Preparation method of hot-dip galvanized coated steel plate

Abstract

The invention provides a preparation method of a hot-dip galvanized coating steel plate. A smelted and cast steel plate blank is subjected to hot continuous rolling and cold continuous rolling to control the plate shape of the steel plate; initial nucleation and growth of gamma-oriented texture grains are promoted through continuous annealing, so that the strip steel obtains good deep drawability; after hot galvanizing is conducted on the strip steel, flattening treatment is conducted to guarantee the steel plate shape; the coating film is prepared on the surface of the hot-dip galvanizing layer, so that the coating film and the hot-dip galvanizing layer form a stable compound layer, the compound layer has excellent stamping and coating lubricating properties, and even under the conditions of high temperature and severe friction of high-speed large-deformation stamping, the coating film on the surface of the hot-dip galvanizing layer has good stamping lubricating property, so that the hot-dip galvanizing layer can be subjected to hot-dip galvanizing. Therefore, the phenomena of surface zinc layer falling and powder falling during processing are greatly reduced, the product surface quality is improved, the manual shutdown die wiping frequency is reduced, the die cleaning frequency is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical manufacturing and relates to a method for preparing a coated steel plate. Background Art

[0002] Hot-dip galvanized steel sheets are mainly used in the automotive field, among which hot-dip galvanized coated steel sheet products are used in large-size deep stamping to manufacture automotive outer panels; hot-dip galvanized coated steel sheet products require both excellent stamping performance and excellent surface quality and coating performance that is resistant to subsequent alkali washing, baking, and painting. However, hot-dip galvanized coated steel sheets are prone to zinc layer shedding and powdering during the strip processing and stamping process. This is because the hot-dip galvanized coated steel sheet generates high temperature under the processing conditions of large deformation and high-speed stamping, and the mold gap changes at the same time, resulting in huge friction between the mold and the hot-dip galvanized coated steel sheet. Because the zinc layer of the hot-dip galvanized coated steel sheet is soft and has weak cohesion, the zinc layer falls off and powders due to friction with the mold under high temperature conditions. The powder is generally the shedding of the surface zinc layer. The fallen powder accumulates on the mold surface, affecting the surface quality of the product, causing customers to stop the machine for cleaning, and the mold wiping frequency is high, which is not conducive to high-speed stamping on-site production, and directly affects production efficiency. Summary of the invention

[0003] In order to solve the problem of zinc layer shedding and powdering of hot-dip galvanized coated steel sheet under large deformation and high-speed stamping processing conditions described in the background technology, the present invention provides a method for preparing hot-dip galvanized coated steel sheet.

[0004] The method of the present invention comprises:

[0005] The steel substrate is smelted and cast into slabs;

[0006] The slab is conventionally heated and then hot-rolled to obtain a plate;

[0007] Spray water to cool the sheet to the coiling temperature and coil it;

[0008] The coiled sheet is subjected to continuous cold rolling to obtain a cold-rolled thin steel sheet;

[0009] The strip steel is cleaned through alkali washing, brushing, degreasing and rinsing processes;

[0010] Continuously annealing the cold-rolled steel sheet;

[0011] The annealed strip steel is subjected to a hot-dip galvanizing process to form a hot-dip galvanized layer on the surface;

[0012] The hot-dip galvanized thin steel sheet is flattened to obtain a strip steel;

[0013] The hot-dip galvanized layer of the steel strip is post-treated to prepare a coating film on the surface of the hot-dip galvanized layer.

[0014] Furthermore, the chemical composition of the steel substrate is calculated by weight percentage as follows: C: ≤0.002, Si: ≤0.01, Mn: 0.06-0.12, P: ≤0.012, S: ≤0.009, Ti: 0.065-0.085, Als: 0.02-0.05, N: ≤0.003, and the rest is Fe and unavoidable impurities. The steel substrate adopts a soft steel composition process design, which further ensures the deep drawing performance of the strip.

[0015] Furthermore, in the hot rolling, the final rolling temperature is controlled at 910-950°C.

[0016] Furthermore, during the coiling, the coiling temperature is controlled at 710-740°C.

[0017] Furthermore, in the cold rolling, the number of cold rolling is at least 5 times, and the total cold rolling reduction rate is controlled to be 73-85%.

[0018] Furthermore, in the continuous annealing, the soaking temperature is 820-840°C, the rapid cooling end temperature is 440-470°C, and the annealing cold-rolled sheet tape speed is controlled to be stable at a fixed value between 120-150m / min. By controlling the annealing cold-rolled sheet tape speed, the temperature of the thin steel sheet is kept stable during the continuous annealing process, further promoting the initial nucleation and growth of γ-oriented texture grains, thereby obtaining good deep drawing performance.

[0019] Furthermore, the annealed strip enters a zinc pot for hot-dip galvanizing, and then is flattened to control the elongation to be 0.5-0.6%.

[0020] Furthermore, in the post-treatment of the hot-dip galvanized layer, a roller coating method is used to evenly coat the surface of the hot-dip galvanized layer with an aqueous solution of pyridine and / or piperazine, and induction heating and hot air baking and curing are performed to obtain a coating film on the surface of the hot-dip galvanized layer.

[0021] Furthermore, in the post-treatment of the hot-dip galvanized layer, the mass concentration of the aqueous solution of pyridine and / or piperazine is 1-5wt%. The use of a coating aqueous solution with lubricity ensures the stamping lubricity of the coating film.

[0022] Furthermore, in the post-treatment of the hot-dip galvanized layer, the induction heating and hot air baking curing and drying control the plate temperature to 90-120°C, and 10-100 mg / m 2 By controlling the drying temperature of the coating aqueous solution after roller coating to match the melting point, a surface coating with stamping lubricity is formed, so that the prepared hot-dip galvanized coated steel sheet has excellent stamping processing and coating lubricity, and significantly reduces the shedding and powdering of the hot-dip galvanized layer during high-speed stamping processing.

[0023] Compared with the prior art, the present invention controls the shape of the steel plate by hot rolling and cold rolling of the smelted and cast steel slab, and performs flattening treatment to ensure the shape of the steel plate; promotes the initial nucleation and growth of γ-oriented texture grains by continuous annealing, so that the strip steel obtains good deep drawing performance; after the strip steel is hot-dip galvanized, a coating film is prepared on the surface of the hot-dip galvanized layer, so that the coating film and the hot-dip galvanized layer form a stable composite layer, and the composite layer has excellent stamping processing and coating lubrication properties. Even under high temperature and severe friction conditions of high-speed and large-deformation stamping, the coating film on the surface of the hot-dip galvanized layer has good stamping lubricity, thereby greatly reducing the shedding and powdering phenomenon of the surface zinc layer during processing. The hot-dip galvanized coated steel sheet prepared by the present invention has excellent stamping forming performance, low dynamic friction coefficient, high cupping value and scratch resistance. After the hot-dip galvanized coated steel sheet is stamped at high speed and large deformation, the product surface is wear-resistant and has no obvious powder loss, which greatly reduces the powder sticking to the mold after the product is processed, and solves the problem of zinc layer shedding and powdering of the hot-dip galvanized coated steel sheet under large deformation and high-speed stamping processing conditions and mold powder sticking in subsequent production. The hot-dip galvanized coated steel sheet of the present invention is suitable for processing conditions of large deformation and high-speed stamping, which greatly reduces the phenomenon of zinc layer shedding and powdering, improves the surface quality of the product, reduces the frequency of manual shutdown and mold wiping, reduces the frequency of mold cleaning, and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a flow chart of the method of the present invention.

[0025] Figure 2 This is the surface electron microscope image of the hot-dip galvanized coated steel plate after stamping. Figure 2 (a) is a surface electron microscope image of the hot-dip galvanized coated steel plate of comparative example 1 after stamping. Figure 2 (b) is a surface electron microscope image of the hot-dip galvanized coated steel sheet of Example 1 after stamping.

[0026] Figure 3 This is a photo of the die surface after hot-dip galvanized coated steel plate has been stamped. Figure 3 (a) is a photo of the die surface of the hot-dip galvanized coated steel plate of comparative example 1 after stamping. Figure 3 (b) is a photograph of the mold surface of the hot-dip galvanized coated steel sheet of Example 1 after stamping. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] A method for preparing a hot-dip galvanized coated steel sheet, the flow chart is as follows Figure 1 As shown, the details are as follows.

[0029] First, the steel base material is smelted and cast into slabs.

[0030] Among them, the steel substrate adopts a soft steel composition process design, and the chemical composition of the steel substrate is calculated by weight percentage: C: ≤0.002, Si: ≤0.01, Mn: 0.06-0.12, P: ≤0.012, S: ≤0.009, Ti: 0.065-0.085, Als: 0.02-0.05, N: ≤0.003, and the rest is Fe and unavoidable impurities.

[0031] Then, the slab is conventionally heated and then hot-rolled to obtain a plate, and the final rolling temperature is controlled at 910-950°C during the hot-rolling.

[0032] The plate is sprayed with water to cool to the coiling temperature and then coiled, and the coiling temperature is controlled at 710-740℃.

[0033] The curled plate is subjected to continuous cold rolling to obtain a cold-rolled thin steel plate; in the continuous cold rolling, the number of cold rolling is at least 5 times, and the total cold rolling reduction rate is controlled to be 73-85%.

[0034] The strip is cleaned through processes including alkali washing, brushing, degreasing, and rinsing, and then continuously annealed; during continuous annealing, the soaking temperature is 820-840℃, the rapid cooling end temperature is 440-470℃, and the annealing cold-rolled sheet conveying speed is controlled to be stable at a fixed value between 120-150m / min. By controlling the annealing cold-rolled sheet conveying speed, the temperature of the thin steel sheet is kept stable during the continuous annealing process, further promoting the initial nucleation and growth of γ-oriented texture grains, thereby obtaining good deep drawing performance.

[0035] The annealed steel strip is subjected to a hot-dip galvanizing process to form a hot-dip galvanized layer on the surface. Specifically, the annealed steel strip enters a zinc pot for hot-dip galvanizing treatment.

[0036] The galvanized thin steel plate is flattened to obtain strip steel. During the flattening process, the elongation is controlled at 0.5-0.6% to ensure the shape of the steel plate.

[0037] The hot-dip galvanized layer of the steel strip is post-treated to prepare a coating film on the surface of the hot-dip galvanized layer. Specifically, the aqueous solution of pyridine and / or piperazine is evenly coated on the surface of the hot-dip galvanized layer by roller coating, and induction heating and hot air baking curing and drying are performed to obtain a coating film on the surface of the hot-dip galvanized layer. More specifically, the mass concentration of the aqueous solution of pyridine and / or piperazine is 1-5wt%; the plate temperature of the induction heating and hot air baking curing and drying is controlled to reach 90-120°C, and 10-100mg / m2 Thickness of coating film.

[0038] In the following examples, the method of the present invention is used to prepare hot-dip galvanized coated steel sheets. The chemical composition of the steel substrate used is as follows by weight percentage: C: ≤0.002, Si: ≤0.01, Mn: 0.06-0.12, P: ≤0.012, S: ≤0.009, Ti: 0.065-0.085, Als: 0.02-0.05, N: ≤0.003, and the rest is Fe and unavoidable impurities.

[0039] Example 1

[0040] The steel base material is smelted and cast into a slab; the slab is conventionally heated and then hot-rolled to obtain a plate, and the final rolling temperature is controlled at 910-950°C; the plate is sprayed with water to cool to the coiling temperature and coiled, and the coiling temperature is controlled at 710-740°C; the coiled plate is cold-rolled to obtain a cold-rolled thin steel plate, the number of cold rolling is 5, and the total cold rolling reduction rate is controlled to be 73-85%; the strip is cleaned through alkali washing, brushing, degreasing, and rinsing processes; after cleaning, the cold-rolled thin steel plate is continuously annealed, the soaking temperature is 820-840°C, the rapid cooling end temperature is 440-470°C, and the annealing cold-rolled thin plate is controlled to be stable at a walking speed of 130m / min. The annealed steel strip is subjected to hot-dip galvanizing process to form a hot-dip galvanized layer on the surface; the galvanized thin steel plate is flattened to obtain the steel strip, and the elongation is controlled at 0.5-0.6%; the hot-dip galvanized layer of the steel strip is post-treated, and a pyridine aqueous solution is evenly coated on the surface of the hot-dip galvanized layer by a roller coating method, and the mass concentration of the pyridine aqueous solution is 3wt%; and induction heating and hot air baking curing and drying are performed, and the plate temperature is controlled to reach 90-120°C, and 100mg / m 2 Thickness of coating film.

[0041] Example 2

[0042] In this embodiment, the hot-dip galvanized layer of the steel strip is post-treated, and a piperazine aqueous solution is evenly coated on the surface of the hot-dip galvanized layer by a roller coating method, and the mass concentration of the piperazine aqueous solution is 3wt%; and induction heating and hot air baking curing and drying are performed, and the plate temperature is controlled to reach 90-120°C, and 100mg / m2 of the hot-dip galvanized layer surface is obtained. 2 Thickness of coating film.

[0043] The rest is the same as Example 1.

[0044] Example 3

[0045] In this embodiment, the hot-dip galvanized layer of the steel strip is post-treated, and a mixed aqueous solution of pyridine and piperazine is evenly coated on the surface of the hot-dip galvanized layer by a roller coating method, and the mass concentration of the mixed aqueous solution of pyridine and piperazine is 3wt%; and induction heating and hot air baking curing and drying are performed, and the plate temperature is controlled to reach 90-120°C, and 100mg / m2 of the hot-dip galvanized layer surface is obtained. 2 Thickness of coating film.

[0046] The rest is the same as Example 1.

[0047] Example 4

[0048] In this embodiment, the hot-dip galvanized layer of the strip is post-treated, and a pyridine aqueous solution is evenly coated on the surface of the hot-dip galvanized layer by a roller coating method, and the mass concentration of the pyridine aqueous solution is 1wt%; and induction heating and hot air baking curing and drying are performed, and the plate temperature is controlled to reach 90-120°C, and 50mg / m 2 Thickness of coating film.

[0049] The rest is the same as Example 1.

[0050] Example 5

[0051] In this embodiment, the hot-dip galvanized layer of the strip is post-treated, and a pyridine aqueous solution is evenly coated on the surface of the hot-dip galvanized layer by a roller coating method, and the mass concentration of the pyridine aqueous solution is 5wt%; and induction heating and hot air baking and curing are performed, and the plate temperature is controlled to reach 90-120°C, and 75mg / m 2 Thickness of coating film.

[0052] The rest is the same as Example 1.

[0053] Comparative Example 1

[0054] Purchase conventional hot-dip galvanized coated steel sheets currently available on the market.

[0055] The hot-dip galvanized coated steel sheets of Examples 1-5 and Comparative Example 1 were subjected to performance tests respectively, and the obtained performance comparison table is shown in Table 1. It can be seen from Table 1 that the yield strength and tensile strength of the hot-dip galvanized coated steel sheets of Examples 1-5 are equivalent to or higher than those of the hot-dip galvanized coated steel sheets of Comparative Example 1, wherein as the coating film thickness of the hot-dip galvanized coated steel sheets in Examples 1-5 increases, the yield strength and tensile strength thereof will be higher than that of Comparative Example 1; the elongation of the hot-dip galvanized coated steel sheets of Examples 1-5 is ≥44%, both greater than that of Comparative Example 1; the zinc layer roughness of the hot-dip galvanized coated steel sheets of Examples 1-5 is 0.8-1.2, both less than that of Comparative Example 1; the scratch resistance load of the hot-dip galvanized coated steel sheets of Examples 1-5 is 6.0-7.4kg, much higher than that of Comparative Example 1; the cupping values ​​of the hot-dip galvanized coated steel sheets of Examples 1-5 are all ≥10, much higher than that of Comparative Example 1; the dynamic friction coefficient of the hot-dip galvanized coated steel sheets of Examples 1-5 is all ≤0.10, much lower than that of Comparative Example 1. From the above, it can be seen that the overall performance of the hot-dip galvanized coated steel sheet prepared by the present invention is much higher than that of the conventional hot-dip galvanized coated steel sheet on the market, and has excellent stamping forming performance, lower dynamic friction coefficient, higher cupping value and scratch resistance.

[0056] Table 1 Performance comparison table

[0057]

[0058]

[0059] The hot-dip galvanized coated steel sheet of Example 1 and the hot-dip galvanized coated steel sheet of Comparative Example 1 were subjected to high-speed stamping with large deformation, respectively. The surface electron microscope images of the steel sheets after stamping are as follows: Figure 2 As shown, Figure 2 (a) is a surface electron microscope image of the hot-dip galvanized coated steel plate of comparative example 1 after stamping. The surface powder is seriously lost after stamping. Figure 2 (b) is a surface electron microscope image of the hot-dip galvanized coated steel plate of Example 1 after stamping. The surface after stamping is good; the surface photo of the mold after stamping is as follows Figure 3 As shown, Figure 3 (a) is a photo of the mold surface after the hot-dip galvanized coated steel plate of comparative example 1 was stamped. The mold was seriously sticky with powder. Figure 3 (b) is a photo of the mold surface after the hot-dip galvanized coated steel sheet of Example 1 was stamped, and the mold powder sticking phenomenon was greatly improved. From the above, it can be seen that after the hot-dip galvanized coated steel sheet of the present invention is stamped at high speed and large deformation, the product surface is wear-resistant and there is no obvious powder loss, which greatly reduces the mold powder sticking of the product after processing, and solves the problem of zinc layer shedding and powdering of hot-dip galvanized coated steel sheet under large deformation and high-speed stamping conditions and mold powder sticking in subsequent production.

[0060] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for preparing a hot-dip galvanized coated steel sheet, characterized in that: include: The steel substrate is smelted and cast into slabs; The slab is conventionally heated and then hot-rolled to obtain a plate; Spray water to cool the sheet to the coiling temperature and coil it; The coiled sheet is subjected to continuous cold rolling to obtain a cold-rolled thin steel sheet; The strip steel is cleaned through alkali washing, brushing, degreasing and rinsing processes; Continuously annealing the cold-rolled steel sheet; The annealed strip steel is subjected to a hot-dip galvanizing process to form a hot-dip galvanized layer on the surface; The hot-dip galvanized thin steel sheet is flattened to obtain a strip steel; The hot-dip galvanized layer of the steel strip is post-treated to prepare a coating film on the surface of the hot-dip galvanized layer.

2. The method for preparing a hot-dip galvanized coated steel sheet according to claim 1, characterized in that: The chemical composition of the steel substrate is calculated by weight percentage as follows: C: ≤0.002, Si: ≤0.01, Mn: 0.06-0.12, P: ≤0.012, S: ≤0.009, Ti: 0.065-0.085, Als: 0.02-0.05, N: ≤0.003, and the rest is Fe and unavoidable impurities.

3. The method for preparing a hot-dip galvanized coated steel sheet according to claim 2, characterized in that: During the hot rolling, the final rolling temperature is controlled at 910-950°C.

4. The method for preparing a hot-dip galvanized coated steel sheet according to claim 3, characterized in that: During the coiling, the coiling temperature is controlled at 710-740°C.

5. The method for preparing a hot-dip galvanized coated steel sheet according to claim 4, characterized in that: In the cold rolling, the number of cold rolling is at least 5 times, and the total cold rolling reduction rate is controlled to be 73-85%.

6. The method for preparing a hot-dip galvanized coated steel sheet according to claim 5, characterized in that: In the continuous annealing, the soaking temperature is 820-840° C., the rapid cooling end point temperature is 440-470° C., and the annealing cold-rolled sheet strip running speed is controlled to be stable at a fixed value in the range of 120-150 m / min.

7. The method for preparing a hot-dip galvanized coated steel sheet according to claim 6, characterized in that: The annealed steel strip enters a zinc pot for hot-dip galvanizing, and is flattened after hot-dip galvanizing to control the elongation to be 0.5-0.6%.

8. The method for preparing a hot-dip galvanized coated steel sheet according to claim 7, characterized in that: In the post-treatment of the hot-dip galvanized layer, a roller coating method is used to evenly coat the surface of the hot-dip galvanized layer with an aqueous solution of pyridine and / or piperazine, and induction heating and hot air baking and curing are performed to obtain a coating film on the surface of the hot-dip galvanized layer.

9. The method for preparing a hot-dip galvanized coated steel sheet according to claim 8, characterized in that: In the post-treatment of the hot-dip galvanized layer, the mass concentration of the aqueous solution of pyridine and / or piperazine is 1-5wt%.

10. The method for preparing a hot-dip galvanized coated steel sheet according to claim 9, characterized in that: In the post-treatment of the hot-dip galvanized layer, the induction heating and hot air baking curing and drying control the plate temperature to 90-120°C, and 10-100 mg / m 2 Thickness of coating film.

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