JPH06333439A - Compound superconductive wire - Google Patents

Abstract

PURPOSE:To obtain a compound superconductive wire having the excellent superconductivity under the high magnetic field. CONSTITUTION:Multiple basic cluster wires 3, which is obtained by laminating compound superconductor layers 1 and copper layers 2 alternately, are unified to form a compound superconductive wire. Thickness of the copper layer 2 is set in a range at 0.4-5 times of coherence length of the compound superconductor layer 1. Since the copper layers 2, which are distributed finely, has the pinning work, superconductivity under the high magnetic field is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound superconducting wire having excellent superconducting properties especially under a high magnetic field.

[0002]

2. Description of the Related Art Nb ₃ Sn, Nb ₃ are used for compound superconductors.
Examples include Al and V ₃ Ga. Since these are inferior in workability, its generation, for example, after processing the composite of the Nb metal and the Cu-Sn alloy to the final shape, the heat treatment by diffusing the Sn into Nb and Nb ₃ Sn compound superconducting It was carried out by a method of producing a reaction. Specifically, bronze (Cu
-Sn-based alloy) pipe is filled with Nb rod, and this is drawn to form a composite wire rod. The step of filling this copper wire pipe into a copper pipe and drawing it is performed a desired number of times to obtain a predetermined wire diameter. There are a bronze method of finishing and heat treatment of this, or an internal diffusion method of using a composite wire material in which a Nb layer or an Nb alloy layer is arranged around a Sn-rich alloy core material in the composite wire material.

[0003]

In the method of producing a compound superconductor as described above, the production rate is in bronze and N.
It is limited by the diffusion rate of Sn in the b ₃ Sn layer. When the heating temperature is raised to increase the production rate, the grain boundaries effective for pinning are reduced, and a non-superconductor compound is produced.
On the other hand, when the heating temperature is lowered, Sn is insufficient in the central portion of the Nb layer, and the stoichiometric composition of the Nb ₃ Sn superconductor cannot be obtained. Thus, there has been a limit to improving the characteristics of the conventional compound superconducting wire such as Nb ₃ Sn.

[0004]

The present invention has been made as a result of intensive studies in view of such a situation, and an object thereof is to obtain excellent superconducting properties particularly in a high magnetic field,
It is to provide a compound superconducting wire. That is, the present invention is a compound superconducting wire in which a large number of basic cluster wires in which a compound superconductor layer and a copper layer are alternately laminated are combined, and the thickness of the copper layer is a coherence length of the compound superconductor layer. It is characterized by being in the range of 0.4 to 5 times the length.

In the compound superconducting wire of the present invention, paying attention to the fact that a normal conductor such as copper has a pinning effect equal to or more than that of a crystal grain boundary, and a copper layer is finely dispersed in a compound superconducting layer to obtain a high magnetic field. This is an improvement of the superconducting properties below. In the present invention, the thickness of the copper layer is limited to 0.4 to 5 times the coherence length of the compound superconductor layer (ξ: transitional distance until the number of superconductors reaches the equilibrium value). The layer thickness is 0.4 of the coherence length of the compound superconductor layer.
If it is less than twice, the superconducting conductor will seep into the copper layer, and if it exceeds 5 times, the pinning effect will be reduced and the space factor of the copper layer will be increased, which will deteriorate the characteristics of the entire superconducting wire. is there. In the present invention, the spacing between the copper layers in the basic cluster line is the lattice spacing a _f (a _f = 1.07 × (φ ₀
/ B) ^1/2 , where φ ₀ is a magnetic flux quantum and B is a magnetic flux density) is desirable from the viewpoint of pinning efficiency.

The compound superconducting wire of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged cross-sectional explanatory view showing an embodiment of the compound superconducting wire of the present invention. A large number of basic cluster wires 3 in which compound superconductor layers 1 and copper layers 2 are alternately laminated are united.

Next, a method for producing the compound superconducting wire of the present invention will be described with reference to the drawings. Figure 2 b-Chi are process explanatory views showing an embodiment of the production method of Nb ₃ Sn compound superconducting wire. N
b plate 4 and copper plate 5 are alternately laminated and filled in a copper pipe 6 to form a primary composite billet 7 (Fig. A), and this primary composite billet 7 is hot extruded to be integrated and cold drawn. Wire it to the primary composite wire rod 8 (Fig. B), fill the primary composite wire rod 8 again into the copper pipe 6 and leave it as the secondary composite billet 17 (Fig. C), heat the secondary composite billet 17 again. Cold working and cold drawing to form the secondary composite wire rod 18 (Fig. 2). The secondary composite wire rod 18 is filled into the copper pipe 6 again to form the tertiary composite billet.
No. 27 (Fig. E), hot working and cold drawing of this tertiary composite billet 27 again to form a multi-layer composite wire 9 (Fig.), And Sn was plated on the outer periphery of this multi-layer composite wire 9 (Fig. G), a predetermined heat treatment is applied to the Sn-plated multi-layer composite wire to cause Nb in the Nb layer to react with the Nb ₃ Sn superconductor to produce N.
b ₃ Sn compound Superconducting wire (Fig. C). In addition to the hot extrusion and the cold wire drawing, the drawing process of the composite billet includes drawing and swaging.

According to this manufacturing method, since Sn is supplied by plating, the required amount of Sn can be supplied without waste. Since Sn is supplied immediately before the heat treatment, a non-superconductor compound containing Sn is not generated during the stretching process. Since Nb and copper are excellent in workability and do not react with each other, the final multilayer composite wire can be processed well.
In the heat treatment process of the Sn-plated multilayer composite wire,
Since Sn diffuses in the copper layer, the diffusion rate is high. Since the Nb layer is thin, the stoichiometric composition of Nb ₃ S
The n superconductor is formed at a low temperature in a short time. Nb ₃ Sn
Since the superconductor is formed at a low temperature in a short time, the production of non-superconductor compounds is suppressed. Various advantages such as are obtained.

[0009]

The compound superconducting wire of the present invention is a combination of basic cluster wires in which compound superconducting layers and copper layers are alternately laminated, and the thickness of the copper layer is equal to the coherence length of the compound superconducting layer. Since it is in the range of 0.4 to 5 times, the normal conductive copper layer efficiently pins the magnetic flux lines, and the superconducting property under a high magnetic field is improved.

[0010]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 A Nb-1 wt% Ti alloy plate having a thickness of 4.5 mm and a copper plate having a thickness of 1 mm were alternately laminated and filled in a copper pipe having an outer diameter of 45 mmφ and an inner diameter of 42 mmφ to form a primary composite billet. The composite billet was hot extruded to an outer diameter of 11 mmφ, and this extruded material was subjected to cold wire drawing to obtain a 1.3 mmφ primary composite wire. Next, 650 primary composite wire rods were filled into a copper pipe with an outer diameter of 45 mmφ and an inner diameter of 38.5 mmφ to form a secondary composite billet.The secondary composite billet was hot-extruded and cold-drawn again to 1.3 mmφ.
It was made into a secondary wire. This secondary wire rod is reapplied with an outer diameter of 45 mmφ,
650 pieces are filled in a copper pipe with an inner diameter of 38.5 mmφ to form a tertiary composite wire rod, and this tertiary composite wire rod is again subjected to hot extrusion and cold drawing to obtain a multilayer composite wire rod with various wire diameters within the range of 0.1 to 1 mmφ. Done Next, Sn was applied to this multilayer composite wire by hot dip plating, and this was kept in Ar atmosphere at a temperature near the melting point of Sn for 24 hours, then heated to 600 ° C for 48 hours and further raised to 700 ° C. Warm up and hold for 24 hours to remove Nb in Nb layer
_An Nb ₃ Sn compound superconducting wire was produced by reacting with a ₃ Sn compound superconductor. The amount of Sn deposited by hot-dip plating was 20 wt% of the amount of copper in the compound superconducting wire.

Comparative Example 1 In Example 1, the wire diameter of the multilayer composite wire was 0.06 mmφ or
Nb _{3 in the} same manner as in Example 1 except that 1.18 mmφ was used.
A Sn compound superconducting wire was manufactured.

Comparative Example 2 Bronze having an outer diameter of 45 mmφ and an inner diameter of 38.5 mmφ (Cu-14.3 wt%
Sn) tube was filled with Nb-1wt% Ti alloy rod and subjected to hot extrusion and cold drawing to form a composite wire with an outer diameter of 1.3mmφ. 650 copper pipes with an inner diameter of 38.5 mm were filled, and hot extrusion and cold drawing were performed again on this to obtain the final wire rod with an outer diameter of 0.3 mmφ. Next this is A
The Nb ₃ Sn compound superconducting wire was manufactured by keeping the temperature at 700 ° C for 24 hours.

The critical current density (Jc) of the Nb ₃ Sn compound superconducting wire thus obtained was measured in liquid He under a magnetic field of 10 to 16T. The results are shown in Table 1. The coherence length ξ of the obtained compound superconductor layer was about 4 nm.

[0014]

[Table 1]

As is clear from Table 1, the products of the present invention (No.
1 to 4) exhibited high Jc under a high magnetic field. This is because the copper layer pinned the magnetic flux. On the other hand, No. 5 of the comparative example product had the copper layer too thin to reduce its pinning effect, and No. 6 had a large proportion of the copper layer in the cross section of the compound superconducting wire.
No. 7 had a low Jc due to the lack of pinning points and the formation of non-superconductor compounds.

Example 2 Nb plates having a thickness of 4.5 mm and copper plates having a thickness of 1 mm were alternately laminated and filled in a copper pipe having an outer diameter of 45 mmφ and an inner diameter of 42 mmφ to form a primary composite billet. Next, this primary composite billet was hot extruded to an outer diameter of 11 mmφ, and this was cold drawn to 1.3 mmφ to obtain a primary wire rod. Next, this primary composite wire 650
The book was filled into a copper tube with an outer diameter of 45 mmφ and an inner diameter of 38.5 mmφ to form a secondary composite billet, and this secondary composite billet was again hot extruded and cold drawn to form a secondary composite wire rod of 1.3 mmφ. , This secondary composite wire again 45mmφ outer diameter, 38.5mmφ inner diameter
650 secondary composite wire rods are filled into the copper pipe to make a tertiary composite wire rod, and this tertiary composite wire rod is stretched to 0.1 to 1 mm.
A multilayer composite wire rod having various wire diameters within the range of φ was prepared. Next, Al was deposited on the outer periphery of this multilayer composite wire by hot dip plating, kept at 380 ° C. for 24 hours in an Ar atmosphere, and subsequently heated to 570 ° C. for 48 hours and further to 850 ° C. the Nb of the Nb layer was held for 48 hours to produce a Nb ₃ Al compound superconducting wire were reacted Nb ₃ Al compound superconductor. In the above, the amount of Al deposited by hot-dip plating was set to 30 wt% of the amount of copper in the compound superconducting wire.

Comparative Example 3 In Example 2, the wire diameter of the multilayer composite wire was 0.06 or 1.18.
Nb ₃ Al was formed by the same method as in Example 1 except that mmφ was used.
A compound superconducting wire was manufactured.

Comparative Example 4 Nb was applied to an Al-Mn alloy pipe having an outer diameter of 45 mmφ and an inner diameter of 38 mmφ.
The rod is filled, hot extruded and drawn to form a composite wire with an outer diameter of 1 mmφ. This composite wire has an outer diameter of 45 mmφ,
1000 copper tubes with an inner diameter of 38 mmφ were filled and again subjected to hot extrusion and wire drawing to obtain a final wire rod with an outer diameter of 0.2 mmφ. Next, this was kept in an Ar atmosphere at 850 ° C. for 48 hours to produce a Nb ₃ Al compound superconducting wire.

The critical current density (Jc) of the Nb ₃ Al compound superconducting wire thus obtained was measured in liquid He under a magnetic field of 10 to 16T. The results are shown in Table 1. The coherence length ξ of the obtained compound superconductor layer was about 4 nm.

[0020]

[Table 2]

As is clear from Table 1, the products of the present invention (No.
8 to 11) exhibited high Jc under any high magnetic field. This is because the copper layer pinned the magnetic flux. On the other hand, No12 of the comparative example product has a thin copper layer and its pinning effect is reduced, and No13 has a too large proportion of the copper layer in the cross section of the compound superconducting wire.
No. 14 had a low Jc due to the lack of pinning points and the formation of non-superconductor compounds.

[0022]

As described above, in the compound superconducting wire of the present invention, since the copper layer having the pinning effect is finely distributed, the Jc under a high magnetic field is improved, and a remarkable industrial effect is achieved.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional explanatory view showing an embodiment of a compound superconducting wire of the present invention.

FIG. 2 is a process explanatory view showing an embodiment of a method for producing a compound superconducting wire of the present invention.

[Explanation of symbols]

 1 compound superconductor layer 2 copper layer 3 basic cluster wire 4 Nb plate 5 copper plate 6 copper pipe 7,17,27 composite billet 8,18 composite wire material 9 multi-layer composite wire material

Claims (1)

[Claims] 1. A compound superconducting wire in which a large number of basic cluster lines in which a compound superconductor layer and a copper layer are alternately laminated are united, and the thickness of the copper layer is the coherence length of the compound superconductor layer. The compound superconducting wire is characterized by being in the range of 0.4 to 5 times.