A flanging method and device for small metal pipe fittings with attractive electromagnetic force using a stepped magnetic collector

Abstract

The present invention discloses a flanging method and device for attracting electromagnetic force metal small pipe fittings with a stepped magnetic collector, which solves the problems that the existing electromagnetic flanging method uses a double-coil double-power supply system with complex control and cumbersome tooling, while the forming effect of using a single-coil system is not good. Through a special stepped magnetic collector, the excellent performance of the stepped magnetic collector in strengthening the magnetic field in a specific area during flanging forming is utilized to achieve the effect of replacing the coil providing the axial background magnetic field. This method makes up for the problem of insufficient radial electromagnetic force in the single-coil system and simplifies the problems of complex control and cumbersome tooling in the double-coil system. Moreover, the stepped magnetic collector is simpler to manufacture and lower in cost compared with the drive coil, can shorten the manufacturing cycle, and is more conducive to actual mass production.

Description

Technical Field

[0001] The present invention belongs to the field of metal forming manufacturing, and particularly relates to a flanging method and device for small metal pipe fittings with an attracting electromagnetic force with a stepped magnetic collector, which are mainly used for the flanging process of small metal pipe fittings. Background Art

[0002] The flanging process of metal pipe fittings is a common processing technology in industry, which can be mainly divided into two types: contact type and non-contact type according to the processing method. Most of the existing contact flanging processes use mechanical force and hydraulic pressure, which require multiple processes and are prone to phenomena such as wrinkling and springback after forming. At present, the non-contact flanging technology, that is, electromagnetic flanging technology, mainly relies on a driving coil to generate pulsed electromagnetic force to drive the pipe fitting to achieve flanging. Although it has been improved, there are still many deficiencies.

[0003] Electromagnetic forming is a high-energy and high-speed pulsed forming technology, which has significant advantages such as fast forming speed, high forming quality, non-contact, clean and pollution-free compared with traditional quasi-static processing. For light metal alloys such as aluminum alloy and magnesium alloy, electromagnetic forming technology can significantly improve the forming ability of the alloy at room temperature and save a large amount of production costs.

[0004] The current electromagnetic flanging process has a complex structure and poor applicability to small metal pipe fittings. For example, in Chinese Patent Application CN112387845A, a device and method for electromagnetic flanging of large-size pipe fittings based on a magnetic collector realizes the flanging forming of large-size pipe fittings. However, the forming coil is difficult to wind, and the forming coil and the magnetic collector can only be placed inside the formed pipe fitting to generate the required repulsive force, and this method cannot be applied to the flanging forming of small metal pipe fittings. Chinese Patent CN107774780A, a method and device for non-contact flaring or flanging of pipe fittings without being placed inside the pipe fitting, realizes electromagnetic flanging of small pipe fittings. This device places two independently powered driving coils at the end of the pipe fitting and controls the acting time of the electromagnetic force by adjusting the power discharge time to complete, but compared with the single-coil flanging system, this system has complex control coordination and cumbersome tooling. Summary of the Invention

[0005] To solve the problems that in the flanging process of existing small metal pipe fittings, the repulsion electromagnetic force flanging method must place the driving coil inside the pipe fitting, which is not applicable in the flanging of small metal pipe fittings, and that placing two driving coils outside the ends of the pipe fitting and using a dual-coil dual-power supply system to generate an attraction electromagnetic force to achieve flanging results in complex system control and cumbersome tooling. The present invention proposes an attraction electromagnetic force flanging method and device for small metal pipe fittings with a stepped magnetic collector. Based on a single-coil dual-power supply system, a special stepped magnetic collector is introduced. By utilizing the excellent performance of the stepped magnetic collector to strengthen the magnetic field in a specific area during flanging forming, the effect of replacing the coil providing the axial background magnetic field is achieved, and there is sufficient radial electromagnetic force to form the flange at the end of the metal pipe fitting.

[0006] The technical solution adopted by the present invention is as follows:

[0007] An attraction electromagnetic force flanging method for small metal pipe fittings with a stepped magnetic collector, comprising the following steps:

[0008] Step 1: Use a winding machine to wind a set of driving coils, cover interlayer insulating materials between layers. After the driving coils are wound, weld copper bar electrodes, reinforce the periphery with high-strength fibers, and electrically connect them to the corresponding two sets of pulse capacitor power supply systems;

[0009] Step 2: Perform an annealing pretreatment operation on the small metal pipe fitting;

[0010] Step 3: Slip the driving coil over the end of the small metal pipe fitting, place the stepped magnetic collector inside the driving coil, and coaxial with the center of the driving coil;

[0011] Step 4: Use hydraulic equipment to fix the driving coil and the small metal pipe fitting;

[0012] Step 5: Charge the pulse capacitors through a charging system, store electrical energy in the pulse capacitor bank, close the circuit, generate a long pulse-width current in the driving coil, thereby generating an axial background magnetic field in the forming area;

[0013] Step 6: When the axial background magnetic field generated by the long pulse-width current reaches the peak value, simultaneously load a reverse short pulse-width current in the driving coil to generate induced eddy currents in the small metal pipe fitting;

[0014] Step 7: Under the combined action of the background magnetic field and the induced eddy currents, the end of the small metal pipe fitting is subjected to a radial electromagnetic force;

[0015] Step 8: Through the adjustment of the stepped magnetic collector, strengthen the magnetic field in the flanging area of the small metal pipe fitting, change the distribution of the electromagnetic force, and drive the flanging of the small metal pipe fitting.

[0016] The driving coil is placed outside the small metal pipe fitting and at the end of the small metal pipe fitting. The stepped magnetic concentrator is placed radially inside the driving coil and coaxial with the center of the driving coil.

[0017] The driving coil is connected to two pulse capacitors simultaneously, which are used to generate a long pulse-width current and load a reverse short pulse-width current in the driving coil.

[0018] The driving coil applies a long pulse-width current and a reverse short pulse-width current. The timing relationship between the long pulse-width current and the reverse short pulse-width current is that the reverse short pulse-width current is loaded when the long pulse-width current reaches its peak.

[0019] The forming time of the flanging of the small metal pipe fitting is the rising edge of the reverse short pulse-width current.

[0020] The stepped magnetic concentrator is used to adjust the magnetic field configuration, strengthen the magnetic field in the area to be flanged of the small metal pipe fitting and the eddy current density inside the pipe fitting, and change the distribution of the electromagnetic force.

[0021] A device for implementing the method for flanging a small metal pipe fitting with an attractive electromagnetic force with a stepped magnetic concentrator, the device comprising:

[0022] A driving coil, which provides electromagnetic force for the small metal pipe fitting to be flanged;

[0023] A stepped magnetic concentrator, which adjusts the position and shape of the magnetic field;

[0024] A pulse capacitor power supply system, which provides energy for the driving coil.

[0025] The device is of an axisymmetric structure. The driving coil and the stepped magnetic concentrator are at the end of the metal pipe fitting to be flanged. The stepped magnetic concentrator is located inside the driving coil and is coaxial with the driving coil.

[0026] The stepped magnetic concentrator is an auxiliary accessory for strengthening the magnetic field in the flanging area during electromagnetic flanging. It uses the stepped structure and the skin effect to cooperate with each other to transfer the coil-induced eddy current. The two-dimensional axisymmetric structure of the stepped magnetic concentrator is stepped, its lower bottom surface is smaller than its upper bottom surface, and there is a longitudinal slit in it, which is placed between the pipe fitting and the driving coil.

[0027] The present invention has the following beneficial effects:

[0028] 1. On the basis of the existing electromagnetic flanging system, the present invention introduces a stepped magnetic concentrator device. Its main function is to transfer the energy of the driving coil to the area to be flanged of the small metal pipe fitting, strengthen the magnetic field in the area to be flanged, make the electromagnetic force more concentratedly distributed, so as to realize the electromagnetic flanging of the small metal pipe fitting under the condition of using a single coil, and the flanging effect is excellent.

[0029] 2. The present invention uses an attractive electromagnetic force to drive small metal pipe fittings, without placing the drive coil and the magnetic collector in the pipe fittings. The flanging forming of metal pipe fittings is no longer limited by the size of the internal space of the metal pipe fittings, greatly expanding the application scenarios of electromagnetic forming technology.

[0030] 3. The present invention improves the economy of the electromagnetic flanging system for small metal pipe fittings. In the existing electromagnetic flanging, the winding process of the drive coil is very cumbersome, and the materials such as epoxy resin and reinforcing fibers required during the winding process are very expensive. Compared with the drive coil, the manufacturing cost of the stepped magnetic collector is lower. At the same time, after introducing the stepped magnetic collector, the stepped magnetic collector bears the electromagnetic force of both the small metal pipe fitting and the drive coil, effectively reducing the electromagnetic force acting on the forming coil and extending the service life of the coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below in conjunction with the drawings and embodiments.

[0032] Figure 1 is a schematic assembly diagram of the flanging of small metal pipe fittings by an attractive electromagnetic force based on a stepped magnetic collector;

[0033] Figure 2 is a schematic diagram of the circuit topology of the pulse power supply system;

[0034] Figure 3 is a schematic diagram of the timing coordination of the pulsed current loading in the coil;

[0035] Figure 4 is a three-dimensional structure schematic diagram of the stepped magnetic collector;

[0036] Figure 5 is a schematic diagram of the current distribution of the flanging system with a stepped magnetic collector;

[0037] Figure 6 is a schematic diagram of the comparison of the magnetic flux density with and without a stepped magnetic collector;

[0038] Figure 7 is a schematic diagram of the comparison of the eddy current density with and without a stepped magnetic collector;

[0039] Figure 8 is a schematic diagram of the flanging result without a magnetic collector;

[0040] Figure 9 is a schematic diagram of the flanging result with a flat magnetic collector;

[0041] Figure 10 is a schematic diagram of the flanging result with a trapezoidal magnetic collector;

[0042] Figure 11 is a schematic diagram of the flanging result with a stepped magnetic collector.

[0043] Figure numerals: 1 is the driving coil, 2 is the stepped magnetic collector, 3 is the small metal tube, 4 is the radial electromagnetic force, 5 is the long pulse width current, 6 is the short pulse width current, 7 is the trapezoidal magnetic collector, and 8 is the flat magnetic collector. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of 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 merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0045] The present invention proposes a device for flanging a small metal tube using an attractive electromagnetic force with a stepped magnetic concentrator, comprising: a driving coil 1, which simultaneously provides a background magnetic field and induced eddy currents for the small metal tube to be flanging; a stepped magnetic concentrator 2, which uses a special structure to adjust the configuration of the magnetic field in the area to be flanging; and a pulse capacitor power supply, which provides energy for the driving coil.

[0046] The device has an axisymmetric structure. The driving coil 1 and the stepped magnetic collector 2 are located at the end of the metal pipe to be flanging. The stepped magnetic collector 2 is located inside the driving coil 1 and is coaxial with the driving coil 1.

[0047] The stepped magnetic collector 2 is an auxiliary accessory for strengthening the magnetic field in the flange area of the electromagnetic flange. It uses the stepped structure and skin effect to cooperate with each other to transmit the coil-induced eddy current. The stepped magnetic collector 2 has a two-dimensional axially symmetrical structure that is stepped. Its lower bottom surface is smaller than the upper bottom surface, and there is a longitudinal fracture, which is placed between the pipe and the driving coil 1.

[0048] The pulse capacitor power supply system is generally composed of a charging system, an energy storage system, and a discharge circuit. First, the charging system charges the capacitor bank, the energy storage system accumulates energy, and the discharge switch is closed. The energy storage system transfers energy to the drive coil through the discharge circuit. Figure 1 shown.

[0049] Figure 2 This is a schematic diagram of the pulse power supply system circuit topology, which is connected to both ends of the driving coil 1. The figures shown in the figure are the equivalent inductance and equivalent resistance of the driving coil 1 respectively.

[0050] A method for flanging a small metal pipe with an attractive electromagnetic force and a stepped magnetic collector, comprising the following steps:

[0051] Step 1: Use a winding machine to wind a set of drive coils 1, and cover an interlayer insulating material between layers. After the drive coils 1 are wound, weld copper bar electrodes, reinforce the periphery with high-strength fibers, and electrically connect them to two corresponding sets of pulse capacitor power supply systems;

[0052] Step 2: Perform an annealing pretreatment operation on the metal small pipe fitting 3;

[0053] Step 3: Sleeve the drive coils 1 outside the metal small pipe fitting 3, and the drive coils 1 are located at the ends of the metal small pipe fitting 3. Place the stepped magnetic collector 2 inside the drive coils 1 and coaxial with the center of the drive coils 1;

[0054] Step 4: Use hydraulic equipment to fix the drive coils 1 and the metal small pipe fitting 3, and the pressure is generally set to 1 - 1.5 Mpa;

[0055] Step 5: Charge the pulse capacitor through a charging system, and store electrical energy in the pulse capacitor bank. Close the air switch to generate a long pulse-width current 5 in the drive coils 1, thereby generating an axial background magnetic field in the forming area;

[0056] Step 6: When the axial background magnetic field generated by the long pulse-width current 5 reaches the peak value, simultaneously apply a reverse short pulse-width current 6 in the drive coils 1 to generate an induced eddy current in the metal small pipe fitting 3;

[0057] Step 7: Under the combined action of the axial background magnetic field and the induced eddy current, the end of the metal small pipe fitting 3 is subjected to a radial electromagnetic force 4;

[0058] Step 8: Through the adjustment of the stepped magnetic collector 2, strengthen the magnetic field in the flanging area of the metal small pipe fitting 3 and the density of the induced eddy current inside the pipe fitting, change the distribution of the electromagnetic force, and drive the flanging of the metal small pipe fitting 3.

[0059] Specifically, the drive coils 1 apply a long pulse-width current 5 and a reverse short pulse-width current 6, and the timing relationship between the long pulse-width current 5 and the reverse short pulse-width current 6 is: apply the reverse short pulse-width current 6 when the long pulse-width current 5 reaches the peak value.

[0060] Specifically, the effective time for loading the radial electromagnetic force is: the rising edge of the short pulse-width current loading.

[0061] Specifically, the drive coil is connected to the long pulse-width current generating circuit through the switching tube T S and the drive coil is simultaneously connected to the short pulse-width current generating circuit through the switching tube T F and the short pulse-width current generating circuit.

[0062] When a pulse current is passed through the drive coils 1, an induced eddy current is generated in the stepped magnetic collector 2, see Figure 4 、 5, the air gap in the trapezoidal magnetic collector 2 blocks the flow of current on the stepped magnetic collector 2. Affected by the skin effect, the induced current only flows on the surface of the stepped magnetic collector 2. Therefore, the direction of the induced current in the stepped magnetic collector 2 is from the upper surface to the lower surface, forming a closed loop. Due to the skin effect and the fact that the lower surface area of the stepped magnetic collector 2 is smaller than the upper surface area, the current density on the lower surface is much larger, and the magnetic field generated in this nearby area will be relatively stronger. Moreover, the induced current in the stepped magnetic collector 2 generates induced eddy currents in the metal small pipe fittings, and the magnetic field generated by this part of the eddy currents will also be strengthened by the magnetic field generated by the current in the driving coil 1. This makes the magnetic field strengthened in the area between the lower surface of the stepped magnetic collector 2 and the metal small pipe fittings 3, and can strengthen the induced eddy current density inside the pipe fittings, thereby effectively enhancing the electromagnetic force, as Figures 5 - 7 shown.

[0063] A pulsed magnetic field is generated by a pulsed current. The pulsed magnetic field will generate induced eddy currents in the metal small pipe fittings. The combined action of the induced eddy currents and the pulsed magnetic field generates the Lorentz force to drive the deformation of the metal material. The calculation formulas for the multi-physical field analysis involved in the present invention are as follows:

[0064]

[0065] In the formula, F z and F r are the axial Lorentz force and the radial Lorentz force respectively; J e is the induced eddy current density on the pipe fitting, and the clockwise direction is specified as the positive direction; Bz and Br are the axial magnetic field component and the radial magnetic field component respectively; J L is the induced eddy current generated by the long pulse-width current on the metal small pipe fitting, and J S is the induced eddy current generated by the short pulse-width current on the metal small pipe fitting; B L-Z is the axial magnetic field generated by the long pulse-width current in the flanging area of the metal small pipe fitting, and B S-Z is the axial magnetic field generated by the short pulse-width current in the flanging area of the metal small pipe fitting; t represents time, t1 is the moment when the long pulse-width current reaches the peak, and t2 is the moment when the short pulse-width current reaches the peak.

[0066] Two groups of pulsed capacitor power supplies are connected in parallel across the two ends of the driving coil 1 (see Figure 2 ). The pulse width of the short pulse-width current 6 is much smaller than that of the long pulse-width current 5 (see Figure 3 ). The influence of the short pulse-width current 6 on the axial background magnetic field can be ignored. At the same time, the rising edge of the long pulse-width current 5 is relatively slow, and its influence on the induced eddy current can be ignored. A reverse short pulse-width current 6 is loaded when the long pulse-width current 5 reaches the peak to make the best use of the axial magnetic field generated by the long pulse-width current 5. At this time, the circumferential eddy current and the axial magnetic field interact with each other to generate the maximum radial electromagnetic force in the metal small pipe fitting 3, realizing the flanging forming of the metal small pipe fitting.

[0067] In Figure 1 the model shown, first, a long-pulse-width current 5 is passed through the driving coil 1, and the direction of the axial background magnetic field is downward. When the long-pulse-width current 5 reaches its peak value, a short-pulse-width current 6 is applied. The direction of the eddy current induced in the small metal pipe fitting 3 is circumferential and counterclockwise. According to the formula above, the Lorentz force generated by the two together is a radial force, thus driving the small metal pipe fitting to complete the flanging forming.

[0068] In this embodiment, the multi-physics software COMSOL is used for numerical analysis, and the simulation results are as shown in Figure 6 、 7 In the flanging scheme without a magnetic collector, the flanging effect of the small metal pipe fitting is as shown in Figure 8 In the flanging scheme with a flat magnetic collector, the flanging effect of the small metal pipe fitting is as shown in Figure 9 In the flanging scheme with a trapezoidal magnetic collector, the flanging effect of the small metal pipe fitting is as shown in Figure 10 In the flanging scheme with a stepped magnetic collector, the flanging effect of the small metal pipe fitting is as shown in Figure 11 By numerical simulation analysis, it can be obtained by comparison that the stepped magnetic collector significantly improves the flanging forming effect of the small metal pipe fitting.

Claims

1. A flanging method for small metal pipe fittings with an attracting electromagnetic force using a stepped magnetic collector, characterized in that The steps include: Step 1: Wind a set of drive coils (1) using a winding machine and cover the layers with interlayer insulation material. After the drive coils (1) are wound, copper busbar electrodes are welded, and the outer periphery is reinforced with high-strength fiber, and electrically connected to the corresponding two sets of pulse capacitor power supply systems; Step 2: performing an annealing pretreatment operation on the small metal tube (3); Step 3: The driving coil (1) is sleeved on the end of the small metal tube (3), and the stepped magnetic collector (2) is placed inside the driving coil (1) and coaxial with the center of the driving coil (1); the stepped magnetic collector (2) is an auxiliary accessory for strengthening the magnetic field in the flanging area of the electromagnetic flanging, and utilizes the stepped structure and the skin effect to cooperate with each other to transmit the coil-induced eddy current. The stepped magnetic collector (2) has a two-dimensional axisymmetric structure of a stepped type, its lower bottom surface is smaller than the upper bottom surface, and there is a longitudinal fracture, and is placed between the small metal tube (3) and the driving coil (1); Step 4: Use hydraulic equipment to fix the drive coil (1) and the small metal pipe (3); Step 5: charging the pulse capacitor through the charging system, storing the electrical energy in the pulse capacitor bank, closing the circuit, generating a long pulse width current (5) in the driving coil (1), thereby generating an axial background magnetic field in the forming area; Step 6: When the axial background magnetic field generated by the long pulse width current (5) reaches a peak value, a reverse short pulse width current (6) is simultaneously loaded into the driving coil (1) to generate an induced eddy current in the small metal tube (3); Step 7: Under the combined action of the background magnetic field and the induced eddy current, the end of the small metal tube (3) is subjected to a radial electromagnetic force (4); Step 8: By adjusting the stepped magnetic concentrator (2), the magnetic field in the area to be flanging the small metal tube (3) is strengthened, the distribution of the electromagnetic force is changed, and the small metal tube (3) is driven to flanging; The driving coil (1) applies a long pulse width current (5) and a reverse short pulse width current (6), and the timing relationship between the long pulse width current (5) and the reverse short pulse width current (6) is: the reverse short pulse width current (6) is loaded when the long pulse width current (5) reaches a peak value.

2. The flanging method for small metal pipe fittings with an attracting electromagnetic force using a stepped magnetic collector according to claim 1, characterized in that: The driving coil (1) is placed outside the small metal tube (3) and at the end of the small metal tube (3); the stepped magnetic collector (2) is placed radially inside the driving coil (1) and coaxial with the center of the driving coil (1).

3. The flanging method for small metal pipe fittings with an attracting electromagnetic force using a stepped magnetic collector according to claim 1, characterized in that: The driving coil (1) is simultaneously connected to two pulse capacitors for generating a long pulse width current (5) and loading a reverse short pulse width current (6) in the driving coil (1).

4. The flanging method for small metal pipe fittings with an attracting electromagnetic force using a stepped magnetic collector according to claim 1, characterized in that: The forming time of the flanging forming of the small metal tube (3) is the rising edge of the reverse short pulse width current (6).

5. The flanging method for small metal pipe fittings with an attracting electromagnetic force using a stepped magnetic collector according to claim 1, characterized in that: The stepped magnetic concentrator (2) is used to adjust the magnetic field configuration, strengthen the magnetic field in the area to be flanging the small metal tube (3) and the eddy current density inside the tube, and change the distribution of electromagnetic force.

6. An apparatus for implementing the flanging method of an attractively electromagnetic metal small pipe fitting with a stepped magnetic collector as claimed in claim 1, characterized in that, The device includes: A driving coil (1) provides electromagnetic force to the small metal tube (3) to be flanging; A stepped magnetic collector (2) for adjusting the position and shape of the magnetic field; A pulse capacitor power supply system for providing energy to the drive coil (1); The device has an axisymmetric structure. The drive coil (1) and the stepped magnetic concentrator (2) are located at the end of the metal pipe fitting to be flanged. The stepped magnetic concentrator (2) is inside the drive coil (1), and the stepped magnetic concentrator (2) is coaxial with the drive coil (1).

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