JPH087681A - A3b type compound superconductive wire rod and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an A3B type compound superconductive wire rod having improved characteristics by enabling the rate of unreacted residual amount of A metal to a produced amount of the A3B compound in to be controlled substantially uniformly. CONSTITUTION:An A3B type compound superconductive wire rod has a filament aggregated part in which a plurality of A3B type compound filament are buried in matrix metal and a matrix part containing B metal. The diameter of the A3B type compound filament arranged adjacent to the matrix part in this filament aggregated part is made larger than that of the A3B type compound filament arranged in the other part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excellent A ₃ B type compound superconducting wire which realizes a high critical current density and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, Nb ₃ Sn, Nb ₃ Al, V ₃ G
Since A ₃ B type compound superconductors such as a (also referred to A15 type compound superconductor) is an intermetallic compound working is extremely difficult, in order to produce a superconducting wire, the A ₃ B
A composite billet composed of a high melting point metal A and a low melting point metal B constituting a type compound superconductor is subjected to a drawing process to form a composite wire, and then the low melting point metal B is diffused and reacted inside the high melting point metal A. A manufacturing method is employed in which the A ₃ B type compound superconductor is reacted and produced by the diffusion heat treatment.

A method for producing an Nb ₃ Sn superconducting wire by the bronze method will be described below as an example of the A ₃ B type compound superconducting wire. In this case, the A metal is Nb and the B metal is Sn. First, a Cu-Sn alloy (hereinafter referred to as bronze) rod is formed as a matrix, and a Nb core material is inserted into the rod to form a primary composite billet, which is then drawn to form a strand. This wire is filled in a bronze tube to form a secondary composite billet, and then drawn to give a composite wire. The composite wire may be used as a wire to form a higher-order composite billet.

The above composite wire has a structure in which Nb filaments are embedded in a matrix metal,
When this composite wire is subjected to a diffusion heat treatment of heating at about 550 ° C. to 600 ° C., Sn in the bronze diffuses and reacts inside the Nb filament to produce Nb ₃ Sn. Thus, the Nb filament is a superconducting filament of Nb ₃ S
It becomes an n-filament, and a multifilamentary superconducting wire can be obtained. There is also a method of coating the outer periphery of the composite wire with Sn and then performing a diffusion heat treatment (called an external diffusion method).

Further, without using bronze, which has poor workability, C
A manufacturing method of assembling a composite billet using a simple substance such as u, Sn, and Nb, stretching the composite billet, and subjecting the composite billet to diffusion heat treatment is also under study. These manufacturing methods can be similarly applied to the case of an A ₃ B type compound superconductor other than Nb ₃ Sn.

By the way, one condition for realizing a superconducting wire having high superconducting characteristics is to produce a large amount of Nb ₃ Sn which is a superconductor. Nb ₃ Sn is produced by subjecting the composite wire to a diffusion heat treatment of heating at about 500 ° C. to 800 ° C. to cause Sn in the bronze to diffuse into the Nb filament and react with it. Naturally, the amount of Nb ₃ Sn produced increases. Therefore, in order to increase the amount of Nb ₃ Sn produced, it is necessary to extend the diffusion heat treatment time as long as possible.

By the way, in order to assemble a magnet using A ₃ B type compound superconducting wire, a method is generally used in which a coil is wound before the diffusion heat treatment and then the diffusion heat treatment is performed. A ₃ B type compound superconducting wire A
_{This is because the 3} B type compound is very fragile, and it becomes difficult to wind it into a coil in a state where the A ₃ B type compound is produced through the diffusion heat treatment.

[0008]

In a current loop formed of a superconductor in a superconducting magnet or the like, a permanent current switch is usually superconductingly connected to both ends of a coil-shaped superconducting wire. The permanent current switch is placed in the cold material together with the superconducting magnet and ideally forms part of the superconducting circuit.

However, in practice, electric resistance remains at the connection between the permanent current switch and both ends of the superconducting wire wound in a coil shape, and this connection causes current attenuation. Therefore, it is necessary to reduce the connection resistance as much as possible. The superconducting connection method is generally a method in which the ends of the superconducting wires with the superconducting filaments exposed are brought into contact with each other and fixed by soldering or the like. At this time, in order to expose the superconducting filament, the matrix metal may be dissolved with a liquid containing sulfuric acid, nitric acid or the like.

However, in the case of the A ₃ B type compound superconducting wire, as described above, the A ₃ B type compound superconductor is very fragile, and if the superconducting filament is exposed by melting it, the superconducting filament may be broken during the superconducting connection. is there. As a countermeasure against this, a method is employed in which an unreacted A metal portion is left in the central portion of the superconducting filament and the toughness of the unreacted A metal portion prevents the superconducting filament from cracking.

In order to adopt the above method, it is necessary to appropriately adjust the diffusion heat treatment so that the unreacted A metal portion remains in the central portion of the superconducting filament. That is, when the composite wire having the structure in which the A metal filament is embedded in the matrix metal is subjected to the diffusion heat treatment, the diffusion of the B metal that proceeds inside the A metal filament naturally proceeds from the outer peripheral portion of the A metal filament. Therefore, it is necessary to stop the diffusion heat treatment and leave the A metal portion before the diffusion of the B metal reaches the central portion of the A metal filament.

Due to the limitation that the unreacted A metal portion remains in the central portion of the superconducting filament, it has been difficult to perform sufficient diffusion heat treatment. Because, due to the position where the superconducting filament is arranged, the variation in the reaction amount due to the diffusion heat treatment is large,
This is because some of the superconducting filaments resulted in leaving more A metal portion than necessary. As described above, one condition for realizing a superconducting wire having high superconducting properties is to generate as many superconductors as possible. Therefore, leaving the A metal portion more than necessary causes the deterioration of superconducting properties. There is a problem of becoming.

[0013]

SUMMARY OF THE INVENTION The present invention has been made as a result of intensive studies in view of such circumstances. The purpose of the present invention is to make it possible to perform a sufficient diffusion heat treatment and to provide A ₃ B having high characteristics. Type compound superconducting wire.

That is, the invention described in claim 1 of the present application includes a plurality of A's.
An A ₃ B type compound superconducting wire having a filament assembly part in which a ₃ B type compound filament is embedded in a matrix metal, and a matrix part containing a B metal, wherein the matrix part in the filament assembly part is There is provided an A ₃ B type compound superconducting wire, wherein the diameter of the A ₃ B type compound filament arranged in the vicinity is larger than the diameter of the A ₃ B type compound filament arranged in other portions.

The invention according to claim 2 of the present application is a composite structure in which an A metal core material and an elemental wire made of a matrix metal are arranged in a matrix member containing a B metal or an outermost sheath made of a stabilized metal material and assembled. A billet, or an element wire composed of an A metal core material and a matrix metal, and a matrix member containing B metal or a stabilizing metal material,
The composite billet, which is arranged and assembled in the outermost sheath made of a matrix member containing B metal or a stabilized metal material, is subjected to a stretching process to obtain a composite wire, and the composite wire is subjected to diffusion heat treatment to obtain A ₃ In the method for producing a B-type compound superconducting wire, the diameter of the A metal core material arranged in the vicinity of the matrix member is set to be larger than the diameter of the A metal core material arranged in other portions. Do A ₃
It is a method for producing a B-type compound superconducting wire.

The third aspect of the invention is to use the external diffusion method A
_{3 In} the case of manufacturing a B-type compound superconducting wire, the outer periphery of a composite wire similar to the above is coated with B metal as a source (one of) of B metal that reacts with the A metal core material, and then subjected to diffusion heat treatment. In this case, the diameter of the A metal core material arranged in the vicinity of the matrix member and the outermost sheath is made larger than the diameter of the A metal core material arranged in the other portion A
_{3 A} method for producing a B-type compound superconducting wire.

[0017]

When the present inventors observed the cross section of the superconducting wire according to the present invention with a microscope, the superconducting filaments arranged in the vicinity of the matrix portion containing B metal contained superconducting filaments in other portions. Compared to A ₃
It was found that the amount of B-type compound superconductor produced was large.
This is because a larger amount of B metal diffuses into the former superconducting filament that was arranged in the vicinity of the matrix portion, which is the source of B metal, than the latter superconducting filament.
It is thought that this is because of the reaction.

However, the superconducting wire of the present invention has more A
₃ B-type compound superconductor is generated, that is, B
Since the diameter of the superconducting filaments arranged in the vicinity of the metal-containing matrix portion is made larger than the diameter of the superconducting filaments arranged in other portions, the latter superconducting filament portion has a sufficient amount of A ₃ B. Even if the diffusion heat treatment is performed until the type compound superconductor is produced, it is possible to leave the A metal in the former superconducting filament.

Therefore, even if the superconducting filament is not arranged in the vicinity of the matrix portion containing the B metal, the A metal portion more than necessary is not left and a sufficient A ₃
It becomes possible to perform a diffusion heat treatment that produces a B-type compound superconductor. Therefore, an A ₃ B type compound superconducting wire that realizes higher superconducting properties can be obtained.

In order to manufacture the A ₃ B type compound superconducting wire of the present invention, the element wire and, if necessary, the B metal are placed in the outermost sheath made of a matrix material containing a stabilizing metal material or a B metal. When the composite billet is assembled by arranging and filling the contained matrix member, the stabilizing metal material, the barrier material, etc., it is sufficient to dispose a wire having a large diameter of the metal A core material in the vicinity of the matrix member. For example, when a matrix metal containing B metal is used as the outermost sheath, a wire having a large diameter of the A metal core material is arranged near the outermost sheath.

[0021]

EXAMPLES The present invention will now be described in detail with reference to Examples.
In the examples, Nb was selected as the A metal and Sn was selected as the B metal to manufacture a Nb ₃ Sn compound superconducting wire. At this time, there were two types of prepared strands, and all were hexagonal strands. First 6
The rectangular wire (α) has an outer diameter of 124 m in a bronze tube (Cu-14 wt% Sn) having an outer diameter of 200 mm and an inner diameter of 125 mm.
After inserting the Nb rod of m and stretching, the distance between opposite sides is 1.7 mm
It is what Hexagonal wire (β) has an outer diameter of 200 m
m, 140 mm inner diameter bronze tube (Cu-14 wt% S
A Nb rod having an outer diameter of 139 mm was inserted in n), and the opposite side distance was 1.7 mm after stretching.

2 and 3 are hexagonal wires (α) and 6 respectively.
It is explanatory drawing which showed the cross section of a square element wire ((beta)) typically. In the figure, the Nb portion 5 of the hexagonal wire (α) 6 and the hexagonal wire (β) 9
Each of the Nb portions 8 has a perfect circular cross section, but actually has a slightly distorted shape.

Next, as shown in FIG. 1, as the outermost sheath 1, a bronze tube (C having an outer diameter of 200 mm and an inner diameter of 178 mm) (C
u-14 wt% Sn) was prepared, and the hexagonal filament (α) and the hexagonal filament (β) were arranged and filled therein to assemble a composite billet. In FIG. 1, a part of the hexagonal wire 2 to be filled is schematically drawn and is drawn larger than it actually is.

Three types of composite billets according to the present invention, No. 1 to No. 3, were prepared. The composite billet No1 has a plurality of hexagonal wires (α) arranged in the center of the outermost sheath 1.
The hexagonal wire (α) bundle was made to have an outer diameter of approximately 162 mm. Then, a plurality of hexagonal wires (β) were arranged between the outer side and the inner wall of the outermost sheath 1. The composite billet No. 2 has a stabilizing metal material (diameter 87 in which a Ta barrier having a thickness of 3 mm is arranged on the outer periphery) at the center of the outermost sheath 1.
mm oxygen-free copper rod), and a plurality of hexagonal filaments (α) were arranged on the outer periphery thereof so that the bundle of hexagonal filaments (α) had an outer diameter of approximately 162 mm. Then, a plurality of hexagonal strands (β) were arranged between the outer side of this bundle and the inner wall of the outermost sheath 1. The composite billet No. 3 has a stabilizing metal material (thickness of 3 m around the periphery of the outermost sheath 1).
87 mm diameter oxygen-free copper rod with a Ta barrier of m on the outer circumference is arranged, and the outer circumference is 105 mm in outer diameter and 95 m in inner diameter.
m bronze tube (Cu-14wt% Sn) is covered, and a plurality of hexagonal wires (α) are further arranged on the outer circumference thereof so that the bundle of the hexagonal wires (α) has an outer diameter of approximately 162 mm. I chose Then, as in the case of Example 2 of the present invention, a plurality of hexagonal wires (β) were arranged between the outer side and the inner wall of the outermost sheath 1.

Three types of composite billets (Nos. 4 to 6) according to the conventional example were prepared. These are the ones in which only the hexagonal element wires (α) are used instead of the hexagonal element wires (β) in the assembly of the composite billet Nos. 1 to 3 and are referred to as composite billet Nos 4 to 6, respectively.

Next, the composite billets No. 1 to 6 were subjected to a drawing process to obtain composite wire rods having a diameter of 0.7 mm. These composite wires were subjected to the diffusion heat treatment shown in Table 1 to produce Nb ₃ Sn superconducting wires. Next, the end of the manufactured Nb ₃ Sn superconducting wire is dissolved with sulfuric acid to expose the superconducting filament,
It was examined whether the superconducting filament had a toughness to withstand superconducting connection. As a result, it was found that in Nos. 4 to 6 (conventional examples) which had been subjected to the diffusion heat treatment under the condition b, a considerable number of superconducting filaments did not have sufficient toughness. These superconducting filaments which did not have sufficient toughness left almost no unreacted A metal portion in the central portion.

However, among the conventional examples Nos. 4 to 6, it was found that most of the superconducting filaments which had been subjected to the diffusion heat treatment under the condition a had sufficient toughness. Therefore, conventional example N
Of o4 to 6, the only one that can be practically used for superconducting connection is the one that has been subjected to the diffusion heat treatment under the condition a.

On the other hand, in the case of Examples 1 to 3 of the present invention, it was found that most of the superconducting filaments have sufficient toughness regardless of the diffusion heat treatment under the conditions a and b. Therefore, the superconducting connection is practically feasible in any of those subjected to the diffusion heat treatment under the conditions a and b.

Further, among Nos. 1 to 3, the superconducting wires subjected to the diffusion heat treatment under the condition b and the cross sections of the superconducting wires subjected to the diffusion heat treatment under the condition a among Nos. , Nb ₃ Sn, the ratio of the cross-sectional areas (hereinafter referred to as the reaction rate) was examined. The cross-sectional area ratio is substantially the same as the volume ratio. The observed superconducting filaments were selected along the radial direction of the superconducting wire, and the minimum value and the maximum value of the area ratio are shown in Table 1.

Regarding the Nb ₃ Sn superconducting wire whose area ratio was examined, the critical current density in the non-copper part was also measured. The critical current density in the non-copper part is the critical current value,
It is a value obtained by dividing the cross-sectional area of the superconducting wire by the area excluding the area corresponding to the stabilizing metal material.

[0031]

[Table 1]

As is clear from Table 1, the present invention has a small variation in the reaction rate, and has a superconducting filament in which the Nb portion is left substantially evenly over the entire cross section of the superconducting wire. On the other hand, in the conventional example, the variation of the reaction rate was large, and there were many superconducting filaments that left unnecessarily large amounts of Nb, so that the critical current density was lower than that of the inventive example. The reaction rate was small because Sn
It was a superconducting filament that was not located near the matrix portion containing.

As described above, the A ₃ B type compound superconducting wire of the present invention realizes excellent characteristics. In the above examples, the bronze tube was used as the outermost sheath when forming the composite billet. However, when an oxygen-free copper sheath is used, it is not necessary to dispose a large strand of Nb in the vicinity thereof. Absent. However, when Sn is coated on the composite wire rod obtained by drawing the composite billet and then the diffusion heat treatment (in the case of the external diffusion method), even if the outermost sheath is oxygen-free copper, the Nb portion near the outermost sheath is Large wires need to be placed. Needless to say, even in this case, similarly excellent characteristics can be realized.

In the above embodiments, the case where Nb is used as the A metal and Sn is used as the B metal has been described, but the same effect can be obtained in the case of other A ₃ B type compound superconducting wires.

[0035]

As described in detail above, in the A ₃ B type compound superconducting wire of the present invention, the ratio of the amount of unreacted A metal remaining to the amount of A ₃ B type compound produced is controlled to be substantially uniform. It is possible to realize excellent superconducting properties. As described above, the present invention realizes high characteristics of the A ₃ B type compound superconducting wire, and its industrial contribution is remarkable.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating assembly of a composite billet of the present invention.

FIG. 2 is an explanatory diagram illustrating a hexagonal wire (α) according to an embodiment.

FIG. 3 is an explanatory diagram illustrating a hexagonal wire (β) of an example.

[Explanation of symbols]

 1 Outermost sheath 2 Hexagonal wire 3 Composite billet 4 Bronze part 5 Nb part 6 Hexagonal wire (α) 7 Bronze part 8 Nb part 9 Hexagonal wire (β)

Claims (3)

[Claims] 1. A plurality of A's₃B type compound filament
Filament assembly embedded in Trix metal
And A having a matrix portion containing B metal₃B
-Type compound superconducting wire, which is in the vicinity of the matrix portion in the filament assembly portion.
The A placed near ₃Diameter of B type compound filament
Is placed in the other part A₃B-type compound philame
A that is larger than the diameter of the component₃B type compound over
Conductive wire. 2. A composite billet assembled by disposing an elemental wire made of an A metal core material and a matrix metal in a matrix member containing a B metal or an outermost sheath made of a stabilized metal material, or an A metal core material and A composite billet in which an elemental wire made of a matrix metal and a matrix member or a stabilizing metal material containing the B metal are arranged in an outermost sheath made of the matrix member containing the B metal or the stabilizing metal material and assembled. In the method for producing a composite wire rod by subjecting the composite wire rod to a drawing treatment and subjecting the composite wire rod to a diffusion heat treatment to produce an A ₃ B type compound superconducting wire, the diameter of the A metal core material arranged in the vicinity of the matrix member is A method for producing an A ₃ B type compound superconducting wire, characterized in that the diameter is made larger than the diameter of the A metal core material arranged in the other portion. 3. A composite billet assembled by disposing an elemental wire composed of an A metal core material and a matrix metal in an outermost sheath composed of a matrix member containing B metal or a stabilized metal material, or an A metal core material. And a composite made by disposing an elemental wire made of a matrix metal and a matrix member or a stabilizing metal material containing the B metal in an outermost sheath made of the matrix member containing the B metal or the stabilizing metal material. In a method for producing a composite wire rod by subjecting a billet to a drawing process, coating the outer periphery of the composite wire rod with a B metal, and then subjecting it to a diffusion heat treatment to produce an A ₃ B type compound superconducting wire, The diameter of the A metal core material arranged in the vicinity of the outermost sheath is set to be larger than the diameter of the A metal core material arranged in other portions. Method for producing a A ₃ B type compound superconductor to symptoms.