JP2007294375A - Nb3Sn SUPERCONDUCTING WIRING MATERIAL FABRICATION PRECURSOR, METHOD FOR FABRICATION THEREOF AND Nb3Sn SUPERCONDUCTING WIRING MATERIAL - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Nb<SB>3</SB>Sn superconducting wiring material capable of minimizing an alternate current loss without losing a desirable critical current density and enabling its application to a superconducting magnet available in NMR analysis equipment and a precursor required for fabricating the Nb<SB>3</SB>Sn superconducting wiring material. <P>SOLUTION: This superconducting wiring material fabrication precursor is used to fabricate an Nb<SB>3</SB>Sn superconducting wiring material by an internal Sn method. In this precursor, either Sn or Sn group alloy core is placed at the center, its surrounding is provided with a layer composed of a Cu or Cu group alloy and its periphery is provided with a roll laminate formed by lapping an Nb or Nb group alloy sheet and a Cu or Cu group alloy sheet. In addition, multiple primary composite wire materials having stabilization copper layers at their peripheries are bundled and inserted into a pipe composed of the Cu or Cu group alloy for diameter reduction and the average thickness of the roll laminate in the final shape after diameter reduction is controlled to be less than or equal to 60 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a precursor (precursor for producing a superconducting wire) for producing an Nb ₃ Sn superconducting wire by an internal Sn method, a method for producing the same, and an Nb ₃ Sn superconducting wire, particularly from a medium magnetic field. The present invention relates to a technique such as a precursor for producing an Nb ₃ Sn superconducting wire useful as a material for a superconducting magnet for generating a high magnetic field by an internal Sn method.

  Among the fields in which superconducting wire is put into practical use, superconducting magnets used in high-resolution nuclear magnetic resonance (NMR) analyzers, fusion devices, accelerators, etc. have higher resolution as the generated magnetic field increases. In recent years, there is an increasing trend toward higher magnetic fields.

As a superconducting wire used for the superconducting magnet for generating a high magnetic field, a Nb ₃ Sn wire is put into practical use, and the bronze method is mainly used for manufacturing this Nb ₃ Sn superconducting wire.

In this bronze method, a composite wire is formed by embedding a core material made of a plurality of Nb or Nb base alloys in a Cu—Sn base alloy (bronze) matrix. The composite wire is subjected to diameter reduction processing such as extrusion or wire drawing to reduce the diameter of the core material to form a filament (hereinafter referred to as Nb-based filament), and the composite wire composed of the Nb-based filament and bronze Are bundled together to form a wire group, and after stabilizing copper (stabilized copper) is arranged on the outer periphery, the diameter is further reduced. Subsequently, the Nb ₃ Sn compound layer is formed at the interface between the Nb-based filament and the bronze matrix by heat-treating (diffusion heat treatment) the wire group after the diameter reduction processing at about 600 ° C. or more and 800 ° C. or less.

However, in this method, there is a limit to the Sn concentration that can be dissolved in bronze (15.8% by mass or less), the thickness of the Nb ₃ Sn compound layer to be formed is thin, and the crystallinity is deteriorated. There is a drawback that the critical current density Jc is not high.

In addition to the bronze method, an internal Sn method is also known as a method for producing the Nb ₃ Sn superconducting wire. In this internal Sn method, since there is no limit on the Sn concentration due to the solid solubility limit as in the bronze method, the Sn concentration can be set as high as possible, and a high-quality Nb ₃ Sn phase can be generated. It is said that the density Jc can be obtained.

In the internal Sn method, as shown in FIG. 1 (schematic diagram of a precursor for producing a Nb ₃ Sn superconducting wire), Cu or a Cu-based alloy (hereinafter sometimes referred to as “Cu matrix”) 4 is formed at the center portion. A core material (hereinafter sometimes referred to as “Sn base metal core”) 3 made of Sn or an Sn base alloy is embedded, and a plurality of Nb or Nb bases are included in the Cu matrix 4 around the Sn base metal core 3. An alloy core material (that is, sometimes referred to as “Nb-based filament”) 2 is arranged so as not to contact each other to form a precursor (precursor for producing a superconducting wire) 1.

Was subjected to diameter reduction of wire drawing or the like to the precursor, the heat treatment to diffuse the Sn in the Sn-based metal core 3 by (diffusion heat treatment), to produce Nb ₃ Sn by reacting with the Nb-based filaments 2 It is a method (for example, patent document 1).

  In the precursor 1 as described above, as shown in FIG. 2, a portion where the Nb-based filament 2 and the Sn-based metal core 3 are disposed (hereinafter, sometimes referred to as “superconducting core portion”); Generally, a configuration in which the diffusion barrier layer 6 is disposed between the external stabilizing copper layer 4a is employed. The diffusion barrier layer 6 is composed of, for example, an Nb layer or a Ta layer, or two layers of an Nb layer and a Ta layer, and Sn (Sn-based metal core 3) in the superconducting core portion diffuses to the outside during the diffusion heat treatment. This exhibits the effect of preventing this and increasing the purity of Sn in the superconducting core.

  In order to manufacture the precursor for manufacturing a superconducting wire as described above, the following procedure is performed. First, an Nb-based filament is inserted into a Cu matrisk tube, and subjected to diameter reduction processing such as extrusion processing or wire drawing processing to form a composite (usually the cross-sectional shape is formed in a hexagonal shape). Cut to. And the said composite body is filled in the billet which has a Cu outer cylinder, and a diffusion barrier layer is provided or not provided, and a Cu matrix (Cu solid billet) is arranged in the center part to reduce the diameter such as extrusion. After processing, the Cu matrix at the center is mechanically drilled to form a pipe-shaped composite. Alternatively, as another method, a plurality of the composites are filled in a hollow billet (between the outer cylinder and the inner cylinder) which is composed of a Cu outer cylinder and a Cu inner cylinder and which has or does not have the diffusion barrier layer 6. Then, a pipe-shaped composite is formed by performing diameter reduction processing such as pipe extrusion.

  Then, a Sn-based metal core is inserted into the central gap of the pipe-shaped composite produced by these methods and the diameter thereof is reduced, so that the precursor (primary composite wire) as shown in FIGS. Is manufactured. Hereinafter, these may be referred to as “monoelement wire”.

  Each of the precursors (monoelement wires) configured as described above is bundled and filled in a plurality of Cu matrix tubes with or without a diffusion barrier layer 6, and further reduced in diameter to be multi-core type. The precursor for manufacturing a superconducting wire (hereinafter sometimes referred to as “multi-element wire”).

  3 and 4 show examples of the configuration of the multi-element wire. Among these, FIG. 3 shows a multi-element wire 11 in which a plurality of precursors 1 (monoelement wire) shown in FIG. 1 are bundled and embedded in a Cu matrix 5 having a diffusion barrier layer 6a. FIG. 4 shows a multi-element precursor 11a formed by bundling a plurality of the precursors (monoelement wires) shown in FIG. 2 in a Cu matrix 5 having no diffusion barrier layer.

  In the internal Sn method as described above, in order to increase the critical current density Jc of the superconducting wire, it is necessary to increase the cross-sectional area of the Nb-based filaments, and as a result, the interval between the Nb-based filaments is reduced. Further, it is preferable that the diffusion barrier layer is arranged for each mono element (FIGS. 2 and 4).

In that case, when the Nb ₃ Sn phase is generated (diffusion heat treatment), Nb-based filaments are bonded (bridging) by volume expansion, or the Nb ₃ Sn phase is ringed on the diffusion barrier layer made of Nb. There is a problem that the AC loss increases.

  AC loss is a loss of energy that occurs when the current or magnetic field to the superconducting wire fluctuates. To reduce such AC loss, the spacing between Nb-based filaments is increased, or Nb-based filaments are Although it is conceivable to arrange the concentric circles to make the Sn-based metal core smaller, these configurations lead to a decrease in the critical current density Jc. As the most effective means for reducing AC loss while realizing a high critical current density Jc, it is expected that a multi-element wire is preferably constructed using a monoelement wire having a wire diameter as small as possible. However, when such a configuration is adopted, it is necessary to add more processing, and problems such as disconnection during processing become obvious.

  In the normal internal Sn method, the diameter-reducing process is performed almost only in the cold without intermediate annealing because the Sn-based metal core is disposed in the center of the wire. In order to realize a mono-element wire having a wire diameter as small as possible, it is necessary to add as much processing as possible. However, in this case, the Nb-based filament is work-hardened and breakage often occurs.

As a technique for realizing good superconducting characteristics (high critical current density Jc, low AC loss) by reducing the processing rate as much as possible, a technique such as Patent Document 2 has also been proposed. In this technique, as shown in FIG. 5, the outer periphery of the Sn-based alloy core 3 disposed in the center is overlapped with a mesh Nb member (hereinafter referred to as Nb mesh) 7 and a Cu sheet 8 (hereinafter referred to as “ A roll-shaped laminate 9 (which may be referred to as “jelly roll winding”) is disposed, a diffusion barrier layer 6b is disposed on the outer periphery thereof, and this is inserted into the Cu pipe 15 to reduce the diameter. An element wire 20 (a precursor for producing a superconducting wire) is obtained. Further, a plurality of monoelement wires 20 are bundled, inserted into a Cu pipe and subjected to diameter reduction processing, whereby a multielement in which a plurality of monoelement wires 20 are embedded in a Cu matrix 21 as shown in FIG. The wire 11b is obtained. Such a method is called an MJR method (Modified Jelly Roll method).
JP-A 49-114389 U.S. Pat. No. 4,262,412

Since the MJR method as described above uses an Nb mesh, there is an advantage that the processing rate when the precursor is manufactured can be reduced accordingly. However, in the precursor as shown in FIGS. 5 and 6, the Cu sheet partially enters the hole portion of the Nb mesh during processing, and when viewed in the cross section of the wire, the Nb portion is scattered. Therefore (see FIG. 5), the reaction efficiency of the Nb ₃ Sn phase can be obtained only to the same extent as when using the precursor (FIGS. 1 to 4) applied to the normal internal Sn method. There's a problem.

  In addition, since this method uses a special Nb mesh, it is not only more expensive than the case of using an Nb-based filament, but there is a problem that internal disconnection is likely to occur even if the processing rate is lowered. . Moreover, since only cold processing is performed, the adhesion between Nb and Cu is poor, and this also causes disconnection. Further, in order to achieve a high critical current density Jc, it is necessary to reduce the Cu ratio in the element as much as possible. For this purpose, it is effective to make the pore diameter of the mesh as small as possible. However, there is a limit in processing, and the actual situation is that a critical current density Jc as high as expected is not obtained.

The present invention has been made under such circumstances, and its purpose is to reduce the AC loss as much as possible while maintaining a good critical current density Jc, and to be used for a superconducting magnet used in an NMR analyzer or the like. The object is to provide a Nb ₃ Sn superconducting wire that can be applied, the construction of precursors for producing such Nb ₃ Sn superconducting wires, and a useful method for producing such precursors.

The precursor for fabricating a superconducting wire of the present invention which could achieve the above object, the precursor for fabricating a superconducting wire used for manufacturing a Nb 3 _Sn superconducting wire by an internal Sn process, Sn or a Sn-based alloy in the center A core is disposed, a layer made of Cu or a Cu-based alloy around the core, an Nb or Nb-based alloy sheet (hereinafter sometimes referred to as “Nb sheet”) and a Cu or Cu-based alloy around the outer periphery A roll-like laminate in which sheets (hereinafter sometimes referred to as “Cu sheets”) are wound in layers is disposed, and a plurality of primary composite wires having a stabilized copper layer on the outer periphery are bundled to form a Cu or Cu base. It is inserted into a pipe made of an alloy and reduced in diameter, and is set so that the average thickness of the roll-like laminate in the final shape after the reduction in diameter is 60 μm or less. It has a gist at a certain point.

In the precursor for producing the Nb ₃ Sn superconducting wire of the present invention, the ratio of the thickness of the Nb or Nb base alloy sheet to the Cu or Cu base alloy sheet (the thickness of the Nb or Nb base alloy sheet / Cu or Cu base alloy). The thickness of the sheet is preferably 2.0 to 5.0. Moreover, it is preferable that the Sn-base alloy core which may be arrange | positioned in the center contains Ti in 1.0-5.0 mass%.

  Furthermore, (a) on the inner side or the outer side of the roll-shaped laminate, a region in which only Nb or Nb-based alloy sheets are superimposed is provided, and a Ti sheet is sandwiched between the sheets in the region, (B) A diffusion barrier layer is formed on the outer periphery of the roll-shaped laminate of the primary composite wire, or a diffusion barrier layer is formed between a primary composite wire inserted in a bundle and a pipe made of Cu or a Cu-based alloy. Forming it is also a preferred embodiment.

Nb ₃ exhibiting desired good superconducting characteristics (high critical current density Jc, low AC loss) by subjecting the precursor for producing a superconducting wire as described above to a diffusion heat treatment to form an Nb ₃ Sn-based superconducting phase. An Sn superconducting wire is obtained.

  In producing the above-described precursor for producing a superconducting wire, hot extruding is performed on a portion of the primary composite wire excluding the Sn or Sn-based alloy core, and then the Sn or Sn-based alloy core is placed in the center portion. The wire may be inserted into a wire and cold drawn, and a plurality of primary composite wires may be bundled and inserted into a pipe made of Cu or a Cu-based alloy to reduce the diameter.

According to the present invention, the Nb sheet and the Cu sheet are wound in a jelly roll, and the roll-like laminate wound with the jelly roll is made as small as possible, thereby reducing the AC loss as much as possible while maintaining a good critical current density Jc. Nb ₃ Sn superconducting wire precursor for manufacturing capable of obtaining a superconducting wire which can can be realized.

  The present inventors have studied from various angles in order to achieve the above object. As a result, when the Nb sheet and the Cu sheet are wound in a jelly roll, and the thickness of the roll-shaped laminate wound in the jelly roll is made as small as possible (specifically, the average thickness in the final shape is 60 μm or less), the critical current is obtained. The inventors have found that AC loss can be reduced as much as possible while maintaining the density Jc in good condition, and have completed the present invention.

In the production of the superconducting wire by the internal Sn method, Nb ₃ Sn phase is formed by the diffusion of Sn in the Sn-based metal core disposed at the center of the precursor. It becomes difficult to proceed in a roll-like laminate in which a sheet and a Cu sheet are wound in a jelly roll, that is, in the roll-like laminate, Sn must be diffused through a thin Nb layer, but only the Cu layer. Compared with the internal Sn method that diffuses through the reaction, it is expected that the reaction efficiency will decrease.

The MJR method has improved the reaction efficiency by using an Nb mesh, but this causes another disadvantage described above. However, according to the study by the present inventors, the average thickness of the Nb sheet that is not an Nb mesh and the roll-like laminate obtained by winding the Cu sheet in a jelly roll can be controlled to be 60 μm or less in the final shape. For example, the diffusion of Sn spreads throughout the roll-shaped laminate, and the Nb ₃ Sn phase was sufficiently formed. The average thickness of the roll-shaped laminate is preferably 40 μm or less, but it is preferable that the thickness is 10 μm or more because there is a limit in processing the surface to make this thickness too thin. The “average thickness” means that even if there is some variation in the thickness of the roll-shaped laminate, it is sufficient to ensure this thickness on average, and it is not necessarily 60 μm over the entire circumference. It is not necessary to ensure:

In the precursor for producing the Nb ₃ Sn superconducting wire of the present invention, the ratio of the thickness of the Nb sheet to the Cu sheet (Nb sheet thickness / Cu sheet thickness) is 2.0 to 5.0. Is preferred. If the value of this ratio is less than 2.0, the area of the Nb ₃ Sn phase decreases, and the critical current density Jc decreases. Cu exhibits the action of promoting the diffusion of Sn. However, when the value of the ratio is larger than 5.0, the action of promoting the Sn diffusion by Cu is reduced, and a sufficient amount of Nb ₃ Sn phase is obtained. Is difficult to form. The ratio value is preferably 3.0 or more and 4.0 or less.

By the way, in the Nb ₃ Sn superconducting wire, it is known that the critical current density Jc in a high magnetic field is improved by containing Ti in the Nb ₃ Sn phase. As a method for adding Ti, it is also effective to add Ti to the Sn-based metal core 3 (Sn alloy core) disposed in the center in the precursor of the present invention. In particular, like the precursor of the present invention, when an appropriate range is set for the average thickness of the roll-shaped laminate, the Ti content in the Sn-based metal core 3 is 1.0% by mass or more. The effect of adding Ti is effectively exhibited. However, if the Ti content exceeds 5.0% by mass, the impurities increase and the stoichiometric composition of the Nb ₃ Sn phase shifts, resulting in a decrease in the critical current density Jc.

  The structure of the precursor of the present invention will be described with reference to the drawings. FIG. 7 is a cross-sectional view schematically showing a configuration example of a primary composite wire (monoelement wire) when producing the precursor (multi-element wire) of the present invention, and the configuration is shown in FIG. The superconducting core part in the precursor is a roll-shaped laminate.

  In the configuration shown in FIG. 7, a layer 25 made of Cu or Cu is disposed around the Sn-based metal core 3, and a roll-shaped laminate 9a in which an Nb sheet 26 and a Cu sheet 27 are wound in a jelly roll is disposed on the outer periphery thereof. It has the structure which has the stabilization copper 4b in the outer periphery. After the primary composite wire 20a (monoelement wire) having such a configuration is subjected to diameter reduction processing, a plurality of bundles are inserted into a Cu or Cu pipe and subjected to diameter reduction processing, whereby the primary matrix wire 5a as shown in FIG. A multi-element wire 11c (a precursor for producing a superconducting wire according to the present invention) in which a plurality of composite wires 20a are embedded is obtained.

  The precursors shown in FIGS. 7 and 8 are manufactured as follows, but the basic procedure is the same as the manufacturing procedure described above except that the roll-shaped laminate 9a is configured. First, the Nb sheet 26 and the Cu sheet 27 are overwrapped to form a roll laminate 9a, which is filled into a billet having a Cu outer cylinder, and a Cu core is disposed at the center of the roll laminate 9a to be hot extruded. After processing, the center Cu core is mechanically drilled to form a pipe-like composite. Alternatively, as another method, a hollow billet having a Cu outer cylinder and a Cu inner cylinder is filled with the roll-shaped laminate 9a and hot-extruded to form a pipe-shaped composite. The precursor (primary composite wire) shown in FIG. 7 is constituted by inserting the Sn-based metal core 3 into the central part of the pipe-shaped composite produced by these methods and performing cold working. And the multi-core precursor shown in FIG. 8 is comprised by bundling a plurality of these primary composite wire rods and inserting them into a Cu pipe for cold wire drawing. And in the final shape shown in FIG. 8, in the precursor of this invention, the average thickness of a roll-shaped laminated body is 60 micrometers or less.

Figure 9 is a cross-sectional view schematically showing another example of the configuration of the primary composite wire (mono-element wire) when making the precursor of the present invention (multi-element wire), the configuration is Nb ₃ Sn phase The structure for adding Ti inside is shown. As described above, it is known that the Nb ₃ Sn superconducting wire contains Ti in the Nb ₃ Sn phase, thereby improving the critical current density Jc in a high magnetic field. It is also effective to make the Sn-based metal core 3 contain Ti. However, the Sn-Ti compound is hard and may cause deterioration in workability during diameter reduction processing, and the amount of Ti contained in the Sn-based metal core 3 is also limited. Therefore, in the precursor of the present invention, as another example of the addition means of Ti, an area in which only the Nb sheet 26 is overlapped on the inner side or the outer side (in FIG. 9) of the roll-shaped laminate 9a is made one round. The primary composite wire 20b (monoelement wire) is configured by providing and placing a Ti sheet 30 between the Nb sheets 26, 26 in that region. By adopting such a configuration, Ti can be further added without impairing workability. The Ti sheet 30 may be semicircular or partial, or may be a plurality of layers.

When Ti is added by such a configuration, the addition amount is preferably 1.0 to 2.0 mass% with respect to the Nb sheet 26. When the amount of Ti added is less than 1.0% by mass, the effect of Ti addition is reduced, and when it exceeds 2.0% by mass, Ti becomes an impurity and the quality of the Nb ₃ Sn phase is deteriorated. It will be.

  Regardless of which procedure is employed, hot extruding is performed on the portion of the primary composite wire excluding the Sn or Sn-based alloy core, and then the Sn or Sn-based alloy core is inserted into the central portion to form the primary composite. Cold drawing is performed as a wire, and a plurality of primary composite wires are bundled and inserted into a pipe made of Cu or a Cu-based alloy to reduce the diameter.

  In such a configuration, since the workability of Nb can be improved, it is possible to reduce the thickness of the roll-shaped laminate (that is, to reduce the size of the single-core wire), and the monoelement in the conventional internal Sn method The effect equal to or better than reducing the AC loss by reducing the wire rod will be exhibited. Further, in the conventional internal Sn method, it is necessary to increase the processing rate as much as possible in order to reduce the number of elements so as to increase the number of elements. If this is done, disconnection is likely to occur. Although it was necessary to increase the ratio of Cu and widen the space between the Nb cores, the precursor of the present invention does not need that, and the AC loss can be reduced without reducing the critical current density Jc.

  According to the precursor of the present invention, by using the Nb sheet 26, not only the processing rate of Nb can be lowered as compared with the conventional internal Sn method, but also an Nb mesh like the MJR method can be used. In addition, by processing by hot processing, the adhesion between the Nb sheet 26 and the Cu sheet 27 can be improved, and the occurrence rate of disconnection during processing is remarkably reduced.

  In the configuration shown in FIGS. 7 to 9, for convenience of explanation, the configuration in which the diffusion barrier layer is omitted is shown. However, like the configuration shown in FIGS. 2 to 4, the roll-shaped laminate 9 a in the primary composite wire rod is used. A diffusion barrier layer is formed on the outer periphery, or a diffusion barrier layer is formed between a primary composite wire 20a inserted in a bundle and a pipe made of Cu or a Cu-based alloy (Cu matrix 5b). Useful as a precursor composition of the invention. In addition, the structure of the diffusion barrier layer at this time can be exemplified by superposing only Nb or Nb-based alloy sheets.

By using the precursor for manufacturing a superconducting wire as described above and performing diffusion heat treatment (usually about 600 ° C. or more and less than about 800 ° C.) for generating Nb ₃ Sn, good superconducting characteristics (high critical current density Jc, low alternating current) it is possible to obtain a Nb ₃ Sn superconducting wire which exhibits loss). In addition, it is good to perform the heat processing which diffuses Sn to Cu in the temperature range of 180-600 degreeC before the said heat processing.

  In the precursor of the present invention, as a basic configuration, a Nb or Nb base alloy sheet and a Cu or Cu base alloy sheet are stacked to form a roll-shaped laminate. The base alloy or Cu-base alloy may be one containing elements such as Ta, Hf, Zr, etc. in Nb or Cu to such an extent that the workability is not hindered (about 1-2% by mass). Further, as the Sn-based alloy used as the Sn-based metal core, it is possible to use an alloy containing elements such as Ti, Ta, Zr, Hf and the like contained in Sn to such an extent that the workability is not hindered (about 5% by mass or less). it can.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and both are included in the technical scope of the present invention.

[Example 1]
A Cu hollow billet comprising a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu inner cylinder (outer diameter: 80 mm, inner diameter: 61 mm) was prepared. Nb sheets (thickness: 0.4 mm) and Cu sheets (thickness: 0.1 mm) are alternately wrapped and pasted on the inner surface of the Cu outer cylinder of the Cu hollow billet (thickness at this stage) 16 mm), the Cu inner cylinder was placed inside and welded to produce a hollow billet.

  The hollow billet obtained in this way was subjected to hot pipe extrusion, and then drawn by inserting an Sn metal core into the Cu inner tube, and a hexagonal cross-section primary composite wire (hexagon opposite side: 4.3 mm) It produced (refer said FIG. 7).

  55 bundles of this composite wire are inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by wire drawing to produce a multi-element wire (superconducting wire manufacture) Precursor (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.2 mm) was subjected to a heat treatment (diffusion heat treatment) of 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The resulting Nb ₃ Sn superconducting wire, was measured critical current density (Jc) and AC loss under the following conditions.

[Measurement of critical current density Jc]
A sample (superconducting wire) is energized in liquid helium (temperature 4.2K) under an external magnetic field of 12T (Tesla) or 18T, and the generated voltage is measured by the four-terminal method. This value is 0.1 μV / cm The current value (critical current Ic) at which the electric field was generated was measured, and this current value was divided by the cross-sectional area per non-Cu portion of the wire to determine the critical current density Jc.

[Measurement of AC loss]
Measurement was performed in a liquid magnetic helium (temperature 4.2 K) in an oscillating magnetic field of ± 3 T (Tesla) by a pickup coil method.

[Example 2]
A Cu hollow billet was prepared in the same manner as in Example 1 and subjected to hot pipe extrusion. Then, an Sn metal core was inserted into the Cu inner cylinder and further drawn, and a hexagonal cross-section primary composite wire ( Hexagon width across flats: 1.9 mm) was produced (see FIG. 7).

  211 primary composite wires are bundled and inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by wire drawing to obtain a multi-element wire (superconducting wire). Production precursor) (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.2 mm) was subjected to heat treatment (diffusion heat treatment) at 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Example 3]
A Cu hollow billet comprising a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu inner cylinder (outer diameter: 80 mm, inner diameter: 61 mm) was prepared. Nb sheets (thickness: 0.4 mm) and Cu sheets (thickness: 0.1 mm) are alternately stacked on the inner surface of the Cu outer cylinder of the Cu hollow billet, and the inner side of the roll-shaped laminate A portion where the Nb sheet is unrolled was provided, and a Ti sheet was inserted between the Nb sheets for one turn, and the inner tube made of Cu was placed inside and welded to produce a hollow billet.

  The hollow billet obtained in this way was subjected to hot pipe extrusion, and then drawn by inserting an Sn metal core into the Cu inner tube, and a hexagonal cross-section primary composite wire (hexagon opposite side: 4.3 mm) It produced (refer said FIG. 9).

  55 bundles of this primary composite wire are inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by wire drawing to obtain a multi-element wire (superconducting wire). Production precursor) (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.2 mm) was subjected to heat treatment (diffusion heat treatment) at 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Example 4]
A Cu hollow billet was prepared in the same manner as in Example 3, and after hot pipe extrusion, an Sn metal core was inserted into the Cu inner cylinder and further drawn, and a hexagonal cross-section primary composite wire ( Hexagon width across flats: 1.9 mm) was produced (see FIG. 7).

  211 primary composite wires are bundled and inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by wire drawing to obtain a multi-element wire (superconducting wire). Production precursor) (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.2 mm) was subjected to heat treatment (diffusion heat treatment) at 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Example 5]
A Cu hollow billet comprising a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu inner cylinder (outer diameter: 80 mm, inner diameter: 61 mm) is prepared, and the inner surface of the Cu outer cylinder of this Cu hollow billet On the side, Nb sheets (thickness: 0.3 mm) and Cu sheets (thickness: 0.05 mm) are alternately overlapped and attached, and the inner tube made of Cu is placed inside and welded, and hollow Billets were made.

  The hollow billet obtained in this way was subjected to hot pipe extrusion, and then drawn by inserting an Sn metal core into the Cu inner tube, and a hexagonal cross-section primary composite wire (hexagon opposite side: 4.3 mm) It produced (refer said FIG. 7).

  55 bundles of this primary composite wire are inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by wire drawing to obtain a multi-element wire (superconducting wire). Production precursor) (see FIG. 8).

The resulting multi-element wire: (outer diameter 1.2mm ones), subjected heat treatment at 400 ° C. × 50 hours + 700 ° C. × 100 hours (diffusion heat treatment) to obtain a Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Example 6]
A Cu hollow billet comprising a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu inner cylinder (outer diameter: 80 mm, inner diameter: 61 mm) was prepared, and the inner surface of the Cu outer cylinder of this Cu hollow billet On the side, Nb sheets (thickness: 0.25 mm) and Cu sheets (thickness: 0.05 mm) are alternately overlapped and pasted, and the inner tube made of Cu is placed inside and welded, and hollow Billets were made.

  The hollow billet obtained in this way was subjected to hot pipe extrusion, and then drawn by inserting an Sn metal core into the Cu inner tube, and a hexagonal cross-section primary composite wire (hexagon opposite side: 4.3 mm) It produced (refer said FIG. 7).

  55 bundles of this primary composite wire are inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by wire drawing to obtain a multi-element wire (superconducting wire). Production precursor) (see FIG. 8).

The obtained primary composite wire (outer diameter: 1.2 mm) was subjected to a heat treatment (diffusion heat treatment) of 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Example 7]
A Cu hollow billet comprising a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu inner cylinder (outer diameter: 80 mm, inner diameter: 61 mm) is prepared, and the inner surface of the Cu outer cylinder of this Cu hollow billet On the side, Nb sheets (thickness: 0.1 mm) and Cu sheets (thickness: 0.05 mm) are alternately wrapped and pasted, and the inner tube made of Cu is placed inside and welded, and hollow Billets were made.

  The hollow billet obtained in this way was subjected to hot pipe extrusion, and then drawn by inserting an Sn metal core into the Cu inner tube, and a hexagonal cross-section primary composite wire (hexagon opposite side: 4.3 mm) It produced (refer said FIG. 7).

  A bundle of 55 jelly roll single core wires is inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by wire drawing to produce a multi-element wire (superconducting wire). (Precursor for wire production) (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.2 mm) was subjected to heat treatment (diffusion heat treatment) at 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Example 8]
A Cu hollow billet comprising a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu inner cylinder (outer diameter: 80 mm, inner diameter: 61 mm) was prepared, and the inner surface of the Cu outer cylinder of this Cu hollow billet On the side, Nb sheets (thickness: 0.2 mm) and Cu sheets (thickness: 0.2 mm) are alternately overlapped and attached, and the inner tube made of Cu is placed inside and welded, and hollow Billets were made.

  The hollow billet obtained in this way was subjected to hot pipe extrusion, and then drawn by inserting an Sn metal core into the Cu inner tube, and a hexagonal cross-section primary composite wire (hexagon opposite side: 4.3 mm) It produced (refer said FIG. 7).

  55 bundles of this primary composite wire are inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by wire drawing to obtain a multi-element wire (superconducting wire). Production precursor) (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.2 mm) was subjected to heat treatment (diffusion heat treatment) at 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Example 9]
In the same manner as in Example 1, a multi-element wire (precursor for producing a superconducting wire) having a diameter of 1.6 mm was obtained (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.6 mm) was subjected to a heat treatment (diffusion heat treatment) of 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Example 10]
A Cu hollow billet comprising a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu inner cylinder (outer diameter: 80 mm, inner diameter: 61 mm) was prepared. Nb sheets (thickness: 0.4 mm) and Cu sheets (thickness: 0.1 mm) are alternately wrapped and pasted on the inner surface of the Cu outer cylinder of the Cu hollow billet (thickness at this stage) 16 mm), the Cu inner cylinder was placed inside and welded to produce a hollow billet.

  The hollow billet thus obtained is subjected to hot pipe extrusion processing, and then inserted into the Cu inner cylinder by inserting an Sn alloy core containing 2.0% by mass of Ti, and then drawn into a primary composite wire having a hexagonal cross section. (Width across flats: 1.9 mm) was produced (see FIG. 7).

  211 pieces of this composite wire are bundled and inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by wire drawing to produce a multi-element wire (superconducting wire manufacture) Precursor (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.2 mm) was subjected to a heat treatment (diffusion heat treatment) of 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The resulting Nb ₃ Sn superconducting wire, was measured critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Comparative Example 1]
The hollow billet produced in the same manner as in Example 1 was subjected to hot pipe extrusion, and then Sn wire was inserted into the Cu inner cylinder and further drawn, and a primary composite wire (hexagon opposite side) having a hexagonal cross-sectional shape. : 7.1 mm) (see FIG. 7).

  Nineteen of these primary composite wires are bundled and inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.5 mm by wire drawing to obtain a multi-element wire (superconducting wire). Production precursor) (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.5 mm) was subjected to heat treatment (diffusion heat treatment) at 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Comparative Example 2]
In the same manner as in Comparative Example 1, a multi-element wire having a diameter of 1.2 mm (a precursor for producing a superconducting wire) was obtained (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.2 mm) was subjected to heat treatment (diffusion heat treatment) at 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Comparative Example 3]
In a Cu pipe (outer diameter: 21 mm, inner diameter: 18 mm), an Nb-1 mass% Ti alloy core with an outer diameter of 17 mm was inserted, and then the diameter was reduced to obtain a Cu / Nb-Ti composite wire having a hexagonal cross section. It produced (hexagon opposite side: 4.3 mm).

  A diffusion barrier made of Nb on the inner surface side of the Cu outer cylinder of a Cu hollow billet made of a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu inner cylinder (outer diameter: 70 mm, inner diameter: 61 mm) After arranging the layer (thickness: 5 mm), 336 Cu / Nb-Ti composite wires are bundled around the inner tube made of Cu (that is, the gap between the outer tube made of Cu and the inner tube made of Cu). Inserted. The Cu hollow billet into which the Cu / Nb—Ti composite wire was inserted was covered and evacuated, and then the lid was welded.

  The hollow billet thus obtained was subjected to pipe extrusion processing and pipe drawing processing, and then Sn wire was inserted into the Cu inner cylinder and further drawn to obtain a monoelement wire (hexagonal opposite side: 4. 3 mm).

  After the obtained mono-element wire is cut, a further 55 bundles are bundled and inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm) to reduce the diameter, and the outer diameter is 1.2 mm. (Precursor for superconducting wire production) was produced.

The obtained malt element wire (outer diameter: 1.2 mm) was subjected to a heat treatment (diffusion heat treatment) of 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Comparative Example 4]
Nb on the outer circumference of a Cu pipe (outer diameter: 43 mm, inner diameter: 37 mm), in which Nb mesh (thickness: 0.2 mm) and Cu sheet (thickness: 0.05 mm) are alternately wound on a Sn metal core A sheet of a diffusion barrier layer formed by wrapping only a sheet was inserted, and the diameter was reduced to prepare a MJR single core wire (hexagonal opposite side: 4.3 mm) having a hexagonal cross section.

  A bundle of 55 of these is inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm) to reduce the diameter, and a multi-element wire (precursor for producing a superconducting wire) having an outer diameter of 1.2 mm is obtained. Produced.

The obtained malt element wire (outer diameter: 1.2 mm) was subjected to a heat treatment (diffusion heat treatment) of 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The resulting Nb ₃ Sn superconducting wire, was measured critical current density (Jc) and AC loss under the same conditions as in Example 1.

[Comparative Example 5]
The hollow billet produced in the same manner as in Example 10 was subjected to hot pipe extrusion, and then inserted into the Cu inner cylinder by inserting an Sn alloy core containing 2.0% by mass of Ti, and then drawn into a hexagonal cross section. A primary composite wire having a shape (width across flats: 7.1 mm) was produced (see FIG. 7).

  Nineteen of these primary composite wires are bundled and inserted into a Cu pipe (outer diameter: 45 mm, inner diameter: 37 mm), and then drawn to a diameter of 1.2 mm by drawing to obtain a multi-element wire (superconducting wire). Production precursor) (see FIG. 8).

The obtained multi-element wire (outer diameter: 1.2 mm) was subjected to heat treatment (diffusion heat treatment) at 400 ° C. × 50 hours + 700 ° C. × 100 hours to obtain an Nb ₃ Sn superconducting wire. The obtained Nb ₃ Sn superconducting wire was measured for critical current density (Jc) and AC loss under the same conditions as in Example 1.

  The superconducting characteristics (critical current density Jc, AC loss) of the superconducting wires obtained in Examples 1 to 10 and Comparative Examples 1 to 5 were determined according to the manufacturing conditions (number of single cores, Nb / Ti thickness ratio, monoelement wire diameter ( Jelly roll single core diameter), roll laminate thickness (jelly roll thickness) and the number of breaks during processing are collectively shown in the following Table 1. In addition, Nb / Ti thickness ratio, jewelry roll single core diameter and Jewelery roll thickness is measured at the final shape (superconducting wire precursor) stage by arbitrarily selecting 5 single cores (10 in total) based on the SEM observation photographic images of the outer periphery and center of the cross section. The average value.

  As is clear from this result, in Examples 1 to 10 that satisfy the requirements (and preferred requirements) defined in the present invention, the AC loss is reduced, and a good critical current density Jc can be realized. I understand that. On the other hand, Comparative Examples 1 to 5 lack any of the requirements defined in the present invention, and any of the superconducting characteristics is deteriorated. Specifically, in Comparative Examples 1, 2, and 5, since the jelly roll thickness exceeds 60 μm, both the critical electric density Jc and the AC loss are deteriorated. In Comparative Examples 3 and 4, the AC loss is also reduced and a good critical current density Jc can be realized, but the number of disconnections is increased.

It is sectional drawing which showed typically the example of a structure of the precursor (monoelement wire) for superconducting wire manufacturing applied to the internal Sn method. It is sectional drawing which showed typically the example of another structure of the precursor (monoelement wire) for superconducting wire manufacture applied to the internal Sn method. It is sectional drawing which showed typically the structural example of the precursor (multi-element wire) for superconducting wire manufacturing applied to the internal Sn method. It is sectional drawing which showed typically the other structural example of the precursor for superconducting wire material (multi-element wire material) applied to the internal Sn method. It is sectional drawing which showed typically the structural example of the precursor (monoelement wire) for superconducting wire manufacture applied to the MJR method. It is sectional drawing which showed typically the structural example of the precursor (multi-element wire) for superconducting wire manufacture applied to MJR method. It is sectional drawing which showed typically the example of a structure of the primary composite wire (monoelement wire) when producing the precursor (multi-element wire) of this invention. It is sectional drawing which showed typically the structural example of the precursor (multi-element wire) of invention. It is sectional drawing which showed typically the example of another structure of the primary composite wire (monoelement wire) when producing the precursor (multi-element wire) of this invention.

Explanation of symbols

1 Precursor for manufacturing superconducting wire (monoelement wire)
2 Nb-based filament 3 Sn-based metal core 4, 5, 5a, 5b, 21 Cu matrix (Cu base material)
4a, 4b Stabilized copper 6, 6a Diffusion barrier layer 9, 9a Rolled laminate 11, 11a, 11b, 11c Precursor for producing superconducting wire (multi-element wire)
20a, 20b Primary composite wire 26 Nb sheet 27 Cu sheet 30 Ti sheet

Claims (7)

In precursor for fabricating a superconducting wire used for manufacturing a Nb 3 _Sn superconducting wire by an internal Sn process, the Sn or Sn based alloy core in the center is placed a layer composed of Cu or Cu-based alloy around it, A roll-like laminate in which an Nb or Nb-based alloy sheet and a Cu or Cu-based alloy sheet are wound on each other is disposed on the outer periphery, and a plurality of primary composite wires having a stabilized copper layer on the outer periphery are bundled to form Cu or It is inserted into a pipe made of a Cu-based alloy and reduced in diameter, and is set so that the average thickness of the roll-shaped laminate in the final shape after the reduction in diameter is 60 μm or less. A precursor for producing a Nb ₃ Sn superconducting wire. The thickness ratio of the Nb or Nb base alloy sheet to the Cu or Cu base alloy sheet (Nb or Nb base alloy sheet thickness / Cu or Cu base alloy sheet thickness) is 2.0 to 5.0. The precursor for manufacturing a Nb ₃ Sn superconducting wire according to claim 1. The precursor for producing a Nb ₃ Sn superconducting wire according to claim 1 or 2, wherein the Sn-based alloy core contains Ti in a range of 1.0 to 5.0 mass%. A region in which only Nb or Nb-based alloy sheets are superposed is provided inside or outside of the roll-shaped laminate, and a Ti sheet is sandwiched between the sheets in the region, and arranged. The precursor for manufacturing the Nb ₃ Sn superconducting wire described in 1. A diffusion barrier layer is formed on the outer periphery of the roll laminate of the primary composite wire, or a diffusion barrier layer is formed between a primary composite wire inserted in a bundle and a pipe made of Cu or a Cu-based alloy. The precursor for producing a Nb ₃ Sn superconducting wire according to any one of claims 1 to 4. A Nb ₃ Sn superconducting wire obtained by subjecting the precursor for manufacturing a superconducting wire according to any one of claims 1 to 5 to a diffusion heat treatment to form an Nb ₃ Sn-based superconducting phase.   In producing the superconducting wire production precursor according to any one of claims 1 to 5, after performing hot extrusion processing on a portion of the primary composite wire excluding Sn or Sn-based alloy core, Sn or Superconducting wire manufacturing, characterized in that a Sn-based alloy core is inserted into the central portion and cold-drawn, and a plurality of primary composite wires are bundled and inserted into a pipe made of Cu or a Cu-based alloy to reduce the diameter. For producing a precursor.

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