JP2011138823A - Bulk superconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that the conventional method for reinforcing a ring made of a metal such as stainless steel, by fitting the ring over a superconducting bulk body requires very high degree of dimensional accuracy, so that it cannot be employed readily. <P>SOLUTION: In a bulk superconductor including a short cylindrical superconducting bulk body and a surrounding belt of a shape memory alloy which surrounds and pressurizes the circumferential surface of the superconducting bulk body, the surrounding belt pressurizes the superconducting bulk body by recovering the shape, after surrounding the superconducting bulk body. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a bulk superconductor capable of maintaining the high trapping magnetic field by reducing the influence of external force and internal stress such as electromagnetic force and thermal strain accompanying rapid temperature rise and cooling.

  Superconducting materials are attracting attention as exhibiting groundbreaking properties in magnet and electronics applications because they have a higher critical current density than normal materials and can pass large currents without loss. Application research to fusion devices, MRI, magnetic levitation trains, generators, energy storage devices, magnetoencephalographs, magnetic separation type water purification devices, etc. are actively conducted

  In order to capture the magnetic field in the superconducting bulk body, a magnetic field is applied before the superconducting bulk body is cooled with liquid nitrogen or the like, and further, the superconducting bulk body is cooled with the magnetic field applied (cooling in the magnetic field). Then, after the superconducting bulk body has cooled sufficiently, the external magnetic field is removed. As a result, a magnetic field is trapped in the superconducting bulk body. Cracks may occur with this cooling and temperature rise.

  Furthermore, when a magnetic field is applied in the superconducting state, a large current flows through the superconducting bulk body, but this causes a problem. This problem will be described with reference to FIG. When a short cylindrical superconducting bulk body (1001) captures a magnetic field, it is necessary to apply a magnetic field (1002) to the superconducting bulk body. Due to the applied magnetic field, a large current (1003) flows in the superconducting bulk body. As a result, electromagnetic force (Lorentz force) may work in the outer circumferential direction (1004). This tensile stress may cause cracks (1005) or the superconducting bulk material may be destroyed.

  The tensile strength of the ceramic material is about 1/15 of the compressive strength. For this reason, in order to prevent destruction of the superconducting bulk body due to external force or internal stress, it is important to relax the tensile stress acting on the superconducting bulk body. In order to relieve the tensile stress, it is necessary to apply a compressive stress to the material from the surroundings. Therefore, a technique for fitting a stainless steel ring into a superconducting bulk body has been proposed (Patent Document 1).

JP 11-335120 A

  The invention described in Patent Document 1 utilizes the thermal expansion of stainless steel and its material strength. The superconducting bulk is formed by fitting the superconducting bulk body into a heated stainless steel ring and cooling it to cause thermal contraction of the stainless steel ring. It applies compressive stress to the body.

  However, the heat shrinkage rate of ordinary metals such as stainless steel is only about 1% even when heated to about 300 ° C, so that sufficient mounting and adhesion cannot be obtained, and sufficient compressive stress is applied. It is difficult to load. In order to realize this, extremely high dimensional accuracy is required.

  In order to solve the above problems, the following bulk superconductor is provided. That is, as a first invention, a bulk superconductor comprising a short cylindrical superconducting bulk body and a shape memory alloy surrounding belt that pressurizes and surrounds a side peripheral surface of the superconducting bulk body, wherein the surrounding belt is Provided is a bulk superconductor in which a superconducting bulk body is pressurized by surrounding the superconducting bulk body and then performing a shape recovery process.

As a second invention, the superconducting bulk material is REBa ₂ Cu ₃ O _y (where RE is selected from Y, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) A bulk superconductor according to the first invention, which is a copper oxide superconductor containing RE ₂ BaCuO ₅ or RE ₄ Ba ₂ Cu ₂ O ₁₀ in one or more elements) phase, is provided.

  As a third invention, there is provided the bulk superconductor according to the first invention or the second invention containing Pt, Rh, Ce or Ag in the superconducting bulk body.

  As a fourth invention, the shape memory alloy is an Ag-Cd alloy, Au-Cd alloy, Cu-Al-Ni alloy, Cu-Sn alloy, Cu-Zn alloy, Fe-Pt alloy, Mn-Cu alloy, Fe -Mn-Si alloy, Pt alloy, Co-Ni-Al alloy, Co-Ni-Ga alloy, Ni-Fe-Ga alloy, Ti-Pd alloy, or Ni-Ti alloy A bulk superconductor according to any one of the above is provided.

  As a fifth invention, there is provided the bulk superconductor according to any one of the first invention to the fourth invention, wherein a gap between the superconducting bulk body and the surrounding belt is impregnated with metal.

  As a sixth invention, there is provided the bulk superconductor according to any one of the first invention to the fourth invention in which a gap between the superconducting bulk body and the surrounding belt is impregnated with a resin.

  As a seventh invention, a superconducting bulk body and a mold surrounding the superconducting bulk body with a gap between them are prepared, and the gap between the mold and the superconducting bulk body is more linearly expanded than the superconducting bulk body. There is provided a method for manufacturing a bulk superconductor in which a metal having a large coefficient is melted and cast, and the molten metal is solidified to pressurize and surround the superconducting bulk body.

  The present invention provides a bulk superconductor capable of reducing the influence of external force and internal stress such as electromagnetic force and thermal strain accompanying rapid temperature rise and cooling, and maintaining a high trapping magnetic field without requiring high dimensional accuracy. be able to.

1 is a conceptual diagram showing a bulk superconductor according to Embodiment 1. FIG. 1 is a conceptual diagram illustrating an example of a bulk superconductor according to Embodiment 1. FIG. 1 is a conceptual diagram illustrating an example of a bulk superconductor according to Embodiment 1. FIG. 1 is a conceptual diagram illustrating an example of a bulk superconductor according to Embodiment 1. FIG. 1 is a conceptual diagram illustrating an example of a bulk superconductor according to Embodiment 1. FIG. The figure which shows the specific example of the shrinkage | contraction behavior by the heating of the shape memory alloy which concerns on Embodiment 1. FIG. The figure which shows the change of the capture magnetic field of the bulk superconductor which concerns on Embodiment 1. FIG. The figure which shows the change of the capture magnetic field of the bulk superconductor which concerns on Embodiment 1. FIG. FIG. 5 is a conceptual diagram showing a superconductor according to a second embodiment. The conceptual diagram for demonstrating the electromagnetic force which acts on a superconducting bulk body. The conceptual diagram for demonstrating the manufacturing method which concerns on Embodiment 4. FIG.

  Hereinafter, modes for carrying out the present invention will be described. In addition, this invention should not be limited to these embodiments at all, and can be implemented in various modes without departing from the gist thereof.

The first embodiment mainly relates to claims 1, 2, 3, 4 and the like. The second embodiment mainly relates to claim 5 and the like. The third embodiment mainly relates to claim 6 and the like. The fourth embodiment mainly relates to claim 7 and the like.
<Embodiment 1>
<Overview of Embodiment 1>

The present embodiment is a bulk superconductor in which a superconducting bulk body is fitted in a shape memory alloy surrounding belt, and then the shape of the superconducting bulk body is pressurized by performing a shape recovery process.
<Configuration of Embodiment 1>

  The bulk superconductor according to this embodiment will be described with reference to FIG. FIG. 1 is a conceptual diagram showing a bulk superconductor according to this embodiment. The bulk superconductor includes a short cylindrical superconducting bulk body (0101) and an enveloping belt (0102) made of a shape memory alloy that pressurizes and surrounds the side peripheral surface of the superconducting bulk body. This go-belt is configured to pressurize the superconducting bulk body by performing a shape recovery process after the superconducting bulk body is fitted. The short cylindrical superconducting bulk material in the figure shows a short cylindrical shape, but the short cylindrical shape is not limited to this, and is a short cylindrical shape having a cross-sectional shape such as a polygon such as a square or a hexagon or an ellipse. May be.

The “superconducting bulk body” (0101) is one of utilization forms of the oxide superconductor and means a lump (bulk) superconductor. Specifically, for example, REBa ₂ Cu ₃ O _y (where RE is one or two selected from Y, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) A copper oxide superconductor containing RE ₂ BaCuO ₅ or RE ₄ Ba ₂ Cu ₂ O ₁₀ in the above element) phase can be mentioned. RE means a rare earth element.

  The “go belt” (0102) is made of a shape memory alloy, and pressurizes and surrounds the side peripheral surface of a short cylindrical superconducting bulk body.

  A “shape memory alloy” is an alloy that recovers to its original shape before deformation by heating it above a predetermined temperature even if it is deformed at a temperature lower than a predetermined temperature after heat treatment for shape memory. is there. For example, a recovery strain of about 2.5 to 4% is recognized in an Fe—Mn—Si based shape memory alloy.

  The shape memory alloy has a characteristic of “super elasticity” in addition to the shape memory characteristics described above. This superelastic property means a property of recovering the original shape by unloading even if the metal is deformed (bent, pulled, or compressed) to a region where plastic deformation occurs at the operating temperature.

  The temperature at which the shape memory effect appears due to the difference in heat treatment conditions can be changed. Superelastic alloys are those that have been regenerated at room temperature. Shape memory alloys are those that do not return to their original shape even when softly bent at room temperature. There is also a case.

  The surrounding belt pressurizes and surrounds the side peripheral surface of the short cylindrical superconducting bulk body due to shape memory characteristics and superelastic characteristics. “Pressurized go” means to go while applying pressure.

  The go belt shown in FIG. 1 is made of an annular shape memory alloy formed to have a height substantially the same as the length in the height direction of a short cylindrical superconducting bulk body. The shape of the surrounding belt is not limited to the annular body shown in FIG. 1, and may be fitted into the superconducting bulk body (0201) with a plurality of annular bodies (0202, 0203) as shown in FIG. Further, it may be made of a wire shape memory alloy.

  FIG. 3 and FIG. 4 are diagrams in which a surrounding belt made of a wire-shaped shape memory alloy is surrounded by a superconducting bulk body. FIG. 3 shows a wire-shaped shape memory alloy ring (0302) and a plurality of superconducting bulk bodies (0301) fitted therein. FIG. 4 shows a wire shape memory alloy formed in a spiral shape and wound around a superconducting bulk body. The go belt can be selected according to the size of the superconducting bulk body and the strength of the magnetic field to be captured.

  The shape memory alloy belt pressurizes and surrounds the superconducting bulk body by fitting the superconducting bulk body and then performing shape recovery treatment. That is, in the case of pressurized surroundings due to shape memory characteristics, after the superconducting bulk body is fitted in the shape memory alloy belt in advance, it is heated to a predetermined temperature or more to recover the shape, whereby the side peripheral surface of the superconducting bulk body Can be subjected to compressive stress. At this time, the extent to which the inner diameter of the surrounding belt when the shape is restored is smaller than the outer diameter of the superconducting bulk body may be determined in accordance with the compressive stress to be applied, the magnitude of the recovery strain, and the like. The same applies to the case of using superelastic characteristics.

  Further, as shown in FIG. 5, a superconducting bulk body (0501) may be fitted into a metal ring (0503), and further fitted into a (shape memory alloy) surrounding belt. The compressive stress is applied through a metal ring, and the compressive stress on the superconducting bulk body can be applied more uniformly. In addition, since it does not directly apply compressive stress to the superconducting bulk body by fitting a metal ring, there is no need to perform shrinkage, for example, a predetermined alloy around the superconducting bulk body. The superconducting bulk body may be surrounded by casting.

  There are various shape memory alloys. For example, Ag-Cd alloy, Au-Cd alloy, Cu-Al-Ni alloy, Cu-Sn alloy, Cu-Zn alloy, Fe-Pt alloy, Mn-Cu alloy, Fe -Mn-Si alloy, Pt alloy, Co-Ni-Al alloy, Co-Ni-Ga alloy, Ni-Fe-Ga alloy, Ti-Pd alloy or Ni-Ti alloy are preferred.

  A specific example of the shrinkage behavior of the shape memory alloy by heating is shown in FIG. FIG. 6 shows the shrinkage behavior of a go belt having a composition of Fe-0.13 wt% C-5.99 wt% Si- 28.35 wt% Mn-4.99 wt% Cr by heating. This test result is a measurement of a state in which a single go belt is heated in a heating furnace with a laser. The test is started from room temperature and heated. Once heated to 450K or higher, cool. Although the inner diameter was 26.9 mm at the start of the test, the shape recovered by heating and reached an inner diameter of less than 26.3 mm.

  FIG. 7 shows the result of measuring the change in the trapping magnetic field of a bulk superconductor in which a surrounding belt is fitted into a single-crystal superconducting bulk body. What is shown on the left side of the figure is one that is not reinforced by a go belt. What is shown on the right side is the measurement result of the case where the goose belt is fitted in the same superconducting bulk body as that on the left. It can be seen that the maximum trapping field is increased and the trapping area is expanded.

  FIG. 8 shows the result of measuring the change in the trapping magnetic field of a bulk superconductor in which a surrounding belt is fitted into a polycrystalline superconducting bulk body. What is shown on the left side of the figure is one that is not reinforced by a go belt. What is shown on the right side is the measurement result of the case where the goose belt is fitted in the same superconducting bulk body as that on the left. It can be seen that the maximum trapping field is increased and the trapping area is expanded. As shown in FIG. 7 and FIG. 8, it has become clear that reinforcing the mechanical strength of the superconducting bulk body with the surrounding belt is effective in capturing a high magnetic field.

  In order to improve the mechanical properties of the superconducting bulk body itself, Pt, Rh, Ce or Ag may be contained in the superconducting bulk body. As a result, the effect of preventing breakage and cracking can be produced in combination with the pressure surrounding with the surrounding belt. In addition, the inclusion of these also has the effect of improving thermal stability by increasing the thermal conductivity.

Examples of the bulk superconductor according to this embodiment will be described below. First, the present invention relates to a bulk superconductor composed of a superconducting bulk body and a surrounding belt.
<Example 1>

A superconducting bulk body containing 1 wt% of CeO ₂ and finely dispersed Y ₂ BaCuO ₅ in the YBa ₂ Cu ₃ O _y phase was processed into a size of 22.8 mm in diameter and 10.0 mm in height. A go-belt with a composition of Fe-27.8wt% Mn-5.97wt% Si-4.93wt% Cr was subjected to 6.5% diameter expansion treatment and then heated at 650 ° C for 1 hour to restore the shape. After that, 5% diameter expansion treatment was performed again. In order to fit the go belt in the superconducting bulk material, the go belt was machined to an inner diameter of 22.9 mm, an outer diameter of 27.5 mm, and a height of 10.3 mm. A go belt was fitted into the superconducting bulk body and heated at 650 ° C. for 1 hour. The bulk superconductor thus obtained was cooled to 77K in a 5T magnetic field, and after removing the external magnetic field, measurement was performed. As a result, a 0.5T magnetic field was captured on the sample surface. On the other hand, when the same experiment was conducted without reinforcement by the go-belt, the superconducting bulk material was destroyed when demagnetized from 5T to 4T. From this, the superconducting bulk body was reinforced by the go ring, and a bulk superconducting magnet capable of capturing a large magnetic field could be produced.
<Example 2>

A superconducting bulk body containing 0.5 wt% Pt and finely dispersed Y ₂ BaCuO ₅ in the YBa ₂ Cu ₃ O _y phase was processed into dimensions of 59.2 mm in diameter and 11.0 mm in height. Fe-20.0wt% Mn-5.0wt% Si-7.99wt% Cr- 5.1wt% Ni was subjected to a 7% diameter expansion treatment on a go belt and then heated at 650 ° C for 1 hour. After restoring the shape, 5% diameter expansion treatment was performed again. In order to fit the go belt in the superconducting bulk body, the go belt was processed to an inner diameter of 59.3 mm, an outer diameter of 63.7 mm, and a height of 11.3 mm. A go belt was fitted into the superconducting bulk body and heated at 650 ° C. for 1 hour. Next, heat treatment was performed in an oxygen atmosphere at a temperature of 400 ° C. for 100 hours. The bulk superconductor thus obtained was cooled to 40K in a 10T magnetic field, and after removing the external magnetic field, measurement was performed. As a result, a 6.2T magnetic field was captured on the sample surface. On the other hand, when a similar experiment was conducted without reinforcement by a go-belt, the superconducting bulk body was destroyed when demagnetized from 10T to 7.2T. From this, the bulk superconducting magnet which can reinforce a superconducting bulk body with a go belt and can capture a large magnetic field could be produced.
<Example 3>

A superconducting bulk body containing 0.5 wt% Pt and 5 wt% Ag and finely dispersing Dy ₂ BaCuO ₅ and BaCeO _{3 in} the DyBa ₂ Cu ₃ O _y phase was processed into dimensions of 59.2 mm in diameter and 11.0 mm in height. Fe- 27.8 wt% Mn-5.97 wt% Si-4.93 wt% Cr ring-shaped goblet belt was subjected to 6.5% diameter expansion treatment and then heated at 650 ° C for 1 hour to recover the shape Then, 5% diameter expansion treatment was performed again. In order to fit the go belt in the superconducting bulk material, the go belt was processed to an inner diameter of 59.3 mm, an outer diameter of 63.8 mm, and a height of 11.3 mm. A go belt was fitted into the superconducting bulk body and heated at 650 ° C. for 1 hour. Next, heat treatment was performed in an oxygen atmosphere at a temperature of 400 ° C. for 100 hours. The bulk superconductor thus obtained was cooled to 40K in a 10T magnetic field, and after removing the external magnetic field, measurement was performed. As a result, a 7.8T magnetic field was captured on the sample surface. On the other hand, when the same experiment was conducted without reinforcement by the go-belt, the superconducting bulk material was destroyed when demagnetization was reduced from 10T to 8.4T. From this, the superconducting material was reinforced by the shape memory ring, and a bulk superconducting magnet capable of capturing a large magnetic field could be produced.
<Example 4>

YBa ₂ Cu ₃ O _y phase in Y ₂ BaCuO ₅ and BaCeO ₃ is finely dispersed diameter 39.5 mm, the side peripheral surface of the bulk superconductor having a height 12.5 mm, it is 7% processed into tensile direction as shrink upon heating A go belt made of a wire of Fe-27.8 wt% Mn-5.97 wt% Si-4.93 wt% Cr having a diameter of 1.2 mm was wound. Then, it heated at 650 degreeC for 1 hour. Thereafter, heat treatment was performed in an oxygen atmosphere at a temperature of 400 ° C. for 100 hours. The bulk superconductor was cooled to 40K in a 10T magnetic field, and after removing the external magnetic field, measurements were taken. As a result, a 7.2T magnetic field was captured on the sample surface. On the other hand, when the same experiment was conducted without reinforcement by the go-belt, the superconducting bulk body was destroyed when demagnetized from 10T to 6.5T. From this, the superconducting bulk body was reinforced by the go belt, and a bulk superconducting magnet capable of capturing a large magnetic field could be produced.

Subsequently, an embodiment will be described in which a goblet is further fitted after it is fitted into a superconducting bulk body by casting a metal ring.
<Example 5>

A superconducting bulk material containing 0.5 wt% Pt and finely dispersed Dy ₂ BaCuO ₅ and BaCeO ₃ in the DyBa ₂ Cu ₃ O _y phase was processed into a size of 39.0 mm in diameter and 13.0 mm in height. An Al-13wt% Si alloy was cast into this bulk body. As a result, a member having a diameter of 42.8 mm and a height of 13.0 mm covering the superconducting bulk body with this alloy was obtained. For this member. Fe- 27.8wt% Mn-5.97wt% Si-4.wt% Cr after a 6.5% diameter expansion treatment, after heating for 1 hour at 650 ° C to recover the shape The diameter was increased by 5% again. In order to fit the go belt in the superconducting bulk material, the go belt was machined to an inner diameter of 42.9 mm, an outer diameter of 47.5 mm, and a height of 13.0 mm. A superconducting bulk material was fitted on the Go belt and heated at 550 ° C. for 1 hour. Since an Al-Si alloy was placed around the superconducting bulk body, it was confirmed that this alloy deformed and filled the gap with the shape memory alloy. Next, heat treatment was performed in an oxygen atmosphere at a temperature of 400 ° C. for 100 hours. The bulk superconductor thus obtained was cooled to 40K in a 10T magnetic field, and after removing the external magnetic field, measurement was performed. As a result, an 8.0T magnetic field was captured on the sample surface. On the other hand, when the same experiment was conducted without reinforcement by the go-belt, the superconducting bulk material was destroyed when demagnetization was reduced from 10T to 8.4T. From this, the superconducting material was reinforced by the go belt, and a bulk superconducting magnet capable of capturing a large magnetic field could be produced.
<Example 6>

An Al-13 wt% Si alloy was cast into a superconducting bulk body having a diameter of 38.9 mm and a height of 12.5 mm in which Y ₂ BaCuO ₅ and BaCeO 3 were finely dispersed in the YBa ₂ Cu ₃ O _y phase. As a result, a member having a diameter of 43.5 mm and a height of 12.5 mm covering the superconducting bulk body with this alloy was obtained. Next, a surrounding belt made of Fe-27.8 wt% Mn-5.97 wt% Si-4.93 wt% Cr wire having a diameter of 1.2 mm processed 5% in the tensile direction so as to shrink during heating was wound. Then, it heated at 650 degreeC for 1 hour. Thereafter, heat treatment was performed in an oxygen atmosphere at a temperature of 400 ° C. for 100 hours. The bulk superconductor was cooled to 40K in a 10T magnetic field, and after removing the external magnetic field, measurements were taken. As a result, a 7.4T magnetic field was captured on the sample surface. On the other hand, when the same experiment was conducted without reinforcement with a go belt, the superconducting bulk material was destroyed when demagnetized from 10T to 5.5T. From this, the bulk superconducting magnet which can reinforce a superconducting bulk body with a go belt and can capture a large magnetic field could be produced.

The wire may be subjected to a so-called training process. That is, before the 5% processing, for example, 7% processing may be performed, heated to 600 ° C., and then processed 5% in the tensile direction.
<Embodiment 1 effect>

The bulk superconductor of this embodiment reduces the influence of external forces and internal stresses such as electromagnetic force, thermal strain caused by rapid temperature rise and cooling, and requires high dimensional accuracy for a bulk superconductor that can maintain a high trapping magnetic field. Can be provided without.
<Embodiment 2>
<Overview of Embodiment 2>

In this embodiment, the gap between the superconducting bulk body and the surrounding belt is impregnated with metal to uniformly apply the compressive stress due to the surrounding belt, and the mechanical properties of the superconducting bulk body itself are improved to improve the superconducting bulk body. It becomes possible to prevent destruction.
<Configuration of Embodiment 2>

  The bulk superconductor of this embodiment is based on Embodiment 1, and is characterized by impregnating a metal in the gap between the superconducting bulk body and the surrounding belt. Since the basic configuration has been described in the first embodiment, the description other than the characteristic configuration of the present embodiment is omitted.

  FIG. 9 is a conceptual diagram of the bulk superconductor of this embodiment. The gap between the superconducting bulk body (0901) and the surrounding belt (0902) can be impregnated with metal to fill the gap and to penetrate into the cracks generated in the superconducting bulk body.

  In order to impregnate the gap between the superconducting bulk body and the surrounding belt with a metal, for example, a low melting point alloy such as an aluminum alloy, an iron alloy, or a copper alloy can be cast into the gap. Low melting point alloys include, for example, Bi-Pb-Sn-Cd-In alloy, Bi-Pb-Sn-Cd-alloy, Bi-Sn-In alloy, Bi-Sn-Cd alloy, Bi-Pb-Sn alloy, Examples include Al-Si alloys. The melting temperature is, for example, 47.0 ° C. for a low melting point alloy of 42.34 wt% Bi-22.86 wt% Pb-11.0 wt% Sn-8.46 wt% Cd-15.34 wt% In.

  The molten alloy fills the gap between the superconducting bulk body and the surrounding belt, so that the compressive stress due to the surrounding belt can be more uniformly applied to the superconducting bulk body. Furthermore, it not only fills the gap, but also smoothly penetrates into the bulk body through the microcracks and pores generated in the superconducting bulk body itself, and fills the microcracks and pores. In a superconducting bulk body in which the internal microcracks and pores are filled with a low melting point alloy in this way, stress concentration at the microcracks and pores is mitigated, and destruction starting from these is prevented. It is possible to maintain a high trapping magnetic field.

In particular, if the oxide superconducting bulk material is exposed to a corrosive atmosphere containing a lot of moisture and carbon dioxide gas for a long time, the material may deteriorate due to corrosion or a reaction phase may be generated, which may cause new cracks to develop. However, the effect of improving the corrosion resistance can be obtained by impregnation with the low melting point alloy.
<Example>

A superconducting bulk body containing 0.5 wt% CeO ₂ and finely dispersed Y ₂ BaCuO ₅ and BaCeO ₃ in the YBa ₂ Cu ₃ O _y phase was processed into dimensions of 39.0 mm in diameter and 13.0 mm in height. When this superconducting bulk material is heated, it is against a go-belt with a composition of Ni-45wt% Ti having an inner diameter of 39.1mm, an outer diameter of 43.7mm, and a height of 13.0mm that is 7% processed in the direction of diameter reduction. The superconducting bulk material was fitted and heated at 650 ° C. for 1 hour. Next, heat treatment was performed in an oxygen atmosphere at a temperature of 400 ° C. for 100 hours. Thereafter, a low melting point alloy of 42.34 wt% Bi-22.86 wt% Pb-11.0 wt% Sn-8.46 wt% Cd-15.34 wt% In having a melting point of 47.0 ° C. is heated to 90 ° C. and cast into this member. It is. As a result, it was confirmed that the low-melting-point alloy entered the gap between the superconducting bulk body and the surrounding belt. The bulk superconductor was cooled to 40K in a magnetic field of 10T, and after removing the external magnetic field, measurements were taken. As a result, a magnetic field of 7.6T was captured on the sample surface. On the other hand, when a similar experiment was conducted without reinforcement by a go-belt, the superconducting bulk body was destroyed when demagnetized from 10T to 7.2T. From this, the bulk superconducting magnet which can reinforce a superconducting bulk body with a go belt and can capture a large magnetic field could be produced.
<Embodiment 2 Effect>

With the bulk superconductor of the present embodiment, a more uniform compressive stress is applied to the superconducting bulk body, and the mechanical strength of the superconducting bulk body itself can be improved.
<Embodiment 3>
<Overview of Embodiment 3>

In this embodiment, the gap between the superconducting bulk body and the surrounding belt is impregnated with resin to uniformly apply the compressive stress due to the surrounding belt, and the mechanical properties of the superconducting bulk body itself are improved. It becomes possible to prevent destruction.
<Configuration of Embodiment 3>

  The bulk superconductor of this embodiment is based on Embodiment 1, and is characterized by impregnating a resin in the gap between the superconducting bulk body and the surrounding belt. Since the basic configuration has been described in the first embodiment, the description other than the characteristic configuration of the present embodiment is omitted.

  The impregnation of the resin can be realized, for example, by immersing a superconducting bulk body in which the surrounding belt is fitted in an epoxy resin, which is a thermosetting resin, heated to about 100 ° C. and melted.

By impregnating the resin, the gap between the superconducting bulk body and the surrounding belt can be filled, and the compressive stress due to the surrounding belt can be uniformly applied to the superconducting bulk body. Furthermore, it not only fills the gap, but also smoothly penetrates into the bulk body through the microcracks and pores generated in the superconducting bulk body itself, and fills the microcracks and pores. In the superconducting bulk body in which the internal microcracks and pores are filled with a low melting point metal as described above, the stress concentration is mitigated at the microcracks and pores, and the breakage starting from these is prevented. Further, it is possible to further improve the corrosion resistance and maintain a high trapping magnetic field.
<Effect of Embodiment 3>

With the bulk superconductor of the present embodiment, a more uniform compressive stress is applied to the superconducting bulk body, and the mechanical strength of the superconducting bulk body itself can be improved.
<Embodiment 4>
<Outline of Embodiment 4>

The present embodiment is a method for manufacturing a bulk superconductor in which a metal having a larger linear expansion coefficient than that of the superconducting bulk body is melted and cast to surround the superconducting bulk body under pressure.
<Configuration of Embodiment 4>

  A method for manufacturing a bulk superconductor according to this embodiment will be described with reference to FIG. First, a superconducting bulk body (1101) and a mold (1102) surrounding the superconducting bulk body with a gap between them are prepared, and the gap between the mold and the superconducting bulk body is more than the superconducting bulk body. A metal (1103) having a large linear expansion coefficient is melted and cast. Then, the molten metal is solidified to produce a bulk superconductor in which the superconducting bulk body is pressurized and surrounded. The superconducting bulk material is the same as that described in the first embodiment.

  The linear expansion coefficient indicates a rate at which the length changes in response to an increase in temperature. A metal having a thermal expansion coefficient larger than that of the superconducting bulk body is used for casting. For example, the aluminum alloy, the iron alloy, the copper alloy, or the like described in the second embodiment can be used.

This molten metal shrinks as it solidifies, and a compressive stress is applied to the superconducting bulk material. By casting the metal in this way, it is possible to apply a uniform compressive stress from the surface to the superconducting bulk body and prevent cracking. Further, as described in Embodiment 2, the mechanical strength is improved by smoothly penetrating the inside of the bulk body through the microcracks and pores generated in the superconducting bulk body itself, and filling those microcracks and pores. It is also possible.
<Embodiment 4 effect>

  According to the present embodiment, it is possible to manufacture a bulk superconductor capable of reducing the influence of external force and internal stress such as electromagnetic force, thermal strain accompanying rapid temperature rise and cooling, and maintaining a high trapping magnetic field.

Claims (7)

A short cylindrical superconducting bulk body;
A shape memory alloy go belt that pressurizes and surrounds the side surface of the superconducting bulk body;
A bulk superconductor comprising:
The go belt is
A bulk superconductor that pressurizes the superconducting bulk body by enclosing the superconducting bulk body and then performing shape recovery treatment. The superconducting bulk is REBa ₂ Cu ₃ O _y (where RE is one or more selected from Y, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu) The bulk superconductor according to claim 1, which is a copper oxide superconductor containing RE ₂ BaCuO ₅ or RE ₄ Ba ₂ Cu ₂ O ₁₀ in the element) phase.   The bulk superconductor according to claim 1 or 2, wherein the superconducting bulk body contains Pt, Rh, Ce, or Ag.   The shape memory alloys are Ag-Cd alloy, Au-Cd alloy, Cu-Al-Ni alloy, Cu-Sn alloy, Cu-Zn alloy, Fe-Pt alloy, Mn-Cu alloy, Fe-Mn-Si alloy, The bulk superconductor according to any one of claims 1 to 3, comprising Pt alloy, Co-Ni-Al alloy, Co-Ni-Ga alloy, Ni-Fe-Ga alloy, Ti-Pd alloy or Ni-Ti alloy. .   The bulk superconductor according to claim 1, wherein a metal is impregnated in a gap between the superconducting bulk body and the surrounding belt.   The bulk superconductor according to claim 1, wherein a resin is impregnated in a gap between the superconducting bulk body and the surrounding belt. A superconducting bulk body;
A mold surrounding the superconducting bulk body with a gap therebetween;
Prepare
In the gap between the mold and the superconducting bulk body, a metal having a larger linear expansion coefficient than the superconducting bulk body is melted and cast,
A method for producing a bulk superconductor, wherein the molten metal is solidified to pressurize and surround the superconducting bulk body.