a covers the periphery of the Nb-based reinforcing filament assembly 52a arranged in the center of the Nb-based superconducting element wire 70a. With this configuration, the Nb ３ In the precursor for Sn superconducting wire 1, Sn diffused from the Sn-based filaments 42 reacts preferentially with the plurality of Nb-based superconducting filament precursors 53. ３ The Sn superconducting wire 2 is made of high-quality Nb ３ It has a Sn compound superconducting phase 73 .

[0059] FIG. 5 shows the Nb ３ 6 is a cross-sectional view showing another example of the Nb-based superconducting element wire precursor constituting the Sn superconducting wire precursor 1. ３ Nb superconducting wire precursor obtained by heating ３ FIG. 2 is a cross-sectional view showing an example of an Sn superconducting wire.

[0060] As shown in FIG. 5, the Nb-based superconducting element wire precursor 50b is made of Nb ３In a cross section perpendicular to the axial direction of the Sn superconducting wire precursor 1, the precursor further comprises a third Sn diffusion barrier layer 54, which is formed between the Nb-based reinforcing filament assembly 52a and the Nb-based superconducting filament assembly precursor 53a and is made of Ta or Nb metal or an alloy containing at least one of Ta and Nb. The third Sn diffusion barrier layer 54 completely covers the periphery of the Nb-based reinforcing filament assembly 52a. The third Sn diffusion barrier layer 54 is cylindrical, and the Nb ３ The Sn superconducting wire precursor 1 has a ring shape in a cross section perpendicular to the axial direction.

[0061] As shown in FIG. 6, the Nb ３ The precursor for Sn superconducting wire 1 is heated to form Nb ３ In the Sn superconducting wire 2, the superconducting element group 60 housed inside the first Sn diffusion barrier layer 20 includes a plurality of strengthening element wires 40a and a plurality of Nb-based superconducting element wires 70b.

[0062] Each of the plurality of Nb-based superconducting element wires 70b includes a second stabilizing matrix 51, and a plurality of Nb-based reinforcing filaments 52, a plurality of superconducting filaments 80, and a third Sn diffusion barrier layer 54 embedded in the second stabilizing matrix 51.

[0063] 5 and 6, during the heat treatment for generating the compound superconducting phase 73, the third Sn diffusion barrier layer 54 is formed so that Sn in the Sn-based filaments 42 diffuses into the Nb-based reinforcing filament aggregates 52a and reacts with the Nb-based reinforcing filaments 52, and the Nb ３ That is, even if heat treatment is performed, the formation of brittle Nb is suppressed from the Nb-based reinforcing filaments 52. ３ This further suppresses the reaction with the compound superconducting phase made of Sn. ３ Sn superconducting wire precursor 1 and Nb ３ This can further suppress the reduction in mechanical strength of the Sn superconducting wire 2 against tensile stress in the axial direction.

[0064] FIG. 7 shows the Nb ３8 is a cross-sectional view showing another example of the Nb-based superconducting element wire precursor constituting the Sn superconducting wire precursor 1. ３ Nb superconducting wire precursor obtained by heating ３ FIG. 2 is a cross-sectional view showing an example of an Sn superconducting wire.

[0065] As shown in FIG. 7, a plurality of Nb-based superconducting element wire precursors 50 c include a plurality of Nb-based strengthening sub-elements 55 and a plurality of Nb-based superconducting sub-element precursors 57 .

[0066] Each of the plurality of Nb-based reinforcing sub-elements 55 includes a third stabilizing matrix 56 and a plurality of Nb-based reinforcing filaments 52. The third stabilizing matrix 56 is made of Cu or a Cu-based alloy. The plurality of Nb-based reinforcing filaments 52 are made of Nb or an Nb-based alloy and are embedded in the third stabilizing matrix 56.

[0067] Each of the plurality of Nb-based superconducting subelement precursors 57 has a fourth stabilizing matrix 58 and a plurality of Nb-based superconducting filament precursors 53. The fourth stabilizing matrix 58 is made of Cu or a Cu-based alloy. The plurality of Nb-based superconducting filament precursors 53 are made of Nb or an Nb-based alloy and are embedded in the fourth stabilizing matrix 58.

[0068] A third stabilizing matrix 56 of the Nb-based reinforced subelement 55 is provided with a plurality of Nb-based reinforced filaments 52, but is not provided with Nb-based superconducting filament precursors 53. A fourth stabilizing matrix 58 of the Nb-based superconducting subelement precursor 57 is provided with a plurality of Nb-based superconducting filament precursors 53, but is not provided with Nb-based reinforced filaments 52. In other words, the Nb-based reinforced filaments 52 and the Nb-based superconducting filament precursors 53 are provided in different subelements (subelement precursors).

[0069] The diameter of the Nb-based superconducting filament precursors 53 embedded in the fourth stabilizing matrix 58 is larger than the diameter of the Nb-based reinforcing filaments 52 embedded in the third stabilizing matrix 56. For example, the diameter of the Nb-based reinforcing filaments 52 is 0.04 μm or more and 0.30 μm or less, and the diameter of the Nb-based superconducting filament precursors 53 is 1 μm or more and 10 μm or less.

[0070] In addition, Nb ３ In a cross section perpendicular to the axial direction of the Sn superconducting wire precursor 1, the ratio of the total area of ​​the plurality of Nb-based reinforcing filaments 52 to the area of ​​an Nb-based reinforcing filament assembly 52a in which the plurality of Nb-based reinforcing filaments 52 are aggregated is smaller than the ratio of the total area of ​​the plurality of Nb-based superconducting filaments 52 to the area of ​​an Nb-based superconducting filament assembly precursor 53a in which the plurality of Nb-based superconducting filament precursors 53 are aggregated. For example, the ratio of the total area of ​​the plurality of Nb-based reinforcing filaments 52 to the area of ​​the Nb-based reinforcing filament assembly 52a is 0.1 or more and 0.5 or less, and the ratio of the total area of ​​the plurality of Nb-based superconducting filament precursors 53 to the area of ​​the Nb-based superconducting filament assembly precursor 53a is 0.6 or more and 0.9 or less. Here, the Nb-based reinforcing filament assembly 52a is defined as including a plurality of Nb-based reinforcing filaments 52, a third stabilizing matrix 56 present between the plurality of Nb-based reinforcing filaments 52, and excluding any third stabilizing matrix 56 that is not sandwiched between the plurality of Nb-based reinforcing filaments 52. The Nb-based superconducting filament assembly precursor 53a is defined as including a plurality of Nb-based superconducting filament precursors 53, a fourth stabilizing matrix 58 present between the plurality of Nb-based superconducting filament precursors 53, and excluding any fourth stabilizing matrix 58 that is not sandwiched between the plurality of Nb-based superconducting filament precursors 53.

[0071] In this way, by providing a plurality of Nb-based reinforcing filaments 52 in the Nb-based superconducting element wire precursor 50c, Nb ３ Sn superconducting wire precursor 1 and Nb ３ The Sn superconducting wire 2 has even higher mechanical strength against tensile stress in the axial direction. ３Sn superconducting wire precursor 1 and Nb ３ When a radial compressive stress is applied to the Sn superconducting wire 2, the third stabilizing matrix 56 in which the Nb-based reinforcing filaments 52 are embedded, in other words, the third stabilizing matrix 56 of the Nb-based reinforcing filament assembly 52a, is preferentially deformed. Therefore, the superconducting filaments are less damaged during twisting or rolling, and the Nb ３ In this way, damage to the superconducting filament precursor due to twisting or rolling can be suppressed, and therefore the superconducting filaments are protected. ３ The Sn superconducting wire can fully exhibit a high critical current density Jc.

[0072] In addition, Nb ３ In a cross section perpendicular to the axial direction of the Sn superconducting wire precursor 1, it is preferable that the plurality of Nb-based superconducting subelement precursors 57 and the plurality of Sn-based strengthened element wires 40 are arranged in the center of the superconducting element group precursor 30, and the plurality of Nb-based strengthened subelements 55 are arranged on the outer periphery of the superconducting element group precursor 30. In this case, the plurality of Nb-based strengthened subelements 55 arranged in an annular shape around the entire outer periphery of the superconducting element group precursor 30 cover the periphery of the plurality of Nb-based superconducting subelement precursors 57 and the plurality of Sn-based strengthened element wires 40 arranged in the center of the superconducting element group precursor 30. With this configuration, Nb ３ The heat treatment for generating the compound superconducting phase 73 made of Sn is performed ３ When the Sn-based superconducting wire precursor 1 is applied, Sn diffused from the Sn-based filaments 42 of the Sn-based strengthening element wire 40 reacts preferentially with the plurality of Nb-based superconducting filament precursors 53, thereby forming high-quality Nb ３ The Sn compound superconducting phase 73 is easily formed.

[0073] As shown in FIG. 8, the Nb ３ Nb, which is a heating product of the precursor 1 for Sn superconducting wire ３In the Sn superconducting wire 2, the superconducting element group 60 housed inside the first Sn diffusion barrier layer 20 includes a plurality of strengthening element wires 40a and a plurality of Nb-based superconducting element wires 70c. The plurality of Nb-based superconducting element wires 70c include a plurality of Nb-based strengthening sub-elements 55 and a plurality of superconducting sub-elements 77.

[0074] Nb ３ The Nb-based reinforced sub-element 55 of the Sn superconducting wire 2 is made of Nb ３ It has the same configuration as the Nb-based strengthening sub-element 55 of the precursor 1 for a Sn superconducting wire.

[0075] Each of the plurality of superconducting subelements 77 includes a fourth stabilizing matrix 58 and a plurality of superconducting filaments 80. The fourth stabilizing matrix 58 is made of Cu or a Cu-based alloy. The plurality of superconducting filaments 80 are embedded in the fourth stabilizing matrix 58.

[0076] Each of the plurality of superconducting filaments 80 is made of Nb ３ The third stabilizing matrix 56 has a compound superconducting phase 73 made of Sn. The diameter of the superconducting filaments 80 is larger than the diameter of the Nb-based reinforcing filaments 52 embedded in the third stabilizing matrix 56. For example, the diameter of the Nb-based reinforcing filaments 52 is 0.04 μm or more and 0.30 μm or less, and the diameter of the superconducting filaments 80 is 1 μm or more and 10 μm or less.

[0077] In addition, Nb ３In a cross section perpendicular to the axial direction of the Sn superconducting wire 2, the ratio of the total area of ​​the plurality of Nb-based reinforced filaments 52 to the area of ​​an Nb-based reinforced filament assembly 52a in which the plurality of Nb-based reinforced filaments 52 are aggregated is smaller than the ratio of the total area of ​​the plurality of superconducting filaments 80 to the area of ​​a superconducting filament assembly 80a in which the plurality of superconducting filaments 80 are aggregated. For example, the ratio of the total area of ​​the plurality of Nb-based reinforced filaments 52 to the area of ​​the Nb-based reinforced filament assembly 52a is 0.1 or more and 0.5 or less, and the ratio of the total area of ​​the plurality of superconducting filaments 80 to the area of ​​the superconducting filament assembly 80a is 0.6 or more and 0.9 or less. Here, the superconducting filament assembly 80a is defined as including the plurality of superconducting filaments 80 and fourth stabilizing matrices 58 present between the plurality of superconducting filaments 80, but excluding the fourth stabilizing matrices 58 that are not sandwiched between the plurality of superconducting filaments 80.

[0078] The third stabilizing matrix 56 of the Nb-based reinforced sub-element 55 is provided with a plurality of Nb-based reinforced filaments 52 but is not provided with a superconducting filament 80. The fourth stabilizing matrix 58 of the superconducting sub-element 77 is provided with a plurality of superconducting filaments 80 but is not provided with an Nb-based reinforced filament 52. In other words, the Nb-based reinforced filaments 52 and the superconducting filaments 80 are provided in different sub-elements.

[0079] Thus, Nb ３ The Sn superconducting wire 2 has a higher mechanical strength against tensile stress in the axial direction because the Nb-based superconducting element wire 70c includes a plurality of Nb-based reinforcing filaments 52. ３ When a radial compressive stress is applied to the precursor 1 for a Sn superconducting wire, the third stabilizing matrix 56 in which the Nb-based reinforcing filaments 52 are embedded is preferentially deformed. ３ Nb during twisting and rolling of Sn superconducting wire precursor 1 ３ The damage to the superconducting filaments 80 of the Sn superconducting wire 2 is small, and the Nb ３This can further suppress a decrease in the critical current density Jc of the Sn superconducting wire 2. In this way, the superconducting filaments 80 are protected, and therefore, the Nb ３ Even if the precursor 1 for the Sn superconducting wire is subjected to twisting or rolling, the Nb ３ The Sn superconducting wire 2 can fully exhibit a high critical current density Jc.

[0080] In addition, Nb ３ In a cross section perpendicular to the axial direction of the Sn superconducting wire 2, it is preferable that the plurality of superconducting subelements 77 and the plurality of strengthening element wires 40a are arranged in the center of the superconducting element group 60, and the plurality of Nb-based strengthening subelements 55 are arranged on the outer periphery of the superconducting element group 60. In this case, the plurality of Nb-based strengthening subelements 55 arranged in an annular shape around the entire outer periphery of the superconducting element group 60 cover the periphery of the plurality of superconducting subelements 77 and the plurality of strengthening element wires 40a arranged in the center of the superconducting element group 60. With this configuration, Sn diffused from the Sn-based filaments 42 reacts preferentially with the plurality of Nb-based superconducting filament precursors 53, so that Nb ３ Sn superconducting wire 2 is made of even better quality Nb ３ It has a Sn compound superconducting phase 73 .

[0081] The above-described Nb ３ The Sn superconducting wire 2 has good strength and can maintain a high critical current density Jc even after being subjected to a twisting process. ３ The Sn superconducting wire 2 is suitably used as a superconducting wire constituting a high-magnetic field superconducting magnet used in large accelerators, nuclear fusion reactors, analytical devices, and the like.

[0082] According to the first embodiment described above, the Sn-based reinforced element wire is provided with a reinforced multi-core wire composed of multiple reinforced filaments, which improves the strength of the Sn-based reinforced element wire and prevents the Sn-based reinforced element wire from deforming significantly during twisting, thereby preventing the arrangement of the elements from becoming distorted, and therefore allows a high critical current density Jc to be maintained even after twisting.

[0083] (Second embodiment) FIG. 9 shows the Nb ３10 is a cross-sectional view showing an example of a precursor for a Sn superconducting wire. ３ Nb superconducting wire precursor obtained by heating ３ FIG. 2 is a cross-sectional view showing an example of an Sn superconducting wire.

[0084] In the following embodiment, the Nb ３ Sn superconducting wire precursor and Nb ３ The same components as those of the Sn superconducting wire are denoted by the same reference numerals, and redundant explanations will be omitted or simplified.

[0085] The second embodiment is basically the same as the first embodiment except for the arrangement of the plurality of reinforcing multifilamentary wires 44. Therefore, the different configuration will be mainly described here.

[0086] As shown in FIG. 9, in the second embodiment, Nb ３ The Sn superconducting wire precursor 1a includes a cylindrical stabilizing copper layer 10, a cylindrical first Sn diffusion barrier layer 20, and a superconducting element group precursor 30. The superconducting element group precursor 30 includes a plurality of Sn-based strengthening element wires 40 and a plurality of Nb-based superconducting element wire precursors 50.

[0087] Nb ３ In a cross section perpendicular to the axial direction of the Sn superconducting wire precursor 1a, in each of the plurality of Sn-based reinforcing element wires 40, a reinforcing multifilamentary wire assembly 44a in which a plurality of reinforcing multifilamentary wires 44 are assembled is arranged in the center, and a Sn-based filament assembly 42a in which a plurality of Sn-based filaments 42 are assembled is arranged on the periphery. ３ The Sn-based reinforcing element wire 40 is disposed at the center of the Sn-based reinforcing element wire 40 in the cross section of the Sn superconducting wire precursor 1a. ３ The annular Sn-based filament assembly 42a arranged around the entire outer periphery of the Sn-based reinforcing element wire 40 in the cross section of the Sn superconducting wire precursor 1a covers the periphery of the reinforcing multifilamentary wire assembly 44a.

[0088] In this configuration, the heat treatment for generating the compound superconducting phase 73 is performed using Nb ３When the Sn superconducting wire precursor 1a is applied, Sn diffused from the Sn-based filaments 42 arranged on the outer periphery of the Sn-based strengthening element wire 40 reacts efficiently with the Nb-based superconducting filament precursor 53 of the Nb-based superconducting element wire precursor 50, thereby producing high-quality Nb. ３ The Sn compound superconducting phase 73 is easily formed.

[0089] As shown in FIG. 10, the heat treatment for generating the compound superconducting phase 73 is performed using Nb ３ Nb obtained by applying to the precursor 1a for Sn superconducting wire ３ In the cross section of the Sn superconducting wire 2a, each of the plurality of reinforcing element wires 40a has a reinforcing multifilamentary wire assembly 44a at its center, which assembly includes a plurality of reinforcing multifilamentary wires 44. The annular cavity assembly, which includes a plurality of cavities V, is formed around the entire outer periphery of the reinforcing element wire 40a and covers the reinforcing multifilamentary wire assembly 44a at the center of the reinforcing element wire 40a.

[0090] As described above, the heat treatment for generating the compound superconducting phase 73 is performed using Nb ３ When applied to the precursor 1a for Sn superconducting wire, Nb ３ In the Sn superconducting wire precursor 1a, Sn diffused from the Sn-based filaments 42 reacts efficiently with the Nb-based superconducting filament precursor 53 of the Nb-based superconducting element wire precursor 50 to produce high-quality Nb. ３ The compound superconducting phase 73 of Sn is easily formed. ３ The critical current density Jc of the Sn superconducting wire 2a can be further improved.

[0091] According to the second embodiment described above, by arranging a plurality of reinforcing multifilamentary wires in a predetermined arrangement, it is possible to further improve the critical current density Jc while maintaining good strength.

[0092] (Third embodiment) FIG. 11 shows the Nb ３ 12 is a cross-sectional view showing an example of a precursor for a Sn superconducting wire. ３ Nb superconducting wire precursor obtained by heating ３ FIG. 2 is a cross-sectional view showing an example of an Sn superconducting wire.

[0093] The third embodiment has basically the same configuration as the second embodiment except for the inclusion of the second Sn diffusion barrier layer 45. Therefore, the different configuration will be mainly described here.

[0094] As shown in FIG. 11, in the third embodiment, Nb ３ The Sn superconducting wire precursor 1b includes a cylindrical stabilizing copper layer 10, a cylindrical first Sn diffusion barrier layer 20, and a superconducting element group precursor 30. The superconducting element group precursor 30 includes a plurality of Sn-based strengthening element wires 40 and a plurality of Nb-based superconducting element wire precursors 50.

[0095] Each of the plurality of Sn-based strengthening element wires 40 is made of Nb ３ In a cross section perpendicular to the axial direction of the Sn superconducting wire precursor 1b, the precursor further includes a second Sn diffusion barrier layer 45 formed between the reinforcing material multifilamentary wire assembly 44a and the Sn-based filament assembly 42a and made of Ta or Nb metal or an alloy containing at least one of Ta and Nb. The second Sn diffusion barrier layer 45 completely covers the periphery of the reinforcing material multifilamentary wire assembly 44a. The second Sn diffusion barrier layer 45 is cylindrical, and the second Sn diffusion barrier layer 45 is made of Nb. ３ The Sn superconducting wire precursor 1b has a ring shape in a cross section perpendicular to the axial direction.

[0096] As shown in FIG. 12, the heat treatment for generating the compound superconducting phase 73 is performed using Nb ３ Nb obtained by applying to the precursor 1b for Sn superconducting wire ３ In the Sn superconducting wire 2b, each of the plurality of reinforcing element wires 40a is made of Nb ３ The Sn superconducting wire 2b further includes a second Sn diffusion barrier layer 45 provided between the reinforcing material multifilamentary wire assembly 44a and the cavity assembly in a cross section thereof.

[0097] With this configuration, during the heat treatment for generating the compound superconducting phase 73, the second Sn diffusion barrier layer 45 prevents Sn in the Sn-based filaments 42 from diffusing into the reinforcing multifilamentary wire assembly 44a and reacting with the reinforcing multifilamentary wires 44, and prevents Nb ３ That is, even if heat treatment is performed, the formation of brittle Nb from the reinforcing multifilamentary wire 44 is suppressed. ３This further suppresses the reaction with the compound superconducting phase made of Sn. ３ Sn superconducting wire precursor 1b and Nb ３ This can further suppress the reduction in mechanical strength of the Sn superconducting wire 2b against tensile stress in the axial direction.

[0098] According to the third embodiment described above, by providing the second Sn diffusion barrier layer, it is possible to maintain a high critical current density Jc even when twisted wire processing is performed, while further suppressing the decrease in mechanical strength against axial tensile stress.

[0099] Although the embodiments have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept and scope of the claims of the present disclosure, and can be modified in various ways within the scope of the present disclosure.

[0100] Next, examples and comparative examples will be described, but the present disclosure is not limited to these examples.

[0101] (Example 1) Nb as shown in FIG. ３ Sn superconducting wire precursor and Nb as shown in FIG. ３ An Sn superconducting wire was produced.

[0102] First, a Sn-Ti alloy rod (diameter 24.2 mmφ) was inserted into a copper tube (oxygen-free copper, outer diameter 27.5 mmφ, inner diameter 24.5 mmφ), and the resulting sample was drawn to form a Sn-based filament hexagonal wire with a face-to-face length of 2.82 mmH.

[0103] In addition, an Nb rod (pure Nb, diameter 103 mmφ) was inserted into a copper tube (oxygen-free copper, outer diameter 214 mmφ, inner diameter 103.7 mmφ), extruded, and then drawn and stripped to form an Nb-based reinforced filament primary hexagonal wire with a face-to-face length of 13.4 mmH.

[0104] Next, 109 of the above-mentioned Nb-based reinforced filament primary hexagonal wires were inserted into a copper tube (oxygen-free copper, outer diameter 214 mmφ, inner diameter 166 mmφ), and the tube was subjected to HIP (hot isostatic pressing), external cutting, extrusion, and further subjected to multiple wire drawing and peeling processes to form a Nb-based reinforced filament secondary hexagonal wire with a face length of 2.82 mmH.

[0105] Next, 48 of the Sn-based hexagonal filament wires and 7 of the Nb-based reinforced filament secondary hexagonal wires were inserted into a copper tube (oxygen-free copper, outer diameter 27.5 mmφ, inner diameter 24.5 mmφ) in an arrangement in which the Nb-based reinforced filament secondary hexagonal wires were gathered at the radial center, and the tube was subjected to HIP and external cutting, followed by extrusion processing and further multiple wiredrawing processing to form a Sn-based reinforced element hexagonal wire with a face-to-face length of 2.24 mmH.

[0106] In addition, a sample was obtained by inserting an Nb rod (pure Nb, diameter 24.3 mmφ) into a copper tube (oxygen-free copper, outer diameter 27.5 mmφ, inner diameter 24.5 mmφ), and the obtained sample was subjected to wire drawing multiple times to form a hexagonal Nb-based superconducting filament precursor wire with an opposite side length of 1.71 mmH.

[0107] Next, 151 of the above-mentioned Nb-based superconducting filament precursor hexagonal wires were inserted into a copper tube (oxygen-free copper, outer diameter 27.5 mmφ, inner diameter 24.5 mmφ), and the tube was subjected to HIP, external cutting, extrusion processing, and further wiredrawing processing multiple times to form an Nb-based superconducting element precursor wire having an opposite side length of 2.24 mmH.

[0108] Next, a 0.3 mm thick Nb sheet was wound around the inner circumference of a copper tube (oxygen-free copper, outer diameter 30 mmφ, inner diameter 20 mmφ), and then 19 of the above Sn-based strengthened element hexagonal wires and 36 of the above Nb-based superconducting element precursor wires were inserted inside the Nb sheet in such a way that the Sn-based strengthened element hexagonal wires were not adjacent to each other. After CIP (cold isostatic pressing) and external cutting, a 0.6 mm diameter Nb superconducting element was obtained by wiredrawing multiple times. ３ A precursor for a Sn superconducting wire was formed.

[0109] Next, the obtained Nb ３ For Sn superconducting wire precursor, Nb ３ To produce a compound superconducting phase consisting of Sn, the alloy was subjected to a heat treatment of 6 hours at 210°C, followed by 18 hours at 350°C, 28 hours at 480°C, 180 hours at 570°C, and 200 hours at 665°C. ３ A Sn superconducting wire was obtained.

[0110] The obtained Nb ３Sn superconducting wire precursor and Nb ３ The Sn superconducting wire had good strength. ３ Sn superconducting wire precursor and Nb ３ Even if the Sn superconducting wire is subjected to twisting processing, the obtained Nb ３ The Sn superconducting wire was able to maintain a high critical current density Jc.

[0111] (Example 2) Nb as shown in FIG. ３ Sn superconducting wire precursor and Nb as shown in FIG. ３ An Sn superconducting wire was produced.

[0112] First, a Sn-Ti alloy rod (diameter 24.2 mm) was inserted into a copper tube (oxygen-free copper, outer diameter 27.5 mm, inner diameter 24.5 mm), and the resulting sample was drawn to form a Sn-based filament wire with a diameter of 2.6 mm.

[0113] In addition, an Nb rod (pure Nb, diameter 103 mmφ) was inserted into a copper tube (oxygen-free copper, outer diameter 214 mmφ, inner diameter 103.7 mmφ), extruded, and then drawn and stripped to form an Nb-based reinforced filament primary hexagonal wire with a face-to-face length of 13.4 mmH.

[0114] Next, 109 of the above-mentioned Nb-based reinforced filament primary hexagonal wires were inserted into a copper tube (oxygen-free copper, outer diameter 214 mmφ, inner diameter 166 mmφ), and the tube was subjected to HIP, external cutting, and then extrusion processing.Furthermore, multiple wire drawing and peeling processing were performed to form an Nb-based reinforced filament secondary wire with a diameter of 2.6 mmφ.

[0115] Next, a 0.1 mm thick Nb sheet was wound six times around the outer periphery of the assembly of seven of the above-mentioned Nb-based reinforced filament secondary wires to form an Nb-based reinforced filament bundle.

[0116] Next, 48 of the Sn-based filament wires and the Nb-based reinforced filament bundle were inserted into a copper tube (oxygen-free copper, outer diameter 27.5 mmφ, inner diameter 24.5 mmφ) so that the Nb-based reinforced filament bundle was positioned at the radial center, and the tube was subjected to CIP and external cutting, followed by extrusion processing and further multiple wiredrawing processing to form a Sn-based reinforced hexagonal element wire with a face-to-face length of 2.24 mmH.

[0117] In addition, a sample was obtained by inserting an Nb rod (pure Nb, diameter 24.3 mmφ) into a copper tube (oxygen-free copper, outer diameter 27.5 mmφ, inner diameter 24.5 mmφ), and the obtained sample was subjected to wire drawing multiple times to form a hexagonal Nb-based superconducting filament precursor wire with an opposite side length of 1.71 mmH.

[0118] Next, 151 of the above-mentioned Nb-based superconducting filament precursor hexagonal wires were inserted into a copper tube (oxygen-free copper, outer diameter 27.5 mmφ, inner diameter 24.5 mmφ), and the tube was subjected to HIP, external cutting, extrusion processing, and further wiredrawing processing multiple times to form an Nb-based superconducting element precursor wire having an opposite side length of 2.24 mmH.

[0119] Next, a 0.3 mm thick Nb sheet was wound around the inner circumference of a copper tube (oxygen-free copper, outer diameter 30 mmφ, inner diameter 20 mmφ), and then 19 of the above Sn-based strengthened element hexagonal wires and 36 of the above Nb-based superconducting element precursor wires were inserted inside the Nb sheet in such a way that the Sn-based strengthened element hexagonal wires were not adjacent to each other. After CIP (cold isostatic pressing) and external cutting, a 0.6 mm diameter Nb superconducting element was obtained by wiredrawing multiple times. ３ A precursor for a Sn superconducting wire was formed.

[0120] Next, the obtained Nb ３ For Sn superconducting wire precursor, Nb ３ To produce a compound superconducting phase consisting of Sn, the alloy was subjected to a heat treatment of 6 hours at 210°C, followed by 18 hours at 350°C, 28 hours at 480°C, 180 hours at 570°C, and 200 hours at 665°C. ３ A Sn superconducting wire was obtained.

[0121] The obtained Nb ３ Sn superconducting wire precursor and Nb ３ The Sn superconducting wire had good strength. ３ Sn superconducting wire precursor and Nb ３ Even if the Sn superconducting wire is subjected to twisting processing, the obtained Nb ３ The Sn superconducting wire was able to maintain a high critical current density Jc.

[0122] 1, 1a, 1b Nb３ Precursor for Sn superconducting wire 2, 2a, 2b Nb ３ Sn superconducting wire 10 stabilizing copper layer 20 first Sn diffusion barrier layer 30 superconducting element group precursor 40 Sn-based strengthening element wire 40a strengthening element wire 41 first stabilizing matrix 42 Sn-based filament 42a Sn-based filament assembly 43 strengthening filament 44 strengthening material multifilamentary wire 44a strengthening material multifilamentary wire assembly 45 second Sn diffusion barrier layer 50, 50a, 50b, 50c Nb-based superconducting element wire precursor 51 second stabilizing matrix 52 Nb-based strengthening filament 52a Nb-based strengthening filament assembly 53 Nb-based superconducting filament precursor 53a Nb-based superconducting filament assembly precursor 54 third Sn diffusion barrier layer 55 Nb-based strengthening sub-element 56 third stabilizing matrix 57 Nb-based superconducting sub-element precursor 58 fourth stabilizing matrix 60 Superconducting element group 70, 70a, 70b, 70c Nb-based superconducting element wire 73 Compound superconducting phase 77 Superconducting sub-element 80 Superconducting filament 80a Superconducting filament assembly V Cavity

Claims

1. A superconducting element group precursor comprising: a cylindrical stabilizing copper layer provided on the outer periphery; a cylindrical first Sn diffusion barrier layer provided inside the stabilizing copper layer; and a superconducting element group precursor housed inside the first Sn diffusion barrier layer, wherein the superconducting element group precursor comprises a plurality of Sn-based reinforced element wires and a plurality of Nb-based superconducting element wire precursors, wherein the plurality of Sn-based reinforced element wires comprise: a first stabilizing matrix made of Cu or a Cu-based alloy; a plurality of Sn-based filaments embedded in the first stabilizing matrix and made of Sn or a Sn-based alloy; and a plurality of reinforced multifilamentary wires embedded in the first stabilizing matrix and made of a plurality of reinforced filaments made of a metal or an alloy, and wherein the plurality of Nb-based superconducting element wire precursors comprise: a second stabilizing matrix made of Cu or a Cu-based alloy; and one or more Nb-based superconducting filament precursors embedded in the second stabilizing matrix and made of Nb or a Nb-based alloy, ３ Precursor for Sn superconducting wire.

2. The Nb ３ 2. The Nb superconducting wire precursor according to claim 1, wherein in a cross section perpendicular to the axial direction of the Sn superconducting wire precursor, in each of the plurality of Sn-based reinforcing element wires, a reinforcing multifilamentary wire assembly in which the plurality of reinforcing multifilamentary wires are assembled is arranged in the center, and a Sn-based filament assembly in which the plurality of Sn-based filaments are assembled is arranged on the periphery. ３ Precursor for Sn superconducting wire.

3. The Sn-based reinforcing element wire is ３ 3. The Sn superconducting wire precursor according to claim 2, further comprising a second Sn diffusion barrier layer formed between the reinforcing material multifilamentary wire assembly and the Sn-based filament assembly in a cross section perpendicular to the axial direction of the Sn superconducting wire precursor, the second Sn diffusion barrier layer being made of Ta or Nb metal or an alloy containing at least one of Ta and Nb. ３ Precursor for Sn superconducting wire.

4. The Nb according to any one of claims 1 to 3, wherein the reinforcing filaments are made of metals selected from Nb, Ta, Ti, V, W, Mo, Fe and Hf, or are made of alloys containing at least one element selected from Nb, Ta, Ti, V, W, Mo, Fe and Hf. ３ Precursor for Sn superconducting wire.

5. A superconducting element assembly comprising: a cylindrical stabilizing copper layer provided on the outer periphery; a cylindrical first Sn diffusion barrier layer provided inside the stabilizing copper layer; and a group of superconducting elements housed inside the first Sn diffusion barrier layer, wherein the group of superconducting elements comprises a plurality of reinforcing element wires and a plurality of Nb-based superconducting element wires, wherein the plurality of reinforcing element wires comprise a first stabilizing matrix made of Cu or a Cu-based alloy and a plurality of reinforcing multifilamentary wires embedded in the first stabilizing matrix and made of a plurality of reinforcing filaments made of a metal or an alloy, and wherein the plurality of Nb-based superconducting element wires comprise a second stabilizing matrix made of Cu or a Cu-based alloy and a plurality of reinforcing multifilamentary wires embedded in the second stabilizing matrix and made of Nb ３ and one or more superconducting filaments having a compound superconducting phase made of Sn, Nb ３ Sn superconducting wire.

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