JPH03246822A - Cu or al stabilized superconducting wire and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the deterioration of superconducting characteristics by covering each of Nb-Ti filaments containing a plurality of scattered materials A not producing an intermetallic compound with Ni-Tb, with a material B not producing any reaction product with the materials. CONSTITUTION:A plurality of Nb-Ti filaments 1 having a sectional structure with a plurality of scattered materials A2 practically free from the generation of an intermetallic compound with Nb-Ti 1, are respectively covered with a material B3 not producing a reaction product with any of a stabilizer 4, Nb-Ti 1 and the material A2. According to the aforesaid construction, an intended wire material can be processed without causing a drop in workability, and superconducting characteristics can be improved, due to the introduction of an artificial pinning center as aforementioned.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a Cu- or Al-stabilized superconducting wire in which a pinning center is artificially introduced into a Nb-Ti filament, and a method for manufacturing the same.

[Conventional technology]

Nb-Ti superconducting wires are manufactured with different superconducting characteristics required depending on their use.

As a method to control the critical current density characteristics of Nb-Ti superconducting wire, - For boat fishing, we apply processing strain by cold working Nb-Ti superconducting wire after hot extrusion.
A method is used in which fine αTi is precipitated in the vicinity of dislocations generated by cold working by adding sequential multi-stage aging heat treatment, and the critical current density characteristics obtained by this cold working rate and aging heat treatment conditions are controlled. is being carried out. According to this method, it is clear that a higher critical current density can be obtained by increasing the cold working rate and increasing the number and duration of multistage aging heat treatment.
Since the workability of Nb-Ti itself is significantly reduced, Nb-T
It is not uncommon for the i-filament to break, resulting in deterioration of the superconducting properties, or for the wire itself to break. Particularly in the case of ultra-fine multi-core Nb-Ti superconducting wires that are required to handle high magnetic fields, such as large magnets for particle accelerators, there have been problems in that workability is significantly reduced and wire breakage occurs frequently.

Due to the above-mentioned problems, a method of artificially introducing a pinning center has been studied as a method of improving the bottle-holding force without requiring severe cold working or aging heat treatment. In this method, a normal conductive substance with good workability to some extent is introduced into the Nb-Ti filament at the stage of wire formation, and the pinning center is refined to several to tens of nanometers by surface reduction processing. That is.

For example, a Nb-Ti thin rod wrapped with a pure Cu sheet of a predetermined thickness is bundled, inserted into a Cu or Cu alloy tube, and then hot extruded to form a composite material with multiple cores. When forming a superconducting wire, Cu serves as a pinning center. Since Cu is a normal conductor even at the temperature of liquid He, it functions as a pinning center. According to this method, pinning centers can be generated without requiring severe cold working or aging heat treatment, and the number of pinning centers can be freely controlled by the design of the strands, so the critical current density This has the advantage that the characteristics can be controlled more accurately and that different superconducting wires can be designed and manufactured depending on the required characteristics.

[Problem to be solved by the invention]

However, as mentioned above, when Cu is used as an artificial pinning center, there is a problem with composite workability because the deformation resistance is significantly different from that of NbTi, and due to intermediate heat treatment etc., the interface between Nb-Ti and Cu Because it produces a Cu-Ti compound with extremely poor processability,
There were problems such as filament breakage occurring during the area reduction process, which significantly deteriorated the superconducting properties, or in the worst case, the wire itself breaking.

[Means to solve the problem]

The present invention was made as a result of intensive studies in view of the above points, and its purpose is to create an Nb-T filament in which a pinning center is artificially introduced into the Nb-Ti filament.
i. Introducing artificial pinning centers in 4g conductive wires will not result in the production of secondary reaction products that are harmful in practice and will not deteriorate the superconducting properties, and will improve workability. The present invention provides a good Cu- or Al-stabilized superconducting wire and a method for manufacturing the same.

In other words, the superconducting wire according to the present invention means that each of a plurality of Nb-Ti filaments has a cross-sectional structure in which a plurality of materials A, which do not practically form an intermetallic compound with NbTi, are interspersed. A Cu or Al stabilized superconducting wire characterized by being coated with a material B that does not produce reaction products with either Nb-Ti or material A, where material A is Nb or Ta and material B is Nb or Ta
is suitable. The manufacturing method is as follows: 1) A Nb-Ti alloy rod is provided with a plurality of through holes parallel to its longitudinal direction, a Nb or Ta rod is inserted into the holes, and then the periphery of the Nb-Ti alloy rod is When using a composite material coated with Nb or Ta, then sealed in a pure Cu tube and hot extruded as a wire, ■
A Nb-Ti alloy rod has one or several through holes parallel to its longitudinal direction, and a plurality of Nb or Ta rods are inserted into the through holes, which are then bundled together and surrounded by Nb or Ta.
Then, when hot-extruding the pure Cu tube and sealing it in a pure Cu tube to make a wire, Bundle multiple pieces together so they don't touch each other, and surround them with N.
b or Ta, and then sealed in a pure Cu tube,
For each case when hot extruded composite material is used as wire,
Cu or Al characterized by bundling a plurality of the wires, inserting them into a pure Cu pipe or pure Al pipe, sealing them, and hot extruding them.
This is a method for producing a stabilized superconducting wire.

[Effect]

In the present invention, since the plurality of materials A scattered within the cross section of one Nb-Ti filament do not practically form intermetallic compounds with Nb-Ti, pinning centers are artificially introduced. No secondary reaction products harmful to plastic working are generated, and processing can be performed in a sound manner. Furthermore, as this material A, for example, Nb such as Nb or Ta
- It is preferable to use a material that does not have a large difference in deformation resistance from Ti because composite workability is also improved. Here, if Nb or Ta is used for the artificial pinning center, these also have liquid H
Nb-Ti exhibits superconductivity at temperatures of The superconductivity of is broken and it becomes a normal conductivity state, so the pinning effect can be obtained without any practical problems. In addition, for practical purposes, each Nb-Ti filament introduced into the artificial pinning center is coated with a stabilizing material, Nb-Ti, and a material B that does not produce reaction products with material A. Since reaction with Nb-Ti and/or material A can be prevented, and secondary reaction products harmful to plastic working are not generated, sound processing can be achieved.

〔Example〕

220 through holes were drilled parallel to the longitudinal direction of the Nb-Ti rod, and Nb thin rods were inserted and filled into the holes to form a Cu
The composite material inserted and fitted into a 0.5 wt% Mn tube was hot extruded at an extrusion temperature of 900°C, drawn and formed into a final hexagonal shape, and then straightened and cut to form a primary wire. 130 of the primary wires were neatly bundled and inserted into a pure Cu tube, both ends of which were sealed with pure Cu lids, and the composite material was hot extruded at an extrusion temperature of 500°C, then drawn and formed into a final hexagonal shape. The straightened and cut wires were used as secondary strands, and 222 secondary strands were neatly bundled and inserted into a pure Cu tube, and both ends were sealed with pure Cu lids.
0 φ×500mmj! A cable billet was produced.

This cable billet was extruded at a temperature of 500"C to 15n+
After hot extrusion to 3.44 mmφ (as-annealed), the operation of adding aging heat treatment of 380"CX24h at every 52% of the total processing rate was repeated 4 times, and then the wire was drawn to 3.44 mmφ (as-annealed), and then non-annealed to 0.520 mm. Draw the wire to mφ,
Finally, running annealing was performed in an annealer at SOO°C x 20m/11in.

At this time, the diameter of one Nb-Ti filament is approximately 1
．． 065-, and the filament has a cross-sectional structure in which Nb with a thickness of about 5.8 nm is scattered at intervals of about 64.9 nm. This 0.520 mmφ wire was cooled with liquid He, the critical current value I, (A) was measured in a 5 T magnetic field, and the critical current density, J c
(A/mj) was determined by calculation. The measurement is 0.5
n− arbitrarily sampled from a long line of 20 amφ
I followed 20. As a result, 3080-3220 (
It was found that a high critical current density of A/-') was stably obtained. As a comparison material, Nb-Ti rod was
B sheet wrapped around Cu-0,,5wt%Mn
The composite material inserted and fitted into the tube was hot-extruded at an extrusion temperature of 900°C, wire-drawn, formed into a final hexagonal shape, straightened and cut, and used as the primary wire. 100
PengφX500mmj! Cable billet (28 strands)
860 pieces) and 0.520mm under the same processing conditions.
Wire drawn to φ, and finally annealed at 500°C
Running annealing was performed at 0 m /11 inch.

At this time, the diameter of one Nb-Ti filament is approximately 1
．． 065-, and nothing in particular is buried in the cross section, I and (A) were measured using the same measuring method and measurement conditions as above for this 0.520 Mφ wire, and J c
(A/mj) was calculated and found to be 5T.
Although the J value was as high as 2,520 to 2,680 (A/■), the result was slightly inferior to that of the example in which an Nb artificial pinning center was introduced.

In addition, as a comparative material for wire rods, a wire rod was produced in which the Nb artificial pinning center introduced above was replaced with pure Cu, that is, Cu was considered as the artificial pinning center. However, in this case, constrictions were observed on the surface of the wire and many wire breaks occurred before the diameter was reduced to 0.520 traφ in the final processing step. The broken part of this wire was immersed in HNO to dissolve and remove the Cu part, and the Nb-Ti filament was extracted and examined using a scanning electron microscope and an electron beam microanalyzer. Particles of Cu-Ti compounds were formed everywhere, and it is thought that this was the cause of the disconnection.

〔Effect of the invention〕

As described above, according to the present invention, when artificially introducing pinning centers into Nb-Ti filaments, secondary reaction products with Nb-Ti that are harmful to plastic working can be practically avoided. By using an artificial pinning center for a material that does not exist, the desired wire material can be processed without deteriorating workability, and the introduction of an artificial pinning center has an industrially excellent effect of improving superconducting properties. be.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the structure of the Cu- or 11-stabilized superconducting wire of the present invention. In FIG. 1, (a) is aggregated to form (b), and (b) is aggregated to form (C). 1...Nb-Ti, 2...Material A, 3...Material B, 4...Stabilizing material, 5...Element wire, 6...
cable.

Claims (6)

[Claims] (1) In practical use, multiple Nb-
In practical use, each Ti filament has a stabilizer or Nb-
Material B that does not produce reaction products with either Ti or material A
A Cu- or Al-stabilized superconducting wire characterized by being coated with. (2) The Cu- or Al-stabilized superconducting wire according to claim 1, wherein the material A is Nb or Ta. (3) The Cu- or Al-stabilized superconducting wire according to claim 1, wherein the material B is Nb or Ta. (4) A plurality of through holes are provided in the Nb-Ti alloy rod in parallel to its longitudinal direction, and after inserting the Nb or Ta rod into the holes, the periphery of the Nb-Ti alloy rod is covered with Nb or Ta. The composite material is coated, then sealed in a pure Cu tube, and hot extruded to form a wire, and a plurality of the wires are bundled, inserted into a pure Cu tube or pure Al tube, sealed, and then hot extruded. A method for producing a Cu- or Al-stabilized superconducting wire. (5) One or several through holes are provided in the Nb-Ti alloy rod in parallel to its longitudinal direction, and Nb or Ta is inserted into the rod.
A plurality of rods are inserted into a bundle, the surrounding area is coated with Nb or Ta, this is then sealed in a pure Cu tube, and the composite material is hot-extruded, and the composite material is made into a wire. A method for producing a Cu- or Al-stabilized superconducting wire, which comprises inserting it into a tube or pure Al tube, sealing it, and then hot extruding it. (6) A plurality of Nb-Ti alloy rods and a plurality of Nb or Ta rods are bundled together so that the plurality of Nb or Ta rods do not touch each other, and the periphery is coated with Nb or Ta. The composite material is sealed in a pure Cu tube and hot extruded as a wire, and a plurality of the wires are bundled, inserted into a pure Cu tube or pure Al tube, sealed, and then hot extruded. Method for producing stabilized superconducting wire.