A method for manufacturing a multi-filament superconducting wire having a high superconducting critical transition coefficient

Abstract

The application belongs to the technical field of superconducting composite wire processing, and discloses a preparation method of a multi-core superconducting wire with a high superconducting critical transition coefficient. The method comprises the following steps: casting a multi-hole copper ingot with multiple precise mounting holes and a single-core rod, assembling after cleaning, vacuum electron beam welding upper and lower covers, obtaining a multi-core composite ingot, and successively extruding, stretching, heat treating and twisting the multi-core composite ingot to obtain a multi-core superconducting wire. The method can prepare a superconducting wire with a large number of cores, improves the assembly efficiency, has good assembly quality, has a very low risk of core wire interlacing, has uniform core wire deformation, has a high superconducting critical transition coefficient (n value), and shortens the preparation period of the superconducting wire.

Description

Technical Field

[0001] This invention relates to the field of superconducting composite wire processing technology, specifically to a method for preparing multi-core superconducting wires with high superconducting critical transition coefficient. Background Technology

[0002] Currently, NbTi superconductors are mainly used in fields such as magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), laboratory instruments, particle accelerators, power generation, mine clearance, magnetic separation of ores, magnetic levitation trains, and superconducting energy storage (SMES). Furthermore, high-precision, ultra-stable, highly uniform, low-field-drift, and low-stray-field superconducting magnets require superconducting wires with high n-values. In the fabrication of multi-core superconducting wires with high superconducting critical transition coefficients, drilling methods or conventional assembly methods are generally employed.

[0003] The drilling method for fabricating superconducting wires has significant advantages: short production cycle and low cost. However, the cost of drilling for fabricating superconducting wires increases with the number of holes drilled, therefore this method is only suitable for fabricating superconducting wires with a small number of cores.

[0004] Conventional assembly methods can be used to prepare multi-core superconducting wires, but they are difficult to assemble, inconvenient to operate, have low assembly efficiency, and there is a risk of cross-linking between the core wires, which increases with the number of cores.

[0005] In summary, existing methods for assembling multi-core superconducting wires using drilling and conventional assembly techniques suffer from low overall assembly efficiency, poor assembly quality, the risk of wire bridging, and high costs. Therefore, we propose a method for preparing multi-core superconducting wires with a high superconducting critical transition coefficient. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing multi-core superconducting wires with high superconducting critical transition coefficients, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a multi-core superconducting wire with a high superconducting critical transition coefficient includes the following steps:

[0009] Step 1: Prepare a porous copper ingot with multiple precision mounting holes;

[0010] Step 2: Prepare a single core rod;

[0011] Step 3: Clean the porous copper ingot and the single core rod, and assemble the single core rods in close-packed arrangement in the mounting holes of the porous copper ingot;

[0012] Step 4: Clean the upper and lower covers, and vacuum electron beam weld the upper and lower covers to both ends of the porous copper ingot to obtain a multi-core composite ingot.

[0013] Step 5: The multi-core composite ingot is extruded, stretched, heat-treated and twisted in sequence to obtain multi-core superconducting wire.

[0014] More preferably, in step 1, when preparing the porous copper ingot with multiple precision mounting holes, it is obtained by casting, and the porous copper ingot has at least two mounting holes in the axial direction.

[0015] More preferably, the dimensional accuracy of the mounting hole is ≤ ±0.01 mm, and the axial deviation is < 0.8 mm.

[0016] More preferably, in step 2, the single core rod includes an NbTi rod and a copper tube, and an Nb barrier layer is disposed between the NbTi rod and the copper tube.

[0017] More preferably, in step 3, when the single core rods are densely packed and assembled in the mounting holes of the porous copper ingot, at least two single core rods are installed in each mounting hole.

[0018] More preferably, the mounting hole and the single core rod are filled with an oxygen-free copper insert.

[0019] More preferably, the single core rod is hexagonal or circular.

[0020] More preferably, the copper ratio of the single core rod is 0.2-3.0.

[0021] More preferably, in step 5, the copper ratio of the obtained multi-core superconducting wire is ≥2.0.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] A porous copper ingot with multiple precision mounting holes and a single-core rod are prepared by casting. After cleaning, they are assembled and the upper and lower covers are welded by vacuum electron beam to obtain a multi-core composite ingot. The multi-core composite ingot is then subjected to extrusion, stretching, heat treatment, and twisting to prepare multi-core superconducting wires with high superconducting critical transition coefficients. This method can prepare superconducting wires with a large number of cores, improves assembly efficiency, provides good assembly quality, has a very low risk of cross-linking between cores, produces uniform core deformation, has a high superconducting critical transition coefficient, and can shorten the preparation cycle of superconducting wires.

[0024] The single-core rod differs from the ordinary NbTi rod. The single-core rod consists of an NbTi rod and a copper tube, with an Nb barrier layer between the NbTi rod and the copper tube. This single-core rod ensures that the surface of the core wire of the superconducting wire is free of Cu-Ti compounds, resulting in a smooth core wire surface and more uniform core wire deformation. Attached Figure Description

[0025] Figure 1This is a schematic cross-sectional view of a porous copper ingot with 61 mounting holes in Embodiment 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the cross-section of the mounting holes for the 37 single core rods in Embodiment 1 of the present invention;

[0027] Figure 3 This is a schematic cross-sectional view of a porous copper ingot with 29 mounting holes in Embodiment 2 of the present invention;

[0028] Figure 4 This is a schematic diagram of the cross-section of the mounting holes for the 19 single core rods in Embodiment 2 of the present invention. Detailed Implementation

[0029] 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.

[0030] Please see Figure 1-4 The present invention provides a technical solution:

[0031] A method for preparing a multi-core superconducting wire with a high superconducting critical transition coefficient includes the following steps:

[0032] Step 1: Prepare a porous copper ingot with multiple precision mounting holes. The porous copper ingot with multiple precision mounting holes is prepared by casting. The porous copper ingot has at least two mounting holes in the axial direction. The dimensional accuracy of the mounting holes is ≤ ±0.01mm and the axial deviation is <0.8mm.

[0033] Step 2: Prepare a single core rod, which consists of an NbTi rod and a copper tube. An Nb barrier layer is placed between the NbTi rod and the copper tube. The single core rod is hexagonal or circular, and the copper ratio of the single core rod is 0.2-3.0.

[0034] Step 3: Clean the porous copper ingot and single core rod, and assemble the single core rods in close-packed arrangement in the mounting holes of the porous copper ingot. At least two single core rods are installed in each mounting hole, and the mounting holes and single core rods are filled with oxygen-free copper inserts.

[0035] Step 4: Clean the upper and lower covers, and vacuum electron beam weld the upper and lower covers to both ends of the porous copper ingot to obtain a multi-core composite ingot.

[0036] Step 5: The multi-core composite ingot is extruded, stretched, heat-treated and twisted in sequence to obtain multi-core superconducting wire, and the copper ratio of the obtained multi-core superconducting wire is ≥2.0.

[0037] Example 1

[0038] A porous copper ingot with multiple precision mounting holes was cast, with an outer diameter of Φ270mm and 61 mounting holes of Φ21.80±0.01mm in diameter. Hexagonal single-core rods were prepared, each consisting of an NbTi rod and a copper tube, with an Nb barrier layer between them. This single-core rod ensures the superconducting wire core is free of Cu-Ti compounds, resulting in a smooth core surface and more uniform core deformation. The hexagonal single-core rod has a height of 3mm and a copper ratio of 0.3. The porous copper ingot and single-core rods were cleaned, and the single-core rods were densely packed and assembled into the mounting holes of the porous copper ingot, with 37 hexagonal single-core rods in each mounting hole. The upper and lower covers were cleaned and vacuum electron beam welded to both ends of the porous copper ingot to obtain a multi-core composite ingot. By sequentially extruding, stretching, heat-treating, and twisting a multi-core composite ingot, a superconducting wire with an assembly copper ratio of 2.85 and a core count of 2257 can be prepared, with a high superconducting critical transition coefficient and an n value (4.2K, 5T) ≥45.

[0039] Example 2

[0040] The porous copper ingot with multiple precision mounting holes has an outer diameter of Φ260mm and contains 20 mounting holes with a diameter of Φ25.80±0.01mm. Hexagonal single-core rods are prepared, each consisting of an NbTi rod and a copper tube, with an Nb barrier layer between them. This single-core rod ensures the superconducting wire core is free of Cu-Ti compounds, resulting in a smooth core surface and more uniform core deformation. The hexagonal single-core rod has a height of 5mm and a copper ratio of 0.25. The porous copper ingot and single-core rods are cleaned, and the single-core rods are densely packed and assembled into the mounting holes of the porous copper ingot, with 19 hexagonal single-core rods in each mounting hole. The upper and lower covers are cleaned and then vacuum electron beam welded to both ends of the porous copper ingot to obtain a multi-core composite ingot. By sequentially extruding, stretching, heat-treating, and twisting a multi-core composite ingot, a superconducting wire with an assembly copper ratio of 6.73 and a core count of 380 can be prepared, and the superconducting critical transition coefficient is relatively high, with an n value (4.2K, 5T) ≥50.

[0041] Example 3

[0042] The porous copper ingot with multiple precision mounting holes has an outer diameter of Φ240mm and consists of 10 mounting holes with a diameter of Φ26.30±0.01mm. Hexagonal single-core rods are prepared, comprising an NbTi rod and a copper tube, with an Nb barrier layer between them. This single-core rod ensures the superconducting wire core is free of Cu-Ti compounds, resulting in a smooth core surface and more uniform core deformation. The hexagonal single-core rod has a height of 8.5mm and a copper ratio of 0.2. The porous copper ingot and single-core rods are cleaned, and the single-core rods are densely packed and assembled into the mounting holes of the porous copper ingot, with 7 hexagonal single-core rods in each mounting hole. The upper and lower covers are cleaned and vacuum electron beam welded to both ends of the porous copper ingot to obtain a multi-core composite ingot. By sequentially extruding, stretching, heat-treating, and twisting a multi-core composite ingot, a superconducting wire with an assembly copper ratio of 11.10 and a core count of 70 can be prepared, with a high superconducting critical transition coefficient and an n value (4.2K, 5T) ≥ 52.

[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a multi-core superconducting wire with a high superconducting critical transition coefficient, characterized in that, Includes the following steps: Step 1: Prepare a porous copper ingot with multiple precision mounting holes; Step 2: Prepare a single core rod, which includes an NbTi rod and a copper tube, with an Nb barrier layer disposed between the NbTi rod and the copper tube, and the copper ratio of the single core rod is 0.2-3.0; Step 3: Clean the porous copper ingot and the single core rod, and assemble the single core rods in close-packed arrangement in the mounting holes of the porous copper ingot. When assembling the single core rods in close-packed arrangement in the mounting holes of the porous copper ingot, at least two single core rods are installed in each mounting hole. The mounting holes and the single core rods are filled with oxygen-free copper inserts. Step 4: Clean the upper and lower covers, and vacuum electron beam weld the upper and lower covers to both ends of the porous copper ingot to obtain a multi-core composite ingot. Step 5: The multi-core composite ingot is extruded, stretched, heat-treated and twisted in sequence to obtain multi-core superconducting wire. The copper ratio of the obtained multi-core superconducting wire is ≥2.

0.

2. The method for preparing a multi-core superconducting wire with a high superconducting critical transition coefficient according to claim 1, characterized in that: In step 1, when preparing a porous copper ingot with multiple precision mounting holes, it is obtained by casting, and the porous copper ingot has at least two mounting holes in the axial direction.

3. The method for preparing a multi-core superconducting wire with a high superconducting critical transition coefficient according to claim 2, characterized in that: The dimensional accuracy of the mounting holes is ≤ ±0.01 mm, and the axial deviation is < 0.8 mm.

4. The method for preparing a multi-core superconducting wire with a high superconducting critical transition coefficient according to claim 1, characterized in that: The single core rod is hexagonal or circular.

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