High-corrosion-resistance coating hot forming steel, hot forming component and preparation method

Abstract

The invention relates to high-corrosion-resistance coating hot forming steel, a hot forming component and a preparation method, and belongs to the technical field of automobile steel. The coating hot forming steel comprises a steel base body and a coating attached to at least part of the surface of the steel base body. Wherein the steel matrix comprises the following chemical components in percentage by mass: 0.15%-0.35% of C, 0.1%-0.4% of Si, 2%-5% of Mn, less than or equal to 0.05% of P, less than or equal to 0.05% of S, 0.05%-0.2% of V, 0.05%-0.1% of Ti, 0.05%-0.5% of Mo, less than or equal to 0.05% of N, 0.001%-0.003% of B and a matrix element Fe; the coating comprises the following chemical components in percentage by mass: 8%-15% of Si, 1%-3% of Fe, 0.5%-5% of Cr and the balance of Al. Through the component design of the plating layer, the Al-rich dendritic crystal layer is formed in the plating layer of the hot forming component, and the existence of the Al-rich dendritic crystal layer can improve the corrosion potential of the plating layer, so that the corrosion resistance of the hot forming component is improved.

Description

Technical Field

[0001] The present application relates to the technical field of automobile steel, and in particular to a high-corrosion-resistant coated hot-formed steel, a hot-formed component, and a preparation method thereof. Background Art

[0002] With the vigorous development of the domestic new energy vehicle industry, the requirements for the endurance of new energy vehicles are constantly increasing, which in turn puts higher requirements on the lightweight body. At the same time, the requirements for vehicle collision safety are also increasing year by year, and these demands urgently need to seek solutions from the body design. Increasing the proportion of high-strength steel used in the white body can not only reduce the weight of the body but also improve the collision safety of the body. At present, the advanced high-strength steels (AHSS) commonly used on the body include: low-alloy high-strength steel (HSLA), DP steel, CP steel, hot-formed steel, etc. Hot-formed steel is the largest single steel type used in the white body, and the use of hot-formed steel on mainstream models is more than 15%. Therefore, domestic hot-formed steel has also developed rapidly.

[0003] Currently, the most commonly used hot-formed steel is at the 1500MPa level, but with the rapid development of related technologies such as integrated door rings, the strength level of hot-formed steel has now extended to 500MPa-2000MPa. Uncoated hot-formed steel presents several problems during the hot-forming process, such as the need for protective gas to flow into the heating furnace, the generation of scale during the forming process, the formation of a decarburized layer during the heating process that affects performance, and the need for shot blasting of parts after forming. Hot-formed steel materials with coatings are now commonly used, with Al-Si coated hot-formed steel being the most widely used. The Al-Si coating offers excellent high-temperature resistance, produces no scale during the hot-forming process, and does not require shot blasting after production. However, the Al-Si coating has poor corrosion resistance and can only provide physical corrosion protection. Furthermore, the Al-Si coating has poor toughness, resulting in a large number of microcracks in the coating during the stamping process that affect corrosion resistance. Pure zinc coating has excellent corrosion resistance and still has cathodic protection even after hot forming. However, pure zinc coating also has its disadvantages, such as the easy occurrence of liquid zinc crack embrittlement (LME) phenomenon, which restricts the development of pure zinc hot-formed steel. Summary of the Invention

[0004] The present application provides a high-corrosion-resistant coated hot-formed steel, a hot-formed component and a preparation method to solve the following technical problem: how to improve the corrosion resistance of the hot-formed component.

[0005] In a first aspect, an embodiment of the present application provides a highly corrosion-resistant coated hot-formed steel, the coated hot-formed steel comprising a steel substrate and a coating attached to at least a portion of the surface of the steel substrate;

[0006] The chemical composition of the steel matrix includes, by mass fraction, C: 0.15% to 0.35%, Si: 0.1% to 0.4%, Mn: 2% to 5%, P≤0.05%, S≤0.05%, V: 0.05% to 0.2%, Ti: 0.05% to 0.1%, Mo: 0.05% to 0.5%, N≤0.05%, B: 0.001% to 0.003%, and matrix element Fe;

[0007] Calculated by mass fraction, the chemical composition of the coating includes: Si: 8% to 15%, Fe: 1% to 3%, Cr: 0.5% to 5%, and Al.

[0008] Optionally, the thickness of the coating is 10 μm to 35 μm.

[0009] In a second aspect, the present application provides a hot-formed component, which is made of the coated hot-formed steel described in the first aspect.

[0010] Optionally, the thermoformed component meets at least one of the following properties: tensile strength of 1400MPa to 2300MPa, yield strength of 900MPa to 1700MPa, and elongation after fracture A50 of 4% to 10%.

[0011] Optionally, the coating thickness of the thermoformed component is 15 μm to 60 μm.

[0012] Optionally, the coating of the hot-formed component includes: an Al-rich dendrite layer, a Si-rich layer, a diffusion layer and an alloy layer.

[0013] Optionally, the thickness of the Al-rich dendrite layer is 3 μm to 15 μm, and the thickness of the Si-rich layer is 1 μm to 3 μm.

[0014] In a third aspect, the present application provides a method for preparing the thermoformed component described in the second aspect, the method comprising:

[0015] Obtaining the coated hot-formed steel;

[0016] The coated hot-formed steel is sequentially heated and press-formed to obtain a hot-formed component.

[0017] Optionally, the heating temperature is 750° C. to 920° C., the heating time is 100s to 400s, and the heating atmosphere is air.

[0018] Optionally, the time interval between the heating and the stamping is 5s to 12s.

[0019] Optionally, the stamping temperature of the stamping forming is 500° C. to 800° C., the die-out temperature of the stamping forming is ≤200° C., and the die cooling rate of the stamping forming is ≥30° C. / s.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] An embodiment of the present application provides a high-corrosion-resistant coated hot-formed steel, wherein the coated hot-formed steel includes a steel substrate and a coating attached to at least a portion of the surface of the steel substrate; wherein, in terms of mass fraction, the chemical composition of the steel substrate includes: C: 0.15% to 0.35%, Si: 0.1% to 0.4%, Mn: 2% to 5%, P≤0.05%, S≤0.05%, V: 0.05% to 0.2%, Ti: 0.05% to 0.1%, Mo: 0.05% to 0.5%, N≤0.05%, B: 0.001% to 0.003%, and matrix element Fe; in terms of mass fraction, the chemical composition of the coating includes: Si: 8% to 15%, Fe: 1% to 3%, Cr: 0.5% to 5%, and Al. By adding the element Cr to the coating, Cr will diffuse to the surface of the coating during the heating process to form a stable oxide, thereby inhibiting the oxidation of element Al and reducing the consumption of Al. This helps to maintain a high Al content in the coating and form an Al-rich dendrite layer in the coating. The presence of the Al-rich dendrite layer can increase the corrosion potential of the coating, thereby improving the corrosion resistance of the hot-formed component. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 A schematic flow chart of a method for preparing a thermoformed component provided in an embodiment of the present application;

[0025] Figure 2 This is an SEM image of the coating cross section of the thermoformed component provided in Example 4 of the present application. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0027] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range; for example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range; in addition, whenever a numerical range is indicated in this document, it is meant to include any cited number (fractional or integer) within the indicated range.

[0028] As used herein, the terms "including," "comprising," and the like mean "including but not limited to." Relational terms such as "first" and "second" are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. "And / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, "plurality" means two or more; "at least one," "at least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items; for example, "at least one of a, b, or c" or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or plural. "Parts" notation, such as parts by weight or parts by mass, indicates the proportional relationship between components. In this article, the parameters described by ratio should be understood as the first term of the proportional formula, in the order in which they are described, and the proportional figures should be understood as the second term. For example, if the mass ratio of substances A, B, and C is 1:2:3, then substances A, B, and C should correspond to the proportional figures in the proportional formula, in the order in which they are described: that is, the mass of substance A:the mass of substance B:the mass of substance C = 1:2:3.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0030] In a first aspect, an embodiment of the present application provides a highly corrosion-resistant coated hot-formed steel, the coated hot-formed steel comprising a steel substrate and a coating attached to at least a portion of the surface of the steel substrate;

[0031] The chemical composition of the steel matrix includes, by mass fraction, C: 0.15% to 0.35%, Si: 0.1% to 0.4%, Mn: 2% to 5%, P≤0.05%, S≤0.05%, V: 0.05% to 0.2%, Ti: 0.05% to 0.1%, Mo: 0.05% to 0.5%, N≤0.05%, B: 0.001% to 0.003%, and matrix element Fe;

[0032] The positive effect of limiting the C mass fraction to 0.15% to 0.35% is that limiting the C addition to this range ensures that the tensile strength of hot-formed components meets the required standards. When the C mass fraction exceeds 0.35%, the material's weldability deteriorates. For example, the C mass fraction can be 0.15%, 0.19%, 0.23%, 0.27%, 0.31%, 0.35%, and so on.

[0033] The positive effect of limiting the mass fraction of Si to 0.1% to 0.4% is that adding 0.1% to 0.4% Si can effectively inhibit the precipitation of carbides during the heating process. The precipitation of carbides often leads to a decrease in material properties, especially in the hot forming process. The precipitation of carbides will affect the plasticity and toughness of the steel matrix, and thus affect the mechanical properties of the final formed component. When the mass fraction of Si is higher than 0.4%, the coating performance of the material will deteriorate. Therefore, controlling the mass fraction of Si within the range of 0.1% to 0.4% can balance the relationship between carbide precipitation and coating performance, and ensure the uniformity and stability of the material during the hot-dip coating process. For example, the mass fraction of Si can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, etc.

[0034] The positive effects of limiting the mass fraction of Mn to 2% to 5% are as follows: Mn is the main strengthening element in the steel matrix. Adding 2% to 5% Mn can significantly improve the tensile strength and yield strength of the material after hot forming, enabling it to meet the mechanical property requirements of applications such as automobiles. In addition, the addition of Mn helps expand the process window for hot stamping and reduce production difficulty. This means that the material can maintain good forming properties over a wider temperature and time range, thereby improving production efficiency and product quality stability. When the mass fraction of Mn exceeds 5%, it may cause severe segregation in the steel matrix. When the mass fraction of Mn is less than 2%, the mechanical properties after hot forming cannot meet the use standards. For example, the mass fraction of Mn can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0035] The positive effect of limiting the mass fraction of V to 0.05% to 0.2% is that V mainly plays a role in refining the grains, which is crucial for improving the cold bending performance of the material. As the tensile strength of the material increases, its cold bending performance tends to decrease significantly. In order to improve the cold bending performance while ensuring strength, it is necessary to adopt a method of grain refinement. By adding V to the steel matrix, the grains can be effectively refined, thereby improving the cold bending performance of the material. When the mass fraction of V is greater than 0.2%, the effect on improving the cold bending performance is limited and will cause an increase in cost. When the mass fraction of V is less than 0.05%, it cannot effectively play a role in grain refinement. For example, the mass fraction of V can be 0.05%, 0.08%, 0.11%, 0.14%, 0.17%, 0.2%, etc.

[0036] The positive effects of limiting the mass fraction of Ti to 0.05% to 0.1% are as follows: One of the main functions of Ti in steel plates is to fix the N element, which helps prevent the N element from combining with other elements (such as B element) during the heat treatment and forming process of the steel plate, thereby avoiding the problem of reduced plasticity of the steel matrix. Ti can also combine with the C element in the steel to form carbides. These carbides can form effective strengthening phases in the steel, which helps to improve the strength and hardness of the steel plate. At the same time, the formation of carbides also helps to refine the grain structure of the steel, further improving the mechanical properties and formability of the steel plate. When the mass fraction of Ti exceeds 0.1%, large-sized inclusions will be formed, resulting in reduced plasticity of the steel matrix. For example, the mass fraction of Ti can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, etc.

[0037] The positive effects of limiting the Mo mass fraction to 0.05% to 0.5% include: Mo refines the original austenite grains, which facilitates the formation of finer martensite during hot forming. This grain refinement improves the elongation of the steel matrix, making it more resistant to fracture under external forces, thereby enhancing its toughness and plasticity. Mo also promotes the precipitation of second-phase particles, which further refine the martensite bulk during hot forming, increasing the strength of the steel matrix. Furthermore, the refined martensite structure contributes to improved hardness and wear resistance. By refining the grains and promoting the precipitation of second-phase particles, Mo can significantly improve the tensile strength, yield strength, and elongation after hot forming of the steel sheet. When the Mo mass fraction is greater than 0.5%, the original austenite grains do not decrease further with the addition of Mo. However, when the Mo mass fraction is less than 0.05%, the grain size cannot be effectively refined. For example, the mass fraction of Mo may be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0038] Fe is a matrix element. The specific content / content range of Fe can be obtained by the upper and lower limit formula of the component, that is:

[0039] The sum of the percentages of the contents of each component in a composition should be equal to 100%, and the content ranges of several components should meet the following conditions: the upper limit of a component + the lower limit of other components ≤ 100; the lower limit of a component + the upper limit of other components ≥ 100.

[0040] Calculated by mass fraction, the chemical composition of the coating includes: Si: 8% to 15%, Fe: 1% to 3%, Cr: 0.5% to 5%, and Al.

[0041] In coated hot-formed steel, Si is added to the coating mainly to improve the heat resistance of the coating and enhance the fluidity of the plating solution. By improving the fluidity of the plating solution, the uniformity of the coating can be improved, and it is beneficial for the Cr element to be evenly distributed in the plating solution, thereby ensuring the uniformity of the coating performance. When the mass fraction of Si in the coating is less than 8%, the heat resistance of the coating cannot be effectively improved, resulting in a failure to provide good protection for the steel substrate during the heating process. When the mass fraction of Si in the coating is greater than 15%, the fluidity of the plating solution will be reduced, and excessive Si will precipitate from the plating solution, resulting in uneven Si distribution. For example, the mass fraction of Si in the coating can be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0042] During the hot forming heating process, the diffusion of Fe within the coating affects its performance. By controlling the Cr content in the coating to 0.5% to 5%, Fe diffusion can be effectively inhibited, ensuring the thickness of the Al-rich dendrite layer meets the required requirements. During heating, Cr diffuses to the coating surface to form stable oxides. These oxides inhibit Al oxidation and reduce Al consumption, further improving the corrosion resistance of the coating after hot forming. When the Cr mass fraction in the coating exceeds 5%, the plating bath temperature exceeds 750°C, significantly reducing equipment life and making post-plating cooling difficult. During cooling, the coating will flow, preventing the Cr from being evenly distributed across the coating surface. When the Cr mass fraction in the coating is less than 0.5%, the corrosion resistance of the coating is not effectively improved. For example, the Cr mass fraction in the coating can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0043] In some embodiments, the coating has a thickness of 10 μm to 35 μm.

[0044] In coated hot-formed steel, the coating thickness is 10 μm to 35 μm to ensure smooth subsequent hot forming process. For example, the coating thickness can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, etc.

[0045] In a second aspect, the present application provides a hot-formed component, which is made of the coated hot-formed steel described in the first aspect.

[0046] In some embodiments, the thermoformed component satisfies at least one of the following properties: a tensile strength of 1400 MPa to 2300 MPa, a yield strength of 900 MPa to 1700 MPa, and an elongation after fracture A50 of 4% to 10%.

[0047] These mechanical properties are achieved through the rational design of the steel substrate and coating, as well as precise control of the hot forming process. Optimizing the steel substrate's composition, such as the appropriate addition of elements like C, Si, Mn, V, Ti, and Mo, and optimizing the ratio of Si, Fe, and Cr in the coating, all play a key role in improving the material's mechanical properties. Furthermore, precise control of parameters such as heating temperature, heating time, and stamping temperature during the hot forming process ensures that the hot-formed components achieve the desired mechanical properties.

[0048] In some embodiments, the coating thickness of the thermoformed component is 15 μm to 60 μm.

[0049] In some embodiments, the coating of the hot-formed component includes: an Al-rich dendrite layer, a Si-rich layer, a diffusion layer, and an alloy layer.

[0050] The Al-rich dendrite layer is located at the outermost layer of the coating, and the Si-rich layer is located below the Al-rich dendrite layer, which hinders the diffusion of Fe elements from the steel matrix into the coating. The diffusion layer is located below the Si-rich layer and serves as a transition zone for the diffusion of Fe elements from the steel matrix to the coating. The alloy layer is located below the diffusion layer and is close to the steel matrix. It is the bonding layer between the coating and the steel matrix, ensuring good bonding between the coating and the steel matrix.

[0051] In some embodiments, the thickness of the Al-rich dendrite layer is 3 μm to 15 μm, and the thickness of the Si-rich layer is 1 μm to 3 μm.

[0052] The Al-rich dendrite layer is part of the coating of hot-formed components, with a thickness of 3μm to 15μm. The presence of the Al-rich dendrite layer can significantly increase the corrosion potential of the coating, thereby improving the corrosion resistance of the coating. By controlling the thickness of the Al-rich dendrite layer, the coating hardness can be reduced, the generation of microcracks during the stamping process can be reduced, and the formability of the coating can be improved. Experiments have shown that compared with coatings without Al-rich dendrite layers, Al-rich dendrite layers can reduce the corrosion potential of the coating, thereby improving the cathodic protection of the coating. When the thickness of the Al-rich dendrite layer is greater than 15μm, the effect of improving the corrosion protection of the steel substrate is limited, and the hardness of the coating is greatly reduced, resulting in easy peeling of the coating during the stamping process. When the thickness of the Al-rich dendrite layer is less than 3μm, the coating has almost no cathodic protection effect, and the increased hardness of the coating causes a large number of microcracks in the coating during stamping. For example, the thickness of the Al-rich dendrite layer can be 3μm, 6μm, 9μm, 12μm, 15μm, etc.

[0053] The thickness of the Si-rich layer is 1μm to 3μm. The main function of the Si-rich layer is to hinder the diffusion of Fe. When the thickness of the Si-rich layer is greater than 3μm, the plasticity of the coating is significantly reduced due to the brittle Si-rich phase. When the thickness of the Si-rich layer is less than 1μm, it cannot effectively hinder the diffusion of Fe. For example, the thickness of the Si-rich layer can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, etc.

[0054] Figure 1 A schematic flow chart of a method for preparing a thermoformed component provided in an embodiment of the present application.

[0055] See Figure 1 In a third aspect, the present application provides a method for preparing the hot-formed component described in the second aspect, the method comprising:

[0056] S1, obtaining the coated hot-formed steel;

[0057] The thickness of the coated hot-formed steel can be 1 mm to 3 mm.

[0058] S2. Heating and stamping the coated hot-formed steel in sequence to obtain a hot-formed component.

[0059] In some embodiments, the heating temperature is 750° C. to 920° C., the heating time is 100 s to 400 s, and the heating atmosphere is air.

[0060] In the embodiments of the present application, a variety of heating methods can be used. If a box-type heating furnace is used for heating, the furnace temperature is directly controlled to a specified range, and the timing is started after the steel plate is placed to ensure that the steel plate is heated at a stable temperature for the required time. If a roller bottom heating furnace is used for heating, a step heating method should be adopted. When the heating time is 1 / 6 to 1 / 3 of the total heating time, the heating temperature is 750℃~830℃; when the heating time is 1 / 3 to 1 / 2 of the total heating time, the heating temperature is 830℃~890℃; when the heating time is 1 / 2 to the end of the total heating time, the heating temperature is 890℃~920℃. If induction heating is used, the heating rate is controlled to 50~100℃ / s, and the heating time is the sum of the time to reach temperature and the holding time.

[0061] The heating atmosphere is air. This ensures that the Cr element oxidizes during the heating process, forming a stable oxide on the surface of the coating. This step is crucial for reducing the formation of Al2O3, increasing the Al content in the coating, and thus improving the corrosion resistance of the coating. Furthermore, reducing the Al2O3 content on the coating surface helps improve the coating performance of the parts, and using air as the heating atmosphere can reduce production costs.

[0062] In some embodiments, the time interval between the heating and the stamping is 5s to 12s.

[0063] After heating is complete, the steel sheet must be quickly transferred to the stamping die area within 5 to 12 seconds to minimize temperature loss and prevent the material from cooling too quickly, which could lead to a decrease in formability. Precise control of this time window helps maintain the material's high-temperature plasticity and reduce oxidation. For example, the time interval between heating and stamping can be 5, 6, 7, 8, 9, 10, 11, or 12 seconds.

[0064] In some embodiments, the stamping temperature of the stamping forming is 500° C. to 800° C., the die ejection temperature of the stamping forming is ≤200° C., and the die cooling rate of the stamping forming is ≥30° C. / s.

[0065] The stamping temperature is set between 500°C and 800°C. This temperature range is key to ensuring that the steel plate has sufficient plasticity and formability during the stamping process. Temperatures above 800°C or below 500°C may lead to a decrease in the material's formability or cracking. For example, the stamping temperature can be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, etc.

[0066] After stamping, the temperature of the component removed from the die should be ≤200°C. This step helps prevent deformation or structural changes caused by continued high temperature, and also helps improve the final mechanical properties of the component. For example, the die exit temperature for stamping can be 160°C, 170°C, 180°C, 190°C, 200°C, etc.

[0067] An efficient mold cooling system can quickly reduce the temperature of the component, helping to stabilize the material's microstructure and mechanical properties. In the embodiments of this application, a mold cooling rate of 30°C / s or higher ensures that the component maintains dimensional stability and reduces thermal stress during rapid cooling. For example, the mold cooling rate can be 30°C / s, 32°C / s, 34°C / s, 36°C / s, 38°C / s, 40°C / s, and so on.

[0068] The present application is further described below with reference to specific examples. Experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with national / industry standards. If there are no corresponding national / industry standards, the methods are carried out in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0069] The chemical compositions (wt%) of the steel substrate and the coating of the coated hot-formed steel are shown in Table 1.

[0070] Table 1

[0071]

[0072] Based on the coated hot-formed steel of the embodiment and the comparative example, heating and stamping were performed in sequence to obtain hot-formed components. The preparation process parameters are shown in Table 2.

[0073] Table 2 Preparation process parameters of Examples and Comparative Examples

[0074]

[0075] The specific heating process in Example 1 and Comparative Examples 1-3 is: heating at 800°C for 50s, heating at 850°C for 150s, and heating at 920°C for 100s; the specific heating process in Example 4 is: heating at 830°C for 80s, heating at 860°C for 100s, and heating at 890°C for 70s.

[0076] The mechanical properties and coating thickness of the hot-formed components were tested, and the specific performance parameters are shown in Table 3. The corrosion potential was obtained electrochemically, using a saturated calomel electrode as the reference electrode, a platinum electrode as the auxiliary electrode, and a 3.5% sodium chloride solution as the electrolyte. The test conditions were room temperature.

[0077] Table 3

[0078]

[0079] It can be seen from Comparative Example 1 that when the Mo element is added inside the steel matrix, the mechanical properties of the hot-formed component are reduced; it can be seen from Comparative Example 2 that when the Cr element is not added to the coating, there is no Al-rich dendrite layer in the coating of the hot-formed component, which leads to an increase in the hardness of the coating and a decrease in the corrosion resistance of the coating to the steel matrix; it can be seen from Comparative Example 3 that when an excessive amount of Si element is added to the coating, the hardness of the coating will increase, thereby affecting the plasticity of the overall material.

[0080] Through Examples 1-4 and Comparative Examples 1-3, it can be seen that by using the coating composition of the application examples and the steel matrix composition, a 3-15 μm thick Al-rich dendrite layer is present in the coating of the obtained hot-formed component, thereby improving the cathodic protection performance and plasticity of the coating.

[0081] Attachment Figure 2 Detailed description:

[0082] Figure 2 This is a SEM image of the coating cross section of the thermoformed component provided in Example 4 of the present application; Figure 2 As shown, the coating consists of an Al-rich dendrite layer, a Si-rich layer, a diffusion layer and an alloy layer. The average thickness of the Al-rich dendrite layer is 12 μm, and the average thickness of the coating is 39 μm.

[0083] One or more technical solutions in the embodiments of the present invention may have at least the following technical effects or advantages:

[0084] The plating solution in the embodiment of the present invention has low cost and simple production process.

[0085] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present 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 the present application. Therefore, the present application is not limited to the embodiments shown herein, but rather is intended to conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A highly corrosion-resistant coated hot-formed steel, comprising a steel substrate and a coating attached to at least a portion of the surface of the steel substrate; in, The chemical composition of the steel matrix includes, by mass fraction, C: 0.15% to 0.35%, Si: 0.1% to 0.4%, Mn: 2% to 5%, P≤0.05%, S≤0.05%, V: 0.05% to 0.2%, Ti: 0.05% to 0.1%, Mo: 0.05% to 0.5%, N≤0.05%, B: 0.001% to 0.003%, and matrix element Fe; Calculated by mass fraction, the chemical composition of the coating includes: Si: 8% to 15%, Fe: 1% to 3%, Cr: 0.5% to 5%, and Al.

2. The coated hot-formed steel according to claim 1, characterized in that: The thickness of the coating is 10 μm to 35 μm.

3. A thermoformed component, characterized in that: The hot-formed component is made of the coated hot-formed steel according to any one of claims 1 to 2.

4. The thermoformed component according to claim 3, characterized in that The thermoformed component meets at least one of the following properties: a tensile strength of 1400 MPa to 2300 MPa, a yield strength of 900 MPa to 1700 MPa, and an elongation after fracture A50 of 4% to 10%.

5. The thermoformed component according to claim 3, characterized in that The coating thickness of the thermoformed component is 15 μm to 60 μm.

6. The thermoformed component according to claim 3, characterized in that The coating of the hot-formed component includes an Al-rich dendrite layer, a Si-rich layer, a diffusion layer and an alloy layer.

7. The thermoformed component according to claim 6, characterized in that The thickness of the Al-rich dendrite layer is 3 μm to 15 μm, and the thickness of the Si-rich layer is 1 μm to 3 μm.

8. A method for preparing a hot-formed component according to any one of claims 3 to 7, characterized in that: The method comprises: Obtaining the coated hot-formed steel; The coated hot-formed steel is sequentially heated and press-formed to obtain a hot-formed component.

9. The method according to claim 8, characterized in that The heating temperature is 750° C. to 920° C., the heating time is 100 s to 400 s, and the heating atmosphere is air.

10. The method according to claim 8, characterized in that The time interval between the heating and the stamping is 5s to 12s; and / or, The stamping temperature of the stamping forming is 500° C. to 800° C., the die-out temperature of the stamping forming is ≤200° C., and the die cooling rate of the stamping forming is ≥30° C. / s.

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