JPH08339728A - Manufacture of nb3sn system superconductive wire - Google Patents

Abstract

PURPOSE: To manufacture an Nb3 Sn system superconductive wire without deteriorating an A.C. loss characteristic, by using material Nb for a diffusion barrier layer. CONSTITUTION: An Sn rod is arranged on the middle of a wire, a Cu matrix embedded with an Nb filament is formed on the outer side of the Sn rod, a sheet is winded on the outer side of the matrix to form a diffusion barrier layer 6a, a diffusion barrier layer 6b composed of an Nb sheet is formed on the periphery of the barrier layer 6b, and a stabilization material 7 is arranged on the utmost outer layer. These billets are diameter-reducingly worked by hydrostatic pressure extrusion, and are performed die wire drawing to manufacture a wire. Consequently, the A.C. loss of a superconductive wire can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an Nb ₃ Sn-based superconducting wire suitable for an AC device such as a superconducting generator or a current limiter, and more specifically to a Nb ₃ S having a stabilizer and a barrier layer.
The present invention relates to a manufacturing method that does not deteriorate the AC loss characteristics of an n-based superconducting wire.

[0002]

2. Description of the Related Art Nb ₃ Sn based superconducting wire is manufactured by drawing a composite material of Nb or Nb alloy and Cu or Cu alloy and subjecting it to heat treatment to react Nb and Sn to generate Nb ₃ Sn. However, they are classified into a bronze method, a tube method, a powder method, an in-situ method, etc., depending on the difference in the starting materials. Hereinafter, the above-mentioned bronze method will be described as a typical example, and a general method for producing an Nb ₃ Sn-based superconducting wire will be described in detail with reference to the drawings.

First, the case of a single core type superconducting wire will be described. As shown in FIG. 1, Cu-Sn alloy and Cu-Sn-T are used.
After the Nb wire 2 is embedded in a billet case 1 (linear base material) made of a Cu-Sn based alloy such as an i alloy, the end portion is electron beam welded to assemble the single core type composite billet 3. The single core type composite billet 3 is subjected to hot isostatic pressing to perform integration and surface reduction at the same time, and further cold drawing is performed to wire drawing to a predetermined size. At this time, by cold drawing,
Since the Cu-Sn alloy is significantly work hardened, the work rate is 30
Intermediate annealing for removing work-hardening strain is required for each processing of about 60%. Then heat treatment (600-70
(0 ° C.), Nb ₃ Sn is generated at the interface between the Cu—Sn alloy linear base material 1 and the Nb wire 2 to obtain an Nb ₃ Sn superconducting wire.

Next, in the case of a multifilamentary superconducting wire, one or a plurality of Nb wires 2 are made of a billet case 1a made of a Cu--Sn base alloy as shown in FIG. 1 or FIG. Material)
It is embedded in and is subjected to cross-section reduction processing and has a hexagonal cross section.
Next, a multi-core billet 8 is formed, and a plurality of cylindrical billets 8 are bundled in a cylindrical shape to form a wire rod group 10 (see FIG. 3). As shown in FIG.
Inserted in a cylindrical outer layer case 9 (outermost layer) made of Cu-Sn-based alloy, drawn in the same manner as in the case of the single core type, and the final shape includes 3000 to 30000 Nb wires 2. To form a secondary multi-core billet 11 (multi-core type composite billet). In the secondary multi-core billet 11, as shown in FIG. 3, a wire / rod-shaped oxygen-free copper or the like is incorporated as a stabilizing material 7 in the central portion thereof, and the wire of the primary multi-core billet 8 is formed. Cu-Sn is provided between the group 10 and the stabilizing material 7.
A cylindrical inner layer 5 made of a base alloy, and a cylindrical Nb layer or Ta layer (hereinafter, referred to as a diffusion barrier layer for preventing diffusion of Sn from a Cu—Sn alloy during diffusion heat treatment for producing Nb ₃ Sn (hereinafter, A diffusion barrier layer) 6 is formed. Therefore, by providing the diffusion barrier layer 6, the stabilizing material 7 can be prevented from being contaminated with Sn. Finally by heat treatment to, a Cu-Sn based alloy linear at the interface of the base material 1a and the Nb line 2 to generate Nb ₃ Sn multi-core Nb ₃ Sn superconducting wire.

As the secondary multi-core billet, as described above, instead of providing the stabilizing material or the diffusion barrier layer on the center side, the primary multi-core billet is stacked on the Cu-Sn base alloy or the like on the outer peripheral side. Some have a diffusion barrier layer followed by a stabilizing material.

As described above, in any of the manufacturing methods, the secondary multi-core billet is provided with a stabilizer having excellent conductivity for the purpose of ensuring the thermal and electrical stability of the superconducting wire. ing. However, when Sn diffuses into the stabilizing material and is contaminated, the electrical resistance increases, the thermal conductivity decreases, and the function as the stabilizing material cannot be achieved. A diffusion barrier layer for stopping the diffusion of Sn is arranged between the and, to prevent Sn from penetrating into the stabilizing material.

As a material of the diffusion barrier layer, it is relatively easy to process, it is difficult to form an alloy with Cu, and S
It is common to use Nb or Ta because it is difficult for n to pass through, but both have the following problems.

First, when Nb is used as the material of the diffusion barrier layer, Sn diffused by the reaction heat treatment reacts with Nb of the barrier material, and the diffusion barrier layer itself becomes an Nb ₃ Sn superconductor. As a result, the outer diameter of the cylindrical diffusion barrier layer becomes like the diameter of the superconducting filament, and the same effect as that of the thick superconducting filament existing inside the superconducting wire is exhibited.

In a superconducting wire used in an AC device such as a superconducting generator or a fault current limiter, AC loss generated in the wire when an AC current is applied is minimized to adversely affect the efficiency of the AC device. From the viewpoint of preventing this, a multicore superconducting wire having a large number of ultrafine superconducting filaments formed as thin as possible is used. However, even if the superconducting filament is made extremely thin and multifilamentary, if the cylindrical diffusion barrier layer becomes a superconductor, AC loss becomes large and there is a problem that it does not function as a superconducting wire for AC.

On the other hand, when Ta is used as the material of the diffusion barrier layer, since Ta has poor workability, wire breakage may occur during wire drawing, and wire drawing with a large reduction in area is possible. Since this is not possible, the number of times wire drawing / annealing is repeated increases. Also, Ta is a more expensive material than Nb, so Ta
If is used for the diffusion barrier layer, the manufacturing cost becomes very high.

[0011]

The present invention has been made in view of the above circumstances, and Nb is used as a material for the diffusion barrier layer instead of Ta, which is poor in workability and disadvantageous in cost. On the premise of this, an object of the present invention is to provide a method for producing an Nb ₃ Sn-based superconducting wire without deteriorating the AC loss characteristics.

[0012]

The manufacturing method of the present invention that achieves the above object is to provide a Nb ₃ Sn-based superconducting wire in which a cylindrical diffusion barrier layer is arranged on the outer peripheral side or the inner peripheral side of a stabilizing material. A method of manufacturing, wherein P is added to the diffusion barrier layer to 0.
The gist is to use an Nb alloy containing 01 to 1 wt%. As the Nb alloy, other than P,
An Nb alloy containing 20 wt% or less (however, 0% is not included) of one or more elements selected from the group consisting of Ta, Zr, Ti, and Hf may be used.

Further, the diffusion barrier layer is concentrically formed from two layers made of different materials, Nb is used for the diffusion barrier layer on one side in contact with the stabilizing material, and P is used for the diffusion barrier layer on the other side. A method using a Cu alloy containing 0.01 to 1 wt% may be adopted. As the Cu alloy, P
Alternatively, a Cu alloy containing 15 wt% or less (not including 0%) of one or more elements selected from the group consisting of Sn, Ge, Mn, Al, Zn, Ti, and Ni may be used.

[0014]

The smaller the diameter of the superconducting filament, the smaller the AC loss of the superconducting wire. However, in the past, Nb ₃ Sn was generated on the surface of the diffusion barrier layer. It behaved like one thick filament, the effect of thinning the superconducting filament disappeared, and the AC loss could not be reduced. On the other hand, according to the manufacturing method of the present invention, Nb ₃ S is formed in the diffusion barrier layer.
n is never generated. Therefore, the AC loss of the superconducting wire can be reduced by thinning the superconducting filament, so that the AC loss can be greatly reduced.

The inventors of the present invention added P to the diffusion barrier layer mainly composed of Nb so that Sn was added during the reaction heat treatment.
Has found that Nb ₃ Sn is not generated even when it penetrates into the diffusion barrier layer, and conceived the present invention. Nb ₃ like this
In order to exert the effect of suppressing the generation of Sn, the content of P in Nb needs to be 0.01 wt or more, preferably 0.05 wt% or more, and more preferably 0.1 wt% or more. On the other hand, if the content of P is too large, the workability of the diffusion barrier layer cannot be ensured, so it is necessary to set it to 1 wt% or less, preferably 0.7 wt% or less, and 0.4 wt%
The following is more preferable.

In the manufacturing method of the present invention, the N
As the b alloy, an Nb alloy containing 20 wt% or less (not including 0%) of one or more elements selected from the group consisting of Ta, Zr, Ti, and Hf may be used as the b alloy. By including these elements, Nb of P
₃ The workability of the Nb alloy can be improved without inhibiting the effect of suppressing Sn generation.

Further, in the manufacturing method of the present invention, the diffusion barrier layer is concentrically divided into two layers, Nb is used for the diffusion barrier layer on one side in contact with the stabilizer, and Nb is used for the diffusion barrier layer on the other side. Is Cu containing 0.01 to 1 wt% of P
A method using an alloy is also recommended. Thus, the diffusion barrier layer has a two-layer structure of Nb and a Cu-P alloy, and the diffusion barrier layer made of the Cu-P alloy is arranged on the side where Sn enters during the reaction heat treatment. Can be prevented from reacting with Sn to produce Nb ₃ Sn.

The content of P in the Cu-P alloy is 0.01 w.
t% or more is necessary, 0.05 wt% or more is preferable,
More preferably, it is 0.1 wt% or more. On the other hand, if the content of P is too large, the workability of the diffusion barrier layer deteriorates, so it is necessary to set it to 1 wt% or less, and 0.7 wt%
% Or less, and more preferably 0.5 wt% or less.

The present invention is not limited by the thickness of the diffusion barrier layer made of a Cu-P alloy, but if it is 5 μm or more after wire drawing (product), it can function as a Sn diffusion barrier layer. it can.

As the Cu alloy, in addition to P, S
15 wt% or less of one or more elements selected from the group consisting of n, Ge, Mn, Al, Zn, Ti and Ni (however, 0
% Cu is not included) may be used. By containing these elements, the workability of the Cu alloy can be improved.

Further, not only the bronze method, but also a method for producing a superconducting wire having a stabilizing material and a diffusion barrier layer,
Tube method, powder method, in situ method, liquid immersion method,
It can be applied to any manufacturing method of superconducting wire such as internal diffusion method and external diffusion method.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification of the design of the present invention can be made in view of the gist of the preceding and the following. It is included in the technical scope.

[0023]

EXAMPLES Example 1 (Bronze method) As shown in FIG. 4, a stabilizing material 7 (oxygen-free copper) is provided in the center of the wire.
A Nb-0.2% P alloy sheet was wound around it to form a diffusion barrier layer 6, and a billet was prepared in which 5893 Nb filaments were arranged on the outside thereof. Also, as shown in FIG.
A Nb sheet is wrapped around the stabilizing material 7 to form the diffusion barrier layer 6b.
At the same time, a billet having a diffusion barrier layer 6a formed by winding a Cu-0.2% P sheet on the outside thereof was prepared.
Further, as a conventional example, a billet using an Nb sheet and a billet using a Ta sheet were prepared for the diffusion barrier layer 6 in FIG.

These billets were reduced in diameter from φ150 to φ35 by hydrostatic extrusion. After hydrostatic extrusion, wire drawing was performed using a die. Nb ₃ after reaction heat treatment
A cross section of the Sn superconducting element wire was observed. 6-9
In addition, the SEM of each diffusion barrier layer after the reaction heat treatment
A photograph is shown. FIG. 6 is a SEM photograph of the billet using only the Nb sheet as the diffusion barrier layer.
It can be seen that b reacts with Sn to become Nb ₃ Sn. On the other hand, in the billet diffusion barrier layer (FIGS. 7 and 8) according to the method of the present invention, Nb ₃ Sn was not generated in any of the billet diffusion barrier layers, and the stabilizing material was contaminated with Sn without degrading the AC loss characteristics. Could be prevented from

Incidentally, FIG. 9 is an SEM photograph of a billet using Ta as a diffusion barrier layer, and shows a processed state of the diffusion barrier layer obtained by dissolving a part of the sample after hydrostatic extrusion with nitric acid. . It can be seen that there are many cracks and the diffusion barrier layer made of Ta is not normally processed.
When this billet is continuously drawn, the diffusion barrier layer made of Ta does not serve as a barrier against Sn diffusion. In contrast, the diffusion barrier layer mainly composed of Nb-P and the diffusion barrier layer according to the present invention composed of the Nb and Cu-0.2% P composite material had no problem in workability.

Example 2 (Internal Diffusion Method) As shown in FIG. 10, a Sn rod was arranged at the center of the wire, and 5893 Nb filaments were embedded on the outside of the Cu matrix, and Cu-0. A 5% P sheet was wound to form a diffusion barrier layer 6a, a diffusion barrier layer 6b made of an Nb sheet was formed around the diffusion barrier layer 6a, and a billet having a stabilizing material 7 (oxygen-free copper) arranged in the outermost layer was prepared. In addition, as shown in FIG. 11, a billet using only an Nb sheet for the diffusion barrier layer 6 was also prepared as a comparative example.

These billets were reduced in diameter from φ150 to φ35 by hydrostatic extrusion. After hydrostatic extrusion, wire drawing was performed using a die. Nb ₃ after reaction heat treatment
The Sn loss was measured as the Sn superconducting wire. 12
Figure 2 shows a comparison of the AC loss of both wires. Both wires are Cu-0.
Except for the presence or absence of the 5% P sheet, the cross section is the same, but N
It can be seen that the AC loss of the composite material barrier of b and Cu-0.5% P is much smaller. From this, it is clear that the present invention is effective in reducing the AC loss of the superconducting wire.

Example 3 (External Diffusion Method) As shown in FIG. 13, a stabilizing material 7 (oxygen-free copper) was formed in the center of the wire.
Was prepared, a Nb-0.2% P sheet was wound around it to form a diffusion barrier layer 6, and a billet in which a Cu matrix in which 5893 Nb filaments were embedded was arranged on the outside thereof was prepared. As shown in FIG. 14, a billet using an Nb sheet for the diffusion barrier layer 6 was also prepared as a comparative example.

The diameter of these billets was reduced from φ150 to φ35 by hydrostatic extrusion. After hydrostatic extrusion, wire drawing was performed using a die. After wire drawing, the surface of the wire was plated with Sn, and this was subjected to reaction heat treatment, and the AC loss was measured as a Nb ₃ Sn superconducting wire. FIG. 15 shows a comparison of AC loss of both wire rods. Both wires have the same cross-sectional structure except that Nb or Nb-0.2% P is used as the barrier material, but it can be seen that the Nb-0.2% P barrier has a significantly smaller AC loss. From this, it is clear that the present invention is effective in reducing the AC loss of the superconducting wire.

Example 4 In the billet shown in FIG. 10, the P content of the diffusion barrier layer 6a made of Cu-P alloy was 0.005%, 0.01.
%, 0.02%, 0.05%, 0.1%, 0.5%, 1
%, 1.5%, and 8 types of billets were prepared.

The diameters of these billets were reduced from 67 to 20 by hydrostatic extrusion. After isostatic pressing, wire drawing was carried out with a die to produce a wire having a wire diameter of φ0.8. After subjecting these to reaction heat treatment to generate Nb ₃ Sn, the cross section was examined. As a result, in the wire having a P content of 0.005%, generation of Nb ₃ Sn was observed in a part of Nb in the diffusion barrier layer.
Further, in the wire material having a P content of 1.5%, the C of the diffusion barrier layer is
Cracks were observed in the u-1.5% P alloy and Sn diffusion was observed in the stabilizer. From this, the P content is 0.005
It can be seen that the barrier material does not function with the wire rods of 1% and 1.5%. Therefore, Cu used for the diffusion barrier layer 6a
It is considered appropriate that the P content in the -P alloy is about 0.01 to 1.0%.

Example 5 In the billet shown in FIG. 13, the P content of the diffusion barrier layer 6 made of Nb-P alloy is 0.005%, 0.01.
%, 0.02%, 0.05%, 0.1%, 0.5%, 1
%, 1.5%, and 8 types of billets were prepared.

The diameter of these billets was reduced from 67 to 20 by hydrostatic extrusion. After isostatic pressing, a die wire was drawn to produce a wire having a wire diameter of φ0.8. After the wire drawing process, the surface of the wire was plated with Sn and subjected to reaction heat treatment to generate Nb ₃ Sn, and then the cross section was examined. As a result, in the wire having a P content of 0.005%, generation of Nb ₃ Sn was observed in a part of Nb in the diffusion barrier layer. In addition, in a wire material having a P content of 1.5%, Nb-1.5% P of the barrier material is used.
Cracks were seen in the alloy and Sn diffusion was seen in the stabilizer. From this, the P content is 0.005% and 1.5%
It can be seen that the barrier material is not functioning with the wire rod of. Therefore, P in the Nb-P alloy used for the diffusion barrier layer 6 is
It is considered that the appropriate content is about 0.01 to 1.0%.

[0034]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, Nb ₃ Sn is not generated even if Nb is used as the material used for the diffusion barrier layer, which deteriorates the AC loss characteristics of the superconducting wire. It is now possible to provide a method for manufacturing a Nb ₃ Sn-based superconducting wire which does not exist.

[Brief description of drawings]

FIG. 1 is a view showing a cross section of a single core type composite billet by a bronze method.

FIG. 2 is a view showing a cross section of a primary multi-core billet 8 by a bronze method.

FIG. 3 is a view showing a cross section of a secondary multi-core billet 11 by the bronze method.

FIG. 4 is an explanatory view showing a cross section of a superconducting wire rod when the method of the present invention is applied to a bronze method.

FIG. 5 is an explanatory view showing a cross section of a superconducting wire rod when the method of the present invention is applied to a bronze method.

FIG. 6 is an SEM photograph of the diffusion barrier layer after the reaction heat treatment, which is based on the conventional method using Nb for the diffusion barrier layer.

FIG. 7 is a SEM photograph of the diffusion barrier layer after the reaction heat treatment, which is obtained by the method of the present invention using an Nb-P alloy for the diffusion barrier layer.

FIG. 8 is a SEM photograph of the diffusion barrier layer after the reaction heat treatment, which is obtained by the method of the present invention using a composite material of Nb and Cu—P alloy for the diffusion barrier layer.

FIG. 9 is an SEM photograph of the diffusion barrier layer after the reaction heat treatment, which is based on the conventional method using Ta for the diffusion barrier layer.

FIG. 10 is an explanatory view showing a cross section of a superconducting wire rod when the method of the present invention is applied to the internal diffusion method.

FIG. 11 is an explanatory view showing a cross section of a superconducting wire according to a conventional internal diffusion method.

FIG. 12 is a graph showing a comparison between a diffusion barrier layer according to the present invention and a diffusion barrier layer according to a conventional method with respect to the external magnetic field amplitude dependency of AC loss.

FIG. 13 is an explanatory view showing a cross section of a superconducting wire rod when the method of the present invention is applied to an external diffusion method.

FIG. 14 is an explanatory view showing a cross section of a conventional superconducting wire by an external diffusion method.

FIG. 15 is a graph comparing the diffusion barrier layer according to the method of the present invention and the diffusion barrier layer according to the conventional method with respect to the external magnetic field amplitude dependency of the AC loss.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Billet case (Cu-Sn base alloy linear base material) 2 Nb wire 3 Mixed billet (single core composite billet) 5 Inner layer 6 Nb layer (diffusion barrier layer) 7 Oxygen-free copper (stabilized copper) 8 1 Next multi-core billet 9 Outer layer case (outermost layer) 10 Wire group 11 Secondary multi-core billet (multi-core composite billet)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hidefumi Kurahashi Inventor Hidefumi Kurahashi 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Research Institute, Kobe Steel Co., Ltd. (72) Takayoshi Miyazaki Nishi-ku, Kobe-shi, Hyogo 1-5-5 Takatsukadai, Kobe Research Institute of Kobe Steel, Ltd. (72) Inventor, Masamichi Chiba 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Institute of Technology, Kobe Steel (72) ) Inventor Masao Shimada 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Works, Ltd. Kobe Research Institute

Claims (4)

[Claims] 1. A method of manufacturing an Nb ₃ Sn-based superconducting wire, wherein a cylindrical diffusion barrier layer is arranged on the outer peripheral side or the inner peripheral side of a stabilizing material, wherein P is 0.01 in the diffusion barrier layer. A method for producing an Nb ₃ Sn-based superconducting wire, which comprises using an Nb alloy containing 1 to 1 wt%. 2. The Nb alloy is Ta, Z in addition to P.
N containing 20 wt% or less (not including 0%) of one or more elements selected from the group consisting of r, Ti, and Hf
The method for producing an Nb ₃ Sn-based superconducting wire according to claim 1, which is a b alloy. 3. A method of manufacturing an Nb ₃ Sn-based superconducting wire, wherein a cylindrical diffusion barrier layer is arranged on the outer peripheral side or the inner peripheral side of a stabilizing material, wherein the diffusion barrier layer is made of concentric material. It is formed of two different layers, Nb is used for the diffusion barrier layer on one side in contact with the stabilizing material, and P is 0.01 for the diffusion barrier layer on the other side.
A method for producing an Nb ₃ Sn-based superconducting wire, characterized in that a Cu alloy containing 1 to 1 wt% is used. 4. The Cu alloy contains Sn, G, in addition to P.
The Nb according to claim 3, which is a Cu alloy containing 15 wt% or less (not including 0%) of one or more elements selected from the group consisting of e, Mn, Al, Zn, Ti and Ni.
₃ Manufacturing method of Sn-based superconducting wire.