JPH01195616A - Manufacture of long oxide superconductive material - Google Patents

Abstract

PURPOSE:To produce a long superconductive material having excellent superconductive characteristics and to improve the productivity by charging a metal pipe with law material powder superconductor to form a long material with a metal coat layer and a core, melting the metal coat layer in a high frequency induction heating coil, and removing the same. CONSTITUTION:A metal pipe 1 is charged with a compact 2 of law powder for oxide superconductor to form a composite body 3, and this body 3 is applied with cold process to form a long material with a metal coat layer 4 made of the metal pipe 1 and a core 5 wire made of the compact 2. Next, it is introduced into a high frequency induction heating coil and heated therein, and the metal coat layer is fused and removed, thereby the core wire 5 is exposed. After that, heat process is applied so as to generate superconductive material. It is thus possible to prevent generation of defect in the core body from being such as cracks due to thermal expansion ratio difference with the metal coat layer. As a result, it is possible to have excellent superconductive characteristics and to enable continuous fusion-removal of the metal layer, and thereby to improve the productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for manufacturing a long superconducting material such as a superconducting wire used in superconducting equipment such as a superconducting magnet coil or a power transmission line.

"Prior art and its challenges" Recently, the critical temperature at which the normal conductive state transitions to the superconducting state (
Various oxide-based superconducting materials are being discovered that exhibit a high value of Tc) higher than the liquid nitrogen temperature.

In order to manufacture a superconductor made of such an oxide-based superconducting material, for example, in the case of a Y-Ba-Cu-0-based superconductor, YtO3 powder, BaO powder, and Cu
A method is known in which a mixed powder mixed with O powder is compacted into a coin-shaped bulk, and then this bulk is heat-treated.

Also, this kind of oxide-based super? Attempts have also been made to make llt conductors into wire rods, such as by filling the above-mentioned mixed powder into a metal sheath made of copper, stainless steel, etc., then reducing the diameter, and then sintering in an oxygen atmosphere. There is a method of processing it to make it into a superconducting wire.

However, in this method, during heat treatment, stress is generated between the metal sheath and the superconductor within the metal sheath due to the difference in coefficient of thermal expansion, and this stress can cause defects such as cracks in the superconductor. Therefore, there is a problem in that it becomes difficult to obtain a superconducting wire exhibiting uniform superconducting characteristics along the length direction. Incidentally, when the present inventors investigated the critical current density (Jc) at liquid nitrogen temperature of the superconducting wires obtained in this way, it was found that the wires that originally had a critical current density of about 10'A/am'' I
The results showed that there were cases where the decrease was as low as 0'A/cm''.

Further, in the above method, there is a problem in that sufficient oxygen is not supplied to the oxide, which is a superconducting material, due to the presence of the sheath material in the final sintering process in an oxygen atmosphere. In order to deal with this problem, oxygen-permeable silver has been used as a material for the sheath, but even with this, sufficient oxygen is not supplied to the oxide in the nail. Therefore, even if a silver sheath is used, a superconducting wire with sufficient superconducting properties cannot be obtained.

Furthermore, in order to solve the above problem, for example, after diameter reduction processing,
Another possible method is to dissolve and remove the metal sheath using acid, alkali, etc., and then perform heat treatment. However, with this method, after dissolution and removal, the obtained linear superconductor must be further washed with water or neutralized, which complicates the process and makes production less efficient. There is. Furthermore, in the case of dissolution with a solution, the internal oxide-based superconductor itself is also eroded;
There are many inherent drawbacks, such as the fact that the solution gets into the internal voids and is difficult to escape.

This invention has been made in view of the above-mentioned problems, and its purpose is to produce a long superconducting material such as a superconducting wire with excellent superconducting properties, and a manufacturing method that can improve productivity. Our goal is to provide the following.

"Means for Solving the Problems" In the method for producing an oxide-based long superconducting material of the present invention, at least one of the raw material powder of the oxide-based superconductor, the superconducting powder, or the molded body of these powders is A tube is filled to form a composite, and this composite is then subjected to cold working to form a long material having a metal coating layer made of the metal tube and a core made of the powder or compact, and then subjected to high frequency treatment. The long material is continuously introduced vertically upward into the induction heating coil from below and heated, the metal coating layer is melted and removed to expose the core wire, and then a superconducting material is generated. The solution to the above problem was to perform heat treatment.

Hereinafter, the method for manufacturing the oxide-based long superconducting material of the present invention will be described.
A case in which the method is applied to the production of superconducting wires will be explained in detail as an example.

First, as shown in FIG. 1, a metal tube 1 made of silver, copper, aluminum, or an alloy thereof, or stainless steel, etc. is prepared, and raw material powder of an oxide superconductor or superconductor powder, Alternatively, at least one of these molded powders is filled to form a composite. Here, the first
The figure shows a composite body 3 made by filling a molded body 2 made of superconductor powder into a metal tube 1. The above-mentioned oxide-based superconductor is an A-B-C-D system (where A is Y, Sc, La, Yb, Er, Ho, Dy, etc. from Group 1 [Ia] elements of the periodic table). B represents one or more elements of group 1Ia of the periodic table such as Sr, Ba, Ca, etc.; C represents Cu, A
g, Group 1b element of the periodic table of Au and Cu of Nb
Or represents two or more types including Cu, and D is O, S, Se
Elements of group Ⅰb of the periodic table such as F, CI2. Represents 0 or two or more types containing 0 among elements of group Ⅰb of the periodic table, such as Br. ), and the raw material powder forming this oxide-based superconductor is a mixture of an oxide of the above element and a carbonate of element B, or a mixture of an oxide and an oxide of element C. It may be a powder or a mixed powder that is calcined and then pulverized. Further, in this case, the mixing ratio of the compounds made of each element shall be appropriately determined depending on the composition of the intended superconductor. Further, the superconductor powder is obtained by subjecting the above-described raw material powder to heat treatment, etc. to form an oxide-based superconductor, and then pulverizing it into powder. Furthermore, the molded body 2 is formed by subjecting the superconductor powder to calcination treatment, pressing treatment, etc., and molding it into a rod shape. Here, the calcination treatment temperature is about 700 to 1000°C in the case of the above superconductor powder. Also,
For example, a rubber press method is used for the powder compaction treatment.

Next, this composite body 3 is subjected to cold working to obtain a wire rod 6 having a metal coating layer 4 made of the metal tube 1 and a core wire 5 made of the molded body 2, as shown in FIG. It is wound onto a feed-out reel which will be described later.

In this case, as a cold working method, a known diameter reduction method such as wire drawing or rolling using a grooved roll is adopted, but among them, the forging method described below is more preferably used. .

When performing diameter reduction using the forging method, for example, the third
A rotary swaging device A shown in the figure is used. This rotary swaging device A includes a plurality of dies 7 and
It is equipped with... These dice 7... are provided around the movement space when the rod-shaped composite body 3 is moved in its length direction so as to surround this movement space, and in the direction perpendicular to the movement space ( It is held movably in the direction of arrow B in FIG. 3) and rotatably in the circumferential direction of the movement space (direction of arrow C in FIG. 3). Further, a tapered surface 7a for reducing the diameter of the composite body 3 is formed on the inner surface of each die 7.
The gap surrounded by a has a tapered shape.

In order to reduce the diameter of the composite body 3 using such a rotary swaging device A, the rotary swaging device A is operated and one end of the composite body 3 is inserted into the die 7 as shown in FIG. Push it into the gap between.

Here, the dice 7 are rotating in the direction of arrow C while reciprocating at a predetermined interval in the direction of arrow B in FIG.
The composite body 3 is sequentially forged and reduced in diameter from one end side, and is reduced in diameter to the wire diameter shown by the dashed line in FIG. 3 to become the wire rod 6.

In this diameter reduction process, the composite body 3 is forged and reduced in diameter by a plurality of dies 7 that move reciprocatingly while rotating, so that large wires are not broken in the composite body 3 during the diameter reduction process. Diameter reduction processing can be performed at the processing rate. In this case, diameter reduction processing is usually performed at a reduction rate of 5 to 25% in one processing.

Note that the diameter reduction process by this forging method is not limited to one time, and if the diameter of the obtained wire 6 has not yet reached the desired wire diameter, the die installed in the rotary swaging device A may be used. Using a rotary swaging device equipped with a die having a forming gap smaller than 7..., the wire 6 is processed to reduce its diameter to a desired wire diameter.

In addition, in the wire rod 6 obtained in this way, since the inner molded body 2 is forged and reduced in diameter by the rotary swaging device A, the core wire 5 is sufficiently consolidated. can get.

Next, as shown in FIG. 4, the wire rod 6 is fed out from the feed-out roll 8 formed by winding the wire rod 6 in the above process,
The glass is continuously introduced into the heating tube IO from the bottom to the top in the vertical direction via the roll 9, heated, and further led out from the heating tube 10, and transferred to the take-up reel I2 via the roll 11. Inner diameter l made of quartz glass, etc.
A glass tube 13 of approximately 0 to 20n+m is arranged with its axes aligned vertically, and is heated by winding a plurality of high-frequency induction heating coils I4.14 arranged below. It consists of a portion 10a and a slow cooling portion 10b in which the induction heating coil disposed above is not wound. The heating tube 10 also includes a plurality of oxygen supply tubes 15 on the outer peripheral surface of the glass tube 13 that communicate with the inside of the glass tube 13.
15... are arranged. High frequency induction heating coil I
4.14... is several kHz due to power supply 16.16...
A high frequency current of about 100 kHz to several hundred kHz is applied, and an output of about 1 kW to 100 kW is thereby obtained.

The wire rod 6 is connected to the heating section +Oa of such a heating tube 10.
A vortex is formed in the metal coating layer 4 by being introduced into the metal coating layer 4? TIq is generated, and the metal coating layer 4 generates heat and melts due to the eddy current, and is removed from the wire 6 to expose the core wire 5. In addition, the core wire 5 made of oxide has a specific resistance (volume resistivity)
is heated slowly due to a loss of 10-3 to 1 Ω·cffl. Furthermore, since the wire rod 6 is heated while being transferred vertically upward, the wire rod 6 is heated without applying a tensile force to both ends of the wire rod 6, for example, compared to the case where the wire rod 6 is transferred laterally. The core wire 5 is prevented from sagging and becomes straight, thereby preventing cracks from occurring when the core wire 5 is heated due to sagging. Furthermore, the sintered core wire 5 is
By passing through the slow cooling section lOb of the heating tube IO, 50
~b It is cooled at an appropriate speed, thereby preventing the occurrence of cracks caused by rapid cooling.

In addition, in this case, high frequency induction heating coil I4.14...
The induction heating treatment on the wire 6 is performed in an oxygen atmosphere. That is, thermal oxygen that has been heated in advance to a high temperature is introduced into the glass tube I3 from the oxygen supply tubes 15, 15, etc., thereby creating an oxygen atmosphere in the glass tube 13.

Then, the core wire 5 exposed after the metal coating layer 4 is removed is still connected to the high frequency induction heating coil 1 in the oxygen atmosphere.
By being heated by 4.14..., it is sintered to become an oxide-based superconductor having a dense crystal structure, and then slowly cooled in the slow cooling section 10b and led out from the heating tube 10. Note that the core wire 5 drawn out from the heating tube 10 may be further subjected to heat treatment to anneal the core wire 5.

In addition, in the above operation, the metal constituting the metal coating layer 4 of the wire rod 6 melted in the glass tube 13 is
3 are arranged in the vertical direction, the glass tube 13 does not remain inside the glass tube 13 and is easily discharged out of the tube due to its own weight.

In this case, it is preferable that a tray 17 as shown in FIG. 5 be disposed below the heating tube IO to receive and recover the discharged molten metal. Here, the receiving tray 17 has a hole 18 with a larger diameter than the wire rod 6 for transferring the wire rod 6 in the center of its bottom, and a guide for guiding the collected molten metal to a recovery container (not shown) around the bottom. Cylinder 1
9, the wire rod 6 can be moved without being subjected to resistance, and the molten metal discharged from the heating tube 10 can be recovered.

Thereafter, the core wire 5 made into a superconductor is subjected to a coating treatment, and a coating layer 2 is placed on the core wire 5 as shown in FIG.
A superconducting wire 21 is obtained by forming 0, and this is further wound onto a take-up reel 12 via a roll II. Here, a dip forming method is suitably employed to perform the coating treatment. In order to perform the coating process using the dip forming method, for example, the fourth
As shown in the figure, a processing bath E filled with molten solder is placed directly above the heating tube 10, and the core wire 5 immediately after heat treatment led out from the heating tube 10 is continuously introduced into the processing bath E from below. The superconducting wire 21 is sequentially immersed in the superconducting wire, and is then continuously pulled up and cooled to solidify the solder E, thereby forming a superconducting wire 21 covered with a coating layer 20 of a predetermined thickness. in this case,
During the coating process, the immersed core wire 5 is irradiated with ultrasonic waves by an ultrasonic oscillator F provided in the treatment bath E in advance to improve the wettability (adhesion) of the core wire 5 and coat it to achieve a stronger adhesion. Coating layer 20
This is desirable because it provides the following. In this example, the coating layer was closed at 20° and solder was used, but other low melting point metals or alloys such as tin, aluminum, zinc, lead, gallium, etc. may also be used, and furthermore, formal, polyimide amide, Teflon, etc. , nylon, vinyl chloride, and other synthetic resins may also be used. Even when coating is performed using these materials, the coating layer 2 is formed on the core wire 5 by processing it while irradiating the core wire 5 with ultrasonic waves.
0 can be strongly strengthened. Further, the frequency of the ultrasonic waves used is preferably about several kHz to 200 kHz.

According to this method of manufacturing an oxide superconducting wire, the core wire 5 made of an oxide superconducting material is heat-treated directly in an oxygen atmosphere without covering it with a sheath or the like, so that sufficient oxygen is supplied and the core wire 5 is heated. A superconductor having a good oxygen content can be obtained, and therefore a superconducting wire exhibiting excellent superconducting properties can be obtained. Further, since the metal tube I having a different coefficient of thermal expansion from the core wire 5 is removed and subjected to heat treatment, it is possible to prevent defects such as cracks from occurring in the core wire 5 due to the difference in the coefficient of thermal expansion. Furthermore, by using induction heating using the high-frequency induction heating coil 14, the metal coating layer 4 can be continuously melted and removed, so that superconducting wires can be manufactured continuously. Not only can manufacturing be made possible, but also productivity can be improved. In addition, by arranging the heating tube in the vertical direction and transferring the wire rod 6 upward in the vertical direction from below and heating it, compared to the case where the wire rod 6 is transferred in the horizontal direction, for example,
The wire rod 6 is prevented from sagging and becomes straight without applying a tensile force to both ends of the wire rod 6, thereby preventing cracks from occurring when the wire rod 6 is heated due to slack.

In the above example, the composite 3 was cold-worked and forged to form the wire rod 6. Alternatively, for example, the composite 3 could be rolled to form a tape-shaped long material, and this could be used as a high-frequency induction heating coil. Alternatively, a long superconducting material may be obtained by introducing the superconducting material into a superconductor and heating it.

In addition, the superconducting wire 21 is further subjected to plating treatment, etc.
Cortinogr! A metal layer 22 made of tin, copper, etc. may be formed on J20 as shown by the dotted line in FIG. 6 to strengthen the core wire 5 and increase the overall strength.

"Example" Hereinafter, the present invention will be described in more detail with reference to an example in which a superconducting wire is manufactured as a long superconducting material.

First, Y B atc uao x (where X=7−
Let it be δ. ) A superconductor powder consisting of a superconductor having a composition of Here, the production of the superconductor powder involves Y,
O, (purity 9999%), BaCO3 (purity 99°9
%), CaO (purity 99.9%) powder, Y:Ba:
They were weighed and mixed so that Cu=l:2:3 (molar ratio), calcined in the air at 900° C. for 24 hours, and then pulverized.

Next, this superconductor powder is molded into a rod shape by a rubber press method, and this rod-shaped compact is further heated at 2t2/min.
It was baked at 890° C. for 12 hours in an oxygen stream. Next, this molded body was inserted into a copper pipe having an outer diameter of 15 am and an inner diameter of 8 mm to obtain a composite body. Next, this composite was forged and wire-drawn to reduce its diameter, so that the outer diameter was 1.5 mm and the core wire diameter was 0.
A wire with a diameter of 8 mm and a length of 500 m was obtained and wound on a delivery reel.

Next, this wire was inserted into the heating tube IO shown in Fig. 4 for 20 m.
The core wire was introduced at a rate of m/min and induction heated to melt and remove the metal coating layer to expose the core wire. Here, in the heating tube 10, only one high-frequency induction coil on the introduction side has a coil length of 0.5 m, which is indicated by L1 in FIG. The coil length is 3m, and each coil has a frequency of 30~
By applying an alternating current of 100 kHz, the coil length of 3 m was set so that an output of 50 kW could be obtained in order to melt the copper that constitutes the metal coating layer.
The exposed oxide (core wire) h (890±5℃
It is adjusted so that an output of 20 to 100 kW can be obtained so as to heat up to 20 to 100 kW. In addition, the slow cooling section is L,
The length shown by is 5 m, so that the heated core wire is gradually cooled down without being cooled down suddenly.

In addition, the induction heating here is performed using the oxygen supply pipe 15.15...
By introducing hot oxygen into the glass tube 13 at a flow rate of 212/min, respectively, an oxygen atmosphere was created in the heating section 10a and the slow cooling section 10b. Further, in the receiver shown in FIG. 5, a plate 17 was placed below the heating tube to collect molten copper from the wire.

Next, the core wire after the heat treatment was introduced from below into the treatment bath E shown in FIG. ) was applied during coating treatment.

Thereafter, the core wire was taken out from the treatment bath E, cooled, and a solder coating layer having a thickness of about 50 μm was formed to obtain a superconducting wire.

In the superconducting wire thus obtained, no disadvantages such as disconnection or cracks were observed over the entire length.

In addition, when we investigated the superconducting properties of the superconductor (core wire) in this superconducting wire, we found that the critical temperature (Tc) was 91.0°C.
1 Also, the critical current density (Jc) is 1500 in liquid nitrogen.
A result of approximately 0 A/cm" was obtained.

"Effects of the Invention" As explained above, the method for producing a long superconducting material according to the present invention is such that at least one of the raw material powder of an oxide superconductor, the superconducting powder, or a compact of these powders is transferred into a metal tube. This composite is then cold-worked to form a long material having a metal coating layer made of the metal tube and a core made of the powder or compact, and then subjected to high-frequency induction. The long material is continuously introduced vertically upward into the heating coil from below and heated, the metal coating layer is melted and removed to expose the core body, and then heat treatment is performed to generate a superconducting substance. It is something to do. Therefore, according to this method, it is possible to prevent defects such as cracks from occurring in the core body due to the difference in thermal expansion coefficient with the metal coating layer, and therefore, a long superconducting material can be obtained from this core body. By doing so, it is possible to create a superconducting material having excellent superconducting properties such as a particularly high critical current density.

In addition, by using induction heating using a high-frequency induction heating coil, the metal coating layer can be continuously melted and removed, making it easier to manufacture long superconducting materials such as superconducting wires, thereby increasing productivity. You can improve your performance. Furthermore, since the long material is continuously introduced vertically upward into the high-frequency induction heating coil from below and heated, it is possible to It is possible to prevent the long material from sagging and make it straight without applying tension to both ends of the wire, thereby preventing the occurrence of cracks when the wire material is heated due to sagging. be able to.

[Brief explanation of the drawing]

1 to 6 are for explaining an example of the case where the method for producing a long superconducting material of the present invention is applied to the production of a superconducting wire, and FIG. 1 shows a composite material suitably used in the present invention. 2 is a schematic sectional view showing a wire rod obtained by reducing the diameter of the composite shown in FIG. Fig. 4 is a schematic configuration diagram for explaining the process of melting and removing the metal coating layer from the wire rod and further applying a coating treatment, Fig. 5 is a side sectional view of a tray suitable for collecting molten metal; FIG. 6 is a schematic diagram showing a superconducting wire obtained by coating a core wire. I...metal tube, 2...molded body, 3...
...Composite, 4...Metal coating layer, 5...
... Core wire, 6 ... Wire rod, IO ... Heating tube, 14 ... High frequency induction heating coil, 21 ...
...Superconducting wire.

Claims (1)

[Claims] A metal tube is filled with at least one of the raw material powder of the oxide superconductor, the superconductor powder, or a compact of these powders to form a composite, and then this composite is subjected to cold working to form the metal tube. A long material comprising a metal coating layer consisting of a metal coating layer and a core body consisting of the above powder or compact is made, and then the long material is continuously introduced vertically upward from below into a high frequency induction heating coil. A method for producing an oxide-based long superconducting material, which comprises heating the material, melting and removing the metal coating layer to expose the core wire, and then performing heat treatment to generate a superconducting material.