JP3428771B2 - Nb3Sn compound superconducting wire - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a device requiring a high magnetic field such as a nuclear fusion device, an energy storage device, and a high magnetic field magnet for studying physical properties, Nb ₃ S having a high critical current density in a high magnetic field is used.
An n-based superconducting wire is used.

In the bronze method, which is one of the methods for producing Nb ₃ Sn based superconducting wire, a matrix material of Cu--Sn alloy containing Sn which is a component of Nb ₃ Sn based compound superconductor, Nb or Nb and others. After the filament material of the Nb-based alloy containing the additive element is processed into a composite in which the filament material is dispersed and embedded in the matrix material, the composite material is heat-treated to form a matrix of Cu-Sn alloy and Nb. Or, Nb ₃ S is added to the interface with the filament of Nb-based alloy.
An n-based superconducting compound is produced (hereinafter, a superconducting composite in which a large number of filaments, at least the surface of which are made of Nb ₃ Sn-based superconducting compound, are dispersed and embedded in a matrix of Cu—Sn based alloy).

On the other hand, in the superconducting wire, a stabilizing metal such as high-purity copper is compounded in consideration of the stability when the superconducting state is broken. However, in the Nb ₃ Sn based superconducting wire by the bronze method, In the intermediate annealing heat treatment for alleviating the work hardening of the matrix material and the heat treatment for forming the compound, the alloying elements in the Cu-Sn alloy matrix diffuse into the stabilized copper and contaminate the stabilized copper. In order not to deteriorate the stability, Ta or N, which is a metal impermeable to Cu, Sn, etc., at the interface between the composite which becomes the superconducting composite and the stabilized copper.
The interposition of b as a diffusion barrier is performed.

[0005]

[SUMMARY OF THE INVENTION When using Nb as a diffusion barrier, Nb ₃ Sn compound superconductor is produced in the interface between the Nb diffusion barrier and Cu-Sn-based alloy matrix material in the final compound generated heat treatment It

Conventionally, Nb ₃ Sn-based superconducting wire is often used in a constant magnetic field or a low fluctuating magnetic field in an AC mode, and the Nb ₃ Sn-based superconducting compound of the Nb diffusion barrier increases the current capacity of the wire. Has the advantage of

In recent years, Nb ₃ Sn-based superconducting wire has been widely used in a fluctuating magnetic field, and a wire used in a fluctuating magnetic field is required to have low AC loss characteristics in addition to current capacity characteristics. However, when the Nb diffusion barrier is arranged so as to surround the superconducting composite, the cylindrical Nb ₃ Sn-based compound generated in the diffusion barrier electromagnetically behaves as a giant filament and causes AC loss. This will greatly increase the history loss, which is the main component. For this reason, the Nb ₃ Sn-based superconducting wire using Nb as a diffusion barrier could not be used in a fluctuating magnetic field.

On the other hand, it is the Nb ₃ Sn based superconducting wire that uses Ta as a diffusion barrier that enables the use in a fluctuating magnetic field without the formation of Nb ₃ Sn based compounds on the diffusion barrier. However, the work hardening of Ta is severe in the wire rod having this configuration, and therefore, when Ta diffusion barrier is combined with other wire rod constituent materials and the composite material is processed at an extremely high surface reduction rate, the wire rod having Nb as the diffusion barrier is formed. However, there is a problem in processing that breakage is likely to occur during cold surface reduction processing, which rarely occurs. This is also the case when Ta and Nb are used together as a diffusion barrier. If Ta is hardened by working and if it is Nb, it does not recover even by the intermediate annealing heat treatment in which some recovery occurs. It is considered that this is due to the plastic instability phenomenon of the Ta layer caused by the expansion of the difference in deformation resistance.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a novel Nb ₃ Sn-based superconducting wire having low AC loss, high magnetic field current characteristics and excellent workability. is there.

[0010]

The essential point of the present invention is that the diffusion barrier layer is composed of a layer of Nb-based alloy disposed on the stabilized copper side and a layer of Ta or Ta-based alloy disposed on the superconducting composite side. It is a composite layer.

[0011]

In the present invention, since the Nb-based alloy material is provided on one of the diffusion barrier layers, this acts as a layer for buffering the deformation resistance difference between the stabilized copper and Ta, and stabilizes due to work hardening of Ta. It is possible to reduce the plastic instability phenomenon due to the expansion of the difference in deformation resistance with copper and prevent the occurrence of disconnection during processing.

In the present invention, an Nb-based alloy is used for one of the diffusion barrier layers. As such an Nb-based alloy, Tb is used.
At least one of a, Hf, Ti, Zr and V is added in a total amount of 10 at% or less. Such an Nb-based alloy does not have a risk of contaminating the stabilized copper, and is formed by adjoining Ta by an intermediate annealing heat treatment that is performed during cold working.
Alternatively, it is possible to easily form a solid solution at the interface with the Ta-based alloy to obtain a strong degree of interfacial bonding and prevent the occurrence of the plastic instability phenomenon of Ta. Further, the above-mentioned alloy elements contained in the Nb-based alloy are the interface between the stabilized copper and the Nb-based alloy and the Nb-based alloy and the Tb.
It has an action of reducing the oxide film layer existing on the interface of a, which has already been formed on the surface of each member at the time of assembling the composite base material, in the intermediate annealing heat treatment, and can form a stronger joint interface. Become.

As for the Ta diffusion barrier used together with such an Nb-based alloy, a Ta-based alloy containing a small amount of at least one of Nb, Hf, Ti, Zr, and V having a reducing action as an alloying element is used. By applying it, the bonding strength at the interface can be made stronger.

The Ta-based alloy to which the above-mentioned alloying elements are added forms a solid solution with Ta as in the case of the Nb-based alloy,
And it has ductility, but its addition amount is Cu-S
The content is limited to 5 at% or less in order to prevent the plastic instability phenomenon of the Ta-based alloy from being caused by the difference in deformation resistance with the n-based alloy matrix.

The volume ratio of the Nb-based alloy and Ta or Ta-based alloy constituting the diffusion barrier in the present invention is the same as that of Nb because the Nb-based alloy has the same magnetization characteristics. Will fall. However,
The volume ratio of Nb-based alloy to Ta or Ta-based alloy is 0.1:
When it is 1 or less, the function of the Nb-based alloy as a buffer material for deformation resistance is lost, and the plastic instability phenomenon easily occurs in Ta or Ta-based alloy.

Nb when not used due to alternating magnetic field
It is not necessary to reduce the volume ratio of the base alloy, but if the volume ratio of the Nb base alloy and Ta or Ta base alloy is 5: 1 or more, the Ta or Ta base alloy will become perpendicular to the axial direction of the wire rod during cold working. It ruptures, and a wire break occurs from the ruptured portion of Ta or a Ta-based alloy as a starting point. Therefore, Nb-based alloy and Ta or T
The volume ratio of the a-based alloy is limited within the range of 0.1: 1 to 5: 1.

As for the Cu-Sn alloy, the addition amount of Sn is 5 to 10 at% or less, and in addition to this, Ti, Ni, and G are added.
at least one of e, Ga, Si, Al, Mn, and Zn
An alloy in which the total amount of seeds is 5 at% or less is applicable.

[0018]

EXAMPLES The present invention will be described below with reference to examples.

As shown in FIG. 1, the wire rod manufactured in the embodiment has a superconducting composite body 3 arranged at the center thereof and a stabilized copper 6 made of oxygen-free copper coated cylindrically on the outermost periphery. A composite diffusion barrier having a layer 4 of Ta or a Ta-based alloy on the side of the superconducting composite 3 and a layer 5 of a Nb-based alloy on the side of the stabilized copper 6 was arranged between them. In this case, the superconducting composite 3
Is composed of a matrix 1 of a Cu—Sn alloy in which a filament 2 of an Nb-based alloy having a layer of an Nb ₃ Sn-based superconducting compound formed on at least the surface thereof is dispersed and embedded. Table 1 shows specific specifications of the wire rod.

[0020]

[Table 1]

In this embodiment, Nb-based alloy and Ta or Ta are used.
The effect was compared by fixing the volume ratio of the base alloy to 1: 1 and changing the material.

As the wire rod, a composite base material (extrusion billet) having a cross-sectional structure as shown in FIG. 1 and a diameter of about 70 mm was assembled, and this was hydrostatically extruded to a diameter of 25 mm at 400 ° C., and then a surface reduction rate of about 35%. Each was subjected to an intermediate annealing heat treatment at about 600 ° C., and cold drawn to a final diameter of 0.9 mm. The twist pitch of the wire rod was 20 mm. The production amount is
The final diameter of each of the examples and comparative examples is about 1500 m.

In order to impart superconductivity to each of the obtained wires, a heat treatment was performed at 650 ° C. for 200 hours, and the S in the matrix 1 was formed on the outer periphery of the filament 2 of the Nb-based alloy.
A layer of a superconducting Nb ₃ Sn-based compound, which is a reaction product of n and Nb of filament 2, was formed.

For each of the superconducting wires thus obtained,
Table 2 shows the history loss based on the volume of the non-copper part when the magnetic field was oscillated at ± 3 Tesla at 4.2 K, and the number of wire breaks that occurred during cold working to the final diameter.

[0025]

[Table 2]

Nb used in these examples and comparative examples,
For each of the Nb-based alloy, Ta and Ta-based alloy, an ingot was produced by electron beam melting, and a plate obtained by cold rolling the ingot was used as a diffusion barrier member in the assembly of the composite base material.

Examples 1 to 9 are the results when Ta is used on the superconducting composite side and the Nb-based alloy on the stabilizing copper side is changed. As can be seen from these results, by using the Nb-based alloy in which at least one kind of Ta, Hf, Ti, Zr, and V is added in a total amount of 10 at% or less for the diffusion barrier on the stabilized copper side, the Nb of Comparative Example 1 is Good cold workability could be obtained as with the single diffusion barrier. History loss is Nb-5
Although the at% Ti alloy slightly increased in Example 6 due to the higher critical magnetic field, the rest of the alloys showed a higher value of the magnetization of the Nb-based alloy than that of Comparative Example 2, but that of Comparative Example 3 The value is similar to that of the composite diffusion barrier (the difference between the measured values is considered to be due to the measurement error). In Comparative Example 1, as described above, Nb ₃ Sn compound is formed at the interface between the Nb diffusion barrier and Cu-Sn-based alloy matrix, it was a very large history loss. On the other hand, Example 10
No. 12 to Nb-5at% Ta is the Nb-based alloy on the stabilized copper side.
And the case where a Ta-based alloy is applied to the superconducting composite side. As a result, it was found that good hysteresis loss characteristics and cold workability can be obtained even when the Ta-based alloy with the addition element and the addition amount within the range of the present invention is used as the diffusion barrier on the superconducting composite side.

As described above, according to the present invention, it can be seen that an Nb ₃ Sn compound superconducting wire having excellent cold workability and low AC loss can be obtained.

In FIG. 2, the stabilizing material 6 is arranged at the central portion and the outermost peripheral portion of the wire, and between the cylindrical superconducting composite body 3 and the stabilizing material 6, the stabilizing material 6 is provided with an Nb-based alloy. 2 is a Nb ₃ Sn-based compound superconducting wire by the bronze method in which the layer 4 of 1 is provided with the layer 3 of Ta or Ta-based alloy on the superconducting composite 1 side.

Further, in FIG. 3, the stabilizing material 6 is arranged only in the central portion of the wire, and between the stabilizing material 6 and the cylindrical superconducting composite body 3, a layer of Nb-based alloy is provided on the stabilizing material 6 side. 5 is an Nb ₃ Sn-based compound superconducting wire by the bronze method in which the layer 4 of Ta or Ta-based alloy is arranged on the superconducting composite 3 side.

Due to the above-described action of the present invention, a wire rod having any structure can be provided with low AC loss and good workability.

In the illustrated example, all of them have a circular cross-sectional shape, but by applying a process such as rolling to form a rectangular cross-section wire rod, it is possible to apply it to a tightly wound superconducting macnet. it can.

The present invention is not limited to the bronze method,
It can also be applied to Nb ₃ Sn-based compound superconducting wire made of copper as a stabilizing material, which is produced by an internal diffusion method, an external diffusion method, an Nb tube method, a jelly roll method, an in situ method, a powder method and the like.

[0034]

The superconducting wire of the present invention has a layer of Nb-based alloy on the side of stabilized copper and a layer of Ta or Ta-based alloy on the side of superconducting composite between the superconducting composite and the stabilized copper. since using the composite diffusion barrier, AC loss is small and the workability excellent Nb ₃ Sn compound superconducting wire makes it possible to industrially mass-feed, its economic effect is very large.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of a superconducting wire according to the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the superconducting wire according to the present invention.

FIG. 3 is a schematic sectional view showing another example of the superconducting wire according to the present invention.

[Explanation of symbols]

1 Cu-Sn alloy matrix 2 Nb-based alloy filament 3 Superconducting complex 4 Ta or Ta-based alloy layer 5 Nb-based alloy layer 6 Stabilizer made of oxygen-free copper

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Tsuji, 801 No. 1 Mukaiyama, Naka-machi, Naka-gun, Naka-gun, Ibaraki Prefecture 1 In the Naka Research Institute, Japan Atomic Energy Research Institute (72) Kiyoshi Yoshida, 801 Mukaiyama, Naka-machi, Naka-gun, Ibaraki Prefecture No. 1 Japan Atomic Energy Research Institute Naka Research Institute (72) Inventor Genzo Iwaki 3550 Kidayo-cho, Tsuchiura City, Ibaraki Prefecture Hitachi Cable Electric Systems Co., Ltd. System Materials Research Laboratory (72) Inventor Shuji Sakai 3550 Kidayo-cho, Tsuchiura City, Ibaraki Prefecture Address: Hitachi Cable, Ltd., System Materials Laboratory (72) Inventor, Kenichi Kikuchi, 3550, Kidayomachi, Tsuchiura, Ibaraki Prefecture, Hitachi Cable, Ltd., Tsuchiura Plant, (72) Inventor, Kazutaka Sasaki 3550, Kidayomachi, Tsuchiura, Ibaraki Prefecture Address Hitachi Cable Ltd. Tsuchiura factory (56) Reference JP-A-56-52807 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01B 12/00-13/00

Claims (3)

(57) [Claims] 1. A superconducting composite in which a Cu—Sn based alloy is used as a matrix, and a large number of Nb or Nb based alloy filaments having a layer of Nb ₃ Sn based superconducting compound on at least the surface thereof are embedded in the matrix, and the superconducting composite. In a superconducting wire comprising a stabilizing material arranged around a composite and a diffusion barrier layer arranged between the stabilizing material and the superconducting composite, the diffusion barrier layer is arranged on the stabilizing material side. been Ri Do from a layer of Nb-based alloy layer and the superconducting composite side in placed Ta or Ta-based alloy, of the stabilizing member side Nb-based alloy
The gold layer is at least one of Ta, Hf, Ti, Zr, and V.
A Nb ₃ Sn-based compound superconducting wire, characterized in that the seed is an alloy layer added in a total amount of 10 at% or less . 2. A Cu—Sn based alloy as a matrix,
Nb ₃ Sn-based superconductivity in at least the surface of the matrix
Filamen of Nb or Nb-based alloy with a layer of conducting compound
And a superconducting composite in which a large number of
A stabilizing material arranged around the stabilizing material and the superconducting material.
Superconducting wire with diffusion barrier layer located between the composite
Material, the diffusion barrier layer was placed on the stabilizing material side.
Ta arranged on the Nb-based alloy layer and the superconducting composite side or
And a Nb-based alloy on the stabilizing material side.
The gold layer is at least one of Ta, Hf, Ti, Zr, and V.
The seed is an alloy layer added in a total amount of 10 at% or less,
The Ta-based alloy layer on the superconducting composite side is Nb, Hf, Ti, Z
At least one of r and V is added in a total amount of 5 at% or less.
Nb ₃ Sn compound superconducting wire, characterized in that the a Ta-based alloy layer. The 3. A volume ratio of Ta or Ta-based alloy and the stabilizing material side Nb-based alloy of the superconducting composite body side 1: 0.1 to 1: 5
The Nb ₃ Sn based compound superconducting wire according to claim 1 or 2, characterized in that