An online oil film detection system for aluminum plate strip for automobiles and a working method thereof

Abstract

The application provides an online oil film detection system for an aluminum plate strip for a vehicle and a working method thereof, and comprises an online oil film detection unit, a process parameter monitoring unit, a hierarchical response control unit and an offline verification and calibration unit. Through calibration curves, monitoring process parameters, hierarchical determination and offline verification, the standardization of oil film detection is realized. The application has reasonable design and solves the problems of curve loss, operation misjudgment and parameter loss of control in the prior art. The detection accuracy is improved from 66.6% to more than 80%, the deviation is less than or equal to a preset comparison deviation threshold, the application is suitable for oil film quality control in large-scale production of vehicle plates, and the loss of customer returns is reduced.

Description

Technical Field

[0001] This invention relates to the field of surface quality testing technology for metallic materials, specifically to an online oil film detection system for automotive aluminum sheets and strips and its working method. Background Technology

[0002] Oiling aluminum sheets and strips for automobiles is a crucial process for ensuring subsequent stamping performance and preventing rust during transportation and storage. The oil film thickness must be precisely controlled within a predetermined acceptable range. Current industry testing technologies suffer from the following key challenges: Low detection accuracy: Online detection equipment relies on preset standard curves to indirectly measure oil film thickness. Due to incomplete curve library coverage (lack of curves for specific products), the online detection accuracy of a certain product in 2024 was only 31.7%. The deviation from offline detection results often exceeded the preset comparison deviation threshold, leading to customer complaints and returns. Moreover, the risk of operational misjudgment is high, and operators are easily confused. Process interference factors are not controlled, resulting in uneven oil film adhesion and even exacerbating the volatility of detection results. After shutdown and restart, the rate of abnormally high local detection values ​​exceeds 30%, and the judgment criteria are lacking. The lack of a graded response mechanism and excessive rework (such as rework of 3-8 spot-like omissions) result in the accuracy of rework roll detection results being less than 50%, and it is impossible to distinguish between "releaseable fluctuations" and "defects requiring rectification", causing resource waste and quality risks. Summary of the Invention

[0003] In view of this, the purpose of this invention is to overcome the shortcomings of the prior art and provide an online oil film detection system and its working method for automotive aluminum sheet and strip. This system is suitable for detecting the oil film thickness of automotive aluminum sheet and strip after oiling during cold rolling and finishing processes. By optimizing the detection system configuration, standardizing process parameters and judgment criteria, it solves the problems of low accuracy and large fluctuations in existing online oil film detection, achieving consistency between the detection results and customer verification, achieving a detection accuracy rate of ≥80%, ensuring that the deviation between the online detection results and the offline weighing method is ≤ a preset comparison deviation threshold, and reducing customer complaint rates and rework losses.

[0004] This invention is implemented using the following solution: an online oil film detection system for automotive aluminum sheet strips, comprising: The online oil film detection unit is used to collect oil film thickness data of aluminum plates and strips in real time, construct real-time oil film thickness curves, and provide standard thickness curve matching. The process parameter monitoring unit is used to collect data on pickling bath concentration, strip temperature, and production speed in real time. The graded response control unit is used to visualize the data collected by the online oil film detection unit and the process parameter monitoring unit in real time, and to determine the grade of aluminum strip based on the real-time collected oil film thickness data of aluminum strip, and to collect abnormal data from the online oil film detection unit and the process parameter monitoring unit and issue real-time alarms. The offline verification and calibration unit is used to periodically calibrate online test results, forming an online-offline comparison closed loop.

[0005] Furthermore, the online oil film detection unit includes: Online oil film detection module: calculates oil film thickness by exciting the fluorescence signal intensity of the oil coating layer, ensuring continuous detection under high-speed rolling; Standard curve management module: Preset exclusive curves, collect data in real time and perform triple matching and comparison based on product model, surface type and width specification to avoid curve confusion. At the same time, according to the process parameter monitoring unit, collect data in real time, perform pickling process and temperature compensation, optimize curves, adjust test results and reduce the impact of process interference.

[0006] Furthermore, the process parameter monitoring unit includes: The online fluoride ion detection module can detect the concentration of the pickling solution in the pickling tank in real time and link it with the dosing system. It can automatically add the solution according to the preset algorithm to ensure that the concentration of the solution is stable within the preset range and avoid uneven oil film adhesion due to insufficient pickling. Strip temperature detection module: Real-time detection of strip and linkage with graded response control unit. Graded response control unit collects the inspection data transmitted by strip temperature detection unit, responds to alarm, and prevents oil film evaporation caused by excessive temperature. Speed ​​detection module: Real-time acquisition of production speed is linked with the graded response control unit. The graded response control unit collects the real-time production speed and monitors speed fluctuations. It responds to speed fluctuations that exceed the preset range to avoid abnormal oil application caused by speed fluctuations.

[0007] Furthermore, the hierarchical response control unit includes: Grading display module: Receives data collected by the online oil film detection unit and process parameter monitoring unit, matches and grades the data, and displays it in real time; Alarm Module: (I) Parameter Alarm: Preset process parameters, alarms are triggered when data collected by the process parameter monitoring unit deviates from the preset process parameters; (II) Detection Alarm: Preset detection data, alarms are triggered when thickness data collected by the line oil film detection unit deviates from the preset detection data. Data storage and traceability module: Stores alarm information and data collected by the online oil film detection unit and process parameter monitoring unit.

[0008] Furthermore, the offline verification and calibration unit includes: an offline oil film detection module: sampling and detecting the strip head and strip surface and comparing the results with the display results of the graded response control unit; and a weighing verification module: if the deviation between the offline oil film detection module and the display results of the graded response control unit exceeds a preset deviation range, the weighing verification module is used to recalibrate the online curve, adjust the compensation coefficient, and form a calibration closed loop.

[0009] A method for operating an online oil film detection system for automotive aluminum sheet strips includes the following steps: Step S1: System calibration and curve configuration: Regularly use the weighing calibration module to calibrate the online oil film detection module and the offline oil film detection module, adjust the curve compensation coefficient, and select the matching curve in the standard curve management system according to the product model, surface type and width specification of the automotive sheet to be tested. Step S2: Process parameter preset and monitoring: preset the fluoride ion concentration of the pickling tank solution, strip temperature, and production speed. At the same time, the graded response control unit collects and displays the data collected by the process parameter monitoring unit in real time, and triggers an alarm for real-time data of process parameters exceeding the preset values. Step S3: Online detection and grading determination: The grading response control unit collects the oil film thickness data collected in real time by the online oil film detection module, and grades it according to the oil film thickness, fluctuation range, number of fluctuation ranges, and fluctuation length, and performs corresponding policy responses according to different grades; Step S4: Offline verification and data archiving: Samples are taken from the strip head and strip and compared with the display results of the graded response control unit. If the deviation deviates from the preset range, the online curve of the online oil film detection module and the offline oil film detection module are recalibrated using the weighing calibration module, and the detection data is archived at the same time.

[0010] Furthermore, the classification and response methods are as follows: Grade A: The oil film thickness meets the preset acceptable range, the fluctuation range is less than the preset acceptable range threshold, there is no missed coating / shutdown, and it is deemed qualified. Grade B: The oil film thickness meets the preset acceptable range, and one unidirectional fluctuation range is within the preset release range and the fluctuation length is less than the preset release length threshold. The review and approval are then carried out. Grade C: The oil film thickness is within the preset rework thickness range, or there are two or more fluctuation ranges that are greater than the preset qualified range threshold, and rework is determined. Grade D: The oil film thickness exceeds the preset acceptable thickness range, or there is missed coating / machine speed reduction, which is deemed unqualified.

[0011] Furthermore, when sampling and testing the strip head and strip, and comparing the results with the display results of the graded response control unit, the preset deviation range is a preset comparison deviation threshold. If the comparison deviation between the sampling and testing and the display results of the graded response control unit is greater than the preset comparison deviation threshold, the online curve is recalibrated.

[0012] Furthermore, the weighing verification method of the weighing verification module is as follows: sample and weigh to obtain mass m1, degrease the sample and weigh to obtain mass m2, calculate the actual average oil film thickness on the sample surface according to oil film thickness = (m1-m2) / sampling area, calibrate the online curve based on the calculated average oil film thickness, and adjust the compensation coefficient and offline oil film detection module.

[0013] Furthermore, in step S3, if a shutdown and restart occurs, the frequency of inspection for the pre-set length of strip needs to be increased after the restart, and the uniformity of the oil coating on the board surface needs to be manually checked to prevent excessive local oil film thickness; in step S4, after the rework roll is processed, steps S2-S3 need to be repeated until the inspection result is grade A or grade B.

[0014] Compared with existing technologies, this invention has the following advantages: It features a rational design that constructs an integrated system of "precise curve matching - real-time process control - hierarchical intelligent response - offline closed-loop calibration." Through multi-module collaborative optimization, it solves problems such as missing curves, operational misjudgments, and process interference. Through standardized processes and hierarchical judgment, it achieves a detection accuracy rate of ≥80%, ensuring that the deviation between online detection results and offline weighing methods is ≤ a preset comparison deviation threshold. This reduces customer complaint rates and rework losses, overcomes the limitations of traditional online oil film detection, and achieves a dual improvement in accuracy and stability. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the online oil film detection system for automotive aluminum sheet and strip of the present invention. Figure 2 This is a schematic diagram of the system flow for the online oil film detection system for aluminum sheet and strip used in automobiles according to the present invention. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0018] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, or combinations thereof.

[0019] like Figure 1-2As shown, an online oil film detection system for automotive aluminum sheet / strip includes: The online oil film detection unit is used to collect oil film thickness data of aluminum plates and strips in real time, construct real-time oil film thickness curves, and provide standard thickness curve matching. The process parameter monitoring unit is used to collect data on pickling bath concentration, strip temperature, and production speed in real time. The graded response control unit is used to visualize the data collected by the online oil film detection unit and the process parameter monitoring unit in real time, and to determine the grade of aluminum strip based on the real-time collected oil film thickness data of aluminum strip, and to collect abnormal data from the online oil film detection unit and the process parameter monitoring unit and issue real-time alarms. The offline verification and calibration unit is used to periodically calibrate online test results, forming an online-offline comparison closed loop.

[0020] In this embodiment, the online oil film detection unit includes: The online oil film detection module can use an EMG online oil film detector: the oil film thickness is calculated by exciting the fluorescence signal intensity of the oil coating layer, ensuring the continuity of detection under high-speed rolling. Specifically, the oil film thickness is calculated by exciting the fluorescence signal intensity of the oil coating layer, and the sampling frequency meets the preset detection frequency requirements to ensure the continuity of detection under high-speed rolling. Standard Curve Management Module: Pre-sets exclusive curves and performs real-time triple matching and comparison based on product model, surface type, and width specification to avoid curve confusion. Simultaneously, it collects data in real time from the process parameter monitoring unit to compensate for pickling process and temperature parameters, i.e., adjusts the constant term in the photon number-oil quantity conversion formula, optimizes the curve, adjusts the test results, and reduces the impact of process interference. Specifically: Based on previous research data, multiple sets of exclusive curves are pre-stored. When selecting a curve, a pop-up window displays the triple matching information of "product model-surface type-specification". The operator must confirm before entering the test interface, achieving a 100% error prevention rate and solving the curve confusion problem in traditional operations.

[0021] In this embodiment, the data recording method of the online oil film detection module is as follows: record one average value at a preset interval, automatically calculate the average number of photons according to the roll length, and call the current standard curve to convert it into an oil coating amount value.

[0022] In this embodiment, the process parameter monitoring unit includes: Fluoride ion online detection module: Real-time detection of the concentration of the pickling solution in the pickling tank and linkage with the dosing system. Automatic addition of solution according to a preset algorithm ensures that the concentration of the solution remains stable within the preset range, avoiding uneven oil film adhesion due to insufficient pickling. Specifically: The fluoride ion online detection module is installed on the outlet pipe of the pickling tank to detect the concentration of the solution in real time. The data update frequency meets the preset data update requirements. When the concentration is lower than the preset lower limit, the linkage with the dosing system automatically adds fluoride solution to ensure that the concentration remains stable within the preset concentration range, avoiding uneven oil film adhesion due to insufficient pickling. Strip temperature detection module: Real-time detection of strip and linkage with graded response control unit. Graded response control unit collects the inspection data transmitted by strip temperature detection unit, responds with alarm, and prevents oil film evaporation due to excessive temperature. Specifically, the strip temperature detection module is installed at the inlet of the oiling machine. When the temperature exceeds the preset upper limit, the graded response unit triggers an alarm to prompt adjustment of the cooling system to prevent oil film evaporation due to excessive temperature. Speed ​​detection module: Real-time acquisition of production speed is linked with the graded response control unit. The graded response control unit collects the real-time production speed and monitors speed fluctuations. It responds to speed fluctuations that exceed the preset range to avoid abnormal oiling amount caused by speed fluctuations. Specifically, the speed detection module is installed on the exit pinch roller to collect the production speed in real time. When the speed fluctuation exceeds the preset speed fluctuation range, the system pushes adjustment suggestions to avoid abnormal oiling amount caused by speed fluctuations. Practical verification shows that after the speed stabilizes, the fluctuation of the detection results meets the preset fluctuation control requirements.

[0023] In this embodiment, the hierarchical response control unit includes: The grading display module receives data collected by the online oil film detection unit and the process parameter monitoring unit, matches and grades the data, and displays it in real time. It displays the data transmitted from the online oil film detection unit in real time, and displays the real-time oil film detection curve with strip length as the horizontal axis and oil film thickness as the vertical axis. Operators can intuitively view the detection status of each roll of product. Alarm Module: (I) Parameter Alarm: Preset process parameters, alarms are triggered when data collected by the process parameter monitoring unit deviates from the preset process parameters, namely fluoride ion concentration, strip temperature, and production speed; (II) Detection Alarm: Preset detection data, alarms are triggered when thickness data collected by the line oil film detection unit deviates from the preset detection data; Data storage and traceability module: Stores alarm information and data collected by the online oil film detection unit and process parameter monitoring unit. Operators can view detection time, curve type, process parameters, grading results and offline verification values, which facilitates quality traceability and problem analysis.

[0024] In this embodiment, the offline verification and calibration unit includes: The offline oil film detection module can use a handheld oil film analyzer NG2 to sample and test the strip head and middle, and compare the results with the display results of the graded response control unit; Weighing calibration module: If the deviation between the display results of the offline oil film detection module and the graded response control unit exceeds the preset deviation range, the online curve is recalibrated and the compensation coefficient is adjusted through the weighing calibration module to form a calibration closed loop. Specifically: sampling locations are one at the head and one at the middle of the strip, and the sampling area meets the preset sampling area requirements. After testing, the results are compared with the online results. If the deviation is greater than the preset comparison deviation threshold, the online curve is recalibrated using the weighing verification module by weighing (the sampling area meets the weighing sampling area requirements, and the material is dried to constant weight before weighing). The compensation coefficient is adjusted to ensure that the "online-offline" deviation meets the preset deviation control requirements, thus forming a calibration closed loop.

[0025] A method for operating an online oil film detection system for automotive aluminum sheet strips includes the following steps: Step S1: System Calibration and Curve Configuration: Regularly calibrate the online oil film detection module and the offline oil film detection module using the weighing calibration module, and adjust the curve compensation coefficient. At the same time, select the matching curve in the standard curve management system according to the product model, surface type, and width specification of the automotive sheet to be tested. If the operator selects the wrong curve, the system will forcibly correct the operation error. Specifically: regularly take multiple sets of standard samples with different thickness specifications, test each sample multiple times, calculate the deviation between the average value and the standard value, and if the deviation exceeds the preset calibration deviation threshold, adjust the curve compensation coefficient. Step S2: Process parameter preset and monitoring: The fluoride ion concentration of the pickling tank solution, strip temperature, and production speed are preset. At the same time, the graded response control unit collects and displays the data collected by the process parameter monitoring unit in real time. Real-time data that exceeds the preset values ​​of process parameters triggers an alarm. Specifically: the fluoride ion concentration of the pickling tank solution is preset to a preset concentration range, the strip temperature is controlled within a preset temperature range, and the production speed is preset to a corresponding speed range according to different thickness specifications. When the fluoride ion concentration, temperature, or speed exceeds the corresponding preset range, the graded response control unit triggers an alarm. According to statistics, the process abnormality rate after parameter monitoring meets the preset abnormality rate control requirements. Step S3: Online detection and grading determination: The grading response control unit collects the oil film thickness data collected in real time by the online oil film detection module, and grades it according to the oil film thickness, fluctuation range, number of fluctuation ranges, and fluctuation length, and performs corresponding policy responses according to different grades; Step S4: Offline Verification and Data Archiving: Samples are taken from the head and middle of the strip and compared with the display results of the graded response control unit. If the deviation deviates from the preset range, the online curve of the online oil film detection module and the offline oil film detection module are recalibrated using the weighing calibration module. At the same time, the test data is archived. Specifically, one sample is taken from each roll of product at the preset positions at the head and middle (the area meets the preset sampling area requirements). The sample is then tested by the offline oil film detection module. If the deviation between the online and offline results meets the requirements, the verification is completed. If the deviation exceeds the preset comparison deviation threshold, step S1 is repeated to calibrate the curve.

[0026] In this embodiment, the grading and response method is as follows: Grade A: The oil film thickness meets the preset acceptable range, the fluctuation range is less than the preset acceptable range threshold, there is no missed coating / shutdown, and it is deemed qualified; Grade B: The oil film thickness meets the preset acceptable range, and one unidirectional fluctuation range is within the preset release range and the fluctuation length is less than the preset release length threshold. The review and approval are then carried out. Grade C: The oil film thickness is within the preset rework thickness range, or there are two or more fluctuation ranges that are greater than the preset qualified range threshold, and rework is determined. Grade D: The oil film thickness exceeds the preset acceptable thickness range, or there is missed coating / stoppage and speed reduction, which is deemed unacceptable; Specifically: if the fluctuation range of the test value of a certain roll of product meets the preset acceptable range threshold, it is judged as Grade A; if the oil film thickness fluctuation of a certain roll of product is within the preset release range and the fluctuation length meets the requirements, it is judged as Grade B, and the system will automatically push the corresponding prompt to avoid excessive rework; if there is missed coating, it is judged as Grade D, triggering an emergency shutdown to prevent unacceptable products from flowing downstream.

[0027] In this embodiment, when sampling and testing the strip head and the strip itself and comparing the results with the display results of the graded response control unit, the preset deviation range is a preset comparison deviation threshold. If the comparison deviation between the sampling and testing results and the display results of the graded response control unit is greater than the preset comparison deviation threshold, the online curve is recalibrated.

[0028] In this embodiment, the weighing verification method of the weighing verification module is as follows: sample and weigh to obtain mass m1, degrease the sample and weigh to obtain mass m2, calculate the actual average oil film thickness on the sample surface according to oil film thickness = (m1-m2) / sampling area, calibrate the online curve based on the calculated average oil film thickness, and adjust the compensation coefficient and offline oil film detection module.

[0029] In this embodiment, in step S3, if a shutdown and restart occurs, the frequency of inspection of the strip of the preset length needs to be increased after the restart, and the uniformity of the oil coating on the board surface needs to be manually checked to prevent the local oil film from being too thick; in step S4, after the rework roll is processed, steps S2-S3 need to be repeated until the inspection result is grade A or grade B.

[0030] Unless otherwise stated, if any of the technical solutions disclosed in this invention specify a numerical range, then the disclosed numerical range is a preferred numerical range. Anyone skilled in the art should understand that the preferred numerical range is merely one among many feasible numerical values ​​that has a more obvious or representative technical effect. Because there are many numerical values, it is impossible to list them all. Therefore, this invention discloses only some numerical values ​​to illustrate the technical solutions of this invention. Furthermore, the numerical values ​​listed above should not constitute a limitation on the scope of protection of this invention.

[0031] If the terms "first" or "second" are used in this document to specify components, those skilled in the art should know that the use of "first" or "second" is merely for the purpose of distinguishing components in description, and unless otherwise stated, the above terms have no special meaning.

[0032] If this invention discloses or relates to mutually fixedly connected components or structural parts, then, unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws), or a non-detachable fixed connection (e.g., riveting, welding). Of course, mutually fixed connections can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0033] Furthermore, the orientations or positional relationships used in any of the technical solutions disclosed in this invention above to indicate positional relationships, such as "longitudinal," "lateral," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing this patent. They are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this patent. In addition, unless otherwise stated, the terms used to indicate shape in any of the technical solutions disclosed in this invention above include shapes that are similar to, close to, or approximate with it.

[0034] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. An online oil film detection system for automotive aluminum sheet and strip, characterized in that: include: Online oil film detection unit: used to collect oil film thickness data of aluminum sheet and strip in real time, construct real-time oil film thickness curve and provide standard thickness curve matching; Process parameter monitoring unit: used to collect real-time data on pickling bath concentration, strip temperature, and production speed; Graded response control unit: Used to visualize the data collected by the online oil film detection unit and process parameter monitoring unit in real time, and to determine the grade of aluminum strip based on the real-time collected oil film thickness data of aluminum strip, and to collect abnormal data from the online oil film detection unit and process parameter monitoring unit and issue real-time alarms; Offline verification and calibration unit: used to periodically calibrate online test results, forming an online-offline comparison closed loop; The online oil film detection unit includes: Online oil film detection module: calculates oil film thickness by exciting the fluorescence signal intensity of the oil coating layer, ensuring continuous detection under high-speed rolling; Standard curve management module: Preset exclusive curves, collect data in real time and perform triple matching and comparison based on product model, surface type and width specification to avoid curve confusion. At the same time, according to the process parameter monitoring unit, collect data in real time, perform pickling process and temperature compensation, optimize curves, adjust test results and reduce the impact of process interference. The process parameter monitoring unit includes: The online fluoride ion detection module can detect the concentration of the pickling solution in the pickling tank in real time and link it with the dosing system. It can automatically add the solution according to the preset algorithm to ensure that the concentration of the solution is stable within the preset range and avoid uneven oil film adhesion due to insufficient pickling. Strip temperature detection module: Real-time detection of strip and linkage with graded response control unit. Graded response control unit collects the inspection data transmitted by strip temperature detection unit, responds to alarm, and prevents oil film evaporation caused by excessive temperature. Speed ​​detection module: Real-time acquisition of production speed is linked with the graded response control unit. The graded response control unit collects the real-time production speed and monitors speed fluctuations. It responds to speed fluctuations that exceed the preset range to avoid abnormal oil application caused by speed fluctuations.

2. The detection system according to claim 1, characterized in that: The hierarchical response control unit includes: Grading display module: Receives data collected by the online oil film detection unit and process parameter monitoring unit, matches and grades the data, and displays it in real time; Alarm Module: (I) Parameter Alarm: Preset process parameters, alarms are triggered when data collected by the process parameter monitoring unit deviates from the preset process parameters; (II) Detection Alarm: Preset detection data, alarms are triggered when thickness data collected by the line oil film detection unit deviates from the preset detection data. Data storage and traceability module: Stores alarm information and data collected by the online oil film detection unit and process parameter monitoring unit.

3. The detection system according to claim 2, characterized in that: The offline verification and calibration unit includes: Offline oil film detection module: Samples are taken from the strip head and the strip surface for detection and compared with the display results of the graded response control unit; Weighing calibration module: If the deviation between the display results of the offline oil film detection module and the graded response control unit exceeds the preset deviation range, the online curve is recalibrated and the compensation coefficient is adjusted through the weighing calibration module to form a calibration closed loop.

4. A method for operating an online oil film detection system for automotive aluminum sheet strips, employing the detection system as described in claim 3, characterized in that: Includes the following steps: Step S1: System calibration and curve configuration: Regularly use the weighing calibration module to calibrate the online oil film detection module and the offline oil film detection module, adjust the curve compensation coefficient, and select the matching curve in the standard curve management system according to the product model, surface type and width specification of the automotive sheet to be tested. Step S2: Process parameter preset and monitoring: preset the fluoride ion concentration of the pickling tank solution, strip temperature, and production speed. At the same time, the graded response control unit collects and displays the data collected by the process parameter monitoring unit in real time, and triggers an alarm for real-time data of process parameters exceeding the preset values. Step S3: Online detection and grading determination: The grading response control unit collects the oil film thickness data collected in real time by the online oil film detection module, and grades it according to the oil film thickness, fluctuation range, number of fluctuation ranges, and fluctuation length, and performs corresponding policy responses according to different grades; Step S4: Offline verification and data archiving: Samples are taken from the strip head and strip and compared with the display results of the graded response control unit. If the deviation deviates from the preset range, the online curve of the online oil film detection module and the offline oil film detection module are recalibrated using the weighing calibration module, and the detection data is archived at the same time.

5. The working method according to claim 4, characterized in that: The classification and response methods are as follows: Grade A: The oil film thickness meets the preset acceptable range, the fluctuation range is less than the preset acceptable range threshold, there is no missed coating / shutdown, and it is deemed qualified. Grade B: The oil film thickness meets the preset acceptable range, and one unidirectional fluctuation range is within the preset release range and the fluctuation length is less than the preset release length threshold. The review and approval are then carried out. Grade C: The oil film thickness is within the preset rework thickness range, or there are two or more fluctuation ranges that are greater than the preset qualified range threshold, and rework is determined. Grade D: The oil film thickness exceeds the preset acceptable thickness range, or there is missed coating / machine speed reduction, which is deemed unqualified.

6. The working method according to claim 4, characterized in that: When sampling and testing the strip head and strip, and comparing the results with the display results of the graded response control unit, the preset deviation range is a preset comparison deviation threshold. If the comparison deviation between the sampling and testing results and the display results of the graded response control unit is greater than the preset comparison deviation threshold, the online curve is recalibrated.

7. The working method according to claim 4, characterized in that: The weighing verification method of the weighing verification module is as follows: take a sample and weigh it to obtain the mass m1, degrease the sample and weigh it to obtain the mass m2, calculate the actual average oil film thickness on the sample surface according to the oil film thickness = (m1-m2) / sampling area, calibrate the online curve based on the calculated average oil film thickness, and adjust the compensation coefficient and the offline oil film detection module.

8. The working method according to claim 4, characterized in that: In step S3, if a shutdown and restart occurs, the frequency of inspection for the pre-set length of strip needs to be increased after the restart, and the uniformity of the oil coating on the board surface needs to be manually checked to prevent the local oil film from being too thick. In step S4, after the reworked roll is processed, steps S2-S3 need to be repeated until the inspection result is grade A or grade B.

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