Hot gas bulging forming system and hot gas bulging forming method

Abstract

The hot gas bulging forming system comprises a pipe bending device, a feeding device, a pre-forming device, a heating device, a bulging quenching device and a discharging device which are sequentially arranged, the heating device comprises a heating cavity, and an electrode chuck used for clamping the end of a metal pipe is arranged in the heating cavity; the electrode chuck is connected with an IGBT induction heating device, an infrared thermometer is arranged in the heating cavity, and the infrared thermometer and the IGBT induction heating device are both in communication connection with a controller. According to the hot air bulging forming system, materials with different thicknesses and pipes with complex shapes can be conveniently heated, the heating rate of the materials with different coatings can be adjusted through the controller according to coating characteristics, accordingly, the coatings are protected to the maximum extent, the better product surface quality is obtained, the application range is wide, the heating speed is high, and the production efficiency is high. And the heating efficiency is greatly improved. The invention further discloses a hot gas bulging forming method.

Description

Technical Field

[0001] The invention relates to the technical field of metal tube forming, and in particular to a hot air bulging forming system and a hot air bulging forming method. Background Art

[0002] The hot metal tube gas expansion forming process is referred to as hot gas expansion. It is a special forming process that heats the hollow tube to a certain temperature, realizes internal high pressure forming in the mold, and quenches it. It can increase the strength of the product from 400-600MPa to 2000MPa. This technology has been widely used in automobile A-pillars, B-pillars, anti-collision beams, rear traction beams and other parts. More and more products using hot gas expansion forming process are used in vehicles, and at the same time, higher anti-corrosion performance and higher requirements for coatings are required. The hot gas expansion forming process generally includes pipe bending process, preforming process, heating process, expansion process and laser cutting process.

[0003] In the prior art, in the heating process, a walking-beam heating furnace or a box-type heating furnace is generally used for heating. The walking-beam heating furnace transfers the raw materials step by step to the continuous heating furnace through rollers, and heats the workpiece by means of heat radiation from the bottom layer upward. It is widely used in hot stamping forming production lines for plates. The box-type heating furnace heats the raw materials inside by heat conduction. Heating tubes are arranged on the upper and lower layers of each cavity of the box-type heating furnace, and the workpiece is heated by means of heat radiation from the bottom layer upward and from the top layer downward. The above two heating methods are radiation heating, and their heating rate is directly related to the thickness of the sheet, resulting in a longer heating time. Summary of the invention

[0004] In view of this, the present invention provides a hot air bulging forming system, which is convenient for heating pipes of different thicknesses and complex shapes, has a wide range of applications, a fast heating speed, and greatly improves the heating efficiency.

[0005] The invention also provides a hot air bulging forming method.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A hot air bulging forming system comprises a tube bending device, a feeding device, a preforming device, a heating device, a bulging quenching device and a feeding device which are arranged in sequence, wherein the heating device comprises a heating chamber, wherein an electrode chuck for clamping the end of a metal tube is arranged in the heating chamber, wherein the electrode chuck is connected to an IGBT induction heating device, wherein an infrared thermometer is arranged in the heating chamber, and both the infrared thermometer and the IGBT induction heating device are communicatively connected to a controller.

[0008] Optionally, the heating device comprises a main frame, a heating platform is arranged on the main frame, and the electrode chuck is arranged on the heating platform;

[0009] A sealing plate body is arranged around and on the top of the heating platform, the sealing plate body is connected to the main frame, and the sealing plate body and the heating platform surround the heating chamber.

[0010] Optionally, a dry gas dew point control component is provided in the heating chamber;

[0011] The dry gas dew point control component includes a dew point sensor and a gas delivery component. The dew point sensor is arranged in the heating chamber. The dew point sensor is communicatively connected with the controller. The gas delivery component is used to deliver dry gas to the heating chamber.

[0012] Optionally, the gas delivery assembly includes a dry gas source and a porous exhaust pipe connected through an air inlet pipe, the porous exhaust pipe is arranged in the heating chamber, the dry gas source is arranged outside the heating chamber, a flow control valve is arranged at the inlet end of the porous exhaust pipe, a plurality of exhaust through holes are arranged on the porous exhaust pipe, and the plurality of exhaust through holes are arranged along the length direction of the porous exhaust pipe, and the exhaust through holes are arranged toward the metal pipe;

[0013] The dry gas source is used to contain dry gas, and the dry gas is air or nitrogen.

[0014] Optionally, a first handling robot is provided between the feeding device and the preforming device, and the first handling robot is used to transfer the metal pipe from the feeding device to the preforming cavity of the preforming device;

[0015] A second handling robot is provided between the preforming device and the heating device, and the second handling robot is used to transfer the metal pipe from the preforming cavity to the heating cavity. After the heating of the metal pipe is completed, the second handling robot is used to transfer the metal pipe from the heating cavity to the bulging cavity of the bulging quenching device;

[0016] A third handling robot is arranged between the bulging and quenching device and the blanking device, and the third handling robot is used to transfer the metal pipe from the bulging die cavity to the blanking conveyor belt of the blanking device.

[0017] Optionally, a lifting door is provided on the side wall of the sealing plate body, and the width of the lifting door is greater than the length of the metal pipe.

[0018] It can be seen from the above technical scheme that in the hot air bulging forming system provided by the present invention, the heating power source in the heating device is an IGBT induction heating device, and the IGBT induction heating device is the power source of the electrode clamp that clamps the end of the metal pipe. When the metal pipe is not demagnetized, the useful work of heating is mainly induction heating. As the temperature of the pipe body rises, the metal pipe gradually loses magnetism, and the useful work of heating is converted from induction heating to resistance heating. The material of the metal pipe is different, and its demagnetization temperature is different. The hot air bulging forming system of the present invention uses induction and resistance heating of the pipe body itself, rather than radiation heating. Its heating speed is adjusted by the input current. Its heating rate has nothing to do with the thickness of the sheet material, which is convenient for heating materials of different thicknesses and complex shapes of pipes. It has a wide range of applications and a fast heating speed. The hot air bulging forming system of the present invention uses induction heating and resistance heating in the heating process, which greatly improves the heating efficiency, reduces energy consumption, and can heat metal pipes of complex shapes.

[0019] The present invention also provides a hot air bulging forming method, comprising the following steps:

[0020] S1. Use a pipe bender to bend the metal pipe into shape;

[0021] S2, transferring the bent metal pipe to a loading device, wherein the loading device positions the metal pipe;

[0022] S3, grabbing the metal pipe from the feeding device and feeding it into the preforming cavity of the preforming device to preform the metal pipe;

[0023] S4, sending the metal pipe in the preforming cavity into the heating chamber of the heating device for heating, clamping the metal pipe on the electrode clamp, and heating by the IGBT induction heating device, and the controller controls the IGBT induction heating device to heat;

[0024] S5, the heated metal pipe is sent into the bulging die cavity of the bulging quenching device to complete the bulging quenching;

[0025] S6, sending the metal pipe after bulging and cooling to a feeding device for feeding.

[0026] Optionally, the heating process in step S4 includes:

[0027] S401, preheating process, adjusting the power on ratio of the IGBT induction heating device, the metal pipe is heated by 10-18°C per second, and the heating is performed for 0-3 seconds;

[0028] S402, rapid heating process, adjusting the power on ratio of the IGBT induction heating device, the metal pipe is heated by 20-24°C per second, the heating time is 3-30 seconds, and the temperature of the metal pipe reaches 600-650°C;

[0029] S403, a slow heating process, wherein the temperature of the metal pipe is raised by less than 10°C per second, and the temperature of the metal pipe is raised from 600-650°C to 840°C;

[0030] S404, a first slow heating and heat preservation process, the metal pipe is slowly heated at 2-4°C per second, from 840°C to 850°C and then kept warm;

[0031] S405, austenitizing process, the metal pipe is heated at 4-6°C per second, from 850°C to 925°C and then kept warm;

[0032] S406, a second slow heating and heat preservation process, the metal pipe is heated at 1-2°C per second, from 925°C to 950°C and then kept warm.

[0033] Optionally, in step S404, the heating time is 55 to 60 seconds; in step S405, the heating time is 60 to 75 seconds; in step S406, the heating time is 76 to 180 seconds.

[0034] Optionally, dry gas is introduced into the heating chamber to control the dew point of the heating chamber to ensure that the dew point of the heating chamber meets the requirements.

[0035] The hot air bulging forming method of the present invention adopts the above-mentioned hot air bulging forming system for forming, and therefore has the advantages of the above-mentioned system, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 A simplified structural diagram of a hot air bulging forming system provided in an embodiment of the present invention;

[0038] Figure 2 A schematic structural diagram of a hot air bulging forming system provided in an embodiment of the present invention;

[0039] Figure 3 A schematic diagram of the structure of a heating device provided in an embodiment of the present invention;

[0040] Figure 4 A schematic diagram of a process window of a hot air bulging forming method provided in an embodiment of the present invention;

[0041] Figure 5 A schematic diagram of the structure of a bulging quenching device provided in an embodiment of the present invention;

[0042] Figure 6 A heating system circuit diagram of an IGBT induction heating device provided in an embodiment of the present invention;

[0043] Figure 7 A schematic diagram of the structure of a porous exhaust pipe provided in an embodiment of the present invention;

[0044] Figure 8 A schematic diagram of the structure in which a dew point sensor and a porous exhaust pipe provided in an embodiment of the present invention are installed in a heating chamber.

[0045] in:

[0046] 1. Pipe bending device,

[0047] 2. Loading device,

[0048] 3. Preforming device,

[0049] 4. Heating device,

[0050] 401. Main frame, 402. IGBT induction heating equipment, 403. Support legs, 404. Electrode chuck, 405. Dry gas dew point control assembly, 4051. Dew point sensor, 4052. Multi-hole exhaust pipe, 4053. Flow control valve, 4054. Air inlet port, 4055. Exhaust through hole, 406. Infrared thermometer, 407. Heating chamber, 408. Heating table, 5. Expansion quenching device,

[0051] 501, lower die, 502, oil cylinder, 503, plug, 504, upper die,

[0052] 6. Feeding device,

[0053] 7. Metal pipes,

[0054] 8. The second handling robot,

[0055] 9. The third transport robot,

[0056] 10. The first handling robot. DETAILED DESCRIPTION

[0057] The invention discloses a hot air bulging forming system, which is convenient for heating materials of different thicknesses and pipes of complex shapes, has a wide application range, a fast heating speed, and greatly improves the heating efficiency.

[0058] The invention also discloses a hot air bulging forming method.

[0059] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] See also Figures 1 to 3 The hot air bulging forming system of the present invention comprises a bending device 1, a feeding device 2, a preforming device 3, a heating device 4, a bulging quenching device 5 and a feeding device 6 which are arranged in sequence. The heating device 4 comprises a heating chamber 407, in which an electrode chuck 404 for clamping the end of the metal pipe 7 is arranged, and the electrode chuck 404 is connected to an IGBT induction heating device 402. An infrared thermometer 406 is arranged in the heating chamber 407, and both the infrared thermometer 406 and the IGBT induction heating device 402 are connected to the controller in communication.

[0061] Among them, the pipe bending device 1, the feeding device 2, the preforming device 3, the bulging and quenching device 5 and the unloading device 6 are all commonly used devices in the prior art. Generally, the pipe bending device 1 is a pipe bending machine. For large arc bends, a mold can also be used for press bending. The feeding device 2 is used to position the metal pipe 7 to ensure that the robot can stably grasp the metal pipe 7. There is a parts recognition sensor in the feeding device 2. The preforming device 3 preforms the metal pipe 7 after bending, preparing for the next step of bulging, ensuring that the preformed metal pipe 7 can be smoothly placed into the bulging mold cavity of the bulging and quenching device 5. The heating device 4 heats the metal pipe 7 according to a set program. The bulging and quenching device 5 is used to bulge and quench the metal pipe 7. The controller is a PLC.

[0062] In the hot air bulging forming system of the present invention, the heating power source in the heating device 4 is an IGBT induction heating device, and the IGBT induction heating device is the power source of the electrode clamp 404 that clamps the end of the metal pipe 7. When the metal pipe 7 is not demagnetized, the useful work of heating includes induction and resistance heating, and the useful work of heating is mainly induction heating. As the temperature of the metal pipe 7 rises, the metal pipe 7 gradually loses magnetism, and the useful work of heating is converted from induction heating to resistance heating. The material of the metal pipe 7 is different, and its demagnetization temperature is different. The hot air bulging forming system of the present invention uses induction and resistance heating of the pipe body itself, rather than radiation heating. Its heating speed is adjusted by the input current, and its heating rate has nothing to do with the thickness of the sheet material, which is convenient for heating materials of different thicknesses and complex shapes of pipes, and has a wide range of applications and a fast heating speed. In the hot air bulging forming system of the present invention, the heating process adopts induction heating and resistance heating, which greatly improves the heating efficiency, reduces energy consumption, and can heat metal pipes of complex shapes. The hot air expansion forming system of the present invention can adjust the heating rate of materials with different coatings according to the coating characteristics by a controller, thereby protecting the coating to the maximum extent, obtaining better product surface quality, and avoiding product surface peeling.

[0063] In one embodiment, the demagnetization temperature of the metal pipe 7 is 750 degrees Celsius. When the heating temperature is below 750 degrees Celsius, the metal pipe 7 is in a non-demagnetized state, and when the heating temperature is above 750 degrees Celsius, the metal pipe 7 is in a demagnetized state. The demagnetization temperature is determined by the material of the metal pipe 7, and the temperature may fluctuate.

[0064] Specifically, the heating device 4 includes a main frame 401, such as Figure 3 As shown, a heating platform 408 is provided on the main frame 401, and an electrode chuck 404 is provided on the heating platform 408. In order to form a sealed chamber, a sealing plate body is provided around and on the top of the heating platform 408, and the sealing plate body is connected to the main frame 401. The sealing plate body and the heating platform 408 are arranged to form a heating chamber 407, so as to facilitate the control of the temperature and atmosphere in the heating chamber 407. A supporting leg 403 is provided at the bottom of the main frame 401.

[0065] In order to improve the anti-hydrogen embrittlement and anti-oxidation performance, a dry gas dew point control component 405 is provided in the heating chamber 407. Specifically, the dry gas dew point control component 405 includes a dew point sensor 4051 and a gas delivery component, such as Figure 7 and Figure 8 As shown, a dew point sensor 4051 is disposed in the heating chamber 407, and the dew point sensor 4051 is in communication connection with the controller, and the gas delivery assembly is used to deliver dry gas to the heating chamber 407. The dew point sensor 4051 is an instrument for detecting the dew point temperature of the heating chamber 407. The controller controls the size of the gas delivery assembly's delivery airflow according to the detection value of the dew point sensor 4051.

[0066] Specifically, the gas delivery assembly includes a dry gas source and a porous exhaust pipe 4052 connected through an air inlet pipe. The porous exhaust pipe 4052 is disposed in the heating chamber 407, and the dry gas source is disposed outside the heating chamber 407. An air inlet port 4054 of the porous exhaust pipe 4052 is connected to the air inlet pipe. A flow control valve 4053 is disposed at the inlet end of the porous exhaust pipe 4052. The porous exhaust pipe 4052 is provided with a plurality of exhaust through holes 4055, such as Figure 7 As shown, a plurality of exhaust through holes 4055 are arranged along the length direction of the porous exhaust pipe 4052, the exhaust through holes 4055 are arranged toward the metal pipe 7, the opening position of the exhaust through holes 4055 is aligned with the lower part of the metal pipe 7, and the port of the porous exhaust pipe 4052 away from the air inlet port 4054 is blocked. Preferably, the plurality of exhaust through holes 4055 are evenly distributed along the length direction of the porous exhaust pipe 4052, and the length of the porous exhaust pipe 4052 provided with the exhaust through holes 4055 is greater than the length of the metal pipe 7. By providing a plurality of exhaust through holes 4055, the dry gas can be evenly diffused into the heating chamber 407, and the dew point temperature of the heating chamber 407 is maintained.

[0067] The dry gas source is used to hold dry gas, and the dry gas is air or nitrogen. The dew point sensor 4051 is provided to detect the dryness in the heating chamber 407, that is, to detect the humidity. The controller controls the opening of the flow control valve 4053 according to the dew point temperature detected by the dew point sensor 4051, thereby controlling the flow of the dry gas and achieving the control of the dew point. Preferably, the dew point sensor 4051 is installed on the heating platform 408. In one embodiment, the dew point temperature in the heating chamber 407 is controlled between -5° and -25°.

[0068] In order to facilitate the transfer of the metal pipe 7 between different devices, a first handling robot 10 is provided between the feeding device 2 and the preforming device 3, a second handling robot 8 is provided between the preforming device 3 and the heating device 4, and a third handling robot 9 is provided between the bulging and quenching device 5 and the unloading device 6. The first handling robot 10 is used to transfer the metal pipe 7 from the feeding device 2 to the preforming cavity of the preforming device 3, and the second handling robot 8 is used to transfer the metal pipe 7 from the preforming cavity to the heating cavity 407. After the heating of the metal pipe 7 is completed, the second handling robot 8 is used to transfer the metal pipe 7 from the heating cavity 407 to the bulging cavity of the bulging and quenching device 5. The third handling robot 9 is used to transfer the metal pipe 7 from the bulging cavity to the unloading conveyor belt of the unloading device 6.

[0069] In order to facilitate placing the metal pipe 7 into the heating chamber 407 , a lifting door is provided on the side wall of the sealing plate body, and the width of the lifting door is greater than the length of the metal pipe 7 .

[0070] The present invention also provides a hot air bulging forming method, comprising the following steps:

[0071] S1. Use a pipe bender to bend the metal pipe 7 into shape.

[0072] There are two main bending methods: pull bending and push bending. The equipment used is a pipe bender. For large arc pipes, molds can also be used for press bending. This step is a pre-forming preparation to ensure that the pipe after bending can be smoothly placed into the pre-formed mold cavity.

[0073] S2, transferring the bent metal pipe 7 to the loading device 2, and the loading device 2 positions the metal pipe 7.

[0074] The feeding device 2 positions the metal pipe 7 to ensure that the handling robot stably grasps the metal pipe 7 and feeds the metal pipe 7 into the pre-forming mold cavity. The feeding device 2 is provided with a parts recognition sensor and a grating protection ergonomic system.

[0075] S3, grab the metal pipe 7 from the feeding device 2 and send it into the preforming cavity of the preforming device 3, and the preforming device 3 preforms the metal pipe 7.

[0076] The bent metal pipe 7 is preformed to prepare for the next step of bulging, ensuring that the preformed workpiece can be smoothly placed into the bulging die cavity.

[0077] S4, sending the metal pipe 7 in the pre-forming cavity into the heating chamber 407 of the heating device 4 for heating, the metal pipe 7 is clamped on the electrode clamp 404, and heated by the IGBT induction heating device 402, and the controller controls the IGBT induction heating device 402 to heat according to the set program.

[0078] S5, the heated metal pipe 7 is fed into the bulging die cavity of the bulging quenching device 5 to complete the bulging quenching.

[0079] The bulging die cavity is provided with an upper die 504 and a lower die 501 which are matched with each other. Figure 5As shown, the lower die 501 is provided with an oil cylinder 502, and the driving end of the oil cylinder 502 is connected with a plug 503. The handling robot delivers the heated metal pipe 7 on the heating table 408 into the bulging die cavity, and the press drives the upper die 504 downward to close the die with the lower die 501. At the same time, the oil cylinder 502 on the die pushes the plug 503. At the moment of closing the die, the plug 503 is pushed into place to block the two ends of the metal pipe 7. The plug 503 is provided with an air inlet. After closing the die, high-pressure nitrogen or air is filled through the air inlet on the plug 503 to complete the bulging. The high-pressure gas is kept at 60Mpa~70Mpa for 1~2 seconds, and the mold insert is cooled by cooling water for 10~15 seconds. The maintenance time is adjusted according to the thickness of the part to ensure that the temperature of the metal pipe 7 out of the die is lower than 80℃, and finally the die is opened to take out the part.

[0080] The metal tube 7 is bulged under the action of high-pressure gas, and the outer surface of the metal tube 7 is completely attached to the mold. The cooling water channel in the mold instantly cools the mold and the metal tube 7. Specifically, the cooling rate is 27°C / s, which realizes rapid cooling of the metal tube 7, and the interior of the metal tube 7 is converted into a uniform martensite structure. The metallographic structure of the metal tube 7 after hot air bulging is not less than 95% martensite.

[0081] After hot air expansion, the surface of the metal tube 7 is covered with a coating of 30 to 40 μm. The coating has a four-layer structure. The microstructure from the outermost side of the coating to the steel substrate is: a surface layer containing Al oxide and a continuous distribution of brittle Fe2Al5, an intermetallic compound FeAl layer, an intermediate layer containing a brittle Fe2Al5 phase, and an interdiffusion layer.

[0082] S6, sending the expanded and cooled metal pipe 7 to the unloading device 6 for unloading.

[0083] The handling robot grabs the expanded and cooled metal pipe 7 out of the mold cavity and delivers it to the unloading conveyor belt on the unloading device 6.

[0084] Further, the heating process in step S4 includes: S401, preheating process, adjusting the power opening ratio of the IGBT induction heating device, the metal pipe is heated at 10-18°C per second, and the heating time is 0-3 seconds. The equipment power is turned on at 40-50%, mainly to allow the contact of the electrode clamp 404 to have an adaptation and stable process. The metal pipe 7 is at room temperature, such as 10-20°C, and is heated to 45-80°C after 3 seconds. S402, rapid heating process, adjusting the power opening ratio of the IGBT induction heating device 402, the equipment power is turned on at 80%-95%, the metal pipe 7 is heated at 20-24°C per second, and the heating time is 3-30 seconds, so that the temperature of the metal pipe 7 reaches 600-650°C. In this stage, the temperature is raised as quickly as possible to shorten the heating time. S403, slow heating process, the metal pipe 7 is heated at less than 10°C per second, and the metal pipe 7 is heated from 600-650°C to 840°C. The heating time of this step is 30-54 seconds. It is not advisable to heat up too fast in this stage, mainly to facilitate coating fusion and protection. S404, the first slow heating and heat preservation process, the metal pipe is slowly heated at 2 to 4 ° C per second, and the temperature is increased from 840 ° C to 850 ° C and then kept warm. The total heating time in this step is 55 to 60 seconds. This step is mainly for heat preservation to improve the uniformity of the material of the metal pipe 7. This step can appropriately increase or decrease the heating time of this stage according to the temperature difference of the metal pipe 7. S405, austenitization process, the metal pipe 7 is heated at 4 to 6 ° C per second, and the temperature is increased from 850 ° C to 925 ° C and then kept warm. The heating time of this step is 60 to 75 seconds. At this stage, the metal pipe 7 begins to austenitize. S406, the second slow heating and heat preservation process, the metal pipe 7 is heated at 1 to 2 ° C per second, and the temperature is increased from 925 ° C to 950 ° C and then kept warm. The heating time of this step is 76 to 180 seconds. This stage is a slow heating and heat preservation process. After heating is completed, the power is turned off and the robot's manipulator takes the part and transfers it to the bulging mold cavity. See the process window of heating time and temperature. Figure 4 The above control process is controlled by the controller. The metal pipe 7 is heated from room temperature, and the heating temperature and time are limited to Figure 4 The graph KLMN is in the graph KLMN, where the coordinates of the limit points of the graph KLMN are: K (25 seconds, 950°C), L (100 seconds, 950°C), M (180 seconds, 900°C), N (75 seconds, 900°C), and the heating rate is performed according to step S4.

[0085] During the heating process of the heating device 4, dry gas is introduced into the heating chamber 407 to control the dew point of the heating chamber 407 to ensure that the dew point of the heating chamber 407 meets the requirements, and dew point control is performed to prevent hydrogen embrittlement and oxidation.

[0086] The hot air expansion forming method of the present invention uses the induction and resistance heating of the tube body of the metal tube 7, and its heating speed is adjusted by the input current. A steel tube with a diameter of φ50, a thickness of 2mm, and a length of 2m can be heated from room temperature to 950°C within 30 seconds, and the heating speed is fast. The heating time of hot air expansion parts for automobiles does not need to exceed 3 minutes. The heating power supply is an IGBT induction heating device 402. When the metal tube 7 is not demagnetized, that is, the temperature is below 750 degrees Celsius, the useful work is the induction heating current. When the metal tube 7 is demagnetized, that is, the temperature is above 750 degrees Celsius, the useful work is the resistance heating current. The heating rate is accurately controlled by PLC and infrared thermometer 406 to better protect the coating layer of the metal tube 7. The hot air expansion forming method of the present invention does not need to divide different process windows according to the thickness of the pipe fittings, define different heating parameters, can meet the material performance requirements of different coating thicknesses, control its heating speed to meet the coating structure of the finished product, and meet the anti-corrosion performance requirements to the maximum extent. It is simple to use and is conducive to stable control of product quality. The hot air bulging forming method of the present invention can add a heating unit according to the production program or the number of cavities of the mold to complete multiple outputs such as double pieces, triple pieces or quadruple pieces. The equipment has high flexibility and is flexible and convenient to use.

[0087] The heating system circuit diagram of the IGBT induction heating device 402 is as follows Figure 6 As shown in the figure, it is a series resonant circuit in the prior art, which removes the large and heavy filter reactor, reduces the loss, and the filter is performed by capacitor C1. The thyristor T1 is used as a switch here, and it is turned on when the power on the capacitor C1 is charged to a certain voltage. The frequency conversion circuit is composed of two IGBTs. The conduction loss of the IGBT is equivalent to that of the thyristor, while the switching loss is lower than that of the thyristor, so the loss of the frequency conversion current is about 3%. The output circuit of this circuit is characterized in that the induction coil and the compensation capacitor are connected in series to form a series resonant circuit. The characteristic of this circuit is that the current flowing through the IGBT is equal to the current flowing through the induction coil and the compensation capacitor, and the voltage on the induction coil is an induction voltage of about 100V. The IGBT is a fully controlled power device. Its opening and closing are directly controlled by its gate, which has nothing to do with the power factor of the oscillation circuit and the Q value of the oscillation circuit. Therefore, it can be successfully started regardless of the load. The series resonant medium-frequency induction heating furnace with IGBT frequency conversion has a high power factor of ≥0.95, significant power saving, 10%-30% power saving compared to the traditional series medium-frequency furnace, and can be successfully started under any load. By adjusting the frequency of the resonant circuit, the useful work proportion of induction heating can be fine-tuned.

[0088] In the description of this solution, it should be understood that the terms "upper", "lower", "vertical", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this solution.

[0089] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this solution, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0090] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0091] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hot air bulging forming system, characterized in that: It includes a pipe bending device, a feeding device, a preforming device, a heating device, a bulging and quenching device and a feeding device which are arranged in sequence. The heating device includes a heating chamber. An electrode chuck for clamping the end of the metal pipe is arranged in the heating chamber. The electrode chuck is connected to an IGBT induction heating device. An infrared thermometer is arranged in the heating chamber. Both the infrared thermometer and the IGBT induction heating device are communicatively connected to a controller.

2. The hot air bulging forming system according to claim 1, characterized in that: The heating device comprises a main frame, a heating platform is arranged on the main frame, and the electrode chuck is arranged on the heating platform; A sealing plate body is arranged around and on the top of the heating platform, the sealing plate body is connected to the main frame, and the sealing plate body and the heating platform surround the heating chamber.

3. The hot air bulging forming system according to claim 2, characterized in that: A dry gas dew point control component is provided in the heating chamber; The dry gas dew point control component includes a dew point sensor and a gas delivery component. The dew point sensor is arranged in the heating chamber. The dew point sensor is communicatively connected with the controller. The gas delivery component is used to deliver dry gas to the heating chamber.

4. The hot air bulging forming system according to claim 3, characterized in that: The gas delivery assembly includes a dry gas source and a porous exhaust pipe connected through an air inlet pipe, the porous exhaust pipe is arranged in the heating chamber, the dry gas source is arranged outside the heating chamber, a flow control valve is arranged at the inlet end of the porous exhaust pipe, and a plurality of exhaust through holes are arranged on the porous exhaust pipe, and the plurality of exhaust through holes are arranged along the length direction of the porous exhaust pipe, and the exhaust through holes are arranged toward the metal pipe; The dry gas source is used to contain dry gas, and the dry gas is air or nitrogen.

5. The hot air bulging forming system according to claim 1, characterized in that: A first handling robot is provided between the feeding device and the preforming device, and the first handling robot is used to transfer the metal pipe from the feeding device to the preforming cavity of the preforming device; A second handling robot is provided between the preforming device and the heating device, and the second handling robot is used to transfer the metal pipe from the preforming cavity to the heating cavity. After the heating of the metal pipe is completed, the second handling robot is used to transfer the metal pipe from the heating cavity to the bulging cavity of the bulging quenching device; A third handling robot is arranged between the bulging and quenching device and the blanking device, and the third handling robot is used to transfer the metal pipe from the bulging die cavity to the blanking conveyor belt of the blanking device.

6. The hot air bulging forming system according to claim 2, characterized in that: A lifting door is arranged on the side wall of the sealing plate body, and the width of the lifting door is greater than the length of the metal pipe.

7. A hot air bulging forming method, characterized in that: The following steps are involved: S1. Use a pipe bender to bend the metal pipe into shape; S2, transferring the bent metal pipe to a loading device, wherein the loading device positions the metal pipe; S3, grabbing the metal pipe from the feeding device and feeding it into the preforming cavity of the preforming device to preform the metal pipe; S4, sending the metal pipe in the preforming cavity into the heating chamber of the heating device for heating, clamping the metal pipe on the electrode clamp, and heating by the IGBT induction heating device, and the controller controls the IGBT induction heating device to heat; S5, the heated metal pipe is sent into the bulging die cavity of the bulging quenching device to complete the bulging quenching; S6, sending the metal pipe after bulging and cooling to a feeding device for feeding.

8. The hot air bulging forming method according to claim 7, characterized in that: The heating process in step S4 includes: S401, preheating process, adjusting the power on ratio of the IGBT induction heating device, the metal pipe is heated by 10-18°C per second, and the heating is performed for 0-3 seconds; S402, rapid heating process, adjusting the power on ratio of the IGBT induction heating device, the metal pipe is heated by 20-24°C per second, the heating time is 3-30 seconds, and the temperature of the metal pipe reaches 600-650°C; S403, a slow heating process, wherein the temperature of the metal pipe is raised by less than 10°C per second, and the temperature of the metal pipe is raised from 600-650°C to 840°C; S404, a first slow heating and heat preservation process, the metal pipe is slowly heated at 2-4°C per second, from 840°C to 850°C and then kept warm; S405, austenitizing process, the metal pipe is heated at 4-6°C per second, from 850°C to 925°C and then kept warm; S406, a second slow heating and heat preservation process, the metal pipe is heated at 1-2°C per second, from 925°C to 950°C and then kept warm.

9. The hot air bulging forming method according to claim 8, characterized in that: In step S404, the heating time is 55 to 60 seconds; in step S405, the heating time is 60 to 75 seconds; in step S406, the heating time is 76 to 180 seconds.

10. The hot air bulging forming method according to claim 7, characterized in that: Dry gas is introduced into the heating chamber to control the dew point of the heating chamber to ensure that the dew point of the heating chamber meets the requirements.

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