JPH04277416A - Manufacture of nb3sn superconducting wire - Google Patents

Abstract

PURPOSE:To provide a superconducting wire having high residual resistance ratio and high critical current density by using a niobium-tube method. CONSTITUTION:A Ta-claded Nb alloy tube is produced by hydrostatic extrusion and roll forming, and subsequently a Cu-claded Sn rod is accommodated in this clad tube while a Cu tube is arranged outside followed by being produced in a composite wire through a drawing process. After a large number of this composite wires are filled in the Cu tube, hydrostatic extrusion process, pulling process, and continuous wire drawing are performed so that they are formed into wire rods of 0.9mm in outside diameter, followed by application of a heat- treatment at 720 deg.C for 20 hours. This Nb3Sn superconducting wire of multi-core structure has critical current density of 830A/mm<2> at 15T and RRR value of 100.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing superconducting wires, and in particular to a method for manufacturing superconducting wires, particularly Nb3 having a multi-core structure using the niobium tube method.
The present invention relates to improvements in the manufacturing method of Sn superconducting wires.

0002

[Prior Art] As a method for manufacturing Nb3Sn superconducting wire, a method using the niobium tube method (or pipe method), which is a type of composite processing method, is known (Japanese Patent Laid-Open No. 52-1
No. 6997). In this method, a large number of composite wires in which the outside of an Sn rod is sequentially coated with a Cu tube, a Nb tube, and a Cu tube serving as a stabilizing material are further housed in a Cu tube and subjected to cold working, and then Nb3Sn This method performs a heat treatment for formation, and has the advantage of eliminating the need for multiple intermediate annealing, which is a drawback of the so-called bronze method using a Cu-Sn alloy.

Superconducting wire made by the niobium tube method has a significantly higher critical current density (Jc) than superconducting wire made by other methods such as the bronze method, so it is often used in high-field magnets, and magnets exceeding 20T. are being produced one after another.

On the other hand, when superconducting wires are used in magnets for equipment such as NMR, stability is required, and for this purpose, in addition to the Jc value of the superconducting wires, the residual resistance ratio (RRR: resistance value at room temperature/critical temperature (resistance value directly above) is required to be high.

[0005]

[Problems to be Solved by the Invention] However, in the above-mentioned niobium tube method, when cold working is performed at a high degree of working, non-uniform deformation of the Nb tube is likely to occur, and furthermore, it may lead to breakage of the tube wall or disconnection. There are cases. If the pipe wall is locally extremely thin, Sn will diffuse into the matrix during the heat treatment to generate Nb3Sn, causing problems such as a decrease in the Jc value and RRR value and unstable cooling.

In order to avoid such problems, it has been considered to place a tube body made of a shielding material such as Ta on the outside of the Nb tube, but as it is difficult to process thin-walled Ta tubes, as a result, I had no choice but to use a thick Ta tube, and the over
There were disadvantages in that the Jc value of ll decreased and the cost increased.

The present invention was made to solve the above problems, and its purpose is to provide a method for manufacturing a superconducting wire with a high RRR value and an excellent overall Jc value using the niobium tube method. do.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the method for manufacturing an Nb3Sn superconducting wire of the present invention
After placing a large number of composites in which Cu-based metal tubes and Nb-based metal tubes are sequentially arranged outside an n-based metal in a Cu-based metal matrix, surface reduction processing is performed, and then Nb3S
A composite tube in which a shielding material for preventing the diffusion of Sn is arranged on the outside of the Nb-based metal tube when performing n-generation heat treatment, and the Nb-based metal tube and the shielding material are integrally formed in advance. It is configured by the following.

[0009] In the present invention, the composite tube formed integrally with the Nb-based metal tube and the shielding material is placed outside the Cu-based metal tube containing the Sn-based metal inside. It can be manufactured by the following method.

(a) Ta tube processed to a specified size and N
A Nb tube is prepared inside the Ta tube, and the Nb tube is housed inside the Ta tube, and the Nb tube is integrated into a composite body by explosive molding (explosion bonding). This is processed by roll forming to a predetermined size while performing intermediate annealing as necessary.

(b) Ta tube and N processed to a predetermined size
A Nb tube is prepared inside the Ta tube, and both ends are sealed by electron beam welding. Next, one end thereof is tapered, and then integrated by hydrostatic extrusion, and further processed to a predetermined size by roll forming, with intermediate annealing as required.

(c) In the method (b) above, the Nb tube is housed inside the Ta tube, and the Cu tube is further housed inside the Nb tube, and both ends are sealed by electron beam welding. Thereafter, it is processed to a predetermined size using the same method.

[0013] By the above method, it is possible to arrange a thin shielding material on the outside of the Nb tube, which could not be processed alone, thereby improving the overall Jc value.

As the Sn-based metal, Cu-based metal, and Nb-based metal in the present invention, in addition to Sn, Cu, and Nb, alloys thereof such as Ti-added Nb alloy can be used, and the shielding material may also be a material other than Ta. Of course, it is also possible to use other materials.

[0015]

[Function] With the above configuration, according to the method for manufacturing Nb3 Sn superconducting wire of the present invention, N
By using a composite pipe in which a Nb-based metal pipe and a shielding material are integrally molded in advance instead of a B-based metal pipe, the shielding material can be placed at the minimum necessary thickness, thereby achieving a high RRR value. It is possible to manufacture a superconducting wire having a Jc value of .

[0016]

[Examples] Examples of the present invention will be described below.

[0017] Outer diameter φ8.0mm, inner diameter φ4.0mm
A Ta-clad Nb alloy tube was manufactured by the method (b) above. The Ta:Nb ratio of this composite tube was 1:9.

[0018] Inside the above composite pipe, there is an outer diameter of φ3.9 mm.
A Cu-clad Sn rod was housed therein, and a Cu tube having an outer diameter of 9.1 mm and an inner diameter of 8.1 mm was disposed outside the rod, and a composite wire having a hexagonal cross section with a distance between opposite sides of 2.13 mm was manufactured by drawing. In this case, S inside the composite pipe
The n concentration was 50 wt%.

[0019] 258 of these composite wires have an outer diameter of φ49 mm.
After filling a Cu tube with an inner diameter of φ41 mm with its sides in contact, both ends were sealed by electron beam welding.
Next, it was extruded to an outer diameter of 33 mm by hydrostatic extrusion, and then subjected to drawing and continuous wire drawing to an outer diameter of 0.9 mm.
A wire rod of m was obtained.

[0020] This wire was heat-treated at 720°C for 20 hours to produce a multicore Nb3Sn superconducting wire, and its properties were measured. As a result, the critical current density (Jc) was 15T.
The power consumption was 830A/mm2, and the RRR value was 100.

On the other hand, instead of the above embodiment, the thickness is 1.8
When using a mm Nb tube, its RRR value is 5.3
Met.

[0022]

[Effect of the invention] As described above, the Nb3 Sn of the present invention
According to the method for manufacturing a superconducting wire, it is possible to manufacture a superconducting wire that has a high RRR value, excellent stability, and a high Jc value in a high magnetic field.

Claims (1)

[Claims] Claim 1: C.C.
A method for producing a superconducting wire in which a superconducting wire is placed in a U-based metal matrix, subjected to area reduction processing, and then subjected to heat treatment to generate Nb3Sn, in which a shielding material for preventing Sn diffusion is provided on the outside of the Nb-based metal tube. At the same time, the Nb
1. A method for manufacturing an Nb3 Sn superconducting wire, characterized in that the Nb3 Sn superconducting wire is constructed of a composite tube in which a metal tube and the shielding material are integrally molded in advance.