JP2871754B2 - Nb Lower 3 Method for Manufacturing Sn Compound Superconducting Wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing an improved Nb ₃ Sn compound superconducting wire, and an object thereof is to improve a critical current density.

[Conventional technology]

Since compound superconducting materials such as Nb ₃ Sn are hard and brittle, they cannot be processed directly into wires as alloy materials, and practical wires are produced by a surface diffusion method or a composite processing method (bronze method). Among them, the bronze method utilizes the diffusion between solids of the Nb / Cu-Sn composite, so that a wire having a complicated cross-sectional structure such as an ultrafine multifilamentary wire can be manufactured. In the conventional method of manufacturing a Nb ₃ Sn compound superconducting wire by the bronze method, a method called a double stack method is mainly used, and FIG.
As shown in (b) and (c), one or a plurality of Nb rods (1) are inserted into a bronze tube (2), and processing such as extrusion, drawing, and rolling, and intermediate annealing are repeated. The manufactured primary element wire (3) is cut into the same length, and the plurality of primary element wires (3) thus obtained are reinserted into a bronze tube, and extruded, drawn, rolled and stretched. The secondary wire (4) is manufactured by repeating the processing of wire and the like and the intermediate annealing, and the process of inserting a plurality of secondary wires (4) into the bronze pipe and drawing again is repeated to obtain a bronze (6). 2), a composite wire (5) in which Nb filaments (7) are dispersed is manufactured, and finally a diffusion heat treatment is performed to obtain a Nb ₃ Sn superconducting wire. The Nb ₃ Sn superconducting wire obtained in this way can reduce the diameter of the Nb filament to about several μm, and the Nb ₃ Sn superconducting layer is formed by diffusion of Sn at the interface between the bronze matrix and the Nb filament. I do.

[Problems to be solved by the invention]

However, when the composite wire is manufactured by the double stack method as described above, the distribution of the Nb filaments in the composite wire becomes non-uniform, and the distribution becomes uneven. As a result, in the diffusion heat treatment of heating at a certain temperature for a certain time, the amount of Sn in the bronze supplied to each Nb filament varies, and
Variations in the thickness, particle size, and stoichiometry of the reaction layer of the Nb filament are increased, and the critical current density is suppressed. As one method to solve this problem, for example, (700 ° C. × 4 h + 600 ° C. × 30)
Although multi-stage heat treatment in which h) is repeated a number of times is effective, it takes a long time and is unsuitable as a mass production condition.

[Means and actions for solving the problem]

The present invention provides a method for producing an Nb ₃ Sn compound superconducting wire that solves the above problems, and performs a composite process on an Nb or Nb alloy material and a bronze (Cu-Sn alloy) matrix to form a bronze matrix. By dispersing Nb or Nb alloy material and then performing diffusion heat treatment, Nb ₃ Sn
In the method for producing a Nb ₃ Sn compound superconducting wire by the bronze method for producing a superconducting wire, a plurality of holes are formed in the bronze billet at equal intervals (d ₁ ), and relation between d ₂₎ is set to be d ₁ = 2d _2, after inserting the Nb or Nb alloy rods in the holes,
After the bronze billet is formed into hexagonal wires by hot extrusion and wire drawing, a plurality of these hexagonal wires are Cu
It is characterized in that Nb or Nb alloy material is substantially uniformly dispersed and arranged in a bronze matrix by inserting into a billet and performing hot extrusion and wire drawing again.

According to the method of the present invention as described above, Nb or Nb alloy material and bronze matrix are subjected to composite processing, wire drawing,
Nb or Nb alloy filaments are subjected to diffusion heat treatment in the state of a composite wire in which the filaments are substantially uniformly dispersed in a bronze matrix, so that each filament is evenly supplied with Sn, and the thickness and granularity of the reaction layer generated in each filament are increased. The diameter and stoichiometry become uniform, and the critical current density increases.

〔Example〕

Hereinafter, the present invention will be described based on embodiments shown in the drawings.

FIG. 1 is a sectional view of a bronze billet used in the first embodiment of the present invention.
% Sn) A 9mmφ hole (12) is drilled in the billet (11) with a gun drill at an interval of d ₁ = 6mm. periphery and the spacing d ₂ of the circumscribed circle (13) and 3mm (d ₁ = 2d ₂₎ of, embedded Nb rods in these holes (12). In the second embodiment, the diameter of the billet hole is 10 mmφ (the center position of each hole is the same as in the first embodiment), and the outside diameters of the holes are changed.
A composite rod having an Nb rod inserted therein was embedded in a Cu pipe having a diameter of 10 mm and an inner diameter of 9 mm. As a comparative example, the outer diameter of the billet in the first embodiment and 51.3Mmfai, was prepared billet spacing d ₂ between the circumscribed circle and the billet periphery of the hole to 6 mm.
The above three types of composite billets are subjected to hot extrusion at 700 ° C.
After drawing and annealing, hexagonal wire (11mm
´). Next, as shown in FIG. 2, 300 wires (11 ') are inserted into a Cu billet (15) having an outer diameter of 45.3 mmφ and an inner diameter of 40 mmφ having a Ta barrier (14) having a thickness of 3 mm inside. Then, hot extrusion was performed at 700 ° C., and then a wire drawing step and intermediate annealing were repeated to produce a composite wire having an outer diameter of 0.5 mmφ and having an Nb filament having a diameter of about 1 μm. In the billets (11) of Examples 1 and 2, Nb bars are arranged so as to satisfy d ₁ = 2d ₂ , so that a predetermined number of hexagonal strands (11 ′) obtained by processing the Nb bars are provided. When inserted into a Cu billet (15) having a Ta barrier (14) on the inside as shown in FIG. 2, the distance between the adjacent Nb filaments between adjacent hexagonal strands (11 ') is The spacing between the Nb filaments in the hexagonal wire (11 ') is substantially equal to the spacing between the Nb filaments. Therefore, in the composite wire obtained by processing the Nb filaments, the Nb filaments are almost uniformly dispersed. On the other hand, in the billet (11) of the comparative example, d ₁ = d ₂
, The 6 inserted in the Cu billet (15)
In the cubic strands (11 '), the spacing between opposing Nb filaments between adjacent hexagonal strands (11') is larger than the Nb filament spacing in each hexagonal strand (11 '); The composite wire obtained by processing this has a non-uniform arrangement of Nb filaments. This wire was subjected to a diffusion heat treatment at 650 ° C. × 5 days, and the critical current density of the Nb filament was measured.

Table 1 shows that the critical current densities of Examples 1 and 2 in which the Nb filaments are uniformly dispersed are larger than those of Comparative Examples. Further, in Example 2 in which the Nb filament was sheathed with Cu, harmful Nb ₃ Sn was not generated by the intermediate annealing in the wire drawing step, and thus the critical current density was higher than in Example 1. Needless to say, the method for producing an Nb ₃ Sn compound superconducting wire of the present invention can be applied to a compound superconducting wire having an A15 type structure other than Nb ₃ Sn.

〔The invention's effect〕

As described above, according to the present invention, since the Nb or Nb alloy material is substantially uniformly dispersed in the bronze matrix, there is an excellent effect that the critical current density is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a bronze billet used in one embodiment of the method for producing an Nb ₃ Sn compound superconducting wire according to the present invention.
The figure is a cross-sectional view of the Cu billet (15) used in the example.
(A), (b), and (c) are cross-sectional views of a primary wire, a secondary wire, and a composite wire in a conventional method for manufacturing an Nb ₃ Sn compound superconducting wire. 1 ... Nb rod, 2 ... Bronze tube, 3 ... Primary wire, 4 ... Secondary wire, 5 ... Compound wire, 6 ... Bronze, 7 ... Nb filament,
11: billet, 11 ': hexagonal wire, 12: hole, 13: circumscribed circle,
14 ... Ta barrier, 15 ... Cu billet.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-212710 (JP, A) JP-A-61-279661 (JP, A) JP-A-53-102694 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H01B 13/00 565 F H01B 12/10

Claims (1)

(57) [Claims] 1. A is subjected to compound processing in the Nb or Nb alloy material and bronze (Cu-Sn alloy) matrix, the Nb or Nb alloy material in the bronze matrix is distributed, then Nb ₃ by applying the diffusion heat treatment Sn In the method for producing a Nb ₃ Sn compound superconducting wire by the bronze method for producing a superconducting wire, a plurality of holes are formed in the bronze billet at equal intervals (d ₁ ), and The relationship with d ₂ ) is set to d ₁ = 2d _2, and after inserting an Nb or Nb alloy rod into these holes, the bronze billet is formed into a hexagonal wire by hot extrusion and wire drawing. , Insert a plurality of these hexagonal wires into Cu billet,
A method for producing an Nb ₃ Sn compound superconducting wire, wherein Nb or an Nb alloy material is substantially uniformly dispersed and arranged in a bronze matrix by performing hot extrusion and wire drawing again.