A method and system for moore-land forming large size ultra-high strength hardened stainless steel tank parts
By characterizing the material properties of ultra-high strength hardened stainless steel raw materials and establishing an elastic-plastic model, optimizing the blank profile design, and adopting multi-stage dynamic loading and partitioned reverse correction of the mold surface, the problems of thinning rate and springback control in the forming of large-size ultra-high strength hardened stainless steel tank parts were solved, and high-precision forming of the parts was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN TIANJIN AVIATION TECH CO LTD
- Filing Date
- 2026-05-11
- Publication Date
- 2026-07-31
AI Technical Summary
In the existing process of forming large-size ultra-high strength hardened stainless steel tank parts using the Mongara process, the control of thinning rate distribution, clamping method, loading path and springback compensation are difficult to adapt to the processing strengthening requirements and the precision requirements of complex curved surface parts, which makes it difficult to achieve both performance and dimensional compliance of the formed parts at the same time.
By characterizing the material properties of various candidate ultra-high strength hardened stainless steel raw materials, an elastic-plastic material constitutive model was established, the billet profile was optimized into a bone-shaped billet, and a multi-stage dynamic loading path and partitioned reverse correction of the mold surface were adopted. Combined with mechanical interlocking clamping and special inspection fixtures, high-precision forming of parts was achieved.
Reduce processing and forming difficulty, improve molding effect and springback compensation accuracy, and achieve the unity of performance and size compliance for large-size ultra-high strength hardened stainless steel storage tank parts.
Smart Images
Figure CN122184190B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of precision plastic forming of aerospace sheet metal, specifically relating to a method and system for forming large-size ultra-high strength hardened stainless steel tank parts using the Mondler process. Background Technology
[0002] With the development of space launch vehicles, reusable spacecraft, and large cryogenic tank structures, ultra-high strength hardened stainless steel is increasingly being used to manufacture tank lobes, top covers, and hyperbolic curved surface parts. These parts not only require specified surface accuracy and welding / assembly precision after forming, but also demand that the material properties meet the usage requirements. Because ultra-high strength hardened stainless steel exhibits significant work hardening, a narrow plastic deformation window, and high springback, directly using a hardened sheet corresponding to the target performance for large-size complex curved surface forming easily leads to localized thinning cracking, insufficient mold application, and uncontrollable springback. While using a softer, harder sheet allows for work strengthening through controlling the thinning rate, enabling the formed part to achieve the target performance, existing large-size sheet forming or lamination processes typically employ rectangular blanks, conventional clamping structures, constant loading paths, and unified overall compensation methods. This makes it difficult to stably control the thinning rate distribution in complex curved surface areas, and stress concentration easily forms at the clamping front end, causing slippage during high-load forming, which in turn affects thickness distribution, mold application accuracy, hole position accuracy, and assembly accuracy.
[0003] The existing process for forming large-size ultra-high strength hardened stainless steel tank parts using the Monla process has the problem that the control of thinning rate distribution, clamping method, loading path and springback compensation are difficult to adapt to the processing strengthening requirements and the precision requirements of complex curved surface parts, resulting in the inability to simultaneously achieve the performance and dimensional requirements of the formed parts. Summary of the Invention
[0004] To address the aforementioned problems in the existing technology, namely the difficulty in simultaneously achieving performance and dimensional accuracy of the formed parts due to the incompatibility between the existing thinning rate distribution control, clamping method, loading path, and springback compensation and the requirements for processing strengthening and precision of complex curved surface parts, this invention provides a method for forming large-size ultra-high strength hardened stainless steel tank parts using the MLB process, comprising:
[0005] S1: The material properties of various candidate ultra-high strength hardened stainless steel raw materials were characterized. Uniaxial tensile tests were conducted using low-speed loading conditions that matched the deformation rate of Monrah to obtain the true stress-strain curves of each candidate raw material. Based on the true stress-strain curves of each candidate raw material, corresponding elastoplastic material constitutive models were established. S2: Based on the constitutive model of the elastic-plastic material corresponding to each candidate raw material, finite element simulation is performed to determine the thinning rate range and strengthening effect parameters of the blank profile and effective surface area of the part under the corresponding optimal working conditions for each candidate raw material. S3: Based on the target strength in the target usage requirements, the target raw material is selected from the thinning rate range and strengthening effect parameters corresponding to each candidate raw material; S4: For the target raw material, optimize the design of the blank profile so that the blank is formed into a bone-shaped blank with the width of the clamping area at both ends being greater than the width of the forming area in the middle, so as to reduce the stress concentration in the area in front of the clamping area and control the thinning rate of the effective surface area of the part within the range of the thinning rate corresponding to the target raw material, so as to make the material properties of the formed part meet the target use requirements through processing and strengthening. S5: Pre-bend both ends of the bone-shaped blank to form a U-shaped pre-bent structure, insert the metal round bar into the pre-bent structure, and clamp the bone-shaped blank into a jaw assembly with concave tooth grooves, so that the metal round bar and the concave tooth grooves mesh to form a mechanical interlock. S6: Control the Monla mold and the jaw components on both sides to execute a multi-stage dynamic loading path, so that the bone-shaped blank gradually fits the mold surface of the Monla mold to complete the forming. In the main deformation stage, the jaw components on both sides perform differentiated dynamic follow-up movements according to the curvature change of the part. S7: Perform a three-dimensional scan on the first formed part to obtain measured springback data, and perform a partitioned reverse correction on the mold surface based on the measured springback data. The compensation coefficient corresponding to the larger springback area is higher than the compensation coefficient corresponding to the smaller springback area. S8: After the forming is completed and the jaw assembly is held in a clamping state, the drilling guide structure set on the Monla mold is used to make holes in place, and after the cutting is completed, a special inspection tool is used to perform the final inspection of the part.
[0006] Specifically, in step S1, the uniaxial tensile test includes cutting tensile specimens along the rolling direction, the 45° direction, and the 90° direction, and measuring the thickness anisotropy coefficient, strain hardening index, yield strength, tensile strength, and elongation after fracture.
[0007] Specifically, in step S1, when the sheet material used for forming adopts a welded plate structure, the weld area is modeled separately when establishing the constitutive model of the elastic-plastic material and performing finite element simulation. The material properties of the weld area are set to 60%-90% of the properties of the base material.
[0008] Specifically, in step S4, the bone-shaped blank meets the following conditions: the ratio of the width of the clamping area to the width of the intermediate forming area is greater than 1.2; the clamping area and the intermediate forming area are connected by an arc transition with an arc radius of not less than 450 mm. The contour of the bone-shaped blank is determined through iterative simulation, so that the thinning rate of the effective surface area of the part is controlled within 2%-6%.
[0009] Specifically, in step S5, the pre-bending structure at both ends of the bone-shaped blank is formed by a 180° pre-bending, and the pre-bending radius is not less than 5mm, and the diameter of the metal rod is 2.0-5.0mm.
[0010] Specifically, the multi-stage dynamic loading path in step S6 includes: a pre-bending and initial bonding stage, a main deformation and encapsulation stage, and a finishing and pressure holding stage. In the pre-bending and initial bonding stage, the MLA mold is lifted at a speed of 1.0-3.0 mm / s, and the jaw assemblies on both sides are simultaneously fed inward by 10-30 mm. In the main deformation and encapsulation stage, the MLA mold is lifted at a speed of 3.0-8.0 mm / s, and the jaw assemblies on both sides perform differentiated dynamic tracking movements according to a preset displacement-time curve. In the finishing and pressure holding stage, the MLA mold is lifted at a speed of 0.1-0.5 mm / s, and the jaw assemblies on both sides maintain a set maximum process tension for 30-60 seconds. The tension of the jaw assemblies on both sides and the lifting force of the MLA mold are monitored in real time during the forming process.
[0011] Specifically, in step S7, a springback deviation distribution map is generated based on the measured springback data, and the mold surface is divided into a central area, a transition area, an edge area, and a high springback corner area. Different compensation coefficients are used for different areas, with the compensation direction opposite to the springback direction. The compensation coefficient for the central area is 1.0-1.2, the compensation coefficient for the transition area is 1.2-1.6, and the compensation coefficients for the edge area and the high springback corner area are 1.4-1.8, with the compensation coefficients for the edge area and the high springback corner area being higher than those for the central area. The curvature continuity of the mold surface after reverse correction is then checked.
[0012] In another aspect, the present invention provides a Mondella forming system for large-size ultra-high strength hardened stainless steel tank parts, for performing the above-described Mondella forming method for large-size ultra-high strength hardened stainless steel tank parts, comprising: The system includes a molding die mechanism, comprising a molding die and a drilling guide structure. The die surface is a profile corrected by partitioned reverse compensation based on the measured springback data of the first formed part. A clamping mechanism includes jaw assemblies arranged opposite each other on both sides. These jaw assemblies have concave toothed grooves adapted to the shape of the metal bar, which engage with the metal bar within the pre-bending structure of the bone-shaped blank to form a mechanical interlock. A dedicated inspection fixture includes a high-strength steel frame and a positioning reference fixing pin and a clamping mechanism mounted on the frame. The positioning reference fixing pin positions the formed part, and the clamping mechanism applies surface pressure to the welding edge area of the formed part. A process control mechanism controls the molding die mechanism and the clamping mechanism to execute a multi-stage dynamic loading path and determines the target raw material by calling the thinning rate range and strengthening effect parameters corresponding to the candidate raw materials based on the target strength.
[0013] Specifically, the Monla mold in the Monla mold mechanism is integrally cast from high-strength cast iron. The mold surface is provided with variable radius transition fillets formed according to the change of the chord length of the part's cross-section. The drilling guide structure is integrally set with the Monla mold. The process control mechanism is equipped with clamping force and lifting force monitoring units, which are used to monitor the tension of the jaw assemblies on both sides and the lifting force of the Monla mold in real time during the Monla forming process, and to store the process parameters corresponding to different candidate raw materials.
[0014] Specifically, the special inspection tool also includes a measuring reference block and a split dial indicator array. The measuring reference block is used to provide a measurement reference for part inspection, and the split dial indicator array is used to detect the curvature of the formed part.
[0015] The beneficial effects that this invention can achieve by combining the above solutions are as follows: This invention provides a method for forming large-size ultra-high strength hardened stainless steel tank parts using the Mondler process, comprising: S1: The material properties of various candidate ultra-high strength hardened stainless steel raw materials were characterized. Uniaxial tensile tests were conducted using low-speed loading conditions that matched the deformation rate of Monrah to obtain the true stress-strain curves of each candidate raw material. Based on the true stress-strain curves of each candidate raw material, corresponding elastoplastic material constitutive models were established. S2: Based on the constitutive model of the elastic-plastic material corresponding to each candidate raw material, finite element simulation is performed to determine the thinning rate range and strengthening effect parameters of the blank profile and effective surface area of the part under the corresponding optimal working conditions for each candidate raw material. S3: Based on the target strength in the target usage requirements, the target raw material is selected from the thinning rate range and strengthening effect parameters corresponding to each candidate raw material; S4: For the target raw material, optimize the design of the blank profile so that the blank is formed into a bone-shaped blank with the width of the clamping area at both ends being greater than the width of the forming area in the middle, so as to reduce the stress concentration in the area in front of the clamping area and control the thinning rate of the effective surface area of the part within the range of the thinning rate corresponding to the target raw material, so as to make the material properties of the formed part meet the target use requirements through processing and strengthening. S5: Pre-bend both ends of the bone-shaped blank to form a U-shaped pre-bent structure, insert the metal round bar into the pre-bent structure, and clamp the bone-shaped blank into a jaw assembly with concave tooth grooves, so that the metal round bar and the concave tooth grooves mesh to form a mechanical interlock. S6: Control the Monla mold and the jaw components on both sides to execute a multi-stage dynamic loading path, so that the bone-shaped blank gradually fits the mold surface of the Monla mold to complete the forming. In the main deformation stage, the jaw components on both sides perform differentiated dynamic follow-up movements according to the curvature change of the part. S7: Perform a three-dimensional scan on the first formed part to obtain measured springback data, and perform a partitioned reverse correction on the mold surface based on the measured springback data. The compensation coefficient corresponding to the larger springback area is higher than the compensation coefficient corresponding to the smaller springback area. S8: After the forming is completed and the jaw assembly is held in a clamping state, the drilling guide structure set on the Monla mold is used to make holes in place, and after the cutting is completed, a special inspection tool is used to perform the final inspection of the part.
[0016] It can be seen that, compared with the existing technology, the Monla forming method for large-size ultra-high strength hardened stainless steel tank parts establishes the constitutive model of the elastoplastic material based on the real stress-strain curve and performs finite element simulation. It reversely selects the target raw material whose original performance parameters are lower than the target performance parameters, but can reach the target performance parameters after forming and strengthening, thereby reducing the processing and forming difficulty. By optimizing the design of the blank contour to form the bone-shaped blank, the thinning rate of the effective surface area of the part is controlled and the stress concentration is reduced. Combined with the Monla mold and the jaw assembly to execute the multi-stage dynamic loading path and perform partitioned reverse correction of the mold surface, the molding effect, forming stability and springback compensation accuracy are improved, thereby achieving the unity of performance and size compliance for large-size ultra-high strength hardened stainless steel tank parts. Attached Figure Description
[0017] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 A schematic diagram illustrating the principle of the MLB forming process for the large-size ultra-high strength hardened stainless steel tank parts provided in this embodiment of the invention. Figure 2 This is a comparative diagram of traditional rectangular blanks and bone-shaped blanks; Figure 3 A comparative schematic diagram of local stress cloud diagrams for traditional rectangular billets and bone-shaped billets; Figure 4 A schematic diagram illustrating the clamping principle when a clamping mechanism clamps a bone-shaped blank. Figure 5 This is a schematic diagram of the overall structure of the Monla mold mechanism; Figure 6 Schematic diagram of the overall structure of the special inspection tool Figure 1 ; Figure 7 Schematic diagram of the overall structure of the special inspection tool Figure 2 ; Figure 8 Schematic diagram of the positioning reference fixing pin Figure 1 ; Figure 9 Schematic diagram of the positioning reference fixing pin Figure 2 ; Figure 10 This is a schematic diagram of the clamping mechanism; Figure 11 This is a schematic diagram of a split-type dial indicator array.
[0018] icon: 001. Bone-shaped blank; 002. Pre-bent structure; 100. Mold mechanism; 110. Mold; 120. Drilling guide structure; 200. Clamping mechanism; 210. Metal round bar; 220. Jaw assembly; 201. Concave toothed groove; 300. Special inspection tool; 310. High-strength steel frame; 311. Contouring support block; 320. Positioning reference fixing pin; 330. Clamping mechanism; 331. Face clamping plate; 340. Measuring reference block; 350. Split dial indicator array. Detailed Implementation
[0019] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.
[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.
[0021] This invention provides a method for forming large-size ultra-high strength hardened stainless steel tank parts using the Mondler process, comprising: S1: The material properties of various candidate ultra-high strength hardened stainless steel raw materials were characterized. Uniaxial tensile tests were conducted using low-speed loading conditions that matched the deformation rate of Monrah to obtain the true stress-strain curves of each candidate raw material. Based on the true stress-strain curves of each candidate raw material, corresponding elastoplastic material constitutive models were established. S2: Based on the constitutive model of the elastic-plastic material corresponding to each candidate raw material, finite element simulation is performed to determine the thinning rate range and strengthening effect parameters of the blank profile and effective surface area of the part under the corresponding optimal working conditions for each candidate raw material. S3: Based on the target strength in the target usage requirements, the target raw material is selected from the thinning rate range and strengthening effect parameters corresponding to each candidate raw material; S4: For the target raw material, optimize the design of the blank profile to form a bone-shaped blank 001 with the width of the clamping area at both ends being greater than the width of the forming area in the middle, so as to reduce the stress concentration in the area in front of the clamping area and control the thinning rate of the effective surface area of the part within the thinning rate range corresponding to the target raw material, so as to make the material properties of the formed part meet the target use requirements through processing and strengthening. S5: The two ends of the bone-shaped blank 001 are pre-bent to form a U-shaped pre-bent structure 002. The metal round bar 210 is inserted into the pre-bent structure 002, and the bone-shaped blank 001 is clamped in the jaw assembly 220 with concave tooth groove 201, so that the metal round bar 210 and the concave tooth groove 201 mesh to form a mechanical interlock. S6: Control the Monla mold 110 and the two side jaw components 220 to execute a multi-stage dynamic loading path, so that the bone-shaped blank 001 gradually fits the mold surface of the Monla mold 110 to complete the forming. In the main deformation stage, the two side jaw components 220 perform differentiated dynamic follow-up movements according to the curvature change of the part. S7: Perform a 3D scan on the first formed part to obtain measured springback data, and perform reverse correction on the mold surface in sections based on the measured springback data. The compensation coefficient corresponding to the larger springback area is higher than the compensation coefficient corresponding to the smaller springback area. S8: After the forming is completed and the jaw assembly 220 is held in the clamping state, the drilling guide structure 120 set on the Monla mold 110 is used to make holes in place, and after the cutting is completed, the part is finally inspected by the special inspection tool 300.
[0022] In summary, the Mondlar forming method for large-size ultra-high strength hardened stainless steel tank parts provided by this invention can achieve the following technical effects: The Monla forming method for this large-size ultra-high strength hardened stainless steel tank part is based on establishing an elastoplastic material constitutive model and performing finite element simulation based on the real stress-strain curve. It reversely selects the target raw material whose original performance parameters are lower than the target performance parameters, but can reach the target performance parameters after forming and strengthening, thereby reducing the difficulty of processing and forming. By optimizing the design of the blank contour to form a bone-shaped blank 001, the thinning rate of the effective surface area of the part is controlled and the stress concentration is reduced. Combined with the Monla mold 110 and the jaw assembly 220, a multi-stage dynamic loading path is executed and the mold surface is partitioned and reversed to improve the mold application effect, forming stability and springback compensation accuracy, thereby achieving the unity of performance and size compliance of the large-size ultra-high strength hardened stainless steel tank part.
[0023] To more clearly explain the Mondler forming method for large-size ultra-high strength hardened stainless steel tank parts of the present invention, the following describes the method in conjunction with... Figures 1 to 11 The steps of the Mondler forming method for large-size ultra-high strength hardened stainless steel tank parts provided in the embodiments of the present invention are described in detail.
[0024] The first embodiment of the present invention provides a method for forming large-size ultra-high strength hardened stainless steel tank parts using the Monel process, comprising: S1: Characterization of candidate raw material properties and establishment of constitutive model Material properties were characterized for several ultra-high strength hardened stainless steel raw materials to be selected. Candidate materials may include plates of different steel grades and hardening states, such as S30110-1 / 2H, S30110-1 / 4H, 12Cr17Ni7-1 / 2H, 12Cr17Ni7-1 / 4H, 06Cr19Ni10-1 / 2H, and 06Cr19Ni10-1 / 4H. Standard tensile specimens were cut from each candidate raw material along the rolling direction, 45° direction, and 90° direction, and uniaxial tensile tests were performed on an electronic universal testing machine. The uniaxial tensile tests employed low-speed loading conditions matching the subsequent tensile deformation rate to obtain true stress-strain curves that accurately reflect the low-speed plastic deformation characteristics of the material. Preferably, the loading rate before yielding was 0.5 mm / min to 1.0 mm / min, and the loading rate after yielding was 5 mm / min to 10 mm / min.
[0025] Based on the experimental results, parameters such as the thickness anisotropy coefficient r, strain hardening exponent n, yield strength Rp0.2, tensile strength Rm, and elongation after fracture A of each candidate raw material were obtained. Corresponding elastoplastic material constitutive models were then established in finite element analysis software for subsequent forming simulation, thinning prediction, strengthening effect evaluation, and springback analysis. For welded plate structures, the weld area can be modeled separately, and the material parameters of the weld and heat-affected zone can be set to 60%–90% of the base material parameters to characterize the performance degradation characteristics of the welded area.
[0026] S2: Finite element simulation analysis based on candidate materials An initial blank model is established based on the 3D digital model of the part, and the elastoplastic material constitutive models corresponding to each candidate raw material established in step S1 are imported to form multiple sets of Monaco forming simulation conditions. The stress distribution, strain distribution, thinning distribution, molding state, and strengthening effect of different candidate raw materials under different loading paths and blank profiles are analyzed through finite element simulation. Through simulation, the blank profile, thinning rate range of the effective surface area of the part, and strengthening effect parameters of each candidate raw material under the corresponding optimal working condition are determined. The strengthening effect parameters can be characterized by the increase in yield strength after forming, the increase in tensile strength, or the margin required to reach the target strength after forming strengthening.
[0027] For material systems that achieve final performance matching through deformation strengthening, a reasonable thinning rate range for the effective surface region can be preset based on simulation results and material strengthening principles. For example, for S30110-1 / 2H, 12Cr17Ni7-1 / 2H, and 06Cr19Ni10-1 / 2H materials, the effective surface region thinning rate is preferably controlled between 3% and 6%; for 06Cr19Ni10-1 / 4H and 12Cr17Ni7-1 / 4H materials, the effective surface region thinning rate is preferably controlled between 5% and 6%.
[0028] S3: Select target raw materials in reverse order based on target usage requirements. Based on the target strength in the intended use requirements, the target raw material is determined by reverse selection from the thinning rate range and strengthening effect parameters corresponding to each candidate raw material obtained in step S2. In other words, instead of prioritizing high-strength materials whose initial strength already meets the target use requirements, materials with initial performance parameters lower than the target performance parameters, but which can reach the target strength requirements after being strengthened by Montella forming under controllable thinning conditions, are prioritized. This approach utilizes the work hardening effect during forming to improve performance while reducing the difficulty of material forming and the risk of cracking.
[0029] In one application, for a large-sized tank segment part of a certain model, the target strength requirement is higher than that of conventional annealed austenitic stainless steel sheet, but lower than the initial strength of some highly hardened sheets. After material testing and simulation analysis, 1 / 2H or 1 / 4H hardened stainless steel was selected as the target raw material from multiple candidate materials. After achieving the preset thinning rate in the effective profile area, the performance of the formed part meets the target usage requirements.
[0030] S4: Optimization design of bone-shaped blank for target raw materials (001) For the target raw material determined in step S3, the blank profile is optimized. First, a preliminary unfolding is performed based on the three-dimensional digital model of the part to form an initial blank model that is rectangular or approximately rectangular. Then, simulation iteration is performed in conjunction with the constitutive model of the target raw material and the target thinning rate range to correct the initial blank, ultimately forming a bone-shaped blank 001 with the width of the clamping areas at both ends greater than the width of the forming area in the middle. The function of the bone-shaped blank 001 is to make the change of the load-bearing cross section in the stretching direction smoother, reduce the stress concentration in the dangerous area in front of the jaw assembly 220, and keep the thinning rate of the effective surface area of the part stably controlled within the thinning rate range corresponding to the target raw material, so that the formed part can achieve the required processing strengthening effect while satisfying the formability requirement. Preferably, the bone-shaped blank 001 meets the following structural conditions: the ratio of the width of the clamping areas on both sides to the width of the forming area in the middle is greater than 1.2; the clamping areas and the middle forming area are connected by a circular arc transition; the radius of the circular arc transition is not less than 450mm.
[0031] In one application, for a 1 / 16-inch segment of a 4500mm diameter storage tank, 1.8mm thick S30110-1 / 2H hardened stainless steel sheet was used. Initial simulation results of the rectangular billet showed that the maximum local thinning rate in the area in front of the jaw assembly 220 reached 15%, posing a significant risk of cracking. After optimizing the billet into a bone-shaped billet 001, the maximum thinning rate decreased to 6.5%, the stress peak in the critical area significantly decreased, and the stress and thinning distribution were improved.
[0032] S5: Pretreatment and mechanical interlocking of bone-shaped billet 001 Cut the blank according to the contour of the bone-shaped billet 001 determined in step S4. Laser cutting is preferred, and the cut edges are deburred. Pre-bend the clamping areas at both ends of the bone-shaped billet 001 to form a U-shaped pre-bent structure 002. To reduce the risk of microcracks in the bending area of the high-strength hardened stainless steel, the bending radius of the pre-bent structure 002 is preferably not less than 5mm.
[0033] A metal rod 210 is inserted into the pre-bent structure 002. The diameter of the metal rod 210 is preferably 2.0 mm to 5.0 mm. Then, a bone-shaped blank 001 containing the metal rod 210 is clamped in the jaw assembly 220. The jaw assembly 220 is provided with concave toothed grooves 201 that match the metal rod 210. The engagement of the metal rod 210 with the concave toothed grooves 201 forms a mechanical interlocking structure, thereby improving clamping reliability and suppressing axial slippage during the forming process. Compared to simply relying on friction clamping, this mechanical interlocking method is more suitable for the forming of large-size, high-load, and low-plasticity-reserve hardened stainless steel sheets.
[0034] S6: Multi-stage dynamic loading molding The pre-treated bone-shaped blank 001 is inserted between the MLM mold mechanism 100 and the clamping mechanism 200, so that the clamping end of the embedded metal rod 210 enters the jaw assembly 220, ensuring stable engagement between the metal rod 210 and the concave toothed groove 201. Preferably, a transparent polyethylene protective film is applied to the mold surface of the MLM mold 110 and the pressing edge area in contact with the bone-shaped blank 001, and a lubricant is sprayed on its surface to reduce forming friction and protect the surface of the part. The thickness of the protective film is preferably 0.03 mm to 0.08 mm.
[0035] The process control mechanism controls the Monla mold 110 and the two side jaw assemblies 220 to execute a multi-stage dynamic loading path, so that the bone-shaped blank 001 gradually fits the mold surface of the Monla mold 110 to complete the forming.
[0036] During the pre-bending and initial bonding stage, the Mongla mold 110 is lifted at a relatively low speed, preferably 1.0 mm / s to 3.0 mm / s; the jaw assemblies 220 on both sides close under a small clamping force and can simultaneously perform a small stroke of inward feeding to provide initial tension and eliminate initial slack in the sheet metal. During the main deformation stage, the Mongla mold 110 continues to lift, preferably at a lifting speed of 3.0 mm / s to 8.0 mm / s; the jaw assemblies 220 on both sides perform differentiated dynamic following movements according to the curvature changes of the part to improve the uniformity of strain distribution in the length direction of the sheet metal. For parts with large curvature changes, the following displacement of the jaw assembly 220 corresponding to the larger end can be greater than that of the jaw assembly 220 corresponding to the smaller end. During the finishing and holding pressure stages, once the sheet metal is basically aligned with the mold surface of the MnLa mold 110, the MnLa mold 110 continues to lift at a low speed, preferably 0.1 mm / s to 0.5 mm / s. The jaw assembly 220 maintains the set maximum process tension and holds pressure for 30 to 60 seconds to improve the degree of mold alignment and reduce springback after unloading. During the forming process, the tension of the jaw assemblies 220 on both sides and the lifting force of the MnLa mold 110 can be monitored in real time, and the measured force-stroke curve can be compared with the simulation prediction curve to determine whether the forming process is stable and to control the maximum forming force within the safety capacity range of the equipment and mold.
[0037] In one application, for a 1 / 16-inch melon-shaped part of a storage tank with a diameter of 4500mm, during the pre-bending and initial bonding stage, the Mongla mold 110 is lifted 350mm at a speed of 2.2mm / s; during the main deformation stage, the Mongla mold 110 continues to lift 580mm at a speed of 4.2mm / s, the jaw assembly 220 corresponding to the large end follows with 300mm at 2.8mm / s, and the jaw assembly 220 corresponding to the small end follows with 100mm at 0.92mm / s, with the maximum process tension set at 220T.
[0038] In another application, for the segmented top cover of a 10600mm diameter storage tank, due to the narrow plastic deformation window of the material, the lifting speed during the main deformation stage can be reduced to 0.1mm / s to mitigate strain concentration.
[0039] S7: Partitioned Reverse Springback Correction Based on First-Article Scan After the first formed part is unloaded, a 3D scan is performed to obtain the actual point cloud data of the part in its free state. The point cloud data is compared with the theoretical digital model to form a springback deviation distribution map, and the spatial distribution pattern of springback in different areas is identified accordingly. Based on the measured springback data, the mold surface of the Monla mold 110 is subjected to zoned reverse correction. Preferably, the mold surface is divided into a central area, a transition area, an edge area, and a high springback corner area. Different compensation coefficients K are set for different areas, and the compensation direction is opposite to the actual springback direction. The compensation coefficient K is the ratio of the mold repair amount to the measured springback amount, that is: K = mold repair amount / measured springback amount.
[0040] For ultra-high strength hardened stainless steel tank parts, a zoned differential compensation method is preferred. The compensation coefficient is preferably 1.0–1.2 for the central area due to its smaller springback; 1.2–1.6 for the transition area; and 1.4–1.8, and more preferably 1.6–1.8, for the edge area and high-springback corner area due to their more pronounced springback. In other words, the compensation coefficient for areas with greater springback is higher than that for areas with smaller springback.
[0041] During the mold repair process, the curvature continuity of the corrected mold surface can be checked to ensure that the mold surface is smooth and continuous without local reverse curvature. The compensated Monla mold 110 is then used for trial production, and further corrections are made based on the trial production results. Typically, after one to two rounds of "forming-scanning-compensation" iterations, a mold surface that meets the accuracy requirements can be obtained.
[0042] In one application, for a 1 / 16-inch melon-shaped part of a storage tank with a diameter of 4500mm, the maximum springback in the two edge areas is 3.1mm, the edge area compensation coefficient is 1.65, and the center area compensation coefficient is 1.0.
[0043] In another application, for the top cover segment of a storage tank with a diameter of 10600mm, if the measured rebound amount is 12mm, the compensation amount can be set to 19mm, corresponding to a compensation coefficient of 1.583.
[0044] S8: In-situ hole making, cutting and final inspection After forming is completed and the jaw assembly 220 remains in the clamping state, the part is drilled in place using the drilling guide structure 120 provided on the Mona mold 110 to ensure the relative positional accuracy between the positioning hole and the forming surface. After the in-place drilling is completed, the jaw assembly 220 is released, the part is removed, and the process allowance is removed by means of laser cutting or five-axis CNC machining to form the final shape of the part. The part is then placed in a special inspection fixture 300 for final inspection.
[0045] A special inspection fixture 300 is used to simulate the welded assembly state of the parts, and a clamping mechanism 330 is used to clamp the welded edge area to reduce secondary deformation introduced by the inspection. Preferably, a contour support block 311 is provided on the high-strength steel frame 310, and the clamping mechanism 330 includes a 12137 type vertical quick clamp and a face clamping plate 331 provided at its clamping end. The face clamping plate 331 cooperates with the contour support block 311 to achieve face contact clamping inspection on both sides of the welded area of the part, i.e., the edge, effectively suppressing secondary deformation caused by local point loads during the inspection process. The inspection content includes at least the following: welded edge contour inspection, which is evaluated by measuring the gap between the outer edge of the part and the measuring reference block 340 using a feeler gauge or gap gauge; and surface conformity inspection, which is obtained by arranging a split dial indicator array 350 in the key area or by using a non-contact scanning method to obtain the deviation data between the part surface and the theoretical digital model. The accuracy of positioning holes is tested using go / no-go gauges or specialized hole position testing fixtures to verify the diameter and spatial position accuracy of the positioning holes. This testing method, combined with the face-clamping structure of the specialized gauge 300, can accurately reflect the geometric conformity of parts in their assembled state, improving the accuracy and engineering applicability of the test results.
[0046] In one application, for a 1 / 16-inch segment of a storage tank with a diameter of 4500mm, the test results showed that the maximum gap of the weld edge was 0.4mm, which meets the requirement that the surface profile within 40mm of the weld edge should not exceed 0.5mm.
[0047] The second embodiment of the present invention provides a Monel forming system for large-size ultra-high strength hardened stainless steel tank parts, used to perform the above-described Monel forming method for large-size ultra-high strength hardened stainless steel tank parts, comprising: The system includes a drawing die mechanism 100, a clamping mechanism 200, a special inspection fixture 300, and a process control mechanism. The drawing die mechanism 100 comprises a drawing die 110 and a drilling guide structure 120. The drawing die 110 provides support for the target profile during the drawing process, and the drilling guide structure 120 performs in-situ drilling while the part is held in a clamped state. In some embodiments, the drawing die 110 is integrally cast from high-strength cast iron to improve overall rigidity and reduce the risk of elastic deformation under ultra-high forming loads. In other embodiments, the local transition regions of the drawing die 110 employ a variable curvature or variable radius transition design to improve the uniformity of material flow during the drawing process for hyperbolic parts.
[0048] The clamping mechanism 200 is disposed on both sides of the molding mechanism 100 and is used to clamp both ends of the bone-shaped blank 001. The clamping mechanism 200 includes jaw assemblies 220 disposed on both sides opposite each other. The jaw assemblies 220 are provided with concave toothed grooves 201 that match the metal round bar 210, so as to form a mechanically interlocked clamping structure after the metal round bar 210 is inserted into the pre-bent structure 002. In some embodiments, the clamping mechanism 200 also includes a clamping status monitoring unit for real-time acquisition of clamping force or hydraulic pressure data of the jaw assemblies 220 and feeding the data back to the process control mechanism.
[0049] A special inspection fixture 300 is used to simulate the assembly state of the formed parts. The special inspection fixture 300 includes a high-strength steel frame 310, a positioning reference fixing pin 320, a clamping mechanism 330, a measuring reference block 340, and a split dial indicator array 350. The positioning reference fixing pin 320 is used to position the parts, the clamping mechanism 330 is used to clamp the welded edge area of the parts, the measuring reference block 340 is used to provide a detection reference, and the split dial indicator array 350 is used to detect the curvature and surface deviation of the parts. In some embodiments, a contour support block 311 is provided on the high-strength steel frame 310, and the clamping mechanism 330 includes a 12137 type vertical quick clamp and a face clamping plate 331 disposed at its clamping end. The contour support block 311 and the face clamping plate 331 are disposed opposite each other on both sides of the welded area of the parts, and the two cooperate to perform face clamping on both sides of the welded area, i.e., the edge, to simulate the welded assembly state of the parts. The support surface of the contour support block 311 is adapted to the shape of the corresponding area of the part. The surface clamping plate 331 moves towards the contour support block 311 under the drive of the 12137 type vertical quick clamp to press the welding area of the part onto the contour support block 311. Compared to point clamping, the surface contact clamping method formed by the cooperation of the surface clamping plate 331 and the contour support block 311 can reduce the additional deformation introduced by localized force concentration during the inspection process, thereby improving the accuracy and repeatability of the weld edge contour and surface conformity inspection results. In some embodiments, the surface clamping plate 331 can be configured as a strip structure extending along the welding edge area of the part, or as multiple segmented clamping units spaced apart along the welding edge direction; the contour support block 311 can be configured as a replaceable structure according to the curvature characteristics of the welding edge area of the part.
[0050] The process control mechanism is connected to the molding die mechanism 100 and the clamping mechanism 200 to control the molding die 110 and the jaw assembly 220 to execute a multi-stage dynamic loading path and to monitor the lifting force, clamping force, and displacement parameters in real time. In some embodiments, the process control mechanism is connected to a simulation analysis module to perform forming analysis of clamping, pre-bending, dynamic stretching, and unloading springback based on the material constitutive model, and outputs thinning, fracture risk, and springback trend. In other embodiments, the process control mechanism is connected to a process parameter database to store material performance data, loading trajectory parameters, springback compensation parameters, and historical process cases to support the process design, raw material selection, and risk assessment of new parts.
[0051] The terms “first”, “second”, etc., are used to distinguish similar objects, not to describe or indicate a specific order or sequence.
[0052] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.
[0053] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.
Claims
1. A method for forming large-size ultra-high strength hardened stainless steel tank parts using the Mondler molding technique, characterized in that... include: S1: The material properties of various candidate ultra-high strength hardened stainless steel raw materials were characterized. Uniaxial tensile tests were conducted using low-speed loading conditions that matched the deformation rate of Monrah to obtain the true stress-strain curves of each candidate raw material. Based on the true stress-strain curves of each candidate raw material, corresponding elastoplastic material constitutive models were established. S2: Based on the constitutive model of the elastic-plastic material corresponding to each candidate raw material, finite element simulation is performed to determine the thinning rate range and strengthening effect parameters of the blank profile and effective surface area of the part under the corresponding optimal working conditions for each candidate raw material. S3: Based on the target strength in the target usage requirements, the target raw material is selected from the thinning rate range and strengthening effect parameters corresponding to each candidate raw material; S4: For the target raw material, the blank contour is optimized to form a bone-shaped blank (001) with the width of the clamping area at both ends being greater than the width of the forming area in the middle, so as to reduce the stress concentration in the area in front of the clamping area and control the thinning rate of the effective surface area of the part within the range of the thinning rate corresponding to the target raw material, so as to make the material properties of the formed part meet the target use requirements through processing and strengthening. S5: The two ends of the bone-shaped blank (001) are pre-bent to form a U-shaped pre-bent structure (002), a metal round bar (210) is inserted into the pre-bent structure (002), and the bone-shaped blank (001) is clamped in a jaw assembly (220) with a concave tooth groove (201), so that the metal round bar (210) and the concave tooth groove (201) mesh to form a mechanical interlock; S6: Control the Monla mold (110) and the jaw assembly (220) on both sides to execute a multi-stage dynamic loading path, so that the bone-shaped blank (001) gradually fits the mold surface of the Monla mold (110) to complete the forming. In the main deformation stage, the jaw assembly (220) on both sides performs differentiated dynamic follow-up movement according to the curvature change of the part. S7: Perform a three-dimensional scan on the first formed part to obtain measured springback data, and perform a partitioned reverse correction on the mold surface based on the measured springback data. The compensation coefficient corresponding to the larger springback area is higher than the compensation coefficient corresponding to the smaller springback area. S8: After the forming is completed and the jaw assembly (220) is held in a clamping state, the drilling guide structure (120) provided on the Monla mold (110) is used to make holes in place, and after the cutting is completed, the part is finally inspected by a special inspection tool (300).
2. The method for forming large-size ultra-high strength hardened stainless steel tank parts according to claim 1, characterized in that: In step S1, the uniaxial tensile test includes cutting tensile specimens along the rolling direction, the 45° direction, and the 90° direction, and measuring the thickness anisotropy coefficient, strain hardening index, yield strength, tensile strength, and elongation after fracture.
3. The method for forming large-size ultra-high strength hardened stainless steel tank parts according to claim 1, characterized in that: In step S1, when the sheet material used for forming adopts a welded plate structure, the weld area is modeled separately when establishing the constitutive model of the elastic-plastic material and performing finite element simulation. The material properties of the weld area are set to 60%-90% of the properties of the base material.
4. The method for forming large-size ultra-high strength hardened stainless steel tank parts according to claim 1, characterized in that: In step S4, the bone-shaped blank (001) satisfies the following conditions: the ratio of the width of the clamping area to the width of the intermediate forming area is greater than 1.2, and the clamping area and the intermediate forming area are connected by an arc transition with an arc radius of not less than 450mm; The contour of the bone-shaped blank (001) is determined by iterative simulation, so that the thinning rate of the effective surface area of the part is controlled at 2%-6%.
5. The method for forming large-size ultra-high strength hardened stainless steel tank parts according to claim 1, characterized in that: In step S5, the pre-bending structures (002) at both ends of the bone-shaped blank (001) are formed by 180° pre-bending, and the pre-bending radius is not less than 5mm. The diameter of the metal round bar (210) is 2.0-5.0mm.
6. The method for forming large-size ultra-high strength hardened stainless steel tank parts according to claim 1, characterized in that: The multi-stage dynamic loading path in step S6 includes: pre-bending and initial bonding stage, main deformation and covering stage, and finishing and pressure holding stage; During the pre-bending and initial bonding stage, the Monla mold (110) is lifted at a speed of 1.0-3.0 mm / s, and the jaw assemblies (220) on both sides are simultaneously fed inward by 10-30 mm; During the main deformation and covering stage, the Monla mold (110) is lifted at a speed of 3.0-8.0 mm / s, and the jaw assemblies (220) on both sides perform differentiated dynamic follow-up movements according to the preset displacement-time curve; During the finishing and holding pressure stage, the Monla mold (110) is lifted at a speed of 0.1-0.5 mm / s, and the jaw assemblies (220) on both sides are kept at the set maximum process tension for 30-60 seconds; During the forming process, the tension of the jaw assembly (220) on both sides and the lifting force of the Mong La mold (110) are monitored in real time.
7. The method for forming large-size ultra-high strength hardened stainless steel tank parts according to claim 1, characterized in that: In step S7, a springback deviation distribution map is generated based on the measured springback data, and the mold surface is divided into a central area, a transition area, an edge area, and a high springback corner area. Different compensation coefficients are used in different areas, and the compensation direction is opposite to the rebound direction. The compensation coefficient of the central area is 1.0-1.2, the compensation coefficient of the transition area is 1.2-1.6, and the compensation coefficient of the edge area and the high rebound corner area is 1.4-1.
8. The compensation coefficient of the edge area and the high rebound corner area is higher than that of the central area. The curvature continuity of the mold surface after reverse correction is checked.
8. A Mondra forming system for large-size ultra-high strength hardened stainless steel tank parts, characterized in that, A method for performing the Mondler forming of large-size ultra-high strength hardened stainless steel tank parts as described in any one of claims 1 to 7, comprising: The MnLa mold mechanism (100) is provided with a MnLa mold (110) and a drilling guide structure (120). The mold surface of the MnLa mold (110) is the surface after partitioned reverse compensation correction based on the measured springback data of the first formed part. The clamping mechanism (200) includes jaw assemblies (220) arranged opposite to each other on both sides. The jaw assemblies (220) are provided with concave tooth grooves (201) that are adapted to the shape of the metal rod (210). The concave tooth grooves (201) are used to engage with the metal rod (210) in the pre-bent structure (002) of the bone-shaped blank (001) to form a mechanical interlock. A special inspection tool (300) includes a high-strength steel frame (310) and a positioning reference fixing pin (320) and a clamping mechanism (330) mounted on the high-strength steel frame (310). The positioning reference fixing pin (320) is used to position the formed part, and the clamping mechanism (330) is used to apply surface pressure to the welding edge area of the formed part. The process control mechanism is used to control the Mong La mold mechanism (100) and the clamping mechanism (200) to execute a multi-stage dynamic loading path, and to call the thinning rate range and strengthening effect parameters corresponding to the candidate raw materials according to the target strength to determine the target raw materials.
9. The Mondler forming system for large-size ultra-high strength hardened stainless steel tank parts according to claim 8, characterized in that: The Monla mold (110) in the Monla mold mechanism (100) is integrally cast from high-strength cast iron. The mold surface is provided with a variable radius transition fillet formed according to the change of the chord length of the part section. The drilling guide structure (120) is integrally set with the Monla mold (110). The process control mechanism is equipped with a clamping force and lifting force monitoring unit, which is used to monitor the tension of the jaw assembly (220) on both sides and the lifting force of the mold (110) in real time during the molding process, and to store the process parameters corresponding to different candidate raw materials.
10. The Mondler forming system for large-size ultra-high strength hardened stainless steel tank parts according to claim 8, characterized in that: The special inspection tool (300) also includes a measuring reference block (340) and a split dial indicator array (350). The measuring reference block (340) is used to provide a measurement reference for part inspection, and the split dial indicator array (350) is used to detect the curvature of the formed part.