Method for preparing MgB2 superconducting wire by drilling Mg ingot

Abstract

The invention discloses a method for preparing an MgB2 superconducting wire by drilling an Mg ingot. The method comprises the following steps: drilling the Mg ingot; pressing the C-coated B powder into a bar B with uniform length; processing the placed B rod and Mg ingot into a circular single-core rod; the round single-core rod and the oxygen-free Cu rod are subjected to acid pickling treatment and then jointly put into an NCu30 pipe subjected to acid pickling treatment to be manufactured into a multi-core composite wire; and performing heat treatment on the multi-core composite wire to prepare the MgB2 superconducting wire. A hole is drilled in the Mg ingot, B powder is pressed into a B rod by a powder rod pressing machine to be stuffed into the hole, and Mg uniformly permeates into the B powder from the periphery to react, so that Mg and B react more thoroughly, the problem that the B powder is left and does not react frequently in the IMD method is avoided, the powder filling problem during preparation of the single-core rod is effectively avoided, rapid preparation of the IMD method single-core rod is realized, and the production cost is reduced. And the powder loading density of the B powder is greatly improved.

Description

Technical Field

[0001] The present 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 holds significant research and application value. Superconducting materials possess two fundamental properties: zero resistance and the Meissner effect. The zero resistance property states that when a superconducting material's temperature falls below a certain critical temperature (Tc), its electrical resistance gradually decreases and eventually vanishes, allowing current to flow through it without loss. However, the lossless current that a superconducting material can carry is limited; exceeding a certain maximum value, known as the superconducting critical current (IC), causes the material to lose its superconducting properties. The Meissner effect occurs when an external magnetic field is applied to a superconducting material in its superconducting state. This field induces a superconducting screening current on its surface, preventing the magnetic field from entering the superconductor's interior. However, this magnetic field shielding effect is limited: when the external magnetic field exceeds a certain critical magnetic field (Hc), the magnetic field enters the superconductor or causes the superconducting material to lose its superconducting properties. These two properties have led to a wide range of applications for superconducting materials, including 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 includes NbTi, Nb3Sn, etc., and the latter includes 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] Currently, the main methods for preparing MgB2 superconducting wires include the powder-in-tube method (PIT) and the integrated magnesium diffusion method (IMD). The IMD method primarily uses Mg rods and boron powder as raw materials. The Mg rod is first inserted into the center of a metal sheath. B powder is then filled between the Mg rod and the sheath, forming a Mg rod / B powder / sheath structure from the inside out. The wire is then processed into specific specifications through swaging, rolling, and drawing. The metal sheath used in the IMD method primarily consists of materials such as Nb, Fe, and Ni. The IMD method can significantly improve the density and grain connectivity of the MgB2 superconducting phase in the wire, increasing the critical current density Jc, thereby enhancing the wire's superconducting current-carrying capacity and reducing losses in AC conditions. However, the IMD method often suffers from the problem of unreacted boron powder residue, and the difficulty of filling the boron powder makes it difficult to prepare quickly. Summary of the Invention

[0005] The embodiment of the present invention provides a method for preparing MgB2 superconducting wire by drilling Mg ingots, which is used to solve the problems in the prior art of residual unreacted B powder in the IMD method, difficulty in filling B powder, and inconvenience in rapid preparation.

[0006] In one aspect, an embodiment of the present invention provides a method for preparing a MgB2 superconducting wire by drilling a Mg ingot, comprising: 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 with uniform length by a powder pressing machine; After placing the B rod into the hole of the Mg ingot, the Mg ingot is placed into the sheath; Processing the sheath containing the B rod and the Mg ingot into a round single core rod through rotary forging and rolling processes; The round single core rod and oxygen-free Cu rod are pickled and then placed together in the pickled NCu30 tube for drawing, swaging and rolling to produce a multi-core composite wire; The multi-core composite wire is heat-treated to prepare a MgB2 superconducting wire.

[0007] In a possible implementation, the Mg ingot is a cylindrical ingot, and a plurality of holes are provided in the Mg ingot.

[0008] 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.

[0009] In a possible implementation, the cross section of the oxygen-free Cu rod is circular, and the heat treatment of the oxygen-free Cu rod is an annealed state.

[0010] 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.

[0011] The method of preparing MgB2 superconducting wire by drilling Mg ingots in the present invention has the following advantages: (1) Drill holes on the Mg ingot and then insert the B rod into the holes. This structure can achieve the final diffusion reaction to generate the MgB2 superconducting phase. Mg will evenly penetrate into the B powder from the surrounding area to react, making the reaction between Mg and B more thorough. This avoids the problem of unreacted B powder residue that often occurs in the IMD method and improves the quality and performance of the wire.

[0012] (2) Then it is 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

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0014] Figure 1 A schematic diagram of drilling holes in a Mg ingot according to a method for preparing MgB2 superconducting wire by drilling holes in a Mg ingot provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0016] Figure 1 A schematic diagram of drilling a hole on a Mg ingot according to a method for producing a MgB2 superconducting wire by drilling a hole on a Mg ingot provided in an embodiment of the present invention; an embodiment of the present invention provides a method for producing a MgB2 superconducting wire by drilling a hole on a Mg ingot, comprising: 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 with uniform length by a powder pressing machine; After placing the B rod into the hole of the Mg ingot, the Mg ingot is placed into the sheath; Processing the sheath containing the B rod and the Mg ingot into a round single core rod through rotary forging and rolling processes; The round single core rod and oxygen-free Cu rod are pickled and then placed together in the pickled NCu30 tube for drawing, swaging and rolling to produce a multi-core composite wire; heat-treating the multi-core composite wire to form a MgB2 superconducting wire; The Mg ingot is a cylindrical ingot, and the Mg ingot is provided with a plurality of holes; 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; The cross section of the oxygen-free Cu rod is circular, and the heat treatment of the oxygen-free Cu rod is annealed; The heat treatment of the multi-core composite wire to form the MgB2 superconducting wire is performed in a vacuum environment.

[0017] For example, first, 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 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.

[0018] 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, and a length of 0.5 m to 10.0 m. The number of holes drilled on the Mg ingot is 1 to 30, the diameter of the holes is 3.00 mm to 10.00 mm, the vacuum pressure is less than 1 Pa or the purity of high-purity Ar gas is greater than 95%, and the average particle size of the C-coated B powder is 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 greater than 95%, the metal sheath is a Nb / Cu composite tube, wherein 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%~99.9%, an outer diameter of 10.00mm~120.00mm, a thickness of 0.50mm~5.00mm, and a processing amount of 5%~25% during the swaging and rolling process. The diameter of the final round single core rod is 2.00mm~10.00mm, and the cross section of the oxygen-free Cu rod is circular, with a purity of 99.90%~99.99% and a diameter of 1.00mm~30.00mm; the outer diameter of the NCu30 tube is 20 mm~70 mm, with a wall thickness of 2 mm~10 mm, in the annealed state; the processing amount of the drawing, swaging, and rolling processes is 5%~25%, and the cross-section of the finally obtained multi-core composite wire is circular with a diameter of 0.1 mm~2 mm. The heat treatment temperature range is 550°C~900°C, the holding time is 0.5h~20h, and the heat treatment conditions are a vacuum environment.

[0019] In one possible embodiment, six holes arranged in a ring are drilled on a Mg ingot using a drilling technique. 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 B rods of uniform length using 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 greater than 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 then inserted into the pickled NCu30 tube. The outer diameter of the NCu30 tube is 35mm and the thickness is 3mm. 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 a MgB2 superconducting wire with superconducting properties.

[0020] In one possible embodiment, eight holes arranged in a ring are drilled on a Mg ingot using a drilling technique. 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 B rods of uniform length using 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 10Mpa, 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 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 then inserted into the pickled NCu30 tube. The outer diameter of the NCu30 tube is 35mm and the thickness is 3mm. 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 a MgB2 superconducting wire with superconducting properties.

[0021] In one possible embodiment, 10 holes arranged in a ring are drilled on a Mg ingot using a drilling technique. 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 B rods of uniform length using 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 greater than 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. 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 a MgB2 superconducting wire with superconducting properties.

[0022] 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 all changes and modifications that fall within the scope of the present invention and the preferred embodiments.

[0023] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing MgB by drilling Mg ingots 2 Superconducting wire method, It is 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 form MgB 2 Superconducting wire.

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

3. A method for preparing MgB by drilling a Mg ingot according to claim 2 2 Superconducting wire method, It is 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 MgB by drilling a Mg ingot according to claim 1 2 Superconducting wire method, It is 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 MgB by drilling a Mg ingot according to claim 1 2 Superconducting wire method, It is characterized in that The multi-core composite wire is heat treated to form MgB 2 Superconducting wire is heat treated in a vacuum environment.

Images