Method for manufacturing large-size densely-wound superconducting coil in high-intensity magnetic field

Abstract

The invention provides a method for manufacturing a large-size densely-wound superconducting coil in a high-intensity magnetic field, and relates to the field of superconducting materials, the superconducting coil is formed by winding a superconducting strip, at least one low-performance position exists on the superconducting strip used for winding the superconducting coil, and any low-performance position is provided with a joint patch structure. The joint patch structure completely covers the low-performance part of the superconducting tape. And the number of parts with lower performance on the superconducting tape for winding the superconducting coil is less than 10. The low-performance position of the superconducting tape is repaired through the patch structure, so that most superconducting performance of the low-performance position of the superconducting tape is kept, then the whole repaired superconducting tape is wound into the high-magnetic-field large-size closely-wound superconducting coil, no connector exists in the middle, the mechanical performance is stable, and the superconducting coil is not prone to deformation. And the preparation of the bulk superconductive densely-wound coils is not limited by the length of the single strip.

Description

Technical Field

[0001] The invention relates to the field of superconducting materials, and in particular to a method for manufacturing a large-size densely wound superconducting coil with a strong magnetic field. Background Art

[0002] The second-generation superconducting tape made of REBCO (Re is a rare earth element) is also called a coated conductor. Compared with bismuth-based tapes, it has a stronger current-carrying capacity, higher magnetic field performance and lower material cost, and has a wider and better application prospect in many fields such as medicine, military, and energy. The second-generation high-temperature superconducting tape is generally produced by a multi-layer coating process on a nickel-based alloy substrate because REBCO, which is the core of the superconducting current carrier, is hard and brittle. Therefore, it is also called a coated conductor. It is generally composed of a base tape, a buffer layer (transition layer), a superconducting layer, and a protective layer.

[0003] The role of the metal substrate is to provide excellent mechanical properties for the strip. The role of the transition layer is to prevent the mutual diffusion of elements between the superconducting layer and the metal substrate. On the other hand, the top transition layer needs to provide a good template for the epitaxial growth of the superconducting layer and improve the quality of grain arrangement. To prepare a coated conductor with excellent superconducting performance, the superconducting layer needs to have a consistent biaxial texture. Biaxial texture means that the grains have almost consistent arrangement in both the a / b axis and the c axis (the c axis is perpendicular to the a / b plane).

[0004] Since the degree of arrangement of YBCO film in the a / b axis direction (in-plane texture) is relatively difficult to achieve, and poor in-plane texture will seriously reduce the superconducting performance. Therefore, it is necessary to epitaxially grow the YBCO superconducting film on a transition layer that already has a biaxial texture and a matching lattice. There are two mainstream technical routes for preparing and realizing biaxial texture: one is the rolling-assisted biaxial texture base tape technology, and the other is the ion beam assisted deposition technology.

[0005] There are many common technologies for preparing REBCO superconducting layers, including pulsed laser deposition, metal organic chemical vapor deposition, reactive co-evaporation, etc. The protective layer is mainly used to protect the superconducting film layer. Generally, a 0.5-5μm silver layer is plated on the front and back surfaces of the superconducting tape by magnetron sputtering or evaporation. In order to pursue lower material costs, the silver layer on the superconducting surface is usually set at 1-2μm, and the silver layer on the non-superconducting surface is usually set at 0.5-1μm. Then, according to the requirements of the specific application for the width of the tape, the 10-12mm tape is cut into 2-8mm. Finally, copper plating or subsequent packaging reinforcement treatment is carried out. The copper plating thickness of the subsequent packaged tape can be 1-10μm. For copper-plated reinforced tape, the thickness of copper plating on one side is 10-30μm, and on both sides it reaches 20-60μm.

[0006] Strong magnetic fields can provide rare extreme experimental conditions for cutting-edge research in multiple disciplines such as physics, materials, chemistry, and life sciences. The development of high-field magnets is of great significance for promoting scientific development. The development of high-field magnets has also promoted the development of high-temperature superconducting tapes. High-field magnets based on REBCO high-temperature superconducting tapes have now reached 26.4T, exceeding the limit of NbTi-Nb3Sn magnets, see "26T 35mm all-GdBa2Cu3O7–x multi-width no insulationsuperconducting magnet". In 2019, Wang Qiuliang's team at the Institute of Electrical Engineering of the Chinese Academy of Sciences inserted a high-field magnet wound by REBCO into the 17T background field generated by the low-temperature superconducting wire and reached 32.35T, breaking the world record for the magnetic field strength of all-superconducting magnets, see "World record 32.35tesla direct-current magnetic field generatedwith an all-superconducting magnet". In 2019, the United States High Magnetic Field Laboratory broke the world record for steady-state magnetic field strength at 45.5T generated by the existing resistive magnet, "45.5-tesla direct-current magneticfield generated with a high-temperature superconducting magnet". In 2023, the Institute of Plasma Physics of the Chinese Academy of Sciences broke the world record for high-field magnets based on REBCO high-temperature superconducting tapes, reaching 26.8T, see "26.86-tesla direct-current magnetic field generated with an all-REBCO superconducting magnet". Currently, high-field magnets using second-generation high-temperature superconducting tapes are mainly used for high-resolution nuclear magnetic resonance (NMR) for biological structure analysis. The existing Ascend 1.1GHz model uses a hybrid magnet mode of HTS / LTS, with a standard aperture of 54mm and a central magnetic field strength of 25.9T. The development of this magnet is designed to meet the increasing scientific needs of scientists for sensitivity and higher resolution in the process of studying larger molecular weight proteins, functional disorder and macromolecular complexes. The 1.2GHz high-resolution protein NMR data were released, and the magnetic field strength of the magnet reached more than 28T. Figure 1As can be seen in the figure, there is a huge difference in the clarity of imaging with or without high-temperature superconductors in the nuclear magnetic resonance spectrometer. Breaking through the limits of human magnetic fields is of great significance. As the most promising way to achieve controlled fusion energy generation, the Tokamak magnetic confinement nuclear fusion device is highly dependent on a strong magnetic field to confine high-temperature plasma to produce fusion reactions. Its unit volume fusion power density is proportional to the fourth power of the magnetic field strength (P∝B4). Therefore, increasing the magnetic field strength of the superconducting magnet system can extremely efficiently increase the unit volume fusion power density and greatly reduce the size of the Tokamak fusion device, greatly reducing the engineering difficulty of the entire system, and is expected to significantly accelerate the development of commercially available controlled nuclear fusion technology. It is equally important in the field of high-energy particle accelerators. For the next generation of the muon collider designed by the European Organization for Nuclear Research (CERN), it is even proposed that the material should work at 55T (which humans have not yet reached). In order to improve the performance of the device or save costs, the increase in the magnetic field has become inevitable.

[0007] When high-field magnets approach their limits, the strips are usually subjected to huge electromagnetic stress. Many magnets are damaged before quenching because the local strips cannot withstand such large stress. Therefore, high-field magnets need to wind the superconducting strips tightly with tension to offset the stress on the material during the later operation to a certain extent. The pre-tension of the strip winding is often greater than 30MPa, and even the pre-tension of the strip winding of 40T magnets is greater than 100MPa. Since the stress on this type of coil in the magnetic field is particularly large, it is not tolerated that the superconducting strip in a pancake coil has joints, because the joints become the weak points of mechanical and electrical properties.

[0008] However, as the magnetic field requirements become higher and higher, these pancake coils are getting bigger and bigger, and the length of a single superconducting tape is getting longer and longer. Some large coils even require 800-1000 meters of single defect-free superconducting tape in batches. Taking the second-generation high-temperature superconducting tape as an example, the industry currently usually produces a single tape of 1000 meters in batches. Due to the complexity of the preparation process, defects will be randomly introduced into the long tape during the operation of raw materials, processes, and equipment, resulting in low points in the transmission current, which results in the average length of a single defect-free tape being distributed between 100-200 meters. After a batch of superconducting tapes is produced, the length of a single defect-free tape is normally distributed, and only a few superconducting tapes are quasi-kilometer long. This makes the supply of materials required for magnets a bottleneck, especially when a device requires a large amount of materials. Summary of the invention

[0009] In view of the defects in the prior art, the object of the present invention is to provide a method for manufacturing a large-size densely wound superconducting coil with a strong magnetic field.

[0010] According to the present invention, a method for manufacturing a large-size, densely wound superconducting coil with a strong magnetic field is provided, comprising a superconducting coil wound from a superconducting tape, wherein the superconducting tape used for winding the superconducting coil has at least one lower performance location, and any of the lower performance locations is provided with a joint patch structure; The method of manufacturing a superconducting tape for winding a superconducting coil comprises the following steps: Step S1, locating a location where the performance of the superconducting tape is relatively low; Step S2, coating flux and solder on the superconducting surface where the superconducting tape has lower performance, and coating flux and solder on the superconducting surface and back side of the patch structure respectively; Step S3, wiping off excess soldering flux on the superconducting tape and / or patch structure with alcohol; Step S4, aligning the patch structure and the superconducting tape in width direction and then welding them; Step S5, attaching the electric soldering iron to the back of the patch structure, moving the electric soldering iron in one direction to squeeze out the excess solder between the layers, and repeating this process multiple times; Step S6: welding small triangles in the transition zone at both ends of the patch structure.

[0011] Preferably, the joint patch structure completely covers the area where the superconducting tape has lower performance.

[0012] Preferably, the joint patch structure is connected across the top of the superconducting tape with lower performance, and at least one side of the patch structure at the superconducting tape with lower performance is larger than 10 cm.

[0013] Preferably, the superconducting surface of the joint patch structure is butted against the superconducting surface of the superconducting tape having the lower performance.

[0014] Preferably, the length direction of the joint patch structure is the same as the length direction of the superconducting tape, and the width direction of the joint patch structure is the same as the width direction of the superconducting tape.

[0015] Preferably, the number of the low-performance locations on a superconducting tape used for winding a superconducting coil is less than ten.

[0016] Preferably, the patch structure is a tape having a superconducting capacity not lower than that of the original superconducting tape; the front and rear ends of the patch structure along the length direction of the superconducting tape are both transition joints with gradually changing widths and inclinations, and the transition joints with gradually changing widths and inclinations do not have sharp ends.

[0017] Preferably, before applying the soldering iron, a soldering flux is applied to the back side of the patch structure.

[0018] Preferably, for step S5, the movement range of the electric soldering iron completely covers the bonding range of the patch structure and the superconducting tape.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention repairs the lower performance part of the superconducting tape through a patch structure, so that the lower performance part of the superconducting tape maintains most of the superconducting performance, and then the repaired whole superconducting tape is wound into a large-size densely wound superconducting coil with a strong magnetic field. There is no joint in the middle, and the mechanical properties are stable, so that the preparation of batches of superconducting densely wound coils is not limited by the length of a single tape. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 It is a schematic diagram of a superconducting tape mainly embodied in the present invention; Figure 2 This is a rendering of the low point of the superconducting tape of the present invention; Figure 3 This is a schematic diagram of the structure of the low point of the superconducting tape of the present invention; Figure 4 This is a schematic diagram of the low-point patch structure of a superconducting tape mainly embodied in the present invention; Figure 5 It is a schematic diagram of a transition joint patch with gradually changing and inclined widths at both the front and rear ends of the present invention; Figure 6 This is a schematic diagram of the present invention mainly showing the joint patch in the coil; Figure 7 This is a rendering of the low-point patch structure of the superconducting tape mainly embodied in the present invention; Figure 8 This is a schematic diagram of the overall structure of a large-size, densely wound superconducting coil with a strong magnetic field, which is mainly embodied in the present invention. DETAILED DESCRIPTION

[0021] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0022] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 as well as Figure 6 As shown, a strong magnetic field large-size densely wound superconducting coil provided according to the present invention includes a superconducting coil wound by a superconducting tape. There is at least one lower performance location on the superconducting tape used for winding the superconducting coil, and any lower performance location is provided with a joint patch structure.

[0023] Based on the requirements of large scientific facilities, a larger magnetic field is needed. The larger the magnetic field, the greater the Lorentz force. Therefore, the tape used to wind the large-sized densely wound superconducting coils in the magnetic field cannot be in the form of joints and splicing of two tapes, otherwise there is a risk of breakage at the joints. However, due to the current production process of superconducting tapes, it is difficult to directly process a defect-free tape of the required length. In order to meet the needs of large scientific facilities and match the current production process of superconducting tapes, the technical solution of this application utilizes a patch structure with superconducting capabilities to compensate for the defects on the superconducting tape, so that the large-sized densely wound superconducting coils can meet the requirements of large magnetic fields of large scientific facilities, and will not be damaged by the Lorentz force formed by the large magnetic field.

[0024] It should be noted that the patch structure of the present application is a tape having a superconducting capacity no less than that of the original superconducting tape, and is used to patch the lower performance areas on the superconducting tape of the present application.

[0025] Specifically, the joint patch structure completely covers the lower performance part of the superconducting tape. The superconducting surface of the joint patch structure is butted against the superconducting surface of the superconducting tape with the lower performance part. The length direction of the joint patch structure is the same as the length direction of the superconducting tape, and the width direction of the joint patch structure is the same as the width direction of the superconducting tape. The lower performance part of the superconducting tape is compensated by patching, so that the lower performance of the superconducting tape can retain most of the superconducting performance. Although the overall performance is not as good as that of a complete superconducting tape, it avoids the risk of fracture of two superconducting tapes spliced ​​in a large-sized densely wound superconducting coil to a certain extent, and can achieve mass production based on the current superconducting tape production process, without being limited by the length of a single tape.

[0026] In a preferred embodiment: both the front and rear ends of the patch structure along the length direction of the superconducting tape are transition joints with gradually changing widths, and the transition joints with gradually changing widths do not have sharp ends. The transition joints with gradually changing widths can reduce the risk of joint breakage caused by the small bending diameter of the belt wheel when the superconducting tape is wound, and the sharp ends of the transition joints are cut off to ensure a smooth cross-sectional cut and prevent the transition joints with gradually changing widths from twisting. It should be noted that the transition joints with gradually changing widths are inclined from the surface of the patch structure away from the superconducting tape to the surface close to the superconducting tape.

[0027] In a preferred embodiment, the joint patch structure is connected across the part of the superconducting tape with lower performance, and at least one side of the patch structure at the part of the superconducting tape with lower performance is larger than 10 cm.

[0028] In a preferred embodiment, the number of low-performance locations on a superconducting tape used for winding superconducting coils is less than 10. The tape can be tested by continuous measurement to select the tape with a superconducting long tape critical current distribution that meets the requirements.

[0029] The present invention also provides a method for manufacturing a strong magnetic field large-size densely wound superconducting coil, comprising the following steps: Step S1, locating the lower performance part of the superconducting tape. Use the continuous measurement method to test the tape, select the tape whose superconducting long tape critical current distribution meets the requirements, that is, the number of lower performance parts on the superconducting tape is less than 10, and then use the continuous long tape critical current test equipment to locate and mark the specific position of the defect.

[0030] Step S2: coating the superconducting surface of the superconducting tape with lower performance with flux and solder, and coating the superconducting surface and back surface of the patch structure with flux and solder respectively. The solder is completely wetted by the flux to ensure the welding effect.

[0031] Step S3, use alcohol to wipe off the excess flux on the superconducting tape and / or patch structure. After the flux completely soaks the solder, some of the flux will remain. If the excess flux is not removed, the flux will enter the weld during welding, affecting the quality of the weld.

[0032] Step S4: align the patch structure and the superconducting tape in width direction and then weld them.

[0033] Step S5, attaching the electric soldering iron to the back of the patch structure, moving the electric soldering iron in one direction to squeeze out the excess solder between the layers, and repeating this process back and forth for multiple times.

[0034] Step S6: welding small triangles in the transition zone at both ends of the patch structure.

[0035] Step S7, winding the superconducting tape produced in step S6 into a superconducting coil.

[0036] The patched strip needs to undergo a critical current test to confirm that the patch structure completely covers the lower performance areas of the superconducting strip.

[0037] Preferably, before using the soldering iron, a soldering flux is applied to the back of the patch structure. By applying the soldering flux to the back of the patch structure, the thermal conductivity of the soldering iron can be increased, thereby improving the welding quality.

[0038] Preferably, for step S5, the movement range of the electric soldering iron completely covers the bonding range of the patch structure and the superconducting tape, ensuring that the patch structure and the superconducting tape are completely bonded.

[0039] Large scientific facilities drive the development of cutting-edge materials. However, due to the high performance requirements of large scientific facilities themselves, once a material is formed, only a small amount of the top materials will be selected for use, and the demand for materials is particularly large. It is impossible for manufacturers to keep most of the materials idle. Blindly expanding production will inevitably hinder the progress of such large scientific facilities, thereby hindering the development of the entire material and even the development of downstream applications. The technical solution of this application has revitalized most of the materials here, so that the batch preparation of superconducting densely wound coils is not limited by the length of a single strip, which is of great significance to promoting the entire industry.

[0040] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0041] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for manufacturing a large-size, densely wound superconducting coil with a strong magnetic field, characterized in that: A superconducting coil is formed by winding a superconducting tape, wherein the superconducting tape used for winding the superconducting coil has at least one lower performance location, and any of the lower performance locations is provided with a joint patch structure; The method of manufacturing a superconducting tape for winding a superconducting coil comprises the following steps: Step S1, locating a location where the performance of the superconducting tape is relatively low; Step S2, coating flux and solder on the superconducting surface where the superconducting tape has lower performance, and coating flux and solder on the superconducting surface and back side of the patch structure respectively; Step S3, wiping off excess soldering flux on the superconducting tape and / or patch structure with alcohol; Step S4, aligning the patch structure and the superconducting tape in width direction and then welding them; Step S5, attaching the electric soldering iron to the back of the patch structure, moving the electric soldering iron in one direction to squeeze out the excess solder between the layers, and repeating this process multiple times; Step S6: welding small triangles in the transition zone at both ends of the patch structure.

2. The method for manufacturing a large-size, densely wound superconducting coil for a strong magnetic field as claimed in claim 1, characterized in that: The joint patch structure completely covers the lower performance area of ​​the superconducting tape.

3. The method for manufacturing a large-size, densely wound superconducting coil for a strong magnetic field as claimed in claim 1, characterized in that: The joint patch structure is connected across the top of the superconducting tape with lower performance, and at least one side of the patch structure at the superconducting tape with lower performance is larger than 10 cm.

4. The method for manufacturing a large-size, densely wound superconducting coil for a strong magnetic field as claimed in claim 1, characterized in that: The superconducting surface of the joint patch structure is butted against the superconducting surface of the superconducting tape having a lower performance.

5. The method for manufacturing a high-magnetic-field large-size densely wound superconducting coil according to claim 1, characterized in that: The length direction of the joint patch structure is the same as the length direction of the superconducting tape, and the width direction of the joint patch structure is the same as the width direction of the superconducting tape.

6. The method for manufacturing a large-size, densely wound superconducting coil for a strong magnetic field as claimed in claim 1, characterized in that: The number of low-performance areas on a superconducting tape used for winding a superconducting coil is less than ten.

7. The method for manufacturing a large-size, densely wound superconducting coil for a strong magnetic field as claimed in claim 1, characterized in that: The patch structure is a tape having a superconducting capacity no less than that of the original superconducting tape; The front and rear ends of the patch structure along the length direction of the superconducting tape are both transition joints with gradually changing widths and inclinations, and the transition joints with gradually changing widths and inclinations do not have sharp ends.

8. The method for manufacturing a large-size, densely wound superconducting coil for a strong magnetic field as claimed in claim 1, characterized in that: Before applying the soldering iron, flux is applied to the back side of the patch structure.

9. The method for manufacturing a high-magnetic-field large-size densely wound superconducting coil according to claim 1, characterized in that: With respect to step S5, the movement range of the electric soldering iron completely covers the bonding range of the patch structure and the superconducting tape.

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