JPH05101723A - Manufacture of oxide superconductive wire - Google Patents

Abstract

PURPOSE:To manufacture a metal coating type oxide superconductive wire, which has the excellent characteristics without sintering growth, stably in performing heat treatment of a metal tube or a flat body filled with the power of an oxide superconductor under the pressurized atmosphere. CONSTITUTION:The powder of Bi group such as Bi2Sr2CaCu2Oy as an oxide superconductor is filled in a tube made of metal such as silver, and the tube is rolled by a pinch roll or the like at need to form a flat body 1. This flat form 1 is housed in a heat-proof container 5, and this container 5 is held by a quartz tube 4, and they are heated by heating machines 3 such as a heater or the like. In the container 5, the inner pressure is increased with a rise of the temperature to prevent the growth of the flat body 1. The wire material having the excellent superconducting characteristic can be thereby obtained. Sintering for bulking the metal tube and the powder therein to integrate them can be performed to the secondary shape such as a coil.

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 metal-coated oxide superconducting wire which prevents sintering swelling.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a metal tube filled with oxide superconductor powder or its flat body 1 is heat-treated to sinter and burn the oxide superconductor powder. A method of manufacturing a superconducting wire as the united body 2 has been known. However, there is a problem that blisters 11 (expanded portions) occur during heating and sintering. The occurrence of such bulging is particularly remarkable in the case of a tape body having a flattened metal tube and having a size of several tens of cm or more, which becomes a cause of deterioration of superconducting properties and an obstacle in processing into a coil or the like.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to develop a method for producing a metal-coated oxide superconducting wire which can be heat treated without sintering swelling.

[0004]

According to the present invention, a metal tube filled with oxide superconductor powder, or a flat body thereof, is heat-treated in a pressurized atmosphere to burn oxide superconductor powder. The present invention provides a method for producing an oxide superconducting wire, which is characterized by binding.

[0005]

By heat-treating the metal tube or its flat body in a pressurized atmosphere, even if the internal pressure of the flat body or the like increases due to heating, the external pressure also increases accordingly.
Swelling due to sintering is prevented. As a result, surprisingly, a wire having excellent superconducting properties can be obtained.

[0006]

EXAMPLE FIG. 2 illustrates an oxide superconducting wire obtained by the manufacturing method of the present invention. Reference numeral 1 is a metal tube, or a flat body thereof, and 2 is a sintered body obtained by sintering a powder of an oxide superconductor.

There is no particular limitation on the type of oxide superconductor used in the present invention. An example is Bi ₂ S
Bi-based oxide superconductors such as r ₂ CaCu ₂ O _y and Bi _2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _y , and Y-based oxide superconductors such as YBa ₂ Cu ₃ O _y and YBa ₂ Cu ₄ O _y. Body, Ba _- based oxide superconductors such as Ba _1-x K _x BiO ₃ , Nd _- based oxide superconductors such as Nd _2-x Ce _x CuO _y , other La-based oxide superconductors, and Tl-based oxide superconductors , Pb-based oxide superconductors and the like.

Further, the above-mentioned components such as Bi are replaced with other rare earth elements, the components such as Sr are replaced with other alkaline earth metals, and the O component is replaced with F and the like. Be done. Furthermore, the thing containing the pinning center etc. is mentioned. The pinning center-containing oxide superconductor has the advantage of exhibiting a large critical current density even under a high magnetic field due to the effect of pinning the magnetic flux by the pinning center. The oxide superconductor containing the pinning center is, for example, the MPMG method (Melt
Powdering Melt Growth) and the like.

The particle size of the oxide superconductor powder packed in the metal tube is 100 μm or less, preferably 0.1 to 10 μm. The powder can be obtained, for example, by crushing a sintered body of an oxide superconductor. As the metal tube, for example, one made of silver, gold, platinum, an alloy containing such a metal, or a high melting point alloy such as a silver-platinum alloy or a silver-palladium alloy is preferably used.

The metal tube filled with the oxide superconductor powder is tape-shaped, if necessary, by a rolling process using a pinch roll or the like, or a wire drawing process using a die or the like.
After being processed into a predetermined form such as a thin wire, it is subjected to a sintering process. In that case, you may perform a press process prior to a sintering process. The pressing process is effective for stabilizing or improving the quality. The pressing process may be repeated multiple times,
In that case, a heating step is provided between the pressing process before and after.

The sintering treatment is for bulking and integrating the powder of the oxide superconductor in the metal tube or the flat body thereof. In the present invention, a secondary treatment such as a coil may be sintered. The sintering temperature is lower than the melting point of the metal tube. Generally, it is 700 to 1200 ° C.

Further, in the present invention, the above-mentioned sintering treatment (heating treatment) is performed in a pressurized atmosphere. The pressurizing and heating method is illustrated in FIG. This is a closed heat-resistant pressure-resistant container 5.
The metal tube to be sintered and the flat body 1 thereof are housed in the container, and the whole heat resistant and pressure resistant container 5 is heated through a heater 3 such as a heater arranged outside the heat resistant and pressure resistant container 5. As a result, the internal pressure increases as the temperature inside the heat and pressure resistant container 5 increases, and the pressure acts as an external pressure on the metal tube to be sintered and the flat body 1 thereof, and the temperature of the metal tube and the flat body 1 rises. This prevents the occurrence of sintering swelling due to an increase in internal pressure. Reference numeral 4 in the figure denotes a quartz tube that holds the heat and pressure resistant container 5.

The heat-resistant and pressure-resistant container 5 is formed as a tubular heating furnace. When the lid 52 attached to the main body 53 via the bolt 51 is removed, the metal tube or the flat body 1 thereof is housed or is removed. It is possible to recover the sintered products. The degree of internal pressure, which increases with the temperature rise in the heat-resistant pressure-resistant container, can be obtained from the equation of state of gas or the like. By the way, at a heating temperature of about 900 ° C., the internal pressure is about 4 atm. Therefore, the pressure resistance of the container can be determined according to the internal pressure.

Example 1 Particle size of Bi ₂ Sr ₂ CaCu ₂ O _y type oxide superconductor 0.1 to 1
0 μm powder is filled in a silver tube with a wall thickness of 1.0 mm and a diameter of 7.0 mm, and it is rolled with a pinch roll to have a width of 3 mm, a thickness of 0.2 mm (the thickness of the superconducting part is 100 μm), and a length of 1 m. After being processed into a tape, the tape was subjected to a press treatment, housed in the tubular closed heating furnace shown in FIG. 1, heated at 850 to 890 ° C. for about 50 hours and sintered to obtain an oxide superconducting wire. .
No swelling was observed in the obtained oxide superconducting wire. The critical temperature was 85K and the critical current density was 12000A / cm ² (63K).

On the other hand, for comparison, an oxide superconducting wire was obtained in the same manner as in Example 1 except that the sintering treatment was performed using an open type heating furnace that was not a pressure type. However, sintering swelling was observed in many places in the obtained oxide superconducting wire. The critical temperature is 80K and the critical current density is 5000A.
/ Cm ² (63K).

In the above, the critical temperature is 0.1 A / c.
The temperature change of the electrical resistance was measured by the 4-terminal method while cooling with liquid nitrogen under a current density of m ² , and the generated voltage between the voltage terminals was 0.
Is the temperature at which

Further, the critical current density was cooled to 63 K while reducing the pressure in liquid nitrogen together with the power lead, the current value was gradually increased, and the change in the voltage between the voltage terminals due to the applied current was measured by the 4-terminal method. 1 μv for XY recorder
It is the value obtained by dividing the current value when a voltage of / cm appears by the cross-sectional area of the superconductor.

[0018]

EFFECTS OF THE INVENTION According to the present invention, since the method of sintering treatment in a pressurized atmosphere is adopted, a metal-covered oxide superconducting wire without sintering swelling can be stably obtained with excellent superconducting characteristics. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a pressure heating system.

FIG. 2 is a partial cross-sectional perspective view illustrating an oxide superconducting wire according to the present invention.

FIG. 3 is a partial cross-sectional perspective view of a conventional example.

[Explanation of symbols]

 1: Metal tube or flat body thereof 11: Swelling of sintered body 2: Sintered body of powder of oxide superconductor 3: Heater 5: Heat-resistant pressure-resistant container

Claims (1)

[Claims] 1. An oxidation, characterized in that a metal tube filled with oxide superconductor powder or a flat body thereof is heat-treated in a pressurized atmosphere to sinter the oxide superconductor powder. Method for manufacturing superconducting wire.