An electromagnetic composite forming method for hole-forming of artificially aged aluminum alloy tank bottom

Abstract

The present invention provides an electromagnetic composite forming method for forming holes in artificially aged aluminum alloy tank bottoms. The method is characterized by constructing an electromagnetic composite forming device in the hole forming area based on the principle of electromagnetic loading, comprising a forming coil, rigid dies of different inner diameters, a rigid punch, and the aluminum alloy tank bottom. First, the rigid die with a smaller inner diameter is placed outside the aluminum alloy bottom, and the forming coil is placed inside the aluminum alloy bottom. Electromagnetic forming is used to complete the first hole forming operation. Then, the rigid die with a larger inner diameter is replaced with the previous rigid die with a smaller inner diameter. The rigid punch passes through the guide pins of the rigid die with a larger inner diameter and is placed inside the aluminum alloy bottom. The forming coil is placed on the rigid punch, and electromagnetic force is used to drive the rigid punch to complete the second hole forming operation. The electromagnetic composite forming method for forming holes in artificially aged aluminum alloy tank bottoms can improve the forming limit of aluminum alloy hole forming, improve stress distribution during forming, and achieve hole forming in artificially aged aluminum alloy tank bottoms.

Description

Technical Field

[0001] The invention relates to the technical field of sheet metal forming, and in particular to an electromagnetic composite forming method for punching holes in a tank bottom of an artificially aged aluminum alloy. Background Art

[0002] Aluminum alloys, a commonly used lightweight alloy material in the aerospace industry, are widely used in launch vehicle and aircraft structural components, playing a significant role in lightweighting. However, aluminum alloys have limited formability at room temperature. Aluminum alloys that require heat treatment for strengthening typically require plastic forming in the annealed state. Furthermore, heating is required to process difficult-to-form features, hindering both production efficiency and process design.

[0003] The curved shells of fuel tanks for launch vehicles and some aircraft feature flared holes for connection to power lines. In recent years, tank structures have tended to use large-scale integral components instead of traditional welded structures, reducing welds and weld thickening areas to improve reliability and reduce weight. For example, if the flaring process were performed on the bottom of a launch vehicle tank, it would have a significant negative impact on subsequent heat treatment deformation control and machining costs. However, the traditional steel die stamping flaring process has a limited forming window and is unable to form the local features of aluminum alloy shells that have been strengthened by heat treatment. Therefore, a flaring forming process method that can post-process the flaring process on artificially aged aluminum alloys is urgently needed.

[0004] Electromagnetic forming, as a high-rate forming process, can effectively improve the formability of materials. Several universities and companies have conducted research on electromagnetic flanging of aluminum alloys, achieving promising results. While early technical development has shown that this technology can achieve some large-diameter flanging of artificially aged aluminum alloys, cracking still persists when flanging with lower flanging coefficients and greater difficulty.

[0005] At the same time, the coil serves as a load release device during the electromagnetic forming process, and its life and reliability directly affect the engineering application of electromagnetic forming technology. The existing coil structure is limited in the number of coil turns when it comes to artificially aged aluminum alloy plates, especially when forming small-diameter holes on thick plates, and shows obvious lack of strength. Under the allowable voltage, there are phenomena of incomplete forming and non-die adhesion, while increasing the voltage will damage the coil. Previous studies have shown that coil-driven rigid dies can also be used for die forming. Due to the lack of the radial drag effect of electromagnetic forming on the material around the die, this method is weaker than electromagnetic forming in improving the die forming ability, but it still has advantages over quasi-static stamping, and its collision contact with the material can also better ensure die adhesion.

[0006] In summary, before a breakthrough in coil technology occurs, the use of a composite forming process based on electromagnetic loading will help expand the hole-flanging forming window of artificially aged aluminum alloys. Summary of the Invention

[0007] The purpose of the present invention is to provide an electromagnetic composite forming method for punching holes in an artificially aged aluminum alloy tank bottom, thereby improving the forming ability of the artificially aged aluminum alloy tank bottom in the punching process.

[0008] In order to achieve the above-mentioned objectives, the present invention provides an electromagnetic composite forming method for punching holes in the bottom of an artificially aged aluminum alloy tank, which is characterized in that, based on the principle of electromagnetic loading, an electromagnetic composite forming device consisting of a forming coil, rigid dies with different inner diameters, a rigid punch and an aluminum alloy tank bottom is constructed in the punching forming area. First, the rigid die with a smaller inner diameter is placed on the outside of the aluminum alloy bottom, and the forming coil is placed on the inside of the aluminum alloy bottom, and electromagnetic forming is used to complete the first punching. Then, the rigid die with a larger inner diameter replaces the previous rigid die with a smaller inner diameter, and the rigid punch passes through the rigid die guide column with a larger inner diameter and is placed on the inside of the aluminum alloy bottom. The forming coil is placed on the rigid punch, and electromagnetic force is used to drive the rigid punch to complete the second punching.

[0009] The above-mentioned electromagnetic composite forming method for punching holes in the bottom of an artificially aged aluminum alloy tank is characterized by comprising the following steps: 1) machining a prefabricated hole on the bottom of the aluminum alloy tank according to the punching hole specifications; 2) adjusting the placement angle of the bottom of the aluminum alloy tank and fixing it on all sides; 3) placing a rigid punching die with a smaller inner diameter outside the punching hole forming area of ​​the bottom of the aluminum alloy tank, and placing a forming coil inside the punching hole forming area of ​​the bottom of the aluminum alloy tank, after aligning the components according to the center of the prefabricated hole, fixing the rigid punching die and the forming coil; 4) connecting the forming coil to the bottom of the aluminum alloy tank. Connect to the electromagnetic forming equipment, discharge according to the preset voltage, and complete the first hole-turning forming of the aluminum alloy tank bottom; 5) Remove the rigid hole-turning die and forming coil; 6) Place the rigid hole-turning die with a larger inner diameter on the outside of the hole-turning forming area of ​​the aluminum alloy tank bottom, and place the rigid punch through the central guide column of the rigid hole-turning die with a larger inner diameter and place it on the inside of the hole-turning forming area of ​​the aluminum alloy tank bottom. Place the forming coil on the rigid punch, and fix the rigid hole-turning die and forming coil; 7) Discharge according to the preset voltage to complete the second hole-turning forming of the aluminum alloy tank bottom.

[0010] The electromagnetic composite forming method for punching holes in the bottom of an artificially aged aluminum alloy tank is characterized in that electromagnetic forming is used for the first punching and electromagnetically driven rigid punch is used for the second punching, and the inner diameters of the punched holes of the two punchings increase from small to large.

[0011] The electromagnetic composite forming method for punching holes in the bottom of an artificially aged aluminum alloy tank is characterized in that the same forming coil is used for both the first punching and the second punching.

[0012] The electromagnetic composite forming method for the bottom hole punching of the artificially aged aluminum alloy tank is characterized in that the target hole outer diameter is greater than the inner diameter of the rigid hole punching die with a smaller inner diameter; and the target hole bending radius is less than or equal to the radius of the rigid hole punching die with a smaller inner diameter.

[0013] The electromagnetic composite forming method for punching holes in the bottom of an artificially aged aluminum alloy tank is characterized in that (inner diameter of the rigid punching die with a smaller inner diameter - wall thickness of the bottom of the aluminum alloy tank) / diameter of the prefabricated hole is greater than 1.15.

[0014] The electromagnetic composite forming method for punching holes in the bottom of an artificially aged aluminum alloy tank is characterized in that the inner diameter of the rigid punching die with a larger inner diameter is consistent with the target outer diameter of the punching die, and the diameter of the rigid punch is consistent with the target inner diameter of the punching die.

[0015] The electromagnetic composite forming method for forming a hole in the bottom of an artificially aged aluminum alloy tank is characterized in that a polyurethane plate is installed at the bottom of a rigid hole-forming die with a larger inner diameter, a guide column is installed at the center, and a copper drive plate is installed at the bottom of the rigid punch, a guide hole is provided at the center, and the guide hole and the guide column are clearance-matched and lubricated.

[0016] The electromagnetic composite forming method for the artificially aged aluminum alloy tank bottom hole-forming is characterized in that the walls of the prefabricated holes on the aluminum alloy tank bottom are polished, sharp edges are rounded, and surface defects are removed.

[0017] The electromagnetic composite forming method for punching holes in the bottom of an artificially aged aluminum alloy tank is characterized in that the rigid punching die and forming coil used for punching holes are designed according to the part size and processing requirements, and the prefabricated hole size is calculated according to an empirical formula.

[0018] The electromagnetic composite forming method for the artificially aged aluminum alloy tank bottom hole-turning can improve the aluminum alloy hole-turning forming limit, improve the stress distribution during forming, and realize the artificially aged aluminum alloy tank bottom hole-turning forming. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The electromagnetic composite forming method for forming a bottom hole of an artificially aged aluminum alloy tank is described in the following embodiments and accompanying drawings.

[0020] Figure 1 Shown is a schematic diagram before the first hole forming in the present invention.

[0021] Figure 2 Shown is a schematic diagram before the second hole forming in the present invention. DETAILED DESCRIPTION

[0022] The following will be combined Figures 1 and 2 The electromagnetic composite forming method for the artificially aged aluminum alloy tank bottom hole-forming of the present invention is further described in detail.

[0023] The aluminum alloy of the present invention is an aluminum alloy strengthened to an artificial aging state through heat treatment.

[0024] The electromagnetic composite forming method for forming holes in artificially aged aluminum alloy tank bottoms is based on the principle of electromagnetic loading. An electromagnetic composite forming device is constructed in the forming area, consisting of a forming coil, rigid dies of varying inner diameters, a rigid punch, and the aluminum alloy tank bottom. The rigid die with a smaller inner diameter is placed outside the aluminum alloy bottom, and the forming coil is placed inside. Electromagnetic forming is used to complete the first hole forming operation. The rigid die with a larger inner diameter replaces the previous smaller one. The punch passes through the larger die guide and is placed inside the aluminum alloy bottom. The forming coil is placed on the punch, and electromagnetic force is used to drive the punch to complete the second hole forming operation.

[0025] Figure 1 Shown is a schematic diagram of the first hole forming process in the present invention; Figure 2 Shown is a schematic diagram of the second hole forming process in the present invention.

[0026] Combine Figure 1 and Figure 2 The electromagnetic composite forming method for the bottom hole of an artificially aged aluminum alloy tank of the present invention comprises:

[0027] 1) According to the hole specifications, prefabricated holes are processed on the bottom 1 of the aluminum alloy tank;

[0028] The bottom 1 of the aluminum alloy tank is an aluminum alloy curved shell that has been artificially aged. The walls of the prefabricated holes should be polished, sharp edges should be rounded, and surface defects in the hole forming area should be removed.

[0029] 2) Adjust the placement angle of the aluminum alloy tank bottom 1 and fix it around;

[0030] According to the location of the flip hole on the bottom of the aluminum alloy tank 1 and the convenience of operation, the placement angle of the bottom of the aluminum alloy tank 1 is determined and clamped and fixed;

[0031] 3) Place the rigid punching die 2 with a smaller inner diameter outside the punching forming area of ​​the aluminum alloy tank bottom 1, and place the forming coil 3 inside the punching forming area of ​​the aluminum alloy tank bottom 1. After aligning all components with the center of the prefabricated hole, secure the rigid punching die 2 and the forming coil 3.

[0032] The target hole outer diameter is greater than the inner diameter of the rigid hole die 2, and the target hole bending radius is less than or equal to the radius of the rigid hole die 2;

[0033] Preferably, (inner diameter of the rigid punching die 2 - wall thickness of the aluminum alloy tank bottom 1) / diameter of the prefabricated hole>1.15;

[0034] After the hole is formed, the outer side of the hole forming area is the outer side of the hole, and the inner side of the hole forming area is the inner side of the hole;

[0035] 4) Connecting the forming coil 3 to the electromagnetic forming equipment and discharging it at a preset voltage to complete the first hole-forming of the aluminum alloy tank bottom 1;

[0036] 5) Remove the rigid hole-turning die 2 and the forming coil 3;

[0037] 6) Place the rigid punching die 4 with a larger inner diameter outside the punching forming area of ​​the aluminum alloy tank bottom 1. Pass the rigid punch 5 through the central guide post 6 of the rigid punching die 4 and place it inside the punching forming area of ​​the aluminum alloy tank bottom 1. Place the forming coil 3 on the rigid punch 5. Secure the rigid punching die 4 and the forming coil 3.

[0038] The inner diameter of the rigid punching die 4 is equal to the outer diameter of the target hole, a polyurethane plate 7 is installed at the bottom, and a guide post 6 is installed in the center; the diameter of the rigid punch 5 is equal to the inner diameter of the target hole, a copper drive plate 8 is installed at the bottom, and a guide hole is provided in the center. The guide hole and the guide post of the rigid punching die 4 are clearance-fitted and lubricated;

[0039] 7) Discharge at a preset voltage to complete the second hole forming of the aluminum alloy tank bottom 1;

[0040] In the punching forming process of the present invention, a composite forming method of electromagnetic forming + electromagnetic force driven steel mold forming is adopted. The first punching forming is carried out by electromagnetic forming, and the second punching forming is carried out by electromagnetic driven rigid punch forming. The inner diameters of the punched holes of the two forming processes increase from small to large, thereby reducing the stress concentration of the material during the forming process and gradually expanding the punching size, thereby improving the punching forming capacity of the bottom of the artificially aged aluminum alloy tank.

[0041] The same forming coil is used for both the first hole forming and the second hole forming.

[0042] The electromagnetic composite forming method for the bottom hole of an artificially aged aluminum alloy tank will now be described in detail with reference to specific embodiments.

[0043] This example involves forming a hole in an aluminum alloy tank bottom component with a partial ellipsoidal profile. The component is a 2219 aluminum alloy with a wall thickness of 6mm, heat-treated to an artificially aged state. The required hole has an inner diameter of 120mm, a 20mm radius, and a flange height of no less than 25mm. The rigid die and forming coil used for the hole forming are designed and optimized based on the part size and processing requirements. The prefabricated hole dimensions are calculated and optimized using empirical formulas. This electromagnetic composite forming method for forming a hole in the artificially aged aluminum alloy tank bottom comprises the following steps:

[0044] 1) Cut a φ99mm prefabricated hole on the bottom 1 of the aluminum alloy tank, polish the hole wall, and round the hole mouth;

[0045] 2) Adjust the placement angle of the aluminum alloy tank bottom 1 and fix it around;

[0046] 3) Place a rigid punching die 2 with an inner diameter of 125 mm outside the punching forming area of ​​the aluminum alloy tank bottom 1, with a die corner radius of 23 mm. Place a forming coil 3 inside the punching forming area of ​​the aluminum alloy tank bottom 1. After aligning all components with the center of the prefabricated hole, secure the rigid punching die 1 and forming coil 3.

[0047] 4) Connect the forming coil 3 to the electromagnetic forming equipment with a discharge voltage of 10 kV to complete the first hole forming of the aluminum alloy tank bottom 1;

[0048] 5) Remove the rigid hole-turning die 2 and the forming coil 3;

[0049] 6) A rigid punch die 4 with an inner diameter of 132 mm is placed outside the punching area of ​​the aluminum alloy tank bottom 1. The die has a radius of 20 mm. A rigid punch die 5 with a diameter of 120 mm is passed through the central guide post 6 of the rigid punch die 4 and placed inside the punching area of ​​the aluminum alloy tank bottom 1. The forming coil 3 is placed on the rigid punch die 5. The rigid punch die 4 and the forming coil 3 are fixed.

[0050] 7) Using a discharge voltage of 8kV, the second punching of the aluminum alloy tank bottom 1 is completed. The diameter of the punching hole is 119.6mm, the height is 26.3mm, and the inner and outer surfaces of the punching hole are smooth and free of cracks, meeting the requirements.

[0051] This embodiment utilizes a hybrid forming method combining electromagnetic forming with electromagnetically driven steel die forming. The same forming coil completes the first hole-forming step and drives the rigid punch for the second hole-forming step. This electromagnetic hybrid forming method reduces stress concentration in the material during the forming process and progressively increases the hole size, reducing the difficulty of each hole-forming step. Compared to a single forming method, this method improves the hole-forming capability of artificially aged aluminum alloy tank bottoms.

[0052] The technical effects of the present invention include:

[0053] (1) The electromagnetic composite forming method for forming the bottom of an artificially aged aluminum alloy tank using electromagnetic forming in the first forming step significantly improves the forming limit of the artificially aged aluminum alloy material at room temperature. The drag effect generated during high-speed forming drives the radial flow of the surrounding material, slowing down the thinning and cracking of the hole-forming area, thus achieving hole-forming on the artificially aged aluminum alloy.

[0054] (2) The present invention adopts a composite forming method of electromagnetic forming + electromagnetic force driven steel die forming, which effectively utilizes the forming characteristics of the two forming methods and expands the hole forming window. During the electromagnetic forming hole forming process, under the action of the inertia effect, the outer material of the hole is driven by the inner ring material to flow radially, forming a filler material on the hole wall, reducing the risk of hole wall rupture. However, when the radial flow of the material is too intense, circumferential rupture will occur at the fillet of the hole, which is the main failure form of electromagnetic hole forming of aluminum alloys. In comparison, steel die forming is contact forming, and the fillet of the hole is basically bent and deformed, which is not easy to rupture, while the hole wall will be thinned or even ruptured due to large tangential strain. The composite forming method of hole forming by the two methods can disperse the main deformation area, make the plastic deformation uniform, and avoid stress concentration and cracking. At the same time, electromagnetic forming significantly improves the forming limit of the material. As the first forming method, it bears most of the plastic forming; electromagnetic force driven steel die forming improves the forming limit of the material relatively less. As the second forming method, the electromagnetic composite forming method can effectively improve the hole forming window;

[0055] (3) The electromagnetic composite forming method for the artificially aged aluminum alloy tank bottom hole forming proposed by the present invention has a smaller hole diameter in the first forming and a larger hole diameter in the second forming, thereby increasing the flanging coefficient of a single hole forming, reducing the forming difficulty, and achieving the purpose of further improving the hole forming window;

[0056] (4) The electromagnetic composite forming method for punching holes in the bottom of an artificially aged aluminum alloy tank proposed in the present invention divides the punching forming into two steps, which reduces the discharge voltage required for single forming compared to direct electromagnetic forming. The forming coil is a key component for realizing energy conversion in electromagnetic forming. During forming, the forming coil passes through a large pulse current and withstands mechanical shock and Joule thermal shock. The transient mechanical and thermal shock has high requirements on the coil structure strength, heat dissipation, and insulation capacity. Reducing the discharge voltage can effectively increase the service life of the forming coil and reduce the requirements on the strength and manufacturing process of the forming coil;

[0057] (5) The present invention uses the forming coil used in the first forming to drive the rigid punch with a copper driving plate to perform the second forming. Compared with the traditional steel die punching and punching, the rigid punch driven by electromagnetic force still has the advantage of high-speed forming during the forming process, which helps to improve the forming performance of the material. Compared with the use of forming coils with tubular features for the second forming, due to the small internal space of the punching hole, the volume and number of turns of the actual coil are greatly limited, and effective reinforcement cannot be formed; the strength of artificially aged aluminum alloy is high, and the discharge voltage required for forming is large. In this case, the coil is easily damaged and fails, and lacks engineering application value; using electromagnetic force to drive the steel die for the second forming can remove the space restriction on the forming coil, and the forming coil used for the first forming can be used to complete the process. While reducing the coil cost, it can effectively cope with the scene of small-diameter punching of artificially aged aluminum alloy thick plates, broadening the scope of application.

[0058] It should be noted that the above is only an illustrative description and explanation of the present invention. Those skilled in the art should understand that any modification and replacement of the present invention falls within the scope of protection of the present invention.

Claims

1. An electromagnetic composite forming method for forming a hole in the bottom of an artificially aged aluminum alloy tank, characterized in that: It is based on the principle of electromagnetic loading. An electromagnetic composite forming device consisting of a forming coil, rigid dies with different inner diameters, a rigid punch and an aluminum alloy tank bottom is constructed in the hole-turning forming area. First, the rigid die with a smaller inner diameter is placed on the outside of the aluminum alloy tank bottom, and the forming coil is placed on the inside of the aluminum alloy tank bottom. Electromagnetic forming is used to complete the first hole-turning. Then, the rigid die with a larger inner diameter replaces the previous rigid die with a smaller inner diameter. The rigid punch passes through the rigid die guide column with a larger inner diameter and is placed on the inside of the aluminum alloy tank bottom. The forming coil is placed on the rigid punch, and electromagnetic force is used to drive the rigid punch to complete the second hole-turning.

2. The electromagnetic composite forming method for the bottom hole of an artificially aged aluminum alloy tank according to claim 1, characterized in that: The following steps are involved: 1) According to the hole specifications, prefabricated holes are processed on the bottom of the aluminum alloy tank; 2) Adjust the angle of the bottom of the aluminum alloy tank and fix it around; 3) Place the rigid punching die with a smaller inner diameter outside the punching forming area of ​​the aluminum alloy tank bottom, and place the forming coil inside the punching forming area of ​​the aluminum alloy tank bottom. After aligning all components with the center of the prefabricated hole, secure the rigid punching die and the forming coil. 4) Connect the forming coil to the electromagnetic forming equipment and discharge it at a preset voltage to complete the first hole forming of the aluminum alloy tank bottom; 5) Remove the rigid hole-turning die and forming coil; 6) Place the rigid punch die with a larger inner diameter outside the punching forming area of ​​the bottom of the aluminum alloy tank. Pass the rigid punch die through the central guide post of the rigid punch die with a larger inner diameter and place it inside the punching forming area of ​​the bottom of the aluminum alloy tank. Place the forming coil on the rigid punch die. Secure the rigid punch die and the forming coil. 7) Discharge at a preset voltage to complete the second hole forming of the bottom of the aluminum alloy tank.

3. The electromagnetic composite forming method for the bottom hole of an artificially aged aluminum alloy tank according to claim 1 or 2, characterized in that: The first hole forming is done by electromagnetic forming, and the second hole forming is done by electromagnetic driven rigid punch forming. The inner diameters of the holes formed in the two forming processes increase from small to large.

4. The electromagnetic composite forming method for the bottom hole of an artificially aged aluminum alloy tank according to claim 1 or 2, characterized in that: The same forming coil is used for both the first hole forming and the second hole forming.

5. The electromagnetic composite forming method for forming a hole in the bottom of an artificially aged aluminum alloy tank according to claim 1 or 2, characterized in that: The target outer diameter of the hole is greater than the inner diameter of the rigid hole die with a smaller inner diameter; the target rounding of the hole bend is less than or equal to the rounding of the rigid hole die with a smaller inner diameter.

6. The electromagnetic composite forming method for forming a hole in the bottom of an artificially aged aluminum alloy tank according to claim 1 or 2, characterized in that: (Inner diameter of the rigid punching die with smaller inner diameter - thickness of the bottom wall of the aluminum alloy tank) / diameter of the prefabricated hole>1.

15.

7. The electromagnetic composite forming method for forming a hole in the bottom of an artificially aged aluminum alloy tank according to claim 1 or 2, characterized in that: The inner diameter of the rigid hole-turning die with a larger inner diameter is consistent with the target hole-turning outer diameter, and the diameter of the rigid punch is consistent with the target hole-turning inner diameter.

8. The electromagnetic composite forming method for forming a hole in the bottom of an artificially aged aluminum alloy tank according to claim 1 or 2, characterized in that: A polyurethane plate is installed at the bottom of the rigid hole-turning die with a larger inner diameter, and a guide column is installed in the center. A copper drive plate is installed at the bottom of the rigid punch, and a guide hole is provided in the center. The guide hole and the guide column are clearance-matched and lubricated.

9. The electromagnetic composite forming method for forming a hole in the bottom of an artificially aged aluminum alloy tank according to claim 2, characterized in that: The walls of prefabricated holes on the bottom of aluminum alloy tanks should be polished, sharp edges should be rounded, and surface defects should be removed.

10. The electromagnetic composite forming method for forming a hole in the bottom of an artificially aged aluminum alloy tank according to claim 1 or 2, characterized in that: The rigid punching die and forming coil used for punching are designed according to the part size and processing requirements, and the prefabricated hole size is calculated according to the empirical formula.

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