JPH05342932A - Manufacture of compound superconductive wire - Google Patents

Abstract

PURPOSE:To prevent generation of troubles such as wire breakage caused by segregation of CuSn alloy in processing. CONSTITUTION:A manufacturing method is provided with a process of forming composite billets by applying hot hydrostatic press work after filling CuSn alloy powder 2 in a pipe 1 made of Cu or Cu alloy in which a core material 3 comprising Nb or Nb alloy is disposed, a process of applying extrusion work, and applying area reduction work to the composite billets, and a process of applying heat treatment to generate Nb3Sn.

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 Nb ₃ Sn compound superconducting wire.

[0002]

2. Description of the Related Art In the method of manufacturing a Nb ₃ Sn compound superconducting wire by the bronze method, conventionally, a method of embedding an Nb core in a CuSn alloy base material made from a CuSn alloy ingot is used. By the way, since the CuSn alloy ingot is an alloy in which the CuSn alloy is inversely segregated, there is a significant difference in the Sn concentration between the surface layer and the inside, and in particular, the surface layer has a high Sn concentration drop-like segregation known as Sn sweat. Come out.

The Sn concentration of the CuSn alloy is desired to be as high as possible from the viewpoint of ensuring good superconducting properties, but it is also necessary to ensure good workability.
It remains within the α-phase solid solution limit of 14% by weight or less.

In the conventional manufacturing method, since the CuSn alloy ingot is segregated, the CuSn alloy is cracked from the CuSn compound layer in the alloy at the time of processing such as surface reduction processing, or at the time of heating such as hot extrusion processing or annealing processing. There has been a problem that an NbSn compound is generated at the contact portion between the Sn-rich portion of the CuSn alloy and Nb, which adversely affects the subsequent workability. That is, Nb
Since the compound formed on the surface exists while breaking even in the subsequent surface reduction processing, when the Nb core is processed to a diameter of 10 μm or less in the practical range, the compound particles are inlaid on the Nb core and the Nb core is inlaid.
There is a problem that the wire breaks in the b core.

As described above, according to the conventional manufacturing method, CuS
Since the n alloy ingot was used, there were many processing problems due to the Sn rich segregation portion.

[0006]

The present invention has been made in order to solve the conventional problems, and is an Nb ₃ Sn compound which prevents the occurrence of processing troubles such as disconnection due to segregation of CuSn alloy. It is intended to provide a method for manufacturing a superconducting wire.

[0007]

The present invention is based on Nb or Nb.
Filling CuSn alloy powder in a tube made of Cu or a Cu alloy in which a core made of an alloy is arranged, and then subjecting it to hot isostatic pressing (hereinafter referred to as HIP) to form a composite billet; After the composite billet is extruded, it is subjected to surface-reduction processing and heat treatment is applied to Nb ₃
And a step of generating Sn.
It is a method for producing a b ₃ Sn compound superconducting wire.

Examples of the alloy forming the CuSn alloy powder include Cu-Sn alloy and Cu-Sn-Ti alloy.

The CuSn alloy powder is preferably one produced by a gas atomizing method. The reason for this is that the CuSn alloy powder produced by the gas atomization method has a homogeneous composition without macrosegregation which is inconvenient for wire rod production processing due to the quenching effect. In addition, the CuSn
The alloy powder may be a powder obtained by subjecting a CuSn alloy ingot to plastic working, cutting, or the like. Even with such a powder, it is possible to mechanically miniaturize the huge segregated portion in the ingot and achieve homogenization.

The CuSn alloy powder preferably has a particle size of 0.5 to 3 mm. The reason for this is that if the particle size is less than 0.5 mm, the specific surface area increases, and gas adsorption or oxidation on the powder surface may adversely affect the subsequent processability and Nb ₃ Sn formation reaction. On the other hand, if the particle size exceeds 3 mm, the segregation portion composed of individual particles becomes large, so that the composition may be similar to an ingot.

As the Nb alloy forming the core material arranged in the CuSn alloy powder, for example, Nb-Ta alloy,
Nb-Ti alloy is mentioned.

The method of the present invention can be performed, for example, as follows.

First, for example, as shown in FIG. 1, a plurality of (or one) core materials 2 made of Nb or Nb alloy are erected on a pedestal not shown in a tube 1 made of Cu or Cu alloy for HIP processing. Then, the tube 1 is filled with the CuSn alloy powder 3. Here, the pedestal may also serve as a lid described later. Subsequently, a lid is electron-beam welded to both ends of the tube in a vacuum, HIP processing is performed, and if necessary, the tube portion, the pedestal portion and the lid portion are shaved to form a composite billet. The bronze ratio of the composite billet (the weight ratio of CuSn alloy and core material)
Can be adjusted by changing the proportion of the core material in the space in the tube.

Next, the composite billet is subjected to hot extrusion processing, and then subjected to surface reduction processing while being annealed to form a composite strand.

Next, a plurality of the composite wires are inserted into a stabilizing oxygen-free copper tube with an Nb tube or Ta tube as a diffusion barrier interposed. Subsequently, lids are electron beam welded to both ends of the Cu tube in a vacuum, and then subjected to HIP processing.
After that, the wire is formed by subjecting it to hot extrusion and then surface-reducing while annealing. afterwards,
By forming a Nb ₃ Sn by heat treatment in the wire, producing a Nb ₃ Sn compound superconducting wire.

Another invention according to the present invention is, for example, as shown in FIG. 2, a large-diameter pipe 11 made of Cu or Cu alloy.
And CuSn in a tubular space formed between the small-diameter pipe 12 made of Cu or Cu alloy and arranged in the pipe 11.
After filling the alloy powder 13, HIP processing is performed to CuS
forming a tube mainly composed of an n-alloy;
A step of forming a composite billet by inserting a core material made of Nb or an Nb alloy into a tube mainly made of an alloy, a step of subjecting the composite billet to an extrusion process, a surface reduction process, and a heat treatment to form Nb. _And a step of producing ₃ Sn, which is a method for producing a Nb ₃ Sn compound superconducting wire.

[0017]

According to the method of the present invention, a CuSn alloy powder is filled in a tube made of Cu or a Cu alloy in which a core made of Nb or an Nb alloy is arranged, and then HIP processing is performed to form a composite billet. Since the CuSn alloy in the composite billet thus obtained is one in which the CuSn alloy powders are joined and integrated, a homogeneous composition can be obtained without causing segregation like CuSn alloy ingots.
Therefore, after subjecting the composite billet to extrusion,
In the process of reducing the surface area, it is possible to prevent the occurrence of processing troubles such as disconnection due to segregation of the CuSn alloy. Further, according to the method of the present invention, since the powdering cost of CuSn alloy is higher than the casting cost, even if the CuSn alloy powder is expensive, the CuSn alloy ingot can be produced by the conventional method using the CuSn alloy ingot. Soaking, HIP processing,
Considering processing costs such as tubular processing and perforation processing, it is possible to manufacture the Nb ₃ Sn compound superconducting wire at a lower cost than the conventional method.

On the other hand, according to another method of the present invention, it is formed between a large-diameter pipe made of Cu or Cu alloy and a small-diameter pipe made of Cu or Cu alloy arranged in the pipe. After filling the CuSn alloy powder into the tubular space,
HIP processing is performed to form a tube mainly composed of CuSn alloy. Subsequently, a core material made of Nb or an Nb alloy is inserted into the tube mainly composed of the CuSn alloy to form a composite billet. CuS in the composite billet thus obtained
Since the n-alloy is obtained by integrally bonding the CuSn alloy powders, a homogeneous composition can be obtained without causing segregation like CuSn alloy ingot. For this reason,
In the step of subjecting the composite billet to the extruding process and then the surface-reducing process, it is possible to prevent processing troubles such as disconnection due to segregation of the CuSn alloy. Further, the method of another invention according to the present invention can manufacture the Nb ₃ Sn compound superconducting wire at a lower cost than the conventional method for the same reason as described above.

[0019]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 First, a pedestal made of Cu having a diameter of 139 mmφ has a diameter of 1+
6000 holes of 0 to 0.05 mmφ were punched at equal intervals in a bales-stacked shape. This base has a diameter of 1 to 0 as the Nb core.
After 6000 pure Nb rods having a diameter of 0.05 mm and a length of 400 mm were forested, a Ta pipe having a thickness of 2.3 mm was fitted thereto, and a Cu pipe having an outer diameter of 218 mmφ and an inner diameter of 144 mmφ was further covered. Subsequently, Cu-17.3 wt% Sn-0.
2 wt% Ti alloy powder (50 mesh to 200 mesh) was filled into the gap between the forested Nb cores while vibrating well. After fitting Cu lids to both ends of this composite, C
A composite material was formed by electron beam welding the fitting portion between the u lid and the Cu tube. The composite material was subjected to HIP processing under the conditions of 650 ° C. for 1 hour and 1500 atm to sinter the powder around the Nb core and metal-bond each constituent material. Subsequently, this was externally cut to form a composite billet having an extrusion billet size of 200 mmφ in diameter.

Next, the composite billet was hot extruded to have a diameter of 40 mmφ. Subsequently, the surface-reducing work and the annealing treatment were alternately repeated, whereby the final molded wire rod having a diameter of 0.93 mmφ could be formed without causing a wire breakage. Examination of the cross section of the final molded wire thus obtained revealed that the surface of the filament made of Nb core was smooth and the cross section of the filament was relatively uniform and nearly circular.

Next, the final molded wire thus obtained was subjected to a diffusion heat treatment to generate Nb ₃ Sn, thereby producing a Cu-stabilized Nb ₃ Sn compound superconducting wire having a diameter of 0.93 mmφ.

Comparative Example 1 First, an outer diameter of 200 mmφ and an inner diameter of 116 m cut out from a Cu-17.3 wt% Sn-0.2 wt% Ti alloy ingot.
A Nb rod with a diameter of 115 mmφ was inserted into a mφ pipe, and after both ends of this pipe were electron beam welded, hot extrusion processing was performed, and further surface-reduction processing and annealing treatment were repeated alternately to obtain a diameter of 1.5 mmφ. A strand was formed. Continuing,
The 6000 strands are assembled and bundled to form a bale stack, and a Ta tube having a wall thickness of 2.3 mm, an outer diameter of 133 mmφ and an inner diameter of 128.4 mmφ is covered on the outer side thereof, and further outer side thereof has an outer diameter of 210 mmφ and an inner diameter of 134 mmφ. A Cu tube was covered.
Subsequently, Cu lids were fitted to both ends of the two ends and electron beam welding was performed to form a composite material. The composite material is HIP processed under the condition of 650 ° C. for 1 hour and 1500 atm, and then externally cut to obtain a diameter of 200 mmφ.
To form a composite billet.

Then, in the same manner as in Example 1, the composite billet was subjected to hot extrusion processing, and then surface-reducing processing and annealing processing were alternately repeated to form a final molded wire having a diameter of 0.93 mmφ. In this process, many wire breaks occurred during surface reduction processing, so the final molded wire rod had an average length of 300 m.
It was broken every time. When the cross section of the final molded wire thus obtained was examined, a coarse filament was found in the cross section, and it was Nb ₃ Sn as a result of examining this with a SEM (scanning electron microscope). In addition, it has been extruded twice, and the filament surface has 1
The filament cross-sectional shape was flat due to the influence of Nb ₃ Sn produced in the extrusion process of the _third time.

Then, the final molded wire thus obtained is subjected to a diffusion heat treatment to generate Nb ₃ Sn, whereby Cu having a cross-sectional structure similar to that of Example 1 and having a diameter of 0.93 mmφ is formed.
A stabilized Nb ₃ Sn compound superconducting wire was manufactured.

With respect to the compound superconducting wires of Example 1 and Comparative Example 1, the critical current density (Jc) excluding the Cu portion was measured under a magnetic field of 12T.

As a result, the compound superconducting wire of Example 1 was
The Jc value is 850 A / mm ^2, which is an extremely high Jc.
It was confirmed that the value was obtained.

On the other hand, the compound superconducting wire of Comparative Example 1 had a Jc value of 450 A / mm ² , and it was confirmed that the Jc value was low. This is due to local disconnection of the superconducting filament and variation of the cross-sectional area in the longitudinal direction.

As described above, in the method for manufacturing the compound superconducting wire of Example 1, although the number of steps for assembling the composite billet is large, the extrusion process can be performed only once.
The homogenization of CuSn alloy powder having a high Sn concentration suppresses generation of harmful Nb ₃ Sn at the interface between Nb and CuSn alloy during high temperature heating during extrusion,
This has the advantage that there is no inconvenience of filament breakage in the final molding step. Furthermore, extrusion processing is 1
It was confirmed that since the Nb core was relatively circular at the time of turning, uniform Nb ₃ Sn could be formed in the longitudinal direction, so that it was possible to obtain a superconducting wire having excellent superconducting properties.

Example 2 First, a large-diameter C having an outer diameter of 220 mmφ and an inner diameter of 114 mmφ
u tube and outer diameter 94m arranged in the center of this Cu tube
One end (lower side) with a small diameter Cu tube with mφ and inner diameter of 90 mmφ
A Cu lid was attached to. Subsequently, 100 meshes (particle size: 0.1) in the tubular space formed between these Cu tubes.
Cu-16.8 having a diameter of 49 mmφ or more and a grain size of 3 mmφ or less
After filling the weight% Sn-0.2 weight% Ti alloy powder while applying vibration, a Cu lid was attached to one upper end of both Cu tubes, and both ends were electron beam welded.
A composite material was formed. Continue to 650 for the composite material
After HIP processing under the condition of 1,500 atm for 1 hour, the inner diameter is reduced to 200
A CuSn alloy tube having a mmφ and an inner diameter of 116 mmφ was formed.

The CuSn alloy pipe thus obtained was measured for Vickers hardness on the outer and inner circumferences, respectively. As a result, it was confirmed that both the outer and inner circumferences had Hv170, indicating a homogeneous composition.

Thereafter, the CuSn alloy tube thus obtained is subjected to composite processing with an Nb core, extrusion processing, surface-reduction processing, diffusion heat treatment and the like to prevent Cu-stabilized Nb from being broken during processing. _A 3Sn compound superconducting wire could be manufactured.

Comparative Example 2 Cu-16.8 wt% Sn-0.2 wt% Ti alloy ingot was machined to form CuSn having the same composition as in Example 2.
C with alloy outer diameter 200 mmφ and inner diameter 116 mmφ
A uSn alloy tube was formed.

The Vickers hardnesses of the outer and inner circumferences of the CuSn alloy pipe thus obtained were measured. The outer circumference was Hv 180 to 190, and the inner circumference was Hv.
It was 150 to 160, and it was confirmed that macroscopic segregation appeared.

Thereafter, this segregation causes cracking of the CuSn alloy during processing, which makes processing difficult.

[0036]

As described above in detail, according to the present invention, Cu
It is possible to provide a method capable of preventing the occurrence of processing troubles such as wire breakage due to segregation of Sn alloy, and eventually producing an Nb ₃ Sn compound superconducting wire having excellent superconducting properties.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an arrangement state of a tube made of Cu or Cu alloy, CuSn alloy powder, and a core material made of Nb or Nb alloy.

FIG. 2 is a cross-sectional view showing an arrangement state of a large diameter tube made of Cu or Cu alloy, a small diameter tube made of Cu or Cu alloy, and CuSn alloy powder.

[Explanation of symbols]

1 ... Tube made of Cu or Cu alloy, 2 ... Core material made of Nb or Nb alloy, 3 ... CuSn alloy powder, 11 ... Large diameter tube made of Cu or Cu alloy, 12 ... Small diameter made of Cu or Cu alloy Tube, 13 ... CuSn alloy powder.

Claims (2)

[Claims] 1. A step of forming a composite billet by filling CuSn alloy powder into a tube made of Cu or a Cu alloy in which a core made of Nb or an Nb alloy is arranged, and then performing hot isostatic pressing. After the composite billet is extruded, a surface-reducing process is performed and a heat treatment is performed to obtain N.
and a step of producing b ₃ Sn, the method for producing a Nb ₃ Sn compound superconducting wire. 2. After filling CuSn alloy powder into a tubular space formed between a large-diameter tube made of Cu or a Cu alloy and a small-diameter tube made of Cu or a Cu alloy arranged in the tube. A step of performing hot isostatic pressing to form a tube mainly composed of CuSn alloy, and a step of inserting a core material made of Nb or Nb alloy into the tube mainly composed of CuSn alloy to form a composite billet And a step of subjecting the composite billet to extrusion processing, then surface-reducing processing, and heat treatment to generate Nb ₃ Sn, a method for producing a Nb ₃ Sn compound superconducting wire. ..