A method for preparing a high-aluminum-zinc-aluminum-magnesium coating and the high-aluminum-zinc-aluminum-magnesium coating.

Abstract

This application relates to the field of coating technology, and more particularly to a method for preparing a high-aluminum-zinc-aluminum-magnesium coating and the high-aluminum-zinc-aluminum-magnesium coating itself. The method includes: obtaining optimal Mg content data and optimal Ti content data based on optimal Mg2Si phase content data and optimal TiAl3 phase content data; determining the optimal Mg addition amount and optimal Ti addition amount in the raw materials; calculating and determining the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature based on the optimal Mg content data and optimal Ti content data using kinetic calculation methods and microscopic analysis methods; preparing the high-aluminum-zinc-aluminum-magnesium coating according to the optimal Mg addition amount, optimal Ti addition amount, optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature, thereby obtaining a high-aluminum-zinc-aluminum-magnesium coating product with high surface quality. This method can reduce the consumption of smelting raw materials and avoid waste, and can also reduce smelting costs and energy consumption.

Description

Technical Field

[0001] This application relates to the field of coating technology, and more particularly to a method for preparing a high-aluminum-zinc-aluminum-magnesium coating and the high-aluminum-zinc-aluminum-magnesium coating. Background Technology

[0002] Coating is an important means of corrosion protection for steel plates. Among them, high-aluminum zinc-aluminum-magnesium coating is a product with excellent corrosion resistance. Because it combines the cathodic protection of pure zinc coatings with the corrosion resistance and high-temperature oxidation resistance of aluminum coatings, it is widely used in construction, home appliances, automobiles, photovoltaics, and other fields. Current research has found that adding an appropriate amount of Mg to high-aluminum zinc-aluminum-magnesium coatings can refine the solidification structure of the coating and further improve its corrosion resistance. In the preparation of high-aluminum zinc-aluminum-magnesium coatings, appropriately increasing the cooling rate helps to refine the primary aluminum-rich phase structure, thereby improving the anode-cathode area ratio and avoiding localized corrosion caused by the "large cathode, small anode" phenomenon. Furthermore, adding trace amounts of Ti to the coating allows the TiAl3 phase precipitated during solidification to increase the nucleation rate of the primary Al phase through heterogeneous nucleation, resulting in a finer solidification structure in the high-aluminum zinc-aluminum-magnesium coating.

[0003] Because this product contains a large amount of Al, suspended slag is easily generated during the hot-dip galvanizing process in the preparation of high-aluminum zinc-aluminum-magnesium coatings. This slag accumulates on the coating surface, which can accelerate localized corrosion and affect the surface quality of the coating. The direct addition of Mg or Ti can affect the Al composition and thus the surface quality of the coating. Currently, the amount of Mg or Ti added to high-aluminum zinc-aluminum-magnesium coatings needs to be determined through a large number of actual smelting experiments. The adjustment of the zinc liquid composition and process parameters in the corresponding production line also needs to be determined based on the actual smelting conditions. This means that improving the quality of existing high-aluminum zinc-aluminum-magnesium coatings will not only waste a lot of smelting raw materials, but also increase the energy consumption and cost of smelting. Summary of the Invention

[0004] This application provides a method for preparing a high-aluminum-zinc-aluminum-magnesium coating and the high-aluminum-zinc-aluminum-magnesium coating itself, in order to solve the technical problems of waste of smelting raw materials and increased smelting costs and energy consumption in the prior art for improving the quality of high-aluminum-zinc-aluminum-magnesium coatings.

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

[0006] Based on the optimal content data of Mg2Si phase and TiAl3 phase in high-aluminum zinc-aluminum-magnesium coating, the optimal Mg content data and optimal Ti content data in high-aluminum zinc-aluminum-magnesium coating are obtained.

[0007] Thermodynamic calculations were performed based on the Mg content data and the Ti content data to determine the optimal Mg and Ti addition amounts in the raw materials for the high-aluminum zinc-aluminum-magnesium coating.

[0008] Based on the optimal Mg content data and the optimal Ti content data, and using kinetic calculation methods and microscopic analysis methods, the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature during the preparation stage of high-aluminum zinc-aluminum-magnesium coating products were determined.

[0009] Based on the optimal Mg and Ti addition amounts, and combined with the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature, a high-aluminum-zinc-aluminum-magnesium coating is prepared to obtain a high-aluminum-zinc-aluminum-magnesium coating product with high surface quality.

[0010] Optionally, obtaining the optimal Mg content data and optimal Ti content data in the high-aluminum-zinc-aluminum-magnesium coating based on the optimal content data of the Mg2Si phase and the optimal content data of the TiAl3 phase in the high-aluminum-zinc-aluminum-magnesium coating includes the following steps:

[0011] To obtain the optimal content data of Mg2Si phase and TiAl3 phase in high-aluminum zinc-aluminum-magnesium coatings;

[0012] Based on the optimal content data of the Mg2Si phase and the optimal content data of the TiAl3 phase, and combined with the temperature and solid fraction property diagram of the high-aluminum zinc-aluminum-magnesium coating, the Mg content data and Ti content data in the high-aluminum zinc-aluminum-magnesium coating were determined respectively.

[0013] Optionally, the step of determining the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature during the preparation stage of the high-aluminum zinc-aluminum-magnesium coating product based on the optimal Mg content data and the optimal Ti content data, using kinetic calculation methods and microscopic analysis methods, includes the following steps:

[0014] Based on the optimal Mg content data and the optimal Ti content data, and using a kinetic calculation method, the secondary dendrite arm spacing and solid fraction information of the high-aluminum zinc-aluminum-magnesium coating were obtained.

[0015] Based on the secondary dendrite arm spacing and the solid fraction information, and using microscopic analysis methods, the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature were determined during the preparation stage of the high-aluminum zinc-aluminum-magnesium coating product.

[0016] Optionally, the microscopic analysis method includes at least one of the following:

[0017] Scanning electron microscopy, electron probe microanalysis, and X-ray diffraction analysis were performed.

[0018] Optionally, the optimal Mg content data is 0.5% to 5%; and / or,

[0019] The optimal Ti content is 0-5%.

[0020] Optionally, the optimal cooling rate is 15°C / s to 25°C / s; and / or,

[0021] The optimal hot-dip plating time is 3s to 10s; and / or,

[0022] The optimal temperature for the strip to enter the pot is 565℃~585℃.

[0023] Optionally, the preparation of the high-aluminum-zinc-aluminum-magnesium coating includes the following steps:

[0024] The aluminum source and zinc source are heated until they melt to obtain a molten alloy liquid;

[0025] The molten alloy liquid is heated, and then an intermediate alloy is added to the molten alloy liquid to obtain a hot-dip galvanizing solution;

[0026] A hot-dip galvanizing coating agent is added to the surface of the hot-dip galvanizing solution and kept at a constant temperature. Then, the hot-dip galvanizing solution is cooled to a preset temperature to obtain a high-aluminum zinc-aluminum-magnesium plating solution.

[0027] The high-alumina-zinc-alumina-magnesium plating solution is used to hot-dip galvanize the surface of a steel substrate, followed by rapid cooling to obtain a high-alumina-zinc-alumina-magnesium plating layer.

[0028] The rapid cooling includes rapid cooling using the optimal cooling rate;

[0029] The hot-dip galvanizing includes hot-dip galvanizing using the optimal hot-dip galvanizing time and the optimal strip entry temperature.

[0030] The intermediate alloys include zinc-magnesium alloys, aluminum-silicon alloys, and aluminum-titanium alloys.

[0031] Optionally, the final heating temperature is 590℃~605℃; and / or,

[0032] The endpoint temperature of the heating is 620℃~660℃; and / or,

[0033] The heat preservation time is 1 hour to 2 hours; and / or,

[0034] The hot-dip galvanizing temperature is 590℃~605℃.

[0035] Optionally, the chemical composition of the hot-dip coating agent, by mass fraction, includes:

[0036] KF: 3%–12%, LiCl: 10%–20%, KCl: 25%–35%, ZnCl2: 3%–8%, and NaAlF6: 30%–40%.

[0037] Secondly, this application provides a high-aluminum-zinc-aluminum-magnesium coating, which is prepared by the method described in the first aspect; the chemical composition of the high-aluminum-zinc-aluminum-magnesium coating, by mass fraction, includes:

[0038] Mg: 0.5%–5%, Al: 30%–70%, Si: 0.03%–5%, Ti: 0.05%–0.5%, with the remainder being Zn and unavoidable impurities.

[0039] The technical solutions provided in this application have the following advantages compared with the prior art:

[0040] This application provides a method for preparing a high-aluminum zinc-aluminum-magnesium (GAMC) coating. Since the TiAl3 phase in the GAMC is a primary trace compound that precipitates first near the steel substrate during solidification, it provides heterogeneous nucleation sites for the precipitation of the aluminum-rich phase, thereby refining the coating structure. The precipitation of the Mg2Si phase can prevent predictable intergranular corrosion in the GAMC, improving its corrosion resistance. Therefore, the optimal content data of these two phases in existing GAMC coatings are analyzed, and the optimal Mg and Ti content data for the GAMC are derived from these optimal content data. Furthermore, the optimal Mg content in the raw materials of the GAMC is directly derived from the optimal Mg and Ti content data. By combining the optimal amounts of Mg and Ti, along with the optimal Mg and Ti content data, and using kinetic calculations and microscopic analysis, the optimal cooling rate, hot-dip galvanizing time, and strip entry temperature can be directly calculated. This method allows for the determination of optimal Mg and Ti amounts, as well as hot-dip galvanizing process parameters, through calculation alone. This reduces the consumption of smelting raw materials and avoids waste. Furthermore, the optimal hot-dip galvanizing process parameters can lower smelting costs and energy consumption. Attached Figure Description

[0041] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic flowchart of a method for preparing a high-alumina-zinc-alumina-magnesium coating, provided in an embodiment of this application.

[0044] Figure 2 This application provides a detailed flowchart illustrating a method for preparing a high-aluminum-zinc-aluminum-magnesium coating.

[0045] Figure 3 This is a schematic diagram of the preparation method of the high-aluminum zinc-aluminum-magnesium coating provided in the embodiments of this application;

[0046] Figure 4 The figure shows the thermodynamic calculation results of a conventional high-aluminum zinc-aluminum-magnesium coating provided in Comparative Example 1 of this application, wherein... Figure 4 (b) is Figure 4 (a) Enlarged view;

[0047] Figure 5 The figure shows the thermodynamic calculation results of the high-aluminum zinc-aluminum-magnesium coating provided in Example 1 of this application, wherein... Figure 5 (b) is Figure 5 (a) Enlarged view;

[0048] Figure 6 The figure shows the thermodynamic calculation results of the high-aluminum zinc-aluminum-magnesium coating provided in Embodiment 2 of this application, wherein... Figure 6 (b) is Figure 6 (a) Enlarged view;

[0049] Figure 7 Solidification curves of conventional high-aluminum zinc-aluminum-magnesium coatings provided in Comparative Example 1 of this application at cooling rates of 10℃ / s and 20℃ / s;

[0050] Figure 8 Solidification curves of the high-aluminum zinc-aluminum-magnesium coating composition provided in Example 2 of this application at cooling rates of 10°C / s and 20°C / s;

[0051] Figure 9 This diagram shows the calculated spacing of the secondary dendrite arms of the high-alumina zinc-alumina magnesium coatings in Comparative Example 1 and Example 2 of this application under different cooling rates. Figure 9 (a) is a diagram showing the calculated spacing of the secondary dendrite arms of the aluminum-rich phase at a cooling rate of 10°C / s for the high-aluminum zinc-aluminum-magnesium coatings of Comparative Example 1 and Example 2. Figure 9 (b) is a diagram showing the calculated spacing of the secondary dendrite arms of the aluminum-rich phase at a cooling rate of 20°C / s for the high-aluminum zinc-aluminum-magnesium coatings of Comparative Example 1 and Example 2.

[0052] Figure 10 The graph shows the kinetic calculation results of the composition of a conventional high-aluminum zinc-aluminum-magnesium coating provided for Comparative Example 1 of this application under a cooling condition of 10℃ / s. Figure 10 (b) is Figure 10 (a) Enlarged view;

[0053] Figure 11 The figure shows the kinetic calculation results of the composition of a conventional high-aluminum zinc-aluminum-magnesium coating provided in Comparative Example 1 of this application under a cooling condition of 20℃ / s. Figure 11 (b) is Figure 11 (a) Enlarged view;

[0054] Figure 12 This is a kinetic calculation result diagram of the high-aluminum zinc-aluminum-magnesium coating composition provided in Example 2 of this application under a cooling condition of 10℃ / s, wherein... Figure 11 (b) is Figure 11 (a) Enlarged view;

[0055] Figure 13 This is a kinetic calculation result diagram of the high-aluminum zinc-aluminum-magnesium coating composition provided in Example 2 of this application under a cooling condition of 20℃ / s, wherein... Figure 11 (b) is Figure 11 (a) Enlarged view;

[0056] Figure 14 The SEM microstructure of the conventional high-aluminum zinc-aluminum-magnesium coating provided for Comparative Example 1 of this application is shown in the image. Figure 14 (a) is a frontal SEM micrograph of a traditional high-aluminum zinc-aluminum-magnesium coating. Figure 14 (b) is a cross-sectional SEM microstructure of a traditional high-aluminum zinc-aluminum-magnesium coating;

[0057] Figure 15 This is a SEM microstructure image of the high-aluminum-zinc-aluminum-magnesium coating provided in Example 1 of this application, wherein... Figure 15 (a) is a frontal SEM micrograph of the high-aluminum zinc-aluminum-magnesium coating provided in Example 1. Figure 15 (b) is a cross-sectional SEM microstructure of the high-aluminum zinc-aluminum-magnesium coating provided in Example 1;

[0058] Figure 16 This is a SEM microstructure image of the high-aluminum zinc-aluminum-magnesium coating provided in Example 2 of this application, wherein... Figure 16 (a) is a frontal SEM micrograph of the high-aluminum zinc-aluminum-magnesium coating provided in Example 1. Figure 16 (b) is a cross-sectional SEM microstructure of the high-aluminum zinc-aluminum-magnesium coating provided in Example 1;

[0059] Figure 17 A schematic diagram illustrating the use of the ultragravity slag removal device provided in the embodiments of this application;

[0060] Figure 18 Polarization curves of the high-aluminum zinc-aluminum-magnesium coatings provided in Comparative Example 1, Example 1, and Example 2 of this application;

[0061] Figure 19 The AC impedance spectra of the high-aluminum zinc-aluminum-magnesium coatings provided in Comparative Examples 1, 1, and 2 of this application are shown. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0063] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0064] Figure 1 An exemplary schematic diagram of a method for preparing a high-aluminum zinc-aluminum-magnesium coating according to an embodiment of this application is shown;

[0065] like Figure 1 As shown in the embodiments of this application, a method for preparing a high-aluminum zinc-aluminum-magnesium coating is provided, the method comprising:

[0066] S1. Based on the optimal content data of Mg2Si phase and TiAl3 phase in high-aluminum zinc-aluminum-magnesium coating, the optimal Mg content data and optimal Ti content data in high-aluminum zinc-aluminum-magnesium coating are obtained.

[0067] S2. Based on the Mg content data and the Ti content data, perform thermodynamic calculations to determine the optimal Mg addition amount and the optimal Ti addition amount in the raw materials of the high-aluminum zinc-aluminum-magnesium coating;

[0068] S3. Based on the optimal Mg content data and the optimal Ti content data, and using kinetic calculation methods and microscopic analysis methods, determine the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature during the preparation stage of the high-aluminum zinc-aluminum-magnesium coating product;

[0069] S4. Based on the optimal Mg addition amount and the optimal Ti addition amount, and combined with the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature, a high-aluminum-zinc-aluminum-magnesium coating is prepared to obtain a high-aluminum-zinc-aluminum-magnesium coating product with high surface quality.

[0070] Figure 2 An exemplary schematic diagram illustrates a detailed process flow diagram of a method for preparing a high-aluminum zinc-aluminum-magnesium coating according to an embodiment of this application;

[0071] like Figure 2 As shown, in some optional embodiments, obtaining the optimal Mg content data and optimal Ti content data in the high-aluminum zinc-aluminum-magnesium coating based on the optimal content data of the Mg2Si phase and the optimal content data of the TiAl3 phase in the high-aluminum zinc-aluminum-magnesium coating includes the following steps:

[0072] S101. Obtain the optimal content data of Mg2Si phase and TiAl3 phase in high-aluminum zinc-aluminum-magnesium coating;

[0073] S102. Based on the optimal content data of the Mg2Si phase and the optimal content data of the TiAl3 phase, and combined with the temperature and solid fraction property diagram of the high-aluminum zinc-aluminum-magnesium coating, determine the Mg content data and Ti content data in the high-aluminum zinc-aluminum-magnesium coating respectively.

[0074] In this embodiment, the TiAl3 phase in the high-aluminum zinc-aluminum-magnesium coating is a primary trace compound that precipitates first near the steel substrate during solidification, providing heterogeneous nucleation sites for the precipitation of the aluminum-rich phase, thereby refining the coating structure. The precipitation of the Mg2Si phase can prevent predictable intergranular corrosion in the high-aluminum zinc-aluminum-magnesium coating and improve the corrosion resistance of the coating. Therefore, by analyzing the content data of these two phases and combining the temperature and solid fraction property diagram of the coating, focusing on the mass fraction of the Mg2Si and TiAl3 phases in the property diagram, the Mg content and Ti content data in the high-aluminum zinc-aluminum-magnesium coating can be directly determined.

[0075] It should be noted that this temperature-solid fraction property diagram was obtained by first calculating the phase fraction in the high-aluminum zinc-aluminum-magnesium coating using thermodynamic calculation methods, and then combining this with temperature changes. The specific steps are as follows:

[0076] (1) Taking the final required aluminum-zinc-aluminum-magnesium coating composition as the design target, relevant technical data were consulted or experiments were designed to determine that the precipitation temperature of the Mg2Si phase required to make the high-aluminum-zinc-aluminum-magnesium coating product have excellent corrosion resistance and surface quality is 480℃~490℃, and the precipitation content is about 1wt%~2wt%; and the zinc pot temperature for high-aluminum-zinc-aluminum-magnesium coating is 590℃~605℃. Therefore, the precipitation temperature of the TiAl3 phase should not be higher than the above temperature range of 590℃~605℃, otherwise the phase will be distributed in the zinc pot in the form of bottom slag, affecting actual production; at the same time, referring to the TiAl3 phase content used in the existing technology, the TiAl3 phase content should not exceed 500ppm, otherwise bottom slag will easily form, which will have an adverse effect on actual production.

[0077] (2) Based on the target precipitation temperature and target precipitation composition of each phase determined in (1), thermodynamic calculations were performed using Pandat software developed by CompuThermLLC Corporation of the United States and a zinc-based database, based on the principle of minimum Gibbs free energy for each phase in (1). Given the initial values ​​of the required Mg and Ti contents, the results were fitted with the target precipitation temperature and target precipitation composition of the Mg2Si and TiAl3 phases. After multiple trials, the optimal Mg and Ti contents required for the high-aluminum zinc-aluminum-magnesium coating were obtained.

[0078] In some optional embodiments, the step of determining the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature during the preparation stage of the high-aluminum zinc-aluminum-magnesium coating product based on the optimal Mg content data and the optimal Ti content data, using kinetic calculation methods and microscopic analysis methods, includes the following steps:

[0079] S301. Based on the optimal Mg content data and the optimal Ti content data, and using a kinetic calculation method, the secondary dendrite arm spacing and solid fraction information of the high-aluminum zinc-aluminum-magnesium coating are obtained;

[0080] S302. Based on the secondary dendrite arm spacing and the solid fraction information, and using microscopic analysis methods, determine the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature during the preparation stage of the high-aluminum zinc-aluminum-magnesium coating product.

[0081] In this embodiment, based on the clearly defined optimal Mg content and optimal Ti content data, a kinetic calculation method is used to explore the microstructure characteristics, solidification curves, and secondary dendrite arm evolution of the high-aluminum-zinc-aluminum-magnesium coating. This clarifies the influence of different temperature changes on the microstructure of the high-aluminum-zinc-aluminum-magnesium coating, facilitating the optimization of the coating's microstructure and thereby improving the corrosion resistance of the coating product. Furthermore, through microscopic analysis, the cooling rate, hot-dip immersion time, and strip entry temperature can be further clarified, thus facilitating the subsequent preparation of high-aluminum-zinc-aluminum-magnesium coating products with high surface quality using these process parameters.

[0082] Based on the optimal Mg content data and the optimal Ti content data, and using kinetic calculation methods and microscopic analysis methods, the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature for the high-aluminum zinc-aluminum-magnesium coating product preparation stage were determined. The specific steps are as follows:

[0083] (1) The spacing of secondary dendrite arms of a large number of high-alumina zinc-alumina magnesium samples produced by the existing production line was experimentally measured, and the value of the spacing of secondary dendrite arms was found to be between 20μm and 60μm.

[0084] (2) Based on the data of secondary dendrite arm spacing, the Pandat software developed by CompuTherm LLC and a zinc-based database were used to set the parameters of initial solidification temperature, final solidification temperature, and cooling time in the software interface. The initial solidification temperature and final solidification temperature are related to the coating composition and are constant values ​​when the chemical composition of the high-aluminum zinc-aluminum-magnesium coating product is constant. According to the calculation results of Pandat software, the larger the secondary dendrite arm spacing, the longer the corresponding cooling time, that is, the smaller the cooling rate.

[0085] (3) According to existing technology, the spacing of secondary dendrite arms that gives high-aluminum zinc-aluminum-magnesium alloys excellent corrosion resistance and high surface quality is generally 20μm to 30μm. Based on multiple kinetic calculations, the optimal cooling rate is found to be 15℃ / s to 25℃ / s. On this basis, combined with the specific production conditions of the existing production line, the hot-dip galvanizing time and the temperature of the strip entering the pot are determined.

[0086] In some optional embodiments, the microscopic analysis method includes at least one of the following:

[0087] Scanning electron microscopy, electron probe microanalysis, and X-ray diffraction analysis were performed.

[0088] In the embodiments of this application, the specific composition of the microscopic analysis method is refined, which can analyze in detail the relevant solid solution phases that affect the surface quality of the high aluminum zinc aluminum magnesium coating, such as the Fe-Al scum phase. Based on these relevant solid solution phases, the control of the solid solution phases that affect the surface quality during temperature changes and raw material control stages can be examined, thereby obtaining a high aluminum zinc aluminum magnesium coating with the best surface quality and corrosion resistance.

[0089] In some alternative embodiments, the optimal Mg content is 0.5% to 5%; and / or,

[0090] The optimal Ti content is 0-5%.

[0091] In some alternative embodiments, the optimal cooling rate is 15°C / s to 25°C / s; and / or,

[0092] The optimal hot-dip plating time is 3s to 10s; and / or,

[0093] The optimal temperature for the strip to enter the pot is 565℃~585℃.

[0094] In this embodiment, by refining the specific optimal Mg content data, optimal Ti content data, and parameters such as optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature, the preparation of high-aluminum-zinc-aluminum-magnesium coatings can be controlled through these parameters, thereby obtaining high-aluminum-zinc-aluminum-magnesium coatings with optimal surface quality and corrosion resistance.

[0095] The optimal hot-dip coating time ensures a complete reaction between iron and aluminum, preventing incomplete reaction and the formation of slag phase. This results in a pure high-aluminum, zinc-aluminum-magnesium (Mg) coating product in subsequent preparation stages. The optimal Mg content can be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 4.5%, or 5.0%.

[0096] The optimal Ti content can be 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 4.5%, or 5.0%.

[0097] The optimal cooling rate can be 15℃ / s, 20℃ / s, or 25℃ / s.

[0098] The optimal hot-dip galvanizing time can be 3s, 4s, 5s, 6s, 7s, 8s, 9s, or 10s.

[0099] It should be noted that the optimal cooling rate is controlled at 15℃ / s to 25℃ / s. Taking a 10μm thick coating product as the research object, the coating microstructure can be optimized by cooling rate within this range. For example, the size of the primary Al-rich phase can be reduced to change the anode-cathode ratio, thereby avoiding the "large cathode, small anode" corrosion phenomenon in high-aluminum-zinc-aluminum-magnesium products, thus improving the corrosion resistance of the coating product and obtaining a high-aluminum-zinc-aluminum-magnesium coating with the best surface quality and corrosion resistance.

[0100] It should be noted that the optimal hot-dip plating time is controlled to be 3 to 10 seconds, which is 2 to 3 seconds longer than the existing hot-dip plating time, ensuring... The inhibition layer formation reaction proceeds fully, preventing the Fe2Al5 phase from being distributed in the coating as slag and causing localized corrosion.

[0101] It should be noted that controlling the optimal strip entry temperature to the pot is 565℃~585℃, which is 5℃~10℃ lower than the existing strip entry temperature, can avoid excessive Fe diffusion.

[0102] It should be noted that, in order to further avoid interference from slag phases generated during the hot-dip galvanizing process, a gravity slag removal device can be used to remove the slag phases generated during the hot-dip galvanizing process. The specific structure of the gravity slag removal device for removing high-alumina, zinc, aluminum, and magnesium slag is as follows: Figure 17As shown, this gravity slag removal device mainly removes slag from the zinc pot using the principle of centrifugal force. It consists of two parts: a reactor and a mobile hypergravity device. The reactor comprises a slag collection bucket, a slag collection bucket base, a centrifugal rotor, and a disturbance prevention bucket. This reactor is mainly placed inside the zinc pot for operation. The mobile hypergravity device consists of a speed controller, connecting rods, and other components, used to control the position and speed of the reactor within the zinc pot. In actual operation, the reactor of the gravity slag removal device is immersed in the zinc pot and adjusted to a suitable position. Then, the speed controller is used to adjust the speed of the centrifugal rotor at the required frequency to encourage the zinc slag to be drawn into the slag collection bucket. After the operation is completed, the reactor is raised out of the zinc pot, and finally, the zinc slag in the slag collection bucket is discharged, completing one operation cycle.

[0103] Figure 3 An exemplary schematic diagram of the preparation method of the high-aluminum zinc-aluminum-magnesium coating provided in the embodiments of this application is shown;

[0104] like Figure 3 As shown, in some optional embodiments, the preparation of the high-aluminum zinc-aluminum-magnesium coating includes the following steps:

[0105] S1. The aluminum source and zinc source are heated until they melt to obtain a molten alloy liquid;

[0106] S2. The molten alloy liquid is heated, and then an intermediate alloy is added to the molten alloy liquid to obtain a hot-dip galvanizing solution;

[0107] S3. Add a hot-dip galvanizing coating agent to the surface of the hot-dip galvanizing solution and keep it warm. Then cool the hot-dip galvanizing solution to a preset temperature to obtain a high-alumina zinc-aluminum-magnesium plating solution.

[0108] S4. The steel substrate surface is hot-dip coated with the high-aluminum-zinc-aluminum-magnesium plating solution and then rapidly cooled to obtain a high-aluminum-zinc-aluminum-magnesium plating layer.

[0109] The rapid cooling includes rapid cooling using the optimal cooling rate;

[0110] The hot-dip galvanizing includes hot-dip galvanizing using the optimal hot-dip galvanizing time and the optimal strip entry temperature.

[0111] The intermediate alloys include zinc-magnesium alloys, aluminum-silicon alloys, and aluminum-titanium alloys.

[0112] In this embodiment of the application, by refining the specific preparation process of the high-aluminum-zinc-aluminum-magnesium coating, the optimal Mg content data, optimal Ti content data, optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature can be combined to prepare a high-aluminum-zinc-aluminum-magnesium coating with the best surface quality and corrosion resistance.

[0113] It should be noted that the Mg content in the zinc-magnesium alloy can be 8% to 15%, the Si content in the aluminum-silicon alloy can be 6% to 15%, and the Ti content in the aluminum-titanium alloy can be 5% to 12%.

[0114] It should be noted that the aluminum source and zinc source can be aluminum blocks and zinc blocks, or they can be aluminum powder or zinc powder.

[0115] It should be noted that the steel substrate can be a DX51D substrate, and the size of the steel substrate can be obtained by cutting to a preset size; before use, the steel substrate can be pre-treated to remove surface impurities.

[0116] In some alternative embodiments, the endpoint temperature of the heating is 590°C to 605°C; and / or,

[0117] The endpoint temperature of the heating is 620℃~660℃; and / or,

[0118] The heat preservation time is 1 hour to 2 hours; and / or,

[0119] The hot-dip galvanizing temperature is 590℃~605℃.

[0120] In this embodiment of the application, controlling the specific endpoint temperature of heating and the specific endpoint temperature of temperature rise can ensure that the aluminum source, zinc source and intermediate alloy are fully melted, thereby obtaining a uniform hot-dip galvanizing solution.

[0121] Controlling the specific holding time allows the hot-dip galvanizing coating agent and the hot-dip zinc plating solution to mix thoroughly, thereby using the hot-dip galvanizing coating agent to inhibit the oxidation of Mg and Ti in the hot-dip zinc plating solution.

[0122] By controlling the specific temperature of hot-dip galvanizing, the high-aluminum-zinc-aluminum-magnesium plating solution can fully react with the steel substrate, thereby forming a high-aluminum-zinc-aluminum-magnesium plating layer with optimal surface quality and corrosion resistance on the steel substrate surface.

[0123] The final temperature of the heating can be 590℃, 595℃, 600℃ or 605℃.

[0124] The endpoint temperature for this heating can be 620℃, 625℃, 630℃, 635℃, 640℃, 645℃, 650℃, 655℃, or 660℃.

[0125] The insulation time can be 1 hour, 1.5 hours, or 2.0 hours.

[0126] The hot-dip galvanizing temperature can be 590℃, 595℃, 600℃ or 605℃.

[0127] In some alternative embodiments, the chemical composition of the hot-dip coating agent, by mass fraction, includes:

[0128] KF: 3%–12%, LiCl: 10%–20%, KCl: 25%–35%, ZnCl2: 3%–8%, and NaAlF6: 30%–40%.

[0129] In this embodiment of the application, the oxidation of Mg and Ti in the hot-dip zinc plating solution can be inhibited by the specific composition of the hot-dip plating coating agent.

[0130] It should be noted that when using this hot-dip galvanizing coating agent, it needs to be ground to a particle size of 1mm to 2mm and dried before being evenly added to the surface of the hot-dip galvanizing solution.

[0131] Based on a general inventive concept, embodiments of this application provide a high-aluminum-zinc-aluminum-magnesium coating, which is prepared by the method described above; the chemical composition of the high-aluminum-zinc-aluminum-magnesium coating, by mass fraction, includes:

[0132] Mg: 0.5%–5%, Al: 30%–70%, Si: 0.03%–5%, Ti: 0.005%–0.5%, with the remainder being Zn and unavoidable impurities.

[0133] The high-alumina zinc-alumina magnesium coating is obtained based on the above method. The specific steps of the method can be referred to the above embodiments. Since the high-alumina zinc-alumina magnesium coating adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0134] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0135] Example 1

[0136] Prepare aluminum blocks with a purity of 99.99 wt%, zinc blocks with a purity of 99.99 wt%, and intermediate alloys of Zn-11%Mg, Al-6%Si, and Al-10%Ti. Weigh and dry each intermediate alloy. After the aluminum and zinc blocks have completely melted, heat the mixture to 620℃~660℃, add the intermediate alloys, and press the intermediate alloys below the surface of the melt using a graphite cover until the alloys are completely melted.

[0137] A certain amount of hot-dip galvanizing agent is added to the surface of the plating bath. The main components, by mass fraction, include 3%–12% KF, 10%–20% LiCl, 25%–35% KCl, 3%–8% ZnCl2, and 30%–40% NaAlF6. The powder is ground to a particle size of 1 mm–2 mm, dried, and then uniformly added to the zinc bath surface to inhibit the oxidation of Mg and Ti in the plating bath. The zinc pot temperature is then maintained within the hot-dip galvanizing temperature range of 590℃–605℃ for 1–2 hours to obtain the plating bath with adjusted composition.

[0138] Next, the steel plate is pre-treated: the DX51D substrate to be plated is cut into 200mm×20mm samples and fixed on the lifting rod of the galvanizing simulator. Then, it is degreased with a 15% Na(OH)2 solution, followed by rust removal with a 10% HCl solution. Finally, an appropriate flux is selected for electroplating, followed by drying. This yields test samples that meet the requirements for hot-dip galvanizing.

[0139] Finally, a galvanizing simulation was conducted, including alloying annealing and hot-dip galvanizing simulations. Using DX51D steel plate as the substrate, the sample was heated from room temperature to an alloying diffusion annealing temperature of 530℃ to 560℃ at a heating rate of 100℃ / s to 150℃ / s. This annealing temperature was held for 30 to 50 seconds, followed by cooling at a rate of 10℃ / s to 40℃ / s. During the hot-dip galvanizing simulation, the distance and angle between the air knife and the steel plate were adjusted, the distance between the air knife and the liquid surface was controlled, and the furnace atmosphere was adjusted. When the resistance furnace and alloying furnace reached the predetermined temperatures, the steel plate after fluxing was installed on the steel plate clamping device of the equipment, and the pull rod was adjusted to immerse the steel plate in the plating solution. After immersion for 50 to 80 seconds, the steel plate was lifted at a set speed into the alloying furnace for the alloying process. Finally, the steel plate was removed from the alloying furnace, cooled, and then removed, completing the hot-dip galvanizing process. Post-plating treatment includes finishing and passivation to obtain DX51D+AZM coating products with added trace amounts of Ti and increased Mg content.

[0140] Example 2

[0141] Prepare aluminum blocks with a purity of 99.99 wt%, zinc blocks with a purity of 99.99 wt%, and Al-6%Si, Zn-11%Mg master alloys. Predict the alloy composition based on thermodynamic kinetic calculations. Weigh and dry all the alloys. First, place the aluminum and zinc blocks in a zinc pot of a galvanizing simulator. Then, slowly raise the temperature of the zinc pot to 590℃~605℃. The zinc blocks melt first, and their molten heat eventually melts the aluminum blocks in the molten zinc. Next, raise the temperature of the zinc pot to 620℃~660℃, add the Zn-11%Mg and Al-6%Si master alloys, and use a graphite shield to press the two master alloys below the molten surface until they are completely melted. Add a hot-dip galvanizing coating agent with the same composition as in Example 1 to the surface of the plating solution, and adjust the zinc pot temperature to obtain a plating solution with adjusted composition.

[0142] Using the same steel plate pretreatment, galvanizing simulation, and post-plating treatment as in Example 1, a DX51D+AZM coating product with increased Mg content was obtained.

[0143] Comparative Example 1

[0144] Comparative Example 1 and Example 1 will be compared. The difference between Comparative Example 1 and Example 1 is as follows:

[0145] Using a traditional high-aluminum-zinc-aluminum-magnesium coating, its chemical composition, by mass fraction, includes:

[0146] Mg: 0.3%–1.5%, Al: 40%–60%, Si: 0.5%–2%, with the remainder being Zn and unavoidable impurities.

[0147] Relevant experimental and effect data:

[0148] Thermodynamic calculations were performed on the traditional high-aluminum zinc-aluminum-magnesium coating of Comparative Example 1, and the results are as follows: Figure 4 As shown.

[0149] Thermodynamic calculations were performed on the high-aluminum zinc-aluminum-magnesium coatings obtained in Examples 1 and 2, and the results are as follows: Figure 5 and Figure 6 As shown.

[0150] Solidification curve experiments were conducted on the conventional high-alumina zinc-alumina-magnesium coating of Comparative Example 1 at cooling rates of 10℃ / s and 20℃ / s. The results are as follows: Figure 7 As shown.

[0151] Solidification curve experiments were conducted on the high-aluminum zinc-aluminum-magnesium coating obtained in Example 2 at cooling rates of 10℃ / s and 20℃ / s. The results are as follows: Figure 8 As shown.

[0152] The spacing of the secondary dendrite arms of the aluminum-rich phase precipitated in the high-alumina-zinc-alumina-magnesium coatings obtained in Example 2 and Comparative Example 1 was calculated, and the results are as follows: Figure 9 As shown.

[0153] Kinetic calculations were performed on the conventional high-aluminum zinc-aluminum-magnesium coating obtained in Comparative Example 1 under cooling conditions of 10℃ / s and 20℃ / s, respectively. The results are as follows: Figure 10 and Figure 11 As shown.

[0154] Kinetic calculations were performed on the high-aluminum-zinc-aluminum-magnesium coating obtained in Example 2 under cooling conditions of 10°C / s and 20°C / s, respectively. The results are as follows: Figure 12 and Figure 13 As shown.

[0155] The high-alumina-zinc-alumina-magnesium alloy samples obtained from Comparative Example 1, Example 1, and Example 2 were cut into... Thin sections were obtained. Scanning electron microscopy (SEM) and electrochemical experiments were used to conduct relevant experimental analyses on the samples.

[0156] Scanning electron microscopy results as follows Figure 14 , Figure 15 and Figure 16 As shown, Figure 14 The image shows the SEM microstructure of the aluminum-zinc-magnesium coating obtained in Comparative Example 1. Figure 15 Here is a SEM micrograph of the aluminum-zinc-magnesium coating obtained in Example 2. Figure 16 The images show the SEM microstructure of the high-aluminum-zinc-aluminum-magnesium coating obtained in Example 2. These results show that with the increase of Mg content in the coating, the content of the Mg2Si phase in the coating structure increases, and the enrichment of the Mg2Si phase on the coating surface is more pronounced. The primary aluminum phase in the coating is refined to a certain extent, especially on the coating surface. With the addition of trace amounts of Ti in the coating, the primary aluminum phase on the coating surface and in the cross-section gradually changes from dendritic growth to cellular growth, exhibiting a more significant refinement.

[0157] Electrochemical test results as follows Figure 18 and Figure 18 As shown. Figure 18 The results of polarization curve tests reflect the high-aluminum zinc-aluminum-magnesium coatings in Comparative Example 1, Example 1, and Example 2. As shown in the figure, the corrosion potential of Comparative Example 1 is -1.1573V, and the corrosion current is 2.41×10⁻⁶. -7 A / cm 2 The corrosion potential in Example 2 was -1.0495V, and the corrosion current was 1.74 × 10⁻⁶. -7 A / cm 2 The corrosion potential in Example 1 was -1.0813V, and the corrosion current was 8.85 × 10⁻⁶. -8 A / cm 2 .

[0158] Figure 19This reflects the AC impedance curves of the high-aluminum-zinc-aluminum-magnesium coatings in Comparative Example 1, Example 1, and Example 2; from Figure 19 As can be seen from the data, the impedance radius of the AC impedance of the high-aluminum-zinc-aluminum-magnesium coating provided in Example 1 shows an increasing trend compared to Example 2, indicating that the method provided in this application is beneficial to improving the corrosion resistance of the high-aluminum-zinc-aluminum-magnesium coating.

[0159] In summary, the method for preparing a high-aluminum zinc-aluminum-magnesium coating provided in this application optimizes the surface quality and corrosion resistance of the coating by predicting the optimal coating composition through thermodynamic kinetic calculations. Theoretical calculations provide a scientific prediction for adjusting the coating composition, reducing the production control costs associated with repeated experiments.

[0160] Meanwhile, this application provides a method for preparing a high-aluminum zinc-aluminum-magnesium coating. Compared with traditional high-aluminum zinc-aluminum-magnesium coatings, the quality of the zinc spangles on the surface and the corrosion resistance are improved to a certain extent after adding Mg or a composite addition of Mg and Ti. Furthermore, increasing the Mg content refines the microstructure of the Mg2Si phase within a certain range, thereby improving the surface morphology and corrosion resistance of the coating. The composite addition of trace amounts of Mg and Ti, forming the TiAl3 compound phase, increases the heterogeneous nucleation sites during the solidification process, similarly refining the solidification structure of the high-aluminum zinc-aluminum-magnesium coating and improving its corrosion resistance. This application also finds that the Ti content should not be too high, otherwise it easily forms bottom slag and increases the melting temperature of the plating solution, which adversely affects the production of the coating.

[0161] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0162] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means 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 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, and c can be a single or multiple.

[0163] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a high-aluminum zinc-aluminum-magnesium coating, characterized in that, The method includes: To obtain the optimal content data of Mg2Si phase and TiAl3 phase in high-aluminum zinc-aluminum-magnesium coatings; Based on the optimal content data of the Mg2Si phase and the optimal content data of the TiAl3 phase, and combined with the temperature and solid fraction property diagram of the high aluminum zinc aluminum magnesium coating, the optimal Mg content data and the optimal Ti content data in the high aluminum zinc aluminum magnesium coating were determined respectively. Thermodynamic calculations were performed based on the Mg content data and the Ti content data to determine the optimal Mg and Ti addition amounts in the raw materials for the high-aluminum zinc-aluminum-magnesium coating. Based on the optimal Mg content data and the optimal Ti content data, and using a kinetic calculation method, the secondary dendrite arm spacing and solid fraction information of the high-aluminum zinc-aluminum-magnesium coating were obtained. Based on the secondary dendrite arm spacing and the solid fraction information, and using microscopic analysis methods, the optimal cooling rate, optimal hot-dip galvanizing time, and optimal strip entry temperature were determined during the preparation stage of the high-aluminum zinc-aluminum-magnesium coating product. Based on the optimal Mg addition amount and the optimal Ti addition amount, and combined with the optimal cooling rate, optimal hot-dip galvanizing time and optimal strip entry temperature, a high-aluminum-zinc-aluminum-magnesium coating is prepared to obtain a high-aluminum-zinc-aluminum-magnesium coating product with high surface quality. The optimal Mg content is 0.5%–5%; the optimal Ti content is 0%–5%. The optimal cooling rate is 15℃ / s to 25℃ / s; the optimal hot-dip galvanizing time is 3s to 10s; and the optimal strip temperature before entering the galvanizing bath is 565℃ to 585℃. The chemical composition of the high-aluminum zinc-aluminum-magnesium coating, by mass fraction, includes: Mg: 0.5%–5%, Al: 30%–70%, Si: 0.03%–5%, Ti: 0.05%–0.5%, with the remainder being Zn and unavoidable impurities.

2. The method according to claim 1, characterized in that, The microscopic analysis method includes at least one of the following: Scanning electron microscopy, electron probe microanalysis, and X-ray diffraction analysis were performed.

3. The method according to claim 1, characterized in that, The preparation of the high-aluminum zinc-aluminum-magnesium coating includes the following steps: The aluminum and zinc sources are heated until they melt to obtain a molten alloy liquid; The molten alloy liquid is heated, and then an intermediate alloy is added to the molten alloy liquid to obtain a hot-dip galvanizing solution; A hot-dip galvanizing coating agent is added to the surface of the hot-dip galvanizing solution and kept at a constant temperature. Then, the hot-dip galvanizing solution is cooled to a preset temperature to obtain a high-aluminum zinc-aluminum-magnesium plating solution. The high-alumina-zinc-alumina-magnesium plating solution is used to hot-dip galvanize the surface of a steel substrate, followed by rapid cooling to obtain a high-alumina-zinc-alumina-magnesium plating layer. The rapid cooling includes rapid cooling using the optimal cooling rate; The hot-dip galvanizing includes hot-dip galvanizing using the optimal hot-dip galvanizing time and the optimal strip entry temperature. The intermediate alloys include zinc-magnesium alloys, aluminum-silicon alloys, and aluminum-titanium alloys.

4. The method according to claim 3, characterized in that, The final temperature of the heating is 590℃~605℃; and / or, The endpoint temperature of the heating is 620℃~660℃; and / or, The heat preservation time is 1 hour to 2 hours; and / or, The hot-dip galvanizing temperature is 590℃~605℃.

5. The method according to claim 3, characterized in that, The chemical composition of the hot-dip coating agent, by mass fraction, includes: KF: 3%–12%, LiCl: 10%–20%, KCl: 25%–35%, ZnCl2: 3%–8%, and NaAlF6: 30%–40%.

Images