A device for rapidly heating magnesium alloy using electromagnetic induction and contact heat transfer

Abstract

The present invention provides a device for rapidly heating magnesium alloys using electromagnetic induction and contact heat transfer, belonging to the field of magnesium alloy heating technology. The device comprises an insulated box, a furnace door, a thermocouple collector, a material receiving plate, and a rapid heating device. The rapid heating device is mounted in a cavity within the insulated box and comprises a rectangular mold and an energized heating coil. At the moment of power application, a significant temperature gradient is generated between the mold wall and the heated material. Because the mold is constructed of insulating and highly thermally conductive material, the surface of the heated material rapidly heats up. Furthermore, the AC current generates eddy currents within the heated material, generating Joule heat that rapidly heats the center of the material. This allows magnesium alloys of varying sizes to be heated both internally and at the edges, reaching the desired temperature in a very short time. Furthermore, due to the hysteresis between magnesium alloy grain size and temperature, the excellent pre-processing properties of the magnesium alloy are retained.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloy heating, in particular to a device for realizing rapid heating by utilizing electromagnetic induction and contact heat transfer. Background Art

[0002] To achieve energy conservation and emission reduction, many lightweight materials are being used in various industries. Magnesium and magnesium alloys, with their high strength-to-weight ratio, low density, and abundant reserves, are the most promising green structural materials in the 21st century.

[0003] Magnesium and magnesium alloys are processed into various forms and are widely used in aerospace, military weapons, transportation, electronic information and other fields. However, since magnesium and magnesium alloys are close-packed hexagonal lattices, only basal slip can be activated at room temperature, and basal slip can only provide two independent slip systems, which cannot provide the five independent slip systems required for uniform plastic deformation and does not meet the von Mises criterion. Therefore, when processing magnesium alloys, the non-basal slip of magnesium alloys is generally activated by heating the magnesium alloy. According to the relationship model of the change of magnesium alloy grain size with heating time proposed by Sellars and Anelli respectively: d n =d o n +Atexp(-Q / RT). Long heating times for magnesium alloys can lead to rapid grain size growth. According to the Hall-Petch equation, this can significantly degrade the performance of magnesium and its alloys. Appropriately shortening heating times can reduce grain size changes in magnesium alloys, rationally utilizing processing time, and increasing processing frequency to meet industrial applications. Rapid heating has great potential for development and application.

[0004] Conduction, convection, and radiation are the three basic modes of heat transfer. Currently, metal heating generally uses box-type resistance furnaces, muffle furnaces, oil bath heating, high-energy lasers, induction heating, and the like. Invention patent CN 217715940 U discloses a rapid mold heating furnace. The aluminum alloy profiles clamped and fixed in the furnace rotate so that the profiles are evenly heated, improving heating efficiency. The furnace is also equipped with a circulating fan that extracts hot air from the bottom of the furnace cavity and discharges it through the air outlet on its outer shell, allowing the heat inside the furnace to circulate with the air flow, thereby evenly distributing the heat in the furnace and rapidly heating the profiles. Invention patent CN109792805 B discloses a rapid heating device for sheet metal blanks used for stamping. The rotating magnetic rotor generates a magnetic field in the metal blank, which rapidly heats the metal blank using the principle of electromagnetic induction. This device can achieve rapid heating of a large number of metal blanks of different shapes. However, these heating devices still have a series of problems: for example, in order to achieve the effect of rapid heating, the temperature of the heating furnace and the temperature of the blank need to reach a very large temperature gradient, which is a huge waste of energy. At the same time, it is not combined with the processing equipment, which makes the processing procedure complicated. For example, the heating amount of invention patent CN109792805 B is related to the inherent resistance of the material. In addition, in order to achieve rapid heating, the equipment needs to rotate the magnetic rotor quickly to generate high-intensity eddy currents inside the material. The equipment is complex, has poor adaptability, and consumes a lot of energy. Due to the many problems with existing rapid heating devices, it is very important to design a set of efficient rapid heating devices. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this paper designs a device that combines induction heating and contact heat transfer to achieve rapid heating of magnesium alloys. This device addresses existing issues such as high energy consumption, low processing efficiency, uneven heating, and complex equipment.

[0006] The present invention adopts the following technical solutions to achieve its invention objectives:

[0007] The present invention provides a rapid heating device utilizing electromagnetic induction and contact heat transfer, which mainly comprises: a heat-insulating box 7, a furnace door 9, a thermocouple sensor 8, a receiving plate 4 and a rapid heating device 6.

[0008] The heat preservation box 7 is composed of a stainless steel shell and asbestos filled on the inner wall of the shell. A furnace door is provided at the opening of the heat preservation box 7. The furnace door 9 is connected to the material receiving plate 4. An asbestos net 3 is provided on the inner side of the furnace door 9. The rapid heating device 6 is installed in the cavity inside the heat preservation box 7. The rapid heating device 6 consists of a rectangular mold 601 and an electric heating coil 602. The interior of the rectangular mold 601 is a heating cavity 603. The electric heating coil 602 is embedded in the rectangular mold 601. The thickness of the rectangular mold 601 is slightly larger than the diameter of the electric heating coil 602, so that the electric heating coil 602 can be close to the metal blank in the heating cavity 603 and the Joule heat generated by the electric heating coil 602 is evenly distributed on the inner surface of the rectangular mold 601.

[0009] The rectangular mold 601 opens at the furnace door, and is provided with a guide rail 10 at the opening. The material receiving plate 4 is installed on the guide rail 10 and slides back and forth on the guide rail 10; the material receiving plate 4 is located directly above the bottom of the heating cavity 603 when the furnace door is closed, and is in contact with the bottom of the heating cavity 603; the rectangular mold 601 is made of insulating, high-temperature resistant and high-thermal conductivity material, and the energized heating coil 602 is made of high-resistance material, preferably white cast iron. The energized heating coil is connected to a medium-frequency AC power supply, the current frequency of the power supply is 600~1200Hz, and the power is 4~8kw. The material receiving plate 4 is made of insulating, high-temperature resistant and high-thermal conductivity material.

[0010] The thermocouple sensor 8 is used to collect the instantaneous temperature of the heated blank. Preferably, the thermocouple sensor 8 is arranged on the central axis just above the receiving plate 4 .

[0011] Preferably, a rectangular baffle is provided at the end of the receiving plate 4 to prevent the furnace door 9 from being pulled out of the heat preservation box 7 as a whole.

[0012] The insulating, high-temperature-resistant, and high-thermal-conductivity material used in the receiving plate 4 and the rectangular parallelepiped mold 601 is preferably AlN.

[0013] Preferably, a buckle 2 is provided on the inner side of the furnace door 9, and the buckle 2 is connected to the knob 1 on the furnace door 9 through a linkage device. The buckle 2 is driven to extend or retract by rotating the knob 1, so that the buckle 2 is inserted into the slot 5 on the insulation box 7 to lock the furnace door 9 or retracted from the slot 5 to unlock the furnace door 9.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The present invention discloses a device for rapidly heating magnesium alloys using electromagnetic induction and contact heat transfer. An alternating current is connected to a powered heating coil. The alternating current generates an induced current inside the powered heating coil, which results in a skin effect. This results in the highest current density on the surface of the powered heating coil. The powered heating coil is made of a material with a high resistance, and its surface temperature rises rapidly. This creates a significant temperature gradient between the heated material and the heated billet. The material surrounding the powered heating coil is made of an insulating material with a high thermal conductivity, which allows for more even heat distribution and increases the contact area between the heat source and the heated magnesium alloy billet. When the power is turned on, a significant temperature gradient is generated between the mold and the heated magnesium alloy billet in a very short period of time. The greater the temperature gradient, the greater the heat transfer, resulting in a rapid temperature increase for the heated magnesium alloy. The rate of temperature increase is unrelated to the resistance of the heated material itself, ensuring controllable temperature rise during heating.

[0016] 2. The present invention primarily utilizes contact heat transfer, but is not limited to a single heating method. Because the mold contains an energized coil connected to an alternating current, eddy currents are generated within the heated magnesium alloy billet, rapidly heating the interior of the magnesium alloy billet due to Joule heating. This allows both the interior and edges of magnesium alloy billets of varying sizes to be heated, rapidly increasing in temperature to the desired temperature in a very short period of time. Furthermore, due to the hysteresis between magnesium alloy grain size and temperature, large-scale recrystallization of the structure during the heating period is prevented, effectively preserving the excellent pre-processing properties of the magnesium alloy and resulting in a magnesium alloy with superior mechanical properties.

[0017] 3. The present invention utilizes electromagnetic induction heating and contact heat transfer for heating, which is not available in many previous rapid heating molds that only utilize induction heating, electric heating and contact heat transfer for heating. It inherits the advantages of previous heating devices, such as electroplasticity and a large range, and eliminates a large number of disadvantages, such as: the temperature rise is related to the resistance of the material itself, the current frequency, and the contact area. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a structural schematic diagram of a device for rapidly heating magnesium alloy by utilizing electromagnetic induction and contact heat transfer.

[0019] Figure 2 The present invention is a schematic diagram of the furnace door structure of a device for rapidly heating magnesium alloy using electromagnetic induction and contact heat transfer.

[0020] Figure 3 The invention provides a cross-sectional view of a rapid heating device for magnesium alloys that utilizes electromagnetic induction and contact heat transfer.

[0021] Figure 4 Figure 2 is the metallographic structure diagram of Examples 1, 2, and 3 after forming.

[0022] Figure 5 The metallographic organization diagrams of comparative examples 1, 2, and 3 after forming are shown.

[0023] The accompanying drawings are marked as follows: 1. knob, 2. buckle, 3. asbestos mesh, 4. receiving plate, 5. slot, 6. rapid heating device, 7. insulation box, 8. thermocouple sensor, 9. furnace door, 601. rectangular mold, 602. energized heating coil, 603. heating cavity. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be located directly or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The directions or positions indicated by the terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the accompanying drawings and are only for the convenience of description and cannot be understood as limitations on this technical solution. The terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0026] See also Figure 1-3 The purpose of this embodiment is to provide a rapid heating device using electromagnetic induction and contact heat transfer, which mainly includes: an insulation box 7, a furnace door 9, a thermocouple sensor 8, a material receiving plate 4 and a rapid heating device 6.

[0027] The heat preservation box 7 is composed of a stainless steel shell and asbestos filled on the inner wall of the shell. A furnace door is provided at the opening of the heat preservation box 7. The furnace door 9 is connected to the material receiving plate 4. An asbestos mesh 3 is provided on the inner side of the furnace door 9. The rapid heating device 6 is installed in the cavity inside the heat preservation box 7. The rapid heating device 6 consists of a rectangular mold 601 and an electric heating coil 602. The interior of the rectangular mold 601 is a heating cavity 603. The electric heating coil 602 is embedded in the rectangular mold 601. The thickness of the rectangular mold 601 is slightly larger than the diameter of the electric heating coil 602, so that the electric heating coil 602 can be close to the metal blank in the heating cavity 603.

[0028] The rectangular mold 601 is opened at the furnace door, and a guide rail 10 is provided at the opening. The material receiving plate 4 is installed on the guide rail 10 and slides back and forth on the guide rail 10; when the furnace door is closed, the material receiving plate 4 is located directly above the bottom of the heating cavity 603 and fits with the bottom of the heating cavity 603; the rectangular mold 601 is made of insulating, high-temperature resistant and high-thermal conductivity material, and the energized heating coil 602 is made of ferromagnetic high-resistance material white cast iron. The energized heating coil is connected to a medium-frequency AC power supply. The current frequency of the power supply is 600~1200Hz and the power is 4~8kw. The material receiving plate 4 is made of insulating, high-temperature resistant and high-thermal conductivity material.

[0029] The thermocouple sensor 8 is arranged on the central axis just above the receiving plate 4 to collect the instantaneous temperature of the heated blank. Preferably, a rectangular baffle is provided at the end of the receiving plate 4 to prevent the furnace door 9 from being pulled out of the insulation box 7 as a whole.

[0030] The insulating, high-temperature-resistant, and high-thermal-conductivity material used in the receiving plate 4 and the rectangular parallelepiped mold 601 is AlN.

[0031] In addition, a buckle 2 is provided on the inner side of the furnace door 9, which is connected to the knob 1 on the furnace door 9 through a linkage device. The buckle 2 is driven to extend or retract by rotating the knob 1, so that the buckle 2 is inserted into the slot 5 on the insulation box 7 to lock the furnace door 9 or retracted from the slot 5 to unlock the furnace door 9.

[0032] Example 1

[0033] Mg-2Al-0.8Sn-0.5Ca (ATX2105) magnesium alloy billets were pre-processed into 65mm*45mm*10mm sheets. The magnesium alloy sheets were placed on a receiving plate, and the furnace door was closed by turning the knob. Simultaneously, the magnesium alloy sheets were fed into the heating cavity. The rapid heating device was connected to a power supply with a medium-frequency AC current of 600Hz and a power of 4kW. The temperature collected by the thermocouple collector was recorded at all times. When the temperature displayed on the thermocouple collector reached 400°C, the heating time was 30 seconds. The knob linkage device was turned to disengage the furnace door latch from the slot. The furnace door was opened and the magnesium alloy sheet was removed from the receiving plate. No obvious oxide layer was found on the magnesium alloy surface. The magnesium alloy sheet was placed in the processing device. The formed magnesium alloy had a smooth surface without edge cracks. Compared with using a traditional muffle furnace to heat the magnesium alloy sheet and then process it, the grain structure was finer and the mechanical properties were better.

[0034] Example 2

[0035] The Mg-2Al-0.8Sn-0.5Ca-0.2Zn (ATX2105-0.2Zn) magnesium alloy billet was pre-processed into a 65mm*45mm*20mm plate. The magnesium alloy plate was placed on a receiving plate, and the furnace door was closed by turning the knob. At the same time, the magnesium alloy plate was fed into the heating cavity. The rapid heating device was connected to a power supply. The power supply was a medium-frequency AC current with a current frequency of 600Hz and a power of 4kW. The temperature collected by the thermocouple collector was recorded at all times. When the temperature displayed on the thermocouple collector reached 400℃, the heating time was 39s. The knob linkage device was turned to disengage the furnace door buckle from the slot. The furnace door was opened and the magnesium alloy plate was taken out of the receiving plate. There was no obvious oxide layer on the surface of the magnesium alloy. The magnesium alloy plate was placed in the processing device. The surface of the formed magnesium alloy was smooth and free of edge cracks. Compared with using a traditional muffle furnace to heat the magnesium alloy plate and then process it, the grain structure was finer and the mechanical properties were better.

[0036] Example 3

[0037] The Mg-2Al-0.8Sn-0.5Ca-0.4Zn (ATX2105-0.4Zn) magnesium alloy billet was pre-processed into a 65mm*45mm*30mm plate. The magnesium alloy plate was placed on a receiving plate, and the furnace door was closed by turning the knob. At the same time, the magnesium alloy plate was fed into the heating cavity. The rapid heating device was connected to a power supply. The power supply was a medium-frequency AC current with a current frequency of 600Hz and a power of 4kW. The temperature collected by the thermocouple collector was recorded at all times. When the temperature displayed on the thermocouple collector reached 400℃, the heating time was 42s. The knob linkage device was turned to disengage the furnace door buckle from the slot. The furnace door was opened and the magnesium alloy plate was taken out from the receiving plate. There was no obvious oxide layer on the surface of the magnesium alloy. The magnesium alloy plate was placed in the processing device. The surface of the formed magnesium alloy was smooth and free of edge cracks. Compared with using a traditional muffle furnace to heat the magnesium alloy plate and then process it, the grain structure was finer and the mechanical properties were better.

[0038] Comparative Example 1

[0039] The Mg-2Al-0.8Sn-0.5Ca (ATX2105) magnesium alloy billet was pre-processed into a 65mm*45mm*10mm plate, and the magnesium alloy plate was placed in a traditional muffle furnace, the furnace door was closed, and the preset temperature was adjusted to 400°C. When the traditional muffle furnace display showed that the temperature reached 400°C, the furnace door was opened and the magnesium alloy plate was taken out. An obvious oxide layer appeared on the surface of the magnesium alloy. The magnesium alloy plate was placed in a processing device. The surface of the formed magnesium alloy was dull and had no edge cracks. Compared with the use of the device of the present invention to heat the magnesium alloy plate and then process it into shape, the grain structure was coarse and the mechanical properties were relatively poor.

[0040] Comparative Example 2

[0041] The Mg-2Al-0.8Sn-0.5Ca-0.2Zn (ATX2105-0.2Zn) magnesium alloy billet was pre-processed into a 65mm*45mm*20mm plate, and the magnesium alloy plate was placed in a traditional muffle furnace, the furnace door was closed, and the preset temperature was adjusted to 400°C. When the traditional muffle furnace display showed that the temperature reached 400°C, the furnace door was opened and the magnesium alloy plate was taken out. An obvious oxide layer appeared on the surface of the magnesium alloy. The magnesium alloy plate was placed in a processing device. The surface of the formed magnesium alloy was dull and had no edge cracks. Compared with the use of the device of the present invention to heat the magnesium alloy plate and then process it into shape, the grain structure was coarse and the mechanical properties were relatively poor.

[0042] Comparative Example 3

[0043] The Mg-2Al-0.8Sn-0.5Ca-0.4Zn (ATX2105-0.4Zn) magnesium alloy billet was pre-processed into a 65mm*45mm*30mm plate, and the magnesium alloy plate was placed in a traditional muffle furnace, the furnace door was closed, and the preset temperature was adjusted to 400°C. When the traditional muffle furnace display showed that the temperature reached 400°C, the furnace door was opened and the magnesium alloy plate was taken out. An obvious oxide layer appeared on the surface of the magnesium alloy. The magnesium alloy plate was placed in a processing device. The surface of the formed magnesium alloy was dull and had no edge cracks. Compared with the use of the device of the present invention to heat the magnesium alloy plate and then process it into shape, the grain structure was coarse and the mechanical properties were relatively poor.

[0044] Effect verification

[0045] For Examples 1, 2, and 3, the uniaxial tensile test was performed on an AGS-X-100 kN tensile testing machine (SHIMADZU, Japan). The tensile tests were performed at room temperature and at a tensile rate of 1.0 × 10 -3 ms -1 Tensile specimens were cut from the center and edge of the formed magnesium alloy, and tensile tests were performed one by one. The average value of the test results is listed in Table 1.

[0046] Table 1

[0047]

[0048] For Comparative Examples 1, 2, and 3, the uniaxial tensile test was performed on an AGS-X-100 kN tensile testing machine (SHIMADZU, Japan). The tensile tests were performed at room temperature and at a tensile rate of 1.0 × 10 -3 ms -1 Tensile specimens were cut from the center and edge of the formed magnesium alloy, and tensile tests were performed one by one. The average test results were taken and listed in Table 2.

[0049] Table 2

[0050]

[0051] From the above comparison, it can be seen that the embodiments of the present invention have significantly improved tensile strength and elongation compared with the control example, and can obtain magnesium alloys with better mechanical properties than the existing method. In addition, compared with using a traditional muffle furnace to heat the magnesium alloy plate, the heating time used is greatly reduced, thereby improving the thermal processing efficiency.

[0052] The embodiments of the present invention have been disclosed above, but they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A rapid heating device utilizing electromagnetic induction and contact heat transfer, characterized in that: The device comprises: a heat-insulating box (7), a furnace door (9), a thermocouple sensor (8), a material receiving plate (4) and a rapid heating device (6); The heat preservation box (7) is composed of a stainless steel shell and asbestos filled on the inner wall of the shell. A furnace door is provided at the opening of the heat preservation box (7). The furnace door (9) is connected to the material receiving plate (4). An asbestos net (3) is provided on the inner side of the furnace door (9). The rapid heating device (6) is installed in the cavity inside the heat preservation box (7). The rapid heating device (6) is composed of a rectangular mold (601) and an energized heating coil (602). The interior of the rectangular mold (601) is a heating cavity (603). The energized heating coil (602) is embedded in the rectangular mold (601). The thickness of the rectangular mold (601) is slightly larger than the diameter of the energized heating coil (602), so that the energized heating coil (602) can be close to the metal blank in the heating cavity (603) and the Joule heat generated by the energized heating coil (602) is evenly distributed on the inner surface of the rectangular mold (601). The rectangular mold (601) is opened at the furnace door, and a guide rail (10) is provided at the opening. The material receiving plate (4) is mounted on the guide rail (10) and slides back and forth on the guide rail (10); when the furnace door is closed, the material receiving plate (4) is located directly above the bottom of the heating cavity (603) and is in contact with the bottom of the heating cavity (603); the rectangular mold (601) is made of an insulating, high-temperature-resistant, and high-thermal-conductivity material, the energized heating coil (602) is made of a ferromagnetic, high-resistance material, the energized heating coil (602) is connected to a medium-frequency AC power supply, the current frequency of the power supply is 600-1200 Hz, and the power is 4-8 kW. The material receiving plate (4) is made of an insulating, high-temperature-resistant, and high-thermal-conductivity material; the thermocouple sensor (8) is used to collect the instantaneous temperature of the heated blank.

2. The rapid heating device using electromagnetic induction and contact heat transfer according to claim 1, characterized in that: The thermocouple sensor (8) is arranged on the central axis just above the material receiving plate (4).

3. The rapid heating device using electromagnetic induction and contact heat transfer according to claim 1, characterized in that: A rectangular baffle is provided at the end of the material receiving plate (4) to prevent the furnace door (9) from being drawn out of the heat-insulating box (7) as a whole.

4. The rapid heating device using electromagnetic induction and contact heat transfer according to claim 1, characterized in that: The insulating, high-temperature-resistant, and high-thermal-conductivity material used in the material receiving plate (4) and the rectangular parallelepiped mold (601) is AlN.

5. The rapid heating device using electromagnetic induction and contact heat transfer according to claim 1, characterized in that: The energized heating coil (602) is made of white cast iron.

6. The rapid heating device using electromagnetic induction and contact heat transfer according to claim 1, characterized in that: A buckle (2) is provided on the inner side of the furnace door (9), and the buckle (2) is connected to the knob (1) on the furnace door (9) through a linkage device. The buckle (2) is driven to extend or retract by rotating the knob (1), so that the buckle (2) is inserted into the slot (5) on the heat preservation box (7) to lock the furnace door (9) or is retracted from the slot (5) to unlock the furnace door (9).

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