JP2012190595A - Elemental wire for superconducting twisted cable, and superconducting twisted cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an elemental wire for a superconducting twisted cable which allows the achievement of a low AC loss even when plural superconducting elemental wires are twisted together to have a large capacity, and which is stable in the manufacturing thereof, and to provide a superconducting twisted cable including the same twisted together, and a method for manufacturing the elemental wire for a superconducting twisted cable.SOLUTION: The elemental wire comprises: a plurality of superconducting primary elemental wires including superconducting filaments; and a plurality of metal composite barrier wires including low-resistance metal wires which are each covered with a high-resistance metal material and are continuously disposed on the periphery of the entire superconducting primary elemental wires along a circumferential direction thereof.

Description

  The present invention relates to a superconducting stranded wire and a superconducting stranded wire.

  Superconducting strands are made by embedding a superconducting filament made of NbTi or the like in a stabilizing metal that is a normal conducting metal such as copper, and twisting many of these superconducting strands into a stranded wire, The wire is further twisted and used, for example, as a formed stranded wire that is compression-molded into a rectangular shape or wedge shape suitable for coiling. Alternatively, a superconducting stranded wire is accommodated in a metal tube and compression molded to be used as a cable in conduit.

  Such superconducting stranded wire, its compression-molded stranded wire, or cable in-conduit is used for elementary particle accelerator, industrial small accelerator (SOR, medical), wiggler magnet, angelator, generator, nuclear fusion reactor, power storage device. It is being put to practical use as a conductor, etc., and is being developed for higher density and higher current.

  By the way, in the superconducting stranded wire using the superconducting strands whose surfaces are not electrically insulated, the superconducting strands are in electrical contact with each other locally. When such a superconducting stranded wire is used under an AC magnetic field or a pulse fluctuation magnetic field, a current induced by the AC magnetic field flows through a closed circuit formed between the superconducting wires, resulting in an AC loss (Joule loss). Due to this AC loss, the amount of evaporation of the helium refrigerant increases, and in some cases there is a risk of transition to a normal conducting state (quenching accident).

  As AC loss at this time, in addition to hysteresis loss occurring in the superconducting filament part in the superconducting strand and coupling loss (including eddy current loss) occurring in the stabilized copper part which is a normal conducting metal, electrical contact is made. There is an inter-element coupling loss due to the current flowing across the sheath metal material of the superconducting element wire between the superconducting element wires.

  As a method for reducing such a coupling loss between strands, as described in Patent Document 1, between a copper tube serving as a stabilizing material and a superconducting primary strand having a hexagonal cross section including a superconducting filament, There is a method of interposing a high-resistance metal wire having a hexagonal cross section. However, according to this method, since the size of the high-resistance metal wire is defined when the electrical resistance composed of the group of high-resistance metal wires is set to a desired value, the size of the superconducting primary wire is also defined. As a result, the diameter of the superconducting filament is limited.

  For this reason, when trying to reduce the size of the high-resistance metal wire, there is a problem that the diameter of the superconducting filament is also reduced, and the superconducting filament is likely to be disconnected when the superconducting element wire is drawn. In addition, when trying to increase the diameter of the superconducting filament, the size of the high-resistance metal wire increases at the same time, so the ratio of the high-resistance metal, which is less workable than the low-resistance metal, to the entire superconducting wire increases. There is a problem that the production stability is not good from the viewpoint of production efficiency (yield and efficiency).

JP-A-7-141939

  The present invention has been made in view of such problems, and realizes a low AC loss even when the superconducting strands are twisted to increase the capacity, and has a manufacturing stability, and this It aims at providing the manufacturing method of the superconducting stranded wire which twisted together, and the strand for superconducting stranded wire.

  In order to solve the above-described problem, a first aspect of the present invention is a plurality of superconducting primary strands including superconducting filaments and an outer periphery of the plurality of superconducting primary strands, which are continuously arranged in the circumferential direction. There is provided a superconducting stranded wire comprising a plurality of metal composite barrier wires including a low resistance metal wire whose surface is coated with a high resistance metal material.

  In such a superconducting stranded wire, a first stabilizing metal layer is disposed outside the plurality of metal composite barrier wires, and the superconducting primary strand is second stabilized around the superconducting filament. It can be set as the structure by which a metal layer is coat | covered.

  Moreover, the volume ratio of the said high resistance metal material with respect to the said low resistance metal wire in the said metal composite wire can be 0.2-2 times.

  Further, the superconducting filament is made of NbTi, the low-resistance metal wire is made of copper, and the high-resistance metal material is made of a copper alloy containing one or more selected from the group consisting of Ni, Mn and Si. be able to.

  The second aspect of the present invention provides a superconducting stranded wire formed by twisting two or more of the above-described superconducting stranded wires.

  According to a third aspect of the present invention, there is provided a step of forming a plurality of superconducting primary strands including a superconducting filament and a plurality of metal composite barrier wires including a low resistance metal wire whose surface is coated with a high resistance metal material; A step of disposing the plurality of superconducting primary strands in a stabilized metal sheath and disposing one or more of the plurality of metal composite barrier wires on the outer periphery thereof to produce a composite billet; and Provided is a method of manufacturing a strand for a superconducting stranded wire, comprising a step of performing hot extrusion.

  In such a method for manufacturing a strand for a superconducting stranded wire, the superconducting primary strand and the metal composite barrier wire may have a hexagonal cross section of the same size.

  According to the present invention, even if the superconducting wire is twisted to achieve a large capacity, a low AC loss is realized, and a superconducting twisted wire with better manufacturing stability than the conventional one, a superconducting twisted wire twisted together, and A strand for a superconducting stranded wire is provided.

It is sectional drawing which shows the structure of the superconducting strand which concerns on the 1st Embodiment of this invention. It is the schematic which shows the structure of the superconducting twisted wire which concerns on the 2nd Embodiment of this invention. 1 is a cross-sectional view showing a configuration of a superconducting element wire according to Example 1. FIG. It is sectional drawing which shows the structure of the superconducting strand which concerns on the comparative examples 1 and 2.

  Embodiments of the present invention will be described below.

First Embodiment FIG. 1 is a diagram showing a cross-sectional configuration of a superconducting element wire according to a first embodiment of the present invention. In this superconducting wire, a superconducting conductor having a substantially hexagonal cross section composed of a superconducting filament 2 whose surface is covered with a stabilizing material 3 on the outer periphery of a core portion composed of a set of a plurality of stabilized hexagonal stabilizing metal wires 1. A plurality of primary strands 4 are arranged in a matrix to constitute a filament assembly. A set of composite barrier wires 7 composed of low-resistance metal wires 5 whose surfaces are covered with a high-resistance metal material 6 is disposed so as to surround the outer periphery of the filament assembly. Here, the composite barrier wires 7 are continuously arranged in the circumferential direction so that the adjacent composite barrier wires 7 are in contact with each other. In the case of a superconducting element wire in which the composite barrier wire 7 is discontinuously arranged in the circumferential direction, a current flows from the discontinuous portion of the assembled composite barrier wire 7 across the stabilizing metal sheath 8. Coupling loss cannot be reduced.

  The composite barrier wire 7 may surround the outer periphery of the filament aggregate in a single layer form, but may be a plurality of layers.

  In this way, the outer periphery of the assembly of the composite barrier wires 7 surrounding the outer periphery of the filament assembly is covered with the stabilizing metal sheath 8 to constitute a superconducting element wire.

In the superconducting wire constructed as described above, the superconducting material constituting superconducting filament 2 is not particularly limited. For example, the present invention is applicable not only to metallic superconductors such as NbTi, Nb ₃ Sn, and MgB ₂ but also to Bi based superconductors.

  The superconducting wire according to the present embodiment is effective in a superconducting wire in which the superconducting material has a multi-core structure, and the superconducting material is not limited to NbTi. Hereinafter, the case where the superconducting material is mainly NbTi will be described below. explain.

  Examples of the low resistance metal constituting the stabilized metal wire 1 in the core include copper, copper alloy, aluminum, aluminum alloy, etc., but it is particularly preferable to use oxygen-free copper. The stabilizing material 3, the low resistance metal wire 5, and the stabilizing metal sheath 8 can also include copper, copper alloy, aluminum, aluminum alloy, etc., but preferably oxygen-free copper can be used.

  When the superconducting material is NbTi, the stabilizing material made of the low resistance metal material constituting the core part and / or the sheath part has a residual resistance ratio (electric resistance ratio between the temperature 273K and the superconducting critical temperature (Tc)). It is preferable that it is 50 or more and 300 or less copper.

  In addition, when the superconducting material is NbTi, the low resistance metal material made of copper or copper alloy constituting the core portion can be divided by the high resistance barrier layer made of CuNi alloy or the like. In the case of the following, it is desirable not to divide by the high resistance barrier layer from the viewpoint of cost.

  Further, in order to increase the critical current of the superconducting element wire, the core part is entirely made of the superconducting primary element wire 4, and the stabilizing metal line 1 made of a low resistance metal need not be provided at all.

  As the high resistance metal material 6 of the composite barrier wire 7, a copper alloy containing one or more selected from the group consisting of Ni, Mn, and Si, Zn, Fe, Mg, Mn, Si, Cu, Ti, and An aluminum alloy containing one or more selected from the group consisting of Cr can be used. Hereinafter, the specific resistance means a value at a temperature when the superconducting wire is used.

Here, the high resistance of the high resistance metal material 6 means a specific resistance of 1 × 10 ⁻⁸ Ωm to 5 × 10 ⁻⁷ Ωm, and the low resistance of the low resistance metal wire 5 is 5 × 10 ^−9. It means a specific resistance of less than Ωm, and it is desirable that both have a specific resistance difference of at least 3 times. When the specific resistance difference is less than 3 times, there is a problem that when a high resistance metal material and a low resistance metal material are combined, a large composite resistance effective as a composite barrier wire cannot be obtained, which is not preferable.

The composite specific resistance ρ _composite of the composite barrier wire 7 composed of the low resistance metal wire 5 whose surface is coated with the high resistance metal material 6 is preferably 5 × 10 ⁻⁹ Ωm to 3 × 10 ⁻⁷ Ωm. If the composite specific resistance ρ _composite exceeds 3 × 10 ⁻⁷ Ωm, the workability is remarkably deteriorated. If the composite specific resistance ρ _composite is less than 5 × 10 ⁻⁹ Ωm, an inter-element coupling loss occurs and is not effective as a composite barrier line.

The composite specific resistance ρ _composite is given by the following equation.

ρ _composite = λ _{low resistance} × ρ _{low resistance} + λ _{high resistance} × ρ _{high resistance}
λ _{Low resistance} : Volume ratio of low resistance metal in composite barrier wire λ _{High resistance} : Volume ratio of high resistance metal in composite barrier wire ρ _{Low resistance} : Specific resistance of low resistance metal ρ _{High resistance} : Specific resistance of high resistance metal The composition ratio of the composite barrier material (volume ratio of high resistance metal material to low resistance metal material λ _{high resistance} / λ _{low resistance} ) is based on the selected ρ _{high resistance} and ρ _{low resistance} so as to obtain an effective composite specific resistance. Moreover, it can select suitably so that the requirements (for example, the tolerance | permissible level of the alternating current loss determined by the magnetic field change rate at the time of operation | use) which use this wire may be satisfy | filled. Further, the number of layers of the composite barrier material can be appropriately selected so as to satisfy the requirements on the device side using the wire.

  However, when the composition ratio of the composite barrier material is less than 0.2 times, it is difficult to obtain an effective composite specific resistance that reduces the coupling loss between the strands. Is preferably 0.2 to 2 times.

Second Embodiment Next, a superconducting stranded wire according to a second embodiment of the present invention in which the superconducting wires described above are twisted together will be described.

  As shown in FIG. 2A, the superconducting stranded wire according to the second embodiment of the present invention is a flat-molded stranded wire 11 obtained by twisting 16 superconducting strands 10 according to the first embodiment. Can do.

  Moreover, as shown in FIG.2 (b), the superconducting element wire 10 which concerns on 1st Embodiment is twisted, the primary twisted wire 20 is produced, 14 pieces are twisted, and the square forming process 2 It is also possible to use a straight flat stranded wire 21.

  Furthermore, as shown in FIG.2 (c), the superconducting strand 10 which concerns on 1st Embodiment is twisted together, the primary twisted wire 30 is produced, and the primary twisted wire is twisted together and 2 A next stranded wire (3 × 3 stranded wire) 31 is produced, and four secondary stranded wires 60 are twisted together to produce a third stranded wire (3 × 3 × 4 stranded wire) 32, which is 4 After the main twisting, forming processing such as roll rolling can be performed to form a quaternary stranded wire (3 × 3 × 4 × 4 stranded wire) 33 having a substantially circular cross section.

  Alternatively, a high-capacity conductor can be manufactured by using a superconducting stranded wire obtained by twisting the superconducting strands according to the first embodiment as a constituent element and combining it with a tube, a tape-shaped SUS member, or a copper member. Depending on the material of the stabilizing material applied to the superconducting element wire and the stranded wire, the residual resistance ratio decreases due to work hardening during production. Therefore, an annealing step may be included in the intermediate step or the final step as necessary. Moreover, in order to adjust a current capacity or adjust the amount of stabilized copper, it is also possible to twist with a copper wire.

  Examples of the present invention and comparative examples are shown below, and the effects of the present invention will be described more specifically.

Example 1
A method for producing the NbTi superconducting wire according to this example will be specifically described with reference to FIG.

  First, a Nb-47 wt% Ti rod was inserted into an oxygen-free copper tube having a residual resistance ratio of 300 to produce a composite billet. By subjecting this composite billet to hot extrusion and cold processing, a rod-shaped superconducting primary strand (Cu / NbTi composite primary strand) having a substantially hexagonal cross section with an opposite side dimension of 4.5 mm was produced.

  Next, an oxygen-free copper rod having a residual resistance ratio of 300, which is a low-resistance metal, was inserted into a tube of Cu-30 wt% Ni, which is a high-resistance metal, to produce a composite billet. By subjecting this composite billet to hot extrusion and cold processing, a bar-shaped composite barrier wire (CuNi / Cu composite barrier wire) having a substantially hexagonal cross section with an opposite side dimension of 4.5 mm was produced. At this time, the composition ratio of Cu-30 wt% Ni (volume ratio to oxygen-free copper) was set to 0.6.

The specific resistance of Cu-30 wt% Ni at 4.2 K, which is the operating temperature of the superconducting wire, is 3 × 10 ⁻⁷ Ωm, and the specific resistance of oxygen-free copper is 1 × 10 ⁻¹⁰ Ωm. Therefore, the composite specific resistance is: λ _{high resistance} = 0.6 / 1.6, ρ _{high resistance} = 3 × 10 ⁻⁷ Ωm, λ _{low resistance} = 1 / 1.6, ρ _{low resistance} = 1 × 10 ⁻¹⁰ Ωm Therefore, (0.6 / 1.6) × 3 × 10 ⁻⁷ + (1 / 1.6) × 10 ⁻¹⁰ ] = 1.1 × 10 ⁻⁷ Ωm.

  Next, an oxygen-free copper ingot was manufactured by hot extrusion and cold processing to produce a bar-shaped stabilizer having a hexagonal cross section with an opposite side dimension of 4.5 mm.

  Thereafter, an oxygen-free copper tube having an inner diameter of 166 mm / outer diameter of 220 mm, which becomes a stabilizing sheath, is produced. In this, 325 rod-shaped stabilizers (Cu: hexagonal cross section) as core portions (Cu core), 690 primary strands (which form the filament group portion) and 120 composite barrier wires (CuNi / Cu composite barrier wires) having a hexagonal cross section are sequentially inserted around the primary strand to obtain a secondary composite billet. It was.

  After subjecting the secondary composite billet thus obtained to hot extrusion processing, heat treatment and cold processing are repeated, and further, twisting processing in the S direction and a pitch of 15 mm, final wire drawing processing, and Through a heat treatment for recovering the residual resistance ratio, an NbTi superconducting wire having a diameter of 0.81 mmφ was obtained.

  FIG. 3 shows a cross section of the NbTi superconducting wire thus obtained. In FIG. 3, a Cu core 41 in which 325 rod-shaped stabilizers are combined and integrated is disposed at the center of the oxygen-free copper tube 40, and 690 primary strands are combined and integrated around it. The filament group 42 is arranged, and further, around it, 120 CuNi / Cu composite barrier wires having a hexagonal cross section are combined and integrated, that is, adjacent CuNi / Cu composite barrier wires in the circumferential direction are in contact with each other. A continuously formed CuNi / Cu composite barrier wire group 43 is arranged and accommodated in the oxygen-free copper tube 40.

  Sixteen NbTi superconducting wires obtained in this example were twisted in the Z direction at a twisting pitch of 65 mm, and then roll-molded to produce a rectangular molded twisted wire having a width of 6.5 mm and a thickness of 1.5 mm.

Comparative Example 1
A method of manufacturing the NbTi superconducting wire according to this comparative example will be specifically described with reference to FIG.

  First, a Nb-47 wt% Ti rod was inserted into an oxygen-free copper tube having a residual resistance ratio of 300 to produce a composite billet. The composite billet was subjected to hot extrusion and cold processing to produce a rod-shaped superconducting primary strand (Cu / NbTi composite primary strand) having a substantially hexagonal cross section with an opposite side dimension of 1.65 mm.

  Next, by subjecting Cu-30wt% Ni billet, which is a high-resistance metal, to hot extrusion and cold processing, a solid barrier wire (CuNi solid barrier wire) with a hexagonal cross section with an opposite side dimension of 1.65mm. Was made. Here, the hexagonal opposite side dimension is set to 1.65 mm instead of 4.5 mm. In Example 1, when the final diameter is 0.81 mmφ, the equivalent thickness of the composite barrier wire is 7 μm. This is to match.

  Next, the oxygen-free copper ingot was subjected to hot extrusion processing and cold processing to produce a rod-shaped stabilizer having a hexagonal cross section with an opposite side dimension of 1.65 mm.

  Thereafter, an oxygen-free copper tube having an inner diameter of 165 mm / an outer diameter of 220 mm serving as a stabilizing sheath was produced. In this, 3168 rod-shaped stabilizers as a core portion (Cu core) and 5173 primary strands ( These formed a filament group portion), and 336 CuNi solid barrier wires were sequentially inserted therearound to obtain a secondary composite billet.

  After subjecting the secondary composite billet thus obtained to hot extrusion processing, heat treatment and cold processing are repeated, and further, twisting processing in the S direction and a pitch of 15 mm, final wire drawing processing, and Through a heat treatment for recovering the residual resistance ratio, an NbTi superconducting wire having a diameter of 0.81 mmφ was obtained.

  FIG. 4 shows a cross section of the NbTi superconducting wire thus obtained. In FIG. 3, a Cu core 51 in which 3168 stabilizing materials are combined and integrated is arranged at the center of the oxygen-free copper tube 50, and a filament in which 5173 primary strands are combined and integrated around it. A group 52 is disposed, and a CuNi solid barrier wire group 53 in which 336 CuNi solid barrier wires are combined and integrated is disposed around the group 52 and accommodated in the oxygen-free copper tube 50.

  Sixteen NbTi superconducting superconducting wires obtained in this comparative example were twisted in the Z direction at a twisting pitch of 65 mm, and then roll-molded to produce a rectangular molded twisted wire having a width of 6.5 mm and a thickness of 1.5 mm. .

Comparative Example 2
A method of manufacturing the NbTi superconducting wire according to this comparative example will be specifically described with reference to FIG.

  First, a Nb-47 wt% Ti rod was inserted into an oxygen-free copper tube having a residual resistance ratio of 300 to produce a composite billet. The composite billet was subjected to hot extrusion and cold processing to produce a rod-shaped superconducting primary strand (Cu / NbTi composite primary strand) having a substantially hexagonal cross section with an opposite side dimension of 4.5 mm.

Next, by subjecting Cu-10wt% Ni billet, which is a high-resistance metal, to hot extrusion and cold working, a solid barrier wire (CuNi solid barrier wire) with a hexagonal cross section with an opposite side dimension of 4.5mm. Was made. Here, in Comparative Example 1, Cu-30 wt% Ni was used, whereas in Comparative Example 2, Cu-10 wt% Ni was used because the equivalent specific resistance of the composite barrier wire in Example 1 was 1.1 × 10. ^This is because the specific resistance is equivalent to ⁻⁷ Ωm.

  Next, the oxygen-free copper ingot was subjected to hot extrusion processing and cold processing to produce a rod-shaped stabilizing material having a hexagonal cross section with an opposite side dimension of 4.5 mm.

  Thereafter, an oxygen-free copper tube having an inner diameter of 165 mm / an outer diameter of 220 mm serving as a stabilizing sheath is produced. In this, 325 rod-shaped stabilizers as a core portion (Cu core), and 690 primary strands ( These formed a filament group part), and 120 CuNi solid barrier wires were sequentially inserted therearound to obtain a secondary composite billet.

  After subjecting the secondary composite billet thus obtained to hot extrusion processing, heat treatment and cold processing are repeated, and further, twisting processing in the S direction and a pitch of 15 mm, final wire drawing processing, and Through a heat treatment for recovering the residual resistance ratio, an NbTi superconducting wire having a diameter of 0.81 mmφ was obtained.

  The cross section of the NbTi superconducting wire obtained in this way is also formed as shown in FIG. In FIG. 4, a Cu core 51 in which 325 rod-shaped stabilizers are combined and integrated is disposed at the center of the oxygen-free copper tube 50, and 690 primary strands are combined and integrated in the periphery thereof. A filament group 52 is arranged, and 120 composite-integrated CuNi solid barrier wires 53 are continuously arranged around the filament group 52 and accommodated in the oxygen-free copper tube 50.

  Sixteen NbTi superconducting wires obtained according to this comparative example were twisted in the Z direction at a twist pitch of 65 mm, and then roll-molded to produce a rectangular molded twisted wire having a width of 6.5 mm and a thickness of 1.5 mm.

Evaluation of superconducting wire The manufacturability and performance of the superconducting wires of Example 1, Comparative Example 1 and Comparative Example 2 were evaluated at the strand level and the stranded wire level, respectively, and cost merit was compared comprehensively.

In the characterization at the wire level, Ic (defined as the value measured with an electric field of 10 μV / m at 4.2 K) is measured, and Jc (critical current density, Ic / NbTi superconducting cross section). ). Further, from an IV curve obtained at the time of Ic measurement, n value (V = K (I / Ic) ⁿ , defined by 10 μV / m to 100 μV / m, V is a generated voltage, I is a conduction current, and K is Which is a constant).

  Further, the hysteresis loss and the coupling time constant (the coupling current time constant, which is proportional to the coupling time constant) were measured by the pickup coil method. For hysteresis loss, a triangular magnetic field with a magnetic field amplitude of ± 3 T and 0.04 T / s is applied in a direction perpendicular to the longitudinal direction of the wire, and after measuring the magnetization, the area is calculated from each magnetization-applied magnetic field curve. Calculated by integrating. On the other hand, the bonding time constant measurement was performed separately for the strand and the stranded wire so that the coupling time constant in the strand and the coupling time constant between the strands could be separated. Apply alternating magnetic field with sine waveform of magnetic field amplitude ± 0.01T, 1-25Hz, calculate the AC loss by integrating the area from each magnetization curve, and find the coupling loss time constant from its frequency dependence It was.

  The inter-element coupling loss is measured by applying a magnetic field from the direction perpendicular to the wide surface of the flat rectangular twisted wire and measuring the total of intra-element coupling loss and inter-element coupling loss. After obtaining the constant, the inter-element coupling time constant was calculated by subtracting the intra-element coupling time constant.

  On the other hand, in terms of energization stability, dynamic stabilization conditions are satisfied at the strand level in the middle and high magnetic field regions. No qualitative observation was observed, and equivalent stability could be confirmed. Regarding the workability, confirmation was performed by the number of disconnections per 20 km.

Table 1 below shows the specifications of the examples and comparative examples and the various evaluation results described above.

From Table 1 above, the following can be understood.
First, in the comparison of manufacturability between Example 1 and Comparative Example 1, the assembly manufacturability was good in Example 1, but in Comparative Example 1, since the opposite-side dimension of the strand was small, it was inserted into a copper tube. The number of the billets was very large, and the billet assembly was extremely difficult. Moreover, although the extrusion process of Example 1 and Comparative Example 1 was both good, the disconnection did not occur in Example 1, whereas the disconnection occurred 10 times in Comparative Example 1. As a result, Example 1 obtained a 30% higher yield than Comparative Example 1.

  Next, the performance comparison between Example 1 and Comparative Example 1 was as follows. The critical current density was about 7% higher in Example 1. In Comparative Example 1, since the n value is small, it is considered that the filament shape in the longitudinal direction is not uniform because the filament is thin. Moreover, since the filament diameter of Comparative Example 1 is 0.37 times that of Example 1, the theoretically expected reduction effect of 63% is not seen, and the hysteresis loss is reduced by about 25%. It wasn't too much. This is considered to be due to the fact that the filament shape became non-uniform and the filament spacing became too small, resulting in an increase in hysteresis loss due to the proximity effect.

  In Example 1, an increase in history loss due to the proximity effect did not occur. The performance of Example 1 was superior in both the intra-element coupling time constant and the inter-element coupling time constant.

  Comparison of manufacturability between Example 1 and Comparative Example 2 was as follows. Example 1 and Comparative Example 2 had the same billet assemblability, but in Comparative Example 2, the extrusion pressure was close to the equipment upper limit during extrusion, and the extrusion processability was unstable. In Example 1, no disconnection occurred, whereas in Comparative Example 1, one disconnection occurred. As a result, Example 1 obtained a 10% higher yield than Comparative Example 1.

  Next, the performance comparison between Example 1 and Comparative Example 2 was as follows. The critical current density, n value, and hysteresis loss showed equivalent performance. However, Example 1 showed better performance in both the intra-element coupling time constant and the inter-element coupling time constant. This means that the composite barrier functions effectively for reducing the coupling loss.

  As described above, the NbTi superconducting wire according to Example 1 has performances such as Jc, n value, and hysteresis loss that are equal to or higher than those of Comparative Examples 1 and 2, and is particularly excellent in the effect of reducing the coupling loss. Has performance. Furthermore, the production yield is high, and it has excellent advantages in cost reduction.

  DESCRIPTION OF SYMBOLS 1 ... Stabilized metal wire, 2 ... Superconducting filament, 3 ... Stabilizing material, 4 ... Superconducting primary strand, 5 ... Low resistance metal wire, 6 ... High resistance metal material, 7 ... Composite barrier wire, 8 ... Stabilization metal Sheath, 10 ... superconducting wire, 11 ... flat-shaped stranded wire, 20,30 ... primary stranded wire, 21 ... double flat stranded wire, 31 ... secondary stranded wire, 32 ... tertiary stranded wire, 33 ... quaternary Twisted wire, 40, 50 ... oxygen-free copper tube, 41, 51 ... Cu core, 42, 52 ... filament group, 43 ... CuNi / Cu composite barrier wire group, 53 ... CuNi solid barrier wire group.

Claims (7)

A plurality of superconducting primary wires including a superconducting filament;
A plurality of metal composite barrier wires including a low resistance metal wire, the outer periphery of the plurality of superconducting primary strands and continuously disposed in the circumferential direction and having a surface coated with a high resistance metal material. A superconducting stranded wire. A first stabilizing metal layer is disposed outside the plurality of metal composite barrier wires;
2. The superconducting stranded wire according to claim 1, wherein the superconducting primary strand is formed by coating a second stabilizing metal layer around the superconducting filament.   The strand for superconducting stranded wire according to claim 1 or 2, wherein a volume ratio of the high-resistance metal material to the low-resistance metal wire in the metal composite barrier wire is 0.2 to 2 times. .   The superconducting filament is made of NbTi, the low-resistance metal wire is made of copper, and the high-resistance metal material is made of a copper alloy containing at least one selected from the group consisting of Ni, Mn and Si. The strand for superconducting stranded wires according to any one of claims 1 to 3.   A superconducting stranded wire formed by twisting two or more strands for a superconducting stranded wire according to any one of claims 1 to 4. Creating a plurality of superconducting primary strands including a superconducting filament and a plurality of metal composite barrier wires including a low resistance metal wire whose surface is coated with a high resistance metal material;
Placing the plurality of superconducting primary strands in a stabilized metal sheath, arranging one or more of the plurality of metal composite barrier wires on the outer periphery thereof, and producing a composite billet;
A method for producing a strand for a superconducting stranded wire, comprising a step of subjecting the composite billet to hot extrusion.   The method of manufacturing a superconducting stranded wire according to claim 6, wherein the superconducting primary strand and the metal composite barrier wire have a hexagonal cross section of the same size.

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