A method for preparing a corrosion-resistant Zn11Al3Mg plating layer for pickling-free hydrogen reduction of high-strength steel plates

Abstract

The present application relates to the field of metal material surface treatment, in particular to a preparation method of a corrosion-resistant Zn11Al3Mg coating for acid-free pickling hydrogen reduction high-strength steel plate. First, after smelting, continuous casting and hot rolling, a hot-rolled high-strength steel plate is formed; second, the hot-rolled high-strength steel plate is degreased with alcohol and then placed in a heat treatment furnace which can be supplied with protective gas for hydrogen reduction; then, the hydrogen-reduced hot-rolled high-strength steel plate is soaked in a plating aid; finally, the hot-rolled high-strength steel plate soaked in the plating aid is immersed in a Zn11Al3Mg alloy plating solution for hot dipping. By adding Ru, Lu and Re elements to the high-strength steel, the grain is refined and the activity of the reduced iron layer is improved; by adding Ru, W, Nd, Eu and Yb elements to the Zn-11Al-3Mg alloy plating solution, the adhesion and corrosion resistance of the coating to the reduced iron layer are enhanced. The acid-free pickling hydrogen reduction process avoids environmental pollution and corrosion of the substrate caused by pickling.

Description

Technical Field

[0001] This invention relates to the field of surface treatment of metallic materials, specifically to a method for preparing a corrosion-resistant Zn11Al3Mg coating for high-strength steel plates that require no acid pickling and hydrogen reduction, which is suitable for long-life protection of advanced ultra-high-strength steel plates in harsh corrosive environments. Background Technology

[0002] In the field of advanced steel materials, the processing of advanced ultra-high strength steel plates and their coated plates is crucial for achieving lightweight and long service life. Traditional pickling processes for high-strength steel plate surfaces suffer from drawbacks such as difficult waste acid treatment, heavy environmental pollution, and susceptibility to hydrogen embrittlement. To overcome this bottleneck, pickling-free hydrogen reduction technology has emerged. It directly treats the steel plate surface through a reducing atmosphere, completely eliminating the pickling step, significantly improving environmental friendliness and avoiding the risk of hydrogen embrittlement, while simultaneously forming a uniquely structured reduced iron layer. However, this highly active and uniquely composed reduced iron layer places unprecedentedly high demands on the wettability, adhesion, and final corrosion resistance of the coating in subsequent hot-dip galvanizing processes. Conventional hot-dip pure zinc or traditional zinc-aluminum coatings on this substrate generally suffer from insufficient bonding strength and limited improvement in corrosion resistance, severely restricting the processing reliability and performance potential of advanced ultra-high strength steel plates and their coated plates based on hydrogen reduction technology (especially for applications in harsh corrosive environments). There is an urgent need to develop novel high-performance alloy coatings and preparation methods suitable for this pickling-free reduced iron layer substrate.

[0003] Currently, various hot-dip galvanizing technologies have been developed and applied both domestically and internationally. However, these technologies often perform poorly when applied to the hot-dip galvanizing of reduced iron layers on the surface of acid-free hydrogen-reduced high-strength steel, demonstrating the limitations of existing technologies. In traditional hot-dip galvanizing processes, while pickling can remove oxide scale from the surface of high-strength steel, it corrodes the substrate, reducing the material's strength and toughness. Furthermore, the acidic wastewater generated during pickling causes serious environmental pollution and increases treatment costs.

[0004] Regarding existing fluxes and alloy plating solutions, traditional fluxes are mostly based on zinc chloride and ammonium chloride, which are difficult to effectively improve the adhesion between the coating and high-strength steel. Although existing Zn-Al-Mg alloy plating solutions have certain corrosion resistance, the adhesion between the coating and the reduced iron layer still needs to be improved in applications on acid-free hydrogen-reduced high-strength steel surfaces. Currently, there is limited research on the adhesion performance of zinc plating layers on acid-free hydrogen-reduced high-strength steel surfaces. Existing patents mostly focus on traditional pickling processes or zinc plating technologies for ordinary high-strength steel, lacking in-depth exploration of the adhesion performance of zinc plating layers on reduced iron surfaces.

[0005] Patent CN103726003A proposes a method for acid-free hot-dip galvanizing of hot-rolled strip steel based on the reduction of iron oxide scale. Although it uses hydrogen reduction to achieve acid-free hot-dip galvanizing, the steel substrate composition only contains conventional elements such as C, Si, and Mn, and the plating solution only contains Zn and a small amount of Al. This fails to solve the interfacial bonding problem between the reduced iron layer and the coating, resulting in limited improvement in the coating's corrosion resistance. Patent CN105648273A proposes a zinc-aluminum-magnesium coated steel sheet with added rare earth elements. Rare earth elements (cerium, lanthanum, etc.) and tungsten and titanium are added to the zinc-aluminum-magnesium coating, but the substrate composition is not designed specifically for the reduced iron layer after acid-free hydrogen reduction, and the special treatment of the substrate surface by the hydrogen reduction process is not addressed. Therefore, the problem of insufficient coating adhesion still exists. Patent CN120443052A discloses a steel plate substrate, a pre-coated steel plate and its preparation method, a hot-formed component and its preparation method, and automotive structural parts. It improves the strength and hydrogen embrittlement resistance of the hot-formed components by adding rare earth elements (Ce, La, etc.), Ti, and Nb. However, its coating is aluminum-silicon based, which cannot solve the interfacial bonding and corrosion resistance issues between the reduced iron layer and the zinc-aluminum-magnesium coating. Patent CN105950997A discloses a high-toughness, high-strength thick steel plate and its production method, focusing on improving the mechanical properties of the thick steel plate. It achieves high strength and toughness through composition design and heat treatment, but does not optimize the bonding strength or corrosion resistance of the zinc coating after acid-free hydrogen reduction. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates, solving the problems of insufficient adhesion and poor corrosion resistance of the zinc coating on the surface of acid-free hydrogen-reduced high-strength steel. This is achieved by adding Ru, Lu, and Re elements to the high-strength steel to refine the grain size and improve the activity of the reduced iron layer; and by adding Ru, W, Nd, Eu, and Yb elements to the Zn-11Al-3Mg alloy plating bath to enhance the adhesion and corrosion resistance of the coating to the reduced iron layer. Simultaneously, the use of an acid-free hydrogen reduction process avoids environmental pollution and corrosion of the substrate caused by acid pickling.

[0007] The technical solution of this invention is:

[0008] A method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates includes the following steps:

[0009] The first step involves the hot-rolled high-strength steel plate, by mass percentage, having the following chemical composition: C: 0.02%–0.2%, Si: 0.02%–0.2%, Mn: 0.5%–3.0%, Cr: 0.4%–4.0%, Mo: 0.05%–0.5%, V: 0.001%–0.01%, Ru: 0.05%–0.2%, Lu: 0.001%–0.02%, Re: 0.05%–0.3%, P: ≤0.05%, S: ≤0.005%, Ti: 0.01%–0.05%, N: 0.002%–0.02%, B: 0.0001%–0.01%, with the balance being Fe. This mixture is then smelted, continuously cast, and hot-rolled to form the hot-rolled high-strength steel plate.

[0010] The second step involves degreasing the hot-rolled high-strength steel plate with alcohol and then placing it in a heat treatment furnace that can be purged with a protective gas. The temperature is raised to 500-1000°C in a high-purity Ar protective atmosphere with a flow rate of 2-4 L / min and a heating rate of 15-30°C / min. Once the temperature is reached, the atmosphere is replaced with a reducing atmosphere with a flow rate of 2-4 L / min. The reducing atmosphere is a hydrogen-nitrogen mixture with a volume fraction of 20-40% H2. The temperature is maintained in the reducing atmosphere for 60-120 min, then the flow rate is switched to high-purity Ar with a flow rate of 2-4 L / min, and the plate is allowed to cool naturally to room temperature.

[0011] The third step is to immerse the hydrogen-reduced hot-rolled high-strength steel plate in a fluxing agent with a temperature of 20-80°C and an immersion time of 10-120 seconds. After immersion, the surface is dried.

[0012] The fourth step involves immersing the hot-rolled high-strength steel sheet, which has been soaked in flux, into a Zn11Al3Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn11Al3Mg alloy plating bath, by mass percentage, is: Si: 0.1%–0.5%, Re: 0.05%–0.5%, Al: 10%–13%, Mg: 2%–5%, Ti: 0.01%–0.1%, V: 0.01%–0.1%, Ru: 0.0 1%–0.02%, W: 0.02%–0.4%, Nd: 0.01%–0.04%, Eu: 0.01%–0.03%, Yb: 0.001%–0.008%, Pb: ≤0.003%, Cu: ≤0.002%, Fe: ≤0.05%, Cd: ≤0.002%, balance Zn, hot-dip plating bath temperature is 465–485℃, hot-dip plating time is 10–90s.

[0013] The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates, preferably, in the first step, Ru is 0.12%, Lu is 0.015%, and Re is 0.15%.

[0014] In the preparation method of corrosion-resistant Zn11Al3Mg coating for high-strength steel plates without acid washing and hydrogen reduction, the third step of the fluxing agent includes the following components: zinc chloride 90-180 g / L, potassium chloride 10-30 g / L, aluminum chloride 15-40 g / L, surfactant 1-5 g / L, and water as the balance.

[0015] The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates uses ammonium polyphosphate as the surfactant.

[0016] In the third step of the method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates, a flux layer with a thickness of 30-60 μm is formed on the surface of the hot-rolled high-strength steel plate.

[0017] The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen reduction high-strength steel plates, preferably, in the fourth step, Ru is 0.016%, W is 0.2%, Nd is 0.02%, Eu is 0.02%, and Yb is 0.004%.

[0018] In the fourth step of the method for preparing a corrosion-resistant Zn11Al3Mg coating for high-strength steel plates that are not acid-washed and hydrogen-reduced, a hot-dip galvanized layer with a thickness of 300-450 μm is obtained on the surface of the flux.

[0019] The design concept of this invention is:

[0020] To address the issue of insufficient adhesion and poor corrosion resistance of zinc coatings on the surface of acid-free hydrogen-reduced high-strength steel sheets, which result in a highly active and uniquely composed reduced iron layer, existing technologies suffer from insufficient adhesion between the coating and the reduced iron layer, leading to peeling and detachment. Furthermore, the coating's poor corrosion resistance fails to meet the demands of applications in harsh environments. This invention proposes a method for preparing a corrosion-resistant Zn-11Al-3Mg alloy coating for the reduced iron layer on the surface of acid-free hydrogen-reduced high-strength steel sheets. This method aims to solve the problems of insufficient adhesion and poor corrosion resistance of zinc coatings on the surface of acid-free hydrogen-reduced hot-rolled high-strength steel sheets. By adding Ru, Lu, and Re elements to the hot-rolled high-strength steel sheet, the grain size is refined and the activity of the reduced iron layer is improved. Furthermore, the addition of Ru, W, Nd, Eu, and Yb elements to the Zn-11Al-3Mg alloy plating bath enhances the adhesion between the coating and the reduced iron layer, as well as the corrosion resistance. Simultaneously, the acid-free hydrogen reduction process avoids environmental pollution and corrosion of the substrate caused by acid pickling.

[0021] Compared with the prior art, the present invention has the following innovations and advantages:

[0022] (1) The innovative hot-rolled high-strength steel plate composition design of this invention adds Ru, Lu and Re (rhenium) elements to the traditional hot-rolled high-strength steel plate composition. These elements can refine the grains, improve the strength and toughness of the steel, and at the same time form stable compounds during the hydrogen reduction process, enhance the activity of the reduced iron layer, and provide a better bonding basis for subsequent galvanizing.

[0023] (2) This invention forms a reduced iron layer on the surface of hot-rolled high-strength steel plate through a hydrogen reduction process, avoiding the environmental pollution and substrate corrosion problems caused by traditional pickling processes. The reduced iron layer has higher activity and can significantly improve the adhesion between the coating and the substrate.

[0024] (3) This invention innovatively adds Ru, W, Nd, Eu and Yb elements to the Zn-11Al-3Mg alloy plating bath. These elements can form stable compounds with zinc, aluminum and magnesium, further enhancing the bonding force between the coating and the reduced iron layer, while improving the hardness and corrosion resistance of the coating.

[0025] (4) This invention particularly emphasizes the bonding performance of the zinc coating on the surface of the reduced iron layer. By adding specific elements to the hot-rolled high-strength steel plate and alloy plating solution, the interfacial bonding between the reduced iron layer and the coating can be effectively improved, which is not available in existing related patents.

[0026] In summary, this invention, through innovative chemical composition design and process optimization, significantly improves the adhesion and corrosion resistance of the reduced iron layer on the surface of hot-rolled high-strength steel sheets without acid washing and hydrogen reduction, overcoming the shortcomings of existing technologies and providing an efficient, environmentally friendly, and high-quality solution for the hot-dip galvanizing of hot-rolled high-strength steel sheets.

[0027] The advantages and beneficial effects of this invention are:

[0028] 1. In terms of environmental protection and high efficiency, the acid-free hydrogen reduction process avoids the environmental pollution and substrate corrosion problems caused by traditional acid washing.

[0029] 2. This invention adds Ru and W elements to the Zn-11Al-3Mg alloy plating bath. These elements can form stable compounds with zinc, aluminum, and magnesium, further improving the hardness and corrosion resistance of the coating, while also enhancing the adhesion between the coating and the hot-rolled high-strength steel plate.

[0030] 3. The coating adhesion of the present invention is significantly improved. The Ru, Lu and Re elements added to the hot-rolled high-strength steel plate and the various elements added to the plating solution enhance the interfacial adhesion between the reduced iron layer and the coating, and significantly improve the adhesion of the coating.

[0031] 4. This invention enhances the corrosion resistance of the coating. The rare earth elements (Nd, Eu, Yb) and elements such as W and Ru added to the alloy plating solution improve the hardness and corrosion resistance of the coating.

[0032] 5. The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen reduction hot-rolled high-strength steel sheets according to the present invention significantly improves the overall quality of hot-rolled high-strength steel galvanized sheets by optimizing the composition of hot-rolled high-strength steel sheets and the formulation of the plating solution, thus expanding their application potential in high-end fields.

[0033] 6. The performance indicators of the hot-rolled high-strength steel galvanized sheet obtained after preparing the corrosion-resistant Zn11Al3Mg hot-dip galvanized layer using the present invention are as follows: the corrosion potential is -1.30 to -1.60 V and the corrosion current density is 1.20 × 10⁻⁶ V, as determined by the electrochemical workstation test results. -8 ~1.90×10 -8 A / cm 2 The polarization resistance is 11500~13900Ω·cm 2 The coating bonding strength is 770–800 MPa. Attached Figure Description

[0034] Figure 1 The image shows the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 1.

[0035] Figure 2 The image shows the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 2.

[0036] Figure 3 The image shows the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 3.

[0037] Figure 4 The image shows the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 4. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1:

[0040] In this embodiment, a method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen reduction high-strength steel plates includes the following steps:

[0041] The first step involves the hot-rolled high-strength steel plate having the following chemical composition by mass percentage: C: 0.02%, Si: 0.2%, Mn: 1.0%, Cr: 2.0%, Mo: 0.5%, V: 0.001%, Ru: 0.05%, Lu: 0.02%, Re: 0.15%, P: 0.02%, S: 0.005%, Ti: 0.01%, N: 0.015%, B: 0.01%, with the balance being Fe. This mixture is then smelted, continuously cast, and hot-rolled to form the hot-rolled high-strength steel plate.

[0042] The second step involves degreasing the hot-rolled high-strength steel plate with alcohol and then placing it in a heat treatment furnace that can be vented with a protective gas. The temperature is raised to 600°C at a rate of 15°C / min in a protective atmosphere of high-purity Ar (volume purity 99.999%) with a flow rate of 4L / min. After reaching the temperature, the temperature is changed to a reducing atmosphere with a flow rate of 2L / min. The reducing atmosphere is a hydrogen-nitrogen mixture with a volume fraction of 20% H2. The temperature is maintained in the reducing atmosphere for 60 minutes, then the flow rate is changed to high-purity Ar with a flow rate of 3L / min, and the plate is allowed to cool naturally to room temperature.

[0043] The third step involves immersing the hydrogen-reduced hot-rolled high-strength steel sheet in a fluxing agent, which comprises the following components: 90 g / L zinc chloride, 30 g / L potassium chloride, 15 g / L aluminum chloride, 5 g / L ammonium polyphosphate, and water as the balance. The fluxing agent temperature is 80°C, and the immersion time is 20 seconds. After immersion, the surface is dried to form a fluxing agent layer with a thickness of 60 μm on the surface of the hot-rolled high-strength steel sheet.

[0044] The fourth step involves immersing the hot-rolled high-strength steel sheet soaked in flux into a Zn11Al3Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn11Al3Mg alloy plating bath, by mass percentage, is: Si: 0.5%, Re: 0.35%, Al: 10%, Mg: 2%, Ti: 0.06%, V: 0.1%, Ru: 0.02%, W: 0.2%, Nd: 0.04%, Eu: 0.01%, Yb: 0.004%, Pb: 0.001%, Cu: 0.002%, Fe: 0.025%, Cd: 0.001%, with the balance being Zn. The hot-dip galvanizing bath temperature is 465℃, and the hot-dip galvanizing time is 60 seconds, resulting in a 410μm thick hot-dip zinc layer on the flux surface.

[0045] like Figure 1As shown in the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 1, the coating exhibits a clear multi-layer structure. The bottom layer is a high-strength steel substrate, providing a good foundation for mechanical properties; above it is a reduced iron layer, on which compounds formed by the reaction of the flux are deposited, constituting a flux layer. This structure facilitates the adhesion of the subsequent galvanized layer; the top layer is a zinc-aluminum-magnesium hot-dip galvanized layer with a thickness of approximately 410 μm, which is uniform and dense, possessing excellent corrosion resistance. The overall multi-layer structure design, progressing from the bottom layer to the surface, effectively improves the comprehensive protective performance of the sample and significantly enhances its service life and reliability in complex environments.

[0046] In this embodiment, the performance indicators of the hot-rolled high-strength steel galvanized sheet are as follows: the corrosion potential is -1.47V and the corrosion current density is 1.371×10⁻⁶ in the electrochemical workstation test results. -8 A / cm 2 The polarization resistance is 13517 Ω·cm 2 The coating bonding strength is 786 MPa.

[0047] Example 2:

[0048] In this embodiment, a method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen reduction high-strength steel plates includes the following steps:

[0049] The first step involves the hot-rolled high-strength steel plate having the following chemical composition by mass percentage: C: 0.1%, Si: 0.02%, Mn: 0.5%, Cr: 4.0%, Mo: 0.3%, V: 0.005%, Ru: 0.12%, Lu: 0.001%, Re: 0.3%, P: 0.05%, S: 0.001%, Ti: 0.03%, N: 0.02%, B: 0.005%, with the balance being Fe. This mixture is then smelted, continuously cast, and hot-rolled to form the hot-rolled high-strength steel plate.

[0050] The second step involves degreasing the hot-rolled high-strength steel plate with alcohol and then placing it in a heat treatment furnace that can be vented with a protective gas. The temperature is raised to 500°C at a rate of 30°C / min in a protective atmosphere of high-purity Ar (volume purity 99.999%) with a flow rate of 2L / min. After reaching the temperature, the temperature is changed to a reducing atmosphere with a flow rate of 4L / min. The reducing atmosphere is a hydrogen-nitrogen mixture with a volume fraction of 30% H2. The temperature is maintained in the reducing atmosphere for 90 minutes, then the flow rate is changed to high-purity Ar with a flow rate of 2L / min, and the plate is allowed to cool naturally to room temperature.

[0051] The third step involves immersing the hydrogen-reduced hot-rolled high-strength steel sheet in a fluxing agent, which comprises the following components: 180 g / L zinc chloride, 10 g / L potassium chloride, 40 g / L aluminum chloride, 1 g / L ammonium polyphosphate, and water as the balance. The fluxing agent temperature is 20°C, and the immersion time is 120 seconds. After immersion, the surface is dried to form a fluxing agent layer with a thickness of 30 μm on the surface of the hot-rolled high-strength steel sheet.

[0052] The fourth step involves immersing the hot-rolled high-strength steel sheet soaked in flux into a Zn11Al3Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn11Al3Mg alloy plating bath, by mass percentage, is: Si: 0.3%, Re: 0.5%, Al: 12.5%, Mg: 3%, Ti: 0.01%, V: 0.08%, Ru: 0.016%, W: 0.4%, Nd: 0.02%, Eu: 0.03%, Yb: 0.003%, Pb: 0.003%, Cu: 0.0015%, Fe: 0.01%, Cd: 0.002%, with the balance being Zn. The hot-dip galvanizing bath temperature is 470℃, and the galvanizing time is 10 seconds, resulting in a 450μm thick hot-dip zinc layer on the flux surface.

[0053] like Figure 2 As shown in the cross-section morphology of the hot-rolled high-strength steel galvanized sheet in Example 2, the coating exhibits a clear multi-layer structure. The bottom layer is a high-strength steel substrate, providing a good foundation for mechanical properties; above it is a reduced iron layer, on which compounds formed by the reaction of the flux are deposited, constituting a flux layer. This structure facilitates the adhesion of the subsequent galvanized layer; the top layer is a zinc-aluminum-magnesium hot-dip galvanized layer with a thickness of approximately 450 μm, which is uniform and dense, possessing excellent corrosion resistance. The overall multi-layer structure design, progressing from the bottom layer to the surface, effectively improves the comprehensive protective performance of the sample and significantly enhances its service life and reliability in complex environments.

[0054] In this embodiment, the performance indicators of the hot-rolled high-strength steel galvanized sheet are as follows: the corrosion potential is -1.51V and the corrosion current density is 1.253×10⁻⁶ in the electrochemical workstation test results. -8 A / cm 2 The polarization resistance is 13845 Ω·cm 2 The coating bonding strength is 792 MPa.

[0055] Example 3:

[0056] In this embodiment, a method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen reduction high-strength steel plates includes the following steps:

[0057] The first step involves the hot-rolled high-strength steel plate having the following chemical composition by mass percentage: C: 0.2%, Si: 0.06%, Mn: 3.0%, Cr: 0.4%, Mo: 0.05%, V: 0.01%, Ru: 0.2%, Lu: 0.015%, Re: 0.05%, P: 0.025%, S: 0.003%, Ti: 0.05%, N: 0.002%, B: 0.0001%, with the balance being Fe. This mixture is then smelted, continuously cast, and hot-rolled to form the hot-rolled high-strength steel plate.

[0058] The second step involves degreasing the hot-rolled high-strength steel plate with alcohol and then placing it in a heat treatment furnace that can be purged with a protective gas. The temperature is raised to 1000°C at a rate of 20°C / min in a protective atmosphere of high-purity Ar (volume purity 99.999%) with a flow rate of 3.5 L / min. Once the temperature is reached, the temperature is changed to a reducing atmosphere with a flow rate of 3 L / min. The reducing atmosphere is a hydrogen-nitrogen mixture with a volume fraction of 40% H2. The temperature is maintained in the reducing atmosphere for 120 min, then the flow rate is changed to high-purity Ar with a flow rate of 4 L / min, and the plate is allowed to cool naturally to room temperature.

[0059] The third step involves immersing the hydrogen-reduced hot-rolled high-strength steel sheet in a fluxing agent, which comprises the following components: 120 g / L zinc chloride, 25 g / L potassium chloride, 24 g / L aluminum chloride, 4 g / L ammonium polyphosphate, and water as the balance. The fluxing agent temperature is 60°C, and the immersion time is 10 seconds. After immersion, the surface is dried to form a fluxing agent layer with a thickness of 43 μm on the surface of the hot-rolled high-strength steel sheet.

[0060] The fourth step involves immersing the hot-rolled high-strength steel sheet soaked in flux into a Zn11Al3Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn11Al3Mg alloy plating bath, by mass percentage, is: Si: 0.1%, Re: 0.05%, Al: 13%, Mg: 5%, Ti: 0.1%, V: 0.01%, Ru: 0.01%, W: 0.02%, Nd: 0.01%, Eu: 0.025%, Yb: 0.008%, Pb: 0.002%, Cu: 0.001%, Fe: 0.05%, Cd: 0.0015%, with the balance being Zn. The hot-dip galvanizing bath temperature is 485℃, and the galvanizing time is 90 seconds, resulting in a 300μm thick hot-dip zinc layer on the flux surface.

[0061] like Figure 3As shown in the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 3, the coating cross-section exhibits a clear multi-layer structure. The bottom layer is a high-strength steel substrate, providing a good foundation for mechanical properties; above it is a reduced iron layer, on which compounds formed by the reaction of the flux are deposited, constituting a flux layer. This structure facilitates the adhesion of the subsequent galvanized layer; the top layer is a zinc-aluminum-magnesium hot-dip galvanized layer with a thickness of approximately 300 μm, which is uniform and dense, possessing excellent corrosion resistance. The overall multi-layer structure design, progressing from the bottom layer to the surface, effectively improves the comprehensive protective performance of the sample and significantly enhances its service life and reliability in complex environments.

[0062] In this embodiment, the performance indicators of the hot-rolled high-strength steel galvanized sheet are as follows: the corrosion potential is -1.32V and the corrosion current density is 1.843×10⁻⁶ in the electrochemical workstation test results. -8 A / cm 2 The polarization resistance is 11529 Ω·cm 2 The coating bonding strength is 772 MPa.

[0063] Example 4:

[0064] In this embodiment, a method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen reduction high-strength steel plates includes the following steps:

[0065] The first step involves the hot-rolled high-strength steel plate having the following chemical composition by mass percentage: C: 0.08%, Si: 0.15%, Mn: 1.35%, Cr: 1.5%, Mo: 0.15%, V: 0.008%, Ru: 0.08%, Lu: 0.05%, Re: 0.08%, P: 0.01%, S: 0.002%, Ti: 0.02%, N: 0.01%, B: 0.005%, with the balance being Fe. This composition is then processed through smelting, continuous casting, and hot rolling to form the hot-rolled high-strength steel plate.

[0066] The second step involves degreasing the hot-rolled high-strength steel plate with alcohol and then placing it in a heat treatment furnace that can be purged with a protective gas. The plate is heated to 900°C at a rate of 25°C / min in a protective atmosphere of high-purity Ar (volume purity 99.999%) with a flow rate of 2.5 L / min. Once the temperature is reached, the plate is replaced with a reducing atmosphere of 3.5 L / min, which is a hydrogen-nitrogen mixture with a volume fraction of 25% H2. The plate is held at the reducing atmosphere for 100 min, then switched to high-purity Ar with a flow rate of 2.5 L / min and allowed to cool naturally to room temperature.

[0067] The third step involves immersing the hydrogen-reduced hot-rolled high-strength steel sheet in a fluxing agent, which comprises the following components: 160 g / L zinc chloride, 15 g / L potassium chloride, 30 g / L aluminum chloride, 2 g / L ammonium polyphosphate, and water as the balance. The fluxing agent temperature is 30°C, and the immersion time is 60 seconds. After immersion, the surface is dried to form a fluxing agent layer with a thickness of 36 μm on the surface of the hot-rolled high-strength steel sheet.

[0068] The fourth step involves immersing the hot-rolled high-strength steel sheet soaked in flux into a Zn11Al3Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn11Al3Mg alloy plating bath, by mass percentage, is: Si: 0.2%, Re: 0.1%, Al: 11.4%, Mg: 4%, Ti: 0.04%, V: 0.05%, Ru: 0.013%, W: 0.1%, Nd: 0.015%, Eu: 0.02%, Yb: 0.005%, Pb: 0.0015%, Cu: 0.0005%, Fe: 0.03%, Cd: 0.0005%, with the balance being Zn. The hot-dip galvanizing bath temperature is 480℃, and the hot-dip galvanizing time is 30 seconds, resulting in a 370μm thick hot-dip zinc layer on the flux surface.

[0069] like Figure 4 As shown in the cross-section morphology of the hot-rolled high-strength steel galvanized sheet in Example 4, the coating exhibits a clear multi-layer structure. The bottom layer is a high-strength steel substrate, providing a good foundation for mechanical properties; a reduced iron layer covers it, and the surface of the reduced iron layer contains compounds formed by the reaction of the flux, constituting a flux layer. This structure facilitates the adhesion of the subsequent galvanized layer; the top layer is a zinc-aluminum-magnesium hot-dip galvanized layer with a thickness of approximately 370 μm, which is uniform and dense, possessing excellent corrosion resistance. The overall multi-layer structure design, progressing from the bottom layer to the surface, effectively improves the comprehensive protective performance of the sample and significantly enhances its service life and reliability in complex environments.

[0070] In this embodiment, the performance indicators of the hot-rolled high-strength steel galvanized sheet are as follows: the corrosion potential is -1.38V and the corrosion current density is 1.293×10⁻⁶ in the electrochemical workstation test results. -8 A / cm 2 The polarization resistance is 13164 Ω·cm 2 The coating bonding strength is 778 MPa.

[0071] The results show that after preparing the corrosion-resistant Zn11Al3Mg hot-dip galvanized layer, the performance indicators of the hot-rolled high-strength steel galvanized sheet obtained in the examples are as follows: the corrosion potential is -1.32 to -1.51 V, and the corrosion current density is 1.253 × 10⁻⁶ V, as determined by the electrochemical workstation test. -8 ~1.843×10 -8 A / cm 2The polarization resistance is 11529~13845Ω·cm 2 The coating bonding strength is 772–792 MPa. This invention adds Ru, Lu, and Re elements to hot-rolled high-strength steel to refine the grains and improve the steel's strength and toughness, while simultaneously enhancing the activity of the reduced iron layer, providing a good bonding foundation for the coating. Ru, W, Nd, Eu, and Yb elements are introduced into the Zn11Al3Mg alloy plating bath to strengthen the interfacial bonding between the coating and the reduced iron layer by forming stable compounds, while also improving the coating's hardness and corrosion resistance. An acid-free hydrogen reduction process is employed to avoid acid pickling contamination and hydrogen embrittlement. By precisely controlling the reduction temperature, time, and hot-dip plating parameters, the performance matching between the substrate and the coating is achieved.

Claims

1. A method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates, characterized in that, Includes the following steps: The first step involves the following chemical composition of hot-rolled high-strength steel plate, by mass percentage: C: 0.02%–0.2%, Si: 0.02%–0.2%, Mn: 0.5%–3.0%, Cr: 0.4%–4.0%, Mo: 0.05%–0.5%, V: 0.001%–0.01%, Ru: 0.05%–0.2%, Lu: 0.001%–0.02%, Re: 0.05%–0.3%, P: ≤0.05%, S: ≤0.005%, Ti: 0.01%–0.05%, N: 0.002%–0.02%, B: 0.0001%–0.01%, with the balance being Fe. This composition is then processed through smelting, continuous casting, and hot rolling to form the hot-rolled high-strength steel plate. The second step involves degreasing the hot-rolled high-strength steel plate with alcohol and then placing it in a heat treatment furnace with a protective gas flow rate of 2-4 L / min. The temperature is raised to 500-1000℃ at a rate of 15-30℃ / min in a high-purity Ar protective atmosphere. After reaching the temperature, the temperature is changed to a reducing atmosphere with a flow rate of 2-4 L / min. The reducing atmosphere is a hydrogen-nitrogen mixture with a volume fraction of 20-40% H2. The temperature is maintained in the reducing atmosphere for 60-120 min, then the flow rate is changed to high-purity Ar with a flow rate of 2-4 L / min, and the plate is allowed to cool naturally to room temperature. The third step is to immerse the hydrogen-reduced hot-rolled high-strength steel plate in a fluxing agent with a temperature of 20-80°C and an immersion time of 10-120 seconds. After immersion, the surface is dried. The fourth step involves immersing the hot-rolled high-strength steel sheet, which has been soaked in flux, into a Zn11Al3Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn11Al3Mg alloy plating bath, by mass percentage, is: Si: 0.1%–0.5%, Re: 0.05%–0.5%, Al: 10%–13%, Mg: 2%–5%, Ti: 0.01%–0.1%, V: 0.01%–0.1%, Ru: 0.0 1%~0.02%, W: 0.02%~0.4%, Nd: 0.01%~0.04%, Eu: 0.01%~0.03%, Yb: 0.001%~0.008%, Pb: ≤0.003%, Cu: ≤0.002%, Fe: ≤0.05%, Cd: ≤0.002%, balance Zn, hot-dip plating bath temperature is 465~485℃, hot-dip plating time is 10~90s.

2. The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates according to claim 1, characterized in that, In the first step, Ru is 0.12%, Lu is 0.015%, and Re is 0.15%.

3. The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates according to claim 1, characterized in that, In the third step, the flux includes the following components: Zinc chloride 90-180 g / L, potassium chloride 10-30 g / L, aluminum chloride 15-40 g / L, surfactant 1-5 g / L, water balance.

4. The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates according to claim 3, characterized in that, The surfactant is ammonium polyphosphate.

5. The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates according to claim 1, characterized in that, In the third step, a flux layer with a thickness of 30 to 60 μm is formed on the surface of the hot-rolled high-strength steel plate.

6. The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates according to claim 1, characterized in that, In the fourth step, Ru is 0.016%, W is 0.2%, Nd is 0.02%, Eu is 0.02%, and Yb is 0.004%.

7. The method for preparing a corrosion-resistant Zn11Al3Mg coating for acid-free hydrogen-reduced high-strength steel plates according to claim 1, characterized in that, In the fourth step, a hot-dip galvanized layer with a thickness of 300–450 μm is obtained on the surface of the flux.

Images