JPH04132114A - Manufacture of nb3x multi-core superconducting wire - Google Patents

Abstract

PURPOSE:To manufacture a longer wire rod having high critical current density by reducing the diameter of a billet by warm extruding at 100-400 deg.C, followed by a heat treatment. CONSTITUTION:An Nb foil 1 and an Al foil 2 in a superposed relation are wound around a Cu rod material 3 by a modified jelly roll process, to be inserted into a Cu pipe 4, followed by drawing, thereby obtaining a segment wire rod 5. the segment wire rod 5 is provided with matrices 6 made of Cu in the center thereof and in the outer periphery thereof, respectively. Between the matrices 6, the Nb foil 1 and the Al foil 2 are spiraled each in one layer. The obtained segment wire rod is inserted into a large-diameter Cu billet, followed by vacuum drawing. The billet is heated at 260 deg.C, followed by ward extruding, thus obtaining a wire rod. The obtained wire rod is repeatedly drawn. In the wire rod 9, a multiplicity of filaments 8 made of Nb, Al and Cu are formed in a matrix 7 made of Cu.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a Nb3X multicore superconducting wire that can be used as a superconducting wire for, for example, nuclear fusion reactors and SMES.

[Prior art and problems to be solved by the invention] Nb
3At superconducting material has a high critical magnetic field said to exceed 30T, and has better strain characteristics than Nb3Sn, so it is considered the third material following NbTi and Nb3Sn.
It is expected to be a practical superconducting material for nuclear fusion reactors, and is particularly expected to be used as a wire for superconducting magnets in nuclear fusion reactors.

In addition, in recent years, Nb and A
When the thickness of I is reduced to about 0.1 μm, the critical current density increases and is equivalent to the critical current density of Nb3Sn.
It has been reported that values even higher than this can be obtained.

However, industrially, there was a problem in that it was difficult to make the wire into a long length because the workability of Nb and human fibers was not good, and it was impossible to obtain a long superconducting wire. Attempts have been made to make Nb3At into a long wire by the jelly roll method, the Nb pipe method, etc., but sufficient results have not yet been obtained. Further, some attempts have been made to make wire rods using Cu-10%Ni as a sheath.

On the other hand, Nb3 used in large superconducting magnets for nuclear fusion reactors
At superconducting wires are required to have the following characteristics.

(1) A material with low electrical resistance, such as Cu or a Cu alloy, is used as the stabilizing material.

(2) It must be at least 1000m long.

(3) The critical current density at the non-edge portion is approximately Nb3Sn.
0A/mm" (12T) or more.

(4) It has a multicore structure in which filaments with a diameter of several tens of μm are dispersed.

In order to manufacture wire rods with such characteristics, vibrator wire drawing methods and the like have been attempted in the past. However, in the conventional method, there was a problem in that during wire drawing, the adhesion between the segments for forming a filament was insufficient, and wire breakage often occurred during wire processing.

The purpose of the present invention is to provide a method for manufacturing Nb5x multicore superconducting wires such as Nb3At, which solves these conventional problems and allows the production of longer wires while having a high critical current density. be.

[Means for Solving the Problems] A method for manufacturing an Nb3X multicore superconducting wire according to the present invention includes
b) N□bj-containing base material made of metal or Nb alloy;
The first wire rod is made of contact with an X-containing base material made of element X or an alloy containing element X, which produces a compound exhibiting superconductivity by reacting with After the process of forming a second wire by bundling and filling a plurality of second wires into a billet made of Cu or Cu alloy, the billet is
A step of processing by warm extrusion at a temperature of 0° C. or higher and 1 to 400° C. to form a reduced-diameter jI3 wire rod, and a step of heat-treating the third wire rod to form Nb3X. It is equipped with

Element 'X that reacts with N'b to create a compound that exhibits superconductivity
Examples include AlζSn or Ge.

``'The alloying elements contained in the Nb alloy and/or the alloy containing element X include Ti, 5i
SHf, Ta.

Examples include Zr5Mg or Be.

Further, in the method for producing a Nb3X multicore superconducting wire according to the present invention, the warm extrusion can be a direct extrusion method or a hydrostatic extrusion method.

Furthermore, if the first wire according to the present invention is obtained by overlapping and winding an N'b-containing sheet and an X-containing sheet by a jelly roll method, the object of the present invention can be more effectively achieved .

[Function] In the Nb3X multicore superconducting wire obtained according to the present invention,
A stabilizing material covering the first wire and the billet serve as a matrix, into which an Nb3X filament formed from the first wire by heat treatment is embedded. Cu or a Cu alloy forming the stabilizing material and billet has low electrical resistance and is optimal as a matrix. Further, the Cu or Cu alloy covering the first wire has good adhesion to each other when processing multifilamentary wires, and is also excellent in terms of processing and workability. (On the other hand, in this invention, when processing a multifilamentary wire, the
Warm extrusion is carried out at a temperature of 0°C.

In warm extrusion, the metal forming the wire softens, and especially since the outer skin of the second wire is Cu or a Cu alloy, the second
The adhesion between the wire rods is improved. In this way, warm extrusion improves the adhesion of the metal structure, so even if the extruded wire is processed to a smaller wire diameter, it can be processed without breaking. Therefore, it becomes easier to manufacture long multifilamentary wires. Additionally, as a result of experiments conducted by the present inventors, it was found that the thermal history during warm extrusion has little effect on the formation of Nb3X during subsequent heat treatment, and does not reduce the critical current density of the resulting wire. .

Although both a direct extrusion method and a hydrostatic extrusion method can be applied to the warm extrusion of the present invention, further improvement in processability can be expected by using the isostatic extrusion method.

[Example 1] First, as shown in FIG. 1, Nb foil 1 and At foil 2 are rolled around a Cu bar 3 one layer at a time according to the jelly roll method, and the rolled up material is placed inside a Cu pipe 4. After inserting the wire into the wire, wire drawing was performed to create a segment wire 5 having a cross section as shown in FIG. As shown in FIG. 2, the segment wire 5 is provided with a matrix made of Cu at the center and the outer periphery, and between this matrix 6 is an Nb foil 1 and an At
The foils 2 are stacked layer by layer in a spiral shape.

Segment wire rod 24 of 2 mmφ obtained in this way
0 was inserted into a large-diameter Cu billet of 70 mmφ x 65 mmφ, the inside of the billet was evacuated, and the opening was closed by electron beam welding. Next, the sealed billet is 26
After heating at 0℃ for 2 hours, warm extrusion was performed to 35mm.
A wire rod of φ was obtained. After that, 15% of the obtained wire
The wire drawing process was repeated at a cross-section reduction rate of , to obtain a wire rod with a diameter of 0.5 mm. FIG. 3 is a cross-sectional view of the wire obtained in this manner. As shown in the figure, the wire 9 has a structure in which a large number of filaments 8 made of Nb, A'' and Cu are formed in a matrix 7 made of Cu.

On the other hand, as a comparative example, after drawing the 2 mmφ segment wire rod to 1 mmφ,
Insert 150 pieces into φ Cu pipe and make 9.5mm cold.
Wire drawing was performed up to φ.

The area reduction rate during processing was also 15%.

Table 1 shows the wire diameter and the number of wire breakages at each processing stage for Examples and Comparative Examples. As shown in the table, in the example 5. During machining from Qmmφ to 0.5mmφ, a total of four disconnections occurred. On the other hand, in the comparative example, wire breakage occurred a total of 10 times during the same processing. Further, in the example, a single length of 1500 mm or more could be obtained as a 0.5 mmφ wire, but in the comparative example, a maximum single length of only 200 mm could be obtained. From the above results, it has become clear that according to the present invention, longer wire rods can be easily manufactured.

Table 2 shows the critical current density when the wire rods obtained in Examples and Comparative Examples were heat-treated under various conditions. As shown in the table, the example and the comparative example showed almost the same critical current density. On the other hand, when measuring the diameter of the filament formed in the matrix and the thickness of Nb and At in the Q, 5 mmφ wire material before heat treatment, the diameter of the filament was 30 mm in both the example and the comparative example.
μm, and the thickness of Nb and At is 0°3 each.
μm and 0.1 μm. In this way, the diameter of the filament and the thickness of Nb and AI are sufficiently small, so 8
Good Nb3A by heat treatment at 00°C to 850°C
It was thought that fine crystals of t were formed, and as a result, a high critical current density could be achieved.

In addition, in the examples, the wire rods obtained at each processing step were
After treatment at 00° C. for 5 hours, the critical current density per non-end portion of the obtained wire was measured. Table 3 shows the relationship between the diameter of the wire at each processing step and the critical current density of the wire obtained after heat treatment. As is clear from the table, as the wire diameter becomes smaller, the critical current density gradually increases. This means that if the wire diameter is reduced according to the present invention, fine crystals of Nb3At can be reliably formed by heat treatment, and as a result, a high critical current density can be obtained.

(Margin below) Table Note that in the above embodiments, the first wire according to the present invention was made by rolling up Nb foil and At foil according to the jelly roll method, but the invention is not limited to this. For example, , a plurality of Nb thin wires and Atn thin wires may be twisted together or bundled together. Furthermore, the segment wire rods shown in the above embodiments may not have a central Cu bar (for example, they may have a structure in which Nb foil and At foil are wound and a Cu vibrator is covered). .

[Effects of the Invention] As explained above, according to the present invention, Nb3 has a multicore structure in which filaments of several tens of μm in diameter are dispersed in a matrix made of Cu or Cu alloy with low electrical resistance.
X superconducting wires can be produced. Furthermore, as a result of improved workability during manufacturing, it is possible to form filaments made of finer crystals of Nb3X, so it is possible to obtain a superconducting wire with a high critical current density. moreover,
Since the diameter reduction process is performed by improving the adhesion of the metal structure by warm extrusion, there is less wire breakage in the subsequent wire drawing process, and a longer superconducting wire can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing the process of forming a segment wire according to the jelly roll method in an embodiment according to the present invention. FIG. 2 is a cross-sectional view of the segment wire rod obtained by the process shown in FIG. 1. FIG. 3 is a sectional view of a wire rod obtained after the diameter reduction process of a multifilamentary wire is completed in an embodiment according to the present invention. In the figure, 1 is Nb foil, 2 is At foil, 3 is Cu bar,
4 is a Cu pipe, 5 is a segment wire, 6 and 7 are matrices, 8 is a filament, and 9 is a wire.

Claims (5)

[Claims] (1) A first structure in which an Nb-containing base material made of Nb metal or a Nb alloy is brought into contact with an X-containing base material made of an element a step of forming a second wire by covering the wire with a stabilizing material made of Cu or a Cu alloy, and after bundling and filling a plurality of the second wire into a billet made of Cu or a Cu alloy, a step of processing the billet by warm extrusion at a temperature of at least 100° C. or higher and 400° C. or lower to form a third wire rod having a reduced diameter; and a step of heat-treating the third wire rod to form Nb_3X. A method for manufacturing a Nb_3X multicore superconducting wire, comprising: (2) The method for producing a Nb_3X multifilamentary superconducting wire according to claim 1, wherein the warm extrusion is performed by a direct extrusion method or a hydrostatic extrusion method. (3) The first wire is made of Nb by the jelly roll method.
The method for producing a Nb_3X multicore superconducting wire according to claim 1, wherein the Nb_3X multicore superconducting wire is obtained by stacking the X-containing sheet and the X-containing sheet and rolling them up. (4) The method for manufacturing a Nb_3X multicore superconducting wire according to claim 1, wherein the element X is at least one selected from the group consisting of Al, Sn, and Ge. (5) The alloying elements contained in the Nb alloy and/or the alloy containing the element X are Ti, Si, Hf, Ta, and Zr.
, Mg, and Be.