JPH1012057A - Nb3al-type superconductive wire material and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Nb3 Al-type superconductive wire material having excellent drawing processibility and excellent critical current density property. SOLUTION: As a core material of Nb/Al layered composite body to be a filament, one metal or alloy selected from pure Nb, Ti, Ta, Zr, Hf, V, Fe, Ni, W, and Mo, which are high melting point metals, and alloys mainly consisting of these metals for industrial use is used to lessen the deformation resistance difference between the Nb/Al layered part and the core material at the time cross-surface decreasing process and at the same time isostatic extrusion method is employed in the initial stage of the cross-section decreasing process to form a mono-filament wire material and multi-filament wire material after production of Nb/Al layered composite body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a superconducting wire, especially Nb ₃
The present invention relates to an Al-based superconducting wire.

[0002]

2. Description of the Related Art In a device requiring a high magnetic field such as a superconducting fusion device, a power storage device, or a high magnetic field magnet for studying physical properties, a critical current density in a high magnetic field is high.
Nb ₃ having a small deterioration in critical current density due to mechanical strain caused by an electromagnetic force acting on the superconducting wire during operation.
The application of Al-based superconducting wires is expected.

[0003] Nb ₃ having a stoichiometric composition excellent in high magnetic field characteristics
The Al phase can stably exist only at a high temperature of 1600 ° C. or higher on the Nb—Al equilibrium diagram, but at a temperature lower than that, the deviation from the stoichiometric composition becomes large, and the critical temperature Tc and the upper temperature The critical magnetic field Bc2 has been reduced, making it difficult to apply to high-field magnets.

[0004] A method of manufacturing an Nb ₃ Al-based superconducting wire having such characteristics is to heat the wire to a high temperature of 1600 ° C. or more, precipitate an Nb ₃ Al phase having a stoichiometric composition, and rapidly cool it. A deposition method for producing an Nb ₃ Al-based superconducting wire having excellent high magnetic field characteristics, and Nb and Al phases are refined to the order of several tens to several hundreds of nm. ₃ Al formation reaction diffusion Diffusion method can be roughly classified.

[0005] In a large-scale magnet such as a nuclear fusion reactor, the stability of the magnet is very important. In order to impart stability to the superconducting magnet, it is necessary to compound a stabilizing metal such as Cu or Al with the superconducting wire. In the above-described deposition method, a high-temperature heat treatment of 1600 ° C. or more is required, so that it is difficult to combine a stabilizing metal, and it is desired to apply an Nb ₃ Al-based superconducting wire by a manufacturing method based on a diffusion method.

[0006] As a method for producing an Nb ₃ Al-based superconducting wire based on a diffusion method, an Nb tube method, a clad tip method, a jelly roll method and the like have been known. Among these, the jelly roll method is the most suitable production method for practical use in terms of manufacturability and characteristics. In conventional Nb ₃ Al-based superconducting wires by the jelly roll method, a Cu material as a stabilizing metal has been used as a core material for forming a monofilament Nb / Al laminated composite.

[0007]

In a conventional method for producing an Nb ₃ Al-based superconducting wire by a jelly roll method using a Cu material as a core material for molding a Nb / Al laminated composite, the degree of drawing of a multifilament wire is reduced. , The deformation resistance difference between the Nb / Al laminated portion in the Nb / Al laminated composite as the filament of the superconducting wire and Cu as the core material increases, and the plastic instability occurs in the laminated composite. This causes a problem that disconnection is likely to occur during wire drawing of the multifilament wire.

In the final heat treatment for forming the Nb ₃ Al-based superconducting phase, Cu of the core material becomes Nb /
As a result of diffusing into the Al laminated portion and contaminating the generated Nb ₃ Al phase, the critical current density characteristics were likely to deteriorate. In order to prevent this, it is necessary to provide a thick diffusion barrier layer between the Cu portion of the core material and the Nb / Al laminated portion. However, the space factor of the Nb ₃ Al-based superconducting phase in the filament is reduced, Apparently, there has been a problem that the critical current characteristics deteriorate.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an Nb ₃ Al-based superconducting wire which solves the above-mentioned drawbacks of the prior art and has excellent drawability and critical current density characteristics. It is in.

[0010]

The gist of the present invention is that, as a core material of an Nb / Al laminated composite to be a filament, industrially pure Nb, Ti, Ta, Zr, Hf, V, Fe, Ni,
It is to reduce the deformation resistance difference between the Nb / Al laminated portion of the multifilament wire and the core material by using W, Mo or one of the alloys mainly composed of these metals.

Further, in order to increase the effect, the present invention also uses hydrostatic extrusion in the initial stage of the surface reduction processing for forming the monofilament wire and the multifilament wire after forming the Nb / Al laminated composite. One of the features.

In the method of manufacturing an Nb ₃ Al-based superconducting wire by the jelly roll method, a composite material in which Nb and Al sheet materials are alternately laminated is used as a filament. This Nb
The deformation rule of the / Al laminated composite portion satisfies the composite rule in a range where the working ratio is low, and is slightly lower than Nb which is the main constituent material. Even if Cu is used as the core material of the laminated composite, no problem occurs. However, as the degree of processing increases, the deformation resistance deviates from the composite rule, resulting in high deformation resistance, and the difference in deformation resistance between the core material and Cu increases. As a result, a plastic instability phenomenon occurs inside the Nb / Al laminated composite, and the multifilament wire is broken starting from that portion. In order to reduce the deformation resistance difference, a material having a high deformation resistance may be used as the core material of the laminated composite.
_{3 In the} heat treatment for forming the Al phase, it is necessary to select a material that is not likely to diffuse into the Nb / Al composite portion. This 2
As materials satisfying the points, Nb, Ti, Ta, Zr, Hf, V, Fe, which are high in deformation resistance and high melting point metals,
Ni, W, Mo or one of the alloys based on these metals is suitable. By using these as a core material, the difference in deformation resistance is reduced as compared with the prior art, and good workability and high critical current density characteristics can be obtained.

The core material in the present invention is a member mainly intended for forming a Nb / Al laminated composite. Nb /
The apparent critical current density characteristic improves as the volume ratio (volume ratio) of the core material to the volume of the Al laminated composite decreases. In consideration of the winding formability of the Nb / Al laminated composite, the above-mentioned volume ratio of the core material is required to be 0.04% or more in the present invention. Conversely, when the volume ratio of the core material increases,
Since the apparent critical current density characteristic decreases, the volume ratio of the core material needs to be 40% or less.

In order to uniformly process an Nb ₃ Al-based superconducting wire by the jelly roll method, which has a very large number of interfaces formed from sheet materials of Nb and Al, it is necessary to perform an initial composite process after assembling the composite billet. , It is necessary to apply high processing strain to give high bonding strength to each interface. Extrusion is generally used as the technique, but hydrostatic extrusion is suitable for manufacturing an Nb ₃ Al-based superconducting wire in which Nb and Al having different deformation resistances are combined. The bonding strength of the interface is changed by the extrusion temperature, but more commonly the extrusion temperature is high bonding strength of the interface is increased, Nb ₃ Al
Since an aluminum having a low melting point is composited in a system superconducting wire, there is an upper limit in the extrusion temperature. The hydrostatic extrusion conditions in which the extrusion temperature is 500 ° C. or lower and the extrusion ratio is 2 or more are conditions under which the above conditions are satisfied and a uniform Nb ₃ Al-based superconducting wire can be manufactured.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows N by the jelly roll method.
1 shows an example of a manufacturing process of a b ₃ Al-based superconducting wire. 2 is a configuration diagram of the jelly roll laminated composite in FIG. 1, FIG. 3 is a cross-sectional configuration diagram of the monofilament billet in FIG. 1, and FIG. 3 is a cross-sectional configuration diagram of the Nb ₃ Al-based superconducting wire in FIG.

In practicing the present invention, first, a round bar (a metal material having a high deformation resistance and a high melting point, for example, a Nb material) having a predetermined outer diameter and a predetermined length is used as a core material 21 and a predetermined value is provided on the outer periphery thereof. Nb sheet material 22 and Al sheet material 23 having the thickness, width and length of
The Al laminated composite 30 is manufactured. Next, the laminated composite 3
0 is inserted into a Cu tube 32 having a predetermined inner and outer diameter and length together with an Nb tube 31 having a predetermined inner and outer diameter and length, and both ends are sealed to form a monofilament billet.

The monofilament billet thus manufactured is processed into a wire having a predetermined outer diameter at room temperature by hydrostatic extrusion, and then processed into a wire having a hexagonal cross section having a predetermined opposite side length by die drawing. You.

Next, after straightening and straightening, a plurality of hexagonal cross-section monofilament wires which have been cut to a predetermined length and washed,
A bundle having a predetermined inner and outer diameter and length, bundled around a plurality of hexagonal cross-section copper wires having the same dimensions as the monofilament wire.
Insert into a u-tube and seal both ends to form a multifilament billet.

This multifilament billet is 500
After being heated to a temperature of not more than 100 ° C. and processed into a wire having a predetermined outer diameter by hydrostatic extrusion, a predetermined twisting process is performed in the middle thereof, and the wire is diced and Nb having a cross-sectional configuration as shown in FIG.
₃ Processed into Al-based superconducting wire. In FIG. 4, 41
Indicates an Nb / Al composite filament, and 42 indicates a Cu matrix.

The Nb ₃ Al-based superconducting wire thus obtained is thereafter subjected to a heat treatment for forming a Nb ₃ Al phase at a predetermined temperature and for a predetermined time, and is used for use. The use of high resistance and high melting point metal materials,
Since processing is performed by hydrostatic extrusion, there is no disconnection during processing and high critical current density characteristics can be obtained.

In this embodiment, a diffusion barrier is not used between the core material and the Nb / Al laminated composite portion. However, an intermediate layer such as a diffusion barrier can be provided as in the prior art. . In this case, the critical current density cannot be improved as much as the embodiment, but the same effect can be obtained with regard to workability. Such an intermediate layer may be formed by winding Nb in a sheet form. In this case, a method of winding a separate Nb sheet material as a diffusion prevention layer, or Nb / A
It is possible to apply a method in which the length of the Nb sheet material used for the 1-layer composite is made longer than that of the Al sheet material by the amount of the diffusion preventing layer and wound.

In the present invention, in many cases, a single metal material is used for the core, but a metal base fiber reinforced composite or a dispersion reinforced composite may be used as the core instead. .

[0023]

Embodiments of the present invention will be described below.

Using a rod having a diameter of 6 mm and a length of 150 mm made of the material shown in Table 1 as a core, a thickness of 0.1 mm and a width of 150 mm were used.
mm, Nb sheet material of length 2610mm and thickness of 0.03m
m, a width of 150 mm, and a length of 2650 mm were laminated and wound in layers to produce Nb / Al laminated composites.

Each of the Nb / Al laminated composites has an outer diameter of 2
A monofilament billet was manufactured by inserting a Nb tube having an outer diameter of 24.6 mm, an inner diameter of 22.3 mm, and a length of 150 mm into a Cu tube having a size of 8.5 mm, an inner diameter of 25 mm and a length of 170 mm, and sealing both ends. In the comparative example, a Cu round bar having the same dimensions as those of the example was used, and was 8.6 mm in outer diameter, 6.1 mm in inner diameter, and 150 mm in length.
After Nb and Al sheets having the same material, thickness and width as those of the example were laminated and wrapped by 2390 mm each to form an Nb / Al laminated composite, the monofilament billet was formed in the same process as the example. Was made.

Each of the obtained monofilament billets was processed to a diameter of 12 mm at room temperature by hydrostatic extrusion. Each of the extruded monofilament wires was drawn by die drawing to obtain a monofilament wire having a hexagonal cross section with a length of opposite side of 2.77 mm.

Next, after straightening and straightening, 48 monofilament wires having a hexagonal cross section cut to a length of 150 mm and washed,
Seven hexagonal Cu wires of the same dimensions as the monofilament wire are bundled in the core, inserted into a Cu tube with an outer diameter of 28.4 mm, an inner diameter of 23.4 mm, and a length of 170 mm, and sealed at both ends to produce a multifilament billet. did.

After heating these billets to 400 ° C., respectively, they were extruded with hydrostatic pressure to a diameter of 12 mm, and were drawn by die drawing to produce an Nb ₃ Al-based superconducting wire having a diameter of 0.6 mm.

The number of breaks during the drawing process of each multifilament wire, and the external magnetic field 1 of the wire obtained by subjecting the final wire to heat treatment at 800 ° C. for 10 hours to form an Nb ₃ Al phase.
The non-copper critical current density at 2T is also shown in Table 1.

[0030]

[Table 1]

The critical current density is a value determined on the basis of 1 μV / cm.

In the examples of the present invention in which a material having a high deformation resistance and a high melting point is used as the core material, it is found that the wire drawing workability and the critical current density characteristics are remarkably improved as compared with the comparative example. The improvement of the critical current density was achieved by using the Nb / Al multilayer composite portion in the monofilament because the Nb diffusion barrier used in the comparative example was not used between the core material and the Nb / Al multilayer composite portion in the example. This is due to the fact that the plastic instability phenomenon did not occur and the filaments in the multifilament wire became more uniform.

[0033]

According to the present invention, Nb ₃ Al-based superconducting wires can be provided with unprecedented high wire workability and critical current density characteristics, because superconducting magnets made of conventional Nb ₃ Al-based superconducting wires. Therefore, there is an effect that the measures for the electromagnetic force which are indispensable in the present invention are greatly relaxed, and the possibility of the magnet winding after the heat treatment for forming the compound superconducting phase, which is not possible with the conventional Nb ₃ Al based superconducting wire, is increased. With these effects, it is possible to greatly reduce the cost of manufacturing a large-scale high-field superconducting magnet such as nuclear fusion.

[Brief description of the drawings]

FIG. 1 is a view showing a manufacturing process of an Nb ₃ Al-based superconducting wire applied in an example.

FIG. 2 is a configuration diagram of a jelly roll laminated composite in FIG.

FIG. 3 is a configuration diagram of a jelly roll laminated composite in FIG.

FIG. 4 is a sectional view of the monofilament billet in FIG. 1;

[Explanation of symbols]

 Reference Signs List 21 core material 22 Nb sheet material 23 Al sheet material 30 laminated composite 31 Nb tube 32 Cu tube 41 Nb / Al composite filament 42 Cu matrix

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazutaka Sasaki 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Within the Tsuchiura Plant of Hitachi Cable, Ltd.

Claims (5)

[Claims] 1. An Nb or Nb-based alloy sheet material and Al
Alternatively, a plurality of filaments made of a laminated composite in which sheet materials of an Al-based alloy are alternately laminated and wrapped and wound are Cu or Cu
In the Nb ₃ Al-based superconducting wire before the Nb ₃ Al generation heat treatment dispersed in the base alloy matrix, Nb, Ti, Ta, Zr, Hf, V,
An Nb ₃ Al-based superconducting wire, which is one of Fe, Ni, W, Mo and alloys mainly composed of these metals. 2. The Nb ₃ Al-based superconducting wire according to claim 1, wherein the volume ratio of the core material in the laminated composite is 0.04 to 40%. 3. A sheet material of Nb or an Nb-based alloy and a sheet material of Al or an Al-based alloy are alternately laminated and wound on a core material, and the laminated composite is placed in a Cu or Cu-based alloy tube. Nb ₃ Al-based superconductivity including a step of forming a monofilament wire by inserting and reducing the surface area to form a monofilament wire, inserting a plurality of the monofilament wires into a Cu or Cu-based alloy tube, and reducing the area to form a multifilament wire. In the method for manufacturing a wire, Nb, Ti, Ta, Zr, H
A method for producing a Nb ₃ Al-based superconducting wire, wherein a laminated composite is formed by using one of f, V, Fe, Ni, W, Mo and an alloy mainly composed of these metals. 4. The Nb ₃ Al according to claim 3, wherein a hydrostatic extrusion method is used at an early stage of the diameter reduction for forming the monofilament wire and the multifilament wire.
Of superconducting superconducting wire. 5. The method of claim 1, wherein the hydrostatic extrusion is performed at an extrusion temperature of 500 ° C.
Nb ₃ manufacturing method of Al superconducting wire according to claim 4, characterized in that the carried out in two or more extrusion ratio.