Aluminum alloy plated steel sheet with high press efficiency and method for manufacturing the same

Abstract

This application relates to a high-stamping-efficiency aluminum alloy coated steel sheet and its preparation method, belonging to the technical field of metal coating sheet. The steel sheet includes a substrate, a coating, and a surface treatment layer; wherein, by mass fraction, the chemical composition of the coating is: Fe: 0.50%~2.50%, Mg: 2%~6%, Si: 5%~10%, RE: 0.05%~0.30%, with the remainder being Al and unavoidable impurities; by mass fraction, the surface treatment layer is composed of raw material powder, the composition of which includes: aluminum alloy powder: 40%~60%, inorganic powder: 15%~25%, and metal oxide powder: 25%~45%. By optimizing the coating composition design and innovating the surface treatment process, a composite powder treatment layer is formed on the substrate surface. This process employs vacuum powder spraying and chromium-free passivation technology, combined with specific hot stamping parameter control, to significantly improve the heating response speed and hot stamping efficiency of steel plates. It is especially suitable for laser-welded plates of unequal thickness and rolled plates of varying thickness, shortening the production cycle by more than 20% while ensuring surface performance, thus achieving efficient and environmentally friendly manufacturing.

Description

Technical Field

[0001] This application relates to the field of metal coating technology, and more particularly to a high-stamping-efficiency aluminum alloy coated steel sheet and its preparation method. Background Technology

[0002] Hot stamping is a key technology for improving vehicle body safety. This process first heats high-strength steel sheets to a fully austenitic state, then stamps them, effectively solving problems such as springback and cracking found in traditional cold stamping, and significantly increasing the application rate of ultra-high-strength steel sheets in vehicle bodies. However, this process requires prolonged high-temperature heating of the steel sheets, resulting in enormous energy consumption. Especially when using aluminum-silicon coated steel sheets, the extremely high thermal reflectivity of the aluminum-silicon coated steel surface further prolongs the heating time, exacerbating energy consumption and carbon emission pressures.

[0003] Currently, hot-stamped steel sheets with aluminum-silicon coatings face a dual challenge in terms of efficiency and compatibility: on the one hand, the high heat reflectivity of the coating significantly reduces the heating rate of the steel sheet, making it difficult to meet the requirements of energy conservation and emission reduction; on the other hand, when applied to laser-welded steel sheets of unequal thickness and rolled steel sheets of varying thickness, the different heating rates between the thick and thin areas often force an extension of the overall heating time. This leads to a deterioration in the mechanical properties of the thin areas of the steel sheet, thereby restricting the design freedom of integrated complex parts.

[0004] Existing technologies attempt to improve steel plates through surface coatings, such as applying silicon-containing compounds or polymer layers to the coating surface. While these methods can improve the heat absorption efficiency of steel plates, they also introduce new process defects: silicon-containing coatings tend to remain on the steel plate surface, affecting the adhesion of subsequent coatings; while excessively thick polymer coatings increase the difficulty of passivation, are prone to cracking, and release harmful substances. These limitations restrict the industrial application potential of such surface coating improvement technologies. Summary of the Invention

[0005] This application provides a high-stamping-efficiency aluminum alloy coated steel sheet and its preparation method to solve the following technical problem: how to improve the hot stamping efficiency of aluminum alloy coated steel sheet.

[0006] In a first aspect, embodiments of this application provide a high-stamping-efficiency aluminum alloy coated steel sheet, the steel sheet comprising a substrate, a coating, and a surface treatment layer;

[0007] The chemical composition of the coating, by mass fraction, is: Fe: 0.50%~2.50%, Mg: 2%~6%, Si: 5%~10%, RE: 0.05%~0.30%, with the remainder being Al and unavoidable impurities; By mass fraction, the surface treatment layer is composed of raw material powder, the composition of which includes: aluminum alloy powder: 40%~60%, inorganic powder: 15%~25%, and metal oxide powder: 25%~45%.

[0008] Optionally, the substrate is hot-stamped steel, and the ratio of the maximum thickness to the minimum thickness of the hot-stamped steel is <3.

[0009] Optionally, the thickness of the coating on one side is 20μm to 60μm.

[0010] Optionally, the thickness of the surface treatment layer is 100nm~1500nm, and the roughness of the surface treatment layer is 0.5μm~2.0μm.

[0011] Optionally, the average particle size of the raw material powder is 400 mesh to 600 mesh.

[0012] Optionally, the chemical composition of the aluminum alloy powder, by mass fraction, is: Mn: 0.50%~1.50%, Fe: 2.50%~5.00%, Cu: 2%~5%, with the remainder being Al and unavoidable impurities.

[0013] Optionally, the metal oxide powder includes: Fe3O4, FeMnCuO4 and Mn3O4; wherein the mass fraction of Fe3O4 is 10%~20%, the mass fraction of FeMnCuO4 is 10%~15%, and the mass fraction of Mn3O4 is 5%~10%.

[0014] Optionally, the inorganic powder includes at least one of molybdenum disulfide, graphite, carbon black, and silicon carbide; The particle size of the molybdenum disulfide is 100nm~500nm.

[0015] Optionally, the surface treatment layer has the following properties: surface reflectivity of 0.1~0.4.

[0016] Secondly, embodiments of this application provide a method for preparing the steel plate described in the first aspect, the method comprising: The coated steel strip with the following chemical composition was obtained: Fe: 0.50%~2.50%, Mg: 2%~6%, Si: 5%~10%, RE: 0.05%~0.30%, with the remainder being Al and unavoidable impurities; The coated steel strip is subjected to powder spraying, passivation treatment and hot stamping in sequence to obtain aluminum alloy coated steel sheet.

[0017] Optionally, before the powder spraying, the raw material powder is pretreated by mixing the alkaline-washed MoS2 with the remaining raw material powder to obtain a composite powder. The pH of the alkaline wash is greater than 11, and the alkaline wash time is 30 min to 60 min.

[0018] Optionally, the temperature of the coated steel strip exiting the plating bath is 630℃~690℃.

[0019] Optionally, the fan cavity for powder spraying is a vacuum environment, the inlet temperature of the powder-sprayed strip is 610℃~650℃, the operating power of the powder-spraying fan is 70%~100% of the rated power of the fan, and the conveying speed of the powder-sprayed strip is 80m / min~120m / min.

[0020] Optionally, the passivation treatment uses a chromium-free passivation solution composed of water-based epoxy resin, and the passivation film thickness is 0.5μm~2.0μm.

[0021] Optionally, the heating temperature of the hot stamping is 700℃~1000℃, and the heating time of the hot stamping is 3min~10min.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a high-stamping-efficiency aluminum alloy coated steel sheet, comprising a substrate, a coating, and a surface treatment layer. The coating, by mass fraction, has the following chemical composition: Fe: 0.50%~2.50%, Mg: 2%~6%, Si: 5%~10%, RE: 0.05%~0.30%, with the remainder being Al and unavoidable impurities. The surface treatment layer, by mass fraction, is composed of raw material powder, comprising: aluminum alloy powder: 40%~60%, inorganic powder: 15%~25%, and metal oxide powder: 25%~45%. Through innovative synergistic design of the surface treatment layer and coating composition, the thermal response mechanism of the steel sheet is fundamentally reconstructed. In the surface treatment layer of the steel sheet, a composite powder system with a specific ratio can form a heat-absorbing and heat-storing medium with a multi-scale structure during the powder spraying process. The nanoscale inorganic particles contained in this medium significantly reduce the light reflectivity of the steel plate coating surface, thereby converting more radiant heat energy into molecular vibrational energy. Simultaneously, the metal oxides and aluminum alloy powder in the medium form a gradient heat dissipation channel, accelerating heat transfer deeper into the steel plate coating. Furthermore, the introduction of rare earth elements and magnesium into the steel plate coating optimizes the thermal conductivity of the aluminum-silicon interface, shortening the heat transfer path required to reach the steel substrate and promote austenitization of the steel matrix. This synergistic mechanism of surface heat absorption enhancement and internal heat conduction significantly shortens the overall heating time of the steel plate and brings the heating rate of thicker areas closer to that of thinner areas. Therefore, while retaining the oxidation resistance advantages of aluminum-silicon coated steel plates, the heating efficiency bottleneck of traditional processes has been successfully overcome.

[0023] In summary, based on a three-level thermal management architecture that combines surface heat absorption enhancement, interfacial thermal conduction, and substrate heat homogenization, high-speed directional heat transfer in coated steel sheets is achieved, systematically solving the problems of heating delay caused by high reflectivity and thermal imbalance in plates of unequal thickness. Attached Figure Description

[0024] 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.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0026] Figure 1 A flowchart illustrating a high-stamping-efficiency aluminum alloy coated steel sheet and its preparation method, provided in an embodiment of this application; Figure 2 The temperature rise curve of the aluminum alloy coated steel sheet provided in the embodiments of this application during the heating process. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0028] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges between 1 and 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including" and "contains" used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship. "And / or" indicates that multiple situations can exist individually or simultaneously. Expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0029] In a first aspect, embodiments of this application provide a high-stamping-efficiency aluminum alloy coated steel sheet, the steel sheet comprising a substrate, a coating, and a surface treatment layer; The chemical composition of the coating, by mass fraction, is: Fe: 0.50%~2.50%, Mg: 2%~6%, Si: 5%~10%, RE: 0.05%~0.30%, with the remainder being Al and unavoidable impurities; The positive effects of limiting the Fe mass fraction in the coating to 0.50%~2.50% include: Adding Fe to the coating can increase the alloying rate of the coating during the heating process of the steel sheet and shorten the time required for complete alloying. However, when the Fe mass fraction exceeds 2.50%, the thermal conductivity of the coating decreases, which adversely affects the heating rate of the steel sheet. Conversely, when the Fe mass fraction is below 0.50%, the alloying rate of the coating cannot be effectively improved. For example, the Fe mass fraction in the coating can be 0.50%, 1.00%, 1.50%, 2.00%, 2.50%, etc.

[0030] The positive effects of limiting the Mg mass fraction in the coating to 2%~6%: Adding Mg to the coating primarily improves its thermal conductivity. After adding Mg, a Mg₂Si phase is formed inside the coating, which consumes some Si, thereby improving the coating's thermal conductivity. However, when the Mg mass fraction exceeds 6%, the excess Mg causes lattice distortion in the aluminum atoms, thus reducing the coating's thermal conductivity. Conversely, when the Mg mass fraction is below 2%, it cannot effectively improve the coating's thermal conductivity. For example, the Mg mass fraction in the coating can be 2%, 3%, 4%, 5%, 6%, etc.

[0031] The positive effects of limiting the Si mass fraction in the coating to 5%~10%: Si can be added to the coating to improve its thermal conductivity. During heating, Fe elements in the substrate diffuse into the coating, forming an Fe-Al phase. This phase causes the coating to expand, thus reducing thermal conductivity. Adding Si can effectively suppress the formation of the Fe-Al phase, thereby improving the thermal conductivity of the coating. However, when the Si mass fraction exceeds 10%, excess Si will precipitate in the coating, leading to a decrease in thermal conductivity; when the Si mass fraction is below 5%, it cannot effectively improve the thermal conductivity of the coating. For example, the Si mass fraction in the coating can be 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0032] The positive effects of limiting the RE (refined organic matter) mass fraction in the coating to 0.05%~0.30% are as follows: Adding RE to the coating mainly refines the grain size, reduces the impurity content, and improves the thermal conductivity. However, when the RE mass fraction exceeds 0.3%, it actually reduces the thermal conductivity of the coating. When the RE mass fraction is below 0.05%, it cannot effectively improve the thermal conductivity of the coating. For example, the RE mass fraction in the coating can be 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, etc.

[0033] By mass fraction, the surface treatment layer is composed of raw material powder, the composition of which includes: aluminum alloy powder: 40%~60%, inorganic powder: 15%~25%, and metal oxide powder: 25%~45%.

[0034] The positive effects of limiting the mass fraction of aluminum alloy powder in the surface treatment layer to 40%~60% are: to ensure consistency in composition and properties between the surface treatment layer and the coating, thereby improving the adhesion between the surface treatment layer and the substrate. When the mass fraction of aluminum alloy powder exceeds 60%, the heat resistance of the surface treatment layer decreases, and the production cost of the steel plate increases accordingly. Conversely, when the mass fraction of aluminum alloy powder is less than 40%, the adhesion of the surface treatment layer is insufficient, and the surface treatment layer is prone to peeling off during subsequent processing of the steel plate. For example, the mass fraction of aluminum alloy powder in the surface treatment layer can be 40%, 45%, 50%, 55%, 60%, etc.

[0035] The advantages of limiting the mass fraction of inorganic powder in the surface treatment layer to 15%~25% are as follows: When the mass fraction of inorganic powder in the surface treatment layer is less than 15%, the softening temperature of the surface treatment layer will drop below 650℃, causing the surface treatment layer to soften prematurely during heating and adhere to the rolls, thereby reducing the heat absorption performance of the surface treatment layer. When the mass fraction of inorganic powder exceeds 25%, it will lead to increased brittleness and pulverization of the surface treatment layer, making it prone to powder shedding during subsequent stamping. Therefore, controlling the mass fraction of inorganic powder within the specified range can ensure that the surface treatment layer maintains stable high heat absorption performance during heating and melting, while preventing powder shedding during stamping. For example, the mass fraction of inorganic powder in the surface treatment layer can be 15%, 20%, 25%, etc.

[0036] The positive effects of limiting the mass fraction of metal oxide powder in the surface treatment layer to 25%~45% are as follows: When the mass fraction of metal oxide powder in the surface treatment layer is less than 25%, the heat resistance of the surface treatment layer will decrease, and it will easily soften or melt when the heating temperature reaches below 700℃. If the mass fraction of metal oxide powder exceeds 45%, it will lead to a decrease in the plasticity of the surface treatment layer, and powder shedding will easily occur during the subsequent production process of the steel plate. For example, the mass fraction of metal oxide powder in the surface treatment layer can be 25%, 30%, 35%, 40%, 45%, etc.

[0037] In some embodiments, the substrate is hot-stamped steel, and the ratio of the maximum thickness to the minimum thickness of the hot-stamped steel is less than 3.

[0038] Hot-stamped steel is a 1500MPa grade hot-formed steel. Its chemical composition includes C, Si, Mn, Cr, B, and Ti, with the remainder being Fe and unavoidable impurities. The thickness of the hot-stamped steel is 1.4mm. If the hot-stamped steel is used for laser-welded plates or differentially thick rolled plates, the ratio of the maximum thickness to the minimum thickness of the hot-stamped steel is <3. This thickness ratio constrains and coordinates the heat conduction process in different thickness regions. For example, the ratio of the maximum thickness to the minimum thickness of the hot-stamped steel can be 1, 2, etc.

[0039] In some embodiments, the thickness of the coating on one side is 20 μm to 60 μm.

[0040] The thickness of the coating on one side is between 20μm and 60μm to balance antioxidant protection and heat transfer efficiency. For example, the thickness of the coating on one side can be 20μm, 30μm, 40μm, 50μm, 60μm, etc.

[0041] In some embodiments, the thickness of the surface treatment layer is 100nm~1500nm, and the roughness of the surface treatment layer is 0.5μm~2.0μm.

[0042] The thickness of the surface treatment layer is between 100nm and 1500nm, which optimizes the photothermal conversion capability and structural stability of the heat absorption layer. For example, the thickness of the surface treatment layer can be 500nm, 1000nm, 1500nm, etc.

[0043] In some embodiments, the average particle size of the raw material powder is 400 mesh to 600 mesh.

[0044] The average particle size of the raw material powder is between 400 mesh and 600 mesh to ensure the uniformity of powder fluidization and the forming quality of the surface treatment layer during the powder spraying process. For example, the average particle size of the raw material powder can be 400 mesh, 500 mesh, 600 mesh, etc.

[0045] In some embodiments, the chemical composition of the aluminum alloy powder, by mass fraction, is: Mn: 0.50%~1.50%, Fe: 2.50%~5.00%, Cu: 2%~5%, with the remainder being Al and unavoidable impurities.

[0046] The positive effects of limiting the Mn mass fraction in aluminum alloy powder to 0.50%~1.50%: Adding Mn primarily improves the heat resistance of the aluminum alloy powder, thereby enhancing the thermal stability of the steel plate surface treatment layer. When the Mn mass fraction exceeds 1.5%, the improvement in the heat resistance of the steel plate surface treatment layer is limited, while significantly deteriorating the processing performance of the aluminum alloy powder. Conversely, when the Mn mass fraction is below 0.5%, it cannot effectively improve the heat resistance of the steel plate surface treatment layer. Therefore, controlling the Mn mass fraction within the specified range can maintain good processability while ensuring the heat resistance of the steel plate surface treatment layer. For example, the Mn mass fraction in the aluminum alloy powder can be 0.50%, 1.00%, 1.50%, etc.

[0047] The positive effects of limiting the Fe mass fraction in aluminum alloy powder to 2.50%~5.00%: The main purpose of adding Fe is to improve the heat resistance of aluminum alloy powder and ensure the performance consistency between the powder and the coating. When the Fe mass fraction exceeds 5%, it significantly deteriorates the processing performance of aluminum alloy powder, leading to embrittlement or cracking during subsequent processing. When the Fe mass fraction is below 2.5%, it cannot effectively improve the heat resistance of aluminum alloy powder. For example, the Fe mass fraction in aluminum alloy powder can be 2.50%, 3.00%, 3.50%, 4.00%, 4.50%, 5.00%, etc.

[0048] The positive effects of limiting the Cu mass fraction in aluminum alloy powder to 2%~5%: The main purpose of adding Cu is to improve the strength and machinability of aluminum alloys and ensure the dimensional uniformity of the aluminum alloy powder. When the Cu mass fraction exceeds 5%, the machinability of the aluminum alloy deteriorates significantly. When the Cu mass fraction is below 2%, it cannot effectively improve the strength of the aluminum alloy. For example, the Cu mass fraction can be 2%, 3%, 4%, 5%, etc. In some embodiments, the metal oxide powder comprises: Fe3O4, FeMnCuO4 and Mn3O4; wherein the mass fraction of Fe3O4 is 10%~20%, the mass fraction of FeMnCuO4 is 10%~15%, and the mass fraction of Mn3O4 is 5%~10%.

[0049] To improve the performance of the surface treatment layer on steel plates, metal oxides are added primarily for two purposes: firstly, to further enhance the heat absorption capacity of the surface treatment layer; and secondly, to strengthen the adhesion and performance consistency between the surface treatment layer and the coating. After high-temperature heating, the surface of the steel plate mainly forms a coating layer composed of oxides of Al2O3, Fe3O4, Mn, and Si. To ensure performance consistency between the surface treatment layer and the coating, Fe and Mn oxides are specifically added to the metal oxide powder. Specifically, the addition of Fe3O4 primarily improves the thermal radiation absorption rate (emissivity) and heat resistance of the surface treatment layer; the addition of FeMnCuO4 aims to enhance the heat absorption capacity of the surface treatment layer; and the addition of Mn3O4 mainly improves the corrosion resistance of the surface treatment layer. For example, the mass fraction of Fe3O4 in the metal oxide powder can be 10%, 15%, 20%, etc.; the mass fraction of FeMnCuO4 in the metal oxide powder can be 11%, 13%, 15%, etc.; and the mass fraction of Mn3O4 in the metal oxide powder can be 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0050] In some embodiments, the inorganic powder includes at least one of molybdenum disulfide, graphite, carbon black, and silicon carbide; The particle size of the molybdenum disulfide is 100nm~500nm.

[0051] Adding inorganic powder to the surface treatment layer of steel plates is primarily to improve the high-temperature resistance and reduce the heat reflectivity of the surface treatment layer. The inorganic powder must contain nano-molybdenum disulfide because, compared to traditional molybdenum disulfide, nano-molybdenum disulfide is easier to uniformly disperse during preparation, and it also exhibits high surface energy and excellent heat resistance. During the heating and stamping processes of the steel plate, nano-molybdenum disulfide can stably adsorb onto the steel plate surface, thus providing effective lubrication during the stamping stage. For example, the particle size of molybdenum disulfide can be 100nm, 200nm, 300nm, 400nm, 500nm, etc.

[0052] In some embodiments, the surface treatment layer has the following properties: surface reflectivity of 0.1 to 0.4.

[0053] Surface reflectivity: The ability of a material surface to reflect incident light, defined as the ratio of reflected luminous flux to incident luminous flux. A surface reflectivity between 0.1 and 0.4 significantly improves the heating rate of steel sheets during hot stamping by enhancing the absorption efficiency of thermal radiation by the coating. Simultaneously, the micro / nano structure formed by powder spraying optimizes heat conduction uniformity to suppress localized overheating, ultimately achieving a dual breakthrough in energy efficiency and forming quality. For example, surface reflectivity can be 0.1, 0.2, 0.3, 0.4, etc.

[0054] Figure 1 This is a flowchart illustrating a high-stamping-efficiency aluminum alloy coated steel sheet and its preparation method, provided as an embodiment of this application.

[0055] Please see Figure 1 Secondly, this application provides a method for preparing the steel plate described in the first aspect, the method comprising: S1. A coated steel strip with the following chemical composition is obtained: Fe: 0.50%~2.50%, Mg: 2%~6%, Si: 5%~10%, RE: 0.05%~0.30%, with the remainder being Al and unavoidable impurities; S2. The coated steel strip is sequentially subjected to powder spraying, passivation treatment and hot stamping to obtain aluminum alloy coated steel sheet.

[0056] In some embodiments, the raw material powder is pretreated before the powder spraying, and the alkaline-washed MoS2 is mixed with the remaining raw material powder to obtain a composite powder. The pH of the alkaline wash is greater than 11, and the alkaline wash time is 30 min to 60 min.

[0057] Before spraying, the raw material powder is pretreated by alkali washing of nano-MoS2 in a solution with pH > 11, accompanied by electromagnetic stirring, for 30-60 minutes, followed by drying. Then, the alkali-washed MoS2 is thoroughly mechanically stirred with the raw material powder to obtain a composite powder. Alkali washing, through a high pH environment and prolonged contact time, purifies the surface oxides of MoS2, enhancing the interfacial activity of the MoS2 powder; electromagnetic stirring enhances the mass transfer efficiency of the alkali washing process, ensuring reaction uniformity; drying removes residual moisture from the surface, maintaining the thermal stability of the MoS2 powder; mechanical mixing integrates the alkali-washed MoS2 with the remaining raw material powder to form a composite powder with homogeneous dispersion characteristics. For example, the pH of the alkali washing can be 12, 13, 14, etc.; the alkali washing time can be 30, 40, 50, 60 minutes, etc.

[0058] In some embodiments, the temperature of the coated steel strip exiting the plating bath is 630°C to 690°C.

[0059] The temperature of the coated steel strip exiting the plating bath is between 630℃ and 690℃ to ensure that the surface treatment layer (including powder) can uniformly cover the coating surface. When the exit temperature of the coated steel strip is below 630℃, the fluidity of the coating decreases, resulting in uneven coverage of the surface treatment layer; while when the exit temperature is above 690℃, it will cause difficulties in the subsequent cooling process of the coating, thus increasing the production difficulty. For example, the exit temperature of the coated steel strip from the plating bath can be 630℃, 650℃, 670℃, 690℃, etc.

[0060] In some embodiments, the blower cavity for powder spraying is a vacuum environment, the inlet temperature of the powder-sprayed strip is 610℃~650℃, the operating power of the powder-spraying blower is 70%~100% of the rated power of the blower, and the conveying speed of the powder-sprayed strip is 80m / min~120m / min.

[0061] The main reasons for adopting powder spraying are as follows: (1) The powder spraying production process is simple and low-cost, and there is no need to develop complex chemical reagents for steel plates, and no pollution is generated during the production process; (2) The sprayed powder can form heterogeneous nucleation points on the surface of the steel plate coating, which promotes grain refinement during the cooling process of the coating, thereby further improving the isotropic degree of the coating surface, reducing the thermal reflectivity of the coating surface, and ultimately improving the heating efficiency of the steel plate.

[0062] The powder coating fan chamber is a vacuum environment to suppress the oxidation of the composite powder and promote uniform suspension. The strip inlet temperature is between 610℃ and 650℃ to control and ensure the melt spreading of the composite powder and the metallurgical bonding strength with the substrate. For example, the strip inlet temperature can be 610℃, 620℃, 630℃, 640℃, 650℃, etc. The powder coating fan operates at 70% to 100% of its rated power to provide the kinetic energy for the fluidized transport of the powder. For example, the fan operating power can be 70%, 80%, 90%, 100% of its rated power, etc. The strip conveying speed is between 80m / min and 120m / min to adjust and balance the deposition efficiency and uniformity of the surface treatment layer. For example, the strip conveying speed can be 80m / min, 90m / min, 100m / min, 110m / min, 120m / min, etc.

[0063] In some embodiments, the passivation treatment uses a chromium-free passivation solution composed of water-based epoxy resin, and the passivation film thickness is 0.5 μm to 2.0 μm.

[0064] The passivation treatment uses a chromium-free passivation solution composed of water-based epoxy resin, providing environmentally friendly corrosion protection while maintaining the interfacial compatibility of the surface treatment layer. The passivation film thickness is between 0.5 μm and 2.0 μm to balance the corrosion protection effectiveness of the passivation layer with the adhesion of the surface treatment layer. For example, the passivation film thickness can be 0.5 μm, 1.0 μm, 1.5 μm, 2.0 μm, etc.

[0065] In some embodiments, the heating temperature of the hot stamping is 700℃~1000℃, and the heating time of the hot stamping is 3min~10min.

[0066] The heating temperature for hot stamping is between 700℃ and 1000℃ to ensure complete austenitization of the matrix and subsequent phase transformation strengthening. For example, the heating temperature for hot stamping can be 700℃, 800℃, 900℃, 1000℃, etc. The heating time for hot stamping is between 3 minutes and 10 minutes to match the microstructure transformation kinetics of the steel sheet and optimize energy efficiency. For example, the heating time for hot stamping can be 3 minutes, 5 minutes, 7 minutes, 9 minutes, etc.

[0067] The product prepared by the method of preparing aluminum alloy coated steel sheet is the aforementioned aluminum alloy coated steel sheet. Since the method of preparing aluminum alloy coated steel sheet adopts some or all of the technical solutions of the embodiments of aluminum alloy coated steel sheet, it has at least all the beneficial effects brought about by the technical solutions of the aforementioned embodiments, which will not be elaborated here.

[0068] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0069] The chemical composition (mass percentage / %) of the coatings in the examples and comparative examples is shown in Table 1.

[0070] Table 1

[0071] The composition (mass percentage / %) of the raw material powder for the surface treatment layer in the examples and comparative examples is shown in Table 2.

[0072] Table 2

[0073] The chemical composition (mass percentage / %) of the aluminum alloy powders in the examples and comparative examples is shown in Table 3.

[0074] Table 3

[0075] The composition (mass percentage / %) of the inorganic powders and metal oxide powders in the examples and comparative examples is shown in Table 4.

[0076] Table 4

[0077] Based on the above embodiments and comparative examples, this embodiment also provides a method for preparing a high-stamping-efficiency aluminum alloy coated steel sheet, comprising the following steps: The coated steel strip with the chemical composition described in Table 1 was obtained; The coated steel strip is sequentially subjected to powder spraying, passivation treatment, and hot stamping to obtain an aluminum alloy coated steel sheet. The process parameters are shown in Table 5.

[0078] The process parameters for the examples and comparative examples are shown in Table 5.

[0079] Table 5

[0080] The performance of the surface treatment layers in the examples and comparative examples is shown in Table 6.

[0081] Table 6

[0082] The data tables above provide a clear comparison of the differences between various embodiments and comparative examples. The following conclusions can be drawn: As can be seen from the data in Table 6, the surface reflectance of the surface treatment layer of the steel plate provided in this application embodiment is 0.11~0.29, the roughness of the surface treatment layer is 1.3μm~1.8μm, the thickness of the surface treatment layer is 500nm~1500nm, and the time for the steel plate to reach 950℃ is 85s~132s.

[0083] As shown in Comparative Example 1, when the mass fraction of Fe in the coating exceeds the range, the thermal conductivity of the coating will decrease, thereby prolonging the time it takes for the steel plate to reach 950°C.

[0084] Comparative Example 2 shows that when the mass fraction of aluminum alloy powder in the raw material powder of the surface treatment layer is lower than required, under the same powder spraying process conditions, the reduction in the thickness of the surface treatment layer leads to a decrease in the heat absorption performance of the steel plate.

[0085] As shown in Comparative Example 3, when the mass fractions of Mn and Fe in aluminum alloy powder exceed the requirements, it will lead to a decrease in the thermal conductivity of the aluminum alloy powder, thereby affecting the heat absorption performance of the steel plate.

[0086] As shown in Comparative Example 4, when MoS2 is not added to the inorganic powder, the reflectivity of the surface treatment layer increases, and the melting point of the surface treatment layer decreases, so it cannot play a good role in heat absorption during heating, resulting in a decrease in the heat absorption performance of the steel plate.

[0087] As can be seen from Examples 1-4 and Comparative Examples 1-4, Examples 1-4, employing the coating and powder composition design scheme provided by this invention and combined with corresponding production process adjustments, can achieve the production of steel plates with high hot stamping efficiency. This scheme can shorten the heating time of the steel plate during the hot stamping process by more than 25% compared to traditional materials. It is particularly suitable for complex components such as laser-welded steel plates and differentially thick rolled steel plates. Furthermore, the embodiments of this invention generate less environmental pollution during the production process and have lower production costs, possessing excellent industrial feasibility and facilitating large-scale industrial production.

[0088] Appendix Figure 2 Detailed explanation: Figure 2 The temperature rise curve of the aluminum alloy coated steel sheet provided in the embodiments of this application during the heating process. Figure 2 It can be seen that compared with aluminum alloy coated steel plates without surface treatment layers, the steel plates of Examples 1 to 4 of this application have significantly improved heating rates during the heating process and significantly shortened the time required to reach the same temperature; and with the optimization of the surface treatment layer performance, the heating time of Examples 1 to 4 shows a gradual shortening trend, which intuitively demonstrates the effective improvement of the surface treatment layer design of this application on the heating efficiency of the steel plate.

[0089] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: This invention provides a high-stamping-efficiency aluminum alloy coated steel sheet. A surface treatment layer is constructed on the steel sheet surface through powder spraying, and the combined effect of inorganic powder and metal oxide powder significantly improves the coating's heat absorption efficiency and interfacial bonding strength while achieving efficient and environmentally friendly production. Ultimately, this achieves synergistic optimization of the steel sheet's heating rate and overall service performance. Powder spraying simplifies the steel sheet production process and avoids pollution. Powder particles act as heterogeneous nucleation points to refine the coating grains, enhancing heat absorption capacity. Inorganic components strengthen the surface treatment layer's high-temperature resistance and photothermal conversion efficiency. Metal oxide components improve the heat absorption uniformity of the surface treatment layer and bridge the interface between the surface treatment layer and the coating, thereby ensuring the steel sheet's thermal conductivity stability and coating structural integrity during hot stamping. This end-to-end solution overcomes the technical bottlenecks of traditional coatings in terms of heating efficiency and reliability.

[0090] 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 in this application.

Claims

1. A high-stamping-efficiency aluminum alloy coated steel sheet, characterized in that, The steel plate includes a substrate, a coating, and a surface treatment layer; The chemical composition of the coating, by mass fraction, is: Fe: 0.50%~2.50%, Mg: 2%~6%, Si: 5%~10%, RE: 0.05%~0.30%, with the remainder being Al and unavoidable impurities; By mass fraction, the surface treatment layer is composed of raw material powder, the composition of which includes: aluminum alloy powder: 40%~60%, inorganic powder: 15%~25%, and metal oxide powder: 25%~45%.

2. The steel plate according to claim 1, characterized in that, The substrate is hot-stamped steel, and the ratio of the maximum thickness to the minimum thickness of the hot-stamped steel is <3; and / or, The thickness of the coating on one side is 20μm~60μm; and / or, The thickness of the surface treatment layer is 100 nm to 1500 nm, and the roughness of the surface treatment layer is 0.5 μm to 2.0 μm; and / or, The average particle size of the raw material powder is 400 mesh to 600 mesh.

3. The steel plate according to claim 1, characterized in that, The chemical composition of the aluminum alloy powder, by mass fraction, is: Mn: 0.50%~1.50%, Fe: 2.50%~5.00%, Cu: 2%~5%, with the remainder being Al and unavoidable impurities; and / or, The metal oxide powder comprises: Fe3O4, FeMnCuO4 and Mn3O4; wherein the mass fraction of Fe3O4 is 10%~20%, the mass fraction of FeMnCuO4 is 10%~15%, and the mass fraction of Mn3O4 is 5%~10%.

4. The steel plate according to claim 1, characterized in that, The inorganic powder includes at least one of molybdenum disulfide, graphite, carbon black, and silicon carbide; The particle size of the molybdenum disulfide is 100nm~500nm.

5. The steel plate according to claim 1, characterized in that, The surface treatment layer has the following properties: surface reflectivity of 0.1~0.

4.

6. A method for preparing a steel plate according to any one of claims 1 to 5, characterized in that, The method includes: A coated steel strip having the chemical composition described in any one of claims 1 to 5 is obtained; The coated steel strip is subjected to powder spraying, passivation treatment and hot stamping in sequence to obtain aluminum alloy coated steel sheet.

7. The method according to claim 6, characterized in that, Before the powder spraying, the raw material powder is pretreated by mixing the alkaline-washed MoS2 with the remaining raw material powder to obtain a composite powder. The pH of the alkaline wash is greater than 11, and the alkaline wash time is 30 min to 60 min.

8. The method according to claim 6, characterized in that, The temperature of the coated steel strip exiting the plating bath is 630℃~690℃; and / or, The fan cavity for powder spraying is a vacuum environment, the inlet temperature of the powder-sprayed strip is 610℃~650℃, the operating power of the powder-spraying fan is 70%~100% of the rated power of the fan, and the conveying speed of the powder-sprayed strip is 80m / min~120m / min.

9. The method according to claim 6, characterized in that, The passivation treatment uses a chromium-free passivation solution composed of water-based epoxy resin, and the passivation film thickness is 0.5μm~2.0μm.

10. The method according to claim 6, characterized in that, The heating temperature for hot stamping is 700℃~1000℃, and the heating time for hot stamping is 3min~10min.

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