A flux and hot-dip galvanizing process for high-strength steel sheet hot-dip galvanized coating based on acid-free hydrogen reduction.

Abstract

This invention relates to hot-dip galvanizing technology for high-strength steel sheets, specifically a flux and hot-dip galvanizing process for a hot-dip galvanized layer of high-strength steel sheets based on acid-free hydrogen reduction. The flux comprises: zinc chloride 110–300 g / L, potassium chloride 40–100 g / L, aluminum chloride 50–100 g / L, cerium nitrate 10–50 g / L, sodium molybdate 10–40 g / L, potassium titanate 1–5 g / L, tetrabutyl titanate 1–3 g / L, triphenyl phosphate 2–10 g / L, surfactant 1–3 g / L, and water as the balance. The corrosion-resistant hot-rolled high-strength steel sheet is degreased with alcohol and then placed in a treatment furnace for hydrogen reduction. The hydrogen-reduced corrosion-resistant hot-rolled high-strength steel sheet is then immersed in the flux, and the flux-treated sheet is then immersed in a Zn-Al-Mg alloy plating bath for hot-dip galvanizing. This invention can effectively improve the bonding performance and corrosion resistance of the Zn-Al-Mg alloy coating on the surface of the reduced iron layer of acid-free hydrogen-reduced high-strength steel, and solve the problem of insufficient bonding between the reduced iron layer and the coating in the prior art.

Description

Technical Field

[0001] This invention relates to hot-dip galvanizing technology for high-strength steel plates, specifically to a flux and hot-dip galvanizing process for hot-dip galvanized layers of high-strength steel plates based on acid-free hydrogen reduction, applicable to hot-rolled high-strength steel plates with high corrosion resistance. Background Technology

[0002] In the field of advanced steel materials, the processing of advanced ultra-high strength steel plates and their coated plates faces increasingly stringent requirements for environmental protection and performance. Acid-free hydrogen reduction technology has become an important direction due to its ability to completely eliminate polluting acid pickling, avoid hydrogen embrittlement, and form a reduced iron layer. However, this reduced iron layer has high activity, and traditional fluxes exhibit poor surface wettability and insufficient purification effect, resulting in weak adhesion, poor uniformity, and poor corrosion resistance of the subsequent hot-dip galvanized layer. This severely restricts the quality and processing efficiency of advanced ultra-high strength steel plates and their coated plates. There is an urgent need to develop new, highly efficient fluxes and processes suitable for acid-free hydrogen reduction substrates to optimize the pretreatment process and ensure high-performance coatings.

[0003] In the hot-dip galvanizing process, the adhesion between the coating and the high-strength steel substrate, as well as its corrosion resistance, have always been major challenges for the industry. In traditional processes, the surface of high-strength steel typically requires pickling to remove oxide scale. However, pickling not only causes environmental pollution but also corrodes the substrate, reducing material performance. In recent years, pickling-free hydrogen reduction processes have gained increasing attention. This process uses hydrogen to reduce the oxide scale on the surface of high-strength steel, forming a reduced iron layer, providing a cleaner and more active surface for subsequent galvanizing. However, existing research on the adhesion performance of the galvanized layer on pickling-free hydrogen-reduced high-strength steel surfaces is still insufficient, especially since the flux formulations in existing patents are no longer suitable for the performance requirements of the hot-dip galvanized coating on the reduced iron layer of pickling-free hydrogen-reduced high-strength steel.

[0004] Patent CN103014578A discloses a hot-dip galvanizing flux formulation, primarily using zinc chloride and ammonium chloride, with added elements such as silicon and sulfur. However, it is designed for traditional pickling processes and cannot solve the problem of poor wettability caused by the high activity of the reduced iron layer, resulting in limited improvement in coating adhesion. Patent CN103589981A discloses a hot-dip galvanizing flux formulation that improves coating quality by adding SnCl2, but it still relies on pickling pretreatment and cannot form a stable transition layer on the reduced iron layer surface, resulting in insufficient improvement in corrosion resistance. Patent CN118685725A discloses an environmentally friendly hot-dip galvanizing flux and its application process, adding nickel trifluoromethanesulfonate to optimize coating uniformity, but it still relies on pickling for rust removal and cannot form a chemically bonded layer to enhance adhesion. The patent with publication number CN115011900A proposes an ammonium-free flux and a hot-dip galvanizing process using an ammonium-free flux. It adopts an ammonium-free formula and relies on zinc chloride and perfluorooctyl sulfonate diethanolamide, but the process still includes an acid pickling step, resulting in limited improvement in the corrosion resistance of the coating.

[0005] Regarding the limitations of traditional pickling 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. Existing flux formulations are no longer suitable; traditional fluxes, mainly composed of zinc chloride and ammonium chloride, are insufficient to effectively improve the adhesion between the coating and high-strength steel, especially on the surface of reduced iron layers after hydrogen reduction without pickling, where existing fluxes are ineffective. Currently, research on flux formulations for hydrogen-reduced high-strength steel surfaces without pickling is limited. Existing patents mostly focus on traditional pickling processes or zinc plating technology for ordinary high-strength steel, lacking in-depth exploration of the coating adhesion performance on the reduced iron layer surface. Summary of the Invention

[0006] The purpose of this invention is to provide a flux and hot-dip galvanizing process for hot-dip galvanized layers of high-strength steel plates based on acid-free hydrogen reduction, which can effectively improve the bonding performance and corrosion resistance of the Zn-Al-Mg alloy coating on the surface of the reduced iron layer of acid-free hydrogen reduction high-strength steel, and solve the problem of insufficient bonding between the reduced iron layer and the coating in the prior art.

[0007] The technical solution of this invention is:

[0008] A flux for hot-dip galvanizing high-strength steel plates based on acid-free hydrogen reduction is disclosed. The flux comprises: zinc chloride 110–300 g / L, potassium chloride 40–100 g / L, aluminum chloride 50–100 g / L, cerium nitrate 10–50 g / L, sodium molybdate 10–40 g / L, potassium titanate 1–5 g / L, tetrabutyl titanate 1–3 g / L, triphenyl phosphate 2–10 g / L, surfactant 1–3 g / L, and water as the balance.

[0009] The flux for hot-dip galvanizing of high-strength steel plates based on acid-free hydrogen reduction preferably contains 20 g / L cerium nitrate, 30 g / L sodium molybdate, 2 g / L potassium titanate, 2 g / L tetrabutyl titanate, 6 g / L triphenyl phosphate, and 2 g / L surfactant.

[0010] The flux used for hot-dip galvanizing of high-strength steel plates based on acid-free hydrogen reduction has ammonium polyphosphate as its surfactant.

[0011] A hot-dip galvanizing process for high-strength steel sheets based on acid-free hydrogen reduction includes the following steps:

[0012] The first step involves degreasing the corrosion-resistant hot-rolled high-strength steel plate with alcohol and then placing it in a treatment furnace that can be purged with a protective gas. The plate is heated to 500-1000°C in a high-purity Ar protective atmosphere with a flow rate of 1-2 L / min and a heating rate of 10-20°C / min. Once the temperature is reached, the plate is replaced with a reducing atmosphere with a flow rate of 1-3 L / min. The reducing atmosphere is a hydrogen-nitrogen mixture with a volume fraction of 30-60% H2. The plate is held at the reducing atmosphere for 60-120 min, then switched to high-purity Ar with a flow rate of 1-2 L / min and allowed to cool naturally to room temperature.

[0013] The second step involves immersing the hydrogen-reduced corrosion-resistant hot-rolled high-strength steel sheet in a fluxing agent, which is a uniform mixture of the following components: zinc chloride 110–300 g / L, potassium chloride 40–100 g / L, aluminum chloride 50–100 g / L, cerium nitrate 10–50 g / L, sodium molybdate 10–40 g / L, potassium titanate 1–5 g / L, tetrabutyl titanate 1–3 g / L, triphenyl phosphate 2–10 g / L, surfactant 1–3 g / L, and water as the balance.

[0014] The third step involves immersing the corrosion-resistant hot-rolled high-strength steel sheet, which has been soaked in flux, into a Zn-Al-Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn-Al-Mg 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: 0.01%–0.02%, W: 0.01%–0.05%, Pb: ≤0.003%, Cu: ≤0.002%, Fe: ≤0.05%, Cd: ≤0.002%, with the balance being Zn.

[0015] In the second step of the hot-dip galvanizing process for high-strength steel plates based on acid-free hydrogen reduction, the flux temperature is 20-80℃, the corrosion-resistant hot-rolled high-strength steel plate is immersed in the flux for 10-120s, and the surface is dried after immersion, forming a flux layer with a thickness of 15-50μm on the surface of the corrosion-resistant hot-rolled high-strength steel plate.

[0016] In the third step of the hot-dip galvanizing process for high-strength steel plates based on acid-free hydrogen reduction, the hot-dip galvanizing bath temperature is 460-480℃, the hot-dip galvanizing time is 5-120s, and a hot-dip galvanized layer with a thickness of 150-320μm is obtained on the surface of the flux.

[0017] In the aforementioned hot-dip galvanizing process for high-strength steel plates based on acid-free hydrogen reduction, preferably, in the third step, Ru: 0.012% and W: 0.03%.

[0018] The design concept of this invention is:

[0019] Traditional fluxes exhibit poor wettability and insufficient purification effect on the reduced iron layer formed by acid-free hydrogen reduction, resulting in weak coating adhesion and poor uniformity. This invention addresses the issue of reduced iron layers formed on the surface of high-strength steel during acid-free hydrogen reduction. It proposes a flux and hot-dip galvanizing process for high-strength steel plates based on this process. By innovatively incorporating sodium molybdate, potassium titanate, tetrabutyl titanate, and triphenyl phosphate into the flux, and using ammonium polyphosphate as a surfactant, the adhesion between the reduced iron layer and the coating is enhanced. Furthermore, the addition of Ru and W elements to the Zn-Al-Mg alloy plating bath further improves coating performance. Therefore, this invention, through innovative flux formulation design and process improvement, significantly enhances the adhesion and corrosion resistance of the reduced iron layer to the zinc coating on acid-free hydrogen-reduced high-strength steel.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) Innovative Flux Formulation: Sodium molybdate, potassium titanate, tetrabutyl titanate, and triphenyl phosphate were innovatively added to the flux, with ammonium polyphosphate used as a surfactant. Specifically: Potassium titanate forms a dense titanium oxide film on the surface of high-strength steel, enhancing the adhesion between the coating and the reduced iron layer, while also improving the corrosion resistance of the coating. Tetrabutyl titanate disperses uniformly in the flux, forming a uniform titanium oxide film, further enhancing the adhesion of the coating. Sodium molybdate forms a molybdenum oxide film on the surface of the reduced iron layer, enhancing the adhesion between the coating and the substrate, while also improving the wear resistance and corrosion resistance of the coating. Triphenyl phosphate reduces the surface tension of the plating solution, improving the uniformity and adhesion of the coating, and simultaneously forming a chemically bonded layer between the coating and the substrate, further enhancing the adhesion. Ammonium polyphosphate, as a surfactant, improves the dispersibility and stability of the plating solution, further improving the uniformity and adhesion of the coating.

[0022] (2) Regarding the optimized design of the reduced iron layer, this invention particularly emphasizes the bonding performance of the coating on the surface of the reduced iron layer. By adding specific compounds to the flux, a stable transition layer can be formed between the reduced iron layer and the coating, enhancing the interfacial bonding force, which is not present in existing related patents.

[0023] (3) The present invention has environmental protection and high efficiency. The acid-free hydrogen reduction process avoids the environmental pollution and substrate corrosion problems caused by traditional acid washing. At the same time, the new flux formulation further improves the zinc plating efficiency and quality.

[0024] (4) This invention can improve product quality. By optimizing the flux formulation, it significantly improves the overall quality of hot-dip galvanized high-strength steel and expands its application potential in high-end fields.

[0025] In summary, this invention, through innovative flux formulation design, significantly improves the adhesion and corrosion resistance of the coating to the substrate by targeting the reduced iron layer on the surface of high-strength steel that requires no acid pickling and hydrogen reduction. It overcomes the shortcomings of existing technologies and provides an efficient, environmentally friendly, and high-quality solution for the hot-dip galvanizing of high-strength steel.

[0026] The advantages and beneficial effects of this invention are:

[0027] 1. This invention significantly enhances adhesion. The titanate and molybdate in the flux can form a stable oxide film on the surface of the reduced iron layer, thereby enhancing the adhesion between the coating and the substrate.

[0028] 2. This invention significantly improves corrosion resistance: compounds such as tetrabutyl titanate and triphenyl phosphate can improve the uniformity and density of the coating, and significantly enhance the corrosion resistance of the coating.

[0029] 3. The acid-free hydrogen reduction process in this invention avoids the environmental pollution and substrate corrosion problems caused by traditional acid washing, while the new flux formulation improves the efficiency and quality of zinc plating.

[0030] 4. By optimizing the flux formulation, this invention significantly improves the overall quality of hot-dip galvanized high-strength steel, making it more suitable for high-end applications.

[0031] 5. This invention introduces a variety of novel compounds into the flux formulation, and the optimized design for the coating adhesion performance on the reduced iron layer surface is not found in existing related patents.

[0032] 6. The performance indicators of the hot-rolled high-strength steel galvanized sheet obtained after preparing the Zn-Al-Mg hot-dip galvanized layer using the present invention are as follows: the corrosion potential is -1.30 to -1.50 V and the corrosion current density is 9.0 × 10⁻⁶ V, as determined by electrochemical workstation testing. -7 ~9.2×10 -7 A / cm 2 The polarization resistance is 10050~12400Ω·cm 2 The coating bonding strength is 750–770 MPa. Attached Figure Description

[0033] Figure 1 The image shows the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 1.

[0034] Figure 2 The image shows the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 2.

[0035] Figure 3 The image shows the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 3.

[0036] Figure 4The image shows the morphology of the cross-section of the hot-rolled high-strength steel galvanized sheet in Example 4. Detailed Implementation

[0037] 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.

[0038] Example 1:

[0039] In this embodiment, a flux for hot-dip galvanizing a high-strength steel plate based on acid-free hydrogen reduction and a hot-dip galvanizing process includes the following steps:

[0040] The first step involves degreasing the corrosion-resistant hot-rolled high-strength steel plate (grade Q450NQR1) with alcohol and then placing it in a treatment furnace that can be vented with a protective gas. The temperature is raised to 500°C at a rate of 10°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 1L / 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 120 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.

[0041] The second step involves immersing the hydrogen-reduced corrosion-resistant hot-rolled high-strength steel sheet in a fluxing agent. The fluxing agent comprises the following components: zinc chloride 110 g / L, potassium chloride 80 g / L, aluminum chloride 100 g / L, cerium nitrate 50 g / L, sodium molybdate 40 g / L, potassium titanate 5 g / L, tetrabutyl titanate 3 g / L, triphenyl phosphate 10 g / L, ammonium polyphosphate 1 g / L, and water as the balance. The fluxing agent temperature is 20°C, and the immersion time is 20 seconds. After immersion, the surface is dried, forming a fluxing agent layer with a thickness of 15 μm on the surface of the corrosion-resistant hot-rolled high-strength steel sheet.

[0042] The third step involves immersing the corrosion-resistant hot-rolled high-strength steel sheet, which has been soaked in flux, into a Zn-Al-Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn-Al-Mg alloy plating bath, by mass percentage, is: Si: 0.1%, Re: 0.05%, Al: 10%, Mg: 5%, Ti: 0.02%, V: 0.03%, Ru: 0.02%, W: 0.02%, Pb: 0.002%, Cu: 0.001%, Fe: 0.03%, Cd: 0.001%, with the balance being Zn. The hot-dip galvanizing bath temperature is 465℃, and the hot-dip galvanizing time is 30 seconds, resulting in a 150μm thick hot-dip zinc layer on the flux surface.

[0043] 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 cross-section exhibits a clear multi-layer structure. The bottom layer is the high-strength steel substrate, providing a good foundation for mechanical properties. Above this is a reduced iron layer, which is a continuous reduced iron layer formed after the reduction of the original iron oxide layer on the high-strength steel surface. The surface of the reduced iron layer contains compound deposits formed by the reaction of the flux, constituting a flux layer. This layer is not continuous; this structure facilitates the adhesion of the subsequent galvanized layer. The top layer is a zinc-aluminum-magnesium hot-dip galvanized layer approximately 150 μm thick, with uniform and dense thickness, exhibiting excellent corrosion resistance. The overall multi-layer structure design, progressing layer by layer from the bottom to the surface, effectively improves the comprehensive protective performance of the sample, significantly enhancing its service life and reliability in complex environments.

[0044] 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 9.152×10⁻⁶ in the electrochemical workstation test results. -7 A / cm 2 The polarization resistance is 10053 Ω·cm 2 The coating bonding strength is 753 MPa.

[0045] Example 2:

[0046] In this embodiment, a flux for hot-dip galvanizing a high-strength steel plate based on acid-free hydrogen reduction and a hot-dip galvanizing process includes the following steps:

[0047] The first step is to degrease the corrosion-resistant hot-rolled high-strength steel plate (grade Q460NQR1) with alcohol and then place it in a heat treatment furnace that can be purged with a protective gas. In a protective atmosphere of high-purity Ar (volume purity 99.999%) with a flow rate of 1L / min, the temperature is raised to 600℃ at a heating rate of 15℃ / min. After the temperature is reached, the temperature is changed to a reducing atmosphere with a flow rate of 1L / min. The reducing atmosphere is a hydrogen-nitrogen mixture with a volume fraction of 40% H2. After holding the temperature in the reducing atmosphere for 80 minutes, the flow rate is changed to high-purity Ar with a flow rate of 1L / min, and the plate is allowed to cool naturally to room temperature.

[0048] The second step involves immersing the hydrogen-reduced corrosion-resistant hot-rolled high-strength steel sheet in a fluxing agent. The fluxing agent comprises the following components: 300 g / L zinc chloride, 40 g / L potassium chloride, 50 g / L aluminum chloride, 10 g / L cerium nitrate, 10 g / L sodium molybdate, 1 g / L potassium titanate, 1 g / L tetrabutyl titanate, 2 g / L triphenyl phosphate, 1 g / L ammonium polyphosphate, and water as the balance. The fluxing agent temperature is 60°C, and the immersion time is 40 seconds. After immersion, the surface is dried, forming a 30 μm thick fluxing agent layer on the surface of the corrosion-resistant hot-rolled high-strength steel sheet.

[0049] The third step involves immersing the corrosion-resistant hot-rolled high-strength steel sheet, which has been soaked in flux, into a Zn-Al-Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn-Al-Mg alloy plating bath, by mass percentage, is: Si: 0.1%, Re: 0.05%, Al: 13%, Mg: 2%, Ti: 0.01%, V: 0.01%, Ru: 0.01%, W: 0.01%, Pb: 0.003%, Cu: 0.002%, Fe: 0.04%, Cd: 0.001%, with the balance being Zn. The hot-dip galvanizing bath temperature is 465℃, and the hot-dip galvanizing time is 30 seconds, resulting in a 190μm thick hot-dip zinc layer on the flux surface.

[0050] like Figure 2 As shown in the cross-section morphology of the hot-rolled high-strength steel galvanized sheet in Example 2, 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 this is a reduced iron layer, which is a continuous reduced iron layer formed after the reduction of the original iron oxide layer on the high-strength steel surface. The surface of the reduced iron layer contains compounds formed by the reaction of the flux, constituting a flux layer. This layer is not continuous; this structure facilitates the adhesion of the subsequent galvanized layer. The top layer is a zinc-aluminum-magnesium hot-dip galvanized layer approximately 190 μm thick, with uniform and dense thickness, exhibiting excellent corrosion resistance. The overall multi-layer structure design, progressing layer by layer from the bottom to the surface, effectively improves the comprehensive protective performance of the sample, significantly enhancing its service life and reliability in complex environments.

[0051] In this embodiment, the performance indicators of the hot-rolled high-strength steel galvanized sheet are as follows: the corrosion potential is -1.41V and the corrosion current density is 9.072×10⁻⁶ in the electrochemical workstation test results. -7 A / cm 2 The polarization resistance is 10189 Ω·cm 2 The coating bonding strength is 759 MPa.

[0052] Example 3:

[0053] In this embodiment, a flux for hot-dip galvanizing a high-strength steel plate based on acid-free hydrogen reduction and a hot-dip galvanizing process includes the following steps:

[0054] The first step involves degreasing the corrosion-resistant hot-rolled high-strength steel plate (grade Q550NQR1) with alcohol and then placing it in a treatment furnace that can be vented 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 2L / min. Once the temperature is reached, the temperature is changed to a reducing atmosphere with a flow rate of 3L / min. The reducing atmosphere is a hydrogen-nitrogen mixture with a volume fraction of 60% 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 2L / min, and the plate is allowed to cool naturally to room temperature.

[0055] The second step involves immersing the hydrogen-reduced corrosion-resistant hot-rolled high-strength steel sheet in a fluxing agent. The fluxing agent comprises the following components: zinc chloride 150 g / L, potassium chloride 80 g / L, aluminum chloride 75 g / L, cerium nitrate 30 g / L, sodium molybdate 25 g / L, potassium titanate 3 g / L, tetrabutyl titanate 2 g / L, triphenyl phosphate 6 g / L, ammonium polyphosphate 3 g / L, and water as the balance. The fluxing agent temperature is 80°C, and the immersion time is 80 seconds. After immersion, the surface is dried, forming a fluxing agent layer with a thickness of 50 μm on the surface of the corrosion-resistant hot-rolled high-strength steel sheet.

[0056] The third step involves immersing the corrosion-resistant hot-rolled high-strength steel sheet, which has been soaked in flux, into a Zn-Al-Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn-Al-Mg alloy plating bath, by mass percentage, is: Si: 0.5%, Re: 0.5%, Al: 11.5%, Mg: 3%, Ti: 0.01%, V: 0.1%, Ru: 0.02%, W: 0.05%, Pb: 0.001%, Cu: 0.002%, Fe: 0.03%, Cd: 0.002%, with the balance being Zn. The hot-dip galvanizing bath temperature is 480℃, and the hot-dip galvanizing time is 120s, resulting in a 270μm thick hot-dip zinc layer on the flux surface.

[0057] like Figure 3 As 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 this is a reduced iron layer, which is a continuous reduced iron layer formed after the reduction of the original iron oxide layer on the high-strength steel surface. The surface of the reduced iron layer contains compounds formed by the reaction of the flux, constituting a flux layer. This layer is not continuous; this structure facilitates the adhesion of the subsequent galvanized layer. The top layer is a zinc-aluminum-magnesium hot-dip galvanized layer approximately 270 μm thick, with uniform and dense thickness, exhibiting excellent corrosion resistance. The overall multi-layer structure design, progressing layer by layer from the bottom to the surface, effectively improves the comprehensive protective performance of the sample, significantly enhancing its service life and reliability in complex environments.

[0058] In this embodiment, the performance indicators of the hot-rolled high-strength steel galvanized sheet are as follows: the corrosion potential is -1.35V and the corrosion current density is 9.146×10⁻⁶ in the electrochemical workstation test results. -7 A / cm 2 The polarization resistance is 10127 Ω·cm 2 The coating bonding strength is 761 MPa.

[0059] Example 4:

[0060] In this embodiment, a flux for hot-dip galvanizing a high-strength steel plate based on acid-free hydrogen reduction and a hot-dip galvanizing process includes the following steps:

[0061] The first step involves degreasing the corrosion-resistant hot-rolled high-strength steel plate (grade Q550NH) with alcohol and then placing it in a treatment furnace that can be vented with a protective gas. The temperature is raised to 800°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 2L / min. After reaching the temperature, the temperature is changed to a reducing atmosphere with a flow rate of 1L / 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 60 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.

[0062] The second step involves immersing the hydrogen-reduced corrosion-resistant hot-rolled high-strength steel sheet in a fluxing agent. The fluxing agent comprises the following components: zinc chloride 300 g / L, potassium chloride 40 g / L, aluminum chloride 75 g / L, cerium nitrate 10 g / L, sodium molybdate 40 g / L, potassium titanate 5 g / L, tetrabutyl titanate 3 g / L, triphenyl phosphate 10 g / L, ammonium polyphosphate 3 g / L, and water as the balance. The fluxing agent temperature is 75°C, and the immersion time is 120 seconds. After immersion, the surface is dried, forming a fluxing agent layer with a thickness of 48 μm on the surface of the corrosion-resistant hot-rolled high-strength steel sheet.

[0063] The third step involves immersing the corrosion-resistant hot-rolled high-strength steel sheet, which has been soaked in flux, into a Zn-Al-Mg alloy plating bath for hot-dip galvanizing. The chemical composition of the Zn-Al-Mg alloy plating bath, by mass percentage, is: Si: 0.3%, Re: 0.3%, Al: 12.3%, Mg: 5%, Ti: 0.01%, V: 0.1%, Ru: 0.02%, W: 0.05%, Pb: 0.002%, Cu: 0.001%, Fe: 0.01%, Cd: 0.002%, with the balance being Zn. The hot-dip galvanizing bath temperature is 470℃, and the hot-dip galvanizing time is 120s, resulting in a 320μm thick hot-dip zinc layer on the flux surface.

[0064] 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. Above this is a reduced iron layer, a continuous layer formed by reducing the original iron oxide layer on the high-strength steel surface. The surface of the reduced iron layer contains compounds formed by the reaction of the flux, constituting a flux layer. This layer is discontinuous, and this structure facilitates the adhesion of the subsequent galvanized layer. The top layer is a zinc-aluminum-magnesium hot-dip galvanized layer approximately 320 μm thick, with uniform and dense thickness, exhibiting 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, significantly enhancing its service life and reliability in complex environments.

[0065] In this embodiment, the performance indicators of the hot-rolled high-strength steel galvanized sheet are as follows: the corrosion potential is -1.43V and the corrosion current density is 9.073×10⁻⁶ in the electrochemical workstation test results. -7 A / cm 2 The polarization resistance is 12361 Ω·cm 2 The coating bonding strength is 768 MPa.

[0066] The results show that after preparing the Zn-Al-Mg 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 in the electrochemical workstation test results is -1.35 to -1.43 V, and the corrosion current density is 9.072 × 10⁻⁶. -7 ~9.152×10 -7 A / cm 2 The polarization resistance is 10053~12361Ω·cm 2 The coating adhesion strength is 753–768 MPa. This invention introduces potassium titanate, sodium molybdate, and tetrabutyl titanate to form a dense oxide film on the surface of the reduced iron layer, enhancing the coating adhesion. Rare earth elements such as cerium nitrate are added; cerium nitrate and sodium molybdate work synergistically to improve corrosion resistance. An acid-free hydrogen reduction process is employed, reducing the oxide scale through a hydrogen-nitrogen mixture, avoiding acid pickling contamination. By optimizing the fluxing and hot-dip plating parameters, the characteristics of the reduced iron layer can be adapted. Adding Ru and W elements to the Zn-Al-Mg alloy plating bath further improves the coating density and corrosion resistance. Combined with microalloying of the plating bath, the interfacial bonding problem between the reduced iron layer and the coating is solved.

Claims

1. A plating aid for a hot-dip galvanized layer of a high-strength steel sheet based on acid-free hydrogen reduction, characterized by, The components of the plating aid include: zinc chloride 110-300 g / L, potassium chloride 40-100 g / L, aluminum chloride 50-100 g / L, cerium nitrate 10-50 g / L, sodium molybdate 10-40 g / L, potassium titanate 1-5 g / L, tetrabutyl titanate 1-3 g / L, triphenyl phosphate 2-10 g / L, surfactant 1-3 g / L, and water in balance, and the surfactant is polyphosphoric acid ammonium.

2. The plating aid for a hot-dip galvanizing layer of a high-strength steel sheet based on a pickling-free hydrogen reduction according to claim 1, characterized by Cerium nitrate 20 g / L, sodium molybdate 30 g / L, potassium titanate 2 g / L, tetrabutyl titanate 2 g / L, triphenyl phosphate 6 g / L, and surfactant 2 g / L.

3. A high-strength steel sheet hot dip galvanizing process based on acid-free hydrogen reduction using the plating accelerator of claim 1 or 2, characterized by, The method comprises the following steps: Firstly, after the corrosion-resistant hot-rolled high-strength steel plate is degreased with alcohol, it is placed in a treatment furnace capable of introducing protective gas, and is heated to 500-1000 ℃ at a heating rate of 10-20 ℃ / min in a high-purity Ar protective atmosphere at a flow rate of 1-2 L / min; after the temperature is raised, a reducing atmosphere is introduced at a flow rate of 1-3 L / min, the reducing atmosphere is hydrogen-nitrogen mixed gas with a hydrogen volume fraction of 30-60%, and the temperature is maintained for 60-120 min in the reducing atmosphere; then, high-purity Ar is introduced at a flow rate of 1-2 L / min, and the corrosion-resistant hot-rolled high-strength steel plate is naturally cooled to room temperature; Secondly, the hydrogen-reduced corrosion-resistant hot-rolled high-strength steel plate is immersed in a plating aid, and the plating aid is uniformly mixed from the following components: zinc chloride 110-300 g / L, potassium chloride 40-100 g / L, aluminum chloride 50-100 g / L, cerium nitrate 10-50 g / L, sodium molybdate 10-40 g / L, potassium titanate 1-5 g / L, tetrabutyl titanate 1-3 g / L, triphenyl phosphate 2-10 g / L, surfactant 1-3 g / L, and water in balance; Thirdly, the corrosion-resistant hot-rolled high-strength steel plate immersed in the plating aid is immersed in a Zn-Al-Mg alloy plating solution for hot-dip plating, and the chemical components in the Zn-Al-Mg alloy plating solution are as follows in percentage by mass: 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: 0.01%-0.02%, W: 0.01%-0.05%, Pb: ≤0.003%, Cu: ≤0.002%, Fe: ≤0.05%, Cd: ≤0.002%, and the balance is Zn. In the second step, the temperature of the plating aid is 20-80 ℃, the corrosion-resistant hot-rolled high-strength steel plate is immersed in the plating aid for 10-120 s, and the surface is dried after immersion to form a plating aid layer with a thickness of 15-50 μm on the surface of the corrosion-resistant hot-rolled high-strength steel plate.

4. High-strength steel sheet hot dip galvanizing process based on acid-free hydrogen reduction according to claim 3, characterized in that, In the third step, the temperature of the hot-dip plating solution is 460-480 ℃, and the hot-dip plating time is 5-120 s, so as to obtain a hot-dip galvanized layer with a thickness of 150-320 μm on the surface of the plating aid.

5. The high strength steel sheet hot dip galvanizing process based on acid-free hydrogen reduction according to claim 3, characterized in that, In the third step, Ru: 0.012%, and W: 0.03%.

6. The high strength steel sheet hot dip galvanizing process based on acid-free hydrogen reduction according to claim 3, characterized in that, ​

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