REBCO strip joint structure and welding process

Abstract

This invention relates to a REBCO strip joint structure and welding process, belonging to the field of REBCO strip technology. The REBCO strip joint structure includes a first REBCO strip and a second REBCO strip back-to-back welded together; it also includes a superconducting connector, which is welded and fixed to at least the upper surfaces of the first REBCO strip and the second REBCO strip; the superconducting connector is a flat superconducting connector strip or a hollow superconducting joint block. This invention can reduce the resistance of the welded joint, improve the mechanical strength of the welded joint, avoid poor contact at the joint, and prevent the resulting performance degradation or superconducting failure of the REBCO strip.

Description

Technical Field

[0001] This invention relates to a REBCO strip joint structure and welding process, belonging to the field of REBCO strip technology. Background Technology

[0002] Superconducting technology has demonstrated significant advantages and plays an irreplaceable role in numerous fields, including power, communications, high-tech equipment, and military equipment. With the rapid advancements in high-temperature superconducting materials and cryogenic refrigeration technology, the performance of high-temperature superconducting materials is continuously improving, their fabrication processes are gradually being optimized, and their applications are becoming increasingly mature and covering a wider range of fields. In many applications, second-generation high-temperature superconducting tapes (REBCO) are crucial core components.

[0003] Due to the conflict between standardized production management and differentiated demand, manufacturers are often unable to directly produce REBCO strips of the appropriate length based on actual application requirements. This means that in most cases, we cannot rely on a single REBCO strip to meet project requirements, and instead need to weld and splice two or more REBCO strips to obtain the required length.

[0004] In the aforementioned welding process, the quality of the weld joint is crucial. A key indicator of weld joint quality is its resistance. In high-performance superconducting applications (such as magnetic resonance imaging (MRI) equipment and particle accelerators), increased resistance leads to current loss and excessive heat generation, thus affecting the equipment's operational performance. To reduce current loss, prevent degradation of superconducting performance, and ensure the current transmission efficiency and superconducting stability of the entire system during operation, the resistance of the weld joint must be minimized.

[0005] While welding superconducting layers together can achieve lower welding resistance, the welding strength is extremely low, making it unsuitable for engineering applications. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention proposes a REBCO strip joint structure and welding process that can reduce the resistance of the welded joint, improve its mechanical strength, and prevent poor contact at the joint and the resulting performance degradation or superconducting failure of the REBCO strip.

[0007] The first aspect of this invention relates to a REBCO strip joint structure, comprising a first REBCO strip and a second REBCO strip stacked back-to-back;

[0008] It also includes a superconducting connector, which is welded and fixed to at least the upper surface of the first REBCO tape and the upper surface of the second REBCO tape.

[0009] The superconducting connector is a flat superconducting connecting strip or a hollow superconducting joint block;

[0010] The flat superconducting connecting band is a stacked structure of copper layer / superconducting layer / base band layer / superconducting layer / copper layer, or a stacked structure of copper layer / superconducting layer / copper layer. The superconducting layer can be deposited and prepared by existing methods such as MOCVD and MOD.

[0011] The superconducting connector hollow block is a stacked structure of an outer copper layer and an inner superconducting layer, or a single copper layer structure, or a stacked structure of copper layer / superconducting layer / copper layer. The superconducting connector hollow block can be prepared by existing methods such as solid-state reaction sintering, melting growth, and seed crystal induced melting growth.

[0012] The second aspect of the present invention relates to a welding and forming process for the above-mentioned REBCO tape joint structure, wherein the superconducting connector is welded and fixed to at least the upper surface of the first REBCO tape and the upper surface of the second REBCO tape.

[0013] Technical effect

[0014] Compared to direct lap welding, the two REBCO tapes are welded together through a superconducting connector, which reduces the resistance during connection. At the same time, the two REBCO tape bodies are directly connected by lap welding, achieving higher joint strength and ensuring the reliability and durability of the low-resistance connection. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the REBCO strip back-to-back lap welding structure in an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of the flat superconducting connecting strip in an embodiment of the present invention;

[0017] Figure 3 This is a schematic cross-sectional view of a flat superconducting connecting strip in an embodiment of the present invention;

[0018] Figure 4 This is a schematic cross-sectional view of another flat superconducting connecting strip in an embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram of the structure of the hollow block of the superconducting connector in an embodiment of the present invention;

[0020] Figure 6 This is a schematic diagram of a welding structure using flat superconducting connecting strips in an embodiment of the present invention;

[0021] Figure 7 This is a schematic diagram of the structure of the REBCO tape strip peeled off to expose the superconducting layer in an embodiment of the present invention;

[0022] Figure 8 This is a schematic diagram of the welding structure using a superconducting connector hollow block connection in an embodiment of the present invention;

[0023] Figure 9 This is a schematic diagram of the structure of REBCO tape directly welded through a superconducting layer in the existing technology;

[0024] In the figure: 101, copper layer; 102, superconducting layer; 103, baseband layer; 201, first REBCO tape; 202, second REBCO tape; 300, flat superconducting connecting tape; 301, first welding arm; 302, second welding arm; 310, connecting arm; 400, hollow block of superconducting connector. Detailed Implementation

[0025] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Experimental methods not specifically described in the embodiments were performed according to conventional methods and conditions.

[0026] It should be noted that, in specific embodiments, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. Terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly defined, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0027] This invention relates to a REBCO strip joint structure, including as follows: Figure 1 The first REBCO strip 201 and the second REBCO strip 202 are shown to be back-to-back laminated; the first REBCO strip 201 and the second REBCO strip 202 both adopt the same laminated structure, which is copper layer 101 / superconducting layer 102 / baseband layer 103 / copper layer 101 in sequence.

[0028] In addition, it also includes a superconducting connector, which is welded and fixed to at least the upper surface of the first REBCO tape 201 and the upper surface of the second REBCO tape 202.

[0029] The superconducting connector is either a flat superconducting connecting strip 300 or a hollow superconducting connector block 400, respectively forming Figure 6 , Figure 8 The structure shown;

[0030] The flat superconducting connecting strip 300 is as follows: Figure 3 The stacked structure shown is copper layer 101 / superconducting layer 102 / baseband layer 103 / superconducting layer 102 / copper layer 101, or as shown in the figure. Figure 4 The stacked structure of copper layer 101 / superconducting layer 102 / copper layer 101 is shown; the superconducting layer can be deposited and prepared by existing methods such as MOCVD and MOD.

[0031] The superconducting connector hollow block 400, as described above Figure 5 As shown, it is a stacked structure of an outer copper layer and an inner superconducting layer, or a single copper layer structure, or a stacked structure of copper layer / superconducting layer / copper layer; the hollow block of the superconducting joint can be prepared by existing methods such as solid-state reaction sintering, melting growth, and seed crystal induced melting growth.

[0032] In some preferred embodiments, the flat superconducting connecting strip 300 includes a first welding arm 301, a connecting arm 310, and a second welding arm 302 connected in sequence. The first welding arm 301 is welded and fixed to the upper surface of the first REBCO strip 201 (i.e., the copper layer 101 near the superconducting layer 102), and the second welding arm 302 is welded and fixed to the upper surface of the second REBCO strip 202 (i.e., the copper layer 101 near the superconducting layer 102). More preferably, it is formed as follows... Figure 2 The "U"-shaped structure is shown. More preferably, the lengths of the first welding arm and the second welding arm in the strip extension direction are 1–20 cm, respectively.

[0033] In some preferred embodiments, the welding and overlapping portions of the flat superconducting connecting strip 300 with the first REBCO strip 201 and the second REBCO strip 202 are staggered, that is, staggered in the extension direction of the strips, so that the connecting arm 310 is inclined relative to the extension direction of the first REBCO strip 201 and the second REBCO strip 202, such as... Figure 6 As shown. More preferably, the connecting arm 310 is welded and fixed to the first REBCO tape 201 and the second REBCO tape 202 on the side, which further improves the connection strength and reduces the connection resistance.

[0034] In some preferred embodiments, the superconducting connector hollow block 400 is fitted onto the overlap of the first REBCO strip 201 and the second REBCO strip 202, and is simultaneously welded and fixed to the sides of the first REBCO strip 201 and the second REBCO strip 202, further improving the connection strength and reducing the connection resistance. In the thickness direction of the overlap, the outer surfaces of both the first REBCO strip 201 and the second REBCO strip 202 have no copper layer. More preferably, in the thickness direction of the strips, the inner top surface of the superconducting connector hollow block abuts against the superconducting layer of the first REBCO strip, and the inner bottom surface abuts against the superconducting layer of the second REBCO strip, or a thin insulating layer is provided between the inner top surface of the superconducting connector hollow block and the superconducting layer of the first REBCO strip, and between the inner bottom surface of the superconducting connector hollow block and the superconducting layer of the second REBCO strip, which can form a Josephson junction and realize current transmission in the superconducting state.

[0035] For some preferred implementation schemes, such as Figure 5 and Figure 8 As shown, the outer top surface of the superconducting connector hollow block 400 is flush with the upper surface of the first REBCO tape 201, and the outer bottom surface is flush with the upper surface of the second REBCO tape 202.

[0036] This invention also relates to a welding and forming process for the above-mentioned REBCO strip joint structure, including:

[0037] Back-to-back lamination step: Lay the first REBCO strip and the second REBCO strip back-to-back;

[0038] Welding steps: The superconducting connector is welded and fixed to at least the upper surface of the first REBCO tape and the upper surface of the second REBCO tape.

[0039] In some preferred embodiments, the length of the back-to-back overlay is 5 to 7 cm.

[0040] Example 1

[0041] For the "U"-shaped flat superconducting connecting strip 300 welding scheme:

[0042] like Figure 1 As shown, the first step is to weld two REBCO strips, the first REBCO strip 201 and the second REBCO strip 202, back to back. During the welding process, on the one hand, precise butt joint is required, that is, the two strips overlap in the width direction at the overlapping area (the welding length is set to 5cm), and on the other hand, the weld is required to be uniform, so as to ensure that the welded connection has good connection strength.

[0043] Next, based on the above REBCO strip selection, as follows: Figure 3The flat superconducting connecting strip 300 shown is cut to match the dimensions of the first welding arm 301 and the second welding arm 302 with the dimensions of the first REBCO tape 201 and the second REBCO tape 202, ensuring accurate welding. The cut flat superconducting connecting strip 300 should be overlapped from the side onto the first REBCO tape 201 and the second REBCO tape 202 in an up-down manner.

[0044] Finally, welding was performed using an appropriate welding process. In this embodiment, 6337 solder was used, the welding temperature was 220℃, and the pressure was 200N, resulting in the following... Figure 6 The connection structure shown.

[0045] Example 2

[0046] For the welding solution of the 400mm hollow block of the superconducting joint:

[0047] like Figure 7 As shown, the two REBCO tapes, the first REBCO tape 201 and the second REBCO tape 202, need to be processed to remove the copper layer on the outermost surface of the part to be stacked (5cm in length) (such as by grinding). After removing the copper layer, a thin insulating layer with a thickness less than that of the copper layer can be added on the superconducting layer.

[0048] Taking REBCO tape with an added thin insulation layer as an example, we will explain by selecting... Figure 5 The hollow superconducting connector 400 shown is cut to the required shape and size. Then, the treated ends of the first REBCO tape 201 and the second REBCO tape 202 are inserted into the hollow superconducting connector 400, so that they fit tightly together, resulting in the desired shape. Figure 8 The structure shown;

[0049] Finally, the two REBCO tapes are welded and fixed to the superconducting connector hollow block 400 module. The REBCO tapes with added insulation layer can form Josephson junctions after back-to-back stacking and welding, thereby realizing current transmission in the superconducting state.

[0050] Comparative Example 1

[0051] Structure as Figure 1 As shown, the length of the back-to-back overlapping weld is 5cm.

[0052] Comparative Example 2

[0053] The connection structure of two superconducting tapes is as follows Figure 9 As shown, a section of the copper plating structure on the superconducting layer side was removed, allowing the superconducting layers to be directly welded together, with a weld length of 5cm.

[0054] The spliced ​​REBCO tapes (4 mm wide) prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to joint resistance and tensile strength tests, and the results are shown in Table 1.

[0055] Table 1 Welding scheme Connector resistance Tensile strength (Ic retention rate > 95%) Example 1 5nΩ ＞500N Example 2 <1nΩ ＞500N Comparative Example 1 15nΩ ＞400N Comparative Example 2 <1nΩ ＜10N

[0056] Comparative Example 2, through direct welding of the superconducting layers, effectively reduced the joint resistance; however, the connection strength between the superconducting layers was very low, making it unsuitable for engineering applications. Compared to Comparative Example 2, the lap-welded structure of Comparative Example 1 significantly improved the tensile strength of the two REBCO strips, but the lap-welded structure had a higher joint resistance. Further comparing Comparative Example 1 and Example 1, the flat superconducting connecting strip reduced the resistance of the connection between the two REBCO strips, while comparing Example 1 and Example 2, the more regular connection structure further reduced the joint resistance.

[0057] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A REBCO strip joint structure, characterized in that: Includes a first REBCO strip and a second REBCO strip that are back-to-back welded together; It also includes a superconducting connector, which is welded and fixed to at least the upper surface of the first REBCO tape and the upper surface of the second REBCO tape. The superconducting connector is a flat superconducting connecting strip or a hollow superconducting connector block; The flat superconducting connecting strip is a stacked structure of copper layer / superconducting layer / baseband layer / superconducting layer / copper layer, or a stacked structure of copper layer / superconducting layer / copper layer; The superconducting connector hollow block is a stacked structure of an outer copper layer and an inner superconducting layer, or a single copper layer structure, or a stacked structure of copper layer / superconducting layer / copper layer.

2. The REBCO strip joint structure according to claim 1, characterized in that: The flat superconducting connecting strip includes a first welding arm, a connecting arm, and a second welding arm connected in sequence. The first welding arm is welded and fixed to the upper surface of the first REBCO strip, and the second welding arm is welded and fixed to the upper surface of the second REBCO strip.

3. The REBCO strip joint structure according to claim 2, characterized in that: The welding and overlapping parts of the flat superconducting connecting strip with the first REBCO strip and the second REBCO strip are staggered, and the connecting arm is inclined relative to the extension direction of the first REBCO strip and the second REBCO strip.

4. The REBCO strip joint structure according to claim 2 or 3, characterized in that: The connecting arm is welded and fixed to the first REBCO strip and the second REBCO strip on the side.

5. The REBCO strip joint structure according to claim 2 or 3, characterized in that: The lengths of the first welding arm and the second welding arm in the strip extension direction are 1 to 20 cm, respectively.

6. The REBCO strip joint structure according to claim 1, characterized in that: The superconducting connector hollow block is sleeved on the overlapping part of the first REBCO strip and the second REBCO strip, and is welded and fixed to at least the upper surface of the first REBCO strip and the upper surface of the second REBCO strip; in the thickness direction of the overlapping part, the combination formed by the first REBCO strip and the second REBCO strip has no copper layer on the two outermost surfaces in the thickness direction.

7. The REBCO strip joint structure according to claim 6, characterized in that: In the thickness direction of the strip, at least one insulating layer is provided between the inner top surface of the superconducting connector hollow block and the superconducting layer of the first REBCO strip, and between the inner bottom surface and the superconducting layer of the second REBCO strip. The insulating layer is a thin insulating layer with a thickness less than that of the copper layer.

8. The REBCO strip joint structure according to claim 7, characterized in that: In the thickness direction of the strip, an insulating layer is provided between the inner top surface of the superconducting connector hollow block and the superconducting layer of the first REBCO strip, and between the inner bottom surface and the superconducting layer of the second REBCO strip.

9. The REBCO strip joint structure according to any one of claims 6 to 8, characterized in that: At the lap welding area, the outer top surface of the superconducting joint hollow block is flush with the upper surface of the first REBCO strip, and the outer bottom surface is flush with the upper surface of the second REBCO strip.

10. A welding forming process for the REBCO strip joint structure according to any one of claims 1 to 9, characterized in that: The superconducting connector is welded and fixed to at least the upper surface of the first REBCO tape and the upper surface of the second REBCO tape.

11. The welding forming process according to claim 10, characterized in that: The superconducting connector is also simultaneously welded and fixed to the sides of the first REBCO tape and the second REBCO tape.

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