Highly corrosion-resistant coated steel plate and preparation method therefor

Abstract

A highly corrosion-resistant coated steel plate and a preparation method therefor. The steel plate is composed of a steel base and a coating layer. The microstructure of the coating layer is a Zn-MgZn2-Al ternary eutectic phase, a Zn-Al binary eutectoid phase, a Zn-MgZn2 binary eutectic phase, an Mg2Si-Zn ternary eutectic phase, and an Al-Zn-Fe-Si alloy layer, and the chemical composition of the coating layer comprises 10-20% of Al, 2.2-6% of Mg, 0.08-0.4% of Si, and 0.05-0.6% of RE. The medium-aluminum-zinc-aluminum-magnesium coated steel prepared by the method has better corrosion resistance than a traditional zinc-aluminum-magnesium coating layer. The microstructure of the coating layer is controlled by means of a composition system and a cooling process. Thus, the microstructure of grains is refined, the occurrence of a pure zinc phase as a weak phase is avoided, the corrosion resistance is improved, the occurrence of brittle phases such as a rare earth phase and a silicon-rich phase is eliminated, and the formability of the coating layer is optimized; moreover, the coating layer, after being bent, shows reduced cracks and still has good corrosion resistance, and thus the use requirements of photovoltaic steel for 30 years can be met.

Description

High corrosion resistance plated steel sheet and preparation method thereof

[0001] The present application claims priority to the Chinese patent application No. 202410848359.8, filed on June 27, 2024, and entitled "High corrosion resistance plated steel sheet and preparation method thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of metal materials, and particularly relates to a high corrosion resistance plated steel sheet and a preparation method thereof. BACKGROUND

[0003] Zn-Al-Mg alloy coating has attracted widespread attention abroad in the 1980s and has become the research focus in the field of hot-dip galvanized and zinc alloy coating. From the research results of domestic and foreign peers, under the condition of the same level of Zn and Al content, the hot-dip Zn-Al-Mg alloy coated steel sheet with Mg addition has better corrosion resistance, and the material has excellent processing and application performance (formability, weldability and paintability), which can replace the current corresponding hot-dip galvanized or zinc alloy coated steel sheet, and has a very broad market demand prospect. China's research on Zn-Al-Mg alloy coating is relatively late. At present, Jinan Steel, Baosteel, Shougang, Jinan Steel and Pansteel have launched hot-dip Zn-Al-Mg alloy coated steel sheet, among which the application in the photovoltaic field is the most widespread. Only about 550,000 tons of zinc-aluminum-magnesium products are needed in the southwest region every year.

[0004] In the prior art, patent CN 116288097 A discloses a zinc-aluminum-magnesium alloy coated steel sheet for photovoltaic and a preparation method. The chemical composition and mass percentage of the zinc-aluminum-magnesium alloy coating of the zinc-aluminum-magnesium coated steel sheet are as follows: Al 5-9%, Mg 2.5-4.5%, Ni 0-0.15%, Ti 0-0.2%. A small amount of pure zinc phase exists in the patent, which affects the overall corrosion resistance of the coating.

[0005] Patent CN 115305386 A provides a high corrosion resistance hot-dip zinc-aluminum-magnesium alloy, a material with ZAM coating and a preparation method thereof. The high corrosion resistance hot-dip zinc-aluminum-magnesium alloy is composed of the following components: Mg 0.3%-3.9%, Al 1.2%-9.8%, RE 0.08%-3.2%, Ge 1.0%-3.0%. The preparation method comprises: heating and melting Mg, Al and Zn raw materials at a first temperature, then adding RE and Ge, and heating to complete dissolution at a second temperature to obtain a liquid alloy; placing the preheated base material into the liquid alloy, and then cooling to obtain the material with ZAM coating. The microstructure of the material changes greatly, and there is a pure zinc phase with poor corrosion resistance, and there may be needle-shaped rare earth phase with poor formability.

[0006] The above prior art research on zinc-aluminum-magnesium alloy mainly focuses on the composition, but there are still defects in the relationship between phase composition and composition and the coordination of each component system. Since the coating structure determines the coating performance, and the coating structure is determined by the composition and process. Therefore, in order to further optimize the corrosion resistance and formability of the coating, it is necessary to develop a high corrosion resistance coating steel plate based on composition coordination control to eliminate weak phases and a preparation method thereof. SUMMARY

[0007] In order to overcome the defects of the above prior art, the present application optimizes the composition system, refines the grain structure, avoids the appearance of weak phase pure zinc phase, and further improves the corrosion resistance; eliminates the appearance of brittle phases such as rare earth phase, silicon-rich phase, and intermediate alloy layer, optimizes the formability of the coating, reduces the crack after bending of the coating, and still has good corrosion resistance, to meet the 30-year use requirements of the steel for photovoltaic.

[0008] In order to achieve the above-mentioned purpose of the application, the present application provides a high corrosion resistance coating steel plate, which is composed of a steel base and a coating. The coating is a zinc-aluminum-magnesium alloy coating with a thickness of 2-50 μm. The coating structure is Zn-MgZn2-Al ternary eutectic phase, Zn-Al binary eutectoid phase, Zn-MgZn2 binary eutectic phase, Mg2Si-Zn ternary eutectic phase, and Al-Zn-Fe-Si alloy layer. The chemical composition of the coating is as follows: Al: 10%-20%, Mg: 2.2%-6%, Si: 0.08%-0.40%, RE: 0.05%-0.60%, and the balance is Zn and other unavoidable impurities.

[0009] Further, the coating structure of the high corrosion resistance coating steel plate does not contain pure zinc phase, rare earth phase, and silicon-rich phase. The rare earth is a mixture of lanthanum and cerium, which is uniformly distributed in the coating and cannot appear in the form of needle-shaped enrichment.

[0010] Further, in order to ensure that the coating is Zn-MgZn2-Al phase, Zn-Al phase, Zn-MgZn2 binary phase, and Mg2Si-Zn phase, the coating composition of the high corrosion resistance coating steel plate satisfies the following conditions in terms of atomic number: 5.5Mg+2.5Al>Zn+0.5Si, and Zn≥Al+2Mg.

[0011] Further, based on the good flowability of the plating solution, the thickness control of the alloy layer, and the good surface quality, the coating composition of the high corrosion resistance coating steel plate satisfies the following condition in terms of mass percentage: 0.3%≤RE+Si≤0.8%.

[0012] Further, the steel base of the high corrosion resistance coating steel plate can be one of low-carbon aluminum killed steel, IF steel, P-containing high-strength IF steel, bake-hardening steel, SPCC, structural steel, QP steel, and the like.

[0013] A preparation method of the high corrosion resistance plated steel sheet, the preparation method comprises the following steps: pickling, rolling (or light reduction), degreasing cleaning, continuous annealing, hot dipping, air knife blowing, cooling, finishing; wherein the rolling adopts rough roller rolling, and the roughness of the strip surface after rolling is controlled to be 1.2-3.5 μm;

[0014] The hydrogen content in the furnace is controlled to be greater than or equal to 2.5% by volume percentage during the continuous annealing process;

[0015] The temperature of the strip entering the zinc pot is 420-620 ℃, the plating solution temperature during the hot dipping process is 420-600 ℃, the temperature of the strip entering the zinc pot is not lower than the temperature of the zinc pot, and the hot dipping time is 1-3 s.

[0016] Further, in the preparation method of the high corrosion resistance plated steel sheet, the degreasing cleaning is rinsing clean after the degreasing treatment; the air knife blowing medium is at least one of N2 and inert gas, the CO2 content of which is less than or equal to 50 ppm, and the O2 content of which is less than or equal to 50 ppm; fast cooling is necessary after plating, the cooling speed is 5-30 ℃ / s, the temperature of the strip reaching the top of the reversing roller is less than or equal to 270 ℃; the roughness Ra of the surface of the finishing roller is controlled to be 2.0-4.5 μm, and the finishing elongation is 0.5-1.5%.

[0017] Further, the mass percentage of the chemical components of the plating solution is as follows: Al: 10.0%-20.0%, Mg: 2.2%-6.0%, Si: 0.08%-0.40%, RE: 0.05%-0.60%, and the balance is Zn and other inevitable impurities.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The corrosion resistance of the prepared medium-aluminum zinc-aluminum magnesium plated steel material is better than that of the conventional zinc-aluminum magnesium plated layer, the plated layer structure is controlled through component system design and cooling process, the grain structure is refined, the appearance of weak phase pure zinc phase is avoided, the corrosion resistance is improved, the appearance of brittle phases such as rare earth phase and silicon-rich phase is eliminated, the thickness of the brittle phase of the intermediate alloy layer is thinned, the formability of the plated layer is optimized, the crack of the plated layer after bending is reduced, and the plated layer still has good corrosion resistance, which can meet the 30-year use requirement of the photovoltaic steel. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 is a microstructure morphology diagram of the cross section of the high corrosion resistance plated steel sheet prepared in Example 1. DETAILED DESCRIPTION

[0021] The present application is further described below in combination with specific embodiments, but the present application is not limited in any way by the embodiments. In order to avoid redundancy, the raw materials in the following embodiments are all commercially available products if not particularly stated, and the methods used are all conventional methods if not particularly stated.

[0022] A high corrosion resistance plated steel sheet, which is composed of a steel base and a plated layer, the plated layer has a structure of Zn-MgZn2-Al ternary eutectic phase, Zn-Al binary eutectoid phase, Zn-MgZn2 binary eutectic phase, Mg2Si-Zn ternary eutectic phase, Al-Zn-Fe-Si alloy layer; the plated layer has a chemical composition of Al: 10.0%~20.0%, Mg: 2.2%~6.0%, Si: 0.08%~0.40%, RE: 0.05%~0.60%, and the balance of Zn and other inevitable impurities.

[0023] The plated layer is a zinc-aluminum-magnesium alloy plated layer with a thickness of 2~50μm. The plated layer has no pure zinc phase, rare earth phase, and silicon-rich phase, and the rare earth is a mixture of lanthanum and cerium. In the plated layer composition, in terms of atomic number, 5.5Mg+2.5Al>Zn+0.5Si, and Zn≥Al+2Mg. In the plated layer composition, in terms of mass percentage, 0.3%≤RE+Si≤0.8%. The steel base is one of low-carbon aluminum killed steel, IF steel, P-containing high-strength IF steel, bake-hardening steel, SPCC, structural steel, QP steel, and the like.

[0024] A preparation method of the above high corrosion resistance plated steel sheet, which comprises the following steps: pickling, rolling, degreasing cleaning, continuous annealing, hot dipping, air knife blowing, cooling, and finishing; wherein,

[0025] The rolling is performed by using a rough roll, and the roughness of the surface of the steel sheet after rolling is controlled to be 1.2~3.5μm;

[0026] The hydrogen content in the furnace during the continuous annealing process is controlled to be ≥2.5% in terms of volume percentage;

[0027] The temperature of the steel sheet entering the zinc pot is 420~620℃, the temperature of the plating solution during the hot dipping process is 420~600℃, the temperature of the steel sheet entering the zinc pot is not lower than the temperature of the zinc pot, and the hot dipping time is 1~3s.

[0028] The degreasing cleaning is performed after degreasing treatment and rinsing; the blowing medium for the air knife is at least one of N2 and inert gas, and the CO2 content and O2 content of the blowing medium are ≤50ppm and ≤50ppm, respectively; the steel sheet must be cooled quickly after plating, the cooling speed is 5~30℃ / s, and the temperature of the steel sheet reaching the top of the reversing roll is ≤270℃; the surface roughness Ra of the finishing roll is controlled to be 2.0~4.5μm, and the elongation of the finishing is 0.5~1.5%. The plating solution has a chemical composition of Al: 10%~20%, Mg: 2.2%~6%, Si: 0.08%~0.40%, RE: 0.05%~0.60%, and the balance of Zn and other inevitable impurities.

[0029] Example 1

[0030] A high corrosion resistance plated steel sheet and a method for manufacturing the same, the specific process flow is as follows:

[0031] The steel base is low-carbon aluminum killed steel DX52D, and the surface roughness of the steel strip after being rolled by a rough roller during cold rolling is controlled to be 1.2 μm; the chemical composition of the plating solution is: Al 10%, Mg 3.0%, Si 0.10, RE 0.20, and the balance is Zn and other inevitable impurities; the degreasing and cleaning is to rinse clean after degreasing treatment, and the hydrogen content in the furnace during the continuous annealing process is controlled to be ≥3.5% by volume percentage, the temperature of the steel sheet entering the zinc pot is 420°C, the plating solution temperature during the hot-dip plating process is 420°C, and the hot-dip plating time is 1 s; the medium for the air knife blowing is N2; the cooling speed after plating is 10°C / s, and the temperature of the steel strip reaching the top deflector roll is 270°C; the surface roughness Ra of the finishing roll is controlled to be 2.0 μm, and the finishing elongation is 0.6%.

[0032] The high corrosion resistance plated steel sheet prepared by the method comprises a steel base and a plating layer, the plating layer is a zinc-aluminum-magnesium alloy plating layer, the thickness of the plating layer is 5 μm, and the plating layer is composed of Zn-MgZn2-Al ternary eutectic phase, Zn-Al binary eutectoid phase, Zn-MgZn2 binary eutectic phase, Mg2Si-Zn ternary eutectic phase and Al-Zn-Fe-Si alloy layer; the chemical composition of the plating layer is: Al 10%, Mg 3.0%, Si 0.10, RE 0.20, and the balance is Zn and other inevitable impurities; and the plating layer does not contain pure zinc phase, rare earth phase and silicon-rich phase.

[0033] The performance test results of the zinc-aluminum-magnesium plated steel material prepared in Example 1 are shown in Table 1.

[0034] Example 2

[0035] A high corrosion resistance plated steel sheet and a method for manufacturing the same, the specific process flow is as follows:

[0036] The steel base is low-carbon aluminum killed steel Ti-IF steel, and the surface roughness of the steel strip after being rolled by a rough roller during cold rolling is controlled to be 1.5 μm; the chemical composition of the plating solution is: Al 12%, Mg 2.5%, Si 0.15%, RE 0.10%, and the balance is Zn and other inevitable impurities; the degreasing and cleaning is to rinse clean after degreasing treatment, the hydrogen content in the furnace during the continuous annealing process is controlled to be 4.0% by volume percentage, the temperature of the steel sheet entering the zinc pot is 480°C, the plating solution temperature during the hot-dip plating process is 460°C, and the hot-dip plating time is 2 s; the medium for the air knife blowing is N2; the cooling speed after plating is 20°C / s, and the temperature of the steel strip reaching the top deflector roll is 240°C; the surface roughness Ra of the finishing roll is controlled to be 3.5 μm, and the finishing elongation is 0.8%.

[0037] The high corrosion resistance plated steel sheet prepared after the preparation is composed of a steel base and a plated layer. The plated layer is a zinc-aluminum-magnesium alloy plated layer with a thickness of 10 μm. The plated layer has a structure of Zn-MgZn2-Al ternary eutectic phase, Zn-Al binary eutectoid phase, Zn-MgZn2 binary eutectic phase, Mg2Si-Zn ternary eutectic phase and Al-Zn-Fe-Si alloy layer. The plated layer has a chemical composition of Al 12%, Mg 2.5%, Si 0.15%, RE 0.10% and the balance of Zn and other inevitable impurities. The plated layer does not contain pure zinc phase, rare earth phase and silicon-rich phase.

[0038] The performance test results of the zinc-aluminum-magnesium plated steel material prepared in Example 2 are shown in Table 1.

[0039] Example 3

[0040] A high corrosion resistance plated steel sheet and a preparation method thereof are provided. The specific process flow is as follows:

[0041] The steel base is structural steel S320GD. The surface roughness of the strip steel after the cold rolling is controlled to be 1.5 μm. The chemical composition of the plating solution is as follows: Al 14%, Mg 3.5%, Si 0.30%, RE 0.20% and the balance of Zn and other inevitable impurities. The degreasing cleaning is to rinse clean after the degreasing treatment. The continuous annealing process controls the hydrogen content in the furnace to be 5.0% by volume. The temperature of the steel sheet into the zinc pot is 480℃. The plating solution temperature during the hot dipping process is 470℃. The hot dipping time is 3 s. The gas knife blowing medium is N2. The cooling speed after the plating is 30℃ / s. The temperature of the strip steel reaching the top of the reversing roller is 220℃. The surface roughness Ra of the finishing roller is controlled to be 4.0 μm. The finishing elongation is 1.0%.

[0042] The high corrosion resistance plated steel sheet prepared after the preparation is composed of a steel base and a plated layer. The plated layer is a zinc-aluminum-magnesium alloy plated layer with a thickness of 20 μm. The plated layer has a structure of Zn-MgZn2-Al ternary eutectic phase, Zn-Al binary eutectoid phase, Zn-MgZn2 binary eutectic phase, Mg2Si-Zn ternary eutectic phase and Al-Zn-Fe-Si alloy layer. The plated layer has a chemical composition of Al 14%, Mg 3.5%, Si 0.30%, RE 0.20% and the balance of Zn and other inevitable impurities. The plated layer does not contain pure zinc phase, rare earth phase and silicon-rich phase.

[0043] The performance test results of the zinc-aluminum-magnesium plated steel material prepared in Example 3 are shown in Table 1.

[0044] Example 4

[0045] A high corrosion resistance plated steel sheet and a preparation method thereof are provided. The specific process flow is as follows:

[0046] The steel base is SPCC, the surface roughness of the strip steel after being rolled by a rough roller during cold rolling is controlled to be 3.0 μm; the chemical composition of the plating solution is: Al 16%, Mg 5.0%, Si 0.40%, RE 0.05%, and the rest is Zn and other inevitable impurities; the degreasing and cleaning is to rinse clean after degreasing treatment, the hydrogen content in the furnace during the continuous annealing process is controlled to be 5.0% by volume percentage, the temperature of the steel plate entering the zinc pot is 500°C, the plating solution temperature during the hot dipping process is 480°C, and the hot dipping time is 2 s; the blowing medium of the air knife is N2; the cooling speed after plating is 25°C / s, the temperature of the strip steel reaching the top deflection roller is 245°C; the surface roughness Ra of the finishing roller is controlled to be 4.5 μm, and the finishing elongation is 0.7%.

[0047] The high corrosion-resistant plated steel plate prepared after the preparation is composed of a steel base and a plated layer, the plated layer is a zinc-aluminum-magnesium alloy plated layer, the thickness of the plated layer is 25 μm, the plated layer is composed of Zn-MgZn2-Al ternary eutectic phase, Zn-Al binary eutectoid phase, Zn-MgZn2 binary eutectic phase, Mg2Si-Zn ternary eutectic phase and Al-Zn-Fe-Si alloy layer, the chemical composition of the plated layer is: Al 16%, Mg 5.0%, Si 0.40%, RE 0.05%, and the rest is Zn and other inevitable impurities, and the plated layer does not contain pure zinc phase, rare earth phase and silicon-rich phase.

[0048] The performance test results of the zinc-aluminum-magnesium plated steel material prepared in Example 4 are shown in Table 1.

[0049] Example 5

[0050] A high corrosion-resistant plated steel plate and a preparation method thereof, and the specific process flow is as follows:

[0051] The steel base is 250P1, the surface roughness of the strip steel after being rolled by a rough roller during cold rolling is controlled to be 3.5 μm; the chemical composition of the plating solution is: Al 15%, Mg 6.0%, Si 0.20%, RE 0.15%, and the rest is Zn and other inevitable impurities; the degreasing and cleaning is to rinse clean after degreasing treatment, the hydrogen content in the furnace during the continuous annealing process is controlled to be 6.0% by volume percentage, the temperature of the steel plate entering the zinc pot is 520°C, the plating solution temperature during the hot dipping process is 520°C, and the hot dipping time is 1 s; the blowing medium of the air knife is N2; the cooling speed after plating is 30°C / s, the temperature of the strip steel reaching the top deflection roller is 255°C; the surface roughness Ra of the finishing roller is controlled to be 3.0 μm, and the finishing elongation is 1.5%.

[0052] The high corrosion resistance plated steel sheet prepared after the preparation is composed of a steel base and a plated layer, the plated layer is a zinc-aluminum-magnesium alloy plated layer, the thickness is 50 μm, the plated layer is composed of Zn-MgZn2-Al ternary eutectic phase, Zn-Al binary eutectoid phase, Zn-MgZn2 binary eutectic phase, Mg2Si-Zn ternary eutectic phase and Al-Zn-Fe-Si alloy layer, the plated layer chemical composition is: Al 15%, Mg 6.0%, Si 0.20%, RE 0.15%, the rest is Zn and other inevitable impurities, and the plated layer does not contain pure zinc phase, rare earth phase and silicon-rich phase.

[0053] The performance test results of the zinc-aluminum-magnesium plated steel material prepared in Example 5 are shown in Table 1.

[0054] Example 6

[0055] A high corrosion resistance plated steel sheet and a preparation method thereof, the specific process flow is:

[0056] The steel base is S550GD, the surface roughness of the strip steel after the rough rolling is controlled to be 2.5 μm; the plated liquid chemical composition is: Al 20%, Mg 4.0%, Si 0.35%, RE 0.25%, wherein the rest is Zn and other inevitable impurities; the degreasing cleaning is to rinse clean after the degreasing treatment, the continuous annealing process controls the hydrogen content in the furnace to be 3.5% by volume percentage, the strip steel enters the zinc pot at a temperature of 550 ℃, the plated liquid temperature in the hot-dip plating process is 540 ℃, the hot-dip plating time is 2 s; the gas knife blowing medium is N2; the cooling speed after the plating is 25 ℃ / s, the temperature of the strip steel reaching the top deflection roller is 245 ℃; the surface roughness Ra of the finishing roller is controlled to be 4.5 μm, and the finishing elongation is 0.9%.

[0057] The micro features of the plated layer of the zinc-aluminum-magnesium plated steel material prepared in Example 6 are shown in Fig. 1. The high corrosion resistance plated steel sheet prepared after the preparation is composed of a steel base and a plated layer, the plated layer is a zinc-aluminum-magnesium alloy plated layer, the thickness is 30 μm, the plated layer is composed of Zn-MgZn2-Al ternary eutectic phase, Zn-Al binary eutectoid phase, Zn-MgZn2 binary eutectic phase, Mg2Si-Zn ternary eutectic phase and Al-Zn-Fe-Si alloy layer, the plated layer chemical composition is: Al 20%, Mg 4.0%, Si 0.35%, RE 0.25%, wherein the rest is Zn and other inevitable impurities, and the plated layer does not contain pure zinc phase, rare earth phase and silicon-rich phase.

[0058] The performance test results of the zinc-aluminum-magnesium plated steel material prepared in Example 6 are shown in Table 1.

[0059] Comparative Example 1

[0060] A high corrosion resistance plated steel sheet and a preparation method thereof, the specific process flow is:

[0061] The steel base grade is low-carbon aluminum killed steel DX51D, and the strip steel is not rough-rolled during cold rolling, with a surface roughness of 1.0 μm. The chemical composition of the plating solution is: Al 6%, Mg 3%, Si 0.20%, RE 0.10%, and the balance is Zn and other inevitable impurities. The degreasing and cleaning is rinsed clean after degreasing treatment, and the continuous annealing process controls the hydrogen content in the furnace at 4.0% by volume percentage. The strip steel enters the zinc pot at a temperature of 480°C, the plating solution temperature during hot dipping is 460°C, and the hot dipping time is 1 s. The gas knife blowing medium is N2. The post-plating cooling speed is 20°C / s, and the temperature of the strip steel reaching the top deflector roll is 240°C. The surface roughness Ra of the skin pass roll is controlled at 3.5 μm, and the skin pass elongation is 0.8%.

[0062] The high corrosion-resistant plated steel sheet prepared comprises a steel base and a plated layer, and the plated layer is a zinc-aluminum-magnesium alloy plated layer with a thickness of 10 μm. The plated layer has a Zn-MgZn2-Al ternary eutectic phase, a Zn-Al binary eutectoid phase, a Zn-MgZn2 binary eutectic phase, a Mg2Si-Zn ternary eutectic phase, an Al-Zn-Fe-Si alloy layer and a pure zinc phase. A large number of zinc blowing defects appear on the surface.

[0063] The performance test results of the zinc-aluminum-magnesium plated steel material prepared in Comparative Example 1 are shown in Table 1.

[0064] Comparative Example 2

[0065] A high corrosion-resistant plated steel sheet and a preparation method thereof, and the specific process flow is as follows:

[0066] The steel base grade is Ti-IF steel, and the surface roughness of the strip steel after rough rolling during cold rolling is controlled at 1.5 μm. The chemical composition of the plating solution is: Al 14%, Mg 3.5%, Si 1.0%, RE 0.5%, and the balance is Zn and other inevitable impurities. The degreasing and cleaning is rinsed clean after degreasing treatment, and the continuous annealing process controls the hydrogen content in the furnace at 5.0% by volume percentage. The strip steel enters the zinc pot at a temperature of 480°C, the plating solution temperature during hot dipping is 470°C, and the hot dipping time is 3 s. The gas knife blowing medium is N2. The post-plating cooling speed is 30°C / s, and the temperature of the strip steel reaching the top deflector roll is 220°C. The surface roughness Ra of the skin pass roll is controlled at 4.0 μm, and the skin pass elongation is 1.0%.

[0067] The high corrosion-resistant plated steel sheet prepared comprises a steel base and a plated layer, and the plated layer is a zinc-aluminum-magnesium alloy plated layer with a thickness of 20 μm. The plated layer has a Zn-MgZn2-Al ternary eutectic phase, a Zn-Al binary eutectoid phase, a Zn-MgZn2 binary eutectic phase, a Mg2Si-Zn ternary eutectic phase, an Al-Zn-Fe-Si alloy layer and a silicon-rich phase.

[0068] The performance test results of the zinc-aluminum-magnesium plated steel material prepared in Comparative Example 2 are shown in Table 1.

[0069] Comparative Example 3

[0070] A high corrosion-resistant plated steel sheet and a method for preparing the same, and a specific process flow is as follows:

[0071] The steel base is S350GD, and the surface roughness of the strip steel after being rolled by a cold rolling mill is controlled at 2.0 μm; the chemical composition of the plating solution is: Al 10%, Mg 3.0%, Si 0.10%, RE 0.20%, and the rest is Zn and other inevitable impurities; the degreasing cleaning is to rinse clean after degreasing treatment, and the hydrogen content in the furnace during the continuous annealing process is controlled at 2.0% by volume; the temperature of the steel sheet into the zinc pot is 420°C; the plating solution temperature during the hot-dip plating process is 420°C; the hot-dip plating time is 1 s; the blowing medium of the air knife is N2; the cooling speed after plating is 3°C / s, and the temperature of the strip steel reaching the top of the reversing roller is 350°C; the surface roughness Ra of the finishing roller is controlled at 1.5 μm, and the finishing elongation is 0.3%.

[0072] The high corrosion-resistant plated steel sheet prepared after the process is composed of a steel base and a plating layer, and the plating layer is a zinc-aluminum-magnesium alloy plating layer with a thickness of 10 μm; the plating layer has a Zn-MgZn2-Al ternary eutectic phase, a Zn-Al binary eutectoid phase, a Zn-MgZn2 binary eutectic phase, a Mg2Si-Zn ternary eutectic phase, and an Al-Zn-Fe-Si alloy layer, and the plating layer has a coarse and uneven structure. There are defects such as plating leakage, poor adhesion, and black spot on the surface of the plating layer. The performance test results of the zinc-aluminum-magnesium plated steel material prepared in Comparative Example 3 are shown in Table 1.

[0073] The zinc-aluminum-magnesium plated steel materials obtained in Examples 1-6 and Comparative Examples 1-3 are compared in terms of plating layer structure, surface quality, corrosion resistance, and formability, so as to evaluate the quality performance of the zinc-aluminum-magnesium plated steel materials.

[0074] Corrosion resistance: The neutral salt spray accelerated corrosion test is performed according to GB / T 10125-2012 “Artificial Atmosphere Corrosion Test Salt Spray Test”, the test instrument is a salt spray corrosion test box, the corrosion medium is a NaCl deionized water solution with a concentration of 50 g / L and a pH value of 6.5, the test temperature is 35±2°C; the sample size is 75mm*150mm*0.8mm, and the size of the edge sealed by transparent tape is 5mm to prevent end corrosion from affecting the results; the sample is placed at an angle of 15°-25° to the vertical direction. The time for red rust to occur on the surface of the sample is observed.

[0075] Formability: the sample was 0T bent (180° bending, bending core radius 0), visually observed whether cracks appeared, the maximum crack width ≤50 μm was 0 level, the maximum crack width 51-100 μm was 1 level, 101-200 μm was 2 level, >200 μm was 3 level; and the bending part was tested for the time of red rust appearing under the neutral salt spray test conditions, the neutral salt spray test conditions and methods were performed according to GB / T 10125-2012 "Artificial Atmosphere Corrosion Test Salt Spray Test".

[0076] Table 1 performance test results of zinc-aluminum-magnesium plated steel materials prepared in the examples and comparative examples

[0077] As shown in Table 1, by controlling the component system and cooling process, the harmful organization phase of the medium-aluminum zinc-aluminum-magnesium plated layer is eliminated, the overall coverage of the beneficial organization is achieved, and the organization grain is further refined, improving the corrosion resistance and formability.

[0078] For any person skilled in the art, without departing from the scope of the technical solutions of the present application, many possible changes and modifications, or equivalent embodiments of equivalent changes can be made to the technical solutions of the present application by using the above disclosed technical content. Therefore, any simple modification, equivalent change and modification made to the above examples according to the technical essence of the present application, which does not deviate from the content of the technical solutions of the present application, should still belong to the scope of protection of the technical solutions of the present application.

Claims

1. A high corrosion resistant plated steel sheet consisting of a steel base and a plated layer, characterized in that, The plating layer is a Zn-Al-Mg alloy plating layer, and the thickness is 2-50 μm.

2. The high corrosion resistant plated steel sheet according to claim 1, characterized by, The plating layer is a Zn-Al-Mg alloy plating layer, and the thickness is 2-50 μm.

3. The high corrosion resistant plated steel sheet according to claim 1, characterized by, The plating layer is a Zn-Al-Mg alloy plating layer, and the thickness is 2-50 μm.

4. The high corrosion resistant plated steel sheet according to claim 1, characterized by, The plating layer is a Zn-Al-Mg alloy plating layer, and the thickness is 2-50 μm.

5. The high corrosion resistant plated steel sheet according to claim 1, characterized by, The plating layer is a Zn-Al-Mg alloy plating layer, and the thickness is 2-50 μm.

6. The high corrosion resistant plated steel sheet according to claim 1, characterized by, The steel base is one of cold-rolled strip steel or hot base strip steel including low-carbon aluminum-killed steel, IF steel, P-containing high-strength IF steel, bake-hardening steel, SPCC, structural steel and QP steel.

7. A method of producing the high corrosion resistant plated steel sheet according to claim 1, characterized by, The preparation method comprises the following steps: pickling, rolling, degreasing cleaning, continuous annealing, hot-dip plating, air knife blowing, cooling and finishing; wherein, The rolling adopts rough roller rolling, and the roughness of the surface of the strip steel after rolling is controlled to be 1.2-3.5 μm; The hydrogen content in the furnace during the continuous annealing process is controlled to be ≥2.5% in volume percentage; The temperature of the steel plate into the zinc pot is 420-620 ℃, the plating solution temperature during the hot-dip plating process is 420-600 ℃, the temperature of the strip steel into the zinc pot is not lower than the temperature of the zinc pot, and the hot-dip plating time is 1-3 s.

8. The method of claim 7, wherein, The air knife blowing medium is at least one of N2 and inert gas, the CO2 content is ≤50 ppm, and the O2 content is ≤50 ppm.

9. The preparation method according to claim 7, characterized in that, The cooling speed is controlled to be 5-30 ℃ / s, the temperature of the strip steel reaching the top deflection roller is ≤270 ℃, the surface roughness Ra of the finishing roller is controlled to be 2.0-4.5 μm, and the finishing elongation is 0.5-1.5%.

10. The method of claim 7, wherein, The plating solution chemical composition is as follows in mass percentage: Al: 10%-20%, Mg: 2.2%-6%, Si: 0.08%-0.40%, RE: 0.05%-0.60%, and the balance is Zn and other inevitable impurities.

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