High-temperature superconducting MgB2 wire hot drawing preparation method based on center MgLi diffusion

Abstract

The invention discloses a hot drawing preparation method of a high-temperature superconducting MgB2 wire based on center MgLi diffusion, which comprises the following steps of: 1, placing an Nb tube in a Cu tube, placing an MgLi alloy rod in the Nb tube, filling carbon-coated B powder or B powder between the MgLi alloy rod and the Nb tube, and carrying out cold rotary swaging to obtain a single-core complex; secondly, head rotating, outer layer graphite coating and hot drawing are sequentially carried out, and a single-core composite round wire is obtained; thirdly, the single-core composite round wires are bundled and assembled in a Monel alloy sheath, and cold rotary swaging, outer-layer graphite coating and hot drawing are carried out; and 4, performing vacuum heat treatment to obtain the high-temperature superconducting MgB2 wire rod. According to the method, the MgLi alloy rod serves as the center and is combined with the Nb pipe, the Cu pipe and the B powder to obtain the single-core complex, the excellent hot working capacity is obtained through hot drawing, cold rotary swaging and other treatment, the uniformity of synergistic deformation is improved, and the method is suitable for the technical field of superconducting wire preparation and machining.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation and processing of superconducting wires, and particularly relates to a method for preparing high-temperature superconducting MgB2 wires by hot drawing based on central MgLi diffusion. Background Art

[0002] MgB2 superconducting materials have become ideal candidate materials for the application of medium and high-field magnets due to their relatively high superconducting transition temperature (T c ≈39K), low raw material cost, and good mechanical processing performance, and have important application prospects in fields such as nuclear magnetic resonance imaging and high-field magnets.

[0003] However, the existing preparation technologies of high-temperature superconducting MgB2 wires still face many bottleneck problems, including low powder density, severe interfacial reaction, insufficient flux pinning, etc. To meet the requirements of high strength and high current-carrying performance, a new generation of high-temperature superconducting MgB2 wires based on the central magnesium diffusion method (IMD) has been developed, and their performance has been significantly improved. Although IMD can significantly improve the current-carrying performance of MgB2, its deformation faces severe problems such as non-uniform co-deformation of metal and powder, wire fracture, pore formation and non-compactness of superconducting phases after sintering. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned existing technologies and provide a method for preparing high-temperature superconducting MgB2 wires by hot drawing based on central MgLi diffusion. This preparation method uses a MgLi alloy rod as the central material, combines it with Nb tubes, Cu tubes and B powder to obtain a single-core composite body, and through processes such as hot drawing and cold rotary forging, the Cu tubes, Nb tubes and MgLi alloy rods obtain excellent hot processing capabilities, greatly improving the uniformity of co-deformation between metal layers and solving the problems of non-uniform co-deformation of metal and powder and wire fracture that are prone to occur in the existing technology preparation process.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a method for preparing high-temperature superconducting MgB2 wires by hot drawing based on central MgLi diffusion, characterized in that this preparation method includes the following steps: Step 1: Place the Nb tube inside the Cu tube, then place the MgLi alloy rod inside the Nb tube, and then fill carbon-coated B powder or B powder between the MgLi alloy rod and the Nb tube, and use copper plugs to seal both ends, and perform cold rotary forging deformation to obtain a single-core composite body; Step 2: Perform swaging, outer graphite coating and hot drawing on the single-core composite body obtained in Step 1 in sequence to obtain a single-core composite round wire; Step 3: Place the single-core composite round wires obtained in Step 2 in a Monel alloy sheath in a bundled manner, and then perform cold rotary forging, outer graphite coating and hot drawing in sequence to obtain a multi-core bundled composite MgB2 round wire; Step 4: Perform vacuum heat treatment on the multi-core bundled composite MgB2 round wire obtained in Step 3 to obtain high-temperature superconducting MgB2 wire.

[0006] By selecting hot drawing treatment during the preparation process, the present invention can greatly increase the pass deformation rate, reduce the use of dies, and improve the preparation efficiency.

[0007] The above-mentioned hot drawing preparation method of high-temperature superconducting MgB2 wire based on central MgLi diffusion is characterized in that the MgLi alloy rod is subjected to hot drawing and annealing before being placed in the Nb tube; the MgLi alloy rod is composed of the following components by mass ratio: 8% - 10% Li, and the rest is Mg and inevitable impurities.

[0008] By performing hot drawing and annealing on the MgLi alloy rod, the present invention can cause the MgLi alloy rod to undergo static recrystallization and remove the internal stress of the MgLi alloy rod.

[0009] The above-mentioned hot drawing preparation method of high-temperature superconducting MgB2 wire based on central MgLi diffusion is characterized in that the temperature of the hot drawing is 300°C - 400°C, the pass deformation rate of the hot drawing is 10% - 12%, the temperature of the annealing is 250°C - 300°C, and the heat preservation duration of the annealing is 2h - 3h.

[0010] The above-mentioned hot drawing preparation method of high-temperature superconducting MgB2 wire based on central MgLi diffusion is characterized in that the mass ratio of the MgLi alloy rod to the carbon-coated B powder or B powder in Step 1 is 1:1.12, the total deformation rate of the cold rotary forging is 30% - 40%, and the pass deformation rate of the cold rotary forging is 15% - 30%.

[0011] The above-mentioned hot drawing preparation method of high-temperature superconducting MgB2 wire based on central MgLi diffusion is characterized in that the method of the hot drawing in Step 2 is: after heating to 400°C - 450°C and holding for 1min - 3min, perform hot drawing with a drawing speed of 1m / min - 2m / min, and the pass deformation rate of the hot drawing is 22% - 28%.

[0012] The above-mentioned hot drawing preparation method of high-temperature superconducting MgB2 wire based on central MgLi diffusion is characterized in that the total deformation rate of the cold rotary forging in Step 3 is 20% - 30%, and the pass deformation rate of the cold rotary forging is 10% - 12%.

[0013] The above-mentioned method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion is characterized in that the hot drawing method in step three is as follows: after heating to 400°C to 450°C and holding for 1 minute to 10 minutes, hot drawing is carried out at a drawing speed of 1 m / min to 1.5 m / min, and the pass deformation rate of the hot drawing is 22% to 28%.

[0014] Based on the thermo-mechanical coupling effect, the present invention controls the hot drawing temperature and drawing speed in the process of preparing the single-core composite body and the single-core composite round wire, so that the Cu, Nb, and MgLi alloys further obtain excellent hot working capabilities, and in particular, can overcome the problems of difficult deformation and deformation anisotropy of Mg in the traditional process, and realize the coordinated and uniform deformation of multi-layer metals.

[0015] The above-mentioned method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion is characterized in that during the hot drawing in steps two and three, after every 2 to 3 passes of drawing, it is soaked in graphite mud and then the drawing is continued.

[0016] The above-mentioned method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion is characterized in that the method of coating the outer layer with graphite in steps two and three is both: soaking in graphite mud.

[0017] In the present invention, the graphite mud is a mixture of graphite particles and water. By wrapping the graphite mud on the outer surface of the wire, the friction during the drawing process can be reduced, the die wear can be reduced, and further the uneven distribution of internal stress or uneven deformation of the wire caused by uneven friction can be reduced; at the same time, graphite has a heat preservation effect and can avoid the rapid temperature drop of the wire.

[0018] The above-mentioned method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion is characterized in that the temperature of the vacuum heat treatment in step four is 630°C to 670°C, and the duration of the vacuum heat treatment is 2 hours.

[0019] The present invention has the following advantages compared with the prior art: 1. The present invention uses a MgLi alloy rod with excellent plastic deformation ability as the central diffusion material, which ensures the continuous deformation of the MgLi alloy rod during the drawing process; at the same time, the diffusion of Li element can be used as a pinning center to pin the grain growth of the MgB2 superconducting phase, which can improve the plastic deformation ability of the high-temperature superconducting MgB2 wire and can improve the current-carrying performance through the flux pinning center.

[0020] 2. The present invention forms a single-core composite by filling carbon-coated B powder or B powder outside the MgLi alloy rod, wrapping an Nb tube and a Cu tube, and then performing cold rotary forging. Subsequently, hot drawing is carried out to improve the hot working ability of the single-core composite, thereby enhancing the uniformity of the co-deformation between metal layers and avoiding problems such as fracture of the central MgLi alloy rod, rupture of the Nb barrier layer, and nodules on the surface of the single-core wire during the preparation process.

[0021] 3. The present invention performs hot drawing with a relatively large pass deformation rate, increasing the axial and radial stresses of the powder, greatly enhancing the fluidity of the powder, and avoiding the hardening and aggregation of the powder to form sausage knots during the cold deformation process. At the same time, it also increases the density of the deformed powder and improves the intergranular connectivity of the superconducting phase after sintering.

[0022] The technical solution of the present invention will be further described in detail below through the accompanying drawings and embodiments. Description of the Drawings

[0023] Figure 1 It is a physical diagram of the single-core composite round wire prepared in Example 1.

[0024] Figure 2 It is a physical diagram of the single-core composite round wire bundle device after being placed in a Monel alloy sheath in Example 1.

[0025] Figure 3 It is a physical diagram of the multi-core bundle composite MgB2 round wire prepared in Example 1.

[0026] Figure 4 It is a longitudinal cross-sectional metallographic diagram of a single core wire in the high-temperature superconducting MgB2 wire prepared in Example 1.

[0027] Figure 5 It is an SEM diagram of the longitudinal cross-section of a single core wire in the high-temperature superconducting MgB2 wire prepared in Example 1 at different magnifications.

[0028] Figure 6 It is an elemental analysis diagram of the longitudinal cross-section of a single core wire in the high-temperature superconducting MgB2 wire prepared in Example 1.

[0029] Figure 7 It is an SEM diagram of the cross-section of a single core wire in the high-temperature superconducting MgB2 wire prepared in Example 1 at different magnifications.

[0030] Figure 8 It is a magnetization intensity change diagram of the high-temperature superconducting MgB2 wire prepared in Example 1.

[0031] Figure 9 It is a test result diagram of the superconducting critical transition temperature of the high-temperature superconducting MgB2 wire prepared in Example 1.

[0032] Figure 10 The critical current density J of the high-temperature superconducting MgB2 wire prepared in Example 1 at a temperature of 4.2 K c Curve graph.

[0033] Figure 11 The critical current density J of the high-temperature superconducting MgB2 wire prepared in Example 1 at a temperature of 20 K c Curve graph. Specific implementation manner

[0034] In Examples 1 to 3 of the present invention, Nb tubes with an outer diameter of 11 mm and a wall thickness of 1 mm are used, and oxygen-free copper tubes with an outer diameter of 13 mm and a wall thickness of 1 mm are used.

[0035] Example 1 The preparation method of this example includes the following steps: Step 1: Perform hot drawing on a MgLi alloy rod with a diameter of 6 mm at 400 °C with a pass deformation rate of 12%, and anneal at 250 °C for 2 h to obtain a MgLi alloy rod with a diameter of 4 mm; place the Nb tube inside the oxygen-free copper tube, then place the MgLi alloy rod with a diameter of 4 mm inside the Nb tube, then fill B powder between the MgLi alloy rod and the Nb tube, fix the MgLi alloy rod at the central position with a copper plug and seal both ends, and perform cold rotary forging with a total deformation rate of 30% and a pass deformation rate of 15% to obtain a single-core composite body; the MgLi alloy rod is composed of the following components by mass ratio: Li 8%, and the rest is Mg and inevitable impurities; the mass ratio of the MgLi alloy rod to the B powder is 1:1.12; Step 2: After performing swaging on the single-core composite body obtained in Step 1, immerse it in graphite mud, then take out the single-core composite body coated with graphite on the surface and put it into a resistance furnace, heat it to 400 °C and keep it warm for 3 min for hot drawing with a drawing speed of 1 m / min and a pass deformation rate of 22% to obtain a single-core composite round wire with a diameter of 4 mm as shown in Figure 1 During the hot drawing process, after every 2 passes of drawing, immerse the single-core composite body in graphite mud, and then continue drawing; Step 3: Cut, seal both ends, polish with 200-mesh to 600-mesh sandpaper, perform alkali washing, and acid washing on the single-core composite round wire obtained in Step 2, and then bundle and assemble it in a Monel alloy sheath (see Figure 2 ), perform cold rotary forging with a total deformation rate of 30% and a pass deformation rate of 12% and then immerse it in graphite mud, and then put it into a resistance furnace and heat it to 400 °C and keep it warm for 10 min for hot drawing with a drawing speed of 1 m / min and a pass deformation rate of 22% to obtain a Figure 3The multi-core bundled composite MgB2 round wire with a diameter of 2 mm as shown; during the hot drawing process, after every 2 to 3 passes of drawing, it is immersed in graphite mud, then heated to 400 °C and kept warm for continuous hot drawing, and when the wire diameter is not less than 10 mm, it is kept warm for 3 min to 5 min, and when the wire diameter is less than 10 mm, it is kept warm for 1 min to 3 min; the outer diameter of the Monel alloy sheath is 32 mm and the wall thickness is 2 mm; Step 4: Vacuum heat-treat the multi-core bundled composite MgB2 round wire obtained in Step 3 at 650 °C for 2 h to obtain a high-temperature superconducting MgB2 wire.

[0036] Cut a single core wire inside the high-temperature superconducting MgB2 wire prepared in this embodiment along the axis for longitudinal cross-section microscopic analysis, as Figures 4 to 6 shown, the center of the core wire is Mg alloy, and the Mg alloy is successively wrapped with a B layer, an Nb layer, and a Cu layer, and the thickness of the B layer is relatively uniform; after magnification, it can be seen that a relatively dense superconducting phase is generated inside. After cutting a single core wire along the radial direction for cross-section microscopic analysis, as Figure 7 shown, the various metal layers of the core wire are tightly combined, and after magnification, it can be seen that a relatively dense superconducting phase is generated inside.

[0037] For the high-temperature superconducting MgB2 wire prepared in this embodiment, under the conditions of a temperature of 4.2 K, 20 K, and 25 K, the change of the magnetization intensity of the wire with the magnetic field M(H) is tested respectively, and the results are as Figure 8 shown, a complete hysteresis loop is measured for this high-temperature superconducting MgB2 wire, indicating that the preparation method of this embodiment can realize the preparation of superconducting wires. For the high-temperature superconducting MgB2 wire, the superconducting critical transition temperature is tested, and the results are as Figure 9 shown, the superconducting critical transition temperature of this high-temperature superconducting MgB2 wire is 37.6 K. Under the conditions of a temperature of 4.2 K and 20 K, the critical current density J c curve of this high-temperature superconducting MgB2 wire is tested respectively, and the test results are as Figure 10 and Figure 11 shown, at a temperature of 4.2 K and B of 2 T, Jc is measured to be 1.043×10 6 A / cm 2 , and at a temperature of 20 K and B of 2 T, Jc is measured to be greater than 1×10 5 A / cm 2 .

[0038] Example 2 The preparation method of this embodiment includes the following steps: Step 1: A MgLi alloy rod with a diameter of 7 mm is subjected to hot drawing with a pass deformation rate of 11% at 375 °C, and annealed at 275 °C for 2.5 h to obtain a MgLi alloy rod with a diameter of 4 mm. The Nb tube is placed inside an oxygen-free copper tube, and then the MgLi alloy rod with a diameter of 4 mm is placed inside the Nb tube. Then, carbon-coated B powder is filled between the MgLi alloy rod and the Nb tube. Copper plugs are used to fix the MgLi alloy rod at the central position and seal both ends. After cold rotary forging with a total deformation rate of 35% and a pass deformation rate of 25%, a single-core composite body is obtained. The MgLi alloy rod is composed of the following components by mass ratio: Li 8%, and the rest is Mg and inevitable impurities. The mass ratio of the MgLi alloy rod to the carbon-coated B powder is 1:1.12; Step 2: The single-core composite body obtained in Step 1 is subjected to swaging and then immersed in graphite mud. Then, the single-core composite body coated with graphite on the surface is taken out and placed in a resistance furnace, heated to 425 °C and held for 2 min for hot drawing with a drawing speed of 1.5 m / min and a pass deformation rate of 24% to obtain a single-core composite round wire with a diameter of 4 mm. During the hot drawing process, after every 2 - 3 passes of drawing, the single-core composite body is immersed in graphite mud, and then drawing continues; Step 3: The single-core composite round wire obtained in Step 2 is successively cut, sealed at both ends, polished with 200 - 600 mesh sandpaper, alkali-washed, acid-washed, and then assembled in a Monel alloy sheath. After cold rotary forging with a total deformation rate of 25% and a pass deformation rate of 11%, it is immersed in graphite mud, and then placed in a resistance furnace and heated to 425 °C and held for 7 min for hot drawing with a drawing speed of 1.2 m / min and a pass deformation rate of 24% to obtain a multi-core bundled composite MgB₂ round wire with a diameter of 1.5 mm. During the hot drawing process, after every 2 - 3 passes of drawing, it is immersed in graphite mud, and then heated to 400 °C and held for continuous hot drawing. When the wire diameter is not less than 10 mm, it is held for 3 - 5 min, and when the wire diameter is less than 10 mm, it is held for 1 - 3 min. The outer diameter of the Monel alloy sheath is 26 mm and the wall thickness is 2 mm; Step 4: The multi-core bundled composite MgB₂ round wire obtained in Step 3 is subjected to vacuum heat treatment at 650 °C for 2 h to obtain a high-temperature superconducting MgB₂ wire.

[0039] After inspection, the high-temperature superconducting MgB₂ wire prepared in this example has a complete hysteresis loop under the conditions of 4.2 K, 20 K, and 25 K.

[0040] Example 3 The preparation method of this example includes the following steps: Step 1: A MgLi alloy rod with a diameter of 8 mm is subjected to hot drawing with a pass deformation rate of 10% at 300 °C, and annealed at 300 °C for 3 h to obtain a MgLi alloy rod with a diameter of 4 mm; the Nb tube is placed inside an oxygen-free copper tube, then the MgLi alloy rod with a diameter of 4 mm is placed inside the Nb tube, and then B powder is filled between the MgLi alloy rod and the Nb tube. Copper plugs are used to fix the MgLi alloy rod at the central position and seal both ends, and a single-core composite is obtained after cold rotary forging with a total deformation rate of 40% and a pass deformation rate of 30%; the MgLi alloy rod is composed of the following components by mass ratio: Li 8%, and the rest is Mg and inevitable impurities; the mass ratio of the MgLi alloy rod to the B powder is 1:1.12; Step 2: The single-core composite obtained in Step 1 is subjected to swaging and then immersed in graphite paste. Then, the single-core composite coated with graphite on the surface is taken out and placed in a resistance furnace, heated to 450 °C and held for 1 min for hot drawing with a drawing speed of 2 m / min and a pass deformation rate of 28% to obtain a single-core composite round wire with a diameter of 1 mm; during the hot drawing process, after every 2 - 3 passes of drawing, the single-core composite is immersed in graphite paste, and then drawing continues; Step 3: The single-core composite round wire obtained in Step 2 is successively cut, sealed at both ends, polished with 200 - 600 mesh sandpaper, alkali-washed, acid-washed, and then assembled in a Monel alloy sheath. After cold rotary forging with a total deformation rate of 20% and a pass deformation rate of 10%, it is immersed in graphite paste, and then placed in a resistance furnace heated to 450 °C and held for 5 min for hot drawing with a drawing speed of 1.5 m / min and a pass deformation rate of 28% to obtain a multi-core bundled composite MgB₂ round wire with a diameter of 1 mm; during the hot drawing process, after every 2 - 3 passes of drawing, it is immersed in graphite paste, and then heated to 400 °C and held for continuous hot drawing. When the wire diameter is not less than 10 mm, it is held for 3 - 5 min, and when the wire diameter is less than 10 mm, it is held for 1 - 3 min; the outer diameter of the Monel alloy sheath is 20 mm and the wall thickness is 2 mm; Step 4: The multi-core bundled composite MgB₂ round wire obtained in Step 3 is subjected to vacuum heat treatment at 650 °C for 2 h to obtain a high-temperature superconducting MgB₂ wire.

[0041] After inspection, the high-temperature superconducting MgB₂ wire prepared in this example has a complete hysteresis loop under the conditions of 4.2 K, 20 K, and 25 K.

[0042] Example 4 The differences between this embodiment and Embodiment 3 are as follows: the MgLi alloy rod used in Step 1 is composed of the following components by mass ratio: Li 9%, and the rest is Mg and inevitable impurities; the heat preservation time of hot drawing in Step 3 is 1 min; the temperature of vacuum heat treatment in Step 4 is 630 °C.

[0043] After inspection, the high-temperature superconducting MgB2 wire prepared in this embodiment has a complete hysteresis loop under the conditions of 4.2 K, 20 K, and 25 K.

[0044] Embodiment 5 The differences between this embodiment and Embodiment 3 are as follows: the MgLi alloy rod used in Step 1 is composed of the following components by mass ratio: Li 10%, and the rest is Mg and inevitable impurities; the temperature of vacuum heat treatment in Step 4 is 670 °C.

[0045] After inspection, the high-temperature superconducting MgB2 wire prepared in this embodiment has a complete hysteresis loop under the conditions of 4.2 K, 20 K, and 25 K.

[0046] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent structural transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion, characterized in that, The preparation method includes the following steps: Step 1: Place the Nb tube inside the Cu tube, then place the MgLi alloy rod inside the Nb tube. Next, fill the space between the MgLi alloy rod and the Nb tube with carbon-coated B powder or B powder, and use copper plugs to seal both ends. After cold rotary forging, a single-core composite is obtained; Step 2: Perform rotary head, outer graphite coating, and hot drawing on the single-core composite obtained in Step 1 in sequence to obtain a single-core composite round wire; Step 3: Bundle and place the single-core composite round wire obtained in Step 2 in a Monel alloy sheath, and then perform cold rotary forging, outer graphite coating, and hot drawing in sequence to obtain a multi-core bundled composite MgB2 round wire; Step 4: Perform vacuum heat treatment on the multi-core bundled composite MgB2 round wire obtained in Step 3 to obtain a high-temperature superconducting MgB2 wire.

2. The method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion according to claim 1, wherein Before the MgLi alloy rod in Step 1 is placed inside the Nb tube, it undergoes hot drawing and annealing; the MgLi alloy rod is composed of the following components by mass ratio: Li 8% - 10%, and the rest is Mg and inevitable impurities.

3. A method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion according to claim 2, characterized in that, The temperature of the hot drawing is 300°C - 400°C, the pass deformation rate of the hot drawing is 10% - 12%, the temperature of the annealing is 250°C - 300°C, and the holding time of the annealing is 2h - 3h.

4. A method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion according to claim 1, characterized in that, In Step 1, the mass ratio of the MgLi alloy rod to the carbon-coated B powder or B powder is 1:1.12, the total deformation rate of the cold rotary forging is 30% - 40%, and the pass deformation rate is 15% - 30%.

5. A method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion according to claim 1, characterized in that, The method of hot drawing in Step 2 is: heat to 400°C - 450°C and hold for 1min - 3min, then perform hot drawing with a drawing speed of 1m / min - 2m / min, and the pass deformation rate of the hot drawing is 22% - 28%.

6. A method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion according to claim 1, characterized in that, In Step 3, the total deformation rate of the cold rotary forging is 20% - 30%, and the pass deformation rate is 10% - 12%.

7. A method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion according to claim 1, characterized in that, The method of hot drawing in Step 3 is: heat to 400°C - 450°C and hold for 1min - 10min, then perform hot drawing with a drawing speed of 1m / min - 1.5m / min, and the pass deformation rate of the hot drawing is 22% - 28%.

8. A method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion according to claim 1, characterized in that, During the hot drawing in Step 2 and Step 3, after every 2 - 3 passes of drawing, soak in graphite paste, and then continue drawing.

9. A method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion according to claim 1, characterized in that, The method of outer graphite coating in both Step 2 and Step 3 is: soak in graphite paste.

10. A method for preparing a high-temperature superconducting MgB2 wire by hot drawing based on central MgLi diffusion according to claim 1, characterized in that, The temperature of the vacuum heat treatment in Step 4 is 630°C - 670°C, and the duration of the vacuum heat treatment is 2h.

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