Preparation method of heterostructure U-shaped slot line for superconducting line

Abstract

The invention discloses a preparation method of a heterostructure U-shaped slot line for a superconducting wire, and relates to the technical field of slot lines for superconducting wires, and the preparation method comprises the following steps: carrying out the pipe-penetrating assembly of an aluminum bar and an oxygen-free copper pipe, and assembling an oxygen-free copper upper cover and an oxygen-free copper lower cover at the front and rear ends to obtain a Cu / Al composite sheath; vacuum welding is conducted on the joint of the oxygen-free copper upper cover, the oxygen-free copper lower cover and the oxygen-free copper pipe, and a Cu / Al composite ingot is obtained; carrying out hot extrusion forming to obtain a Cu / Al composite rod; carrying out one-time scaling and multi-pass stretching to obtain a Cu / Al composite round wire; and multi-pass rolling is carried out, and the heterostructure U-shaped groove line is obtained. The U-shaped groove line is prepared by adopting the aluminum bar and the oxygen-free copper pipe and combining pipe penetrating assembly, vacuum welding, hot extrusion, stretching and rolling technologies, the preparation cost is reduced while the U-shaped groove line and the superconducting line are conveniently combined, the quality is improved, and the method is suitable for batch production.

Description

Technical Field

[0001] The present application relates to the technical field of slot wires for superconducting wires, and in particular to a method for preparing a heterostructure U-shaped slot wire for superconducting wires. Background Art

[0002] As a typical representative of low-temperature superconducting materials, NbTi has advantages such as good processing performance, excellent superconducting performance and relatively low cost, and has extremely wide applications in the field of magnetic resonance imaging. In the field of magnetic resonance imaging, NbTi / Cu composite wires need to be placed in U-shaped slots. The U-shaped slots are used as bypasses when the superconductor quenches, flowing most of the current, and can quickly conduct the heat generated in the superconductor to the surrounding cooling medium, thereby reducing the temperature and restoring it to a superconducting state. Therefore, it is necessary to study U-shaped slots for superconducting wires.

[0003] In the prior art, Chinese patent CN114898941A discloses a method for preparing a U-shaped copper groove wire for a superconducting wire, comprising the following steps: step S1: drawing the copper wire in multiple passes to a diameter of 1.75-1.85 mm; step S2: rolling the drawn copper wire into a U-shaped copper groove wire in three passes, wherein the specific rolling process is as follows: in the first pass, the copper wire is rolled from a circle to a rectangle, in the second pass, the copper wire is rolled from a rectangle to a rectangle with a semicircular groove, and in the third pass, the copper wire is rolled from a rectangle with a semicircular groove to a rectangle with a U-shaped groove, and the preset width and preset height rolled in each pass are derived from the design size; step S3: performing atmosphere protection online annealing on the rolled U-shaped copper groove wire using an online annealing device; and step S4: using a stretching die to stretch the annealed U-shaped copper groove wire to the design size.

[0004] The above-mentioned prior art uses copper material to prepare U-shaped slot wires, and the preparation cost is relatively high. There is currently a view to replace copper with aluminum. Although aluminum material has the advantages of abundant resources, low cost, low density, and high conductivity, a dense oxide film will be produced on the surface of the U-shaped aluminum slot wire, which is difficult to combine with the superconducting wire. In addition, the existing U-shaped slot wires are of poor quality and are not suitable for mass production. Summary of the invention

[0005] The present application provides a method for preparing a heterostructure U-shaped slot wire for a superconducting wire, which is used to solve the problems in the prior art that the preparation cost of the U-shaped copper slot wire is high, the U-shaped aluminum slot wire is difficult to combine with the superconducting wire, and the existing U-shaped slot wire is of poor quality and is not suitable for mass production.

[0006] In one aspect, the present application provides a method for preparing a heterostructure U-shaped slot wire for a superconducting wire, comprising the following steps: Step 1: assemble the aluminum rod and the oxygen-free copper tube through the tube, and assemble the oxygen-free copper upper and lower covers at the front and rear ends to obtain a Cu / Al composite sheath.

[0007] Step 2: vacuum welding is performed on the joints between the oxygen-free copper upper and lower covers in the Cu / Al composite sheath and the oxygen-free copper tube to obtain a Cu / Al composite ingot.

[0008] Step three, hot extruding the Cu / Al composite ingot to obtain a Cu / Al composite rod.

[0009] Step 4: peeling the Cu / Al composite rod once and stretching it multiple times to obtain a Cu / Al composite round wire.

[0010] Step 5: performing multiple rolling on the Cu / Al composite round wire to obtain a Cu / Al composite U-shaped groove wire, that is, a heterogeneous structure U-shaped groove wire.

[0011] In a possible implementation, in step 1, the oxygen content of the oxygen-free copper tube and the oxygen-free copper upper and lower covers is less than 3 ppm.

[0012] In a possible implementation, in step 1, before the aluminum rod and the oxygen-free copper tube are assembled through tube threading, the aluminum rod and the oxygen-free copper tube are first pickled.

[0013] In a possible implementation, in step 2, before performing the vacuum welding, argon gas is first introduced into the welding furnace chamber, and vacuum is then drawn after stabilization. When the vacuum degree of the welding furnace chamber reaches 3.0×10 -6 MPa, vacuum welding is performed on the joints of the oxygen-free copper upper and lower covers in the Cu / Al composite sheath and the oxygen-free copper tube in the welding furnace chamber.

[0014] The welding beam current of the vacuum welding is 6-8×10 -2 A. The welding method is rotary welding head welding, the welding speed is 90-150° / min, and the number of welding times is 6-8 times.

[0015] In a possible implementation, in step three, before hot extrusion forming the Cu / Al composite ingot, a lubricant is applied to the surface of the Cu / Al composite ingot, and a heat preservation treatment is performed at a temperature of 250-350° C. for 4 hours.

[0016] The lubricant includes: asphalt and graphite emulsion.

[0017] In a possible implementation, in step three, the hot extrusion speed is 200-500 mm / min, and the extrusion pressure is 20-50 MN.

[0018] In a possible implementation, in step 4, in the multiple stretching passes, the processing rate of each stretching is 10%-15%, and the stretching rate is 100-150 m / min.

[0019] In a possible implementation, in step five, before rolling the Cu / Al composite round wire, the Cu / Al composite round wire is first subjected to stress relief annealing treatment, the annealing temperature is 300° C., and the annealing time is 2 h.

[0020] In a possible implementation, in step five, in the multiple rolling passes, the processing rate of each rolling is 5%-10%.

[0021] In a possible implementation, in step five, after obtaining the Cu / Al composite U-shaped groove wire, online eddy current detection and infrared dimension detection are performed on the Cu / Al composite U-shaped groove wire.

[0022] The method for preparing a heterostructure U-shaped slot wire for a superconducting wire in the present application has the following advantages: The U-shaped slotted wire is prepared by using aluminum rods and oxygen-free copper tubes, combined with tube assembly, vacuum welding, hot extrusion, stretching and rolling technology. This makes it easier to combine the U-shaped slotted wire with the superconducting wire, while reducing the preparation cost and improving the quality, making it suitable for mass production.

[0023] The proposed pickling of the aluminum rod and the oxygen-free copper tube improves the cleanliness of the tube assembly.

[0024] It is proposed that before vacuum welding, argon gas is first introduced into the welding furnace chamber to avoid the introduction of H, O and other elements during the welding process, thereby improving the welding quality.

[0025] The proposed method of applying lubricant on the surface of the Cu / Al composite ingot and performing heat preservation treatment improves the smoothness of hot extrusion and promotes uniform deformation of the Cu / Al composite ingot during hot extrusion.

[0026] It is proposed to perform one-pass peeling and multi-pass stretching on the Cu / Al composite rod, wherein the peeling removes impurities on the surface of the Cu / Al composite rod, and the multi-pass stretching improves the deformation uniformity of the Cu / Al composite rod.

[0027] The proposed multi-pass rolling of Cu / Al composite round wire improves the surface quality of the U-groove wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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.

[0029] Figure 1A schematic flow chart of a method for preparing a heterostructure U-shaped slot wire for a superconducting wire provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] 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.

[0031] Embodiment 1: like Figure 1 As shown, the embodiment of the present application provides a method for preparing a heterostructure U-shaped slot wire for a superconducting wire, comprising the following steps: Step 1: assemble the aluminum rod and the oxygen-free copper tube through the tube, and assemble the oxygen-free copper upper and lower covers at the front and rear ends to obtain a Cu / Al composite sheath.

[0032] Step 2: vacuum welding is performed on the joints between the oxygen-free copper upper and lower covers in the Cu / Al composite sheath and the oxygen-free copper tube to obtain a Cu / Al composite ingot.

[0033] Step three, hot extruding the Cu / Al composite ingot to obtain a Cu / Al composite rod.

[0034] Step 4: peeling the Cu / Al composite rod once and stretching it multiple times to obtain a Cu / Al composite round wire.

[0035] Step 5: performing multiple rolling on the Cu / Al composite round wire to obtain a Cu / Al composite U-shaped groove wire, that is, a heterogeneous structure U-shaped groove wire.

[0036] Exemplarily, in step one, the oxygen content of the oxygen-free copper tube and the oxygen-free copper upper and lower covers is below 3 ppm.

[0037] Specifically, in this embodiment, the aluminum rod uses 1350 type high-purity aluminum as raw material. The outer diameter of the oxygen-free copper tube is 500mm, the inner diameter is 350mm, and the length is 1000mm. The upper and lower covers of the oxygen-free copper both adopt an integrated two-layer circular step structure, including a large circular step and a small circular step, wherein the diameter of the large circular step of the oxygen-free copper upper cover is 500mm, the length is 55mm, and the diameter of the small circular step is 350mm, and the length is 55mm; the diameter of the large circular step of the oxygen-free copper lower cover is 500mm, the length is 45mm, and the diameter of the small circular step is 350mm, and the length is 45mm. The diameter of the aluminum rod is 350mm and the length is 900mm.

[0038] Exemplarily, in step one, before the aluminum rod and the oxygen-free copper tube are assembled through tube threading, the aluminum rod and the oxygen-free copper tube are first pickled.

[0039] Specifically, in this embodiment, in step 1, the aluminum rod and the oxygen-free copper tube are placed in 60% by volume nitric acid for pickling to remove oil stains and impurities on the surface.

[0040] For example, in step 2, before the vacuum welding is performed, argon gas is first introduced into the welding furnace chamber, and vacuum is then drawn after stabilization. When the vacuum degree of the welding furnace chamber reaches 3.0×10 -6 MPa, vacuum welding is performed on the joints of the oxygen-free copper upper and lower covers in the Cu / Al composite sheath and the oxygen-free copper tube in the welding furnace chamber.

[0041] The welding beam current of the vacuum welding is 6-8×10 -2 A. The welding method is rotary welding head welding, the welding speed is 90-150° / min, and the number of welding times is 6-8 times.

[0042] Specifically, in this embodiment, in step 2, the welding beam current of the vacuum welding is 6×10 -2 A. The welding method is rotary welding head welding, the welding speed is 90° / min, and the number of welding times is 6 times.

[0043] Exemplarily, in step three, before hot extrusion forming the Cu / Al composite ingot, a lubricant is applied to the surface of the Cu / Al composite ingot, and a heat preservation treatment is performed at a temperature of 250-350° C. for 4 hours.

[0044] The lubricant includes: asphalt and graphite emulsion.

[0045] Specifically, in this embodiment, in step three, a mixture of asphalt and graphite emulsion is applied to the surface of the Cu / Al composite ingot, and the insulation temperature of the insulation treatment is 250° C. and the insulation time is 4 hours.

[0046] Exemplarily, in step three, the hot extrusion speed is 200-500 mm / min, and the extrusion force is 20-50 MN.

[0047] Specifically, in this embodiment, in step three, the hot extrusion speed is 200 mm / min, and the extrusion force is 20 MN.

[0048] Exemplarily, in step 4, in the multiple stretching passes, the processing rate of each stretching is 10%-15%, and the stretching rate is 100-150 m / min.

[0049] Specifically, in this embodiment, in step 4, the processing rate of each stretching is 10%, and the stretching rate is 100 m / min. The diameter of the obtained Cu / Al composite round wire is 2.2 mm, wherein the diameter of the Al core is 1.54 mm.

[0050] Exemplarily, in step five, before rolling the Cu / Al composite round wire, the Cu / Al composite round wire is subjected to stress relief annealing treatment, the annealing temperature is 300° C., and the annealing time is 2 h.

[0051] Exemplarily, in step five, in the multiple rolling passes, the processing rate of each rolling is 5%-10%.

[0052] Specifically, in this embodiment, in step five, the processing rate of each rolling is 5%, and the outer fillet of the obtained Cu / Al composite U-shaped groove wire is 0.4mm, the inner fillet is 0.2mm, the cross-sectional length of the U-shaped groove wire is 2.4mm, the cross-sectional width is 1.6mm, and the height of the U-shaped groove is 0.9mm.

[0053] Exemplarily, in step five, after obtaining the Cu / Al composite U-shaped groove wire, online eddy current detection and infrared dimensional detection are performed on the Cu / Al composite U-shaped groove wire.

[0054] Specifically, in this embodiment, in step five, the Cu / Al composite U-shaped groove wire having eddy current signals or dimensional deviation exceeding ±0.010 mm is sheared.

[0055] Example 1 successfully prepared more than 50,000 meters of Cu / Al composite U-shaped slotted wire, that is, a heterostructure U-shaped slotted wire.

[0056] Embodiment 2: Specifically, in this embodiment, the aluminum rod uses 1350 type high-purity aluminum as the raw material. The outer diameter of the oxygen-free copper tube is 500mm, the inner diameter is 400mm, and the length is 1000mm. The upper and lower covers of the oxygen-free copper both adopt an integrated two-layer circular step structure, including a large circular step and a small circular step, wherein the diameter of the large circular step of the oxygen-free copper upper cover is 500mm, the length is 55mm, and the diameter of the small circular step is 400mm, and the length is 55mm; the diameter of the large circular step of the oxygen-free copper lower cover is 500mm, the length is 45mm, and the diameter of the small circular step is 400mm, and the length is 45mm. The diameter of the aluminum rod is 400mm and the length is 900mm.

[0057] Specifically, in this embodiment, in step 1, the aluminum rod and the oxygen-free copper tube are placed in 60% by volume nitric acid for pickling to remove oil stains and impurities on the surface.

[0058] Specifically, in this embodiment, in step 2, the welding beam current of the vacuum welding is 7×10 -2 A. The welding method is rotary welding head welding, the welding speed is 120° / min, and the number of welding times is 7 times.

[0059] Specifically, in this embodiment, in step three, a mixture of asphalt and graphite emulsion is applied to the surface of the Cu / Al composite ingot, and the insulation temperature of the insulation treatment is 300° C. and the insulation time is 4 hours.

[0060] Specifically, in this embodiment, in step three, the hot extrusion speed is 350 mm / min, and the extrusion force is 35 MN.

[0061] Specifically, in this embodiment, in step 4, the processing rate of each stretching is 12%, and the stretching rate is 120 m / min. The diameter of the obtained Cu / Al composite round wire is 2 mm, wherein the diameter of the Al core is 1.6 mm.

[0062] Specifically, in this embodiment, in step five, the processing rate of each rolling is 7%, and the outer fillet of the obtained Cu / Al composite U-shaped groove wire is 0.4mm, the inner fillet is 0.2mm, the cross-sectional length of the U-shaped groove wire is 2.5mm, the cross-sectional width is 1.5mm, and the height of the U-shaped groove is 0.8mm.

[0063] The other steps and parameters of Example 2 are the same as those of Example 1.

[0064] Example 2 successfully prepared more than 50,000 meters of Cu / Al composite U-shaped slotted wire, that is, a heterostructure U-shaped slotted wire.

[0065] Embodiment 3: Specifically, in this embodiment, the aluminum rod uses 1350 type high-purity aluminum as raw material. The outer diameter of the oxygen-free copper tube is 500mm, the inner diameter is 425mm, and the length is 1000mm. The upper and lower covers of the oxygen-free copper both adopt an integrated two-layer circular step structure, including a large circular step and a small circular step, wherein the diameter of the large circular step of the oxygen-free copper upper cover is 500mm, the length is 55mm, and the diameter of the small circular step is 425mm, and the length is 55mm; the diameter of the large circular step of the oxygen-free copper lower cover is 500mm, the length is 45mm, and the diameter of the small circular step is 425mm, and the length is 45mm. The diameter of the aluminum rod is 425mm and the length is 900mm.

[0066] Specifically, in this embodiment, in step 1, the aluminum rod and the oxygen-free copper tube are placed in 60% by volume nitric acid for pickling to remove oil stains and impurities on the surface.

[0067] Specifically, in this embodiment, in step 2, the welding beam current of the vacuum welding is 8×10 -2A. The welding method is rotary welding head welding, the welding speed is 150° / min, and the number of welding times is 8 times.

[0068] Specifically, in this embodiment, in step three, a mixture of asphalt and graphite emulsion is applied to the surface of the Cu / Al composite ingot, and the insulation temperature of the insulation treatment is 350° C. and the insulation time is 4 hours.

[0069] Specifically, in this embodiment, in step three, the hot extrusion speed is 500 mm / min, and the extrusion force is 50 MN.

[0070] Specifically, in this embodiment, in step 4, the processing rate of each stretching is 15%, and the stretching rate is 150 m / min. The diameter of the obtained Cu / Al composite round wire is 3 mm, wherein the diameter of the Al core is 2.55 mm.

[0071] Specifically, in this embodiment, in step five, the processing rate of each rolling is 10%, and the outer fillet of the obtained Cu / Al composite U-shaped groove wire is 0.4mm, the inner fillet is 0.2mm, the cross-sectional length of the U-shaped groove wire is 2.1mm, the cross-sectional width is 1.65mm, and the height of the U-shaped groove is 0.75mm.

[0072] The other steps and parameters of Example 3 are the same as those of Example 1.

[0073] Example 3 successfully prepared more than 50,000 meters of Cu / Al composite U-shaped slotted wire, that is, a heterostructure U-shaped slotted wire.

[0074] The embodiment of the present application adopts aluminum rods and oxygen-free copper tubes, combined with tube assembly, vacuum welding, hot extrusion, stretching and rolling technology to prepare U-shaped slot wires, which not only facilitates the combination of U-shaped slot wires and superconducting wires, but also reduces the preparation cost and improves the quality, making it suitable for mass production.

[0075] The proposed pickling of the aluminum rod and the oxygen-free copper tube improves the cleanliness of the tube assembly.

[0076] It is proposed that before vacuum welding, argon gas is first introduced into the welding furnace chamber to avoid the introduction of H, O and other elements during the welding process, thereby improving the welding quality.

[0077] The proposed method of applying lubricant on the surface of the Cu / Al composite ingot and performing heat preservation treatment improves the smoothness of hot extrusion and promotes uniform deformation of the Cu / Al composite ingot during hot extrusion.

[0078] It is proposed to perform one-pass peeling and multi-pass stretching on the Cu / Al composite rod, wherein the peeling removes impurities on the surface of the Cu / Al composite rod, and the multi-pass stretching improves the deformation uniformity of the Cu / Al composite rod.

[0079] The proposed multi-pass rolling of Cu / Al composite round wire improves the surface quality of the U-groove wire.

[0080] Although the preferred embodiments of the present application have been described, those skilled in the art may make other 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.

[0081] 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 a heterostructure U-shaped slot wire for a superconducting wire, characterized in that: The following steps are involved: Step 1: assemble the aluminum rod and the oxygen-free copper tube through the tube, and assemble the oxygen-free copper upper and lower covers at the front and rear ends to obtain a Cu / Al composite sheath; Step 2: vacuum welding the joints of the oxygen-free copper upper and lower covers in the Cu / Al composite sheath and the oxygen-free copper tube to obtain a Cu / Al composite ingot; Step 3, hot extruding the Cu / Al composite ingot to obtain a Cu / Al composite rod; Step 4, performing a peeling and multiple stretching on the Cu / Al composite rod to obtain a Cu / Al composite round wire; Step 5: performing multiple rolling on the Cu / Al composite round wire to obtain a Cu / Al composite U-shaped groove wire, that is, a heterogeneous structure U-shaped groove wire.

2. The method for preparing a heterostructure U-shaped slot wire for a superconducting wire according to claim 1, characterized in that: In step 1, the oxygen content of the oxygen-free copper tube and the oxygen-free copper upper and lower covers is less than 3 ppm.

3. The method for preparing a heterostructure U-shaped slot wire for a superconducting wire according to claim 1, characterized in that: In step 1, before the aluminum rod and the oxygen-free copper tube are assembled through pipe threading, the aluminum rod and the oxygen-free copper tube are firstly pickled.

4. The method for preparing a heterostructure U-shaped slot wire for a superconducting wire according to claim 1, characterized in that: In step 2, before the vacuum welding, argon gas is first introduced into the welding furnace chamber, and vacuum is then drawn after stabilization. When the vacuum degree of the welding furnace chamber reaches 3.0×10 -6 MPa, vacuum welding is performed on the joints of the oxygen-free copper upper and lower covers in the Cu / Al composite sheath and the oxygen-free copper tube in the welding furnace chamber; The welding beam current of the vacuum welding is 6-8×10 -2 A. The welding method is rotary welding head welding, the welding speed is 90-150° / min, and the number of welding times is 6-8 times.

5. The method for preparing a heterostructure U-shaped slot wire for a superconducting wire according to claim 1, characterized in that: In step 3, before hot extrusion forming the Cu / Al composite ingot, a lubricant is applied to the surface of the Cu / Al composite ingot, and a heat preservation treatment is performed at a temperature of 250-350° C. for 4 hours. The lubricant includes: asphalt and graphite emulsion.

6. The method for preparing a heterostructure U-shaped slot wire for a superconducting wire according to claim 1, characterized in that: In step three, the hot extrusion speed is 200-500 mm / min, and the extrusion pressure is 20-50 MN.

7. The method for preparing a heterostructure U-shaped slot wire for a superconducting wire according to claim 1, characterized in that: In step 4, in the multiple stretching steps, the processing rate of each stretching step is 10%-15%, and the stretching rate is 100-150 m / min.

8. The method for preparing a heterostructure U-shaped slot wire for a superconducting wire according to claim 1, characterized in that: In step five, before rolling the Cu / Al composite round wire, the Cu / Al composite round wire is subjected to stress relief annealing treatment, the annealing temperature is 300° C., and the annealing time is 2 h.

9. The method for preparing a heterostructure U-shaped slot wire for a superconducting wire according to claim 1, characterized in that: In step 5, in the multiple rolling passes, the processing rate of each rolling is 5%-10%.

10. The method for preparing a heterostructure U-shaped slot wire for a superconducting wire according to claim 1, characterized in that: In step five, after obtaining the Cu / Al composite U-shaped groove wire, online eddy current detection and infrared dimension detection are performed on the Cu / Al composite U-shaped groove wire.

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