JPH0211733A - Manufacture of nb3 sn superconducting wire by internal diffusing method - Google Patents

Abstract

PURPOSE:To manufacture the title wire of multicore structure having high residual resistance ratio by disposing tin and an Nb tube in a copper member, subjecting a composite body of which copper or Al having specific purity is housed to the Nb tube to reduction working and thereafter subjecting it to heat treatment at specific temp. CONSTITUTION:A copper member is housed to an Nb3SN superconducting wire of multicore structure in which shielding materials are closely disposed. Tin and a niobium tube are disposed into the copper member. Copper or aluminum having >=99.9999% purity is housed into the niobium tube to form a composite body. The composite body is subjected to reduction wording and is thereafter subjected to heat treatment at <=660 deg.C to generate an Nb3Sn layer outside of the niobium tube. By this method, the Nb3Sn superconducting wire of multicore structure having high residual resistance ratio can be manufactured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an Nb3Sn superconducting wire, and in particular a multicore Nb3Sn superconducting wire having a high residual resistance ratio (hereinafter referred to as I?RR). The present invention relates to an improved manufacturing method.

[Prior Art] A method using an internal diffusion method is known as one of the methods for manufacturing superconducting wires. This method involves reducing the area of a composite body in which a Sn rod serving as a diffusion source and multiple Nl wires are arranged in a Cu matrix, and then performing diffusion heat treatment to generate an Nb3Sn layer on the outside of the Nb wires. Otherwise, since the Cu matrix is contaminated with Sn, a stabilizing material is usually placed on the outer periphery via a shield. The role of this stabilizing material is to suppress the occurrence of quenching due to the local transition of the superconducting filament to normal conductivity, and to maintain a stable superconducting state.The smaller the resistivity value, the more stable the conductor is. I can say that.

[Problems to be Solved by the Invention] In the above method, oxygen-free copper is generally used as a stabilizing material, but R1? In other words, the value of (resistance at room temperature/resistance just above the critical temperature (Tc)) is 10
There is a limit to about 0, and if a value higher than this is required, there is a problem that sufficient stability cannot be obtained.

In other words, the structure of the superconducting wire is mainly determined by the area of the superconducting part and the area of the stabilizing copper, or because the resistivity of the stabilizing copper is almost constant, in high magnetic field coils, the stability of the coil must be sacrificed to some extent. It is possible to create a design that prioritizes high magnetic field characteristics. For this reason, the copper ratio is set to about 1.0, and the energy stored in the coil is released to the outside as much as possible, and the temperature rise of the conductor is minimized. In this case, sufficient stability cannot be obtained. .

The present invention was made to solve the above problems,
I without reducing Jc of Nb3Sn superconducting wire with multi-core structure
? R+? The purpose is to provide an improved manufacturing method using an internal diffusion method that can improve the

[Means for Solving the Problems] The method of manufacturing an Nb3 Sn superconducting wire using the internal diffusion method of the present invention includes accommodating a copper member inside a copper tube in which a shielding material is closely arranged inside, and After arranging tin and a plurality of niobium tubes and accommodating copper or aluminum with a purity of 99.9999% or more inside the niobium tube, the composite is subjected to area reduction processing, and then heated at 660°C.
The present invention is characterized in that a Nb3Sn layer is formed on the outside of the niobium tube by performing heat treatment at a temperature below.

As the shielding material in the present invention, Nb, Ta, or an alloy thereof can be used. In addition, oxygen-free copper is usually used for copper parts, ie, 7 trix, but N
An alloy to which elements such as 11 are added can also be used for the b-tube.

Further, the Sn arranged within the 7-trix can be arranged at a plurality of locations, or a plurality of Cu-coated Sn wires can be arranged in a group.

[Function] In the present invention, by accommodating Cu or Al of the same purity inside the plurality of Nb tubes arranged in the matrix, the processability of the composite is also good, and the l?
I? It is possible to improve R. That is, in general, in oxygen-free copper, l? RR is about 100, but 6N
(99,9999%) or higher purity Cu or A1
In this case, a value of 5000 or more can be obtained.

Furthermore, with the internal diffusion method, Nb3Sn can be generated at a temperature lower than 660°C, which is the melting point of pure A1.
Even if high purity A1 is used, problems such as melting will not occur.

Example] High purity AI with an outer diameter of 4.9 mmφ and a purity of 99.99995% was inserted into a Nb tube with an outer diameter of 8IIIlφ and an inner diameter of 5 mmφ, and this was inserted into a Nb tube with an outer diameter of 10 mmφ and an inner diameter of 8. After being housed in an oxygen-free copper tube of Immφ, wire drawing was performed to produce a composite wire with a regular hexagonal cross section and a distance between opposite sides of 2.27 nv.

On the other hand, a Sn rod was housed in a Cu tube, and wire drawing was performed on the Sn rod to form a Cu tube with a regular hexagonal cross section with a distance between opposite sides of 2.27 mm.
A coated Sn wire was manufactured. The ratio of Cu and Sn in this wire is
It was selected so that it would become Cu-70wt%S after diffusion.

Next, 91 Cu-coated Sn wires were brought together with their sides touching, and 210 composite wires were densely arranged on the outside of the wires, and a wire with an outer diameter of 45 mmφ and an inner diameter of 43.5 mm was placed on the outside.
mmφ Ta tube, outer diameter 55mmφ, inner diameter 4[imm]
A composite was constructed by sequentially arranging oxygen-free copper tubes of φ.

This composite was subjected to area reduction processing such as hydrostatic extrusion processing and wire drawing processing to produce a wire rod with an outer diameter of 1.0 mmφ.
Cu-Sn at ℃×48 hours and 550℃×48 hours
Diffusion heat treatment for alloy formation followed by 650°C
A superconducting wire was manufactured by performing a heat treatment to generate Nb3Sn for 40 hours. The critical current density Jc of this superconducting wire is 13.
At 5T, the RRR showed a value of 250A/mm2 and 200. These values indicate that Jc is almost the same compared to the conventional method. R is approximately twice as large.

[Effects of the Invention] As described above, according to the present invention, high l? R
It is possible to manufacture a multicore Nb3Sn superconducting wire having R.

Claims (1)

[Claims] A copper member is housed inside a copper tube with a shielding material closely arranged inside, tin and a plurality of niobium tubes are arranged inside the copper member, and 99.9% is placed inside the niobium tube.
After reducing the area of the composite containing copper or aluminum with a purity of 999% or more, heat treatment is performed at a temperature of 660°C or less to form Nb_3 on the outside of the niobium tube.
A method for manufacturing a Nb_3Sn superconducting wire by an internal diffusion method, characterized by forming a Sn layer.