JP4723345B2 - Method for producing Nb3Sn superconducting wire and precursor therefor - Google Patents

Description

The present invention relates to a method for producing an Nb ₃ Sn superconducting wire by an internal diffusion method, and a precursor (precursor for producing a superconducting wire) for producing such an Nb ₃ Sn superconducting wire. The present invention relates to a technique for producing a Nb ₃ Sn superconducting wire useful as a material for a superconducting magnet for use.

  Among the fields in which superconducting wire is put to practical use, superconducting magnets used in high-resolution nuclear magnetic resonance (NMR) analyzers have higher resolution as the generated magnetic field increases. There is a tendency.

As a superconducting wire used for the superconducting magnet for generating a high magnetic field, an Nb ₃ Sn wire has been put into practical use, and the bronze method is mainly employed for manufacturing this Nb ₃ Sn superconducting wire. In this bronze method, a plurality of Nb base materials are embedded in a Cu-Sn base alloy (bronze) matrix and drawn to reduce the diameter of the Nb base material into filaments. A plurality of filaments and bronze composites are bundled to form a wire group, and after stabilizing copper (stabilized copper) is placed, wire drawing is performed. In this method, the wire group is heat-treated (diffusion heat treatment) at about 600 ° C. or higher and 800 ° C. or lower to form an Nb ₃ Sn compound layer at the interface between the Nb-based filament and the matrix. 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 disadvantage that the high magnetic field characteristics are not good.

As a method for producing a Nb 3 _Sn superconducting wire, in addition to the bronze process, a tube process and an internal diffusion method are known. In these methods, 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 layer can be generated. Therefore, a superconducting wire having excellent high magnetic field characteristics Is shown to be obtained.

Among these, in the internal diffusion method, as shown in FIG. 1 (schematic diagram of a precursor for producing a Nb ₃ Sn superconducting wire), the center of Cu or a Cu-based alloy (hereinafter sometimes referred to as “Cu base material”) 4 A core made of Sn or an Sn-based alloy (hereinafter sometimes referred to as an “Sn-based metal core”) 3 is embedded in the portion, and a plurality of Nb or Nb in the Cu base material 4 around the Sn-based metal core 3 is embedded. An Nb-based alloy core (hereinafter sometimes referred to as “Nb-based metal core”) 2 is disposed to form a precursor (precursor for producing a superconducting wire), which is drawn, and then subjected to heat treatment (diffusion heat treatment). In this method, Sn in the Sn-based metal core 3 is diffused and reacted with the Nb-based metal core 2 to generate Nb ₃ Sn (for example, Patent Document 1).

  Further, in the precursor 1 as described above, as shown in FIG. 2, a portion where the Nb-based metal core 2 and the Sn-based metal core 3 are disposed (hereinafter sometimes referred to as “superconducting matrix portion”) A configuration in which a diffusion barrier layer 6 is disposed between the external stabilizing copper layer 4a is also known. 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 matrix 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 matrisk portion.

  In order to manufacture the precursor for manufacturing a superconducting wire as described above, the following procedure is performed. First, an Nb-based metal core (Nb-based metal filament) is inserted into a Cu matrisk tube, subjected to extrusion, wire diameter reduction or the like to obtain a composite, and this is cut into an appropriate length. And, after having a Cu outer cylinder, filling the composite in a billet with or without a diffusion barrier layer, placing a Cu matrix (Cu solid billet) in the center and extruding it, A 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. The pipe is extruded to form a pipe-shaped composite.

  Then, the Sn-based metal core 3 is inserted into the central gap portion of the pipe-shaped composite produced by these methods and the diameter is reduced to produce the precursor as shown in FIGS.

  In the precursors shown in FIGS. 1 and 2, one Sn metal core 3 and a plurality of Nb-based metal cores 2 are shown, but a plurality of Sn-based metal cores 3 may be formed. It is. Hereinafter, these are also referred to as “monoelement precursors”.

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

  3 and 4 show examples of the structure of the multi-element precursor, and FIG. 3 shows the Cu matrix having the diffusion barrier layer 6a as the precursor 1 (monoelement precursor) shown in FIG. 5 is a multi-element precursor 11 that is bundled and embedded in a multi-element, and FIG. 4 shows a Cu matrix that does not have a diffusion barrier layer for the precursor (mono-element precursor) shown in FIG. The multi-element precursor 11a is formed by bundling and embedding a plurality of bundles in the interior 5.

In producing a superconducting wire by the internal diffusion method using the precursor as described above, it has also been proposed to contain elements such as Ti, Ta, Zr, and Hf in the Nb ₃ Sn phase. Inclusion of such elements in the Nb ₃ Sn phase is said to improve the superconducting properties in a high magnetic field as compared with Nb ₃ Sn superconducting wires not containing these elements. As a means of containing Nb ₃ Sn said elements in Aiuchi, for example, Patent Document 2, 30 atomic% or less Sn metal core, or Nb metal cores By containing 5 atomic% or less of Ti, 15T ( It has been shown that the critical current density Jc in a high external magnetic field can be improved.

  Patent Document 3 uses an Sn-based alloy core containing an Sn-Ti compound instead of the Sn core, and the Sn-Ti compound has a maximum size of 30 μm or less and an average particle size of 20 to 15 μm. There has been proposed a melting / casting method within the above range.

Furthermore, Patent Document 4 proposes a method in which a fine Ti powder having a maximum particle size of 10 μm or less and a Sn—Ti linear body containing Sn are used as the Sn metal core.
Japanese Patent Laid-Open No. 49-114389 Patent Claims, etc. Japanese Patent Publication No. 1-8698 Patent Claim etc. JP, 2002-317232, A Claims etc. JP, 2003-331669, A Claims etc.

Of the methods of incorporating elements such as Ti, Ta, Zr, and Hf into the Nb ₃ Sn phase, the method of incorporating these elements into the Nb core (Patent Document 2) compares these with those of the Nb core. Since the workability of the Nb-based alloy core containing the element is deteriorated, there is a problem that it causes non-uniform deformation or disconnection during the diameter reduction processing.

  On the other hand, in the method of adding elements such as Ti, Ta, Zr, and Hf to the Sn core (Patent Documents 3 and 4), compared to the case of adding to the Nb core, the melting and casting in a vacuum or in an inert atmosphere is large. A large amount of equipment is required, and it is necessary to handle Ti fine powder of 10 μm or less, which causes problems in terms of safety and cost. Further, the Ti or Sn-Ti compound having a large particle size may not remain sufficiently cooled in the manufacturing process, which may cause disconnection.

The present invention has been made under such circumstances, and its purpose is to prevent non-uniform deformation and disconnection during diameter reduction processing, and without requiring large-scale equipment, and further safety in handling. And a configuration of a precursor for manufacturing a Nb ₃ Sn superconducting wire that can effectively contain elements such as Ti, Zr, and Hf in the Nb ₃ Sn phase without causing problems in terms of cost and cost, and using such a precursor The object is to provide a method for producing a Nb ₃ Sn superconducting wire.

The precursor for producing a superconducting wire of the present invention that has achieved the above object is a precursor for producing a superconducting wire used when producing a Nb ₃ Sn superconducting wire by an internal diffusion method, and is a Cu or Cu-based alloy Inside, one or more Nb or Nb-based alloy cores and one or more Sn or Sn-based alloy cores are arranged so that they do not contact each other, and the outer periphery is stabilized. In the precursor for producing a superconducting wire having a copper layer, the superconducting matrix portion is selected from one or more metals or alloys selected from the group consisting of Ti, Zr and Hf, or a group consisting of Ti, Zr and Hf. It has a gist in that a sheet-like layer made of an Nb-based alloy containing one or more elements is disposed.

  In the precursor for producing a superconducting wire according to the present invention, the sheet-like layer is (1) disposed so as not to contact the Nb or Nb-based alloy core, or (2) annealed. Is preferred. A configuration in which a diffusion barrier layer is disposed between the superconducting matrix portion and the stabilized copper can also be employed. Moreover, a multi-core precursor for manufacturing a superconducting wire (multi-element precursor) can be configured by arranging a plurality of the above-described precursors for manufacturing a superconducting wire in Cu or a Cu-based alloy.

  Moreover, the superconducting wire which exhibits the desired characteristic can be manufactured by heat-processing the precursor for single-conductor or multi-core superconducting wire manufacture as mentioned above.

According to the present invention, a sheet made of one or more metals or alloys selected from the group consisting of Ti, Zr and Hf, or an Nb-based alloy containing one or more elements selected from the group consisting of Ti, Zr and Hf. since so arranged as Jo layer, without causing problems such as in the prior art, Ti, Zr, the elements of Hf, etc. can be effectively contained in the Nb 3 _Sn Aiuchi. Such a precursor for producing a superconducting wire does not require a large facility for melting and casting in a vacuum or in an inert atmosphere, compared to the case where Ti, Zr, Hf, etc. are added to the Sn core, and a metal of 10 μm or less. The Nb ₃ Sn superconducting wire that exhibits high critical current density can be efficiently manufactured because it is not necessary to handle the fine powder of the material, and can ensure work safety during handling, and in addition, the cost can be reduced. Can do.

  The present inventors have studied from various angles in order to achieve the above object. As a result, as an addition form of the element, it is not contained in the Sn-based metal core or the Nb-based metal core, but one or more metals or alloys selected from the group consisting of Ti, Zr and Hf, or Ti, Zr and The present invention has been completed by finding that the above object can be achieved brilliantly if a sheet-like layer made of an Nb-based alloy containing one or more elements selected from the group consisting of Hf is separately arranged in the Cu matrix.

In the present invention, the sheet-like layer disposed in the precursor may have any of a cylindrical shape, a band shape, a plate shape, and a foil shape. By arranging such a sheet-like layer in the Cu matrix, the Nb ₃ Sn phase is arranged. The diffusion of these elements into the inside can be effectively advanced, and the characteristics of the Nb ₃ Sn superconducting wire can be further improved. The structure of the precursor of the present invention will be described below with reference to the drawings.

  FIG. 5 is a cross-sectional view schematically showing an example of the configuration of the precursor for manufacturing a superconducting wire according to the present invention. In this configuration, a sheet-like layer 10 made of, for example, an Nb—Ti alloy is formed in a cylindrical shape on the outer periphery of the Sn-based metal core 3 with respect to the configuration of the precursor 1 (monoelement precursor) in FIG. (Precursor 1a). 5 is the same as that shown in FIG. 2, and the corresponding parts are denoted by the same reference numerals.

If such a configuration is adopted, Sn in the Sn-based metal core 3 diffuses during the heat treatment (diffusion heat treatment) and reacts with the sheet-like layer 10 made of the Nb—Ti alloy. By reducing the thickness of the sheet-like layer 10 to such an extent that the Nb-based metal core 2 can be sufficiently reacted (for example, about 1 to 50 μm at the stage immediately before the heat treatment), Sn is outside the sheet-like layer. Can diffuse. At that time, the Ti element is also diffused into the Nb-based metal core 2 at the same time, whereby the Ti element can be diffused into the Nb ₃ Sn phase. Note that the configuration of the sheet-like layer 10 shown in FIG. 5 shows a configuration in which a single layer of Nb—Ti metal layer is formed, but the material of the sheet-like layer may be a single element or a different element. Of course, a two-layer film structure may be used. The Sn-based metal core 3 and the sheet-like layer 10 do not necessarily need to be in contact with each other, and the Sn-based metal core 3 and the sheet-like layer 10 do not contact each other by interposing Cu between them. A configuration in a state can also be adopted.

FIG. 6 is a cross-sectional view schematically showing another example of the configuration of the precursor for producing a superconducting wire (precursor 1b) of the present invention. In this configuration, instead of providing the sheet-like layer 10 on the outer peripheral portion of the Sn-based metal core 3 in the configuration of FIG. 5, the sheet-like layer 10 a made of, for example, an Nb—Ti alloy is used over the entire inner peripheral portion of the diffusion barrier layer 6. Is formed. Even if such a configuration is adopted, similarly to the configuration shown in FIG. 5, the Ti element diffuses into the Nb-based metal core 2 during the heat treatment, so that the Ti element can be diffused into the Nb ₃ Sn phase.

  FIG. 6 shows the configuration in which the sheet-like layer 10a is formed on the entire inner peripheral portion of the diffusion barrier layer 6; however, the sheet-like layer 10a is not necessarily provided on the entire surface, and the shape (cross-sectional shape) of the sheet-like layer 10a is divided into an arc shape. Of course, the above-described configuration may be used. Further, the sheet-like layer 10a does not necessarily need to be in contact with the diffusion barrier layer 6, and by interposing Cu between both, the sheet-like layer 10a and the diffusion barrier layer 6 are not in contact with each other. It is also possible to adopt a configuration that

FIG. 7 is a cross-sectional view schematically showing still another example of the configuration of the precursor for producing a superconducting wire (precursor 1c) of the present invention. In this configuration, a sheet-like layer 10b (fin shape) made of, for example, an Nb-Ti alloy is arranged at an interface so as to extend in the radial direction at the interface of the Nb-based alloy core 2 arranged in the matrix portion. is there. Even if such a configuration is adopted, similarly to the configuration shown in FIGS. 5 and 6, the Ti element diffuses into the Nb-based metal core 2 during the heat treatment, so that the Ti element can be diffused into the Nb ₃ Sn phase. Become.

  The configurations shown in FIGS. 5 to 7 exemplify the configuration of the precursor of the present invention, and are not limited to these configurations. In short, Nb containing one or more metals or alloys selected from the group consisting of Ti, Zr and Hf, or one or more elements selected from the group consisting of Ti, Zr and Hf, at any location of the superconducting matrix portion. If a sheet-like layer made of a base alloy is arranged, the effect of the present invention is exhibited. Moreover, although the structure of FIGS. 5-7 showed the structure by which the diffusion barrier layer 6 is arrange | positioned, with respect to the single core wire which does not provide the diffusion barrier layer 6 (for example, said FIG. 1), it is a sheet form as mentioned above Even if the layers 10, 10a and 10b are formed, the effect of the present invention is achieved. In FIGS. 5 to 7, the basic mono-element precursor has a single Sn-based metal core 3 and a plurality of Nb-based metal cores 2 arranged around it. The basic form of the precursor is not limited to this, and it is of course possible to arrange a plurality of Sn-based metal cores 3.

  In the configuration shown in FIGS. 5 to 7, the case of a mono-element precursor is shown. However, a multi-element precursor is formed by arranging a plurality of the precursors described in any one of Cu or a Cu-based alloy. Can be configured. FIG. 8 is a cross-sectional view schematically showing a configuration example of such a multi-element precursor. In this configuration, a plurality of mono-element precursors 1c shown in FIG. The multi-element precursor 11b is configured.

  When configuring such a multi-element precursor, when a mono-element precursor (basic configuration shown in FIG. 1) that does not form the diffusion barrier layer 6 is used to form a multi-core type, A configuration in which the diffusion barrier layer 6a is formed around the bundle of monoelement precursors can be employed (see FIG. 3).

In the precursor for manufacturing a superconducting wire according to the present invention, at any location of the superconducting matrix portion, one or more metals or alloys selected from the group consisting of Ti, Zr and Hf, or an Nb-based alloy containing these elements are used. By forming the sheet-like layers 10, 10a, 10b, the element can be diffused into the Nb ₃ Sn phase while maintaining good processability. The thickness of 10b is preferably about 1 to 50 μm before the heat treatment. If this thickness is less than 1 μm, disconnection is likely to occur, and if it exceeds 50 μm, the elements cannot be diffused and become thick, resulting in a decrease in Jc characteristics. However, this sheet-like layer is preferably annealed (for example, about 960 to 1200 ° C.) before being placed on the precursor, and the workability can be further improved by performing such treatment.

The Nb-based alloy (Nb-based alloy containing one or more elements selected from the group consisting of Ti, Zr, and Hf) that may be used as the sheet-like layers 10, 10a, and 10b has a content of the above elements of 0.2. It is preferable that it is about 1-60 mass%. If this content is too low, it will be difficult to ensure the content by diffusing these elements in the Nb ₃ Sn phase, and if it is too high, the superconducting properties will be adversely affected. The more preferable lower limit of this content is about 5% by mass, and the preferable upper limit is about 50% by mass.

  In addition, it is preferable to appropriately adjust the area ratios of the sheet-like layers 10, 10a, and 10b, and the matrix portion of the precursor (in the case of forming the diffusion barrier layers 6 and 6a, the cross-sectional area inside thereof) On the other hand, the area ratio is preferably about 0.5 to 20%. When the area ratio is less than 0.5%, it does not contribute to the improvement of the characteristics, and when it exceeds 20%, the characteristics are deteriorated. A more preferable lower limit of the area ratio is about 1%, and a more preferable upper limit is about 5%.

The precursor of the present invention has a basic configuration in which an Nb-based metal core (Nb or Nb-based alloy core) and an Sn-based metal core (Sn or Sn-based alloy core) are arranged in Cu or a Cu-based alloy. It is. As the Cu alloy used in such a configuration, an alloy containing elements such as Nb and Ni in Cu can be used. As also material used as the Nb-based metal core and Sbn-based metal core, Ti, Ta, Zr, the elements Hf, etc., can be used one obtained by Do含 chromatic enough not to inhibit the processability.

  In the method of the present invention, the above-described precursor is constituted, and annealing and wire drawing are performed on the precursor, and then diffusion heat treatment (usually about 650 ° C. or more and less than 750 ° C.) is performed to exhibit good characteristics. A superconducting wire can be obtained.

  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 they are all included in the technical scope of the present invention.

Example 1
An Nb-based metal core with an outer diameter of 54 mm was inserted into a Cu pipe having an outer diameter of 68 mm and an inner diameter of 55 mm, and then reduced in diameter to form a hexagonal cross-section Cu / Nb composite wire (hexagonal opposite side: 4.3 mm). ) And was cut into a length of 400 mm.

  On the other hand, diffusion of Nb inside the Cu outer cylinder of a Cu hollow billet composed of a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu inner cylinder (outer diameter: 68 mm, inner diameter: 60 mm). After disposing the barrier layer (thickness: 5 mm), an Nb-50 mass% Ti alloy sheet (thickness: 0.2 mm) is wound around the inner cylinder made of Cu so that the total thickness becomes 2 mm. A sheet-like layer was formed.

  The bundled Cu / Nb composite wires: 336 previously prepared were inserted into the Cu hollow cylinder of the Cu hollow billet, and then the lid was capped to perform vacuuming and welding.

  This billet was subjected to a pipe extrusion process, and then an Sn metal core was inserted and further drawn to produce a composite wire (monoelement precursor).

  Next, after cutting this composite wire rod, a further 19 wires are bundled and inserted into a Cu pipe (outer diameter: 21 mm, inner diameter: 18 mm), and then subjected to diameter reduction processing by wire drawing to obtain a composite wire rod having an outer diameter of 1 mm (multiple Element precursor) (see FIG. 5). At this time, no breakage during wire drawing was observed.

The obtained multi-element precursor was subjected to a heat treatment (diffusion heat treatment) at 670 ° C. for 200 hours to obtain a Nb ₃ Sn superconducting wire. With respect to the obtained Nb ₃ Sn superconducting wire, the critical current (Ic) was measured in a state where an external magnetic field 12T (Tesla) was applied, and Ic was divided by the area of the non-copper portion of the wire cross section to obtain the critical current density (Jc). Was evaluated. As a result, the critical current density (Jc) at a temperature of 4.2 K was a high critical current density (Jc) of 1220 A / mm ² .

Example 2
In the same manner as in Example 1, a Cu / Nb composite wire (hexagonal opposite side: 4.3 mm) was prepared, and then cut into a length of 400 mm.

  On the other hand, a diffusion barrier layer made of Nb is formed on the inside of the Cu outer tube of a Cu solid billet made of a Cu outer tube (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu matrix rod (outer diameter: 68 mm) ( (Thickness: 5 mm) was placed, and then an Nb-50 mass% alloy sheet (thickness: 0.2 mm) on the inner wall was attached to make the entire thickness 2 mm. Further, 336 Cu / Nb composite wires prepared in advance were bundled and inserted therein, and then a Cu matrix rod was placed in the center, a lid was put on, and vacuuming and welding were performed.

  This billet was extruded, a central Cu matrix region was perforated (diameter: 20 mm), a Sn core having a diameter of 20 mm was inserted into the perforated portion, and further drawn to produce a composite wire.

  Next, after cutting this composite wire rod, a further 19 wires are bundled and inserted into a Cu pipe (outer diameter: 21 mm, inner diameter: 18 mm), and then subjected to diameter reduction by wire drawing to obtain a composite wire rod having an outer diameter of 1 mm (multiple Element precursor) (see FIG. 6). At this time, no breakage during wire drawing was observed.

The obtained multi-element precursor was subjected to a heat treatment (diffusion heat treatment) at 670 ° C. for 200 hours to obtain a Nb ₃ Sn superconducting wire. With respect to the obtained Nb ₃ Sn superconducting wire, the critical current (Ic) was measured in a state where an external magnetic field 12T (Tesla) was applied, and Ic was divided by the area of the non-copper portion of the wire cross section to obtain the critical current density (Jc). Was evaluated. As a result, the critical current density (Jc) at a temperature of 4.2 K was a high critical current density (Jc) of 1204 A / mm ² .

Example 3
In the same manner as in Example 1, a Cu / Nb composite wire (hexagonal opposite side: 4.3 mm) was prepared, and then cut into a length of 400 mm.

  On the other hand, a diffusion barrier layer made of Nb is formed on the inside of the Cu outer tube of a Cu solid billet made of a Cu outer tube (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu matrix rod (outer diameter: 68 mm) ( (Thickness: 5 mm), 6 Nb-50 mass% Ti alloy sheets (thickness: 2 mm) in the fin state, and a Cu matrix rod in the center are placed in the gap. Cu / Nb composite wires prepared: 336 wires were bundled and inserted, and then the lid was capped to perform vacuuming and welding.

  This billet was extruded, a central Cu matrix region was perforated (diameter: 20 mm), a Sn core having a diameter of 20 mm was inserted into the perforated portion, and further drawn to produce a composite wire.

  Next, after cutting this composite wire rod, a further 19 wires are bundled and inserted into a Cu pipe (outer diameter: 21 mm, inner diameter: 18 mm), and then subjected to diameter reduction by wire drawing to obtain a composite wire rod having an outer diameter of 1 mm (multiple Element precursor) (see FIG. 7). At this time, no breakage during wire drawing was observed.

The obtained multi-element precursor was subjected to a heat treatment (diffusion heat treatment) at 670 ° C. for 200 hours to obtain a Nb ₃ Sn superconducting wire. With respect to the obtained Nb ₃ Sn superconducting wire, the critical current (Ic) was measured in a state where an external magnetic field 12T (Tesla) was applied, and Ic was divided by the area of the non-copper portion of the wire cross section to obtain the critical current density (Jc). Was evaluated. As a result, the critical current density (Jc) at a temperature of 4.2 K was a high critical current density (Jc) of 1240 A / mm ² .

Example 4
A Cu / Nb composite wire (diameter: hexagonal opposite side: 4.3 mm) was prepared in the same manner as in Example 1, and then cut into a length of 400 mm.

  On the other hand, an Nb-50 mass% Ti alloy is placed inside the Cu outer cylinder of a Cu solid billet made of a Cu outer cylinder (outer diameter: 143 mm, inner diameter: 127 mm) and a Cu matrix rod (outer diameter: 68 mm). Six sheets (thickness: 0.2 mm) in a fin state and a Cu matrix rod in the center are arranged, and 336 Cu / Nb composite wires prepared in advance are bundled and inserted into the obtained gap. Then, the lid was put on and vacuuming and welding were performed.

  This billet was extruded, a central Cu matrix region was perforated (diameter: 20 mm), a Sn core having a diameter of 20 mm was inserted into the perforated portion, and further drawn to produce a composite wire.

  Next, after cutting this composite wire, a further 19 bundles were inserted into a Cu pipe (outer diameter: 21 mm, inner diameter: 18 mm) in which a diffusion barrier layer (thickness: 2 mm) made of Nb was placed. Then, the diameter was reduced by drawing to obtain a composite wire (multi-element precursor) having an outer diameter of 1 mm (see FIG. 8). At this time, no breakage during wire drawing was observed.

The obtained multi-element precursor was subjected to a heat treatment (diffusion heat treatment) at 670 ° C. for 200 hours to obtain a Nb ₃ Sn superconducting wire. With respect to the obtained Nb ₃ Sn superconducting wire, the critical current (Ic) was measured in a state where an external magnetic field 12T (Tesla) was applied, and Ic was divided by the area of the non-copper portion of the wire cross section to obtain the critical current density (Jc). Was evaluated. As a result, the critical current density (Jc) at a temperature of 4.2 K was a high critical current density (Jc) of 1213 A / mm ² .

Comparative Example 1
After inserting an Nb-based alloy core (Nb-1 mass% Ti alloy core) having an outer diameter of 54 mm into a Cu pipe having an outer diameter of 68 mm and an inner diameter of 55 mm, the steel is extruded and reduced in diameter by wire drawing. An Nb-based alloy composite wire (hexagonal opposite side: 9.3 mm) was prepared and cut into a length of 400 mm.

  On the other hand, after arranging a diffusion barrier layer with a Nb-based metal inside a Cu outer cylinder of a Cu solid billet, a Cu matrix is arranged at the center, and the Cu / Nb-based alloy previously prepared in the obtained void Composite wire: After 336 wires were bundled and inserted to form a multi-core wire, the lid was capped and vacuuming and welding were performed.

  After extruding this billet, the center Cu matrix region was perforated to make a hole with a diameter of 20 mm, and then a Sn metal core was inserted and further drawn to produce a Cu / Nb / Sn composite wire.

  Next, after cutting this composite wire rod, a further 19 wires are bundled and inserted into a Cu pipe (outer diameter: 21 mm, inner diameter: 18 mm), and then subjected to diameter reduction processing by drawing to a composite wire rod having an outer diameter of 1 mm (superconductivity) Precursor wire for wire production). At this time, a total of 6 disconnections were observed during the wire drawing. When the cross section of the wire in which the disconnection occurred was observed with an SEM, it was confirmed that the Nb-1 mass% Ti alloy core was partially deformed unevenly.

The obtained precursor wire was subjected to a heat treatment (diffusion heat treatment) at 670 ° C. for 200 hours to obtain a Nb ₃ Sn superconducting wire. With respect to the obtained Nb ₃ Sn superconducting wire, the critical current (Ic) was measured with an external magnetic field 12T (Tesla) applied, and Ic was divided by the area of the non-copper portion of the wire cross section to obtain the critical current density (Jc). Was evaluated. As a result, the critical current density (Jc) at a temperature of 4.2 K was only 1095 A / mm ² .

Comparative Example 2
After melting Sn at 1300 ° C in an argon gas atmosphere and adding Sn at 1300 ° C, stirring and adding sponge Ti to a target of 2% by mass, casting into a copper mold, Sn-2% by mass Ti alloy An ingot was produced.

  The obtained Sn group-2 mass% Ti alloy ingot was machined into an extruded billet shape, and then extruded to have a diameter of 19.8 mm to obtain a bar.

  After inserting an Nb core with an outer diameter of 54 mm into a Cu pipe with an outer diameter of 68 mm and an inner diameter of 55 mm, the diameter is reduced by drawing to produce a Cu / Nb composite wire (hexagonal opposite side: 4.3 mm). This was cut into a length of 400 mm.

  On the other hand, after arranging a diffusion barrier layer with Nb metal inside a Cu outer cylinder of a Cu solid billet, a Cu matrix is arranged in the center, and a Cu / Nb composite wire prepared in advance in the obtained void: After 336 wires were bundled and inserted into a multi-core wire, the lid was capped and vacuuming and welding were performed.

  After extruding this billet, the center Cu matrix region was perforated to make a hole with a diameter of 20 mm, and then a Sn-based metal core was inserted and further drawn to obtain a Cu / Nb / Sn—Ti composite wire. Produced.

  Next, after cutting this composite wire rod, a further 19 wires are bundled and inserted into a Cu pipe (outer diameter: 21 mm, inner diameter: 18 mm), and then subjected to diameter reduction processing by drawing to a composite wire rod having an outer diameter of 1.0 mm. (Precursor wire for production of superconducting wire). At this time, a total of two disconnections were observed during wire drawing. When the cross section of the wire material in which the disconnection occurred was observed with an SEM, it was confirmed that Sn-Ti inclusions having a particle diameter of about 35 μm remained and caused the disconnection.

The obtained precursor wire was subjected to a heat treatment (diffusion heat treatment) at 670 ° C. for 200 hours to obtain a Nb ₃ Sn superconducting wire. With respect to the obtained Nb ₃ Sn superconducting wire, the critical current (Ic) was measured in a state where an external magnetic field 12T (Tesla) was applied, and Ic was divided by the area of the non-copper portion of the wire cross section to obtain the critical current density (Jc). Was evaluated. As a result, the critical current density (Jc) at a temperature of 4.2 K was only a critical current density (Jc) of 1104 A / mm ² .

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

Explanation of symbols

1 Mono-element precursor 2 Nb-based metal core 3 Sn-based metal core 4 Cu-based alloy (Cu base material)
4a Stabilized copper layer 5 Cu matrix 6 Diffusion barrier layers 10, 10a, 10b Sheet-like layers 11, 11a, 11b Multi-element precursor

Claims (5)

A precursor for fabricating a superconducting wire used for manufacturing a Nb 3 _Sn superconducting wire by an internal diffusion method, in a Cu or Cu-based alloy, one or a plurality of Nb or Nb-based alloy cores, one or A superconducting matrix portion in which a plurality of Sn or Sn-based alloy cores are arranged so as not to contact each other, and a precursor for producing a superconducting wire having a stabilizing copper layer on the outer periphery thereof, and any location in the superconducting matrix portion A sheet-like layer made of one or more metals or alloys selected from the group consisting of Ti, Zr and Hf, or an Nb-based alloy containing one or more elements selected from the group consisting of Ti, Zr and Hf The precursor for manufacturing a Nb ₃ Sn superconducting wire , wherein the sheet-like layer is annealed before being placed on the precursor.   2. The precursor for manufacturing a superconducting wire according to claim 1, wherein the sheet-like layer is disposed so as not to contact the Nb or Nb-based alloy core. The precursor for manufacturing a superconducting wire according to claim 1 or 2 , wherein a diffusion barrier layer is disposed between the superconducting matrix portion and the stabilizing copper layer. A precursor for producing a superconducting wire, wherein a plurality of the precursors for producing a superconducting wire according to any one of claims 1 to 3 are arranged in Cu or a Cu-based alloy. The precursor for fabricating a superconducting wire according to any one of claims 1-4, the heat treatment method for producing a Nb 3 _Sn superconducting wire and forming a Nb 3 _Sn based superconducting phase by.

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