Preparation method of Ni3Sn composite wire for extremely high magnetic field and composite wire

Abstract

The invention discloses a preparation method of a Ni3Sn composite wire for an extremely high magnetic field and the composite wire, and relates to the technical field of superconducting composite wires, and the preparation method comprises the following steps: forming an NbTi single-core rod; the hexagonal oxygen-free copper rod and the NbTi single-core rod are densely arranged in the Nb pipe and then integrally assembled in the oxygen-free copper pipe, and a composite rod is formed; forming a composite pipe; the SnCu alloy bar is arranged in the center of the composite tube and is processed into a subcomponent; the subcomponents and the fan-shaped NbTi rods are densely arranged and assembled into an oxygen-free copper pipe to form a composite wire; and the composite wire is sequentially subjected to multi-pass cold stretching and heat treatment procedures, and the Ni3Sn composite wire is prepared. The NbTi single-core rod and the Nb tube are adopted, the specific preparation technological process is combined, the Nb3Sn is generated in a continuous Nb area, the uniformity and consistency of superconducting current-carrying crystal grains are improved, and then the wire performance under the extremely high magnetic field is improved.

Description

Technical Field

[0001] The present application relates to the technical field of superconducting composite wires, and particularly to a preparation method and a composite wire of a niobium-tin composite wire for an extremely high magnetic field. Background Art

[0002] The superconducting current-carrying capacity of niobium-tin superconducting wires is considered to be related to the number of flux pinning, the magnitude of the pinning force, the superconducting transition temperature, the uniformity of the superconducting phase, etc. At lower magnetic fields, the number and quality of flux pinning centers play a decisive role in the critical current density of niobium-tin. However, as the applied magnetic field increases, such as exceeding 14T, the superconducting current-carrying mechanism of niobium-tin superconducting wires gradually changes from a single pinning-determined mechanism to a multi-current-carrying mechanism determined by pinning and superconducting transition temperature, etc. The change in the superconducting current-carrying mechanism means that in different magnetic field application environments, the structure of the superconducting wire may need to be adjusted to obtain higher superconducting current-carrying performance. To meet the requirements for the high superconducting current-carrying performance of niobium-tin superconducting wires under extremely high magnetic fields (16T magnetic field and higher), it is necessary to develop niobium-tin superconducting wires for 16T magnetic field and higher according to a specific superconducting current-carrying mechanism.

[0003] In the prior art, Chinese Patent CN118866461A discloses a preparation method and a superconducting wire of an internal tin method Nb3Sn superconducting wire. The method includes: adding Ti element to molten Nb to prepare a NbTi rod; inserting multiple NbTi rods into a casting cylinder, injecting oxygen-free copper liquid into the casting cylinder to prepare a CuNb composite ingot; extruding the CuNb composite ingot to obtain a CuNb composite rod; drilling a hole in the center of the CuNb composite rod to obtain a CuNb composite tube; inserting a SnCu alloy rod into the CuNb composite tube to obtain a sub-component; loading multiple sub-components into a Ta tube, and loading the Ta tube into an oxygen-free copper tube to obtain a final blank; performing drawing and twisting on the final blank to obtain a Nb3Sn superconducting wire.

[0004] However, the above prior art does not study the multi-current-carrying mechanism of niobium-tin superconducting wires under extremely high magnetic fields (16T magnetic field and higher), and the performance of the wires under extremely high magnetic fields is poor. Summary of the Invention

[0005] The present application provides a preparation method and a composite wire of a niobium-tin composite wire for an extremely high magnetic field, so as to solve the problem that the existing superconducting wire preparation technology does not study the multi-current-carrying mechanism of niobium-tin superconducting wires under extremely high magnetic fields (16T magnetic field and higher), and the performance of the wires under extremely high magnetic fields is poor.

[0006] On the one hand, the present application provides a preparation method of a niobium-tin composite wire for an extremely high magnetic field, including the following steps: Step 1: Assemble the NbTi rod into an oxygen-free copper tube with an outer hexagonal and inner circular shape to form a NbTi single-core rod.

[0007] Step 2: Compact the hexagonal oxygen-free copper rod and the NbTi single-core rod in sequence from the center outwards along the wire diameter into the Nb tube, and then assemble the whole into an oxygen-free copper tube to form a composite rod.

[0008] Step 3: Subject the composite rod to hot isostatic pressing, extrusion, skinning, multi-pass cold drawing, and drilling processes in sequence to form a composite tube.

[0009] Step 4: Insert the SnCu alloy rod into the center of the composite tube, and then process the whole through multi-pass cold drawing to form a sub-element.

[0010] Step 5: Compact and assemble the sub-element and the fan-shaped NbTi rod into an oxygen-free copper tube to form a composite wire.

[0011] Step 6: Subject the composite wire to multi-pass cold drawing and heat treatment processes in sequence to prepare a niobium-tin composite wire.

[0012] In a possible implementation, in Step 1, the cross-section of the NbTi rod is circular, with a diameter of 2 - 10 mm, and the proportion of Ti atoms is 20% - 60%.

[0013] In Step 1, the inner diameter of the oxygen-free copper tube is 2 - 10.5 mm, and the width of the opposite sides of the outer hexagon is 2.6 - 11.8 mm.

[0014] The copper ratio of the NbTi single-core rod is 0.2 - 0.5.

[0015] In a possible implementation, in Step 2, compact the hexagonal oxygen-free copper rod in the center of the Nb tube, and compact the NbTi single-core rod on the outside of the hexagonal oxygen-free copper rod. The number of compacted layers of the NbTi single-core rod is 1 - 3 layers.

[0016] The gap between the outermost NbTi single-core rod and the Nb tube is filled with an oxygen-free copper rod with a diameter of 1 mm.

[0017] The width of the opposite sides of the hexagonal oxygen-free copper rod is 2.6 - 11.8 mm.

[0018] The outer diameter of the Nb tube is 38.8 - 205.5 mm, and the inner diameter is 26 - 130 mm.

[0019] The outer diameter of the oxygen-free copper tube is 48 - 235 mm, and the inner diameter is 39 - 206 mm.

[0020] In a possible implementation, in step three, the hot isostatic pressing temperature is 650 - 720 °C, the extrusion temperature is 450 - 550 °C, the extrusion ratio is 6 - 15, the extrusion speed is 10 - 20 mm / s, the peeling amount is 2% - 5%, peeling is performed once, and the processing rate between passes of multi-pass cold drawing is 15% - 30%.

[0021] The outer diameter of the composite tube is 18.1 - 60.7 mm, the inner diameter is 7.8 - 28.5 mm, and the copper ratio is 0.1 - 0.5.

[0022] In a possible implementation, in step four, the diameter of the SnCu alloy rod is 7.5 - 28.1 mm, and the proportion of Cu atoms is 0.5% - 4%.

[0023] In step four, the processing rate between passes of multi-pass cold drawing is 15% - 30%.

[0024] The cross-section of the sub-component is circular, with a diameter of 3 - 7 mm, a copper ratio of 0.1 - 0.5, the volume proportions of Nb and Sn elements are 0.5 - 0.65 and 0.27 - 0.29 respectively, and the Nb / Sn atomic ratio is 2.8 - 3.5.

[0025] In a possible implementation, in step five, the outer diameter of the oxygen-free copper tube is 58 - 115 mm, and the inner diameter is 47 mm.

[0026] The number of the sub-components is 31 - 163, the number of the sector-shaped NbTi rods is 6, and the sector-shaped NbTi rods are assembled in the gaps of the outermost sub-components in different directions.

[0027] The width between the sector edges of the sector-shaped NbTi rod and the opposite side is 1.8 - 4.8 mm, the straight-edge length is 3 - 7 mm, and the composition is the same as that of the NbTi single-core rod.

[0028] The copper super ratio of the composite wire is 0.5 - 5.

[0029] In a possible implementation, in step six, the processing rate between passes of multi-pass cold drawing of the composite wire is 15% - 30%.

[0030] The heat treatment includes: treatment at 340 °C for 96 h, subsequent treatment at 550 - 600 °C for 200 h, and subsequent treatment at 630 - 720 °C for 100 - 300 h.

[0031] On the other hand, the present application also provides a niobium-tin composite wire for extremely high magnetic fields, which is prepared by using the preparation method of a niobium-tin composite wire for extremely high magnetic fields described above.

[0032] A method for preparing a niobium-tin composite wire for extremely high magnetic fields and the composite wire in the present application have the following advantages: By using a NbTi single core rod and a Nb tube, combined with a specific preparation process flow, continuous Nb regions are used to generate niobium-tin, improving the uniformity and consistency of superconducting current-carrying grains, and thus enhancing the performance of the wire at extremely high magnetic fields. Among them, by replacing the Cu core rod near the Nb tube with a NbTi core rod, on the one hand, it improves the problem that the Sn content is too high and prone to generating coarse grains in the initial stage of Nb heat treatment to generate niobium-tin, and on the other hand, it also enables the Ti element to participate in the formation of niobium-tin through the Sn-Ti interdiffusion method throughout the process, all of which greatly promote the improvement of the wire performance. Further, by adjusting the wire structure of traditional multi-core Nb core wires to a single Nb tube structure, when using continuous Nb regions to generate niobium-tin, the uniformity and consistency of superconducting current-carrying grains are higher, improving the wire performance at 16T extremely high magnetic fields and higher magnetic fields. The change in high magnetic field performance is the same as that of traditional PIT (Powder-in-Tube) structure superconducting wires. The niobium-tin composite wire formed by the preparation method of the present application is more suitable for use environments at 16T extremely high magnetic fields and higher magnetic fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is a schematic flow chart of a method for preparing a niobium-tin composite wire for extremely high magnetic fields provided by an embodiment of the present application; Figure 2 It is the critical current density test results of the niobium-tin composite wires prepared in four embodiments of the present application and conventional superconducting wires under a magnetic field of 12T to 16T. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0036] As Figure 1 shown, an embodiment of the present application provides a method for preparing a niobium-tin composite wire for extremely high magnetic fields, including the following steps: Step 1: Assemble the NbTi rod into an oxygen-free copper tube with an outer hexagonal and inner circular shape to form a NbTi single-core rod.

[0037] Step 2: Arrange the hexagonal oxygen-free copper rod and the NbTi single-core rod in a close-packed manner from the center to the outside along the wire diameter into the Nb tube, and then assemble the whole into an oxygen-free copper tube to form a composite rod.

[0038] Step 3: Subject the composite rod to hot isostatic pressing, extrusion, peeling, multi-pass cold drawing, and drilling processes in sequence to form a composite tube.

[0039] Step 4: Load the SnCu alloy rod into the center of the composite tube, and then process the whole through multi-pass cold drawing to form a sub-element.

[0040] Step 5: Assemble the sub-element and the fan-shaped NbTi rod in a close-packed manner into an oxygen-free copper tube to form a composite wire.

[0041] Step 6: Subject the composite wire to multi-pass cold drawing and heat treatment processes in sequence to prepare a niobium-tin composite wire.

[0042] The embodiment of the present application also provides a niobium-tin composite wire for an extremely high magnetic field, which is prepared by using the preparation method of a niobium-tin composite wire for an extremely high magnetic field described above.

[0043] Specifically, the copper ratio refers to the volume ratio of copper material to other materials, and the copper-superconducting ratio refers to the volume ratio of copper material to superconducting material.

[0044] Example 1: Exemplarily, in Step 1, the cross-section of the NbTi rod is circular with a diameter of 2 mm, and the proportion of Ti atoms is 35%. In Step 1, the inner diameter of the oxygen-free copper tube is 2 mm, and the width of the opposite sides of the outer hexagon is 2.6 mm. The copper ratio of the NbTi single-core rod is 0.5.

[0045] Exemplarily, in Step 2, arrange the hexagonal oxygen-free copper rod in the center of the Nb tube in a close-packed manner, arrange the NbTi single-core rod on the outside of the hexagonal oxygen-free copper rod, and the number of close-packed layers of the NbTi single-core rod is 1 layer. The gap between the outermost NbTi single-core rod and the Nb tube is filled with an oxygen-free copper rod with a diameter of 1 mm. The width of the opposite sides of the hexagonal oxygen-free copper rod is 2.6 mm. The outer diameter of the Nb tube is 38.8 mm, and the inner diameter is 26 mm. The outer diameter of the oxygen-free copper tube is 48 mm, and the inner diameter is 39 mm.

[0046] Exemplarily, in step three, the hot isostatic pressing temperature is 650 °C, the extrusion temperature is 450 °C, the extrusion ratio is 6, the extrusion speed is 20 mm / s, the peeling amount is 5%, the peeling is carried out once, and the processing rate between passes of multi-pass cold drawing is 15% - 30%. The outer diameter of the composite tube is 18.1 mm, the inner diameter is 7.8 mm, and the copper ratio is 0.5.

[0047] Exemplarily, in step four, the diameter of the SnCu alloy rod is 7.5 mm, and the proportion of Cu atoms is 0.5%. In step four, the processing rate between passes of multi-pass cold drawing is 15% - 30%. The cross-section of the sub-component is circular, with a diameter of 3 mm, the copper ratio is 0.5, and the volume proportions of Nb and Sn elements are 0.55 and 0.29 respectively, and the Nb / Sn atomic ratio is 2.8.

[0048] Exemplarily, in step five, the outer diameter of the oxygen-free copper tube is 115 mm, and the inner diameter is 47 mm. The number of the sub-components is 163, and the number of the fan-shaped NbTi rods is 6. The fan-shaped NbTi rods are assembled in the gaps of the outermost sub-components in different directions. The width between the fan-shaped sides and the opposite sides of the fan-shaped NbTi rod is 1.8 mm, the straight side length is 3 mm, and the composition is the same as that of the NbTi single-core rod. The copper super-ratio of the composite wire is 5.

[0049] Exemplarily, in step six, the processing rate between passes of multi-pass cold drawing of the composite wire is 15% - 30%. The heat treatment includes: treatment at 340 °C for 96 h, followed by treatment at 550 °C for 200 h, and then treatment at 630 °C for 300 h.

[0050] Example 2: Exemplarily, in step one, the cross-section of the NbTi rod is circular, with a diameter of 5 mm, and the proportion of Ti atoms is 35%. In step one, the inner circle diameter of the oxygen-free copper tube is 5 mm, and the width between the opposite sides of the outer hexagon is 5.9 mm. The copper ratio of the NbTi single-core rod is 0.2.

[0051] Exemplarily, in step two, the hexagonal oxygen-free copper rod is closely arranged in the center of the Nb tube, the NbTi single-core rod is closely arranged outside the hexagonal oxygen-free copper rod, and the number of closely arranged layers of the NbTi single-core rod is 1 layer. The gap between the outermost NbTi single-core rod and the Nb tube is filled with an oxygen-free copper rod with a diameter of 1 mm. The width between the opposite sides of the hexagonal oxygen-free copper rod is 5.9 mm. The outer diameter of the Nb tube is 109.9 mm, and the inner diameter is 65 mm. The outer diameter of the oxygen-free copper tube is 115 mm, and the inner diameter is 110 mm.

[0052] Exemplarily, in step three, the hot isostatic pressing temperature is 700 °C, the extrusion temperature is 500 °C, the extrusion ratio is 9, the extrusion speed is 15 mm / s, the peeling amount is 2%, the peeling is done once, and the processing rate between passes of multi-pass cold drawing is 15% - 30%. The outer diameter of the composite tube is 36.4 mm, the inner diameter is 18.5 mm, and the copper ratio is 0.1.

[0053] Exemplarily, in step four, the diameter of the SnCu alloy rod is 18.3 mm, and the proportion of Cu atoms is 4%. In step four, the processing rate between passes of multi-pass cold drawing is 15% - 30%. The cross-section of the sub-component is circular, with a diameter of 5.1 mm, the copper ratio is 0.1, and the volume proportions of Nb and Sn elements are 0.65 and 0.28 respectively, and the Nb / Sn atomic ratio is 3.5.

[0054] Exemplarily, in step five, the outer diameter of the oxygen-free copper tube is 81.4 mm, and the inner diameter is 47 mm. The number of the sub-components is 55, the number of the sector-shaped NbTi rods is 6, and the sector-shaped NbTi rods are assembled in the gaps of the outermost sub-components in different directions. The width between the sector edges and the opposite edges of the sector-shaped NbTi rod is 3.5 mm, the straight-edge length is 5.1 mm, and the composition is the same as that of the NbTi single-core rod. The copper super-ratio of the composite wire is 2.

[0055] Exemplarily, in step six, the processing rate between passes of multi-pass cold drawing of the composite wire is 15% - 30%. The heat treatment includes: treatment at 340 °C for 96 h, followed by treatment at 585 °C for 200 h, and then treatment at 700 °C for 200 h.

[0056] Example 3: Exemplarily, in step one, the cross-section of the NbTi rod is circular, with a diameter of 10 mm, and the proportion of Ti atoms is 60%. In step one, the inner diameter of the oxygen-free copper tube is 10.5 mm, and the width between the outer hexagonal opposite sides is 11.8 mm. The copper ratio of the NbTi single-core rod is 0.2.

[0057] Exemplarily, in step two, the hexagonal oxygen-free copper rod is closely arranged at the center of the Nb tube, the NbTi single-core rod is closely arranged on the outside of the hexagonal oxygen-free copper rod, and the number of closely arranged layers of the NbTi single-core rod is 2. The gap between the outermost NbTi single-core rod and the Nb tube is filled with an oxygen-free copper rod with a diameter of 1 mm. The width between the opposite sides of the hexagonal oxygen-free copper rod is 11.8 mm. The outer diameter of the Nb tube is 205.5 mm, and the inner diameter is 130 mm. The outer diameter of the oxygen-free copper tube is 235 mm, and the inner diameter is 206 mm.

[0058] Exemplarily, in step three, the hot isostatic pressing temperature is 720 °C, the extrusion temperature is 550 °C, the extrusion ratio is 15, the extrusion speed is 10 mm / s, the peeling amount is 2%, the peeling is done once, and the processing rate between passes of multi-pass cold drawing is 15% - 30%. The outer diameter of the composite tube is 60.7 mm, the inner diameter is 28.5 mm, and the copper ratio is 0.3.

[0059] Exemplarily, in step four, the diameter of the SnCu alloy rod is 28.1 mm, and the proportion of Cu atoms is 2%. In step four, the processing rate between passes of multi-pass cold drawing is 15% - 30%. The cross-section of the sub-component is circular, with a diameter of 5.1 mm, the copper ratio is 0.3, and the volume proportions of Nb and Sn elements are 0.6 and 0.28 respectively, and the Nb / Sn atomic ratio is 3.2.

[0060] Exemplarily, in step five, the outer diameter of the oxygen-free copper tube is 66.5 mm, and the inner diameter is 47 mm. The number of the sub-components is 55, and the number of the sector-shaped NbTi rods is 6. The sector-shaped NbTi rods are assembled in the gaps of the outermost sub-components in different directions. The width between the sector edges and the opposite edges of the sector-shaped NbTi rod is 3.5 mm, the straight-edge length is 5.1 mm, and the composition is the same as that of the NbTi single-core rod. The copper super-ratio of the composite wire is 1.

[0061] Exemplarily, in step six, the processing rate between passes of multi-pass cold drawing of the composite wire is 15% - 30%. The heat treatment includes: treatment at 340 °C for 96 h, followed by treatment at 585 °C for 200 h, and then treatment at 700 °C for 200 h.

[0062] Example 4: Exemplarily, in step one, the cross-section of the NbTi rod is circular, with a diameter of 5 mm, and the proportion of Ti atoms is 20%. In step one, the inner diameter of the oxygen-free copper tube is 5 mm, and the width between the opposite sides of the outer hexagon is 6.1 mm. The copper ratio of the NbTi single-core rod is 0.3.

[0063] Exemplarily, in step two, the hexagonal oxygen-free copper rod is closely arranged in the center of the Nb tube, the NbTi single-core rod is closely arranged outside the hexagonal oxygen-free copper rod, and the number of closely arranged layers of the NbTi single-core rod is 3 layers. The gap between the outermost NbTi single-core rod and the Nb tube is filled with an oxygen-free copper rod with a diameter of 1 mm. The width between the opposite sides of the hexagonal oxygen-free copper rod is 6.1 mm. The outer diameter of the Nb tube is 91.9 mm, and the inner diameter is 65 mm. The outer diameter of the oxygen-free copper tube is 101 mm, and the inner diameter is 92 mm.

[0064] Exemplarily, in step three, the hot isostatic pressing temperature is 720 °C, the extrusion temperature is 550 °C, the extrusion ratio is 9, the extrusion speed is 15 mm / s, the peeling amount is 3%, the peeling is carried out once, and the processing rate between passes of multi-pass cold drawing is 15% - 30%. The outer diameter of the composite tube is 31.8 mm, the inner diameter is 15.5 mm, and the copper ratio is 0.2.

[0065] Exemplarily, in step four, the diameter of the SnCu alloy rod is 15 mm, and the atomic proportion of Cu is 1%. In step four, the processing rate between passes of multi-pass cold drawing is 15% - 30%. The cross-section of the sub-component is circular, with a diameter of 7 mm, the copper ratio is 0.2, and the volume proportions of Nb and Sn elements are 0.5 and 0.27 respectively, and the Nb / Sn atomic ratio is 2.8.

[0066] Exemplarily, in step five, the outer diameter of the oxygen-free copper tube is 58 mm, and the inner diameter is 47 mm. The number of the sub-components is 31, and the number of the sector-shaped NbTi rods is 6. The sector-shaped NbTi rods are assembled in the gaps of the outermost sub-components in different directions. The width between the sector edges and the opposite edges of the sector-shaped NbTi rods is 4.8 mm, the straight-edge length is 7 mm, and the composition is the same as that of the NbTi single-core rod. The copper super-ratio of the composite wire is 0.5.

[0067] Exemplarily, in step six, the processing rate between passes of multi-pass cold drawing of the composite wire is 15% - 30%. The heat treatment includes: treatment at 340 °C for 96 h, followed by treatment at 600 °C for 200 h, and then treatment at 720 °C for 100 h.

[0068] As Figure 2 shown, the critical current density test results of the niobium-tin composite wires prepared in four embodiments of the present application and conventional superconducting wires under a magnetic field of 12 T - 16 T are Figure 2 The legends 1, 2, 3, and 4 in Figure 2 correspond to Embodiment 1, Embodiment 2, Embodiment 3, and Embodiment 4 respectively. The conventional wire is a conventional superconducting wire, which is a multi-core and thin-core Nb wire structure. It can be 2 seen that the critical current density of the conventional superconducting wire and the niobium-tin composite wires prepared in four embodiments of the present application is comparable under a magnetic field of 12 T. However, as the magnetic field increases, at higher magnetic fields, especially at an extremely high magnetic field of 16 T, the critical current density of the niobium-tin composite wires prepared in four embodiments of the present application is all above 1200 A / mm

[0069] In the embodiments of the present application, by using a NbTi single core rod and a Nb tube, combined with a specific preparation process flow, niobium tin is generated in a continuous Nb region, improving the uniformity and consistency of superconducting current-carrying grains, and thus improving the wire performance under extremely high magnetic fields. Among them, by replacing the Cu core rod close to the Nb tube with a NbTi core rod, on the one hand, it improves the problem that the Sn content is too high and prone to generate coarse grains in the initial stage of Nb heat treatment to generate niobium tin, and on the other hand, it also enables the Ti element to participate in the generation of niobium tin through the Sn-Ti interdiffusion method throughout the process, all of which greatly promote the improvement of wire performance. Further, by adjusting the wire structure of traditional multi-core Nb core wires to a single Nb tube structure, when generating niobium tin in a continuous Nb region, the uniformity and consistency of superconducting current-carrying grains are higher, improving the wire performance under 16T extremely high magnetic fields and higher magnetic fields. Consistent with the change of the high magnetic field performance of traditional PIT (powder-in-tube method) structure superconducting wires, the niobium tin composite wire formed by the preparation method of the present application is more suitable for the use environment of 16T extremely high magnetic fields and higher magnetic fields.

[0070] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present application.

[0071] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A method for preparing a niobium-tin composite wire for extremely high magnetic fields, characterized in that: The following steps are involved: Step 1: Assemble the NbTi rod into an oxygen-free copper tube with an outer hexagonal shape and an inner circular shape to form a NbTi single core rod; Step 2, the hexagonal oxygen-free copper rod and the NbTi single core rod are densely arranged in the Nb tube from the center to the outside along the wire diameter, and then assembled into the oxygen-free copper tube as a whole to form a composite rod; Step 3, the composite rod is subjected to hot isostatic pressing, extrusion, peeling, multiple cold drawing and drilling processes in sequence to form a composite tube; Step 4, inserting the SnCu alloy rod into the center of the composite tube, and then subjecting the whole to multiple cold drawing processes to form subcomponents; Step 5, closely assembling the subcomponents and the fan-shaped NbTi rods into an oxygen-free copper tube to form a composite wire; Step six, subjecting the composite wire to multiple cold drawing and heat treatment processes in sequence to prepare a niobium-tin composite wire.

2. The method for preparing a niobium-tin composite wire for extremely high magnetic fields according to claim 1, characterized in that: In step 1, the cross section of the NbTi rod is circular, with a diameter of 2-10 mm, wherein the Ti atoms account for 20%-60%; In step 1, the inner diameter of the oxygen-free copper tube is 2-10.5 mm, and the width of the outer hexagonal side is 2.6-11.8 mm; The copper ratio of the NbTi single core rod is 0.2-0.

5.

3. The method for preparing a niobium-tin composite wire for extremely high magnetic fields according to claim 1, characterized in that: In step 2, the hexagonal oxygen-free copper rod is densely arranged in the center of the Nb tube, and the NbTi single core rod is densely arranged on the outside of the hexagonal oxygen-free copper rod, and the number of densely arranged layers of the NbTi single core rod is 1 to 3 layers; The gap between the outermost NbTi single core rod and the Nb tube is filled with an oxygen-free copper rod with a diameter of 1 mm; The width of the opposite side of the hexagonal oxygen-free copper rod is 2.6-11.8 mm; The outer diameter of the Nb tube is 38.8-205.5 mm, and the inner diameter is 26-130 mm; The oxygen-free copper tube has an outer diameter of 48 to 235 mm and an inner diameter of 39 to 206 mm.

4. The method for preparing a niobium-tin composite wire for extremely high magnetic fields according to claim 1, characterized in that: In step 3, the hot isostatic pressing temperature is 650-720°C, the extrusion temperature is 450-550°C, the extrusion ratio is 6-15, the extrusion speed is 10-20 mm / s, the peeling amount is 2%-5%, the peeling is 1 time, and the processing rate between passes of multi-pass cold drawing is 15%-30%; The outer diameter of the composite pipe is 18.1-60.7 mm, the inner diameter is 7.8-28.5 mm, and the copper ratio is 0.1-0.

5.

5. The method for preparing a niobium-tin composite wire for extremely high magnetic fields according to claim 1, characterized in that: In step 4, the diameter of the SnCu alloy rod is 7.5-28.1 mm, wherein the Cu atom accounts for 0.5%-4%; In step 4, the processing rate between passes of multi-pass cold drawing is 15%~30%; The subcomponent has a circular cross-section with a diameter of 3-7 mm, a copper ratio of 0.1-0.5, a volume fraction of Nb and Sn elements of 0.5-0.65 and 0.27-0.29, respectively, and a Nb / Sn atomic ratio of 2.8-3.

5.

6. The method for preparing a niobium-tin composite wire for extremely high magnetic fields according to claim 1, characterized in that: In step 5, the outer diameter of the oxygen-free copper tube is 58-115 mm, and the inner diameter is 47 mm; The number of the subcomponents is 31 to 163, the number of the fan-shaped NbTi rods is 6, and the fan-shaped NbTi rods are assembled in the gaps of the outermost subcomponents in different directions; The fan-shaped NbTi rod has a fan-shaped side and an opposite side with a width of 1.8 to 4.8 mm, a straight side length of 3 to 7 mm, and the composition is the same as that of the NbTi single core rod; The copper excess ratio of the composite wire is 0.5-5.

7. The method for preparing a niobium-tin composite wire for extremely high magnetic fields according to claim 1, characterized in that: In step 6, the processing rate between passes of the multi-pass cold drawing of the composite wire is 15% to 30%; The heat treatment includes: 340°C / 96h treatment, followed by 550-600°C / 200h treatment, and then 630-720°C / 100-300h treatment.

8. A niobium-tin composite wire for extremely high magnetic fields, characterized in that: The wire is prepared by the method for preparing a niobium-tin composite wire for extremely high magnetic fields as claimed in any one of claims 1 to 7.

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