JPH0286015A - Stabilized copper element wire for compound superconducting strand wire and manufacture of superconducting strand wire - Google Patents

Abstract

PURPOSE:To satisfactorily stabilize the superconductive characteristic by providing a core section made of pure copper and a diffusion preventing layer covering this core section then covering a cover metal layer on it. CONSTITUTION:An in situ ingot 10 of a bar with the diameter of about tens mm is first formed as the structure dispersed with numerous Nb dendrite crystals in a raw material made of Cu or Cu-Sn alloy. An insitu element wire 11 is then formed, and the torsion with the pitch of several mm is applied to it to obtain an insitu wire 12. An Sn-plated layer with the thickness of several mum to tens mum is formed on the outer periphery of the wire 12, and multiple (seven in the figure) plated wires 14 are collected and twisted to form a strand wire 15. On the other hand, a composite body 16 having a diffusion preventing layer 18 made of To or Nb and covered on a core section 17 made of pure copper and a cover layer 19 made of Cu-Sn alloy on its outer periphery is formed. This composite body 16 is shrunk to the same diameter as that of the strand wire 15 to obtain a stabilized copper element wire 20, multiple wires 15 and 20 are collected in turn and twisted, it is heat-treated at 500-650 deg.C, Nb and Sb are reacted, the strand wire 15 is made a superconducting strand wire 22, and a superconducting strand wire A is obtained together with the copper element wire 20.

Description

Detailed Description of the Invention "Field of Industrial Application" This invention relates to stabilized copper wires for superconducting stranded wires based on compounds such as Nb3Sn, and methods for producing superconducting stranded wires, and in particular to methods for producing superconducting stranded wires. This is to prevent contamination of the stabilized copper due to the diffusion heat treatment that produces .

"Prior Art" Conventionally, the bronze method, internal tin diffusion method, and external tin diffusion method have been known as representative examples of methods for manufacturing this type of compound-based superconducting wire.

The bronze method involves creating a wire with a large number of Nb filaments arranged inside a base made of a Cu-Sn alloy (bronze), and then performing diffusion heat treatment on this wire to diffuse Sn.
This is a method for producing n-superconducting filaments.

In addition, the internal tin diffusion method is when placing an Nb filament inside a base made of copper or a prepared alloy, a tin rod or a Nb rod coated with a tin plating layer is composited inside the base and degenerated processing is performed. Next, diffusion heat treatment is performed to diffuse Sn, and Nb5Sn is formed around the Nb filament.
This is a method for producing superconducting intermetallic compound filaments.

Furthermore, the external tin diffusion method involves arranging a large number of Nb filaments inside a copper or copper alloy base to create a wire, forming a tin plating layer on the outer surface of this wire to create a wire,
This wire is subjected to diffusion heat treatment to diffuse Sn, and Nb is added to the outer periphery of the Nb filament.

This is a method for producing Sn superconducting filaments.

By the way, conventionally, Nb produced by the various methods mentioned above,
As examples of structures of stabilized copper applied to Sn-based superconducting wires, structures shown in FIGS. 6 and 7 are known.

In the conventional stabilized copper structure shown in Fig. 6, a large number of Nb3Sn superconducting filaments are arranged inside a base made of a stabilizing base material to form a superconducting conductor part I, and this superconducting conductor part ■ is prevented from diffusing. It has a structure in which a layer 2 is interposed and a stabilized copper layer 3 is covered. In addition, in the structure example of stabilized copper shown in FIG. 7, the outer periphery of a core-shaped stabilized copper 5 is covered with a diffusion prevention layer 6, and a large number of Nb5Sn superconducting filaments are arranged around the outer periphery inside the stabilizing base material. This structure is covered with a cylindrical superconducting conductor portion 7.

``Problems to be Solved by the Invention'' In the structural example shown in FIG. 6, there is a problem in which the bronze method or the internal tin diffusion method can be applied, but the external tin diffusion method cannot be applied. That is, when manufacturing the superconducting wire shown in FIG. 6, if the outer periphery of the stabilized copper 3 is tinned and then subjected to diffusion heat treatment, the stabilized copper will be contaminated with tin due to the diffusion heat treatment, and the electricity at extremely low temperatures will deteriorate. This is because resistance increases.

Although the structure example shown in FIG. 7 is suitable for the bronze method or the external tin diffusion method, this structure has the drawback that the ratio of stabilized copper (ratio to parts other than stabilized copper) cannot be increased. For example, if the ratio of the stabilizing steel to the other parts is l=1, the diameter of the stabilizing steel will exceed 70% of the diameter of the wire. Furthermore, when manufacturing such a superconducting wire, the ratio of stabilizing copper in the composition of the superconducting wire is determined in advance and manufacturing is started, so there is a problem that the ratio of stabilizing copper cannot be changed unnecessarily.

By the way, superconducting wires used for superconducting power generators or large-capacity applications do not have sufficient current capacity if they are made only of strands, so they are generally made into stranded conductors.

In particular, in the case of compound-based superconducting wires, multiple superconducting wires 8 are designed as formed strands as shown in Figure 8, and the entire wire, including the space factor of the superconducting wires 8, has excellent mechanical strength. Twisted wires are used.

Moreover, when stranding the wires, in order to further increase the mechanical strength,
As shown in FIG. 9, a structural material 9 such as a stainless steel strip is composited in the center of the stranded wire.

Here, when designing the superconducting wire 8 as a shaped stranded wire, if the stabilized copper wire can be twisted into the shaped stranded wire, the superconducting wire 8 can be stabilized and easily realized. 111 The ratio of stabilizing copper can be easily adjusted depending on the number of pieces.
There is a point. However, when a superconducting stranded wire is used as a formed stranded wire using the external suzmetuki method, and the suzmetuki wire and stabilized copper wire are stranded and then subjected to diffusion heat treatment to produce a superconducting stranded wire, the Sn of the suzmetuki is absorbed during the diffusion heat treatment. There is a problem that the stabilized copper is contaminated by diffusion to the stabilized copper wire side, and the electrical resistance of the stabilized copper increases at extremely low temperatures.

The present invention has been made to solve the above problems,
A stabilized copper wire in which the ratio of stabilized copper can be easily controlled and the superconducting properties of the superconducting stranded wire can be easily stabilized, and
The object of the present invention is to provide a method for manufacturing a superconducting stranded wire that is excellent for AC use and has stable superconducting properties.

“Means for solving the problem” Claim! In order to solve the above problems, the invention described in
A stabilized copper wire that is stranded together with a superconducting wire containing two or more elements constituting a superconducting intermetallic compound, and is subjected to diffusion heat treatment together with the superconducting wire after the stranding, and includes a core made of pure copper and a core made of pure copper. It is provided with a diffusion prevention layer covering the core and a coating metal layer covering the diffusion prevention layer.

In order to solve the above problem, the invention described in claim 2 has the following features:
A plurality of stabilized copper wires each having a core made of pure copper and a diffusion prevention layer covering this core are assembled together with superconducting wires containing two or more elements constituting a superconducting intermetallic compound. The wires are twisted, and after the wires are twisted, a diffusion heat treatment is performed to generate a superconducting intermetallic compound.

``Function'' Since the stabilized copper strand is constructed by covering the pure copper core with a diffusion prevention layer, when the superconducting strand and the stabilized steel strand are stranded and then subjected to diffusion heat treatment, Even if an element contained in the wire diffuses toward the stabilized copper strand, this element will not diffuse into the core. Furthermore, since the stabilized copper wire and the superconducting wire are twisted, the ratio of the stabilized copper wire can be easily adjusted by adjusting the number of twisted wires, and the superconducting properties can be easily stabilized.

"Example" Figures 1 (a) to h) show an example of loading Nb3Si-based superconducting stranded wires using the method of the present invention and the in-situ method, and manufacturing superconducting stranded wires. In order to do this, first, the diameter number 1 is
A rod-shaped in-situ in-situ tip lO of about On+m is created. To create this in-situ ingot 10, a CuNb alloy of a specific composition or a Cu-Nb-
It can be obtained by melting a Sn alloy or the like using an arc melting method or the like.

This in-situ ingot 10 is made of Cu or Cu.
It has a structure in which countless Nb dendrites are dispersed inside a base made of -Sn alloy, and has poor workability.

Next, this in-situ ingot 10 is suitably subjected to a diameter reduction process such as forging, groove rolling, or wire drawing to create an in-situ wire 11 having a diameter of approximately 0.2 to 1 mm as shown in FIG. 1(b). .

Next, this in-situ strand 11 is subjected to a twisting process in which the wire is twisted at several pitches, and after being twisted, a final wire drawing process is performed to form the in-situ wire 12 shown in FIG. 1(c).
get. By reducing the diameter of the in-situ ingot 10 as described above, the Nb dendrites can be processed into fine filaments, and by performing the twisting process, the fine filaments can be twisted.

Subsequently, a Sn plating layer with a thickness of several μm to several lθ μm is formed on the outer periphery of the in-situ wire 12 to create the plating in-situ wire 14 shown in FIG. 1(d). A plurality of wires (seven in this example) are collected and twisted to create the twisted wire 15 shown in FIG. 1(e).

On the other hand, a composite body 16 shown in FIG. 1 ('') is created.

This composite i6 includes a core 17 made of pure copper, a diffusion prevention layer 18 made of Ta or Nb coated on the core 17, and a metal made of a Cu-Sn alloy coated on the outer peripheral surface of the diffusion prevention layer 18. It is made up of a coating layer 19, and is made by combining a copper rod, a Ta tube, and a Cu-Sn alloy tube. In this example, the entire core portion 17 is made of pure copper, but the core portion 17 may optionally be provided with reinforcing metal wire or the like.

Next, the composite body 16 is reduced in diameter to the same outer diameter as the stranded wire 15 to obtain a stabilized copper wire 20 shown in FIG. 1(g).

Next is the twisted wire! A plurality of stabilized copper wires 2o are prepared, and the plurality of stabilized copper wires 2o are alternately assembled and twisted as shown in FIG. 1(h). Then, this twisted wire is heated at 500 to 650℃ to several tens of
Diffusion heat treatment is performed by heating for several hours. Through this diffusion heat treatment, Sn diffuses into the Nb fibrous filament, Nb and Sn react, and a Nb*Sn intermetallic compound superconducting filament is generated. A superconducting stranded wire A shown in FIG. 1(h) in which the copper chloride wires 2o are twisted is obtained.

In the superconducting stranded wire A manufactured in this way, since the superconducting stranded wire material 22 and the stabilized copper wire 2o are twisted, the superconducting properties are extremely stable. In addition, inside the superconducting stranded wire 22, twisted Nb3S
Since the n-superconducting filament is provided, there is little loss when AC current is applied, and the structure is suitable as an AC superconducting wire for use in superconducting generators and the like.

Here, during the diffusion heat treatment, there is a possibility that Sn may diffuse from the tin layer existing on the outer periphery of the stranded wires 15 to the side of each stabilized copper wire 20. When Sn diffuses into the core 17 of the stabilized copper strand 20, the electrical resistance of the core 17 at low temperatures increases, which may impair the effect of stabilizing superconducting properties. However, in the stabilized copper wire 20,
Since the core portion 17 is covered with the diffusion prevention layer 18,
Even if the Sn of the stranded wires 15 in contact diffuses during the diffusion heat treatment, the diffusion is suppressed by the diffusion prevention layer 18, and the core 17h<Sn
will not be contaminated. Therefore, contamination of the core portion 17 of the stabilized copper wire 20 is prevented, and the superconducting stranded wire material 22 is stabilized, so that the superconducting strand A has excellent superconducting properties. Note that a metal coating layer 19 made of a Cu-Sn alloy is formed on the outer periphery of the stabilized copper wire 20, but this metal coating layer 19 is made of Cu-8n-P alloy, Cu-Sn-
It may be formed from a high resistance metal material such as a Ni alloy or a Cu-Ni alloy. However, the constituent material of the metal coating layer 19 is preferably an element that does not diffuse to the superconducting stranded wire material 22 side during the diffusion heat treatment and do not adversely affect the superconducting properties. In this respect, the Cu-Sn alloy not only does not have the above-mentioned effect, but also causes the metal in-situ line to 14 during the diffusion heat treatment.
It does not take Sn away from the sparrow layer. That is,
If the metal coating layer 19 is made of pure copper, there is a risk that a large amount of Sn in the tin plating layer will diffuse toward the stabilized copper wire 20 side during the diffusion heat treatment, reducing the amount of Nb1Sn superconducting intermetallic compound produced. Furthermore, when the stabilized copper element wire 20 and the superconducting stranded wire material 22 are twisted, if the number of each is adjusted appropriately, the ratio of the stabilized copper part to the superconducting conductor part can be easily adjusted to a desired value. can do.

FIG. 2 shows another example of the structure of the superconducting stranded wire. In this example, the superconducting stranded wire B consists of a superconducting strand 25 and a stabilized copper strand 26.
This structure has a structure in which a superconducting conductor B is formed by aligning a plurality of conductors and then aligning a plurality of conductors. The superconducting strands 25 used here are in-situ wires of the superconducting stranded wires A! It has the same structure as 4, and stabilized copper wire 2
6 has the same structure as the stabilized copper wire 20 of the superconducting stranded wire A.

Even with the superconducting stranded wire B having the structure shown in FIG. 2, the same effect as the superconducting stranded wire A described above can be obtained.

FIG. 3 shows a second structural example of a stabilized steel wire, in which a stabilized copper wire 30 has a core 31 made of pure copper and a diffusion prevention layer 32 made of Ta or Nb surrounding the outer periphery. It has a covered structure. Further, FIG. 4 shows a third structural example of the stabilized copper wire, in which the stabilized copper wire 35 of this example has a core portion 36 covered with a diffusion prevention layer 37, and the outer side of the stabilized copper wire 35 covered with a diffusion prevention layer 37. Covering layer 3
It has a structure covered with 8.

Even when the stabilized copper wire 3035 having the structure shown in FIGS. 3 and 4 is used, the same effect as in the example described above can be obtained.

FIG. 5 shows yet another structural example of the superconducting stranded wire, in which a plurality of (13 in the drawing) superconducting strands 114 are placed around the outer periphery of the stabilized copper strands 20 with gaps between them. Even if such a structure is adopted, the same effect as the above example can be obtained.

In the above embodiments, an example in which the present invention is applied to a method for manufacturing a stabilized copper wire for a Nb3Sn-based superconducting stranded wire and a method for producing a Nb3Sn-based superconducting stranded wire has been described. It goes without saying that the present invention can be applied to a method for producing stabilized copper wires for compound-based superconducting stranded wires or superconducting stranded wires such as.

"Manufacturing example" Made of Cu-Nb alloy with a diameter of 50 mm using the crucible melting method.
An in-situ ingot of 1Il was prepared, and this in-situ ingot was reduced in diameter by swaging and wire drawing to produce an in-situ wire of 0.215 mm. This in-situ wire was twisted at a pitch of 5o+o+ and further wire-drawn to a pitch of 0.2
An m+s in situ line was obtained.

Thereafter, a tin plating layer with a thickness of 30 μm was formed on the surface of the in-situ wire by electroplating, and seven in-situ wires after tin plating were further assembled to obtain a stranded wire with an outer diameter of 0.6 mm.

On the other hand, a core part with a diameter of 10 am made of pure copper with an RRR (residual resistance ratio) of 300, a Ta tube with an outer diameter of 11 mm and an inner diameter of 10041 mm, and a 6mm diameter tube with an outer diameter of 14.5 mm and an inner diameter of 11.5 mi
A composite body was obtained by integrating the tube bodies made of Sn bronze with a weight percent of Sn, and the diameter of the whole was reduced to 0.6+am to obtain a stabilized copper wire.

Next, prepare 6 of the stranded wires and 5 in-situ wires, twist each wire alternately as shown in FIG. And so. This strip conductor was placed at 550°C in an Nt gas atmosphere.
A superconducting conductor was obtained by performing diffusion heat treatment for 250 hours.

This superconducting conductor is 95O under a magnetic field of 10T (Tesla).
The critical current characteristics of A are shown. Moreover, this superconducting conductor exhibited extremely stable characteristics because superconducting twisted wires made of in-situ twisted wires and stabilized copper wires were twisted alternately.

"Example 2" The stabilized copper wire created in Example 1 was drawn to a diameter of 0.2 mm, and the in-situ wire created in Example 1 was further drawn to a diameter of 0.2 mm.
．． The wire is drawn to 2 mm, and four stabilized copper wires and three in-situ wires are twisted together as shown in Figure 2 to obtain a stranded wire, and 11 of these stranded wires are assembled to form a stranded wire, which is then subjected to diffusion heat treatment. A superconducting conductor having the structure shown in FIG. 2 was obtained.

This superconducting conductor also exhibited extremely stable superconducting properties similar to the superconducting conductor of Example 1.

"Effects of the Invention" As explained above, when a superconducting stranded wire is manufactured using the stabilized copper strands of the present invention, the superconducting Even if the element contained in the strand diffuses toward the stabilized copper strand, the element will not diffuse to the core side. Therefore, an increase in the electrical resistance of the core is prevented at extremely low temperatures.
This has the effect of favorably stabilizing the superconducting properties of the superconducting stranded wire. In addition, since the stabilized copper strands and superconducting strands are twisted together and heat treated to produce superconducting stranded wires, the ratio of stabilizing copper can be easily adjusted by the number of strands twisted, and the superconducting properties are stabilized. can be easily realized. Therefore, if a superconducting stranded wire is manufactured using the stabilized copper wire having the structure of the present invention, it is possible to provide a superconducting stranded wire that exhibits excellent stability even when AC current is applied.

[Brief explanation of the drawing]

FIGS. 1(a) to (h) show an example of the manufacturing method of the present invention. FIG. 1(a) is a cross-sectional view of an in-situ ingot, and FIG. 1(b) is a reduced diameter state of the in-situ ingot. FIG. 1(e) is a cross-sectional view of the in-situ line, FIG. 1(d) is a cross-sectional view of the met in-situ line, and FIG. 1(e) is a cross-sectional view showing the assembled state of the met in-situ line. Figure 1(f) is a cross-sectional view of the composite, Figure 1(g) is a cross-sectional view of a stabilized copper wire, Figure 1(h) is a cross-sectional view of a superconducting stranded wire, and Figure 2 is a cross-sectional view of a superconducting stranded wire. A cross-sectional view showing another example of
The figure is a sectional view showing a second structural example of a stabilized copper strand, FIG. 4 is a sectional view showing a third structural example of a stabilized copper strand, and FIG. 5 is a sectional view showing another example of a superconducting stranded wire. 6 is a cross-sectional view showing an example of a conventional stabilized copper bridge structure, FIG. 7 is a cross-sectional view showing another example of a conventional stabilized copper structure, and FIG. 8 is a conventional superconducting stranded wire. FIG. 9 is a perspective view showing another example of a conventional superconducting stranded wire. lO... In-situ ingot, 12... In-situ wire, 14... Metsuki in-situ wire (superconducting wire), 15... Twisted wire, 17... Core, 18... Diffusion prevention layer, I9 ...Cu-8n alloy layer, 20... Stabilized copper strand, 25... Superconducting strand, 26... Stabilized copper strand, 30° 35... Stabilized copper strand, 31 ,36・
... core, 32, 37... diffusion prevention layer.

Claims (2)

[Claims] (1) A stabilized copper wire that is stranded together with a superconducting wire containing two or more elements constituting a superconducting intermetallic compound, and subjected to diffusion heat treatment together with the superconducting wire after the stranding, with a core made of pure copper. A stabilized copper strand for a compound-based superconducting stranded wire, comprising a core part, a diffusion prevention layer covering the core part, and a coating metal layer covering the diffusion prevention layer. (2) A plurality of stabilized copper wires each having a core made of pure copper and a diffusion prevention layer covering this core along with superconducting wires containing two or more elements constituting a superconducting intermetallic compound. 1. A method for producing a compound-based superconducting stranded wire, which comprises gathering together, stranding, and then subjecting the stranded wire to diffusion heat treatment to generate a superconducting intermetallic compound.