JP3522306B2 - Bi-based oxide superconducting wire and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconducting wire and a manufacturing method thereof, and more particularly to a tape-shaped Bi-based oxide superconducting wire having a structure reinforced by a silver sheath method and a manufacturing method thereof.

[0002]

2. Description of the Related Art Bi-based oxide superconductors are 80 to 11
Since it has a critical temperature (Tc) of 0K and Tc exceeds the liquid nitrogen temperature (77.3K),
It is expected to be put to practical use in fields such as electric power transportation and generation of a strong magnetic field, and its critical current density (Jc) is now reaching a practical level.

In order to put oxide superconductors into full-scale practical use, it is indispensable to establish a wire rod forming technique, and one of the promising methods for producing long wire rods having a high Jc is a silver sheath. The law is known.

According to this method, a silver pipe is filled with a mixed powder or a calcined powder in which the constituent elements of the oxide superconductor are mixed in a predetermined molar ratio, and this is processed into a linear shape by wire drawing or rolling. After that, heat treatment is performed.Using silver has excellent workability, and does not react with the internal oxide during heat treatment,
This is also because silver has a substantially oxygen permeable function. This silver sheath method is used especially for Bi-based oxide superconductors.
Since each crystal grain has a plate-like structure, a c-axis of the crystal is oriented perpendicular to the plate surface by applying a compressive force by rolling or the like during the heat treatment to form a tape shape,
There is an advantage that the crystal orientation can be enhanced and, as a result, Jc can be enhanced. At present, a tape-shaped wire rod having a high Jc of 10 ⁴ A / cm ² order at a liquid nitrogen temperature and a length of several meters to several tens of meters has been obtained by this method, and application development to a superconducting magnet is proceeding. Has been.

[0005]

However, in the above tape-shaped wire produced by the silver sheath method, the mechanical strength depends on the silver sheath, and therefore the tensile strength is 7
It is as small as kgf / mm ² . Moreover, since the superconductor inside is a brittle material, Jc irreversibly decreases due to elongation of about 0.5%. Therefore, when a magnet is formed, there is a problem that its characteristics are deteriorated due to stress due to electromagnetic force.

In order to solve such a problem, alloying of the sheath material to improve the strength has been studied, but since the additive element diffuses inside and lowers Jc,
The results satisfying both mechanical strength and Jc have not been obtained.

The present invention has been made to solve the above problems, and provides a tape-shaped Bi-based oxide superconducting wire by a silver sheath method, which is excellent in mechanical strength and superconducting properties, and a method for producing the same. Is its purpose.

[0008]

In order to achieve the above object, a Bi-based oxide superconducting wire of the present invention is a Bi-based oxide superconducting tape having a silver sheath and a range in which superconducting characteristics are not deteriorated by diffusion. laminate formed by laminating a reinforcing tape composed of silver based alloy containing an additive element of (outside of the stack
Excluding those with sheath material placed in. ) Heat treatment
By expanding the oxide superconducting tape and the reinforcing tape.
It is a spliced joint .

In this superconducting wire, a mixed powder or a calcined powder in which the constituent elements of the Bi-based oxide superconductor are blended in a predetermined molar ratio is filled in a silver pipe, and the tape is molded. After forming a laminated body by laminating a wire-shaped wire and a reinforcing tape made of a silver-based alloy containing an additive element in a range that does not deteriorate the superconducting property due to diffusion (outside the laminated body)
Excluding those with sheath material placed in. ) , Heat treatment is performed to generate a superconducting phase inside the tape-shaped wire, and the tape-shaped wire and the reinforcing tape are diffusion-bonded to each other.

The superconducting wire in the present invention is formed by laminating an oxide superconducting tape and a reinforcing tape having the same width, and fixing and integrating these. This is because if the oxide superconducting tape and the reinforcing tape have different widths, the coil cannot be wound densely. The fixing and integration can be performed by solder joining, but diffusion joining by heat treatment is suitable.

As the material of the reinforcing tape, Ag-
It is preferable to use a Cu-based alloy, an Ag-Pt alloy, or a silver-based alloy such as alumina dispersion strengthened silver. By using a silver-based alloy as a reinforcing tape, it becomes easy to fix and integrate it with a superconducting tape having a silver sheath by heat treatment. In this case, the amount of the additional element in the alloy is J due to diffusion during heat treatment.
It is necessary to set the range so as not to decrease c.

In the heat treatment in the method of the present invention, the ratio of oxygen gas to nitrogen or argon gas is approximately O ₂ : N ₂ = 1: 1.
It is desirable to carry out in 12 atmospheres. Thereby, the heat treatment temperature can be lowered and the time can be shortened, and further, diffusion of the additional element from the reinforcing tape can be suppressed.

As shown in FIG. 2, the above-mentioned superconducting wire is B
The i-type oxide superconducting material 1 has a structure in which a superconducting tape 3 having a silver sheath 2 and a reinforcing tape 4 made of a silver-based alloy are laminated on the outer side, and these are fixed and integrated.

In this case, as shown in FIG. 1, the superconducting tapes 3, 3, ... May be laminated in multiple layers, and further laminated with the reinforcing tape 4 so as to be fixedly integrated. Thereby, the critical current value (Ic) can be increased.

Further, as shown in FIG. 3, superconducting tapes 3 and 3 are laminated on both sides of the reinforcing tape 4 so as to be fixed and integrated, or as shown in FIG. It is also possible to have a structure in which 3, 3, ... And reinforcing tapes 4, 4, ... Of course, in FIGS. 3 and 4, the superconducting tape 3 can be laminated in multiple layers.

[0016]

With the above structure, the superconducting wire of the present invention has a structure in which the superconducting tape and the reinforcing tape are laminated and integrated. Therefore, when a magnet is formed, the reinforcing tape can bear the stress due to the electromagnetic force. It is possible to prevent the deterioration of the characteristics.

Further, since the superconducting tape and the reinforcing tape are laminated in a state where silver and a silver-based alloy are in contact with each other, the superconducting wire production method of the present invention can simultaneously produce a superconducting phase and fix and integrate the tapes together. It can be carried out. Further, since the reinforcing tape is made of a silver-based alloy, it is possible to suppress the deterioration of the superconducting property due to the diffusion of the alloy element, as compared with the case where the silver sheath is alloyed.

[0018]

EXAMPLES An example of the present invention will be described below. EXAMPLE _{1~3 Bi 2 O 3, SrCO 3} , CaCO 3, CuO powders, Bi: Sr: Ca: Cu = 2: 2: 2: After mixing by wet mixing method was blended at a molar ratio of 3 , In the atmosphere, 84
A heat treatment was performed at a temperature of 0 ° C., and this was crushed to prepare a calcined powder.

This calcinated powder was used to obtain an outer diameter of 7.0 mm and an inner diameter of φ
After filling into a 5.0 mm Ag pipe, it was cold drawn to form a circular cross section.

This wire is cold rolled to form a tape having a thickness of 0.15 mm, a width of 4.0 mm and a length of 1 m, and then four tape-shaped wires are laminated on the tape. A superconducting wire was manufactured by laminating reinforcing tapes having a thickness of 0.5 mm, a width of 4.0 mm and a length of 1 m, and then heat treating the tape-shaped wire and the reinforcing tape to be fixed and integrated.

The results of measuring the tensile strength and Jc (77.3K, 0T) of the superconducting wire thus obtained are shown in Table 1 together with the material of the reinforcing tape and the heat treatment conditions.

[0022]

[Table 1] Comparative Example 1 A tape-shaped wire was manufactured by the same method as that of the example, and after superposing four tape-shaped wires, heat treatment was performed to manufacture a superconducting wire.

The measurement results of the tensile strength and Jc (77.3K, 0T) of the superconducting wire thus obtained are shown in Table 2 together with the heat treatment conditions.

[0024]

[Table 2] Comparative Example 2 A superconducting wire was manufactured by the same method as in Example except that the material of the reinforcing tape and the heat treatment conditions were changed.

The results of measuring the tensile strength and Jc (77.3K, 0T) of the superconducting wire thus obtained are shown in Table 2 together with the material of the reinforcing tape and the heat treatment conditions.

[0026]

As described above, according to the Bi-based oxide superconducting wire of the present invention and the manufacturing method thereof, a tape-shaped superconducting wire having excellent mechanical properties and superconducting properties can be easily obtained. Further, since the structure is simple, it has an advantage in forming a superconducting magnet.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a superconducting wire according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the superconducting wire according to the present invention.

FIG. 3 is a sectional view showing another embodiment of the superconducting wire according to the present invention.

FIG. 4 is a sectional view showing another embodiment of the superconducting wire according to the present invention.

[Explanation of symbols]

1 ... Bi-based oxide superconducting material 2 ... silver sheath 3 ... Superconducting tape 4 ... Reinforcing tape

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Claims (7)

(57) [Claims] 1. A laminated body in which a Bi-based oxide superconducting tape having a silver sheath and a reinforcing tape made of a silver-based alloy containing an additive element in a range that does not deteriorate the superconducting property due to diffusion are laminated (outer side of the laminated body). The oxide-based superconducting wire is characterized in that the oxide-based superconducting tape and the reinforcing tape are diffusion-bonded to each other by heat treatment to the oxide-based superconducting wire. 2. A silver pipe is filled with a mixed powder or a calcined powder in which constituent elements of a Bi-based oxide superconductor are mixed in a predetermined molar ratio, and a tape-shaped wire rod formed by molding the silver pipe and diffusion. After forming a laminated body by laminating a reinforcing tape made of a silver-based alloy containing an additive element in a range that does not deteriorate the superconducting property (excluding the case where a sheath material is arranged outside the laminated body), heat treatment is performed. A method for producing a Bi-based oxide superconducting wire, characterized in that a superconducting phase is generated inside the tape-shaped wire by performing the application, and the tape-shaped wire and the reinforcing tape are diffusion-bonded. 3. The Bi-based oxide superconducting wire according to claim 1, wherein the generation of the oxide superconducting phase and the diffusion bonding are simultaneously performed by heat treatment. 4. The superconducting tape is stacked on both sides of the reinforcing tape.
The Bi-based oxide superconducting wire according to claim 1, which is layered . 5. The Bi-based oxide superconducting wire according to claim 1, wherein the superconducting tape and the reinforcing tape are alternately laminated in multiple layers. 6. The Bi-based oxide superconducting wire according to claim 1, 3, 4 or 5, wherein the superconducting tape is laminated in multiple layers. 7. The reinforcing tape made of a silver-based alloy is Ag-
The Bi-based oxide superconducting wire according to claim 1, which is made of a Cu alloy, an Ag-Pt alloy, or an alumina dispersion strengthened silver.