JPH0355719A - Manufacture and manufacturing device of oxide superconducting line material - Google Patents

Abstract

PURPOSE:To stably manufacture superconducting line materials of fine line size simultaneously by forming a melting part by partially heating sintered line materials of oxide superconducting structure after preliminary heating, and by coagulating the molten liquid after being lowered from pipes. CONSTITUTION:After a molded body of oxide powder such as La-Ba-Cu-O is filled and sealed in a Ag pipe, it is contracted in its size up to 3mm, after which a Ag sheathe is dissolved, and a residual oxide line material is hated in an oxidation atmosphere of 780 deg.C, so as to obtain a line material 1. The upper edge of the line material 1 is fixed on a line material holder 6a, while the lower edge thereof is fitted in a coil 4. The upper edges of three platinum guide line materials 2 for lowering which are thinner than the inner diameter of pipes 5a are inserted into the pipes 5a, while the lower edges thereof are fixed on a line material holder 6b, and the line material 1 in a heating furnace 9 is heated not less than 700 deg.C in oxidation gas, while a heating coil 4 is electrified so as to partially melt the line material 1. A melting part is formed in this way, and driving shafts 8, 7 for supply and for lowering are lowered at a certain relative rate, and by lowering the melted liquid in the pipes 5a, whereby superconducing line materials 11 of fine line shape are obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses a sintered wire having an oxide superconducting composition as a starting material,
By once melting this wire and then solidifying it,
A method and apparatus for manufacturing an oxide superconducting wire that removes voids in the wire and controls the crystal structure in the wire to produce an oxide superconducting wire having a high critical current density, particularly a fine wire with a uniform wire diameter. B i -S r-Ca-
The present invention relates to a method and apparatus for manufacturing an oxide superconducting wire suitable for manufacturing a Cu-0 superconducting wire.

[Prior art] As oxide superconducting materials, La-Ba-Cu-O system,
Y-Ba-Cu-0 system and Bi-Sr-Ca-Cu-0
(hereinafter referred to as BSCCO) type. Generally, these oxide superconducting materials are processed into wire rods by the method shown below.

First, a powder having an oxide superconducting composition is pressure-molded to form a compact. Then, this molded body is filled into a metal pipe and sealed. Next, after drawing this wire to a desired wire diameter, the surface metal pipe portion is dissolved and removed using acid. Next, the oxide wire is heat treated to form a sintered body.

Since the oxide superconducting wire formed in this manner is a sintered body, it is porous and has many voids. Further, grain boundaries are also extremely small. Therefore, when this wire is made superconducting,
The disadvantage is that the obtained critical current density is small.

By the way, there is also a method of manufacturing a superconducting material by once melting a sintered body having an oxide superconducting composition and then solidifying it. However, in this method, although voids in the superconducting material can be removed, mechanical wire drawing cannot be performed. Therefore, with this method, it is not possible to obtain a wire rod having a desired shape.

Therefore, after forming a sintered body of oxide superconducting wire in the desired shape by the method described above, this sintered wire is placed on a platinum or alumina (A7.03) boat and locally melted using the zone melting method. Attempts have been made to remove voids by continuously moving the resulting molten zone in the longitudinal direction of the wire.

However, for example, a melt of BSCCO ceramics in an oxidizing atmosphere becomes highly viscous near its melting point,
Since it easily wets with zone melting equipment such as platinum and alumina boats, it is difficult to obtain a good melting zone, and it also tends to form compounds with these equipment. Therefore, zone melting of the raw material wire having such an oxide superconducting composition needs to be carried out without contact with equipment by a floating zone melting method.

However, since ceramics cannot be heated by induction, high-frequency induction heating, which is normally used in the floating zone melting method, has a BS
It is not possible to obtain a molten zone of CCO ceramics.

For this reason, for BSCCO ceramics, attempts have been made to form a floating molten zone using a condensed heating method using a laser.

[Problems to be solved by the invention] However, in the conventional method of forming a floating molten zone by condensed light heating, when the raw material wire is a thin wire (wire diameter is 5 mm or less), a stable molten zone cannot be formed. I can't. For this reason, the conventional technology for producing oxide superconducting wires using condensed light heating has the problem that it is not possible to obtain oxide superconducting wires with a small wire diameter without voids and having a desired high critical current density.

In addition, the conventional technique involves locally heating the raw material wire by condensed light heating and solidifying a single wire from the formed molten zone, which also has the drawback of poor productivity.

The present invention has been made in view of such problems, and includes:
Not only can a stable molten zone be formed, but also the wire from which voids have been removed can be stably solidified, making it possible to produce oxide superconducting wire with a desired thin wire diameter and high critical current density with high productivity. It is an object of the present invention to provide a manufacturing method and a manufacturing apparatus for an oxide superconducting wire that can be manufactured.

[Means for Solving the Problems] The method for producing an oxide superconducting wire according to the present invention includes a step of preheating a sintered raw material wire having an oxide superconducting composition to a temperature of 700° C. or higher, and a step of preheating the preheated raw material. A process of locally heating a wire rod to a temperature higher than its melting point in an oxidizing atmosphere to form a molten part, and passing the molten liquid through a plurality of pipes arranged in parallel below the molten part. It is characterized by having a step of simultaneously pulling down the wire rods from their lower ends and solidifying them to obtain a plurality of wire rods.

The apparatus for producing an oxide superconducting wire according to the present invention includes: a first heating means for heating the sintered raw material wire having an oxide superconducting composition to a temperature of 700° C. or higher while the material wire is relatively moving; a second heating means that locally heats the raw material wire to a temperature equal to or higher than its melting point in the melting region of the first heating means to form a melting part; and a second heating means that contacts the lower end of the melting part; It is characterized by having a plurality of pipes that are arranged in parallel and solidify the melt into a plurality of wire rods having a desired diameter by passing the melt through the inside and pulling it down, and a means for creating an oxidizing atmosphere in the melting part. do.

[Function] In the method of the present invention, after a sintered wire having an oxide superconducting composition is preheated to a temperature of 700°C or higher, the preheated raw material wire is further locally heated to a temperature higher than the melting point to form a molten part. Form. Therefore, the temperature difference in the longitudinal direction of the sintered raw material wire in the vicinity of the fusion zone and the temperature difference between the surface layer and the core of the fusion zone are small, and a stable fusion zone can be obtained.

In addition, the melt in the molten zone is passed through multiple pipes arranged in parallel below the molten zone and is pulled down from the lower end to solidify, so the resulting oxide superconducting wire has a substantially is equal to the outside diameter of the pipe. This results in
A wire having a wire diameter determined by the pipe diameter is obtained, and by setting the pipe diameter to a desired thin wire diameter, a thin oxide superconducting wire having a uniform diameter can be easily manufactured. Further, a plurality of oxide superconducting wires can be simultaneously produced from one melting section using a plurality of pipes.

In this case, if the pipe is heated to a temperature equal to or higher than the melting point of the raw material wire, the melt will not solidify when passing through the pipe, so the melt will smoothly pass through the pipe.

Further, since the melt passing through the vibrator is pulled downward and solidification progresses, air bubbles in the melt are easily caught in the solidification interface and floated inside the melted portion to be removed. Furthermore, in the present invention, since the melt in the melting zone is pulled out in the same direction as the direction of gravity, the melt is reliably replenished at the solidification interface. For these reasons, in the present invention, long wire rods can be stably manufactured without causing wire breakage during manufacturing. Thereby, an oxide superconducting wire having a desired wire diameter can be continuously manufactured.

The temperature at which the raw material wire is preheated is 700''C or higher.

When the preheating temperature is less than 700° C., the temperature difference between the temperature of the melting zone and the raw material wire immediately before melting becomes excessive, making it impossible to obtain a stable melting zone and making wire breakage more likely to occur during production. For this reason, the preheating temperature of the wire is set to TOO° C. or higher.

In the apparatus of the present invention, the raw material wire is preheated to a temperature of 700° C. or higher by the first heating means, and then locally heated to a temperature higher than the melting point by the second heating means. Then,
The region heated by the second heating means melts to form a molten part, and the melt descends in a plurality of pipes arranged in parallel in contact with the lower end of this molten part. , is pulled down from its lower end and solidifies. Therefore, even if the raw material wire has a large diameter or the diameter of the melted part is large, the wire obtained by solidifying the melt has a desired wire diameter determined by the diameter of the pipe.

[Embodiments] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an apparatus for manufacturing an oxide superconducting wire according to this embodiment. The raw material wire 1 of the sintered body is fixed at its upper end to a wire holder 6a attached to a raw material wire supply drive shaft 8, and is supported with its longitudinal direction perpendicular.

Further, a pull-down drive shaft 7 is arranged below the supply drive shaft 8, and a pull-down guide wire 2 made of platinum or the like is fixed to a wire holder 6b attached to the pull-down drive shaft 7. ing. In this embodiment, there are three guide wire rods 2 for pulling down, and each guide wire rod 2 is fixed to the wire rod holder 6b with an appropriate length interval between them and with their longitudinal direction vertical. The supply drive shaft 8 and the pull-down drive shaft 7 can be moved up and down in conjunction with each other at a predetermined relative speed by a drive device (not shown).

In the passage area of the raw material wire 1, a cylindrical heating furnace 9 is arranged with its axial direction perpendicular and surrounding the raw material wire 1. This heating furnace 9 has a coil-shaped heating element 10 installed therein, and by supplying power to this heating element 10 from an appropriate power source and causing the heating element 10 to generate resistance heat, the heating element 10 is located inside the heating furnace 9. The raw material wire 1 etc. are heated to a temperature of 700°C or higher.

A resistance heating coil 4 is disposed inside the heating furnace 9 in a region where the raw material wire 1 descends. The resistance heating coil 4 is formed by forming a platinum wire having a wire diameter of 0.2 to 1.0 into a coil shape, for example. Further, a resistance heating wire 5b is arranged below and adjacent to the coil 4, and this resistance heating wire 5b also has a wire diameter of, for example, Q. It is formed by winding a platinum wire with a diameter of 0.3 mm coaxially with the coil 4 once. The coil 4 and the heating wire 5b are supplied with power from an appropriate power source, and by energizing the coil 4 and the heating wire 5b to generate resistance heat, the area surrounded by the coil 4 and the heating wire 5b is heated. The raw material wire 1 is heated to a temperature equal to or higher than its melting point and melted. As a result, the obtained molten material is held in the area surrounded by the coil 4 and the heating wire 5b by surface tension using the wetting property of the molten material, and a molten part 3 is formed. Furthermore, directly below the center of the coil 4, there are 3
A main pipe 5a is disposed with its upper end in contact with the melting section 3. At least the lower half of the pipe 5a extends vertically, and the lower end thereof is positioned to align with the guide wire 2 below. For example, each pipe 5a has an outer diameter of 0.1 to 0.5 film, and an inner diameter of 0.05 to 0.5 film.
It is made of platinum and is fixed to the platinum resistance heating wire 5b. Note that these pipes 5a are also heated to a temperature equal to or higher than the melting point of the raw material wire 1 due to resistance heating of the heating wire 5b. Since each pipe 5a is disposed in contact with the lower end of the melting section 3 in this manner, the melt in the melting section 3 permeates through each pipe 5a according to the capillary principle and descends to the lower end of the pipe.

The locations of the coil 4 and pipe 5a and their surroundings are maintained in an oxidizing atmosphere. This may be done, for example, by placing the entire heating furnace 9 in an oxidizing gas atmosphere, or by blowing an oxidizing gas around the coil 4 and pipe 5a.

The coil 4, the resistance heating wire 5b, and the pipe 5a are not limited to those molded from platinum as described above, but they must be able to be used in this oxidizing atmosphere.

Next, a method for producing an oxide superconducting wire using the above-described production apparatus will be described. In this example, the oxide superconducting composition is BSCCO-based, but oxide superconducting materials having other compositions can be manufactured in the same manner.

First, a molded body of BSCCO-based oxide powder is filled and sealed in an Ag pipe, and then the pipe is swaged.
For example, it is made into a wire by reducing its diameter to three dimensions. Thereafter, the Ag sheath on the surface layer is dissolved with nitric acid and methanol.

Next, the remaining oxide wire is heat-treated for 10 hours in an oxidizing atmosphere at a temperature of, for example, 780°C, so that the BS
A raw material wire l made of a sintered body of CCO-based oxide is obtained.

Next, the upper end of the raw material wire 1 is fixed to the aforementioned wire holder 6a, and the supply drive shaft 8 is lowered to arrange the raw material wire 1 so that the lower end of the raw material wire 1 fits into the coil 4. 10,000, insert the upper ends of three pull-down guide wires 2 made of platinum that are thinner than the inner diameter of the pipe 5a into the pipe 5a,
Its lower end is fixed to the wire holder 6b. After supplying the oxidizing gas around the coil 4 and the pipe 5a,
The preheating heating element 10 is energized to heat the raw material wire 1 in the heating furnace 9 to a temperature of 700° C. or higher. Further, the resistance heating coil 4 for melting is energized to locally heat the raw material wire 1 and melt it. As a result, a melted portion 3 is formed in a region surrounded by the coil 4. In addition, the resistance heating wire 5b for supporting the pipe is also energized to connect the resistance heating wire 5b and the pipe 5a to the raw material wire 1.
heated to a temperature above the melting point of

Next, the supply drive shaft 8 and the pull-down drive shaft 7 are lowered at a predetermined relative speed.

The melt in the melting section 3 permeates inside the pipe 5a and descends, exits from the lower end of the pipe, cools down, and solidifies into a thin wire shape having a wire diameter determined by the wire diameter of the pipe 5a, forming the oxide superconducting wire 11. is obtained. This oxide superconducting wire 11 is carried out downward by the lowering of the pull-down drive shaft 7. On the other hand, the raw material wire 1 is continuously supplied into the heating furnace 9 from above by lowering the supply r drive shaft 8 . In this way, the raw material wire 1 is melted by passing through the arrangement position of the coil 4, and the diameter of the molten part 3 is reduced by the pipe 5a to the desired wire diameter, thereby making the oxide superconductor without voids. Wire rod 11
is produced continuously. Moreover, since three oxide superconducting wires 11 can be manufactured at the same time, productivity is extremely high.

In this case, since the raw material wire 1 just before melting and the oxide superconducting wire 1l just after solidification have been preheated to a temperature of 700°C or higher in the heating furnace 9, this melting part 3, the raw material wire 1 and the oxide superconducting wire 11 The temperature difference between the boundary between the two and the center of the melting zone 3 is small. Therefore, stable molten zone 3
is obtained. Furthermore, since the melt passes through the inside of the pipe 5a and is pulled down from the lower end of the pipe 5a to solidify, its wire diameter is determined by the diameter of the pipe 5a, and by making the diameter of the pipe 5a a desired thin wire diameter. A superconducting wire 11 having a fine wire diameter and a uniform diameter can be easily obtained.

In the device of this embodiment, the wire rods are supplied and pulled down by the supply drive shaft 8 and the pull-down drive shaft 7, but the present invention is not limited to this, and the wire rods are supplied and pulled down by, for example, pinch rolls. The same effect can be obtained by doing this.

Next, the results of actually manufacturing an oxide superconducting wire using the method and apparatus of this example will be explained.

A pipe 5a with an outer diameter of 0.5 is provided at the bottom of the L-shaped resistance heating coil 4.
were arranged in combination of five. Then, the BSCCO-based oxide sintered raw material wire 1 produced as described above is placed in a heating furnace 9.
was heated to 700° C. and heated to a temperature higher than the melting point by a resistance heating coil 4 to form a molten portion 3. At this time, the surface temperature of the pipe 5a was maintained at 950°C.

The melt was drawn down from the lower end of the pipe 5a to produce an oxide superconducting wire with a fine wire diameter.

A BSCCO-based oxide superconducting wire was produced in the same manner as in Example 1, except that the preheating temperature was 800° C. and the outer diameter of each pipe was 0.3°.

A BSCCO-based oxide superconducting wire was produced in the same manner as in Example 1, except that only one Hiji gripping pipe 5a was provided.

After feeding the raw material wire l from below the resistance heating coil 4 and heating and melting it, the molten liquid in the molten part permeates the inside of the pipe placed directly above the resistance heating coil 4 and is pulled up. oxide superconducting wire was manufactured.

A superconducting wire was manufactured by forming a suspended molten zone on the BSCCO-based sintered raw material wire 1 produced in the same manner as in Example 1 with a CO2 gas laser.

This is the BSCCO-based sintered body raw material wire 1 itself produced in the same manner as in Example 1, and was not subjected to melting treatment to remove voids.

As a result, in the case of Comparative Example 3, it was not possible to obtain a wire rod with a wire diameter of 5 cm or less.

For Examples 1 and 2 and Comparative Examples 1 to 4, the temperature at which the electrical resistance becomes O (μΩ·cm) (Tc; hereinafter referred to as critical temperature) and the critical current density in liquid nitrogen were measured. The results are shown in Table 1 below. Note that the critical current density is shown as a ratio to Comparative Example 4, which is a sintered body. Also,
The wire diameter of each oxide superconducting wire is also shown.

As shown in Table 1, in both Example 1.2 of the present invention and Comparative Example 1.2, a stable molten zone can be formed, and superconducting wires with a desired fine wire diameter without voids can be produced. We were able to. In addition, the critical temperature of Example 1.2 and Comparative Example 1.2 is higher than that of Comparative Example 2, which is a conventional method, and Comparative Example 3, which is a sintered body, and the critical current density is also 8 times or more. showed an extremely high value.

Table 1 Next, the results of comparing the number of disconnections during the manufacturing process for Example 1 and Comparative Examples 1.2 will be described.

That is, after starting production using both production methods, an experiment for producing 20 cm of oxide superconducting wire was repeated 10 times. As a result, in the case of the pull-down method of Example 1, a total of 50 oxide superconducting wires could be continuously manufactured from the five pipes 5a without any wire breakage. However, in the case of Comparative Example 2 of the pulling method, 22 out of 50
The wire broke within c+s. Further, in the case of Comparative Example 1, there was no wire breakage during production, but only 10 wires could be produced in 10 production experiments, so the productivity was 175, which is lower than that in Example 1.

[Effects of the Invention] As explained above, according to the present invention, a sintered wire having an oxide superconducting composition is heated to 700° C. or higher in advance, and then locally heated to a temperature higher than the melting point, thereby forming a molten part. The oxide superconducting wire is produced by solidifying the melt by drawing it down through multiple pipes, so it is possible to manufacture oxide superconducting wire with a thin wire diameter determined by the pipe diameter while suppressing wire breakage. It can be manufactured stably. Furthermore, since a plurality of oxide superconducting wires can be manufactured at the same time, productivity is extremely high. Since voids have been removed from this oxide superconducting wire, its critical current density is extremely high.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an apparatus for manufacturing an oxide superconducting wire according to an embodiment of the present invention.

Claims (3)

[Claims] (1) 700 sintered raw material wires with oxide superconducting composition
a step of preheating the preheated raw material wire to a temperature of ℃ or higher; a step of locally heating the preheated raw material wire in an oxidizing atmosphere to a temperature higher than its melting point to form a molten zone; A method for manufacturing an oxide superconducting wire, comprising the step of passing through a plurality of pipes arranged in parallel and simultaneously pulling down from the lower ends of the pipes and solidifying the wires to obtain a plurality of wires. (2) The method for manufacturing an oxide superconducting wire according to claim 1, wherein the pipe has a temperature higher than the melting point of the raw material wire. (3) a first heating means that heats the sintered raw material wire of the oxide superconducting composition to a temperature of 700°C or higher while it moves relatively; and a heating area of the first heating means. a second heating means that locally heats the raw material wire to a temperature equal to or higher than its melting point to form a molten part; An apparatus for manufacturing an oxide superconducting wire, comprising: a plurality of pipes that are passed through and pulled down to solidify into a plurality of wires having a desired diameter; and means for creating an oxidizing atmosphere in the molten zone.