Method for controlling surface color difference defects of cold-rolled steel sheet

Abstract

The application discloses a cold-rolled steel plate surface color difference defect control method, and relates to the related field of cold-rolled steel plate processing.The cold-rolled steel plate surface color difference control method has the advantages that the online spectrum color difference detection is combined with the annealing furnace exhaust odor characteristic monitoring, the double-dimension judgment of the annealing process atmosphere state and the surface oxidation film change is realized, compared with the traditional mode of only relying on the color difference result for after-regulation, the method is more real-time and predictive, the system can identify the atmosphere abnormal trend in advance through the odor characteristic change before the color difference has obvious deviation, and the compensation adjustment of the hydrogen proportion, the dew point and the furnace temperature is automatically executed, so that the generation of the color difference defect is effectively prevented; when the color difference and the odor signal are synchronously abnormal, the system can also quickly respond and recover to the stable interval, the color difference control precision is greatly improved, the method can significantly improve the consistency of the steel plate surface brightness and color, improve the color difference qualified rate and reduce the product waste caused by the annealing abnormality.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cold-rolled steel sheet processing, in particular to a cold-rolled steel sheet surface color difference defect control method. BACKGROUND

[0002] Chinese patent publication No. CN113522971B discloses a method for controlling the surface color difference of engineering machinery steel, which specifically comprises the following steps: (1) adjusting the heating section and soaking section temperature of the engineering machinery steel according to the thickness of the steel plate, controlling the heating section at about 1230-1240℃, and controlling the heating time at 198-330min. If the heating time of the billet in the furnace exceeds the control node 230min, the temperature should be reduced by 5℃ for every 10min extension, and the heating time should not exceed the upper limit value 330min. The heating section temperature should not be lower than 1230℃. The soaking section is controlled at 1210-1230℃. (2) pressing the engineering machinery steel according to its thickness. The present application can effectively control the surface color difference of the steel plate, solve the surface defects such as regular strip rust on the surface of the steel plate after offline and "water ripple" similar pitted surface after shot blasting, and improve the surface appearance of the engineering machinery steel.

[0003] Compared with the color difference control of hot-rolled steel plates through temperature control, color difference defects are prone to occur on the surface of cold-rolled steel plates during continuous annealing, mainly manifested as uneven brightness, color bands, local darkening or local brightening, etc. Such defects not only affect the apparent quality of the steel plate and the customer's acceptance, but also may lead to instability of subsequent coating, hot dipping or cold working performance. At present, defects are mainly found through online color difference detection or manual visual inspection during production, and process parameters such as annealing furnace temperature, atmosphere composition or strip speed are adjusted after the problem is found. However, the existing method has obvious hysteresis: color difference defects are often found after they form on the surface of the steel plate, and the adjustment measures are difficult to completely eliminate the defects, resulting in high scrap rate and increased production cost. In addition, the existing annealing furnace atmosphere control mainly relies on the macroscopic control of oxygen content, temperature and humidity parameters, lacks real-time monitoring of the change of volatile substances in the chemical reaction in the furnace, and it is difficult to accurately judge the generation state of the oxidation film and the potential risk of color difference defects. SUMMARY

[0004] Therefore, in order to solve the above problems, the present application provides a cold-rolled steel plate surface color difference defect control method.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme: a cold-rolled steel plate surface color difference defect control method, the specific steps are as follows:

[0006] S1 reference collection: after the cold-rolled steel plate is cleaned, degreased and dried, the initial brightness value and reference color coordinates of the steel plate surface are collected by an online spectral brightness detection device;

[0007] S2 annealing atmosphere control: the steel plate is sent into a continuous annealing furnace, the proportion of hydrogen and nitrogen in the annealing atmosphere, the furnace temperature curve and the dew point parameters are controlled, the surface oxide film of the steel plate is stably formed, and the atmosphere parameters in the furnace are collected in real time;

[0008] S3 surface color difference detection: after annealing, the brightness, color difference deviation value and local color spots of the full-width area of the steel plate are measured by using an online color difference detection system, and when any index exceeds the preset threshold value, an abnormal alarm is triggered;

[0009] S4 odor monitoring data fusion determination: the odor characteristics of the exhaust gas of the annealing furnace are collected in real time by the odor monitoring device, and the atmosphere deviation determination signal is formed by matching analysis with the standard odor model;

[0010] S5 process automatic control: the color difference detection signal and the odor determination signal are input into the process control system, when any signal reaches the determination condition, the hydrogen proportion, the dew point and the furnace temperature compensation parameters are automatically adjusted, so that the surface color difference of the steel plate is maintained within the allowable range.

[0011] Preferably, the color difference detection system is an online spectral color difference detection system, which detects the full-width area of the steel plate and supports surface partition data output.

[0012] Preferably, the odor monitoring device is used for continuous sampling of the exhaust gas of the annealing furnace, and the abnormal trend of the atmosphere is predicted in advance through the change of the odor characteristics, and the odor monitoring device comprises:

[0013] A gas collection module for online collection of gas samples from the exhaust port of the continuous annealing furnace;

[0014] An odor sensing module comprising at least one electronic nose array sensor for identifying changes in volatile gas components containing hydrocarbons, sulfur or nitrogen;

[0015] An odor characteristic analysis module for extracting odor fingerprints and comparing with database standard odor models;

[0016] An abnormality determination module for determining the oxidation film formation deviation trend according to the preset threshold value and outputting an abnormal signal;

[0017] A feedback control module for feeding back the abnormal signal to the process control system to perform annealing atmosphere adjustment operation.

[0018] 4、Preferably, the process control system comprises:

[0019] A data acquisition module for receiving the brightness data, color difference deviation and surface defect position signal output by the online color difference detection system, and simultaneously receiving the odor characteristic parameters and atmosphere deviation determination signal output by the odor monitoring device;

[0020] a data fusion analysis module for time series fusion, trend matching analysis and abnormal type identification of the color difference detection data and the odor monitoring data, and generating corresponding process adjustment instruction parameters according to the deviation level;

[0021] a process parameter calculation module for automatically calculating the hydrogen proportion adjustment amount, the dew point adjustment compensation value, the furnace temperature fine adjustment range and the protective gas flow adjustment amount according to the fusion analysis result;

[0022] an execution control module for issuing the adjustment instructions generated by the process parameter calculation module to the atmosphere control system, the dew point adjustment device and the temperature control system of the continuous annealing furnace, so as to perform hydrogen / nitrogen proportion adjustment, furnace temperature compensation and furnace zone pressure fine adjustment operation;

[0023] a feedback monitoring module for continuously monitoring the color difference recovery trend, the oxidation film formation stability and the furnace atmosphere change after process adjustment, and performing secondary compensation or maintaining steady state control on the adjustment parameters according to the feedback result.

[0024] The beneficial effects of the present application are as follows:

[0025] The cold-rolled steel plate surface color difference control method provided by the present application realizes double-dimensional judgment of the annealing process atmosphere state and the surface oxidation film change by combining online spectral color difference detection with annealing furnace discharge odor characteristic monitoring, which is more real-time and predictive than the traditional post-adjustment method relying only on color difference results. The system can identify the abnormal trend of the atmosphere in advance through the change of the odor characteristics before the color difference deviates significantly, and automatically perform compensation adjustment of the hydrogen proportion, dew point and furnace temperature to effectively prevent the generation of color difference defects. When the color difference and odor signal are abnormal at the same time, the system can also quickly respond and recover to the stable interval, greatly improving the color difference control precision. The method can significantly improve the consistency of the brightness and color of the steel plate surface, improve the color difference qualified rate, and reduce the product waste caused by annealing abnormalities. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a process schematic diagram of the present application. DETAILED DESCRIPTION

[0027] In order to further explain the technical scheme of the present application, the following specific embodiments are described in detail.

[0028] The present application provides a cold-rolled steel plate surface color difference defect control method, the steps are as follows:

[0029] Before the steel plate enters the continuous annealing process, the surface of the steel plate is first cleaned, degreased and dried to ensure that the subsequent optical detection signal is not affected by oil stains, water film and surface residual particles. The treated steel plate passes under the online spectral brightness detection equipment arranged at the inlet section. The equipment uses multi-band spectral acquisition technology to detect the brightness value and chroma coordinates of the current surface of the steel plate in real time. The collected data is used as the initial reference value of the current batch of steel, which is used for subsequent color difference offset judgment and comparison analysis with the detection results after annealing.

[0030] After the steel plate enters the continuous annealing furnace at a set speed, the process system accurately configures the proportion of hydrogen and nitrogen in the protective gas according to the process requirements preset for different furnace sections, and sets the furnace temperature curve for different temperature zones according to the oxidation film formation mechanism. At the same time, the dew point instrument and the atmosphere analyzer continuously monitor the dew point fluctuation, oxygen content change and hydrogen concentration fluctuation in the furnace. The system adjusts the atmosphere composition according to real-time data to make the high-temperature oxidation film on the surface of the steel plate form stably and uniformly in the heating zone, the soaking zone and the cooling zone.

[0031] After the steel plate completes annealing and exits the furnace, an online color difference detection system is arranged at the outlet section to scan the full-width transverse range of the steel plate. The system obtains the brightness value, color offset and possible local color spots at each position of the steel plate in real time through a multi-point array sensor. The system compares the detection results with the reference threshold value. When the brightness of any area decreases or the color difference increases beyond the set range, the system immediately issues an abnormal alarm and transmits the deviation data to the subsequent process control system for automatic regulation and control.

[0032] An odor monitoring device is installed at the pipeline of the annealing furnace exhaust system to detect changes in hydrocarbons, sulfides and nitrogen-containing volatile components in the exhaust gas sample continuously taken from the furnace. The monitoring system matches and analyzes the collected odor characteristic signals with the established standard odor fingerprint model. When the characteristic odor profile is detected to deviate, it is determined that the annealing atmosphere has changed or the oxidation film formation mechanism is abnormal, and an atmosphere deviation judgment signal is formed as an auxiliary judgment basis.

[0033] When the color difference detection system or the odor monitoring system outputs any abnormal signal, the process control system automatically calculates the process adjustment amount to be executed according to the deviation type, affected area and deviation trend. The system can directly adjust the hydrogen proportion of the protective gas, adjust the output parameters of the dew point control device, or implement fine tuning compensation on the furnace temperature set value. Through continuous adjustment, the color difference on the surface of the steel plate gradually recovers to the allowable range, realizing closed-loop automatic control of the annealing process.

[0034] In the present embodiment, the online spectral color difference detection system adopts a wide-line scanning structure, and the scanning coverage of the full width of the steel plate is achieved by arranging multiple photoelectric array modules. The data output by the system not only contains the overall average color difference value, but also can be divided into multiple transverse partitions according to the width of the steel strip, and the color difference changes in each region are independently analyzed. The partition detection function can be used to determine the formation position of local color spots, local oxide film abnormalities and other problems, and provide more accurate control basis for subsequent process adjustment.

[0035] The odor monitoring device sets a continuous sampling port on the exhaust pipe of the annealing furnace, continuously samples through a gas pump with a set flow rate, and the monitoring system observes the fluctuation of the odor characteristic signal in real time. By identifying the characteristic peak value, characteristic ratio and signal change trend, the possible deviation of the annealing atmosphere can be identified in advance. Compared with the traditional monitoring method relying only on the atmosphere sensor, this odor monitoring method can detect the trend of imbalance of the atmosphere ratio, abnormal oxygen content or increase of impurity gas in the furnace earlier, thereby improving the advance amount of color difference control.

[0036] The odor monitoring device includes the following modules: a gas collection module: provided at the exhaust end of the annealing furnace, which realizes continuous collection of exhaust gas samples through a high-temperature-resistant exhaust pipe and a flow stabilizing unit to ensure the stability of the odor analysis input; an odor sensing module: this module uses an electronic nose array sensor, which responds to volatile components such as hydrocarbons, sulfides and amines through multiple sensitive materials, and outputs multi-dimensional electrical signals representing different gas characteristics; an odor characteristic analysis module: extracts features from the response matrix output by the electronic nose, including principal component analysis and feature vector construction, and compares the extracted odor fingerprint with the standard odor model database to identify whether the current atmosphere has deviated; an abnormality determination module: according to the set determination threshold, when the odor characteristic changes reach the critical value, it is determined that the oxidation film formation trend is abnormal, and an abnormal signal is output; a feedback control module: submits the abnormality determination signal to the process control system, and the control system performs atmosphere adjustment operations such as increasing the hydrogen proportion, adjusting the dew point control unit, etc. to restore the normal atmosphere environment in the furnace.

[0037] In the present embodiment, when the odor monitoring device detects that the fluctuation amplitude of the odor characteristic exceeds the pre-set proportion threshold, such as a change in the characteristic peak value exceeding 10% or a characteristic vector deviation exceeding a set distance, the process system automatically starts a compensation mechanism. The compensation operation can include: temporarily increasing the hydrogen concentration in the protective gas to inhibit oxidation, performing furnace area pressure relief to remove accumulated impurity gas, or slightly increasing or decreasing the temperature of part of the furnace area to make the oxidation film formation dynamics return to a stable range.

[0038] The process control system is composed of multiple functional modules, which work together to realize the automatic adjustment of annealing color difference: data acquisition module: used to access the data of color difference detection system and odor monitoring device at the same time, including brightness, color difference, defect position, odor characteristic value and atmosphere deviation signal, etc., and to perform time synchronization processing on the data; data fusion analysis module: fuses optical data and odor data in time dimension and trend dimension, judges the deviation type through trend analysis algorithm, and outputs the type and level of required adjustment instruction; process parameter calculation module: automatically calculates the hydrogen / nitrogen ratio adjustment amplitude, dew point compensation value and temperature fine adjustment value according to the deviation level, to ensure that the adjustment parameters are quantized and accurate; execution control module: sends the calculated process adjustment instruction to the relevant execution units of the annealing furnace through the control interface, including atmosphere control valve group, dew point adjustment equipment and temperature control system; feedback monitoring module: continues to monitor the color difference and atmosphere change after adjustment, further optimizes the adjustment amplitude through closed-loop control algorithm, and keeps the stability of the atmosphere in the furnace and the surface state of the steel plate.

[0039] Example one

[0040] This example is aimed at annealing a batch of cold-rolled steel plates with a specification of 0.35mm×1250mm to verify the effectiveness of the dual-signal fusion regulation method of the present application;

[0041] Baseline collection:

[0042] The coil is detected by the entrance section spectral brightness detector after alkaline cleaning, hot water rinsing and air knife drying before entering the annealing furnace;

[0043] The detection results show that the initial brightness L0=82.5, the initial chromaticity coordinates (a0, b0)=(0.5, -1.8), which are taken as the color difference evaluation baseline after annealing of this coil of steel;

[0044] Annealing atmosphere setting:

[0045] According to the annealing process requirements of this specification of steel plate, the annealing furnace protective gas is set as follows: hydrogen volume fraction: 6%, nitrogen volume fraction: 94%, dew point setting: -25℃, furnace temperature setting curve: heating zone 780℃, soaking zone 820℃, rapid cooling zone 450℃, hydrogen concentration, oxygen content and dew point in the furnace are continuously recorded by the atmosphere monitor;

[0046] Color difference detection results and alarm triggering:

[0047] After the coil is discharged from the furnace, the online color difference system scans and detects that the brightness L value of the middle region of the steel plate decreases to 78.2, which deviates from the baseline value by more than 3 points; at the same time, the b value of the local region has a +1.2 deviation trend, the system triggers a color difference abnormal alarm, and the deviation is judged as: the brightness decreases due to the thickening of the oxidation film;

[0048] Odor monitoring results:

[0049] The odor monitoring system detected that the characteristic peak of hydrocarbon odor increased by about 14% compared with the standard model in the same time period, and determined that there was a trend of "insufficient reduction in the furnace". The output atmosphere deviation determination signal was output;

[0050] Control system regulation and execution:

[0051] After fusing the two signals, the process control system automatically executed the following adjustments: the hydrogen proportion was increased from 6% to 8%, the dew point was adjusted from -25°C to -30°C, and the furnace temperature in the rapid cooling zone was increased by +8°C as brightness compensation. After 10 minutes of adjustment, the brightness was restored to 81.4, and the color difference was restored to the allowable range. The odor characteristic model returned to the normal interval.

[0052] Example two

[0053] In this example, high-strength steel with a specification of 0.28mm x 980mm was continuously annealed, and process compensation was performed in advance through the trend judgment of odor monitoring;

[0054] Baseline collection:

[0055] After the steel plate was cleaned and dried, the initial brightness L0 was detected by a spectral brightness instrument: L0=79.8, the initial color coordinates (a0, b0) were (-0.2, -2.3), and this was recorded as the baseline for subsequent comparison;

[0056] Annealing atmosphere and furnace temperature setting:

[0057] The protective gas was set as follows: hydrogen volume fraction: 5%, nitrogen volume fraction: 95%, dew point: -20°C, and furnace temperature setting curve: heating zone 760°C, soaking zone 800°C, and slow cooling zone 520°C;

[0058] The color difference detection system did not show any abnormalities initially:

[0059] 15 minutes before the coiled material was discharged from the furnace, the color difference detection system did not find any deviation, and the brightness was maintained within the range of 79-80;

[0060] Odor monitoring trend judgment triggered early compensation operation:

[0061] Without color difference deviation, the odor monitoring device detected that the characteristic peak of hydrocarbons increased by 9% compared with the standard model, and the sulfide characteristic response deviated by 11%. Although it did not reach the color difference warning standard, the trend analysis module judged that the atmosphere would deviate, which might cause the subsequent oxidation film to thin or locally yellow. The system generated an atmosphere deviation prediction signal in advance;

[0062] Process control system early compensation execution:

[0063] The control system automatically adjusts the following parameters according to the odor trend: the hydrogen proportion is increased from 5% to 6.2%, the dew point is lowered to -24℃, and the furnace temperature in the soaking zone is lowered by -6℃ to inhibit excessive reduction. The advance operation avoids the occurrence of an excessively thin oxidation film.

[0064] After the steel plate is discharged, the color difference detection result is as follows:

[0065] After the steel plate is discharged, the brightness is 80.1, and the color difference (ΔE) is 0.7, both of which are in the excellent range, and no color difference defects occur.

[0066] The results of the two groups of examples show that the control method of the present application using the dual-signal fusion of "color difference detection + odor monitoring" can significantly improve the real-time regulation and control capability of the annealing process on the color difference of the steel plate. In example one, when the color difference and odor signals are abnormal at the same time, the system automatically increases the hydrogen proportion, adjusts the dew point, and fine-tunes the furnace temperature, so that the brightness and color difference are restored to the reference range in a short time. In example two, even if the color difference has not deviated, the odor monitoring has already identified the abnormal trend of the furnace atmosphere in advance, and the process system effectively avoids the color difference deviation caused by the subsequent abnormal oxidation film through advance compensation. In summary, the two groups of results show that the present application realizes the leap from "abnormal post-correction" to "trend pre-control", significantly enhances the color difference stability of the steel plate, improves the color difference qualified rate, and makes the process response speed faster.

[0067] The above only describes the preferred examples of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for controlling color difference defects on the surface of cold-rolled steel sheets, characterized in that: The specific steps are as follows: S1 reference acquisition: After cleaning, degreasing and drying, the cold-rolled steel sheet is used to acquire the initial brightness value and reference color coordinates of the steel sheet surface through an online spectral brightness detection device; S2 Annealing Atmosphere Control: The steel plate is fed into a continuous annealing furnace, and the ratio of hydrogen to nitrogen, furnace temperature curve and dew point parameters in the annealing atmosphere are controlled to ensure the stable formation of oxide film on the surface of the steel plate. The furnace atmosphere parameters are collected in real time. S3 Surface Color Difference Detection: After annealing, the brightness, color difference deviation value and local color spots of the steel plate are measured by an online color difference detection system. When any indicator exceeds the preset threshold, an abnormal alarm is triggered. S4 Odor Monitoring Data Fusion Judgment: The odor characteristics of the gas emitted from the annealing furnace are collected in real time by the odor monitoring device, and an atmosphere deviation judgment signal is formed by matching and analyzing with the standard odor model; S5 process automatic control: The color difference detection signal and the odor judgment signal are input into the process control system. When either signal reaches the judgment condition, the hydrogen ratio, dew point and furnace temperature compensation parameters are automatically adjusted to keep the color difference on the steel plate surface within the allowable range. The odor monitoring device is used to continuously sample the gas emitted from the annealing furnace and to predict abnormal atmospheric trends in advance by analyzing changes in odor characteristics. The odor monitoring device includes: The gas acquisition module is used for online acquisition of gas samples from the exhaust port of the continuous annealing furnace; An odor sensing module, including at least one electronic nose array sensor, for identifying changes in the composition of hydrocarbon-containing, sulfur-containing, or nitrogen-containing volatile gases; The odor feature analysis module is used to extract odor fingerprints and compare them with standard odor models in the database; The anomaly detection module determines the oxide film formation offset trend based on a preset threshold and outputs an anomaly signal. The feedback control module is used to feed back abnormal signals to the process control system to perform annealing atmosphere adjustment operations.

2. The method for controlling color difference defects on the surface of cold-rolled steel sheet according to claim 1, characterized in that: The color difference detection system is an online spectral color difference detection system that covers the entire width of the steel plate and supports surface partition data output.

3. The method for controlling color difference defects on the surface of cold-rolled steel sheet according to claim 1, characterized in that: The process control system includes: The data acquisition module is used to receive the brightness data, color difference offset and surface defect location signal output by the online color difference detection system, and simultaneously receive the odor characteristic parameters and atmosphere offset judgment signal output by the odor monitoring device. The data fusion and analysis module is used to perform time series fusion, trend matching analysis, and anomaly type identification on color difference detection data and odor monitoring data, and generate corresponding process adjustment instruction parameters based on the deviation level; The process parameter calculation module is used to automatically calculate the hydrogen ratio adjustment amount, dew point adjustment compensation value, furnace temperature fine-tuning range, and protective gas flow rate adjustment amount based on the fusion analysis results. The execution control module is used to send the adjustment commands generated by the process parameter calculation module to the atmosphere control system, dew point adjustment device and temperature control system of the continuous annealing furnace, thereby performing hydrogen / nitrogen ratio adjustment, furnace temperature compensation and furnace area pressure fine adjustment operations. The feedback monitoring module is used to continuously monitor the color difference recovery trend, oxide film formation stability and furnace atmosphere changes after process adjustment, and to perform secondary compensation or maintain steady-state control of the adjustment parameters based on the feedback results.

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