Progressive stamping process for high-strength supporting sheet metal part of automobile seat
By introducing localized plastic pre-stretching during the stamping process of automotive seat support sheet metal parts, the dimensional accuracy problem caused by the springback of high-strength steel was solved, achieving efficient and stable parts production and reducing mold debugging costs and time.
Patent Information
- Application Number
- CN202511683800.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-01-23
AI Technical Summary
In the existing technology, high-strength steel has a serious springback phenomenon during the stamping process of automotive seat support sheet metal parts, which makes it impossible to guarantee the dimensional accuracy of the parts. Moreover, the traditional solution relies on empirical compensation of the mold surface and additional correction processes, which is costly, time-consuming and unstable.
By adopting a progressive die production process, local plastic pre-stretching is introduced during the stamping process. The punch on the die is used to perform controllable local plastic pre-stretching of the material at the same station, which offsets the residual compressive stress generated in the subsequent flanging and side shaping processes, thereby actively controlling the springback.
It achieves feedforward control of the springback of high-strength steel, improves the dimensional accuracy and production stability of parts, reduces mold debugging cycle and cost, and increases the yield.
Smart Images
Figure CN121373174A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of sheet metal stamping processing, and particularly relates to a progressive stamping process for a high-strength support sheet metal part of an automobile seat. BACKGROUND
[0002] The support sheet metal part of an automobile seat is a connecting component in the seat framework, and high-strength steel such as S500MC is generally used to achieve lightweight. However, the material has high yield strength and low plasticity reserve, and after stamping forming, especially after flanging and bending, a large amount of residual stress will accumulate in the material, resulting in serious springback phenomenon, so that the dimensional accuracy of the part cannot be guaranteed. The traditional solution mainly relies on empirical compensation of the die surface and addition of a correction process, which is a passive correction measure for the formed springback result. Not only is the mold debugging period long and the cost high, but also the production stability is poor and the yield fluctuates greatly. SUMMARY
[0003] The present application provides a progressive stamping process for a high-strength support sheet metal part of an automobile seat, which actively intervenes and optimizes the material stress distribution before forming, thereby fundamentally inhibiting the springback and cracking of high-strength steel stamping sheet metal parts.
[0004] Technical scheme: In order to achieve the above-mentioned purpose, the progressive stamping process for a high-strength support sheet metal part of an automobile seat of the present application adopts a progressive die production, and the die stations are arranged in sequence along the feeding direction. The progressive stamping process comprises the following sequential steps:
[0005] a. Punching guide holes: punching precise positioning guide holes on the strip;
[0006] b. First trimming and local pre-stretching: trimming the scrap area outside the final contour of the workpiece for the first time, and using the male die on the die to perform controllable local plastic pre-stretching on the material adjacent to the trimming line and located in the subsequent flanging deformation affected area within the same stamping stroke in the same station, so that the material in the area is plastically deformed;
[0007] Wherein, the local plastic pre-stretching is to introduce controllable tensile stress in the area before forming, so as to offset the residual compressive stress generated in the subsequent flanging and side shaping processes, thereby actively controlling and reducing the overall springback of the workpiece;
[0008] c. Second trimming and third trimming: gradually trimming the remaining scrap in the subsequent two stations to complete the final forming of the workpiece contour;
[0009] d. Flanging: flanging the trimmed workpiece;
[0010] e. Side shaping: side pressing and shaping the flanged workpiece;
[0011] f. cutting: separating the finished workpiece from the strip.
[0012] Further, the local plastic pre-stretching in step b causes the material to generate a plastic strain range of 1% to 3%.
[0013] Further, the material adjacent to the trimming line and located in the subsequent flanging deformation influence area is the material area outside the flanging contour line in the subsequent flanging station within a range of 2mm to 8mm.
[0014] Further, the tensile stress introduced in step b causes the area to have a residual stress state close to neutral after the completion of the subsequent flanging process.
[0015] Further, the local plastic pre-stretching in step b is realized by a pressure-adjustable hydraulic punch or a rigid punch with a circular arc end face, and the pressure acting on the material surface is in the range of 150-250MPa.
[0016] Further, the secondary trimming in step c and the tertiary trimming have a processing overlap of 0.5-1.0mm between the trimming contour and the first trimming contour of step b.
[0017] Further, before flanging in step d and after side shaping in step e, an empty step station is provided, which is provided with a visual sensor or a mechanical probe for monitoring the position accuracy of the workpiece.
[0018] Further, the side shaping processing station in step e is not less than 450 tons, and the holding time is 3-5 seconds.
[0019] Further, after the cutting in step f, a step g of laser shock peening the flanged and side-shaped area of the workpiece is further included.
[0020] Further, the strip used in the progressive stamping process is high-strength microalloyed steel S500MC.
[0021] Beneficial effects: The present application introduces a controllable tensile stress in the key area of the material before flanging deformation by local plastic pre-stretching in the same station as the first trimming, which counteracts the residual compressive stress inevitably generated in subsequent forming, thereby actively weakening the driving force of springback from the root, realizing fundamental and feedforward control of the size accuracy of the part, and effectively solving the problem of difficult control of springback and unstable accuracy of high-strength sheet metal parts in progressive die production. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 The figure is a schematic diagram of the sequence of the stamping process of the present application. DETAILED DESCRIPTION
[0023] The application will be further described below in conjunction with the drawings.
[0024] As Figure 1 shown, the progressive stamping process of high-strength support sheet metal parts of automobile seats adopts progressive die production, and the die stations are arranged in sequence along the feeding direction. The core is that through a series of processes, especially the integration of trimming and local plastic pre-stretching, active and feed-forward control of springback of high-strength steel sheet is realized. The progressive stamping process comprises the following sequential steps:
[0025] a. Punching guide hole: punching a precisely positioned guide hole on the strip.
[0026] This step provides an accurate feeding reference for all subsequent stations, ensures the relative position accuracy of each processing step, and is the key to stable and efficient production of progressive die.
[0027] b. First trimming and local pre-stretching: trimming the scrap area outside the final profile of the workpiece for the first time, and using the male die on the die to perform controllable local plastic pre-stretching on the material adjacent to the trimming line and located in the subsequent flanging deformation affected area within the same stamping stroke, so that the material in the area is plastically deformed.
[0028] Among them, the local plastic pre-stretching is to introduce a controllable tensile stress in the area before forming, so as to offset the residual compressive stress generated in the subsequent flanging and side shaping processes, thereby actively controlling and reducing the overall springback of the workpiece.
[0029] 1. The same station and the same stamping stroke mode improve processing efficiency.
[0030] 2. The essence of local plastic pre-stretching: this operation is not bending, but using the male die to act vertically on the material surface to produce a small plastic tensile deformation similar to bulging. The core purpose of this deformation is to actively introduce a controllable and macroscopic residual tensile stress field in the material.
[0031] 3. Principle of active control of springback: the subsequent flanging and side shaping processes will leave residual compressive stress in the deformation area due to plastic deformation of the material, which is the fundamental driving force for part springback. The tensile stress introduced in advance is opposite in direction to the compressive stress that will be generated later. According to the stress superposition principle, they can offset each other, so that the net residual stress level of the area after final forming is greatly reduced, even close to neutral. This is a feed-forward control method of pre-applied counterforce, which weakens the tendency of springback from the root, and the effect is more stable and more accurate than passive shaping correction.
[0032] c. Secondary and tertiary trimming: In the next two stations, the remaining scrap is gradually removed, and the final shape of the workpiece is completed.
[0033] The multi-station progressive trimming, rather than one-time cutting, can effectively disperse the blanking force, reduce the single-side stress of the die, and improve the service life and stability of the die. Meanwhile, the step-by-step cutting mode is beneficial to the gradual release and redistribution of the material, and can reduce the deformation of the workpiece caused by stress mutation.
[0034] d. Flanging: The workpiece after trimming is flanged.
[0035] e. Side shaping: The workpiece after flanging is side-shaped.
[0036] After the pre-stretching treatment of step b, the stress state of the material in the flanging area has been optimized, and the springback tendency has been significantly reduced. Therefore, the subsequent flanging and side shaping processes can be carried out on a more "stable" material basis, and the dimensional stability after forming is greatly improved.
[0037] f. Cutting: The formed workpiece is separated from the strip.
[0038] Therefore, the progressive stamping process of the present application can actively introduce controllable tensile stress in the material deformation affected area before flanging by locally pre-stretching the workpiece during trimming, thereby intervening from the stress source, using the introduced tensile stress to pre-compensate the residual compressive stress generated by subsequent forming (flanging, side shaping), thereby actively weakening the springback driving force, achieving feedforward control of high-strength steel springback, rather than traditional passive correction, optimizing material internal stress distribution, and fundamentally inhibiting the springback and cracking of high-strength steel stamping sheet metal parts.
[0039] Since plastic strain is a direct physical quantity that measures the degree of plastic deformation of the material, in the present application, as a preferred, the local plastic pre-stretching in step b causes the plastic strain of the material to be in the range of 1% to 3%.
[0040] Lower limit 1%: Ensure that the material has indeed undergone plastic deformation beyond its elastic limit. Too small strain (such as <0.5%) may still be in the elastic-plastic transition zone, and cannot form stable and significant residual tensile stress, so the pre-stretching effect is limited.
[0041] Upper limit 3%: Balance between introducing effective tensile stress and avoiding material damage. The uniform elongation of S500MC high-strength steel is limited, and excessive pre-stretching (such as >5%) may cause local over-thinning of the material, and even cause micro-cracks. A strain range of 1%-3% can effectively mobilize the plasticity of the material, introduce sufficient tensile stress, and ensure the safety of processing, which is within the key interval of ideal plastic deformation of the material.
[0042] The material adjacent to the trimming line and within the subsequent flanging deformation influence zone is the material area within 2mm to 8mm outside the flanging profile line in the subsequent flanging station.
[0043] Outside the flanging profile line means that the pre-stretching acts on the base of the final flanged feature rather than the facade itself. And the range of 2mm to 8mm means that this area is the main area of material flow and stress concentration during flanging forming. Acting on it, it can most directly and effectively affect the stress state of the flanging process. Too close ( < 2mm) may interfere with the formation of the flanged vertical wall; too far ( > 8mm) the stress effect is attenuated and the effect is not significant. This range is the preferred influence zone determined by finite element analysis and a large number of process tests, which ensures that the tensile stress is precisely applied to the position where the residual compressive stress can be effectively offset.
[0044] Through the tensile stress introduced in step b, the residual stress state of the area after the completion of the subsequent flanging process is close to neutral, which is the ultimate goal of the present application. The residual stress state close to neutral means that the internal stress of the material in this area is basically balanced, which is macroscopically manifested as the rebound is minimized. This provides a clear and scientific criterion for measuring the success of the stamping process of the present application, indicating that the stress compensation mechanism has fully played its role.
[0045] The local plastic pre-stretching in step b is realized by a pressure-adjustable hydraulic punch or a rigid punch with a circular arc end face, and the pressure range acting on the material surface is 150-250MPa.
[0046] Hydraulic punch: allows precise closed-loop control of the acting pressure, easy to realize precise reproduction and optimization of process parameters, strong adaptability. Rigid punch (circular arc end face): realizes gradual contact and loading through the design of the circular arc end face (such as R2-R5mm), avoids stress concentration, and has simple and reliable structure.
[0047] 150-250MPa pressure range: this range is set according to the characteristics of S500MC material (yield strength above about 500MPa). The pressure needs to be sufficient to cause 1%-3% plastic strain (about 150MPa or more), but not too high to crush or deform excessively (about 250MPa or less).
[0048] The secondary trimming and the tertiary trimming in step c have a processing overlap of 0.5-1.0mm between the trimming profile and the first trimming profile of step b.
[0049] After the first trimming, burrs, micro-cracks or work-hardened layer may exist on the section. A work-overlapping strip of 0.5-1.0 mm is set, so that in the subsequent trimming station, a thin layer of the first trimmed section is trimmed again to eliminate the quality defects possibly caused by the first trimming.
[0050] Before the flanging of step d and after the side shaping of step e, an empty step station is arranged, which is provided with a visual sensor or a mechanical probe for monitoring the position accuracy of the workpiece.
[0051] By setting monitoring before and after the key forming process, real-time monitoring and early warning of the feeding accuracy and whether the forming is in place can be realized. Once the deviation is detected, the system can alarm or stop in time to prevent batch waste.
[0052] The tonnage of the side shaping station of step e is not less than 450 tons, and the holding time is 3-5 seconds. For S500MC and other high-strength materials, very high static pressure (≥450 tons) is required to make them flow plastically to correct the shape. At the same time, the pressure is applied and maintained for 3-5 seconds, which utilizes the creep effect of the material at high temperature (although it is room temperature, but under high stress), which helps to relax and redistribute the stress in the material, so as to stabilize the corrected shape and effectively suppress the springback.
[0053] After the cutting of step f, a step g of laser shock peening the flanging and side shaping area of the workpiece is further included, and the pulse laser energy density used in the laser shock peening is 5-9 GW / cm². This is a preferred additional step, which combines stamping and forming with advanced surface modification technology. Laser shock peening uses high-energy pulse laser to generate a high-pressure shock wave on the surface of the workpiece, which makes the surface layer of the material plastically deform, thereby introducing a deep layer of high numerical residual compressive stress. The compressive stress layer can significantly inhibit the propagation of fatigue cracks and improve the fatigue life of the workpiece.
[0054] The strip used in the progressive stamping process is high-strength micro-alloyed steel S500MC. The progressive stamping process of the present application is specially designed to solve the forming problems of high-strength micro-alloyed steel such as S500MC. The material has high strength and large springback, which is difficult to control by traditional process, and the effectiveness of the present application is fully embodied in this material.
[0055] The progressive stamping process of the present application changes the traditional passive springback correction to active internal stress control, and has the following advantages:
[0056] 1) By the local plastic pre-stretching implemented in the same station as the first trimming, controllable tensile stress is introduced in the key area of the material before the flanging deformation, which counteracts the residual compressive stress inevitably generated in the subsequent forming, thus actively weakening the driving force of springback from the root, realizing the fundamental and feedforward control of the part size precision, and effectively solving the problem of uncontrollable springback and unstable precision of high-strength sheet metal parts in progressive die production.
[0057] 2) The product precision and qualification rate are significantly improved, and repeated trial molding and strong passive shaping depending on experience are avoided, thus greatly shortening the mold development cycle.
[0058] The above is only the preferred embodiment of the present application, it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.
Claims
1. A progressive stamping process for high-strength support sheet metal parts for automotive seats, employing progressive die production, with die stations arranged sequentially along the feeding direction, characterized by: The progressive stamping process includes the following sequential steps: a. Punching guide holes: Punching precise positioning guide holes into the strip material; b. First trimming and local pre-stretching: The scrap area outside the final contour of the workpiece is trimmed for the first time. In the same station and the same stamping stroke, the punch on the die is used to perform controllable local plastic pre-stretching on the material adjacent to the trimming line and located in the subsequent flanging deformation influence area, so that the material in this area undergoes plastic deformation. The localized plastic pre-stretching involves introducing controllable tensile stress into the region before forming to counteract the residual compressive stress generated during subsequent flanging and side shaping processes, thereby actively controlling and reducing the overall springback of the workpiece. c. Secondary and tertiary trimming: In the subsequent two workstations, the remaining waste material is gradually removed to complete the final shaping of the workpiece. d. Flanging: Flanging the workpiece after it has been trimmed. e. Side shaping: Performing lateral precision pressing on the workpiece after flanging; f. Cutting: Separating the formed workpiece from the conveyor belt.
2. The progressive stamping process for high-strength support sheet metal parts for automotive seats according to claim 1, characterized in that: The localized plastic pre-stretching in step b results in a plastic strain in the material ranging from 1% to 3%.
3. The progressive stamping process for high-strength support sheet metal parts for automotive seats according to claim 1, characterized in that: The material adjacent to the cutting edge line and located within the subsequent flanging deformation influence area is the material area within 2mm to 8mm outside the flanging outline line in the subsequent flanging station.
4. The progressive stamping process for high-strength support sheet metal parts for automotive seats according to claim 1, characterized in that: The tensile stress introduced in step b ensures that the residual stress state of the region is close to neutral after the subsequent flanging process.
5. The progressive stamping process for high-strength support sheet metal parts for automotive seats according to claim 1, characterized in that: The localized plastic pre-stretching in step b is achieved by a hydraulic punch with adjustable pressure or a rigid punch with a circular arc end face, and the pressure applied to the material surface ranges from 150 to 250 MPa.
6. The progressive stamping process for high-strength support sheet metal parts for automotive seats according to claim 1, characterized in that: The secondary and tertiary cutting edges in step c have a processing overlap of 0.5-1.0 mm with the first cutting edge outline in step b.
7. The progressive stamping process for high-strength support sheet metal parts for automotive seats according to claim 1, characterized in that: Before and after the flanging in step d, and after the side shaping in step e, there are idle step stations. The idle step stations are equipped with visual sensors or mechanical probes for monitoring the positional accuracy of the workpiece.
8. The progressive stamping process for high-strength support sheet metal parts for automotive seats according to claim 1, characterized in that: The side shaping tonnage in step e shall not be less than 450 tons, and the pressure holding time shall be 3-5 seconds.
9. The progressive stamping process for high-strength support sheet metal parts for automotive seats according to claim 1, characterized in that: After the cutting in step f, the process also includes step g, which involves laser shock strengthening of the workpiece's flanging and side-shaping areas.
10. The progressive stamping process for high-strength support sheet metal parts for automotive seats according to claim 1, characterized in that: The strip used in the progressive stamping process is high-strength microalloyed steel S500MC.