JPS62270756A - Manufacture of superconductive nb3sn wire - Google Patents

Abstract

PURPOSE:To manufacture a superconductive Nb3Sn wire preventing the lowering of the residual resistance ratio by putting a composite body consisting of an Sn rod, a Cu pipe, a pipe of an Nb alloy contg. Ti and an Nb pipe in a Cu matrix, reducing the resulting composite member and heat treating it. CONSTITUTION:The outside of an Sn or Sn alloy rod 4 is successively coated with a Cu or Cu alloy pipe 3, a pipe 2 of an Nb alloy contg. 0.1-5atom% Ti and an Nb or Nb alloy pipe 1 to form a composite body 5. This composite body 5 is put in an oxygen-free copper matrix 6 and the resulting composite member is reduced and heat treated at about 600-800 deg.C to form a circular Nb3Sn layer 7 and a Cu-Sn alloy core 8 on the inside of an Nb pipe 1' in the Cu matrix 6. Thus, a superconductive Nb3Sn wire maintaining the residual resistance ratio is obtd. by a pipe method.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a superconducting wire, and particularly relates to an improvement in the method for manufacturing a NbaSn superconducting wire by a pipe method. .

(Prior art) As a method for manufacturing Nl)3sn superconducting wire, a method using a pipe method has been known (Japanese Patent Laid-Open No. 1699-1699).
Publication No. 7). In this method, a Cu tube is placed around the Sn rod, and an N
A large number of composite wires sequentially coated with B tubes and Cu tubes that serve as stabilizers are roughly housed in CLI tubes and subjected to cold working, followed by heat treatment to generate Nb3Sn.
This method has the advantage of eliminating the need for multiple intermediate annealing steps, which is a disadvantage of the so-called bronze method using alloys.

However, in the above-mentioned pipe method, when the degree of area reduction exceeds 10', breakage of the tube wall of the Nb tube tends to occur, and Sn diffuses into the matrix during heat treatment. To prevent a decrease in critical current value and instability of cooling 4
This causes the problem of <.

As a method to eliminate such drawbacks of the pipe method, the present applicant and others would like to first apply for a method of containing 0°1 to 5 dt% Ti in the Nb pipe.
).

In the improved pipe method described above, the 7-
The improvement of workability and critical current density (JC) in high magnetic fields of about 14 to 151 due to i addition is remarkable, and currently N
It is widely used as a wire for MR and for magnets that generate high magnetic fields, and the world's highest level of magnetic field generation of 16.71 has been achieved using this wire.

(Problem to be solved by the invention) However, in the above method, Nb
It has been found that li in the pipe diffuses into the stabilized CLI, resulting in a significant decrease in residual resistance ratio (hereinafter referred to as RRR), which is an undesirable phenomenon for superconducting coils.

Figure 3 shows the RRR measurement results for single wires with different structures.
The values are shown when heated at 25°C. Here A is pure copper, B
is Cu-coated Nb-1at%Zr alloy, C is Cu-coated iNb
, D indicates a CLJ coated 1Nb-1, 9 at% Ti alloy, and E indicates a wire in which the outer periphery of Sn is sequentially coated with a Nb-1, 9 at% Ti alloy and CO. As is clear from this figure, N
b The RRR of the wire rod with Ti added to the tube is significantly reduced.

The present invention relates to the improved pipe method described above, that is, Nb
This method was developed to solve the problems of the pipe method in which Ti is added to the pipe, and its purpose is to provide a method for manufacturing Nb3Sn superconducting wire using a pipe that prevents a decrease in RRR.

[Structure of the invention] (Means and effects for solving the problems) Nt of the present invention)
The manufacturing method of 3Sn superconducting wire is to attach a CLI or Cu alloy tube, 0.1 to 5
A composite formed by sequentially coating an Nl alloy tube containing atomic percent Ti and a Nb or Nb alloy tube is placed in a Cu matrix, and then subjected to area reduction processing, and then coated with Nb3
By performing the heat treatment to generate Sn, diffusion of Ti from the Nb tube into the stabilized copper during the heat treatment is prevented, thereby preventing a decrease in RRR.

In the present invention, the Sn-based metal placed in the center may be a collection of multiple composites each coated with a CIJ-based metal, and in this case, workability can be further improved. . Similarly, the workability of a Cu-based alloy tube is improved by arranging a plurality of wire rods in an annular shape. It goes without saying that a large number of composite bodies arranged in the CLI stabilizing material can be arranged to form a multicore V4 structure.

(Example) An embodiment of the present invention will be described below.

Figure 2 shows a cross section of a composite member before surface reduction processing by the method of the present invention, in which Nb tube 1 has Ti added inside it.
b An alloy tube 2 is placed and the inside thereof is coated with Cu 3.
It has a structure in which a composite body 5 containing n rods 4 is placed in an oxygen-free copper matrix 6 which is a stabilizing material.

After surface reduction processing, this composite member was made of Nb at 600-800'C.
3Sn generation heat treatment is performed, and as shown in Figure 1, N
An annular Nb38r1 layer 7 is formed inside the b-tube 1'.

In addition, in FIG. 1, the reference numeral 8 indicates a Cu-Sn alloy portion.

Specific example: Inside a Nb tube with an inner diameter of 7 φ and a thickness of 0.5 mm, an outer diameter of 6,
811tnφ, thickness 0.7mm Nb-1,9at%T
A composite body was formed by placing an Nt alloy tube with an i-shaped structure and placing a Cu-coated Sn rod inside the tube. After covering the outside of this composite with a Cu tube, it was subjected to surface reduction processing to produce a wire rod having a regular hexagonal cross section with a distance between opposite sides of 2.13+++ m. 264 of these wire rods were bundled and housed in a Cu tube with an outer diameter of 49 mm and an inner diameter of 41 mm, and then wire-drawn to produce a multicore wire with an outer diameter of 1.0 mm.

As a result of measuring the RRR of the Nk)3Sn superconducting wire obtained by heat-treating the above multi-core wire at 725°C for 30 hours, the value was 100, which is about twice the value when no Nb barrier is provided. Indicated.

[Effects of the Invention] As described above, according to the method of the present invention, the following effects can be obtained.

b) By being able to prevent Ti from diffusing into the stabilizing material during heat treatment, it is possible to suppress a decrease in RRR.

Nb-T
It becomes extremely easy to select the heat treatment conditions for changing the content of the i-alloy tube to Nb3Sn, and it becomes possible to generate a uniform N1)3S layer.

c) An unreacted Nb-based metal tube can be used as a tension member, which is economically advantageous compared to the conventional method in which a part of the Ti-added Nb alloy tube is made into an unreacted region.

[Brief explanation of the drawing]

FIG. 1 shows Nb 3 S produced by the method of the present invention.
FIG. 2 is a cross-sectional view showing an example of an n-superconducting wire, FIG. 2 is a cross-sectional view showing the state before heat treatment, and FIG. 3 is a graph showing changes in RRR due to heat treatment of single wires of various structures. 1.1'...Nb tube

Claims (3)

[Claims] (1) On the outer periphery of Sn or Sn-based alloy rod, Cu or Cu-based alloy tube, N containing 0.1 to 5 at% Ti
An Nb_3Sn superconducting wire characterized in that a composite body formed by sequentially covering a b-based alloy tube and a Nb or Nb-based alloy tube is placed in a Cu matrix, then subjected to area reduction processing, and then subjected to heat treatment to generate Nb_3Sn. Production method. (2) The method for manufacturing a Nb_3Sn superconducting wire according to claim 1, wherein the Sn or Sn-based alloy rod is an aggregate of Sn or Sn-based alloy rods coated with copper or a copper alloy. (3) The Cu or Cu-based alloy tube is formed by arranging a plurality of Cu or Cu-based alloy wires in a ring shape.
A method for manufacturing a Nb_3Sn superconducting wire according to item 1 or 2.