JPH0528859A - Manufacture of superconductive wire of nb3sn type - Google Patents

Abstract

PURPOSE:To provide a long stretching and uniform wire without dropping the cold processing property of Nb3Sn type superconductive wire to be used in high magnetic field and also enhance the superconductive characteristics to a great extent. CONSTITUTION:An Nb type pipe is filled with pressure powder consisting of Cu and Sn, and thus is subjected to a cold processing for reduction of the dia., which is followed by a heat treatment for production of Nb3Sn. Thus an Nb3Sn type superconductive wire is manufactured, wherein the processes are characterized by filling a Cu pipe with Cu and Sn powder, subjecting it to a pressure powder processing by means of swaging, inserting the resultant into an Nb pipe, and subjecting it to a dia. reducing process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a compound superconducting wire used in a high magnetic field, and particularly to Nb by a powder method.
_{The present} invention relates to a method for manufacturing a Sn-based superconducting wire.

[0002]

2. Description of the Related Art Conventionally, there have been bronze method, internal diffusion method, external diffusion method, in-situ method, etc. as a method of manufacturing Nb ₃ Sn based superconducting wire. However, in recent years, these methods have produced a hard Cu-Sn alloy during processing,
Nb using Nb pipe because there are many processing problems
The tube method is being considered. That is, a copper or tin core material or powder is densely arranged in an Nb pipe, and the wire material is subjected to various processing steps in a cold state to be a wire material and finally heat-treated, so that the wire material can be processed without intermediate annealing. Since a pure metal such as copper or tin is used, there is no processing problem even if a high tin composition is used, and there is an advantage that a wire having a high current density can be obtained. In the powder method, Nb pipe is filled with a powder mixture of copper and tin powder, a composite powder, or a powder powder containing a catalyst, and the both ends of the pipe are vacuum-processed into cold filaments to form filaments. Alternatively, there has been proposed a method in which several hundreds are integrated into a composite wire and subjected to hydrostatic extrusion or cold working. However, in the method of processing such powder, the wire is often broken during the processing. There are several causes of wire breakage, but one of them was that a powder compact that was not uniform in the longitudinal direction of the wire could not be formed, and a crack was generated from the discontinuous powder part, resulting in wire breakage. In other words, in the conventional production of green compacts, powder that has been hydraulically or hydrostatically pressed is put into an Nb pipe for processing, so if the Nb pipe is long, a large number of green compacts will be put in. The joints of the body became discontinuous, and as the processing continued, there were often breaks from this part.

[0003]

SUMMARY OF THE INVENTION According to the present invention, a long and uniform green compact can be easily formed by changing the green compact processing method, and in the wire rod processing using this, cold working is possible. This is a method for producing a Nb ₃ Sn-based superconducting wire which can be satisfactorily performed and can significantly improve the critical current density of the final wire.

[0004]

According to the present invention, a Nb pipe is filled with a green compact of copper powder and tin powder, and then a diameter reduction process is performed by cold working, and then Nb ₃ Sn is produced. In the production of Nb ₃ Sn-based superconducting wire that undergoes the heat treatment described in (1), copper powder and tin powder are filled in a copper pipe, which is then pressed by swaging and then inserted into the Nb pipe, which is then reduced in diameter. Is a method of manufacturing a Nb ₃ Sn-based superconducting wire.

[0005]

The above-mentioned copper and tin powders may have any particle size and shape. Further, an additive element such as Ti or Ta for improving the current density by refining Nb ₃ Sn crystal grains may be added thereto. The powder is mixed or pelletized by pressing, and the powder is filled in a thin copper pipe, preferably vacuum sealed, and then swaged. The swaging may be carried out by a usual processing apparatus, and the present method enables the production of a green compact having a high density and uniform in the longitudinal direction, which cannot be achieved by a hydraulic press or a hydrostatic press. Furthermore, the present method can produce an arbitrary diameter of several millimeters to several tens of millimeters and a length of several meters, and has a material structure suitable for subsequent insertion into an Nb pipe. After compounding with Nb pipe, swaging or drawing process to make a hexagonal filament of 2-3 mm, then bundling hundreds of them into a copper pipe, hydrostatically extruding or drawing process, and finally Use a wire rod of about 1 mm. It was found that the cold workability of the wire rod was extremely good when the green compact processed by this method was used. It is considered that such good workability is due to the fact that the green compact is uniform in the longitudinal direction, and therefore discontinuity points are not created in the processing such as drawing with a die. After the desired wire diameter is obtained in this way, a final heat treatment is performed. This final heat treatment is for forming a copper-tin alloy and diffusing tin in the copper-tin alloy matrix into Nb to generate Nb ₃ Sn. The heating may be performed at a temperature of ~ 800 ° C for about 10 to 300 hours.

[0006]

EXAMPLE An example of the present invention will be described below. Example 1 Copper powder and tin powder having an average particle size of 20 microns were thoroughly mixed by a ball mill, put into a pure copper pipe having an outer diameter of 30 mmφ and an inner diameter of 27 mmφ, and both ends of the pipe were beam-welded while vacuuming to 0.001 Torr with a vacuum pump. did. After processing this by swaging to an outer diameter of 10 mmφ, insert it into an Nb pipe with an inner diameter of 10 mmφ, an outer diameter of 16 mmφ, and a length of 100 cm, then insert it into a copper pipe of an inner diameter of 16 mmφ and an outer diameter of 18 mmφ, and reduce it to 8 mmφ by swaging. Surface processed. This is drawn by a draw bench and the opposite side length is 2
mm hexagonal filament. 350 hexagonal filaments were put in a pure copper pipe having an inner diameter of 50 mm and an outer diameter of 55 mm, and a billet for extrusion was manufactured while beam welding both ends in a vacuum. The extrusion was carried out by hydrostatic extrusion at room temperature to give an outer diameter of 20 mmφ. Further, this was drawn and drawn to have an outer diameter of 1 mm. This wire was heat-treated in high-purity argon gas at 750 ° C. for 200 hours to generate Nb ₃ Sn in the Nb part of the filament, and a superconducting wire as a final product was produced. This wire was immersed in liquid helium at 4.2K, and the critical current density was measured in an applied magnetic field of 8 to 12 Tesla. As a result, at 8 Tesla, 680 A / mm ² , 1
620A / mm ² at 0 Tesla, 380A / mm ² at 12 Tesla
A current value of ² was obtained. Comparative Example 1 In the manufacturing method of Example 1, a large number of powder compacts of copper and tin having an outer diameter of 10 mm and a length of 20 mm were filled in a Nb pipe having an inner diameter of 10 mm, an outer diameter of 16 mm, and a length of 100 cm without gaps, and swaging was performed. By processing, the outer diameter was processed to 8 mmφ, and a hexagonal filament having an opposite side length of 2 mm was manufactured by drawing.
There was already a break in 2-4mmφ during filament processing. Moreover, even during the wire drawing after extrusion similar to the example, wire breakage frequently occurred and a wire having a diameter of 4 mm or less could not be formed. In the method of filling the Nb pipe with the metal powder as described above, the powder is put into the pipe in advance and a powder compact bar is produced by swaging, and the Nb pipe and the Nb pipe are combined and processed. It is possible to eliminate processing troubles such as disconnection that occurs inside, and since powder is used, there is no compositional limitation, which makes it possible to manufacture high-performance superconducting wire. The manufacturing method of the present invention is applicable not only to Nb ₃ Sn superconductivity but also to V ₃ Ga. V
₃ Si. It is also suitable for manufacturing a superconducting wire such as Nb ₃ Al, and the same effect can be obtained.

[0007]

As described above, according to the present invention, it is possible to solve various troubles during the process of processing a wire rod and to manufacture a superconducting wire rod having a high current density. By using this for a magnet or the like, a high-performance device can be obtained. It is possible to obtain a remarkable industrial effect.

Claims (1)

Claims: 1. A Nb-based pipe is filled with a green compact made of copper powder and tin powder, and then cold-worked to reduce the diameter, and then Nb ₃ Sn is produced. Heat treatment of Nb ₃
The method of manufacturing a Sn-based superconducting wire, the copper powder and tin powder and insert the those powder processed by swaging after filling into the copper pipe Nb pipe, characterized in that thereafter reduced diameter processing Nb ₃ Sn -Based superconducting wire manufacturing method.