A device for preparing high-performance MgB2 superconducting wire by fast hot rolling and quenching

Abstract

The application relates to a device for preparing high-performance MgB2 superconducting wire through fast hot rolling and quenching, which comprises a closed space with protective gas formed by an insulating epoxy plate, two positive electrode brushes arranged on an aluminum profile frame in the closed space, the two positive electrode brushes being in close contact with each other through corresponding built-in springs in an opposite mode; a double-roller rolling machine is arranged at the right end of the two positive electrode brushes, two negative electrode brushes are arranged on the outer aluminum profile frame of the double-roller rolling machine, and the two negative electrode brushes are in close contact with the surfaces of the upper roller shaft and the lower roller shaft of the double-roller rolling machine through corresponding built-in springs respectively; a low-temperature Dewar is arranged on the aluminum profile frame at the right end of the double-roller rolling machine, and the low-temperature Dewar is internally provided with a coolant. The device can perform fast hot rolling and quenching treatment on MgB2 superconducting wire, is simple in operation, low in cost, shortens the preparation time, and produces MgB2 wire which is excellent in performance and practical.

Description

Technical Field

[0001] This invention relates to the field of superconducting material preparation technology, specifically to an apparatus for preparing high-performance MgB2 superconducting wires by rapid hot rolling and quenching. Background Technology

[0002] Since the discovery of superconductivity in MgB2 in 2001, its superconducting properties have been greatly improved over the past 20 years, and its current-carrying capacity under external fields has also been significantly enhanced. As a major application of MgB2 superconductors, MgB2 superconducting wires have received considerable attention in recent years. Due to its large coherence length and low anisotropy, it can be more easily fabricated into practical wires. Its relatively high critical transition temperature (…) T C =39K), which can greatly reduce application costs. In terms of practical applications, Columbus Superconductor in Italy has achieved mass production of kilometer-level MgB2 wire, and Hyper Tech in the United States has also produced 18-core high-performance, practical MgB2 wire. The Institute of Electrical Engineering of the Chinese Academy of Sciences and the Northwest Institute of Nonferrous Metals of China have also produced MgB2 wire with high performance.

[0003] It can be seen that through continuous research in recent years, the performance of MgB2 wire has been fundamentally improved, and it possesses great potential for practical application. However, due to defects in the current preparation process, there are still many problems in the preparation technology of MgB2 wire that urgently need to be solved. For example, the density of wire prepared by the in-situ method is poor, while the weak grain bonding phenomenon is serious in the wire prepared by the pre-situ method. At the same time, the lack of effective pinning centers leads to a rapid decrease in the performance of the wire under high fields. At present, the preparation of wire still mainly relies on heat treatment equipment such as tube furnaces and muffle furnaces. Although these equipment can meet the normal preparation requirements, they cannot overcome the problems caused by the in-situ and pre-situ methods mentioned above. These preparation problems will seriously affect the superconducting performance of MgB2 wire and hinder its further application development. Summary of the Invention

[0004] To effectively address the problems existing in the current MgB2 wire preparation technology, this invention proposes a device for preparing high-performance MgB2 superconducting wires by rapid hot rolling and quenching. This device can roll the wire to a certain thickness at high temperature and immediately quench it after rolling. The wire produced has a high qualification rate, short preparation time, and low cost, which can effectively improve the problems in the current MgB2 wire preparation technology and greatly meet the needs of practical application.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An apparatus for preparing high-performance MgB2 superconducting wires by rapid hot rolling and quenching includes a sealed space filled with a protective gas and constructed of insulating epoxy board. Two positive electrode brushes are mounted on an aluminum profile frame inside the sealed space, and the two positive electrode brushes are in close contact with each other via corresponding internal springs. A twin-roll mill is placed at the right end of the two positive electrode brushes. Two negative electrode brushes are mounted on the outer aluminum profile frame of the twin-roll mill, and the two negative electrode brushes are in close contact with the surfaces of the upper and lower rolls of the twin-roll mill via corresponding internal springs. A cryogenic Dewar is placed on the right-end aluminum profile frame of the twin-roll mill, and the cryogenic Dewar contains a coolant. Positive and negative leads of an external power supply are welded to the two positive electrode brushes and the two negative electrode brushes, respectively.

[0007] Furthermore, the upper roller of the twin-roll mill is fixed with an upper gear at its shaft end, and the lower roller of the twin-roll mill is fixed with a lower gear at its shaft end, with the upper gear and the lower gear meshing with each other; the mill handle is fixed to the outside of the upper transmission gear.

[0008] Furthermore, a gas cylinder through-plate connector is installed on the high-insulation epoxy board at the front end.

[0009] Furthermore, the twin-roll mill is equipped with a roller movement valve above it, which is connected to the upper and lower rollers and is used to adjust the distance between the upper and lower rollers.

[0010] Furthermore, the external power supply is a DC regulated power supply.

[0011] Furthermore, the cryogenic Dewar is equipped with a rotatable roller inside.

[0012] Furthermore, the coolant is liquid nitrogen, liquid gallium, or a gallium-indium alloy.

[0013] Furthermore, the two positive electrode brushes and the two negative electrode brushes are composed of high-carbon brushes, high-copper brushes, or other similar single electrode devices or any combination of two or more electrode devices.

[0014] Furthermore, high-precision thermocouple probes or infrared thermometers are placed at the contact points between the MgB2 precursor wire to be rolled and the twin rollers, as well as near the twin rollers.

[0015] Furthermore, the device is applicable to wire diameters ranging from 0.2 to 5 mm, and the deformation range after rolling is 5% to 75% of the original wire thickness or diameter.

[0016] By adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0017] (1) This invention uses a rapid hot rolling quenching device to process MgB2 superconducting wire, which can raise the wire temperature to above 800°C in a short time, greatly shortening the sample phase formation time. After rolling, the wire can be quenched immediately, and the wire temperature can be reduced to an extremely low temperature in a very short time;

[0018] (2) The present invention processes MgB2 superconducting wires through a fast hot rolling quenching device. When the wire is rolled, it is mainly subjected to the tension of the rolling mill roller shaft and the friction of the positive electrode assembly on the wire. Therefore, the wire will be straightened during heating and will not be over-tightened. Thus, the wire will be rolled evenly during heating and will not break or be thinned due to excessive tension during heating.

[0019] (3) The present invention processes MgB2 superconducting wires by a fast hot rolling quenching device. By controlling the output current of the external power supply, adjusting the size of the distance between the two rollers, and using different coolants, MgB2 superconducting wires with different heating temperatures, different rolling thicknesses, and different cooling rates can be prepared. It requires less equipment, is easy to operate, low in cost, safe and efficient, and has good practical potential. Attached Figure Description

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0021] Figure 1 This is a schematic diagram of the main view structure of an embodiment of the present invention.

[0022] Figure 2 This is a top view of the structure according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the left-side structure according to an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the right-side structure according to an embodiment of the present invention;

[0025] Figure 5 The diagram shows the self-field critical current density of MgB2 superconducting wires prepared using the apparatus of this invention under different conditions (current value, heating time, rolling temperature) at 10K and 20K. Detailed Implementation

[0026] like Figure 1-4As shown, the present invention discloses an apparatus for preparing high-performance MgB2 superconducting wires by rapid hot rolling and quenching. The apparatus includes a sealed space containing a protective gas, formed by an insulating epoxy board 1. Two positive electrode brushes 3 and 3a are mounted on an aluminum profile frame 6 inside the sealed space, and are in close contact with each other via corresponding internal springs 4 and 4a. A twin-roll mill is placed at the right end of the two positive electrode brushes 3 and 3a. Two negative electrode brushes 7 and 7a are mounted on the outer aluminum profile frame 6a of the twin-roll mill, and are in close contact with the surfaces of the upper and lower rollers 11a of the twin-roll mill via corresponding internal springs 8 and 8a. A low-temperature Dewar 14 is placed on the right-end aluminum profile frame 6b of the twin-roll mill, and contains a coolant 15. The positive and negative leads of an external power supply 17 are welded to the two positive electrode brushes 3 and 3a and the two negative electrode brushes 7 and 7a, respectively.

[0027] The high-insulation epoxy board 1 primarily uses transparent insulating material and consists of six panels: front, back, left, right, top, and bottom. Except for the top panel, the gaps between the other panels are filled with high-strength epoxy adhesive. The top panel is connected to the other panels using movable metal hinges, facilitating easy opening and sample placement. A locking system ensures the top panel fits tightly against the other panels, and rubber gaskets seal all contact points to prevent air leakage and enhance airtightness. Notably, a notch is located in the center of the front epoxy board, allowing the rolling mill handle to extend.

[0028] The upper roll 11 and lower roll 11a of the twin-roll mill are both made of metals with high heat capacity, high thermal conductivity and good electrical conductivity, so that they can maintain good stability while providing a good current path when rolling wire.

[0029] An upper gear 12 is fixed to the end of the upper roller 11 of the twin-roll mill, and a lower gear 12a is fixed to the end of the lower roller 11a. The upper gear 12 and the lower gear 12a mesh with each other. The mill handle 9 is fixed to the outside of the upper drive gear 12. The mill handle 9 can control the upper drive gear 12 to drive the lower drive gear 12a, thereby manually controlling the rotational speed and direction of the upper roller 11 and the lower roller 11a, and thus controlling the mill's feed speed, wire infeed, and wire retraction.

[0030] A gas cylinder through-plate connector 2 is installed on the high-insulation epoxy board 1 at the front end for introducing protective gas into the confined space.

[0031] A roller movement valve 10 is installed above the twin-roll mill. The roller movement valve 10 is connected to the upper roller 11 and the lower roller 11a and is used to adjust the distance between the upper roller 11 and the lower roller 11a. The roller movement valve can rotate clockwise or counterclockwise at different angles as required. Different directions of rotation can increase or decrease the distance between the upper roller 11 and the lower roller 11a accordingly. Rotating at different angles can achieve precise control of the increment of the distance between the upper and lower rollers, thereby improving rolling accuracy.

[0032] External power supply 17 is a DC regulated power supply. The DC regulated power supply is stably connected to the positive and negative brush groups through multi-core copper wires. The current output value of the DC regulated power supply can be used to adjust parameters such as the heating rate, temperature gradient, and maximum temperature of the wire.

[0033] The low-temperature Dewar 14 is made of insulating material to prevent leakage. At the same time, the wire inlet of the low-temperature Dewar 14 is precisely aligned with the middle wire outlet position of the upper roller 11 and the upper roller 11a. The low-temperature Dewar 14 is very close to the upper roller 11 and the upper roller 11a but does not contact them. This ensures that the wire can enter the interior of the low-temperature Dewar 14 for quenching immediately and accurately after rolling.

[0034] The low-temperature Dewar 14 has a rotatable roller 13 inside, which can introduce the rolled wire and lead out the quenched wire 16.

[0035] The coolant 15 can be liquid nitrogen, liquid gallium metal, or gallium-indium alloy. By using different coolants, the quenching rate and minimum quenching temperature of the rolled wire can be controlled.

[0036] The two positive electrode brushes 3, 3a and the two negative electrode brushes 3, 3a are composed of high carbon brushes, high copper brushes or other similar single electrode devices or any combination of two or more electrode devices.

[0037] The contact surfaces of the two positive electrode brushes 3 and 3a have a certain curvature, which ensures contact between the two brushes while allowing them to make contact with wires of a certain diameter, enabling the wires to pass through and preventing open circuits during rolling. The contact surfaces of the two negative electrode brushes 7 and 7a with the upper roller shaft 11 and the lower roller shaft 11a also have a certain curvature, which allows them to fit tightly against the surfaces of the upper roller shaft 11 and the lower roller shaft 11a, thereby preventing open circuits.

[0038] High-precision thermocouple probes or infrared thermometers are placed at the contact points between the MgB2 precursor wire 5 to be rolled and the twin rollers, as well as near the twin rollers.

[0039] In addition, all the metal equipment and accessories such as fixing screws of the aluminum profile frames, brushes, rolling mill handles, roller movement valves and connecting parts in this invention are isolated from the outside world by insulating materials such as insulating tape and insulating sleeves.

[0040] This invention is applicable to wire diameters ranging from 0.2 to 5 mm, with the deformation after rolling ranging from 5% to 75% of the original wire thickness or diameter. The specific working principle is as follows:

[0041] Step 1: Pass the MgB2 precursor wire 5 through the middle of the two opposite positive electrode brushes 3 and 3a until it just contacts and locks into place between the upper roller 11 and the lower roller 11a of the biaxial rolling mill.

[0042] Step 2: Adjust the roller movement valve 10 and rotate it at an appropriate angle until the upper roller 11 and the lower roller 11a are consistent with the target rolling thickness.

[0043] Step 3: Check and ensure that all circuit components are properly connected. Slowly add coolant 15 from the upper edge of the cryogenic Dewar 16 until the coolant 15 submerges the lower part of the internal roller 13 of the cryogenic Dewar 16 and does not overflow from the cryogenic Dewar 16.

[0044] Step 4: Close the device door and introduce a flow of protective gas into the device.

[0045] Step 5: Turn on the external power supply 17 and set an appropriate current value. Then turn on the current input switch to input DC current into the device to heat the MgB2 wire.

[0046] Step 6: Observe the temperature of the wire and calculate the temperature rise rate using a high-precision thermocouple probe. After the wire has been heated to a certain temperature for a specified time, roll it immediately. The rolled wire is then placed into the low-temperature Dewar 16 through a pre-reserved opening for low-temperature quenching treatment.

[0047] Step 7: After all the wire rods have been hot-rolled and quenched, immediately turn off the power and protective gas, and take out the quenched wire rod 16.

[0048] Figure 5 The diagram shows the self-field critical current density of MgB2 superconducting wires prepared using the device of this invention under different conditions (current value, heating time, rolling temperature) at 10K and 20K.

[0049] The specific embodiments of the present invention have been described above. However, those skilled in the art should understand that this is merely an example. Those skilled in the art can make various changes or modifications to this embodiment without departing from the principles and essence of the present invention, but all such changes and modifications fall within the protection scope of the present invention.

Claims

1. An apparatus for preparing high-performance MgB2 superconducting wires by rapid hot rolling and quenching, characterized in that: The system includes a sealed space filled with protective gas, consisting of an insulating epoxy board (1). Two positive electrode brushes (3) and (3a) are mounted on an aluminum profile frame (6) inside the sealed space. The two positive electrode brushes (3) and (3a) are in close contact with each other via corresponding built-in springs (4) and (4a). A twin-roll mill is placed at the right end of the two positive electrode brushes (3) and (3a). Two negative electrode brushes (7) and (7a) are mounted on the outer aluminum profile frame (6a) of the twin-roll mill. a) The two negative electrode brushes are in close contact with the surfaces of the upper roller shaft (11) and the lower roller shaft (11a) of the twin-roll mill respectively through corresponding built-in springs (8) and (8a); the low temperature Dewar (14) is placed on the aluminum profile frame (6b) at the right end of the twin-roll mill, and the low temperature Dewar (14) is filled with coolant (15); the positive and negative leads of the external power supply (17) are respectively welded to the two positive electrode brushes (3) and (3a) and the two negative electrode brushes (7) and (7a); The upper roller (11) of the twin-roll mill is fixed with an upper gear (12) at its shaft end, and the lower roller (11a) of the twin-roll mill is fixed with a lower gear (12a) at its shaft end. The upper gear (12) and the lower gear (12a) mesh with each other. The mill handle (9) is fixed to the outside of the upper gear (12). A gas cylinder through-plate connector (2) is installed on the high-insulation epoxy board (1) at the front end; The twin-roll mill is equipped with a roller movement valve (10) above it. The roller movement valve (10) is connected to the upper roller (11) and the lower roller (11a) and is used to adjust the distance between the upper roller (11) and the lower roller (11a). High-precision thermocouple probes or infrared thermometers are placed at the contact points between the MgB2 precursor wire (5) to be rolled and the twin rollers, as well as near the twin rollers. The device is applicable to wire diameters ranging from 0.2 to 5 mm, and the deformation range after rolling is 5% to 75% of the original wire thickness or diameter.

2. The apparatus for preparing high-performance MgB2 superconducting wires by rapid hot rolling and quenching according to claim 1, characterized in that: The external power supply (17) is a DC regulated power supply.

3. The apparatus for preparing high-performance MgB2 superconducting wires by rapid hot rolling and quenching according to claim 1, characterized in that: The cryogenic dewar (14) has a rotatable roller (13) inside.

4. The apparatus for preparing high-performance MgB2 superconducting wires by rapid hot rolling and quenching according to claim 1, characterized in that: The coolant (15) is liquid nitrogen, liquid gallium metal, or gallium-indium alloy.

5. The apparatus for preparing high-performance MgB2 superconducting wires by rapid hot rolling and quenching according to claim 1, characterized in that: The two positive electrode brushes (3) and (3a) and the two negative electrode brushes (7) and (7a) are composed of a single electrode device or a combination of two electrode devices from high carbon brushes and high copper brushes.

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