A hot forging process for 7-series aluminum sheet product with thick-thin gap structure

Abstract

The application discloses a hot forging process for a 7-series aluminum thin material product with a thick-thin gap structure. The application introduces a new process path of "pre-fabricated compensation deformation and partition collaborative control", effectively solves the problem of shear stress concentration and cracking at the junction caused by the mismatch of deformation capacity of the thick-thin area of the aluminum thin material in the background technology, and provides a systematic solution for the limit thin-wall forging of the 7-series aluminum. The stability of the extreme thin-wall structure in the forming and phase change process is ensured, so that the 7-series aluminum can be reliably forged to about 0.5mm thickness without cracking.

Description

Technical Field

[0001] This invention relates to the field of hot forging technology, specifically a hot forging process for 7-series aluminum sheet products with thickness difference structure. Background Technology

[0002] In the field of lightweight manufacturing, hot forging of aluminum alloy sheets (aluminum sheet metal) to form parts with varying thicknesses is an important way to achieve high performance and lightweight in complex components. Such parts are commonly found in structural components of electronic products such as watches and mobile phones. However, this process has long faced a prominent technical challenge: due to significant thickness differences between different areas of the part, the metal flow velocity and deformation resistance differ greatly between the thicker and thinner areas during hot forging, leading to severe shear stress concentration at the thickness transition points. This stress concentration easily triggers micro or macro cracks, severely impairing the structural rigidity and fatigue life of the part, resulting in low yield.

[0003] Traditional solutions mainly focus on optimizing overall forging parameters (such as temperature and speed) or improving die surface design. However, these methods are essentially passive adjustments to homogeneous billets, which are difficult to fundamentally meet the different deformation requirements between thick and thin regions. Stress and micro-cracks are still likely to exist at the thick-thin interface.

[0004] Therefore, the industry urgently needs a new process concept that can compensate for this deformation difference during forging and achieve precise force matching during forming, thereby eliminating the risk of cracking at the thickness-thin interface. Summary of the Invention

[0005] To overcome the shortcomings mentioned above, this invention aims to provide a technical solution for hot forging processes of 7-series aluminum sheet products with thickness variations that can solve the aforementioned problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A hot forging process for 7-series aluminum sheet products with thickness variations includes the following steps:

[0008] S100, billet pretreatment and differential coating application: After cleaning the surface of the aluminum alloy sheet billet, apply a high thermal conductivity lubricating coating to the surface area corresponding to the product thickness area, and apply a heat insulation and energy absorption coating to the surface area corresponding to the product thin area and the thickness-thin junction area.

[0009] S200, Local Pre-fabricated Compensation Deformation: Based on the product digital model, low-power pulsed laser shock technology is used to perform micro-deformation treatment on the area corresponding to the thin area of ​​the product on the aluminum alloy sheet blank, forming a micro-bulging structure.

[0010] S300, gradient energy field heating: The aluminum alloy sheet blank is placed in a zoned temperature-controlled induction heating device. The thick area of ​​the product is heated to the first target temperature T1, and the thin area and the thick-thin junction area of ​​the product are heated to the second target temperature T2, which is lower than T1. During the heating process, a directional magnetic field is applied to the thin area and the thick-thin junction area of ​​the product to induce grain pre-orientation.

[0011] S400, Multi-head Partition Forging: The heated aluminum alloy sheet blank is placed into a partition forging mold with multiple independent and controllable pressure head units. The pressure head unit corresponding to the product's thick area is controlled to operate according to a first pressure-speed program, the pressure head unit corresponding to the product's thin area is controlled to operate according to a second pressure-speed program, and the pressure head unit corresponding to the thickness-thin junction area is controlled to operate according to a third pressure-speed program. The third pressure-speed program is a non-linear variation program. The first, second, and third pressure-speed programs are respectively completed by the central controller in coordination to complete the forging process.

[0012] S500, In-situ Pressure Holding and Gradient Cooling: After forging, pressure holding is carried out in the mold in sections. At the same time, low temperature medium is introduced into the cooling channel of the thick part of the product in the mold, and high temperature medium is introduced into the cooling channel of the thin part of the product and the junction of thick and thin parts to implement gradient cooling.

[0013] S600, Post-processing: Open the mold and remove the part, trim the edges, correct and remove the surface coating to obtain the finished product.

[0014] As a further aspect of the present invention: step S100 specifically includes:

[0015] S101. Surface cleaning and activation: The aluminum alloy sheet blank is ultrasonically degreased using an alkaline cleaning solution, and then surface activated using an acidic solution to obtain a clean blank substrate with high surface activity.

[0016] S102. Coating material preparation: Prepare a high thermal conductivity solid lubricating coating material and a heat insulation and energy absorption coating material; wherein, the high thermal conductivity solid lubricating coating material is a composite ceramic slurry containing graphene and boron nitride; the heat insulation and energy absorption coating material is a microporous composite slurry with silica aerogel and elastic polymer as the matrix;

[0017] S103, Partition Masking and Precise Application: Based on the product's 3D model data, create a rigid mask plate that corresponds to the shape of the product's thick area on the surface of the aluminum alloy sheet blank.

[0018] A rigid mask is placed over the surface of the aluminum alloy sheet blank to expose the thin area and the thick-thin interface area of ​​the product; the heat-insulating and energy-absorbing coating material is uniformly applied to the exposed area using a plasma spraying process to form a heat-insulating and energy-absorbing coating, thus forming the first coating area.

[0019] After removing the mask and applying a second mask to expose the thick area of ​​the product, a physical vapor deposition process is used to deposit the high thermal conductivity solid lubricating coating material on the surface of the thick area of ​​the product to form a high thermal conductivity lubricating coating, thus forming the second coating area.

[0020] S104. Coating curing and thickness control: The aluminum alloy sheet blank after coating is subjected to step heating curing treatment. The thickness of the first coating area after curing is controlled between 20 micrometers and 100 micrometers, and the thickness of the second coating area after curing is controlled between 5 micrometers and 30 micrometers. A smooth thickness transition zone is formed at the junction of the first and second coating areas.

[0021] As a further aspect of the present invention: step S200 specifically includes:

[0022] S201. Digital Modeling and Compensation Calculation: Based on the final three-dimensional model of the product, the metal flow law during the hot forging process is analyzed through finite element simulation to determine the equivalent volume that needs to be compensated in the thin area and the thickness-thin interface area of ​​the product; and a three-dimensional data model of the compensation structure is calculated and generated to guide the pre-deformation.

[0023] S202, Laser Selective Impact Pre-deformation: A pulsed fiber laser system equipped with a dynamic focusing lens is used to scan and process the corresponding thin product area on the aluminum alloy sheet blank according to the three-dimensional data model of the compensation structure.

[0024] Lasers, with their low energy density, short pulse width, and high frequency, non-ablatively impact thin areas of products, inducing microscopic plastic flow and grain refinement in the surface material, thereby forming localized, precise micro-arched bulge structures.

[0025] S203. Structural parameter control: The height of the micro-arched bulge structure is controlled between 15% and 40% of the initial thickness of the aluminum alloy sheet blank. The distribution density of the micro-arched bulge structure is adaptively adjusted according to the equivalent strain gradient obtained from the finite element simulation, and the distribution is more dense in the area with a large strain gradient. The micro-arched bulge structure exhibits a gradually decreasing distribution in the thickness-thin junction area.

[0026] S204. Pre-deformation inspection and calibration: A three-dimensional optical scanner is used to collect the morphology of the pre-deformed aluminum alloy sheet blank. The actual data is compared with the three-dimensional data model of the compensation structure. If the deviation of the micro-arched bulge structure in a local area exceeds the set threshold, step S202 is performed in that area for calibration.

[0027] As a further aspect of the present invention: step S300 specifically includes:

[0028] S301. Blank Surface Condition Confirmation and Loading: Before the aluminum alloy sheet blank that has completed step S200 is transported to the heating station, confirm that the differential coating on the surface of the aluminum alloy sheet blank is intact and free from peeling.

[0029] The aluminum alloy sheet blank is precisely placed above the coil array of the zoned temperature control induction heating device, ensuring that the thick area, thin area and junction area of ​​the aluminum alloy sheet blank are aligned with the corresponding independent heating coil unit below.

[0030] S302, Rapid heating of the thick area of ​​the product: Start the first set of medium frequency induction heating coils corresponding to the thick area of ​​the product, set the frequency to 1-10 kHz, and rapidly heat the entire thick area of ​​the product to the first target temperature T1 within 10-30 seconds. The range of T1 is 40-80℃ below the solidus temperature of the aluminum alloy material.

[0031] S303, Slow Heating and Grain Control of Thin and Thick Areas of the Product: Synchronous with or slightly delayed from step S302, the second set of low-frequency induction heating coils corresponding to the thin and thick areas of the product are started, with a frequency set to 50-500 Hz, and the area is heated to the second target temperature T2 within 40-80 seconds with a low power density, where T2 is 30-120℃ lower than T1; while the second set of low-frequency induction heating coils are working, a steady-state directional magnetic field with a direction at an angle of 15-45 degrees to the subsequent forging main deformation direction is applied to the thin and thick areas of the product, with a magnetic field strength of 0.5-3 Tesla, to induce the grains in the area to align in a predetermined direction along the magnetic field direction;

[0032] S304. Temperature field balance and uniform heating: After all areas reach their respective target temperatures, adjust the coil power to enter the heat preservation and uniform heating stage, which lasts for 5-15 seconds, in order to balance the transverse heat conduction gradient that may be generated inside the billet due to the zoned heating, while maintaining the continuous effect of the directional magnetic field.

[0033] S305. Online monitoring and feedback adjustment: Throughout the S300 process, multiple non-contact infrared thermometers are used to monitor the surface temperature of the thick, thin, and interface areas of the product in real time, and the data is fed back to the heating control system to dynamically fine-tune the power of the corresponding coils to ensure that the actual temperature deviates from the preset T1 and T2 temperature curves within ±5℃.

[0034] S306. Billet Transfer and Temperature Holding: After the heating process is completed, the aluminum alloy sheet billet is quickly transferred to the forging die by a robot. The transfer time is controlled within 3 seconds. During the transfer, the aluminum alloy sheet billet is placed in a heat preservation cover to reduce the temperature drop and ensure that the actual temperature of the thick and thin areas of the aluminum alloy sheet billet still meets the preset temperature gradient requirements when it enters the S400 step.

[0035] As a further aspect of the present invention: step S400 specifically includes:

[0036] S401. Preparation and preheating of multi-head mold: The upper part of the partitioned forging mold is composed of an array of multiple independent servo hydraulic cylinder driven press head units. The shape of the imprint surface of each press head unit matches the geometry of the corresponding local area of ​​the product.

[0037] Before loading the aluminum alloy sheet blank, all pressure head units and the lower mold cavity are preheated, and the preheating temperature is controlled between 150℃ and 280℃.

[0038] S402, Precise positioning of billet and initial mold closing: The aluminum alloy sheet billet processed in step S300 is precisely placed into the lower mold cavity by the robot according to the visual positioning marks on the partition forging mold; then, the central controller instructs all pressing head units to descend synchronously at a uniform low speed until the pressing surface of each pressing head unit makes slight contact with the upper surface of the billet, establishing the initial contact zero point.

[0039] S403, Zoned Coordinated Forging Execution:

[0040] S403a. For the pressure head unit group corresponding to the thick area of ​​the product, the central controller calls the first pressure-speed program to make the pressure head unit group corresponding to the thick area of ​​the product press down at the first initial speed V1. When the actual pressure is detected to reach the preset first threshold P1, it switches to the low-speed pressure holding mode, and the pressing speed is reduced to 10%-20% of V1. The final filling of the area is completed in this mode.

[0041] S403b: For the pressure head unit group corresponding to the thin area of ​​the product, the central controller calls the second pressure-speed program to make the pressure head unit group corresponding to the thin area of ​​the product press down rapidly at a second initial speed V2 higher than V1, but the pressure upper limit is limited to a second threshold P2 lower than P1 to ensure that the material flows rapidly but does not become excessively thinned or unstable.

[0042] S403c: For the pressure head unit group corresponding to the thick-thin boundary zone, the central controller calls the third pressure-speed program. This program is set as follows: In the initial stage of forging, a higher initial pressure similar to that of the thick area of ​​the product is used to suppress the tendency of the material in the thin area of ​​the product to flow too quickly; in the middle stage of forging, as the material is filled, the pressure value is dynamically interpolated and adjusted according to the displacement difference of the pressure heads in adjacent thick and thin areas to achieve a smooth transition; in the final stage of forging, the pressure and speed are reduced to a level that is coordinated with the pressure holding mode of the thick area of ​​the product.

[0043] S404, Centralized Coordinated Control and Real-time Compensation: Throughout the forging process, the central controller collects data from the displacement and pressure sensors of each pressure head unit in real time and calculates the theoretical flow rate and filling state of the material in each region. When the actual displacement of any pressure head unit at the thickness-thin interface exceeds the allowable value of the theoretical model, the central controller immediately and dynamically adjusts the parameters of the third pressure-speed program described in S403c to fine-tune and compensate the pressure or speed of the adjacent product thick or thin pressure head units.

[0044] S405, Final Forging Position Judgment and Signal Unification: When the displacement of all pressure head units reaches their respective set final forging positions and the pressure value is stably maintained within the preset range for at least 0.5 seconds, the central controller determines that the forging is complete and issues a unified command to all pressure head units to stop and switch to the pressure holding mode.

[0045] As a further aspect of the present invention: step S500 specifically includes:

[0046] S501, Zone holding pressure parameter setting and loading: After the forging is completed in step S400, all pressure head units remain closed and enter the holding pressure mode;

[0047] The central controller sets different holding pressures and durations for the pressure head unit groups corresponding to the thick, thin, and thick-thin boundary areas of the product.

[0048] Among them, the holding pressure in the thick zone is set to 80%-95% of the final forging pressure, the holding pressure in the thin zone is set to 50%-70% of the final forging pressure, and the holding pressure in the boundary zone adopts a linear transition value.

[0049] The total pressure holding time is set to 10-30 seconds;

[0050] S502, Gradient Cooling System Start-up: At the start of the pressure holding stage, the gradient cooling system built into the mold is started; specifically, cooling water at a temperature of 20℃-40℃ is pumped into the first set of cooling channels embedded in the mold below the corresponding product thickness area, at a flow rate of 5-15 L / min, for rapid and strong cooling.

[0051] At the same time, constant temperature heat transfer oil at a temperature of 80℃-150℃ is pumped into the second set of cooling channels embedded in the mold, corresponding to the thin area and the thick-thin junction area of ​​the product, at a flow rate of 2-8 L / min, for slow temperature control cooling.

[0052] S503, Real-time monitoring and feedback adjustment of thermal stress: During the pressure holding and cooling process, thermocouples pre-embedded at specific points in the mold cavity are used to monitor and record the temperature change curves of the thick area, thin area and junction area of ​​the product mold in real time; the central controller dynamically fine-tunes the flow rate of the cooling medium in step S502 according to the monitored temperature difference of each area, so as to ensure that the temperature difference between the thick area and the thin area of ​​the mold is maintained within the preset reasonable gradient range when the pressure holding ends.

[0053] S504, Pressure Holding and Unloading and Mold Pre-opening: After the preset pressure holding time is reached, the central controller controls the pressure of all pressure head units to be linearly unloaded to zero in stages, but the pressure head units do not completely retract; then, only the pressure head units corresponding to the thin area of ​​the product are slightly raised by 0.1-0.3 mm to form a small gap, allowing the area to have a small amount of elastic recovery space under residual thermal stress, while the pressure head units in the thick area of ​​the product remain in their final position.

[0054] S505 Final mold opening and part removal condition determination: After step S504 is completed, the central controller comprehensively determines whether the following conditions are met simultaneously: the temperature of the thick mold area drops below 100℃; the temperature difference between the thin and thick mold areas is less than 30℃; the pressure of all pressure head units has returned to zero; when all conditions are met, the central controller instructs all pressure head units to synchronously retract to the fully open position, completing the final mold opening and preparing for the robot to remove the part.

[0055] As a further aspect of the present invention: step S600 specifically includes:

[0056] S601. Preliminary inspection and removal of parts inside the mold: After the final mold opening in step S500, the outline of the forging inside the cavity is quickly scanned by the vision sensor built into the mold. After confirming that there is no sticking or severe deformation, the high-temperature resistant gripper robot smoothly removes the forging from the lower mold cavity and transfers it to the cooling conveyor belt.

[0057] S602. Online trimming and flash removal: The forging is fed to the fine stamping machine and a special trimming die preheated to 100-150℃ is used to perform hot trimming along the parting line of the forging. The cutting speed is 5-20 mm / s. After trimming, the forging is then leveled by a set of rollers with preset angles to eliminate slight warping that may be caused by trimming.

[0058] S603, Differentiated Coating Chemical Removal:

[0059] S603a. Immerse the forging in the first alkaline cleaning tank at a temperature of 40-60°C and clean it with ultrasonic assistance for 5-10 minutes to completely remove the high thermal conductivity solid lubricating coating applied to the thick area surface in step S100.

[0060] S603b: After cleaning the forging, immerse it in the second organic solvent cleaning tank. The tank solution is a microemulsion solvent with a specific formula. Spray it in a circulating manner at room temperature for 10-20 minutes to dissolve and remove the heat-absorbing coating applied to the thin area and the junction area in step S100.

[0061] S604. Surface finishing and stress reduction: After removing the coating, the forging is sandblasted using glass beads with a particle size of 80-120 mesh at a pressure of 0.2-0.4 MPa to uniformly treat the surface of the forging, so as to remove the oxide scale and achieve surface homogenization; then the forging is placed in a vibration aging device and vibrated at a specific frequency lower than its resonant frequency for 15-30 minutes to reduce internal residual stress.

[0062] S605. Final geometric dimensions and defect inspection: A coordinate measuring machine is used to fully inspect the key dimensions of the finished forging; at the same time, local fluorescent penetrant testing or micro-focus X-ray inspection is performed on the thickness-thinning interface area to confirm that there are no micro-cracks or defects.

[0063] S606 Cleaning, Rust Prevention and Finished Product Delivery: Forgings that pass inspection are cleaned with deionized water and dried. Then, a temporary water-based rust inhibitor is sprayed onto their surface. After drying, they are packaged and stored to complete the entire forming process.

[0064] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0065] This invention effectively solves the problem of shear stress concentration and cracking at the interface caused by the mismatch in deformation capacity between the thick and thin areas of aluminum sheet in the background technology by introducing a novel process path of "pre-compensated deformation and zoned synergistic control". First, by actively microscopically pre-deforming the thin area and applying a differentiated coating before forging, a physical basis conducive to the coordinated flow of materials is pre-established. Second, by using gradient heating and zoned controllable forging pressure field, a dynamic balance between the deformation speed and resistance of the thick and thin areas is achieved during the forming process. Finally, by in-situ pressure holding and gradient cooling, the uniform release of internal stress is ensured. These steps work together to fundamentally inhibit crack initiation and significantly improve the forming accuracy, structural integrity and yield of aluminum forgings with thickness difference structures. Attached Figure Description

[0066] Figure 1 This is a flowchart of steps S100-S600 in this invention. Detailed Implementation

[0067] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0068] Please see Figure 1 A hot forging process for 7-series aluminum sheet products with thickness variations includes the following steps:

[0069] S100, billet pretreatment and differential coating application: After cleaning the surface of the aluminum alloy sheet billet, apply a high thermal conductivity lubricating coating to the surface area corresponding to the product thickness area, and apply a heat insulation and energy absorption coating to the surface area corresponding to the product thin area and the thickness-thin junction area.

[0070] S200, Local Pre-fabricated Compensation Deformation: Based on the product digital model, low-power pulsed laser shock technology is used to perform micro-deformation treatment on the area corresponding to the thin area of ​​the product on the aluminum alloy sheet blank, forming a micro-bulging structure.

[0071] S300, gradient energy field heating: The aluminum alloy sheet blank is placed in a zoned temperature-controlled induction heating device. The thick area of ​​the product is heated to the first target temperature T1, and the thin area and the thick-thin junction area of ​​the product are heated to the second target temperature T2, which is lower than T1. During the heating process, a directional magnetic field is applied to the thin area and the thick-thin junction area of ​​the product to induce grain pre-orientation.

[0072] S400, Multi-head Partition Forging: The heated aluminum alloy sheet blank is placed into a partition forging mold with multiple independent and controllable pressure head units. The pressure head unit corresponding to the product's thick area is controlled to operate according to a first pressure-speed program, the pressure head unit corresponding to the product's thin area is controlled to operate according to a second pressure-speed program, and the pressure head unit corresponding to the thickness-thin junction area is controlled to operate according to a third pressure-speed program. The third pressure-speed program is a non-linear variation program. The first, second, and third pressure-speed programs are respectively completed by the central controller in coordination to complete the forging process.

[0073] S500, In-situ Pressure Holding and Gradient Cooling: After forging, pressure holding is carried out in the mold in sections. At the same time, low temperature medium is introduced into the cooling channel of the thick part of the product in the mold, and high temperature medium is introduced into the cooling channel of the thin part of the product and the junction of thick and thin parts to implement gradient cooling.

[0074] S600, Post-processing: Open the mold and remove the part, trim the edges, correct and remove the surface coating to obtain the finished product;

[0075] This invention systematically and fundamentally eliminates the risk of cracking at the interface between thick and thin sections through a series of interconnected active control processes.

[0076] First, the differentiated coating in step S100 not only lays the foundation for surface properties in subsequent steps, but its high thermal conductivity coating accelerates the heating of the thick area while the thermal insulation coating slows down the temperature drop of the thin area. Combined with the gradient energy field heating in step S300, it creates an optimized initial state of "high temperature and high plasticity thick area" and "low temperature and high strength thin area" inside the billet for the first time. This fundamentally reduces the difference in deformation resistance between the two at the initial moment of hot forging and alleviates the root stress that leads to cracks.

[0077] Secondly, the local prefabrication compensation deformation pretreatment in step S200, by actively creating micro-bulges in the thin area, physically increases the material volume and local strength of the area, which is equivalent to "filling" part of the flow velocity difference before deformation, providing geometric and mechanical dual compensation for uniform deformation.

[0078] Based on this, the multi-head partitioned forging in step S400 plays a decisive role. It can apply distinct but coordinated forces and speeds to the thick, thin, and junction areas like "precise fingers," dynamically directing the material flow, ensuring that the material in the thin area does not flow away too quickly, the material in the thick area is fully filled, and the material flow at the junction is smoothly transitioned, thereby actively suppressing the generation of shear stress at the moment of forming.

[0079] Subsequently, the in-situ pressure holding and gradient cooling in step S500 are not simply static maintenance, but rather, through different holding pressures and differentiated cooling rates, the thick area is quickly shaped and the thin area is fully creep-healed under pressure, thus achieving active relaxation and rational distribution of residual stress and preventing the generation of secondary cracks after demolding or during cooling.

[0080] Finally, step S600 ensures the surface quality and dimensional accuracy of the finished product;

[0081] In summary, by introducing a novel process approach of "pre-compensated deformation and zoned synergistic control," the problem of shear stress concentration and cracking at the interface caused by the mismatch in deformation capacity between the thick and thin areas of aluminum sheet in the background technology is effectively solved. First, by actively performing microscopic pre-deformation on the thin area and applying a differentiated coating before forging, a physical basis conducive to coordinated material flow is pre-established. Second, by utilizing gradient heating and a zoned controllable forging pressure field, a dynamic balance between deformation speed and resistance in the thick and thin areas is achieved during the forming process. Finally, by in-situ pressure holding and gradient cooling, the uniform release of internal stress is ensured. These steps work synergistically to fundamentally suppress crack initiation and significantly improve the forming accuracy, structural integrity, and yield of aluminum forgings with thickness differences.

[0082] In this embodiment of the invention, step S100 specifically includes:

[0083] S101. Surface cleaning and activation: The aluminum alloy sheet blank is ultrasonically degreased using an alkaline cleaning solution, and then surface activated using an acidic solution to obtain a clean blank substrate with high surface activity.

[0084] S102. Coating material preparation: Prepare a high thermal conductivity solid lubricating coating material and a heat insulation and energy absorption coating material; wherein, the high thermal conductivity solid lubricating coating material is a composite ceramic slurry containing graphene and boron nitride; the heat insulation and energy absorption coating material is a microporous composite slurry with silica aerogel and elastic polymer as the matrix;

[0085] S103, Partition Masking and Precise Application: Based on the product's 3D model data, create a rigid mask plate that corresponds to the shape of the product's thick area on the surface of the aluminum alloy sheet blank.

[0086] A rigid mask is placed over the surface of the aluminum alloy sheet blank to expose the thin area and the thick-thin interface area of ​​the product; the heat-insulating and energy-absorbing coating material is uniformly applied to the exposed area using a plasma spraying process to form a heat-insulating and energy-absorbing coating, thus forming the first coating area.

[0087] After removing the mask and applying a second mask to expose the thick area of ​​the product, a physical vapor deposition process is used to deposit the high thermal conductivity solid lubricating coating material on the surface of the thick area of ​​the product to form a high thermal conductivity lubricating coating, thus forming the second coating area.

[0088] S104. Coating curing and thickness control: The aluminum alloy sheet blank after coating is subjected to step heating curing treatment. The thickness of the first coating area after curing is controlled between 20 micrometers and 100 micrometers, and the thickness of the second coating area after curing is controlled between 5 micrometers and 30 micrometers. A smooth thickness transition zone is formed at the junction of the first and second coating areas.

[0089] First, the specific cleaning and activation process of S101 (alkaline degreasing followed by acid activation) is not a routine cleaning process, but rather creates an ideal surface chemical state and micro-roughness for the subsequent adhesion of high-performance coatings. This fundamentally avoids the risk of peeling off under high temperature and pressure during forging due to poor adhesion between the coating and the substrate, thus ensuring the stability of the process foundation.

[0090] Secondly, the explicit definition of the coating material in S102 has key physical significance: the high thermal conductivity lubricating coating formed by the graphene-boron nitride composite ceramic slurry not only achieves extraordinary thermal conductivity in the thick area to facilitate rapid heating, but its extremely low coefficient of friction also directly reduces the shear resistance between the area and the die during forging; while the heat-insulating and energy-absorbing coating based on silica aerogel plays a dual role as a "thermal barrier" and a "microscopic damper" in the thin area, which can effectively maintain the temperature gradient in the area, and its microporous structure can absorb some deformation energy and buffer stress impact;

[0091] Furthermore, the partitioned masking and combined process application of S103 (plasma spraying for the insulation layer and physical vapor deposition for the lubrication layer) is a decisive process innovation. It ensures that two coatings with different functions can be applied precisely, densely and uniformly to the preset complex area. In particular, the extremely thin and strong solid lubrication film formed by physical vapor deposition in the thick area avoids the problems of uneven thickness or blockage of mold cavity details that may be caused by traditional spraying.

[0092] Finally, S104’s precise control over coating thickness and transition zone not only enables the functional (thermal conductivity / insulation) strength of the coating to be quantified, but its “smooth transition zone” design also avoids the step change in coating performance from thick to thin areas at the microscale, thereby eliminating a potential source of interfacial stress concentration caused by the coating itself.

[0093] In summary, the refined definition of step S100 yields clear and highly operable results: its rigorous surface cleaning and activation treatment provides a solid substrate for subsequent coating adhesion, ensuring process stability; the specific combination of the selected graphene-boron nitride composite coating and silica aerogel-based coating achieves optimal performance matching in terms of high thermal conductivity lubrication and thermal insulation energy absorption, respectively, laying a reliable physical property foundation for subsequent gradient heating and differential flow control; and the precise application process combining masking, plasma spraying, and physical vapor deposition, along with strict thickness and transition zone control, ensures that the two functional coatings can perform their intended functions in the correct locations, while avoiding abrupt performance changes at the interface, optimizing heat flow and stress distribution from the source, and further eliminating the risk of localized stress that may be introduced due to improper coating application.

[0094] In this embodiment of the invention, step S200 specifically includes:

[0095] S201. Digital Modeling and Compensation Calculation: Based on the final three-dimensional model of the product, the metal flow law during the hot forging process is analyzed through finite element simulation to determine the equivalent volume that needs to be compensated in the thin area and the thickness-thin interface area of ​​the product; and a three-dimensional data model of the compensation structure is calculated and generated to guide the pre-deformation.

[0096] S202, Laser Selective Impact Pre-deformation: A pulsed fiber laser system equipped with a dynamic focusing lens is used to scan and process the corresponding thin product area on the aluminum alloy sheet blank according to the three-dimensional data model of the compensation structure.

[0097] Lasers, with their low energy density, short pulse width, and high frequency, non-ablatively impact thin areas of products, inducing microscopic plastic flow and grain refinement in the surface material, thereby forming localized, precise micro-arched bulge structures.

[0098] S203. Structural parameter control: The height of the micro-arched bulge structure is controlled between 15% and 40% of the initial thickness of the aluminum alloy sheet blank. The distribution density of the micro-arched bulge structure is adaptively adjusted according to the equivalent strain gradient obtained from the finite element simulation, and the distribution is more dense in the area with a large strain gradient. The micro-arched bulge structure exhibits a gradually decreasing distribution in the thickness-thin junction area.

[0099] S204. Pre-deformation inspection and calibration: A three-dimensional optical scanner is used to collect the morphology of the pre-deformed aluminum alloy sheet blank. The actual data is compared with the three-dimensional data model of the compensation structure. If the deviation of the micro-arched bulge structure in a local area exceeds the set threshold, step S202 is performed in that area for calibration.

[0100] First, there is precise prediction and design based on digital twins (S201): This step first elevates the traditional "trial and error" or "empirical estimation" compensation design to a scientific design method based on physical simulation. By accurately reproducing the metal flow, temperature field and stress field evolution during the hot forging process through finite element simulation, it is possible to quantitatively calculate the precise equivalent volume that needs to be compensated at the thickness-thin interface and the optimal compensation location. This avoids the problems of insufficient compensation (failure to eliminate stress concentration) or excessive compensation (leading to material accumulation, folding and other defects), so that the subsequent pre-deformation operation has a clear and scientific goal, ensuring the effectiveness of intervention from the design source.

[0101] Secondly, a non-thermal-damage precision micro-forming technology (S202) was used: the core technological advantage of this step is the use of pulsed laser shock with specific parameters (low energy density, short pulse, high frequency). This "cold working" mechanism (laser shock strengthening principle) allows energy to be transferred to the interior of the material in the form of stress waves, mainly inducing microscopic plastic deformation and grain refinement, while producing almost no thermal effect (the heat-affected zone is negligible). This brings multiple benefits: First, it maintains the original excellent plasticity and metallurgical state of the aluminum sheet, avoiding adverse effects such as grain coarsening, oxidation, or phase transformation that may be caused by heat input; Second, the formed micro-arched bulge structure is precise and controllable, and the strength and hardness of the material below it are significantly improved due to grain refinement, which is equivalent to "embedding" micro-reinforcing ribs in the thin area that needs reinforcement, directly improving the area's ability to resist excessive thinning and coordinate deformation; Third, the non-contact processing has no tool wear and no mechanical stress, is suitable for complex curved surfaces, and has extremely high repeatability.

[0102] Secondly, an adaptive topology optimization structure (S203) is formed: This step refines the parameters of the compensation structure, making it no longer a uniform or simple geometric shape, but an intelligent topology structure that matches the expected deformation field; height control (15%-40% of billet thickness): ensures that the compensation amount is sufficient to balance the flow without interfering with the normal material filling during subsequent forging; distribution density is adaptively adjusted according to strain gradient: in the area predicted by finite element simulation as where the future deformation is most severe (large equivalent strain gradient), denser micro-bulges are arranged to provide stronger local support and flow resistance adjustment, achieving precise reinforcement "where it is most needed, it is strengthened"; gradual attenuation distribution at the interface: avoids the appearance of hard geometric and performance boundaries between the compensation structure and the matrix, ensuring that the transition of material flow from the thick area to the thin area after compensation is smooth and continuous, fundamentally eliminating the possibility of new stress concentration caused by improper design of the compensation structure itself;

[0103] Finally, a manufacturing quality closed loop (S204) is formed: the introduction of three-dimensional optical scanning online inspection and calibration constitutes a complete quality closed loop of "design-manufacturing-inspection-feedback". This not only ensures the consistency between the pre-deformation size of a single blank and the design model, but more importantly, it provides a guarantee for process stability. Through real-time comparison and deviation calibration, it can compensate for possible small fluctuations in the laser system or the initial differences in the blank itself, ensuring that each blank entering the subsequent key forging process has a highly consistent and qualified pre-deformation state, which greatly improves the reliability and yield of the entire process.

[0104] In summary, digital simulation-driven design ensured the scientific rigor of the intervention, laser shock non-thermal forming achieved precision and material friendliness, adaptive topology parameters optimized the effectiveness and efficiency of the intervention, and online detection and calibration ensured the stability and repeatability of the intervention.

[0105] In this embodiment of the invention, step S300 specifically includes:

[0106] S301. Blank Surface Condition Confirmation and Loading: Before the aluminum alloy sheet blank that has completed step S200 is transported to the heating station, confirm that the differential coating on the surface of the aluminum alloy sheet blank is intact and free from peeling.

[0107] The aluminum alloy sheet blank is precisely placed above the coil array of the zoned temperature control induction heating device, ensuring that the thick area, thin area and junction area of ​​the aluminum alloy sheet blank are aligned with the corresponding independent heating coil unit below.

[0108] S302, Rapid heating of the thick area of ​​the product: Start the first set of medium frequency induction heating coils corresponding to the thick area of ​​the product, set the frequency to 1-10 kHz, and rapidly heat the entire thick area of ​​the product to the first target temperature T1 within 10-30 seconds. The range of T1 is 40-80℃ below the solidus temperature of the aluminum alloy material.

[0109] S303, Slow Heating and Grain Control of Thin and Thick Areas of the Product: Synchronous with or slightly delayed from step S302, the second set of low-frequency induction heating coils corresponding to the thin and thick areas of the product are started, with a frequency set to 50-500 Hz, and the area is heated to the second target temperature T2 within 40-80 seconds with a low power density, where T2 is 30-120℃ lower than T1; while the second set of low-frequency induction heating coils are working, a steady-state directional magnetic field with a direction at an angle of 15-45 degrees to the subsequent forging main deformation direction is applied to the thin and thick areas of the product, with a magnetic field strength of 0.5-3 Tesla, to induce the grains in the area to align in a predetermined direction along the magnetic field direction;

[0110] S304. Temperature field balance and uniform heating: After all areas reach their respective target temperatures, adjust the coil power to enter the heat preservation and uniform heating stage, which lasts for 5-15 seconds, in order to balance the transverse heat conduction gradient that may be generated inside the billet due to the zoned heating, while maintaining the continuous effect of the directional magnetic field.

[0111] S305. Online monitoring and feedback adjustment: Throughout the S300 process, multiple non-contact infrared thermometers are used to monitor the surface temperature of the thick, thin, and interface areas of the product in real time, and the data is fed back to the heating control system to dynamically fine-tune the power of the corresponding coils to ensure that the actual temperature deviates from the preset T1 and T2 temperature curves within ±5℃.

[0112] S306, Billet Transfer and Temperature Holding: After the heating process is completed, the aluminum alloy sheet billet is quickly transferred to the forging die by a robot. The transfer time is controlled within 3 seconds. During the transfer, the aluminum alloy sheet billet is placed in a heat preservation cover to reduce the temperature drop and ensure that the actual temperature of the thick and thin areas of the aluminum alloy sheet billet still meets the preset temperature gradient requirements when it enters the S400 step.

[0113] Through dual and differentiated control of temperature and microstructure, a precise and proactive optimization foundation is laid for subsequent uniform deformation. The detailed effects are broken down as follows:

[0114] First, a reverse temperature field design (S302, S303) was implemented to precisely match the deformation requirements: traditional heating aims for overall uniformity, while this step creatively implements a "regional temperature gradient" heating strategy; for thick areas, medium frequency (1-10 kHz) is used to rapidly heat to a higher temperature (T1), so that it is in a supersaturated high plasticity and low rheological stress state at the beginning of forging, which is easy to fill and not easy to crack; for thin areas and junction areas, low frequency (50-500 Hz) is used to slowly heat to a lower temperature (T2); the core physical significance of this design is that: thin areas themselves are prone to overheating in conventional heating due to their small thickness and fast heat dissipation, while this solution actively heats them to a lower temperature, so that they maintain high deformation resistance and strength; this actively constructed temperature gradient of "high temperature soft state in thick areas and low temperature strong state in thin areas" precisely compensates for the natural uneven deformation trend caused by cross-sectional differences (thin area materials are prone to flow too fast), and balances the flow "will" of different areas from the energy source, directly reducing the shear strain at the junction;

[0115] Secondly, the active pre-control of grain orientation is introduced to reduce micro-flow resistance (S303): This is the innovative aspect of this scheme that goes beyond simple temperature control. While heating the thin and interface regions at a lower temperature, a steady-state strong magnetic field (0.5-3 T) is applied at an angle to the main deformation direction. Under the action of the magnetic field, the easily slipping crystal planes in the aluminum crystal will gradually turn to maintain a specific orientation with the magnetic field direction. This is equivalent to "pre-deforming" or "texture pre-fabricating" the material at the microscale before forging begins. When the actual forging is performed later, these pre-oriented grains tend to slip along the preset, most favorable direction, significantly reducing the deformation incoordination between grains and the tendency of dislocation accumulation in this region. As a result, from the perspective of the intrinsic deformation mechanism of the material, the effective flow resistance in the thin and interface regions is reduced, enabling smoother deformation at relatively lower temperatures, which is more in line with the deformation behavior of the thick region, fundamentally suppressing the initiation of microcracks caused by grain disorder and difficulty in initiating multiple slip systems.

[0116] Secondly, the accuracy and stability of the gradient temperature field (S304, S305, S306) are ensured: S304's short-term uniform heating does not make the temperature uniform, but rather eliminates unnecessary lateral temperature differences perpendicular to the gradient direction that may be caused by independent heating of different zones, ensuring that the temperature of the entire thick or thin zone is uniform and avoiding secondary local thermal stress; S305's online monitoring and feedback adjustment, through a multi-point infrared temperature measurement and control system closed loop, controls the zone temperature deviation within ±5℃; this precise temperature control is the key to ensuring the repeatable and reliable execution of the "reverse temperature gradient" strategy, as any large temperature fluctuation will disrupt the carefully designed balance; S306's rapid heat preservation and transfer (≤3 seconds with heat preservation cover) minimizes the temperature drop of the billet from the heating furnace to the press, especially preventing the sudden temperature drop in the thin zone due to its large specific surface area; this ensures that the preset, precisely calculated T1 and T2 temperature gradient values ​​of the billet entering the die are well maintained, making the entire forging process based on a stable and reliable initial thermal state.

[0117] In this embodiment of the invention, step S400 specifically includes:

[0118] S401. Preparation and preheating of multi-head mold: The upper part of the partitioned forging mold is composed of an array of multiple independent servo hydraulic cylinder driven press head units. The shape of the imprint surface of each press head unit matches the geometry of the corresponding local area of ​​the product.

[0119] Before loading the aluminum alloy sheet blank, all pressure head units and the lower mold cavity are preheated, and the preheating temperature is controlled between 150℃ and 280℃.

[0120] S402, Precise positioning of billet and initial mold closing: The aluminum alloy sheet billet processed in step S300 is precisely placed into the lower mold cavity by the robot according to the visual positioning marks on the partition forging mold; then, the central controller instructs all pressing head units to descend synchronously at a uniform low speed until the pressing surface of each pressing head unit makes slight contact with the upper surface of the billet, establishing the initial contact zero point.

[0121] S403, Zoned Coordinated Forging Execution:

[0122] S403a. For the pressure head unit group corresponding to the thick area of ​​the product, the central controller calls the first pressure-speed program to make the pressure head unit group corresponding to the thick area of ​​the product press down at the first initial speed V1. When the actual pressure is detected to reach the preset first threshold P1, it switches to the low-speed pressure holding mode, and the pressing speed is reduced to 10%-20% of V1. The final filling of the area is completed in this mode.

[0123] S403b: For the pressure head unit group corresponding to the thin area of ​​the product, the central controller calls the second pressure-speed program to make the pressure head unit group corresponding to the thin area of ​​the product press down rapidly at a second initial speed V2 higher than V1, but the pressure upper limit is limited to a second threshold P2 lower than P1 to ensure that the material flows rapidly but does not become excessively thinned or unstable.

[0124] S403c: For the pressure head unit group corresponding to the thick-thin boundary zone, the central controller calls the third pressure-speed program. This program is set as follows: In the initial stage of forging, a higher initial pressure similar to that of the thick area of ​​the product is used to suppress the tendency of the material in the thin area of ​​the product to flow too quickly; in the middle stage of forging, as the material is filled, the pressure value is dynamically interpolated and adjusted according to the displacement difference of the pressure heads in adjacent thick and thin areas to achieve a smooth transition; in the final stage of forging, the pressure and speed are reduced to a level that is coordinated with the pressure holding mode of the thick area of ​​the product.

[0125] S404, Centralized Coordinated Control and Real-time Compensation: Throughout the forging process, the central controller collects data from the displacement and pressure sensors of each pressure head unit in real time and calculates the theoretical flow rate and filling state of the material in each region. When the actual displacement of any pressure head unit at the thickness-thin interface exceeds the allowable value of the theoretical model, the central controller immediately and dynamically adjusts the parameters of the third pressure-speed program described in S403c to fine-tune and compensate the pressure or speed of the adjacent product thick or thin pressure head units.

[0126] S405, Final Forging Position Judgment and Signal Unification: When the displacement of all pressure head units reaches their respective set final forging positions, and the pressure value is stably maintained within the preset range for at least 0.5 seconds, the central controller determines that the forging is completed and issues a unified command to all pressure head units to stop and switch to the pressure holding mode.

[0127] The core process of "forging" has been transformed from a black box process based on integral molds and relying on experience into an "intelligent" precision forming process based on discrete execution units, driven by digital programs, and with real-time perception and closed-loop feedback capabilities. This fundamental transformation provides a dynamic, precise, and adaptive direct force field intervention method to solve the problem of cracking at the thickness-thin interface.

[0128] First, the "spatiotemporal programmability" and "geometric self-matching" of the deformation force field were realized (S401, S402):

[0129] The S401 employs an independent servo pressure head unit array, with the imprinting surface matching the local geometry of the product. This is the basis for achieving independent zone control. This is equivalent to replacing a single large hammer with countless independently operable "intelligent small hammers." Each pressure head is only responsible for the local area corresponding to its shape, avoiding the "force flow" interference and "idle stroke" problems that are unavoidable when traditional integral upper dies are pressing complex drop parts. Mold preheating (150-280℃) significantly reduces surface cooling when the blank comes into contact with the mold, ensuring stable material flowability.

[0130] Secondly, the S402's visual precision positioning and initial mold closing establish a unified and precise physical coordinate system and mechanical "zero point" for all subsequent independent control actions. This ensures that the force and displacement applied by each pressure head can be accurately applied to the preset target area of ​​the billet, which is a prerequisite for realizing "zoning measures".

[0131] Secondly, a "customized" deformation strategy (S403) is provided to address the differences in thickness, thinness, and boundary areas: This is the core innovation of the control logic. Instead of using a single set of parameters, dedicated programs are preset for each of the three types of areas: Thick area program (high pressure, slow speed): For areas with abundant material and high deformation resistance, higher pressure is used to ensure that the material fully fills the depth of the cavity, while a slower speed avoids inertial effects or internal shearing due to excessive flow; Thin area program (low pressure, fast speed): For areas prone to over-thinning, the maximum forming pressure (P2) is limited to prevent crushing; at the same time, it allows for faster downward pressure to promote rapid material flow to the predetermined position, avoiding material loss due to excessive speed. Premature material cooling reduces fluidity; the interface program (non-linear dynamic adjustment): this is a key program for crack prevention; it is not a fixed value, but a function that dynamically changes according to the forging process (time / displacement) and the state of adjacent areas; in the initial stage, a higher pressure is applied to "hold down" the thin area material, preventing it from flowing out too early and too quickly, waiting for the thick area material to begin flowing; in the middle stage, the pressure is smoothly interpolated and adjusted according to the actual displacement difference between the pressure heads of the thick and thin areas, acting like an "intelligent mediator" to dynamically balance the flow rate difference on both sides; in the final stage, its parameters are coordinated with the thick area holding pressure mode to ensure that the whole process ends synchronously; this program actively manages the strain rate at the interface, making it transition smoothly;

[0132] Secondly, an integrated real-time disturbance rejection system (S404) integrating "perception-decision-execution" was constructed: this is the key to upgrading the preset program to intelligent control; the central collaborative control and real-time compensation function of S404 makes the system no longer simply play according to the preset program, but has the ability to deal with "unexpected" situations online.

[0133] Sensing: Through displacement and pressure sensors in each pressure head unit, the system can "sense" the actual flow resistance and filling progress of the material in each area in real time; Decision-making: The central controller compares the real-time data with the theoretical model. Once it detects that the actual displacement (representing the material flow rate) of a pressure head in a certain interface zone deviates from the expectation, the system immediately determines that there is uneven flow at that point (e.g., the thin area flows too fast or the thick area flows too slow); Execution: The system does not adjust the pressure head in the interface zone in isolation, but dynamically fine-tunes the pressure or speed setpoints of its adjacent thick or thin pressure heads to correct the deviation at its source (inflow or outflow end); This cross-regional linkage closed-loop control can effectively compensate for actual production disturbances such as material batch fluctuations, slight differences in heating temperature, or changes in lubrication conditions, ensuring that the material flow converges towards the goal of homogenization under any circumstances;

[0134] Finally, a precise forming endpoint based on global coordination (S405) was established: the final forging determination mechanism of S405 abandons the simple judgment based on a single press stroke or pressure in the traditional way; it requires all press head units to reach their respective preset final forging positions at the same time, and the pressure to be stable; this forcibly ensures that every local area of ​​the product reaches a fully filled state, and no area is "fallen" or "over-compressed"; this globally coordinated termination condition is the ultimate guarantee for obtaining high dimensional accuracy and uniform and dense structure;

[0135] In summary, the fundamental advantage of the refined multi-head partitioned forging system lies in decoupling the complex, macroscopic, continuous, and interconnected metal plastic deformation process into multiple independently measurable and controllable microscopic sub-processes. By providing differentiated initial strategies through pre-set customized programs and then dynamically and precisely controlling them through a real-time closed-loop feedback system, it can proactively guide, match, and even "correct" the inherent differences in deformation behavior between thick and thin zones. This is akin to introducing an intelligent traffic light system and a real-time traffic control center into a chaotic traffic situation, ensuring that vehicles with different loads and speeds (thick and thin materials) can safely, orderly, and synchronously pass through the intersection (thick-thin boundary zone), thereby completely avoiding "traffic accidents" (cracks).

[0136] In this embodiment of the invention, step S500 specifically includes:

[0137] S501, Zone holding pressure parameter setting and loading: After the forging is completed in step S400, all pressure head units remain closed and enter the holding pressure mode;

[0138] The central controller sets different holding pressures and durations for the pressure head unit groups corresponding to the thick, thin, and thick-thin boundary areas of the product.

[0139] Among them, the holding pressure in the thick zone is set to 80%-95% of the final forging pressure, the holding pressure in the thin zone is set to 50%-70% of the final forging pressure, and the holding pressure in the boundary zone adopts a linear transition value.

[0140] The total pressure holding time is set to 10-30 seconds;

[0141] S502, Gradient Cooling System Start-up: At the start of the pressure holding stage, the gradient cooling system built into the mold is started; specifically, cooling water at a temperature of 20℃-40℃ is pumped into the first set of cooling channels embedded in the mold below the corresponding product thickness area, at a flow rate of 5-15 L / min, for rapid and strong cooling.

[0142] At the same time, constant temperature heat transfer oil at a temperature of 80℃-150℃ is pumped into the second set of cooling channels embedded in the mold, corresponding to the thin area and the thick-thin junction area of ​​the product, at a flow rate of 2-8 L / min, for slow temperature control cooling.

[0143] S503, Real-time monitoring and feedback adjustment of thermal stress: During the pressure holding and cooling process, thermocouples pre-embedded at specific points in the mold cavity are used to monitor and record the temperature change curves of the thick area, thin area and junction area of ​​the product mold in real time; the central controller dynamically fine-tunes the flow rate of the cooling medium in step S502 according to the monitored temperature difference of each area, so as to ensure that the temperature difference between the thick area and the thin area of ​​the mold is maintained within the preset reasonable gradient range when the pressure holding ends.

[0144] S504, Pressure Holding and Unloading and Mold Pre-opening: After the preset pressure holding time is reached, the central controller controls the pressure of all pressure head units to be linearly unloaded to zero in stages, but the pressure head units do not completely retract; then, only the pressure head units corresponding to the thin area of ​​the product are slightly raised by 0.1-0.3 mm to form a small gap, allowing the area to have a small amount of elastic recovery space under residual thermal stress, while the pressure head units in the thick area of ​​the product remain in their final position.

[0145] S505, Final mold opening and part removal condition determination: After step S504 is completed, the central controller comprehensively determines whether the following conditions are met simultaneously: ① The temperature of the thick mold area drops below 100℃; ② The temperature difference between the thin and thick mold areas is less than 30℃; ③ The pressure of all pressure head units has returned to zero; When all conditions are met, the central controller instructs all pressure head units to synchronously retract to the fully open position, completing the final mold opening and preparing for the robot arm to remove the part;

[0146] The holding and cooling stage after forging is transformed from a relatively passive and uniform process into a critical precision treatment stage that actively engages in "stress field design, phase transformation control, and defect healing." This stage does not simply maintain the shape, but rather locks in and enhances the results of the previous process through differentiated control of time, space, and strength, ensuring that the forging transforms from a high-temperature plastic body into a room-temperature solid component. Its detailed effects are reflected in the following multiple synergistic effects:

[0147] First, differentiated stress relaxation management based on regional mechanical requirements (S501) was implemented. Traditional pressure holding uses a single pressure, while this step implements zoned pressure holding: a strong pressure holding of up to 80%-95% of the final forging pressure is applied to the thick area, aiming to take advantage of the material's optimal plasticity to promote the welding of internal voids, increase density, and offset the significant solidification shrinkage stress caused by the large volume of this area through continuous high pressure; a moderate pressure holding of only 50%-70% is applied to the thin area, the purpose of which is not compaction, but to provide a controllable constraint background, allowing the area to undergo sufficient creep deformation under lower hydrostatic pressure, so that the dislocations that have already emerged at the microscale rearrange and the subgrain boundaries migrate, thereby achieving self-healing of micro-defects and relaxation of internal stress; a linear transition value is used in the boundary area to ensure a smooth transition of stress states; this "on-demand" pressure holding field actively guides the redistribution of residual stress and prevents it from concentrating in uneven areas;

[0148] Secondly, a "reverse" intelligent cooling field (S502, S503) was constructed in coordination with the pressure field, which is the core design to prevent secondary thermal stress and cracks. This step did not adopt uniform cooling, but instead designed a physically meaningful "reverse cooling strategy": "rapid and strong cooling" (20-40℃ cooling water) was implemented for thick areas: the purpose is to allow areas with thick cross-sections and large heat storage to pass through the recrystallization temperature zone first and solidify rapidly; rapid solidification allows the thick areas to establish strength early, forming a "rigid skeleton" that supports the entire part, which fixes the shape accuracy obtained by forging; "slow temperature-controlled cooling" (80-150℃ constant temperature oil) was implemented for thin areas and junction areas: the purpose is to allow areas that are easy to cool but require stress relaxation to be cooled for a longer period of time. Maintaining a relatively high temperature (above the recrystallization temperature but below the solidus line); under the continuous action of holding pressure, the high temperature provides the driving force for atomic diffusion, enabling the material in this region to continuously undergo dynamic recovery and recrystallization, while the creep effect is fully utilized, thereby maximizing the reduction of deformation energy stored during forging; this synergistic mechanism of "rapid cooling and shaping of thick areas into a skeleton, and slow cooling and softening of thin areas to relieve stress" actively matches the shrinkage behavior of different regions, greatly compensating for the difference in natural cooling shrinkage caused by thickness differences, and fundamentally suppressing the risk of generating huge tensile stress (thermal stress) at the interface due to asynchronous shrinkage during the cooling process; real-time monitoring and feedback of S503 ensure the precise execution of this complex cooling field;

[0149] Secondly, a scientific unloading and pre-mold opening mechanism was introduced to release elastic constraint stress (S504). At the end of the holding pressure, the material has partially cooled and strengthened, and is in an elastoplastic state. Traditional one-time rapid mold opening will cause the parts to suddenly break free from the mold constraint, and the elastic recovery of different parts will be inconsistent, which may cause instantaneous cracking. The phased unloading and zoned pre-mold opening strategy in this step is extremely ingenious: phased linear unloading of pressure: avoids the impact caused by sudden stress release; only the pressure head in the thin area is slightly raised by 0.1-0.3 mm: this is the key innovation point; the thin area has the strongest elastic recovery trend, and the slight rise provides it with a controlled and small amount of elastic recovery space, allowing the elastic strain energy accumulated in this area to be released smoothly, while the pressure head in the thick area remains stationary to maintain the main shape; this is like installing a precision pressure relief valve on a pressure vessel, which releases the stress in the most dangerous part in a directional manner while maintaining the overall structural stability.

[0150] Secondly, a safe mold-opening criterion based on multi-physics field states (S505) was established. Mold opening is no longer based solely on time, but on a comprehensive set of temperature and mechanical state criteria (thick area temperature <100℃, regional temperature difference <30℃, pressure zero). This mechanism ensures that mold opening is only performed when the following conditions are met: ① the thick area has fully solidified and has sufficient strength; ② the overall temperature gradient has been reduced to a level insufficient to generate destructive thermal stress; ③ the mold has no mechanical constraints. This maximizes the guarantee that the internal stress and thermal state of the forging are within a stable and safe window when it leaves the mold, avoiding cold cracking or deformation caused by improper mold opening timing.

[0151] Ultimately, a closed-loop optimization process was formed, encompassing everything from macroscopic mechanics to microscopic structure. Overall, the refined step S500, closely integrated with the preceding S400 (forming), forms a complete closed loop of "precision forming → stress management → microstructure optimization." It not only solves the macroscopic shrinkage stress problem caused by thickness differences through differentiated pressure holding and cooling strategies, but also promotes the recovery and recrystallization of the microscale in thin areas and at the interface through the setting of a high-temperature slow cooling zone, refining the grains in this region and improving its toughness and fatigue performance. This step ultimately transforms a freshly formed "hot blank" into a near-net-shape high-performance forging with low residual stress, uniform microstructure, and stable dimensions, providing the final guarantee for the entire process to achieve high yield and high reliability.

[0152] In this embodiment of the invention, step S600 specifically includes:

[0153] S601. Preliminary inspection and removal of parts inside the mold: After the final mold opening in step S500, the outline of the forging inside the cavity is quickly scanned by the vision sensor built into the mold. After confirming that there is no sticking or severe deformation, the high-temperature resistant gripper robot smoothly removes the forging from the lower mold cavity and transfers it to the cooling conveyor belt.

[0154] S602. Online trimming and flash removal: The forging is fed to the fine stamping machine and a special trimming die preheated to 100-150℃ is used to perform hot trimming along the parting line of the forging. The cutting speed is 5-20 mm / s. After trimming, the forging is then leveled by a set of rollers with preset angles to eliminate slight warping that may be caused by trimming.

[0155] S603, Differentiated Coating Chemical Removal:

[0156] S603a. Immerse the forging in the first alkaline cleaning tank at a temperature of 40-60°C and clean it with ultrasonic assistance for 5-10 minutes to completely remove the high thermal conductivity solid lubricating coating applied to the thick area surface in step S100.

[0157] S603b: After cleaning the forging, immerse it in the second organic solvent cleaning tank. The tank solution is a microemulsion solvent with a specific formula. Spray it in a circulating manner at room temperature for 10-20 minutes to dissolve and remove the heat-absorbing coating applied to the thin area and the junction area in step S100.

[0158] S604. Surface finishing and stress reduction: After removing the coating, the forging is sandblasted using glass beads with a particle size of 80-120 mesh at a pressure of 0.2-0.4 MPa to uniformly treat the surface of the forging, so as to remove the oxide scale and achieve surface homogenization; then the forging is placed in a vibration aging device and vibrated at a specific frequency lower than its resonant frequency for 15-30 minutes to reduce internal residual stress.

[0159] S605. Final geometric dimensions and defect inspection: A coordinate measuring machine is used to fully inspect the key dimensions of the finished forging; at the same time, local fluorescent penetrant testing or micro-focus X-ray inspection is performed on the thickness-thinning interface area to confirm that there are no micro-cracks or defects.

[0160] S606 Cleaning, Rust Prevention and Finished Product Delivery: Forgings that pass inspection are cleaned with deionized water and dried. Then, a temporary water-based rust inhibitor is sprayed on their surface. After drying, they are packaged and stored to complete the entire forming process.

[0161] A "final precision processing and verification system" was constructed that is precisely matched with, functionally complementary to, and forms a quality closed loop with the aforementioned innovative processes (S100-S500). This step ensures that all previous efforts to prevent cracking and ensure uniform deformation can ultimately be transformed without damage into a high-value finished product with excellent surface condition, accurate dimensions, internal integrity, and traceable quality. Its detailed effects are reflected in the following six interconnected aspects:

[0162] First, it achieves "non-destructive transfer" and "instant status confirmation" (S601) from the mold to the conveying process; rapid visual scanning within the mold: immediately after mold opening and before part removal, its primary purpose is to prevent sticking; if sticking occurs, the robot's forced removal will cause irreversible plastic deformation or surface tearing of the forging, rendering all previous precision control efforts futile; early detection can trigger mold maintenance and avoid batch accidents; high-temperature resistant grippers and smooth transfer: using special grippers and designing them to ensure smooth transfer, preventing mechanical damage or deformation of forgings with relatively low strength at high temperatures (especially thin areas) due to uneven clamping force or collisions; this step is the first safety valve to ensure the geometric integrity of the forging as it leaves the production line;

[0163] Secondly, the "hot precision separation" technology (S602) with optimal material condition matching was adopted; online hot trimming of preheated mold: trimming was performed before the forging temperature had completely dropped to room temperature (usually still above 200℃), at which time the material plasticity was still good; using a preheated (100-150℃) special mold can avoid the rapid cooling of the material at the cut due to the cold state of the mold, thus significantly reducing the risk of micro-tears or cut cracks during trimming; low-speed punching (5-20 mm / s) further controlled the impact load of the separation process; subsequent roller leveling: trimming itself is a local plastic shearing process, which will introduce new residual stress and possible uneven springback, resulting in the flatness of the forging exceeding the tolerance; immediate leveling is to quickly compensate and correct these new stresses and deformations within the window period when the material still has a certain degree of thermoplasticity, preventing them from being "frozen" in the cold workpiece and ensuring the initial geometric accuracy of the forging;

[0164] Secondly, a "targeted removal and substrate protection" process (S603) based on coating function design was implemented. The two previously applied coatings (high thermal conductivity lubricating coating and heat-insulating energy-absorbing coating) have very different compositions and physical properties. This step did not use a crude single method (such as strong sandblasting or strong acid immersion), but instead designed a differentiated chemical removal path: S603a alkaline cleaning removes the lubricating coating: the graphene-boron nitride composite ceramic coating is alkali-resistant but not acid-resistant, and the alkaline environment can effectively break down its bonds without excessively corroding the aluminum substrate; ultrasonic assistance enhances the cleaning effect and ensures recovery. The coating in the corners and crevices was also removed; S603b organic solvent removal of the insulation coating: microporous coatings based on silica aerogel and polymer are more suitable for removal by specific formulation of microemulsion solvents through penetration and dissolution, avoiding the problem that alkaline solutions may not be able to completely remove organic residues; the core benefit of this "targeted" step-by-step cleaning method is that while completely removing the functional coating, it maximizes the protection of the surface quality and chemical composition of the aluminum forging body, providing a clean base for subsequent possible surface treatments such as anodizing or direct use;

[0165] Secondly, a non-thermal "surface homogenization and stress reduction" composite treatment (S604) was implemented; controlled sandblasting: using glass beads of a specific particle size (80-120 mesh) under moderate pressure, multiple objectives were achieved: ① removing the extremely thin oxide scale formed on the surface of the forging during heating and forging; ② making the surface morphology and gloss from different areas (thick area, thin area, original billet surface, pre-deformed area) uniform and consistent, improving the appearance quality; ③ introducing a uniform compressive stress layer on the surface, which is beneficial to improving fatigue performance; vibration aging treatment: this is a key low-stress treatment technology; compared with thermal aging (which may cause deformation or grain growth), vibration aging, by applying mechanical energy at a sub-resonant frequency, promotes the homogenization and reduction of the peak value of residual stress inside the forging (especially the stress concentration point at the thick-thin interface) through microscopic plastic deformation; this is equivalent to performing a "stress massage" on the forging at room temperature, further consolidating the stress relief effect of S500 gradient cooling, and improving the long-term dimensional stability and stress corrosion resistance of the product;

[0166] Secondly, a two-dimensional quality inspection closed loop (S605) was established, encompassing both macroscopic dimensions and microscopic defects. A coordinate measuring machine (CMM) was used for full-dimensional inspection: this rigorously verified whether the forgings met the drawing requirements from a macroscopic perspective, confirming the final geometric accuracy of all previous deformation control steps (S200 pre-deformation, S400 zone forging). Specialized non-destructive testing (fluorescent penetrant testing or micro-focus X-ray testing) was conducted on the thickness-to-thickness interface: this is the final and most targeted checkpoint in quality control; it focuses inspection resources on the core risk area that the entire process aims to address—the thickness-to-thickness interface. Fluorescent penetrant testing is extremely sensitive to surface cracks, while micro-focus X-ray testing can detect internal microscopic pores or cracks. This step provides direct evidence that the aforementioned entire process (S100-S600) successfully eliminated crack defects in this area, forming a complete technical closed loop from "problem definition" to "problem-solving verification," providing authoritative data support for process reliability and product quality.

[0167] Finally, the final protection (S606) to ensure product flowability is completed; qualified products that have passed rigorous testing are cleaned and dried, and then sprayed with a temporary water-based rust inhibitor. This protective film ensures that the surface of the forgings does not corrode during storage, transportation, and until the customer proceeds with the next processing step, maintaining its excellent surface condition and commercial value. In summary, the detailed steps of S600 are by no means a simple "post-processing"; it is a comprehensive terminal system that integrates safe transfer, precision finishing, functional cleaning, stress optimization, final verification, and factory protection. It ensures that forgings that have undergone complex and precise forming can perfectly complete the "last mile" of manufacturing, completely and reliably encapsulating the technical value created by the preceding processes in the final product, and providing quantifiable and traceable quality certificates. It is an indispensable endpoint and quality assurance link in the entire innovative process chain.

[0168] The present invention also includes a central process management unit, a status tracking and sensing module, an adaptive parameter tuning module, and a process data closed-loop recording module. The central process management unit stores a cross-process status transfer model based on the product model and material parameters.

[0169] The state tracking and sensing module includes:

[0170] The first 3D scanner, located behind S200, is used to acquire the actual geometric data of the prefabricated compensation structure.

[0171] A multi-band infrared thermal imager is installed at the outlet of the S300 heating device to acquire temperature field data of the billet zone.

[0172] A distributed displacement and pressure sensor array is installed inside the S400 multi-head mold;

[0173] Temperature and flow sensors are installed at the outlet of the S500 cooling channel;

[0174] The adaptive parameter tuning module connects the central process management unit and the status tracking and sensing module. The adaptive parameter tuning module is configured as follows:

[0175] The system receives data from the first 3D scanner and compares it with the 3D data model of the compensation structure in S201. If the deviation exceeds the threshold, it automatically generates a calibration command for the laser shock parameters in S202.

[0176] The system receives data from the multi-band infrared thermal imager and compares it with the preset temperature curve in S305, dynamically adjusting the power parameters of the induction heating coil in S302 and S303.

[0177] Before S400 is executed, the pressure-velocity program parameters in S403a, S403b and S403c are dynamically calculated and initialized based on the actual geometric data and the partitioned temperature field data, combined with the cross-process state transfer model.

[0178] During the execution of S500, the flow rate and temperature of the cooling medium in S502 are dynamically adjusted based on the temperature and flow rate data at the outlet of the cooling channel.

[0179] The process data closed-loop recording module is used to associate and store the actual execution values ​​of all adjustable parameters, sensor monitoring data, and the final test results of S605 for each product throughout the entire process from S100 to S600, forming a traceable process digital twin.

[0180] This technical solution provides a systematic solution for the extreme thin-wall forging of 7-series aluminum through the innovative approach of "pre-fabricated compensation deformation" and "multi-field collaborative control". Combined with the zoned pressure holding and gradient cooling process, it ensures the stability of the extreme thin-wall structure during the forming and phase transformation process, thereby achieving a breakthrough in reliably forging 7-series aluminum to a thickness of about 0.5 mm without cracking.

[0181] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A hot forging process for 7-series aluminum sheet products with thickness variations, characterized in that, Includes the following steps: S100, billet pretreatment and differential coating application: After cleaning the surface of the aluminum alloy sheet billet, apply a high thermal conductivity lubricating coating to the surface area corresponding to the product thickness area, and apply a heat insulation and energy absorption coating to the surface area corresponding to the product thin area and the thickness-thin junction area. S200, Local Pre-fabricated Compensation Deformation: Based on the product digital model, low-power pulsed laser shock technology is used to perform micro-deformation treatment on the area corresponding to the thin area of ​​the product on the aluminum alloy sheet blank, forming a micro-bulging structure. S300, gradient energy field heating: The aluminum alloy sheet blank is placed in a zoned temperature-controlled induction heating device. The thick area of ​​the product is heated to the first target temperature T1, and the thin area and the thick-thin junction area of ​​the product are heated to the second target temperature T2, which is lower than T1. During the heating process, a directional magnetic field is applied to the thin area and the thick-thin junction area of ​​the product to induce grain pre-orientation. S400, Multi-head Partition Forging: The heated aluminum alloy sheet blank is placed into a partition forging mold with multiple independent and controllable pressure head units. The pressure head unit corresponding to the product's thick area is controlled to operate according to a first pressure-speed program, the pressure head unit corresponding to the product's thin area is controlled to operate according to a second pressure-speed program, and the pressure head unit corresponding to the thickness-thin junction area is controlled to operate according to a third pressure-speed program. The third pressure-speed program is a non-linear variation program. The first, second, and third pressure-speed programs are respectively completed by the central controller in coordination to complete the forging process. S500, In-situ Pressure Holding and Gradient Cooling: After forging, pressure holding is carried out in the mold in sections. At the same time, low temperature medium is introduced into the cooling channel of the thick part of the product in the mold, and high temperature medium is introduced into the cooling channel of the thin part of the product and the junction of thick and thin parts to implement gradient cooling. S600, Post-processing: Open the mold and remove the part, trim the edges, correct and remove the surface coating to obtain the finished product.

2. The hot forging process for 7-series aluminum sheet products with thickness difference structures according to claim 1, characterized in that, Step S100 specifically includes: S101. Surface cleaning and activation: The aluminum alloy sheet blank is ultrasonically degreased using an alkaline cleaning solution, and then surface activated using an acidic solution to obtain a clean blank substrate with high surface activity. S102. Coating material preparation: Prepare a high thermal conductivity solid lubricating coating material and a heat insulation and energy absorption coating material; wherein, the high thermal conductivity solid lubricating coating material is a composite ceramic slurry containing graphene and boron nitride; the heat insulation and energy absorption coating material is a microporous composite slurry with silica aerogel and elastic polymer as the matrix; S103, Partition Masking and Precise Application: Based on the product's 3D model data, create a rigid mask plate that corresponds to the shape of the product's thick area on the surface of the aluminum alloy sheet blank. A rigid mask is placed over the surface of the aluminum alloy sheet blank to expose the thin area and the thick-thin interface area of ​​the product; the heat-insulating and energy-absorbing coating material is uniformly applied to the exposed area using a plasma spraying process to form a heat-insulating and energy-absorbing coating, thus forming the first coating area. After removing the mask and applying a second mask to expose the thick area of ​​the product, a physical vapor deposition process is used to deposit the high thermal conductivity solid lubricating coating material on the surface of the thick area of ​​the product to form a high thermal conductivity lubricating coating, thus forming the second coating area. S104. Coating curing and thickness control: The aluminum alloy sheet blank after coating is subjected to step heating curing treatment. The thickness of the first coating area after curing is controlled between 20 micrometers and 100 micrometers, and the thickness of the second coating area after curing is controlled between 5 micrometers and 30 micrometers. A smooth thickness transition zone is formed at the junction of the first and second coating areas.

3. The hot forging process for 7-series aluminum sheet products with thickness difference structures according to claim 2, characterized in that, Step S200 specifically includes: S201. Digital Modeling and Compensation Calculation: Based on the final three-dimensional model of the product, the metal flow law during the hot forging process is analyzed through finite element simulation to determine the equivalent volume that needs to be compensated in the thin area and the thickness-thin interface area of ​​the product; and a three-dimensional data model of the compensation structure is calculated and generated to guide the pre-deformation. S202, Laser Selective Impact Pre-deformation: A pulsed fiber laser system equipped with a dynamic focusing lens is used to scan and process the corresponding thin product area on the aluminum alloy sheet blank according to the three-dimensional data model of the compensation structure. Lasers, with their low energy density, short pulse width, and high frequency, non-ablatively impact thin areas of products, inducing microscopic plastic flow and grain refinement in the surface material, thereby forming localized, precise micro-arched bulge structures. S203. Structural parameter control: The height of the micro-arched bulge structure is controlled between 15% and 40% of the initial thickness of the aluminum alloy sheet blank. The distribution density of the micro-arched bulge structure is adaptively adjusted according to the equivalent strain gradient obtained from the finite element simulation, and the distribution is more dense in the area with a large strain gradient. The micro-arched bulge structure exhibits a gradually decreasing distribution in the thickness-thin junction area. S204. Pre-deformation inspection and calibration: A three-dimensional optical scanner is used to collect the morphology of the pre-deformed aluminum alloy sheet blank. The actual data is compared with the three-dimensional data model of the compensation structure. If the deviation of the micro-arched bulge structure in a local area exceeds the set threshold, step S202 is performed in that area for calibration.

4. The hot forging process for 7-series aluminum sheet products with thickness difference structures according to claim 3, characterized in that, Step S300 specifically includes: S301. Blank Surface Condition Confirmation and Loading: Before the aluminum alloy sheet blank that has completed step S200 is transported to the heating station, confirm that the differential coating on the surface of the aluminum alloy sheet blank is intact and free from peeling. The aluminum alloy sheet blank is precisely placed above the coil array of the zoned temperature control induction heating device, ensuring that the thick area, thin area and junction area of ​​the aluminum alloy sheet blank are aligned with the corresponding independent heating coil unit below. S302, Rapid heating of the thick area of ​​the product: Start the first set of medium frequency induction heating coils corresponding to the thick area of ​​the product, set the frequency to 1-10 kHz, and rapidly heat the entire thick area of ​​the product to the first target temperature T1 within 10-30 seconds. The range of T1 is 40-80℃ below the solidus temperature of the aluminum alloy material. S303, Slow Heating and Grain Control of Thin and Thick Areas of the Product: Synchronous with or slightly delayed from step S302, the second set of low-frequency induction heating coils corresponding to the thin and thick areas of the product are started, with a frequency set to 50-500 Hz, and the area is heated to the second target temperature T2 within 40-80 seconds with a low power density, where T2 is 30-120℃ lower than T1; while the second set of low-frequency induction heating coils are working, a steady-state directional magnetic field with a direction at an angle of 15-45 degrees to the subsequent forging main deformation direction is applied to the thin and thick areas of the product, with a magnetic field strength of 0.5-3 Tesla, to induce the grains in the area to align in a predetermined direction along the magnetic field direction; S304. Temperature field balance and uniform heating: After all areas reach their respective target temperatures, adjust the coil power to enter the heat preservation and uniform heating stage, which lasts for 5-15 seconds, in order to balance the transverse heat conduction gradient that may be generated inside the billet due to the zoned heating, while maintaining the continuous effect of the directional magnetic field. S305. Online monitoring and feedback adjustment: Throughout the S300 process, multiple non-contact infrared thermometers are used to monitor the surface temperature of the thick, thin, and interface areas of the product in real time, and the data is fed back to the heating control system to dynamically fine-tune the power of the corresponding coils to ensure that the actual temperature deviates from the preset T1 and T2 temperature curves within ±5℃. S306. Billet Transfer and Temperature Holding: After the heating process is completed, the aluminum alloy sheet billet is quickly transferred to the forging die by a robot. The transfer time is controlled within 3 seconds. During the transfer, the aluminum alloy sheet billet is placed in a heat preservation cover to reduce the temperature drop and ensure that the actual temperature of the thick and thin areas of the aluminum alloy sheet billet still meets the preset temperature gradient requirements when it enters the S400 step.

5. The hot forging process for 7-series aluminum sheet products with thickness difference structures according to claim 4, characterized in that, Step S400 specifically includes: S401. Preparation and preheating of multi-head mold: The upper part of the partitioned forging mold is composed of an array of multiple independent servo hydraulic cylinder driven press head units. The shape of the imprint surface of each press head unit matches the geometry of the corresponding local area of ​​the product. Before loading the aluminum alloy sheet blank, all pressure head units and the lower mold cavity are preheated, and the preheating temperature is controlled between 150℃ and 280℃. S402, Precise positioning of billet and initial mold closing: The aluminum alloy sheet billet processed in step S300 is precisely placed into the lower mold cavity by the robot according to the visual positioning marks on the partition forging mold; then, the central controller instructs all pressing head units to descend synchronously at a uniform low speed until the pressing surface of each pressing head unit makes slight contact with the upper surface of the billet, establishing the initial contact zero point. S403, Zoned Coordinated Forging Execution: S403a. For the pressure head unit group corresponding to the thick area of ​​the product, the central controller calls the first pressure-speed program to make the pressure head unit group corresponding to the thick area of ​​the product press down at the first initial speed V1. When the actual pressure is detected to reach the preset first threshold P1, it switches to the low-speed pressure holding mode, and the pressing speed is reduced to 10%-20% of V1. The final filling of the area is completed in this mode. S403b: For the pressure head unit group corresponding to the thin area of ​​the product, the central controller calls the second pressure-speed program to make the pressure head unit group corresponding to the thin area of ​​the product press down rapidly at a second initial speed V2 higher than V1, but the pressure upper limit is limited to a second threshold P2 lower than P1 to ensure that the material flows rapidly but does not become excessively thinned or unstable. S403c: For the pressure head unit group corresponding to the thick-thin boundary zone, the central controller calls the third pressure-speed program. This program is set as follows: In the initial stage of forging, a higher initial pressure similar to that of the thick area of ​​the product is used to suppress the tendency of the material in the thin area of ​​the product to flow too quickly; in the middle stage of forging, as the material is filled, the pressure value is dynamically interpolated and adjusted according to the displacement difference of the pressure heads in adjacent thick and thin areas to achieve a smooth transition; in the final stage of forging, the pressure and speed are reduced to a level that is coordinated with the pressure holding mode of the thick area of ​​the product. S404, Centralized Coordinated Control and Real-time Compensation: Throughout the forging process, the central controller collects data from the displacement and pressure sensors of each pressure head unit in real time and calculates the theoretical flow rate and filling state of the material in each region. When the actual displacement of any pressure head unit at the thickness-thin interface exceeds the allowable value of the theoretical model, the central controller immediately and dynamically adjusts the parameters of the third pressure-speed program described in S403c to fine-tune and compensate the pressure or speed of the adjacent product thick or thin pressure head units. S405, Final Forging Position Judgment and Signal Unification: When the displacement of all pressure head units reaches their respective set final forging positions and the pressure value is stably maintained within the preset range for at least 0.5 seconds, the central controller determines that the forging is complete and issues a unified command to all pressure head units to stop and switch to the pressure holding mode.

6. The hot forging process for 7-series aluminum sheet products with thickness difference structures according to claim 5, characterized in that, Step S500 specifically includes: S501, Zone holding pressure parameter setting and loading: After the forging is completed in step S400, all pressure head units remain closed and enter the holding pressure mode; The central controller sets different holding pressures and durations for the pressure head unit groups corresponding to the thick, thin, and thick-thin boundary areas of the product. Among them, the holding pressure in the thick zone is set to 80%-95% of the final forging pressure, the holding pressure in the thin zone is set to 50%-70% of the final forging pressure, and the holding pressure in the boundary zone adopts a linear transition value. The total pressure holding time is set to 10-30 seconds; S502, Gradient Cooling System Start-up: At the start of the pressure holding stage, the gradient cooling system built into the mold is started; specifically, cooling water at a temperature of 20℃-40℃ is pumped into the first set of cooling channels embedded in the mold below the corresponding product thickness area, at a flow rate of 5-15 L / min, for rapid and strong cooling. At the same time, constant temperature heat transfer oil at a temperature of 80℃-150℃ is pumped into the second set of cooling channels embedded in the mold, corresponding to the thin area and the thick-thin junction area of ​​the product, at a flow rate of 2-8 L / min, for slow temperature control cooling. S503, Real-time monitoring and feedback adjustment of thermal stress: During the pressure holding and cooling process, thermocouples pre-embedded at specific points in the mold cavity are used to monitor and record the temperature change curves of the thick area, thin area and junction area of ​​the product mold in real time; the central controller dynamically fine-tunes the flow rate of the cooling medium in step S502 according to the monitored temperature difference of each area, so as to ensure that the temperature difference between the thick area and the thin area of ​​the mold is maintained within the preset reasonable gradient range when the pressure holding ends. S504, Pressure Holding and Unloading and Mold Pre-opening: After the preset pressure holding time is reached, the central controller controls the pressure of all pressure head units to be linearly unloaded to zero in stages, but the pressure head units do not completely retract; then, only the pressure head units corresponding to the thin area of ​​the product are slightly raised by 0.1-0.3 mm to form a small gap, allowing the area to have a small amount of elastic recovery space under residual thermal stress, while the pressure head units in the thick area of ​​the product remain in their final position. S505 Final mold opening and part removal condition determination: After step S504 is completed, the central controller comprehensively determines whether the following conditions are met simultaneously: the temperature of the thick mold area drops below 100℃; the temperature difference between the thin and thick mold areas is less than 30℃; the pressure of all pressure head units has returned to zero; when all conditions are met, the central controller instructs all pressure head units to synchronously retract to the fully open position, completing the final mold opening and preparing for the robot to remove the part.

7. The hot forging process for 7-series aluminum sheet products with thickness difference structures according to claim 6, characterized in that, Step S600 specifically includes: S601. Preliminary inspection and removal of parts inside the mold: After the final mold opening in step S500, the outline of the forging inside the cavity is quickly scanned by the vision sensor built into the mold. After confirming that there is no sticking or severe deformation, the high-temperature resistant gripper robot smoothly removes the forging from the lower mold cavity and transfers it to the cooling conveyor belt. S602. Online trimming and flash removal: The forging is fed to the fine stamping machine and a special trimming die preheated to 100-150℃ is used to perform hot trimming along the parting line of the forging. The cutting speed is 5-20 mm / s. After trimming, the forging is then leveled by a set of rollers with preset angles to eliminate slight warping that may be caused by trimming. S603, Differentiated Coating Chemical Removal: S603a. Immerse the forging in the first alkaline cleaning tank at a temperature of 40-60°C and clean it with ultrasonic assistance for 5-10 minutes to completely remove the high thermal conductivity solid lubricating coating applied to the thick area surface in step S100. S603b: After cleaning the forging, immerse it in the second organic solvent cleaning tank. The tank solution is a microemulsion solvent with a specific formula. Spray it in a circulating manner at room temperature for 10-20 minutes to dissolve and remove the heat-absorbing coating applied to the thin area and the junction area in step S100. S604. Surface finishing and stress reduction: After removing the coating, the forging is sandblasted using glass beads with a particle size of 80-120 mesh at a pressure of 0.2-0.4 MPa to uniformly treat the surface of the forging, so as to remove the oxide scale and achieve surface homogenization; then the forging is placed in a vibration aging device and vibrated at a specific frequency lower than its resonant frequency for 15-30 minutes to reduce internal residual stress. S605. Final geometric dimensions and defect inspection: A coordinate measuring machine is used to fully inspect the key dimensions of the finished forging; at the same time, local fluorescent penetrant testing or micro-focus X-ray inspection is performed on the thickness-thinning interface area to confirm that there are no micro-cracks or defects. S606 Cleaning, Rust Prevention and Finished Product Delivery: Forgings that pass inspection are cleaned with deionized water and dried. Then, a temporary water-based rust inhibitor is sprayed onto their surface. After drying, they are packaged and stored to complete the entire forming process.

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