Preparation method of ultra-long NbTi / Cu superconducting wire and superconducting wire

Abstract

The invention provides a preparation method of an ultra-long NbTi / Cu superconducting wire, which comprises the following steps of: preparing a U-shaped casting mold which is provided with a plurality of grooves; the porous copper plate consists of a porous disc and a convex combination part which is formed by extending the circle center of the porous disc towards the edge direction; assembling a plurality of NbTi single-core rods and a plurality of porous copper plates, clamping the NbTi single-core rods and the porous copper plates in the grooves of the U-shaped casting mold through the convex combination parts of the porous copper plates, and then carrying out heat preservation treatment on the whole module; the module obtained after heat preservation is cast through molten oxygen-free copper, and meanwhile the module is moved through a traction mechanism; when the mold advances, a cooling module is arranged to cool the cast part; and after all the parts are cast and formed, redundant parts on the outer side are removed, and the multi-core NbTi / Cu superconducting wire is manufactured by drawing a wire rod after passing through a continuous drawing module. The continuous casting method is suitable for continuous casting of the ultra-long multi-core superconducting wire.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting wires, and relates to a preparation method of an ultra-long NbTi / Cu superconducting wire and the superconducting wire. Background Art

[0002] NbTi / Cu superconducting wire is the most commonly used wire for low-temperature superconducting magnets, and is commonly used in MRI, MCZ, NMR, nuclear fusion experimental reactors, accelerators and other fields. In the preparation of superconducting wires, assembly and welding followed by extrusion molding is the most common processing method for NbTi / Cu superconducting wires. It requires three processes: assembly, welding and extrusion, and the front-end process of superconducting wires takes a long time. The assembly and welding processes have high requirements for the environment and are prone to introduce impurities, causing defects. The extrusion process has risks such as bulging, delamination, and uneven deformation of the core wire, resulting in low Jc performance of the superconducting wire, and the extrusion requires a long insulation time, which affects production efficiency. In addition, vacuum welding equipment and extrusion equipment have great restrictions on the size of the processed superconducting composite ingots. These processing equipment limits the preparation of ultra-long superconducting composite wires. There are many assembly, welding and extrusion processes and the cost is high, and the precision requirements of each component that needs to be controlled for processing are high. After extrusion, the wire is stretched on the drawing machine, which occupies a large space and needs to be optimized. The size of composite ingots that can be processed by vacuum welding equipment and extrusion equipment is limited, and currently only 50,000m of superconducting composite wire can be produced. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that the preparation of traditional NbTi / Cu superconducting wires requires a large amount of equipment, and when used for the preparation of ultra-long multi-core superconducting wires, it takes up a large space and is difficult to prepare NbTi / Cu superconducting wires of more than 50,000 m. In this regard, the present invention provides a method for preparing an ultra-long NbTi / Cu superconducting wire and a superconducting wire to solve this need in the art.

[0004] In one aspect, the present invention relates to a method for preparing an ultra-long NbTi / Cu superconducting wire, comprising: a U-shaped casting mold, wherein the U-shaped casting mold is provided with a plurality of grooves; A porous copper plate, the porous copper plate is composed of a porous disk and a convex portion extending from the center of the porous disk to the edge; Assembling a plurality of NbTi single core rods and a plurality of the porous copper plates, engaging the convex parts of the porous copper plates in the grooves of the U-shaped casting mold, and then subjecting the entire module to heat preservation treatment; The insulated module is cast with molten oxygen-free copper, and a traction mechanism is used to move the module; As the mold moves forward, a cooling module is provided to cool the casted part; After all the castings are completed, the redundant outer parts are removed, and then after passing through the continuous drawing module, the coil is stretched to produce a multi-core NbTi / Cu superconducting wire.

[0005] Furthermore, in the method for preparing the ultra-long NbTi / Cu superconducting wire provided by the present invention, the cross-sectional diameter of the porous disk is 50-200 mm.

[0006] Furthermore, in the method for preparing the ultra-long NbTi / Cu superconducting wire provided by the present invention, the length of the U-shaped casting mold is 5 to 30 m.

[0007] Furthermore, in the method for preparing the ultra-long NbTi / Cu superconducting wire provided by the present invention, the aperture of a single hole in the porous disk matches the diameter of the NbTi single core rod, and the aperture of the single hole and the diameter of the NbTi single core rod are 2 to 15 mm.

[0008] Furthermore, in the method for preparing the ultra-long NbTi / Cu superconducting wire provided by the present invention, the number of holes in the porous disk is 12-60.

[0009] Furthermore, in the method for preparing the ultra-long NbTi / Cu superconducting wire provided by the present invention, when the porous copper plates are assembled and fixed, the spacing distance between the grooves in the U-shaped casting mold is 0.3-1.5 m.

[0010] Furthermore, in the method for preparing the ultra-long NbTi / Cu superconducting wire provided by the present invention, the insulation temperature is 600-1000° C. and the time is 2-4 hours.

[0011] Furthermore, in the method for preparing the ultra-long NbTi / Cu superconducting wire provided by the present invention, the temperature of the melt used in the casting is 1000-1200°C.

[0012] Furthermore, in the method for preparing the ultra-long NbTi / Cu superconducting wire provided by the present invention, the continuous drawing module comprises a plurality of continuous drawing machines, and cooling devices are provided between the plurality of continuous drawing machines.

[0013] On the other hand, the present invention relates to a NbTi / Cu superconducting wire, which is prepared by the method for preparing the ultra-long NbTi / Cu superconducting wire.

[0014] Furthermore, in the NbTi / Cu superconducting wire provided by the present invention, the length of the NbTi / Cu superconducting wire is not less than 50000 m.

[0015] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: The present invention can prepare ultra-long composite superconducting wires, and can save assembly, welding and extrusion processes, saving process and material transfer time. The present invention reduces the extrusion process and avoids the risks of bulging, delamination and core wire deformation that may occur during the extrusion process. At the same time, the utilization rate of NbTi wires is greatly improved, greatly reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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 some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a cross-sectional view of a 12-hole porous copper plate.

[0018] Figure 2 Schematic diagram of the cross section of the NbTi / Cu superconducting wire after casting.

[0019] Description of the accompanying drawings: 1. porous disc; 2. convex part; 3. U-shaped casting mold; 4. NbTi single core rod. DETAILED DESCRIPTION

[0020] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials can be purchased on the market unless otherwise specified. The % in the following embodiments, unless otherwise specified, are all mass percentages. The ratios in the following embodiments, unless otherwise specified, are all mass ratios.

[0021] Example 1 This embodiment provides the preparation of a 12-core NbTi / Cu superconducting wire.

[0022] According to the performance requirements of superconducting wire, 12-core NbTi / Cu superconducting wire was designed and made. Figure 1 There are 11 porous copper plates with a diameter of 100 mm and a thickness of 10 mm. The porous copper plates are composed of porous discs and convex parts extending from the center of the porous discs to the edge. The porous copper plates and NbTi rods are pickled for use. The diameter of the NbTi rods is 10 mm and the length is 15 m. There are 12 rods in total. The NbTi rods are passed through the porous copper plates. The spacing between the porous copper plates is 1.5 m. The convex parts on the lower side of the porous copper plates are clamped in a U-shaped casting mold with multiple grooves. After assembly, Figure 2As shown. The fixed mold is placed as a whole in a 20m heat treatment furnace and kept at 800℃ for 2h. The mold after insulation is placed under the casting module, and the casting starts while the traction mechanism moves. During the advancement of the mold, a cooling water tank is used for cooling. After all the superconducting rods are cast, the redundant parts on the outside are machined out. After the superconducting rods are machined and passed through the continuous drawing module, there are multiple continuous drawing machines in the continuous drawing module, and cooling devices are provided between the continuous drawing machines. After coiling, subsequent stretching is performed to obtain 100,000m of 12-core NbTi / Cu superconducting wire.

[0023] Compared with the 12-core NbTi / Cu superconducting wire produced by the conventional method of assembly welding and then extrusion molding, the yield rate of the 12-core NbTi / Cu superconducting wire produced by the present invention is improved from 81.7% to 90.2%, and the utilization rate of the NbTi wire is comprehensively improved by about 5%.

[0024] Example 2 This embodiment provides the preparation of 60-core NbTi / Cu superconducting wire.

[0025] According to the performance requirements of superconducting wire, 60-core NbTi / Cu superconducting wires were designed, and 41 porous copper plates with a diameter of 50mm and a thickness of 10mm were prepared. The porous copper plates consisted of porous discs and convex parts extending from the center of the porous discs to the edge. The porous copper plates and NbTi rods were pickled for standby use. The diameter of the NbTi rods was 2mm and the length was 20m, with a total of 60 rods. The NbTi rods were passed through the porous copper plates with a spacing of 0.5m, and the convex parts on the lower side of the porous copper plates were clamped in a U-shaped casting mold with multiple grooves. The fixed mold was placed in a 20m heat treatment furnace as a whole and kept warm at 800℃ for 2h. The mold after insulation was placed under the casting module, and the casting started while the traction mechanism moved. During the forward movement of the mold, a cooling water tank was used for cooling. After all the superconducting rods were cast, the redundant parts on the outside were machined out. After the superconducting rod is machined, it passes through a continuous drawing module, which has multiple continuous drawing machines, and cooling devices are provided between the continuous drawing machines. After coiling, subsequent stretching is performed to obtain 50,000 m of 60-core NbTi / Cu superconducting wire.

[0026] Compared with the 60-core NbTi / Cu superconducting wire produced by the conventional method of assembly welding and then extrusion molding, the yield rate of the 60-core NbTi / Cu superconducting wire produced by the present invention is improved from 76.6% to 85.1%, and the utilization rate of the NbTi wire is comprehensively improved by about 5%.

[0027] Example 3 This embodiment provides the preparation of 30-core NbTi / Cu superconducting wire.

[0028] According to the performance requirements of superconducting wire, 30-core NbTi / Cu superconducting wires were designed, and 11 porous copper plates with a diameter of 200mm and a thickness of 10mm were prepared. The porous copper plates consisted of porous discs and convex parts extending from the center of the porous discs to the edge. The porous copper plates and NbTi rods were pickled for standby use. The diameter of the NbTi rods was 4mm and the length was 10m, with a total of 30 rods. The NbTi rods were passed through the porous copper plates with a spacing of 1m, and the convex parts on the lower side of the porous copper plates were clamped in a U-shaped casting mold with multiple grooves. The fixed mold was placed in a 20m heat treatment furnace as a whole and kept warm at 800℃ for 2h. The mold after insulation was placed under the casting module, and the casting started while the traction mechanism moved. During the forward movement of the mold, a cooling water tank was used for cooling. After all the superconducting rods were cast, the redundant parts on the outside were machined out. After the superconducting rod is machined, it passes through a continuous drawing module, which has multiple continuous drawing machines, and cooling devices are provided between the continuous drawing machines. After coiling, subsequent stretching is performed to obtain 200,000 m of 30-core NbTi / Cu superconducting wire.

[0029] Compared with the 30-core NbTi / Cu superconducting wire produced by the conventional method of assembly welding and then extrusion molding, the yield rate of the 30-core NbTi / Cu superconducting wire produced by the present invention is improved from 83.5% to 92.3%, and the utilization rate of the NbTi wire is comprehensively improved by about 5%.

[0030] As described above, the basic principle, main features and advantages of the present invention are well described. The above embodiments and descriptions are only descriptions of the preferred implementation modes of the present invention, and the present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the protection scope determined by the present invention.

Claims

1. A method for preparing an ultra-long NbTi / Cu superconducting wire, characterized in that: include: A U-shaped casting mold, wherein the U-shaped casting mold is provided with a plurality of grooves; A porous copper plate, the porous copper plate is composed of a porous disk and a convex portion extending from the center of the porous disk to the edge; Assembling a plurality of NbTi single core rods and a plurality of the porous copper plates, engaging the convex parts of the porous copper plates in the grooves of the U-shaped casting mold, and then subjecting the entire module to heat preservation treatment; The insulated module is cast with molten oxygen-free copper, and a traction mechanism is used to move the module; As the mold moves forward, a cooling module is provided to cool the casted part; After all the castings are completed, the redundant outer parts are removed, and then after passing through the continuous drawing module, the coil is stretched to produce a multi-core NbTi / Cu superconducting wire.

2. The method for preparing an ultra-long NbTi / Cu superconducting wire according to claim 1, characterized in that: The cross-sectional diameter of the porous disc is 50-200 mm.

3. The method for preparing an ultra-long NbTi / Cu superconducting wire according to claim 1, characterized in that: The length of the U-shaped casting mold is 5 to 30 m.

4. The method for preparing an ultra-long NbTi / Cu superconducting wire according to claim 1, characterized in that: The aperture of a single hole in the porous disk matches the diameter of the NbTi single core rod, and the aperture of the single hole and the diameter of the NbTi single core rod are 2 to 15 mm; The number of holes in the porous disc is 12 to 60.

5. The method for preparing an ultra-long NbTi / Cu superconducting wire according to claim 1, characterized in that: When the porous copper plate is assembled and fixed, the spacing distance between the grooves in the U-shaped casting mold is 0.3~1.5m.

6. The method for preparing an ultra-long NbTi / Cu superconducting wire according to claim 1, characterized in that: The temperature of the heat preservation treatment is 600-1000° C. and the time is 2-4 hours.

7. The method for preparing an ultra-long NbTi / Cu superconducting wire according to claim 1, characterized in that: The temperature of the melt used in the casting is 1000-1200°C.

8. The method for preparing an ultra-long NbTi / Cu superconducting wire according to claim 1, characterized in that: The continuous drawing module is provided with a plurality of continuous drawing machines, and cooling devices are arranged between the plurality of continuous drawing machines.

9. A NbTi / Cu superconducting wire, characterized in that: The superconducting wire is prepared by the method for preparing the superlong NbTi / Cu superconducting wire according to any one of claims 1 to 8.

10. The NbTi / Cu superconducting wire according to claim 9, characterized in that: The length of the NbTi / Cu superconducting wire is not less than 50000 m.

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