JPH0193010A - Manufacture of oxide type superconductive wire - Google Patents

Abstract

PURPOSE:To obtain a superconductive wire of an excellent mechanical strength and an excellent superconductive property by applying a diameter reduction process to a composite formed by filling at least either an oxide superconductor or a precursor of an oxide superconductor in a metal pipe while forging it with a die. CONSTITUTION:Y2O3 powder, BaCO3 powder, and CuO powder are mixed at the ratio Y:Ba:Cu=1:2:3, to obtain a mixture powder, which is heated in the atmospheric ambiance at 700 deg.C for 24 hours to carry out a temporary treatment. Then the temporarily heated powder is filled in a pipe made of Ag, and the resultant composite is processed for diameter reduction while forging in a cold condition by using a rotary swaging device A with a die 6, to reduce the diameter of the Ag pipe, from the outer diameter 10mm to 1.4mm, for example, step by step. In this diameter reduction process, the section reduction rate in one pass is set about 20%. In such a way, the powder can be pressed densely in the rate higher than the case of a drawing-out process using a die. As a result, when the heat treatment is applied to produce a superconductor, the elements are diffused easily inside the powder formation, and a superconductor wire of an excellent mechanical strength and superconductive property can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to superconducting magnet coils, superconducting wires used for power transport, etc., and relates to superconducting wires using oxide-based superconductors as the superconductor.

"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 temperature of liquid nitrogen.

This type of oxide superconducting material has the general formula A-B-Cu
-0 (However, A represents one or more elements of group MA of the periodic table, such as La, Ce, Yb, Sc, Er, etc., and B represents Ba, Sr.
(indicates one or more elements of group na of the periodic table). To manufacture this type of oxide superconductor, a powder containing the Ma group element, a powder containing the IIa group element, and a copper oxide powder are mixed to create a mixed powder, and this mixed powder is shaped into a predetermined shape. After molding, the obtained molded body is heat-treated and each element undergoes a solid phase reaction 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 or the like to obtain a wire rod of the desired diameter.The wire rod is heat-treated to cause a solid phase reaction of the elements in the powder compact inside, and the metal A method of obtaining a superconducting wire by producing a superconducting substance inside a 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 heat-treated and sintered, the resulting superconducting wire tends to not undergo sufficient face-to-face reactions between the various elements. There is a problem that excellent superconducting properties cannot be obtained. In addition, as mentioned above, when a superconducting wire is manufactured by sintering a powder compact with insufficient compaction density, the porosity inside the superconductor is relatively large.
There are problems with major dissatisfaction in terms of strength, such as the lack of bending strength of superconducting wires.

For this reason, when a superconducting wire is wound around a winding drum for use in winding a superconducting magnet, the superconductor is likely to be easily cracked, and the superconducting properties may be significantly degraded.

The present invention has been made in view of the above problems, and provides 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 manufacturing an oxide superconducting wire comprising a superconducting conductor made of an oxide superconductor, the method comprising: an oxide superconductor; At least one of the seed precursors is filled into a metal sheath to form a composite, and then when this composite is moved in its length direction and reduced in diameter, the movement around the movement space of the composite is A plurality of dies surrounding the space and movable in a direction intersecting the movement space of the composite press the composite from the outer peripheral side to forge the composite and reduce its diameter. The solution to the problem was to perform heat treatment after processing.

"Operation" A composite body filled with powder inside a metal tube is pressed from the outside with multiple dies to reduce its diameter while being forged, making it possible to reduce the diameter at a high processing rate and improve the compaction density of the powder. .

The present invention will be explained in more detail below.

FIG. 1 is for explaining one embodiment of the present invention. In order to carry out the present invention and manufacture an oxide-based superconducting wire, starting materials are first prepared. As this starting material, an oxide superconductor, a material containing an element constituting the 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.

S m, Eu, Gd, Tb, Dy, Ho, Er, Tm,
Indicates one or more elements of the Iffa group of the periodic table such as Yb and Lu, and B represents S r, Ba, Ca, Be.
, Mg, Ra, and other elements of the Ua group of the periodic table, and C represents one or more elements of the RB group of the periodic table, such as Cu, Ag, and Au; (D represents two or more elements of Group B of the Periodic Table, such as O, S, Se, Te, and Po, and Group B elements of the Periodic Table, such as F, CI, and Br, including O or 0) are used.

In addition, as a material containing elements constituting the oxide superconductor, a mixed powder consisting of a powder containing an element of group Ua of the periodic table, a powder containing an element of group Ia of the periodic table, and a copper oxide powder, or a mixed powder of this kind may be used. A calcined powder or a mixed powder of the above-mentioned mixed powder and calcined powder is used. The periodic table IIa group element powder used here includes Be, S r
, Mg, Ba, and Ra, compound powders such as carbonate powders, oxide powders, chloride powders, sulfide powders, and fluoride powders, and alloy powders. Also, periodic table 11
Group 1a element powders include Sc, Y, La, Ce, and P.
r, Nd, Pm.

Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
Compound powders or alloy powders such as oxide powders, carbonate powders, chloride powders, sulfide powders, and fluoride powders of the elements B and Lu are used. Further, as the copper oxide powder, CuO, CuzO, CutO*, Cu*Os, etc. are 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 an oxalate, 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 oxyketone 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 the gel is further heated to form a solid phase, which is then pulverized to obtain a mixed powder.

Next, the powder 1 prepared as described above is filled into a metal tube 2 shown in FIG. 1 to prepare a composite 3. Said tube body 2
is made of CuSAg5Al, an alloy thereof, or a metal material such as stainless steel. Note that the constituent material of the tubular body 2 is not limited to a metal material as long as it can be plastically worked.

Next, the composite body 3 is subjected to a diameter reduction process using a rotary swaging device A shown in FIG. This rotary swaging device A includes a plurality of dies 6 that are movably provided by a drive device along the path shown in the figure. These dice 6 are provided around a movement space when the rod-shaped composite body 3 is moved in its length direction, so as to surround this movement space, and are arranged in a direction perpendicular to the movement space (see Fig. 1). It is held movably in the direction of the arrow a shown in FIG. 1) and rotatably around the movement space (in the direction of the arrow shown in FIG. 1). Further, a taper 6a for reducing the diameter of the composite body 3 is formed on the inner surface of each die 6, so that the gap surrounded by the taper 6a of each die 6 becomes tapered. ing.

To reduce the diameter of the composite body 3, the rotary swaging device A is operated and one end of the composite body 3 is pushed into the gap between the dies 6, as shown in FIG. Here, since the dies 6 are rotating while reciprocating at a predetermined interval in the vertical direction of FIG. 1, the composite body 3 is sequentially forged from one end and is reduced in diameter to two points in FIG. 1. The wire diameter is reduced to the wire diameter shown by the chain line to obtain composite I3. In this diameter reduction process, in order to reduce the diameter while forging the composite body 13 using a plurality of dies 6 that rotate and reciprocate, the composite body 13 is reduced in diameter at a high processing rate without causing wire breakage in the composite body 3 during the diameter reduction process. Diameter processing is possible.

When the diameter reduction process shown in FIG. 1 is completed and the wire diameter of the composite 13 thus created has not yet reached the desired wire diameter, the composite I3 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, to obtain 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, the tube portion serving as the outer metal sheath is removed from the composite, thereby exposing the powder compact portion. To remove the metal sheath, for example, the composite is immersed in a treatment solution such as an acid or alkali aqueous solution.
A chemical method or the like is used in which only the metal sheath is dissolved in the processing liquid. This method includes copper in a metal sheath,
When silver or alloys of these are used, dilute nitric acid is used as the treatment liquid, when aluminum is used for the metal sheath, caustic soda is used as the treatment liquid, and when stainless steel is used for the metal sheath, the treatment liquid is Although aqua regia or the like is used, 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. Note that cutting may be another method for removing the metal sheath, but
When this cutting process is used, if the molded body has a small diameter, it may cause problems such as bending during the removal operation, which is not preferable. For this reason, in this example, the above-mentioned chemical method, which is less likely to cause the above-mentioned disadvantages in the molded article, was adopted.

Next, the thus exposed molded body is subjected to heat treatment. This heat treatment is preferably carried out by heating to 800 to 1100° C. for about 1 to 100 hours in an oxidizing atmosphere and then slowly cooling. Through this heat treatment, the constituent elements in the molded body undergo a sufficient solid phase reaction with each other, and since the surface of the molded body is exposed, oxygen elements are efficiently transferred from the entire surface of the molded body to the inside. Well spread. Therefore, the above-mentioned molded body has A-B-Cu which exhibits uniform superconducting properties over its entire line.
A -0-based oxide superconductor is produced, and thereby an oxide-based superconducting wire exhibiting good superconducting properties is obtained.

Then, such an oxide-based superconducting wire can be coated as necessary to form a protective coat 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. may be 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 manufactured as described above, the internal powder compact is reduced in diameter by forging at least 61 times using a rotary swaging device, and is sufficiently compacted and powder compacted. Since the body is shaped, the elements can be diffused smoothly when they undergo a solid phase reaction through heat treatment. Therefore, the produced superconductor has low porosity and high mechanical strength. Therefore, the superconducting wire can be wound without cracking even when used as a winding wire for a superconducting magnet.

"Example" Y, 03 powder, BaCO3 powder and CuO powder Y;B
A:Cu=I:2:3 was obtained by mixing to obtain a mixed powder, and this mixed powder was heated in the air for 70 minutes.
Calcination treatment was performed by heating at 00°C for 24 hours.

Next, this calcined powder was filled into a silver tube having an outer diameter of 10 mm and an inner diameter of 7 mm to obtain a composite. Next, using a rotary swaging device equipped with a die having the same configuration as the die shown in FIG. 1, the composite was cold forged to a diameter of 1.4 mm and reduced in diameter in stages. In addition, in order to reduce the diameter of the composite in stages, prepare multiple dies with different gaps between the dies, and set the cross-sectional reduction rate of the pass to approximately 20%.
The forging operation was performed multiple times to reduce the diameter, and the processing speed was 1 m/min.

In the above-mentioned processing, it was possible to process the wire up to the final wire diameter without any problems such as wire breakage.In wire rods manufactured by Moeji, the compaction of the powder was reduced by the wire drawing process using dies. This was an improvement compared to the wire rod.

Next, this wire was immersed in nitric acid to dissolve and remove the silver source, exposing the core wire.

Next, this core wire is heated to 850 to 950 in an oxygen atmosphere.
C1: Heated for 24 hours, and then subjected to a heat treatment of slow cooling to room temperature at -100° C./hour to generate an oxide superconductor over the entire core wire, thereby obtaining a superconducting core wire. Next, the surface of this superconducting core wire is soldered to a thickness of 1 m.
An oxide-based superconducting wire was manufactured by forming a protective coat layer of M.

The superconducting wire manufactured as described above has a critical temperature of 91 and a critical current density of about 10,000 A/am' (77K
) was shown.

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

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

"Effects of the Invention" As explained above, the present invention provides a die hole for reducing the diameter of a metal tube filled with at least one of an oxide superconductor and its precursor while forging it with a die. It is possible to compact the powder to a higher degree than by drawing with a die having the following properties. 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. Further, when the superconducting wire manufactured by the method of the present invention 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]

FIG. 1 is a cross-sectional view for explaining an embodiment of the present invention, and for explaining diameter reduction processing. 1...Powder, 2...Tube (metal tube), 3...Composite, 6...Dice, A...Rotary swaging. Device.

Claims (1)

[Claims] A method for producing an oxide superconducting wire comprising a superconducting conductor made of an oxide superconductor, the method comprising filling a metal sheath with at least one of the oxide superconductor and a precursor of the oxide superconductor. to form a composite body, and then when this composite body is moved in its length direction and reduced in diameter, a spacer is provided around the movement space of the complex body and intersects with the movement space of the complex body. An oxide-based superconducting wire characterized in that the diameter of the composite is reduced while being forged by pressing the composite from the outer peripheral surface side using a plurality of dies provided movably in the direction, and the wire is heat treated after the diameter reduction process. manufacturing method.