JPH10321065A - Manufacture of superconducting wire material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase critical current density by forming a raw material tape by filling bismuth, lead, strontium, calcium, and copper in a sheath material containing silver and heat-treating the raw material tape to which tensile stress of the specified value or less has been applied. SOLUTION: Bi2 O3 , PbO, SrCO3 , CaCO3 , and CuO powders are mixed, heat- treated, then crushed to form powder. The powder is filled in a silver pipe, then they are drawn, the wire materials obtained are bundled, put into a silver pipe, then they are drawn and rolled to form a raw material tape 5. The raw material tape 5 is suspended from a fixed clamp 10, and tensile stress applied to the raw material is limited to 20 kPa or less in a part, where the largest tensile stress of the raw material tape 5 is applied, or in a part 5a coming in contact with the fixed clamp 10 of the raw material part 5. Then the raw material tape 5 is heat-treated at 840 deg.C or higher so as to obtain a wire material with high critical current density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a superconducting wire, and more particularly to a method for manufacturing a superconducting wire made of oxide ceramics.

[0002]

2. Description of the Related Art Among superconducting wires, oxide superconducting wires have a relatively high critical temperature, and are being studied and developed for practical use.
In order to manufacture an oxide superconducting wire, first, a raw material of the oxide superconductor is sufficiently mixed. Next, this raw material is placed in a silver sheath, and the sheath is drawn to form an ultrafine wire. A raw material tape is formed by rolling a plurality of ultrafine wires into a silver sheath and rolling the silver sheath.

FIG. 9 is a view showing one step of a conventional method for manufacturing a superconducting wire. Referring to FIG. 9, winding 101 is formed by winding raw material tape 104 manufactured in the above-described process and release tape 103 made of glass fiber or the like around winding shaft 102 while applying a load. The winding shaft 1 of this winding 101
The superconducting material in the raw material tape 104 is reacted by performing a heat treatment while keeping the H.02 in the horizontal direction to form a superconducting wire.

In the above-described conventional method of manufacturing a superconducting wire, the superconducting material is hardly generated at the top 104a of the winding, that is, at the highest portion of the winding of the raw material tape, and the superconducting material is hardly generated. There has been a problem that the critical current density becomes low as a whole wire.

Accordingly, the present invention has been made to solve the above-mentioned problems, and has as its object to provide a method of manufacturing a superconducting wire having a high critical current density.

[0006]

Means for Solving the Problems The present inventors have studied the reason why it is difficult to form a superconducting wire at the top 104a of the winding. As a result, the following was found.

At the top 104a of the winding, the tension when the raw material tape is wound and the weight of the raw material tape 104 themselves act as tensile stress. That is, the tensile stress applied to the raw material tape 104 becomes the maximum at the top 104a of the winding. When the raw material tape is subjected to heat treatment in a state where a large tensile stress is applied to the raw material tape, reactions that significantly affect superconducting characteristics, such as growth of crystal grains and bonding of crystal grain boundaries, cannot be sufficiently performed. As a result, generation of a superconductor is suppressed at the top of the winding, and the critical current density of the superconducting wire is reduced.

Further investigations have revealed that when the raw material tape is heat-treated in a state where the tensile stress applied to the raw material tape exceeds 20 kPa, the critical current density of the superconducting wire is greatly reduced.

Therefore, a method of manufacturing a superconducting wire according to one aspect of the present invention is directed to a method of manufacturing a superconducting wire by heat-treating a raw material tape, wherein the raw material tape is subjected to a tensile stress of 20 kPa or less while applying a tensile stress of 20 kPa or less. The tape is heat-treated.

According to such a method, since the heat treatment is performed in a state where no large tensile stress is applied to the raw material tape, a superconducting substance is easily generated. As a result, a superconducting wire having a high critical current density can be manufactured.

Further, the raw material tape is preferably a material in which a sheath material containing silver is filled with bismuth, lead, strontium, calcium, and copper. In this case, since the bismuth-based superconducting wire is generated by the heat treatment, the critical current density of the superconducting wire can be maintained in a high state.

Further, it is preferable that the raw material tape is wound and heat-treated so as to have a tensile stress of 20 kPa or less and a direction in which the winding shaft extends in a vertical direction. According to such a method, since the direction in which the winding axis extends is the vertical direction, the weight of the raw material tape itself does not become the tensile stress of the raw material tape, so that the tensile stress applied to the raw material tape is 20 kPa or less. Therefore, a superconducting wire having a high critical current density can be easily produced by heat-treating the raw material tape in this state.

Further, the raw material tape is preferably wound in a pancake coil shape. In this case, a longer superconducting wire can be manufactured.

The raw material tape wound in a pancake shape is preferably formed on a flat plate having a core. In this case, by winding the raw material tape in a pancake shape on a flat plate, almost no tensile stress is generated in the raw material tape.

Further, the raw material tape wound in a pancake shape is preferably formed on two or more flat plates. In this case, a long superconducting wire can be manufactured by winding a series of raw material tapes over a plurality of flat plates.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) A method of manufacturing a superconducting wire according to Embodiment 1 of the present invention will be described below. First, Bi ₂
O ₃ , PbO, SrCO ₃ , CaCO ₃ , and CuO powder are mixed. After heat-treating this mixed powder, it is further pulverized to form a powder. This powder is filled in a silver pipe, the silver pipe is drawn, and the obtained wires are bundled and fitted into the silver pipe. Next, the silver pipe is subjected to wire drawing and rolling to obtain a raw material tape.

FIG. 1 is a side view for illustrating a method of manufacturing a superconducting wire according to the first embodiment of the present invention. Referring to FIG. 1, raw material tape 5 manufactured in the above-described steps is suspended on stainless steel fixed clamp 10. A portion of the raw material tape 5 to which the largest tensile stress is applied, that is, a portion 5 where the raw material tape 5 is in contact with the fixing clamp 10
In a, in order to reduce the tensile stress applied to the raw material tape 5 to 20 kPa or less, if the density of the raw material tape 5 is 9 g / cm ³ , the length (L) of the raw material tape 5 must be 22 cm or less.

In this state, the raw material tape 5 is heated at a temperature of 8 ° C.
If the heat treatment is performed at 40 ° C. or more, since no tensile stress exceeding 20 kPa is applied to any part of the raw material tape 5, the crystal grains of the superconducting material grow during the heat treatment, and the crystal grain boundaries are joined, so that the critical current A superconducting wire having a high density can be manufactured.

(Embodiment 2) In Embodiment 2, first, a raw material tape is manufactured in the same manner as in Embodiment 1. Next, a bobbin is prepared.

FIG. 2 is a perspective view showing a bobbin used in the method of manufacturing a superconducting wire according to the second embodiment of the present invention. Referring to FIG. 2, winding frame 1 includes a flat plate 2 and a core 3. The flat plate 2 is made of stainless steel and has a cylindrical shape with a diameter of 500 mm and a thickness of 8 mm. A through hole is provided at the center of the flat plate 2, and a winding core 3 is provided so as to be inserted into the through hole. The core 3 is made of stainless steel and has a diameter of φ
It is a cylinder having a thickness of 300 mm and a thickness of 10 mm. A through hole is provided in the center of the core 3. A raw material tape is wound around the reel 1.

FIG. 3 is a perspective view showing a release tape as the raw material tape wound around the reel 1 shown in FIG. Referring to FIG. 3, release tape 4 and raw material tape 5 are wound around reel 1 around winding shaft 6 so as to overlap each other. The release tape 4 is used to prevent the raw material tapes 5 from contacting each other, and is made of, for example, alumina fiber or glass fiber. The raw material tape 5 has the same structure as the raw material tape 5 shown in FIG. 1, but is longer than that shown in FIG. When winding the release tape 4 and the raw material tape 5 around the winding frame 1, the winding is performed with a tensile stress of 20 kPa or less.

FIG. 4 is a perspective view showing a superconducting wire manufactured according to the second embodiment of the present invention. Referring to FIG. 4, superconducting wire 7 can be manufactured by subjecting raw material tape 5 wound on reel 1 to a heat treatment at a temperature of 845 ° C. for 80 hours with the direction in which reel 6 extends as a vertical direction.

In such a manufacturing method, the raw material tape 5
Is heat-treated with the direction in which the winding shaft 6 extends in the vertical direction, so that the gravity acting on the raw material tape 5 does not become a stress that pulls the raw material tape 5 in the length direction, so that the raw material tape 5 exceeds 20 kPa during this heat treatment. No tensile stress works. Therefore, a solid-phase reaction that generates a superconducting substance occurs,
The superconducting wire 7 having a high critical current density can be manufactured.

During the heat treatment of the raw material tape 5, the raw material tape 5 is stretched, so that some stress may be applied to the raw material tape 5. However, if the raw material tape 5 is stretched, only a compressive stress is applied to the raw material tape 5, and no tensile stress which is a factor that hinders generation of the superconducting substance is applied. Further, when the temperature is lowered after the heat treatment, the superconducting wire shrinks, so that a tensile stress exceeding 20 kPa may be applied to the superconducting wire. In this case, since the heat treatment has already been completed, this tensile The stress does not cause a reduction in the critical current density of the superconducting wire.

(Embodiment 3) In the manufacturing method according to Embodiment 3, first, a raw material tape is manufactured in the same manner as in Embodiment 1. Next, a bobbin is prepared.

FIG. 5 is a perspective view showing a bobbin used in the method for manufacturing a superconducting wire according to the third embodiment of the present invention. Referring to FIG. 5, a bobbin 11 includes flat plates 12 and 13,
A winding core 14 and a crossover 15 are provided. The flat plate 12 is made of stainless steel and has a cylindrical shape with a diameter of 500 mm and a thickness of 8 mm. The flat plate 12 is provided with a through hole. A core 14 having a diameter of 300 mm and a height of 100 mm is formed in the through hole.
Is inserted. The flat plate 13 is made of stainless steel and has a cylindrical shape with a diameter of 500 mm and a thickness of 8 mm. Flat plate 1
3 is provided with a through hole at the center, and the core 14 is inserted into this through hole. A spiral transition portion 15 is provided along the core 14 so as to continue from the flat plate 12 to the flat plate 13. The raw material tape is wound around the reel 11.

FIG. 6 is a perspective view showing the raw material tape and the release tape wound on the reel shown in FIG. Referring to FIG. 6, release tape 4 and raw material tape 5 are wound on core 14 located on flat plate 12 so as to overlap with each other and away from core 14. Of the release tape 4 and the raw material tape 5 wound on the flat plate 12, the outermost release tape 4 and the raw material tape 5 extend to the lower part in the drawing via the crossover portion 15. The release tape 4 and the raw material tape 5 are
3 is wound in a direction away from the core 14. When the release tape 4 and the raw material tape 5 are wound, a tensile stress of 20
kPa or less.

The raw material tape 5 wound in the form of a pancake coil on the winding frame 11 in this manner is set so that the direction in which the winding core 14 extends, that is, the direction in which the winding shaft 19 extends, is set to the vertical direction,
Heat treatment at 5 ° C. for 60 hours.

FIG. 7 is a perspective view showing a superconducting wire manufactured according to the third embodiment of the present invention. Referring to FIG. 7, if the raw material tape 5 is heat-treated under the above-described conditions, the superconducting material 23 in the raw material tape 5 undergoes a solid-phase reaction, whereby the superconducting wire 23 can be manufactured.

In such a method for manufacturing a superconducting wire, the gravity acting on the raw material tape 5 wound on the flat plates 12 and 13 does not cause a tensile stress in the raw material tape 5 in the longitudinal direction. Since a tensile stress exceeding 20 kPa is not applied, the same effect as that of the method for manufacturing a superconducting wire shown in the second embodiment can be obtained. In the raw material tape 5 located at the crossover portion 15, a part of the gravity applied to the raw material tape 5 acts on the raw material tape 5 as a tensile stress. However, this tensile stress has a sufficiently small value, so that there is almost no problem.

Further, since the raw material tape is wound in a pancake coil shape, a superconducting wire longer than that of the second embodiment can be manufactured.

The number of the flat plates 12 and 13 can be three or more.

[0033]

EXAMPLES (Example 1) Bi ₂ O ₃ , PbO, SrCO ₃ , CaC
The weight ratio of O ₃ and CuO is 0.35: 0.056: 0.2
A powder of 3: 0.16: 0.19 was prepared. This powder is heat-treated at a temperature of 800 ° C. for 12 hours, and further heated at a temperature of 850 ° C.
For 6 hours to form a sintered body. The powder obtained by pulverizing the sintered body was filled in a silver pipe having an outer diameter of 26 mm and an inner diameter of 22 mm. A bundle of 61 wires obtained by drawing the silver pipe is fitted into a silver pipe having an outer diameter of 26 mm and an inner diameter of 22 mm, and is drawn and rolled to a width of 3.8 mm and a thickness of 0.3 mm. A raw material tape having a length of 25 mm and a length of 1.1 cm was obtained. The raw material tape 5 was suspended on a fixed clamp 10 as shown in FIG. At this time, the calculated tensile stress applied to the raw material tape 5 at the portion 5a in contact with the fixed clamp 10 was 1 kPa. For comparison, a raw material tape of the same length was placed on a horizontal plane so that no tensile stress was applied. These two raw material tapes were heated at a temperature of 8
A superconducting wire was manufactured by heat treatment at 45 ° C. for 80 hours. In addition, the length is 6cm, 11cm, 22cm, 5cm.
5cm, 110cm, 220cm, 550cm, 110
Two 0 cm raw material tapes 5 were prepared in accordance with the above-described steps. One of these raw material tapes 5 was suspended on a fixed clamp 10 as shown in FIG. For wires longer than the furnace height, the lower part of the wires was bundled. The other was placed on a horizontal surface so that tensile stress was not applied. Raw material tape 5 suspended on fixed clamp 10
, The tensile stress acting on the portion 5a in contact with the fixed clamp 10 is calculated as 5 kPa, 10 kPa,
20kPa, 50kPa, 100kPa, 200kP
a, 500 kPa and 1000 kPa. These superconducting wires were heat-treated under the following conditions to produce superconducting wires.

Used superconducting wire Silver sheath Bi2223 superconducting rectangular wire Cross section dimensions 3.8 (mm) x thickness 0.25 (mm) Silver / superconductor volume ratio 2.5 Superconducting drawn wire number 61 Heat treatment temperature 845 ° C Heat treatment time 80 hours Characteristics (Jc / Jco) Value obtained by dividing the critical current density under each condition by the critical density at zero tension. FIG. 8 is a graph showing the characteristics of the obtained superconducting wire. From FIG. 8, it can be seen that the sample subjected to a heat treatment with a tensile stress exceeding 20 kPa has a reduced superconducting property, that is, a lower critical current density.
It is considered that this is because a solid-state reaction for generating a superconducting material did not sufficiently occur due to a tensile stress applied during the heat treatment.

(Example 2) A raw material tape 5 having a length of 400 m was manufactured in the same procedure as in Example 1. This raw material tape 5
And a release tape 4 made of glass fiber were wound on a bobbin 1 as shown in FIG. 3 under a tensile stress of 20 kPa or less. The direction in which the winding shaft 6 extends is the vertical direction.
Was heat-treated at a temperature of 845 ° C. for 80 hours to produce a superconducting wire 7 shown in FIG. When the critical current density of this superconducting wire 7 was measured, it was 2.2 kA / cm ² ,
Good value.

(Embodiment 3) The length is made in the same procedure as in Embodiment 1.
An 800 m raw material tape was prepared. This raw material tape 5
FIG. 6 shows the release tape 4 made of glass fiber.
And apply a tensile stress of 20 kPa or less to the winding frame 11
I did. The direction in which the winding shaft 19 extends is set to the vertical direction.
Heat treatment at a temperature of 845 ° C. for 80 hours.
The conductive wire 23 was manufactured. Critical current density of superconducting wire 23
2.0 kA / cm ^Two And good
The value was shown.

The examples and embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for manufacturing a superconducting wire according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a bobbin used in a method of manufacturing a superconducting wire according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing a release tape and a raw material tape wound around a bobbin shown in FIG. 2;

FIG. 4 is a perspective view showing a superconducting wire manufactured according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing a bobbin used in Embodiment 3 of the present invention.

FIG. 6 is a perspective view showing a release tape and a raw material tape wound around the bobbin shown in FIG. 5;

FIG. 7 is a perspective view showing a superconducting wire manufactured according to a third embodiment of the present invention.

FIG. 8 is a graph showing characteristics of a superconducting wire obtained according to the present invention.

FIG. 9 is a view showing a conventional method for manufacturing a superconducting wire.

[Explanation of symbols]

 5 Raw material tape 7,23 Superconducting wire

Claims (6)

[Claims] 1. A method for producing a superconducting wire by heat-treating a material tape, wherein the material tape is heat-treated while a tensile stress of 20 kPa or less is applied to the material tape. Production method. 2. The method for producing a superconducting wire according to claim 1, wherein the raw material tape is formed by filling a sheath material containing silver with bismuth, lead, strontium, calcium, and copper. 3. The raw material tape is wound and heat-treated with a tensile stress of 20 kPa or less and a direction in which a winding shaft extends is a vertical direction.
Or the method for producing a superconducting wire according to 2. 4. The method for producing a superconducting wire according to claim 3, wherein the raw material tape is wound in a pancake coil shape. 5. The method for producing a superconducting wire according to claim 4, wherein the raw material tape wound in a pancake coil shape is formed on a flat plate having a core. 6. The method for producing a superconducting wire according to claim 5, wherein the raw material tape wound in a pancake coil shape is formed on two or more flat plates.