Preparation method of high-strength niobium-tin superconducting wire and superconducting wire

Abstract

The application discloses a preparation method of high-strength niobium-tin superconducting wire and the superconducting wire, and relates to the technical field of superconducting wires, wherein the method comprises the following steps: an Nb ingot is subjected to extrusion, drawing and cutting to obtain an Nb rod / wire, and a Ti layer and a Cu layer are covered on the surface of the Nb rod / wire; an SnTiTa alloy rod is loaded into a first oxygen-free Cu tube, and then subjected to drawing and cutting; the NbTiCu core rod and the SnTiTa / Cu central rod are bundled, loaded into an NbTa alloy tube, and then loaded into a second oxygen-free Cu tube, and then subjected to drawing and cutting, and then the bundle is loaded into a Ta tube and then loaded into a third oxygen-free Cu tube, and then subjected to drawing to obtain the high-strength niobium-tin superconducting wire. By covering a Ti layer on the surface of the Nb rod / wire, cooperating with the SnTiTa alloy rod and the NbTa alloy tube, the problem that the core wire is damaged and the performance is degraded after heat treatment of the niobium-tin superconducting wire prepared by the internal tin method, and the stable operation of a magnet is affected is solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of superconducting wires, in particular to a preparation method of a high-strength niobium-tin superconducting wire and the superconducting wire. BACKGROUND

[0002] The niobium-tin superconducting wire is a key material for manufacturing high-field superconducting magnets and is widely used in the fields of nuclear fusion, particle accelerators, nuclear magnetic resonance spectrometers and the like and plays an important role in practical superconducting materials. The internal tin method is a mainstream process for preparing high-performance niobium-tin superconducting wires, and different critical properties of the niobium-tin wire can be obtained by adjusting the contents of Cu, Nb and Sn, and the process route is simple. The manufacturing of the niobium-tin superconducting wire and the superconducting magnet by the internal tin method usually includes the following processes: a plurality of Nb components and oxygen-free Cu are compounded and Sn is added to prepare a CuNbSn composite, a plurality of CuNbSn composites and an oxygen-free copper matrix are compounded and drawn to obtain a niobium-tin wire; the niobium-tin wire is wound into a superconducting magnet coil and the shape is fixed; the coil is subjected to overall heat treatment to make Nb react with Sn to generate a niobium-tin superconducting phase with an A15 structure; the coil after heat treatment is insulated, vacuum-impregnated and completed with subsequent assembly and system integration. The heat treatment is a key process for the niobium-tin superconducting wire to have superconducting properties. The core wire of the niobium-tin wire after heat treatment is a brittle intermetallic compound, which may be damaged and the performance may be degraded in an extremely low temperature and strong magnetic field environment, thereby affecting the stable operation of the magnet, and therefore the preparation of the niobium-tin wire should not only focus on the improvement of the critical performance of the wire itself, but also consider the correlation between the core wire damage, performance degradation of the wire and the preparation process of the wire under actual service conditions.

[0003] In the prior art, the patent CN118866461A discloses a preparation method of an internal tin method Nb3Sn superconducting wire and the superconducting wire, wherein the method comprises the following steps: adding Ti element into molten Nb to prepare NbTi rods; inserting a plurality of NbTi rods into a casting cylinder, injecting oxygen-free copper liquid into the casting cylinder to prepare CuNb composite ingots; extruding the CuNb composite ingots to obtain CuNb composite rods; drilling holes in the center of the CuNb composite rods to obtain CuNb composite tubes; inserting SnCu alloy rods into the CuNb composite tubes to obtain sub-components; assembling a plurality of sub-components into a Ta tube, assembling the Ta tube into an oxygen-free copper tube to obtain a final blank; and drawing and twisting the final blank to obtain the Nb3Sn superconducting wire.

[0004] However, the above prior art does not study or solve the above problems, and the niobium-tin superconducting wire prepared by the internal tin method has core wire damage and performance degradation after heat treatment, which affects the stable operation of the magnet. SUMMARY

[0005] The application provides a preparation method of high-strength Nb3Sn superconducting wire and the superconducting wire, so as to solve the problems of core wire damage and performance degradation after heat treatment of the Nb3Sn superconducting wire prepared by the internal tin method in the prior art, and affect the stable operation of a magnet.

[0006] In one aspect, the application provides a preparation method of high-strength Nb3Sn superconducting wire, comprising the following steps:

[0007] Step one, a pure Nb ingot is subjected to extrusion, drawing and cutting to obtain an Nb rod / wire.

[0008] Step two, a layer of Ti is coated on the surface of the Nb rod / wire, and a layer of Cu is further coated on the surface of the Ti layer to obtain an NbTiCu core rod.

[0009] Step three, a SnTiTa alloy rod is loaded into a first oxygen-free Cu tube, and is subjected to drawing and cutting to obtain a SnTiTa / Cu center rod.

[0010] Step four, a plurality of NbTiCu core rods and one SnTiTa / Cu center rod are bundled and loaded into a NbTa alloy tube, and then loaded into a second oxygen-free Cu tube, and are subjected to drawing and cutting to obtain a sub-element.

[0011] Step five, a plurality of sub-elements are bundled and loaded into a Ta tube, and then loaded into a third oxygen-free Cu tube to obtain a final billet.

[0012] Step six, the final billet is subjected to drawing to obtain a high-strength Nb3Sn superconducting wire.

[0013] In one possible implementation, in step one, the extrusion temperature of the pure Nb ingot is 300-600 DEG C, and the extrusion ratio is 5-15.

[0014] In one possible implementation, in step two, the PVD coating method or the electroplating method is used to coat the layer of Ti on the surface of the Nb rod / wire and to coat the layer of Cu on the surface of the Ti layer.

[0015] The PVD coating method comprises vacuum evaporation coating, vacuum sputtering coating and vacuum ion coating.

[0016] In one possible implementation, in step two, the area ratio of the Ti layer on the cross section of the NbTiCu core rod is 0.5%-2%, and the area ratio of the Cu layer is 10%-25%.

[0017] In one possible implementation, in step three, the mass ratio of Ti in the SnTiTa alloy rod is 1%-5%, and the mass ratio of Ta is 0.5%-2%.

[0018] In a possible implementation, in step four, the number of NbTiCu core rods is 50-300.

[0019] In a possible implementation, in step four, the mass percentage of Ta in the NbTa alloy tube is 2%-10%.

[0020] In a possible implementation, in step four, the cross-sectional shape of the subunit is hexagonal, circular, or special-shaped.

[0021] In a possible implementation, in step five, the number of subunits is [3n(n-1)+1], where n represents the number of layers of the subunit bundle.

[0022] In another aspect, the application provides a high-strength Nb3Sn superconducting wire prepared by the above method.

[0023] The method for preparing a high-strength Nb3Sn superconducting wire and the superconducting wire have the following advantages:

[0024] By covering a Ti layer on the surface of the Nb rod / wire, the strength of the Nb rod / wire is improved, and the damage to the core wire during processing and after heat treatment is reduced. The proposed SnTiTa alloy rod reduces the hardness difference between the Sn alloy and the Nb rod / wire and the Cu matrix by adding a small amount of Ti and Ta to the Sn alloy, thereby improving the cooperative deformation capability between different subunits. The proposed bundle of several NbTiCu core rods and one SnTiTa / Cu center rod in a NbTa alloy tube further increases the strength of the entire subunit while ensuring good plastic deformation. In summary, the problems of core wire damage and performance degradation after heat treatment of the Nb3Sn superconducting wire, which affect the stable operation of the magnet, are solved. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0026] Figure 1 A flowchart of a method for preparing a high-strength Nb3Sn superconducting wire is provided for the embodiments of the application.

[0027] Figure 2 A cross-sectional structure diagram of a NbTiCu core rod is provided for the embodiments of the application.

[0028] Figure 3A schematic diagram of the cross-sectional structure of a SnTiTa / Cu central rod provided in an embodiment of the present application;

[0029] Figure 4 A schematic diagram of the cross-sectional structure of a subcomponent provided in an embodiment of the present application;

[0030] Figure 5 This is a schematic diagram of the cross-sectional structure of the final blank provided in an embodiment of the present application.

[0031] Description of reference numerals:

[0032] 1-Nb rod / wire, 2-Ti layer, 3-Cu layer, 4-SnTiTa alloy rod, 5-first oxygen-free Cu tube, 6-NbTiCu core rod, 7-SnTiTa / Cu center rod, 8-NbTa alloy tube, 9-second oxygen-free copper tube, 10-subcomponent, 11-Ta tube, 12-third oxygen-free copper tube. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] like Figure 1 As shown, the embodiment of the present application provides a method for preparing a high-strength niobium-tin superconducting wire, comprising the following steps:

[0035] Step 1: A pure Nb ingot is extruded, drawn, and cut to obtain a Nb rod / wire 1.

[0036] Step 2: Cover the surface of the Nb rod / wire 1 with a Ti layer 2, and then cover the surface of the Ti layer 2 with a Cu layer 3 to obtain a NbTiCu core rod 6.

[0037] Step 3: The SnTiTa alloy rod 4 is loaded into the first oxygen-free Cu tube 5, and the SnTiTa / Cu center rod 7 is obtained by drawing and cutting.

[0038] Step 4: Bundle a plurality of the NbTiCu core rods 6 and one SnTiTa / Cu center rod 7 into a NbTa alloy tube 8 and then into a second oxygen-free Cu tube 9 , and then draw and cut to obtain a subcomponent 10 .

[0039] Step 5: Bundle a number of the subcomponents into a Ta tube 11, and then into a third oxygen-free Cu tube 12 to obtain a final billet.

[0040] Step six, the final billet is drawn to obtain high-strength niobium three-tin superconducting wire.

[0041] Embodiment 1

[0042] Illustratively, in this embodiment, in step one, the extrusion temperature of the pure Nb ingot is 300 DEG C, and the extrusion ratio is 5.

[0043] Illustratively, in this embodiment, in step two, a layer of Ti layer 2 is covered on the surface of the Nb rod / wire 1 by vacuum evaporation plating, and a layer of Cu layer 3 is covered on the surface of the Ti layer 2 by vacuum sputtering plating, to obtain a NbTiCu core rod 6, and the area ratio of the Ti layer 2 on the cross section of the NbTiCu core rod 6 is 0.5%, and the area ratio of the Cu layer 3 is 10%.

[0044] Illustratively, in this embodiment, in step three, the mass ratio of Ti in the SnTiTa alloy rod 4 is 1%, and the mass ratio of Ta is 0.5%.

[0045] Illustratively, in this embodiment, in step four, the number of NbTiCu core rods 6 is 50; the mass ratio of Ta in the NbTa alloy tube 8 is 2%; and the cross-sectional shape of the sub-element 10 is circular.

[0046] Illustratively, in this embodiment, in step five, the number of sub-elements 10 is 19, and the number of layers of the bundle is 3.

[0047] Embodiment 2

[0048] Illustratively, in this embodiment, in step one, the extrusion temperature of the pure Nb ingot is 450 DEG C, and the extrusion ratio is 10.

[0049] Illustratively, in this embodiment, in step two, a layer of Ti layer 2 is covered on the surface of the Nb rod / wire 1 by vacuum sputtering plating, and a layer of Cu layer 3 is covered on the surface of the Ti layer 2 by vacuum ion plating, to obtain a NbTiCu core rod 6, and the area ratio of the Ti layer 2 on the cross section of the NbTiCu core rod 6 is 1%, and the area ratio of the Cu layer 3 is 15%.

[0050] Illustratively, in this embodiment, in step three, the mass ratio of Ti in the SnTiTa alloy rod 4 is 3%, and the mass ratio of Ta is 1%.

[0051] Illustratively, in this embodiment, in step four, the number of NbTiCu core rods 6 is 150; the mass ratio of Ta in the NbTa alloy tube 8 is 5%; and the cross-sectional shape of the sub-element 10 is hexagonal and special-shaped.

[0052] Exemplarily, in the embodiment, in step five, the number of subunits 10 is 37, and the number of bundle layers is 4 (of which 19 are hexagons located in the inner three layers, and 18 are irregular shapes located in the outermost layer).

[0053] Embodiment 3

[0054] Exemplarily, in the embodiment, in step one, the extrusion temperature of the pure Nb ingot is 600°C, and the extrusion ratio is 15.

[0055] Exemplarily, in the embodiment, in step two, a layer of Ti layer 2 is covered on the surface of the Nb rod / wire 1 by vacuum ion plating, and a layer of Cu layer 3 is covered on the surface of the Ti layer 2 by electroplating, to obtain a NbTiCu core rod 6. The area ratio of the Ti layer 2 on the cross section of the NbTiCu core rod 6 is 2%, and the area ratio of the Cu layer 3 is 25%.

[0056] Exemplarily, in the embodiment, in step three, the mass ratio of Ti in the SnTiTa alloy rod 4 is 5%, and the mass ratio of Ta is 2%.

[0057] Exemplarily, in the embodiment, in step four, the number of NbTiCu core rods 6 is 300; the mass ratio of Ta in the NbTa alloy tube 8 is 10%; and the cross-sectional shape of the subunit 10 is circular.

[0058] Exemplarily, in the embodiment, in step five, the number of subunits 10 is 61, and the number of bundle layers is 5.

[0059] The high-strength Nb3Sn superconducting wires prepared by the embodiments 1, 2 and 3 have a tensile strength of 612 MPa, 753 MPa and 875 MPa, respectively, and a performance degradation of 2.1%, 1.6% and 0.9% respectively after heat treatment in a low-temperature strong magnetic field. The tensile strength of a conventional Nb3Sn superconducting wire prepared by an internal Sn method is 480 MPa, and the performance degradation after heat treatment in a low-temperature strong magnetic field is 5%. Therefore, the high-strength Nb3Sn superconducting wire obtained by the method of the present application has a tensile strength increased by more than 27% and a performance degradation reduced by more than 58%, and the stability of the superconducting magnet wound therefrom is significantly improved.

[0060] In a possible embodiment, as shown in Figures 2 to 5 , the cross-sectional structure of the NbTiCu core rod 6, the SnTiTa / Cu center rod 7, the subunit 10 and the final blank are shown. In Figure 2 , the cross-sectional structure of the NbTiCu core rod 6 is sequentially Nb rod / wire 1, Ti layer 2 and Cu layer 3 from inside to outside; in Figure 3 , the cross-sectional structure of the SnTiTa / Cu center rod 7 is sequentially SnTiTa alloy rod 4 and first oxygen-free Cu tube 5 from inside to outside; inFigure 4 In the sub-element 10, the cross-sectional structure from inside to outside is SnTiTa / Cu center rod 7, NbTiCu core rod 6, NbTa alloy tube 8, second oxygen-free Cu tube 9. Figure 5 In the final billet, the cross-sectional structure from inside to outside is sub-element 10, Ta tube 11, third oxygen-free Cu tube 12.

[0061] The embodiment of the present application improves the strength of the Nb rod / wire 1 by covering a layer of Ti 2 on the surface of the Nb rod / wire 1, and reduces the damage of the core wire during the processing and after the heat treatment. The proposed SnTiTa alloy rod 4 reduces the hardness difference between the Sn alloy and the Nb rod / wire 1 and the Cu matrix by adding a small amount of Ti and Ta in the Sn alloy, and improves the synergistic deformation ability between different elements. The proposed NbTiCu core rod 6 and the SnTiTa / Cu center rod 7 are bundled into the NbTa alloy tube 8, which further increases the strength of the entire sub-element 10 while ensuring good plastic deformation. In summary, the problems of the core wire damage and performance degradation after heat treatment of the inner tin method niobium tri-tin superconducting wire, which affect the stable operation of the magnet, are solved.

[0062] Although the preferred embodiments of the present application have been described, those skilled in the art who are familiar with the basic inventive concept can make additional changes and modifications to the embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0063] Obviously, those skilled in the art can make various modifications and variations 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 of producing a high-strength niobium tri-tin superconducting wire, characterized by, The method comprises the following steps: Step one, pure Nb ingot is extruded, drawn and cut to obtain Nb rod / wire; Step two, a layer of Ti is coated on the surface of the Nb rod / wire, and a layer of Cu is coated on the surface of the Ti layer to obtain NbTiCu core rod; Step three, SnTiTa alloy rod is loaded into a first oxygen-free Cu tube, drawn and cut to obtain SnTiTa / Cu center rod; Step four, a plurality of NbTiCu core rods and a SnTiTa / Cu center rod are bundled and loaded into a NbTa alloy tube and then loaded into a second oxygen-free Cu tube, and then drawn and cut to obtain sub-element; Step five, a plurality of sub-elements are bundled and loaded into a Ta tube and then loaded into a third oxygen-free Cu tube to obtain final billet; Step six, the final billet is drawn to obtain high-strength niobium three-tin superconducting wire.

2. The method of claim 1, wherein the Nb3Sn superconducting wire has a strength of at least 100 MPa. In step one, the extrusion temperature of the pure Nb ingot is 300-600°C, and the extrusion ratio is 5-15.

3. The method of claim 1, wherein the Nb3Sn superconducting wire has a strength of at least 100 MPa. In step two, the PVD coating method or the electroplating method is used to coat a layer of Ti on the surface of the Nb rod / wire and a layer of Cu on the surface of the Ti layer. The PVD coating method includes vacuum evaporation coating, vacuum sputtering coating and vacuum ion coating.

4. The method of claim 1, wherein the Nb3Sn superconducting wire has a strength of at least 100 MPa. In step two, the area ratio of the Ti layer on the cross section of the NbTiCu core rod is 0.5%-2%, and the area ratio of the Cu layer is 10%-25%.

5. The method of claim 1, wherein the Nb3Sn superconducting wire has a strength of at least 100 MPa. In step three, the mass ratio of Ti in the SnTiTa alloy rod is 1%-5%, and the mass ratio of Ta is 0.5%-2%.

6. The method of claim 1, wherein the Nb3Sn superconducting wire has a strength of at least 100 MPa. In step four, the number of NbTiCu core rods is 50-300.

7. The method of claim 1, wherein the Nb3Sn superconducting wire has a strength of at least 100 MPa. In step four, the mass ratio of Ta in the NbTa alloy tube is 2%-10%.

8. The method of claim 1, wherein the Nb3Sn superconducting wire has a high strength. In step four, the cross-sectional shape of the sub-element is hexagonal, circular or irregular.

9. The method of claim 1, wherein the Nb3Sn superconducting wire has a high strength.

9. The method of claim 1, wherein the Nb3Sn superconducting wire has a high strength. In step five, the number of sub-elements is [3n(n-1)+1], wherein n represents the number of layers of the sub-element bundle.

10. A high-strength niobium tri-tin superconducting wire, characterized by, The high-strength niobium three-tin superconducting wire is prepared by the method of any one of claims 1-9.

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