Multi-pass forming method for large-variable-diameter-ratio ultrathin special-shaped conical shell
By combining three-pass processes with forward and reverse deep drawing and elastic mold bulging technology, the problems of local thinning and cracking in the forming of ultra-thin irregular cone shells with large diameter ratios were solved, achieving high precision and uniformity and ensuring the overall performance of the components.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-29
- Publication Date
- 2026-04-10
AI Technical Summary
Existing forming processes are difficult to effectively form ultra-thin irregular cone shells with large diameter ratios, resulting in problems such as local thinning, cracking, poor shape accuracy, and overall performance degradation.
The process employs a three-pass technique, including a first pass of liquid-filled deep drawing, a second pass of liquid-filled reverse deep drawing, and an elastic mold bulging stage in the final forming stage. By combining forward and reverse deep drawing with liquid-filled deep drawing technology, the fluid medium and elastic mold are used to disperse deformation stress and improve forming accuracy and uniformity.
It achieves the forming of ultra-thin irregular cone shells with high precision, high wall thickness uniformity and excellent mechanical properties, avoiding local thinning and cracking, and improving the service stability of components.
Smart Images
Figure CN121820451A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal forming and manufacturing technology, specifically to a multi-pass forming method for ultra-thin irregular cone shells with large diameter ratio. Background Technology
[0002] There is a type of complex curved thin-walled integral component at the hot end of aero-engines, such as the rear cone section, the lobe mixer, the afterburner heat shield, and the flame tube stabilizer, which account for more than 40% of the total weight of the new generation of military aero-engines. These components face multi-dimensional composite loads such as high temperature and high pressure (800-1000℃), composite stress and high flow scouring (>800℃ gas) during service, and high temperature alloys are mostly used to meet their stringent service requirements. The manufacturing difficulty of these components lies in: (1) large size and ultra-thinness, with a thickness-to-diameter ratio D / t≤0.003; (2) ultra-large diameter ratio, D / d=5; (3) complex shape.
[0003] Currently, these high-strength parts are formed using a segmented hot stamping and then welding process. However, the presence of weld seams makes it difficult to guarantee their service reliability. On the other hand, conventional steel die stamping is prone to springback and has poor shape accuracy, often requiring prolonged high-temperature creep combined with manual reshaping to improve the dimensional accuracy of the components. However, prolonged creep under high-temperature conditions can easily lead to the precipitation of microstructure defects such as carbides in the microstructure of high-temperature alloys, reducing their mechanical properties and thus impairing the high-temperature service performance of the components.
[0004] Hot stamping or superplastic forming processes can alleviate the problems of poor formability and high springback of high-temperature alloys at room temperature to some extent. However, sheet metal hot stamping often uses rigid dies. During the forming process, when the rigid punch is applied to areas with complex local features, stress concentration can easily occur in the material, leading to local thinning or even cracking. In traditional rigid punch stamping, the blank is subjected to point contact, resulting in an excessively large suspended area, which increases the stress difference during the stamping process and easily causes wrinkling defects. Superplastic forming is a conventional technique for obtaining large, complex, and difficult-to-deform thin-walled components. It generally requires heating the sheet to a specified temperature and utilizing its properties at a specific strain rate (1.3 × 10⁻⁶). -4 ~10 -3 s -1 Superplasticity occurs under conditions of fine grain structure (≤3μm). By precisely controlling the feed rate of inert gas, complex structural parts can be obtained by causing superplastic deformation of the billet at high temperature. However, superplastic forming has problems such as low forming efficiency, poor wall thickness uniformity, and high equipment requirements.
[0005] In summary, existing forming processes easily lead to localized thinning or even cracking in small feature areas of components. Furthermore, the formed workpieces suffer from poor shape accuracy, micro-cracks at welds, and overall performance degradation, severely impacting the service stability of ultra-thin irregular-shaped conical shells with large diameter ratios. Therefore, a high-performance forming method for ultra-thin irregular-shaped conical shells with large diameter ratios is urgently needed. Summary of the Invention
[0006] To solve the above-mentioned technical problems, the present invention provides a multi-pass forming method for ultra-thin irregular cone shells with large diameter ratio.
[0007] The specific technical solution is as follows: A multi-pass forming method for ultra-thin irregular conical shells with large diameter ratios includes two stages: a pre-forming stage and a final forming stage. The pre-forming stage employs two-pass liquid-filled deep drawing. The first pass is a forward liquid-filled deep drawing to form a flat-bottomed cylindrical part. A second pass is then a reverse liquid-filled deep drawing based on the flat-bottomed cylindrical part to form a spherical-bottomed cylindrical part. The final forming stage uses an elastic mold bulging method to form the spherical-bottomed cylindrical part into a final part that meets the requirements. Specifically, the method includes the following steps: (1) Design the blank according to the shape and size of the first preformed workpiece, and set the blank holder force loading curve, liquid chamber pressure loading curve, punch diameter, forming height and stroke in the first preformed die; place the blank on the first preformed die and use liquid filling positive drawing to form a flat bottom cylindrical part; (2) Take the flat-bottomed cylindrical part out of the first preforming mold and check its forming quality. If there is no problem, proceed to the next step directly. If there is a problem, return to the above steps to modify the process parameters or mold and retest until the requirements are met. Set the blank holder force loading curve, liquid chamber pressure loading curve, and punch stroke of the second preforming mold. Install the second preforming mold and place the flat-bottomed cylindrical part on the die in the second preforming mold. Use liquid filling reverse drawing to form the spherical bottom cylindrical part. (3) Remove the ball-bottom cylindrical part from the second pre-forming mold and check its forming quality. If there is no problem, proceed to the next step directly. If there is a problem, return to the above steps to modify the process parameters and repeat the test until the requirements are met. Cut off the flange edge of the ball-bottom cylindrical part, set the diameter, forming height and stroke of the punch of the final forming mold, install the final forming mold, and place the ball-bottom cylindrical part in the final forming mold. Use the elastic mold expansion method to form the final formed part that meets the requirements. (4) Take out the final formed part and check whether its wall thickness reduction rate, mold fit, wrinkling and surface roughness meet the requirements. If there are no problems, proceed to the next step. If there are problems, return to the above steps to modify the process parameters or mold and retest until the requirements are met. 3D cut the outer contour and inner hole to obtain the final part.
[0008] In step (1), the first preforming mold includes a base plate A, a stretching slider adapter plate A, and a back plate A. The stretching slider adapter plate A is connected to the stretching slider of the double-action press, and the back plate A is connected to the pressing slider of the double-action press. The base plate A is installed on the lower worktable by T-bolts. The base plate A has a cylindrical liquid chamber A. A fluid medium channel A is opened inside the base plate A and is connected to the inner cavity of the liquid chamber A. A cylindrical die A is installed on the liquid chamber A, and the blank is placed on the upper surface of the die A. A pressure block A is installed below the stretching slider adapter plate A, a punch adapter plate A is installed below the pressure block A, and a punch A is installed below the punch adapter plate A. The back plate A is connected to the pressing ring A by six circumferential columns. The pressing ring A can close with the die A and press the blank between the two. The punch A enters the cylindrical inner cavity of the pressing ring A, the die A, and the liquid chamber A from top to bottom.
[0009] In step (2), the second preforming mold includes a base plate B, a stretching slider adapter plate B, and a back plate B. The stretching slider adapter plate B is connected to the stretching slider of the double-action press, and the back plate B is connected to the pressing slider of the double-action press. The base plate B is installed on the lower worktable by T-bolts. The base plate B has a cylindrical liquid chamber B. A fluid medium channel B is opened inside the base plate B and is connected to the inner cavity of the liquid chamber B. A cylindrical die B is installed on the liquid chamber B, and a flat-bottomed cylindrical part is placed on the upper surface of the die B. A pressure block B is installed below the stretching slider adapter plate B, a punch adapter plate B is installed below the pressure block B, and a punch B is installed below the punch adapter plate B. A pressing ring B is connected below the back plate B. The pressing ring B can close with the die B and press the flat-bottomed cylindrical part between the two. The punch B enters the cylindrical inner cavity of the pressing ring B, the die B, and the liquid chamber B from top to bottom.
[0010] The final forming mold in step (3) includes a base plate C and a stretching slider adapter plate C. The stretching slider adapter plate C is connected to the upper worktable of the single-action press. The base plate C is installed on the lower worktable by T-bolts. The base plate C has a concave mold C and a spherical cylindrical part is placed on the concave mold C. A pressure block C is installed below the stretching slider adapter plate C. A punch adapter plate C is installed below the pressure block C. An elastic punch is installed below the punch adapter plate C. The elastic punch can close with the concave mold C.
[0011] All of the pressure blocks A, B, and C, the punch adapter plate A, B, and C, and the punches A and B have air holes.
[0012] The edge of the die A is provided with a positioning device for positioning the blank.
[0013] In the first and second preforming molds, sealing rings are provided between the concave mold A and the top of the liquid chamber A, and between the concave mold B and the top of the liquid chamber B; sealing rings are provided between the bottom plate A and the bottom of the liquid chamber A, and between the bottom plate B and the bottom of the liquid chamber B.
[0014] In the first and second preforming molds, the fillet radii of punch A, punch B, die A, and die B are determined based on the mold design manual and finite element simulation optimization.
[0015] The fluid medium in fluid medium channel A and fluid medium channel B is a cold fluid medium or a hot fluid medium, a gas or liquid medium with flow properties, and the temperature of the fluid medium is adjusted according to the forming requirements.
[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention employs a three-pass forming process: the first pass involves liquid-filled deep drawing to form a flat-bottomed cylindrical part; the second pass involves liquid-filled reverse deep drawing based on the flat-bottomed cylindrical part to form a spherical-bottomed cylindrical part; after pre-forming, an elastic mold bulging method is used to form the final part that meets the requirements. The pre-forming stage of this invention combines forward and reverse deep drawing with liquid-filled deep drawing technology. Reverse deep drawing helps to offset the residual stress formed by forward deep drawing, reducing the drawing coefficient compared to forward deep drawing; during liquid-filled deep drawing, the high-pressure liquid allows the sheet metal to adhere tightly to the punch, creating beneficial friction and establishing fluid lubrication in the flange area between the blank and the die, which helps to improve the forming limit of the sheet metal part; the final forming uses an elastic punch, generating a nearly uniformly distributed stress field on the load-bearing contact surface between the blank and the die, fully utilizing the blank's global hardening capacity, dispersing concentrated deformation, improving the uniformity of thin plate deformation and forming limit, suppressing local thinning of the component, achieving overall forming of the component, and ensuring that the component has high forming accuracy, high wall thickness uniformity, and excellent mechanical properties.
[0017] This invention addresses the problems of excessive local thinning in small feature areas of the formed workpiece, poor uniformity of wall thickness, poor shape accuracy, and overall performance degradation of the component in existing forming methods, as well as cracking caused by the deformation of small features of the component exceeding the forming limit in existing forming processes. It achieves integral forming of the component, eliminates splicing welds, and ensures that the component has high forming accuracy, high wall thickness uniformity, and excellent mechanical properties.
[0018] The specific beneficial effects are as follows: (1) High forming accuracy: The pre-forming stage combines forward and reverse drawing and liquid drawing forming technology. Reverse drawing is beneficial to offset the residual stress formed by forward drawing and can reduce the drawing coefficient compared with forward drawing. During liquid drawing, the high pressure liquid can cause the sheet to expand upward and form soft drawing beads, which can play the role of material aggregation and is beneficial to improve the forming limit of the sheet. In the final forming stage, the elastic mold expansion method is adopted. Under the premise of ensuring the microstructure and mechanical properties of the component, the springback of the component is reduced and its forming accuracy is improved.
[0019] (2) Good forming stability: The final forming stage uses an elastomer punch. Compared with the traditional single-point loading method of rigid mold, the elastomer punch undergoes elastic deformation during the loading process. The blank and the mold always maintain surface contact, so that the load-bearing contact surface between the blank and the mold generates a stress field that is close to uniformly distributed. It makes full use of the blank's global hardening ability, disperses concentrated deformation, improves the uniformity and deformation limit of thin plate deformation, suppresses local thinning of components, improves its forming limit, and thus avoids cracking.
[0020] (3) Good wall thickness uniformity: The preforming stage adopts liquid drawing technology. High pressure liquid applies a uniform load on the surface of the sheet, which can make the sheet tightly adhere to the punch and form beneficial friction. Fluid lubrication is established in the flange area between the blank and the die. The combined effect of forward and reverse drawing, beneficial friction and fluid lubrication can offset part of the tensile stress of the blank, effectively improve the material distribution in the component forming process, and thus obtain a reasonable wall thickness distribution. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the shapes of the parts in each forming process of the ultra-thin irregular cone shell with a large diameter ratio according to the present invention; Figure 2 This is a schematic diagram of the structure of the first-pass preforming mold of the present invention; Figure 3 This is a schematic diagram of the second-stage preforming mold structure of the present invention; Figure 4 This is a schematic diagram of the final forming mold structure of the present invention.
[0022] In the diagram, 1. billet; 2. base plate A; 3. stretching slider adapter plate A; 4. liquid chamber A; 5. fluid medium channel A; 6. pressure block A; 7. punch adapter plate A; 8. punch A; 9. back plate A; 10. column; 11. pressure ring A; 12. die A; 13. flat-bottomed cylindrical part; 14. base plate B; 15. stretching slider adapter plate B; 16. liquid chamber B; 17. fluid medium channel B; 18. pressure block B; 19. punch adapter plate B; 20. punch B; 21. back plate B; 22. pressure ring B; 23. die B; 24. spherical bottom cylindrical part; 25. base plate C; 26. stretching slider adapter plate C; 27. die C; 28. pressure block C; 29. punch adapter plate C; 30. elastic punch; 31. final formed part; 32. final part. Detailed Implementation
[0023] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the specific embodiments and accompanying drawings.
[0024] Figure 1The figure shows a schematic diagram of the part shape in each forming process of the ultra-thin irregular conical shell with a large diameter ratio according to the present invention. It includes two stages: a pre-forming stage and a final forming stage. The pre-forming stage employs two passes of liquid-filled deep drawing. The first pass is a forward deep drawing with liquid filling, forming a flat-bottomed cylindrical part. Based on the flat-bottomed cylindrical part, a second pass is a reverse deep drawing with liquid filling, forming a spherical-bottomed cylindrical part. The final forming stage uses an elastic mold bulging method to form the spherical-bottomed cylindrical part into the final part that meets the requirements. Specifically, the process is as follows: (1) Figure 2 This is a schematic diagram of the first-pass preforming mold structure of the present invention. As shown in the figure, the first-pass preforming mold includes a base plate A2, a stretching slider adapter plate A3, and a back plate A9. The stretching slider adapter plate A3 is connected to the stretching slider of the double-action press, and the back plate A9 is connected to the pressing slider of the double-action press. The base plate A2 is mounted on the lower worktable by T-bolts. The base plate A2 has a cylindrical liquid chamber A4, and a fluid medium channel A5 is opened inside the base plate A2, which communicates with the inner cavity of the liquid chamber A4. A cylindrical liquid chamber A4 is mounted on the liquid chamber A4. A cylindrical die A12 is used, and the blank 1 is placed on the upper surface of the die A12. A pressure block A6 is installed below the stretching slider adapter plate A3, a punch adapter plate A7 is installed below the pressure block A6, and a punch A8 is installed below the punch adapter plate A7. A pressure ring A11 is connected to the back plate A9 through six circumferential columns 10. The pressure ring A11 can close with the die A12 and press the blank 1 between the two. The punch A8 enters the cylindrical inner cavity of the pressure ring A11, the die A12, and the liquid chamber A4 from top to bottom.
[0025] The blank 1 is designed according to the shape and size of the first pre-formed workpiece, and the blank 1 is set according to the blank 1 ... (2) Take the flat-bottomed cylindrical part 13 out of the first pre-forming mold and check its forming quality. If there is no problem, proceed directly to the next step. If there is a problem, return to the above steps to modify the process parameters or mold and retest until the requirements are met. Figure 3This is a schematic diagram of the second-pass preforming mold structure of the present invention. As shown in the figure, the second-pass preforming mold includes a base plate B14, a stretching slider adapter plate B15, and a back plate B21. The stretching slider adapter plate B15 is connected to the stretching slider of the double-action press, and the back plate B21 is connected to the pressing slider of the double-action press. The base plate B14 is mounted on the lower worktable by T-bolts. A cylindrical liquid chamber B16 is located on the base plate B14. A fluid medium channel B17 is formed inside the base plate B14, communicating with the inner cavity of the liquid chamber B16. A cylindrical die B23 is installed, and a flat-bottomed cylindrical part 13 is placed on the upper surface of the die B23. A pressure block B18 is installed below the stretching slider adapter plate B15, a punch adapter plate B19 is installed below the pressure block B18, and a punch B20 is installed below the punch adapter plate B19. A pressure ring B22 is connected below the back plate B21. The pressure ring B22 can close with the die B23 and press the flat-bottomed cylindrical part 13 between them. The punch B20 enters the cylindrical inner cavity of the pressure ring B22, the die B23, and the liquid chamber B16 from top to bottom.
[0026] Install the second-pass preforming mold, and set the blank holder force loading curve, liquid chamber pressure loading curve, and punch stroke for the second-pass preforming mold. Place the flat-bottomed cylindrical part 13 on the concave die B23 in the second-pass preforming mold, and adopt the liquid-filled reverse drawing forming scheme. The blank holder slider of the double-action press drives the blank holder ring B22 down to the upper surface of the flat-bottomed cylindrical part 13. According to the liquid chamber pressure loading curve, high-pressure liquid is introduced into the liquid chamber B16. The stretching slider of the double-action press drives the punch B20 down to form the spherical bottom cylindrical part 24 that meets the requirements. (3) Remove the ball-bottom cylindrical part 24 from the second pre-forming mold and check its forming quality. If there are no problems, proceed to the next step. If there are problems, return to the above steps, modify the process parameters, and repeat the test until the requirements are met. Cut off the flange edge of the ball-bottom cylindrical part 24. Figure 4 The schematic diagram of the final forming mold structure of the present invention is shown in the figure. The final forming mold includes a base plate C25 and a stretching slider adapter plate C26. The stretching slider adapter plate C26 is connected to the upper worktable of the single-action press. The base plate C25 is installed on the lower worktable by T-bolts. The base plate C25 is a concave mold C27, and the spherical bottom cylindrical part 24 is placed on the concave mold C27. A pressure block C28 is installed below the stretching slider adapter plate C26. A punch adapter plate C29 is installed below the pressure block C28. An elastic punch 30 is installed below the punch adapter plate C29. The elastic punch 30 can close with the concave mold C27.
[0027] Install the final forming mold and place the ball-bottom cylindrical part 24 in the final forming mold. Set the diameter, forming height and stroke of the punch of the final forming mold. Use the elastic mold expansion method. The upper worktable of the single-action press drives the elastic punch 30 to move downward. Under the action of the elastic punch 30, the ball-bottom cylindrical part 24 is attached to the die C27 to form the final forming part 31 that meets the requirements. (4) Take out the final formed part 31 and check whether its wall thickness reduction rate, mold fit, wrinkling and surface roughness meet the requirements. If there are no problems, proceed to the next step. If there are problems, return to the above steps to modify the process parameters or mold, and retest until the requirements are met. Cut the outer contour and inner hole to obtain the final part 32.
Claims
1. A multi-pass forming method for ultrathin irregular cone shells with large diameter ratios, characterized in that, The process includes two stages: a pre-forming stage and a final forming stage. The pre-forming stage employs two-pass liquid-filled deep drawing. The first pass is a forward liquid-filled deep drawing to form a flat-bottomed cylindrical part (13). Based on the flat-bottomed cylindrical part (13), a second pass is a reverse liquid-filled deep drawing to form a spherical-bottomed cylindrical part (24). The final forming stage uses an elastic mold bulging method to form the spherical-bottomed cylindrical part (24) into a final part (32) that meets the requirements. Specifically, it includes the following steps: (1) Design the blank (1) according to the shape and size of the first preformed workpiece, and set the blank holder force loading curve, liquid chamber pressure loading curve, punch diameter, forming height and stroke in the first preformed mold; place the blank (1) on the first preformed mold and use liquid filling positive drawing to form a flat bottom cylindrical part (13); (2) Take the flat-bottomed cylindrical part (13) out of the first preforming mold and check its forming quality. If there is no problem, proceed to the next step directly. If there is a problem, return to the above steps to modify the process parameters or mold and retest until the requirements are met. Set the blank holder force loading curve, liquid chamber pressure loading curve, and punch stroke of the second preforming mold. Install the second preforming mold and place the flat-bottomed cylindrical part (13) on the die in the second preforming mold. Use liquid filling reverse drawing to form the spherical bottom cylindrical part (24). (3) Take the ball bottom cylindrical part (24) out of the second pre-forming mold and check its forming quality. If there is no problem, proceed to the next step directly. If there is a problem, return to the above steps to modify the process parameters and repeat the test until the requirements are met. Cut off the flange edge of the ball bottom cylindrical part (24), set the diameter, forming height and stroke of the punch in the final forming mold, install the final forming mold, and place the ball bottom cylindrical part (24) in the final forming mold. Use the elastic mold expansion method to form the final forming part (31) that meets the requirements. (4) Take out the final formed part (31) and check whether its wall thickness reduction rate, mold fit, wrinkling and surface roughness meet the requirements. If there are no problems, proceed to the next step. If there are problems, return to the above steps to modify the process parameters or mold, and retest until the requirements are met. 3D cut the outer contour and inner hole to obtain the final part (32).
2. The method for multi-pass forming of ultra-thin irregular cone shells with large diameter ratio according to claim 1, characterized in that: In step (1), the first preforming mold includes a base plate A (2), a stretching slider adapter plate A (3), and a back plate A (9). The stretching slider adapter plate A (3) is connected to the stretching slider of the double-action press, and the back plate A (9) is connected to the pressing slider of the double-action press. The base plate A (2) is installed on the lower worktable by T-bolts. The base plate A (2) has a cylindrical liquid chamber A (4). A fluid medium channel A (5) is opened inside the base plate A (2) and is connected to the inner cavity of the liquid chamber A (4). A cylindrical die A (12) is installed on the liquid chamber A (4). The blank (1) Placed on the upper surface of the die A (12); a pressure block A (6) is installed below the stretching slider adapter plate A (3), a punch adapter plate A (7) is installed below the pressure block A (6), and a punch A (8) is installed below the punch adapter plate A (7); a pressure ring A (11) is connected to the back plate A (9) through six circumferential columns (10); the pressure ring A (11) can close with the die A (12) and press the blank (1) between the two, and the punch A (8) enters the cylindrical inner cavity of the pressure ring A (11), the die A (12) and the liquid chamber A (4) from top to bottom.
3. The multi-pass forming method for ultra-thin irregular cone shells with large diameter ratio according to claim 1, characterized in that: In step (2), the second preforming mold includes a base plate B (14), a stretching slider adapter plate B (15), and a back plate B (21). The stretching slider adapter plate B (15) is connected to the stretching slider of the double-action press, and the back plate B (21) is connected to the pressing slider of the double-action press. The base plate B (14) is installed on the lower worktable by T-bolts. The base plate B (14) has a cylindrical liquid chamber B (16). A fluid medium channel B (17) is opened inside the base plate B (14) and communicates with the inner cavity of the liquid chamber B (16). A cylindrical die B (23) is installed on the liquid chamber B (16). The bottom cylindrical part (13) is placed on the upper surface of the die B (23); the pressure block B (18) is installed below the stretching slider adapter plate B (15), the punch adapter plate B (19) is installed below the pressure block B (18), and the punch B (20) is installed below the punch adapter plate B (19); the back plate B (21) is connected to the pressure ring B (22); the pressure ring B (22) can close with the die B (23) and press the flat bottom cylindrical part (13) between the two, and the punch B (20) enters the cylindrical inner cavity of the pressure ring B (22), the die B (23) and the liquid chamber B (16) from top to bottom.
4. The multi-pass forming method for ultra-thin irregular cone shells with large diameter ratio according to claim 1, characterized in that: The final forming mold described in step (3) includes a base plate C (25) and a stretching slider adapter plate C (26). The stretching slider adapter plate C (26) is connected to the upper worktable of the single-action press. The base plate C (25) is installed on the lower worktable by T-bolts. The base plate C (25) has a die C (27) on it, and a spherical cylindrical part (24) is placed on the die C (27). A pressure block C (28) is installed below the stretching slider adapter plate C (26). A punch adapter plate C (29) is installed below the pressure block C (28). An elastic punch (30) is installed below the punch adapter plate C (29). The elastic punch (30) can close with the die C (27).
5. The method for multi-pass forming of ultra-thin irregular conical shells with large diameter ratio according to any one of claims 2, 3 or 4, characterized in that: The pressure block A (6), pressure block B (18), pressure block C (28), punch adapter plate A (7), punch adapter plate B (19), punch adapter plate C (29), and punch A (8) and punch B (20) are all provided with air holes.
6. The multi-pass forming method for ultra-thin irregular cone shells with large diameter ratio according to claim 2, characterized in that: The edge of the die A (12) is provided with a positioning device for positioning the blank (1).
7. The method for multi-pass forming of ultra-thin irregular conical shells with large diameter ratio according to any one of claims 2 or 3, characterized in that: In the first and second preforming molds, sealing rings are provided between the top of the concave mold A (12) and the liquid chamber A (4), and between the top of the concave mold B (23) and the liquid chamber B (16); sealing rings are provided between the bottom plate A (2) and the bottom of the liquid chamber A (4), and between the bottom plate B (14) and the bottom of the liquid chamber B (16).
8. The method for multi-pass forming of ultra-thin irregular conical shells with large diameter ratio according to any one of claims 2 or 3, characterized in that: In the first and second preforming molds, the fillet radii of punch A (8), punch B (20), die A (12), and die B (23) are determined according to the mold design manual and finite element simulation optimization.
9. The method for multi-pass forming of ultra-thin irregular conical shells with large diameter ratio according to any one of claims 2 or 3, characterized in that: The fluid medium in the fluid medium channel A (5) and fluid medium channel B (17) is a cold fluid medium or a hot fluid medium, a gas or liquid medium with flow properties, and the temperature of the fluid medium is adjusted according to the forming requirements.