JPS6233688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a compound-based superconducting wire, particularly a Nb ₃ Sn superconducting wire.

A billet of superconducting strands made of a Nb core material coated with a Cu-Sn alloy is thinned by hot extrusion and drawing, and a large number of superconducting strands thinned in this way are made into thin wires. A large number of superconducting strands in the copper tube (stabilizing material) are incorporated into a copper tube, which is a stabilizing material for the superconducting material, and then processed through hot extrusion, drawing, etc., and finally subjected to heat treatment. at the interface of Nb and Cu-Sn alloy, respectively.
There is a method for manufacturing a Nb ₃ Sn superconducting wire that forms an Nb ₃ Sn layer.

In this method of manufacturing Nb ₃ Sn superconducting wire, conventionally, the billet of the superconducting wire is made of pure Nb as a core material, and Cu-4 to 8% by weight is added on the circumference of the billet.
Those coated with Sn alloy are used. However, the Cu--Sn alloy having the above composition is extremely difficult to machine, such as extrusion or drawing, and the reality is that it is still hardly manufactured on an industrial basis.

This Cu-Sn alloy is difficult to cast, and when it is cast, Sn segregates near the surface of the casting surface.
There is a problem in that defects such as protrusions tend to remain. If such surface defects exist, cracks will occur in the material during subsequent hot or cold working, making it impossible to obtain industrially stable and good products.

In view of the above, an object of the present invention is to
A method for manufacturing Nb ₃ Sn superconducting wire has been developed, which enables the billet of superconducting wire coated with Cu-Sn alloy on the periphery to be processed well without cracking, making manufacturing extremely stable and easy. It's about submitting.

The gist of the present invention is that Cu--
A billet of superconducting wire coated with an Sn alloy is processed into fine wires, and a large number of the thinned superconducting wires are assembled into a copper tube, which is a stabilizing material for the superconducting material, and further processed. A method for producing a Nb ₃ Sn superconducting wire in which a Nb ₃ Sn layer is formed at each interface between Nb and Cu-Sn alloy of a large number of superconducting wires in the copper tube (stabilizing material) by finally performing heat treatment. In this method, the billet of the superconducting wire is thinned by processing, at least initially by hydrostatic extrusion, and at that time, the surface of the billet of the superconducting wire is coated with pure copper, which is a metal with good workability, and then the billet is thinned by static extrusion. A method for producing a Nb ₃ Sn superconducting wire, which is characterized by hydraulic extrusion.

According to the present invention, Cu-
By coating the billet of superconducting wire coated with Sn alloy with pure copper, which is a metal with good workability, its workability is significantly improved, and furthermore, by using hydrostatic extrusion as a processing method, it is advantageous in its processing. Due to its properties, it completely eliminates the occurrence of cracks.

Hydrostatic extrusion is a very advantageous processing method that can make the most of the objects of the present invention, since there is no container friction and die lubrication is very good.

Next, embodiments of the method of the present invention will be described with reference to the accompanying drawings.

FIGS. 1 and 2 each show a composite billet for single-core hydrostatic extrusion for the production of Nb ₃ Sn superconducting wire. This billet 1 is made by coating a single Nb billet 2 with a Cu--Sn alloy 3, which is further coated with pure copper 4, which is a metal with good workability.

Further, both ends thereof are covered with a front end plug 5 and a rear end plug 5' and sealed by electron beam welding after vacuum degassing.

The billet 1 manufactured in this way does not have to worry about internal oxidation even if it is heated as a whole, and since the surface is coated with pure copper 4, it has good workability and extremely good extrusion behavior. In particular, by hydrostatic extrusion using the method shown in FIG. 3, an extremely sound extruded superconducting wire material can be obtained.

In FIG. 3, the billet 1 is inserted into the container 6 of the isostatic extruder, and by moving the ram 7, the billet 1 can be extruded through the die 9 by the downward force of the pressure medium 8. It's summery.

In the case of a billet whose surface is not coated with pure copper, cracks may occur in the extruded material due to defects in the Cu-Sn alloy, or cracks may occur at the connection part with the tip plug during extrusion, not only in hot extrusion but also in hydrostatic extrusion. In many cases, the extruded material breaks, and stable industrial production is not possible.

Also, if there is no pure copper coating on the billet surface,
During extrusion, a copper plug (cone-shaped) is usually welded to the tip of the billet, but in this case, the copper plug and the Cu-Sn alloy of the billet are welded together, which involves evaporation of Sn, which requires tools and equipment. The disadvantage is that electron beam welding cannot be used because of the damage it causes.

For this reason, it must be sealed using another joining method, and with normal welding, the entire billet is heated, which causes internal oxidation and deteriorates the adhesion between the Nb and Cu-Sn alloy interfaces. , which worsens the extrusion behavior and makes the subsequent drawing process unstable, making the wire more likely to break.

On the other hand, superconducting wires made by hydrostatically extruding a billet whose surface is coated with pure copper are then drawn out and repeatedly coated with pure copper to form hexagonal wires on the order of several millimeters as shown in Figure 4. A billet for multipurpose use is produced by gathering together hundreds or thousands of pieces and incorporating them into a steel pipe as a stabilizing material as shown in Fig. 5, which is then hydrostatically extruded again and drawn into thin wires. Processing of this multi wire from 1 to
This process is repeated twice to finally produce a multi-wire containing several thousand to tens of thousands of single-filament wires, and this multi-wire is heated to 600 to 800°C in a final heat treatment to add Nb to the interface between the Nb and Cu-Sn alloy. Even if a multi-core Nb ₃ Sn superconducting wire is manufactured by forming a ₃ Sn layer, the wire is uniform in the longitudinal direction, has no broken parts, and is extremely stable in size and shape.

Incidentally, for this multi-superconducting wire, the number of cores is
In the case of a 0.8φ Nb ₃ Sn superconducting wire made by twisting 2317 multi-wires with a core diameter of 0.007 mm and an outer diameter of 0.245 mm, the wire produced experimentally using the conventional method was 1480 A/cm in a magnetic field of 7 T. ² , whereas the product manufactured on an industrial scale using the above method showed a critical current density of 1520 A/cm ² , confirming that its characteristics are superior to those of the conventional method. It was done.

As specific examples shown in FIGS. 1 to 3,
Pre-prepared outer diameter 160φ, inner diameter 148φ, length 1200mm
Made of pure copper tube, outer diameter 147φ, inner diameter 91φ, length 1200mm.
Insert a Cu-13%Sn alloy hollow tube with a diameter of 90 mm and a solid billet of Nb with an outer diameter of 90 mm and a length of 1100 mm. The composite billet obtained by air-sealing by electron beam welding was inserted into the container of a hydrostatic extruder, and the outer diameter was 29φ at an extrusion temperature of 370℃ and a maximum extrusion pressure of 14000Kg/cm ² using castor oil as a pressure medium. was hydrostatically extruded.

In addition, the cross-sectional area ratio of Cu and Cu-Sn alloy to Nb in this extruded material was 2, and the Nb diameter was approximately 16φ.

As is clear from the above explanation, the present invention Nb ₃ Sn
According to the manufacturing method of superconducting wire, hydrostatic extrusion is adopted as a method for thinning the billet of superconducting wire, which is made by coating a Cu-Sn alloy on the circumference of Nb, which is the core material, and At this time, the surface of the billet is coated with pure copper, which is a metal with good workability, and isostatically extruded, whereby the billet is hydrostatically extruded through the pure copper coating layer, thereby reducing the billet well without causing cracks. It is possible to process the surface of the superconducting wire, making it extremely easy to manufacture this type of superconducting wire and making it stable. This has the effect of improving the properties of the superconducting wire, and its industrial value can be said to be extremely large.

[Brief explanation of the drawing]

Fig. 1 is a front cross-sectional view of a composite billet of superconducting wire according to the present invention, Fig. 2 is a side cross-sectional view of the same, Fig. 3 is a diagram showing the state of hydrostatic extrusion of the composite billet, and Fig. 4 is a diagram showing hydrostatic extrusion. FIG. 5 is a partial cross-sectional view of a billet for multi-purpose use in which a large number of thinned superconducting wires are assembled into a copper tube. 1: Composite billet, 2: Nb single billet,
3: Cu-Sn alloy, 4: Pure copper.

Claims (1)

[Claims] 1. A billet of superconducting wire made of Nb core material coated with Cu-Sn alloy is processed into fine wires, and many of the thinned superconducting wires are used as a stabilizing material for the superconducting material. By incorporating it into a certain copper tube, further processing it, and finally performing heat treatment, Nb ₃ is added to the interface between the Nb and Cu-Sn alloys of the many superconducting wires in the copper tube (stabilizing material). Sn
In the method for manufacturing a Nb ₃ Sn superconducting wire in which a layer is formed, the billet of the superconducting wire is thinned by processing at least initially by hydrostatic extrusion, and at that time, the billet of the superconducting wire is thinned. A method for producing a Nb 3 Sn superconducting wire, which is characterized by coating Nb ₃ Sn superconducting wire with pure copper, which is a metal with good workability, and hydrostatically extruding it.