JPS60170113A - Method of producing nb3sn superconductive lead - 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 [Technical Field of the Invention] The present invention relates to a method for manufacturing a Nb3Sn-based superconducting wire for use in high magnetic fields.

[Prior art]

Superconducting materials are used as essential materials in various devices that require high magnetic fields, such as nuclear fusion devices, accelerators, and high-energy physics experiment equipment, but they are also used in fields such as nuclear fusion where performance is being improved. Therefore, there is a need for a wire that has excellent critical current characteristics and high reliability in a high magnetic field of 10 T (Tesla) or higher.

A typical Nb3Sn compound superconducting wire conventionally used in high magnetic fields consists of a Nb-based metal layer (1) and a Cu layer as shown in Figure 1.
-There is a method of reducing the cross section of the structure consisting of the Sn alloy layer (2) and forming Nb3Sn on the Nb surface in the final step. Attempts have been made to improve the critical current density at high magnetic fields by increasing the upper critical magnetic field of the layer or by suppressing the martensitic transformation of Nb3Sn at liquid helium temperatures. That is, if we take Ti as an example as the third element added to Nb3Sn, Nb and Ti
A binary alloy of Nb −
There is a known method for manufacturing an Nb3Snb compound superconducting wire containing a third element by a so-called bronze method in which a Ti alloy rod and a Cu--Sn alloy are integrally processed to reduce their cross section, and the final shape is heat-treated to form a compound.

However, this method has a weight ratio of 10 to 14% Sn.
However, this alloy is very difficult to melt into a homogeneous ingot with excellent workability, and the manufacturing cost is high. Because the hardening is remarkable, intermediate annealing during the process is required several dozen times or more, and during each intermediate annealing, Nb3Sn is added to the surface of the Nb filament.
+ As the Nb filament becomes thinner, local deformation tends to occur, and the
There are disadvantages such as a high incidence of disconnection of the Sn filament.

In order to improve the drawbacks of the method of adding a third element to the bronze method, Nb rods are placed in a Cu tube, the cross section is reduced to make them thinner, the wires are refocused and sealed in a Cu container. , a Cu-Nb composite brass pipe material having a hollow part is manufactured by hollow extrusion or perforation after extrusion, and then the hollow part is filled with Sn, the aggregate is integrated, the cross section is reduced, and the final shape is heat treated. , an internal diffusion method for forming Nb3Sn on the surface of Nb has been proposed, and a method using a Cu--Ti alloy instead of Cu has also been proposed.

In this internal diffusion method, the aggregate is made of a metal with excellent workability, so unlike the bronze method, intermediate annealing is not required. The effect of adding Ti as a third element can be produced without producing Nb3Sn. However, even with this method, C
Since a Cu-Ti alloy is used as the base material, it is necessary to manufacture a Cu-Ti pipe material coated with Nb, which increases industrial manufacturing costs compared to oxygen-free steel pipe material, which is industrially easily available. However, when the Ti content of the Cu-Ti alloy approaches 4% by weight, work hardening becomes significant, which is disadvantageous in that it may become a hindrance when performing high-strength forming processing.

[Summary of the invention]

This invention was made for the purpose of improving the drawbacks of the above-mentioned conventional method, and the structure in which the Cu-based metal layer is arranged around the Nb-based metal layer and the Sn-based metal layer is integrally subjected to cross-sectional reduction processing, and the final By performing heat treatment on the cross-sectional shape, Nb3S
In the internal diffusion method for manufacturing n-based superconducting wire, by using an Nb alloy containing 0.1 to 20 weight percent of any one or more elements among Hf, Ta, Ti, and Zr as the Nb-based metal layer. This paper proposes a method for manufacturing a Nb3Sn-based superconducting wire that can produce a superconducting wire that has excellent high magnetic field characteristics and excellent industrial reliability.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

- Fig. 2 is a sectional view of a composite rod in an embodiment of the present invention, and Fig. 3 is a sectional view of a constituent body. First, as shown in Fig. 2, a Nb-based metal layer (1) consisting of 1200 Nb-3 weight percent Ti alloy core wires with a diameter of 0.4n+m is formed.
is embedded in the Cu-based metal layer (3), which is the parent phase, with an outer diameter of 25
Sn-based metal layer (4) consisting of Sn rods with a diameter of 8.8 mm in the central hollow part of a composite multi-core tube with an inner diameter of 9 m + i
A stabilizing metal layer (6) made of a Cu tube is placed over the outer periphery of the composite rod via a diffusion barrier (5) made of a Ta tube to form a structure as shown in FIG. This composite structure was subjected to cold drawing as one body, and wire was drawn to a diameter of 0.5 mm. In this drawing process, wire drawing was easy even without intermediate annealing, and good workability was confirmed without any wire breakage throughout the entire process. Next, this wire was heat treated at 750° C. for 50 hours to generate a Nb3Sn compound.

The liquid helium temperature of the wire made by the above method (
Measure the critical current density (Jc) at 4,2K),
It is shown in curve A in Figure 4 as a function of the applied magnetic field. For comparison, Nb-Ti was used as the Nb-based metal layer (1).
Nb core wire is used instead of the alloy, and oxygen-free copper (O
A wire rod with the same cross-sectional configuration using FG) was prepared using the conventional method, and the characteristics of the wire rod heat-treated under the same heat treatment conditions were measured for critical current density (Jc), and the results are shown in curve B in Figure 4. According to this result, the Nb3Sn compound superconducting wire made using the Nb-Ti alloy powder by the method of the present invention has a higher critical current in a high magnetic field of IOT or higher than the Nb3Sn compound wire using the conventional Nb core wire. Comparing the critical current density (Jc) of the part excluding the stabilized copper at 12T, it is found that Nb3S by the conventional method
While the n-wire rod had a magnetic field strength of 495 A/mm2, the wire rod produced by the method of the present invention showed a magnetic field strength of 592 A/mm'', confirming its excellent characteristics in high magnetic fields.

Elements that can be added to the Nb-based metal layer (1) of the present invention to improve the critical current density (Jc) in a high magnetic field are not limited to Ti in the above embodiments, but include Hf, T
Elements such as a and Zr can also produce the same effect as the addition of Ti. Furthermore, Hf, Ta added to the Nb-based metal layer (1)
Regarding the amount of addition of elements such as , Ti, and Zr, if the weight ratio is less than 0.1%, no improvement effect on the critical current density in high magnetic fields is observed, and if the weight ratio is less than 20%.
If the amount exceeds 5%, the current characteristics will not be further improved even if the amount added is increased, and work hardening during wire drawing will become significant, which tends to cause problems during wire manufacturing.6 In the above example used Ta as a diffusion barrier (5) for metal elements such as Sn into the stabilizing metal layer (6);
Similar effects can be obtained by using Nb in addition to the above, and although Cu is used as the stabilizing metal in the above embodiments, highly pure Ag or Al can also be used.

Note that the manufacturing method of the present invention, which uses an alloy to which at least one element among Hf, Ta, Ti, Zr, etc. is added as the Nb-based metal layer within a range that is not subject to restrictions on wire drawing, can be used in accordance with other methods. Patent application No. 58-206 to further improve current characteristics in high magnetic fields by adding three elements to a Sn-based metal layer at the same time
Compared to the No. 933 invention, Nb in the conventional internal diffusion method
If the base metal layer is simply If, Ta, Ti, Zr, etc.
Excellent properties in high magnetic fields can be obtained by industrially simpler means simply by using a Nb-based alloy layer to which more than one element is added.

〔Effect of the invention〕

As explained above, according to the present invention, by using a simple structure in which an Nb alloy containing one or more of Hf, Ta, Ti, and Zr is used in the Nb-based metal layer, 10
It has become possible to industrially and stably manufacture superconducting wires with excellent critical current characteristics and reliability in high magnetic fields of T or higher, and they can be used in floor desks for high magnetic field magnets in nuclear fusion devices and high-energy physics-related devices. be able to.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a wire made by the conventional bronze method, Fig. 2 is a cross-sectional view of a composite bar according to an embodiment of the present invention, Fig. 3 is a cross-sectional view of the structure, and Fig. 4 is a cross-sectional view of a wire rod applied at 4.2K. 1 is a characteristic diagram showing the relationship between magnetic field and critical current density, where curve A shows the characteristics of the wire according to the present invention, and curve B shows the characteristics of the wire according to the conventional internal diffusion method. In the figure, (1) is an Nb-based metal layer, (2) is a Cu-S
(3) is a Cu-based metal layer, (4) is a Sn-based metal layer, (5) is a diffusion barrier, and (6) is a stabilizing metal layer. Agent Masuo Oiwa Figure 1 Figure 3 Figure 2 Figure 4 Ishihiro Kai (T)

Claims (4)

[Claims] (1) 'Nb3Sn
In the method for manufacturing superconducting wire, H is added to the Nb-based metal layer.
A method for producing a Nb3Sn-based superconducting wire, the method comprising using an Nb alloy containing 0.1 to 20 weight percent of one or more elements selected from f, Ta, Ti, and Zr. (2) The method for manufacturing a Nb3Sn-based superconducting wire according to claim 1, wherein the structure has a stabilizing metal layer around the structure via a diffusion barrier. (3) Nb3Sn according to claim 2, wherein the diffusion barrier is an Nb-based metal or a Ta-based metal.
Method for manufacturing superconducting wire. (4) A method for manufacturing an Nb5S, n-based superconducting wire according to claim 2 or 3, wherein the stabilizing metal layer is Cu, AI or Ag.