JPH08298030A - Superconducting wire - Google Patents

Abstract

PURPOSE: To provide a superconducting wire in which a superconducting filament is hardly damaged at drawing work even if a stabilizing member on the outer circumference of a filament composite part is divided by a resistance layer. CONSTITUTION: A stabilizing material part 5 consisting of oxygen free copper is provided on the peripheral part of a filament composite part including a Nb-Ti filament 1 and steady conductive matrixes 2, 3, and the stabilizing material part 5 is divided by a resistance layer 6. In the resistance layer 6, the route extending from the inner end in section to the outer end is inclined to the radial direction. Thus, the resistance layer 6 never locally compresses the Nb-Ti filament 11 at drawing work, and a superconducting wire of high quality minimized in damage of a superconducting filament can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting wire used for passing a pulse current or an alternating current.

[0002]

2. Description of the Related Art A superconducting wire has a structure in which a large number of superconducting filaments are embedded in a normal conducting matrix. As a superconducting filament, Nb-Ti filament is often used at a practical level. Oxygen-free copper is generally used as the normal-conducting matrix, and a copper alloy is used particularly in a portion requiring high resistance.

When a pulse current or an alternating current is passed through the superconducting wire, an alternating loss due to the fluctuating magnetic field occurs. AC loss is divided into hysteresis loss, coupling loss, and eddy current loss. To reduce the AC loss of the superconducting wire,
It is necessary to take reduction measures for each of them.

Of these, as a measure for reducing the coupling loss, N
It is effective to surround the b-Ti filaments one by one or a plurality of each with a resistance layer. This measure is intended to reduce the coupling current flowing between the filaments by the resistance layer surrounding the filaments and to reduce the loss due to the coupling current.

As a measure for reducing the eddy current loss, the stabilizing material portion provided on the outer periphery of the filament composite portion including the superconducting filament and the normal conducting matrix is divided into a plurality of portions in the circumferential direction by a plurality of resistance layers. Are effective (JP-A-59-79905 and JP-A-63-37515).
No. The countermeasure is to divide the eddy current flowing in the stabilizing material portion provided on the outer periphery of the filament composite portion by the resistance layer to shorten the eddy current path and reduce the loss due to the eddy current.

FIG. 5 shows a cross section of a conventional superconducting wire in which measures for reducing such coupling loss and eddy current loss are taken. In the figure, 1 is a Nb-Ti filament, 2 is an oxygen-free copper layer, 3 is a resistance layer surrounding the filament 1, 4 is a resistance barrier, 5 is a stabilizer made of oxygen-free copper, and 6 is a stabilizer. 5 is a resistance layer that is radially embedded. Conventionally, a Cu—Ni alloy having a sufficiently higher specific resistance than oxygen-free copper has been used for the resistance layer 3, the resistance barrier 4, and the resistance layer 6. Its composition is generally Cu-10 wt% Ni.

[0007]

It has been found that the conventional superconducting wire constructed as described above has the following problems when it is subjected to wire drawing. That is, since the resistance layer embedded in the stabilizing material portion of the outermost layer is a copper alloy, it has higher strength than oxygen-free copper. When such a high-strength resistance layer is radially (radially) embedded in the outermost layer portion, the resistance layer acts as a tension member against processing stress during wire drawing, and the resistance layer portion is Hard to process. Therefore, the processing stress concentrates on the resistance layer portion, and the Nb-Ti inside
As the filament is locally compressed, the Nb-Ti filament is likely to be deformed, damaged or broken.

In view of the above problems, an object of the present invention is to prevent damage to the superconducting filament during wire drawing even if the stabilizing material portion on the outer periphery of the filament composite portion is divided by the resistance layer. It is to provide a superconducting wire that is hard to generate.

[0009]

In order to achieve this object, the present invention comprises a superconducting wire as follows. That is, a stabilizing material portion is provided on an outer peripheral portion of a filament composite portion including a superconducting filament and a normal conducting matrix, and the stabilizing material portion is divided into a plurality of circumferential portions by a plurality of resistance layers. Is configured such that the path from the inner end to the outer end in the cross section is inclined or bent with respect to the radial direction.

[0010]

By doing so, the processing stress applied almost perpendicularly to the wire rod outer peripheral surface during wire drawing is applied as a force in the direction of tilting or bending the resistance layer in the stabilizing material portion, and the resistance layer is processed. It does not act as a tension member against stress. Therefore, the force for locally compressing the internal superconducting filament can be significantly reduced as compared with the case where the resistance layer is arranged in the radial direction (radial direction).

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an embodiment of the present invention. This superconducting wire differs from the conventional superconducting wire shown in FIG. 5 in that the resistance layer 6 is inclined in the radial direction in the stabilizing material part 5 made of oxygen-free copper (that is, in the cross section of the resistance layer 6). The path from the inner end to the outer end is embedded (inclined with respect to the radial direction). Since the other parts are the same as those in FIG. 5, the same parts are designated by the same reference numerals. The resistance layer 6 embedded as described above receives a processing stress such that the resistance layer 6 is sandwiched between the oxygen-free copper stabilizing material portions 5 and compressed during wire drawing, and the internal Nb-Ti filaments 1 are Local compression is significantly reduced.

Next, a prototype of the superconducting wire shown in FIG. 1 will be described.
Cu-10 wt% Ni / oxygen-free copper / Nb-Ti = 0.35
8860 primary hexagonal wires with an area ratio of /0.30/1,
Oxygen-free copper hexagonal wire of the same size (for stabilizing material) and C
Using u-10 wt% Ni hexagonal wire (for resistance layer and barrier), the total number of wires is 18,000 so that the cross section is as shown in FIG.
A complete hexagonal assembly of the book was performed, the outer circumference was wrapped with an oxygen-free copper tube, oxygen-free copper lids were attached to both end faces, and sealing was performed by electron beam welding in vacuum to manufacture a composite billet.

After this composite billet was hot extruded, cold drawing and stripping were performed while intermediate heat treatment was performed to manufacture a superconducting wire. In the peeling process, the oxygen-free copper tube portion was removed. The obtained superconducting wire has an outer diameter of 0.59 mm and a Nb-Ti filament diameter of 3.5.
μm. This superconducting wire is called an example product.

For comparison, a superconducting wire having a cross section of FIG. 5 was manufactured under the same conditions. This superconducting wire is called a conventional product. Critical current density and hysteresis loss of both superconducting wires (5T
Table 1 shows the measurement results of bias ± 1T. The critical current density of the example product is improved by 6% as compared with the conventional product. In addition, the hysteresis loss of the example product is 5% lower than that of the conventional product. This is because there is less abnormal deformation of the filament in the vicinity of the resistance layer of the stabilizing member than in the conventional product.

Further, each of the superconducting wires coated with an organic insulator having a thickness of 5 μm is twisted into 7 pieces, and 11 pieces of the 7 pieces of twisted wires are twisted together and flatly compression molded to produce a compression molded twisted wire. did. At this time, the workability of the superconducting wire was evaluated with a void ratio of the limit at which the filament was not damaged. Table 1 shows the results. The void ratio F is defined as follows.

[0016]

## EQU1 ## F = [1-{(π / 4) × d ₀ ² × m × n} /
(T × w)] × 100% where d ₀ : diameter of superconducting wire m: number of primary twists (= 7) n: number of secondary twists (= 11) t: thickness of compression molded twisted wire w: Width of compression molded stranded wire

[0017]

[Table 1]

As described above, when the superconducting wire of the present invention is used, the void ratio is lowered and a superconducting stranded wire having high rigidity can be obtained. As a result, it is possible to obtain a superconducting stranded wire which is unlikely to be quenched by the wire movement.

FIG. 2 shows another embodiment of the present invention. This superconducting wire is in a state in which the resistance layer 6 is bent in a crank shape in the stabilizing material portion 5 of oxygen-free copper (that is, the path from the inner end to the outer end in the cross section of the resistance layer 6 is bent in a crank shape. It is embedded. Other than that is the same as the embodiment of FIG. With such a structure, the same effect as that of the embodiment of FIG. 1 can be obtained.

FIG. 3 shows still another embodiment of the present invention.
This superconducting wire has a resistance layer 6 in the stabilizing member 5 made of oxygen-free copper.
Are embedded in a state of being bent into a substantially "V" shape (that is, in a state where the path from the inner end to the outer end in the cross section of the resistance layer 6 is bent into a substantially "C" shape). Other than that is the same as the embodiment of FIG. With such a structure, the same effect as that of the embodiment of FIG. 1 can be obtained.

FIG. 4 shows still another embodiment of the present invention.
This superconducting wire has a resistance layer 6 on the stabilizing material part 5 of oxygen-free copper.
However, in a state where the inner end portion is oriented in the radial direction and the outer end side is inclined with respect to the radial direction (that is, the path from the inner end to the outer end in the cross section of the resistance layer 6 is bent into a substantially “V” shape. It is embedded. Other than that is the same as the embodiment of FIG. With such a structure, the same effect as that of the embodiment of FIG. 1 can be obtained.

In each of the above embodiments, the maximum displacement in the circumferential direction of the other portion from the inner end portion in the cross section of the resistance layer 6 should be larger than the thickness of the resistance layer 6 as shown in the figure. desirable. By doing so, it is possible to more reliably prevent the filament from being deformed, damaged, or broken. In addition, the resistance layer 6
As the copper alloy, a copper alloy other than the Cu-Ni alloy can be used.

[0023]

As described above, according to the present invention, the resistance layer for partitioning the stabilizing material portion on the outer periphery of the filament composite portion is less likely to locally compress the superconducting filament during wire drawing. A high-quality superconducting wire with less damage to the superconducting filament can be obtained.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing another embodiment of the superconducting wire according to the present invention.

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

FIG. 4 is a sectional view showing still another embodiment of the superconducting wire according to the present invention.

FIG. 5 is a sectional view showing a conventional superconducting wire.

[Explanation of symbols]

 1: Nb-Ti filament 2: Oxygen-free copper layer 3: Resistive layer 4: Resistive barrier 5: Stabilizing material part 6: Resistive layer

Claims (1)

[Claims] 1. A stabilizing material portion is provided on an outer peripheral portion of a filament composite portion including a superconducting filament and a normal conducting matrix, and the stabilizing material portion is divided into a plurality of portions in the circumferential direction by a plurality of resistance layers, The resistance layer is a superconducting wire in which a path from an inner end to an outer end in a cross section is inclined or bent with respect to a radial direction.