A method for preparing MgB2 superconducting wire by drilling a hole in a Mg ingot

Abstract

The invention discloses a method for preparing MgB by drilling a Mg ingot. 2 The method for producing a superconducting wire comprises: drilling a Mg ingot; pressing C-coated B powder into a B rod with uniform length; processing the B rod and the Mg ingot into a round single-core rod; pickling the round single-core rod and the oxygen-free Cu rod and placing them together in an NCu30 tube that has been pickled to form a multi-core composite wire; heat-treating the multi-core composite wire to form a MgB 2 Superconducting wire. The present invention drills holes on the Mg ingot, uses a powder rod press machine to press B powder into B rods and inserts them into the holes, and Mg evenly permeates and reacts in the B powder from the surroundings, so that the reaction of Mg and B is more thorough, avoiding the problem of unreacted B powder residue that often occurs in the IMD method, and effectively avoiding the powder loading problem when preparing a single core rod, realizing the rapid preparation of a single core rod by the IMD method, and greatly improving the powder loading density of the B powder.

Description

Technical Field

[0001] The invention relates to the technical field of superconducting wires, and in particular to a method for preparing MgB2 superconducting wires by drilling holes in Mg ingots. Background Art

[0002] As a macroscopic quantum phenomenon, superconductivity has important research and application value. Superconducting materials have two basic characteristics: zero resistance and Meissner effect. Zero resistance means that when the temperature of a superconducting material is lower than a certain critical temperature Tc, its resistance will gradually decrease and eventually disappear, so the current can flow through the superconducting material without loss. The lossless current that a superconducting material can carry is limited. When it exceeds a certain maximum value, the material will lose its superconducting properties. This maximum value is called the superconducting critical current Ic. The Meissner effect means that when a superconducting material is in a superconducting state, an external magnetic field is applied to it. The external magnetic field will stimulate a circle of superconducting shielding current on the surface of the superconducting material, preventing the magnetic field from entering the superconductor. However, this magnetic field shielding effect is also limited. When the external magnetic field exceeds a certain critical magnetic field Hc, the magnetic field will enter the superconductor or cause the superconducting material to lose its superconducting properties. In view of the above two characteristics, superconducting materials have been widely used, such as in various fields such as current transmission, rail transportation, medical imaging, superconducting energy storage, wind power generation, quantum computing, nuclear fusion and high-energy physics. Currently, practical superconducting materials are mainly divided into low-temperature superconducting materials and high-temperature superconducting materials. The former include NbTi, Nb3Sn, etc., and the latter include MgB2, Bi system and YBCO, etc.

[0003] As a practical superconducting material, MgB2 has the advantages of high superconducting transition temperature Tc=40K, large critical current density Jc and upper critical magnetic field Hc2, small anisotropy, excellent grain connectivity, non-toxic and cheap raw materials, and light weight. Therefore, it has been widely studied and applied.

[0004] At present, the preparation methods of MgB2 superconducting wire mainly include powder in tube method (PIT) and central magnesium diffusion method (IMD). The IMD method mainly uses Mg rod and B powder as raw materials. First, the Mg rod is inserted into the center of the metal sheath, and then B powder is filled between the Mg rod and the metal sheath to form a structure of Mg rod / B powder / metal sheath from the inside to the outside, and then it is processed into a wire of specific specifications by rotary forging, rolling, drawing, etc. The metal sheath used in the IMD method mainly includes materials such as Nb, Fe, and Ni. The use of the IMD method can greatly improve the density and grain connectivity of the MgB2 superconducting phase in the wire, improve the critical current density Jc of the wire, thereby improving the superconducting current carrying capacity of the wire, and reducing the loss of the wire under AC and other conditions. However, the problem of unreacted B powder residue often occurs in the IMD method, and the filling of B powder is difficult, which is not convenient for rapid preparation. Summary of the invention

[0005] The embodiment of the present invention provides a method for preparing MgB2 superconducting wire by drilling holes in Mg ingots, so as to solve the problems in the prior art that unreacted B powder remains in the IMD method, and the filling of B powder is difficult, which makes it inconvenient to prepare quickly.

[0006] On the one hand, an embodiment of the present invention provides a method for preparing a MgB2 superconducting wire by drilling a Mg ingot, comprising:

[0007] Drilling Mg ingots in a vacuum environment or a high-purity Ar gas protection environment;

[0008] In a vacuum environment or a high-purity Ar gas protection environment, the C-coated B powder is pressed into B rods of uniform length by a powder rod pressing machine;

[0009] After placing the B rod into the hole of the Mg ingot, the Mg ingot is placed into a sheath;

[0010] Processing the sheath in which the B rod and the Mg ingot are placed into a round single core rod by rotary forging and rolling processes;

[0011] The round single core rod and the oxygen-free Cu rod are pickled and placed together in the pickled NCu30 tube to be drawn, swaged and rolled to form a multi-core composite wire;

[0012] The multi-core composite wire is heat treated to produce a MgB2 superconducting wire.

[0013] In a possible implementation manner, the Mg ingot is a cylindrical ingot, and a plurality of holes are provided in the Mg ingot.

[0014] In a possible implementation, the sheath is a Nb / Cu composite metal sheath, the inner side of the sheath is a Nb tube, and the outer side of the sheath is an oxygen-free Cu tube.

[0015] In a possible implementation manner, the cross section of the oxygen-free Cu rod is circular, and the heat treatment of the oxygen-free Cu rod is an annealing state.

[0016] In a possible implementation, the heat treatment of the multi-core composite wire to form the MgB2 superconducting wire is performed in a vacuum environment.

[0017] The method of preparing MgB2 superconducting wire by drilling a hole in a Mg ingot in the present invention has the following advantages:

[0018] (1) Drill holes in the Mg ingot and insert the B rod into the holes. This structure allows Mg to evenly penetrate into the B powder from the surrounding area when the MgB2 superconducting phase is finally generated by diffusion reaction, making the reaction between Mg and B more thorough, avoiding the problem of unreacted B powder residue that often occurs in the IMD method, and improving the quality and performance of the wire.

[0019] (2) It is then loaded into the holes on the Mg ingot, which effectively avoids the powder loading problem when preparing a single-core rod by the IMD method, realizes the rapid preparation of a single-core rod by the IMD method, and greatly improves the powder loading density of the B powder, which helps to generate a denser MgB2 superconducting phase and improve the current carrying capacity of the wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention 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 invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of drilling holes on a Mg ingot in a method for preparing MgB2 superconducting wire by drilling holes in a Mg ingot provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Figure 1 A schematic diagram of drilling holes on a Mg ingot in a method for preparing a MgB2 superconducting wire by drilling holes on a Mg ingot provided in an embodiment of the present invention; an embodiment of the present invention provides a method for preparing a MgB2 superconducting wire by drilling holes on a Mg ingot, comprising:

[0024] Drilling Mg ingots in a vacuum environment or a high-purity Ar gas protection environment;

[0025] In a vacuum environment or a high-purity Ar gas protection environment, the C-coated B powder is pressed into B rods of uniform length by a powder rod pressing machine;

[0026] After placing the B rod into the hole of the Mg ingot, the Mg ingot is placed into a sheath;

[0027] Processing the sheath in which the B rod and the Mg ingot are placed into a round single core rod by rotary forging and rolling processes;

[0028] The round single core rod and the oxygen-free Cu rod are pickled and placed together in the pickled NCu30 tube to be drawn, swaged and rolled to form a multi-core composite wire;

[0029] Processing the multi-core composite wire into a MgB2 superconducting wire through heat treatment;

[0030] The Mg ingot is a cylindrical ingot, and the Mg ingot is provided with a plurality of holes;

[0031] The sheath is a Nb / Cu composite metal sheath, the inner side of the sheath is a Nb tube, and the outer side of the sheath is an oxygen-free Cu tube;

[0032] The cross section of the oxygen-free Cu rod is circular, and the heat treatment of the oxygen-free Cu rod is annealed;

[0033] The heat treatment of the multi-core composite wire to form the MgB2 superconducting wire is performed in a vacuum environment.

[0034] Exemplarily, firstly, a hole is drilled on the Mg ingot using a drilling technology, and the C-coated B powder is pressed into a B rod using a powder rod pressing machine. The B rod is inserted into the hole on the Mg ingot, and then the whole is placed in a metal sheath to be processed into a round single-core rod. Then, the round single-core rod and the oxygen-free Cu rod are inserted into the NCu30 tube to be processed into a round composite wire. Finally, the round composite wire is heat treated to generate a MgB2 superconducting wire.

[0035] The Mg ingot is a cylindrical ingot with a purity of 99.00% to 99.99%, a diameter of 10.00 mm to 50.00 mm, a length of 0.5 m to 10.0 m, 1 to 30 holes drilled on the Mg ingot, a hole diameter of 3.00 mm to 10.00 mm, a vacuum pressure of less than 1 Pa or a purity of high-purity Ar gas of > 95%, and an average particle size of the C-coated B powder of 20 nm to 1000 nm. nm, the mass fraction of C in the powder is 0%~10%, the diameter of the pressed B rod is 2.00mm~10.00mm, the length is 0.5m~10.0m, the pressure used by the powder pressing machine is 1Mpa~1Gpa, the vacuum pressure is less than 1Pa or the purity of high-purity Ar gas is>95%, the metal sheath is a Nb / Cu composite tube, the inner layer is a Nb tube with a purity of 99.0%~99.9%, an outer diameter of 10.00mm~100.00mm, and a thickness of 0.50mm~5.00m m; the outer layer is an oxygen-free Cu tube with a purity of 99.0% to 99.9%, an outer diameter of 10.00mm to 120.00mm, a thickness of 0.50mm to 5.00mm, and a processing amount of 5% to 25% during the rotary forging and rolling process. The diameter of the final round single core rod is 2.00mm to 10.00mm. The cross-section of the oxygen-free Cu rod is circular, with a purity of 99.90% to 99.99% and a diameter of 1.00mm to 30.00mm; the outer diameter of the NCu30 tube is 20 mm~70 mm, wall thickness is 2 mm~10 mm, annealed state; the processing amount of each pass in the drawing, rotary forging and rolling process is 5%~25%, and the cross-section of the multi-core composite wire finally obtained is circular with a diameter of 0.1mm~2 mm. The heat treatment temperature range is 550℃~900℃, the holding time is 0.5h~20h, and the heat treatment condition is a vacuum environment.

[0036] In a possible embodiment, six holes arranged in an annular pattern are drilled on a Mg ingot by drilling technology. The Mg ingot is a cylindrical ingot with a purity of 99.99%, a diameter of 20.00 mm, a length of 0.5 m, and a diameter of 3.00 mm. The process is carried out in a high-purity Ar gas protection environment. The purity of the high-purity Ar gas is greater than 99%. The C-coated B powder is pressed into a B rod with uniform length by a powder pressing machine. The average particle size of the C-coated B powder is 1000 nm, the mass fraction of C in the powder is 10%, the diameter of the pressed B rod is 2.50mm, the length is 0.5m, the pressure used by the powder pressing machine is 30Mpa, the process is carried out in a high-purity Ar gas protection environment, the purity of the high-purity Ar gas is >99%, the B rod is inserted into the hole on the Mg ingot, and then the whole is inserted into the pickled Nb / Cu composite tube, the outer diameter of the Nb tube is 27.00mm, and the thickness is 3.00mm; the outer diameter of the oxygen-free Cu tube is 34.00mm, and the thickness is 3.00mm; after rotary forging and rolling, it is processed into a round single core rod, the pass processing amount is 10%, and the final diameter of the round single core rod is 4.00mm, the round single core rod with a diameter of 4.00mm and an oxygen-free Cu rod with a diameter of 4.00mm are pickled and inserted into the pickled NCu30 tube, the outer diameter of the NCu30 tube is 35mm, and the thickness is 3mm, and it is drawn into Φ0.8 The Φ0.5 mm circular composite wire was finally obtained by processing 10% of the wire in each pass. The Φ0.5 mm circular composite wire was kept at 700 °C for 3 h in a vacuum environment to obtain the MgB2 superconducting wire with superconducting properties.

[0037] In a possible embodiment, 8 holes arranged in an annular pattern are drilled on a Mg ingot by drilling technology. The Mg ingot is a cylindrical ingot with a purity of 99.99%, a diameter of 20.00 mm, a length of 0.5 m, and a diameter of 3.00 mm. The process is carried out in a high-purity Ar gas protection environment. The purity of the high-purity Ar gas is greater than 99%. The C-coated B powder is pressed into a B rod with uniform length by a powder pressing machine. The average particle size of the C-coated B powder is 1000 nm, the mass fraction of C in the powder is 10%, the diameter of the pressed B rod is 2.50mm, the length is 0.5m, the pressure used by the powder rod press is 10Mpa, the process is carried out in a high-purity Ar gas protection environment, the purity of the high-purity Ar gas is >99%, the B rod is inserted into the hole on the Mg ingot, and then the whole is inserted into the Nb / Cu composite tube after pickling, the outer diameter of the Nb tube is 27.00mm, and the thickness is 3.00mm; the outer diameter of the oxygen-free Cu tube is 34.00mm, and the thickness is 3.00mm; after rotary forging and rolling, it is processed into a round single core rod, the pass processing amount is 10%, and the final diameter of the round single core rod is 4.00mm, the round single core rod with a diameter of 4.00mm and an oxygen-free Cu rod with a diameter of 4.00mm are pickled and inserted into the pickled NCu30 tube, the outer diameter of the NCu30 tube is 35mm, and the thickness is 3mm, and it is drawn into Φ0.8 The Φ0.5 mm circular composite wire was finally obtained by processing 10% of the wire in each pass. The Φ0.5 mm circular composite wire was kept at 700 °C for 3 h in a vacuum environment to obtain the MgB2 superconducting wire with superconducting properties.

[0038] In a possible embodiment, 10 holes arranged in an annular pattern are drilled on a Mg ingot by drilling technology. The Mg ingot is a cylindrical ingot with a purity of 99.99%, a diameter of 30.00 mm, a length of 0.5 m, and a diameter of 3.00 mm. The process is carried out in a high-purity Ar gas protection environment. The purity of the high-purity Ar gas is greater than 99%. The C-coated B powder is pressed into a B rod with uniform length by a powder pressing machine. The average particle size of the C-coated B powder is 1000 nm, the mass fraction of C in the powder is 10%, the diameter of the pressed B rod is 2.50mm, the length is 0.5m, the pressure used by the powder pressing machine is 20Mpa, the process is carried out in a high-purity Ar gas protection environment, the purity of the high-purity Ar gas is >99%, the B rod is inserted into the hole on the Mg ingot, and then the whole is inserted into the pickled Nb / Cu composite tube, the outer diameter of the Nb tube is 27.00mm, and the thickness is 3.00mm; the outer diameter of the oxygen-free Cu tube is 34.00mm, and the thickness is 3.00mm; after rotary forging and rolling, it is processed into a round single core rod, the pass processing amount is 10%, and the final diameter of the round single core rod is 4.00mm, the round single core rod with a diameter of 4.00mm and an oxygen-free Cu rod with a diameter of 4.00mm are pickled and inserted into the pickled NCu30 tube, the outer diameter of the NCu30 tube is 35mm, and the thickness is 3mm, and it is drawn into Φ0.8 The Φ0.5 mm circular composite wire was finally obtained by processing 10% of the wire in each pass. The Φ0.5 mm circular composite wire was kept at 700 °C for 3 h in a vacuum environment to obtain the MgB2 superconducting wire with superconducting properties.

[0039] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional 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 that fall within the scope of the present invention.

[0040] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing MgB2 superconducting wire by drilling a Mg ingot, characterized in that: include: Drilling Mg ingots in a vacuum environment or a high-purity Ar gas protection environment; In a vacuum environment or a high-purity Ar gas protection environment, the C-coated B powder is pressed into B rods of uniform length by a powder rod pressing machine; After placing the B rod into the hole of the Mg ingot, the Mg ingot is placed into a sheath; Processing the sheath in which the B rod and the Mg ingot are placed into a round single core rod by rotary forging and rolling processes; The round single core rod and the oxygen-free Cu rod are pickled and placed together in the pickled NCu30 tube to be drawn, swaged and rolled to form a multi-core composite wire; The multi-core composite wire is heat treated to produce a MgB2 superconducting wire.

2. The method for preparing MgB2 superconducting wire by drilling a hole in a Mg ingot according to claim 1, characterized in that: The Mg ingot is a cylindrical ingot, and a plurality of holes are provided in the Mg ingot.

3. The method for preparing MgB2 superconducting wire by drilling a hole in a Mg ingot according to claim 2, characterized in that: The sheath is a Nb / Cu composite metal sheath, the inner side of the sheath is a Nb tube, and the outer side of the sheath is an oxygen-free Cu tube.

4. The method for preparing MgB2 superconducting wire by drilling a hole in a Mg ingot according to claim 1, characterized in that: The cross section of the oxygen-free Cu rod is circular, and the heat treatment of the oxygen-free Cu rod is annealed.

5. The method for preparing MgB2 superconducting wire by drilling a hole in a Mg ingot according to claim 1, characterized in that: The heat treatment of the multi-core composite wire to form the MgB2 superconducting wire is performed in a vacuum environment.

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