JP2010244745A - Nb3Al superconducting wire and method for producing Nb3Al superconducting wire - Google Patents

Abstract

An object of the present invention is to provide a Nb ₃ Al superconducting wire that can be lengthened and a method for producing an Nb ₃ Al superconducting wire.
An Nb ₃ Al superconducting wire includes a wire containing Nb and Al, an Nb layer or a Ta layer covering the wire, and a metal layer provided on the Nb layer or the Ta layer. A precursor wire forming step for forming a precursor wire in which a wire formed containing Nb and Al is covered with an Nb layer or a Ta layer, and a supersaturated solid solution wire is formed by heating and cooling the precursor wire. A method for producing a Nb3Al superconducting wire comprising a heat treatment step and a metal layer forming step of forming a metal layer on the surface of a supersaturated solid solution wire.
[Selection] Figure 1

Description

The present invention relates to a Nb ₃ Al superconducting wire and a method for producing an Nb ₃ Al superconducting wire. In particular, the present invention relates to a restack Nb ₃ Al superconducting wire and a method for manufacturing a restack Nb ₃ Al superconducting wire.

As a superconducting wire, an Nb ₃ Al compound-based superconducting wire is superior in critical current density (Jc) characteristics in a high magnetic field as compared with a NbTi superconducting wire, and is therefore used for a superconducting magnet that operates in an environment of about 12 to 23 T (Tesla). Expected as a material. In order to apply a superconducting wire to a superconducting magnet, it is important not only to obtain high Jc, but also to increase the length, that is, to stably manufacture a long wire.

As one of conventional Nb ₃ Al compound-based superconducting wires, Nb is produced by filling a metal pipe with a Nb (Al) supersaturated solid solution wire with Nb or Ta exposed on the surface. ₃ Al compound-based superconducting wire is known (for example, Non-Patent Document 1). In the wire described in Non-Patent Document 1, since a stabilizing material made of Cu is applied to the Nb (Al) supersaturated solid solution after the rapid heating and quenching treatment, the superconducting wire can be processed strongly. it can. And since high strain energy by transition etc. can be accumulate | stored in a Nb (Al) supersaturated solid solution phase by such strong processing, high Jc can be obtained in the 12-15T medium magnetic field area | region. In addition, the superconducting wire described in Non-Patent Document 1 can reduce the filament diameter by an order of magnitude compared to the conventional one. Therefore, the superconducting wire has excellent strain resistance and is anxious in a low magnetic field, which is a problem with the next accelerator magnets. Qualitative can be suppressed.

Superconductor Science and Technology, Vol. 21 (2008), p.115020-115026

However, the Nb ₃ Al compound-based superconducting wire described in Patent Document 1 does not have sufficient adhesion between the outer peripheral metal pipe and the supersaturated solid solution wire, and there is room for improvement in lengthening the length.

Accordingly, an object of the present invention is to provide lengthening may Nb 3 _Al superconducting wire, and a method for manufacturing a Nb 3 _Al superconducting wire.

To achieve the above object, the present invention provides an Nb ₃ Al superconducting wire comprising a wire containing Nb and Al, an Nb layer or Ta layer covering the wire, and a metal layer provided on the Nb layer or the Ta layer. Provided.

In the Nb ₃ Al superconducting wire, the metal layer can be formed including a metal material having an electric resistance of 0.4 μΩ · m or less.

In the Nb ₃ Al superconducting wire, the metal layer can have a thickness of 1 nm or more.

In the Nb ₃ Al superconducting wire, the metal layer can be formed of a metal material that is not alloyed with a metal pipe to be provided on the outer periphery of the metal layer.

In the Nb ₃ Al superconducting wire, the metal layer can include at least one metal material selected from the group consisting of Au, Al, Cu, Li, Mg, Mn, Ni, Pd, and Pt.

Further, in the Nb ₃ Al superconducting wire, the metal layer includes Ag, and is provided between the metal pipe and the metal layer to be provided on the outer periphery of the metal layer, and alloying between the metal layer and the metal pipe is performed. An additional barrier layer can be provided.

In order to achieve the above object, the present invention provides a precursor wire forming step for forming a precursor wire in which a wire formed containing Nb and Al is covered with an Nb layer or a Ta layer, and heating the precursor wire Then, by cooling, a method for producing an Nb ₃ Al superconducting wire comprising a heat treatment step for forming a supersaturated solid solution wire and a metal layer forming step for forming a metal layer on the surface of the supersaturated solid solution wire is provided.

The Nb ₃ Al superconducting wire manufacturing method includes a metal pipe filling step of filling a metal pipe with a supersaturated solid solution wire having a metal layer formed on the surface thereof, and reducing the surface of the filled metal pipe. It is also possible to further include a surface-reduction processing step for performing processing.

Further, in the method of manufacturing the Nb ₃ Al superconducting wire, the surface reduction process is performed on the filled metal pipe so that the thickness of the metal layer included in the Nb ₃ Al superconducting wire to be manufactured is 1 nm or more. A surface-reducing process can also be performed.

In the method for producing the Nb ₃ Al superconducting wire, the metal pipe filling step may use a metal pipe containing at least one metal selected from the group consisting of Cu and Ag.

_Nb 3 Al superconducting wire according to the present invention, and according to the method of manufacturing a _Nb 3 Al superconducting wire can be provided _Nb 3 Al superconducting wire can lengthening, and a method for manufacturing a _Nb 3 Al superconducting wire.

It is a flowchart of the outline of the manufacturing flow of the Nb 3 _Al superconducting wire according to an embodiment of the present invention. It is a schematic view showing a manufacturing process of the Nb 3 _Al superconducting wire according to an embodiment of the present invention. It is a schematic view showing a manufacturing process of the Nb 3 _Al superconducting wire according to an embodiment of the present invention. It is a schematic view showing a manufacturing process of the Nb 3 _Al superconducting wire according to an embodiment of the present invention. It is a schematic view showing a manufacturing process of the Nb 3 _Al superconducting wire according to an embodiment of the present invention. It is a schematic view showing a manufacturing process of the Nb 3 _Al superconducting wire according to the embodiment of the present invention. It is a schematic view showing a manufacturing process of the Nb 3 _Al superconducting wire according to an embodiment of the present invention. It is a schematic view showing a manufacturing process of the Nb 3 _Al superconducting wire according to an embodiment of the present invention. It is a diagram showing a comparison result between Jc of Risutakku _Nb 3 Al superconducting wire according to Comparative Example 1 and Jc of Risutakku _Nb 3 Al superconducting wire according to Example 1.

FIG. 1 is a flowchart showing an outline of the flow of manufacturing an Nb ₃ Al superconducting wire according to an embodiment of the present invention. 2 to 8 show an outline of the manufacturing process of the Nb ₃ Al superconducting wire according to the embodiment of the present invention.

The Nb ₃ Al superconducting wire according to the present embodiment is a Nb ₃ Al compound-based superconducting wire formed including an Nb ₃ Al compound, and is a restacked Nb ₃ Al superconducting wire formed by a restacking method. The Nb ₃ Al superconducting wire according to the present embodiment can be formed using, for example, a jelly roll / rapid heating / quenching process. Details will be described below.

(Method for producing Nb ₃ Al superconducting wire)
First, formed from a first metal material containing aluminum (Al) or an Al alloy and having a predetermined thickness and an Al sheet 10 having a predetermined thickness and a second metal material including Nb or Nb alloy and having a predetermined thickness And a core 30 formed of a high melting point metal material such as Nb or Ta and having a predetermined diameter. Furthermore, a compound formation preventing sheet 40 (barrier layer sheet) formed of Nb or Ta and having a predetermined thickness is prepared.

  Next, as shown in FIG. 2A, the Al sheet 10 and the Nb sheet 20 are wound around the core 30. Subsequently, as illustrated in FIG. 2B, the compound generation preventing sheet 40 is wound around the surface of the Al sheet 10 or the Nb sheet 20 wound around the core 30. As a result, a jelly roll / single line 1 as a single line as shown in FIG. 2C is produced (jelly roll / single line forming process, FIG. 1: Step 10 (hereinafter, step is abbreviated as “S”). )).

  Next, as shown in FIG. 2 (c), the single billet 2 is filled with the jelly roll / single wire 1 (single billet filling step: S12). The single billet 2 has an inner diameter equal to or larger than the outer diameter of the jelly roll / single wire 1 and has a substantially cylindrical outer shape (that is, a pipe shape). And the single billet 2 can be formed, for example from copper (Cu) or Cu alloy, and it is preferable to form from Cu in this Embodiment.

  Here, the reason why the single billet 2 covers the outer periphery of the jelly roll / single wire 1 by filling the single billet 2 with the jelly roll / single wire 1 is as follows. That is, when the jelly roll / single wire 1 is subjected to a process such as die drawing described later with the outer surface of the jelly roll / single wire 1 exposed to the outside, die die seizure at the time of die drawing, jelly roll winding Since the workability deteriorates due to the occurrence of the shift of the part, the object is to suppress such deterioration of the workability.

  Next, the single billet 2 filled with the jelly roll / single wire 1 is processed to a desired diameter and a desired length to form a precursor single wire 3 as a precursor wire (precursor wire forming step: S14). For example, a single billet 2 filled with a jelly roll / single wire 1 is subjected to a process (drawing process) by hydrostatic extrusion and die drawing (drawing process), and a process by hydrostatic extrusion and die drawing. The process of applying a heat treatment is stopped at a predetermined stage, and the processed single billet 2 is subjected to an intermediate heat treatment (annealing process) (intermediate heat treatment process) once for the single billet 2 filled with the jelly roll / single wire 1. Alternatively, the single billet 2 filled with the jelly roll / single wire 1 is processed to a desired diameter and a desired length by being repeatedly applied multiple times. Thereby, the precursor single wire 3 as shown to Fig.3 (a) is obtained.

  Note that in this embodiment, the step of performing the intermediate heat treatment is performed under a condition that an intermetallic compound of the first metal material (for example, Nb) and the second metal material (for example, Al) is not generated. For example, a temperature lower than the melting point of the first metal material (for example, a temperature that is about a half of the melting point of the first metal material) and an intermediate heat treatment in an inert atmosphere or vacuum is applied to the single billet 2. Apply. More specifically, for example, the intermediate heat treatment is performed in a flow of an inert gas (for example, argon gas) or in a vacuum at a temperature of 250 ° C. to 550 ° C. for 0.5 hours to 2 hours.

  Next, since the single billet 2 is unnecessary in the heating and quenching process described later, the single billet 2 exposed on the surface of the precursor single wire 3 is removed. For example, when the single billet 2 is made of Cu, the precursor single is obtained by immersing in a single billet remover mainly composed of nitric acid having a concentration of about 10% for a predetermined time (for example, about several hours). The single billet 2 is removed from the surface of the line 3 (single billet removal step: S16). Thereby, the precursor single line 3a from which the single billet 2 as shown in FIG.3 (b) was removed is formed.

Subsequently, a plurality of precursor single wires 3a, a plurality of central dummy members 4, and an alloy pipe 5 are prepared. Then, as shown in FIG. 3C, the alloy pipe 5 is filled with a plurality of precursor single wires 3a and a plurality of central dummy members 4 (multi-core billet forming step: S18). Thereby, the multi-core billet 6 as shown to Fig.4 (a) is obtained. As an example, a multi-core billet 6 having a 241-core structure is manufactured by filling a Cu alloy pipe with 222 precursor single wires 3 a and 19 central dummy members 4. The number of precursor single wires 3a and the number of central dummy materials 4 can be appropriately increased or decreased depending on the application of the Nb ₃ Al superconducting wire to be produced.

The central dummy material 4 can be formed from a metal material such as Nb or Ta. For example, when the Nb ₃ Al superconducting wire to be manufactured is used for an accelerator or the like and low radiation is required, Ta having less magnetic instability than Nb at the temperature of liquid helium is used. It is preferable. On the other hand, when low radiation is not required, Nb or Ta can be used. The alloy pipe 5 has a substantially cylindrical shape with a predetermined inner diameter. And the alloy pipe 5 is formed from a CuNi alloy as an example.

  Next, the multi-core billet 6 is processed to a desired diameter and a desired length. That is, the process of applying hydrostatic extrusion and die drawing to the multi-core billet 6 and the process of applying hydrostatic extrusion and die drawing to the multi-core billet 6 are stopped at a predetermined stage. The multi-core billet 6 is processed to a desired diameter and a desired length by repeatedly performing the intermediate heat treatment step on the multi-core billet 6. Thereby, as shown in FIG.4 (b), the multi-core wire 7 processed without breaking to a desired diameter and desired length is obtained (multi-core wire formation process: S20).

  An alloy pipe 5 is coated on the surface of the multifilamentary wire 7. Since the alloy pipe 5 is unnecessary in the heating / cooling process described later, it is removed (alloy pipe removing step: S22). For example, when the alloy pipe 5 is formed of a Cu alloy such as a CuNi alloy, the surface of the multifilamentary wire 7 is covered with an etching solution mainly containing nitric acid (for example, nitric acid having a concentration of about 10%). The alloy pipe 5 is removed. Thereby, the multifilamentary wire 7a from which the alloy pipe 5 has been removed is obtained.

  Subsequently, the multi-core wire 7a from which the alloy pipe 5 has been removed is subjected to a heating and cooling process (rapid heating and quenching process) to produce a supersaturated solid solution wire 8 (heat treatment step: S24). This heating / cooling process is a process of forming a supersaturated solid solution of the first metal material and the second metal material constituting the multifilamentary wire 7a. Specifically, the heating and cooling treatment forms an Nb / Al supersaturated solid solution from Al and Nb constituting the multifilamentary wire 7a. For example, the heating and cooling treatment can be performed as follows using the rapid heating and quenching apparatus shown in FIG.

  First, the multicore wire 7 a is wound around the delivery reel 100. Then, the multifilamentary wire 7 a is sent out from the delivery reel 100 through the capstan 115. Subsequently, the multi-core wire 7 a is heated and cooled through the gallium (Ga) bus 130, and then wound up by the take-up reel 120. Specifically, a current is supplied from the power supply 110 to the multifilamentary wire 7 a between the capstan 115 and the Ga bus 130. When a current is supplied to the multicore wire 7a, the temperature of the multicore wire 7a increases from 1500 ° C. to 2000 ° C. due to self-heating. Since heating is performed by self-energization heating, the multifilamentary wire 7a is rapidly heated to a predetermined temperature in a short time. Subsequently, the heated multi-core wire 7 a is rapidly cooled by immersing it in the Ga bus 130. Thereby, Al and Nb which comprise the multicore wire 7a react, and the supersaturated solid solution wire 8 which consists of a Nb / Al supersaturated solid solution is formed. Then, the supersaturated solid solution wire 8 is continuously wound around the take-up reel 120.

Next, a metal layer is formed on the outer surface of the supersaturated solid solution wire 8 (metal layer forming step: S26). For example, as shown in FIG. 6A, the supersaturated solid solution wire 8 is installed in the chamber 150 of the film forming apparatus, and the metal layer 50 is formed on the outer surface of the supersaturated solid solution wire 8. The metal layer 50 is preferably formed of a metal material that is not alloyed with the metal pipe provided on the outer periphery of the restacked Nb ₃ Al superconducting wire 90 that is finally formed. Thereby, as shown in FIG.6 (b), the supersaturated solid solution wire 9 in which the metal layer 50 was formed in the outer surface is produced.

In the present embodiment, the metal layer 50 is formed including a metal material having an electric resistance of 0.4 μΩ · m or less at room temperature (25 ° C.). Specifically, the metal layer 50 is formed including at least one metal material selected from the group consisting of Au, Al, Ag, Cu, Li, Mg, Mn, Ni, Pd, and Pt. For example, the metal layer 50 can be formed of these metals alone or an alloy formed by including two or more metal materials selected from these metal materials. When the restacking method is used, the transformation heat treatment temperature of the metal layer 50 can be lowered by subjecting the wire including the metal layer 50 to strong processing. Thereby, for example, a restacked Nb ₃ Al superconducting wire 90 that is finally formed, which will be described later, can be applied to an aluminum stabilizing conductor for an accelerator detector.

Further, when the metal layer 50 is in the form of a restacked Nb ₃ Al superconducting wire 90 that is finally formed, which will be described later (that is, after the surface reduction processing to the restacked Nb ₃ Al superconducting wire 90 that is the final form). It is formed having a thickness of 1 nm or more. The metal layer 50 can be formed using a film forming method such as an ion plating method, an arc ion plating method, a sputtering method, an electron beam evaporation method, a microwave plasma CVD method, or an electroplating method.

  For example, the case where the metal layer 50 is formed using an arc ion plating method will be described. First, the target 160 made of a metal material constituting the metal layer 50 to be formed and the supersaturated solid solution wire 8 are placed in the chamber 150. Next, a bias voltage is applied between the target 160 and the electrode at the installation site where the supersaturated solid solution wire 8 is installed to generate an arc on the target 160. And the metal oxide layer which exists on the surface of the supersaturated solid solution wire 8 is removed by the generated arc. Further, the metal material constituting the target 160 is ionized and the generated metal ions reach the surface of the supersaturated solid solution wire 8, whereby the metal layer 50 is formed. Thereby, the supersaturated solid solution wire 9 is formed.

  In addition, when the temperature of the supersaturated solid solution wire 8 rises due to the metal ions reaching the surface of the supersaturated solid solution wire 8, an intermetallic compound (for example, Nb and Al and the like) is contained in the supersaturated solid solution forming the supersaturated solid solution wire 8. At a temperature at which no intermetallic compound is formed. For example, it can suppress that the temperature of the supersaturated solid solution wire 8 rises by providing a cooling mechanism in the location where the supersaturated solid solution wire 8 is installed. Further, in the present embodiment, the metal layer 50 is a supersaturated solid solution directly on the surface of the supersaturated solid solution wire 8 or via a metal layer made of another metal material (for example, Ti) excluding the metal material constituting the metal layer 50. It can be formed above the surface of the wire 8.

Next, as shown in FIG. 7A, a plurality of supersaturated solid solution wires 9 having the metal layer 50 formed thereon are formed as Cu pipes 60 as metal pipes that are the outer periphery of the restacked Nb ₃ Al superconducting wire 90. To fill. As an alternative to the Cu pipe 60, a pipe made of Ag can be used. Thereby, as shown in FIG.7 (b), the restacking billet 70 by which the metal pipe was filled with the supersaturated solid solution wire is produced (metal pipe filling process: S28). When the inner wall of the Cu pipe 60 and the metal layer 50 form an intermetallic compound by heat treatment (for example, when the metal layer 50 is made of Ag), the Cu pipe 60 and the metal layer 50 are formed on the surface of the supersaturated solid solution wire 90. It is also possible to insert a barrier layer made of Nb or Ta that suppresses the reaction with Nb.

Subsequently, the restack billet 70 is subjected to isostatic pressing and die drawing to reduce the surface of the restack billet 70, thereby forming a restack wire 80 which is a supersaturated solid solution restack wire having a predetermined diameter. That is, the process of applying the hydrostatic extrusion and die drawing to the restacking billet 70 and the process of applying the hydrostatic extrusion and die drawing to the restacking billet 70 are stopped at a predetermined stage, and the processed restacking billet 70 is processed. By repeating the step of performing the intermediate heat treatment on the restacking billet 70, the restacking billet 70 is processed to a desired diameter and a desired length. As a result, a restacked wire 80 processed to a desired diameter and desired length as shown in FIG. 7C is obtained (area reduction processing step: S30). Also, if the Nb 3 _Al superconducting wire to be manufactured by the manufacturing method according to the present embodiment is used in the device of the AC applied may be subjected to twisting in Risutakku wire 80.

Subsequently, the restacked wire 80 is subjected to a reheating treatment (transformation heat treatment) for a predetermined time at a predetermined temperature. For example, the restacked wire 80 is introduced into the heat treatment furnace 170, and is subjected to a predetermined time (for example, about 650 ° C. to 1000 ° C.) for a predetermined time (for example, in a vacuum or an inert atmosphere). For example, the restacked wire 80 is held for about 10 hours. Thereby, an Nb ₃ Al compound is generated, and a restacked Nb ₃ Al superconducting wire 90 as an Nb ₃ Al-based compound superconducting wire as shown in FIG. 8B is manufactured (transformation heat treatment step: S32).

The restacked Nb ₃ Al superconducting wire 90 manufactured through the above steps is a compound generation preventing sheet 40 as an Nb layer or Ta layer on the outer periphery of an Nb ₃ Al superconducting material made of an Nb ₃ Al compound as a wire containing Nb and Al. A plurality of Nb ₃ Al superconducting wires having a metal layer 50 provided on a plurality of the wires via a Ti film are formed as Cu as metal pipes. It has a shape covered with a pipe.

  In addition, the die drawing as a diameter reduction process which reduces the diameter implemented after hydrostatic extrusion can be implemented as follows. That is, the diameter reduction processing can be performed using a draw bench, a swager, a cassette roller die, or a groove roll. And the wire drawing which the cross-sectional reduction rate per pass in diameter reduction processing is about 10 to 30% is repeatedly implemented.

In addition, when the wire rod is multi-core (for example, S20, S28), the wire rod (for example, the precursor single wire 3a, the supersaturated solid solution wire rod 9) drawn into a round cross-sectional shape or a hexagonal cross-sectional shape is connected to a pipe ( For example, it is incorporated into an alloy pipe 5 and a Cu pipe 60), and is drawn to a desired wire diameter at a cross-section reduction rate of about 10 to 30% per pass using the above-described apparatus. And the wire (for example, the supersaturated solid solution wire 9) processed to a desired shape is subjected to a predetermined heat treatment at a predetermined temperature and in a predetermined atmosphere, whereby a wire having a high Jc (for example, restacked Nb ₃ Al superconductor). Wire 90). For the purpose of realizing high Jc, the volume ratio (Nb / Al) of Nb or Nb alloy of the filament part that finally forms the Nb ₃ Al phase to Al or Al alloy is 2.5 to A range of 3.5 is desirable.

In addition, when the restacked Nb ₃ Al superconducting wire 90 according to the present embodiment is used in, for example, liquid helium, a stronger magnetic field is generated by combining it with a metallic superconductor or an oxide superconductor. Practical conductors such as superconducting magnets can be realized. In this case, as the metal-based superconductor, NbTi-based alloys, Nb ₃ Sn-based compounds, V ₃ Ga-based, MgB _2- based, and / or Chevrel-based compounds can be used, or two kinds as necessary. The above magnets can be arranged. As the oxide superconductor, a Y-based, Bi-based, Tl-based, Hg-based, or Ag-Pb-based superconductor can be used.

Furthermore, when the restack Nb ₃ Al superconducting wire 90 according to the present embodiment is used in refrigerator conduction cooling, by combining the restack Nb ₃ Al superconducting wire 90 and an MgB ₂ -based or oxide superconductor, Practical conductors such as higher performance superconducting magnets can be realized.

In addition, the restacked Nb ₃ Al superconducting wire 90 according to the present embodiment exhibits superconductivity in an environment at a critical temperature or lower, and maintains a high transport critical current density (Jc), while being a km-class long wire. Can be used. For example, the restack Nb ₃ Al superconducting wire 90 is composed of a power transmission cable, a nuclear magnetic resonance analyzer, a medical magnetic resonance diagnostic device, a magnetic separation device, a single crystal pulling device in a magnetic field, a superconducting generator, a fusion reactor magnet, a high energy It can be applied to devices such as a particle accelerator magnet.

(Effect of embodiment)
In the restacked Nb ₃ Al superconducting wire 90 according to the present embodiment, the metal layer 50 is formed on the outer surface of the supersaturated solid solution wire 9, and the supersaturated solid solution wire 9 and the Cu pipe 60 that is an electrically stable material are connected to each other. Since the adhesion is improved, the workability of the restacked Nb ₃ Al superconducting wire 90 can be remarkably improved as compared with the case where the metal layer 50 is not formed. Specifically, in the restacked Nb ₃ Al superconducting wire 90 according to the present embodiment, the metal layer 50 is formed on at least a part of the surface of the supersaturated solid solution wire covered with the compound formation prevention sheet 40 made of Nb or Ta. Therefore, the adhesion between the Cu pipe 60 and the metal layer 50, which are electrically stable materials, or between the supersaturated solid solution wires 9 which are superconducting filaments can be improved. Thereby, while having a length sufficient for practical use (for example, km class), high superconducting performance (for example, 1000 A / mm ² low in a magnetic field in which the restacked Nb ₃ Al superconducting wire 90 is used). A restacked Nb ₃ Al superconducting wire 90 having Jc) can be provided.

A method of manufacturing a Risutakku Nb 3 _Al superconducting wire 90 according to this embodiment, after removing the single billet 2 and alloy pipe 5 containing Cu, since carrying out the rapid heating and quenching treatment, the copper in the cross section of the wire An alloy is not formed. This can suppress a decrease in the rapid heating and quenching treatment after wire (i.e., supersaturated solid solution wire 8) Residual resistance ratio Risutakku Nb 3 _Al superconducting wire 90 which is formed by using a. The residual resistance ratio is represented by the ratio of the electrical resistance at 300 K to the electrical resistance just above the critical temperature, and is referred to as “RRR”. Then, Risutakku _Nb 3 Al superconducting wire 90 according to this embodiment may have a RRR of 100 or more. If a copper alloy can be formed between the Cu pipe 60 and the metal layer 50 by performing the transformation heat treatment, a barrier layer that suppresses the alloying reaction is provided between the Cu pipe 60 and the metal layer 50. You can also.

[Example 1]
The restacked Nb ₃ Al superconducting wire 90 according to Example 1 was manufactured as follows. First, an Al sheet 10 having a thickness of 0.03 mm and an Nb sheet 20 having a thickness of 0.10 mm were prepared as starting materials. Next, the Al sheet 10 and the Nb sheet 20 were wound around an Nb bar having a diameter of 2 mm as the winding core 30. After the Al sheet 10 and the Nb sheet 20 were wound around the core 30, a Ta sheet having a thickness of 0.1 mm was wound around the outer periphery thereof as the compound formation prevention sheet 40 (barrier layer). Thereby, the jelly roll / single wire 1 which concerns on Example 1 whose outer diameter is about 13 mm was obtained.

  Next, the obtained jelly roll / single wire 1 was filled into a Cu pipe as a single billet 2 having an outer diameter of 16 mm, an inner diameter of 14 mm, and a length of 150 mm. The Cu pipe filled with the jelly roll / single wire 1 was extruded to a wire diameter of 7.5 mm using an extruder. Next, after drawing to a wire diameter of 3.1 mm using a draw bench, the wire was further drawn so that the opposite side length of the hexagon was 2.80 mm. Thereby, the precursor single wire 3 was obtained.

  Subsequently, the Cu pipe covering the outer periphery of the precursor single wire 3 was completely removed by immersing the entire precursor single wire 3 in nitric acid having a concentration of 10%. Thereby, the precursor single wire 3a whose hexagon opposite side length is 2.55 mm was obtained. Next, the precursor single wire 3a was cut every 300 mm in length. Thus, 276 precursor single wires 3a were produced. Then, 37 Ta rods as the central dummy material 4 having a hexagonal opposite side length of 2.55 mm and a Cu alloy pipe as the alloy pipe 5 having an outer diameter of 59 mm and an inner diameter of 54 mm were prepared.

  Next, a Cu alloy pipe was filled with a Ta rod as the central dummy material 4 and the precursor single wire 3a. Specifically, the Ta rod was arranged so as to be located near the center of the Cu alloy pipe, and the precursor single wire 3a was arranged in each Cu alloy pipe so as to be located around the plurality of Ta rods. Thereby, the multi-core billet 6 was obtained. Subsequently, the multi-core billet 6 was extruded to a wire diameter of 29 mm using an extruder. Further, the extruded multi-core billet 6 was processed to a wire diameter of 1.2 mm using a draw bench and a hook-shaped wire drawing machine. Thereby, the multifilamentary wire 7 was obtained. Then, in order to remove the Cu alloy pipe covering the surface of the multicore wire 7, the multicore wire 7 was immersed in nitric acid having a concentration of 10%. Thereby, the Cu alloy pipe was removed, and a multi-core wire 7a in which Ta was exposed was manufactured.

  Next, the supersaturated solid solution wire 8 was manufactured by subjecting the multi-core wire 7a to a rapid heating and quenching process using a rapid heating and quenching apparatus. In the rapid heating / cooling treatment, the maximum temperature reached was about 2000 ° C. The rapid cooling was performed by submerging the multi-core wire 7a rapidly heated to about 2000 ° C. in the Ga bus 130. Furthermore, the supersaturated solid solution wire 8 was subjected to wire drawing processing so that the opposite side length of the hexagon was 1.0 mm.

  Subsequently, a Ti layer as the metal layer 50 was formed on the surface of the supersaturated solid solution wire 8 having a hexagonal cross section. Specifically, first, the supersaturated solid solution wire 8 having a hexagonal cross section was placed in the chamber 150 of the arc ion plating apparatus. Then, the Ta surface exposed in the chamber 150 was irradiated with Ti ions, thereby removing the oxide layer on the Ta surface and simultaneously forming a Ti layer. When the temperature in the chamber 150 during the formation of the Ti layer was measured, it was 500 ° C. ± 25 ° C.

  Next, without removing the supersaturated solid solution wire 9 on which the Ti layer was formed from the chamber 150, a Cu layer as a metal layer 50 having a thickness of about 1 μm was formed on the surface of the Ti layer. The Cu layer formation conditions were the same as the Ti ion irradiation conditions. Moreover, when the temperature in the chamber 150 during the formation of the Cu layer was measured, it was 500 ° C. ± 25 ° C.

  Subsequently, 55 supersaturated solid solution wires 9 on which a Cu layer was formed were restacked on a Cu pipe 60 having an outer diameter of 13 mm, an inner diameter of 10 mm, and a length of 150 mm. Thereby, the billet 70 for restacking was formed. This restack billet 70 was extruded to a wire diameter of 8 mm using an extruder. Thereafter, the wire was further drawn to a wire diameter of 1.0 mm using a draw bench. Thereby, the restack wire 80 was formed.

  Here, the cross-sectional state of supersaturated solid solution wire 9 having a Cu layer after wire drawing, that is, restack wire 80 was observed with an optical microscope. As a result, there is no gap between the Cu layer and the supersaturated solid solution wire 9, and between the plurality of supersaturated solid solution wires 9 (that is, the Cu layer that is the outer skin of the supersaturated solid solution wire 9), and the adhesion is good. It was confirmed that.

Next, transformation heat treatment was performed on the restacked wire 80 using the heat treatment furnace 170. The conditions for the transformation heat treatment were 800 ° C. and 10 hours in vacuum. Thus, Risutakku _Nb 3 Al superconducting wire 90 according to Embodiment 1 were obtained. In addition, the thickness of the Cu layer of the restacked Nb ₃ Al superconducting wire as the final form, that is, the thickness of the Cu layer formed with a film thickness of 1 μm on the surface of the metal layer 50 was about 80 nm.

Jc measurement of the restacked Nb ₃ Al superconducting wire according to Example 1 was performed in a temperature of 4.2 K and a magnetic field of 14T. The Jc measurement was performed using a DC four-terminal method with an electric field reference of 1 μV / cm. As a result, Jc of the restacked Nb ₃ Al superconducting wire according to Example 1 was 900 A / mm ² , indicating that it was a good Nb ₃ Al superconducting wire. Regarding Risutakku _Nb 3 Al superconducting wire according to Example 1, was measured AC losses in a magnetic field 3T, was AC loss of 400 mJ / cm ^3. Therefore, it was shown that the restacked Nb ₃ Al superconducting wire according to Example 1 has an AC loss enough to be practically used even when applied to an accelerator, a nuclear fusion reactor, or the like.

In the manufacturing process of the restacked Nb ₃ Al superconducting wire according to Example 1, various metal materials having an electrical resistance of 0.1 μΩ · m to 200 μΩ · m at room temperature in the step of forming the metal layer 50 are selected. A plurality of types of restacked Nb ₃ Al superconducting wires were manufactured. As a result, the metal layer 50 is formed using a metal material having an electric resistance of 0.4 μΩ · m or less from the viewpoint of adhesion between the Cu layer and the supersaturated solid solution wire 9 and between the plurality of supersaturated solid solution wires 9. It has been shown to be preferable. By forming the metal layer 50 using such a metal material having electrical resistance, a restacked Nb ₃ Al superconducting wire having good workability can be provided.

[Examples 2 to 7]
Each Risutakku Nb 3 _Al superconducting wire according to Example 2-7, the Risutakku Nb 3 _Al superconducting wire according to Example 1, except that variously changing the thickness of the Cu layer is a metal layer 50, It formed in the same manner as Example 1. Therefore, a detailed description is omitted except for differences.

Each of the restacked Nb ₃ Al superconducting wires according to Examples 2 to 7 changes the thickness of the Cu layer that is the metal layer 50, and the thickness of the restacked Nb ₃ Al superconducting wire that is the final form is changed from 0.1 nm to 100 nm. It was adjusted and manufactured.

Specifically, a restacked Nb ₃ Al superconducting wire having a Cu layer thickness (hereinafter, simply referred to as “Cu layer thickness”) of 0.1 nm in the restacked Nb ₃ Al superconducting wire as the final form is referred to as Reference Example 1, Cu. the thickness of the thickness of the Risutakku _Nb 3 Al superconducting wire 0.5nm reference example 2, Cu layer reference to Risutakku _Nb 3 Al superconducting wire 0.8nm example of a layer 3, Cu layer Risutakku thickness of 1nm of Nb ₃ Al superconducting wire of example 2, Risutakku thickness is 2nm of Cu layer _Nb 3 Al superconducting wire of example 3, the thickness of the Cu layer is carried out Risutakku _Nb 3 Al superconducting wire 5nm example 4, Cu layer Risutakku _Nb 3 Al superconducting wire of example 5, Risutakku thickness of 30nm of Cu layer _Nb 3 Al superconducting wire of example 6, Cu thickness 100nm of layer Li thickness of 10nm Tack _Nb 3 Al superconducting wire was as in Example 7.

In the restacked Nb ₃ Al superconducting wire according to Reference Example 1, after forming a Cu layer, 55 supersaturated solid solution wires according to Reference Example 1 were restacked on a Cu pipe 60 having an outer diameter of 13 mm, an inner diameter of 10 mm, and a length of 150 mm. Thus, the billet 70 for restacking was formed. The restack billet 70 was extruded to a wire diameter of 8 mm using an extruder. Thereafter, the number of breakage occurrences when the wire was further drawn to a wire diameter of 1.1 mm using a draw bench was measured. The number of occurrences of disconnection was similarly measured for the restacked Nb ₃ Al superconducting wires according to Reference Examples 2 and 3, and Examples 2 to 7.

Table 1 shows the Cu layer thickness and the number of breakage occurrences of the restacked Nb ₃ Al superconducting wires according to Reference Examples 1 to 3 and Examples 2 to 7, respectively.

As can be seen by referring to Table 1, in the wire drawing up to 1.1 mm, when the thickness of the Cu layer in the final form is thinner than 1 nm (Reference Examples 1 to 3), the disconnection occurred. Indicated. On the other hand, when the thickness of the Cu layer is 1 nm or more (Examples 2 to 7), it was shown that the wire drawing can be performed without disconnection. In addition, when the cross section of the restacked Nb ₃ Al superconducting wire of Reference Examples 1 to ₃ was observed with an optical microscope, peeling of the Cu layer based on the heterogeneity of the Cu layer thickness was observed when Cu was thinner than 1 nm. It was done. On the other hand, in Examples 2 to 7, the film thickness of the Cu layer was substantially uniform, and no peeling of the Cu layer was observed. Therefore, in Examples 1 to 7, due to the presence of the Cu layer, the adhesion between the Cu layer and the supersaturated solid solution wire 9 and between the plurality of supersaturated solid solution wires 9 is good, and as a result, no disconnection occurs. It has been shown.

[Example 8]
Risutakku Nb 3 _Al superconducting wire according to Example 8, the Risutakku Nb 3 _Al superconducting wire according to Example 1, except that instead of the Ag metal material constituting the metal layer 50 from Cu, in Example 1 The restacked Nb ₃ Al superconducting wire was manufactured in the same manner. That is, in the restacked Nb ₃ Al superconducting wire according to Example 8, an Ag layer having a thickness of 1 μm was formed as the metal layer 50.

In Example 8 in which the Cu layer was replaced with an Ag layer, the restacked Nb ₃ Al superconducting wire as the final form could be drawn without disconnection until the wire diameter became 1.0 mm.

Further, in manufacturing the restacked Nb ₃ Al superconducting wire according to Example 8, two kinds of restacked Nb ₃ Al superconducting wires were obtained by performing transformation heat treatment under two temperature conditions of 700 ° C. and 850 ° C. Manufactured. Then, using the direct current four-terminal method, Jc was measured in a temperature of 4.2 K and a magnetic field of 14 T, and the two were compared. As a result, Jc was 860 A / mm ² for both. However, although the restack Nb ₃ Al superconducting wire subjected to transformation heat treatment at 700 ° C. has a residual resistance ratio RRR exceeding 200, the restacked Nb ₃ Al superconducting wire subjected to transformation heat treatment at 850 ° C. has a residual resistance RRR of 88.

Risutakku Nb 3 _Al superconducting wire which has been subjected to transformation heat treatment of 700 ° C., and Risutakku Nb 3 _Al superconducting wire composition observation of each cross-section subjected to the transformation heat treatment of 850 ° C., was carried out composition analysis. As a result, in the restacked Nb ₃ Al superconducting wire subjected to transformation heat treatment at 850 ° C., the alloy layer is formed between the formed Ag layer and Cu for electrical stabilization (that is, Cu pipe 60) disposed on the outer periphery. Was observed to form. On the other hand, in the restacked Nb ₃ Al superconducting wire subjected to the transformation heat treatment at 700 ° C., such an alloy layer was not formed.

Therefore, when an Ag layer is formed as the metal layer 50, it is preferable to provide a barrier layer made of Nb or Ta between the Ag layer and the Cu pipe 60. A restacked Nb ₃ Al superconducting wire having a barrier layer made of Nb or Ta (a layer that suppresses the reaction between Ag and Cu) between the Ag layer and the Cu pipe 60 was manufactured, and a transformation heat treatment at 850 ° C. It was confirmed that an alloy layer was not formed between the Ag layer and the Cu pipe 60 even when the above was applied. Thereby, when an alloy layer can be formed between the Ag layer and the Cu pipe 60, the phenomenon of the residual resistance ratio RRR is suppressed by forming a barrier layer in advance between the Ag layer and the Cu pipe 60. It was confirmed.

  In addition, it was also confirmed that it is effective to use Ag, Au, Cu, Li, Mg, Mn, Ni, Pd, Pt alone, or an alloy thereof as the metal layer 50. Further, when transformation heat treatment can be performed at a melting point of Al or lower, Al can be used as the metal layer 50.

[Comparative Example 1]
Risutakku Nb 3 _Al superconducting wire according to Comparative Example 1, the Risutakku Nb 3 _Al superconducting wire according to Example 1, except that on the supersaturated solid solution wire 8 after rapid heating and quenching treatment is not provided with the metal layer 50, performed Prepared as in Example 1. That is, the restacked Nb ₃ Al superconducting wire according to Comparative Example 1 does not include the metal layer 50 made of Cu.

Specifically, the restacked Nb ₃ Al superconducting wire according to Comparative Example 1 was manufactured as follows. That is, 55 supersaturated solid solution wires 8 having no Cu layer were restacked on a Cu pipe 60 having an outer diameter of 13 mm, an inner diameter of 10 mm, and a length of 150 mm to form a restacking billet. And this billet for restacking was extruded to the wire diameter of 8 mm using the extruder. Then, it was drawn using a draw bench to obtain a restacked wire. Thereafter, the restacked wire was subjected to transformation heat treatment to obtain a restacked Nb ₃ Al superconducting wire according to Comparative Example 1.

  Here, when a billet for restacking is extruded using an extruder to a wire diameter of 8 mm and drawn using a draw bench, the wire is constricted on the surface of the wire when drawn to a wire diameter of 3.2 mm. There has occurred. Thereafter, when the wire drawing process was continued, disconnection occurred frequently at a wire diameter of 1.8 mm. Then, when the cross section of the wire after drawing to a wire diameter of 2.3 mm was observed with an optical microscope, the gap between the Cu pipe 60 and the supersaturated solid solution wire and between the plurality of supersaturated solid solution wires was about 3 μm to 30 μm. Has been confirmed to occur. This indicates that the adhesion between the Cu pipe 60 and the supersaturated solid solution wire and between the plurality of supersaturated solid solution wires is not good.

The restacked wire according to Comparative Example 1 drawn to a wire diameter of 1.9 mm was subjected to transformation heat treatment at 800 ° C. for 10 hours in a vacuum. Thus, Risutakku Nb 3 _Al superconducting wire according to Comparative Example 1 was obtained. With respect to the restacked Nb ₃ Al superconducting wire according to Comparative Example 1, Jc was measured in a temperature of 4.2 K and a magnetic field of 14 T using the DC four-terminal method.

FIG. 9 shows a comparison result between Jc of the restacked Nb ₃ Al superconducting wire according to Example 1 and Jc of the restacked Nb ₃ Al superconducting wire according to Comparative Example 1.

In FIG. 9, the horizontal axis represents Jc and the vertical axis represents the electric field. Compared to Jc of Risutakku _Nb 3 Al superconducting wire according to Example 1, Jc of Risutakku _Nb 3 Al superconducting wire according to Comparative Example 1 was low results. This is considered to be due to the poor adhesion between the Cu pipe 60 and the supersaturated solid solution wire and between the plurality of supersaturated solid solution wires in the restacked Nb ₃ Al superconducting wire according to Comparative Example 1. It is done. In Comparative Example 1, a resistance component due to poor adhesion was confirmed immediately after the start of energization, and Jc was defined as 1 μV / cm, and it was 400 A / mm ² . Moreover, in the comparative example 1 of FIG. 9, assuming that the place where the voltage was suddenly generated is a quench current, Jc was predicted to be 650 A / mm ² . This result was shown to be lower than Jc (900 A / mm ² ) of the restacked Nb ₃ Al superconducting wire according to Example 1.

Incidentally, Jc, because there is a tendency to increase in accordance with the diameter of the _Nb 3 Al superconducting wire in Comparative Example 1, Risutakku _Nb 3 Al superconducting where wire diameter of Risutakku _Nb 3 Al superconducting wire according to Example 1 It was estimated that Jc was lower than Jc of Example 1 due to being thicker than the wire diameter of the wire. That is, since the restacked Nb ₃ Al superconducting wire according to Comparative Example 1 does not include the metal layer 50, the adhesion between the Cu pipe 60 and the supersaturated solid solution wire and between the plurality of supersaturated solid solution wires is small. As a result, the restack Nb ₃ Al superconducting wire according to Comparative Example 1 has a smaller diameter due to disconnection due to wire drawing than the restack Nb ₃ Al superconducting wire according to Example 1, and as a result, Jc Was estimated to be lower than the Jc of Example 1.

From the above, in Comparative Example 1, Risutakku Nb 3 _Al superconducting wire formed supersaturated solid solution wire and finally with Nb or Ta on the surface between the Cu pipe 60 having the outer periphery, or between the supersaturated solid solution wire together Since the adhesion was not sufficient, it was shown that it was difficult to lengthen the wire. This is because when Nb or Ta formed on the outer surface of a supersaturated solid solution wire containing Nb and Al is exposed to the outside, Nb oxide or Ta oxide is generated, and thus a supersaturated solid solution wire and a Cu pipe are formed. This is because the adhesion between the two decreases. On the other hand, in the restacked Nb ₃ Al superconducting wire according to Examples 1 to 8, since a metal layer is formed on Nb or Ta formed on the outer surface of the supersaturated solid solution wire, adhesion between the supersaturated solid solution wire and the Cu pipe is performed. The decrease in power can be suppressed. Thus, it was shown that a restacked Nb ₃ Al superconducting wire that can exhibit a high superconducting performance and can be lengthened can be provided.

  While the embodiments and examples of the present invention have been described above, the embodiments and examples described above do not limit the invention according to the claims. It should be noted that not all combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention.

DESCRIPTION OF SYMBOLS 1 Jerry roll / single wire 2 Single billet 3, 3a Precursor single wire 4 Center dummy material 5 Alloy pipe 6 Multi-core billet 7, 7a Multi-core wire 8, 9 Supersaturated solid solution wire 10 Al sheet 20 Nb sheet 30 Core 40 Compound formation Prevention sheet 50 Metal layer 60 Cu pipe 70 Billet for restack 80 Restack wire 90 Restack Nb ₃ Al superconducting wire 100 Delivery reel 110 Power supply 115 Capstan 120 Take-up reel 130 Ga bus 150 Chamber 160 Target 170 Heat treatment furnace

Claims (10)

A wire containing Nb and Al;
Nb layer or Ta layer covering the wire,
An Nb ₃ Al superconducting wire comprising a metal layer provided on the Nb layer or the Ta layer. 2. The Nb ₃ Al superconducting wire according to claim 1, wherein the metal layer includes a metal material having an electric resistance of 0.4 μΩ · m or less. The Nb ₃ Al superconducting wire according to claim 2, wherein the metal layer has a thickness of 1 nm or more. The Nb ₃ Al superconducting wire according to claim 3, wherein the metal layer is formed of a metal material that is not alloyed with a metal pipe to be provided on an outer periphery of the metal layer. The Nb ₃ Al superconducting wire according to claim 4, wherein the metal layer includes at least one metal material selected from the group consisting of Au, Al, Cu, Li, Mg, Mn, Ni, Pd, and Pt. The metal layer includes Ag,
The Nb according to claim 3, further comprising a barrier layer provided between a metal pipe to be provided on an outer periphery of the metal layer and the metal layer, and suppressing alloying between the metal layer and the metal pipe. ₃ Al superconducting wire. A precursor wire forming step of forming a precursor wire in which a wire formed by including Nb and Al is covered with an Nb layer or a Ta layer;
A heat treatment step of forming a supersaturated solid solution wire by heating and cooling the precursor wire; and
Method for producing a Nb 3 _Al superconducting wire and a metal layer forming step of forming a metal layer on the surface of the supersaturated solid solution wire. A metal pipe filling step of filling the metal pipe with the supersaturated solid solution wire having the metal layer formed on the surface to form a filled metal pipe;
Nb 3 _Al method of manufacturing a superconducting wire according to claim 7, comprising the further the reduction process step of performing reduction process to fill the metal pipe. The area reduction processing step, the thickness of the metal layer Nb 3 _Al superconducting wire to be produced is provided to a thickness of more than 1 nm, according to claim 8 for performing the reduction process in the filler metal pipe the method for producing _Nb 3 Al superconducting wire. The method for producing an Nb ₃ Al superconducting wire according to claim 9, wherein the metal pipe filling step uses the metal pipe containing at least one metal selected from the group consisting of Cu and Ag.

Images