JPH02297809A - Superconductive wire - Google Patents

Abstract

PURPOSE:To reduce alternating-current loss with reduced diameters of stabilizer member and a superconductor filament by disposing a diffusion barrier layer either in a boundary region located between the stabilizer member and a high resistance matrix or in a boundary region located between the stabilizer member and a superconductor filament. CONSTITUTION:Because diffusion barrier layers 7, 5 are disposed in a boundary region between a stabilizer member 6 and a high resistance matrix 8 and/or in a boundary region between the stabilizer member 6 and a superconductor filament 4, elements do not diffuse from the superconductor filament 4 or the high resistance matrix 8 into the stabilizer member 6. This makes the stabilizer member 6 fill its essential role sufficiently. Because the pollution due to the diffusion reaction of the stabilizer member 6 is prevented, the diameters of the stabilizer member 6 and the superconductor filament 4 can be reduced to reduce alternating-current loss.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an AC or DC superconducting wire used in generators, AC equipment, etc.

[Prior art] Superconducting wires used in superconducting magnets for alternating current equipment such as generators and transformers must be stable against alternating magnetic fields, that is, do not undergo normal conduction transition, and have no alternating current loss in response to fluctuating magnetic fields. Small is required.

In order to satisfy the requirements necessary for such an AC superconducting wire, it is necessary to reduce AC loss and to arrange a stabilizing material. For this reason, conventional superconducting wires for alternating current have the following structure.

■ In order to reduce the hysteresis loss that occurs inside the superconducting filament among alternating current losses, the diameter of the superconducting filament is increased from several microns to submicron, that is, 1 μm.
m or less.

■ In order to reduce the coupling loss between superconducting filaments among AC losses, superconducting filaments are arranged in a high resistance matrix such as CuNi.

■ In order to reduce coupling loss and eddy current loss through the stabilizing material among AC losses, the diameter of the stabilizing material is made small and the stabilizing material is partitioned by a high-resistance matrix.

[Problems to be Solved by the Invention] However, in such conventional superconducting wires, in order to reduce the diameter of the stabilizing material in order to reduce coupling loss and eddy current loss, it is difficult to connect the stabilizing material and the high resistance matrix. When the interface area increases and heat treatment is performed, elements in the high-resistance matrix diffuse into the stabilizing material, increasing the specific resistance of the stabilizing material and making it no longer play its role as a stabilizing material. There was a problem. For example, using Cu as the stabilizing material and CuNi or CuM as the high resistance matrix.
When n is used, the heat treatment causes Ni or Mn in the high resistance matrix to diffuse into the stabilizer Cu, increasing the resistance of CI4.

In addition, when providing a stabilizing material around the superconducting filament, the diameter of the superconducting filament must be made small in order to reduce hysteresis loss, and at the same time, the area of the interface with the stabilizing material around the superconducting filament must be reduced. increases, and upon heat treatment, the elements in the superconducting filament diffuse into the stabilizing material, which similarly increases the resistance of the stabilizing material, causing the problem that it no longer functions as a stabilizing material. For example, Nb as a superconducting filament
When Ti, Nb, or Sn is used, Ti or Sn is diffused into the stabilizing material by heat treatment.

The purpose of this invention is to solve such conventional problems,
By preventing the elements in the high-resistance matrix or the superconducting filament from diffusing into the stabilizing material, the diameters of the stabilizing material and the superconducting filament can be made smaller, thereby reducing AC loss. The object of the present invention is to provide a superconducting wire for alternating current.

Means for Solving Problem C] In the superconducting wire of the present invention, a diffusion barrier layer number is provided in the boundary area between the stabilizing material and the high-resistance matrix or the boundary area between the stabilizing material and the superconducting filament. It is a feature.

The material of the diffusion barrier layer must be a material that does not react with the stabilizing material, and Cu or Am may be used as the stabilizing material.
When using the like, Ta, Nb, etc. can be used. Furthermore, Nb and Ta are also excellent in terms of workability.

In this invention, the thickness of the diffusion barrier layer is not particularly limited, but is preferably 10 μm or less, more preferably 1 to 5 μm or less.

The diameter of the stabilizing material is preferably 300 μm or less.

Further, the thickness of the high-resistance matrix layer that partitions the stabilizing materials between the stabilizing materials is preferably 1 μm or more.

[Operations and Effects of the Invention] In the superconducting wire of the present invention, a diffusion barrier layer is provided in the boundary area between the stabilizing material and the high-resistance matrix and/or the boundary area between the stabilizing material and the superconducting filament, so that heat treatment is not required. At the same time, elements from the high-resistance matrix and superconducting filaments do not diffuse into the stabilizing material. Therefore, the original role of the stabilizing material can be fully demonstrated, and contamination due to the diffusion reaction of the stabilizing material can be prevented by making the diameter of the stabilizing material and superconducting filament sufficiently small. AC loss can be reduced.

Additionally, since the diameter of the stabilizing materials can be made smaller, the thickness of the high-resistance matrix that partitions the stabilizing materials can be made thicker, making it possible to further reduce coupling loss and eddy current loss. . Specifically, as a superconducting wire for a generator, the AC loss under magnetic field fluctuation is several tens of kilograms.
W/m” or less, but by setting the diameter of the copper as a stabilizing material to 300 μm or less and making the thickness of the high-resistance matrix between the stabilizing materials to be 1 μm or more, such a requirement can be met. characteristics can be achieved.

The superconducting wire to which this invention is applied includes NbTi, N
Superconducting materials such as B, Sn, etc. can be used as superconducting filaments. For example, when NbTi is used as a material for superconducting filaments, heat treatment at around 400° C. is required after wire drawing in order to increase the critical current density. Further, in the case of Nb and Sn, heat treatment at around 700° C. is required because the superconducting phase is formed by a diffusion reaction. In such heat treatment at any temperature,
Ta and Nb do not react with stabilizers such as Cu and Afl.

In the superconducting wire of this invention, by providing a diffusion barrier layer in the boundary region with the stabilizing material, the stabilizing material is prevented from being contaminated during heat treatment, and the original function of the stabilizing material is fully exhibited. be able to.

Therefore, by reducing the diameters of the superconducting filament and the stabilizing material, a superconducting wire with low AC loss can be obtained. Therefore, the superconducting wire of the present invention can be effectively used in field windings of superconducting generators that are subjected to strong fluctuating magnetic fields and are required to have low alternating current losses. It can also be effectively used in AC superconducting wires used in AC equipment operated at commercial frequencies. Furthermore, it is stable against sudden external disturbances caused by strong magnetic fields and heat.
It can also be effectively used in superconducting wires for MRI, which are used for direct current applications, and superconducting wires for power storage superconducting magnets.

[Embodiment] FIG. 1 is a sectional view showing an embodiment of the present invention. In the superconducting wire 1 shown in FIG. 1, an outer peripheral part 3 in which superconducting filaments coated with a stabilizing material are arranged in a high-resistance matrix is provided around a central part 2 in which a stabilizing material is arranged in a high-resistance matrix. It is being

FIG. 2 is a partially enlarged cross-sectional view showing the outer peripheral portion 3 of the embodiment shown in FIG. As shown in FIG. 2, in the superconducting wire of this example, a diffusion barrier layer 5 is provided at the boundary area between the superconducting filament 4 and the stabilizing material 6, and a diffusion barrier layer 5 is provided at the boundary between the stabilizing material 6 and the high-resistance matrix 8. A diffusion barrier layer 7 is provided in the region.

Although the illustrations are simplified in FIGS. 2, 3, and 6, the superconducting filaments and stabilizing materials are evenly distributed and arranged in locations other than those shown in the high-resistance matrix.

- FIG. 3 is a partially enlarged sectional view showing the central portion 2 of the embodiment of FIG. 1. As shown in FIG. 3, in this embodiment, a diffusion barrier layer 12 is provided in the boundary region between the stabilizing material 11 and the high-resistance matrix 13, each having a hexagonal cross section.

FIG. 4 is a sectional view showing another embodiment of the invention,
It shows the cross-sectional structure of a rectangular molded stranded wire.

As shown in FIG. 4, the rectangular molded stranded wire 20 of this embodiment
is composed of nine twisted wires 21.

FIG. 5 is a diagram showing a cross-sectional structure of this twisted wire 21. As shown in FIG. 5, the stranded wire 21 is composed of four strands 22 including the wire located at the center and three strands 23. The strand 22 is a wire having a cross-sectional structure as shown in FIG. 1, and the strand 23 is a wire having a structure corresponding to the center portion 2 of FIG. 1, that is, the structure shown in FIG. 3.

Examples 1 and 2 and Comparative Examples 1 and 2 A structure as shown in FIG. 1, that is, a center part 2 in which a stabilizing material is arranged in a high resistance matrix, and an outer periphery in which superconducting filaments are arranged in a high resistance matrix. A superconducting wire having a structure in which part 3 was provided was manufactured. However, here, the outer peripheral part 3 is
As shown in FIG. 6, a superconducting wire having a structure in which no stabilizing material was provided around the superconducting filament 31 was produced.

The diameter of the superconducting filament, the material of the high-resistance matrix metal, the diameter of the stabilizing copper in the center, and the thickness of the diffusion barrier layer covering the stabilizing copper were set as shown in Table 1, and the results of Examples 1 and 2 were A superconducting wire was created. In addition, as a comparison, Comparative Example 1 in which no diffusion barrier layer is provided around the stabilized copper
And a superconducting wire of Comparative Example 2 was produced.

The resulting superconducting wires of Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated for residual resistance ratio and stability in a varying magnetic field. The results are shown in Table 1.

The superconducting wires of Examples 1 and 2 in which the stabilized copper was covered with a diffusion barrier layer both exhibited a high residual resistance ratio of 140. On the other hand, in Comparative Example 1 and Comparative Example 2 in which no diffusion barrier layer was provided, as the diameter of the superconducting filament became smaller, the residual resistance ratio became 100.70, and the decrease in the residual resistance ratio became remarkable.

As for the stability in a fluctuating magnetic field, the superconducting wires of Examples 1 and 2 having a diffusion barrier layer showed good results, with no transition from superconductivity to normal conductivity. Comparative Example 1, which did not have a barrier layer, had some transfer and was in a somewhat good state. Furthermore, in Comparative Example 2 in which the diameter of the superconducting filament was reduced to 0.5 μm, all the superconducting filaments were transferred. As a result, it was found that even if the diameter of the superconducting filament was reduced, the stability of the superconducting wire of the present invention hardly deteriorated.

(Leaving space below) Table 1 Example 3 and Comparative Examples 3 and 4 The structure was similar to that of Examples f11 and 2 above, and the diameter of the superconducting filament, the material of the high-resistance matrix, and the amount of stabilized copper were as shown in Table 2. Superconducting wires with different diameters and diffusion barrier layer thicknesses were fabricated, and the residual resistance ratio and stability in a varying magnetic field were measured. In addition, AC loss (kW/m'') was calculated. These results are also shown in Table 2.

Table 2 As is clear from Comparative Example 3 and Comparative Example 4, AC loss can be reduced by reducing the diameter of the stabilizing copper, but the residual resistance ratio decreases from 140 to 110.
Stability deteriorates. On the other hand, in Example 3 in which a diffusion barrier layer was provided according to the present invention, the residual resistance ratio was lower than that in Comparative Example 3.
The value was <140, which is the same as that of the sample, and the stability was good.

As is clear from the above results, it was confirmed that in Examples 1, 2, and 3 according to the present invention, the residual resistance ratio does not change even when the diameter of the stabilizing material is made small, and exhibits excellent stability. Ta.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view showing the outer peripheral part of the embodiment shown in FIG. FIG. 3 is a partially enlarged sectional view showing the central part of the embodiment shown in FIG. FIG. 4 is a sectional view showing another embodiment of the invention. FIG. 5 is a cross-sectional view of one of the strands of the embodiment of FIG. FIG. 6 is a partially enlarged sectional view showing the outer peripheral portion of still another embodiment of the present invention. In the figure, 1 is the superconducting wire, 2 is the center, 3 is the outer periphery,
4 is a superconducting filament; 5. 7. 12 is a diffusion barrier layer, 6 and 11 are stabilizing materials, and 8 and 13 are high resistance matrices. Figure 1 Figure 2 Figure 6

Claims (5)

[Claims] (1) A superconducting wire in which a superconducting filament and a stabilizing material are arranged in a high-resistance matrix, characterized in that a diffusion barrier layer is provided in a boundary region with the stabilizing material. (2) The superconducting wire according to claim 1, wherein the diffusion barrier layer is made of Nb or Ta. (3) The superconducting wire according to claim 1, wherein the diameter of the stabilizing material is 300 μm or less. (4) Claim 1, wherein the stabilizing material is Cu or Al.
The superconducting wire described. (5) Claim 1, wherein the thickness of the high-resistance matrix partitioning the stabilizing materials between the stabilizing materials is 1 μm or more.
The superconducting wire described.