Superconducting device and superconducting cable

FIELD: electrical engineering.

SUBSTANCE: proposed superconducting device has superconducting oxide wire made of superconducting oxide material whose post-sintering density is 93% and more, best 95% and more, or most preferably 99% or more, which is attained by heat treatment of wire in enhanced pressure environment of at least 1 MPa and below 50 MPa. Heat treatment of wire at enhanced pressure prevents formation of gaps and bubbles. Stable superconducting oxide phase of Bi2223 is formed in the process.

EFFECT: enhanced critical current density of superconducting device and superconducting cable.

6 cl, 27 dwg, 4 tbl, 6 ex

 

The technical FIELD

The present invention relates to a superconducting device and a superconducting cable, in particular it relates to a superconducting device and a superconducting cable, which is able to suppress the swelling even when the temperature without temperature control.

The LEVEL of TECHNOLOGY

When using superconducting devices, such as superconducting cables, this superconducting device is immersed in liquid refrigerant, such as liquid nitrogen or liquid helium, and is maintained at cryogenic temperature for cooling the fibers of the superconductor in the superconducting device below the critical temperature (Twith). On the other hand, the superconducting device are removed from the liquid refrigerant, for example, during the inspection, or the like, and for heating the device from cryogenic temperatures to room temperature around a superconducting device serves gaseous refrigerant or the like at room temperature. However, when the device is heated to room temperature after it has been immersed in liquid refrigerant, in the conventional superconducting device, there arises the following problem.

On the surface of the oxide superconducting wire, part of the superconducting device, usually there are small surface of the main pores. When this oxide superconducting wire for a long time immersed in the refrigerant, the liquid refrigerant through these surface pores seeps into the gaps of the fibers of the oxide superconductor in the superconducting wire. When the temperature is raised to normal from this state, the liquid refrigerant that leaked in the oxide superconducting wire, evaporates, and, if the rate of temperature rise is too large, then evaporated gas does not have time to go out. This increases the internal pressure in the oxide superconducting wire, and it extends this oxide superconducting wire (causing swelling). When swelling occurs, the fiber superconductor, unfortunately, damaged, resulting in the characteristic performance, such as reduction in critical current density.

In this regard, for example, laid the Japan patent No. 2002-260458 (Patent document 1) discloses a method of regulating the rate of evaporation to prevent expansion of the superconducting cable. The method of regulating the rate of evaporation, disclosed in the above publication, is a method of regulating the rate of evaporation of the refrigerant by setting the speed of raising the temperature of the superconductor in the superconducting cable is not more than 10 K/h. In particular, the evaporation rate is of LanAgent regulate by setting the speed of raising the temperature of the superconductor in the superconducting cable is not more than 10/hour with means for supplying coolant flowing in the superconducting cable at a higher temperature than the temperature at normal cooling; means for supplying coolant flowing in a superconducting cable with a speed less than the normal cooling; means the introduction of raise the temperature of the fluid with the temperature exceeding the temperature of the refrigerant during normal cooling, the refrigerant supplied to the superconducting cable; or means for supplying coolant to the superconducting cable with a simultaneous gradual increase of the pressure of the refrigerant from the state in which the temperature of the refrigerant does not exceed the boiling point or close to the boiling point. Thus, the rate of evaporation of the liquid refrigerant that leaked in the superconducting wire, a relatively decreases so that the extension wire can be suppressed.

DISCLOSURE of INVENTION

Objectives of the invention

However, in the method described in said publication, the heating rate of the superconductor from cryogenic temperatures to room temperature is to be regulated, and the temperature control when the temperature is difficult. In addition, the rate of temperature rise of the superconductor is so low, constituting no more than 10 K/hour to raise the temperature necessary is tsya a lot of time.

As a method capable of suppressing swelling after increasing the temperature without temperature control, also can be used the following way. That is, can also be used a method of suppressing the swelling by applying to the periphery of the shell of the oxide superconducting wire, part of the superconducting device, metal to block pores, whereby it is difficult to seepage of liquid refrigerant into the gaps of the fibers of the oxide superconductor in the superconducting wire.

According to this method, however, the mass of the superconducting device is increased by the mass of deposited material, increasing the size of the superconducting device. In addition, it also increases the number of steps of manufacturing the superconducting device.

Accordingly, the present invention is to create a superconducting device and a superconducting cable capable of suppressing swelling even when the temperature without temperature control.

Means for solving these problems

A superconducting device according to the present invention has an oxide superconducting wire. The density after sintering of the oxide superconductor in the oxide superconducting wire is at least 93%.

Superconducting cable according to Nast is Adamu invention has an oxide superconducting wire. The density after sintering of the oxide superconductor in the oxide superconducting wire is at least 93%.

In the superconducting device and a superconducting cable according to the present invention, the number of gaps in the oxide superconductor is so low that liquid refrigerant is not essentially seeps into the gaps of the oxide superconductor. Therefore, when the temperature increases from the state of immersion in the liquid refrigerant to a normal temperature without temperature control the amount of evaporated liquid refrigerant is extremely small. Therefore, the internal pressure in the oxide superconducting wire is essentially not increased, and the swelling can be suppressed.

In the superconducting device according to the present invention, the density after sintering of the oxide superconductor in the oxide superconducting wire is preferably at least 95%.

In the superconducting cable according to the present invention, the density after sintering of the oxide superconductor in the oxide superconducting wire is preferably at least 95%.

Thus, the number of gaps in the oxide superconductor is reduced so that the liquid refrigerant is not essentially seeps into the gaps of the oxide superconductor. Therefore, when the temperature and the state of immersion in the liquid refrigerant to a normal temperature without temperature control swelling can be suppressed to a greater degree.

In the superconducting device according to the present invention, the density after sintering of the oxide superconductor in the oxide superconducting wire is preferably at least 99%.

In the superconducting cable according to the present invention, the density after sintering of the oxide superconductor in the oxide superconducting wire is preferably at least 99%.

Thus, the number of gaps in the oxide superconductor is reduced so much that the liquid refrigerant is not essentially seeps into the gaps of the oxide superconductor. Therefore, when the temperature increases from the state of immersion in the liquid refrigerant to a normal temperature without temperature control swelling can be suppressed even more.

The oxide superconducting wire having an oxide superconductor having mentioned density after sintering, can be manufactured by the following manufacturing method:

prepare the wire that has a configuration obtained by coating the metal powder source material for an oxide superconductor. The wire is subjected to heat treatment in an atmosphere of high pressure. The total pressure in the atmosphere of high pressure is at least 1 MPa and less than 50 MPa.

According to the proposed Nast the present invention the method of manufacturing an oxide superconducting wire, due to significant external pressure on the wire, of at least 1 MPa, there are plastic deformation and creep data generated during the heat treatment of the superconducting crystals, due to which the number of gaps between the oxide superconducting crystals decreases (density after sintering of oxide superconductor is increased). In addition, the expansion of the gas in the gaps formed during thermal treatment of a powder of an oxide superconducting crystals or gas that is present due to the adhesion to the heat treatment of the powder of the oxide superconducting crystals, can be difficult during the heat treatment due to the pressure on the outside of a metal tube, whereby possibility of puzyrchatogo in the oxide superconducting wire. Therefore, improved critical current density.

For the formation of a stable oxide superconducting phase partial pressure of oxygen must continually be adjusted in a constant range regardless of the value of the total pressure in the atmosphere of high pressure. If the total pressure in the atmosphere of high pressure in this case is higher than 50 MPa, the partial pressure of oxygen in relation to the total pressure decreases. Thus, the value of the oxygen concentration in the atmosphere is ore increased pressure decreases so that that it has a significant impact measurement error or the like, and therefore the partial pressure of oxygen, unfortunately, it is difficult to regulate. According to the proposed method of manufacturing an oxide superconducting wire, the heat treatment is performed in an atmosphere of high pressure of less than 50 MPa, whereby the partial pressure of oxygen in relation to the total pressure in the atmosphere of high pressure is not reduced so much, and the concentration of oxygen in the atmosphere increased pressure is high enough, resulting in the partial pressure of oxygen is easily adjustable, and without significant influence from measurement error or the like of the Oxide superconducting wire having an oxide superconductor having a density after sintering, the component, at least about 93% and no more than about 96%, obtained by heat treatment of the wire in an atmosphere of high pressure, in which the total pressure is at least 1 MPa and less than 50 MPa.

In the aforementioned method of manufacturing an oxide superconducting wire stage heat treatment is preferably performed by hot isostatic pressing (GISP).

Thus, the oxide superconducting wire is so isotropic exposed to pressure, tapaaminen it gaps and puzyrchatogo prevented consistent manner.

In the aforementioned method of manufacturing an oxide superconducting wire of an oxide superconductor is preferably an oxide superconductor on the basis of Bi-Pb-Sr-Ca-Cu-O, which includes the Bi2223 phase containing bismuth, lead, strontium, calcium and copper in the atomic relations (bismuth and lead):strontium:calcium:copper, constituting approximately 2:2:2:3.

Thus, the gaps between the crystals and usercost oxide superconducting wire is suppressed so that the result can be improved critical current density.

In the aforementioned method of manufacturing an oxide superconducting wire stage heat treatment is preferably performed in an oxygen atmosphere, and the partial pressure of oxygen is at least of 0.003 MPa and not more than 0.02 MPa.

Thus, the oxygen partial pressure is maintained within the range at least of 0.003 MPa and not more than 0.02 MPa, so that a stable oxide superconducting phase, and therefore can be improved critical current density. If the partial pressure of oxygen greater than 0.02 MPa, formed heterophase, while the formation of oxide superconducting phase is difficult and therefore decreases the critical current density, if the partial pressure of oxygen is less ,003 MPa.

In the aforementioned method of manufacturing an oxide superconducting wire of the oxygen partial pressure to regulate its increase after (according to) the temperature rise in the atmosphere of high pressure with increasing temperature before heat treatment under heat treatment.

The value of the optimal partial pressure of oxygen for the formation of an oxide superconducting phase increases following the increase of temperature. Thus, the proper partial pressure of oxygen is ensured also when the temperature before heat treatment under heat treatment, resulting in the formation of a stable oxide superconducting phase, and thus can be improved critical current density.

In the aforementioned method of manufacturing an oxide superconducting wire of the total pressure in the atmosphere of high pressure is preferably adjusted so that it is constant during the heat treatment.

The heat treatment of the total pressure may show a tendency to decrease due to the flow of gaseous oxygen due to oxidation of the carrier wire supports in a vessel of high pressure, cast pressure regulator, such as a supporting pressure of the valve, while the pressure control or pressure fluctuations in the administered gas, added to replenish the consumed oxygen. If these circumstances lead to a sharp drop in pressure in the vessel, the internal pressure in the wire reaches a high level compared with the external pressure, and as a result, the wire appears swelling. According to a preferred aspect of the present invention, however, the total pressure during the heat treatment is adjusted so that it was permanent, the result of which can be prevented the occurrence of puzyrchatogo on the wire due to a sharp decrease of pressure during the heat treatment.

In the aforementioned method of manufacturing an oxide superconducting wire stage heat treatment is preferably performed in an oxygen atmosphere, and the partial pressure of oxygen during the heat treatment regulate so that it is constant with range of fluctuation within 10%.

Thus, the partial pressure of oxygen can be maintained in the optimal range for formation of an oxide superconducting phase regardless of temperature fluctuations, resulting in the formation of a stable oxide superconducting phase, and thus can be improved critical current density.

In the aforementioned method of manufacturing an oxide superconducting wire for FOTS the log of pressure reduction, the resulting temperature reduction, which occurs directly after heat treatment, is preferably introduced gas.

When the temperature drops immediately after the heat treatment following the temperature change should reduce pressure. If at this time the heating vessel is subjected to sudden decompression, the internal pressure of the wire is increased compared with the external pressure, which leads to the appearance of puzyrchatogo wire. According to a preferred aspect of the present invention, however, to compensate for the pressure decrease due to decrease in temperature of the injected gas, which can be prevented the occurrence of puzyrchatogo, due to a sharp decrease in pressure when the temperature drops directly after heat treatment.

In the aforementioned method of manufacturing an oxide superconducting wire speed reduction pressure (decompression speed) at lower temperature directly after heat treatment regulate at the level of not more than 0.05 MPa/min, if the metal covering the powder source material contains silver, and the ratio of the area of the metal part to the area of the oxide superconductor in the cross-sectional areas (hereinafter - "the proportion of silver") after stage heat treatment is 1.5.

Thus, more noticeable E. the effect of preventing the occurrence of puzyrchatogo, the resulting sharp reduction in pressure can be achieved in the case when the proportion of silver is 1.5.

In the aforementioned method of manufacturing an oxide superconducting wire, the rate of pressure reduction in total pressure in the atmosphere of high pressure preferably regulate at the level of not more than 0.05 MPa/min, when the temperature of the atmosphere at the stage of heat treatment is at least 200aboutIf the metal powder coating source material contains silver, and the share of silver is 1.5.

If the heating vessel is subjected to sudden decompression, when the temperature of the atmosphere is at least 200aboutWith the internal pressure of the wire is increased compared with the external pressure, resulting in the wire appears usercost. Therefore, a more noticeable effect prevent puzyrchatogo on the wire due to sudden pressure reduction at the stage of heat treatment (before heat treatment, the heat treatment and after heat treatment) is provided in the case, when the proportion of silver is 1.5.

In the aforementioned method of manufacturing an oxide superconducting wire, the speed of pressure decrease during temperature reduction directly after heat treatment, it is preferable to regulate the level of no more than 0.03 in the PA/min, if the metal covering the powder source material contains silver, and the share of silver is 3.0.

Thus, the more noticeable the effect of preventing puzyrchatogo on the wire resulting from sudden pressure reduction, may be provided in the case, when the proportion of silver is 3.0.

In the aforementioned method of manufacturing an oxide superconducting wire, the rate of pressure reduction in total pressure in the atmosphere increased pressure to regulate the level of 0.03 MPa/min, if the metal covering the powder source material contains silver, the proportion of silver is 3.0, and the temperature of the atmosphere at the stage of heat treatment is at least 200aboutC.

If the heating vessel is subjected to sudden decompression, when the temperature of the atmosphere is at least 200aboutWith the internal pressure of the wire is increased compared with the external pressure, resulting in usercost wire. Therefore, more effective prevention effect of puzyrchatogo wires, resulting from a sharp reduction in pressure at the stage of heat treatment (before heat treatment, the heat treatment and after heat treatment), provided in the case, when the proportion of silver is 3.0.

In the aforementioned method of manufacturing an oxide with erprobte wire speed reduction pressure total pressure in the atmosphere of high pressure regulate at the level of not more than 0.05 MPa/min, if the total pressure of the atmosphere high pressure stage of the heat treatment is at least 1 MPa.

If the heating vessel is subjected to sudden decompression, when the total pressure in the atmosphere is at least 1 MPa, the internal pressure of the wire is increased compared with the external pressure, resulting in the wire appears usercost. So there is a more noticeable effect prevent puzyrchatogo wires, resulting from a sharp reduction in pressure at the stage of heat treatment (before heat treatment, the heat treatment and after heat treatment).

The aforementioned method of manufacturing an oxide superconducting wire preferably also includes a stage rolling wire using a roller after the preparation stage of the wires and at the stage of heat treatment, the thickness of the outer layer sheath of the wire after rolling is at least 20 microns.

Surface pores are formed mainly by holes penetrating from the outside into the fiber of the oxide superconductor, when the surface of the wire is attached to the roughness due to friction between the wire and the roller. When on stage rolling rolls to such a state that the thickness of the outer layer of the shell of the oxide superconducting wire is less than the least 20 μm at each site, pores do not penetrate from the outside into the fiber of the oxide superconductor, even if the surface of the wire by rolling attached roughness, and therefore, the surface pores are not formed. Thus, the formation of gaps and puzyrchatogo during the above stage heat treatment is suppressed, and therefore can be improved critical current density.

Throughout this description, the term "surface time" denotes a hole penetrating from the outside into the fiber of the oxide superconducting wire and having a diameter that allows the passage of liquid refrigerant. In addition, the term "wire, having surface pores" refers to the wire containing at least two surface pores on the length of 1000 meters

The aforementioned method of manufacturing an oxide superconducting wire preferably also includes a stage of deposition of silver or a silver alloy on the surface of the said wire after the preparation stage of the wires and at the stage of heat treatment.

The proportion of silver in the oxide superconducting wire minimize in order to increase the amount of current of superconductivity, the noise per unit area. In the wire with a small proportion of silver, the metallic part is so small that the thickness of the outer layer of the shell cannot be increased. In particular, in the wire when the thickness of the outer layer of the shell after the stage of heat treatment is less than 20 μm, the surface pores are easily formed under this treatment, as rolling, before the stage of heat treatment. In the wire, having surface pores, creating a high pressure gas seeps into the wire through the surface pores also in the case when the above-mentioned stage heat treatment of the wire is performed in an atmosphere of high pressure. Therefore, the difference between internal and external pressures wire disappears, and it gives the weak effect of preventing reduction of the critical current density by suppressing the formation of gaps and puzyrchatogo by increasing pressure. Therefore, the silver or silver alloy is applied to the wire surface after the preparation stage of the wire and before stage heat treatment so that the surface pores are covered with silver or a silver alloy and disappear from the surface. Therefore, the stage of heat treatment performed after the removal of surface pores with wires, resulting in creating a high pressure gas does not penetrate into the wire through these surface pores on the stage of heat treatment. Thus, the formation of gaps and puzyrchatogo suppressed in all the above stages of heat treatment of the wire in an atmosphere of high pressure, and therefore can be improved critical current density.

The aforementioned method of manufacturing an oxide superconducting wire preferably also includes at SEB the stage of rolling the wire through the roll after the preparation stage of the wires and at the stage of heat treatment, while the roughness Rythe surface of the portion of the roll which comes into contact with the wire is not more than 320 nm.

Thus, the friction between the wire and the roller is reduced so that the surface of the wire almost never gets roughness, and therefore receive the wire surface without pores, regardless of the thickness of the outer layer of its shell. Therefore, creating a high pressure gas escapes into the wire through the surface pores on the stage of heat treatment. Thus, inhibited the formation of gaps and puzyrchatogo at the said stage of the heat treatment of the wire in an atmosphere of high pressure regardless of the thickness of the outer layer sheath of the wire, and therefore can be improved critical current density. The term "roughness Rysurface" indicates the maximum height defined Industrial Standards Japanese (JIS).

In the aforementioned method of manufacturing an oxide superconducting wire pressure it is preferable to regulate its speed increase following the increase of temperature in the atmosphere with increasing temperature before heat treatment under heat treatment.

In the wire, having surface pores, creating a high pressure gas seeps into the wire through these surface pores even when the stage thermobreak the wire in an atmosphere of high pressure to perform the usual way of increasing pressure, and so the difference between internal and external pressures wire disappears, resulting in a small effect of preventing reduction of the critical current density due to the formation of gaps and puzyrchatogo when the pressure increases. When controlling pressure to speed increase following the increase of temperature in the atmosphere, however, the external pressure is increased to seepage creates gas pressure in the wire through the surface pores. Thus, there is a difference between internal and external pressures wire, so that the formation of gaps and puzyrchatogo suppressed, and therefore the critical current density can be improved regardless of the presence or absence of surface pores at the stage of heat treatment.

In the aforementioned method of manufacturing an oxide superconducting wire of the total pressure of the atmosphere is preferably regulate to increase with the speed of at least 0.05 MPa/min. when the temperature before heat treatment under heat treatment.

The authors of the present invention found that the rate of increase of the pressure of the gas seeping into the wire through the surface pores on the stage of heat treatment, the wire is less than about 0.05 MPa/min. So the pressure in the atmosphere may be continuously maintained above inside the th pressure of the wire by adjusting the total pressure of the atmosphere for continuous improvement with a speed of at least 0.05 MPa/min. when the temperature before heat treatment. Thus, during the increase of temperature before heat treatment to the wire can be applied compressive force, regardless of the presence or absence of surface pores in the wire at the stage of heat treatment, resulting in suppressed the formation of gaps and puzyrchatogo. As a consequence, can be effectively suppressed the decrease in critical current density during thermal treatment in an atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa.

In the aforementioned method of manufacturing an oxide superconducting wire of the total pressure in the atmosphere is preferably adjust for continuous improvement during the heat treatment at the stage of heat treatment.

Thus, balancing the internal pressure of the wire and the pressure of the atmosphere may be delayed during the heat treatment, so that the state in which the pressure in the atmosphere above the internal pressure of the wire can be maintained over a longer period of time. Therefore, the formation of gaps and puzyrchatogo during heat treatment is suppressed, and can be effectively suppressed the reduction of critical current density during heat treatment in the atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa.

The aforementioned method of manufacturing an oxide superconducting wire is also preferably includes a stage rolling wire after the preparation stage of the wires and at the stage of heat treatment, and the degree of compression of the wire at the stage of rolling is not less than 84%, more preferably not more than 80%.

When the heat treatment stage of the wires is performed in an atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa, the oxide superconducting wire is compressed and also at the stage of heat treatment. Also, when the stage rolled wire do with the degree of compression of no more than 84%less compared to conventional compression, and therefore the powder source material impact on the subsequent stage of the heat treatment, therefore, the result can be increased fibre density of the superconductor. On the other hand, the stage rolled wire do with the degree of compression of no more than 84%less compared to conventional compression, so that the gaps in the powder source material is essentially not formed, resulting in can be suppressed formation of gaps perpendicular to the longitudinal direction of the oxide superconducting wire. Thus, it can be enhanced critical current density of the oxide superconducting wire. In addition, the stage rolled wire is preferably performed with a degree of compression of no more than 80%, so that the powder source material are not formed surface pores, which may be even more suppressed Faure is the funding gap, perpendicular to the longitudinal direction of the oxide superconducting wire.

Throughout this description, the degree of compression (in %) is defined as follows:

[Equation 1]

The degree of compression (%) = (1 - wire thickness after rolling/wire thickness before rolling) × 100.

In the aforementioned method of manufacturing an oxide superconducting wire heat treated wire is preferably performed many times, and at least one of the multiple heat treatments performed in the atmosphere of high pressure, the total pressure which is at least 1 MPa and less than 50 MPa.

Thus, there can be suppressed the formation of gaps between the oxide superconducting crystals during thermal treatment and usercost on the oxide superconducting wire.

The oxide superconducting wire having an oxide superconductor with a higher density after sintering, can be manufactured by the following manufacturing method. In addition, the oxide superconducting wire can be transformed (converted) into the oxide superconducting wire having an oxide superconductor with a higher density after sintering, by using the following method reformation:

a method of manufacturing an oxide superconducting wire with the according to the present invention includes a stage of preparation of the wire, has a configuration obtained by coating the metal powder source material for an oxide superconductor, and the stage of heat treatment by performing heat treatment of the wire in an atmosphere of high pressure, the total pressure which during the heat treatment is at least 1 MPa and less than 50 MPa. In the course of raising temperature before heat treatment under heat treatment, the pressure increase begins with the temperature at which the 0.2%conditional yield strength of the metal used for coating, less the total pressure during the heat treatment.

The way of reformation of the oxide superconducting wire according to the present invention includes a stage heat treatment of the oxide superconducting wire having a configuration obtained by coating a metal oxide superconductor, in an atmosphere of high pressure, the total pressure which during the heat treatment is at least 1 MPa and less than 50 MPa. When the temperature before heat treatment under heat treatment, the pressure increase begins with the temperature at which the 0.2%conditional yield strength of the metal used for coating, less the total pressure during the heat treatment.

According to the proposed in the present invention the method of manufacturing or proposed by the present invention method reformation of the oxide superconducting wire, pressure to the wire is applied in a state in which the 0.2%conditional yield strength of the metal used for coating, less the total pressure in the atmosphere of heightened pressure during the heat treatment. Thus, the metal part that perceives the compressive force due to the increased pressure, easily shrinks due to the effect similar to hot processing. Therefore, the wire is compressed before creating high pressure gas seeps into the wire through the surface pores, resulting in increased pressure can effectively suppress the formation of gaps and userquota. As a consequence, can be improved density after sintering of the oxide superconductor, so that may be a superior critical current density of the oxide superconducting wire.

Another method of manufacturing an oxide superconducting wire according to the present invention includes a stage of preparation of wire that has a configuration obtained by coating containing silver powder metal source material for an oxide superconductor, and the stage of heat treatment by performing heat treatment of the wire in an atmosphere of high pressure, the total pressure which during the heat treatment is at least 1 MPa and less than 50 MPa. In the course of increasing the pace of atory before heat treatment under heat treatment, the pressure increase start after as the temperature of the atmosphere exceeds 400aboutC.

Another way of reformation of the oxide superconducting wire according to the present invention includes a stage heat treatment by performing heat treatment of the oxide superconducting wire having a configuration obtained by coating containing silver metal oxide superconductor, in an atmosphere of high pressure, the total pressure which during the heat treatment is at least 1 MPa and less than 50 MPa. In the course of raising temperature before heat treatment under heat treatment increased the pressure starts after the temperature of the atmosphere exceeds 400aboutC.

According to the proposed in the present invention the method of manufacturing or proposed in the present invention method reformation of the oxide superconducting wire, the pressure to the wire is applied in a state in which the 0.2%conventional yield strength containing silver metal is reduced to a level equal to the total pressure of the atmosphere increased pressure during the heat treatment. Thus, the metal part that perceives the compressive force due to the increased pressure, easily compressed because of the effect similar to hot processing. Therefore, the wire is compressed before creating high Yes what of the gas seeps into the wire through the surface pores, resulting in the formation of gaps and puzyrchatogo at high pressure can be sufficiently suppressed. As a consequence, can be improved density after sintering of the oxide superconductor, so that may be a superior critical current density of the oxide superconducting wire. The oxide superconducting wire having an oxide superconductor having a density after sintering, the component of at least 95%, is obtained using the above-mentioned manufacturing method or the above-mentioned method of reformation, regardless of the presence or absence of surface pores.

And in the above method of manufacture, and in the aforementioned method of reshaping the pressure increase is preferably starts after the temperature of the atmosphere exceeds 600aboutWith increasing temperature before heat treatment under heat treatment.

Thus, pressure is applied to the wire in a state in which the 0.2%conventional yield strength containing silver metal is reduced to about half of the total pressure of the atmosphere increased pressure during the heat treatment. Due to this, the metal part that perceives the compressive force due to the increased pressure, is compressed more easily. As a consequence, the density after sintering OK odnogo superconductor can be improved even more, so even more can be enhanced critical current density of the oxide superconducting wire. The oxide superconducting wire having an oxide superconductor having a density after sintering, the component at least 97%, obtained using the above-mentioned manufacturing method or the above-mentioned method of reformation, regardless of the presence or absence of surface pores.

And in the above method of manufacture, and in the aforementioned method of reshaping the rate of pressure increase is preferably at least 0.05 MPa/min.

The authors of the present invention found that the rate of increase of the pressure of the gas seeping into the wire through the surface pores at the stage of heat treatment is less than about 0.05 MPa/min. So the pressure in the atmosphere may be continuously maintained above the internal pressure of the wire by adjusting the total pressure of the atmosphere for continuous improvement with a speed of at least 0.05 MPa/min. during raise the temperature before heat treatment. Thus, to the wire during a temperature increase before heat treatment can be applied compressive force, regardless of the presence or absence of surface pores in the wire at the stage of heat treatment, resulting in suppressed is formirovanie gaps and the emergence of puzyrchatogo. As a consequence, the density after sintering of the oxide superconductor can be effectively improved by heat treatment in an atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa, and thus can be effectively improved critical current density of the oxide superconducting wire.

And in the above method of manufacture, and in the aforementioned method of reshaping the rate of pressure increase is preferably at least 0.1 MPa/min

Thus, the pressure in the atmosphere can be maintained higher than the internal pressure in the wire. Therefore, the compressive force may be even more attached to the wire during a temperature increase before heat treatment, regardless of the presence or absence of surface pores in the wire at the stage of heat treatment, resulting in suppressed the formation of gaps and userquota. As a consequence, the density after sintering of the oxide superconductor can be more effectively increased by heat treatment in an atmosphere of high pressure in at least 1 MPa and less than 50 MPa, and can be more effectively improved critical current density of the oxide superconducting wire.

When the rate of increase of the pressure set at the level of at least 0.15 MPa/min to about what their cases started increasing pressure after as the temperature of the atmosphere reaches respectively 400aboutC and 600aboutWith, you receive an oxide superconducting wire having an oxide superconductor having a density after sintering, the component at least 99%, regardless of the presence or absence of surface pores.

In the aforementioned method of manufacturing a powder source material for an oxide superconductor contains a Bi2223 phase, and thus the oxide superconducting wire is annealed in an oxygen-containing atmosphere at a temperature of at least 100aboutWith not more than 600aboutWith, at the stage of heat treatment.

Thus, all the wire improves the critical current density Jwithat low temperature at about 20K.

The effect of the invention

As proposed in the present invention a superconducting device, the number of gaps in the oxide superconductor is so extremely small that the liquid refrigerant is not essentially seeps into the gaps of the oxide superconductor. Therefore, when the temperature increases from the state of immersion in the liquid refrigerant to a normal temperature without temperature control the amount of evaporated liquid refrigerant is extremely small. As a result, the internal pressure of the oxide superconducting wire is essentially not increased, uspokojenie can be suppressed.

BRIEF DESCRIPTION of DRAWINGS

Figa is a view in cross section of a superconducting cable according to the first variant implementation of the present invention.

Figw - enlarged view of the cable conductor by Figa.

Figure 2 is a partial detail view in perspective schematically showing the structure of an oxide superconducting wire.

Figure 3 - flow chart, showing the stage of manufacturing the oxide superconducting wire.

4 is a schematic view in cross section of the device hot isostatic pressing (GISP).

Figure 5(a)-5(d) schematic image, Paladino shows the behavior of the gaps between the oxide superconducting crystals.

6 is a chart showing the relation between the total pressure P (MPa) atmosphere of high pressure and number of userquota on the wire (number/10 m).

Fig.7 is a graph showing the total pressure and partial pressure of oxygen in the gas mixture, prepared at a ratio of approximately 80% nitrogen and about 20% oxygen.

Fig - chart showing the relation between the total pressure and oxygen concentrations in the case of an assignment of oxygen partial pressure constant.

Figa is a graph showing the relationship between time and temperature of the wire in case of execution speed reduction giving is placed directly after heat treatment.

Figw - chart showing the relation between time and the total pressure in the vessel when performing the speed control of the pressure reduction immediately after treatment.

Figa is a chart showing the thickness of the oxide superconducting wire having no surface long before heat treatment and after heat treatment in the atmosphere of high blood pressure.

FIGU is a chart showing the thickness of the oxide superconducting wire having surface pores, before heat treatment and after heat treatment in the atmosphere of high blood pressure.

11 is a partial detail view in perspective, schematically depicting the structure of an oxide superconducting wire having surface pores.

Fig is a schematic view in cross section showing the method of rolling in the second embodiment.

Fig - flow chart showing other stages of manufacturing the oxide superconducting wire.

Fig is a partial detail view in perspective schematically showing the structure of an oxide superconducting wire after the stage of deposition of silver or a silver alloy on the wire.

Fig - chart showing the relation between temperature and pressure during the heat treatment and time according to the fourth method in the second embodiment is carried out is I.

Figa is a graph showing the relation between temperature at the stage of heat treatment and the time when the proportion of silver is 1.5, in the second embodiment of the present invention.

Figw - chart showing the relation between the pressure at the stage of heat treatment and the time when the proportion of silver is 1.5, in the second embodiment of the present invention.

Figs is a graph showing the relationship between the concentration of oxygen at the stage of heat treatment and the time when the proportion of silver is 1.5, in the second embodiment of the present invention.

Fig.16D - chart showing the relation between the partial pressure of oxygen at the stage of heat treatment and the time when the proportion of silver is 1.5, in the second embodiment of the present invention.

Fig - chart showing the relation between temperature and pressure at the stage of heat treatment and time according to the fifth method in the second embodiment of the present invention.

Fig is a graph showing the optimum combination of temperature and partial pressure of oxygen during the heat treatment.

Fig - view in cross-section, schematically showing the structure of an oxide superconducting wire having the rest of it stand restie pores.

Fig is a diagram schematically showing the relation between degrees of compression and critical current density in the primary rolling in the oxide superconducting wires.

Fig - chart showing the approximate ratio of temperature, total pressure and partial pressure of oxygen when the temperature before heat treatment and during heat treatment and time according to the sixth method in the sixth embodiment of the present invention.

Fig is a graph showing the relationship between velocity pressure and the density after sintering at different temperatures start increasing the pressure.

Fig is a graph showing the temperature dependence of 0.2%of the conventional yield strength of silver.

Fig - chart showing the relation between the densities after sintering of oxide superconductors and values of the critical current of the oxide superconducting wires.

Fig - chart showing the approximate ratio of temperature, total pressure and partial pressures of oxygen and time in the case of performing annealing after heat treatment in the seventh embodiment of the present invention.

Fig is a graph showing the values of the critical current Iwithat appropriate temperatures (in K) on the sydnaya superconducting wires before annealing and after annealing, performed at a temperature of 500aboutC.

LIST of REFERENCE NUMBERS

1, 1A, 1b oxide superconducting wire, 2 - fiber oxide superconductor, 3 - shell, 4 - gas inlet, 5 - upper lid 6 is a cylindrical vessel, 7 - thermal barrier, 8 - processed product, 9 - heater, 10 - bearing, 11 - lower cover, 12 - superconducting crystal, 13 - press hot isostatic pressing, 14 - surface time, 15 - swath, 15A - surface roll, 16 - silver or silver alloy, 20 - gap, 30 - superconducting cable, 31 - lived cable, 32 - bearing frame for winding, 34 - insulating paper, 35 - Kraft paper, a 37 - channel for the refrigerant, 38 - adiabatic pipe 39 - corrosion layer.

The BEST WAYS of carrying out the INVENTION

Embodiments of the present invention are described below with reference to the drawings.

The first option exercise

Figa shows a view in cross section of a superconducting cable according to the first variant implementation of the present invention, and Figv shows the enlarged view of the cable conductor by Figa.

Addressing Figa and 1B, a superconducting cable 30 contains the cable core 31, adiabatic pipe 38 and an anticorrosive layer 39. Each single-fibre or twisted multi-fiber cable lived 31 is inserted into the channel 37 of the refrigerant generated within Adia eticheskoi pipe 38 and an anticorrosive layer 39. The refrigerant circulates along the outer periphery of the cable core 31 in the channel 37 of the refrigerant. Cable lived 31 consists of a supporting frame 32 for winding (of multiple copper strands or wires), many of oxide superconducting wires 1A, Kraft paper 35, one of many oxide superconducting wires 1b and insulating paper 34 in order from the inside out. Ribbon-like oxide superconducting wire 1A and 1b helically wound on the outer periphery of the supporting frame 32 for winding consisting of a number of copper strands (wires) with an external diameter of, for example, 20 mm Many of oxide superconducting wires 1A and a lot of the oxide superconducting wires 1b, forming a layered structure, isolated from each other Kraft paper 35. In the lower layer of the multiple oxide superconducting wire 1A is placed, for example, 13 of the oxide superconducting wires 1A increments of 200 mm In the top layer of the multiple oxide superconducting wires 1b are, for example, 14 of the oxide superconducting wires 1b increments of 200 mm Each of the oxide superconducting wires 1A and 1b has a rectangular cross section with dimensions of, for example, 0.21 mm × 4,1 mm Oxide superconducting wire 1b is covered with insulating paper 34, made for example of polypropylene laminated paper (PPLR(R)).

The following describes the structure of each of the sydnaya superconducting wire, part of the superconducting cable.

Figure 2 is a partial detail view in perspective schematically showing the structure of an oxide superconducting wire.

Multi-fiber oxide superconducting wire, for example, is described with reference to Figure 2. The oxide superconducting wire 1 has many passing longitudinally of the fibers 2 of oxide superconductor and closing their shell 3. The material of each of this set of fibers 2 of oxide superconductor preferably has a composition, for example, on the basis of Bi-Pb-Sr-Ca-Cu-O, and in which the material containing the Bi2223 phase, having an atomic ratio (bismuth and lead):strontium:calcium:copper, essentially amounting to approximately 2:2:2:3 is the most optimal. Sheath material 3 is, for example, of silver.

Although the above has been described a multi-fiber wire, alternatively, can be used an oxide superconducting wire having a single-fibre structure and formed by a single fiber 2 of oxide superconductor coated 3.

The following describes a method of manufacturing the above-mentioned oxide superconducting wire.

Figure 3 is a process flowchart showing the stage of manufacturing the oxide superconducting wire.

Referring to Figure 3, the first metal is th tube load the powder source material for an oxide superconductor (stage S1). This powder source material for an oxide superconductor, for example, consists of a material containing a Bi2223 phase.

The metal tube is preferably made of silver or silver alloy having a high thermal conductivity. Thus, the heat generated in the case where the superconductor partially undergoes "damping" (loss of superconductivity), can be quickly allocated from this metal tube.

Then a metal tube, loaded with powder source material is treated in the wire of the desired diameter by drawing (stretching) in the wire (stage S2). So, get a wire that has a configuration obtained by coating the metal powder source material for oxide superconducting wire. For manufacturing a multi-fiber wire in a metal tube insert lots of drawn wires, with the subsequent drawing into wire. Primary rolling carry out on the wire (stage S3), and then performing the first heat treatment (stage S4). During these operations from a powder source material is formed of an oxide superconducting phase. Secondary rolling carry out on the wire, the last heat treatment (stage S5). Thus, eliminate voids formed in the first heat treatment. The second heat treatment performed on the WTO is ichno laminated wire (stage S6). This is the sintering of the oxide superconducting phase, and at the same time during the second heat treatment is allocated oxide superconducting phase.

The above method can be manufactured, for example, an oxide superconducting wire shown in figure 2.

According to this variant implementation, at least either the first heat treatment (stage S4)or the second heat treatment (stage S6) is performed in an atmosphere of high pressure, which as a total pressure exert a pressure of at least 1 MPa and less than 50 MPa.

The heat treatment in the atmosphere of high pressure is performed, for example, by hot isostatic pressing (GISP). The following describes this hot isostatic pressing.

Figure 4 is a schematic view in cross section of the device hot isostatic pressing (GISP).

Referring to Figure 4, the unit 13 for performing a hot isostatic pressing consists of a cylindrical vessel 6 high pressure, the top cover 5 and the bottom cover 11 covering both ends of the cylindrical vessel 6 high pressure input 4 gas provided on the top cover 5 for the introduction of gas into the cylindrical vessel 6 high-pressure heater 9, the heating of the processed product 8, thermal barrier 7 and the support 10, on which the location is N. the processed product 8.

According to this variant implementation, the cylindrical vessel 6 high pressure in the quality of the processed product 8 on the support 10 install wire prepared by loading a metal tube with powder starting material and subsequent drawing wire and rolling. In this state, in a cylindrical vessel 6 high pressure from the inlet 4 gas enter the appropriate gas, resulting in a cylindrical vessel 6 high pressure is formed in the atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa, so that the wire 8 is heated by the heater 9 to a predetermined temperature, in this atmosphere of increased pressure. Such heat treatment is preferably performed in an oxygen atmosphere, and the oxygen partial pressure is preferably at least of 0.003 MPa and not more than 0.02 MPa. Thus, the wire 8 perform the heat treatment and hot isostatic pressing.

According to this variant implementation, the heat treatment is performed in an atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa, according to the above, to achieve, mainly the following three effects.

First, it can be reduced the number of gaps formed between the oxide superconducting crystals during thermal treatment.

AB the ora of the present invention have found, the number of gaps between the oxide superconducting crystals, mainly formed during the heat treatment can be greatly reduced by performing heat treatment in an atmosphere of increased pressure which is at least 1 MPa, as compared to the case with a pressure less than 1 MPa.

Figure 5(a)-5(d) are schematic diagrams Paladino shows the behavior of the gaps between the oxide superconducting crystals.

Referring to Figure 5(a)-5(d), the contact area between the oxide superconducting crystals formed during the heat treatment increases due to plastic deformation when performing heat treatment in an atmosphere of high pressure, with fewer gaps ranging in size from several microns to several tens microns, present between the superconducting crystals (Figure 5(a)-5(b)). When this condition is maintained, then it is the creep strain, as shown in Figure 5(C), which reduces the gaps present at the transition boundary, and contaminated part, such as an oxide film, partially destroyed/degraded, causing the diffusion of atoms and the continuation of sintering. Finally, most of the gaps between the superconducting crystals disappears, as shown in Figure 5(d), with the formation of a stable transition boundaries of the partition.

Applying a current in a superconducting wire means passing current between the superconducting crystals, forming a superconducting wire. Typically, the transition between the superconducting crystals, showing the status of weak superconductivity and superconducting crystals have stronger superconductivity than the transition between the crystals), limits the amount of noise current, while maintaining the superconducting state (without any electrical resistance) in refrigerant (for example, liquid nitrogen or liquid helium) to use superconducting wires and cooling of the refrigerating device (refrigerator). Under normal annealing under atmospheric pressure in the transition between the superconducting crystals inevitably remain gaps. Therefore, the number of gaps between the superconducting crystals can be reduced (density after sintering of the superconductor can be improved) by heat treatment in an atmosphere of high pressure, resulting in improved performance superconducting wires and can be prevented by reducing the critical current density.

In particular, the density after sintering of the oxide superconductor, the last heat treatment at atmospheric pressure is from 80 to 90% for oxide superconducting what the wires contains a Bi2223 phase, while the density after sintering the fibers of the oxide superconductor obtained by the manufacturing method according to the present invention when setting the total pressure in the atmosphere of high pressure to 10 MPa, was at least 93%, and has been found to decrease the number of gaps formed between the oxide superconducting crystals.

The oxide superconducting wire obtained by using the above manufacturing method, applied in a superconducting device, such as superconducting cables, since the liquid refrigerant is not essentially seeps into the gaps of the oxide superconductor. Even when the temperature without temperature control, when the superconducting device is heated from the state of immersion in the liquid refrigerant to the normal temperature, for this reason, the liquid refrigerant is not essentially evaporates. As a result, the internal pressure of the oxide superconducting wire is essentially not increased, and in a superconducting device such as a superconducting cable can be suppressed swelling.

Secondly, it can be prevented the emergence caused by heat treatment of puzyrchatogo on the oxide superconducting wire.

The authors of the present invention have studied a number of userquota, about razvivayushihsya during heat treatment of the wire in those cases, when varying the total pressure during the heat treatment of the oxide superconducting wire in an atmosphere of high pressure. 6 is a diagram showing the relation between the total pressure P (MPa) in the atmosphere of high pressure and number of userquota (number/10 m) in this wire.

Referring to Fig.6, we can see that the number of userquota in the oxide superconducting wire markedly decreased in the case where the total pressure of the atmosphere increased pressure exceeded 0.5 MPa, and puzyrchatogo in the oxide superconducting wire essentially disappear when the total pressure exceeds 1 MPa. These results, presumably, were obtained for the following reasons.

The powder of the oxide superconductor in a metal tube usually has before sintering the fill factor is about 80% of theoretical density, and therefore in the gaps powder is present in the gas. The gas in the gaps powder volumetrically expands when heated to a high temperature during the heat treatment, and appears usercost. According to this variant implementation, however, the heat treatment is performed in an atmosphere of high pressure of at least 10 MPa, whereby external to a metal pipe pressure can be made higher than the internal pressure of the metal is practical tube. Thus, presumably, prevented the emergence of puzyrchatogo in the presence of gas in the gaps powder.

The authors present invention further investigated the cause of puzyrchatogo on the wire and also found that the adsorbates, such as carbon (C), water (H2O) and oxygen (O2)present due to adhesion to the powder source material for an oxide superconductor, evaporated during sintering and expanding in volume in a metal tube, with heaving wire this gas. However, this usercost wires, resulting from evaporation of the adsorbates on the powder, also allegedly prevented by performing heat treatment in an atmosphere of high pressure of at least 1 MPa, because the external pressure can be made higher compared with the internal pressure in a metal tube.

Thus, not only usercost arising due to the presence of gas in the gaps of the powder source material for an oxide superconductor, but also usercost resulting from evaporation of adsorbates present on the surfaces of its grains due to adhesion, can, presumably, be essentially eliminated by setting the total pressure of the atmosphere increased pressure at the level of at least 1 MPa. Puserdata the ü oxide superconducting wire causes a decrease in the critical current density, and so the decline of this critical current density can be prevented by preventing the emergence of puzyrchatogo on the wire.

Thirdly, can be simplified regulation of the partial pressure of oxygen during the heat treatment.

The authors of the present invention found that the 2223-phase oxide superconductor based on Bi stably formed in the case, when the partial pressure of oxygen regulate at the level at least of 0.003 MPa and not more than 0.02 MPa, regardless of the total pressure. In other words, if the partial pressure of oxygen greater than 0.02 MPa, formed heterophase, such as Ca2PbO4and if the partial pressure of oxygen is less than 0,003 MPa, the Bi2223 phase is formed it is difficult, which reduces the critical current density.

Fig.7 is a graph showing the total pressure and the partial pressure of oxygen in the mixed gas prepared in the ratio of about 80% nitrogen and about 20% oxygen. Fig is a diagram showing the relation between the total pressure and oxygen concentrations in the case of an assignment of oxygen partial pressure constant.

Referring to Fig.7, when, for example, the total pressure of the atmosphere increased pressure corresponds to the atmospheric pressure of 1 ATM (0.01 MPa), the partial is providing oxygen level equivalent to 0.2 ATM (0.02 MPa), shown in dashed lines, and the Bi2223 phase is formed stably without control of oxygen partial pressure. By increasing the total pressure of the atmosphere high pressure up to 2 ATM (0.2 MPa), 3 bar (0.3 MPa) and the like, the partial pressure of oxygen also increases and exceeds shown by the dotted line level at 0.2 ATM (0.02 MPa). As a result, the Bi2223 phase is not formed a stable manner. Therefore, the oxygen partial pressure must be regulated at the level at least of 0.003 MPa and not more than 0.02 MPa by changing the relationship of mixing (proportion) of gaseous oxygen in the mixed gas, as shown in Fig. The dotted line on Fig shows the level at 0.2 ATM (0.02 MPa), similar to the dotted lines in Fig.7.

In practice, the partial pressure of oxygen regulate when tracking (monitoring) of the total pressure and oxygen concentration. In other words, the partial pressure of oxygen is calculated by multiplying the value of the total pressure on the oxygen concentration. Thus, if the total pressure is, for example, 50 MPa, the oxygen concentration is 0.01% in the case where the heat treatment is performed at a partial oxygen pressure of 0.005 MPa. Therefore we introduce the mixed gas must be adjusted to measure the oxygen concentration of 0.01%. However, the measurements of oxygen concentration of 0.01% leads to significant measurement errors, and so it is difficult to properly control the partial pressure of oxygen in the processing chamber by regulating the amount of gaseous oxygen in the introduced mixed gas. According to this variant implementation, the oxygen concentration can be maintained at a level less affected by measurement errors, by setting the total pressure in the atmosphere of high pressure at less than 50 MPa, resulting in the partial pressure of oxygen can be easily adjusted.

When heat treatment is performed in an atmosphere of high pressure in at least 1 MPa, the rate of pressure reduction is preferably adjusted so as to avoid a sharp drop of pressure in the atmosphere of heightened pressure during the heat treatment and after heat treatment.

When heat treatment is performed in an atmosphere of high pressure in at least 1 MPa, supplied from the outside gas, presumably, seeps into the wire through the surface pores of the wire and balances the internal and external pressure in the wire with each other. The authors of the present invention found that the gas inside can not keep up with the reduction in ambient pressure, and therefore the internal pressure exceeds the external pressure with the formation of puzyrchatogo in the case when the external pressure is reduced, for the reasons for the sharp drop in pressure in this high pressure environment.

Therefore, to prevent this puzyrchatogo in the vessel during heat treatment is preferably introduced mixed gas of an inert gas, such as Ar (argon) or N2(nitrogen), and gaseous oxygen (O2) so that the total pressure remains constant. When the temperature drops immediately after the heat treatment, in addition mixed gas of inert gas and oxygen gas is introduced into the vessel to compensate for the pressure reduction caused by the temperature decrease. The formation of puzyrchatogo due to a sharp reduction in pressure can be prevented by regulating these speeds reduce the pressure during the heat treatment and the temperature immediately after the heat treatment.

Figa is a graph showing the relationship between time and temperature of the wire in the vessel is subjected to speed control pressure directly after heat treatment. FIGU is a graph showing the relationship between time and the total pressure in the vessel is subjected to speed control of pressure reduction immediately after treatment.

Addressing Figa and 9B, the total pressure is regulated at a constant level, as shown in Figv, during the heat treatment (temperature of approximately 800about(C)shown in Fi is A. In other words, the gaseous oxygen in the vessel is consumed during heat treatment due to the oxidation of a support, on which is mounted a wire in the heating vessel, or the like, and therefore the pressure in the vessel decreases. To prevent this, in the vessel, introducing the mixed gas to maintain the pressure constant. In the course of lowering the temperature (temperature range from about 800aboutWith up to approximately 300about(C) immediately after the heat treatment shown in Figa, the mixed gas is introduced into the vessel to compensate for the pressure reduction caused by the temperature decrease, as shown in Figv, to regulate the rate of pressure reduction. In other words, the gas pressure also begins to decline sharply with regard to the equation of state of the gas due to the reduction of temperature in the course of such a lower temperature, and therefore pressure reduction should be slowed down by introducing a mixed gas. At a temperature in the range of not higher than 300aboutWith the pressure in the wire is already quite low, because the temperature is low in comparison with the case of the approximately 800aboutWith up to approximately 300aboutC. Therefore, usercost on the wire does not occur even in the case when the rate of pressure reduction is not regulated.

The authors present invention also found that the range of speeds reduce the pressure required to prevent vosn is knowone puzyrchatogo on the oxide superconducting wire, varies with a change in the ratio of the area of the metal part to the area of the oxide superconductor cross-section of the wire (the proportion of silver) after heat treatment. In other words, the rate of pressure decrease in the course of lowering the temperature (in the temperature range from 800aboutWith up to 300aboutC) directly after heat treatment does not exceed 0.05 MPa/min, if the proportion of silver is 1.5, and the rate of pressure decrease in the course of lowering the temperature (in the temperature range from 800aboutWith up to 300about(C) immediately after the heat treatment is less than 0.03 MPa/min, if the proportion of silver is 3.0.

Although the method of manufacturing an oxide superconducting wire having a Bi2223 phase, by hot isostatic pressing set forth with reference to this alternative implementation, the present invention can also be implemented using other way of pressing, not hot isostatic pressing, provided that it is a method of performing heat treatment in an atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa. In addition, the present invention is also applicable to the method of manufacturing an oxide superconducting wire having a different composition, such as the composition of yttrium, and not the composition on the basis of bismuth.

The second option exercise

Figa p is ecstasy a graph showing the thickness of the oxide superconducting wire having no surface long before heat treatment and after heat treatment in the atmosphere of high pressure. FIGU is a graph showing the thickness of the oxide superconducting wire having surface pores. Conditions of the heat treatment according Figa and 10V are: the total pressure is 20 MPa, the partial pressure of oxygen - 0,008 MPa, a temperature of 825aboutWith some atmosphere, and duration of heat treatment is 50 hours.

Addressing Figa, the thickness of each oxide superconducting wire having no surface pores decreased after heat treatment at a value of from about 0,006 mm to 0.01 mm Is due to the fact that the number of gaps between the oxide superconducting crystals decreased, and therefore excluded the appearance of puzyrchatogo on the oxide superconducting wire due to heat treatment in an atmosphere of high pressure with the total pressure of 20 MPa. Addressing Figv, on the other hand, the thickness of each oxide superconducting wire having surface pores decreased after heat treatment only to the value of about from 0.002 mm to 0.005 mm, and the decline in the number of gaps between the oxide superconducting crystals and suppression of puzyrchatogo oxide superconducting wire is provided in defects in the exact degree. In addition, the thickness of one plot (plot A) wire with "prisoners" (closed) surface pores, after heat treatment increased in comparison with the thickness before heat treatment.

Thus, it was found that the formation of gaps and userquota can be effectively suppressed by heat treatment in the proposed range of pressures (at least 1 MPa and less than 50 MPa) according to the first variant of implementation in the case when the surface pores are absent, while the formation of gaps and userquota cannot sufficiently be suppressed simply by heat treatment in the proposed range of pressures according to the first variant of implementation in the case when the surface pores are present.

During the heat treatment in the atmosphere of high pressure according to the present invention the plastic deformation and creep deformation of the superconducting crystals formed during the heat treatment caused a lot of pressure on the outside of the wire constituting at least 1 MPa, which suppresses formed during thermal treatment of the gaps between the oxide superconducting crystals. In addition, the expansion of the gas in the gaps of the powder of the oxide superconducting crystals formed during the heat treatment, and gas that is present due to the desii on the powder of the oxide superconducting crystals, formed during the heat treatment, may be excluded during the heat treatment due to the pressure on the outside of a metal tube, resulting in preventing the emergence of puzyrchatogo on the oxide superconducting wire. As a consequence, prevents the reduction of the critical current density due to gaps or usertostame.

In the wire, having surface pores, creating a high pressure gas seeps into the wire through these surface pores despite the heat treatment in the above-mentioned atmosphere of high pressure, and therefore no difference between internal and external pressures of the wire, and thus the formation of gaps and puzyrchatogo suppressed due to the increased pressure is not sufficient. As a consequence, reduces the effect of preventing the decrease of the critical current density.

The authors of the present invention performed in-depth research to develop techniques that are able to sufficiently suppress the generation gap and userquota in forming wire, no surface long before heat treatment.

According to the first method, the thickness of the outer layer of the shell of the oxide superconducting wire set at the level of at least 20 μm after rolling (stage S3 or S5) and before heat treatment (stage S4 or the adiya S6) figure 3.

According to the second method, the surface roughness Ry of the surface of those parts of the rolls, which are used to perform shown in Figure 3 rolling (stage S3 or S5) and in contact with the wire, set at the level of not more than 320 nm.

According to the third method, the oxide superconducting wire perform electrodeposition of silver or silver alloy (plating) after rolling (stage S3 or S5) and before heat treatment (stage S4 or S6) figure 3.

Below is a detailed description of these methods.

The authors of the present invention have found that the surface pores are not formed during rolling (stage S3 or S5) in the case when the thickness W of the outer layer of the shell of the oxide superconducting wire is installed at the level of at least 20 μm on each plot after rolling (stage S3 or S5) and before heat treatment (stage S4 or S6) figure 3, as in the first method.

11 is a partial detail view in perspective showing the structure of an oxide superconducting wire having surface pores.

The thickness W of the outer layer sheath denotes the distance W between the fibers 2 of oxide superconductor, located in the outer peripheral area in the cross section of the wire 1, and the outer surface of the wire 1 after rolling, as shown in figure 11. When the thickness W of the outer layer of the shell was the set at the level of at least 20 μm, no surface pores 14 formed was not, presumably, for the following reasons.

Surface pores 14 are formed mainly by holes penetrating from the outside into the fibers 2 of oxide superconductor, when the surface of the wire 1 is attached to the roughness due to friction between the wire 1 and the pinch rollers. However, when the oxide superconducting wire 1 was laminated so that the thickness W of the outer layer of the shell was at least 20 μm on each plot after rolling, whatever the surface pores 14, penetrating from the outside into the fibers 2 of oxide superconductor formed were not. The structure shown at 11, is essentially identical with the structure shown in figure 2, except for the above point, and therefore, the same elements are denoted by the same reference numbers, positions, and redundant description is not repeated.

The authors of the present invention found that the wire that does not have surface pores 14, is obtained before heat treatment in the case of the above-mentioned second and third methods are also used, when the thickness W of the outer layer of the shell laminated oxide superconducting wire is less than 20 μm, and the formation of gaps and puzyrchatogo when this is suppressed by the heat treatment in the atmosphere of heightened Yes the population, and at the same time effectively prevents the reduction of the critical current density.

Fig is a schematic view in cross section illustrating the method of rolling in accordance with the second embodiment.

Addressing Pig, rolling is a method of treatment by passing material such as plates or rods through multiple (usually two) rotating rolls 15 to reduce its thickness or cross-sectional, thus forming the cross-section of the desired shape. During rolling of the oxide superconducting wire 1 to be drawn into the solution between multiple rolls 15 by friction forces on the rolls 15 and deform the compressive force developed by the surfaces 15A of the rolls 15.

According to the second method, the rolls 15, having a surface roughness Ry of the surface is not more than 320 nm on the surfaces 15A in contact with the wire 1, used at least either the first rolling (stage S3), or when the secondary rolling (stage S5)shown in Figure 3.

In other words, the friction between the wire 1 and the surfaces 15A of the rolls 15 is reduced to such an extent that the surface of the wire 1 is not essentially becomes roughness, and the wire 1, having surface pores, get, regardless of the thickness of the outer layer sheath wire 1 in the case when the surface roughness Ry of the surface 15A used in the rolling rolls no greater than 320 nm. Therefore, creating a high pressure gas escapes in the wire 1 through the surface pores on the stage of heat treatment. Thus, the formation of gaps and userquota mentioned on stage performing heat treatment in an atmosphere of high pressure is suppressed regardless of the thickness W of the outer layer sheath wire 1, and effectively prevents the reduction of the critical current density.

Fig is a process flowchart showing the other stages of manufacturing the oxide superconducting wire.

According to the third method, after rolling (stage S3 or S5) and before heat treatment (stage S4 or S6) on the wire surface perform electrodeposition (stage S11 or S12) of silver or a silver alloy, as shown in Fig. This method is essentially identical to the method according to Figure 3, except that additionally perform the electrodeposition (stage S11 or S12), and it is therefore appropriate stage corresponding reference numbers, and redundant description is not repeated.

Fig is a partial detail view in perspective schematically showing the structure of an oxide superconducting wire after the stage of deposition of silver or a silver alloy on the wire.

Addressing Pig, the outer periphery of the shell 3 was covered by electr the deposition of silver or silver alloy 16, whereby opening to the outside surface of the pores 14 were blocked by the silver or silver alloy 16. In the rest of the structure are essentially the same with the structure according to Figure 2, and therefore, the same elements are denoted by the same reference numbers, positions, and redundant description is not repeated.

In General, the proportion of silver in the oxide superconducting wire 1 minimize in order to increase the current value of superconductivity transmitted per unit area. In the wire 1 having a small proportion of silver, however, the proportion of the metal parts is so small that the thickness W of the outer layer of the shell cannot be increased. Therefore, the thickness of the outer layer of the sheath wire 1 having a small proportion of silver is less than 20 μm, and the surface of the pores 14 are easily formed during processing (e.g., by rolling) before stage heat treatment. In the wire 1 having surface pores 14, the formation of gaps and userquota not sufficiently suppressed due to the increased pressure, as mentioned above. Therefore, the effect of preventing the decrease of the critical current density decreases. When at the stage of heat treatment of the wire surface 1 perform the electrodeposition of silver or silver alloy 16, the surface of the pores 14 are blocked by this silver or silver alloy 16, and W is taut from the surface. Therefore, the stage of heat treatment performed after the disappearance of surface pores 14 with the wire 1, and thereby creating a high pressure gas escapes in the wire 1 through the surface pores 14 at the stage of heat treatment. Thus, the formation of gaps and userquota suppressed in the above-mentioned stage performing heat treatment in an atmosphere of high pressure regardless of the thickness W of the outer layer sheath wire 1 and the values of roughness Ry of the surface used for rolling rolls 15, and the reduction of the critical current density is effectively prevented.

The authors of the present invention have found that the formation of gaps and userquota suppressed (density after sintering is improved also in the wire 1 having surface pores 14, and the reduction of the critical current density is effectively prevented when used below the fourth technique or fifth method. According to the fourth method, the pressure to regulate its speed increase following the rise in temperature when the temperature before heat treatment during at least either the first heat treatment (stage S4)or the second heat treatment (stage S6)shown in Figure 3. According to the fifth method, the total pressure of the atmosphere regulate to increase soon with the capacity of at least 0.05 MPa/min. when the temperature before heat treatment in the course, at least either the first heat treatment (stage S4)or the second heat treatment (stage S6)shown in Figure 3. During heat treatment the total pressure of the atmosphere to regulate its continuous improvement. When the temperature drops directly after heat treatment are also regulated to compensate for the lower pressure (to increase pressure)caused by the temperature decrease. First described fourth method.

Fig is a graph showing the relationship between temperature and pressure during the heat treatment and time according to the fourth method of the second variant implementation.

Addressing Pig, the heat treatment is performed under conditions in the form of a heat treatment temperature of 800aboutC and a pressure of 20 MPa. The pressure to regulate its speed increase following the rise in temperature. In other words, the pressure regulating to repeat the process increasing the pressure after keeping a predetermined pressure within the constant time and withstand high pressure during a constant time again when the pressure increases. In particular, in the process of increasing the pressure support level of about 7 MPa, about 10 MPa, about 12.5 MPa and about 15 MPa and about 17 MPa for a constant time. The time interval for which ysenia pressure after standing for a constant time is determined on the basis of measured values of temperature in the atmosphere. In other words, regulate pressure so that the pressure rises to about 7 MPa at room temperature, the pressure increases to about 10 MPa when the temperature reaches approximately 400aboutWith the pressure increases to approximately 12.5 MPa when the temperature reaches 500aboutWith the pressure increases to about 15 MPa, when the temperature reaches 600aboutWith, and the pressure increases to about 17 MPa, when the temperature reaches 700aboutC. In order to form a stable oxide superconducting phase, the partial pressure of oxygen constantly adjust in the range from 0.003 to 0.008 MPa.

In wires with surface pores through these surface pores in the wire seeps creating a high pressure gas, when the stage performing heat treatment in an atmosphere of high pressure is performed using a General method of increasing the pressure, and therefore the difference between internal and external pressures wire disappears, and the effect of preventing the decrease of the critical current density resulting from the presence of gaps and userquota, due to the pressure increase is small. However, when the pressure to regulate its speed increase following the rise in temperature according to the fourth method, the external pressure is increased before creating increased pressure ha is seeping into the wire through the surface pores. As a result, there is a difference between internal and external pressures wire, so that the formation of gaps and userquota suppressed (improves the density after sintering), and effectively prevents the reduction of critical current density regardless of the presence or absence of surface pores in the wire at the stage of heat treatment.

In addition, the formation of gaps and userquota in the wire can be suppressed more effectively by combining the following techniques with the above methods from the first to the fourth. Below is a description of this method.

According to this method, the speed of decrease of pressure (decompression speed) by the total pressure in the atmosphere increased pressure to regulate the level below a constant speed during at least either the first heat treatment (stage S4)or the second heat treatment (stage S6)shown in Figure 3, if the temperature of the atmosphere is at least 200aboutWith on-stage heat treatment.

Figa is a graph showing the relation between temperature at the stage of heat treatment and time in the case when the proportion of silver in the second embodiment of the present invention is 1.5. FIGU is a graph showing the relationship between the pressure at the stage of heat treatment of the time in that case when the proportion of silver in the second embodiment of the present invention is 1.5. Figs is a graph showing the relationship between the concentration of oxygen at the stage of heat treatment and time in the case when the proportion of silver in the second embodiment of the present invention is 1.5. Fig.16D is a graph showing the relationship between the partial pressure of oxygen at the stage of heat treatment and time in the case when the proportion of silver in the second embodiment of the present invention is 1.5.

Addressing Figa-16D, pressure adjust to a gradual increase followed by a rise of temperature in the atmosphere with increasing temperature before heat treatment, similarly to the above-mentioned fourth method. Although pressure, as we saw, is not supported on the specified level during a constant time Figv, the scale of the elapsed time on FIGU so far beyond the scale Pig that a plot of pressure maintenance looks absent, and the pressure is almost kept at a specified level during a constant time, as in the case shown on Fig. Temperature and pressure are set respectively at the level of 815aboutC and 20 MPa, at this stage, temperature increase, and in this state, heat treatment of the imp who play for 50 hours. When the temperature before heat treatment and during the heat treatment, the rate of pressure reduction in total pressure in the atmosphere of high pressure regulate at the level of not more than 0.05 MPa/min, if the temperature of the atmosphere is at least 200aboutC. After heat treatment, the temperature decrease at 50aboutC/hour. Also after heat treatment, the rate of pressure reduction in total pressure in the atmosphere of high pressure regulate at the level of not more than 0.05 MPa/min, if the temperature of the atmosphere is at least 200aboutC. If the rate of temperature decrease after heat treatment is 50aboutC/h, then the natural rate of pressure reduction followed by a temperature decrease constantly is not more than 0.05 MPa/min, and the rate of pressure reduction can not be adjusted. In addition, the oxygen concentration is maintained at the level of 0.04% before heat treatment, the heat treatment and after heat treatment. Thus, the partial pressure of oxygen is always in the range from 0.003 to 0.008 MPa, and therefore may be formed of a stable oxide superconducting phase.

If the heating vessel is subjected to a sharp decrease in pressure when the temperature in the atmosphere is at least 200aboutWith internal pressure wire manufacture the Xia compared with the external pressure, and on the wire appears usercost. When the rate of pressure reduction in total pressure in the atmosphere increased pressure to regulate values below a constant level, for this reason, the effect of preventing the occurrence of puzyrchatogo on the wire due to sudden reduction of pressure during the heat treatment (before heat treatment, the heat treatment and after heat treatment) becomes more pronounced.

As for the wires with a bit of silver in 3.0, then the reduction rate of the pressure regulating level of 0.03 MPa/min, when the temperature of the atmosphere is at least 200aboutC.

Below is a description of the fifth method. According to the fifth method, the total pressure of the atmosphere to regulate its constant increase with the speed of at least 0.05 MPa/min. when the temperature rises during at least either the first heat treatment (stage S4)or the second heat treatment (stage S6)shown in Figure 3. During heat treatment the total pressure of the atmosphere to regulate its continuous improvement. When the temperature drops directly after heat treatment are also regulated to compensate for the lower pressure (to increase pressure)occurring as a result of lower temperature.

Fig is a graph showing the relationship between the rate is torami and pressures at the stage of heat treatment and time according to the fifth method of the second variant of implementation of the present invention.

Addressing Pig, the pressure is slowly increased according to the equation of state of gas when the temperature before heat treatment, if the temperature of the atmosphere is not more than, for example, 700aboutC. When the temperature exceeds 700aboutWith the pressure of the atmosphere will increase to about 10 MPa. The pressure of the atmosphere increases in one move with the speed of pressure increase, which constitutes at least 0.05 MPa/min.

The authors of the present invention found that the rate of increase of the pressure of the gas seeping into the wire through the surface of the pores is less than about 0.05 MPa/min, when the oxide superconducting wire with surface pores is subjected to heat treatment in an atmosphere of high pressure. Therefore, the atmospheric pressure can be constantly maintained higher than the internal pressure in the wire when the temperature before heat treatment by controlling the total pressure of the atmosphere for continuous improvement with a speed of at least 0.05 MPa/min. when the temperature before heat treatment.

After that, during the heat treatment the temperature of the support at the level of, for example, 830aboutC. on the other hand, the pressure of the atmosphere continuously improve. While the rate of increase of pressure during the heat treatment preferably maximize,the total pressure exceeds 50 MPa, if this speed is too high, and therefore the pressure must be continually improved with an appropriate rate of increase of pressure to the total pressure during the heat treatment does not exceed 50 MPa. Addressing Pig, the pressure is increased to about 30 MPa. So time to trim the internal pressure of the wire and the pressure of the atmosphere with each other may be delayed (delayed) time t1before time t2in comparison with a case of maintaining the pressure constant during the heat treatment. Thus, the state in which the atmospheric pressure is higher than the internal pressure in the wire can be maintained during the heat treatment for a longer period of time.

Then in the course of lowering the temperature directly after heat treatment, the pressure also begins to decrease along with the decrease in atmospheric temperature according to the equation of state of gas. At this time, the pressure is adjusted to compensate (offset) the decrease in pressure due to temperature reduction (to increase pressure). To form a stable oxide superconducting phase, the partial pressure of oxygen is adjusted so that it was constantly in the range of from 0.003 to 0.008 MPa.

According to the fifth method, the pressure in the atmosphere exceeds the internal the pressure of the wire when the temperature before heat treatment, as a result, the wire can be applied compressive force. Moreover, the state in which the pressure of the atmosphere above the internal pressure of the wire can be maintained over a longer period of time during heat treatment. As a consequence, the formation of gaps and userquota suppressed in the course of raising temperature before heat treatment and during the heat treatment, and therefore a reduction of critical current density can be effectively suppressed due to the heat treatment in the atmosphere of increased pressure which is at least 1 MPa, or less than 50 MPa.

Although the above refers to this variant has been described the case of performing the stage of deposition of silver or a silver alloy on the wire, the present invention can also be implemented using, for example, spraying, provided that the deposition of silver or a silver alloy on the wire at this stage. In addition, although Fig and 16A-16D show the specific conditions for the regulation of temperature, pressure, oxygen concentration and partial pressure of oxygen, the present invention is not limited to these conditions, and the pressure may be adjusted for the speed of its increase after the temperature rise and the rate of pressure reduction in total pressure in the atmosphere high is Alenia may be regulated at the level of not more than 0.05 MPa/min, when the temperature in the atmosphere is at least 200aboutC.

The formation of surface pores can be prevented or can be effectively suppressed the formation of gaps and userquota in the formation of surface pores, by combining the techniques from the first to the fifth version of the implementation conditions of the heat treatment according to the first variant implementation.

The formation of gaps and userquota in the wire can be effectively suppressed by appropriately combining the methods from the first to the fifth version of the implementation.

Although the fifth method of this variant has been described with reference to the case of conduct regulation to compensate for the lower pressure (to increase pressure)occurring as a result of lower temperature directly after heat treatment, the present invention also is not limited to this case, and the pressure in the atmosphere can be adjusted for continuous improvement, at least during thermal treatment.

A third option exercise

With the aim of improving the critical current density of the oxide superconducting wire, the authors of the present invention conducted in-depth research concerning the optimal partial pressure of oxygen in the course of temperature increase before termopan is rigid and during the heat treatment. Thus, we have obtained the results presented in Fig.

Fig is a graph showing the optimum combination of temperature and partial pressure of oxygen during the heat treatment.

Addressing Pig, it is seen that a stable oxide superconducting phase is formed, and the critical current density is improved in the temperature range of at least 815aboutWith not more than 825aboutWith at a partial pressure of oxygen, for example, 0.007 MPa. Although it is not shown in this figure, but it should be noted that a stable oxide superconducting phase is formed, and the critical current density is improved in the temperature range comprising at least 750aboutWith not more than 800aboutWith, preferably in the temperature range of at least 770aboutWith not more than 800aboutWhen the oxygen partial pressure is of 0.003 MPa. When the oxygen partial pressure is 0.02 MPa, stable oxide superconducting phase is formed, and the critical current density is improved in the temperature range of at least 820aboutWith not more than 850aboutWith, preferably in the temperature range of at least 830aboutWith not more than 845aboutC. it was Also found that the partial pressure of oxygen should be regulated in the range of at least 0,00005 MPa and not more 02 MPa, when the temperature is not more than 650aboutC.

Based on the above-mentioned relationship between the temperature and the partial pressure of oxygen, the optimal value of partial pressure of oxygen for the formation of an oxide superconducting phase increases following a rise in temperature. Therefore, the oxygen partial pressure can be set in the optimum range for formation of an oxide superconducting phase by regulating the partial pressure of oxygen to increase following the rise of temperature in the atmosphere. Thus, there is a stable oxide superconducting phase, and the critical current density can be improved.

When the wire is maintained at a constant temperature during the heat treatment, often variations (fluctuations) temperature (error) in a few °C (degrees Celsius). Given the relationship between temperature variations and optimal range of oxygen partial pressure, the optimum partial pressure of oxygen is at least 0,006 MPa and not more than 0.01 MPa, when the wire is maintained at a temperature of, for example, 822,5aboutC, while the optimum partial pressure of oxygen is at least 0.07 MPa and not more to 0.011 MPa when the temperature fluctuates around 825aboutC. When the temperature stake is letsa around 820 aboutWith optimal oxygen partial pressure is at least 0,005 MPa and not more than 0,009 MPa. Therefore, the oxygen partial pressure can be regulated to be constant in the range of these fluctuations (shaded area on Fig)comprising at least 0.007 MPa and not more than 0,009 MPa, when the wire is kept at 822,5aboutIn order to provide optimum oxygen partial pressure despite such fluctuations in temperature.

This range of fluctuations in the partial pressure of oxygen is about 10% of the value of oxygen partial pressure. Therefore, the partial pressure of oxygen during the heat treatment is adjusted so that it is constant over the range of fluctuation within 10%, so that the oxygen partial pressure can be set in the optimum range of oxygen partial pressure despite fluctuations in temperature, resulting in the formation of a stable oxide superconducting phase, and can be improved critical current density.

Although with reference to this alternative implementation has been described here as an example, the range of oxygen partial pressure during the increase of temperature before heat treatment and during the heat treatment, the present invention is not restricted to regulation parcial the aqueous oxygen pressure in the range of numeric values, and the partial pressure of oxygen can be adjusted to increase following the rise of temperature in the atmosphere.

The fourth option exercise

To further improve the critical current density of the oxide superconducting wire, the authors of the present invention regulate the rate of pressure reduction in total pressure during the heat treatment at the level of 0.05 MPa/min, and held in-depth study of the relationship between the value of the total pressure and puzyrchatogo on the wire.

Was prepared powder starting material with a composition having a ratio of Bi:Pb:Sr:Ca:Cu= 1,82:0,33:1,92:2,01:3,02. This powder starting material was subjected to heat treatment at 750aboutC for 10 hours, and then heat-treated at 800aboutC for 8 hours. After that, the powder obtained by grinding (heat-treated material) powder was subjected to heat treatment at 850aboutC for 4 hours, and then crushed. Obtained after grinding, the powder was subjected to heat treatment under reduced pressure, and then was loaded into a metal tube of silver with an outer diameter of 36 mm and an inner diameter of 31 mm, Then this metal tube filled her powder was subjected to drawing (stretching) in the wire. Further, the drawn wire in quantity is TBE 61 were rolled into the harness and inserted in a metal tube with an outer diameter of 36 mm and an inner diameter of 31 mm Then were fulfilled the drawing in the wire and primary rolling to obtain a ribbon-like superconducting wire having a Bi2223 phase, of a thickness of 0.25 mm and a width of 3.6 mm, Then the wire was made of the first heat treatment.

The first heat treatment was performed in an atmosphere at a temperature of heat treatment 842aboutAnd during the time of heat treatment for 50 hours. Then after performing the secondary rolling was performed in the second heat treatment. The second heat treatment was performed when setting the partial pressure of oxygen at the level 0,008 MPa, temperature of heat treatment is at the level of 825aboutWith, and the time of heat treatment at 50 hours, with a speed control of pressure reduction by the total pressure during the heat treatment at the level of not more than 0.05 MPa/min. and the variation of the total pressure as shown in Table 1. After the second heat treatment studied the presence/absence of userquota. Table 1 shows the results for the total pressure and the presence/absence of userquota in the wire.

Table 1
Total pressure (MPa)The extension wire
0,1No
0,2No
0,3No
0,4No
0,5No
0,8No
1,0Yes
2,0Yes
3,0Yes
5,0Yes
10,0Yes
20,0Yes
30,0Yes

According to the results presented in Table 1, the wire appears usercost, when the total pressure is at least 1 MPa. Thus, the speed of decrease of pressure in the atmosphere of high pressure must be regulated at the level not more than 0.05 MPa/min, when the total pressure is at least 1 MPa, in order to suppress the occurrence of puzyrchatogo on the wire.

Then heat treatment temperature for the second heat treatment was set to 500aboutFor a similar study of the presence/absence of userquota on the wire. Table 2 shows the total pressure and the presence/absence of userquota on the wire.

Table 2
Total pressure (MPa)The extension wire
0,1No
0,2No
0,3 No
0,4No
0,5No
0,8No
1,0Yes
2,0Yes
3,0Yes
5,0Yes
10,0Yes
20,0Yes
30,0Yes

According to the results presented in Table 2, the wire appears usercost, when the total pressure is at least 1 MPa, also in the case when the heat treatment temperature is 500aboutC. Thus, the rate of reduction of pressure in the atmosphere of high pressure must be regulated at the level not more than 0.05 MPa/min, when the total pressure is at least 1 MPa, and when the heat treatment temperature is 500aboutWith, in order to suppress the occurrence of puzyrchatogo on the wire.

The fifth option exercise

Fig is a view in cross-section, schematically showing the structure of an oxide superconducting wire having the remaining gaps in it.

Addressing Pig, clearances, elongated in the longitudinal direction (transverse direction Fig)essentially disappear, while the gaps 20 perpendicular to the longitudinal N. the Board, to some extent remain in the fiber 2 of the oxide superconducting wire 1 after heat treatment in the atmosphere of high pressure, with a total pressure of at least 1 MPa and less than 50 MPa. Fig shows unifiber oxide superconducting wire having a single fiber superconductor.

The authors of the present invention found that the number of gaps 20 perpendicular to the longitudinal direction of the oxide superconducting wire 1, it is difficult to reduce due to the heat treatment in the atmosphere of high pressure. This presumably occurs for the following reason. In the atmosphere of increased pressure equivalent is applied to all surfaces of the oxide superconducting wire. Oxide superconducting crystals under the influence of this pressure undergo creep strain with tightening gaps present at the transition boundary between the crystals. Thus, a reduced number of gaps formed between the oxide superconducting crystals. However, the oxide superconducting wire 1 has a shape elongated in the longitudinal direction, and therefore the force is essentially not transmitted in the longitudinal direction, and the wire 1 being not compressed in the longitudinal direction. As a result, the number of gaps 20, rohtash perpendicular to the longitudinal direction of the oxide superconducting wire 1, essentially not reduced by heat treatment in an atmosphere of high blood pressure.

The gaps 20 perpendicular to the longitudinal direction of the oxide superconducting wire 1 and the blocking current in the fiber superconductor, are one of the factors that reduce a critical current density of the oxide superconducting wire 1. Therefore, when the formation of the gap 20 is suppressed critical current density of the oxide superconducting wire 1 can be improved even more.

Accordingly, the authors of the present invention have found that the formation of the gap perpendicular to the longitudinal direction of the oxide superconducting wire can be suppressed before heat treatment, and consequently, the critical current density of the oxide superconducting wire can be improved by setting the degree of compression of the oxide superconducting wire at the level of not more than 84%, preferably not more than 80%, during the initial rolling (stage S5) figure 3. The reasons for this are explained below.

Initial rolling stage is performed to increase the density of the powder source material loaded in a metal tube. As increasing the degree of compression of the oxide superconducting wire (increases the rate of processing) during the initial p is katki, increases the density of the powder source material loaded in a metal tube. When increasing the density of the powder source material density of superconducting crystals formed during the subsequent heat treatment (stage stage S4, and S5)increases, which improves the critical current density of the oxide superconducting wire.

However, when the degree of compression of the oxide superconducting wire during the initial rolling is increased, can be selected the following three phenomena that arise owing to the increased coefficient processing. The first phenomenon is that in the powder source material are formed gaps (cracks). Secondly, it is easy to occur the phenomenon of "kovacovich" thickening, which makes the shape of the fiber in the oxide superconducting wire is non-uniform in the longitudinal direction. Thirdly, part of the fiber of the superconductor, having a locally enlarged cross-sectional area due to kovacovich thickening, easily enters into another fiber superconductor, which causes the formation of bridges. All these phenomena can serve as factors that reduce the critical current density of the oxide superconducting wire.

Therefore, the primary rolling must be performed with a degree of compression that increases the density of the powder source material, but without the formation of gaps or p in the powder source material. In the case of conventional primary rolling of the oxide superconducting wire is rolled with a degree of compression of approximately from 86 to 90%.

However, if heat treatment is performed in an atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa, the compression effect of the oxide superconducting wire is also provided during heat treatment. Also, when performing the initial rolling with the degree of compression of no more than 84%, the powder source material is compressed due to the subsequent heat treatment in an atmosphere of high pressure, resulting in a fiber density of the superconductor forming the oxide superconducting wire can be further increased. On the other hand, the primary perform rolling with the degree of compression of no more than 84%, and therefore the gap is essentially not formed in the powder source material, resulting in the formation of the gap perpendicular to the longitudinal direction of the oxide superconducting wire can be suppressed. In addition, the primary perform rolling with the degree of compression of no more than 80%, so that the powder source material not formed any gaps. The critical current density of the oxide superconducting wire in the power of the above reasons may be increased.

Fig presented yet a chart, schematically showing the relation between degrees of compression and values of critical current density in the primary rolling in the oxide superconducting wires.

Addressing Pig, the critical current density of the oxide superconducting wire is maximized in the case where the heat treatment performed in the atmosphere, and the primary rolling perform with a degree of compression of about 86%. On the other hand, when the heat treatment is performed in an atmosphere of high pressure according to the present invention, the critical current density is maximized in the case where the primary rolling perform with a degree of compression of about 82%. Thus, it is clear that the degree of compression during the initial rolling optimal for increasing the critical current density of the oxide superconducting wire is shifted to lower values when the heat treatment is performed in an atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa.

To confirm the above effect, the authors of the present invention prepared an oxide superconducting wire according to this variant implementation for measuring critical current density under the following conditions.

Based on the stages of manufacturing the oxide superconducting wire shown in Figure 3, the metal tube is loaded powder starting material and subjected to drawing in the wire. Then, use the primary rolling were obtained thin superconducting wires. Primary rolling was performed with two degrees of compression: 82% and 87%. In addition to the primary rolling used rolls with a diameter of 100 mm and a lubricating oil with a kinematic viscosity of 10 mm2/s Then these wires was performed first heat treatment. The first heat treatment performed when setting the partial pressure of oxygen, heat treatment temperature and time of heat treatment on the level accordingly 0,008 MPa, 830aboutAnd 30 hours. Then was fulfilled the secondary rolling. Secondary rolling was performed with a degree of compression from 5 to 30% by using rolls with a diameter of 300 mm and without lubricating oil. Then was fulfilled the second heat treatment. The second heat treatment performed when setting the total pressure, the partial pressure of oxygen, heat treatment temperature and time of heat treatment on the level of respectively 25 MPa, 0,008 MPa, 820aboutWith 50 hours. After the second heat treatment were measured critical current density obtained oxide superconducting wires.

As a result, the oxide superconducting wire is subjected to the primary rolling with the degree of compression in 87%, showed a critical current density of 30 kA/cm2. On the other hand, the oxide superconducting wire, the lead is bent primary rolling with the degree of compression in 82%, demonstrated critical current density, equal to 40 kA/cm2. From the above results it follows that the formation of the gap perpendicular to the longitudinal direction of the oxide superconducting wire can be suppressed before heat treatment, and a critical current density of the oxide superconducting wire can be consequently improved by setting the degree of compression of the oxide superconducting wire at the level of not more than 84% during the initial rolling (stage S5).

Although this embodiment has been listed here as an example, the kinematic viscosity of lubricating oil and cited as an example the diameter used for rolling rolls, the present invention is not limited to these conditions of rolling, and the degree of compression of the wire at the stage of rolling may not exceed 84%.

The sixth option exercise

The authors of the present invention have conducted an in-depth study on the establishment, is suppressed if the formation of gaps and userquota, and prevented if effective, the reduced critical current density in the wire 1 having surface pores 14, in the case of the following six methods. They also found that the swelling can be suppressed while increasing temperatures temperature control in the oxide superconducting wire, manufactured using the sixth method.

According to the sixth method, increasing the pressure starts after the temperature of the atmosphere exceeds 400aboutWith, preferably 600aboutWith increasing temperature before heat treatment or during the first heat treatment (stage S4)or during the second heat treatment (stage S6)shown in Figure 3. The rate of increase of pressure is preferably set at the level of at least 0.05 MPa/min, more preferably at least 0.1 MPa/min

Fig is a diagram showing cited as an example of the relationship between temperature, total pressure and partial pressure of oxygen in the course of raising temperature before heat treatment and the heat treatment and time according to the sixth method in the sixth embodiment of the present invention.

Addressing Pig, the temperature of the atmosphere is slowly increased to 820aboutC. the pressure of the atmosphere increases slowly according to the equation of state of gas, when the temperature is less than 600aboutC. the pressure Increase start after the temperature of the atmosphere has reached 600aboutWith, and increasing pressure to perform about 25 MPa with the speed increase pressure of about 0.1 MPa/min oxygen Partial pressure maintained within the range for men is her least of 0.003 MPa and less than 0.02 MPa. When performing heat treatment under these conditions can be further improved critical current density of the oxide superconducting wire. To confirm the effect of the above-mentioned method of heat treatment, the authors present invention was subjected to a heat treatment of the oxide superconducting wire at different temperatures started increasing pressure as described below and, respectively, measured density after sintering the prepared oxide superconducting wires.

Fig is a graph showing the relationship between velocity pressure and the density after sintering for different temperatures at the beginning of pressure increase.

Addressing Pig, the density after sintering fibers oxide superconductor (oxide superconductor) is from about 93% to 96% when the rate of pressure increase of at least 0.05 MPa in the case of a start of pressure increase, when the temperature of the atmosphere is 30aboutC. on the other hand, in case the temperature rise, when the temperature of the atmosphere reaches 400aboutWith the density after sintering the fibers of the oxide superconductor is at least 95% when the rate of pressure increase of at least 0.05 MPa/min. Later, at the beginning of the pressure increase after the temperature of the atmosphere value 600 With the density after sintering the fibers of the oxide superconductor is at least about 97% when the rate of pressure increase of at least 0.05 MPa/min, and the density after sintering the fibers of the oxide superconductor is at least about 98% when the rate of pressure increase of at least 0.1 MPa/min In addition, in both cases, the beginning of the pressure increase after the temperature of the atmosphere has reached 400aboutWith, and the beginning of the pressure increase after the temperature had reached approximately 600aboutWith the density after sintering the fibers of the oxide superconductor is at least about 99% when the rate of pressure increase of at least 0.15 MPa/min

The density after sintering, apparently, is improving at the speed of pressure increase of at least 0.05 MPa/min, because the rate of pressure increase of the gas seeping into the wire through the surface of the pores is less than about 0.05 MPa/min, and the wire runs in the danger pressure at a speed higher than the speed of infiltration, resulting in the pressure in the atmosphere may be continuously maintained higher than the internal pressure of the wire. According to the results presented on Fig, the density after sintering the fibers of the oxide superconductor increases when increasing pressure is I begins after as the temperature of the atmosphere exceeds 400aboutWith, preferably 600aboutC. in Addition, this implies that the density after sintering the fibers of the oxide superconductor increases additionally, when the rate of increase of pressure is preferably set at the level of at least 0.05 MPa/min, more preferably at least 0.1 MPa/min It seems, for the following reasons.

Fig is a graph showing the temperature dependence of 0.2%of the conventional yield strength of silver.

Addressing Pig, 0,2%conditional yield strength is about 370 MPa, when the atmosphere is at room temperature, and decreases with increasing temperature of the atmosphere. In particular, the 0.2%conventional yield strength is reduced to about 50 MPa when the temperature of the atmosphere reaches 400aboutWith, and 0.2%conventional yield strength is reduced to about 25 MPa when the temperature of the atmosphere reaches 600aboutC. Thus, the 0.2%conditional yield of silver is reduced to the extent that is essentially identical to the total pressure (at least 1 MPa and less than 50 MPa above atmospheric high pressure, when the temperature of the atmosphere is 400aboutC. When the temperature of the atmosphere is 600aboutWith 0,2%conditional yield of silver is reduced when the Arno to one-half the total pressure of at least 1 MPa and less than 50 MPa above atmospheric high pressure. Of the above methods, it follows that the pressure applied to the wire in a state in which the strength of the casing is reduced. Therefore, the membrane can be easily compressed compressive force created by the high pressure, due to the effect similar to the effect of hot working. As a result, the wire is compressed before creating high pressure gas seeps into the wire through the surface pores, resulting in the formation of gaps and userquota can be sufficiently suppressed by increasing pressure to increase the density after sintering the fibers of the oxide superconductor. Values of 0.2%of the conventional yield stress shown in Fig were obtained by executing the burst test according to Industrial Standards of Japan (JIS), conducted on a wire of pure silver with a diameter of 1.5 mm.

The density after sintering the fibers of oxide superconductor on Fig calculated according to the following method. First, separate the oxide superconducting wire weight 5 g (= Mt(g)).Then the separated oxide superconducting wire is immersed in alcohol for measuring mass (W (g)) the wires in alcohol, and calculate the buoyancy acting on the oxide superconducting wire. Volume (Vt(cm3)) the oxide superconducting wire is calculated by the known density of alcohol (Á = 0,789 (g/cm3). In particular, Vtcalculated using the following formulas (1) and (2), assuming that Ftdenotes buoyancy.

Ft= Mt- W ... (1)

Vt= Ft/ρ ... (2)

Then the oxide superconducting wire is dissolved in nitric acid in order to expose the solution to the learning method of emission spectroscopy with an induction-coupled plasma (ICP), thereby to determine the amount of silver and calculate the proportion (Y) of silver in the mass of the oxide superconducting wire. Mass (Mf(g)fibre) of the oxide superconductor and the mass (Ms(g)) of the shell is calculated based on the weight of the oxide superconducting wire according to the following formulas (3) and (4):

Ms= Mt× Y ... (3)

Mf= Mt- Ms... (4)

Then the volume (Vs(cm3)) the shell is calculated based on the known density of silver is 10.5 g/cm3)), and based on the volume of shell calculate the volume (Vf(cm3)) fibers of the oxide superconductor. Next, based on the fiber volume of the oxide superconductor calculate density ρffibers of the oxide superconductor. In particular ρfcalculated by the following formulas (5) to (7):

Vs= Ms/10,5 ... (5)

Vf= Vt- Vs... (6)

ρf= Mf/Vf... (7)

On the other hand, as a theoretical p is h fiber of oxide superconductor use the value of 6.35 g/cm 3. This value is calculated according to the following method. Nuclear relations in the Bi2223 phase in the fiber of the oxide superconductor is calculated using the method of emission spectroscopy with an induction-coupled plasma (ICP) method and energy dispersive x-ray fluorescence analysis (EDX). Constant of the crystal lattice of the Bi2223 phase obtained using the method of x-ray diffraction analysis to calculate the values of a - and C-axes. theoretical density is calculated based on these values.

The density after sintering the fibers of the oxide superconductor is calculated by the ratio between the density of the fibers of the oxide superconductor and theoretical density of the fibers of the oxide superconductor obtained by the aforementioned method. In particular, the density after sintering is calculated using the following formula (8):

The density after sintering (%) = (ρf/6.35mm) × 100 ... (8).

Fig is a graph showing a relationship between densities after sintering of the fibers of the oxide superconductor and the values of the critical current in the oxide superconducting wires.

Addressing Pig, the values of the critical current in the oxide superconducting wires with densities after sintering is not more than about 95% is less than 80 And, while the values of the critical current in the oxide superconducting p is the botflies with densities after sintering, components, at least about 95%, are mostly in the range of larger than 80 A. the Value of the critical current is obtained by multiplying the critical current density in the cross-sectional area of the fibers of the oxide superconductor, and therefore the critical current density is proportional to the value of the critical current. Therefore, the critical current density is improved in the oxide superconducting wire having a high density after sintering. This is, apparently, due to the large number of flows of electric current through the fiber superconductor, as in the oxide superconducting wire having a high density after sintering, the number of gaps between the crystals of the superconductor in the fiber is small.

From the above results, shown in Fig and Fig, it follows that the density after sintering the fibers of the oxide superconductor has increased, with improved critical current density of the oxide superconducting wire, when the boost pressure is started after the temperature of the atmosphere exceeded 400aboutS, more preferably 600aboutWith, and preferably at a speed component of at least 0.05 MPa/min, more preferably at least 0.1 MPa/min

The oxide superconducting wire having a density after sintering at least 95%, predpochtite the flax - at least 99%, will receive the above method of manufacture. The oxide superconducting wire obtained by the aforementioned manufacturing method, used in a superconducting device such as a superconducting cable, and therefore, the liquid refrigerant is already essentially not seeping into the gap of the oxide superconductor. Also, when heating of the superconducting device from the state of immersion in the liquid refrigerant to room temperature without temperature control, the liquid refrigerant is not essentially evaporates. As a result, the internal pressure of the oxide superconducting wire is essentially not increased, and therefore this superconducting device, such as a superconducting cable can be prevented from swelling.

To confirm the above effect, the authors of the present invention performed the following experiment.

Two types of oxide superconducting wires were prepared by the method of manufacture shown in Figure 3. The first oxide superconducting wire was subjected to a heat treatment at a temperature of 820aboutWith over 50 hours at a pressure of 30 MPa and the partial pressure of oxygen 0,008 MPa during the second heat treatment (stage S6). During temperature increase before the second heat treatment (stage S6), the pressure increase was begun after the CSOs, as the temperature of the atmosphere has reached 600aboutWith regulation, essentially the same as the regulation of the total pressure, the partial pressure of oxygen and temperature, shown in Fig. The second oxide superconducting wire was subjected to heat treatment at atmospheric pressure in both the first heat treatment (stage S4)and the second heat treatment (stage S6). Superconducting cables 30, similar to those shown in Figa were prepared from the oxide superconducting wires of these two types, according to the above-mentioned ways. The corresponding superconducting cables 30 were immersed in liquid nitrogen for 24 hours and heated to room temperature without controlling the speed of temperature increase. After that examined the presence/absence of swelling. As a result, the superconducting cable 30, is formed with an oxide superconducting wire, cooked at atmospheric pressure, was expanded. On the other hand, the superconducting cable 30, which was used for the oxide superconducting wire is subjected in the manufacture of regulation total pressure, partial pressure of oxygen and temperature, similar to that shown in Fig, has shown absolutely no swelling. From this it follows that in the superconducting cable, and have eaten of the oxide superconducting wire, manufactured by the aforementioned method, the swelling can be prevented.

In the method of manufacturing an oxide superconducting wire according to this variant of implementation, the pressure applied to the wire in this state, in which the 0.2%conventional yield strength of the shell was reduced to a level that is essentially identical to the total pressure of the atmosphere increased pressure during the heat treatment. Therefore, the membrane can be easily compressed to a compressive force, caused by increased pressure due to the effect similar to hot processing. Therefore, the wire is compressed before creating high pressure gas seeps into the wire through the surface pores, resulting in the formation of gaps and userquota can be effectively suppressed by increasing the pressure. As a consequence, the density after sintering the fibers of the oxide superconductor can be increased to improve the critical current density of the oxide superconducting wire.

When the above-mentioned manufacturing increased pressure preferably starts after the temperature of the atmosphere reaches 600aboutIn the course of raising temperature before heat treatment under heat treatment.

Thus, pressure is applied to the wire in this state, in which the 0.2%conventional yield strength of the glasses is reduced to approximately half the total pressure of the atmosphere increased pressure during the heat treatment. Therefore, the shell is more easily compressed compressive force caused by the pressure increase. As a consequence, the density after sintering the fibers of the oxide superconducting wire can be further increased to further improve the critical current density of the oxide superconducting wire.

In the aforementioned method of manufacturing the rate of pressure increase is preferably at least 0.05 MPa/min, more preferably at least 0.1 MPa/min

Thus, the density after sintering the fibers of the oxide superconductor can be further increased to further improve the critical current density of the oxide superconducting wire.

In the aforementioned method of manufacturing stage heat treatment is preferably performed in an oxygen atmosphere, and the partial pressure of oxygen is at least of 0.003 MPa and not more than 0.02 MPa.

Thus, there is a stable oxide superconducting phase, and therefore can be improved critical current density. Heterophase is formed in the case, if the partial pressure of oxygen greater than 0.02 MPa, while the oxide superconducting wire is essentially not formed, and the critical current density decreases, if the partial pressure of oxygen is less than 0,003 MPa.

In this embodiment was described method (a method of manufacturing an oxide superconducting wire) improvement of critical current density by performing a specified method of heat treatment during at least either the first heat treatment (stage S4)or the second heat treatment (stage S6)shown in Figure 3. However, in addition to this occasion, the present invention is also applicable as a stage heat treatment is performed on the already made of the oxide superconducting wire (i.e. the oxide superconducting wire after completion of stages S1-S6 figure 3), i.e. as a way of reformation of the oxide superconducting wire. Also, when the heat treatment according to the present invention is used as a way of reformation of the oxide superconducting wire, the density after sintering of the oxide superconductor can be increased to improve the critical current density of the oxide superconducting wire.

In this embodiment, there was described the case of heat treatment of the oxide superconducting wire having a sheath of silver, in an atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa during the heat treatment and the start of pressure increase after the temperature of the atmosphere exceeds 400aboutIn the course of increasing t is mperature before heat treatment under heat treatment. However, the present invention is not limited to this case and is applicable in General to an oxide superconducting wire having a configuration obtained by coating an oxide superconductor metal. In this case, heat treatment is performed in an atmosphere of high pressure with the total pressure of the components during heat treatment of at least 1 MPa and less than 50 MPa, and the pressure increase start with the temperature at which the 0.2%conventional yield stress of the metal is smaller than the total pressure (at least 1 MPa and less than 50 MPa) during heat treatment. Thus, the pressure to the wire put in such a state, in which the 0.2%conventional yield stress of the metal is less than the total pressure of the atmosphere increased pressure during the heat treatment, resulting in made from this metal part is easily compressed compressive force caused by the pressure increase. Therefore, the density after sintering of the oxide superconducting wire can be increased to improve the critical current density of the oxide superconducting wire for a reason similar to that described in relation to an oxide superconducting wire having a coating of silver.

The seventh option exercise

The oxide superconducting wire based on bismuth (Bi) is overall the known oxide superconducting wire. The oxide superconducting wire based on bismuth can be used at the temperature of liquid nitrogen and can provide a relatively high critical current density. In addition, it is expected that such an oxide superconducting wire based on bismuth, which can be relatively easily extended, will find application in superconducting cables or magnets. To date, however, there was a problem, which was that the usual oxide superconducting wire based on bismuth unsuitable for applications requiring high performance at low temperature, due to the low critical current density (Jc) at a low temperature of approximately 20K.

In this regard, the authors of the present invention have found that the critical current density of the oxide superconducting wire on the basis of bismuth at low temperatures of about 20K can be improved by combining the following techniques with the above-mentioned methods. Below is a description of this method.

According to this method, the wire is annealed in an oxygen-containing atmosphere at a temperature of at least 100aboutWith not more than 600aboutWith during either the first heat treatment (stage S4)or the second heat treatment (stage S6)shown in Figure 3.

Fig before the hat is a chart showing cited as an example of the relationship between temperature, total pressure and partial pressures of oxygen and time in the case of performing annealing after heat treatment in the seventh embodiment of the present invention.

Addressing Pig, the oxide superconducting wire can withstand for a constant time in a state in which the temperature of the atmosphere is 820aboutC and the pressure is 25 MPa, and then the temperature of the lower atmosphere. At this time the total pressure of the atmosphere is also slowly reduced. The wire is maintained at a constant temperature, when the temperature and pressure of the atmosphere reaches, respectively, approximately 300aboutWith and about 16 MPa, and annealed for about 30 hours. Simultaneously with maintaining the wire at a constant temperature, the total pressure is also continuously and slowly reduce. The temperature of the atmosphere is lowered again after annealing. The partial pressure of oxygen is approximately 0,008 MPa during heat treatment, and increases to about 0,024 MPa during annealing. The partial pressure of oxygen is reduced together with the total pressure after annealing.

To confirm the effect of the above-mentioned annealing, the authors of the present invention performed the following experiment.

It examined nasal is to much critical current at 20K improved in the case of performing annealing in the case without performing this annealing stages of heat treatment. The annealing was performed with different annealing times and with different partial pressures of oxygen. Table 3 shows the average values of the coefficients of increasing values of the critical current at 20K with respect to the values of the critical current at 77 K after stages of heat treatment for the respective samples. Values of the critical current was measured in a magnetic field of 3 T.

Table 3
Sample # TemperatureTimeThe partial pressure of oxygenAverage ratio: Ic(20K)/

Ic(Between 77K)
1Neotony1,6
2Neotony1,7
3Neotony1,5
4Annealed300°30 h24 kPa2,1
5annealed300°30 h12 kPa1,9
6annealed 300°40 h20 kPa2

Referring to Table 3, the average values of the coefficients of increasing values of the critical current at 20K in the case without performing annealing, respectively, to 1.6, and 1.7 and 1.5. On the other hand, the average values of the coefficients increase critical currents at 20K in the case of performing annealing respectively of 2.1, 1.9 and 2. Therefore, it is clear that the value of the critical current at 20K can be even more improved in the case of performing annealing in comparison with the case without performing annealing. Any change Iwithat 77 K has not been established.

To confirm the effect of annealing the wire in oxygen-containing atmosphere at a temperature of at least 100aboutWith not more than 600aboutWith the authors of the present invention performed the following experiment.

First, there were prepared ribbon-like oxide superconducting wire based on bismuth, each of which had a multi-fiber structure and was equipped with 61 fiber with external dimensions of 4.2 mm and 0.24 mm in thickness and with a bit of silver and 1.5. Then these oxide superconducting wires was performed heat treatment, and in the course of this heat treatment was performed annealing. Annealing was performed in an oxygen stream at the time of annealing for 20 hours at various temperatures the annealing, shown in Table 4. In addition, there were prepared oxide superconductors with different quantities of Bi2212 phase (superconducting phase(BiPb)2Sr2Ca1Cu2O8+z). Table 4 also shows the values of the critical current Iwiththe respective samples at 77 K and 20K respectively before annealing and after annealing.

Used wire were selected from the same party, and it was assumed that the superconducting part of all wires have the same cross-sectional area. Thus, the values of the critical current Iwithin Table 4 are proportional to the values of critical current density Jc(Jc= Ic/the cross-sectional area of the superconducting part).

Table 4
Sample # The number of Bi2212 phase

(%)
Before annealing

Ic(A) at 77 K
Before annealing

Ic(A) at 20K

(1)
The temperature of annealing (aboutC)After annealing

Ic(A) at 77 K
After annealing

Ic(A) at 20K

(2)
(2)/(1)
7995500No---
8995500 100955151,03
9995500200955351,07
10995500300945451,09
11995500400925501,1
12995500500905751,15
13995500600895501,1
14995500700704800,96
15995500800603450,69
162100527500995281,0
17597511500965431,06
18995500 500905551,11
191392485500885401,11
201990474500825301,12
212583437500755001,14
225060316500504101,3

From the results in Table 4 shows that the value of the critical current Iwith(critical density Jccurrent) at low temperature (20K) improved to a greater extent compared with its value before annealing, when the annealing is performed in an oxygen atmosphere at a temperature of at least 100aboutWith not more than 600aboutC. In particular, when the annealing temperature is at least 300aboutWith not more than 600aboutWith, and the number of Bi2212 phase in the oxide superconductor is at least 5 mol.% and not more than 20 mol.%, the value of the critical current Icafter annealing is at least 530 A, and from this it follows that the absolute value of the critical current Iwith(critical density Jwithcurrent) is velocipede.

The authors present invention also learned the value of the critical current Iwiththe oxide superconducting wire at appropriate temperatures (in K) before annealing and after annealing at a temperature of 500aboutC. Fig shows the results. On Fig results, it follows that the values of the critical current Iwithannealed samples are higher than the samples have not been subjected to annealing, in the case of a temperature not more than about 20K.

In the method of manufacturing the oxide superconducting wire in accordance with this embodiment of the oxide superconducting wire includes a Bi2223 phase, and this oxide superconducting wire is annealed in an oxygen-containing atmosphere at a temperature of at least 100aboutWith not more than 600aboutC. Thus improving the critical current density of the oxide superconducting wire at a low temperature of around 20K.

In this embodiment was explained as a way to improve the critical current density by performing a specified method of heat treatment during at least either the first heat treatment (stage S4)or the second heat treatment (stage S6)shown in Figure 3. However, in addition to this occasion, the present invention is also applicable as a stage heat treatment is performed on the already manufactured the nom oxide superconducting wire (i.e. the oxide superconducting wire after completion of stages S1-S6 figure 3), i.e. as a way of reformation of the oxide superconducting wire. Also, when the heat treatment according to the present invention is used as a way of reformation of the oxide superconducting wire can be enhanced critical current density of this oxide superconducting wire at a low temperature of around 20K.

The present invention is applicable to a superconducting device such as a superconducting transformer (transformer with superconducting windings), the superconducting current limiter or a generator of a magnetic field using a superconducting magnet made of an oxide superconducting wire or superconducting cable, a superconducting electric bus or a superconducting coil using an oxide superconducting wire, and is particularly applicable to superconducting device in which an oxide superconducting wire is used in immersed in the refrigerant condition. In addition, the present invention can effectively suppress the swelling, especially in relation to the superconducting cable from other superconducting devices.

The described above embodiments of should be considered in all respects paashaus the mi, and not limiting. Scope of the present invention is defined not by the above variants of implementation, and the scope of the patent claims set forth in the formula of the present invention, and this implies that the scope of the invention includes all corrections and modifications within the essence and scope equivalent to the scope of patent claims set forth in the formula of the present invention.

1. Superconducting device (30)having an oxide superconducting wire (1) with the oxide superconductor (2), with density after sintering at least 93%, and mentioned oxide superconductor (2) is an oxide superconductor on the basis of Bi-Pb-Sr-Ca-Cu-O containing bismuth, lead, strontium, calcium and copper, and includes a phase V with atomic relations (bismuth and lead):strontium:calcium:copper approximately 2:2:2:3.

2. Superconducting device (30) according to claim 1, having mentioned the oxide superconducting wire (1) with the said oxide superconductor (2), possessing mentioned density after sintering at least 95%.

3. Superconducting device (30) according to claim 2, having mentioned the oxide superconducting wire (1) with the said oxide superconductor (2), possessing mentioned density after sintering at least 99%.

4. Superconducting cable (30)having Oxydry the superconducting wire (1) with the oxide superconductor (2), with the density after sintering at least 93%, and mentioned oxide superconductor (2) is an oxide superconductor on the basis of Bi-Pb-Sr-Ca-Cu-O containing bismuth, lead, strontium, calcium and copper, and includes a Bi2223 phase with the atomic relations (bismuth and lead):strontium:calcium:copper approximately 2:2:2:3.

5. Superconducting cable (30) according to claim 4, having mentioned the oxide superconducting wire (1) with the said oxide superconductor (2), possessing mentioned density after sintering at least 95%.

6. Superconducting cable (30) according to claim 5, having mentioned the oxide superconducting wire (1) with the said oxide superconductor (2), possessing mentioned density after sintering at least 99%.



 

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EFFECT: enhanced temperature of superconducting junction.

1 cl

The invention relates to the production of superconducting materials and can be used in the electrical industry and other branches of science and technology in the manufacture of superconducting magnetic systems for various applications

FIELD: electrical engineering including superconductivity; improved technologies for producing semiconductors.

SUBSTANCE: when specimen of desired size is produced from working charge, it is pierced with thin threads, such as silk ones, disposed in parallel with direction of current flow in product so as to raise superconducting junction temperature; during heat treatment these threads burn out to form superconducting passages due to free movement of conducting electrons.

EFFECT: enhanced temperature of superconducting junction.

1 cl

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