An electromagnetic step-by-step forming method based on three coils

Abstract

The present invention discloses an electromagnetic step-by-step forming method and device based on three coils, which solves the problems of uneven bulging of existing attraction-type pipe fittings and difficulty in placing molds. The uniformity of pipe deformation can be improved by step-by-step forming, and the most unevenly processed area of ​​the pipe fitting can be processed twice to make the pipe fitting more uniformly formed, and no mold is required, thus bypassing the problem of difficulty in placing the attraction-type pipe fitting bulging mold.

Description

Technical Field

[0001] The invention belongs to the field of metal forming manufacturing, and particularly relates to an electromagnetic step-by-step forming method and device based on three coils, which is mainly used for rapid and uniform forming processing of metal pipe fittings. Background Art

[0002] At present, metal pipe fittings are widely used in the fields of automobiles, aerospace, etc. to meet the demand for lightweight in these industries. Among them, pipe fittings made of lightweight alloys such as aluminum and magnesium are the forefront and hot spot of development. Commonly used electromagnetic processing technologies for pipe fittings, such as repulsive force pipe fitting bulging and attractive force pipe fitting bulging, still have a lot of shortcomings. In actual production and processing, pipe fittings are often bulged unevenly. Therefore, a pipe fitting processing method that can make pipe fittings bulge more evenly is urgently needed.

[0003] The existing tube bulging technology, whether rolling, stamping, or traditional repulsive or attractive electromagnetic forming, has the following shortcomings: 1. The traditional rolling, stamping, forging and other methods have cumbersome procedures, and the material strain rate during the processing is low, especially for light alloys such as aluminum and magnesium, which have a low forming limit at a low strain rate. These processing methods can easily cause parts to break before reaching the target shape; at the same time, the springback of the parts after unloading from the cold stamping die will be relatively large, the component has low dent resistance, and is prone to distortion, deformation, wrinkling and other phenomena. The accuracy is difficult to control, which also affects subsequent processing. 2. Although the traditional tube bulging technology can improve the forming limit of aluminum alloys, due to the uneven distribution of its Lorentz force, the deformation of the tube is also uneven, and the tube is often convex.

[0004] At the same time, whether the traditional tube bulging method is based on repulsive force or attractive force, the distribution of Lorentz force is uneven, so the tube bulging is also uneven, and the tube position corresponding to the coil center often has the largest bulging depth. Tube bulging based on repulsive force can add a mold outside the tube to make the tube bulging more uniform, but the position relationship between the coil and the tube based on the attractive force tube bulging device makes it difficult to add a mold to this method, making it very difficult to improve the bulging uniformity of the attractive force tube bulging.

[0005] Patents for suction-type pipe bulging, for example: Patent CN109622721A - A device and method for regulating electromagnetic forming force for metal pipes, the device includes a driving magnetic field coil, an auxiliary magnetic field coil and a single power supply control circuit. Two sets of coils are regulated by a single power supply, the driving magnetic field coil is used to generate induced eddy currents in the pipe, and the auxiliary magnetic field coil is used to generate a background magnetic field. The induced eddy currents interact with the background magnetic field to generate an attractive force to drive the pipe to form; this method reduces the cost of double-coil electromagnetic forming of metal pipes and solves the problem of timing control. However, the radial electromagnetic force generated by this method is unreasonable, resulting in uneven deformation of the pipe. The present invention uses step-by-step forming to provide a reasonable radial electromagnetic force for the pipe, bypassing the problem of difficult placement of the attraction-type pipe bulging mold, and greatly improving the uniformity of pipe deformation without a mold. Summary of the invention

[0006] In view of the above defects or improvement needs of the prior art, the present invention provides an electromagnetic step-by-step forming method and device based on three coils, which solves the problems of uneven bulging of the existing attraction-type pipe fittings and difficulty in placing the mold. The uniformity of pipe deformation can be improved by step-by-step forming, and the most unevenly processed area of ​​the pipe fitting can be subjected to secondary processing to make the pipe fitting forming more uniform, and no mold is required, which bypasses the problem of difficult placement of the attraction-type pipe fitting bulging mold.

[0007] To achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided an electromagnetic step-by-step forming device based on three coils, comprising a pipe, three groups of forming coils: a first group of coils 1, a second group of coils 2, a third group of coils 3, a long pulse width power supply, a short pulse width power supply, and a secondary processing power supply, wherein the three groups of coils are placed on the outside of the pipe, wherein the long pulse width power supply is the first group of coils 1 that passes a long pulse width pulse current to generate a background magnetic field, the second group of coils 2 and the third group of coils 3 are connected in parallel, and short pulse width currents are passed through them respectively to induce eddy currents on the pipe, providing a controllable Lorentz force for the pipe, so that it is expanded under the attraction; after the expansion is completed, the third group of coils 3 is powered by the secondary processing power supply, and the most uneven expansion area of ​​the pipe is subjected to secondary processing to make the expansion of the pipe uniform.

[0008] Preferably, a capacitor power supply system with high-precision thyristors is used to provide long pulse width current, short pulse width current and secondary processing current to the three groups of coils respectively.

[0009] According to another aspect of the present invention, there is provided an electromagnetic step-by-step forming method based on three coils, the method specifically comprising the following steps:

[0010] Step 1: Select an alloy pipe that meets the required production specifications and perform annealing pretreatment operations;

[0011] Step 2: a coil skeleton is made according to the geometric shape of the coil, and a coil is wound into a shaped coil using a winding machine, and interlayer insulation materials are covered between layers. After the coil is wound, copper bar electrodes are welded, and high-strength fibers are used for peripheral reinforcement;

[0012] Step 3: Use hydraulic equipment to fix the formed coils and pipes;

[0013] Step 4: Select the appropriate number of capacitors according to the pipe material, thickness and discharge energy required for forming, and assemble and connect the three groups of capacitor groups of pulse power generation devices according to the process;

[0014] Step 5: The long pulse width current generating device selects a capacitor group with a larger total capacity, the short pulse width current generating device selects a capacitor group with a smaller total capacity, and the secondary processing current generating device also selects a capacitor group with a smaller total capacity;

[0015] Step 6: The three power supply devices are remotely controlled by a computer; the first coil generates a background magnetic field in the forming area under the action of the long pulse current; the second three coils are first connected in parallel and run under the action of the short pulse current. When the long pulse current is about to reach its peak, the short pulse current is turned on to cause the pipe to expand due to the attraction;

[0016] Step 7: After the bulging is completed, the third set of coils is fed with secondary processing current to perform secondary processing on the most unevenly bulged area of ​​the tube to make the bulging of the tube uniform.

[0017] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0018] 1. Three groups of coils that can be changed according to the forming requirements of the workpiece are realized to make the pipe expand in steps. By adjusting the discharge voltage and capacitor capacitance value in the three groups of power supply devices, the eddy current and magnetic field can be flexibly controlled to achieve more flexible Lorentz force loading.

[0019] 2. The present invention realizes that a group of position coils generate induced eddy currents in the most unevenly deformed area of ​​the pipe fitting, and the bulging uniformity of pipe fittings of different materials and thicknesses can be improved by changing the power supply parameters in the secondary processing power supply device;

[0020] 3. The method proposed in the present invention not only reduces the production cost and production cycle, but also improves the forming quality of the workpiece.

[0021] 4. The mold of the present invention can improve the uniformity of the tube bulging without using a mold, thereby avoiding the problem that the attraction type tube bulging mold is difficult to place. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall connection of the step-by-step processing forming device.

[0023] Figure 2 It is a schematic diagram of the power supply loading of the step-by-step processing forming device.

[0024] Figure 3 To process the circuit schematic step by step

[0025] Figure 4 The waveforms of the pulse currents loaded on the three sets of coils.

[0026] Figure 5 To improve the uniformity effect. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain 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 can be combined with each other as long as they do not conflict with each other.

[0028] The electromagnetic step-by-step forming method and device based on three coils described in the present invention are arranged so that three groups of coils are placed on the outside of the pipe and their positions can be arbitrarily changed according to the forming requirements of the workpiece. The first group mainly generates a background magnetic field under the timing control of a long pulse width pulse current. The second three groups of coils are first operated in parallel under the timing control of a short pulse width current, so that the pipe is expanded by attraction. After the expansion of the pipe is completed, a secondary processing current is passed through the third group of coils to perform secondary processing on the most unevenly deformed area of ​​the pipe to make the expansion of the pipe uniform. The positional relationship between the coil and the pipe is shown in the figure. Figure 1 shown.

[0029] According to the left-hand rule, the present invention first generates a background magnetic field through one set of coils, and the other two sets of coils are connected in parallel to generate induced eddy currents in the pipe. According to Lenz's law, under the mutual influence of the axial component of the background magnetic field and the induced eddy currents in the pipe, the pipe will be subjected to radial attraction bulging. After the bulging is completed, the secondary processing current is passed into the third set of coils. According to Lenz's law, the magnetic field generated by the secondary processing current interacts with the eddy currents generated in the pipe, and the pipe will be subjected to an inward repulsive force when passing through the most uneven area of ​​the attraction bulging.

[0030] The electromagnetic step-by-step forming method based on three coils has the following specific implementation steps:

[0031] Step 1: Select an alloy pipe that meets the required production specifications and perform annealing pretreatment operations;

[0032] Step 2: Make the following according to the geometry of the coil: Figure 2The coil frame shown is then wound into a coil using a winding machine, and the interlayer insulation material is covered between the layers. After the coil is wound, the copper bar electrode is welded, and finally the outer periphery is reinforced with high-strength fiber;

[0033] Step 3: Use hydraulic equipment to press the formed coils and pipes Figure 1 The arrangement order is fixed, and the pressure is generally set to 1-1.5MPa;

[0034] Step 4: Figure 1 As shown, according to the pipe material, thickness and the discharge energy required for forming, a suitable number of capacitors are selected, and three groups of capacitor groups are assembled and connected according to the process to form a pulse power supply generating device;

[0035] Step 5: In the present invention, the long pulse width current generating device selects a capacitor group with a larger total capacity, the short pulse width current generating device selects a capacitor group with a smaller total capacity, and the secondary processing current generating device also selects a capacitor group with a smaller total capacity;

[0036] Step 6: Remotely control the three power supply devices through the computer; Figure 3-5 As shown, the first group of coils generates a background magnetic field in the forming area under the action of the long pulse current; the second and third groups of coils are first operated in parallel under the action of the short pulse current (when the long pulse current is about to reach its peak, the short pulse current is turned on), so that the pipe is expanded by the attraction.

[0037] Step 7: After the bulging is completed, the third set of coils is fed with secondary processing current to perform secondary processing on the most unevenly bulged area of ​​the tube to make the bulging of the tube uniform.

[0038] Step 8: Finally, compare the forming effects.

[0039] The multi-physics field analysis calculation formula involved in the present invention is as follows:

[0040] In the formula, F z and F r are the axial Lorentz force and the radial Lorentz force respectively; J e B is the induced eddy current density on the pipe, and the clockwise direction is defined as the positive direction; r and B z are the axial magnetic field component and the radial magnetic field component respectively, and B is specified r The positive direction is pointing to the center; and The induced eddy currents on the pipes are formed by long pulse width current, short pulse width current and secondary processing current respectively; B Z-l , B Z-s and B Z-Tare the axial magnetic fields generated by the long pulse current, short pulse current and secondary forming current in the forming area; t represents time, t1 is the moment when the long pulse current reaches its peak value, and t2 is the moment when the attractive force bulging ends; I long is the current value of the coil with long pulse width current, I short It is the current value of the coil with short pulse width current.

[0041] In the present invention, the bulging of pipe fittings is analyzed as an example, and verified by theory and simulation; the present invention provides a device for realizing the above method, which mainly includes three groups of forming coils, all of which are placed outside the pipe fittings, and one group of coils is fed with a long pulse width pulse current to generate a background magnetic field. The second three groups of coils are first connected in parallel to feed a short pulse width current to mainly induce eddy currents on the pipe fittings, provide a controllable Lorentz force for the pipe fittings, and make it bulge under the attraction force. The third group of coils is powered by the third power supply at the end of the bulging, and the most uneven bulging area of ​​the pipe fittings is secondary processed to make the bulging of the pipe fittings uniform. And three groups of capacitor power supply systems with high-precision thyristors are provided to provide long pulse width current, short pulse width current and secondary processing current to the three groups of coils respectively. The present invention realizes uniform bulging of attractive force-type pipe fittings, can meet a variety of processing requirements, and enrich the processing methods of aluminum alloy pipe fittings. The present invention can greatly improve the uniformity of pipe fitting bulging based on attraction force, and meet the needs of large-scale mass production of pipe fittings in the fields of automobiles, aerospace, etc.

[0042] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope of the present invention.

Claims

1. An electromagnetic step-by-step forming method based on three coils, characterized in that: The forming method comprises the following steps: Step 1: Select an alloy pipe that meets the required production specifications and perform annealing pretreatment operations; Step 2: a coil skeleton is made according to the geometric shape of the coil, and a coil is wound into a shaped coil by a winding machine, and interlayer insulation materials are covered between layers. After the shaped coil is wound, copper bar electrodes are welded, and high-strength fibers are used for peripheral reinforcement; Step 3: Use hydraulic equipment to fix the formed coils and pipes; Step 4: Select the appropriate number of capacitors according to the pipe material, thickness and discharge energy required for forming, and assemble and connect the three groups of capacitor groups of pulse power generation devices according to the process; Step 5: The long pulse width current generating device selects a capacitor group with a larger total capacity, the short pulse width current generating device selects a capacitor group with a smaller total capacity, and the secondary processing current generating device also selects a capacitor group with a smaller total capacity; Step 6: The three power supply devices are remotely controlled by a computer; the first coil generates a background magnetic field in the forming area under the action of the long pulse current; the second three coils are first connected in parallel and run under the action of the short pulse current. When the long pulse current is about to reach its peak, the short pulse current is turned on to cause the pipe to expand due to the attraction; Step 7: After the bulging is completed, the third set of coils is fed with secondary processing current to perform secondary processing on the most unevenly bulged area of ​​the tube to make the bulging of the tube uniform; The following multi-physics field analysis is used to calculate the forces on the pipe fittings and realize the processing and forming of the pipe fittings. In the formula, and are the axial Lorentz force and the radial Lorentz force respectively; is the induced eddy current density on the pipe, and the clockwise direction is defined as the positive direction; and are the axial magnetic field component and the radial magnetic field component respectively, and the regulations The positive direction is pointing to the center; , and These are the induced eddy currents formed on the pipe by long pulse width current, short pulse width current and secondary processing current; , and These are the axial magnetic fields generated in the forming area by the long pulse width current, the short pulse width current and the secondary forming current; Represents time, is the moment when the long pulse current reaches its peak value, Bulging end moments for attraction; The forming method realizes the processing of the pipe fitting through a forming device, which includes the pipe fitting, a first group of coils, a second group of coils, a third group of coils, a long pulse width power supply, a short pulse width power supply, and a secondary processing power supply. The three groups of forming coils are all placed outside the pipe fitting, wherein the long pulse width power supply is for the first group of coils to pass a long pulse width pulse current to generate a background magnetic field, the second group of coils and the third group of coils are connected in parallel, and short pulse width current is passed respectively to induce eddy currents on the pipe fitting, providing a controllable Lorentz force for the pipe fitting, so that it is expanded by the attraction; after the expansion is completed, the third group of coils is powered by the secondary processing power supply, and the most uneven expansion area of ​​the pipe fitting is subjected to secondary processing to make the expansion of the pipe fitting uniform.

2. The electromagnetic step-by-step forming method based on three coils according to claim 1 is characterized in that: A capacitor power supply system with high-precision thyristors is used to provide long pulse width current, short pulse width current and secondary processing current to three groups of forming coils respectively.

3. The three-coil electromagnetic step-by-step forming method according to claim 1, characterized in that: In step 3, the pressure of the hydraulic equipment is set to 1-1.5 MPa.

Images