Non-destructive laser paint removal method, apparatus, equipment and medium for cold-rolled color-coated steel sheet substrates

Abstract

This invention discloses a non-destructive laser paint removal method, apparatus, equipment, and medium for cold-rolled color-coated steel sheet substrates, belonging to the field of laser application technology. The method includes: acquiring information about the cold-rolled color-coated steel sheet and the substrate color difference, and detecting the thickness of the sheet containing the paint film; decomposing the cold-rolled color-coated steel sheet into RGB three primary colors, determining laser processing parameters based on the cold-rolled color-coated steel sheet information, and obtaining a paint removal model; calling the paint removal model to control laser paint removal, and detecting the color difference between the RGB information on the sheet surface and the RGB information on the substrate; if the color difference is less than a preset threshold, paint removal is completed, and the paint film thickness is determined; if the color difference is not less than the preset threshold, the paint removal model is called again, and the laser processing parameters are adjusted to control laser paint removal. This invention can effectively replace traditional physical or chemical paint removal technologies, avoiding the environmental pollution and human health risks associated with them.

Description

Technical Field

[0001] This invention belongs to the field of laser application technology, and more specifically, relates to a non-destructive laser paint removal method, apparatus, equipment and medium for cold-rolled color-coated steel sheet substrates. Background Technology

[0002] Color-coated steel sheet refers to a composite material formed by pre-treating cold-rolled galvanized steel substrate, applying one or more layers of organic coating, and then baking. Color-coated steel sheet production generally employs a roller coating and baking process, often using a two-coat, two-bake method. Coating types include general polyester, silicone-modified polyester, high-durability polyester, and polyvinylidene fluoride (PVDF). Measuring the paint film thickness of cold-rolled color-coated steel sheets is a crucial indicator for evaluating paint film quality, directly impacting supplier pricing and user experience. Measurement accuracy must reach 1µm. Generally, manual removal of the paint film using a micrometer is employed. Traditional methods for removing paint from products primarily include two approaches: The first is chemical removal, which utilizes cleaning solutions to swell and dissolve the paint layer, such as concentrated sulfuric acid, alkaline agents, or organic paint removers. The second is physical removal, which uses mechanical force to remove the paint layer, such as scraping or high-pressure water jetting. Obvious drawbacks: Chemical paint removal methods primarily use chemical reagents, causing environmental pollution, hindering localized cleaning, easily damaging the substrate, requiring a long removal time, and having low efficiency. Furthermore, the corrosive or volatile nature of chemical reagents can have some impact on human health. Physical paint removal methods are highly prone to damaging the substrate, mechanical paint removal is noisy, labor-intensive, and the cleaning effect is not ideal. Color-coated steel sheet topcoats are composed of four parts: resin, pigment, solvent, and additives.

[0003] (1) Resin

[0004] Resin, the film-forming substance, is the most important component and foundation of coatings, also known as the binder. It is the main factor determining the properties of the coating film. The resin used as a film-forming substance must be relatively stable during the coating's storage period, without undergoing significant physical or chemical changes; during film formation, it must be able to rapidly cure into a film under specified conditions. There are many types of resins; commonly used resins in coil coatings include acrylic resins, epoxy resins, polyester resins, and polyurethanes. Different resins have different physical and chemical properties, as well as varying weather resistance and corrosion resistance.

[0005] (2) Pigment

[0006] Pigments must be used in combination with resins. Their main function in coatings is to color the coating film. Different pigment ratios will affect the hardness, gloss, and corrosion resistance of the coating film.

[0007] (3) Solvent

[0008] Solvents are an important component of liquid coatings and are volatile during the coating drying process. Solvents are also commonly used to adjust the viscosity of coatings; these solvents used to adjust coating viscosity are called thinners.

[0009] Solvents have a significant impact on the manufacturing, storage, application, film formation, and film quality of coatings.

[0010] (4) Additives

[0011] Additives are small amounts of additives added to improve the performance of coatings. Although used in very small quantities, additives have significant effects; for example, some can improve the properties of the coating and the film, some can improve drying time, and some can prevent coating defects. There are many types of additives, including driers, curing agents, leveling agents, defoamers, matting agents, and stabilizers.

[0012] In steel coil coatings, the resin and pigments play a role in durability. The most commonly used topcoats include polyester, silicone-modified polyester, high-durability polyester, and polyvinylidene fluoride.

[0013] a) PE paint is a polyethylene (PE) based coating. Its physical properties are generally similar to those of polyethylene. It exhibits good adhesion, a wide range of colors, a broad range of formability and outdoor durability, moderate chemical resistance, and low cost, making it widely used as a primer for color-coated steel sheets. The following are some typical physical properties of PE paint and their quantitative indicators:

[0014] Optical absorption coefficient: PE paint has a strong absorption effect on visible light, and its optical absorption coefficient is generally between 0.01 and 0.1 in the wavelength range of 400-700nm.

[0015] Thermal conductivity: PE paint has low thermal conductivity, generally between 0.1-0.4 W / (m·K).

[0016] Elastic modulus: The elastic modulus of PE paint is usually between 100-500MPa.

[0017] Melting point: The melting point of PE paint is generally between 100-130℃, but it actually depends on the specific polyethylene material and additives.

[0018] Specific heat capacity: The specific heat capacity of PE paint is generally between 1700-2300 J / (kg·K).

[0019] b) High-durability polyester paint (HDP) is a high-density polyethylene-based coating. During synthesis, monomers containing cyclohexane structures are used to achieve a balance between resin flexibility, weather resistance, and cost. Aromatic-free polyols and polyacids are used to reduce the resin's absorption of UV light, achieving high weather resistance. UV absorbers and hindered amines (HALS) are added to the coating formulation to improve film weather resistance. HDP uses high-molecular-weight resins with fewer polymer branches, stable bond energy, and is less prone to photodegradation, thus reducing chalking and gloss reduction. It uses inorganic ceramic pigments, making it resistant to fading in sunlight and offering a 15-year coating quality guarantee. The following are some typical physical performance parameters and their quantitative indicators for HDPE paint:

[0020] Optical absorption coefficient: HDPE paint has a strong absorption effect on visible light, and its optical absorption coefficient is generally between 0.01 and 0.1 in the wavelength range of 400-700nm.

[0021] Thermal conductivity: HDPE paint has a low thermal conductivity, generally between 0.3-0.5 W / (m·K).

[0022] Elastic modulus: The elastic modulus of HDPE paint is usually between 500-1000 MPa.

[0023] Melting point: The melting point of HDPE paint is generally between 120-135℃, but it actually depends on the specific HDPE material and additives.

[0024] Specific heat capacity: The specific heat capacity of HDPE paint is generally between 1900-2200 J / (kg·K).

[0025] c) The PVDF fluorocarbon coating is made of polyvinylidene fluoride. The high electronegativity of fluorine atoms forms very stable fluorocarbon bonds. Combined with its unique molecular symmetry, PVDF possesses exceptional stability, unique resistance to UV photolysis, and excellent insulation and mechanical properties. Unlike most organic pigments that degrade or structurally break down and fade under sunlight and atmospheric conditions, the inorganic components of this fluorocarbon coating, after high-temperature calcination of metal oxide ceramic pigments, exhibit very stable chemical properties, providing a 20-year coating quality guarantee. PVDF film related parameters:

[0026] Optical absorption coefficient: generally between 0.1 and 1, depending on factors such as coating color, light wavelength, and material formulation;

[0027] Thermal conductivity: typically in the range of 0.1 to 0.3 W / (m*K), but can vary depending on the material composition and filler properties;

[0028] Elastic modulus: Generally 2000-3000 MPa, but can also be as high as 5000 MPa or more. The higher the elastic modulus, the less easily the material deforms under stress.

[0029] With the application of laser technology, laser removal of paint from products can avoid the inherent drawbacks of traditional cleaning methods. However, the diversity of paint types and the complexity of their components in color-coated steel sheets increase the difficulty of laser paint removal. Conventional fiber laser paint removal methods are prone to damaging the substrate, affecting subsequent thickness measurements. Carbon dioxide light sources, due to their 10.6µm wavelength, have extremely low absorption rates in metallic materials and react with non-metallic materials, but the reaction releases a large amount of heat, causing substrate deformation and producing a large amount of residue adhering to the substrate surface, both affecting subsequent thickness measurements. Therefore, how to remove paint without damaging the substrate surface, and the quality assessment method, are key to this approach. Summary of the Invention

[0030] Chemical removal methods for different types of color-coated steel sheets mainly involve the use of chemical reagents, which can cause environmental pollution, are not conducive to local cleaning, easily damage the substrate, require a long time to remove paint, and have low efficiency. At the same time, chemical reagents are corrosive or volatile, which can also have a certain impact on human health. Physical removal methods are prone to damaging the substrate, and mechanical paint removal methods are noisy, labor-intensive, and have unsatisfactory cleaning results. This invention provides a non-destructive laser paint removal method, device, equipment, and medium for cold-rolled color-coated steel sheet substrates, which is dedicated to using carbon dioxide lasers for non-destructive paint removal.

[0031] To achieve the above objectives, according to one aspect of the present invention, a non-destructive laser paint removal method for cold-rolled color-coated steel sheet substrates is provided, comprising:

[0032] Information on cold-rolled steel sheets and color-coated steel sheets, as well as the color difference of the substrate, is obtained. The thickness of the sheet including the paint film is also measured. The substrate of cold-rolled steel sheets and color-coated steel sheets refers to galvanized steel products with a thickness of less than 3mm, rolled at recrystallization temperature. Its C content is ≤0.3%, Si content ≤1.0%, Mn content ≤3.0%, P content ≤0.040%, S content ≤0.025%, and Alt content ≥0.005%, with the addition of trace alloying elements. Galvanized sheets are classified according to coating type as hot-dip aluminum-zinc-magnesium sheet, hot-dip aluminum-zinc sheet, and hot-dip ordinary zinc sheet. The surface paint film coatings are: pretreatment with phosphate or composite oxide film; polyester, polyurethane, or epoxy primer layers; and topcoat and primer layers of various colors and types of coatings.

[0033] The cold-rolled steel plate with color coating is decomposed into RGB three primary colors. The laser processing parameters are determined based on the information of the cold-rolled steel plate with color coating to obtain the paint removal model. Among them, the selected laser processing parameters are: a carbon dioxide laser is selected; the average laser power, laser focus overlap distance, and laser paint removal speed range are selected based on the ability to remove the paint film without generating too much heat accumulation or burning marks during the test; the number of laser processing times and scanning direction are selected based on the ability to completely remove the paint film.

[0034] The laser paint removal model is invoked to control the paint removal process, and the color difference between the RGB information on the board surface and the RGB information on the substrate is detected.

[0035] If the color difference is less than the preset threshold, the paint removal is completed, and the paint film thickness is determined.

[0036] If the color difference is not less than the preset threshold, the paint removal model is called again, and the laser processing parameters are adjusted to control the laser paint removal.

[0037] In some alternative implementations, determining the laser processing parameters includes:

[0038] The test samples were grouped. For the test samples in the same group, the samples were processed by laser paint removal method and traditional artificial chemical paint removal method respectively. The sampling sites of the laser paint removal method and the traditional artificial chemical paint removal method should correspond one by one. During laser processing, different combinations of laser processing parameters should be configured. It is recommended to use experimental design for parameter combination design, and the parameter combination should be no less than 27 times.

[0039] For test samples using traditional manual chemical paint stripping methods and laser paint stripping methods, the paint film thickness before and after paint stripping was measured using the same measurement scheme by the same measurer and the same measuring tool within the same time period.

[0040] The paint film thickness of the test samples processed by the traditional artificial chemical paint stripping method was used as a control group. The residual paint film thickness after laser paint stripping was measured to measure the relative deviation of the test samples under different laser processing parameter combinations with the test samples processed by the traditional artificial chemical method in the same part without damaging the substrate.

[0041] The original substrates for color coating are classified according to the content of the main elements in the hot-dip galvanized layer, including but not limited to hot-dip aluminum-zinc-magnesium plates with approximately 55% aluminum, 41% zinc, and 2.0% magnesium; hot-dip aluminum-zinc plates with approximately 55% aluminum and 43% zinc; and hot-dip ordinary zinc plates with approximately 0.25% aluminum and 99.5% zinc.

[0042] Different zinc flower morphologies and traces on the substrate surface exhibit characteristic color differences. By using visual recognition technology and deep learning, a corresponding standard color difference database is established. Different types and thicknesses of residual paint film affect the color difference results. By analyzing color difference differences, the determination of whether the paint removal on the board surface is complete can be automatically evaluated.

[0043] A mathematical model was established using the relative deviation of the paint film as the dependent variable and different laser processing parameters as independent variables, employing the least squares method.

[0044] In some optional implementations, the relative deviation of the coating thickness result is set, and the expected weight of the corresponding index is set according to the product requirements. If it must be met, it is set to 1; if it does not need to be met, it is set to 0. Other performance weight requirements are set to any value between 0 and 1.

[0045] In some alternative implementations, if the mathematical model R of the dependent variable with a weight ≥ 0.8 is desired... 2 If the value is below 0.8, the mathematical model is rebuilt and other potential independent variables that may be ignored are considered; then the optimal solution is obtained for the mathematical model to get the best combination of independent variable levels.

[0046] In some optional implementations, a mathematical model is established to represent the relative deviation between the laser processing parameters and the resulting coating thickness, including:

[0047] The mathematical model was fitted using multiple linear regression, and a second-order model was selected to fit the paint film thickness. Its basic form is as follows: ε is the normal random error; n is the number of influencing factors in the experiment; β i and β ii These are the first-order and second-order offset coefficients, respectively; β ij α0 represents the interaction coefficient and is a constant.

[0048] In some alternative implementations, for general polyester coatings, the average laser power of the carbon dioxide laser ranges from 20 to 100 W, the laser focus overlap distance is 0.03-0.12 mm, the laser paint removal speed is 1000-4000 mm / min, and the number of laser processing passes is 2-6.

[0049] For silicone-modified polyester and high-durability polyester coatings, the average laser power of the carbon dioxide laser ranges from 50 to 150W, the laser focus overlap distance is 0.03-0.12mm, the laser paint removal speed is 1000-4000mm / min, and the number of laser processing times is 2-6.

[0050] For polyvinylidene fluoride (PVDF) coatings, the average laser power of a carbon dioxide laser ranges from 50 to 150 W, the laser focus overlap distance is 0.01-0.1 mm, the laser paint removal speed is 500-3000 mm / min, and the number of laser processing passes is 2-6.

[0051] According to another aspect of the present invention, a non-destructive laser paint removal device for cold-rolled color-coated steel sheet substrates is provided, comprising:

[0052] The sample information interaction module is used to acquire information on cold-rolled steel sheets and color-coated steel sheets, as well as the color difference of the substrate, and to detect the thickness of the sheet containing the paint film. The substrate of the cold-rolled steel sheet and color-coated steel sheet refers to galvanized steel products with a thickness of less than 3mm rolled at recrystallization temperature, with a C content ≤0.3%, Si content ≤1.0%, Mn content ≤3.0%, P content ≤0.040%, S content ≤0.025%, and Alt content ≥0.005%, and the addition of several trace alloying elements. Galvanized sheets are classified according to coating type as hot-dip aluminum-zinc-magnesium sheet, hot-dip aluminum-zinc sheet, and hot-dip ordinary zinc sheet. Their surface paint film coatings are: pretreatment with phosphate or composite oxide film; polyester, polyurethane, or epoxy primer layers; and topcoat and primer layers of various colors and types of coatings.

[0053] The laser paint removal module is used to decompose cold-rolled steel sheet into RGB three primary colors, determine laser processing parameters based on the information of the cold-rolled steel sheet, obtain a paint removal model, and call the paint removal model to control laser paint removal. Among them, the selected laser processing parameters are: selecting a carbon dioxide laser; based on the type of paint film, testing can remove the paint film without generating too much heat accumulation or burning marks, selecting the average laser power, laser focus overlap distance, and laser paint removal speed range; and selecting the number of laser processing times and scanning direction based on the ability to completely remove the paint film.

[0054] The image detection sample module is used to detect the color difference between the RGB information on the board surface and the RGB information on the substrate.

[0055] The plate thickness measurement module is used to complete the paint removal and determine the paint film thickness when the color difference is less than the preset threshold; when the color difference is not less than the preset threshold, the paint removal model is called again and the laser processing parameters are adjusted to control the laser paint removal.

[0056] In some alternative implementations, determining the laser processing parameters includes:

[0057] The test samples were grouped. For the test samples in the same group, the samples were processed by laser paint removal method and traditional artificial chemical paint removal method respectively. The sampling sites of the laser paint removal method and the traditional artificial chemical paint removal method should correspond one by one. During laser processing, different combinations of laser processing parameters should be configured. It is recommended to use experimental design for parameter combination design, and the parameter combination should be no less than 27 times.

[0058] For test samples using traditional manual chemical paint stripping methods and laser paint stripping methods, the paint film thickness before and after paint stripping was measured using the same measurement scheme by the same measurer and the same measuring tool within the same time period.

[0059] The paint film thickness of the test samples processed by the traditional artificial chemical paint stripping method was used as a control group. The residual paint film thickness after laser paint stripping was measured to measure the relative deviation of the test samples under different laser processing parameter combinations with the test samples processed by the traditional artificial chemical method in the same part without damaging the substrate.

[0060] The original substrates for color coating are classified according to the content of the main elements in the hot-dip galvanized layer, including but not limited to hot-dip aluminum-zinc-magnesium plates with approximately 55% aluminum, 41% zinc, and 2.0% magnesium; hot-dip aluminum-zinc plates with approximately 55% aluminum and 43% zinc; and hot-dip ordinary zinc plates with approximately 0.25% aluminum and 99.5% zinc.

[0061] Different zinc flower morphologies and traces on the substrate surface exhibit characteristic color differences. By using visual recognition technology and deep learning, a corresponding standard color difference database is established. Different types and thicknesses of residual paint film affect the color difference results. By analyzing color difference differences, the determination of whether the paint removal on the board surface is complete can be automatically evaluated.

[0062] A mathematical model was established using the relative deviation of the paint film as the dependent variable and different laser processing parameters as independent variables, employing the least squares method.

[0063] According to another aspect of the present invention, an electronic device is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of any of the methods described above.

[0064] According to another aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the methods described above.

[0065] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0066] 1. Designed and developed a carbon dioxide laser non-destructive paint removal technology for cold-rolled color-coated steel sheets, established a mathematical model of laser processing parameters and paint film thickness, and recommended laser processing parameter combinations corresponding to common paint film colors. This technology can effectively replace traditional physical or chemical paint removal techniques, avoiding the environmental pollution and human health risks associated with them.

[0067] 2. It shortens the paint removal process of cold-rolled color-coated steel sheets, improves production efficiency, and is easy to integrate with Industry 4.0, promoting the improvement of industry automation. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of a laser paint removal control method for PE coating provided in an embodiment of the present invention;

[0069] Figure 2 This is a schematic diagram of a laser paint stripping control method for Baosteel Blue HDP paint film provided in an embodiment of the present invention;

[0070] Figure 3 This is a schematic diagram of a laser paint stripping control method for silver-gray PVDF paint film provided in an embodiment of the present invention. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0072] This invention provides a sampling and parameter range for a non-destructive laser paint removal method for general polyester coating substrates of cold-rolled color-coated steel sheets, including the following operation steps:

[0073] In a first aspect, embodiments of the present invention provide a method for removing the paint film from cold-rolled color-coated steel sheets using a carbon dioxide laser non-destructive substrate stripping method, specifically including:

[0074] 1) Cold-rolled color-coated steel sheets, whose substrates mainly refer to galvanized steel products with a thickness of less than 3mm rolled at recrystallization temperature, generally have a C content ≤0.3%, Si content ≤1.0%, Mn content ≤3.0%, P content ≤0.040%, S content ≤0.025%, and Alt content ≥0.005%, and may also contain some trace alloying elements; galvanized sheets are classified according to the coating type as hot-dip aluminum-zinc-magnesium sheet (AM sheet), hot-dip aluminum-zinc sheet (GL sheet), hot-dip ordinary zinc sheet (GI sheet), etc.; their surface paint film coatings are as follows: pretreatment with phosphate or composite oxide film; polyester, polyurethane, epoxy primer layer; topcoat and primer layers of various colors and types of coatings;

[0075] 2) When using laser processing technology, appropriate laser processing parameters should be determined first. The selection parameters include: laser type, laser intensity, average laser power, laser focal radius, laser frequency, peak power, laser intensity attenuation coefficient, paint removal speed, laser focal overlap distance, number of paint removal cycles, and laser processing atmosphere.

[0076] 3) The key factors after screening by this invention are: to avoid damaging the metal substrate, the carbon dioxide laser with extremely low absorption reaction with the metal material is selected; according to the type of paint film, the laser average power, laser focus overlap distance, and laser paint removal speed range are selected based on the ability to remove the paint film without generating too much heat accumulation or burning marks; and the number of laser processing times and scanning direction are selected based on the ability to completely remove the paint film.

[0077] 4) For implementation of this invention, a carbon dioxide laser is recommended. For general polyester (PE) films, the average laser power range is 20-100W, the laser focus overlap distance is 0.03-0.12mm, the laser paint removal speed is 1000-4000mm / min, and the number of laser processing times is 2-6. For silicone-modified polyester and high-durability polyester films, the average laser power range is 50-150W, the laser focus overlap distance is 0.03-0.12mm, the laser paint removal speed is 1000-4000mm / min, and the number of laser processing times is 2-6. For polyvinylidene fluoride (PVDF) films, the average laser power range is 50-150W, the laser focus overlap distance is 0.01-0.1mm, the laser paint removal speed is 500-3000mm / min, and the number of laser processing times is 2-6.

[0078] Secondly, this invention provides a method for determining laser processing parameters for removing the paint film from cold-rolled color-coated steel sheets using a non-destructive laser paint removal method, specifically including:

[0079] 1) First, the samples are grouped according to the following criteria: general polyester, silicone-modified polyester, high-durability polyester, polyvinylidene fluoride topcoat color, substrate coating type, etc.

[0080] 2) For samples in the same group, use both laser paint removal and traditional manual chemical paint removal methods to process the test samples. The sampling sites for the laser processing method and the traditional manual chemical method must correspond one-to-one. Simultaneously, during laser processing, different combinations of laser processing parameters should be configured. It is recommended that the parameter combination design adopt an experimental design, with no fewer than 27 parameter combinations.

[0081] 3) For test samples using traditional artificial chemical methods and laser paint stripping methods, the paint film thickness before and after paint stripping was measured using the same measurement scheme by the same measurer and the same measuring tool within the same time period.

[0082] 4) The paint film thickness of samples processed using traditional artificial chemical methods was used as a control group. The thickness was calculated to meet the requirements of GB / T 16601.4-2017 Lasers and Laser-Related Equipment - Laser Damage Thresholds - Part 4: Inspection, Detection and Measurement. Electron microscopy was used to analyze the surface morphology after processing, and a roughness meter was used to test the roughness of the processed board surface compared to the original substrate to confirm no damage to the board surface. Glow chromatography was used to analyze the paint residue on the surface after paint removal. Metallography, DJH drilling technology, and artificial chemical reagent etching were used to measure the residual paint film thickness after laser paint removal. This allowed for comparison of the results of samples with different laser processing parameter combinations with samples processed using traditional artificial chemical methods at the same location without damaging the substrate. The relative deviation of the results; further classification of the original color-coated substrates according to the main element content of the hot-dip galvanized layer, including but not limited to hot-dip aluminum-zinc-magnesium board (AM board) with approximately 55% aluminum, 41% zinc, and 2.0% magnesium content; hot-dip aluminum-zinc board (GL board) with approximately 55% aluminum and 43% zinc content; and hot-dip ordinary zinc board (GI board) with approximately 0.25% aluminum and 99.5% zinc content. Due to different zinc liquid compositions, the zinc flower morphology and traces on the substrate surface are different, exhibiting characteristic color differences. Deep learning is used through visual recognition technology to establish a corresponding standard color difference database; different paint film types and thicknesses of residues all affect the color difference results. By analyzing color difference differences, the determination of whether the paint removal on the board surface is complete can be automatically evaluated.

[0083] 5) Using the relative deviation of the paint film result as the dependent variable and different laser processing parameters as independent variables, a mathematical model is established using the least squares method;

[0084] 6) Set the relative deviation of the paint film thickness result, generally F≤0.5um. Since it belongs to a mathematical model with multiple dependent variables, the expected weight of the corresponding indicators can be set according to the product requirements. If it must be met, set it to 1; if it does not need to be met, set it to 0. Other performance weight requirements can be set to any value between 0 and 1.

[0085] 7) If the mathematical model R of the dependent variable with expected weight ≥ 0.8 2 If the value is below 0.8, the model should be remodeled and other potential independent variables that may have been overlooked should be considered.

[0086] 8) Find the optimal solution for the mathematical model to obtain the best combination of independent variable levels.

[0087] Thirdly, this invention provides a set of laser processing parameters for a non-destructive laser paint removal method for cold-rolled color-coated steel substrates, specifically including:

[0088] 1) Establish a paint stripping processing parameter table: Code each laser paint stripping parameter range according to the selection, as shown in Table 1;

[0089] Table 1

[0090] Serial Number power speed Overlap frequency 1 1 0 0 -1 2 0 1 -1 0 3 -1 0 1 0 4 0 0 0 0 5 -1 0 0 1 6 0 1 0 -1 7 -1 0 -1 0 8 1 1 0 0 9 0 1 1 0 10 0 -1 0 1 11 -1 -1 0 0 12 0 0 0 0 13 0 -1 -1 0 14 0 0 -1 1 15 1 -1 0 0 16 0 0 1 -1 17 0 0 1 1 18 0 1 0 1 19 0 -1 0 -1 20 1 0 1 0 21 -1 1 0 0 22 -1 0 0 -1 23 0 0 0 0 24 0 -1 1 0 25 1 0 0 1 26 1 0 -1 0 27 0 0 -1 -1

[0091] 2) Establish a mathematical model for the relative deviation between laser processing parameters and coating thickness results:

[0092] The model was fitted using multiple linear regression, and a second-order model was selected to fit the paint film thickness. Its basic form is as follows:

[0093]

[0094] In the formula, ε is the normal random error; n is the number of influencing factors in the experiment; β i and β ii These are the first-order and second-order offset coefficients, respectively; β ij The interaction coefficient is used. A stepwise regression method is employed to build the prediction model. Term(s) with P < αin are included in the model, while term(s) with P > αout are successively removed (αin = 0.1, αout = 0.15).

[0095] 3) such as Figure 1 As shown, the final model obtained from testing Baosteel's blue general polyester paint film is as follows:

[0096] F = 0.0024 + 0.0071 * ((Power - 75) / 25) + 0.00058 * ((Speed ​​- 1750) / 1250) + (-0.00041) * ((Overlap - 0.055) / 0.045) + (-0.00008) * ((Number of times - 4) / 2) + ((((Power - 75) / 25) * (Speed ​​- 1750)) / 1250 )*0.005+((((Power-75) / 25)*(Overlap-0.055)) / 0.045)*0.00275+((((Speed-1750) / 1250)*(Number of times-4)) / 2)*0.0015+((((Power-75) / 25)*(Power-75)) / 25)*0.0063, further deriving the optimal parameters for laser paint removal;

[0097] The recommended laser paint stripping parameters for common colors of general polyester paint films are shown in Table 2:

[0098] Table 2

[0099]

[0100] 4) such as Figure 2 As shown, the final model of Baosteel's blue high-durability polyester coating is as follows:

[0101] F = 0.00394 + 0.0105 * power + (-0.00616) * speed + (-0.010166) * overlap + 0.00683 * number of times + power * (power * 0.0161) + power * overlap * (-0.01975) + overlap * (overlap * 0.0173) + overlap * number of times * (-0.01775), further deriving the optimal parameters for laser paint removal;

[0102] Recommended laser paint stripping parameters for common color high-durability polyester paint films are shown in Table 3:

[0103] Table 3

[0104]

[0105]

[0106] 5) such as Figure 3 As shown, the final model of the silver-gray polyvinylidene fluoride paint film is as follows:

[0107] F = 0.00686 + 0.0121 * power + (-0.003) * speed + -0.0112 * overlap + 0.00458 * number of times + power * power 0.00813 + overlap * overlap * 0.0147 + speed * number of times * 0.00625 + overlap * number of times * (-0.0165), further deriving the optimal parameters for laser paint removal;

[0108] Recommended laser paint stripping parameters for common colored polyvinylidene fluoride (PVDF) coatings are shown in Table 4.

[0109] Table 4

[0110]

[0111] Fourthly, this invention provides an automatic laser paint stripping measurement device for detecting the paint film thickness of cold-rolled color-coated steel sheets. The device includes: a sample information interaction module, an image detection sample module, a laser paint stripping module, and a sheet thickness measurement module. By setting corresponding laser paint stripping models and image detection color difference calculation thresholds for different paint film types, the thickness of different types of paint films can be detected.

[0112] Fifthly, embodiments of the present invention provide an electronic device, the electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the processing parameter determination method provided in the first aspect or the sample processing method provided in the second aspect.

[0113] This application also provides a computer-readable storage medium, such as flash memory, hard disk, multimedia card, card-type memory (e.g., SD or DX memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, disk, optical disk, server, App application store, etc., which stores a computer program. When the program is executed by a processor, it implements the steps of the processing parameter determination method provided in the first aspect or the sample processing method provided in the second aspect.

[0114] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0115] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A non-destructive laser paint removal method for cold-rolled color-coated steel sheet substrates, characterized in that, include: Information on cold-rolled steel sheets and color-coated steel sheets, as well as the color difference of the substrate, is obtained. The thickness of the sheet including the paint film is also measured. The substrate of cold-rolled steel sheets and color-coated steel sheets refers to galvanized steel products with a thickness of less than 3mm, rolled at recrystallization temperature. Its C content is ≤0.3%, Si content ≤1.0%, Mn content ≤3.0%, P content ≤0.040%, S content ≤0.025%, and Alt content ≥0.005%, with the addition of trace alloying elements. Galvanized sheets are classified according to coating type as hot-dip aluminized zinc-magnesium sheet, hot-dip aluminized zinc sheet, and hot-dip ordinary zinc sheet. The surface paint film coatings are: pretreatment with phosphate or composite oxide film; polyester, polyurethane, or epoxy primer layers; and topcoat and primer layers of various colors and types of coatings. The cold-rolled steel plate with color coating is decomposed into RGB three primary colors. The laser processing parameters are determined based on the information of the cold-rolled steel plate with color coating to obtain the paint removal model. Among them, the selected laser processing parameters are: a carbon dioxide laser is selected; the average laser power, laser focus overlap distance, and laser paint removal speed range are selected based on the ability to remove the paint film without generating too much heat accumulation or burning marks during the test; the number of laser processing times and scanning direction are selected based on the ability to completely remove the paint film. The laser paint removal model is invoked to control the paint removal process, and the color difference between the RGB information on the board surface and the RGB information on the substrate is detected. If the color difference is less than the preset threshold, the paint removal is completed, and the paint film thickness is determined. If the color difference is not less than the preset threshold, the paint removal model is called again, and the laser processing parameters are adjusted to control the laser paint removal. The determination of laser processing parameters includes: The test samples were grouped. For the test samples in the same group, the laser paint removal method and the traditional artificial chemical paint removal method were used to process the samples respectively. The sampling sites of the laser paint removal method and the traditional artificial chemical paint removal method should correspond one by one. During laser processing, different combinations of laser processing parameters should be configured. The parameter combination design adopts experimental design, and the parameter combination should be no less than 27 times. For test samples using traditional manual chemical paint stripping methods and laser paint stripping methods, the paint film thickness before and after paint stripping was measured using the same measurement scheme by the same measurer and the same measuring tool within the same time period. The paint film thickness of the test samples processed by the traditional artificial chemical paint stripping method was used as a control group. The residual paint film thickness after laser paint stripping was measured to measure the relative deviation of the test samples under different laser processing parameter combinations with the test samples processed by the traditional artificial chemical method in the same part without damaging the substrate. The original substrates for color coating are classified according to the content of the main elements in the hot-dip galvanized layer: hot-dip aluminum-zinc-magnesium plate contains 55% aluminum, 41% zinc, and 2.0% magnesium; hot-dip aluminum-zinc plate contains 55% aluminum and 43% zinc; and hot-dip ordinary zinc plate contains 0.25% aluminum and 99.5% zinc. Different zinc flower morphologies and traces on the substrate surface exhibit characteristic color differences. By using visual recognition technology and deep learning, a corresponding standard color difference database is established. Different types and thicknesses of residual paint film affect the color difference results. By analyzing color difference differences, the determination of whether the paint removal on the board surface is complete can be automatically evaluated. A mathematical model was established using the relative deviation of the paint film as the dependent variable and different laser processing parameters as independent variables, employing the least squares method. A mathematical model is established to determine the relative deviation between laser processing parameters and the resulting paint film thickness, including: The mathematical model was fitted using multiple linear regression, and a second-order model was selected to fit the paint film thickness. Its basic form is as follows: ε is the normal random error; n is the number of influencing factors in the experiment; β i and β ii These are the first-order offset coefficient and the second-order offset coefficient, respectively; β ij The interaction coefficient, Represents a constant.

2. The method according to claim 1, characterized in that, Set the relative deviation of the paint film thickness result, and set the expected weight of the corresponding index according to the product requirements. If it must be met, set it to 1; if it does not need to be met, set it to 0. Other performance weight requirements are set to any value between 0 and 1.

3. The method according to claim 2, characterized in that, If the mathematical model of the dependent variable has an expected weight ≥ 0.8 R 2 If the value is below 0.8, the mathematical model is rebuilt and other potential independent variables that may be ignored are considered; then the optimal solution is obtained for the mathematical model to get the best combination of independent variable levels.

4. The method according to claim 3, characterized in that, For general polyester coatings, the average laser power of a carbon dioxide laser ranges from 20 to 100W, the laser focal overlap distance is 0.03-0.12mm, the laser paint removal speed is 1000-4000mm / min, and the number of laser processing passes is 2-6. For silicone-modified polyester and high-durability polyester coatings, the average laser power of the carbon dioxide laser ranges from 50 to 150W, the laser focus overlap distance is 0.03-0.12mm, the laser paint removal speed is 1000-4000mm / min, and the number of laser processing times is 2-6. For polyvinylidene fluoride (PVDF) coatings, the average laser power of a carbon dioxide laser ranges from 50 to 150 W, the laser focus overlap distance is 0.01-0.1 mm, the laser paint removal speed is 500-3000 mm / min, and the number of laser processing passes is 2-6.

5. A non-destructive laser paint removal device for cold-rolled color-coated steel sheet substrates, characterized in that, include: The sample information interaction module is used to acquire information on cold-rolled steel sheets and color-coated steel sheets, as well as the color difference of the substrate, and to detect the thickness of the sheet containing the paint film. The substrate of the cold-rolled steel sheet and color-coated steel sheet refers to galvanized steel products with a thickness of less than 3mm rolled at recrystallization temperature, with a C content ≤0.3%, Si content ≤1.0%, Mn content ≤3.0%, P content ≤0.040%, S content ≤0.025%, and Alt content ≥0.005%, and the addition of several trace alloying elements. Galvanized sheets are classified according to coating type as hot-dip aluminized zinc-magnesium sheet, hot-dip aluminized zinc sheet, and hot-dip ordinary zinc sheet. Their surface paint film coatings are: pretreatment with phosphate or composite oxide film; polyester, polyurethane, or epoxy primer layers; and topcoat and primer layers of various colors and types of coatings. The laser paint removal module is used to decompose cold-rolled steel sheet into RGB three primary colors, determine laser processing parameters based on the information of the cold-rolled steel sheet, obtain a paint removal model, and call the paint removal model to control laser paint removal. Among them, the selected laser processing parameters are: selecting a carbon dioxide laser; based on the type of paint film, testing can remove the paint film without generating too much heat accumulation or burning marks, selecting the average laser power, laser focus overlap distance, and laser paint removal speed range; and selecting the number of laser processing times and scanning direction based on the ability to completely remove the paint film. The image detection sample module is used to detect the color difference between the RGB information on the board surface and the RGB information on the substrate. The plate thickness measurement module is used to complete the paint removal and determine the paint film thickness when the color difference is less than a preset threshold; when the color difference is not less than the preset threshold, the paint removal model is called again and the laser processing parameters are adjusted to control the laser paint removal. The determination of laser processing parameters includes: The test samples were grouped. For the test samples in the same group, the laser paint removal method and the traditional artificial chemical paint removal method were used to process the samples respectively. The sampling sites of the laser paint removal method and the traditional artificial chemical paint removal method should correspond one by one. During laser processing, different combinations of laser processing parameters should be configured. The parameter combination design adopts experimental design, and the parameter combination should be no less than 27 times. For test samples using traditional manual chemical paint stripping methods and laser paint stripping methods, the paint film thickness before and after paint stripping was measured using the same measurement scheme by the same measurer and the same measuring tool within the same time period. The paint film thickness of the test samples processed by the traditional artificial chemical paint stripping method was used as a control group. The residual paint film thickness after laser paint stripping was measured to measure the relative deviation of the test samples under different laser processing parameter combinations with the test samples processed by the traditional artificial chemical method in the same part without damaging the substrate. The original substrates for color coating are classified according to the content of the main elements in the hot-dip galvanized layer: hot-dip aluminum-zinc-magnesium plate contains 55% aluminum, 41% zinc, and 2.0% magnesium; hot-dip aluminum-zinc plate contains 55% aluminum and 43% zinc; and hot-dip ordinary zinc plate contains 0.25% aluminum and 99.5% zinc. Different zinc flower morphologies and traces on the substrate surface exhibit characteristic color differences. By using visual recognition technology and deep learning, a corresponding standard color difference database is established. Different types and thicknesses of residual paint film affect the color difference results. By analyzing color difference differences, the determination of whether the paint removal on the board surface is complete can be automatically evaluated. A mathematical model was established using the relative deviation of the paint film as the dependent variable and different laser processing parameters as independent variables, employing the least squares method. A mathematical model is established to determine the relative deviation between laser processing parameters and the resulting paint film thickness, including: The mathematical model was fitted using multiple linear regression, and a second-order model was selected to fit the paint film thickness. Its basic form is as follows: ε is the normal random error; n is the number of influencing factors in the experiment; β i and β ii These are the first-order offset coefficient and the second-order offset coefficient, respectively; β ij The interaction coefficient, Represents a constant.

6. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the method according to any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 4.

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