REBCO high temperature superconducting coil internal joint, welding device and preparation method

Abstract

The invention discloses an inner joint of a REBCO high-temperature superconducting coil, a welding device and a preparation method thereof, and relates to the technical field of joint structures, wherein the inner joint comprises: a lower REBCO strip, an upper REBCO strip and a bridge strip; the upper REBCO strip and the lower REBCO strip are arranged in parallel and staggered, and one end of the upper REBCO strip is connected to the lower REBCO strip through the bridge strip; the inner joint disclosed by the invention has the characteristics of low resistance, high mechanical strength and smooth surface, and solves the problem of excessive in-plane bending strain existing in the traditional double-cake winding method.

Description

Technical Field

[0001] The present invention relates to the technical field of joint structures, and more particularly to a REBCO high-temperature superconducting coil inner joint, a welding device and a preparation method. Background Art

[0002] At present, future nuclear fusion devices, high-energy particle accelerators, large scientific facilities such as strong magnetic fields, and MRI / NMR require higher and higher magnetic field strengths. Compared with water-cooled magnets, superconducting magnets have a more compact structure, lower power consumption, and are easy to achieve higher magnetic fields. The critical current of low-temperature superconducting materials (NbTi, Nb3Sn) under high fields is very low, and they have almost no current carrying capacity under magnetic fields above 24T. Compared with other high-temperature superconducting materials, REBCO high-temperature superconducting tapes have the advantages of high current carrying capacity, high irreversible field and high mechanical strength. In addition, REBCO materials have been commercialized, with mature preparation technology, no need for high-temperature heat treatment, and low cost. They have great application advantages in the future field of high-field magnets.

[0003] However, in order to obtain a strong magnetic field environment, research institutions at home and abroad currently usually adopt a hybrid magnet solution, that is, inserting the REBCO high-temperature superconducting coil into the back field magnet. Limited by the aperture of the back field magnet, and in order to achieve a higher magnetic field, the winding radius of the REBCO high-temperature superconducting coil is relatively small. At this time, if the traditional double-cake winding method is used, the innermost layer of the strip will have a bandwidth transition, resulting in large out-of-plane bending strain and in-plane bending strain in this layer of strip, which is enough to cause a significant decline in the critical performance of the REBCO strip. Therefore, only the single-cake winding method can be used, with an inner joint replacing the innermost transition. Adjacent single cakes are "electrically connected" through the inner joint to form a double cake, and then several double cakes are stacked and formed into a REBCO high-temperature superconducting coil through an external joint.

[0004] Therefore, it is necessary to develop an inner joint structure, a preparation method and a welding device suitable for REBCO high-temperature superconducting coils. Summary of the invention

[0005] In view of this, the present invention provides a REBCO high-temperature superconducting coil inner joint, a welding device and a preparation method. The inner joint has the characteristics of low resistance, high mechanical strength and smooth surface, and solves the problem of excessive in-plane bending strain in the traditional double-pancake winding method.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A REBCO high temperature superconducting coil inner joint, comprising: a lower REBCO strip, an upper REBCO strip and a bridge strip;

[0008] The upper REBCO strip and the lower REBCO strip are arranged in parallel and staggered manner, and one end of the upper REBCO strip is connected to the lower REBCO strip through the bridge strip.

[0009] Preferably, the width of the bridge strip is twice that of the upper REBCO strip and the lower REBCO strip.

[0010] Furthermore, the present invention also provides a welding device for a REBCO high-temperature superconducting coil inner joint suitable for any one of the above items, comprising: an arc-shaped pressing block, a screw pressure structure, a central support column and a support member;

[0011] The arc-shaped pressing block is located between the central support column and the support member, and the central support column and the support member are integrally arranged;

[0012] The support member is provided with a threaded hole, and the screw pressure structure passes through the arc-shaped pressure block and the support member in sequence through the threaded hole.

[0013] Preferably, the diameter of the arc-shaped pressing block is the same as the winding inner diameter of the REBCO high-temperature superconducting coil.

[0014] Preferably, the screw pressure structure is a pressure screw, and the pressure screw corresponds to the threaded hole.

[0015] Furthermore, the present invention also provides a method for preparing a welding device for a REBCO high-temperature superconducting coil inner joint using any one of the above-mentioned methods, comprising:

[0016] S1: Surface pretreatment is performed on the upper REBCO strip, the lower REBCO strip and the bridge strip, and a thin layer of tin is applied after the surface to be connected is exposed;

[0017] S2: Tinning the surfaces to be connected of the upper REBCO strip and the lower REBCO strip;

[0018] S3: Arrange the upper REBCO strip and the lower REBCO strip in parallel on the bridge strip, and the two ends of the upper REBCO strip and the lower REBCO strip are parallel to the two ends of the bridge strip respectively;

[0019] S4: placing the inner joint into the gap between the arc-shaped pressing block and the central support column, and then controlling the screw pressure structure to apply pre-pressure to the inner joint;

[0020] S5: After the solder on the surfaces of the upper REBCO strip, the lower REBCO strip and the bridge strip to be connected is melted, the inner joint is pressed by the screw pressure structure, and the overflowed solder is removed;

[0021] S6: After removing the welding device and the inner joint, the temperature is quickly lowered to remove the pressure of the screw pressure structure, and the inner joint is removed from the welding device to complete the preparation.

[0022] Preferably, the length of the tinning area on the surface to be connected of the lower REBCO strip and the upper REBCO strip is 3-6 mm longer than the length of the tinning area on the surface to be connected of the bridge strip.

[0023] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a REBCO high-temperature superconducting coil inner joint, welding device and preparation method, which solves the problem of excessive in-plane bending strain in the traditional double-pancake winding method. The inner joint prepared by this method and welding device has the characteristics of low resistance, high mechanical strength, stable performance and smooth surface. The present invention is of great significance to the research of REBCO superconducting coils, and lays an important foundation for the application of REBCO superconducting coils in high-field fields such as NMR, nuclear fusion devices and accelerators. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0025] Figure 1 A schematic structural diagram of a REBCO high-temperature superconducting coil internal joint provided by the present invention;

[0026] Figure 2 The present invention is a schematic structural diagram of a welding device for a REBCO high-temperature superconducting coil inner joint provided by the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] See attached Figure 1 As shown, the embodiment of the present invention discloses a REBCO high temperature superconducting coil inner joint, comprising: a lower REBCO tape 1, an upper REBCO tape 2 and a bridge tape 3;

[0029] The upper REBCO strip 2 and the lower REBCO strip 1 are arranged in parallel and staggered manner, and one end of the upper REBCO strip 2 is connected to the lower REBCO strip through a bridge strip 3 .

[0030] In a specific embodiment, the width of the bridge strip 3 is twice that of the upper REBCO strip 2 and the lower REBCO strip 1 .

[0031] See attached Figure 2 As shown, the embodiment of the present invention further provides a welding device for a REBCO high temperature superconducting coil inner joint applicable to any of the above items, comprising: an arc-shaped pressing block 4, a screw pressure structure 5, a central support column 7 and a support member 8;

[0032] The arc-shaped pressing block 4 is located between the central support column 7 and the support member 8, and the central support column 7 and the support member 8 are integrated;

[0033] The support member 8 is provided with a threaded hole 6 , and the screw pressure structure 5 passes through the arc-shaped pressing block 4 and the support member 8 in sequence through the threaded hole 6 .

[0034] In a specific embodiment, the diameter of the arc-shaped pressing block 4 is the same as the winding inner diameter of the REBCO high-temperature superconducting coil.

[0035] In a specific embodiment, the screw pressure structure 5 is a pressure screw, and the pressure screw corresponds to the threaded hole 6 .

[0036] Specifically, the arc-shaped pressing blocks 4 are made of aluminum alloy. There are three of them, which are separated from each other and have smooth surfaces. The angle of each arc-shaped surface is 90°, and its diameter is the same as the winding inner diameter of the coil.

[0037] The central support column 7 and the support member 8 are integrated and made of aluminum alloy with a smooth surface. The diameter thereof is the same as the inner diameter of the coil. The support member 8 is made of aluminum alloy and serves as a support for the inner joint and other functional structures, and conducts the heat of the heating platform to the inner joint strip.

[0038] The embodiment of the present invention further provides a method for preparing a welding device for a REBCO high temperature superconducting coil inner joint using any one of the above embodiments, comprising:

[0039] S1: Perform surface pretreatment on the upper REBCO strip 2, the lower REBCO strip 1 and the bridge strip 3. After the surfaces to be connected are exposed, a thin layer of tin is applied to keep the ends neat. The length of the bridge strip 3 should be three quarters of the circumference of the coil.

[0040] S2: Tinning the surfaces to be connected of the upper REBCO strip 2 and the lower REBCO strip 1;

[0041] S3: Arrange the upper REBCO tape 2 and the lower REBCO tape 1 in parallel on the bridge tape 3, and the two ends of the upper REBCO tape 2 and the lower REBCO tape 1 are parallel to the two ends of the bridge tape 3 respectively; at the same time, in order to reduce the joint resistance, the surfaces of the tapes where the superconducting layers are located should contact each other, and then use an electric iron to spot weld the ends of the upper REBCO tape 2 and the lower REBCO tape 1 respectively to fix their relative positions;

[0042] S4: placing the inner joint into the gap between the arc-shaped pressing block 4 and the central support column 7, and then controlling the screw pressure structure 5 to apply pre-pressure to the inner joint;

[0043] S5: After the solder on the surfaces of the upper REBCO strip 2, the lower REBCO strip 1 and the bridge strip 3 to be connected is melted, the inner joint is pressed by the screw pressure structure 5, and the overflowed solder is removed;

[0044] S6: After removing the welding device and the inner joint, the temperature is quickly lowered to remove the pressure of the screw pressure structure 5, and the inner joint is removed from the welding device to complete the preparation.

[0045] In a specific embodiment, the length of the tinning area of ​​the surfaces to be connected of the lower REBCO strip 1 and the upper REBCO strip 2 is 3-6 mm longer than the length of the tinning area of ​​the surface to be connected of the bridge strip 3.

[0046] In a specific embodiment, in S5, the temperature of the heating platform at the bottom of the welding device is adjusted to 200° C. After the solder is bent and melted, the inner joint is pressed again by the screw pressure structure, and the overflowed solder is removed.

[0047] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0048] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a REBCO high temperature superconducting coil inner joint, characterized in that: include: The REBCO high temperature superconducting coil inner joint comprises: a lower REBCO tape (1), an upper REBCO tape (2) and a bridge tape (3); The upper REBCO strip (2) and the lower REBCO strip (1) are arranged in parallel and staggered manner, and one end of the upper REBCO strip (2) is connected to the lower REBCO strip via the bridge strip (3); The preparation method comprises the following steps: S1: Perform surface pretreatment on the upper REBCO strip (2), the lower REBCO strip (1) and the bridge strip (3), and apply a thin layer of tin after exposing the surface to be connected; S2: Tinning the surfaces to be connected of the upper REBCO strip (2) and the lower REBCO strip (1); S3: Arrange the upper REBCO strip (2) and the lower REBCO strip (1) in parallel on the bridge strip (3), and the two ends of the upper REBCO strip (2) and the lower REBCO strip (1) are parallel to the two ends of the bridge strip (3); S4: placing the inner joint into the gap between the arc-shaped pressing block (4) and the central support column (7), and then controlling the screw pressure structure (5) to apply pre-pressure to the inner joint, wherein the arc-shaped pressing block (4) is located between the central support column (7) and the support member (8), and the support member (8) is provided with a threaded hole (6); S5: After the solder on the connecting surfaces of the upper REBCO strip (2), the lower REBCO strip (1) and the bridge strip (3) is melted, the inner joint is pressed by the screw pressure structure (5) and the overflowed solder is removed; S6: After removing the welding device and the inner joint, the temperature is quickly lowered to remove the pressure of the screw pressure structure (5), and the inner joint is removed from the welding device to complete the preparation.

2. The method for preparing a REBCO high temperature superconducting coil inner joint according to claim 1, characterized in that: The width of the bridge strip (3) is twice that of the upper REBCO strip (2) and the lower REBCO strip (1).

3. The method for preparing a REBCO high temperature superconducting coil inner joint according to claim 1, characterized in that: The diameter of the arc-shaped pressing block (4) is the same as the winding inner diameter of the REBCO high-temperature superconducting coil.

4. The method for preparing a REBCO high temperature superconducting coil inner joint according to claim 1, characterized in that: The screw pressure structure (5) is a pressure screw, and the pressure screw corresponds to the threaded hole (6).

5. The method for preparing a REBCO high temperature superconducting coil inner joint according to claim 1, characterized in that: The length of the tinning area of ​​the surfaces to be connected of the lower REBCO strip (1) and the upper REBCO strip (2) is 3-6 mm longer than the length of the tinning area of ​​the surface to be connected of the bridge strip (3).

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