High-temperature superconducting MgB2 wire thermoforming preparation method based on resistance heating

Abstract

The invention discloses a hot forming preparation method of a high-temperature superconducting MgB2 wire rod based on resistance heating. The method comprises the following steps: 1, carrying out cold rotary swaging deformation after tubing to obtain a single-core complex; 2, after resistance heating, carrying out hot drawing deformation to obtain a single-core composite round wire; thirdly, the single-core composite round wires are bundled and assembled and then subjected to cold rotary swaging, and a multi-core bundled and assembled complex is obtained; 4, after resistance heating, carrying out hot drawing deformation to obtain a multi-core clustered composite MgB2 round wire; and 5, carrying out vacuum heat treatment to obtain the high-temperature superconducting MgB2 wire rod. Resistance heating is carried out before hot drawing deformation, so that the center Mg rod and the middle Nb barrier layer obtain excellent thermoplasticity, coordinated and uniform plastic deformation of the center Mg rod and the middle Nb barrier layer and the outer Cu sheath and uniform flowing of filled powder are achieved, and the MgB2 superconducting wire which is free of knots on the surface, free of core breakage in the interior and uniform in deformation is obtained and is suitable for the field of high-temperature superconducting. And meanwhile, the machining pass is reduced, the machining time is greatly shortened, and the preparation process is simplified.

Description

Technical Field

[0001] The present invention belongs to the technical field of superconducting wire preparation and processing, and specifically relates to a high-temperature superconducting MgB based on resistance heating. 2 Wire hot forming preparation method. Background Art

[0002] High temperature superconducting MgB 2 The wire has the advantages of high current carrying performance, high critical temperature, high adjacent current density and low cost. It has important applications in energy, information, medical and military fields, and has become a key material for magnetic resonance imaging (MRI) winding and superconducting cables. In order to meet the requirements of high strength and high current carrying performance, a new generation of high-temperature superconducting MgB based on the central magnesium diffusion technology (IMD) is developed. 2 The wires were developed and their performance was significantly improved. However, the preparation of kilometer-long wires still had serious problems such as broken cores, broken wires, and cracks in the internal barrier layer, which seriously restricted the performance of the wires and their applications.

[0003] In high temperature superconducting MgB 2 During the forming process of the wire, the coordinated rheological behavior of the metal material and the powder seriously affects the performance of the wire and the success rate of its preparation. Among them, the deformation of the pure Mg rod and the uniformity of the B powder filling affect the superconducting phase MgB during the heat treatment process. 2 The formation and distribution of MgB in high temperature superconducting 2 In the process of wire preparation, there are problems such as the difficulty in deformation of pure Mg rods, uneven deformation and obvious anisotropy, which can easily cause local stress concentration and uneven powder flow during the wire drawing process, and then lead to the rupture of the outer niobium barrier layer, wire breakage during drawing, and large porosity of superconducting powder after heat treatment, which seriously affect the stability of wire production. Therefore, a new hot working forming process is proposed to enable the central Mg rod and Nb tube to obtain excellent thermoplasticity, and at the same time achieve coordinated and uniform deformation of the central Mg rod, the outer Cu sheath, and the middle Nb barrier layer, which is very important for achieving uniform flow distribution of the middle B powder and solving the problem of high-temperature superconducting MgB 2 Problems such as central Mg rod fracture, Nb barrier layer rupture, and single-core wire surface nodules that occur during the single-core and multi-core wire drawing process are of great engineering significance. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a high-temperature superconducting MgB based on resistance heating in view of the shortcomings of the above-mentioned prior art. 2The method is a method for preparing wire hot forming. The method performs resistance heating before hot drawing deformation, so that the central Mg rod and the middle Nb barrier layer in the wire obtain excellent thermoplasticity, and realizes coordinated and uniform plastic deformation of the central Mg rod, the middle Nb barrier layer, and the outer Cu sheath, as well as uniform flow of the filling powder, to obtain a MgB wire with no nodules on the surface, no broken core inside, and uniform deformation. 2 Superconducting wire solves the problem of high-temperature superconducting MgB 2 Problems such as central Mg rod breakage, Nb barrier layer rupture, and single-core wire surface nodules occur during the single-core and multi-core wire drawing process.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a high-temperature superconducting MgB based on resistance heating 2 A wire hot forming preparation method, characterized in that the method comprises the following steps:

[0006] Step 1: insert the Nb tube into the Cu tube, and insert the Mg rod into the Nb tube, then fill the carbon-coated B powder or B powder between the Nb tube and the Mg rod, and use copper plugs to fix the Mg rod in the center and seal it at both ends, and then perform cold rotary forging deformation, so that the Cu tube and the Nb tube fit together, and the internal B powder is compacted, so as to obtain a Cu / Nb / (B,Mg) single-core composite with a compact interior;

[0007] Step 2, spinning the Cu / Nb / (B, Mg) single core composite obtained in step 1, and then immersing it in graphite mud, taking it out and putting the Cu / Nb / (B, Mg) single core composite coated with graphite on the surface into a resistance heating furnace for heating and heat preservation, and then performing hot drawing deformation to obtain a Cu / Nb / (B, Mg) single core composite round wire;

[0008] Step 3, the Cu / Nb / (B, Mg) single-core composite round wire obtained in step 2 is intercepted in sequence, and both ends are sealed, and 200-600 mesh sandpaper is used to polish and remove surface graphite, alkali washing is used to remove surface oil, and acid washing is used to remove surface oxide layer, and then the bundle is assembled in a Monel alloy sheath for cold rotary forging, so that the Monel alloy sheath is in interface contact with the internal Cu / Nb / (B, Mg) single-core composite round wire, and the internally assembled Cu / Nb / (B, Mg) single-core composite round wires are in interface contact with each other, so as to obtain a Cu / Nb / (B, Mg) multi-core bundle assembly complex;

[0009] Step 4: The Cu / Nb / (B, Mg) multi-core cluster assembly complex obtained in step 3 is spun, and then immersed in graphite mud. After taking out, the Cu / Nb / (B, Mg) multi-core cluster assembly complex with graphite coated on the surface is placed in a resistance heating furnace for heating and insulation, and then hot-drawn to obtain a multi-core cluster composite MgB 2 round line;

[0010] Step 5: The multi-core cluster composite MgB obtained in step 4 2 The round wire is vacuum heat treated to obtain high-temperature superconducting MgB 2 Wire.

[0011] The present invention first uses Cu as a sheath and Nb tube as an intermediate barrier layer for assembly, inserts a central Mg rod and fills carbon-coated B powder or B powder, and performs cold rotary forging deformation to prepare a Cu / Nb / (B, Mg) single-core composite body. Then, the surface of the Cu / Nb / (B, Mg) single-core composite body is coated with graphite, and then subjected to resistance heating and heat preservation, and then hot drawing deformation is performed to obtain a Cu / Nb / (B, Mg) single-core composite round wire. Then, the Cu / Nb / (B, Mg) multi-core cluster assembly composite body is bundled and assembled for cold rotary forging to obtain a Cu / Nb / (B, Mg) multi-core cluster assembly composite body, and the surface is coated with graphite to increase lubrication and reduce the friction effect with the mold. After resistance heating and heat preservation, hot drawing deformation is performed to obtain a multi-core cluster composite MgB 2 Round wire, high temperature superconducting MgB obtained by vacuum heat treatment 2 In the preparation process, resistance heating is performed before the two hot drawing deformations, so that the central Mg rod and the middle Nb barrier layer obtain excellent thermoplasticity, and the coordinated and uniform plastic deformation of the central Mg rod, the middle Nb barrier layer, and the outer Cu sheath is achieved, as well as the uniform flow of the middle carbon-coated B powder or B powder, so as to obtain MgB wire with no nodules on the surface, no broken core inside, and uniform deformation. 2 Superconducting wire solves the problem of high-temperature superconducting MgB 2 Problems such as central Mg rod breakage, Nb barrier layer rupture, and single-core wire surface nodules occur during the single-core and multi-core wire drawing process.

[0012] The above-mentioned high-temperature superconducting MgB based on resistance heating 2 The wire hot forming preparation method is characterized in that the outer diameter of the Nb tube in step 1 is Φ11mm and the wall thickness is 1mm, the outer diameter of the Cu tube is Φ13mm and the wall thickness is 1mm, the mass content of Mg in the Mg rod is 99.99%, and the diameter is Φ4mm; the powder density of the carbon-coated B powder or B powder is 0.5g / cm 2 The total deformation rate of the cold rotary forging deformation is 30% to 40%, and the pass deformation rate is 15% to 30%.

[0013] The above-mentioned high-temperature superconducting MgB based on resistance heating 2The wire hot forming preparation method is characterized in that the temperature of the heating and heat preservation in step 2 is 350℃~450℃, and the time is 1min~3min; the deformation rate of the hot drawing deformation is 16%~20%, the drawing temperature is 350℃~450℃, the drawing speed is 1m / min~4m / min, and the wire is immersed in graphite mud after every 2~3 hot drawing deformations. The present invention controls the degree and speed of dynamic recrystallization of the central Mg rod, the middle Nb barrier layer, and the outer Cu sheath by adjusting the temperature and time of heating and heat preservation, combined with adjusting the deformation rate, drawing temperature and drawing speed of the hot drawing deformation, to achieve uniform plastic deformation of the three and uniform flow of the filling powder; at the same time, the internal stress / strain distribution and organizational properties of the Cu / Nb / (B,Mg) single-core composite round wire are regulated to control the vacuum heat treatment phase formation process and the mechanical properties of the product high-temperature superconducting MgB2 wire.

[0014] The above-mentioned high-temperature superconducting MgB based on resistance heating 2 The wire hot forming preparation method is characterized in that the diameter of the Cu / Nb / (B, Mg) single-core composite round wire in step 2 is Φ2mm~Φ3.9mm.

[0015] The above-mentioned high-temperature superconducting MgB based on resistance heating 2 The wire hot forming preparation method is characterized in that the diameter of the Cu / Nb / (B, Mg) single-core composite round wire used for bundle assembly in step three is Φ2mm~Φ3.9mm, the outer diameter of the Monel alloy sheath is Φ20mm~Φ32mm and the wall thickness is 2mm; the total deformation rate of the cold rotary forging is 20%~30%, and the pass deformation rate is 10%~12%.

[0016] The above-mentioned high-temperature superconducting MgB based on resistance heating 2 The wire hot forming preparation method is characterized in that the heating and insulation temperature in step 4 is 350°C to 450°C, and the time is 5min to 10min; the deformation rate of the hot drawing deformation is 12% to 16%, the drawing temperature is 350°C to 450°C, the drawing speed is 1m / min to 2m / min, and during the hot drawing deformation process, when the diameter of the Cu / Nb / (B, Mg) multi-core bundle assembly complex is greater than 10mm, the insulation time before the hot drawing deformation is 3min to 5min, when the diameter of the Cu / Nb / (B, Mg) multi-core bundle assembly complex is less than 10mm, the insulation time before the hot drawing deformation is 1min to 3min, and the wire is immersed in graphite mud after every 2 to 3 hot drawing deformations.

[0017] The above-mentioned high-temperature superconducting MgB based on resistance heating 2The wire hot forming preparation method is characterized in that the multi-core clustered composite MgB 2 The diameter of the round wire is Φ1mm~Φ2mm.

[0018] The above-mentioned high-temperature superconducting MgB based on resistance heating 2 The wire hot forming preparation method is characterized in that the temperature of the vacuum heat treatment in step five is 570°C to 650°C, and the time is 1h to 2h.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The present invention performs resistance heating before the two hot drawing deformations in the preparation of single-core composite round wire and multi-core bundled composite round wire, so that the central Mg rod and the middle Nb barrier layer in the wire have excellent thermoplasticity, overcome the difficulty of deformation and deformation anisotropy of Mg, achieve coordinated and uniform plastic deformation of the central Mg rod, the middle Nb barrier layer, and the outer Cu sheath, and uniform flow of the middle carbon-coated B powder or B powder, and obtain MgB with no nodules on the surface, no broken core inside and uniform deformation. 2 Superconducting wire is conducive to ultra-long high-temperature superconducting MgB 2 Smooth preparation of wire.

[0021] 2. The present invention controls the temperature of resistance heating and hot drawing deformation to 350℃~450℃, so as to ensure that the central Mg rod and the middle Nb barrier layer in the wire undergo dynamic recrystallization during hot drawing deformation, thereby having excellent thermoplasticity. At the same time, this temperature range is lower than that of MgB 2 The transition temperature of superconducting phase is 570℃~650℃, which effectively prevents the formation of MgB during hot drawing deformation. 2 Superconducting ceramic phase, thus ensuring high temperature superconducting MgB 2 Smooth preparation of wire.

[0022] 3. The present invention improves the plasticity of the central Mg rod, the middle Nb barrier layer, and the outer Cu sheath by means of resistance heating. Therefore, a larger pass deformation rate can be used during hot drawing deformation to obtain a larger axial force of the wire, so that the loaded carbon-coated B powder or B powder has a larger axial and radial flow stress, and the distribution is more uniform. Finally, after heat treatment, a uniformly distributed MgB 2 Superconducting ceramic phase, improving high-temperature superconducting MgB 2 At the same time, due to the increase in the deformation rate of hot drawing (usually from 8% of cold drawing to 16% to 20%), the processing passes are greatly reduced, and compared with cold drawing, the number of drawing dies is reduced by more than half, which greatly reduces the processing time and simplifies the preparation process.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The high temperature superconducting MgB based on resistance heating of the present invention 2 Flowchart of the wire thermoforming preparation method.

[0025] Figure 2 This is the high temperature superconducting MgB based on resistance heating in Example 1 of the present invention. 2 On-site flow chart of the wire hot forming preparation method.

[0026] Figure 3 The high-temperature superconducting MgB prepared in Example 1 of the present invention 2 Physical picture of the wire.

[0027] Figure 4 The high-temperature superconducting MgB prepared in Example 1 of the present invention 2 CT image of a single-core wire. DETAILED DESCRIPTION

[0028] Example 1

[0029] like Figure 1 and Figure 2 As shown, this embodiment includes the following steps:

[0030] Step 1: Cut the Cu tube, Nb tube and Mg rod, wash the Cu tube and Nb tube with alkali and pickling, polish the Mg rod, insert the Nb tube with an outer diameter of Φ11mm, a wall thickness of 1mm and a length of 60mm into the Cu tube with an outer diameter of Φ13mm, a wall thickness of 1mm and a length of 60mm, and insert the Mg rod with a Mg mass content of 99.99%, a diameter of Φ4mm and a length of 65mm into the Nb tube, and then 2 13g of B powder is filled between the Nb tube and the Mg rod, and the Mg rod is fixed at the center and sealed with copper plugs at both ends, and then cold rotary forging is performed to make the Cu tube and the Nb tube fit together, and the internal B powder is compacted to obtain a Cu / Nb / (B,Mg) single-core composite with a compact interior; the total deformation rate of the cold rotary forging deformation is 30%, and the pass deformation rate is 15%;

[0031] Step 2, the Cu / Nb / (B, Mg) single core composite obtained in step 1 is spun, and then immersed in graphite mud, and after taking out, the Cu / Nb / (B, Mg) single core composite coated with graphite is placed in a resistance heating furnace and heated at 450° C. for 1 min, and then hot drawing is performed, the pass deformation rate is 20%, the drawing temperature is 450° C., the drawing speed is 4 m / min, and after every 3 passes of hot drawing deformation, the wire is immersed in graphite mud to obtain a Cu / Nb / (B, Mg) single core composite round wire with a diameter of Φ2 mm;

[0032] Step 3, the Cu / Nb / (B, Mg) single-core composite round wire obtained in step 2 is intercepted in sequence, and both ends are sealed, and 200-600 mesh sandpaper is used to polish and remove surface graphite, alkali washing is used to remove surface oil, and acid washing is used to remove surface oxide layer, and then the bundle is assembled in a Monel alloy sheath with an outer diameter of Φ20 mm and a wall thickness of 2 mm for cold rotary forging, with a total deformation rate of 30% and a pass deformation rate of 12%, so that the Monel alloy sheath is in interface contact with the internal Cu / Nb / (B, Mg) single-core composite round wire, and the internally assembled Cu / Nb / (B, Mg) single-core composite round wires are in interface contact with each other, to obtain a Cu / Nb / (B, Mg) multi-core bundle assembly complex;

[0033] Step 4: The Cu / Nb / (B, Mg) multi-core cluster assembly complex obtained in step 3 is spun, and then immersed in graphite mud. After taking out, the Cu / Nb / (B, Mg) multi-core cluster assembly complex with graphite coated on the surface is placed in a resistance heating furnace and heated at 450°C for 5 minutes, and then hot-drawn, with a deformation rate of 16%, a drawing temperature of 450°C, and a drawing speed of 2m / min. During the hot-drawing deformation process, when the diameter of the Cu / Nb / (B, Mg) multi-core cluster assembly complex is greater than 10mm, the insulation time before hot-drawing deformation is 5min, and when the diameter of the Cu / Nb / (B, Mg) multi-core cluster assembly complex is less than 10mm, the insulation time before hot-drawing deformation is 3min, and after every 3 hot-drawing deformations, the wire is immersed in graphite mud to obtain a multi-core cluster composite MgB with a diameter of Φ1mm. 2 round line;

[0034] Step 5: The multi-core cluster composite MgB obtained in step 4 2 The round wire was vacuum heat treated at 650℃ for 2h to obtain high-temperature superconducting MgB 2 Wire, such as Figure 3 As shown.

[0035] Figure 4 The high-temperature superconducting MgB prepared in this embodiment 2 CT image of single core wire in wire, from Figure 4 It can be seen that the single-core wire obtained by resistance heating combined with hot drawing in the present invention has uniform deformation of the copper layer, niobium layer, magnesium rod layer and intermediate powder layer during the deformation process based on the thermomechanical coupling effect, and there is no broken core, no niobium barrier layer rupture and no nodule phenomenon, which improves the wire processing capability and solves the problems of broken core, broken wire and nodule.

[0036] The powder loaded in step 1 of the present invention can also be replaced by carbon-coated B powder.

[0037] Example 2

[0038] like Figure 1 As shown, this embodiment includes the following steps:

[0039] Step 1: Cut the Cu tube, Nb tube and Mg rod, wash the Cu tube and Nb tube with alkali and pickling, polish the Mg rod, insert the Nb tube with an outer diameter of Φ11mm, a wall thickness of 1mm and a length of 60mm into the Cu tube with an outer diameter of Φ13mm, a wall thickness of 1mm and a length of 60mm, and insert the Mg rod with a Mg mass content of 99.99%, a diameter of Φ4mm and a length of 65mm into the Nb tube, and then 2 13g of B powder is filled between the Nb tube and the Mg rod, and the Mg rod is fixed at the center and sealed with copper plugs at both ends, and then cold rotary forging is performed to make the Cu tube and the Nb tube fit together, and the internal B powder is compacted to obtain a Cu / Nb / (B,Mg) single-core composite with a compact interior; the total deformation rate of the cold rotary forging deformation is 35%, and the pass deformation rate is 20%;

[0040] Step 2, the Cu / Nb / (B, Mg) single core composite obtained in step 1 is spun, and then immersed in graphite mud, and after taking out, the Cu / Nb / (B, Mg) single core composite coated with graphite is placed in a resistance heating furnace and heated at 400°C for 2 minutes, and then hot drawing is performed, the deformation rate of each pass is 18%, the drawing temperature is 400°C, the drawing speed is 2m / min, and the wire is immersed in graphite mud after every 2 hot drawing deformations to obtain a Cu / Nb / (B, Mg) single core composite round wire with a diameter of Φ2.5mm;

[0041] Step 3, the Cu / Nb / (B, Mg) single-core composite round wire obtained in step 2 is intercepted in sequence, and both ends are sealed, and 200-600 mesh sandpaper is used to polish and remove surface graphite, alkali washing is used to remove surface oil, and acid washing is used to remove surface oxide layer, and then the bundle is assembled in a Monel alloy sheath with an outer diameter of Φ28 mm and a wall thickness of 2 mm for cold rotary forging, with a total deformation rate of 25% and a pass deformation rate of 11%, so that the Monel alloy sheath is in interface contact with the internal Cu / Nb / (B, Mg) single-core composite round wire, and the internally assembled Cu / Nb / (B, Mg) single-core composite round wires are in interface contact with each other, to obtain a Cu / Nb / (B, Mg) multi-core bundle assembly complex;

[0042] Step 4: The Cu / Nb / (B, Mg) multi-core cluster assembly complex obtained in step 3 is spun, and then immersed in graphite mud. After taking out, the Cu / Nb / (B, Mg) multi-core cluster assembly complex with graphite coated on the surface is placed in a resistance heating furnace and heated at 400°C for 8 minutes, and then hot-drawn. The deformation rate is 14%, the drawing temperature is 400°C, and the drawing speed is 1.5 m / min. During the hot-drawing deformation process, when the diameter of the Cu / Nb / (B, Mg) multi-core cluster assembly complex is greater than 10 mm, the insulation time before hot-drawing deformation is 4 minutes, and when the diameter of the Cu / Nb / (B, Mg) multi-core cluster assembly complex is less than 10 mm, the insulation time before hot-drawing deformation is 2 minutes, and after every 2 hot-drawing deformations, the wire is immersed in graphite mud to obtain a multi-core cluster composite MgB with a diameter of Φ1.5 mm. 2 round line;

[0043] Step 5: The multi-core cluster composite MgB obtained in step 4 2 The round wire was vacuum heat treated at 600℃ for 1.5h to obtain high-temperature superconducting MgB 2 Wire.

[0044] Example 3

[0045] like Figure 1 As shown, this embodiment includes the following steps:

[0046] Step 1: Cut the Cu tube, Nb tube and Mg rod, wash the Cu tube and Nb tube with alkali and pickling, polish the Mg rod, insert the Nb tube with an outer diameter of Φ11mm, a wall thickness of 1mm and a length of 60mm into the Cu tube with an outer diameter of Φ13mm, a wall thickness of 1mm and a length of 60mm, and insert the Mg rod with a Mg mass content of 99.99%, a diameter of Φ4mm and a length of 65mm into the Nb tube, and then 213g of B powder is filled between the Nb tube and the Mg rod, and the Mg rod is fixed at the center and sealed with copper plugs at both ends, and then cold rotary forging is performed to make the Cu tube and the Nb tube fit together, and the internal B powder is compacted to obtain a Cu / Nb / (B,Mg) single-core composite with a compact interior; the total deformation rate of the cold rotary forging deformation is 40%, and the pass deformation rate is 30%;

[0047] Step 2, the Cu / Nb / (B, Mg) single core composite obtained in step 1 is spun, and then immersed in graphite mud, and after taking out, the Cu / Nb / (B, Mg) single core composite coated with graphite is placed in a resistance heating furnace and heated at 350° C. for 1 min, and then hot drawing is performed, the pass deformation rate is 16%, the drawing temperature is 350° C., the drawing speed is 1 m / min, and the wire is immersed in graphite mud after every 2 passes of hot drawing deformation to obtain a Cu / Nb / (B, Mg) single core composite round wire with a diameter of Φ3.9 mm;

[0048] Step 3, the Cu / Nb / (B, Mg) single-core composite round wire obtained in step 2 is intercepted in sequence, and both ends are sealed, and 200-600 mesh sandpaper is used to polish and remove surface graphite, alkali washing is used to remove surface oil, and acid washing is used to remove surface oxide layer, and then the bundle is assembled in a Monel alloy sheath with an outer diameter of Φ32 mm and a wall thickness of 2 mm for cold rotary forging, with a total deformation rate of 20% and a pass deformation rate of 10%, so that the Monel alloy sheath is in interface contact with the internal Cu / Nb / (B, Mg) single-core composite round wire, and the internally assembled Cu / Nb / (B, Mg) single-core composite round wires are in interface contact with each other, to obtain a Cu / Nb / (B, Mg) multi-core bundle assembly complex;

[0049] Step 4: The Cu / Nb / (B, Mg) multi-core cluster assembly complex obtained in step 3 is spun, and then immersed in graphite mud. After taking out, the Cu / Nb / (B, Mg) multi-core cluster assembly complex with graphite coated on the surface is placed in a resistance heating furnace and heated at 350°C for 10 minutes, and then hot-drawn, with a deformation rate of 12%, a drawing temperature of 350°C, and a drawing speed of 1m / min. During the hot-drawing deformation process, when the diameter of the Cu / Nb / (B, Mg) multi-core cluster assembly complex is greater than 10mm, the insulation time before hot-drawing deformation is 5min, and when the diameter of the Cu / Nb / (B, Mg) multi-core cluster assembly complex is less than 10mm, the insulation time before hot-drawing deformation is 3min, and after every 3 hot-drawing deformations, the wire is immersed in graphite mud to obtain a multi-core cluster composite MgB with a diameter of Φ2mm. 2 round line;

[0050] Step 5: The multi-core cluster composite MgB obtained in step 42 The round wire was vacuum heat treated at 570℃ for 1h to obtain high-temperature superconducting MgB 2 Wire.

[0051] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for hot forming a high-temperature superconducting MgB2 wire based on resistance heating, characterized in that: The method comprises the following steps: Step 1: insert the Nb tube into the Cu tube, and insert the Mg rod into the Nb tube, then fill the carbon-coated B powder or B powder between the Nb tube and the Mg rod, and use copper plugs to fix the Mg rod in the center and seal it at both ends, and then perform cold rotary forging deformation, so that the Cu tube and the Nb tube fit together, and the internal B powder is compacted, so as to obtain a Cu / Nb / (B,Mg) single-core composite with a compact interior; Step 2, spinning the Cu / Nb / (B, Mg) single core composite obtained in step 1, and then immersing it in graphite mud, taking it out and putting the Cu / Nb / (B, Mg) single core composite coated with graphite on the surface into a resistance heating furnace for heating and heat preservation, and then performing hot drawing deformation to obtain a Cu / Nb / (B, Mg) single core composite round wire; Step 3, the Cu / Nb / (B, Mg) single-core composite round wire obtained in step 2 is intercepted in sequence, and both ends are sealed, and 200-600 mesh sandpaper is used to polish and remove surface graphite, alkali washing is used to remove surface oil, and acid washing is used to remove surface oxide layer, and then the bundle is assembled in a Monel alloy sheath for cold rotary forging, so that the Monel alloy sheath is in interface contact with the internal Cu / Nb / (B, Mg) single-core composite round wire, and the internally assembled Cu / Nb / (B, Mg) single-core composite round wires are in interface contact with each other, so as to obtain a Cu / Nb / (B, Mg) multi-core bundle assembly complex; Step 4: The Cu / Nb / (B, Mg) multi-core cluster assembly complex obtained in step 3 is spun, and then immersed in graphite mud. After taking out, the Cu / Nb / (B, Mg) multi-core cluster assembly complex with graphite coated on the surface is placed in a resistance heating furnace for heating and heat preservation, and then hot-drawn to obtain a multi-core cluster composite MgB2 round wire; Step 5: subject the multi-core clustered composite MgB2 round wire obtained in step 4 to vacuum heat treatment to obtain a high-temperature superconducting MgB2 wire.

2. A method for hot forming a high temperature superconducting MgB2 wire based on resistance heating according to claim 1, characterized in that: In step 1, the outer diameter of the Nb tube is Φ11 mm and the wall thickness is 1 mm, the outer diameter of the Cu tube is Φ13 mm and the wall thickness is 1 mm, the mass content of Mg in the Mg rod is 99.99%, and the diameter is Φ4 mm; the powder density of the carbon-coated B powder or B powder is 0.5 g / cm 2 The total deformation rate of the cold rotary forging deformation is 30% to 40%, and the pass deformation rate is 15% to 30%.

3. The method for hot forming a high temperature superconducting MgB2 wire based on resistance heating according to claim 1, characterized in that: The heating and insulation temperature in step 2 is 350°C to 450°C, and the time is 1min to 3min; the deformation rate of the hot drawing deformation is 16% to 20%, the drawing temperature is 350°C to 450°C, the drawing speed is 1m / min to 4m / min, and the wire is immersed in graphite mud after every 2 to 3 hot drawing deformations.

4. The method for hot forming a high temperature superconducting MgB2 wire based on resistance heating according to claim 1, characterized in that: The diameter of the Cu / Nb / (B,Mg) single-core composite round wire in step 2 is Φ2mm to Φ3.9mm.

5. The method for preparing high-temperature superconducting MgB2 wire by hot forming based on resistance heating according to claim 1, characterized in that: The diameter of the Cu / Nb / (B,Mg) single-core composite round wire used for bundle assembly in step 3 is Φ2mm~Φ3.9mm, the outer diameter of the Monel alloy sheath is Φ20mm~Φ32mm and the wall thickness is 2mm; the total deformation rate of the cold rotary forging is 20%~30%, and the pass deformation rate is 10%~12%.

6. The method for hot forming a high temperature superconducting MgB2 wire based on resistance heating according to claim 1, characterized in that: The heating and insulation temperature in step 4 is 350°C to 450°C, and the time is 5min to 10min; the deformation rate of the hot drawing deformation is 12% to 16%, the drawing temperature is 350°C to 450°C, the drawing speed is 1m / min to 2m / min, and during the hot drawing deformation process, when the diameter of the Cu / Nb / (B, Mg) multi-core bundle assembly complex is greater than 10mm, the insulation time before the hot drawing deformation is 3min to 5min, when the diameter of the Cu / Nb / (B, Mg) multi-core bundle assembly complex is less than 10mm, the insulation time before the hot drawing deformation is 1min to 3min, and the wire is immersed in graphite mud after every 2 to 3 hot drawing deformations.

7. The method for hot forming a high temperature superconducting MgB2 wire based on resistance heating according to claim 1, characterized in that: The diameter of the multi-core bundled composite MgB2 round wire described in step 4 is Φ1mm~Φ2mm.

8. The method for hot forming a high temperature superconducting MgB2 wire based on resistance heating according to claim 1, characterized in that: The temperature of the vacuum heat treatment in step 5 is 570° C. to 650° C., and the time is 1 h to 2 h.

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