JPH01122520A - Manufacture of oxide superconducting wire - Google Patents

Abstract

PURPOSE:To obtain a superconducting wire with mechanical strength and excellent superconductivity by inserting a core made of nonoxidizing material into a metal sheath and shrinking a composite body filled with at least one of the oxide superconductor and its precursor while forging it with dice. CONSTITUTION:At least one core 2 made of nonoxidizing material is inserted into a metal sheath 3, at least one of the oxide superconductor and the precursor of the oxide superconductor is filled to form a composite body 4. A rotary swaging device A is operated to push one end of the composite body 4 between dice 6.... The dice 6... are rotated while being reciprocated by the preset distance in the direction (a), thus the composite body 4 is forged in sequence from one end side and shrunk to obtain a composite body 11. No open circuit occurs while the composite body 4 is processed, and it is shrunk with a large processing factor. The external metal sheath portion is then removed from the composite body, heat treatment is applied to the exposed molding, an oxide superconductor 12 with uniform superconductivity is generated, and an oxide superconducting wire 13 with the core 2 at the center of the conductor is obtained.

Description

[Detailed Description of the Invention] "Field of Industrial Application" The present invention is directed to superconducting magnets! -Related to superconducting wires used for coils, power transportation, etc., and those using oxide-based superconductors as superconductors.

"Prior Art" Recently, various oxide-based superconducting materials have been discovered whose critical temperature (Tc) for transitioning from a normal conducting state to a superconducting state is higher than the liquid nitrogen temperature.

This type of oxide superconducting material has the general formula A-B-Cu
-0 (However, A indicates La, Ce, Yb, Sc, Er, etc. in the periodic table ■A group element 1), B indicates Ba, S
It is indicated by the symbol ``1'' of the Ha group element of the periodic table, such as r. In order to manufacture this type of oxide superconductor, a powder containing the group Ia element, a powder containing the group Ila element, and a copper oxide powder are mixed to create a mixed powder,
After this mixed powder is molded into a predetermined shape, the resulting molded body is heat-treated to cause each element to react in a solid phase to produce a superconducting material.

In addition, as a method for producing a superconducting wire comprising the A-B-Cu-0 system superconductor, conventionally, the mixed powder is filled into a metal tube, or the mixed powder is heat-treated to obtain a superconducting powder. is filled into a metal tube, and after filling, the metal tube is drawn using a die with die holes to obtain a wire rod of the desired diameter, and this wire rod is heat-treated to solidify the elements of the powder compact inside. A method of obtaining a superconducting wire by causing a reaction to produce a superconducting substance inside a metal tube is known.

``Problems to be Solved by the Invention'' In the conventional method, since the metal tube is reduced in diameter and the mixed powder is compacted by drawing using a die, it is necessary to process the metal tube to the extent that it does not break during the drawing process. However, since there is a limit to the processing rate, there is a problem that the compaction density of the powder cannot be sufficiently increased. Therefore, since a powder compact with insufficient compaction density is subjected to heat treatment and sintered, the obtained superconducting wire tends to have insufficient in-phase reactions of each element. There is a problem that excellent superconducting properties cannot be obtained. In addition, when a superconducting wire is manufactured by sintering a powder compact with insufficient compaction as mentioned above, the porosity inside the superconductor is relatively large.
There is a problem with the lack of bending strength of superconducting wires, which is a major problem in terms of strength.

For this reason, when a superconducting wire is wound around a winding drum as a winding material for a superconducting magnet, cracks may easily occur in the superconductor, and the superconducting properties may deteriorate significantly.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an oxide-based superconducting wire that can sufficiently increase the compaction density of a powder compact, exhibits excellent superconducting properties, and has high mechanical strength. With the goal.

"Means for Solving the Problems" The present invention provides a method for producing an oxide superconducting wire, in which when at least one core wire made of non-oxidizing feed is inserted into a metal sheath, the oxide superconducting When filling at least one of the 677 precursors of a superconductor and an oxide superconductor to form a composite, and then moving this composite in its length direction and reducing its diameter, the periphery of the moving space of the composite is In this method, the diameter of the composite is reduced while forging the composite by pressing the composite from the outer peripheral surface side with a plurality of movably provided dies, and the metal sheath is removed after the diameter reduction process, and then heat treatment is performed. It was used as a means of problem solving.

``Operation'' The core wire is inserted into the metal sheath, and the powder-filled composite is pressed from the outside with multiple dies to reduce the diameter while forging. The degree of compaction is improved. Furthermore, since the core wire is inserted into the composite, when the composite is reduced in diameter by forging, the powder is uniformly compacted between the metal sheath and the core wire.

"Example" FIGS. 1 to 3 are for explaining an example of the present invention. In order to carry out the present invention and produce an oxide-based superconducting wire, starting materials are first prepared.

As this starting material, an oxide superconductor, a precursor of an oxide superconductor, or a mixture thereof is used.

The above-mentioned oxide superconductors include A-B-C-D system (where A is Y, Sc, La, Ce, Pr, Nd, P
m.

Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
b, represents one or more of the Ha group elements of the periodic table such as Lu, and B represents Sr, Ba, Ca, Be, Mg,
C represents one or more elements of the Ha group of the periodic table such as Ra, and C represents Cu or two or more of the elements of the RB group of the periodic table such as Cu, Ag, and Au and Nb. , D is the periodic table of O, S, Se, Te, Po, etc.■b
O or two or more elements containing O among the group elements and elements of group IIb of the periodic table such as P, CI, and Br are used.

In addition, as a precursor of an oxide superconductor, Ha
Powder containing group element and periodic table] Mixed powder consisting of powder containing Ta group element and copper oxide powder, calcined powder obtained by calcining this mixed powder, mixed powder of the above mixed powder and calcined powder, etc. is used. The Ha group element powder of the periodic table used here includes Be, Sr, Mg, Ba,
Carbonate powder, oxide powder, chloride powder of each element of Ra,
These include compound powders such as sulfide powders and fluoride powders, and alloy powders. In addition, as the periodic table group 11a element powder, S c, Y , La, Ce, Pr, Nd, P
m, S m, Eu, Gd, Tb.

Compound powders or alloy powders such as oxide powders, carbonate powders, chloride powders, sulfide powders, fluoride powders, and nokorate powders of the elements Dy, I(o, Er, Tm, Yb, I, and u) Furthermore, as the copper oxide powder, C
uO, Cu, O, Cu309. Cu403 or the like is used.

By the way, to prepare the mixed powder, the powder method described above is usually used, but the method is not limited to this method. Each element is coprecipitated as a nokorate, and the precipitate is dried to form a powder. It is also free to apply a coprecipitation method to obtain a mixed powder. In addition, an alkoxide compound, an oxine ketone compound, a cyclopentagenyl compound, etc. of the necessary elements are mixed in a predetermined ratio to form a mixed solution, and water is added to this mixed solution to hydrolyze it to form a sol, A sol-gel method may be applied in which this sol-like substance is heated to form a gel, and this gel is further heated to form a solid phase, and then pulverized to obtain a mixed powder.

Next, apply the powder I prepared as described above to the core wire 2 in the center.
A composite body 4 as shown in FIG. 1 is prepared by filling a metal sheath 3 with

The core wire 2 is made of non-oxidizing ha which does not deprive the powder 1 of oxygen during firing of the composite 4. This core wire 2
Examples of non-oxidizing materials that are preferably used as non-oxidizing materials include metal wires such as silver, gold, platinum, titanium, tantalum, and silver alloys, and ceramic fibers such as carbon fiber, quartz fiber, and alumina. It is a material that can obtain high tensile strength. Further, it is desirable to use the core wire 2 having a cross-sectional area of 10% or less of the cross-sectional area of the powder 1 in the composite body 4. Even if the core wire 2 has a cross-sectional area of 10% or more of the cross-sectional area of the powder I, the effect of consolidating the powder 1 by the core wire 2 reaches a ceiling, and the ratio of the superconductor in the superconducting wire decreases, which is not preferable.

Further, the metal sheath 3 is made of a metal material such as Cu, Ag, AI, an alloy thereof, or stainless steel.

Next, the composite body 4 is subjected to a diameter reduction process using a rotary swaging device A (not shown in FIG. 2).

This rotary swaging device A includes a plurality of dies 6 that are movably provided by a drive device (not shown). These dice 6 are placed around the movement space when the rod-shaped composite body 4 is moved in its length direction.
It is provided so as to surround this movement space, and is movable in a direction perpendicular to the movement space (direction of arrow a shown in Fig. 1), and around the movement space (in the direction of arrow a shown in Fig. 1). direction) so that it can rotate freely. Further, a tapered surface 6a for reducing the diameter of the composite body 4 is formed on the inner surface of each die 6, and the gap surrounded by the tapered surface 6a of each die 6 is configured to have a tapered shape. has been done.

To reduce the diameter of the composite 4, the rotary swaging device A is operated and one end of the composite 4 is pushed into the gap between the dies 6, as shown in FIG. Here, since the dice 6 are rotating while reciprocating at a predetermined interval in the direction of the arrow a in FIG.
is sequentially forged from one end side and is reduced in diameter to a wire diameter not shown by the two-dot chain line in FIG. 2, thereby obtaining a composite body 11. In this diameter reduction process, a core wire 2 is arranged at the center of the composite body 4, and a plurality of dies 6 are rotated and reciprocated.
Since the diameter of the composite body 11 is reduced while being forged, the diameter reduction process can be performed at a large processing rate without causing wire breakage in the composite body 4 during the diameter reduction process. Note that the cross-sectional reduction rate of the I-pass can be 5 to 30%, but it is usually 10 to 2%.
0% is often selected, and about 10% is desirable in order to obtain good surface properties and uniform processing performance.

After the diameter reduction process shown in FIG. 2 has been completed, if the wire diameter of the resulting composite 11 has not yet reached the desired wire diameter, the composite 11 is placed in the rotary swaging device A ( A diameter reduction process is performed using a rotary swaging device equipped with a die having a molding gap smaller than that of the die 6 that was used to form the wire, thereby forming a composite having a desired wire diameter.

As mentioned above, once the diameter of the composite is reduced to the desired wire diameter by performing diameter reduction processing one or more times, the composite after diameter reduction is subjected to the treatment described below to form a superconducting wire. Manufacture.

That is, removing the outer metal sheath portion from the composite;
This exposes the powder compact portion.

To remove the metal sheath here, a chemical method is used, for example, in which the composite is immersed in a treatment liquid such as an aqueous acid or alkali solution, and only the metal source is dissolved in the treatment liquid. In this method, when the metal sheath is made of copper, silver, or an alloy thereof, dilute nitric acid is used as the treatment liquid, and when aluminum is used for the metal sheath, caustic soda is used as the treatment liquid. When stainless steel is used, aqua regia or the like is used as the treatment liquid, but the combination of the sheath material and the treatment liquid is not limited to these. After such a removal operation, it is desirable to immediately wash or neutralize the surface of the molded article to eliminate the influence of the treatment liquid on the molded article.

Next, the thus exposed molded body is subjected to heat treatment. This heat treatment is preferably carried out by heating to 800 to 1050°C for about 05 to 300 hours in an oxidizing atmosphere and then slowly cooling. With this heat treatment,
Each of the constituent elements in the above-mentioned compact undergoes a sufficient solid phase reaction with each other, and since the surface of the compact is exposed, oxygen elements are efficiently diffused from the entire surface of the compact into the interior. . Therefore, the above-mentioned molded body does not exhibit uniform superconducting properties over its entire line.
-Cu-0 based oxide superconductor 12 is produced. On the other hand, the core wire 2 remains at the center of the oxide superconductor 12 without being oxidized during the heat treatment, and serves as a reinforcing material that increases the mechanical strength of the oxide superconductor (2).

By the above operations, as shown in FIG. 3, an oxide superconducting wire 13 having a core wire 2 is obtained.

Then, such oxide-based superconducting wire 13 may be subjected to a coating treatment, if necessary, to form a protective coating layer. As the material for forming this protective coat layer, for example, low melting point metals such as tin and lead, alloys such as solder, etc. are suitably used. As a method for forming this protective coat layer, methods such as electroplating, melt plating, and solder plating are suitably used. Alternatively, a method may be used in which the powder of the low melting point metal or the alloy powder is applied to the surface of the oxide superconducting wire to a predetermined thickness and then the powder is sintered. By forming the protective coat layer in this manner, it becomes possible to stabilize the good superconducting properties of the oxide-based superconducting wire over a long period of time.

By the way, in the superconducting wire 13 manufactured as described above, the internal powder compact is reduced in diameter while being forged at least once using a rotary swaging device, and is sufficiently compacted to form a powder compact. Because it is shaped, the elements can be diffused smoothly when each element undergoes a solid phase reaction through heat treatment. In addition, since the metal sheath 3 of the composite after diameter reduction is removed, heat treatment is performed in an oxidizing atmosphere.
Oxygen deficiency does not occur in the superconductor 12 produced. Therefore, the produced superconductor 12 has a low porosity,
It has a uniform composition and exhibits excellent superconducting properties.

Further, in this superconducting wire 13, a core wire 2 is embedded in the superconductor 12, and this core wire 2 acts as a reinforcing material for the superconductor 2. Therefore, the superconducting wire 13 has good mechanical strength.

In addition, although the number of core wires 2 is one in the double series of superconducting wires 13, the number of core wires 2 is not limited to this and may be two.
It's good to have two.

(Production example) Y 203 powder, B a C03 powder and CuO powder
Y.

Mix the mixture so that Ba:Cu=I:2:3 and obtain the mixed powder in the air atmosphere.
Calcination treatment was performed by heating at 900° C. for 12 hours.

After pulverizing this mixed powder, it was heat-treated at 890°C for 12 hours in an oxygen flow of 2ρ/min.

Next, a silver core wire with a diameter of 2 mm was inserted into a silver metal source with an outer diameter of 10 mm and an inner diameter of 7 mm, and the calcined powder was filled into the metal sheath to obtain a composite. Next, a die of the same configuration as the die shown in Fig. 2 is used.
The composite was cold-forged to a diameter of 1.4 mm and reduced in diameter in stages using a rotary swaging device equipped with a rotary swaging device. In addition, in order to reduce the diameter of the composite in stages, prepare multiple dies with different gaps between the dies, set the section reduction rate of the pass to approximately 10%, and perform the forging operation multiple times to reduce the diameter. The processing speed was 1 m/min.

In the subsequent processing, we were able to process the wire to the final diameter without any problems such as wire breakage.

Further, in the wire manufactured as described above, the compaction density of the powder was superior to that of a wire whose diameter was reduced by drawing using a die.

Next, this wire was impregnated in nitric acid to dissolve and remove the silver metal sheath to expose the molded body inside the wire.

Next, this molded body is heated to 850 to 950°C for 24 hours in an oxygen atmosphere, and then heat-treated to slowly cool it to room temperature at -200'C/hour, so that the entire line of the molded body is oxidized. A physical superconductor was produced and a superconducting wire was obtained.

Next, the surface of this superconducting wire was soldered to form a wire having an outer diameter of 1+n+n and provided with a protective coating layer.

The superconducting wire manufactured as described above has a critical temperature (Tc)
-92K, critical current density (, Jc) -12000A/
cm2 (at 77K).

Furthermore, when this superconducting wire was wound around a winding drum and filtered, it was found that the wire could be wound without any cracks and the mechanical strength was sufficiently high.

From the above, it has become clear that the superconducting wire produced by carrying out the present invention has high mechanical strength and excellent superconducting properties.

[Effects of the Invention] As explained above, the present invention provides a composite material in which a core wire made of non-oxidizing material is inserted into a metal source, and at least one of an oxide superconductor and its precursor is filled. In order to reduce the diameter of the powder while forging it with a die, it is possible to compact the powder at a higher rate than in the case of drawing using a die having a die hole. Therefore, when a superconductor is produced by heat treatment, elements are easily diffused inside the powder compact, which has the effect of producing a superconducting wire with excellent mechanical strength and superconducting properties.

In addition, in the superconducting wire manufactured by the method of the present invention, the core wire embedded within the superconductor reinforces the superconductor, and the superconductor or precursor is consolidated by being sandwiched between the core wire and the die, so the superconducting wire is machined. can increase strength,
For example, when this superconducting wire is wound around a winding drum to be used as a winding wire for a superconducting magnet, it can be wound without causing any cracks.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining one embodiment of the present invention, in which FIG. 1 is a cross-sectional view of a composite, and FIG. 2 is a cross-sectional view for explaining diameter reduction processing of the composite. 3 are cross-sectional views of the superconducting wire. 1... Powder, 2... Core wire, 3... Metal north, 4
...Composite, 6...Dice, A...Rotary swaging device, 12...Superconductor, 13...
superconducting wire.

Claims (2)

[Claims] (1) In a method for manufacturing an oxide superconducting wire, at least one core wire made of a non-oxidizing material is inserted into a metal sheath, and at least one of an oxide superconductor and a precursor of the oxide superconductor is One side is filled to form a composite, and then when this composite is moved in its length direction and reduced in diameter, a plurality of movably provided dies are used around the moving space of the composite to form a composite. A method for manufacturing an oxide-based superconducting wire, which comprises reducing the diameter of the composite by pressing it from the outer peripheral surface side while forging the composite, removing the metal sheath after the diameter reduction process, and then performing heat treatment. (2) The oxidation according to claim 1, characterized in that the cross-sectional area of the core wire is 10% or less of the cross-sectional area of the oxide superconductor or the precursor of the oxide superconductor in the composite. Method for manufacturing physical superconducting wire.