JPH076641A - Superconducting wire manufacturing method - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a method for producing a superconducting wire with less loss of a superconducting alloy material. [Structure] A metallic lid (3) corresponding to the tip of a composite superconducting billet (4) is provided with a tapered portion having a volume equal to or larger than the internal volume of the tapered portion of an extrusion die (6). In the extruded material obtained by extruding the composite superconducting billet (4), the advanced rate of the billet center portion becomes small, so that the defective portion where the superconducting alloy material is insufficient is reduced, and thus the loss of the superconducting alloy material is reduced. Reduce.

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 superconducting wire with a low loss of a superconducting alloy material.

2. Description of the Related Art A superconducting wire is made of Nb-T in order to prevent a rapid temperature rise, that is, quench, accompanying flux flow.
It is configured by combining a superconducting alloy material such as an i alloy with copper or a copper alloy having excellent thermal conductivity. For manufacturing the superconducting wire having such a structure, for example, one Nb-Ti superconducting alloy wire is filled in a copper pipe, the inside of the pipe is deaerated in a vacuum, and a copper lid is fixedly attached to both ends of the pipe to form a composite. A billet is formed by extruding the composite billet into a desired shape and subjecting the extruded material to surface reduction processing such as drawing.
The superconducting wire manufactured in this way is a single-core superconducting wire in which one superconducting alloy wire is compounded in a copper matrix. Actually, however, many single-core superconducting wires are filled in a copper pipe. , By reducing the surface of this to make a multi-core superconducting wire,
A superconducting alloy material, that is, a superconducting filament is dispersed as finely as possible and is used as a material having good thermal diffusion.

[0002]

By the way, in general, an extruded material is extruded billet due to the influence of frictional resistance between the extruded billet 5 and the inner surface of an extruding die (not shown) as shown in the metal flow of FIG. The deformation of the portion corresponding to the surface of No. 5 is delayed, and the tendency of this delay is remarkable in the front end portion and the rear end portion of the extruded material. On the other hand, the composite billet used in the production of superconducting wire is
As shown in the vertical cross-sectional view in FIG. 4, the billet is manufactured so that the thickness of the metal lid 3 is reduced and the portion filled with the superconducting alloy material 2 is located as long as possible during extrusion. As a result, the extruded material obtained by extruding the composite billet 4 has a superconducting alloy material 2 at its front end portion and rear end portion as shown in the longitudinal sectional view of FIG.
There is a problem in that a large amount of defective portions lacking in the number of defects occur, and the defective portions are cut and removed, so that a large amount of expensive superconducting alloy material is lost.

[0003]

[Means and Actions for Solving the Problems] The present invention has been made as a result of intensive research in such a situation.
It is an object of the invention to provide a method for producing a superconducting wire with less loss of the superconducting alloy material. That is, the present invention is a single-core or multi-core composite superconducting billet in which a superconducting material is embedded in a stabilizing base material, and a surface-reducing surface including hot extrusion for extruding it using an extrusion die having an arbitrary taper angle. In the method of manufacturing a superconducting wire to be processed, hot extruding is performed by providing a taper portion having a volume equal to or larger than the inner volume of the taper portion of the extrusion die at the tip of the composite superconducting billet. It is characterized by.

In the present invention, the stabilizing base material is mainly made of oxygen-free copper, tough pitch copper, copper or a copper alloy such as a copper-tin alloy, as long as it has excellent thermal conductivity. Any metal material is used. Further, the hot extrusion method can be applied to any of a direct extrusion method, an indirect extrusion method, and a hydrostatic extrusion method. Further, in the present invention, the reason why the volume of the taper portion provided at the tip of the composite superconducting billet is equal to or larger than the inner volume of the extrusion die taper portion is as shown in FIG. 6 (1). If the volume of the taper part provided at the tip of the composite superconducting billet is less than the inner volume of the extrusion die / taper part, when the die is set up at the time of extrusion as shown in Fig. 6 (2), the die before the cross-sectional area begins to decrease. This is because the billet tip portion is deformed to fill the inside, and the central portion of the superconducting alloy material is advanced at that time, which results in increasing the number of defective portions, and the original purpose cannot be achieved.
The superconducting wire manufacturing method of the present invention will be specifically described below with reference to the drawings. 1 (1) and 1 (2) are longitudinal sectional views showing an example of the embodiment of the composite billet used in the method of the present invention, and FIG. 1 (3).
Is an extrusion die used for hot extrusion, and FIG. 2 is a vertical cross-sectional explanatory view showing an example of the metal flow of the extruded material of the composite billet. In the composite billet of FIG. 1 (1), the volume of the taper portion provided at the tip end is equal to the inner volume of the taper portion of the extrusion die 6, and in the composite billet of FIG. 1 (2), the contents of the taper portion of the extrusion die 6 are included. Greater than product. The composite billet is produced by filling the metal pipe 1 with the superconducting alloy material 2 as shown in FIG. 1, then degassing the inside of the metal pipe 1 in vacuum, and then welding the metal lids 3 to both ends. To be done.
Next, the composite billet 4 produced in this way is subjected to tapping, HIP treatment, or the like as necessary to enhance the adhesion between the metal pipe 1 on the outer periphery and the superconducting alloy material 2 inside, and then hot working Extrude into desired shape. As shown in Fig. 2, the obtained extruded material was able to suppress the deformation (advancement at the center of the billet) during upset before extrusion, so the advance rate was small, and therefore the superconducting alloy material was insufficient. The number of defective parts is reduced. The extruded material thus obtained is then cut to remove the defective portion, and then processed into a superconducting wire having a predetermined shape by a surface-reducing method such as swaging or drawing.

[0005]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 A pipe made of oxygen-free copper having an outer diameter of 220 mm and an inner diameter of 158 mm was filled with a Nb-Ti superconducting alloy material having an outer diameter of 150 mm and a length of 750 mm wound in one layer with a Nb plate having a thickness of 1.7 mm as a barrier. Next, after degassing the inside of the pipe under vacuum, various oxygen-free copper lids (taper angle 120 °) shown in Table 1 were electron beam welded to one end of the pipe to produce a composite billet. Then HI is added to this composite billet.
After P treatment and compressing to an outer diameter of 215 mm, an outer diameter of 20
It was externally machined to 0 mm, heated to 850 ° C., and extruded by a direct extrusion method using an extrusion die having a taper angle of 120 ° and a hole diameter of 25 mmφ. With respect to the extruded material thus obtained, the length (yield length) of the non-defective portion filled with the Nb-Ti superconducting alloy material having a predetermined diameter was measured, and The length ratio (non-defective rate) was determined. The results are shown in Table 1.

[0006]

[Table 1]

As is clear from Table 1, the invention example (No.
1) and 2) all had high yield length and high yield rate. On the other hand, in Comparative Examples (Nos. 3 to 4), the yield length and the non-defective rate were lower than those of the present invention, and the lower the inner volume ratio, the lower.

Example 2 The 25 mmφ extruded material obtained under the No. 2 condition of Example 1 was subjected to drawing and wire drawing to obtain 2.5 mmφ and a length of 8
A 50 mm single-core superconducting wire was produced. Next, 7000 single-core superconducting wires were filled in an oxygen-free copper pipe having an outer diameter of 250 mm and an inner diameter of 195 mm, and the inside of the pipe was deaerated under vacuum, and then various oxygen-free copper lids shown in Table 2 were attached to one end of the pipe ( A taper angle of 120 °) was electron beam welded to form a composite billet. H is added to the composite billet produced in this way.
Outer diameter 2 after IP treatment and compression to an outer diameter of 240 mm
The composite billet was externally machined to 35 mm, heated to 500 ° C., and extruded by an indirect extrusion method using an extrusion die having a taper angle of 120 ° and a hole diameter of 75 mmφ. With respect to the extruded material thus obtained, the length (yield length) of a non-defective portion in which 7,000 single-core superconducting wires were filled inside was measured, and the non-defective rate was calculated. The results are shown in Table 2.

[0009]

[Table 2]

As is clear from Table 2, the invention example (No.
In all of 5 to 6), the yield length and the yield rate were high. On the other hand, in each of the comparative examples (Nos. 7 to 8), the yield length and the non-defective rate were lower than those of the examples of the present invention, and were lower as the internal volume ratio was smaller. This point is the same as in the case of Example 1, and it can be seen that it holds regardless of the extrusion method and the difference between single core and multiple cores. The example of manufacturing a superconducting wire by using a composite billet in which one superconducting alloy material or a large number of single-core superconducting wires are filled in a metal pipe has been described above. The same effect can be obtained when a billet is used. Also, an example of using Nb-Ti superconducting alloy as the superconducting alloy material has been described.
The same effect can be obtained even when applied to the manufacture of other superconducting wires such as Nb ₃ Sn superconducting wires.

[0011]

As described above, according to the method of the present invention, the tip portion of the composite superconducting billet is provided with the taper portion having a volume equal to or larger than the inner volume of the taper portion of the extrusion die. It is possible to reduce the loss of expensive superconducting alloy material that sometimes occurs, and it is possible to achieve a remarkable industrial effect.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a composite billet used in the method of the present invention,
FIG. 3 is a schematic view of an extrusion die.

FIG. 2 is an explanatory view of a metal flow of an extruded material in the method of the present invention.

FIG. 3 is an explanatory diagram of a metal flow of an extruded material.

FIG. 4 is a vertical sectional view of a conventional composite billet.

FIG. 5 is an explanatory view of a metal flow of a conventional extruded material for a composite billet.

FIG. 6 is a vertical cross-sectional view of a composite billet at the time of upsetting before extrusion by a conventional extrusion method.

[Explanation of symbols]

 1 Metal Pipe 2 Superconducting Alloy Material 3 Metal Lid 4 Composite Billet 5 Extrusion Billet 6 Extrusion Die 7 Container

Claims (2)

[Claims] 1. Surface-reduction processing including hot extrusion, in which a single-core or multi-core composite superconducting billet having a superconducting material embedded in a stabilizing base material is extruded using an extrusion die having an arbitrary taper angle. In the method for producing a superconducting wire, the tip of the composite superconducting billet is provided with a taper portion having a volume equal to or larger than the inner volume of the taper portion of the extrusion die to perform hot extrusion. A method of manufacturing a superconducting wire, which is characterized. 2. A method for producing a superconducting wire, characterized in that the hot extrusion is any one of a direct extrusion method, an indirect extrusion method and a hydrostatic extrusion method.