A method for manufacturing a Nb3Sn superconducting wire for a magnet wound after a reaction heat treatment

Abstract

The application relates to a preparation method of a Nb3Sn superconducting wire for winding a magnet after reaction heat treatment, which comprises the following steps: selecting a Nb3Sn composite wire and a copper slot wire; performing surface chromium plating on the Nb3Sn composite wire and immersing the Nb3Sn composite wire in an electroplating solution to perform electroplating; immersing the copper slot wire and the Nb3Sn composite wire obtained after electroplating in a tin slot to obtain a Nb3Sn inlaid wire; immersing the Nb3Sn inlaid wire in a flowing nitric acid-based tin removal solution to ensure that the surface solder of the Nb3Sn inlaid wire is completely removed, and obtaining a Nb3Sn tin-removed wire; winding the Nb3Sn tin-removed wire on a steel wheel and placing the Nb3Sn tin-removed wire in a heat treatment furnace to perform vacuum heat treatment on the furnace body, and obtaining a Nb3Sn superconducting wire. The method strengthens the strength of a copper matrix outside a Nb3Sn superconducting phase through a process flow of wire surface chromium plating-inlaid soldering-surface solder removal-reaction heat treatment, and realizes winding of a magnet after reaction heat treatment of a Nb3Sn wire.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of superconducting wire processing, and relates to a preparation method of Nb3Sn superconducting wire after reaction heat treatment and winding of a magnet. BACKGROUND

[0002] Nb3Sn superconducting material has been widely concerned due to its transport current density far higher than that of NbTi superconducting material, and is currently widely applied to nuclear magnetic resonance (NMR), high-energy physics (HEP) and international thermonuclear experimental reactor (ITER). However, Nb3Sn is a brittle intermetallic compound, and the wire preparation and use process is drawing (Nb and Sn separation)-insulation-winding of a magnet-reaction heat treatment (formation of brittle Nb3Sn superconducting phase), which has the disadvantage that the reaction heat treatment after winding of the magnet cannot identify the wire defects in time, resulting in a low yield of Nb3Sn superconducting magnets and a certain limitation on the development of Nb3Sn. Therefore, it is urgent to obtain a preparation method of Nb3Sn superconducting wire in which the reaction heat treatment is performed first to form the Nb3Sn superconducting phase, and then the magnet is wound. SUMMARY

[0003] The application aims to overcome the above-mentioned shortcomings of the prior art, and provides a preparation method of Nb3Sn superconducting wire after reaction heat treatment and winding of a magnet, which solves the problem that the reaction heat treatment after winding of the magnet cannot identify the wire defects in time, resulting in a low yield of Nb3Sn superconducting magnets.

[0004] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0005] The application provides a preparation method of Nb3Sn superconducting wire after reaction heat treatment and winding of a magnet, which comprises the following steps:

[0006] S1, selecting Nb3Sn composite wire and copper slot wire;

[0007] S2, immersing the Nb3Sn composite wire into an electroplating solution for surface chromium plating;

[0008] S3, immersing the copper slot wire selected in step S1 and the Nb3Sn composite wire obtained after electroplating in step S2 into a tin bath to obtain Nb3Sn inlaid wire;

[0009] S4, immersing the Nb3Sn inlaid wire obtained in step S3 into flowing nitric acid-based tin removal solution to ensure that the surface solder of the Nb3Sn inlaid wire is completely removed, and obtaining Nb3Sn tin-removed wire;

[0010] S5, winding the Nb3Sn tin-removed wire obtained in step S4 on a steel wheel, and placing it in a heat treatment furnace, and performing vacuum heat treatment on the furnace body to obtain Nb3Sn superconducting wire.

[0011] Furthermore, in step S1, the diameter of the Nb3Sn composite wire is 0.82mm to 1.30mm, the width and height of the copper groove wire are 2.1mm to 2.6mm and 1.3mm to 2.6mm respectively, and the groove width of the copper groove wire is 0.87mm to 1.35mm.

[0012] Furthermore, in step S2, after the Nb3Sn composite wire is electroplated, the thickness of the electroplated layer is >8µm.

[0013] Furthermore, in step S2, the electroplating speed is 0.2 to 0.3 m / min, and the size of the Nb3Sn wire after electroplating is 0.828 mm to 0.832 mm.

[0014] Furthermore, in step S3, the solder temperature is 230–450°C, the stretching speed is 10–80 m / min, and the width and height of the obtained Nb3Sn damascene wire are 1.95 mm–2.45 mm and 1.15 mm–1.35 mm, respectively.

[0015] Furthermore, in step S4, the temperature of the desoldering solution is 40℃~50℃, the length of the wire immersed in the desoldering solution is 20m~40m, and the desoldering speed is 12~15m / min.

[0016] Furthermore, in step S5, the vacuum degree is <5×10⁻⁶. -3 Pa, heat treatment temperature is 630℃~650℃, heat treatment time is 60h~61h.

[0017] Furthermore, the Nb3Sn superconducting wire was tested using the following methods:

[0018] Step 1: Braid the Nb3Sn superconducting wire with glass wire insulation to obtain glass wire insulated braided wire. Wrap the glass wire insulated braided wire to make a magnet. Test the Ic and RRR values ​​of the wound wire.

[0019] Step 2: The Nb3Sn composite wire selected in step S1 is wound onto the Ic test skeleton as a sample and placed in a heat treatment furnace for Ic value testing.

[0020] Step 3: Compare the Ic values ​​from Step 1 and Step 2. If the difference between the two is less than 5A, it indicates that the performance of the heat-treated Nb3Sn superconducting wire is consistent with that of the sample Nb3Sn superconducting wire.

[0021] Furthermore, after step S5, eddy current testing is used to detect defects in the Nb3Sn superconducting wire.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The strength of the outer copper substrate of the Nb3Sn superconducting phase is enhanced by a process of chrome plating on the wire surface, inlay welding, removal of surface solder, and reaction heat treatment, so as to realize the winding of magnets after reaction heat treatment of Nb3Sn wire.

[0024] 2. Eddy current testing and other detection methods can be added between the Nb3Sn superconducting phase formed by reaction heat treatment and the wound magnet to confirm the wire defects. Defective wires can be identified in advance and stopped from use, avoiding the scrapping of the entire magnet due to defective wires being wound into it.

[0025] Other features and advantages of the present invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0026] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is the cross-section of the Nb3Sn composite wire used in this invention;

[0029] Figure 2 This is the cross-section of the copper channel wire used in this invention;

[0030] Figure 3 This is a schematic diagram of the Nb3Sn composite line after electroplating according to the present invention;

[0031] Figure 4 This is a schematic diagram of the Nb3Sn mosaic line of the present invention;

[0032] Figure 5 This is a schematic diagram of the Nb3Sn desoldering wire of the present invention. Detailed Implementation

[0033] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses consistent with some aspects of the invention as detailed in the appended claims.

[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] A method for preparing Nb3Sn superconducting wire with a magnet wound after reaction heat treatment includes the following steps:

[0036] S1. Select Nb3Sn composite wire and copper channel wire; the diameter of Nb3Sn composite wire is 0.82mm~1.30mm, the width and height of copper channel wire are 2.1mm~2.6mm and 1.3mm~2.6mm respectively, and the channel width of copper channel wire is 0.87mm~1.35mm.

[0037] S2. The Nb3Sn composite wire is chromium plated on its surface and then immersed in an electroplating solution for electroplating. After electroplating, the thickness of the electroplated layer is >8µm to prevent solder from diffusing into the copper substrate of the Nb3Sn composite wire. The electroplating speed is 0.2-0.3m / min, and the size of the Nb3Sn wire after electroplating is 0.828mm-0.832mm.

[0038] S3. Immerse the copper wire selected in step S1 and the Nb3Sn composite wire obtained after electroplating in step S2 into a tin bath to obtain Nb3Sn etched wire, thereby enhancing the strength of the outer copper substrate of the Nb3Sn superconducting phase. The solder temperature is 230-450℃, the stretching speed is 10-80m / min, and the width and height of the obtained Nb3Sn etched wire are 1.95mm-2.45mm and 1.15mm-1.35mm, respectively.

[0039] S4. Immerse the Nb3Sn etched wire obtained in step S3 into a flowing nitrate-based solder stripping solution, ensuring that the surface solder of the Nb3Sn etched wire is completely removed, to obtain a stripped Nb3Sn wire. The temperature of the solder stripping solution is 40℃~50℃, the length of the wire immersed in the solution is 20m~40m, and the solder stripping speed is 12~15m / min. Overly thorough solder stripping can cause the copper bath wire to separate from the Nb3Sn composite wire. Incomplete removal of the surface solder can cause localized solder diffusion to adjacent wires during the reactive heat treatment process, leading to adhesion and, after forced separation, localized dimensional deviations in the wire.

[0040] S5. The Nb3Sn detinned wire obtained in step S4 is wound onto a steel wheel and placed in a heat treatment furnace. The furnace is then subjected to vacuum heat treatment to obtain Nb3Sn superconducting wire. The vacuum level inside the furnace is <5×10⁻⁶. -3 The heat treatment temperature is 630℃~650℃, and the heat treatment time is 60h~61h. Eddy current testing is used to detect defects in Nb3Sn superconducting wires, avoiding the risk of non-conductivity and preventing inaccurate defect localization caused by performing defect detection after the wire is wound into a magnet, thus saving manufacturing costs.

[0041] The Nb3Sn superconducting wire was tested using the following method:

[0042] Step 1: Braid the Nb3Sn superconducting wire with glass wire insulation to obtain glass wire insulated braided wire. Wrap the glass wire insulated braided wire to make a magnet. Test the Ic and RRR values ​​of the wound wire.

[0043] Step 2: The Nb3Sn composite wire selected in step S1 is wound onto the Ic test skeleton as a sample and placed in a heat treatment furnace for Ic value testing.

[0044] Step 3: Compare the Ic values ​​from Step 1 and Step 2. If the difference between the two is less than 5A, it indicates that the performance of the heat-treated Nb3Sn superconducting wire is consistent with that of the sample Nb3Sn superconducting wire.

[0045] The following explanation details the specific processing steps:

[0046] Example 1:

[0047] Step 1: Select Nb3Sn composite wire with a diameter of 0.82mm and copper channel wire with a width of 2.1mm, a height of 1.3mm, and a channel width of 0.87mm according to the process requirements;

[0048] Step 2: Perform chromium plating on the Nb3Sn composite wire selected in Step 1. Immerse the wire in the electroplating solution and perform electroplating at a speed of 0.2 to 0.3 m / min to ensure that the wire size after electroplating is (0.830 ± 0.002) mm.

[0049] Step 3: Immerse the copper wire selected in Step 1 and the Nb3Sn composite wire electroplated in Step 2 into the tin bath, and perform inlay welding at an inlay welding temperature of 230℃ and a stretching speed of 10m / min to obtain an Nb3Sn inlay wire with a width of 1.95mm and a height of 1.15mm.

[0050] Step 4: Immerse the Nb3Sn etched wire obtained in Step 3 into a flowing nitrate-based desoldering solution at a temperature of 50°C. The length of the wire immersed in the desoldering solution is 40m. Desoldering is performed at a speed of 15m / min to ensure that the surface solder of the Nb3Sn etched wire is completely removed, thus obtaining the Nb3Sn desoldered wire.

[0051] Step 5: Wind the Nb3Sn detinning wire obtained in Step 4 onto a steel wheel, and wind the Nb3Sn composite wire selected in Step 1 onto the Ic test frame. Place both in a heat treatment furnace, and perform vacuum heat treatment in the furnace. The vacuum degree is required to be less than 5 × 10⁻⁶. - 3Pa was subjected to reaction heat treatment at 640℃ / 60h to obtain Nb3Sn superconducting wire 1 and Nb3Sn superconducting wire 2, respectively; eddy current testing was used to detect defects in Nb3Sn 1 superconducting wire.

[0052] Step 6: According to the process requirements, the Nb3Sn superconducting wire 1 obtained in step 5 is braided with glass wire insulation. The braided wire is 2.1mm wide and 1.3mm high.

[0053] Step 7: The glass fiber insulated braided wire obtained in Step 6 is tightly wound onto a 400mm diameter spool with a tension of 3kg. After rewinding, the wire has an Ic of 264A under a 12T magnetic field and an RRR value of 144 under 273K / 20K conditions.

[0054] In step 8, the Ic of the Nb3Sn superconducting wire 2 obtained in step 5 was tested under a magnetic field of 12T, which is 266A, and is basically consistent with the Ic performance of the test wire tested in step 7.

[0055] Therefore, the current-carrying capacity of the Nb3Sn superconducting wire obtained through the process of chrome plating on the wire surface, inlay soldering, removal of surface solder, and reactive heat treatment is not reduced, and it will not cause the magnet to lose quench. The RRR is greater than 100, with sufficient margin to ensure the stability of the final magnet's magnetic field.

[0056] Example 2

[0057] Step 1: Select Nb3Sn composite wire with a diameter of 1.30mm and copper channel wire with a width of 2.6mm, a height of 2.6mm, and a channel width of 1.35mm according to the process requirements;

[0058] Step 2: Perform chromium plating on the Nb3Sn composite wire selected in Step 1. Immerse the wire in the electroplating solution and electroplat at a speed of 0.3 m / min to ensure that the wire size is 0.828 mm after electroplating.

[0059] Step 3: Immerse the copper wire selected in Step 1 and the Nb3Sn composite wire electroplated in Step 2 into the tin bath, and perform inlay welding at an inlay welding temperature of 450℃ and a stretching speed of 80m / min to obtain an Nb3Sn inlay wire with a width of 2.45mm and a height of 1.35mm.

[0060] Step 4: Immerse the Nb3Sn etched wire obtained in Step 3 into a flowing nitrate-based stripping solution at a temperature of 50°C. The length of the wire immersed in the stripping solution is 40m. Strip the wire at a speed of 15m / min to ensure that the surface tin of the Nb3Sn etched wire is completely removed, and obtain the Nb3Sn stripped wire.

[0061] Step 5: Wind the Nb3Sn detinning wire obtained in Step 4 onto a steel wheel, and wind the Nb3Sn composite wire selected in Step 1 onto the Ic test frame. Place both in a heat treatment furnace, and perform vacuum heat treatment in the furnace. The vacuum degree is required to be less than 5 × 10⁻⁶. - 3 Pa was subjected to reaction heat treatment at 650℃ / 61h to obtain Nb3Sn superconducting wire 1 and Nb3Sn superconducting wire 2, respectively; eddy current testing was used to detect defects in Nb3Sn superconducting wire 1.

[0062] Step 6: According to the process requirements, the Nb3Sn superconducting wire 1 obtained in step 5 is braided with glass wire insulation. The braided wire is 2.63mm wide and 1.53mm high.

[0063] Step 7: The glass fiber insulated braided wire obtained in Step 6 is tightly wound onto a 400mm diameter spool with a tension of 3kg. After rewinding, the wire has an Ic of 266A under a 12T magnetic field and an RRR value of 125 under 273K / 20K conditions.

[0064] In step 8, the Ic of the Nb3Sn superconducting wire 2 obtained in step 5 was tested under a magnetic field of 12T and was 265A, which is basically consistent with the Ic performance of the test winding wire tested in step 7.

[0065] Therefore, the current-carrying capacity of the Nb3Sn superconducting wire obtained through the process of chrome plating on the wire surface, inlay soldering, removal of surface solder, and reactive heat treatment is not reduced, and it will not cause the magnet to lose quench. The RRR is greater than 100, with sufficient margin to ensure the stability of the final magnet's magnetic field.

[0066] Given that Nb3Sn wire forms a brittle intermetallic compound structure after reactive heat treatment, directly winding the wire into magnets after reactive heat treatment easily leads to wire breakage. This can be addressed by strengthening the outer copper substrate of the Nb3Sn superconducting phase, but it is crucial to ensure that the wire's Ic and RRR do not significantly decrease during magnet winding, and that its dimensions remain stable. Replacing the outer copper substrate of the Nb3Sn wire with bronze can solve the strength problem, but the wire's RRR will decrease, failing to meet requirements. Adding an additional bronze substrate to the outside of the Nb3Sn wire can simultaneously solve the problems of insufficient substrate strength, reduced wire RRR, and dimensional instability. Furthermore, chrome-plating the Nb3Sn wire surface followed by inlay soldering, removing the surface solder, and then performing reactive heat treatment can resolve all of the above issues. Inlay welding adds an external copper substrate. During the reactive heat treatment process, residual solder between the copper channel wire and the Nb3Sn wire enters the external copper substrate, becoming a bronze substrate and solving the wire strength problem. Because the Nb3Sn wire surface is chromium-plated, external solder cannot penetrate the Nb3Sn wire copper substrate during reactive heat treatment, ensuring a high RRR (Reduced Range Ratio) value. Removing the surface solder of the inlaid wire prevents localized solder diffusion to adjacent wires during reactive heat treatment, avoiding wire adhesion and subsequent uneven wire dimensions if forcibly separated, thus ensuring dimensional stability. Therefore, the method of chromium plating on the Nb3Sn wire surface, inlay welding, surface solder removal, and reactive heat treatment enhances the strength of the external copper substrate of the Nb3Sn superconducting phase, does not significantly reduce the RRR, and maintains dimensional stability, enabling the winding of magnets from Nb3Sn wire after reactive heat treatment. Meanwhile, after the Nb3Sn superconducting phase is formed by reaction heat treatment, eddy current testing and other detection methods can be added between the wire and the wound magnet to confirm the wire defects. Defective wires can be identified in advance and stopped from use, avoiding the scrapping of the entire magnet due to defective wires being wound into it.

[0067] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0068] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing Nb3Sn superconducting wire with a magnet wound after reaction heat treatment, characterized in that, Bag Includes the following steps: S1. Select Nb3Sn composite wire and copper trench wire; S2. Immerse the Nb3Sn composite wire in an electroplating solution for surface chromium plating; S3. Immerse the copper trench wire selected in step S1 and the Nb3Sn composite wire obtained after electroplating in step S2 into tin. Groove, to obtain Nb3Sn inlay wire; S4. Immerse the Nb3Sn etched wire obtained in step S3 into a flowing nitric acid-based desoldering solution to ensure that the surface solder of the Nb3Sn etched wire is completely removed, and obtain the Nb3Sn desoldering wire. S5. The Nb3Sn detinned wire obtained in step S4 is wound onto a steel wheel and placed in a heat treatment furnace. The furnace body is then vacuumed for heat treatment to obtain Nb3Sn superconducting wire. In step S2, after electroplating the Nb3Sn composite wire, the thickness of the electroplated layer is >8µm. In step S4, the temperature of the desoldering solution is 40℃~50℃, the length of the Nb3Sn damascene immersed in the desoldering solution is 20 m~40 m, and the desoldering speed is 12~15 m / min; In step S5, the vacuum degree is <5×10⁻⁶. -3 Pa, heat treatment temperature is 630℃~650℃, heat treatment time is 60h~61h.

2. The method for preparing Nb3Sn superconducting wire with a wound magnet after reaction heat treatment according to claim 1, characterized in that, In step S1, the diameter of the Nb3Sn composite wire is 0.82 mm to 1.30 mm, the width and height of the copper groove wire are 2.1 mm to 2.6 mm and 1.3 mm to 2.6 mm respectively, and the groove width of the copper groove wire is 0.87 mm to 1.35 mm.

3. The method for preparing Nb3Sn superconducting wire with a wound magnet after reaction heat treatment according to claim 1, characterized in that, In step S2, the electroplating speed is 0.2~0.3 m / min, and the size of the Nb3Sn wire after electroplating is 0.828 mm~0.832 mm.

4. The method for preparing Nb3Sn superconducting wire with a wound magnet after reaction heat treatment according to claim 1, characterized in that, The Nb3Sn superconducting wire was tested using the following method: Step 1: Braid the Nb3Sn superconducting wire with glass wire insulation to obtain glass wire insulated braided wire. Wrap the glass wire insulated braided wire to make a magnet. Test the Ic and RRR values ​​of the wound wire. Step 2: The Nb3Sn composite wire selected in step S1 is wound onto the Ic test skeleton as a sample and placed in a heat treatment furnace for Ic value testing. Step 3: Compare the Ic values ​​from Step 1 and Step 2. If the difference between the two is less than 5A, it indicates that the performance of the heat-treated Nb3Sn superconducting wire is consistent with that of the wire in Step 1.

5. The method for preparing Nb3Sn superconducting wire with a wound magnet after reaction heat treatment according to claim 1, characterized in that, After step S5, eddy current testing is used to detect defects in the Nb3Sn superconducting wire.

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