Method for quickly and accurately evaluating paint treatment adaptability of high-strength steel cold-rolled plate

Abstract

This invention discloses a method for rapidly and accurately evaluating the paintability of high-strength cold-rolled steel sheets. Specifically, the method involves performing pre-coating corrosion resistance tests, surface activity tests, and inherent corrosion resistance tests on the high-strength cold-rolled steel sheets. If both the pre-coating corrosion resistance test and the inherent corrosion resistance test show no rust on the sheet surface, and the surface activity test shows a bubble formation time of 20-50 seconds, then the high-strength cold-rolled steel sheet is suitable for painting; otherwise, it is not. This method can accurately and efficiently evaluate the paintability of high-strength cold-rolled steel sheets.

Description

Technical Field

[0001] This invention belongs to the field of materials chemistry, and specifically relates to a method for rapidly and accurately evaluating the adaptability of high-strength cold-rolled steel sheets to paint treatment. Background Technology

[0002] In the rapid development of the modern automotive manufacturing industry, high-strength steel (HSS) has become the preferred material for vehicle body structural components due to its superior mechanical properties, lightweight potential, and significant advantages in crash safety. In particular, the precise thickness control, high surface flatness, and excellent processability of cold-rolled high-strength steel sheets make them an indispensable material in the automotive manufacturing field. However, the high silicon and manganese enrichment on the surface of cold-rolled high-strength steel sheets results in poor corrosion resistance during the painting process, making pre-treatment for paintability a key factor limiting its widespread application.

[0003] Traditional methods for evaluating the corrosion resistance of high-strength cold-rolled steel sheets mainly rely on constant temperature and humidity tests and electrochemical detection. These methods cannot accurately predict the pretreatment quality of the sheet surface. While they offer some accuracy in revealing the paintability characteristics of materials, the conclusions often fail to fully reflect the true performance of the sheet during actual paintability treatments. Especially in the early stages of new material development, rapid and accurate assessment of corrosion resistance is crucial for shortening the development cycle and reducing development costs. However, existing methods are still insufficient in this regard.

[0004] In light of the above background, this invention aims to provide a method for rapidly and accurately assessing the paintability of high-strength cold-rolled steel sheets. This method ingeniously integrates key modern chemical analysis techniques, aiming to achieve rapid and accurate evaluation of the paintability of high-strength cold-rolled steel sheets. This method can not only provide strong support for the research and development of new materials, but also effectively guide production quality control and subsequent paintability optimization, thereby comprehensively improving the overall quality and market competitiveness of automotive products. Furthermore, this method is expected to promote automotive materials science towards a more intelligent and green direction, injecting new vitality into the sustainable development of the industry. Summary of the Invention

[0005] The purpose of this invention is to provide a method for rapidly and accurately assessing the adaptability of high-strength cold-rolled steel sheets to paint treatment.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for rapidly and accurately assessing the paint treatment adaptability of high-strength cold-rolled steel sheets includes conducting pre-coating treatment film corrosion resistance tests, sheet surface activity tests, and sheet inherent corrosion resistance tests on the high-strength cold-rolled steel sheets, as detailed below:

[0008] Corrosion resistance test of pre-coating treatment film: Immerse the pre-coating high-strength cold-rolled steel sheet in a sulfuric acid solution with pH=3-6 for 1-4 minutes, then quickly immerse it in high conductivity water for 1.5-2 minutes. Remove the sheet and spray it with high conductivity water at a pressure of 0.10-0.30 MPa for 0.5-2.5 minutes. Observe whether there is rust on the surface of the sheet.

[0009] Surface activity test of sheet material: Immerse thoroughly degreased cold-rolled sheet material in 0.9-1.0 mol / L sulfuric acid solution and observe the time it takes for bubbles to appear on the sheet material surface;

[0010] Corrosion resistance test of the sheet material: The thoroughly degreased cold-rolled sheet material is immersed in high conductivity water for 20-180 seconds. After that, the sheet material is removed and sprayed with low conductivity water at a pressure of 0.10-0.30 MPa for 80-180 seconds. The high conductivity water has a conductivity of 500-1000 μS / cm and a pH of 8-10, while the low conductivity water has a conductivity of 90-150 μS / cm and a pH of 7-10. The sheet material surface is then observed for any signs of rust.

[0011] If the corrosion resistance test results of the pre-coating treatment film and the corrosion resistance test results of the plate itself are both that there is no rust on the plate surface, and the time for bubbling on the plate surface during the surface activity test is between 20s and 50s, then it indicates that the high-strength cold-rolled steel plate is suitable for painting treatment; otherwise, it is not suitable.

[0012] Furthermore, in the method of the present invention, the temperature of the sulfuric acid solution in the corrosion resistance test of the pre-coating treatment film is 30-40°C.

[0013] Furthermore, in the method of the present invention, the high conductivity water used in the corrosion resistance test of the pre-coating treatment film has a conductivity of 500-1000 μS / cm, a pH of 4-6, and a temperature of 20-40℃.

[0014] Furthermore, in the method of the present invention, the high conductivity water used in the corrosion resistance test of the pre-coating treatment film has a chloride ion concentration of 50-100 ppm, a sulfate concentration of 0.5-1.5 ppm, a bicarbonate concentration of 200-300 ppm, a calcium ion concentration of 10-300 ppm, and a magnesium ion concentration of 10-300 ppm.

[0015] Furthermore, in the method of the present invention, the corrosion inhibitor points of both the high conductivity water and the low conductivity water in the corrosion resistance test of the plate are 0-6pt, and the temperature is 20-50℃.

[0016] Furthermore, in the method of the present invention, the high conductivity water used in the corrosion resistance test of the plate itself has a chloride ion concentration of 50-100 ppm, a sulfate concentration of 0.5-1.5 ppm, a bicarbonate concentration of 200-300 ppm, a calcium ion concentration of 10-300 ppm, and a magnesium ion concentration of 10-300 ppm.

[0017] Furthermore, in the method of the present invention, the chloride ion concentration of the low conductivity water in the corrosion resistance test of the plate itself is 50-80 ppm.

[0018] The inventive principle of the technical solution of this invention lies in:

[0019] (1) In the simulated pre-coating process, the pre-treatment plates (including phosphate plates, film plates, silane plates, zirconium plates, etc.) are immersed in acidic solutions and industrial water. If there are leaks in the pre-coating film, the surface of the plate is prone to rust, making the plate unusable. Conversely, if there are no leaks in the pre-treatment film, the plate has good rust prevention performance and can be used for paintability treatment.

[0020] (2) By immersing the board in sulfuric acid solution, the surface activity of the board can be judged according to the time it takes for bubbles to emerge from the board surface. The shorter the bubble emergence time, the greater the surface activity of the board. The board is more prone to rusting during the water washing stage after degreasing. However, if there is no rust on the board surface, it is easier to form a pretreatment film. Conversely, a long bubble emergence time indicates that the activity is too low. The board is not easy to rust during the water washing stage after degreasing, but it is difficult to form a pretreatment film. Therefore, the bubble emergence time should be controlled between 20s and 50s.

[0021] (3) Due to the addition of more alloying elements, high-strength steel is prone to surface enrichment after annealing, and galvanic corrosion is likely to occur during the water washing stage after degreasing in the painting workshop. Therefore, it is necessary to simulate the water washing process after degreasing in the painting workshop, immerse the degreased plates in an industrial water environment, and observe whether they rust. If they do not rust, the plates can be painted; if they rust, they cannot be used for painting.

[0022] The beneficial effects of adopting the above technical solution are as follows:

[0023] This invention, through the deep integration of modern chemical analysis technology, achieves accurate and efficient evaluation of the adaptability of high-strength steel to paint treatment. This not only significantly improves the efficiency and accuracy of the evaluation, but also provides a solid scientific basis for the research and development of new materials and the quality control of production. Detailed Implementation

[0024] The technical solution of the present invention will be further described in detail below through embodiments.

[0025] Examples 1-4

[0026] High-strength cold-rolled steel sheets produced by a certain company were selected as test materials. Example 1 used HC420LA as the test material, Example 2 used HC340 / 590DP, Example 3 used HC420 / 780DP, and Example 4 used HC550 / 980DP. The methods for evaluating their paint treatment adaptability included testing the corrosion resistance of the pre-coating treatment film, the surface activity of the sheet, and the inherent corrosion resistance of the sheet itself, as detailed below:

[0027] (1) Corrosion resistance test of pre-coating treatment film: The high-strength cold-rolled steel plate after pre-coating treatment is immersed in sulfuric acid solution with pH=3-6 and temperature of 30-40℃ for 1-4 min, and then quickly immersed in high conductivity water. After 1.5-2 min, the plate is taken out and then sprayed with high conductivity water. The spraying pressure is 0.10-0.30MPa and the spraying time is 0.5-2.5 min. The plate surface is observed for rust. The high conductivity water has a conductivity of 500-1000μS / cm, pH of 4-6, and temperature of 20-40℃. The high conductivity water has a chloride ion concentration of 50-100ppm, a sulfate concentration of 0.5-1.5ppm, a bicarbonate concentration of 200-300ppm, a calcium ion concentration of 10-300ppm, and a magnesium ion concentration of 10-300ppm.

[0028] (2) Surface activity test of sheet material: The thoroughly degreased cold-rolled sheet material is immersed in a 0.9-1.0 mol / L sulfuric acid solution;

[0029] (3) Corrosion resistance test of the sheet material itself: The thoroughly degreased cold-rolled sheet material is immersed in high conductivity water for 20-180 seconds. After that, the sheet material is removed and the surface of the sheet material is sprayed with low conductivity water at a spraying pressure of 0.10-0.30 MPa for 80-180 seconds. The high conductivity water has a conductivity of 500-1000 μS / cm and a pH of 8-10. The low conductivity water has a conductivity of 90-150 μS / cm and a pH of 7-10. Observe the surface of the plate for rust; wherein, the corrosion inhibitor points of the high conductivity water and the low conductivity water are 0-6pt, and the temperature is 20-50℃; the chloride ion concentration of the high conductivity water is 50-100ppm, the sulfate concentration is 0.5-1.5ppm, the bicarbonate concentration is 200-300ppm, the calcium ion concentration is 10-300ppm, and the magnesium ion concentration is 10-300ppm; the chloride ion concentration of the low conductivity water is 50-80ppm.

[0030] The detection parameters for each test item in each embodiment are shown in Table 1; the ion concentrations of high-conductivity water and low-conductivity water used for the corrosion resistance test of the pre-coating treatment film and the corrosion resistance test of the substrate itself in each embodiment are shown in Table 2. The test results of each embodiment are shown in Table 3.

[0031] Table 1 Detection parameters for each embodiment

[0032]

[0033] Table 2. Ion concentrations in high-conductivity and low-conductivity water used in each embodiment.

[0034]

[0035] Table 3 Test results of each embodiment

[0036]

[0037] The high-strength cold-rolled steel sheets evaluated in each embodiment were painted on 5 different painting production lines, and the results are shown in Table 4.

[0038]

[0039] As can be seen from Tables 3 and 4, the evaluation results of the method of the present invention are consistent with the actual implementation effect, indicating that the method of the present invention can effectively evaluate and predict the paint treatment adaptability of high-strength steel cold-rolled sheets.

[0040] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for rapidly and accurately assessing the paint treatment adaptability of high-strength cold-rolled steel sheets, characterized in that, The high-strength steel cold-rolled sheets were subjected to corrosion resistance tests on the pre-coating treatment film, surface activity tests, and inherent corrosion resistance tests, as detailed below: Corrosion resistance test of pre-coating treatment film: High-strength cold-rolled steel sheets after pre-coating treatment are immersed in a sulfuric acid solution with pH 3-6 for 1-4 minutes, then quickly immersed in high-conductivity water with a conductivity of 500-1000 μS / cm, pH 4-6, and temperature 20-40℃ for 1.5-2 minutes. The sheets are then removed and sprayed with the same high-conductivity water at a pressure of 0.10-0.30 MPa for 0.5-2.5 minutes. The surface of the sheets is observed for rust. In the corrosion resistance test of the pre-coating treatment film, the high-conductivity water has a chloride ion concentration of 50-100 ppm, a sulfate concentration of 0.5-1.5 ppm, a bicarbonate concentration of 200-300 ppm, a calcium ion concentration of 10-300 ppm, and a magnesium ion concentration of 10-300 ppm. Surface activity test of sheet material: Immerse thoroughly degreased cold-rolled sheet material in 0.9-1.0 mol / L sulfuric acid solution and observe the time it takes for bubbles to appear on the sheet material surface; Corrosion resistance test of the sheet material: The thoroughly degreased cold-rolled sheet was immersed in high-conductivity water (500-1000 μS / cm, pH 8-10) for 20-180 seconds. After immersion, the sheet was removed and sprayed with low-conductivity water (90-150 μS / cm, pH 7-10) at a pressure of 0.10-0.30 MPa for 80-180 seconds. The surface of the sheet was then observed for rust. In the self-corrosion resistance test, the corrosion inhibitor points for high-conductivity water and low-conductivity water were 0-6 pt, the temperature was 20-50℃, the chloride ion concentration of high-conductivity water was 50-100 ppm, the sulfate concentration was 0.5-1.5 ppm, the bicarbonate concentration was 200-300 ppm, the calcium ion concentration was 10-300 ppm, and the magnesium ion concentration was 10-300 ppm; in the self-corrosion resistance test of the plate, the chloride ion concentration of low-conductivity water was 50-80 ppm. If the corrosion resistance test results of the pre-coating treatment film and the corrosion resistance test results of the plate itself are both that there is no rust on the plate surface, and the time for bubbling on the plate surface during the surface activity test is between 20s and 50s, then it indicates that the high-strength cold-rolled steel plate is suitable for painting treatment; otherwise, it is not suitable.

2. The method for rapidly and accurately evaluating the paint treatment adaptability of high-strength cold-rolled steel sheets according to claim 1, characterized in that, The temperature of the sulfuric acid solution used in the corrosion resistance test of the pre-coating treatment film is 30-40℃.

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