Precursor wire for compound superconducting wires, compound superconducting wire, and method for rewinding compound superconducting wires

Abstract

This precursor wire (1) for a compound superconducting wire includes: a compound superconducting precursor section (10) configured from a plurality of compound superconducting precursor filaments (11) and a first matrix precursor (12) that includes a first stabilizing material and in which the compound superconducting precursor filaments are embedded; a reinforcing material section (30) configured from a plurality of reinforcing filaments (31) arranged on the outside of the compound superconducting precursor section and a second matrix (32) that includes a second stabilizing material and in which the reinforcing filaments are embedded; and a cylindrical stabilizing material section (40) that comprises a third stabilizing material and is arranged on at least one of the inner circumferential side and the outer circumferential side of the reinforcing material section. The aspect ratio Ab1(Wb1 / Tb1) of the width dimension Wb1 of the compound superconducting precursor section to the thickness dimension Tb1 in a cross section perpendicular to the lengthwise direction of the compound superconducting precursor section is 1.80 or more.

Description

[Technical Field]

[0001] This disclosure relates to a precursor wire for compound superconducting wires, compound superconducting wires, and a method for rewinding compound superconducting wires. [Background technology]

[0002] The manufacture of superconducting magnets using compound superconducting wires, such as Nb3Sn, typically employs the wind-and-react (W&R) method, which involves winding a precursor wire for the compound superconducting wire onto a superconducting coil bobbin and then performing a heat treatment to create the compound. This is because the compound superconducting wire obtained through heat treatment is extremely susceptible to strain.

[0003] When manufacturing large magnets, such as high-field, large-diameter magnets, using compound superconducting wires like Nb3Sn via the wind-and-react method, the compound formation heat treatment for Nb3Sn generation must be carried out in a furnace under vacuum or an inert gas atmosphere at a predetermined temperature of 600°C or higher, requiring the preparation of a large heat treatment apparatus appropriate to the magnet dimensions.

[0004] Another method is the React-and-Wind (R&W) method, which uses heat-treated compound superconducting wires such as Nb3Sn to wind coils. The React-and-Wind method has the advantage of providing flexibility in the selection of materials for electrical insulation on the surface of the compound superconducting wire and for coil components such as winding frames, as well as allowing adjustment of the strain on the compound superconducting wire after heat treatment.

[0005] However, since the superconducting properties of compound superconducting wires such as Nb3Sn change depending on the strain state of the wire, it is necessary to carefully consider the strain state of the compound superconducting wire. For example, if a compound superconducting wire is damaged by strain caused by an external force applied to it after heat treatment, or if it experiences compressive residual strain due to differences in thermal contraction of the composite materials during cooling, or if it experiences tensile or lateral compressive strain due to electromagnetic force during coil operation, the superconducting properties of the compound superconducting wire, such as the critical current, may decrease. To date, many technological developments have been carried out to address this issue.

[0006] For example, Patent Document 1 describes how to improve coil performance by forming a laminated conductor using a rectangular compound superconductor with magnetic field anisotropy of the critical current, thereby suppressing critical current anisotropy. However, since this does not improve the properties of the rectangular compound superconductor itself, the conductor design and the coil design using it are limited, making it difficult to achieve a significant improvement in critical current performance.

[0007] Furthermore, Patent Document 2 describes a method for suppressing the flattening of the filament when processing it into a rectangular shape by softening the copper alloy surrounding the filament and arranging alumina-dispersed copper tubes, thereby suppressing the magnetic field anisotropy of the critical current density. However, this technique does not improve the critical current density of the flattened filament itself.

[0008] Furthermore, Patent Document 3 discloses a processing method for obtaining a good filament shape in a rectangular wire.

[0009] The conventional technologies represented by the above-mentioned Patent Documents 1 to 3 concern conductor structures that take into account the magnetic field anisotropy of the critical current of compound superconducting wires having a rectangular shape, in order to prevent a decrease in the current-carrying characteristics of the coil, and structures and processing methods to suppress abnormal deformation of the superconducting parts inside the compound superconducting wire that occur when it is processed into a rectangular shape. In particular, these technologies do not provide sufficient effect when applied to superconducting coils wound using the react-and-wind method, in which winding is performed after the compound formation heat treatment. Therefore, in the react-and-wind method, it is necessary to take a large operating margin for the superconducting coil in consideration of the risk of a decrease in the performance of the superconducting coil, and the challenge is to suppress the increase in the amount of wire used and the increase in manufacturing costs.

[0010] Furthermore, Patent Documents 4-6 describe compound superconducting wires suitable for the react-and-wind method, as well as practical winding methods for adjusting bending strain during winding.

[0011] When applying the technologies described in Patent Documents 4-6 to actual coils and bending them to a small diameter, a method is employed to reduce the strain on the compound superconductor by reducing the outer diameter of the individual wires. As a result, the critical current per individual wire decreases, which can increase the length of the coil's wire winding while also increasing the coil's manufacturing time. Furthermore, in methods of twisting multiple small-diameter wires together to form a conductor, the number of twists increases, which increases the number of twists and can lower the critical current per unit cross-sectional area of ​​the entire twisted conductor, including the air gaps.

[0012] Furthermore, Non-Patent Document 1 describes the mechanism by which flattening compound superconducting wires causes superconducting properties such as critical current characteristics to exhibit anisotropy in external magnetic fields. Non-Patent Document 2 describes the anisotropy of wires with an aspect ratio of about 5 and proposes a conductor structure to avoid this anisotropy. Non-Patent Documents 3 and 4 also describe design examples and characteristics of compound superconducting wires applicable to coils wound using the react-and-wind method. However, these documents only mention that in order to obtain compound superconducting wires that satisfy the required characteristics of individual superconducting magnets, it is necessary to design them with a predetermined structure according to the required characteristics, manufacture them using a predetermined processing method, and use them in a predetermined manner. What these non-patent documents state is that by comprehensively optimizing the wire structure, manufacturing method, and usage method, it is possible to obtain compound superconducting wires that can be manufactured using the react-and-wind method with high reliability.

[0013] As described above, conventional compound superconducting wires proposed in Patent Documents 1-3 are conductor structures for mitigating the anisotropy of flat wires in external magnetic fields, or technologies for suppressing the flattening deformation of the superconducting part in order to suppress anisotropy. Non-Patent Documents 1-2 show characteristic data regarding the anisotropy of compound superconductors, but do not describe the characteristics when these technologies are applied to the react-and-wind method. Furthermore, while Patent Documents 4-6 and Non-Patent Documents 3-4 describe structures or their usage suitable for the react-and-wind method, they only disclose the technique of twisting multiple strands together in order to reduce the outer diameter in order to bend to a small diameter and increase the critical current. On the other hand, when compound superconducting wires without reinforcing materials are actually applied to magnet manufacturing using the react-and-wind method, the reliability of the wire itself is low, making it impossible to accurately predict the performance as a magnet. Therefore, it is necessary to design magnets with a high operational safety factor, which requires increasing the current capacity margin of the wires and increasing the wire length. This leads to larger coils and cooling systems, resulting in high costs, and thus has not yet been put into practical use on a commercial basis. [Preliminary Technology Documents] [License]

[0014] [License 1] Special Announcement No. 53-107296 [License 2] Special Announcement No. 4-298917 [License 3] Special Announcement No. 2007-173102 [License 4] Patent No. 5718171 [Patent Document 5] Patent No. 6155253 [License 6] Patent No. 6182577 [Non-licensed literature]

[0015] [Non-licensed Document 1] Tanaka Yoshiaki, "V3Ga composite processing crystal structure and critical current characteristics", Journal of the Japan Metal Society, Volume 40 (1976), 515-521 [Non-licensed Document 2] P. Kovac, et al., "Ic anisotropy in flattened Nb3Sn superconductors and possible ways for overcoming it", Cryogenics, 35(1995), 83-86 [Non-licensed Document 3] M. Sugimoto, et al., "Nb-Rod-Method Cu-Nb / Nb3Sn Wires for Practical React-and-Wind Applications", IEEE Trans. Appl. Super. Vol.28 No.3(2018)600011.0 [Non-licensed Document 4] M. Sugimoto, et al., "Performance of Polyvinyl Formal Insulated Cu-Nb / Nb3Sn Wires for React-and-Wind Process", IEEE Trans. Appl. Super. Vol.29 No.5(2019)6001205

Summary of the Invention

Problems to be Solved by the Invention

[0016] An object of the present disclosure is to provide a precursor wire for a compound superconducting wire, a compound superconducting wire, and a method for rewinding a compound superconducting wire that enable coil manufacturing on a commercial basis, have excellent winding properties for small diameters, and have a large critical current.

Means for Solving the Problems

[0017] [1] A compound superconducting precursor wire including a plurality of compound superconducting precursor filaments, a compound superconducting precursor part composed of the plurality of compound superconducting precursor filaments embedded in a first matrix precursor containing a first stabilizer, disposed on the outer peripheral side of the compound superconducting precursor part, a plurality of reinforcing filaments, and a cylindrical reinforcing part composed of the plurality of reinforcing filaments embedded in a second matrix containing a second stabilizer, and a cylindrical stabilizer part made of a third stabilizer disposed on at least one of the inner peripheral side and the outer peripheral side of the reinforcing part, wherein an aspect ratio Ab1 (Wb1 / Tb1) of a width dimension Wb1 of the compound superconducting precursor part to a thickness dimension Tb1 of the compound superconducting precursor part in a cross section perpendicular to the longitudinal direction of the compound superconducting precursor part is 1.80 or more. [2] The precursor wire for a compound superconducting wire according to [1] above, wherein the aspect ratio Ab1 is 11.00 or less. [3] The precursor wire for a compound superconducting wire according to [1] or [2] above, wherein the aspect ratio Ab1 is 2.00 or more and 10.00 or less. [4] In a cross section perpendicular to the longitudinal direction of the compound superconducting wire precursor, the sum of the cross-sectional area of ​​the compound superconducting precursor portion, the cross-sectional area of ​​the reinforcing material portion, and the cross-sectional area of ​​the stabilizing material portion is 0.40 mm². 2 4.00 mm 2 The following is a precursor wire for compound superconducting wires as described in any one of the above [1] to [3]. [5] The compound superconducting precursor wire according to any one of [1] to [4] above, wherein the compound superconducting precursor filament is Nb, and a Sn diffusion prevention portion made of Nb or Ta or an alloy or composite thereof is further provided between the compound superconducting precursor portion and the reinforcing material portion. [6] A precursor wire for compound superconducting wires according to any one of [1] to [5] above, wherein the first stabilizing material is copper or a copper alloy, the reinforcing filament is made of one metal selected from the group Nb, Ta, V, W, Mo, Fe, Ti, and Hf or an alloy composed of two or more metals, the second stabilizing material is copper or a copper alloy, and the third stabilizing material is copper or a copper alloy. [7] A compound superconducting wire comprising: a compound superconducting portion comprising a plurality of compound superconducting filaments containing a compound superconducting phase and a first matrix containing a first stabilizing material in which the plurality of compound superconducting filaments are embedded; a cylindrical reinforcing portion disposed on the outer circumference side of the compound superconducting portion and comprising a plurality of reinforcing filaments and a second matrix containing a second stabilizing material in which the plurality of reinforcing filaments are embedded; and a cylindrical stabilizing portion disposed on at least one of the inner and outer circumference sides of the reinforcing portion and comprising a third stabilizing material, wherein the aspect ratio Ab2(Wb2 / Tb2) of the width dimension Wb2 of the compound superconducting portion to the thickness dimension Tb2 of the compound superconducting portion in a cross section perpendicular to the longitudinal direction of the compound superconducting portion is 1.80 or more. [8] The compound superconducting wire according to [7] above, wherein the aspect ratio Ab2 is 11.00 or less. [9] The compound superconducting wire according to [7] or [8] above, wherein the aspect ratio Ab2 is 2.00 or more and 10.00 or less.

[10] In a cross section perpendicular to the longitudinal direction of the compound superconducting wire, the sum of the cross-sectional area of ​​the compound superconducting portion, the cross-sectional area of ​​the reinforcing material portion, and the cross-sectional area of ​​the stabilizing material portion is 0.40 mm². 2 4.00 mm 2 The following are compound superconducting wires as described in any one of the above [7] to [9]:

[11] The compound superconducting wire according to any one of [7] to

[10] above, wherein the compound superconducting phase is Nb3Sn, and further comprises a Sn diffusion prevention portion made of Nb or Ta or an alloy or composite thereof between the compound superconducting portion and the reinforcing portion.

[12] The compound superconducting wire according to any one of [7] to

[11] above, wherein the first stabilizing material is copper or a copper alloy, the reinforcing filament is made of one metal selected from the group Nb, Ta, V, W, Mo, Fe, Ti, and Hf or an alloy composed of two or more metals, the second stabilizing material is copper or a copper alloy, and the third stabilizing material is copper or a copper alloy.

[13] A compound superconducting wire according to any one of [7] to

[12] above, further comprising an electrical insulating portion containing resin on its outermost circumference.

[14] A method for rewinding a compound superconducting wire according to any one of [7] to

[13] above, wherein when rewinding the compound superconducting wire from a first winding member to a second winding member, the compound superconducting wire is extended from the first winding member in the tangential direction to the first winding member, and the compound superconducting wire is wound onto the second winding member while bending it in the same bending direction as when it was wound around the first winding member. [Effects of the Invention]

[0018] This disclosure provides a precursor wire and compound superconducting wire for compound superconducting wires that enable coil manufacturing on a commercial basis, have excellent winding properties for small diameters, and have a high critical current, as well as a method for rewinding compound superconducting wires. [Brief explanation of the drawing]

[0019] [Figure 1]Figure 1 is a cross-sectional view showing an example of a precursor wire for compound superconducting wires according to the embodiment. [Figure 2] Figure 2 is a cross-sectional view showing another example of a precursor wire for compound superconducting wires according to the embodiment. [Figure 3] Figure 3 is a cross-sectional view showing an example of a compound superconducting wire according to the embodiment. [Figure 4] Figure 4 is a cross-sectional view showing another example of a compound superconducting wire of the embodiment. [Figure 5] Figure 5 is a process flow illustrating a precursor wire for compound superconducting wires and a method for manufacturing superconducting coils using compound superconducting wires by the react-and-wind method according to an embodiment. [Figure 6] Figure 6 is a process flow illustrating a precursor wire for compound superconducting wires and a method for manufacturing superconducting coils using the wind-and-react method with compound superconducting wires according to an embodiment. [Figure 7] Figure 7 is a schematic diagram illustrating the rewinding method of a compound superconducting wire according to an embodiment. [Figure 8] Figure 8 is a graph showing the relationship between the critical current (non-Cu-Jc value) per unit cross-sectional area of ​​the compound superconductor portion (including the Sn diffusion prevention portion) and the aspect ratio Ab2 for compound superconducting wires obtained by the react-and-wind method and the wind-and-react method. [Figure 9] Figure 9 is a graph showing the critical current (non-Cu-Jc value) per unit cross-sectional area of ​​compound superconducting wires obtained by the react-and-wind method and the wind-and-react method, with respect to axial tensile stress of the wire. [Modes for carrying out the invention]

[0020] The following will provide a detailed explanation based on the embodiments.

[0021] The inventors of this invention have conducted extensive research to develop a material that can be bent to a small diameter and to increase the critical current per wire. As a result, by focusing on the structure of the compound superconducting precursor portion of the compound superconducting wire precursor and the compound superconducting portion of the compound superconducting wire, they have made it possible to manufacture coils on a commercial basis and have found that winding ability to small diameters and critical current are improved compared to conventional methods. Based on these findings, they have completed this disclosure.

[0022] The compound superconducting wire precursor wire of the embodiment has a compound superconducting precursor section composed of a plurality of compound superconducting precursor filaments and a first matrix precursor containing a first stabilizing material in which the plurality of compound superconducting precursor filaments are embedded; a cylindrical reinforcing material section disposed on the outer circumference side of the compound superconducting precursor section and composed of a plurality of reinforcing filaments and a second matrix containing a second stabilizing material in which the plurality of reinforcing filaments are embedded; and a cylindrical stabilizing material section disposed on at least one of the inner and outer circumference sides of the reinforcing material section and consisting of a third stabilizing material, wherein the aspect ratio Ab1(Wb1 / Tb1) of the width dimension Wb1 of the compound superconducting precursor section to the thickness dimension Tb1 of the compound superconducting precursor section in a cross section perpendicular to the longitudinal direction of the compound superconducting precursor section is 1.80 or more.

[0023] The compound superconducting wire of the embodiment has a compound superconductor portion composed of a plurality of compound superconducting filaments containing a compound superconducting phase and a first matrix containing a first stabilizing material in which the plurality of compound superconducting filaments are embedded; a cylindrical reinforcing material portion disposed on the outer circumference side of the compound superconducting portion and composed of a plurality of reinforcing filaments and a second matrix containing a second stabilizing material in which the plurality of reinforcing filaments are embedded; and a cylindrical stabilizing material portion disposed on at least one of the inner and outer circumference sides of the reinforcing material portion and composed of a third stabilizing material, wherein the aspect ratio Ab2(Wb2 / Tb2) of the width dimension Wb2 of the compound superconducting portion to the thickness dimension Tb2 of the compound superconducting portion in a cross section perpendicular to the longitudinal direction of the compound superconducting portion is 1.80 or more.

[0024] Figure 1 is a cross-sectional view showing an example of a precursor wire for a compound superconducting wire according to an embodiment. As shown in Figure 1, the precursor wire 1 for a compound superconducting wire has a compound superconducting precursor portion 10, a reinforcing material portion 30, and a stabilizing material portion 40.

[0025] The compound superconducting precursor section 10 constituting the compound superconducting wire precursor wire 1 is composed of a plurality of compound superconducting precursor filaments 11 and a first matrix precursor 12. The compound superconducting precursor section 10 is linear and extends along the longitudinal direction of the compound superconducting wire precursor wire 1. The first matrix precursor 12 has a plurality of compound superconducting precursor filaments 11 embedded in it and contains a first stabilizing material.

[0026] The compound superconducting precursor filament 11 becomes a compound superconducting filament 21 containing the compound superconducting phase by undergoing a heat treatment process to generate the compound superconducting phase, as described later. Since the compound superconducting phase constituting the compound superconducting wire 2, described later, is preferably a metallic compound superconducting phase formed of Nb3Sn, it is preferable that the compound superconducting precursor filament 11 is formed of Nb. Depending on the type of compound superconducting phase, the material constituting the compound superconducting precursor filament 11 is appropriately selected.

[0027] The first matrix precursor 12 containing the first stabilizing agent becomes the first matrix 22 containing the first stabilizing agent by undergoing a heat treatment process to generate a compound superconducting phase. The first matrix 22 containing the first stabilizing agent can suppress damage to the compound superconducting filament 21 in the compound superconducting wire 2, provide magnetic stabilization, and provide thermal stabilization. These effects are further enhanced if the first stabilizing agent constituting the first matrix precursor 12 is copper or a copper alloy.

[0028] Furthermore, since the compound superconducting phase is preferably a metallic compound superconducting phase formed of Nb3Sn, the first stabilizing material is preferably made of a Cu-Sn alloy. Depending on the type of compound superconducting phase constituting the compound superconducting wire 2, the material constituting the first stabilizing material is appropriately selected.

[0029] When the first stabilizer of the first matrix precursor 12 is a Cu-Sn alloy, the first stabilizer of the first matrix precursor 12 can contain up to 15.8 mass% (solid solubility limit) of Sn. In addition, the first stabilizer of the first matrix precursor 12 may contain small amounts of other elements other than Cu and Sn, and it is preferable to contain, for example, Ti in a range of 0.2 mass% to 0.3 mass%.

[0030] Figure 1 and Figures 2-4, described later, show an example of generating a compound superconducting phase of Nb3Sn by the bronze method. However, other methods, such as the internal tin method, may be applied to generate the compound superconducting phase of Nb3Sn. Furthermore, although an example where the compound superconducting phase is Nb3Sn is shown here, the compound superconducting phase may be a compound superconductor having superconducting properties that are more strain-sensitive compared to alloy superconductors such as NbTi.

[0031] The reinforcing material section 30 constituting the compound superconducting wire precursor wire 1 is cylindrical and is positioned on the outer circumference of the compound superconducting precursor section 10. The reinforcing material section 30 is composed of a plurality of reinforcing filaments 31 and a second matrix 32. The second matrix 32 embeds the plurality of reinforcing filaments 31 and includes a second stabilizing material.

[0032] The reinforcing filament 31 constituting the reinforcing material portion 30 is preferably made of one metal selected from the group consisting of Nb, Ta, V, W, Mo, Fe, Ti, and Hf, or an alloy composed of two or more metals. The reinforcing filament 31 may contain unavoidable impurities.

[0033] For example, if the reinforced filament 31 mainly contains Nb, unavoidable impurities may include, for example, O at 150 ppm or less, H at 15 ppm or less, C at 100 ppm or less, N at 100 ppm or less, Fe at 50 ppm or less, Ni at 50 ppm or less, Ti at 20 ppm or less, Si at 50 ppm or less, W at 300 ppm or less, and Ta at 1000 ppm or less. Also, if the reinforced filament 31 mainly contains Ta, unavoidable impurities may include O, H, C, N, Fe, Ni, Ti, Si, W, Nb, and Mo.

[0034] These metals or alloys constituting the reinforced filament 31 do not readily dissolve in Cu during the heat treatment process for generating the compound superconducting phase, thus making it difficult for compounds with Cu to form, and effectively contributing to the improvement of bending strain characteristics. Among these, considering the effect on the compound superconducting wire 2, the reinforced filament 31 is preferably made of one metal selected from the group of Nb, Ta, V, W, Mo, and Hf that does not exhibit ferromagnetism, or an alloy composed of two or more metals. Furthermore, from the viewpoint of processability, it is preferable that the reinforced filament 31 is made of one metal selected from the group of Nb, Ta, and V, or an alloy composed of two or more metals.

[0035] Furthermore, the alloy composed of two or more metals selected from the above group of elements that constitute the reinforcing filament 31 is preferably an Nb-Ta alloy in that it has excellent composite machinability with copper or copper alloys. Furthermore, the alloy composed of a metal selected from the above group of elements and copper is preferably a Cu-Nb alloy or a Cu-V alloy in that it has excellent composite machinability with copper or copper alloys.

[0036] The above statement that it is difficult to dissolve in Cu means that in the heat treatment process for generating the compound superconducting phase (for example, 600°C to 750°C), the proportion of the metal or alloy constituting the reinforced filament 31 that dissolves in Cu is less than 1 at%.

[0037] As described above, in the reinforcing material section 30, multiple reinforcing filaments 31 made of a metallic material that does not easily dissolve in Cu are embedded in the second matrix 32. Therefore, the formation of intermetallic compounds in the reinforcing filaments 31 within the reinforcing material section 30 can be suppressed, and the reinforcing material section 30 can function as a high-strength component that is resistant to tensile and bending strains.

[0038] The second stabilizing material constituting the second matrix 32 of the reinforcing material section 30 is preferably copper or a copper alloy. The second stabilizing material may contain unavoidable impurities. Examples of unavoidable impurities in the second stabilizing material include O, Fe, S, and Bi. The second matrix 32, including the second stabilizing material, can provide the reinforcing material section 30 with a stabilizing function in addition to its reinforcing function.

[0039] The stabilizing material portion 40 constituting the compound superconducting wire precursor wire 1 is cylindrical and is arranged on at least one of the inner and outer circumferences of the reinforcing material portion 30. The stabilizing material portion 40 is made of a third stabilizing material. Figure 1 and Figures 2 to 4 described later show an example in which the stabilizing material portion 40 is arranged on both the inner and outer circumferences of the reinforcing material portion 30. The stabilizing material portion 40 can suppress abnormal deformation of the reinforcing material portion 30 during processing and provide a stabilizing function.

[0040] The third stabilizing material constituting the stabilizing material section 40 is preferably copper or a copper alloy, and more preferably oxygen-free copper. The third stabilizing material may contain unavoidable impurities. Examples of unavoidable impurities in the third stabilizing material include O, Fe, S, and Bi.

[0041] Furthermore, as described above, the compound superconducting wire precursor wire 1 uses a first stabilizing material constituting the compound superconducting precursor section 10, a second stabilizing material constituting the reinforcing material section 30, and a third stabilizing material constituting the stabilizing material section 40. The stabilizing material referred to here is a generally metallic material that ensures thermal contact with a coolant and / or is electrically and / or thermally contacted with the superconductor to act as an electrical shunt circuit, as defined in JIS H 7005:2005, and is a normal conducting metallic material that is compounded with the superconductor to increase the stability of the superconductor. Specifically, normal conducting metals such as copper and aluminum have low resistivity at extremely low temperatures and good thermal conductivity, so when used as the matrix of a superconducting wire, even if there is a transition from the superconducting state to the normal conducting state, the current bypasses and flows through these normal conducting metals. As a result, in the compound superconducting wire 2 described later, heat generation is suppressed, and the generated heat is quickly propagated and diffused, resulting in cooling. Furthermore, ordinary conducting metals such as copper and aluminum, which dampen external magnetic flux fluctuations and prevent them from being directly transmitted to the superconductor, are widely used as stabilizing materials for superconducting wires.

[0042] When the compound superconducting precursor filament 11 of the compound superconducting precursor portion 10 is an Nb3Sn precursor, that is, when the compound superconducting precursor filament 11 is Nb, it is preferable that the precursor wire 1 for compound superconducting wire further has a Sn diffusion prevention portion 50 made of Nb or Ta or an alloy or composite material thereof between the compound superconducting precursor portion 10 and the reinforcing material portion 30.

[0043] The Sn diffusion prevention section 50 prevents Sn in the Cu-Sn alloy constituting the first matrix precursor 12 for forming Nb3Sn filaments in the compound superconductor section 20 from diffusing into the reinforcing material section 30 and the stabilizing material section 40 during the heat treatment process for generating the compound superconducting section described later. It also suppresses a decrease in the residual resistance ratio of the second stabilizing material constituting the reinforcing material section 30 and the third stabilizing material constituting the stabilizing material section 40, and has the function of retaining in the Cu-Sn alloy the amount of Sn necessary to react with the Nb filament of the compound superconducting precursor filament 11 to generate Nb3Sn.

[0044] Regarding the compound superconducting precursor portion 10 constituting the compound superconducting wire precursor wire 1, as shown in Figure 1, the aspect ratio Ab1(Wb1 / Tb1) of the width dimension Wb1 of the compound superconducting precursor portion 10 to the thickness dimension Tb1 of the compound superconducting precursor portion 10 in a cross section perpendicular to the longitudinal direction of the compound superconducting precursor portion 10 is 1.80 or greater.

[0045] Here, since the compound superconducting precursor portion 10 extends along the longitudinal direction of the compound superconducting wire precursor wire 1, the longitudinal direction of the compound superconducting precursor portion 10 is the same as the longitudinal direction of the compound superconducting wire precursor wire 1. Also, as shown in Figure 1, in a cross-section perpendicular to the longitudinal direction of the compound superconducting precursor portion 10, i.e., in the cross-section of the compound superconducting precursor portion 10, the thickness dimension Tb1 of the compound superconducting precursor portion 10 is smaller than the width dimension Wb1 of the compound superconducting precursor portion 10.

[0046] Furthermore, in the cross-section of the compound superconducting precursor portion 10, the thickness dimension Tb1 of the compound superconducting precursor portion 10 is the maximum thickness dimension of the compound superconducting precursor portion 10 when the precursor wire 1 for compound superconducting wire does not have an Sn diffusion prevention portion 50, and when the precursor wire 1 for compound superconducting wire does have an Sn diffusion prevention portion 50, it is the maximum thickness dimension of the combined area of ​​the compound superconducting precursor portion 10 and the Sn diffusion prevention portion 50.

[0047] Furthermore, in the cross-section of the compound superconducting precursor portion 10, the width dimension Wb1 of the compound superconducting precursor portion 10 is the maximum width dimension of the compound superconducting precursor portion 10 when the precursor wire 1 for compound superconducting wire does not have an Sn diffusion prevention portion 50, and when the precursor wire 1 for compound superconducting wire does have an Sn diffusion prevention portion 50, it is the maximum width dimension of the combined area of ​​the compound superconducting precursor portion 10 and the Sn diffusion prevention portion 50.

[0048] If the aspect ratio Ab1 (Wb1 / Tb1) is 1.80 or higher, a compound superconductor 20 with a high aspect ratio is generated by subjecting the compound superconductor precursor wire 1, which has a compound superconductor precursor 10 with a high aspect ratio, to a heat treatment process for generating a compound superconducting phase, as described later. A compound superconductor 2 having a compound superconductor 20 with a high aspect ratio can maintain a higher critical current than a compound superconductor having a compound superconductor having an aspect ratio Ab2 of less than 1.80 with the same cross-sectional area as the compound superconductor 20. In particular, a compound superconductor 2 having a compound superconductor 20 with a high aspect ratio can maintain an even higher critical current than a compound superconductor having a compound superconductor having an aspect ratio Ab2 of less than 1.80, because it can suppress the decrease in current-carrying characteristics due to distortion when bent to a small diameter in coil winding using the react-and-wind method. As a result, high-performance, small-diameter superconducting coils can be manufactured. For this reason, the aspect ratio Ab1(Wb1 / Tb1) is 1.80 or higher, preferably 2.00 or higher, and more preferably 3.00 or higher.

[0049] Furthermore, the aspect ratio Ab1(Wb1 / Tb1) is preferably 11.00 or less, more preferably 10.50 or less, even more preferably 10.00 or less, particularly preferably 9.00 or less, and most preferably 8.00 or less. When the aspect ratio Ab1(Wb1 / Tb1) is 11.00 or less, the critical current of the compound superconducting wire 2 obtained by subjecting the precursor wire 1 for compound superconducting wires to a heat treatment process for generating a compound superconducting phase is further improved.

[0050] In a cross-section perpendicular to the longitudinal direction of the compound superconducting wire precursor wire 1, the sum of the cross-sectional area of ​​the compound superconducting precursor portion 10, the cross-sectional area of ​​the reinforcing material portion 30, and the cross-sectional area of ​​the stabilizing material portion 40 is 0.40 mm². 2 4.00 mm 2The following is preferable. When the total cross-sectional area is within the above range, winding performance to small diameters is excellent and the critical current can be improved. Here, the cross-sectional area of ​​the compound superconducting precursor portion 10 is the cross-sectional area of ​​the compound superconducting precursor portion 10 when the precursor wire 1 for compound superconducting wire does not have an Sn diffusion prevention portion 50, and when the precursor wire 1 for compound superconducting wire does have an Sn diffusion prevention portion 50, it is the sum of the cross-sectional area of ​​the compound superconducting precursor portion 10 and the cross-sectional area of ​​the Sn diffusion prevention portion 50.

[0051] In Figure 1, T11 is the maximum thickness dimension of the compound superconducting wire precursor wire 1. W11 is the maximum width dimension of the compound superconducting wire precursor wire 1. W01 is the length of the widthwise flat portion in the outermost layer of the compound superconducting wire precursor wire 1.

[0052] Figure 2 is a cross-sectional view showing another example of a compound superconducting wire precursor wire of the embodiment. T01 is the length of the thickness-direction flat portion in the outermost layer of the compound superconducting wire precursor wire 1. The compound superconducting wire precursor wire 1 shown in Figure 2 has basically the same configuration as the compound superconducting wire precursor wire 1 shown in Figure 1, except that it has T01. For example, in the compound superconducting wire precursor wire 1 shown in Figure 1, the cross-sectional shapes of the compound superconducting wire precursor wire 1 and the compound superconducting precursor portion 10 are such that a pair of opposing sides in the width direction are straight (approximately parallel), and a pair of opposing sides in the thickness direction are arc-shaped. Also, in the compound superconducting wire precursor wire 1 shown in Figure 2, the cross-sectional shapes of the compound superconducting wire precursor wire 1 and the compound superconducting precursor portion 10 are such that a pair of opposing sides in the width direction are straight (approximately parallel), a pair of opposing sides in the thickness direction are straight (approximately parallel), and all corners are arc-shaped.

[0053] Next, the compound superconducting wire of the embodiment will be described. Figure 3 is a cross-sectional view showing an example of the compound superconducting wire of the embodiment. As shown in Figure 3, the compound superconducting wire 2 has a compound superconductor portion 20, a reinforcing material portion 30, and a stabilizing material portion 40. The compound superconducting wire 2 can be obtained by subjecting the compound superconducting wire precursor wire 1 to a heat treatment process described later. Specifically, the compound superconducting wire 2 shown in Figure 3 can be obtained by subjecting the compound superconducting wire precursor wire 1 shown in Figure 1 to a heat treatment process.

[0054] The compound superconductor portion 20 constituting the compound superconducting wire 2 is composed of a plurality of compound superconducting filaments 21 containing a compound superconducting phase and a first matrix 22. The compound superconducting portion 20 is linear and extends along the longitudinal direction of the compound superconducting wire 2. The first matrix 22 embeds the plurality of compound superconducting filaments 21 and contains a first stabilizing material.

[0055] The compound superconducting phase is preferably a metallic compound superconducting phase formed of Nb3Sn. However, the compound superconducting phase is not limited to Nb3Sn, and may be formed of, for example, Nb3Al or other metallic compound superconducting phases having superconducting properties.

[0056] The first matrix 22, which includes the first stabilizing material, can provide effects such as suppressing damage to the compound superconducting filament 21, magnetic stabilization, and thermal stabilization in the compound superconducting wire 2. These effects are further enhanced if the first stabilizing material constituting the first matrix 22 is copper or a copper alloy.

[0057] Since the compound superconducting phase is preferably a metallic compound superconducting phase formed of Nb3Sn, the first stabilizing material is preferably made of a Cu-Sn alloy. Furthermore, the material constituting the first stabilizing material is appropriately selected depending on the type of compound superconducting phase.

[0058] When the first stabilizing material of the first matrix 22 is a Cu-Sn alloy, the Sn content in the first matrix 22 is smaller than the Sn content in the first matrix precursor 12 that constitutes the compound superconducting wire precursor wire 1. As a result of the Sn in the Cu-Sn alloy being used to produce the Nb3Sn filament as the compound superconducting filament 21, even if the Sn content in the first matrix 22 decreases to about 1.0 mass% to 2.0 mass%, the first matrix 22 does not function as a stabilizing material equivalent to Cu.

[0059] Figure 3 shows the compound superconductor section 20 manufactured by the bronze method. In the bronze method, when a compound superconducting wire precursor wire 1, in which multiple Nb filaments, which are compound superconducting precursor filaments 11, are embedded in a first matrix precursor 12 of a Cu-Sn alloy, which is the first stabilizing material, is subjected to a heat treatment process to generate a compound superconducting phase, Sn in the first matrix precursor 12 diffuses and reacts with the surface of the Nb filaments, thereby generating Nb3Sn filaments, which are compound superconducting filaments 21, from the Nb filaments.

[0060] Furthermore, the enlarged views of the compound superconductor portion 20 shown in Figure 3 and Figure 4 (described later) show an example in which an unreacted core portion 23 of Nb that remained unreacted with Sn exists. However, depending on the amount of Sn contained in the first matrix precursor 12 of the compound superconducting wire precursor 1, and the diameter size of the compound superconducting precursor filament 11 of the compound superconducting wire precursor 1, the unreacted core portion 23 may not be present in the compound superconducting filament 21 of the compound superconducting portion 20, and the compound superconducting filament 21 may consist of Nb3Sn.

[0061] The reinforcing material section 30 constituting the compound superconducting wire 2 is cylindrical and is positioned on the outer circumference of the compound superconducting section 20. The reinforcing material section 30 is composed of a plurality of reinforcing filaments 31 and a second matrix 32. The second matrix 32 embeds the plurality of reinforcing filaments 31 and includes a second stabilizing material.

[0062] The reinforcing material portion 30 constituting the compound superconducting wire 2 has basically the same structure and function as the reinforcing material portion 30 constituting the compound superconducting wire precursor wire 1. Similar to the compound superconducting wire precursor wire 1, the reinforcing filament 31 is preferably made of one metal selected from the group of Nb, Ta, V, W, Mo, Fe, Ti, and Hf, or an alloy composed of two or more metals. Similarly, the second stabilizing material constituting the second matrix 32 is preferably copper or a copper alloy.

[0063] The stabilizing material portion 40 constituting the compound superconducting wire 2 is cylindrical and is arranged on at least one of the inner and outer circumferences of the reinforcing material portion 30. The stabilizing material portion 40 is made of a third stabilizing material. Figure 3 shows an example in which the stabilizing material portion 40 is arranged on both the inner and outer circumferences of the reinforcing material portion 30. The stabilizing material portion 40 can suppress abnormal deformation of the reinforcing material portion 30 during processing and provide a stabilizing function.

[0064] The stabilizing material portion 40 constituting the compound superconducting wire 2 has basically the same configuration and function as the stabilizing material portion 40 constituting the precursor wire 1 for compound superconducting wires. Similar to the precursor wire 1 for compound superconducting wires, the third stabilizing material constituting the stabilizing material portion 40 is preferably copper or a copper alloy, and more preferably oxygen-free copper.

[0065] Furthermore, as described above, the compound superconducting wire 2 uses a first stabilizing material constituting the compound superconducting section 20, a second stabilizing material constituting the reinforcing material section 30, and a third stabilizing material constituting the stabilizing material section 40. A stabilizing material is a generally metallic material that, as defined in JIS H 7005:2005, ensures thermal contact with a coolant and / or is electrically and / or thermally contacted with the superconductor to act as an electrical shunt circuit, and is compounded with a superconductor to increase the stability of the superconductor. Specifically, normal conducting metals such as copper and aluminum have low resistivity at extremely low temperatures and good thermal conductivity, so when used as the matrix of a superconducting wire, even if there is a transition from the superconducting state to the normal conducting state, the current bypasses and flows through these normal conducting metals. As a result, heat generation is suppressed in the compound superconducting wire 2, and the generated heat is quickly propagated and diffused for cooling. Furthermore, ordinary conducting metals such as copper and aluminum, which dampen external magnetic flux fluctuations and prevent them from being directly transmitted to the superconductor, are widely used as stabilizing materials for superconducting wires.

[0066] When the compound superconducting phase of the compound superconducting portion 20 is Nb3Sn, it is preferable that the compound superconducting wire 2 further has an Sn diffusion prevention portion 50 made of Nb or Ta or an alloy or composite material thereof between the compound superconducting portion 20 and the reinforcing material portion 30. The Sn diffusion prevention portion 50 constituting the compound superconducting wire 2 has basically the same configuration and function as the Sn diffusion prevention portion 50 constituting the precursor wire 1 for compound superconducting wires.

[0067] Figure 4 is a cross-sectional view showing another example of the compound superconducting wire of the embodiment. As shown in Figure 4, the compound superconducting wire 2 may further have an electrical insulating portion 60 containing resin on its outermost circumference. The compound superconducting wire 2 shown in Figure 4 has basically the same configuration as the compound superconducting wire 2 shown in Figure 3, except that it has an electrical insulating portion 60 and T02 which will be described later. For example, in the compound superconducting wire 2 shown in Figure 3, the cross-sectional shapes of the compound superconducting wire 2 and the compound superconducting portion 20 are such that a pair of opposing sides in the width direction are straight (approximately parallel), and a pair of opposing sides in the thickness direction are arc-shaped. Also, in the compound superconducting wire 2 shown in Figure 4, the cross-sectional shapes of the compound superconducting wire 2 and the compound superconducting portion 20 are such that a pair of opposing sides in the width direction are straight (approximately parallel), a pair of opposing sides in the thickness direction are straight (approximately parallel), and all corners are arc-shaped.

[0068] In the method for manufacturing compound superconducting wire 2 by the react-and-wind method, as described later, an insulating coating step is performed to form the electrical insulating portion 60 after the heat treatment step to generate the compound superconducting phase. Therefore, the electrical insulating portion 60 of the compound superconducting wire 2 manufactured by the react-and-wind method is composed of insulating materials such as low-melting-point resin in addition to insulating materials such as high-melting-point glass.

[0069] On the other hand, in the manufacturing method of compound superconducting wire 2 by the wind-and-react method, as described later, a heat treatment step is performed to generate the compound superconducting phase after the insulating coating step that forms the electrical insulating portion 60. The electrical insulating portion 60 must retain its electrical insulating properties even after the heat treatment step. Low-melting-point materials such as resins are thermally decomposed in the heat treatment step. Therefore, the electrical insulating portion 60 of compound superconducting wire 2 manufactured by the wind-and-react method is composed of an insulating material such as glass with a high melting point.

[0070] In terms of excellent winding properties for small diameters and electrical insulation, and improving critical current, the resin constituting the electrical insulating part 60 is preferably an enamel or epoxy resin such as polyvinyl formal resin, polyamide-imide resin, or polyimide resin.

[0071] Regarding the compound superconductor portion 20 constituting the compound superconducting wire 2, as shown in Figures 3-4, the aspect ratio Ab2(Wb2 / Tb2) of the width dimension Wb2 of the compound superconducting portion 20 to the thickness dimension Tb2 of the compound superconducting portion 20 in a cross section perpendicular to the longitudinal direction of the compound superconducting portion 20 is 1.80 or greater.

[0072] Here, since the compound superconductor portion 20 extends along the longitudinal direction of the compound superconductor wire 2, the longitudinal direction of the compound superconductor portion 20 is the same as the longitudinal direction of the compound superconductor wire 2. Also, as shown in Figures 3-4, in a cross-section perpendicular to the longitudinal direction of the compound superconductor portion 20, i.e., in the cross-section of the compound superconductor portion 20, the thickness dimension Tb2 of the compound superconductor portion 20 is smaller than the width dimension Wb2 of the compound superconductor portion 20.

[0073] Furthermore, in the cross-section of the compound superconductor portion 20, the thickness dimension Tb2 of the compound superconductor portion 20 is the maximum thickness dimension of the compound superconductor portion 20 when the compound superconducting wire 2 does not have an Sn diffusion prevention portion 50, and when the compound superconducting wire 2 has an Sn diffusion prevention portion 50, it is the maximum thickness dimension of the combined area of ​​the compound superconductor portion 20 and the Sn diffusion prevention portion 50.

[0074] Furthermore, in the cross-section of the compound superconductor portion 20, the width dimension Wb2 of the compound superconductor portion 20 is the maximum width dimension of the compound superconductor portion 20 when the compound superconducting wire 2 does not have an Sn diffusion prevention portion 50, and when the compound superconducting wire 2 has an Sn diffusion prevention portion 50, it is the maximum width dimension of the combined area of ​​the compound superconductor portion 20 and the Sn diffusion prevention portion 50.

[0075] When the aspect ratio Ab2(Wb2 / Tb2) is 1.80 or higher, the compound superconductor portion 20 has a high aspect ratio. A compound superconducting wire 2 equipped with a compound superconducting portion 20 with a high aspect ratio can maintain a higher critical current than a compound superconducting wire equipped with a compound superconducting portion having an aspect ratio Ab2 of less than 1.80 with the same cross-sectional area as the compound superconducting portion 20. In particular, a compound superconducting wire 2 with an aspect ratio Ab2 of 1.80 or higher can suppress the deterioration of current-carrying characteristics due to distortion when bent to a small diameter during coil winding using the react-and-wind method, and thus can maintain an even higher critical current. As a result, high-performance small-diameter superconducting coils can be manufactured. For these reasons, the aspect ratio Ab2(Wb2 / Tb2) is 1.80 or higher, preferably 2.00 or higher, and more preferably 3.00 or higher.

[0076] Furthermore, the aspect ratio Ab2(Wb2 / Tb2) is preferably 11.00 or less, more preferably 10.50 or less, even more preferably 10.00 or less, particularly preferably 9.00 or less, and most preferably 8.00 or less. When the aspect ratio Ab2(Wb2 / Tb2) is 11.00 or less, the critical current of the compound superconducting wire 2 is further improved.

[0077] In a cross-section perpendicular to the longitudinal direction of the compound superconducting wire 2, the sum of the cross-sectional areas of the compound superconducting portion 20, the reinforcing portion 30, and the stabilizing portion 40 is 0.40 mm². 2 4.00 mm 2 The following is preferable. When the total cross-sectional area is within the above range, winding performance to small diameters is excellent and the critical current can be improved. Here, the cross-sectional area of ​​the compound superconductor portion 20 is the cross-sectional area of ​​the compound superconductor portion 20 when the compound superconductor wire 2 does not have an Sn diffusion prevention portion 50, and when the compound superconductor wire 2 has an Sn diffusion prevention portion 50, it is the sum of the cross-sectional area of ​​the compound superconductor portion 20 and the cross-sectional area of ​​the Sn diffusion prevention portion 50.

[0078] In Figures 3-4, T12 is the maximum thickness dimension of the compound superconducting wire 2 excluding the electrical insulation portion 60. W12 is the maximum width dimension of the compound superconducting wire 2 excluding the electrical insulation portion 60. T02 is the length of the thickness-direction flat portion of the outermost layer of the compound superconducting wire 2 excluding the electrical insulation portion 60. W02 is the length of the width-direction flat portion of the outermost layer of the compound superconducting wire 2 excluding the electrical insulation portion 60.

[0079] Figure 5 is a process flow diagram illustrating a method for manufacturing a superconducting coil using the react-and-wind method with a compound superconducting wire precursor wire 1 and a compound superconducting wire 2 according to the embodiment. The method for manufacturing a superconducting coil using the react-and-wind method mainly comprises a compound superconducting wire precursor wire 1 formation step S11, a heat treatment step S12, a pre-bending strain application step S13, an insulation coating step S14, and a winding step S15. Here, an example is described in which the compound superconducting phase is Nb3Sn and the manufacturing method is the bronze method.

[0080] In the formation process S11, a precursor wire 1 for compound superconducting wires is formed. Forming process S11 involves extruding a billet formed by sequentially arranging a compound superconducting precursor section, which consists of a compound superconducting precursor section composed of multiple Nb filaments, which are compound superconducting precursor filaments, and a first matrix precursor made of a Cu-Sn alloy in which multiple Nb filaments are embedded, and a Sn diffusion prevention section, a reinforcing section, and a stabilizing section on the outer circumference of the compound superconducting precursor section, followed by wire drawing, thereby forming the precursor wire 1 for compound superconducting wires.

[0081] For the formation step S11, if the compound superconducting phase is Nb3Sn, in addition to the bronze method described above, known methods for producing Nb3Sn wires, such as the internal tin diffusion method or the powdery tube method, can be applied.

[0082] In the heat treatment step S12, the precursor wire 1 for compound superconducting wire obtained in the formation step S11 is heated to generate a compound superconducting phase and form a compound superconducting wire 2.

[0083] The pre-bending strain application step S13 involves bending the compound superconducting wire 2 obtained in the heat treatment step S12 to apply a predetermined bending strain. In the pre-bending strain application step S13, which repeatedly applies bending strain to the compound superconducting wire 2, the bending direction of the compound superconducting wire 2 is maintained by controlling the bending direction, bending diameter, and tensile stress. As a result, the residual strain distribution within the cross-section is continuously maintained along the longitudinal direction of the compound superconducting wire 2. Therefore, the strength of the stabilizing material located near the neutral line of the bending becomes smaller than the strength of the stabilizing material located on the outside or inside of the bending direction that receives the bending strain. If the difference is significant, it can be detected by micro-Vickers hardness testing. By controlling the direction of maintaining the bending direction of the compound superconducting wire 2 to be the same as the springback direction (the direction in which it tries to return to its original shape) on the bending direction side during heat treatment, more specifically, on the side in which it is wound in an arc shape on the heat treatment bobbin, it is possible to prevent the compound superconducting filament from breaking due to reverse bending strain exceeding the allowable limit being applied not only in the pre-bending strain application step S13 but also in subsequent steps. The allowable strain limit at which the compound superconducting filament breaks varies depending on the superconductor material, the cross-sectional structure of the compound superconducting wire, the heat treatment conditions, the pre-bending strain application conditions, etc.

[0084] Furthermore, if the bending strain applied during the formation of the electrical insulation portion in the insulating coating process S14 alone is sufficient to increase the critical current of the compound superconducting wire 2 compared to before the electrical insulation portion was coated, the pre-bending strain application process S13 can be omitted.

[0085] In the insulation coating step S14, an electrical insulating portion is formed on the outermost circumference of the compound superconducting wire 2, and the outermost circumference of the compound superconducting wire 2 is covered with the electrical insulating portion. In the insulation coating step S14, it is preferable that the maximum temperature of the compound superconducting wire 2 when the electrical insulating portion is formed is less than 500°C. Furthermore, it is preferable that the maximum bending strain applied to the compound superconducting wire 2 is less than the bending strain applied in the pre-bending strain application step S13. Also, it is preferable that the tensile strain is 0.2% or less. When the insulation coating step S14 is carried out under these conditions, the critical current of the compound superconducting wire 2 with the electrical insulating portion may increase compared to the compound superconducting wire 2 before the electrical insulating portion is applied.

[0086] The winding process S15 involves winding the compound superconducting wire 2 onto a coil winding frame (winding member) while limiting the bending strain applied to the wire to form a superconducting coil.

[0087] The maximum strain experienced by the compound superconducting filament constituting compound superconducting wire 2 can be discussed by adding the maximum tensile bending strain due to the bending diameter and the tensile strain due to axial tension applied during winding. In other words, the maximum strain experienced by the compound superconducting filament must not exceed the strain at which filament damage occurs. In particular, it is necessary to control the maximum strain applied when bending in the opposite direction to the bending direction during heat treatment. Furthermore, the operating current of the superconducting magnet is determined by considering the superconducting properties under the maximum pure bending strain experienced by the compound superconducting filament.

[0088] Figure 6 is a process flow diagram illustrating a method for manufacturing a superconducting coil using the wind-and-react method with a compound superconducting wire precursor wire 1 and a compound superconducting wire 2 according to the embodiment. The method for manufacturing a superconducting coil using the wind-and-react method mainly comprises a compound superconducting wire precursor wire 1 formation step S21, an insulation coating step S22, a winding step S23, and a heat treatment step S24. Here, an example is described in which the compound superconducting phase is Nb3Sn and the manufacturing method is the bronze method.

[0089] In formation step S21, a precursor wire 1 for compound superconducting wires is formed. Formation step S21 is basically the same as formation step S11 described above.

[0090] In the insulating coating step S22, an electrical insulating portion 60 is formed on the outermost circumference of the compound superconducting wire precursor wire 1, thereby covering the outermost circumference of the compound superconducting wire precursor wire 1 with the electrical insulating portion. In the insulating coating step S22, it is preferable that the maximum temperature of the compound superconducting wire precursor wire 1 during the formation of the electrical insulating portion is less than 500°C.

[0091] The winding process S23 involves winding the precursor wire 1 for compound superconducting wire onto a coil reel while limiting the bending strain applied to it.

[0092] In the heat treatment step S24, the precursor wire 1 for compound superconducting wire, which has been wound onto a coil bobbin, is heated to generate a compound superconducting phase and form a compound superconducting wire 2. In this way, a superconducting coil can be manufactured. Note that if the electrical insulating layer coated on the precursor wire 1 for compound superconducting wire in the insulating coating step S22 is a low-melting-point material such as resin, the electrical insulating layer will be thermally decomposed in the heat treatment step S24. Therefore, the electrical insulating layer is often made of an insulating material such as glass with a high melting point.

[0093] Figure 7 is a schematic diagram illustrating the rewinding method of a compound superconducting wire according to an embodiment. When rewinding the compound superconducting wire 2 from the first winding member 71 to the second winding member 74, the compound superconducting wire 2 is extended from the first winding member 71 in the tangential direction to the first winding member 71, and the compound superconducting wire 2 is wound onto the second winding member 74 while bending it in the same bending direction as when it was wound on the first winding member 71. For example, as shown in Figure 7, the compound superconducting wire 2 is rewinded from the first winding member 71 with a diameter Dh, for example, a heat treatment bobbin, via a forward bending pulley 72 with a diameter D1 and a reverse bending pulley 73 with a diameter D2, to the second winding member 74 with a diameter D3, for example, a coil winding frame for forming a superconducting coil. Regarding the pre-bending strain application conditions, an example is shown combining one forward bending pulley 72 and one reverse bending pulley 73. However, the number of forward bending pulleys 72 and reverse bending pulleys 73 is not particularly limited, and multiple forward bending pulleys 72 and reverse bending pulleys 73 may be combined. In this case, the compound superconducting wire 2 is unwound from the first winding member 71 in the tangential direction to the first winding member 71, and then wound onto the second winding member 74 while bending the compound superconducting wire 2 in the same bending direction as when it was wound on the first winding member 71. This rewinding method is suitable for rewinding compound superconducting wire obtained by the react-and-wind method.

[0094] Thus, the compound superconducting wire 2 obtained by heat-treating the precursor wire 1 for compound superconducting wires has superior superconducting properties compared to conventional compound superconducting wires, such as a large critical current even when bent to a small diameter. In particular, in the manufacturing of superconducting coils that have a heat treatment process by the react-and-wind method, a pre-bending strain application process, and an insulation coating process, the internal strain of the compound superconductor part is controlled, so by controlling the winding direction on the coil winding bobbin (heat-treated bobbin), damage to the compound superconducting wire 2 during manufacturing can be further suppressed, and even better current-carrying properties can be obtained when the manufactured superconducting magnet is operated. Furthermore, by setting the composition ratio of the constituent members such as the compound superconductor part 20, reinforcing material part 30, and stabilizing material part 40 that make up the compound superconducting wire 2 according to the application of the superconducting coil, it is possible to achieve more practical superconducting coil manufacturing. As a result, it becomes possible to realize superconducting magnets designed with a more appropriate operating safety factor, thereby reducing the total cost of manufacturing superconducting coils, including the precursor wire 1 and compound superconducting wire 2, compared to conventional methods.

[0095] According to the embodiments described above, by having a predetermined structure for the compound superconducting precursor portion of the compound superconducting wire precursor and the compound superconductor portion of the compound superconducting wire, it is possible to achieve superior winding performance to smaller diameters and larger critical current characteristics compared to conventional designs, thereby streamlining the design and manufacture of superconducting coils.

[0096] Although embodiments have been described above, the present invention is not limited to the embodiments described above, and includes all aspects included in the concepts and claims of this disclosure, and can be modified in various ways within the scope of this disclosure. [Examples]

[0097] Examples and comparative examples will be described next, but this disclosure is not limited to these examples.

[0098] (Examples 1A-4A, Examples 1B-4B, Comparative Examples 1a-4a, Comparative Examples 1b-4b) A compound superconducting wire was manufactured in which the compound superconductor portion is Nb3Sn formed by the bronzing process, a Sn diffusion prevention portion made of Nb is provided, the reinforcing material portion is a Cu-Nb composite material, an oxygen-free copper stabilizing material portion is provided on the outer circumference of the reinforcing member, and there is no electrical insulation portion. A detailed explanation follows below.

[0099] First, the manufacturing process for precursor wires for compound superconducting wires is described. A composite wire of Nb rods and CuSn alloy was obtained by extruding and drawing a billet in which multiple Nb rods were embedded in a Ti-added CuSn alloy. Next, multiple of these composite wires were placed in the center of an oxygen-free copper tube to form an assembly, and tubular Nb was placed on the outer circumference of this assembly as a Sn diffusion prevention part. Multiple wires for the Cu-Nb reinforcement part, which were obtained by extruding and drawing a billet in which multiple Nb rods were embedded in oxygen-free copper and which served as a stabilizing part, were placed on the outer circumference of the tubular Nb, thereby obtaining a billet for precursor wires for compound superconducting wires.

[0100] Next, the billet for compound superconducting wire precursors was subjected to extrusion and drawing to make the cross-section roughly circular, and then, if necessary, rolling and drawing processes were performed to produce a compound superconducting wire precursor having an aspect ratio Ab1 as shown in Table 1.

[0101] In Examples 1A to 4A and Comparative Examples 1a to 4a, compound superconducting wires were manufactured by the react-and-wind method. Specifically, a precursor wire for compound superconducting wires was heat-treated at 670°C for 96 hours to generate a compound superconducting phase. Subsequently, a pre-bending strain application process and a winding process were performed on the heat-treated bobbin shown in Table 1 so that the pure bending strain would be the value shown in Table 1, thereby obtaining a compound superconducting wire having a compound superconductor portion with an aspect ratio Ab2 as shown in Table 1. For compound superconducting wires with an aspect ratio Ab2 greater than 1, the direction of the pre-bending strain application process and the winding process was set to the flatwise direction.

[0102] In Examples 1B to 4B and Comparative Examples 1b to 4b, a compound superconducting wire was manufactured by the wind-and-react method. Specifically, after winding around a heat treatment bobbin having the diameter shown in Table 1, a heat treatment at 670 °C for 96 hours was performed to generate a compound superconducting phase, thereby obtaining a compound superconducting wire provided with a compound superconductor part having an aspect ratio Ab2 shown in Table 1. For the precursor wire for the compound superconducting wire with an aspect ratio Ab2 exceeding 1, the direction of the winding process was set to the flatwise direction.

[0103] The critical current of the obtained compound superconducting wire was measured under a DC magnetic field of 4.2 K and 14.5 T. Also, the critical current density of the compound superconductor part in the compound superconducting wire was defined as the value with respect to the cross-sectional area of the compound superconductor part (including the Sn diffusion prevention part). The applied magnetic field for the compound superconductor part with an aspect ratio Ab2 exceeding 1 was set to the direction parallel to the width direction of the compound superconductor part. On the other hand, the pre-bending strain ε_pre-bent is the positive pre-bending strain ε_pre-bent + =Tb2×(+1 / D1 - 1 / Dh) and the reverse pre-bending strain ε_pre-bent - =Tb2×(-1 / D2 - 1 / Dh ). Here, Dh is the diameter of the heat treatment bobbin, D1 is the diameter of the positive bending pulley, and D2 is the diameter of the reverse bending pulley. Regarding the magnitude and number of times of this positive pre-bending strain ε_pre-bent + and the reverse pre-bending strain ε_pre-bent - , it is desirable that the pre-bending strain is 0.10% or more and 0.60% or less and is applied at least once or more in both the positive and reverse directions or only in one of the positive and reverse directions even when applying both pre-bending strains.

[0104] Also, the bending direction in the react-and-wind method was set to the same direction (positive direction) as the bending direction during heat treatment, and the pure bending strain ε_pure was calculated from ε_pure = Tb2×(+1 / D3 - 1 / Dh). Here, Dh is the heat treatment bobbin diameter, and D3 is the bobbin diameter at the time of critical current measurement.

[0105] [Table 1]

[0106] Table 1 shows examples and comparative examples. Here, the width Wb1 and thickness Tb1 of the compound superconducting precursor portion, and the width Wb2 and thickness Tb2 of the compound superconductor portion were calculated using the following formulas, respectively.

[0107] Wb1 = (V01 / 100) (1 / 2) ×W11 Tb1=(V01 / 100) (1 / 2) ×T11 Wb2 = (V02 / 100) (1 / 2) ×W12 Tb2 = (V02 / 100) (1 / 2) ×T12

[0108] Examples 1A-4A and 1B-4B exhibit superior winding performance for smaller diameters compared to Comparative Examples 1a-4a and 1b-3b, and the compound superconductor portion (including the Sn diffusion prevention portion) The critical current density (Non-Cu-Jc) per unit cross-sectional area was large. The critical current was defined as the current value when a magnetic field of 14.5T was applied parallel to the wide surface of a 38mm diameter spiral-shaped compound superconducting wire in liquid helium at 4.2K, and the generated electric field for the current was 0.1μV / cm. In particular, the critical current was further increased in Examples 1A to 4A of compound superconducting wires obtained by the react-and-wind method compared to Examples 1B to 4B of compound superconducting wires obtained by the wind-and-react method.

[0109] In particular, in Examples 1A to 4A, the critical current density (non-Cu-Jc value) per unit cross-sectional area of ​​the compound superconductor portion (including the Sn diffusion prevention portion) was larger than in Comparative Examples 1a to 4a. This indicates that by increasing the aspect ratio and reducing the thickness dimension of the compound superconductor portion, even after generating the compound superconductor by heat treatment on a 76 mm diameter bobbin using the react-and-wind method, the pure bending strain when wound on a small diameter of 38 mm was reduced, and the decrease in the non-Cu-Jc value increased by the application of pre-bending strain was suppressed. In Examples 2A and 2B, the thickness dimension of the compound superconductor portion was 0.30 mm, the same as Comparative Examples 1a and 1b, but because the aspect ratio of the compound superconductor wire was large and the cross-sectional area was large, and furthermore, the non-Cu-Jc value was improved, the critical current value was significantly increased. On the other hand, in Comparative Examples 2a, 3a, and 4a, where the react-and-wind method was applied, the pure bending strain increased, and the wind-and • Non-Cu-Jc was significantly reduced compared to Comparative Examples 2b, 3b, and 4b, which were treated using the React method.

[0110] Furthermore, the relationship between the aspect ratio Ab2 and the critical current of compound superconducting wires was investigated. Figure 8 is a graph showing the relationship between the critical current per unit cross-sectional area of ​​the compound superconducting portion (including the Sn diffusion prevention portion) and the aspect ratio Ab2 for compound superconducting wires obtained by the react-and-wind method and the wind-and-react method.

[0111] Figure 8 shows that when a parallel magnetic field is applied to the wide surface of a compound superconducting wire, the react-and-wind method yields larger values ​​than the wind-and-react method, regardless of the aspect ratio Ab2. In both cases, there was no significant difference in non-Cu-Jc values ​​in the aspect ratio Ab2 range of approximately 1.50 to 8.00, and a decreasing trend was observed at an aspect ratio of 10.40.

[0112] On the other hand, when a perpendicular magnetic field is applied to the wide surface of a compound superconducting wire, the react-and-wind method yields a larger value than the wind-and-react method regardless of the aspect ratio Ab2. In the react-and-wind method, the aspect ratio range is approximately 1.80 to 10.40, resulting in a magnetic field of 600 A / mm². 2 The above non-Cu-Jc values ​​were obtained, but in the case of the wind-and-react method, the aspect ratio Ab2 is around 1.80 to 6.00, and the voltage is 500 A / mm². 2 A value close to the specified value was obtained. Thus, it was found that when the aspect ratio Ab2 of the compound superconductor is 1.80 or higher, the above-mentioned effect of increasing non-Cu-Jc can be achieved in both the react-and-wind method and the wind-and-react method, and furthermore, a value of 11.00 or lower is preferable. In addition, compared to the wind-and-react method, compound superconducting wires obtained by the react-and-wind method have a high non-Cu-Jc value regardless of the magnetic field direction, indicating that compound superconducting wires manufactured by the react-and-wind method can be designed to be more efficient and rational than those produced by the wind-and-react method.

[0113] Furthermore, the relationship between tensile stress and the critical current value of compound superconducting wires was investigated. Figure 9 is a graph showing the non-Cu-Jc values ​​under axial tensile stress for compound superconducting wires obtained by the react-and-wind method and the wind-and-react method. For the samples used here, after heat treatment for compound superconductor formation in a linear shape, a pre-bending strain of ±0.38% was applied to the compound superconductor (including the Sn diffusion prevention portion) portion of the sample wire simulating the react-and-wind method 10 times back and forth, while no pre-bending strain was applied to the sample wire simulating the wind-and-react method immediately after heat treatment.

[0114] As shown in Figure 9, in the react-and-wind method, in Examples 1A to 3A, compared to Comparative Example 4a, the non-Cu-Jc value was larger as the aspect ratio Ab2 increased in the tensile stress region of 250 MPa or higher. This is thought to be the effect of uniform bending strain stress being applied in the pre-bending strain application process in the thickness direction of the compound superconducting wire by increasing the aspect ratio Ab2, thereby uniformly relaxing the compressive residual strain of the compound superconducting portion. On the other hand, in the wind-and-react method, in Example 2B, the non-Cu-Jc value was larger in the range of 260 MPa to 340 MPa compared to Comparative Example 4b. Thus, the effect of increasing non-Cu-Jc under the above-mentioned tensile stress was more pronounced when used in the react-and-wind method compared to the wind-and-react method. Thus, it was suggested that coil manufacturing on a commercial basis is possible for the compound superconducting wires produced in Examples 1A to 4A and 1B to 4B.

[0115] 1 Precursor wire for compound superconducting wire 2 Compound superconducting wires 10 Compound superconducting precursor section 11 Compound Superconducting Precursor Filaments 12 First Matrix Precursor 20 Compound superconductor section 21 Compound Superconducting Filaments 22 First Matrix 23 Core part 30 Reinforcement section 31 Reinforced Filament 32 The Second Matrix 40 Stabilizing material section 50 Sn diffusion prevention section 60 Electrical insulation part 71 First coil attached member 72 Forward bending pulley 73 Reverse-bent pulley 74 Second volume attached component

Claims

1. A compound superconducting precursor section is composed of multiple compound superconducting precursor filaments and a first matrix precursor containing a first stabilizing material in which the multiple compound superconducting precursor filaments are embedded, A cylindrical reinforcing material portion is arranged on the outer periphery of the compound superconducting precursor portion and is composed of a plurality of reinforcing filaments and a second matrix containing a second stabilizing material in which the plurality of reinforcing filaments are embedded, A cylindrical stabilizing member portion made of a third stabilizing member is disposed on at least one of the inner and outer circumferences of the reinforcing member portion. It has, A precursor wire for compound superconducting wires, wherein the aspect ratio Ab1 (Wb1 / Tb1) of the width dimension Wb1 of the compound superconducting precursor portion to the thickness dimension Tb1 of the compound superconducting precursor portion in a cross section perpendicular to the longitudinal direction of the compound superconducting precursor portion is 1.80 or more.

2. The compound superconducting wire precursor wire according to claim 1, wherein the aspect ratio Ab1 is 11.00 or less.

3. The precursor wire for compound superconducting wires according to claim 1 or 2, wherein the aspect ratio Ab1 is 2.00 or more and 10.00 or less.

4. In a cross-section perpendicular to the longitudinal direction of the compound superconducting wire precursor, the sum of the cross-sectional area of ​​the compound superconducting precursor portion, the cross-sectional area of ​​the reinforcing material portion, and the cross-sectional area of ​​the stabilizing material portion is 0.40 mm². ２ 4.00 mm ２ The following is a precursor wire for compound superconducting wires according to claim 1 or 2.

5. The compound superconducting precursor wire according to claim 1 or 2, wherein the compound superconducting precursor filament is Nb, and a Sn diffusion prevention portion made of Nb or Ta or an alloy or composite thereof is further provided between the compound superconducting precursor portion and the reinforcing material portion.

6. The precursor wire for compound superconducting wires according to claim 1 or 2, wherein the first stabilizing material is copper or a copper alloy, the reinforcing filament is made of one metal selected from the group Nb, Ta, V, W, Mo, Fe, Ti, and Hf or an alloy composed of two or more metals, the second stabilizing material is copper or a copper alloy, and the third stabilizing material is copper or a copper alloy.

7. A compound superconductor section comprising a plurality of compound superconducting filaments containing a compound superconducting phase, and a first matrix containing a first stabilizing material in which the plurality of compound superconducting filaments are embedded, A cylindrical reinforcing material section is arranged on the outer circumference of the compound superconductor section and consists of a plurality of reinforcing filaments and a second matrix containing a second stabilizing material in which the plurality of reinforcing filaments are embedded, A cylindrical stabilizing member portion made of a third stabilizing member is disposed on at least one of the inner and outer circumferences of the reinforcing member portion. It has, A compound superconducting wire in which the aspect ratio Ab2 (Wb2 / Tb2) of the width dimension Wb2 of the compound superconducting portion to the thickness dimension Tb2 of the compound superconducting portion in a cross section perpendicular to the longitudinal direction of the compound superconducting portion is 1.80 or more.

8. The compound superconducting wire according to claim 7, wherein the aspect ratio Ab2 is 11.00 or less.

9. The compound superconducting wire according to claim 7, wherein the aspect ratio Ab2 is 2.00 or more and 10.00 or less.

10. In a cross-section perpendicular to the longitudinal direction of the compound superconducting wire, the sum of the cross-sectional area of ​​the compound superconducting portion, the cross-sectional area of ​​the reinforcing material portion, and the cross-sectional area of ​​the stabilizing material portion is 0.40 mm². ２ 4.00 mm ２ The compound superconducting wire according to claim 7, which is as follows:

11. The compound superconducting phase is Nb ３ The compound superconducting wire according to claim 7, wherein the compound superconducting portion is Sn, and further comprises a Sn diffusion prevention portion made of Nb or Ta or an alloy or composite material thereof between the compound superconducting portion and the reinforcing portion.

12. The compound superconducting wire according to claim 7 or 11, wherein the first stabilizing material is copper or a copper alloy, the reinforcing filament is made of one metal selected from the group Nb, Ta, V, W, Mo, Fe, Ti, and Hf or an alloy composed of two or more metals, the second stabilizing material is copper or a copper alloy, and the third stabilizing material is copper or a copper alloy.

13. The compound superconducting wire according to claim 7 or 11, further comprising an electrical insulating portion containing resin on its outermost circumference.

14. A method for rewinding a compound superconducting wire according to claim 7 or 11, When the compound superconducting wire is re-wound from the first winding member to the second winding member, A method for rewinding a compound superconducting wire, comprising extending the compound superconducting wire from the first winding member in the tangential direction to the first winding member, and winding the compound superconducting wire onto the second winding member while bending the compound superconducting wire in the same bending direction as when it was wound around the first winding member.

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