JPH033323B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a compound internally stabilized superconducting conductor, and aims to prevent damage to a diffusion barrier material surrounding a stabilizing metal during the manufacturing process, thereby preventing contamination of the stabilizing metal. shall be.

In the production of conventional compound internally stabilized superconducting conductors, the internal stabilizing material (hereinafter referred to as island) is used to transform the stabilizing metal into a diffusion barrier material (hereinafter referred to as barrier).
It was made by reducing the area of this two-layer composite. For example, stabilizing metals as shown in Figure 1
The barrier Nb tube 2 is combined with the Cu rod 1 and processed into the required size. Other methods include processing a Nb plate into a seam pipe of the required size and inserting a Cu rod into it, or seamless processing into the required size.
It was made by inserting a Cu rod into a Nb tube. The two-layer composite stabilizing material produced as described above is coordinated in the metal material forming the superconductor to form a billet, and the billet is hot extruded and further reduced in area to form an internally stabilized superconductor. A conductor is created. For example, a stabilized metal Cu bar can be used as a barrier.
A stabilizing material made by inserting it into a Nb tube and processing it into the required size is arranged as an island in a group consisting of a large number of superconducting constituent metals that form a superconductor, that is, Nb wires and Cu-Sn alloys. The billet is then assembled into a billet, which is then hot extruded and then subjected to area reduction processing to produce an internally stabilized superconducting conductor of the desired size.

However, the cross section of the superconducting conductor made in this way is shown in FIG. In other words, 5 in the figure is Nb
Element wire 6 is Cu-Sn alloy, barrier Nb tube 2
deforms into a star shape, thus creating a locally thin area in the thickness of the barrier Nb, which is broken by the area reduction process after extrusion, and as a result, the stabilizing metal
Cu is contaminated, and some of the Sn in the Cu-Sn alloy diffuses into the stabilizing metal Cu through the cracks in the barrier Nb, so it reacts with the Nb that makes up the superconductor.
The amount of Sn required to create Nb ₃ Sn decreases accordingly, and the superconducting properties are no longer fully exhibited. In order to prevent this, it is necessary to use a large Nb barrier that is thicker than necessary. To make a thick Nb tube, a seam Nb tube is made from a thick Nb plate and Cu
There is also a stabilizing material made by inserting a rod, but the strength of the welded seam is weak and there is a risk of tearing during processing before and after hot extrusion. There is also a method of inserting a Cu rod into a thick-walled Nb seamless tube, but this is extremely expensive and not a practical method.

The present invention has been made in view of the above points, and the present invention has been made in such a way that the purity of the stabilized metal is maintained even when a barrier having an appropriate thickness is used instead of a large barrier having an unnecessarily thick barrier. The purpose is to prevent damage to the That is, the present invention reduces the area of a structure in which a stabilizing metal material is coordinated in a superconducting constituent metal group forming a compound superconductor containing niobium or vanadium into a predetermined shape, and then performs diffusion heat treatment to form a superconducting conductor. In the method for producing a stabilized superconducting conductor, the stabilized metal material is a composite in which copper is wrapped with niobium or vanadium and further a copper-tin alloy or a copper-gallium alloy is arranged on the outside. It is a manufacturing method.

The structure and effects of the present invention will be described in more detail with reference to the drawings as follows. Metals that form superconducting compounds by diffusion heat treatment, such as Nb, Cu-
As shown in Figure 3, the stabilizing metal Cu1 is placed as an island inside the Sn alloy metal group as a barrier Nb.
A billet with a cross section shown in FIG. 4a is assembled by placing a hot extruded three-layer composite 4 surrounded by 2 and covered with a Cu--Sn alloy 3 as a shell on the outside. The billet is hot extruded, further reduced in area to a predetermined size, and subjected to diffusion reaction treatment to produce the stabilized superconducting conductor according to the present invention.As mentioned above, the island 4 is covered with the Cu-Sn shell 3. Therefore, the shell acts as a buffer material during hot extrusion of the billet, and the cross section after extrusion area reduction processing is shown in Figure 4b.
As shown in FIG. 2, the barrier Nb2 is processed to have a substantially circular shape with a uniform thickness, and does not have a star shape with an uneven thickness as shown in FIG. Therefore, even when the area is reduced after extrusion, the Nb barrier does not break, and there is an effect of preventing barrier damage. FIG. 5 shows an enlarged view of the vicinity of the island 4 in FIG. 4b. In the figure, the shell Cu-Sn3 of the island and the Cu-Sn6 superconducting metal are both in a state where they can react with the Nb filament 5, and the Nb barrier 2 has been prevented from being damaged, so there is no contamination of Cu1 and there is no risk of property deterioration. It disappears. Also, during the diffusion reaction treatment, Cu−Sn
The Sn can be properly reacted with the Nb filament 5 without being consumed in unnecessary reactions with the Cu1, and the Nb barrier 2 is also unnecessary because there is no risk of uneven thickness due to processing. You can use an appropriate thickness of Nb barrier without increasing the thickness.
In addition, when assembling a billet for hot extrusion, the metal group of the Nb thin wire, the Cu-Sn alloy, and the island of the above-mentioned three-layer composite are almost the same in terms of strength, so it is easier to reduce the area than before. Although the above description has been made regarding the Nb ₃ Sn compound superconducting conductor, the same applies to the production of the V ₃ Ga compound superconducting conductor. That is, in a composite body in which a V core is placed in a Cu-Ga alloy matrix, V is coated around the Cu core, and a Cu-Ga alloy coated on top is placed as an island to form an extruded billet. After reducing the area of this billet by extrusion processing or the like, a V ₃ Ga compound superconductor is manufactured by performing diffusion heat treatment to form a V ₃ Ga compound superconductor around the V core. In this case as well, due to the presence of the Cu--Ga alloy coating layer, which is the outermost layer of the island, the V of the barrier can be uniformly processed even by processing such as extrusion, and will not be torn.

Next, an example will be described.

139mmφ OFHC rod with outer diameter of 174mmφ and inner diameter of 140mm
Cover with a Nb cylinder of φ, and then add an outer diameter of 198 mm to the outside.
φ, a Cu-14.5%Sn bronze tube with an inner diameter of 175 mmφ was covered, a bronze lid of the same composition was placed on both ends, electron beam welding was performed to create a billet, and this billet was hot extruded to a size of 25 mmφ to form a three-layer composite. Making,
It was used as an internal stabilizing material. Next, the outside shown in Figure 4a
This internal stabilizing material is inserted as an island 4 into the Nb thin wire 5 and the Cu-Sn alloy 6 placed in the Nb tube 7, and an OFHC tube 8 is then placed over the outside of the Nb tube 7 to create a billet. This billet was hot extruded and subjected to area reduction processing to produce a superconducting conductor of the present invention having a diameter of 5 mm. The cross section of this superconducting conductor is the fourth
As shown in Figure b, the island barrier Nb2 was processed into a substantially circular shape, with no thinner areas and no tears observed. In the next diffusion reaction treatment, the compound Nb ₃ Sn was formed to a thickness of about 2 μm, and had good properties without any Cu contamination.

On the other hand, as a comparative example, an OFHC rod with an outer diameter of 174mm was used as a 139mmφ OFHC rod.
When a two-layer island covered only with a Nb cylinder with an inner diameter of 140 mm was used and the same process as in the example was carried out, the island was deformed into a star shape.
The thickness of Nb ₃ Sn was about 1 μm, and the characteristics were degraded.
As described above, the superconducting conductor according to the present invention is
The barrier of the internal stabilizing material also has an appropriate thickness, and there are no tears caused by processing, so there is no contamination of the stabilizing material, and the properties are very good, making it effective for use in superconducting magnets, etc.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the stabilizing material by the conventional method, Figure 2
3 is a perspective view of a stabilizing material according to the present invention, FIG. 4a is a sectional view of an extruded billet according to the present invention, and FIG. 4b is a cross-sectional view of a superconducting conductor according to the present invention. Cross-sectional view, Figure 5 is Figure 4b
FIG. 2 is an enlarged view of the vicinity of the island. 1: Cu rod, 2: Nb tube (barrier), 3: Cu-
Sn shell, 4: Internal stabilizing material (island),
5: Nb thin wire, 6: Cu-Sn alloy, 7: outer Nb tube,
8: OFHC tube.

Claims (1)

[Claims] 1. After reducing the area of a structure in which a stabilizing metal material is coordinated in a superconducting constituent metal group forming a compound superconductor containing niobium or vanadium into a predetermined shape,
In the method of manufacturing a superconducting conductor by diffusion heat treatment, the stabilizing metal material is a composite in which copper is wrapped in niobium or vanadium and further a copper-tin alloy or a copper-gallium alloy is arranged on the outside. A method for producing characteristic compound-stabilized superconducting conductors.