JP2878390B2 - Method of manufacturing Nb (3) Sn superconducting wire for superconducting generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" The present invention relates to Nb used for a superconducting generator magnet.
_{The present} invention relates to a method for manufacturing a ₃ Sn superconducting wire.

"Conventional technology" In a superconducting wire, heat may be generated due to the movement of quantum flux lines, and in such a case, normal conduction buds are partially generated in the superconducting wire, and the entire superconducting wire becomes There is a risk of dislocation to the normal conduction state. Therefore, in order to stabilize the superconducting wire by preventing such magnetic instability, normal conduction dislocation, and the like, conventionally, the following technology has been adopted.

A superconductor is buried inside a stable base material of good conductivity such as Cu. In particular, the stabilizing base material is formed from high-purity Cu.

The superconductor is thinned into a filament having a diameter of several μm to several tens μm.

Twist multi-core wire.

Adopt a braided or formed stranded wire structure.

Intermetallic compound superconductors are extremely hard and brittle,
When the mechanical strain is applied, the superconductivity tends to deteriorate. Therefore, a reinforcing material is added to the superconducting wire to prevent the mechanical strain from being applied.

Under the above background, research and development have been promoted, but conventionally, an in-situ method is known as a method of manufacturing a superconducting wire having a structure in which countless superfine superconducting fibers are arranged inside a metal base. I have.

In order to produce a Nb ₃ Sn superconducting wire by this in-situ method, a Cu—Nb—Sn alloy or Cu—Nb alloy of a predetermined component is melted, and Nb dendrites are formed inside a Cu or Cu—Sn alloy matrix. No. 11 which has a structure in which crystals are dispersed and has high processability
An in-situ ingot 1 shown in FIG.

Next, the in-situ ingot 1 is subjected to a drawing process to form an in-situ rod 2 in which a large number of Nb fibers are closely arranged and dispersed in a metal matrix as shown in FIG. Subsequently, an Sn plating layer 2a is formed on the outer peripheral surface of the in-situ rod 2 to form a wire 3 shown in FIG. 13, and then the wire 3 is subjected to a diffusion heat treatment to remove Sn of the plating layer 2a. by by diffusing the inner side of the line 3 is reacted with the fibers of Nb, it is possible to produce Nb ₃ Sn superconducting wire 5 of the structure shown in Figure 14.

"Problem to be Solved by the Invention" In the method of manufacturing the superconducting wire 5, the plating layer 2a
Since Sn is diffused from the outer peripheral side to the inner side of the strand 3, even when the diffusion heat treatment is sufficiently performed for a long time.
There was a problem that Sn was not sufficiently diffused to the center side of the strand 3. As a result, an unreacted region where Nb ₃ Sn is not generated is generated on the center side of the superconducting wire 5, causing a problem that the critical current density is reduced. Further, when the superconducting wire 5 manufactured by the above method is used for alternating current such as a superconducting generator, there is a problem that it is electromagnetically unstable.

The present invention has been made to solve the above problems,
A sufficient amount of Nb ₃ Sn superconducting fiber can be produced,
In addition, the diameter of the superconducting fiber is small and the electromagnetic stability is high, and since it has a stabilizing material, there is no risk of burning even in the event of normal conduction transition, and it has sufficient strength for superconducting generators An object of the present invention is to provide an Nb ₃ Sn superconducting wire.

"Means for Solving the Problems" The present invention provides a resinous crystal of Nb for solving the above problems.
Form an in-situ rod dispersed inside a substrate made of Cu or Cu alloy,
After covering with a tube made of Cu or Cu alloy, diameter reduction processing is performed to form a primary composite wire, and a plurality of these primary composite wires are assembled and inserted into a tube made of Cu or Cu alloy. Perform a diameter reduction process at least once to obtain a secondary composite wire, and form a diffusion prevention layer on the outer periphery of the Cu stabilizing material to create a stabilizing material. A plurality of the secondary composite wires are arranged in a state surrounding the periphery of the stabilizing material, and a tube made of Cu or a Cu alloy is further covered on the outside thereof, and thereafter, a wire is created by performing a diameter reduction process. Then, a covering layer of Sn is formed on the strand to form a covering strand. Subsequently, the covering strand is subjected to a diffusion heat treatment, and the Sn of the covering layer is transferred to a side of the stabilizing material on the inner side of the strand. To generate Nb ₃ Sn superconducting fibers on the peripheral side of the stabilizing material.

"Function" 2 with Nb fibers outside the stabilizer provided in the center
From the coating layer formed on the outside of these
Is diffused, the diffusion distance of Sn when diffusing to the Nb fiber is shortened, and the generation efficiency of Nb ₃ Sn is improved. Also, N
b. In-situ rods with fibers of diameter b
Since a plurality of the next composite wires are assembled and further reduced in diameter, the Nb fiber can be processed to a sufficiently small diameter, and a superconducting fiber having a sufficiently small diameter can be obtained. Further, since the stabilizing material is compounded inside the superconducting wire, the stabilizing material stabilizes the superconducting characteristics and increases the mechanical strength.

 Hereinafter, the present invention will be described in more detail.

FIGS. 1 to 10 show one embodiment of the method of the present invention. In order to manufacture a superconducting wire by carrying out the method of the present invention, first, FIG. The in-situ ingot 1 shown in FIG. 1 is prepared, and the in-situ rod 10 shown in FIG. 1 is prepared by reducing the diameter of the ingot 1 by forging, rolling or drawing. This in-situ rod 10 has a structure in which Nb fibers are dispersed inside a matrix made of Cu or a Cu alloy.
The Nb fiber has a diameter of several μm to several tens μm. Incidentally, as alloying elements to be added to the Cu alloy,
Examples include magnetic elements such as Sn, Ti, Al, Mn, Ag, Be, Fe, Co, and Ni.

Next, as shown in FIG.
A tube 11 made of Cu or Cu alloy is covered, and then plastic working such as forging is performed, and the diameter is reduced to obtain a primary composite wire 12 shown in FIG.

Once the primary composite wire 12 is obtained, a plurality of the primary composite wires 12 are assembled as shown in FIG. 4 and inserted into a tube 13 made of Cu or a Cu alloy. 2 shown in Fig. 5
The next composite line 14 is obtained. It is preferable that the metal material constituting the tube 13 be the same as the material constituting the tube 11 used previously. In the secondary composite line 14,
The fiber has a structure in which fibers having a finer diameter than the Nb fibers dispersed in the primary composite wire 12 are dispersed in the metal matrix.

On the other hand, a stabilizing material 15 shown in FIG. 6 made of pure copper such as oxygen-free copper is prepared, and a diffusion preventing layer 16 made of a metal material such as Ta or Nb is formed around the stabilizing material 15 to stabilize the material. Material
Create 17. The diffusion prevention layer 16 is provided to prevent unnecessary elements from diffusing into the stabilizer 15 and prevent contamination of the stabilizer 15 during a diffusion heat treatment performed in a later step, Its constituent material is a metal material with a melting point of 800 ° C or higher, and Ta or Nb with low reactivity to Cu.
Etc. are preferably used. Further, the means for forming the diffusion prevention layer 16 may cover the outer periphery of the stabilizing material 15 with a metal tube,
Means such as winding of a metal tape or plating can be appropriately selected and used.

After the diffusion preventing layer 16 is formed, the secondary composite wires 14 are arranged and provided over the entire circumference of the stabilizing material 17 as shown in FIG.

If the secondary composite wire 14 is attached, a tube body 14 made of Cu or Cu-Sn alloy or the like is covered on the outer side as shown in FIG. The wire 20 shown in FIG. 8 is created by reducing the diameter to a wire diameter equivalent to the wire.

Next, a covering layer 21 such as a Sn plating layer is formed on the outer periphery of the strand 20 to form a covering strand 22 shown in FIG. The coating layer 21 may be formed by winding Sn tape or Sn foil.

Subsequently, a first heat treatment of heating the above-described coated wire 22 at a temperature of 100 ° C. or higher and a temperature lower than the melting point of Sn, more preferably at 180 ° C. to 220 ° C. for several tens hours to several hundred hours is performed.
A second heat treatment of heating at a temperature higher than the melting point of about 250 ° C. for about several tens of hours, followed by a third heat treatment of heating at 300 to 450 ° C. for about tens of hours, and then 500 to 650
A final diffusion heat treatment of heating at ℃ for tens to hundreds of hours is performed.

In the case of the heat treatment of each stage described above, in the first heat treatment, Sn
By heating at a temperature lower than the melting point of the coating layer 21, Sn of the coating layer 21 can be diffused into the inside of the strand 20 and the coating layer 21 can be eliminated while preventing burn-through of the coating layer 21. Further, by successively heating in the second heat treatment and the third heat treatment, Sn can be sufficiently diffused into the inside of the strand 20 while preventing generation of a Cu-Sn compound or the like. Then, by performing the final diffusion heat treatment, the Nb ultrafine fiber inside the strand 20 reacts with Sn to generate Nb ₃ Sn superconducting fiber, and the superconducting wire 23 having the structure shown in FIG. 10 can be obtained.

When Sn diffuses as described above, in the strand 20,
Since the ultrafine fibers of Nb are dispersed on the outer peripheral side, Sn
Can be made shorter than before. Therefore, as a result of the Sn reacting with the Nb ultrafine fiber, the generation rate of the Nb ₃ Sn superconducting fiber can be sufficiently increased.

When Sn diffuses into the inside of the strand 20 during the heat treatment, the diffusion preventing layer 16 provided on the outer periphery of the stabilizing material 15 prevents the diffusion of Sn to the stabilizing material 15 side. Prevention of contamination by 15 Sn. In addition, Sn was added to the stabilizer 15 made of pure Cu.
Seems to diffuse, stabilizing material when cooled to cryogenic temperatures
It is not preferable because the electrical resistance of the device increases.

In the superconducting wire 23 manufactured as described above, a stabilizing material 24 made of pure Cu is provided at a central portion, a diffusion prevention layer 25 is formed on a peripheral surface thereof, and an in-situ superconducting portion is formed on an outer periphery of the diffusion prevention layer 25. 26 is formed.

The superconducting wire 23 is used after being cooled to an extremely low temperature by a coolant such as liquid helium. In the superconducting wire 23, the contamination of Sn to the stabilizing material 24 provided at the center is prevented, so that the electric resistance of the stabilizing material 24 at a cryogenic temperature is a sufficiently low value, and the stability of the superconducting wire 23 is It will be high enough. Further, even if the superconducting wire 23 undergoes a normal-conductivity transition, since the stabilizing material 24 is provided, the stabilizing material 24 can be used as a current path, and burning of the superconducting wire 23 can be prevented.

Furthermore, since the structure is such that the stabilizing material 24 is compounded at the center of the superconducting wire 23, it is more compact than a conventional superconducting wire that needed to additionally add a stabilizer outside. Can be structured. The superconducting wire 23 has a stabilizing material 24 and a diffusion preventing layer 25 inside thereof, so that they function as a reinforcing material, and have higher mechanical strength than a conventional superconducting wire.

In addition, the first having Nb fibers having a diameter of several μm to several tens μm.
After reducing the diameter of the in-situ rod 10 shown in FIG.
Since the superconducting fiber of Nb ₃ Sn is generated based on 20, the superconducting fiber can have a much smaller diameter than before.
Therefore, the obtained superconducting wire 23 has superconducting fibers finer than the conventional superconducting fiber inside the base, so that it has excellent superconducting characteristics and also has excellent electromagnetic stability.

"Example" A Cu-40wt% Nb alloy (ingot with a diameter of 50mm) was prepared by the induction heating melting method, and this alloy was forged to form a diameter.
A 16mm in-situ rod was obtained. Next, cover the in-situ rod with a pure Cu tube with an outer diameter of 17 mm and an inner diameter of 16.5 mm,
A primary composite wire having a diameter of 1.0 mm was obtained by wire drawing.

Next, bundle 91 composite wires to make outer diameter 13.5mm, inner diameter 11.5mm
Into a pure Cu tube, and reduce the diameter to 1.0 mm.
The following composite line was obtained.

In addition, a pipe made of pure Cu with an outer diameter of 17 mm and an inner diameter of 16.5 mm
Insert a tube made of Ta with a diameter of 16 mm and an inner diameter of 14.5 mm,
After inserting a 14 mm pure Cu rod, the whole was reduced in diameter to 14 mm to obtain a stabilized material.

Next, 47 secondary composite wires are arranged and attached to the outer periphery of the stabilizing material, and an outer diameter of 17 mm and an inner diameter of 16.5
The tube was covered with a pure Cu tube having a diameter of 0.4 mm, and the diameter was reduced to 0.4 mm by a diameter reducing process to obtain a strand.

Next, Sn plating is performed on this wire by electroplating,
A coating layer of Sn plating was formed to obtain a coated strand, and the coated strand was heated at 180 ° C. for 250 hours to dissipate the coating layer.
Heating at 0 ° C for 50 hours and 350 ° C for 50 hours to promote the diffusion of Sn inside the wire, and finally performing diffusion heat treatment at 550 ° C for 360 hours to convert the Nb ultrafine fiber and Sn inside the wire. A superconducting wire was manufactured by reacting to produce a superfine superconducting fiber. The atmosphere for the heat treatment was an inert gas inert gas such as an Ar gas or a N ₂ gas or a vacuum atmosphere.

When the critical current density (Jc) of the Nb ₃ Sn superconducting wire manufactured as described above was measured in a magnetic field of 10 T, it showed an excellent value of Jc = about 1200 A / mm ² .

Also, when the structure of the obtained superconducting wire was observed,
It was found that the ultrafine Nb fibers in the in-situ superconducting portion reacted sufficiently to form Nb ₃ Sn.

[Effects of the Invention] As described above, according to the present invention, a primary composite wire obtained by providing a stabilizing material on the center side of a strand and reducing the diameter of an in-situ rod having Nb fibers on the outer periphery of the stabilizing material is provided. Further, secondary composite wires having ultra-fine fibers formed by reducing the diameter are arranged, and the Sn of the coating layer formed on the outer periphery thereof is diffused, so that when the Sn of the coating layer diffuses to the inner side of the secondary composite wire. Can be reduced, and the diffusion distance between the Sn and Nb ultrafine fibers of the coating layer can be reduced. Therefore, the Nb ultrafine fiber and Sn can be sufficiently reacted by the diffusion heat treatment, and the Nb ₃ Sn superconducting fiber can be generated with a sufficiently high production efficiency.

Furthermore, a plurality of in-situ rods having Nb fibers having a diameter of several μm to several tens μm are assembled, and a process of reducing the diameter is further performed as necessary to form a secondary composite wire having Nb ultrafine fibers. Since the superconducting wire is manufactured by assembling the composite wires, reducing the diameter, and performing diffusion heat treatment, the ultrafine fibers of Nb can be processed into a sufficiently small diameter. Therefore, the obtained superconducting wire is an ultrafine Nb ₃ Sn with a smaller diameter
Since it has superconducting fibers, it has the feature of being excellent in electromagnetic stability.

In addition, since the stabilizing material of the structure covered with the diffusion prevention layer is compounded at the center of the superconducting wire, the stabilizing material is not contaminated by the diffusion of Sn during the diffusion heat treatment, and the stabilizing material at extremely low temperatures is used. Can be kept low, and a superconducting wire excellent in stabilizing superconducting characteristics can be obtained.
Furthermore, since a stabilizer is compounded inside the superconducting wire,
A superconducting wire that is smaller and lighter than a conventional superconducting wire that required the addition of a separate stabilizing material outside can be obtained. A superconducting wire having high strength can be obtained.

[Brief description of the drawings]

1 to 10 are views for explaining an example of the method of the present invention. FIG. 1 is a sectional view of an in-situ rod, and FIG.
The figure is a cross-sectional view showing the combined state of the in-situ rod and the tube, FIG. 3 is a sectional view showing the primary composite line, FIG. 4 is a sectional view showing the assembled state of the primary composite line, and FIG. FIG. 6 is a cross-sectional view of a stabilizing material, FIG. 7 is a cross-sectional view of a composite state, FIG. 8 is a cross-sectional view of a strand, FIG. 9 is a cross-sectional view of a covering strand, FIG. The figure is a cross-sectional view of the superconducting wire, and FIGS.
The figure shows an example of a conventional method for manufacturing a superconducting wire.
11 is a cross-sectional view of an in-situ ingot, FIG. 12 is a cross-sectional view of an in-situ rod, FIG. 13 is a cross-sectional view of a sheath wire,
FIG. 14 is a sectional view of a superconducting wire. 10 ... in-situ rod, 11 ... tubular body, 12 ... primary composite wire, 13 ... tubular body, 14 ... secondary composite wire, 15 ... stabilizer, 16 ... coating layer, 20 ... Element wire, 21 ... Coating layer, 23 ...
Superconducting wire, 24 Stabilizer, 25 Diffusion prevention layer, 26
In-situ superconducting unit.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Goto 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Electric Wire Co., Ltd. (72) Inventor Hiroyuki Hayakawa 1-5-1, Kiba, Koto-ku, Tokyo Fuji Electric Cable (56) References JP-A-2-109212 (JP, A) JP-A-63-133406 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01B 13/00 H01B 12/10

Claims (1)

(57) [Claims] 1. An in-situ rod formed by dispersing a resinous crystal of Nb inside a substrate made of Cu or Cu alloy, and reducing the diameter of the in-situ rod after covering the tube made of Cu or Cu alloy. To form a primary composite line, and then assemble a plurality of the primary composite lines into Cu or Cu
Inserting into a tube made of alloy and reducing the diameter one or more times to obtain a secondary composite wire, and forming a diffusion prevention layer on the outer periphery of a stabilizer made of Cu to create a stabilizing material ,
Around the stabilizing material, a plurality of the secondary composite wires are arranged in a state of surrounding the stabilizing material, and a tube made of Cu or Cu alloy is further covered on the outside thereof. Thereafter, a wire is formed by performing diameter reduction processing, and then a coating layer of Sn is formed on the wire to form a coated wire, and then, the coated wire is subjected to diffusion heat treatment to form Sn of the coating layer. is diffused into the stabilizing material surrounding the side of the inner side of the strand, Nb ₃ Sn method of manufacturing a superconducting generator for Nb ₃ Sn superconducting wire superconducting fibers, characterized in that to produce the perimeter of the stabilizing material.