Device and method for preheating and forming square groove pipe under driving of electromagnetic force

Abstract

The invention discloses a device and method for preheating and forming a square groove pipe under electromagnetic force driving, the device comprises a first strategy module and a second strategy module, and the operation method comprises the steps that firstly, a workpiece is placed in a mold M1, a mold M2 is placed in the workpiece, and a punch and a driving piece are sequentially placed above the workpiece; current generated when the switch S1 closes the storage battery power source flows into the heating rod, the temperature of the heating rod gradually rises, the rise of the temperature can improve plastic deformation of workpiece forming, pulse current is introduced into the coil closed by the switch S1, at the moment, induction eddy current is generated in the driving piece, and according to the electrodynamic force effect, the driving piece moves downwards so as to push the punch to move downwards. According to the electromagnetic drive forming device, the square groove pipe is machined and manufactured through the electromagnetic drive forming technology, and the electromagnetic drive forming device has the advantages of being simple in structure and high in forming speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal pipe fitting forming, and particularly relates to a device and method for preheating and forming a square groove pipe driven by electromagnetic force. Background Art

[0002] The unique technical advantages of electromagnetic forming technology in processing light alloys have made it a new research hotspot. Currently, electromagnetic forming technology is mainly applied to sheet metal processing, pipe fitting processing, and metal welding processes. Among them, pipe fitting processing includes the processing of ordinary cylindrical pipe fittings and special-shaped pipe processing. Most of the forming of special-shaped pipe fittings is carried out by traditional mechanical stamping, forcing the workpiece to undergo plastic deformation. However, due to the poor formability of light alloys at room temperature, traditional processing methods are prone to cracking and have a large springback. If electromagnetic force-driven forming is used, the forming limit of light alloys can be significantly improved, effectively solving the above problems. However, in the current electromagnetic drive forming process, there are still defects in the forming accuracy when forming workpieces. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a device and method for preheating and forming a square groove pipe driven by electromagnetic force, which solves the problems of easy cracking, large springback, and poor formability at room temperature in traditional processing methods, can meet the processing requirements of various light metals, and enriches the processing methods for forming special-shaped pipes.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is: A device for preheating and forming a square groove pipe driven by electromagnetic force includes a first strategy module and a second strategy module. The first strategy module includes a capacitor-type power supply, which forms a series circuit with a first resistor R1, a first inductor L1, and a drive coil. A third resistor R3 is connected in series with a diode D1 and is connected in parallel with the capacitor-type power supply; the drive coil cooperates with a drive piece, and the drive piece is connected to a punch. The second strategy module includes a mold M1 and a mold M2. The mold M2 is installed inside the mold M1. A heating rod is provided inside the mold M2, and the heating rod is connected in series with a battery power supply, a second switch S2, and a second resistor R2; The punch is located above the mold M2.

[0005] A usage method of a device for preheating and forming a square groove pipe driven by electromagnetic force includes the following steps: Step 1: Select an annealed workpiece and place it on the mold M1, then place the mold M2 inside the workpiece, and sequentially place the drive piece and the punch above the workpiece. The drive coil is fixed above the drive piece; Step 2: Control the second strategy module to discharge. At this time, the current flowing through the heating rod slowly rises and quickly reaches a flat top, and the temperature of the workpiece gradually rises; Step 3: When the discharge current of the second strategy module reaches the flat top and the workpiece is heated, control the first strategy module to discharge. At this time, a downward electromagnetic force is generated on the driving plate, pushing the punch to move downward mechanically, causing plastic deformation of the workpiece.

[0006] Preferably, the discharges of the first strategy module and the second strategy module are realized by controlling the closing of the first switch S1 and the second switch S2; the first switch S2 is closed after the second switch S1 is closed for T seconds, and T seconds is the heating completion time of the workpiece.

[0007] Preferably, in Step 2, first control the switch S2 to close. At this time, the current generated by the battery power supply is introduced into the heating rod. At this time, the temperature of the heating rod rises slowly. When it reaches 1.5 ms, the current introduced into the heating rod tends to the flat top, and the heating rod gradually completes heating. Then in Step 3, control the switch S1 to close, and a pulsed current is introduced into the driving coil. The interaction between the time-varying eddy current generated on the driving plate and the alternating magnetic field generated by the driving coil pushes the punch to move downward. At this time, the workpiece is plastically deformed by the impact of the punch. The electromagnetic force formula of the driving coil is: ,

[0008] where is the proportionality coefficient; is the exciting current of the forming coil; represents the repulsive electromagnetic force directed outward; represents the slope steepness of the current waveform;

[0009] During use, when the discharge current is on the rising edge, the driving plate is mainly affected by the axial electromagnetic force directed downward. The axial electromagnetic force between the driving coils is simplified to: ,

[0010] where F is the Lorentz force when the current generated by the pulsed power supply rises slowly, J e1 is the induced eddy current density on the driving plate after the pulsed current is introduced, and the clockwise direction is specified as the positive direction; B is the axial component of the magnetic field generated by the pulsed current.

[0011] Preferably, a pulsed current is generated in the driving coil, a flat-top current is generated in the heating rod, and the battery power supply is composed of lead-acid batteries connected in series. The voltage of the lead-acid battery is 12.8 V and the internal resistance is 3.3 mΩ.

[0012] The present invention can achieve the following beneficial effects: An apparatus for preheating and forming a square groove tube driven by electromagnetic force provided by the present invention includes a heating device composed of a storage battery power supply and a heating rod, and an electromagnetic assisted forming device composed of a pulse power supply, a freewheeling circuit, a drive coil, a drive piece, and a punch. Since the plasticity of a metal workpiece increases with temperature rise, the present invention introduces a heating system to improve its forming rate and workpiece forming accuracy. Also, since the forming speed of a traditional stamping forming device is slow during the workpiece forming process, the present invention integrates the stamping forming method and the electromagnetic forming method, which can be achieved only by a single discharge of the forming coil. Therefore, two independent power supply systems are introduced in the design of the present invention, which not only effectively compensates for the problem of insufficient forming depth of the workpiece at room temperature, but also realizes the precise control of the complex shape of the part and the high-speed forming of the workpiece, and can be effectively applied to the forming systems of complex parts made of different materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be further described below with reference to the drawings and embodiments: Figure 1 It is an equivalent circuit diagram of the electromagnetic assisted forming module of the present invention.

[0014] Figure 2 It is an equivalent circuit diagram of the heating module of the present invention.

[0015] Figure 3 It is an ideal current waveform diagram of the double drive coil.

[0016] Figure 4 It is a structural schematic diagram of the invention.

[0017] In the figure: the first strategy module 1, the second strategy module 2, the capacitor type power supply 3, the drive coil 4, the drive piece 5, the punch 6, the capacitor type power supply 7, the heating rod 8. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The preferred solution is as Figures 1 to 4 shown. An apparatus for preheating and forming a square groove tube driven by electromagnetic force includes a first strategy module 1 and a second strategy module 2. The first strategy module 1 is an electromagnetic assisted forming module, and the second strategy module 2 is a heating module. The first strategy module includes a circuit composed of a capacitor type power supply 3, a first resistor R1, a first switch S1, a first inductor L1, a drive coil 4, and a diode D1, and a drive piece 5 and a punch 6 are sequentially placed below the drive coil. The second strategy module includes a circuit formed by connecting a capacitor type power supply 7, a second resistor R2, a second inductor L2, a second switch S2, and a heating rod 8 in series, wherein the heating rod is fixed inside the mold M2 and placed inside the workpiece, and the mold M1 is placed outside the workpiece.

[0019] Preferably, the first switch S1 and the second switch S2 are connected to a control system.

[0020] Preferably, a forming die is provided below and inside the workpiece.

[0021] A method for using a device for electromagnetic force-driven preheating and forming of a square groove tube below includes the following steps. Step 1: Select an annealed workpiece and place it on die M1. Then place die M2 inside the workpiece, and sequentially place the driving piece and the punch above the workpiece. Fix the driving coil above the driving piece. Step 2: Control the second strategy module to discharge. At this time, the current flowing through the heating rod slowly rises and quickly reaches a flat top, and the temperature on the workpiece gradually rises. Step 3: When the discharge current of the second strategy module reaches the flat top and the workpiece is heated, control the first strategy module to discharge. At this time, a downward electromagnetic force is generated on the driving piece, pushing the punch to move downward mechanically, causing plastic deformation of the workpiece.

[0022] Preferably, the discharges of the first strategy module 1 and the second strategy module 2 are realized by controlling the closing of the first switch S1 and the second switch S2 through a control system.

[0023] Preferably, the first switch S2 is closed for a certain time and then the first switch S1 is closed. This time is the time when the workpiece is heated.

[0024] Under the action of the battery power supply, the current flowing into the heating rod slowly rises and tends to a flat top, and the heating rod gradually completes heating. Then a pulsed current is passed into the driving coil, and the current waveform in the system is as Figure 3 shown.

[0025] Figure 1 is the equivalent circuit diagram of the circuit required for the first strategy module. Figure 2 is the equivalent circuit diagram of the circuit required for the second strategy module.

[0026] In this solution, a pulsed current is generated in the driving coil and a flat-top current is generated in the heating rod. When in use, the battery power supply for the flat-top current selects 12 lead-acid batteries connected in series as the battery power supply. The voltage of a single lead-acid battery is 12.8V and the internal resistance is 3.3 mΩ. The pulsed power supply for the pulsed current selects a capacitor bank with a relatively large total capacity.

[0027] First, control the switch S2 to close. At this time, the current generated by the battery power supply flows into the heating rod. At this time, the temperature of the heating rod slowly rises. At 1.5 ms, the current flowing into the heating rod tends to a flat top, and the heating rod gradually completes heating. At this time, control the switch S1 to close. At this time, a pulsed current is passed into the driving coil, and the interaction between the time-varying eddy current generated on the driving piece and the alternating magnetic field generated by the driving coil pushes the punch downward. At this time, the workpiece is impacted by the punch and undergoes plastic deformation.

[0028] The electromagnetic force formula of the driving coil is as follows: , where is the proportionality coefficient; is the exciting current of the forming coil; represents the repulsive electromagnetic force directed outward; represents the slope steepness of the current waveform. During use, when the discharge current is on the rising edge, the driving piece is mainly subjected to an axial electromagnetic force directed downward.

[0029] The axial electromagnetic force between the driving coils is simplified to: , where F is the Lorentz force when the current generated by the pulse power supply rises slowly, J e1 is the induced eddy current density on the driving piece after passing the pulsed current, and the clockwise direction is specified as the positive direction; B is the axial component of the magnetic field generated by the pulsed current. During use, when a pulsed current is passed through the driving coil, at this time, the driving piece generates a downward Lorentz force and moves downward, thereby pushing the punch downward and causing the workpiece to undergo plastic deformation behavior.

[0030] According to the characteristic that the battery power supply can generate a flat-top magnetic field, the present invention first passes the battery power supply through the heating rod. Since the current generated by the battery power supply rises slowly, the temperature of the heating rod gradually rises at this time, and the current passing through the heating rod only tends to be stable after 1.5 ms. After a period of time, the heating rod completes heating. At this time, the pulse power supply is passed through the driving coil again, and the time-varying pulsed current causes the driving piece to generate an induced eddy current. At this time, the driving piece starts to move downward under the interaction of the magnetic field generated by the capacitor-type power supply and the induced eddy current, pushing the punch downward, and the punch impacts downward to cause plastic deformation of the workpiece.

[0031] The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The protection scope of the present invention should be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, the equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. An apparatus for preheating and forming a square groove tube driven by electromagnetic force, characterized in that: It includes a first strategy module (1) and a second strategy module (2). The first strategy module (1) includes a capacitor-type power supply (3). The capacitor-type power supply (3), a first resistor R1, a first inductor L1, and a drive coil (4) form a series circuit loop. A third resistor R3 is connected in series with a diode D1 and then forms a parallel connection with the capacitor-type power supply (3). The drive coil (4) cooperates with a drive piece (5), and the drive piece (5) is connected to a punch (6). The second strategy module (2) includes a mold M1 and a mold M2. The mold M2 is installed inside the mold M1. A heating rod (8) is provided inside the mold M2. The heating rod (8) is connected in series with a battery power supply (7), a second switch S2, and a second resistor R2. The punch (6) is located above the mold M2.

2. The usage method of the device for preheating and forming a square groove tube driven by electromagnetic force according to claim 1, characterized in that It includes the following steps: Step 1: Select an annealed workpiece and place it on the mold M1. Then place the mold M2 inside the workpiece. The drive piece (5) and the punch (6) are sequentially placed above the workpiece, and the drive coil (4) is fixed above the drive piece (5). Step 2: Control the second strategy module (2) to discharge. At this time, the current flowing through the heating rod (8) slowly rises and quickly reaches a flat top, and the temperature of the workpiece gradually rises. Step 3: When the discharge current of the second strategy module (2) reaches the flat top and the workpiece is completely heated, control the first strategy module (1) to discharge. At this time, a downward electromagnetic force is generated on the drive piece (5), pushing the punch (6) to move downward mechanically, causing plastic deformation of the workpiece.

3. The usage method of the device for preheating and forming a square groove tube driven by electromagnetic force according to claim 2, characterized in that: The discharges of the first strategy module and the second strategy module are achieved by controlling the closing of the first switch S1 and the second switch S2. The first switch S2 is closed after closing the first switch S1 for T seconds, and T seconds is the time when the workpiece is completely heated.

4. The method of using the device for preheating and forming a square groove tube driven by electromagnetic force according to claim 3, characterized in that: In Step 2, first control the switch S2 to close. At this time, the current generated by the battery power supply is introduced into the heating rod. At this time, the temperature of the heating rod slowly rises. At 1.5 ms, the current flowing into the heating rod tends to reach the flat top, and the heating rod gradually completes heating. Then in Step 3, control the switch S1 to close. A pulsed current is introduced into the drive coil. The interaction between the time-varying eddy current generated on the drive piece and the alternating magnetic field generated by the drive coil pushes the punch downward. At this time, the workpiece undergoes plastic deformation under the impact of the punch. The electromagnetic force formula of the drive coil is: ， Among them, is the proportionality coefficient; is the exciting current of the forming coil; represents the repulsive electromagnetic force directed outward; represents the slope steepness of the current waveform; During use, when the discharge current is on the rising edge, the drive piece is mainly subjected to an axial electromagnetic force in the downward direction. The axial electromagnetic force between the drive coils is simplified to: , Among them, F is the Lorentz force when the current generated by the pulsed power supply rises slowly, J e1 is the induced eddy current density after a pulsed current is applied to the driving chip, and the clockwise direction is specified as the positive direction; B is the axial component of the magnetic field generated by the pulsed current.

5. The method of using the device for preheating and forming a square groove tube driven by electromagnetic force according to claim 3, characterized in that: A pulsed current is generated in the drive coil, and a flat-top current is generated in the heating rod. The battery power supply (7) is composed of lead-acid batteries connected in series. The voltage of the lead-acid battery is 12.8 V and the internal resistance is 3.3 mΩ.

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