JPH01321033A - Manufacture of nb3x series superconducting material - Google Patents

Abstract

PURPOSE:To obtain Nb3X series superconducting material having fine crystal grains agreeing with the stoichiometric composition and excellent in superconducting properties by heat-treating Nb and an element at a specified temperature to make diffusion-reaction on them in a base composed of Ag. CONSTITUTION:A rod composed of Nb is inserted into a pipe composed of Ag-Ga alloy and this compound material is deduced in diameter to obtain a primary element wire 14. Plural element wires 14 are collected, inserted into a pipe body 15 composed of Ag-Ga alloy and contracted in diameter to obtain a secondary element wire 16. Plural secondary element wires are collected, inserted into a pipe body 17 composed of Ag-Ga alloy and reduced further in diameter to create a compound material 18. Plural compound materials 18 are collected, inserted into a diffusion prevention pipe 19 and reduced in diameter by covering the outside with a pure copper coated pipe 20. This wire is heat-treated at 600-1,000 deg.C under the atmosphere of vacuum or under the atmosphere or inert gas. In this way, Ga makes diffusion-reaction on an extrafine Nb filament in the base composed of Ag-Ga alloy in the core part to generate an Nb-Ga superconductive filament.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a method for producing Nb5Ga-based or Nb, Al-based superconducting materials, which are known to have high critical temperatures and critical magnetic fields.

"Prior art" N bs S n, V s Ga,
A15 type compounds such as N bs G asNb3A1 are known.

In these A15 type compound superconductors, Nb.

Superconducting wires using compound superconductors such as 5nSVsGa have been put into practical use through the development of various manufacturing methods that apply external diffusion methods or internal diffusion methods, and Nb5Sn
It has come to be put to practical use as superconducting wire or superconducting magnet of VsGa-based or VsGa-based superconducting wires.

However, in the A15 type compound superconductor, Nb
In compound superconductors such as 5GaSNb3Al, in an equilibrium state, the composition tends to deviate toward less Ga or Al than the stoichiometric ratio. When carried out, there was a problem in that a compound superconductor with a composition that did not match the stoichiometric composition and a significantly low critical temperature was produced.

Therefore, conventionally, when manufacturing Nb, Ga, or Nb+Al compound superconductors, the composition was forcibly made uniform using a special manufacturing method such as vapor deposition, or the compound superconductor was stable at high temperatures of 1600°C or higher. It was possible to generate these compound superconductors by performing a melting reaction at a high temperature of 1,600° C. or higher by taking advantage of the fact that they are in a phase of 1,600° C. or higher.

``Problem to be Solved by the Invention'' However, the above-mentioned vapor deposition method has the disadvantage that there is a limit to the size of the compound superconductor that can be manufactured, and it cannot be applied to long objects such as wire rods.

In addition, with the manufacturing method that involves heating to a high temperature of 1600°C or higher to cause a melting reaction, it is difficult to find a structural material that can withstand heat treatment at a high temperature of 1600°C or higher when considering the production of wire rods including stabilizing base materials. There's a problem. Furthermore, the crystal grains of the compound superconductor produced by heating to such a high temperature have become coarse due to the influence of the high temperature heat treatment, so there is an interlayer with a low critical current density.

By the way, for example, when trying to manufacture a N bs Ga-based compound superconducting wire by applying the melt reaction method, the first
θ diagram and 1st! It can be assumed that the method described below can be implemented based on the figures.

First, a rod 2 made of Ga is inserted into the inside of a tube l made of Nb to create a composite 3, and this composite 3 is heated at 1600°C or higher to cause a melt-diffusion reaction between Nb and Ga. A Nb5Ga-based superconducting wire 5 can be manufactured by forming a compound superconducting layer 4 made of Nb3Ga at the boundary between the tube 1 and the rod 2 as shown in FIG.

However, in the Nb5Ga-based superconducting wire 5 manufactured by the method described above, although a compound superconducting layer 4 can be generated at the boundary between the tube 1 and the rod 2, unreacted Ga remains in the center of the wire. Moreover, there is a problem that voids 6 are generated inside the unreacted Ga. Note that since the melting point of Ga remaining in the center of the wire is 29.78° C., it is not desirable that such a low melting point substance remains inside the wire.

On the other hand, when attempting to manufacture a tape-shaped Nb5Ga-based superconducting conductor, it can be assumed that the method described below can be implemented based on FIGS. 12 and 13.

First, as shown in FIG. 12, a tape material 7 made of Nb
A plating layer 8 made of Ga is formed on the upper surface of the
By heating above 00°C to cause a melting reaction, Nb+Ga is formed on the upper part of the tape material 7 as shown in FIG.
A compound superconducting layer 9 consisting of the following can be produced.

However, in this method, since the melting point of Ga is extremely low, the vapor pressure of Ga during heat treatment heated to 1,600°C or higher becomes extremely high, and Ga tends to evaporate and disappear during heat treatment, resulting in less generation. There is a problem in that the Ga content in the Nb5Ga superconductor produced is significantly insufficient, the stoichiometric composition of the Nb5Ga superconductor is distorted, and as a result, excellent superconducting properties cannot be obtained.

Based on the above background, Nb5Ga series or Nb.

Although various methods for producing Al-based superconducting wires have been attempted, an effective method for producing superconducting wires with excellent characteristics by heat treatment at a temperature of 1000° C. or less has not yet been developed. However, the present inventors have recently discovered that Nb, Ga, Nb, and Al having excellent properties can be produced by causing a diffusion reaction inside the Ag base.

The present invention has been made in view of the above background and based on the findings of the present inventors, and is a method for producing an Nb5x-based superconducting material having a composition that matches the stoichiometric composition and a high critical temperature and critical magnetic field. The purpose is to provide

"Means for solving the problem" In order to solve the problem, the invention described in claim 1 has the following features:
In the method for manufacturing Nb3X (where X represents Ga or A1) based superconducting material, a wire is created by covering a Nb core material with an Ag-X alloy layer, and then a plurality of these wires are assembled. Insert into a tube made of Ag-X alloy, further perform diameter reduction processing, and repeat the process of collecting the strands and inserting them into the tube and diameter reduction processing one or more times to create a composite, Next, this composite is heat treated at 600 to 1000°C.

In addition, in order to solve the above-mentioned problem, the invention described in claim 2 provides a method for manufacturing a Nb3X-based superconducting material, in which a wire is prepared by covering a Nb core material with an Ag-X alloy layer, and then this Collecting a plurality of strands of wire and inserting them into a tube made of Ag-X alloy, and further performing diameter reduction processing, and performing the process of collecting and inserting the strands into the tube and diameter reduction processing at least once. Repeat this process to create a composite, then assemble a plurality of these composites and insert them into a diffusion prevention tube made of Ta or Nb, etc., and cover the outside of the diffusion prevention tube with a tube made of a stabilizing material. Then, after reducing the diameter of the whole, 600-1000℃
A heat treatment is performed to generate Nb3X superconductor inside the composite.

"Action" In order to cause a diffusion reaction between Nb and element A system of superconducting filaments is produced. In addition, element .

``Example'' Figures 1 to 9 show examples in which the method of the present invention is applied to the manufacturing method of Nb5Ga-based superconducting wire. A rod 10 made of Nb is attached to a vibrator 11 made of an Ag-Ga alloy.
to create a composite material 13. In addition, the pipe! (2) is not limited to a single tube as shown in the drawing, but a columnar body with multiple through holes formed therein, and a rod IO inserted into each of the multiple through holes to create a composite structure. It can also be used to form materials.

Next, this composite material 13 is reduced to a desired diameter by a diameter reduction process such as swaging or drawing to obtain a primary strand 14 shown in FIG. This -order strand 14 has a structure in which the outer peripheral surface of a core material made of Nb is covered with an Ag-Ga valley metal layer.

Next, a plurality of the secondary strands 14 are assembled and inserted into a tube 15 made of Ag-Ga alloy as shown in FIG. We get line 16.

Next, as shown in FIG. 5, a plurality of the secondary wires I6 are assembled and inserted into a tube body 17 made of Ag-Ga alloy, and further diameter-reduced to create a composite body 18 shown in FIG. 6. do.

The internal structure of the composite body 18 is such that a large number of extremely thin filaments made of Nb are dispersed inside a base made of an Ag-Ga alloy. Incidentally, a plurality of the secondary strands 16 may be further assembled and inserted into the Ag-Ga alloy tube, and the diameter reduction process may be performed multiple times as necessary to create a composite body.

Next, a plurality of the composites 18 are assembled and inserted into a diffusion prevention tube I9 made of Ta or Nb as shown in FIG.
A pure copper cladding tube 20 to serve as a stabilizing material is placed on the outside of the diffusion prevention tube 19, and the whole is further reduced in diameter to the final diameter to obtain the wire rod 2 shown in FIG. 8! get. This wire 21 is a composite! 8, a diffusion barrier layer 23 coated on the outside of this core 22, and a stabilizing layer 24 made of pure copper coated on the outside of this diffusion barrier layer 23. has been done. The core portion 22 has a structure in which a large number of ultrafine filaments made of Nb are dispersed inside a base made of an Ag-Ga alloy.

Next, this wire 21 is subjected to heat treatment in which it is heated to 600 to 1000° C. for several hours to several tens of hours in a vacuum atmosphere or an inert gas atmosphere. Through this heat treatment, in the core part 22, the ultrafine Nb in the base made of Ag-Ga alloy
Ga constituting the base diffuses into the filament and reacts, producing a Nb5Ga superconducting filament. In addition, when a superconducting filament is generated by diffusing Ga inside a base made of Ag-Ga, 600 to 1
Nb5 matches the stoichiometric composition even at a heating temperature of 1,000°C
Ga can be generated. This is presumed to be because Ag constituting the base exerted some kind of catalytic effect.

In addition, since the diffusion barrier layer 23 is formed outside the core portion 22 during the diffusion heat treatment, the outermost stabilizing layer 23
Ga does not diffuse up to 4, and contamination of the stabilizing layer 24 due to Ga diffusion is prevented. Therefore, even after the heat treatment, the pure copper stabilizing layer 24 remains on the outermost periphery.

Through the above heat treatment, the Nb5Ga-based superconducting wire A shown in FIG. 9 can be obtained. This superconducting wire A is used after being cooled to below a critical temperature using a coolant such as liquid helium. Since this superconducting wire A includes a Nb5Ga superconducting filament, its critical temperature is high. Also, 600 to 10
Since the Nb5Ga superconductor is generated by the heat treatment performed at 00° C., it is possible to suppress coarsening of crystal grains and to generate a Nb, Ga superconductor with finer crystal grains than conventional ones.

Therefore, a superconducting wire with a high critical current density can be obtained even in a high magnetic field exceeding 10 T (Tesla). In addition, a stabilizing layer 24 made of pure copper is formed on the outermost periphery of the superconducting wire A, and since this layer has sufficiently low electrical resistance at extremely low temperatures, the stabilizing layer 24
4 acts as a stabilizing material for the superconducting wire A. That is, when the superconducting filament attempts to transition to a normal conductive state for some reason, the stabilizing layer 24 serves as a current path, prevents heat generation, stabilizes the superconducting state, and causes the superconducting filament to transition to a normal conductive state. When dislocated, it becomes a current path.

In the above embodiment, the diffusion prevention tube I9 and the cladding tube 20 are coated after the composite I8 is assembled, and the heat treatment is performed after the diameter is reduced.
It is also possible to produce a superconducting wire by producing a Nb5Ga superconducting filament inside the 8.

Furthermore, in the above embodiment, an example in which the present invention is applied to a Nb5Ga-based superconducting wire has been described, but it is also possible to apply the present invention to a Nb3Al-based superconducting wire. Nb3
When applied to Al-based wires, a Nb rod is inserted into an Ag-Al alloy tube to create a composite, and the same steps as above are performed using this composite as a starting material to create Nb and Al-based superconducting wires. can be manufactured.

"Manufacturing example 1" Made of Ag-10at%Ga alloy, outer diameter 10mm.

A Nb rod with a diameter of 6.7III was inserted into a pipe with an inner diameter of 7 mm, and the entire diameter was reduced to an outer diameter of 0.8 m+n to prepare a primary wire. Next, 91 of these secondary strands were assembled, inserted into a tube made of an Ag-10 at% Ga alloy, and subjected to wire drawing to obtain a secondary strand of diameter T. Next, 91 of these secondary strands were assembled, and Ag-10at%Ga
They were gathered inside a tube made of an alloy with an outer diameter of 13 ma+ and an inner diameter of 12 mm, and wire-drawn to create a composite body with a diameter of 1.0 mm.

Next, 91 pieces of this complex were assembled to have an outer diameter of 131111
, is inserted into a Ta tube with an inner diameter of 12 mm, and a pure copper stabilizing pipe with an outer diameter of 18 ma+ and an inner diameter of 14 a+ m is placed on the outside of this Ta tube to reduce the diameter. A wire rod of 0 mm was made.

Subsequently, the wire was heat-treated at 800° C. for 24 hours in an Ar gas atmosphere to produce a superconducting wire.

When the critical temperature (Tc) of the obtained superconducting wire was measured, it showed an excellent value of Tc (mid point) = 18, 5 K, and the critical current density (Jc) in the magnetic field of IOT was found to be excellent.
) was measured and found that J c == 2 x 10 'A
/cII' was shown.

Therefore, it has been found that by carrying out the above method, a Nb5Ga-based superconducting wire with excellent superconducting properties can be manufactured.

"Effects of the Invention" As explained above, the present invention diffuses Ga into the Nb filament arranged inside the base made of Ag-X alloy, so that the critical temperature matching the stoichiometric composition and the high critical current density can be achieved. Nb3X superconducting filaments can be generated, and heat treatment is performed at 600 to 1000°C, so Nb3 has fine crystal grains and a high critical current density even in high magnetic field regions.
An X-based superconducting wire can be obtained. Furthermore, since diffusion of element Therefore, when the superconducting wire is cooled with a refrigerant and energized, the stabilizing material has a sufficiently low electrical resistance, so that the superconducting state of the superconducting wire can be stabilized.

[Brief explanation of the drawing]

Figures 1 to 9 show one embodiment of the present invention.
The figure is a cross-sectional view showing a combined state of the Nb rod and Ag-Ga vibe, Figure 2 is a cross-sectional view of the primary wire, Figure 3 is a cross-sectional view showing the state where the primary wire is inserted into the tube body, Figure 4 is a sectional view of the secondary strand, Figure 5 is a sectional view showing the secondary strand inserted into the tube, Figure 6 is a sectional view of the composite, and Figure 7 is the composite inside the tube. Fig. 8 is a cross-sectional view of a wire with a reduced diameter composite, Fig. 9 is a cross-sectional view of a superconducting wire, and Figs. 10 and 11 show an example of a conventional manufacturing method. Fig. 10 is a cross-sectional view of the composite, Fig. 11 is a cross-sectional view of the superconducting wire, Fig. 12 and Fig. 13 show other examples of the conventional manufacturing method, and Fig. 12 shows the plating layer. FIG. 13 is a cross-sectional view of the superconducting tape. A...Superconducting wire, lO...rod, 11...pipe, 13...composite, 14...-order strand, 15...
・Pipe body! 6... Secondary wire, 17... Tube body, 18.
... Composite, 19... Diffusion prevention tube, 20... Covering tube, 21... Wire, 22... Core portion, 23... Diffusion barrier layer, 24... Stabilizing layer.

Claims (2)

[Claims] (1) In the method for manufacturing Nb_3X (where X represents Ga or Al) based superconducting material, a strand is created by covering a Nb core material with an Ag-X alloy layer, and then a plurality of strands of this strand are made. The strands are assembled and inserted into a pipe made of Ag-X alloy, and further subjected to diameter reduction processing, and the process of collecting the strands and inserting them into the pipe and diameter reduction processing is repeated one or more times to obtain a composite. and then convert this complex to 6
Nb_ characterized by heat treatment at 00~1000℃
Method for producing 3X superconducting material. (2) In the method for manufacturing Nb_3X-based superconducting material, Nb
A wire is made by covering the core material with an Ag-X alloy layer, and then a plurality of these wires are assembled and inserted into a tube made of Ag-X alloy, and the diameter is further reduced. A composite body is created by repeating the process of gathering and inserting the strands into a tube body and diameter reduction process one or more times, and then assembling a plurality of this composite body to form a diffusion prevention tube made of Ta or Nb, etc. At the same time, a tube body made of a stabilizing material is placed on the outside of the diffusion prevention tube, and after the entire diameter is reduced, heat treatment is performed at 600 to 1000 °C to generate Nb_3X superconductor inside the composite. A method for producing a featured Nb_3X superconducting material.