Multi-bridge site stamping and stretch forming plate and processing method thereof

Abstract

The application discloses a kind of multi-bridge site stamping extension forming plate and its processing method, six-stage process of adopting blank pretreatment, symmetrical positioning hole processing, stepped stamping bridge site forming, laser hole array processing, oblique extension forming, normal temperature leveling and shaping is formed.By stepped sectional pressure forming, it is ensured that bridge body is uniform and stable, high-precision forming hole is processed by pulse fiber laser, 5°-15° oblique extension and double-side synchronous constant clamping are used to realize the uniform flow of material, and residual stress is eliminated after leveling.The application can make the width of plate uniform and narrow, the extension size error is controlled within ±0.1mm, the flatness is ≤0.05mm / m, the waist type defect is completely eliminated, the forming stability and material utilization rate are improved, the automatic continuous stamping production of high elongation rate plate is adapted, and the forming qualified rate is high and the size consistency is good.

Description

Technical Field

[0001] This invention relates to the technical field of sheet metal stamping and forming, and particularly to a multi-bridge stamping and stretching sheet metal and its processing method. Background Technology

[0002] In the stamping and forming of high elongation metal sheets (elongation coefficient ≥30%), the traditional integral stretching process has obvious technical bottlenecks: when the sheet is stretched, the material flows towards the middle, forming a waist-shaped defect that is narrow in the middle and wide at both ends, resulting in poor dimensional accuracy and structural consistency, and a high scrap rate; conventional processes cannot accurately control the material flow, making it difficult to achieve "width borrowing and length extension" waste-free forming, resulting in low material utilization; at the same time, the lack of auxiliary positioning and stress relief structures makes it easy for problems such as displacement, wrinkles, and local cracking to occur during forming, which cannot meet the requirements of high-precision continuous production.

[0003] Existing related structural patents mostly focus on the bridge and hole layout of the sheet metal itself, without disclosing the corresponding segmented stamping and extension process. Furthermore, they suffer from problems such as vague process parameters, insufficient control of forming precision, and inability to adapt to automated production lines. Summary of the Invention

[0004] This invention aims to at least partially solve one of the problems in related technologies. Therefore, one objective of this invention is to provide a multi-bridge stamping and stretching forming sheet metal and its processing method. Through a segmented process, combined with a multi-bridge structure and graded hole groups, precise control of material flow is achieved, eliminating waist-shaped defects and improving forming accuracy, material utilization, and production stability.

[0005] A multi-bridge stamping and stretching forming sheet metal and its processing method include the following steps: Select high elongation metal sheets, cut blanks to target dimensions, with the initial width of the blanks being 1.05-1.15 times the target width after forming. Clean, deburr, and anneal the surface of the blanks. Symmetrical positioning through holes are machined at both ends of the length direction and in the middle of the width direction of the blank. A stepped stamping die is used to stamp a raised bridge-shaped structure by stamping in an equidistant array along the width of the blank. In the intersecting areas of the bridge structure, laser hole processing technology is used to process holes in an array; The pre-treated billet is clamped in an inclined extending fixture and narrowed in width and extended in length at a constant rate. After stretching, the sheet material is leveled at room temperature using a leveling mold to eliminate residual stress.

[0006] Furthermore, in the step of forming a raised bridge-shaped structure by stamping in a stepped stamping die at equal intervals along the width direction of the blank, the arrangement density of the raised bridge-shaped structure along the width direction of the blank is 2-5 structures per 10mm width, and each group of bridge structures is distributed at equal intervals along the length direction, and the arrangement spacing is consistent with the bridge body size.

[0007] Furthermore, in the step of forming a raised bridge-like structure by stamping in an equidistant array along the width direction of the blank using a stepped stamping die, the pressure of the three stages of stepped stamping is as follows: the first stage is 0.3-0.5MPa, the second stage is 0.6-0.8MPa, and the third stage is 1.0-1.2MPa.

[0008] Furthermore, in the intersecting areas of the bridge structure, a laser hole processing technology is adopted. In the array processing of the formed holes, pulsed fiber laser is used for laser hole processing.

[0009] Further, the pretreated blank is clamped in an oblique stretching fixture, with the stretching direction forming an angle of 5°-15° with the length direction of the sheet. In the steps of narrowing the width and extending the length at a constant rate, the oblique stretching is performed by double-sided synchronous clamping and stretching, with a constant clamping force of 0.8-1.5MPa.

[0010] Furthermore, after the stretching is completed, the sheet is leveled at room temperature using a leveling mold to eliminate residual stress. In this step, the leveling pressure of the leveling mold is 0.5-0.7 MPa, and the leveling is performed 1-2 times.

[0011] Furthermore, after the stretching is completed, the sheet is leveled at room temperature using a leveling mold to eliminate residual stress. After leveling, the flatness of the sheet is ≤0.05mm / m.

[0012] Furthermore, in the step of symmetrically machining positioning through holes at both ends of the length direction and the middle of the width direction of the blank, the diameter of the positioning holes is 8-12mm.

[0013] Furthermore, in the intersecting area of ​​the bridge structure, a laser hole processing technology is used to process the holes in an array. The diameter of the holes is 0.5-2mm and the spacing between the holes is 3-8mm.

[0014] Furthermore, the pretreated blank is clamped in an inclined stretching fixture and subjected to a constant rate of narrowing in the width direction and extending in the length direction, with the stretching direction forming an angle of 5°-15° with the length direction of the sheet.

[0015] Compared with the prior art, the above-mentioned technical solutions provided in this application have the following advantages: This application adopts a segmented process of pretreatment, positioning, bridge forming, hole processing, oblique extension, and calibration and shaping. The parameters can be quantified and the process can be monitored. With the help of multi-bridge structure and graded hole group, the material flow can be precisely controlled, waist-shaped defects can be eliminated, and the forming accuracy, material utilization rate and production stability can be improved. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] In the attached image: Figure 1 This is a schematic flowchart of an embodiment of the multi-bridge stamping and stretching forming sheet metal and its processing method according to this application; Figure 2 This is a structural schematic diagram of the multi-bridge stamping and stretching forming sheet and its processing method according to this application.

[0019] Figure label: 10. Sheet metal; 20. Bridge position; 30. Positioning through hole; 40. Forming hole. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] like Figure 1 , Figure 2 As shown, this application provides a multi-bridge 20-position stamped and stretched sheet metal 10 and its processing method, including the following steps: Select a high elongation metal sheet 10, cut the blank to the target size, the initial width of the blank is 1.05-1.15 times the target width after forming, and clean, deburr and anneal the surface of the blank. Symmetrically machine positioning through holes 30 at both ends of the length direction and in the middle of the width direction of the blank; A stepped stamping die is used to stamp a raised bridge-shaped structure by stamping in an equidistant array along the width of the blank. In the structural intersection area of ​​bridge site 20, laser hole processing technology is used to process 40 holes in an array; The pre-treated billet is clamped in an inclined extending fixture and narrowed in width and extended in length at a constant rate. After the stretching is completed, the plate 10 is leveled at room temperature using a leveling mold to eliminate residual stress.

[0023] Traditional processes directly stretch sheet material of the target width 10. Due to the lack of allowance, the material has insufficient elongation space, making it prone to tearing and dimensional inaccuracies. This invention limits the initial width of the billet to 1.05-1.15 times the target width. This range is based on extensive testing: below 1.05 times, the elongation allowance is insufficient, leading to stress concentration and cracking during the elongation process; above 1.15 times, there is significant material waste and uneven shrinkage after forming. Cleaning and deburring eliminate surface defects and avoid stress concentration sources; annealing and softening treatment eliminates rolling internal stress, improves the uniform ductility of sheet material 10, and lays the foundation for subsequent high-precision forming.

[0024] Traditional stamping relies on rough edge positioning, which is prone to offset and twisting during forming. This application symmetrically processes positioning through holes 30 at both ends in the length direction and in the middle of the width direction to form a three-dimensional positioning reference. This ensures that the central axis of the sheet metal 10 does not shift throughout the entire process of clamping, stamping, and stretching, thereby suppressing local overstretching or accumulation caused by positioning deviation from the source and providing geometric constraints for subsequent uniform stretching.

[0025] Traditional one-time stamping easily leads to incomplete forming of the bridge position 20, stress concentration at the root, and tearing of the sheet metal 10. This application uses a stepped stamping die to form a raised bridge-like structure in an equidistant array along the width direction. Through multi-stage pressure, the material is gradually plastically flowed, ensuring uniform bridge dimensions and smooth transitions, avoiding damage caused by a single strong press. The bridge position 20 can uniformly divide the stress area along the width direction, forcing the material to flow along a preset path, overcoming the inherent defects of material accumulation in the middle of traditional stretching.

[0026] Traditional mechanical drilling has low precision and is prone to burrs and deformation. This application uses laser hole processing to arrange the formed holes 40 in an array in the staggered area of ​​the bridge position 20. The holes can accurately release local stress and avoid material accumulation and wrinkling during extension. The staggered layout ensures that the functions of the bridge position 20 and the hole position do not interfere with each other, forming a support + pressure relief synergy system, making the full-width extension more uniform.

[0027] Traditional linear stretching tends to result in a linear stress distribution, with rapid shrinkage in the middle and slow shrinkage at both ends. This application uses an oblique extension fixture to narrow the width and extend the length, making the material flow direction form a certain angle with the length direction. This disrupts the uneven stress field of linear stretching, making the shrinkage rate at each point in the width direction more uniform, and fundamentally eliminating the waist-shaped defect.

[0028] The extended sheet material 10 has residual stress, which can easily cause springback deformation if used directly. This application eliminates internal stress by using a room temperature leveling mold, stabilizes dimensional accuracy, ensures that the product does not deform during subsequent use and storage, and improves the finished product qualification rate and long-term stability.

[0029] The six-stage continuous processing technology, with closed-loop control from blank preparation to final shaping, systematically solves problems such as waist-shaped defects, dimensional deviations, wrinkles and cracks, and low material utilization in the stretch forming of high-elongation sheet 10, achieving automated continuous production with high precision, high consistency, and high stability. The six interconnected and progressive processes, from blank preparation, positioning, forming, pressure release, stretching to shaping, achieve full process control, significantly reducing the forming dimensional error of high-elongation sheet 10, significantly improving material utilization, and making it suitable for automated continuous production lines.

[0030] Furthermore, in the step of forming a raised bridge-shaped structure by stamping in a stepped stamping die at equal intervals along the width direction of the blank, the arrangement density of the raised bridge-shaped structure along the width direction of the blank is 2-5 structures per 10mm width, and each group of 20 bridge positions is equally distributed along the length direction, and the arrangement spacing is consistent with the size of the bridge body.

[0031] The density of bridge positions 20 directly determines the material flow constraint effect. When the density is below 2 positions / 10mm, there are too few support points, which cannot effectively divide the material flow field, and the middle area will still shrink excessively, making it impossible to eliminate waist-shaped defects. When the density is above 5 positions / 10mm, the bridge positions 20 are too dense, the rigidity of the sheet 10 increases, the ductility decreases, the stamping difficulty increases, and the interference between bridge positions 20 can easily cause stress superposition. Through extensive experimental verification, 2-5 positions / 10mm can achieve the optimal balance between constraint effect, forming difficulty, and sheet 10 strength, forming a continuous and uniform force network that guides synchronous shrinkage in the width direction.

[0032] Equal spacing ensures consistent stress across all sections along the length, preventing excessive or insufficient stretching due to uneven spacing. The spacing matches the bridge dimensions, ensuring equal material flow space between bridge positions 20, preventing localized material accumulation or shortages, and guaranteeing uniform stretching across the entire plate. This layout creates a regular array support system for the bridge positions 20, providing "equal-distance guidance and equal-quantity distribution" of material during stretching. This ensures highly uniform shrinkage and elongation across the width direction, structurally eliminating deformation issues such as thinner middle sections and wider ends. Simultaneously, it ensures uniform stress on the stamping die, extending die life and reducing production failure rates.

[0033] Furthermore, in the step of forming a raised bridge-like structure by stamping in an equidistant array along the width direction of the blank using a stepped stamping die, the pressure of the three stages of stepped stamping is as follows: the first stage is 0.3-0.5MPa, the second stage is 0.6-0.8MPa, and the third stage is 1.0-1.2MPa.

[0034] The first stage employs low-pressure preforming, causing initial plastic deformation in the localized areas of the sheet 10, forming the prototype of the bridge position 20. This avoids instantaneous stress overload caused by direct impact from high pressure. If the pressure is too low at this stage, plastic deformation cannot be triggered; if it is too high, localized indentations and burrs are likely to occur. 0.3-0.5 MPa can gently guide the material flow, laying a stable foundation for subsequent molding.

[0035] The second stage is the main body forming stage, where moderate pressure is applied to gradually bring the bridge body to the preset height and cross-sectional shape, ensuring structural uniformity. Insufficient pressure in this stage will result in under-forming and smaller-than-expected dimensions at bridge section 20; excessive pressure will cause stress concentration at the base of the bridge body, leading to cracks. A pressure of 0.6-0.8 MPa is sufficient for complete forming without damaging the substrate.

[0036] The third stage of high-pressure finishing ensures that the bridge's dimensions and cross-sectional shape fully meet the standards, eliminates springback, and guarantees structural stability. Insufficient pressure results in poor shaping and easy deformation during use; excessive pressure can cause the plates to penetrate and crack. 1.0-1.2MPa can achieve precise shaping, ensuring the bridge's strength and dimensional consistency.

[0037] The three-stage pressure increase, conforming to the plastic deformation law of metallic materials, avoids impact loads and ensures optimal forming quality for bridge position 20. Compared with traditional one-time stamping, this process can improve the yield rate of bridge position 20 by more than 90%, control dimensional errors within a very small range, and provide reliable structural support for subsequent uniform elongation.

[0038] Furthermore, in the structurally intersecting area of ​​bridge position 20, a laser hole processing technology is used to process the array of holes in step 40. The laser hole processing uses a pulsed fiber laser.

[0039] Traditional mechanical drilling suffers from low precision, burrs, rough hole walls, and stress concentration; ordinary CO2 lasers have a large heat-affected zone, easily causing ablation and deformation of the sheet material. Pulsed fiber lasers, on the other hand, feature high peak power, a small heat-affected zone, fine spot size, and strong controllability, making them ideal for machining holes ranging from 0.5 to 2 mm.

[0040] Pulsed lasers use high-frequency, short pulses to instantly vaporize and remove material, resulting in no cutting force, no burrs, no orifice collapse, and smooth orifice walls, avoiding stress concentration points caused by traditional processes. As stress relief units, the roundness, perpendicularity, and smoothness of the orifice directly affect the stress relief effect. Fiber lasers ensure consistent or extremely precise orifice dimensions, allowing for uniform release of localized stress during the stretching process of the sheet material 10, preventing defects such as wrinkles, ripples, and localized build-up.

[0041] Pulsed fiber lasers enable non-contact processing that does not damage the surface of the sheet 10 or the structure of the bridge position 20, making it suitable for integration with automated production lines. The processing is stable and has high repeatability, ensuring consistent hole parameters in mass production and providing uniform stress relief for each sheet 10, thus improving overall product consistency.

[0042] Further, the pretreated blank is clamped in an oblique stretching fixture, with the stretching direction forming an angle of 5°-15° with the length direction of the sheet 10. In the steps of narrowing the width and extending the length at a constant rate, the oblique stretching is performed by double-sided synchronous clamping and stretching, with a constant clamping force of 0.8-1.5MPa.

[0043] Traditional single-sided or asynchronous clamping can easily cause uneven loading and twisting of the sheet material 10, resulting in inconsistent elongation on both sides and exacerbating dimensional deviations. Double-sided synchronous clamping uses the center of the sheet material 10 as a reference, with the tension and speed on both sides being completely synchronized, ensuring that the axis of the sheet material 10 is always centered, eliminating sway and torsion from a mechanical perspective, and making the elongation uniform at all points in the width direction.

[0044] Insufficient clamping force can lead to slippage, positioning failure, and uncontrolled dimensional extension; excessive clamping force can damage the edges of the sheet material, causing stress concentration and edge cracking. Experiments have verified that a clamping force between 0.8-1.5 MPa achieves the optimal balance between clamping strength and edge protection. A constant clamping force ensures stable friction throughout the extension process, uniform material flow velocity, and avoids excessive or insufficient localized stretching due to fluctuations in clamping force.

[0045] The dual-sided synchronous and constant clamping maximizes the effect of the oblique extension fixture, allowing material to flow in a preset direction and rate. Combined with stress control of the bridge position 20 and the hole, it achieves consistent width and height across the entire width, completely eliminating waist-shaped defects, and controlling dimensional errors within ±0.1mm. Simultaneously, stable clamping reduces equipment debugging difficulty, improves automated production efficiency, and reduces scrap loss.

[0046] Furthermore, after the stretching is completed, the plate 10 is leveled at room temperature using a leveling mold to eliminate residual stress. In this step, the leveling pressure of the leveling mold is 0.5-0.7 MPa, and the leveling is performed 1-2 times.

[0047] After stretching, residual stress exists inside the sheet 10, making it prone to warping and springback if used directly. Too low a leveling pressure will not eliminate internal stress and will not achieve the desired shaping effect; too high a pressure will cause secondary plastic deformation, altering existing dimensional accuracy. A pressure of 0.5-0.7 MPa can gently release residual stress, allowing the internal stress of the sheet 10 to redistribute and reach equilibrium, while not damaging the bridge position 20 and the hole structure, ensuring that the formed dimensions remain unchanged.

[0048] A single leveling operation can eliminate most residual stress; for high-elongation, high-extension sheet material 10, two leveling operations can further stabilize dimensions and improve flatness. Too many leveling operations will increase processing time and cost, and may cause surface scratches; too few operations will result in incomplete stress elimination. One to two leveling operations achieve the optimal balance between efficiency, effectiveness, and cost, making it suitable for continuous production.

[0049] This leveling process allows the sheet metal 10 to release stress at room temperature, avoiding deformation and oxidation problems caused by high-temperature annealing. After leveling, the sheet metal 10 has stable dimensions and a smooth surface, and does not spring back, deform, or warp during storage, transportation, or subsequent processing, significantly improving product qualification rate and reliability, and meeting the requirements of high-precision components.

[0050] Furthermore, after the stretching is completed, the plate 10 is leveled at room temperature using a leveling mold to eliminate residual stress. After leveling, the flatness of the plate 10 is ≤0.05mm / m.

[0051] The flatness of ordinary molded sheet metal 10 is typically 0.2-0.5 mm / m, which cannot meet the requirements for precision applications. This application, through segmented processing and precise leveling, controls the flatness to ≤0.05 mm / m, which is considered an ultra-high precision level. This indicator is based on the requirements of precision equipment; high flatness ensures uniform assembly gaps, reliable sealing, and smooth movement. For appearance parts, it improves surface gloss and aesthetics; for functional structural parts, it ensures uniform stress distribution, strong resistance to deformation, and long service life. Insufficient flatness can lead to problems such as assembly jamming, sealing failure, uneven stress, and premature failure. This design ensures that sheet metal 10 can be used directly without additional grinding or reshaping during subsequent processing and assembly.

[0052] Furthermore, in step 30, symmetrically machining positioning through holes at both ends of the length direction and the middle of the width direction of the blank, the diameter of the positioning holes is 8-12mm.

[0053] If the diameter is too small, the locating pin will lack rigidity and easily deform under clamping force, failing to guarantee positioning accuracy. If the diameter is too large, it will occupy too much blank area, increasing material waste and potentially interfering with the subsequent machining layout of the bridge position 20 and holes. Experimental verification has shown that a hole diameter of 8-12mm balances the structural rigidity and material utilization of the locating pin, matches the locating pin size of conventional automated clamping, has strong versatility, and can stably ensure that the positioning datum does not shift throughout the entire process. Symmetrically machined locating holes can form bidirectional constraints, avoiding angular errors caused by single positioning, further improving positioning accuracy, ensuring the machining position accuracy of each process from the source, and improving the overall consistency of the product.

[0054] Furthermore, in the structurally intersecting area of ​​bridge position 20, laser hole processing technology is used to array and form holes 40. The diameter of the holes is 0.5-2mm and the spacing between the holes is 3-8mm.

[0055] Diameters less than 0.5mm are difficult to process, prone to clogging, and result in insufficient stress release; diameters greater than 2mm weaken the structural strength of the sheet material and easily cause inter-hole tearing. A diameter of 0.5-2mm can achieve a balance between stress release and structural strength, effectively dispersing local stress and avoiding wrinkles and ripples during stretching.

[0056] If the spacing is too small, the holes will be too dense, resulting in decreased strength and a tendency for cracks to appear between the holes; if the spacing is too large, stress release will be insufficient, and localized deformation will still occur. A spacing of 3-8mm forms a uniform and dense stress-relieving network that fully covers the surface of the board 10, eliminating stress dead corners, and together with the bridge position 20 structure, it achieves uniform extension throughout the entire area.

[0057] The equidistant array ensures uniform stress release, allowing the shrinkage and extension of the sheet 10 to be synchronized at every point during the stretching process, further suppressing waist-shaped defects and improving dimensional accuracy and surface quality.

[0058] Furthermore, the pretreated blank is clamped in an inclined stretching fixture and narrowed in the width direction and extended in the length direction at a constant rate. The stretching direction forms an angle of 5°-15° with the length direction of the plate 10.

[0059] When the included angle is less than 5°, the oblique effect is not obvious, and the stress field remains close to a linear distribution, failing to effectively eliminate waist-shaped defects. When the included angle is greater than 15°, the material is subjected to stress offset, easily causing dimensional deviations and excessive edge stretching. An angle of 5°-15° can optimally guide the material to flow obliquely and uniformly, breaking the stretching pattern of fast in the middle and slow at both ends, ensuring a consistent shrinkage rate across the entire width. This angle range equipment is easy to implement and its parameters are easy to adjust. It is adaptable to different materials and thicknesses of sheet metal, exhibiting strong versatility, stable production process, and high yield.

[0060] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A multi-bridge stamping and stretching forming sheet metal and its processing method, characterized in that, Includes the following steps: Select high elongation metal sheets, cut blanks to target dimensions, with the initial width of the blanks being 1.05-1.15 times the target width after forming. Clean, deburr, and anneal the surface of the blanks. Symmetrical positioning through holes are machined at both ends of the length direction and in the middle of the width direction of the blank. A stepped stamping die is used to stamp a raised bridge-shaped structure by stamping in an equidistant array along the width of the blank. In the intersecting areas of the bridge structure, laser hole processing technology is used to process holes in an array; The pre-treated billet is clamped in an inclined extending fixture and narrowed in width and extended in length at a constant rate. After stretching, the sheet material is leveled at room temperature using a leveling mold to eliminate residual stress.

2. The multi-bridge stamping and stretching forming sheet metal and its processing method according to claim 1, characterized in that, In the step of forming a raised bridge-like structure by stamping in a stepped stamping die at equal intervals along the width of the blank, the arrangement density of the raised bridge-like structure along the width of the blank is 2-5 structures per 10mm width, and each group of bridge structures is equally distributed along the length direction, with the arrangement spacing consistent with the size of the bridge body.

3. The multi-bridge stamping and stretching forming sheet metal and its processing method according to claim 1, characterized in that, In the step of forming a raised bridge-like structure by stamping in an equidistant array along the width direction of the blank using a stepped stamping die, the pressure of the three stages of stepped stamping is as follows: the first stage is 0.3-0.5MPa, the second stage is 0.6-0.8MPa, and the third stage is 1.0-1.2MPa.

4. The multi-bridge stamping and stretching forming sheet metal and its processing method according to claim 1, characterized in that, In the intersecting areas of the bridge structure, laser hole processing technology is used. In the array processing of the formed holes, pulsed fiber laser is used for laser hole processing.

5. The multi-bridge stamping and stretching forming sheet metal and its processing method according to claim 1, characterized in that, The pretreated blank is clamped in an oblique stretching fixture, with the stretching direction forming an angle of 5°-15° with the length direction of the sheet. During the narrowing in the width direction and the stretching in the length direction at a constant rate, the oblique stretching is performed by double-sided synchronous clamping and stretching, with a constant clamping force of 0.8-1.5MPa.

6. The multi-bridge stamping and stretching forming sheet metal and its processing method according to claim 1, characterized in that, After stretching, the sheet is leveled at room temperature using a leveling mold to eliminate residual stress. The leveling pressure of the leveling mold is 0.5-0.7 MPa, and the leveling is performed 1-2 times.

7. The multi-bridge stamping and stretching forming sheet metal and its processing method according to claim 6, characterized in that, After stretching, the sheet is leveled at room temperature using a leveling mold to eliminate residual stress. After leveling, the flatness of the sheet is ≤0.05mm / m.

8. The multi-bridge stamping and stretching forming sheet metal and its processing method according to claim 1, characterized in that, In the step of symmetrically machining positioning through holes at both ends of the length direction and the middle of the width direction of the blank, the diameter of the positioning holes is 8-12mm.

9. The multi-bridge stamping and stretching forming sheet metal and its processing method according to claim 1, characterized in that, In the intersecting area of ​​the bridge structure, laser hole processing technology is used to form holes in an array. The diameter of the holes is 0.5-2mm and the spacing between the holes is 3-8mm.

10. The multi-bridge stamping and stretching forming sheet metal and its processing method according to claim 1, characterized in that, The pre-treated blank is clamped in an inclined stretching fixture and narrowed in width and extended in length at a constant rate. The stretching direction is at an angle of 5°-15° to the length direction of the sheet.

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