A method for preparing low-cost niobium-tin wire

Abstract

The present application provides a method for preparing a low-cost niobium-tin wire, comprising: first, placing a tin rod into a first single cylindrical copper tube, and obtaining a Cu / Sn single core rod after multiple drawing and cutting; second, placing the obtained Cu / Sn single core rod into a Nb or Nb alloy tube, and then placing it into a second single cylindrical copper tube, and obtaining a tubular niobium-tin subcomponent after multiple drawing and cutting; third, placing the obtained tubular niobium-tin subcomponent into a first porous cylindrical copper tube, and obtaining a niobium-tin subcomponent primary composite rod after multiple drawing and cutting; fourth, placing the obtained niobium-tin subcomponent primary composite rod into a second porous cylindrical copper tube to obtain a niobium-tin composite wire blank, and obtaining a niobium-tin wire with a high critical current density after multiple drawing. The method solves the problem of niobium waste and performance degradation caused by heat treatment reaction in the prior art.

Description

Technical Field

[0001] The present application relates to the technical field of superconducting material preparation, and in particular to a method for preparing a low-cost niobium-tin wire. Background Art

[0002] Nb3Sn superconducting wire is an essential low-temperature superconducting material for making superconducting magnets above 10T. It is widely used in nuclear fusion, high-energy particle accelerators and magnetic resonance medical imaging. The main raw materials for producing niobium-tin wire are niobium, tin and copper. Among these materials, the cost of niobium is much higher than the other two. Therefore, maximizing the efficiency of niobium use during the preparation process is a key method to reduce the cost of niobium-tin wire.

[0003] In order to ensure the thermal stability during the operation of the magnet, the Nb3Sn superconducting phase in the Nb3Sn superconducting wire must be surrounded by high-purity oxygen-free copper as a stabilizer to promptly transfer the heat generated during the magnetic flux jump. The niobium and tin of commercial Nb3Sn wires are separated before heat treatment. During the heat treatment, tin diffuses into the niobium to form the Nb3Sn phase. In order to ensure that tin does not diffuse through the subcomponent during the heat treatment, causing the oxygen-free copper outside the subcomponent to be contaminated and the thermal conductivity to decrease, the periphery of the Nb3Sn subcomponent contains an annular barrier layer. In order to facilitate close-packed bundling, the subcomponents in traditional Nb3Sn wires are usually hexagonal in shape. During the heat treatment of the wire, tin gradually diffuses radially outward from the center of the subcomponent. The niobium of the hexagonal barrier layer at the top corner is relatively thick, and a large amount of niobium is often left at the top corner after the heat treatment reaction, resulting in niobium waste and performance degradation. Summary of the invention

[0004] The embodiment of the present application provides a method for preparing a low-cost niobium-tin wire, which is used to solve the problem of waste of niobium and degradation of performance after heat treatment reaction in the prior art.

[0005] On the one hand, the present application embodiment provides a method for preparing a low-cost niobium-tin wire, comprising the following steps:

[0006] 1. Put the tin rod into the first single cylindrical copper tube, and obtain the Cu / Sn single core rod after multiple drawing and cutting to a certain length;

[0007] 2. The Cu / Sn single core rod obtained in step 1 is loaded into a Nb or Nb alloy tube, and then loaded into a second single cylindrical copper tube, and after multiple drawing and cutting to a certain length, a tubular niobium-tin subcomponent is obtained;

[0008] 3. The tubular niobium-tin subcomponent obtained in step 2 is loaded into a first porous cylindrical copper tube, and after multiple drawing and cutting to a predetermined length, a niobium-tin subcomponent primary composite rod is obtained;

[0009] Fourth, the niobium-tin subcomponent primary composite rod obtained in step three is loaded into the second porous cylindrical copper tube to obtain a niobium-tin composite wire blank, and a niobium-tin wire with a high critical current density is obtained through multiple drawing passes.

[0010] Optionally, the Cu / Sn single core rod copper ratio ranges from [0.1, 0.5].

[0011] Optionally, the Nb alloy tube includes but is not limited to any one of Nb-Ta, Nb-Ti, and Nb-Zr.

[0012] Optionally, the copper ratio of the tubular niobium-tin subcomponent is in the range of [0.1, 0.4].

[0013] Optionally, the multiple holes in the first porous cylindrical copper tube and the second porous cylindrical copper tube are circular and centrally symmetrically distributed, the number of holes ranges from [7,37], and the outer diameter of the copper tube ranges from [φ25mm,φ90mm], wherein the number of holes in the first porous cylindrical copper tube is smaller than the number of holes in the second porous cylindrical copper tube, and the outer diameter of the copper tube of the first porous cylindrical copper tube is smaller than the outer diameter of the copper tube of the second porous cylindrical copper tube.

[0014] Optionally, a barrier layer material may be provided on the inner walls of the first single cylindrical copper tube, the second single cylindrical copper tube, the first porous cylindrical copper tube, and the second porous cylindrical copper tube.

[0015] Optionally, the barrier layer material is a rare earth element-doped Nb foil or Ta foil wound into a barrier layer with uniform thickness.

[0016] Optionally, the cross section of the tubular niobium-tin subcomponent is circular, and the residual Nb content after heat treatment is less than 6%.

[0017] The technical solution in this application has the following advantages:

[0018] The present application proposes a method for preparing a low-cost niobium-tin wire, which can prepare a circular tubular niobium-tin subcomponent, which saves more materials than the traditional oxygen-free copper with a circular outer circle and a hexagonal inner circle. After that, the porous copper tube is used multiple times to assemble the blank and perform multiple drawing passes to finally obtain the finished wire. After the circular niobium-tin subcomponent is prepared, the niobium-tin composite wire prepared in this way always maintains a circular shape without deformation in each subsequent assembly and stretching process, and the thickness of the barrier layer is evenly distributed in the radial direction. During the heat treatment process, the tin in the center of the subcomponent can diffuse outward to the greatest extent, avoiding the problem of excessive niobium remaining after heat treatment, and effectively improving the critical current density of the niobium-tin wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the cross-sectional structure of a tubular niobium-tin subcomponent provided in an embodiment of the present application.

[0020] Figure 2 A schematic diagram of the cross-sectional structure of a primary composite rod of a low-cost, high critical current density niobium-tin composite wire provided in an embodiment of the present application.

[0021] Figure 3 It is a schematic diagram of the cross-sectional structure of a low-cost, high critical current density niobium-tin composite wire provided in an embodiment of the present application.

[0022] Illustration Description:

[0023] 1 is a first single cylindrical copper tube; 2 is a Nb or Nb alloy tube; 3 is a second single cylindrical copper tube; 4 is a tin rod. DETAILED DESCRIPTION

[0024] 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.

[0025] The following are combined with the attached Figure 1-Figure 3 A method for preparing a low-cost niobium-tin wire provided in an embodiment of the present application is introduced, which includes the following steps:

[0026] 1. Put the tin rod into the first single cylindrical copper tube, and obtain the Cu / Sn single core rod after multiple drawing and cutting to a certain length.

[0027] In one embodiment, the tin rod: a tin rod with a purity of 99.9% is selected, and its diameter is determined according to the subsequent copper tube size so that it can be smoothly loaded into the copper tube. Copper tube: a copper tube with an inner diameter slightly larger than the diameter of the tin rod is prepared, for example, the inner diameter of the copper tube is 25.5 mm, the outer diameter is 28 mm, and the material is oxygen-free copper with a purity of 99.99%.

[0028] A 25 mm diameter tin rod is carefully loaded into the above copper tube, and then placed on the drawing equipment for multiple drawing passes. During the drawing process, the drawing speed is controlled at 0.5-1 m / s, and the deformation of each pass is controlled at 10%-15%. After 8 drawing passes, it is cut to a fixed length to obtain a Cu / Sn single core rod. At this time, by controlling the initial size of the tin rod and the copper tube and the drawing process parameters, the copper ratio of the Cu / Sn single core rod is 0.3 (within the range of [0.1,0.5]).

[0029] 2. The Cu / Sn single core rod obtained in step 1 is loaded into a Nb or Nb alloy tube, and then loaded into a second single cylindrical copper tube, and after multiple drawing passes and cut-to-length cutting, a tubular niobium-tin subcomponent is obtained.

[0030] In one embodiment, the prepared Cu / Sn single core rod is loaded into a Nb-Ta alloy tube, and the combination is then loaded into another copper tube. Similarly, multiple drawing operations are performed on the drawing equipment, the drawing speed is adjusted to 0.3-0.8 m / s, and the deformation amount of each pass is 8%-12%. After 10 drawing passes and cut-to-length cutting, a tubular niobium-tin subcomponent is obtained. In this process, by adjusting the initial ratio of each layer of material and the drawing process, the copper ratio of the tubular niobium-tin subcomponent reaches 0.25 (within the range of [0.1,0.4]). Among them, Nb-Ta alloy tube: select Nb-Ta alloy tube, in which the Ta content is 10% (mass fraction), and the tube diameter is determined according to the subsequent process requirements, such as the inner diameter is 30 mm and the outer diameter is 33 mm.

[0031] It should be noted that in this process, the Nb or Nb alloy tube provides the Nb element, while the Cu / Sn single core rod provides the Sn element and the Cu element. These elements will react to form the Nb3Sn superconductor during the subsequent heat treatment process. Through multiple drawing and cutting to size, a tubular niobium-tin subcomponent with a specific size and shape can be obtained. The tubular niobium-tin subcomponent obtained by step one and step two is as follows: Figure 1 As shown in the figure, 1 is the first single cylindrical copper tube; 2 is the Nb or Nb alloy tube; 3 is the second single cylindrical copper tube; 4 is the tin rod. Among them, 1 and 3 are both oxygen-free copper tubes. It should be noted that the numbers here are only used for Figure 1 The different material markings in the cross-sectional structure of a tubular niobium-tin subcomponent are described. The "first" and "second" are only used to distinguish different materials and do not represent the order of precedence. Cu is used as the outer layer and Sn is used as the core. Through mechanical processing (drawing), they are tightly combined together. On the macro level, it appears as a single core rod. On the micro level, the copper layer and the tin core can still be distinguished.

[0032] 3. The tubular niobium-tin subcomponent obtained in step 2 is loaded into a first porous cylindrical copper tube, and after multiple drawing and cutting to a certain length, a niobium-tin subcomponent primary composite rod is obtained.

[0033] In one embodiment, if Figure 2 As shown, the tubular niobium-tin subcomponent 6 is loaded into the first porous cylindrical copper tube 5, and the porosity of the first porous cylindrical copper tube is 30% (which can be adjusted according to actual needs). The drawing operation is performed again, and the drawing speed is set to 0.2-0.6m / s, and the deformation amount of each pass is 6%-10%. After 6 drawing passes and cutting to a fixed length, a niobium-tin subcomponent primary composite rod is obtained.

[0034] Fourth, the niobium-tin subcomponent primary composite rod obtained in step three is loaded into the second porous cylindrical copper tube to obtain a niobium-tin composite wire blank, and a niobium-tin wire with a high critical current density is obtained through multiple drawing passes.

[0035] In one embodiment, the niobium-tin subcomponent primary composite rod 8 is loaded into another second porous cylindrical copper tube 7 to obtain a niobium-tin composite wire blank. Finally, the niobium-tin composite wire blank is subjected to multiple drawing passes, with a drawing speed of 0.1-0.5 m / s and a deformation amount of 5%-8% per pass. After 12 drawing passes, a niobium-tin wire with low cost and high critical current density is obtained. Optionally, the cross section of the tubular niobium-tin subcomponent is circular, and the residual Nb content after heat treatment is less than 6%.

[0036] It should be noted that during the entire preparation process, appropriate annealing treatment can be carried out between each drawing pass as needed to eliminate work hardening. The annealing temperature is controlled at 300-500°C, the annealing time is 30-60 minutes, and strict cleaning measures are taken on the drawing equipment and processing environment to prevent impurities from mixing in, so as to ensure the high quality and high critical current density characteristics of the final niobium-tin wire.

[0037] Optionally, the Cu / Sn single core rod copper ratio ranges from [0.1, 0.5].

[0038] Optionally, the Nb alloy tube includes but is not limited to any one of Nb-Ta, Nb-Ti, and Nb-Zr.

[0039] Optionally, the copper ratio of the tubular niobium-tin subcomponent is in the range of [0.1, 0.4].

[0040] Optionally, the multiple holes in the first porous cylindrical copper tube and the second porous cylindrical copper tube are circular and centrally symmetrically distributed, the number of holes ranges from [7,37], and the outer diameter of the copper tube ranges from [φ25mm,φ90mm], wherein the number of holes in the first porous cylindrical copper tube is smaller than the number of holes in the second porous cylindrical copper tube, and the outer diameter of the copper tube of the first porous cylindrical copper tube is smaller than the outer diameter of the copper tube of the second porous cylindrical copper tube.

[0041] Optionally, the inner walls of the first single cylindrical copper tube, the second single cylindrical copper tube, the first porous cylindrical copper tube, and the second porous cylindrical copper tube may be provided with a barrier layer material having a uniform thickness.

[0042] Optionally, the barrier layer material is a rare earth element-doped Nb foil or Ta foil that is wound to form the barrier layer.

[0043] It should be noted that the barrier layer is crucial for the practical application of Nb3Sn wire to maintain good thermal conductivity of oxygen-free copper. For example, in superconducting magnet applications, good thermal conductivity can effectively dissipate the heat generated by superconducting materials during operation, preventing superconducting materials from losing their superconducting properties due to excessive temperatures.

[0044] The presence of the barrier layer ensures the performance stability of each part of the material, allowing the Nb3Sn wire to exert its superconducting properties in complex working environments while maintaining the thermal stability and other physical properties of the entire wire structure.

[0045] The present invention also provides several groups of other specific embodiments:

[0046] Example 1

[0047] Step 1: After the φ25mm tin rod is loaded into the φ28mm / φ25.5mm copper tube, a Cu / Sn single core rod with a size of φ13.5mm is obtained after multiple drawing and cutting to a fixed length, and the copper ratio of the Cu / Sn single core rod is 0.1.

[0048] Step 2: The Cu / Sn single core rod obtained in step 1 is loaded into a φ20mm / φ13.8mm Nb7.5wt.%Ta alloy tube and then loaded into a φ22.0mm / φ20.5mm copper tube. After multiple drawing and cutting to size, a tubular niobium-tin subcomponent with a size of φ4.7mm is obtained, and the copper ratio of the tubular niobium-tin subcomponent is 0.1.

[0049] Step 3: The tubular niobium-tin subcomponent obtained in step 2 is loaded into a porous copper tube with a diameter of φ25.0 mm, 7 holes, and each hole has a diameter of φ4.9 mm. After multiple drawing passes and cut-to-size, a niobium-tin subcomponent primary composite rod with a size of φ3.5 mm is obtained.

[0050] Step 4: The niobium-tin subcomponent primary composite rod obtained in step 3 is loaded into a porous copper tube with a diameter of φ25.0 mm, 7 holes, and each hole has a diameter of φ3.7 mm to obtain a niobium-tin composite wire blank. After multiple drawing passes to φ1.0 mm, a low-cost niobium-tin wire with high critical current density is obtained.

[0051] Example 2

[0052] Step 1: After the φ25mm tin rod is loaded into the φ28mm / φ25.5mm copper tube, a Cu / Sn single core rod with a size of φ13.5mm is obtained after multiple drawing and cutting to a fixed length, and the copper ratio of the Cu / Sn single core rod is 0.3.

[0053] Step 2: The Cu / Sn single core rod obtained in step 1 is loaded into a φ20mm / φ13.8mm Nb alloy tube and then loaded into a φ22.0mm / φ20.5mm copper tube. After multiple drawing and cutting to size, a tubular niobium-tin subcomponent with a size of φ4.7mm is obtained, and the copper ratio of the tubular niobium-tin subcomponent is 0.25.

[0054] Step 3: The tubular niobium-tin subcomponent obtained in step 2 is loaded into a porous copper tube with a diameter of φ57.5 mm, containing 22 holes, each with a diameter of φ4.9 mm. After multiple drawing passes and cut-to-size, a niobium-tin subcomponent primary composite rod with a size of φ3.5 mm is obtained.

[0055] Step 4: The niobium-tin subcomponent primary composite rod obtained in step 3 is loaded into a porous copper tube with a diameter of φ57.5 mm, 22 holes, and each hole has a diameter of φ3.7 mm to obtain a niobium-tin composite wire blank. After multiple drawing passes to φ1.0 mm, a low-cost niobium-tin wire with high critical current density is obtained.

[0056] Example 3

[0057] Step 1: After the φ25mm tin rod is loaded into the φ28mm / φ25.5mm copper tube, a Cu / Sn single core rod with a size of φ13.5mm is obtained after multiple drawing and cutting to a fixed length, and the copper ratio of the Cu / Sn single core rod is 0.5.

[0058] Step 2: The Cu / Sn single core rod obtained in step 1 is loaded into a φ20mm / φ13.8mm Nb1.5at.%Ti alloy tube and then loaded into a φ22.0mm / φ20.5mm copper tube. After multiple drawing and cutting to size, a tubular niobium-tin subcomponent with a size of φ4.7mm is obtained, and the copper ratio of the tubular niobium-tin subcomponent is 0.4.

[0059] Step 3: The tubular niobium-tin subcomponent obtained in step 2 is loaded into a porous copper tube with a diameter of φ90 mm, 37 holes, and each hole has a diameter of φ4.9 mm. After multiple drawing passes and cut-to-size, a niobium-tin subcomponent primary composite rod with a size of φ4.7 mm is obtained.

[0060] Step 4: The niobium-tin subcomponent primary composite rod obtained in step 3 is loaded into a porous copper tube with a diameter of φ90 mm, 37 holes, and each hole has a diameter of φ4.9 mm to obtain a niobium-tin composite wire blank. After multiple drawing passes to φ1.0 mm, a low-cost niobium-tin wire with high critical current density is obtained.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application rather than to limit it. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present application can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of protection of the claims of the present application.

Claims

1. A method for preparing a low-cost niobium-tin wire, characterized in that: It includes the following steps:

1. Put the tin rod into the first single cylindrical copper tube, and obtain the Cu / Sn single core rod after multiple drawing and cutting to a certain length; 2. The Cu / Sn single core rod obtained in step 1 is loaded into a Nb or Nb alloy tube, and then loaded into a second single cylindrical copper tube, and after multiple drawing and cutting to a certain length, a tubular niobium-tin subcomponent is obtained; 3. The tubular niobium-tin subcomponent obtained in step 2 is loaded into a first porous cylindrical copper tube, and after multiple drawing and cutting to a predetermined length, a niobium-tin subcomponent primary composite rod is obtained; Fourth, the niobium-tin subcomponent primary composite rod obtained in step three is loaded into the second porous cylindrical copper tube to obtain a niobium-tin composite wire blank, and a niobium-tin wire with a high critical current density is obtained through multiple drawing passes.

2. The method for preparing a low-cost niobium-tin wire according to claim 1, characterized in that: The Cu / Sn single core rod copper ratio ranges from [0.1, 0.5].

3. The method for preparing a low-cost niobium-tin wire according to claim 1, characterized in that: The Nb alloy tube includes but is not limited to any one of Nb-Ta, Nb-Ti, and Nb-Zr.

4. The method for preparing a low-cost niobium-tin wire according to claim 1, characterized in that: The copper ratio of the tubular niobium-tin subcomponent is in the range of [0.1, 0.4].

5. The method for preparing a low-cost niobium-tin wire according to claim 1, characterized in that: The multiple holes in the first porous cylindrical copper tube and the second porous cylindrical copper tube are all circular and centrally symmetrically distributed. The number of holes ranges from [7,37], and the outer diameter of the copper tube ranges from [φ25mm,φ90mm]. Among them, the number of holes in the first porous cylindrical copper tube is smaller than the number of holes in the second porous cylindrical copper tube, and the outer diameter of the copper tube of the first porous cylindrical copper tube is smaller than the outer diameter of the copper tube of the second porous cylindrical copper tube.

6. The method for preparing a low-cost niobium-tin wire according to claim 1, characterized in that: The inner walls of the first single cylindrical copper tube, the second single cylindrical copper tube, the first porous cylindrical copper tube and the second porous cylindrical copper tube may be provided with a barrier layer material.

7. A method for preparing a low-cost niobium-tin wire according to claim 6, characterized in that: The barrier layer material is a rare earth element-doped Nb foil or Ta foil which is wound to form a barrier layer with uniform thickness.

8. The method for preparing low-cost niobium-tin wire according to claim 1, characterized in that: The cross section of the tubular niobium-tin subcomponent is circular, and the residual Nb content after heat treatment is less than 6%.

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