JP4532369B2 - Compound superconducting wire and compound superconducting cable manufacturing method - Google Patents

Description

  The present invention relates to a compound superconducting wire, a compound superconducting cable, and a method for producing the same, and in particular, a compound superconducting wire, a compound superconducting cable having excellent superconducting properties such as a high critical current by reducing or removing strain inside the superconductor, and It relates to the manufacturing method.

Conventionally, as a method for producing a compound superconducting cable such as an Nb ₃ Sn superconducting cable, a compound superconducting wire is formed by subjecting a wire containing a compound superconducting raw material to a heat treatment for generating a compound, and forming the compound superconducting wire. There is a so-called “React and Wind” method in which the wires are twisted together, and a so-called Wind and React method in which the wires before the heat treatment are twisted and then subjected to heat treatment (for example, , Patent Literature 1, Patent Literature 2, Patent Literature 3, and Non-Patent Literature 1). Hereinafter, a heat treatment for generating a compound, that is, a heat treatment in which a wire containing the above-described compound superconducting raw material is used as a compound superconducting wire is simply referred to as a compound generating heat treatment.

Here, large magnets such as a dipole magnet for a high magnetic field accelerator and a high magnetic field large-diameter magnet generally use Nb ₃ Sn superconducting cables manufactured using a react and wind method. The reason for this is that the compound generation heat treatment for Nb ₃ Sn generation needs to be performed in a vacuum or inert gas atmosphere furnace at a predetermined temperature of 600 ° C. or higher. This is because the wind-and-react method in which the compound-forming heat treatment is performed after the magnet is formed cannot be applied.

This wind-and-react method is a manufacturing process that avoids distortions caused by processing and prevents deterioration of superconducting properties such as critical current by not processing the compound superconducting wire after forming the compound superconducting wire. Is the method. When using the wind-and-react method, in order to avoid introduction of distortion caused by processing such as winding into the compound superconducting wire, the superconducting compound raw material in an unreacted state is wound in a coil shape in advance. A Nb ₃ Sn in a coil shape is generated by reacting Nb and Sn by performing a compound generation heat treatment. There is also an attempt to improve the critical current by removing the residual strain inherent in the compound superconducting wire manufactured using the react-and-wind method (see Non-Patent Document 1, for example).
JP 2000-164419 A JP 2001-126554 A Japanese Patent Laid-Open No. 2004-063128 Improvement of Ic by Loading and Unloading Bending Strain for High Strength Nb3Sn Wires (IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, Vol. 14, No.2, June 2004)

However, the Nb 3 _Sn superconducting wire and Nb 3 _Sn superconducting cable produced using the REACT-and-wind method described above, reinforcement Nb 3 _Sn superconductor is located at the center portion and disposed on the outer periphery and / Or, distortion such as compressive strain generated in the Nb ₃ Sn superconductor due to the difference in thermal expansion coefficient with the stabilizing material, bending strain generated during winding of the Nb ₃ Sn superconducting cable subjected to compound generation heat treatment, and strain due to winding tension As a result, there is a problem that the critical current Ic and the like are significantly reduced. FIG. 9 is a graph showing the bending strain dependence characteristics of the critical current obtained for the Nb ₃ Sn superconducting wire manufactured using the conventional technique. In FIG. 9, the vertical axis represents normalized critical current Ic / Icm (%), and the horizontal axis represents bending strain (%). In addition, the strength of the applied magnetic field is 12T, 14T, and 16T, respectively, from the higher standardized critical current. As shown in FIG. 9, in the Nb ₃ Sn superconducting wire manufactured by using the conventional technique, it is known that the critical current rapidly decreases when the bending strain exceeds about 0.2% to 0.4%.

For this reason, large magnets such as high-field accelerator magnets and high-field large-diameter magnets using Nb ₃ Sn superconducting wires and Nb ₃ Sn superconducting cables manufactured using the react and wind method are critical as described above. Since the current decreased, the operating current had to be lowered. In order to generate a high magnetic field, the inductance of the superconducting magnet has to be increased, and there has been a problem that high-speed excitation or pulse excitation cannot be performed. In order to solve the above-described problems, attempts have been made to improve the deterioration of the characteristics of the superconducting wire by applying a bending strain to the compound superwire material produced using Nb ₃ Sn or the like.

For example, Patent Document 1 discloses a reinforced and stabilized superconducting wire in which a compound superconducting wire that is susceptible to strain is covered with a reinforcing and stabilizing material. Patent Document 1 discloses that a superconducting magnet can be manufactured by using the react-and-wind method by using a reinforced and stabilized superconducting wire as the wire to be used, and the strain resistance characteristics of the compound superconducting wire are improved. It is described. Specifically, the yield stress of a thin wire having a diameter of 0.3 mm to 2 mm is obtained in a reinforced and stabilized superconducting wire whose superconductor is Nb ₃ Sn obtained by performing a compound generation heat treatment at a temperature of about 700 ° C. for about 10 days. Increases from 250 to 300 Mpa, and there is no degradation of critical current at bending strains up to 0.5%.

  In Patent Document 2, in a compound superconducting wire in which enamel is coated on a compound superconducting bare wire in which a compound superconducting phase is formed, the compound superconducting bare wire has a cross-sectional minimum width of 50 times or more of the compound superconducting bare wire. It is disclosed that it is possible to avoid the superconducting property from being significantly deteriorated by coating the enamel under a condition in which bending is performed a plurality of times with a bending radius and a tension of 70 MPa or less is applied.

Also, in Patent Document 3, by adding bending strain to a compound superconducting wire exhibiting strain dependence subjected to a react treatment, the bending strain is unloaded, thereby improving the mechanical characteristics and the stress characteristics of critical current values. Has been disclosed.
In the various attempts described above, the critical current characteristic deterioration due to the strain stress of the compound superconductivity and the improvement of the strain resistance characteristic were observed to some extent, but satisfactory superconducting characteristics could not be obtained.

Under such circumstances, Non-Patent Document 1 discloses that superconducting characteristics greatly surpassing conventional ones can be obtained by repeatedly applying a bending strain in the opposite direction to the Nb ₃ Sn superconducting wire. Specifically, by applying a bending strain of 0.3% to 0.5% five times from both the forward and reverse directions, a high critical current characteristic exceeding the critical current when no bending strain is applied can be obtained. Has been. As a reason for improving the superconducting characteristics, it has been pointed out that the residual stress generated inside the Nb ₃ Sn superconducting wire during the compound generation heat treatment was partially relaxed.

  However, the strain resistance characteristic, which is an important characteristic for a superconducting cable, has not been studied and is unknown. For example, if the strain resistance is not excellent even when the critical current Ic is high, the sea current Ic is drastically reduced due to the distortion generated in the wire by twisted wire processing or the like at the time of cable formation, and it is difficult to put it to practical use. However, this point is not mentioned. Even if the technique disclosed in Non-Patent Document 1 is used, it is difficult to put it to practical use while maintaining a high critical current Ic.

  The present invention provides a compound superconducting wire, a compound superconducting cable, and a method for producing the same, which can relieve strain remaining in the compound superconducting wire and improve superconducting characteristics such as strain resistance and critical current as compared with the prior art. With the goal.

The first aspect of the present invention includes a wire material forming step in which a compound superconducting material that becomes a superconductor by performing a predetermined heat treatment forms a wire material that occupies at least a part of the cross section, and the wire material formed in the wire material forming step The heat treatment is performed on the compound superconducting material to be a superconductor, the wire is used as a compound superconducting wire, and the compound superconducting wire obtained in the heat treatment step is subjected to bending bending from both the positive and negative directions. It is a manufacturing method of a compound superconducting wire characterized by comprising a double-bending bending process for performing processing.

According to a second aspect of the present invention, in the first aspect, in the double swing bending process, a bending strain is added to the compound superconducting wire in a range of 0.5% to 1.0%. This is a method for producing a compound superconducting wire.

According to a third aspect of the present invention, in the first or second aspect, the compound superconducting wire is subjected to a single double swing process in which bending strain is applied once in both the forward and reverse directions in the double swing bending process. It is a manufacturing method of the compound superconducting wire characterized by performing the treatment more than 20 times and less than 20 times.

According to a fourth aspect of the present invention, the compound superconducting wire manufactured using the method for manufacturing a compound superconducting wire described in any of the first to third aspects is stranded or twisted. A method of manufacturing a compound superconducting cable, comprising a cable forming step of forming a cable by performing a molding process after.
A fifth aspect of the present invention is the method for producing a compound superconducting cable according to the fourth aspect, wherein a stabilizing material is formed on the outer periphery of the compound superconductor.
A sixth aspect of the present invention is a method for manufacturing a compound superconducting cable according to the fourth or fifth aspect, wherein the compound superconductor is made of Nb ₃ Sn or Nb ₃ Al.
According to a seventh aspect of the present invention, in the fourth to sixth aspects, a reinforcing material made of any one conductive material of CuNb, CuAl ₂ O ₃ , CuNbTi, and Ta is formed. It is a manufacturing method of the compound superconducting cable characterized.

  According to the present invention, the internal strain of the compound superconducting wire can be relaxed by subjecting the compound superconducting wire to a double bending process that applies bending strain from both the positive and negative directions. It is possible to realize a compound superconducting wire, a compound superconducting cable, and a method for producing the same, which can improve the superconducting characteristics of the above.

  In addition, because the bending swing processing conditions are optimized so that bending strain in the range of 0.5% to 1.0% is applied from both the positive and negative directions, the performance of the compound superconducting wire can be further increased. Possible compound superconducting wire, compound superconducting cable, and manufacturing method thereof can be realized.

  In addition, compound superconducting wire and compound superconductivity that can further bring out the performance of compound superconducting wire because the conditions of double-bending bending are optimized so as to add a single double swinging process of 5 to 20 times. A cable and a manufacturing method thereof can be realized.

  In addition, because the strain resistance was improved, it became possible to apply the react-and-wind method to compound superconducting wires, which had previously been difficult to make into cables, making cables easy and cost-effective. The economic effect is high.

  In addition, since the strain resistance can be improved, a coil with a short pitch between the strands can be created, and a superconducting coil with excellent quality can be realized with little loosening between the strands.

Hereinafter, the compound superconducting wire, the compound superconducting cable, and the manufacturing method thereof according to the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1 (a), one embodiment of the method for producing a compound superconducting wire according to the present invention is a method in which a compound superconducting material that becomes a superconductor by performing a predetermined heat treatment occupies at least a part of the cross section. The wire forming step S101 to be formed, the heat treatment step S102 to heat-treat the wire formed in the wire forming step S101 to make the compound superconducting raw material a superconductor, and to make the wire a compound superconducting wire, and the compound obtained in the heat treatment step S102 A compound superconducting wire manufacturing method comprising: a superconducting wire including a double-bending bending step S103 for performing a double-bending bending process for applying a bending strain from both the positive and negative directions.

  An example of a cross-sectional structure of the wire formed in the wire forming step S101 is shown in FIG. In FIG. 2, the raw material of the superconductor occupies the central region 1, the stabilizing region occupies the outermost region 3, and the reinforcing material occupies the region 2 between the central region 1 and the outer region 3. . However, the cross-sectional structure of the wire formed in the wire forming step S101 is not limited to that described above, and other cross-sectional structures may be used.

As the reinforcing material and the stabilizing material, a conductive material such as a metal or an alloy material is used. For example, CuNb, CuAl ₂ O ₃ , CuNbTi, Ta, or the like may be used as the reinforcing material. Further, Cu may be used as the stabilizing material. However, other materials may be used for the reinforcing material and the stabilizing material. For example, Nb ₃ Sn, Nb ₃ Al, or the like is used for the compound superconductor that will occupy the region 1. Further, the compound superconductor may have a structure obtained by combining a plurality of filaments having a diameter of 1 μm or more.

In addition, the cross-sectional structure of the compound superconducting wire of the present invention is not limited to that shown in FIG. 2, and may have other cross-sectional structures. Specifically, it may have the cross-sectional structure shown in FIG. In FIG. 3, the outermost layer is a stabilizing material made of Cu. FIG. 3A is a cross-sectional view of a CuNb reinforced bronze method Nb ₃ Sn compound superconducting wire occupied by a reinforcing material made of CuNb or the like between the central compound superconductor and the outermost stabilizing material. A cross-sectional view of a CuNbTi reinforced bronze Nb ₃ Sn compound superconducting wire occupied by a compound superconductor between a reinforcing material made of CuNbTi or the like in the center and an outermost stabilizing material is shown in (b), and one of Nb ₃ Sn filaments is shown. A cross section of a Ta reinforced bronze method Nb ₃ Sn compound superconducting wire having one Ta core is shown in (c), and the compound superconductor occupies between the central core wire made of Cu and the outermost stabilizing material. A cross-sectional view of the bronze Nb ₃ Sn compound superconducting wire is shown in (d).

Table 1 is a table for explaining the structure of the bronze process Nb 3 _Sn compound superconducting wire. In Table 1, (Ta) written in the column of reinforcing material indicates that the filament has a core wire made of Ta, and <Cu> in the column of reinforcing material is provided with reinforcing material. Although it does not, it represents that the center part of a wire cross section occupies Cu. As shown in Table 1, the bronze component of each Bronze method Nb ₃ Sn compound superconducting wire is 14% Sn by weight, 0.2% Ti, Cu, except for the Ta reinforced bronze method Nb ₃ Sn compound superconducting wire. Is the rest. For the Ta reinforced bronze Nb ₃ Sn compound superconducting wire, Sn is 15%, Ti is 0.3%, and Cu is the remaining by weight composition.

Each of the bronze Nb ₃ Sn compound superconducting wires has a wire diameter of φ1 mm, and the filament diameter is φ3.5 μm except for those having a Ta core (φ7.9 μm). The ratio of the area of the stabilizer, reinforcing material and superconductor occupying the cross-sectional area of each bronze Nb ₃ Sn compound superconducting wire is described in Table 1 as “Cu / RM / SC”. The Nb ₃ Sn compound superconductor occupies an area of 44 to 51.3% of the cross-sectional area of the wire.

In the heat treatment step S102, a compound generation heat treatment is performed under a predetermined condition, and the wire formed in the wire forming step S101 is made into a compound superconducting wire. For example, in the case of Nb ₃ Sn, this compound generation heat treatment may be performed at a predetermined temperature of 600 ° C. or higher, such as 650 ° C. to 700 ° C., in a vacuum or in an inert gas atmosphere for 100 hours. However, the conditions for the compound generation heat treatment generally vary depending on the compound superconductor to be generated, the compound superconducting raw material, the configuration, dimensions, etc. of the wire.

  In the double bending process S103, the compound superconducting wire obtained by the compound generation heat treatment is subjected to a double bending process in which bending strain is applied from both the positive and negative directions. As the double swing bending process, for example, a single double swing process in which bending strain is applied once to the superconducting wire from both the positive and negative directions may be performed once or more. When a single double swing process is performed once or more as the double swing process, for example, a bending strain may be applied using a pulley as shown in FIG.

  In FIG. 4, the compound superconducting wire 10 is wound around a compound generation heat treatment bobbin 11 and subjected to heat treatment. The compound superconducting wire 10 is drawn to the stranded wire bobbin 14 with a predetermined tension, and is wound around the stranded wire bobbin 14 from the compound generation heat treatment bobbin 11 via the rotating member 12 and the pulley 13. However, as a double-bend bending process, a process of applying a double-bend bending from various directions while rotating or twisting the wire to be processed, a process of repeatedly applying tension and compression, and applying force from both the positive and negative directions Processing may be applied.

FIG. 5 shows the change in critical current when the range of the double bending strain applied to the compound superconducting wire is 0 to 1.5%. In FIG. 5, the vertical axis represents the normalized critical current Ic / Icm, the horizontal axis represents the double bending strain εpb (%), and the double bending when a 14T magnetic field is applied at a temperature of 4.2K. Shows distortion characteristics. From the critical current double-bending strain characteristics shown in FIG. 5, for the CuNb reinforced bronze method Nb ₃ Sn compound superconducting wire (a), the critical due to the addition of the double-bending strain to the range of 0 to over 1.2%. There is an improvement in current. With respect to the CuNbTi reinforced bronze method Nb ₃ Sn compound superconducting wire (b), improvement or maintenance of the critical current is observed due to the addition of the double bending strain to the range of 0 to 1.0%. The non-reinforcing bronze method Nb ₃ Sn compound superconducting wire (d) and the Ta reinforced bronze method Nb ₃ Sn compound superconducting wire (c) are critical due to the addition of double bending strain to a range of 0 to over 0.8%. There is an improvement in current.

  Moreover, it turns out that it is preferable to set it as 0.5 to 0.8% as the double bending strain added to a compound superconducting wire from FIG. Furthermore, about 0.8% is more preferable. In addition to the one shown in FIG. 5, the maximum value of improvement of the critical current may be about twice as shown in FIG. Further, the number of times of performing the single swing process is preferably 1 to 20 times.

Table 2 Reversed bending of the Nb 3 _Sn compound superconducting wire Nb 3 not subjected to _Sn compound superconducting wire and Reversed bending subjected is a table showing the magnetic field dependence of the critical current, FIG. 6 The magnetic field dependence characteristics of this critical current are graphed.

This Nb ₃ Sn compound superconducting wire includes a reinforcing material made of CuNb and a stabilizing material made of Cu. Thin solid line, the curve represented using dashed and bold solid lines, respectively, Reversed bending is not subjected to processing conventional Nb 3 _Sn compound superconducting wire, Nb 3 _Sn compound superconducting wire plus bending strain of 0.3%, ₃ represents the magnetic field dependence characteristics of the critical current for the Nb ₃ Sn compound superconducting wire to which a bending strain of 0.8% is added.

As is clear from Table 2 and FIG. 6, the critical current characteristics of the Nb ₃ Sn superconducting wire subjected to the double-bending are compared with the critical current characteristics of the conventional Nb ₃ Sn superconducting wire not subjected to the double-bending. Is remarkably superior in any of the applied magnetic fields 10T to 17T. In other words, the Nb ₃ Sn compound superconducting wire that has been strengthened with CuNb described above is subjected to a double swing bending process, compared to a conventional Nb ₃ Sn compound superconducting wire that is not subjected to a double swing bending process. It is shown that the critical current characteristic is remarkably enhanced. Further, the critical current is higher when the applied bending strain is 0.8% than when the bending strain is 0.3%.

Specifically, the critical current characteristics of the Nb ₃ Sn superconducting wire subjected to the double bending process according to the present invention are compared with the critical current characteristics of the Nb ₃ Sn superconducting wire which is not subjected to the conventional double bending process indicated by the broken line. As for the current characteristics, when the applied bending strain is 0.8%, it is about twice, and when it is 0.3%, it is about 1.3 times. Furthermore, in the compound superconducting cable produced by twisting the above-described Nb ₃ Sn superconducting wire as a superconducting element wire, the critical current was hardly lowered due to the strain generated when twisted. Thus, a heat-treated compound superconducting cable excellent in superconducting properties was obtained. The above indicates that the double bending process has an effect that is more than the effect of reducing the influence of strain associated with stranded wire processing, winding processing, etc. on the critical current, that is, the effect of increasing the critical current characteristics. .

  Since the magnetomotive force of the superconducting magnet is expressed as the number of windings multiplied by the operating current, the upper limit of the operating current can be increased by improving the critical current characteristics, and the superconducting magnet can be downsized. As described above, the improvement in the critical current characteristic is expected to reduce the number of windings to about ½.

FIG. 7 is a diagram showing the strain resistance characteristics of the Nb ₃ Sn superconducting wire described above. In FIG. 7, the vertical axis represents the normalized critical current Ic / Icm, and the horizontal axis represents the bending strain ε (%) generated by stranded wire, winding processing, or the like. Further, the curve denoted by the broken line, represents the strain tolerance of the conventional Nb 3 _Sn superconducting wire, the curve denoted by the solid line, represents the strain tolerance of the Nb 3 _Sn superconducting wire of the present invention. As shown in FIG. 7, in the conventional Nb ₃ Sn superconducting wire, the critical current Ic / Icm, which is normalized from about 0.4% of the strain applied by stranded wire processing, winding processing, etc., occurs. On the other hand, in the Nb ₃ Sn superconducting wire subjected to the double bending process of the present invention, the applied strain is not reduced to the critical current Ic / Icm normalized to about 1.5%, and the strain resistance characteristics However, this is an improvement of about 4 times.

  As shown in FIG. 1 (b), one embodiment of the method for producing a compound superconducting cable of the present invention is a method in which a compound superconducting material that becomes a superconductor by performing a predetermined heat treatment occupies at least a part of the cross section. The wire rod forming step S101 to be formed, the heat treatment step S102 to heat-treat the wire rod formed in the wire rod forming step S101 to make the compound superconducting raw material a superconductor, and the wire rod to the compound superconducting wire, and the compound obtained in the heat treatment step S102 A double swing bending process S103 for applying a bending strain to the superconducting wire from both the forward and reverse directions, and a compound superconducting wire subjected to the double bending process for the twisted wire processing or rolling after the twisted wire processing. A compound superconducting cable comprising a cable forming step S104 for forming a cable by performing a molding process such as It is a production method.

  Here, the above-described stranded wire processing refers to processing for twisting compound superconducting wires, and the forming processing refers to processing for forming compound superconducting wires into a predetermined shape or the like. As described above, the compound superconducting cable of the present invention is manufactured by subjecting the compound superconducting wire of the present invention to stranded wire processing or forming processing such as rolling after stranded wire processing.

  As described above, the compound superconducting wire subjected to the processing in the cable forming step S104 has a strain resistance improved by about four times that of the conventional one. It can be greatly expanded from about 4% to about 1.5%. As a result, the radius of curvature of the spiral at the time of stranded wire processing can be greatly shortened, and it becomes possible to easily manufacture the compound superconducting cable.

Specifically, when a compound superconducting wire having a strand diameter of φ1 mm is spirally twisted, the compound superconducting wire having an allowable bending strain ε of 0.4% is 125 mm or more based on the following formula (1). However, in the compound superconducting cable of the present invention, since the allowable bending strain ε of the compound superconducting wire is 1.5%, the curvature radius ρ may be 33 mm or more.
ε = t / (2ρ) (1)
Here, t is a wire diameter.

Further, when six compound superconducting wires having a wire diameter of φ1 mm are wound around a core wire of φ1 mm at a predetermined pitch, compound superconductivity having an allowable bending strain ε of 0.4% based on the following equation (2) For the wire, a pitch h of 64 mm or more is necessary. However, in the compound superconducting cable of the present invention, since the allowable bending strain ε of the compound superconducting wire is 1.5%, the pitch h may be 30 mm or more.
ρ = [a ² + (h / 2π) ² ] / a (2)
Here, a is the distance from the center of the core wire to the center of the compound superconducting wire. From the viewpoint of the stranded wire coil, the stranded wire coil with a short pitch between the strands hardly causes loosening between the strands, and the product quality can be improved.

The compound superconducting wire and the compound superconducting cable of the present invention will be described in more detail with reference to the drawings with reference to the drawings. A compound superconducting cable was produced using the CuNb reinforced bronze method Nb ₃ Sn compound superconducting wire of the present invention whose cross-sectional structure is shown in FIG. That is, a compound superconductor material composed of Nb ₃ Sn is disposed at the center of the cross section of the wire material, and a composite material serving as a reinforcement material composed of CuNb is disposed around the reinforcement material to constitute a wire material. The wire material is subjected to a compound generation heat treatment to cause a compound formation reaction in the composite to form an Nb ₃ Sn compound superconductor, and after the compound generation heat treatment, the superconducting wire is bent 0.3% or 0.8% from both the positive and negative directions. A double swing bending process for applying strain was performed five times to produce a CuNb reinforced bronze method Nb ₃ Sn compound superconducting wire.

FIG. 8 is a partial perspective view of one embodiment of the compound superconducting cable of the present invention thus manufactured. As shown in FIG. 8, this compound superconducting cable 100 is formed by using 36 CuNb reinforced Nb ₃ Sn compound superconducting wires having a diameter of 1 mm as strands 20 and twisting 36 strands 20. The specifications of the strand 20 are as follows, and the strand 20 was prepared with a length of 12 km. That is, the outer diameter of the strand 20 is φ1.0 mm, the ratio of the area occupied by the Nb ₃ Sn compound superconductor occupying the cross-sectional area of the strand 20 and other CuNb and Cu, etc. is 1 to 2, and the twist pitch is 8 mm. When a magnetic field of 12 T is applied at a temperature of 4.2 K, the critical current value is 198 A when the double-bending is not performed, and 440 A is when the double-bending is performed. As described above, the critical current value measured under the above-described conditions was more than twice the value of the value subjected to the double bending process and the value not applied.

Hereinafter, a specific example will be described. First, a compound-forming heat treatment and a double-bending bending process were performed on the element wire to produce a CuNb-reinforced Nb ₃ Sn compound superconducting wire having a diameter of 1 mm. Here, the above-described compound generation heat treatment was performed as follows. The compound superconductor was formed by being wound around a stainless steel compound generation heat treatment bobbin 11 having a diameter of 500 mm and a winding width of 200 mm shown in FIG. 4 and subjected to heat treatment at a temperature of 670 ° C. for 96 hours in an argon gas atmosphere.

  Next, the compound superconducting wire subjected to the compound generation heat treatment as described above was subjected to a double bending process as follows. That is, as shown in FIG. 4, the element wire 20 that has been subjected to the compound generation heat treatment as described above is passed through a pass line in which ten pulleys having a diameter of 100 mm are arranged in series, and a single double swing process is repeatedly performed. A double swing bending process was performed. That is, a single double swing process for applying a bending strain of 0.8% to the wire 20 was repeated 10 times. At this time, a tension of about 50 Mpa was applied to the strand 20.

  Next, the strand 20 subjected to the double-bending bending process was cut into 36 strips each having a length of 300 m, and wound around a stranded wire bobbin 14 having a trunk diameter of 80 mm. The critical current was measured by applying a magnetic field in liquid helium before and after performing the double bending process. As a result, a critical current characteristic similar to that shown in FIG. 6 was obtained. Even in this case, the critical current of the strand 20 to which repeated strain was applied was about twice as large as that of the strand to which no strain was applied.

  Next, the 36 stranded bobbins 14 were set in a stranded wire machine and twisted at a pitch of 50 mm to produce a compound superconducting cable 100 as shown in FIG. The compound superconducting cable 100 is wound around a bobbin having a diameter of 300 mm to form a coil, and the critical current is measured under the same conditions as those shown in the specifications of the element wire 20, that is, in a magnetic field of 12 T in liquid helium. The current was 12.2 KA.

Conventionally, the critical current is greater strain dependency, when Nb 3 _Sn wire twisted wire was heat-treated, but the critical current was thought to degrade to less than half, according to the present invention, the compounds generated heat treated Nb ₃ Sn By applying repeated strain to the superconducting wire, the residual stress existing inside the superconducting wire can be eliminated, and even if it is cabled, the critical current is deteriorated, rather it can be increased, and excellent superconducting characteristics can be obtained. It is done.

FIG. 1 is a process diagram for explaining one embodiment of a method for producing a compound superconducting wire and a compound superconducting cable of the present invention. FIG. 2 is a diagram showing an example of a cross-sectional shape of the compound superconducting wire of the present invention. FIG. 3 is a diagram showing an example of another cross-sectional shape of the compound superconducting wire of the present invention. FIG. 4 is a diagram illustrating an example of a configuration of an apparatus that performs the double bending process in the double bending process. FIG. 5 is a diagram showing an example of a double bending strain characteristic of the compound superconducting wire shown in FIG. FIG. 6 is a diagram illustrating an example of the magnetic field dependence characteristics of the critical current for the Nb ₃ Sn compound superconducting wire of the present invention and the conventional Nb ₃ Sn compound superconducting wire. FIG. 7 is a diagram showing an example of strain resistance characteristics of the Nb ₃ Sn compound superconducting wire of the present invention and the conventional Nb ₃ Sn compound superconducting wire. FIG. 8 is a perspective view of the compound superconducting cable of the present invention. FIG. 9 is a graph showing the bending strain dependence characteristics of the critical current obtained for the Nb ₃ Sn superconducting wire manufactured using the conventional technique.

Explanation of symbols

1, 2, 3 Region 10 Compound superconducting wire 11 Compound generation heat treatment bobbin 12 Rotating member 13 Pulley 14 Stranded bobbin 20 Bronze method Nb3Sn compound superconducting wire 100 Compound superconducting cable

Claims (7)

A wire material forming step in which a compound superconducting raw material that becomes a superconductor by performing a predetermined heat treatment forms a wire material that occupies at least part of the cross section; and
A heat treatment step of applying the heat treatment to the wire formed in the wire forming step to make the compound superconducting raw material a superconductor, and making the wire a compound superconducting wire;
A compound superconducting wire manufacturing method comprising: a compound superconducting wire obtained in the heat treatment step, and a double-bending bending process in which a double-bending bending process is applied to apply bending strain from both directions.   2. The method for producing a compound superconducting wire according to claim 1, wherein, in the double bending process, bending strain is applied to the compound superconducting wire within a range of 0.5% to 1.0%.   2. The double swing bending step, wherein a single double swing process in which bending strain is applied once in both the forward and reverse directions is applied to the compound superconducting wire 5 times or more and 20 times or less. 2. A method for producing a compound superconducting wire according to 2.   The said compound superconducting wire manufactured using the manufacturing method of the said compound superconducting wire of any one of Claim 1 thru | or 3 is shape | molded after twisted wire processing or twisted wire processing. A method for producing a compound superconducting cable, comprising a cable forming step for forming a cable. The method for producing a compound superconducting cable according to claim 4 , wherein a stabilizing material is formed on an outer periphery of the compound superconductor. The method of manufacturing a compound superconducting cable according to claim 4 or 5 , wherein the compound superconductor is made of Nb ₃ Sn or Nb ₃ Al. The compound superconductivity according to any one of claims 4 to 6, wherein a reinforcing material made of any one of conductive materials of CuNb, CuAl ₂ O ₃ , CuNbTi, and Ta is formed. Cable manufacturing method.

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