JPH03252008A - Cu stabilizing nb3sn superconductive wire and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance critical current density by filling Cu-Sn compounds and graphite particles into spaces among element wire units, and covering a combination of the plural units with a Cu-Sn alloy layer, an Nb or Ta layer and a pure Cu layer in order. CONSTITUTION:A unit is constituted of an Nb core 1 covered with an Nb3Sn layer 2 covered with a Cu-Sn alloy layer 3. There exist Cu-Sn compounds and graphite particles 4 in spaces among the units. A combination of the plural units is covered with a sectional structure consisted of a Cu-Sn alloy layer 5, an Nb or Ta layer 6 and a pure Cu layer 7 in order. The spaces among element wires are filled with Cu3Sn alloy powder and the graphite particle 4 so that a larger amount of Sn can be supplied by the Nb core in a thermal treatment. Consequently, a large amount of Nb3Sn which cannot be obtained in a conventional bronzing method can be produced. Therefore, a critical current value can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a Cu-stabilized NbzSn superconducting wire and a method for manufacturing the same.

[Conventional technology]

Conventional Nb3Sn superconducting wires are made by making a composite by inserting a Nb core into a Cu-Sn alloy tube, which is made into a thin wire by extrusion and wire drawing, and then subjected to diffusion heat treatment at about 700°C to form a Nb layer around the Nb core. It is mainly manufactured by a method called the so-called bronze method, which generates +Sn. In this case, the Sn concentration in the Cu-Sn alloy is 13-14-1% and serves as a Sn supply source. This method has excellent mass productivity and is relatively easy to process.

[Problems to be Solved by the Invention] However, in Cu-Sn alloys, the upper limit of the Sn concentration is about 14-t% at most due to workability problems.

Therefore, in the final diffusion heat treatment, it reacts with Nb to form Nb zS.
Sn supplied from Cu-Sn alloy when producing n
Since the amount is limited, there is also a limit to the amount of Ntl+Sn.

Therefore, there is a limit to the critical current density J when Cu-stabilized superconducting wire is used, and it can only be used for magnet windings of 13 T at most.

[Means to solve the problem]

In view of this situation, the present invention was made as a result of intensive studies to develop a Cu-stabilized Nb3Sn superconducting wire having a higher critical current density J, and a manufacturing method thereof. A structure in which a N b sSn layer exists and a Cu-5n alloy layer exists on the outside is considered to be one unit, and a Cu5n compound and graphite particles exist in the gaps between the units, and an aggregate of multiple units 7. Sequential C on the outside
Cu-stabilized Nb3 characterized by having a cross-sectional structure in which a u-3n alloy layer, a Nb or Ta layer, and a pure Cu layer are present.
The Sn superconducting wire is a Sn superconducting wire, and the invention of claim 2 is a wire in which an Nb rod is inserted into a Cu-3n alloy tube, the end portion is reduced in diameter by extrusion processing after sealing, and a plurality of the wires are made of Cu. - After inserting into a 5n alloy tube and filling the gap between the strands with Cu3Sn alloy powder and graphite powder, the outside is coated with Nb or Ta, the outside is further coated with pure Cu, and the end is sealed and hot extruded. This method of manufacturing a Cu-stabilized Nb5sn superconducting wire is characterized in that the wire is reduced in diameter to a predetermined size and then heat-treated.

[Effect]

In the present invention, a plurality of strands of Nb core coated with Cu-5n alloy are further inserted into a Cu-3n alloy tube, and during processing, the gaps between the strands are filled with Cu, Sn alloy powder, and graphite powder. The reason for this is to supply more Sn to the Nb core during heat treatment, and this allows a large amount of Nb3Sn to be produced, which could not be obtained with the conventional so-called bronze method, leading to an improvement in the critical current value. . Cu3Sn
The alloy powder avoids sintering during processing and maintains its powder state, resulting in good workability due to the sliding effect.

This can be made more effective by mixing Cuzsn alloy powder with graphite powder.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

A composite was fabricated by inserting a Nb rod into a 14.3i+t%5n-Cu alloy tube. S n −Cu / of this complex
The Nb ratio was adjusted to 2.5. 4. Reduce the diameter of this.
The wire had a diameter of 5 mm. These 1200 strands are
Insert into a triple pipe consisting of a pure Cu tube with an inner diameter of 185 mm, an Nb tube with an outer diameter of 184 w, an inner diameter of 176 mm, and a 5n-Cu alloy tube with an outer diameter of 175 m and an inner diameter of 169 m, and insert Cu3Sn into the gap between the wires. A mixture of alloy powder (particle size 10x or less) and graphite powder (particle size 10x or less) in a volume ratio of 9:1 was filled. The filling rate of the wire was 78.5%, and the filling rate of the powder was approximately 70%. Pure Cu was added to both ends of this triple tube in a vacuum.
After electron beam welding the lid, it was extruded to a diameter of 30 m at 670°C.

When the cross section of the extruded material was observed, the powder filled between the wires was slightly solidified, but during further drawing and wire drawing, it collapsed into a powdery state and was not sintered during subsequent annealing.

After repeated annealing and processing to obtain a final diameter of 2.4 mm, final heat treatment was performed at 690°C for 72 hours, and JC was measured.

J excluding Cu was 300 A/- at 16T.

For comparison, a wire without powder filled between the strands was processed in the same manner as in the example and Je was measured, and it was found to be 20 at 16T.
It was 0A/-.

〔Effect of the invention〕

As described above, according to the present invention, a Cu-stabilized Nb3Sn superconducting wire having a high limiting current value can be obtained, which has an industrially significant effect.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of the Cu-stabilized Nb3Sn superconducting wire of the present invention. 1.Nb core, 2.=NbsSn layer, 3-Cu
-sn layer, 4... Layer of Cu-3n compound and graphite particles, 5... Cu-3n alloy layer, 6... Nb or Ta layer, 7... Pure Cu layer.

Claims (2)

[Claims] (1) One unit has a structure in which an Nb_3Sn layer exists around an Nb core and a Cu-Sn alloy layer exists on the outside thereof,
CuSn compounds and graphite particles exist in the gaps between the units, and CuSn compounds and graphite particles are present in the gaps between the units.
-Cu-stabilized Nb_3 characterized by having a cross-sectional structure in which a Sn alloy layer, a Nb or Ta layer, and a pure Cu layer are present
Sn superconducting wire. (2) Insert a Nb rod into a Cu-Sn alloy tube, and after sealing the can, reduce the diameter by extrusion processing to obtain a strand, insert a plurality of the strands into the Cu-Sn alloy tube, and Cu_ in the gap between
After filling with 3Sn alloy powder and graphite powder, the outside is coated with Nb or Ta, the outside is further coated with pure Cu, the end is sealed, hot extruded, reduced in diameter to a predetermined size, and then heat treated. A method for producing a Cu-stabilized Nb_3Sn superconducting wire, characterized in that: