An electromagnetic forming apparatus and method for reducing pipe diameter

Abstract

This invention discloses an electromagnetic forming apparatus and method for reducing pipes, comprising: an electromagnetic forming module and a power supply module; the electromagnetic forming module includes: a forming coil and a metal shielding ring; the forming coil generates a magnetic field and induced eddy currents in the pipe to be formed, thereby generating electromagnetic force to drive the pipe to be formed to deform; the metal shielding ring improves the electromagnetic force distribution at the end of the pipe to be formed, enabling the pipe to be formed to adhere to the mold from bottom to top, thus improving the mold-adhering performance of traditional electromagnetic forming of reducing pipes. This invention, by introducing a metal shielding ring at the end of the pipe, improves the electromagnetic force field distribution on the pipe, enabling the pipe to adhere to the mold from bottom to top, solving the problem of poor mold-adhering accuracy in traditional electromagnetic forming when processing reducing pipes. This invention achieves different electromagnetic force field distributions by changing the discharge voltage, the material and thickness of the shielding ring, and the distance between the shielding ring and the pipe, for forming reducing pipes with different flaring degrees, demonstrating flexibility in electromagnetic force field control.

Description

Technical Field

[0001] This invention belongs to the field of metal sheet and tube forming, and more specifically, relates to an electromagnetic forming device and method for reducing pipes based on a metal shielding ring. Background Technology

[0002] A reducer is a type of metal pipe fitting with different diameters at both ends and a tapered gradient along its body. It is commonly used to connect pipes of different diameters. Reducers made of lightweight alloys (magnesium, aluminum, titanium alloys) are widely used in pipeline transportation due to their high structural strength, light weight, and corrosion resistance.

[0003] Because lightweight alloys have poor formability at room temperature, cracking is prone to occur when processing reducers using traditional cold extrusion techniques. Electromagnetic forming is a special forming process that uses pulsed electromagnetic force to drive plastic deformation of the workpiece. Its high strain rate and non-contact force application characteristics can significantly improve the forming limit of the material and suppress wrinkling and springback. It is one of the effective ways to solve the current processing problems of lightweight alloys and has been used to process various types of metal pipes.

[0004] However, processing reducers using traditional electromagnetic forming technology also faces challenges: due to the excessive electromagnetic force on the pipe end, the pipe end will contact the mold first, forming a local gap. Air within this gap cannot escape, resulting in poor mold-fitting accuracy of the reducer. Figure 1 As shown. To address this issue, reference 1, "Gradient electromagnetic forming (GEMF): A new forming approach for variable-diameter tubes by use of sectional coil," proposes a special coil for forming variable-diameter tubes. By increasing the spacing of the coils at the end of the tube, the electromagnetic force on the end of the tube is weakened, allowing the tube to be sequentially attached to the mold from bottom to top, greatly improving the mold-fitting accuracy. Patent CN11515291B also proposes a device and method for electromagnetic forming of metal reducers based on multi-coil, multi-power supply. An additional small coil is set at the end of the tube, controlled by an independent power supply. By changing the discharge parameters of different coils, the electromagnetic force at the end of the tube is weakened, thus allowing the tube to be attached to the mold from bottom to top.

[0005] Although the above-mentioned solutions can solve the problem of poor mold application accuracy during electromagnetic forming of reducers, they still have significant shortcomings: (1) After the variable-pitch coil is wound, the electromagnetic force field distribution generated on the pipe is relatively simple, which is difficult to meet the forming requirements of reducers with different flaring degrees; (2) The multi-coil-multi-power supply forming method can flexibly adjust the force field distribution by changing the discharge parameters of different coils, but it has problems such as complex forming system and difficulty in promotion. Therefore, it is urgent to develop an electromagnetic forming method with simple device and flexible force field control. Summary of the Invention

[0006] To address the shortcomings or improvement needs of existing electromagnetic forming technology for reducing pipes, this invention provides an electromagnetic forming device and method for reducing pipes, which solves the problem of poor mold application accuracy in traditional electromagnetic forming when processing reducing pipes. At the same time, this application also has the advantages of simple device and flexible force field control, and can be used to meet the processing needs of reducing pipes of different sizes.

[0007] This invention provides an electromagnetic forming device for reducing pipes, including an electromagnetic forming module and a power supply module; the power supply module is used to generate current in the coil; the electromagnetic forming module includes a forming coil and a metal shielding ring; the forming coil is used to generate a magnetic field and induced eddy currents in the pipe to be formed, thereby generating electromagnetic force to drive the pipe to be formed to deform; the metal shielding ring is used to improve the distribution of electromagnetic force at the end of the pipe to be formed, so that the pipe to be formed can adhere to the mold from bottom to top, thus improving the mold-adhering performance of traditional electromagnetic forming of reducing pipes.

[0008] Furthermore, the inner diameter of the metal shielding ring is the same as the inner diameter of the tube to be formed.

[0009] Furthermore, the material of the metal shielding ring can be selected to have an electrical conductivity of 1×10⁻⁶. 7 S / m~5.8×10 7 The material of the S / m is preferably a high-strength magnesium alloy, aluminum alloy, or copper.

[0010] Furthermore, the axial distribution of the electromagnetic force field can be controlled by changing the distance D between the metal shielding ring and the tube to be formed, the thickness L of the metal shielding ring, or by using metal shielding rings with different electrical conductivity.

[0011] When the discharge voltage remains constant, the electromagnetic force at the end of the tube to be formed can be adjusted within a large range by simply adjusting the distance D between the metal shielding ring and the tube to be formed.

[0012] Furthermore, as the distance D between the metal shielding ring and the tube to be formed increases, the shielding effect of the metal shielding ring on electromagnetic force weakens, and the electromagnetic force in the end region of the tube to be formed will increase.

[0013] When the flaring degree of the pipe to be formed is large, and adjusting the discharge voltage or the relative height of the shielding ring alone cannot make the pipe fit on the mold, the fitting accuracy of the flaring pipe can be improved by simultaneously adjusting the relative height of the shielding ring and the discharge voltage.

[0014] Furthermore, the electromagnetic forming module also includes a mold, which is coaxially placed with the forming coil, the tube to be formed, and the metal shielding ring. When it is necessary to form reducers with different flare degrees, it is only necessary to replace the stainless steel mold and adjust the relative height of the shielding ring and the discharge voltage.

[0015] Furthermore, the forming coil uses a solenoid coil with the same wire turn spacing.

[0016] The present invention also provides an electromagnetic forming method for reducing pipes, comprising the following steps:

[0017] Place the tube to be formed between the forming coil and the stainless steel mold;

[0018] An epoxy mold to prevent deformation is nested inside the metal shielding ring and placed coaxially on the upper end of the pipe to be formed.

[0019] By energizing the forming coil with a pulse power supply, the energized forming coil generates a pulse magnetic field, which in turn generates eddy currents in the tube to be formed and the metal shielding ring. The magnetic field generated by the metal shielding ring weakens the eddy currents at the end of the tube. Under the condition that the eddy currents at the end of the tube are weakened, they interact with the pulse magnetic field to generate an electromagnetic force to drive the deformation of the metal tube.

[0020] With the electromagnetic force at the end of the pipe weakened, the pipe is driven to deform at high speed and then adhere to the mold from bottom to top.

[0021] By adjusting the distance D between the metal shielding ring and the pipe to be formed, the thickness L of the shielding ring, the conductivity of the shielding ring, and the discharge voltage, the distribution of the electromagnetic force field on the pipe can be adjusted, thereby meeting the forming requirements of reducers with different flaring degrees.

[0022] Compared with the prior art, the method and apparatus proposed in this invention have the following advantages:

[0023] (1) At the device level, only an additional metal shielding ring and a matching fixing device are introduced into the original forming device, and the coil used is a traditional tube forming coil, which does not require complex design.

[0024] (2) At the force field control level, different force field distributions can be achieved by changing the discharge voltage, the material and thickness of the shielding ring, and the relative distance between it and the pipe fitting, so as to meet different processing requirements. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the electromagnetic force distribution and forming process in traditional electromagnetic forming of reducing pipes.

[0026] Figure 2 This is a schematic diagram of the forming apparatus proposed in this invention.

[0027] Figure 3 This is a schematic diagram comparing the electromagnetic force distribution on the present invention and on an electromagnetically formed pipe fitting without a shielding ring.

[0028] Figure 4 This is a schematic diagram of the forming process of the tube after adopting the forming method proposed in this invention.

[0029] Figure 5 This is a schematic diagram illustrating the adjustable range of the electromagnetic force when only D is changed under the same discharge voltage, according to the present invention.

[0030] Figure 6 This is a schematic diagram illustrating the adjustable range of the electromagnetic force when only L is changed under the same discharge voltage, according to the present invention.

[0031] Figure 7 This is a schematic diagram illustrating the adjustable range of electromagnetic force under the same discharge voltage when only the conductivity of the shielding ring is changed.

[0032] Figure 8 The figure shows the experimental results of this invention.

[0033] In the attached diagram, the same reference numerals represent the same components, where: 1 is a capacitor, 2 is a thyristor, 3 is a forming coil, 4 is a shielding ring and frame, 5 is a pipe fitting, 6 is a stainless steel mold, and 7 is an electromagnetic force distribution. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 illustrative and not intended to limit the invention.

[0035] This invention provides an electromagnetic forming device for reducing pipes based on a metal shielding ring, comprising an electromagnetic forming module and a power supply module. The power supply module generates current in the coil. The electromagnetic forming module includes a forming coil and a metal shielding ring. The forming coil generates a magnetic field and induced eddy currents in the pipe, thereby generating electromagnetic force to drive the pipe to deform. The metal shielding ring improves the distribution of electromagnetic force at the pipe end, enabling the pipe to adhere to the mold from bottom to top, thus improving the mold-adhering performance of traditional reducing pipe electromagnetic forming.

[0036] In this embodiment of the invention, the material of the metal shielding ring can be selected to have an electrical conductivity of 1×10⁻⁶. 7 S / m~5.8×10 7The material of the S / m is preferably a high-strength magnesium alloy, aluminum alloy, or copper.

[0037] More preferably, the metal shielding ring is made of copper, with an inner diameter identical to that of the pipe to be formed, a wall thickness L of 2 mm, and a height of 10 mm. It is then nested within an epoxy skeleton to prevent deformation. Figure 2 As shown.

[0038] Building upon this, a more flexible electromagnetic force control method is provided. By changing the material, thickness, and relative distance between the shielding ring and the pipe fitting, different electromagnetic force field distributions can be generated for processing reducers with varying degrees of flaring. Specifically, the axial distribution of the electromagnetic force field can be controlled by changing the distance D between the metal shielding ring and the pipe fitting, the shielding ring thickness L, and by using shielding rings made of materials with different electrical conductivity. Figures 5-7 As shown.

[0039] like Figure 2 As shown, the coil is connected across the capacitor and discharge is controlled by a thyristor or mechanical switch. The mold, coil, tube, and shielding ring are placed coaxially. The coil can be a solenoid coil with the same wire turn spacing. The height, thickness, and relative distance of the shielding ring to the tube are flexibly adjustable. The outer mold is made of stainless steel. When it is necessary to form reducers with different flare degrees, it is only necessary to change the stainless steel mold and adjust the relative height of the shielding ring and the discharge voltage.

[0040] To further illustrate the electromagnetic forming apparatus and method for reducing pipes provided in the embodiments of the present invention, detailed descriptions are provided below with reference to specific examples:

[0041] like Figure 2 As shown, this embodiment of the invention provides an electromagnetic forming device for a reducing pipe, comprising a forming module and a control circuit module. The forming module consists of a forming coil 3, a magnetic field shielding ring and a frame 4, a 6063-O aluminum alloy pipe fitting 5, and a stainless steel mold 6. The forming coil 3 is coaxially placed inside the pipe fitting with a gap of 0.1 mm between it and the pipe fitting. The stainless steel mold 5 is coaxially placed outside the pipe fitting with a gap of 0.1 mm between its lower end and the pipe fitting. The magnetic field shielding ring has the same inner diameter as the pipe fitting and is coaxially embedded in the epoxy frame 4. The magnetic field shielding ring and the frame 4 are coaxially placed with the coil, and the distance D from the bottom of the shielding ring to the upper end of the pipe fitting is 3 mm. By closing the thyristor 2 in the control circuit, the electrical energy stored in the capacitor 1 can be conducted to the coil, thereby generating eddy currents in the pipe fitting and the shielding ring. The induced eddy currents generated on the metal shielding ring are in the same direction as the induced eddy currents in the pipe fitting, thereby introducing mutual inductance in the eddy current loop of the pipe fitting, thus achieving the purpose of weakening the electromagnetic force at the end of the pipe fitting.

[0042] The electromagnetic forming device for reducing pipes provided in this embodiment of the invention only introduces an additional metal shielding ring and a matching fixing device into the original forming device, and the coil used is a traditional pipe forming coil, which does not require complex design.

[0043] The distribution of electromagnetic force on the pipe fitting along the axial direction is as follows: Figure 3 As shown, the electromagnetic forces in regions A and B differ significantly. Using traditional electromagnetic forming methods, the electromagnetic force near region A is much greater than that in region B. Therefore, region A of the fitting will contact the mold first, creating a gap between regions A and B, affecting the final mold-fitting accuracy of the fitting. Using the method proposed in this paper, the electromagnetic force in region A is significantly reduced, thus the deformation process of the fitting will be as follows: Figure 4 As shown, it adheres to the mold from bottom to top, improving the accuracy of the mold application.

[0044] The proposed solution also provides a more flexible method for controlling electromagnetic force. Besides adjusting the discharge voltage, the distribution of electromagnetic force can also be controlled by changing the material and thickness of the shielding ring, as well as its relative distance to the pipe. More specifically, such as... Figure 4 As shown, when the discharge voltage remains constant, the electromagnetic force at the end of the tube can be adjusted within a wide range simply by adjusting the distance D between the metal shielding ring and the tube to be formed. As the distance D between the metal shielding ring and the tube to be formed increases, the shielding effect of the shielding ring on the electromagnetic force weakens, thus increasing the electromagnetic force in region A at the end of the tube. When the inner diameter of the tube to be formed is large, and adjusting only the discharge voltage or the relative height of the shielding ring is insufficient to make the tube fit onto the mold, the relative height of the shielding ring and the discharge voltage can be adjusted simultaneously to improve the mold fitting accuracy of the large-diameter reducer. Similarly, adjusting the thickness of the shielding ring or using a shielding ring made of different materials can also achieve the above effect, but since both require adjustments to the structure and material properties of the shielding ring itself, they are more complex than the distance adjustment method and will not be elaborated upon. Compared to variable-distance coils or multi-coil-multi-power-source methods, without changing the coil structure, only the structure or geometric parameters of the shielding ring need to be adjusted to meet the forming requirements of reducers of different sizes. The experimental results of the method proposed in this invention are as follows: Figure 8 As shown, the fitting between the pipe and the mold is quite good, further proving that the method proposed in this invention is very effective.

[0045] The present invention also provides an electromagnetic forming method for reducing pipes, comprising the following steps:

[0046] Place the tube to be formed between the forming coil and the stainless steel mold;

[0047] An epoxy mold to prevent deformation is nested inside the metal shielding ring and placed coaxially on the upper end of the pipe to be formed, with a spacing of 3mm, which is flexibly adjustable.

[0048] By energizing the forming coil with a pulse power supply, the energized forming coil generates a pulse magnetic field, which in turn generates eddy currents in the tube to be formed and the shielding ring. The magnetic field generated by the metal shielding ring weakens the eddy currents at the end of the tube. When the eddy currents at the end of the tube are weakened, they interact with the pulse magnetic field to generate an electromagnetic force that drives the metal tube to deform.

[0049] With the electromagnetic force at the end of the pipe weakened, the pipe can be driven to deform at high speed and fit onto the mold from bottom to top.

[0050] By adjusting the distance D between the metal shielding ring and the pipe to be formed, the thickness L of the shielding ring, the conductivity of the shielding ring, and the discharge voltage, the distribution of the electromagnetic force field on the pipe can be adjusted, thereby meeting the forming requirements of reducers with different flaring degrees.

[0051] The electromagnetic forming method for reducing pipes provided in this invention can achieve different force field distributions and meet different processing requirements by changing the discharge voltage, the material and thickness of the shielding ring, and the relative distance between the shielding ring and the pipe at the force field control level.

[0052] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electromagnetic forming device for reducing pipes, characterized in that, Includes an electromagnetic forming module and a power supply module; The power module is used to generate current in the coil; The electromagnetic forming module includes: a forming coil, a metal shielding ring, and a stainless steel mold. The forming coil is coaxially placed inside the tube and is used to generate a magnetic field and induced eddy currents in the tube to be formed, thereby generating electromagnetic force to drive the tube to be formed to deform. The metal shielding ring is coaxially placed at the upper end of the tube to be formed, and the inner diameter of the metal shielding ring is the same as the inner diameter of the tube to be formed and is coaxially embedded in the epoxy skeleton. The stainless steel mold is coaxially placed on the outside of the tube. The metal shielding ring is used to improve the electromagnetic force distribution at the end of the tube to be formed, and the generated magnetic field weakens the induced eddy currents at the end of the tube to be formed, so that the tube to be formed can be molded from bottom to top along the stainless steel mold, thus improving the molding performance of traditional reducing tube electromagnetic forming.

2. The electromagnetic forming device for reducing pipes as described in claim 1, characterized in that, The metal shielding ring is made of a material with an electrical conductivity of 1×10⁻⁶. 7 S / m ~ 5.8 × 10 7 Materials with S / m.

3. The electromagnetic forming device for reducing pipes as described in claim 1, characterized in that, The axial distribution of the electromagnetic force field can be controlled by changing the distance between the metal shielding ring and the tube to be formed, the thickness of the metal shielding ring, or the conductivity.

4. The electromagnetic forming device for reducing pipes as described in claim 3, characterized in that, As the distance between the metal shielding ring and the tube to be formed increases, the shielding effect of the metal shielding ring on electromagnetic force weakens, and the electromagnetic force in the end region of the tube to be formed will increase.

5. The electromagnetic forming apparatus for reducing tubes as described in any one of claims 1-4, characterized in that, The forming coil is a solenoid coil with the same wire turn spacing.

6. A method for electromagnetic forming of a reducing tube based on the reducing tube electromagnetic forming apparatus according to any one of claims 1-5, characterized in that, Includes the following steps: Place the tube to be formed between the forming coil and the stainless steel mold; The metal shielding ring is nested in an epoxy mold to prevent its deformation and is placed coaxially on the upper end of the tube to be formed. By energizing the forming coil with a pulse power supply, the energized forming coil generates a pulse magnetic field, which in turn generates eddy currents in the tube to be formed and the metal shielding ring. The magnetic field generated by the metal shielding ring weakens the eddy currents at the end of the tube to be formed. Under the condition that the eddy currents at the end of the tube to be formed are weakened, they interact with the pulse magnetic field to generate an electromagnetic force that drives the metal tube to deform. With the electromagnetic force at the end of the tube to be formed weakened, the tube is driven to deform at high speed and then sequentially adhere to the stainless steel mold from bottom to top. By adjusting the distance between the metal shielding ring and the tube to be formed, the thickness of the shielding ring, or by using shielding rings made of materials with different electrical conductivity and the discharge voltage, the distribution of the electromagnetic force field on the tube to be formed can be adjusted, thereby forming reducers with different degrees of flaring.

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