A method of welding a high-field magnet REBCO outer joint

Abstract

The application discloses a welding method for a high-field magnet REBCO outer joint and belongs to the technical fields of REBCO joints and high-field magnets, and comprises the following steps: S10, cutting a bridging strip and coating a solder layer on a superconducting surface of the bridging strip; S20, marking welding areas on upper pie strip and lower pie strip of a superconducting coil; S30, laying an insulating isolation layer on the inside of the superconducting coil corresponding to the welding areas; S40, coating a solder layer on the inside of the welding areas of the upper pie strip and the lower pie strip of the superconducting coil; S50, coating a soldering flux on the side of the bridging strip coated with the solder; S60, pulling the upper pie strip and the lower pie strip of the superconducting coil along the strip direction of the upper pie strip and the lower pie strip, so that the upper pie strip and the lower pie strip press the lower half of the bridging strip; S70, sequentially welding the upper pie strip, the lower pie strip and the bridging strip by using an electric soldering iron; and S80, cleaning the welding position. According to the application, the coil strip only needs to be straightened and welded on the bridging strip position, and the operation is convenient.

Description

Technical Field

[0001] This invention belongs to the field of REBCO connectors and high-field magnet technology, and more specifically relates to a welding method for a high-field magnet REBCO external connector. Background Technology

[0002] High-temperature superconductivity is a highly cutting-edge and groundbreaking field in condensed matter physics and materials science. At relatively high critical temperatures, the electrical resistance of a material suddenly drops to zero, and it exhibits perfect diamagnetism (Meissner effect).

[0003] High-field magnets are currently the most important and valuable application area for high-temperature superconducting technology. Simply put, the task of high-field magnets is to generate continuous and stable strong magnetic fields that far exceed those of ordinary electromagnets (about 1-2 Tesla), providing extreme experimental conditions for cutting-edge science and technology.

[0004] Traditional low-temperature superconducting materials (such as niobium-titanium and niobium-tin alloys) lose their superconductivity in magnetic fields exceeding 20 Tesla. Therefore, inserting a high-temperature superconducting coil is the only realistic technical approach to withstand magnetic fields above 30 Tesla. Currently, only high-temperature superconductors (such as REBCO tapes) can maintain a high current-carrying capacity in extreme magnetic fields above 20 Tesla. During excitation, the larger the current and the stronger the magnetic field, the greater the electromagnetic stress and the greater the centripetal compressive force on the coil, almost crushing it. Simultaneously, with a large current input, the issue of coil-to-coil series connections arises. Therefore, the external coil connectors require higher mechanical strength and stability to ensure successful high-field testing. In high-field magnets, the welding quality of the external coil connectors directly determines the resistance, which has a decisive impact on magnet performance. Under high current, the connector resistance must be extremely low (typically in the nanoohm range) to reduce heat generation and losses during testing; otherwise, serious consequences may occur.

[0005] Chinese patent publication number CN122091986A discloses a REBCO strip joint structure and welding process. This welding method involves directly butt-connecting the strips, so the superconducting surfaces of the two strips must be connected. Although this method can achieve extremely low resistance, between coils, due to the requirements of the high-field magnet for the magnetic field, the field strength formed when the superconducting surface faces inward is greater. Therefore, two strips in the same direction cannot be directly butt-connected between their superconducting surfaces. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A welding method for the external connector of a high-field magnet REBCO includes the following steps: S10. Cut the bridging strip and coat the superconducting surface of the bridging strip with a solder layer; S20. Remove the ends of the upper and lower superconducting coil strips from the REBCO double coil body and adjust them to the same plane position. Mark the welding areas on the upper and lower superconducting coil strips. S30. An insulating layer is laid inside the superconducting coil corresponding to the welding area. S40. Apply a solder layer to the inside of the welding area of ​​the upper strip of the superconducting coil and the lower strip of the superconducting coil; S50. The bridging strip is placed with the solder-coated side facing outwards and coated with flux, and then placed at the series connection position between the upper strip of the superconducting coil and the lower strip of the superconducting coil. S60. Pull the end of the upper strip of the superconducting coil in its exit direction so that it presses against the upper half of the bridging strip; pull the end of the lower strip of the superconducting coil in its exit direction so that it presses against the lower half of the bridging strip. S70. Simultaneously pull in the upper and lower strips of the superconducting coil, apply flux to the welding positions of the upper and lower strips of the superconducting coil, and then use a soldering iron to sequentially weld the upper and lower strips of the superconducting coil to the bridging strip along the coil's output direction. S80. Clean the welding area.

[0007] Further, in step S10, the bridging strip has a width of 7-10mm, a thickness of 0.05-0.2mm, and a cutting length of 60-80mm.

[0008] Furthermore, in step S20, the same plane is a plane with the same outer diameter as the coil body.

[0009] Furthermore, in step S30, the insulating layer is a polyimide tape, and the length and width of the polyimide tape are both greater than the dimensions of the bridging tape.

[0010] Furthermore, in step S40, the inner side of the welding area is the superconducting surface of the upper and lower superconducting coil strips.

[0011] Further, in steps S10 and S40, a soldering iron is used to coat a solder layer, and the temperature of the soldering iron is set above the melting point of the solder but not exceeding 180°C; in step S70, the temperature of the soldering iron is set above the melting point of the solder but not exceeding 210°C.

[0012] Furthermore, in step S70, the single welding time of the upper superconducting coil strip, the lower superconducting coil strip, and the bridging strip does not exceed 2 minutes.

[0013] Further, in step S80, the cleaning process involves wiping the welding position with gauze soaked in 99% alcohol to remove flux residue.

[0014] Furthermore, in steps S10 and S70, the solder used for the bridging strip, the upper superconducting coil strip, and the lower superconducting coil strip is the same solder material.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The welding method for the external connector of the high-field magnet REBCO provided by this invention is applicable to the bridging welding between all high-temperature magnet REBCO coils. The bridging connector and the coil strip solder are made of the same solder material. The welding steps are simple, requiring only the coil strip to be straightened and soldered to the bridging strip position, making the operation convenient.

[0016] The direct connection between the coil strip and the bridging strip greatly reduces the resistance of the joint. Through multiple tests, the resistance can be maintained below 50nΩ. The resistance will be even lower when immersed in liquid helium, reducing heat generation and losses. This allows the bridging joint to remain stable even under extremely high field strength in high-temperature superconducting magnets. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the high-temperature superconducting coil structure of the present invention; Figure 2 This is a schematic diagram of the bridging strip of the present invention; Figure 3 This is a schematic diagram of the welding of the bridging joint between the high-field magnet coils of the present invention.

[0019] The components include: 1. REBCO double-pane coil body; 2. Upper pane strip of superconducting coil; 3. Lower pane strip of superconducting coil; 4. Bridging strip; 5. Copper terminal; 6. Copper terminal connector; 7. Upper pane strip of top coil. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1

[0022] refer to Figure 1 - Figure 3 A welding method for the external connector of a high-field magnet REBCO includes the following steps: S10. Cut the bridging strip 4 and coat the superconducting surface of the bridging strip 4 with a solder layer. The bridging strip 4 has a width of 7-10mm, a thickness of 0.05-0.2mm, and a cutting length of 60-80mm.

[0023] Preferably, the bridging strip 4 has a width of 8mm, a thickness of 0.1mm, and a cutting length of 70mm.

[0024] A solder layer is applied to the superconducting surface of the bridging strip 4 using a soldering iron. The temperature of the soldering iron is set above the melting point of the solder and does not exceed 180°C. S20. Remove the ends of the upper superconducting coil strip 2 and the lower superconducting coil strip 3 from the REBCO double coil body 1 and adjust them to the same plane position. Mark the welding areas on the upper superconducting coil strip 2 and the lower superconducting coil strip 3; wherein, the same plane is the same as the outer diameter of the coil body.

[0025] S30. Lay an insulating layer inside the superconducting coil corresponding to the welding area; Specifically, the insulating layer is a polyimide tape, and the length and width of the polyimide tape are both greater than the dimensions of the bridging tape 4.

[0026] S40. Apply a solder layer to the inside of the welding area of ​​the upper strip 2 and the lower strip 3 of the superconducting coil; The inner side of the welding area consists of the superconducting surfaces of the upper superconducting coil strip 2 and the lower superconducting coil strip 3. A soldering iron is used to coat the inner side of the welding area with solder, and the temperature of the soldering iron is set above the melting point of the solder but not exceeding 180°C.

[0027] S50. Place the bridging strip 4 with the solder-coated side facing outwards and apply flux, and place it at the series connection position between the upper strip 2 and the lower strip 3 of the superconducting coil. S60. Pull the end of the superconducting coil upper strip 2 in its exit direction so that it presses against the upper half of the bridging strip 4; pull the end of the superconducting coil lower strip 3 in its exit direction so that it presses against the lower half of the bridging strip 4. S70. Simultaneously pull in the upper superconducting coil strip 2 and the lower superconducting coil strip 3. Apply flux to the welding positions of the upper superconducting coil strip 2 and the lower superconducting coil strip 3. Then, in the direction of coil exit, use a soldering iron to sequentially weld the upper superconducting coil strip 2, the lower superconducting coil strip 3 and the bridging strip 4. The welding time for a single welding of the upper superconducting coil strip 2, the lower superconducting coil strip 3, and the bridging strip 4 does not exceed 2 minutes.

[0028] S80. Clean the welding area.

[0029] Specifically, the cleaning process involves wiping the welding area with gauze soaked in 99% alcohol to remove residual flux and other contaminants.

[0030] In this embodiment, in steps S10 and S70, the solder for the bridging strip 4 and the upper and lower superconducting coil strips uses the same solder material.

[0031] Example 2

[0032] This embodiment is based on Embodiment 1 and is illustrated with a specific implementation case.

[0033] A welding method for the external connector of a high-field magnet REBCO includes the following steps: S10. Prepare a bridging strip 4 with a width of 8mm, a length of 70mm, and a thickness of 0.1mm. Turn on the soldering iron and set the temperature to 180℃. Apply a layer of solder evenly to the superconducting surface of the bridging strip 4 and set it aside for later use.

[0034] S20. Remove the ends of the upper superconducting coil strip 2 and the lower superconducting coil strip 3 from the coil at the reserved positions until the outer diameters are the same and there is no height difference. Adjust the positions where the upper superconducting coil strip 2, the lower superconducting coil strip 3 and the bridging strip 4 need to be soldered, mark them clearly with a marker, turn on the soldering iron and set it to 180°C, and evenly apply a layer of solder to the inner superconducting surface of the marked positions of the upper superconducting coil strip 2 and the lower superconducting coil strip 3.

[0035] S30. Apply a layer of polyimide tape with a width of 8mm and a length of 120mm to the layer below the coil strip at the bridging position to ensure that flux and solder do not seep into the coil.

[0036] S40. Turn on the soldering iron and set the temperature to 180℃. Apply a layer of solder evenly to the inner superconducting surface of the marked positions of the upper superconducting coil strip 2 and the lower superconducting coil strip 3.

[0037] S50. Place the tin-plated side of the bridging strip 4 outwards and apply a layer of flux evenly. Then place it in the middle position between the upper strip 2 and the lower strip 3 of the superconducting coil, which are connected in series.

[0038] S60. At this time, the end of the upper strip 2 of the superconducting coil is pulled tight along the strip exit direction to press down the upper half of the bridging joint, and the end of the lower strip 3 of the superconducting coil is pulled tight along the strip exit direction to press down the lower half of the bridging joint.

[0039] S70. Simultaneously pull in the upper superconducting coil strip 2 and the lower superconducting coil strip 3. Apply a layer of flux evenly to the surface of the upper superconducting coil strip 2 and the lower superconducting coil strip 3 at the bridging joint position. Turn on the soldering iron and adjust the temperature to 200℃. Sequentially solder the upper superconducting coil strip 2 and the lower superconducting coil strip 3 to the bridging strip 4 at the bridging positions along the coil output direction.

[0040] S80. The soldering time should be controlled within 2 minutes. If the solder of the bridging joint is uniform and full, the soldering is considered to be completed. Finally, use gauze with a small amount of alcohol to wipe the soldering position to remove flux and other stains.

[0041] The copper terminal 5 is fixedly welded to the strip 7 on the top coil, using the same connection method as the coil series connector welding method. The copper terminal connector 6 connects the coil and the copper terminal 5 in series, electrically connecting the superconducting coil to the external excitation power supply. This connection uses low-temperature soldering, with a soldering temperature not exceeding 200℃, to ensure good conductive contact while avoiding adverse effects on the superconducting performance of the REBCO strip. The copper terminal 5 provides a stable current injection and output port for the coil and withstands the mechanical stress from the external leads.

[0042] This invention uses direct connection between coil strip and bridging strip to greatly reduce the resistance of the joint. Through multiple test data, it can be maintained within 50nΩ. The resistance will be even lower when immersed in liquid helium, reducing heat generation and loss. This allows the bridging joint to remain stable even under extremely strong electric fields in high-temperature superconducting magnets.

[0043] The technical solutions of the present invention have been fully described above. It should be noted that the specific embodiments of the present invention are not limited to the above description. All technical solutions formed by those skilled in the art based on the spirit and essence of the present invention by adopting equivalent transformations or equivalent transformations in terms of structure, method or function fall within the protection scope of the present invention.

Claims

1. A welding method for the external connector of a high-field magnet REBCO, characterized in that, Includes the following steps: S10. Cut the bridging strip and coat the superconducting surface of the bridging strip with a solder layer; S20. Remove the ends of the upper and lower superconducting coil strips from the REBCO double coil body and adjust them to the same plane position. Mark the welding areas on the upper and lower superconducting coil strips. S30. An insulating layer is laid inside the superconducting coil corresponding to the welding area. S40. Apply a solder layer to the inside of the welding area of ​​the upper strip of the superconducting coil and the lower strip of the superconducting coil; S50. The bridging strip is placed with the solder-coated side facing outwards and coated with flux, and then placed at the series connection position between the upper strip of the superconducting coil and the lower strip of the superconducting coil. S60. Pull the end of the upper strip of the superconducting coil in its exit direction so that it presses against the upper half of the bridging strip; pull the end of the lower strip of the superconducting coil in its exit direction so that it presses against the lower half of the bridging strip. S70. Simultaneously pull in the upper and lower strips of the superconducting coil, apply flux to the welding positions of the upper and lower strips of the superconducting coil, and then use a soldering iron to sequentially weld the upper and lower strips of the superconducting coil to the bridging strip along the coil's output direction. S80. Clean the welding area.

2. The welding method for the high-field magnet REBCO external connector according to claim 1, characterized in that, In step S10, the bridging strip has a width of 7-10mm, a thickness of 0.05-0.2mm, and a cutting length of 60-80mm.

3. The welding method for the REBCO external connector of a high-field magnet according to claim 1, characterized in that, In step S20, the same plane is the same as the outer diameter of the coil body.

4. The welding method for the high-field magnet REBCO external connector according to claim 1, characterized in that, In step S30, the insulating layer is a polyimide tape, and the length and width of the polyimide tape are both greater than the dimensions of the bridging tape.

5. The welding method for the high-field magnet REBCO external connector according to claim 1, characterized in that, In step S40, the inner side of the welding area is the superconducting surface of the upper and lower superconducting coil strips.

6. The welding method for the REBCO external connector of a high-field magnet according to claim 1, characterized in that, In steps S10 and S40, a soldering iron is used to coat a solder layer, and the temperature of the soldering iron is set above the melting point of the solder but not exceeding 180°C; in step S70, the temperature of the soldering iron is set above the melting point of the solder but not exceeding 210°C.

7. The welding method for the high-field magnet REBCO external connector according to claim 1, characterized in that, In step S70, the single welding time of the upper superconducting coil strip, the lower superconducting coil strip, and the bridging strip does not exceed 2 minutes.

8. The welding method for the REBCO external connector of a high-field magnet according to claim 1, characterized in that, In step S80, the cleaning process involves wiping the welding area with gauze soaked in 99% alcohol to remove flux residue.

9. The welding method for the REBCO external connector of a high-field magnet according to claim 1, characterized in that, In steps S10 and S70, the solder used for the bridging strip, the upper superconducting coil strip, and the lower superconducting coil strip is the same solder material.

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