A method for preparing Nb3Sn superconducting wire by internal tin method and superconducting wire

Abstract

The present application discloses a method for preparing a Nb3Sn superconducting wire by an internal tin method and a superconducting wire, and relates to the technical field of superconducting cables. The method comprises: adding Ti element to molten Nb to prepare NbTi rods; inserting multiple NbTi rods into a casting tube, injecting oxygen-free copper liquid into the casting tube, and preparing CuNb composite ingots; 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 subcomponent; loading multiple subcomponents into a Ta tube, loading the Ta tube into an oxygen-free copper tube, and obtaining a final billet; drawing and twisting the final billet to obtain a Nb3Sn superconducting wire. The preparation method of the present application overcomes the shortcomings of the prior art, and while ensuring that the risk of wire breakage during wire preparation is greatly reduced, it also overcomes the problem of poor uniformity of Ti element diffusion during wire heat treatment.

Description

Technical Field

[0001] The present application relates to the technical field of superconducting cables, and in particular to a method for preparing a Nb3Sn superconducting wire by an internal tin process and a superconducting wire. Background Art

[0002] Nb3Sn (niobium tin) superconducting wire is an important material for manufacturing large particle accelerators. At present, the Jc (critical current density) of bronze-process Nb3Sn and ITER (International Thermonuclear Reactor Project) type Nb3Sn superconducting wires delivered in batches in various scientific projects in the world can reach 1100~1300A / mm under 12T and 4.2K conditions. 2 Obtaining stable Nb3Sn wire long-wire preparation technology and mass production capabilities with high critical current density is an important basic material problem that needs to be solved to guide large-scale particle accelerators.

[0003] The main factors affecting the critical current density of Nb3Sn superconducting wires are the Nb3Sn phase content and the Nb3Sn grain interface density. In order to improve the critical current carrying capacity of Nb3Sn superconducting wires, it is necessary to fully ensure that the Nb element in the wire fully reacts to form the Nb3Sn phase, and at the same time ensure that the Nb3Sn grains generated in the wire are uniform and small. Ti (titanium) element doping can significantly refine Nb3Sn grains. There are currently two Ti element doping methods. First, a certain amount of Ti element is dissolved into the Sn ingot to prepare a SnTi alloy rod, which is used as the Sn and Ti element source of the internal tin method Nb3Sn wire; second, a certain number of Nb47Ti rods are inserted into the core wire area of ​​the internal tin method Nb3Sn wire, and the remaining core wires are pure Nb rods, and the wire Sn source is SnCu alloy rods. After the wire preparation is completed, combined with the heat treatment experiment, it is concluded that the wire with the addition of Nb47Ti rods has a Ti element diffusion slightly lagging behind the Nb element reaction to form Nb3Sn phase. Therefore, after the heat treatment, part of the Nb3Sn phase in the wire does not contain Ti elements, and the grain size of this part of the Nb3Sn phase is larger; while the wire with the addition of SnTi alloy rods has a large hard SnTi particle size in the SnTi alloy rods, which is very easy to cause wire breakage during the wire processing process. Summary of the invention

[0004] The embodiments of the present application provide a method for preparing a Nb3Sn superconducting wire by an internal tin method and a superconducting wire, so as to solve the problems of uneven diffusion of Ti element and easy wire breaking in the superconducting wire in the prior art.

[0005] On the one hand, an embodiment of the present application provides a method for preparing a Nb3Sn superconducting wire by an internal tin method, the method comprising:

[0006] Adding Ti element to molten Nb to prepare NbTi rods;

[0007] Inserting a plurality of NbTi rods into a casting cylinder, injecting oxygen-free copper liquid into the casting cylinder, and preparing a CuNb composite ingot;

[0008] Extruding the CuNb composite ingot to obtain a CuNb composite rod;

[0009] Drill a hole in the center of the CuNb composite rod to obtain a CuNb composite tube;

[0010] Inserting SnCu alloy rod into CuNb composite tube to obtain subcomponent;

[0011] Loading a plurality of subcomponents into a Ta tube, loading the Ta tube into an oxygen-free copper tube, and obtaining a final blank;

[0012] The final billet is drawn and twisted to obtain a Nb3Sn superconducting wire.

[0013] On the other hand, an embodiment of the present application further provides an internal tin method Nb3Sn superconducting wire, which is prepared by the above method.

[0014] The internal tin method for preparing Nb3Sn superconducting wire and the superconducting wire in the present application have the following advantages:

[0015] The preparation method overcomes the shortcomings of the existing technology and ensures that the risk of wire breakage in the wire preparation process is greatly reduced. At the same time, it overcomes the problem of poor diffusion uniformity of the Ti element during the heat treatment of the wire, thereby improving the stability of the long-wire preparation process and the critical current value of the wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application 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 application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic cross-sectional view of a CuNb composite sheath provided in an embodiment of the present application;

[0018] Figure 2 This is a schematic cross-sectional view of the Nb3Sn superconducting wire provided in an embodiment of the present application.

[0019] Explanation of the accompanying drawings: 1. NbTi rod; 2. Oxygen-free copper ingot; 3. Oxygen-free copper tube; 4. Ta tube; 5. Subcomponent. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] The present application provides a method for preparing a Nb3Sn superconducting wire by an internal tin method, the method comprising the following steps:

[0022] S100, adding Ti element to molten Nb to prepare NbTi rod 1.

[0023] For example, after the Nb ingot is melted into a liquid state, a certain amount of Ti element is added into the liquid Nb, stirred evenly and then cooled to prepare a cylindrical NbTi rod 1.

[0024] Furthermore, the content of Ti in the NbTi rod 1 is 1.0 wt% to 2.0 wt%.

[0025] S110, inserting a plurality of NbTi rods 1 into a casting cylinder, injecting oxygen-free copper liquid into the casting cylinder, and preparing a CuNb composite ingot.

[0026] For example, Figure 1 As shown, the casting cylinder is also made of oxygen-free copper. After injecting oxygen-free copper liquid into the casting cylinder, an oxygen-free copper ingot 2 is prepared. Oxygen-free copper caps are welded at both ends of the casting cylinder to obtain a CuNb composite ingot. Specifically, the oxygen-free copper caps can be welded to the casting cylinder using electron beam welding technology.

[0027] The number of the NbTi rods 1 is 120 to 200, the specification of the NbTi rods 1 is φ10 mm to φ13 mm, and the outer diameter of the CuNb composite ingot is φ250 mm to φ280 mm.

[0028] S120, extruding the CuNb composite ingot to obtain a CuNb composite rod.

[0029] For example, the CuNb composite ingot needs to be heated and kept warm before extrusion, and the extrusion temperature of the CuNb composite ingot is 450°C to 550°C, and the holding time is 60min to 90min. The outer diameter of the extruded CuNb composite rod is φ50mm to φ60mm.

[0030] S130, drilling a hole in the center of the CuNb composite rod to obtain a CuNb composite tube.

[0031] Exemplarily, the diameter of the drilled hole is φ20 mm to φ25 mm.

[0032] S140, inserting a SnCu alloy rod into the CuNb composite tube to obtain subcomponent 5.

[0033] For example, the diameter of the SnCu alloy rod is 1.2 mm to 1.8 mm smaller than the diameter of the drilled hole. After the subcomponent 5 is obtained, the subcomponent 5 is further drawn and straightened to obtain a plurality of subcomponents 5 of equal length and uniform arrangement.

[0034] The subcomponent 5 obtained after drawing is hexagonal, and the size of its opposite sides is 10 mm to 20 mm.

[0035] Furthermore, the content of Cu in the SnCu alloy rod is 2.0 wt %.

[0036] S150, multiple subcomponents 5 are loaded into the Ta tube 4, and the Ta tube 4 is loaded into the oxygen-free copper tube 3 to obtain a final blank.

[0037] For example, Figure 2 As shown, the outer diameter of the oxygen-free copper tube 3 is φ55mm~φ75mm, the inner diameter is φ40mm~φ55mm, and the size of the Ta tube 4 is φ39mm~φ54mm.

[0038] S160, drawing and twisting the final billet to obtain a Nb3Sn superconducting wire.

[0039] Exemplarily, after obtaining the Nb3Sn superconducting wire, the Nb3Sn superconducting wire is further heat-treated by first keeping the wire at 550°C for 200 hours and then keeping the wire at 650°C for 250 hours.

[0040] Further, the pitch of twisting is 40 mm.

[0041] The embodiment of the present application also provides an internal tin method Nb3Sn superconducting wire, which is prepared by the above method.

[0042] The following is an explanation of the specific process:

[0043] Example 1

[0044] Step 1: During the smelting process of Nb ingot, 1.0 wt% of Ti element is added to the molten liquid Nb, and the molten liquid Nb is prepared into a cylindrical NbTi rod 1 with a diameter of 10.0 mm.

[0045] Step 2, insert 120 NbTi rods 1 obtained in step 1 into a casting tube, then inject oxygen-free copper liquid to form an oxygen-free copper ingot 2, add oxygen-free copper covers at both ends of the casting tube and weld by electron beam to obtain a CuNb composite ingot used for preparing the inner tin Nb3Sn wire, the outer diameter of the composite ingot is φ250mm.

[0046] Step 3, heating the CuNb composite ingot obtained in step 2 to 450°C, keeping the temperature for 60 minutes, and extruding to obtain a CuNb composite rod, the outer diameter of the composite rod after extrusion is φ50mm. Drilling a hole at the center of the composite rod, the hole diameter is φ20mm, and inserting a SnCu alloy rod with an outer diameter of φ18.5mm into the drilled CuNb composite tube to obtain the inner tin Nb3Sn superconducting wire subcomponent 5, drawing the subcomponent 5, the side length of the subcomponent 5 after drawing is 10mm, and cutting the drawn subcomponent 5 into multiple equal lengths and evenly arranging them.

[0047] Step 4, load the multiple tin-containing Nb3Sn superconducting wire subcomponents 5 in step 3 into a φ39mm Ta tube 4, and then load them into a φ55mm / φ40mm oxygen-free copper tube 3 to obtain a final billet, and draw and twist the final billet to finally obtain a Nb3Sn superconducting wire with a wire torque of 40mm and a finished wire specification of φ0.820mm.

[0048] Step 5, heat treating the Nb3Sn superconducting wire obtained in step 4 at 550°C / 200h and 665°C / 250h.

[0049] The critical current value of the Nb3Sn superconducting wire prepared in Example 1 is as follows:

[0050] Table 1 Critical current of Example 1

[0051]

[0052] In Example 1, a wire with a length of 14000 m was successfully prepared by using a Ti element doping method in which a small amount of Ti element was dissolved into a Nb rod. The wire was not broken during the wire processing, while the wire prepared by the SnTi doping method broke twice during the processing. In addition, the critical current value of the wire of the Ti element doping method of the present application is significantly higher than that of the Nb47Ti doping method wire, and is equivalent to the SnTi doping method Nb3Sn superconducting wire.

[0053] Example 2

[0054] Step 1: During the smelting process of Nb ingot, 1.5 wt% of Ti element is added to the molten liquid Nb, and the Nb ingot is prepared into a round bar of φ11.0 mm.

[0055] Step 2, insert 150 NbTi rods 1 obtained in step 1 into a casting tube, then inject oxygen-free copper liquid to form an oxygen-free copper ingot 2, add oxygen-free copper covers at both ends of the casting tube and weld by electron beam to obtain a CuNb composite ingot used for preparing the inner tin Nb3Sn wire, the outer diameter of the composite ingot is φ260mm.

[0056] Step 3, heating the CuNb composite ingot obtained in step 2 to 500°C, keeping the temperature for 70 minutes, and extruding to obtain a CuNb composite rod, the outer diameter of the composite rod after extrusion is φ55mm. Drilling a hole at the center of the rod, the hole diameter is φ23mm, and inserting a SnCu alloy rod with an outer diameter of φ21.8mm into the drilled CuNb composite tube to obtain the inner tin Nb3Sn superconducting wire subcomponent 5, and drawing the obtained subcomponent 5, the side length of the subcomponent 5 after drawing is 15mm, and the drawn subcomponent 5 is cut into multiple equal lengths and evenly arranged.

[0057] Step 4, load the multiple tin-containing Nb3Sn superconducting wire subcomponents 5 in step 3 into a φ49mm Ta tube 4, and then load them into a φ60mm / φ50mm oxygen-free copper tube 3 to obtain a final billet, and draw and twist the final billet to finally obtain a Nb3Sn superconducting wire with a wire torque of 40mm and a finished wire specification of φ0.820mm.

[0058] Step 5, heat treating the Nb3Sn superconducting wire obtained in step 4 at 550°C / 200h and 665°C / 250h.

[0059] The critical current value of the Nb3Sn superconducting wire obtained in Example 2 is as follows:

[0060] Table 2 Critical current of Example 2

[0061]

[0062] In Example 2, a wire with a length of 15,000 m was successfully prepared by using a Ti element doping method in which a small amount of Ti element was dissolved into a Nb rod. The wire was not broken during the wire processing, while the wire prepared by the SnTi doping method broke 3 times during the processing. In addition, the critical current value of the wire of the Ti element doping method of the present application is significantly higher than that of the Nb47Ti doping method wire, and slightly higher than that of the SnTi doping method Nb3Sn superconducting wire, because the Ti element doping amount in the core rod is increased by 0.5wt%.

[0063] Example 3

[0064] Step 1: During the smelting process of Nb ingot, 2.0 wt% of Ti element is added to the molten liquid Nb, and the Nb ingot is prepared into a round bar of φ13.0 mm.

[0065] Step 2: insert 200 NbTi rods 1 obtained in step 1 into a casting tube, then inject oxygen-free copper liquid to form an oxygen-free copper ingot 2, add oxygen-free copper covers at both ends of the casting tube and weld by electron beam to obtain a CuNb composite ingot for preparing the inner tin Nb3Sn wire, the outer diameter of the composite ingot is φ280mm.

[0066] Step 3, heating the CuNb composite ingot obtained in step 2 to 550°C, keeping the temperature for 90 minutes, and extruding to obtain a CuNb composite rod, the outer diameter of the composite rod after extrusion is φ60mm. Drilling a hole at the center of the rod, the hole diameter is φ25mm, and inserting a SnCu alloy rod with an outer diameter of φ23.5mm into the drilled CuNb composite tube to obtain the inner tin Nb3Sn superconducting wire subcomponent 5, and drawing the obtained subcomponent 5, the opposite side length of the subcomponent 5 after drawing is 20mm, and the drawn subcomponent 5 is cut into multiple equal lengths and evenly arranged.

[0067] Step 4, load the multiple tin-containing Nb3Sn superconducting wire subcomponents 5 in step 3 into a φ54mm Ta tube 4, and then load them into a φ75mm / φ55mm oxygen-free copper tube 3 to obtain a final billet, and draw and twist the final billet to finally obtain a Nb3Sn superconducting wire with a wire torque of 40mm and a finished wire specification of φ0.820mm.

[0068] Step 5, heat treating the Nb3Sn superconducting wire obtained in step 4 at 550°C / 200h and 665°C / 250h.

[0069] The critical current value of the Nb3Sn superconducting wire obtained in Example 3 is as follows:

[0070] Table 3 Critical current of Example 3

[0071]

[0072] In Example 3, a wire with a length of 18,000 m was successfully prepared by using a Ti element doping method in which a small amount of Ti element was dissolved into a Nb rod. The wire was not broken during the processing of the wire, while the wire prepared by the SnTi doping method broke twice during the processing. In addition, the critical current value of the wire of the Ti element doping method of the present application is significantly higher than that of the Nb47Ti doping method wire, and is equivalent to the SnTi doping method Nb3Sn superconducting wire. The reason is that the Ti element doping amount in the core rod reaches 2.0wt%, which is too high.

[0073] The preparation method of the present application solves the adverse effects of SnTi doping and Nb47Ti rod doping on wire processing and critical current value by dissolving a small amount of Ti element into all Nb core wires. The risk of wire breakage during wire preparation is greatly reduced, and the uniformity of Ti element diffusion during wire heat treatment is significantly improved. The stability of long-line preparation process is improved, and the critical current value of wire is improved.

[0074] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. 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.

[0075] 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 equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for preparing Nb3Sn superconducting wire by internal tin method, characterized in that: include: Adding Ti element to molten Nb to prepare a NbTi rod (1): After the Nb ingot is melted into a liquid state, the Ti element is added to the liquid Nb, stirred evenly and then cooled to prepare the NbTi rod (1), wherein the Ti content in the NbTi rod (1) is 1.0wt% to 2.0wt%; Inserting a plurality of the NbTi rods (1) into a casting cylinder, and 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 subcomponent (5), wherein the content of Cu in the SnCu alloy rod is 2.0wt%; Loading a plurality of the subcomponents (5) into a Ta tube (4), and loading the Ta tube (4) into an oxygen-free copper tube (3) to obtain a final blank; The final billet is drawn and twisted to obtain a Nb3Sn superconducting wire.

2. The method for preparing Nb3Sn superconducting wire by internal tin method according to claim 1, characterized in that: After injecting oxygen-free copper liquid into the casting cylinder, an oxygen-free copper ingot (2) is prepared, and oxygen-free copper covers are welded at both ends of the casting cylinder to obtain the CuNb composite ingot.

3. The method for preparing Nb3Sn superconducting wire by internal tin method according to claim 2, characterized in that: The oxygen-free copper cover is welded to the casting cylinder by electron beam welding technology.

4. The method for preparing Nb3Sn superconducting wire by internal tin method according to claim 1, characterized in that: The CuNb composite ingot is heated and kept warm before being extruded.

5. The method for preparing Nb3Sn superconducting wire by internal tin method according to claim 4, characterized in that: The extrusion temperature of the CuNb composite ingot is 450°C to 550°C.

6. The method for preparing Nb3Sn superconducting wire by internal tin method according to claim 1, characterized in that: After the subcomponent (5) is obtained, the subcomponent (5) is further drawn and straightened.

7. The method for preparing Nb3Sn superconducting wire by internal tin method according to claim 1, characterized in that: After the Nb3Sn superconducting wire is obtained, the Nb3Sn superconducting wire is further subjected to heat treatment.

8. The method for preparing Nb3Sn superconducting wire by internal tin method according to claim 7, characterized in that: The heat treatment method is to first keep the temperature at 550° C. for 200 hours and then keep the temperature at 650° C. for 250 hours.

9. An internal tin method Nb3Sn superconducting wire, characterized in that: The Nb3Sn superconducting wire is prepared by the method described in any one of claims 1-8.

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