VCM steel plate film coating process based on multi-stage pretreatment

Abstract

The invention relates to the technical field of VCM steel plate film coating, and discloses a VCM steel plate film coating process based on multistage pretreatment, which comprises the following steps: pretreatment, film coating and post-treatment, i.e., the pretreatment comprises the following steps: step 1, taking out a coiled VCM steel plate, unfolding, adopting an alkaline degreasing agent, and taking out the coiled VCM steel plate; main components of the degreasing agent comprise 5%-8% of sodium hydroxide, 3%-5% of sodium carbonate, 2%-3% of sodium phosphate and fatty alcohol-polyoxyethylene ether with the nonionic surfactant content being 1%-2%, the main components are mixed with other components of a scale inhibitor, an accelerant and a complexing agent, and stirring and filtering are conducted to prepare a degreasing agent solution. According to the VCM steel plate film coating process based on multi-stage pretreatment, the multi-stage pretreatment process is provided for the steel plate, through a plurality of fine cleaning and activating steps, oil stains, rust and other impurities on the surface of the steel plate can be thoroughly removed, and the surface of the steel plate can reach the proper roughness and active state; and the microstructure is more beneficial to the adhesion of the film.

Description

Technical Field

[0001] The invention relates to the technical field of VCM steel plate coating, in particular to a VCM steel plate coating process based on multi-stage pre-treatment. Background Art

[0002] VCM steel plate, or coated steel plate, is a material with a layer of polyvinyl chloride film on the surface of a metal plate. It is widely used in many fields such as home appliances, construction, and transportation. In the home appliance industry, such as the manufacture of refrigerator and washing machine shells, the use of VCM steel plates can provide good appearance effects, including rich color and pattern selection, and also has certain corrosion resistance and wear resistance. In the field of construction, VCM steel plates can be used for indoor and outdoor decorative panels, and their beauty and durability can meet the needs of architectural decoration. In terms of transportation, VCM steel plates are also used in parts such as automotive interiors because they can provide a comfortable touch and good decorativeness. However, traditional coating processes are difficult to meet the needs of high-quality products. The coating part of the VCM steel plate prepared by traditional processes has some defects, such as:

[0003] Traditional processes are not sophisticated enough in the surface treatment process, resulting in residual impurities on the surface of the steel plate. After the film is attached, over time and under the influence of environmental factors, the film may experience local bubbling and falling off, affecting the bonding between the film and the steel plate. In addition, the lack of weathering treatment of the film during the lamination process makes the product's weather resistance and durability poor. When used in harsh environments for a long time, the film is affected by ultraviolet radiation, temperature changes, humidity changes and other factors, and is prone to fading, aging and falling off.

[0004] In view of the above problems, it is urgent to carry out innovative design based on the original VCM steel plate coating. Summary of the invention

[0005] The purpose of the present invention is to provide a VCM steel plate coating process based on multi-stage pre-treatment to solve the problems mentioned in the above background technology that the traditional process is not fine enough in the surface treatment link, resulting in residual impurities on the surface of the steel plate, affecting the bonding strength between the film and the steel plate, and the lack of weathering treatment of the film during the coating process, resulting in poor weather resistance and durability of the product, and the film is prone to fading, aging and falling off.

[0006] To achieve the above object, the present invention provides the following technical solution: a VCM steel plate coating process based on multi-stage pre-treatment, comprising the following steps: pre-treatment, coating and post-treatment, namely:

[0007] Pre-treatment includes:

[0008] Step 1: Take out the rolled VCM steel plate and unfold it, use an alkaline degreasing agent, the main components of which are 5%-8% sodium hydroxide, 3%-5% sodium carbonate, 2%-3% sodium phosphate and 1%-2% fatty alcohol polyoxyethylene ether of non-ionic surfactant, and mix the remaining components of scale inhibitor, promoter and complexing agent, stir and filter to make a degreasing agent solution;

[0009] Step 2: Immerse the VCM steel plate in the degreasing agent solution, control the solution temperature at 50-60°C, and immerse for 3-5 minutes to remove the oil stains from the surface of the VCM steel plate;

[0010] Step 3: Using a hydrochloric acid solution with a concentration of 10%-15% as the main raw material of the rust remover, and mixing the remaining raw materials of hexamethylenetetramine, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, urea, triethanolamine, sodium chloride, emulsifier and non-ionic surfactant to prepare a rust remover solution, immersing the steel plate in the rust remover solution at a temperature of 20-25°C for 2-3 minutes, the rust reacts chemically with the hydrochloric acid to generate water-soluble ferric chloride floating on the surface of the steel plate;

[0011] Step 4: After the rust removal in step 3 above, immediately rinse the steel plate with plenty of clean water to prevent the acid residue from corroding the steel plate. Then immerse the steel plate in a 1%-2% sodium bicarbonate solution for 1-5 minutes to neutralize the residual acidic substances, and then rinse it with clean water;

[0012] Step 5: Use zinc phosphate solution as an activator and phosphating agent with a solution concentration of 3%-5%, and soak the steel plate in the activator solution for 1-2 minutes;

[0013] Step 6: After the activation treatment in step 5 above, rinse the steel plate with clean water and dry it at 80-100°C to dry the surface of the steel plate. Apply a primer of weather-resistant coating on the surface of the steel plate, and wait for the primer to dry before preparing for subsequent lamination.

[0014] Lamination includes:

[0015] Step 7: preheat the VCM steel plate after being dried in the above steps 1 to 6 through a preheating furnace to reach the required temperature of 30-45°C for lamination;

[0016] Step 8: Select high-quality polyvinyl chloride film with a thickness of 0.1-0.5mm. Pre-print various patterns and colors on the film as needed. Preheat the film before lamination at a temperature of 40-50°C to make the film soft and easy to fit.

[0017] Step 9: Using hot pressing laminating process, the hot pressing temperature is controlled at 150-180℃, the pressure is 0.3-0.5MPa, and the preheated film is laminated with the steel plate after multi-stage pretreatment through a laminating machine;

[0018] Step 10: After the lamination in step 9 above, the steel plate is cooled by combining air cooling and water cooling. First, the surface temperature of the steel plate is quickly reduced to below 50°C by air cooling, and then water cooling is performed to cool the steel plate to room temperature to ensure that the film and the steel plate are more firmly bonded;

[0019] Post-processing includes:

[0020] Step 11: Trim the edges of the coated VCM steel plate to remove the excess film edge to make the edge of the steel plate neat and beautiful. Use a high-precision laser cutting machine with a cutting accuracy of up to ±0.5mm to ensure the trimming quality;

[0021] Step 12: Perform a comprehensive quality inspection on the VCM steel plate after trimming in step 11 above, including adhesion test between the film and the steel plate, appearance inspection and weather resistance inspection.

[0022] By adopting the above technical solution and performing multiple pre-treatment steps, the cleaning intensity of the steel plate surface is increased and the dirt residue on the steel plate surface is reduced.

[0023] Preferably, the remaining components of the alkaline degreasing agent solution include 10-24 parts of scale inhibitor, 8-17 parts of promoter and 3-8 parts of complexing agent by weight.

[0024] By adopting the above technical solution, the amounts of other components for preparing the alkaline degreasing agent solution are determined.

[0025] Preferably, after the main components of the alkaline degreasing agent solution are mixed, the scale inhibitor is added and stirred with a stirrer for 5-8 minutes, and then the promoter and the complexing agent are added in sequence and stirred clockwise and filtered to form an alkaline degreasing agent solution.

[0026] The above technical solution is adopted to prepare the components of the alkaline degreasing agent solution by mixing.

[0027] Preferably, after the degreasing treatment of the VCM steel plate is completed, the steel plate is washed with high-pressure water, and the water pressure is maintained at 2-4 MPa to ensure that the degreasing agent residue and the detached oil stains are cleaned.

[0028] The above technical solution is used to reduce the degreasing agent residue and further improve the cleanliness of the steel plate surface.

[0029] Preferably, the remaining ingredients of the rust remover include, by weight, 1-10 parts of hexamethylenetetramine, 1-10 parts of sodium dodecylbenzenesulfonate, 0-2 parts of sodium dodecyl sulfate, 0.1-0.2 parts of urea, 0.1-0.2 parts of triethanolamine, 0.1-0.3 parts of sodium chloride, 0.1-0.2 parts of nonionic surfactant, and 0.1-0.3 parts of emulsifier.

[0030] By adopting the technical solution, the remaining components of the rust remover and their amounts are clearly identified, which facilitates the preparation of the rust remover.

[0031] Preferably, the emulsifier in the remaining components of the rust remover is TX-10, and the nonionic surfactant in the remaining components of the rust remover is detergent 6501.

[0032] The above technical solution is used to prepare a rust remover to treat the rusted surface of a steel plate.

[0033] Preferably, the hot pressing lamination speed in step 9 is 5-10 m / min.

[0034] The above technical solution is used to control the stability of hot pressing lamination and avoid mold warping caused by too fast lamination.

[0035] Preferably, the adhesion test in step 12 adopts the cross-hatch method, and 6 straight lines with a spacing of 1 mm are drawn on the surface of the steel plate in both horizontal and vertical directions. A special tape is used to stick the film and then it is torn off to observe the film shedding situation, and the shedding area is required to be no more than 5%.

[0036] The above technical solution is adopted to facilitate the detection and processing of VCM steel plates that have been coated in the same batch.

[0037] Preferably, the appearance inspection in step 12 is performed by visual inspection to check whether there are defects such as wrinkles, bubbles, scratches, etc. on the surface of the film.

[0038] The above technical solution makes it easy to reprocess the abnormal parts of the lamination process.

[0039] Preferably, in the weather resistance test of step 12, the selected samples are placed in an aging test box simulating a harsh environment, exposed to ultraviolet light for 800-1000 hours, and then placed in a high temperature and high humidity cycle simulation box to check the color change, gloss reduction, and cracking of the film. The color change ΔE value is required to be no more than 5, and the gloss reduction rate is required to be no more than 30%.

[0040] The above technical solution is used to carry out weather resistance testing on the treated steel plate coating and check the status of the steel plate.

[0041] Compared with the prior art, the beneficial effects of the present invention are: the VCM steel plate coating process based on multi-stage pre-treatment:

[0042] By providing the steel plate with a multi-stage pre-treatment process and multiple fine cleaning and activation steps, the oil, rust and other impurities on the surface of the steel plate can be completely removed, and the surface of the steel plate can reach a suitable roughness and activity state. The microstructure of the steel plate after chemical degreasing, pickling and surface activation treatment is more conducive to the adhesion of the film. Compared with the traditional process, the adhesion between the film and the steel plate is greatly improved, which effectively avoids the quality problems of the film such as blistering and shedding during use, making the product quality more stable and reliable;

[0043] During the surface treatment process, a weather-resistant coating primer is added, or the steel plate is subjected to special oxidation treatment to form a protective film. These pretreatment measures can effectively block the erosion of the film by external factors such as ultraviolet rays, moisture, and chemicals. Good adhesion also makes the film less likely to peel off during long-term use, thereby extending the service life of the VCM steel plate and enabling it to maintain good performance outdoors or in harsh environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the VCM steel plate coating preparation process of the present invention. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] See also Figure 1 , the present invention provides a technical solution: a VCM steel plate coating process based on multi-stage pre-treatment;

[0047] The inspection contents of the VCN steel plate after film coating and trimming include: the adhesion test between the film and the steel plate, using the cross-cut method, draw 6 lines with a spacing of 1mm on the surface of the steel plate, and then stick it with special tape and tear it off, observe the film shedding situation, and the shedding area is required to not exceed 5%;

[0048] Appearance inspection: check whether there are wrinkles, bubbles, scratches and other defects on the film surface;

[0049] Weathering test: Place the sample in an aging test chamber that simulates a harsh environment. After a certain period of ultraviolet irradiation, high temperature and high humidity cycle tests, check the color change, gloss reduction, and cracking of the film. The color change ΔE value is required to be no more than 5, and the gloss reduction rate is required to be no more than 30%;

[0050] The data of ΔE value comes from CIELAB color space, L represents lightness, and the value range is 0-100, 0 is black, and 100 is white;

[0051] a represents the color component on the red to green axis, with positive values ​​representing the red direction and negative values ​​representing the green direction;

[0052] b represents the color component on the yellow to blue axis, with positive values ​​representing the yellow direction and negative values ​​representing the blue direction;

[0053] Before the weathering test of the VCM steel plate coating process begins, a professional color measuring instrument, a spectrophotometer, is required to perform an initial color measurement on the sample. The instrument will read the initial color in the CIELAB color space. value;

[0054] The VCM steel plate coated samples were placed in an aging test chamber simulating a harsh environment. After the test, the spectrophotometer was used again to measure the color of the samples under the same measurement conditions to obtain the color after the weathering test. value;

[0055] The calculation formula for the color change ΔE value of the weather resistance test is:

[0056]

[0057] Example 1

[0058] Step 1: Take a VCM steel plate with a size of 1000mm×2000mm×0.5mm, first put it into a degreasing tank, and the degreasing tank is filled with an alkaline degreasing agent solution. The alkaline degreasing agent solution is made of 10% sodium hydroxide content, 5% sodium carbonate content, 3% surfactant content, and 1% fatty alcohol polyoxyethylene ether with a non-ionic surfactant content. The remaining ingredients are 10 parts of scale inhibitor, 8 parts of promoter and 3 parts of complexing agent to make a solution. The solution is soaked at 55°C for 4 minutes and rinsed with 2.5MPa high-pressure water;

[0059] Step 2: Then immerse the steel plate in a 12% hydrochloric acid rust remover at room temperature for 2.5 minutes. The rust remover contains 8 parts of hexamethylenetetramine, 8 parts of sodium dodecylbenzene sulfonate, 2 parts of sodium dodecyl sulfate, 0.2 parts of urea, 0.2 parts of triethanolamine, 0.3 parts of sodium chloride, 0.3 parts of emulsifier and 0.2 parts of non-ionic surfactant. Rinse with clean water, soak in a sodium bicarbonate solution for 1.5 minutes for neutralization, and then rinse with clean water.

[0060] Step 3: Soak the steel plate in 4% zinc phosphate activator solution for 1.5 minutes, rinse and dry at 90°C;

[0061] Step 4: Select a colored PVC film with a thickness of 0.3 mm, preheat it at 45°C, and then laminarize it on a hot press laminating machine at 160°C and 0.4MPa. The laminating speed is 8 m / min. After laminating, first air cool it to 40°C, and then water cool it to room temperature.

[0062] Step 5: Use a laser cutting machine to trim the coated steel plate and inspect it according to the above quality inspection method;

[0063] The test results of the VPN steel plate sample prepared in Example 1 showed that the film had good adhesion to the steel plate, and the peeling area was only 3%;

[0064] There are no obvious defects in appearance;

[0065] In the weathering test, the color change ΔE value was 3, and the gloss reduction rate was 20%;

[0066] Example 2

[0067] Step 1: using the same steel plate as in Example 1, only changing the formula of the alkaline degreasing agent, adjusting the sodium hydroxide content to 8%, the sodium carbonate content to 3%, the sodium phosphate content to 3%, the fatty alcohol polyoxyethylene ether content to 1%, the scale inhibitor to 15 parts, the promoter to 12 parts and the complexing agent to 6 parts, and keeping other degreasing conditions unchanged, soaking at 55° C. for 4 minutes, and then washing the surface of the steel plate with 2.5 MPa high-pressure water;

[0068] Step 2: The rust removal, neutralization, activation and drying steps are the same as those in Example 1;

[0069] Step 3: In the laminating step, the hot pressing temperature is adjusted to 170°C, the pressure is 0.45 MPa, the laminating speed is 6 m / min, the film thickness is still 0.3 mm, and the preheating and cooling conditions remain unchanged;

[0070] Step 4: Quality inspection after trimming;

[0071] The test results of the VPN steel plate sample prepared in Example 2: the film has good adhesion to the steel plate, and the peeling area is 4%;

[0072] There are no obvious defects in appearance;

[0073] In the weathering test, the color change ΔE value was 4, and the gloss reduction rate was 25%;

[0074] Example 3

[0075] Step 1: Using the same steel plate again, the alkaline degreasing agent is restored to the formula of Example 1, and the degreasing conditions remain unchanged;

[0076] Step 2: In the rust removal step, the concentration of hydrochloric acid is adjusted to 13%, hexamethylenetetramine 5 parts, sodium dodecylbenzene sulfonate 5 parts, sodium dodecyl sulfate 1 part, urea 0.1 parts, triethanolamine 0.2 parts, sodium chloride 0.2 parts, emulsifier 0.1 parts and nonionic surfactant 0.1 parts, the soaking time is 2 minutes, and the subsequent neutralization, activation and drying steps remain unchanged;

[0077] Step 3: During lamination, the hot pressing temperature is 165°C, the pressure is 0.42MPa, the lamination speed is 7m / min, the film thickness is 0.3mm, and the preheating and cooling conditions remain unchanged;

[0078] Step 4: Quality inspection after trimming;

[0079] Test results of VPN steel plate sample prepared in Example 3: After quality inspection, the film has good adhesion to the steel plate, and the peeling area is 3.5%;

[0080] There are no obvious defects in appearance;

[0081] The color change ΔE value in the weathering test was 3.5, and the gloss reduction rate was 22%;

[0082] Comparative Example

[0083] Step 1: Use the traditional steel plate that has been cleaned with ordinary detergent to coat the steel plate;

[0084] Step 2: Select the same 0.3mm PVC film and directly laminate it without preheating. The lamination is carried out by hot pressing, with a hot pressing temperature of 150°C, a pressure of 0.3MPa, a laminating speed of 10m / min, and no cooling treatment;

[0085] Step 3: Quality inspection after trimming;

[0086] The test results of the VPN steel plate sample prepared in the comparative example showed that the film had poor adhesion to the steel plate, with the peeling area reaching up to 20%;

[0087] The appearance has obvious wrinkles and a small amount of bubbles;

[0088] In the weathering test, the color change ΔE value is 10 and the gloss reduction rate is 50%;

[0089] Comparison table of the embodiment data of the VCM steel plate coating process based on the above multi-stage pre-treatment and the traditional process:

[0090]

[0091] By comparing the data of the above embodiment with the comparative embodiment, it can be clearly seen that:

[0092] In terms of adhesion, the adhesion between the film and the steel plate in the multi-stage pre-treatment process embodiment of the present invention is significantly better than that of the traditional process, and the peeling area is much lower than the 5% required by the traditional process, and can reach a minimum of 3%, indicating that the multi-stage pre-treatment effectively improves the bonding between the two;

[0093] In terms of appearance quality, the defects such as wrinkles and bubbles that occur in the traditional process are effectively avoided in the process embodiment of the present invention, and the product appearance is smoother and more beautiful;

[0094] In terms of weather resistance, after aging tests, the color change ΔE value and gloss reduction rate of the products of the process embodiments of the present invention are much lower than those of the traditional processes, indicating that their weather resistance and durability have been greatly improved, and they can better adapt to the test of long-term use and harsh environments.

[0095] In summary, the VCM steel plate coating process based on multi-stage pretreatment of the present invention shows obvious advantages in many aspects, can effectively improve the quality and performance of VCM steel plate coating products, and has broad application prospects.

[0096] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A VCM steel plate coating process based on multi-stage pre-treatment, characterized in that: The following steps are involved: Pre-treatment, lamination and post-treatment, namely: Pre-treatment includes: Step 1: Take out the rolled VCM steel plate and unfold it, use an alkaline degreasing agent, the main components of which are 5%-8% sodium hydroxide, 3%-5% sodium carbonate, 2%-3% sodium phosphate and 1%-2% fatty alcohol polyoxyethylene ether of non-ionic surfactant, and mix the remaining components of scale inhibitor, promoter and complexing agent, stir and filter to make a degreasing agent solution; Step 2: Immerse the VCM steel plate in the degreasing agent solution, control the solution temperature at 50-60°C, and immerse for 3-5 minutes to remove the oil stains from the surface of the VCM steel plate; Step 3: Using a hydrochloric acid solution with a concentration of 10%-15% as the main raw material of the rust remover, and mixing the remaining raw materials of hexamethylenetetramine, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, urea, triethanolamine, sodium chloride, emulsifier and non-ionic surfactant to prepare a rust remover solution, immersing the steel plate in the rust remover solution at a temperature of 20-25°C for 2-3 minutes, the rust reacts chemically with the hydrochloric acid to generate water-soluble ferric chloride floating on the surface of the steel plate; Step 4: After the rust removal in step 3 above, immediately rinse the steel plate with plenty of clean water to prevent the acid residue from corroding the steel plate. Then immerse the steel plate in a 1%-2% sodium bicarbonate solution for 1-5 minutes to neutralize the residual acidic substances, and then rinse it with clean water; Step 5: Use zinc phosphate solution as an activator and phosphating agent with a solution concentration of 3%-5%, and soak the steel plate in the activator solution for 1-2 minutes; Step 6: After the activation treatment in step 5 above, rinse the steel plate with clean water and dry it at 80-100°C to dry the surface of the steel plate. Apply a primer of weather-resistant coating on the surface of the steel plate, and wait for the primer to dry before preparing for subsequent lamination. Lamination includes: Step 7: preheat the VCM steel plate after being dried in the above steps 1 to 6 through a preheating furnace to reach the required temperature of 30-45°C for lamination; Step 8: Select high-quality polyvinyl chloride film with a thickness of 0.1-0.5mm. Pre-print various patterns and colors on the film as needed. Preheat the film before lamination at a temperature of 40-50°C to make the film soft and easy to fit. Step 9: Using hot pressing laminating process, the hot pressing temperature is controlled at 150-180℃, the pressure is 0.3-0.5MPa, and the preheated film is laminated with the steel plate after multi-stage pretreatment through a laminating machine; Step 10: After the lamination in step 9 above, the steel plate is cooled by combining air cooling and water cooling. First, the surface temperature of the steel plate is quickly reduced to below 50°C by air cooling, and then water cooling is performed to cool the steel plate to room temperature to ensure that the film and the steel plate are more firmly bonded; Post-processing includes: Step 11: Trim the edges of the coated VCM steel plate to remove the excess film edge to make the edge of the steel plate neat and beautiful. Use a high-precision laser cutting machine with a cutting accuracy of up to ±0.5mm to ensure the trimming quality; Step 12: Perform a comprehensive quality inspection on the VCM steel plate after trimming in step 11 above, including adhesion test between the film and the steel plate, appearance inspection and weather resistance inspection.

2. The VCM steel plate coating process based on multi-stage pre-treatment according to claim 1 is characterized in that: The remaining components of the alkaline degreasing agent solution include 10-24 parts of scale inhibitor, 8-17 parts of promoter and 3-8 parts of complexing agent by weight.

3. The VCM steel plate coating process based on multi-stage pretreatment according to claim 1 is characterized in that: After the main components of the alkaline degreasing agent solution are mixed, the scale inhibitor is added and stirred with a stirrer for 5-8 minutes. After stirring, the promoter and the complexing agent are added in sequence, stirred clockwise, and then filtered to form an alkaline degreasing agent solution.

4. The VCM steel plate coating process based on multi-stage pre-treatment according to claim 1 is characterized in that: After the degreasing treatment of the VCM steel plate is completed, the steel plate is washed with high-pressure water, and the water pressure is maintained at 2-4 MPa to ensure that the residual degreasing agent and the fallen oil stains are cleaned.

5. The VCM steel plate coating process based on multi-stage pre-treatment according to claim 1 is characterized in that: The remaining ingredients of the rust remover include, by weight, 1-10 parts of hexamethylenetetramine, 1-10 parts of sodium dodecylbenzenesulfonate, 0-2 parts of sodium dodecyl sulfate, 0.1-0.2 parts of urea, 0.1-0.2 parts of triethanolamine, 0.1-0.3 parts of sodium chloride, 0.1-0.2 parts of nonionic surfactants, and 0.1-0.3 parts of emulsifiers.

6. The VCM steel plate coating process based on multi-stage pre-treatment according to claim 1 is characterized in that: The emulsifier in the remaining components of the rust remover is TX-10, and the nonionic surfactant in the remaining components of the rust remover is detergent 6501.

7. The VCM steel plate coating process based on multi-stage pre-treatment according to claim 1 is characterized in that: The hot pressing laminating speed in step 9 is 5-10 m / min.

8. The VCM steel plate coating process based on multi-stage pre-treatment according to claim 1 is characterized in that: The adhesion test in step 12 adopts the cross-hatch method, in which 6 straight lines with a spacing of 1 mm are drawn on the surface of the steel plate, and then a special tape is used to stick and then torn off, and the film shedding is observed, and the shedding area is required to be no more than 5%.

9. The VCM steel plate coating process based on multi-stage pre-treatment according to claim 1, characterized in that: The appearance inspection in step 12 is performed by visual inspection to check whether there are defects such as wrinkles, bubbles, scratches, etc. on the surface of the film.

10. The VCM steel plate coating process based on multi-stage pre-treatment according to claim 1, characterized in that: The weather resistance test in step 12 is to place the selected samples in an aging test box simulating a harsh environment, expose them to ultraviolet rays for 800-1000 hours, and then place them in a high temperature and high humidity cycle simulation box to check the color change, gloss reduction, and cracking of the film. The color change ΔE value is required to be no more than 5, and the gloss reduction rate is required to be no more than 30%.

Images