A thermally-based zinc-aluminum-magnesium coated steel plate and a preparation method thereof

Abstract

The present application relates to a hot-rolled zinc-aluminum-magnesium coated steel plate and a preparation method thereof, and belongs to the field of cold rolling process technology; the chemical composition of the coating described in the present application includes: Al: 2% to 12% by weight, Mg: 1% to 4% by weight, and the rest is Zn and unavoidable impurities; the purpose of the present application is to solve the problem of coating shedding of hot-rolled zinc-aluminum-magnesium coated steel plates; the technical solution provided by the present application to solve the above technical problems is: by controlling comprehensive process parameters such as heating atmosphere, flame stiffness, calorific value fluctuation, burner control method, etc., a hot-rolled zinc-aluminum-magnesium coated steel plate with strong coating adhesion is obtained, and the steel plate has no dezincification phenomenon.

Description

Technical Field

[0001] The present application relates to the field of cold rolling process technology, and in particular to a thermally-based zinc-aluminum-magnesium coated steel plate and a preparation method thereof. Background Art

[0002] With the increasing requirements for corrosion, traditional pure zinc-coated steel plates can no longer meet the requirements for corrosion resistance. Zinc-aluminum-magnesium products have good corrosion resistance and good cut corrosion resistance, making the promotion and application of thick-specification products feasible.

[0003] At present, thick-gauge hot-dip galvanized steel sheets are generally made of hot-rolled substrates. The bonding between the coating and the substrate is poor, and dezincification occurs directly in severe cases. Therefore, how to produce hot-dip zinc-aluminum-magnesium products with strong coating adhesion has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a thermally-based zinc-aluminum-magnesium coated steel plate and a preparation method thereof, so as to solve the technical problem that the thermally-based zinc-aluminum-magnesium produced by the prior art has poor coating adhesion.

[0005] In a first aspect, the present application provides a method for preparing a thermally-based zinc-aluminum-magnesium coated steel sheet, the method comprising:

[0006] Under the conditions of set roughness of the working roll of the leveling mill and set leveling rolling force, the strip is leveled;

[0007] The flattened steel strip is heated in stages;

[0008] The strip steel after the heat treatment is hot-dipped using a plating solution containing a set chemical composition, so that the plating solution at least partially adheres to the surface of the strip steel after the heat treatment, thereby obtaining a hot-dip zinc-aluminum-magnesium coated steel plate.

[0009] Optionally, the roughness of the working roll of the leveling mill is set to a value of 4 μm to 5 μm, and the leveling rolling force is set to a value of 2000 KN to 4000 KN.

[0010] Optionally, the set chemical composition includes: Al: 2 weight % to 12 weight %, Mg: 1 weight % to 4 weight %, Zn.

[0011] Optionally, the step of heating the flattened steel strip in stages includes:

[0012] The strip steel after flattening treatment is heated through a heating section, a soaking section and a cooling section, wherein the burner control method of the heating section includes: the number of burners opened increases zone by zone from back to front, and decreases zone by zone from front to back when closed; wherein the burner power of each zone is set to be greater than or equal to 20%.

[0013] Optionally, the step of heating the flattened steel strip in stages includes:

[0014] The flattened steel strip is heated through a heating section, a soaking section and a cooling section, wherein the process parameters of the heating section include: setting the heating atmosphere temperature to 1250°C to 1350°C, setting the steel strip temperature to 650°C to 710°C, setting the CO content to be greater than 1.5 volume %, and setting the SO2 content to be less than 50 mg / m 3 .

[0015] Optionally, the step of heating the flattened steel strip in stages includes:

[0016] The strip steel after flattening treatment is heated through a heating section, a soaking section and a cooling section, wherein the soaking section includes: setting the heating atmosphere temperature to 650°C ~ 710°C, setting the strip steel temperature to 650°C ~ 710°C, setting the O2 content volume concentration to no more than 10ppm, and setting the H2 content to 15% by volume ~ 25% by volume.

[0017] Optionally, the step of heating the flattened steel strip in stages includes:

[0018] The strip steel after flattening treatment is heated through a heating section, a heat equalizing section and a cooling section, wherein the cooling section includes: setting the heating atmosphere temperature to 420°C ~ 450°C, setting the strip steel temperature to 420°C ~ 450°C, setting the O2 content volume concentration to no more than 10ppm, and setting the H2 content to 15% by volume ~ 25% by volume.

[0019] Optionally, the step of heating the flattened steel strip in stages includes:

[0020] Under the conditions of set pressure and set gas calorific value, the flattened steel strip is heated in stages, wherein the pressure is not less than 100 Pa and the gas calorific value is 3500 kCal to 4400 kCal.

[0021] Optionally, the hot-dip coating temperature is 420°C to 460°C.

[0022] In a second aspect, the present application provides a thermally-based zinc-aluminum-magnesium coated steel plate, which is obtained by any method described in the first aspect.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] The embodiments of the present application provide a thermal-based zinc-aluminum-magnesium coated steel plate and a preparation method thereof. By controlling comprehensive process parameters such as heating atmosphere, flame stiffness, calorific value fluctuation, and burner control method, the zinc-aluminum-magnesium coated steel plate produced has strong adhesion and no dezincification. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 The bending without zinc removal diagram provided in Example 1 of the present application;

[0028] Figure 2 This is the bending dezincification diagram provided for comparative example 1 of this application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] The present application provides a method for preparing a thermally-based zinc-aluminum-magnesium coated steel plate, the method comprising:

[0032] Under the conditions of set roughness of the working roll of the leveling mill and set leveling rolling force, the strip is leveled;

[0033] The flattened steel strip is heated in stages;

[0034] The strip steel after the heat treatment is hot-dipped using a plating solution containing a set chemical composition, so that the plating solution at least partially adheres to the surface of the strip steel after the heat treatment, thereby obtaining a hot-dip zinc-aluminum-magnesium coated steel plate.

[0035] In this embodiment, the substrate used is a hot-rolled raw material. In order to reduce the morphology differences between different positions of the same steel coil and between different steel coils, the pickling process must be flattened. The flattening treatment can enable the strip to obtain the necessary performance and surface quality to meet the requirements of subsequent processing steps. Its essence is a rolling deformation with a small reduction.

[0036] In some embodiments, the roughness of the working roll of the leveling mill is set to a value of 4 μm to 5 μm, and the leveling rolling force is set to a value of 2000 KN to 4000 KN.

[0037] In this embodiment, the roughness of the working roll and the rolling force have an impact on the surface roughness of the strip steel. Within this range, a relatively uniform surface roughness of the strip steel can be obtained, which is more conducive to the combination of the coating and the strip steel and increases the adhesion of the coating.

[0038] In some embodiments, the set chemical composition includes: Al: 2 wt% to 12 wt%, Mg: 1 wt% to 4 wt%, Zn.

[0039] In this embodiment, the Al content and the Mg content are controlled in order to balance the corrosion resistance of the plating solution on the surface of the strip and the surface quality of the coating. When the content increases, the corrosion resistance increases, but the surface quality of the coating deteriorates. When the content decreases, the corrosion resistance decreases, and the surface quality improves.

[0040] In some embodiments, the step of heating the flattened steel strip in stages includes:

[0041] The strip steel after flattening treatment is heated through a heating section, a soaking section and a cooling section, wherein the burner control method of the heating section includes: the number of burners opened increases zone by zone from back to front, and decreases zone by zone from front to back when closed; wherein the burner power of each zone is set to be greater than or equal to 20%.

[0042] In this embodiment, open flame heating can be used in the heating section, and radiant tube equalization can be used in the equalization section. The number of burners opened increases from the back to the front zone by zone, which means that when the burner is turned on, the number of burners opened increases from the end to the front according to the heating temperature requirements of the steel plate, and when closed, it is closed from the front to the back. Controlling the number and sequence of burners opened and the burner power in each zone is to improve the rigidity of the flame and the completeness of combustion.

[0043] In some embodiments, the step of heating the flattened steel strip in stages includes:

[0044] The flattened steel strip is heated through a heating section, a soaking section and a cooling section, wherein the process parameters of the heating section include: setting the heating atmosphere temperature to 1250°C to 1350°C, setting the steel strip temperature to 650°C to 710°C, setting the CO content to be greater than 1.5%, and setting the SO2 content to be less than 50mg / m 3 .

[0045] In this embodiment, the contents of CO and SO2 are controlled to prevent the oxidizing substances in the combustion products from increasing the oxidizing property of the strip. CO plays a reducing role in the combustion atmosphere, and SO2 plays an oxidizing role in the combustion atmosphere. When the CO content is lower than 1.5%, the reducing atmosphere is insufficient. When the SO2 content is greater than 50 mg / m 3 When the oxidizing atmosphere is enhanced, the surface of the strip is not fully reduced, resulting in poor adhesion of the coating and dezincification.

[0046] In some embodiments, the step of heating the flattened steel strip in stages includes:

[0047] The strip steel after flattening treatment is heated through a heating section, a soaking section and a cooling section, wherein the soaking section includes: setting the heating atmosphere temperature to 650°C ~ 710°C, setting the strip steel temperature to 650°C ~ 710°C, setting the O2 content volume concentration to no more than 10ppm, and setting the H2 content volume percentage to 15% ~ 25%.

[0048] In this embodiment, the heating atmosphere temperature is controlled in order to control the surface reduction degree and physical properties of the steel strip. Too low a temperature will result in insufficient reduction, while too high a temperature will result in fluctuations in the performance of the steel strip and failure to meet the performance requirements.

[0049] In this embodiment, the content of hydrogen and oxygen is controlled in order to reduce oxidation and obtain a good reduction effect. Hydrogen plays a reducing role in the combustion atmosphere, and oxygen plays an oxidizing role in the combustion atmosphere. When the hydrogen content is lower than 15%, the reducing atmosphere is insufficient. When the hydrogen content is higher than 25%, there is a hidden danger to safe production. When the oxygen content is greater than 10ppm, the oxidizing atmosphere is enhanced, resulting in insufficient reduction of the strip surface, poor coating adhesion, and dezincification.

[0050] In some embodiments, the step of heating the flattened steel strip in stages includes:

[0051] The strip steel after flattening treatment is heated through a heating section, a soaking section and a cooling section, wherein the cooling section includes: setting the cooling atmosphere temperature to 420°C ~ 450°C, setting the strip steel temperature to 420°C ~ 450°C, setting the oxygen content volume concentration to no more than 10ppm, and setting the hydrogen content volume percentage to 15% ~ 25%.

[0052] In this embodiment, the cooling atmosphere temperature is controlled in order to control the consistency between the strip temperature and the plating solution temperature. When the temperature is too high or too low, it will affect the combination of the plating solution and the strip, and affect the adhesion and surface quality of the coating.

[0053] In this embodiment, the contents of hydrogen and oxygen are controlled in order to reduce oxidation and obtain a good reduction effect.

[0054] In some embodiments, the step of heating the flattened steel strip in stages includes:

[0055] Under the conditions of set pressure and set gas calorific value, the flattened steel strip is heated in stages, wherein the pressure is not less than 100 Pa and the gas calorific value is 3500 kCal to 4400 kCal.

[0056] In this embodiment, the pressure is set to be not less than 100 Pa in order to avoid the convection penetration of oxygen at the joints of the furnace area and the leaking points. When the furnace pressure is lower than 100 Pa, oxygen will penetrate into the furnace area, causing oxidation of the steel strip, resulting in poor coating adhesion and dezincification. The gas calorific value is set in consideration of economic efficiency and production controllability. When the gas calorific value is too high or too low, the operator will frequently adjust the air ratio, which will affect the stable operation of various parameters in the furnace area and easily destroy the relatively balanced reducing atmosphere.

[0057] In some embodiments, the hot-dip temperature is 420°C to 460°C.

[0058] In this embodiment, the heat temperature affects the fluidity of the plating solution. When the temperature is lower than 420°C, the fluidity of the plating solution is poor and zinc flow defects are easily generated. When the temperature is higher than 460°C, the plating solution is prone to react with air to produce zinc ash and zinc slag defects, affecting the surface quality of the strip.

[0059] In a second aspect, the present application provides a thermally-based zinc-aluminum-magnesium coated steel plate, which is obtained by any method described in the first aspect.

[0060] The hot-based zinc-aluminum-magnesium coated steel plate is realized based on the preparation method of the hot-based zinc-aluminum-magnesium coated steel plate mentioned above. The specific steps of the preparation method of the hot-based zinc-aluminum-magnesium coated steel plate can refer to the above embodiment. Since the hot-based zinc-aluminum-magnesium coated steel plate adopts part or all of the technical solutions of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment, which will not be repeated here one by one.

[0061] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed according to general international standards, normal conditions, or are carried out.

[0062] Example 1

[0063] After hot rolling, the strip has a thickness of 3mm, and the chemical composition of the plating solution is: Al: 7%, Mg: 2.2%, and the rest is Zn and inevitable impurities. The working roller Ra of the leveling machine used in the pickling process is 4.0μm, the rolling force is 2000KN, and the strip is heated by a direct-fired furnace. During the heating process, the temperature of the heating furnace zone is 1250℃~1350℃, and the strip temperature is 670℃~690℃; the calorific value of the coal gas is 4200kCal~4400kCal, the excess air coefficient is 0.95~0.98, the minimum power of the burner in each zone of the direct-fired furnace is 20%, the furnace pressure in each section of the furnace zone is 100pa~120pa, the oxygen content in the furnace zone is <10ppm, the hydrogen content is 15%~18%, the CO in the direct-fired section of the non-oxidizing heating furnace is >1.5%, and the SO2 content in the combustion gas is ≤50mg / m 3 , galvanizing temperature 420℃, relevant data are shown in Table 1. The prepared hot-base zinc-aluminum-magnesium coated steel sheet is as follows Figure 1 As mentioned above, bending does not remove zinc.

[0064] Example 2

[0065] After hot rolling, the strip has a thickness of 3mm, and the chemical composition of the plating solution is: Al: 7%, Mg: 2.2%, and the rest is Zn and inevitable impurities. The working roller Ra of the leveling machine used in the pickling process is 5.0μm, the rolling force is 4000KN, and the strip is heated by a direct-fired furnace. During the heating process, the temperature of the heating furnace zone is 1250℃~1350℃, and the strip temperature is 670℃~690℃; the calorific value of the coal gas is 4200kCal~4400kCal, the excess air coefficient is 0.95~0.98, the minimum power of the burner in each zone of the direct-fired furnace is 20%, the furnace pressure in each section of the furnace zone is 100pa~120pa, the oxygen content in the furnace zone is <8ppm, the hydrogen content is 15%~18%, the CO in the direct-fired section of the non-oxidizing heating furnace is >1.5%, and the SO2 content in the combustion gas is ≤50mg / m 3 ; Galvanizing temperature is 420℃, and the relevant data are shown in Table 1.

[0066] Example 3

[0067] After hot rolling, the strip has a thickness of 3mm, and the chemical composition of the plating solution is: Al: 7%, Mg: 2.2%, Si: 0.02%, and the rest is Zn and inevitable impurities. The working roller Ra of the leveler used in the pickling process is 4.0μm, and the rolling force is 2000KN. The strip is heated by a direct-fired furnace. During the heating process, the temperature of the heating furnace zone is 1250℃~1350℃, and the strip temperature is 670℃~690℃; the calorific value of the coal gas is 4200kCal~4400kCal, the excess air coefficient is 0.95~0.98, the minimum power of the burner in each zone of the direct-fired furnace is 20%, the furnace pressure in each section of the furnace zone is 100pa~120pa, the oxygen content in the furnace zone is <7ppm, the hydrogen content is 15%~18%, the CO in the direct-fired section of the non-oxidizing heating furnace is >1.5%, and the SO2 content in the combustion gas is ≤30mg / m 3 ; Galvanizing temperature is 460℃, and the relevant data are shown in Table 1.

[0068] Example 4

[0069] After hot rolling, the strip has a thickness of 3mm, and the chemical composition of the plating solution is: Al: 7%, Mg: 2.2%, and the rest is Zn and unavoidable impurities. The working roller Ra of the leveling machine used in the pickling process is 4.5μm, and the rolling force is 3000KN. The strip is heated by a direct-fired furnace. During the heating process, the temperature of the heating furnace zone is 1250℃~1350℃, and the strip temperature is 670℃~690℃; the calorific value of the coal gas is 4200kCal~4400kCal, the excess air coefficient is 0.95~0.98, the minimum power of the burner in each zone of the direct-fired furnace is 25%, the furnace pressure in each section of the furnace zone is 130pa~150pa, the oxygen content in the furnace zone is <5ppm, the hydrogen content is 23%~25%, the CO in the direct-fired section of the non-oxidizing heating furnace is >2.3%, and the SO2 content in the combustion gas is ≤45mg / m 3 ; Galvanizing temperature is 445℃, and the relevant data are shown in Table 1.

[0070] Example 5

[0071] After hot rolling, the strip has a thickness of 4mm, and the chemical composition of the plating solution is: Al: 7%, Mg: 2.2%, and the rest is Zn and inevitable impurities. The working roller Ra of the leveler used in the pickling process is 4.5μm, and the rolling force is 3000KN. The strip is heated by a direct-fired furnace. During the heating process, the temperature of the heating furnace zone is 1250℃~1350℃, and the strip temperature is 670℃~690℃; the calorific value of the coal gas is 4200kCal~4400kCal, the excess air coefficient is 0.95~0.98, the minimum power of the burner in each zone of the direct-fired furnace is 50%, the furnace pressure in each section of the furnace zone is 130pa~150pa, the oxygen content in the furnace zone is <5ppm, the hydrogen content is 21%~24%, the CO in the direct-fired section of the non-oxidizing heating furnace is >2.5%, and the SO2 content in the combustion gas is ≤20mg / m 3 ; Galvanizing temperature is 445℃, and the relevant data are shown in Table 1.

[0072] Comparative Example 1

[0073] After hot rolling, the strip has a thickness of 2.5 mm, and the chemical composition of the plating solution is: Al: 7%, Mg: 2.2%, and the rest is Zn and inevitable impurities. The working roller Ra of the leveling machine used in the pickling process is 4.5 μm, and the rolling force is 3000 KN. The strip is heated by a direct-fired furnace. During the heating process, the temperature of the heating furnace zone is 1250°C to 1350°C, and the strip temperature is 670°C to 690°C; the calorific value of the coal gas is 4200 kCal to 4400 kCal, the excess air coefficient is 0.95 to 0.98, the minimum power of the burner in each zone of the direct-fired furnace is 20%, the furnace pressure in each section of the furnace zone is 90 Pa to 100 Pa, the oxygen content in the furnace zone is <6 ppm, the hydrogen content is 18% to 20%, the CO in the direct-fired section of the non-oxidizing heating furnace is >1.7%, and the SO2 content in the combustion gas is ≤100 to 120 mg / m 3 ; Galvanizing temperature is 440℃, and the relevant data are shown in Table 1. The prepared hot-base zinc-aluminum-magnesium coated steel sheet is as follows Figure 2 As mentioned above, bending and dezincification.

[0074] Comparative Example 2

[0075] After hot rolling, the strip has a thickness of 3mm, and the chemical composition of the plating solution is: Al: 7%, Mg: 2.2%, and the rest is Zn and inevitable impurities. The working roller Ra of the leveling machine used in the pickling process is 3μm, the rolling force is 1500KN, and the strip is heated by a direct-fired furnace. During the heating process, the temperature of the heating furnace zone is 1250℃~1350℃, and the strip temperature is 670℃~690℃; the calorific value of the coal gas is 4200kCal~4400kCal, the excess air coefficient is 0.95~0.98, the minimum power of the burner in each zone of the direct-fired furnace is 50%, the furnace pressure in each section of the furnace zone is 130pa~150pa, the oxygen content in the furnace zone is <5ppm, the hydrogen content is 21%~24%, the CO in the direct-fired section of the non-oxidizing heating furnace is >2.5%, and the SO2 content in the combustion gas is ≤20mg / m 3 ; Galvanizing temperature is 445℃, and the relevant data are shown in Table 1.

[0076] Comparative Example 3

[0077] After hot rolling, the strip has a thickness of 3mm, and the chemical composition of the plating solution is: Al: 7%, Mg: 2.2%, and the rest is Zn and inevitable impurities. The working roller Ra of the leveler used in the pickling process is 4.5μm, and the rolling force is 3000KN. The strip is heated by a direct-fired furnace. During the heating process, the temperature of the heating furnace zone is 1250℃~1350℃, and the strip temperature is 670℃~690℃; the calorific value of the coal gas is 4200kCal~4400kCal, the excess air coefficient is 0.95~0.98, the minimum power of the burner in each zone of the direct-fired furnace is 25%, the furnace pressure in each section of the furnace zone is 120pa~140pa, the oxygen content in the furnace zone is <6ppm, the hydrogen content is 20%~23%, the CO in the direct-fired section of the non-oxidizing heating furnace is >2.0%, and the SO2 content in the combustion gas is ≤15mg / m 3 ; Galvanizing temperature is 400℃, and the relevant data are shown in Table 1.

[0078] Related experimental test methods: Take samples of finished coils for bending tests to detect whether the strip coating is dezincified.

[0079] Related experiments and effect data:

[0080] Table 1

[0081]

[0082]

[0083] The technical solution provided by the present invention has the following technical effects and advantages:

[0084] (1) The present invention provides a method for producing a zinc-aluminum-magnesium alloy coated steel plate having a strong coating adhesion by using a direct-fired furnace process;

[0085] (2) The present invention provides a comprehensive process method involving direct-fired furnace atmosphere, flame stiffness, calorific value fluctuation, burner control method, etc., and the zinc-aluminum-magnesium product produced has a strong coating adhesion and no dezincification phenomenon.

[0086] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0087] In this application, unless otherwise specified, directional words such as "upper" and "lower" used refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of this application specification, the terms "include", "comprises", etc. mean "including but not limited to".

[0088] In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, a~b (i.e. a and b), a~c, b~c, or a~b~c, where a, b, c can be single or multiple.

[0089] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a thermally-based zinc-aluminum-magnesium coated steel sheet, characterized in that: The method comprises: Under the conditions of set roughness of the working roll of the leveling mill and set leveling rolling force, the strip is leveled; Under the conditions of set pressure and set gas calorific value, the flattened steel strip is heated in stages, the pressure is not less than 100 Pa, and the gas calorific value is 3500 kcal to 4400 kcal; Hot-dip the heated steel strip using a plating solution containing a set chemical composition, so that the plating solution at least partially adheres to the surface of the heated steel strip, to obtain a hot-dip zinc-aluminum-magnesium coated steel plate; The roughness of the working roll of the leveling mill is set to be 4 μm to 5 μm, and the leveling rolling force is set to be 2000 kN to 4000 kN; The step of heating the flattened steel strip in stages comprises: The flattened steel strip is heated through a heating section, a soaking section and a cooling section, wherein the burner control method of the heating section includes: the number of burners opened increases from the back to the front, and when closed, the number of burners decreases from the front to the back; wherein the burner power of each zone is set to be greater than or equal to 20%, and the process parameters of the heating section include: setting the heating atmosphere temperature to 1250°C to 1350°C, setting the strip temperature to 650°C to 710°C, setting the CO content to be greater than 1.5 volume%, and setting the SO2 content to be no more than 50 mg / m 3 The soaking section includes: setting the heating atmosphere temperature to 650℃~710℃, setting the strip temperature to 650℃~710℃, setting the O2 volume content to no more than 10ppm, and setting the H2 content to 15vol%~25vol%. The cooling section includes: setting the heating atmosphere temperature to 420℃~450℃, setting the strip temperature to 420℃~450℃, setting the O2 volume concentration to no more than 10ppm, and setting the H2 content to 15vol%~25vol%.

2. The preparation method according to claim 1, characterized in that: The set chemical composition is: Al: 2 weight % to 12 weight %, Mg: 1 weight % to 4 weight %, and the rest is Zn and unavoidable impurities.

3. The preparation method according to claim 1, characterized in that: The hot-dip coating temperature is 420°C to 460°C.

4. A thermally-based zinc-aluminum-magnesium coated steel sheet, characterized in that: The steel plate is obtained by the method according to any one of claims 1 to 3.

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