JPH04132115A - Manufacture of nb3x multi-core superconducting wire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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
, 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 A
It is reported that when the thickness of t is reduced to about 0.1 μm, the critical current density increases, and a high value equivalent to or exceeding the critical current density of Nb3Sn 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, 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 1,000 meters long.

(3) The critical current density at the non-edge part is about Nb3Sn4
Must be 0OA/mm2 (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, pipe drawing methods and the like have been attempted. 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
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
forming a second wire by covering the wire with a stabilizing material made of Cu or a Cu alloy, and bundling a plurality of the second wires into a billet made of Cu or a Cu alloy,
a step of processing the billet by hot extrusion at a temperature of at least 400° C. or more and 600° C. or less to form a third wire rod having a reduced diameter, and heat treating the third wire rod, and a step of forming Nb and X.

Examples of the element X that reacts with Nb to form a compound exhibiting superconductivity include AI, Sn, and Ge.

As the alloying element contained in the Nb alloy and/or the alloy containing element X, T iz S is Hf s T a
Examples include sZr, Mg or Be.

Moreover, if the first wire according to the present invention is obtained by stacking and winding up an Nb-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,
The stabilizing material covering the first wire and the billet serve as a matrix, into which Nb, X filaments formed from the first wire by heat treatment are 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, hot extrusion is performed during multifilamentary wire processing. In hot extrusion, the entire metal structure is softened by heating, so that sufficient adhesion between metals can be achieved during extrusion processing. In this way, hot 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. Further, through experiments conducted by the present inventors, it was found that the thermal history during hot extrusion has little effect on the formation of Nb3X by subsequent heat treatment, and does not reduce the critical current density of the resulting wire.

In this invention, the temperature during hot extrusion is 400°C from the viewpoint of sufficiently improving the adhesion between the second wires covered with the outer sheath made of Cu or Cu alloy.
The temperature is preferably 60 °C or higher, from the viewpoint of preventing melting of AI within the material.
The temperature is preferably 0°C or lower.

[Example] 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 has a matrix 6 made of Cu at the center and outer periphery, and between the matrix 6, Nb foil 1 and A2 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 inserted into a large-diameter Cu billet of 120 mmφ x 100 mmφ, the inside of the billet was evacuated, and the opening was closed by electron beam welding.

Next, the sealed billet was heated at 450° C. for 1 hour and then hot extruded to obtain a wire rod with a diameter of 50 mm. A hot direct extrusion press was used for hot extrusion. after that,
The wire rod thus obtained was repeatedly drawn at a cross-sectional area reduction rate of 20% to obtain a wire rod with a diameter of Q and 5 mmφ. FIG. 3 is a cross-sectional view of the wire obtained in this manner. As shown in the figure, the wire 9 has a matrix 7 made of Cu, Nb,
It has a structure in which a large number of filaments 8 made of AL and Cu are formed.

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 cold cut it to Q, 5mm.
Wire drawing was performed up to φ.

The area reduction rate during processing was also 20%.

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 two 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 example, a wire rod of 0.5 mmφ was able to obtain a single length of 1000 mm or more, 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 per non-body 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.

On the other hand, in the 0.5 mmφ wire before heat treatment, the diameter of the filament formed in the matrix and the Nb
The diameter of the filament was 30 μm in both the example and the comparative example, and the thickness of At was measured.
The thicknesses of b and At are 0.3 μm and 0.1 μm, respectively.
It was m. In this way, the filament diameter and Nb
And since the thickness of At is sufficiently small, 85℃ from 800℃
It was considered that good Nb3At fine crystals were formed by the heat treatment at 0° C., 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-body portion of the obtained wire was measured. Table 31: 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 table, as the wire diameter becomes smaller, the critical current density gradually increases. This means that if the wire diameter is made thinner according to this invention,
This means that fine crystals of Nb and AI can be reliably formed by heat treatment, and as a result, a high critical current density can be obtained.

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. The At thin wires may be twisted or bundled together. Further, the segment wire shown in the above embodiment may be one without the central Cu bar,
For example, a structure in which a Cu pipe is placed over a Nb foil and an At foil wound thereon may be used.

Table 2 Table 1 Table 3 [Effects of the Invention] As explained above, according to the present invention, a multicore structure in which filaments with a diameter of several tens of μm are dispersed in a matrix made of Cu or Cu alloy with low electrical resistance can be obtained. Nb3X superconducting wire 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 hot extrusion, there are fewer wire breaks during the subsequent wire drawing process, and longer superconducting wires can be easily produced.

[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 (4)

[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; a step of processing the billet by hot extrusion at a temperature of at least 400° C. or higher and 600° 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 producing a Nb_3X multicore superconducting wire. (2) 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. (3) 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. (4) 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.