Leveling process for improving flatness of aluminum plate

Abstract

The invention discloses a leveling process for improving the flatness of an aluminum plate, and belongs to the technical field of precise leveling of metal composite components. In order to solve the problems of aluminum plate warping, out-of-tolerance of fitting gaps and the like caused by steel-aluminum linear expansion coefficient difference and residual stress, the invention provides a leveling method combining rigid constraint and thermal cycling. The technology comprises the steps that firstly, an aluminum plate and a steel structure are rigidly pre-tightened and fixed, and a fitting gap is eliminated; then the aluminum plate is subjected to partitioned gradient cold and hot circulation treatment, specifically, high-temperature softening is conducted firstly to relax residual stress, then targeted rapid cooling is conducted on a deformation high point, and finally stepped slow cooling is conducted to homogenize the stress; meanwhile, the steel structure keeps low-temperature rigidity in the whole process through heat insulation and independent cooling; and after circulation, pressure maintaining and unloading are conducted, and leveling is completed. Through the synergistic effect of rigid positioning constraint and stress homogenization shaping, high-precision leveling of the aluminum plate is achieved, the flatness can reach 0.05-0.1 mm / m, the attaching gap is smaller than or equal to 0.05 mm, and the aluminum plate does not have complex change after being subjected to cold and heat cycle service.

Description

Technical Field

[0001] This invention belongs to the field of precision leveling technology for metal composite components, specifically relating to a leveling process for improving the flatness of aluminum plates. Background Technology

[0002] Steel-aluminum composite components, combining the high strength of steel with the lightweight properties of aluminum, are widely used in high-end equipment fields such as building curtain walls, rail transportation, and shipbuilding. However, due to the significant differences in their physical properties, their manufacturing and service processes face severe challenges.

[0003] First, the coefficients of thermal expansion of steel and aluminum differ by nearly double (steel's coefficient is approximately 12 × 10⁻⁶). -6 / ℃, aluminum approximately 23×10 -6 When the temperature changes, the aluminum plate is prone to uncoordinated deformation, which can lead to problems such as warping and wavy flatness. In addition, gaps can be formed during thermal cycles such as coating and baking, affecting the assembly accuracy.

[0004] Secondly, residual stress is one of the key factors affecting the dimensional stability of components. Residual stress is introduced into aluminum sheets during rolling, bending, welding, or riveting, and the mismatch between steel and aluminum deformation further exacerbates the stress complexity. If not effectively relaxed, even if temporarily leveled, subsequent springback and deformation are still likely to occur.

[0005] Existing technologies such as CN116802045A suppress the deformation of composite components by optimizing the thickness ratio of aluminum plates to steel plates; CN121289715A uses friction stir additive manufacturing to alleviate interfacial stress, but these technologies focus on prevention and control during the manufacturing stage and are difficult to achieve high-precision leveling for deformed components that have already been formed or are in service.

[0006] Currently, there is no systematic leveling solution in existing technologies that couples prestressed steel structure constraints, differentiated temperature control between steel and aluminum, and targeted thermal cycling, which cannot meet the stringent requirements of high-end equipment for the flatness (≤0.1 mm / m) and dimensional stability of aluminum plates. Summary of the Invention

[0007] The purpose of this invention is to provide a leveling process to improve the flatness of aluminum plates, achieving high-precision, non-destructive, and anti-recurrence leveling, and solving the problems of steel-aluminum thermal mismatch and stress deformation.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: S1. The pre-treated aluminum plate, after cleaning and degreasing, is bonded to the steel structure assembly surface. Several evenly distributed adjustable pressure blocks are used to apply an in-plane prestress of 0.4-1.6 MPa to make the aluminum plate and the steel structure rigidly bonded, eliminating the bonding gap between them. The bonding gap is ≤0.05 mm. S2. The aluminum plate is heated in sections to raise its temperature to 170-230℃ and held for 8-20 minutes to relax its internal residual stress; at the same time, heat conduction is blocked by the heat insulation module set between the aluminum plate and the steel structure, and the steel structure is cooled independently to keep its temperature in a low temperature range of ≤80℃. S3. Under the condition of maintaining the prestress throughout the process, the aluminum plate is subjected to 1-3 alternating hot and cold cycles. Each cycle includes: targeted rapid cooling of the local high temperature area where the surface temperature of the aluminum plate is ≥10℃ higher than the surrounding area, with a cooling rate of 60-120℃ / min, so that the temperature drops to 60-90℃, and then stepwise slow cooling to room temperature at a cooling rate of 3-10℃ / min. S4. After the aluminum plate has cooled to room temperature, hold it under pressure for 5-15 minutes, then gradually remove the in-plane prestress at a rate of ≤0.2 MPa / min and check the flatness of the aluminum plate. When the flatness of a local area exceeds 0.1 mm / m, the area is considered an out-of-tolerance area, and the hot and cold alternation cycle is repeated for correction until the flatness is ≤0.1 mm / m.

[0009] As a preferred embodiment, in step S1, the in-plane prestress is 0.4-1.6 MPa, and the gap between the aluminum plate and the steel structure after application is ≤0.05 mm. This parameter setting aims to ensure a rigid fit between the aluminum plate and the steel structure, providing a stable benchmark for subsequent leveling: the prestress range takes into account the load-bearing capacity of aluminum plates of different thicknesses, avoiding excessive pressure that could damage thin plates or insufficient pressure that could result in a loose fit; a gap of ≤0.05 mm prevents localized stress concentration during heating and thermal cycling, ensuring leveling accuracy.

[0010] As a preferred embodiment, in step S2, the thermal softening temperature of the aluminum plate is 170-230℃, and the holding time is 8-20 minutes. This temperature range is lower than the overheating temperature of aluminum alloys, which can fully relax residual stress without deteriorating material properties; the holding time is adapted according to the thickness of the aluminum plate to ensure uniform internal temperature and full stress release, laying the foundation for subsequent thermal cycling.

[0011] As a preferred embodiment, in step S3, the targeted rapid cooling rate is 60-120℃ / min, with the goal of reducing the temperature at the highest point of deformation to 60-90℃. This parameter can generate moderate shrinkage stress locally to flatten the protrusion, while avoiding excessively rapid cooling that could introduce new residual stress or microcracks; cooling to 60-90℃ can create a reasonable temperature difference with the aluminum plate as a whole, achieving precise deformation correction.

[0012] As a preferred embodiment, in step S3, the overall stepped slow cooling rate is 3-10℃ / min until room temperature is reached. This cooling rate ensures a uniform temperature decrease inside the aluminum plate, avoids excessive temperature gradients that could cause secondary deformation, and also takes into account process efficiency, achieving a uniform stress distribution.

[0013] As a preferred option, in step S3, the number of hot and cold cycles is 1-3 times, depending on the thickness of the aluminum plate and the initial deformation.

[0014] As a preferred embodiment, in step S4, the pressure holding and static setting time is 5-15 min; the rate of prestress removal is ≤0.2 MPa / min. Pressure holding and static setting can consolidate the leveling effect and prevent springback after unloading; slow unloading can avoid secondary deformation caused by sudden stress changes, ensuring the final flatness stability.

[0015] As a preferred embodiment, the aluminum plate is a 5xxx or 6xxx series aluminum alloy plate with a thickness of 1-10 mm. This type of aluminum alloy has good plasticity and is easily softened by heat. The 1-10 mm thickness is suitable for this process, balancing leveling effect and production efficiency.

[0016] As a preferred option, the zoned heating employs either infrared radiation or high-frequency electromagnetic induction. Both methods provide uniform heating and precise temperature control, enabling zoned gradient heating of the aluminum plate and preventing localized overheating.

[0017] As a preferred solution, the targeted rapid cooling is achieved using liquid nitrogen injection or compressed air jet cooling. Both methods offer controllable cooling rates, allowing for precise application to the highest deformation points, rapidly generating shrinkage stress, and without damaging the aluminum plate surface.

[0018] As a preferred option, the flatness test uses a laser flatness meter with a measurement accuracy of ±0.01 mm / m, which meets the stringent testing requirements of high-end equipment.

[0019] As a preferred embodiment, the number of correction cycles shall not exceed 2, and the total processing time shall not exceed 2 hours.

[0020] As a preferred solution, before the alternating hot and cold cycle, the surface temperature field distribution of the aluminum plate is obtained by an infrared thermal imager, and the abnormally high temperature points are identified as targeted rapid cooling areas. This can accurately locate the abnormal temperature areas associated with deformation, improve the targeting of rapid cooling, and optimize the leveling accuracy.

[0021] On the other hand, the present invention also provides a leveling device for performing any of the above processes, comprising a rigid positioning platform, an adjustable pressure block, and a temperature control system: The rigid positioning platform is used to support and fix the steel structure. The platform body is made of high-rigidity material and the overall flatness error is ≤0.02 mm / m. The adjustable pressure block is set on the rigid positioning platform and includes several pressure heads that can independently adjust the pressure and provide real-time feedback, used to apply an in-plane prestress of 0.4-1.6 MPa to the aluminum plate; The temperature control system includes a zone heating module, a heat insulation module, an independent cooling module, a temperature monitoring module, and a controller. The zoned heating module is configured above or to the side of the aluminum plate and consists of an array of infrared radiation heating tubes or a high-frequency electromagnetic induction coil, supporting multiple independent temperature control zones.

[0022] The thermal insulation module is installed between the steel structure and the aluminum plate. It is made of aluminum silicate fiber felt or aerogel felt, with a thickness of 10-20 mm and a thermal conductivity of ≤0.03 W / (m·K).

[0023] An independent cooling module is installed on the steel structure side to maintain the steel structure in a low temperature range of ≤80℃. It consists of circulating water cooling pipes or air-cooled fins pre-embedded inside the steel structure.

[0024] The temperature monitoring module includes K-type thermocouples arranged in each section of the aluminum plate and embedded sensors or non-contact infrared thermal imagers at key locations of the steel structure, for real-time acquisition of temperature field data.

[0025] The controller is connected to the partitioned heating module, the independent cooling module and the temperature monitoring module respectively, and is used to automatically adjust the heating and cooling power according to the preset process curve.

[0026] The beneficial effects of this invention are: 1. This invention achieves a flatness of 0.05 to 0.1 mm / m and a bonding gap of ≤0.05 mm after leveling of the aluminum plate through the synergistic effect of prestressed rigid bonding and alternating hot and cold cycles. The leveling accuracy is significantly better than that of traditional cold straightening or overall hot straightening processes.

[0027] 2. This invention effectively suppresses springback by first relaxing residual stress through gradient heating and then cooling it down in stages for uniform temperature reduction. The treated components maintain high flatness and no secondary deformation after multiple thermal cycles, exhibiting excellent dimensional stability and resistance to repeated deformation.

[0028] 3. The aluminum sheet is treated in the softening range of 170 to 230°C to release stress, and the steel structure is kept below 80°C through heat insulation and independent cooling, which maintains its basic rigidity and avoids overheating of the aluminum.

[0029] 4. The invention uses non-contact heating and cooling throughout the process, without the need for mechanical rollers or hammers. The aluminum plate surface is free of indentations, scratches or work hardening, making it suitable for scenarios requiring high gloss.

[0030] 5. This invention supports zoned temperature control, targeted rapid cooling, and local correction. Parameters can be flexibly adjusted according to the thickness and deformation of the aluminum plate, resulting in a high first-pass yield. It is suitable for high-precision aluminum component leveling applications such as building curtain walls, rail transit, and ships.

[0031] Instruction manual illustrations

[0032] Figure 1 This is a flowchart of the leveling process of the present invention.

[0033] Figure 2 This is a schematic diagram of the leveling device of the present invention. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can understand it.

[0035] It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope defined by the claims should be included within the scope of protection of the present invention.

[0036] The testing methods for each parameter in this embodiment of the invention are as follows: 1. Flatness inspection According to GB / T 11337 "Flatness Error Detection", a laser flatness meter (accuracy ±0.01mm / m) is used to scan and detect the surface of the aluminum plate. The maximum deviation between the measured surface and the ideal plane is taken as the flatness error. The initial flatness before leveling and the final flatness after leveling are detected separately.

[0037] 2. Fitting gap detection

[0038] According to GB / T 22523 "Feeler Gauge", a feeler gauge (thickness specification 0.02-1.00 mm) should be inserted between the aluminum plate and the steel structure mating surface to measure the maximum gap between them. During measurement, the feeler gauge should be inserted with slight resistance; the maximum thickness that can be inserted should be recorded as the mating gap.

[0039] 3. Temperature monitoring

[0040] Aluminum plate temperature: K-type thermocouples conforming to GB / T 18404 are placed at the center of each zone of the aluminum plate to monitor temperature changes in real time during heating, heat preservation and cooling processes.

[0041] Steel structure temperature: K-type thermocouples are pre-embedded in key locations of the steel structure (such as the area in contact with aluminum plates), or non-contact monitoring is carried out using an infrared thermal imager.

[0042] Example 1

[0043] This embodiment follows the following... Figure 1 The leveling process shown employs, for example... Figure 2 The leveling device shown is used to level a 5083 aluminum alloy plate (5xxx series) with dimensions of 2000mm×1500mm×5mm. The aluminum plate and the H-shaped steel beam form a composite component with an initial flatness error of 0.8 mm / m.

[0044] (1) Tooling pre-tightening and positioning: After cleaning and degreasing the aluminum plate assembly surface, it is attached to the H-beam assembly surface. Several evenly distributed adjustable pressure blocks are used to apply an in-plane prestress of 1.2 MPa to achieve rigid bonding between the aluminum plate and the H-beam, eliminating the bonding gap between them to 0.03 mm.

[0045] (2) Differentiated gradient preheating: The infrared radiation heating tube array is activated to heat the aluminum plate in sections, raising its temperature to the thermal softening temperature range of 200℃. The plate is then held at this temperature for 15 minutes to relax its internal residual stress. At the same time, an independent steel structure cooling and heat insulation protection system is activated. The heat transfer is blocked by aluminum silicate fiber insulation modules (15 mm thick) laid on the steel-aluminum contact surface. This is combined with the circulating water cooling pipes embedded in the H-shaped steel beam for independent cooling. The temperature of the H-shaped steel beam is maintained at around 45℃ through closed-loop control by temperature sensors.

[0046] (3) Alternating hot and cold cycles: After preheating and heat preservation, the aluminum plate is subjected to two alternating hot and cold cycles while maintaining a prestress of 1.2 MPa throughout the process. Targeted rapid cooling: The surface temperature field distribution of the aluminum plate is obtained by infrared thermal imaging. Local high temperature areas with temperatures ≥10℃ higher than the surrounding area are identified as deformation high points. Liquid nitrogen is used to rapidly cool these areas at a rate of 100℃ / min, reducing the temperature of the deformation high point to 80℃. The shrinkage stress generated by the local temperature difference is used to flatten the protrusion. Step-cooling: Stop targeted cooling and perform step-cooling at a cooling rate of 5°C / min until room temperature is reached.

[0047] (4) Pressure Holding, Unloading, and Final Inspection: After the aluminum plate has cooled to room temperature, maintain the pre-tightening pressure and let it stand for 10 minutes. Then, gradually remove the in-plane prestress at a rate of 0.15 MPa / min. Using a laser flatness meter, the flatness of the aluminum plate reaches 0.06 mm / m, and the bonding gap is 0.04 mm. In this embodiment, the flatness meets the standard after one correction cycle, and the total processing time is 1.5 hours, which meets the design requirements.

[0048] Example 2

[0049] In this embodiment, a 6061 aluminum alloy plate (6xxx series) with dimensions of 1000mm×800mm×2mm is leveled. The aluminum plate and the steel structure platform form a composite component with an initial flatness error of 0.6 mm / m.

[0050] (1) Tooling pre-tightening and positioning: After cleaning and degreasing the aluminum plate assembly surface, it is attached to the steel structure platform assembly surface. Several evenly distributed adjustable pressure blocks are used to apply an in-plane prestress of 0.5 MPa to eliminate the bonding gap to 0.02 mm.

[0051] (2) Differentiated gradient preheating: The aluminum plate is heated in sections using a high-frequency electromagnetic induction coil, and the temperature is raised to 180℃ and held for 8 minutes. The steel structure platform is equipped with air-cooled fins, and the fan speed is controlled by a temperature sensor to keep the steel structure temperature below 35℃.

[0052] (3) Alternating hot and cold cycle: Under the condition of maintaining prestress, the aluminum plate is subjected to one alternating hot and cold cycle: Targeted rapid cooling: The surface temperature field distribution of the aluminum plate is obtained by an infrared thermal imager. Local high temperature areas with temperatures ≥10℃ higher than the surrounding area are identified as deformation high points. Compressed air cooling nozzles are used to rapidly cool the high points locally at a cooling rate of 80℃ / min, reducing the temperature of the deformation high points to 70℃. Stepped slow cooling: Stop cooling and allow the aluminum plate to cool naturally to room temperature at a rate of 3℃ / min.

[0053] (4) Pressure holding, unloading, and final inspection: After holding the pressure for 5 minutes, the prestress was removed at a rate of 0.2 MPa / min. The flatness of the aluminum plate was measured to be 0.05 mm / m, and the bonding gap was 0.03 mm. In this embodiment, the initial deformation was small and no further correction was required; the total processing time was approximately 45 minutes.

[0054] Example 3

[0055] In this embodiment, a 5052 aluminum alloy plate (5xxx series) with dimensions of 1500mm×1000mm×8mm is leveled. The aluminum plate and the steel structure frame form a composite component, and the initial flatness error is 1.2 mm / m.

[0056] (1) Tooling pre-tightening and positioning: After cleaning and degreasing the aluminum plate assembly surface, it is attached to the steel structure frame assembly surface. Several evenly distributed adjustable pressure blocks are used to apply an in-plane prestress of 1.5 MPa to eliminate the bonding gap to 0.04 mm.

[0057] (2) Differentiated gradient preheating: The aluminum plate is heated in sections using an infrared radiation heating tube array, and the temperature is raised to 220℃ and held for 20 minutes. Aerogel felt insulation modules (10 mm thick) are laid on the surface of the steel structure and independently cooled by pre-embedded circulating water cooling pipes. The temperature of the steel structure is precisely maintained below 55℃ by a PID controller.

[0058] (3) Alternating hot and cold cycles: Under the condition of maintaining prestress, the aluminum plate is subjected to three alternating hot and cold cycles: Targeted rapid cooling: The surface temperature field distribution of the aluminum plate is obtained by an infrared thermal imager. Local high temperature areas with temperatures ≥10℃ higher than the surrounding area are identified as deformation high points. Liquid nitrogen is used for cooling at a rate of 120℃ / min to reduce the temperature of the deformation high points to 90℃. Step cooling: Cool to room temperature in steps at a rate of 8°C / min.

[0059] (4) Pressure holding, unloading and final inspection

[0060] After holding the pressure for 15 minutes, the prestress was gradually removed at a rate of 0.1 MPa / min. The flatness of the aluminum plate was measured to be 0.08 mm / m, and the bonding gap was 0.05 mm. In this embodiment, the flatness met the standard after two rounds of correction, with a total processing time of 1.8 hours.

[0061] Comparative Example 1 (Traditional Cold Straightening Process)

[0062] The same 5083 aluminum alloy plate as in Example 1 was leveled using a traditional cold straightening process. The specific steps were as follows: the aluminum plate was placed at room temperature, and a pressure of 1.2 MPa was applied using a pressure block. The pressure was maintained for 30 minutes before being released. No heating or cooling was used during the leveling process; deformation was corrected entirely by mechanical pressure.

[0063] The results showed that the flatness of the aluminum plate was only 0.5 mm / m, and there was obvious rebound after unloading, with a bonding gap of 0.15 mm.

[0064] Comparative Example 2 (Traditional heat straightening process)

[0065] The same 5083 aluminum alloy plate as in Example 1 was leveled using a traditional hot straightening process. The specific steps were as follows: the aluminum plate and the steel structure were heated together to 200°C, held at that temperature for 15 minutes, and then allowed to cool naturally without applying any prestress.

[0066] The results showed that the H-beams underwent significant thermal deformation, with a flatness error of 0.3 mm / m, while the aluminum plates had a flatness of only 0.6 mm / m.

[0067] Comparative Example 3 (No prestressed thermal cycling)

[0068] The same heating and cooling parameters as in Example 1 were used, but without applying in-plane prestress, to level the 5083 aluminum alloy plate. The specific steps were as follows: the aluminum plate was attached to the surface of the steel structure (without pressure blocks for fixation), and the same zoned heating, targeted rapid cooling, and stepped slow cooling were performed.

[0069] The results showed that the flatness of the aluminum plate was 0.3 mm / m and the bonding gap was 0.10 mm, which was significantly worse than that of Example 1.

[0070] Comparative Example 4 (unstepped slow cooling)

[0071] The same prestressing, heating, and targeted rapid cooling parameters as in Example 1 were used, but the stepped slow cooling was replaced with rapid cooling to room temperature. The specific steps were as follows: after the targeted rapid cooling was completed, the temperature was directly and rapidly cooled to room temperature at a rate of 50°C / min.

[0072] The results showed that the flatness of the aluminum plate was 0.25 mm / m, and new minor warping appeared on the surface.

[0073] The specific data for Examples 1-3 and Comparative Examples 1-4 are shown in Table 1: Table 1 Comparison of effects between the examples and the comparative examples

[0074] As shown in Table 1: (1) Examples 1-3 adopt the process of combining prestressed rigid bonding, differentiated gradient preheating and alternating hot and cold cycles of the present invention. After leveling, the flatness of the aluminum plate reaches 0.05-0.08 mm / m, the bonding gap is ≤0.05 mm, and the leveling accuracy is high.

[0075] (2) Comparative Example 1 (traditional cold straightening) had a flatness of only 0.5 mm / m after leveling and severe springback; Comparative Example 2 (traditional hot straightening) caused severe deformation of the steel structure and loss of reference rigidity; Comparative Example 3 (without prestress) had poor leveling effect; Comparative Example 4 (without stepped slow cooling) produced secondary deformation. None of the comparative examples could achieve the leveling effect of the embodiments of the present invention.

[0076] (3) In Examples 1-3, the aluminum plate fully releases stress in the thermal softening range of 170-230℃, and the steel structure is always kept at ≤55℃ through independent cooling, with no thermal deformation and good reference rigidity.

[0077] (4) In Examples 1-3, there were no indentations or scratches on the aluminum plate surface, while in Comparative Example 1, slight indentations and work hardening were observed, proving that the present invention is applicable to scenarios requiring high gloss.

[0078] In summary, this invention achieves no deformation of the steel structure, no damage to the aluminum plate surface, and no recurrence after service through thermal cycling by the synergistic effect of prestress constraint and alternating hot and cold cycles.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A leveling process for improving the flatness of aluminum plates, characterized in that, Includes the following steps: S1. The pre-treated aluminum plate, after cleaning and degreasing, is bonded to the steel structure assembly surface. Several evenly distributed adjustable pressure blocks are used to apply an in-plane prestress of 0.4-1.6 MPa to make the aluminum plate and the steel structure rigidly bonded, eliminating the bonding gap between them. The bonding gap is ≤0.05 mm. S2. The aluminum plate is heated in sections to raise its temperature to 170-230℃ and held for 8-20 minutes to relax its internal residual stress; at the same time, heat conduction is blocked by the heat insulation module set between the aluminum plate and the steel structure, and the steel structure is cooled independently to keep its temperature in a low temperature range of ≤80℃. S3. Under the condition of maintaining the prestress throughout the process, the aluminum plate is subjected to 1-3 alternating hot and cold cycles. Each cycle includes: targeted rapid cooling of the local high temperature area where the surface temperature of the aluminum plate is ≥10℃ higher than the surrounding area, with a cooling rate of 60-120℃ / min, so that the temperature drops to 60-90℃, and then stepwise slow cooling to room temperature at a cooling rate of 3-10℃ / min. S4. After the aluminum plate has cooled to room temperature, hold it under pressure for 5-15 minutes, then gradually remove the in-plane prestress at a rate of ≤0.2 MPa / min and check the flatness of the aluminum plate. When the flatness of a local area exceeds 0.1 mm / m, the area is considered an out-of-tolerance area, and the hot and cold alternation cycle is repeated for correction until the flatness is ≤0.1 mm / m.

2. The leveling process according to claim 1, characterized in that, The aluminum plate is a 5xxx series or 6xxx series aluminum alloy plate with a thickness of 1-10 mm.

3. The leveling process according to claim 1, characterized in that, The zoned heating uses infrared radiation or high-frequency electromagnetic induction.

4. The leveling process according to claim 1, characterized in that, The targeted rapid cooling is achieved by liquid nitrogen injection or compressed air jet cooling.

5. The leveling process according to claim 1, characterized in that, The flatness test was performed using a laser flatness meter with a measurement accuracy of ±0.01 mm / m.

6. The leveling process according to claim 1, characterized in that, The number of correction cycles shall not exceed 2, and the total processing time shall not exceed 2 hours.

7. The leveling process according to claim 1, characterized in that, Before the alternating hot and cold cycle, the surface temperature field distribution of the aluminum plate is obtained by an infrared thermal imager, and the abnormally high temperature points are identified as targeted rapid cooling areas.

8. A leveling apparatus for performing the leveling process according to any one of claims 1 to 7, characterized in that, include: A. A rigid positioning platform for supporting and fixing the steel structure; B. An adjustable pressure block, set on the rigid positioning platform, is used to apply the in-plane prestress to the aluminum plate; C. A temperature control system, wherein the temperature control system includes: C1. A zone heating module, configured on the side of the aluminum plate, is used to perform independent gradient heating on several areas of the aluminum plate; C2. A heat insulation module, installed between the aluminum plate and the steel structure, is used to block heat conduction; C3. An independent cooling module, located on the steel structure side, is used to maintain the steel structure in a low temperature range of ≤80℃; C4. Temperature monitoring module, used to collect temperature data of each zone of the aluminum plate and the steel structure in real time; C5. Controller, which is connected to the partitioned heating module, independent cooling module and temperature monitoring module respectively, and is used to automatically adjust the heating and cooling power according to the preset process curve.

9. The leveling device according to claim 8, characterized in that, The overall flatness error of the rigid positioning platform is ≤0.02 mm / m; the adjustable pressure block contains several pressure heads that can independently adjust the pressure and provide real-time feedback, used to apply in-plane prestress of 0.4-1.6 MPa.

10. The leveling device according to claim 8, characterized in that: The partitioned heating module is an infrared radiation heating tube array or a high-frequency electromagnetic induction coil. The thermal insulation module is made of aluminum silicate fiber felt or aerogel felt, with a thickness of 10-20 mm and a thermal conductivity of ≤0.03 W / (m·K); The independent cooling module is a circulating water cooling pipe or air-cooled fin pre-embedded inside the steel structure. The temperature monitoring module is a K-type thermocouple, an embedded temperature sensor, or a non-contact infrared thermal imager.

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