JP2703802B2 - Manufacturing method of oxide superconducting wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a superconducting wire by forming an oxide superconducting layer around the core wire using an oxide superconducting powder or the like. The present invention relates to a method for forming a dense and good-adhesion oxide superconducting layer without causing peeling and falling off of the oxide superconducting layer.

`` Conventional technology '' Conventionally, when manufacturing oxide superconducting wires using oxide superconducting powder, a metal tube such as silver is filled with superconducting powder or its precursor powder, stretched and densified with a die or rolling roll. A method of heat treatment after forming into a wire is adopted.

The reason for adopting such a method is that the superconducting powder is extremely brittle and molding is difficult. Further, in the above-mentioned method, there is a problem that it is difficult to manufacture a long object, a product having a large wire diameter, or a product having a small wire diameter.

From such a background, recently, it has been attempted to apply the oxide superconducting powder on a certain kind of metal wire and then sinter it into a wire.

Here, as the metal wire constituting the core material, a metal having excellent heat resistance and oxidation resistance, or an alloy thereof is used, and the surface thereof may be subjected to silver plating or oxidation resistance treatment.

Further, as a method of forming the oxidizing superconducting layer or its precursor layer on the outer periphery of the core material, there are electrochemical electrophoretic electrodeposition, electrostatic coating, physical spraying, and further, including superconducting powder. An immersion method for applying a slurry to be applied is known.

According to the electrophoretic deposition method, a film having a thickness of about 1000 μm can be uniformly formed on the outer periphery of the core material using only the superconducting powder regardless of the thickness of the core material. In the immersion method, a film having a total thickness of about 2000 μm can be generated by passing the powder through a mixed bath of an organic and inorganic binder.

"Problems to be Solved by the Invention" However, even when the oxide superconducting layer is formed on the outer peripheral surface of the core material using these conventional methods, since the attached layer is brittle, An organic overcoat is applied to the outer peripheral surface after the formation of the adhesion layer, and the treatment is performed in consideration of various conditions of drying and baking (combination of time and temperature). However, the adhesion and denseness of the adhesion layer are improved. That is not expected at the moment. Therefore, there is a problem that the critical current density required as a superconducting wire cannot be obtained because the adhesion and the density of the oxide superconducting layer cannot be improved.

The present invention has been made to solve the above problems,
It is an object of the present invention to provide a method for manufacturing an oxide superconducting wire in which a dense oxide superconducting layer having good adhesion is formed on the outer periphery of a core material.

“Means for Solving the Problems” In order to solve the above problems, the present invention provides a method of forming a wire by forming a coating layer made of an oxide superconductor or a precursor thereof on an outer periphery of a core wire, and forming the wire. After passing the wire through a pressure die and performing wire drawing, compacting the coating layer and simultaneously attaching it to the core wire to obtain a superconducting element wire, then performing heat treatment,
The coating layer is an oxide superconducting layer.

"Operation" After the coating layer made of the oxide superconductor or its precursor is attached to the core wire, the coating layer is compacted with a pressing die, so that the density of the coating layer is improved and the oxide superconducting layer obtained after the heat treatment is formed. The critical current density is improved.

Embodiment FIG. 1 to FIG. 5 show an embodiment of the present invention. In this embodiment, first, an oxide superconducting material is applied to the outer periphery of the core wire 1 by using the electrophoresis apparatus shown in FIG. A coating layer consisting of the body or its precursor is formed.

The core wire 1 is, for example, a simple metal such as a noble metal, Ti, Cu, or Ni, which has a good melting point of 800 ° C. or more and has good oxidation resistance and good conductivity, or a Cu—Ni alloy, a Ni—Al alloy, A metal core made of stainless steel, or a core obtained by applying a highly conductive metal coating on the outer periphery of a core material having high mechanical strength can be used.

After the core wire 1 is prepared, the electrodeposition liquid 3 in the electrodeposition tank 2
The electrode wire is immersed in the electrode and subjected to electrophoretic electrodeposition to form an electrodeposition layer 4 on the outer peripheral surface thereof, thereby forming a wire 5 shown in FIG. Electrodeposition liquid 3
As the target oxide superconductor powder, for example,
A superconducting powder having a composition of Y ₁ Ba ₂ Cu ₃ O _7-δ dispersed in a dispersion medium such as formaldehyde or acetone is used. The oxide superconducting powder dispersed in the electrodeposition liquid 3 has a particle size of
It is preferable to use one having a particle size of 50 μm or less.
Powders of μm or less are preferably used. Also, the dispersion medium 1
The concentration of the oxide superconducting powder contained therein is preferably in the range of 1 to 500 g.

As a method for preparing this oxide superconducting powder, for example, each raw material powder of Y ₂ O ₃ , BaCO ₃ and CuO is mixed at a ratio of Y: Ba: Cu = 1: 2: 3, and the mixed powder is mixed in the air. Alternatively, a calcined powder is obtained by calcining at 500 to 1000 ° C. for several minutes to several tens of hours in an oxygen atmosphere, and a series of steps of compacting, heating, and pulverizing the calcined powder is repeated a required number of times. As a means for producing this oxide superconducting powder, a commonly known coprecipitation method, sol-gel method, or the like may be used. As the powder to be dispersed in the electrodeposition liquid 3, a calcined powder (precursor powder) may be used instead of the oxide superconducting powder.

In order to form an electrodeposition layer 4 around the core wire 1 using the electrophoretic electrodeposition apparatus shown in FIG. 2, the core wire 1 is immersed in an electrodeposition liquid 3 and the core wire 1 is used as a cathode or an anode. What is necessary is just to apply a voltage between the electrode 14 disposed in the bath 2 as an anode or a cathode.

By applying a voltage as described above, the superconducting powder or the precursor powder dispersed in the electrodeposition liquid 3 is charged, and is electrodeposited on the outer peripheral surface of the core wire 1 charged to a different polarity. In this way, the dense covering layer 4 is formed on the outer periphery of the core wire 1 to form the element wire 5 shown in FIG. Coating layer 4 in electrodeposition tank 2
Is coated to a predetermined thickness, the element wire 5 is pulled up, and then a drying treatment is performed with hot air or the like to remove the dispersion medium on the surface.

Then subjected to wire drawing by pressure die D ₁ shown in FIG. 3 to wire 5. The pressure die D ₁ is made of a increasing pressure pipe 20 and the condensed diameter contouring die body 21., increasing pressure pipe 20 has a tapered hole 20a formed in tapered-off shape, the tip of the tapered bore 20a The side is joined to the entrance side of the die hole 21a of the die body 21. The tapered hole 20a has its approach full angle a set at 2 to 4 degrees. The pressure intensifier tube 20 may be formed of any of metal, ceramic, and plastic. The approach angle of the die hole 21a is preferably small so that the coating layer 4 on the surface of the wire 5 does not peel off. When the diameter of the wire 5 is reduced by the die main body 21, the diameter of the core wire 1 is hardly reduced, and the reduction rate of the die hole 21a is adjusted so as to reduce mainly the thickness of the coating layer 4. It is necessary to.

Wherein the performing drawing using a pressurized die D ₁ of the structure, increasing pressure pipe 20 of solid lubricant together with wires 5 prepared above
, And then the wire 5 is pulled out through the die body 21. As the solid lubricant used here, it is preferable to use oxide superconductor powder or precursor powder, but a graphite-based general solid lubricant may be used. By this drawing, the coating layer 4 of the element wire 5 is consolidated and the core 1
Adhered to. Also, when drawing by drawing,
Since the tapered hole 20a of the pressure intensifier tube 20 is formed in a tapered shape, and the approach full angle a thereof is sufficiently small as 2 to 4 °, the solid lubricant is supplied to the die hole 21a side by the wire 5. Can be fully retracted. Accordingly, the coating layer 4 can be uniformly compacted without peeling, and the adhesion of the coating layer 4 to the core wire 1 can be improved.

The above-described wire drawing may be performed immediately after the coating layer 4 is formed on the core wire 1 or may be performed after drying.

After wire drawing, the wire 51 after diameter reduction is subjected to heat treatment. This heat treatment is performed by heating the wire 51 to about 800 to 1000 ° C. in the air or an oxygen atmosphere for about several tens to several tens hours, and then gradually cooling it to room temperature. Note that, here, the crystal structure of the oxide superconductor that has been subjected to the treatment of maintaining the temperature in the temperature range of 400 to 600 ° C. for a predetermined time during the slow cooling may be promoted to be transformed from tetragonal to orthorhombic.

By this heat treatment, the coating layer 4 on the surface of the wire 51 is sintered and has a composition such as Y ₁ Ba ₂ Cu ₃ O _7-δ, and the oxide superconducting layer 7 having a sectional structure shown in FIG. 4 is formed. I do. The oxide superconducting wire A manufactured in this manner is heat-treated after consolidating the coating layer 4 formed by electrophoresis, so that the sintering density can be increased, and the critical current density is high. A superconducting wire A having an oxide superconducting layer 7 having characteristics can be obtained.

Then, a protective layer 8 is formed on the surface of the oxide superconducting wire A thus obtained as required, as shown in FIG. The protective layer 8
Metals such as Ag, Cu, and Ni, and synthetic resins such as polyester, polyurethane, and polyamide are preferably used. In the oxide superconducting wire B having this structure, since the protective layer 8 covers the oxide superconducting layer 7, deterioration of superconducting characteristics can be prevented for a long period of time.

In the above example, the case where the coating layer 4 is formed on the outer periphery of the core wire 1 by electrophoresis has been described. However, the means for forming the coating layer 4 may be an electrostatic coating method, a physical spraying method, Of course, any method such as an erosion method of applying a slurry containing an oxide superconducting powder may be used.

Figure 6 shows the second example of the pressing die used in the practice of the present invention, pressure die D ₂ of this example, the inlet of the increasing pressure pipe 20 of the pressure die D ₁ shown in the previous example On the side, a plastic seal die 30 is joined.

In pressure die D ₂ of this example, it is possible to suppress the reversion phenomenon of the fixed lubricant seal die 30, can be so that no peeling of the coating layer 4 of the wire 5, effectively The coating layer 4 can be compacted and adhered without stripping the coating layer 4 by performing wire drawing.

Figure 7 shows a third example of the pressing die used in the practice of the present invention, the die D ₃ in this example, a die of the low approach angle set approach full-width die hole 40 in the 2 to 4 ° It is.

By using the dice D2 having a low approach angle of ₂ to 4 [deg.], The coating layer of the strand 5 can be compacted without causing the coating layer 4 to peel off.

FIG. 8 shows a fourth example of the pressing dice used in the embodiment of the present invention. The dice D _{4 in} this example is a die having an approach angle equal to the low approach angle dice shown in FIG. It has a structure in which a concave portion 42 is formed in the center of the die hole 41. The recess 42 formed in the die hole 41 has a depth of 0.
About 1 to 0.15 mm is preferable.

By providing the concave portion 42, the solid lubricant can be collected in the concave portion 42 during wire drawing, and the solid lubricant collected in the concave portion 42 can exert a more effective lubricating effect to draw the wire 5. Processing can be performed, and the coating layer 4 of the strand 5 can be efficiently compacted without causing separation or the like.

"Preparation" Y: Ba: Cu1: 2: to be a ratio of 3 were mixed Y ₂ O ₃ powder and BaCO ₃ powder and CuO powder, the mixed powder in the air 9
After temporary sintering at 00 ° C. for 24 hours, the powder was pulverized to an average particle diameter of 3 μm, and an electrodeposition solution was prepared by dispersing the calcined powder in acetone dispersion medium 1 at a ratio of 5 g. . A commercially available pure nickel wire polished with # 600 emery paper was used as the core wire, and electrophoresis was performed at a constant voltage of 600 V in the above-mentioned electrodeposition solution to obtain a strand.

Next, after this wire was dried at room temperature (20 ° C.) for 10 minutes, it was introduced into the four types of pressing dies shown in the above four examples, and was 25 mm in diameter (core wire diameter 1.5 mm, coating layer thickness 500 μm). , Wire drawing was performed until the diameter became 22 mm (drawing diameter 1.5 mm, coating layer 350 μm).

Thereafter, firing was performed at 950 ° C. in an oxygen atmosphere, and the critical current density at 77 K was measured in liquid nitrogen by a four-terminal method, and the effect of each pressing die was compared.

Also, for comparison, a film thickness of 500
Table 1 shows the results of measuring the critical current densities of two kinds of samples, a film having a thickness of μm and a film having a thickness of 350 μm.

As is clear from the results shown in Table 1, it was found that the method of the present invention can increase the critical current density by two to three times as compared with the case where the method is not performed.

[Effect of the Invention] As described above, the present invention forms a coating layer of an oxide superconductor or a precursor thereof on the outer periphery of a core wire, and then consolidates the coating layer with a pressing die to improve adhesion with the core wire. Since the sintering is performed after the improvement, the densification of the coating layer and the adhesion of the coating layer to the core wire can be improved without causing the separation of the coating layer.

As a result, there is an effect that it is possible to manufacture an oxide superconducting wire having excellent critical current characteristics, which exhibits a critical current density that is two to three times higher than that of the related art.

[Brief description of the drawings]

1 to 5 are views for explaining an embodiment of the present invention. FIG. 1 is a cross-sectional view of a strand, FIG. 2 is a configuration diagram of an electrophoresis apparatus, and FIG. The first of the pressing dies for drawing wire
FIG. 4 is a sectional view of an oxide superconducting wire, FIG. 5 is a sectional view of an oxide superconducting wire provided with a protective coating, and FIG. 6 is a sectional view of a pressing die used in the embodiment of the present invention. Second
FIG. 7 is a cross-sectional view showing a third example of a pressing die used to carry out the present invention, and FIG. 8 is a fourth example of a pressing die used to carry out the present invention. It is sectional drawing. DESCRIPTION OF SYMBOLS 1 ... Core wire, 2 ... Electrodeposition tank, 3 ... Electrodeposition liquid, 4 ... Coating layer, 5 ... Element wire, 7 ... Oxide superconducting layer, A ... Oxide superconducting wire, 14 ... Electrodes, D ₁ , D ₂ , D ₃ , D ₄ … Pressure dies.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Cho Fukuda 1-5-1 Kiba, Koto-ku, Tokyo Inside Fujikura Electric Wire Co., Ltd. (72) Inventor Hiroshi Koyamauchi 1-1-5-1 Kiba, Koto-ku, Tokyo Fujikura Electric Wire Inside (72) Inventor Satoru Kono 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (56) References JP-A-63-232215 (JP, A) JP-A-1-183012 (JP) , A)

Claims (1)

(57) [Claims] 1. A wire is formed by forming a coating layer made of an oxide superconductor or a precursor thereof on the outer periphery of a core wire, and the wire is passed through a pressing die to be drawn to form a coating layer. A method for producing an oxide superconducting wire, comprising: consolidating and contacting a core wire with a core wire to obtain a superconducting wire, and then performing a heat treatment to make the coating layer an oxide superconducting layer.