JPH0735562B2 - Method for producing fiber-dispersed superconducting wire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a superconducting wire with improved critical current characteristics in a high magnetic field region, such as a toroidal magnet for a fusion reactor, a magnet for a particle accelerator, and a superconductivity. The present invention relates to a method for manufacturing a fiber-dispersed superconducting wire used for a generator magnet or the like.

“Prior Art” When a Cu—Nb—Sn ternary alloy having a predetermined component is melted, an ingot having a structure in which dendrite of Nb is dispersed in a copper alloy matrix and having high workability can be obtained. Then, by subjecting this ingot to a wire drawing process or the like and subjecting it to a strong process, it is possible to obtain an in-situ rod in which a large number of Nb fibers are in close contact and dispersedly arranged in a copper alloy matrix. ) Known as the law. Further, the in-situ rod of the composition produced by adopting the in-situ method is subjected to a diffusion heat treatment to generate an Nb ₃ Sn superconducting intermetallic compound, thereby producing a fiber-dispersed Nb ₃ Sn superconducting wire. ing.

It is also known that the critical current characteristics of a superconducting intermetallic compound in a high magnetic field region can be improved by adding a third element such as Ti to a superconducting intermetallic compound such as Nb ₃ Sn.

Therefore, conventionally, a method of compounding the third element inside the in-situ rod has been carried out for the purpose of improving the critical current characteristics in the high magnetic field region of the fiber-dispersed superconducting wire manufactured by the in-situ method.

Here, in general, as a method of adding the third element in the case of producing a fiber-dispersed superconducting wire using the in-situ method, the third element is added in advance when the Cu—Nb—Sn alloy is melted. The method has been adopted.

If a third element is added to produce a fiber distributed Nb ₃ Sn superconducting wire upon dissolution of the "invention will to Problems Solved" However Cu-Nb-Sn alloy, a problem resulting in disadvantages as described below It was

(1) Since the added third element is consumed in the melting step or the casting step, the content of the third element in the obtained in-situ rod becomes insufficient, and the fiber-dispersed superconducting material having the desired composition is obtained. It's hard to get a line.

(2) Cu or Nb dendrite in the matrix reacts with the third element or forms a solid solution to form an alloy or compound with poor workability, resulting in good workability inherent in the in-situ method. Are lost, and problems occur during diameter reduction processing, and intermediate annealing must be frequently performed.

(3) Segregation of the added third element is likely to occur, and the concentration of the third element becomes nonuniform.

The present invention has been made in view of the above problems, and it is possible to manufacture a fiber-dispersed superconducting wire containing a necessary and accurate amount of the third element, and the workability is also good. It is an object of the present invention to provide a method for producing a superconducting wire, which allows an element to be uniformly added to the inside of the superconducting wire.

[Means for Solving Problems] In order to solve the above problems, the present invention provides at least one of two or more kinds of metal elements constituting a superconducting intermetallic compound.
Prepare an in-situ rod formed by forming ultrafine fibers consisting of two inside the base, Ti, Ta, In, Hf to improve the critical current value in the high magnetic field region of the superconducting intermetallic compound outside the in-situ rod. A thin-walled member made of one or more of the third elements such as Al, Zr, etc. is arranged outside the thin member.
A tube made of Cu or Cu-Sn alloy is placed, and Sn is placed around the tube.
Plating is performed, and then diffusion heat treatment is performed to diffuse and react the metal element in the matrix, the metal element of the ultrafine fibers, and the third element to generate a superconducting intermetallic compound.

"Function" Since the third element is compounded with the in-situ rod, and the alloying of the third element with the matrix is not performed before the diffusion heat treatment, it is possible to reduce the diameter while maintaining the excellent workability originally possessed by the in-situ rod. At the same time, the intermediate annealing condition becomes advantageous. In addition, after making the in-situ rod,
Since the element is added, it is possible to add an accurate amount of the third element as compared with the conventional method in which the third element was consumed during melting or casting.

"Examples" FIG. 1 (A) ~ (G) is, shows one embodiment of the present invention applied to the production of Nb ₃ Sn superconducting wire, FIG. 1 (A) ~
By performing the processing shown in (G), the fiber-dispersed Nb ₃ Sn superconducting wire T shown in FIG. 1 (G) is manufactured.

To manufacture the fiber-dispersed Nb ₃ Sn superconducting wire T, first, the in-situ rod 1 shown in FIG. 1 (A) is manufactured. To prepare this in-situ rod 1, Cu-having a structure in which Nb dendrites are dispersed in a copper alloy matrix.
It is manufactured by melting an Nb-Sn ternary alloy ingot, subjecting the ingot to a drawing process, and closely contacting the Nb dendrite into a fibrous shape. This in-situ rod 1
This is a known one having a structure in which a large number of Nb fibers 2 are closely arranged and dispersed in a copper alloy matrix 3.

Next, the in-situ rod 1 is reduced in diameter as shown in FIG. 1 (B), and the thin member 5 made of Ti, which is a third element, further improves the critical current value of Nb ₃ Sn in the high magnetic field region outside thereof. Are covered as shown in FIG. 1 (C). The thin member 5 is formed of a tubular body, or a tape or foil. When the thin member 5 is formed of a tape or foil, it is formed by means such as being vertically attached to the in-situ rod 1. The elements forming the thin member 5 are Ti, Ta, Hf, Al, In,
It is also possible to use a high-purity material made of a third element such as Ga or Zr, or an alloy material thereof. Further, by setting the thickness of the thin member 5 that covers the in-situ rod 1 to a required value, the amount of the third element contained in the superconducting wire T can be set to a desired value. This makes it possible to manufacture the superconducting wire T that exhibits a desired critical current value.

Subsequently, the outer periphery of the thin member 5 is covered with a tube body 4 made of Cu or Cu-Sn as shown in FIG. 1 (D), and further subjected to an intermediate annealing treatment if necessary, as shown in FIG. 1 (E). The composite wire F is manufactured by reducing the diameter as shown. In this diameter reduction step, since the thin member 5 and the copper alloy base 3 are not alloyed, good workability originally possessed by the in-situ rod 1 can be maintained. Therefore, as compared with the conventional method for manufacturing a superconducting wire in which Ti is added at the time of melting to manufacture an in-situ rod, the intermediate annealing condition is more advantageous, and there is an effect that troubles during the diameter reducing process are eliminated. Further, since the third element is not added during melting and casting for manufacturing the in-situ rod 1, consumption of the added third element is eliminated, and the thin member 5 made of the third element having a required thickness is combined. By doing so, the desired amount of the third element can be accurately contained. Next, a Sn plating layer 6 is formed on the outer periphery of the composite wire F to produce a plated composite wire 7 shown in FIG. 1 (F).

Next, the plated composite wire 7 is subjected to a heat treatment for heating to about 200 to 300 ° C. to diffuse the Sn plating layer 6 to the inside of the composite wire F, and further diffusion heat treatment (about 550 to 850 ° C. for about 20 to 300 hours). Heat treatment) to perform Nb dendrite inside the copper alloy matrix 3 and Sn and Sn plating layers 6 inside the copper alloy matrix 3.
To react with Sn to generate Nb ₃ Sn, and diffuse Ti inside the thin member 5 to generate fibrous Nb ₃ Sn-Ti.
The superconducting wire T shown in FIG.

Since the superconducting wire T thus manufactured has Ti diffused in the Nb ₃ Sn layer, it exhibits excellent critical current characteristics in a high magnetic field region. In addition, in the process of producing Nb ₃ Sn, Sn of the Sn plating layer 6 diffuses to the inside of the in-situ rod 1 and the Nb fibers 2 to Nb on the outer peripheral side of the in-situ rod 1
For thin member 5 is arranged on ₃ begin to generate Sn Although periphery situ rod 1 wherein the third element of the thin-walled member 5 is to efficiently and uniformly diffuse into the Nb ₃ Sn layer Nb ₃ Sn-
Generate Ti.

On the other hand, FIG. 2 shows an example in which the present invention is applied to the production of a fiber-dispersed multi-core Nb ₃ Sn superconducting wire.

In this embodiment, the in-situ rod 1 shown in FIG. 2 (A) is reduced in diameter as shown in FIG. 2 (B), and the thin member 5 made of Ti is covered as shown in FIG. 2 (C). , In addition,
The pipe 15 made of Cu or Cu-Sn alloy is covered as shown in FIG. 2 (D), and further reduced in diameter to produce the composite wire F shown in FIG. 2 (E). The Sn plating layer 6 is formed to produce the plating composite wire 7 shown in FIG. 2 (F).
Then, as shown in FIG. 2G, a large number of the plated composite wires 7 are assembled and inserted into a pipe 20 made of a Cu-Sn alloy or copper having a low Sn concentration, and a pipe made of Ta or Nb for a diffusion barrier. Then, the superconducting element wire S shown in FIG. 2 (H) is manufactured by inserting it into the tubular body 22 made of Cu or Al as a stabilizing material and reducing the diameter. Next, this superconducting wire S is subjected to diffusion heat treatment to manufacture a fiber-dispersed Nb ₃ Sn superconducting wire.

When the fiber-dispersed Nb ₃ Sn multi-core superconducting wire is manufactured by performing the method described above, the plated composite wire 7 is connected to the pipe 20.
Since it is inserted inside, there is an effect that it is possible to prevent the Sn plating layer 6 from being burnt through during the diffusion heat treatment. In this respect, in the above-described example, in order to prevent the Sn plating layer 6 from being burnt through, the Sn plating layer 6 is diffused into the base by heating at a low temperature for a long time before the diffusion heat treatment. Since it is necessary to perform a diffusion heat treatment for Nb ₃ Sn generation after that, the heat treatment time becomes long, but in the present embodiment, the heat treatment at the low temperature is not necessary, so the heat treatment time can be shortened. You can do it. The superconducting wire manufactured as described above has a large current capacity because it has a large number of Nb ₃ Sn—Ti fibers inside.

By the way, conventionally, in order to expand the capacity of the superconducting wire and increase the number of cores, a plurality of Nb ₃ Sn superconducting wires consisting of in-situ rods have been bonded around the stabilizing rod with a fixing material such as solder to form a braid. However, there is a problem that superconducting characteristics are deteriorated due to mechanical stress due to formation of braid after Nb ₃ Sn formation.

In this respect, when the fiber-dispersed multi-core Nb ₃ Sn superconducting wire is manufactured as described above, a large number of plated composite wires 7 are piped.
In order to perform the diffusion heat treatment after arranging in the inside and reducing the diameter, it is not necessary to perform machining after the superconducting intermetallic compound is formed unlike the conventional braiding method, and there is an effect that the superconducting characteristics are not deteriorated.

"Production Example 1" An in-situ rod having an outer diameter of 20 mm is prepared, and the in-situ rod is extruded and drawn to obtain a wire rod. Next, cover this wire with a tube made of Ti with an outer diameter of 11 mm and an inner diameter of 10.4 mm, and further cover these with an outer diameter of 13 mm and an inner diameter of 12 mm.
Inserted into a bronze tube containing t%, and further reduced in diameter and subjected to intermediate annealing treatment to produce a composite wire. Next, a 5 μm thick Sn plating layer was formed on this composite wire by an electroplating method to prepare a plated composite wire.

Then, the plated composite wire is subjected to a heat treatment of gradually raising the temperature to 200 ° C. and 350 ° C. to diffuse the Sn plating layer into the matrix, and then subjected to a diffusion heat treatment of heating to 650 ° C. for 75 hours to form Nb ₃ Sn.
Was produced and Ti of the thin member was diffused into the Nb ₃ Sn layer to manufacture a superconducting wire.

When the critical current characteristics of this superconducting wire were measured, it showed a critical current density of 500 A / mm ² under an external magnetic field of 14 T (Tesla). Under the same conditions, the conventional superconducting wire to which Ti is not added has an extremely excellent critical current value if the critical current density is about 200 A / mm ^2. Became clear.

[Manufacturing Example 2] An in-situ rod made of a Cu-Nb alloy containing 30 wt% of Nb and having a configuration in which Nb fibers were arranged inside a copper matrix having a diameter of 20 mm was produced by using an arc melting method. This in-situ rod was subjected to diameter reduction processing to produce a rod having a diameter of 6 mm. This rod is covered with a Ti foil with a thickness of 60 μm vertically, and is further inserted into a bronze tube having an outer diameter of 10 mm and an inner diameter of 7 mm and containing Sn6 wt% to reduce the diameter, and the diameter is 1 m.
A composite wire of m was made.

Next, the electroplating method is applied to this composite wire to a thickness of 30 μm.
Sn plating layer is formed to make a plated composite wire, 91 of these plated composite wires are assembled, and further, a Nb tube for diffusion barrier and a stabilized copper tube are covered to reduce the diameter, and an outer diameter of 1 mm I got a superconducting wire.

A fiber-dispersed Nb ₃ Sn superconducting wire was produced by subjecting this multi-core superconducting wire to diffusion heat treatment at 650 ° C for 100 hours.

The fiber-type Nb ₃ Sn superconducting wire prepared as described above showed remarkable improvement in the critical current characteristics, especially in the high magnetic field region of 14 T (tesla) or more.

Incidentally, in the above example it has been described the example of applying the present invention in the manufacture of fiber dispersion type Nb ₃ Sn superconducting wire, V ₃
Needless to say, the present invention may be applied to other compound-based superconducting wires such as Ga. When manufacturing a fiber-dispersed V ₃ Ga superconducting wire, an in-situ rod is made from a Cu-V-Sn ternary alloy, a composite wire is made using this, and the composite wire is plated with Ga to plate it. A fiber-dispersed V ₃ Ga superconducting wire can be manufactured by producing a composite wire, and assembling a large number of plated composite wires and subjecting them to diffusion heat treatment, if necessary.

"Effects of the Invention" As described above, according to the present invention, the effects described below are achieved.

(1) Compound the core of the third element with the in-situ rod,
Prior to the diffusion heat treatment, the in-situ rod is reduced in diameter without reacting the metal element and the third element. In order to reduce the diameter while maintaining the good workability originally possessed by the in-situ rod, Compared to the conventional method in which 3 elements were added, there are no problems during the diameter reduction process,
Intermediate annealing conditions also have the effect of becoming advantageous.

(2) If the thickness of the thin member covering the in-situ rod is adjusted to an appropriate value, there is an effect that a superconducting wire containing a desired amount of the third element can be manufactured. Moreover, since the amount of the third element to be contained can be adjusted by changing the thickness of the thin member, there is an effect that the amount of the third element can be easily adjusted.

(3) In the conventional method in which the third element was added during melting, there was a problem of segregation of the third element, but since the third element is compounded in the in-situ rod in the state of the core, the problem of segregation occurs. Is not generated, and the third element is not consumed during melting or casting, so that an accurate amount of the third element can be added.

[Brief description of drawings]

1 (A) to (G) show an embodiment of the present invention. FIG. 1 (A) is a cross-sectional view of an in-situ rod, and FIG. 1 (B) shows a reduced in-situ rod. FIG. 1 (C) is a cross-sectional view showing a state in which the in-situ rod is covered with a thin member, and FIG. 1 (D) is a cross-sectional view showing a state in which the base is covered outside the thin member. 1 (E) is a cross-sectional view showing a composite wire, FIG. 1 (F) is a cross-sectional view of a plated composite wire, FIG. 1 (G) is a cross-sectional view of a superconducting wire, and FIG. 2 (A). )-(H) show another embodiment of the present invention, FIG. 2 (A) is a cross-sectional view of the in-situ rod, FIG. 2 (B) is a cross-sectional view of the in-situ rod after diameter reduction, Second
FIG. 2C is a cross-sectional view showing a state where the thin-walled member is covered on the in-situ rod after the diameter reduction, and FIG. 2D is a cross-sectional view showing a state where the tubular body is covered on the thin-walled member. E) is a cross sectional view of the composite wire, FIG. 2 (F) is a cross sectional view of the plated composite wire,
FIG. 2 (G) is a cross-sectional view showing the state of assembly of the plated composite wire, and FIG. 2 (H) is a cross-sectional view of the superconducting element wire. T ... Superconducting wire, S ... Superconducting element wire, 1 ... In-situ rod, 2 ... Nb fiber, 3 ... Copper alloy base, 4 ...
Tube, 5 ... Thin-walled member, 6 ... Sn plated layer, 7 ... Plated composite wire.

Claims (1)

[Claims] 1. An in-situ rod formed by forming an ultrafine fiber made of at least one of two or more kinds of metal elements constituting a superconducting intermetallic compound inside a matrix is provided on the outside of the in-situ rod. , Ti, Ta for improving the critical current value in the high magnetic field region of the superconducting intermetallic compound,
A thin member made of at least one of the third elements such as In, Hf, Al, Zr, etc. is arranged, a tube body made of Cu or Cu-Sn alloy is arranged on the outside thereof, and Sn plating is applied on the outer periphery thereof. A method for producing a fiber-dispersed superconducting wire, characterized in that the superconducting intermetallic compound is produced by diffusing heat treatment and then diffusing and reacting the metal element in the matrix, the metal element of the ultrafine fibers and the third element.