JPH07192547A - Composite multi-core superconducting wire - Google Patents

Abstract

PURPOSE:To manufacture a composite multiconductor superconductive wire useful to an application wherein a small diameter or light weight is required by specifying the volume ratio of a local matrix to a superconductive filament and the volume ratio of the total of the local matrix to the superconductive filament and a stabilizing matrix. CONSTITUTION:A composite multiconductor superconductive wire 4 is formed which consists of a coexistent part 1, composed of a local matrix, arranged in the outer periphery of each superconductive filament, and a superconductive filament; and a stabilizing matrix 2 arranged in the periphery of the coexistent part 1. The local matrix and the stabilizing matrix 2 are composed of high- purity copper, the volume ratio of the local matrix to the superconductive filament is made 0.35 or less, and the volume ratio of a whole matrix composed of the total of the local matrix to the superconductive filament and the stabilizing matrix 2 is made 1.5 or less. This can provide a composite multiconductor superconductive electric wire 4 capable of coping with application wherein a small diameter or light weight is required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite multifilamentary superconducting wire in which a large number of superconducting filaments are embedded using high-purity copper as a matrix, and more specifically, for a magnetic levitation train in which a diameter reduction and a weight reduction are required. The present invention relates to a composite multifilamentary superconducting wire that can be used for various purposes.

[0002]

2. Description of the Related Art A composite multifilamentary superconducting wire has a structure in which a large number of ultrafine superconducting filaments made of NbTi or the like are embedded in a pure copper or copper alloy matrix. In the case of a composite multicore superconducting wire used for a special purpose for alternating current, a copper alloy with high electrical resistance may be used for the above matrix from the viewpoint of reducing AC loss, but in other normal cases, electrical resistance or Pure copper with low thermal resistance is used. This is to improve the electrical and thermal stability of the composite multicore superconducting wire during energization.

In general, a composite multicore superconducting wire has a coexisting portion in which each superconducting filament is embedded in a local matrix and a stabilizing matrix arranged on the outer or inner periphery of the coexisting portion. It consists of Explaining with reference to FIG. 1, the composite multicore superconducting wire 4 has a stabilized pure copper layer 2 provided on the outer periphery of a superconducting filament / pure copper coexisting portion 1 in which a superconducting filament is embedded in pure copper as a local matrix. See also FIG.
As shown in FIG. 5, a stabilized pure copper core 3 may be arranged as needed in order to improve thermal stability and the like.

[0004]

Recently, in a superconducting coil used for a magnetic levitation train or the like, it has been required to reduce the diameter and weight of a composite multicore superconducting wire in order to reduce its size and weight. Conventionally, in order to improve the electrical and thermal stability of the composite multi-core superconducting wire, the volume ratio of the matrix in the composite multi-core superconducting wire has been increased, but if the volume ratio of the matrix is increased, Naturally, there was a problem that the diameter of the composite multifilamentary superconducting wire became thick and the weight also became large.

For this reason, efforts have been made to lower the volume ratio of the matrix by lowering the electrical resistance and thermal resistance of the matrix, such as increasing the purity of pure copper as the matrix and removing processing strain as much as possible. The electrical resistance of the matrix (pure copper) is usually a value obtained by dividing the resistance value at a temperature of 300K by the resistance value at a temperature of 10K (referred to as RRR).
Currently, for applications such as magnetic levitation trains, when the volume ratio of the matrix is 1.5 or less, RRR ≧ 20.
0 is required.

However, even if a composite multifilamentary superconducting wire is manufactured by using high-purity copper having an initial RRR of about 400, a processing strain due to a drawing process or the like remains in the matrix, and even if annealing is performed, the RRR is up to about 250. It is inevitable that it will drop. In addition, in the case of the local matrix, the wall thickness is extremely thin. Therefore, when the wall thickness becomes thin to some extent, the RRR does not reach 250 due to the mean free path of electrons, and the wall thickness (μm) is substantially reduced. It is known that the value is only about 23.6 times. Therefore, in the coexistence part where each superconducting filament is embedded in the local matrix, the RRR of the local matrix becomes small.

Therefore, even if a composite multicore superconducting wire is manufactured using high-purity copper having an initial RRR of the same level, the RRRs of the local matrix and the stabilizing matrix after manufacture are different. Therefore, the distribution ratio influences the RRR of the entire matrix forming the composite multicore superconducting wire. The RRR of the entire matrix that constitutes the composite multicore superconducting wire is theoretically the sum of the volume fraction of each part of the matrix and the RRR at that part, but it is actually obtained by measurement. It is a value that can be. From the viewpoint of stability of the composite multi-core superconducting wire, it is desirable that the RRR of the entire matrix described above is as high as possible.
At present, the distribution ratio that affects the RRR is determined by experience, and it has not been possible to achieve both a reduction in diameter (weight reduction) of the composite multicore superconducting wire and a high level of RRR.

[0008]

SUMMARY OF THE INVENTION The present invention has been made as a result of intensive studies in view of such a situation, and its purpose is to provide a composite multicore superconducting wire so as to be applicable to applications such as magnetic levitation trains. It is an object of the present invention to provide a composite multi-core superconducting wire capable of achieving both a reduction in diameter (reduction in weight) and a high level of RRR (200 or more). That is, in a composite multi-core superconducting wire consisting of a coexisting portion composed of a local matrix and a superconducting filament arranged on the outer periphery of each superconducting filament, and a stabilizing matrix arranged around the coexisting portion, the local matrix is The stabilizing matrix is made of high-purity copper, and the volume ratio of the local matrix to the superconducting filament is 0.35 or less, and the whole matrix composed of the total of the local matrix and the stabilizing matrix to the superconducting filament. Is a composite multifilamentary superconducting wire having a volume ratio of 1.5 or less.

[0009]

The composite multifilamentary superconducting wire of the present invention realizes the diameter reduction (weight reduction) of the composite multifilamentary superconducting wire so that it can be used for applications such as magnetic levitation trains. The volume ratio of the entire matrix consisting of the totalized matrix to the superconducting filament is 1.
It is 5 or less. If this volume ratio exceeds 1.5,
Since the composite multifilamentary superconducting wire is thick and heavy, it cannot be applied to applications such as magnetic levitation trains, which are required to be lightweight and compact.

Under the limitation that the total volume ratio of the entire matrix and the superconducting filament is 1.5 or less, the RRR of the entire matrix constituting the composite multicore superconducting wire is set to a high level (200 or more). Difficult to do. The present invention realizes a composite multifilamentary superconducting wire having an RRR of 200 or more in the entire matrix by reducing the volume ratio of the local matrix having a reduced RRR and a reduced RRR to 0.35. The volume ratio of the local matrix is preferably 0.2 to 0.35 in terms of manufacturing. If it is 0.2 or less, the possibility that the superconducting filament will be exposed during the drawing process increases.

[0011]

EXAMPLES The present invention will now be described in detail with reference to Examples.
First, a NbTi rod was inserted into a primary high-purity copper sheath, and this was drawn to prepare a primary composite strand. Initial (before processing) RRR of high-purity copper that forms this primary high-purity copper sheath
Was 400. After filling 1550 secondary high-purity copper sheaths with this primary strand, drawing and annealing were performed to produce a composite multicore superconducting wire (diameter 1.67 mm). The initial (before processing) R of the high-purity copper that forms this secondary high-purity copper sheath
The RR was 480.

The cross section of the produced composite multifilamentary superconducting wire was observed with a microscope, and the average diameter of the NbTi filaments and the N
The volume ratio (referred to as the volume ratio of the local matrix) of the local matrix (the portion where the primary high-purity copper sheath was processed) to the bTi filament was measured. The volume ratio is substantially the same as the area ratio in the cross section of the composite multicore superconducting wire. Further, the volume ratio of the stabilizing matrix (the portion where the secondary high-purity sheath is processed) to the NbTi filament (referred to as the stabilizing matrix volume ratio) was measured. There are two types of composite multifilamentary superconducting wires produced (inventive example and comparative example), and the above two volume ratios and their total values (referred to as the volume ratio of the entire matrix) and the average diameter of the NbTi filaments are shown in Table 1. .

[0013]

[Table 1]

The RRR of the entire matrix of the manufactured composite multifilamentary superconducting wire was measured. The results are also shown in Table 1. Table 1
According to the above, in the comparative example in which the volume ratio of the local matrix is 0.5, the RRR of the whole matrix was 170, while in the example of the present invention, it was 220, and the present invention showed high R
It turned out that RR was realized.

[0015]

As described in detail above, the composite multifilamentary superconducting wire according to the present invention has a small volume ratio of the whole matrix and a small diameter (light weight).
It has a high R of 200 or more, and achieves both a small diameter (light weight) and a high level of RRR. Therefore, the composite multifilamentary superconducting wire of the present invention makes a significant industrial contribution, for example, for magnetic levitation trains and in other applications requiring a smaller diameter and lighter weight.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a composite multicore superconducting wire in which a superconducting filament is embedded in a matrix.

[Explanation of symbols]

 1 Superconducting filament / pure copper coexistence part 2 Stabilized pure copper layer 3 Stabilized pure copper core 4 Composite multi-core superconducting wire

Claims (1)

[Claims] 1. A composite multi-core superconducting wire comprising a coexisting portion composed of a local matrix and a superconducting filament arranged on the outer periphery of each superconducting filament, and a stabilizing matrix arranged around the coexisting portion, The local matrix and the stabilizing matrix are made of high-purity copper, and the volume ratio of the local matrix to the superconducting filament is 0.35 or less and the total of the local matrix and the stabilizing matrix to the superconducting filament. The composite multicore superconducting wire, wherein the volume ratio of the entire matrix is 1.5 or less.