JPH04132113A - 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 hydrostatic extruding, 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, for hydrostatic extruding at a room temperature, 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 manufacturing a Nb,

[Prior art and problems to be solved by the invention] Nb
, At superconducting material has a high critical magnetic field said to exceed 30T, and has better strain characteristics than Nb3Sn, so it is 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 wire for superconducting magnets in nuclear fusion reactors.

In addition, in recent years, Nb and At superconducting wires have been
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 is a problem in that it is difficult to lengthen the wire because Nb and At have poor workability, and it is impossible to obtain a long superconducting wire. Attempts have been made to make Nb3At into a long wire by the jelly roll method, Nb vibe 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.
Must be 0A/mm2 (12T) or higher.

(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 solve such conventional problems and provide a method for manufacturing Nb, X multicore superconducting wires made of Nb, At, etc., which can produce longer wires while having a high critical current density. It is about providing.

[Means for Solving the Problems] A method for manufacturing a Nb,X multicore superconducting wire according to the present invention includes
A first material made by contacting an Nb-containing base material made of a b metal or a Nb alloy with an X-containing base material made of an element X or an alloy containing the element
a step of forming a second wire by covering the wire with a stabilizing material made of Cu or a Cu alloy; and a step of bundling and filling a plurality of second wires into a billet made of Cu or a Cu alloy; Processing the billet by at least hydrostatic extrusion to form a third wire having a reduced diameter;
The third wire is heat treated to form Nb.

and a step of forming an X.

Examples of the element X that reacts with Nb to form a compound exhibiting superconductivity include A L SS n or Ge.

Examples of alloying elements contained in the Nb alloy and/or the alloy containing element X include Ti5St, HfSTalZr5Mg, and Be.

In addition, in the method for manufacturing Nb3X multicore superconducting wire according to the present invention, the temperature during hydrostatic extrusion is from room temperature to 100°C.
It can be as follows.

Furthermore, if the first wire rod according to the present invention is obtained by stacking and winding up an Nb-containing sheet and an X-containing sheet using a jelly roll method, the object of the present invention can be achieved more effectively.

[Function] In the Nb,X multicore superconducting wire obtained according to the present invention,
The stabilizing material and billet covering the jlfl wire serve as a matrix, into which the 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 workability.

On the other hand, in this invention, hydrostatic extrusion is performed during multifilamentary wire processing. In hydrostatic extrusion, isotropic extrusion is performed, so that close contact between the Nb-containing base material and the X-containing base material, the Nb-containing base material and the stabilizing material, and the stabilizing materials are achieved by the hydrostatic pressure during extrusion. In this way, hydrostatic extrusion improves the adhesion of the metal structure, so even if a wire subjected to isostatic pressure processing is processed to an even smaller wire diameter, it can be processed without breaking. Therefore, it becomes easier to manufacture long multifilamentary wires. Furthermore, the stress state of the processed deformed portion acts in such a way that hydrostatic stress is accumulated, so that workability is improved. Therefore, sufficient processing can be performed even at temperatures from room temperature to about 100°C. Such a temperature range is suitable for Nb,
(e.g. 800°C for Nb1Al)
(near), there is no concern at all about the influence of heat generation during extrusion on the formation of Nb3X, and furthermore, the decrease in the critical current density of Nb and X.

[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 rolled up into 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. 5, the segment wire 5 is provided with a matrix 6 made of Cu at the center and outer periphery, and between the matrix 6, a Nb foil 1 and an At foil 2 are stacked one layer at a time in a spiral shape.

Segment wire rod 36 of 3 mmφ obtained in this way
0 was placed in a large diameter Cu billet of 120 mmφ x 105 mmφ, and after the inside of the billet was evacuated, the opening was closed by electron beam welding.

Next, the sealed billet was subjected to hydrostatic extrusion at room temperature to obtain a wire rod with a diameter of 5 Q mm.

A hydrostatic extrusion press was used for the hydrostatic extrusion.6 Thereafter, the wire rod obtained was repeatedly drawn at a cross-section reduction rate of 25% to obtain a wire rod with a diameter of 0.5 mm. Figure 3 shows
It is a sectional view of the wire obtained in this way. As shown in the figure, the wire 9 has a matrix 7 made of Cu.
This structure has a large number of filaments 8 made of Nb, At, and Cu.

On the other hand, as a comparative example, after drawing the above-mentioned 3 mmφ segment wire to 1 mmφ,
Insert 150 pieces into a φ Cu pipe and make it 0.5mm cold.
Wire drawing was performed up to φ.

The area reduction rate during processing was also 25%.

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, wire breakage occurred a total of five times during processing from 5.0 mmφ to 0.5 mmφ. On the other hand, in the comparative example, wire breakage occurred a total of 10 times during the same processing. Further, in the examples, a single length of 1000 mm or more could be obtained as a 0.5 mmφ wire, but in the comparative example, only a maximum single length of 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 per non-end portion 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. - side, 0.5m before heat treatment
When measuring the diameter of the filament formed in the matrix and the thickness of Nb and At in the mφ wire, the diameter of the filament was 30 μm in both Examples and Comparative Examples, and the thickness of Nb and AI was 0.3 μm, respectively. It was 0.1 μm. As the diameter of the filament and the thickness of Nb and AI are sufficiently small, good Nb and AI microcrystals are formed by heat treatment at 800°C to 850°C, and as a result, a high critical current density can be achieved. It was considered possible.

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. FIG. 4 shows the relationship between the diameter of the wire at each processing stage and the critical current density of the wire obtained after heat treatment. As is clear from the figure, as the wire diameter becomes smaller, the critical current density gradually increases. This means that if the wire diameter is made thinner according to the present invention, fine crystals of Nb and At can be reliably formed by heat treatment, and as a result, a high critical current density can be obtained. There is.

(Margins below) Table 1 Table 2 In the above embodiments, the first wire according to the present invention was made by rolling up Nb foil and AI foil according to the jelly roll method, but the present invention is not limited to this. For example, a plurality of Nb wires and A-thin wires may be bundled or twisted together. Further, the segment wire rod shown in the above embodiment may be one without the central CU rod, for example, it may have a structure in which Nb foil and At foil are wound and a Cu pipe is covered.

[Effects of the Invention] As explained above, according to the present invention, Nb3X with a multi-core structure in which filaments of several tens of μm in diameter are dispersed in a matrix varnish made of Cu or Cu alloy with low electrical resistance.
Superconducting wires can be manufactured. Moreover, as a result of improved workability during manufacturing, it is possible to form filaments made of finer crystals of Nb3X, so that a superconducting wire with a high critical current density can be obtained. Furthermore, since the diameter reduction process is performed by improving the adhesion of the metal structure by hydrostatic 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. Figure 4 shows the diameter of the wire obtained in the example and 127
．． It is a figure showing the relationship of critical current density at 4.2K. 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. Figure 3 Figure 4 Figure 4 Illustrated record A1hi (mm)

Claims (5)

[Claims] (1) A first Nb-containing base material made of Nb metal or Nb alloy and an X-containing base material made of element X or an alloy containing element X that reacts with Nb to form a compound exhibiting superconductivity. 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; Manufacturing a Nb_3X multifilamentary superconducting wire comprising the steps of processing a billet by at least hydrostatic extrusion to form a diameter-reduced third wire, and heat-treating the third wire to form Nb_3X. Method. (2) The temperature during the hydrostatic extrusion is from room temperature to 100°C
The method for manufacturing a Nb_3X multicore superconducting wire according to claim 1, which is as follows. (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.