JP2017054579A - Manufacturing method of compound-based superconducting wire rod and manufacturing method of compound-based superconducting cable - Google Patents

Abstract

The present invention provides a compound superconducting wire that not only has excellent superconducting properties (particularly high critical current) during coil operation, but also enables coil design with an appropriate driving safety factor. It is to provide a method and the like. A method 100 for producing a compound superconducting wire according to the present invention includes a wire forming step S101 for forming a wire 20 from a composite material having a compound superconducting raw material 21 and a reinforcing material 22 arranged around the raw material 21. The heat treatment is performed in a state in which bending strain is applied to the wire 20 to obtain the raw material 21 as the superconductor 1, and the heat treatment step S102 to obtain the wire 20 as the compound superconducting wire 10 and the heat treatment step S102. Bending process S103 in which bending work is applied to superconducting wire 10 and bending strains of-(0.1 to 0.6)% and + (0.1 to 0.6)% are each applied twice or more and superconducting wire 10 after this bending process S103 And a winding step S104 in which a bending strain is continuously limited to within a range of ± 0.7% and wound to form a superconducting coil. [Selection] Figure 1

Description

  The present invention relates to a method for producing a compound-based superconducting wire suitable for use in forming a superconducting coil, and a method for producing a compound-based superconducting cable including a cable forming step for forming a superconducting cable using these compound-based superconducting wires. About.

Conventionally, superconducting magnets using compound superconducting wires such as Nb ₃ Sn or these compound superconducting cables are generally manufactured after winding a superconducting wire around a superconducting coil winding frame to form a magnet. A so-called wind-and-react method, in which a compound-forming heat treatment is performed, is applied. This is because the heat treatment of compound superconducting wires such as Nb ₃ Sn and these compound superconducting cables are very weak against strain, and the winding process in which large strain acts after heat treatment cannot be performed. It is.

When manufacturing large magnets such as dipole magnets for high magnetic field accelerators and high magnetic field large-diameter magnets using the wind-and-react method, a compound generation heat treatment for generating Nb ₃ Sn is performed at a predetermined temperature of 600 ° C. or higher. Although it is necessary to perform in a furnace in a vacuum or an inert gas atmosphere, in order to perform this heat treatment, a large heat treatment furnace that can accommodate the entire large magnet must be prepared, and the size of the magnet is limited. was there.

Furthermore, in order to produce a compact superconducting magnet with a high magnetic field, it is effective to increase the critical current density of the superconducting conductor so that a large current can flow. One of the means is a twisted superconducting wire. Can be mentioned. However, even if it is twisted using a compound superconducting wire such as Nb ₃ Sn, a large strain cannot be given as long as a compound superconducting wire such as Nb ₃ Sn is used. However, the problem described above is not solved.

The reason why compound superconducting wires such as Nb ₃ Sn are weak against strain is that the superconductor tends to become brittle after heat treatment, and that the compound superconducting wires are composed of a composite material composed of a plurality of different materials. This is due to the fact that compressive residual strain is generated in the superconductor due to the difference in thermal shrinkage of each material constituting the superconducting wire when cooled, but recently, strengthening including reinforcing materials such as CuNb and CuAl ₂ O ₃ A type Nb ₃ Sn wire has been developed, and due to its strength improvement, a superconducting wire obtained by heat-treating the wire is then wound to form a superconducting coil, so-called a react and wind method, Magnets can be manufactured.

  For example, Patent Documents 1 and 2 disclose a conventional method for producing a compound superconducting coil by the react and wind method. However, the manufacturing methods disclosed in Patent Documents 1 and 2 only adopt a configuration in which the upper limit of the allowable strain acting on the superconducting wire in the winding process is limited to about 1%. No consideration is given to the occurrence of compressive residual strain in the superconductor, and with such a configuration, there is a problem in that current characteristics deteriorate as the compressive residual strain in the superconductor occurs.

  Patent Document 3 discloses a method of manufacturing a superconducting magnet in which a reinforced and stabilized superconducting wire is preliminarily made into a superconducting material by heat treatment and then wound into a coil shape under application of tension. If the bending process is up to 50%, the coil (superconducting magnet) can be manufactured by the react-and-wind method. However, Patent Document 3 merely discloses that the coil shape can be designed relatively freely if bending is performed up to 0.5% from the viewpoint of performance degradation. It is not intended to optimize the superconducting characteristics (especially critical current) by controlling the strain characteristics of the wire.

  Furthermore, the present applicant has proposed a method of manufacturing a compound superconducting wire or the like using the react and wind method in Patent Documents 4 to 6.

  Patent Document 4 discloses a method for producing a compound superconducting wire or the like that 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. No. 5 discloses a method for producing a compound superconducting stranded wire that relieves strain remaining inside the compound superconducting wire and does not deteriorate the performance of superconducting characteristics during twisting.

  The manufacturing method described in Patent Documents 4 and 5 includes a bending process step of applying bending strain to each of the compound superconducting wire (Patent Document 4) and the compound superconducting stranded wire (Patent Document 5) obtained in the heat treatment process. However, none of the manufacturing methods considered bending strain in the winding process of winding to form a superconducting coil after the bending process, so, for example, the body diameter of the superconducting coil winding frame Depending on the difference, the bending strain acting on the compound superconducting wire constituting the superconducting coil changes, so that sufficient superconducting characteristics (particularly critical current) may not be obtained.

  In the patent documents 4 and 5, the present applicant can reduce or remove the residual strain without damaging the reaction heat-treated compound superconducting wire or compound superconducting stranded wire, and improve their performance. Proposed to be used as a wire for react and wind or a stranded wire, but the actual usage is not specifically disclosed, and in order to confirm the proper conditions when using it Work was necessary.

  Further, in Patent Document 6, after adding bending strain to the compound-based superconducting wire exhibiting strain dependence subjected to the react treatment, the bending strain is unloaded and coiled to improve the mechanical characteristics and critical current value. Although a superconducting magnet using a compound superconducting wire has been disclosed, in this case as well, as in Patent Documents 4 and 5, bending distortion in the winding process of winding to form a superconducting coil after the bending process is described. There was a case where sufficient superconducting characteristics (especially critical current) could not be obtained because of no consideration.

  Furthermore, Patent Document 7 discloses a method for improving the critical current value of a superconducting coil by applying a bending strain to the superconducting coil. However, since the method described in Patent Document 7 does not consider removing or alleviating the residual strain of the wire itself before winding, there is a problem that an essential performance improvement effect cannot be obtained.

From the above, even if the Nb ₃ Sn wire material that has been proposed so far is actually wound to form a superconducting coil, the performance as a coil cannot be predicted, so a design with a high driving safety factor must be made. I didn't get it. Therefore, the current situation is that the energization capacity of the wire is increased, the length of the wire is increased, the coil itself and the cooling system are enlarged, the cost is increased, and commercial use has not been achieved yet.

  Also, for the purpose of increasing current carrying capacity, the superconducting characteristics when a strain is applied to a cable conductor such as a round cable or a flat Rutherford cable in which a plurality of superconducting wires are twisted together constitute the cable. This is due to the characteristics of the wire. For example, regarding improvement of superconducting characteristics when pre-bending strain is applied, Non-Patent Document 1 describes a round cable and Non-Patent Document 2 describes a flat-type Rutherford cable. In addition, the present applicant has published Non-Patent Document 3 and Non-Patent Document 4, but at this point, no specific knowledge has been obtained that will lead to commercialization on a commercial basis.

JP 2002-231524 A JP-A-6-204029 Japanese Patent No. 3340323 Japanese Patent No. 4532369 Japanese Patent No. 5718171 JP 2004-63128 A JP 2003-332122 A

G.Nishijima, H. Oguro, S. Awaji, H. Tsubouchi, S. Hanai, and Kazuo Watanabe, “Application of prebending effect to triplet cables using bronze-rote Nb3Sn strands,” IEEE Trans. Appl. Supercond., Vol. 17, no. 2, Jun. 2007, pp. 2595-2598. M. Sugimoto, H. Tsubouchi, S. Endoh, A. Takagi, K. Watanabe, S. Awaji, and H. Oguro, “Development of Nb-rod-method Cu-Nb reinforced Nb3Sn Rutherford cables for react-and-wind processed wide-bore high magnetic field coils, ”IEEE Trans. Appl. Supercond., vol. 25, no. 3, Jun. 2015, Art. ID. 6000605. Takuya Omura, Hidetoshi Oguro, Satoshi Awaji, Kazuo Watanabe, Masahiro Sugimoto, Hirokazu Tsubouchi, "Effect of Coil Diameter on the Critical Current of CuNb / Nb3Sn Wire", Proc. Takuya Omura, Hidetoshi Oguro, Satoshi Awaji, Kazuo Watanabe, Masahiro Sugimoto, Hirokazu Tsubouchi, "Analysis of the relationship between critical current and pure bending strain of CuNb / Nb3Sn wire", Proceedings of the 91st Spring 2015 Low Temperature Engineering and Superconductivity Society p92 .

  The object of the present invention is to provide a compound-based superconducting wire suitable for use in forming a superconducting coil, in particular, a heat treatment process, a bending process (pre-bending strain introduction process) and a winding process (pure bending strain). By properly controlling the internal strain (particularly bending strain) of the wire through a series of steps consisting of the introduction step), not only has excellent superconducting properties (particularly high critical current) during coil operation, Method for producing compound superconducting wire that enables coil design with an appropriate driving safety factor, and method for producing compound superconducting cable including a cable forming step for forming a superconducting cable using these compound superconducting wires Is to provide.

  The gist configuration of the present invention is as follows.

(1) A wire forming step of forming a wire from a composite material having a raw material before compound superconductor generation and a reinforcing material disposed around the raw material, and a heat treatment is performed in a state where bending strain is applied to the wire. The raw material is made into a compound superconductor, the heat treatment step to make the wire into a compound superconducting wire, and the superconducting wire obtained in the heat treatment step is subjected to bending, and-(0.1-0. 6) Bending process in which bending strain (pre-bending strain) of% and + (0.1-0.6)% is applied twice or more, and bending strain (pure bending strain) in the superconducting wire after the bending process And a winding step of forming a superconducting coil by continuously winding the wire while restricting it within a range of ± 0.7%.

(2) The method for producing a compound superconducting wire according to (1), wherein the composite material further includes an Sn diffusion preventing material between the raw material and the reinforcing material.

(3) The method for producing a compound superconducting wire according to (1) or (2), wherein the composite material further includes a stabilizing material around the reinforcing material.

(4) The method for producing a compound superconducting wire according to (3), wherein the stabilizing material is made of Cu or a Cu alloy.

(5) The composite material is any one of (1) to (4), wherein the superconductor is composed of Nb ₃ Sn, and the reinforcing material is composed of at least Cu and Nb. The manufacturing method of the compound type superconducting wire described in 1.

(6) The bending strain is applied by winding the wire around a heat treatment bobbin having a predetermined body diameter in the heat treatment step, and the superconducting wire is drawn from the heat treatment bobbin in the bending step. Then, it is added by passing between a plurality of bending jigs having a predetermined cylinder diameter arranged at intervals, and, in the winding step, a predetermined cylinder different from the cylinder diameter of the bobbin for heat treatment The method for producing a compound-based superconducting wire according to any one of (1) to (5) above, wherein the compound-based superconducting wire is added while being wound around a winding frame for a superconducting coil having a diameter.

(7) After the wire forming step and before the heat treatment step, the plurality of wires formed by the wire forming step are subjected to stranded wire processing or forming processing after stranded wire forming to form a cable. A method for producing a compound superconducting cable, further comprising a cable forming step, wherein the method for producing a compound superconducting wire according to any one of (1) to (6) is applied to the cable. .

  According to the present invention, a wire forming step of forming a wire from a composite material having a raw material before compound superconductor generation and a reinforcing material disposed around the raw material, and in a state where bending strain is applied to the wire A heat treatment is performed to turn the raw material into a compound superconductor, a heat treatment step to turn the wire into a compound superconducting wire, and bending to the superconducting wire obtained in the heat treatment step. ~ 0.6)% and + (0.1-0.6)% bending process each of which is applied twice or more, and bending stress is continuously added to the superconducting wire after the bending process by ± 0. In addition to the winding process of forming a superconducting coil by winding while limiting within the range of 7%, the internal strain (especially bending strain) of the wire is appropriately controlled, and during coil operation Excellent superconducting properties (especially high critical current) A compound system comprising a compound superconducting wire manufacturing method and a cable forming process for forming a superconducting cable using these compound superconducting wires, which enables coil design with an appropriate driving safety factor. It has become possible to provide a method for manufacturing a superconducting cable.

FIG. 1 is a typical process flow diagram for explaining a method for producing a compound superconducting wire of the present invention. FIG. 2 is a schematic sectional view showing an example of a typical compound-based superconducting wire of the present invention. FIG. 3 is a diagram for explaining a state before the heat treatment of the wire wound around the heat treatment bobbin and heat-treated in the heat treatment step. FIG. 4 is a diagram for explaining a state in which bending strain is applied to the superconducting wire in the bending process. FIG. 5 is a diagram for explaining a state when a superconducting wire is wound around a superconducting coil winding frame in the winding step. FIG. 6 is a conceptual diagram for explaining a state in which bending strain is applied to the wire in each of the heat treatment step, the bending step (preliminary bending strain introduction step), and the winding step (pure bending strain introduction step). FIG. 7 is a diagram showing current-carrying characteristics of the compound superconducting wire in the present invention.

  Below, the manufacturing method of the compound type superconducting wire of this invention is demonstrated in detail, referring drawings.

  FIG. 1 shows a process flow of one embodiment of a method for producing a compound superconducting wire of the present invention. A method 100 for manufacturing a compound superconducting wire shown in FIG. 1 includes a wire forming step S101 for forming a wire from a composite material having a raw material before compound superconductor generation and a reinforcing material arranged around the raw material, A heat treatment is performed in a state where bending strain is applied to the wire to make the raw material into a compound superconductor, and a heat treatment step S102 to convert the wire into a compound superconducting wire, and bending to the superconducting wire obtained in the heat treatment step S102 And bending process S103 in which bending strains of-(0.1 to 0.6)% and + (0.1 to 0.6)% are each applied twice or more, and bending strain in this bending process S103. A winding step S104 in which a superconducting coil is formed by adding a bending strain to the superconducting wire after being added while continuously limiting the bending strain within a range of -0.7% to + 0.7% to form a superconducting coil; including This is a method for producing a compound superconducting wire.

<Wire forming process>
The wire forming step S101 is a step for forming a wire from a composite material having a raw material before compound superconductor generation and a reinforcing material arranged around the raw material. The wire is formed from the composite material, and becomes a reinforced compound superconducting wire by the heat treatment process described below. Further, the composite material and the wire formed from this composite material may further have an Sn diffusion preventing material between the raw material before the compound superconductor generation and the reinforcing material, and in addition, stable around the reinforcing material. You may further have a chemical.

As an example of the cross-sectional structure of the wire 20, for example, as shown in FIG. 3, a reinforced unreacted Nb ₃ Sn superconducting filament group 21 having a diameter d _fb is arranged at the center of the cross section of the wire, and Ta or A tin (Sn) diffusion prevention material 23 made of Nb is arranged, and a reinforcing material 22 in which Nb filaments of less than 1 μm are embedded in copper or a copper alloy is arranged in a ring shape around it, and then a stable consisting of a copper sheath around it. There is a case where a Cu—Nb reinforced Nb ₃ Sn wire structure having a diameter d, in which the chemical material 24 is disposed, is used.

For the reinforcing material 22 and the stabilizing material 24, a conductive material such as a metal or an alloy material is used. Reinforcement 22 is preferably configured with at least Cu and Nb, for example CuNb and CuNbTi and the like, but it is more preferable to particularly use CuNb, not limited to the such compositions, for example, CuAl ₂ It may be composed of O ₃ , Ta or the like. Moreover, it is preferable that the stabilizing material 24 is comprised with Cu or Cu alloy.

The raw material before compound superconductor production is preferably configured to be a compound such as Nb ₃ Sn, Nb ₃ Al, etc., through a heat treatment step for making a superconductor. Moreover, the raw material before compound superconductor production | generation can be made into the structure obtained by combining several Nb filament which has a diameter of 1 micrometer or more, for example.

As the wire forming step S101, for example, when the compound superconductor is Nb ₃ Sn, a method for producing a known Nb ₃ Sn wire such as a bronze method, an internal tin (Sn) diffusion method, or a powder tube (PIT) method is used. Is suitable from the viewpoint of obtaining good processability.

<Heat treatment process (generation process of compound superconductor)>
The heat treatment step S102 is formed in the wire forming step S101 while subjecting the wire with the bending strain ε _hi to heat treatment under a predetermined heat treatment condition to make the compound superconductor raw material before the compound superconductor generation. This is a process for making the wire 20 into the compound superconducting wire 10. The bending strain ε _hi is preferably applied to the wire rod 20 by, for example, winding the wire rod 20 on a heat treatment bobbin 29 having a predetermined body diameter D _h , and suitable bending strain ε _hi (%) is, for example, It is in the range of 0.01 to 0.7%. If the bending strain ε _hi at the time of heat treatment is too small, there is a problem in the manufacturing cost that the heat treatment furnace itself becomes large. If the bending strain ε _hi at the time of heat treatment is too large, the wire is straightened from the heat treatment bobbin 29 after the heat treatment. This is because a large bending strain ε _{hi in the} opposite direction is applied to the compound superconducting filament simply by pulling out, and filament breakage may occur. FIG. 3 is a diagram for explaining a state before the heat treatment of the wire 20 that is wound around the heat treatment bobbin in a coil shape and heat-treated in the heat treatment step S102.

The bending strain ε _hi applied to the wire 20 in the heat treatment step S102 can be calculated by the following equation (1). That is, the number of winding layers when the wire 20 is wound around the heat treatment bobbin is i (i = 1 to n), the bending radius of the wire 20 of the i-th layer is R _hi (mm), and the diameter of the superconducting filament group 21 is When d _fb (mm) and the diameter of the wire 20 is d (mm), the bending strain ε _hi is
ε _hi (%) = (d _fb / 2) × (1 / R _hi ) × 100 (1)
Can be expressed as When the above equation (1) is rewritten into an equation including the body diameter D _h of the heat treatment bobbin 29, the following equation (1) ′ is obtained.
ε _hi (%) = (d _fb / 2) × (2 / (D _h + 2d × id)) × 100 (1 ′)

The bending strain ε _hi is the maximum at the bending strain ε _h1 (= (d _fb / 2) × (1 / R _h1 ) × 100) when the number of winding layers is the first layer and the bending radius of the wire is R _h1. The bending strain ε _hn (= (d _fb / 2) × (1 / R _hn ) × 100) when the number of winding layers is the outermost layer of the nth layer and the bending radius of the wire is R _hn is minimized.

For example, in the case of the bronze method Nb ₃ Sn, this heat treatment is performed under conditions of 600 ° C. or higher, for example, a temperature of 650 to 700 ° C. for 50 hours or longer, preferably 50 to 150 hours in a vacuum or in an inert gas atmosphere. Can be done. Moreover, before performing the heat treatment, for example, preheating under a condition of 50 to 150 hours at a temperature of 550 to 590 ° C. may be applied. The conditions for this heat treatment generally vary depending on the compound superconductor to be produced, the raw material before production of the compound superconductor, the configuration, dimensions, etc. of the wire.

  FIG. 2 shows an example of a cross-sectional structure of the compound superconducting wire 10. The superconducting wire 10 has a compound superconductor 1 at the center of the cross section, and has a cross-sectional structure having a reinforcing material 2 around the compound superconductor 1, and in FIG. The Sn diffusion preventing material 3 is provided between the materials 2 and the stabilizing material 4 is provided around the reinforcing material 2.

<Bending process (pre-bending strain introduction process)>
In the bending process, bending is performed on the superconducting wire 10 obtained in the heat treatment process, so that bending strains of − (0.1 to 0.6)% and + (0.1 to 0.6)% are 2 respectively. It is a process of adding more than once. FIG. 4 is a diagram for explaining a state in which bending strain is applied to the superconducting wire 10 in the bending process.

As a method of applying (introducing) bending strain to the superconducting wire 10, as shown in FIG. 4, the superconducting wire 10 that has undergone the heat treatment step is drawn from the bobbin 30 for heat treatment with a predetermined tension, and then arranged at intervals. A method of bending the superconducting wire 10 through a plurality of bending jigs having a predetermined body diameter, for example, pulleys 31, 32,... Is wound around the bobbin 30 for heat treatment in FIG. A pulley 31 having a diameter D _p1 that is smaller than the bobbin diameter D _h of the heat treatment bobbin 30, and a direction wound around the heat treatment bobbin 30. passing two or more times in succession and the pulley 32 with the bobbin diameter D _b larger diameter D _p2 than in the reverse direction to be disposed in a position subjected to bending a superconducting wire 10 and the heat treatment bobbins 30 By is shown as an example the case of applying a bending a superconducting wire 10.

  In the bending process of the present invention, the superconducting wire 10 after the heat treatment process is subjected to bending strains of − (0.1 to 0.6)% and + (0.1 to 0.6)% two times or more, respectively. The reason for the addition is that the bending strain in the positive direction obtained by passing through the pulley 31 disposed at a position where the superconducting wire 10 is bent in the same direction as the direction wound around the bobbin 30 for heat treatment, and for heat treatment The absolute value of one or both of the bending strains in the negative direction obtained by passing through the pulley 32 disposed at the position where the superconducting wire 10 is bent in the direction opposite to the direction wound around the bobbin 30 is 0. If it is less than 1%, even if a predetermined bending strain is applied in the subsequent winding process, the residual strain relaxation effect of the compound superconducting filament by the pre-bending process is small. If the absolute value of one or both of the positive direction bending strain and the negative direction bending strain is larger than 0.6%, the local effect of the compound superconducting filament cannot be expected. This is because damage may occur, and in addition, an effect of improving the superconducting characteristics cannot be expected.

In the bending step S103, the positive bending strain applied to the superconducting wire 10 having the diameter d is ε _{pbi +} , the negative bending strain is ε _pbi−, and the i layer when the wire 20 in the heat treatment step is wound around the heat treatment bobbin. corresponding to the bending radius R _hi eye of the wire, bending jig (e.g. a pulley) 31 by forward bending radius R _Pb1i, a bending jig (e.g. a pulley) 32 by reverse (negative) direction bending radius When R _Pb2i The positive bending strain ε _{pbi +} and the negative bending strain ε _pbi- can be calculated by the following equations (2) and (3), respectively.
ε _{pbi +} (%) = (d / 2) × {(1 / R _Pb1i ) − (1 / R _hi )} × 100 (2)
ε _pbi− (%) = (d / 2) × {(1 / R _Pb2i ) − (1 / R _hi )} × 100 (3)
Therefore, when ε _{pbi +} and ε _pbi− are determined from the above equations (2) and (3), R _Pb1i and R _Pb2i are uniquely determined according to R _hi .

The bending strain applied to the superconducting wire 10 is preferably applied by performing a double bending process in which bending strains from both the positive and negative directions are applied twice or more, preferably 5 to 10 times. The reason why the bending strain is applied twice or more from both the forward and reverse directions is that the bending strain is applied to Nb ₃ Sn in the wire unless the number of bending strains is twice or more in one or both of the forward and backward directions. This is because the residual strain is not alleviated uniformly, resulting in a problem that the superconducting performance in the longitudinal direction becomes non-uniform.

<Winding process (pure bending strain introduction process)>
In the winding step S104, the superconducting wire 10 after the bending step S103 is subjected to winding with a bending strain ε _purej being continuously limited within a range of −0.7% to + 0.7%. This is a step of forming a superconducting coil. FIG. 4 shows a case where the bobbin 33 the winding superconducting coil having a body diameter (bobbin diameter) D _c as an example. FIG. 5 is a view for explaining a state when the superconducting wire 10 is wound around the superconducting coil winding frame 41 in the winding step S104. In the winding step S104, the method of continuously applying (introducing) the bending strain ε _purej to the superconducting wire 10 is different from the body diameter D _h of the heat treatment bobbin 29 (or 30) as shown in FIG. , and a method applied by winding a superconducting coil winding frame 41 having a predetermined body diameter D _c.

In the winding process S104 after the bending process S103, the present invention appropriately controls the internal strain of the wire 20 and the superconducting wire 10 in a series of processes including a heat treatment process, a bending process, and a winding process. _However , it is necessary to continuously _{limit the} bending strain ε _purej applied to the superconducting wire 10 within a range of ± 0.7%. When the bending strain ε _purej introduced into the superconducting wire 10 in the winding step S104 is within a range of ± 0.7%, − (0.1 to 0.6)% and + (0 As a result of the critical current of the superconducting wire introduced with 0.1 to 0.6)% bending strain being significantly increased and the superconducting characteristics being improved, it is possible to design a coil with an appropriate driving safety factor. On the other hand, when the bending strain ε _purej introduced into the superconducting wire 10 is outside the range of ± 0.7%, even if the predetermined bending strains ε _{pbi +} and ε _pbi- are introduced in the bending step S103, the superconducting wire This is because an effect of improving the critical current of 10 cannot be expected.

In the winding step S104, the bending strain ε _purej introduced into the superconducting wire 10 can be calculated by the following equation (4). That is, the number of winding layers when the superconducting wire 10 is wound around the superconducting coil winding frame 41 is j (j = 1 to m), the bending radius of the j-th layer of wire is R _cj (mm), and the superconducting filament group When the diameter of 21 is d _fb (mm) and the bending radius of the wire material 20 of the i-th layer when the wire 20 is wound around the heat treatment bobbin 29 is R _hi (mm), the bending strain ε _purej is
ε _purej (%) = (d _fb / 2) × {(1 / R _cj ) − (1 / R _hi )} × 100 (4)
Can be expressed as

In the embodiment described above, the superconducting wire 10 has been described in the case of having a circular cross section having a diameter d and a diameter _dfb of the superconducting filament group 21, but the superconducting wire of the present invention has a rectangular cross section, Similar effects can be achieved.

  Furthermore, in the method for producing a compound superconducting cable according to the present invention, after the wire forming step, before the heat treatment step, the plurality of wires formed by the wire forming step are twisted or twisted. And a cable forming step for forming a cable after forming a compound superconducting wire. The compound superconducting wire having the same effect as the above-described compound superconducting wire by applying the above-described compound superconducting wire manufacturing method to the cable. A cable can be manufactured.

  Next, although the manufacturing method of the compound superconducting wire of this invention is demonstrated still in detail according to an Example, referring drawings, this invention is not limited at all by these Examples.

(Example)
A compound superconducting wire 10 having a cross-sectional structure shown in FIG. 2 was produced by the following production method.
As the wire 20 before the heat treatment step, as shown in FIG. 3, a reinforced unreacted Nb ₃ Sn superconducting filament group 21 having a diameter d _fb of 0.51 mm is arranged at the center of the cross section of the wire, and around it. A Cu—Nb reinforced Nb ₃ Sn wire having a diameter d of 0.8 mm, in which an Sn diffusion preventing material 23 made of Ta, a CuNb reinforcing material 22, and a stabilizing material 24 made of copper are arranged was used. The area ratio in the cross-sectional area of the wire 20 was 45% for the superconducting portion including the Sn diffusion preventing material 23, 38% for the CuNb reinforcing material, and 17% for the Cu stabilizing material. Since the bending radius R _hi cannot be said to be sufficiently large with respect to the diameter of the wire 20, the bending is performed using the equation (1 ′) in consideration of the diameter d of the wire 10 and the diameter d _fb of the filament group 21. The radius was calculated.
ε _hi (%) = (d _fb / 2) × (2 / (D _h + 2d × id)) × 100 (1 ′)

Next, the obtained wire 20 is wound around a plurality of heat treatment bobbins 51 each having a different body diameter (bobbin diameter D _h ), and each wire 20 is bent with different bending radii R _{h as} shown in Table 1. The wire 20 is subjected to Nb ₃ Sn generation heat treatment at 670 ° C. × 96 hr in an argon gas atmosphere in a state where bending strain is applied, so that the compound-based superconductor raw material 21 becomes the compound-based superconductor 1 and the wire 20 is After forming the Cu—Nb reinforced Nb ₃ Sn superconducting wire 10, the superconducting wire 10 was taken out from the heat treatment bobbin 51 without applying bending strain. Thereafter, as shown in FIG. 6, using the pre-bending strain applied jig 52 having a barrel diameter D _P1 site and the barrel diameter D _P2 site, a superconducting wire 10, the barrel diameter D _P1 site and the barrel diameter D _P2 site By passing 10 turns alternately, the pre-bending strains ε _{pbi +} and ε _pbi- of ± 0.5% are _applied to the superconducting wire 10 at the forward bending radius R _Pb1i and the reverse bending radius R _Pb2i shown in Table 1, respectively. Added 10 times. Thereafter, the superconducting wire 10 is wound around a winding frame 53 for a superconducting coil having a body diameter D _{C of} 31.2 mm (bending radius R _c : 15.6 mm), and the superconducting wire 10 is shown in Table 1 (pure ) A superconducting coil was fabricated with bending strain ε _purej introduced. FIG. 7 shows the energization characteristics of each produced superconducting coil. The definition of critical current was given at 1 μV / cm. The measurement was performed in liquid helium (liquid temperature: 4.14K). The external magnetic field was measured in three cases of 12T, 14.5T, and 17T. For comparison, a superconducting coil (comparative example) was produced by the same manufacturing method as in the example, except that the bending process of pre-bending the superconducting wire was not performed, and the current-carrying characteristics of each produced superconducting coil were measured. Therefore, those measurement results were also plotted in FIG.

From the results shown in FIG. 7, it was confirmed that the critical current Ic was increased when the pure bending strain ε _purej was added within an appropriate range of ± 0.7%. That is, the _{embodiment in} which the bending bending strain (pre-bending strain) ε _{pbi +} or ε _pbi- of ± 0.5% is properly introduced before coil winding and then the pure bending strain ε _purej in the appropriate range is introduced is a pre-bending. Compared with the comparative example in which the strain ε _{pbi +} or ε _pbi− is not introduced, the current-carrying characteristics are improved in the range of −0.7% to + 0.7% pure bending strain ε _purej regardless of the strength of the external magnetic field. In particular, the critical current Ic of the example that is in the range of −0.5% to + 0.6% pure bending strain ε _purej is significantly higher than the critical current Ic of the comparative example. Recognize.

  According to the present invention, a compound superconducting wire that not only has excellent superconducting characteristics (particularly high critical current) during coil operation but also enables coil design with an appropriate driving safety factor, It has become possible to provide a method for manufacturing a compound superconducting cable formed using a superconducting wire.

1 Superconductor 10 Compound Superconducting Wire 20 Wire 21 Compound Superconducting Raw Material (or Reinforced Unreacted Nb ₃ Sn Superconducting Filament Group)
2, 22 Reinforcing material 3, 23 Sn diffusion preventing material 4, 24 Stabilizing material 29, 30, 51 Bobbin for heat treatment 31, 32 Bending jig (or pulley)
33, 41, 53 Superconducting coil reel 52 Pre-bending strain application jig

Claims (7)

A wire forming step of forming a wire from a composite material having a raw material before compound superconductor generation and a reinforcing material arranged around the raw material;
A heat treatment step of applying a heat treatment in a state where bending strain is applied to the wire to make the raw material a compound superconductor, and making the wire a compound superconducting wire,
Bending in which the superconducting wire obtained in the heat treatment step is subjected to bending, and bending strains of-(0.1-0.6)% and + (0.1-0.6)% are each applied twice or more. Processing steps,
A winding step of forming a superconducting coil by adding a winding strain to the superconducting wire after the bending step while continuously limiting the bending strain within a range of ± 0.7%. A method for producing a compound superconducting wire.   The method for producing a compound superconducting wire according to claim 1, wherein the composite material further includes an Sn diffusion preventing material between the raw material and the reinforcing material.   The method for producing a compound-based superconducting wire according to claim 1, wherein the composite material further includes a stabilizing material around the reinforcing material.   4. The method for producing a compound superconducting wire according to claim 3, wherein in the composite material, the stabilizing material is made of Cu or a Cu alloy. 5. 5. The compound superconductor according to claim 1, wherein the superconductor is made of Nb ₃ Sn, and the reinforcing material is made of at least Cu and Nb. A manufacturing method of a wire.   In the heat treatment step, the bending strain is applied by winding the wire around a heat treatment bobbin having a predetermined body diameter. In the bending step, the superconducting wire is pulled out from the heat treatment bobbin and then spaced. And is passed by passing between a plurality of bending jigs having a predetermined body diameter arranged at a position, and in the winding step, has a predetermined body diameter different from the body diameter of the heat treatment bobbin. The method for producing a compound-based superconducting wire according to any one of claims 1 to 5, wherein the compound-based superconducting wire is added while being restricted by being wound around a superconducting coil winding frame. After the wire forming step, before the heat treatment step, a cable forming step of forming a cable by subjecting the plurality of wires formed by the wire forming step to a twisting process or a forming process after the twisting process. A method for producing a compound superconducting cable, wherein the method for producing a compound superconducting wire according to any one of claims 1 to 6 is applied to the cable.