Zinc-aluminum-magnesium coating product and preparation method thereof

Abstract

The invention relates to the technical field of steel smelting, in particular to a zinc-aluminum-magnesium coating product and a preparation method thereof. The method comprises the following steps: carrying out hot rolling and coiling on a plate blank to obtain strip steel; pickling the strip steel to obtain a steel substrate; preheating the surface of the steel substrate, and then annealing to obtain a pretreated steel substrate; carrying out hot galvanizing on the pretreated steel substrate to obtain a zinc-aluminum-magnesium coating product; the annealing comprises annealing by adopting a heating section, a soaking section and a cooling section, and the heating section comprises heating by adjusting the air-fuel ratio according to the real-time temperature of different heating sections; the cooling section is used for cooling under the atmosphere condition of nitrogen and hydrogen mixed gas; the cooling section further comprises a furnace nose area, and the dew point temperature of the furnace nose area is smaller than or equal to-30 DEG C; according to the method, the problems of residual oxide scale on the surface of the steel substrate and selective oxidation of alloy elements in the annealing stage can be avoided, so that a zinc-aluminum-magnesium coating product without the surface plating leakage defect can be finally obtained.

Description

Technical Field

[0001] The present application relates to the technical field of steel smelting, and in particular to a zinc-aluminum-magnesium coating product and a preparation method thereof. Background Art

[0002] With the large-scale development of thermal-based zinc-aluminum-magnesium coating products, thermal-based zinc-aluminum-magnesium coating products can be applied in a variety of fields, such as photovoltaics, highway guardrails, granaries, underground pipe corridors, etc. At the same time, due to the good corrosion resistance of thermal-based zinc-aluminum-magnesium coating products, they can be applied to related fields of automobile chassis. In order to meet the working requirements of automobile chassis, 780Mpa grade thermal-based ferritic bainitic steel zinc-aluminum-magnesium coating products are currently generally used as automobile chassis.

[0003] However, due to the high content of alloy elements in the zinc-aluminum-magnesium coating product, problems such as residual iron oxide scale and selective oxidation of alloy elements are prone to occur during the production process of the zinc-aluminum-magnesium coating product, thereby forming plating leakage defects on the surface of the zinc-aluminum-magnesium coating product, and these defects will affect the surface quality of the zinc-aluminum-magnesium coating product. Summary of the invention

[0004] The present application provides a zinc-aluminum-magnesium coating product and a preparation method thereof, so as to solve the technical problem in the prior art that the production process of the zinc-aluminum-magnesium coating product is prone to form plating leakage defects on the surface of the zinc-aluminum-magnesium coating product.

[0005] In a first aspect, the present application provides a method for preparing a zinc-aluminum-magnesium coating product, the method comprising:

[0006] Hot rolling and coiling the slab to obtain strip steel;

[0007] Pickling the steel strip to obtain a steel matrix;

[0008] Preheating the surface of the steel substrate, and then annealing the preheated steel substrate to obtain a pretreated steel substrate;

[0009] Hot-dip galvanizing the pretreated steel substrate to obtain a zinc-aluminum-magnesium coating product;

[0010] Wherein, the annealing includes annealing in the form of a heating section, a soaking section and a cooling section, and the heating section includes heating in the form of adjusting the air-fuel ratio according to the real-time temperature of different heating sections;

[0011] The cooling section includes cooling under the atmosphere of nitrogen and hydrogen mixture;

[0012] The cooling section also includes a furnace nose area, and the dew point temperature of the furnace nose area is ≤-30°C.

[0013] Optionally, when the real-time temperature of the heating section is less than 600° C., the air-fuel ratio is greater than 1;

[0014] When the real-time temperature of the heating section is ≥600° C., the air-fuel ratio is <1.

[0015] Optionally, when the real-time temperature of the heating section is less than 600° C., the air-fuel ratio is 1.0:0.95 to 1.0:0.90; and / or,

[0016] When the real-time temperature of the heating section is ≥600° C., the air-fuel ratio is 0.85:1.0 to 0.92:1.0.

[0017] Optionally, in terms of volume fraction, the components of the nitrogen-hydrogen mixed gas include: hydrogen: 5% to 8% and nitrogen: 92% to 95%.

[0018] Optionally, the dew point temperature of the furnace nose area is -40°C to -30°C.

[0019] Optionally, the plating solution used in the hot-dip galvanizing satisfies:

[0020] [Si] / [Al]=0.5%~1.5%,

[0021] Wherein, [Si] is the mass fraction of Si in the plating solution, and [Al] is the mass fraction of Al in the plating solution.

[0022] Optionally, the temperature of the hot rolling coiling is ≤560°C.

[0023] Optionally, the pickling includes pickling at a preset pickling speed, and the preset pickling speed is ≤120m / min.

[0024] Optionally, the reagent used in the pickling includes an inhibitor, and the mass concentration of the inhibitor is 0.8% to 1.5%.

[0025] In a second aspect, the present application provides a zinc-aluminum-magnesium coating product, which is prepared by the method described in the first aspect.

[0026] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0027] A zinc-aluminum-magnesium coating product provided in an embodiment of the present application can fully remove the residual iron oxide scale on the surface of the steel substrate by hot rolling and pickling; then the refinement annealing includes a heating section, a soaking section and a cooling section, and then the heating section is controlled to adjust the air-fuel ratio according to the real-time temperature of different heating sections for heating, which can promote the air-fuel ratio and the real-time temperature of the heating section to match each other, so as to promote the full progress of the heating section, so that the pre-oxidation and preliminary reduction of the steel substrate surface can be completed through the heating section to improve the selective oxidation problem of the alloy elements in the steel substrate; then the atmosphere of the cooling section is controlled to be a nitrogen-hydrogen mixture and the dew point temperature of the furnace nose area in the cooling section. On the one hand, the oxidation of the steel substrate surface can be avoided in the cooling stage by the reducing property of the nitrogen-hydrogen mixture, and on the other hand, the re-oxidation of the steel substrate surface can be avoided in the cooling stage by controlling the dew point temperature of the furnace nose area; therefore, the method of the present application can avoid the residual iron oxide scale on the surface of the steel substrate and the selective oxidation of the alloy elements in the annealing stage, so that a zinc-aluminum-magnesium coating product without surface plating defects can be finally obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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.

[0029] 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.

[0030] Figure 1 A schematic diagram of a process for preparing a zinc-aluminum-magnesium coating product provided in an embodiment of the present application;

[0031] Figure 2 This is a scanning electron microscope image of the zinc-aluminum-magnesium coating sample provided in Example 1 of the present application;

[0032] Figure 3 A scanning electron microscope image of the zinc-aluminum-magnesium coating sample provided for Comparative Example 1 of the present application;

[0033] Figure 4 This is a positron emission tomography scanning result diagram of the zinc-aluminum-magnesium coating provided in Example 1 of the present application. DETAILED DESCRIPTION

[0034] 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.

[0035] 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.

[0036] Figure 1 A schematic diagram of a process for preparing a zinc-aluminum-magnesium coating product provided in an embodiment of the present application is exemplarily shown;

[0037] like Figure 1 As shown, a method for preparing a zinc-aluminum-magnesium coating product provided in an embodiment of the present application comprises:

[0038] S1. hot rolling and coiling the slab to obtain a strip;

[0039] S2. pickling the steel strip to obtain a steel matrix;

[0040] S3. Preheating the surface of the steel substrate, and then annealing the preheated steel substrate to obtain a pretreated steel substrate;

[0041] S4. The pretreated steel substrate is hot-dip galvanized to obtain a zinc-aluminum-magnesium coating product;

[0042] Wherein, the annealing includes annealing in the form of a heating section, a soaking section and a cooling section, and the heating section includes heating in the form of adjusting the air-fuel ratio according to the real-time temperature of different heating sections;

[0043] The cooling section includes cooling under the atmosphere of nitrogen and hydrogen mixture;

[0044] The cooling section also includes a furnace nose area, and the dew point temperature of the furnace nose area is ≤-30°C.

[0045] In some optional embodiments, when the real-time temperature of the heating section is less than 600° C., the air-fuel ratio is greater than 1;

[0046] When the real-time temperature of the heating section is ≥600°C, the air-fuel ratio is <1; since the heating process of the heating section is a continuous heating process, there are different heating temperatures in the heating section. If a uniform air-fuel ratio is used under conditions of different heating temperatures, it will lead to uneven heating, thereby causing the problem of selective oxidation of alloy elements on the surface of the steel matrix; in these embodiments, if the real-time temperature of the heating section is below 600°C, it means that the heating section is in the initial stage of heating, and a large amount of air needs to be introduced to promote the combustion of the fuel gas and release a large amount of heat to meet the heat demand of the heating section, so as to quickly increase the real-time temperature of the heating stage to the preset end temperature, and at this time the air-fuel ratio is controlled to be >1, which means that the air is in an excessive temperature relative to the fuel gas. The state of the excess mode, therefore, the real-time temperature of the heating section can be quickly increased to the terminal temperature of the heating section, and a large amount of heat is released in the process to heat the steel matrix; if the real-time temperature of the heating section is 600℃ or above, it means that the real-time temperature of the heating section has reached the terminal temperature of the heating section. At this time, the heat in the heating section is sufficient to heat the steel matrix. Therefore, it is necessary to control the air content in the heating section to avoid the selective oxidation of the alloy elements in the steel matrix by the oxygen molecules in the air. At this time, the air-fuel ratio is controlled to be less than 1. The air-fuel ratio indicates that the fuel gas is in the excess mode relative to the air, and most of the fuel gas is carbon-containing reducing gas. Therefore, the contact surface of the alloy elements in the steel matrix can be isolated, avoiding the problem of selective oxidation of the alloy elements in the steel matrix during the annealing process.

[0047] In some optional embodiments, when the real-time temperature of the heating section is less than 600° C., the air-fuel ratio is 1.0:0.95 to 1.0:0.90; and / or,

[0048] When the real-time temperature of the heating section is ≥600°C, the air-fuel ratio is 0.85:1.0~0.92:1.0; in these embodiments, if the real-time temperature of the heating section is below 600°C, the air-fuel ratio can be 1.0:0.95~1.0:0.90, which can increase the proportion of air in the mixture of air and gas, so as to promote the real-time temperature of the heating section to rise quickly to the terminal temperature of the heating section. In addition, a large amount of heat is released in the process, which can fully heat the steel matrix; if the real-time temperature of the heating section is 600°C and above, the air-fuel ratio can be 0.85:1.0~0.92:1.0. At this time, the gas is in a surplus mode relative to the air, and the carbon-containing reducing gas in the gas can be used to isolate the contact surface between the steel matrix and the air, so as to avoid the problem of selective oxidation of alloy elements in the steel matrix during the annealing process.

[0049] The air-fuel ratio may be 1.0:0.95, 1.0:0.94, 1.0:0.93, 1.0:0.92, 1.0:0.91 or 1.0:0.90.

[0050] The air-fuel ratio may be 0.85:1.0, 0.86:1.0, 0.87:1.0, 0.88:1.0, 0.89:1.0, 0.90:1.0, 0.91:1.0, or 0.92:1.0.

[0051] In some optional embodiments, the components of the nitrogen-hydrogen mixture include, by volume fraction: hydrogen: 5% to 8% and nitrogen: 92% to 95%; in these embodiments, the volume fraction of hydrogen can be 5% to 8%, and the volume fraction of nitrogen can be 92% to 95%, so that there is sufficient hydrogen in the cooling section to reduce the alloy elements on the surface of the steel matrix. In addition, the nitrogen can isolate the contact surface between the steel matrix and the air to avoid re-oxidation of the steel matrix during the annealing process.

[0052] In some optional embodiments, the dew point temperature of the furnace nose area is -40°C to -30°C; since the furnace nose is a channel connecting the annealing area and the hot-dip galvanizing area, in these embodiments, the dew point temperature of the furnace nose area can be -40°C to -30°C, which can promote the full combination of the steel substrate and the zinc liquid, and facilitate the subsequent hot-dip galvanizing to obtain a zinc-aluminum-magnesium coating product with good surface quality on the surface of the steel substrate.

[0053] The dew point temperature in the furnace nose area may be -40°C, -39°C, -38°C, -37°C, -36°C, -35°C, -34°C, -33°C, -32°C, -31°C or -30°C.

[0054] In some optional embodiments, the plating solution used in the hot-dip galvanizing satisfies:

[0055] [Si] / [Al]=0.5%~1.5%,

[0056] In the formula, [Si] is the mass fraction of Si in the plating solution, and [Al] is the mass fraction of Al in the plating solution; in these embodiments, the mass ratio of the mass fraction of Si in the plating solution to the mass fraction of Al in the plating solution can be 0.5% to 1.5%, which can promote the formation of a good quality inhibition layer between the zinc-aluminum-magnesium coating and the surface of the steel substrate.

[0057] The mass ratio of the mass fraction of Si in the plating solution to the mass fraction of Al in the plating solution can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%.

[0058] In some optional embodiments, the hot rolling and coiling temperature is ≤560°C; in these embodiments, the hot rolling and coiling temperature can be 560°C and below, which can reduce the thickness of the iron oxide scale on the surface of the strip obtained after hot rolling and coiling.

[0059] In some optional embodiments, the pickling includes pickling at a preset pickling speed, and the preset pickling speed is ≤120m / min; in these embodiments, the preset pickling speed can be 120m / min and below, and the preset pickling speed can be used to control the time of the overall pickling process, so as to ensure sufficient contact between the pickling liquid and the strip, thereby improving the removal effect of the pickling liquid on the surface of the strip during the pickling stage.

[0060] In some optional embodiments, the reagents used in the pickling include inhibitors, and the mass concentration of the inhibitor is 0.8% to 1.5%; in these embodiments, the mass concentration of the inhibitor can be 0.8% to 1.5%, which can reduce the inhibitory effect of the inhibitor on the pickling solution, prompting the pickling solution to fully pickle the strip, thereby improving the pickling solution's effect on removing iron oxide scale on the strip surface during the pickling stage.

[0061] The mass concentration of the inhibitor may be 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%.

[0062] Figure 2 The scanning electron microscope image of the zinc-aluminum-magnesium coating sample provided in Example 1 of the present application is shown as an example;

[0063] like Figure 2 As shown, based on a general inventive concept, an embodiment of the present application provides a zinc-aluminum-magnesium coating product, and the zinc-aluminum-magnesium coating product is prepared by the method.

[0064] The zinc-aluminum-magnesium coating product is realized based on the above-mentioned preparation method. The specific steps of the preparation method can refer to the above-mentioned embodiment. Since the zinc-aluminum-magnesium coating product adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0065] 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 industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0066] Example 1

[0067] Taking the 780Mpa grade hot-base ferrite and bainite steel zinc aluminum magnesium coating product as an example, the specifications of the steel zinc aluminum magnesium coating product are: thickness 3.0mm and width 1300mm.

[0068] like Figure 1 As shown, a method for preparing a zinc-aluminum-magnesium coating product comprises:

[0069] S1. heating the slab, and then hot rolling and coiling the slab to obtain a strip;

[0070] S2. pickling the steel strip to obtain a steel matrix;

[0071] S3. Preheating the surface of the steel substrate, and then annealing the preheated steel substrate to obtain a pretreated steel substrate;

[0072] S4. hot-dip galvanizing the pretreated steel substrate to obtain a zinc-aluminum-magnesium coating product;

[0073] Wherein, annealing includes annealing in the form of a heating section, a soaking section and a cooling section, and the heating section includes heating in the form of adjusting the air-fuel ratio according to the real-time temperature of different heating sections;

[0074] The cooling stage includes cooling under the atmosphere of nitrogen and hydrogen mixture;

[0075] The cooling section also includes the furnace nose area, and the dew point temperature of the furnace nose area is ≤-30℃.

[0076] The real-time temperature of the heating section from the 1st to the 3rd zone in the annealing furnace is less than 600°C, and the air-fuel ratio is controlled to be 1.0:0.95;

[0077] When the real-time temperature of the heating section from the 3rd to the 8th zone in the annealing furnace is ≥600°C, the air-fuel ratio is controlled to be 0.92:1.0.

[0078] Measured by volume fraction, the components of the nitrogen-hydrogen mixture include: hydrogen: 6% and nitrogen: 94%.

[0079] The dew point temperature in the furnace nose area is -32°C.

[0080] The plating solution used in hot-dip galvanizing meets the following requirements:

[0081] [Si] / [Al]=1.2%,

[0082] Wherein, [Si] is the mass fraction of Si in the plating solution, and [Al] is the mass fraction of Al in the plating solution.

[0083] The hot rolling coiling temperature is 540°C.

[0084] The pickling includes pickling at a preset pickling speed, and the preset pickling speed is 100 m / min.

[0085] The reagents used in the pickling process include an inhibitor, and the mass concentration of the inhibitor is 1.1%.

[0086] Example 2

[0087] Comparing Example 2 with Example 1, the difference between Example 2 and Example 1 is:

[0088] The real-time temperature of the heating section from the 1st to the 3rd zone in the annealing furnace is less than 600°C, and the air-fuel ratio is controlled to be 1.0:0.92;

[0089] When the real-time temperature of the heating section from the 3rd to the 8th zone in the annealing furnace is ≥600°C, the air-fuel ratio is controlled to be 0.90:1.0.

[0090] Measured by volume fraction, the components of the nitrogen-hydrogen mixed gas include: hydrogen: 5% and nitrogen: 95%.

[0091] The dew point temperature in the furnace nose area is -40°C.

[0092] The plating solution used in hot-dip galvanizing meets the following requirements:

[0093] [Si] / [Al]=0.5%,

[0094] Wherein, [Si] is the mass fraction of Si in the plating solution, and [Al] is the mass fraction of Al in the plating solution.

[0095] The mass concentration of the inhibitor was 0.8%.

[0096] Example 3

[0097] Comparing Example 3 with Example 1, the difference between Example 3 and Example 1 is:

[0098] The real-time temperature of the heating section from the 1st to the 3rd zone in the annealing furnace is less than 600°C, and the air-fuel ratio is controlled to be 1.0:0.90;

[0099] When the real-time temperature of the heating section from the 3rd to the 8th zone in the annealing furnace is ≥600°C, the air-fuel ratio is controlled to be 0.86:1.0.

[0100] Measured by volume fraction, the components of the nitrogen-hydrogen mixture include: hydrogen: 7% and nitrogen: 93%.

[0101] The dew point temperature in the furnace nose area is -36°C.

[0102] The plating solution used in hot-dip galvanizing meets the following requirements:

[0103] [Si] / [Al]=1.2%,

[0104] Wherein, [Si] is the mass fraction of Si in the plating solution, and [Al] is the mass fraction of Al in the plating solution.

[0105] The mass concentration of the inhibitor was 1.5%.

[0106] Comparative Example 1

[0107] Comparative Example 1 and Example 1 are compared. The difference between Comparative Example 1 and Example 1 is:

[0108] The real-time temperature of the heating section from the 1st to the 3rd zone in the annealing furnace is less than 600°C, and the air-fuel ratio is controlled to be 0.96:1.0;

[0109] When the real-time temperature of the heating section from the 3rd to the 8th zone in the annealing furnace is ≥600°C, the air-fuel ratio is controlled to be 0.93:1.0.

[0110] Measured by volume fraction, the components of the nitrogen-hydrogen mixed gas include: hydrogen: 4% and nitrogen: 96%.

[0111] The dew point temperature in the furnace nose area is -25°C.

[0112] The plating solution used in hot-dip galvanizing meets the following requirements:

[0113] [Si] / [Al]=0.04%,

[0114] Wherein, [Si] is the mass fraction of Si in the plating solution, and [Al] is the mass fraction of Al in the plating solution.

[0115] The hot rolling coiling temperature is 570°C.

[0116] The pickling includes pickling at a preset pickling speed, and the preset pickling speed is 140 m / min.

[0117] The reagents used in the pickling process include an inhibitor, and the mass concentration of the inhibitor is 2.8%.

[0118] Related experiments and effect data:

[0119] The zinc-aluminum-magnesium coatings obtained in each embodiment and comparative example were collected and then observed by scanning electron microscope. The results showed that:

[0120] like Figure 2 As shown, the surface of the zinc-aluminum-magnesium coating of Example 1 has no plating leakage defects, and the surface quality of the zinc-aluminum-magnesium coating is good. At the same time, the surfaces of the zinc-aluminum-magnesium coatings of Examples 2 and 3 have no plating leakage defects, and the surface quality of the zinc-aluminum-magnesium coatings is good.

[0121] like Figure 3 As shown, the zinc-aluminum-magnesium coating obtained in Comparative Example 1 has a missing plating defect, and the surface quality of the zinc-aluminum-magnesium coating is poor.

[0122] In addition, the zinc-aluminum-magnesium coating product of Example 1 was subjected to positron emission tomography, and the results were as follows: Figure 4 As shown, Figure 4 This indicates that a relatively thin, complete and continuous inhibition layer is formed between the zinc-aluminum-magnesium coating and the steel substrate in the zinc-aluminum-magnesium coating product.

[0123] In summary, the preparation method of a zinc-aluminum-magnesium coating product provided in an embodiment of the present application can fully remove the residual iron oxide scale on the surface of the steel substrate by hot rolling and pickling, and then refine annealing includes a heating section, a soaking section and a cooling section, and then the heating section is controlled to heat according to the real-time temperature of different heating sections by adjusting the air-fuel ratio, and the atmosphere of the cooling section is controlled to be a nitrogen-hydrogen mixed gas and the dew point temperature of the furnace nose area in the cooling section. This can avoid the residual iron oxide scale on the surface of the steel substrate and the selective oxidation of alloy elements in the annealing stage, so that a zinc-aluminum-magnesium coating product without surface plating defects can be finally obtained.

[0124] At the same time, the embodiment of the present application provides a zinc-aluminum-magnesium coating, the surface of which has no plating leakage defects, and in addition, the surface quality of the zinc-aluminum-magnesium coating is good.

[0125] 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.

[0126] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". 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 the associated objects, indicating that there may 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, 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 singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0127] 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 zinc-aluminum-magnesium coating product, characterized in that: The method comprises: Hot rolling and coiling the slab to obtain strip steel; Pickling the steel strip to obtain a steel matrix; Preheating the surface of the steel substrate, and then annealing the preheated steel substrate to obtain a pretreated steel substrate; Hot-dip galvanizing the pretreated steel substrate to obtain a zinc-aluminum-magnesium coating product; Wherein, the annealing includes annealing in the form of a heating section, a soaking section and a cooling section, and the heating section includes heating in the form of adjusting the air-fuel ratio according to the real-time temperature of different heating sections; The cooling section includes cooling under the atmosphere of nitrogen and hydrogen mixture; The cooling section also includes a furnace nose area, and the dew point temperature of the furnace nose area is ≤-30°C.

2. The method according to claim 1, characterized in that When the real-time temperature of the heating section is less than 600° C., the air-fuel ratio is greater than 1; When the real-time temperature of the heating section is ≥600° C., the air-fuel ratio is <1.

3. The method according to claim 2, characterized in that When the real-time temperature of the heating section is less than 600° C., the air-fuel ratio is 1.0:0.95 to 1.0:0.90; And / or, when the real-time temperature of the heating section is ≥600° C., the air-fuel ratio is 0.85:1.0 to 0.92:1.

0.

4. The method according to claim 1, characterized in that: Calculated by volume fraction, the components of the nitrogen-hydrogen mixed gas include: hydrogen: 5% to 8% and nitrogen: 92% to 95%.

5. The method according to claim 1, characterized in that The dew point temperature of the furnace nose area is -40°C to -30°C.

6. The method according to claim 1, characterized in that The plating solution used in the hot-dip galvanizing satisfies: [Si] / [Al]=0.5%~1.5%, Wherein, [Si] is the mass fraction of Si in the plating solution, and [Al] is the mass fraction of Al in the plating solution.

7. The method according to claim 1, characterized in that The temperature of the hot rolling coiling is ≤560°C.

8. The method according to claim 1, characterized in that The pickling includes pickling at a preset pickling speed, wherein the preset pickling speed is ≤120 m / min.

9. The method according to claim 1, characterized in that: The reagent used in the pickling includes an inhibitor, and the mass concentration of the inhibitor is 0.8% to 1.5%.

10. A zinc-aluminum-magnesium coating product, characterized in that: The zinc-aluminum-magnesium coating product is prepared by the method described in any one of claims 1-9.

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