High corrosion-resistant high-strength zinc-aluminum-magnesium plated steel sheet and method for manufacturing the same

Abstract

This invention belongs to the technical field of hot-dip galvanized aluminum-magnesium steel, and discloses a high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet and its manufacturing method. The high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet of this invention comprises a substrate and a zinc-aluminum-magnesium coating formed by hot-dip galvanizing aluminum-magnesium bath; wherein the chemical composition and mass percentage of the substrate are: C: 0.02-0.07%, Si: 0.02-0.10%, Mn: 0.7-0.9%, Als: 0.02-0.07%, P≤0.025%, S≤0.02%, with the balance being Fe and other unavoidable impurities; the chemical composition and mass percentage of the zinc-aluminum-magnesium bath are: Al: 30.0-45.0%, Mg: 5.0-8.0%, Si: 0.5-1.2%, with the balance being Zn and other unavoidable impurities. This invention achieves high strength and high corrosion resistance by adjusting the chemical composition of the zinc-aluminum-magnesium plating solution and optimizing the manufacturing process, without adding strengthening elements such as Nb and Ti to the substrate with low Si and low Mn content.

Description

Technical Field

[0001] This invention belongs to the technical field of hot-dip galvanized aluminum-magnesium steel, specifically relating to a high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet and its manufacturing method. Background Technology

[0002] Zinc-aluminum-magnesium (ZAM) coatings are new coatings that add a certain amount of Al and Mg to traditional zinc-based coatings. These coatings offer 3 to 5 times better corrosion resistance than pure zinc coatings and are widely used in industries such as construction, photovoltaic brackets, and highway guardrails. Currently, the widely used "China Aluminum" ZAM coatings on the market contain no more than 11% Al and no more than 3% Mg. For applications requiring materials in relatively harsh environments, such as building materials in coastal areas or high-humidity and high-temperature regions, the corrosion resistance of the coating needs to be further improved.

[0003] In addition, the concept of high-strength steel with thinner profiles can be applied to industries such as building materials. By replacing ordinary steel plates with high-strength steel plates with a yield strength of 500MPa or higher, and through reasonable structural design, the amount of steel used can be reduced without compromising safety. However, for producing steel plates with a yield strength of 500MPa or higher, traditional steel plate alloy compositions typically involve increasing the content of Si and Mn, and adding elements such as Nb and Ti to enhance strength through precipitation strengthening and phase transformation strengthening. This approach not only increases alloy and process costs, but also introduces difficulties to the hot-dip galvanizing process due to the increased content of alloying elements. For example, the enrichment of alloying elements on the coating surface can cause problems such as incomplete coating and poor coating adhesion. Therefore, achieving both high corrosion resistance and high strength is a key technical challenge. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet and its manufacturing method, which achieves high strength and high corrosion resistance without adding strengthening elements such as Nb and Ti to the substrate with low Si and low Mn content.

[0005] To address the technical problems raised in this invention, this invention provides a high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet, comprising a substrate and a zinc-aluminum-magnesium coating formed by hot-dip galvanizing and zinc-aluminum-magnesium plating solution.

[0006] In the above scheme, the chemical composition and mass percentage of the substrate are as follows: C: 0.02-0.07%, Si: 0.02-0.10%, Mn: 0.7-0.9%, Als: 0.02-0.07%, P≤0.025%, S≤0.02%, with the balance being Fe and other unavoidable impurities.

[0007] In the above scheme, the chemical composition and mass percentage of the zinc-aluminum-magnesium plating solution are: Al: 30.0-45.0%, Mg: 5.0-8.0%, Si: 0.5-1.2%, with the balance being Zn and other unavoidable impurities.

[0008] In the above scheme, the high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet has a yield strength ≥550MPa, a tensile strength ≥550MPa, and an elongation ≥4%.

[0009] This invention also provides a method for manufacturing a high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet, comprising the following steps:

[0010] 1) Smelting and continuous casting

[0011] Continuous casting is performed after smelting according to the composition of the substrate;

[0012] 2) Hot rolling

[0013] The continuously cast slab is heated and then hot-rolled.

[0014] 3) Pickling and cold rolling

[0015] The obtained hot-rolled coils are pickled and then cold-rolled.

[0016] 4) Hot-dip galvanizing

[0017] The cold-rolled substrate is heated to the annealing temperature in an annealing furnace using radiant tubes and held at that temperature. Then, it is hot-dip galvanized magnesium-aluminum plating solution in a zinc pot, removed from the pot and cooled to obtain a high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet.

[0018] In the above scheme, the furnace exit temperature of the heated slab is 1150-1190℃.

[0019] In the above scheme, the final rolling temperature of the hot rolling is 800-840℃.

[0020] In the above scheme, the hot-rolled strip is cooled to 520-570°C and then coiled.

[0021] In the above scheme, the acid temperature of the pickling solution is 85-90℃.

[0022] In the above scheme, the total reduction rate of cold rolling is 50-70%.

[0023] In the above scheme, the thickness of the substrate is 0.40 to 2.5 mm.

[0024] In the above scheme, the heating rate of the radiant tube is 5 to 30 K / s.

[0025] In the above scheme, the annealing temperature is 570-590℃ and the holding time is 40-80s.

[0026] Furthermore, the annealing temperature and holding time satisfy the formula: t=1220-2×T; where T is the annealing temperature in °C; and t is the holding time in seconds.

[0027] In the above scheme, the hydrogen concentration in the annealing furnace is ≥15%, and the dew point is ≤-40℃.

[0028] In the above scheme, the microstructure of the substrate after annealing includes ferrite and carbides, wherein the area of ​​the deformed, non-recrystallized microstructure accounts for 85-96%.

[0029] In the above scheme, the temperature of the substrate when it enters the zinc pot is 5 to 10°C higher than the temperature of the zinc-magnesium-aluminum plating solution.

[0030] In the above scheme, the temperature of the zinc-magnesium-aluminum plating solution is 30-40°C higher than its melting point.

[0031] In the above scheme, the average cooling rate of the cooling process after the pot is cooled is greater than 35 K / s.

[0032] In the above scheme, the single-sided thickness of the zinc-aluminum-magnesium coating is 30-350 g / m. 2 .

[0033] In the above scheme, the zinc-aluminum-magnesium coating includes a coating layer and an interface layer between the substrate and the coating layer.

[0034] Furthermore, the microstructure of the coating layer includes primary (Al) phase, MgZn2 phase, multi-element eutectic Al / Zn / MgZn2 microstructure, and Mg2Si phase.

[0035] Furthermore, the interface layer is a dense Al-Fe compound containing a small amount of Si.

[0036] The design concept of this invention regarding the chemical composition of the substrate is as follows:

[0037] Since the high strength of the steel in this invention mainly comes from the large amount of deformed, unrecrystallized microstructure retained in the substrate after low-temperature annealing, a low-Si, low-Mn composition design can be adopted for the selection of substrate alloying elements, and strengthening elements such as Nb and Ti are not added. The content of the main alloying elements is controlled as follows:

[0038] C: Carbon exists in two forms: dissolved in ferrite and forming carbides, which improve the strength of steel. In the cold rolling process of this invention, conventional hot-rolled coils or CSP hot-rolled coils can be used. In the CSP hot rolling process, the peritectic region must be avoided, and the improvement in material strength mainly comes from the cold-rolled deformation structure. Therefore, this invention controls the C content to 0.02–0.07%.

[0039] Silicon (Si): Silicon is an important reducing agent and deoxidizer in steelmaking. Si does not form carbides but is dissolved in ferrite, increasing its strength. However, when the Si content is high, during heating in an oxidizing atmosphere, Si on the steel surface easily forms oxides with oxygen (O), reducing the wetting effect of the plating solution on the steel substrate, resulting in defects such as exposed plating or poor coating adhesion. Since the strength improvement of the steel in this invention mainly comes from the cold-rolled deformation structure, the Si content can be controlled at a low level. This invention controls the Si content to be between 0.02% and 0.10%.

[0040] Manganese (Mn) is an excellent deoxidizer and desulfurizer in steelmaking. Mn dissolves in ferrite, increasing its strength. However, when the Mn content is high, during heating in an oxidizing atmosphere, the Mn on the steel surface easily forms oxides with oxygen (O), reducing the wetting effect of the plating solution on the steel substrate, resulting in defects such as exposed plating or poor coating adhesion. Since the strength improvement of the steel in this invention mainly comes from the cold-rolled deformation structure, the Mn content can be controlled at a low level. Therefore, this invention controls the Mn content to 0.7–0.9%.

[0041] The design concept of this invention regarding the chemical composition of zinc-aluminum-magnesium plating solution is as follows:

[0042] Al: Increased aluminum content improves the corrosion resistance of the coating. Since this invention uses low-temperature annealing, the cleaning effect on the substrate surface is weaker. The surface cleanliness of the strip before entering the zinc bath is not as good as that of strip heated at high temperatures. For example, there may be a small amount of fine iron oxide residue or localized oxidation. The reactivity between the strip and the plating solution is reduced, thus easily leading to defects such as incomplete plating or poor adhesion during hot-dip galvanizing. Because the reaction between Al and Fe is very vigorous, increasing the Al content in the plating solution can enhance the erosion of the steel plate by the solution, promoting the formation of the Al-Fe interface layer on the substrate, thereby reducing the incidence of defects such as incomplete plating or poor adhesion. When the Al content is below 30%, a continuous Al-Fe interface layer is difficult to form on the substrate when there is localized oxidation on the strip surface, resulting in defects such as incomplete plating or poor adhesion. When the Al content is above 45%, the melting point of the plating solution increases, and the plating solution temperature will exceed the production temperature of the substrate, reducing the strength of the substrate during hot-dip galvanizing. In addition, increasing the Al content will generate more zinc dross, affecting the plating process. Therefore, the Al content in the coating is controlled to be 30-45% in this invention.

[0043] Mg: Increased magnesium content improves the corrosion resistance of the coating, and Mg has a greater effect on improving corrosion resistance than Al. The corrosion products of Zn, Al, and Mg are fluid and can effectively protect the cut edges. However, since Mg is easily oxidized, an increase in Mg content leads to an increase in slag during the production process. Simultaneously, an increase in Mg content leads to a significant increase in the blocky MgZn2 phase, which is prone to cracking during processing. Therefore, this invention controls the Mg content in the coating to be 5.0–8.0%.

[0044] Si: This invention uses a higher Al content to enhance the reaction between the plating solution and the substrate, promoting the formation of an Al-Fe interface layer on the substrate. However, the Al-Fe interface layer should not grow excessively. To prevent the interface layer from becoming too thick, the Si content is controlled between 0.5% and 1.2%. Too low a Si content cannot effectively inhibit the growth of the Al-Fe interface layer, and the plating solution will severely corrode the steel substrate. Too high a Si content will form excessive amounts of brittle Si-containing compounds on the substrate interface layer, reducing the processability of the plating layer.

[0045] The design concept of the manufacturing method of this invention is as follows:

[0046] To ensure high strength by retaining a significant amount of deformed, unrecrystallized microstructure after hot-dip galvanizing, the annealing temperature before immersion in the zinc bath must be below the recrystallization temperature to prevent recrystallization of most of the substrate's microstructure and a substantial decrease in strength. However, due to the low heating temperature, the cleaning effect on the strip surface during heating is weak. Therefore, controlling the iron oxide scale on the substrate surface before the hot-dip galvanizing process is crucial to ensuring the surface quality and adhesion of the coating. The main process points are as follows:

[0047] Slab tapping temperature: Excessively high tapping temperatures will cause an excessively thick layer of iron oxide to form on the surface of the slab during the heating process. This invention sets the tapping temperature to 1150–1190°C.

[0048] Final rolling temperature: During the cooling process after rolling, secondary iron oxide scale will form on the surface of the steel coil. Excessively high temperatures will lead to the formation of a large amount of secondary iron oxide scale during cooling. This invention sets the final rolling temperature to 800–840℃.

[0049] Coiling Temperature: During the air cooling process after coiling, a tertiary iron oxide scale will form on the surface of the steel coil. Excessively high coiling temperatures will result in the formation of a large amount of tertiary iron oxide scale during air cooling, while excessively low temperatures may cause the coil head to curl up during coiling, thus affecting the coiling process. This invention sets the coiling temperature to 520–570℃.

[0050] Pickling temperature: During the pickling process, the iron oxide scale on the surface of the strip steel is dissolved and removed. If the acid temperature is too high, the acid will corrode the substrate surface; if the temperature is too low, the iron oxide scale cannot be fully removed. This invention sets the pickling temperature to 85-90℃.

[0051] Cold rolling reduction: The greater the degree of deformation during cold rolling, the higher the internal stress, the more unstable the internal state of the steel, and the easier it is for the microstructure to recrystallize. In order to suppress recrystallization during the homogenization process and retain more than 85% of the rolled microstructure, the cold rolling reduction is controlled at 50-70%.

[0052] Annealing Temperature: To ensure high strength by retaining a significant amount of deformed, unrecrystallized microstructure after hot-dip galvanizing, the heating temperature before immersion in the zinc bath must be below the recrystallization temperature. Excessively high annealing temperatures will cause extensive recrystallization of the deformed microstructure after cold rolling, drastically reducing the material's strength. Insufficiently low annealing temperatures will result in a completely rolled microstructure after annealing, leading to excessively high strength but excessively low elongation. Therefore, this invention controls the temperature between 560 and 580°C. Below 560°C, the material remains entirely rolled, resulting in excessively low elongation; above 580°C, partial recrystallization occurs, significantly reducing strength.

[0053] Holding time: At a given annealing temperature, the longer the holding time, the greater the degree of recovery and recrystallization of the deformed structure, and the lower the material strength. To maintain a non-recrystallized structure of over 85%, the annealing time should be controlled between 40 and 80 seconds. The higher the annealing temperature, the shorter the holding time; the relationship between the two is t = 1220 - 2 × T; where T is the annealing temperature in °C; and t is the holding time in seconds.

[0054] Radiant tube heating: Because the properties of steel change drastically with temperature variations near the recrystallization temperature, the temperature must be strictly controlled within the set range. Therefore, radiant tube heating is used instead of open flame heating during the annealing process.

[0055] Furnace hydrogen concentration: In this invention, low-temperature homogenization is adopted. Compared with high-temperature homogenization, the reducing effect of hydrogen is weaker. Therefore, in order to improve the reducing effect of hydrogen, the hydrogen concentration needs to be increased. In this invention, the hydrogen concentration is controlled at not less than 15%.

[0056] Zinc-magnesium-aluminum plating bath temperature: The high Al content of this invention results in a high melting point of the plating bath, thus requiring a higher bath temperature. This leads to increased zinc ash and zinc dross, and also intensifies the corrosion of the substrate by the plating bath, negatively impacting the surface quality and adhesion of the coated product. Therefore, the plating bath temperature of this invention is controlled to be 30–40°C above the melting point of the plating bath.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0058] This invention, with a substrate containing low Si and low Mn content and without the addition of strengthening elements such as Nb and Ti, ensures high strength by retaining a large amount of deformed, unrecrystallized structure in the substrate through low-temperature annealing. Furthermore, by adjusting the chemical composition of the zinc-aluminum-magnesium plating solution and optimizing the manufacturing process, the problems of incomplete plating and poor coating adhesion caused by residual iron oxide scale due to low-temperature annealing are solved, ultimately achieving high strength and high corrosion resistance of the steel plate. Attached Figure Description

[0059] Figure 1 This is a microstructure diagram of the substrate after annealing in Example 1.

[0060] Figure 2 This is a microstructure diagram of the substrate after annealing in Comparative Example 2.

[0061] Figure 3 This is a microstructure diagram of the substrate after annealing in Comparative Example 3.

[0062] Figure 4 This is a diagram of the coating structure in Example 1. Detailed Implementation

[0063] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0064] A high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet includes a substrate and a zinc-aluminum-magnesium coating formed by hot-dip galvanizing and zinc-aluminum-magnesium plating solution; wherein the chemical composition and mass percentage of the substrate are: C: 0.02-0.07%, Si: 0.02-0.10%, Mn: 0.7-0.9%, Als: 0.02-0.07%, P≤0.025%, S≤0.02%, with the balance being Fe and other unavoidable impurities; the chemical composition and mass percentage of the zinc-aluminum-magnesium plating solution are: Al: 30.0-45.0%, Mg: 5.0-8.0%, Si: 0.5-1.2%, with the balance being Zn and other unavoidable impurities.

[0065] The manufacturing method of the above-mentioned high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet includes the following steps:

[0066] 1) Smelting and continuous casting

[0067] Continuous casting is performed after smelting according to the composition of the substrate;

[0068] 2) Hot rolling

[0069] The continuously cast slab is heated to a furnace temperature of 1150–1190℃; then it is hot rolled to a final rolling temperature of 800–840℃; the hot-rolled strip is cooled to 520–570℃ and then coiled.

[0070] 3) Pickling and cold rolling

[0071] The obtained hot-rolled coil is pickled at an acid temperature of 85–90°C; then it is cold-rolled with a total reduction of 50–70% to obtain a substrate.

[0072] 4) Hot-dip galvanizing

[0073] The substrate is heated to the annealing temperature in an annealing furnace using radiant tubes and held at that temperature. The heating rate is 5–30 K / s, the annealing temperature is 570–590℃, and the holding time is 40–80 s. The annealing temperature and holding time satisfy the formula: t = 1220 - 2 × T; where T is the annealing temperature in ℃ and t is the holding time in s. The hydrogen concentration in the annealing furnace is ≥15%, and the dew point is ≤-40℃.

[0074] After annealing, the substrate is hot-dip galvanized magnesium-aluminum plating solution in a zinc pot. The temperature of the substrate when it enters the zinc pot is 5-10°C higher than the temperature of the zinc-aluminum plating solution, and the temperature of the zinc-aluminum plating solution is 30-40°C higher than its melting point. After being removed from the pot and cooled, the average cooling rate is greater than 35K / s, resulting in a high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet.

[0075] The following examples illustrate the manufacture of high corrosion-resistant, high-strength zinc-aluminum-magnesium coated steel sheets according to the above-described composition and method. Comparative examples are also included for comparison. Specific parameters are shown in Tables 1-4. The properties of the steel sheets obtained in the examples and comparative examples were tested, including yield strength, tensile strength, elongation, CCT plane resistance to red rust cycle, and a 1T bending test. For better comparison, the coating thickness of the test steel sheets was 100 g / m² on one side. 2 The results are shown in Table 5. The test for the red rust resistance cycle of the CCT surface was conducted according to standard JASO M609-91. The specific test conditions were as follows: one cycle lasting 8 hours; including 2 hours of salt spray using a 5% NaCl solution at 35℃; followed by 4 hours of drying at 60℃ with a relative humidity of 20-30%; then 2 hours of wetting at 50℃ with a relative humidity of 95%; this process was repeated until red rust appeared. The period from the start of the experiment to the appearance of red rust was defined as the red rust resistance cycle of the CCT surface.

[0076] Table 1 Chemical composition of the substrate

[0077] substrate number C(％) Si (%) Mn(%) Als(%) P(％) S(％) 1 0.04 0.07 0.7 0.020 0.024 0.012 2 0.02 0.10 0.9 0.043 0.016 0.009 3 0.07 0.05 0.7 0.068 0.012 0.011 4 0.05 0.02 0.8 0.037 0.019 0.007

[0078] Table 2 Chemical composition and melting point of zinc-magnesium-aluminum plating solution

[0079] Plating solution number Al(％) Mg (%) Si (%) Melting point of plating solution (°C) 1 30.1 5.0 0.51 507 2 35.4 7.7 0.60 509 3 36.7 6.3 0.69 518 4 40.5 7.1 0.92 523 5 45.0 7.9 1.20 529 <![CDATA[ 6 ]]> <![CDATA[ 22.4 ]]> 5.1 0.52 483 <![CDATA[ 7 ]]> 30.0 5.2 <![CDATA[ 0.32 ]]> 506

[0080] Table 3 Manufacturing Process Parameters (I)

[0081]

[0082]

[0083] Table 4 Manufacturing Process Parameters (II)

[0084]

[0085] Table 5. Specific conditions and performance results for each embodiment and comparative example.

[0086]

[0087]

[0088] Note: √: Adhesion is qualified; ×: Adhesion is unqualified, and there is zinc desorption.

[0089] As can be seen from Table 5, the steel plates obtained in each embodiment of the present invention exhibit high strength and high corrosion resistance, and the coating has excellent adhesion. The coating does not crack or fall off when bent at 1T. Figure 1 The image shows the microstructure of the substrate after annealing in Example 1. As can be seen from the image, the microstructure of the substrate after annealing includes ferrite and carbides, and the area of ​​the deformed, non-recrystallized microstructure accounts for 93%. Figure 2 The image shows the microstructure of the substrate after annealing in Comparative Example 2. When the annealing temperature is too low, the microstructure does not recover recrystallize at all, resulting in high strength, but the elongation is less than 4%, which is not conducive to simple processing. Figure 3 The image shows the microstructure of the substrate after annealing in Comparative Example 3. When the annealing temperature is too high, most of the microstructure recrystallizes after rolling, resulting in a significant decrease in strength. According to Comparative Examples 1 and 4, when the reduction ratio is too high or the annealing time is too long, partial recrystallization occurs in the microstructure after rolling, leading to a decrease in strength.

[0090] The zinc-aluminum-magnesium coating formed in various embodiments of the present invention includes a coating layer and an interface layer between the substrate and the coating layer; Figure 4 The diagram shows the microstructure of the coating layer in Example 1, which includes a primary (Al) phase, a MgZn2 phase, a multi-element eutectic Al / Zn / MgZn2 structure, and a Mg2Si phase. The interface layer is a dense Al-Fe compound containing a small amount of Si. Comparative Example 5 shows that when the Al content of the plating solution is low, the reaction between the plating solution and the steel sheet after low-temperature annealing is weak, resulting in defects such as exposed plating and poor adhesion, leading to failure in the bending test. Comparative Example 6 shows that when the Si content of the plating solution is too low, Si cannot effectively inhibit the growth of the Al-Fe interface layer, and the plating solution will severely corrode the steel substrate, resulting in an excessively thick interface layer, leading to failure in the bending test.

[0091] Comparative Examples 7-9 show that when the billet exit temperature, final rolling temperature, or coiling temperature is too high, a thick layer of iron oxide scale forms on the substrate surface, which cannot be completely removed in subsequent processes, reducing the corrosion resistance and adhesion of the hot-dip galvanized coating. Comparative Example 10 shows that when the pickling temperature is too low, the iron oxide scale cannot be effectively removed, reducing the corrosion resistance and adhesion of the coating. Comparative Example 11 shows that when the hydrogen concentration is too low, the reduction effect of hydrogen is weak, leaving an oxide layer on the strip surface, affecting the wetting of the plating solution on the substrate, and reducing the corrosion resistance and adhesion of the coating. Comparative Example 12 shows that when the dew point in the annealing furnace is too high, localized oxidation occurs on the strip surface, affecting the wetting of the plating solution on the substrate, and reducing the corrosion resistance and adhesion of the coating. Comparative Example 13 shows that when the plating solution temperature is too high, zinc ash and zinc dross increase significantly, reducing the adhesion of the coating.

[0092] The above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high corrosion-resistant, high-strength zinc-aluminum-magnesium coated steel sheet, characterized in that, The invention comprises a substrate and a zinc-aluminum-magnesium plating layer formed by hot-dip zinc-aluminum-magnesium plating solution; the chemical composition and mass percentage of the substrate are: C: 0.02~0.07%, Si: 0.02~0.10%, Mn: 0.8~0.9%, Als: 0.02~0.07%, P≤0.025%, S≤0.02%, with the balance being Fe and other unavoidable impurities; the chemical composition and mass percentage of the zinc-aluminum-magnesium plating solution are: Al: 35.4~45.0%, Mg: 5.0~8.0%, Si: 0.5~1.2%, with the balance being Zn and other unavoidable impurities; The zinc-aluminum-magnesium coating includes a coating layer and an interface layer between the substrate and the coating layer; the microstructure of the coating layer includes primary (Al) phase, MgZn2 phase, multi-element eutectic Al / Zn / MgZn2 microstructure, and Mg2Si phase; the interface layer is a dense Al-Fe compound containing a small amount of Si; the high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel plate has a yield strength ≥550MPa, a tensile strength ≥550MPa, and an elongation ≥4%; The manufacturing method of the high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel sheet includes the following steps: 1) Smelting and continuous casting Continuous casting is performed after smelting according to the composition of the substrate; 2) Hot-rolled The continuously cast slab is heated to a furnace temperature of 1150~1190℃; then it is hot rolled to a final rolling temperature of 800~830℃; the hot-rolled strip is cooled to 520~570℃ and then coiled. 3) Pickling and cold rolling The obtained hot-rolled coil is pickled and then cold-rolled with a total reduction of 50-70% to obtain a substrate. 4) Hot-dip galvanizing The substrate is heated to the annealing temperature in an annealing furnace and held at that temperature for 40-80 seconds. The resulting microstructure consists of ferrite and carbides, with the area of ​​the deformed, non-recrystallized microstructure accounting for 85-96%. After annealing, the substrate is hot-dip galvanized magnesium-aluminum plating solution in a zinc pot. The temperature of the plate when entering the zinc pot is 5-10°C higher than the temperature of the zinc-aluminum plating solution, and the temperature of the zinc-aluminum plating solution is 30-40°C higher than its melting point. After being removed from the pot and cooled, the average cooling rate is greater than 35K / s, resulting in a high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel plate.

2. A method for manufacturing a high corrosion-resistant, high-strength zinc-aluminum-magnesium coated steel sheet as described in claim 1, characterized in that, Includes the following steps: 1) Smelting and continuous casting Continuous casting is performed after smelting according to the composition of the substrate; 2) Hot-rolled The continuously cast slab is heated to a furnace temperature of 1150~1190℃; then it is hot rolled to a final rolling temperature of 800~830℃; the hot-rolled strip is cooled to 520~570℃ and then coiled. 3) Pickling and cold rolling The obtained hot-rolled coil is pickled and then cold-rolled with a total reduction of 50-70% to obtain a substrate. 4) Hot-dip galvanizing The substrate is heated to the annealing temperature in an annealing furnace and held at that temperature for 40-80 seconds. The resulting microstructure consists of ferrite and carbides, with the area of ​​the deformed, non-recrystallized microstructure accounting for 85-96%. After annealing, the substrate is hot-dip galvanized magnesium-aluminum plating solution in a zinc pot. The temperature of the plate when entering the zinc pot is 5-10°C higher than the temperature of the zinc-aluminum plating solution, and the temperature of the zinc-aluminum plating solution is 30-40°C higher than its melting point. After being removed from the pot and cooled, the average cooling rate is greater than 35K / s, resulting in a high corrosion-resistant and high-strength zinc-aluminum-magnesium coated steel plate.

3. The method for manufacturing high corrosion-resistant, high-strength zinc-aluminum-magnesium coated steel sheet according to claim 2, characterized in that, The annealing temperature and holding time satisfy the formula: t=1220-2×T; where T is the annealing temperature in °C and t is the holding time in seconds.

4. The method for manufacturing high corrosion-resistant, high-strength zinc-aluminum-magnesium coated steel sheet according to claim 2, characterized in that, The annealing furnace is heated by radiant tubes at a rate of 5~30K / s, with a hydrogen concentration ≥15% and a dew point ≤-40℃.

5. The method for manufacturing high corrosion-resistant, high-strength zinc-aluminum-magnesium coated steel sheet according to claim 2, characterized in that, The thickness of the substrate is 0.40~2.5mm.

6. The method for manufacturing high corrosion-resistant, high-strength zinc-aluminum-magnesium coated steel sheet according to claim 2, characterized in that, The acid temperature for pickling is 85~90℃.

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