JPH044519A - Compound superconducting stranded wire and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve mechanical strength by arranging a stabilized conductor around a superconducting conductor comprising conglomerated superconducting wires, so as to form an element wire, and by forming the element wire into a stranded wire. CONSTITUTION:A superconducting conductor 12 is formed by gathering multiple superconducting wire 11 formed out of a number of filaments comprising intermetallic compound dispersed in a metallic base. A conductor 13 of good conductivity is coated with an anti-diffusion layer 14 made of metal of high melting point, so as to form a stabilized conductor 15, while an element wire 15 is formed by coating the circumference of the superconducting conductor 12 with the multiple stabilized conductors 15, and the multiple element wires 18 are twisted together. Since the element wire is formed by arranging multiple stabilized conductors 15 around the superconducting conductor 12, and the element wire is formed into a stranded wire the structure of the superconducting conductor 12 reinforced by the stabilized conductor 15, is obtained. Mechanical strength is increased thereby, and deterioration in superconducting characteristic can be suppressed even when mechanical deformation is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a compound-based superconducting stranded wire used in superconducting applied equipment such as a superconducting generator, and a method for manufacturing the same.

``Prior art'' In superconducting wires, heat may be generated due to the movement of quantum magnetic flux lines, etc. In such cases, buds of normal conductivity occur partially in the superconducting wire, and the entire superconducting wire becomes There is a risk of transition to a normally conducting state.

Therefore, in order to stabilize superconducting wires by preventing such magnetic instability and normal conductive dislocations, the techniques described below have been employed.

■ Embed the superconductor inside a stable base material with good conductivity such as Cu. In particular, the stabilizing matrix is formed from high purity copper.

(2) Ultra-fine superconductors into filament shapes with diameters of several micrometers to several tens of micrometers.

■Twisting multi-core wires.

■Use braided or stranded wire structures.

■Intermetallic compound superconductors are extremely hard and brittle, so
When mechanical strain is applied, superconducting properties tend to deteriorate, so reinforcing materials are attached to superconducting wires to prevent mechanical strain from being applied.

From the above background, conventionally, as an example of the structure of AC superconducting wire, a method of stranding wires such as Nb-Ti wires has been adopted, but Compound-based superconducting wires have the disadvantage of being susceptible to mechanical strain, and it is difficult to strand them directly. Therefore, technological development has not progressed to produce superconducting stranded wires with a structure suitable for AC applications. ing.

In this background, the method described below based on FIGS. 3 to 6 is known as an example of a method for manufacturing N bs S n-based superconducting stranded wires.

As shown in FIG. 3, a strand 1 is prepared by dispersing a large number of Nb ultra-fine filaments inside a base made of Cu or Cu alloy, and then the outer surface of this strand 1 is coated with strands as shown in FIG. 4. Composite by forming pure Sn coating layer 2! 3.

Next, a plurality of composite wires 3 are assembled as shown in FIG. 5 to obtain a composite wire 4, and a plurality of composite wires 4 are aligned and twisted to obtain a twisted wire 5 as shown in FIG. 6.

Then, this stranded wire 5 is subjected to diffusion heat treatment, and the S of the coating layer 2 is
By diffusing n into the inside of the wire l and reacting with the Nb filament, an N bs S n superconducting filament can be generated, and a Nb, Sn superconducting strand can be obtained.

"Problems to be Solved by the Invention" However, in the above manufacturing method, when the composite wires 3 are twisted together, a strong compressive force acts on each of the composite wires 301. Therefore, the coating layers 2 made of Sn may rub against each other, resulting in uneven thickness or peeling of the coating layers 2. If the coating layer 2 becomes non-uniform in this way, a phenomenon occurs in which Sn is non-uniformly diffused to the inner side of the strand l during the diffusion heat treatment, resulting in the Nb
, there was a problem that the formation state of Sn became non-uniform, causing deterioration of superconducting properties.

Furthermore, when the stranded wire 5 shown in FIG. 6 is subjected to diffusion heat treatment,
Molten Sn remaining on the outer periphery of the composite wire 3 may cause adjacent composite wires 4 to be fixed to each other.

In this way, if the adjacent strands 4 are fixed to each other by Sn, the strands 4 cannot slide against each other when stress is applied to the stranded wires 5. As a result of the loss of flexibility, there is a risk that the fixed portion may become a stress concentration point, resulting in a decrease in mechanical strength.

Furthermore, when the superconducting stranded wire is used for alternating current, if stress concentrates on the fixed portion, a large strain will occur in the superconducting wire in the stress concentrated portion, causing a problem that the superconducting properties of this portion will deteriorate.

The present invention has been made to solve the above problems, and has high mechanical strength, no sticking between superconducting wires constituting a stranded wire, excellent flexibility, and exhibits key superconducting properties. The object of the present invention is to provide a compound-based superconducting stranded wire having an excellent structure for alternating current applications such as generators, and a method for manufacturing the same.

"Means for solving the problem" In order to solve the problem, the invention stated in claim 1 has the following features:
A superconducting conductor section is constructed by assembling multiple superconducting wires made of a large number of filaments made of superconducting intermetallic compounds dispersed inside a metal base, and the highly conductive conductor is covered with a diffusion prevention layer made of a high melting point metal. In addition to forming a stabilizing conductor, the superconducting conductor portion is surrounded by a plurality of stabilizing conductors to form a wire, and a plurality of these wires are twisted together.

In order to solve the above problem, the invention described in claim 2 has the following features:
The intermetallic compound is formed around the outer periphery of the rod using a rond in which filaments made of at least one element among the two or more metal elements constituting the superconducting intermetallic compound are dispersed inside a metal base. Out of two or more metal elements, a coating layer of the remaining element is formed to create a coated composite wire, and then a plurality of coated composite wires are assembled to form an aggregate strand, while a highly conductive A stabilized conductor is formed by covering a conductor with a diffusion prevention layer made of a high-melting point metal, and the wire assembly is covered with a plurality of stabilized conductors and then twisted.

"Function" A stabilizing conductor is arranged around a superconducting conductor section made up of a collection of superconducting wires to form a strand, and this strand is twisted, so the stabilizing conductor reinforces the superconducting wire. As a result, mechanical strength is improved. In addition, when the wires are twisted together,
What mainly rubs against each other when the wires are twisted are the stabilizing conductors provided on the outer periphery of the wires, and the wires come into contact with each other via the stabilizing conductors.

Therefore, when heat treatment is performed, the wires are not stuck to each other, and the flexibility of the wires is not impaired, so that mechanical strength does not decrease.

The present invention will be explained in more detail below.

FIG. 1 is for explaining an example in which the method of the present invention is applied to the production of Nbsεn-based AC superconducting stranded wires.
The in-situ rod 9 shown in a) is manufactured.

In order to manufacture this in-situ rod 9, an in-situ ingot is created by melting a Cu-N b alloy or a Cu-N b-5n alloy with a predetermined composition, and this in-situ ingot is subjected to plastic processing such as rolling or forging. Manufactured by drawing during processing.

The in-situ ingot is made of Cu or Cu-S.
It has a structure in which countless dendrites made of Nb are dispersed inside a metal base made of an n-alloy, etc., and has good workability. By drawing this in-situ ingot, it is possible to obtain an in-situ rod 9 having a structure in which numerous fibrous Nb filaments are dispersed and arranged within a metal base.

Next, a coating layer 10 of Sn is formed on the outer circumferential surface of this in-situ rod 9 by means such as electroplating or melt plating to form a coating anti-contact line l] having the structure shown in FIG. 1(b). . Here, the means for forming the coating 1ilO is not limited to the above-mentioned means, but may also be performed by winding a Sn tape or the like.

Next, a plurality of coated composite wires 11, for example seven wires, are assembled to form a set of wires I2 shown in FIG. 1(c).

On the other hand, a rod-shaped, highly conductive conductor 13 shown in FIG. 1(d) is prepared, and this conductor 13 is inserted into the tubular body I4.

The conductor 13 is made of highly conductive pure Cu, and the tube body 14 is made of Ta or Nb.

After the conductor 13 is inserted into the tube 14, a diameter reduction process is performed to obtain the stabilized conductor 15 shown in FIG. 1(e). This stabilizing conductor 15 has a structure in which an internal conductor 16 is covered with a diffusion prevention layer 17.

The metal material constituting the diffusion prevention layer 17 is a conductor! 6
It is a material that does not form unnecessary compounds with pure Cu that constitutes the conductor 16, and is made of a metal material such as Ta or Nb with a high melting point. This is provided to prevent elements from diffusing.

In addition, as a means for forming the diffusion prevention layer 17 on the outside of the conductor 16, plating is performed on the outside of the conductor 13, or a tape or foil made of the above-mentioned material is applied on the outside of the conductor 13. It is also possible to adopt methods such as covering the wire with wire drawing processing.

Once the group wire 12 and the stabilizing conductor 15 have been created as described above, a plurality of stabilizing conductors 15 are attached so as to cover the outer periphery of the group wire 12 to form a cross-sectional structure as shown in FIG. 1 Cf). A strand I8 is formed.

Subsequently, a plurality of the strands 18 are prepared and twisted.
Get strands. In this stranding process, there is a risk that the outer peripheries of the cable wires 18 may rub against each other and damage the outer periphery of the strands 18, but since the stabilizing conductor 15 is arranged on the outer periphery of the strands 18, There is no problem even if some wear and tear occurs on the stabilizing conductor (5).

Once the strands have been created, the stepwise heat treatment described below can be performed to obtain the superconducting strands 20 shown in FIG.

First, a first heat treatment is performed in which the stranded wire is heated for several hours to several tens of hours at a temperature of 180 to 220° C., which is lower than the melting point of Sn and at which the diffusion of Sn proceeds. Through this first heat treatment, Sn
The melting causes the Sn coating layer 2 to diffuse into the inside of the in-situ rod 1 while preventing it from falling off. Note that this first heat treatment is preferably performed until Sn is sufficiently diffused to the in-situ rod 9 side and disappears.

After the first heat treatment is completed, the stranded wire is further
A second heat treatment is performed at a temperature of 450° C. for several hours to several tens of hours. By this second heat treatment, the in-situ rod 1
While Sn is sufficiently diffused to the center side of the Cu
Avoid the formation of unnecessary compound phases of Sn and Sn.

After the second heat treatment is completed, the stranded wire is further heated to 450°C.
for several tens of hours at a higher temperature, e.g. 500-750℃.
A third heat treatment in which the Nb filament is heated for several hundred hours is performed to react the Nb filament with Sn to produce a Nb, Sn superconducting intermetallic compound filament.

In the first to third heat treatments described above, the coated composite wire 1
Since the coating layer 1O of No. 1 is in contact with the surrounding stabilizing conductor 15, there is a concern that Sn will diffuse to the stabilizing conductor 15 side. is formed and the diffusion prevention layer 17 prevents the diffusion of Sn, so that the conductor 16 is not contaminated with Sn. Note that if the conductor 16 is contaminated with Sn, the electrodes will be damaged.

This is not preferable because the electrical resistance of the conductor 16 increases when it is cooled to a low temperature and energized.

Furthermore, even if the Nb5Sn superconducting filament is generated by a single heat treatment of heating at 500 to 700°C for several tens of hours to several hundreds of hours, without performing the first to third heat treatments stepwise as described above. No problem.

Through the above processing, Nb3S is formed inside the coated composite wire 11.
A superconducting wire 19 is formed by generating n superconducting filaments, and a superconducting stranded wire 20 shown in FIG. 2 is manufactured.

The superconducting stranded wire 20 is a superconducting wire in which N bs S n superconducting intermetallic compound filaments are formed! A superconducting conductor section formed by a plurality of superconducting conductor sections 9 and a plurality of stabilizing conductors 15 covering this superconducting conductor section are twisted together.

In the superconducting stranded wire 20 manufactured as described above, each strand 18
A stabilizing conductor 15 is arranged on the outer periphery of the strands, and even if the strands 18 rub against each other during twisting, the stabilizing conductor 15 functions as a buffer layer. Composite line! The degree of damage to the coating layer 10 of I can be suppressed to a minimum. For this reason, the coating layer 10 is applied to the in-situ rod 9 during the diffusion heat treatment performed after the wire twisting.
When Sn diffuses, the Sn diffuses uniformly toward the inside of the in-situ rod 9. Therefore, Nb5Sn superconducting filaments can be uniformly generated inside the in-situ rod 9.

Furthermore, the superconducting twisted wires having the above structure are arranged in the in-situ rod 9.
Since the superconducting wire 21 is reinforced with a plurality of stabilizing conductors 15, it has excellent critical current characteristics and is resistant to mechanical strain (very superconducting characteristics). It also has excellent mechanical strength, with little deterioration.

Therefore, the superconducting stranded wire 20 having the above structure can be suitably used for alternating current applications such as field windings of superconducting generators.

In addition, in the above example, the superconducting wire 2 of the superconducting conductor part
1 was formed using the in-situ rod 9, but a composite multi-core wire manufactured by assembling a large number of composites in which a Nb core material was covered with a Sn pipe and performing the diameter reduction operation multiple times was fabricated using the in-situ rod 9. Of course, superconducting wires may be manufactured by using it as a substitute.

Furthermore, in the above examples, the method of the present invention is applied to Nb.

Although an example in which the method of the present invention is applied to a method for producing Sn-based superconducting stranded wires has been described, the method of the present invention can also be applied to V s Ga-based, Nb-based superconducting stranded wires.

It goes without saying that the present invention can also be applied as a method for producing superconducting stranded wires based on other compounds such as Ge-based and Nb3Al-based wires.

"Example" An in-situ ingot having a composition of Cu-30vt%Nb was melted and subjected to forging, extrusion, and wire drawing to create an in-situ rod with a diameter of 0.185 as. 7.5μ thick by electroplating
A coated composite wire was obtained by coating with a Sn plating layer of m, and seven of the coated composite wires were assembled to obtain an assembled wire.

On the other hand, a pure Cu rod with an outer diameter of 13.5a+a was inserted into a Ta tube with an outer diameter of 16 mm and an inner diameter of 14 mm, and the whole was reduced in diameter to obtain a stabilized conductor with a diameter of 0.2 mm.

Next, 12 of the above-mentioned stabilizing conductors are attached around the Fuki group wire to form a strand, and 9 of these strands are twisted into a rectangular shape, so that the thickness is l, the width is 8cm-1, and the width is 4mm. 51 stranded wires with a rectangular cross-section were obtained.

This stranded wire was subjected to diffusion heat treatment for Nb5Sn production to obtain a superconducting stranded wire.

When we measured the critical current density of the obtained superconducting stranded wire, we found that
In an external magnetic field of 8T, it exhibited approximately 1700 A/am''.

In addition, in the superconducting conductor section consisting of in-situ rods that make up this superconducting stranded wire, the critical current density of one superconducting wire is 2000 A/mm', so approximately 85
This means that the characteristics and characteristics of % have been obtained.

In addition, when bending strain was added to the obtained superconducting stranded wire,
No deterioration of characteristics occurred up to approximately 2% strain.

Further, the superconducting wires constituting the superconducting conductor portion did not adhere to each other, and the entire superconducting stranded wire had sufficient flexibility.

"Effects of the Invention" As explained above, according to the present invention, a plurality of stabilizing conductors are arranged around a superconducting wire to constitute a wire, and since the wire is twisted, the superconducting wire The structure is reinforced with stabilizing conductors. Therefore, it is possible to provide a superconducting stranded wire that has high mechanical strength and exhibits little deterioration in superconducting properties even when subjected to mechanical strain.

In addition, when stranding strands, the strands rub against each other, but since stabilizing conductors are placed around the outer periphery of the strands, these stabilizing conductors act as a buffer layer and prevent the strands from rubbing against each other. Damage to the provided rod and coating layer can be reduced. Therefore,
Since the rate of damage to the coating layer provided on the inside of the stabilizing conductor is reduced, when diffusion heat treatment is applied, the elements of the coating layer can be uniformly diffused to the rod side, and the superconducting intermetallic compound is uniformly distributed within the rod. Superconducting wire can be obtained by producing filaments.

Furthermore, since a stabilizing conductor coated with a high-melting point metal is arranged around the outer periphery of each strand, the strands will not be stuck to each other even if the strands are heat treated after being twisted. Therefore, since the superconducting stranded wire has excellent flexibility, it is suitable for use in alternating current applications such as superconducting generators where mechanical strain is likely to be applied.

[Brief explanation of the drawing]

FIGS. 1(a) to (r) are cross-sectional views of combined lines for explaining the method of the present invention, FIG. 1(d) is a cross-sectional view showing a hearing device in which a conductor is inserted into a tube body, and FIG. (e) is a cross-sectional view of the stabilizing conductor;
Fig. 1(f) is a cross-sectional view of the strand, Fig. 2 is a cross-sectional view of the twisted wire, Figs. 3 to 6 are for explaining the conventional method, and Fig. 3 is a cross-sectional view of the in-situ rod. 4 is a sectional view of the coated composite wire, FIG. 5 is a sectional view of the assembled wire, and FIG. 6 is a sectional view of the superconducting stranded wire. 9...In-situ rod, IO...Coating layer,! l
... Covered composite wire, 12 ... Gathered wire, 15 ... - Stabilizing conductor, 16 - Electrical conductor, 17 ... Diffusion prevention layer, 18 ...
Element wire, 19... superconducting wire, 20... superconducting stranded wire.

Claims (2)

[Claims] (1) A superconducting conductor section is constructed by assembling a plurality of superconducting wires made by dispersing a large number of filaments made of a superconducting intermetallic compound inside a metal base, and a highly conductive conductor is layered with a diffusion prevention layer of a high melting point metal. A compound characterized in that a stabilizing conductor is constructed by covering the superconducting conductor portion, a strand is constructed by covering the periphery of the superconducting conductor portion with a plurality of stabilizing conductors, and a plurality of these strands are twisted together. system superconducting stranded wire. (2) Using a rod in which filaments made of at least one element among the two or more metal elements constituting the superconducting intermetallic compound are dispersed inside a metal base, the intermetallic compound is attached to the outer periphery of the rod. A coated composite wire is created by forming a coating layer of the remaining element among two or more metal elements constituting the metal element, and then a plurality of coated composite wires are assembled to form an aggregate strand, while a good conductive wire is formed. A stabilized conductor is formed by covering a conductor with a high melting point with a diffusion prevention layer made of a high melting point metal, and after covering the periphery of the aggregated strands with a plurality of stabilizing conductors, the wire is twisted, and then a diffusion heat treatment is performed. A method for manufacturing a compound-based superconducting stranded wire, characterized by: