JP2013004242A - Method of manufacturing compound superconductive twisted wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a compound superconductive twisted wire, reducing strain remaining inside the twisted wire, and preventing superconducting properties from being lowered during wire twisting processing.SOLUTION: A method of manufacturing a compound superconductive twisted wire comprises the steps of: forming a wire where a compound superconductive material to be a superconductor by being subjected to predetermined heat processing occupies at least part of a cross section thereof (wire forming step); forming a twisted wire by using the plurality of wires (wire twisting step); subjecting the twisted wire after the wire twisting step to the heat processing to transform the compound superconductive material to the superconductor to thereby transform the twisted wire to the compound superconductive twisted wire (heat processing step); and applying bending strain to the compound superconductive twisted wire obtained at the heat processing step (bending step).

Description

  The present invention relates to a method for producing a compound superconducting stranded wire, and more particularly, to a method for producing a compound superconducting stranded wire having excellent superconducting properties such as high critical current by reducing or removing strain inside the superconductor.

Conventionally, in the production of a superconducting magnet using a compound superconducting wire such as Nb ₃ Sn, a wind-and-react method in which a compound-forming heat treatment is generally performed after magnet formation is applied. This is because the heat-treated compound superconducting wire such as Nb ₃ Sn is very weak against strain, and the winding process in which a large strain acts after the heat treatment cannot be performed.

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 carry out in a furnace in a vacuum or an inert gas atmosphere, a large heat treatment has to be prepared, and there is a problem that the magnet size is limited.

In order to manufacture a compact superconducting magnet with a high magnetic field, it is effective to increase the current density of the superconducting conductor and flow a large current, but one of the means is to twist the superconducting wire. . However, when a compound superconducting wire such as Nb ₃ Sn is used, a large strain cannot be given, and the above-mentioned problems cannot be solved.

Nb 3 _Sn compound causes superconducting wire is susceptible to distortion, such as, it superconductor after heat treatment brittle, since a composite material, the compression residual superconductor caused by differences in the thermal contraction of each material when cooled Recently, a reinforced Nb ₃ Sn wire containing a reinforcing material such as CuNb or CuAl ₂ O ₃ has been developed, and due to its strength improvement, a magnet is applied by a react and wind method in which a winding process is performed after heat treatment. It can be manufactured. However, even in the react-and-wind method, the strain acting on the superconducting wire in the winding process must not exceed the allowable value, and the current characteristics due to the compressive residual strain of the superconductor due to cooling still remain. ing.

  Therefore, in order to solve the problem of residual strain, in Patent Document 1, in order to alleviate the strain remaining in the compound superconducting wire, a double-bending bending process is applied to add a bending strain after the compound generation heat treatment, and then a twisted wire process is performed. A method for producing a compound superconducting wire for a magnet is disclosed.

JP 2007-59136 A

  However, when the superconducting element wire is made into a conductor by twisting, if the compound superconducting wire formed by heat treatment is twisted after bending, it is difficult to handle in the case of a twisted wire with a large strain. Problems arise.

  Therefore, an object of the present invention is to provide a production method that alleviates strain remaining in a compound superconducting wire and does not deteriorate the performance of superconducting properties during stranded wire processing.

  The method for producing a compound superconducting stranded wire according to the first aspect of the present invention includes a wire forming step in which a compound superconducting raw material that becomes a superconductor by performing a predetermined heat treatment forms a wire that occupies at least part of the cross section, and A stranded wire forming step of forming a stranded wire using a plurality of the wires, and the heat treatment is performed on the stranded wire after the stranded wire step to make the compound superconducting raw material a superconductor, and the stranded wire into a compound superconducting stranded wire And a bending step of applying bending strain to the compound superconducting stranded wire obtained in the heat treatment step.

  In the method for producing a compound superconducting stranded wire according to the second aspect of the present invention, in the bending step, bending strain is added to the compound superconducting stranded wire within a range of 0.5% to 1.0%. Features.

  The method for manufacturing a compound superconducting stranded wire according to the third aspect of the present invention is characterized in that the bending step includes a double-bending bending step in which bending strain is applied from both the positive and negative directions.

  In the compound superconducting stranded wire manufacturing method according to the fourth aspect of the present invention, the compound superconducting wire is subjected to a single swinging process in which bending strain is applied once in both the forward and reverse directions in the double swing bending process. It is characterized in that it is applied more than 20 times and less than 20 times.

The compound superconducting stranded wire manufacturing method according to the fifth aspect of the present invention is characterized in that the compound superconductor is made of Nb ₃ Sn or Nb ₃ Al.

The manufacturing method of the compound superconducting stranded wire according to the sixth aspect of the present invention is such that a reinforcing material made of any one conductive material of CuNb, CuAl ₂ O ₃ , CuNbTi, and Ta is formed. Features.

  According to the present invention, the inside of a compound superconducting stranded wire can be controlled without controlling the strain of each strand constituting the stranded wire by applying a bending process that applies bending strain to the compound superconducting stranded wire that has been heat-treated after the stranded wire processing. In addition, it was possible to realize a method for producing a compound superconducting stranded wire that can alleviate the strain of the material and can improve superconducting properties such as critical current.

FIG. 1 is a process diagram for explaining a method for producing a compound superconducting stranded wire of the present invention. FIG. 2 is a diagram showing an example of a cross-sectional shape of a strand used for the compound superconducting stranded wire of the present invention. FIG. 3 is a diagram showing an example of another cross-sectional shape of the strand used for the compound superconducting stranded wire of the present invention. FIG. 4 is a diagram showing an example of a cross-sectional shape of the compound superconducting stranded wire of the present invention. FIG. 5 is a diagram illustrating an example of a configuration of an apparatus that performs a double bending process in the bending process. FIG. 6 is a diagram illustrating an example of a configuration of an apparatus that performs a swing bending process in the bending process.

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

  In one embodiment of the method for producing a compound superconducting stranded wire of the present invention, as shown in FIG. 1, a compound superconducting raw material that becomes a superconductor is formed by performing a predetermined heat treatment to form a wire that occupies at least part of the cross section. Compound superconducting raw material by performing heat treatment on wire forming step S101, stranded wire forming step S102 that forms a stranded wire using a plurality of wires formed in wire rod forming step S101, and stranded wire formed in stranded wire forming step S102 A heat treatment step S103 for converting the superconductor into a compound superconducting stranded wire, and a bending step S104 for subjecting the compound superconducting stranded wire obtained in the heat treatment step S103 to bending bending strain. It is the manufacturing method of the compound superconducting stranded wire characterized.

<Wire forming process>
An example of a cross-sectional structure of the wire 10 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. .

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 wire 10 used for a twisted wire process is not limited to what is shown in FIG. 2, You may have another cross-sectional structure. 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. 3 shows a wire material that becomes a CuNb reinforced bronze method Nb ₃ Sn compound superconductor in which a reinforcing material made of CuNb or the like occupies between the superconducting raw material portion that becomes the central compound superconductor and the outermost stabilizing material. A cross-sectional view of (a) shows a wire material that becomes a CuNbTi reinforced bronze method Nb ₃ Sn compound superconductor occupied by a superconducting raw material that becomes a compound superconductor between a reinforcing material made of CuNbTi or the like in the center and an outermost stabilizing material. A cross-sectional view is (b), a cross-sectional view of a wire rod that becomes a Ta-reinforced bronze Nb ₃ Sn compound superconductor in which each Nb ₃ Sn filament has a Ta core is shown in (c), and a central core wire made of Cu (D) shows a cross-sectional view of a wire material that becomes an unreinforced bronze Nb ₃ Sn compound superconductor in which the superconducting raw material of the compound superconductor occupies between the outermost layer stabilizing material and the outermost layer stabilizer.

Table 1 is a table for explaining an example of the configuration of the wire to be the bronze process Nb 3 _Sn compound superconductor. 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 the wire material that becomes each Bronze method Nb ₃ Sn compound superconductor, except for the wire material that becomes the Ta-reinforced bronze method Nb ₃ Sn compound superconductor, has a weight composition of Sn of 14% and Ti. 0.2% Cu remains. With respect to the wire used as the Ta-reinforced bronze Nb ₃ Sn compound superconductor, Sn is 15%, Ti is 0.3%, and Cu is the remaining by weight composition.

In addition, the wire diameter of each bronze method Nb ₃ Sn compound superconducting wire 20 that has undergone the stranded wire processing step and the heat treatment step is 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.

<Strand wire processing process>
In the twisted wire processing step S102, processing for twisting the wire 10 formed in the wire material forming step S101 is performed. Furthermore, you may perform the shaping | molding process which shape | molds a wire to a predetermined shape.
As a form of the compound superconducting stranded wire obtained by the present invention, a round compound superconducting stranded wire 100 as shown in FIG. 4A or a flat type compound superconducting stranded wire 200 as shown in FIG. Commonly called Rutherford cable). The number of wire rods (elements) 10 used for processing, the twist pitch, the composition and dimensions of the compound superconducting stranded wires 100 and 200 to be generated, and the material to be wound together (co-winding material 30 in FIG. 4A) ) And so on.

<Heat treatment process>
In the heat treatment step S103, a compound generation heat treatment is performed under a predetermined condition so that the wire 10 formed in the wire forming step S101 is made into the compound superconducting wire 20. 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.

<Bending process>
In the bending step S104, bending is performed on the compound superconducting stranded wires 100 and 200 obtained by performing the compound generation heat treatment. In the bending step, it is preferable to add bending strain to the compound superconducting stranded wires 100 and 200 constituting the compound superconducting stranded wires 100 and 200 within a range of 0.5% to 1.0%. When the content is less than 0.5%, sufficient improvement in the properties of the compound superconducting stranded wires 100 and 200 cannot be obtained. When the content exceeds 1.0%, the strand 20 is deteriorated.

  Note that the bending process may include a double-bending process in which bending strain is applied from both the positive and negative directions. As the double bending process, for example, a single double swing process in which bending strain is applied to the compound superconducting stranded wires 100 and 200 from both the positive and negative directions once may be performed one or more times. In the case of the double bending process, it is preferable in that a uniform bending strain can be applied to the strands 20 constituting the compound superconducting stranded wires 100 and 200. In the case where a single double swing process is performed one or more times as the double swing bending process, for example, a bending strain may be applied using a pulley 13 as shown in FIG. At this time, since the pitch of the compound superconducting stranded wires 100 and 200 and the diameter of the strand are determined as desired values, the bending strain applied to the wire can be controlled by selecting the diameter of the pulley 13 to be used. .

  In FIG. 5, a compound superconducting stranded wire 100 is wound around a bobbin 11 for compound generation heat treatment and subjected to heat treatment. The compound superconducting stranded wire 100 is drawn to the winding bobbin 14 with a predetermined tension, and is wound from the compound generation heat treatment bobbin 11 to the winding bobbin 14 via the rotating member 12 and the pulley 13. However, as the double bending process, the twisted wire to be processed is rotated or twisted while twisting and bending is applied from various directions, the process of repeatedly applying tension and compression, and other positive and negative directions. You may perform the process to add.

  In addition to the double swing bending process, a single swing bending process may be used. Single swing bending is a processing method in which a compound superconducting stranded wire 100, 200 is once linearized after bending strain is applied to the compound superconducting stranded wire from one direction. In the case of performing a single piece swing process once or more as a single swing bending process, for example, a bending strain may be applied using a pulley 13 as shown in FIG. At this time, since the pitch of the compound superconducting stranded wires 100 and 200 and the diameter of the strand 20 are determined to desired values, the bending strain applied to the strand 20 is controlled by selecting the diameter of the pulley 13 to be used. be able to.

In FIG. 6, compound superconducting stranded wires 100 and 200 are wound around a compound-forming heat treatment bobbin 11 and subjected to heat treatment. The compound superconducting stranded wires 100 and 200 are drawn to the take-up bobbin 14 with a predetermined tension, and are taken up from the compound generating heat treatment bobbin 11 via the pulley 13 to the take-up bobbin 14. However, as a single swing bending process, a process of applying a single swing bending from various directions while rotating or twisting the compound superconducting stranded wires 100 and 200 to be processed, or a process of repeatedly applying tension and compression may be performed. Good.
In FIG. 6, the compound superconducting stranded wires 100 and 200 wound around the compound generation heat treatment bobbin 11 are already given a bending strain determined by the bobbin diameter of the compound generation heat treatment bobbin 11. By pulling the compound superconducting stranded wires 100 and 200 from the bobbin 11 and making them once straight, and then passing through the pulley 13, reverse bending strain can be applied.

  5 and 6, when the compound superconducting stranded wires 100 and 200 are subjected to insulation treatment when the compound superconducting stranded wires 100 and 200 are bent, the compound superconducting stranded wires 100 and 200 are pulleys. After passing 13, it may be performed while being wound on the winding bobbin 14.

The method for producing a compound superconducting stranded wire of the present invention will be described in more detail with reference to the drawings, but the present invention is not limited to these examples.
A compound superconducting stranded wire 100 having a cross-sectional structure as shown in FIG. In this embodiment, the wire 10 to be the element wire 20 is provided with stabilized copper on the outer periphery, Nb ₃ Sn is used for the superconductor, and Ta is used as a diffusion barrier material between the stabilized copper and the superconductor. A wire 10 (element diameter φ is 1 mm) to be an Nb ₃ Sn compound superconductor was used.

That is, a composite in which a raw material of a compound superconductor composed of Nb ₃ Sn is disposed at the center of the cross section of the wire, Ta is disposed on the outer periphery of the superconductor raw material, and stabilized copper is disposed on the outer periphery. The wire 10 which consists of was comprised. Using three wires and four stainless wires, a stranded wire as shown in FIG. The twist pitch at this time was 45 mm.
The twisted wire was heat-treated to cause a compound formation reaction in the composite to form an Nb ₃ Sn compound superconductor, and a compound superconducting twisted wire 100 was obtained.

In order to apply a bending strain of about 0.8% from both the forward and reverse directions to the obtained compound superconducting stranded wire 100, the diameter of the pulley 13 is set to 125 mm, the double swing bending process is performed 5 times, and the Nb ₃ Sn compound A superconducting stranded wire was produced.

(Comparative example)
A wire rod to be a superconductor was prepared in the same manner as in the examples, and the wire rod was heat-treated to cause a compound formation reaction in the composite to form an Nb ₃ Sn compound superconductor to obtain a compound superconducting wire. In order to apply a bending strain of 0.8% from both the positive and negative directions to the obtained compound superconducting wire, the diameter of the pulley 13 was set to 125 mm, and the double swing bending process was performed five times to obtain the Nb ₃ Sn compound superconducting wire. Manufactured.
The obtained Nb ₃ Sn compound superconducting wire and four stainless steel wires were twisted as shown in FIG. The twist pitch at this time was 45 mm. Nb3Sn compound superconducting wire at this time

(Evaluation)
The critical current (Ic) was measured by applying an external magnetic field in the range of 12T to 16T to the Nb ₃ Sn compound superconducting stranded wire obtained as described above. As a result, the Ic of the present example was 12T to 16T, which was about 1.4 to 1.6 times that of the comparative example.

  This is because the bending strain given the strand of the comparative example has both a bending strain derived from a stranded wire and a bending strain due to bending.

  The strand which comprises the compound superconducting stranded wire of the comparative example has the bending strain derived from a twisted wire other than the bending strain by bending by the bending being periodically added by the helical structure.

  Here, the curvature due to bending during the bending process is the distance from the center position of the stranded wire to the center of the strand arranged at the outermost periphery of the stranded wire, the pitch parameter of the spiral structure, and the bending It depends on the bending radius. Further, the curvature derived from the stranded wire is determined by the radius that is the distance from the center position of the stranded wire to the center of the strand arranged at the outermost periphery of the stranded wire and the pitch parameter of the spiral structure. Moreover, the curvature in the bending process performed with respect to a compound superconducting stranded wire becomes the sum of the curvature by a spiral structure and the curvature by the bending in the case of a bending process.

  As a result, in the comparative example, since it further has a bending strain derived from the stranded wire, the bending strain of the strand forming the compound superconducting stranded wire in the comparative example exceeds 1.0%, and the superconducting characteristics Seems to have declined.

  From the above, in this example, since there is no bending strain derived from the stranded wire, the bending strain of each strand constituting the compound superconducting stranded wire can be controlled only by controlling the bending strain applied in the bending process. Can be controlled. Therefore, in the case of a twisted wire with a large strain (for example, a twisted wire having a small pitch or a flat twisted wire), the twisted wire can be easily handled by using the manufacturing method of the present invention.

1, 2, 3 Region 10 Wire 11 Heat treatment bobbin 12 Rotating member 13 Pulley 14 Winding bobbin 20 Compound superconducting wire 30 Co-winding material 100, 200 Compound superconducting stranded wire

Claims (6)

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 stranded wire forming step of forming a stranded wire using a plurality of the wires;
A heat treatment step of applying the heat treatment to the stranded wire after the stranded wire step to make the compound superconducting raw material a superconductor, and making the stranded wire a compound superconducting stranded wire;
A method for producing a compound superconducting stranded wire, comprising a bending step of applying bending strain to the compound superconducting stranded wire obtained in the heat treatment step.   2. The method for producing a compound superconducting stranded wire according to claim 1, wherein in the bending step, bending strain is applied to the compound superconducting stranded wire within a range of 0.5% to 1.0%.   The method for producing a compound superconducting stranded wire according to claim 1 or 2, wherein the bending step includes a double-bending bending step in which bending strain is applied from both the positive and negative directions.   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 stranded wire according to 2. The method for producing a compound superconducting stranded wire according to any one of claims 1 to 4, wherein the compound superconductor is composed of Nb ₃ Sn or Nb ₃ Al. The compound superconductivity according to any one of claims 1 to 5, wherein a reinforcing material made of any one of conductive materials of CuNb, CuAl ₂ O ₃ , CuNbTi, and Ta is formed. A method of manufacturing a stranded wire.

Images