JP3143903B2 - Manufacturing method of oxide superconducting wire - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an oxide superconducting wire rod by plastically processing an oxide superconductor or a raw material thereof into a wire.

[Prior art] A conventional oxide superconducting wire is generally manufactured by filling a metal pipe with an oxide raw material powder, performing plastic processing such as extrusion, drawing, rolling, etc., forming a wire, and then performing heat treatment. I have. It is known that it is effective to repeat such plastic working and heat treatment in order to improve the critical current density of the obtained wire.

[Problems to be Solved by the Invention] However, in the oxide superconducting wire obtained by such a conventional manufacturing method, a polycrystalline body or a multi-particle body forms a bridge structure in the wire, and a large number of pores are formed. Therefore, there has been a problem that densification is not sufficient and the critical current density is insufficient.

An object of the present invention is to provide a method for producing an oxide superconducting wire exhibiting higher critical current density by improving densification inside the wire.

[Means for Solving the Problems] The production method of the present invention is a method for producing an oxide superconducting wire in which an oxide superconductor or a raw material thereof is plastically processed into a wire, and the oxide superconducting wire is formed immediately before plastic working. It is characterized by irradiating the body or its raw material with ultrasonic waves.

In the present invention, the oxide superconductor or its raw material can be plastically worked in a form wrapped by a metal member or in a form sandwiched by metal members. In this case, a metal member made of, for example, silver or a silver alloy can be used as the metal member.

In the present invention, to irradiate the ultrasonic wave to the oxide superconductor or its raw material, an ultrasonic generator is provided so as to be in contact with the oxide superconductor or its raw material via a metal member,
Ultrasonic waves can be generated by this ultrasonic generator. Further, in order to effectively irradiate the superconductor or the raw material thereof with the ultrasonic wave, it is preferable that the ultrasonic generator is brought into close contact with the metal member with a finite pressure.

The oxide superconductor to which the present invention is applied is not particularly limited. For example, Y-Ba-Cu-based oxide superconductor, Bi-Sr-Ca-Cu-based oxide superconductor, and Tl-
Ba-Ca-Cu-based oxide superconductors and the like,
Some of these elements may be replaced with other elements.

[Action] In the conventional manufacturing method of performing plastic working without ultrasonic irradiation,
As shown in the schematic diagram of FIG. 3, the internal crystal grains 4 formed a bridge structure, had many vacancies, and were not a dense structure. According to the present invention, if ultrasonic waves are applied immediately before plastic working, the crystal grains inside vibrate finely and the fluidity increases. When plastic working is performed in such a state,
The crystal particles move to the most stable position, and as shown in the schematic diagram of FIG. 2, the crystal particles 4 are arranged and the number of pores is reduced.
Therefore, according to the present invention, the internal density is improved,
When the wire is heat-treated after plastic working, the grain boundaries are in close contact with each other and the number of paths through which the current flows increases, so that a wire having a high critical current density can be obtained.

In addition, since the fluidity of the crystal particles is improved, disconnection or the like during plastic working can be ignored, and a wire having a uniform density and critical current density can be obtained over the longitudinal direction of the wire.

Embodiment FIG. 1 is a schematic side view for explaining one embodiment of the present invention. Referring to FIG. 1, the oxide superconductor is sandwiched between rolling rollers 2a and 2b and subjected to plastic working to be converted into a wire. An ultrasonic generator 3 is provided immediately before the oxide superconductor 1 is sandwiched between the rolling rollers 2a and 2b so as to be in contact with the oxide superconductor 1. Ultrasonic waves are emitted from the ultrasonic generator 3 to the oxide superconductor 1, and immediately thereafter, the oxide superconductor 1 is subjected to plastic working by the rolling rollers 2a and 2b.

The following experiment was conducted using an apparatus as shown in FIG.

Example 1 Bi ₂ O ₃ , PbO, SrCO ₃ , CaCO ₃ and CuO were converted to Bi: Pb: Sr: Ca: C
The respective powders were mixed so that u = 1.8: 0.4: 2: 2.2: 3, and heat-treated at 800 ° C. for 8 hours and at 860 ° C. for 8 hours. After heat treatment, it is pulverized by pulverization.
It was filled in a silver pipe with an outer diameter of 6 mm. This was drawn to a diameter of 1 mm, and the obtained wire was rolled to a thickness of 0.5 mm with a rolling roller as shown in FIG. In this case, immediately before the rolling, the vibration frequency was 2000 Hz and the amplitude was 5 μm.
m of ultrasonic waves. Next, a heat treatment was performed at 840 ° C. for 50 hours, and a rolling process was performed to a thickness of 0.3 mm, and then a heat treatment was performed.

As a comparison, a wire was produced in the same manner as in the above example except that no ultrasonic wave was applied immediately before the rolling.

The critical current density of the obtained wire was measured. The critical current density was 77.3K, and the critical current density at zero magnetic field was measured.

As a result, when irradiated with ultrasonic waves immediately before rolling according to the present invention, a critical current density of 15,120 A / cm ² was obtained, whereas in the case of the comparative non-irradiated ultrasonic wires, 5,30 A / cm ² was obtained.
According to the present invention, an oxide superconducting wire having a critical current density of 0 A / cm ² and about three times higher critical current density was obtained.

Example 2 The heat-treated powder produced in Example 1 was used for an inner diameter of 8 mm.
It was filled into a silver alloy pipe with an outer diameter of 12 mm and drawn. At this time, it was examined to what extent the diameter of the composition required to wire the wire to cause wire breakage. Before drawing wire, frequency 5000Hz, amplitude 2μ
When the ultrasonic wave of m was irradiated, the wire could be drawn without breaking until the outer diameter became 0.05 mm. On the other hand, when the ultrasonic wave was not irradiated before drawing, the wire was broken at the stage of drawing to an outer diameter of 0.2 mm.

Example 3 With respect to the oxide superconducting wire obtained in Example 1, the distance between the electrode tube terminals was changed at 1 cm, 5 cm and 50 cm in the longitudinal direction, and the critical current density at 77K was measured. Further, as a comparison, the critical current density was similarly measured for a wire rod plastically processed without ultrasonic irradiation. Table 1 shows the results. In Table 1, the critical current density in the case where the distance between the electrode terminals is 1 cm is standardized as 1, and the critical current density is shown as a relative value.

Table 1 Between the electrode terminals 1cm 5cm 50cm Ultrasonic irradiation 1 0.95 0.9 Ultrasonic non-irradiation 10.8 0.5 As is evident from Table 1, the ultrasonic irradiation immediately before plastic working according to the present invention is the one without ultrasonic irradiation. In comparison, it was confirmed that even when the distance between the electrode terminals was increased, the critical current density did not decrease much.

[Effects of the Invention] As described above, by irradiating ultrasonic waves immediately before plastic working according to the present invention, the internal oxide superconductors or the raw materials thereof become close to each other and are densified.
A higher critical current density than before can be obtained. Also, since a wire with a uniform density can be obtained in the longitudinal direction,
A more uniform wire can be obtained along the longitudinal direction than before. Therefore, the manufacturing method of the present invention is useful particularly in the field of using a long high-temperature superconducting wire, such as a high-temperature superconducting cable and a magnet.

[Brief description of the drawings]

FIG. 1 is a schematic side view for explaining one embodiment of the present invention. FIG. 2 is a schematic diagram showing a state of crystal grains when plastic processing is performed by irradiating ultrasonic waves according to the present invention. FIG. 3 is a schematic diagram showing a state of crystal grains when plastic working is performed without irradiating ultrasonic waves. In the figure, 1 is an oxide superconductor, 2a and 2b are rolling rollers, and 3 is an ultrasonic generator.

Claims (5)

(57) [Claims] 1. A method for producing an oxide superconducting wire, which comprises forming a wire by plastically processing an oxide superconductor or a raw material thereof, comprising: irradiating the oxide superconductor or a raw material thereof with ultrasonic waves immediately before the plastic working. A method for producing an oxide superconducting wire, characterized in that: 2. The method for producing an oxide superconducting wire according to claim 1, wherein said oxide superconductor or its raw material is plastically worked in a form wrapped by a metal member or sandwiched by a metal member. 3. The method for producing an oxide superconducting wire according to claim 2, wherein the metal member is made of silver or a silver alloy. 4. The method for producing an oxide superconducting wire according to claim 1, wherein said oxide superconductor or a raw material thereof comprises a polycrystal or a polyparticle. 5. The oxide superconductor or the raw material thereof is irradiated with ultrasonic waves by an ultrasonic generator provided so as to be in contact with the oxide superconductor or the raw material thereof via the metal member. The method for producing an oxide superconducting wire according to the above.