JP2808874B2 - Nb (3) Manufacturing method of Al multi-core superconducting wire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a Nb ₃ Al multi-core superconducting wire that can be used as a superconducting wire for a nuclear fusion reactor and for a SMES, for example.

[Prior Art] Nb ₃ Al superconducting material has a high critical magnetic field which is said to more than 30T, since the distortion characteristic is also better than Nb ₃ Sn, the third following NbTi and Nb ₃ Sn Is expected as a practical superconducting material, particularly as a wire for a superconducting magnet in a fusion reactor.

In recent years, in the Nb ₃ Al superconducting wire, when the thickness of Nb and Al is reduced to about 0.1 μm, the critical current density increases, and a high value equal to or exceeding the critical current density of Nb ₃ Sn is obtained. It is reported to be obtained.

However, since the workability of Nb and Al is not good, it is difficult to increase the length industrially, and there is a problem that a long superconducting wire cannot be obtained. Attempts have been made to make Nb ₃ Al long wires by the jelly roll method and the Nb pipe method, but no satisfactory results have yet been obtained. For example, a wire rod used for a superconducting magnet in a fusion reactor needs to be at least 600 m long, and the current goal is to increase the length to 1000 m or more. Also, Cu
Some attempts have been made to use -10% Ni as a sheath, but it is necessary to use Cu as a stabilizer.

[Problems to be Solved by the Invention] As described above, the reason why it is difficult to increase the length of the Nb ₃ Al multi-core superconducting wire is that the mutual interface in the laminated portion of Nb and Al is large in area and different from each other. This is because Al and Nb are different in the amount of deformation during wire drawing due to metal-to-metal bonding, resulting in poor adhesion and disconnection.

Conventionally, the thickness of Nb and Al for which long wires can be manufactured is
They are about 8 μm and 0.2 μm. At such a thickness,
Even after heat treatment, a high critical current density (Jc) was not obtained.
It is about 0A / mm ² (12T). For this reason, it is only about half of the Nb ₃ Sn superconducting wire currently in practical use.

The purpose of this invention is to solve such conventional problems, Nb ₃ X based multi-filamentary superconducting wire, such as Nb ₃ Al, which can be obtained thinner to high critical current density thickness of the Nb and Al It is to provide a manufacturing method of.

[Means for Solving the Problems] The production method of the present invention comprises Nb metal or Nb alloy.
A primary stack in which an Nb-containing sheet and an X-containing sheet made of an element X or an alloy containing the element X, which forms a compound showing a superconducting wire by reacting with Nb, are overlapped and wound on a roll and inserted into a Cu or Cu alloy pipe Reducing the diameter of at least one extrusion to form a primary segment;
Inserting a secondary segment into a Cu or Cu alloy pipe to form a secondary stack, reducing the diameter of the secondary stack by extrusion to form a secondary segment, and reducing the secondary segment to a desired wire diameter. The method includes a step of forming a diameter and a step of heat-treating the secondary segment to form Nb ₃ X.

Examples of the element X that forms a compound exhibiting superconductivity by reacting with Nb include Al, Sn, and Ge.

 The present invention particularly uses Al as the element X.

Examples of alloy elements contained in the Nb alloy and / or the alloy containing the element X include Ti, Hf, Ta, Zr, Mg, and Be.

[Effects of the Invention] In the present invention, since the primary segments are formed by reducing the diameter by extrusion, the adhesion at the mutual interface between Cu, X and Nb is improved, and therefore the workability of the entire wire is reduced. improves.

In the present invention, as an extrusion method for forming the primary segment, a hot extrusion method, an isostatic extrusion method, or the like can be employed.

In the present invention, hydrostatic extrusion is particularly preferably used as the extrusion.

Further, in the present invention, the thickness of Nb and X can be reduced to the minimum by extruding a plurality of times when forming the primary segment. Therefore, the critical current density (Jc) can be significantly improved. Further, by extruding a plurality of times, the mutual adhesion of Cu, Nb and X can be further improved, and the workability of the entire wire can be improved.

Further, according to the present invention, extrusion is used to form the primary segment, and the extrusion can be performed at a high degree of processing, so that productivity can be improved.

Example 1 Example 1 As shown in FIG. 1, an Al sheet 2 was arranged side by side on an Nb sheet 1, and the Nb sheet 1 and the Al sheet 2 were rolled up around a Cu bar 3 and rolled. I made it. This was inserted into a Cu pipe 4 as a matrix pipe. Thereafter, both ends were covered with Cu by electron beam welding, and the diameter was reduced from 70 mm to 25 mm by hydrostatic extrusion.

FIG. 2 shows the primary segment 5 thus obtained.
FIG.

The primary segment obtained in this manner is drawn to form a primary segment 6 having a hexagonal cross section, and as shown in FIG. Stacked. The secondary stack is again subjected to hydrostatic extrusion to form a secondary segment.
The next segment was drawn to obtain a Nb ₃ Al multicore superconducting wire having a desired wire diameter.

FIG. 4 is a cross-sectional view showing the Nb ₃ Al multi-core superconducting wire thus obtained. Referring to FIG. 4, a large number of primary segments 6 are formed in a Cu matrix 8.
In this example, as shown in Table 1, wire drawing was performed so that the final wire diameter was 0.81 mm, the thickness of the Nb layer in the Nb ₃ Al filament was 295 nm, and the thickness of the Al layer was 80 nm. The thickness of the Nb sheet and Al sheet to be used is determined.

Example 2 An Nb ₃ Al multifilamentary superconducting wire was produced in the same manner as in Example 1 except that the primary stack was reduced in diameter to form a primary segment, and was extruded twice by hydrostatic extrusion. did.

In the final superconducting wire diameter, the thicknesses of Nb and Al were 110 nm and 30 nm, respectively, which were much smaller than those in Example 1.

Example 3 In this example, as in Example 2, the extrusion for reducing the diameter from the primary stack to the primary segment was performed by two hot direct extrusions. However, the thicknesses of the Nb sheet and the Al sheet were adjusted in advance so that the final thicknesses of Nb and Al were almost the same as in Example 1 above.

Comparative Example For reducing the diameter of the primary stack into primary segments,
An Nb ₃ Al multi-core superconducting wire was produced in the same manner as in the above example except that wire drawing was used instead of extrusion.

Nb at the final wire diameter of Examples 1 to 3 and Comparative Example
Table 1 shows the thickness of the layer and the Al layer, the single length (average length of the wire obtained by the final drawing), and the critical current density (Jc) per non-copper portion at 12T and 4.2K. It was shown to.

As is clear from Table 1, according to the present invention, in Examples 1 to 3 in which the processing method for reducing the diameter from the primary stack to the primary segment was extruded, the final wire length was compared with the conventional one. The superconducting wire with high Jc could be obtained longer than the example.

Further, as is apparent from Example 2, the Nb layer and the Al layer can be further reduced in thickness by performing extrusion plural times when reducing the diameter from the primary stack to the primary segment. It turned out that high Jc can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a method of forming a primary stack according to the present invention. FIG. 2 is a sectional view showing a primary segment formed according to the present invention. FIG. 3 is a perspective view showing a method of forming a secondary stack according to the present invention. FIG. 4 is a sectional view showing a secondary segment formed according to the present invention. In the figure, 1 is an Nb sheet, 2 is an Al sheet, 3 is a Cu rod,
4 is a Cu pipe, 5 is a primary segment, 6 is a hexagonally shaped primary segment, 7 is a Cu pipe, 8 is a Cu matrix, and 9 is a secondary segment.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-130699 (JP, A) JP-A-2-148620 (JP, A) JP-A-55-163710 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) H01B 13/00 565 F H01B 12/10

Claims (4)

(57) [Claims] 1. An Nb-containing sheet made of Nb metal or an Nb alloy and an Al-containing sheet made of Al or an alloy containing Al are overlapped and wound into a roll and inserted into a Cu or Cu alloy pipe. Reducing the diameter of the primary stack by at least one hydrostatic extrusion to form a primary segment; and inserting the plurality of primary segments into a Cu or Cu alloy pipe to form a secondary stack. Reducing the diameter of the secondary stack by hydrostatic extrusion to form a secondary segment; reducing the diameter of the secondary segment to a desired wire diameter; and heat-treating the secondary segment to Nb ₃ Al Forming a multi-core Nb ₃ Al superconducting wire. 2. The two types of sheets are superimposed around a Cu rod, wound into a roll, inserted into a Cu pipe to form a primary stack, and a plurality of the primary segments are placed in a Cu pipe. The method of claim 1, wherein the secondary stack is formed by inserting. 3. The method according to claim 1, wherein in the step of forming the primary segment, the hydrostatic extrusion is performed a plurality of times.
The method according to claim 1. 4. After the obtained primary segment is drawn into a hexagonal cross section, a plurality of the primary segments are
The secondary stack is formed by being inserted into a Cu or Cu alloy pipe.
The production method according to the paragraph.