JPH02213009A - Compound superconductive stranded wire and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a superconductive stranded wire applicable to alternating current use in such as a superconductive generator by coating an outer peripheral surface of a diffusion preventing layer with a alloy layer of high resistance to form a stabilized conductor and providing an outer peripheral surface of the stabilized conductor with a compound superconductor formed in a stranded wire. CONSTITUTION:An outer peripheral surface of a core conductor 2 made of pure copper is coated with a diffusion preventing layer 3 made of metal material such as Ta and Nb. An outer peripheral surface of the diffusion preventing layer 3 is further coated with Cu-Sn alloy layer 4 to form a stabilized conductor 1. A stranded in situ wire 8 plated with Sn is arranged around the conductor 1 to form a primary stranded conductor 10. The conductor 10 is treated under a low temperature and stranded to form a secondary stranded conductor 11. The secondary stranded conductor 11 is diffused by heat to form the wire 8 into a superconductor 9. Thus, a superconductive stranded wire 12 of less alternating current loss in alternating current use is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an alternating current compound superconducting stranded wire suitable as a field winding of a superconducting generator, and a method for manufacturing the same.

"Conventional technology" In a superconducting wire, heat may be generated due to the motion of m-sons and lines of magnetic flux. There is a possibility that the entire structure will be transposed into a normal 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.

■The superconductor is buried inside a stable base material with good conductivity such as copper. 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 formed stranded wire structures.

(2) When using a superconducting wire for alternating current, a stabilizing base material is made of a high-resistance metal material such as a CuNi alloy to suppress the coupling current generated between superconducting filaments.

■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, when manufacturing stranded super 711f4 wire in compound superconducting wire for AC,
A composite wire that can be processed by forming a coating layer containing the remaining elements among the elements constituting the superconducting gold intermetallic compound on a wire containing at least one element among the elements constituting the superconducting intermetallic compound. A method is used in which superconducting strands are manufactured by forming a composite wire, stranding it at the stage of this composite strand, and performing a diffusion heat treatment after the strand processing.

[Problem to be Solved by the Invention J] By the way, in order to improve the stability of AC superconducting wires, secondary twisted wires are constructed by assembling a plurality of wires of 6 that have been twisted once and then twisting them again. Attempts have been made to adopt a linear structure.

In such cases, conventionally, a plurality of the composite strands are assembled into a primary strand, and then a plurality of the primary strands are assembled to form a secondary strand, and then O-wire processing is performed. After this, a diffusion heat treatment is performed to generate a superconducting intermetallic compound to obtain a superconducting stranded wire for alternating current.

However, as mentioned above, in the case of alternating current superconducting wires that are formed into stranded wires, the cross-sectional area of each superconducting wire is made extremely small for stability, so processing beyond diffusion heat treatment is difficult. Even when the composite wire is in a state where it is possible to twist the wire, troubles such as wire breakage occur during multiple twisting processes.

On the other hand, conventionally, as an example of the structure of superconducting wire for superconducting generators, a method has been adopted in which wires such as Nb-Ti wires are stranded, but in superconducting wires made of compounds such as Nb5Sn, mechanical strain Because of its weakness, there have been few applications of it as a conductor in AC superconducting generators.

Therefore, when considering the application of compound-based superconducting wires for superconducting power generators, the biggest challenges are countermeasures against mechanical strain when coiled and reducing AC loss during energization.

Here, in order to reduce the strain characteristics during coil processing, if a structure is adopted in which the Nb5Sn superconductor is placed at the center of the conductor and the stabilizing conductor is placed on the outside, the amount of bending of the superconductor during coil processing is However, when this structure is adopted, the stabilizing conductor is placed on the center side,
There is a problem in that AC loss increases compared to a superconducting wire having a structure in which a superconductor is disposed on the outside.

The present invention has been made to solve the above problems, and therefore, a superconducting PAt suitable for AC use such as 4-engine 11-engine superelectric
A compound-based superconducting tat that can provide 1A and prevent wire breakage during production even when the superconducting stranded wire is produced by performing the stranding process multiple times.
The purpose of the present invention is to provide a method for producing lA.

“A means to solve problems”! -1 In order to solve the above-mentioned problem, the invention described in claim 1 includes a core conductor made of a metal material with good conductivity, a diffusion prevention layer provided covering the outer peripheral surface of this core conductor, and a diffusion prevention layer provided to cover the outer peripheral surface of this core conductor. A stabilizing conductor is formed from a high electrical resistance alloy layer provided covering the outer circumferential surface of the stabilizing conductor, and on the outer circumference of the stabilizing conductor,
It is made by stranding compound-based superconducting conductors with a diameter smaller than that of the stabilizing conductor.

In order to solve the above problem, the invention described in claim 2 has the following features:
A composite tree formed by forming a coating layer containing the remaining elements among the plurality of elements constituting the superconducting intermetallic compound on a wire containing at least one element among the plurality of elements constituting the superconducting intermetallic compound. A stranded wire conductor is created by preparing a wire, further collecting and stranding the composite strands a necessary number of times, and then producing a superconducting intermetallic compound in this stranded wire conductor. In the method of manufacturing a superconducting stranded wire by performing a diffusion heat treatment to produce a superconducting intermetallic compound, the composite wire before the stranding process or the twisted JIQ conductor before the second or subsequent stranding process is subjected to a diffusion heat treatment to generate a superconducting intermetallic compound. A low-temperature heat treatment is performed at a temperature lower than the above temperature to diffuse the elements of the yl coating layer into the inside of the cotton, and after this low-temperature heat treatment, the wire is further twisted.
Next, a diffusion heat treatment is performed.

[Function] Since the stranded superconducting conductor is provided outside the stabilizing conductor, the AC loss is lower than that of a conventional superconducting wire having a structure in which the superconducting conductor is provided at the center of the conductor. Further, the high electrical resistance alloy layer formed on the stabilizing conductor reduces the vortex iX flow loss between the superconducting conductors and the stabilizing conductor.

On the other hand, due to the low-temperature heat treatment performed before l@ wire processing, the elements of the coating layer diffuse into the inside of the wire, and the wire and coating layer become integrated, and the mechanical strength of the composite wire improves, so during the stranding process. This prevents wire breakage. Further, the diffusion prevention layer formed on the stabilizing conductor ζ prevents unnecessary elements from diffusing to the core conductor side during heat treatment.

The present invention will be explained in more detail below.

Figures 1 to 3 are for explaining an example in which the method of the present invention is applied to the production of Nb5Sn-based AC superconducting stranded wires. A stabilizing conductor I shown in Figure 1 is prepared.

This stabilizing conductor 1 includes a core conductor 2 made of pure copper and a diffusion prevention layer 3 provided covering the outer peripheral surface of the core conductor 2.
and an alloy rIJ4 provided to cover the outer peripheral surface of this diffusion prevention layer 3. Said anti-diffusion Ji!
Reference numeral 13 is a material that does not form unnecessary compounds with the pure copper constituting the core conductor 2, and is made of a metal material such as Ta or Nb that has a high melting point.
This is provided to prevent unnecessary elements from diffusing into the core conductor 2 from the outside. Further, the alloy layer 4 is made of a Cu--Ni alloy or a Cu--Sn alloy having high electrical resistance.

Note that a diffusion prevention layer 3 and an alloy layer 4 are provided on the outside of the core conductor 2.
This can be easily done by plating the outside of the core conductor 1, or by covering the outside of the core conductor 1 with a tape or foil made of the above-mentioned material and then drawing it. can be formed.

Next, composite wires to be twisted and provided outside the stabilizing conductor 1 are prepared. In this example, an inside wire coated with Sn is used as the composite wire. The inside due line is a Cu-N b alloy with a predetermined composition or a Cu-N
It is created by wire-drawing an Insage 21 ingot 6 shown in FIG. 2 obtained by melting b-5n alloy or the like. The in-situ ingot 6 has a structure in which countless dendrites made of Nb are dispersed inside a metal base made of Cu or Cu-Sn. By the wire drawing process, an inside wire 7 shown in FIG. 3 having a structure in which fibrous Nb filaments are dispersed within a metal base can be obtained.

Next, a Sn coating mva is formed on the outer peripheral surface of this in-situ wire 7 by force plating to form a plating in-situ-Jl;1 (composite lf: line) 8 shown in FIG.
Once this Metsuki in-situ wire 8 is prepared, prepare multiple Metsuki in-situ wires 8 and connect them to 671
A primary twisted conductor IO having a cross-sectional structure as shown in FIG. 5 is obtained by providing the stabilized conductor I in a cylindrical manner on the outside.

Once the primary stranded conductor 10 is created, a low-temperature heat treatment is performed to heat the primary stranded conductor 10 to a temperature of 180 to 450° C. for a predetermined period of time to diffuse the elements of the coating layer into the inside of the inside wire 7. In this low-temperature heat treatment, if the temperature is initially higher than the melting point of Sn (231.9°C), the Sn
Since the coating layer melts down from the in-situ line 7, in the low-temperature heat treatment, the temperature is lower than the melting point of Sn and at which the diffusion of S11 easily progresses, that is, 180~2
It is preferable to perform the primary heat treatment at a temperature of about 20° C. for several hours to several tens of hours to sufficiently diffuse Sn in the coating layer into the in-situ wire 7 and eliminate the coating layer. After this, heat treatment is performed at a temperature of about 300 to 450°C for several hours to several tens of hours to promote the diffusion of Sn and suppress the formation of unnecessary compound phases of Cu and Sn within the in-situ line 7. - Stable C for the metal base of line 7
U-8 membered alloy phase. In the low-temperature heat treatment, if the heat treatment is performed at a temperature higher than 450° C., the diffusion reaction between Sn and Nb will proceed and Nb5Sn will start to be produced, which will reduce the workability of the in-situ wire 7, which is not preferable.

Next, a plurality of the primary stranded conductors 10 that have been subjected to the low-temperature heat treatment are assembled and twisted to form a secondary stranded conductor II shown in FIG. 6. When creating this secondary stranded wire conductor 11, the Sn coating layer in the primary l@ wire conductor 9 is eliminated by the low temperature heat treatment, Sn is diffused into the inside of the in-situ wire 7, and the in-situ wire 7 is strengthened. Therefore, even if the in-situ wire 7 with a small diameter is used, it will not break during the wire stranding process.

Next, this secondary stranded wire conductor 11 is subjected to diffusion heat treatment in which it is heated to 500 to 700° C. for several tens to hundreds of hours, and the Sn diffused inside the inside wire 7 reacts with the Nb filament, thereby forming Nb3S nM3 '15. By forming the inside wire 7 into a superconducting conductor 9 by generating a filament of a conductive intermetallic compound, a secondary stranded superconducting stranded wire having a cross-sectional structure equivalent to that of the secondary stranded conductor II (not shown in FIG. 6) is formed. 12 can be obtained. During the diffusion heat treatment, Sn or Ni contained in the alloy layer 4 or Sn contained in the coating layer tends to diffuse into the stabilizing conductor l, but the diffusion prevention layer 3 Since diffusion to the inside is prevented, the core conductor 2 made of pure Cu is not contaminated with unnecessary elements such as Sn.

Note that if the core conductor 2 is contaminated with Sn, the electrical resistance of the core conductor 2 at extremely low temperatures will increase and the performance of the core conductor 2 as a stabilizing conductor will deteriorate, which is not preferable.

The superconducting stranded wire manufactured as described above has a secondary stranded structure, so it is highly stable for AC use. In addition, since the superconducting conductor portion created from the in-situ wire 7 and the core conductor 2 are isolated by the high electrical resistance alloy JI4, eddy current loss that is about to occur between the superconducting conductor portion and the core conductor 2 is prevented. can be reduced. Furthermore, since the superconducting conductor part is manufactured from INSIDU JI7, it has excellent critical current characteristics and is also excellent in terms of mechanical strength, with little deterioration of superconducting characteristics even when subjected to mechanical strain.

Therefore, the superconducting stranded wire having the above structure is suitable for use in alternating current applications such as field windings of superconducting generators.

By the way, in the above example, the secondary stranded conductor 11 was subjected to diffusion heat treatment, but it is also possible to produce a superconducting stranded wire by subjecting the primary stranded conductor 10 to diffusion heat treatment to generate a superconducting intermetallic compound. Of course.

In the above example, the superconducting conductor portion was formed using the in-situ wire 7, but a composite multi-core wire manufactured by using a Sn vibrator on a Nb core material and reducing the diameter multiple times. Of course, it may be used as a substitute for the inside due line 7.

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-, Ga-based, and Nb-based superconducting stranded wires.

It goes without saying that the present invention can be applied as a method for manufacturing superconducting stranded wires based on compounds such as Go and Nb*Δl.

[Example J A rod-shaped inside ingot having a composition of Cu-40vt%Nb was melted and made into this! Two-layer processing, extrusion processing, and wire drawing processing are applied, and an 8μ-thick Sn layer is applied to the outer periphery.
An inside wire with a diameter of 0.2 g+i was obtained by covering with a plating layer. In addition, a stabilized conductor with a diameter of 1.31 is prepared by coating a core conductor made of oxygen-free copper with a purity of 99.9% with an Nb layer and a Cu-Ni alloy layer, and The above-mentioned inside-due wire was formed into a stranded wire to create a primary stranded wire conductor.

Thereafter, after heating at 180° C. for 96 hours in a N gas atmosphere, low-temperature heat treatment was performed by heating at 400° C. for 48 hours to diffuse Sn into the in-situ wire and integrate the in-situ wire.

Thereafter, as shown in FIG. 3, five of the first stranded wire conductors were used to perform secondary stranding to obtain a secondary stranded wire conductor having a thickness of 3 s+s and a width of 5 ms. This 2 o'clock stranded wire conductor! 1. ! During the construction, no breakage of the in-situ wire occurred. Moreover, winding processing could be easily performed on this secondary stranded wire conductor.

After the winding process, a diffusion heat treatment for Nb5Sn production was performed by heating the wire at 500 to 550° C. for 150 to 200 hours, and a high-flow Nb5Sn superconducting stranded wire could be obtained.

“Effect of the invention” Claim as explained above! According to the invention described in
Since the superconducting conductor and the core conductor are separated by an alloy layer of high electrical resistance, the superconducting conductor tends to occur between the superconducting conductor and the core conductor. Ifi current loss can be lowered. Also,
Since the stranded superconducting conductor is provided outside the stabilizing conductor, the AC loss is lower than that of conventional superconducting wires having a structure in which the superconducting conductor is provided at the center of the conductor.

Therefore, the superconducting stranded wire of the invention described in Claim 1 of 111 is suitable for use in alternating current applications such as field Y8 wires of superconducting generators.

Further, according to the method of the invention described in claim 2, when a composite wire consisting of a wire rod and a coating layer is twisted, or a stranded wire conductor obtained by twisting the composite wire is further twisted. When processing liη, the composite wire and the coating layer are integrated and strengthened by low-temperature heat treatment, and then the wire is processed, so the wire can be processed without breaking the composite wire or the stranded wire conductor. Can be done. Further, according to the method of the present invention, it is possible to produce a superconducting stranded wire that exhibits the effects described in claim 1.

Therefore, superconducting stranded wires that are excellent for use in alternating current applications such as field windings of superconducting generators can be manufactured without disconnection during manufacturing.

[Brief explanation of the drawing]

Figures 1 to 6 are for explaining an example in which the method of the present invention is applied to a method for manufacturing a superconducting stranded wire with a diameter of Nb5Sn. Figure 1 is a cross-sectional view of a stabilizing conductor, and Figure 2 is an in-situ Figure 3 is a cross-sectional view of the ingot, Figure 4 is a cross-sectional view of the inside-due wire, Figure 5 is a cross-sectional view of the primary stranded conductor, and Figure 6 is the secondary stranded conductor. FIG. DESCRIPTION OF SYMBOLS 1... Stabilizing conductor, 2... Core conductor, 3... Diffusion prevention layer, 4... Alloy layer, 6... In-situ ingot, 7... In-situ wire, 8... Metsuki In-situ wire (composite wire), 9... superconducting conductor, IO
...Primary stranded conductor, eyes! ...Secondary stranded conductor. Figure 1 Figure 2 Figure 6

Claims (2)

[Claims] (1) A core conductor made of a highly conductive metal material, a diffusion prevention layer provided to cover the outer peripheral surface of this core conductor, and a high electrical resistance alloy layer provided to cover the outer peripheral surface of this diffusion prevention layer. A compound-based superconducting twisted wire, characterized in that a stabilized conductor is formed from the stabilized conductor, and a compound-based superconducting conductor having a diameter smaller than that of the stabilized conductor is twisted around the outer periphery of the stabilized conductor. (2) forming a coating layer containing the remaining elements among the plurality of elements forming the superconducting intermetallic compound on a wire containing at least one element among the plurality of elements forming the superconducting intermetallic compound; A stranded wire conductor is prepared by preparing a composite strand of wire, stranding the stranded composite wire, and performing the necessary number of twisting operations to create a stranded wire conductor. In a method of manufacturing a superconducting stranded wire by performing diffusion heat treatment to generate a compound, a superconducting intermetallic compound is generated in the composite wire before the stranding process or the stranded wire conductor before the second or subsequent stranding process. A low-temperature heat treatment is performed at a temperature lower than the diffusion heat treatment temperature to diffuse the elements of the coating layer into the inside of the wire, and after this low-temperature heat treatment, the wire is further twisted, and then a diffusion heat treatment is performed. A method for manufacturing a compound-based superconducting stranded wire.