A process control method for preparing an inorganic covering layer on the surface of an aluminum plate

Abstract

The application relates to the technical field of metal surface treatment, and discloses a preparation process control method for an inorganic covering layer on the surface of an aluminum plate, aiming to solve the technical problems of poor adaptability, low control precision, unstable film layer quality and the like of the existing phosphating process of the aluminum plate. The method comprises five core steps of working condition diagnosis, parameter pre-adjustment, dynamic parameter compensation, differential post-processing and effect verification, realizes real-time sensing, intelligent decision and accurate execution of process parameters based on a PLC control system. The method has the following innovative points: a dynamic mapping relationship between working condition parameters and process parameters is established, real-time compensation is carried out on the spraying pressure and reaction time through a quantitative model, and customized post-processing is implemented according to different alloy characteristics. The method effectively ensures the uniformity and compactness of the zinc phosphate covering layer, significantly improves the corrosion resistance and adhesion of the product, and realizes continuous optimization of the process and stable and controllable product quality.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, specifically to a method for controlling the preparation process of an inorganic coating layer on an aluminum plate surface. Background Technology

[0002] Aluminum and its alloy sheets are widely used in home appliances, construction, automobiles, and other fields due to their excellent physical properties. To improve their corrosion resistance and provide a good substrate for subsequent coatings, a zinc phosphate conversion film (an inorganic coating layer) is often prepared on their surface. The quality of this film layer directly determines the service life and appearance quality of aluminum components.

[0003] However, existing aluminum plate phosphating processes generally suffer from several technical bottlenecks that urgently need to be addressed. First, process parameters largely rely on fixed, empirically set parameters, lacking adaptability. Aluminum plates vary significantly in alloy type, thickness, and other characteristics due to different application scenarios, and the production environment experiences frequent temperature and humidity fluctuations. Fixed process parameters cannot consistently form a uniform and dense film under all conditions, easily leading to films that are too thin, loose, or too thick and cracked, severely impacting product yield. Second, production process control is rudimentary. Traditional methods struggle to accurately compensate for key parameters in the phosphating process (such as spray pressure and reaction time) in real-time, in conjunction with substrate characteristics and environmental factors, resulting in poor film consistency. Finally, post-treatment processes are simplistic and lack specificity. Phosphating films with different alloy compositions exhibit inherent differences in microstructure, such as varying porosity and insufficient adhesion. General post-treatment methods cannot effectively compensate for these specific defects, limiting further improvements in the final film performance.

[0004] Therefore, a process control method for preparing inorganic coatings on aluminum plates is proposed, the core of which lies in constructing a closed-loop intelligent control system for the entire process. This scheme provides precise input for subsequent processes through systematic operational condition diagnosis; utilizes a pre-stored process parameter library and real-time monitoring data for pre-adjustment and dynamic compensation to ensure the phosphating reaction remains within the optimal range; and implements differentiated post-treatment based on substrate characteristics. Finally, through effect verification and data-driven cyclic optimization, the process parameters achieve self-improvement, fundamentally solving the problems of poor adaptability, low control precision, and unstable film quality in existing technologies, significantly improving the industrial efficiency and product quality of aluminum plate surface treatment. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for controlling the preparation process of an inorganic coating layer on an aluminum plate surface.

[0006] To achieve the above-mentioned objective, the present invention provides the following technical solution: a method for controlling the preparation process of an inorganic coating layer on the surface of an aluminum plate, comprising the following steps:

[0007] Step 1: Operating Condition Diagnosis and Initial Parameter Setting: Collect the alloy type, thickness, surface roughness, and ambient temperature of the aluminum plate using industrial sensors; use the alloy type, thickness, surface roughness, and ambient temperature as composite query conditions to retrieve the initial chemical parameters, reference reaction time, and reference spraying pressure of the phosphating solution from the pre-stored process parameter library;

[0008] Step 2, Pre-adjustment: Based on the surface roughness test results, the aluminum plate surfaces that do not meet the requirements are sandblasted or returned to the degreasing process; based on the ambient temperature test results, the temperature, zinc ion concentration and pH of the phosphating bath are adjusted.

[0009] Step 3: Dynamic parameter compensation for the phosphating process: Based on the difference between the actual thickness of the aluminum plate and the reference thickness, the target spray pressure is calculated and adjusted using a pressure compensation model; based on the difference between the average temperature of the environment and the bath and the reference temperature, the target reaction time is calculated and adjusted using a time compensation model; and the spray pressure and reaction time are controlled in a closed-loop feedback manner by real-time detection of the zinc phosphate film thickness.

[0010] Step 4, Post-processing control: Select the corresponding drying temperature curve and sealing process based on the aluminum plate alloy type; monitor the crystallinity of the zinc phosphate film in real time, and calibrate the post-processing parameters based on the test results;

[0011] Step 5: Effect Verification and Parameter Optimization: Test the film thickness, adhesion, and corrosion resistance of the treated aluminum plate samples; adjust the process parameters based on the test results; store the process parameters and test results, and optimize the process parameters through machine learning algorithms.

[0012] Furthermore, the initial chemical parameters mentioned in step one include: zinc ion concentration of 8 to 12 grams per liter, nitrate ion concentration of 3 to 5 grams per liter, and pH value of 2.5 to 3.0.

[0013] Furthermore, the pressure compensation model described in step three is as follows: the target spray pressure equals the reference spray pressure plus the thickness pressure compensation coefficient multiplied by the difference between the actual thickness of the aluminum plate and the reference thickness.

[0014] Furthermore, the thickness pressure compensation coefficient is 0.05 MPa per millimeter, the reference thickness is 2 millimeters, and the reference spray pressure is 0.35 MPa.

[0015] Furthermore, the time compensation model described in step three is as follows: the target reaction time equals the baseline reaction time plus the temperature time compensation coefficient multiplied by the difference between the baseline temperature and the average temperature of the environment and the bath solution.

[0016] Furthermore, the temperature-time compensation coefficient is 1.5 seconds per degree Celsius, the reference reaction time is 55 seconds, and the reference temperature is 25 degrees Celsius.

[0017] Furthermore, the post-treatment process selected based on the alloy type in step four includes: a low-temperature drying curve containing trivalent chromium passivation sealing liquid for alloy 5052; a medium-temperature curing curve for alloy 3003; and a drying curve containing silane sealing liquid for alloy 6061.

[0018] Furthermore, in step five, the process parameters are adjusted based on the test results, including: if the film thickness is less than 5 micrometers, the spray pressure is increased by 0.03 MPa; if the spray pressure has reached the upper limit of 0.6 MPa, the reaction time is extended by 8 seconds; if the adhesion grade is less than 4B, the drying oven curing time is extended by 10 seconds and the sealing liquid concentration is increased by 1 gram per liter; if red rust appears in the salt spray test, the sealing soaking time is extended by 3 seconds and the sealing liquid pH value is increased by 0.2; if the Zn / P ratio is less than 3.0, the Zn²⁺ concentration in the phosphating solution is increased by 1 to 2 grams per liter and the phosphating solution pH value is decreased by 0.1.

[0019] Compared with the prior art, the present invention provides a method for controlling the preparation process of an inorganic coating layer on the surface of an aluminum plate, which has the following beneficial effects:

[0020] 1. In this solution, through the progressive design of "substrate multi-dimensional state diagnosis - pretreatment quantitative adjustment - dynamic parameter compensation", the core characteristics of the substrate (alloy type, thickness, surface roughness, degreasing residue) are first accurately identified. Then, sandblasting pretreatment or degreasing rework is performed in a targeted manner. Subsequently, the spraying pressure is dynamically adjusted based on the substrate thickness and the post-treatment curve is customized based on the alloy type to ensure that a uniform and dense zinc phosphate film can be formed on different substrates. This solves the problem of film quality fluctuation caused by insufficient substrate compatibility in existing technologies, realizes personalized adaptation of "one substrate, one process", and breaks through the application limitations of traditional fixed parameters.

[0021] 2. In this solution, the ambient temperature and humidity are monitored in real time, and the temperature, ion concentration, pH value and reaction time of the phosphating solution are adjusted accordingly. At the same time, in the post-treatment stage, the temperature of the drying zone, the temperature of the sealing solution and the soaking time are dynamically fine-tuned according to the ambient temperature. This forms a real-time linkage compensation mechanism of "environmental parameters - process parameters", which ensures that the phosphating reaction can proceed stably even under environmental fluctuations and that the crystallinity and density of the film layer meet the standards. This overcomes the shortcomings of existing technologies, such as strong dependence on the environment and poor process stability.

[0022] 3. In this solution, the PLC control system links all equipment and testing units throughout the process, collecting data such as film thickness, bath temperature, environmental parameters, and crystallinity in real time. Based on a preset algorithm, the spray pressure and reaction time are dynamically compensated. At the same time, the process parameters are finely adjusted in reverse by combining the offline test results of the first piece. The compensation accuracy is continuously improved through data accumulation and algorithm optimization, forming a closed-loop control system of "real-time monitoring - dynamic compensation - offline verification - cyclic optimization". This upgrades from "experience control" to "data-driven precision control", solving the problems of process loss of control and low product qualification rate in existing technologies.

[0023] 4. In this solution, based on the characteristics of film defects in different alloy substrates, a customized post-treatment curve is developed: for substrates with high porosity, a specific passivation sealing liquid is used to fill the pores; for substrates with dense film layers, the sealing process is simplified to improve efficiency; and for substrates with weak adhesion, a special sealing liquid is used to strengthen the interface bond, thereby achieving "targeted treatment of defects". This ensures that the corrosion resistance and adhesion of the film layer of aluminum plates for different applications can match the requirements of their application scenarios, breaking through the problem of insufficient performance adaptability caused by the "one-size-fits-all" approach to post-treatment in existing technologies. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the method steps of the present invention. Detailed Implementation

[0025] 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.

[0026] Please see Figure 1 A method for controlling the preparation process of an inorganic coating on an aluminum plate surface is proposed. This method achieves a closed-loop process encompassing "condition diagnosis – pre-adjustment – ​​dynamic compensation – post-processing control – effect verification," with all data linked through a PLC control system. The specific steps are as follows:

[0027] Step 1: Operating Condition Diagnosis and Initial Parameter Setting

[0028] This step provides precise input for the preparation of the inorganic capping layer and requires the completion of four key operations, with data transmitted to the PLC in real time to ensure zero deviation:

[0029] 1. Confirmation of substrate identity and surface condition

[0030] Industrial barcode scanners are used to read the factory markings on aluminum sheets and record key parameters.

[0031] Alloy types: 3003 (for household appliances, thermal conductivity 190W / (m·K)), 5052 (for building curtain walls, thermal conductivity 130W / (m·K)), 6061 (for automotive parts, thermal conductivity 160W / (m·K)).

[0032] Substrate thickness: 1-5mm (graded in 0.1mm increments), width 1000-2000mm (graded in 100mm increments).

[0033] Surface roughness: A laser roughness meter (accuracy ±0.01μm) was used to test at 3 points at the entrance end of the aluminum plate. The required surface roughness is Ra0.4~1.6μm (if it exceeds 1.6μm, subsequent sandblasting pretreatment is required).

[0034] Degreasing residue: The surface of the substrate is tested using an infrared oil meter (detection limit 0.1 mg / m²), and the residue should be ≤5 mg / m² (to avoid affecting the phosphating reaction).

[0035] 2. Environmental condition measurement

[0036] Temperature and humidity sensors with an accuracy of ±0.5℃ / ±2%RH were installed at three points (1.5m above the ground) in the upper left, center, and lower right corners of the phosphating workshop, away from the heat source / spray area. Data was collected every 10 seconds and the average value was taken. The ambient temperature was recorded as 5~40℃ and the relative humidity as 30%~70%RH.

[0037] 3. Initial parameter call

[0038] The PLC, based on a four-dimensional index of "alloy type - substrate thickness - surface roughness - ambient temperature", retrieves initial parameters from a pre-stored "inorganic coating process parameter library" (established through 1000 sets of orthogonal experiments), specifically including:

[0039] Key parameters of phosphating solution: Zn²⁺ concentration 8–12 g / L, NO₃⁻ (accelerator) concentration 3–5 g / L, pH value 2.5–3.0;

[0040] Reference reaction time: 55s (at an ambient temperature of 25℃);

[0041] Reference spray pressure: 0.35MPa (when the substrate thickness is 2mm);

[0042] Post-processing reference curves: three types of templates are used, including thick plates (≥3mm), thin plates (≤1mm), and medium-thick plates (1~3mm).

[0043] Step 2: Pretreatment and pre-adjustment of phosphating solution

[0044] This step, based on the diagnostic results, quantitatively adjusts the substrate surface pretreatment and phosphating solution state to ensure a stable phosphating reaction:

[0045] 1. Substrate surface pretreatment and adjustment

[0046] If the surface roughness Ra > 1.6 μm: start the automatic sandblasting device (white corundum abrasive particles, diameter 80-120 mesh, sandblasting pressure 0.3-0.4 MPa, sandblasting time 10-15 s), and re-measure Ra to 0.4-1.6 μm after treatment;

[0047] If the defatting residue is >5mg / m²: return to the defatting process (the defatting solution is an alkaline defatting agent, concentration 50-60g / L, temperature 50±2℃, soaking time 30s), and retest after rework.

[0048] 2. Phosphating solution state adjustment

[0049] The concentrations of Zn²⁺ and NO₃⁻ were monitored in real time using an online ion chromatograph (detection accuracy ±0.1 g / L), and the pH value of the phosphating solution was monitored using an online pH meter (accuracy ±0.01). Adjustments were made quantitatively based on ambient temperature.

[0050] When the ambient temperature is <15℃:

[0051] The temperature of the phosphating bath solution was raised to 45±2℃ using a titanium coil heating device (temperature control accuracy ±0.5℃);

[0052] Add 1-2 L of Zn²⁺ stock solution (concentration 50 g / L) every hour to maintain Zn²⁺ concentration at 10-12 g / L;

[0053] Add nitric acid (65% concentration) to adjust the pH to 2.5–2.8, extend the reaction time to 70 seconds, and ensure that the zinc phosphate film thickness reaches 6–8 μm;

[0054] When the ambient temperature is ≥15℃:

[0055] Maintain the phosphating bath temperature at 38±2℃, Zn²+ 8~10g / L, pH 2.8~3.0, and reaction time at 55s to avoid excessive film thickness and cracking.

[0056] Step 3: Dynamic parameter compensation for the phosphating process

[0057] This step utilizes precise equipment configuration and multi-parameter linkage compensation to achieve dynamic adaptation between substrate characteristics and ambient temperature, ensuring a uniform and dense zinc phosphate film.

[0058] (a) Equipment Configuration

[0059] 1. Phosphating Unit: Spray-type phosphating tank (304 stainless steel, 10m³ volume), core components:

[0060] Spray nozzles: fan-shaped nozzles (spray angle 60°, flow rate 15L / min), symmetrically arranged up and down along the tank with a spacing of 100mm to ensure full coverage of the substrate surface;

[0061] Spray pump: Variable frequency centrifugal pump (pressure range 0.2~0.6MPa, accuracy ±0.01MPa), connected to PLC to achieve real-time pressure adjustment;

[0062] Stirring system: Three built-in submersible stirrers (power 1.5kW, speed 300r / min) are evenly arranged along the bottom of the tank (spaced 2m apart) to ensure that the radial deviation of Zn²+ and NO3- concentrations in the tank solution is ≤0.5g / L, thus avoiding local reaction imbalance.

[0063] 2. Detection Unit:

[0064] Eddy current thickness gauge (range 0~50μm, accuracy ±0.1μm): installed 1m from the outlet of the phosphating tank, with the lens vertically aligned with the center of the aluminum plate, and collecting film thickness data every 0.3s.

[0065] Dual-channel infrared thermometer (resolution 640×512, temperature range -20~120℃): one channel measures ambient temperature and the other channel measures phosphating bath temperature, with data collected every 0.5s.

[0066] 3. Control Unit: PLC controller (model S7-1200) with built-in phosphating compensation algorithm, communicates with the equipment via industrial Ethernet, and the data transmission delay is ≤10ms.

[0067] (II) Specific Implementation Steps

[0068] 1. Spray pressure compensation related to substrate thickness

[0069] The laser thickness gauge collects the aluminum plate thickness every 0.1 seconds. After removing outliers with a deviation >0.05mm, the PLC takes the average of three measurements and calculates the target spray pressure using the following formula:

[0070]

[0071] In the formula, Target spray pressure (MPa); The reference pressure is 0.35 MPa, corresponding to the reference thickness. =2mm); The thickness-pressure compensation coefficient is 0.05 MPa / mm, fitted by 100 sets of experiments. The actual thickness of the aluminum plate (mm); The base thickness is 2mm.

[0072] Example: 5052 alloy thick plate ( =5mm) → =0.35+0.05×(5-2)=0.5MPa, increase the spraying pressure to ensure the phosphating solution penetrates to the substrate surface; 3003 alloy thin plate ( =1mm) → =0.35+0.05×(1-2)=0.3MPa, to avoid excessive corrosion of the substrate.

[0073] 2. Temperature-related reaction time compensation

[0074] The dual-channel infrared thermometer calculates the ambient and average bath temperature (fluctuation ≤ ±1℃), and the target reaction time is calculated using the following formula:

[0075]

[0076] In the formula, The target reaction time (s); The reference time corresponding to the reference temperature ( =55s), Reference temperature ( =25℃); The temperature-time compensation coefficient is 1.5 s / ℃, verified by 50 sets of experiments. The average temperature of the environment and the bath solution (°C).

[0077] Example: Summer high temperatures ( =35℃) → =55+1.5×(25-35)=40s, shortening the reaction time avoids a loose film layer; low temperature in winter ( =10℃) → =55+1.5×(25-10)=77.5s, to ensure a complete reaction.

[0078] 3. Closed-loop calibration of zinc phosphate film thickness

[0079] Preset film thickness range: thick plate (≥3mm) 6~8μm, thin plate (≤1mm) 5~7μm, medium-thick plate (1~3mm) 5.5~7.5μm;

[0080] Real-time calibration: If the eddy current thickness gauge detects a value below the lower limit for three consecutive times, the spray pressure will be increased by 0.02 MPa (maximum 0.6 MPa). If the value still does not meet the standard, the reaction time will be extended by 5 seconds. If the value is above the upper limit for three consecutive times, the spray pressure will be decreased by 0.02 MPa (minimum 0.2 MPa). If the value still does not meet the standard, the reaction time will be shortened by 5 seconds.

[0081] Parameter storage: The parameters "thickness-temperature-spray pressure-reaction time-film thickness" are stored in the database in association, and the deviation rate is ≤3% when the same working conditions are called next time.

[0082] Step 4: Post-processing control of inorganic coating layer

[0083] This step enhances the corrosion resistance and adhesion of the zinc phosphate film through segmented post-treatment equipment, differentiated curves, and environmental linkage.

[0084] (a) Equipment Configuration

[0085] 1. Post-processing unit: Three-stage hot air drying oven + sealing trough (total length 15m, suitable for conveyor speed 3~8m / min):

[0086] Drying oven (made of 304 stainless steel):

[0087] First temperature zone (preheating zone): 4m in length, equipped with two 20kW electric heating tubes (surface load 2W / cm²), and a hot air circulation fan (air volume 1500m³ / h, wind speed 1.8±0.3m / s).

[0088] Second temperature zone (curing zone): 6m in length, equipped with 3 20kW electric heating tubes, with the same fan configuration as the first temperature zone;

[0089] Third temperature zone (cooling zone): 3m in length, equipped with a cooling fan (air volume 2000m³ / h);

[0090] Sealing tank: 5m³ volume (304 stainless steel), with built-in Cr³+ passivation sealing solution (concentration 8-10g / L, pH 3.5-4.5) or silane sealing solution (concentration 5-6g / L, pH 4.0-4.5); equipped with a 5μm precision bag filter (flow rate 20m³ / h), the filter bag is replaced every 8 hours to ensure that the suspended solids in the sealing solution are ≤10mg / L, and to avoid particulate defects in the membrane layer.

[0091] 2. Detection Unit:

[0092] X-ray diffractometer (XRD, accuracy ±0.1°): installed 0.5m from the outlet of the drying oven, collecting the crystallinity of the zinc phosphate film every 1s (requirement ≥85%).

[0093] Embedded K-type thermocouple (0.5mm diameter, ±1℃ accuracy): embedded at the midpoint of the aluminum plate thickness to collect the core temperature of the substrate in real time;

[0094] 3. Control Unit: Shares the same PLC as in step 3, with a built-in PID temperature control algorithm (proportional coefficient). =2.5, integration time =80s, differential time =20s), the internal temperature difference of the temperature zone is ≤±2℃, and the temperature fluctuation is ≤±3℃.

[0095] (II) Specific Implementation Steps

[0096] 1. Differentiated post-processing curves based on substrate characteristics

[0097] 5052 alloy thick plate (film layer is easily porous): Low temperature drying + Cr³ + passivation sealing curve

[0098] (Because magnesium can easily lead to a high porosity of the phosphating film (about 8% to 12%), the Cr³+ passivation solution can fill the pores with Cr(OH)3 colloid, reducing the porosity to below 5%)

[0099] Drying oven: First temperature zone 120±5℃ (preheating 20s) → Second temperature zone 150±5℃ (curing 40s) → Third temperature zone 80±5℃ (cooling down 15s);

[0100] Sealing tank: Immerse in Cr³+ passivation solution at room temperature for 10 seconds, then remove and dry with cold air (wind speed 2m / s, time 10s).

[0101] 3003 alloy sheet (dense film): medium-temperature curing curve

[0102] (The membrane itself has low porosity (≤5%), so no additional sealing is required, and medium temperature can promote stable crystallization.)

[0103] Drying oven: First temperature zone 160±5℃ (preheating 15s) → Second temperature zone 180±5℃ (curing 30s) → Third temperature zone 70±5℃ (cooling down 10s);

[0104] 6061 alloy medium-thick plate (weak film adhesion): Drying + silane sealing curve

[0105] (Silicon easily forms a SiO2 isolation layer, reducing the compatibility between the phosphating film and subsequent coatings. Silane sealing solution can bridge the gap through Si-O bonds, improving the interfacial adhesion by more than 30%)

[0106] Drying oven: First temperature zone 140±5℃ (preheating 18s) → Second temperature zone 170±5℃ (curing 35s) → Third temperature zone 75±5℃ (cooling down 12s);

[0107] Sealing tank: Immerse in silane solution at 80±5℃ for 5s, then dry with hot air (temperature 100±5℃, time 15s).

[0108] 2. Adjustment of post-processing parameters related to ambient temperature

[0109] If the ambient temperature deviates from the reference 25℃ by more than ±5℃:

[0110] Ambient temperature < 20℃: Increase the temperature of each zone of the drying oven by 5℃, raise the temperature of the sealing liquid to 30±2℃ (use heating control to regulate temperature), and extend the soaking time by 2s;

[0111] Ambient temperature > 30℃: Reduce the temperature of each zone of the drying oven by 5℃, allow the sealing liquid to cool naturally, and shorten the soaking time by 1 second;

[0112] Crystallinity calibration: If the crystallinity detected by XRD is <85%, increase the temperature of the second temperature zone by 5℃ (maximum 200℃). If it still does not meet the standard, reduce the conveying speed by 0.5m / min (minimum 3m / min).

[0113] Step 5: Effect Verification and Parameter Fine-tuning

[0114] This step continuously improves the process accuracy of inorganic coatings through offline detection and closed-loop optimization:

[0115] 1. First Article Inspection: Offline inspection is performed on the first 5 meters of aluminum plates on the production line (one sample is taken every 1 meter, for a total of 5 samples), which must meet the following standards:

[0116] Film thickness: According to GB / T4956-2017 "Eddy current method for measuring the thickness of metallic coatings", 5 points were measured for each sample and the average value was taken, 5~8μm;

[0117] Adhesion: According to GB / T9286-1998 "Paints and Varnishes Cross-cut Test", using a 1mm pitch cross-cut tester + 3M 610 tape, ≥4B;

[0118] Corrosion resistance: According to GB / T10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", no red rust was observed after 48 hours of neutral salt spray.

[0119] Film composition: The Zn / P ratio in the zinc phosphate film was ≥3.0 (using X-ray fluorescence spectrometry (XRF, accuracy ±0.1%) to ensure that the film is in the Zn3(PO4)2·4H2O crystalline phase).

[0120] 2. Feedback, adjustments, and exception handling:

[0121] Establish a quantitative correspondence between test results and process parameters:

[0122] For films with a thickness of <5μm: increase the spray pressure by 0.03MPa (and extend the reaction time by 8s after reaching 0.6MPa).

[0123] Adhesion <4B: Extend the drying time in the second temperature zone of the drying oven by 10s (or increase the sealing liquid concentration by 1g / L).

[0124] Red rust appears in the salt spray test: extend the immersion time for sealing by 3 seconds (or increase the pH of the sealing solution by 0.2).

[0125] Zn / P ratio < 3.0: Increase the Zn²+ concentration of the phosphating solution by 1-2 g / L (or decrease the pH by 0.1).

[0126] Non-conforming handling procedure: If any one of the indicators fails to meet the standard in the first piece inspection, stop the machine immediately, retrieve the real-time parameters (spray pressure, reaction time, temperature curve) stored in the PLC, and locate the cause in combination with the XRD / XRF test results; after adjusting the parameters, produce 3 trial samples, and only when 3 consecutive samples pass all items can mass production be resumed.

[0127] 3. Iterative optimization: The "operating condition parameters (alloy, roughness, temperature) - process parameters (spray pressure, reaction time, post-treatment temperature) - test results (film thickness, corrosion resistance)" are associated and stored in the database. After accumulating 100 sets of data, the compensation coefficient is optimized through the random forest algorithm (e.g., the thickness-pressure coefficient is optimized from 0.05MPa / mm to 0.048MPa / mm), which improves the film thickness adaptation accuracy to within ±0.5μm, and the salt spray qualification rate is improved from 85% to 99%.

[0128] Finally, it should be noted that the above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for controlling the preparation process of an inorganic coating layer on the surface of an aluminum plate, characterized in that: Includes the following steps: Step 1: Operating Condition Diagnosis and Initial Parameter Setting: Collect the alloy type, thickness, surface roughness, and ambient temperature of the aluminum plate using industrial sensors; use the alloy type, thickness, surface roughness, and ambient temperature as composite query conditions to retrieve the initial chemical parameters, reference reaction time, and reference spraying pressure of the phosphating solution from the pre-stored process parameter library; Step 2, Pre-adjustment: Based on the surface roughness test results, the aluminum plate surfaces that do not meet the requirements are sandblasted or returned to the degreasing process; based on the ambient temperature test results, the temperature, zinc ion concentration and pH of the phosphating bath are adjusted. Step 3: Dynamic Parameter Compensation for the Phosphating Process: Based on the difference between the actual thickness of the aluminum plate and the reference thickness, the target spray pressure is calculated and adjusted using a pressure compensation model. The pressure compensation model is as follows: the target spray pressure equals the reference spray pressure plus a thickness pressure compensation coefficient multiplied by the difference between the actual thickness of the aluminum plate and the reference thickness. The thickness pressure compensation coefficient is 0.05 MPa per millimeter, the reference thickness is 2 millimeters, and the reference spray pressure is 0.35 MPa. Based on the difference between the average ambient and bath temperature and the reference temperature, the target reaction time is calculated and adjusted using a time compensation model. The time compensation model is as follows: the target reaction time equals the reference reaction time plus a temperature time compensation coefficient multiplied by the difference between the reference temperature and the average ambient and bath temperatures. The temperature time compensation coefficient is 1.5 seconds per degree Celsius, the reference reaction time is 55 seconds, and the reference temperature is 25 degrees Celsius. Closed-loop feedback control of the spray pressure and reaction time is achieved by real-time detection of the zinc phosphate film thickness. Step 4, Post-processing control: Select the corresponding drying temperature curve and sealing process based on the aluminum plate alloy type; monitor the crystallinity of the zinc phosphate film in real time, and calibrate the post-processing parameters based on the test results; Step 5: Effect Verification and Parameter Optimization: Test the film thickness, adhesion, and corrosion resistance of the treated aluminum plate samples; Adjust process parameters based on test results; The storage process parameters and test results are used to optimize the process parameters through machine learning algorithms. Among them, the process parameters are adjusted according to the test results, including: if the film thickness is less than 5 micrometers, the spray pressure is increased by 0.03 MPa; if the spray pressure has reached the upper limit of 0.6 MPa, the reaction time is extended by 8 seconds; if the adhesion grade is less than 4B, the drying oven curing time is extended by 10 seconds and the sealing solution concentration is increased by 1 g / L; if red rust appears in the salt spray test, the sealing immersion time is extended by 3 seconds and the sealing solution pH is increased by 0.2; if the Zn / P ratio is less than 3.0, the Zn²⁺ concentration in the phosphating solution is increased by 1 g / L to 2 g / L and the phosphating solution pH is decreased by 0.

1.

2. The method for controlling the preparation process of an inorganic coating layer on an aluminum plate according to claim 1, characterized in that: The initial chemical parameters mentioned in step one include: zinc ion concentration of 8 to 12 grams per liter, nitrate ion concentration of 3 to 5 grams per liter, and pH value of 2.5 to 3.

0.

3. The method for controlling the preparation process of an inorganic coating layer on an aluminum plate surface according to claim 1, characterized in that: Step four involves selecting post-treatment processes based on alloy type: for 5052 alloy, a low-temperature drying curve containing trivalent chromium passivation sealing solution is used; for 3003 alloy, a medium-temperature curing curve is used; and for 6061 alloy, a drying curve containing silane sealing solution is used.

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