Electromagnetic tube bulging method using reinforced conductor ring and bulging device

Abstract

The present application relates to a pipe electromagnetic bulging method using a reinforced conductor ring, and belongs to the field of electromagnetic forming control of metal workpieces. The present application increases a reinforced conductor ring between a driving coil and a pipe to be formed, and the reinforced conductor ring is arranged at the end of the bulging area of the pipe to be formed. The reinforced conductor ring is used to enhance the magnetic field intensity at the end of the bulging area of the pipe to be formed, and the uniform bulging of the pipe is realized by using the reinforced conductor ring. The present application also discloses a corresponding pipe electromagnetic bulging device. The present application solves the problem of the influence of the end effect on the uniformity of the pipe bulging in the traditional pipe bulging method, realizes the uniform bulging of the pipe, improves the flatness of the bulged pipe, and effectively improves the problem of the wall thickness reduction of the pipe bulging area in the traditional pipe bulging method.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic forming control of metal workpieces, and in particular relates to a pipe electromagnetic expansion method and an expansion device using a reinforced conductor ring. Background Art

[0002] The new energy vehicle industry is currently experiencing rapid growth, and lightweighting technology is an effective way to reduce vehicle weight. Research shows that reducing the curb weight of a conventional vehicle by 10% can reduce fuel consumption by 8%. Furthermore, reducing vehicle weight by 100 kg reduces CO2 emissions by 5 g / km, and reducing exhaust emissions by 20 kg over its entire lifecycle. Aluminum alloy is a relatively mature lightweight material and is already being used in the new energy vehicle industry.

[0003] Electromagnetic forming (EMF) is a high-speed machining method that utilizes pulsed electromagnetic forces. It can improve forming efficiency and expand the range of materials that can be formed. It can also reduce production costs and improve forming quality. Therefore, EMF is an effective option for machining lightweight materials.

[0004] The existing literature on electromagnetic forming to improve the uniformity of pipe fittings mainly focuses on changing the coil shape and using a magnetic collector to change the magnetic field distribution. In 2018, Qiu Li's paper "Analysis of the expansion electromagnetic force and deformation characteristics of concave coil electromagnetic tube based on finite element method" [1] "It is proposed to use concave coils to replace the original cylindrical coils to improve the forming performance. The basic principle is to use concave coils to strengthen the electromagnetic force at both ends of the forming. This method solves the problems of uneven magnetic field forming and thinning of wall thickness. However, due to the complex coil winding, the processing cost is high and it is not easy to package. The patent invention with publication number CN114769408A is "Electromagnetic bulging method and device for bidirectional loading of inner and outer walls of magnetic collector [2] "An electromagnetic bulging device is disclosed, the main components of which are a forming coil and a new type of magnetic concentrator. This invention uses a bidirectional loading method on the inner and outer walls of the annular magnetic concentrator to improve the axial uniformity of the bulging and effectively suppress the thinning of the wall thickness during the bulging process. However, this new type of magnetic concentrator has a complex structure and a high manufacturing process. After manufacturing, its application range is mostly the same size workpiece, the reuse rate is low, and the control method is inflexible.

[0005] In summary, the prior art lacks a method and device for improving electromagnetic forming performance with flexible control methods and lower costs.

[0006] References:

[0007] [1]Li Q,Yijie Y,Qi X, et al. Analysis of Electromagnetic Force andDeformation Behavior in Electromagnetic Tube Expansion With Concave CoilBased on Finite Element Method[J].IEEE Transactions on AppliedSuperconductivity,2018,28(3):1-5.

[0008] [2]Qiu L,He Q,Wu WY. Electromagnetic tube expansion method and device with bidirectional loading on inner and outer walls of magnetic collector[P]. Hubei Province:CN202210422853.9,2024-03-12. SUMMARY

[0009] The purpose of the present application is to solve the above problems, provide a pipe electromagnetic expansion method using a reinforced conductor ring, by introducing a reinforced conductor ring between the drive coil and the formed workpiece, the reinforced conductor ring strengthens the magnetic field strength of the end part of the pipe to be formed, and realizes uniform pipe expansion.

[0010] In order to achieve the above purpose, the technical scheme provided by the present application is:

[0011] The pipe electromagnetic expansion method using a reinforced conductor ring comprises the following steps:

[0012] Step 1: According to the material and forming specification of the pipe to be formed, determine the parameters of the drive coil, and make the drive coil;

[0013] Step 2: According to the parameters of the drive coil and the pipe forming specification, determine the size parameters of the reinforced conductor ring;

[0014] Step 3: According to the parameters obtained in step 2, make the reinforced conductor ring and the conductor ring support, and arrange the reinforced conductor ring on the conductor ring support;

[0015] Step 4: Arrange and fix the pipe to be formed, the conductor ring support and the drive coil on the workpiece base in sequence;

[0016] Step 5: Connect the drive coil with the pulse power source through the switch, control the air switch to supply power to the drive coil, control the discharge time of the pulse power source, and perform electromagnetic expansion on the pipe to be formed;

[0017] Step 6: Determine whether the pipe expansion effect meets the pipe forming specification, if it meets the forming specification, end, otherwise, perform step 5 to perform electromagnetic expansion on the pipe again.

[0018] Preferably, the reinforcing conductor ring is provided with a split.

[0019] Preferably, the reinforcing conductor ring is rectangular in cross section.

[0020] Preferably, in step 2, a pipe electromagnetic bulging simulation model containing the drive coil, the reinforcing conductor ring and the pipe is constructed by using the finite element software COMSOL Multiphysics, a pulse current is applied to the drive coil in the pipe electromagnetic bulging simulation model, the bulging effect of the pipe is simulated, and compared with the pipe forming specification, the size parameters of the reinforcing conductor ring are adjusted to make the pipe bulging effect meet the needs of the pipe forming specification, and the size parameters of the reinforcing conductor ring are determined by simulation.

[0021] Preferably, the longitudinal distance between the reinforcing conductor ring and the end of the pipe bulging area is 10 mm.

[0022] Preferably, the distance between the reinforcing conductor ring and the drive coil is 2-8 mm.

[0023] Preferably, the distance between the reinforcing conductor ring and the pipe to be formed is 1-5 mm.

[0024] Preferably, the reinforcing conductor ring is made of red copper material.

[0025] Preferably, in step 5, the pulse power source is a capacitor power source, the capacitance of the capacitor power source is 10-1000 μF, and the discharge voltage of the capacitor power source is 1-10 kv.

[0026] The bulging device of the pipe electromagnetic bulging method comprises a drive coil, a reinforcing conductor ring, a conductor ring support and a pulse power source; the conductor ring support is used to support and fix the reinforcing conductor ring; and the drive coil is connected with the pulse power source through a switch.

[0027] Further, the bulging device further comprises a workpiece base, which is used to fix the pipe, the conductor ring support and the drive coil.

[0028] Compared with the prior art, the beneficial effects of the present application include:

[0029] 1) The pipe bulging method of the present application solves the problem of uneven pipe bulging caused by end effect in the traditional pipe bulging method by adding a reinforcing conductor ring between the drive coil and the pipe to be formed, thereby enhancing the magnetic field strength at the end of the pipe bulging area, realizing uniform bulging of the pipe, and effectively improving the problem of wall thickness reduction in the pipe bulging area in the traditional pipe bulging method.

[0030] 2) The reinforcing conductor ring of the present invention has a rectangular cross-section, is easy to manufacture, and is low-cost. Compared with the method of improving the driving coil, it is less difficult. Moreover, by replacing the reinforcing conductor ring with different size parameters, different tube expansion effects can be achieved to meet the requirements of various tube forming specifications.

[0031] 3) The tube bulging method of the present invention weakens the magnetic field strength in the middle of the tube bulging zone by adding a shielded conductor ring between the driving coil and the bulging tube. This also solves the problem of the traditional tube bulging method affecting the uniformity of the tube bulging due to the end effect, thereby achieving uniform bulging of the tube.

[0032] 4) The shielded conductor ring of the present invention has a rectangular cross-section, is easy to manufacture, has low cost, and is less difficult than improving the driving coil. Different pipe expansion effects can be achieved by replacing shielded conductor rings with different size parameters or using multiple shielded conductor rings, meeting the requirements of various pipe forming specifications.

[0033] 5) The present invention combines a shielded conductor ring with a reinforced conductor ring for tube bulging. The shielded conductor ring weakens the magnetic field strength and electromagnetic force in the middle of the tube bulging zone, while the reinforced conductor ring enhances the magnetic field strength at the end of the bulging zone of the tube to be formed. Compared with using only the reinforced conductor ring or the shielded conductor ring, the present invention can further improve the flatness of the bulging zone after the tube is bulged, thereby improving the problem of thinning of the tube wall thickness in the bulging zone in traditional tube bulging methods.

[0034] 6) The present invention uses a reinforced conductor ring and / or a shielded conductor ring to reduce the reaction force generated by the induced current of the pipe on the drive coil during the pipe forming process, effectively protecting the drive coil and extending the service life of the drive coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below with reference to the accompanying drawings and examples.

[0036] Figure 1 Schematic diagram of the process of the electromagnetic bulging method for pipes using a reinforced conductor ring according to the first embodiment.

[0037] Figure 2 FIG. 4 is an equivalent circuit diagram of the connection between the driving coil and the power supply according to an embodiment of the present invention.

[0038] Figure 3 Schematic diagram of the tube expansion device of Example 1.

[0039] Figure 4 Schematic diagram of the reinforced conductor ring of Example 1.

[0040] Figure 5 Schematic diagram of the induced eddy current of the reinforcing conductor ring according to the first embodiment.

[0041] Figure 6A schematic diagram of a pipe expansion device combining the shielded conductor ring and the reinforced conductor ring of Example 2.

[0042] Figure 7 A schematic diagram of the shielded conductor ring and the reinforced conductor ring of Example 2.

[0043] Figure 8 A schematic diagram of the induced eddy current of the shielded conductor ring and the reinforced conductor ring of Example 2.

[0044] Figure 9 A comparison diagram of the forming effect of the pipe electromagnetic expansion method of Example 1 and the traditional pipe expansion method.

[0045] Legend: workpiece base 1, pipe to be formed 2, expansion zone 201, conductor ring support 3, reinforced conductor ring 4, drive coil 5, shielded conductor ring 6. DETAILED DESCRIPTION

[0046] Example 1

[0047] In the example, by introducing a reinforced conductor ring between the drive coil and the forming workpiece, the reinforced conductor ring strengthens the local area where the electromagnetic force is weak, and finally realizes uniform expansion. The reinforced conductor ring has a gap, and the cross section of the reinforced conductor ring is rectangular.

[0048] As shown in Figure 1 , the pipe electromagnetic expansion method using the reinforced conductor ring includes the following steps:

[0049] Step 1: According to the material and forming specification of the pipe to be formed, determine the parameters of the drive coil, and make the drive coil;

[0050] Step 2: According to the parameters of the drive coil and the forming specification of the pipe, determine the size parameters of the reinforced conductor ring;

[0051] Use the finite element software COMSOL Multiphysics to establish a pipe electromagnetic expansion simulation model, including the reinforced conductor ring, the pipe to be formed, and the drive coil. Load pulse current on the drive coil to generate electromagnetic force in the pipe. Analyze the final forming effect, adjust the model parameters, compare the uniformity of the final forming effect of the pipe, and get the optimal geometric size and spacing of the reinforced conductor ring.

[0052] Step 3: According to the parameters obtained in step 2, make the reinforced conductor ring and the conductor ring support, and arrange the reinforced conductor ring on the conductor ring support;

[0053] Step 4: Arrange and fix the pipe to be formed, the conductor ring support, and the drive coil on the workpiece base in sequence;

[0054] Step 5: connecting the driving coil with the pulse power source through the switch, controlling the air switch to supply power to the driving coil, controlling the discharge time of the pulse power source, and electromagnetically expanding the pipe to be formed;

[0055] Step 6: judging whether the expansion effect of the pipe meets the forming specification of the pipe, and if so, ending the process, otherwise, executing Step 5 to electromagnetically expand the pipe again.

[0056] As shown in Figure 3 , the pipe electromagnetically expanding device of Example One includes a workpiece base 1, a pipe to be formed 2, a conductor ring support 3, reinforced conductor rings 4, a driving coil 5, and a pulse power source. The workpiece base serves to fix the pipe to be formed, the conductor ring support, and the driving coil, and sequentially fixes the pipe to be formed, the conductor ring support, and the driving coil from outside to inside. The reinforced conductor rings are nested in the conductor ring support. The driving coil 5 is connected with the pulse power source through an air switch, as shown in Figure 2 .

[0057] In the example, the length of the pipe to be formed is 60 mm, the number of the reinforced conductor rings is 2, the height h of the two reinforced conductor rings is 8 mm, the width is 2 mm, and the interval d is 40 mm. The geometric shape of the reinforced conductor ring is shown in Figure 4 .

[0058] In the process of electromagnetically expanding the pipe, the pulse power source supplies power to the driving coil, and the induced current of the driving coil, the pipe to be formed, and the reinforced conductor rings is shown in Figure 5 . The driving coil on the right side of the symmetry axis forms an outward current, and the reinforced conductor ring is a metal ring with a gap. According to the law of electromagnetic induction, an induced eddy current opposite to the pulse magnetic field is generated on the side of the reinforced conductor ring close to the driving coil, and after two reversals, an induced eddy current same as the pulse magnetic field is generated at the end of the pipe expansion zone, so as to strengthen the electromagnetic field at the end of the pipe expansion zone near the reinforced conductor ring. The introduction of the reinforced conductor ring causes the electromagnetic force on the two ends of the pipe to be greater than that in the conventional electromagnetic expansion method. Therefore, the radial electromagnetic force on the two ends of the pipe is greater, the axial uniformity of the pipe is improved, the forming effect is better, and the flatness of the expanded pipe is better.

[0059] In the example, the pipe forming effect of the pipe electromagnetically expanding method using the reinforced conductor ring is compared with that of the conventional pipe expanding method, as shown in Figure 9 . It can be seen that the pipe electromagnetically expanding method using the reinforced conductor ring of the present application solves the problem of affecting the uniformity of pipe expansion due to end effect in the conventional pipe expanding method, and the expanded pipe obtained by the present application has a more flat and uniform expansion zone.

[0060] Example Two

[0061] The difference between the embodiment one and the embodiment two is that the embodiment two adds a shielding conductor ring on the basis of the embodiment one, the shielding conductor ring is used to weaken the electromagnetic field in the middle of the pipe expansion area, and in combination with the reinforced conductor ring, the uniformity of the pipe is realized, and the flatness of the pipe expansion area is improved.

[0062] The pipe electromagnetic expansion method combining the shielding conductor ring and the reinforced conductor ring comprises the following steps:

[0063] Step 1: according to the material and forming specification of the pipe to be formed, the driving coil parameters are determined, and the driving coil is made.

[0064] Step 2: according to the driving coil parameters and the pipe forming specification, the size parameters of the reinforced conductor ring are determined;

[0065] A pipe electromagnetic expansion simulation model is established by using the finite element software COMSOL Multiphysics, including the reinforced conductor ring, the pipe to be formed and the driving coil. The driving coil is loaded with pulse current to generate electromagnetic force in the pipe, the pipe forming effect is simulated, compared with the pipe forming specification, and the geometric size parameters and the spacing of the reinforced conductor ring are adjusted to make the pipe expansion effect meet the needs of the pipe forming specification, and the geometric size parameters and the spacing of the reinforced conductor ring are determined.

[0066] Step 3: according to the size parameters of the reinforced conductor ring and the pipe forming specification, the size parameters of the shielding conductor ring are determined;

[0067] The shielding conductor ring is added to the pipe electromagnetic expansion simulation model obtained in step 2, and the pipe expansion simulation is performed again by using the pipe electromagnetic expansion simulation model, the size parameters of the shielding conductor ring are adjusted to make the flatness and uniformity of the expansion area of the expanded pipe after forming best, and the optimal size parameters and the number of the shielding conductor ring are obtained.

[0068] Step 4: according to the parameters obtained in steps 2 and 3, the reinforced conductor ring, the shielding conductor ring and the conductor ring support are made, and the reinforced conductor ring and the shielding conductor ring are arranged on the conductor ring support.

[0069] Step 5: the pipe to be formed, the conductor ring support and the driving coil are arranged on the workpiece base in sequence and fixed.

[0070] Step 6: the driving coil is connected with the pulse power source through the switch, the air switch is controlled to supply power to the driving coil, the discharge time of the pulse power source is controlled, and the electromagnetic expansion of the pipe to be formed is performed.

[0071] Step 7: whether the pipe expansion effect meets the pipe forming specification is judged, if it meets the forming specification, the process is ended, otherwise step 6 is executed to perform electromagnetic expansion on the pipe again.

[0072] The pipe electromagnetic bulging device of the embodiment two, combining the shielding conductor ring and the reinforced conductor ring, as shown in Figure 6 The pipe electromagnetic bulging device of the embodiment two, combining the shielding conductor ring and the reinforced conductor ring, as shown in

[0073] The pipe electromagnetic bulging device of the embodiment two, combining the shielding conductor ring and the reinforced conductor ring, as shown in

[0074] In the process of pipe electromagnetic bulging, the pulse power supplies power to the drive coil, and the drive coil on the right side of the symmetry axis forms outward current, and according to the right-hand screw rule, it can be known that the magnetic field in the vicinity is counterclockwise. The specific geometry of the shielding conductor ring and the reinforced conductor ring of the embodiment is shown in Figure 7 The shielding conductor ring is a whole metal ring, so according to the electromagnetic induction law, the induced eddy current opposite to the drive coil is generated, so that the electromagnetic field generated by the drive coil in the middle of the pipe bulging area is weakened. The reinforced conductor ring is a metal cylindrical ring with a thin slit, and the reinforced conductor ring generates induced eddy current opposite to the pulse magnetic field near the drive coil side, and generates induced eddy current same as the pulse magnetic field after reversing twice near the pipe side, so that the magnetic field near the reinforced conductor ring is strengthened.

[0075] The current direction of the pipe to be formed, the drive coil, the shielding conductor ring and the reinforced conductor ring of the embodiment is shown in Figure 8 The introduction of the shielding conductor ring leads to that the force received by the middle of the pipe is smaller than the electromagnetic force of the conventional pipe electromagnetic bulging, and the introduction of the reinforced conductor ring leads to that the force received by the two ends of the pipe is greater than the electromagnetic force of the conventional electromagnetic bulging. Therefore, the radial electromagnetic force of the conventional pipe electromagnetic bulging is improved, the radial electromagnetic force of the two ends and the interval between the shielding conductor rings is greater, so that the axial uniformity is improved, and the forming effect is better.

Claims

1. The electromagnetic bulging method of pipes using a reinforced conductor ring is characterized in that: A reinforcing conductor ring is added between the driving coil and the tube to be formed. The reinforcing conductor ring is provided with a slit and is arranged at the end of the expansion zone of the tube to be formed. The reinforcing conductor ring is used to enhance the magnetic field strength at the end of the expansion zone of the tube to be formed, and the uniform expansion of the tube is achieved by using the reinforcing conductor ring. The electromagnetic bulging method for pipe fittings comprises the following steps: Step 1: Determine the drive coil parameters and manufacture the drive coil according to the material and forming specifications of the pipe to be formed; Step 2: Determine the size parameters of the reinforcing conductor ring based on the drive coil parameters and the tube forming specifications; Step 3: According to the parameters obtained in step 2, a reinforcing conductor ring and a conductor ring bracket are manufactured, and the reinforcing conductor ring is arranged on the conductor ring bracket; Step 4: Arrange the pipe to be formed, the conductor ring bracket, and the driving coil on the workpiece base in sequence and fix them; Step 5: Connect the driving coil to the pulse power supply through the switch, control the air switch to power the driving coil, control the discharge time of the pulse power supply, and perform electromagnetic bulging on the pipe to be formed; Step 6: Determine whether the expansion effect of the pipe meets the forming specifications of the pipe. If it meets the forming specifications, the process ends. Otherwise, execute step 5 to perform electromagnetic expansion on the pipe again to shield the conductor ring.

2. The electromagnetic bulging method for pipe fittings according to claim 1, characterized in that: In step 2, a finite element software is used to construct a pipe electromagnetic bulging simulation model including a driving coil, a reinforcing conductor ring and a pipe. A pulse current is applied to the driving coil in the pipe electromagnetic bulging simulation model to simulate the bulging effect of the pipe. The bulging effect is compared with the pipe forming specifications, and the size parameters of the reinforcing conductor ring are adjusted so that the pipe bulging effect meets the requirements of the pipe forming specifications. The size parameters of the reinforcing conductor ring are determined by simulation.

3. The electromagnetic bulging method for pipe fittings according to claim 1, characterized in that: The cross section of the reinforcing conductor ring is rectangular.

4. The electromagnetic bulging method for pipe fittings according to claim 1, characterized in that: The distance between the reinforcing conductor ring and the driving coil is 2mm-8mm.

5. The electromagnetic bulging method for pipe fittings according to claim 1, characterized in that: The distance between the reinforcing conductor ring and the pipe to be formed is 1 mm to 5 mm.

6. The electromagnetic bulging method for pipe fittings according to claim 1, characterized in that: The reinforcing conductor ring is made of copper.

7. The electromagnetic bulging method for pipe fittings according to claim 1, characterized in that: In step 5, the pulse power supply is a capacitor power supply, the capacitance of the capacitor power supply is 10-1000 μF, and the discharge voltage of the capacitor power supply is 1-10 kV.

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