Powder loading device and method for preparing magnesium diboride superconducting wire by central Mg diffusion method

Abstract

The present invention discloses a powder loading device and method for preparing magnesium diboride superconducting wire using a central Mg diffusion method. The method comprises preparing two matching semicircular stainless steel troughs and four copper tubes, and forming closed grooves in each of the two semicircular stainless steel troughs. A copper tube is sleeved and fixed at one end of the semicircular stainless steel trough. One end of a niobium foil is pressed against the copper tube and spread over the inner wall of the stainless steel trough, with the niobium foil being pressed against the inner wall of the stainless steel trough. Another copper tube is fixed to the niobium foil at the other end of the stainless steel trough. Boron powder is filled and continuously compacted to form two semicircular boron powder grooves wrapped with niobium foil. A magnesium rod is inserted into the center of the two matching copper tubes, and a semicircular groove for the magnesium rod is pressed into the center of the boron powder in the semicircular groove. The two semicircular boron powder columns wrapped with niobium foil and with magnesium rod grooves are combined and inserted into a barrier sleeve serving as a barrier layer. After drawing and rolling, a uniform and dense single-core wire is produced. The present invention facilitates optimization of the tube loading process and is more conducive to automated tube loading.

Description

Technical Field

[0001] The present invention relates to the technical field of superconducting material processing, in particular to a powder loading device and method for preparing magnesium diboride superconducting wires using a central Mg diffusion method. Background Art

[0002] Since MgB2 was discovered by Japanese scholars in 2001, it has been widely used due to its high transition temperature ( T c =39K), a large coherence length, low anisotropy, and strongly coupled grain boundaries—excellent superconducting properties—have attracted widespread attention in both the academic and applied fields of superconductivity, injecting new vitality into the development of superconducting materials. Due to the abundance and availability of materials for preparing MgB2 and its excellent performance, it is expected to be used in magnetic resonance imaging (MRI), superconducting transmission cables, wind turbine power generation, and other fields.

[0003] In the two decades since the discovery of MgB2's superconductivity, the production methods for MgB2 superconductors have evolved into two methods: the PIT (Powder in Tube) method and the IMD (also known as AIMI) method. The PIT method is further divided into the ex-situ and in-situ methods. The difference between the two is that the ex-situ method involves placing MgB2 powder into a metal tube, while the in-situ method involves mixing Mg and B powders in a specific ratio and then placing them into the tube. The single-core wire undergoes multiple forging and drawing steps to a specific size, then is cut into lengths and assembled into multi-core wires. These assembled multi-core wires are then forged and drawn again to a specific size. The PIT method is simple and suitable for large-scale wire production. However, wires produced by the PIT method suffer from poor grain connectivity, the formation of numerous voids after heat treatment, and a low density of the resulting MgB2 phase, all of which severely limit the performance of MgB2. Subsequently, researchers developed the central magnesium diffusion (IMD) method. As the name suggests, this method involves fixing a Mg rod in the center of a metal tube and filling the gap with boron powder. During heat treatment, the central magnesium rod penetrates and diffuses into the outer boron powder layer, where it reacts with the boron powder to form MgB2.

[0004] Compared to the PIT method, the IMD method produces a denser MgB2 layer with better grain connectivity. This overcomes the limitation of the PIT method, where a large number of voids in the superconducting phase limit the superconducting performance of MgB2. Instead, the central void is left after the magnesium rod has fully diffused and reacted. Therefore, wires produced by the IMD method have superior performance and should be the only choice to replace the PIT method for large-scale production of MgB2 superconducting wires. However, this often goes against expectations. Compared to the PIT method, which directly loads powder into the tube, the IMD method loads boron powder into the gap between the magnesium rod and the barrier layer and compacts it. The gap is often very small, and the powder loading process is complicated and tedious. These unfavorable factors have seriously limited the promotion and application of the IMD method. Summary of the Invention

[0005] The purpose of the present invention is to provide a powder loading device and method for preparing magnesium diboride superconducting wires using a central Mg diffusion method, thereby simplifying the tube loading steps and thereby shortening the preparation cycle of MgB2 superconducting wires.

[0006] The technical solution adopted in the present invention is:

[0007] A powder loading method for preparing magnesium diboride superconducting wire by a central Mg diffusion method comprises the following steps:

[0008] Step 1: Prepare two matching semicircular stainless steel troughs and four copper tubes. The outer diameter of the copper tubes is smaller than the inner diameter of the semicircular stainless steel troughs.

[0009] Step 2: Make a closed groove at both ends for filling boron powder on each of the two semicircular stainless steel tanks; the method for making each closed groove is as follows:

[0010] A copper tube is fixed at one end of a semicircular stainless steel trough. Then, one end of a niobium foil is pressed against the copper tube to cover the inner wall of the stainless steel trough. A stainless steel rod with the same outer diameter as the copper tube is used to press the niobium foil against the inner wall of the stainless steel trough. Another copper tube is then fixed to the niobium foil at the other end of the stainless steel trough.

[0011] Step 3: Fill the closed grooves at both ends with boron powder and continuously compact until the grooves are full of boron powder, thereby obtaining two semicircular boron powder grooves wrapped with niobium foil;

[0012] Step 4: Insert the magnesium rod into the center of the two copper tubes at both ends of the same semicircular stainless steel groove, and press out a semicircular groove for the magnesium rod in the center of the boron powder in the semicircular groove;

[0013] Step 5: Put two niobium foil-wrapped semicircular boron powder columns with magnesium rod grooves together and insert them into a barrier sleeve as a barrier layer, and prepare a uniform and dense single-core wire through drawing and rolling.

[0014] Furthermore, in step 1, the inner diameter of the semicircular stainless steel trough is 7.8 mm, and the outer diameter is 10 mm; the inner diameter of the copper tube is 3 mm, the outer diameter is 7.5 mm, and the length is 2 cm.

[0015] Furthermore, in step 2, the niobium foil has a width of 24.5 mm, a length of 30 cm, and a thickness of 0.1 mm.

[0016] Furthermore, in step 2, the outer diameter of the stainless steel rod is 7.5 mm.

[0017] Furthermore, in step 5, the inner diameter of the barrier sleeve is larger than the inner diameter of the stainless steel tank; the inner diameter of the barrier sleeve is 8 mm.

[0018] Furthermore, in step 5, a rotary swaging machine is used to make the niobium foil wrapped with the semicircular boron powder with the magnesium rod groove completely adhere to the inner wall of the barrier sleeve before drawing and rolling.

[0019] The powder loading device for preparing magnesium diboride superconducting wire by the central Mg diffusion method includes a matching barrier sleeve, two semicircular stainless steel tanks and four copper tubes;

[0020] A copper tube is fixed on one end of each semicircular stainless steel trough, and one end of a niobium foil is pressed against the copper tube and covers the inner wall of the stainless steel trough; the outer diameter of the stainless steel rod is the same as the outer diameter of the copper tube, and the stainless steel rod is used to press the niobium foil laid on the inner wall of the stainless steel trough so that the niobium foil is pressed against the inner wall of the stainless steel trough, and another copper tube is fixed on the niobium foil at the other end of each stainless steel trough to form a closed trough at both ends for filling boron powder, and the closed trough is filled with boron powder to obtain a semicircular boron powder; the inner diameter of the copper tube is larger than the outer diameter of the magnesium rod, and the magnesium rod can be removably inserted into the center of the two copper tubes at both ends of the same semicircular stainless steel trough, and the magnesium rod is used to press out a semicircular groove for the magnesium rod in the center of the semicircular boron powder; the inner diameter of the barrier sleeve is larger than the outer diameter of the semicircular stainless steel trough, so that the barrier sleeve can be inserted after the two semicircular stainless steel troughs are combined.

[0021] Furthermore, the barrier sleeve is a niobium tube.

[0022] This invention utilizes the above technical solution, based on an improved external-tube powder loading method based on the central magnesium diffusion (IMD) method. This makes the loading process simpler and faster, and produces a more uniform and dense boron powder. This ensures the quality of the MgB2 superconducting wire from the source, replacing the complex and tedious gap loading process, resulting in improved longitudinal uniformity of the wire. The loading process offers greater controllability, deconstructing and simplifying the complex original IMD method, further facilitating its industrialization. Furthermore, this provides a new approach to the industrialization of the IMD method, allowing desired drawing dimensions to be achieved by varying the dimensions of materials such as stainless steel troughs, copper tubes, and niobium foil. This makes the loading process easier to optimize and facilitates automated production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments;

[0024] Figure 1 This is a structural diagram of a copper tube sleeve fixed at one end in a semicircular stainless steel groove;

[0025] Figure 2 This is a schematic diagram of the structure after the copper tube is fixed on the semicircular niobium foil;

[0026] Figure 3 Schematic diagram of the structure of the boron powder tank wrapped with niobium foil;

[0027] Figure 4 This is a schematic diagram of the structure after the magnesium rod is pressed into a semicircular groove;

[0028] Figure 5Schematic diagram of the structure of two semicircular boron powder columns inserted into the barrier sleeve. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0030] like Figures 1 to 5 As shown in FIG1 , the present invention discloses a powder loading method for preparing magnesium diboride superconducting wire by a central Mg diffusion method, which comprises the following steps:

[0031] Step 1: prepare two matching semicircular stainless steel tanks 1 and four copper tubes 2, where the outer diameter of the copper tubes 2 is smaller than the inner diameter of the semicircular stainless steel tank 1;

[0032] Step 2: Make a closed groove at both ends for filling boron powder on each of the two semicircular stainless steel tanks 1; the method for making each closed groove is as follows:

[0033] A copper tube 2 is fixed on one end of a semicircular stainless steel tank 1. Then, one end of a niobium foil 3 is pressed against the copper tube 2 to cover the inner wall of the stainless steel tank 1. A stainless steel rod with the same outer diameter as the copper tube 2 is used to press the niobium foil 3 against the inner wall of the stainless steel tank 1. Another copper tube 2 is then fixed to the niobium foil 3 at the other end of the stainless steel tank 1.

[0034] Step 3: Fill the closed grooves at both ends with boron powder and continuously compact until the grooves are full of boron powder, thereby obtaining two semicircular boron powder grooves 4 wrapped with niobium foil 3;

[0035] Step 4: Insert the magnesium rod into the center of the two copper tubes 2 at both ends of the same semicircular stainless steel groove 1, and press out a semicircular groove 5 of the magnesium rod in the center of the boron powder in the semicircular groove;

[0036] In step 5, two semicircular boron powder columns with magnesium rod grooves wrapped in niobium foils 3 are put together and inserted into a barrier sleeve 6 as a barrier layer, and then drawn and rolled to prepare a uniform and dense single-core wire.

[0037] Furthermore, in step 1, the inner diameter of the semicircular stainless steel tank 1 is 7.8 mm, and the outer diameter is 10 mm; the inner diameter of the copper tube 2 is 3 mm, the outer diameter is 7.5 mm, and the length is 2 cm.

[0038] Furthermore, in step 2, the niobium foil 3 has a width of 24.5 mm, a length of 30 cm, and a thickness of 0.1 mm.

[0039] Furthermore, in step 2, the outer diameter of the stainless steel rod is 7.5 mm.

[0040] Furthermore, in step 5, the inner diameter of the barrier sleeve 6 is larger than the inner diameter of the stainless steel tank 1; the inner diameter of the barrier sleeve 6 is 8 mm.

[0041] Furthermore, in step 5, a rotary swaging machine is used to make the semicircular boron powder-wrapped niobium foil 3 with magnesium rod grooves completely adhere to the inner wall of the barrier sleeve 6 before drawing and rolling.

[0042] A powder loading device for preparing magnesium diboride superconducting wire using a central Mg diffusion method, comprising a matching barrier sleeve 6, two semicircular stainless steel troughs 1, and four copper tubes 2;

[0043] A copper tube 2 is fixed on one end of each semicircular stainless steel trough 1, and one end of a niobium foil 3 is pressed against the copper tube 2 and covers the inner wall of the stainless steel trough 1; the outer diameter of the stainless steel rod is the same as the outer diameter of the copper tube 2, and the stainless steel rod is used to press the niobium foil 3 laid on the inner wall of the stainless steel trough 1 so that the niobium foil 3 is pressed against the inner wall of the stainless steel trough 1, and another copper tube 2 is fixed on the niobium foil 3 at the other end of each stainless steel trough 1 to form a closed trough at both ends for filling boron powder, and the closed trough is filled with boron powder to obtain a semicircular boron powder; the inner diameter of the copper tube 2 is larger than the outer diameter of the magnesium rod, and the magnesium rod can be removably inserted into the center of the two copper tubes 2 at both ends of the same semicircular stainless steel trough 1, and the magnesium rod is used to press out a semicircular groove 5 for the magnesium rod in the center of the semicircular boron powder; the inner diameter of the barrier sleeve 6 is larger than the outer diameter of the semicircular stainless steel trough 1, so that the barrier sleeve 6 can be inserted after the two semicircular stainless steel troughs 1 are combined.

[0044] Furthermore, the barrier sleeve 6 is a niobium tube.

[0045] The specific working principle of the present invention is described in detail below:

[0046] As an embodiment, a powder loading method for preparing magnesium diboride superconducting wire by a central Mg diffusion method comprises the following steps:

[0047] Step 1, prepare a material device for rapid powder loading;

[0048] (1) Take two semicircular stainless steel tanks 1 with an inner diameter of 7.8 mm and an outer diameter of 10 mm.

[0049] (2) Cut a copper tube 2 with an inner diameter of 3 mm, an outer diameter of 7.5 mm, and a length of 2 cm.

[0050] (3) Cut a niobium foil 3 with a width of 24.5 mm, a length of 30 cm, and a thickness of 0.1 mm.

[0051] (4) Prepare a magnesium rod 32 cm long and 3 mm in diameter and boron powder.

[0052] (5) Prepare a stainless steel rod with a diameter of 7.5 mm.

[0053] (6) Take a niobium tube with an inner diameter of 8 mm and clean it to use as a barrier layer.

[0054] Step 2, such as Figure 1As shown, the copper tube 2 is fixed in the semicircular stainless steel tank 1 and then one end of the prepared niobium foil 3 is placed close to the copper tube 2 and laid on the inner wall of the stainless steel tank 1. The niobium foil 3 is pressed tightly with a stainless steel rod. Figure 2 As shown, a copper tube 2 is then fixed on the niobium foil 3 at the other end of the stainless steel tube, thus forming a groove with closed ends as shown below. Repeat step 2 to make two grooves.

[0055] Step 3, such as Figure 3 As shown, the trough is then filled with boron powder and compacted continuously until the trough is filled with boron powder. Two such boron powder troughs 4 wrapped with niobium foil 3 are installed:

[0056] Step 4: Then insert the magnesium rod into the center of the two copper tubes 2 and press out the boron powder in the center of the semicircular groove. Figure 4 The area of the magnesium rod semicircular groove 5 is shown. Two such samples were made by combining two semicircular boron powder columns wrapped with niobium foil 3 and inserting them into the barrier layer.

[0057] Step 5, such as Figure 5 As shown in the figure, the two semi-cylindrical boron powders are combined into a diameter of 7.8mm, which can be easily inserted into a niobium tube with an inner diameter of 8mm. Then, a rotary swaging machine can be used to make the inner wall completely close to each other. After drawing and rolling, a uniform and dense single-core wire is produced.

[0058] This invention utilizes the above technical solution, based on an improved external-tube powder loading method based on the central magnesium diffusion (IMD) method. This makes the loading process simpler and faster, and produces a more uniform and dense boron powder. This ensures the quality of the MgB2 superconducting wire from the source, replacing the complex and tedious gap-loading process, resulting in improved longitudinal uniformity of the wire. The loading process offers greater controllability, deconstructing and simplifying the cumbersome original IMD method, further facilitating its industrialization. Furthermore, this provides a new approach to the industrialization of the IMD method, allowing desired drawing dimensions to be achieved by varying the dimensions of materials such as the stainless steel tank 1, copper tube 2, and niobium foil 3. This makes the loading process easier to optimize and facilitates automated production.

[0059] Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. In the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present application is not intended to limit the scope of the application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

Claims

1. A powder loading method for preparing magnesium diboride superconducting wire by a central Mg diffusion method, characterized in that: A powder loading device for preparing a magnesium diboride superconducting wire using a central Mg diffusion method is used, and the powder loading method includes the following steps: Step 1: Prepare two matching semicircular stainless steel troughs and four copper tubes. The outer diameter of the copper tubes is smaller than the inner diameter of the semicircular stainless steel troughs. Step 2: Make a closed groove at both ends for filling boron powder on each of the two semicircular stainless steel tanks; the method for making each closed groove is as follows: A copper tube is fixed at one end of a semicircular stainless steel trough. Then, one end of a niobium foil is pressed against the copper tube to cover the inner wall of the stainless steel trough. A stainless steel rod with the same outer diameter as the copper tube is used to press the niobium foil against the inner wall of the stainless steel trough. Another copper tube is then fixed to the niobium foil at the other end of the semicircular stainless steel trough. Step 3: Fill the closed grooves at both ends with boron powder and continuously compact until the grooves are full of boron powder, thereby obtaining two semicircular boron powder grooves wrapped with niobium foil; Step 4: Insert the magnesium rod into the center of the two copper tubes at both ends of the same semicircular stainless steel groove, and press out a semicircular groove for the magnesium rod in the center of the boron powder in the groove; Step 5: Two semicircular boron powder columns wrapped with niobium foil and having semicircular grooves for magnesium rods are combined and inserted into a barrier sleeve as a barrier layer, and then drawn and rolled to prepare a uniform and dense single-core wire; In step 5, a rotary swaging machine is used to make the niobium foil wrapped with the semicircular boron powder and the semicircular groove of the magnesium rod completely close to the inner wall of the barrier sleeve before drawing and rolling; Wherein, the powder loading device comprises a barrier sleeve and two semicircular stainless steel grooves; A copper tube is fixed on one end of each semicircular stainless steel trough, and one end of a niobium foil is pressed against the copper tube and covers the inner wall of the semicircular stainless steel trough; the outer diameter of the stainless steel rod is the same as the outer diameter of the copper tube, and the stainless steel rod is used to press the niobium foil laid on the inner wall of the stainless steel trough so that the niobium foil is pressed against the inner wall of the semicircular stainless steel trough, and another copper tube is fixed on the niobium foil at the other end of each semicircular stainless steel trough to form a closed trough at both ends for filling boron powder, and the closed trough is filled with boron powder to obtain a semicircular boron powder; the inner diameter of the copper tube is larger than the outer diameter of the magnesium rod, and the magnesium rod can be removably inserted into the center of the two copper tubes at both ends of the same semicircular stainless steel trough, and the magnesium rod is used to press out a semicircular groove for the magnesium rod in the center of the semicircular boron powder; the inner diameter of the barrier sleeve is larger than the outer diameter of the semicircular stainless steel trough; the barrier sleeve is a niobium tube.

2. The powder loading method for preparing magnesium diboride superconducting wire by central Mg diffusion method according to claim 1, characterized in that: The inner diameter of the semicircular stainless steel trough is 7.8 mm and the outer diameter is 10 mm; the inner diameter of the copper tube is 3 mm, the outer diameter is 7.5 mm, and the length is 2 cm.

3. The powder loading method for preparing magnesium diboride superconducting wire by central Mg diffusion method according to claim 1, characterized in that: The niobium foil is 24.5 mm wide, 30 cm long and 0.1 mm thick.

4. The powder loading method for preparing magnesium diboride superconducting wire by central Mg diffusion method according to claim 1, characterized in that: The outer diameter of the stainless steel rod is 7.5 mm.

5. The powder loading method for preparing magnesium diboride superconducting wire by central Mg diffusion method according to claim 1, characterized in that: The inner diameter of the barrier sleeve is 8 mm.

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