JPH0419920A - Manufacture of nb3sn superconductor wire - Google Patents

Abstract

PURPOSE:To produce a sufficient amount of Nb3Sn superconductor fibers within a short time heat treatment by gathering a plurality of coated composite wires having an Sn coating layer formed on the outer circumferences of in-situ rods and carrying out heat treatment for diffusion after drawing. CONSTITUTION:A plurality of coated composite wires 14 prepared by putting in-situ rods 10 in the inside and coating the outer circumference of them with an Sn coating layer 13 are gathered and drawn to form a secondary composite wire 17 and then heat-diffusion treatment is carried out so as to diffuse Sn while the Sn coating layer 13 and the Nb fibers in the in-situ rods 10 are made close each other. Diffusion distance between Sn of the coating layer 13 and Nb superfine fibers is thus shortened. As a result, Nb superfine fibers and Sn are sufficiently reacted by the heat-diffusion treatment and Nb3Sn superconductor fibers are produced at sufficiently high production efficiency.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a method for manufacturing N b3S n superconducting wires used in toroidal magnets for nuclear fusion reactors, magnets for particle accelerators, magnets for superconducting generators, etc. .

``Prior art'' In superconducting wires, heat may be generated due to interlocking 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 Cu.

(2) Ultra-fine superconductor into a filament with a diameter of several μm to several tens of μm.

■Twisting multi-core wires.

■Use braided or formed 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.

Against this background, research and development is progressing, but the in-situ method has been known as a method for manufacturing superconducting wires with a structure in which countless ultra-fine superconducting fibers are arranged inside a metal base. There is.

To manufacture Nb3Sn-based superconducting wire using this in-situ method, a Cu-Nb-3n alloy or a Cu-Nb alloy with a predetermined composition is melted, and Nb dendrites are formed inside the Cu or Cu5n alloy matrix. Has a dispersed organization,
Moreover, the in-situ alloy l shown in Figure 1O has high workability.
Create.

Next, this in-situ alloy 1 is subjected to wire drawing, and the 11th
As shown in the figure, an in-situ rod 2 is prepared in which a large number of Nb fibers are closely distributed and arranged in a metal base. Subsequently, Sn plating is applied to the outer peripheral surface of the in-situ tube 2.
l! i 2 g is formed to create the strand 3 shown in FIG.

Next, the wire 3 is heat treated for a long time at a temperature slightly lower than the melting temperature of Sn. This heat treatment causes the plating layer 2a to diffuse into the interior of the in-situ rod 2 and disappear. Then, the S
By reacting n with the Nb fibers inside the cable wire 3, Nb3Sn superconducting fibers can be generated, and thereby the Nb3Sn superconducting wire 5 having the structure shown in FIG. 13 can be obtained.

"Problems to be Solved by the Invention" In the method for manufacturing the superconducting wire 5, Sn in the plating layer 2a is diffused from the outer peripheral side of the wire 3 to the inside.
Even when the diffusion heat treatment is sufficiently performed over a long period of time, there is a problem in that Sn is not sufficiently diffused to the center of the wire 3. As a result, the center side of the superconducting wire 5! 'i
There is a problem in that the critical current density decreases due to the formation of an unreacted region where b3S n is not produced.

In addition, since the plating layer 2a is formed on the outer circumferential surface of the in-situ rod 2, it is necessary to perform heat treatment for a long time at a temperature slightly lower than the melting point of Sn so that the plating layer 2a does not melt. There was a problem that the heat treatment time was long.

In addition, the superconducting wire 5 manufactured by the above method undergoes superelectric volatilization*
When used for alternating current applications such as mi, there was a problem of electromagnetic instability.

The present invention was made to solve the above problems, and it is possible to generate a sufficient amount of Nb3Sn superconducting fibers with a shorter heat treatment time than before, and the superconducting fibers have a small diameter and are highly electromagnetically stable. , an object of the present invention is to provide a Nb, Sn superconducting wire with a high critical current density.

"Means for Solving the Problems" In order to solve the problems described above, the present invention uses an in-situ alloy in which Nb dendrites are dispersed inside a base made of Cu or a Cu alloy. The in-situ rod is formed by drawing a Cu or Cu alloy, and one or more of the in-situ rods are made of Cu or Cu.
A primary composite wire is formed by inserting it into a tube made of U alloy and further reducing the diameter.A coating layer of Sn is formed on this primary composite wire to form a coated composite wire, and then this coated composite wire is formed. A secondary composite wire is made by collecting multiple wires and inserting them into a tube made of Ta or Nb, and then inserting them into a tube made of Cu or Cu alloy and reducing the diameter at least once. At the same time, this secondary composite wire is subjected to diffusion heat treatment to diffuse the Sn of the coating layer into the interior of the base, thereby producing Nb+Sn superconducting fibers.

"Function" A plurality of coated composite wires with a Sn coating layer formed on the outer surface of the in-situ rod are assembled and subjected to diffusion heat treatment after being reduced in diameter, so the distance between the Sn and Nb fibers of the coating layer becomes short, and the Sn diffusion distance becomes shorter.

Therefore, the reaction efficiency of Sn and Nb is improved, and the production efficiency of NtgSn is improved. In addition, a plurality of in-situ rods having Nb fibers were assembled and reduced in diameter, and fTI was added to the r-water.
Since it is possible to process the -Nh wound to a sufficiently small diameter, superconducting fibers with a sufficiently small diameter can be obtained, and the magnetic stability is improved.

The present invention will be explained in more detail below.

FIGS. 1 to 9 show an embodiment of the method of the present invention, and in order to manufacture a superconducting wire by implementing the method of the present invention,
First, the in-situ alloy 9 shown in FIG. 1, which is equivalent to the in-situ alloy l shown in FIG. An in-situ rod 10 shown in FIG.

This in-situ rod 10 has a structure in which Nb fibers are dispersed inside a base made of Cu or Cu alloy.
The size is about several tens of μm. The alloying elements added to the Cu alloy include Sn Ti, A1. M
Examples include magnetic elements such as n, Ag, Be, Fe, Co, and Ni.

Next, the in-situ rod IO is covered with a tube 11 made of Cu or a Cu alloy as shown in FIG. Get 12.

Subsequently, a coating layer 13 such as a Sn plating layer is formed on the outer periphery of this primary composite wire 12 to create a coated composite wire 14 shown in FIG. 5. Note that the coating layer 13 may be formed by winding Sn tape or Sn foil.

Once the coated composite wire 14 is obtained, a plurality of coated composite wires 14 are assembled as shown in FIG. 6, and inserted into a tube body 15 made of Ta or Nb. It is inserted into the tubular body 16 and then subjected to diameter reduction processing to obtain the secondary composite wire 17 shown in FIG.

This secondary composite wire 17 includes a consolidated part 18 at the center obtained by consolidating the coated composite wire 14, a diffusion prevention layer 19 provided on the outside of this consolidation part 18, and an outside of the diffusion prevention fi 19. It is composed of a stabilizing layer 20 provided on. The internal structure of the compaction section 18 is as shown in FIG. That is, it is composed of a consolidated in-situ part 21 formed by consolidating the in-situ rod 10, a consolidated layer 22 provided surrounding this consolidated in-situ part 21, and a boundary layer 23 that partitions adjacent consolidated layers 22. .

The consolidation in-situ portion 21 is an in-situ rod l.
Since it is formed by consolidating O, it has a structure in which ultrafine Nb fibers are dispersed inside a base made of Cu or Cu alloy. The Nb fibers in the in-situ part 21 are the Nb fibers dispersed inside the in-situ rod lO.
Nb fibers with a diameter of 1 μm or less, which is much smaller than the fibers in the above, are dispersed.

The compacted layer 22 is formed by compacting the tubular body 11, and is therefore made of Cu or a Cu alloy. In addition, the boundary layer 23 is made of Sn formed on the peripheral surface of the primary composite wire 12
It is formed by compressing and deforming the covering layer 13 of.

The tubular body 15 is heated during the diffusion heat treatment performed in a subsequent process.
This is provided to prevent unnecessary elements from diffusing into the tube 16 side and contamination of the tube body 16, and its constituent material is a metal material with a melting point of 800°C or higher,
Ta and Nb, which have low reactivity toward u, are preferably used.

Subsequently, the above-described secondary composite wire 17 is subjected to a diffusion heat treatment in which the secondary composite wire 17 is heated at 500 to 650° C. for several tens of hours to several hundreds of hours. Through this diffusion heat treatment, Sn in the boundary layer 23 begins to diffuse into the inside of the consolidated layer 22, and when the Sn reaches the consolidated in-situ WI 21, it reacts with the Nb fibers to generate Nb3Sn superconducting fibers.

By proceeding with the above diffusion reaction and producing NbzSn superconducting fibers, an Nb3Sn superconducting wire 25 having the structure shown in FIG. 9 can be obtained.

In this superconducting wire 25, a superconducting portion 26 formed by dispersing Nb3Sn superconducting fibers in a metal base is provided with a diffusion prevention 51.
9 and a stabilizing FW 20.

When Sn diffuses as described above, in the consolidated in-situ portion 21 of the secondary composite wire 17, as shown in FIG. , Sn diffusion distance can be made smaller than before. Therefore, as a result of the sufficient reaction between the Nb ultrafine fibers and Sn, the production rate of NbsSn superconducting fibers can be sufficiently increased.

In addition, when Sn diffuses, the diffusion prevention layer 19 provided on the outer periphery of the consolidation in-situ portion 26 or the Sn to the stabilizing layer 20 side
Since diffusion of Sn is prevented, contamination of the stabilizing layer 20 by Sn is prevented. Incidentally, it is not preferable if Sn diffuses into the stabilizing layer 20 because the electrical resistance of the stabilizing layer 20 will increase when it is cooled to an extremely low temperature.

This superconducting wire 25 is used after being cooled to an extremely low temperature using a coolant such as liquid helium. In the superconducting wire 25, contamination of the stabilizing layer 20 provided on the outer periphery with Sn is prevented, so the electrical resistance of the stabilized N20 at extremely low temperatures becomes a sufficiently low value, and the stability of the superconducting wire 25 is sufficient. It will be expensive.

In addition, even if the superconducting wire 25 transitions to normal conductivity,
Since the stabilizing layer 20 is provided, the stabilizing layer 20 can be used as a current path, and burning of the superconducting wire 25 can be prevented.

Furthermore, since it has a structure in which the stabilizing layer 20 is combined on the outer periphery of the superconducting wire 25, it is more compact than the conventional superconducting wire, which requires adding a new stabilizing material to the outside. It can be made into a structure. The superconducting wire 25 has a stabilizing layer 20 and a diffusion prevention layer inside it! 9, these act as reinforcing materials and have higher mechanical strength than conventional superconducting wires.

In addition, a plurality of in-situ rods 10 shown in FIG.
A secondary composite wire 17 is obtained by performing diameter reduction processing, and then collecting a plurality of wires and performing diameter reduction processing, and based on this secondary composite wire 17, Nb3Sn
Since this method produces superconducting fibers, the diameter of the superconducting fibers can be made even smaller than that of the conventional method. Therefore, the superconducting wire 25 has superconducting fibers that are thinner than conventional ones inside the base, and therefore has excellent superconducting properties and excellent electromagnetic stability.

"Example" A Cu-30vt%Nb alloy (ingot with a diameter of 50 mm) was created by an induction heating melting method, and this alloy was forged to obtain an in situ lot with a diameter of 15 mm. Next, this in-situ rod has an outer diameter of 17 mm and an inner diameter of 16 m.
It is covered with a pipe made of pure copper with a diameter of l. OLll
A linear composite line of m was obtained.

Next, this primary composite wire is electroplated to a thickness of 30 μm.
A coating layer of Sn was formed to obtain a coated composite wire.

Next, 37 coated composite wires were bundled and inserted into a Ta tube with an outer diameter of 8.5 mm and an inner diameter of 7.5 mm, and then the whole was inserted into a copper tube with an outer diameter of 15 mm and an inner diameter of 91 mm, and the wires were shrunk. The diameter is 1. A secondary composite wire with On+m stabilized copper was obtained.

Next, this secondary composite wire was heated at 600°C for 1.0 days,
A NbjSn superconducting wire was produced by reacting Nb ultrafine fibers with Sn to avoid producing ultrafine superconducting fibers. The atmosphere in which the heat treatment was performed was an inert gas atmosphere such as Ar gas, N gas, or a vacuum atmosphere.

Nb3Sn superconducting m M manufactured as explained above
1m III-m 7m / Tha9+n 1M
When m[rh +-, a- were measured, the entire wire showed an excellent value of Jc=about 450 A/mm'.

Further, when the structure of the obtained superconducting wire was observed, it was found that the ultrafine Nb fibers in the in-situ superconducting portion were sufficiently reacted to become NbaSn. Furthermore,
The obtained Nb3Sn superconducting wire has a diameter of 005μ
The superconducting fibers were mainly composed of superconducting fibers with a diameter of 0.01 μm or less and a diameter of 0.01 μm or less.

Furthermore, for comparison, Nb3Sn superconducting wires were manufactured using the conventional method shown in FIGS. 10 to 13.

When the critical current density of this Nb, Sn superconducting wire was measured in the magnetic field of IOT, it was found to be Jc-about 270 A/mm'.

In addition, this i'it)+Sn superconducting wire was mainly composed of superconducting fibers with a diameter of 0.5 μm or less and 0.1 μm or more.

"Effects of the Invention" As explained above, according to the present invention, an in-situ lot is composited inside, the outer periphery is coated with Sn to form a secondary composite wire, and then a diffusion process is performed to form a Sn coating layer. Since Sn is diffused after bringing the Nb fibers in the in-situ rod close to each other, the diffusion distance between the Sn and Nb ultrafine fibers of the coating layer can be reduced. Therefore, by the diffusion heat treatment, the Nb ultrafine fibers and Sn can be sufficiently reacted, and Nk13Sn superconducting fibers can be produced with sufficiently high production efficiency.

Furthermore, a plurality of in-situ rods having Nb fibers with a diameter of several μm to several tens of μm are assembled, and a diameter reduction process is performed to form a secondary wire having ultrafine Nb fibers.
Since superconducting wires are manufactured by subjecting strands to diffusion heat treatment, ultrafine Nb fibers can be processed into sufficiently small diameters. Therefore, the obtained superconducting wire has ultrafine Nb3Sn superconducting fibers with a diameter smaller than that of the conventional wire in the metal base, and therefore has excellent 1aWL chemical stability.

In addition, since the stabilizing layer is separated from the Sn coating layer by the diffusion prevention layer and is provided on the outer periphery of the superconducting wire, the stabilizing layer is not contaminated by the diffusion of Sn during diffusion heat treatment, and the ultra-low temperature The electrical resistance of the stabilizing layer can be maintained low, and a superconducting wire with excellent stabilization of superconducting properties can be obtained.

Furthermore, since the stabilizing material is compounded on the outer periphery of the superconducting wire, it is possible to obtain a superconducting wire that is smaller and lighter than conventional superconducting wires that require a separate external stabilizing material. The stabilizing material and anti-diffusion layer also serve as reinforcing materials.
A superconducting wire with high mechanical strength can be obtained.

[Brief explanation of drawings]

Figures 1 to 9 are for explaining an example of the method of the present invention. Figure 1 is a sectional view of an in-situ alloy, Figure 2 is a sectional view of an in-situ rod, and Figure 3 is an in-situ rod and a tube body. Figure 4 is a cross-sectional view showing the primary composite wire, Figure 5 is a cross-sectional view of the covered composite wire, and Figure 6 is a cross-sectional diagram showing the composite deafness.
The figure is a sectional view showing the assembled state of the coated composite wire, FIG. 7 is a sectional view of the secondary composite wire, FIG. 8 is a sectional view showing the in-situ consolidation part, FIG. 9 is a sectional view of the Nb3Sn superconducting wire, and FIG. Figures 1 to 13 are for explaining the conventional method. Figure 1O is a cross-sectional view of the in-situ alloy, Figure 11 is a cross-sectional view of the in-situ rod, Figure 12 is a cross-sectional view of the coated composite wire, and Figure 13 is a cross-sectional view of the in-situ rod. is conventional Nb. FIG. 2 is a cross-sectional view of a Sn superconducting wire. 19... In-situ alloy, 10... In-situ lot, 11- Tube body, 12- Primary composite wire, 13 Covering layer,
14... Covered composite wire, 15... Tube body, 16 Tube body, 1
72nd order composite line, 19 diffusion prevention layer, 20... stabilization layer,
21... Consolidation in situ part, 23. Boundary layer, 25
Superconducting wire, 26. In-situ superconducting section. Applicant Superconducting Power Generation Related Equipment and Materials Technology Research Association Figure 1 F-10 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13

Claims (1)

[Claims] Using an in-situ alloy in which Nb dendrites are dispersed inside a base made of Cu or a Cu alloy, this in-situ alloy is wire-drawn to disperse Nb fibers inside the base made of Cu or a Cu alloy. one or more Cu in-situ rods.
Alternatively, the primary composite wire is formed by inserting it into a tube made of a Cu alloy and further reducing the diameter, and at the same time forming a coating layer of Sn on this primary composite wire to form a coated composite wire. A secondary composite wire is obtained by collecting a plurality of composite wires and inserting them into a tube made of Ta or Nb, and then inserting them into a tube made of Cu or Cu alloy and performing diameter reduction processing one or more times. At the same time, this secondary composite wire is subjected to diffusion heat treatment to diffuse Sn in the coating layer to the inside of the base, forming Nb_3S.
Nb_3S characterized by producing n superconducting fibers
A method for manufacturing n-superconducting wire.